低成本衬底上晶体硅薄膜太阳电池的研究
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摘要
本文主要研究了低成本衬底上薄膜的生长以及薄膜太阳电池的制备。本文的主要工作包括三个部分：首先是在模拟低成本衬底(非活性重掺杂单晶硅衬底)上外延薄膜并制备太阳电池。其主要目的是检验外延系统、研究薄膜生长特性、研究薄膜太阳电池的设计和工艺；其次是陶瓷衬底上多晶硅薄膜的生长和区熔再结晶的研究；最后是颗粒硅带衬底上多晶硅薄膜太阳电池的制备。
作为在该项研究的先期工作，首先在非活性重掺杂单晶硅衬底上制备了薄膜太阳电池。研究了外延工艺、电池制备工艺对太阳电池性能的影响。实验中发现，在我们现有设备上，采用优化的工艺条件，可以获得低缺陷密度、高质量的单晶硅薄膜。通过上述研究并结合器件模拟的有关结果，设计了优化的电池结构和工艺条件。在此基础上制备的太阳电池效率达到15.12％(J_(SC)=30.45mA，V_(OC)=637.1mV，FF=0.7797)。该结果已属国际同类研究的先进水平。
其次，研究了多种非硅衬底(主要是陶瓷衬底)上多晶硅薄膜的生长。对薄膜形貌以及生长特性等进行了分析。提出了一种简化的区熔再结晶方法，利用这种方法在非硅衬底获得了晶粒尺寸达到毫米级、致密的籽晶层。该研究工作对今后陶瓷衬底薄膜太阳电池的研究打下了良好的基础。
作为本文的主要内容，对低成本的颗粒硅带衬底作了较详细的研究。分析了衬底特性、外延薄膜的生长规律和特性。采用加入重掺杂层、快速生长等办法减少衬底对薄膜的影响。对低成本衬底上薄膜电池的工艺，特别是氢退火效应、氮化硅的制备和特性等作了深入的研究。发现这些工艺对钝化薄膜太阳电池的缺陷和晶界，改善薄膜质量和电池性能有明显的作用。通过这些研究工作，在高纯度颗粒硅带衬底上采用直接生长方式制备的薄膜电池效率达到8.25％(J_(SC)=26.69mA／cm~2，V_(OC)=506.8mV，FF=0.6101)，在低纯度衬底上制备的电池效率达到4.5％(J_(SC)=20.39mA／cm~2，V_(OC)=386.9mV，FF=0.57)，这些结果已达到国外同
The wide use of solar cells will be a feasible way to solve the energy and environmental protection problems. The development of solar cells is showing a tendency to improve efficiency and reduce cost. Silicon thin-film solar cells are considered the most promising cells in the future for their advantages, such as low cost, high efficiency, great stability, simple processing, and none-pollution.
To achieve this aim, silicon thin film solar cells on low cost substrates are studied in this thesis. Three kinds of substrates are adopted in our work, include heavily doped mono-crystalline silicon wafer, ceramics, and silicon sheets from powder (SSP).
Firstly, crystalline silicon thin films were deposited on heavily doped mono-crystalline silicon wafer by rapid thermal chemical vapor deposition (RTCVD). With the optimized deposition parameters, mono crystalline silicon films with low defects density were obtained. Based on experiments and computer simulations, optimized processing conditions for cells' fabrication were achieved. The best conversion efficiency of 15.12% (Voc=637.1mV, Jsc=30.45mA/cm~2, FF=0.7797, AM=1.5G ) has been reached, which is close to the best result in the world.
Secondly, growth and recrystallization of silicon films on ceramic substrates were studied. Heavily doped polycrystalline silicon thin films were deposited on low cost ceramics substrates by RTCVD. Compact and uniform films with grain size in the order of some micrometers were fabricated. By means of zone melting recrystallization (ZMR) method, polycrystalline silicon thin films with large grains and relative high carrier mobility were obtained, which could act as a seeding layer. The maximum grain of these films was about one millimeter in width and some millimeters in length, and hole mobility exceeded 50cm~2/Vs. Active silicon films deposited on these seeding layers showed the same morphologies. These results show that these films have great potential for photovoltaic applications.
