Browsing by Author "Chen, Chao-Hsuan"

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A 0.05 V driven ammonia gas sensor based on an organic diode with a top porous layered electrode and an air-stable sensing film
(2019-06-07)
Madhaiyan, Govindasamy
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Chen, Chao-Hsuan
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Wu, Yi-Chu
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Horng, Sheng-Fu
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Zan, Hsiao-Wen
In this work, we successfully demonstrated an extremely-low-voltage (0.05 V) gas sensor based on a vertical organic diode with work-function-matched electrodes. With the designed electrodes (MoO3/Al vs. Al), the built-in field in the vertical diode is greatly reduced and hence the diode can be turned on at a very low voltage. By producing nanometer pores in the top electrode, the diode becomes a very sensitive gas sensor to detect ammonia in parts-per-billion (ppb) concentrations. Upon reducing the voltage from 5 V to 0.05 V, this sensor device shows an over 5-times enhancement in the sensitivity. The air-stable sensing film also exhibits a lifetime of 30 days in air. Finally, by connecting with an organic photovoltaic (OPV) device, the gas sensor can be directly powered and switched on by irradiating light on the OPV.
All-Solution-Processed Red and Orange-Red Organic Light-Emitting Diodes with High-Efficiencies: The Effect of Mixed-Host Emissive Layers and Thermal Annealing Treatment
(2019-09-01)
Chang, Yu-Fan
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Yang, Lan-Sheng
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Su, Hsiao-Tso
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Liao, Si-Yi
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Niu, Mu-Chun
The instability of the organic light-emitting diodes (OLEDs) during operation can be attributed to the existence of point defects on the organic layers. In this work, the effect of mixed-host emissive layer and the thermal annealing treatment were investigated to eliminate defects and to boost the device performance. The mixed-host system includes 4,4 ',4 ''-tri (9-carbazoyl) triphenylamine (TCTA) and 2,7-bis(diphenylphosphoryl)-9, 9 '-spirobi[fluorene] (SPPO13). The mixed-host emissive layer with thermal annealing treatment showed low roughness and few pinholes, and the devices fabricated from this emissive layer exhibited high efficiencies, high stabilities, and long lifetimes. The red and orange-red OLEDs exhibited efficiencies of 13.9 cd/A and 24.35 cd/A, respectively. The longest half-lifetime (L-0=500 cd/m(2)) of the red and orange-red OLEDs were 158 h and 180 h, respectively. Efforts were made to solve problems in large-area coating and to reduce the number of defects on in organic layer. Large-active-area (active area=3 cmx4 cm) red phosphorescent OLEDs (PhOLEDs) devices were realized with very high current efficiency up to 9 cd/A.
Design and Simulation of High Performance Lattice Matched Double Barrier Normally Off AlInGaN/GaN HEMTs
(2020-01-01)
Shrestha, Niraj Man
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Li, Yiming
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Chen, Chao-Hsuan
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Sanyal, Indraneel
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Tarng, Jenn-Hawn
A novel lattice matched double barrier Al0.72In0.16Ga0.12N/Al0.18In0.04Ga0.78N/GaN normally-off high electron mobility transistor (HEMT) is designed and simulated by solving a set of thermodynamic transport equations. Using the experimentally calibrated physical models with bearing mobility degradation by surface roughness in account, the recess gate and double barrier of the proposed device achieves a maximum drain current density (I-D,I-max) of 1149 mA/mm and a maximum transconductance (g(m,max)) of 358 mS/mm with a positive threshold voltage (Vth) of 0.2 V. The small polarization charge of first barrier is responsible for positive Vth. I-DS,I-max in the double barrier HEMT at high gate bias condition is due to injection of electrons from upper 2DEG which is almost impossible at lower gate voltage because of insufficient energy to cross the barrier. The injection of electrons is further supported by the second peak in the g(m) curve at low gate bias V-G = 1V. The outcome of this study suggests that the proposed device will be beneficial for high-frequency and high-power electronic applications.
