High performance low-bandgap perovskite solar cells based on a high-quality mixed Sn–Pb perovskite film prepared by vacuum-assisted thermal annealing

Vacuum-assisted thermal annealing not only could improve film morphology and crystallinity, but also could accelerate the sublimation of undesired MACl. With the help of this process, we obtain a highly efficient low-bandgap CH₃NH₃Sn_0.5Pb_0.5IxCl_3−xperovskite solar cell with a power conversion efficiency of 12.3%.