Proton‐transfer‐induced in situ defect passivation for highly efficient wide‐bandgap inverted perovskite solar cells

Wide‐bandgap (≥1.68 eV) inverted perovskite solar cells (PSCs) have been recognized as promising top component cells on the commercial crystalline silicon cell to surpass its Shockley–Queisser efficiency limit. However, the power conversion efficiency (PCE) is dramatically limited by the huge open‐circuit voltage ( V OC ) loss. Herein, we propose a proton‐transfer‐induced in situ defect passivation strategy to reduce the nonradiative recombination to minimize the V OC loss. Specifically, a liquid‐form neutral amine, 3,4,5‐trifluorobenzylamine (TFBA) was added into ethyl acetate (EA) as anti‐solvent for the film preparation, which induces proton‐transfer from the formamidinium (FA) and methylammonium (MA) in the perovskite precursors to the TFBA. The protonated TFBA exhibits a gradient distribution near the surface of the perovskite film, achieving in situ defect passivation. As a result, TFBA‐based 1.68 eV‐bandgap inverted PSCs afforded a PCE of 20.39%, one of the highest for cells with this bandgap. Meanwhile, due to the strong interaction between TFBA and the perovskite film, the mixed‐halide perovskites demonstrate much better photostability. Our findings offer an effective strategy to passivate defects in PSCs.