Browsing by Author "Li, Hung-Hsien"

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A Novel Coaxial-Structured Amorphous-Silicon p-i-n Solar Cell With Al-Doped ZnO Nanowires
(2011-07-01)
Li, Hung-Hsien
;
Yang, Po-Yu
;
Chiou, Si-Ming
;
Liu, Han-Wen
;
Cheng, Huang-Chung
A novel coaxial-structured amorphous-silicon (a-Si) p-i-n solar cell with 1-mu m-long low-temperature hydrothermally synthesized Al-doped-ZnO (AZO) nanowires was demonstrated for the first time. The conversion efficiency. increased from 3.92% to 4.27% when the intrinsic a-Si thickness was increased from 25 to 150 nm and then decreased to 3.66% when the intrinsic layer thickness was further increased to 250 nm. It was attributed to an excessively thick intrinsic a-Si layer that would decrease the internal electrical field and interfere with charge separation. With the optimum intrinsic a-Si thickness of 150 nm, the conversion efficiency increased from 4.27% to 4.73% when the AZO wire length was increased from 1 to 2 mu m. Moreover, the proposed coaxial-structured solar cell exhibited a nearly 46% efficiency enhancement over a conventional a-Si thin-film solar cell.
An Extended-Gate Field-Effect Transistor With Low-Temperature Hydrothermally Synthesized SnO2 Nanorods as pH Sensor
(2012-10-01)
Li, Hung-Hsien
;
Dai, Wei-Syuan
;
Chou, Jung-Chuan
;
Cheng, Huang-Chung
;
電子工程學系及電子研究所
An extended-gate field-effect transistor (EGFET) with low-temperature hydrothermally synthesized SnO2 nanorods as the pH sensor was demonstrated for the first time. The SnO2 nanorod sensor exhibited the higher sensitivity of 55.18 mV/pH and larger linearity of 0.9952 in the wide sensing range of pH 1-13 with respect to the thin-film one. The nearly 15% sensitivity enhancement for such a sensor was attributed to the high surface-to-volume ratio of the nanorod structure, reflecting larger effective sensing areas. The characteristics of the output voltage versus sensing time also indicated good reliability and durability for the SnO2 nanorod sensor. Furthermore, the hysteresis was only 3.69 mV after the solution was changed as pH7 --> pH3 --> pH7 --> pH11 --> pH7.
Coaxial-Structured Solar Cells with Silicon Nanostructures
(2012)
Li, Hung-Hsien
;
Chen, Kuan-Heng
;
Chiou, Si-Ming
;
Liu, Han-Wen
;
Juan, Chuan-Ping
Coaxial-structured solar cells with different lengths silicon nanowires (SiNWs) fabricated by e-beam lithography and transformer coupled plasma reactive ion etching (TCP-RIE) were demonstrated in this paper. With the intrinsic amorphous silicon thickness of 15 nm and n-layer thickness of 25 nm, the short-current density and the conversion efficiency of the flat film solar cell were 17.58 mA/cm(2) and 3.16 %, respectively. Furthermore, the short-current density increased from 20.75 to 27.90 mA/cm(2) and the conversion efficiency increased from 3.59 to 4.69 % when the silicon nanowires length was increased from 0.5 to 1 mu m. The proposed coaxial-structured solar cells with SiNWs exhibited nearly 48.42 % efficiency enhancement over the plat film solar cell.
Coaxial-structured ZnO/silicon nanowires extended-gate field-effect transistor as pH sensor
(2013-02-01)
Li, Hung-Hsien
;
Yang, Chi-En
;
Kei, Chi-Chung
;
Su, Chung-Yi
;
Dai, Wei-Syuan
An extended-gate field-effect transistor (EGFET) of coaxial-structured ZnO/silicon nanowires as pH sensor was demonstrated in this paper. The oriented 1-mu m-long silicon nanowires with the diameter of about 50 nm were vertically synthesized by the electroless metal deposition method at room temperature and were sequentially capped with the ZnO films using atomic layer deposition at 50 degrees C. The transfer characteristics (I-DS-V-REF) of such ZnO/silicon nanowire EGFET sensor exhibited the sensitivity and linearity of 46.25 mV/pH and 0.9902, respectively for the different pH solutions (pH 1-pH 13). In contrast to the ZnO thin-film ones, the ZnO/silicon nanowire EGFET sensor achieved much better sensitivity and superior linearity. It was attributed to a high surface-to-volume ratio of the nanowire structures, reflecting a larger effective sensing area. The output voltage and time characteristics were also measured to indicate good reliability and durability for the ZnO/silicon nanowires sensor. Furthermore, the hysteresis was 9.74 mV after the solution was changed as pH 7 -> pH 3 -> pH 7 -> pH 11 -> pH 7. (C) 2012 Elsevier B.V. All rights reserved.
Experimental and Theoretical Study of Low-Cost Hydrothermally Grown Nanowire Silicon Solar Cell
(2013)
Li, Hung-Hsien
;
Lin, Albert S.
;
Zhong, Yan-Kai
;
Fu, Sze-Ming
;
Lai, Shih-Yun
The low cost and high absorbance is the two most important considerations for thin-film silicon photovoltaics. In this work, aluminum doped zinc oxide(AZO) nanowire is grown by low cost hydrothermal method and nano-structured amorphous silicon(alpha-Si) solar cell is realized on these AZO nanowire substrate. The experimental result shows superior light trapping property compared to conventional planar structure with 18.83% improvement in photocurrent. Simulation result shows the required thickness for full absorption for high aspect ratio AZO nanowire solar cell is similar to 0.3 square m, much thinner than planar type solar cell. The calculation reveals that solar cell absorbance increases with the nanowire length and packing density, indicating material volume is the first order effect for nanowire solar cells. The proposed low-cost AZO nanowire array amorphous silicon solar cell is very promising for future nanostructured silicon photovoltaics.
pH Sensing Characteristics of Extended-Gate Field-Effect Transistor Based on Al-Doped ZnO Nanostructures Hydrothermally Synthesized at Low Temperatures
(2011-11-01)
Yang, Po-Yu
;
Wang, Jyh-Liang
;
Chiu, Po-Chun
;
Chou, Jung-Chuan
;
Chen, Cheng-Wei
The pH sensing properties of an extended-gate field-effect transistor (EGFET) with Al-doped ZnO (AZO) nanostructures are investigated. The AZO nanostructures with different Al dosages were synthesized on AZO/glass substrate via a simple hydrothermal growth method at 85 degrees C. The pH sensing characteristics of pH-EGFET sensors with an Al dosage of 1.98 at% can exhibit a higher voltage sensitivity of 57.95 mV/pH, a larger linearity of 0.9998, and a wide sensing range of pH 1-13, attributed to the well-aligned nanowire (NW) array, superior crystallinity, less structural defects, and better conductivity. Consequently, the hydrothermally grown AZO NWs demonstrate superior pH sensing characteristics and reveal the potentials for flexible and disposable biosensors.