Structural, electronic, and optoelectronic properties in hybrid system Cs2Sn (I1_ xBrx)6: DFT-based study

Cesium tin halide based Cs2SnI6 has been extensively investigated owing to its potentiality toward achieve environmentally friendly Pb-free and stable halide perovskites. Herein, the hybrid system Cs2Sn(I1-xBrx)6 is constructed by Br- substitution of I- with replacement ratios of 1/4, 1/2, 3/4 and 1. The structural, electronic and optoelectronic properties are investigated based on density functional theory (DFT). The calculated structural parameters found that the formation energies decrease and the structural stability improves with increasing Br content. The electronic properties show that the bandgaps (0.971-2.401 eV) overlay almost the entire visual light of the direct-bandgap semiconductor Cs2Sn(I1-xBrx)6 and the bandgap increases by increasing Br replacement ratio. Partial density of states (PDOS) indicate that the electron orbitals at the band edges of Cs2Sn(I1-xBrx)6 are mainly dedicated by I/ Br-p and Sn-5p. In addition, the hybrid system Cs2Sn(I1-xBrx)6 exhibits similar photoelectric properties, and the absorption coefficients heighten. Our results are valuable for developing stable, green lead-free and high performance substitute perovskites materials.