Pneumatic Spray Pyrolysis Technique Research Articles

Physicochemical investigation of pure cadmium hydroxide Cd(OH)2 and Cd(OH)2–CdO composite material deposited by pneumatic spray pyrolysis technique

Physicochemical investigation of pure cadmium hydroxide Cd(OH)2 and Cd(OH)2–CdO composite material deposited by pneumatic spray pyrolysis technique

Study on the physical properties of Cu2ZnSnS4 thin films deposited by pneumatic spray pyrolysis technique

The acquisition of new materials for the manufacturing of high efficiency and low-cost photovoltaic devices has currently become a challenge. Thin films of CuInGaSe and CdTe have been widely used in solar cell of second generation, achieving efficiencies about 20 %; however, the low abundance of In and Te as well as the toxicity of Cd is the primary obstacles to their industrial production. Compounds such as Cu2ZnSnS4, Cu2ZnSnSe4 and Cu2ZnSn(SSe)4 have emerged as an important and less costly alternative for efficient energy conversion in the future. In addition, these compounds have the required characteristics to be used as an absorber material in solar cells (band-gap close to 1.4 eV, an absorption coefficient greater than 104 cm-1 and a p-type conductivity). In this work, we present a study of the structural, compositional, morphological and optical properties of Cu2ZnSnS4 thin films deposited by spray pyrolysis technique as well as their dependence on temperature.

Role of substrate temperature on spray pyrolysed metastable π-SnS thin films

We report the synthesis of π-SnS thin films using a pneumatic chemical spray pyrolysis technique. The substrate temperature was varied in the range 300–400 °C to optimise the suitable growth condition and to investigate its effect on the phase stability of π-SnS. X-ray diffraction (XRD) pattern indicated the formation of π-SnS with a lattice constant of a = 11.59 Å. Films deposited at a substrate temperature of 325 °C exhibited higher crystallinity with a larger crystallite size. Besides that, the phase formation of π-SnS was confirmed using Raman spectroscopy vibrational modes. The direct optical band gap varied from 1.61 to 1.82 eV with the variation of substrate temperature. Needle shaped grain morphology was obtained in the scanning electron microscopy (SEM) micrographs. The defects present in the as-deposited films are determined using Photoluminescence (PL) spectra. Hall measurement studies showed that thin films has an n-type conductivity with resistivity in the range 10–103 Ωcm and mobility of the carriers 0.47–1.97 cm2/V with the variation of substrate temperature.

Influence of nitrogen doping on TiO2 nanoparticles synthesized by pneumatic spray pyrolysis method

Improving the photon harvesting efficiency of dye sensitized solar cells (DSSCs) employing TiO2 photo-anode has been the major issue since 1991. So it is very important to discover new techniques that will enhance the properties of TiO2 nanoparticles (NPs) which will then prevent recombination of the photo-generated electron hole pairs and as well as improving the visible absorption properties of the TiO2. This will in turn improve the performance of the DSSC photo-electrode. The optical, electronic and structural properties of TiO2 NPs rely on factors like morphology, surface area, particle size and the presence of beneficial defects caused by dopants. This study focuses on the fabrication and characterization of nitrogen doped TiO2 (NPs) prepared by pneumatic spray pyrolysis (PSP) technique. The un-doped and nitrogen doped TiO2 NPs were prepared using titanium butoxide as a precursor and urea as the dopant. The morphological and structural properties of PSP synthesized NPs were evaluated using SEM, EDX, Raman Spectroscopy (RS), XRD and FTIR. SEM analysis revealed that the presence of nitrogen dopant results in a significant change in the surface morphology of the PSP synthesized NPs. RS revealed the presence of Raman vibrational modes and symmetry at 158 (Eg(1)), 208 (Eg(2)), 258 (B1g), 255 (B1g) 396 (B1g), 514 (A1g + B1g(2)) and 640 (Eg(3)) belonging to a mixed Anatase-Rutile phase. XRD analysis revealed that the PSP synthesized NPs have particles sizes of 10.90 nm, 11.31 nm, 11.93 nm and 14.14 nm for un-doped TiO2, 0.005 M TiO2, 0.015 M TiO2 and 0.025 M TiO2 NPs respectively. FTIR spectra of the PSP fabricated samples exhibited a peak at 616.22 cm−1 that is assigned to Ti–O vibrational stretching of the anatase phase of TiO2. UV–vis spectroscopy revealed a decrease in energy band gap with increase in dopant level for the TiO2 samples prepared.

