Showing papers on "Chemical bath deposition published in 2020"

Comparative studies of CdS thin films by chemical bath deposition techniques as a buffer layer for solar cell applications

Abstract: Cadmium sulfide (CdS) buffer layer that decouples the absorber layer and window layer in thin-film solar cells was synthesized by two different chemical bath deposition (CBD) techniques with varying deposition parameters. X-ray diffraction (XRD) revealed that the CdS thin film crystallizes in a stable hexagonal wurtzite structure having a preferential orientation along (002) reflection plane with a crystallite size varying from 20 to 40 nm. First longitudinal optical phonon mode was identified at Raman shift of 305 cm−1. Uniform, granular, continuous, and smooth surface with an average grain sizes (< 100 nm) as well as small roughness (< 9 nm) was observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM), respectively. The symmetric composition of cadmium and sulfur along with larger grains (20 nm) was observed at higher deposition temperatures and times. The optical band gap of CdS samples obtained from process one was in the range of 2.3–2.35 eV, while the band gap by the second CBD process lay in between 2.49 and 2.65 eV, showing the most stable compound of CdS. The presence of a green emission band in photoluminescence spectra (PL) demonstrated that the CdS material has better crystallinity with minimum defect density. Hall effect studies revealed the n-type conductivity of CdS thin films with a carrier concentration values in the order of 1016 cm−3. Furthermore, CdS thin films fabricated by CBD process exposed better quality that might be more suitable material as a buffer layer for thin-film solar cells.

One-Dimensional NiSe–Se Hollow Nanotubular Architecture as a Binder-Free Cathode with Enhanced Redox Reactions for High-Performance Hybrid Supercapacitors

Abstract: Selenium-enriched nickel selenide (NiSe–Se) nanotubes supported on highly conductive nickel foam (NiSe–Se@Ni foam) were synthesized using chemical bath deposition with the aid of lithium chloride a...

A MoNiO4 flower-like electrode material for enhanced electrochemical properties via a facile chemical bath deposition method for supercapacitor applications

Abstract: Recently, binary metal oxides with the multifunctional properties of nickel foam-based architectures have attracted considerable interest as desirable electrode materials for applications as well capability supercapacitors (SCs). In this study, the MoNiO4 flower-like nanostructure with enhanced supercapacitance performance was successfully synthesized via a chemical bath deposition (CBD) method and subsequent calcination in air. This approach was primarily due to the availability of more surface-active sites in a well-defined hierarchical architecture, which allowed the rapid diffusion of electrolyte ions and minimized the electron transport limitation. The as-fabricated MoNiO4 electrode yielded a maximum specific capacitance of 1140 F g−1 at 2 A g−1, which is comparable to those of the state-of-the-art MoNiO4 electrodes. Moreover, the MoNiO4 material exhibited an excellent energy density of 64.2 W h kg−1 at 2 A g−1, an outstanding power density of 1750 W kg−1, and an excellent electrochemical stability with 97.8% retention after 3000 continuous charge–discharge cycles, even at a high current density of 4 A g−1, which are comparable to those of the state-of-the-art MoNiO4 flower-like structure. The outstanding performance of the MoNiO4-based flower-like electrode was successfully utilized to drive efficient electrode for SCs applications. Moreover, the electrochemical performance of an unique hierarchically structured MoNiO4-based binder-free electrode with our facile approach paves a new pathway for the low-cost production of electrodes with the development of novel metal oxides for high-performance SC applications.

WO3 porous nanosheet arrays with enhanced low temperature NO2 gas sensing performance

Abstract: WO3 porous nanosheet arrays have been prepared by a facile chemical bath deposition. The as-prepared nanosheet arrays are found to be precursors of tungstite and hydrotungstite. The nanosheets become porous upon annealing of the precursors due to the removal of crystalline water. Constructed from porous nanosheets with ultra-thin thickness of 20 nm, WO3 arrays exhibit enhanced low temperature NO2 gas sensing performance. A high response of 460 toward 10 ppm NO2 is achieved at a working temperature of 100 °C. The superior sensing performance of the WO3 porous nanosheet arrays compared to the thick WO3 layer is ascribed to the high degree of participation in surface reaction with the gas for the nanosheet arrays. The temperature-dependant gas response to NO2 is interpreted by the competitive adsorption of oxygen and NO2 at low temperature and their desorption at high temperature.

