Quadruple-Cation Wide-Bandgap Mixed-Halide Tin Perovskite Solar Cells

Tin-based perovskite solar cells (TPSCs) are a promising alternative to the traditional lead-based PSCs for lead-free photovoltaic applications. To further promote the performance and stability, a tandem type of TPSC is an attractive direction to pursue. To serve as a low-bandgap TPSC with the bandgap (Eg) of around 1.4 eV, searching for a high-bandgap TPSC with an Eg in the range 1.8–2.0 eV is an important task to build a lead-free tandem TPSC. Herein, we report the first quadruple-cation wide-bandgap TPSC with the perovskite structure of FA0.55MA0.25Cs0.1PMA0.1SnBr2I (FA, formamidinium; MA, methylammonium; PMA, phenylmethylammonium) and an Eg of 1.93 eV to give the efficiency of power conversion of 6.2%. We found that PMA plays a key role in passivating the grain surface of perovskites and the interface between the perovskite and the hole-transport layer to give high performance and great stability for a wide-bandgap TPSC with a quadruple-cation configuration.