Photoelectrochemical (PEC) studies on CdSe thin films electrodeposited from non-aqueous bath on different substrates

Thin films of CdSe were deposited by potentiostatic mode on different substrates such as stainless steel, titanium and fluorine tin-oxide (FTO) coated glass using non-aqueous bath. The preparative parameters were optimized to get good quality CdSe thin films. These films were characterized by X-ray diffraction (XRD), optical absorption and photoelectrochemical (PEC) techniques. XRD study revealed that the films were polycrystalline in nature with hexagonal phase. Optical absorption study showed that CdSe films were of direct band gap type semiconductor with a band gap energy of 1·8 eV. PEC study revealed that CdSe film deposited on FTO coated glass exhibited maximum values of fill factor (FF) and efficiency (η) as compared to the films deposited on stainless steel and titanium substrate.     

Properties of electrochemically deposited CdTe thin films: annealing effect

CdTe thin film have been deposited onto stainless steel and fluorine doped tin oxide coated glass substrates from aqueous acidic bath using electrodeposition technique. The different preparative parameters, such as deposition time, bath temperature, pH of the bath have been optimized by photoelectrochemical (PEC) technique get good quality photosensitive material. The deposited films are annealed at different temperature in presence of air. Annealing temperature is also optimized by PEC technique. The film annealed at 200 °C showed maximum photosensitivity. Different techniques have been used to characterize the as deposited and also annealed (at 200 °C) CdTe thin film. The X-ray diffraction (XRD) analysis showed the polycrystalline nature and a significant increase in the XRD peak intensities is observed for the CdTe films after annealing. Optical absorption shows the presence of direct transition with band gap energy 1.64 eV and after annealing it decreases to 1.50 eV. Energy dispersive analysis by X-ray study for the as-deposited and annealed films showed nearly stoichiometric compound formation. Scanning electron microscopy reveals that spherically shaped grains are more uniformly distributed over the surface of the substrate for the annealed CdTe film. Photovoltaic output characteristics and spectral response of the annealed film have been carried. The fill factor and power conversion efficiency (η) of the cell are found to be 71 and 3.89 %.     

Synthesis and studies on effect of indium doping on physical properties of electrodeposited CdSe thin films

Semiconducting CdSe and indium doped CdSe (In: CdSe) thin films have been synthesized on stainless steel and fluorine doped tin oxide coated glass substrates in an aqueous medium using a potentiostatic mode of electrodeposition. The doping concentration of indium has been optimized to 0.15 vol% using the reliable photoelectrochemical technique. To study the effect of indium doping these films are characterized using X-ray diffraction, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, elemental mapping, Raman spectroscopy, contact angle measurement and UV–visible spectrophotometry techniques. CdSe and In: CdSe thin films are low crystalline with a cubic crystal structure. The valence states of CdSe and In: CdSe thin films are analyzed by means of XPS. Undoped CdSe thin film shows fiberlike morphology, which transforms into a beautiful web of nanofibers upon doping. The Elemental composition of both films analyzed by means of energy dispersive X-ray spectroscopy. Raman studies show transverse optical and longitudinal optical modes of phonon. Indium doping improves the hydrophilic nature of CdSe photoanode. The optical band gap (direct) found to be decreased from 2.02 to 1.67 eV upon indium doping. Both films are photoactive in nature.     

Structural, optical and photoelectrochemical properties of electrodeposited CdSe thin films

Cadmium Selenide thin films have been electrodeposited from an acidic bath using CdSO₄ as a cadmium source and SeO₂ as a selenium source at pH=3 on to stainless steel and fluorine-tin oxide coated glass substrates. The CdSe films have been characterized by X-ray diffraction, scanning electron microscopy and optical absorption. X-ray diffraction spectra showed that CdSe is polycrystalline with single hexagonal phase. The intensity of the (0 0 2) peak increases remarkably by annealing in nitrogen atmosphere. A microstructural study revealed that the films were uniform and well covered the substrate. Optical absorption studies showed that the bandgap of the CdSe is 1.70 eV. It is observed that the conductivity of the CdSe films increases by annealing in nitrogen atmosphere. The photoelectrochemical activities of CdSe films deposited on stainless steel and fluorine-tin oxide coated glass have been studied by using CdSe/ 1 M NaOH-1 M Na₂S-1 MS / C cell configuration and it is found that films deposited on stainless steel give better performance, photoelectrochemical (PEC) studies also reveal that the CdSe has n-type conductivity.     

