CdS薄膜的制备及其性能

采用化学池沉积(CBD)法,在三种衬底(玻片、ITO玻片、SnO2玻片)上沉积CdS薄膜,并利用扫描电镜(SEM)、透射光谱、X射线衍射(XRD)和微电流高阻计等方法对沉积膜进行了测试分析,计算出CdS薄膜的能隙宽度和电导激活能,阐述了CBD法中CdS薄膜的生长沉积机制以及不同衬底对沉积效果的影响.结果表明:不同衬底的成膜效果差异较大,其中以SnO2玻片效果最佳.     

CdS薄膜的制备及其性能

采用化学池沉积(CBD)法,在三种衬底(玻片、ITO玻片、SnO2 玻片)上沉积CdS薄膜,并利用扫描电镜(SEM)、透射光谱、X射线衍射(XRD)和微电流高阻计等方法对沉积膜进行了测试分析,计算出CdS薄膜的能隙宽度和电导激活能,阐述了CBD法中CdS薄膜的生长沉积机制以及不同衬底对沉积效果的影响.结果表明:不同衬底的成膜效果差异较大,其中以SnO2 玻片效果最佳     

CdS纳米薄膜的水浴法制备与表征

CdS是一种直接能隙半导体，其带隙约为2．42eV，是一种良好的太阳能电池窗口层材料和过渡层材料。化学水浴法沉积CdS薄膜具有工艺简单，成本低廉，成膜均匀、致密以及可大面积生产等优点。本文通过对化学水浴法沉积CdS薄膜的研究，阐述了CdS膜的生成和生长过程及其机理，并不断优化此方法中的各种工艺参数，得到了适合做铜铟镓硒薄膜太阳能电池过渡层的CdS薄膜，并对该薄膜的形貌、结构和性能进行了分析。     

太阳电池中CdS多晶薄膜的微结构及性能

采用化学水浴法制备了CdS多晶薄膜,通过XRD,AFM,XPS和光学透过率谱等测试手段研究了CdS多晶薄膜生长过程中的结构和性能.结果表明,随着沉积的进行,薄膜更加均匀、致密,与衬底粘附力增强,其光学能隙逐渐增大,薄膜由无定形结构向六方(002)方向优化生长,同时出现了Cd(OH)2相.在此基础上,通过建立薄膜的生长机制与性能的联系,沉积出优质CdS多晶薄膜,获得了转化效率为13.38%的CdS/CdTe小面积电池.     

太阳电池中CdS多晶薄膜的微结构及性能

采用化学水浴法制备了CdS多晶薄膜，通过XRD，AFM，XPS和光学透过率谱等测试手段研究了CdS多晶薄膜生长过程中的结构和性能.结果表明，随着沉积的进行，薄膜更加均匀、致密，与衬底粘附力增强，其光学能隙逐渐增大，薄膜由无定形结构向六方(002)方向优化生长，同时出现了Cd(OH)2相.在此基础上，通过建立薄膜的生长机制与性能的联系，沉积出优质CdS多晶薄膜，获得了转化效率为13.38%的CdS/CdTe小面积电池.     

高阻光敏CdS膜的制备与性质

采用真空蒸发工艺,用掺杂(Cu)敏化和H_2S热处理敏化两种制备方式获得了高阻光敏CdS膜,描述了CdS膜的性质及其与制备参数的关系。     

光敏器件

<正> 光敏器件包括光敏电阻、光敏二极管及光敏三极管等。光敏器件可以用来以可见光或红外光的形式控制报警器、测试仪、自动开关、继电器等多种装置或执行机构。因此光敏器件在自动化技术中起着极其重要的作用。 光敏电阻受光照后,其阻值会变小。光敏电阻的符号如图1所示,用来制作光敏电阻的典型材料有硫化镉(CdS)及硒化镉(CdSe)两种。光敏电阻的CdS或CdSe沉积膜面积越大,其受光照后的阻值变化也越大,故通常将沉积膜做成“弓”字形,以增大其面积。光敏电阻工作时的响应速度较慢,如CdSe光敏电阻的响应时间约为10ms,CdS的响应时间约为100ms。因此,光敏电阻通常都工作于直流或低频状态下。     

溶液PH值对CdS薄膜结构特性的影响

采用化学水浴沉积(CBD)工艺在玻璃衬底上制 备CdS薄膜,研究溶液PH值对CdS 薄膜结构特性的影响。薄膜的厚度、组份、晶相结构和表观形貌分别由台阶仪、X射线荧光 光谱(XRF)、X射线衍射(XRD)和场发射扫描电子显微镜(FESEM)来表征。溶液的 PH值为11.26、 11.37和11.48时,CdS薄膜的晶相以六方相为主,薄膜的厚度先增大后减小; PH值为11.62、11.66时,薄膜的晶相以立方相为主,薄 膜的厚度进一步减小。同时,随着溶液PH值 增大,CdS薄膜的晶格常数也逐渐增大。两种晶相的CdS薄膜缓冲层与CIGS薄膜分别构成异 质 对形成异质结时的晶格失配分别为32.297%和1.419%,界面态密度分别为2.792×10¹⁴和8.507×10¹²,因此高效CIGS薄 膜太阳电池更需要立方相的CdS薄膜。     

