Synthesis and characterization of cyclopentadithiophene-based low bandgap copolymers containing electron-deficient benzoselenadiazole derivatives for photovoltaic devices

I. N.Hwan Jung, Kim Hqyeon, Moo Jin Park, Bongjun Kim, Jong Hwa Park, Eunjae Jeong, Han Young Woo, Seunghyup Yoo, Hong K.U. Shim

Research output: Contribution to journalArticle

36 Citations (Scopus)

Abstract

We have synthesized two cyclopentadithiophene (CDT)-based low bandgap copolymers, poly[(4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b′] dithiophene-2,6-diyl)-alt-(benzo[c] [1,2,5]selenadiazole-4,7-diyl)] (PCBSe) and poly[(4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-0:3,4-b′]dithiophene-2, 6-diyl)-alt-(4,7dithiophen-2-yl-benzo[c][1,2,5]selenadiazole-5,5'-diyl)] (PCT2BSe), for use in photovoltaic applications. Through the internal charge transfer interaction between the electron-donating CDT unit and the electron-accepting benzoselenadiazole, we realized exceedingly low bandgap polymers with bandgaps of 1.37-1.46 eV, The UV-vis absorption maxima of PCT2BSe were subjected to larger hypsochromic shifts than those of PCBSe, because of the distorted electron donor-acceptor (D-A) structures of the PCT2BSe backbone, These results were supported by the calculations of the D-A complex using the ab initio Hartree-Fock method with a splitvalence 6-31 G* basis set. However, PCT2BSe exhibited a better molar absorption coefficient in the visible region, which can lead to more efficient absorption of sunlight. As a result, PCT2BSe blended with [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) exhibited a better photovoltaic performance than PCBSe because of the larger spectral overlap integral with respect to the solar spectrum. Furthermore, when the polymers were blended with PC71BM, PCT2BSe showed the best performance, with an open circuit voltage of 0.55 V, a short-circuit current of 6.63 mA/cm2, and a power conversion efficiency of 1.34% under air mass 1.5 global illumination conditions.

Original languageEnglish
Pages (from-to)1423-1432
Number of pages10
JournalJournal of Polymer Science, Part A: Polymer Chemistry
Volume48
Issue number6
DOIs
Publication statusPublished - 2010 Mar 15

Keywords

  • Conducting polymers
  • Conjugated polymers
  • Copolymerization

ASJC Scopus subject areas

  • Polymers and Plastics
  • Organic Chemistry
  • Materials Chemistry

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