![]() Carbazole is usually utilized to construct organic functional materials due to its good carriers transporting ability, good thermal stability and weak electron-donating property. Up to now, various organic molecules based on anthracene, fluorine, pyrene, fluoranthene, oxadiazoles, phosphineoxide, carbazole, triphenylamine and phenanthroimidazole have been synthesized and employed as deep blue emitters for efficient non-doped OLED. ![]() replaced the triphenylamine by lower electron-donating ability of carbazole moiety, achieving CIEy value of 0.077 closing to the standard of EBU (y = 0.06). obtained a twisted donor-acceptor (D-A) triphenylamine-imidazole deep blue emitter of TPA-PPI with the y value of OLED approached to 0.11. reported a series of bipolar blue emitters containing triphenylamine as electron-donor and benzimidazole as electron-acceptor, and the non-doped OLED exhibited CIE with y value in range of 0.12–0.23. However, the bipolar deep blue materials always do not match the standard of European Broadcasting Union (EBU) with the Commission International de L'Eclairage (CIE) coordinates of (0.15, 0.06) due to the fluorescence bathochromic-shift. Therefore, the exploration of highly efficient deep blue emitter with low efficiency roll-off and high color quality with CIEy<0.1 is meaningful and pressing.Ĭonstructing bipolar molecules is an effective strategy to develop highly efficient deep blue emitting materials, , ]. However, the blue phosphorescent complex contains the heavy metal of Ir/Pt, which suffers from high cost and unsustainable development, while the serious efficiency roll-off of blue TADF material need be resolved further due to the low reverse intersystem crossing (RISC) rate, , ]. Subsequently, blue phosphorescent materials and blue thermally activated delayed fluorescence (TADF) materials were developed gradually. The study find that the intrinsic wide band-gap of deep blue material with relatively lower highest occupied molecular orbital (HOMO) energy levels and higher lowest unoccupied molecular orbital (LUMO) energy levels is the reason of low efficiency compared to red and green materials. Especially for deep blue emitter with CIEy<0.1, that is important for high color purity display. However, the application of blue emitter is behind to red and green due to the low efficiency and poor stability, , ]. Among them, red and green emitters almost satisfy the commercial needs in efficiency and stability. As we know, red, green and blue emitters are the three basic colors for full-colors display, ,, , ]. Organic light-emitting diodes (OLED) has attracted strong attention due to its huge application in solid-state lighting and flat-panel display. The small CIEy value of 0.04 and 0.05 obtained in this work are very significant for high color purity full-color display, which is also among the best CIEy value results ever reported as deep blue bipolar emitters. ![]() Besides, the deep blue emission peak of 412 nm with Commission Internationale de l’Eclairage (CIE) coordinate of (0.16, 0.04), and 420 nm with CIE coordinate of (0.16, 0.05) were also realized. The non-doped fluorescent OLED devices using the two compounds as emitting layers are designed among which the devices achieved the maximum external quantum efficiency of 1.66% and 1.56%, respectively. Single carrier devices were also fabricated to show that two compounds have good bipolar carrier transport characteristic. The photophysical, thermal and electrochemical properties are investigated with high decomposition temperature up to 391 and 380 ☌, and strong deep blue emission. Two fluorescent emitters based imidazole and carbazole were synthesized for deep blue emission organic light-emitting diodes (OLED) with non-doped structure.
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