Investigations of modulation effect of co-metal ions on the optical properties of the hybrid double perovskites (MA)2AgBi1-xSbxBr6.

Composition engineering plays an important role in generating novel properties and decreasing the lead (Pb) toxicity for halide perovskite materials. To find out the modulation effect introduced by the composition engineering, namely,B'-site co-metal ions, in (MA)2AgBi1-xSbxBr6systems with various Bi/Sb ratios ofx= 0, 0.25, 0.75, 1.00, series of theoretical simulations and analyses are carried out. For the (MA)2AgBi1-xSbxBr6systems, the Goldschmidt tolerance factortand the octahedral factorμindicate that all samples are in a standard double perovskite structure with alternating AgBr6and Bi/SbBr6octahedra. The calculated electronic structures show that the band gap of (MA)2AgBi1-xSbxBr6decreases with the increase of Sb content, but the indirect band gaps are maintained for all samples. By analyses of the imaginary partɛ2(ω) of dielectric function and the absorption spectra, we find that all (MA)2AgBi1-xSbxBr6systems show absorption in the visible-light region. All these results indicate that the composition engineering adopted in this paper is an effective strategy to modulate the optical properties of (MA)2AgBi1-xSbxBr6systems and may open a new way to put it into applications in the fields of solar cells and other optoelectronic devices.