Browsing by Author "Chung, Chen-Chen"

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Broadband antireflection sub-wavelength structure of InGaP/InGaAs/Ge triple junction solar cell with composition-graded SiNx
(2015-05)
Chung, Chen-Chen
;
Lo, Hsiao-Chieh
;
Lin, Yen-Ku
;
Yu, Hung-Wei
;
Binh Tinh Tran
This work reports a fabrication strategy to improve the antireflective ability of a InGaP/GaAs/Ge triple-junction solar cell, by combining a nano-templating technique and a chemical-synthesis approach. SiH4 and N-2 were used as ammonia-free reaction gases in a plasma-enhanced chemical vapor deposition (PECVD) to prepare Si3N4 as an original antireflective coating (ARC) layer with better chemical stability. Composition-graded SiNx was successfully integrated with sub-wavelength structure by modulating SiH4/N-2 ratio during PECVD deposition, and followed by a controllable gold-nanoparticle masking technique on top of the solar cell. Finite-difference time-domain solution was employed to simulate and optimize the aspect-ratio of the ARC, under the condition of variable refractive index over a broad wavelength window, and followed by the masking technique to obtain the desired ARC dimension. This enabled a low light reflectance (<10%) over a broad spectral bandwidth (300-1800 nm) for the solar cell with excellent stability, because of the triple advantages of structural optimization, better chemical stability and graded refractive index of the ARC. The solar cell\'s performance was tested and showed great competitiveness to those of forefront studies, suggesting the feasibility of the proposed technology.
Characterization of Al2O3/ZnO Grown on Si Substrate by Plasma Enhanced Atomic Layer Deposition
(2013-01-01)
Chung, Chen-Chen
;
Tran, Binh-Tinh
;
Lin, Kung-Liang
;
Wang, Ching-Chiun
;
Chen, Chien-Chih
Characterization of nanolaminate Al2O3/ZnO oxide films grown on Si substrates was conducted by using plasma enhanced atomic layer deposition (PE-ALD) method. PE-ALD can minimize the structural imperfections in films and reduce substrate damage. The film deposition by using PE-ALD are dense, defect-free, highly uniform, conformal films and show excellent step coverage. Moreover, compared to other deposition techniques, it is possible to deposit high quality films at much lower temperatures. High resolution transmission electron microscope (TEM) images showed the existence of sharp interfacial layers among the Al2O3, ZnO layer, and the Si substrate for the growth rate of 1.56 angstrom/cycle, and the surface roughness of about 0.2 nm. The nanolaminate-stacking layer can be used in organic light emitting diode encapsulation application as the gas barrier.
Characterizations of GaN Films Grown on Si (111) Substrates with Various Growth Temperatures of Multiple AlN Buffer Layers
(2012)
Binh-Tinh Tran
;
Chang, Edward Yi
;
Lin, Kung-Liang
;
Luong, Tien-Tung
;
Yu, Hung-Wei
We present the effect of multiple AlN buffer layers on characterizations of GaN film quality, which includes a thin high-low-high-temperature (HLHT) AlN buffer layers. The study is based on two different thicknesses of the GaN films on the buffers and found that the HLHT AlN buffer layers could significantly affect on the GaN films qualities. The buffer plays a very important role for the growth of GaN film on Si (111) substrate. The GaN film with an uniformly faceted surface and very high-quality has been obtained at the optimized multiple HLHT AlN buffer layers of 50-nm-thick at 1010-800-1010 degrees C.
