Conductive Passivator and Dipole Layer Mixture Enabling High-Performance Stable Perovskite Photoelectrode-Based Solar Water Splitting

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. The combined application of polyethylenimine ethoxylated (dipole interlayer) and chlorobenzenesulfonic acid (passivator) at the SnO2/perovskite interface of a perovskite photoanode drastically enhances its performance and stability up to 225 h. By pairing the perovskite photoanode with a perovskite photocathode, bias-free solar water splitting is successfully demonstrated with a record-high efficiency (approximate to 10.9%) and reasonable stability of 22 h.image