有机无机铅卤钙钛矿光催化产氢加磁场加快反应

Organic-inorganic hybrid halide perovskites have emerged as promising photocatalysts for hydrogen production because of their high absorption coefficients and large carrier diffusion lengths. However, the synthesis and development of organic-inorganic perovskite bromide photocatalysts have not been fully explored. Herein, we report on a novel high-activity Bismuth (Bi) doped CH3NH3PbBr3 (MAPbBr3) photocatalyst that was successfully synthesized using the reverse-temperature crystallization method. This material exhibited a reduced band gap and increased free-carrier concentration compared to pure MAPbBr3. Molecular dynamics and lattice changes within the photocatalyst were systematically investigated using solid-state nuclear magnetic resonance spectroscopy (NMR). The photocatalyst employs hypophosphorous acid (H3PO2) as a stabilizer and platinum (Pt) as a co-catalyst in the photocatalytic hydrogen bromide (HBr) splitting system, achieving a hydrogen evolution rate of 3946.52 μmol·g-1·h-1 under visible light irradiation. Our experimental results suggest that the enhanced photocatalytic performance is attributed to Bi doping, which modifies the charge distribution in the region of the lead (Pb) octahedron, thereby promoting effective charge separation and improving the hydrogen production efficiency. This study provides new insights into the photocatalytic hydrogen production capabilities of organic-inorganic hybrid bromide perovskites.

Cesium lead bromide (CsPbBr3) is a representative material of the emerging class of lead halide perovskite semiconductors that possess remarkable optoelectronic properties. Its optical properties in the vicinity of the bandgap energy are greatly contributed by excitons, which form exciton polaritons due to strong light–matter interactions. Exciton–polaritons in solution‐grown CsPbBr3 crystals are examined by means of circularly polarized reflection spectroscopy measured in high magnetic fields up to 60 T. The excited 2P exciton state is measured by two‐photon absorption. Comprehensive modeling and analysis provides detailed quantitative information about the exciton–polariton parameters: exciton binding energy of 32.5 meV, oscillator strength characterized by longitudinal–transverse splitting of 5.3 meV, damping of 6.7 meV, reduced exciton mass of 0.18m0, exciton diamagnetic shift of 1.6 μeV T−2, and exciton Landé factor gX = +2.35 . It is shown that the exciton states can be described within a hydrogen‐like model with an effective dielectric constant of 8.7. From the measured exciton longitudinal–transverse splitting, Kane energy of Ep = 15 eV is evaluated, which is in reasonable agreement with values of 11.8–12.5 eV derived from the carrier effective masses.

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A theory of dynamic polarization of the nuclear spin system via optically-oriented charge carriers in lead halide perovskites is developed and compared with the experiments performed on a FA$_{0.9}$Cs$_{0.1}$PbI$_{2.8}$Br$_{0.2}$ crystal. The spin Hamiltonians of the electron and hole hyperfine interaction with the nuclear spins of lead and halogen are derived. The hyperfine interaction of the halogen spins with charge carriers is shown to be anisotropic and depending on the position of the halogen nucleus in the cubic elementary cell. The quadrupole splitting is absent for the lead spins, but plays an important role for the halogen spins and affects their dynamic polarization by charge carriers. The Overhauser fields of the dynamically polarized nuclei are calculated as functions of the tilting angle of an external magnetic field and compared with the experimentally measured angular dependence of the Hanle effect. The comparison of the theoretical model with the experimental data reveals an enhanced spin polarization of the lead nuclei, whose mean spin exceeds several times the mean spins of localized electrons and holes. This unexpectedly strong spin polarization is explained by the interaction of the lead nuclei with excitons having a high degree of spin orientation due to their short lifetime after excitation by circularly-polarized light. The dynamic polarization of the quadrupole-split halogen spins manifests itself via the magnetic field they produce at the lead nuclei. This field maintains the magnetization of the lead nuclei at zero external magnetic field. The dynamics of the nuclear spin polarization is measured under optical pumping and in the dark, yielding a nuclear spin-lattice relaxation time on the order of 10 seconds.

Colloidal lead halide perovskite quantum dots (QDs) exhibit size-dependent optical and electronic properties due to quantum confinement, a feature that substantiates their widespread application as classical and quantum light sources. This property is commonly characterized by photoluminescence spectroscopy, where the emission peaks blueshift with decreasing QD size. Apart from the size of the QDs, the electronic structure is strongly influenced by phonons and local disorder, being vastly different between the all-inorganic and hybrid perovskite compositions. In this study, we demonstrate that nuclear magnetic resonance (NMR) spectroscopy can serve as a powerful complementary tool to probe the local characteristics of the ground-state electronic structure. We combine optical and 207Pb NMR spectroscopy to investigate size-dependent confinement in three archetypal lead halide perovskite QDs: CsPbBr3, MAPbBr3, and FAPbBr3. While all compositions exhibit expected size-dependent photoluminescence energy, the hybrid perovskites (MAPbBr3 and FAPbBr3) display strongly reduced size-dependent confinement at room temperature when assessed via NMR. Ab initio molecular dynamics simulations suggest that this effect arises from the disorder-induced wave function modulation driven by dynamic disorder in hybrid perovskites. Experimental support for the hypothesis is provided by freezing the cation dynamics in MAPbBr3 QDs, which leads to the reappearance of the size-dependent chemical shift. By integrating local and global probes of electronic structure, our findings challenge the conventional understanding of quantum effects in soft lead halide perovskite QDs and highlight the role of disorder in shaping the local electronic structure.

The coherent spin dynamics of electrons and holes are studied in a FA0.9Cs0.1PbI2.8Br0.2 perovskite bulk crystal, using time-resolved Kerr ellipticity in a two-color pump-probe scheme. The probe photon energy is tuned to the exciton resonance, while the pump photon energy is detuned from it up to 0.75 eV to higher energies. The spin-oriented electrons and holes photogenerated with significant excess kinetic energy relax into states in vicinity of the band gap, where they undergo Larmor precession in an external magnetic field. At cryogenic temperatures down to 1.6 K, the spin dephasing time reaches the nanosecond range. During energy relaxation, the carrier spin relaxation is inefficient and only happens when the carriers become localized. In experiments with two pump pulses, all-optical control of the amplitudes and phases of the electron and hole spin signals is achieved in the additive regime by varying the intensities of the pump pulses and the time delay between them.

Photocatalytic water splitting using semiconductors is a promising approach for converting solar energy to clean energy. However, challenges such as sluggish water oxidation kinetics and limited light absorption of photocatalyst cause low solar-to-hydrogen conversion efficiency (STH). Herein, we develop a photocatalytic overall water splitting system using I3-/I- as the shuttle redox couple to bridge the H2-producing half-reaction with the O2-producing half-reaction. The system uses the halide perovskite of benzylammonium lead iodide (PMA2PbI4, PMA = C6H5CH2NH2) loaded with MoS2 (PMA2PbI4/MoS2) as the H2 evolution photocatalyst, and the RuOx-loaded WO3 (WO3/RuOx) as the O2 evolution photocatalyst, achieving a H2/O2 production in stoichiometric ratio with an excellent STH of 2.07%. This work provides a detour route for photocatalytic water splitting with the help of I3-/I- shuttle redox couple in the halide perovskite HI splitting system and enlightens one to integrate and utilize multi catalytic strategies for solar-driven water splitting.

Low-dimensional metal halide perovskites have unique optical and electrical properties that render them attractive for the design of diluted magnetic semiconductors. However, the nature of dopant-exciton exchange interactions that result in spin-polarization of host-lattice charge carriers as a basis for spintronics remains unexplored. Here, we investigate Mn2+-doped CsPbCl3 nanocrystals using magnetic circular dichroism spectroscopy and show that Mn2+ dopants induce excitonic Zeeman splitting which is strongly dependent on the nature of the band-edge structure. We demonstrate that the largest splitting corresponds to exchange interactions involving the excited state at the M-point along the spin-orbit split-off conduction band edge. This splitting gives rise to an absorption-like C-term excitonic MCD signal, with the estimated effective g-factor (geff) of ca. 70. The results of this work help resolve the assignment of absorption transitions observed for metal halide perovskite nanocrystals and allow for a design of new diluted magnetic semiconductor materials for spintronics applications.

Lead halide perovskites have shown great potential in photovoltaic and photocatalytic fields. However, the toxicity of lead impedes their wide application. Herein composites of lead-free halide perovskite Cs2AgBiBr6 supported on nitrogen-doped carbon (N-C) materials were synthesized successfully through a facile one-pot method for the first time. Without deposition of noble metals as the cocatalyst, the optimal composite Cs2AgBiBr6/N-C (Cs2AgBiBr6/N-C-140) exhibits outstanding photocatalytic performance with a high hydrogen evolution rate of 380 μmol g-1 h-1 under visible light irradiation (λ ≥ 420 nm), which is about 19 times faster than that of pure Cs2AgBiBr6 and 4 times faster than that of physically mixed Cs2AgBiBr6/N-C-140, respectively. The Cs2AgBiBr6/N-C-140 composite also displays high stability with no significant decrease after six cycles of repeated hydrogen evolution experiments. The addition of N-C with a high surface area helps to prevent aggregation of Cs2AgBiBr6 NPs and provides more pathways for the migration of photoinduced carriers. The nitrogen dopant can facilitate photoinduced electron transfer from Cs2AgBiBr6 to N-C to result in spatially separated electrons and holes with prolonged electron time and greatly enhance the photocatalytic performance. This study indicates that Cs2AgBiBr6-based perovskite materials are promising candidates for photocatalytic hydrogen evolution.

The quest for sustainable hydrogen production through solar energy conversion has directed attention towards photoelectrochemical (PEC) cell water splitting, a promising avenue for hydrogen (H₂) generation. Traditional metal-oxide-based photoelectrodes such as TiO2 and WO3, despite their extensive study, fail to absorb visible light effectively and exhibit poor charge transport properties. In contrast, lead halide perovskites (LHPs) emerge as a superior alternative, endowed with exceptional optoelectronic properties that enhance the solar spectrum photoresponse, critical for the efficient utilization of solar energy in hydrogen production. This study focused on optimizing the photoanode materials by improving the intrinsic properties of LHPs through bandgap tuning and enhanced charge transfer to the oxygen evolution reaction (OER) catalyst. However, the operational stability of LHPs in PEC applications poses a formidable challenge, primarily due to vulnerability to moisture-induced degradation. Addressing the stability concerns, some researches about application of ultrathin Ni surface layers and the use of low-melting-point field metals for protective encapsulation are reported. However, these methods have shown limited success in preventing moisture-induced degradation. In response, this work proposes the innovative use of conductive carbon poweder (CCP) as a superior alternative for enhancing electrical connectivity and stability between LHP solar cells and the OER catalyst. Our findings reveal that CCP's superior conductivity facilitates efficient charge transfer from LHP-based solar cells to OER catalysts, maintaining negligible current and voltage loss. To optimize the LHP photoanode's performance, we focused on enhancing the individual efficiencies and stabilities of the PSC and OER catalyst components. For the PSC, we improved stability by integrating a smaller cation (methylammonium, MA) into the FAPbI3 (formamidinium, FA) lattice, thereby stabilizing the α-phase and enhancing hydrogen bonding. This modification was substantiated through various spectroscopic and X-ray diffraction. Meanwhile, the OER catalyst's efficiency was amplified by employing a 3D-structured NiFe on an Ni foil substrate, improving catalytic activity and stability through enhanced hole mobility and increased electrochemically active surface area. The integrated LHP photoanode demonstrated a notable onset potential of 0.56 V and a peak photocurrent density of 24.26 mA/cm² at 1.23 V vs RHE, achieving a 9.16% applied bias photon-to-current efficiency and sustained performance over 48 hours in a pH 14 aqueous solution under simulated solar illumination. This performance is attributed to the synergistic effect of the optimized PSC and OER catalyst, facilitated by CCP's efficient electrical connectivity.

Inorganic lead-free metal halide perovskites have garnered much attention as low-toxicity alternatives to lead halide perovskites for luminescence and photovoltaic applications. However, the electronic structure and properties of these materials, including the composition dependence of the band structure, spin-orbit coupling, and Zeeman effects, remain poorly understood. Here, we investigated vacancy-ordered Cs3Bi2X9 (X= Cl, Br) perovskite nanocrystals using magnetic circular dichroism spectroscopy. Our results indicate that the excitonic spectra are predominantly composed of direct and indirect band gap transitions and that the Zeeman splitting energy of the direct exciton increases from 0.50 to 0.63 meV at 7 T by substituting Br for Cl. Comparison with analogous results for Cs2AgBiCl6 nanocrystals, obtained by cation substitution, suggests an important effect of charge distribution within electronic bands on the excitonic Zeeman splitting. This work demonstrates that the magneto-optical properties of these materials can be effectively manipulated via chemical composition, suggesting promising applications in photonics, spintronics, and optoelectronics.

