Doped CdS Films Research Articles

Structural, optical, dielectric and photovoltaic properties of Sn doped CdS films prepared with green synthesis route

Energy harvesting from renewable energy sources is one of the burning topics in today's research community. Solar cells are emerging as a potential candidate to harvest solar energy into electrical one. Here, we tested a series of pure and Sn-doped CdS as photoabsorbers in solar cells prepared by the sol-gel technique via the green synthesis route. The formation of a hexagonal wurtzite crystal structure of pure and Sn-doped CdS is confirmed using X-ray diffraction analysis. Doping of Sn caused a slight change in lattice parameters, crystallite size, d-spacing, and dislocation line density. UV–vis measurement revealed the direct bandgap nature of the material with bandgap value of 2.50 eV which reduced the 2.20 eV upon 3% Sn doping. Optical parameters, including extinction coefficient and refractive index, are measured. The film prepared with 3% of Sn doping has a high refractive index, i.e., 2.56. In addition, the imaginary and real parts of the dielectric constant are measured in the frequency range of 20Hz to 20 MHz, which exposed the presence of different relaxation phenomena in this composition. The solar cell prepared with 3% of Sn doping has a high value of current density (3.57 mA-cm−2), open circuit voltage (0.49 V), fill factor (0.654) and efficiency (1.14%). This solar cell is a stable cell due to the absence of liquid corrosion like in dye-sensitized solar cells.

Structural and optical properties of CdS & Pb doped CdS thin films coated by spin coating technique

CdS thin film has a wide range of applications in fabrication of hetero-junction solar cells, which are considered to be a promising alternative to the widely used silicon based devices for many years. Here we have deposited, CdS and Pb doped CdS thin films on a glass substrate at room temperature using spin coating technique. The intention of fabrication of Group II-VI type of thin films is that they can be used in the fabrication of transistors, sensors, light emitting devices etc. The structural, crystalline properties and average crystallite sizes of CdS and Pb doped CdS thin films were determined by X-ray Diffraction. FTIR spectrum was used to analyze the different functional groups and molecular vibrations present in CdS and Pb doped CdS thin films. The UV–Visible spectroscopy reveals the fact that, these thin films transmit all wavelengths in the visible region and the Photoluminescence (PL) spectrum shows that the CdS and Pb doped CdS films emit yellow and green color. From this we can conclude that, these types of thin films can be used for fabrication of optoelectronic devices in the visible range. Surface morphology of the deposited thin films is studied by Scanning Electron Microscopy (SEM) and the study shows that the deposited thin films have nanorods and nano flowers.

Structural, Morphology and Optical properties of Ag-doped Nanostructured CdS thin films

Chemical Spray Pyrolysis (CSP) method is employed to deposit CdS and Silver (Ag)-doped CdS films. The effect of Ag doping at 1, and 3 wt-% levels is considered. The principal X-ray diffraction peak was along (020) plane. Maximum grain size was observed at the (CdS:3% Ag) films. The dislocation density parameter increased from 53.04 to 37.08, whereas the strain(%) parameter decreases from 25.23 to 21.10. Atomic force Microscope (AFM) images indicate a polycrystalline structure, and reveal that the undoped CdS and doped CdS:Ag films have discontinuous surfaces with spherically grains decreased from (58.05 to 45.77 nm) with the increase of doping from 0% to 3%. Root-mean square (Rrms) roughness of surface is about (9.81-5.42) nm. Also, there was a clear decrement in transmittance as Ag increment. The optical energy bandgap Eg has been decreased from 2.47 to 2.37 eV due to increase in Ag content. The absorption coefficients with photon energy increase with increasing concentration doping in Ag.

Spray pyrolysis deposited Cr and In doped CdS films for laser application

Abstract By using the spray pyrolysis technique, CdS films uniform in composition and structure with different contents of chromium and indium ions were deposited on quartz substrates. Their structure, optical properties, and surface morphology were investigated. Employing the films as dopant sources, a correlation has been revealed between the composition of the films and the content of optically active centers in bulk ZnSe samples after doping at the HIP treatment. The process of Cr2+ ions diffusion in polycrystalline zinc selenide was studied, concentration profiles were measured, and the diffusion coefficients of Cr2+ions in one-side doped CVD-ZnSe samples were determined.

