Poly(acrylic acid)‐Modified SnO 2 Electron Transport Layer for Perovskite Solar Cells

Abstract SnO 2 is one of the most used inorganic electron transport materials for organic‐inorganic halide perovskite solar cells. However, the surface defects of SnO 2 will block the electron transport at the SnO 2 /perovskite buried interface and limit the device performance. Here, poly(acrylic acid) (PAA) is employed to modify the SnO 2 electron transport layer. Carboxyl groups can react with KOH in the commercial SnO 2 aqueous colloidal dispersion to produce potassium polyacrylate, the −COO − can combine not only with oxygen and Sn 4+ on SnO 2 , but also can chelate with uncoordinated Pb 2+ defects on perovskite. Moreover, carboxyl groups can form a chemical linker between SnO 2 and perovskite via the esterification reaction, leading to the reduction of surface hydroxyl group defects of SnO 2 . The optimal solar cells with PAA modification achieve an enhanced power conversion efficiency of 18.88 % and improved stability.