Photoluminescent properties in perylene PVD films: Influence of molecular aggregates and supramolecular arrangement.

Organic thin films are at the forefront of basic studies and applications in the field of physics, chemistry, biochemistry and materials science. For example, the intrinsic supramolecular arrangement, or simply the formation of aggregates may alter the optical and electrical properties, which would impact the potential applications of the material. Here, an attempt is made to correlate the molecular structures of two perylene derivatives, bis butylimido perylene (BuPTCD) and bis phenethylimido perylene (PhPTCD), with their film formation, in particular, the supramolecular arrangement and the photoluminescent properties. Emission spectra show that the PhPTCD has a radiative efficiency (RE) higher than that for BuPTCD when both are in solutions (monomers). Complementary, regarding PVD films, UV–Vis absorption measurements reveal that PhPTCD forms, predominantly, J aggregates, which are responsible for perylene derivative emission. However, BuPTCD PVD films are found to provide higher RE than PhPTCD PVD film. This apparent controversy could be explained considering other features such as crystallinity and molecular organization. The PVD film of BuPTCD is crystalline while PhPTCD PVD film is amorphous; BuPTCD has an edge-on while PhPTCD has a face-on molecular organization in PVD films.