Cu(In,Ga)S-2 solar cells with different absorber layer thicknesses prepared by means of a three-stage co-evaporation process are investigated to determine the electrical losses depending on the absorber layer thickness. The absorber material is characterized by energy dispersive X-ray spectroscopy, time of flight secondary ion mass spectroscopy and optical transmission and reflectance measurements. The acceptor concentration is determined admittance spectroscopy in the range of 8.4 center dot 10(15) cm(-3) to 3.8 center dot 10(16) cm(-3). From external quantum efficiency and current-voltage-measurements combined with the determined absorption coefficient we attribute the losses in the short circuit current density to incomplete absorption. (C) 2015 Elsevier B.V. All rights reserved.