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Recently, lead halide perovskites have attracted significant attention as promising absorber materials for photoelectrochemical (PEC) solar water splitting. However, charge‐accumulation‐induced ion migration at the interface causes perovskite degradation and efficiency loss. To suppress the charge accumulation and improve the PEC performance of the perovskite photoanode, a simple interface engineering is proposed by decorating the SnO2/perovskite interface with a mixture of polyethylenimine ethoxylated (PEIE) and chlorobenzenesulfonic acid (CBSA). The mixed CBSA+PEIE treatment effectively passivates the oxygen vacancies in SnO2 and adjusts the band alignment between SnO2 and the perovskite. The synergistic effects of the mixture treatment facilitate an effective carrier extraction at the SnO2/perovskite interface, enhance the PEC performance, and improve the stability of the device. The perovskite photoanode exhibits an impressive applied bias photon‐to‐current efficiency of 12.9% with an outstanding durability for 225 h. Furthermore, an unbiased solar water splitting is achieved using all the perovskite photoelectrodes, resulting in a remarkable unassisted solar‐to‐hydrogen efficiency of 10.9% and a continuous 22 h stable operation. [ABSTRACT FROM AUTHOR]

Oxygen evolution reaction (OER) as a half‐anodic reaction of water splitting hinders the overall reaction efficiency owing to its thermodynamic and kinetic limitations. Iodide oxidation reaction (IOR) with low thermodynamic barrier and rapid reaction kinetics is a promising alternative to the OER. Herein, we present a molybdenum disulfide (MoS2) electrocatalyst for a high‐efficiency and remarkably durable anode enabling IOR. MoS2 nanosheets deposited on a porous carbon paper via atomic layer deposition show an IOR current density of 10 mA cm–2 at an anodic potential of 0.63 V with respect to the reversible hydrogen electrode owing to the porous substrate as well as the intrinsic iodide oxidation capability of MoS2 as confirmed by theoretical calculations. The lower positive potential applied to the MoS2‐based heterostructure during IOR electrocatalysis prevents deterioration of the active sites on MoS2, resulting in exceptional durability of 200 h. Subsequently, we fabricate a two‐electrode system comprising a MoS2 anode for IOR combined with a commercial Pt@C catalyst cathode for hydrogen evolution reaction. Moreover, the photovoltaic–electrochemical hydrogen production device comprising this electrolyzer and a single perovskite photovoltaic cell shows a record‐high current density of 21 mA cm–2 at 1 sun under unbiased conditions. [ABSTRACT FROM AUTHOR]

Antisolvent treatment has been developed to effectively fabricate dimethylammonium‐iodide (DMAI)‐assisted CsPbI3 perovskite solar cells (PSC) under moisture conditions. However, a clear understanding of its effect on the crystallization mechanism is still elusive. Here, the antisolvent bathing effect on DMAI‐assisted CsPbI3 crystallization is investigated under ambient conditions. For films bathed into antisolvents with Lewis basic oxygen (i.e., diethyl ether, anisole, ethyl acetate, and methyl acetate), rapid crystallization kinetics are observed due to the interaction between Cs4PbI6 and antisolvent in the form of the adduct. The Cs4PbI6‐antisolvent adduct lowers the transformation energy barrier, thereby enabling immediate phase transformation to CsPbI3 as soon as DMAPbI3 is decomposed. Based on this observation, a new crystallization mechanism is proposed for DMAI‐assisted CsPbI3 in which Cs4PbI6, instead of DMAPbI3, plays the role of the predominant phase of crystallization. Accelerated crystallization due to anisole antisolvent bathing results in a uniform film morphology and better coverage with fewer defects and pinholes. This enhances the power conversion efficiency of the n‐i‐p‐structured PSCs based on anisole‐bathed CsPbI3 to 18.84%, even under moisture conditions. [ABSTRACT FROM AUTHOR]