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Dynamics of energy level alignment at ITO/organic semiconductor interfaces

Coutinho, Douglas J. and Faria, Gregório C. and Faria, Roberto M. and von Seggern, Heinz (2015):
Dynamics of energy level alignment at ITO/organic semiconductor interfaces.
In: Organic Electronics, 26Elsevier Science, Netherlands, pp. 408-414, ISSN 15661199,
[Online-Edition: http://dx.doi.org/10.1016/j.orgel.2015.08.012],
[Article]

Abstract

Time-dependence of space-charge built-up at the ITO/organic semiconductor interface has been investigated for the first time using the charge extraction by linearly increasing voltage ( CELIV) technique in the dark. It will be demonstrated that space-charge next to an ITO/P3HT interface is extracted during the initial CELIV ramp establishing a non-equilibrium situation whose temporal recovery can be probed by utilizing sequentially prolonged delay times for successive voltage ramps. It will be reported that the buildup time constant for space charge at the ITO/P3HT interface amounts to 230 mu s. The dynamics of the relatively slow charge transfer at the interface of the transparent conducting oxide and the organic semiconductor as well as time-limiting processes will be discussed by considering tunneling, thermal detrapping and diffusion of the involved electrons and holes. It will be shown that thermal detrapping of electrons from molecules with their ground state close the center of the HOMO-DOS to vibronic states within the same molecule followed by tunneling to neighboring molecules with their not occupied ground state within the tail states of the DOS is the time limiting process and responsible for the long build-up time. (C) 2015 Published by Elsevier B.V.

Item Type: Article
Erschienen: 2015
Creators: Coutinho, Douglas J. and Faria, Gregório C. and Faria, Roberto M. and von Seggern, Heinz
Title: Dynamics of energy level alignment at ITO/organic semiconductor interfaces
Language: English
Abstract:

Time-dependence of space-charge built-up at the ITO/organic semiconductor interface has been investigated for the first time using the charge extraction by linearly increasing voltage ( CELIV) technique in the dark. It will be demonstrated that space-charge next to an ITO/P3HT interface is extracted during the initial CELIV ramp establishing a non-equilibrium situation whose temporal recovery can be probed by utilizing sequentially prolonged delay times for successive voltage ramps. It will be reported that the buildup time constant for space charge at the ITO/P3HT interface amounts to 230 mu s. The dynamics of the relatively slow charge transfer at the interface of the transparent conducting oxide and the organic semiconductor as well as time-limiting processes will be discussed by considering tunneling, thermal detrapping and diffusion of the involved electrons and holes. It will be shown that thermal detrapping of electrons from molecules with their ground state close the center of the HOMO-DOS to vibronic states within the same molecule followed by tunneling to neighboring molecules with their not occupied ground state within the tail states of the DOS is the time limiting process and responsible for the long build-up time. (C) 2015 Published by Elsevier B.V.

Journal or Publication Title: Organic Electronics
Volume: 26
Publisher: Elsevier Science, Netherlands
Uncontrolled Keywords: Poly(3-hexylthiophene), Dark-CELIV, Space-charge, Build-up time, Charge transport
Divisions: 11 Department of Materials and Earth Sciences > Material Science > Electronic Materials
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences
Date Deposited: 22 Feb 2016 12:21
Official URL: http://dx.doi.org/10.1016/j.orgel.2015.08.012
Identification Number: doi:10.1016/j.orgel.2015.08.012
Funders: The authors are grateful to the Brazilian research agencies FAPESP, CNPq and MCT/INEO for funding., HvS acknowledges the scholarship "Special Visiting Researcher" by the Brazilian Science without Borders Program.
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