Alternating copolymers of cyclopenta[2,1-b;3,4-b′]dithiophene and thieno[3,4-c]pyrrole-4,6-dione for high-performance polymer solar cells

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journal

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Author(s)

  • Zhao Li
  • Xiaomei Du
  • Ludmila Scoles
  • Gilles Robertson
  • Yanguang Zhang
  • Floyd Toll
  • Ye Tao
  • Jianping Lu
  • Jianfu Ding

Detail(s)

Original languageEnglish
Pages (from-to)3331-3336
Journal / PublicationAdvanced Functional Materials
Volume21
Issue number17
Publication statusPublished - 9 Sep 2011
Externally publishedYes

Abstract

A series of alternating copolymers of cyclopenta[2,1-b;3,4-b′] dithiophene (CPDT) and thieno[3,4-c]pyrrole-4,6-dione (TPD) have been prepared and characterized for polymer solar cell (PSC) applications. Different alkyl side chains, including butyl (Bu), hexyl (He), octyl (Oc), and 2-ethylhexyl (EH), are introduced to the TPD unit in order to adjust the packing of the polymer chain in the solid state, while the hexyl side chain on the CPDT unit remains unchanged to simplify discussion. The polymers in this series have a simple main chain structure and can be synthesized easily, have a narrow band gap and a broad light absorption. The different alkyl chains on the TPD unit not only significantly influence the solubility and chain packing, but also fine tune the energy levels of the polymers. The polymers with Oc or EH group have lower HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) energy levels, resulting higher open circuit voltages (V oc) of the PSC devices. Power conversion efficiencies (PCEs) up to 5.5% and 6.4% are obtained from the devices of the Oc substituted polymer (PCPDTTPD-Oc) with PC61BM and PC71BM, respectively. This side chain effect on the PSC performance is related to the formation of a fine bulk heterojunction structure of polymer and PCBM domains, as observed with atomic force microscopy. A series of alternating copolymers of cyclopenta[2,1-b:3,4-b]dithiophene and thieno[3,4- c]pyrrole-4,6-dione, (PCPDTTPD) are designed and synthesized. These polymers show a low-enery band gap and a broad absorption. Polymer solar cell devices based on their blends with PC61BM and PC71BM show a high power conversion efficiency up to 5.5% and 6.4%, respectively. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Research Area(s)

  • bulk heterojunction, conjugated polymers, photovoltaic devices, polymer solar cells

Citation Format(s)

Alternating copolymers of cyclopenta[2,1-b;3,4-b′]dithiophene and thieno[3,4-c]pyrrole-4,6-dione for high-performance polymer solar cells. / Li, Zhao; Tsang, Sai-Wing; Du, Xiaomei; Scoles, Ludmila; Robertson, Gilles; Zhang, Yanguang; Toll, Floyd; Tao, Ye; Lu, Jianping; Ding, Jianfu.

In: Advanced Functional Materials, Vol. 21, No. 17, 09.09.2011, p. 3331-3336.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journal