Horizontally Orientated Sticklike Emitters: Enhancement of Intrinsic Out-Coupling Factor and Electroluminescence Performance

Liu, Ming; Komatsu, Ryutaro; Cai, Xinyi; Hotta, Katsuyuki; Sato, Shugo; Liu, Kunkun; Chen, Dongcheng; Kato, Y.; Sasabe, Hiroyuki; Ohisa, Satoru; Suzuri, Yoshiyuki; Yokoyama, Daisuke; Su, Shi‐Jian; Kido, Junji

doi:10.1021/acs.chemmater.7b02403

Cited by 172 publications

(145 citation statements)

References 46 publications

(61 reference statements)

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“…[8][9][10][11][12][13][14][15][16][17][18][19][20] The use of pure organic TADF emitters allows almost 100% internal electroluminescence (EL) quantum efficiency by harvesting the triplet excitons (T 1 ) to the emissive singlet excited states (S 1 ) via reverse intersystem crossing (RISC). [8][9][10][11][12][13][14][15][16][17][18][19][20] The use of pure organic TADF emitters allows almost 100% internal electroluminescence (EL) quantum efficiency by harvesting the triplet excitons (T 1 ) to the emissive singlet excited states (S 1 ) via reverse intersystem crossing (RISC).…”

mentioning

confidence: 99%

High‐Performance Nondoped Blue Delayed Fluorescence Organic Light‐Emitting Diodes Featuring Low Driving Voltage and High Brightness

Zou

Xie

et al. 2019

Advanced Science

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TADF) materials without using heavy metals have gained great attention as the third-generation organic light-emitting diode (OLED) emitters. [8][9][10][11][12][13][14][15][16][17][18][19][20] The use of pure organic TADF emitters allows almost 100% internal electroluminescence (EL) quantum efficiency by harvesting the triplet excitons (T 1 ) to the emissive singlet excited states (S 1 ) via reverse intersystem crossing (RISC). To date, high external quantum efficiency (EQE) exceeding 20% has been achieved for blue, green, and red TADF emitters in OLEDs. [8][9][10][11][12][13][14][15][16][17][18][19][20] However, achieving high-performance deep blue TADF OLEDs is still challenging, since most of them suffer from poor color purity, low brightness, severe EL efficiency roll-off, as well as short operational stability. [21][22][23][24][25] It remains an urgent demand to develop new blue TADF emitters that can simultaneously achieve high efficiency, high brightness, low driving voltage, long operational lifetime, and low Commission Internationale de l'Eclairage (CIE) y coordinate (CIEy) for various applications.Several strategies have been proposed to realize highly efficient blue TADF emitters. Generally, the TADF molecules are designed with a donor-acceptor-type rigid and symmetrical molecular configuration, exhibiting high optical bandgap (E g ), small S 1 -T 1 energy splitting (ΔE ST ), and high photoluminescence quantum yield (PLQY). [26][27][28] For narrowband emission, Thermally activated delayed fluorescence (TADF) provides great potential for the realization of efficient and stable organic light-emitting diodes (OLEDs). However, it is still challenging for blue TADF emitters to simultaneously achieve high efficiency, high brightness, and low Commission Internationale de l'Eclairage (CIE) y coordinate (CIEy) value. Here, the design and synthesis of two new benzonitrile-based TADF emitters (namely 2,6-di(9H-carbazol-9-yl)-3,5-bis(3,6-diphenyl-9H-carbazol-9-yl)benzonitrile (2PhCz2CzBn) and 2,6-di(9H-carbazol-9-yl)-3,5-bis(3,6-di-tert-butyl-9H-carbazol-9-yl)benzonitrile (2tCz2CzBn)) with a symmetrical and rigid heterodonor configuration are reported. The TADF OLEDs doped with both the emitters can achieve a high external quantum efficiency (EQE) over 20% and narrowband blue emission of 464 nm with a CIEy < 0.2. Moreover, the incorporation of a terminal tert-butyl group can weaken the intermolecular π-π stacking in the nondoped TADF emitter, and thus significantly suppress self-aggregation-caused emission quenching for enhanced delayed fluorescence. A peak EQE of 21.6% is realized in the 2tCz2CzBn-based nondoped device with an extremely low turn-on voltage of 2.7 V, high color stability, a high brightness over 20 000 cd m −2 , a narrow fullwidth at half-maximum of 70 nm, and CIE color coordinates of (0.167, 0.248).

