A novel selenization-free chalcopyrite CIGSSe formation in a heat-treated Cu2Se/S/Ga3Se2/S/In3Se2 multilayer thin film (ML) and ML/n-Si heterojunction characteristics

Abstract

Selenization or sulphurization is a standard method for developing copper-selenium-based ternary to quinary compounds. The route proved effective, but there are concerns about the high-risk management and potential explosion if mishandled. This article discusses a selenization/sulphurization-free fabrication of a CIGSSe thin film structure. Instead of selenization, a Cu2Se/S/Ga3Se2/S/In3Se2 multilayer thin film structure is chosen, and a simple post-annealing in high vacuum is used. The x-ray diffraction analysis hinted at a composite structure in as-deposited and a phase pure dominant chalcopyrite structure in the annealed film. The bandgap of 1.71 eV with a high absorption coefficient of 104/cm with smaller Urbach energy of 59 meV supports the dominant microstructure of the annealed thin film. Room temperature hall measurements also ensured the charge carrier transformation of n-type to p-type during annealing with the carrier concentration of 1016/cm3. The Au/p-CIGS/n-Si/Au heterojunction is developed, and current-voltage measurements are investigated.