近空间升华沉积CdTe薄膜的微结构和PL谱

用近空间升华法在CdS薄膜上沉积了CdTe薄膜.研究了在两种保护气氛下所沉积的多晶CdTe薄膜在后处理后的微结构、表面形貌及光致发光(PL)谱,并研究了CdTe表面和CdS/CdTe界面的PL谱的区别,根据薄膜的微结构对碲化镉在太阳电池中的应用进行了讨论.     

掺Bi热蒸发CdS光导薄膜

本文用三种方法制备了掺Bi的CdS光导薄膜。一种方法是将Bi粉和CdS粉均匀混合蒸发;第二种方法是将CdS薄膜在CdS掺杂的Bi气氛中扩散,扩散温度为400～450℃;第三种方法是在CdS膜外再镀上一层很薄的Bi膜。文中介绍了它们的制备条件和光导特性,同时讨论了制备条件与光电导特性的关系。     

Cadmium telluride films and solar cells

CdTe thin films for solar cell applications have been deposited by close-spaced vapor transport and by hot-wall vacuum evaporation. As-deposited films are p-type with hole densities that increase to values of 1 × 10¹⁶cm^-3with increasing substrate temperature. A variety of experimental results can be interpreted either in terms of doping by native defects such as cadmium vacancies or doping by diffusion from the graphite substrate, with evidence for self-compensation. Many CdS/CdTe/graphite solar cells have been prepared by vacuum evaporation of CdS onto thin-film CdTe, which have low values ofJ_{O} sim 10^{-9}A/cm²and high values ofJ_{SC} sim 17mA/cm². The open-circuit voltage is low at 0.48 V for CdS deposition at 300° C, but increases with decreasing CdS deposition temperature. The highest efficiency prepared to date is 6.4 percent. Tile efficiency is limited at present by the fill factor, associated with a total series resistivity in the light of the order of 10 Ω-cm². Supporting research on low-resistance contacts to p-type CdTe, grain boundary properties and passivation in p-type CdTe bicrystals and thin films, and high-resolution transmission electron microscopy of junction interfaces is briefly described.     

CuxS背接触层制备及在碲化镉薄膜太阳电池中应用研究

本文采用化学水浴法沉积CuxS薄膜,通过改变Cu元素比例研究其对碲化镉电池效率的影响。研究表明化学水浴法沉积的CuxS是非晶的,采用适当退火条件可以使其晶化,随着退火温度的提高,薄膜变得致密且结晶明显。CuxS薄膜厚度对电池性能有很大的影响,结果表明,随着CuxS薄膜厚度增加,电池性能先增加后减少。薄膜厚度为75nm时,CdS/CdTe电池性能最佳,达到了最高转化效率(η)为12.19%,填充因子(FF)为68.82%,开路电压(Voc)为820mV。     

Optimization of physical properties of vacuum evaporated CdTe thin films with the application of thermal treatment for solar cells

This paper reports the optimization of physical properties of cadmium telluride (CdTe) thin films with the application of thermal treatment. The films of thickness 650 nm were deposited on glass and indium tin oxide (ITO) coated glass substrates employing vacuum evaporation followed by thermal annealing in the temperature range 250–450 °C. The films were characterized using X-ray diffraction (XRD), source meter and atomic force microscopy (AFM) for structural, electrical and surface topographical properties respectively. The X-ray diffraction patterns reveal that films are polycrystalline with predominant zinc-blende structure having preferred reflection (111). The structural parameters are calculated and discussed in detail. The current–voltage characteristics show Ohmic behavior and the electrical conductivity is found to increase with annealing treatment. The AFM studies show that the surface roughness of films is observed to increase with annealing. The experimental results reveal that the thermal annealing plays an important role to enhance the physical properties of CdTe thin films and annealed films may be used as absorber layer in CdTe/CdS solar cells.     

硫化镉薄膜的XPS研究

用XPS分析了CdS薄膜的结构。硫化镉薄膜是用化学沉积法制备的胶体颗粒，然后再通过真空蒸发法在平面玻璃上形成的多晶薄膜。XPS分析表明CdS薄膜中的Cd3d和S2p峰值均比块状CdS向高能方向偏移了10eV。这主要是由于表面效应所致。     

近空间升华沉积CdTe薄膜的微结构和PL谱

用近空间升华法在CdS薄膜上沉积了CdTe薄膜.研究了在两种保护气氛下所沉积的多晶CdTe薄膜在后处理后的微结构、表面形貌及光致发光(PL)谱,并研究了CdTe表面和CdS/CdTe界面的PL谱的区别,根据薄膜的微结构对碲化镉在太阳电池中的应用进行了讨论.     