Structural, Morphological, Optical, and Electrical Characterization of Fluorine Doped Tin Oxide (FTO) Thin Films Synthesized by PSP

This paper reports a study of Fluorine-doped Tin Oxide (FTO) thin films deposited by the Pneumatic Spray Pyrolysis (PSP) technique. The films were deposited on glass substrates at 450 °C with a ~125 nm thickness, using an F/Sn ratio of 0, 0.2, 0.35, 0.5, 0.65 and 0.85, respectively. The samples were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), UV-visible Spectroscopy and Hall Effect techniques, respectively. XRD results revealed that the FTO thin films were polycrystalline with a tetragonal rutile-type structure and had preferential orientations along (110) planes. SEM studies showed that FTO thin film morphology was totally affected by an increased F/Sn ratio. The calculated grain mean sizes were 10-35 nm. Optical transmittance spectra of the films showed a high transparency of approximately 80-90 % in the visible region. The optical gap of FTO thin films was in a 3.70-4.07 eV range. Electrical and optical properties of these films were studied as a function of the F/Sn ratio. Therefore, the optimal FTO (F/Sn = 0.5) films revealed a maximum value of the figure of merit approximately 8.05 × 10-3 (Ω-1) at λ = 400 nm. The high-conducting and transparent-elaborating FTO thin films may have several promising applications due to its multifunctional properties.

Compositional dependence of optical and electrical properties of indium doped zinc oxide (IZO) thin films deposited by chemical spray pyrolysis

The structural and optoelectronic properties of undoped and indium doped zinc oxide (IZO) thin films grown on glass substrates through a simple reproducible custom-made pneumatic chemical spray pyrolysis technique are presented. X-ray diffraction (XRD) results showed a polycrystalline structure of hexagonal wurtzite phase growing preferentially along the (002) plane for the undoped sample. Increase in dopant content modified the orientation leading to more pronounced (100) and (101) reflections. Optical transmission spectra showed high transmittance of 80–90% in the visible range for all thin films. The optical band gap energy (Eg) was evaluated on the basis of the derivative of transmittance (dT/dλ) versus wavelength (λ) model and Tauc's extrapolation method in the region where the absorption coefficient, α ≥ 104 cm−1. The observed values of Eg were found to decrease generally with increasing In dopant concentration. From the figure of merit calculations a sample with 4 at.% In dopant concentration showed better optoelectronic properties.

Evaluation of the photodiscoloration efficiency of β-Bi2O3 films deposited on different substrates by pneumatic spray pyrolysis

Immobilization of β-Bi2O3 over corning glass and sintered silica discs was performed to evaluate a competing fixed support as an alternative to slurry based photocatalytic systems. Pneumatic spray pyrolysis technique was used to produce coatings of β-Bi2O3 at 450°C. Coated substrates were characterized using X-ray diffraction (XRD) and UV–Vis diffused reflectance spectroscopy (DRS), field emission scanning electron microscope (FESEM) and energy dispersive X-ray spectrometry (EDS). The XRD analysis showed that the obtained crystalline structure of the films is tetragonal β-Bi2O3 for both glass and silica. DRS showed the broad absorbance spectra of the films, correlated to β-Bi2O3 with an energy band gap of 2.4eV. FESEM showed that the morphology of the films was different according to the substrate. In the case of corning glass, random non-compact distribution of particles was observed while over silica discs overlapped sheets of β-Bi2O3 were seen. This is probably due to differences in the wetting and evaporation rate of the sprayed droplets. During photodiscoloration of anionic indigo carmine (IC) dye solution, the β-Bi2O3 coated silica was found more effective than the coated glass, response associated to the larger interaction between the dye molecules and catalysts assisted by the roughness and porosity induced by the silica. Furthermore, photocatalytic evaluation of coated silica in discoloration of other two organic dyes: cationic rhodamine B (RhB) and anionic acid blue 113 (AB) revealed that adsorption and interaction of the dye molecules with coated films could vary due to the presence of different functional and branched groups that overall affect the photocatalytic process, the kinetic rate of discoloration and the TOC analysis. Finally, after the assessment of stability of films and suitability of silica, it was confirmed that silica discs are favorable as a photocatalyst support and last long usage for photodiscoloration of organic dyes.

