Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/9184
標題: 利用金字塔結構製作異質接面矽晶太陽能電池之特性研究
Study on the Fabrication and Characteristics of Heterojunction c-Si Solar Cell with Pyramid Textured Structure
作者: 吳士銘
Wu, Shih-Ming
關鍵字: 異質接面;heterojunction;太陽能電池;粗糙化;solar cell;textured
出版社: 電機工程學系所
引用: [1] 莊嘉琛, 太陽能工程-太陽能電池篇. 全華圖書股份有限公司出版, 中華民國九十六年六月(六版). [2] 楊昌中, 能源領域中的奈米科技研究. 工業研究院能源與環境研究所, 中華民國95年12月26日. [3] K. K. M. Taguchi, S. Tsuge, T. Baba, H. Sakata, M. Morizane, K. Uchihashi, N. Nakamura, S. Kiyama, O. Oota, "HIT Cells-High-Efficiency Crystalline Si Cells with Novel Structure," Progress in Photovoltaics: Research and Applications 8, pp. 503–513, 2000. [4] M. T. M. Tanaka, T. Matsuyama, T. Sawada, S. Tsuda, S. Nakano, H. Hanafusa, Y. Kuwano, "Development of New a-Si / c-Si Heterojunction Solar Cells ACJ-HIT (Artificially Constructed Junction-Heterojunction with Intrinsic Thin Layer)," Japanese Journal of Applied Physics 31, pp. 3518–3522, 1992. [5] M. Taguchi, A. Terakawa, E. Maruyama, and M. Tanaka, "Obtaining a higher Voc in HIT cells," Progress in Photovoltaics: Research and Applications, vol. 13, pp. 481-488, 2005. [6] http://us.sanyo.com/Solar/SANYO-HIT-Technology. (2010年12月17日). [7] A. T. E. Maruyama, M. Taguchi, Y. Yoshimine, D. Ide, T. Baba, M. Shima, H. Sakata and M. Tanaka, "Sanyo''s Challenges to the Development of High-efficiency HIT Solar Cells and the Expansion of HIT Business," IEEE Photovoltaic Energy Conversion, pp. 1455–1460, 2006. [8] Y. Tsunomura, Y. Yoshimine, M. Taguchi, T. Baba, T. Kinoshita, H. Kanno, H. Sakata, E. Maruyama, and M. Tanaka, "Twenty-two percent efficiency HIT solar cell," Solar Energy Materials and Solar Cells, vol. 93, pp. 670-673, 2009. [9] M. Taguchi, E. Maruyama, and M. Tanaka, "Temperature Dependence of Amorphous/Crystalline Silicon Heterojunction Solar Cells," Japanese Journal of Applied Physics, vol. 47, pp. 814-818, 2008. [10] A. W. J. Zhao, M. A. Green, "High-efficiency PERL and PERTsilicon solar cells on FZ and MCZ substrates," Solar Energy Materials and Solar Cells, vol. 65, pp. 429-435, 2001. [11] A. S. A. Parretta, P. Tortora, H. Yakubu, P. Maddalena, J. Zhao,A Wang, "Angle-dependent reflectance measurements on photovoltaic materials and solar cells," optics communicatons, vol. 172, pp. 139-151, 1999. [12] 黃惠良/曾百亨, 太陽電池. 五南圖書出版股份有限公司, 中華民國九十八年十月(二版) [13] L. D. Partain, Solar Cells and Their Applications. John Wiley & Sons, Inc., 1995. [14] D. A. Neamen, An Introduction to Semiconductor Devices. McGraw-Hill Higher Education, 2006. [15] 林明獻, 太陽電池技術入門(修訂版). 全華圖書股份有限公司, 2008.03. [16] N. I. M. Gregory T. A. Kovacs, Kurt E. Petersen, "Bulk micromachining of silicon," Proceedings of the IEEE, vol. 86, pp. 1536-1551, No.8,August 1998. [17] M. Elwenspoek, "The form of etch rate minima in wet chemical anisotropic etching of silicon," Journal of Micromechanical and Microengineering, vol. 6, pp. 405-409, 1996. [18] W. Lang, "Silicon microstructuring technology," Materials Science and Engineering, pp. 1-55, (R17)1996. [19] S. H. Shin, MasterThesis. Hanyang University, 1998. [20] L. C. H. Seidel, A. Heuberger, and H. Baumgartel, "Anisotropic etching of crystalline silicon in alkaline solution-PartⅠ. Orientation dependence and behavior of passivation layer," J. Electrochem. Soc., vol. 137, pp. 3612-3626, No. 11, November 1990. [21] L. C. H. Seidel, A. Heuberger, and H. Baumgartel, "Anisotropic etching of crystalline silicon in alkaline solution-Part Ⅱ. Influence of dopants," J. Electrochem. Soc., vol. 137, pp. 3626-3632, No. 11, November 1990. [22] Y. M. Fung, W. Y. Cheung, I. H. Wilson, D. Chen, J. B. Xu, S. P. Wong, and R. W. M. Kwok, "Electron field emission characteristics of textured silicon surface," Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, vol. 19, p. 884, 2001. [23] R. G. J. Tauc, A.Vancu, "Original Paper Optical Properties and Electronic Structure of Amorphous Germanium," Phys. Status Solidi B, vol. 15, pp. 627-637, 1996. [24] T. M. Mok and S. K. O’Leary, "The dependence of the Tauc and Cody optical gaps associated with hydrogenated amorphous silicon on the film thickness: αl Experimental limitations and the impact of curvature in the Tauc and Cody plots," Journal of Applied Physics, vol. 102, p. 113525, 2007. [25] 許嘉巡, 利用嵌入式奈米晶矽之量子效應進行高效率薄膜太陽能電池技術研究. 碩士論文: 元智大學先進能源研究所, 2011. [26] A. MATSUDA, "Thin-Film Silicon —Growth Process and Solar Cell Application," Japanese Journal of Applied Physics, vol. 43, No. 12, pp. 7909-7920, 2004. [27] S. B. U. Das, M. Burrows, S. Hegedus, R. Birkmire, "Effect of Process Parameter Variation in Deposited Emitter and Buffer Layers on the Performance of Silicon Heterojunction Solar cells," 4th IEEE World Conference on Photovoltaic Energy Conversion, vol. 2, pp. 1283-1286, 2006. [28] Y. K. Tawada, M.; Okamoto, H.; Hamakawa, Y.; Tsuge, K., "Properties and structure of a-SiCH for high-efficiency a-Si solar cell," Journal of Applied Physics, vol. 53, pp. 273-5281, July 1982. [29] T. Toyama, Y. Nakano, T. Ichihara, and H. Okamoto, "p- and n-type microcrystalline Si1−xCx fabricated by plasma CVD with 40.68-MHz excitation source," Journal of Non-Crystalline Solids, vol. 338-340, pp. 106-109, 2004. [30] S.-Y. Lien and D.-S. Wuu, "Simulation and fabrication of heterojunction silicon solar cells from numerical computer and hot-wire CVD," Progress in Photovoltaics: Research and Applications, vol. 17, pp. 489-501, 2009.
摘要: 
  在本篇論文中,主要研究非晶矽/單晶矽組合而成的異質接面太陽能電池的轉換效率變化;我們改變矽晶圓表面的結構(pyramid distributed),探討結構的變化與反射率的關係。在n型矽晶圓上沉積p型氫化非晶矽薄膜,並且針對p型非晶矽薄膜作變化,製作成異質接面太陽能電池,經由I-V量測後的電性參數作討論與分析。

