First-principles investigations of structural, electronic and optical properties of ternary chalcopyrite semiconductors CuInY2 (Y = S, Se and Te)

The copper-indium-based tetragonal chalcopyrite semiconductors CuInY2 (Y = S, Se and Te) have garnered significant attention due to their suitable bandgap for solar cell applications. In this study, we investigate the structural, electronic, and optical properties of CuInY2 using state-of-the-art density functional theory (DFT) with the modified Becke-Johnson (mBJ) semilocal exchange functional. Our band structure calculations reveals that these compounds exhibit a p-type semiconductors character with a direct band gap at the Gamma point. The calculated band gaps are in good agreement with the experimental data. Density of state analysis shows that these compounds are primarily influenced by Cu d-states at the upper valence band and their hybridization with Y p-states bellow the first valence band. Furthermore, we validate our results by calculating optical properties, including the dielectric function, absorption coefficient, the real part of optical conductivity, optical reflectivity, and the refractive index. Our refractive index findings show reasonable agreement with the experimental data. Our findings indicate that all three compounds exhibit high absorption (approximate to 105 cm(-1)) in the visible light range with CuInTe2 showing the highest absorption compared to CuInS2 and CuInSe2. Additionally, CuInS2 is less reflective (0.21%) in the visible light range in this series. These structures, with their suitable band gaps, are capable of absorbing a significant amount of light, making them prospective choices for solar cell applications.