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

Campbell F. R. Mackenzie; Le Zhang; David B. Cordes; Alexandra M. Z. Slawin; Ifor D. W. Samuel; Eli Zysman-Colman

doi:10.1002/adom.202201495

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

Campbell F. R. Mackenzie, Le Zhang, David B. Cordes, Alexandra M. Z. Slawin, Ifor D. W. Samuel^*, Eli Zysman-Colman^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

Abstract

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, Φ_PL, 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 [λ_EL = 429 nm, CIE = (0.16, 0.08)] emission and a maximum external quantum efficiency (EQE_max) 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 CIE_y ≤ 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 language	English
Article number	2201495
Number of pages	14
Journal	Advanced Optical Materials
Volume	11
Issue number	2
Early online date	28 Nov 2022
DOIs	https://doi.org/10.1002/adom.202201495
Publication status	Published - 18 Jan 2023

Keywords

Blue emission
Iridium
NHC ligands
Organic light-emitting diodes

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Mackenzie-2022-Bulky-iridium-NHC-complexes-01495-CCBY
Copyright © 2022 The Authors. Advanced Optical Materials published by Wiley-VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
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Cite this

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

abstract = "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.",

keywords = "Blue emission, Iridium, NHC ligands, Organic light-emitting diodes",

author = "Mackenzie, {Campbell F. R.} and Le Zhang and Cordes, {David B.} and Slawin, {Alexandra M. Z.} and Samuel, {Ifor D. W.} and Eli Zysman-Colman",

note = "Funding: C.F.R.M. and L.Z. contributed equally to this work. The authors thank the University of St Andrews and EPSRC for financial support (grants EP/P010482/1 and EP/M02105X/1, EP/K503940/1). The authors thank Umicore AG for the gift of materials. E.Z.-C. was a Royal Society Leverhulme Trust Senior Research fellow (SRF\R1\201089).",

year = "2023",

month = jan,

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doi = "10.1002/adom.202201495",

language = "English",

volume = "11",

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AU - Mackenzie, Campbell F. R.

AU - Zhang, Le

AU - Cordes, David B.

AU - Slawin, Alexandra M. Z.

AU - Samuel, Ifor D. W.

AU - Zysman-Colman, Eli

N1 - Funding: C.F.R.M. and L.Z. contributed equally to this work. The authors thank the University of St Andrews and EPSRC for financial support (grants EP/P010482/1 and EP/M02105X/1, EP/K503940/1). The authors thank Umicore AG for the gift of materials. E.Z.-C. was a Royal Society Leverhulme Trust Senior Research fellow (SRF\R1\201089).

PY - 2023/1/18

Y1 - 2023/1/18

N2 - 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.

AB - 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.

KW - Blue emission

KW - Iridium

KW - NHC ligands

KW - Organic light-emitting diodes

UR - https://doi.org/10.26434/chemrxiv-2022-gwf1r

U2 - 10.1002/adom.202201495

DO - 10.1002/adom.202201495

M3 - Article

SN - 2195-1071

VL - 11

JO - Advanced Optical Materials

JF - Advanced Optical Materials

IS - 2

M1 - 2201495

ER -

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

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Keywords

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