  首先,利用氫氧化鉀(KOH)於矽晶圓表面產生非等向性蝕刻,由於晶相(100)和(111)面蝕刻速率不同的關係,產生金字塔結構。反應中矽晶圓表面會釋放出氫氣,通常會於溶液中加入異丙醇來降低氣泡所帶來的影響。實驗中利用氫氧化鉀與異丙醇混合液,搭配不同濃度、時間和溫度進行蝕刻,可得到大小顆粒不均勻之金字塔結構,可將拋光之矽晶圓平均反射率由40 %降至11.9 % (350奈米至800奈米)。

  我們採用極高頻(40.68 MHz)電漿輔助化學氣相沉積系統,沉積p型氫化非晶矽薄膜;其優點為沉積薄膜時,可使電漿內產生較高的離子密度及降低離子能量,提升沉積的速率也可降低離子轟擊對薄膜造成的損傷,比一般射頻(13.56 MHz)電漿輔助化學氣相沉積系統具有更高的氫原子解離率,可以獲得良好的薄膜品質。實驗中,我們改變製程的溫度、薄膜厚度後,進而調變B2H6、CH4的流量以及H2的稀釋比,沉積p型氫化非晶矽薄膜與本質氫化非晶矽薄膜於玻璃基板,使用UV-VIS分析薄膜的光學特性與光暗電導的電性;並利用以上的調變參數製作成異質接面太陽能電池。

