Issue 14, 2018

Thermal behaviour of dicarboxylic ester bithiophene polymers exhibiting a high open-circuit voltage

Abstract

Nine different polythiophene derivatives based on dialkyl-(2,2′-bithiophene-5,5′-diyl)-4,4′-dicarboxylate (DCB) alternating with thiophene (T), bithiophene (2T) or thienothiophene (TT) as co-monomer have been synthesized to study the effect of the polymer backbone and side chain length on the thermal properties, the tendency to aggregate, and the photovoltaic performance. Polymers incorporating DCB and 2T show increased crystallinity and a large effect of the side chain length on the morphology of the photoactive layer blends. Thermal annealing increases the crystallinity of the polymers and enhances the long-wavelength light absorption. The concomitant increase in polymer fibre width, however, deteriorates the photovoltaic performance. The best devices were made using the PDCB-2T polymer with 2-butyloctyl side chains providing a power conversion efficiency of 5.18%. The PDCB-T polymer with 2-ethylhexyl substituents shows a comparable efficiency (5.08%), but with a significantly higher open-circuit voltage due to deeper frontier orbitals levels.

Graphical abstract: Thermal behaviour of dicarboxylic ester bithiophene polymers exhibiting a high open-circuit voltage

Supplementary files

Article information

Article type
Paper
Submitted
21 sep 2017
Accepted
24 okt 2017
First published
26 okt 2017
This article is Open Access
Creative Commons BY-NC license

J. Mater. Chem. C, 2018,6, 3731-3742

Thermal behaviour of dicarboxylic ester bithiophene polymers exhibiting a high open-circuit voltage

R. Heuvel, F. J. M. Colberts, M. M. Wienk and R. A. J. Janssen, J. Mater. Chem. C, 2018, 6, 3731 DOI: 10.1039/C7TC04322H

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