Browsing by Author "Tsai, Min-An"

Now showing 1 - 20 of 22

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
;
交大名義發表
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.
Efficiency Enhancement and Beam Shaping of GaN-InGaN Vertical-Injection Light-Emitting Diodes via High-Aspect-Ratio Nanorod Arrays
(2009-01-01)
Tsai, Min-An
;
Yu, Peichen
;
Chao, C. L.
;
Chiu, C. H.
;
Kuo, H. C.
The enhanced light extraction and collimated output beam profile from GaN-InGaN vertical-injection light-emitting diodes (VI-LEDs.) 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. The fabricated nanorod arrays not only provide an omnidirectional escaping zone for photons, but also serve as waveguiding channels for the emitted light, resulting in a relatively collimated beam profile. The light output power of the VI-LED with nanorod arrays is enhanced by 40 %, compared to a conventional VI-LED. The measured far-field profiles indicate that the enhancement is mainly along the surface normal direction, within a view angle of 20 degrees.
Efficiency Enhancement InGaP/GaAs Dual-Junction Solar Cell with Subwavelength Antireflection Nanorod Arrays
(2011-12-01)
Tsai, Min-An
;
Chen, Hsin Chu
;
Tseng, Ping Chen
;
Yu, Peichen
;
Chiu, Chin Hua
The enhanced conversion efficiency of the InGaP/GaAs dual-junction solar cell was demonstrated utilizing broad-band and omnidirectional antireflection nanorod arrays. The nanorod arrays were fabricated by self-assembled Ni clusters, followed by inductively-coupled-plasma reactive ion etching. The conversion efficiency measured under one-sun air mass 1.5 global illuminations at room temperature was improved by 10.8%. The light absorption efficiencies of the top InGaP and bottom GaAs cells were also studied under the influence of nanorod arrays. The enhanced absorption efficiency was mostly contributed from the short wavelength absorption by top cell. Surface nanorod arrays served not only as broad-band omnidirectional antireflection layers but also scattering sources. The structure can be further optimized to obtain the maximum conversion efficiency.
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 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 efficiency for c-Si solar cell with nanopillar array via quantum dots layers
(2011-09-12)
Chen, Hsin-Chu
;
Lin, Chien-Chung
;
Han, Hao-Wei
;
Tsai, Yu-Lin
;
Chang, Chia-Hua
The enhanced efficiency of the crystalline silicon (c-Si) solar cell with nanopillar arrays (NPAs) was demonstrated by deployment of CdS quantum dots (QDs). The NPAs was fabricated by the colloidal lithography and reactive-ion etching techniques. Under a simulated one-sun condition, the device with CdS QDs shows a 33% improvement of power conversion efficiency, compared with the one without QDs. For further investigation, the excitation spectrum of photoluminescence (PL), absorbance spectrum, current-voltage (I-V) characteristics, reflectance and external quantum efficiency of the device was measured and analyzed. It is noteworthy that the enhancement of efficiency could be attributed to the photon down-conversion, the antireflection, and the improved electrical property. (C) 2011 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.
High Efficiency InGaP/GaAs Solar Cell with Sub-wavelength Structure on AlInP Window Layer
(2010)
Tsai, Min-An
;
Yu, Peichen
;
Chiu, C. H.
;
Kuo, H. C.
;
Lu, T. C.
In this study, InGaP/GaAs solar cells fabricated by a Sub-wavelength surface texture process are presented. The characteristics of the InGaP/GaAs solar cells with and without the Sub-wavelength surface texture are studied. The conversion efficiency measured under one-sun air mass 1.5 global illumination at room temperature can also be improved from 10.8%. The simulated result of the Sub-wavelength structure by the RCWA was demonstrated that absorption of the solar cell will increase by the Sub-wavelength surface texture.
