Theoretical study of structural, electronic, and optical properties of mixed chalcogenide-halide bismuth perovskites CH₃NH₃BiChI₂ (Ch = S, Se, Te)

Abstract

We investigate the structural, electronic, and optical properties of the mixed chalcogenide-halide bismuth perovskites CH3NH3BiChI2 (Ch = S, Se, Te) using the relativistic all-electron calculations. We use the structural model where the Ch atoms are placed at the apical position in the BiCh2I4 octahedron. It is found that the structures of CH3NH3BiChI2 are contracted in the apical direction and the Bi–Ch bond lengths decrease in the order of Ch = S, Se, and Te. CH3NH3BiChI2 exhibit anisotropic optical properties and show higher absorption coefficients than CH3NH3PbI3. Furthermore, employing the spectroscopically limited maximum efficiency as a metric for quantifying the photovoltaic performance, we find that CH3NH3BiSI2 and CH3NH3BiSeI2 are promising candidates for thin-film solar cells.

First‐principles study ofCs2Ti1−xMxBr6(M = Pb, Sn) and numerical simulation of the solar cells based onCs2Ti0.25Sn0.75Br6perovskite

“…The absence of one B‐site cation in the double perovskite A 2 B′B″X 6 yields the vacancy‐ordered double perovskite structure 16 . In the past, the band gap tuning of these vacancy ordered perovskites 17 (A 2 BX 6 ) have been achieved by considering various combinations of ‘A’ the cation, ‘X’, the halogen anion and metal cation ‘B’, for example, the band gap of Cs 2 TeI 6 reported by Cai et al 18 have indirect nature while Cs 2 SnI 6 , Rb 2 SnI 6 , have direct band gaps. Similarly, Cs 2 PtI 6 and Rb 2 PtI 6 have indirect band gaps, 18 which point towards the importance of the choice of B cation.…”