Thiophene rings improve the device performance of conjugated polymers in polymer solar cells with thick active layers

C. Duan, K. Gao, F.J.M. Colberts, F. Liu, S.C.J. Meskers, M.M. Wienk, R.A.J. Janssen

Research output: Contribution to journalArticleAcademicpeer-review

36 Citations (Scopus)
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Abstract

Developing novel materials that tolerate thickness variations of the active layer is critical to further enhance the efficiency of polymer solar cells and enable large-scale manufacturing. Presently, only a few polymers afford high efficiencies at active layer thickness exceeding 200 nm and molecular design guidelines for developing successful materials are lacking. It is thus highly desirable to identify structural factors that determine the performance of semiconducting conjugated polymers in thick-film polymer solar cells. Here, it is demonstrated that thiophene rings, introduced in the backbone of alternating donor–acceptor type conjugated polymers, enhance the fill factor and overall efficiency for thick (>200 nm) solar cells. For a series of fluorinated semiconducting polymers derived from electron-rich benzo[1,2-b:4,5-b′]dithiophene units and electron-deficient 5,6-difluorobenzo[2,1,3]thiazole units a steady increase of the fill factor and power conversion efficiency is found when introducing thiophene rings between the donor and acceptor units. The increased performance is a synergistic result of an enhanced hole mobility and a suppressed bimolecular charge recombination, which is attributed to more favorable polymer chain packing and finer phase separation.

Original languageEnglish
Article number1700519
Number of pages11
JournalAdvanced Energy Materials
Volume7
Issue number19
DOIs
Publication statusPublished - 11 Oct 2017

Keywords

  • active layer
  • fill factor
  • polymer solar cells
  • thick film
  • thiophene ring

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