Browsing by Author "Tsai, M. A."

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2-Step self-assembly method to fabricate broadband omnidirectional antireflection coating in large scale
(2011-02-01)
Yeung, K. M.
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Luk, W. C.
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Tam, K. C.
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Kwong, C. Y.
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Tsai, M. A.
We have developed a simple and reproducible 2-step self-assembly method for the fabrication of broadband, omnidirectional antireflection coating on glass substrate with 4 in. size. The glass surface has been modified to be positively charged, then the negatively charged nano silica is self-assembled to the glass substrate by electrostatic attraction. The nanostructure on the glass substrate reduces the reflection significantly, which results in enhanced transmittance. Transmittance as high as 97.7% at 499 nm has been obtained for a double-side coated glass substrate. Obvious reduction in weighted reflectance is still observed up to 60 degrees incident angle. (C) 2010 Elsevier B.V. All rights reserved.
Antireflection and Light Trapping of Periodic Subwavelength Surface Structures Formed by Colloidal Monolayer Spheres Lithography on Thin Film Solar Cells
(2010)
Tseng, P. C.
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Tsai, M. A.
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Yu, Peichen
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Kuo, H. C.
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光電工程學系
Solar cell efficiency enhancement by gradient periodic TiO(2) nanoislands formed with the facilitation of polystyrene-spheres was studied. The enhancement mechanism was categorized by antireflection and light-trapping and achieves 72% relative increase of short-circuit current density. @ 2010 Optical Society of America
Beam Shaping of GaN/InGaN Vertical-Injection Light Emitting Diodes via High-Aspect-Ratio Nanorod Arrays
(2009)
Tsai, M. A.
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Yu, Peichen
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Chao, C. L.
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Chiu, C. H.
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Kuo, H. C.
The enhanced light extraction and collimated output beam profile from GaN/InGaN vertical-injection light emitting diodes are demonstrated utilizing high-aspect-ratio nanorod arrays. The nanorod arrays are patterned by self-assembled silica spheres, followed by inductively-coupled-plasma reactive-ion-etching. (C) 2008 Optical Society of America
Biomimetic Antireflection Coating for Efficiency Enhancement of Triple-Junction Solar Cells Utilizing Nanosphere Lithography
(2010)
Chiu, M. Y.
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Chang, F. Y.
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Chang, C. H.
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Tsai, M. A.
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Yu, Peichen
In this work, we demonstrate a thorough device design, fabrication, characterization, and analysis of biomimetic antireflective structures implemented on a Ga(0.5)In(0.5)P/GaAs/Ge triple-junction solar cell. The sub-wavelength structures are fabricated on a silicon nitride passivation layer using polystyrene nanosphere lithography followed by anisotropic etching. Both the reflectance spectroscopy and external quantum efficiency measurements confirm the improved optical absorption in the ultraviolet/blue and near-infrared wavelengths. Hence, the conversion efficiency of cell with sub-wavelength structure (SWS) is enhanced by 46.1% and 3.4% due to much improved current-matching, compare to cells without an ARC and SL ARC, respectively. We further employ RCWA method to analyze the reflectance by tuning structural factors such as periodicity or height of the SWS.
Conversion Efficiency Enhancement of GaN/In(0.11)Ga(0.89)N Solar Cells With Nano Patterned Sapphire and Biomimetic Surface Antireflection Process
(2011-09-15)
Wang, H. W.
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Chen, H. C.
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Chang, Y. A.
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Lin, C. C.
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Han, H. W.
In this study, p-i-n double-heterojunction GaN/In(0.11)Ga(0.89)N solar cells grown by metal-organic chemical vapor deposition on pattern sapphire substrate are presented. The solar cell with standard process has a conversion efficiency of 3.1%, which corresponds to a fill factor of 58%, short circuit current density of 2.86 mA/cm(2), and open circuit voltage of 1.87 V under AM1.5G illumination. To further improve the conversion efficiency of the GaN/In(0.11)Ga(0.89)N solar cells, two-dimensional polystyrene nanospheres were deposited and self-organized as mask in the anisotropic inductively coupled plasma reactive ion etching process to form a biomimetic surface roughing texture. The surface morphology of the solar cell shows a periodically hexagonal bead pattern and the beads are formed in a diameter of 160 nm with a period of 250 nm. An increase of 15% in short circuit current density is found, thus improving the conversion efficiency to 3.87%. If we optimize the structure for 180 nm of the height and 375 nm of the period, a 10% gain can be expected when compared to the current structure.
Conversion Efficiency Enhancement of GaN/In0.11Ga0.89N Solar Cells With Nano Patterned Sapphire and Biomimetic Surface Antireflection Process
(2011-09-15)
Wang, H. W.
