CdS薄膜的结构特性及其对Cu(In,Ga)Se2(CIGS)薄膜太阳电池的影响

报道了CdS薄膜的CBD法沉积及其结构特性,其中的水浴溶液包括硫脲、乙酸镉、乙酸铵和氨水溶液.研究了水浴溶液的pH值、温度、各反应物溶液的浓度和滴定硫脲与倾倒硫脲等基本工艺参数对CdS薄膜结构特性的影响.其中,溶液的pH值对CdS薄膜的特性起着关键的作用.XRD图显示了随着溶液pH值的变化,薄膜的晶相由六方相向立方相转变.CdS薄膜的这两种晶相对CIGS薄膜太阳电池性能的影响不相同.c-CdS(立方相的CdS)与CIGS之间的晶格失配和界面态密度分别为1.419%和8.507×1012cm-2,而h-CdS(六方相的CdS)与CIGS之间的晶格失配和界面态密度则分别为32.297%和2.792×1012cm-2.高效CIGS薄膜太阳电池需要的是立方相CdS薄膜.     

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。     

Research on structural characteristics of large-scale CdS thin films deposited by CBD under low ammonia condition

Cadmium sulfide (CdS) buffer layers with the scale of 10 cm×10 cm are deposited by chemical bath deposition (CBD) with different temperatures and thiourea concentrations under low ammonia condition. There are obvious hexagonal phases and cubic phases in CdS thin films under the conditions of low temperature and high thiourea concentration. The main reason is that the heterogeneous reaction is dominant for homogeneous reaction. At low temperature, CdS thin films with good uniformity and high transmittance are deposited by adjusting the thiourea concentration, and there is almost no precipitation in reaction solution. In addition, the low temperature is desired in assembly line. The transmittance and the band gap of CdS thin films are above 80% and about 2.4 eV, respectively. These films are suitable for the buffer layers of large-scale Cu(In,Ga)Se2 (CIGS) solar cells.     

Cu(In,Ga)Se2太阳电池缓冲层ZnS薄膜性质及应用

在含有ZnSO4,SC(NH2)2,NH4OH的水溶液中采用CBD法沉积ZnS薄膜,XRF和热处理前后的XRD测试表明,ZnS沉积薄膜为立方相结构,薄膜含有非晶态的Zn(OH)2.光学透射谱测试表明,制备的薄膜透过率(λ＞500nm)约为90%,薄膜的禁带宽度约为3.51eV.ZnS薄膜沉积时间对Cu(In,Ga)Se2太阳电池影响显著,当薄膜沉积时间在25～35min时,电池的综合性能最好.对比了不同缓冲层的电池性能,采用CBD-CdS为缓冲层的电池转换效率、填充因子、开路电压稍高于CBD-ZnS为缓冲层的无镉电池,但无镉电池的短路电流密度高于前者,两者转换效率相差2%左右.ZnS可以作为CIGS电池的缓冲层,替代CdS,实现电池的无镉化.     

Cu(In,Ga)Se2太阳电池缓冲层ZnS薄膜性质及应用

在含有ZnSO4,SC(NH2)2,NH4OH的水溶液中采用CBD法沉积ZnS薄膜,XRF和热处理前后的XRD测试表明,ZnS沉积薄膜为立方相结构,薄膜含有非晶态的Zn(OH)2.光学透射谱测试表明,制备的薄膜透过率(λ＞500nm)约为90%,薄膜的禁带宽度约为3.51eV.ZnS薄膜沉积时间对Cu(In,Ga)Se2太阳电池影响显著,当薄膜沉积时间在25～35min时,电池的综合性能最好.对比了不同缓冲层的电池性能,采用CBD-CdS为缓冲层的电池转换效率、填充因子、开路电压稍高于CBD-ZnS为缓冲层的无镉电池,但无镉电池的短路电流密度高于前者,两者转换效率相差2%左右.ZnS可以作为CIGS电池的缓冲层,替代CdS,实现电池的无镉化.     

Control of the crystalline phase and morphology of CdS deposited on microstructured surfaces by chemical bath deposition

Chemical bath deposition (CBD) has been used extensively to deposit thin films of CdS for window layers in solar cells. The microtopography or roughness of the surface, however, can affect the quality of the film by influencing the morphology, uniformity, or crystal phase of the CdS film. Here, we have demonstrated that thin films of CdS can be successfully patterned on surfaces bearing micropillars as a model surface for roughness. The phase purity of CdS deposited on the micropillar surfaces is uniform and conformal with the formation of packed clusters on the micropillars at pH 10 that form flower-like structures at long deposition times. Smaller crystallites were observed on micropillar arrays at pH 8 with “network” like structures observed at long deposition times. Additionally, by controlling the pH of the chemical bath, the hexagonal and cubic crystal phases of CdS were both accessible in high purity at temperatures as low as 85 °C.     

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.     

