Chemical Bath Deposition Films Research Articles

A comparative study of CdS thin films grown on ultra-thin glass substrates by RF magnetron sputtering and chemical bath deposition

The structural, morphological and optoelectrical characteristics of cadmium sulfide (CdS) thin films grown on ultra-thin glass substrates via Radio Frequency (RF) magnetron sputtering and chemical bath deposition (CBD) have been explored in this study. CdS thin films were characterized using the X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Atomic Force Microscopy (AFM), UV–Vis spectrophotometer and Hall effect measurement system. As obvious from XRD investigation, the stable hexagonal wurtzite crystalline structure with (002) preferential orientation was resulted from both deposition methods. FESEM study demonstrated uniform grain structure for the sputtered films. Compositional analysis confirmed that S/Cd ratio is 0.28 for the sputtered films and 0.20 for the CBD films. AFM study exhibited spherical crystal surface formation, hills and valleys for CBD films. The optical analysis showed a band gap of 2.40 eV and 2.32 eV for the sputtering and the CBD methods, respectively. Hall effect analysis recorded carrier concentration and resistivity in the order of 1013 cm−3 and 104 Ω cm, respectively. The experimental results recommend that the CdS thin films grown by the sputtering might be favourable as the window layer for solar cell application.

Electrochemically and chemically deposited polycrystalline CdSe electrodes with high photoelectrochemical performance by recycling from waste films

Waste CdSe film electrodes can be recycled into useful films without sacrificing their photoelectrochemical performance. Cd2+ aqueous ions have been recovered from waste CdSe electrodes by soaking in minimal amount of HCl (10.0 M) at 80 °C for 60 min. The Se2− ions, converted into H2Se(g) by the acid, have been trapped in basic NaOH solution for further use. The recovered Cd2+ ions have been used to deposit new (recycled) CdSe film electrodes onto fluorine doped tin oxide films (FTO/Glass) using aqueous Na2SeSO3 solutions by two methods. Electrochemical deposition (ECD) has been performed using applied potential (−1.0 V vs Ag/AgCl). Chemical bath deposition (CBD) has been performed in a basic medium at 70 °C. Both ECD and CBD recycled films have been prepared using recovered Cd2+ solutions, whereas fresh films have been prepared using fresh solutions. In both cases, the recycled CdSe films do not show any inferior characteristics to the freshly prepared counterparts. Effects of annealing at 150 °C and cooling rate on physical and photoelectrochemical (PEC) characteristics have been studied for different CdSe film electrodes. In both recycled and fresh systems, the CBD film electrodes exhibit enhanced uniformity, compactness and photo-electrochemical (PEC) performance by annealing. Upon annealing, the recycled and fresh ECD films exhibit less film uniformity and compactness, and consequently lower PEC performance. In ECD and CBD films, fast cooling is advantageous over slow cooling. Conversion efficiency values of ~8% are observed for the CBD recycled pristine films once carefully annealed and quickly cooled. This is higher than literature values for pristine CdSe (~5%), TiO2/CdS/CdSe (~4%) film electrodes, and resembles that for Tl/CdSe0.65Te0.35 (~8) multi-layer systems. The results show the feasibility of recycling waste CdSe film electrodes.

Copper selenide film electrodes prepared by combined electrochemical/chemical bath depositions with high photo-electrochemical conversion efficiency and stability

Copper selenide (of the type Cu2-xSe) film electrodes, prepared by combined electrochemical (ECD) followed by chemical bath deposition (CBD), may yield high photo-electrochemical (PEC) conversion efficiency (∼14.6%) with no further treatment. The new ECD/CBD-copper selenide film electrodes show enhanced PEC characteristics and exhibit high stability under PEC conditions, compared to the ECD or the CBD films deposited separately. The electrodes combine the advantages of both ECD-copper selenide electrodes (in terms of good adherence to FTO surface and high surface uniformity) and CBD-copper selenide electrodes (suitable film thickness). Effect of annealing temperature, on the ECD/CBD film electrode composition and efficiency, is discussed.

