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ABSTRACT: Highly ordered arrays of Cu-rich and -deficient CuInSe(2) nanotubes as well as ZnO/CuInSe(2) core/sheath nanocables have been synthesized on glass substrates by using ZnO nanorod arrays as sacrificial templates via a low-cost solution method. Chemical conversions from hexagonal ZnO to cubic ZnSe, hexagonal CuSe and tetragonal CuInSe(2) are demonstrated as a novel means for synthesis of I-III-VI nanomaterials. Large differences in their solubility product constant (K(sp)) are crucial for direct exchange in the conversions. In solvothermal reaction of ZnO/CuSe core/shell nanocables with InCl(3), the triethylene glycol solvent serves as a reducing agent for the reduction of cupric (Cu(2+)) to cuprous (Cu(+)) ions and also as an agent for the dissolution of ZnO cores. The absorption coefficient of the CuInSe(2) nanotubes in the visible region is on the order of 10(4) cm(-1). Photoelectrochemical solar cells were fabricated with arrays of ZnO/Cu(1.57±0.10)In(0.68±0.10)Se(2) and ZnO/CuSe nanocables. It was found that power conversion efficiency of the ZnO/Cu(1.57±0.10)In(0.68±0.10)Se(2) cell is about two times higher than that based on ZnO/CuSe.
ACS Nano 10/2010; 4(10):6064-70. · 10.77 Impact Factor
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Jun Xu,
Yong-Bing Tang,
Xue Chen,
Chun-Yan Luan,
Wen-Feng Zhang,
Juan Antonio Zapien,
Wen-Jun Zhang, Hoi-Lun Kwong,
Xiang-Min Meng,
Shuit-Tong Lee,
Chun-Sing Lee
Advanced Functional Materials 09/2010; 20(23):4190 - 4195. · 10.18 Impact Factor
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09/2008;
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ABSTRACT: An efficient nondoped green organic light-emitting device was demonstrated by using a dual-functional electroluminescent material, 4,4<sup>′</sup>,4<sup>″</sup> -tris[8-(7,10-diphenylfluoranthenyl)] phenylamine (TDPFPA). TDPFPA was shown to be a good hole transporting [with a mobility of (1.1–1.2)×10<sup>-4</sup> cm <sup>2</sup> V <sup>-1</sup> s <sup>-1</sup> at (1.8–5.6)×10<sup>5</sup> V cm <sup>-1</sup> ] and efficient fluorescent material with an exceptionally high glass transition temperature of 237 ° C . The device with a simple structure of indium tin oxide/TDPFPA/4,7-diphenyl-1,10-phenanthroline/ Li F / Al showed green emission with Commission Internationale de L’Eclairage coordinates of (0.24, 0.54), a current efficiency of 9.9 cd / A , and power efficiency of 10.6 lm / W .
Applied Physics Letters 11/2007; · 3.84 Impact Factor
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ABSTRACT: This paper reports the synthesis of a new starburst molecule, 4,4′,4′′-tris[(2,3,4,5-tetraphenyl)phenyl]phenylamine (TTPPPA) and its application as a hole-transporting material in organic light-emitting devices (OLEDs). Although TTPPPA has almost the same ionization potential as 1,4-bis(1-naphthylphenylamino)biphenyl (NPB), the TTPPPA-based device of ITO/TTPPPA/Alq3/LiF/Al yields much better efficiency of 5.3 cd/A and 4.3 lm/W than the standard ITO/NPB/Alq3/LiF/Al device (3.0 cd/A and 2.9 lm/W). The remarkable performance enhancement is attributed to a better balance of hole and electron injection in the TTPPPA-based device. Further, TTPPPA has a much higher glass-transition temperature (Tg, 202 °C) than NPB (Tg, 98 °C), suggesting that TTPPPA can be an alternative material to NPB especially for high-temperature applications of OLEDs and other organic electronic devices.
10/2007;
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ABSTRACT: High-efficiency nondoped white organic light-emitting devices (WOLEDs) were demonstrated by using both the intrinsic and exciplex emissions from a single electroluminescent material, 4,4′,4″-trispyrenylphenylamine (TPyPA). The simple device structure of indium tin oxide/N,N′-bis(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine/TPyPA/4,7-diphenyl-1,10-phenanthroline/LiF/Al exhibited a luminance of 10 000 cd/m2 at a low driving voltage of 4.5 V, and high current and power efficiencies of 9.4 cd/A and 9.0 lm/W, respectively. Such WOLED showed excellent color stability and purity with the Commission Internationale de L’Eclairage coordinates of (0.31, 0.35), which remained unchanged over a wide range of luminance from 100 to 20 000 cd/m2.
