Impact of Donor Substitution Pattern on the TADF Properties in the Carbazolyl-Substituted Triazine Derivatives

Matulaitis, Tomas; Imbrasas, Paulius; Kukhta, Nadzeya A.; Baronas, Paulius; Buciunas, Tadas; Banevičius, Dovydas; Gražulevičius, Juozas V.; Juršėnas, Saulius

doi:10.1021/acs.jpcc.7b08034

Cited by 55 publications

(28 citation statements)

References 56 publications

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“…This low‐energy absorption could be ascribed to the intramolecular charge transfer (ICT) transition from nido ‐carborane donor (HOMO) to the PhBMes 2 acceptor (LUMO) moiety (see the TD‐DFT results below). Nido ‐ p1 – p4 also exhibited similar absorption patterns, but had low‐energy absorptions much more intense than those of the meta compounds, indicating substantial HOMO–LUMO overlap (Supporting Information, Figure S11) . Electrochemical measurements of nido ‐ m1 – m4 display typical features for the triarylborane‐centered, reversible reduction (LUMO) and the nido ‐carborane‐centered, irreversible oxidation (HOMO; Supporting Information, Figure S10) .…”

Section: Methodscontrasting

confidence: 56%

Nido‐Carboranes: Donors for Thermally Activated Delayed Fluorescence

et al. 2018

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Section: Methodscontrasting

confidence: 56%

Nido‐Carboranes: Donors for Thermally Activated Delayed Fluorescence

et al. 2018

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“…The FL spectra of SFI nx Tz in dilute toluene solution showed CT‐featured structure‐less broad blue emissions peaked from 430 to 460 nm. It is noteworthy that compared to their meta‐analogs the emissions of SFI n pTz are hypochromatically shifted by ≈10 nm, revealing their weaker ICT states and reduced nonradiation energy loss . And the emissions from SFI n pTzs are remarkably brighter, consistent with their higher radiative transition probabilities as indicated by more overlap of HOMO and LUMO .…”

Section: Resultsmentioning

confidence: 91%

Integrating the Emitter and Host Characteristics of Donor–Acceptor Systems through Edge‐Spiro Effect Toward 100% Exciton Harvesting in Blue and White Fluorescence Diodes

Zhang

Ding

et al. 2018

Advanced Optical Materials

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EQE) and power efficiencies (PE) beyond 20% and 50 lm W −1 , respectively, they are indeed inferior to their fluorescence (FL) counterparts in all other aspects. [2] However, the drawback of FL emitters in triplet exciton-harvesting forces the employment of combined emissive layers (EMLs) containing blue FL emitters and low-energy phosphors, viz., so-called hybrid WOLEDs, which can also realize the high efficiencies, but actually sacrifice the other advantages of FL devices. [3] Recently, pure-organic molecule-based thermally activated delayed fluorescent (TADF) emitters and their diodes were emerged with the feature of 100% exciton harvesting through converting irradiative triplet excitons to radiative singlet excitons in virtue of the reverse intersystem crossing (RISC) process, [4] which provide a promising way to develop pure FL WOLEDs with the state-of-the-art efficiencies. Nevertheless, the key issue for constructing high-performance white FL diodes is still remained about TADF-involved WOLEDs, namely, how to achieve the rational and efficient exciton allocation. Figure 1 shows four types of the potential emitter combinations for EMLs in FL WOLEDs. Superior to type-I devices, the other types can theoretically achieve 100% internal quantum efficiency (IQE), but still accompanied by the respective challenges. It is known that FL emitters can utilize all of the electrogenerated excitons through Förster resonance energy transfer from high-energy TADF sensitizers, which can be further used to construct type-II WOLEDs. [5] However, for both type-II and III devices, their white emissions are based on rational exciton allocations, viz., either triplet exciton confinement on TADF sensitizers for the former or singlet exciton confinement on FL emitters for the latter through doping concentration and position management, which is believed to be crucial for device efficiencies and therefore renders the contradiction between white emission and electroluminescence (EL) efficiencies. [6] In this sense, type-IV devices, namely, TADF WOLEDs, would be more flexible and superior in realizing highly efficient WOLEDs since the singlet and triplet excitons can be utilized by both high-energy and low-energy TADF emitters, giving rise to high EL efficiencies Herein, by utilizing edge-spiro effect to modulate intramolecular charge transfer and intermolecular interactions, emitter and host characteristic are integrated in simple donor-acceptor systems named SFInxTz. As emitter, SFI34pTz realizes true-blue thermally activated delayed fluorescent (TADF) diodes with an external quantum efficiency (EQE) of 25.3% and Commission Internationale de L'Eclairage (CIE) coordinates of (0.15, 0.20). As host, it can endow the yellow devices with the maximum EQE about 18%. When SFI34pTz serves as both blue emitter and yellow host material in pure fluorescence white device, the maximum efficiencies are as high as 22.9% for EQE and 52.4 lm W −1 for power efficiency, and stable electroluminescence spectra are successfully realized with CIE coordi...

