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Ab Initio Study of K${_3}$Cu${_3}$P${_2}$ Material for Photovoltaic Applications

Search for efficient materials for application in the fields of optoelectronics and photovoltaics are active areas of research across the world. The potential of compounds such as K${_3}$Cu${_3}$P${_2}$ is not yet fully realized. Therefore, we perform the ab initio studies based on density functional theory to investigate the structural, electronic, elastic, and optical properties of K${_3}$Cu${_3}$P${_2}$. Ground state properties were computed in three different scenarios, i.e: with spin-orbit coupling (SOC), without spin-orbit coupling, and with Hubbard U parameter. Direct electronic bandgaps of 1.338 eV, 1.323 eV and 1.673 eV were obtained for K${_3}$Cu${_3}$P${_2}$ without SOC, K${_3}$Cu${_3}$P${_2}$ with SOC and K${_3}$Cu${_3}$P${_2}$ with Hubbard U respectively. In all the cases, Cu-d orbitals were dominant at the top of the valence band. The effect of SOC on the K${_3}$Cu${_3}$P${_2}$ computed lattice constant and bandgap was insignificant. The mechanical stability test indicated that K${_3}$Cu${_3}$P${_2}$ is mechanically stable at zero pressure. The optical band gap was found to increase by 0.635 eV when Hubbard U was taken into consideration. Generally, the inclusion of the Hubbard U parameter in density functional theory improves the predictions of the bandgap and optical properties.