Cd1-xZnxS Thin Films Research Articles

Optimization of the properties of CdxZn1-xS films prepared by chemical bath deposition

CdxZn1-xS thin films were deposited on glass substrates by chemical bath deposition (CBD) in solutions containing cadmium sulfate, zinc sulfate, thiourea, ammonia sulfate and ammonia. The effect of low Cd2+ concentration on the film properties was systematically studied by experiments and simulations, while the film properties were greatly improved by optimizing the concentration ratios of different solutions. The SEM results show that the films have optimal homogeneity and denseness at a Cd2+ concentration of 0.007 M. Also, XRD results at this concentration indicate that the films have better crystallinity. The optical characterization results illustrate that the transmittance of the films is up to 90% at 500 nm–800 nm, and the band gap value of the films varies from 3.05 eV to 3.72 eV when the Cd2+ concentration is 0.001–0.009 M.

Features of photoconductivity and luminescence of CdS thin films and Cd-=SUB=-1-x-=/SUB=-Zn-=SUB=-x-=/SUB=-S solid solutions under laser excitation

The features of photoconductivity and luminescence of CdS thin films and Cd1-xZnxS solid solutions obtained by chemical pulverization with subsequent pyrolysis under laser excitation have been studied experimentally. Pulsed liquid (473-547 nm) and nitrogen (337 nm) lasers were used as a radiation source. An experimental study was made of the photoconductivity and photoluminescence spectra of Cd1-xZnxS thin films depending on the composition x at different excitation intensities and the relaxation curves of nonequilibrium photoconductivity. It is shown that the observed features in the photoconductivity and photoluminescence spectra of Cd1-xZnxS thin films are due to direct band-to-band transitions. Amplification of light is observed at high intensities of optical excitation in thin CdS films. Keywords: Thin films CdS, Cd1-xZnxS, laser, photoconductivity spectra, photoluminescence

Investigation on the structural properties and correlation of the optical constants of Cd1-xZnxS thin films with bath deposition temperature

Cd1-xZnxS thin films were deposited by chemical bath deposition (CBD) technique, which is simple and cost effective, in a chemical bath containing appropriate amount of cadmium acetate, zinc acetate, and thiourea as precursors, in a clean glass substrate. The deposition was carried out by varying the bath temperatures (70 °C, 75 °C, 80 °C, and 85 °C) of the precursor solution. The XRD results indicate the existence of hexagonal structures of Cd1-xZnxS with an average crystallite size of ∼ 27–41 nm. EDX studies confirm the presence of Cd, Zn, and S in the films. HRTEM and SAED patterns show the crystalline nature of the films with the coexistence of the hexagonal phase. The optical constants viz; optical band gap, Urbach energy, static refractive index, and optical conductivity were studied by using UV- Vis transmission spectra as a function of CBD temperature. It was observed that with the increase of bath temperature in the above range, there were concomitant decreases in optical band gap from ∼3.3 to 2.8 eV. The Urbach energy, optical conductivity, and static refractive index of the films increase with the increase in bath deposition temperature. FTIR studies confirm the formation of ternary Cd1-xZnxS thin films.

Optical and structural characteristics of electrodeposited Cd 1-xZnxS nanostructured thin films

Abstract The structural and optical characteristics of Cd1-xZnxS (CdZnS) thin films grown by the electrodeposition method were investigated in the present paper. The crystalline structure of the grown CdZnS thin film was determined as cubic wurtzite due to observed diffraction peaks associated with (111) and (220) planes. Atomic compositional ratios of the constituent elements were obtained using energy dispersive spectroscopy and doping concentration of the Zn was found as 5% (x ~ 0.05). Scanning electron microscopy image of the studied thin film indicated that grown film is nanostructured. Raman spectra of CdS and CdZnS thin films were measured and it was seen that observed longitudinal optical modes for CdZnS present a blue-shift. Temperature-dependent band gap energy characteristics of the thin films were studied performing transmission experiments in the 10–300 K temperature range. The analyses of the recorded transmittance spectra showed that direct band gap energy of the films decreases from 2.56 eV (10 K) to 2.51 eV (300 K) with the increase of temperature. The band gap energy vs. temperature dependency was studied applying well-known Varshni optical model and various optical parameters of the films were reported according to the results of the applied model.

