Spectroscopy and transport of the triplet exciton in a terthiophene end-capped poly(phenylene ethynylene).

Triplet states of poly(phenylene ethynylene), (3)PPE(*), not easily formed by direct photoexcitation, were produced by pulse radiolysis in toluene, along with triplet states of T(3)PPE having terthiophene end-caps. Intense triplet-triplet absorption maxima, epsilon(680)((3)PPE(*)) = 9.5 x 10(4) M(-1) cm(-1) and epsilon(780)((3)T(3)PPE(*)) = 2.8 x 10(4) M(-1) cm(-1) enable identification of these two species, which have triplet energies of 2.12 and 1.77 eV determined in bimolecular energy transfer equilibria. Bleaching of ground-state absorption measures (3)PPE(*) to be the delocalized over a 1.8-nm length. Triplet states formed in the PPE chains were transported to and trapped by the end caps in a time <<5 ns.