Abstract
The luminescence of single crystals of CuGaS2 grown by iodine‐vapor transport was studied. As‐grown crystals and crystals annealed in S, Ga, or in a vacuum were used. The crystals annealed in S showed a very intensive green luminescence, which was ascribed to donor‐acceptor pair transitions interacting with lattice phonons. Studies in terms of excitation intensity, temperature, and time allow us to extract two impurity levels:ED∼50 meV and EA∼130 meV. The acceptor may be due to cation vacancies. The crystals annealed in Ga (or vacuum) showed a red luminescence which was attributed to S vacancies associated with another impurity.