Browsing by Author "Wu, Meng-Chyi"

Now showing 1 - 20 of 51

1.7 to 2.3 Gbps OOK LED VLC Transmission Based on 4 x 4 Color-Polarization-Multiplexing at Extremely Low Illumination
(2019-08-01)
Yeh, Chien-Hung
;
Weng, Jui-Hung
;
Chow, Chi-Wai
;
Luo, Chien-Ming
;
Xie, Yue-Ru
To achieve the high traffic rate of a GaN LED-based visible light communication (VLC), a 4 x 4 color-polarization-multiplexing system is demonstrated by using two blue and two green LEDs. In the measurement, an available bandwidth of blue and green LEDs can be greater than 465 MHz for VLC modulation traffic by using the suitable analogy front end circuit. Hence, the proposed VLC system can deliver 1.7 to 2.3 Gbit/s ON-OFF keying traffic rates in the free space transmission length of 1-4 m under the extremely low illumination of 6.9-136.1 lux for the indoor application. Moreover, the measured BER of each LED is less than the forward error correction target of 3.8 x 10(-3) to maintain the better signal performance.
A cascade energy band structure enhances the carrier energy in organic vertical-type triodes
(2013-09-01)
Cheng, Shiau-Shin
;
Ramesh, Mohan
;
Chen, Guan-Yuan
;
Fung, Chun-Lin
;
Chen, Li-Ming
Organic vertical-type triodes (OVTs) based on the cascade energy band structure as emitter layer are studied. The electric characteristics were dramatically enhanced while incorporating the cascade energy under current driving and voltage driving modes. The improvement is attributed to that injection carriers can obtain higher energy through a stepwise energy level. When the device has a layered structure of F16CuPC (10 nm)/PTCDI (10 nm)/pentacene (100 nm) in emitter, it exhibits a common-base transport factor of 0.99 and a common-emitter current gain of 225 under current driving mode and exhibits a high current modulation-exceeding -520 mu A for a low collector voltage of -5 V and a base voltage of -5 V and the current on/off ratio of 10(3) under voltage driving mode. Furthermore, we realized first organic current mirror that exhibited out/in current ratio of 0.75 and output resistance of 10(5) Omega by using the OVTs. (C) 2013 Published by Elsevier B.V.
A non-selenization technology by co-sputtering deposition for solar cell applications
(1970-01-01)
Jheng, Bao-Tang
;
Liu, Po-Tsun
;
Wu, Meng-Chyi
;
Shieh, Han-Ping D.
;
光電工程學系
"This work presents a novel method to form polycrystalline Cu(In1-xGax)Se-2 (CIGS) thin film by co-sputtering of In-Se and Cu-Ga alloy targets without an additional selenization process. An attempt was also made to thoroughly elucidate the surface morphology, crystalline phases, physical properties, and chemical properties of the CIGS films by using material analysis methods. Experimental results indicate that CIGS thin films featured densely packed grains and chalcopyrite phase peaks of (112), (220), (204), (312), and (116). Raman spectroscopy analysis revealed chalcopyrite CIGS phase with Raman shift at 175 cm(-1), while no signal at 258 cm(-1) indicated the exclusion of Cu2-xSe phase. Hall effect measurements confirmed the polycrystalline Cu(In, Ga)Se-2 thin film to be of p type semiconductor with a film resistivity and mobility of 2.19 x 102 Omega cm and 88 cm(2)/V s, respectively. (C) 2012 Optical Society of America"
A promising sputtering route for dense Cu2ZnSnS4 absorber films and their photovoltaic performance
(2014-09-01)
Jheng, Bao-Tang
;
Liu, Po-Tsun
;
Wu, Meng-Chyi
;
光電工程學系
;
顯示科技研究所
Copper zinc tin sulfide (Cu2ZnSnS4, CZTS) is highly abundant in nature. It is an important absorber material for the development of low-cost and sustainable next-generation I-2-II-IV-VI4 thin-film solar cells because it has a the tunable direct band gap energy, inexpensive constituent elements, and a large absorption coefficient in the visible wavelength region. This work develops an efficient one-step vacuum-based approach to depositing CZTS films without the need to supply excess sulfur during/after deposition or to perform any post-sulfurization treatment. This one-step RF sputtering process produces CZTS films that are crystalline, phase-pure, dense, smooth, and continuous. Air Mass 1.5 G power conversion efficiencies of as high as 6% have been achieved with an antireflection coating, demonstrating that this new approach has great potential as a low-cost alternative for high-efficiency CZTS solar cell production. (C) 2014 Elsevier B.V. All rights reserved.