INFLUENCE OF ANNEALING TEMPERATURE ON THE CHARACTERISTICS OF NANOCRYSTALLINE SnO2 THIN FILMS PRODUCED BY Sol–Gel AND CHEMICAL BATH DEPOSITION FOR GAS SENSOR APPLICATIONS

Pure nanocrystalline SnO2 films were grown on a clean glass substrate by using sol–gel dip coating and chemical bath deposition (CBD) techniques for gas sensor applications. The films were annealed in air at 300[Formula: see text]C, 400[Formula: see text]C, and 500[Formula: see text]C for 60[Formula: see text]min. The deposited films with a thickness of approximately 300 [Formula: see text] 20 nm were analyzed through X-ray diffraction, scanning electron microscopy (SEM), atomic force microscopy (AFM), and optical absorption spectroscopy. Results revealed that the films produced by dip coating exhibited a tetragonal rutile structure and those produced by CBD showed a tetragonal rutile and orthorhombic structure. The crystalline sizes of the films produced by dip coating annealed at 300[Formula: see text]C, 400[Formula: see text]C, and 500[Formula: see text]C were 8, 14, and 22.34 nm and those for CBD films at these temperatures were 10, 15, and 22 nm, respectively. AFM and SEM results indicated that the average grain size increased as annealing temperature increased. The transmittance and absorbance spectra were then recorded at wavelengths ranging from 300[Formula: see text]nm to 1000[Formula: see text]nm. The films produced by both the methods yielded high transmission at visible regions. The optical band gap energy of dip-coated films also increased as annealing temperature increased. In particular, their optical band gap energies were 3.5, 3.75, and 3.87[Formula: see text]eV at 300[Formula: see text]C, 400[Formula: see text]C, and 500[Formula: see text]C, respectively. By comparison, the energy band gap of CBD-prepared films decreased as annealing temperature increased, and their corresponding band gaps were 3.95, 3.85, and 3.8[Formula: see text]eV at the specified annealing temperatures. The films were further investigated in terms of their sensing abilities for carbon monoxide (CO) gas at 50 ppm by measuring their sensitivity to this gas at different times and temperatures. Our results demonstrated that dip-coated and CBD-prepared films were highly sensitive to CO at 200[Formula: see text]C and 250[Formula: see text]C, respectively.

Study of the optical properties of CuAlS2 thin films prepared by two methods

CuAlS2 thin films were successfully deposited on glass substrates using two methods: chemical spray pyrolysis (CSP) and chemical bath deposition (CBD). It was confirmed from the X-ray diffraction (XRD) analysis that CSP films exhibited a polycrystalline nature while amorphous nature was diagnosed for CBD films. Also XRD analysis was utilized to compute grain size, strain and dislocation density. Surface morphology was characterized using scanning electron microscope and photomicroscope images. The optical absorption measurement revealed that the direct allowed electronic transition with band gaps 2.8 eV and 3.0 eV for CBD and CSP methods, respectively. The optical constants, such as extinction coefficient (k), refractive index (n), real and imaginary dielectric constants (e 1, e 2) were discussed. The photoluminescence (PL) spectra of CuAlS2 thin films appeared as a single peak for each of them, and this is attributed to band-to-band transition.

Enhanced PEC characteristics for CdSe polycrystalline film electrodes prepared by combined electrochemical/chemical bath depositions

Polycrystalline CdSe films have been deposited onto fluorine doped tin oxide (FTO/glass) substrates by three different techniques, electrochemical deposition (ECD), chemical bath deposition (CBD) and, for the first time, combined ECD and CBD (ECD/CBD). The films were comparatively characterized by photoluminescence spectra (PL), electronic absorption spectra, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The SEM micrographs show that the films involved rod shaped agglomerates with various lengths and widths. XRD patterns show that the three systems involved nano-sized CdSe particles with cubic type crystals. Based on Scherrer's equation, the ECD film showed larger particle size than the CBD film, while the ECD/CBD film showed largest particles among the series. Similarly, the band gap values varied for different films as CBD>ECD>ECD/CBD. Photo-electrochemical (PEC) characteristics, including photo-current density vs. voltage (J-V) plots, conversion efficiency (ƞ), fill factor (FF) and stability were all studied for different film electrodes. The films exhibited n-type behaviors with direct band gaps. The new ECD/CBD-CdSe electrode exhibited higher conversion efficiency (ƞ% ~4.40) than other counterparts. The results show the added value of combining ECD and CBD methods in enhancing PEC characteristics of CdSe film electrodes, even with no additional treatment.

Chemical bath deposition of Zn(O,S) and CdS buffers: Influence of Cu(In,Ga)Se2 grain orientation

The present contribution discusses buffer growth by chemical bath deposition (CBD) on polycrystalline Cu(In,Ga)Se2 (CIGS) films deposited by in-line co-evaporation with an integral [Ga]/([Ga]+[In]) ratio of 0.3. We report a correlation of the coverage of CBD Zn(O,S) and CdS films with the CIGS grain orientation as determined by electron backscatter diffraction. 〈221〉-oriented CIGS grains are sparsely covered with the CBD films, whereas on 〈100〉/〈001〉- and 〈110〉/〈201〉-oriented CIGS grains, we found very dense coverage of the CIGS surfaces. This result may be explained by lower energies of CIGS {112} surfaces compared with those of {100}/{001} and {110}/{102}.