Lead‐free perovskites Cs3Bi2xSb2–2xI9 (x = 0.1, 0.3, 0.5, 0.7, 0.9) are prepared by a co‐precipitation method and their photocatalytic performance for hydrogen production is studied in aqueous HI solution. Compared with the lead‐based perovskite (CH3NH3)PbI3, Cs3Bi2xSb2–2xI9 has a better catalytic performance under air mass 1.5 G (AM 1.5 G) simulated sunlight (100 mW cm−2), powders of Cs3Bi0.6Sb1.4I9 (100 mg) loaded with Pt nanoparticles show < H2 evolution rate of 92.6 µmol h−1, which greatly exceeds that of (CH3NH3)PbI3 powders loaded with Pt nanoparticles (100 mg catalyst, 4 µmol h−1). The Cs3Bi2xSb2–2xI9 has a high stability, with no apparent decrease in catalytic activity after five consecutive H2 evolution experiments. The doping of Sb in Cs3Bi2xSb2–2xI9 effectively reduces the contribution of Bi3+ on the conduction band, attenuating the effect of Bi vacancy on band structure. Compared with pure Cs3Bi2I9 and Cs3Sb2I9, Cs3Bi2xSb2–2xI9 has fewer midgap states and better optical absorption, which greatly enhances its performance for the hydrogen evolution reaction.

The tunability of the optical properties of lead halide perovskite nanocrystals makes them highly appealing for applications. Halide anion exchange and quantum confinement enable tailoring of the band gap. For spintronics, the Landé g-factors of electrons and holes are essential. Using empirical tight-binding and k·p methods, we calculate them for nanocrystals of all-inorganic lead halide perovskites CsPbX3 (X = I, Br, Cl). The hole g-factor band gap dependence follows the universal law found for bulk perovskites, while for electrons, a considerable modification is predicted. Based on the k·p analysis, we conclude that this difference arises from the interaction of the bottom conduction band with the spin-orbit split electron states. These predictions are confirmed experimentally for electron and hole g-factors in CsPbI3 nanocrystals in a glass matrix, measured by time-resolved Faraday ellipticity in a magnetic field at cryogenic temperatures.

We present a comprehensive investigation of the Landé g ‐factor of the exciton Rydberg series and band‐edge electron‐hole pairs in two‐dimensional phenethylammonium lead iodide (PEPI) films using magnetic circular dichroism (MCD) spectroscopy. At low magnetic field ( B < 0.5 T), we observe a sizable difference of 15%–20% between the effective g ‐factors of the 1s exciton and that of the higher energy Rydberg excitons, which overlap with the interband (IB) electron‐hole (e‐h) pair transitions at the band‐edge (labeled here as the “2s+” band). At  T = 3 K, we obtained g 1 s = 1.86 ± 0.15 and g 2 s + = 2.33 ± 0.15. These results demonstrate that the exciton g ‐factor is smaller than the sum of the individual electron and hole band edge g ‐factors, namely g exciton < g e +   g h = g IB  . The experimental results are rationalized by theoretical calculations of the g ‐factors using a multiband effective‐mass model that includes the electron‐hole interaction for the different exciton states. It is shown that with the decreasing spatial extent of the exciton wavefunction, the exciton g ‐factor also decreases. At B > 10 T, the interband Landau level transition (N = 1) extrapolates to the bandgap value in PEPI at E g = 2.62 ± 0.016 eV, providing further evidence of the formation of Rydberg excitons.

Solar-driven photocatalysis holds promise for fuel production, with halide perovskites leading owing to superior light absorption and carrier diffusion. However, precise control and understanding of interfacial charge separation dynamics in their heterostructures remain challenging. Using formamidinium lead bromide/molybdenum disulfide (FAPbBr3/MoS2) as a model, we engineered Pb-rich, Pb-neutral, and Pb-deficient surfaces via precursor stoichiometry tuning, modulating interface coupling through Pb-S bonds. High-density atomic bridging in Pb-rich interfaces boosts photogenerated charge separation efficiency from 29% to 63%, yielding a 98-fold hydrogen production increase and record 8.69% solar-to-hydrogen efficiency. Theoretical and experimental results demonstrate that the long carrier diffusion length and high photogenerated charge density of perovskites create a steep charge density gradient at the interface. This gradient directly induces a non-equilibrium internal electric field, which governs the charge transport dynamics. This work demonstrates the feasibility of sophisticated heterointerface tailoring and advances the understanding of the driving forces behind interfacial charge separation for perovskite photocatalysts.

The lead halide perovskite nanocrystals embedded into a glass matrix exhibit strong interaction with light and demonstrate exceptional optical and spin related features along with long-term chemical and physical stability. We apply the spin noise spectroscopy technique which offers a number of specific opportunities to study the spin system of CsPbI$_3$ nanocrystals in a fluorophosphate glass matrix. A pronounced spin precession peak with an isotropic $g$-factor absolute value of 2.7 and record dephasing time of T$_{2\text{,e}}$ = 2.7 ns is ascribed to resident electrons in the perovskite nanocrystals. The experimentally observed Faraday rotation noise with no noise of ellipticity is explained by saturation of the inhomogeneously broadened optical transition. Increasing the probe intensity, we went beyond the non-perturbative regime and observed a number of light-induced effects. In particular, the illumination with shorter wavelength light gives rise to a persistent recharging of the quantum dots by holes ($|g|=0.17$ and T$^*_{2\text{,h}}$ = 1.4 ns, T$^*_{1\text{,h}}$ $\geq$ 30 ns), which remains stable over multiple cycles of heating to the room temperature and cooling. In addition, elliptically polarized light induced an"optical"magnetic field on the system due to the AC Stark effect. It is confirmed using a new modification of polarization noise spectroscopy with a small degree of circular polarization of the probe light added with different frequencies.

In search for new technology to preserve global warming caused by fossil fuel, solar energy driven devices have been high in demand. For instance, photovoltaics (PV) are a promising technology that can produce high power conversion efficiency (PCE). In addition, photoelectrochemical (PEC) water splitting, a promising artificial photosynthesis method, is a potential alternative technique to generate renewable fuel. PEC devices can generate renewable energy sources such as hydrogen, which can alleviate CO2 emission from fossil fuels. However, most readily employed PEC devices require external bias to function as a hydrogen producer. Thus, utilizing PV active layer as a photo absorber, PEC system is a suitable approach to the breakthrough of efficient hydrogen production. In the past decade of PV technology advances, organic-inorganic lead halide perovskite (LHP) can be arguably the most progressive research because of its tunable bandgap, fast charge separation, broad light absorption spectra, low cost, facile fabrication, and high efficiency. These advantageous properties led LHPs to be used as an active layer of water splitting devices. However, LHP-based PECs have flaws to be addressed to be viable material for PEC. LHP are known for their fragile nature from exposure to water. Hence, LHP-based PECs are commonly protected with metal foil encapsulation while covering the edges with epoxy resins. However, the metal foil provides poor contact with the LHP leading to poor charge transfer for water splitting. To solve this problem, we applied carbon conductive powder (CCP) as the interlayer to successfully facilitate charge transfer. With the proposed device modeling, monolithic PEC device that is capable of generating hydrogen in presence of low external applied bias is fabricated. Nonetheless, single monolithic PEC devices still need external applied bias to function as water splitting device which seek for further research. Therefore, adding another photoelectrode will eliminate the necessity of external bias resulting in an only solar powered water splitting device. Herein, we report unassisted solar to hydrogen conversion by using inverted and planar type LHP solar cells as photocathode and photoanode, respectively. With the integration of catalyst, 3D Ni.NiFe and NiPCoP, LHP-based PEC with exceptional performance was attained. We demonstrated unbiased PEC water splitting using a coupled LHP-based photoelectrode under alkaline conditions. Each LHP-based photoelectrode exhibited a outstanding performance of 22.42 mA cm-2 at 1.23 VRHE and 21.96 mA cm-2 at 0 VRHE for the photoanode and photocathode, respectively. Thus, we achieved solar to hydrogen (STH) of 10.64% and unassisted photo-current density of 8.65 mA/cm2. In addition, unbiased catalytic reactivity over 20 h retaining about 60% of photo-current density was attained.

Molecular ferroelectrics have attracted extensive research interest due to their ferroelectric and piezoelectric properties, along with their tunable band structures, making them promising candidates for piezo-photocatalysis. However, the role of spontaneous polarization and piezoelectric fields in charge transfer remains insufficiently understood. In this study, we explored the ferroelectric organic-inorganic perovskite (4,4-difluorocyclohexylammonium)2PbI4 ((4,4-DFPD)2PbI4) as a piezo-photocatalyst in the HI splitting process for hydrogen production. Under combined ultrasonic and visible light irradiation, the hydrogen production rate of (4,4-DFPD)2PbI4 reached 1185.1 µmol·h-1·g-1, 1.95 times higher than under visible light alone and 12.1 times greater than that of the conventional MAPbI3 perovskite catalyst. Experimental and theoretical analyses reveal that the combination of light and pressure synergistically enhances charge separation and boosts catalytic efficiency, driven by built-in electric fields from spontaneous polarization, piezoelectric fields, and photoexcitation. This work provides valuable insights for the design of novel molecular ferroelectric catalysts with high efficiency for photocatalytic hydrogen evolution.

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Metal halide perovskites hold significant promise as photocatalysts for hydrogen evolution reaction. However, the low stability and insufficient exposure of active sites impair their catalytic efficiency. Herein, we utilized an extra-large-pore zeolite ZEO-1 as a host to confine and stabilize the CsPbBr3 nanocrystals for boosting hydrogen iodide splitting. The as-prepared CsPbBr3@ZEO-1 featured sufficiently exposed active sites, superior stability, along with extra-large pores of ZEO-1 that were favorable for adsorption and diffusion. Most importantly, the unique nanoconfinement effect of ZEO-1 led to the narrowing of the band gap of CsPbBr3, allowing for more efficient light utilization. As a result, the photocatalytic HER rate of the as-prepared CsPbBr3@ZEO-1 photocatalyst was increased to 1734 μmol·h-1·g-1, and the long-term stability. Furthermore, Pt was incorporated with well-dispersed CsPbBr3 nanocrystals into ZEO-1, resulting in a significant enhancement in activity. Further investigation revealed that the boosted photocatalytic performance of Pt/CsPbBr3@ZEO-1 could be attributed to the promotion of charge separation and transfer, as well as to the substantially lowered energy barrier for HER. This work highlights the advantage of extra-large-pore zeolites as the nanoscale platform to accommodate multiple photoactive components, opening up promising prospects in the design and exploitation of novel zeolite-confined photocatalysts for energy harvesting and storage.

Low-dimensional perovskites show great promise due to their stronger structural stability against external stressors, in particular, moisture. However, the alternance of organic and inorganic layers contributes to form a quantum-well structure leading to the bi-dimensional confinement of the carrier's transport, thus limiting the performances in solar-to-fuel conversion applications. To overcome this issue, the synthesis of the 1D vinylenedipyridine-based (4,4'-VDP)Pb2X6 perovskite (X = Br, I), whose specificity is to combine pi-conjugated spacer and cation-pi interactions, is reported. The pi-conjugation electronically connects the inorganic layers, and the cation-pi interactions facilitate stability against water. As a result, exceptional structural and photostability in a large range of aqueous pH is demonstrated. Whereas (4,4'-VDP)Pb2Br6 does not show photocatalytic activity toward hydrogen production due to misaligned band energy position with HBr, the iodide counterpart (4,4'-VDP)Pb2I6 perovskite produces a substantial amount of hydrogen (1.81 mmol g-1 after 24 h of photoreaction), without noble metal catalyst utilization and under standard AM 1.5 G illumination conditions.

To combat the energy crisis and environmental pollution, developing renewable energy technology such as hydrogen (H2) production is necessary. The sulfur–iodine thermochemical cycle has high commercial potential in conducting hydrogen iodide (HI) splitting for H2 generation, but it requires high‐temperature conditions. In comparison, photocatalytic HI splitting of halide perovskites is non‐polluted and low‐cost for H2 production at room temperature. Herein, an in situ constructed multidimensional bismuth (Bi)‐based 3D/2D EDABiI5/MA3Bi2I9 perovskite heterojunction is developed first by synergistically integrating dimensionality control with heterostructure engineering. Accordingly, the optimal EDABiI5/MA3Bi2I9 without any co‐catalysts exhibits the H2 evolution rate of 213.63 µmol h−1g−1 under irradiation. Equally importantly, interfacial dynamics of solid/solid and solid/liquid interfaces play a crucial role in photocatalytic performance. Therefore, using temperature‐dependent transient photoluminescence and electrochemical voltammetric techniques, it is confirmed that the exciton transportation of EDABiI5/MA3Bi2I9 is accelerated by stronger electronic coupling arising from an enhanced overlap of electronic wavefunctions. Moreover, the effective diffusion coefficient and electron transfer rate of EDABiI5/MA3Bi2I9 demonstrate efficient heterogeneous electron transfer, resulting in improved photocatalytic hydrogen production. Consequently, the in situ formation of perovskite heterostructures studied by a combination of photophysical and electrochemical techniques provides new insights into green hydrogen evolution and interfacial interaction dynamics for commercial applications of solar‐to‐fuel technology.