  改變矽晶圓表面的變化,搭配p型氫化非晶矽薄膜製作成異質接面太陽能電池;從電性可以發現短路電流密度的確有小幅提升,這是矽晶圓表面金字塔結構發揮光封存的效果,增加電流的產生;但開路電壓卻有下降的趨勢,這是因為p型非晶矽薄膜沉積在矽晶圓初期會有磊晶的現象,再加上沉積於在表面凹凸不平的結構上,更會使薄膜的覆蓋率不佳,無法達到表面鈍化的效果,進而使開路電壓降低。加入本質氫化非晶矽薄膜後,由短路電流密度參數發現,短路電流密度有提升的趨勢,這是因為對矽晶圓產生鈍化的效果,減少載子在接面復合的機會;而開路電壓數值變小的原因推判,可能是本質氫化非晶矽薄膜厚度所影響。我們知道非晶矽與單晶矽接面會有能階差的問題(ΔEv),所以效率的相形比較下,高氫稀釋比(R25)比低氫稀釋比(R5)些許提升。


  矽晶圓經過氫氧化鉀的蝕刻(1%KOH、蝕刻時間30分鐘、加熱溫度90℃),表面多少還有金屬離子的殘留;所以,除了標準的RCA清潔外,我們再加上乾式氧化的方式使得矽晶圓表面形成氧化層後,再經由HF沖洗浸泡後,隨即沉積p型氫化非晶矽薄膜;經計算後的各項相關電性參數:最佳轉換效率為6.82 %,開路電壓為0.405 V,短路電流密度為26.4 mA/cm2,填充因子為64.3 %,串聯電阻為4.3 Ω-cm2,並聯電阻為2080 Ω-cm2。

  In this study, we focus on amorphous / crystalline silicon hetero-junction solar cell efficiency conversion diversification, The pyramid reflectance structure of the silicon wafer surface are used to investigate the change related this novel structure relationship. Various p-type hydrogenated amorphous silicon thin film are deposited on n-type silicon wafer and analyzed. Then we fabricate the hetero-junction solar cell and analyze the electrical characteristics from I-V measurements.

  First, we use the potassium hydroxide (KOH) solution to etch the polish silicon wafer, showing the pyramid structures due to different etching rate between the (100) & (111) orientation. The reaction of the silicon wafer with KOH will release hydrogen. So we use the isopropyl alcohol (IPA) to reduce the impact by the bubbles. In the experiments, the KOH and IPA mixture solution with different concentrations, etching times and temperatures, the pyramidical structures with different sizes can be formed on the polished wafer. It could be found that the average reflectivity from 40% to 11.9% (350nm ~800nm) for the polished wafer and KOH etched wafer.

  We use very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD;40.68 MHz) to deposit p-type hydrogenated amorphous silicon thin films. VHF-PECVD can produce the high density and low ion energy plasma to enhance the deposition rate and reduce ion bombardment and destruction. As compared with the ratio-frequency plasma-enhanced chemical vapor deposition (RF-PECVD;13.56 MHz), VHF-PECVD can achieve better quality of thin films because of higher generation rate of atomic hydrogen. In the experiments, we change the process temperature, film thickness, and then adjust the B2H6 and CH4 flow rate and H2 dilution ratio. The p-type hydrogenated amorphous silicon film and intrinsic hydrogenated amorphous silicon film are deposited on the glass substrates, and then thin film optical properties are analyzed by UV-VIS and photo/dark conductivity by I-V measurement.

  Depositing the p-type hydrogenated amorphous silicon thin films on the textured silicon wafer to fabricate hetero-junction solar cells, the short-circuit current density increases slightly, due to the pyramidical structures of silicon wafer to enhance light trapping. However the open circuit voltage decreases, due to the p-type amorphous silicon film deposited on the crystal silicon which epitaxial growth appears initially. Thin film deposited on the un-smooth surface leads to poor step coverage, resulting in lower open circuit voltage. Then we insert the intrinsic hydrogenated amorphous silicon between the p layer and silicon wafer, and the short circuit current density parameter is enhanced due to the surface passivated, which reduces the opportunity of carriers recombination open-circuit voltage reduces, which is influenced by the thickness of intrinsic hydrogenated amorphous silicon thin film.

  Silicon wafer after KOH etching, there are some metal ions residues on the surface. Therefore besides the standard RCA cleaning the dry oxidation is adopted to grow oxide layer and then rinsed the diluted HF, P-type hydrogenated amorphous silicon thin film is deposited on textured wafer right now. The calculated electrical parameters of the hetero-junctions solar cell are as below:the best conversion efficiency of 6.82 %, open circuit voltage of 0.405 V, the short-circuit current density of 26.4 mA/cm2, the fill factor of 64.3 %, RS of 4.3 Ω-cm2, and Rsh of 2080 Ω-cm2 for the solar cell with the textured wafer ( 1% KOH etching 30min, on 90℃ ) and only P-type hydrogenated amorphous silicon thin film deposited
URI: http://hdl.handle.net/11455/9184
其他識別: U0005-3107201217072100
Appears in Collections:電機工程學系所

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