Properties Of Cadmium Sulfide Thin Films Research Articles

Gamma radiation effect on the structural and optical properties of CdS thin films prepared by spray pyrolysis technique

One way to increase the solar cell efficiency is to increase the range of transmitted visible light throughout the window layer. This could be achieved via broadening its band gap; an aim that could be attained through doping and/or irradiation technique. In this way, cadmium sulfide (CdS) thin films have been successfully prepared on pre-heated glass substrates at 400 °C by spray pyrolysis technique and the effect of gamma radiation dose on the structural and optical properties of CdS thin films has been investigated in the range of 250 to 450 Gy. The XRD results manifest the formation of hexagonal phase of CdS with a crystallite size of 58.73 nm, which decreased to 47.26 nm after exposure to 350 Gy. Also, the SEM micrographs show the formation of some randomly oriented groups of nano-rods on the surface of highly condensed nanorods of CdS thin film. The optical investigation illustrates that a blue shift in the optical gap from 2.4 to 3.34 eV has been occurred as the radiation dose reached 350 Gy. The sensitivity of the films to the applied dose has approached 0.005 eV/Gy. Moreover, the shifted band gap exhibited less fading up to 74 days.

Impact of post-deposition annealing on the optical, electrical, and structural properties of CdS thin films for solar cell applications

In this study thermally evaporated cadmium Sulfide (CdS) thin films with the thickness of 100 nm were fabricated at 150 °C under the pressure of 2 × 10−5 mbar and subjected to annealing treatment at various temperatures. The optical, electrical, and structural properties of CdS thin films, which were influenced by annealing treatment, were then studied using ultraviolet–visible (UV–Vis) spectroscopy, Hall effect measurement system, X-ray diffraction (XRD), Raman spectroscopy and Atomic force microscopy (AFM) analysis. The energy band gap was found to decrease from 2.402 eV for the as-grown CdS film to 2.250 eV for the film annealed at 450 °C. The electrical parameters of CdS thin films, such as carrier concentration, resistivity and mobility, were then calculated using the Hall effect measurement system; these were improved with the increase of the annealing temperature up to 350 °C. The crystallite size of the preferred (111) orientation was in the range of 12–40 nm and increased with annealing temperature. The increase in the intensity of peaks and shifting peaks toward the single-crystal mode was observed in the Raman spectra of the annealed CdS thin films. The AFM images also revealed that the film roughness increased with heat treatment. Further, the obtained SEM images showed the uniform surface of the film. The efficiency of the designed solar cell was in the range of 21.84–22.18 %; it was increased by using the annealed CdS films. The present work, thus, introduced the annealed CdS thin film at 350 °C as a promising window layer to fabricate highly efficient CdTe-based solar cells.

To Study the Cadmium Sulphide Thin Films Synthesis by Simple Spin Coating Method for Energy Application

The paper examines the properties of CdS thin film, which is used for window material of solar cells and optical devices. The cadmium sulfide (CdS) thin film was prepared by sol-gel method on glass and ITO substrate. Prepared thin film dried in a vacuum oven at 70℃. Thin film and powder of CdS characterized for structural, optical, and electrical properties by X-ray Diffractometer (XRD), UV-Visible spectrometer, and Keithley spectrometer. The average crystallite sizes, microstrain, and dislocation density of the samples were calculated by the Debye Scherrer formula. The optical band gap of CdS calculated by the Tauc-plot method and obtained 2.40 and 2.41eV for powder and film. The absorption wavelength of CdS is suddenly decreased near 280nm and becomes flat in the higher wavelength region. The FTIR spectrometer is used to identification of unknown materials and bond formation. The bond formation, imperfections, and impurities were observed by the PL spectrometer. Keithley spectrometer is used for I-V characteristics and calculates electrical resistivity by Ohms law.

Comprehensive Analysis of CdS Ultrathin Films Modified by the Substrate Position inside the Reactor Container Using the CBD Technique.

