Electronic and optical properties of mixed perovskites CsSnxPb(1−x)I3

The electronic structure and optical properties of the new solar cells absorber material: mixed perovskites CsSnxPb(1−x)I3 are studied by the first-principle calculations with mBJ + SOC (modified Beak Johnson approximation plus spin-orbit coupling) method. The band gap of the serial of compounds almost quasi-linearly reduces with increasing Sn content from 0.96 eV (x = 0) to 0.16 eV (x = 1). Optical absorption coefficient revealed a progressive red shift with the increment of the Sn content, accompanying with the absorption edge broadening. The absorption coefficient and Ideal Power Absorption Coefficient (IPAC) increase greatly with the Pb atoms being partially substituted by Sn atoms. The pure CsSnI3 has the highest IPAC, but it is unstable in the air because the Sn2+ will be oxidized to Sn4+. So our results indicate that partially substituted CsSnxPb(1−x)I3 might be the good solar cell absorption material.