This work reports on processing, analysis and characterization of copper indium gallium diselenide (CIGS) used as a photosensitive layer for sensors such as sun angle detectors in space applications. CIGS-based solar cell devices with different CIGS layer thicknesses and the pn-junction located on the opposite side of the incidence of light were illuminated through their ultra-thin transparent molybdenum back contacts. The results from the Current density versus Voltage and quantum efficiency measurement indicate that the CIGS absorber layer may nor exceed 750 nm at backside illumination, due to the limited CIGS diffusion length. (C) 2008 Elsevier B.V. All rights reserved.