The cadmium sulfide (CdS) n-type semiconductor is one of the most used as a window layer in thin-film solar cells, such as CdTe, CIS, CIGS, and CZTS. Optoelectronic properties are the most important characteristics for window materials. CdS thin films obtained using the chemical bath deposition technique (CBD) have been reported; however, large amounts of precursor solutions are used, which generate considerable amounts of toxic waste. The aim of this work is to reduce the amount of precursor solutions used for CdS growth; for this, it is necessary to consider an efficient position for the substrate inside the reactor container and at the same time allow obtaining CdS thin films with adequate physical properties to be applied in the photovoltaic solar cell development. CdS thin films were deposited on soda-lime/SnO2:F substrates (FTO) using the CBD technique; the substrates were placed in three different arrangements [rack system, step system (up), and step system (down)]. CdS samples with areas of 4 cm2 and a thickness of 27-48 nm were obtained; the X-ray diffraction patterns show CdS thin films with different polycrystalline structures. The morphological measurements reveal different surface formations depending on the substrate position, and resistivity values of around 105 Ω*cm were measured. UV-vis spectra show transmittance values of around 45-94% in the visible region with band gap energy values of around 2.1-2.36 eV. The best physical properties of CdS thin films and an efficient CBD process were obtained when the FTO substrates were located near the bottom of the reactor container with the FTO side down, leading to an optimal configuration that allows reducing the amount of precursor solutions and in this way reduces the toxic waste generated. These results are important in the photovoltaic technology process and environmental impact.

Structural, surface morphological and optical properties and their correlation with the thickness of spin coated superior quality CdS thin film synthesized using a novel chemical route

Cadmium sulfide (CdS) is considered as a superior buffer/window layer in thin-film solar cells apart from its various applications. The thickness of the buffer/window layer that defines the interface between the absorber layer is very important and needs to be thoroughly investigated for optimized device performance, particularly when a novel synthesis route and deposition technique is used. This manuscript presents the investigation on the various structural, morphological, and optical parameters and their correlation with the thickness of CdS thin film synthesized using a novel thiol-amine cosolvent with the help of Triton-X 100 surfactant. Spin coating technique is used to deposit CdS thin-films having thicknesses ranging from 100 to 300 nm on a glass substrate. X-ray diffraction (XRD) exposed the polycrystalline nature of the CdS films. All the diffraction peak intensities were found to increase with the thickness. Structural parameters like dislocation density, lattice strain, and crystallites per unit area calculated from the XRD data were found superior to those parameters for CdS films synthesized through various chemical routes, and the parameters indicated a positive correlation of the degree of crystallinity on the thickness. Similarly,surface morphology and optical properties of CdS films that were investigated by the scanning electron microscope (SEM) and UV–VIS spectrophotometer, were also dependent on film thickness. These results show that CdS thin film with superior crystallinity can be synthesized using thiol-amine cosolvent along with the Triton-X 100 surfactant and deposited by low-cost spin-coating on glass substrate. Moreover, the thickness variation appeared to be a single tool for obtaining application-specific various properties of CdS thin-film.

Effect of Cd/S ratio on growth and physical properties of CdS thin films for photosensor application

In the present work, we have successfully deposited cadmium sulfide (CdS) thin films with quantum dot size on a silica glass substrate by using simple and commercial chemical bath deposition (CBD) with varying the concentration of the solution at ~ 50 °C bath temperature, where we found that the deposition parameters such as the precursor ratio of cadmium and thiourea strongly influence the morphology, physical properties, and photoresponse. There has been a disparity in the proportion of the equivalent elements of the precursors, where the stoichiometric ratio of Cd/S of the precursor was changed, which allows us to understand more about the conditions and influences on growth. There was a match when comparing standard Joint Committee on Powder Diffraction Standards (JCPDS) data with the study of X-ray diffraction and confirming the formation of a hexagonal crystal structure for CdS where is observed the size of the crystal varied and it was found that the estimated average of the CdS varied with the varying concentration and resulted in the least crystallite size of ~ 2.9 nm for the ratio of 0.01 M for cadmium and 0.02 M for sulfur. The field emission scanning electron microscopy (FE-SEM) images show the formation of nanosheets having micrometer-sized petals which got uniformity with varying Cd/S ratio. It can be seen absorption spectra near band edge ~ 400 nm with a slight deviation and presence of an excitonic peak for all samples with an estimated bandgap of CdS Quantum Dot (QD) thin films found to be varying from ~ 3.124 to ~ 3.11 eV. The photosensitivity was calculated for all CdS QD thin films and it was found that the photosensitivity increases with an increase in the Cd/S ratio.

