稀土元素(Gd,Y)掺杂CdS薄膜的制备及其性能研究

采用化学水浴法两次沉积CdS,结合电子束真空蒸发法在两层CdS之间引入稀土层,制备含有不同厚度稀土Gd、Y掺杂层的CdS多晶薄膜。利用XRD、SEM、EDX、UV-VIS透射光谱和霍尔效应测试仪对薄膜的晶型、表面形貌、化学组成、光学及电学性能进行研究。结果表明:未掺杂的薄膜为沿(111)晶面择优生长的立方相闪锌矿结构,导电类型为n型。含有稀土Gd(Y)掺杂层的CdS多晶薄膜为立方相和六方相的混合结构,导电类型仍为n型,薄膜的均匀性和致密性得到改善,薄膜中Cd和S的原子比更接近CdS的化学计量比,稀土掺杂可提高CdS薄膜在可见光范围内的透过率,使薄膜载流子浓度增大、导电性能明显增强。     

化学沉积法中立方相和六方相CdS薄膜的制备及其特性

采用化学沉积法制备了多晶CdS薄膜;利用X射线衍射仪、原子力显微镜、透射光谱以及光电导测试等方法表征了CdS薄膜的晶体结构、光学特性和电学特性。结果表明:通过改变反应液中Cd2 离子浓度(0.002~0.008mol.L-1)和提高沉积温度(80~90℃)来加快沉积速率,CdS薄膜晶相由六方相(H)向立方相(C)转变,且禁带宽度随Cd2 离子浓度增大逐渐变大;当Cd2 离子浓度从0.002mol.L-1增加到0.005mol.L-1时,薄膜呈六方相,浓度为0.006mol.L-1时出现六方与立方两种晶相共存,而浓度为0.008mol.L-1时薄膜转变为立方相。CdS薄膜表面形貌、光学特性、电学特性也随Cd2 离子浓度的增大而有规律的变化。     

CIGS电池缓冲层CdS的制备工艺及物理性能

在含有醋酸镉、醋酸氨、硫脲和氨水的水溶液中,化学沉积CdS半导体薄膜,薄膜的厚度与搅拌强度有很大关系,表明薄膜的生长速度是由OH-和SC(NH2)2的扩散传质为控制步骤。CdS薄膜的电阻率在104~105Ω.cm之间。CdS薄膜的晶格在乙酸胺浓度较小时,为六方晶和立方晶混合结构;乙酸胺浓度较大时,为立方晶结构。利用六方晶与立方晶混合的CdS制备的CIGS太阳电池,光电转换效率最大可达12.1%,3.5×3.6cm2小面积组件为6.6%。立方相CdS制备的最佳电池效率达到12.17%。两种晶相结构的CdS薄膜对CIGS太阳电池的性能影响没有明显的差别。     

CdS/CuInSe_2异质结薄膜太阳电池

用蒸发方法制备CdS/CuInSe_2(CdS/CIS)异质结薄膜太阳电池。在Mo/玻璃或Mo/Al_2O_3衬底上,用双源法蒸发CIS多晶材料+Cu或CIS多晶材料+Se,通过控制对黄铜矿结构的微小偏离,淀积电阻率不同的两层p-CIS层,然后用蒸发CdS方法,通过控制In的蒸发,在高阻p-CIS层上淀积两层电阻率不同的n-CdS层,并在低阻n-CdS层上蒸发Al栅和SiOx减反射膜,构成n-CdS/p-CIS异质结薄膜太阳电池。对电池的I—V特性和光谱响应特性进行了研究。     

溶液pH值对化学浴沉积CdS薄膜性能的影响

研究了溶液pH值对化学浴沉积CdS薄膜表面形貌及光学性能的影响.在CdSO4、硫脲和氨水的混合溶液中,在玻璃基底上制备了CdS薄膜.实验表明,pH值对CdS薄膜的表面形貌有很大影响,pH=11.6条件下CdS薄膜致密度最高;随着pH值的增加薄膜的可见光透过率增加,薄膜中S/Cd比减小;但是,pH值对CdS薄膜的晶体结构没有影响.用扫描电镜观察了CdS薄膜的表面形貌;用XRD检测了CAS薄膜的晶体结构;用分光光度计检测了薄膜的透过率;用EDS检测了薄膜成分.     