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mentioning

confidence: 99%

High‐Performance Nondoped Blue Delayed Fluorescence Organic Light‐Emitting Diodes Featuring Low Driving Voltage and High Brightness

Zou

Xie

et al. 2019

Advanced Science

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“…10). 30,72,76 pyrimidine-based blue TADF OLEDs at this stage: (i) long-term stability at practical luminance, (ii) efficiency roll-off at high brightness, and (iii) low-driving voltage.…”

Section: Discussionmentioning

confidence: 99%

“…11,12,27,28,30,81 Actually, a high Θ of up to 100% have been reported using sticklike TADF molecules, such as Cis-BOX2 (Θ ¼ 100% at substrate temperature ¼ 200 K) and IPN-SBA (Θ ¼ 93%). 28,30 These values are much higher than the reported Θ of iridium complex with a sphere-like structure. Moreover, the planer structure TADF molecule is very attractive and should be investigated for pyrimidine-based emitters from the perspective of long-term stability and small structural relaxation energy, which can realize narrow emission band and shorter τ d (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…30,73 Gomez-Bombarelli et al 73 developed an A-D-A type emitter based on indolocarbazole skeleton, and the device showed sky-blue emission with an EQE of 12%. Recently, a collaboration team of Liu et al 30 developed spirobiacridine-based sticklike TADF emitters called PM-SBA with the structure of A-D-σ-D-A. In addition, the emission peak of PM-SBA doped DPEPO film is located at 471 nm.…”

Section: Other Type Emittersmentioning

confidence: 99%

“…[14][15][16][17][18][19][20][21][22][23][24][25] Until recently, several TADF OLEDs have achieved a high EQE of over 30% at maximum. [26][27][28][29][30][31][32] The efficiency of the TADF-based OLEDs is expected to exceed that of OLEDs based on phosphorescent emitters due to the unlimited molecular design of pyrimidine derivative-based TADF emitters.…”

Section: Introductionmentioning

confidence: 99%

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Recent progress of pyrimidine derivatives for high-performance organic light-emitting devices

2018

Self Cite

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Abstract. Pyrimidine is an electron-deficient azaaromatic compound containing two nitrogen atoms at 1, 3-positions that plays a key role as an organic semiconductor or semiconducting material. Because of the high electron-accepting property induced by C═N double bonds and due to its coordination ability, pyrimidine has been incorporated as a building block in phosphorescent emitters, fluorescent emitters, bipolar host materials, and electron transporting materials in organic light-emitting devices (OLEDs). Recently, pyrimidine-based thermally activated delayed fluorescent emitters combined with various electron donors have been developed, and their device performances were far better than those based on conventional fluorescent emitters. In this review, recent progress of pyrimidine-based OLED materials is presented and accompanied by a historical overview, current status, key issues, and outlook for the next generation of high-performance OLED materials.

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High‐Performance Dibenzoheteraborin‐Based Thermally Activated Delayed Fluorescence Emitters: Molecular Architectonics for Concurrently Achieving Narrowband Emission and Efficient Triplet–Singlet Spin Conversion

Park

Matsuo

Aizawa

et al. 2018

Adv Funct Materials

301

234

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Thermally activated delayed fluorescence (TADF) materials, which enable the full harvesting of singlet and triplet excited states for light emission, are expected as the third-generation emitters for organic light-emitting diodes (OLEDs), superseding the conventional fluorescence and phosphorescence materials. High photoluminescence quantum yield (Φ PL ), narrow-band emission (or high color purity), and short delayed fluorescence lifetime are all strongly desired for practical applications. However, to date, no rational design strategy of TADF emitters is established to fulfill these requirements.Here, an epoch-making design strategy is proposed for producing high-performance TADF emitters that concurrently exhibiting high Φ PL values close to 100%, narrow emission bandwidths, and short emission lifetimes of ≈1 µs, with a fast reverse intersystem crossing rate of over 10 6 s −1 . A new family of TADF emitters based on dibenzoheteraborins is introduced, which enable both doped and non-doped TADF-OLEDs to achieve markedly high external electroluminescence quantum efficiencies, exceeding 20%, and negligible efficiency roll-offs at a practical high luminance. Systematic photophysical and theoretical investigations and device evaluations for these dibenzoheteraborin-based TADF emitters are reported here.

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Horizontally Orientated Sticklike Emitters: Enhancement of Intrinsic Out-Coupling Factor and Electroluminescence Performance

Cited by 172 publications

References 46 publications

High‐Performance Nondoped Blue Delayed Fluorescence Organic Light‐Emitting Diodes Featuring Low Driving Voltage and High Brightness

High‐Performance Nondoped Blue Delayed Fluorescence Organic Light‐Emitting Diodes Featuring Low Driving Voltage and High Brightness

Recent progress of pyrimidine derivatives for high-performance organic light-emitting devices

High‐Performance Dibenzoheteraborin‐Based Thermally Activated Delayed Fluorescence Emitters: Molecular Architectonics for Concurrently Achieving Narrowband Emission and Efficient Triplet–Singlet Spin Conversion

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