Abstract
Simultaneously achieving both a high efficiency and long lifetime in deep-blue organic light-emitting diodes is challenging. Here we report thermally activated delayed fluorescence (TADF) organic light-emitting diodes that aim to meet this goal by combining a new design of blue TADF materials with a triplet-exciton recycling protocol. Two TADF materials, one distributing and one emitting, were doped into a host to form triplet-exciton-distributed TADF devices. The singlet excitons were transferred from the host to the emitter via the distributing TADF material by cascade energy transfer, whereas the triplet excitons were transferred to the emitter as singlet excitons by a triplet-exciton recycling process between the low-triplet-energy host and the distributing TADF material. The resulting triplet-exciton-distributed TADF devices achieved a high external quantum efficiency of 33.5 ± 0.1, a colour coordinate corrected current efficiency over 400 cd A–1, a lifetime of >5,000 h and a y colour coordinate below 0.10.
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Acknowledgements
This material is based on work supported in the part by the Samsung Advanced Institute of Technology (SAIT). We thank S. Park for helpful discussions and support with the nuclear magnetic resonence spectrometer.
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S.O.J. and K.H.L. contributed equally to this work. H.L. performed the calculations. S.O.J. designed the molecules and assessed the synthetic feasibility of molecular candidates from the calculations. S.O.J. and Y.S.C. synthesized the compounds and analysed the spectroscopic data. K.H.L. fabricated and tested devices for bottom-emitting devices and characterized the electrical and optical properties of the thin films. J.S.K. performed the anisotropic horizontal orientation study. S.-G.I. and J.S.K. fabricated and characterized electrical and optical properties of the top-emitting devices. J.W.K. performed optical simulations and optimized the device structures for the top-emitting devices. S.O.J., K.H.L. and J.Y.L. wrote the first version of the manuscript. All authors contributed to the discussion, writing and editing of the manuscript. S.K. organized the project. H.C. supervised the computational chemistry study. J.Y.L. supervised the device fabrication and the project.
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S.O.J., Y.S.C., H.L and S.-G.I. have filed a patent application (condensed cyclic compound and organic light-emitting device including the same; US patent application no. US 16/244,431; 10 January 2019). S.O.J, K.H.L, J.S.K, S.-G.I., Y.S.C, J.W.K, H.L, H.C and J.Y.L have submitted a patent application for this work, which was assigned to Samsung Electronics and Sungkyunkwan University.
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Synthesis, Experimental, Methods for Device fabrication and measurements, Supplementary Figs. 1–15, Tables 1–6 and references.
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Jeon, S.O., Lee, K.H., Kim, J.S. et al. High-efficiency, long-lifetime deep-blue organic light-emitting diodes. Nat. Photonics 15, 208–215 (2021). https://doi.org/10.1038/s41566-021-00763-5
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DOI: https://doi.org/10.1038/s41566-021-00763-5
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