A promising sputtering route for dense Cu2ZnSnS4 absorber films and their photovoltaic performance
(2014-09-01)
Jheng, Bao-Tang
;
Liu, Po-Tsun
;
Wu, Meng-Chyi
;
光電工程學系
;
顯示科技研究所
Copper zinc tin sulfide (Cu2ZnSnS4, CZTS) is highly abundant in nature. It is an important absorber material for the development of low-cost and sustainable next-generation I-2-II-IV-VI4 thin-film solar cells because it has a the tunable direct band gap energy, inexpensive constituent elements, and a large absorption coefficient in the visible wavelength region. This work develops an efficient one-step vacuum-based approach to depositing CZTS films without the need to supply excess sulfur during/after deposition or to perform any post-sulfurization treatment. This one-step RF sputtering process produces CZTS films that are crystalline, phase-pure, dense, smooth, and continuous. Air Mass 1.5 G power conversion efficiencies of as high as 6% have been achieved with an antireflection coating, demonstrating that this new approach has great potential as a low-cost alternative for high-efficiency CZTS solar cell production. (C) 2014 Elsevier B.V. All rights reserved.
Ambipolar transport behavior in In(2)O(3)/pentacene hybrid heterostructure and their complementary circuits
(2008-07-21)
Dhananjay
;
Ou, Chun-Wei
;
Yang, Chuan-Yi
;
Wu, Meng-Chyi
;
Chu, Chih-Wei
In this Letter, ambipolar transport properties of a bilayer of In(2)O(3) and a pentacene heterostructure have been realized. While In(2)O(3) thin film transistors exhibited a n-channel behavior, pentacene presumed p-channel characteristics on bare SiO(2)/p-Si substrates. However, when a bilayer of In(2)O(3)/pentacene was realized on the gate dielectrics, the hybrid structure exhibited both n- and p-channel conductions, depicting an ambipolar transistor behavior. When two identical ambipolar transistors were integrated to establish an inverter structure, a voltage gain of 10 was obtained. The results indicate that these heterostructures can be utilized for the complementary circuits. (C) 2008 American Institute of Physics.
Annealing effect of polymer bulk heterojunction solar cells based on polyfluorene and fullerene blend
(2009-02-01)
Huang, Jen-Hsien
;
Yang, Chuan-Yi
;
Ho, Zhong-Yo
;
Kekuda, Dhananjay
;
Wu, Meng-Chyi
Control of blend morphology at the nanoscale and high charge mobility is essential for polymer photovoltaic devices in terms of their power conversion efficiencies (PCE). In the case of bulk heterojunctions solar cells, both blend morphology and charge mobility are influenced by thermal treatment. In this manuscript, we study the effects of annealing temperature on polymer PV devices with blends of poly[9,9'-dioctyl-fluorene-co-bithiophene] (F8T2) and [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM). The morphological changes of blended films were observed upon thermal annealing temperature near and above glass transition temperature (130 degrees C). Such microstructural transformations resulted in modified charge transport pathways and therefore greately influenced the device performance. The highest PCE of 2.14% with an open-circuit voltage (V(OC)) of 0.99 V and a short-circuit current (J(SC)) of 4.24 mA/cm(2) was achieved by device annealing at 70 degrees C for 20 min. (C) 2008 Elsevier B.V. All rights reserved.
