Cd_（1-x）Zn_xTe多晶薄膜的制备、性能研究与光伏应用
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摘要
发展太阳能光伏技术是当今世界解决能源危机与环境污染的一个重要途径。本文目的在于研究Cd_(1-x)Zn_xTe多晶薄膜的沉积与性质并将需要的Cd_(1-x)Zn_xTe多晶薄膜作为过渡层应用于CdS／CdTe／ZnTe:Cu太阳电池以提高电池效率。
我们用共蒸发法制备了一系列组分的Cd_(1-x)Zn_xTe多晶薄膜。用XRD表征薄膜结构，发现退火前后Cd_(1-x)Zn_xTe薄膜都是立方相；用AFM观察薄膜表面形貌，发现刚沉积的多晶Cd_(1-x)Zn_xTe薄膜致密、均匀、无微孔；用温差电动势法测定沉积的Cd_(1-x)Zn_xTe多晶薄膜为P型半导体；通过透射光谱的测量，计算出光能隙，得出光能隙与x值满足二次方关系变化。
将Cd_(1-x)Zn_xTe多晶薄膜作为过渡层的思想来源于能带修饰。在CdS／CdTe／ZnTe:Cu太阳电池中，CdTe与ZnTe:Cu的导带有1.1ev的势差；将Cd_(1-x)Zn_xTe多晶薄膜作为过渡层加在CdTe与ZnTe:Cu之间，使导带上的1.1ev的高势差变成两个小势差的台阶变化，以提高电池效率。并在相同的工艺条件下，制备了CdS／CdTe／ZnTe:Cu与CdS／CdTe／Cd_(0.4)Zn_(0.6)Te／ZnTe:Cu电池。测试结果表明，后者比前者效率提高了平均35.0％。
本文是国家自然科学基金项目“新型结构的CdS／CdTe多晶薄膜太阳电池研究”的起始性研究，也是973“低价长寿新型光伏电池的基础研究”中“多晶薄膜材料和电池的探索研究”课题的一部分。本文的基本思路和所取得的主要结果尚未见报道，并对进一步提高CdTe电池效率具有一定的参考与实用价值。
Photovoltaic solar energy conversion is one of the important ways to resolve the global energy crisis and environment pollution. The intention of this paper is to study the deposition of polycrystalline Cd1-xZnxTe thin films and to make a proper Cd1-xZnxTe thin film as a buffer layer of CdS/CdTe/ZnTe:Cu solar cell in order to improve the performance of the cells.
A series of Cd1-xZnxTe thin films of varied compositions have been prepared by simultaneous evaporation. The films' cubic phase is demonstrated by XRD before and after annealing. The film surface appearance is characterized as uniformed and without phis by AFM. Cd1-xZnxTe thin films are testified of p-type conductivity by electromotive forces with difference in temperature. Predominant direct optical transitions have been observed and the optical energy gap varies with zinc content in a quadratic way.
The original intention of using a polycrystalline Cd1-xZnxTe thin film as a buffer layer is to modify the energy band diagram of CdS/CdTe/ZnTe:Cu solar cell. There is a 1.1 ev barrier between the conduction band of CdTe and the conduction band of ZnTerCu. When introducing a buffer layer of Cd1-xZnxTe with proper band gap between the CdTe layer and the ZnTerCu layer, the 1.1ev barrier becomes two small barriers, which will improve the performance of solar cells.
CdS/ CdTe/ZnTe:Cu solar cells and CdS/CdTe /Cd0.4Zn0.6Te /ZnTe:Cu solar cells have been fabricated in the same conditions, and we find the average conversion efficiency of the latter is unproved by 35% than the former.
The work is an introductory step of the program "Studies of polycrystalline CdS/CdTe solar cells with new structures" supported by The Nation Natural Science Funds of China. It is also a part of the program "Explorations and studies of polycrystalline film materials and solar cells" in "The fundamental studies of solar cells with low prices, long lives and new types" supported by 973 Program of China. The main ideals and results of this paper have not been found in previous reports, and will be valuable to improve the efficiency of CdTe solar cells.
