Intra-chain triplet–triplet annihilation and delayed fluorescence in soluble conjugated polymers

Pulse radiolysis has been used to generate high triplet populations on isolated conjugated polymer chains in benzene solutions. This allows direct observation of delayed fluorescence (DF) arising from intramolecular triplet–triplet annihilation (TTA). In poly(2-methoxy,5-(2′-ethyl-hexyloxy)-p-phenylenevinylene) the triplet lifetime at low triplet concentration is 90 μs which decreases to 15 μs as the number of triplets saturates at ca. 30 triplets per chain. Analysis of the DF kinetics gives an upper limit of 1.5% for the number of triplets that contribute to TTA. We also observed DF in a range of other conjugated polymers.