CdZnS Films Research Articles

Investigation of the Annealing and Cu Doping Effect on Structural and Optical Properties of CdZnS Nanomaterial Deposited by Ultrasonic Spray Pyrolysis

This study investigates doped CdZnS thin films synthesized through the ultrasonic spray pyrolysis technique, followed by annealing at temperatures of 400 and 500 °C. X-ray diffraction analysis demonstrated that both undoped CdZnS and Cu-doped CdZnS thin films exhibit cubic crystal structures, with a preferred orientation along the (111) plane. Scanning electron microscopy (SEM) measurements indicated that the CdZnS thin film has a smooth surface, whereas the Cu-doped CdZnS film shows clustered particles, attributed to the effect of copper doping acting as an activator metal ion. Electron dispersive scanning (EDS) analysis confirmed that the Cd, Zn, and S elements are present in acceptable chemical stoichiometry (Cd + Zn/S = 1:1), with a ratio of 3:1, consistent with the molar amounts used in the precursor solutions. The band gap of the CdZnS thin film decreased from 3.12 to 2.56 eV after annealing at 500 °C, attributed to an increase in crystal size. In contrast, the band gap of the Cu-doped CdZnS thin film decreased from 2.51 to 2.22 eV, lower than that of pure CdZnS, due to the formation of additional phases such as zinc oxide and copper oxide within the CdZnS host structure during annealing.

Comparative studies on pinhole free CBD-CdZnS thin films on ITO and FTO substrate

The development of CdZnS thin films using the chemical bath deposition process in nonaqueous media is a technological challenge. In this work, 75 millilitres of ethylene glycol and ethanol (1:2 ratios) were used to develop a CdZnS thin film on ITO and FTO glass substrates using cadmium acetate, zinc sulphate, and thiourea. The ideal bath temperature was kept at 1300C and the anneal temperature of the film that had been deposited in the air was maintained at 3500C. The films have been examined using FTIR, WCA, FESEM, and XRD. XRD studies reveal that CdZnS films have a hexagonal crystal structure with a preference for orientation (002) during the deposition and annealing processes and the assessment of the various attributes have been done, such as dislocation density, micro strain, and grain size. FESEM study indicates that as deposited film on ITO glass have smooth surface and grains appear in the form of small needle shape of equal sizes where as FTO substrate reveals the grains of equal size throughout the entire surface in cluster form. It is also confirmed that both the CdZnS films formed on ITO and FTO substrates have hydrophilic quality. The presence of chemical bonds and functional groups was confirmed by FTIR analysis.

Formation and characterization of ZnS and CdZnS films using open-air chemical vapor deposition for buffer layers of compound semiconductor solar cells

ZnS and CdZnS (a mixed crystal phase of ZnS and CdS) were formed using the open-air CVD method. Cadmium diethyldithiocarbamate (C10H20CdN2S4) and zinc diethyldithiocarbamate (C10H20ZnN2S4) were used as the source materials for CdS and ZnS, respectively. By changing the ratio of source materials, it was found that the bandgap and the lattice constant of the CdZnS film were continuously changing without a miscibility gap. Furthermore, the bandgap of the obtained ZnS films was less than the reported bandgap of ZnS (3.68 eV) due to incorporation of oxygen. X-ray diffraction analysis revealed that the increase of Zn in CdZnS film generated a crystalline disorder. When the substrate temperature was changed from 421 °C to 464 °C, the deposition rate increased fourfold for the CdS and ZnS films. The impact of substrate temperature on the bandgap and lattice constant was found to be less pronounced.

Study the Effect of Deposition Time on Optical Properties of CdZnS Nanofilms

The optical properties of CdZnS nanofilms are studied in this paper in relation to the deposition time. Deposition times ranged from 15 to 60 minutes for the CdZnS thin films, which had been developed on surface of glassy substrates. The other factors, such as reactant concentration, solution pH, and bath temperature, were held constant throughout the deposition process. The films were annealed at 200 °C for 120 minutes in a thermal furnace after the deposition process. Measurements of absorbance, transmission spectrum, and direct and indirect energy gaps were made using UV-VIS spectrophotometers. Transmittance in the 400-1000 nm range was 70-90 percent for all of the prepared films. With a wavelength of 600 nm and higher, transmittance was around 90%. CdZnS films have bandgap energies ranging from 2.4–2.15 eV for direct transitions and from 2.1–1.97 eV for indirect band gaps.

