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Lai S.-L.,City University of Hong Kong | Tao S.-L.,University of Electronic Science and Technology of China | Chan M.-Y.,University of Hong Kong | Lo M.-F.,City University of Hong Kong | And 4 more authors.
Journal of Materials Chemistry | Year: 2011

We report the synthesis of a new biscyclometalated yellow phosphorescent dopant iridium(iii) bis[2-(2-naphthyl)pyridine](acetylacetonate) (Ir(npy) 2acac) and studies of its application in organic light-emitting devices (OLEDs), in which highly efficient yellow-emitting OLEDs with high peak forward viewing efficiencies of 34 cd A-1, 22 lm W-1, and 11% can be obtained, along with the Commission de L'Eclairage 1931 chromaticity coordinates of (0.45, 0.54). More importantly, yellow phosphorescence can be achieved without the formation of excimer emission. Particularly, such devices exhibit a very broad and featureless peak at ca. 550 nm with a wide full spectral width at half maximum (FWHM) of 87 nm. Furthermore, combination with iridium(iii) bis[(3,4,5,-trifluorophenyl)-pyridinato-N,C2′] picolinate doped p-bis-(triphenylsilyly)benzene as the blue-emitting layer yields highly efficient white OLEDs with maximum efficiencies as high as 46 cd A-1 and 41 lm W-1 in the forward direction, making Ir(npy)2acac a promising organic phosphor for applications in yellow and white OLEDs. © The Royal Society of Chemistry 2011. Source


Huang D.,CAS Technical Institute of Physics and Chemistry | Huang D.,University of Chinese Academy of Sciences | Ye J.,CAS Technical Institute of Physics and Chemistry | Ye J.,University of Chinese Academy of Sciences | And 8 more authors.
Yingxiang Kexue yu Guanghuaxue/Imaging Science and Photochemistry | Year: 2010

A new bipolar phosphorescence host material carbostyril derivative 3-(4-(9H-carbazol-9-yl) phenyl)-1-methyl-4-phenylquinolin-2(1H)-one was designed and synthesized. Through theoretical calculations we found that the HOMO and LUMO obitals respectively localed in carbazole group and carbostyril group, that imply this compound is a good bipolar material. The compound phosphorescence emission is 515 nm (2.41 eV), meet the basic requirement of green phosphorescence host material (> 2.40 eV). TGA and DSC results show the compound has high thermal stabilities, the decomposition temperature and glass transition temperature are 312°C and 105°C respectively. The results show that the new compound is a potential green phosphorescence host material with bipolar feature. Source


Tao S.,University of Electronic Science and Technology of China | Tao S.,City University of Hong Kong | Jiang Y.,University of Electronic Science and Technology of China | Lai S.-L.,City University of Hong Kong | And 5 more authors.
Organic Electronics: physics, materials, applications | Year: 2011

A new multifunctional compound, 4,4′-di-(1-pyrenyl)-4′′- [2-(9,9′-dimethylfluorene)]-triphenylamine (DPFA) has been designed, synthesized and applied respectively as host-emitter, electron- and hole-transporters in organic light-emitting devices (OLEDs). The compound exhibits good thermal stability with a glass transition temperature (T g) of 161 °C and shows blue emissions in both solution and films. OLEDs with DPFA playing various roles have been fabricated and characterized. The results show that DPFA has efficient bipolar charge transport properties for both hole and electron. By using DPFA as a blue emitter in a typical three layer device with a configuration of ITO/NPB(50 nm)/DPFA(20 nm)/TPBI(30 nm)/LiF(0.5 nm)/MgAg, highly efficient blue emission with a maximum luminescence efficiency of 5.1 cd/A (5.3 lm/W) is obtained. © 2010 Elsevier B.V. All rights reserved. Source


Tao S.,University of Electronic Science and Technology of China | Tao S.,Soochow University of China | Tao S.,City University of Hong Kong | Lai S.L.,University of Hong Kong | And 6 more authors.
Organic Electronics: physics, materials, applications | Year: 2011

Highly efficient blue phosphorescent organic light-emitting devices have been achieved by using a new emitter Iridium complex, bis[(3,4,5- trifluorophenyl)-pyridinato-N,C 2′] picolinate (F 3Irpic). For a mCP:4%F 3Irpic device, blue emission with a maximum power efficiency of 18.1 lm/W has been realized, which is much higher than those of FIrpic based devices. The emission peak was located at 480 nm with a subpeak at 511 nm. By using an optimized device structure with a better host material, performance of the device can be further increased to give a maximum power efficiency of 33.7 lm/W. © 2011 Elsevier B.V. All rights reserved. Source


Jiang Y.,University of Electronic Science and Technology of China | Tao S.,University of Electronic Science and Technology of China | Huang J.,University of Electronic Science and Technology of China | Zhou C.,University of Electronic Science and Technology of China | And 2 more authors.
Chemistry Letters | Year: 2012

A novel strategy for preparing large-area, vertically aligned silicon nanotip arrays at near-room temperature by combining a silver mirror reaction with metal-catalyzed electroless etching has been developed. It has been demonstrated that silicon nanotip arrays of lengths 4-7 μm and middle part diameters ranging from 100 to 300nm have been successfully fabricated on silicon wafers. Furthermore, the resultant large-area vertically aligned Si nanotip arrays on Si substrates are expected to be used in field-emission applications in the future and to have broad scope for development. Silicon nanotip films show very low reflectance (<10% at 300-800 nm) and strong broadband optical absorption (>90% at 500 nm). This transmission would be important for use as antireflection coatings on processed solar cells. These optical phenomena may lead to the realization of efficient solar cells based on Si nanostructures. © 2012 The Chemical Society of Japan. Source

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