CdS/FTO thin film electrodes deposited by chemical bath deposition and by electrochemical deposition: A comparative assessment of photo-electrochemical characteristics

CdS thin films have been deposited onto FTO/glass substrates by two different techniques, electrochemical deposition (ECD) and chemical bath deposition (CBD). Feasibility of using these two film types in photoelectrochemical processes has been critically investigated here. The films were comparatively characterized by a number of techniques (solid state absorption spectra, solid state photoluminescence spectra, XRD and SEM). PEC characteristics of the electrodes, including current density–voltage (J–V) plots, conversion efficiency (η), stability and fill-factor (FF) were then studied. The results show that both systems involved nano-sized CdS particles living in coagulates. The ECD was thinner and more uniform than the CBD system. The CBD films were more effective in PEC processes than the ECD counterparts. Effect of annealing on characteristics of both electrode systems has been investigated. Annealing enhanced both film characteristics, but the CBD was affected to a higher extent, and the annealed CBD film was more effective than the ECD counterpart.

Comparison of Structural and Optical Properties of CdS Thin Films Grown by CSVT, CBD and Sputtering Techniques

CdS thin films were deposited by three different processes; close spaced vapour transport (CSVT), chemical bath deposition (CBD), and sputtering technique on ITO coated glasses and their structural and optical properties were investigated through XRD, SEM, EDX and UV-Vis spectrometry, respectively. The as-grown films are annealed at 400°C and 500°C for 30 min in air and the change in structural properties with the thermal stress were also investigated. The crystallite grain size, lattice constant, microstrain and dislocation densities of the films are quite different in these processes as observed from XRD analysis. The highest crystallinity is observed for sputtered CdS thin films. However, the crystalline property of CBD and sputtered CdS increases with the thermal annealing, while CSVT-CdS loses its crystalline form. No significant grain changes are observed for thermally annealed CdS thin films but some cracked lines are observed in CBD and CSVT CdS thin films from SEM images. The absorbance in the visible wavelength decreased for annealed CdS thin films, which might be due to fact that films are becoming denser followed by thermal annealing. Significant blue shifts observed for thermally annealed CdS thin films have been found from all processes. The band gap found for as-grown CSVT-CdS is 2.44 eV, for CBD-CdS is 2.38 eV and for sputtered-CdS is 2.42 eV. The disorder of phonon states in the films are observed from Urbach's tail. The absorption edges due to the exciton–phonon interaction or electron-phonon interaction are also observed from the values of steepness parameter.

Optical characterization of In 2S 3 solar cell buffer layers grown by chemical bath and physical vapor deposition

In this paper, we study the optical properties of indium sulfide thin films to establish the best conditions to obtain a good solar cell buffer layer. The In 2S 3 buffer layers have been prepared by chemical bath deposition (CBD) and thermal evaporation (PVD). Optical behavior differences have been found between CBD and PVD In 2S 3 thin films that have been explained as due to structural, morphological and compositional differences observed in the films prepared by both methods. The resultant refractive index difference has to be attributed to the lower density of the CBD films, which can be related to the presence of oxygen. Its higher refractive index makes PVD film better suited to reduce overall reflectance in a typical CIGS solar cell.

Comparative optical and structural studies of CdSe films grown by chemical bath deposition and pulsed laser deposition

Cadmium selenide thin films were prepared by chemical bath deposition (CBD) and pulsed laser deposition (PLD) methods. For CBD films, cadmium chloride (CdCl 2) and cadmium acetate (Cd(CH 3COO) 2) solutions were employed as Cd 2+ source while a freshly prepared sodium selenosulfite (Na 2SeSO 3) solution provided the Se 2− ions. The pH of the bath was adjusted by adding ammonium hydroxide. The effects of the bath temperatures (30–90 °C) and the Cd/Se ratio on film properties were investigated. On the other hand, PLD films were grown by the ablation of a sintered pure CdSe target using a Nd:YAG laser beam (355 nm) with 1 J/cm 2 fluence. The deposition chamber was maintained under vacuum pressure (10 −6 mbar) and at room temperature. The CBD films are constituted by crystallites of metastable cubic phase (7 nm) with some amorphous phase present, whereas the PLD films showed better crystalline quality and higher crystalline size. Optical absorption analysis shows that the band gap value of the CBD films is higher than that of the bulk material and decreases with the bath temperature. Annealing transforms the metastable cubic phase into the hexagonal phase and causes a “redshift” in the band gap of the CBD and PLD films due to the crystal size increase.

