Theoretical investigation of the optoelectronic response of highly correlated Cu 3 P photocatalyst.

Photocatalytic materials attract immense scientific interest due to their possible applications in energy harvesting. These applications are strongly dependent on the material's band gap and efficient visible light absorption, which ultimately relies on the underlying electronic structure of the material. In this work, we have theoretically studied the electronic and optical response of a CuP semiconductor. We have used Density Functional Theory (DFT), and the Many-Body Perturbation Theory (MBPT) based Bethe-Salpeter Equation (BSE). CuP has intriguing band gap nature, as DFT predicts a semi-metallic state which was corrected by employing the Hubbard potentials. Only astronomically large values of Hubbard potentials reproduced the semiconducting state of CuP. The optical response of the material is computed within a Random Phase Approximation (RPA) and using the BSE on top of DFT+ wavefunctions and on the ground state computed with the PBE0 functional. The BSE captures the excitonic physics, and the optical absorption obtained from it was red-shifted compared to the RPA, which shows the significance of electron-hole interactions in CuP. The comparison of the BSE with experiments suggests that BSE@PBE0 reproduces the optical absorption much more closely to the experimental data.