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ABSTRACT: Highly efficient deep-blue organic light-emitting devices (OLEDs) have been fabricated using 2,7-di(2,2':6',2″-terpyridin-4-yl)-9,9-dioctyl-9H-fluorene (DTPF) as the emitter, which has a wide energy gap, high emission quantum yield (Φ(f) = 0.88), and high electron transporting property to improve the charge balance. A high efficiency of 2.55 cd/A and 2.67 lm/W are obtained in OLED. The device also exhibits a low turn-on voltage of 3.0 V and Commission Internationale de l'Éclairage (CIE) coordinates of (0.16, 0.09).
ACS Applied Materials & Interfaces 06/2012; · 4.53 Impact Factor
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ABSTRACT: Since 1987, the possibility of realizing a new generation display based on organic light-emitting diodes (OLEDs) has inspired
much interest in both academic and industrial groups. This review elucidates recent process in materials for OLEDs, approaches
to improve electroluminescent properties of devices, and recent works based on conjugated materials in our laboratory.
Frontiers of Optoelectronics in China 04/2012; 2(1):92-102.
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ABSTRACT: The spectral response of Poly(3-hexylthiophene) (P3HT): 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 (PCBM) heterojunction film is between 350 nm and 650 nm, meaning that a lot of the sunlight is lost at ultraviolet and infrared regions. We fabricated solar cells by the attachment of a fluorescence layer which absorbs UV light, and emit visible light which will be re-used by P3HT, and thus the absorption spectrum is expanded. Since N,N'-bis(3-methylphenyl)-N,N'-bis(phenyl)-benzidine (TPD) has high reflectance in the visible range, the usage of UV light will not manifest; when LiF is added as an antireflection layer, PCE was enhanced from 2.50% to 2.68%.
Optics Express 05/2011; 19 Suppl 3:A361-8. · 3.59 Impact Factor
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Yu Ye,
Yu Dai,
Lun Dai,
Zujin Shi,
Nan Liu,
Fei Wang,
Lei Fu,
Ruomin Peng,
Xiaonan Wen, Zhijian Chen,
Zhongfan Liu,
Guogang Qin
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ABSTRACT: High-performance single CdS nanowire (NW) as well as nanobelt (NB) Schottky junction solar cells were fabricated. Au (5 nm)/graphene combined layers were used as the Schottky contact electrodes to the NWs (NBs). Typical as-fabricated NW solar cell shows excellent photovoltaic behavior with an open circuit voltage of ∼0.15 V, a short circuit current of ∼275.0 pA, and an energy conversion efficiency of up to ∼1.65%. The physical mechanism of the combined Schottky electrode was discussed. We attribute the prominent capability of the devices to the high-performance Schottky combined electrode, which has the merits of low series resistance, high transparency, and good Schottky contact to the CdS NW (NB). Besides, a promising site-controllable patterned graphene transfer method, which has the advantages of economizing graphene material and free from additional etching process, was demonstrated in this work. Our results suggest that semiconductor NWs (NBs) are promising materials for novel solar cells, which have potential application in integrated nano-optoelectronic systems.
ACS Applied Materials & Interfaces 11/2010; 2(12):3406-10. · 4.53 Impact Factor
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ABSTRACT: Although organic light-emitting devices have been commercialized as flat panel displays since 1997, only singlet excitons were emitted. Full use of singlet and triplet excitons, electrophosphorescence, has attracted increasing attentions after the premier work made by Forrest, Thompson, and co-workers. In fact, red electrophosphorescent dye has already been used in sub-display of commercial mobile phones since 2003. Highly efficient green phosphorescent dye is now undergoing of commercialization. Very recently, blue phosphorescence approaching the theoretical efficiency has also been achieved, which may overcome the final obstacle against the commercialization of full color display and white light sources from phosphorescent materials. Combining light out-coupling structures with highly efficient phosphors (shown in the table-of-contents image), white emission with an efficiency matching that of fluorescent tubes (90 lm/W) has now been realized. It is possible to tune the color to the true white region by changing to a deep blue emitter and corresponding wide gap host and transporting material for the blue phosphor. In this article, recent progresses in red, green, blue, and white electrophosphorescent materials for OLEDs are reviewed, with special emphasis on blue electrophosphorescent materials.
Advanced Materials 10/2010; 23(8):926-52. · 13.88 Impact Factor
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ABSTRACT: The electroluminescent properties in red organic light-emitting diodes (OLEDs) doped with polar and non-polar red emitting molecules were studied. The emission chrominance changed from red to orange along with the increase in the bias voltage in the devices doped with polar molecules; however, the emitted colour in the devices doped with non-polar molecules was unaffected by the bias voltage and the viewing angle. The reason was assumed to be the orientation of polar molecules under the electric field, so that non polar molecule is the optimum candidate for red emitting dopants used in red OLEDs to obtain stable chrominance.
