2,2'-Bipyridyl-4,4'-Dicarboxylic Acid Modified Buried Interface of High-Performance Perovskite Solar Cells

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 SnO₂ and perovskite layers in PSCs. The two carboxylic acid moieties on HBPDC bind to SnO₂ through esterification, while its nitrogen atoms, possessing lone electron pairs, interact with uncoordinated lead (Pb²⁺) atoms through Lewis acid-base interactions. This dual functionality enables simultaneous passivation of surface defects on both the SnO₂ 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 SnO₂. 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.