First-principles study of the effect of alkali metals on the electronic and optical properties of SnS2

Abstract

In this paper, the photovoltaic properties of alkali metal atom X ( X is Li, Na, K, and Rb) doped monolayer SnS2 system have been investigated based on first principles calculations. After the doping of alkali metal atoms, the bond lengths of the doped systems increase compared to the pure SnS2 system. When alkali metal atoms are doped in the pure SnS2 system, the band gap of the doped systems increases and the SnS2 system changes from an indirect band gap to a direct band gap. It is found that the density of states in the valence band near the Fermi energy level of all doped systems is primarily contributed by S atoms, and the conduction band is primarily contributed by Sn and S atoms. The ionic bonds are formed between X and S atoms. The polarizability of the doped SnS2 systems is enhanced. Moreover, the absorption and reflection peaks of the SnS2 doping systems are redshifted, which improves the effective utilization rate of the infrared light region.