The structure and photoelectrochemical activity of Cr-doped PbS thin films grown by chemical bath deposition

Abstract: Nanocrystalline undoped and Cr-doped PbS thin films were prepared on glass substrates by a simple chemical bath deposition method. The X-ray diffraction analyses of the films showed their polycrystalline nature with cubic structure and preferential growth along the (111) orientation. Cr incorporation decreases the average PbS crystallite size from 59.97 to 37.59 nm, whereas the strain and dislocation density showed an increasing trend. The atomic ratio of doping for Cr is about 0.63, 1.75, and 4.70% according to energy-dispersive X-ray (EDX) spectroscopy. Morphological analysis showed that the average sizes of nanoclusters decreased from 73 to 41 nm as the Cr concentration increased. The optical band gap values are increased with increasing Cr doping. The photoelectrochemical (PEC) behaviors and the stability of the Cr doped PbS photoelectrodes were studied in 0.3 M Na2SO3 electrolyte solution. Also, the incident photon-to-current efficiency and applied bias photon-to-current efficiency are calculated and showed optimized values of 13.5% and 1.44% at 0.68 V and 390 nm. Moreover, the optimized electrode shows high chemical stability and a long lifetime. Finally, the effect of temperature on the PEC behaviors is evaluated and the different thermodynamic parameters are calculated.

Enhancement in the performance of nanostructured CuO–ZnO solar cells by band alignment

Abstract: In this study, we investigated the effect of cobalt doping on band alignment and the performance of nanostructured ZnO/CuO heterojunction solar cells. ZnO nanorods and CuO nanostructures were fabricated by a low-temperature and cost-effective chemical bath deposition technique. The band offsets between Zn1−xCoxO (x = 0, 0.05, 0.10, 0.15, and 0.20) and CuO nanostructures were estimated using X-ray photoelectron spectroscopy and it was observed that the reduction of the conduction band offset with CuO. This also results in an enhancement in the open-circuit voltage. It was demonstrated that an optimal amount of cobalt doping could effectively passivate the ZnO related defects, resulting in a suitable conduction band offset, suppressing interface recombination, and enhancing conductivity and mobility. The capacitance–voltage analysis demonstrated the effectiveness of cobalt doping on enhancing the depletion width and built-in potential. Through impedance spectroscopy analysis, it was shown that recombination resistance increased up to 10% cobalt doping, thus decreased charge recombination at the interface. Further, it was demonstrated that the insertion of a thin layer of molybdenum oxide (MoO3) between the active layer (CuO) and the gold electrode hinders the formation of a Schottky junction and improved charge extraction at the interface. The ZnO/CuO solar cells with 10% cobalt doped ZnO and 20 nm thick MoO3 buffer layer achieved the best power conversion efficiency of 2.11%. Our results demonstrate the crucial role of the band alignment on the performance of the ZnO/CuO heterojunction solar cells and could pave the way for further progress on improving conversion efficiency in oxide-based heterojunction solar cells.

Synthesis and characterization of PbS nanowires doped with Tb3+ ions by using chemical bath deposition method

Abstract: Crystalline lead sulfide (PbS) nanowires doped with terbium (Tb3+) ions were synthesized by the chemical bath deposition method at room temperature. The powder was obtained from an aqueous solutions using lead acetate dehydrate, terbium nitrate, thiourea, potassium hydroxide and ammonia. The terbium molar concentrations were varied in the deposition process to investigate the effect on the structural, optical, morphological and luminescent properties of PbS nanowires. The crystalline size was found to be dependent on the concentration of the Tb3+ ions used. The estimated average crystalline sizes were calculated from the X-ray diffraction and found to be 34, 33 and 37 nm for PbS: 0% Tb3+, PbS: 0.2% Tb3+ and PbS: 0.5% Tb3+, respectively. The scanning electron microscopy micrographs depict nanowire shape for the undoped as well as Tb-doped samples. The energy-dispersive X-ray and Auger electron spectroscopy analyses confirmed the presence of all the expected elements. The solid powder nanowires exhibited high absorptions in the UV–Vis regions. The band gap energies were estimated in the range of 1.99–2.46 eV. The absorption edge and the band gap energies of these PbS nanowires have shifted depending on the concentration of the dopant. The maximum luminescence intensity was obtained for PbS: 0.2% Tb3+ ions and luminescent quenching was observed for higher terbium concentrations.

Electrosprayed MnO2 on ZnO nanorods with atomic layer deposited TiO2 layer for photoelectrocatalytic water splitting

Abstract: We have designed and produced a hierarchical photocatalyst for water splitting by first fabricating ZnO nanorods via a chemical bath deposition (CBD) process using ZnO seeds electrosprayed onto In-doped tin oxide (ITO), then electrospraying MnO2 particles as a co-catalyst, and finally depositing an ultrathin passivation layer of TiO2 via atomic layer deposition. These hierarchical photocatalysts exhibit excellent photoelectrochemical properties and reduced photocorrosion compared to materials without TiO2 coating. Moreover, the MnO2-garnished ZnO nanorods obtained at 550 °C deliver a 1.7-fold enhancement in photocurrent density (0.95 mA/cm2) at 1.2 VAg/AgCl in 0.5-M Na2SO3 solution compared to ZnO nanorods without MnO2. We attribute improved photocurrent density to rapid charge transfer and charge separation at the ZnO–MnO2 interface. This investigation illustrates a balanced design of a nanoarchitecture for photoelectrodes that favors formation of effective photoelectrocatalytic sites while improving stability for potential large-scale water splitting applications.