Anomalous p-channel amorphous oxide transistors based on tin oxide and their complementary circuits
(2008-03-24)
Ou, Chun-Wei
;
Ho, Zhong Yo
;
Chuang, You-Che
;
Cheng, Shiau-Shin
;
Wu, Meng-Chyi
In this article, we report the fabrication of SnO(2) thin film transistors (TFTs) fabricated by reactive evaporation. Different from the previous reports, the fabricated TFTs exhibit p-type conductivity in its undoped form. The postdeposition annealing temperature was tuned to achieve p-channel SnO(2) TFTs. The on/ off ratio and the field-effect mobility were similar to 10(3) and 0.011 cm(2)/V s, respectively. To demonstrate inverter circuit, two devices with different threshold voltages were combined and an output gain of 2.8 was achieved. The realization of p-channel oxide TFTs would open up new challenges in the area of transparent electronics. (C) 2008 American Institute of Physics.
Balancing the ambipolar conduction for pentacene thin film transistors through bifunctional electrodes
(2008-06-23)
Yang, Chuan-Yi
;
Dhananjay
;
Cheng, Shiau-Shin
;
Ou, Chun-Wei
;
Chuang, You-Che
We report an effective way to equilibrate hole and electron transport in ambipolar pentacene thin film transistors (TFTs). It was achieved by inserting an ultra thin lithium fluoride (LiF) layer at the electrode/organic interface to form a bifunctional source/drain electrode. It can be observed that the presence of ultrathin LiF layer will facilitate the injection of electrons from source/drain electrodes to organic semiconductor, resulting in a significant enhancement of the n-channel conduction, without sacrificing p-channel conduction for ambipolar pentacene TFTs. These factors make them potential candidates for the organic complementary circuits and inverter circuits of these ambipolar TFTs are also demonstrated. (c) 2008 American Institute of Physics.
Broadband Quantum-Dot Infrared Photodetector
(2010-07-01)
Lin, Wei-Hsun
;
Tseng, Chi-Che
;
Chao, Kuang-Ping
;
Kung, Shu-Yen
;
Lin, Shih-Yen
In this letter, we report the five-period quantum-dot infrared photodetectors (QDIPs) with a bi-stacked quantum-dot (QD) structure for a wide and relatively flat detection response ranging from 4 to 11 m with high responsivities. The bi-stacked QD structure consists of a standard InAs QD and an InGaAs-capped InAs QD layer separated by a 50-nm GaAs barrier layer. The device exhibits a wide detection window in the range of 4-11 mu m with high responsivities, which suggests that similar responsivities can be obtained for the standard QD and the InGaAs-capped QD layers in the mid-wavelength (MWIR) and long-wavelength (LWIR) infrared ranges, respectively. The results are advantageous for the development of broadband QDIPs covering MWIR and LWIR ranges based on the stacked QD structures.
Charge-trap non-volatile memories fabricated by laser-enabled low-thermal budget processes
(2015-11-02)
Huang, Wen-Hsien
;
Shieh, Jia-Min
;
Pan, Fu-Ming
;
Yang, Chih-Chao
;
Shen, Chang-Hong
We fabricated charge-trap non-volatile memories (NVMs) using low thermal budget processes, including laser-crystallization of poly-Si thin film, chemical vapor deposition deposition of a stacked memory layer, and far-infrared-laser dopant activation. The thin poly-Si channel has a low defect-density at the interface with the bulk, resulting in a steep subthreshold swing for the NVM transistors. The introduction of the stacked SiO2/AlOxNy tunnel layer and the SiNx charge-trap layer with a gradient bandgap leads to reliable retention and endurance at low voltage for the NVMs. The low thermal budget processes are desirable for the integration of the nano-scaled NVMs into system on panels. (C) 2015 AIP Publishing LLC.
Complementary inverter circuits based on p-SnO(2) and n-In(2)O(3) thin film transistors
(2008-06-09)
Dhananjay
;
Chu, Chih-Wei
;
Ou, Chun-Wei
;
Wu, Meng-Chyi
;
Ho, Zhong-Yo
Thin film transistors (TFTs) of indium oxide (In(2)O(3)) and tin oxide (SnO(2)) were fabricated on SiO(2) gate dielectric using reactive evaporation process. Structural investigation of the films revealed that In(2)O(3) films were polycrystalline in nature with preferred (222) orientation and SnO(2) films exhibited amorphous nature. The x-ray photoelectric spectroscopy measurements suggest that SnO(2) films were oxygen rich and presume mixed oxidation states of Sn, namely Sn(2+) and Sn(4+). While the In(2)O(3) based TFTs possess n-type channel conduction, SnO(2) based TFTs exhibited anomalous p-type conductivity. Integration of these n- and p-type devices resulted in complementary inverter with a gain of 11. (C) 2008 American Institute of Physics.
