Engel-Vosko GGA Approach Within DFT Investigations of the Optoelectronic Structure of the Metal Chalcogenide Semiconductor CsAgGa₂Se₄

Abstract

Metal chalcogenide semiconductors have a significant role in the development of materials for energy and nanotechnology applications. First principle calculations were applied on CsAgGa₂Se₄ to investigate its optoelectronic structure and bonding characteristics, using the full-potential linear augmented plane wave method within the framework of generalized gradient approximations (GGA) and Engel-Vosko GGA functionals (EV-GGA). The band structure from EV-GGA shows that the valence band maximum and conduction band minimum are situated at Γ with a band gap value of 2.15 eV. A mixture of orbitals from Ag 4p ⁶/4d ¹⁰, Se 3d ¹⁰, Ga 4p ¹, Se 4p ⁴ , and Ga 4s ² states have a primary role to lead to a semiconducting character of the present chalcogenide. The charge density iso-surface shows a strong covalent bonding between Ag-Se and Ga-Se atoms. The imaginary part of dielectric constant reveals that the threshold (first optical critical point) energy of dielectric function occurs 2.15 eV. It is obvious that with a direct large band gap and large absorption coefficient, CsAgGa₂Se₄ might be considered a potential material for photovoltaic applications.