An Exciplex Host for Deep-Blue Phosphorescent Organic Light-Emitting Diodes

Lim, Hyoungcheol; Shin, Hyun Mu; Kim, Kwon‐Hyeon; Yoo, Sung Jin; Huh, Jin-Suk; Kim, Jang‐Joo

doi:10.1021/acsami.7b10914

Cited by 64 publications

(33 citation statements)

References 34 publications

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“…Exciplexes are intermolecular complexes of a p‐type donor and an n‐type acceptor by electron transfer from the p‐type donor to the n‐type donor. They are popular as the hosts of light‐emitting materials, but they can also efficiently emit by themselves through thermally activated delayed fluorescence (TADF) mechanism . Since the first demonstration of efficient light emission of the exciplexes by TADF process, the external quantum efficiency (EQE) of the exciplexes has been dramatically improved …”

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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“…In this case, the two hosts should have higher triplet energy than the phosphor, and the HOMO and LUMO gaps should be large enough to drive exciplex formation. One example is the exciplex between mCP and 2,4-bis(4-(diphenylphosphoryl)phenyl)pyridine (BM-A10) [55]. The mCP was a weak p-type host with a deep HOMO level, and the BM-A10 was a weak n-type host with a shallow LUMO level.…”

Section: Exciplex Host For Deep-blue Phosphorescent Oledsmentioning

confidence: 99%

Exciplex hosts for blue phosphorescent organic light-emitting diodes

Jung

Lee

2019

Journal of Information Display

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The host material of organic light-emitting diodes (OLEDs) has been advanced from a single host to a mixed host for high efficiency and long lifetime. Several types of mixed host have been reported in the literature, but the exciplex host has been popular as the mixed host of OLEDs. The exciplex host has been developed mostly for red and green phosphorescent OLEDs, and has upgraded device performances, but it is difficult to develop the exciplex host for blue phosphorescent OLEDs. Recently, several works demonstrated the potential of the exciplex host for blue phosphorescent OLEDs. In this paper, the exciplex host for blue OLEDs is reviewed, and its prospects are presented.

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“…Films of exciplex-forming materials have given rise to organic light-emitting diodes (OLEDs) with good efficiencies either as emissive layers or as hosts for phosphorescent, thermally activated delayed fluorescence (TADF), or fluorescent emitters. [1][2][3][4][5][6][7][8][9] A reported feature of bulk exciplex films when used as a host for guest emitters is their ambipolarity, 10 which arises from the fact that they are composed of a blend of low ionisation potential (donor) and high electron affinity (acceptor) materials. The blend of the two materials has been observed to reduce both the operating voltage and efficiency roll-off, which in the case of the latter has been attributed to the placement and broadening of the recombination zone in the emissive layer.…”

Section: Introductionmentioning

confidence: 99%