High-resolution proximity sensor using flexible semi-transparent organic photo detector
(2017-10-01)
Chen, Chao-Hsuan
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Lin, Ching-Fu
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Wang, Kuan-Hsun
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Liu, Hung-Chuan
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Zan, Hsiao-Wen
We propose a flexible proximity sensor to detect sub-centimeter distance with an ultra-high displacement resolution. The proximity sensor is realized by integrating a semi-transparent organic photo detector with a transparent top electrode and a finger-type bottom electrode. By placing the semitransparent finger-type photodetector on a light source, such as a light-emitting diode (LED), the photodetector can detect the light reflected from an object on top of the sensor. With the highly compact structure, the detecting range is from 1 mm to 30 mm. From 1 mm to 10 mm, the sensor is particularly sensitive and delivers a resolution of 1 mm. The air-stable photodetector can also be fabricated on a flexible substrate without encapsulation, enabling the integration with arbitrary light sources. After 1000 times bending, the flexible photodetector shows no obvious degradation. (C) 2017 Elsevier B.V. All rights reserved.
Highly efficient and stable organic solar cell modules processed by blade coating with 5.6% module efficiency and active area of 216 cm(2)
(2019-03-01)
Huang, Kuan-Min
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Wong, Ying Qian
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Lin, Man-Chun
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Chen, Chao-Hsuan
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Liao, Chung-Hung
In this study, an efficient and stable large-area blade-coated organic solar cell (OSC) module with an active area of 216 cm(2) (16 elementary cells connected in series) is demonstrated by combining appropriate thermal annealing treatment with the use of 4,4 '-(((methyl(4-sulphonatobutyl)ammonio)bis(propane-3,1-diyl))bis(dimethyl-ammoniumdiyl))bis-(butane-1-sulfonate) (MSAPBS) as the cathode interfacial layer. For the opaque device using poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b ']dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl)] (PBDTTT-EFT (PTB7-Th)):[6,6]-phenyl C-71-butyric acid methyl ester (PC71BM) blend film as the active layer, the power conversion efficiency (PCE) of 5.6% is achieved under AM 1.5G solar light illumination. Very encouragingly, our strategy can be applicable for semitransparent OSCs, and a remarkable PCE up to 4.5% is observed. To the best of our knowledge, the PCE of 5.6% for opaque device and 4.5% for semitransparent device represent the highest PCE ever reported for OSCs with the active area exceeding 100 cm(2). The devices also show an impressive stability under outdoor environment, where the efficiency decay is less than 30% for 60 days. Our findings can pave the way toward the development of organic solar cell modules with high performance and long-term stability.
Large-area blade-coated organic solar cells processed from halogen-free solvent
(2019-12-01)
Chen, Szu-Han
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Liao, Chung-Hung
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Chang, Chih-Yu
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Huang, Kuan-Min
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Chen, Jen-Yueh
High performance organic solar cells (OSCs) are generally prepared by halogenated solvents, which are detrimental to the environment and human health. The replacement of hazardous halogenated solvents is a priority in the commercialization of solution-processed OSCs. In this study, poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl) benzo [1,2-b;4,5-b'] dithiophene-2,6-diyl-alt-(4- (2-ethylhexyl)-3-fluorothieno [3,4-b] thiophene-)-2-carboxylate-2-6-diyl)] (PBDTTT-EFT):[6,6]-phenyl C-71 -butyric acid methyl ester (PC71BM)-based device processed with binary halogen-free solvents (toluene and N-methyl-2-pyrrolidone) is fabricated by blade-coating method. Through the combination of morphological manipulation of active layer and interfacial engineering, the resulting OSCs deliver a promising power conversion efficiency (PCE) up to 11.09%. Importantly, large-area (216 cm(2)) blade-coated bulk-heterojunction OSCs is also demonstrated, and the resulting devices deliver a high PCE up to 5.03%, which is comparable to those of the devices processed with halogenated solvents (PCE = 5.20%). Additionally, the devices processed with halogen-free solvents also exhibit superior stability, maintaining 88% of its initial efficiency after 3960 h of continuous operation. More encouragingly, halogen-free solvents-based manufacturing process can also be performed under ambient conditions, and a moderate PCE of 3.67% is attained for large-area (216 cm(2)) OSCs. To the best of our knowledge, 3.67% represents the highest efficiency ever reported for air-processed large-area OSCs. This work paves the way towards the realization of environmentally-friendly large-area OSCs with high performance and long-term stability.