Effect of Different Tunnel diodes on The Efficiency of Multi-junction III-V Solar cells
(2014-01-01)
Yu, Hung-Wei
;
Hong-Quan Nguyen
;
Chung, Chen-Chen
;
Hsu, Ching-Hsiang
;
Hsiao, Chih-Jen
InGaP/GaAs dual-junction solar cells with different tunnel diodes (TDs) grown on misoriented GaAs substrates are investigated. It is found that the solar cells with P++-AlGaAs/N++-GaAs TDs grown on 10 degrees off GaAs substrates show a higher external quantum efficiency (EQE) but also generate a higher peak current density (J(peak)) than the solar cells with P++-GaAs/N++-InGaP TDs grown on 10 degrees off GaAs substrates. Furthermore, smooth surface (rms roughness: 1.54 angstrom) and sharp interface for the GaAs/Al0.3Ga0.7As TDs were obtained when the (100) tilted 10 degrees off toward [111] GaAs substrate was used. The conversion efficiency of InGaP/GaAs dual-junction solar cell with N++-GaAs/P++-AlGaAs TD grown on the (100) tilted 10 degrees off toward (111) GaAs substrate is close to 20%.
Effect of Multiple AlN Layers on Quality of GaN Films Grown on Si Substrates
(2014-11-01)
Binh Tinh Tran
;
Lin, Kung-Liang
;
Sahoo, Kartika Chandra
;
Chung, Chen-Chen
;
Chi-Lang Nguyen
In this paper, we present the effect of multiple thin high-low-high-temperature AlN (HLHT AlN) nucleation layers on GaN film quality. A 1.9-mu m-thick GaN film gown on Si (111) substrate shows that the multiple HLHT AlN nucleation layers have a significant effect on GaN film quality. This process also plays a very important role in the growth of GaN films on Si (111) substrates. A high quality GaN film with a uniformly faceted surface with very low dislocation densities is obtained at the optimized multiple HLHT AlN nucleation layers 50-nm thick at a temperature of 1010-800-1010 degrees C and a growth pressure of 50 Torr.
Effect of the Circle-Grid Electrodes on Concentrated GaAs Solar Cell Efficiency
(2014-09-01)
Chung, Chen-Chen
;
Binh Tinh Tran
;
Han, Ming-Hung
;
Lin, Kung-Liang
;
Yu, Hung-Wei
In this study, we investigate the effect of the shading factor of the front grid pattern on concentrated solar cell efficiency, taking the trade-off between the series resistance of the electrodes and the amount of incident light into consideration. We examine the thermal effect with regard to five different circle-grid electrode patterns of the front contact. The front contacts with different grid patterns affect the characteristics of light-concentrated-type GaAs single-junction solar cells. The device parameters analyzed include the open-circuit voltage (V-oc), short-circuit current (I-sc), fill factor (FF) and conversion efficiency (eta). The results of our study show that for a concentration ratio greater than 60x with AM1.5G, the device with a shading factor of 7.1% has the best cell efficiency of 27.05%, due to the smaller current crowding at the center spot. The results indicate that the conversion efficiency of solar cells can be improved by establishing a compromise between the shading effect and the series resistance effect.
Efficiency improvement of InGaP/GaAs/Ge solar cells by hydrothermal-deposited ZnO nanotube structure
(2014-07-05)
Chung, Chen-Chen
;
Binh Tinh Tran
;
Lin, Kung-Liang
;
Ho, Yen-Teng
;
Yu, Hung-Wei
In this paper, a zinc oxide (ZnO) nanotube, fabricated by the hydrothermal growth method on triple-junction (T-J) solar cell devices to enhance efficiency, is investigated. Compared to those of bare T-J solar cells (without antireflection (AR) coating) and solar cells with Si3N4 AR coatings, the experimental results show that the T-J solar cells, which use a ZnO nanotube as an AR coating, have the lowest reflectance in the short wavelength spectrum. The ZnO nanotube has the lowest light reflection among all experimental samples, especially in the range of 350 to 500 nm from ultraviolet (UV) to visible light. It was found that a ZnO nanotube can enhance the conversion efficiency by 4.9%, compared with a conventional T-J solar cell. The Si3N4 AR coatings also enhance the conversion efficiency by 3.2%.The results show that a cell with ZnO nanotube coating could greatly improve solar cell performances.
