Fast spin-flip enables efficient and stable organic electroluminescence from charge-transfer states
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Cui, L., Gillett, A., Zhang, S., Ye, H., Liu, Y., Chen, X., Lin, Z., et al. (2020). Fast spin-flip enables efficient and stable organic electroluminescence from charge-transfer states. Nature Photonics https://doi.org/10.1038/s41566-020-0668-z
© 2020, The Author(s), under exclusive licence to Springer Nature Limited. 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).
Is supplemented by: https://doi.org/10.17863/CAM.52923
External DOI: https://doi.org/10.1038/s41566-020-0668-z
This record's URL: https://www.repository.cam.ac.uk/handle/1810/310564
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