High-triplet-energy tri-carbazole derivatives as host materials for efficient solution-processed blue phosphorescent devices

Jiang, Wei; Duan, Lian; Qiao, Juan; Dong, Guifang; Zhang, Deqiang; Wang, Liduo; Qiu, Yong

doi:10.1039/c0jm03365k

Cited by 126 publications

(49 citation statements)

References 44 publications

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“…These side chains are expected to enable the twisted confi guration of the molecule, resulting in a higher T g . [ 9 ] These ter -carbazole hosts exhibit a higher E T (>2.90 eV) and a higher T g (>140 °C) compared with mCP. (Details on synthesis and photophysical properties are provided in the Supporting Information.)…”

Section: Introductionmentioning

confidence: 99%

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Efficiency Roll‐Off in Blue Emitting Phosphorescent Organic Light Emitting Diodes with Carbazole Host Materials

Xiang

Wei³

et al. 2016

Adv Funct Materials

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1463wileyonlinelibrary.com dynamics. By nature, triplet excitons have a long lifetime. Under high current injection conditions, high density of triplet excitons leads to triplet-triplet annihilation (TTA) and triplet-polaron quenching (TPQ), which are the dominating loss mechanisms contributing to effi ciency roll-off. [ 3 ] Therefore, in order to determine the detail quenching mechanisms and the origin of effi ciency roll-off, it is important to characterize the interactions between triplet excitons and polarons. In this work, we use different carbazole hosts and study how these interactions affect the effi ciency roll-off. We studied the effi ciency roll-off in blue emitting phosphorescent OLEDs using iridium (III) bis(4,6-(di-fl uorophenyl) pyridinato-N,C 2 ′) picolinate (FIrpic) as the emitter and carbazole derivatives as the hosts. One carbazole compound commonly used as a host for FIrpic is 1,3-bis( N -carbazolyl)benzene (mCP). While high effi ciencies and long operating lifetimes have been realized in green and red emitting phosphorescent OLEDs, the performance of the blue emitting devices is still a bottleneck. [ 4 ] mCP is used as a host for FIrpic for the following reasons. First, carbazole compounds such as mCP have a high hole mobility value ( µ h ) of 5 × 10 −4 cm 2 V −1 s −1 . Second, mCP has a high triplet energy ( E T ) of 2.9 eV to prevent back energy transfer. [ 5 ] Because of the high E T , FIrpic doped mCP has a PL quantum yield of over 90% when used as the emitting layer. [ 6 ] Third, carbazole compounds have a small singlet and triplet energy splitting. This energy splitting can be as small as about 0.3-0.5 eV, [ 7 ] resulting in a lower turn-on voltage in blue phosphorescent OLEDs. [ 2 ] However, mCP has a low glass transition temperature ( T g ) of 60 °C, [ 8 ] due to its fl at molecular shape. It is therefore desirable to increase the T g of the carbazole materials to improve device stability.Here, we compare the device performance and effi ciency roll-off in blue phosphorescent devices using four carbazole derivatives as the host materials. In addition to the molecular weight of a compound, the T g of an organic material can be controlled by manipulating the steric hindrance of a molecule without lowering the E T . [ 9 ] For carbazole compounds, this can be done by adding additional carbazole units. Figure 1 shows the molecular structures of the derivatives in addition to mCP used in this study. While keeping the same peripheral carbazole groups, three additional derivatives were synthesized: a phenyl group is attached to the 9′-position of the carbazole core for 9′-phenyl-9,3′:6′9″-(9CI)-Ter-9H-carbazole (PTC), an ethyl group is attached to the 9′-position on the core carbazole for Effi ciency Roll-Off in Blue Emitting Phosphorescent Organic Light Emitting Diodes with Carbazole Host MaterialsChaoyu Xiang , Xiangyu Fu , Wei Wei , Rui Liu , Yong Zhang , Viktor Balema , Bryce Nelson , and Franky So * The effi ciency roll-off in blue phosphorescent organic light emitting diodes (OLEDs)...

