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Science 28 April 2000:
Vol. 288. no. 5466, p. 573
DOI: 10.1126/science.288.5466.573c
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This Week in Science
In polymer light-emitting diodes (LEDs), charge carriers (electrons and holes) move along conducting conjugated polymers and can recombine to form an excited state, or exciton, that can emit light. Nguyen et al. (p. 652; see the Perspective by Mazumdar) have explored the relative rate of exciton movement along chains, versus hopping between chains, by studying a polymer that was adsorbed both on a mesoporous silicon host (forming a bulk structure with overlapping chains) and inside the pores (formed isolated individual chains). By studying the polarization of the emitted light on a femtosecond time scale, they established that exciton transfer between chains is about two orders of magnitude faster than movement along chains. This result is opposite that for the initial charge carriers--electrons and holes move much more rapidly along chains than between them, which suggests that device architectures in polymer LEDs could be further optimized.
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Science. ISSN 0036-8075 (print), 1095-9203 (online)
