Efficient doublet emission from radical materials and devices
State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Qianjin Avenue 2699, Changchun, 130012, P. R. China
(E-mail address: email@example.com)
A new kind of OLEDs based on radicals, in which the emission comes from a spin doublet rather than from a singlet or triplet exciton was developed. The emission process is spin-allowed in these systems, usefully, the classical triplet-limiting efficiency for OLEDs is circumvented for doublets . After continually optimizing materials and devices [2,3], a D-A type luminescent radical emitter, TTM-3NCz, was used as the emitter of an OLED with a maximum external quantum efficiency of 27 %—the highest reported value for deep-red and infrared LEDs .
There is only one family of room-temperature luminescent radicals, triphenylmethyl radicals, so far. We synthesized a new stable room-temperature luminescent radical, (N-carbazolyl)bis(2,4,6-tirchlorophenyl)methyl radical (CzBTM), which is beyond the family of triphenylmethyl radicals. A new family of stable luminescent radicals based on CzBTM is anticipated .
 Q.M. Peng, A. Obolda, M. Zhang, F. Li, Organic Light-Emitting Diodes Using a Neutral pi Radical as Emitter: The Emission from a Doublet, Angew. Chem.-Int. Edit., 54 (2015) 7091-7095.
 Y. Gao, W. Xu, H. Ma, A. Obolda, W. Yan, S. Dong, M. Zhang, F. Li, Novel Luminescent Benzimidazole-Substituent Tris(2,4,6-trichlorophenyl)methyl Radicals: Photophysics, Stability, and Highly Efficient Red-Orange Electroluminescence, Chem. Mat., 29 (2017) 6733-6739.
 A. Obolda, X. Ai, M. Zhang, F. Li, Up to 100% Formation Ratio of Doublet Exciton in Deep-Red Organic Light-Emitting Diodes Based on Neutral pi-Radical, ACS applied materials & interfaces, 8 (2016) 35472-35478.
 X. Ai, E.W. Evans, S. Dong, A.J. Gillett, H. Guo, Y. Chen, T.J.H. Hele, R.H. Friend, F. Li, Efficient radical-based light-emitting diodes with doublet emission, Nature, 563 (2018) 536-540.
 X. Ai, Y. Chen, Y. Feng, F. Li, A Stable Room-Temperature Luminescent Biphenylmethyl Radical, Angew. Chem.-Int. Edit., 57 (2018) 2869-2873.