Electronic excited state energy competition between donor and acceptor in oligo(phenylene vinylene) microcrystal

Abstract

Energy transfer (ET) is an important strategy to lower threshold and to extend output spectrum range for organic semiconductor lasers. The key issue of ET assisted lasing is to balance ET rate kET and stimulated emission rate kSE of donor. In this research we studied ET process between Oligo(Phenylene Vinylene), 1,4-dimethoxy-2,5-di[4′-(methylthio)styryl]benzene (TDSB) and 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM) in the microcrystal. The stimulated emission rate kSE of TDSB is estimated to be 7.6×1010 s∧{-1}, and the ET rate kET between TDSB and DCM is calculated on the order of ~ 109 s∧{-1}. In addition, we experimentally investigated the influences of DCM doping concentration and temperature on the ET process between TDSB and DCM, showing that the ET rate kET increases with high DCM doping concentration. But in microcrystal matrix DCM was prone to non-uniform distribution in high doping region to deteriorate the ET rate kET. We also compared the ET rate kET and ET efficiency at different temperatures, and found the ET efficiency at room temperature is nearly twice of that at 35 K. The dependence of ET process on temperature can be well explained with exciton diffusion assisted ET mode.