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Han H.-V.,King Abdullah University of Science and Technology | Han H.-V.,Institute of Electro Optical Engineering | Lu A.-Y.,King Abdullah University of Science and Technology | Lu L.-S.,National Chiao Tung University | And 11 more authors.
ACS Nano | Year: 2016

Atomically thin two-dimensional transitionmetal dichalcogenides (TMDCs) have attracted much attention recently due to their unique electronic and optical properties for future optoelectronic devices. The chemical vapor deposition (CVD) method is able to generate TMDCs layers with a scalable size and a controllable thickness. However, the TMDC monolayers grown by CVD may incorporate structural defects, and it is fundamentally important to understand the relation between photoluminescence and structural defects. In this report, point defects (Se vacancies) and oxidized Se defects in CVD-grown MoSe2 monolayers are identified by transmission electron microscopy and X-ray photoelectron spectroscopy. These defects can significantly trap free charge carriers and localize excitons, leading to the smearing of free band-To-band exciton emission. Here, we report that the simple hydrohalic acid treatment (such as HBr) is able to efficiently suppress the trapstate emission and promote the neutral exciton and trion emission in defective MoSe2 monolayers through the p-doping process, where the overall photoluminescence intensity at room temperature can be enhanced by a factor of 30. We show that HBr treatment is able to activate distinctive trion and free exciton emissions even from highly defective MoSe2 layers. Our results suggest that the HBr treatment not only reduces the n-doping in MoSe2 but also reduces the structural defects. The results provide further insights of the control and tailoring the exciton emission from CVD-grown monolayer TMDCs. © 2015 American Chemical Society.


Chang H.-W.,National Tsing Hua University | Meng H.-F.,National Chiao Tung University | Horng S.-F.,National Tsing Hua University | Zan H.-W.,Institute of Electro Optical Engineering
Synthetic Metals | Year: 2016

Large-area top-emitting organic light-emitting diodes (TEOLEDs) with multi-layer structure are successfully demonstrated using the solution-processable blade coating on ITO-free substrate. The semitransparent cathode of TEOLED is composed of lithium fluoride (LiF), aluminum (Al) and silver (Ag). The composition of 3 nm Al and 10 nm Ag has a transmittance of 56% and a sheet resistance of 11 Ω/□. It is applied to the green phosphorescence device with an emissive area of 2 cm by 2.5 cm. The maximum current efficiency is 25.2 cd/A with high light-emission uniformity within 10% variation. The large-area TEOLEDs show comparable current efficiency as the small-area devices with an emissive area of 2 mm by 2 mm (having the same device structure) and better efficiency than traditional large-area bottom-emitting devices. Cesium fluoride (CsF) and n-doped electron transport layer are applied to improve electron injection. At 6 V, the luminance is raised from 141 cd/m2 to 502 cd/m2 and 304 cd/m2, respectively. In n-doped device, a simple Al/Ag cathode is used without LiF. © 2015 Elsevier B.V. All rights reserved.


Tsai P.-T.,National Chiao Tung University | Tsai C.-Y.,National Tsing Hua University | Wang C.-M.,National Chiao Tung University | Chang Y.-F.,Institute of Electro Optical Engineering | And 7 more authors.
Organic Electronics: physics, materials, applications | Year: 2014

High-performance polymer cells are typically fabricated by employing toxic solvents such as dichlorobenzene and chlorobenzene. In this study, blade coating with the chlorine-free solvents toluene and xylene is applied to polymer solar cells that contained the low band-gap polymer PBDTTT-C-T blended with [6,6]-phenyl-C71-butyric acid methyl ester ([70]PCBM). The highest efficiencies of the cells fabricated in toluene and xylene solutions were 6.09% and 6.11%, respectively. Atomic force microscopy images show that the films formed by blade coating using toluene and xylene were extremely smooth, with roughness of only 1 nm. This blade coating has a rapid-drying in a few seconds without the long-running thermal or solvent annealing. The possibility of high-volume environmentally-friendly fabrication of efficient polymer solar cells with minimal material waste is thus demonstrated using a combination of chlorine-free solvents and blade coating. © 2014 Elsevier B.V. All rights reserved.


Zan H.-W.,Institute of Electro Optical Engineering | Zan H.-W.,National Chiao Tung University | Chen W.-T.,Institute of Electro Optical Engineering | Chou C.-W.,Institute of Electro Optical Engineering | And 4 more authors.
Electrochemical and Solid-State Letters | Year: 2010

Instead of the conventional furnace annealing process with a temperature higher than 300° C, two low temperature annealing methods are successfully demonstrated to suppress the instability problem of amorphous indium gallium zinc oxide (IGZO) thin film transistors (TFTs). With adequate Nd:yttrium aluminum garnet laser (266 nm) annealing energy density or Xe excimer UV lamp (172 nm) irradiation time, the on voltage shift is greatly suppressed from over 10 to 0.1 V. The influence of laser energy density and UV lamp irradiation time on the performance of IGZO TFTs is also investigated and explained. The proposed methods are promising for the development of amorphous IGZO TFTs on flexible substrates. © 2010 The Electrochemical Society.


