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The role of driving energy and delocalized states for charge separation in organic semiconductors

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Title: The role of driving energy and delocalized states for charge separation in organic semiconductors
Authors: Bakulin, AA
Rao, A
Pavelyev, VG
Van Loosdrecht, PHM
Pshenichnikov, MS
Niedzialek, D
Cornil, J
Beljonne, D
Friend, RH
Item Type: Journal Article
Abstract: The electron-hole pair created via photon absorption in organic photoconversion systems must overcome the Coulomb attraction to achieve long-range charge separation. We show that this process is facilitated through the formation of excited, delocalized band states. In our experiments on organic photovoltaic cells, these states were accessed for a short time (<1 picosecond) via infrared (IR) optical excitation of electron-hole pairs bound at the heterojunction. Atomistic modeling showed that the IR photons promote bound charge pairs to delocalized band states, similar to those formed just after singlet exciton dissociation, which indicates that such states act as the gateway for charge separation. Our results suggest that charge separation in efficient organic photoconversion systems occurs through hot-state charge delocalization rather than energy-gradient–driven intermolecular hopping.
Issue Date: 16-Mar-2012
Date of Acceptance: 10-Feb-2012
URI: http://hdl.handle.net/10044/1/66697
DOI: https://dx.doi.org/10.1126/science.1217745
ISSN: 0036-8075
Publisher: American Association for the Advancement of Science
Start Page: 1340
End Page: 1344
Journal / Book Title: Science
Volume: 335
Issue: 6074
Copyright Statement: © 2012 American Association for the Advancement of Science. This is the author’s version of the work. It is posted here by permission of the AAAS for personal use, not for redistribution. The definitive version was published in Science 335(6074):1340-1344, 16 Mar 2012, DOI: https://doi.org/10.1126/science.1217745
Keywords: cond-mat.mes-hall
cond-mat.mtrl-sci
MD Multidisciplinary
General Science & Technology
Publication Status: Published
Online Publication Date: 2012-02-23
Appears in Collections:Chemistry
Faculty of Natural Sciences