Excited state spectral and dynamics studies of meh-ppv

Femtosecond spectroscopy studies of several thin conjugated polymer films and solutions were performed in order to examine the gain/loss in the excited state. The excited state shows bimolecular interaction at distances higher than 10 nm between excitations/The ultrafast dynamics are consistent with bimolecular dipole-diplole interaction, but a quantum delocalization of at least 5 nm has to be assumed. We show how the photoinduced absorption affects the emission of light in long as opposed to short (thin film) optical path configurations: the photoluminescence from thick sample spectrally overlaps the net gain (stimulated emission minus photoinduced absorption). The results show that the observed spectral narrowing occurs through amplified spontaneous emission.