我们用共蒸发法制备了一系列组分的Cd_(1-x)Zn_xTe多晶薄膜。用XRD表征薄膜结构，发现退火前后Cd_(1-x)Zn_xTe薄膜都是立方相；用AFM观察薄膜表面形貌，发现刚沉积的多晶Cd_(1-x)Zn_xTe薄膜致密、均匀、无微孔；用温差电动势法测定沉积的Cd_(1-x)Zn_xTe多晶薄膜为P型半导体；通过透射光谱的测量，计算出光能隙，得出光能隙与x值满足二次方关系变化。
将Cd_(1-x)Zn_xTe多晶薄膜作为过渡层的思想来源于能带修饰。在CdS／CdTe／ZnTe:Cu太阳电池中，CdTe与ZnTe:Cu的导带有1.1ev的势差；将Cd_(1-x)Zn_xTe多晶薄膜作为过渡层加在CdTe与ZnTe:Cu之间，使导带上的1.1ev的高势差变成两个小势差的台阶变化，以提高电池效率。并在相同的工艺条件下，制备了CdS／CdTe／ZnTe:Cu与CdS／CdTe／Cd_(0.4)Zn_(0.6)Te／ZnTe:Cu电池。测试结果表明，后者比前者效率提高了平均35.0％。
本文是国家自然科学基金项目“新型结构的CdS／CdTe多晶薄膜太阳电池研究”的起始性研究，也是973“低价长寿新型光伏电池的基础研究”中“多晶薄膜材料和电池的探索研究”课题的一部分。本文的基本思路和所取得的主要结果尚未见报道，并对进一步提高CdTe电池效率具有一定的参考与实用价值。
Photovoltaic solar energy conversion is one of the important ways to resolve the global energy crisis and environment pollution. The intention of this paper is to study the deposition of polycrystalline Cd1-xZnxTe thin films and to make a proper Cd1-xZnxTe thin film as a buffer layer of CdS/CdTe/ZnTe:Cu solar cell in order to improve the performance of the cells.
A series of Cd1-xZnxTe thin films of varied compositions have been prepared by simultaneous evaporation. The films' cubic phase is demonstrated by XRD before and after annealing. The film surface appearance is characterized as uniformed and without phis by AFM. Cd1-xZnxTe thin films are testified of p-type conductivity by electromotive forces with difference in temperature. Predominant direct optical transitions have been observed and the optical energy gap varies with zinc content in a quadratic way.
The original intention of using a polycrystalline Cd1-xZnxTe thin film as a buffer layer is to modify the energy band diagram of CdS/CdTe/ZnTe:Cu solar cell. There is a 1.1 ev barrier between the conduction band of CdTe and the conduction band of ZnTerCu. When introducing a buffer layer of Cd1-xZnxTe with proper band gap between the CdTe layer and the ZnTerCu layer, the 1.1ev barrier becomes two small barriers, which will improve the performance of solar cells.
CdS/ CdTe/ZnTe:Cu solar cells and CdS/CdTe /Cd0.4Zn0.6Te /ZnTe:Cu solar cells have been fabricated in the same conditions, and we find the average conversion efficiency of the latter is unproved by 35% than the former.
The work is an introductory step of the program "Studies of polycrystalline CdS/CdTe solar cells with new structures" supported by The Nation Natural Science Funds of China. It is also a part of the program "Explorations and studies of polycrystalline film materials and solar cells" in "The fundamental studies of solar cells with low prices, long lives and new types" supported by 973 Program of China. The main ideals and results of this paper have not been found in previous reports, and will be valuable to improve the efficiency of CdTe solar cells.
