The formation of small gold clusters at the initial stage of the metal growth on a thin film of the conjugated organic semiconductor diindenoperylene (DIP) leads to charging during ultraviolet photoemission spectroscopy (UPS) investigations. Additional irradiation of the sample with visible light was successfully applied to re-establish charge neutrality on the sample surface. By varying the light energy, we demonstrate that the optical formation of excitons and/or polarons results in efficient electron transfer from DIP to the positively charged An clusters and thus the elimination of charging in UPS. This allows the collection of reliable information on the interface electronic structure. (C) 2003 Elsevier Science B.V. All rights reserved.