Formation and properties of cadmium sulfide buffer layer for CIGS solar cells grown using hot plate bath deposition

In the present study, cadmium sulfide (CdS) thin films were deposited on different substrates [soda glass, fluoride doped tin oxide, and tin doped indium oxide (ITO) coated glass] by a hot plate method. To control the thickness and the reproducibility of the sample production, the thin films were coated at different temperatures and deposition times. The CdS thin films were heated at 400 °C in air and forming gas (FG) atmosphere to investigate the effect of the annealing temperatures. The thickness of the samples, measured by ellipsometry, could be controlled by the deposition time and temperature of the hot plate. The phase formation and structural properties of CdS thin films were studied by X-ray diffraction and scanning electron microscopy, whereas the optical properties were obtained by UV–vis spectroscopy. A hexagonal crystal structure was observed for CdS thin films and the crystallinity improved upon annealing. The structural and optical properties of CdS thin films were also enhanced by annealing at 400 °C in FG atmosphere (95 % N₂, 5 % H₂). The optical band gap was changed from 2.25 to 2.40 eV at different annealing temperatures and gas atmospheres. A higher electrical conductivity, for the sample annealed at FG, was noticed. The samples deposited on ITO and annealed in FG atmosphere showed the best structural and electrical properties compared to the other samples. CdS thin films can be widely used for application as a buffer layer for copper–indium–gallium–selenide solar cells.     

Chemical bath deposition of CdS thin films and their partial conversion to CdO on annealing

CdS thin films prepared by chemical bath deposition technique are characterized using X-ray diffraction, optical absorption spectrometry and scanning electron microscopy. The results of the annealing studies on the films in flowing argon and air atmospheres are also presented in this paper. The resistivity has drastically reduced on annealing in flowing air which is attributed to the partial conversion of CdS to CdO phase.     

Influence of the Cd/S Molar Ratio on the Optical and Structural Properties of Nanocrystalline CdS Thin Films

Nanocrystalline CdS thin films have been deposited using precursors with different thiourea concentrationonto glass substrates by sol-gel spin coating method.The crystalline nature of the films has been observedto be strongly dependent on thiourea concentration and annealing temperature.The CdS films are found tobe nanocrystalline in nature with hexagonal structure.The grain size is found to be in the range of 7.6 to11.5 nm depending on the thiourea concentration and annealing temperature.The high resolution transmissionelectron microscopy (HRTEM) results of the CdS films prepared using cadmium to thiourea molar ratio of0.3:0.3 indicate the formation of nanocrystalline CdS with grain size of 5 nm.Fourier transform infrared (FTIR)analysis shows the absorption bands corresponding to Cd and S.The optical study carried out to determinethe band gap of the nanostructured CdS thin films shows a strong blue shift.The band gap energy has beenobserved to lie in the range of 3.97 to 3.62 eV following closely the quantum confinement dependence ofenergy on crystallite radius.The dependence of band gap of the CdS films on the annealing temperature andthiourea concentration has also been studied.The photoluminescence (PL) spectra display two main emissionpeaks corresponding to the blue and green emissions of CdS.     

Deposition of CdS thin films onto Si(111) substrate by PLD with femtosecond pulse

The effect of laser fluence (laser incident energy in the range of 0.5-1.5 mJ/pulse with the same laser spot size of 0.5 mm × 0.7 mm) on the structural quality and optical properties synthesized by femtosecond pulsed-laser deposition has been studied. The structural quality and optical properties of the deposited CdS thin films were investigated by X-ray diffraction, atomic force microscopy and photoluminescence measurement. The studies revealed an improvement in the structural quality and optical properties of the CdS thin films with increasing the laser fluence in some range. However, too high laser fluence could lead to the structural quality and optical properties of the CdS thin films to degrade. We defined the optimum laser incident energy was around 1.2 mJ/pulse. And the kinetic energy of the plasma produced by femtosecond laser strongly affects the structure and properties of the deposited CdS thin films.     

Annealing effect on structural, optical and electrical properties of pure and Mg doped tin oxide thin films

This study describes the effect of annealing at different temperatures (400–600 °C) on structural, optical and electrical behaviors of pure and Mg doped tin oxide thin films grown on the glass substrate by electron beam evaporation technique. The transformation of tetragonal to orthorhombic form due to annealing, introduced a change in the optical and electrical properties of pure and Mg doped tin oxide thin films. X-ray diffraction studies or analysis revealed the phase transformation and change in the crystalline size with increase in the annealing temperature. The morphology and roughness of the thin films were studied by Atomic force microscopy. Optical band gap increased with annealing temperature confirms the improvements of crystallinity. The quality of thin films transparency was investigated by UV/Vis-spectroscopy. Photoluminescence of pure and Mg doped tin oxide thin films shows two extra peaks one at 486 nm and other at 538 nm is due to the crystal defect created as a result of annealing temperature. These peaks became stronger and shifted to longer wavelength with increasing the annealing temperature. The complex plot (Nyquist plot) showed the data point laying on two semicircles and the resistance of grains and grain boundaries increases with the increase in annealing temperature for both pure and Mg doped tin oxide thin films.     