不同方法及衬底类型对CdS多晶薄膜性能的影响

采用化学水浴法和磁控溅射法分别在AZO、FTO、ITO透明导电玻璃衬底上制备了CdS薄膜,利用扫描电镜、XRD以及透射光谱等测试手段,研究了两种制备方法对不同衬底生长CdS薄膜形貌、结构和光学性能的影响.研究结果表明,不同方法制备的CdS薄膜表面形貌均依赖于衬底的类型,水浴法制备的CdS薄膜晶粒度较大,表面相对粗糙.不同方法制备的CdS薄膜均为立方相和六角相的混相结构,溅射法制备的多晶薄膜衍射峰清晰、尖锐,结晶性较好.水浴法制备的CdS薄膜透过率整体低于溅射法,但在短波处优势明显.     

Cadmium sulfide thin films growth by chemical bath deposition

Cadmium sulfide (CdS) thin films have been prepared by a simple technique such as chemical bath deposition (CBD).A set of samples CdS were deposited on glass substrates by varying the bath temperature from 55 to 75 ℃ at fixed deposition time (25 min) in order to investigate the effect of deposition temperature on CdS films physical properties.The determination of growth activation energy suggests that at low temperature CdS film growth is governed by the release of Cd2+ ions in the solution.The structural characterization indicated that the CdS films structure is cubic or hexagonal with preferential orientation along the direction (111) or (002),respectively.The optical characterization indicated that the films have a fairly high transparency,which varies between 55％ and 80％ in the visible range of the optical spectrum,the refractive index varies from 1.85 to 2.5 and the optical gap value of which can reach 2.2 eV.It can be suggested that these properties make these films perfectly suitable for their use as window film in thin films based solar cells.     

CIGS薄膜太阳能电池缓冲层CdS薄膜的制备研究

目前CdS材料的制备方法有很多种,但是最常用的是化学水浴法。本文研究了浓度、反应溶液pH值、温度、沉积时间对CdS缓冲层薄膜的影响,对CIGS薄膜太阳能电池缓冲层CdS薄膜的制备方法进行了论述。     

Identification of the impurity phase in chemically deposited CdS thin films

Identification of the impurity phase present in chemically deposited CdS thin films and in the precipitate used for screen printing CdS/CdTe solar cells is reported in this paper. X-ray diffraction (XRD) studies of the films and the precipitate showed that the impurity phase is a mixture of cadmium oxide sulphate (Cd₃O₂SO₄) and cadmium oxide (CdO). Analysis of the films and the powders obtained using thiourea (TU) and thioacetamide (TA) as sulphursing agents showed that the impurity phase is predominantly present when TU is used in the chemical bath. The high conductivity shown by chemically deposited CdS films (using TU) when annealed at higher temperatures in air is attributed to the predominance of the conducting CdO phase in the film.     

High Performance PbS Colloidal Quantum Dot Solar Cells by Employing Solution‐Processed CdS Thin Films from a Single‐Source Precursor as the Electron Transport Layer

CdS thin films are a promising electron transport layer in PbS colloidal quantum dot (CQD) photovoltaic devices. Some traditional deposition techniques, such as chemical bath deposition and RF (radio frequency) magnetron sputtering, have been employed to fabricate CdS films and CdS/PbS CQD heterojunction photovoltaic devices. However, their power conversion efficiencies (PCEs) are moderate compared with ZnO/PbS and TiO₂/PbS heterojunction CQD solar cells. Here, efficiencies have been improved substantially by employing solution‐processed CdS thin films from a single‐source precursor. The CdS film is deposited by a straightforward spin‐coating and annealing process, which is a simple, low‐cost, and high‐material‐usage fabrication process compared to chemical bath deposition and RF magnetron sputtering. The best CdS/PbS CQD heterojunction solar cell is fabricated using an optimized deposition and air‐annealing process achieved over 8% PCE, demonstrating the great potential of CdS thin films fabricated by the single‐source precursor for PbS CQDs solar cells.     

The influence of bath composition on the photocurrent response and morphology of chemically deposited CdS thin films

The influence of the chemical bath composition on the photocurrent response, film morphology and optical transmittance of chemically deposited CdS thin films is reported. The bath parameters such as concentrations of triethanolamine, thiourea, ammonia and cadmium acetate and the bath temperature controlled the photosensitivity, photocurrent decay, morphology and optical transmittance of the films. The optimum concentration of the bath for getting good-quality photosensitive films with good optical transmittance was identified in this investigation.     

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。     

Effect of bath temperature on the properties of CuInxGa1-x Se2 thin films grown by the electrodeposition technique

Electrodeposition is a promising and low cost method to synthesize CulnxGa1-xSe2 (CIGS)thin films as an absorber layer for solar cells. The effect of bath temperature on the properties of CIGS thin films was investigated in this paper. CIGS films of 1 μm thickness were electrodeposited potentiostatically from aqueous solution, containing trisodium citrate as a complexing agent, on Mo/glass substrate under a voltage of-0.75 V, and bath temperatures were varied from 20 to 60 ℃. The effects of bath temperature on the properties of CIGS thin films were characterized by X-ray diffraction (XRD) and scanning electron microscopy. XRD revealed the presence of the CuIn0.7Ga0.3Se2 phase, the optimal phase for application in solar cells. The grain dimensions and crystallizability increase along with the increase of the bath temperature, and the films become stacked and homogeneous. There were few changes in surface morphology and the composition of the films.     

