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Please use this identifier to cite or link to this item: http://hdl.handle.net/1942/19009

Title: Molar Mass versus Polymer Solar Cell Performance: Highlighting the Role of Homocouplings
Authors: VANGERVEN, Tim
Himmelberger, Scott
Salleo, Alberto
MAES, Wouter
Issue Date: 2015
Citation: CHEMISTRY OF MATERIALS, 27 (10), p. 3726-3732
Abstract: Although a strong link between the molar mass of conjugated polymers and the performance of the resulting polymer:fullerene bulk heterojunction organic solar cells has been established on numerous occasions, a clear understanding of the origin of this connection is still lacking. Moreover, the usual description of molar mass and polydispersity does not include the shape of the polymer distribution, although this can have a significant effect on the device properties. In this work, the effect of molar mass distribution on photovoltaic performance is investigated using a combination of structural and electro-optical techniques for the state-of-the-art low bandgap copolymer PTB7. Some of the studied commercial. PTB7 batches exhibit a bimodal distribution, of which the low molar mass fraction contains multiple homocoupled oligomer species, as identified by MALDI-TOF analysis. This combination of low molar mass and homocoupling drastically reduces device performance, from 7.0 to 2.7%. High molar mass batches show improved charge carrier transport and extraction with much lower apparent recombination orders, as well as a more homogeneous surface morphology. These results emphasize the important effect of molar mass distributions and homocoupling defects on the operation of conjugated polymers in photovoltaic devices.
Notes: [Vangerven, Tim; Drijkoningen, Jeroen; Dierckx, Wouter] Hasselt Univ, Inst Mat Res IMO IMOMEC, Div Mat Phys, B-3590 Diepenbeek, Belgium. [Verstappen, Pieter; Vanderzande, Dirk; Maes, Wouter] Hasselt Univ, Inst Mat Res IMO IMOMEC, DSOS, B-3590 Diepenbeek, Belgium. [Himmelberger, Scott; Salleo, Alberto] Stanford Univ, Dept Mat Sci & Engn, Stanford, CA 94305 USA. [Vanderzande, Dirk; Maes, Wouter] Imec Vzw, Div IMOMEC, B-3590 Diepenbeek, Belgium. [Manca, Jean V.] Hasselt Univ, X LaB, B-3590 Diepenbeek, Belgium.
URI: http://hdl.handle.net/1942/19009
DOI: 10.1021/acs.chemmater.5b00939
ISI #: 000355382700022
ISSN: 0897-4756
Category: A1
Type: Journal Contribution
Validation: ecoom, 2016
Appears in Collections: Research publications

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