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Fast Photoresponse of Functionalized Pentacene and Anthradithiophene Thin Films

Published online by Cambridge University Press:  01 February 2011

Jonathan Day
Affiliation:
[email protected], Oregon State University, Corvallis, OR, 97331, United States
Oksana Ostroverkhova
Affiliation:
[email protected], Oregon State University, Physics, 301 Weniger Hall, Corvallis, OR, 97331, United States
John Anthony
Affiliation:
[email protected], University of Kentucky, Lexington, KY, 40506, United States
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Abstract

We present photoconductivity of high-performance functionalized pentacene and anthradithiophene thin films on time scales from picoseconds to many seconds after photoexcitation. The polycrystalline thin films were deposited from solution on glass substrates with patterned interdigitated aluminum electrodes. In studies of fast transient photoconductivity, the samples were excited with laser pulses of ~100 fs duration at a wavelength of 400 nm, and the photocurrent due to transport of photoexcited charge carriers was monitored using 50 GHz digital sampling oscilloscope. The photoconductivity at longer (milliseconds through seconds) time scales was investigated using continuous wave (cw) illumination and a source-delay-measure unit. Both experiments were performed under conditions of varied electric field strength, fluence and temperature. In all samples, we observed fast charge carrier photogeneration (<30 ps, limited by time resolution of our setup) followed by decay of the photocurrent over the period of 5-50 ns, depending on the material, due to charge trapping and recombination, linear dependence of the peak photoconductivity on the fluence and super-linear dependence of the peak photocurrent on the applied electric field.

Type
Research Article
Copyright
Copyright © Materials Research Society 2007

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