引文
1．雷永泉 万群 石永康编．新能源材料．天津大学出版社．(2000)
2．赵秦生 胡海南主编．新材料和新能源．轻工业出版社．(1987)
3．王立功 王玉学 孔繁建．美国的新千年(2000～2004)光伏(PV)计划．电源技术．Vol．25，192-194，(2001)
4．刘祖明 涂洁磊 廖华等．中国第六届光伏会议论文集．中国昆明，2000．10．14-17，266-269
5.X.Wu,P.Sheldon,Y.Mahathongy et al.NCPV,September 8-11,1998,Denver,Colorado
6．冯良桓 蔡伟 郑家贵等．中国第六届光伏会议论文集．中国昆明，2000．10．14-17，110-113
7．冯良桓 蔡伟 郑家贵等．太阳能学报．22(4)，2001，403-408
8．[美]胡晨明R．M．怀特 李采华译．太阳电池．北京大学出版社．(1990)
9．王家骅 李长健 牛文成编著．半导体器件物理．科学出版社．(1983)
10．叶良修 编著．半导体物理学．高等教育出版社．(1983)
11．周永溶 编．半导体材料．北京理工大学出版社．(1992)
12．张静全 蔡伟 郑家贵等．半导体光电．21(2)，2000，88
13.Gessert. US Patent 5909632, June 1, (1999)
14.R.Weil, M.Joucal, J.L.Loison et al. Applied Optics, 1998,37(13): 2681-2685
15.Liu X, Sites.J.R. AIP Conference Proceedings. 13th NREL Photovoltaic Program Review[C],1995,444-452
16.B.M.Basol, V.K.Kapur and M.L.Ferris. J.Appl.Phys. 1989,66(4):1816-1821
17．李奇峰 金应荣 朱兴华等．广西师范大学学报．2000年，第2期，7-9
18．于福聚 徐三保 张恕明．半导体学报．8(5)，1986
19.P.V. Meyers. Solar cells, 1988,23(59).
20.K.K.Chattopadhyay, A.Sakar. Vacuum, 1991, 42 (17): 1113-1116.
21.P. Gupta, K.K.Chattopadhyay and S.Chaudhuri. J.Materials Science, 1993, 28:496-500
22.J.González-Hernández, O.Zelaya and J.G.Mendoza-Alverez. J.Vac. Sci. Technol,1991,A9(3):550-553
23.A.Aydinli, A.compaan, G.Contreras-Puente et al. Solid State Communications, 1991,80(7):465-468
24．王华馥 吴自勤主编．固体物理实验方法．高等教育出版社．(1990)，P15
25. S.M.Johnson, S.Sen, W.H.Konkel et al. J.Vac. Sci.Technol. 1991,B9(3):1897-1901
26. J.L.Reno and E.D.Jones, Physical Review B, 1992,45(3): 1440-1442
27．唐晋发 编著．光学中的固体薄膜．科学出版社．(1987)P91
28．沈学础 著．半导体光学性质．科学出版社．(1992)
29．邵烨 郑家贵 张静全等．材料科学与工艺．2001，Vol．9 Sup：473-475
30. T.L.Chu, S.S.Chu and F. Firszt, J.Appl.Phys. 1986, 59(4):1259-1263
31. K.Kimmerle, R.Menner, H.W. Schock et al. Thin Solid Film. 1985,126:23-29
32．夏建白 编著．现代半导体物理．北京大学出版社．(2000)：P140
33. R.Hill. J.Phys. C:Solid State Phys. 1974,Vol7:521-525
34. A.Ebina, K. Saito and T. Takahashi. J.Appl.Phys, 1973,44(8):3659-3662
35. J.A.V. Vechten. Solid State Communication, 1972,Vol. 11:7-10
36．黎兵 蔡亚萍 朱居木等．四川大学学报．1999，36(3)，497-500
37．蔡伟 张静全 郑家贵等．半导体光电．2001，22(2)：121-123
38．武莉莉．四川大学硕士学位论文．(2001)
39．冯良桓．发明专利申请公开说明书．申请号：95111437．9
40. C.Narayanswamy, T.A.Gessert and S.E.Asher. in "NCPV Photovoltaics Program Review"(M.A1-JASSIM, J.P. THORONTON and L.M.GEE, 1999) p. 248.
