Simple bipolar host materials incorporating CN group for highly efficient blue electrophosphorescence with slow efficiency roll-off

Deng, Lijun; Li, Jiuyan; Wang, Gexia; Wu, Li‐Zhu

doi:10.1039/c3tc31893a

Cited by 84 publications

(84 citation statements)

References 19 publications

(24 reference statements)

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Electron transport can be plausible through dibenzofuran and the CN-modified biphenyl backbone with electron accepting ability. [21][22][23][24][25] It is expected that the management of the substitution position and interconnectionp ositionm ay control the carrier transport properties and energy levels of the hosts. The molecular design for electron transport properties was confirmed by picturing the highest-occupied molecular orbital (HOMO)a nd lowest-unoccupied molecular orbital (LUMO), based on frontier molecular orbital calculations using the B3LYP 6-31G* basis set in the Gaussian software.…”

Section: Resultsmentioning

confidence: 99%

“…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%

See 1 more Smart Citation

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

View full text Add to dashboard Cite

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.

show abstract

Section: Resultsmentioning

confidence: 99%

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

View full text Add to dashboard Cite

show abstract

“…In the UV‐vis absorption spectra, the two compounds showed similar absorption profiles, with three distinguishable absorption bands in the range of 240–350 nm. The higher energy absorption band appearing below ≈290 nm was assigned to the localized π–π* electronic transitions of the carbazole and dibenzofuran building blocks, while the longer wavelength absorption band above ≈320 nm corresponds to the delocalized π–π* electronic transitions of the conjugative aromatic segments comprising of cyanocarbazole and dibenzofuran units . The long wavelength absorption band of the di‐substituted derivative ( dBFCzCN ) was slightly red‐shifted (≈8 nm) compared to that of the mono‐substituted analogue ( mBFCzCN ).…”

Section: Resultsmentioning

confidence: 99%

“…Other than the hole transport and electron transport units, aromatic moieties such as dibenzofuran, dibenzothiophene, and biphenyl were also incorporated into the molecular structure as rigid building units . However, the design and development of dibenzofuran, carbazole and cyano merged bipolar host materials for PhOLEDs are rarely studied in the literature . Therefore, further research into using these units in the design of high triplet energy host materials for PhOLEDs is highly desirable.…”

Section: Introductionmentioning

confidence: 99%

“…[11,12] However,t he design and development of dibenzofuran, carbazole and cyano mergedb ipolar host materialsf or PhOLEDsa re rarely studied in the literature. [13] Therefore, further research into using theseu nits in the designo fh igh triplet energy host materials for PhOLEDsi sh ighly desirable. We envisaged that the introductiono ft he carbazole and cyano units into the dibenzofuranb uilding block would impartg ood bipolar charge transport characteristics,improvethermalstability,p rovide high triplet energy,a nd consequently improve the performances of PhOLEDs.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Decoration of Dibenzofuran Using Cyanocarbazole via 6‐Position as a Molecular Design Approach for High‐Triplet‐Energy Bipolar Host Materials

Konidena

Lee

2018

Chemistry An Asian Journal

View full text Add to dashboard Cite

In this study, two new dibenzofuran derivatives featuring one or two cyanocarbazole units, 6‐(dibenzo[b,d]furan‐4‐yl)‐9‐phenyl‐9H‐carbazole‐3‐carbonitrile (mBFCzCN) and 6,6′‐(dibenzo[b,d]furan‐4,6‐diyl)bis(9‐phenyl‐9H‐carbazole‐3‐carbonitrile) (dBFCzCN), were developed as host materials for phosphorescent organic light emitting diodes (PhOLEDs). A new molecular design connecting the cyanocarbazole to the dibenzofuran using the cyanocarbazole 6‐position instead of its 9‐position was created, and the effects of number of cyanocarbazole units in the dibenzofuran building block on the photophysical and electroluminescence properties were investigated in detail. The mBFCzCN compound revealed high triplet energy (2.78 eV) than that of dBFCzCN (2.68 eV) and good bipolar charge transporting properties. The potential of these materials as hosts for blue and green PhOLEDs was investigated using bis(4,6‐(difluorophenyl)pyridinato‐N,C2′)picolinate iridium(III) (FIrpic) and tris(2‐phenylpyridinato)iridium(III) (Ir(ppy)3) dopants, respectively. The results indicated that the mBFCzCN with one cyanocarbazole unit showed better device performance than the dBFCzCN with two cyanocarbazole units in the blue and green devices. High external quantum efficiencies of 19.0 and 21.2 % were demonstrated in the blue and green PhOLEDs with the mBFCzCN host due to its high triplet energy and good bipolar charge transporting characteristics.

