Incorporation of a CN group into mCP: a new bipolar host material for highly efficient blue and white electrophosphorescent devices

Lin, Ming-Shiang; Yang, Shang-Jung; Chang, Hsiu-Ju; Huang, Yi‐Hsiang; Tsai, Yi-Wen; Wu, Chung‐Chih; Chou, Shu-Hua; Mondal, Ejabul; Wong, Ken‐Tsung

doi:10.1039/c2jm32717a

Cited by 157 publications

(101 citation statements)

References 53 publications

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“…The absorption peaks in the UV/Vis spectrum at around 293 nm can be assigned to p!p* transitions of the carbazole moiety and weaker absorption peaks at longer wavelengths of 326 and 339 nm are attributed to the n!p* transitions of extended conjugation of the carbazole moiety. [25] In addition, a relatively wide energy gap (E g ) of 3.56 eV is obtained from the onset of absorption. The photoluminescence (PL) spectrum of displays intense UV emission peaks at 346 and 363 nm.…”

Section: Photophysical Propertiessupporting

confidence: 79%

“…[17,23,24] Efforts have also been made to improve the thermal stability of mCP while still maintaining the molecules' desirable optoelectronic properties. [21,[25][26][27] Organic-inorganic hybrid materials are one of the best solutions for ideal host materials because the functionality and structural strength are easily achieved by design of the organic and the inorganic parts, respectively. [28][29][30][31][32][33] For instance, 3,5-di(N-carbazolyl)tetraphenylsilane (SimCP) is a good host for blue PhOLEDs: by linking the bulky triphenylsilyl group to the carbazole moiety in a non-conjugated way, the thermal stability is improved and steric hindrance favourably affects the molecular packing in the condensed phase.…”

Section: Introductionmentioning

confidence: 99%

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Oligosiloxane Functionalized with Pendant (1,3‐Bis(9‐carbazolyl)benzene) (mCP) for Solution‐Processed Organic Electronics

Sun¹,

Yang²,

Ren³

et al. 2014

Chemistry A European J

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A new oligosiloxane derivative (ODCzMSi) functionalized with the well‐known 1,3‐bis(9‐carbazolyl)benzene (mCP) pendant moiety, directly linked to the silicon atom of the oligosiloxane backbone, has been synthesized and characterized. Compared to mCP, the attachment of the oligosiloxane chain significantly improves the thermal and morphological stabilities with a high decomposition temperature (Td=540 °C) and glass transition temperature (Tg=142 °C). The silicon–oxygen linkage of ODCzMSi disrupts the backbone conjugation and maintains a high triplet energy level (ET=3.0 eV). A phosphorescent organic light‐emitting diode (PhOLED) using iridium bis(4,6‐difluorophenyl)pyridinato‐N,C2 picolinate (FIrpic) as the emitter and ODCzMSi as the host shows a relatively low turn‐on voltage of 5.0 V for solution‐processed PhOLEDs, maximum external quantum efficiency of 9.2 %, and maximum current efficiency of 17.7 cd A−1. The overall performance of this device is competitive with the best reported solution‐processed blue PhOLEDs. Memory devices using ODCzMSi as an active layer exhibit non‐volatile write‐once read‐many‐times (WORM) characteristics with high stability in retention time up to 104 s and a low switch on voltage. This switching behaviour is explained by different stable conformations of ODCzMSi with high or low conductivity states which are obtained under the action of electric field through a π–π stacking alignment of the pendant aromatic groups. These results with both PhOLEDs and memory devices demonstrate that this oligosiloxane–mCP hybrid structure is promising and versatile for high performance solution‐processed optoelectronic applications.

