大面积CdTe多晶薄膜的制备及其性能

通过研究大面积CdTe多晶薄膜沉积的升温过程,并调节石墨群边改进加热灯管的分布获得了较均匀的温场,在混合氩氧气氛下,用自行设计制造的近空间升华系统制备出了面积为300 mm×400 mm的大面积CdTe多晶薄膜,利用XRD、SEM研究其结构、成分和形貌,结果表明:CdTe薄膜呈(111)择优取向,且薄膜总体致密均匀,晶粒大小约为1 μm左右.用此大面积CdTe薄膜的不同部分制备的CdS/CdTe/ZnTe:Cu小面积太阳电池效率相差不大,说明薄膜的均匀性较好.     

CdTe多晶薄膜制备及后处理对CdS/CdTe界面的影响

采用近空间升华法分别在玻璃、CdS及CdS1-xTex衬底上沉积了CdTe多晶薄膜,通过原子力显微镜的观察和X射线衍射的分析,比较了它们的微结构。结果表明,用CdS和CdS1-xTex多晶薄膜作为衬底沉积的CdTe多晶薄膜结构与衬底相似,具有(111)面择优取向。通过对在不同氧分压下进行后处理的CdS/CdTe薄膜的断面及光能隙的研究,发现在氮氧(4∶1)气氛下后处理的薄膜CdS层明显减薄,这样的结果有利于改善CdTe太阳电池的光谱响应,增加载流子收集。我们认为氧在退火中促进了CdS/CdTe界面互扩散,扩散的结果不仅弥补了CdS、CdTe间的晶格失配,而且降低了界面的位错密度,并获得了面积为0.52 cm2,转换效率为13.38%的CdTe多晶薄膜电池。     

溅射功率对CdZnTe薄膜成分和结构的影响

采用Cd0.9Zn0.1Te晶体作为溅射靶在玻璃衬底上利用磁控溅射法制备出CdZnTe薄膜,研究了溅射功率对CdZnTe薄膜的成分、结构特性的影响。制备的CdZnTe薄膜是具有闪锌矿结构的多晶薄膜,沿（111）择优取向。随着溅射功率的增大,薄膜沉积速率增大,薄膜结晶质量提高。采用晶体靶Cd0.9Zn0.1Te溅射CdZnTe薄膜时,无论是在何种功率下CdZnTe薄膜中的Cd原子成分均高于Te原子成分,Cd原子表现为择优溅射原子。     

具有复合背接触层的 CdTe多晶薄膜太阳电池

为了提高CdTe太阳电池的背接触性能,用共蒸发法制备了ZnTe：Cu和Cd1-xZnxTe多晶薄膜。研究结果表明：Cd1-xZnxTe多晶薄膜的能隙与锌含量呈二次方关系,ZnTe：Cu多晶薄膜能隙随着掺Cu浓度的增加而减小。分别用ZnTe／ZnTe：Cu和Cd1-xZnxTe／ZnTe:Cu复合膜作为背接触层,既能修饰异质结界面,改善电池的能带结构,又能防止Cu原子向电池内部扩散。因此获得了面积0．502cm^2,转换效率为13．38％的CdTe多晶薄膜太阳电池。     

电沉积CdTe半导体薄膜中Cd和Te含量的极谱分析

用极谱法分析电沉积 CdTe 半导体薄膜中 Cd 和 Te 的含量随电沉积电位、沉积温度和热处理温度的变化,获得 Cd 和 Te 原子数之比几乎为1∶1的 CdTe 薄膜。热处理能改变 CdTe 薄膜的导电类型。     

CdS多晶薄膜的制备及性质研究

分别采用近空间升华法和电子束蒸发法在透明导电玻璃和普通载玻片上制备了硫化镉(CdS)多晶薄膜.对制备样品的表征结果表明:(1)两种方法制备样品都沿(002)晶向择优生长,属于六方相多晶结构,但择优取向度不同;(2)CdS薄膜表面连续而致密,粒径均匀,但两种工艺制备样品的S:Cd原子比有较大差异;(3)CdS薄膜的光能隙在2.39～2.44eV之间,电子束蒸发制备样品光能隙稍小.分析认为,两种方法制备样品的上述差异可能与衬底温度、沉积时间及成膜机制的不同相关.     

气相CdCl2退火对CdTe多晶薄膜性能的影响

利用近空间升华法在Ar O2气氛下沉积了CdTe多晶薄膜,并在气相CdCl2氛围下进行了不同温度的退火,对样品进行了厚度、XRD、SEM、透过谱,σ-T等性能测试,结果表明:退火后CdTe多晶薄膜在(111)面上仍具有择优取向,退火能使晶界钝化,增加再结晶并促进晶粒长大;但对薄膜的透过率没有影响,退火后,暗电导(σdark)增加,电导激活能(Ea)减少.得到了最优化的退火条件.     

