Temperature- and size-effects on optical properties of perylene microcrystals

Perylene microcrystals with different sizes were prepared by the reprecipitation and subsequent microwave irradiation method. Their excitonic absorption peaks were blue-shifted with decreasing crystal size in the size range of sub-micrometer. Perylene microcrystal films were also fabricated by means of the electrostatic adsorption method to investigate the dependence of the excitonic absorption spectra on temperature. As a result, the temperature-dependence of half-width of the excitonic absorption spectra was well explained by Toyozawa's theoretical prediction, which was based upon an interaction between exciton and lattice vibration. In addition, it was revealed that the peak position of emission spectra from the self-trapped exciton (STE) state was relatively blue-shifted in comparison with the bulk crystal, and that the lifetime of STE emission became shorter in perylene microcrystal in any temperature.