Browsing by Author "Tseng, Ping-Chen"

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Angle-resolved characteristics of silicon photovoltaics with passivated conical-frustum nanostructures
(2011-09-01)
Tseng, Ping-Chen
;
Yu, Peichen
;
Chen, Hsin-Chu
;
Tsai, Yu-Lin
;
Han, Hao-Wei
Passivation plays a critical role in silicon photovoltaics, yet how a passivation layer affects the optical characteristics of nano-patterned surfaces has rarely been discussed. In this paper, we demonstrate conical-frustum nanostructures fabricated on silicon solar cells using polystyrene colloidal lithography with various silicon-nitride (SiN(x)) passivation thicknesses. The omnidirectional and broadband antireflective characteristics were determined by utilizing angle-resolved reflectance spectroscopy. The conical-frustum arrays with a height of 550 nm and a SiN(x) thickness of 80 nm effectively suppressed the Fresnel reflection in the wavelength range from 400 to 1000 nm, up to an incidence angle of 60 degrees. As a result, the power conversion efficiency achieved was 13.39%, which showed a 9.13% enhancement compared to that of a conventional KOH-textured silicon cell. The external quantum efficiency measurements confirmed that the photocurrent was mostly contributed by the increased optical absorption in the near-infrared. The angular cell efficiencies were estimated and showed improvements over large angles of incidence. (C) 2011 Elsevier B.V. All rights reserved.
ANGLE-RESOLVED REFLECTANCE SPECTROSCOPY OF PASSIVATED TRAPEZOID-CORN NANOSTRUCTURES FOR CRYSTALLINE SILICON PHOTOVOLTAICS
(2010)
Tseng, Ping-Chen
;
Chen, Hsin-Chu
;
Tsai, Min-An
;
Kuo, Hao-Chung
;
Yu, Peichen
In this work, we demonstrate an omnidirectional and broadband antireflective nanostructures incorporating a silicon nitrides (SiNx) passivation layer. The antireflective trapezoid-cone nanostructures are fabricated on a silicon wafer using polystyrene colloidal lithography with 550nm in height and then passivated with SiNx in different thicknesses to serve as the antireflection layer for silicon photovoltaics. The angle-resolved reflectance spectroscopy reveals that the trapezoid-cone nanostructures with an 80-nm-thick SiNx passivation layer effectively suppressed the Fresnel reflection over a broad spectral range and large angle of incidence (AOI). The AM1.5g weighted reflectance from 400 nm to 1000 nm is as low as 4.2% at normal incidence and <9.5% up to an AOI of 60 degrees, which is much superior to a conventional textured silicon substrate with passivation.
Antireflection and light trapping of subwavelength surface structures formed by colloidal lithography on thin film solar cells
(2012-03-01)
Tseng, Ping-Chen
;
Tsai, Min-An
;
Yu, Peichen
;
Kuo, Hao-Chung
;
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In this paper, we present a novel design of a surface nanostructure that suppresses the reflectivity and provides forward diffraction for light trapping. The structure under study comprises periodic nanoislands fabricated using self-assembly polystyrene spheres, which are applicable to large-area fabrication. We also show preliminary fabrication results of the proposed structure. The periodic nanoislands reduce the reflectivity through gradient effective refractive indices and enhance light trapping through diffraction in a periodic structure. We first systematically study the antireflection and light trapping effects using a rigorous coupled-wave analysis and then calculate the short-circuit current density of a 2-mu m-thick crystalline silicon with periodic nanoislands and an aluminum back reflector. The optimum short-circuit current density with periodic nanoislands achieves 25?mA/cm2 theoretically, which shows a 76.9% enhancement compared with that of bare silicon. Moreover, the structure also provides superior photocurrent densities at large angles of incidence, compared with conventional antireflection coatings. Copyright (c) 2011 John Wiley & Sons, Ltd.
