Browsing by Author "Chen, Chun-Wei"

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Creation of 3D Textured Graphene/Si Schottky Junction Photocathode for Enhanced Photo-Electrochemical Efficiency and Stability
(2019-08-01)
Ku, Che-Kuei
;
Wu, Po-Hsieh
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Chung, Cheng-Chu
;
Chen, Chun-Chi
;
Tsai, Kaijie
This work presents a novel photo-electrochemical architecture based on the 3D pyramid-like graphene/p-Si Schottky junctions. Overcoming the conventional transfer technique by which only planar graphene/Si Schottky junctions are currently available, this work demonstrates the 3D pyramid-like graphene/p-Si Schottky junction photocathode, which greatly enhances light harvesting efficiency and exhibits promising photo-electrochemical performance for hydrogen generation. The formation of 3D pyramid-like graphene/p-Si Schottky junctions exhibits enhanced electrochemical activity and promotes charge separation efficiency compared with the bare pyramid Si surface without graphene. The inherent chemical inertness of graphene significantly improves the operational stability of 3D graphene/p-Si Schottky junction photo-electrochemical cells. The 3D pyramid-like graphene/p-Si Schottky junction photocathode delivers an onset potential of 0.41 V and a saturated photocurrent density of -32.5 mA cm(-2) at 0 V (vs RHE) with excellent stability comparable to values reported for textured or nanostructured p-Si photocathodes coated with ultrathin oxide layers by the conventional atomic layer deposition technique. These results suggest that the formation of graphene/Si Schottky junctions with a 3D architecture is a promising approach to improve the performance and durability of Si-based photo-electrochemical systems for water splitting or solar-to-fuel conversion.
Development of the Robot of Living Aid: RoLA
(2008)
Song, Kai-Tai
;
Tsai, Chi-Yi
;
Huang, Fu-Sheng
;
Hong, Jung-Wei
;
Lin, Chen-Yang
With increasing number of aging people, taking care of the elderly will become more and more important for future society, especially for those elderly living alone. This paper presents an autonomous mobile robot Rola (Robot of LivingAid), which can handle certain emergency conditions in a home setting to help the elderly through multi-modal sensing and control functions. The implemented functions include visual tracking, video transmission, location aware, navigation, body pose recognition and emergency call out. Rola can accommodate smoothly to the movement of a user through face tracking and performs robot-assisted video conferencing. Rola follows the elderly in the living room using the developed RF-based location aware system. It avoids obstacles in a narrow space employing a laser scanner. Further, Rola can help the elderly as he/she falls down at home. This accidental situation can be detected with a tri-axial accelerometer mounted on the waist of the elderly. It approaches to the elderly by the help of location-aware system and provides timely help through automatic call out and wireless video transmission.
Intrinsic Carrier Transport of Phase-Pure Homologous 2D Organolead Halide Hybrid Perovskite Single Crystals
(2018-12-27)
Li, Min-Ken
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Chen, Tzu-Pei
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Lin, Yen-Fu
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Raghavan, Chinnambedu Murugesan
;
Chen, Wei-Liang
This work reveals the intrinsic carrier transport behavior of 2D organolead halide perovskites based on phase-pure homologous (n = 1, 2, and 3) Ruddelsden-Popper perovskite (RPP) (BA)(2)(MA)(n-1)PbnI3n+1 single crystals. The 2D perovskite field effect transistors with high-quality exfoliated 2D perovskite bulk crystals are fabricated, and characteristic output and transfer curves are measured from individual single-crystal flakes with various n values under different temperatures. Unipolar n-type transport dominated the electrical properties of all these 2D RPP single crystals. The transport behavior of the 2D organolead halide hybrid perovskites exhibits a strong dependence on the n value and the mobility substantially increases as the ratio of the number of inorganic perovskite slabs per organic spacer increases. By extracting the effect of contact resistances, the corrected mobility values for n = 1, 2, and 3 are 2 x 10(-3), 8.3 x 10(-2), and 1.25 cm(2) V-1 s(-1) at 77 K, respectively. Furthermore, by combining temperature-dependent electrical transport and optical measurements, it is found that the origin of the carrier mobility dependence on the phase transition for 2D organolead halide perovskites is very different from that of their 3D counterparts. Our findings offer insight into fundamental carrier transport behavior of 2D organic-inorganic hybrid perovskites based on phase-pure homologous single crystals.