CdTe solar cell in a novel configuration

Polycrystalline thin‐film CdTe/CdS solar cells have been developed in a configuration in which a transparent conducting layer of indium tin oxide (ITO) has been used for the first time as a back electrical contact on p‐CdTe. Solar cells of 7·9% efficiency were developed on SnO_x:F‐coated glass substrates with a low‐temperature (<450°C) high‐vacuum evaporation method. After the CdCl₂ annealing treatment of the CdTe/CdS stack, a bromine methanol solution was used for etching the CdTe surface prior to the ITO deposition. The unique features of this solar cell with both front and back contacts being transparent and conducting are that the cell can be illuminated from either or both sides simultaneously like a ‘bi‐facial’ cell, and it can be used in tandem solar cells. The solar cells with transparent conducting oxide back contact show long‐term stable performance under accelerated test conditions. Copyright © 2004 John Wiley & Sons, Ltd.     

Modeling of temperature profile,thermal runaway and hot spot in thin film solar cells

Hot spot and thermal runaway are serious phenomena leading to the degradation of CdTe thin film solar cells. Here, we show that these issues are well related to temperature variation in the device structures mostly because of current flowing across transparent conducting oxide (TCO) layer or back contact of a CdTe device structure: glass/TCO/CdS/CdTe/graphene. Graphene nanolayer was chosen as the back contact because of its high thermal conductivity. We present a modeling of the temperature profile in CdTe thin film devices considering both uniform and nonuniform temperature distribution and current flowing across TCO layer. Temperature profile for hot spots at the edges of devices are modeled and compared to literature reports of both modelled and measured data. The model is based on the heat transfer equation (which uses thermal resistances) and in particular accounts for convection and conduction resistances by means of their ratio, the Biot number – a factor that could be optimized in the design of photovoltaic devices. Profiles were modelled taking into account both uniform and non-uniform temperature profiles for the glass, and currents flowing though the TCO. It is shown that the current flowing across the TCO layer can contribute to thermal runaway and its spreading to neighbouring areas. Overall the modelling data suggests that thin film solar devices could be designed to minimise hot spot runaway issues by taking into account the thickness and temperature dependence of the layers thermal conductivity, convection and conduction resistances. This can be extended to other solar cell structures or large scale modules.     

Copper migration in cdte heterojunction solar cells

CdTe solar cells were fabricated by depositing a Au/Cu contact with Cu thickness in the range of 50 to 150Å on polycrystalline CdTe/CdS/SnO₂/glass structures. The increase in Cu thickness improves ohmic contact and reduces series resistance (R_s), but the excess Cu tends to diffuse into CdTe and lower shunt resistance (R_sh) and cell performance. Light I-V and secondary ion mass spectros-copy (SIMS) measurements were performed to understand the correlations between the Cu contact thickness, the extent of Cu incorporation in the CdTe cells, and its impact on the cell performance. The CdTe/CdS/SnO₂/glass, CdTe/ CdS/GaAs, and CdTe/GaAs structures were prepared in an attempt to achieve CdTe films with different degrees of crystallinity and grain size. A large grain polycrystalline CdTe thin film solar cell was obtained for the first time by selective etching the GaAs substrate coupled with the film transfer onto a glass substrate. SIMS measurement showed that poor crystallinity and smaller grain size of the CdTe film promotes Cu diffusion and decreases the cell performance. Therefore, grain boundaries are the main conduits for Cu migration and larger CdTe grain size or alternate method of contact formation can mitigate the adverse effect of Cu and improve the cell performance.     

Preparation of CuInxGa1−xSe2 solar cells by electron beam evaporation of powdered evaporants

Cu(In,Ga)Se₂ (CIGS) thin films were deposited by electron beam evaporation of ball-milled powders containing various amounts of gallium. The effects of the gallium concentration in the Cu(In,Ga)Se₂ on the structure, surface morphology and optical properties of the films were investigated using X-ray diffraction, energy-dispersive X-ray analysis, atomic force microscopy and optical spectroscopy. All of the films, which were deposited at 450 °C, were polycrystalline and exhibited a chalcopyrite structure with a (112) preferred orientation. The optical constants of the films were calculated. The grain size, the roughness and the band gap increased with increasing amounts of gallium in the films. A glass/TCO/CdS/CIGS/Au solar cell with 12.87% efficiency was prepared directly from the powdered material.