Multifunctional Modification of the Buried Interface in all-inorganic perovskite solar cells

The buried interface in perovskite solar cells (PSCs) is a significant source of recombination centers, which can critically impede device performance and stability. Regulating the properties of this buried interface is thus crucial for optimizing perovskite crystallization and charge transport. In this work, we propose a multifunctional modification strategy utilizing a series of small molecule-metal acetate salts (RbAc, SrAc, and SmAc) to address these challenges. The acetate (Ac-) anions were found to passivate the uncoordinated Sn4+ on the tin oxide (SnO2) electron transport layer (ETL) as well as the Pb2+ in the perovskite absorber layer at the buried interface. This dual-interface passivation approach effectively reduced both oxygen and halide vacancy defects, leading to improved crystal growth and energy level alignment at the buried interface. Consequently, the charge carrier transport properties were significantly enhanced. As the result, the champion CsPbBr3 PSC modified with SrAc achieved a power conversion efficiency of 11.15 %. Notably, the unencapsulated SrAc-treated device maintained 81 % of its initial efficiency after 1000 h of continuous maximum power point (MPP) tracking under illumination, demonstrating exceptional operational stability.