Integrating Low-Cost Earth-Abundant Co-Catalysts with Encapsulated Perovskite Solar Cells for Efficient and Stable Overall Solar Water Splitting

Abstract

Metal halide perovskite solar cells have an appropriate bandgap (1.5–1.6 eV), and thus output voltage (>1 V), to directly drive solar water splitting. Despite significant progress, their moisture sensitivity still hampers their application for integrated monolithic devices. Furthermore, the prevalence of the use of noble metals as co-catalysts for existing perovskite-based devices undermines their use for low-cost H2 production. Here, a monolithic architecture for stable perovskite-based devices with earth-abundant co-catalysts is reported, demonstrating an unassisted overall solar-to-hydrogen efficiency of 8.54%. The device layout consists of two monolithically encapsulated perovskite (FA0.80MA0.15Cs0.05PbI2.55Br0.45) solar cells with low-cost earth-abundant CoP and FeNi(OH)x co-catalysts as the photocathode and photoanode, respectively. The CoP-based photocathode demonstrates more than 17 h of continuous operation, with a photocurrent density of 12.4 mA cm−2 at 0 V and an onset potential as positive as ≈1 V versus reversible hydrogen electrode (RHE). The FeNi(OH)x-based photoanode achieves a photocurrent of 11 mA cm−2 at 1.23 V versus RHE for more than 13 h continuous operation. These excellent stability and performance demonstrate the potential for monolithic integration of perovskite solar cells and low-cost earth-abundant co-catalysts for efficient direct solar H2 production.