Fluorinated Methylammonium Cation Containing Perovskite Solar Cells With Over 25% Power Conversion Efficiency
Justina Mikuciunaite, Bin Ding, Yuxuan Yang, Xiao‐Xin Gao, Vida Valipour, Yong Ding, Negar Ashari Astani, Jan Romano‐deGea, Lindsey E. K. Frederiksen, Farzaneh Fadaei Tirani, Vytautas Getautis, Yi Zhang, Mohammad Khaja Nazeeruddin, Kasparas RakstysABSTRACT
High‐performance perovskite solar cells (PSCs) are typically made using formamidinium CH(NH 2 ) 2 + (FA + ), cesium Cs +, and the thermally unstable methylammonium CH 3 NH 3 + (MA + ) monovalent cations. Excluding unstable MA + leads to perovskite compositions with increased stabilities and decreased bandgaps. This study introduces a novel approach using a simple fluorinated methylammonium CFH 2 NH 3 + (FMA + ) cation capable of doping into the perovskite‐framework. With the addition of an optimized quantity of 0.8 mol% FMAI, perovskite compositions are thermally more stable, enabling more reproducible n‐i‐p PSC performance with a power conversion efficiency of 25.67%. The PSCs exhibit operational stability over 2000 h. Spectroscopic and computational analyses suggest that FMAI may play a dual role as a fluorinated ammonium additive capable of doping into the perovskite and as a chemically non‐innocent precursor producing passivating species.