High Extraction Efficiency of GaN-Based Vertical-Injection Light-Emitting Diodes Using Distinctive Indium-Tin-Oxide Nanorod by Glancing-Angle Deposition
(2011-05-01)
Tsai, Min-An
;
Wang, Hsun-Wen
;
Yu, Peichen
;
Kuo, Hao-Chung
;
Lin, Shiuan-Huei
The enhanced light extraction and reduced forward voltage of a GaN-based vertical injection light emitting diode (VI-LED) with an indium-tin-oxide (ITO) nanorod array were demonstrated. The ITO nanorod array was fabricated by the glancing-angle deposition method. The employment of ITO nanostructures amplified not only the broadband transmission but also the current spreading. The optical output power of GaN-based VI-LEDs with ITO nanorods was enhanced by 50% compared with a conventional VI-LED at an injection current of 350 mA. The extraction efficiency was dramatically raised from 62 to 93% by the surface ITO nanorods. We also optimized the extraction efficiency of the GaN-based VI-LED with an ITO nanorod array by tuning the thickness of the n-GaN top layer via three-dimensional finite difference time domain (3D-FDTD) simulation. (C) 2011 The Japan Society of Applied Physics
Improved efficiency for nanopillar array of c-Si photovoltaic by down-conversion and anti-reflection of quantum dots
(2012)
Lin, Chien-Chung
;
Chen, Hsin-Chu
;
Han, Hau-Vei
;
Tsai, Yu-Lin
;
Chang, Chia-Hua
Improvement of efficiency for crystalline silicon (c-Si) with nanopillar arrays (NPAs) solar cell was demonstrated by deployment of CdS quantum dots (QDs). The NPAs was fabricated by colloidal lithography of self-assembled polystyrene (PS) nanospheres with a 600 nm in size and reactive-ion etching techniques, and then a colloidal CdS QDs with a concentration of 5 mg/mL was spun on the surface of c-Si with NPAs solar cell. Under a simulated one-sun condition, the device with CdS QDs shows a 33% improvement of power conversion efficiency, compared with the one without QDs. Additionally, we also found that the device with CdS QDs shows a 32% reduction in electrical resistance, compared with the one without QDs solar cell, under an ultraviolet (UV) light of 355nm illumination. This reduced electrical resistance can directly contribute to our fill-factor (FF) enhancement. For further investigation, the excitation spectrum of photoluminescence (PL), absorbance spectrum, current-voltage (I-V) characteristics, reflectance and external quantum efficiency (EQE) of the device were measured and analyzed. Based on the spectral response and optical measurement, we believe that CdS QDs not only have the capability for photon down-conversion in ultraviolet region, but also provide extra antireflection capability.
Improving Light Output Power of the GaN-Based Vertical-Injection Light-Emitting Diodes by Mg(+) Implanted Current Blocking Layer
(2009-05-01)
Tsai, Min-An
;
Yu, Peichen
;
Chen, J. R.
;
Huang, J. K.
;
Chiu, C. H.
A method for forming a current blocking layer (CBL) by ion implantation in GaN-based vertical-injection light-emitting diodes (VI-LEDs) was proposed. It was found that the use of CBL in VI-LEDs can effectively reduce the current crowding effect and enhance the light output power. The uniform emission intensity distribution of VI-LEDs with CBL was demonstrated by electroluminescence measurements. Experimental results show that the wall-plug efficiency was enhanced by 12.3% at an injection current of 20 mA, compared to that of VI-LEDs without CBL, and by 56.2% compared to that of conventional LEDs. The device simulation results reveal that the current path can be blocked by CBL, resulting in high light extraction efficiencies and large current densities within the effective emission region of active layers.
Improving Light Output Power of the GaN-Based Vertical-Injection Light-Emitting Diodes by Mg+ Implanted Current Blocking Layer
(2009-05-01)
Tsai, Min-An
;
Yu, Peichen
;
Chen, J. R.
;
Huang, J. K.
;
Chiu, C. H.
A method for forming a current blocking layer (CBL) by ion implantation in GaN-based vertical-injection light-emitting diodes (VI-LEDs) was proposed. It was found that the use of CBL in VI-LEDs can effectively reduce the current crowding effect and enhance the light output power. The uniform emission intensity distribution of VI-LEDs with CBL was demonstrated by electroluminescence measurements. Experimental results show that the wall-plug efficiency was enhanced by 12.3% at an injection current of 20 mA, compared to that of VI-LEDs without CBL, and by 56.2% compared to that of conventional LEDs. The device simulation results reveal that the current path can be blocked by CBL, resulting in high light extraction efficiencies and large current densities within the effective emission region of active layers.
Influence on light-induced degradation in Cz-Si PERC cells under light soaking of variant wavelength and intensity
(2018-01-01)
Wu, Ching-Wen
;
Lee, Yen-Chun
;
Yu, Li-Chieh
;
Tsai, Min-An
;
Wu, Hung-Sen
We have carried out multiple analysis on the acceleration factors of LID for Cz-Si PERC cells, including temperatures, intensities and wavelengths at 396nmand 969nm. The recovery time of LID at 130 degrees C under 1 SUN shrinks down to 4 hrs and the maximum degradation in Pmax is less than 3 % due the elimination of B-O LID under high carrier-injection. However, it seems that higher intensities couldn't stop the second degradation from happening, indicating the formation of other defects. Therefore, we employ LED light source of different wavelengths and obtain that both maximum degradation of Pmax are quite different. The consequence implies that behavior of LID might be originated from the particular position (penetration depth) where carriers are located.
