Cohosts with efficient host-to-emitter energy transfer for stable blue phosphorescent organic light-emitting diodes

Ihn, Soo‐Ghang; Kwon, Eun Suk; Jung, Yongsik; Kim, Jong Soo; Nam, Sungho; Kim, Sangmo; Jeon, Soon Ok; Chung, Yeon Sook; Park, Sang-Ho; Huh, Dal Ho; Kim, Hyun Jung; Kang, Hyung Seok; Lee, Namheon; Bae, Hye Jin; Choi, Hye Jung

doi:10.1039/d1tc04680b

Cited by 11 publications

(2 citation statements)

References 35 publications

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“…This is because the TADF material’s strong intramolecular charge transfer characteristics lead to red-shifted emission behavior, which in turn results in higher bandgap and triplet energy characteristics. These higher energy values can cause some reduction in the device stability of blue TADF OLEDs 6 , 8 . As a result, phosphorescence and TADF materials have emerged as potential candidates for deep blue OLEDs because of their longer device lifetime and higher color purity.…”

Section: Introductionmentioning

confidence: 99%

“…As a result, phosphorescence and TADF materials have emerged as potential candidates for deep blue OLEDs because of their longer device lifetime and higher color purity. Later, Choi et al reported a long-lifetime blue phosphorescent OLED employing the CN-Ir(III) dopant 8 . This device exhibited LT 95 of 232 h at an initial luminescence of 500 nits with a maximum EQE of 25.1% by using an optimized exciplex host combination system, which could have good charge balance and efficient energy transfer characteristics.…”

Section: Introductionmentioning

confidence: 99%

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Modified t-butyl in tetradentate platinum (II) complexes enables exceptional lifetime for blue-phosphorescent organic light-emitting diodes

Jung,

Lee,

Muruganantham

et al. 2024

Nat Commun

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In blue phosphorescent dopants, the tetradentate platinum(II) complex is a promising material showing high efficiency and stability in devices. However, metal-metal-to-ligand charge transfer (MMLCT) formation leads to low photo-luminescence quantum yields (PLQYs), wide spectra, and intermolecular interaction. To suppress MMLCT, PtON-tb-TTB and PtON-tb-DTB are designed using theoretical simulation by modifying t-butyl in PtON-TBBI. Both materials effectively suppress MMLCT and exhibit high PLQYs of 99% and 78% in 5 wt% doped film, respectively. The PtON-tb-TTB and PtON-tb-DTB devices have maximum external quantum efficiencies of 26.3% and 20.9%, respectively. Additionally, the PtON-tb-DTB device has an extended lifetime of 169.3 h with an initial luminescence of 1200 nit, which is 8.5 times greater than the PtON-TBBI device. Extended lifetime because of suppressed MMLCT and smaller displacement between the lowest triplet and triplet metal-centered states compared to other dopants. The study provides an effective approach to designing platinum(II) complexes for long device lifetimes.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Modified t-butyl in tetradentate platinum (II) complexes enables exceptional lifetime for blue-phosphorescent organic light-emitting diodes

Jung,

Lee,

Muruganantham

et al. 2024

Nat Commun

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Role of Tailoring Exciplex‐Forming Cohosts in the Longevity of Blue Phosphorescent Organic Light‐Emitting Diodes

Lee,

Jo,

Kim

et al. 2024

Adv Funct Materials

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Although exciplex hosts have been used to enhance the operational lifetime of blue phosphorescent organic light‐emitting diodes, their detailed design rule has not been established because of their unresolved degradation. In this work, the underlying mechanisms involved in device degradation are investigated, focusing on the tailor‐tuning effect of the exciplex host to maximize the device's lifetime with a given phosphorescent dopant. Analysis of trap dynamics shows that the stability improvement caused by adding an electron‐donating unit to the N‐type host does not originate from the stable positive polaron state. It is found that the exciplex host modified with minor substituents opens extra pathways for polaron transport and exciton generation rather than chemical stability, resulting in the spatial dispersion of polarons and excitons. The dispersion of excitons and polarons, in turn, enhances the recombination coefficient and suppresses exciton–exciton and exciton–polaron bimolecular interactions, enabling further improved device stability. With comprehensive analysis, a perspective on the role of the host in the degradation mechanism is presented.

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Blue Electrophosphorescence from Iridium(III) Phosphors Bearing Asymmetric Di‐N‐aryl 6‐(trifluoromethyl)‐2H‐imidazo[4,5‐b]pyridin‐2‐ylidene Chelates

Yan

Feng

et al. 2023

Advanced Materials

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Efficient blue phosphors remain as the formidable challenges for organic light‐emitting diodes (OLEDs). To circumvent this obstacle, a series of Ir(III) based carbene complexes bearing asymmetric di‐N‐aryl 6‐(trifluoromethyl)‐2H‐imidazo[4,5‐b]pyridin‐2‐ylidene chelates, namely, f‐ct6a ‒ c, were synthesized and their structures and photophysical properties were comprehensively investigated. Moreover, these emitters can undergo interconversion in refluxing 1,2,4‐trichlorobenzene, catalyzed by a mixture of sodium acetate (NaOAc) and p‐toluenesulfonic acid monohydrate (TsOH·H2O) without decomposition. All Ir(III) complexes present good photoluminescence quantum yield (ΦPL = 83 – 88%) with peak maximum (max.) at 443 ‒ 452 nm and narrowed full width at half maximum (FWHM = 66 – 73 nm). Among all fabricated OLED devices, f‐ct6b delivered a max. external quantum efficiency (EQE) of 23.4% and Commission Internationale de L'Eclairage CIE(x,y) coordinates of (0.14, 0.12), whereas the hyper‐OLED device based on f‐ct6a and 5H,9H,11H,15H‐[1,4] benzazaborino [2,3,4‐kl][1,4]benzazaborino[4′,3′,2′:4,5][1,4]benzazaborino[3,2‐b]phenazaborine‐7,13‐diamine, N7,N7,N13,N13,5,9,11,15‐octaphenyl (ν‐DABNA) exhibited max. EQE of 26.2% and CIE(x,y) of (0.12, 0.13). Finally, the corresponding tandem OLED with f‐ct6b as dopant gave a max. luminance of over 10000 cd⋅m‒2 and max. EQE of 42.1%, confirming their candidacies for making true‐blue OLEDs.This article is protected by copyright. All rights reserved

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Cohosts with efficient host-to-emitter energy transfer for stable blue phosphorescent organic light-emitting diodes

Cited by 11 publications

References 35 publications

Modified t-butyl in tetradentate platinum (II) complexes enables exceptional lifetime for blue-phosphorescent organic light-emitting diodes

Modified t-butyl in tetradentate platinum (II) complexes enables exceptional lifetime for blue-phosphorescent organic light-emitting diodes

Role of Tailoring Exciplex‐Forming Cohosts in the Longevity of Blue Phosphorescent Organic Light‐Emitting Diodes

Blue Electrophosphorescence from Iridium(III) Phosphors Bearing Asymmetric Di‐N‐aryl 6‐(trifluoromethyl)‐2H‐imidazo[4,5‐b]pyridin‐2‐ylidene Chelates

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