Browsing by Author "Chen, Li-Yin"

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A facile approach to fabricate Ni inverse opals at controlled thickness
(2009-11-15)
Huang, Yi-Jui
;
Lai, Chun-Han
;
Wu, Pu-Wei
;
Chen, Li-Yin
;
材料科學與工程學系
A vertical electrophoretic deposition method was employed to fabricate polystyrene (PS) colloidal crystals with negligible defects and considerable surface uniformity. Subsequently, the interstitial voids within the colloidal crystals were electroplated with Ni, followed by selective removal of the PS microspheres. With careful adjustment in the processing parameters. we were able to obtain Ni inverse opals at predetermined thickness in relatively short time. The inverse opals revealed superb structural stability and surface uniformity. Because the electrophoresis and electrodeposition were both carried out in a solution state, this fabrication scheme enables facile construction of inverse opals on conductive substrates over conventional approaches. (C) 2009 Elsevier B.V. All rights reserved.
Dibenzothiophene/oxide and quinoxaline/pyrazine derivatives serving as electron-transport materials
(2006-07-21)
Huang, Tai-Hsiang
;
Whang, Wha-Tzong
;
Shen, Jiun Yi
;
Wen, Yuh-Sheng
;
Lin, Jiann T.
A series of 2,8-disubstituted dibenzothiophene and 2,8-disubstituted dibenzothiophene-SS-dioxide derivatives containing quinoxaline and pyrazine moieties are synthesized via three key steps: i) palladium-catalyzed Sonogashira coupling reaction to form dialkynes; ii) conversion of the dialkynes to diones; and iii) condensation of the diones with diamines. Single-crystal characterization of 2,8-di(6,7-dimethyl-3-phenyl-2-quinoxalinyl)-5H-5 lambda(6)-dibenzo[b,d]thiophene-5,5-dione indicates a triclinic crystal structure with space group P1 and a non-coplanar structure. These new materials are amorphous, with glass-transition temperatures ranging from 132 to 194 degrees C. The compounds (Cpd) exhibit high electron mobilities and serve as effective electron-transport materials for organic light-emitting devices. Double-layer devices are fabricated with the structure indium tin oxide (ITO)/Qn/Cpd/LiF/Al, where yellow-emitting 2,3-bis[4-(N-phenyl-9-ethyl-3-carbazolylamino)phenyl]quinoxaline (Qn) serves as the emitting layer. An external quantum efficiency of 1.41 %, a power efficiency of 4.94 lm W-1, and a current efficiency of 1.62 cd A(-1) are achieved at a current density of 100 mA cm(-2).
Effect of Crystallinity on the Optical Reflectance of Cylindrical Colloidal Crystals
(2011)
Lai, Chun-Han
;
Yang, Yu-Lin
;
Chen, Li-Yin
;
Huang, Yi-Jui
;
Chen, Jing-Yu
We fabricate cylindrical colloidal crystals (CCCs) via electrophoretic depositions of polystyrene microspheres on a carbon fiber in a concentric arrangement. Images from optical and scanning electron microscope indicate that the CCCs of 460 nm microspheres reveal a semicrystalline structure in close-packed lattice, while the CCCs of 660 exhibit an amorphous arrangement. In optical reflectance spectra, both CCCs demonstrate a dispersive photonic bandgap as compared to that from planar counterparts. The curved contour for the CCCs renders incident light interacting with reflecting planes at slightly different angles, leading to a notable reduction in the reflectance intensity and minor relocation of photonic bandgap contingent on their crystallinity. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3536511] All rights reserved.
Electrowetting of Superhydrophobic ZnO Inverse Opals
(2011)
Chen, Li-Yin
;
Lai, Chun-Han
;
Wu, Pu-Wei
;
Fan, Shih-Kang
;
材料科學與工程學系
ZnO inverse opals are fabricated by electrophoresis of polystyrene (PS) microspheres (720 nm in diameter) on a ITO glass to form a close-packed colloidal crystal, followed by potentiostatic deposition of ZnO in the interstitial voids among the PS microspheres and chemical removal of the PS colloidal template. By adjusting the electrodeposition time, we obtain semi-layered and multi-layered ZnO inverse structures with significantly reduced defects and considerable surface uniformity. The semi-layered ZnO inverse opals display a bowl-like morphology with individual cavities isolated from each other. In contrast, the multi-layered ZnO inverse opals exhibit a three-dimensional skeleton with hexagonally-arranged cavities interconnected to each other. After surface coating of perfluorodecyltriethoxysilane, both samples reveal a superhydrophobic nature with contact angle larger than 150 degrees. In electrowetting measurements, the contact angles are decreasing with increasing applied voltages. The droplet on the semi-layered ZnO inverse opals demonstrates a notable transition from the Cassie-Baxter state to the Wenzel one. However, the droplet on the multi-layered ZnO inverse opals indicates three distinct regimes; Cassie-Baxter state, mixed Cassie-Baxter/Wenzel state, and Wenzel state. Repelling pressure of the entrapped air in the cavities is estimated to explain the observed contact angle variation upon the applied voltage for both samples. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3594723] All rights reserved.