Energy band gaps and optical absorption properties of the CdZnS and CdZnS:PEO thin films prepared by chemical bath deposition

The optical characteristics of (CdZnS) and (CdZnS:PEO) nanofilms made by the chemical bath deposition technique were examined in the current paper. The films displayed an typical transmission of 65-90% ranging between 500-900 nm. Transmission touched the 90% for wavelength of 600 nm and above. The bandgap energy of CdZnS film was 3eV and was found to be increased to 3.1 eV after using poly ethylen oxide (PEO). All of these results show that PEO can make CdZnS film better. The better transmission of the prepared films also shows that the method described is good for making CdZnS thin films for solar cells.

Investigation of the role of annealing time in the optical, structural and morphological properties of trinary CdZnS thin films prepared by chemical bath deposition

In this paper, CdZnS nanocrystalline films have been deposited by using chemical bath deposition (CBD) technique on glassy substrates. After deposition process, the films were annealed at different period of time (30, 60 and 120 minute) using thermal furnace. Optical properties of CdZnS films such as absorbance and optical band gap, have been investigated. From this measurements, the bandgaps energies were found to be 3 eV, 2.69 eV, 2.5 eV and 2.2 eV for (0, 30, 60 and 120 minute) respectively. The optical energy gap decreased as the annealing time increased. In this study, the influence of annealing time on the structure, optical, and surface properties of CdZnS thin films was examined, and the results were thoroughly discussed. This demonstrates their potential applicability in optoelectronic and photovoltaic devices, among other things.

The influence of posttreatment processes on the structures and the optical and electrical properties of CuInS2 and its heterojunction with various sulfides (CdS, CdZnS, and CdCuS)

As the first essential step toward understanding how to obtain an efficient CuInS2-based solar cell, this paper studied the photoelectric properties of CuInS2 and sulfide P–N heterojunction. For this purpose, the single-source evaporation method and the chemical bath deposition had been applied to prepare CuInS2 films and sulfide films (CdS, CdZnS, and CdCuS), respectively. The powder source was obtained from CuInS2 polycrystalline ingot, which consists of CuInS2 chalcopyrite phase. The segregated CuxS secondary phase on the surfaces of CuInS2 films could be removed by etching of bromine–methanol (BM) solution. The structures of ternary sulfide films (CdZnS and CdCuS) were similar to that of CdS film. The transient photocurrent of CdZnS thin film was highest, which might be related to the high reaction activity and the good crystal quality. Furthermore, the I–V response of CuInS2 and CdZnS heterojunction was studied, which was close to the ideal diode type behavior. The low reverse saturation current density, the optimal diode ideality factor, and the high barrier height were obtained from the I–V curve of CuInS2 and CdZnS heterojunction, which might mean that the CdZnS film could be suitable to use in photovoltaic application.

The nonmonotonicity of the photocurrent increase due to the barrier photoconductivity of nanocluster Cd1−xZnxS films

The results of a study of the excitation kinetics of photoconductivity of pyrolytic CdZnS films with a nanostructured surface are presented in this paper. It is observed that the time dependences of the photoconductivity of the studied structures under their own excitation have a flash character. To explain the flash character of the time dependences of photoconductivity excitation, the model is proposed that takes into account the localization centers whose cross-section of charge carrier capture is functionally related to the optical modulation of the surface potential barrier.

Explosion Dependence of the Photoconductivity of Nanostructured CdZnS Films on the Excitation Time

The kinetics of photoconductivity excitation in pyrolytic CdZnS films is studied. It is established that the time dependences of the photocurrent in the investigated structures are of an explosion character. To explain these features, a model is proposed that considers the centers of localization for which the charge carrier capture cross section is functionally related to the optical modulation of the surface potential barrier.

Hydrothermal assisted chemical bath deposition of (Cd:Zn)S thin film with high photosensitivity and low dark current

In this work we observed high-quality nanocrystalline ternary films obtained by hydrothermal assisted chemical bath deposition on glass substrates. Deposition has been carried out at 200 °C for one hour. The alloying effect and the photoelectric properties of the material is enumerated in this paper along with the structural, Optical, morphological and photoluminescence properties. The structural properties analysed by X-ray diffraction (XRD) reveals the hexagonal phase of CdZnS film with preferred orientation along the (1 0 0) plane and the average grain size was observed to be 28 nm. Scanning electron microscopy (SEM) images showed clusters of nanofibers grown on the film. The optical bandgap obtained from the optical absorption studies using UV–Vis-NIR spectroscopy was 2.98 eV. Broad and asymmetric emission from intrinsic point defects was observed in the PL spectrum recorded using Fluromax-4Spectrofluorometer. The photoconductivity of the film was investigated by using Keithley SMU2450 four probe source measure unit under illumination by light from 300 W/82 V halogen lamp. In the dark condition, the I–V Curve showed non-linear behaviour, whereas the film showed ohmic behaviour under illumination. The photoresponse of the film was recorded at intervals of 100 s. The photocurrent increased under illumination and the current recovered to the original dark level when light was switched off. Under 100 s of illumination the photocurrent increased and became almost constant. This work presents a simple way to obtain photodetectors and will benefit in the manufacture of optoelectronic devices.

