Effect of Na substitution on electronic and optical properties of CuInS2 chalcopyrite semiconductor

Abstract

Electronic & optical properties of Na substituted CuNaIn2S4 chalcopyrite semiconductors are significantly modified due to Na substitution in the Cu deficient CuInS2 semiconductor. These properties are obtained form first principle calculation using density functional theory based tight binding Linear muffin tin orbital method. The presence of Na alters the structural distortion and enhances strengths of Cu d and S p hybridization in CuNaIn2S4. This effect reduces band gap, in agreement with experimental observations and modify other properties significantly. Calculations of optical matrix elements (OME) and joint density of states (JDOS) show that effects of Na substitution on optical properties come through p–d hybridization and structural distortion. OME contribution is prominent near band edge. Both systems show anisotropic optical properties.