Effect of Nb, Ta and V replacements on electronic, optical and elastic properties of NbCu3Se4: A GGA+U study

Abstract

Development of efficient, renewable and eco-friendly energy sources is on rise and is the main quest of the researchers to meet the energy challenges of future due to vanishing fossil fuels. In this connection, chalcogenides are the most promising materials to be used in state-of-the-art next generation solar cells for efficient production of clean energy from solar radiations. Hereby, we have presented an organized investigation of the optical and electronic properties of XCu3Se4 (X ​= ​Nb, Ta, V) by using first-principles GGA ​+ ​U calculations for their potential applications in optoelectronic devices such as solar cells. Our calculations show that NbCu3Se4 and TaCu3Se4 are semiconductor compounds; however, VCu3Se4 is intermetallic in nature because it shows semiconducting nature in the minority spin channel and metallic nature in the majority spin channel. NbCu3Se4 and TaCu3Se4 possess indirect band gaps as valence band maxima (VBM) and conduction band minima (CBM) are present at two different axes of IBZ (irreducible Brillouin zone), however, VCu3Se4 possess direct band gap in minority spin channel and shows metallic nature in majority spin channel. Energy band gaps of aforesaid compounds increase by replacing Nb with Ta and V. We have reported a detailed investigation of the optical constants to explore the prospect of these materials for optoelectronic applications. This study reveals that these compounds are weak reflectors of incident photons in infrared and visible regions, however, these compounds show up to 50% reflection of incident photons in the upper UV region. Elastic results reveal that these cubic compounds are elastically anisotropic materials with covalent bonding. Material shows ductile nature if value of (B/G) is greater than 1.75 otherwise it must be brittle. In our case, values of (B/G) or NbCu3Se4, TaCu3Se4 and VCu3Se4 are less than 1.75. Therefore, these chalcogenides are brittle in nature.