Browsing by Author "Huang, Yu-Ming"

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Advances in Quantum-Dot-Based Displays
(2020-07-01)
Huang, Yu-Ming
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Singh, Konthoujam James
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Liu, An-Chen
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Lin, Chien-Chung
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Chen, Zhong
In terms of their use in displays, quantum dots (QDs) exhibit several advantages, including high illumination efficiency and color rendering, low-cost, and capacity for mass production. Furthermore, they are environmentally friendly. Excellent luminescence and charge transport properties of QDs led to their application in QD-based light-emitting diodes (LEDs), which have attracted considerable attention in display and solid-state lighting applications. In this review, we discuss the applications of QDs which are used on color conversion filter that exhibit high efficiency in white LEDs, full-color micro-LED devices, and liquid-type structure devices, among others. Furthermore, we discuss different QD printing processes and coating methods to achieve the full-color micro-LED. With the rise in popularity of wearable and see-through red, green, and blue (RGB) full-color displays, the flexible substrate is considered as a good potential candidate. The anisotropic conductive film method provides a small controllable linewidth of electrically conductive particles. Finally, we discuss the advanced application for flexible full-color and highly efficient QD micro-LEDs. The general conclusion of this study also involves the demand for a more straightforward QD deposition technique, whose breakthrough is expected.
All Inorganic Perovskite Quantum Dots Hybrid Green Light-Emitting Diode with Stable Performance
(2018-01-01)
Yu, Chung-Ping
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Chung, Meng-Ting
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Chen, Tzu-Yu
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Huang, Yu-Ming
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Huang, Chung-Ping
A silica-coated inorganic perovskite quantum dot hybrid light-emitting diodes is aged continuously in high and low light intensity conditions. Both blue and ultra-violet-pumped samples showed stable performances up to 104 hours.
An Investigation on Stable and Continuous Operation of Hybrid Perovskite Quantum Dot Light Emitting Diodes
(2019-01-01)
Cho, Yu-Yun
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Hsu, Shun-Chieh
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Huang, Yu-Ming
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Shih, Hsiang-Yun
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Lee, Ting-Yu
Two different package structures of hybrid perovskite quantum dots light emitting diodes were demonstrated with stable and continuous light emission. With boron nitride nanoparticles, the lifetime of device is expected to be thousands of hours.
Channel-Aware Construction of Polar Codes
(2016-01-01)
Huang, Yu-Ming
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Chang, Hsie-Chia
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Li, Hsiang-Pang
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
The conventional construction of polar codes is designed in advance for a specific channel, the performance of polar codes deteriorates if the construction does not match the current channel. In other words, we suffer from performance loss when either a time-variant channel or an inaccurate estimation of channel are considered. To put polar codes into practice, a channel-aware construction of polar codes, which optimizes the construction on the fly, is proposed in this paper. Unlike universal polar codes, the receiver of the proposed scheme does not need to know any knowledge of actual channel. In addition, the proposed algorithm constructs polar codes only based on decoding results, it is well suited to not only i.i.d. channels but general channels. Simulation results show that the proposed schemes over a time-variant parallel channel (i.e. multi-channel) are always achieved a relatively good performance.
Enhanced MAC Protocol for Cognitive Radios over IEEE 802.11 Networks
(2011)
Wang, Shie-Yuan
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Huang, Yu-Ming
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Lau, Lee-Chin
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Lin, Chih-Che
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資訊工程學系
The Cognitive Radio (CR) technology is proposed for solving the spectrum underutilization problem and has gained great attention. By allowing unauthorized users to opportunistically access frequencies authorized to specific networks (called primary networks), the CR technology can increase the bandwidth utilization of the radio spectrum in a global perspective. In [1], the authors proposed a MAC protocol for CRs that aims to "borrow" the link bandwidth from IEEE 802.11 networks. This protocol allows CR users to opportunistically exchange data on an idle 802.11 channel. However, the protocol proposed in [1] selects an 802.11 channel for data exchange in a random manner. This random channel selection process is time-consuming for CR users to start a data transmission. In addition, the protocol does not consider the effects of hidden terminals (HTs), which often exist in wireless networks and significantly decrease the goodputs of a network. To address these problems, in this paper we propose enhancements to the protocol proposed in [1]. The proposed protocol is evaluated using extensive simulations. Our simulation results show that our proposed protocol can effectively decrease the time required for finding an idle 802.11 channel to transmit data and therefore increase the network goodputs in networks with and without the existence of HTs.
