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Photoexcited carrier relaxation dynamics in pentacene probed by ultrafast optical spectroscopy: Influence of morphology on relaxation processes |
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| Authors: | V.K. Thorsmø lle,R.D. Averitt,J. Demsar,D.L. Smith,R.L. Martin,B.K. Crone,A.J. Taylor |
| Affiliation: | a Los Alamos National Laboratory, Los Alamos, NM 87545, USA b Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland c Boston University, Boston, MA 02215, USA d Department of Physics and Center for Applied Photonics, Universität Konstanz, D-78457 Konstanz, Germany e Department of Complex Matter, Jozef Stefan Institute, Ljubljana, Slovenia f Texas A&M University-Kingsville, Kingsville, TX 78363, USA g Bell Laboratories, Alcatel-Lucent, 600 Mountain Avenue, Murray Hill, NJ 07974, USA |
| Abstract: | We present a comparative study of ultrafast photoexcited state relaxation in pentacene single crystals and in pure and C60-doped pentacene films using optical pump-probe spectroscopy. The photoinduced absorption spectra in pentacene crystals is consistent with a dominant singlet-triplet fission decay channel for above-gap excitation. This decay channel is suppressed in thin films and even further suppressed by electron trapping in C60-doped films. Thus we show that suppression of triplet state production, which is necessary for free carrier formation and thus photovoltaic and photodiode performance, is controllable via sample morphology. |
| Keywords: | Ultrafast spectroscopy Organic semiconductors Sample morphology |
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