Center for Display Research

Kowloon, Hong Kong

Center for Display Research

Kowloon, Hong Kong
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Zhao Z.,Hangzhou Normal University | Lam J.W.Y.,Hong Kong University of Science and Technology | Chan C.Y.K.,Hong Kong University of Science and Technology | Chen S.,Center for Display Research | And 10 more authors.
Advanced Materials | Year: 2011

Stereoregular tetraphenylethene derivatives (Z)-o-BCaPTPE and (Z)-o-BTPATPE featured with chiasmatic conformations and aggregation-enhanced emission characteristics are synthesized using a McMurry reaction. Both luminogens exhibit high hole and electron mobilities. Organic light-emitting diodes (OLEDs) using (Z)-o-BCaPTPE and (Z)-o-BTPATPE as both the light-emitting and electron-transporting layers show high efficiencies. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Yuan W.Z.,Hong Kong University of Science and Technology | Yuan W.Z.,Shanghai JiaoTong University | Chen S.,Center for Display Research | Lam J.W.Y.,Hong Kong University of Science and Technology | And 8 more authors.
Chemical Communications | Year: 2011

Combination of an aggregation-induced emission (AIE) moiety and a dimesitylboron group yields a new three-coordinate boron compound exhibiting a synergistic effect: the resultant TPEDMesB shows AIE feature with solid-state emission efficiency up to unity and good electron-transport property, and thus remarkable electroluminescence (EL) performances. © 2011 The Royal Society of Chemistry.


Liu Y.,Hong Kong University of Science and Technology | Liu Y.,Shandong University | Chen S.,Center for Display Research | Lam J.W.Y.,Hong Kong University of Science and Technology | And 4 more authors.
Journal of Materials Chemistry | Year: 2012

In organic light-emitting devices, materials with efficient electron-transporting properties, are essential. In this report, oxadiazole-containing tetraphenylethene TPE-Oxa is synthesized and its optical physics and electronic properties are investigated. The dye is almost nonluminescent when molecularly dissolved in solutions, but becomes highly emissive when aggregated in poor solvents or fabricated as thin films in the solid state. A quantum yield of unity has been achieved in its solid thin film. Inherited from the oxadiazole component, the dye molecule enjoys low-lying electronic band energies. Benefiting from the good electron-transporting and hole-blocking properties of the dye, the two-layer OLED devices using TPE-Oxa as both light-emitting and electron-transporting materials show superior performance, i.e., lower turn-on voltage, higher brightness and efficiencies, to the devices of typical configuration with a dedicated electron-transporting layer. © 2012 The Royal Society of Chemistry.


Zhao Z.,Hangzhou Normal University | Chan C.Y.K.,Hong Kong University of Science and Technology | Chen S.,Center for Display Research | Deng C.,Hong Kong University of Science and Technology | And 10 more authors.
Journal of Materials Chemistry | Year: 2012

Tetraphenylethene (TPE) is an archetypal luminogen that exhibits a phenomenon of aggregation-induced emission (AIE), while carbazole is a conventional chromophore which shows the opposite effect of aggregation-caused quenching (ACQ) of light emission in the condensed phase. Melding the two units at the molecular level generates a group of new luminescent materials that suffer no ACQ effect but depict high solid-state fluorescence quantum yields up to unity, demonstrative of the uniqueness of the approach to solve the ACQ problem of traditional luminophores. All the TPE-carbazole adducts are thermally and morphologically stable, showing high glass-transition temperatures (up to 179 °C) and thermal-degradation temperatures (up to 554 °C). Multilayer electroluminescence devices with configurations of ITO/NPB/emitter/TPBi/Alq 3/LiF/Al are constructed, which exhibit sky blue light in high luminance (up to 13650 cd m -2) and high current and external quantum efficiencies (up to 3.8 cd A -1, and 1.8%, respectively). The devices of the luminogens fabricated in the absence of NPB or hole-transporting layer show even higher efficiencies up to 6.3 cd A -1 and 2.3%, thanks to the good hole-transporting property of the carbazole unit. © 2012 The Royal Society of Chemistry.