Highly oriented and conducting Bi doped ZnO (BZO) layers chemically sprayed using nitrogen gas carrier

In this work, we have successfully prepared the highly conducting and transparent Bi doped ZnO (BZO) thin films using pneumatic spray pyrolysis technique with nitrogen (N2) carrier gas. The evolutions of structural, morphological and opto-electrical properties of the BZO films as a function of Bi concentration were analyzed. It is found that the films are uniform with no haze or visible clusters. X-ray diffraction shows that all the films were polycrystalline with hexagonal wurtzite structure, without secondary phases. All the BZO layers exhibit the classical preferential orientation of (002) plane and it changes in favor of (100) plane at 3wt% Bi. The BZO thin films showed 83% as a value of average optical transmittance in the visible region. The optical band gap values oscillated around 3.23 and 3.27eV. The SEM micrographs show clusters and nano-crystalline grains with special shape on the surface. The photoluminescence spectra of the films exhibits ultraviolet and green emissions. The electrical resistivity reaches a minimum value (8.4310−3Ωcm) at 1wt% Bi.

Influence of Carbon Modification on the Morphological, Structural, and Optical Properties of Zinc Oxide Nanoparticles Synthesized by Pneumatic Spray Pyrolysis Technique

This paper reveals the influence of doping on the morphological, structural, and optical properties of zinc oxide (ZnO) nanoparticles (NPs) synthesized by pneumatic spray pyrolysis technique (PSP), using zinc ethoxide ZnO2CH32 as the precursor. The prepared samples were characterized by XRD, HRTEM, SEM-EDX, UV-Vis spectroscopy, and RS. RS analysis has revealed that the unmodified ZnO and carbon modified ZnO samples have characteristic Raman optic modes at 325 cm−1, 373 cm−1, and 432 cm−1 belonging to Wurtzite ZnO structure. The XRD ZnO (C:ZnO) NPS have characteristic peaks of hexagonal Wurtzite ZnO structure. HRTEM analysis has revealed that the synthesized ZnO NPs have particle size range of 8.8–11.82 nm. EDX spectra of both unmodified and modified ZnO nanoparticles have revealed prominent peaks at 0.51 keV, 1.01 keV, 1.49 keV, 8.87 keV, and 9.86 keV. The occurrence of these peaks in the EDX spectra endorses the existence of Zn and O atoms in the PSP synthesized ZnO NPs. The UV-Vis spectroscopy has revealed a red shift of the absorption edge, with the increase in C dopant level. The effect of nanocrystallite size and the gradual prominence of C into ZnO matrix due to increase in C dopant level in the PSP synthesized ZnO NPs was meticulously elaborated through Raman spectroscopy analysis.

Selenization of Cu2ZnSnS4 thin films obtained by pneumatic spray pyrolysis

Cu2ZnSnS4 thin films have been deposited by pneumatic spray pyrolysis technique under Argon atmosphere followed by a selenization step to induce film crystallization. This study deals with two different annealing parameters: the variation of annealing temperature in the range of 450°C–580°C and the variation of elemental Se weight available for annealing. With these two parameters it is possible to obtain films with a systematic reduction of the optical band gap energy as the composition of the films shifts from S-pure towards Se-rich as confirmed by Raman and X-ray diffraction. Pulsed glow discharge spectrometry was used to disclose the in-depth compositional profiles of the films; finding that the films results to be Se-rich but not S-free. Solar cells were processed with efficiencies up to 2.1%, with Jsc=21.9ma/cm2, Voc=287.7 and F.F.=33.4%.

Structure, X-ray photoelectron spectroscopy and photoluminescence investigations of the spray deposited cobalt doped ZnO thin films

A simple and cost-effective pneumatic spray pyrolysis technique (SPT) was employed to synthesize cobalt-doped zinc oxide (Co-ZnO) thin films onto the glass substrates at 450°C. The effects of Co doping on the structural, optical, compositional, morphological and photoluminescence properties of ZnO thin films were investigated. XRD analysis confirmed the polycrystalline nature of the films having hexagonal crystal structure as well as successful incorporation of Co2+ ions into the lattice position of Zn2+ ions in the ZnO host. The traces of Co incorporation were confirmed by the shift of peak position of (002) plane, change in lattice parameters, the shift of optical absorption edge towards higher wavelength and observations of three bands related to d–d transitions. The observed band gap energy of Co-ZnO films decreases from 3.22 to 2.76eV. The transmittance of the ZnO thin films decreases after Co doping. The X-ray photoemission spectra of doped films indicate the Co substitutes for Zn2+ and exist in +2 state. All the deposited pure and Co-ZnO thin films exhibit room temperature photoluminescence (PL).

