Alternating copolymers incorporating cyclopenta[2,1-b: 3,4-b′] dithiophene unit and organic dyes for photovoltaic applications

Yen Ju Cheng, Lung Chang Hung, Fong Yi Cao, Wei Shun Kao, Chih Yu Chang, Chain Shu Hsu

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

We have synthesized six p-type copolymers, CPDT-co-TPADCN, CPDT-co-TPADTA, CPDT-co-TPATCN, CPDT-co-DFADCN, CPDT-co-DFADTA, and CPDT-co-DFATCN, consisting of a cyclopenta[2,1-b:3,4-b′]dithiophene (CPDT) unit and an organic dye in an alternating arrangement. Triphenylamine (TPA) or difluorenylphenyl amine (DFA) units serve as the electron donors, whereas dicyanovinyl (DCN), 1,3-diethyl-2-thiobarbituric acid, or tricyanovinyl (TCN) units act as the electron acceptors in the dyes. The target polymers were prepared via Stille coupling, followed by postfunctionalization to introduce the electron acceptors to the side chains. Because of the strongest withdrawing ability of TCN acceptor to induce efficient intramolecular charge transfer, CPDT-co-TPATCN and CPDT-co-DFATCN exhibit the broader absorption spectra covering from 400 to 900 nm and the narrower optical band gaps of 1.34 eV. However, the CPDT-co-TPATCN:PC71BM and CPDT-co-DFATCN:PC71BM based solar cells showed the power conversion efficiencies (PCEs) of 0.22 and 0.31%, respectively, due to the inefficient exciton dissociation. The DFA-based polymers possess deeper-lying HOMO energy levels than the TPA-based polymer analogues, leading to the higher Voc values and better efficiencies. The device based on CPDT-co-DFADTA:PC71BM blend achieved the best PCE of 1.38% with a Voc of 0.7 V, a Jsc of 4.57 mA/cm 2, and a fill factor of 0.43.

Original languageEnglish
Pages (from-to)1791-1801
Number of pages11
JournalJournal of Polymer Science, Part A: Polymer Chemistry
Volume49
Issue number8
DOIs
Publication statusPublished - Apr 15 2011
Externally publishedYes

Keywords

  • conjugated polymers
  • copolymerization
  • organic dyes
  • polycondensation
  • polymer solar cells

ASJC Scopus subject areas

  • Materials Chemistry
  • Polymers and Plastics
  • Organic Chemistry

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