Study on cobalt doped tin based perovskite material with enhanced air stability

Although the power conversion efficiency of the lead-halide perovskite solar cells boost to >20%, the toxicity of lead hinders their large-scale implementation. Tin based perovskite have less toxicity, however its air stability is a big challenge. In this study, the air stability of tin based perovskite is improved by doping cobalt. The cobalt doped tin based perovskite thin films (GASn1−xCoxI2−2xCl1+2x) with cubic structure are prepared by one-step spin coating method. All GASn1−xCoxI2−2xCl1+2x (0.025≤x≤0.15) perovskite materials exhibit strong absorption in the visible light spectrum range. According to voltammetric measurement, the highest occupied molecule orbit (HOMO) and the lowest unoccupied molecule orbit (LUMO) of GASn1−xCoxI2−2xCl1+2x (x=0.15) are −5.45 and −3.99 eV, respectively, and the bandgap is calculated to be 1.46 eV. The binding energy increase of Sn3d and I3d for the cobalt doped tin based perovskite thin film might be the reason for enhanced air stability.