Fast spin-flip enables efficient and stable organic electroluminescence from charge-transfer states

Lin Song Cui, Alexander J. Gillett, Shou Feng Zhang, Hao Ye, Yuan Liu, Xian Kai Chen, Ze Sen Lin, Emrys W. Evans, William K. Myers, Tanya K. Ronson, Hajime Nakanotani, Sebastian Reineke, Jean Luc Bredas, Chihaya Adachi, Richard H. Friend

Research output: Contribution to journalArticle

Abstract

A spin-flip from a triplet to a singlet excited state, that is, reverse intersystem crossing (RISC), is an attractive route for improving light emission in organic light-emitting diodes, as shown by devices using thermally activated delayed fluorescence (TADF). However, device stability and efficiency roll-off remain challenging issues that originate from a slow RISC rate (kRISC). Here, we report a TADF molecule with multiple donor units that form charge-resonance-type hybrid triplet states leading to a small singlet–triplet energy splitting, large spin–orbit couplings, and a dense manifold of triplet states energetically close to the singlets. The kRISC in our TADF molecule is as fast as 1.5 × 107 s−1, a value some two orders of magnitude higher than typical TADF emitters. Organic light-emitting diodes based on this molecule exhibit good stability (estimated T90 about 600 h for 1,000 cd m−2), high maximum external quantum efficiency (>29.3%) and low efficiency roll-off (<2.3% at 1,000 cd m−2).

Original languageEnglish
JournalNature Photonics
DOIs
Publication statusAccepted/In press - 2020

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics

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    Cui, L. S., Gillett, A. J., Zhang, S. F., Ye, H., Liu, Y., Chen, X. K., Lin, Z. S., Evans, E. W., Myers, W. K., Ronson, T. K., Nakanotani, H., Reineke, S., Bredas, J. L., Adachi, C., & Friend, R. H. (Accepted/In press). Fast spin-flip enables efficient and stable organic electroluminescence from charge-transfer states. Nature Photonics. https://doi.org/10.1038/s41566-020-0668-z