Semiconductor and ceramic nanoparticle films deposited by chemical bath deposition

Chemical bath deposition (CBD) has been used to deposit films of metal sulfides, selenides and oxides, together with some miscellaneous compounds, beginning nearly 140 years ago. While it is a well-known technique in a few specific areas (notably photoconductive lead salt detectors, photoelectrodes and more recently, thin film solar cells), it is by and large an under-appreciated technique. The more recent interest in all things 'nano' has provided a boost for CBD: since it is a low temperature, solution (almost always aqueous) technique, crystal size is often very small. This is evidenced by the existence of size quantization commonly found in CBD semiconductor films. The intention of this review is to provide readers, many of whom may not even be aware of the CBD technique, with an overview of how the technique has been used to fabricate nanocrystalline semiconductor (this terminology also includes oxides often classified as ceramics) films and some properties of these films. The review begins, after a short introduction, with a general description of the CBD method, designed to give the reader a basic knowledge of the technique. The rest of the review then focuses on nanocrystalline (or, in the few cases of amorphous deposits, nanoparticle) films. The various factors which determine crystal size are first discussed. This is followed by some of the many examples of size quantization observed in the films. Since CBD films are usually porous, surface effects can be very important, and various surface-dependent properties (light emission and surface states) as well as surface modification, are treated: (although some properties, like emission, can be strongly dependent on both surface and 'bulk'). Because of the fact that many CBD films have been made specifically for use as photoelectrodes in photoelectrochemical cells, there is next a chapter on this topic with a few examples of such photoelectrodes. Film structure and morphology follows with examples of patterning, porosity and crystal shape. The review concludes with some of the author's opinions as to what the near future holds for CBD development in general.

Comparison of CdS films deposited by different techniques: Effects on CdTe solar cell

Polycrystalline cadmium sulfide (CdS) thin-films were deposited on glass substrate by chemical bath deposition (CBD) and vacuum evaporation (VE) techniques. VE-CdS films consisted primarily of hexagonal phase, whereas CBD CdS films containing primarily the cubic form. VE-grown films were shown to have better crystallinity than CBD-grown films. The grain size of the CBD films is smaller than the ones of VE films. VE-CdS films exhibited relatively high transmittance in the above-gap region and band gap compared with CBD films. However, CdTe solar cells with these low quality CBD–CdS layers yield higher and more stable characteristics. Current–voltage–temperature measurements showed that the current transport for both cells was controlled by both tunneling and interface recombination but the cells with CBD–CdS displayed less tunneling.

CdS 박막의 제조 방법에 따른 물성 및 CdS/CdTe 이종접합의 전기적 특성 분석

Polycrystalline cadmium sulfide(CdS) thin films were deposited on glass substrate by chemical bath deposition(CBD) and vacuum evaporation (VE) techniques. VE-CdS films consisted primarily of hexagonal phase, whereas CBD CdS films containing primarily the cubic form. VE-grown films were shown to have better crystallinity than CBD-grown films. The grain size of the CBD films is smaller than the ones of VE films. VE-CdS films exhibited relatively high transmittance in the above-gap region and band gap compared with CBD films. However, CdTe solar cells with these low quality CBD-CdS layers yield higher and more stable characteristics. Current-voltage-temperature measurements showed that the current transport for both cells was controlled by both tunneling and interface recombination but the cells with CBD-CdS displayed less tunneling

Comparison of the physico-chemical properties of NiO thin films deposited by chemical bath deposition and by spray pyrolysis