Journal of Physics D Applied Physics 02/2009; 42(5):055116. · 2.54 Impact Factor
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ABSTRACT: A facile way to fabricate highly efficient organic light emitting devices with insulator MnO as an electron injecting and transporting material was devised, which eliminates the problem of the oxidation of reactive dopants. The power efficiency of 1.1 lm / W by inserting 3- nm -thick MnO as the electron injecting layer was obtained, higher than the 0.8 lm / W efficiency for the reference device with 0.5- nm -thick LiF. A thermal coevaporation layer containing 10% weight of MnO and tris(8-hydroxyquinolato)aluminum ( Al q <sub>3</sub>) as the electron transporting layer showed more efficient electron transport ability, with turn-on voltage of 3.8 V , lower than 7.4 V for the intrinsic Al q <sub>3</sub> .
Applied Physics Letters 10/2008; · 3.84 Impact Factor
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ABSTRACT: An electroluminescent polymer was synthesized by Wittig condensation and characterized by the measurements of 1H-NMR, IR, gel permeation chromatography (GPC), UV–Vis, PL, and cyclic voltammetry (CV). The polymer can be dissolved in common organic solvents such as tetrahydrofuran (THF), chloroform, and dichloromethane. The electroluminescent investigation showed that the non-doped devices with a double-layer configuration (ITO/PEDOT:PSS/Polymer/Mg:Ag) have a stable green emission property. The maximum luminance of the annealed device reaches 2317 cd/m2. The emission maximum and the CIE 1931 coordinate values are respectively stabilized at 552 nm and near (x, y) = (0.43, 0.55) with different voltages. Copyright © 2008 John Wiley & Sons, Ltd.
Polymers for Advanced Technologies 09/2008; 19(12):1839 - 1843. · 2.01 Impact Factor
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ABSTRACT: A conjugated polymer with a carbazole moiety, poly(3,6-divinylene-N-octyl-carbazole-p-phenylene), was synthesized by Wittig reaction. The polymer can be dissolved in common organic solvents such as THF, chloroform, etc. Using this polymer as an active layer, single-layer non-doped PLEDs with different thicknesses were fabricated by a spin-coating approach. The results suggested that electroluminescence spectra are changed with the film thickness of the polymer emitter. Fortunately, CIE 1931 coordinate values are moved to the white-light region only by changing the film thickness. Copyright © 2008 John Wiley & Sons, Ltd.
Polymers for Advanced Technologies 07/2008; 19(8):1084 - 1091. · 2.01 Impact Factor
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ABSTRACT: The optical upconversion of infrared light to visible light has been achieved in photosensitizer-doped organic light-emitting diodes, where poly(N-vinylcarbazole) doped with infrared photosensitizer of 2,4,7-trinitro-9-fluorenylidene)malonitrile was used as hole-transporting layer, and tris(8-hydroxyquinoline) aluminum acted as both emitting and electron-transporting layers. Both electroluminescent intensity and current were enhanced under infrared illumination. The enhancement ratio was obtained as 2.45 times for electroluminescent emission and 1.45 times for current. This work brought forth a prototype design for novel flexible organic optical upconversion device used in near infrared field.
Applied Physics Letters 11/2007; 91(20):201107-201107-3. · 3.84 Impact Factor
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Journal of Polymer Science Part A Polymer Chemistry 09/2007; 45(21):4867 - 4878. · 3.92 Impact Factor
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ABSTRACT: The deliberate use of a thin SiO2 blocking layer between the indium tin oxide (ITO) electrode and the photorefractive (PR) composite to enhance the PR performance was reported. The extra SiO2 layer can provide a barrier for the hole injection so as to reduce the leaking current through the PR composite and improve the stability of devices. As a result, a stronger space-charge field was formed, that was represented by much higher diffraction efficiency η and two-beam coupling (TBC) coefficient Γ compared with the device without a SiO2 layer.
Journal of Optics A Pure and Applied Optics 04/2007; 9(5):486. · 1.92 Impact Factor
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ABSTRACT: Several conjugated polymers containing phenothiazine moieties in the main chain were synthesized by Knovenagel or Wittig condensations. The polymers were identified and characterized by 1H-NMR, IR, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), UV-vis and fluorescent (FL) spectra. Results indicated that the m-polymer, which was prepared from the polycondensation of N-octyl-3,7-diformylphenothiazine with m-phenylene diacetonitrile, is the most thermally stable one in all the polymers synthesized. While, the p-polymer, which was prepared from the polycondensation of N-octyl-3,7-diformylphenothiazine with p-phenylene diacetonitrile, is the most thermally instable one. The introduction of a cyano group made the absorption and emissive maxima red-shift from 429 and 537 nm for the Ph-polymer to 465 and 597 nm for the p-polymer respectively. The quinoid structure formation allows the p-polymer to have a lower band gap than any other polymers. Emissive spectra of all these polymers in tetrahydrofuran (THF) solution have a narrow half-peak width. Copyright © 2006 John Wiley & Sons, Ltd.
