Outstanding Passivation Effect by a Mixed-Salt Interlayer with Internal Interactions in Perovskite Solar Cells

Nonradiative recombination is a major limiting factor in obtaining efficient metal-halide perovskite photovoltaics. Here, a passivation treatment is developed by applying a mixture of a new ammonium salt, CF 3 (CF 2 ) 2 CH 2 NH 3 I (HBAI), and a conventional formamidinium halide, FAX, on top of the 3D perovskite bulk film. The introduction of such an optimized passivation layer effectively suppressed charge recombination by passivating the surface traps of the 3D perovskite film, enabling a well-matched energy alignment at the interface of perovskite/HTM, leading to a high power conversion efficiency (PCE) of over 23% from current–voltage ( I – V ) measurements and a stabilized 22.7% PCE, owing to a substantial V OC improvement (above 80 mV on average), coupled with an improved stability.