Cadmium Sulfide Thin Films Research Articles

Electrical Characterization of Chemically Grown CdS and CdTe Thin Films for Solar Cell Application

Thin films of Cadmium Sulphide (CdS) and Cadmium Telluride (CdTe) have gained a great deal of interest due to their potential applications in solar cells. Deposition of CdS and CdTe thin films were performed on Soda Lime glass and FTO substrate at 400℃ and 300℃ respectively using spray pyrolysis technique. The Hall Effect property was measured for the deposited CdS and CdTe films. These results shows the resistivity and mobility of CdS films deposited at 400℃ were 1.588×104 Ωcm and 5.619×102 cm2/Vs, respectively, The annealed CdTe thin film had a resistivity value of 1.016×104 Ωcm, while the annealed and etched CdTe thin film had a resistivity value of 4.52×104 Ωcm, The resultant films are observed to be good to make a solar cell with CdS as a window layer and CdTe as absorber layer.

Morphology and optical properties of CdS thin films prepared by Physical Vapor Deposition method

The optical properties of cadmium sulfide thin films obtained by thermal evaporation in vacuum were studied. The stoichiometric compositions of the binary compound previously synthesized from high-purity powders of the initial components were used. Films of different thicknesses deposited on a glass substrate were investigated using scanning electron microscopy and absorption coefficient was defined by the Swanepoel method. It was found that with increasing film thickness, surface formations decrease and at a thickness of 1 μm the film surface is continuous. It is determined that thin films of cadmium sulfide have optimal optical parameters for use as photovoltaic buffer layer. All the obtained films except the film with a thickness of 1215 nm show the usual interference pattern in the reflection spectra.

A comprehensive study on Co-doped CdS nanostructured films fit for optoelectronic applications

This research explores the novel photo-response properties of cobalt (Co) doped cadmium sulfide (CdS) thin films developed using a facile and cost-effective spray coating technique. The microstructural parameters were evaluated using XRD patterns and the estimated values of crystallite sizes, lattice strains, dislocation densities and induced stress were found to be in the range of 16.1–25.9 nm, 5.9 × 10−3-3.4 × 10−3, 3.8 × 10−3-1.4 × 10−3 and 3.4–1.9 (GPa) for undoped and Co:CdS films, respectively. The optical band gap energies were found to be 2.369, 2.454, 2.469, and 2.501 eV for undoped, 1 wt. %, 3 wt. %, and 5 wt. % Co: CdS films, respectively using Tauc's plots. The values of extinction coefficient (k) and refractive index (n) were observed in the range of 0.45–0.69 and 2.72–3.05 for as-prepared thin films. Photocurrent (Iph)-applied voltage (V) characteristic of the prepared thin films was measured under visible light condition of low power densities (0.15, 0.25, 0.50, 1.57, 2.50 and 5.0 mW/cm2). A remarkable photosensitivity of 0.165–8.842 × 103 (mW/cm2) at 5.0 mW/cm2 was observed. Saturated surface resistivity of as-prepared thin films was measured for pure CdS, which decreases by increasing Co content. External quantum efficiency (EQE) and Detectivity (DET) were enhanced with Co contents. The values of EQE and DET were found to be 1.0 × 103-2.47 × 1012 and 9.88 × 1012 -2.41 × 1012 for 5.0 wt. % Co: CdS films, respectively at power densities (0.15, 0.25, 0.50, 1.57, 2.50 and 5.0 mW/cm2). Our findings proposed the major role of such prepared films in the fabrication of advanced photodetectors suitable for optoelectronic devices developments.

