Photoinduced absorption and photoluminescence in poly(2,5-dimethoxy-p-phenylene vinylene)

H. S. Woo, S. C. Graham, D. A. Halliday, D. D. C. Bradley, R. H. Friend, P. L. Burn, and A. B. Holmes
Phys. Rev. B 46, 7379 – Published 15 September 1992
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Abstract

We report a study of the photoexcited states in the conjugated polymer poly(2,5-dimethoxy-p-phenylene vinylene). Photoluminescence due to radiative recombination of singlet excitons is observed at energies just below the onset of the π-π* absorption band at 2.1 eV. Photoinduced absorption at 80 K shows bands peaking at 0.68, 1.35, and 1.80 eV. The features at 0.68 and 1.8 eV are associated with the same excited state which we propose is a doubly charged bipolaron, while the third at 1.35 eV is unrelated. We assign this 1.35-eV absorption to a triplet-triplet transition of a triplet exciton. The bipolarons are long lived with significant numbers surviving in excess of 100 ms at 80 K, and have a weak temperature dependence such that photoinduced absorption is readily detectable even at room temperature. The triplet exciton has a lifetime of order 2.5 ms at 80 K but this falls rapidly at higher temperature and the response is not detected at room temperature. We contrast these results with those obtained previously for the related poly(arylene vinylene) polymers poly(p-phenylene vinylene), and poly(2,5-thienylene vinylene) and for other conjugated polymers, and draw attention to the important role played in the photophysics of these materials by neutral excited states.

  • Received 27 April 1992

DOI:https://doi.org/10.1103/PhysRevB.46.7379

©1992 American Physical Society

Authors & Affiliations

H. S. Woo, S. C. Graham, D. A. Halliday, D. D. C. Bradley, and R. H. Friend

  • Cavendish Laboratory, Madingley Road, Cambridge CB3 0HE, United Kingdom

P. L. Burn and A. B. Holmes

  • University Chemical Laboratory, Lensfield Road, Cambridge CB2 1EW, United Kingdom

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Issue

Vol. 46, Iss. 12 — 15 September 1992

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