电沉积制备中络合剂对光伏材料CdS的影响

利用电沉积（Electrodeposition)方法来制备六方相的CdS薄膜。实验指出从0．04mol/L Na2S2O3,0.04mol/L,CdSO4和0.04mol/L柠檬酸钠组成的溶液中，在pH值为5．4，温度为60℃的条件下，在ITO玻璃上电沉积得到CdS的前驱体。在300℃氮气氛下中热处理1h后，经X射线衍射（XRD）分析表明薄膜是呈六方相的CdS，且几乎沿（002）方向定向生长。扫描电镜（SEM）表明CdS晶粒为亚微米尺寸。研究表明，利用这种方法，可以得到结晶良好的六方相CdS薄膜。     

低成本Cu_2S/CdS陶瓷太阳电池研究

多晶Cu_2S/CdS太阳电池是一种有前途的低成本太阳电池,很多国家对此开展了研究。Barnett等人不久前报道了Cu_2S/CdS薄膜太阳电池的阳光效率已达到9.15％。N.Nakayama等人控制烧结时保护气氛中氧的含量,制成n-CdS烧结体,经抛光腐蚀后,用电化学方法处理约60分钟形成Cu_2S,电池的阳光效率最高达9％,扣除栅网面积后效率为11％。     

衬底温度对PLD法沉积CdS及ZnS薄膜材料的影响

以ITO玻璃为衬底,利用脉冲激光沉积(PLD)法在温度为50、200和400℃下制备了CdS、ZnS薄膜。测量分析了温度对CdS及ZnS薄膜的透射光谱特性、光学带隙、Raman光谱特性等的影响。结果显示,在实验温度范围内:①ZnS薄膜比CdS薄膜透射性能好,光学带隙大;②ZnS薄膜的Raman光谱复杂,Raman特征峰较弱;CdS薄膜的Raman特征峰明显;③随温度升高,CdS与ZnS相比禁带宽度增加明显、Raman特征峰增高变窄。对此现象进行了解释,为利用CdS或ZnS薄膜作为CIGS薄膜太阳电池缓冲层提供了参考。     

一种适用于CdS薄膜太阳电池的新型填料保温蒸发源

在CdS薄膜太阳电池的工艺中,为了克服常用的蒸镀CdS多晶膜蒸发源——“直接加热坩埚源”的缺点,我们设计制作了一种新型填料保温蒸发源,取得了良好的效果。 一、填料保温源的结构和特点     

水浴温度对化学水浴法沉积CdS和ZnS薄膜性能的影响

分别采用硫酸镉、硫脲、氨水溶液体系及硫酸锌、硫脲、氨水、联氨溶液体系,以化学水浴法(CBD)制备CdS和ZnS薄膜,研究水浴温度对薄膜沉积过程及性能的影响,分析不同水浴温度下沉积得到的CdS和ZnS薄膜性能的差异。试验表明,随着水浴温度的升高,薄膜的沉积速率增大,致密度变高,薄膜的禁带宽度更接近其理论值。当水浴温度大于70℃时,CdS薄膜的沉积速率远大于ZnS;随着水浴温度的升高,CdS晶粒逐渐变小而ZnS晶粒逐渐变大,CdS薄膜中S/Cd原子比逐渐下降,而ZnS薄膜中S/Zn原子比逐渐升高;ZnS薄膜能够透过更多短波高能光子且禁带宽度大于CdS,有利于提高太阳电池的效率。     

Electrodeposited CdS on CIS pn junctions

We have been investigating the electrochemical deposition of thin films and junctions of cadmium sulfide (CdS) and copper indium diselenide (CIS). We show that it is possible to fabricate pn junctions based on n-type CdS and p-type CIS entirely by electrodeposition. CIS is considered to be one of the best absorber materials for use in polycrystalline thin-film photovoltaic solar cells. CdS provides a closely lattice-matched window layer for CIS. Electrodeposition is a simple and inexpensive method for producing thin-film CdS and CIS. We have produced both p- and n-type CIS thin films, as well as a CdS on CIS pn junction via electrodeposition. Elemental analysis of the CdS and CIS thin films was performed using X-ray photoelectron spectroscopy and energy dispersive spectroscopy. Optical band gaps were determined for these films using optical transmission spectroscopy. Carrier densities of the CIS films as a function of their deposition voltage were determined from capacitance vs. voltage measurements using Al Schottky barriers. Current vs. voltage characteristics were measured for the Al on CIS Schottky barriers and for the CdS on CIS pn junction.     