Effect of diode laser on physical properties of CdS thin films

In this study, Cadmium Sulphide (CdS) thin films are deposited on glass substrates by means of Spray Pyrolysis method to examine the influence of electromagnetic and optical features of these films by diode laser . Accordingly, samples are feasibly irradiated by laser pointer with a power of 500 mw and a wavelength of 532 nm at distance of 10 cm from the source during dissimilar exposure times of 10, 20, 30, 40, 50, 60, 70 and 80 minutes. The absorbance spectrums have been measured by UV-visible spectrophotometer under range of 190-1100 nm. Optical parameters such as transmission, reflection, absorption coefficient (α), extinction coefficient (K), optical band gap (Eg), refractive index (n), and complex dielectric constants were evaluated from absorbance spectra. The results shows that the laser pointer irradiation cause decreased in transmittance (T), reflectance (R), absorption coefficient α, the extinction coefficient (K), refractive index (n) and the real and imaginary parts of dielectric constant and decrease in the value of the energy gap (Eg). In study of FTIR-spectrum of CdS films in different ratio of irradiation times, there was no change in the peak positions just bigger or smaller with increase in times of irradiation.

The effects of the metal acetate on the deposition and properties of the cadmium sulfide thin films grown by chemical bath deposition technique

Cadmium sulfide (CdS) thin film is one of the important wideband gap semiconductor materials, which has the important applications in solar cells and photocatalysis. In this paper, chemical bath deposition was used to prepare the CdS thin films on glass substrates, while metal acetate was added to adjust the properties of thin film. Some characterization techniques were used to study the microstructure, optical properties of CdS thin films. X-ray diffraction, x-ray photoelectron spectroscopy, Raman and other results showed that metal in metal salts did not exist as impurities in CdS thin film. And, CdS thin film prepared by chemical bath deposition with metal acetate is amorphous thin films. Transmission spectrum showed that the transmittance of CdS films without additives was relatively low. When the concentration of additives increased, the transmittance in the visible region increased obviously, and the absorption edge blue shifted obviously. Photoluminescence spectroscopy showed that there were two emission peaks in CdS thin films, and the presence of additives can adjust the ratio of intensity for the two emission peaks. Finally, the role of additives in the deposition process was analyzed in detail.

ZnxCd1-xS thin films: A study towards its application as a reliable photodetector

Abstract A reliable and stable photodetector shows enormous potential applications in health monitoring, intelligent wearable devices, and biological sensing. The noble opto-electrical properties of cadmium sulfide (CdS) makes it a favorable semiconductor for opto-electrical devices. The properties of CdS thin film can further be enhanced by alloying it with zinc sulfide (ZnS) to form ZnxCd1-xS compound semiconductor. Herein, a high performance, ZnxCd1-xS (x = 0, 0.15, 0.30, and 0.45) photodetector with good stability is designed and fabricated via a simple vacuum thermal evaporation technique. The various photodetector parameters of the ZnxCd1-xS films were investigated as a function of its composition. Among the various compositions of the ZnxCd1-xS thin films, the Zn0.15Cd0.85S films displayed excellent photosensitivity as high as 2.22 which is ~1.6 times higher than that of undoped CdS thin films. The research data suggests that a high-performance single layer ZnxCd1-xS photodetector with good stability and reproducibility can be fabricated using a thermal evaporation technique.

Structural, chemical and electrical properties of CdS thin films fabricated by pulsed laser deposition using varying background gas pressure

The present study outlines the evolution of the composition, strain and electrical properties of cadmium sulfide (CdS) thin films deposited via pulsed laser deposition (PLD), under varied chamber pressure ranging from 0.13 to 13.33 Pa. The CdS thin films presented a hexagonal crystalline structure at the various deposition pressures as well as improved crystallinity at higher deposition pressures. The electrical resistivity of the resulting films ranged from 10−1 to 107 Ω-cm for deposition pressures of 2.66 to 10.66 Pa. Such a change is closely related to stoichiometry variations in the CdS films, which comprise an excess of Cd compared to S. This change in chemical composition is accompanied by an increase in deposition rate, a decrease in electrical resistivity and grain size, and a broadening of the longitudinal optical (LO) Raman peak, which indicates structural disorder in the CdS films. This disorder is attributed to defects in the crystalline lattice that manifest as a cadmium excess and/or sulfur vacancy left by the evaporated material at low deposition pressures, due to the increased kinetic energy of depositing species during PLD and the desorption of sulfur.

