Triplet exciton generation and decay in a red polydiacetylene studied by femtosecond spectroscopy

Results from femtosecond/picosecond transient absorption spectra measuremen ts in the near-infrared/visible spectral region of the red form of a solubl e polycarbazolyldiacetylene in a polyethylene matrix are reported. Intracha in singlet and triplet excitons are identified by the different dynamics of the photoinduced bands. The results are consistent with the ultrafast gene ration (< 200 fs) of triplet pairs by fission of a singlet state located be low the first optically allowed electronic state. In the picosecond time do main, triplet pairs undergo a random walk in a one-dimensional path with st atistically distributed traps and partially dissociate into long-lived (con gruent to 150 mu s) localized triplets. (C) 1999 Elsevier Science B.V. All rights reserved.