Optical characterization study of thin film for PV cell applications

In this investigation n-type CdxZn1-xS and p-type PbS thin films were synthesized using chemical bath deposition (CBD) method for solar cell applications. The thin films were prepared using nitrates of cadmium and thiourea, lead and zinc. Deposition of optimised CdxZn1-xS was complete by CBD at 820 °C, in alkaline circumstances, while that of PbS ended at room temperature and both films at normal atmospheric pressure exploiting aqueous environments. Optical constant appropriate for photovoltaic applications were attempted for and to resolve this, a UV VIS IR spectrophotometer 3700 DUV was utilized. The optical band gap of deposited CdxZn1-xS films range from 2.47 eV (x = 0.6) to 2.72 eV (x = 1.0), and transmittance overhead 79% in the VIS - NIR region for the concentration range of × = 0.6 to 1.0. The band gap enlarged with increasing Zn concentration of the alloy and Cd0.6Zn0.4S sample exhibited the broadest band gap. It is observed that the concentration of zinc increased optical band gap. PbS thin films consumed a band gap of 0.89 eV and a transmittance underneath of 55% appropriate for absorber layers of solar cells. The fabricated photovoltaic cell had a small circuit current, Isc = 0.031 A, exposed voltage, Voc = 0.37 V, efficiency, η = 0.9% and a fill factor, FF = 0.66 inferring that the two materials are suitable for photovoltaic applications particularly in the VIS and IR light spectrum.

CdxZn1-xS thin films deposited by Chemical Bath Deposition (CBD) method

CdxZn1-xS thin films have been deposited on glass substrates by simple and cost-effective chemical method i.e. Chemical Bath Deposition (CBD) for their potential applications in photovoltaics. The structural, morphological, chemical and optical properties of deposited thin films were investigated by X-ray Diffraction, Scanning Electron Microscopy, UV–vis and Raman spectrometry. Structural properties revealed that deposited thin films exhibit both cubic and hexagonal crystal structure. The CdxZn1-xS thin films with grain size between 6−25 nm exhibit transmittance from 50 to 80% in the visible region. The optical band gap energy of deposited thin films was observed to be in the range from 2.6 to 3.6 eV illustrating their potential viability for optoelectronic and photovoltaic devices.

Electrochemical deposition and characterization of thin-film Cd1-xZnxS for solar cell application: The effect of cathodic deposition voltage

Cd1-xZnxS thin films have been grown by two-electrode electrodeposition method using an electrolytic bath containing cadmium chloride, zinc chloride and sodium thiosulphate. The deposition was carried out at three different cathodic voltages of 1695 mV, 1700 mV and 1705 mV. The characterization of the films was done using grazing incidence X-ray diffraction (GIXRD), energy-dispersive X-ray (EDX) spectroscopy, Raman spectroscopy, UV–Vis spectrophotometry, and scanning electron microscopy (SEM). From the GIXRD results, it is observed that the films have only hexagonal phase. With increase in deposition voltage the intensities of the characteristic peaks decrease because of incorporation of more Zn into the film resulting in reduced deposition rate, and therefore thinner films. A similar trend is observed in the Raman spectroscopy results. EDX results reveal that increase in deposition voltage increases the amount of zinc atoms incorporated into the Cd1-xZnxS thin film. Optical characterization shows that, as more Zn is incorporated into the film with increase in growth voltage, the energy band gap gradually increase from 2.42 eV to 2.51 eV, making the Cd1-xZnxS films more beneficial for application as window/buffer material in solar cells compared to CdS. The optical absorbance and transmittance of the Zn-incorporated films also decrease and increase, respectively as deposition voltage increases (i.e as more Zn is incorporated), to support this application. SEM images show uniform and densely packed surface morphology, with the grains becoming less distinctly shaped as more Zn is incorporated into the film with increase in deposition voltage.

Crystalline Structure and Optical Properties of Cd1-xZnxS Thin Films Prepared by CBD

Cd1-xZnxS thin films were deposited on glass substrates by chemical bath deposition. The influence of x on the crystalline structure, surface morphology and optical properties of Cd1-xZnxS thin films were studied by measures of XRD, SEM, and spectrophotometer, respectively. The SEM images indicated that, with the increase of x, the particles of Cd1-xZnxS changed from small and compact to larger and sparser, which was thought to be the transformation of two reaction mechanisms in the deposition process, from ion-by-ion process to cluster-by-cluster process. The average transmittance values of Cd1-xZnxS samples in visible spectrum were all above 70%, and the band gaps of the Cd1-xZnxS thin films varied from 2.47 eV to 3.66 eV during the x from 0 to 1.

