Homogenized chlorine distribution for >27% power conversion efficiency in perovskite solar cells

The spatial heterogeneity of halogen distribution in perovskite thin films represents a critical factor currently limiting both the power conversion efficiency and stability of solar cells. We identified pronounced through-film inhomogeneity in chlorine distribution in formamidinium lead iodide films, with the generally used additive methylammonium chloride. We demonstrated that incorporating alkali metal oxalates could effectively homogenize the chlorine distribution. These compounds underwent thermal dissociation, releasing alkali metal cations that selectively bound chloride ions, which considerably suppressed surface defects and eliminated interfacial barriers. A certified steady-state power conversion…