Structural, electrical and optical properties of CdS thin films and the effect of annealing on photoconductivity

Cadmium sulfide (CdS) thin films with n-type semiconductor characteristics were prepared by flash evaporating method on glass substrates. Some films were annealed at 250 oC for 1hr in air. The thicknesses of the films was estimated to be 0.5µ by the spectrometer measurement. Structural, morphological, electrical, optical and photoconductivity properties of CdS films have been investigated by X-ray diffraction, AFM, the Hall effect, optical transmittance spectra and photoconductivity analysis, respectively. X-ray diffraction (XRD) pattern shows that CdS films are in the stable hexagonal crystalline structure. Using Debye Scherrerś formula, the average grain size for the samples was found to be 26 nm. The transmittance of the samples was determined from optical trasmittance spectra. It is observed that the direct band gap energy for as deposited and annealed films are (2.55, 2.45) eV, respectively. The effect of annealing at 250 oC for 1hr in air on optical and photoconductivity of films under various intensity of illuminations (43.81 and 115.12) mW/cm2 was studied. The dark and photocurrents of the annealed films were found to be greater than that of as deposited.

Study Influence of Substrate Temperature on Optical Properties of CdS Thin Films Prepared by Chemical Spray pyrolysis

This study aims to prepare Cadmium Sulphide (CdS) thin films using thermal Chemical Spray Pyrolysis (CSP) on glass of different temperatures substrate from cadmium nitrate solution. Constant thickness was (430 ± 20 nm) and the effect of substrate temperature on the optical properties of prepared thin films.
 Optical properties have been studied from transmittance and absorbance spectral within wavelengths range (360 - 900 nm). The results show that all the prepared films have a direct electron transitions and optical energy gap between (2.31-2.44 eV). They also show that the transmittance and optical energy gap of films prepared from nitrate solution increase with increasing of substrate temperature, then transmittance start downward with the continued increase in temperature (400, 450) oC.

Synthesis and characterization of CdS window layers for PbS thin film solar cells

Window layers, cadmium sulfide (CdS) thin films were synthesized on tin doped indium oxide coated glass substrates (ITO) with two different temperatures of 85 °C and 90 °C and ammonium hydroxide concentration of 1 M and 9.96 M, respectively via the chemical bath deposition (CBD) method, while absorption layers, lead sulfide (PbS) thin film were deposited on ITO substrates at room temperature using the successive ionic layer absorption and reaction (SILAR) technique. Then, these layers were integrated in ITO/CdS/PbS/Ag solar cell structures. The structural, morphological and optical properties of the thin films as well as electrical properties of the solar cells were investigated. X-ray diffraction studies showed that the CdS thin films have hezagonal structure while PbS thin films have cubic structure. The photovoltaic performance of the solar cells showed that the solar cell fabricated with CdS film deposited at 90 °C exhibited higher efficiency (η) of 4.85% including JSC = 12.44 mA cm−2, VOC = 1 V, FF = 0.39 than the CdS film deposited at 85 °C (η = 3.59%, JSC = 9.43 mA cm−2, VOC = 1 V, FF = 0.38. These results reveal that the crystal structure, surface morphology and optical properties of CdS thin film have a significiant effect on device performance and the solar cell fabricated using CdS film deposited at 90 °C shows better photovoltaic performance.

