兰州大学机构库 >物理科学与技术学院
太阳电池中 CdTe 多晶薄膜的制备及其性能研究
Alternative TitleA Study of Preparation and Properties of CdTe Polycrystalline Films for Solar Cells
Thesis Advisor谢二庆
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name博士
KeywordCdTe 多晶薄膜 近空间升华技术(CSS) 太阳电池

1.采用近空间升华沉积 CSS(closed-space sublimation)法制备 CdTe 多晶薄膜的原理在于, CdTe 在一定温度下的升华和凝结过程。由于 CdTe 升华温度在 470℃左右, CdS 升华温度在 630℃左右,当源上的 CdTe 升华分解为Cd、 Te2 时,衬底上的 CdS 仍然稳定。本论文系统研究了源温度、衬底温度与沉积速率的关系。用 XRD, AFM 等测试分析手段,分析了近空间沉积的物理机制。利用不同升温过程,沉积制备了 CdTe 多晶薄膜。通过实验确定了最好的升温过程为:衬底温度 500℃,源温度 620℃,以氢气刻蚀后拉开衬底与源之间的设定温差 120℃,并保持固定温差至设定温度,随后沉积 6 分钟的工艺为最佳。2.在氩氧气氛下,氧浓度为 9%时,不同气压下制备的样品,均有立方相CdTe。此外,还有 CdS 和 SnO2:F 衍射峰。 CdTe 晶粒随气压增加有减小趋势,随气压的增加,透射率呈下降趋势,相应的 CdTe 吸收边向短波方向移动。3. 研究了退火气氛对电池性能的影响。太阳电池 J-V 曲线的测试结果表明,用经过后处理的 CdTe 薄膜制备的电池性能较好,而有氧气氛下后处理的样品性能要比纯氮气气氛后处理的好。不同氧气气氛下后处理的样品的性能差别不是很大。4.通过研究确定了目前最好的近空间制备 CdTe 多晶薄膜的工艺为:通过采用优化的升温方法,在氩氧气氛中,氧浓度为 9%时,采用衬底温度 500℃,源温度 620℃,沉积时间 6 分钟,制备了 CdTe 多晶薄膜,获得了转换效率优良的结构为 SnO2:F/CdS/CdTe/Au 的集成电池。在上述研究的基础上制备出CdS/CdTe 电池的转换效率为 13.38%,填充因子、开路电压单项指标分别达到了 73.1%和 860mV,接近国外 CdTe 太阳电池的领先水平。5.从实验和理论上解释了 CdTe 多晶薄膜上的小沙眼的成因。

Other Abstract

For the present, the energy is vitally related with social existence and development of mankind. Keeping on the development is the whole mankind's common purpose. The technique of developing the solar energy light is an important path of a world solving these wishes taday. The research and manufacture of thin film solar cells of the compound semi-conductor is the heat research realm of in the photovoltaic field today. CdTe/CdS thin film solar cells are doubly focused attention in the next generation thin film cells. Owing to its optoelectronic and chemical properties, CdTe is an ideal absorber material for high-efficiency, low cost thin film polycrystalline. However, a key factor of fabricating high-efficiency CdTe/CdS solar cells is gaining high-quality polycrystalline CdTe thin film. In this thesis, the several important steps of preparing CdS/CdTe solar cells have been deeply investigated. The steps include the deposition of CdTe thin films and the function layers in CdS/CdTe solar cells. The main structural and optoelectronic characteristics of CdTe polycrystalline thin films of CdS/CdTe solar cells have been analyzed and measured.
The influence of the deposition and annealing process to the CdTe performance has been studied by theoretical calculation. From the researches, high efficiency of CdS /
CdTe polycrystalline solar cells fabricated by us has been demonstrated. The main creative results of the thesis have been achieved as follows:
1. The deposition of CdTe polycrystalline thin films by the CSS technique is based on the reversible dissolution and combination process of CdTe at high temperature. The temperatures of CdTe beginning to dissociate has been observed to be about 470℃. As the same , the temperature of CdS beginning to dissociate has been observed to be about 630℃ that is enough higher than the dissolution temperature of CdTe. So CdS films keep compound when CdTe films havem dissociated into Cd and Te2.The result has been an important foundation that determines the CSS procedure. The deposition rate dependence of source temperature、substrate temperature and deposition pressure has been studied systematically. According to the results of XRD and AFM images, the physical mechanism of CSS is analyzed and the temperature distribution in CSS system is measured. We get the best increasing temperature process: The best method is that pulls difference in temperature first and keeps difference in temperature to the initialization temperature. The substrate temperature is 500℃, source temperature is 620℃ and a depositing duration is 6 minutes. 2. The samples depositing in the different pressure in 9% oxygen concentration are all cubical structure of CdTe and still appear the diffraction peaks of CdS and SnO2:F. Following the gas pressure increasing, the crystal size of CdTe minutes, the rate of the transparency of the thin film goes down and the absorption side faces to the shortwave direction. 3. The performance of solar cells depend on annealing ambiences have been studied. The J-V curve test illuminated: the performance of solar cells are better annealed at O2 atmosphere than those N2,and changes little after annealed at different percent of O2 atmosphere. 4. The polycrystalline thin films with the high quality are depositing in 6 minutes by the best increasing temperature process and the depositing condition that substrate temperature is 500℃ and source temperature is 620℃ in 9% oxygen concentration. The highest conversion efficiency of our CdS/CdTe solar cells without any antireflection layer is 13.4 %; which closes the lead level in the world; and the best individual parameters of performance, such as the filling factor ( FF ) and open circuit voltage (Voc) are 7.31% and 860mV, respectively. 5. It is determined by theoretical and experimental studies the main factor of causing pinholes of CdTe thin films.

Document Type学位论文
Recommended Citation
GB/T 7714
郑华靖. 太阳电池中 CdTe 多晶薄膜的制备及其性能研究[D]. 兰州. 兰州大学,2006.
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