Surface-Anchored Acetylcholine Regulates Band-Edge States and Suppresses Ion Migration in a 21%-Efficient Quadruple-Cation Perovskite Solar Cell

Although incorporating multiple halogen (bromine) anions and alkali (rubidium) cations can improve the open-circuit voltage (V-oc) of perovskite solar cells (PSCs), severe voltage loss and poor stability have remained pivotal limitations to their further commercialization. In this study, acetylcholine (ACh(+)) is anchored to the surface of a quadruple-cation perovskite to provide additional electron states near the valence band maximum of the perovskite surface, thereby enhancing the band alignment and minimizing the V-oc loss significantly. Moreover, the quaternary ammonium and carbonyl units of ACh(+) passivate the antisite and vacancy defects of the organic/inorganic hybrid perovskite. Because of strong interactions between ACh(+) and the perovskite, the formation of lead clusters and the migration of halogen anions in the perovskite film are suppressed. As a result, the device prepared with ACh(+) post-treatment delivers a power conversion efficiency (PCE) (21.56%) and a value of V-oc (1.21 V) that are much higher than those of the pristine device, along with a twofold decrease in the hysteresis index. After storage for 720 h in humid air, the device subjected to ACh(+) treatment maintained 70% of its initial PCE. Thus, post-treatment with ACh(+) appears to be a useful strategy for preparing efficient and stable PSCs.

Automated summary

This study demonstrated that anchoring acetylcholine (ACh(+)) on the surface of a quadruple-cation perovskite can improve band alignment, minimize V-oc loss, and passivate defects, resulting in efficient and stable perovskite solar cells. The ACh(+) treatment significantly enhanced power conversion efficiency (PCE) and open-circuit voltage (V-oc) while reducing hysteresis index, making it a promising strategy for PSCs preparation.