Grain growth in thermally evaporated CdS thin films: An approach to MgF2 activation for window layer applications

• Grain growth evolution is undertaken in CdS films by MgF 2 activation. • Films are crystallized along cubic phased (2 2 0) plane with increased band gap. • Surface roughness is varied with treatment and films showed Ohmic behavior. • PL peak at ∼685 nm owing to surface states and morphology demonstrated grain growth. • Findings warrant that films activated at 200 °C could be applied as window layer. Cadmium sulfide (CdS) is an attracting window layer material to Cadmium telluride (CdTe) solar cells where pristine CdS thin films consist of colossal amount of native defects and grain boundaries (GBs) which behave like recombination centers and trap states and are major roadblocks in achievement of higher device performances. Typically, the influence of these defects is controlled employing post-deposition Cadmium chloride (CdCl 2 ) activation while its toxic character demands investigation of alternative eco-friendly compounds. Hence in the present study, Magnesium fluoride (MgF 2 ) activation at 100 °C, 200 °C and 300 °C temperature is carried out on thermally evaporated CdS thin films in order to seek viability of other halide composites as an activation agent. The XRD findings show that all the MgF 2 activated CdS films are polycrystalline in nature having mixed hexagonal and cubic crystalline phases with (2 2 0)C preferred reflection where intensity of this orientation is diminished with activation temperature. The crystallite size is observed to be increased from 35 nm to 39 nm, optical transmittance is found to fluctuate and the optical energy band gap of CdS films is enhanced from 2.35 eV to 2.39 eV with MgF 2 activation temperature. AFM images demonstrated hill-like topography wherein grain size is varied from 54 nm to 68 nm with activation temperature. The current voltage characteristics revealed to the development of Ohmic contacts where electrical resistivity is determined in range 4.7 × 10 1 –1.3 × 10 2 Ωcm. The intensity of photoluminescence (PL) emission peaks is found to be enhanced and the surface morphology demonstrated grain growth with maximum for 200 °C activated films. Appearance of Cd, S, Mg and F peaks in EDS patterns validated deposition of CdS films with incorporation of Mg and F into the CdS lattice. Findings demonstrated applicability of activated films at 200 °C as optical window to photovoltaic (PV) devices.

Engineering of window layer cadmium sulphide and zinc sulphide thin films for solar cell applications

The synthesis of cadmium sulfide (CdS) and zinc sulfide (ZnS) thin films materials was carried out in three electrode configurations on electrically conductive fluorine doped tin oxide (FTO) substrates. The materials were synthesized due to their wide range of applications in photovoltaic devices. Despite the potentials of the materials in heterojunction-based devices, little efforts have been made to place the materials side by side to be able to suggest the most environmentally friendly with good potentials for solar cell applications. In this paper, we synthesized and characterized the materials using electrodeposition (ED) technique for materials’ synthesis, X-Ray Diffractometer (XRD) for structural properties, Scanning Electron Microscopy (SEM) for morphological properties, Energy Dispersive X-ray (EDX) with X-Ray Fluorescence (XRF) for elemental composition and Ultraviolet Visible spectrophotometer (UV–vis) for optical properties. The XRD results show an increase in the crystallite sizes of the materials with increasing cathodic voltages from 10.30 to 15.20 nm; the SEM results show evenly distributed and adherent materials on the substrate; the EDX and XRF results show the qualitative and quantitative elements present; and the UV-vis results show a decrease in the energy band gap with increasing cathodic voltage of both CdS and ZnS thin films from 2.53 to 2.29 eV and 3.78–3.56 eV, respectively.

Swift heavy ion irradiation induced modifications in electron beam deposited CdS thin films

The field of tailoring the physio-chemical properties by the way of radiation leads to the immense opportunities in the domain of advanced photonics and optoelectronic devices. In the present contribution, 120 MeV silver ions (Ag9+) induce electronic excitations which instigate modifications in crystalline cadmium sulphide (CdS) thin films deposited via electron beam evaporation are examined. X-ray Diffraction (XRD) reveals that the peak intensity and FWHM get affected as a consequence of swift heavy ions (SHI) irradiation while crystal phase remains preserved even after irradiation. Raman analysis exhibits the asymmetry in the fundamental longitudinal optical (LO) phonon mode which is directly related to the surface defects, reduction in particle size, and amorphization after irradiation. Field emission scanning electron microscopy (FESEM) images exhibit the reduction in particle size followed by highly strained as-deposited samples get stabilize with the deposited energy. The spherical shaped nanoparticles are observed for as-deposited and irradiated films through atomic force microscopy (AFM) and also, declared the nano-grain formation as resulted from negative surface tension induced at higher fluences. Photoluminescence (PL) spectra indicate the electronic excitations inspired additional yellow band due to generation of ICd-Vcd Frenkel pair defects along with the green and red emission.

