Design of wide-bandgap polymers with deeper ionization potential enables efficient ternary non-fullerene polymer solar cells with 13% efficiency

Delong Liu, Ying Zhang, Lingling Zhan, Tsz Ki Lau, Hang Yin, Patrick W.K. Fong, Shu Kong SO, Shaoqing Zhang, Xinhui Lu*, Jianhui Hou, Hongzheng Chen, Wai Yeung WONG, Gang Li

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)

Abstract

Two regioisomeric wide-bandgap (WBG) polymers, PDBT(E)BTz-p and PDBT(E)BTz-d, with different nitrogen topologies along the conjugated backbone were developed and applied in non-fullerene polymer solar cells. Both polymers exhibit deeper ionization potential (IP) enabled by the synergistic electron-withdrawing effect of chlorine atoms and ester substituents. The effects of different nitrogen topologies on polymeric backbone linearity and optoelectronic and photovoltaic properties are systematically investigated. When blended with the electron acceptor IT-4F, the PDBT(E)BTz-p-based device delivers a PCE of 6.96% with a high VOC of 0.98 V and a low energy loss of 0.55 eV, while the PDBT(E)BTz-d-based device exhibits a higher PCE of 7.81% with an improved FF. Furthermore, PDBT(E)BTz-d is found to be effective as the third component in a binary PBDB-T-SF:IT-4F system to enhance device efficiencies from 12.1% for the binary device to 13.4% for the ternary device with 5 wt% PDBT(E)BTz-d relative to PBDB-T-SF. It is observed that an internal Förster resonance energy transfer (FRET) between PDBT(E)BTz-d and PBDB-T-SF gives rise to the improvement of external quantum efficiency and JSC. These results demonstrate that the WBG polymer featuring deeper IP can not only enhance the VOC but can also act as a sensitizer to transfer energy through the FRET mechanism toward highly efficient ternary PSCs. In addition, this contribution provides a new idea for the design and synthesis of conjugated polymers for organic electronics.

Original languageEnglish
Pages (from-to)14153-14162
Number of pages10
JournalJournal of Materials Chemistry A
Volume7
Issue number23
DOIs
Publication statusPublished - 2019

Scopus Subject Areas

  • Chemistry(all)
  • Renewable Energy, Sustainability and the Environment
  • Materials Science(all)

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