衬底温度对碲化镉薄膜性质及太阳电池性能的影响

蒸汽输运法是制备高质量且大面积均匀的CdTe薄膜的一种优良的方法。采用自主研发的一套蒸汽输运沉积系统制备了CdTe多晶薄膜, 并研究了衬底温度对CdTe薄膜性质及太阳电池性能的影响。利用XRD、SEM、UV-Vis和Hall等测试手段研究了衬底温度对薄膜的结构、光学性质和电学性质的影响。结果表明, 蒸汽输运法制备的CdTe薄膜具有立方相结构, 且沿(111)方向高度择优。随着衬底温度的升高(520℃~640℃), CdTe薄膜的平均晶粒尺寸从2 μm增大到约6 μm, CdTe薄膜的载流子浓度也从1.93×10¹⁰ cm^-3提高到2.36×10¹³ cm^-3, 说明提高衬底温度能够降低CdTe薄膜的缺陷复合, 使薄膜的p型更强。实验进一步研究了衬底温度对CdTe薄膜太阳电池性能的影响, 结果表明适当提高衬底温度, 能够大幅度提高电池的效率、开路电压和填充因子, 但是过高的衬底温度又会降低电池的长波光谱响应, 导致电池转换效率的下降。经过参数优化, 在衬底温度为610℃、无背接触层小面积CdTe薄膜太阳电池的转换效率达到11.2%。     

近距离升华制备CdTe掺Te薄膜的结构与电性能研究

采用近距离升华(Close-Spaced-Sublimation,CSS)技术制备CdTe及掺Te薄膜.并利用XRF、XRD、SEM及Hall系统研究了其含量、结构、表面形貌和电性能.结果表明,CSS技术制备的CdTe薄膜晶形好,晶粒度较RF方法制备的薄膜增大约100倍.Te掺入CdTe薄膜后,改变了CdTe膜的结晶特性,适当掺入Te可以促进CdTe晶格的生长,并导致Cdrre膜晶格常数变大.薄膜面电阻率降低,面载流子浓度增大,以及载流子迁移率的增大,表明掺杂Te后CdTe膜的电导性能大大改善.     

不同沉积条件下ZnTe与ZnTe:Cu复合背接触层对CdTe太阳电池性能的影响

制备高效的CdTe太阳电池,改善电池的背接触特性是一关键技术。背接触层中掺Cu能够得到性能良好的电池,但Cu在CdTe中进一步扩散,会形成缺陷,造成CdTe太阳电池性能不稳定。因此,有必要系统研究Cu原子在薄膜中的存在状态,进而有效控制Cu的浓度;另一方面,要获得良好的背接触层,必须制备出结构致密的ZnTe与ZnTe:Cu多晶薄膜。研究了衬底温度及沉积速率的变化对ZnTe:Cu薄膜质量及电池性能的影响。在常温下沉积ZnTe后,提高衬底温度沉积ZnTe:Cu对太阳能电池的影响明显,得到了转化效率达10.28%的电池。     

SEM characterization of CdTe growth on CdTe(111) by close-spaced sublimation

A close-spaced sublimation (CSS) reactor is used to explore the growth of CdTe thin films on CdTe(111) substrates in order to determine the parameters required for high quality smooth film growth. Growth rates below 1 μm/h were targeted based on a preliminary sublimation study of the substrate material. The CSS technique is of interest due to its low cost and the potential for producing high quality films at higher growth rates compared to molecular beam epitaxy (MBE). Films were characterized by optical and scanning electron microscopy (SEM), atomic force microscopy (AFM), and the film thickness was determined using an alpha-step IQ profilometer. The initial quality of the films was determined by the electron back scattering diffraction (EBSD) technique.     

