Rational Tuning of Bis-Tridentate Ir(III) Phosphors to Deep-Blue with High Efficiency and Sub-microsecond Lifetime

Wun-Shan Tai; Premkumar Gnanasekaran; Yi-Yang Chen; Wen-Yi Hung; Xiuwen Zhou; Tai-Che Chou; Gene-Hsiang Lee; Pi-Tai Chou; Caifa You; Yun Chi

doi:10.1021/acsami.1c00238

Rational Tuning of Bis-Tridentate Ir(III) Phosphors to Deep-Blue with High Efficiency and Sub-microsecond Lifetime

ACS Appl Mater Interfaces. 2021 Apr 7;13(13):15437-15447. doi: 10.1021/acsami.1c00238. Epub 2021 Mar 24.

Authors

Wun-Shan Tai¹, Premkumar Gnanasekaran¹, Yi-Yang Chen², Wen-Yi Hung², Xiuwen Zhou³, Tai-Che Chou⁴, Gene-Hsiang Lee⁴, Pi-Tai Chou⁴, Caifa You⁵, Yun Chi^{1

5}

Affiliations

¹ Department of Chemistry and Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing Hua University, Hsinchu 30013, Taiwan.
² Department of Optoelectronics and Materials Technology, National Taiwan Ocean University, Keelung 20224, Taiwan.
³ School of Mathematics and Physics, The University of Queensland, Brisbane, Queensland 4072, Australia.
⁴ Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan.
⁵ Department of Chemistry, Department of Materials Sciences and Engineering, and Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong, Kowloon 999077, Hong Kong SAR, China.

PMID: 33759493
DOI: 10.1021/acsami.1c00238

Abstract

A new class of bis-tridentate Ir(III) complexes (Dap-1-4) was synthesized using carbene pincer pro-chelates PC1·H₃(PF₆)₂ or PC2·H₃(PF₆)₂ with either imidazolylidene or imidazo[4,5-b]pyridin-2-ylidene appendages, together with a second cyclometalating 2,6-diaryoxypyridine chelate, L1H₂ and L2H₂, 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.

Keywords: blue; carbene; cyclometalate; iridium; organic light-emitting diodes.