Unexpected bowing band evolution in an all-inorganic CsSn_1−xPb_xBr₃perovskite

Abstract

We theoretically investigated the structural and electronic properties of the all-inorganic perovskite CsSn1−xPbxBr3, compared with the mixed perovskite compound MAyCs1−ySn1−xPbxBr3, based on first-principle calculations.

Wavelength-Tuneable Near-Infrared Luminescence in Mixed Tin–Lead Halide Perovskites

“…While the Cs-based perovskite did not exhibit this behaviour, with the observed trend being nearly linear, the bandgap decreased as the Sn content increased and CsSnI 3 exhibited lowest bandgap. These findings are consistent with those reported previously, in which the absence of this trend was attributed to the absence of organic cations ( Hu et al, 2020 ; Xia et al, 2020 ). Xia et al investigated the electronic properties of all-inorganic perovskite CsSn 1-x Pb x Br 3 and MA y Cs 1-y Sn 1-x Pb x Br 3 materials.…”

“…The authors demonstrated that the Sn and Pb atoms occupied distinct sites in the two mixed compounds, and the bandgap bowing parameter of CsSn 1-x Pb x Br 3 was the smallest among all the considered perovskite materials. This result indicated the influence of cations on bandgap bowing effect ( Xia et al, 2020 ). Comparing the maximum and minimum bandgaps for the three perovskite systems showed that the bandgap for the Cs-based perovskites exhibited the largest change, from approximate 1.7 eV to near 1.3 eV, indicating that bandgap tuning is easier to achieve with Cs-based perovskites.…”

“…These results are consistent with those reported previously ( Hao et al, 2014 ; Goyal et al, 2018 ). In contrast to the MA- and FA-based perovskites, the Cs-based perovskites did not exhibit a blue-shift at the high Sn-Pb ratio ( Figure 2C ), probably because of the absence of organic cations ( Hu et al, 2020 ; Xia et al, 2020 ), as discussed in the following paragraph. In addition, we compared the absorption intensity of each composition, as shown in Figure 2D .…”