Evaluation of Luminescent Downshifting Effect of Perovskite Quantum Dots on Semiconductor Solar Cells
(2018-01-01)
Chen, Chun-Hong
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Yu, Chung-Ping
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Huang, Yu-Ming
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Chan, Yueh-Lin
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Huang, Chung-Ping
The luminescent down-shifting effect of the perovskite quantum dots on single junction GaAs solar cells are examined and discussed. The perovskite quantum dots can provide an effective way to convert ultra-violet photons in solar spectrum to visible ones which can be transformed into electron-hole pairs more efficiently. Three different designs are tried: direct-dispense, ITO nano-whisker up and ITO nano-whisker down. In this experiment, we use perovskite quantum dots(QDs) with the concentration of 1mg/ml and emit photons of the wavelength 530nm (CsPbBr3), and the various volume of perovskite QDs were deposited on the solar cell to observe the possible luminescent down-shifting phenomenon.
Feasibility Study for Double Luminescent Down-shifting Effect in A Dual Junction Solar Cell
(2019-01-01)
Huang, Yu-Ming
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Cho, Yu-Yun
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Hsu, Shun-Chieh
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Kao, Sheng-Feng
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Shih, Hsiang-Yun
In this work, we discuss the feasibility of two color photons for boosting up the short-circuit current and power conversion efficiency in tandem solar cell. One of them is by luminescent down-shifting (LDS) effect, and the other one is the infrared light emitting diode at 820nm. The CdZnSeS/ZnS quantum dots are used in this study. It can convert ultra-violet photons to visible ones which could be efficiently transformed into electron-hole pairs. The infrared-radiation LED can increase photo-generated carriers of the bottom GaAs solar cell. Finally, short-circuit current would significantly increase from 10.46 mA/cm(2) to 13.81 mA/cm(2), and power conversion efficiency increase from 19.89 to 25.22%. This result shows the possible double-LDS effect for solar cell enhancement in the future.
Full-color micro-LED display with high color stability using semipolar (20-21) InGaN LEDs and quantum-dot photoresist
(2020-05-01)
Chen, Sung-Wen Huang
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Huang, Yu-Ming
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Singh, Konthoujam James
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Hsu, Yu-Chien
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Liou, Fang-Jyun
Red-green-blue (RGB) full-color micro light-emitting diodes (mu-LEDs) fabricated from semipolar (20-21) wafers, with a quantum-dot photoresist color-conversion layer, were demonstrated. The semipolar (20-21) InGaN/GaN mu-LEDs were fabricated on large (4 in.) patterned sapphire substrates by orientation-controlled epitaxy. The semipolar mu-LEDs showed a 3.2 nm peak wavelength shift and a 14.7% efficiency droop under 200 A/cm(2 )injected current density, indicating significant amelioration of the quantum-confined Stark effect. Because of the semipolar mu-LEDs' emission-wavelength stability, the RGB pixel showed little color shift with current density and achieved a wide color gamut (114.4% NTSC space and 85.4% Rec. 2020). (C) 2020 Chinese Laser Press
High performance ultraviolet micro-LED arrays for fine-pitch micro displays
(2019-01-01)
Tsai, Yi-Lin
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Huang, Yu-Ming
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Yang, Shu-Mei
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Kuo, Wei-Hung
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Fang, Yen-Hsiang
Highly efficient ultraviolet micro LED arrays are demonstrated. Small devices (5 microns in size) suitable for high resolution (725 ppi) can be produced with low leakage current and good emission spectra stability. A 10 by 10 array is achieved with passive-matrix driving connection.
