Investigations of Efficiency Improvement on InGaP/GaAs/Ge Triple-Junction Solar Cell

• Main Authors: Chung,Chen-Chen, 鍾珍珍
• Other Authors: Edward Yi Chang
• Format: Others
• Language: en_US
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/31551369230813256892

博士 === 國立交通大學 === 材料科學與工程學系所 === 103 === Solar cell is a photovoltaic device designed to convert sunlight into electrical power, solar energy benefits have been constaulty discussed, such as inexhaustibility, safety, convenience, non-polluting, and high practicality, etc. Due to these characteristics, solar energy plays an important role on the recycled research. III-V solar cell is known to hance super-high efficiency and radiation damage resistant is now used for space application. The production cost of III-V materials is higher than that of Si solar cells. We study the novel materials, news process ways and news structure design for III-V solar cells to increase the solar cell efficiency, thus reducing the total cost of traditional III-V solar cell. The efficiency improvement on InGaP/GaAs/Ge Triple-junction solar cell study here are divided into three parts Part1 : The optical and electrical characteristics of InGaP/ GaAs/ Ge triplejunction (TJ) solar cells with CdS quantum dots (QDs) fabricated by a novel chemical solution are presented. With antireflective feature at long wavelength and down conversion at UV regime, the CdS quantum dot effectively enhance the overall power conversion efficiency of the III-V solar cell. The measurement under one sun air mass 1.5 global illumination, an increase of 0.33 mA/cm2 in the short circuit current was observed for the triple junction solar cells with CdS QDs of about 3.5nm in diameter. The conversion efficiency was improved from 28.25% to 29.04%. Part2: A 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 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 antireflection (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 350-500 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. Part3: The effects of front contacts with different grid patterns on the characteristics of light-concentrated type GaAs single-junction solar cell. The device parameters analyzed include the open-circuit voltage (Voc), short-circuit current (Isc), fill factor (FF) and conversion efficiency (η). In this study, we investigate the effect of the shadowing 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 (Voc), short-circuit current (Isc), fill factor (FF) and conversion efficiency (η). 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 indicated that the conversion efficiency of solar cells can be improved by establishing a compromise between the shading effect and the series resistance effect.