Toward a high Cu2ZnSnS4 solar cell efficiency processed by spray pyrolysis method

In this work, a review about the influence of the growth parameters on the chemical and physical properties of Cu2ZnSnS4 (CZTS) deposited by pneumatic spray pyrolysis technique and its impact on the thin film solar cells is presented and analyzed in order to identify the major drawbacks of this technique and the possibility to improve the device efficiency. Our best solar cell using sprayed CZTS shows an open-circuit voltage of 361 mV, a short-circuit current density of 7.5 mA/cm2, a fill factor of 0.37, and an efficiency of 1% under irradiation of AM 1.5 and 100 mW/cm2. Some of the key mechanisms related to the properties of sprayed CZTS layers, as well as those concerning the solar cells mechanisms that limit the cell performance, are also analyzed.

Compositional optimization of photovoltaic grade Cu2ZnSnS4 films grown by pneumatic spray pyrolysis

We report on the compositional optimization of thin film deposition of Cu2ZnSnS4 (CZTS) onto Mo/glass substrates for low-cost solar cell applications, using pneumatic spray pyrolysis technique in air ambient. The influence of both, the starting-solution precursor's concentrations (mainly copper chloride and zinc acetate) and the further annealing conditions on the properties of the CZTS have been investigated. Before and after annealing, the films were analyzed with regards to its compositional, structural, morphological and electrical properties. Globally it was found that Cu poor and Zn rich conditions are needed to obtain the desired properties on the CZTS films, minimizing the probability for secondary phase occurrence. Solar cell prototypes were fabricated using a classical CZTS/CdS/i-ZnO/ZnO:Al structure and characterized, correlating their optoelectronic properties with the chemico-physical, structural and electrical characteristics of the layers. Selective oxidation of Zn containing phases is identified as the major drawback of the technique, and its elimination as the most important challenge to improve the device's performance.

Characterisation of ZnO thin films doped and co-doped grown by pneumatic spray pyrolysis

From all the transparent conducting oxides (TCOs) studied in recent years, zinc oxide has emerged as one of the most promising materials. In the present work and in the order to obtain the high TCO materials, ZnO films were deposited by pneumatic spray pyrolysis technique on glass substrates. Our interest is on the investigation of the doping kinds influence on the structural and optical properties of ZnO thin films. One has used two dopants i.e., Bi and Sn. All the films were found to be polycrystalline and show a (0 0 2) preferential growth, the preferred orientation does not depend on the nature of dopant. The optical characterisation of deposited films was carried out using UV-Vis spectrometry. The analysis of the transmittance spectra allows us to deduce the films thicknesses and optical band gaps. Hence, the values of the gap were found to be between 3.24 to 3.32 eV.

Nickel-induced microwheel-like surface morphological evolution of ZnO thin films by spray pyrolysis

Nickel–zinc oxide (Ni–ZnO) thin films were deposited onto glass and tin-doped indium oxide-coated glass substrates by using a pneumatic spray pyrolysis technique at 450 °C from aqueous solutions of zinc acetate and nickel acetate precursors. The effect of nickel doping on structural, morphological and optical properties of the ZnO thin films has been studied. The X-ray diffraction patterns confirmed the polycrystalline nature of the films having hexagonal crystal structure. Ni–ZnO films with appropriate nickel doping revealed the occurrence of novel wheel-like surface morphology. The absorption edge of the Ni–ZnO films showed a red shift, meaning that the optical band gap energy decreases as the nickel doping concentration increases. A growth model is developed and proposed for the novel wheel-like morphology. All the thin films exhibited room-temperature photoluminescence. Pure ZnO and Ni–ZnO thin films were tested for their photoelectrochemical performance in 0.5 M Na2SO4 electrolyte solution. The values of fill factor and open circuit voltage were improved for the Ni–ZnO thin films.

Studies on Structural, Optical and Electrical Properties of ZnO Thin Films Prepared by the Spray Pyrolysis Method

Zinc oxide transparent thin films have been deposited on glass substrates by a pneumatic spray pyrolysis technique. Surface investigations such as AFM, SEM and XRD patterns of the films were investigated for as-deposited and annealed in air atmosphere. The morphology of the films is strongly related to the annealing temperature. By XRD, the amorphous phase is identified for as-deposited films and it changes to polycrystalline with the (1 0 0) and (1 0 1) as preferential crystallographic orientation for annealed samples. The as-deposited films exhibited highest optical transmittance and the direct band gap energy was found to vary from 3.23 to 3.07 eV with annealing temperatures. The electrical parameters of the samples were obtained by applying the dc four-probe technique. The effects of annealing environment on the luminescence characteristics of ZnO thin films were investigated by PL films are described here.

