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APS » Journals » Phys. Rev. Lett. » Volume 88 » Issue 19
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Phys. Rev. Lett. 88, 197401 (2002) [4 pages]

Conjugation-Length Dependence of Spin-Dependent Exciton Formation Rates in Π-Conjugated Oligomers and Polymers

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M. Wohlgenannt
Department of Physics and Astronomy, The University of Iowa, Iowa City, Iowa 52242

X. M. Jiang and Z. V. Vardeny
Department of Physics, University of Utah, 115 South 1400 East, Salt Lake City, Utah 84112-0830

R. A. J. Janssen
Laboratory for Macromolecular and Organic Chemistry, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands

Received 14 December 2001; published 25 April 2002

We have measured the ratio, r = σS/σT of the formation cross section, σ of singlet and triplet excitons from polarons in π-conjugated oligomer and polymer films, using a spectroscopic technique we developed recently. We discovered a universal relation between r and the conjugation length (CL): r-1 depends linearly on CL-1, irrespective of the chain structure. Since r is directly related to the maximum possible electroluminescence quantum efficiency in organic light emitting diodes (OLED), our results indicate that polymers have an advantage over small molecules in OLED applications.

© 2002 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.88.197401
DOI:
10.1103/PhysRevLett.88.197401
PACS:
78.55.Kz, 72.20.Jv, 78.30.Jw, 78.66.Qn
 
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