Fabrication and characterization of n-In0.4Ga0.6N/p-Si solar cell
(2012-07-01)
Tran, Binh-Tinh
;
Chang, Edward-Yi
;
Trinh, Hai-Dang
;
Lee, Ching-Ting
;
Sahoo, Kartika Chandra
Electro-optic characteristics of a fabricated n-In0.4Ga0.6N/p-Si hetero-structure solar cell on Si substrate with Al and ITO (or Ti/Al/Ni/Au) materials for p and n-type contacts were investigated in this letter. The solar cell devices with ITO as n-type contacts were also compared to the solar cell using Ti/Al/Ni/Au as n-type contact in this study. High short-circuit current density observed for solar cell with ITO as n-type contacts due to the increased amount of light reaching the solar cell. The device with ITO contact exhibited an open-circuit voltage (V-oc) of 1.52 V and a short-circuit current density (J(sc)) of 8.68 mA/cm(2) with 54% fill factor. The conversion and external quantum efficiency (EQE) of the solar cell were 7.12 and 20.8%, respectively. Besides, a relationship between V-oc and In content in the InxGa1-xN alloys for this type of solar cell was also derived. (C) 2012 Elsevier B.V. All rights reserved.
Gold-Free Fully Cu-Metallized InGaP/InGaAs/Ge Triple-Junction Solar Cells
(2014-12-01)
Hsu, Ching-Hsiang
;
Chang, Edward Yi
;
Chang, Hsun-Jui
;
Yu, Hung-Wei
;
Hong Quan Nguyen
Copper contacts and interconnects were developed for GaAs and Ge for low-cost solar cell application. In addition, thermally annealed Pd/Ge and Pt/Ti/Pt metallizations were created for ohmic contacts to n-GaAs and p-Ge with contact resistance of 4.4 x 10(-6) and 6.9 x 10(-6) Omega cm(2), respectively. Utilizing such metallization structure for InGaP/InGaAs/Ge triple-junction device structure solar cells were fabricated that delivered conversion efficiency of 23.11%, which is average efficiency for the above device structure.
Growth and Fabrication of GaN Light Emitting Diode on Patterned-Sapphire Substrate
(2013-01-01)
Binh-Tinh Tran
;
Ming, Chen-Hauw
;
Lin, Kung-Liang
;
Chen, Hao-Ming
;
Wang, Ching-Chian
In this study, the growth of GaN-films-based light emitting diodes (LEDs), have been clearly demonstrated on wet-etching patterned sapphire substrate (PSS) and conventional LEDs. The wet-etching PSS LED device showed a significantly higher performance than the conventional LED device. The wet-etching PSS LED device exhibited a leakage current of 9 mA under a bias of 8 V, an external quantum efficiency and output powers of 35.09 % and 19.23 mW under 20 mA injection current as compared to 12 mA, 27.23%, and 15.02 mW of the conventional LED device.
Growth of GaN films on circle array patterned Si (111) substrates
(2014-09-01)
Lin, Kung-Liang
;
Binh Tinh Tran
;
Chung, Chen-Chen
;
Chang, Edward-Yi
;
材料科學與工程學系
Low stress, low defect density GaN was successfully grown on circle array patterned Si (111) substrate using AlN as the buffer followed by two steps growth of the GaN film. Raman measurement shows a reduction of in plane biaxial stress for the GaN film grown on patterned substrate. The slight blueshifL of PL peaks further provides evidence that the tensile stress in the GaN film was relaxed, It is believed that the grain boundaries of the polycrystalline AlN buffer layer and the dislocations in the GaN film grown helped to relieve the stress induced by the lattice and the thermal coefficient mismatches during growth. (C) 2014 Elsevier By. All rights reserved.