MULTI-PERSON POSE RECOGNITION SYSTEM USING A ZIGBEE WIRELESS SENSOR NETWORK
(2009-06-25)
Chen, Chun-Wei
;
Song, Kai-Tai
In the present invention, a multi-person pose recognition system has been developed. This system includes a body pose detection module, a CC2420DBK board and a multi-person pose monitoring software module. The body pose detection module includes a triaxial accelerometer, a Zigbee chip and an 8-bit microcontroller. Several body pose detection modules and the CC2420DBK board form a Zigbee wireless sensor network (WSN). The CC2420DBK board functions as the receiver of the Zigbee WSN and communicates with a robot onboard computer or a host computer through a RS-232 port. The multi-person pose monitoring software monitors and records activities of multiple users simultaneously. The present invention provides a pose recognition algorithm by combining time-domain analysis and wavelet transform analysis. This algorithm has been implemented in the microcontroller of a body pose estimation module. Through the algorithm, the system can recognize seven body poses: falling, standing, sitting, lying, walking, going upstairs and going downstairs.
NURSING SYSTEM
(2009-08-06)
Tsai, Chi-Yi
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Huang, Fu-Sheng
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Lin, Chen-Yang
;
Lin, Zhi-Sheng
;
Chen, Chun-Wei
A nursing system of the present invention can position where a person to be nursed through a sensor network widely deployed in an environment, instantaneously detect if the person to be nursed has an accident, and forward a message to inform a relative or medical staff. An autonomous robot will actively move beside the person to be nursed and transmit real-time images to a remote computer or PDA so that the relative or medical staff can swiftly ascertain the situation of the person to be nursed and the person to be nursed in case of emergency can be rescued as soon as possible.
Origin of Extended UV Stability of 2D Atomic Layer Titania-Based Perovskite Solar Cells Unveiled by Ultrafast Spectroscopy
(2019-06-19)
Thilakan, Anusha Puliparambil
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Li, Jia-Xing
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Chen, Tzu-Pei
;
Li, Shao-Sian
;
Chen, Chun-Wei
The inherent instability of UV-induced degradation in TiO2-based perovskite solar cells was largely improved by replacing the anatase-phase compact TiO2 layer with an atomic sheet transport layer (ASTL) of two-dimensional (2D) Ti1-delta O2. The vital role of microscopic carrier dynamics that govern the UV stability of perovskite solar cells was comprehensively examined in this work by performing time-resolved pump-probe spectroscopy. In conventional perovskite solar cells, the presence of a UV-active oxygen vacancy in compact TiO2 prohibits current generation by heavily trapping electrons after UV degradation. Conversely, the dominant vacancy type in the 2D Ti1-delta O2 ASTL is a titanium vacancy, which is a shallow acceptor and is not UV-sensitive. Therefore, it significantly suppresses carrier recombination and extends UV stability in perovskite solar cells with a 2D Ti1-delta O2 ASTL. Other carrier dynamics, such as electron diffusion, electron injection, and hot hole transfer processes, were found to be less affected by UV irradiation. Quantitative pump-probe data clearly show a correlation between the carrier dynamics and UV aging of perovskite solar cells, thus providing a profound insight into the factors driving UV-induced degradation in perovskite solar cells and the origin of its performance.
Phase retrieval by using the transport-of-intensity equation with Hilbert transform
(2016-04-01)
Li, Wei-Shuo
;
Chen, Chun-Wei
;
Lin, Kuo-Feng
;
Chen, Hou-Ren
;
Tsai, Chih-Ya
Phase recovery by solving the transport-of-intensity equation (TIE) is a non-iterative and non-interferometric phase retrieval technique. From solving the TIE with conventional, one partial derivative and Hilbert transform methods for both the periodic and aperiodic samples, we demonstrate that the Hilbert transform method can provide the smoother phase images with edge enhancement and fine structures. Furthermore, compared with the images measured by optical and atomic force microscopy, the Hilbert transform method has the ability to quantitatively map out the phase images for both the periodic and aperiodic structures. (C) 2016 Optical Society of America