Observation of long-range exciton diffusion in highly ordered organic semiconductors

H. Najafov, B. Lee, Q. Zhou, L. C. Feldman, V. Podzorov

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323 Citations (Scopus)

Abstract

Excitons in polycrystalline and disordered films of organic semiconductors have been shown to diffuse over distances of 10-50 nm. Here, using polarization- and wavelength-dependent photoconductivity in the highly ordered organic semiconductor rubrene, we show that the diffusion of triplet excitons in this material occurs over macroscopic distances (2-8 μm), comparable to the light absorption length. Dissociation of these excitons at the surface of the crystal is found to be the main source of photoconductivity in rubrene. In addition, we observe strong photoluminescence quenching and a simultaneous enhancement of photoconductivity when the crystal surface is functionalized with exciton splitters. In combination with time-resolved measurements, these observations strongly suggest that long-lived triplet excitons are indeed generated in molecular crystals by fission of singlets, and these triplets provide a significant contribution to the surface photocurrent generated in organic materials. Our findings indicate that the exciton diffusion bottleneck is not an intrinsic limitation of organic semiconductors.

Original languageEnglish
Pages (from-to)938-943
Number of pages6
JournalNature materials
Volume9
Issue number11
DOIs
Publication statusPublished - Nov 2010

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ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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