Investigation of post-growth Cu-diffusion in In-rich CuInSe2 films

In-rich CuInSe2 films have been submitted to post-growth Cu diffusion. The photoluminescence investigation carried out shows a transition from the com monly observed broad band around 0.94 eV to a much sharper peak around 0.98 (5) eV under low excitation density. This recombination appears at a slight ly but definitely larger energy than the recombination usually reported aro und 0.96 eV. The excitation power dependence leads us to ascribing the peak observed here to a donor-acceptor pair band, as evidenced by the 2.5 meV/d ecade shift of the peak-energy and the temperature-dependence of the photol uminescence signal. From the Arrhenius plot of the luminescence intensity a n activation energy of 40 meV is extracted, When these data are analyzed in the frame of the most recent theoretical predictions of Cu- and In-related defects a possible candidate for the center appears to be [Cu-ln-Cu-i]. Ho wever Cu-Se could equally be involved. (C) 2000 Elsevier Science S.A. All r ights reserved.