Spectrally resolved thermoluminescence versus electroluminescence spectra of PVK doped with 1 wt % of Ir(btp) 2 (acac)

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

doi:10.1016/j.orgel.2016.01.021

Cited by 10 publications

(7 citation statements)

References 31 publications

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“…Thus, taking into account the observations presented above, we can suppose that the iridium complex molecules work as dominant emission centres in the system. A similar effect has been previously observed for PVK and the mixture of PVK/PBD doped with Ir(ppy) 3 [18] and PVK with Ir(btp) 2 (acac) [19].…”

Section: Resultssupporting

confidence: 86%

“…This radius is smaller than the R 0 = 2.0 nm and R 0 = 2.2 nm for PVK doped with Ir (btp) 2 (acac) [19] and rubrene [34], respectively. A large Förster radius is generally observed when the emission spectrum of the host and absorption spectrum of the guest overlap strongly and this is the case for PVK doped with Ir(ppy) 3 (value of R 0 = 4.4 nm) [35].…”

Section: Resultsmentioning

confidence: 65%

“…Our previous studies of SRTL for PVK doped with Ir(ppy) 3 or Ir (btp) 2 (acac) show that the molecules of these dopants create deep trap states for holes in the matrix [18,19]. Moreover, even at 1 wt% of the dopants, emission originates almost exclusively from triplet excitons of the iridium complexes molecules.…”

Section: Introductionmentioning

confidence: 97%

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

2016

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Section: Resultssupporting

confidence: 86%

Section: Resultsmentioning

confidence: 65%

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

2016

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“…The short wavelength band contribution is significant just after the excitation is switched off and disappears with the time. This high energetic emission is similar to the isothermal spectrum of pure PVK layer recorded at 20 K, associated with both monomeric and excimeric triplet states (high and low energetic) of carbazole groups [ 35 ]. The prevailing band resembles the EL spectrum of OLED based on PVK + 2 wt% Ir emitting layer ( Figure S5c ) that was attributed to triplet excitons of the iridium complex.…”

Section: Resultssupporting

confidence: 71%

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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“…On the basis of the data for the absorption by Btp 2 Ir(acac) [18] and the polymer fluorescence, we calculated that, at room temperature, 0 ≈ 2.2 and 2.3 nm for the PVK and PEPK matrices, respectively. It is worth noting that the value of 0 obtained by us for the Btp 2 Ir(acac) molecules in the PVK matrix was confirmed in work [30].…”

Section: Discussion Of Experimental Resultssupporting

confidence: 66%

Peculiarities of the Energy Transfer of Electronic Excitation in Carbazolyle-Containing Polymers

Skryshevski¹,

Vakhnin²

2019

Ukr. J. Phys.

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Luminescence spectra of poly-N-vinylcarbazole (PVK), poly-N-epoxypropylcarbazole (PEPK), poly-N-vinyl-3-chlorocarbazole (Cl-PVK), and polystyrene (PS) films doped with bis[2-(2′-benzothienyl)-pyridinato-N,C3′](acetylacetonate) iridium [Btp2Ir(acac)] have been studied. The indicated carbazole-containing polymers are promising for the application in electroluminescence devices. The quantum yield of sensitized phosphorescence by Btp2Ir(acac) molecules in carbazole-containing polymer matrices is found to be lower than at their direct excitation in the PS matrix. The additional doping of the PVK-based composite with benzophenone, which transforms some of singlet excitons into triplet ones, diminishes the intensity of the sensitized phosphorescence of Btp2Ir(acac) molecules, which testifies that the efficiency of energy transfer via singlet excitons is higher than via triplet ones. The results obtained can be explained by a competition between the process of energy transfer onto the acceptor site, on the one hand, and the processes of exciton localization at the tail energy states and the trapping of triplet excitons by the products of polymer oxidation, on the other hand. The quantum yield of sensitized phosphorescence by Btp2Ir(acac) molecules in the PVK matrix is found to be almost 1.5 times lower than in the PEPK one. A conclusion is drawn that, in the PVKmatrix, the process of singlet exciton autolocalization at excimer-forming centers followed by the creation of sandwich-like excimers competes with the process of excitation energy transfer onto the acceptor.

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Spectrally resolved thermoluminescence versus electroluminescence spectra of PVK doped with 1 wt % of Ir(btp) 2 (acac)

Cited by 10 publications

References 31 publications

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

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

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

Peculiarities of the Energy Transfer of Electronic Excitation in Carbazolyle-Containing Polymers

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