Narrow Band Gap Ternary Absorber Layer for Solar Cell for Small Business Enterprises in Equatorial Africa

According to recent studies, on the Daily nation newspaper, in Kenya of 6th January 2017 featured the story, the number of people doing the same thing in surrounding villages was so high that many of them had to leave their phones behind at the charging centre (for up to three days) before returning to pick them. To fight darkness, up to 80 percent of Africans depend on personal generators, candles and kerosene (paraffin) lamps to provide basic lighting. Let’s not even talk about all the other things we desperately need electricity for – iron clothes, pump water, charge mobile phones etc. In this article, we shall focus on the types of solar cell materials that can be used to fabricate solar cell to be installed on roof tops to generate electricity used by individuals and households. Photovoltaic devices are used to convert solar radiation energy into electrical forms of energy for various uses. Current research is geared towards using thin films with wide band gaps to allow optimum penetration of radiation within the VIS - NIR region. Inorganic wide band gap, CdxZn1-xS thin films and narrow band gap, PbS thin films were optimized through chemical solution technique in this study. Wide band gap thin films of CdxZn1-xS were grown at about 82°C while those of narrow band gap thin films of PbS were grown at room temperature utilizing aqueous conditions. Their optical constants were investigated and found to be suitable for solar cells applications.

Comprehensive Study of Growth Mechanism and Properties of Low Zn Content Cd1-xZnxS Thin Films by Chemical Bath

Cd1-xZnxS thin films have been studied extensively as window layers for solar cell applications. However, a mismatch between the Cd1-xZnxS and copper-indium-gallium-selenide absorber layers increases with Zn film concentration, which reduces the device efficiency. In this work, Cd1-xZnxS thin films with low Zn concentrations were analyzed. The effect of the addition of different molar Zn concentrations to the reaction mixture on the growth mechanism of Cd1-xZnxS thin films and the influence of these mechanisms on structural, optical and morphological properties of the films has been studied. Cd1-xZnxS thin films were synthesized by chemical bath deposition using an ammonia-free alkaline solution. Microstructural analysis by X-ray diffraction showed that all deposited films grew with hexagonal structure and crystallite sizes decreased as the Zn concentration in the film increased. Optical measurements indicated a high optical transmission between 75% and 90% for wavelengths above the absorption edge. Band gap value increased from 2.48 eV to 2.62 eV, and the refractive index values for Cd1-xZnxS thin films decreased as the Zn increased. These changes in films and properties are related to a modification in growth mechanism of the Cd1-xZnxS thin films, with the influence of Zn(OH)2 formation being more important as Zn in solution increases.

Structural, optical, and photoelectrochemical properties of nanosphere-like CdXZn1-XS synthesized by electrochemical route

Here, we present the effect of different Zn contents on the structural, morphological, and optical properties of CdXZn1-XS thin films deposited by electrodeposition method on stainless steel and indium-doped tin oxide (ITO) glass substrates. Electrosynthesized CdXZn1-XS thin films are characterized by using X-ray diffraction (XRD), UV-Vis spectrophotometer, field emission scanning electron microscope (FE-SEM), and surface wettability analysis. XRD pattern reveals that the CdXZn1-XS thin films are polycrystalline in nature with hexagonal crystal structure. FE-SEM micrograph displays that these CdXZn1-XS thin films exhibit the different sizes of sphere-like nanostructures by varying the X value. The optical absorption study indicates that drastic variation in band gap energy of CdXZn1-XS thin films. In advance photovoltaic measurements, CdXZn1-XS thin films are to be studied by forming the photoelectrochemical (PEC) cell having CdXZn1-XS/0.5 M (Na2SO3)/C configuration. The efficiency values of CdXZn1-XS are found to be 0.2, 0.35, 0.32, 0.25, and 0.23 % respectively at X content.

