Systematic study on the optoelectronic and elastic properties of Cu-based ternary chalcogenides: Using ab-initio Approach

The first principles-based GGA approach is used to investigate the elastic and optoelectronic properties of Cu -based ternary chalcogenides QCu3Te4 (Q = Ta, V, Nb) to explore their potential and significance in photovol-taic applications. The calculated energy band structures using GGA approach were corrected using hybrid GGA + U functional. Our study demonstrates that QCu3Te4 (Q = Ta, V, Nb) are the semiconductors with indirect energy band gaps as CBM and VBM occur at different symmetric points (R-X). The Bandgap values of QCu3Te4 (Q = Ta, V, Nb) are reduced by replacing Ta with V and Nb; thereby, the values of bandgaps are 1.5, 0.49, and 1.41 eV for TaCu3Te4, VCu3Te4 and NbCu3Te4, respectively. Therefore, a detailed examination of the optical parameters is performed to demonstrate the prospect of QCu3Te4 (Q = Ta, V, Nb) for optoelectronic device applications. The calculated results revealed that QCu3Te4 (Q = Ta, V, Nb) could be used as antireflecting coatings as such materials are weak reflectors of incident photons and reflect a maximum of 45% photo radia-tions in the upper UV region. Since VCu3Te4 is an efficient absorber of incident photo radiations in the infrared region, the TaCu3Te4 and NbCu3Te4 show maximum absorption in the visible and near UV regions. Furthermore, in the elastic properties the Poisson's ratio 'sigma' indicates that QCu3Te4 (Q = Ta, V, Nb) are covalent compounds and are anisotropic as the values of Zener anisotropy factor 'A' is not equal to 1. Also, the Pugh's ratio (B/G) values for QCu3Te4 (Q = Ta, V, Nb) are under 1.75. Thus, these Cu-based chalcogenide materials are brittle compounds that can provide an efficient route for optoelectronic devices. It is evident from the spectra of S that NbCu3Te4/TaCu3Te4 are p-type semiconductors; however, VCu3Te4 is an n-type semiconductor. We can predict that TaCu3Te4 is the most promising thermoelectric material for TE devices.