- 學位論文
高效率Ⅲ-V族聚光型太陽能電池之正電極研究
Study on the front grid of high-efficiency Ⅲ-V concentrator solar cells
摘要
本論文主要分析比較具有不同形狀的正電極之Ⅲ-V族太陽能電池在不同聚光倍率下的I-V特性，根據測得參數，我們可以判斷各個正電極圖形所適合的聚光倍率為何。在高聚光倍率下，串聯電阻會影響太陽能電池的轉換效率。所以這篇論文，我們也討論到不同正電極圖形對於串聯電阻關係如何。此篇論文重點也在找出何種正電極圖形可以降低串聯電阻，來提升轉換效率。 在遮蔽效應和阻抗效應間有著對抗性。光學損失是由於前電極金屬遮蔽所造成，要將遮蔽效應降低必須要減少金屬電極在主動區面積。但是太少的遮蔽面積則會造成在高電流時充填因子(Fill Factor)下降。所以我們試著去妥協這兩個效應以達到最佳的轉換效率。 在實驗上我們利用模擬太陽光在AM1.5G下利用Fresnel 透鏡聚光。聚光倍率是藉由短路電流比定義。本研究我們利用圓形電極來做探討是因為圓形電極的對稱性適合發展聚光型太陽能電池。由本研究獲知，圓形電極圈數要多、兩圓之間的距離要短和電極線間的角度要小，當聚光倍率越高時候，其所產生的損耗才會較小，因此電極的圈數、電極線數目相對來講必須要跟著多才能得到較佳的效益。
並列摘要
This study analyzes and compares the I-V characteristics of light-concentrated type Ⅲ-Vs solar cells using different front grids. For each pattern of front grid used, a suitable light concentration ratio to obtain the highest efficiency was investigated. In high concentration ratio, the cell was strongly influenced by the series resistance. The aim of this work is to minimize the series resistance of solar cell in order to increase the conversion efficiency of the solar cells under high concentration of solar radiation. Particular the effect of the concentration ratio on the solar cells with different grid patterns was systematically analyzed. It was found that an antagonism existed between the shadowing effect and the resistance effect. Optical losses were ascribed to the shadowing of the cell surface by the metal grids. The shadowing loss was reduced with decreasing contact area. However, once the cells were used under light concentration this would also bring in high current density though the grids themselves, namely, a current crowding behavior was quite possibly to happen. And consequently a proportional drop in the fill factor of solar cell was observed. Hence, a maximum conversion efficiency can be achieved only after a compromise between the above two effects is found. For measurements under light concentration, the illumination from an AM1.5G solar simulator was focused by Fresnel lenses. The concentration ratio was controlled by varying the short-circuit current (Isc) of the solar cell. In this study, circular grids were used for the front contact of solar cell. From the present study, it was found that for solar cells used circular-grid type front contact to improve their efficiency, there should be denser arranged in circularly radiant distribution.