Exploring the mechanisms of exciton diffusion improvement in ternary polymer solar cells: From ultrafast to ultraslow temporal scale

Kang Ning Zhang, Zhi Nan Jiang, Tong Wang, Jia Wei Qiao, Lin Feng, Chao Chao Qin, Hang Yin, Shu Kong SO, Xiao Tao Hao*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)

Abstract

Long-range exciton diffusion on picosecond time scale, which serves to efficient charge separation at the donor/acceptor (D/A) interfaces, has been regarded as a key step for the working mechanisms of organic photovoltaics. Rationally understanding and manipulating this vital process over a wide temporal scale remains some challenges, especially in ternary organic solar cells (OSCs). Herein, we reveal how exciton migration behaviors are reasonably improved and maintained relying on the simultaneously enhanced efficiency and thermal stability in the PM6:IT4F:PC71BM and PM6:BTP-4Cl:PC71BM ternary devices. Two separate factors can be responsible for these benefits: (1) the coexistence of dual Förster-type energy transfer (FRET) can contribute to the directed exciton diffusion and rapidly quench the highly excited states to stabilize the “energy donors”. (2) The more favorable multi-length scale morphologies optimized by the addition of guest PC71BM yield the plentiful interfacial region to shorten the real distance of diffusion process and boost the stability of microstructure. In particular, the diffusion lengths > 10 nm of IT4F singlet excitons induced by dual FRET effects were obtained by employing the exciton-exciton annihilation strategy. These experimental results open a novel horizon for further strengthening efficiency and stability of ternary OSCs from the perspective of improving exciton diffusion.

Original languageEnglish
Article number105513
JournalNano Energy
Volume79
DOIs
Publication statusPublished - Jan 2021

Scopus Subject Areas

  • Renewable Energy, Sustainability and the Environment
  • Materials Science(all)
  • Electrical and Electronic Engineering

User-Defined Keywords

  • Exciton diffusion
  • Förster resonance energy transfer
  • Morphology control
  • Ternary organic photovoltaics
  • Thermal stability

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