2,2′‐Bipyridyl‐4,4′‐Dicarboxylic Acid Modified Buried Interface of High‐Performance Perovskite Solar Cells

Abstract The regulation of interfaces remains a critical and challenging aspect in the pursuit of highly efficient and stable perovskite solar cells (PSCs). Here, 2,2′‐bipyridyl‐4,4′‐dicarboxylic acid ( HBPDC ) is incorporated as an interfacial layer between SnO 2 and perovskite layers in PSCs. The two carboxylic acid moieties on HBPDC bind to SnO 2 through esterification, while its nitrogen atoms, possessing lone electron pairs, interact with uncoordinated lead (Pb 2+ ) atoms through Lewis acid‐base interactions. This dual functionality enables simultaneous passivation of surface defects on both the SnO 2 and buried perovskite layers. In addition, the electron‐deficient nature of HBPDC enhances interfacial energy band alignment and facilitates electron transfer from the perovskite to SnO 2 . Furthermore, the incorporation of HBPDC strengthens the interfacial adhesion, improving mechanical reliability. As a result, the PSCs exhibited an impressive power conversion efficiency (PCE) of 25.41 % under standard AM 1.5G conditions, along with remarkable environmental stability.