Finally, low cost SSP substrates were used in our experiments. Poly-crystalline silicon thin films were deposited on SSP substrates directly without any intermediate layer. A P~+ layer between active layer and substrate was applied as a barrier for defects and impurities, and relative high deposition rate was achieved. Suitable processing conditions for cells' fabrication, such as phosphorous diffusion, hydrogen passivation, SiN_x anti-reflection coating deposited by plasma enhanced chemical deposition (PECVD) were also studied. Based on these works, efficiency of 8.25 % (J_(sc)=26.69mA/cm2, V_(oc)=506.8mV, FF=0.6101) and 4.5% (J_(sc)=20.39mA/cm~2, V_(oc)=386.9mV, FF=0.57) have been obtained on high-purity and low-purity SSP substrates respectively. These results reach the better level in the world.
作为在该项研究的先期工作，首先在非活性重掺杂单晶硅衬底上制备了薄膜太阳电池。研究了外延工艺、电池制备工艺对太阳电池性能的影响。实验中发现，在我们现有设备上，采用优化的工艺条件，可以获得低缺陷密度、高质量的单晶硅薄膜。通过上述研究并结合器件模拟的有关结果，设计了优化的电池结构和工艺条件。在此基础上制备的太阳电池效率达到15.12％(J_(SC)=30.45mA，V_(OC)=637.1mV，FF=0.7797)。该结果已属国际同类研究的先进水平。
其次，研究了多种非硅衬底(主要是陶瓷衬底)上多晶硅薄膜的生长。对薄膜形貌以及生长特性等进行了分析。提出了一种简化的区熔再结晶方法，利用这种方法在非硅衬底获得了晶粒尺寸达到毫米级、致密的籽晶层。该研究工作对今后陶瓷衬底薄膜太阳电池的研究打下了良好的基础。
作为本文的主要内容，对低成本的颗粒硅带衬底作了较详细的研究。分析了衬底特性、外延薄膜的生长规律和特性。采用加入重掺杂层、快速生长等办法减少衬底对薄膜的影响。对低成本衬底上薄膜电池的工艺，特别是氢退火效应、氮化硅的制备和特性等作了深入的研究。发现这些工艺对钝化薄膜太阳电池的缺陷和晶界，改善薄膜质量和电池性能有明显的作用。通过这些研究工作，在高纯度颗粒硅带衬底上采用直接生长方式制备的薄膜电池效率达到8.25％(J_(SC)=26.69mA／cm~2，V_(OC)=506.8mV，FF=0.6101)，在低纯度衬底上制备的电池效率达到4.5％(J_(SC)=20.39mA／cm~2，V_(OC)=386.9mV，FF=0.57)，这些结果已达到国外同
The wide use of solar cells will be a feasible way to solve the energy and environmental protection problems. The development of solar cells is showing a tendency to improve efficiency and reduce cost. Silicon thin-film solar cells are considered the most promising cells in the future for their advantages, such as low cost, high efficiency, great stability, simple processing, and none-pollution.
To achieve this aim, silicon thin film solar cells on low cost substrates are studied in this thesis. Three kinds of substrates are adopted in our work, include heavily doped mono-crystalline silicon wafer, ceramics, and silicon sheets from powder (SSP).
Firstly, crystalline silicon thin films were deposited on heavily doped mono-crystalline silicon wafer by rapid thermal chemical vapor deposition (RTCVD). With the optimized deposition parameters, mono crystalline silicon films with low defects density were obtained. Based on experiments and computer simulations, optimized processing conditions for cells' fabrication were achieved. The best conversion efficiency of 15.12% (Voc=637.1mV, Jsc=30.45mA/cm~2, FF=0.7797, AM=1.5G ) has been reached, which is close to the best result in the world.
Secondly, growth and recrystallization of silicon films on ceramic substrates were studied. Heavily doped polycrystalline silicon thin films were deposited on low cost ceramics substrates by RTCVD. Compact and uniform films with grain size in the order of some micrometers were fabricated. By means of zone melting recrystallization (ZMR) method, polycrystalline silicon thin films with large grains and relative high carrier mobility were obtained, which could act as a seeding layer. The maximum grain of these films was about one millimeter in width and some millimeters in length, and hole mobility exceeded 50cm~2/Vs. Active silicon films deposited on these seeding layers showed the same morphologies. These results show that these films have great potential for photovoltaic applications.