PH值对化学沉积制备CdS薄膜性质的影响

实验研究了pH值对化学沉积制备CdS薄膜性质的影响。表明：在柠檬酸钠作为络合剂的体系中随着溶液中氨水浓度的提高CdS薄膜会发生相变，从立方相变为六方相，即当氨水浓度为0．31M时，得到立方相的CdS薄膜；而当氨水的浓度大于0．51M时，得到六方相的CdS薄膜。氨水浓度的提高也使得CdS薄膜的形貌有了很大的改善，且制备得到的CdS薄膜从富CA变为富S，但是薄膜仍是n型。氨水浓度对CdS薄膜的光学性质也有很大的影响，随着氨水浓度的提高所得到的CdS薄膜的禁带宽度增大。     

Hydrogenation effect on structural,electrical and optical properties of CdS thin films for solar cell

Adsorption effects would be expected to be of considerable importance with thin films because of the changes in electron location accompanying adsorption. The effects of hydrogenation on structural, optical and electrical properties of the CdS thin films have been reported. GIXRD patterns shows that films have polycrystalline nature with a hexagonal structure. The optical band gap increased after hydrogenation of the film. The variation of conductivity of CdS films have been investigated depending upon the applied voltage at room temperature. The resistivity increased after hydrogenation of the films. Hydrogenated thin films can be used in solar cells because hydrogen plays an important role to modify the physical properties.     

Thin CdS films prepared by metalorganic chemical vapor deposition

Polycrystalline CdS thin films have been deposited on borosilicate glass substrates coated with ITO film by metalorganic chemical vapor deposition using dimethyl cadmium and diethyl sulfide as source materials. The growth of CdS film occurred at substrate temperatures within the range of 280–360°C. The deposition rate increased with increasing VI/II molar ratio at any substrate temperature and showed a maximum value at the VI/II molar ratio of 4. The grain size of as-deposited CdS film prepared at substrate temperatures from 300°C to 360°C was about 0.1 μm. The CdS films consist of hexagonal form with a preferential orientation of the (0 0 2) plane parallel to the substrate. Thin CdS film with high optical transmittance was prepared at 350°C with the VI/II molar ratio of 4. The CdS film deposited by MOCVD may be used as a window layer for CdS/CdTe solar cell.     

Modification in the chemical bath deposition apparatus, growth and characterization of CdS semiconducting thin films for photovoltaic applications

In this paper, growth and characterization of CdS thin films by Chemical Bath Deposition (CBD) technique using the reaction between CdCl₂, (NH₂)₂CS and NH₃ in an aqueous solution has been reported. The parameters actively involved in the process of deposition have been identified. A commonly available CBD system has been sucessfully modified to obtain the precious control over the pH of the solution at 90°C during the deposition and studies have been made to understand the fundamental parameters like concentrations of the solution, pH and temperature of the solution involved in the chemical bath deposition of CdS. It is confirmed that the pH of the solution plays a vital role in the quality of the CBD–CdS films. Structural, optical and electrical properties have been analysed for the as-deposited and annealed films. XRD studies on the CBD–CdS films reveal that the change in Cadmium ion concentration in the bath results in the change in crystallization from cubic phase with (1 1 1) predominant orientation to a hexagonal phase with (0 0 2) predominant orientation. The structural changes due to varying cadmium ion concentration in the bath affects the optical and electrical properties. Optimum electrical resistivity, band gap and refractive index value are observed for the annealed films deposited from 0.8 M cadmium ion concentration. The films are suitable for solar cell fabrication. Further on, annealing the samples at 350°C in H₂ for 30 min resulted in an increased diffraction intensity as well as shifts in the peak towards lower scattering angles due to enlarged CdS unit cell. This in turn brought about an increase in the lattice parameters and narrowing in the band-gap values. The results are compared with the analysis of previous work.     

Magnetic field influenced growth kinetics in chemical CdS thin-film deposition

The kinetics of growth for the deposition of CdS thin films from chemical solutions has been studied without and under the action of an external magnetic field. It has been established that the growth takes place out of a narrow near-surface transition layer between liquid and solid, where mobile ions are moved by the field, resulting in thin, adherent and specularly reflecting films. The presence of an external magnetic field affects the formation process of the CdS films in a characteristic manner, and allows to control thickness, grain size and optical quality of the grown layers. Optical transmission spectroscopy measurements reveal, that the band gap energy of 2.36 eV for films grown without the application of a magnetic field, increases to 2.51 eV for the highest field strength applied. The film thickness under otherwise identical conditions increases by about a factor of 3, while the medium grain size shrinks to almost half the value of about 70 nm found without external field action. AFM images are applied in the study, showing an improved smoothness of the films.     

