The demand for direct analytical techniques for characterization and damage evaluation of organic devices has increased dramatically in recent years, along with an increase in the importance of these devices. In this study, we demonstrate direct analysis of model structures for organic light emitting diode (OLED) devices by using SIMS with large Ar cluster ion beams. We prepared single and multilayer films of organic semiconductor materials by vacuum evaporation and analyzed their surfaces with time-of-flight secondary ion mass spectrometry (ToF-SIMS). Under bombardment with large Ar cluster ions, the predominant species observed were molecular ions from the organic materials, while small fragment ions were strongly suppressed. Moreover, the multilayer films were depth profiled with Ar cluster ion beams, and the interfaces between the organic layers could be clearly distinguished. These results show the promising potential of large Ar cluster ion beams for direct analysis of real organic semiconductor devices. Copyright (C) 2010 John Wiley & Sons, Ltd.