Aggregation, thermal annealing, and hosting effects on performances of an acridan-based TADF emitter

Skuodis, Eigirdas; Bezvikonnyi, Oleksandr; Tomkevičienė, Aušra; Volyniuk, Dmytro; Mimaitė, Viktorija; Lazauskas, Algirdas; Bučinskas, Audrius; Keruckienė, Rasa; Sini, Gjergji

doi:10.1016/j.orgel.2018.09.002

Cited by 49 publications

(41 citation statements)

References 45 publications

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“…[24] Af urther study shows that such intramolecular structurald ifferences were affected by aggregate formation in host-guest systems. [23] Apparently,i n comparison to PL spectra of non-doped films, the blueshift of spectra of 5:mCP, 6:mCP, 9:mCP and 12:mCP films are caused by both solvatochromic-like and aggregation effects because of the specific host-guestinteractions.…”

Section: Photophysical Propertiesmentioning

confidence: 99%

“…Aggregate formation is apparently the reason for smaller DE ST values of the studied compounds doped in mCP. [23] PL spectra andP Ld ecay curvesf or non-degassed and degassed toluene solutionso ft he compounds are shown in Figure 3c,d. SimilarP Ls pectra were observed for non-degassed and degassed toluene solutionso fa ll the studied compounds, indicating that the emission originated from the same excited singlet state.…”

Section: Photophysical Propertiesmentioning

confidence: 99%

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Synthesis of Linear and V‐Shaped Carbazolyl‐Substituted Pyridine‐3,5‐dicarbonitriles Exhibiting Efficient Bipolar Charge Transport and E‐Type Fluorescence

Vı̄gante

Leitonas

Volyniuk

et al. 2019

Chemistry A European J

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With the aim of developing all-organic bipolar semiconductors with high chargem obility and efficient Etype fluorescence(so-called TADF) as environmentally friendly light-emitting materials for optoelectronica pplications, four noble metals-free dyes with linear and V-shapesw ere designed usinga ccepting pyridine-3,5-dicarbonitrile and donating carbazole units. By exploiting ad onor-acceptor design strategya nd using moieties with different donating and accepting abilities,T ADF emitters with aw ide variety of molecular weights were synthesized to achievethe optimum combination of charge-transporting and fluorescent properties in one TADF molecule. Depending on molecule structures, differentT ADF emittersc apable of emitting in the range from 453 to 550 nm with photoluminescenceq uantum yields up to 98 %f or the solutions in oxygen-free toluene wereo btained. All compounds showedb ipolar chargetransport. Hole mobility of 2.8 10 À3 cm 2 /Vs at 7 10 5 Vcm À1 was observedf or the compound containing two di-tertbutyl-substituted carbazole moieties. The compounds were testedi nb oth non-doped and dopedo rganic light-emitting diodesu sing different hosts.I tw as shown that the developed TADF emitters are suitable for different color devices with electroluminescence ranging from blue to yellow and with brightness, maximum current and external quantum efficiencies exceeding 10 000 cd m À2 ,1 5cd/A, and 7%,r espectively.

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Section: Photophysical Propertiesmentioning

confidence: 99%

Section: Photophysical Propertiesmentioning

confidence: 99%

Synthesis of Linear and V‐Shaped Carbazolyl‐Substituted Pyridine‐3,5‐dicarbonitriles Exhibiting Efficient Bipolar Charge Transport and E‐Type Fluorescence

Vı̄gante

Leitonas

Volyniuk

et al. 2019

Chemistry A European J

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“…As the system is then cooled down to room temperature, the dynamics of the oBFCzTrz molecules again become reminiscent of those seen for typical glassy materials, with memory of the initial configuration persisting to a large extent throughout the simulation. This result highlights the importance of the experimental protocols in the preparation of emissive layers since previous studies have shown that thermal annealing strongly influences device performance …”

Section: Resultsmentioning

confidence: 61%

Suppression of Concentration Quenching in Ortho‐Substituted Thermally Activated Delayed Fluorescence Emitters