Nickel oxide (NiO) thin films were obtained by two methods: chemical bath deposition (CBD) and spray pyrolysis. During the CBD deposition process, the bath was heated at 100 °C. The CBD as-deposited films corresponded to 3Ni(OH) 2·2H 2O. After an annealing time of 96 h at 350 °C, they became NiO. For the spray deposition, the nickel chloride hexahydrate (NiCl 2·6H 2O) was chosen as precursor, the glass substrates were heated at 350 °C. All the films were p-type semiconductors with a band gap of 3.5 eV. The X-ray diffraction diagrams revealed that all the films are crystallized in the cubic NiO phase with the expected value for the lattice parameters. Nevertheless, the orientation and the size of the grains depend on the deposition method. The films are oriented along the (1 1 1) plane in the case of spray, while they are oriented in the (1 1 1) and (2 0 0) planes in the case of CBD. The electron probe microanalysis and the X-ray photoelectron spectroscopy was used to measure the composition of the films. The X-ray photoelectron spectroscopy shows the presence of hydroxyl groups at the surface of the films, while the electron probe microanalysis shows that the films are stoichiometric in the bulk. The scanning electron microscope microphotographs show that all the films exhibit a rough surface with a presence of microstructural features in the case of CBD films. These properties are desired for an eventual application in microcrystalline solar cells.

Deposition and properties of CBD and CSS CdS thin films for solar cell application

We deposited cadmium sulfide (CdS) thin films using the chemical-bath deposition (CBD) and close-spaced sublimation (CSS) techniques. The films were then treated in CdCl 2 vapor at 400 °C for 5 min. The CSS CdS films had hexagonal structure, and good crystallinity. The CdCl 2 treatment did not produce major changes, but there was a decrease in the density of planar defects. The untreated CBD CdS films had cubic structure and poorer crystallinity than the CSS films. After the CdCl 2 treatment, these films recrystallized to the hexagonal phase, resulting in better crystallinity and a lower density of planar defects. The conformal coverage and the presence of bulk oxygen are the key issues in making the CBD films more suitable for photovoltaic applications.

Recent studies on In 2S 3 containing oxygen thin films

Attention has recently been paid to In 2S 3 thin films because of their potential application as buffer layer in CIGS-based solar cells. In this paper, the recent studies performed on such thin films deposited by chemical bath deposition (CBD) and physical vacuum deposition (PVD) are reported and compared. The main part of the experimental results exposed concerns the wide band gap PVD deposited β-In 2S 3 thin films. The influence of the synthesis conditions on the physico-chemical, optical, and electrical properties are reported and discussed in the paper. The oxygen present in the CBD and PVD films has been found to be the origin of their optical properties, which make them a good candidate to substitute CdS in thin films solar cells as buffer layer. The films have a n-type electrical conductivity and their optical band gap is about 2.8 eV.

Formation of the band gap energy on CdS thin films growth by two different techniques

The band gap formation during the first stages of growth of CdS thin films, deposited on glass substrates by chemical bath deposition (CBD) and close spaced sublimation (CSS) techniques was studied. To obtain the first stages of growth, we used deposition times between 5 and 40 min for CBD films, and 4–60 s for CSS films. CBD technique with two chemical bath agitation modalities — the traditional magnetic agitation and ultrasonic vibration — was used for film preparation. Morphological, structural, optical, and stoichiometrical results were obtained on each CdS films group. Higher values of the band gap energy (3.2 eV) were obtained for the thinnest films (2–3 nm) by CBD with ultrasonic vibration; others films, showed similar band gap energy values to those reported for polycrystalline CdS films (2.42 eV). Energy vs. α 2 curves, presented strong differences between the two deposition techniques used. The behavior of the optical window effects, the surface roughness, the structural results, and the films thickness related to the deposition techniques are discussed. The CBD technique with ultrasonic vibration produces films with cleaner surfaces, controlled thickness and better optical properties.

Influence of preparation technique on the structural, optical and electrical properties of polycrystalline CdS films

CdS films were prepared by three different techniques—vacuum evaporation (VE), screen printing (SP), and chemical bath deposition (CBD). The influence of the preparation technique on the structural, optical and electrical properties of the polycrystalline CdS films was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), optical transmission and electrical resistivity. Evaporated and chemical bath deposited films were polycrystalline with a preferred (002) orientation. Film optical parameters (n , k , α, E g ) were evaluated and correlated with the preparation technique. The electrical resistivity of VE films is found to be about one hundredth of the resistivity of an SP film, and one millionth that of a CBD film.

Photoelectrochemical studies on polycrystalline CdS (chemical bath deposition) and CdSe (chemical bath and electro deposition) thin film electrodes

The photoelectrochemical behaviour of polycrystalline CdS and CdSe thin film electrodes prepared by a chemical bath deposition (CBD) method has been examined in an aqueous sulfide—polysulphide electrolyte. The open circuit voltage, short circuit current, flat band potentials, and efficiencies are reported. The CBD technique is simple and promising for the preparation of polycrystalline metal chalcogenides. The behaviour of CdSe prepared by electrodeposition has also been examined.