Integrated Perovskite/Silicon Tandems for Unassisted Water Splitting and CO2-to-Liquid Fuel Conversion

Abstract Integrated photoelectrochemical systems offer a promising pathway to produce value-added fuels from sunlight and abundant reagents. However, practical implementation remains challenging due to insufficient operating photovoltage, charge-carrier losses at the electrode–catalyst interface, and high catalytic overpotentials. Here, we fabricate a perovskite/silicon photoanode that combines a wide-bandgap metal-halide perovskite top junction with a double-textured crystalline silicon bottom junction to increase operating photovoltage. To minimize charge-transfer losses and promote catalyst adhesion, we integrate a photoanode with a graphite layer and further functionalize it with a low-overpotential Co-doped IrRu catalyst. The integrated photoanode achieves an open-circuit voltage of 1.86 V and a current density of 19 mA cm−2 at +1.23 VRHE. During unassisted two-electrode water splitting, the system achieves a solar-to-hydrogen efficiency of 16.06% and operates for 157 h. Extending to CO2-to-formate conversion, the two-electrode device reaches an applied-bias photon-to-current efficiency of 10.08% over 60 h. Our study highlights the potential of integrated photoelectrochemical systems for efficient solar-to-fuel conversion.