Characterization and antibacterial capabilities of nanocrystalline CdS thin films prepared by chemical bath deposition

Antibacterial capabilities of nanocrystalline cadmium sulfide (CdS) thin films have been developed against Gram-positive and Gram-negative bacteria in dark and sunlight at 60 °C. For this purpose, a strain of Gram-positive Staphylococcus aureus, and two strains of Gram-negative bacteria (Pseudomonas aeruginosa, and Escherichia coli) were used. The nanocrystalline CdS thin films have been prepared using a chemical bath deposition (CBD) method at different thicknesses (50, 80 and 100 nm). The different deposition parameters including the speed of rotation of substrate, temperature of chemical bath, pH of solution and time of the deposition were optimized. The Polyvinylpyrrollidone (PVP) was successfully used as capping agent in order to stop the agglomeration in the CdS thin films. It was found that, CdS thin films have remarkable antibacterial activity in dark and sunlight and it could be applied as antimicrobial agent in medical field. In order to confirm the crystalline structure of CdS thin films, the polycrystalline nature of the deposited CdS thin films with hexagonal structure was obtained. Furthermore, the structural parameters including lattice parameters, cell volume, the space group, average grain size, dislocation density and the strain have been calculated. The topography and surface roughness of the CdS thin films have been studied before and after the bacteriostatic effect using Scanning Electron Microscopy (SEM). Furthermore, the compositions of nanocrystalline CdS thin films have been evaluated using Energy Dispersive X-ray emission (EDX) and a Transmission Electron Microscope (TEM). Based on the optical measurements in the range of 300–2500 nm, the band gap energy of the prepared CdS thin films was found to be 2.4 eV.     

Compositional engineering of chemical bath deposited (Zn,Cd)S buffer layers for electrodeposited CuIn(S,Se)2 and coevaporated Cu(In,Ga)Se2 solar cells

A comparative study of chemical bath deposition (CBD) of ZnS, CdS, and a mixture of (Cd,Zn)S buffer layers has been carried out on electrodeposited CuIn(S,Se)₂ (CISSe) and coevaporated Cu(In,Ga)Se₂ (CIGS) absorbers. For an optimal bath composition with the ratio of [Zn]/[Cd] = 25, efficiencies higher than those obtained with CdS and ZnS recipes, both on co‐evaporated CIGS and electrodeposited CISSe, have been obtained independent of the absorber used. In order to better understand the (Cd,Zn)S system and its impact on the increased efficiency of cells, predictions from the solubility diagrams of CdS and ZnS in aqueous medium were made. This analysis was completed by in situ growth studies with varying bath composition by quartz crystal microbalance (QCM). The morphology and composition of the films were studied using scanning electron microscopy (SEM) and X‐ray photoelectron spectra (XPS) techniques. Preliminary XPS studies showed that films are composed of a mixture of CdS and Zn(O,OH) phases and not a pure ternary Cd_{1 − x}Zn_xS compound. The effect of the [Zn]/[Cd] molar ratio on properties of the corresponding CISSe and CIGS solar cells was investigated by current voltage [J(V)] and capacitance voltage [C(V)] characterizations. The origin of optimal results is discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

太阳电池中CdS薄膜的制备及其性能的研究

分别采用化学池沉积(CBD)和真空蒸发法,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)等方法对沉积膜进行了测试分析,同时阐述了两种不同方法下CdS膜的生长沉积机制。     

A study of the physical properties of sprayed CdS thin films

CdS films have been prepared by spray pyrolysis and characterized by several methods. The spray solution is made of cadmium chloride or cadmium acetate and thiourea. Optical and compositional properties and structure of the CdS films have been investigated. An analysis of the film's structure, preferred cyrstallographic orientation and presence of impurity phases have been obtained using X-ray diffraction technique as well as infrared spectroscopy. The visible absorption measurements have been carried out for the study of the impurity phases. Quantitative Auger analysis shows the composition of the spray solution and a post-spray heat treatment have also been investigated.     

ZnS thin films deposition by thermal evaporation for photovoltaic applications

ZnS thin films were deposited on a glass substrate by thermal evaporation from millimetric crystals of ZnS.The structural, compositional and optical properties of the films are studied by X-ray diffraction, SEM microscopy, and UV-VIS spectroscopy.The obtained results show that the films are pin hole free and have a cubic zinc blend structure with (111) preferential orientation.The estimated optical band gap is 3.5 eV and the refractive index in the visible wavelength ranges from 2.5 to 1.8.The good cubic structure obtained for thin layers enabled us to conclude that the prepared ZnS films may have application as buffer layer in replacement of the harmful CdS in CIGS thin film solar cells or as an antireflection coating in silicon-based solar cells.