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Degradation kinetics in different polymer–fullerene blends investigated by electron spin resonance

Published online by Cambridge University Press:  13 July 2018

Marek Havlicek
Linz Institute for Organic Solar Cells (LIOS), Johannes Kepler University Linz, Linz A-4040, Austria; and Department of Primary Nanometrology and Technical Length, Czech Metrology Institute, Brno 638 00, Czech Republic
Niyazi Serdar Sariciftci
Linz Institute for Organic Solar Cells (LIOS), Johannes Kepler University Linz, Linz A-4040, Austria
Markus C. Scharber*
Linz Institute for Organic Solar Cells (LIOS), Johannes Kepler University Linz, Linz A-4040, Austria
a)Address all correspondence to this author. e-mail:
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We investigate the photostability of a set of organic semiconductor blends comprising a conjugated polymer as the donor and a fullerene as the acceptor using electron spin resonance (ESR). In the absence of oxygen, all blends show excellent stability. Even after several hundred hours of exposure to solar or UV radiation, the ESR spectra and the recombination of photoinduced charges recorded at low temperature are found to be unchanged. By contrast, the presence of oxygen leads to a fast light-induced degradation rendering the ability of the donor/acceptor system to form photoinduced charge carriers. Our findings suggest that conjugated polymer–fullerene blends exhibit very good photostability and that oxygen needs to be excluded in optoelectronic applications. Our findings also suggest that at low temperature, a universal recombination process of long-lived photoinduced charges is active, which does not depend on the electronic structure or the morphology of the investigated materials.

Invited Article
Copyright © Materials Research Society 2018 

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