Fabrication and Characterization of UV Photodetectors with Cu-Doped ZnO Nanorod Arrays

Abstract: In this study, metal–semiconductor–metal (MSM) ultraviolet (UV) photodetectors (PDs) based on Cu-doped ZnO (CZO) nanorods (NRs) were fabricated and investigated. The CZO NRs were prepared on a Corning glass substrate by the chemical bath deposition (CBD) method with photolithography processes. It was found that the diameter and length of ZnO NRs increased with Cu-doped concentration. The X-ray diffraction (XRD) analysis showed that the growth of NR arrays along the c-axis was hexagonal wurtzite crystal. Compared with pure ZnO NRs, it can be seen that the main UV peak (378 nm) of photoluminescence (PL) spectra showed a blue-shift phenomenon with the increase of Cu-doped concentration. Additionally, it was found that the rise and recovery time of such a fabricated PD were shortened under the UV illumination. The UV sensing properties of the CZO PDs were improved since the trapping and de-trapping of electrons by Cu-related complexes were faster than the adsorption and desorption of oxygen molecules. With a 3 V applied bias and 380 nm UV illumination, the optimal sensitivity of our PDs is 196.6.

Enhancement of ZnO Nanorods Properties Using Modified Chemical Bath Deposition Method: Effect of Precursor Concentration

Abstract: In this study, the effects of different precursor concentrations on the growth and characteristics properties of the zinc oxide (ZnO) nanorods (NRs) synthesized by using modified and conventional chemical bath deposition (CBD) methods were investigated. The morphologic, structural and optical properties of synthesized ZnO NRs with different precursor concentrations were studied using various characterization techniques. The experimental results show that the varying precursor concentration of the reactants has a remarkable and significant effect on the growth and characteristics properties of ZnO NRs. In addition, the characteristic properties of ZnO NRs grown using the modified method showed significantly improved and enhanced properties. The average length of grown ZnO NRs increased with increased precursor concentration; it can be seen that longer ZnO NRs have been investigated using the modified CBD methods. The ZnO NRs synthesized at 0.05 M using the modified method were grown with high aspect ratios than the ZnO NRs grown using conventional means which were 25 and 11, respectively. The growth rate increased with increased precursor concentration; it can be observed that a higher growth rate was seen using the modification CBD method. Furthermore, XRD results for the two cases reveal that the grown ZnO samples were a nanorod-like in shape and possessed a hexagonal wurtzite structure with high crystal quality. No other phases from the impurity were observed. The diffraction peaks along (002) plane became higher, sharper and narrower as precursor concentration increased, suggesting that the crystalline quality of ZnO NRs grown using the modified method was more enhanced and better than conventional methods. However, optical studies show that the transmittance at each concentration was more than two times higher than the transmittance using the modified CBD method. In addition, optical studies demonstrated that the ZnO NRs grown by using modified and conventional methods had a direct Eg in the range of (3.2–3.26) eV and (3.15–3.19) eV, respectively. It was demonstrated in two methods that ZnO NRs grown at a precursor concentration 0.05 M gave the most favorable result, since the NRs had best characteristic properties.

Facile synthesis of nanoparticles anchored on honeycomb-like MnCo2S4 nanostructures as a binder-free electroactive material for supercapacitors

Abstract: In the present study, nanoparticles filled with honeycomb-like MnCo2S4 (MCS) nanostructures are prepared successfully on the surface of nickel foam using a simple and cost-effective chemical bath deposition method and can be used as a promising electroactive material for high performance supercapacitor applications. The electrochemical behavior of the as-prepared electroactive materials was studied by the cyclic voltammetry, galvanostatic charge/discharge, electron impedance spectroscopy. The crystalline phase, structure, morphology and composition of the as-prepared electroactive materials were analyzed by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The performance of the as-prepared electroactive materials was carried out in a 3 M KOH electrolyte in the three-electrode system. The unique nanoparticle structures enable and provides the more efficient pathways for the rapid mobility of electrons and ions. As a result, the as-prepared binder-free MCS electrode exhibits a higher specific capacity of 129.7 mA h g−1 at 1 A g−1, superior rate capability of 88.51% after 4000 cycles and excellent cycling stability of 87.81% respectively, which are much higher than that of MCO electrode. These results reveal that the as synthesized MCS electrode found to be the most promising candidate for high-performance supercapacitor applications.