Despite achievements in the remarkable photoelectrochemical (PEC) performance of photoelectrodes based on organometal halide perovskites (OHPs), the scaling up of small‐scale OHP‐based PEC systems to large‐scale systems remains a great challenge for their practical application in solar water splitting. Significant resistive losses and intrinsic defects are major obstacles to the scaling up of OHP‐based PEC systems, leading to the PEC performance degradation of large‐scale OHP photoelectrodes. Herein, a scalable design of the OHP‐based PEC systems by modularization of the optimized OHP photoelectrodes exhibiting a high solar‐to‐hydrogen conversion efficiency of 10.4% is suggested. As a proof‐of‐concept, the OHP‐based PEC module achieves an optimal PEC performance by avoiding major obstacles in the scaling up of the OHP photoelectrodes. The constructed OHP module is composed of a total of 16 OHP photoelectrodes, and a photocurrent of 11.52 mA is achieved under natural sunlight without external bias. The successful operation of unassisted solar water splitting using the OHP module without external bias can provide insights into the design of scalable OHP‐based PEC systems for future practical application and commercialization.

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Metal halide perovskites (MHPs) have emerged as attractive candidates for producing green hydrogen via photocatalytic pathway. However, the presence of abundant defects and absence of efficient hydrogen evolution reaction (HER) active sites on MHPs seriously limit the solar-to-chemical (STC) conversion efficiency. Herein, to address this issue, we present a bi-functionalization strategy through decorating MHPs with a molecular molybdenum-sulfur-containing co-catalyst precursor. By virtue of the strong chemical interaction between lead and sulfur and the good dispersion of the molecular co-catalyst precursor in the deposition solution, a uniform and intimate decoration of the MHPs surface with lead sulfide (PbS) and amorphous molybdenum sulfide (MoSx) co-catalysts is obtained simultaneously. We show that the PbS co-catalyst can effectively passivate the Pb-related defects on the MHPs surface, thus retarding the charge recombination and promoting the charge transfer efficiency significantly. The amorphous MoSx co-catalyst further promotes the extraction of photogenerated electrons from MHPs and facilitates the HER catalysis. Consequently, drastically enhanced photocatalytic HER activities are obtained on representative MHPs through the synergistic functionalization of PbS and MoSx co-catalysts. A solar-to-chemical (STC) conversion efficiency of ca. 4.63% is achieved on the bi-functionalized FAPbBr3-xIx, which is among the highest values reported for MHPs.

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A magnetic skyrmion is a topologically stable state with potential applications for realizing the next-generation spintronic devices. Here, we demonstrate the real-space observation of skyrmions in Dion-Jacobson phase perovskite, Ca2Nan-3NbnO3n+1- (CNNO), nanosheets by using optical injection. The CNNO4 and CNNO6 nanosheets exhibit weak ferromagnetics, while the CNNO5 nanosheet is superparamagnetic. The magnetic skyrmion can be clearly observed in those 2D nanosheets in the absence of the external magnetic field. First-principles calculations and micromagnetic simulations predict that the magnetic skyrmions in CNNO nanosheets is Néel-type with a diameter of 11-15 nm, in corresponding to the experiments. Our findings provide insights for developing room-temperature skyrmions in CNNO nanosheets for skyrmionic water-splitting performance in future energy generation and quantum computing devices.

All‐inorganic halide perovskite quantum dots (PQDs) encounter significant challenges related to degradation and self‐oxidation in aqueous electrolytes, which remain critical obstacles for their efficient utilization in photoelectrochemical (PEC) water oxidation. In this study, we demonstrate the hybridization of zero‐dimensional CsPbBr 3 PQDs with a SiO 2 shell (PQD@SiO 2 ) and the direct harnessing of PQD@SiO 2 on a two‐dimensional WO 3 nanoflake photoanode for boosting PEC water splitting. The ultra‐thin SiO 2 shell protects the PQDs from the aqueous environment and suppresses undesirable charge recombination. Incorporating PQD@SiO 2 enhances light harvesting and manipulates photogenerated charges, amplifying the interfacial electric field of the WO 3 photoanode to facilitate PEC water oxidation kinetics. Consequently, PQD@SiO 2 ‐incorporated WO 3 (PQD@SiO 2 /WO 3 ) exhibits 2.2‐fold higher PEC performance compared to pristine WO 3 at 1.23 V RHE , with long‐term durability over 12 h and a remarkable Faradaic efficiency of 85.5% for overall solar water splitting to produce H 2 at 1.23 V under 1 sun illumination. This novel strategy of a heterostructure consisting of PQDs passivated by an ultra‐thin SiO 2 shell on a WO 3 photoanode paves the way for improving PEC water splitting and efficient hydrogen production.

Photocatalysis is an intricate process that involves a multitude of physical and chemical factors operating across diverse temporal and spatial scales. Identifying the dominant factors that influence photocatalyst performance is one of the central challenges in the field. Here, we synthesized a series of perovskite RTaON2 semiconductors with different A-site rare earth atoms (R = Pr, Nd, Sm, and Gd) as model photocatalysts to discuss the influence of the A-site modulation on their local structures as well as both physical and chemical properties and to get insight into the rate-determining step in photocatalytic Z-scheme overall water splitting (OWS). It is interesting to find that, with a decreasing ionic radius of the A-site cations, the RTaON2 compounds exhibit continuous blue shift of light absorption and a concomitant reduction in the lifetime of photogenerated carriers, revealing a significant influence of A-site atoms on the light absorption and charge separation processes. On the other hand, the A-site atomic substitution was revealed to significantly modulate the valence band positions as well as surface oxidation kinetics. By employing the Pt-modified RTaON2 as H2-evolving photocatalysts, the activity of photocatalytic Z-scheme OWS for hydrogen production on them is found to be determined by its surface oxidation process instead of light absorption or charge separation. Our results give the first experimental demonstration of the rate-determining step during the photocatalytic Z-scheme OWS processes, as should be instructive for the design and development of other efficient solar-to-chemical energy conversion systems.

The synthesis of photocatalysts with both broad light absorption and efficient charge separation is significant for a high solar energy conversion, which still remains to be a challenge. Herein, a narrow-bandgap Y2Ti2O5S2 (YTOS) oxysulfide nanosheet coexposed with defined {101} and {001} facets synthesized by a flux-assisted solid-state reaction was revealed to display the character of an anisotropic charge migration. The selective photodeposition of cocatalysts demonstrated that the {101} and {001} surfaces of YTOS nanosheets were the reduction and oxidation regions during photocatalysis, respectively. Density functional theory (DFT) calculations indicated a band energy level difference between the {101} and {001} facets of YTOS, which contributes to the anisotropic charge migration between them. The exposed Ti atoms on the {101} surface and S atoms on the {001} surface were identified, respectively, as reducing and oxidizing centers of YTOS nanosheets. This anisotropic charge migration generated a built-in electric field between these two facets, quantified by spatially resolved surface photovoltage microscopy, the intensity of which was found to be highly correlated with photocatalytic H2 production activity of YTOS, especially exhibiting a high apparent quantum yield of 18.2% (420 nm) after on-site modification of a Pt@Au cocatalyst assisted by Na2S-Na2SO3 hole scavengers. In conjunction with an oxygen-production photocatalyst and a [Co(bpy)3]2+/3+ redox shuttle, the YTOS nanosheets achieved a solar-to-hydrogen conversion efficiency of 0.15% via a Z-scheme overall water splitting. Our work is the first to confirm anisotropic charge migration in a perovskite oxysulfide photocatalyst, which is crucial for enhancing charge separation and surface catalytic efficiency in this material.

We present a study on the electrocatalysis of 214-type perovskite oxides LnSrCoO4 (Ln = La, Pr, Sm, Eu, and Ga) with semiconducting-like behavior synthesized using the sol-gel method. Among these five catalysts, PrSrCoO4 exhibits the optimal electrochemical performance in both the oxygen evolution reaction and the hydrogen evolution reaction, mainly due to its larger electrical conductivity, mass activity, and turnover frequency. Importantly, the weak dependency of LSV curves in a KOH solution with different pH values, revealing the adsorbate evolving mechanism in PrSrCoO4, and the density functional theory (DFT) calculations indicate that PrSrCoO4 has a smaller Gibbs free energy and a higher density of states near the Fermi level, which accelerates the electrochemical water splitting. The mutual substitution of different rare-earth elements will change the unit-cell parameters, regulate the electronic states of catalytic active site Co ions, and further affect their catalytic performance. Furthermore, the magnetic results indicate strong spin-orbit coupling in the electroactive sites of Co ions in SmSrCoO4 and EuSrCoO4, whereas the magnetic moments of Co ions in the other three catalysts mainly arise from the spin itself. Our experimental results expand the electrochemical applications of 214-type perovskite oxides and provide a good platform for a deeper understanding of their catalytic mechanisms.

Here, a microfluidic paper‐based analytical device (µ‐PADs) with editable electron configuration and conductivity is proposed for sensitive point‐of‐care (POC) detection of acetamiprid (ACE). The CdS‐protected CsPbX3:Mn (X = Cl, Br) halide perovskite (CPCBM/CdS) quantum dots (QDs) with a core/shell structure are prepared for the first time. This advancement not only addresses the challenge of the inherent water instability of perovskites but also imparts spin‐related charge‐transfer properties to the composite material. Additionally, a simple magnetic stimulation method is employed to rearrange the spin electron occupation in perovskites, effectively enhancing the charge separation efficiency in paper‐based PEC (µ‐PEC) sensing systems. The underlying mechanism is systematically investigated using density functional theory simulations and ultrafast transient absorption spectroscopy. These studies revealed a spin‐dependent reaction pathway and the carrier lifetime extended to 4244 ps under a magnetic field (MF), which is 2.2 times longer than that of the pristine perovskite. As a proof‐of‐concept application, a µ‐PEC sensor is developed for sensitive POC monitoring of ACE in environmental samples with a low detection limit of 23 fm. This study shows that manipulating spin‐polarized electrons in photosensitive semiconductors provides an effective strategy to enhance sensing sensitivity, which holds great prospects for future environmental detection and health monitoring.

Perovskite-based photoelectrodes have a high light absorption coefficient, long carrier diffusion length, and adjustable band gap, making them a hotspot in the field of green hydrogen production. By optimizing the behavior of photogenerated carriers and the kinetics of interfacial reactions, we form a complementary mechanism, which can significantly enhance the overall performance. Using rubidium fluoride (RbF) to enhance electron mobility and carrier lifetime and octylammonium iodide (OAI) to suppress carrier recombination at the hole transport layer (HTL)/perovskite (PVK) interface and on the hydrophobic perovskite surface can improve the intrinsic recombination losses. The average photogenerated carrier lifetime has been increased from 126 to 238 ns. Moreover, the effective passivation of defects in target perovskite solar cells (PSCs) leads to a reduction in defect density. Depositing a NiFe catalyst to promote the transfer of charges to the electrolyte can improve the interface's reaction losses. During the oxygen evolution reaction, the overpotential is 220 mV at a current density of 10 mA cm-2. Subsequent encapsulation and integration of the catalyst with the PSCs enable dual strategies for carrier management and interfacial catalysis, synergistically enhancing the water-splitting performance. Finally, a system with parallel illumination of perovskite photoanodes and photocathodes achieves an unassisted solar-to-hydrogen (STH) efficiency of 13.7%. This work provides an important strategy for controlling the photogenerated carrier loss in photoelectrodes that can effectively enhance the STH efficiency of the photoelectrodes.

The advancement of photocatalytic water splitting requires going beyond charge migration control to the greater challenge of utilizing the spin degree of freedom as a handle to precisely steer reaction pathways. Here, it is identified 67 magnetic heterojunctions composed of magnetic 2D transition metal halide and non-magnetic transition metal chalcogenide monolayers via high-throughput screening. These selected structures exhibit a lattice mismatch below 5%, with each constituent monolayer possessing a band gap in the optimal range of 0.5 - 2.5 eV. First-principles calculations confirm a type-II staggered band alignment and a built-in electric field that promotes efficient charge separation. More importantly, the unique spin-polarized electronic configuration of Cr3+ in CrI3 preferentially facilitates the generation of triplet oxygen, significantly boosting the oxygen evolution reaction. Meanwhile, the anchoring of Pt single atoms on the MoTe2 and WTe2 layers addresses their weak hydrogen adsorption, enhancing the HER kinetics to balance the overall water splitting process. This synergistic engineering of spin-polarization for OER and single-atom sites for HER works cooperatively within the heterojunction. Together with strong visible-light absorption and a predicted solar-to-hydrogen efficiency that surpasses industrial benchmarks, this study highlights a high-throughput-guided strategy for designing high-performance magnetic photocatalysts through multi-component active site optimization.

Achieving simultaneous circularly polarized luminescence (CPL) with opposite handedness introduces additional complexity in CPL modulation, which is difficult, as it requires the generation of two excited states with distinct spin orientations. Here, dual magnetic circular polarization of luminescence (MCPL) is demonstrated in BA2Pb0.8Mn0.2Br4 （BA = butylamine）, where exciton and Mn2+ d‐d emissions exhibit CPL with opposite handedness under an external magnetic field, with gMCPL values of ‐5.2/5.7 × 10−3 for exciton emission and 2.4/‐2.1 × 10−3 for Mn2+ emission under ±1.6 T. Structural analyses confirm the substitution of Pb2+ with Mn2+ in the perovskite lattice, while magnetic measurements reveal the paramagnetic nature of BA2Pb0.8Mn0.2Br4, originating from the high‐spin configuration of Mn2+. Zeeman splitting for both the ground state and excited state is considered for Mn2+, generating CPL signals opposite to those of exciton emission. This observation is further validated in Mn2+‐doped perovskites with different organic cations and dimensions, providing a new approach for modulating multi‐peak CPL with opposite handedness for applications in spintronics, quantum information, and magneto‐optical technologies.

