Browsing by Author "Chen, Yu-An"

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A Novel Structure to Reduce Degradation Under Mechanical Bending in Foldable Low Temperature Polysilicon TFTs Fabricated on Polyimide
(2020-05-01)
Wang, Yu-Xuan
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Chang, Ting-Chang
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Huang, Shin-Ping
;
Tai, Mao-Chou
;
Zheng, Yu-Zhe
In this study, a novel structural device, named as a wing-shaped TFT, is proposed and is demonstrated to prevent fast deterioration under mechanical bending in foldable devices. After long-term mechanical bending, standard low-temperature polysilicon TFTs exhibit instability behaviors such as sub-channel formation, serious threshold voltage shifts, an on-current (I-ON) increase, and an off-current (I-OFF) decrease. These phenomena are believed to be due to additional oxide traps along the channel-width edges of the gate insulator after bending. In order to suppress this degradation, a wing-shaped structure is proposed. By extending the active layer, degradation regions are shifted away from the main channel. Therefore, the reliability of the devices is enhanced. The transfer characteristics show enhanced electrical behavior after being held for 48 hours in a static bent condition, with an 88% drop in threshold voltage shift as well as a 55% decrease in subthreshold swing degradation, proving better durability of the foldable TFT to bending stress for devices with these wings. Time-dependent transfer characteristics, a COMSOL simulation, and device geometry are discussed to support our findings.
Accurate real-time sensing tip for aqueous NO with optical fibers embedded in active hydrogel waveguide
(2018-02-01)
Chung, Chieh-Wen
;
Tsai, May-Jywan
;
Lin, Peng-Wei
;
Huang, Ding-Wen
;
Wang, Kuan-Hsun
A NO sensing tip is made by inserting two parallel optical fibers inside a poly 2-hydroxyethyl methacrylate (PolyHEMA) hydrogel waveguide mixed with the probe molecule 1, 2-Diaminoanthraquinone (DAQ). There is a length difference of 1 mm between the two fibers, and the light has to propagate through the difference from the short fiber to the long fiber. The total cross section area of the active hydrogel waveguide embedded with the fibers is only 3mm x 1.2 mm. For practical use the tip is housed in a needle for mechanical protection and the sensing tip is able to detect aqueous NO concentration around 1 mu M with time resolution about 5 minutes. Such a sensing tip can be used to monitor the medical conditions inside the brain after a stroke or a brain injury. (C) 2018 Author(s).
Composition-balanced trimetallic MOFs as ultra-efficient electrocatalysts for oxygen evolution reaction at high current densities
(2020-12-15)
Raja, Duraisamy Senthil
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Huang, Chun-Lung
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Chen, Yu-An
;
Choi, YongMan
;
Lu, Shih-Yuan
Engineering synergistic effects of multi-component catalysts is the key for breakthrough catalyst design. Here, a maximized-entropy approach was proposed to maximize the synergistic effects for maximum enhancements in electrocatalytic efficiencies of multi-component catalysts. Accordingly, composition-balanced iron, cobalt, and nickel based trimetallic MOFs was developed and demonstrated outstanding oxygen evolution reaction (OER) performances with ultra-low overpotentials of 196 and 284 mV achieved at current densities of 10 and 1000 mA cm(-2), respectively, as well as an ultra-low Tafel slope of 29.5 mV dec(-1) in alkaline aqueous media. The catalyst was ultra-stable even when operated at ultra-high current densities, experiencing only 5% loss in current densities, when chronoamperometrically tested at an industrially relevant current density of 1000 mA cm(-2) for over 50 h. in situ Raman spectroscopy study and density functional theory simulations were conducted to explore the OER mechanism and to illustrate the validity of the proposed maximized-entropy approach.
Effect of ELA Energy Density on Self-Heating Stress in Low-Temperature Polycrystalline Silicon Thin-Film Transistors
(2020-08-01)
Huang, Shin-Ping
;
Chen, Hong-Chih
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Chen, Po-Hsun
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Zheng, Yu-Zhe
;
Chu, Ann-Kuo
The extent of the poly-silicon crystalline protrusion, a result of differences in excimer laser annealing (ELA), affects the performance and reliability of thin-film transistors (TFTs). This study investigates the degradation mechanism of the low-temperature polycrystalline silicon (LTPS) TFT devices with differences in crystalline protrusion under self-heating stress (SHS). Higher ELA energy will induce higher protrusion height in the interface between the poly-silicon and gate insulator (GI). This surface morphology leads to serious charge trapping into the GI layers; in contrast, the smallest degradation after SHS can be seen in the devices with the lowest protrusion height. This indicates that the degradation is caused by the surface morphology between the poly-Si and GI interface. In addition, the COMSOL simulation results confirm that the large electric field in the GI layer appears in the rough surface morphology devices; therefore, choosing the appropriate ELA energy of the poly-Si is beneficial for the applications of the driving TFT in organic light-emitting diode (OLED) display in the manufacturing industry.
Enabling High-Injection Current Light-Emitting Diodes Prepared on 10-mu m-Thick GaN Films Grown by Hydride Vapor Phase Epitaxy
(2015-09-01)
Chen, Yu-An
;
Chang, Chia-Wei
;
Kuo, Cheng-Huang
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照明與能源光電研究所
;
Institute of Lighting and Energy Photonics
In this paper, we successfully introduced the sputtered AlN/patterned sapphire substrate template into hydride vapor phase epitaxy (HVPE) using a two-step growth method. This method simplified the procedure, realized uninterrupted growth, and improved the crystal quality of GaN films. The effects of light-emitting diodes (LEDs) grown on a 10-mu m-thick GaN film through HVPE were also compared with those of the LEDs grown on a 2.4-mu m-thick GaN film through metal organic chemical vapor deposition (MOCVD). Compared with the LEDs grown on the 2.4-mu m-thick GaN film through MOCVD, the LEDs grown on the 10-mu m-thick GaN film through HVPE had significantly enhanced light output power (3.24-4.79 mW) and extended saturation current (300-355 mA). These improvements of the LEDs were attributed to the better thermal conductivities and better crystal quality of the 10-mu m-thick GaN film through HVPE than those of the 2.4-mu m-thick GaN film through MOCVD.