Influence of pH on electrochemically deposited CdSe thin films

Polycrystalline CdSe thin films have been electrodeposited at room temperature on stainless steel (ss) and fluorine doped tin oxide (FTO) coated glass substrate from aqueous electrolytes containing salts of cadmium acetate and selenium dioxide. The pH of the bath is varied from 1.75, at the interval of 0.25, to 3. The effect of pH on the photoelectrochemical (PEC), structural and optical properties of the deposited film is studied. The pH of the bath is optimized by the PEC technique and is observed to be 2.75. The analysis of the XRD patterns show that the deposited CdSe material is polycrystalline with a hexagonal crystal structure. SEM study shows that the total substrate surface is well covered by uniformly distributed spherical shaped grains. The optical absorption studies reveal that the pH of the electrolytic solution has a significant effect on the band gap of the CdSe thin film. The transition involved is direct with band gap energy E_g of 1.72 eV.     

Structural and optical characterizations of chemically deposited cadmium selenide thin films

Synthesis of cadmium selenide thin films by CBD method has been presented. The deposited film samples were subjected to XRD, SEM, UV-vis-NIR and TEP characterization. X-ray diffraction analysis showed that CdSe film sample crystallized in zinc blende or cubic phase structure. SEM studies reveal that the grains are spherical in shape and uniformly distributed all over the surface of the substrates. The optical band gap energy of as deposited film sample was found to be in the order of 1.8 eV. The electrical conductivity of the film sample was found to be 10⁻⁶ (Ω cm)⁻¹ with n-type of conduction mechanism.     

Morphology, structural and optical characterization of electron beam evaporated bromoaluminium phthalocyanine (BrAlPc) thin films

Bromoaluminium phthalocyanine (BrAlPc) thin films have been deposited onto pre-cleaned glass substrates by electron beam evaporation technique. Thin films have been characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and optical absorption (UV–Vis) spectra. XRD studies of BrAlPc thin film deposited at room temperature shows the indication of the α-phase. FESEM images have shown that the most of particles are spherical in shape with an average size about 26–34 nm. Using UV–Visible spectra over the wavelength range 300–800 nm, the optical band gap, absorption coefficient and extinction coefficient of BrAlPc thin films are evaluated. The optical absorption measurements of thin films show that the absorption mechanism is due to direct transition.     

Preparation of colloidal cadmium selenide nanoparticles by pulsed laser ablation in methanol and toluene

Colloidal spherical nanoparticles (NPs) of cadmium selenide (CdSe) have been prepared by laser ablation of cadmium target in methanol and toluene solutions. The properties of CdSe nanoparticles ablated in methanol and toluene were investigated and compared. The morphology and structure of synthesised CdSe NPs were analyzed by X-ray diffraction (XRD), scanning electron microscopy and transmission electron microscope (TEM). XRD investigation revealed that the nanoparticles are crystalline and have hexagonal structure. Optical absorption showed that the value of optical energy gap of ablated CdSe nanoparticles depends on the solution type. TEM measurements showed that CdSe NPs with diameters ranging from 25 to 35 nm were synthesised in methanol while, the nanoparticles ablated in toluene have diameters in the range of (40–50) nm.     

Influence of Fe dopant concentration and annealing temperature on the structural and optical properties of ZnO thin films deposited by sol–gel method

