Origin of line broadening in the electronic absorption spectra of conjugated polymers: Three-pulse-echo studies of MEH-PPV in toluene
- Department of Chemistry, University of California, Berkeley, California 94720 (United States)
- Centre for Electronic Materials and Devices, Department of Chemistry, Imperial College of Science, Technology, and Medicine, Exhibition Road, London SW7 2AY, (United Kingdom)
- Dyson Perrins Laboratory, Oxford University, Oxford OX1 3QY, (United Kingdom)
Integrated three-pulse stimulated echo peak shift data are compared for N,N-bis-dimethylphenyl-2,4,6,8-perylenetetracarbonyl diamide and poly[2-(2{sup '}-ethylhexyloxy)-5-methoxy-1,4-phenylenevinylene] (MEH-PPV) in toluene solvent. These two molecules represent a model probe of solvation dynamics and a prototypical soluble, electroluminescent conjugated polymer, respectively. The results indicate that it is inappropriate to describe the linear absorption spectrum of MEH-PPV as being primarily inhomogeneously broadened. Conformational disorder along the polymer backbone gives rise to an ensemble of polyene electronic oscillators that are strongly coupled to each other. As a consequence, fluctuations in the electronic energy gap on a time-scale of 50-fs derive primarily from bath-mediated exciton scattering. The data reported here provide an explanation for the broad, structureless electronic absorption of MEH-PPV. This interpretation provides a valuable insight into the nature of the initial photoexcited state, and the efficient population of the emissive state. (c) 2000 The American Physical Society.
- OSTI ID:
- 20216558
- Journal Information:
- Physical Review. B, Condensed Matter and Materials Physics, Vol. 61, Issue 20; Other Information: PBD: 15 May 2000; ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- English
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