Perovskite solar cells (PSCs) based on 2D/3D composite structure have shown enormous potential to combine high efficiency of 3D perovskite with high stability of 2D perovskite. However, there are still substantial non-radiative losses produced from trap states at grain boundaries or on the surface of conventional 2D/3D composite structure perovskite film, which limits device performance and stability. In this work, a multifunctional magnetic field-assisted interfacial embedding strategy is developed to construct 2D/3D composite structure. The composite structure not only improves crystallinity and passivates defects of perovskite layer, but also can efficiently promote vertical hole transport and provide lateral barrier effect. Meanwhile, the composite structure also forms a good surface and internal encapsulation of 3D perovskite to inhibit water diffusion. As a result, the multifunctional effect effectively improves open-circuit voltage and fill factor, reaching maximum values of 1.246 V and 81.36%, respectively, and finally achieves power conversion efficiency (PCE) of 24.21%. The unencapsulated devices also demonstrate highly improved long-term stability and humidity stability. Furthermore, an augmented performance of 21.23% is achieved, which is the highest PCE of flexible device based on 2D/3D composite perovskite films coupled with the best mechanical stability due to the 2D/3D alternating structure.

Photoelectrochemical (PEC) water splitting stands as a promising strategy for sustainable hydrogen (H2) production, driven by renewable solar energy conversion. However, the lack of highly efficient photoanodes has constrained high-performance PEC water splitting due to poor light absorption, charge transportation, and sluggish catalytic kinetics of the oxygen evolution reaction (OER). Extensive efforts have focused on developing transition metal oxide (TMO)-based semiconductors as highly efficient photoanodes, owing to their favorable band structure, eco-friendliness, abundance on Earth, and good stability in aqueous environments. However, TMO-based materials encounter challenges such as undesired rapid charge recombination, insufficient surficial reaction kinetics, and low light absorption coefficients. To address these limitations, a systematic design of heterostructured TMO-based photoanodes has been considered a potential strategy. On the other hand, lead halide perovskite quantum dots (PQDs), including all-inorganic CsPbX3 (where X represents one of the halogens), have been extensively investigated for optical energy conversion systems due to their high absorption coefficient, defect tolerance, moderate carrier mobility, and cost-effective preparation. However, the significant instability of PQDs against polar solvents, even under anodic reaction conditions, leading to critical self-oxidation and deformation, has hindered their practical application in solar water splitting. To overcome these restrictions, numerous investigations have explored methods such as encapsulation, ligand modification, and surface engineering to prevent PQD decomposition and modulate charge dynamics based on interfacial characteristics. Constructing a core-shell structure for PQDs with an oxide-based passivation layer has been proposed as an efficient approach to protect PQDs from water molecules and tune the dynamics of photogenerated charges. However, charge extraction from PQDs could be hindered by the high dielectric properties of the oxide-based passivation layer. Thus, a conformal and sub-nanometer scale introduction of the passivation layer can facilitate successful PQD incorporation on TMO-based photoanodes. In this study, we propose a rational heterostructured photoanode for boosting solar water splitting, and we report for the first time that PQDs exposed to an aqueous electrolyte demonstrate excellent stability even under oxidation reaction conditions. We demonstrate a core-shell structured CsPbBr3 PQDs with an ultrathin SiO2 passivation layer (CS-PQDs), less than 1 nm thick, incorporated on a WO3 nanoflake photoanode (CS-PQD/WO3). The SiO2 passivation prevents undesirable recombination of CsPbBr3, and the extraction of photogenerated charges is prominently promoted, indicating not only improved stability of CsPbBr3 PQDs but also manipulated charge dynamics of the CS-PQD/WO3 photoanode. The heterostructured photoanode achieves a 2.2-fold improvement in photocurrent density at 1.23 V versus the reversible hydrogen electrode (RHE) under 1 sun illumination, attributed to enhanced interfacial catalytic kinetics with improved light harvesting and efficient charge migration facilitated by the built-in electric field. Additionally, the CS-PQD/WO3 exhibits moderate durability over 12 hours and excellent Faraday efficiency for H2 production through solar water splitting. This study provides insight into the rational heterostructure of PQDs and TMO, in the presence of an ultrathin oxide passivating layer, raising the potential of perovskite-based nanomaterials as a facilitator for manipulating photogenerated charge dynamics for solar energy conversion in aqueous media.

Photocatalytic water splitting has always been a field where breakthroughs are expected to solve energy and environmental problems. However, current catalysts suffer from low activity in mismatched catalytic environments and high cost. Herein, we designed a series of integrated CsPbBr3-CsPbCl3 heterostructures to explore their catalytic capability. Based on extensive calculations, we discovered the inner connection between dopant atoms and the catalytic performance and proposed a new descriptor by applying the Least Absolute Shrinkage and Selection Operator (LASSO) analysis. After systematic screening, the CsPbBr3:Ni-CsPbCl3:Co system is found to be promising for single-catalyst overall water splitting under the same environment. Furthermore, a smaller bandgap that covers the redox potential of water splitting suggests the capability for photocatalysis. Besides, the CsPbBr3:Ni-CsPbCl3:Co system bulk-doped by Co could conduct the photocatalysis with better performance.

Chiral organic-inorganic hybrid metal halides as promising circularly polarized luminescence (CPL) emitter candidates hold great potential for high-definition displays and future spin-optoelectronics. The recent challenge lies primarily in developing high-performance red CPL emitters. Here, coupling the f-f transition characteristics of trivalent europium ions (Eu3+) with chirality, we construct the chiral Eu-based halides, (R/S-3BrMBA)3EuCl6, which exhibit strong and predictable red emission with large photoluminescence quantum yield (59.8%), narrow bandwidth (≈2 nm), long lifetime (≈2 ms), together with large dissymmetry factor |glum| of 1.84 × 10−2. Compared with the previously reported chiral metal halides, these chiral Eu-based halides show the highest red CPL brightness. Furthermore, the degree of photoluminescence polarization in (R/S-3BrMBA)3EuCl6 can be manipulated by the external magnetic field. Particularly, benefiting from the field-generated Zeeman splitting and spin mixing at exciton states, an anomalously positive magneto-photoluminescence was observed at room temperature. This work provides an efficient strategy for constructing both high-performance and pure-red CPL emitters. It also opens the door for chiral rare-earth halides toward chiral optoelectronic and spintronic applications. Chiral organic-inorganic perovskites are promising materials for circularly polarized luminescence. Here the authors present chiral europium halides leading to red circularly polarized luminescence with large dissymmetry factor and strong magneto-chiroptical properties.

Enhancing the ferroelectric polarization field and tuning the electron spin polarization as novel approaches to improve photocatalytic performance have sparked considerable research interest. Obviously, a straightforward strategy to simultaneously regulate ferroelectric and spin polarization will have a very attractive application prospect. In this study, a series of Bi4NbO8Cl-Ni photocatalysts are synthesized by doping different concentrations of magnetic element Ni into ferroelectric semiconductor Bi4NbO8Cl. Due to the significant difference in atomic radius, Ni doping induces greater structural distortion and enhances the deviation of positive and negative charge centers in the crystal, thereby resulting in a stronger ferroelectric polarization field. Moreover, spin polarization is induced in the electrons, and photogenerated carriers exhibit higher spatial separation efficiency under magnetic field. Thanks to the synchronous regulation of ferroelectric and spin polarization by Ni doping, the average rates of H2 and O2 production from photocatalytic water splitting over Bi4NbO8Cl-Ni under visible light are 342.6 and 207.1 µmol g-1 h-1, respectively, which are 10.6 and 2.7 times those of pure Bi4NbO8Cl. Notably, under an applied magnetic field of 300 mT, the average production rates are further promoted up to 616.7 and 331.4 µmol g-1 h-1. This study offers a novel strategy to significantly improve photocatalytic performance.

No abstract available

The photocatalytic system using hydrohalic acid (HX) for hydrogen production is a promising strategy to generate clean and renewable fuels as well as value‐added chemicals (such as X2/X3−). However, it is still challenging to develop a visible‐light active and strong‐acid resistive photocatalyst. Hybrid perovskites have been recognized as a potential photocatalyst for photovoltaic HX splitting. Herein, a novel environmentally friendly mixed halide perovskite MA3Bi2Cl9–xIx with a bandgap funnel structure is developed, i.e., confirmed by energy dispersive X‐ray analysis and density functional theory calculations. Due to gradient neutral formation energy within iodine‐doped MA3Bi2Cl9, the concentration of iodide element decreases from the surface to the interior across the MA3Bi2Cl9–xIx perovskite. Because of the aligned energy levels of iodide/chloride‐mixed MA3Bi2Cl9–xIx, a graded bandgap funnel structure is therefore formed, leading to the promotion of photoinduced charge transfer from the interior to the surface for efficient photocatalytic redox reaction. As a result, the hydrogen generation rate of the optimized MA3Bi2Cl9–xIx is enhanced up to ≈341 ± 61.7 µmol h−1 with a Pt co‐catalyst under visible light irradiation.

Photocatalytic hydrogen evolution (PHE) is attractive for sustainable energy production, yet its efficiency lags photovoltaic conversion mainly due to the step of H‒H bonding for hydrogen generation on photocatalysts. Herein, the spin-enhanced PHE using photocatalysts of chiral perovskites (MBPI) are reported, where the spin orientations of photocarriers are aligned antiparallelly for H‒H bonding via the chiral-induced spin selectivity (CISS) effect. It is observed that the rac-MBPI shows a 3.5-fold enhancement in PHE activity compared with R/S-MBPI under visible light illumination, which is related to the chiral distortions of octahedral units in perovskite structures. Structural distortions lead to the spin polarization of photogenerated carriers in chiral perovskites due to the CISS effect, as revealed by magneto-photocurrent measurements. Compared with the parallel spins in R/S-MBPI, the antiparallel spins in rac-MBPI are more favorable for the coupling of H* radicals, as proven by the electron paramagnetic resonance experiments. The spin-enhanced mechanism for PHE is universal for reduced dimensional (quasi-2D) chiral perovskites, and the H2 yield rate is optimized up to 0.61 mmol g-1 h-1 with an excellent stability over 100 hours.

No abstract available

Hybrid organic-inorganic perovskites (HOIPs) have gained substantial attention due to their excellent photovoltaic and optoelectronic properties. Herein, we comprehensively investigate a typical two-dimensional (2D) hybrid perovskite (C6H5CH2NH3)2PbI4 to track its structural and band gap evolution applied by the maximum pressure of 27.2 GPa. Remarkably, an unprecedented band gap narrowing down to the Shockley-Queisser limit is observed upon compression to 20.1 GPa. Two phase transitions have been observed during this process: the ambient Pbca phase converts into the Pccn phase at 4.6 GPa and then undergoes an isostructural phase transition at 7.7 GPa. The Fourier Transform Infrared (FTIR) spectroscopy reveals that pressure-enhanced hydrogen bonding plays an important role in structural modifications and band gap variations. This work not only enables high pressure as a clean tool to tune the structure and band gap of hybrid perovskite, but also maps a pioneering route towards realizing ideal photovoltaic materials-by-design.

A wireless solar water splitting device provides a means to achieve an inexpensive and highly distributed solar-to-fuel system owing to its portability, flexible scale, and simple design. Here, a highly efficient hydrogen-generating artificial leaf is introduced, which is a wireless configuration for converting solar energy into chemical energy, by integrating a hybrid perovskite (PSK) as the light absorber with catalysts for electrochemical reaction. First, a single integrated photoelectrochemical photocathode, and a spatially decoupled hydrogen evolution reaction catalyst, are fabricated. A decoupled geometry is adopted to enable the physical protection of the PSK layer from the electrolyte, thus allowing excellent stability for over 85 h. Additionally, an efficient dual photovoltaic module photocathode is fabricated to produce sufficient photovoltage to drive water splitting reactions, as well as a high photocurrent to achieve the applied-bias photoconversion efficiency (13.5%). To investigate the overall water splitting performance, a NiFe-OH catalyst is employed, and the device with a wired configuration achieves a photocurrent density of 9.35 mA cm-2 , corresponding to a solar to hydrogen (STH) efficiency of 11.5%. The device with a fully integrated wireless artificial leaf configuration exhibited a similar STH efficiency of over 11%, demonstrating the effectiveness of this cell design.

A key innovation in this work is the development of a trapping method to synthesize perovskite Cs2PtCl6 nanoparticles at a liquid-liquid interface under ambient conditions. The resulting nanoscale Cs2PtCl6 particles are able to combine with various MXenes via PtCl6 2- units, among which V4C3TX MXene forms strongly coupled Cs2PtCl6@V4C3TX composites. Cs2PtCl6@V4C3TX exhibits excellent hydrogen evolution reaction (HER), delivering a dramatically reduced overpotential of ∼39 mV a current density of 10 mA cm- 2, which outperforms the pristine V4C3TX, Cs2PtCl6, and other Cs2PtCl6@MXenes composites investigated. On the other hand, Cs2PtCl6@V4C3TX exhibits negligible oxygen evolution reaction, but remarkably high-performance urea oxidation reaction. The selective anodic reactivity simultaneously reduces the overall energy input required for HER. Comprehensive studies with other MXenes and their Cs2PtCl6 hybrids highlight the unique and critical role of V4C3TX in facilitating electron transfer and catalytic stability, paving the way for simultaneous production of clean energy and remediation of organic pollutants.

