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“Hot or cold” : how do charge transfer states at the donor–acceptor interface of an organic solar cell dissociate?

Title data

Bässler, Heinz ; Köhler, Anna:
“Hot or cold” : how do charge transfer states at the donor–acceptor interface of an organic solar cell dissociate?
In: Physical Chemistry Chemical Physics. (September 2015) .
ISSN 1463-9084
DOI: https://doi.org/10.1039/C5CP04110D

Abstract in another language

Electron transfer from an excited donor to an acceptor in an organic solar cell (OSC) is an exothermic process, determined by the difference in the electronegativities of donor and acceptor. It has been suggested that the associated excess energy facilitates the escape of the initially generated electron–hole pair from their mutual coulomb well. Recent photocurrent excitation spectroscopy on conjugated polymer/PCBM cells challenged this view. In this perspective we shall briefly outline the strengths and weaknesses of relevant experimental approaches and concepts. We shall enforce the notion that the charge separating state is a vibrationally cold charge transfer (CT) state. It can easily dissociate provided that (i) there is electrostatic screening at the interface and (ii) the charge carriers are delocalized, e.g. if the donor is a well ordered conjugated polymer. Both effects diminish the coulomb attraction and assure that the in-built electric field existing in the OSC under short current condition is already sufficient to separate most the CT states. The remaining CT excitations relax towards tail states of the disorder controlled density of states distribution, such as excimer forming states, that are more tightly bound and have longer lifetimes.

Further data

Item Type: Article in a journal
Refereed: Yes
Additional notes: First published online 28 Sep 2015
Institutions of the University: Faculties > Faculty of Mathematics, Physics und Computer Science > Department of Physics > Lehrstuhl Experimentalphysik II - Optoelektronik weicher Materie > Lehrstuhl Experimentalphysik II - Optoelektronik weicher Materie - Univ.-Prof. Dr. Anna Köhler
Faculties
Faculties > Faculty of Mathematics, Physics und Computer Science
Faculties > Faculty of Mathematics, Physics und Computer Science > Department of Physics
Faculties > Faculty of Mathematics, Physics und Computer Science > Department of Physics > Lehrstuhl Experimentalphysik II - Optoelektronik weicher Materie
Result of work at the UBT: Yes
DDC Subjects: 500 Science > 530 Physics
Date Deposited: 28 Oct 2015 08:05
Last Modified: 28 Oct 2015 08:05
URI: https://eref.uni-bayreuth.de/id/eprint/20835