The Luminescence of the Pyrene-Perylene System: Evidence for Mixed Excimers in the Solid State

Abstract

Absorption and fluorescence data are presented for the mixed crystal system—perylene in pyrene. It is shown that there is an anomalous luminescence from the mixed crystals above ca. 125°K, at which temperature we suggest there is a phase transition occurring in the host lattice. The anomalous emission is studied between 125°K and 450°K and the temperature dependence of its spectral shape and location is consistent with there being two superimposed emission spectra, one corresponding to a perylene weakly associated with pyrene, and the other corresponding to perylene more strongly associated to host molecules. The latter emission is spectrally diffuse, and could be the mixed excimer, or exciplex of perylene and host pyrene.