Structural and optical properties of Cd1-xZnxS (x = 0, 0.4, 0.8 and 1) thin films prepared using the precursor obtained from microwave irradiation processes

Synthesizing Cd1-xZnxS (CdZnS) nanoparticles via a facile microwave-assisted method as starting material for coating processes and characterization of their thin films deposited on glass were performed. Compositional ratio and structural properties of the nanoparticles and films were studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), and energy dispersive analysis of X-ray technique (EDAX). Surface morphology of the prepared films was studied by field emission scanning electron microscopy (FESEM). Also, optical properties of thin films were characterized by photoluminescence (PL) and UV–vis. spectroscopy techniques. Structure of CdZnS of the nanoparticles and thin films were found as hexagonal and cubic, depending on Zn2+ ion doping value on Cd2+ ion sites. PL spectra of the specimens showed a blue shift and a strong correlation between PL pattern and doping level. The prepared CdZnS films were found to have direct band gaps varying from 2.33eV for CdS to 3.33eV for ZnS.

Preparation and Characterization of Cd<sub>1-x</sub>Zn<sub>x</sub>S Thin Films with Chemical Bath Deposition

Cd1-xZnxS thin films were grown on soda-lime glass substrates by chemical-bath deposition (CBD). The surface morphology, thickness, composition, state of the constituent elements and optical properties of the films were studied with X-ray diffraction (XRD), scanning electron microscopy (SEM), step height measurement instrument, X-ray photoelectron spectroscopy (XPS) and spectrophotometer, respectively. The affect of annealing for the Cd1-xZnxS thin films was studied. The Cd1-xZnxS thin films had cubic crystal structure and the average transmittance was 86.8% in the visible range with the optical band gap of 2.61eV and the films thickness was about 50nm. The atomic ratio of (Cd + Zn): S increased after annealing.

Influence of the Reaction Temperature on Cd1-xZnxS Thin Films with Chemical Bath Deposited

Cd1-xZnxS thin films were deposited on soda-lime glass substrates with chemical-bath deposition (CBD) using cadmium acetate, zinc sulfate, thiourea, ammonia and ammonium acetate aqueous solution at different with stirring. All the samples were annealed at 200 °C for 60 min in the air. The crystal structure, surface morphology, thickness and optical properties of Cd1-xZnxS thin films with increasing ammonia concentration were studied with X-ray diffraction (XRD), scanning electron microscopy (SEM), step height measurement instrument and spectrophotometer respectively. The results revealed that Cd1-xZnxS thin films had cubic crystal structure and the intensity of the diffraction peak decreased gradually as reaction temperature rose and the average crystal size was from 7.0 nm to 8.9 nm. All of Cd1-xZnxS thin films had a granular surface with some smaller pores. The Cd1-xZnxS thin films band gap was from 2.68 eV to 2.83 eV. The transmission of film deposited at 80 °C was highest. The suitable reaction temperature was from 70 °C to 80 °C.

EFFECT OF Zn CONTENT ON OPTICAL PROPERTIES AND TUNING OF OPTICAL BAND GAP OF CHEMICALLY DEPOSITED Cd1-xZnxS THIN FILMS

The Cd1-xZnxS(x = 0.0,0.2,0.4,0.6,0.8,1.0) thin films were deposited using the Chemical Bath Deposition Method (CBD). The prepared Cd1-xZnxS thin films were optically characterized. The effect of Zn content on absorption and transmission spectra was investigated. The significant blue shift of absorption edge as well as tuning of band gap was observed with Zn content. In the composition x = 0.8Cd1-xZnxS thin films exhibit maximum 78% transmittance. The SEM study confirms that even though Zn content was low the microstructure of Cd1-xZnxS thin films effectively changes.

Study of structural, Morphological and Electrical Properties of CdxZn1-xS Thin Films

The CdxZn1-xS (x=00, 0.2, 0.4, 0.6, 0.8, and 1.0) were prepared by using Chemical Bath Deposition (CBD) Technique. The prepared CdxZn1-xS thin films were characterized by X-ray diffractometer (XRD) and Scanning Electron Microscopy (SEM). The structural and morphological properties have been investigated. XRD pattern exhibits the hexagonal crystal structure of CdxZn1-xS. The dark electrical resistivity measurement was carried out in the temperature range 298 to 383 K by using two point probe method. The dark resistivity measurement shows that the prepared CdxZn1-xS thin films have high resistivity. The dark resistivity at room temperature was found to be of the order of ≥10 Ω cm for pure CdS and ≥10 Ω cm for CdxZn1-xS thin films. The dark resistivity was observed increased with Zn content.

