Accelerating Additive-Assisted Defect Passivation via the Structural Isomer Effect for Highly Efficient and Stable Perovskite Solar Cells

Defects in hybrid perovskites have hindered the development of highly efficient and stable hybrid perovskite solar cells (PSCs). Therefore, researchers have used additives to passivate defects in hybrid perovskites; however, detailed studies on multifunctional group additives with structural isomers are limited. In this letter, we report the improved defect passivation ability of additives through the structural isomer effect and enhanced photovoltaic performance using this effect. l-Alanine methyl ester hydrochloride (l-AMECl) and its structural isomer, β-AMECl, were used to understand the influence of structural variations in functional groups. The structural isomer β-AMECl effectively reduced the trap density in the hybrid perovskite, thereby enhancing the photovoltaic parameters. Consequently, we achieved a power conversion efficiency of 24.25% with β-AMECl, which is the best result among PSCs using additives. Additionally, the PSCs with β-AMECl maintained an initial efficiency of 94% over 2500 h at 25 °C and 25% relative humidity, showing improved long-term stability.