Optical and structural properties of CdS thin films prepared using electro-deposition technique

Cadmium Sulfide (CdS) thin films were electrodeposited successfully on to Indium Tin Oxide (ITO) coated glass substrates from an aqueous solution of pH 1.4 containing 0.3M CdCl2 and 0.03M Na2S2O3 or Thiourea with the aim of using in CdS/CdTe solar cells. Properties of CdS thin films prepared at different deposition voltages, deposition time periods, deposition temperatures and annealing temperatures were investigated using the current-voltage (I-V) plots. It was found that good quality CdS layers were formed under the deposition conditions of -1.13V for a period of 45 minutes in a solution of temperature at 46 oC. The performance of the CdS layers was improved significantly after annealing the samples at 400 oC for a period of 20 min. The properties of CdS thin films prepared by two and three electrode configurations and using two different electrolytes were compared using the current-voltage plots. It was found that there is a significant improvement of photocurrent of the samples prepared with two electrodes in Thiourea as the S source in comparison with the samples prepared with Na2S2O3. The analysis of XRD spectra showed the hexagonal crystal structure of CdS films confirming the quality of the films prepared by this method. In addition, absorption spectra showed band gap value of 2.42 eV proving that the samples were of good quality. Atomic Force Microscopy (AFM) analysis showed that the roughness values of CdS samples were in the range of 10-15 nm. Film thicknesses of the samples were in the range of 175-225 nm according to the optical profilometric data. Keywords. Cadmium sulfide, electrodeposition, electrolyte, two-electrode, photocurrent.

Self-cleaning lanthanum doped cadmium sulfide thin films and linear/nonlinear optical properties

A high quality lanthanum (La) doped cadmium sulfide (CdS) thin films were synthesized onto a glass substrates by chemical bath deposition. The effects of lanthanum doping concentration on the composition, structural and optical properties of CdS thin films have been studied. The transmittance of CdS thin film is 80% and gradually decreased as the La content was increased. Analysis of the optical absorption coefficient of CdS and La doped CdS thin films revealed that a presence of direct optical transition and the optical direct band gap of the films apparently decreased from 2.45 to 2.09 eV when the lanthanum content was increased from 0 to 12 wt %. The values of optical and electrical conductivity of CdS and La doped CdS thin films have been increases with increasing the lanthanum content. The self cleaning test shows that 12% La doped CdS thin films have excellent photocatalytic activity.

Structural, optical and impurity-absorption properties of CdS thin films deposited by a chemical bath using four cadmium sources

This study examines the effects of four cadmium sources on the properties of cadmium sulfide (CdS) thin films prepared using chemical bath methods. The reaction solutions used cadmium acetate, cadmium sulfate, cadmium iodide and cadmium chloride as cadmium sources. The surface morphology, crystal structure, optical properties and impurities absorption of CdS films were analyzed. The CdS films deposited with different Cd sources showed similar crystalline structures and surface morphologies. In addition, the Cd film band gaps differed unobviously. Measurements made with Fourier transform infrared spectrum showed that CN bonds were the main impurities absorbed in the CdS films. After the CdS films had been annealed at 120 °C in air, the CN peak intensity for cadmium acetate, cadmium sulfate and cadmium chloride decreased while the CN peak intensity for cadmium iodide increased. We found that the performance of a copper indium gallium selenide (CIGS) solar cell was influenced by the Cd sources; this was especially true for the fill factor (FF). Higher values of CN bonds absorption yielded lower values of FF and conversion efficiency of CIGS solar cells. Among the four tested Cd sources, cadmium acetate and cadmium sulfate proved much more suitable as Cd sources for depositing CdS thin films.

Influence of (Ar + O2) atmosphere and CdCl2 coating heat treatment on physical properties of CdS thin film for solar cell applications

