Comprehensive DFT analysis of structural, optoelectronic, and thermoelectric properties of ZnGa2X4 (X = S, Se, and Te) defect chalcopyrites for energy applications

Abstract

This study comprehensively investigates the physical properties of Zinc digallium ternary materials ZnGa₂X₄ (X = S, Se, Te) with a tetragonal defective chalcopyrite structure. We performed a first-principles calculation within the density functional theory (DFT) framework. We begin with volume optimization as well as determining the structural parameters. Then, the calculated electronic band structure reveals that all three samples are semiconductors exhibiting a direct band gap nature, with corresponding values of 3.51 eV, 2.55 eV, and 1.76 eV for ZnGa₂S₄, ZnGa₂Se₄, and ZnGa₂Te₄, respectively, as determined using the Tran-Blaha modified Becke-Johnson (TB-mBJ) potential. The optical properties were examined across energy intervals up to 14 eV, covering infrared, visible, and ultraviolet regions. Our findings show that Zinc digallium telluride (ZnGa₂Te₄) shows higher dielectric function, absorption coefficient (I ≈ 10⁶ cm⁻¹), and refractive index values, suggesting its strong potential for photovoltaic applications. The temperature analysis of the Seebeck and Hall coefficients indicates p-type charge transport in the investigated compounds. At ambient temperature, ZnGa₂Te₄ exhibited the highest Seebeck coefficient of 242.933 μV/K. The figure of merit, along with the significant power factor values and electrical conductivity of ZnGa₂X₄ materials, highlights their potential for thermoelectric applications, particularly at elevated temperatures. In summary, this study illuminates the essential physical properties of ZnGa₂X₄ (X = S, Se, Te) compounds, offering valuable insights for advancing research in optoelectronic and thermoelectric materials.