Finally, low cost SSP substrates were used in our experiments. Poly-crystalline silicon thin films were deposited on SSP substrates directly without any intermediate layer. A P~+ layer between active layer and substrate was applied as a barrier for defects and impurities, and relative high deposition rate was achieved. Suitable processing conditions for cells' fabrication, such as phosphorous diffusion, hydrogen passivation, SiN_x anti-reflection coating deposited by plasma enhanced chemical deposition (PECVD) were also studied. Based on these works, efficiency of 8.25 % (J_(sc)=26.69mA/cm2, V_(oc)=506.8mV, FF=0.6101) and 4.5% (J_(sc)=20.39mA/cm~2, V_(oc)=386.9mV, FF=0.57) have been obtained on high-purity and low-purity SSP substrates respectively. These results reach the better level in the world.
引文
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[3] Y. Bai, et al. 26th IEEE Photovoltaic Spocialists Conference, 1997, p35-38.
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[2] 施敏，半导体器件物理，电子工业出版社，1986[3] 刘恩科等，光电池及其应用，科学出版社，1991
[4] 赵富鑫等，太阳电池及其应用，国防工业出版社，1985
[5] J. Werner, et al., Advances in solid state physics, V34, 1994
[6] J.Rand et al., 22nd IEEE Photovoltaic Spec. Conf. p192, 1991[1] Solar energy materials and solar cells. Vol 69, p115-121, 2001
[2] 28th IEEE PVSC, p146, 2000
[3] Solar energy materials and solar cells. Vol 71, p245, 2002
[4] Solar energy materials and solar ceils. Vol 65, p593, 2001
[5] G. Beaucarne, et al. Solar energy materials and solar ceils. Vol 61, p301, 2000
[6] 28th IEEE PVSC, p146, 2000
[7] 陈哲艮．第5届全国光伏技术学术研讨会论文集，p34，1998．
[8] Imaizumi M, et al. 14th European PV solar energy conversion conference, p1385, 1997.
[9] Walter Zimmermann et al; 2nd World Conference and Exhibition on Photovoltaic Solar Energy Conversion, 1998[1] 王阳元等，多晶硅薄膜及其在集成电路中的应用。科学出版社，2001
[2] 电子工业生产技术手册，第6册，国防工业出版社，1989
[3] Yuwen Zhao, etc., Solar Energy Materials and Cells, pp321-326,48(1-4)(1997)
[4] A.Staoui, R. Monna, D.Angermeier, et al. 26th IEEE PVSC, 1997, 627
[5] Lin T and Hon M. J.Materials Science 1995, 30:2675
[6] Ehrenwall B, Selamidt C, Braun A, et al. 2nd world conference and exhibition on photovoltaie solar energy conversion, 1998, 1370-1373[1] P. Basore, et al, 20th IEEE-PVSC, 1988
[2] Imaizumi M, Ito T, Yamaguchi M et al. 14th European PV solar energy conversion conference, 1997. p1385
[3] 1st WCPEC, p1564, 1998
[4] H. Naomoto et al. Solar Energy Materials & Solar Cells, Vo148, p261, 1997
[5] Walter Zimmermann, Sandra Bau, Achim Eyer et al; 16th European Conf. On PV Solar Conversion, 2000
[6] 王玉亭，赵玉文，吸杂技术在硅电池中的应用，中国太阳能学会2001年学术会议
[7] G.Beaucarne, et al, Solar Energy Materials & Solar Cells, 61,2000
[8] T. Lauinger, et al. 14th European PVSEC, p853, 1997
[9] J.Jeong, et al. 28th IEEE PVSC, p83, 2000[10] G.hahn. et al. PVSEC-12, P-41, 2001.