Nano-patterned glass superstrates with different aspect ratios for enhanced light harvesting in a-Si:H thin film solar cells
(2012-05-07)
Chen, Ting-Gang
;
Yu, Peichen
;
Tsai, Yu-Lin
;
Shen, Chang-Hong
;
Shieh, Jia-Min
Nano-patterned glass superstrates obtained via a large-area production approach are desirable for antireflection and light trapping in thin-film solar cells. The tapered nanostructures allow a graded refractive index profile between the glass and material interfaces, leading to suppressed surface reflection and increased forward diffraction of light. In this work, we investigate nanostructured glass patterns with different aspect ratios using scalable nanosphere lithography for hydrogenated amorphous silicon (a-Si:H) thin film solar cells. Compared to flat glass cell and Asahi U-type glass cell, enhancements in short-circuit current density (J(sc)) of 51.6% and 8%, respectively, were achieved for a moderate aspect ratio of 0.16. The measured external quantum efficiencies (EQE) spectra confirmed a broadband enhancement due to antireflection and light trapping properties. (C) 2012 Optical Society of America
Observation of unusual optical transitions in thin-film Cu(In,Ga)Se-2 solar cells
(2012-11-05)
Liao, Yu-Kuang
;
Kuo, Shou-Yi
;
Lin, Woei-Tyng
;
Lai, Fang-I
;
Hsieh, Dan-Hua
In this paper, we examine photoluminescence spectra of Cu(In,Ga)Se-2 (CIGS) via temperature-dependent and power-dependent photoluminescence (PL). Donor-acceptor pair (DAP) transition, near-bandedge transition were identified by their activation energies. S-shaped displacement of peak position was observed and was attributed to carrier confinement caused by potential fluctuation. This coincides well with the obtained activation energy at low temperature. We also present a model for transition from V-Se to V-In and to V-Cu which illustrates competing mechanisms between DAPs recombinations. (C) 2012 Optical Society of America
Photon recycling characteristics of InGaAs/GaAsP multiple quantum well solar cells incorporating a spectrally selective filter and distributed Bragg reflector
(2019-12-09)
Hong, Chung-Yu
;
Wang, Yi-Chin
;
Su, Yu-Chih
;
Tsai, Jia-Ling
;
Tung, Chao-Ming
Photon management plays a vital role in the power conversion efficiency of III-V semiconductor solar cells. However, the photon recycling characteristics of GaAs-based multi-quantum-well (MQW) solar cells employed different optical designs had yet been fully explored. In this work, we investigate the impact of the spectrally selective filter (SSF) and distributed Bragg reflector (DBR) on the photovoltaic characteristics of single-junction, strain-balanced In0.1Ga0.9As/ GaAs0.85P0.15 MQW solar cells. Specifically, the SSFs with cutoff wavelengths of 880, 910, and 940 nm are designed and implemented on MQW solar cells with and without the incorporation of a rear DBR. Photon confinement in the vertical direction is verified based on the characterizations of reflectance, electroluminescence, and external quantum efficiency. We show that the photon confinement reduces the saturation current density, up to 26 times and 3 times for the 880 nm SSF-MQW and SSF-MQW-DBR devices, respectively, compared to that of the 940 nm devices. Furthermore, by comparing the SSF-MQW-DBR solar cells under simulated one-sun and concentrated illumination conditions, the open-circuit voltage exhibits a maximal net increase for the 910 nm SSF due to tradeoff between the short-circuit and saturation current density. The proposed SSF design may offer a viable approach to boost the performance of GaAs-based MQW solar cells. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Photovoltaic Characteristics of Multiple Quantum Well Solar Cells with Distributed Bragg Reflector and Selective Filters
(2016-01-01)
Hong, Chung-Yu
;
Wang, Yi-Chin
;
Hung, Mu-Min
;
Su, Yu-Chih
;
Tsai, Jia-Ling
We investigate the photon recycling characteristics of single junction solar cells incorporating 50-pairs multiple quantum wells (MQW) to exploit the high radiative recombination rate in one-dimensional carrier-confinement structures. In particular, we systematically compare solar cells with monolithically grown distributed Bragg reflectors (DBRs), as well as selective filters (SFs) with cutoff wavelengths of 880, 910, and 930 nm under standard and concentrated illumination conditions. Optical confinement in the vertical direction is verified based on the reflective spectra and electroluminescence properties. Consequently, the photo-recycling effect manifests under concentrated conditions, where the maximal open circuit voltage difference, by 12mV under 200x illumination, is achieved for MQW solar cells incorporating both the DBR and the 910-nm-cutoff SF, compared to those without the DBR or SFs. It is also revealed that the fill factor (FF) is also affected by the photon recycling effect, where incorporating SF results in the FF enhancement compared to the counterpart without the SF and the enhancement is higher for those with DBRs than without the DBRs.