Fully Vacuum-Processed Wide Band Gap Mixed-Halide Perovskite Solar Cells

Methylammonium lead mixed-halide perovskites MAPb(BrxI1-x)(3) are promising materials for the preparation of tandem devices. When exposed to light, MAPb(BrxI1-x)(3) segregates in iodide- and bromide-rich phases, limiting the achievable photovoltage and hence the attainable device efficiency. To date only solution processed mixed-halide perovskites have been demonstrated. We present fully vacuum-deposited mixed-halide perovskite thin films with band gap of 1.72 and 1.87 eV, prepared by controlling the deposition rates of the different halide precursors. When used in thin-film devices, these materials lead to power conversion efficiencies of 15.9 and 10.5%, respectively, which are among the highest reported to date for these types of wide band gap absorbers.