Regioselective Syntheses of Imidazo[4,5-b]pyrazin-2-ylidene-Based Chelates and Blue Emissive Iridium(III) Phosphors for Solution-Processed OLEDs

Jie Yan, Qin Xue, Hui Yang, Shek-Man Yiu, Ye-Xin Zhang*, Guohua Xie*, Yun Chi*

*Corresponding author for this work

Research output: Journal Publications and ReviewsRGC 21 - Publication in refereed journalpeer-review

30 Citations (Scopus)

Abstract

Six homoleptic Ir(III) complexes bearing imidazo-[4,5-b]pyrazin-2-ylidene chelates were successfully designed and synthesized. Narrowband blue emission (λmax = 466-485 nm) and broadened green emission (λmax = 518-532 nm) in degassed toluene solution with high photoluminescent quantum yields in the range of 75-81 and 45-48% were observed for ƒ-timpz, t2impz, and t2empz as well as m-timpz, t2impz, and t2empz, respectively. In addition, the tert-butylphenyl cyclometalate is more electron donating than N-phenyl cyclometalate and, hence, all tert-butylphenyl-substituted derivatives, that is, m- and ƒ-t2impz and m- and ƒ-t2empz, give more red-shifted emission in comparison to that of m- and ƒ-timpz. Moreover, solution-processed OLED with ƒ-t2empz (20 wt %) as the dopant gave electrophosphorescence at 474 nm with maximum external quantum efficiency (max. EQE) of 5.1%, while hyper-OLED with assistant sensitizer ƒ-t2empz (10 wt %) and the multi-resonance thermally activated delayed fluorescence emitter BCzBN (0.5 wt %) afforded narrowband emission centered at 485 nm and max. EQE up to 17.4%, confirming the high potential of this class of Ir(III) metal phosphors.
Original languageEnglish
Pages (from-to)8797-8805
JournalInorganic Chemistry
Volume61
Issue number23
Online published2 Jun 2022
DOIs
Publication statusPublished - 13 Jun 2022

Funding

This work was supported by the funding from the Innovation and Technology Fund (ITS/158/19FP), Research Grant Council (CityU 11304221), and City University of Hong Kong, Hong Kong SAR. J.Y. thanks Dr. GAN Lin for providing some initial experimental data. G.X. acknowledges the financial support from the National Natural Science Foundation of China (nos. 62175189 and 51873159).

Research Keywords

  • LIGHT-EMITTING-DIODES
  • HIGH-EFFICIENCY
  • ENERGY-TRANSFER
  • COMPLEXES
  • DOPANT

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