Chan C.Y.K.,Hong Kong University of Science and Technology | Zhao Z.,Hong Kong University of Science and Technology | Lam J.W.Y.,Hong Kong University of Science and Technology | Liu J.,Hong Kong University of Science and Technology | And 11 more authors.
Advanced Functional Materials | Year: 2012

Benzene-cored luminogens with multiple triarylvinyl units are designed and synthesized. These propeller-shaped molecules are nonemissive when dissolved in good solvents, but become highly emissive when aggregated in poor solvents or in the solid state, showing the novel phenomenon of aggregation-induced emission. Restriction of intramolecular motion is identified as the main cause for this effect. Thanks to their high solid-state fluorescence quantum yields (up to unity) and high thermal and morphological stabilities, light-emitting diodes with the luminogens as emitters give sky-blue to greenish-blue light in high luminance and efficiencies of 10800 cd m -2, 5.8 cd A -1, and 2.7%, respectively. The emissions of the nanoaggregates of the luminogens can be quenched exponentially by picric acid, or selectively by Ru 3+, with quenching constants up to 10 5 and ∼2.0 × 10 5 L mol -1, respectively, making them highly sensitive (and selective) chemosensors for explosives and metal ions. Benzene-cored luminogens with multiple triarylvinyl units exhibit aggregation-induced emission. The high solid-state fluorescence quantum yields and high thermal and morphological stabilities of such emitters gave light-emitting diodes with sky-blue to greenish-blue light in high luminance and efficiencies. The emission could be quenched exponentially by picric acid, or selectively by Ru 3+, making them highly sensitive (and selective) chemosensors for explosives and metal ions. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Li J.,Hong Kong University of Science and Technology | Jiang Y.,Center for Display Research | Cheng J.,HKUST | Zhang Y.,HKUST | And 8 more authors.
Physical Chemistry Chemical Physics | Year: 2015

In this contribution, we finely tuned the singlet-triplet energy gap (ΔEST) of AIE-active materials to modulate their fluorescence, phosphorescence and delay fluorescence via rational molecular design and investigated the possible ways to harvest their triplet energy in OLEDs. Noteworthily, two molecules o-TPA-3TPE-o-PhCN and o-TPA-3TPE-p-PhCN with larger ΔEST values (0.59 eV and 0.45 eV, respectively) emitted efficient long-lived low temperature phosphorescence in their glassy solutions and exhibited efficient crystallization-induced room temperature phosphorescence (RTP). Meanwhile, it was the first time to observe a novel crystallization-induced delay fluorescence phenomenon in another AIE-active molecule p-TPA-3TPE-p-PhCN owing to its very small ΔEST value (0.21 eV). It was also found that molecules with various ΔEST values showed significantly different temperature sensitivity. Non-doped electroluminescent (EL) devices using these molecules as light-emitting layers were fabricated, exhibiting external quantum efficiencies (EQE) higher than theoretical values of purely singlet emitter type devices. Particularly, p-TPA-3TPE-p-PhCN showed outstanding device performances with high luminance and efficiencies up to 36 900 cd m-2, 11.2 lm W-1, 12.8 cd A-1 and 4.37%, respectively, considering that its solid-state quantum yield was only 42%. All the above observations suggested that tuning the ΔEST values of AIE materials is a powerful methodology to generate many more interesting and meaningful optoelectronic properties. © the Owner Societies 2015.