Two series of hybrid inorganic–organic materials, prepared via interlayer organic modification of protonated Ruddlesden–Popper phases HLnTiO4 (Ln = La, Nd) with n-alkylamines and n-alkoxy groups of various lengths, have been systematically studied with respect to photocatalytic hydrogen evolution from aqueous methanol under near-ultraviolet irradiation for the first time. Photocatalytic measurements were organized in such a way as to control a wide range of parameters, including the hydrogen generation rate, quantum efficiency of the reaction, potential dark activity of the sample, its actual volume concentration in the suspension, pH of the medium and stability of the photocatalytic material under the operating conditions. The insertion of the organic modifiers into the interlayer space of the titanates allowed obtaining new, more efficient photocatalytic materials, being up to 68 and 29 times superior in the activity in comparison with the initial unmodified compounds HLnTiO4 and a reference photocatalyst TiO2 P25 Degussa, respectively. The hydrogen evolution rate over the samples correlates with the extent of their interlayer hydration, as in the case of the inorganic–organic derivatives of other layered perovskites reported earlier. However, the HLnTiO4-based samples demonstrate increased stability with regard to the photodegradation of the interlayer organic components as compared with related H2Ln2Ti3O10-based hybrid materials.

The quest for dynamic and cost‐effective electrocatalysts to substitute carbon‐supported platinum (Pt) in alkaline hydrogen evolution reaction (HER) remains a pressing challenge. The incorporation of transition metal atoms through electron donation and spin regulation dominates the HER performance of Pt nanoparticles. Herein, we demonstrate that Co‐N coordination was utilized to regulate and stabilize the chemical microenvironment of Pt nanoparticles to fabricate hybrid electrocatalysts (Pt/CoNC). The resultant Pt/CoNC delivers ultralow overpotentials of 15.2 and 171.2 mV at current densities of 10 and 100 mA cm−2, surpassing commercial Pt/C. The poisoning tests, where η10 values of Pt/CoNC depict negative shifts of 161 and 13 mV by potassium thiocyanide (KSCN) and ethylenediaminetetraacetic acid disodium (EDTA), suggest the combined impact of Pt nanoparticles and Co‐N coordination on HER, with Pt nanoparticles playing a decisive role. The magnetic characterization and spin density diagrams reveal that Pt induces a higher spin state of Co2+, creating a wider spin‐related channel for electron donation to Pt. Moreover, Co‐N effectively modifies the electronic structure of Pt, thereby reducing the energy barriers for H2O dissociation (from 0.41 to −0.22 eV) and H2 generation (from −0.35 to 0.03 eV). This finding provides insights to fabricate advanced electrocatalysts through regulating spin state and modulating interfacial electron transfer.

We describe the solid-state structural evolution in four hybrid hexaiodoplatinate(IV) compounds, demonstrating the increasingly important role that extended hydrogen bonding plays in directing the structure across the series. The compounds are A2PtI6, where A is one of the following amines: ammonium, NH4+; methylammonium, CH3NH3+; formamidinium, CH(NH2)2+; guanidinium, C(NH2)3+. These are closely related in structure and properties to the hybrid halide perovskites of lead(II) that have recently established their prowess in optoelectronics. The first three of these compounds crystallize in the vacancy-ordered double perovskite A2Pt□I6 (□ indicates a vacant site) structure in the K2PtCl6 archetype, despite the relatively large perovskite tolerance factors involved. The last compound, (GUA)2PtI6, crystallizes in a vacancy-ordered variant of the hexagonal CsNiCl3 structure: the K2MnF6 structure. A combination of solid-state 195Pt and 1H NMR spectroscopy and detailed density functional theory calculations helps to reveal structural trends and establish the hydrogen-bonding tendencies. The calculations and measured optical properties support the surprising observation in these iodosalt compounds that, for smaller A cations, the conduction bands are considerably disperse, despite lacking extended I-Pt-I connectivity.

No abstract available

The ‘power-to-hydrogen’ strategy aims at splitting water into O2 and H2 via the oxygen and hydrogen evolution reactions. The complex four-step oxygen evolution reaction (OER) limits the overall efficiency of hydrogen production. An important reason of the low efficiency is that the production of ground-state (triplet) O2 is a spin-forbidden reaction: in fact, the reactants, OH- or H2O, are diamagnetic, but the final product, O2, is a paramagnetic molecule. Recently, this was well-recognized theoretically1 and the use of spin selective catalysts was described as a possible way to promote the OER.2 . However, it remains complex to understand and exploit intrinsic and extrinsic magnetic features to enhance catalytic performance. Here, we investigate the role of magnetic moments in individual active sites in the catalyst surface layer and the role of spin order in ferromagnetic vs. paramagnetic catalysts, focussing on perovskite oxides. First, we investigated the role of Ni magnetic moment in the the (001), (110) and (111) facet of LaNiO3 electrocatalysts, which we studied using electrochemical measurements, X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), and density functional theory (DFT+U) calculations.3 The results show a facet-dependent activity, where the (111) overpotential is ~60 mV lower as compared to the other facets. Closer investigation of the (001) and (111) facets reveals a surface transformation to a oxyhydroxide-like NiOO with edge-sharing octahedra,4 and we observed that the transformed surface is thicker for (111) than for (001).3 The detailed DFT+U analysis reveals important distinctions that give rise to the increased activity: the transformed LaNiO3 (111) surface exhibits a better match to the underlying perovskite layer. Moreover, protonation induces reduced Ni3+ with a finite magnetic moment. A moderate Jahn-Teller distortion enables a favorable binding of reaction intermediates. In contrast, the structural mismatch to the underlying LaNiO3(001)-substrate leads to a strong distortion of the transformed layer for this orientation and a weak binding of *O and ultimately to a different potential determining step (PDS), *OH→*O, compared to *O→*OOH for the transformed LaNiO3(111) surface. Second, we experimentally demonstrate the effect of intrinsic magnetic order on the OER on catalytic performance. Thin films of La0.67Sr0.33MnO3 grown by pulsed laser deposition with appropriate magnetic and electronic properties were chosen as well-defined model systems. Using the ferromagnetic to paramagnetic transition at the Curie temperature in these ferromagnetic perovskite oxides, the magnetic order of the catalysts were switched in situ during the OER by changing the temperature. For ferromagnetic films, the decrease in current density with decreasing temperature, induced by the reduction of thermal energy, was suppressed for temperatures below the Curie temperature, indicating that the presence of ferromagnetic ordering below Curie temperature enhances OER activity. This claim is further supported by an enhancement of OER activity for the same ferromagnetic film upon alignment of magnetic domains with an external magnetic field. All in all, our results reveal that the spin state, intrinsic spin order, and extrinsic magnetic fields are decisive for the OER activity. Biz, C., Fianchini, M. & Gracia, J. Strongly Correlated Electrons in Catalysis: Focus on Quantum Exchange. ACS Catal 11, 14249–14261 (2021). Sun, Y. et al. Spin‐Related Electron Transfer and Orbital Interactions in Oxygen Electrocatalysis. Advanced Materials 32, 2003297 (2020). Füngerlings, A. et al. Crystal-facet-dependent surface transformation dictates the oxygen evolution reaction activity in lanthanum nickelate. in preparation (2023). Baeumer, C. et al. Tuning electrochemically driven surface transformation in atomically flat LaNiO3 thin films for enhanced water electrolysis. Nat Mater 20, 674–682 (2021).

Organic-inorganic hybrid perovskites are widely utilized in solar driven chemistry such as photocatalysis, hydrogen evolution, and oxygen reduction. Hybrid perovskites contain various components with high polarity and/or charge values, which undergo transformations due to ion exchange, photoinduced phase segregation, or ion migration. These variable characteristics make perovskites "soft materials". Meanwhile, optoelectronic devices often operate under electrochemical reactions in the presence of an electrical field. To examine the effect of this field on the material/photophysical properties of hybrid perovskites, hybrid FAPbBr3 (FA+: CH(NH2)2+) perovskite quantum dots (PQDs) were synthesized. In this study, we report the spectroelectrochemical investigation of the hybrid FAPbBr3 PQDs to understand the electrochemical stability and degradation process. We also found that the electrochemical condition played an important role in inducing defect-mediated oxidation/reduction reactions, changing the photophysical properties of hybrid PQDs, and causing their irreversible transformations to various lead halide plumbate complexes. These findings can help develop a strategy for enhancing the operational performance of PQDs for the solar driven chemistry.

Metal halide perovskites, such as iodine methylamine lead (MAPbI3), have received extensive attention in the field of photocatalytic decomposition of HI for hydrogen evolution, due to their excellent photoelectric properties. In this paper, a new MAPbI3-based composite, MoC/MAPbI3, was synthesized. The results show that 15 wt% MoC/MAPbI3 has the best hydrogen production performance (38.4 μmol h-1), which is approximately 24-times that of pure MAPbI3 (1.61 μmol h-1). With the extension of the catalytic time, the hydrogen production rate of MoC/MAPbI3 reached 165.3 μmol h-1 after 16 h due to the effective separation and transfer of charge carriers between MoC and MAPbI3, showing excellent hydrogen evolution rate performance under visible light. In addition, the cycling stability of MoC/MAPbI3 did not decrease in multiple 4 h cycle tests. This study used the non-precious metal promoter MoC to modify MAPbI3, and provides a new idea for the synthesis of efficient MAPbI3-based composite catalysts.

It was thought that the organic-inorganic hybrid perovskite MAPbI3 could be used to collect visible light for the photocatalytic hydrogen evolution reaction (HER). However, its ability to generate H2 is limited. Herein, we synthesized amorphous NiCoB through a redox method and coupled it with MAPbI3 to form the NiCoB/MAPbI3 composite photocatalyst by electrostatic self-assembly. 30% NiCoB/MAPbI3 exhibited the maximum H2 generation yield of 2625.57 μmol g-1 h-1, which was approximately 114 fold that of pristine MAPbI3 and much better than that of Pt/MAPbI3. In addition to the excellent photocatalytic HER capability, NiCoB/MAPbI3 maintained good stability in the 24 h cycling hydrogen evolution experiment. The photoelectric analysis showed that NiCoB as a cocatalyst could realize rapid charge separation. This work can offer a reference for the construction of efficient photocatalysts based on lead halide perovskites.

Abstract The development of photoelectrochemical water oxidation (PEC) systems has gained significant relevance in recent years due to the quest for clean fuels, where green hydrogen is one of the main actors in the energy transition. Particularly, there has been a need for precious metal‐free electrodes and photoelectrodes that demonstrate high efficiency and stability aiming at having large‐scale and low‐cost green hydrogen production systems. This work shows advances toward this goal by using nonprecious catalysts and solution‐processed materials to achieve efficient, low‐cost, and stable photoelectrodes. Specifically, carbon‐based hybrid perovskite photoelectrodes coupled with an earth‐abundant Nickel‐Iron layered double hydroxide (NiFe‐LDH) catalyst (carbon/NiFe‐LDH) are fabricated and evaluated for oxygen evolution reaction (OER). Devices with an active area of 1.1 cm2 exhibit evaluated over 12 h of continuous operation, a 4.57% ABPE at 0.64 VRHE, and a photocurrent density of 11.71 mA cm−2 at 1.23 VRHE. The incorporation of graphite tape results in a system (C/GT/NiFe‐LDH) that shows an exceptional operational stability over 125 h and efficiency for this type of photoelectrode with a high photocurrent density of 18.07 mA cm−2 at 1.23 VRHE and 8.51% ABPE at 0.67 VRHE.

Efficient coupling solar energy conversion and N2 fixation by photocatalysis has been shown promising potentials. However, the unsatisfied yield rate of NH3 curbs its forward application. Herein, defective typical perovskite, BaTiO3 , shows remarkable activity under an applied magnetic field for photocatalytic N2 fixation with the NH3 yield rate exceeding 1.90mg/L/h. Through steered surface spin states and oxygen vacancies, the electromagnetic synergistic effect between the internal electric field and an external magnetic field is stimulated. X-ray absorption structure (XAS) spectrum and density functional theory (DFT) calculations reveal the regulation of electronic and magnetic properties through manipulations of oxygen vacancies and inducements of Lorentz force and spin selectivity effect. The electromagnetic synergistic effect suppresses the recombination of photoexcited carriers in semiconducting nanomaterials, which acts synergistically to promote N2 adsorption and activation while facilitating fast charge separation under UV-vis irradiation. Therefore, this work offers a promising alternative route for exploring high-photocatalytic-property N2 fixation materials and shed light on stimulating the development of synergistic effect in photocatalysts.