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Section: Introductionmentioning

confidence: 99%

“…In addition to the molecular weight of a compound, the T g of an organic material can be controlled by manipulating the steric hindrance of a molecule without lowering the E T . [ 9 ] For carbazole compounds, this can be done by adding additional carbazole units. Figure 1 shows the molecular structures of the derivatives in addition to mCP used in this study.…”

mentioning

confidence: 99%

Efficiency Roll‐Off in Blue Emitting Phosphorescent Organic Light Emitting Diodes with Carbazole Host Materials

Xiang

Wei³

et al. 2016

Adv Funct Materials

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“…Previous molecular designs have been mostly focused on networking through the 3,6-positions of the carbazole. For example,Jiang et al [9] synthesized a novel carbazole derivative,using a carbazole monomer as the rigid core with two pyridine containing groups linked to the core though the 3,6-positions. Very recently, Li et al [10] also reported a series of carbazole derivatives whose energy gaps should be 3.59 and 3.43 eV, respectively.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and characterization of novel 2,7-carbazole derivatives for blue light-emitting diodes

Liu

Zhao

et al. 2014

J Mater Sci: Mater Electron

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Two 2,7-carbazole based low molecular weight derivatives, 9-hexyl-N 2 ,N 2 ,N 7 ,N 7 -tetraphenyl-carbazole-2,7-diamine (TPCA) and 9 0 -hexyl-9 0 H-9,2 0 :7 0 ,9 00 -tercarbazole (HTC), were synthesized by Buchwald and Ullmann coupling reactions, respectively. The optical, electrochemical and thermal properties of this two analogous small molecule hosts have been characterized. The HOMO level of TPCA and HTC were -5.25 and -5.29 eV indicating good hole-transporting properties. Both of the compounds emit deep blue light peaked at 410 and 428 nm in solid state. According to the measurement, the luminescence quantum yield of TPCA is 0.98, almost 1.7 times higher than that of HTC (0.59) in dilute THF solution. The geometrical and electronic properties of the compounds were studied using density functional theory calculations. The studies mentioned above indicate that both TPCA and HTC are suitable for active materials of blue light-emitting diodes.

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“…Although in this paper, it was noted that 35IPNDCz-based OLED exhibited larger EQE roll-off at high current density than 26IPNDCz counterpart (at 0.05 => 100 mAcm -2 , 9.2 => 1.4% and 9.6 => 4.3%, respectively, effects of their structure deviation (2,6- was obtained from CuI-1,10-phenanthroline-catalyzed coupling between 7a and phenyl iodide in 90% yield 6) . 8) .…”

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confidence: 97%

[Paper] Syntheses and Physical Properties of Carbazole-Phthalonitrile-Hybridized Light-Emitting Materials

Shinohara

Suzuma

Nishida

et al. 2015

MTA

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between the first singlet (S 1 ) and triplet (T 1 ) excited states. Adachi group reported that dimeric carbazolephthalonitrile-hybrid molecules 26IPNDCz and 35IPNDCz sieved as TADF light-emitting material to achieve EQE = 9.6% and 9.2%%, respectively ( Fig. 1) 3) .Although in this paper, it was noted that 35IPNDCz-based OLED exhibited larger EQE roll-off at high current density than 26IPNDCz counterpart (at 0.05 => 100 mAcm -2 , 9.2 => 1.4% and 9.6 => 4.3%, respectively, effects of their structure deviation (2,6-vs 3,5-phthalonitriles) to their physical properties were not investigated. We were intrigued in electronic interaction between carbazole and phthalonitrile moieties in 26 and

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High-triplet-energy tri-carbazole derivatives as host materials for efficient solution-processed blue phosphorescent devices

Cited by 126 publications

References 44 publications

Efficiency Roll‐Off in Blue Emitting Phosphorescent Organic Light Emitting Diodes with Carbazole Host Materials

Efficiency Roll‐Off in Blue Emitting Phosphorescent Organic Light Emitting Diodes with Carbazole Host Materials

Synthesis and characterization of novel 2,7-carbazole derivatives for blue light-emitting diodes

[Paper] Syntheses and Physical Properties of Carbazole-Phthalonitrile-Hybridized Light-Emitting Materials

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