Cationic and anionic modification of CdS thin films by surface chemical treatment

Structural and physical properties of thin solid films can be modified by surface treatment. In this work, chemical bath deposited CdS thin films were treated both by a mercury chloride solution and by a saturated H2S gas. The effect of these treatments on electrical properties is clearly observed. Hg2+ doped CdS films show the highest dark and photo-conductivities, whereas the sulfurized CdS films become photo-insensitive. In Hg2+ doped CdS samples, new crystalline Hg3S2Cl2 and Hg2(ClO4)24H2O phases are found, and particle size reduction is observed at the surface. Both optical and electrochemical Mott-Schottky (M–S) analysis suggest an intraband level in the electronic structure of Hg2+ modified CdS. Sulfurized CdS films, on the other hand, keep unchanged their crystalline and morphological structure, as well as optical properties. Energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and M–S analysis indicate an increase of sulfur concentration at the surface of sulfurized CdS thin films, leading to a more stoichiometric CdS compound, which used to have lower conductivity. It demonstrates that ion exchange process or cationic substitution is effective for structural and physical property modification, whereas a gaseous saturation method or anionic modification results in a notable surface energy alteration in thin solid CdS films.

Influence of Zinc Content in Ternary ZnCdS Films Deposited by Chemical Bath Deposition for Photovoltaic Applications

Cadmium Zinc Sulfide thin films with different Zn concentration were synthesized in aqueous solution by chemical bath deposition (CBD) method using CdSO4, ZnSO4, CH4N2S for Cd+2, Zn+2, and S−2 ions source, respectively. The as-deposited films are well homogeneous, adherent and free from pinholes. The incorporation of Zn in CdS was found to be dependent on the annealing temperature. Structure, morphology, elemental analysis, optical and photoelectrochemical (PEC) properties of ZnCdS were characterized using X-ray diffraction, atomic force microscopy, energy dispersive spectroscopy, transmission electron microscopy and UV-Vis absorption measurements, respectively. According to EDS analysis the films are non-stoichiometric due to a deficit of sulfur, which becomes more important as the Zn content increases. The absorption edge shifts toward the lower wavelength region and hence the bandgap of the films increases as the Zn content increases. The values of optical absorption edge are found to change from 2.42 eV for CdS and 2.90 eV for ZnS thin films. The PEC and linear sweep voltammetry performance of the Zn doped CdS films were examined by chronoamperometry technique which provided a significant high potential current due to increase of the electrical conductivity as compared to CdS film.

Indium doping on the structural, surface and optical properties of CdS thin films prepared by ultrasonic spray pyrolysis method

CdS nanostructures are important and useful materials for photovoltaic applications. In this paper, pure CdS and In doped CdS (CdS:In) thin films were fabricated on soda lime glass substrate using ultrasonic spray pyrolysis (USP) method, to investigate the effect In concentration on the structural behavior, surface and optical properties of the CdS thin films by X-ray diffraction (XRD), Atomic Force Microscopy (AFM) and Ultraviolet–visible (Uv-vis) spectrophotometry. X-ray diffraction patterns of the pure and In doped CdS films indicated that pure CdS film had a mixed of cubic and hexagonal structure with polycrystalline nature while In doped CdS had a hexagonal structure with polycrystalline nature. Increasing the In doping ratio improve the (002) preferential orientation. The optical properties of the In-doped CdS and pure CdS films showed that the energy band gap of the In-doped CdS is a slightly lower than the energy band gap of the pure CdS film. The surface properties of the films showed that all thin films are compact and uniform.

Characterization of chemically-deposited aluminum-doped CdS thin films with post-deposition thermal annealing

Aluminium-doped CdS thin films were grown, using chemical bath deposition, on glass substrates in an ammonia-free system, with post-deposition thermal annealing at 300° C in air atmosphere. Their structural, morphological, mechanical, electrical and optical properties were studied by X-ray diffraction (XRD), atomic force microscope (AFM), nanoindentation, four-point probes method and UV-Vis spectrophotometer, respectively. XRD patterns show that doped CdS films have an hexagonal structure, with preferred orientation along the (0 0 2) plane, and their average crystallite size start to decrease when Al content reaches a certain value. The AFM studies reveal that surface roughness decreases with thermal annealing. Additionally, we found that the Young's modulus and hardness of the films decreases with increasing Al doping, and the electrical resistivity decreases with thermal annealing. The band gap was found to be in the range of 2.39–2.49eV for as-deposited films and 2.33–2.39eV for annealed films. Current-voltage (I-V) measurements were also carried out to the films, which showed rectifying behavior with Ag contacts for some doping levels.

