Phosphorescence from a ladder-type conjugated polymer in solid solutions at low temperature

Spectra and kinetics of phosphorescence (Ph) and delayed fluorescence (DF) of a conjugated polymer (methyl-substituted poly(paraphenylene)) have been investigated in frozen solutions at 77 K. It has been established that in solid solutions Ph decays exponentially with the rate constant of 1.1 s−1 which is four orders of magnitude smaller than the mean decay rate in films of the same polymer. DF in solutions was found to be due to triplet–triplet annihilation, i.e. different from the DF origin in the bulk films which is due to the recombination of geminate pairs of charges. The observed difference in the origin of DF and in the decay dynamics of triplet excitations in solutions and in films is discussed in terms of the interchain coupling.