Some Physical Properties of Pure and Cu, Fe-doped CdS Thin Films

In the present work, Cadmium sulfide (CdS) and CdS doped with copper (Cu) and iron (Fe) metals thin films were deposited on glass slides using chemical bath deposition technique. 1% content of Cu and Fe were used as dopants. The films were prepared at a reaction temperature of approximately 80∘C and for an hour as the reaction time without any heat treatment. The pure and doped films were diagnosed and examined by several techniques such as X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and UV-visible spectrometry to study the effect of the doping and the type of dopant material on the surface, structural and optical properties of CdS films. From the results of XRD can be noticed there is no effect for the dopant on the type of crystal structure except small shifting in the position of main peak after doping. The bandgap energy of the Fe-doped CdS films has been found to be lower than that of the undoped films between 2.62 eV and 2.43 eV.

Highly induced photosensing behavior of Erbium (Er), Yttrium (Y) and Terbium (Tb) doped nanostructured Cadmium Sulphide (CdS) thin films prepared by nebulizer spray pyrolysis method

Using nebulizer spray pyrolysis method, we investigate the optoelectronic properties of Erbium (Er:2 %), Yttrium (Y:2 %) and Terbium (Tb:2 %) doped CdS thin films. The pure CdS film belongs to the II-IV semiconductor chalcogenide family, and it has good optical properties, making it appropriate for photo-detector applications. In addition, rare earth (RE) elements such as Erbium (Er), Yttrium (Y) and Terbium (Tb) doped CdS thin film is more suitable for photo sensing applications due to their good physical and optical properties. The polycrystalline structure of pure and doped CdS films with the structure of hexagonal and preferential orientation (002) was shown by structural analysis (XRD). In addition, the phase purity of RE doped CdS thin films was confirmed using Raman spectra. The direct bandgap values fell (2.52–2.47 eV) for the RE dopant, reaching a minimum for the film formed with RE of high ionic radius Tb. Three emission peaks were discovered in photoluminescence (PL) spectra: a strong dominant peak at 525 nm due to interband transitions and a peak with minimum intensity at 475 and 640 nm. With the exception of two RE materials, Er and Y, the CdS film coated with Tb had improved photo-sensitivity characteristics. Responsivity (3.32 AW−1), detectivity (2.82 × 1011 Jones), and external quantum efficiency (883 %) are the photo sensing values of Tb doped CdS film. The Tb coated films were found to exhibit good optical properties, making them suitable for photodetector applications.

Chemical and gas sensing property tuning of cadmium sulfide thin films

A simplistic chemical bath deposition (CBD) technique was used to synthesize the hierarchical morphology of cadmium sulfide (CdS) thin films with altered chemical compositions. The novelty of the work does not lies in the surface morphology of the product, but is found in the influence of the CBD reaction time (mainly after post-optimization) on the Cd contents in the films, subsequently the presence of defects and consequently their electrical conductivity and NO2 gas sensing performance. The morphology of the CdS thin films was characterized by field-effect scanning electron microscopy and defects estimated using photoluminescence spectroscopy. The increment in the deposition time affects the precursor contents in the produced film effectively. In the case of the CdS, the Cd contents increase with the rise in the CBD deposition period. Consequently, it affects the presence of the secondary phase and the conductivity of the compound. As the concentration of the films slightly differs from the standard value, we utilized the films for the sensor application. The low-temperature gas sensing measurements of this Cd-rich CdS structure to NO2 gas were carried out, and we found encouraging outcomes.