MOEMS Vibration Sensor with Organic Semiconductor Readout
(2016-01-01)
Kainz, A.
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Hortschitz, W.
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Steiner, H.
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Hong, Yi-Hong
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Chen, Chao-Hsuan
We present a first proof of principle of applying organic semiconductors as key components in micro-mechanical vibration sensors. The mechanical part of the MOEMS sensor readout is etched into the device layer of an SOI chip and consists of a laterally deflecting inertial mass that features a two-dimensional grid of rectangular holes. An identical grid is evaporated onto a glass chip bonded onto the silicon chip in such way that any deflection of the seismic mass will modulate the light flux passing through the device. The light flux is provided in this case by an OLED and detected by an OPD. It is shown with a proof of concept device that for such sensors organic optoelectronics can replace inorganic ones, which is the starting point for developing a variety of MOEMS sensors based on printed optoelectronic devices. (C) 2016 The Authors. Published by Elsevier Ltd.
Organic transistors fabricated by contact coating at liquid-solid interface for nano-structures
(2015-10-01)
Cheng, Yu-Wen
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Chen, Chao-Hsuan
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Meng, Hsin-Fei
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Zan, Hsiao-Wen
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Chao, Yu-Chiang
A contact coating method is developed to cover the nano-channels with 100 nm or 200 nm diameter and 400 nm depth with a poly(4-vinylphenol) (PVP). In such coating the nano-channels faces downwards and its vertical position is controlled by a motor. The surface is first lowered to be in immediate contact with the polyvinylpyrrolidone (PVPY) water solution with concentration from 1 to 5 wt%, then pulled at the speed of 0.004 to 0.4 mm/s. By tuning the pulling speed and concentration we can realize conformal, filled, top-only, as well as floating film morphology. For a reproducible liquid detachment from the solid, the sample has a small tilt angle of 3 degree. Contact coating is used to cover the Al grid base of the vertical space-charge-limited transistor with PVPY. Poly(3-hexylthiophene-2,5-diyl) (P3HT) as the semiconductor. The transistor breakdown voltage is raised due to base coverage achieved by contact coating. (C) 2015 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.
Overcoming Multidrug Resistance of Breast Cancer Cells by the Micellar Doxorubicin Nanoparticles of mPEG-PCL-Graft-Cellulose
(2011-01-01)
Chen, Chao-Hsuan
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Cuong, Nguyen-Van
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Chen, Yung-Tsung
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So, Regina Cheng
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Liau, Ian
The amphiphilic block copolymer methoxy-poly(ethylene glycol)-poly(epsilon-caprolactone) (mPEG-PCL) was grafted to 2-hydroxyethyl cellulose (HEC) to produce nano-sized micellar nanoparticles. The nanoparticles were loaded with anti-tumor drug, doxorubicin (DOX) and the size of the DOX-loaded nanoparticles were determined by dynamic light scattering (DLS) in aqueous solution to be from 197.4 to 230 nm. The nanoparticles subjected to co-culture with macrophage cells showed that these nanoparticles used as drug carrier are not recognized as foreign bodies. Overexpression of P-glycoprotein (P-gp) is an important factor in the development of multidrug resistance (MDR) in many cancer cells. In this study, Western blot and Rhodamine 123 were used to monitor the relative P-glycoprotein expression in human breast cancer cell lines MCF-7/WT and MCF-7/ADR. The endocytosis of the DOX-loaded nanoparticles by breast cancer cells is more efficient observed under a confocal laser scanning microscopy (CLSM) and a flow cytometry in MCF7/ADR cells, compared to the diffusion of the free drug into the cytoplasm of cells. Based on these findings, we concluded that the nanoparticles made from mPEG-PCL-g-cellulose were effective in overcoming P-gp efflux in MDR breast cancer cells.
