Efficient Exciton Diffusion in Organic Bilayer Heterojunctions with Nonfullerene Small Molecular Acceptors

Tack Ho Lee, Song Yi Park, Won Woo Park, Xiaoyan Du, Jae Hoon Son, Ning Li, Oh Hoon Kwon, Han Young Woo, Christoph J. Brabec, Jin Young Kim

Research output: Contribution to journalArticlepeer-review

46 Citations (Scopus)


Solution-processed bilayer organic solar cells (OSCs) with high performance are demonstrated for nonfullerene small molecular acceptors (NFAs). Unlike fullerene acceptors, NFAs show significant spectral overlap between their absorption and the photoluminescence (PL) of a polymer donor, which makes the design of an efficient exciton-harvesting bilayer heterojunction possible. Efficient exciton diffusion in the organic bilayer heterojunction is realized by long-range energy transfer between a polymer donor and NFAs. We observed efficient exciton diffusion from the polymer/NFA bilayer heterojunctions via thickness-dependent PL quenching and time-resolved PL measurements. Despite the strongly reduced donor-acceptor interface area, a substantial density of charge-transfer states is observed for the polymer/NFA bilayer heterojunctions by electroluminescence measurements. Overall, polymer/NFA bilayer heterojunction OSCs demonstrate a power conversion efficiency of 9%-10%, which is comparable to the photovoltaic performance of bulk heterojunction OSCs, with the additional advantage of simplified microstructure formation.

Original languageEnglish
Pages (from-to)1628-1635
Number of pages8
JournalACS Energy Letters
Issue number5
Publication statusPublished - 2020 May 8

ASJC Scopus subject areas

  • Chemistry (miscellaneous)
  • Renewable Energy, Sustainability and the Environment
  • Fuel Technology
  • Energy Engineering and Power Technology
  • Materials Chemistry


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