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% (VOC = 1.126 V, JSC = 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%.