- 學位論文
以多晶矽薄膜吸雜法提升提純冶金級矽太陽能電池效率
Improving the efficiency of upgraded metallurgical grade silicon solar cells by polysilicon film gettering technique
摘要
本論文使用提純冶金級矽(UMG-Si)作為矽太陽能電池的基板，其成本相對於單晶矽與太陽能級矽材料較低，對於太陽能材料需求日漸增加的矽基板提供了的一個材料的來源。然而UMG-Si基板材料的內部含有大量有害的金屬雜質易形成載子的複合中心，嚴重的衰減太陽能電池元件的品質與效率，因此使用外部去疵法來吸除不想要的有害金屬雜質。 我們使用的去疵法在本實驗稱“多晶矽薄膜去疵”(PSFG)，它是利用去疵的基本概念所設計出來的特殊去疵法。我們使用常壓式滷化物化學氣相沉積來成長多晶矽薄膜，並利用這薄膜當作吸收與儲存提純冶金級矽基板內部有害雜質的儲雜層，多晶矽含有許多晶粒界與空隙可當作吸收與存放金屬雜質的空間。我們嘗試使用不同成膜溫度(800˚C, 900˚C及1000˚C)及不同回火溫度(600˚C - 850˚C)來尋求讓PSFG法發揮功能的最佳條件。且用微波光電流衰減(µW-PCD)儀器來量測利用PSFG法處理過之UMG-Si基板內少數載子的生命期值，以評估PSFG法成效。 最後將PSFG法處理過與未利用該法處理的UMG-Si基板製作成太陽能電池元件並比較其電性與效率。由結果發現以800˚C成長多晶矽薄膜且利用700˚C回火的情況下，所量測出的少數載子生命期為最大，達33.2 µs，同時發現少數載子生命期的長短會直接影響太陽能效率。特別是所使用的PSFG法在上述最佳條件下進行時所研製成的太陽能電池效率為13.66%，比未利用PSFG法處理的元件之效率12.06%提升了1.6%。
並列摘要
The cost of Si wafers has been the bottleneck for a widespread use of Si solar cells. The upgraded metallurgical grade silicon ( UMG-Si ) is inexpensive compared to the single crystal or solar grade polysilicon material. In this study, the UMG-Si substrates are used to fabricate solar cells with a view to reducing the production cost of Si solar cells. However, these substrate materials contain a large number of harmful internal metal impurities. These impurities tend to be the recombination centers for carriers and cause a serious degradation in the efficiency of solar cells. To solve this problem, we use an extrinsic gettering technique to remove those unwanted impurities. The extrinsic gettering process is denoted as polysilicon film gettering (PSFG) and was conducted as follows. First, a polysilicon film was deposited using atmosphere pressure halide chemical vapor deposition ( APHCVD ) at different temperatures: 800, 900, and 1000˚C. Then this film was annealed at various temperatures ranging from 600 to 850˚C. The as-deposited polysilicon film (what is called, a sink layer) contains a large number of grain boundaries and cavities, which can be used as the dumps or places for absorbing and storing metal impurities present in UMG-Si substrate. The annealing treatment was performed to promote the interdiffusion behavior of metal impurities. The minority carrier lifetime of the UMG-Si substrate treated with PSFG was obtained from microwave photocurrent decay (μW-PCD) measurements, which was used to evaluate the effect of PSFG. Finally, the electrical properties of solar cells fabricated on the UMG-Si substrates with and without PSFG treatment were compared. It was found that depositing a polysilicon film at at 800˚C and annealing it at 700˚C for 15 minutes would have the lifetime of UMG-Si substrate increase to 33.2 µs. Also, the higher the minority carrier lifetime of UMG-Si substrate, the higher the efficiency of solar cell fabricated thereon. Ultimately, an efficiency high to 13.66 % has been achieved for the cell fabricated on the PSFG-treated substrate, which is elevated by 1.6 % compared to that of the solar cell without PSFG treatment.
參考文獻
延伸閱讀
- Yang, C. W. (2009). 以多孔隙矽吸雜法提昇冶金矽太陽能電池效率 [master's thesis, Chung Yuan Christian University]. Airiti Library. https://doi.org/10.6840/cycu200901097
- 郭鎮維（2010）。利用新型光捕捉結構提升矽薄膜太陽能電池元件效率〔碩士論文，國立虎尾科技大學〕。華藝線上圖書館。https://www.airitilibrary.com/Article/Detail?DocID=U0028-2807201014260800
- Chieh, H. C. (2012). 使用反應式離子蝕刻製作改良式柵欄狀結構多晶矽太陽電池 [master's thesis, National Tsing Hua University]. Airiti Library. https://www.airitilibrary.com/Article/Detail?DocID=U0016-2002201315444325
- 許翔林（2019）。以分子界面工程提升高分子及鈣鈦礦太陽能電池效能〔博士論文，國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342/NTU201900376
- Shiu, J. Y. (2009). Improving the efficiency of low-cost metallurgical silicon solar cells by amorphous Si gettering technique [master's thesis, Chung Yuan Christian University]. Airiti Library. https://doi.org/10.6840/cycu200900877