Citation: Hao-Sen LIAO, Jun-Yi GAN, Xin XIA, Yong-Xu HU, Dong-Dong XIE, Dong-Yu ZHANG, Xiao LI. Synthesis of Fluorinated Diphenylbenzimidazole Iridium Complexes Based on Different Auxiliary Ligands and Solution-Processed Electroluminescent Devices[J]. Chinese Journal of Inorganic Chemistry, ;2022, 38(3): 399-406. doi: 10.11862/CJIC.2022.052 shu

Synthesis of Fluorinated Diphenylbenzimidazole Iridium Complexes Based on Different Auxiliary Ligands and Solution-Processed Electroluminescent Devices

1.
School of Chemical Engineering, University of Science and Technology Liaoning, Anshan, Liaoning 114051, China
2.
Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou, Jiangsu 215123, China

Corresponding author: Xiao LI, lixiao@ustl.edu.cn
Received Date: 13 September 2021
Revised Date: 30 November 2021

Figures(6)

Nine benzimidazole-iridium(Ⅲ) complexes Ir-1a-Ir-3c were designed and synthesized by using fluorinated diphenylbenzimidazole derivatives as the main ligands and acetylacetone (corresponding complexes: Ir-1a-Ir-3a), 2-pyridine carboxylic acid (corresponding complexes: Ir-1b-Ir-3b), and 2-(5-trifluoromethyl-2H-[1,2,4]triazol-3-yl)-pyridine (tftp, corresponding complexes: Ir-1c-Ir-3c) as the auxiliary ligands, respectively. The effects of the degree of fluorination and different auxiliary ligands on the photophysical properties of the corresponding iridium complexes were investigated. The maximum emission wavelengths of the nine complexes were located in a range of 487-502 nm, showing green to blue-green phosphorescent emission. The largest blue shift was observed for the complexes based on tftp as an auxiliary ligand, especially for Ir-1c compared to Ir-1a with a blue shift of 17 nm. The nine complexes showed excellent photoluminescence efficiencies of 52%-87%. Furthermore, all iridium(Ⅲ) complexes exhibited good thermal stability, and the thermal decomposition temperatures were 313-390 ℃ (5% weight loss). Four iridium complexes of Ir-1c, Ir-2c, Ir-3c, and Ir-2b were selected for spin-coated electroluminescent devices with a doping concentration of 9%. The results show that the change of the primary and secondary ligands has a large effect on the luminescent color and luminescent efficiency of the light-emitting diodes. The Ir-3c-doped spin-coated devices had the highest device efficiency with an external quantum efficiency of 10.2%, a current efficiency of up to 30.3 cd·A^-1, and a maximum power efficiency of 14.7 lm·W^-1.
- benzimidazole,
- iridium complexes,
- fluorine chemistry,
- auxiliary ligands,
- solution spin-coating
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