We investigate the photophysical properties of as-deposited films of the perylene derivative N,N'-bis(phenylethyl)-perylene-3,4,9,10-bis(dicarboximide) (PPEI), grown by organic molecular beam deposition. The film morphology, consisting of coexisting phases, was studied using optical and atomic force microscopy and was found to be independent of film thickness. However, a reduction in PPEI film thickness results in an increase in the relative contribution from aggregated species to the photophysical properties of the films, which can be attributed to a room-temperature annealing process. (c) 2009 Published by Elsevier B. V.