Investigating the Effect of Steric Hindrance within CdS Single-Source Precursors on the Material Properties of AACVD and Spin-Coat-Deposited CdS Thin Films.

Cadmium sulfide (CdS) is an important semiconductor for electronic and photovoltaic applications, particularly when utilized as a thin film for window layers in CdTe solar cells. Deposition of thin-film CdS through the decomposition of single-source precursors is an attractive approach due to the facile, low-temperature, and rapid nature of this approach. Tailoring the precursor to affect the decomposition properties is commonly employed to tune desirable temperatures of decomposition. However, altering the precursor structure and the effect this has on the nature of the deposited material is an area far less commonly investigated. Here, we seek to investigate this by altering the ligands around the Cd metal center to increase the steric hindrance of the precursor and investigate the effect this has on the decomposition properties and the properties of deposited thin-film CdS from these precursors. For this, we report the synthesis of four CdS precursors with xanthate and pyridyl ligands ([Cd(n-ethyl xanthate)2(3-methyl pyridine)2] [1], [Cd(n-ethyl xanthate)2(3,5-lutidine)2] [2], [(Cd2(isopropyl xanthate)4(3-methyl pyridine)2)n] [3], and [Cd(isopropyl xanthate)2(3,5-lutidine)2] [4]). These single-source precursors for CdS were fully characterized by elemental analysis, NMR spectroscopy, single-crystal X-ray diffraction (XRD), and thermogravimetric analysis. It was found that even with subtle alterations in the xanthate (n-ethyl to isopropyl) and pyridine (3-methyl and 3,5-dimethyl) ligands, a range of hexa-coordinate precursors were formed (two with cis configuration, one with trans configuration, and one as a one-dimensional (1D) polymer). These four precursors were then used in aerosol-assisted chemical vapor deposition (AACVD) and spin-coating experiments to deposit eight thin films of CdS, which were characterized by Raman spectroscopy, powder X-ray diffraction, and scanning electron microscopy. Comparative quantitative information concerning film thickness and surface roughness was also determined by atomic force microscopy. Finally, the optical properties of all thin films were characterized by ultraviolet–visible (UV–Vis) absorption spectroscopy, from which the band gap of each deposited film was determined to be commensurate with that of bulk CdS (ca. 2.4 eV).

The 60th Anniversary of TFTs and the Evolution of High‐Resolution Displays

The 60th Anniversary of TFTs and the Evolution of High‐Resolution Displays

Epitaxial Growth and Optical Properties of Laser Deposited CdS Thin Films

In this study, cadmium Sulfide (CdS) thin films were synthesized on quartz substrates using an infrared pulsed laser deposition (IR-PLD) technique under high vacuum (~10−6 Torr) conditions. X-ray diffraction was used to evaluate the structural features. According to X-ray analysis, the deposited CdS films are crystalline and have a favored orientation on a plane (110) of an orthorhombic. The peak intensity and the average crystallite size increases with increasing the film thickness. After annealing at 300 °C, the orthorhombic phase transformed into a predominant hexagonal phase and the same result was obtained by SEM photographs as well. Spectrophotometric measurements of transmittance and reflectance of the CdS films were used to derive optical constants (n, k, and absorption coefficient α). The optical band gap energy was found to be 2.44 eV. The plasma plume formation and expansion during the film deposition have also been discussed. The photocurrent response as a function of the incident photon energy E (eV) at different bias voltages for different samples of thicknesses (85, 180, 220 and 340 nm) have been studied, indicating that the photocurrent increases by increasing both the film thickness and photon energy with a peak in the vicinity of the band edge. Thus, the prepared CdS films are promising for application in optoelectronic field.

