Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/2957
標題: Hydrogenated Microcrystalline Silicon Thin Film Solar Cells Fabricated by VHF-PECVD
以超高頻電漿增強化學氣相沉積製作氫化微晶矽薄膜太陽電池
作者: 洪偉哲
Hung, Wei-Che
關鍵字: μc-Si:H;氫化微晶矽;thin-film solar cell;VHF-PECVD;crystal volume ratio;crystal structure;薄膜太陽電池:超高頻電漿增強化學氣相沉積;結晶比例;結晶型態
出版社: 光電工程研究所
引用: [1] A.V. Shah, H. Schade, M. Vanecek, J. Meier, E. Vallat-Sauvain , N. Wyrsch U. Kroll, C. Droz and J. Bailat, Thin-film silicon solar cell technology, Prog Photovolt: Res Appl 12 (2004), pp. 113-142 [2] A.V. Shah, J. Meier, E. Vallat-Sauvain, N. Wyrsch, U. Kroll, C. Droz and U. Graf, Solar Energy Materials & Solar Cells 78 (2003) 469-491 [3] Baojie Yan,a) Guozhen Yue, Jessica M. Owens, Jeffrey Yang, and Subhendu Guha, Appl. Phys. Lett., Vol. 85, No. 11, Pages 1925-1927, 13 September 2004 [4] Heintze, M., Zedlitz, R., 1996. New diagnostic aspects of high rate a-Si:H deposition in a VHF plasma. J. Non-Cryst. Solids 198-200, 1038 [5] O. Vetter, F. Finger, R. Carius, P. Hapke, L. Houben, O. Kluth , A. Lambertz, A. Muck, B. Rech and H. Wagner “Intrinsic microcrystalline silicon : A new material for photovoltaics” , Solar Energy Materials & Solar Cells 62 p.97~108 , (2000) [6] Y. Mai, S. Klein, R. Carius, J. Wolff, A. Lambertz, and F. Finger and X. Geng, J. Appl. Phys. 97, 114913, 2005. [7] R. W. Collins, A. S. Ferlauto, G. M. Ferreira, Chi Chen, Joohyun Koh, R. J. Koval, Yeeheng Lee, J. M. Pearce and C. R. Wronski, Sol. Energy Mater. Sol. Cells 78,143, 2003. [8] H. Keppner, J. Meier, P. Torres, D. Fischer, A. Shah, Appl. Phys., A Mater. Sci. Process. 69 (1999) 169. [9] J. Meier, R. Fluckiger, H. Keppner, A. Shah, Appl. Phys. Lett. 65 (7) (1994) 860. [10] Makoto Fukawa, Susumu Suzuki, Lihui Guo, Michio Kondo and Akihisa Matsuda, Solar Energy Materials & Solar Cells 66 (2001) 217-223. [11] A. Shah, J. Faist, A. Perret, B. Rech, H. Schade and M. Vanecek, University of Neuchatel , “Thin Film Microcrystalline Silicon Layers and Solar Cells:Microstructure and Electrical Performances”2003 [12] A. H. M. Smets, Matsui, and Kondo, J. Appl. Phys. 104, 034508 (2008) [13] L. Feitknecht, O. Kluth, Y. Ziegler, X. Niquille, P. Torres, J. Meier, N. Wyrsch and A. Shah“Microcrystalline n-i-p solar cells deposited at 10 A/sec by VHF-GD” [14] J. C. Lee, K. H. Kang, S. K. Kim, K. H. Yoon, J. Song, S. W. Kwon, K. S. Lim, and I. J. Park. “DEPOSITION OF DEVICE QUALITY pcSi:H FILMS BY HOT-WIRE CVD FOR SOLAR CELL APPLICATIONS” , Photovoltaic Specialists Conference, 2002. Conference Record of the Twenty-Ninth IEEE 19-24 May 2002 Page(s):1258 - 1261 [15] Yuan-Min Li, Liwei Li, J.A. Anna Selvan, Alan E. Delahoy and Roland A. Levy. Thin Solid Films, Volume 483, Issues 1-2, 1 July 2005, Pages 84-88. [16] Hou Guo-Fu, Xue Jun-Ming, Guo Qun-Chao, Sun Jian, Zhao Ying, GengXin-Hua, and Li Yi-Gang, Chin. Phys. Soc. and IOP Publishing Ltd, Vol 16 No 2(2007). [17] Y. Nasuno, M. Kondo, A. Matsuda, Solar Energy Materials & Solar Cells 74 (2002) 497-503 [18] Joohyun Koh, A. S. Ferlauto, P. I. Rovira, C. R. Wronski, and R. W. Collins, Appl. Phys. Lett., Vol. 75, No. 15, Pages 2286-2288, 11 October 1999
摘要: 
The crystalline volume fraction and crystal structure of hydrogenated microcrystalline silicon (μc-Si:H) films are controlled by plasma deposition conditions. The properties of the μc-Si:H films are significantly influenced by their crystalline volume fractions and crystal structures.
In this thesis, we use 40.68 MHz very-high-frequency plasma-enhanced chemical vapor deposition (VHF-PECVD) to fabricate μc-Si:H films. The ion density will increase and the ion energy will reduce in the plasma generated by this 40.68 MHz very-high-frequency radio wave source, which can increase the deposition rate and reduce the damage of the film due to high-energy ion bombardment. Deposition pressure and hydrogen dilution ratio are changed to deposit μc-Si:H films with various crystalline volume fractions and crystal structures. These films are used to fabricate the i layers of p-i-n solar cells to investigate the effect of crystalline volume fractions and crystal structures on the performance of solar cells.
