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

Herein, the authors report the optoelectronic and mechanical properties of Cu 2 HgSn(Se x S 1− 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‐3 d and Hg‐4 d 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 Cu 2 HgSn(Se x S 1− 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 ≈10 4 cm −1 , and a rising degree of polarization is seen when approaching x = 1. This study provides the potential of Cu 2 HgSn(Se x S 1− x ) 4 alloy system for a photo‐absorber layer in graded and tandem thin‐film solar cells together with low‐bandgap Cu 2 HgSnSe 4 as a suitable material for an infrared detector and thermoelectric applications.