以濺鍍硒化/硫化法沉積銅銦鎵硒薄膜太陽能電池

Abstract

本研究探討製程變因對CIGSSe薄膜太陽能電池的研究，並優化各層薄膜改善元件光電轉換效率。Mo背電極的研究顯示，雙層Mo薄膜提供低電阻、以及良好的結晶性以及附著性。另一方面，Mo頂層(top layer)的形貌改變能夠控制Na元素的含量，Na含量的添加能改善CIGSe太陽能元件效率從6.21到8.54%。CIGSe的元素比例Cu/(In+Ga)為0.95時，因為符合期待的化學計量比導致有著較佳的光電轉換效率。硒化製備CIGSe吸收層後，SIMS分析顯示CIGSe表面的Ga元素缺乏，這將導致在CIGSe與CdS的介面處載子複合增加。為了解決表面Ga元素缺乏問題，本研究提出CuGa/In/CuGa堆疊方式以硒化製備CIGSe吸收層，結果顯示元件轉換效率由8.54%提升至10.37%。硫化製程中，硫擴散至CIGSe表面將會提高短路電流密度(Jsc)，這是因為表面載子複合減少並且鈍化缺陷所致。此外，硫化後因材料能隙改變使元件開路電壓提升，轉換效率由10.37%提升至12.71%。對CdS緩衝層而言，CdS的厚度相對於製程反應溫度對元件轉換效率影響較大。本研究以濺鍍硒化與硫化法沉積反應CIGSSe太陽能電池並優化各層，結果顯示最佳的元件轉換效率為12.71%。

This thesis presents a comprehensive study on the CIGSSe solar cell via optimized experimental setup and parameters. The Mo bilayer had a lower sheet resistance, a better crystalline quality, and an exceptional adhesion property. Amount of Na can be controlled by varying Mo top layer structure to improve the CIGSe cell efficiency from 6.21 to 8.54 %. The CIGSe composition (Cu/(In+Ga)) at 0.95 revealed an excellent cell efficiency than the ratio of 0.75, 0.85, 1.05. The results indicated that Ga depletion at the CIGSe surface during the selenization process. To reduce the recombination at the CIGSe/CdS interface owing to Ga depletion, the CIGSe was performed by a double-graded bandgap using CuGa/In/CuGa stacked. The cell efficiency improved from 8.54 to 10.37% due to bandgap alignment. The S incorporated into the CIGSe surface contributes to a higher JSC due to the formation of hole-recombination barrier and passivation of defects after sulfurization. After sulfurization process, the VOC, JSC, FF, and efficiency increased from 0.524 to 0.564 V, 31.65 to 33.05 mA/cm2, 62.50 to 68.13, and 10.37 to 12.71%, respectively. The experimental results of CdS confirmed that the efficiency of the CIGSSe solar cell was mainly dependent on the thickness of CdS than reaction temperature during chemical bath deposition. In this thesis, the growth of CIGSSe thin films by sequential sputtering-selenization and sulfurization has been optimized with a maximum coversion efficiency of 12.71%.