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Chen, H. C.
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Chang, Y. A.
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Lin, C. C.
;
Han, H. W.
In this study, p-i-n double-heterojunction GaN/In0.11Ga0.89N solar cells grown by metal-organic chemical vapor deposition on pattern sapphire substrate are presented. The solar cell with standard process has a conversion efficiency of 3.1%, which corresponds to a fill factor of 58%, short circuit current density of 2.86 mA/cm(2), and open circuit voltage of 1.87 V under AM1.5G illumination. To further improve the conversion efficiency of the GaN/In0.11Ga0.89N solar cells, two-dimensional polystyrene nanospheres were deposited and self-organized as mask in the anisotropic inductively coupled plasma reactive ion etching process to form a biomimetic surface roughing texture. The surface morphology of the solar cell shows a periodically hexagonal bead pattern and the beads are formed in a diameter of 160 nm with a period of 250 nm. An increase of 15% in short circuit current density is found, thus improving the conversion efficiency to 3.87%. If we optimize the structure for 180 nm of the height and 375 nm of the period, a 10% gain can be expected when compared to the current structure.
Efficiency and Droop Improvement in GaN-Based High-Voltage Light-Emitting Diodes
(2011-08-01)
Wang, C. H.
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Lin, D. W.
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Lee, C. Y.
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Tsai, M. A.
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Chen, G. L.
The efficiency and electrical characteristics of GaN-based high-voltage light-emitting diodes (HV-LEDs) are investigated in detail. The spatial distribution of light output and simulation results showed that 100-V HV-LED with smaller microchips had superior current spreading. As a result, under 1-W operation, the luminous efficiency of 100-V HV-LED with smaller microchips was enhanced by 7.8% compared to that of 50-V HV-LED, while the efficiency droop behaviors were reduced from 28% in 50-V HV-LED to 25.8% in 100-V HV-LED. Moreover, smaller microchips exhibited lower series resistance and forward voltage, leading to higher wall-plug efficiency.
EFFICIENCY ENHANCEMENT IN SINGLE JUNCTION INGAP SOLAR CELLS BY USING SELF-ASSEMBLED NANOSPHERES
(2010)
Chen, H. C.
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Tsai, Y. L.
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Wang, H. W.
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Tsai, M. A.
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Tseng, P. C.
A single-junction InGaP solar cells with polystyrene (PS) nanospheres on the surface has been developed. The self-assembly of PS nanospheres is one of the simplest and the fastest methods with which to build a 20 closely packed periodic structure. Based on the scattering of the PS nanospheres, the light path length can be increased. As compared to the InGaP solar cells without PS nanospheres on the top surface the standard process. An increase short-circuit current form 8.93% to 10.31% is improved when a single-junction InGaP solar cells with PS nanospheres. The conversion efficiency measured can also be improved from 8.79% to 9.71%. The single-junction InGaP solar cell with PS nanospheres was achieved.
Efficiency Enhancement in Single-Junction InGaP Solar Cells by Using Self-Assembled Nanospheres
(2011-06-01)
Chen, H. C.
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Lin, C. C.
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Wang, H. W.
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Tsai, M. A.
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Tseng, P. C.
A single-junction InGaP solar cell with polystyrene (PS) nanospheres on the surface has been developed. The self-assembly of PS nanospheres is one of the simplest and the fastest methods with which to build a 2-D closely packed periodic structure. Due to the scattering of the PS nanospheres, the light path length can be increased when compared to the InGaP solar cells without PS nanospheres on the top. An increase short-circuit current from 8.93 to 10.31 mA is improved when a single-junction InGaP solar cell is coated with PS nanospheres. The conversion efficiency measured can also be improved from 8.79% to 9.71%. The single-junction InGaP solar cell with PS nanospheres was achieved.
Efficiency Enhancement InGaP/GaAs Dual-junction Solar Cell by Broad-band and Omnidirectional Antireflection Nanorod Arrays
(2010)
Tsai, M. A.
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Tseng, P. C.
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Yu, Peichen
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Chiu, C. H.
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Kuo, H. C.
10% efficiency enhancement of the solar cell by Broad-band and Omnidirectional Antireflection Nanorod Arrays was demonstrated. The enhanced efficiency attributed to increased light entry and optical path in both the top cell and bottom cell. @2008 Optical Society of America
EFFICIENCY ENHANCEMENT InGaP/GaAs DUAL-JUNCTION SOLAR CELL WITH SUB-WAVELENGTH ANTIREFLECTION NANOROD ARRAYS
(2010)
Wang, H. W.
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Tsai, M. A.
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Chen, H. C.
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Tsai, Y. L.
