High Efficiency Exciplex Emitters Using Donor–Acceptor Type Acceptor Material

Oh, Chahyun; Kang, Yu Ri; Jeon, Sang Kyu; Lee, Jun Yeob

doi:10.1021/acs.jpcc.5b05292

Cited by 40 publications

(27 citation statements)

References 25 publications

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“…High EQE exciplexes were also reported by mixing an n‐type acceptor with an intramolecular TADF material. The TADF material is a kind of bipolar material with a donor–acceptor structure and it could make the intermolecular type exciplex with the n‐type or p‐type material . For instance, 6‐(9,9‐dimethylacridin‐10(9H)‐yl)‐3‐methyl‐1H‐isochromen‐1‐one (MAC):PO‐T2T exciplexes were derived from a n‐type acceptor and an TADF emitter .…”

Section: External Quantum Efficiency Current Efficiency and Color Cmentioning

confidence: 99%

Ternary Exciplexes for High Efficiency Organic Light‐Emitting Diodes by Self‐Energy Transfer

Jeon

Jang

Lee

2019

Advanced Optical Materials

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High EQE exciplexes were also reported by mixing an n-type acceptor with an intramolecular TADF material. The TADF material is a kind of bipolar material with a donor-acceptor structure and it could make the intermolecular type exciplex with the n-type or p-type material. [24][25][26] For instance, 6-(9,9-dimethylacridin-10(9H)-yl)-3-methyl-1H-isochromen-1-one (MAC):PO-T2T exciplexes were derived from a n-type acceptor and an TADF emitter. [20] The exciplexes could also be developed by integrating two TADF emitters which have the large highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) offset. Bis [4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (DMAC-DPS): 9,9′,9″-(5-(4,6-diphenyl-1,3, 5-triazin-2-yl)benzene-1,2,3-triyl)tris (9H-carbazole) (TCzTrz) is an example of the exciplex derived from two TADF emitters. [27] A high EQE of 15.3% was attained in the exciplex. However, the EQE of the exciplexes was rather limited because of low photoluminescence quantum yield (PLQY) of the exciplex. Unlike the common emitting layer system comprised of host and dopant, the exciplex emitting layer is like a nondoped emitting layer. Therefore, the exciton quenching of the exciplexes may occur in the emitting layer, decreasing the EQE of the exciplex organic light-emitting diodes (LEDs) (OLEDs). Another reason is the nature of the exciplex emission which is known as the intermolecular charge transfer emission. Compared with the intramolecular TADF emission, the intermolecular exciplex emission is relatively inefficient by loss mechanisms between two materials. Therefore, a new way of improving the EQE of the exciplexes is strongly required.Herein, we describe a host-dopant type ternary exciplex system with a high EQE of 17.5%. A p-type donor and a n-type acceptor were introduced to form a high energy exciplex and an additional donor-acceptor type TADF emitter was mixed as another p-type donor to generate a low energy exciplex with the n-type acceptor. The high energy exciplex functioned as a host and the low energy exciplex behaved as a dopant in the ternary exciplex. Final exciplex emission was observed from the low energy exciplex. It was demonstrated that the dispersion of the low energy exciplex in the high energy exciplex and the energy transfer from the high energy exciplex to the low energy exciplex increased the EQE of the exciplex devices. The EQE of the exciplex device achieved in this work is one of the best EQEs reported in the exciplex OLEDs.Ternary exciplexes with an external quantum efficiency of 17.5% are developed by mixing a p-type donor material, an n-type acceptor material, and a donor-acceptor type material together. In the ternary mixture, the n-type donor generates exciplexes with the p-type donor and the donor-acceptor type material at the same time. Two different exciplexes with dissimilar emission wavelengths are formed and the emission of the high-energy exciplex is transferred to the low-energy exciplex by energy transfer. The high-energy exciplex and low-energy ex...

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Section: External Quantum Efficiency Current Efficiency and Color Cmentioning

confidence: 99%

Ternary Exciplexes for High Efficiency Organic Light‐Emitting Diodes by Self‐Energy Transfer

Jeon

Jang

Lee

2019

Advanced Optical Materials

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“…To realize efficient TADF OLEDs based on exciplex, the donor and acceptor materials should: a) possess proper HOMOs and LUMOs, other than would not forming intermolecular CT; [13] b) have lowest triplet energy levels (T 1 s) not lower than the CT states ( 1 CT and 3 CT) to prevent the energy leakage from exciplex to donor or acceptor; [12,[15][16] c) have strong electron donating and electron accepting characteristics to facilitate the forming of exciplex. [22] And it was found that donor-acceptor (D-A) type molecule would possess stronger electron donating or electron accepting characteristics. [22] Besides, exciplex can not only realizing TADF emission, but also can be used as host sensitizing phosphorescent, fluorescent and TADF emitters.…”

