PbS/CdS heterojunction thin layer affords high-performance carbon-based all-inorganic solar cells

Inherent defects such as ion migration, halide vacancies and ionic dangling bonds based on CsPbIxBr3−x devices are the main reasons for deep-level defects, non-radiative recombination and poor moisture resistance. Interface engineering has been proven to be the most direct and effective way to solve these problems. In this work, a PbS/CdS heterojunction thin layer between the CsPbI1.5Br1.5 and carbon electrode is constructed. The thin layer interacts with perovskite to reduce the trap density, inhibit carrier recombination, increase the built-in potential, inhibit ion migration and greatly improve the stability of the device. As a result, the carbon-based CsPbI1.5Br1.5 PSC achieves an open-circuit voltage of 1.315 V, a fill factor of 77.06% and a power conversion efficiency of 13.65%. As far as we know, this may be the highest efficiency reported for carbon-based CsPbI1.5Br1.5 PSCs so far. The optimized device can maintain more than 90% of the original efficiency and can be stored for 1200 h in atmospheric environment with relative humidity ≈ 30%. It can still retain 87% of the initial efficiency at temperature of 85 °C for 400 h in nitrogen environment. Our work provides a new optimization direction for the high-efficiency and stable all-inorganic PSCs.