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Managing defects in SnO2 is critical for improving the power conversion efficiency (PCE) of halide perovskite-based solar cells. However, typically reported SnO2‑based perovskite solar cells have inherent defects in the SnO2 layer, which lead to a lower PCE and hysteresis. Here, we report that a dual-coating approach for SnO2 with different annealing temperatures can simultaneously form a SnO2 layer with high crystallinity and uniform surface coverage. Along with these enhanced physical properties, the dual-coated SnO2 layer shows favorable band alignment with a mixed halide perovskite. After careful optimization of the dual-coating method, the average PCE of the perovskite solar cell based on the dual-coated SnO2 layer increases from 18.07 to 19.23% with a best-performing cell of 20.03%. Note that a facile two-step coating and annealing method can open new avenues to develop SnO2-based perovskite solar cells with stabilized and improved photovoltaic performances.

The power conversion efficiency (PCE) of solution-processed organic–inorganic hybrid perovskite solar cells has been drastically improved. Despite this considerable progress, systematic research on precursor solution chemistry and its effects on photovoltaic parameters has been limited thus far. Herein, we report on the tracking of changes in chemical species in a precursor solution under solar illumination and investigate the correlation between the equilibrium change and the corresponding perovskite film formation. The illuminated perovskite precursors display a higher density of high-valent iodoplumbate, where the resulting perovskite film exhibits reduced defect density with uniform film formation. Conclusively, the perovskite solar cells prepared by the photoaged precursor solution demonstrate not only improved average PCE but also enhanced reproducibility with a narrow PCE distribution. This discovery shows robust control of perovskite precursor solutions from a simple treatment and suggests that the resulting uniform film may be applicable to various halide perovskite-based devices.

Although lead halide perovskite (LHP) solar cells can be externally applied to water electrolysis for solar-to-hydrogen conversion, an LHP device with a monolithic configuration for photoelectrochemical (PEC) cells is more economically ideal for viable hydrogen production. To this end, the hydrogen evolution reaction (HER)/oxygen evolution reaction (OER) catalyst attachment on the LHP solar cell terminals is a governing factor for high efficiency and stable operation. Herein, we report monolithic PEC cells with a double-cation perovskite solar cell connected to a robust 3D OER catalyst using conductive carbon powders for minimal ohmic contact loss. The monolithic PEC cell exhibits 0.56 V onset potential and a maximum photocurrent density of 24.26 mA/cm2 at 1.23 VRHE (reversible hydrogen electrode (RHE)) with a 9.16% applied bias photon-to-current efficiency. This result will stimulate commercial-level application of LHP-based PEC cells for solar water splitting as well as solar-to-fuel conversion with high efficiency.

Hydrogen is a promising future sustainable fuel candidate with boundless opportunities. Research into photoelectrochemical (PEC) water splitting based on a lead halide perovskite (LHP) has progressed significantly with the aim of more efficient solar hydrogen production. Herein, we unite a well-known photo-absorbing LHP with cost-effective water-splitting catalysts, and we introduce two types of monolithic LHP-based PEC devices that act as a photocathode and a photoanode for the hydrogen evolution reaction and oxygen evolution reaction, leading to efficient unbiased overall water splitting.Through the integration of these two monolithic LHP-based photoelectrodes, an unbiased solar-to-hydrogen conversion efficiency of 10.64% and a photocurrent density of 8.65 mA cm −2 are achieved.perovskite, photoelectrochemical cell, photoelectrode, unassisted | INTRODUCTIONPhotoelectrochemical (PEC) water splitting, 1 a promising artificial photosynthesis method, is a potential alternative technique for generating renewable fuel. Conventional PEC devices with metal oxides can generate renewable energy sources, such as hydrogen, from water splitting, which can alleviate CO 2 emissions from fossil fuels. However, most readily employed metal oxide-based PEC devices exhibit poor photocurrent density under 1 sun conditions and Carbon Energy.