Optical properties of Cu(In, Ga)Te2 thin films

Abstract

Structural and optical properties of polycrystalline Cu(In, Ga)Te2 thin films were analysed. They were deposited onto glass substrate by the flash evaporation technique and annealed at 450 °C in an argon atmosphere. Their optical properties in the near-infrared and visible range, 500–3000 nm, were studied to determine the gap. To identify the energy levels associated with various defect structures, photoluminescence (PL) measurements were carried out. The behaviour of the PL spectrum as a function of temperature and excitation intensity in these samples is reported. The PL spectrum of thin films after annealing in an argon atmosphere at 450 °C showed two peaks ranging from 0.90 to 1.15 eV. The first one, localized at 1.00 eV, was attributed to donor–acceptor pair transition while the second one at 1.05 eV was ascribed to a free-to-bound (F–B) transition.