The results demonstrate that crystal structures and crystalline volume ratios are strongly influenced by the substrate materials. The crystal structure of the films deposited on the Corning 1737 F glass is totally different from that of deposited on the Asahi U-type (SnO2:F)/p-type μc-Si:H substrate.
For hydrogen dilution ratio fixed at R = 60 and changed the deposition pressure from 3 to 9 torr, the crystalline volume fraction of the films reduced when the deposition pressure increased. The crystalline volume fraction of the solar cells deposited at 3 torr is 79%, at 7 torr is 67% and is 0% at 8 and 9 torr. The results indicate that high deposition pressure reduces the ion mean free path, the film structure is changed from the crystalline to amorphous phase. The amorphous to microcrystalline (a→μc) transition region is between 7 and 8 torr. For deposition pressure fixed at 5 and 6 torr, the crystalline volume fraction of the solar cells can also be reduced by decreasing the hydrogen dilution ratio from R = 60 to 50. SEM images display that the crystal structures of solar cells are columnar structure for the deposition pressure from 3 to 7 torr. There is more amorphous phase for films deposited larger than 7.25 torr, and no crystal structure can be observed over 8 torr deposition. X-ray diffraction patterns demonstrate that the strong signals of (111) and (220) peaks could be observed for the film deposited less than 7 torr. Over 7 torr deposition, the signal of (220) peak is decreased compared with (111) peak. Only signal of (111) peak can be observed for 7.5 torr deposition, and no any crystal signals can be further observed for films deposited over 8 torr.
The open-circuit voltages of solar cells are increased by reducing the crystalline volume fractions. As the pressure increasing from 3 to 7.5 Torr, the short-circuit current density and fill factor are increased and reached maximum for film deposited at 7 torr, then these values are decreased for films deposited over 7.25 torr. The energy transfer efficiency of solar cells has the maximum value for the cell deposited at 7 Torr. The results indicate that solar cells have better performance when the crystal structure is in the transition region. For the cells deposited at 7 torr, the conversion efficiency, open-circuit voltage, short-circuit current density and fill factor are 3.34%, 0.41 V, 16.74 mA/cm2 and 48%, respectively.

氫化微晶矽(μc-Si:H)薄膜的結晶比例及結晶結構受電漿增強化學氣相沉積製程條件控制。結晶比例的高低及不同的結晶結構影響氫化微晶矽薄膜的特性。
在本論文中,我們採用40.68 MHz超高頻電漿增強化學氣相沉積(VHF-PECVD)製作μc-Si:H薄膜,使用超高頻電波可以在電漿內產生較高的離子密度及降低離子能量,使沉積速率提升及降低離子轟擊破壞。我們改變沈積壓力及氫氣稀釋比例製作具有不同結晶比例及結晶結構的氫化微晶矽薄膜,這些薄膜應用至p-i-n太陽電池的i層以探討不同結晶比例及結晶結構對於太陽電池性能所造成的影響。
實驗結果顯示當薄膜成長在不同基板上時,其結晶結構很強烈的被基板所影響。薄膜的結晶結構沉積在Corning 1737 F玻璃基板上和沉積在Asahi U-type (SnO2:F)/p-type μc-Si:H基板上之p-i-n太陽電池的i層是完全不同的結晶形態。
在固定氫稀釋比R為60,改變沈積壓力3~9 torr的情況下,隨著壓力的上升,薄膜的結晶比例逐漸降低。太陽電池的結晶比例由3 torr時的79%下降至7 torr的67%,當壓力到達8及9 torr時薄膜結晶比例為0%,代表薄膜因為沈積壓力過大,反應氣體密度過高而使得離子的平均自由徑降低,離子復合導致薄膜結構從結晶被壓回非晶結構,此時沉積壓力7~8 torr之間為一薄膜由非晶至微晶(a→μc)的轉介區。固定沉積壓力為5及6 torr,降低氫稀釋比R = 50~60,太陽電池的結晶比例也隨著氫稀釋比的降低而降低。由SEM的量測結果可以看出太陽電池的結晶型態在沉積壓力3到7 torr間為柱狀結構,在7.25 torr以後非晶比例變多,超過8 torr以後薄膜沒有結晶出現;XRD的量測指出,沉積壓力小於7 torr以前的薄膜可以量測到強烈的(111)和(220)結晶方向的訊號,超過7 torr以後(220)相對(111)的訊號減低很多,7.5Torr時只剩下(111)結晶訊號,超過8 torr以後沒有結晶方向的訊號產生。
太陽電池的開路電壓隨著結晶比例下降而逐漸變大;當沉積壓力從3 torr增加到7.5 torr,短路電流密度和填充因子在壓力上升至7 torr時達最大值後開始下降;此時7 torr的太陽電池具有最佳的轉換效率,結果顯示當結晶結構位於轉介區時太陽電池的確具有良好的特性,其轉換效率、開路電壓、短路電流密度以及填充因子分別為3.34%、0.41 V、16.74 mA/cm2以及48%。
URI: http://hdl.handle.net/11455/2957
其他識別: U0005-2708200908074100
Appears in Collections:光電工程研究所

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