Deep-Blue High-Efficiency TTA OLED Using <i>Para</i>- and <i>Meta</i>-Conjugated Cyanotriphenylbenzene and Carbazole Derivatives as Emitter and Host

Kukhta, Nadzeya A.; Matulaitis, Tomas; Volyniuk, Dmytro; Ivaniuk, Khrystyna; Turyk, Pavlo; Stakhira, Pavlo; Gražulevičius, Juozas V.; Monkman, Andrew P.

doi:10.1021/acs.jpclett.7b02867

Cited by 133 publications

(101 citation statements)

References 41 publications

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“…Secondly, such increased HOMO/LUMO overlap serves to weaken/destabilize the CT state, creating an increased separation between the mediated 1 CT and 3 LE states- Figure 6e and f. Both of these conditions result in a ∆EST which is larger (0.29 and 0.24 +/-0.02 eV, respectively) than the -ortho isomers. The PH of both emitters shows similar shapes to other D-A-D moieties based on the same units 35 . The decays of 34CT and 35CT were left out of this analysis because of the poor DF performance at room temperature.…”

Section: Further Comparisons Can Be Established Between the Four -Ortmentioning

confidence: 61%

Dihedral Angle Control of Blue Thermally Activated Delayed Fluorescent Emitters through Donor Substitution Position for Efficient Reverse Intersystem Crossing

Pereira

Han

et al. 2018

ACS Appl. Mater. Interfaces

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This study shows a molecular design strategy for controlling the dihedral angle of two carbazole donors linked to a 2,4-diphenyl-1,3,5-triazine acceptor by a phenyl unit. Using this approach, six thermally-activated delayed fluorescence emitters were synthesised with donors placed in various positions around a central phenyl core and the photophysical relationship between the donor position and its dihedral angle was investigated. We demonstrate that this angle can affect both the strength of the charge transfer state and the conjugation across the entire molecule, effectively changing the singlet-triplet energy gap of the system. We conclude that materials containing two substituted-ortho donors or one-ortho and an adjacent-meta have the smallest energy gaps and the shortest delayed fluorescence lifetimes. On the other hand, emitters with no-ortho substituted donors have larger energy gaps and slow-to-negligible delayed fluorescence. When applying these materials to organic light-emitting diodes , these blue-emitting devices have a range of electrical properties, the best producing efficiencies as high as 21.8% together with high resistance to roll-off that correlate with the rISC rates obtained.

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Section: Further Comparisons Can Be Established Between the Four -Ortmentioning

confidence: 61%

Dihedral Angle Control of Blue Thermally Activated Delayed Fluorescent Emitters through Donor Substitution Position for Efficient Reverse Intersystem Crossing

Pereira

Han

et al. 2018

ACS Appl. Mater. Interfaces

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“…The triplet-triplet annihilation (TTA) induced enhancement of h ex cannot be ruled out because TTA is complex in OLEDs. 55,56 The horizontal-dipole array of anisotropic emitting molecules can remarkably improved the h out thereby enhancing h ex of OLEDs [57][58][59][60][61] (Fig. 7).…”

Section: Electroluminescent Studiesmentioning

confidence: 99%

Efficient donor–acceptor emitter based nonsymmetrical connection for organic emitting diodes with improving exciton utilization

et al. 2020

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“…In this Communication, we show that a new device architecture can significantly improve TTAUC blue emission efficiencies, which is one of the important issues for OLED development . The basic idea is to separate the triplet sensitization and upconversion layers while still allowing triplet energy migration.…”

Section: Eqe Performances Of Devices Blue and Green Emission Were Sementioning

confidence: 99%

Efficient Triplet–Triplet Annihilation Upconversion in an Electroluminescence Device with a Fluorescent Sensitizer and a Triplet‐Diffusion Singlet‐Blocking Layer

et al. 2018

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energy transfer (TET) populates the triplet state of the TTA emitter. When two triplet excitons encounter each other, the TTA process puts the emitter into its singlet excited state to emit fluorescence. One criterion for the sensitizer is efficient ISC to convert the singlet to the triplet, and sensitizers like phosphors, thermally activated delay fluorescence emitters, inorganic quantum dots, and perovskites have been used. [5][6][7] Charge transfer states between electron donor and acceptor materials can also act as sensitizers, resulting in efficient sub-bandgap emission (i.e., the driving voltage is ≈1/2 of the emitted photon energy) for organic light-emitting diode (OLED) applications. [8] For electrical excitation, 75% of the electron-hole pairs recombine as triplets without any ISC. By harnessing these triplet excitons to generate luminescence, TTAUC provides a path to higher efficiency devices.In this Communication, we show that a new device architecture can significantly improve TTAUC blue emission efficiencies, which is one of the important issues for OLED development. [9] The basic idea is to separate the triplet sensitization and upconversion layers while still allowing triplet energy migration. To demonstrate this concept, tris-(8-hydroxyquinoline)aluminum (Alq 3 ) was used as the sensitizer. This molecule has been used as an electron-transporting layer (ETL) and emitting layer material in one of the first OLED Solid-state triplet-triplet annihilation upconversion (TTAUC) blue emission in an electroluminescence device (i.e., an organic light-emitting diode (OLED)) is demonstrated. A conventional green fluorophore, tris-(8-hydroxyquinoline)aluminum (Alq 3 ), is employed as the sensitizer that generates 75% triplet under electrical pumping for the blue triplet-triplet annihilation emitter, 9,10-bis(2′-naphthyl) anthracene (ADN), with the heterojunction bilayer structure. The operation lifetime is elongated both for ADN blue (4.1x) and Alq 3 green (34.8%) emission due to efficient use of excitons and separation of recombination and emission zone. To reduce the singlet quenching (SQ) of blue TTAUC signal by the Alq 3 sensitizer with lower bandgap, 1-(2,5-dimethyl-4-(1-pyrenyl)phenyl)pyrene (DMPPP) is inserted between the Alq 3 and ADN as a triplet-diffusion-and-singlet-blocking layer. DMPPP exhibits triplet energy close to Alq 3 and higher than ADN, as well as higher singlet energy than both Alq 3 and ADN. It allows triplet diffusion from Alq 3 to ADN, but blocks the SQ of the blue TTAUC signal by Alq 3 . 86.1% intrinsic efficiency of TTAUC is demonstrated in this trilayer (Alq 3 /DMPPP/ADN) OLED. Organic Light-Emitting DiodesThe ORCID identification number(s) for the author(s) of this article can be found under https://doi.

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Deep-Blue High-Efficiency TTA OLED Using Para- and Meta-Conjugated Cyanotriphenylbenzene and Carbazole Derivatives as Emitter and Host

Cited by 133 publications

References 41 publications

Dihedral Angle Control of Blue Thermally Activated Delayed Fluorescent Emitters through Donor Substitution Position for Efficient Reverse Intersystem Crossing

Dihedral Angle Control of Blue Thermally Activated Delayed Fluorescent Emitters through Donor Substitution Position for Efficient Reverse Intersystem Crossing

Efficient donor–acceptor emitter based nonsymmetrical connection for organic emitting diodes with improving exciton utilization

Efficient Triplet–Triplet Annihilation Upconversion in an Electroluminescence Device with a Fluorescent Sensitizer and a Triplet‐Diffusion Singlet‐Blocking Layer

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