Bromine doping effect on some properties of CdS films

The suitability of bromine as an anionic dopant influencing the properties of CdS thin films is discussed in this paper. The as-deposited films were characterised respectively by XRD, SEM, UV-vis-NIR spectrophotometer and two-point probe setup. All the films appear to be polycrystalline in nature exhibiting hexagonal crystal structure with a (002) preferential growth texture. The 2θ value of the (002) plane shifts towards lower Bragg angle with doping inferring an expansion in their lattice volumes. Increased transparency and blue shift in optical band gap value are observed for the doped films. Electrical resistivity decreased with increase in Br-doping concentration. Increased transparency, widened band gap and decreased electrical resistivity values achieved confirm that Br is a suitable anionic dopant that can strongly influence the physical properties of pure CdS towards future optoelectronic devices.     

Analytical characterization of cadmium cyanamide in CdS thin films and bulk precipitates produced from CBD process in pilot plant

CdS thin films and bulk precipitates were obtained by chemical bath deposition (CBD) in a well-closed reactor. X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy, thermal analysis, elemental analysis and leaching have been used to characterize solids and thin films. It has been shown that the proportion of cadmium cyanamide in solids may vary from about 50% to 2% according to physicochemical conditions in solution (time after CBD, ammonia concentration) and that CdO results from CdCN₂ after air annealing of thin films. This last step also increases the crystallinity of the films.     

Augmented photoelectrochemical response of CdS/ZnS quantum dots sensitized hematite photoelectrode

A visible light active and stable photoelectrode has been developed by depositing a passivating layer of ZnS QDs on CdS QDs sensitized hematite photoelectrode (Hematite‐CdS/ZnS) for PEC generation of hydrogen. Photoelectrochemical properties, in terms of stability and efficiency, have been investigated on the various hematite photoelectrodes sensitized with CdS QDs and CdS/ZnS QDs by varying number of SILAR cycles. I–V characteristics show that two layers of ZnS QDs deposited over three layers of CdS could enhance PEC response of hematite and efficiency by a factor of 3 and 11 respectively. Chronoamperometry measurement ensures that after adding a layer of ZnS QDs, CdS sensitized hematite film turns out to be a stable photoelectrode in the electrolyte. Prepared photoelectrodes have been characterized by XRD, SEM, HRTEM and UV–Vis spectrophotometer for various structural, morphological and optical properties to analyze PEC results. Mott–Schottky analysis and incident photon to current conversion efficiency (IPCE) measurements of sensitized hematite photoelectrode supported the improved PEC response of CdS/ZnS QDs sensitized hematite thin films. Copyright © 2016 John Wiley & Sons, Ltd.     

The effect of heteropolyacids and isopolyacids on the properties of chemically bath deposited CdS thin films

The deposition of CdS films on ITO/glass substrates from a chemical bath containing cadmium acetate, ammonia, ammonium acetate and thiourea has been carried out with and without small amounts of heteropolyacids (HPA) (phosphotungstic acid (PTA): H₃[PW₁₂O₄₀], silicotungstic acid (STA): H₄[SiW₁₂O₄₀], phosphomolybdic acid (PMA): H₃[PMo₁₂O₄₀]) and isopolyacids (IPA) (tungstic acid (TA): H₂WO₄ and molybdic acid (MA): H₂MoO₄) for different deposition times. The chemical, morphological, structural and optical properties of the films have been determined. The composition in sulphur and in cadmium of the films’ surface and volume was determined for various HPA and IPA used in the deposition bath. The HPA and IPA which give the thickest film with the biggest grain size were deduced. The optical transmission at 400 nm of CdS films deposited with STA at short time (20 min) (50%) is higher than those of CdS deposited at longer time (6 h) (7%). The optical transmission of CdS deposited with STA at short time is higher (50%) than that of CdS deposited without STA (20%). The performances of heterojunctions CdS/CdTe solar cells fabricated from CdS films deposited with and without STA and CdTe films deposited without STA have been determined. It was shown that the CdS/CdTe heterojunction solar cells fabricated from CdS films deposited with STA exhibited better photon collection efficiency and solar cell efficiency (η=6%) than CdS/CdTe heterojunction solar cells fabricated from CdS films deposited without STA (η=3.3%).