Complementary inverter circuits based on p-SnO2 and n-In2O3 thin film transistors
(2008-06-09)
Dhananjay
;
Chu, Chih-Wei
;
Ou, Chun-Wei
;
Wu, Meng-Chyi
;
Ho, Zhong-Yo
Thin film transistors (TFTs) of indium oxide (In2O3) and tin oxide (SnO2) were fabricated on SiO2 gate dielectric using reactive evaporation process. Structural investigation of the films revealed that In2O3 films were polycrystalline in nature with preferred (222) orientation and SnO2 films exhibited amorphous nature. The x-ray photoelectric spectroscopy measurements suggest that SnO2 films were oxygen rich and presume mixed oxidation states of Sn, namely Sn2+ and Sn4+. While the In2O3 based TFTs possess n-type channel conduction, SnO2 based TFTs exhibited anomalous p-type conductivity. Integration of these n- and p-type devices resulted in complementary inverter with a gain of 11. (C) 2008 American Institute of Physics.
Design of Bi-Directional Transmission Gate Driver in Amorphous Silicon Technology for TFT-LCD Application
(2016-01-01)
Zheng, Guang-Ting
;
Liu, Po-Tsun
;
Wu, Meng-Chyi
;
Lu, I-Hsiang
;
顯示科技研究所
A novel bi-directional transmission gate driver circuit integrated by amorphous silicon thin film transistors (a-Si: H TFTs) has been proposed. In the proposed design, the noise suppression structure of the gate driver utilized the AC drive inverter to reduce the degradation of the pull down TFTs. The clock frequency of AC signal is 30 Hz, which could reduce dynamic power consumption of the circuit. In addition, the synchronous controlled method in this research could reduce the amount of device in gate driver. The simulated result shows the good output performance of the gate driver and match the circuit design.
Design of Bidirectional and Low Power Consumption Gate Driver in Amorphous Silicon Technology for TFT-LCD Application
(2013-02-01)
Zheng, Guang-Ting
;
Liu, Po-Tsun
;
Wu, Meng-Chyi
;
Chu, Li-Wei
;
Yang, Meng-Chuan
A new gate driver has been designed and fabricated by amorphous silicon (a-Si) technology. With utilizing four clock signals in the design of gate driver on array (GOA), the pull-up transistor has ability for both output charging and discharging, and layout size of the proposed gate driver can be narrowed for bezel panel application. Moreover, lower duty cycle of clock signals can decrease static power loss to further reduce the overall power consumption of the proposed gate driver. The scan direction of the proposed gate driver can be adjusted by switching two direct control signals to present the reversal display of image. The proposed gate driver has been successfully demonstrated in a 4.5-inch WVGA (480 x RGB x 800) TFT-LCD panel and passed reliability tests of the supporting foundry.
Design of dual-outputs-single-stage a-Si:H TFT gate driver for high resolution TFT-LCD application
(2016-05)
Zheng, Guang-Ting
;
Liu, Po-Tsun
;
Wu, Meng-Chyi
;
光電工程學系
;
顯示科技研究所
A new gate driver has been designed and fabricated by amorphous silicon technology. With utilizing the concept of sharing the noise free block in a single stage for gate driver, dual-outputs signals could be generated in sequence. By increasing the number of output circuit block in proposed gate driver, number of outputs per stage could also be adding that improves the efficiency for area reduction. Besides, using single driving thin-film-transistor (TFT) for charging and discharging, the area of circuit is also decreased by diminishing the size of pulling down TFT. Moreover, the proposed gate driver has been successfully demonstrated in a 5.5-inch Full HD (1080xRGBx1920) TFT-liquid-crystal display panel and passed reliability tests of the supporting foundry.