Structural characterization of CdS thin film on quartz formed by femtosecond pulsed laser deposition at high temperature

CdS thin films have been grown on quartz substrates using femtosecond pulsed laser deposition. The structural and optical properties of the CdS thin films were characterized by X-ray diffraction, scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. The results indicate that the compositional segregation of the CdS films could be drawn from the selective evaporation of sulfur from the film surface as a result of heating up the substrates. Growth temperature played an important role on changing crystal structure and optical properties of the CdS films.     

AlSb多晶薄膜材料的性能研究

采用共蒸法制备了新型AlSb多晶薄膜. 通过XRF、XRD、Hall测试及电导率温度关系等研究了AlSb多晶薄膜的组分、结构及性能. 分析表明,刚沉积的AlSb薄膜为非晶相,在540℃以上退火转变为AlSb相,转变的程度取决于退火的温度及Al、Sb的原子配比,其中N_Al∶N_Sb为47.2∶52.8,580℃退火后的薄膜多晶转变最为明显,结晶度较高;测试结果表明,退火后的AlSb薄膜为p型间接带隙半导体,载流子浓度为10¹⁹cm^-1,吸收系数为10⁴,而且在升降温阶段电导率发生不可逆变化. 这种薄膜用于TCO/CdS/AlSb结构的太阳电池器件中已经得到200mV左右的开路电压.     

Structural, photoluminescence and optical properties of chemically deposited (Cd1−xBix)S thin films as a function of dopant concentration

In this study, (Cd_1?xBi_x)S thin films were successfully deposited on suitably cleaned glass substrate at 60 °C temperature, using the chemical bath deposition technique. After deposition, the films were also annealed at 400 °C for 2 min in air. The structural properties of the deposited films were characterized using X-ray diffraction and AFM. Formation of cubic structure with preferential orientation along the (111) plane was confirmed together with BiS second phase from structural analysis. The interplanar spacing, lattice constant, and crystallite size of (Cd_1?xBi_x)S thin films were calculated by the XRD. The crystallite size of the un-doped CdS thin films was found to be 7.84 nm, which increased to 11.1 nm with increasing Bi content from 0 to 10 %. The surface roughness of the films was measured by AFM studies. The photoluminescence spectra were observed at red shifted band edge peak with increasing doping concentration of Bi from 0 to 5 % in the un-doped CdS thin films. The optical properties of the films are estimated using optical absorption and transmission spectra in the range of 400–800 nm using UV–VIS spectrophotometer. The optical band gap energy of the films was found to be decreased from 2.44 to 2.23 eV with the Bi content being from 0 to 5 %. After annealing, the band gap of these films further decreased.     

Studies on thin films of cadmium sulphide prepared by a chemical deposition method

A new method of chemical deposition consisting of the formation of thin films of a substance at the interface of a solution and a gas was used to form thin films of semiconducting and photoconducting CdS. The structural, electrical and optical properties of these films were studied. A special feature is the cubic zinc-blende structure of the films. A possible explanation for the optical and electrical properties of these films is given.     

Influence of (Zn + F) double doping on the structural,morphological, photoluminescence,optoelectrical properties and antibacterial activity of CdS thin films

The effects of (Zn + F) double doping on the structural, morphological, optical and electrical properties of CdS thin films is reported in this paper. Polycrystalline nature is observed for all the films. Zn-doped and (Zn + F) doubly doped CdS films exhibit a strong (0 0 2) preferential orientation similar to that of the undoped film. The (0 0 2) plane of the Zn-doped and (Zn + F) doubly doped films shift towards higher Bragg angles favoring a contraction in their lattice parameter values. Increased transparency and blue shift in optical band gap is observed for the doubly doped films. The electrical resistivity values of the undoped, Zn-doped, (Zn + F) doubly doped CdS thin films are found to be in the order of 10^?1 Ω-cm. From the obtained results it is found that the physical properties of Zn-doped CdS films got enhanced when co-doped with fluorine, and the (Zn + F) doubly doped CdS thin films seem to be a potential candidate for future optoelectronic device applications. Antibacterial activity of the as deposited films were carried against E. coli gram negative bacteria and from the zone of inhibition it is confirmed that the (Zn + F) doubly doped CdS thin films can be used as a good antimicrobial agent against pathogenic microorganisms.     

