Excimer emission from evaporated pyrene films

Emission spectra and decay times of fluorescence of pyrene thin films prepared by evaporation onto glass substrate at low temperatures were measured. The band positions of the excimer emission from the films evaporated onto substrates at temperatures below about 200 K, are found to the lower energy side of those of the crystal. The decay time of excimer emission in a film prepared by evaporation onto a substrate cooled with liquid nitrogen is about 100 ns at 85 K and is shorter than that of the crystal. These results are discussed in relation to an amorphous structure in the pyrene evaporated thin films. The energy transfer was also studied in evaporated pyrene films containing perylene as a dopant. The results are explained in terms of excimer exciton diffusion through the crystalline structure in the film.