High-Bandwidth Green Semipolar (20-21) InGaN/GaN Micro Light-Emitting Diodes for Visible Light Communication
(2020-08-19)
Chen, Sung-Wen Huang
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Huang, Yu-Ming
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Chang, Yun-Han
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Lin, Yue
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Liou, Fang-Jyun
The light-emitting diode (LED) is among promising candidates of light sources in visible light communication (VLC); however, strong internal polarization fields in common c-plane LEDs, especially green LEDs, result in low frequency and limited transmission performance. This study aims to overcome the limited 3-dB bandwidth of long-wavelength InGaN/GaN LEDs. Thus, semipolar (20-21) micro-LEDs (mu LEDs) were fabricated through several improved approaches on epitaxy and chip processes. The mu LED exhibits a 525 nm peak wavelength and good polarization performance. The highest 3-dB bandwidth up to 756 MHz and 1.5 Gbit/s data rate was achieved under a current density of 2.0 kA/cm(2). These results suggest a good transmission capacity of green semipolar (20-21) mu LEDs in VLC applications.
Microwave behavior of a monolithic dual-wavelength DFB laser based on current model
(2020-09-15)
Huang, Chung-Ping
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Huang, Yu-Ming
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Hwang, Yi-Chia
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Dong, Yao-Zhong
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Hsu, Shun-Chieh
A driving current based model describing the optical heterodyne output of a monolithic dual-wavelength DFB laser is established. The linear relationship between the driving current and the laser output wavelength was applied to obtain the simple equation for this purpose. Actual measured data from the real devices were used for the initial parameter extraction and the practical model can then be built. By using this model, the influence of different laser parameters towards the radio frequency signal generation and different current configuration on the output characteristic can be demonstrated. This can facilitate the future design of such integrated photonic devices.
Microwave Spectral Characteristics of the Three-Section Distributed Feedback Lasers
(2018-01-01)
Chen, Chun-Hong
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Hsiao, Fu-Chun
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Dong, Yao-Zhong
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Chan, Yueh-Lin
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Chen, Yi-Hsun
The three-section DFB lasers are used for RF signal generation. With an extra section, it can lime the RF peak frequency farther than the two-section one, and can also simultaneously generate two single-mode RF signals.
Performance Enhancement of A GaAs Solar Cell with Colloidal Quantum Dots Embedded in Trenches
(2017-01-01)
Shu, Chia-Jhe
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Huang, Yu-Ming
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Hsu, Shun-Chieh
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Shu, Jinn-Kong
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Tsai, Jia-Lin
A hybrid colloidal quantum dot (CQD) single junction GaAs solar cell was fabricated and measured. The CQDs are cast into the different sizes of trenches on the device surface. The introduction of CQD layer brings wide-range EQE enhancement, particularly in the ultra-violet band. The analysis reveals possible luminescent down-shifting effect due to our embedded quantum dots. As high as 2 times of EQE enhancement can be observed at specific short wavelength.
Re-Polarization Processing in Extended Polar Codes
(2017-10-01)
Huang, Yu-Ming
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Chang, Hsie-Chia
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Li, Hsiang-Pang
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
In this paper, extended polar codes based on re-polarization technique are proposed. The presented schemes extend a conventional polar code of length N to length N + q, which stand in contrast to known length-compatible schemes such as puncturing and shortening techniques that reduce the length from N to N q. For certain specific lengths, the waterfall region performance of our extended polar code is superior to that of other length-compatible polar codes. It provides better reliability and reduces the management overhead in several storage devices and communications systems. In essence, extended polar codes are created by re-polarizing the q least reliable nonfrozen bit-channels with the help of q additional frozen bit-channels. It is proved that this re-polarization enhances the reliability of these bits. Moreover, the extended schemes can be not only modified to improve decoding performance, but generalized as a m-stage scheme to improve throughput significantly. With parallel operation, the throughput is improved around 2(m-1) times when q is small. Compared to a shortened polar code with length 1536, the encoding and decoding complexities of an extended polar code are only 50% and 60.5%, respectively.