Mei J.,Zhejiang University | Wang J.,Zhejiang University | Sun J.Z.,Zhejiang University | Zhao H.,Zhejiang University | And 11 more authors.
Chemical Science | Year: 2012

Three dimethyltetraphenylsiloles (DMTPSs) symmetrically substituted on their 2,5-positions with electron-accepting (A), i.e. aldehyde (ALD) and dicyanovinyl (DCV) or donating (D), i.e. diphenylamine (DPA) moieties were designed and synthesized via facile reaction procedures. The propeller-shaped luminogens exhibit aggregation-induced/enhanced emission characteristics with high quantum yields up to 74.0% in the solid state, and are thermally stable, showing high degradation temperatures and melting points up to 388 and 246 °C, respectively. Thanks to the contained A or D moieties, the siloles show intriguing solvatochromism: DMTPS-ALD exhibits almost no response to solvents due to the balance of electron affinities of the aldehyde and the silole core. Whereas, DMTPS-DCV and DMTPS-DPA possess outward intramolecular charge-transfer (ICT) from the silole core and the phenyl rings on its 3,4-positions to dicyanovinyl groups, and inward ICT from diphenylamine groups to the silole core, respectively, showing positive solvatochromism. A multilayer organic light-emitting diode using DMTPS-DPA among the luminogens as an emitter layer shows the highest performance with turn-on voltage, maximum luminance, current, power, and external efficiencies of 3.1 V, 13405 cd m -2, 8.28 cd A -1, 7.88 lm W -1, and 2.42%, respectively. Furthermore, DMTPS-DPA can also serve in hole-transporting layers because of its high hole-mobility. Therefore, the incorporation of a triphenylamine moiety into a silole system not only changes the classical aggregation-caused quenching fluorophore into AEE-active DMTPS-DPA, another example of "turning stone into gold", but also enhances the hole-transporting ability of siloles. © 2012 The Royal Society of Chemistry.


Zhao Z.,Hong Kong University of Science and Technology | Zhao Z.,Hangzhou Normal University | Deng C.,Hong Kong University of Science and Technology | Chen S.,Center for Display Research | And 8 more authors.
Chemical Communications | Year: 2011

Full color luminogens are constructed from tetraphenylethene, benzo-2,1,3-thiadiazole and thiophene building blocks. OLED fabricated using one of the luminogens exhibits orange-red electroluminescence with high luminance and efficiencies of 8330 cd m-2, 6.1 cd A-1 and 3.1%, respectively. © 2011 The Royal Society of Chemistry.


Yuan W.Z.,Hong Kong University of Science and Technology | Yuan W.Z.,Fok Ying Tung Research Institute | Lu P.,Hong Kong University of Science and Technology | Lu P.,Fok Ying Tung Research Institute | And 11 more authors.
Advanced Materials | Year: 2010

(Figure Presented) Efficient solid-state emitters developed by a new approach are described. While emission from triphenylamine (TPA) and its dimer (DTPA) is weakened by aggregation, attaching tetraphenylethene (TPE) units to the amines boosts their emission efficiencies up to 100% in the aggregate state. without harming their hole-transport properties. The resultant 3TPETPA and 4TPEDTPA luminogens show excellent electroluminescence performance. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA.


Zhao Z.,Hong Kong University of Science and Technology | Zhao Z.,Hangzhou Normal University | Chen S.,Center for Display Research | Lam J.W.Y.,Hong Kong University of Science and Technology | And 9 more authors.
Journal of Materials Chemistry | Year: 2011

Pyrene-substituted ethenes, 1,2,2-tripheny-1-pyrenylethene (TPPyE) and 1,2-diphenyl-1,2-dipyrenylethene (DPDPyE), are synthesized and characterized. Whereas they are weakly emissive in solution they become strong emitters when aggregated in the condensed phase. In contrast to the general observation that excimer formation quenches the light emission of fluorophores, TPPyE and DPDPyE exhibit efficient excimer emissions in the solid state with high fluorescence quantum yields up to 100%. The π-π intermolecular interactions between the pyrene rings, coupled with multiple C-H⋯π hydrogen bonds, efficiently restrict intramolecular rotations, which block the nonradiative energy decay channel, and hence make the dye molecules highly emissive in the solid state. Non-doped organic light-emitting diodes using TPPyE and DPDPyE as emitters are fabricated, which give green light at low turn-on voltages (down to 3.2 V) with maximum luminance and power, current, and external quantum efficiencies of 49830 cd m-2, 9.2 lm W-1, 10.2 cd A-1 and 3.3%, respectively. © 2011 The Royal Society of Chemistry.

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