Nanostructured Fe doped ZnO thin films were deposited onto glass substrates by sol–gel spin coating method. Influence of Fe doping concentration and annealing temperature on the structural, compositional, morphological and optical properties were investigated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), UV–Vis spectroscopy and photoluminescence (PL) measurements. XRD analysis showed that all the films prepared in this work possessed a hexagonal wurtzite structure and were preferentially oriented along the c-axis. Pure ZnO thin films possessed extensive strain, whereas Fe doped films possessed compressive strain. In the doped films, least value of stress and strain was observed in the 0.5 at.% Fe doped thin film, annealed at 873 K. Average crystallite size was not significantly affected by Fe doping, but it increased from 15.57 to 17.79 nm with increase in annealing temperature from 673 to 873 K. Fe ions are present in +3 oxidation state as revealed by XPS analysis of the 0.5 at.% Fe doped film. Surface morphology is greatly affected by changes in Fe doping concentration and annealing temperature which is evident in the SEM images. The increase in optical band gap from 3.21 to 3.25 eV, with increase in dopant concentration was attributed to Moss–Burstein shift. But increase in annealing temperature from 673 to 873 K caused a decrease in band gap from 3.22 to 3.20 eV. PL spectra showed emissions due to excitonic combinations in the UV region and defect related emissions in the visible region in all the investigated films.     

Band gap engineering in PbSe thin films from near-infrared to visible region by photochemical deposition method

Lead selenide (PbSe) thin films have been synthesized by the established photochemical deposition technique using lead nitrate and lead acetate as sources for the metal ions and sodium seleno sulphate as the selenium source along with triethanolamine, ammonia and hydrazine hydrate as complexing agents. A comprehensive study of the effect of substrate materials on physical properties of as deposited PbSe thin films is reported in this work. Two substrates were used in this investigation, namely soda lime glass slides and gold coin corning glass slides. The solution is irradiated with UV light and the photochemical reactions in the aqueous solution resulted in highly adherent metallic thin films. X-ray diffraction (XRD), scanning electron microscopy, optical and electrical measurement techniques were used for film characterization. The XRD analysis confirmed that all films were cubic, regardless of the cationic precursors and substrates used. The scanning electron microscope micrographs showed variations in morphology. The optical studies revealed that the films have good absorption in the visible region. The remarkable success of our effort was that we have been able to modify optical band gap of PbSe thin films over a wide spectral range by a cost effective route. The band gaps estimated from the transmission spectra were in the range 1.32–1.40 eV for films deposited on soda lime glass substrates and 1.46–1.55 eV for corning glass substrates. The room temperature conductivity of the PbSe films were in the range of 3.71 × 10^?7–513 × 10^?7 (Ω cm)^?1. The as deposited PbSe thin films with low transmittance in the visible region coupled with an appreciable reflectance in infrared region were found to satisfy the basic requirements for solar control coatings for window glazing applications in warm climates. Through this work we established that irrespective of metal salts, soda lime glass substrate was superior to corning glass substrate.     

Studies on hexagonal cadmium selenide thin film deposited by chemical route using ascorbic acid

We have successfully deposited cadmium selenide (CdSe) thin films by simple dip method using ascorbic acid as complexing agent. Variation of thickness with time and temperature were studied. Deposited samples were characterized by X-ray diffraction, scanning electron microscopy. The absorption, electrical and photoelectrochemical properties are also studied. The X-ray diffraction analysis shows that the film samples are in hexagonal structure. The optical band gap energy was found to be 1.70 eV. Activation energy was found to be 0.447 and 0.034 eV for higher temperature and lower temperature respectively. For CdSe photoelectrode, the open circuit voltage and short circuit current are found to be 267 mV and 175 mA respectively. The calculation shows the fill factor is 28.67 %. The power conversion efficiency is found to be 1.01 %.     

Synthesis and characterization of zinc stannate thin films prepared by spray pyrolysis technique

The zinc stannate thin films were synthesized by simple and inexpensive spray pyrolysis technique on the glass and fluorine doped tin oxide coated conducting glass substrates. The as deposited films were further annealed at 500 °C temperature for 12 h. The structural optical and morphological characterization of as prepared and annealed films was carried out by XRD, UV–Vis spectroscopy, SEM and AFM techniques respectively. The structural analysis shows that films are polycrystalline and crystallized in cubic inverse spinel crystal structure. SEM studies show that grain size increases after annealing and exhibits spherical morphology. AFM study shows that roughness is higher for the post annealed film. Further the samples were tested for testing their applicability for dye sensitized solar cells. The as prepared, annealed and CNT doped samples exhibits photoconversion efficiencies 2.7, 2.8 and 3.1 % respectively.     

