We investigate light-induced degradation of Cu(In,Ga)Se2 (CIGSe) layers by means of time-resolved photoluminescence (TRPL) measurements. Illumination in the range of minutes with 1 sun white light equivalent leads to a strong reduction of the carrier lifetime as determined by TRPL. Ambient storage in the dark, however, does not cause degradation. X-ray photoelectron spectroscopy of the CIGSe surface reveals a light induced enhancement of Na 1s and O 1s core-level emission. The position of the O 1s peak at 531.6eV is related to a Na-O-CIGSe bonding complex. The light-induced degradation of the CIGSe layer finally translates into inferior open circuit voltages due to the dominance of interface recombination in completed solar cell devices. This study has implications for laboratory research and may need to be regarded in CIGSe module production.