Additive Engineering for Efficient and Stable MAPbI₃-Perovskite Solar Cells with an Efficiency of over 21

The high density of defects in MAPbI₃ perovskite films brings about severe carrier nonradiative recombination loss, which lowers the performance of MAPbI₃-based perovskite solar cells (PSCs). Here, methylamine cyanate (MAOCN) molecules were introduced into MAPbI₃ solutions to manipulate the crystallizatsion of the MAPbI₃ films. MAOCN molecules can slow down the volatilization rate of the solvent and delay the crystallization process of the MAPbI₃ film. The crystal quality of the MAPbI₃ films is effectively optimized without an additive residue. Perovskite films treated by MAOCN have lower defect density and longer carrier lifetime, which lowers the carrier recombination loss. Meanwhile, the MAPbI₃ film based on MAOCN has a more hydrophobic surface. The final MAPbI₃-based device efficiency reached 21.28% (V_OC = 1.126 V, J_SC = 23.29 mA/cm², and FF = 81.13). After 30 days of storage under atmospheric conditions, the efficiency of unencapsulated MAOCN-based PSCs only dropped by about 5%.