Section: Introductionmentioning

confidence: 99%

“…[22] And it was found that donor-acceptor (D-A) type molecule would possess stronger electron donating or electron accepting characteristics. [22] Besides, exciplex can not only realizing TADF emission, but also can be used as host sensitizing phosphorescent, fluorescent and TADF emitters. And exciplex host based OLEDs normally exhibit good device performance because exciplex host has the advantages of bipolar charge transporting, wide exciton recombination zone and barrier free from hole transporting layer (HTL) and electron transporting layer (ETL) to the emitting layer (EML).…”

Section: Introductionmentioning

confidence: 99%

Efficient Exciplex‐based Green and Near‐Infrared Organic Light‐Emitting Diodes Employing a Novel Donor‐Acceptor Type Donor

Zhao

Ye²,

et al. 2020

Chemistry An Asian Journal

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Widely investigated thermally activated delayed fluorescence (TADF) can be achieved by intramolecular and intermolecular charge transfer between an electron donor and electron acceptor which corresponds to a TADF material and exciplex, respectively. However, the development of efficient organic light-emitting diodes (OLEDs) based on an exciplex lags far behind the development of those based on efficient TADF materials. In this work, a novel D-A type electron donor TPAFPO was designed and synthesized. TPAFPO:PO-T2T exhibits a small ΔE ST of 79 meV and significant delayed emission, demonstrating TADF characteristics. OLEDs based on TPAFPO:PO-T2T exhibit a low turn-on voltage of 2.4 V and high an EQE value of 17.0%. Besides, NIR OLEDs utilizing TPAFPO:PO-T2T as host exhibit a turn-on voltage of 3.0 V and high EQE of 9.2% with a NIR emission peak at 690 nm. Furthermore, solution-processed exciplex and NIR devices also can maintain high efficiencies of 15.1% and 8.1%, respectively.

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“…However, the development of bimolecular TADF lags far behind. Most exciplex-type TADF OLEDs showed maximum EQE close to 10% (Jankus et al, 2014; Liu et al, 2015a,b; Oh et al, 2015; Zhang L. et al, 2015; Hung et al, 2016, 2017; Jeon et al, 2016), with only one example approaching to 18% (Liu et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

N-Benzoimidazole/Oxadiazole Hybrid Universal Electron Acceptors for Highly Efficient Exciplex-Type Thermally Activated Delayed Fluorescence OLEDs

et al. 2019

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Recently, donor/acceptor type exciplex have attracted considerable interests due to the low driving voltages and small singlet-triplet bandgaps for efficient reverse intersystem crossing to achieve 100% excitons for high efficiency thermally activated delayed fluorescence (TADF) OLEDs. Herein, two N -linked benzoimidazole/oxadiazole hybrid electron acceptors were designed and synthesized through simple catalyst-free C-N coupling reaction. 24 i PBIOXD and i TPBIOXD exhibited deep-blue emission with peak at 421 and 459 nm in solution, 397 and 419 nm at film state, respectively. The HOMO/LUMO energy levels were −6.14/−2.80 for 24 i PBIOXD and −6.17/−2.95 eV for i TPBIOXD. Both compounds could form exciplex with conventional electron donors such as TAPC, TCTA, and mCP. It is found that the electroluminescent performance for exciplex-type OLEDs as well as the delayed lifetime was dependent with the driving force of both HOMO and LUMO energy offsets on exciplex formation. The delayed lifetime from 579 to 2,045 ns was achieved at driving forces close to or larger than 1 eV. Two TAPC based devices possessing large HOMO/LUMO offsets of 1.09–1.34 eV exhibited the best EL performance, with maximum external quantum efficiency (EQE) of 9.3% for 24 i PBIOXD and 7.0% for i TPBIOXD acceptor. The TCTA containing exciplex demonstrated moderate energy offsets (0.88–1.03 eV) and EL efficiency (~4%), while mCP systems showed the poorest EL performance (EQE <1%) and shortest delayed lifetime of <100 ns due to inadequate driving force of 0.47–0.75 eV for efficient exciplex formation.

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High Efficiency Exciplex Emitters Using Donor–Acceptor Type Acceptor Material

Cited by 40 publications

References 25 publications

Ternary Exciplexes for High Efficiency Organic Light‐Emitting Diodes by Self‐Energy Transfer

Ternary Exciplexes for High Efficiency Organic Light‐Emitting Diodes by Self‐Energy Transfer

Efficient Exciplex‐based Green and Near‐Infrared Organic Light‐Emitting Diodes Employing a Novel Donor‐Acceptor Type Donor

N-Benzoimidazole/Oxadiazole Hybrid Universal Electron Acceptors for Highly Efficient Exciplex-Type Thermally Activated Delayed Fluorescence OLEDs

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