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“…It is obvious that the absorption band at the range of 350–425 nm belongs to the CT transition between the ACRPh unit and the TRZ unit since the similar absorption band was observed for TRZ‐ p ‐ACR and TRZ‐ m ‐ACR. Since the TRZ based materials with meta‐position configuration usually have stronger CT states than their isomers with para‐position configuration, TRZ‐ p ‐ACRSA is expected to have higher PLQY due to its higher oscillator strength ( f ) of transition between S 0 and S 1 , which has positive correlation with ε. Meanwhile, as shown in Figure S7 in the Supporting Information, PL spectra of the ACRSA based materials show obvious blueshift compared with the ACRPh based materials due to the weaker electron‐donating ability of the ACRSA moiety, which are in accord with the results of the TDDFT calculation.…”

Section: Resultsmentioning

confidence: 99%

Utilizing a Spiro TADF Moiety as a Functional Electron Donor in TADF Molecular Design toward Efficient “Multichannel” Reverse Intersystem Crossing

Gan

Wang

et al. 2019

Adv Funct Materials

121

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Designing thermally activated delayed fluorescence (TADF) materials with an efficient reverse intersystem crossing (RISC) process is regarded as the key to actualize efficient organic light-emitting diodes (OLEDs) with low efficiency roll-off. Herein, a novel molecular design strategy is reported where a typical TADF material 10-phenyl-10H, 10′H-spiro[acridine-9, 9′-anthracen]-10′-one (ACRSA) is utilized as a functional electron donor to design TADF materials of 2,4,6-triphenyl-1,3,5-triazine(TRZ)-p-ACRSA and TRZ-m-ACRSA. It is unique that the intramolecular charge transfer of the ACRSA moiety and the intramolecular and through-space intermolecular charge transfer between the TRZ and ACRSA moieties, provide a "multichannel" effect to enhance the rate of the reverse intersystem crossing process (k risc ) exceeding 10 −6 s −1 . TADF OLEDs based on TRZ-p-ACRSA as an emitter show a maximum external quantum efficiency (EQE) of 28% with reduced efficiency roll-off (EQEs of 27.5% and 22.1% at 100 and 1000 cd m −2 , respectively). Yellow phosphorescent OLEDs utilizing TRZ-p-ACRSA as a host material show record-high EQE of 25.5% and power efficiency of 115 lm W −1 , while phosphorescent OLEDs based on TRZ-m-ACRSA show further lower efficiency roll-off with EQEs of 25.2%, 24.3%, and 21.5% at 100, 1000, and 10 000 cd m −2 , respectively.being consistent with the El-Sayed rule of intersystem crossing (ISC) process, when the natures of 1 CT and 3 CT are different, the SOC between 1 CT and 3 CT might be efficient as well. [2] More importantly, avoiding dual emission phenomenon, which caused by conformational transforming brought by flexible moieties, is considered as the first priority of TADF molecular design strategy. [9] Conformational transforming not only results in energy loss, but also limits the triplet exciton utilization because not all possible conformations have potential to achieve TADF phenomenon. [10] On the basis of this understanding, the key to design TADF

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Impact of Donor Substitution Pattern on the TADF Properties in the Carbazolyl-Substituted Triazine Derivatives

Cited by 55 publications

References 56 publications

Nido‐Carboranes: Donors for Thermally Activated Delayed Fluorescence

Nido‐Carboranes: Donors for Thermally Activated Delayed Fluorescence

Integrating the Emitter and Host Characteristics of Donor–Acceptor Systems through Edge‐Spiro Effect Toward 100% Exciton Harvesting in Blue and White Fluorescence Diodes

Utilizing a Spiro TADF Moiety as a Functional Electron Donor in TADF Molecular Design toward Efficient “Multichannel” Reverse Intersystem Crossing

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