[11] S.Schaefer. et al. 16th European PVSEC, 2000
[12] M.Spiegel, et al. 14th European PVSEC, p743,1997
[13] M.Spiegel, et al. Solar energy materials and solar cells. Vol55, p331, 1998
[14] H.Elgamel, et al. 1~(st) WCPEC, pl323, 1994
[15] C.T.Sah, et al. J.Appl.Phys. Vol54, p944,1983
[16] R.Gale. et al. J.Appl.Phys. Vol54, p6938,1983
[17] P.Sana, et al, Appl. Phys. Lett, Vol64, p97, 1994
[18] B.Sopori, et al. 1~(st) WCPEC, pl615, 1994
[19] B.Sopori, et al. 26~(th) IEEE PVSC, p25,1997
[20] V.Yelundur, et al. 28~(th) IEEE PVSC, p91,2000
[21] L.Cai, et al. IEEE trans, on ED. Vol44, p97,1997
[22] H.Elgamel. et al. Solar energy materials and solar cells. Vol53, p277,1998
[23] Lanford W A. J.Appl.Phys, 1978,49(4):2473-2477
[24] Lucovsky G, et al.. J.Vac.Sci.Tech. A, 1986,4(3): 681-688[1] G.Zheng, et al. Prog. in PV, Vol.4, p369, 1996
[2] F. Faller, et al. 2nd WCPEC, p1278, 1998
[3] H. Campe, et al. 13th European PVSEC, p1489, 1995
[4] O.Eward, et al, 13th European PVSEC, p440, 1995
[5] F. Faller, et al. 14th European PVSEC, p784, 1997
[6] T.Vermeulen, et al. 25th IEEE PVSC, p653, 1996
[7] S. Reber et al. Solar energy matierials and solar cells. Vol.65, 10409, 2001
[2] J. Zhao, et al. Appl. Phys. Lett. 73, p1991 (1998)
[3] Y. Bai, et al. 26th IEEE Photovoltaic Spocialists Conference, 1997, p35-38.
[4] R.D.Little et al. Progress in PV, Vol5, p309, 1997
[5] J.Yang et al. Appl. Phys.Lett., Vol70, p2975, 1997[6] A. Yamada. High efficiency CdTe thin film solar cells. PVSEC-12, 2001
[7] M. Contreras, et al. Progress in photovoltaies, Vol7, p311, 1999
[8] C. Hebling, et al. 14th Euro. PVSEC, p2318, 1997
[9] J. Christophe, M. G-ratzel et al. J.Am.Ceram.Soc.,Vol80, p3157, 1997
[10] H.Morikawa, et al. PVSEC-11, p529,1999
[11] H.Tayanaka, et al. 2nd WCPSEC, p1272, 1998
[12] Z. Shi, et al. Sol. Engergy Mater.Sol.Cells, Vol31, p51, 1993
[13] Y. Chu. J. Cryst.Growth. Vol39, p45, 1997
[14] A. Goetzberger. 26th IEEE PVSC, p1, 1997
[15] K.Yamamoto, et al.. 2nd WCPSEC, p1284, 1998
[16] M.Spitzer, et al. 14th IEEE PVSC, p375, 1980
[17] K.Zweibel. Sol. Engergy Mater. Sol.Cells, Vol63,p375, 2000
[18] M. Pauli, et al. Sol. Engergy Mater.Sol.Cells, Vol41,p119, 1996
[19] K. Peter et al. Thin film silicon solar cells on upgraded metallurgical silicon substrates prepared by liquid phase epitaxy. PVSEC-12,2001
[20] H. Wagemann et al. Sol. Engergy Mater. Sol.Cells, Vol69, p115, 2001
[21] D.Angermeier et al. 2nd WCPSEC, p1778, 1998
[22] S. Reber et al. 28th IEEE PVSC, p146, 2000
[23] R. Ludemann et al. 26th IEEE PVSC, p159, 1997
[24] R. Shimokawa et al. Sol. Engergy Mater.Sol.Cells, Vol34,p277, 1994
[25] C. Hebling et al. 26th IEEE PVSC, p623, 1997
[26] R. P. Gale, et al. 21st IEEE Photovoltaic Specialists Conference, p. 53,1990[1] 叶良修，半导体物理学，高等教育出版社，1983
[2] 施敏，半导体器件物理，电子工业出版社，1986[3] 刘恩科等，光电池及其应用，科学出版社，1991
[4] 赵富鑫等，太阳电池及其应用，国防工业出版社，1985
[5] J. Werner, et al., Advances in solid state physics, V34, 1994
[6] J.Rand et al., 22nd IEEE Photovoltaic Spec. Conf. p192, 1991[1] Solar energy materials and solar cells. Vol 69, p115-121, 2001
[2] 28th IEEE PVSC, p146, 2000
[3] Solar energy materials and solar cells. Vol 71, p245, 2002
[4] Solar energy materials and solar ceils. Vol 65, p593, 2001
[5] G. Beaucarne, et al. Solar energy materials and solar ceils. Vol 61, p301, 2000
[6] 28th IEEE PVSC, p146, 2000
[7] 陈哲艮．第5届全国光伏技术学术研讨会论文集，p34，1998．
[8] Imaizumi M, et al. 14th European PV solar energy conversion conference, p1385, 1997.