Hydrothermal growth of ZnO nanotubes on InGaP/GaAs/Ge Solar Cells
(2014-01-01)
Chung, Chen-Chen
;
Lin, Kung-Liang
;
Yu, Hung-Wei
;
Quan, Nguyen-Hong
;
Dee, Chang-Fu
A new design where ZnO nanotubes were grown on the antireflection (AR) layer coated on triple-junction (T-J) solar cell devices to enhance the light conversion efficiency. Compared to the bare T-J solar cells (without an AR layer), the performance of Si3N4 AR coated solar cell showed improvement. The sample with a layer of ZnO nanotubes grown in top of AR layer showed the lowest light reflection compared with the bare and solely AR coated T-J solar cell especially in the spectrum range of 350-500 nm. The use of ZnO nanotubes have increased the conversion efficiency by 4.9% compared with the conventional T-J solar cell. While the Si3N4 AR coated sample only increased the conversion efficiency by 3.2%. This result is quite encouraging as further refinement and variation in the experiment procedures could possibly bring more exciting performance in the future.
The Circle-grid Electrode on Concentrated GaAs Solar Cells Efficiency
(2011)
Chung, Chen-Chen
;
Yu, Hung-Wei
;
Hsu, Li-Han
;
Kuo, Chien-I
;
Nguyen-Hong Quan
The relationship between front contact pattern of GaAs single-junction solar cell with conversion efficiency at different concentration ratios is studied in this paper. Five different front circle-grid patterns were designed and patterned on the in-house fabricated single junction GaAs solar cells. At high light concentration ratio, the cell efficiency is strongly dependent on the series resistance of the electrode. At the same time, the thermal effect should also be taken into consideration, especially when a device is operating under high concentration ratio. Therefore, the aim of this work is to find a suitable front contact pattern for a GaAs single-junction solar cell to increase the conversion efficiency under high concentration solar radiation. It is found that the device with proper pattern design geometrical shadowing factor of 7.1% has the best cell efficiency of 27.05% at CR>100x, AM1.5G.
The Effect of CdS QDs Structure on the InGaP/GaAs/Ge Triple Junction Solar Cell Efficiency
(2014-03-01)
Chung, Chen-Chen
;
Tran, Binh Tinh
;
Han, Hau-Vei
;
Ho, Yen-Teng
;
Yu, Hung-Wei
This work describes optical and electrical characteristics of InGaP/GaAs/Ge triple-junction (T-J) solar cells with CdS quantum dots (QDs) fabricated by a novel chemical solution. With the anti-reflective feature at long wavelength and down-conversion at UV regime, the CdS quantum dot effectively enhance the overall power conversion efficiency more than that of a traditional GaAs-based device. Experimental results indicate that CdS quantum dot can enhance the short-circuit current by 0.33 mA/cm(2), which is observed for the triple-junction solar cells with CdS QDs of about 3.5 nm in diameter. Moreover, the solar cell conversion efficiency is improved from 28.3% to 29.0% under one-sun AM 1.5 global illumination I-V measurement.
Threading Dislocation Blocking in Metamorphic InGaAs/GaAs for Growing High-Quality In0.5Ga0.5As and In0.3Ga0.7As on GaAs Substrate by Using Metal Organic Chemical Vapor Deposition
(2012-05-01)
Hong-Quan Nguyen
;
Chang, Edward Yi
;
Yu, Hung-Wei
;
Hai-Dang Trinh
;
Dee, Chang-Fu
High quality In0.3Ga0.7As and In0.51Ga0.49As epilayers have been successfully grown on the GaAs substrate by MOCVD. A cross-sectional study by transmission electron microscopy showed that the threading dislocations (TDs) have been successfully contained and limited within the buffer layers designed to stop the elongation of TDs into the In0.3Ga0.7As and In0.51Ga0.49As epilayers. A TD density of 1 x 10(6) cm(-2) in a fully relaxed In0.51Ga0.49As epilayer was achieved. The measurement of lifetimes of n- and p-type In0.51Ga0.49As has been done by using time-resolved photoluminescence. A great reduction in the number of recombination centers in the InGaAs epilayer has been shown. (c) 2012 The Japan Society of Applied Physics