Blue iridium complexes as electron trapping sites and efficient recombination centres in poly(N-vinylcarbazole) seen by spectrally resolved thermoluminescence

Glowacki, Ireneusz; Szamel, Zbigniew; Wiosna-Sałyga, Gabriela

doi:10.1016/j.synthmet.2016.06.015

Cited by 5 publications

(2 citation statements)

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“…It also reflects in isothermal spectra of emitted light at temperatures corresponding to TL maxima ( Figure 8 c). Accordingly, incorporation of any dopant into PVK results in disappearing of the short-wavelength emission, that is associated with the singlet excimers of carbazole groups (band with λ max ~410 nm) and the monomeric triplet excitons (band with λ max ~430 nm) ( Figure 8 c) [ 30 ]. Furthermore, PVK characterizes more intensive and broad emission, with the maximum at 530 nm, that is derived from the low energetic triplet excimers of fully overlapped carbazole groups [ 31 ].…”

Section: Resultsmentioning

confidence: 99%

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Effect of TADF Assistance on Performance Enhancement in Solution Processed Green Phosphorescent OLEDs

et al. 2021

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Many methods have been proposed to increase the efficiency of organic electroluminescent materials applied as an emissive layer in organic light emitting diodes (OLEDs). Herein, we demonstrate enhancement of electroluminescence efficiency and operational stability solution processed OLEDs by employing thermally activated delayed fluorescence (TADF) molecules as assistant dopants in host-guest systems. The TADF assistant dopant (SpiroAC–TRZ) is used to facilitate efficient energy transfer from host material poly(N–vinylcarbazole) (PVK) to a phosphorescent Ir(III) emitter. We present the analysis of energy transfer and charge trapping—two main processes playing a crucial role in light generation in host–guest structure OLEDs. The investigation of photo-, electro- and thermoluminescence for the double-dopant layer revealed that assistant dopant does not only harvest and transfer the electrically generated excitons to phosphorescent emitter molecules but also creates exciplexes. The triplet states of formed PVK:SpiroAC–TRZ exciplexes are involved in the transport process of charge carriers and promote long–range exciton energy transfer to the emitter, improving the efficiency of electroluminescence in a single emissive layer OLED, resulting in devices with luminance exceeding 18 000 cd/m2 with a luminous efficiency of 23 cd/A and external quantum efficiency (EQE) of 7.4%.

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Section: Resultsmentioning

confidence: 99%

“…The efficiency of Förster energy transfer from the donor to the acceptor molecules is estimated as follows: [ 41 , 42 ]

where

—the average separation distance between the donor and the acceptor molecules, estimated pursuant to previously published procedure [ 30 ].…”

Section: Resultsmentioning

confidence: 99%

Effect of TADF Assistance on Performance Enhancement in Solution Processed Green Phosphorescent OLEDs

et al. 2021

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New diarylaminophenyl derivatives of carbazole: Effect of substituent position on their redox, spectroscopic and electroluminescent properties

et al. 2017

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Microwave-assisted one-pot synthesis of new ionic iridium complexes of [Ir(bzq)₂(N^N)]⁺A⁻ type and their selected electroluminescent properties

et al. 2017

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Iridium C,N-cyclometalated complexes with an ionic structure are considered to be promising candidates for application in host/guest solid-state phosphorescent single-layer devices because the employment of such dopants offers the possibility of reducing their concentration in organic matrices as well as allows obtaining organic light emitting devices (OLEDs) with interesting emission parameters. We report herein a methodology enabling the synthesis of cyclometalated ionic iridium(iii) complexes of the type [Ir(C^N)(N^N)]A according to a three-component one-pot strategy involving the acceleration of the reaction via microwave irradiation. The developed protocol allowed efficient synthesis of a series of new cationic iridium(iii) coordination derivatives, which were isolated and spectroscopically characterized, while the structures of two of them were determined by the X-ray method. Moreover, the iridium(iii) derivatives were subjected to the cyclic voltammetry studies in order to determine the energies of the HOMO and LUMO levels as well as to estimate their electrochemical properties and to predict some electronic properties. Additionally, the ONIOM calculation scheme that was used to predict HOMO-LUMO gaps for the studied Ir(iii) complexes showed a good correlation between the experimental and calculated values. In order to determine the influence of the structure and nature of the ancillary ligand on the location of the maximum emission band, the photophysical properties of the synthesized iridium complexes were characterized. Finally, the selected compounds were used as emitters for the construction of polymer light emitting diodes (PLEDs) based on a poly(N-vinylcarbazole)/2-(4-tert-butylphenyl)-5-(4-biphenyl)-1,3,4-oxadiazole (PVK/PBD) matrix. The highest luminance, above 10 000 cd m, was recorded for the device containing only 1.0 wt% of [Ir(bzq)(1,10-phenanthroline)]PF in the PVK/PBD. The fabricated PLEDs exhibit current efficiency in the range of 1.0 to 2.2 cd A.

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Blue iridium complexes as electron trapping sites and efficient recombination centres in poly(N-vinylcarbazole) seen by spectrally resolved thermoluminescence

Cited by 5 publications

References 33 publications

Effect of TADF Assistance on Performance Enhancement in Solution Processed Green Phosphorescent OLEDs

Effect of TADF Assistance on Performance Enhancement in Solution Processed Green Phosphorescent OLEDs

New diarylaminophenyl derivatives of carbazole: Effect of substituent position on their redox, spectroscopic and electroluminescent properties

Microwave-assisted one-pot synthesis of new ionic iridium complexes of [Ir(bzq)₂(N^N)]⁺A⁻ type and their selected electroluminescent properties

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Blue iridium complexes as electron trapping sites and efficient recombination centres in poly(N-vinylcarbazole) seen by spectrally resolved thermoluminescence

Cited by 5 publications

References 33 publications

Effect of TADF Assistance on Performance Enhancement in Solution Processed Green Phosphorescent OLEDs

Effect of TADF Assistance on Performance Enhancement in Solution Processed Green Phosphorescent OLEDs

New diarylaminophenyl derivatives of carbazole: Effect of substituent position on their redox, spectroscopic and electroluminescent properties

Microwave-assisted one-pot synthesis of new ionic iridium complexes of [Ir(bzq)2(N^N)]+A− type and their selected electroluminescent properties

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Microwave-assisted one-pot synthesis of new ionic iridium complexes of [Ir(bzq)₂(N^N)]⁺A⁻ type and their selected electroluminescent properties