Highly Stable All-Inorganic CsPbIBr2 Perovskite Solar Cells with 11.30% Efficiency Using Crystal Interface Passivation

Passivation of methylammonium (MA) and polyethylenimine (PEI) is introduced into the preparation process of CsPbIBr2 film. MA and PEI can precisely control the grain size and continuity of CsPbIBr2, and the compact and full coverage perovskite film can be fabricated. The crystal size is uniform and is going to be the exciton diffusion length of the perovskite. Compared with the untreated CsPbIBr2 perovskite solar cells, the power conversion efficiency (PCE) of CsPbIBr2 perovskite solar cells with polyethylenimine (PEI) passivation has reached 11.30%, which is an increase of nearly 50%, which is the highest efficiency of CsPbIBr2 perovskite solar cells reported so far. At room temperature, the efficiency of CsPbIBr2 perovskite solar cells passivated by PEI remained unchanged after 300 days. After heating at 100 degrees C for 30 days, the efficiency of CsPbIBr2 perovskite solar cells passivated by polyethylenimine was only reduced by 10%, showing excellent thermal stability, which is mainly due to the introduction of inorganic materials with high thermal stability in device preparation, i.e., SnO2 and NiOx as an electronic transport layer (ETL) and hole transport layer (HTL), respectively.