Air exposure induced recombination in PTB7:PC71BM solar cells
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Understanding degradation pathways in organic photovoltaic cells (OPV) is essential to achieve long term device stability and allow commercialisation. Upon exposure to an ambient atmosphere the power conversion efficiency (PCE) of PTB7:PC71BM solar cells, cast using the solvent additive DIO, is markedly reduced. Using electrically detected magnetic resonance (EDMR) spectroscopy, trap sites, which are formed when the blend is exposed to air and DIO, are identified. Spin-Rabi oscillations reveal that the resonance arises from a weakly coupled pair of spin 1/2 species, while selective injection of charge carriers into the cell demonstrates that the spin-pair corresponds to recombination of electrons and holes. The recombination is assigned to holes on the PTB7 recombining with electrons localised to oxygen induced PC71BM trap sites.
Thomson , S A J , Hogg , S C , Samuel , I D W & Keeble , D J 2017 , ' Air exposure induced recombination in PTB7:PC 71 BM solar cells ' Journal of Materials Chemistry A , vol 5 , no. 41 , pp. 21926-21935 . DOI: 10.1039/c7ta03741d
Journal of Materials Chemistry A
© 2017 The Authors. Open Access article. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
SAJT acknowledges studentship funding from EPSRC under grant number EP/G03673X/1. I. D. W. S. acknowledges support EPSRC (EP/L012294/1) and a Royal Society Wolfson Research Merit Award. S. C. H. acknowledges funding from EPSRC under grant number EP/J500045/1. We also acknowledge support from the Wellcome Trust (099149) and from EPSRC (EP/F039034/1)
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