Bulky iridium NHC complexes for bright, efficient deep-blue OLEDs

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Four new deep-blue-emitting iridium(III) NHC complexes containing sterically demanding ligands are synthesized. The four complexes show bright, deep-blue emission, with emission maxima between 420 and 427 nm in both acetonitrile solution and 30 wt% doped films in TSPO1; the two meridional isomers showing photoluminescence quantum yields, ΦPL, in doped films of 80% and 89%. The two meridional isomers are used to assess the impact of emitters containing bulky, sterically demanding ligands on the performance of organic light-emitting diodes (OLEDs). OLEDs employing a stepped doping profile with mer-Ir(tfpi_tmBn)3 as the emitter produce the highest performing devices in this study, with these devices exhibiting deep-blue [λEL = 429 nm, CIE = (0.16, 0.08)] emission and a maximum external quantum efficiency (EQEmax) of 14.9%, which decreases to 11.7% at 100 cd m−2. The performance of the OLEDs shows very good efficiencies and moderate efficiency roll-offs in comparison to reported phosphorescent deep-blue OLEDs with CIEy ≤ 0.08, as required for commercial displays. The promising results suggest that the design strategy of adding steric bulk to blue emitting iridium complexes containing NHC ligands is a useful strategy for reducing intermolecular interactions between emitters in OLEDs.
Original languageEnglish
Article number2201495
Number of pages14
JournalAdvanced Optical Materials
Issue number2
Early online date28 Nov 2022
Publication statusPublished - 18 Jan 2023


  • Blue emission
  • Iridium
  • NHC ligands
  • Organic light-emitting diodes


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