Photocatalysis, as a form of solar energy conversion, has considerable development prospects for solving energy exhaustion and environmental pollution. Promoting the utilisation of photocarriers is the key way to enhance photocatalytic activity and quantum efficiency. The g-C3N4 with the width of the band gap responsive to visible light, which is a great concern for researchers, was prepared by thermal decomposition and the insides were stripped from the outer wall and then curled to form the nanotubes (NTs), microtubes and shorten the migration distance of the electrons and holes. To promote the separation of the photocarriers in the g-C3N4, Ag particles are deposited by photoreduction as electron "traps" with surface plasmon resonance (SPR), and an external magnetic field is introduced during the photocatalysis. Under the Lorentz force, the photocatalytic efficiency of the Ag@g-C3N4 NTs is 200% higher than that of bulk g-C3N4, as a result of being able to prolong the life of the photogenerated carriers to bypass the recombination sites.

Understanding the interplay between the kinetics and energetics of photophysical processes in perovskite–chromophore hybrid systems is crucial for realizing their potential in optoelectronics, photocatalysis, and light-harvesting applications. By combining steady-state optical characterizations and transient absorption spectroscopy, we have investigated the mechanism of interfacial charge transfer (CT) between colloidal CsPbBr3 nanoplatelets (NPLs) and surface-anchored perylene derivatives and have explored the possibility of controlling the CT rate by tuning the driving force. The CT driving force was tuned systematically by attaching acceptors with different electron affinities and by varying the bandgap of NPLs via thickness-controlled quantum confinement. Our data show that the charge-separated state is formed by selectively exciting either the electron donors or acceptors in the same system. Upon exciting attached acceptors, hole transfer from perylene derivatives to CsPbBr3 NPLs takes place on a picosecond time scale, showing an energetic behavior in line with the Marcus normal regime. Interestingly, such energetic behavior is absent upon exciting the electron donor, suggesting that the dominant CT mechanism is energy transfer followed by ultrafast hole transfer. Our findings not only elucidate the photophysics of perovskite–molecule systems but also provide guidelines for tailoring such hybrid systems for specific applications.

Perovskite quantum dots (PQDs) hold immense potential as photocatalysts for CO2 reduction due to their remarkable quantum properties, which facilitates the generation of multiple excitons, providing the necessary high-energy electrons for CO2 photoreduction. However, harnessing multi-excitons in PQDs for superior photocatalysis remains challenging, as achieving the concurrent dissociation of excitons and interparticle energy transfer proves elusive. This study introduces a ligand density-controlled strategy to enhance both exciton dissociation and interparticle energy transfer in CsPbBr3 PQDs. Optimized CsPbBr3 PQDs with the regulated ligand density exhibit efficient photocatalytic conversion of CO2 to CO, achieving a 2.26-fold improvement over unoptimized counterparts while maintaining chemical integrity. Multiple analytical techniques, including Kelvin probe force microscopy, temperature-dependent photoluminescence, femtosecond transient absorption spectroscopy, and density functional theory calculations, collectively affirm that the proper ligand termination promotes the charge separation and the interparticle transfer through ligand-mediated interfacial electron coupling and electronic interactions. This work reveals ligand density-dependent variations in the gas-solid photocatalytic CO2 reduction performance of CsPbBr3 PQDs, underscoring the importance of ligand engineering for enhancing quantum dot photocatalysis.

The construction of efficient heterojunction photocatalysts critically relies on the precise regulation of interfacial charge dynamics. However, conventional heterojunctions are often constrained by rigid band alignments and sluggish interfacial charge transfer due to severe charge‐carrier recombination. Herein, we report a novel strategy for directional interfacial charge modulation through the construction of Cs2AgBiI6/Cu@ultrathin g‐C3N4 (CABI/Cu@UCN) heterojunction. Cu nanoclusters were anchored onto ultrathin g‐C3N4 via a hydrothermal–photoreduction process, forming Schottky junctions that functioned as efficient electron extractors. Subsequently, the lead‐free double perovskite Cs2AgBiI6 was coupled with Cu@UCN to construct a type‐II heterojunction. Owing to the synergistic driving force of interfacial built‐in electric fields, the distinctive “CABI→g‐C3N4→Cu” cascade charge‐transfer pathway enabled nearly dissipation‐free spatial separation efficiency of photogenerated electron–hole pairs. Under visible‐light irradiation, the optimized CABI/Cu@UCN composite exhibited outstanding photocatalytic activity and stability, achieving efficient degradation of various organic pollutants and antibiotics. The construction of the cascading heterogeneous structures facilitated the directional migration of electrons from CABI to UCN, and then to Cu, accompanied by significant interfacial charge redistribution. This work demonstrates that perovskite‐based heterostructures enable efficient photocatalytic degradation of dye and antibiotic pollutants through rational heterojunction design and interfacial charge regulation.

Wavelength conversion based on hybrid inorganic–organic sensitized triplet–triplet annihilation upconversion (TTA‐UC) is promising for applications such as photovoltaics, light‐emitting‐diodes, photocatalysis, additive manufacturing, and bioimaging. The efficiency of TTA‐UC depends on the population of triplet excitons involved in triplet energy transfer (TET), the driving force in TET, and the coupling strength between the donor and acceptor. Consequently, achieving highly efficient TTA‐UC necessitates the precise control of the electronic states of inorganic donors. However, conventional covalently bonded nanocrystals (NCs) face significant challenges in this regard. Herein, a novel strategy to exert control over electronic states is proposed, thereby enhancing TET and TTA‐UC by incorporating ionic‐bonded CsPbBr3 and lanthanide Ce3+ ions into composite NCs. These composite‐NCs exhibit high photoluminescence quantum yield, extended single‐exciton lifetime, quantum confinement, and uplifted energy levels. This engineering strategy of electronic states engendered a comprehensive impact, augmenting the population of triplet excitons participating in the TET process, enhancing coupling strength and the driving force, ultimately leading to an unconventional, dopant concentration‐dependent nonlinear enhancement of UC efficiency. This work not only advances fundamental understanding of hybrid TTA‐UC but also opens a door for the creation of other ionic‐bonded composite NCs with tunable functionalities, promising innovations for next‐generation optoelectronic applications.

Copper‐based halide perovskite, as an ideal alternative to lead‐based halide perovskite, has attracted much attention in many applications owing to its earth‐abundant element, non‐toxicity, and excellent optical properties. In this report, magnetic Mn‐incorporated lead‐free copper halide perovskite (Cs3Cu2Br5) nanocrystal (NC) is for the first time designed and prepared using a one‐pot hot‐injection route, resulting in a new emission band at ≈540 nm accompanied with self‐trapped exciton (STE) emission centered at ≈445 nm from Cs3Cu2Br5 NC. In situ X‐ray photoelectron spectroscopy and in situ kelvin probe force microscopy (KPFM) confirm that the Mn2+ incorporation causes efficient electron–hole separation and extended charge lifetime in Mn‐doped Cs3Cu2Br5 NC, which exhibits significantly raised selectively photocatalytic biomass conversion coupled with obviously enhanced H2O2 evolution. With an external magnetic field, the spin‐polarized electrons in Mn‐doped Cs3Cu2Br5 NC arouses reduced charge recombination and more available electrons/holes for surface redox reaction, further raising the photocatalytic performance. This is confirmed by in situ steady‐state/transient‐state photoluminescence (PL) spectroscopy, in situ transient photocurrent measurement, and in situ electrochemical impedance spectroscopy with external magnetic field. In situ electron paramagnetic resonance (EPR) spectra reveal the radical‐involved reaction pathway for biomass conversion. This research exhibits the great potential of spin‐polarization‐enhanced photocatalysis by an external magnetic field without additional energy consumption.

The flexoelectric effect, which refers to the mechanical-electric coupling between strain gradient and charge polarization, should be considered for use in charge production for catalytically driving chemical reactions. We have previously revealed that halide perovskites can generate orders of higher magnitude flexoelectricity under the illumination of light than in the dark. In this study, we report the catalytic hydrogen production by photo-mechanical coupling involving the photoflexoelectric effect of flexible methylammonium lead iodide (MAPbI3) nanowires (NWs) in hydrogen iodide solution. Upon concurrent light illumination and mechanical vibration, large strain gradients were introduced in flexible MAPbI3 NWs, which subsequently induced significant hydrogen generation (at a rate of 756.5 μmol g−1 h−1, surpassing those values from either photo- or piezocatalysis of MAPbI3 nanoparticles). This photo-mechanical coupling strategy of mechanocatalysis, which enables the simultaneous utilization of multiple energy sources, provides a potentially new mechanism in mechanochemistry for highly efficient hydrogen production.

Hybrid perovskites with mixed organic cations such as methylammonium (CH3NH3, MA) and formamidinium (CH(NH2)2, FA) have attracted interest due to their improved stability and capability to tune their properties varying the composition. Theoretical investigations in the whole compositional range for these mixed perovskites are scarce in part due to the limitations of modeling cationic orientation disorder. In this work, we report on the local variation of the structural and electronic properties in mixed A-site cation MA/FA lead iodide perovskites FAxMA1-xPbI3 evaluated from static first-principles calculations in certain structures where the orientations of organic cations result from examining the energy landscape of some compositions. The cation replacement at the A-site to form the solid solution causes an increased tilting of the inorganic PbI6 octahedra: in the FA-rich compounds the replacement of FA by a smaller cation like MA is to compensate for the reduced space filling offered by the smaller cation, whereas in the MA-rich compounds it is to expand the space needed for the larger cation. In fact, the effect of octahedron tilting exceeds that of unit-cell size in determining the band gap for these organic cation mixtures. Our calculations indicate that the key role played by hydrogen bonds with iodine anions in the pure compounds, MAPbI3 and FAPbI3, is preserved in the cation mixed perovskites. It is found that MA-I bonds remain stronger than FA-I bonds throughout the composition range regardless of the unit-cell expansion as the FA content increases. Finally, from the analysis of electronic structures we unravel how the hydrogen bonds stabilize the non-bonding I-5p orbitals, spatially perpendicular to the Pb-I-Pb bond axis, lowering their energy when the H-I interaction occurs, which would explain the well-known role of hydrogen bonding in the structural stabilization of hybrid perovskites. These results contribute to the understanding of the role played by cation mixing at A sites in the physics of lead halide perovskites.

Hybrid organic–inorganic perovskites combine outstanding optoelectronic properties with low-cost fabrication, yet their structural fragility under environmental factors limits device stability. In this context, the use of pressure offers the enticing possibility of unveiling the microscopic mechanisms behind structural changes and the eventual collapse or decomposition of the material. In this work, we have employed high-resolution inelastic neutron scattering in the gigapascal regime alongside first-principles calculations to probe the pressure–temperature phase behavior of methylammonium lead iodide (MAPbI3). Below 1 GPa and 150 K, pressurization leads to a stiffening of spectral features sensitive to NH···I hydrogen-bonding motifs, concomitant with a contraction of the inorganic framework. Between 1 and 1.25 GPa at these low temperatures, the INS data undergo a pronounced broadening, corresponding to the formation of an orientational glass of organic cations whose immediate environment is reminiscent of the high-pressure cubic phase. This hitherto unexplored derailed state of MAPbI3 is characterized by a broad distribution of NH···I bond lengths, in stark contrast with the well-defined hydrogen-bond network of the low-temperature phase observed at lower pressures. Our experimental and computational results bring to the fore the rather subtle role played by the NH···I bonding topology across organic and inorganic sublattices in dictating the regions of physical stability and metastability of this important material.

Methylammonium lead halide perovskite-based solar cells have demonstrated efficiencies as high as 24.2%, highlighting their potential as inexpensive and solution-processable alternatives to silicon solar cell technologies. Poor stability towards moisture, ultraviolet irradiation, heat, and a bias voltage of the perovskite layer and its various device interfaces limits the commercial feasibility of this material for outdoor applications. Herein, we investigate the role of hydrogen bonding interactions induced when metal halide perovskite crystals are crosslinked with alkyl or π-conjugated boronic acid small molecules (-B(OH)2). The crosslinked perovskite crystals are investigated under continuous light irradiation and moisture exposure. These studies demonstrate that the origin of the interaction between the alkyl or π-conjugated crosslinking molecules is due to hydrogen bonding between the -B(OH)2 terminal group of the crosslinker and the I of the [PbI6]4- octahedra of the perovskite layer. Also, this interaction influences the stability of the perovskite layer towards moisture and ultraviolet light irradiation. Morphology and structural analyses, as well as IR studies as a function of aging under both dark and light conditions show that π-conjugated boronic acid molecules are more effective crosslinkers of the perovskite crystals than their alkyl counterparts thus imparting better stability towards light and moisture degradation.

No abstract available

Lead (Pb)–zinc (Zn) slags contain large amounts of Pb, causing irreversible damage to the environment. Therefore, developing an effective strategy to extract Pb from Pb–Zn slags and convert them into a renewable high‐value catalyst not only solves the energy crisis but also reduces environmental pollution. Herein, we present a viable strategy to recycle Pb and iron (Fe) from Pb–Zn slags for the fabrication of efficient methylammonium lead tri‐iodide (r‐MAPbI3) piezocatalysts with single‐atom Fe–N4 sites. Intriguingly, atomically dispersed Fe sites from Pb–Zn slags, which coordinated with N in the neighboring four CH3NH3 to form the FeN4 configuration, were detected in the as‐obtained r‐MAPbI3 by synchrotron X‐ray absorption spectroscopy. The introduction of Fe single atoms amplified the polarization of MAPbI3 and upshifted the d‐band center of MAPbI3. This not only enhanced the piezoelectric response of MAPbI3 but also promoted the proton transfer during the hydrogen evolution process. Due to the decoration of Fe single atoms, r‐MAPbI3 showed a pronounced H2 yield of 322.4 μmol g−1 h−1, which was 2.52 times that of MAPbI3 synthesized using commercially available reagents. This simple yet robust strategy to manufacture MAPbI3 piezocatalysts paves a novel way to the large‐scale and value‐added consumption of Pb‐containing waste residues.