Optical and Morphological Studies of Chemical Bath Deposited Nanocrystalline Cd<sub>1-x</sub>Zn<sub>x</sub>S Thin Films

Cadmium Zinc Sulfide, Cd1-xZnxS thin films were deposited by chemical bath deposition technique at bath temperature of 75°C. The morphology of the films was analyzed by scanning electron microscope, the optical constants of the films were estimated from the transmission and reflection spectra of the films in the wavelength range of 300 - 900 nm. The films had a transmittance between 75% and 85% and optical band gap in the range 2.8 - 3.4 eV. The dependence of the refractive index of the films on the wavelength was investigated using the single oscillator model, from which the dispersion parameters were determined. The high frequency dielectric constant eL and the ratio of the carrier concentration to the effective mass N/m* were estimated based on the Spitzer and Fan model. Both eL and N/m* show a decrease in value with increase in Zinc content.

Effect of Adding Zn in Cd1-XZnXS Thin Films Prepared by an Ammonia-Free Chemical Bath Deposition Process

ABSTRACTThe present investigation work shows the results of Cd1-XZnXS thin films (where X= 0.04, 0.08, 0.12, 0.16 and 0.2), obtained by total ammonia-free chemical bath processes. The reaction solutions were prepared with precursors of metallic salts as CdCl2 and ZnCl2 and replacing the ammonia with trisodic citrate (C6H5O7Na3) as complexing agent. The reaction solutions were stabilized with KOH to get alkaline solutions. As result of adding Zn, the as deposited films showed changes in their morphological, structural and optical properties. Moreover, additional changes were obtained when thermal treatments to 400°C under N2 environment were applied to the as deposited films. The agglomerates at the surface of the annealed films showed larger grain sizes compared to that of the as deposited films. Due to preferential orientation of the hexagonal wurtzite-type structure in the films, changes in the intensity in the (002), (100) and (101) peaks from x-ray diffraction analysis were observed. Finally, a reduction on the maximum energy band gap from 2.65 to 2.59 eV was obtained as effect of the annealing treatment to the films.

Preparation and Characterization of CoevaporatedCd1−xZnxSAlloy Thin Films

Cd1-xZnxSthin films have been prepared by the vacuum coevaporation method. The structural, compositional, and optical properties ofCd1-xZnxSthin films have been investigated using X-ray diffraction, X-ray fluorescence, and optical transmittance spectra. As-depositedCd1-xZnxSthin films are polycrystalline and show the cubic structure forx=1and hexagonal one forx<1with the highly preferential orientation. The composition ofCd1-xZnxSthin films determined from Vegard's law and quartz thickness monitors agrees with that determined from the X-ray fluorescence spectra. Optical absorption edge of optical transmittance forCd1-xZnxSthin films shows a blue shift with the increase of the zinc content. The band gap forCd1-xZnxSthin films can be tuned nonlinearly withxfrom about 2.38 eV for CdS to 3.74 eV for ZnS. A novel structure for CuInS2-based solar cells with aCd0.4Zn0.6Slayer is proposed in this paper.

The Effect of Thermal Annealing on the Optical Band Gap of Cd1-xZnxS Thin Films Deposited by the Dip Technique

The effect of thermal annealing on the optical band gap of Cd1-xZnxS (x= 0.2, 0.4, 0.6, 0.8) thin films have been investigated. The films were deposited using the dip technique. The fundamental optical property which has been investigated here is the absorbance of light at room temperature, using the KLB Ultraspec II 4050 (UV/Visible) spectrophotometer over the wavelength range 300 – 900 nm. The energy band gap and absorption coefficient of the films were determined from the absorption spectrum. The optical band gap of the as-deposited films varied from 2.42 eV (x =0.2) to 3.61 eV (x =0.8), that is, the band gap increased with increasing Zn concentration of the alloy. These values compare favorably well with that obtained from literature of similar films prepared using other deposition techniques. The as-deposited samples were thermally annealed in air for an hour at temperatures of 100°C, 200°C and 300°C and the absorption spectra again recorded. It was observed that thermal annealing decreased the band gap of the samples; this may be due to improving crystallinity or alternatively, a phase transformation taking place in the samples as a result of the heat treatment.