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

V. K. Thorsmølle, R. D. Averitt, J. Demsar, D. L. Smith, S. Tretiak, R. L. Martin, X. Chi, B. K. Crone, A. P. Ramirez, and A. J. Taylor

Phys. Rev. Lett. 102, 017401 – Published 5 January 2009

Abstract

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 $C_{60}$ -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.

Received 22 July 2008

DOI:https://doi.org/10.1103/PhysRevLett.102.017401

Authors & Affiliations

V. K. Thorsmølle^1,2, R. D. Averitt^1,3, J. Demsar^1,4,5, D. L. Smith¹, S. Tretiak¹, R. L. Martin¹, X. Chi^1,6, B. K. Crone¹, A. P. Ramirez^1,7, 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

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Vol. 102, Iss. 1 — 9 January 2009

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