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Tseng, P. C.
The enhanced conversion efficiency of the InGaP/GaAs dual-junction solar cell was demonstrated antireflection nanorod arrays. After self-assembled Ni clusters, the nanorod arrays were fabricated by inductively-coupled-plasma reactive ion etching. The conversion efficiency were measured under one-sun air mass 1.5 global illuminations at room temperature. The short current of the nanorod arrays cell was enhanced 10.0% and the efficiency was enhanced 10.8%. We were also studied the light absorption efficiencies of the top InGaP and bottom GaAs cells under the influence of nanorod arrays. Surface nanorod arrays were not only as antireflection layers but also scattering sources. The nanorod arrays structure can be significant improved the maximum conversion efficiency.
Electron-beam Evaporation of Distinctive Indium-tin-oxide Nanorods for Enhanced Light Extraction from InGaN/GaN Light Emitting Diodes
(2009)
Chiu, C. H.
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Yu, Peichen
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Tsai, M. A.
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Kuo, H. C.
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光電工程學系
In this paper, we present a novel and mass-producible technique to fabricate indium-tin-oxide (ITO) nanorods arrays on InGaN/GaN light em itting diodes (LEDs) surface to be served as an omnidirectional transparent conductive layer. The characteristics nanorods, prepared by the electron-beam evaporation with an obliquely incident nitrogen flux on an ITO glass, demonstrate high optical tran smittance ( T>95%) for a broad wavelength ranging from 350 to 900 nm. The light output power of an InGaN/GaN LED with incorporated ITO nanorods increases by 35.1 % at an injection current of 350 mA, compared to a conventional LED. The higher efficiency is attributed to the better transmission and gradient refractive index resulted from the fabricated ITO nanorod on the surface.
Enhanced Omnidirectional Photon Coupling via Quasi-Periodic Patterning of Indium-Tin-Oxide for Organic Thin-Film Solar Cells
(2011-01-01)
Tseng, P. C.
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Hsu, M. H.
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Chen, H. C.
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Tsai, M. A.
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Yu, Peichen
Enhanced optical coupling with respect to all incident angles via an indium tin oxide quasi-periodic structure (ITO-QPS) for organic thin-film solar cells was demonstrated. The cell @2010 Optical Society of America
High Light-Extraction Efficiency GaN-Based Vertical Injection LEDs with Surface Nipple Array
(2009)
Chiu, C. H.
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Tsai, M. A.
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Yu, Peichen
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Kuo, H. C.
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Lu, T. C.
The surface nipple arrays were formed by self-assembled polystyrene nano-spheres and inductively coupled plasma etching. The light output power of the vertical-Injection LEDs with nipple array shows 68% enhancement than that of without the nipple array at a driving current of 350 mA
LARGE-SCALE AND ENHANCED EFFICIENCY C-SI SOLAR CELL WITH MOTH-EYE-LIKE BY USING SELF-ASSEMBLED LITHOGRAPHY
(2010)
Tsai, M. A.
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Chen, H. C.
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Wang, H. W.
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Tsai, Y. L.
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Tseng, P. C.
We demonstrated the Si solar cell with ladder-shaped nanorod array, fabricated by combined the self-assembled lithography and reactive-ion etching technique. The measurement of angular reflective spectrums of the solar cell with ladder-shaped nanorod array using an integration sphere remained lower at broadband spectra and large angle of incident compared to the solar cell with micro-textured surface. The I-V measurement shown the current density and conversion efficiency could be improved by the ladder-shaped nanorod array. The enhancement conversion efficiency approached to 34.54%.
Oblique electron-beam evaporation of distinctive indium-tin-oxide nanorods for enhanced light extraction from InGaN/GaN light emitting diodes
(2009-11-09)
Chiu, C. H.
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Yu, Peichen
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Chang, C. H.
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Yang, C. S.
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Hsu, M. H.
This paper presents a novel and mass-producible technique to fabricate indium-tin-oxide (ITO) nanorods which serve as an omnidirectional transparent conductive layer (TCL) for InGaN/GaN light emitting diodes (LEDs). The characteristic nanorods, prepared by oblique electron-beam evaporation in a nitrogen ambient, demonstrate high optical transmittance (T>90%) for the wavelength range of 450nm to 900nm. The light output power of a packaged InGaN/GaN LED with the incorporated nanorod layer is increased by 35.1% at an injection current of 350mA, compared to that of a conventional LED. Calculations based on a finite difference time domain (FDTD) method suggest that the extraction enhancement factor can be further improved by increasing the thickness of the nanorod layer, indicating great potential to enhance the luminous intensity of solid-state lighting devices using ITO nanorod structures. (C) 2009 Optical Society of America