An in-situ chemical reaction deposition of nanosized wurtzite CdS thin films

Nanocrystalline CdS thin films were deposited on glass substrates by an ammonia-free in-situ chemical reaction synthesis technique using cadmium cationic precursor solid films as reaction source and sodium sulfide based solutions as anionic reaction medium. Effects of ethanolamine addition to the cadmium cationic precursor solid films, deposition cycle numbers and annealing treatments in Ar atmosphere on structure, morphology, chemical composition and optical properties of the resultant films were investigated by X-ray diffraction, field emission scanning electron microscope, energy dispersive X-ray analysis and UV-Vis spectra measurements. The results show that CdS thin films deposited by the in-situ chemical reaction synthesis have wurtzite structure with (002) plane preferential orientation and crystallite size is in the range of 16 nm-19 nm. The growth of film thickness is almost constant with deposition cycle numbers and about 96 nm per cycle.     

Structural and optical properties of CdS thin films prepared by chemical bath deposition at different ammonia concentration and S/Cd molar ratios

CdS thin films were prepared by chemical bath deposition technique using the precursors of SC(NH₂)₂, CdCl₂, NH₄Cl, NH₃·H₂O and deionized water. The obtained thin films were characterized by scanning electron microscopy, X-ray diffraction, energy dispersive spectrometer, UV–VIS specrophotometry and photoluminescence spectroscopy. The morphology, structural and optical properties of CdS thin films were investigated as a function of ammonia concentration and S/Cd molar ratios in precursors. The results reveal that morphology of CdS films change from flake like into spherical particle like, crystal structure from wurtzite structure to zinc blende structure, S/Cd atom ratios in CdS thin films increase and optical band gap E _g decrease with increasing ammonia concentration in precursors. The room temperature photoluminescence spectrum of CdS thin films shows a strong peak at about 500 nm and a weak peak at about 675 nm.     

CdS annealing treatments in various atmospheres and effects on performances of CdTe/CdS solar cells

In this work, a systematic research on CdS annealing treatments under various atmospheres had been done to understand their effects on CdS/CdTe solar cells. CdS films were prepared by a standard CBD method and annealed under various atmospheres, including Ar, Ar+H₂, O₂, Ar+S and Ar+CdCl₂. Morphological, structural, optical and chemical properties were investigated using Atom force microscope (AFM), X-ray diffraction (XRD), UV–VIS spectroscopy and X-ray photoelectron spectroscopy (XPS). Annealing treatments enhanced modifications of morphology, structure and electrical properties of CdS films. AFM showed different surface morphologies and roughnesses of CdS films annealed under various atmospheres. XRD indicated the transition of CdS films from metastable cubic structure to stable hexagonal structure after annealing treatment, especially annealed in Ar+CdCl₂. From XPS analysis, Fermi levels of CdS films shifted closer to conduction band after annealing under O₂ and Ar+CdCl₂, while the levels shifted away from conduction band under Ar+H₂ and Ar+S. The relationships between those modifications by annealing treatments and effects on the performance of solar cells were discussed. Solar cell based on CdS annealed with Ar+CdCl₂ had the best performance due to the high n-doping of CdS layer introduced by annealing process.     

Chemically deposited CdS films in an ammonia-free cadmium-sodium citrate system

In this work, we report the properties of chemically deposited CdS thin films in a cadmium-sodium citrate system. This chemical bath deposition process does not employ ammonia. We deposited four series of films at different cadmium content in the chemical bath process and determined their properties. The obtained information can be very useful for the optimization of the deposition process in order to reduce the amount of toxic chemical waste, mainly Cd-containing waste. The structural and optical properties of the CdS films were determined from X-ray diffraction, optical transmission and reflection spectroscopy and scanning electron microscopy measurements. We found that the properties of the films are very sensitive to the amount of cadmium in the deposition process. The process allows the deposition of good quality CdS thin films using 1.12, 0.84 and 0.76 mg of cadmium per milliliter of reaction solution.     

Electric field assisted growth of self-organized CdS films: size dependent structural and optical properties

This paper presents a systematic study of electric field assisted growth of self-organized cadmium sulphide (CdS) quantum dots (Q-CdS). CdS thin films of self-organized quantum dot like structure with different particle size have been successfully deposited simply by varying the concentration of surfactant in the reaction matrix. The model to describe the self-organization is also discussed. The size of CdS nanoparticles can be altered from 68 nm (corresponding to bulk) to 2 nm. The structural, optical, and morphological properties of Q-CdS films have been investigated. A blue shift has been observed in optical absorption and photoluminescence spectra. The strained growth of Q-CdS films has been observed. The microstructural strain calculated from peak broadening reveals an increase in strain with decreasing particle size. This study may provide a convenient method to deposit size selective and organized nanocrystalline semiconductor thin films.     