[9] Walter Zimmermann et al; 2nd World Conference and Exhibition on Photovoltaic Solar Energy Conversion, 1998[1] 王阳元等，多晶硅薄膜及其在集成电路中的应用。科学出版社，2001
[2] 电子工业生产技术手册，第6册，国防工业出版社，1989
[3] Yuwen Zhao, etc., Solar Energy Materials and Cells, pp321-326,48(1-4)(1997)
[4] A.Staoui, R. Monna, D.Angermeier, et al. 26th IEEE PVSC, 1997, 627
[5] Lin T and Hon M. J.Materials Science 1995, 30:2675
[6] Ehrenwall B, Selamidt C, Braun A, et al. 2nd world conference and exhibition on photovoltaie solar energy conversion, 1998, 1370-1373[1] P. Basore, et al, 20th IEEE-PVSC, 1988
[2] Imaizumi M, Ito T, Yamaguchi M et al. 14th European PV solar energy conversion conference, 1997. p1385
[3] 1st WCPEC, p1564, 1998
[4] H. Naomoto et al. Solar Energy Materials & Solar Cells, Vo148, p261, 1997
[5] Walter Zimmermann, Sandra Bau, Achim Eyer et al; 16th European Conf. On PV Solar Conversion, 2000
[6] 王玉亭，赵玉文，吸杂技术在硅电池中的应用，中国太阳能学会2001年学术会议
[7] G.Beaucarne, et al, Solar Energy Materials & Solar Cells, 61,2000
[8] T. Lauinger, et al. 14th European PVSEC, p853, 1997
[9] J.Jeong, et al. 28th IEEE PVSC, p83, 2000[10] G.hahn. et al. PVSEC-12, P-41, 2001.
[11] S.Schaefer. et al. 16th European PVSEC, 2000
[12] M.Spiegel, et al. 14th European PVSEC, p743,1997
[13] M.Spiegel, et al. Solar energy materials and solar cells. Vol55, p331, 1998
[14] H.Elgamel, et al. 1~(st) WCPEC, pl323, 1994
[15] C.T.Sah, et al. J.Appl.Phys. Vol54, p944,1983
[16] R.Gale. et al. J.Appl.Phys. Vol54, p6938,1983
[17] P.Sana, et al, Appl. Phys. Lett, Vol64, p97, 1994
[18] B.Sopori, et al. 1~(st) WCPEC, pl615, 1994
[19] B.Sopori, et al. 26~(th) IEEE PVSC, p25,1997
[20] V.Yelundur, et al. 28~(th) IEEE PVSC, p91,2000
[21] L.Cai, et al. IEEE trans, on ED. Vol44, p97,1997
[22] H.Elgamel. et al. Solar energy materials and solar cells. Vol53, p277,1998
[23] Lanford W A. J.Appl.Phys, 1978,49(4):2473-2477
[24] Lucovsky G, et al.. J.Vac.Sci.Tech. A, 1986,4(3): 681-688[1] G.Zheng, et al. Prog. in PV, Vol.4, p369, 1996
[2] F. Faller, et al. 2nd WCPEC, p1278, 1998
[3] H. Campe, et al. 13th European PVSEC, p1489, 1995
[4] O.Eward, et al, 13th European PVSEC, p440, 1995
[5] F. Faller, et al. 14th European PVSEC, p784, 1997
[6] T.Vermeulen, et al. 25th IEEE PVSC, p653, 1996
[7] S. Reber et al. Solar energy matierials and solar cells. Vol.65, 10409, 2001