Embedded biomimetic nanostructures for enhanced optical absorption in thin-film solar cells
(2011-07-04)
Tsai, Min-An
;
Han, Hao-Wei
;
Tsai, Yu-Lin
;
Tseng, Ping-Chen
;
Yu, Peichen
Light-management is critical to thin film solar cells due to their usually limited optical absorption in the active layer. Conventional approaches involve employing separate techniques for anti-reflection and light trapping. Here, we demonstrate an embedded biomimetic nanostructure (EBN) that achieves both effects for hydrogenated amorphous silicon (a-Si: H) solar cells. The fabrication of EBNs is accomplished by patterning an index-matching silicon-nitride layer deposited on a glass substrate using polystyrene nanospheres lithography, followed by reactive ion etching. The profile of EBN is then reproduced layer by layer during the deposition of a-Si: H cells. We show that a solar cell with an optimized EBN exhibits a broadband enhanced external quantum efficiency due to both antireflection and light-trapping, with respect to an industrial standard cell using an Asahi U glass substrate which is mostly optimized for light trapping. Overall, the cell with an optimized EBN achieves a large short-circuit current density of 17.74 mA/cm(2), corresponding to a 37.63% enhancement over a flat control cell. The power conversion efficiency is also increased from 5.36% to 8.32%. Moreover, the light management enabled by the EBN remains efficient over a wide range of incident angles up to 60 degrees, which is particularly desirable for real environments with diffused sun light. The novel patterning method is not restricted to a-Si:H solar cells, but is also widely applicable to other thin film materials. (C) 2011 Optical Society of America
Enhanced angular characteristics of indium tin oxide nanowhisker-coated silicon solar cells
(2011-05-09)
Chang, Chia-Hua
;
Hsu, Min-Hsiang
;
Tseng, Ping-Chen
;
Yu, Peichen
;
Chang, Wei-Lun
Omnidirectional and broadband light harvesting is critical to photovoltaics due to the sun's movement and its wide spectral range of radiation. In this work, we demonstrate distinctive indium-tin-oxide nanowhiskers that achieve superior angular and spectral characteristics for crystalline silicon solar cells using angle-resolved reflectance spectroscopy. The solar-spectrum weighted reflectance is well below 6% for incident angles of up to 70 and for the wavelength range between 400nm and 1000nm. As a result, the nanowhisker coated solar cell exhibits broadband quantum efficiency characteristics and enhanced short-circuit currents for large angles of incidence. (C) 2011 Optical Society of America
Enhanced conversion efficiency of a crystalline silicon solar cell with frustum nanorod arrays
(2011-01-03)
Tsai, Min-An
;
Tseng, Ping-Chen
;
Chen, Hsin-Chu
;
Kuo, Hao-Chung
;
Yu, Peichen
Enhanced photoelectric conversion is demonstrated in a crystalline silicon (c-Si) solar cell with frustum nanorod arrays (FNAs), fabricated using colloidal lithography and reactive-ion etching techniques. Under a simulated one-sun condition, the cell with FNAs improves the power conversion efficiency by nearly 30%, compared to a conventional wet-chemical-textured reference. The enhancement mostly arises from the superior antireflective properties for wavelengths between 400 nm and 1000 nm. In that spectral range, we show that photons gained by reflection reduction directly contribute to collected carriers without auxiliary losses due to nano-fabrication. Moreover, the omnidirectional antireflection of FNAs is also investigated using an angle-resolved reflectance spectroscopy. The dimensions of FNAs are further analyzed with numerical calculations based on Maxwell's equations. The optimized short-circuit current density achieves nearly 40 mA/cm(2), corresponding to a 16% enhancement compared to the conventional device. (C)2010 Optical Society of America
Enhanced conversion efficiency of a crystalline silicon solar cell with frustum nanorod arrays
(2011-01-01)
Tsai, Min-An
;
Tseng, Ping-Chen
;
Chen, Hsin-Chu
;
Kuo, Hao-Chung
;
Yu, Peichen
Enhanced photoelectric conversion is demonstrated in a crystalline silicon (c-Si) solar cell with frustum nanorod arrays (FNAs). The omnidirectional antireflection of FNAs is also investigated using an angle-resolved reflectance spectroscopy and simulated by RCWA method. (C) 2010 Optical Society of America
Enhanced omnidirectional photon coupling via quasi-periodic patterning of indium-tin-oxide for organic thin-film solar cells
(2011-06-01)
Tseng, Ping-Chen
;
Hsu, Min-Hsiang
;
Tsai, Min-An
;
Chu, Chih-Wei
;
Kuo, Hao-Chung
Enhanced optical coupling via an indium tin oxide quasi-periodic structure (ITO-QPS) as the frontal electrode for organic thin film solar cells was demonstrated. The QPS was fabricated via scalable polystyrene colloidal lithography, which effectively coupled the incident light to the photo-active layer through antireflection and light-trapping mechanisms. The cell efficiency was boosted from 2.91% to 3.26%, corresponding to a 12% enhancement after ITO patterning. Moreover, the angle-resolved absorption spectroscopy also confirmed excellent light coupling at large angles of incidence to 45 degrees, particularly in the wavelength range between 540 and 670 nm. The ITO-QPS guarantees broadband and omnidirectional light harvesting and is widely applicable to a variety of thin film solar cells. (C) 2011 Elsevier B.V. All rights reserved.
Optical touch display device, optical touch sensing device and touch sensing method
(2010-04-08)
Tseng, Ping-Chen
;
Tien, Chung-Hao
The present invention provides an optical touch display device, an optical touch sensing device, and a method for calculating a touch position. The optical touch sensing device can be detachably attached on a display panel using adhesive or other method. The present invention includes a first light source, a second light source, a light sensing element, and a processing unit. When an object blocks the path of light, some light sensing elements will receive some or no light. The processing unit will then compute two line segments based on the positions of light sensing elements receiving some or no light. The two line segments cross each other and their intersection is defined as the position of object or the touch position.