Selenizing Possibilities of Cu2HgSnS4—i.e., Cu2HgSn(SexS1−x)4 Compound Semiconductor: Potential Candidate for Solar Photovoltaics and Photodetectors

Abstract

Herein, the authors report the optoelectronic and mechanical properties of Cu2HgSn(SexS1−x)4 alloy (0 ≤ x ≤ 1) using density‐functional calculations. The alloy exhibits a range of bandgap 1.33–0.81 eV with small bowing 0.395, preserving direct nature at Γ point for any value of x. Hubbard parameter of ≈0.52 Ry is considered viewing the strongly correlated Cu‐3d and Hg‐4d orbitals, together with modified Becke–Johnson potential with spin–orbit coupling, to ensure accurate eigenvalues. When analyzing the charge density with a Bader charge analysis, decreasing ionic character with increasing Se concentrations is observed. The noticed elastic constant also satisfies the Born–Huang criteria and exhibits the ductile nature of Cu2HgSn(SexS1−x)4 system, making it a good candidate for flexible devices. The partial density of states highlights the dominance of Cu‐d states in the valence band edge, while the conduction band edge majorly emerges with Se states. In addition, the absorption coefficient is also found at ≈104 cm−1, and a rising degree of polarization is seen when approaching x = 1. This study provides the potential of Cu2HgSn(SexS1−x)4 alloy system for a photo‐absorber layer in graded and tandem thin‐film solar cells together with low‐bandgap Cu2HgSnSe4 as a suitable material for an infrared detector and thermoelectric applications.