Journal
ACS APPLIED MATERIALS & INTERFACES
Volume 13, Issue 13, Pages 15437-15447Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsami.1c00238
Keywords
iridium; carbene; blue; organic light-emitting diodes; cyclometalate
Funding
- Ministry of Science and Technology (MOST)
- Innovation and Technology Fund [ITS/158/19FP]
- Research Grant Council [N_CityU/19]
- City University of Hong Kong, Hong Kong SAR
- Australian Research Council Discovery Early Career Researcher Award (ARC DECRA) [DE190100144]
- National Computational Infrastructure of Australia [12587]
- Australian Research Council [DE190100144] Funding Source: Australian Research Council
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A new class of bis-tridentate Ir(III) complexes was synthesized and their emission tuning between the ultraviolet and blue region was rationalized using time-dependent density functional theory (TD-DFT) approaches. A highly efficient blue emitter was successfully synthesized and used to fabricate practical blue-emitting OLEDs with superior performance.
A new class of bis-tridentate Ir(III) complexes (Dap-1-4) was synthesized using carbene pincer pro-chelates PC1 center dot H-3(PF6)(2) or PC2 center dot H-3(PF6)(2) with either imidazolylidene or imidazo[4,5-b]pyridin-2-ylidene appendages, together with a second cyclometalating 2,6-diaryoxypyridine chelate, L1H(2) and L2H(2), differed by a NMe2 donor at the central pyridinyl fragment. The respective emission tuning between the ultraviolet and blue region was rationalized using time-dependent density functional theory (TD-DFT) approaches. Next, a highly efficient blue emitter (Dap-5) was synthesized by concomitant addition of two methyl groups and a single CF3 substituent at the central phenyl and peripheral imidazo[4,5-b]pyridin-2-ylidene entities of the carbene pincer chelate, respectively. The organic light-emitting diode (OLED) device with 15 wt % Dap-5 in DPEPO shows electroluminescence at 468 nm and with CIE (0.14, 0.15) and a max external quantum efficiency (max EQE) of 16.8% with low efficiency roll-off (EQE of 14.4% at 1000 cd m(-2)); the latter is attributed to the relatively shortened triplet excited-state radiative lifetime. These results highlight the adequateness of bis-tridentate Ir(III) phosphors in fabrication of practical blue-emitting OLEDs.
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