The electrical characteristics of Cu(In,Ga)Se-2-based solar cells with In2S3 buffer were investigated. The effects of post-deposition annealing in helium or in air on current-voltage characteristics, net acceptor density profiles and admittance spectra were studied. Analysis of the current-voltage characteristics showed that interface recombination dominated transport in the as-deposited devices was reduced after annealing and partially replaced by bulk recombination. This was accompanied by a decrease in the saturation current and diode ideality factor. The influence of the heat treatment on the buffer/hetero-interface region as determined by capacitance measurements was minor. We conclude that a reduction in the interface states density and in the p+ layer doping caused by the chemical modification of the hetero-interface region is the major source of the improvement. (C) 2012 Elsevier B.V. All rights reserved.