The photoluminescence of thin films and solar cells was investigated, as a function of post-deposition treatment, by using various temperatures and excitation intensities. It was found that annealing in a H atmosphere led to an increase in photoluminescence intensity, at 1.445eV, by more than a factor of 100. Subsequent annealing in O or air passivated this transition, which was attributed to donor-acceptor pair recombination between a S vacancy and a Cu vacancy. A defect mechanism was proposed which assumed a passivation of S vacancies, by O in grain surfaces, which could be activated by H annealing.

K.Töpper, J.Bruns, R.Scheer, M.Weber, A.Weidinger, D.Bräunig: Applied Physics Letters, 1997, 71[4], 482-4