Size-matched dicarboxylic acid for buried interfacial engineering in high-performance perovskite solar cells

Abstract

Tin dioxide (SnO2) is considered to be one of the most promising electron transport layers (ETLs) in perovskite solar cells (PSCs). Considering high concentrations of defects and energy level mismatch at the ETL/perovskite interface, buried interfacial engineering aids in boosting the efficiency and stability of PSCs. Herein, three dicarboxylic acids (DAs) including oxalic acid (OA), propanedioic acid (PA) and succinic acid (SA) are selected to modify the interface between perovskite layers and ETLs. It is demonstrated that DAs can enhance interfacial interaction between SnO2 and perovskite by esterification reaction and hydrogen bonding. In particular, OA with appropriate size can passivate two hydroxyl groups on SnO2 surfaces simultaneously, resulting in more favorable energy level alignment and better defect passivation ability amongst the three dicarboxylic buffer layers. Correspondingly, the power conversion efficiency of the OA-modified PSC increases substantially from 21.20% (reference device) to 22.91%, with a fill factor up to 83.1%. This work verifies that the buried interfacial engineering can effectively improve PSC performance, and also suggests the possibility of using size-matched symmetric molecules to modify ETLs for performance enhancement.