Novel synthesis of interconnected nanocubic PbS thin films by facile aqueous chemical route

In the present investigation, we have successfully synthesized lead sulfide (PbS) thin films by using simple, cost effective and facile aqueous chemical route. The effect of deposition time on optical, structural and morphological properties of PbS thin films were investigated by using UV–Vis–NIR absorption spectroscopy, X-ray diffraction (XRD), photoluminescence, field emission scanning electron microscopy (FESEM), high-resolution-transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The optical band gap energy was varied in the range of 0.96–1.56 eV. The XRD patterns revealed the formation of pure cubic crystal structure. FESEM micrographs demonstrated the conversion of morphology from pyramidal to interconnected nanocubic. HRTEM and selected area electron diffraction (SAED) pattern illustrated that nanoparticles are compact, well interconnected and single crystalline in nature. EDS spectrum confirms that deposited PbS thin films are in good stoichiometry.     

Thickness effect on properties of titanium film deposited by d.c. magnetron sputtering and electron beam evaporation techniques

This paper reports effect of thickness on the properties of titanium (Ti) film deposited on Si/SiO₂ (100) substrate using two different methods: d.c. magnetron sputtering and electron beam (e-beam) evaporation technique. The structural and morphological characterization of Ti film were performed using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). XRD pattern revealed that the films deposited using d.c. magnetron sputtering have HCP symmetry with preferred orientation along (002) plane, while those deposited with e-beam evaporation possessed fcc symmetry with preferred orientation along (200) plane. The presence of metallic Ti was also confirmed by XPS analysis. FESEM images depicted that the finite sized grains were uniformly distributed on the surface and AFM micrographs revealed roughness of the film. The electrical resistivity measured using four-point probe showed that the film deposited using d.c. magnetron sputtering has lower resistivity of ～13 μΩcm than the film deposited using e-beam evaporation technique, i.e. ～60 μΩcm. The hardness of Ti films deposited using d.c. magnetron sputtering has lower value (～7·9 GPa) than the film deposited using e-beam technique (～9·4 GPa).     

X-ray line broadening and photoelectrochemical studies on CdSe thin films

Cadmium Selenide (CdSe) thin films have been prepared on Indium doped tin oxide coated conducting glass (ITO) substrates at various deposition potential and solution pH values using potentiostatic cathodic electrodeposition technique. The deposited films are characterized using X-ray diffraction, scanning electron microscopy, energy dispersive analysis by X-rays, optical absorption, and photoelectrochemical techniques, respectively. X-ray diffraction pattern revealed that the deposited films are found to exhibit hexagonal structure with preferential orientation along (002) plane. X-ray line profile analysis technique by the method of variance has been used to evaluate the microstructural parameters such as crystallite size, rms microstrain, dislocation density, and stacking fault probability. The variation of microstructural parameters with deposition potential, solution pH values, and annealing temperature are studied. Surface morphology and film composition are investigated by scanning electron microscopy and energy dispersive analysis by X-rays, respectively. Optical absorption analysis has been carried out to evaluate the optical parameters such as refractive index, extinction coefficient, real and imaginary dielectric constants, and packing density, respectively. Photoelectrochemical solar cells are constructed using as-deposited and annealed CdSe thin films as photocathode, and their power output characteristics are studied. The experimental observations are discussed in detail.     

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 (T _s) 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 (T _s ).     

A chemical synthesized Al-doped PbS nanoparticles hybrid composite for optical and electrical response

Structural, morphological, optical and electrical investigations of pure and Al-doped lead sulfide (PbS) nanoparticles hybrid composite was synthesized by simple chemical route. The detail analysis of the nanoparticle morphology of hybrid composites through optical investigation, phase purity and crystalline size had been characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), ultraviolet spectroscopy (UV), photoluminescence (PL). The lower angle XRD results confirmed that the phase purity and average crystalline size of the pure and Al doped PbS nanoparticles were determined by using the Debye–Scherrer’s formula. The average grain sizes of the pure and the Al-doped PbS nanoparticles were calculated and found to be 22 and 16 nm respectively. Surface morphology analysis was carried out by using SEM and TEM analysis. The surface morphology of pure and Al doped PbS nanoparticles is without any pinholes or cracks and hence they appear to be densely packed with spherical shaped grains. The optical properties of pure and Al-doped PbS analyzed using UV–Vis. absorption spectroscopy and Photoluminiscence (PL) spectra. The band gap values for the pure and the Al-doped PbS nanoparticles were found to be 1.94 and 2.04 eV respectively. The dielectric properties of the Al-doped PbS nanoparticle composites typical response e.g. dielectric constant, dielectric loss, and AC conductivity were analyzed at various frequencies and temperatures.     

