Synergistic Enhancement of Stability and Performance for Perovskite Solar Cells Using Fluorinated Benzoic Acids as Additives

The introduction of additives with specific functional groups is an important approach to extend the operational lifetime of perovskite solar cells (PSCs). Herein, the effect of the additives of benzoic acid (0F‐B), 4‐fluorobenzoic acid (1F‐B), and 2,3,4,5,6‐pentafluorobenzoic acid (5F‐B) on the performance and stability of MAPbI3‐based PSCs is systematically investigated. These additives can both chelate onto lead ions and form hydrogen bond with methyl ammonium ions. These combined interactions result in an increased activation energy for nucleation of perovskite crystals, thereby, increasing crystal size, reducing defect formation, improving electronic properties, as well as reducing ion migration. As a result, PSCs added with 5F‐B achieve the highest power conversion efficiency (PCE) of 20.50% with a narrow distribution compared to those PSC devices added with 1F‐B (19.25 %), 0F‐B (18.80 %), and pristine devices (18.53 %). Notably, 5F‐B‐added PSCs retain 80% of their initial PCE after ≈100‐day humidity test (at 25 °C and 50% relative humidity), 30‐day thermal stability test (at 85 °C in nitrogen environment), and 12‐day light illumination test (under continuous simulated solar radiation).