CdTe薄膜的制备方法比较及其结构性能研究

采用真空热蒸发VE，射频溅射沉积RF和近距离升华CSS技术制备CdTe薄膜，并对其进行掺杂研究，样品利用XRD，SEM，紫外－可见分光光度计和霍尔系数测量系统进行测试。结果显示，CSS制备的CdTe薄膜与VE和RF法制备的薄膜相比，晶粒大，晶形好，适当的掺杂某些元素，适当的掺杂量，可以改善CdTe薄膜的结晶性能，提高其导电性能，掺杂对CdTe薄膜的光能隙影响不大。     

Comparison between the effects of CdCl2 heat treatment on CdTe films prepared by RF magnetron sputtering and close spaced sublimation methods

CdTe films were prepared on Fluorine-doped tin oxide substrate by RF magnetron sputtering and close spaced sublimation (CSS) methods, respectively. These CdTe films were then treated with a wet CdCl₂ heat process at different temperatures. The structural and optical properties of CdTe films were investigated by X-ray diffraction, scanning electron microscope and UV–Visible spectrophotometer. The results reveal that both types of CdTe films have a better crystalline and larger grain size after CdCl₂ heat treatment. However, the (422) peak has a more preferential orientation than (511) peak after CdCl₂ activation for CdTe films prepared by sputtering method, while these two peaks almost have the same intensity for CSS-prepared CdTe films. The transmittance of CdTe films prepared by CSS is apparently lower than sputtered CdTe films. Correspondingly, the efficiency of solar cells with CSS-prepared CdTe is 7.3, 2.6 % of sputtered CdTe films.     

CdS薄膜的制备及其在CdTe电池中的应用

CdTe薄膜电池是发展最快、应用前景最好的一类太阳能电池。CdS层是CdTe电池的窗口层材料,其薄膜质量直接影响电池的转换效率。本文介绍了化学水浴沉积(CBD)和闭空间升华(CSS)两种方法沉积CdS薄膜,并完成单电池器件的制备和测试。CSS方法制备的薄膜结晶较大,光学和电学性能好于CBD方法制备的薄膜,太阳能电池的光电转换效率达到10.9%。CSS方法镀膜速度快,真空环境工作,有利于大规模产业化应用。     

Pathways to thin absorbers in CdTe solar cells

We present approaches to reduce the absorber thickness of CdTe solar cells. The investigations were done with CdTe absorber films deposited by the close-space sublimation (CSS) technique. Using these CdTe films, complete solar cells were produced in our own laboratory. The absorber thickness as the crucial parameter was varied between 1 and 11 µm in these experiments. It is analyzed how process steps following the CdTe layer deposition influence the structure of the absorber films as well as the solar cell properties. Three ways of back contact formation are compared. These include (i) the wet chemical etching of the CdTe surface, (ii) a plasma etching step, and (iii) the vacuum deposition of a thin intermediate copper layer. In the latter case, voids and shunts related to preferential etching at grain boundaries are avoided admitting the use of thinner absorber films. Thus, the solar-cell efficiencies were increased from below 9% to more than 10% while the CdTe film thickness was reduced from 11 µm to less than 4 µm.     

Substrate temperature dependent structural,optical, morphology and electrical properties of RF sputtered CdTe thin films for solar cell application

In this work, we have studied the influence of substrate temperature on structural, morphology optical, and electrical properties of CdTe thin films deposited by RF magnetron sputtering. Films were analyzed by using variety of techniques such as low angle X-ray Diffraction, UV–Visible spectroscopy, Raman spectroscopy, Field emission scanning electron microscopy (FE-SEM), Energy-dispersive X-ray spectroscopy (EDAX) Hall Measurement etc. Low angle XRD analysis showed that CdTe films are polycrystalline and has cubic structure with preferred orientation is along (111) direction. Raman scattering studies revealed the presence of single phase CdTe over the entire range of substrate temperature studied. The FE-SEM analysis showed that CdTe growth process occurred predominantly by grain growth and not through the layer-by-layer mode. Compositional analysis carried out using EDAX suggests that CdTe films deposited at low substrate temperatures are Te rich and that at higher temperatures is Cd rich. Electrical resistivity of CdTe films decreases with increase in substrate temperature and whereas positive increase in Hall coefficient suggests as-deposited CdTe films are p-type. The UV–Visible spectroscopy analysis showed that the band gap increases from 1.47 to 1.51 eV when the substrate temperature increased from 50 to 300 °C. Such optimum band gap CdTe can be use as absorber material in photovoltaic applications like the CdS/CdTe and ZnO/CdTe solar cells.     

Effect of growth conditions on the flatness of micro-crystal terraces of CdTe thin film

An atomic force microscopy study of the surface roughness of CdTe thin films growth by the close-space vapor transport technique on Corning glass substrate under different growth conditions (substrate temperature, Cd overpressure, and annealing) is presented. The roughness measurements show that under certain growth conditions the surface of the micro-crystals is flatter—on the micrometer scale—than in the case of CdTe layers grown by molecular beam epitaxy (MBE) on a CdTe substrate. ©1999 Kluwer Academic Publishers