Enhancement of Mechanical Bending Stress Endurance Using an Organic Trench Structure in Foldable Polycrystalline Silicon TFTs
(2020-05-01)
Zheng, Yu-Zhe
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Huang, Shin-Ping
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Chen, Po-Hsun
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Chang, Ting-Chang
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Tsai, Tsung-Ming
This letter proposes a new organic trench structure which can enhance the endurance of polycrystalline silicon thin film transistors (TFTs) under mechanical bending stress. It compares conventional structure TFTs to devices with an organic trench to examine reliability after undergoing 100,000 iterations of channel width-axis (100,000'WC) compression at R = 2mm. Due to the low Young's modulus of organic materials, stress while undergoing bending strain is desorbed to the buffer layer, which can lower the overall stress in TFTs. Furthermore, an optimal location and ideal length for such an organic trench is evaluated by mechanical bending simulation.
Numerical Simulation and Experimental Analysis of Current Spreading Length in Nitride-Based Light-Emitting Diodes Prepared on 10-mu m-Thick n-GaN Template
(2015-11-01)
Chen, Yu-An
;
Chang, Chia-Wei
;
Kuo, Cheng-Huang
;
照明與能源光電研究所
;
Institute of Lighting and Energy Photonics
Numerical and experimental demonstrations were performed in this letter to enhance the current spreading length of nitride-based light-emitting diodes (LEDs) with a 10-mu m-thick n-GaN template on an AlN/high-aspect ratio patterned sapphire substrate template via hydride vapor phase epitaxy. At an injection current of 20 mA, the output powers were 4.34 and 6.39 mW for a conventional LED and an LED with a 10-mu m-thick n-GaN template, respectively. The larger LED output power is attributed to the enhanced current spreading length, which improved the heat dissipation ability and the improved crystal quality.
Perovskite film-wire transformation: Preparation, characterization and device application
(2019-06-01)
Chen, Yu-An
;
Yang, Sheng-Hsiung
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Chen, Po-Chih
;
Lin, Li-Jyuan
;
Wu, Zong-Yu
In this research, we demonstrate regular-type perovskite solar cells based on tungsten trioxide nanoparticles layer (WO3 NL) as the electron transport layer and methylammonium lead iodide nanowires (MAPbI(3) NWs) as the absorbing layer. By adjusting the amount of the anti-solvent DMF, MAPbI(3) NWs with different diameters ranging from 50 to 100 nm and lengths extending to several micrometers were obtained. [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM) and cesium carbonate (Cs2CO3) were introduced between WO3 NL and MAPbI(3) NWs to improve film morphology and charge transfer ability. Meanwhile, spiro-MeOTAD doped with bis(trifluoromethane)sulfonimide lithium salt (Li-TFSI) was utilized to enhance hole transport. Finally, the perovskite solar cells with the configuration of ITO/WO3 NL/Cs2CO3/PCBM/MAPbI(3) NWs/spiro-MeOTAD/Au were fabricated and evaluated. To date, perovskite NWs treating with the proper amount of the anti-solvent DMF possess higher absorption, faster carrier transportation and lower recombination that are responsible for photovoltaic application.
Spatial Correlation Between Efficiency and Crystal Structure in GaN-Based Light-Emitting Diodes Prepared on High-Aspect Ratio Patterned Sapphire Substrate With Sputtered AlN Nucleation Layer
(2014-07-01)
Chang, Li-Chuan
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Chen, Yu-An
;
Kuo, Cheng-Huang
;
照明與能源光電研究所
;
Institute of Lighting and Energy Photonics
In this paper, we investigate sputtered physical vapor deposition (PVD) AlN nucleation layer effects on crystal quality and efficiency of GaN-based light-emitting diodes (LEDs) prepared on high-aspect ratio patterned sapphire substrate (HARPSS). The crystal quality of the GaN epitaxial layer prepared on HARPSS with a PVD AlN nucleation layer was significantly better than that with a conventional metal organic chemical vapor deposition (MOCVD)-grown AlN nucleation layer. In addition, the pure wurzite structure GaN prepared on HARPSS could be obtained using PVD AlN nucleation layer. With the PVD AlN nucleation layer, the 20-mA LED light output power of the LEDs can be enhanced by 47.7% compared with the LEDs with the conventional MOCVD-grown AlN nucleation layer.
Void Shapes Controlled by Using Interruption-Free Epitaxial Lateral Overgrowth of GaN Films on Patterned SiO2 AlN/Sapphire Template
(2014)
Chen, Yu-An
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Kuo, Cheng-Huang
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Chang, Li-Chuan
;
Wu, Ji-Pu
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照明與能源光電研究所
GaN epitaxial layers with embedded air voids grown on patterned SiO2 AlN/sapphire templates were proposed. Using interruption-free epitaxial lateral overgrowth technology, we realized uninterrupted growth and controlled the shape of embedded air voids. These layers showed improved crystal quality using X-ray diffraction and measurement of etching pits density. Compared with conventional undoped-GaN film, the full width at half-maximum of the GaN (0 0 2) and (1 0 2) peaks decreased from 485 arcsec to 376 arcsec and from 600 arcsec to 322 arcsec, respectively. Transmission electron microscopy results showed that the coalesced GaN growth led to bending threading dislocation. We also proposed a growth model based on results of scanning electron microscopy.