Abroshan

Cho

Coropceanu

et al. 2019

Advcd Theory and Sims

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Thermally activated delayed fluorescence (TADF) emitters are typically embedded at low concentrations in a host matrix to suppress emission quenching. However, recent studies indicate that TADF compounds such as the oBFCzTrz emitter (5‐(2‐(4,6‐diphenyl‐1,3,5‐triazin‐2‐yl)phenyl)‐5H‐benzofuro[3,2‐c]carbazole) display insignificant concentration quenching dependence. To understand the origin of this beneficial behavior, the morphology, dynamics, electronic properties, and charge transport and energy transfer in a neat film of the oBFCzTrz emitter are characterized via molecular dynamic simulations combined with density functional theory calculations. The emissive layer shows glassy behavior at room temperature with the twisted configurations of the emitter molecules allowing for intramolecular donor–acceptor interactions, but disfavoring intermolecular π–π stacking, which suppresses the formation of intermolecular aggregate states. As a result, the electronic structure and luminescence of oBFCzTrz are not significantly altered by intermolecular interactions. The calculated diffusion lengths of the singlet and triplet excitons are small enough that there occurs no substantial concentration quenching effect. Overall, the design of new TADF emitters with structural motifs similar to those of oBFCzTrz offers potential to develop efficient organic light‐emitting diode devices in which the emissive layers are entirely composed of TADF molecules without the need for a host component.

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“…These defects are the cause of the reduction in luminance efficiency and device stability. Several authors have reported that they reduced these defects through thermal annealing, thus effectively improved the stability of the OLEDs devices . Besides, it was reported that the proper thermal annealing condition of the emissive layer resulted in a denser film with suitable packing and interplanar distance of the molecules, leading to better carrier mobility and higher efficiency.…”

Section: Introductionmentioning

confidence: 99%

“…Several authors have reported that they reduced these defects through thermal annealing, thus effectively improved the stability of the OLEDs devices. [27,28] Besides, it was reported that the proper thermal annealing condition of the emissive layer resulted in a denser film with suitable packing and interplanar distance of the molecules, [29] leading to better carrier mobility [30] and higher efficiency. Such a better molecular orientation in the emissive layer, the optimized hostguest interaction [31,32] could be realized to achieve better efficiency.…”

Section: Introductionmentioning

confidence: 99%

All‐Solution‐Processed Red and Orange‐Red Organic Light‐Emitting Diodes with High‐Efficiencies: The Effect of Mixed‐Host Emissive Layers and Thermal Annealing Treatment

Chang

Yang

et al. 2019

ChemPlusChem

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The instability of the organic light‐emitting diodes (OLEDs) during operation can be attributed to the existence of point defects on the organic layers. In this work, the effect of mixed‐host emissive layer and the thermal annealing treatment were investigated to eliminate defects and to boost the device performance. The mixed‐host system includes 4,4′,4′′‐tri (9‐carbazoyl) triphenylamine (TCTA) and 2,7‐bis(diphenylphosphoryl)‐9, 9′‐spirobi[fluorene] (SPPO13). The mixed‐host emissive layer with thermal annealing treatment showed low roughness and few pinholes, and the devices fabricated from this emissive layer exhibited high efficiencies, high stabilities, and long lifetimes. The red and orange‐red OLEDs exhibited efficiencies of 13.9 cd/A and 24.35 cd/A, respectively. The longest half‐lifetime (L0=500 cd/m2) of the red and orange‐red OLEDs were 158 h and 180 h, respectively. Efforts were made to solve problems in large‐area coating and to reduce the number of defects on in organic layer. Large‐active‐area (active area=3 cm×4 cm) red phosphorescent OLEDs (PhOLEDs) devices were realized with very high current efficiency up to 9 cd/A.

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Aggregation, thermal annealing, and hosting effects on performances of an acridan-based TADF emitter

Cited by 49 publications

References 45 publications

Synthesis of Linear and V‐Shaped Carbazolyl‐Substituted Pyridine‐3,5‐dicarbonitriles Exhibiting Efficient Bipolar Charge Transport and E‐Type Fluorescence

Synthesis of Linear and V‐Shaped Carbazolyl‐Substituted Pyridine‐3,5‐dicarbonitriles Exhibiting Efficient Bipolar Charge Transport and E‐Type Fluorescence

Suppression of Concentration Quenching in Ortho‐Substituted Thermally Activated Delayed Fluorescence Emitters

All‐Solution‐Processed Red and Orange‐Red Organic Light‐Emitting Diodes with High‐Efficiencies: The Effect of Mixed‐Host Emissive Layers and Thermal Annealing Treatment

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