Phonon coupling to organic molecule dynamics yields giant isotope effects on transport properties. Lead halide perovskites are strong candidates for high-performance low-cost photovoltaics, light emission, and detection applications. A hot-phonon bottleneck effect significantly extends the cooling time of hot charge carriers, which thermalize through carrier–optic phonon scattering, followed by optic phonon decay to acoustic phonons and finally thermal conduction. To understand these processes, we adjust the lattice dynamics independently of electronics by changing isotopes. We show that doubling the mass of hydrogen in methylammonium lead iodide by replacing protons with deuterons causes a large 20 to 50% softening of the longitudinal acoustic phonons near zone boundaries, reduces thermal conductivity by ~50%, and slows carrier relaxation kinetics. Phonon softening is attributed to anticrossing with the slowed libration modes of the deuterated molecules and the reduced thermal conductivity to lowered phonon velocities. Our results reveal how tuning the organic molecule dynamics enables control of phonons important to thermal conductivity and the hot-phonon bottleneck.

Working organic-inorganic lead halide perovskite-based devices are notoriously sensitive to surface and interface effects. Using a combination of Density Functional Theory (DFT) and Time-Dependent (TD)-DFT methods, we report a comprehensive study of the changes (with respect to the bulk) in geometric and electronic structures going on at the (001) surface of a (tetragonal phase) methylammonium lead iodide (MAPbI3) perovskite slab, in the dark and upon photoexcitation. The formation of a hydrogen bonding pattern between the -NH3 groups of the organic cations and the iodine atoms of the outer inorganic layout is found to critically contribute to the relative thermodynamic stability of slabs with varying surface compositions and terminations. Most importantly, our results show that the hydrogen bond locking effects induced by the MA groups tend to protect the external two-dimensional lattice against large local structural deformations, i.e. the formation of small exciton-polaron, at variance with purely inorganic lead halide perovskites.

Deprotonation of organic cations in hybrid perovskites generates nitrogen‐site hydrogen vacancies that activate lone‐pair electrons and induce configuration‐dependent nonradiative losses. Here, we introduce a novel cyclic A‐site organic cation, aziridinium, into the APbI 3 perovskite lattice and establish a direct structure–function correlation between the molecular configuration of the organic cation and the lone‐pair electron activity associated with nitrogen‐site hydrogen vacancies defects. Compared with conventional formamidinium and methylammonium cations, the geometrically constrained, distorted coordination environment of aziridinium promotes facile deprotonation, resulting in a higher tendency for nitrogen‐site hydrogen vacancies formation. The deprotonated aziridinium species exhibit markedly enhanced lone‐pair electron activity, acting as strong Lewis bases that perturb the local PbI 6 octahedra by detaching Pb 2+ ions and forming stable Pb–AZ dimers. These defect complexes serve as highly efficient nonradiative recombination centers, yielding an ultrahigh carrier capture coefficient of 10 −5 cm 3  s −1 . This work reveals the decisive influence of A‐site cation chemistry on defect energetics and recombination kinetics, emphasizing the necessity of simultaneously optimizing iodide stoichiometry and aziridinium incorporation to suppress nonradiative losses in aziridinium‐based halide perovskites.

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A detailed examination of the electronic structures of methylammonium lead triiodide (MAPI) and methylammonium iodide (MAI) is performed with ab initio molecular dynamics (AIMD) simulations based on density functional theory, and the theoretical results are compared to experimental probes. The occupied valence bands of a MAPI single crystal and MAI powder are probed with X-ray photoelectron spectroscopy, and the conduction bands are probed from the perspective of nitrogen K-edge X-ray absorption spectroscopy. Combined, the theoretical simulations and the two experimental techniques allow for a dissection of the electronic structure unveiling the nature of chemical bonding in MAPI and MAI. Here, we show that the difference in band gap between MAPI and MAI is caused chiefly by interactions between iodine and lead but also weaker interactions with the MA+ counterions. Spatial decomposition of the iodine p levels allows for analysis of Pb–I σ bonds and π interactions, which contribute to this effect with the involvement of the Pb 6p levels. Differences in hydrogen bonding between the two materials, seen in the AIMD simulations, are reflected in nitrogen valence orbital composition and in nitrogen K-edge X-ray absorption spectra.

Two-dimensional (2D) Ruddlesden-Popper perovskites (RPPs) are a class of quantum well (QW) materials showing large exciton binding energy owing to quantum confinement. The existence of localized edge states was proposed to accelerate exciton dissociation into long-lived charge carriers in 2D RPPs, but recent experimental reports suggested that highly efficient internal exciton dissociation is achievable in 2D RPPs despite the absence of edge states. Herein, we adopt first-principles calculations to unveil the physical origin of the high internal quantum efficiency in the bulk region of widely familiar (BA)2(MA)n-1PbnI3n+1 (BA = butylammonium; MA = methylammonium) materials. We discover that the dipolar nature of MA cations provides the driving force for the separation of photoexcited electron-hole pairs inside QWs as the inorganic layer thickens from n = 1 to n = 3. Concurrently, electronic coupling between organic spacer layers and QWs is enhanced in the energetically favorable configurations where MA cations orient with their CH3 groups towards the exterior PbI2 layers of QWs in the n = 3 structure. Consequently, hole delocalization is promoted along the out-of-plane direction of QWs, which in turn facilitates exciton dissociation into free charge carriers despite large exciton binding energy. Our simulations reveal that the hydrogen bonding between organic species (including both MA and BA cations) and iodine atoms, which is subtly interconnected, engineers the response of morphology in QWs and electronic interactions at organic-inorganic interfaces, providing novel insights for the exciton-free carrier behavior in the bulk area of 2D RPPs.

The hybrid halide perovskite CH3NH3PbI3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {CH}_3\hbox {NH}_3\hbox {PbI}_3$$\end{document} is easy to manufacture and inexpensive. Despite these, its efficiency as a solar cell is comparable to today’s efficient solar cells. For these reasons, it is attracting a lot of attention today. However, the effects of the CH3NH3+\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {CH}_3\hbox {NH}_3^+$$\end{document} (MA) cation in the perovskite structure on the electronic and structural properties are still a matter of debate. Previous studies have generally focused on the rotation of the MA cation. In this study, from a different perspective, the effects of the movement of the MA cation along the C–N axis are investigated. With this method, the effects of the MA cation were examined in a more controlled way. In this study, density functional theory that accounts for van der Waals interactions was used in the calculations for the cases. According to the data obtained, H–I bonds are formed between the MA cation and the inorganic framework. Although these bonds are predominantly hydrogen bonds, they also have ionic bond characteristics. Within the structure, the H–I-bond length tends to be preserved, although the position of the MA changes. In this mechanism, the I ion plays an important role by moving away from its place in the Pb–I–Pb alignment. The position of the I ion determines the nature of the band-gap transition. Another effect is on the value of the band gap. Depending on the position of the I ion, the band gap may narrow by about 0.26 eV. The separation of the I ion from the Pb–I–Pb alignment by the effect of the MA cation breaks the inverse symmetry. According to the data obtained from this study, this mechanism in the band gap is due to the breaking of the inverse symmetry in the crystal structure.

Herein, a new energy cycle called the “hydrogen iodide (HI) cycle” is proposed that involves the repeated generation of solar hydrogen and battery power. Solar hydrogen generation using an HI solution allows for the use of a narrow‐bandgap photocatalyst. It is demonstrated that the addition of single‐walled carbon nanotubes (SWCNTs) effectively enhances solar hydrogen generation from HI solution with methylammonium lead iodide. Electron microscopy observations and spectroscopic experiments reveal that SWCNTs improve hydrogen generation by adsorbing byproduct iodine molecules. Additionally, a zinc‐iodine battery, utilizing paper I@SWCNTs recovered from the photocatalyst test cell and zinc metal, operates efficiently with an initial cell voltage of approximately 1.2 V. The battery's capacity, corresponding to the amount of encapsulated iodine molecules, indicates that SWCNTs can effectively adsorb the byproduct iodine molecules within the photocatalyst test cell. It is also discussed that the electrolyte solution after the discharge experiment should include iodide ions, indicating that the solution after battery discharge returns to the starting point of the “HI cycle.” Raman measurements reveal that I@SWCNTs are transformed back into empty tubes during the discharge experiment. Therefore, SWCNTs can be repeatedly used in the new cyclic energy scheme referred to as the “HI cycle.”

No abstract available

Organic-inorganic hybrid perovskites (OIHPs) like methylammonium lead iodide perovskite (MAPbI3) are attractive candidates for solar hydrogen production. However, the serious charge recombination occurring on OIHPs seriously impairs the photocatalytic performance,...

Significance Hybrid organic–inorganic perovskites (HOIPs) are among the most promising materials for next-generation solar cells that combine high efficiency and low cost. The record efficiency of HOIP-based solar cells has reached above 25%, and they can be manufactured using simple solution-processing methods that can be drastically cheaper than the current commercial solar cell technologies. Despite the progress so far, the microscopic mechanism for the high solar cell efficiency in HOIPs is yet to be understood. In this study, we show that the ability of organic molecules to rotate on an appropriate time scale in HOIPs can extend the lifetime of photoexcited charge carriers and lead to higher efficiency. This insight can guide the progress toward improved solar cell performance. The long charge carrier lifetime of the hybrid organic–inorganic perovskites (HOIPs) is the key for their remarkable performance as a solar cell material. The microscopic mechanism for the long lifetime is still in debate. Here, by using a muon spin relaxation technique that probes the fluctuation of local magnetic fields, we show that the muon depolarization rate (Δ) of a prototype HOIP methylammonium lead iodide (MAPbI3) shows a sharp decrease with increasing temperature in two steps above 120 K and 190 K across the structural transition from orthorhombic to tetragonal structure at 162 K. Our analysis shows that the reduction of Δ is quantitatively in agreement with the expected behavior due to the rapid development of methyl ammonium (MA) jumping rotation around the C3 and C4 symmetry axes. Our results provide direct evidence for the intimate relation between the rotation of the electric dipoles of MA molecules and the charge carrier lifetime in HOIPs.

Lead halide perovskites are new key materials in various application areas such as high efficiency photovoltaics, lighting, and photodetectors. Doping with Mn, which is known to enhance the stability, has recently been reported to lead to ferromagnetism below 25 K in methylammonium lead iodide (MAPbI_3) mediated by superexchange. Two most recent reports confirm ferromagnetism up to room temperature but mediated by double exchange between Mn^2+ and Mn^3+ ions. Here we investigate a wide concentration range of MAMn_ x Pb_1− x I_3 and Mn-doped triple-cation thin films by soft X-ray absorption, X-ray magnetic circular dichroism, and quantum interference device magnetometry. The X-ray absorption lineshape shows clearly an almost pure Mn^2+ configuration, confirmed by a sum-rule analysis of the dichroism spectra. A remanent magnetization is not observed down to 2 K. Curie-Weiss fits to the magnetization yield negative Curie temperatures. All data show consistently that significant double exchange and ferromagnetism do not occur. Our results show that Mn is not suitable for creating ferromagnetism in lead halide perovskites. There have been recent studies reporting that Mn-doped MAPBI_3 houses a ferromagnetic phase mediated by a double exchange mechanism. Here, however, using X-ray magnetic circular dichroism and magnetic susceptibility measurements, the authors uncover contradicting experimental evidence to indicate an absence of magnetic ordering in this material, suggesting that our understanding of Mn-doped lead halide perovskites may need reassessing.

No abstract available

No abstract available

Summary Promoting solar fuels as a viable alternative to hydrocarbons calls for technologies that couple efficiency, durability, and low cost. In this work we elucidate how hybrid organic-inorganic systems employing hybrid photocathodes (HPC) and perovskite solar cells (PSC) could eventually match these needs, enabling sustainable and clean hydrogen production. First, we demonstrate a system comprising an HPC, a PSC, and a Ru-based oxygen evolution catalyst reaching a solar-to-hydrogen (STH) efficiency above 2%. Moving from this experimental result, we elaborate a perspective for this technology by adapting the existing models to the specific case of an HPC-PSC tandem. We found two very promising scenarios: one with a 10% STH efficiency, achievable using the currently available semiconducting polymers and the widely used methylammonium lead iodide (MAPI) PSC, and the other one with a 20% STH efficiency, requiring dedicated development for water-splitting applications of recently reported high-performing organic semiconductors and narrow band-gap perovskites.