Nanostructure Zn–Cu co-doped CdS chalcogenide electrodes for opto-electric-power and H2 generation

An efficient photoanode of Zn–Cu: doped nanostructure CdS film has been fabricated by a very simple and commercially usable chemical bath deposition methodology. The electrodes of various sizes were deposited, those ranged from 10 × 10 mm to 100 × 100 mm. Physico-chemical property of the film is investigated in-depth for the photo-electrochemical (PEC) hydrogen production and electric-power generation application. Especially, we studied the effect of Zn and Cu co-doping in the hexagonal CdS-lattice w.r.t. the structural, optical and PEC properties of the nanostructure film. Zn-doping induces an increase in the absorption of visible light photons. The doping enhances the photocurrent by twice as to the undoped, and generates a net photocurrent of ∼817 μA/cm2, at a very low applied potential of 0.1 V/SCE, in contrast to 366 μA/cm2 of its undoped counterpart. Electrochemical impedance spectroscopy demonstrated that the reduced e–h recombination is responsible for the superior performance of the electrodes. PEC cell fabricated by these electrodes showed a maximum hydrogen generation rate of ∼6.74 μmol/h as compared to 0.58 μmol/h from undoped counterpart; Further a photo to electric-power conversion efficiency of ∼0.16% has been achieved even at low biasing potential of 0.1 V/SCE under AM 1.5 solar simulated illumination. Undoped, Zn doped and Cu co-doped films are highly useful for dual applications of “solar power-generation” and “solar hydrogen-generation”, revealing that the Zn doped PEC solar cell is most efficient system for the hydrogen generation even at a very low voltage bias of 0.1 V/SCE.

Influence of (Zn + F) double doping on the structural, morphological, photoluminescence, optoelectrical properties and antibacterial activity of CdS thin films

The effects of (Zn + F) double doping on the structural, morphological, optical and electrical properties of CdS thin films is reported in this paper. Polycrystalline nature is observed for all the films. Zn-doped and (Zn + F) doubly doped CdS films exhibit a strong (0 0 2) preferential orientation similar to that of the undoped film. The (0 0 2) plane of the Zn-doped and (Zn + F) doubly doped films shift towards higher Bragg angles favoring a contraction in their lattice parameter values. Increased transparency and blue shift in optical band gap is observed for the doubly doped films. The electrical resistivity values of the undoped, Zn-doped, (Zn + F) doubly doped CdS thin films are found to be in the order of 10−1 Ω-cm. From the obtained results it is found that the physical properties of Zn-doped CdS films got enhanced when co-doped with fluorine, and the (Zn + F) doubly doped CdS thin films seem to be a potential candidate for future optoelectronic device applications. Antibacterial activity of the as deposited films were carried against E. coli gram negative bacteria and from the zone of inhibition it is confirmed that the (Zn + F) doubly doped CdS thin films can be used as a good antimicrobial agent against pathogenic microorganisms.

Structural, morphological, optical and electrical properties of CdS thin films simultaneously doped with magnesium and chlorine

CdS thin films simultaneously doped with Mg and Cl at different doping concentrations (0, 2, 4, 6 and 8 at%) were prepared on glass substrates by spray pyrolysis technique using perfume atomizer at 400 °C. The effect of Mg and Cl doping concentration on the structural, morphological, optical and electrical properties of the deposited films were investigated using X-ray diffraction (XRD), scanning electron microscopy, UV–Vis spectroscopy and dc electrical measurements, respectively. XRD analysis showed that the undoped and doped CdS films exhibit hexagonal structure with a preferential orientation along the (0 0 2) plane. The 2θ angle position of the (0 0 2) peak of the doped films was shifted towards a higher angle with increasing Mg and Cl concentration. The UV–Vis–NIR absorption spectra of Mg and Cl doped thin films are measured and classical Tauc approach was employed to estimate their band gap energies. The increase in band gap energy from 2.46 to 2.73 eV with the reduction in crystallite size supports quantum size effect. Raman spectra implied that more defects existed in the doped samples. Electrical studies showed that all the films have resistivity in the order of 101 Ω-cm and the CdS film with 6 at% Mg and Cl concentration has a minimum resistivity of 1.332 × 101 Ω-cm.

