Analysis of Na2CuP ternary semiconductor compound for optoelectronic application by first-principles methods using GGA and mGGA functionals

Abstract

An ab initio study of Zintl Na2CuP ternary semiconductor compounds was carried out by applying first-principles methods to calculate the structural, electronic, elastic, mechanical, and optical properties using generalised gradient approximation (GGA) and metaGGA exchange-correlation functionals. The bandgap was determined to be 0.7523 eV and 0.7848 eV using GGA with Wu-Cohen and Perdew-Burke-Ernzerhof (PBE) functionals, respectively. The bandgap was re-approximated using the more accurate metaGGA functionals as 1.078 eV and 1.084 eV using the Tran-Blaha modified Becke Johnson exchange and correlation functional (TB-mBJ) and the strongly constrained and appropriately normed (SCAN) functional, respectively. The projected density of states using the GGA revealed that the conduction band formation was mainly by Cu 2p, P 2p, and Na 2s orbitals with the rest of the orbitals making a minor contribution. In contrast, the valence band formation was mainly formed by Cu 3d and P 2p, with the rest of the orbital playing a minor role in the formation. The material was found to be mechanically brittle with a covalent bond, which is a characteristic of Zintl-phased materials. The Na2CuP material was also observed to have a strong absorption coefficient between 1.15 eV and 15 eV, a characteristic suitable for photovoltaic applications.