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Phys. Rev. Lett. 89, 227403 (2002) [4 pages]

Picosecond Transient Photoconductivity in Functionalized Pentacene Molecular Crystals Probed by Terahertz Pulse Spectroscopy

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F. A. Hegmann1,*, R. R. Tykwinski2, K. P. H. Lui1, J. E. Bullock3, and J. E. Anthony3
1Department of Physics, University of Alberta, Edmonton, Alberta, Canada T6G 2J1
2Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2
3Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506-0055

Received 11 July 2002; published 11 November 2002

We have measured transient photoconductivity in functionalized pentacene molecular crystals using ultrafast optical pump–terahertz probe techniques. The single crystal samples were excited using 800 nm, 100 fs pulses, and the change in transmission of time-delayed, subpicosecond terahertz pulses was used to probe the photoconducting state over a temperature range from 10 to 300 K. A subpicosecond rise in photoconductivity is observed, suggesting that mobile carriers are a primary photoexcitation. At times longer than 4 ps, a power-law decay is observed consistent with dispersive transport.

© 2002 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.89.227403
DOI:
10.1103/PhysRevLett.89.227403
PACS:
78.47.+p, 72.20.–i, 72.40.+w, 72.80.Le

*Electronic address: hegmann@phys.ualberta.ca