Cadmium sulphide (CdS) thin films have been grown on corning glass substrate by thermal evaporation technique under base pressure 2 × 105 mbar. In this study we investigate the influence of Cadmium chloride (CdCl2) heat treatment and argon and oxygen (Ar + O2) annealing on the structural, morphological optical and electrical properties of CdS thin films to achieve high quality thin films for solar cells applications. X-ray diffraction (XRD), Field Emission scanning electron microscope (FE-SEM) and UV–Vis-NIR spectrophotometer were used to confirm and investigate the different physical properties of CdS films. The quality of CdS thin films crystallinity including the average grain size (Davg), the average lattice strain (εls) and the dislocation density (ρD) were extracted via XRD line broadening analysis. XRD analysis revealed that the samples are polycrystalline in nature with a mixed (hexagonal + cubic) structure and the crystallinity of the films increases with both (Ar + O2) annealing and CdCl2 heat treatment. After (Ar + O2) annealing and CdCl2 heat treatment processes the mean values of the grain size indicating the grain growth of CdS films. The surface morphology of the CdS films was examined by (FE-SEM) analysis; which confirmed the nano-crystalline nature of the CdS films with uniform coverage of the substrate surface; The optical properties of as-deposited, (Ar + O2) annealed and CdCl2 treated CdS films were discussed in detail. The optical energy gap was calculated using Tauc plot extrapolation. It was found to be increased from 2.43 eV for as-deposited film to 2.45 for CdCl2 treated CdS film. Swanepoel method was employed to estimate the thicknesses and extract the refractive index of the CdS films. The Room temperature resistivity decreased from 13.4 Ω cm for as-deposited CdS film to 2 and 0.8 Ω cm for (Ar + O2) annealed and CdCl2 treated CdS films respectively. The CdCl2 treated CdS film has the highest figure of merit value of 29 × 10−4 Ω−1. The obtained results confirm that the CdCl2 heat treatment process in (Ar + O2) atmosphere can enhance the physical properties of CdS thin films as a promising window layer or buffer layer material for CdS/CdTe and Cu(In,Ga)Se2 solar cells.

Effects of bacteria on CdS thin films used in technological devices

Cadmium sulfide (CdS) thin films were fabricated on glass substrates by the chemical bath deposition method at considering deposition times ranging from 2 h to 5 h. The optical band gaps of CdS thin films were found to be in the 2.42–2.37 eV range. CdS thin films had uniform spherical nano-size grains which had polycrystalline, hexagonal and cubic phases. The films had a characteristic electrical resistivity of the order of and n-type conductivity at room condition.CdS thin films were incubated in cultures of B.domonas aeruginosa and Staphylococcus aureus, which exist abundantly in the environment, and form biofilms. SEM images showed that S. aureus and K. pneumonia were detected significantly on the film surfaces with a few of P. aeruginosa and B. subtilis cells attached. CdS thin film surface exhibits relatively good resistance to the colonization of P. aeruginosa and B. subtilis. Optical results showed that the band gap of CdS thin films which interacted with the bacteria is . The crystal structure and electrical properties of CdS thin films were not affected by bacterial adhesion. The antimicrobial effect of CdS nanoparticles was different for different bacterial strains.

Optimization of substrates and physical properties of CdS thin films for perovskite solar cell applications

The physical properties of cadmium sulfide (CdS) thin films have been optimized using different substrates for perovskite solar cell applications as electron-transport layer. The films were deposited by electron beam evaporation on glass, fluorine doped tin oxide (FTO), indium tin oxide and silicon wafer (n-type) and characterized by different respective tools. XRD results show that the films have cubic zinc blende structure with (111) as preferred orientation for all substrates and the calculated crystallographic constants are also discussed. The direct band gap is found 2.41 eV for the films deposited on FTO substrates which is suitable for electron-transport layer in perovskite solar cells due to its good conductivity, crystallinity and an appropriate conduction band level. The electrical studies show that the characteristic behavior is almost linear in both the directions and the conductivity is found to maximum for FTO substrate. The films are also found to be homogeneous, smooth, uniform and free from crystal defects as revealed by SEM studies.

Investigation of annealing temperature effect on magnetron sputtered cadmium sulfide thin film properties

Cadmium sulfide (CdS) thin films are deposited on the fluorine doped tin oxide coated glass substrate using the radio frequency magnetron sputtering setup. The effects of annealing in air on the structural, morphological, and optical properties of CdS thin film are studied. Optimal annealing temperature is investigated by annealing the CdS thin film at different annealing temperatures of 300, 400, and 500 °C. Thin films of CdS are characterized by X-ray diffractometer analysis, field emission scanning electron microscopy, atomic force microscopy, UV–Vis–NIR spectrophotometer and four point probe. The as-grown CdS films are found to be polycrystalline in nature with a mixture of cubic and hexagonal phases. By increasing the annealing temperature to 500 °C, CdS film showed cubic phase, indicating the phase transition of CdS. It is found from physical characterizations that the heat treatment in air increased the mean grain size, the transmission, and the surface roughness of the CdS thin film, which are desired to the application in solar cells as a window layer material.