Unexpected bowing band evolution in an all-inorganic CsSn1-xPbxBr3perovskite

作者：Xia, Yufan; Chen, Yuxuan; Luo, Tian; Liang, Hongyao; Gao, Yujia; Xu, Xin; Xie, Weiguang; Liu, Pengyi; Wang, Xin; Zhao, Yu-Jun^*; Shi, Tingting^*

来源：2020, 10(44): 26407-26413.

DOI：10.1039/d0ra03709e

• PEROVSKITE
• GAP
• EFFICIENCY
• DENSITY
• STABILITY
• ENERGY
• BR

We theoretically investigated the structural and electronic properties of the all-inorganic perovskite CsSn1-xPbxBr3, compared with the mixed perovskite compound MA(y)Cs(1-y)Sn(1-x)Pb(x)Br(3), based on first-principle calculations. It has been demonstrated that Pb and Sn atoms are inclined to occupy the lattice sites uniformly in the all-inorganic perovskite, and this is distinguished from the most stable configurations observed in the mixed Cs-MA system. It is interesting that small Sn atoms prefer to stay close to the large MA(+)cations, leading to smaller local structural distortion. Through spin-orbital coupling calculations, we found non-linear bowing band evolution in the all-inorganic mixed Sn-Pb system with a small bowing parameter (b= 0.35), while the band gap of MA(y)Cs(1-y)Sn(1-x)Pb(x)Br(3)was clearly reduced as the ratio of MA was around 0.5 (y >= 0.25). We determined the bowing band evolution in the mixed cation perovskites and the intrinsic electronic deficiency of the all-inorganic perovskite to obtain the optimal band gap.