Overcoming Multidrug Resistance of Breast Cancer Cells by the Micellar Drug Carriers of mPEG-PCL-graft-cellulose
(2009)
Chen, Yung-Tsung
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Chen, Chao-Hsuan
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Hsieh, Ming-Fa
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Chan, Ann Shireen
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Liau, Ian
The amphiphilic block copolymers methoxypoly (ethylene glycol)-poly (epsilon-caprolactone) (mPEG-PCL) was grafted to 2-hydroxyethyl cellulose (HEC) to produce water-soluble copolymers. Doxorubicin (DOX)-loaded nanoparticles were prepared by dialysis method and the sizes of nanoparticles were determined by dynamic light scattering (DLS) in solution. The size of the nanoparticles was in the range of 197.4 to 340.7 nm. Rhodamine 123 was used to probe the relative P-glycoprotein (P-gp) expression in human breast cancer cell lines MCF-7/WT and MCF-7/ADR. Confocal laser scanning microscopy (CLSM) showed a difference between the fluorescence images of DOX-loaded micelles and free DOX. For a quantitative basis, flow cytometry was done on both cell lines treated with DOX-loaded micelles and free DOX to compare a difference in effect. The amount of DOX-loaded micelles in MCF-7/ADR increased compared to that in the MCF-7/WT cells. This gives insight into how the micellar system developed in this study overcomes the multidrug resistance (MDR) effect.
Pre-Distortion Scheme to Enhance the Transmission Performance of Organic Photo-Detector (OPD) Based Visible Light Communication (VLC)
(2018-01-01)
Chow, Chi-Wai
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Wang, Hao-Yu
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Chen, Chao-Hsuan
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Zan, Hsiao-Wen
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Yeh, Chien-Hung
Organic photo-detector (OPD) is lightweight and physically flexible. It can transform plastic or glass into smart surfaces. Visible light communication (VLC) is considered as one of the promising technologies for the future wireless communications. VLC combines the advantages of lighting and communication simultaneously. Besides, it can be deployed using existing lighting infrastructure; hence little extra cost is needed to provide this wireless communication. As the OPD has a large optical detection area, it would be interesting to employ the OPD as VLC receiver (Rx). If the OPD can be used in the VLC systems, it can benefit the Internet-of-Thing (IoT) networks by providing efficient human-to-machine and machine to-machine communications. However, implementing VLC using OPD Rx is challenging. Due to the slow charging and discharging processes of the OPD, the optical-to-electrical response speed is limited. Besides, the OPD requires external bias to be operated. Here, we propose and demonstrate using pre-distortion scheme for pulse-amplitude-modulation (PAM) signal to a self-powered PCBM:P3HT OPD to enhance the VLC transmission performance. The operation of the self-powered PCBM:P3HT OPD is discussed. Both experiments using PAM-2 and PAM-4 (with and without pre-distortion) are evaluated. The performance, requirement and capability limitations of the pre-distortion schemes are also analyzed and discussed by using numerical simulations.
Soldering of solution-processed organic vertical transistor and light-emitting diode on separate glass substrates by tin micro-balls
(2013-11-01)
Lin, Yu-Hsin
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Chang, Yu-Fan
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Meng, Hsin-Fei
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Zan, Hsiao-Wen
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Hsu, Wensyang
The vertical organic space-charge-limited transistor made of P3HT and small-molecule phosphorescent organic light-emitting diode (OLED) are made on two separate glass substrate by blade coating, then soldered vertically together by tin balls with 40 mu m diameter. The soldering is done by hot wind of 150 degrees C for 5 min Contact resistance is only 10 Omega. The vertical transistor is annealed at 150 degrees C for 5 min before soldering to enhance the output current up to 25 mA/cm(2) and give high thermal stability. Both OLED and the annealed vertical transistor are not affected by the soldering process. The vertical transistor has 1/4 of the OLED area and turns on the bottom-emission white OLED up to 300 cd/m(2) and orange OLED up to 600 cd/m(2). The entire operation is within 8 V. OLED and transistor array can therefore be made on separate glass substrates then soldered together to form the display. (C) 2013 Elsevier B. V. All rights reserved.
