Luminescence and lifetime measurements of 2,5-distyrylpyrazine (DSP), 1,4-bis(β-pyridyl-2-vinyl)benzene (P2VB) and their mixed crystals in the temperature range 8–300 K

Abstract

The emission spectra and lifetime measurements of 2,5-distrylpyrazine (DSP), 1,4-bis-(β-pyridyl-2-vinyl)benzene (P2VB) and their mixed crystals have been studied. The study shows the feasibility of photoreactivity at defects as well as in the bulk.

It is found that excimeric bands prominent in the emission of α-DSP and P2VB have unusually short fluorescence lifetimes (3–4 ns) although longer than the 1 ns lifetimes observed for the monomeric emission at shorter wavelength. These excimeric bands may correspond to emission from defects in the lattice and if so it seems that the electronic excitation produces delocalized excitonic states which only convert to excimeric states as a result of trapping at defects. The photoreactivity of the α and γ forms of DSP, P2VB and their mixed crystals can satisfactorily be accounted for on this basis.