Simulation Model of Oxide-Aperture Strain Quantum Well VCSEL
(2019-01-01)
Shih, Hsiang-Yun
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Cho, Yu-Yun
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Hsu, Shun-Chieh
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Huang, Yu-Ming
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Wang, Shou-Wei
An oxide aperture strained quantum well VCSEL model was built based on measured results. The indium composition of MQW was changed to maximize the frequency response. The simulation result shows that the bandwidth can be improved and reach 30.88GHz.
The Aging Study for Fine Pitch Quantum-Dot Array on LEDs
(2019-01-01)
Huang, Yu-Ming
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Liang, Kai-Ling
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Cho, Yu-Yun
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Hsu, Shun-Chieh
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Kuo, Wei-Hung
In this paper, we fabricated the photoresist mold whose pitch is smaller than 15. m on light-emitting diode and printed two different cadmium-based quantum dots. Also, we burn-in the LED to compare their lifetime which are pasted barrier film by two different methods. (C) 2019 The Author(s)
The Analysis of Dual-Junction Tandem Solar Cells Enhanced by Surface Dispensed Quantum Dots
(2018-09-01)
Hsu, Shun-Chieh
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Huang, Yu-Ming
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Kao, Yu-Cheng
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Kuo, Hao-Chung
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Horng, Ray-Hua
The luminescent down-shifting (LDS) effect of a colloidal quantum dot layer on a dual junction solar cell is explored and analyzed. A 5.47% enhancement of power conversion efficiency is recorded when green quantum dots are dispersed on device surface. The surface reflectance spectra before and after the quantum dot dispenses are necessary to decouple the different mechanisms between antireflective and LDS effects. A further deduction of formulation on the dual-junction device with antireflection and LDS effect is presented and as high as 44.6% of short-circuit current increase in the green quantum dot case can be attributed to the LDS effect according to our calculation.
The Photothermal Stability Study of Quantum Dots Embedded in Sodium Chlorides
(2020-01-01)
Huang, Yu-Ming
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Hsu, Shun-Chieh
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Li, Ning
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Yu, Chung-Ping
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Ke, Li-Ann
An efficient and useful method for the incorporation of colloidal quantum dots (QDs) into ionic matrices is demonstrated. We prepared three different synthesis methods, which are traditional saturated-salt water, methanol-assisted, and ethanol-assisted methods. The continuous thermal and photonic stress tests indicate that the high temperature, instead of photonic excitation stress, is more detrimental to the illumination capability of the quantum dots. While the traditional saturated-salt water synthesis and methanol-assisted method are quite effective in low temperature and low photon excitation intensity, the quantum dots sealed by the ethanol-assisted method cannot hold under all conditions. An over-1000-h aging test can provide crucial information for the longevity of these quantum dots, and more than 10,000 h of lifetime can be expected.
Widely Tunable Single/Dual RF Signal Generation by a Monolithic Three-Section DFB Laser
(2020-04-17)
Huang, Chung-Ping
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Huang, Yu-Ming
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Shih, Hsiang-Yun
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Hsiao, Fu-Chun
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Chen, Chun-Hong
A three-section distributed feedback laser with a 2.5 InP/air pair of distributed Bragg reflectors (DBRs) was fabricated and analyzed in terms of its microwave generation capability. A widely tunable single radio frequency (RF) signal can be detected using optical heterodyning, and the tuning range is from 2 to 45 GHz. The incorporation of the third section provides an opportunity to present the dual RF operation when three emission peaks are near to each other in the wavelength domain. The proposed design provides a 21.3% enhancement in the RF tuning range compared with the range of a two-section laser (35.29 GHz versus 42.81 GHz). The compactness of the proposed device can be useful for future radio-over-fiber applications.