Cowrie-shell architectures: Low temperature growth of Ni doped CdS film

In this work, we report the synthesis of Ni doped CdS cowrie-shell architectures and submicron balls like structures via low temperature chemical bath deposition method. The as-synthesized materials were systematically characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDAX), Raman spectroscopy and FTIR spectra. XRD results revealed the existence of cubic phase of CdS based material. SEM pictures depicted the growth of well define morphologies i.e. cowries-shell and submicron balls. Deposition time and dopant played significant role in the growth of CdS based different architectures. The EDAX spectra confirmed the presence of Ni into the CdS lattice. Surface structure of synthesized material was derived by FTIR analysis.

Growth of CdS thin films on indium coated glass substrates via chemical bath deposition and subsequent air annealing

In the present work attempts were made to synthesize indium doped CdS films by fabricating In/CdS bilayers using CBD-CdS on vacuum evaporated In thin films and subsequent air annealing. 135nm CdS films were grown onto 20nm and 35nm indium coated glass substrate employing chemical bath deposition technique. The In/CdS bilayers thus formed were subjected to heat treatment at the temperatures between 200 and 400°C for 4min in the muffle furnace to facilitate indium to diffuse into the CdS films. XRD pattern ascertained no noticeable shift in lattice constant implying grain boundary metal segregation, while secondary ion mass spectrometry indicated the diffusion profile of indium into CdS matrices. Mass spectrometry results showed that substantial diffusion of indium had been taken place within CdS at 400°C. Dark and photocurrent with different illumination time were measured to ascertain the photosensitivity of pure and composite CdS films.

CdS:In Filmlerinin Karakterizasyonu ve Fotovoltaik Güneş Pillerinde Kullanılabilirliği

CdS is important II-VI group compounds semiconductor materials which are used as the window material in photovoltaic solar cells. Solar energy is an enormous amount of energy that is produced by the sun. It is a free and widely available energy source. A solar cell is a device that converts the energy of sunlight directly into electricity by the photovoltaic effect. In this study, CdS:In thin films have been produced by the ultrasonic spray pyrolysis (USP) technique onto glasses. The deposition is carried out at substrate temperature of 300±5 ◦ C. In this study, we have reported some properties such as optical, electrical and surfaces, of In doped CdS films for different annealing temperatures. The optical parameters such as transmittance, absorbance and energy band gap of the films were investigated by UV/VIS spectrophotometer. The band gap of all the films were obtained from the absorbance measurements in the visible range. Their optical gap values were recorded in the range between 2.11-2.32 eV. Thickness of the films and optical parameters (refractive index, extinction coefficient) has been determined using spectroscopic ellipsometry (SE) technique. Atomic force microscope (AFM) images were taken to see the effect of annealing temperature on surface topography and roughness of the films. The electrical resistivity values of the films determined by using four probe techniques.

Chemical bath deposition of CdS thin films doped with Zn and Cu

Zn- and Cu-doped CdS thin films were deposited onto glass substrates by the chemical bath technique. ZnCl2 and CuCl2 were incorporated as dopant agents into the conventional CdS chemical bath in order to promote the CdS doping process. The effect of the deposition time and the doping concentration on the physical properties of CdS films were investigated. The morphology, thickness, bandgap energy, crystalline structure and elemental composition of Zn- and Cu-doped CdS films were investigated and compared to the undoped CdS films properties. Both Zn- and Cu-doped CdS films presented a cubic crystalline structure with (1 1 1) as the preferential orientation. Lower values of the bandgap energy were observed for the doped CdS films as compared to those of the undoped CdS films. Zn-doped CdS films presented higher thickness and roughness values than those of Cu-doped CdS films. From the photoluminescence results, it is suggested that the inclusion of Zn and Cu into CdS crystalline structure promotes the formation of acceptor levels above CdS valence band, resulting in lower bandgap energy values for the doped CdS films.

Effect of the substrate temperature on the structural, optical and electrical properties of spray-deposited CdS:B films

Boron doped CdS films have been deposited by spray pyrolysis method onto glass substrate temperature in the range of 350–450 °C. And the effect of substrate temperature (Ts) on the structural, electrical and optical properties of the films were studied. The structural properties of boron doped CdS films have been investigated by (XRD) X-ray diffraction techniques. The X-ray diffraction spectra showed that boron doped CdS films are polycrystalline and have a hexagonal (wurtzite) structure. By using SEM analysis, the surface morphology of the films was observed as an effect of the variation of substrate temperature. The substrate temperature is directly related with the shift detected in the band gap values derived from optical of parameters and the direct band gap values were found to be in the region of 2.08–2.44 eV. The electrical studies showed that the film deposited at the substrate temperature 400 °C had high carrier concentration and Hall mobility and minimum resistivity. This resistivity value decreased with increase in temperature up to 400 °C indicating the semiconducting nature of B- doped CdS films. The lattice parameter, grain size, microstrain and dislocation densities were calculated and correlated with the substrate temperature (Ts).