Precursor aging effect on the properties of CdZnS films

Nanostructured ternary Zn-doped CdS (CdZnS) thin films were fabricated from fresh and aged (1, 2, 3 and 4 days) starting solutions by the spray pyrolysis technique using a perfume atomizer. X-ray diffraction studies showed that the films are polycrystalline in nature exhibiting hexagonal crystal structure with a (0 0 2) preferential orientation. SEM images showed that the film prepared from 1 day aged solution possesses randomly oriented CdS crystallites of elongated needle shape. The optical band gap values exhibit a red shift with aging time of the precursor solution. A minimum resistivity of 3.94 × 10−3 Ω cm is obtained for the film prepared from 1 day aged solution. The obtained results infer that the CdZnS film prepared from 1 day aged solution exhibits better physical properties.

Structural, optical and electrical properties of Cl-doped ternary CdZnS thin films towards optoelectronic applications

This paper reports the effect of chlorine doping on the structural, morphological, optical and electrical properties of spray deposited ternary CdZnS thin films. Cadmium chloride (CdCl2·2H2O), thiourea (SC(NH2)2) and ZnCl2·6H2O were used as precursors to prepare CdZnS thin films. Cl doping is achieved by adding NaCl with concentrations 0, 2, 4, 6 and 8at.%. XRD analysis showed that the CdZnS and Cl-doped CdZnS films exhibit hexagonal crystal structure with a (002) preferential orientation. Film transparency increased with Cl doping and the band gap values exhibit a blue shift from 2.55eV to 2.78eV. Electrical studies showed that the CdZnS film resistivity decreased from 4.96×10−3ohm-cm to 0.614×10−3ohm-cm with Cl doping. The Raman studies confirmed the presence of defects in samples. Improved transparency, widened band gap and decreased resistivity values observed for the Cl-doped CdZnS films confirm that chlorine might be a suitable anionic dopant which can enhance the physical properties of CdZnS thin films.

English

English

CdZnS/CdTe 이종접합의 커패시턴스-전압 특성에 관한 연구

본 연구에서는 CdZnS와 CdTe로 구성되는 이종접합 소자를 제작하고 커패시턴스-전압 특성을 조사하였다. CdS/CdTe 접합의 경우, 역방향 바이어스가 증가함에 따라 공핍층의 폭이 커져 커패시턴스 값이 약간 감소하였으나 CdZnS/CdTe 접합에서는 CdTe 박막 내에서의 공핍층 폭이 바이어스에 크게 영향을 받지 않아 커패시턴스 값이 역방향 바이어스에 따라 거의 변화가 없었다. 바이어스 전압을 인가하지 않은 상태에서의 공핍층 폭은 높은 CdZnS 박막의 비저항 및 낮은 캐리어 농도로 인해 CdS/CdTe 접합보다 CdZnS/CdTe 접합에서 보다 큰 값을 나타내었다. CdZnS/CdTe 태양전지의 개방전압은 Zn의 비율이 커짐에 따라 CdZnS 박막과 CdTe 박막의 전자 친화력 차이의 감소로 인하여 크게 증가하였으나, Zn 비율이 0.35 이상인 경우 오히려 감소함을 알 수 있었다. 또한 CdZnS 박막의 높은 비저항이 태양전지의 직렬저항을 상승시켜 전지의 변환 효율은 오히려 감소함을 알 수 있었다. In this work, we fabricated the CdZnS/CdTe heterojunction and investigated the C-V characteristics to determine the depletion width and the charge density distribution. A parallel experiment on CdS/CdTe heterojunction was also carried out for comparison. The depletion region width, for CdZnS/CdTe heterojunction, was nearly constant, regardless of bias voltage. However, the depletion region was wider than that of CdS/CdTe heterojunction due to high resistivity of CdZnS film. The interface charge density of CdZnS/CdTe heterojunction was increased linearly with the bias voltage and showed lower values than those for CdS/CdTe junction. The open circuit voltage of CdZnS/CdTe heterojunction solar cells increased with zinc mole ratio due to reducing of the electron affinity difference between CdZnS and CdTe films. However, the increase of series resistance due to the high resistivity of Cd1-xZnxS films results in reducing conversion efficiency.