Elaboration and characterization of cadmium sulfide (CdS) thin films prepared by chemical bath deposition (CBD)

The chemical bath deposition technique has found great success in recent years as it has become an integral part of the industrial process for the preparation of large-scale solar cells. In this work we have elaborated CdS thin films on glass substrates by the CBD chemical bath deposition technique from an aqueous solution containing CdCl2 and (NH2)2CS as sources of sulfide and cadmium ions for different deposition temperatures. The structural, optical and electrical properties measured before and after thermal annealing, showed that the obtained CdS layers crystallize in the hexagonal structure with a preferential orientation (002) and that the gap value deduced from the transmission measurements is “2.4 eV” with an optical transmission about 80% and resistivity varies between 102 and 103 Ω.cm depending on the bath temperature.

Synthesis and characterization of thermally-evaporated CdS thin-films

Cadmium sulfide (CdS) thin films (thickness: 200 nm) were grown over silicon (Si) substrate via thermal evaporation deposition method, where the ultimate pressure and deposition rate were 1 × 10−6 torr and 1.0-1.2 Å/sec, respectively. X-ray diffraction established polycrystalline films with a hexagonal crystal structure and preferred orientation (002). The energy dispersive analysis of X-ray has recognized pure and stoichiometric films. The uniform, dense and smooth films with low roughness (1.4 nm) appeared in atomic force microscopy. The scanning electron microscopy characterization has recognized a continuous and defects-free film (like cracks, pinholes and overhang) with a uniform distribution of interconnected nanoparticles (size: 24.5–35.1 nm). The good adhesion of the film was confirmed via a scotch tape test. Ellipsometry revealed that the grown CdS film has a refractive index of 2.42–2.45. Thus, polycrystalline CdS film with hexagonal phase (highly stable, wide bandgap, high transmission, environmentally tolerable, and good mechanical strength) could be utilized as a suitable window material and passivation agent in the fabrication of solar cell and infrared detector, respectively.

Structural and Optical Characterization of Spray Deposited Cadmium Sulphide Thin Film

Structural and Optical Characterization of Spray Deposited Cadmium Sulphide Thin Film

Cadmium sulphide thin films deposition and characterization for device applications

Thin films of metal chalcogenides (sulphides, selenides, and tellurides) are investigated, and group II-VI semiconducting materials are more attracted to the thin films, and researchers are more interested in group II-VI semiconducting materials because of their use in photovoltaic cells, photoconductors, optical filters, solar cells, sensors, and other optoelectronic devices. Cadmium sulphide is a semiconducting material that corresponds to the II-VI family and has an energy bandgap of 2.42 eV. It is significant because of their numerous applications in optoelectronic devices, solar cells, LEDs, photoconductors, and other fields. It's also beneficial for window layers in CdTe or CuInSe2-based high-efficiency thin-film solar cells. It can be prepared by several techniques like chemical bath deposition (CBD), electrodeposition, thermal evaporation, spray pyrolysis, molecular beam epitaxy, etc. We have prepared CdS thin films over Molybdenum substrate using a non-aqueous medium by the CBD method. The electrolyte was made by combining the AR grade of cadmium acetate (0.24 M) dissolved with ethylene glycol and ethanol (ratio = 1:2) and the electrolyte temperature was kept at 130 °C with 220 rpm. Molybdenum substrate was dipped into the electrolyte using rigid support and thiourea (0.35 M) was influenced by the prepared electrolyte. The film was deposited for 20 min, and the deposited films was found to be well adherent to the substrate and free of voids, pinholes, and pits. XRD, FESEM, EDS, AFM, and FTIR were used to see into the solid-state features of the films which have been deposited. The deposited film shows a significant peak at 2θ = 26.240 with the (002) plane, suggesting that the film has a crystalline hexagonal structure. Using AFM, RMS roughness value is equal to 92 nm. Compositional analysis peaks reveal the availability of Cd and S.