Chen T.-G.,Institute of Electro Optical Engineering | Huang B.-Y.,Institute of Electro Optical Engineering | Liu H.-W.,Institute of Electro Optical Engineering | Huang Y.-Y.,Institute of Electro Optical Engineering | And 3 more authors.
ACS Applied Materials and Interfaces | Year: 2012

Hybrid organic-silicon heterojunction solar cells promise a significant reduction on fabrication costs by avoiding energy-intensive processes. However, their scalability remains challenging without a low-cost transparent electrode. In this work, we present solution-processed silver-nanowire meshes that uniformly cover the microtextured surface of hybrid heterojunction solar cells to enable efficient carrier collection for large device area. We systematically compare the characteristics and device performance with long and short nanowires with an average length/diameter of 30 μm/115 nm and 15 μm/45 nm, respectively, to those with silver metal grids. A remarkable power conversion efficiency of 10.1% is achieved with a device area of 1 × 1 cm2 under 100 mW/cm2 of AM1.5G illumination for the hybrid solar cells employing long wires, which represents an enhancement factor of up to 36.5% compared to the metal grid counterpart. The high-quality nanowire network displays an excellent spatial uniformity of photocurrent generation via distributed nanowire meshes and low dependence on efficient charge transport under a high light-injection condition with increased device area. The capability of silver nanowires as flexible transparent electrodes presents a great opportunity to accelerate the mass deployment of high-efficiency hybrid silicon photovoltaics via simple and rapid soluble processes. © 2012 American Chemical Society.


Chung W.-F.,Institute of Electronics | Chang T.-C.,National Sun Yat - sen University | Li H.-W.,Institute of Electro Optical Engineering | Tseng T.-Y.,Institute of Electronics | Tai Y.-H.,National Chiao Tung University
Electrochemical and Solid-State Letters | Year: 2011

The original influence of water on the back-channel of sol-gel derived amorphous indium-gallium-zinc-oxide thin film transistors was studied in various relative humidity environments. As humidity increased from 0 to 80%, the mobility increased from 0.22 to 0.24 cm2 / (V s), threshold voltage decreased from 6.6 to 4.4 V, and subthreshold swing changed from 0.77 to 1.27 V/dec. The conflicting phenomenon among the three parameters was suggested to be due to a division of the gate voltage by the water molecules which adsorbed on the thin film transistor back-channel and acted as dipoles. © 2010 The Electrochemical Society.


Chou Y.-T.,Institute of Electro Optical Engineering | Hsu T.-H.,National Chiao Tung University
Electrochemical and Solid-State Letters | Year: 2011

In this study, an aluminum-nickel-lanthanum (Al-Ni-La) alloy is introduced, for the first time, to hydrogenated amorphous silicon thin film transistor (a-Si:H TFT) for gate metallization technology. Ni atoms in Al-Ni-La can effectively improve contact characteristic with ITO film, while La can increase the uniformity of contact resistance during film deposition compared to the conventional Al-Nd alloy. Besides, Al-Ni-La alloy has advantages of a simple process and better prevention against hillock issues, which benefits active matrix liquid-crystal display (AMLCD) manufacture. The Al-Ni-La gate thin film transistor (TFT) also exhibited reliable electrical characteristics. The process compatibility with typical TFT manufacture makes Al-Ni-La gate metallization greatly promising for AMLCD technology application. © 2010 The Electrochemical Society.


Huang Y.-P.,National Chiao Tung University | Chen C.-W.,Institute of Electro Optical Engineering | Huang Y.-C.,Institute of Electro Optical Engineering
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2011

The fast response Fresnel liquid crystal lens with multiple electrodes structure had been proposed and optimized. The multi electrodes in the new Fresnel LC lens were placed at both inner surfaces of LC cell. By supplying specific operating voltages on each electrode, the optimized Fresnel LC lens was closed to the ideal Fresnel lens. The experiment results indicated that the Fresnel LC lens not only performed fast switching rate without over-drive method, but also had the advantage of low operating voltage. Furthermore, by using overdriving method, the response time could be further reduced but just need 15 volts in a short time. It meant that a fast switching between 2D and 3D image display could be obtained by switching Fresnel LC lens on and off. In the end, the fast switching display was also demonstrated.


Liou J.-H.,Institute of Electro Optical Engineering | Huang S.-S.,Institute of Electro Optical Engineering | Yu C.-P.,Institute of Electro Optical Engineering
Optics Communications | Year: 2010

We have theoretically investigated the birefringence and loss properties of the selectively liquid-filled photonic crystal fibers with the liquid asymmetrically infiltrated into one-line air holes along x-axis. A high birefringence value B = 1.74 × 10-3 can be achieved at λ = 1.55 μm. By varying the index of the infiltrating liquid, the birefringence values are shown to be well tuned. In addition, the confinement losses can be efficiently reduced by diminishing the number of liquid holes, which is quite useful for optical devices. © 2009 Elsevier B.V. All rights reserved.


Hong G.-H.,Institute of Electro Optical Engineering | Yu P.,Institute of Electro Optical Engineering
Conference Record of the IEEE Photovoltaic Specialists Conference | Year: 2011

Tunnel diodes, also known as Esaki diodes, play an important role in III-V multi junction solar cells. In this work, we theoretically investigated the electrical characteristics of a GaAs tunnel diode and its performance against the illumination conditions such as light intensity, spatial profile, etc. We then developed a methodology to optimize a triple junction InGap/GaAs/Ge solar cell with a GaAs tunnel junction. The conversion efficiency drops with the increase of the concentration ratio is also discussed. © 2011 IEEE.

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