Excellent Moisture Stability and Efficiency of Inverted All-inorganic CsPbIBr2 Perovskite Solar Cells through Molecule Interface Engineering.

All-inorganic lead halide perovskite solar cells (PSCs) have drawn widespread interest due to their better thermal stability compared to their organic-inorganic hybrid counterpart. Poor phase stability caused by moisture, however, has thus far limited their commercial application. Herein, by modifying the interface between the hole transport layer (HTL) and the perovskite layer, and by optimizing the HTL for better energy alignment, we controlled growth of perovskite, reduced carrier recombination, facilitated carrier injection and transport, and improved PSC's power conversion efficiency (PCE) and moisture stability. When tested using positive bias scans, a PCE of 9.49 % it is a significant improvement compared to the pre-interface passivation PCE (6.28 %) which is the highest efficiency of CsPbIBr2-based inverted devices at present. The stability measurement shows that the passivated CsPbIBr2-based inverted PSCs can maintain 86 % of its initial value after 1000 h stored in ambient air with 65 % relative humidity (RH). This study presents a simple and efficient way to improve the moisture stability and efficiency of CsPbIBr2-based PSCs.