The influence of UV filter and Al/Ag moisture barrier layer on the outdoor stability of polymer solar cells
(2020-03-15)
Weng, Chia-Ning
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Yang, Hao-Chun
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Tsai, Cheng-Yu
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Chen, Szu-Han
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Chen, Yan-Syun
The degradation of the polymer solar cells in the outdoor condition was studied. It was found that the devices with normal structure (ITO/PEDOT:PSS/PBDTTT-EFT:PC71BM/ZrOx/Al) show better stability than those with inverted device structure (ITO/ZnO/PBDTTT-EFT:PC71BM/MoO3/Ag). PBDTTT-EFT is poly[4, 8-bis(5-(2-ethylhexyl) thiophen-2-yl) benzo [1,2-b;4,5-b] dithiophene-2, 6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno [3,4-b] thiophene-) - 2-carboxylate-2-6-diyl)] and PC71BM is [6,6]-phenyl-C71-butyric acid methyl ester. The major cause of degradation was attributed to the ultraviolet (UV) part of the sunlight. When the UV filter with cut-off wavelength of 400 nm was used to protect the device, the decay rate was improved by 50 times and the protected device retains 95% of their initial power conversion efficiency after 13 days outside. In the meanwhile, the decay of device fabricated by toluene was found 8 times faster than device by chlorobenzene. Thin 20 nm of Ag capping layer can further improve the stability. Degradation under water immersion indicates that the major effect of Ag is to protect against the residual moisture inside the encapsulation.
Thermal and angular dependence of next-generation photovoltaics under indoor lighting
(1970-01-01)
Chen, Chia-Yuan
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Kuo, Ting-Yang
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Huang, Chien-Wu
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Jian, Zih-Hong
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Hsiao, Po-Tsung
Next-generation photovoltaic technologies such as dye-sensitized solar cells, organic thin-film photovoltaics and perovskite solar cells are promising to efficiently harvest ambient light energy. However, more and deeper understanding of their photovoltaic characteristics is essential to create new applications under room light illumination. In this study, for the first time, the difference in temperature coefficients and angular dependence of photovoltaic parameters for the large-area devices are investigated systematically under the compact fluorescent lamp and light-emitting diode light. These emerging photovoltaic devices, compared with the single crystalline silicon solar cells, not only have higher open-circuit voltage (up to approximate 1 V) and better power conversion efficiency (in the range of 9.2% similar to 22.6%) but also exhibit less temperature dependent voltage and output power (< -0.6% degrees C-1), as well as broader angular response (over 75 degrees). The state-of-the-art dye-sensitized and organic thin-film devices also show advantageously positive temperature coefficients of current, and the latter even has positive thermal dependence of fill factor. These features suggest the next-generation photovoltaic devices are more favorable than the conventional crystalline silicon solar cells for real-life indoor applications.
Thermally Stable High-Performance Polymer Solar Cells Enabled by Interfacial Engineering
(2018-07-20)
Chen, Chao-Hsuan
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Lin, Zhi-Wei
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Huang, Kuan-Min
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Meng, Hsin-Fei
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Chen, Szu-Han
Interfacial engineering plays an important role in determining the performance and stability of polymer solar cells (PSCs). In this study, thermally stable highly efficient PSCs are fabricated by incorporating a solution-processed cathode interfacial layer (CIL), including 4,4'-({[methyl(4-sulfonatobutyl)ammonio]bis(propane-3,1-diyl)}bis(dimethylammoniumdiyl))bis(butane-1-sulfonate) (MSAPBS) and polyethylenimine (PEI). For PSCs based on blends of poly{4,8-bis[5-(2-ethylhexyl)thiophen-2-yl]benzo[1,2-b;4,5-b]dithiophene-2,6-diyl-alt-[4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-2-carboxylate-2,6-diyl]} (PBDTTT-EFT) and [6,6]-phenyl C-71-butyric acid methyl ester (PC71BM), the maximum power conversion efficiency (PCE) of inverted PSCs reaches 8.1% and 7.2% for MSAPBS and PEI CILs, respectively. The inverted PEI devices exhibit remarkable stability (lifetime >6000h) under accelerated thermal aging (at 80 degrees C in ambient environment), which is much superior to that of the device with commonly used LiF CIL (lifetime approximate to 33h). This stability represents the best result reported for PSCs. The promising results based on this strategy can stimulate further work on the development of novel CILs for PSCs and pave the way towards the realization of commercially viable PSCs with high performance and long-term stability.