Enhancement of Photoluminescence Lifetime of ZnO Nanorods Making Use of Thiourea

We have investigated correlation of photoluminescence lifetime between zinc oxide (ZnO) nanorods and thiourea‐doped ZnO nanorods (tu: CH4N2S). Aqueous solutions of ZnO nanorods were deposited on glass substrate by using pneumatic spray pyrolysis technique. The as‐prepared specimens were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), and time‐resolved photoluminescence spectroscopy (TRPL). The photoluminescence lifetime of ZnO nanorods and ZnO nanorods containing thiourea was determined as τ = 1.56 ± 0.05 ns (χ2 = 0.9) and τ = 2.12 ± 0.03 ns (χ2 = 1.0), respectively. The calculated lifetime values of ZnO nanorods revealed that the presence of thiourea in ZnO nanorods resulted in increasing the exciton lifetime. In addition to the optical quality of ZnO nanorods, their exciton lifetime is comparable to the longest lifetimes reported for ZnO nanorods. The structural improvement of ZnO nanorods, containing thiourea, was also elucidated by taking their SEM images which show the thinner and longer ZnO nanorods compared to those without thiourea.

Sprayed lanthanum doped zinc oxide thin films

Lanthanum doped zinc oxide thin films were deposited on soda-lime glass substrates using a pneumatic spray pyrolysis technique. The films were prepared using different lanthanum concentrations at optimum deposition parameters. We studied the variations in structural, morphological and optical properties of the samples due to the change of doping concentration in precursor solutions. X-ray diffraction (XRD) patterns show that pure and La-doped ZnO thin films are highly textured along c-axis perpendicular to the surface of the substrate. Scanning electron micrographs show that surface morphology of ZnO films undergoes a significant change according to lanthanum doping. All films exhibit a transmittance higher than 80% in the visible region.

Enhanced photoelectrochemical performance of Ag–ZnO thin films synthesized by spray pyrolysis technique

Silver doped zinc oxide (Ag–ZnO) thin films were deposited on glass and tin doped indium oxide (ITO) coated glass substrates by using pneumatic spray pyrolysis technique (SPT) at 450°C from aqueous solutions of zinc acetate and silver nitrate precursors. The effect of silver doping on structural, morphological and optical properties of films was studied. The XRD spectra of the Ag–ZnO films indicate the polycrystalline nature having hexagonal crystal structure. SEM micrographs show the uniform distribution of spherical grains of about 80–90nm grain size for the pure ZnO thin films. The Ag nanoparticles are clearly visualized in SEM images of Ag–ZnO samples. The optical band gap energy decreases as the percentage of silver doping increases. Surface Plasmon Resonance (SPR) related phenomena are observed and correlated to the optical properties of Ag–ZnO thin films. The overall photoelectrochemical (PEC) performance of the samples was investigated and discussed. Moreover, the samples are more photoactive as compare to the pure ZnO sample and the sample ZnOAg15 shows the highest current. The photocurrent increases upto 249μAcm−2 and 303μAcm−2 in visible light and in UV illumination, respectively, and then decreases as the Ag doping increases into the film.

Synthesis and characterization of ZnO and ZnO:Al by spray pyrolysis with high photocatalytic properties

The pneumatic spray pyrolysis technique was used to deposit zinc oxide and aluminum doped zinc oxide films. X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and optical transmission were used to characterize the films and their photocatalytic activities were measured by the degradation of an organic dye under ultraviolet irradiation. A thickness-based rate constant was calculated for both, undoped and Al-doped thin films, obtaining values of k t(ZnO) = 0.25 and k t(ZnO:Al) = 0.32 h −1 μm −1, respectively, which resulted higher than that of a TiO 2 film ( k t = 0.21 h −1 μm −1). The stability of the films was also evaluated by the repetition of the degradation test three times. A slight decrease in the activity was observed after the third cycle particularly for the doped film. These results along with the characterization results show that the incorporation of aluminum to the zinc oxide matrix produce a slight increase in the optical band gap of ZnO:Al (3.26 eV) compared to the pure ZnO film (3.23 eV), and favors the formation of surface structures that contributed to enhance the photocatalytic activity.