Molecular locking of defects via H-bonding/coordination dual-interaction enables efficient perovskite solar cells

Abstract

The emergence of intrinsic defects during the growth of perovskite films severely constrains further advancements in the efficiency and stability of perovskite solar cells (PSCs). To address the challenge of mitigating defects in perovskite films, we incorporated 4-methylsulfonylbenzoic acid (4-MeSBA), a multifunctional additive, into the perovskite precursor solution. This additive significantly reduces defects in perovskites through a molecular locking mechanism. Specifically, the molecule's two oxygen-bearing functional groups engage in simultaneous bonding interactions with uncoordinated lead ions, formamidine species, and iodine atoms present at the grain boundaries of the perovskite. Furthermore, the synergistic effect mediated by 4-MeSBA through hydrogen bonding and coordination interactions not only facilitates more controlled crystal growth of perovskites but also enhances the overall quality of the perovskite film, thereby contributing to improved performance of PSCs. Indeed, we achieved a champion PSC with a power conversion efficiency of 26.35% measured in-house, along with a certified efficiency of 26.00%. The encapsulated 4-MeSBA-based PSC retained over 92% of its initial efficiency after 1200 hours of maximum power point tracking in air.