Enhanced light extraction from organic light-emitting devices through non-covalent or covalent polyimide-silica light scattering hybrid films
(2020-03-28)
Yen, Jui-Hua
;
Wang, Yi-Jyun
;
Hsieh, Chung-An
;
Chen, Yung-Chung
;
Chen, Li-Yin
In this work, two polyimide/silica composites were prepared via physical blending (A series) and chemical bonding (B series) and compared for light extraction from organic light-emitting devices (OLEDs). In the physical blending process, the hybrids were prepared from the corresponding poly(amic acid) (PAA) and tetramethyl orthosilicate (TMOS) by thermal imidization and sol-gel processes. In contrast, in the chemical bonding process, a series of hybrids were prepared using (3-aminopropyl)triethoxysilane (APTES) as a coupling agent followed by sol-gel and thermal imidization processes. Their optical, thermal, and morphological properties were investigated. The well-dispersed B series hybrid films showed higher optical transparency and lower haze characteristics than A series hybrid films. Furthermore, the scattering behavior was apparent as the silica content increased. They also exhibited high thermal stability with T-d (5% weight loss temperature) higher than 510 degrees C. Finally, these hybrid films were applied into OLEDs. The external quantum efficiency (EQE) of all devices employing the hybrid films on the viewer's side of the substrate as the outcoupling layer increased as the silica content increased. For the OLED utilizing A3 (26 wt% of silica content), an increase of 21% in the light extraction efficiency was achieved.
Ni Inverse Opals for Water Electrolysis in an Alkaline Electrolyte
(2010)
Huang, Yi-Jui
;
Lai, Chun-Han
;
Wu, Pu-Wei
;
Chen, Li-Yin
;
材料科學與工程學系
A vertical electrophoretic deposition technique was employed to prepare polystyrene (PS) colloidal crystals with negligible crystallographic defects. The colloidal crystals were plated with Ni, followed by selective removal of PS microspheres to fabricate inverse opals. With adjustments in relevant processing parameters, we were able to obtain inverse opals in multiple layers with excellent surface uniformities. The inverse opals were used as the electrode material for water electrolysis. Results from current-potential polarizations in 1 M KOH aqueous solution indicated that the catalytic abilities for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) increased with the layers of inverse opals. Estimation of the effective current densities determined that the entire area of the inverse opals was available for electrochemical reactions. In galvanostatic measurements for both OER and HER, the inverse opals demonstrated stable voltage profiles without notable degradations for 120 h. Compared with a planar Ni plate, the inverse opals exhibited a significantly reduced overpotential for the water electrolysis.
Rapid Fabrication of Cylindrical Colloidal Crystals and Their Inverse Opals
(2010)
Lai, Chun-Han
;
Huang, Yi-Jui
;
Wu, Pu-Wei
;
Chen, Li-Yin
;
材料科學與工程學系
We employed an electrophoretic deposition technique to prepare cylindrical colloidal crystals (CCCs) from polystyrene (PS) microspheres of 460 and 660 nm diameters using a carbon fiber (CF) with 7 mu m diameter as the substrate. Measurements on the CCC diameter demonstrated growth rates that slowed down as time progressed. Scanning electron microscope images confirmed that the CCCs of 460 nm microspheres formed a face-centered cubic close-packed lattice, whereas an amorphous structure appeared for the CCCs of 660 nm. Subsequently, both CCCs underwent a potentiostatic electroplating to deposit Ni into the interstitial voids among the PS microspheres. After chemical removal of the PS microspheres, we fabricated cylindrical inverse opals (CIOs) in various diameters. As expected, better crystallinity was found on the CIOs of 460 nm microspheres as opposed to the 660 nm ones. The electrical resistivity for both CIOs exhibited a substantial reduction over that of the CF. Our CCCs and CIOs revealed considerable structure stability with excellent surface uniformity. The fabrication scheme enables rapid preparations of CCCs and CIOs in desirable lengths and diameters.
Violet Laser Diode Enables Lighting Communication
(2017-09-05)
Chi, Yu-Chieh
;
Huang, Yu-Fang
;
Wu, Tsai-Chen
;
Tsai, Cheng-Ting
;
Chen, Li-Yin
Violet laser diode (VLD) based white-light source with high color rendering index (CRI) for lighting communication is implemented by covering with Y3Al5O12:Ce3+ (YAG:Ce) or Lu3Al5O12:Ce3+/CaAlSiN3: Eu2+ (LuAG: Ce/CASN: Eu) phosphorous diffuser plates. After passing the beam of VLD biased at 70 mA (similar to 2I(th)) through the YAG: Ce phosphorous diffuser, a daylight with a correlated color temperature (CCT) of 5068 K and a CRI of 65 is acquired to provide a forward error correction (FEC) certified data rate of 4.4 Gbit/s. By using the VLD biased at 122 mA (similar to 3.5I(th)) to excite the LuAG: Ce/CASN: Eu phosphorous diffuser with 0.85-mm thickness, a warm white-light source with a CCT of 2700 K and a CRI of 87.9 is obtained at a cost of decreasing transmission capacity to 2.4 Gbit/s. Thinning the phosphor thickness to 0.75 mm effectively reduces the required bias current by 32 mA to achieve the same CCT for the delivered white light, which offers an enlarged CRI of 89.1 and an increased data rate of 4.4 Gbit/s. Further enlarging the bias current to 105 mA remains the white-light transmission capacity at 4.4 Gbit/s but reveals an increased CCT of 3023 K and an upgraded CRI of 91.5.