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Photocrosslinking of low band-gap conjugated polymers using alkyl chloride sidechains: Toward high-efficiency, thermally stable polymer solar cells

Published online by Cambridge University Press:  23 April 2018

Chi Zhang  and
Steven Holdcroft
Chi Zhang
Affiliation:
Department of Chemistry, Simon Fraser University, Burnaby, BC, V5A 1S6, Canada
Steven Holdcroft*
Affiliation:
Department of Chemistry, Simon Fraser University, Burnaby, BC, V5A 1S6, Canada
*
a)Address all correspondence to this author. e-mail: holdcrof@sfu.ca
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Abstract

We report the synthesis and photovoltaic characterization of four novel polymers based on poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}) (PTB7) incorporating various numbers of photocrosslinkable n-octyl chloride sidechains (PTB-Cl). These polymers showed similar optoelectronic properties to PTB7 and readily cross-linked in the form of thin films after deep-UV exposure. Photolithography with micrometer-scale patterning is demonstrated. PTB-Cls exhibit similar PV performances to PTB7 and lightly cross-linked PTB-Cls showed stable high photoconversion efficiencies after prolonged thermal treatment. However, it is found that a high-degree cross-linking is needed to prevent the formation of PCBM crystallites at high annealing temperatures even though the PV performance is stabilized with a much lower degree of cross-linking. This implies that the complete prevention of PCBM crystallite formation is not necessary to affect the stabilization of PV devices against excessive heat.

Keywords

polymerphotovoltaicsolution deposition
Type
Invited Article
Information
Journal of Materials Research , Volume 33 , Issue 13: Focus Issue: Stabilization of Organic Electronic Materials and Devices , 14 July 2018 , pp. 1879 - 1890
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Copyright
Copyright © Materials Research Society 2018 

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