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Phys. Rev. Lett. 102, 017401 (2009) [4 pages]

Morphology Effectively Controls Singlet-Triplet Exciton Relaxation and Charge Transport in Organic Semiconductors

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V. K. Thorsmølle1,2, R. D. Averitt1,3, J. Demsar1,4,5, D. L. Smith1, S. Tretiak1, R. L. Martin1, X. Chi1,6, B. K. Crone1, A. P. Ramirez1,7, and A. J. Taylor1
1Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
2École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
3Boston University, Boston, Massachusetts 02215, USA
4Department of Physics and CAP, Universität Konstanz, D-78457 Konstanz, Germany
5Complex Matter Department, Jozef Stefan Institute, SI-1000 Ljubljana, Slovenia
6Texas A&M University-Kingsville, Kingsville, Texas 78363, USA
7Bell Laboratories, Alcatel-Lucent, 600 Mountain Avenue, Murray Hill, New Jersey 07974, USA

Received 22 July 2008; published 5 January 2009

We present a comparative study of ultrafast photoconversion dynamics in tetracene (Tc) and pentacene (Pc) single crystals and Pc films using optical pump-probe spectroscopy. Photoinduced absorption in Tc and Pc crystals is activated and temperature-independent, respectively, demonstrating dominant singlet-triplet exciton fission. In Pc films (as well as C60-doped films) this decay channel is suppressed by electron trapping. These results demonstrate the central role of crystallinity and purity in photogeneration processes and will constrain the design of future photovoltaic devices.

© 2009 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.102.017401
DOI:
10.1103/PhysRevLett.102.017401
PACS:
78.47.−p, 71.35.−y, 72.80.Le, 73.61.Ph
 
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