Electronic and optical modeling of solar cell compounds CuGaSe 2 and CuInSe 2
Résumé
We present dielectric-function-related optical properties such as absorption coefficient, refractive index, and reflectivity of the semiconducting chalcopyrites CuGaSe 2 and CuInSe 2. The optical properties were calculated in the framework of density functional theory (DFT) using linear combination of atomic orbitals (LCAO) and full-potential linearized augmented plane wave (FP-LAPW) methods. The calculated spectral dependence of complex dielectric functions is interpreted in terms of interband transitions within energy bands of both chalcopyrites; for example, the lowest energy peak in the ε 2ωx spectra for CuGaSe2 corresponds to interband transitions from Ga/Se-4p → Ga-4s while that for CuInSe2 emerges as due to transition between Se-4p →In-5s bands. The calculated dielectric constant, ε 10, for CuInSe 2 is higher than that of CuGaSe 2. The electronic structure of both compounds is reasonably interpreted by the LCAO (DFT) method. The optical properties computed using the FP-LAPW model (with scissor correction) are close to the spectroscopic ellipsometry data available in the literature. © 2011 TMS.