show abstract

Orthogonal Molecular Structure for Better Host Material in Blue Phosphorescence and Larger OLED White Lighting Panel

Liu

Dong

Jiang

et al. 2014

Adv Funct Materials

147

View full text Add to dashboard Cite

1wileyonlinelibrary.com power effi ciency (PE) >50 lm W −1 and low effi ciency roll-off at 5000 cd m −2 are still rare. [ 5 ] Considering the pursuit of various blue emitters is still ongoing, [ 6 ] it is also necessary to develop new host materials to test different kinds of emitting phosphors. Furthermore, another main application for blue hosts is for the high-effi ciency white light emission; their performances on large-size lighting panels are fascinating but still a blank in recent literature reports. [ 6 ] Therefore, constant efforts should be devoted to developing good host materials that can achieve high efficiency and fl at effi ciency roll-off simultaneously in blue/white PHOLEDs.The compounds with spiro-core are good candidates in constructing bipolar materials for the inherent orthogonal structure of two molecular halves. In addition, this approach can also effi ciently suppress intermolecular interaction by their adamant backbone, resulting in better solubility and cause entanglement in the amorphous state, then hinder recrystallization. [ 7 ] The development of spiro host material, however, is relatively slower as compared with other series of host materials. In 2005, the fi rst example of spiro host materials named SSS based on 9,9′-spirobifl uorene core is reported, which obtained EQE of ≈10% for red phosphorescence. [ 8 ] In 2008, the fi rst spiro bipolar molecule D2ACN integrated with electron-rich diphenylamine and electron-defi cient nitrile is prepared, but the EQE is just slightly improved to 10.8% with PE of 13 lm W −1 as red host material. [ 9 ] To date, there are just several attempts on blue hosts based on spiro-structure and the device performances are moderate. [ 10 ] Recently, we reported a blue host material SSTF based on new STF core, which could achieved a PE of 41.5 lm W −1 and an EQE of 18.7%. [ 11 ] In the STF molecular structure, a triphenylamine moiety is placed in vertical confi guration to fl uorene. This confi guration endows good hole-transporting ability to STF and makes it unnecessary to introduce any other arylamine groups on spiro backbone that always reduces the triplet energy (such as D2ACN). On the other hand, the fl uorene moiety can be further modifi ed by appending electron-deficient groups to enhance bipolar property. Herein, we design and prepare a new spiro host material POSTF by appending phosphine oxide group on the fl uorene moiety. It demonstrates very high EQE and extremely low effi ciency roll-offs for sky-blue (small size) and white (large size) phosphorescent devices. Orthogonal Molecular Structure for Better Host Material in Blue Phosphorescence and Larger OLED White Lighting PanelLei Ding , Shou-Cheng Dong , Zuo-Quan Jiang , * Hua Chen , and Liang-Sheng Liao * High-effi ciency blue phosphorescence devices with external quantum effi ciencies above 25% are developed using a new bipolar host material, diphenyl(10-phenyl-10 H -spiro[acridine-9,9′-fl uoren]-2′-yl)phosphine oxide (POSTF), which is constructed in orthogonal molecular structure with a ...

show abstract

Simple bipolar host materials incorporating CN group for highly efficient blue electrophosphorescence with slow efficiency roll-off

Cited by 84 publications

References 19 publications

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

Decoration of Dibenzofuran Using Cyanocarbazole via 6‐Position as a Molecular Design Approach for High‐Triplet‐Energy Bipolar Host Materials

Orthogonal Molecular Structure for Better Host Material in Blue Phosphorescence and Larger OLED White Lighting Panel

Contact Info

Product

Resources

About