Effects of ZnO-nanostructure antireflection coatings on sulfurization-free Cu2ZnSnS4 absorber deposited by single-step co-sputtering process
(2013-07-29)
Jheng, Bao-Tang
;
Liu, Po-Tsun
;
Wang, Min-Chuan
;
Wu, Meng-Chyi
;
電子工程學系及電子研究所
ZnO nanostructures as anti-reflective coatings were synthesized by using hydrothermal technique for a sulfurization-free Cu2ZnSnS4 absorber prepared by co-sputtering deposition. By controlling the morphology of solution-grown ZnO nanostructures, the average reflectance of the Cu2ZnSnS4 solar cell with branched ZnO nanorods decreased from 7.6% to 1.12%, and the energy conversion efficiency promoted by 10.4% from the initial value of 4.8% to 5.3%. The efficiency improvement was well studied with the effects of the gradually increased refractive index between the air and the top electrode of Cu2ZnSnS4 solar device, due to the presence of the ZnO nanostructure. (C) 2013 AIP Publishing LLC.
Efficiency enhancement of non-selenized Cu(In,Ga)Se-2 solar cells employing scalable low-cost antireflective coating
(2014-07-04)
Jheng, Bao-Tang
;
Liu, Po-Tsun
;
Wu, Meng-Chyi
;
光電工程學系
;
顯示科技研究所
In this study, a non-selenized CuInGaSe2 (CIGS) solar device with textured zinc oxide (ZnO) antireflection coatings was studied. The ZnO nanostructure was fabricated by a low-temperature aqueous solution deposition method. With controlling the morphology of the solution-grown tapered ZnO nanorod coatings, the average reflectance of the CIGS solar device decreased from 8.6% to 2.1%, and the energy conversion efficiency increased from 9.1% to 11.1%. The performance improvement in the CuInGaSe2 thin-film solar cell was well explained due to the gradual increase of the refractive index between air and the top electrode of solar cell device by the insertion of the ZnO nanostructure. The results demonstrate a potential application of the ZnO nanostructure array for efficient solar device technology.
Efficiency Improvement of Blue LEDs Using a GaN Burried Air Void Photonic Crystal With High Air Filling Fraction
(2014-05-01)
Liu, Jia-Zhe
;
Charlton, Martin D. B.
;
Lin, Chung-Hsiang
;
Lee, Kang-Yuan
;
Krishnan, Chirenjeevi
In this paper, we investigate the efficiency enhancement of blue InGaN/GaN light-emitting diodes (LEDs) by incorporating a burried air void photonic crystal (BAVPC) layer within the epitaxial structure. As compared with the conventional patterned sapphire substrate (C-PSS) LEDs and flat sapphire substrate LEDs with BAVPC, the fabricated patterned sapphire substrate (PSS) LEDs with BAVPC exhibit the lowest full-width at half-maximum of (002) and (102) diffraction peaks, the highest light output power of 20.6 mW, and the highest external quantum efficiency of 37.4%. Remarkable performance improvement in the PSS LED with BAVPC is attributed to the better epitaxial quality with threading dislocations terminated by the BAVPC and the higher scattering at interface between GaN and air-void. By positioning the BAVPC directly below the multiple quantum wells (MQWs), it would cause the reduction in the number of trapped optical modes. The methodology optically isolates the MQWs from the underlying substrate and increases the optical output power. Moreover, threading dislocations are significantly suppressed using the BAVPC with high air filling fraction of similar to 50%. It is well proposed that this methodology provides a promising alternative to C-PSS LEDs.
Enhanced normal-incident absorption of quantum-dot infrared photodetectors with smaller quantum dots
(2008-07-01)
Tseng, Chi-Che
;
Chou, Shu-Ting
;
Chen, Yi-Hao
;
Chen, Cheng-Nan
;
Lin, Wei-Hsun
Ten-period InAs-GaAs quantum-dot (QD) infrared photodetectors grown under different In adatom supply procedures are investigated. Two In adatom supply procedures of In shutter 1) always opened and 2) periodically opened/closed are adopted in this letter. Larger QD sizes in both height and diameter and more uniform size distribution are observed for samples grown under an In shutter periodically opened/closed condition. The device with QDs grown under the In shutter always opened condition has revealed shorter detection wavelengths and enhanced normal incident absorption. The phenomenon shows that beside the increase of energy difference between confinement states, smaller QD sizes would also enhance the normal incident absorption predicted for the theoretically zero-dimensional QD structures.