Highly Efficient Perovskite Solar Cells via Nickel Passivation

Abstract Today's state‐of‐the‐art perovskite solar cells (PSCs) are utilizing polycrystalline perovskite thin films via solution‐processing at low temperature (<150 °C). It is extremely significant to enlarge grain size and passivate trap states for perovskite thin films to achieve high power conversion efficiency. Herein, a strategy for defect passivation of perovskite films via metal ion Ni 2+ is for the first time reported. It is found that addition of Ni 2+ can significantly generate polyporous PbI 2 films due to a different solubility between NiCl 2 and PbI 2 which benefits penetration of MAI and thus formation of large grain perovskite films eventually. It further demonstrated that Ni 2+ ions can effectively passivate PbI 3 − antisite defects and restrain the generation of Pb 0 by interacting with the under‐coordinated halide anions and halide‐rich antisites. Therefore, introducing moderate Ni 2+ ions result in a significant increase in photoluminescence lifetime from 285 to 732 ns. Accordingly, a power conversion efficiency of 20.61% can be achieved for the 3% Ni 2+ addition‐based PSCs with an enhanced cell stability under ambient conditions. This work provides a promising route toward perovskite films featuring with high crystallinity and low trap‐density.