STRUCTURAL AND OPTICAL CHARACTERIZATION OF CdS:Fe THIN FILMS PREPARED BY FLASH EVAPORATION METHOD

CdS thin layers of 250 nm thick doped with zero, 0.1, 0.2 and 0.3 weight percents iron were deposited on glass substrates by modified flash evaporation technique in vacuum at the pressure of 5 × 10−6 mbar. The structure of the films was investigated by X-ray diffractometry. It was revealed that the films had hexagonal structure with (002) preferred orientation. Field emission scanning electron microscopy (FESEM) was employed to study the surface morphology of the prepared samples. It was found from FESEM images that the Fe -doped CdS film showed more surface uniformity. Optical absorption data of the films were used to measure the band gap of the films. It was found that the band gap of the samples decreased upon increasing the Iron concentration. Photoluminescence (PL) spectra of the CdS:Fe thin films were used to study most prominent excitation peaks within the energy range (1.6–2.6 eV). The variation in peak energy was observed upon increasing the Fe content in the films.

The Effect of Zn Concentration on the Optical Properties of Cd<sub>10–x</sub>Zn<sub>x</sub>S Films for Solar Cells Applications

In this paper, Cd10–xZnxS (x = 0.1, 0.3, 0.5) films were deposited by using chemical spray pyrolysis technique, the molar concentration precursor solution was 0.15 M/L. Depositions were done at 350?C on cleaned glass substrates. X-ray diffraction technique (XRD) studies for all the prepared film; all the films are crystalline with hexagonal structure .The optical properties of the prepared films were studied using measurements from VIS-UV-IR spectrophotometer at wave-length with the range 300 - 900 nm; the average transmission of the minimum doping ratio (Zn at 0.1%) was about 55% in the VIS region, it was decrease at the increasing of Zn concentration in the CdS films, The band gap of the doped CdS films was varied as 3.7, 3.8, 3.6 eV at x = 0.1, 0.3 and 0.5 respectively.

Structural, electrical and optical properties of carbon-doped CdS thin films prepared by pulsed-laser deposition

CdS compounds have attracted interest due to their applications in optoelectronic devices such as solar cells and optical switches. The efficiency of these devices strongly depends on homogeneity, structural quality and morphology of the layers. The purpose of this work is to develop pure and carbon-doped CdS thin films on glass substrates, using pulsed laser deposition (PLD) process at relatively low deposition temperature. A computer controlled multi-target system allows the deposition of ITO conductive films as well as the one of pure or doped CdS films. In this case, predefined precise sequences of laser shots (KrF, wavelength 248 nm, pulse duration 20 ns) on the CdS and vitreous carbon targets, respectively lead to a well controlled carbon doping of deposited CdS films. Structural and chemical characteristics of the films and the multilayers investigated using XRD and Raman spectroscopy as well as optical and electrical properties are studied as a function of PLD deposition parameters and carbon doping.

Optical characterization and determination of carrier density of ultrasonically sprayed CdS:Cu films

In this work, CdS and Cu doped CdS films (at the Cu percentages of 1, 3 and 5) have been deposited onto glass substrates at 350 ± 5 °C by ultrasonic spray pyrolysis technique and their application potential for photovoltaic solar cells have been investigated. Optical properties and thicknesses of the films have been investigated by spectroscopic ellipsometry (SE). Ellipsometric angle ψ was used as the source point for optical characterizations. The optical constants ( n and k) and the thicknesses of the films have been fitted according to Cauchy model. Also, optical properties of the produced films have been analyzed by transmittance and reflectance spectra. Refractive index ( n), extinction coefficient ( k) and reflectance ( R) spectra have been taken by spectroscopic ellipsometer, while transmittance spectra have been taken by UV/vis spectrophotometer. The optical method has been used to determine the band gap type and value of the films. Mott-Schottky (M-S) measurements have been made to determine the conductivity type and carrier concentration of the films. Samples showed n-type conductivity and carrier concentration of undoped CdS sample was found to be 1.19 × 10 19 cm −3. Also, it was concluded that Cu doping has an acceptor effect in CdS samples. From the results of these investigations, the application potential of CdS:Cu films for photovoltaic solar cells as window layer was searched.