Triplet state spectroscopy of conjugated polymers studied by pulse radiolysis

Using the technique of pulse radiolysis we have elucidated the energies and kinetics of triplet states in soluble luminescent conjugated polymers. Usi ng poly(2-methoxy,5-(2'-ethyl-hexoxy)-p-phenylenevinylene) MEH-PPV as an ex ample we explain this technique and show how it can be used to study the tr iplet states in conjugated polymers. Triplet energy transfer is used to det ermine 1(1)A(g)-1(3)B(u) energy gaps and the kinetics of triplet-triplet ab sorption yields triplet lifetimes. In the case of MEH-PPV, at concentration s up to 50 mg/l, the triplet decay rate shows no change, indicating self-qu enching of triplets is not significant. However, if very high electron beam doses are used, high intra chain triplet concentrations can be generated. In this high concentration regime triplet-triplet annihilation becomes effe ctive, as determined by the onset of delayed fluorescence. (C) 2001 Elsevie r Science B.V. All rights reserved.