Optoelectronic properties and Effect of annealing on structural of Zn mixed CdS thin film by SILAR method

In this research, the zinc mixed cadmium sulfide thin films were synthesized on the glass substrate by simple and easy successive ionic layer adsorption and reaction (SILAR) process. The thin films were prepared by different mixing percentage of Zinc with cadmium sulfide. The Zn-CdS films have been characterized by X-Ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and optical properties were investigated by ultraviolet-visible spectrophotometer. X-Ray studies show the hexagonal crystal structure of CdS film. The surface morphology is found different in both annealed and unannealed structure from FESEM image. It is smooth, dense and uniform in structure in case of unannealed condition. And it is non-uniform structure when annealed. The absorbance spectra of pure CdS and Zn mixed CdS has compared and it is observed that Zn-mixed CdS have greater absorbance than pure CdS.

3D micromorphology-contact resistance-conductivity insights of quasi 2D Cd1-xPbxS thin films: Investigation based on stereometric and fractal analysis

In this work, stereometric and fractal analysis of Lead (Pb) doped Cadmium sulfide (CdS) thin films synthesized by pulsed laser deposition is reported. The atomic force microscopy (AFM) data were studied to understand the influence of doping on micromorphology, contact resistance and conductivity of CdS films. Stereometric analysis exhibits a non-linear behavior, from Pb doping, in surface roughness with non-Gaussian height distribution in addition to influence on microtexture surface porosity and elastic deformation. A sinusoidal behavior of local surface smoothness with lesser surface complexities for higher Pb concentrations is confirmed from the Hurst coefficient and fractal dimension values of the film surfaces. Surface entropy reveals a uniform deposition of the thin films while a non-linear variation in surface percolation is justified from fractal succolarity values. The tuning of contact resistance between window and buffer layer and thus, enhancement in efficiency of Cadmium indium gallium selenide (CIGS) solar cells is possible with Pb doping in CdS thin films, in the framework of fractal dimension. Additionally, the enhancement in conductivity of Cd1-xPbxS thin films is attributed to surface smoothening process mediated by the large values of Hurst coefficient and autocorrelation length with a consequent decline in RMS roughness.

Cadmium Sulfide (CdS) Thin Films with Improved Morphology for Humidity Sensing by Chemical Bath Deposition at Lower pH.

Cadmium sulfide (CdS), an II-VI group semiconductor material, is one of the most investigated semiconductors in thin film form. In this work, we synthesized CdS thin films with improved film morphology in the presence of ethylene diamine (EA) as the complexing agent by chemical bath deposition (CD) at lower pH. Detailed characterization reveals the presence of cubic phase CdS with a band gap of 2.39 eV with the resultant morphology significantly influenced by the composition of the growth solution. The resultant CdS films finds prospective application as a humidity sensor with a high sensor response of 2.61 corresponding to 80% relative humidity.

Growth mechanism of pulse electrodeposited cadmium sulfide and zinc sulfide thin films with tartaric acid and glycerol as additives

Room temperature electrodeposition of thin films is beneficial, especially for cadmium sulfide (CdS) and zinc sulfide (ZnS), which are utilized in optoelectronic applications. The present study is unique, owing to its utilization of tartaric acid in the electrochemical deposition of these binary sulfides. This organic acid has been shown to play a vital role in mitigating the precipitation of sulfides and facilitating deposition. Also, the impact of this organic acid on the growth mechanism is evaluated by electroanalytical techniques including cyclic voltammetry and chronoamperometry. From the Randles-Sevcik plot, it is verified that the deposition is governed by a diffusion-controlled process. The elemental analyses unveil that the composition at deposition potentials of -1.1 V for cadmium sulfide and -1.4 V for zinc sulfide are near stoichiometric. The electrocrystallization of the films is interpreted employing Scharifker-Hills nucleation model and is observed to follow progressive nucleation for cadmium sulfide and instantaneous nucleation for zinc sulfide. The deposition process is characterized using impedance measurements that have affirmed the formation of cadmium sulfide and zinc sulfide via intermediate metal tartrate complex. The X-ray diffraction and Raman spectroscopy of as-deposited cadmium sulfide and zinc sulfide thin films confirm the hexagonal and cubic phases, respectively. The results show the adequacy of the method for the deposition of crystalline quality thin films at room temperature in the presence of tartaric acid.