Blue Electrophosphorescence from Iridium(III) Phosphors Bearing Asymmetric Di-N-aryl 6-(trifluoromethyl)-2H-imidazo[4,5-b]pyridin-2-ylidene Chelates

Jie Yan; Zi-Qi Feng; Yixin Wu; Dong-Ying Zhou; Shek-Man Yiu; Chin-Yiu Chan; Yi Pan; Kai Chung Lau; Liang-Sheng Liao; Yun Chi

doi:10.1002/adma.202305273

Blue Electrophosphorescence from Iridium(III) Phosphors Bearing Asymmetric Di-N-aryl 6-(trifluoromethyl)-2H-imidazo[4,5-b]pyridin-2-ylidene Chelates

Adv Mater. 2024 Apr;36(17):e2305273. doi: 10.1002/adma.202305273. Epub 2023 Sep 21.

Authors

Jie Yan¹, Zi-Qi Feng², Yixin Wu¹, Dong-Ying Zhou², Shek-Man Yiu³, Chin-Yiu Chan¹, Yi Pan³, Kai Chung Lau³, Liang-Sheng Liao², Yun Chi^{1

3}

Affiliations

¹ Department of Materials Sciences and Engineering, City University of Hong Kong, Hong Kong, Hong Kong SAR, 999077, China.
² Institute of Functional Nano and Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University, Suzhou, 215123, China.
³ Department of Chemistry and Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong, Hong Kong, Hong Kong SAR, 999077, China.

PMID: 37461316
DOI: 10.1002/adma.202305273

Abstract

Efficient blue phosphors remain a formidable challenge for organic light-emitting diodes (OLEDs). To circumvent this obstacle, a series of Ir(III)-based carbene complexes bearing asymmetric di-N-aryl 6-(trifluoromethyl)-2H-imidazo[4,5-b]pyridin-2-ylidene chelates, namely, f-ct6a‒c, are synthesized, and their structures and photophysical properties are comprehensively investigated. Moreover, these emitters can undergo interconversion in refluxing 1,2,4-trichlorobenzene, catalyzed by a mixture of sodium acetate (NaOAc) and p-toluenesulfonic acid monohydrate (TsOH·H₂O) without decomposition. All Ir(III) complexes present good photoluminescence quantum yield (Φ_PL = 83-88%) with peak maximum (max.) at 443-452 nm and narrowed full width at half maximum (FWHM = 66-73 nm). Among all the fabricated OLED devices, f-ct6b delivers a max. external quantum efficiency (EQE) of 23.4% and Commission Internationale de L'Eclairage CIE_x _, _y coordinates of (0.14, 0.12), whereas the hyper-OLED device based on f-ct6a and 5H,9H,11H,15H-[1,4] benzazaborino [2,3,4-kl][1,4]benzazaborino[4',3',2':4,5][1,4]benzazaborino[3,2-b]phenazaborine-7,13-diamine, N7,N7,N13,N13,5,9,11,15-octaphenyl (ν-DABNA) exhibits max. EQE of 26.2% and CIE_x _, _y of (0.12, 0.13). Finally, the corresponding tandem OLED with f-ct6b as dopant gives a max. luminance of over 10 000 cd m^-2 and max. EQE of 42.1%, confirming their candidacies for making true-blue OLEDs.

Keywords: carbene; cyclometalate; hyperphosphorescence; iridium; organic light‐emitting diodes.

Abstract

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