Comparison of cadmium sulfide thin films deposited on glass and polyethylene terephthalate substrates with thermal evaporation for solar cell applications

Cadmium sulfide (CdS) thin films have been deposited onto glass and polyethylene terephthalate (PET) substrates at room temperature with thermal evaporation in a vacuum of about 3 × 10⁻⁵ Torr for use as window materials for solar cells. Effects of substrate types on the structural and optical characteristics of the films were studied. Sets of experiments were conducted to optimize the deposition of CdS films with appropriate deposition parameters. The deposited films were analyzed with atomic force microscopy, energy dispersive X-ray, X-ray diffraction and optical transmittance measurements to determine their structural and optical characteristics. X-ray diffraction patterns confirm the proper phase formation of the CdS. PET substrate exhibited the larger roughness than that for the glass because of large particles adsorbed on the PET substrate. The average transmittance of the films PET is about 71% and increases up to 81% for glass substrate.     

磁控溅射法制备的CdS:Al薄膜的性质研究

采用Al和CdS双靶共溅射的方法, 调控Al和CdS源的沉积速率, 制备出不同Al掺杂浓度的CdS:Al薄膜。通过XRD、SEM、AFM、紫外-可见透射光谱分析、常温霍尔测试对CdS: Al薄膜的结构、形貌、光学和电学性质进行表征。XRD结果表明, 不同Al掺杂浓度的CdS:Al薄膜均为六方纤锌矿结构的多晶薄膜, 并且在(002)方向择优生长。SEM和AFM结果表明, CdS:Al薄膜的表面均匀致密, 表面粗糙度随着Al掺杂浓度的增加略有增加。紫外-可见透射光谱分析表明, CdS:Al薄膜禁带宽度在2.42~2.46 eV 之间, 随着Al掺杂浓度的增加而略微减小。常温霍尔测试结果证明, 掺Al对CdS薄膜的电学性质影响显著, 掺Al原子浓度3.8%以上的CdS薄膜, 载流子浓度增加了3个数量级, 电阻率下降了3个数量级。掺Al后的CdS薄膜n型更强, 有利于与CdTe形成更强的内建场, 从而提高太阳电池效率。用溅射方法制备的CdS:Al薄膜的性质适合用作CdTe薄膜太阳电池的窗口层。     

Variations of interlayer structure in Cu x S/CdS bilayer thin film with annealing of CdS: an ellipsometric study

Irregularities at the interface in Cu _x S/CdS thin films can be controlled by annealing CdS film prior to chemiplating. The interlayer formed on CdS films annealed at 200°C is comparatively smooth. In CdS films annealed at higher temperatures, the interlayer is rather thick and the CdS intrusions into this layer are thin. An ellipsometric technique is used for this study and the effective medium theory which is utilized to interpret the results is based on the difference in reaction rate in the grains as well as grain boundaries during chemiplating.     

化学水浴沉积时间对CdS薄膜性质的影响

采用CBD法在醋酸镉溶液体系中制备CdS半导体薄膜,通过XRD、XRF、SEM和光学透过率谱等测试手段研究了沉积时间对CdS薄膜沉积过程和性质的影响.结果表明,随着沉积时间的增加,薄膜增厚;S/Cd原子比增加,但都为富Cd的CdS薄膜;XRD研究表明,薄膜结构由立方、六方混合相向立方相转变,(111)方向成为择优生长方向;SEM研究表明,随沉积时间增加,薄膜变致密,薄膜表面出现的白色附着颗粒增多,尺寸增大;沉积时间对薄膜的光学性质也有很大的影响,随着沉积时间的增加薄膜透过率减小,而禁带宽度值增大.     

Structural,optical and magnetic properties of Ba and Ni doped CdS thin films prepared by spray pyrolysis method

Pure, Barium and Nickel doped cadmium sulphide (CdS) thin films have been coated on glass substrates at 400?°C by spray pyrolysis technique. The prepared CdS and doped CdS thin films were analysed by various measurements such as X-ray diffraction (XRD), SEM, optical and Vibrating Sample Magnetometer (VSM). X-ray diffraction measurements show that the coated pure, Ba and Ni-doped CdS thin films belong to the cubic crystal structure with orientation preferentially along (111) direction. The average crystallite size of pure, Ba and Ni doped CdS thin films were determined as 31, 33 and 45 nm, respectively. The average dislocation density (δ) and stacking fault (SF) of pure, Ba and Ni doped CdS thin films were also determined. The surface morphology and elemental analysis of the thin films were determined by scanning electron microscopy and energy dispersive X-ray spectrum (SEM with EDAX). It is observed that the optical energy bandgap has been decreased from 2.43 to 2.1 eV due to the doping Ba. The luminescence spectrum shows a strong emission peak at 517 nm in the case of pure CdS thin film and a meager red shift has been observed due to the doping. VSM studies were employed to study the magnetic behaviour of Ba and Ni doped CdS thin films.