Investigation of structural, optoelectronic and thermoelectric properties of GaCuX2 (X = S, Se and Te) chalcopyrites semiconductors using the accurate mBJ approach

Abstract

Ternary chalcopyrites have recently been the focus of scientists due to their optoelectronic and thermoelectric application as solar energy converters, nonlinear optical devices and detectors. In the present study, we used the first principle calculations based on the density functional theory (DFT) to explore the structural, optoelectronic and thermoelectric properties of GaCuX2 (X = S, Se and Te). The electronic band structure, density of states and optical properties were investigated using the modified Becke Johnson (TB-mBJ) approximation. These materials were discovered to be direct band gap semiconductors in this study, which agrees well with previously reported results. When compared to GaCuS2 and GaCuTe2, GaCuSe2 has a smaller gap value, due to the lower chemical bonding nature of Ga and Se atoms. The density of states of these three ternary chalcopyrites, as well as their optical properties including dielectric functions, optical conductivity and absorption coefficient have also been examined and discussed in details. The maximum reflectivity occurs at 13.5 eV, which exists in the ultra-violet region, showing that investigated materials can be employed to shield high frequency ultraviolet radiations. The calculated maximum refractive index static value varies from 1.5 to 5.5 eV, predicting that the materials under consideration can be used in a vast range of optoelectronic applications, especially in the visible range. GaCuS2 shows high refraction among these compounds. Finally, the thermoelectric properties of these materials, such as the Seebeck coefficient, the power factor and figure of merit, are analyzed using the semi-classical Boltzmann theory as executed in the BoltzTraP code. The high Seebeck coefficient and figure of merit values reveal that these systems belong to a new class of high-efficiency thermoelectric materials (TE) for high-temperature application fields. These findings are likely to open up new route for researchers looking into the potential areas of application of these compounds in thermoelectric and optoelectronic devices.