41. M.G. Peter, A.L.Fahrenbruch and R.H.Bube. J.Vac. Sci. Technol. 1988,A6(6):3098-3102
42. Power Diffraction File. 1965, set. 15
43．王世中 臧鑫士主编．北京航空航天大学出版社．(1990)，P373
2．赵秦生 胡海南主编．新材料和新能源．轻工业出版社．(1987)
3．王立功 王玉学 孔繁建．美国的新千年(2000～2004)光伏(PV)计划．电源技术．Vol．25，192-194，(2001)
4．刘祖明 涂洁磊 廖华等．中国第六届光伏会议论文集．中国昆明，2000．10．14-17，266-269
5.X.Wu,P.Sheldon,Y.Mahathongy et al.NCPV,September 8-11,1998,Denver,Colorado
6．冯良桓 蔡伟 郑家贵等．中国第六届光伏会议论文集．中国昆明，2000．10．14-17，110-113
7．冯良桓 蔡伟 郑家贵等．太阳能学报．22(4)，2001，403-408
8．[美]胡晨明R．M．怀特 李采华译．太阳电池．北京大学出版社．(1990)
9．王家骅 李长健 牛文成编著．半导体器件物理．科学出版社．(1983)
10．叶良修 编著．半导体物理学．高等教育出版社．(1983)
11．周永溶 编．半导体材料．北京理工大学出版社．(1992)
12．张静全 蔡伟 郑家贵等．半导体光电．21(2)，2000，88
13.Gessert. US Patent 5909632, June 1, (1999)
14.R.Weil, M.Joucal, J.L.Loison et al. Applied Optics, 1998,37(13): 2681-2685
15.Liu X, Sites.J.R. AIP Conference Proceedings. 13th NREL Photovoltaic Program Review[C],1995,444-452
16.B.M.Basol, V.K.Kapur and M.L.Ferris. J.Appl.Phys. 1989,66(4):1816-1821
17．李奇峰 金应荣 朱兴华等．广西师范大学学报．2000年，第2期，7-9
18．于福聚 徐三保 张恕明．半导体学报．8(5)，1986
19.P.V. Meyers. Solar cells, 1988,23(59).
20.K.K.Chattopadhyay, A.Sakar. Vacuum, 1991, 42 (17): 1113-1116.
21.P. Gupta, K.K.Chattopadhyay and S.Chaudhuri. J.Materials Science, 1993, 28:496-500
22.J.González-Hernández, O.Zelaya and J.G.Mendoza-Alverez. J.Vac. Sci. Technol,1991,A9(3):550-553
23.A.Aydinli, A.compaan, G.Contreras-Puente et al. Solid State Communications, 1991,80(7):465-468
24．王华馥 吴自勤主编．固体物理实验方法．高等教育出版社．(1990)，P15
25. S.M.Johnson, S.Sen, W.H.Konkel et al. J.Vac. Sci.Technol. 1991,B9(3):1897-1901
26. J.L.Reno and E.D.Jones, Physical Review B, 1992,45(3): 1440-1442
27．唐晋发 编著．光学中的固体薄膜．科学出版社．(1987)P91
28．沈学础 著．半导体光学性质．科学出版社．(1992)
29．邵烨 郑家贵 张静全等．材料科学与工艺．2001，Vol．9 Sup：473-475
30. T.L.Chu, S.S.Chu and F. Firszt, J.Appl.Phys. 1986, 59(4):1259-1263
31. K.Kimmerle, R.Menner, H.W. Schock et al. Thin Solid Film. 1985,126:23-29
32．夏建白 编著．现代半导体物理．北京大学出版社．(2000)：P140
33. R.Hill. J.Phys. C:Solid State Phys. 1974,Vol7:521-525
34. A.Ebina, K. Saito and T. Takahashi. J.Appl.Phys, 1973,44(8):3659-3662
35. J.A.V. Vechten. Solid State Communication, 1972,Vol. 11:7-10
36．黎兵 蔡亚萍 朱居木等．四川大学学报．1999，36(3)，497-500
37．蔡伟 张静全 郑家贵等．半导体光电．2001，22(2)：121-123
38．武莉莉．四川大学硕士学位论文．(2001)
39．冯良桓．发明专利申请公开说明书．申请号：95111437．9
40. C.Narayanswamy, T.A.Gessert and S.E.Asher. in "NCPV Photovoltaics Program Review"(M.A1-JASSIM, J.P. THORONTON and L.M.GEE, 1999) p. 248.
41. M.G. Peter, A.L.Fahrenbruch and R.H.Bube. J.Vac. Sci. Technol. 1988,A6(6):3098-3102
42. Power Diffraction File. 1965, set. 15
43．王世中 臧鑫士主编．北京航空航天大学出版社．(1990)，P373