Low-temperature processed solar cells with formamidinium tin halide perovskite/fullerene heterojunctions

A new type of lead-free, formamidinium （FA）-based halide perovskites, FASnf2Br, are investigated as light-harvesting materials for low-temperature processed p-i-n heterojunction solar cells with different configurations. The FASnlaBr perovskite, with a band-gap of 1.68 eV, exhibits optimal photovoltaic performance after low-temperature annealing at 75 ~C. By using C60 as electron-transport layer, the device yields a hysteresis-less power conversion efficiency of 1.72%. The possible use of an inorganic MoO~ film as a new type of independent hole-transport layer for the present tin-based perovskite solar cells is also demonstrated.