乙矽烷電漿沉積技術於矽基薄膜太陽能電池之應用

Abstract

本論文是利用高密度電漿化學氣相沉積系統製備氫化非晶矽基薄膜之研究，由於氫化非晶矽薄膜能隙較高(1.8~1.9eV)，在太陽光譜中長波長的部分(750nm以上)無法有效吸收。為了更有效的利用太陽光頻譜，我們發展摻雜鍺元素之氫化非晶矽鍺合金(a-SiGe)薄膜，其能隙範圍為界於1.4~1.6 eV。透過鍺烷的摻雜及製程參數的優化，我們可得能隙為1.45 eV的單接面氫化非晶矽鍺薄膜太陽能電池，其轉換效率達5.26%，吸收頻譜為300~850 nm。 我們導入非晶矽鍺薄膜作為堆疊型太陽能電池中底電池的吸收層，在非晶矽/非晶矽鍺雙接面太陽能電池中，當上層與下層子電池達到電流匹配後，其轉換效率可達8.38%。而非晶矽/非晶矽/非晶矽鍺三接面太陽能電池則擁有超高的光照穩定度，其光致效率衰減只有2.5%。 本文中也展示了不同氣源製作以及不同基板應用的薄膜太陽能電池。藉由乙矽烷電漿技術製作的非晶矽及非晶矽鍺薄膜太陽能電池，其轉換效率達9.01%及4.76%。而利用背反射基板製作的n-i-p結構非晶矽太陽能電池，經過摻雜層厚度的調整之後，其轉換效率也高達8.47%。未來研究的方向將致力於改善乙矽烷製作的非晶矽鍺太陽能電池，進而整合成高效率的雙接面與三接面太陽能電池。

In this article, we investigate the performance of hydrogenated amorphous silicon-based thin-film fabricated by high-density plasma chemical vapor deposition system. The solar spectra in near infrared regime (<750 nm) can not be effective absorbed due to the high optical band gap of a-Si:H thin film (1.8 ~1.9 eV). In order to utilize the solar spectra in near infrared regime effectively, we develop the hydrogenated amorphous silicon-germanium alloys (a-SiGe:H) films with low optical band gap (1.4 to 1.6 eV). The single junction a-SiGe:H thin film solar cells with the band gap of 1.45 eV can be obtained by the optimization of Ge doping and deposition parameter. We demonstrate single-junction a-SiGe solar cells with the conversion efficiency of 5.26% and the broadband quantum efficiency in the range of 300-850 nm. We introduce a-SiGe thin film as the absorber layer of bottom sub-cell in stacked solar cells. As achieving current matching between the top sub-cell and bottom sub-cell in the a-Si/a-SiGe double junction solar cells, conversion efficiency can be reached up to 8.38%. Moreover, highly light-soaking stable a-Si/a-Si/a-SiGe triple junction solar cells were demonstrated with photo-induced degradation in conversion-efficiency as low as 2.5%. We also show the solar cells fabricated by different gas source and different substrate. By using disilane-plasma technology, the conversion efficiency of single-junction a-Si and a-SiGe solar cells achieves 9.01% and 4.76%. For n-i-p structure a-Si solar cells integrated into the back reflective substrate show the conversion efficiency of 8.47% through the optimized thickness of doped layers. In the future, our research will focus on tuning the optical and electrical performance of a-SiGe:H thin film fabricated by using disilane-plasma technology to obtain the double-junction and triple-junction thin film solar cells with high conversion efficiency.