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Section: Photophysical Propertiessupporting

confidence: 79%

Section: Introductionmentioning

confidence: 99%

Oligosiloxane Functionalized with Pendant (1,3‐Bis(9‐carbazolyl)benzene) (mCP) for Solution‐Processed Organic Electronics

Sun¹,

Yang²,

Ren³

et al. 2014

Chemistry A European J

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“…530-550 nm without any evidence of mCP emission at 360 nm. 37 It is notable that the  max value of the EL spectra shifts to longer wavelength in the sequence Copo1 (533 nm) ˂ Copo2 (536 nm) ˂ Copo3 To elucidate the reason why Copo1 based OLEDs display the best performance in this series, the triplet energies of the four polymers were determined as shown in Figure 5b according to the phosphorescent spectra for which the highest energy peak defines the triplet energy (E T ). 14 As shown in Table 1, Copo1 has the highest E T (2.46 eV) and E T decreases with decreasing the content of styrene.…”

mentioning

confidence: 99%

Pendant Homopolymer and Copolymers as Solution-Processable Thermally Activated Delayed Fluorescence Materials for Organic Light-Emitting Diodes

Ren

Nobuyasu²,

Dias³

et al. 2016

Macromolecules

145

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The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. This study reports a series of polymers with an insulating backbone and varying ratios of 2-(10H-phenothiazin-10-yl)dibenzothiophene-S,S-dioxide as a pendant TADF unit. Steady-state and time-resolved fluorescence spectroscopic data confirm the efficient TADF properties of the polymers. Styrene, as a co-monomer, is shown to be a good dispersing unit for the TADF groups, by greatly supressing the internal conversion and triplet-triplet annihilation.Increasing the styrene content within the copolymers results in relatively high triplet energy, small energy splitting between the singlet and triplet states (E ST ) and a strong contribution from delayed fluorescence to the overall emission. Green emitting OLED devices employing these polymers as spin-coated emitting layers give high performance, which is dramatically enhanced in the copolymers compared to the homopolymer. Within the series, Copo1 with a regiorandom ratio of 37% TADF units : 63% styrene units displays the best performance with a maximum external quantum efficiency (EQE) of 20.1% and EQE at 100 cd m -2 of 5.3%.2

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“…Thus, the exciton formation is dominated by the host, and variousk inds of hosts have been used.A mong the many hostt ypes,b ipolar hosts and mixedh osts have been popularb ecause of balancedc arrier transporta nd wider ecombination zone for high external quantum efficiency( EQE) andl ong lifetime. [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] In particular, the mixed host has been provent ob ee ffective to upgrade the device performances. However,i nt he case of deep blue OLEDs, it has been challenging to develop mixed hosts because of difficulty of the design of high triplet energye lectron transport( n-type) host for phosphors or TADF emitters.…”

Section: Introductionmentioning

confidence: 99%

Zig‐Zag Type Molecular Design Strategy of N‐Type Hosts for Sky‐Blue Thermally‐Activated Delayed Fluorescence Organic Light‐Emitting Diodes

Yang

Lee

2020

Chemistry A European J

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N‐type hosts for long lifetime in sky‐blue thermally‐activated delayed fluorescence (TADF) organic light‐emitting diodes (OLEDs) were investigated by synthesizing four hosts with zig‐zag‐type backbone structure for high triplet energy. The four hosts had two CN units at different positions of the zig‐zag‐type backbone structure and two dibenzofuran units through either the 2 or 4‐position of dibenzofuran. The position of the CN unit was controlled at the meta and para‐positions in the zig‐zag‐type backbone to study the relationship between material parameters and lifetime of the TADF OLEDs. It was revealed that the meta‐orientation of the CN units in the backbone was advantageous to extend device lifetime of the sky‐blue TADF OLEDs.

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Incorporation of a CN group into mCP: a new bipolar host material for highly efficient blue and white electrophosphorescent devices

Cited by 157 publications

References 53 publications

Oligosiloxane Functionalized with Pendant (1,3‐Bis(9‐carbazolyl)benzene) (mCP) for Solution‐Processed Organic Electronics

Oligosiloxane Functionalized with Pendant (1,3‐Bis(9‐carbazolyl)benzene) (mCP) for Solution‐Processed Organic Electronics

Pendant Homopolymer and Copolymers as Solution-Processable Thermally Activated Delayed Fluorescence Materials for Organic Light-Emitting Diodes

Zig‐Zag Type Molecular Design Strategy of N‐Type Hosts for Sky‐Blue Thermally‐Activated Delayed Fluorescence Organic Light‐Emitting Diodes

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