Efficient perovskite solar cells by interface optimization with l-aspartic acid in air atmosphere

SnO 2 -based halide perovskite solar cells (PSCs) have recently garnered attention due to their simple and low-temperature fabrication processing. However, the interface defects due to the low temperature process of SnO 2 and imperfect energy band alignment between electron transport layer (ETL) and perovskite layer limit the improvement in efficiency of PSCs. In this study, an amino-acid self-assembled layer was employed onto the SnO 2 ETL as the buffer layer to optimize the interface of the perovskite and SnO 2 ETL. With addition of L-Aspartic acid (L-Asp), the amino molecule interacts with perovskite framework though the strong N–H⋯I hydrogen bonds , and its carboxylic acid groups reacts with SnO 2 by esterification reaction, thus enhancing the interface interaction between SnO 2 and perovskite. The hydrogen bonds and chemical reaction together affect the charge extraction and transfer efficiency at the SnO 2 /perovskite interface in PSCs. As a result, the highest power conversion efficiency (PCE) of PSCs fabricated in air atmosphere was 18.46%. The study unveils the critical role of interface contact modulation of MA-based perovskite and provides an insightful strategy for efficiency and stable low-temperature PSCs.