Highly efficient green TADF organic light-emitting diodes by simultaneously manipulating hole and electron transport

Wang, Chao; Zheng, Yi; Tang, Jie; Yu, Jun-Le; Yang, Fang; Wei, Bin; Zhang, Jianhua

doi:10.1088/1361-6528/aaf8c2

Cited by 8 publications

(6 citation statements)

References 28 publications

(13 reference statements)

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“…EQE value greater than 25% has been reported for novel or exciplex hosts developed to incorporate the 4CzIPN emitter. [18][19][20][21][22][23][24] The reported high EQE of 31.7% was obtained using 35Cbz4BzCN as the host. [7] The EQE max of the device decreased with an increase in x because the CQ effect reduced the PLQY.…”

Section: Wwwadvopticalmatdementioning

confidence: 99%

Long‐Distance Triplet Diffusion and Well‐Packing Hosts with Ultralow Dopant Concentration for Achieving High‐Efficiency TADF OLED

Chen

Ding

Lin

et al. 2021

Advanced Optical Materials

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High‐efficiency organic light emitting diodes (OLEDs) are fabricated using a group of benzimidazole‐carbazole derivatives with good molecular packing as hosts. The hosts are separately doped with a green thermally activated delayed fluorescence (TADF) emitter, 1,2,3,5‐tetrakis(carbazol‐9‐yl)‐4,6‐dicyanobenzene (4CzIPN). An ultralow concentration (0.5% volume ratio) of 4CzIPN is required in the emitting layer (EML) to achieve a record‐high external quantum efficiency of 31.8% by comparison with reported 4CzIPN‐relative devices. This result is attributed to efficient energy transfer, alleviation of concentration quench of 4CzIPN, long‐distance triplet exciton diffusion ability of host materials, and excellent horizontal molecular packing. With an increase in dopant concentration from 0.5% to 15%, the diodes exhibit a tiny variation in power efficiencies (82.9−78.7 lm W−1) and current efficiencies (92.2−87.5 cd A−1). In particular, the long‐distance triplet exciton diffusion ability of hosts exceeds the typical distance limitation (less than 10 Å) of Dexter energy transfer. Thus, high‐efficiency OLEDs are obtained with the scarce dopants . The aforementioned long‐distance triplet diffusion results are verified by the almost‐identical high‐efficiency device performances and the longer delayed emission lifetime in transient electroluminescence signals of a series of partially doped devices, conducting by separately doping low‐concentration TADF emitters in different EML regions.

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Section: Wwwadvopticalmatdementioning

confidence: 99%

Long‐Distance Triplet Diffusion and Well‐Packing Hosts with Ultralow Dopant Concentration for Achieving High‐Efficiency TADF OLED

Chen

Ding

Lin

et al. 2021

Advanced Optical Materials

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“…The research on materials that exhibit thermally activated delayed fluorescence (TADF) has increased dramatically since the introduction of TADF materials into organic light-emitting diodes (OLEDs) for lighting and display applications. − Although highly efficient green TADF OLED materials have been widely reported, − research to create efficient and stable red and especially blue TADF OLEDs has not progressed as rapidly. , …”

Section: Introductionmentioning

confidence: 99%

Molecular Design Strategies for Color Tuning of Blue TADF Emitters

Stachelek

Ward

Santos

et al. 2019

ACS Appl. Mater. Interfaces

113

107

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New thermally activated delayed fluorescence (TADF) blue emitter molecules based on the known donor−acceptor−donor (D−A−D)type TADF molecule, 2,7-bis(9,9-dimethylacridin-10-yl)-9,9-dimethylthioxanthene-S,S-dioxide (DDMA-TXO2), are reported. The motivation for the present investigation is via the use of rational molecular design, based on DDMA-TXO2, to elevate the organic light emitting diode (OLED) performance and obtain deeper blue color coordinates. To achieve this goal, the strength of the donor (D) unit and acceptor (A) units have been tuned with methyl substituents. The methyl functionality on the acceptor was also expected to modulate the D−A torsion angle in order to obtain a blue shift in the electroluminescence. The effect of regioisomeric structures has also been investigated. Herein, we report the photophysical, electrochemical, and single-crystal X-ray crystallography data to assist with the successful OLED design. The methyl substituents on the DDMA-TXO2 framework have profound effects on the photophysics and color coordinates of the emitters. The weak electron-donating methyl groups alter the redox properties of the D and A units and consequently affect the singlet and triplet levels but not the energy gap (ΔE ST ). By systematically manipulating all of the aforementioned factors, devices have been obtained with acceptor-substituted III with a maximum external quantum efficiency of 22.6% and Commission Internationale de l'E ́clairage coordinates of (0.15, 0.18) at 1000 cd m −2 .

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“…For a similar purpose, double emissive layers have also been studied. 76,77 Additionally, red [21][22][23] and green [29][30][31][32][33] TADF emitters have been shown to be efficient, low cost alternatives to the expensive precious heavy metals found in phosphorescent emitters.…”

Section: Hole Transport Layer (Htl)mentioning

confidence: 99%

“…Considering the individual emitters, at present, there exist stable and efficient triplet emitters for red, [14][15][16][17][18][19][20][21][22][23] green, [24][25][26][27][28][29][30][31][32][33] and yellow (for use in white OLED-TV stacks), with blue falling short. Blue emitters continue to be problematic and many ongoing research efforts target this specifically.…”

Section: Introductionmentioning

confidence: 99%

Computer aided design of stable and efficient OLEDs

Paterson

May

Andrienko

2020

Journal of Applied Physics

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Organic light emitting diodes (OLEDs) offer a unique alternative to traditional display technologies. Tailored device architecture can offer properties such as flexibility and transparency, presenting unparalleled application possibilities. Commercial advancement of OLEDs is highly anticipated, and continued research is vital for improving device efficiency and lifetime. The performance of an OLED relies on an intricate balance between stability, efficiency, operational driving voltage, and color coordinates, with the aim of optimizing these parameters by employing an appropriate material design. Multiscale simulation techniques can aid with the rational design of these materials, in order to overcome existing shortcomings. For example, extensive research has focused on the emissive layer and the obstacles surrounding blue OLEDs, in particular, the trade-off between stability and efficiency, while preserving blue emission. More generally, due to the vast number of contending organic materials and with experimental pre-screening being notoriously time-consuming, a complementary in silico approach can be considerably beneficial. The ultimate goal of simulations is the prediction of device properties from chemical composition, prior to synthesis. However, various challenges must be overcome to bring this to a realization, some of which are discussed in this Perspective. Computer aided design is becoming an essential component for future OLED developments, and with the field shifting toward machine learning based approaches, in silico pre-screening is the future of material design.

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Highly efficient green TADF organic light-emitting diodes by simultaneously manipulating hole and electron transport

Cited by 8 publications

References 28 publications

Long‐Distance Triplet Diffusion and Well‐Packing Hosts with Ultralow Dopant Concentration for Achieving High‐Efficiency TADF OLED

Long‐Distance Triplet Diffusion and Well‐Packing Hosts with Ultralow Dopant Concentration for Achieving High‐Efficiency TADF OLED

Molecular Design Strategies for Color Tuning of Blue TADF Emitters

Computer aided design of stable and efficient OLEDs

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