Structural and optical characterization of CdS and CdHgTe thin films for the fabrication of CdHgTe/CdS structure

This article presents the deposition and characterization of CdS and CdHgTe thin films for the fabrication of CdHgTe/CdS structure. The growth of CdS and CdHgTe thin films on FTO-coated conducting glass substrates have been performed by chemical bath deposition (CBD) and electrodeposition methods, respectively. The deposition conditions have been optimized for getting better quality layers of CdS and CdHgTe. The grown layers of both CdS and CdHgTe have been characterized by photoelectrochemical cell (PEC) measurement, X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV–vis spectrophotometer. Annealing effect of the deposited films has also been investigated. Finally the fabrication of CdHgTe/CdS structure has been performed and investigated by I–V characteristics. PEC, XRD, SEM and UV–vis spectrophotometer studies reveal that chemically deposited CdS layers are n-type with band gap values vary from 2.29 to 2.41 eV and cubic with (111) preferential orientation, and have spherical grain distributed over the surface. However, electrodeposited CdHgTe layers are p-type with band gap values varying from 1.50 to 1.53 eV and cubic with highly oriented CdHgTe crystallites with the (111) planes parallel to the substrate, and have uniform distribution of granular grains over the surface. The fabricated CdHgTe/CdS structure gave an open-circuit photovoltage and a short-circuit photocurrent of 510 mV and 13 mA/cm² respectively, under AM 1.5 illumination.     

Effect of substrate temperature on the structural,morphological and optical properties of copper bismuth sulfide thin films deposited by electron beam evaporation method

Copper bismuth sulfide thin films were deposited at 200 °C, 300 °C, 400 °C and 500 °C on the glass substrates by electron beam evaporation method. X-ray diffraction study revealed that the copper bismuth sulfide films of single and mixed phases were formed as a function of substrate temperatures. Substrate temperature of 300 °C and 400 °C formed single phase Cu₄Bi₄S₉ and Cu₄Bi₅S₁₀ films respectively whereas substrate temperature of 500 °C formed mixed phases of Cu₄Bi₄S₉ and Cu₄Bi₅S₁₀ film. Crystallite size, dislocation density and microstrain of the films were modified by the various substrate temperatures. Surface morphology of the film Cu₄Bi₅S₁₀ deposited at 400 °C examined by scanning electron microscopy showed the distribution of spherical shaped particles on the film surface. The presence of copper, bismuth and sulfur elements in the deposited films was confirmed using energy dispersive spectral studies. The calculated direct optical band gap energy of the films deposited at different substrate temperature varied from 1.47 to 1.64 eV and the absorption coefficient is in the order of 10⁶ cm^?1.     

Structural and optical properties of electron beam evaporated CdSe thin films

Thin films of cadmium selenide (CdSe) as a semiconductor is well suited for opto-electronic applications such as photo detection or solar energy conversion, due to its optical and electrical properties, as well as its good chemical and mechanical stability. In order to explore the possibility of using this in optoelectronics, a preliminary and thorough study of optical and structural properties of the host material is an important step. Based on the above view, the structural and optical properties of CdSe films have been studied thoroughly in the present work. The host material, CdSe film, has been prepared by the physical vapour deposition method of electron beam evaporation (PVD: EBE) technique under a pressure of 5 × 10⁻⁵ mbar. The structural properties have been studied by XRD technique. The hexagonal structure with a preferred orientation along the (0 0 2) direction of films has been confirmed by the X-ray diffraction analysis. The films have been analysed for optical band gap and absorbed a direct intrinsic band gap of 1·92 eV.