The photocatalytic conversion of CO2 into the renewable fuels is a promising strategy to address energy and environmental challenges, however, its limited application is mainly attributed to the inefficient charge separation and lack of active sites in conventional catalysts. Here, a spin‐polarization strategy using Co2⁺ doping in lead‐free perovskite Cs3Bi2Br9 (CBB) synergized with an external magnetic field (MF), is reported to achieve highly efficient CO2 reduction. The optimized Co‐doped CBB (0.2CBB) exhibited a 2.6‐fold enhancement in CO production rate (35.04 µmolg−1h−1) compared to the pristine CBB, with further improvement to 86.56 µmolg−1h−1 under 200 mT MF. Advanced characterizations together with the density functional theory calculations further revealed that the Co doping introduces spin‐polarized electrons, suppresses charge recombination, and elongates the carrier lifetime (6.68 ns vs 5.20 ns in CBB). The Zeeman effect under MF activates the additional spin‐polarized carriers, while the Co sites lower the energy barrier for *COOH intermediate formation (ΔG = −0.59 vs −0.38 eV in CBB), as confirmed by the in situ FT‐IR and Gibbs free energy analysis. This work pioneers the integration of spin manipulation and MF‐assisted catalysis in perovskites, offering a novel pathway for the design of high‐performance photocatalytic systems.

The doped perovskite phase compounds exhibit unique electromagnetic properties and high activity in oxidation-reduction, hydrogenation, isomerization, electrocatalysis, etc., which is also a current research hotspot in materials science. Therefore, exploring the photocatalytic performance of the composite prepared by CaTiO3 and TiO2 in a strong magnetic environment is naturally of great interest. Composite materials of Ca2+/Ti4 with varying molar ratios were prepared by using the sol-gel method, and these materials were subjected to experiments for the photocatalytic degradation of methylene blue. Comparative analysis revealed that the catalytic effect was most favorable when Ca2+/Ti4+=0.3. At this ratio, the adsorption rate of the composite material showed minimal change with an increase in the dosage, while the initial concentration of the solution significantly affected the adsorption rate. The catalytic effect of the Ca2+/Ti4+=0.3 composite material prepared under a 9T magnetic field was improved compared to those prepared under 6T and no magnetic field conditions. The 9T composite material exhibited a reduction in cell size, a redshift in the absorption spectrum, and a decrease in powder particle size.

In recent years, magnetic fields have been widely applied in catalysis to increase the performance of electrocatalysis, photocatalysis, and thermocatalysis through an important noncontact way. This work demonstrated that doping CsPbCl3 halide perovskite nanocrystals with nickel ions (Ni2+) and applying an external magnetic field can significantly enhance the performance of the photocatalytic carbon dioxide reduction reaction (CO2RR). Compared with its counterpart, Ni-doped CsPbCl3 exhibits a sixfold increase in CO2RR efficiency under a 500 mT magnetic field. Insights into the mechanism of this enhancement effect were obtained through photogenerated current density measurements and X-ray magnetic circular dichroism. The results illustrate that the significant enhancement in catalytic performance by the magnetic field is attributed to the synergistic effects of magnetic element doping and the external magnetic field, leading to reduced electron‒hole recombination and extended carrier lifetimes. This study provides an effective strategy for enhancing the efficiency of the photocatalytic CO2RR by manipulating spin-polarized electrons in photocatalytic semiconductors via a noncontact external magnetic field.

Motivated by the need to reduce toxic organic dyes in wastewaters, we studied the preparation of different amounts of Mn-doped cesium lead halide perovskite in PMMA matrix (CsPb x Mn1–x Cl y Br3–y @PMMA) composite fibrous membranes (CFM) as a photocatalyst to degrade dyes via a one-step in situ electrospinning method. The composite fibrous membranes exhibit excellent environmental stability, attributed to the protective three-dimensional network structure of the electrospun fibers, which shields the internal perovskite nanocrystals from direct contact with water and light. Structural characterization by X-ray diffraction (XRD) reveals that Mn2+ substitution induces a phase transformation from cubic CsPbBr3 to tetragonal CsPbCl3. The optimal Mn/Pb ratio of 2.5:1 achieves excellent photocatalytic activity, degrading 94.7% of methyl orange (MO) within 90 min under Xe lamp irradiation with a rate constant of 0.031 min–1, 4.6 times higher than that of the undoped sample. In addition, a single monochromatic CFM with a blue LED light source can be combined to construct a white LED (WLED) with good chromaticity coordinates (0.3267, 0.3298) and color temperature of 5775 K. This work highlights the great potential of Mn-doped perovskite composite fibrous membranes for practical photocatalytic and LED applications.

Recent experiments have demonstrated impressive photocatalytic performances in spin-polarized materials. The existence of spin-dependent recombination between spin split bands has been suggested as the cause for at least part of the improved photocatalysis. To test the efficacy of this mechanism, we develop a set of rate equations for carrier charge and spin to shed light on recent experiments with metal-defected or doped oxides, magnetically decorated metal-organic frameworks, and magnetically doped perovskites. Our results show that recombination will be dependent on the band spin polarization and the lengthening of decay times can be optimized by engineering the electronic structure.

Metal halide perovskite (MHP)‐based photocatalysts encounter significant stability challenges in water‐containing systems, posing a major obstacle to their application in artificial photosynthesis. Herein, an innovative and universal strategy is present to create MHP‐based ternary heterojunctions based on a self‐templating method. A series of composite catalysts featuring sandwich hollow structures are constructed, with MHPs such as CsPbBr3, Cs3Bi2I9, Cs3Sb2Br9, and Cs2AgBiBr6 serving as the intermediate layers. The unique sandwich structure effectively shields MHPs from direct water contact, allowing MHP‐based photocatalysts to exhibit exceptional stability in water‐containing photocatalytic environments for durations exceeding 200 h. Furthermore, the hollow design ensures complete contact between the reaction substrates with both the oxidation and reduction functional areas. Compared to single perovskite materials, MHP‐based ternary heterojunction photocatalysts exhibit stronger oxidation capability and improved charge separation efficiency, leading to a substantial enhancement in photocatalytic CO2 reduction performance. Notably, the ternary heterojunction with CsPbBr3 as the intermediate layer achieves an electron consumption rate of up to 1824 µmol g−1 h−1 for CO2 reduction, which is far superior to other reported MHP‐based catalysts under similar conditions. This study provides a potent strategy for simultaneously enhancing the stability and activity of MHP‐based photocatalysts, paving the way for their potential applications in artificial photosynthesis.

Constructing metal halide perovskites with intrinsic ferroelectric properties represents an effective strategy to enhance the performance of perovskite-based optoelectronic devices. For the most common ferroelectric hybrid organic-inorganic halide perovskites, the...

Photoelectrochemical water oxidation is a challenging reaction in solar water splitting due to the parasitic recombination process, sluggish catalytic activity, and electrode stability. Oxide semiconductors are stable in an aqueous medium but show huge charge carrier recombination. Creation of a heterojunction is found to be effective for extracting the photogenerated electrons/holes before they recombine to the ground state. In this work, we created a heterojunction of BiVO4 with vacancy-ordered halide perovskite Cs2PtI6 and used it as a photoanode in PEC water oxidation. Cs2PtI6 is the only halide perovskite that is found to be extremely stable even in strong acids and bases. We utilized the stability of this material and its panchromatic visible light absorption property and made the first unprotected heterojunction dual-absorber photoanode for PEC water oxidation. At 1.23 V (vs RHE), bare BiVO4 gave 0.6 mA cm-2 photocurrent density, whereas the BiVO4/Cs2PtI6 heterojunction shows 0.92 mA cm-2. With the addition of IrOx cocatalyst, at 1.23 V (vs RHE), the heterojunction gave ∼2 mA cm-2. To obtain 2 mA cm-2 photocurrent, pure BiVO4 requires 560 mV overpotential, whereas the heterojunction requires 250 mV. The increase in the photocurrent arises from the increase in the efficiency of charge separation from BiVO4 to Cs2PtI6 and the complementary absorption offered by the latter.

To further develop lead halide perovskites for their application in solar cells, understanding the material’s fundamental behavior under illumination is necessary. Investigating light-induced charge dynamics in single crystals can give insight into material inherent properties. Time-resolved photoelectron spectroscopy (TR-PES) allows to monitor the photovoltage build-up and decay between the sample surface and bulk over time and gives information on light-induced charge redistribution within the crystal. Additionally, this method enables us to follow compositional changes and surface degradation and distinguish these from purely electronic effects. Here we investigated the charge dynamics of two distinct lead halide perovskite single crystal surfaces (CsPbBr3, Cs-doped FAPbI3) using TR-PES in different timescales (ps to μs and s to min). It was found that CsPbBr3 shows photovoltage rise and decay on the nanosecond to microsecond time-range, which can be assigned to electron–hole pair separation between surface and bulk. On the other hand, such electron dynamics could not be resolved for Cs-doped FAPbI3 at these fast timescales. Instead, for Cs-doped FAPbI3, the observed photovoltage decay was dominated by much slower dynamics and relaxation to the dark equilibrium state took around 10 min. This suggests that ion migration is responsible for a photovoltage build-up between surface and bulk of the crystal.

Crafting rational heterojunctions with nanostructured materials is instrumental in fostering effective interfacial charge separation and transport for optoelectronics. Layered halide perovskites (LHPs) that form heterojunctions between organic spacer molecules and inorganic metal halide layers exhibit tunable photophysics owing to their customizable band alignment. However, controlling photogenerated carrier dynamics by strategically designing layered perovskite heterojunctions remains largely unexplored. We combine a data-driven approach with time-domain density functional theory (TD-DFT) and non-adiabatic molecular dynamics (NAMD) to screen and select electronically active spacer dications (A') that introduce a type-II heterojunction in the lead iodide-based Dion-Jacobson phase LHPs. The composition-structure-electronic property correlations reveal that the number of nitrogens in aromatic heterocycles is the key factor in designing electron-accepting spacers in these perovskites. The detailed atomistic simulations validate the design strategy further by modeling (A')PbI4 perovskites, which incorporate three different screened electroactive A' spacers. The computed excited charge carrier dynamics illustrate the phonon-mediated ultrafast interfacial electron transfer from the inorganic conduction band edge to the lower-lying unoccupied orbitals of spacers, exhibiting photoluminescence quenching in these (A')PbI4 perovskites. The spatially separated electrons and holes at the type-II heterojunction interface prolong the excited charge carrier lifetime, boosting the carrier transport and exciton dynamics. Our work illustrates a robust in silico approach for designing LHPs with exciting optoelectronic properties originating from their fine-tuned heterojunctions.

Dilute magnetic semiconductors (DMSs) have attracted much attention because of their potential use in spintronic devices. Here, we demonstrate the observation of robust ferromagnetism in a solution-processable halide perovskite semiconductor with dilute magnetic ions. By codoping of magnetic (Fe2+) and aliovalent (Bi3+) metal ions into CH3NH3PbCl3 (MAPbCl3) perovskite, ferromagnetism with well-saturated magnetic hysteresis loops and a maximum coercivity field of 1280 Oe was observed below 12 K. The ferromagnetic resonance measurements revealed that the incorporation of aliovalent ions modulates the carrier concentration and plays an essential role in realizing the ferromagnetism in dilute magnetic halide perovskites. Magnetic ions are proposed to interact through itinerant charge carriers to achieve ferromagnetic coupling. Our work provides a new avenue for the development of solution-processable magnetic semiconductors.

Sn-doped lead halide perovskites (LHPs) have attracted considerable attention for their lower bandgap and lower toxicity. While it is well-established that Sn doping easily introduces a lot of structural defects into LHP films, the extent to which these defects impact carrier dynamics has yet to be fully elucidated. Herein, we take Sn-doped MAPbBr3 films as an example to explore the influence of Sn doping on their carrier dynamics. The results show that Sn doping can simultaneously introduce many fillable electron traps and unfillable hole traps, consequently instigating an ultrafast carrier capture process. This further elicits long-lived internal charge separation between band edge and trap states or between two kinds of trap states, thereby enabling these carriers to persist for up to ∼2.6 μs. Our findings suggest that Sn doping potentially serves as an effective strategy to prolong the carrier lifetime in LHPs, which could pave the way for potential applications within Sn-based perovskites.

Control of forward and back electron transfer processes in semiconductor nanocrystals is important to maximize charge separation for photocatalytic reduction/oxidation processes. By employing methyl viologen as the electron acceptor, we have succeeded in mapping the electron transfer from excited CsPbI3 nanocrystals to viologen as well as the hole trapping process. The electron transfer to viologen is an ultrafast process (ket = 2 × 1010 s-1) and results in the formation of extended charge separation as electrons are trapped at surface-bound viologen sites and holes at iodide sites. The I2─• formation, which is confirmed through the transient absorption at 750 nm, provides a convenient way to probe trapped holes and its participation in the back electron transfer process. By employing a series of mixed halide compositions, we were able to tune the bandgap and valence band energy of the perovskite donor. The back electron transfer rate constant (kbet = 1.3-2.6 × 107 s-1) is nearly three orders of magnitude smaller than that of forward electron transfer, thus extending the lifetime of the charge-separated state. The weak dependence of the back electron transfer rate constant on the valence band energy suggests that trapping of holes at halide (I or Br) sites is involved in the back electron transfer process. The ability to extend the lifetime of the charge-separated pair can offer new strategies to improve the redox properties of semiconductor-based photocatalytic systems.