Optimization of sintering temperature in CdZnS films using reflection spectroscopy

In the present investigation, the polycrystalline films of Cd X Zn1–X S were prepared using a sintering technique. We coated slurry consisting of CdS, ZnS in the desired proportion—CdCl2 (as adhesive) and ethylene glycol (as binder)—onto the glass substrates. The films were sintered at a range of temperatures in air atmosphere for the optimization of sintering temperatures using reflection spectroscopy. It was noticed that below 500°C, CdS-dominated films were obtained, and above 500°C, ZnS-dominated films were obtained. The films of desired composition giving appropriate results are obtained at 500°C. The reason is easily understood through reflection spectroscopic studies. Thus, we found 500°C to be the optimum sintering temperature and 10 min was the proper sintering time.

Electrodeposition of Ternary CdZnS Semiconductor Thin Films Using a S-Modified Polycrystalline Au Electrode

This paper describes a two-step approach for the electrochemical deposition of CdZnS thin films on the polycrystalline Au electrode. Initially, an Au substrate is electrochemically modified with a sulfur layer. In the second step, the layer is electroreduced to <TEX>$S^{2-}$</TEX> in the electrolyte dosed with the requisite amount of <TEX>$Cd^{2+}$</TEX> and <TEX>$Zn^{2+}$</TEX> ions to generate CdZnS films in situ. This approach was validated using a combination of linear sweep voltammetry and electrochemical quartz crystal microgravimetry. Thus synthesized CdZnS thin films have different composition depending on the composition of electrolytes. CdZnS thin films are characterized by energy-dispersive X-ray analysis and Raman spectroscopy.

Deposition of cadmium sulphide and cadmium zinc sulphide thin films by photochemical deposition and their characterisation

CdS and CdZnS films were successfully deposited on glass/indium tin oxide (ITO) substrates from an aqueous solution. The ratio of Cd/Zn has been identified by auger electron spectroscopy (AES). The deposited films have been confirmed by X-ray diffraction (XRD) and were found to crystallise in the hexagonal crystal system. The surface of the as deposited and annealed films was analysed using SEM. The improvement of crystallinity was confirmed by Raman spectroscopy and XRD. Photoelectrochemical studies were carried out by fabricating a PEC cell of configuration CdS/0·1M Na2SO4/ITO and the physical parameters were studied. Current–voltage measurements were performed. The results of the present investigation are discussed in detail.

Structural and optical properties of vacuum evaporated CdxZn1−xS thin films

Abstract II–VI semiconductors are of great importance due to their applications in various electro-optic devices. Sulphides of zinc and cadmium have been utilized effectively in various opto-electronic devices. We have prepared vacuumed CdZnS films by the vacuum evaporation method. Wide band gap binary films have wide application in solar cells. The structural and optical properties of these films have been studied. The band gap of these films is studied by absorption spectra in the wavelength range 400–650 nm. The films have a direct band gap, which varies from 3.50 eV for zinc sulphide to 2.44 eV for cadmium sulphide. The X-ray diffraction pattern of these films for structural analysis is also reported.

Characteristics of the CdZnS thin film doped by indium diffusion

Effects of the thickness of indium films and the annealing temperature on structural, optical and electrical properties of chemically deposited CdZnS films were investigated. The diffusion process of evaporated indium was carried out by heating the sample in air at 150–550 °C for 1 h. X-Ray diffraction patterns of CdZnS films indicate that the minimum thickness and annealing temperature for the formation of an In 2O 3 layer, which acts as a barrier preventing the out-diffusion of indium and gives a high optical transmittance, are 20 nm and 350 °C, respectively. As the thickness of indium film and the annealing temperature increase, the conductivity of CdZnS films improves and the lowest resistivity of 0.3 Ω-cm is attained for CdZnS films with a 40 nm indium coating and annealed at 450 °C.

Structural, optical and photoelectrochemical properties of screen-printed and sintered (CdS)x(ZnS)1−x (0&lt;x&lt;1) films

Sulfides of zinc and cadmium have been used effectively in various optolectronic devices and recently as photocatalysts in the production of molecular hydrogen in photoelectrochemical processes. We have prepared sintered CdZnS films by the screen printing method without the presence of the typical flux material. The formation of crystalline ternary compounds is inferred fromthe X-ray diffraction pattern of these film s. Their structural and optical properties are studied by reflection spectra in a wavelength range of 300–600 nm. The films have a direct band gap, which varies from3.7 eV for zinc sulfide to 2.45 eV for cadm ium sulfide. Films with a narrow range of composition were found to be stable in Na2SO3 solution under cathodic or anodic polarization in dark and illuminated conditions. This potential interval allowed to determine the flat band potentials from capacity measurements in the dark, which indicated strong contribution of double layer capacitance, surfaces states, and nonuniform doping concentration. Electrochemical impedance measurements where further performed, giving detailed information about the relevance of these factors and the optimum composition of coupled semiconductor films for photocatalytic purposes. r 2002 Elsevier Science B.V. All rights reserved.