Polymers for Advanced Technologies 07/2006; 17(6):468 - 473. · 2.01 Impact Factor
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ABSTRACT: A new kind of non-doping red OLED was fabricated, using partially conjugated PPV as hole-transport material and non-doping DCM as emitter. The new OLED shows good performance of pure red luminescence.
Lasers and Electro-Optics, 2005. (CLEO). Conference on; 06/2005
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ABSTRACT: A photorefractive composite composed of 8-pertyloxy-4-cyanobiphenyl (8OCB)/N, N-diphenyl-N, N-bis(3-methylphenyl)-[1,1-biphenyl]-4,4-diamine (TPD)/2,4,7-trinitro-9-fluorenone (TNF)/tris(8-hydroxyquinoline) aluminium (Alq3)/polycarbonate plastic was fabricated. The additive of Alq3 in the composite leads to a larger two-beam coupling coefficient Γ and shorter response time. Γ over 330 cm−1 at an applied electric field of 26 V µm−1 was measured while Γ of the sample without Alq3 was only 213 cm−1. It is presumed that the electron-injecting material Alq3 and charge-transporting material TPD form more effective traps in the composite, which leads to the improvement in the PR performance.
Journal of Optics A Pure and Applied Optics 08/2004; 6(9):890. · 1.92 Impact Factor
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Journal of Materials Science 05/2004; 39(11):3783-3785. · 2.02 Impact Factor
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ABSTRACT: Doped with nanometer Au particles, a low- T<sub>g</sub> photorefractive polymer composite, poly( N -vinylcarbazole):2,4,7-trinitro-9-fluorenone:4- (dicyanovinyl- N,N -diethylaniline), exhibited an effective enhancement on its photorefractivity. Measurements on two-beam coupling (TBC) as well as four-wave mixing were carried out at 633 nm wavelength. At an applied electric field of 118 V/μm, TBC coefficient as high as 206 cm<sup>-1</sup> was obtained in the sample doped with Au particles, while only 152 cm<sup>-1</sup> in the sample without Au particles. The measurements on the effective electro-optic coefficient and the photorefractive phase shift for two samples with and without doping Au particles were performed, respectively. The observations of distinct difference on the photorefractive phase shift and no difference on the effective electro-optic coefficient implied that enhancement on the photorefractivity was due to the increment of the density of the effective trap center by doping Au particles. © 1999 American Institute of Physics.
Applied Physics Letters 12/1999; · 3.84 Impact Factor
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ABSTRACT: In this paper, the photorefractive properties of a low-glass-transition-temperature polymeric composite based on poly(N-vinylcarbazole) doped with an azo dye system with various lengths of alkoxy chain as an electro-optical (EO) chromophore and 2,4,7-trinitro-9-fluorenone as photosensitizer were studied by using two-beam coupling and four-wave-mixing experiments. The results showed that the alkoxy chain attached to azo dye can perform plasticization. An optimal length of alkoxy chain was selected.
Journal of Physics D Applied Physics 12/1998; 31(18):2245. · 2.54 Impact Factor
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ABSTRACT: A nonlinear optical molecule, β,β-diacetyl-4-methoxylstyrene (DAMST), was synthesized and used as the electro-optic chromophore in a photorefractive polymeric composite. Its absorption peak lies at 320 nm and shows no absorption at wavelengths longer than 400 nm. In a 100 μm thickness film of DAMST:poly(N-vinylcarbazole):2,4,7-trinitro-9-fluorenone with a weight ratio of 59:40:1, two-beam coupling gain was measured as high as 32 cm−1 at a wavelength of 543 nm. A response time as short as 17 ms was estimated at an applied electric field of 84 V/μm with a writing beam intensity of 1 W/cm2. © 1998 American Institute of Physics.
Applied Physics Letters 12/1998; 73(25):3629-3631. · 3.84 Impact Factor
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ABSTRACT: We has successfully synthesized a new bifunctional electro-optic chromophore, β,β-diacetyl-4-methoxylstyrene (DAMST) and fabricated the photorefractive polymer film doped with this chromophore. This composite was proved to possess good photorefractive properties at short wavelengths. Research at the 440 nm wavelength is in progress
Nonlinear Optics '98: Materials, Fundamentals and Applications Topical Meeting; 09/1998