Applied Physics Letters 07/2007; 91(2):023503-023503-3. · 3.84 Impact Factor
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ABSTRACT: A new hole-transporting material, 1,3,4,5,6,7-hexaphenyl-2-{3‘-(9-ethylcarbazolyl)}-isoindole (HPCzI), has been synthesized. The new compound is a highly phenylated isoindole with good thermal and chemical stabilities. Thermal analysis using scanning calorimetry shows the compound to have a high melting point at 311.5 °C. Its bulky structure leads to good film-forming properties of the compound via thermal evaporation. Aside from the high hole mobility, the compound possesses other important attributes required for a good hole-transporting host material for applications in organic electroluminescence. The photophysical property of HPCzI and its performance as a hole-transporting material in a double-layered electroluminescent device were investigated. At a drive voltage of 8.8 V and a current density of 20 mA/cm2, the device with a configuration of ITO/HPCzI/AlQ3/MgAg (30 Ω/□:700 Å:700 Å:2000 Å) showed a green AlQ3 emission with a current efficiency of 3.5 cd/A.
07/2003;
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ABSTRACT: A new blue light-emitting fluorene derivative 2,7-di[8-(7,10-diphenylfluoranthenyl)]-9,9-dimethylfluorene (DFDF) with good thermal stability at 420 °C has been synthesized and characterized. An organic light-emitting device (OLED) with the structure of ITO/NPB (70 nm)/DFDF (30 nm)/TPBI (20 nm)/LiF (0.5 nm)/ Al (100 nm) has been investigated, where DFDF serves as a nondoped host emitter. Such a device possesses high current and power efficiencies of 3.8 cd/A and 2.6 lm/W, respectively, and stable bright blue-light emission at λ) 474 nm with Commission Internationale de L'Eclairage coordinates of (0.16, 0.23) over a wide range of operating voltages. The present results verify that DFDF is a promising candidate for a fluorescent blue-light-emitting OLED.
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ABSTRACT: A new compound with intramolecular charge transfer (ICT) property—5,6-Bis-[4-(naphthalene-1-yl-phenyl-amino)-phenyl]-pyrazine-2,3-dicarbonitrile(BNPPDC) was synthesized. The new compound was strongly fluorescent in non-polar and moderately polar solvents, as well as in thin solid film. The absorption and emission maxima shifted to longer wavelength with increasing solvent polarity. The fluorescence quantum yield also increased with increasing solvent polarity from non-polar to moderately polar solvents, then decreased with further increase of solvent polarity. This indicates both “positive” and “negative” solvatokinetic effects co-existed. Using this material as hole-transporting emitter and host emitter, we fabricated two electroluminescent (EL) devices with structures of A (ITO/BNPPDC (45 nm)/1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene (TPBI) (45 nm)/Mg:Ag (200 nm) and B (ITO/N,N′-diphenyl-N,N′-bis-(3-methylphenyl) (1,1′-diphenyl)4,4′-diamine (TPD) (50 nm)/BNPPDC (20 nm)/1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene (TPBI) (45 nm)/Mg:Ag (200 nm). The devices showed green-yellow EL emission with good efficiency and high brightness. For example, the device A exhibited a high brightness of 17400 cd/m2 at a driving voltage of 11 V and a very low turn-on voltage (2.9 V), as well as a maximum luminous efficiency 3.61 cd/A. The device B showed a similar performance with a high brightness of 12650 cd/m2 at a driving voltage of 13 V and a maximum luminous efficiency 3.62 cd/A. In addition, the EL devices using BNPPDC as a host and 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) as a dopant (configuration: ITO/TPD (60 nm)/BNPPDC:DCJTB (2%) (30 nm)/TPBI (35 nm)/Mg:Ag (200 nm)) showed a good performance with a brightness of 150 cd/m2 at 4.5 V, a maximum brightness of 12600 cd/m2 at 11.5 V, and a maximum luminous efficiency of 3.30 cd/A.
Journal of Luminescence. 124(2):221-227.
