Radiative recombination processes in CuGaSe2/CdS/ZnO heterostructures have been investigated comparing standard photoluminescence (PL) and electromodulated photoluminescence (EMPL). The CuxGaySe2 absorbers are grown epitaxially. Their luminescence spectra originate from exciton and two donor-acceptor-pair (DAP) transitions depending on the ratio x/y. Defect density ratios with respect to the absorption depth are evaluated. EMPL offers the possibility to investigate the influence of the electric field exclusively. The combination of steady state PL and EMPL are sensitive to the defect states at the interface just where the depletion layer is located. In a first result, the location of the space charge region was determined. There is no indication for an extension into the buffer or n-type layer. Second, from the PL intensity dependence on the applied voltage the point of recombination in the presence of a various internal field is discussed in terms of the dead-layer model and excess carrier concentrations. The failure of the dead-layer model for DAP transitions in CuGaSe2 solar cells are shown. (C) 2003 Elsevier Science B.V. All rights reserved.