Investigation of electronic and optical properties of alkali atom doped CuInSe2 using density functional theory

Abstract

In this study, the effect of alkali metal (Rb, Cs) doping on the electronic structure of CuInSe2 chalcopyrite have been investigated. The electronic structure of pure and doped chalcopyrites has been interpreted in terms of energy bands and density of states. The doping of Rb and Cs increases the band gap of CuInSe2 from 0.81 eV and attains its maximum value of 1.16 eV with 25% doping of Rb at Cu site. The forbidden gap of doped compounds is found to be suitable for optoelectronic and photovoltaic applications. Therefore, the investigations of various optical properties such as, dielectric tensors, absorption, reflection and refraction spectra, for Cu1−xAxInSe2 (A = Rb, Cs; x = 0, 0.125 and 0.25) compounds are performed to understand the optical performance of all these compounds. The imaginary part of dielectric tensor of pure and doped CuInSe2 are explained with the help of the various inter-band transitions. The refractive index for CuInSe2 is found to be 2.60 which reduces to 2.40 and 2.53 for Cu0.75Rb0.25InSe2 and Cu0.75Cs0.25InSe2 compounds, respectively. All investigations for Cu1−xAxInSe2 (A = Rb, Cs; x = 0, 0.125 and 0.25) compounds have been carried out using density functional theory. Present study shows that doping of Rb and Cs enhances the optoelectronic response of CuInSe2 for its utilization in photovoltaic and optoelectronic applications.