Room temperature detection and modelling of sub-ppm NO2 by low-cost nanoporous NiO film

Abstract: NiO-based NO2 sensors operating at room temperature are attracting great attentions due to their promising energy and cost saving performances. However, only a few reports showed high sensitivity and selectivity in the sub-ppm concentration range and low limit of detection (LoD). In this work, we designed and fabricated by a low-cost chemical bath deposition (CBD) and thermal annealing a nanostructured and porous NiO thin film (nanoporous NiO film) composed of NiO nanoparticles (30−50 nm). The nanoporous NiO film was then applied as sensing element for the NO2 detection at room temperature, demonstrating a high response to sub-ppm level NO2 (140 ppb), excellent selectivity and stability, and a very low LoD of 20 ppb. The NO2 sensing mechanism was investigated and satisfactorily modelled by two energetically different and independent adsorption sites at room temperature. Both sites contribute to the NO2 detection at room temperature while only one site contributes at higher temperatures. The described low-cost fabrication method and the discussed superior NO2 sensing performances at room temperature make the nanoporous NiO film a promising NO2 sensor for environmental monitoring.

Synthesis and photoluminescence properties of hybrid 1D core─shell structured nanocomposites based on ZnO/polydopamine

Abstract: In the present work, we report on the modelling of processes at the zinc oxide and polydopamine (ZnO/PDA) interface. The PDA layer was deposited onto ZnO nanorods (NRs) via chemical bath deposition. The defect concentrations in ZnO before and after PDA deposition were calculated and analysed. The ZnONRs/PDA core–shell nanostructures were studied by transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman and Fourier-transform infrared (FTIR) spectroscopy, photoluminescence (PL) measurements, and diffuse reflectance spectroscopy. The TEM and electron energy loss spectroscopy (EELS) measurements confirmed the conformal coating of PDA, while the PL emission from ZnO and ZnONRs/PDA samples showed a reduction of intensity after the PDA deposition. The decrease of defect concentration participating in PL and quantum efficiency explains the PL reduction. Finally, the observed decrease of activation energies and a shift of the PL peaks are attributed to the formation of an additional local electrical field between the PDA and ZnO nanostructures.

Wearable Carbon Monoxide Sensors Based on Hybrid Graphene/ZnO Nanocomposites

Abstract: In this work, wearable resistive gas sensors based on hybrid graphene/zinc oxide (ZnO) nanocomposites were fabricated on a flexible cotton fabric and employed to monitor odorless and colorless carbon monoxide (CO). Dip-coating and chemical bath deposition (CBD) was used to deposit the graphene layer and grow the ZnO nanorods, respectively. The films were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-Ray diffraction (XRD) to investigate their morphological structures, elemental composition, and crystal phase, respectively. Those characterizations were also confirming the growth of ZnO nanorods on the already-deposited graphene layer on fabrics. From the gas sensor measurements at room temperature, it was revealed that these graphene/ZnO nanocomposites were highly sensitive and selective towards CO gas at low concentration down to 10 ppm. The shortest response and recovery times of the sensors were measured to be 280 s and 45 s, respectively. Moreover, in comparison to bare graphene sensors, the surface modification by ZnO nanorods could obviously enhance the sensing response by up to 40% (i.e., doubled sensitivity). These flexible hybrid sensors are therefore expected to be a promising alternative for the existing rigid CO sensors in the market by offering unique nanostructures, low-cost fabrication, high flexibility, and good sensing performances.

One-step facile synthesis of dense cloud-like tiny bundled nanoparticles of CuS nanostructures as an efficient electrode material for high-performance supercapacitors

Abstract: The dense cloud like tiny bundles consisting of CuS nanoparticles were prepared successfully by a simple facile one-step chemical bath deposition method. The CuS electrodes at three different time periods such as 5, 10 and 20 h were prepared and their crystallographic phase, structural, morphological and the composition of the as-prepared electrodes are studied in detail. The CuS-10 h electrode possessed the dense cloud like structured nanoparticles on the surface of the Ni foam created pathways in a more efficient manner that allows the swift mobility of electrons/ions. Moreover, the electrochemical behavior and performance of the electrodes are carried out in a 3 M KOH electrolyte in the three-electrode system. The cyclic voltammetry and galvanostatic charge/discharge results confirm that all the fabricated CuS electrodes exhibit the battery-type behavior. As a battery-type material, the binder-free CuS-10 h electrode exhibits the enhanced specific capacity of 164.053 m Ah g−1 at 1 A g−1, higher rate capability of 82.54% and good cycling stability of 97.12% after 4000 cycles, respectively, that is very high when compared to the CuS-5 h and CuS-20 h electrodes. As a result, from the detailed analysis, it is found that CuS as an excellent electrode material for high energy storage supercapacitor applications.

Synthesis and characterization of the chemically deposited SnS 1−x Se x thin films: structural, linear and nonlinear optical properties

Abstract: This article reported the synthesis of tin sulfide selenide (SnS1−x Sex) thin films with different compositions (0 ≤ x ≤ 1) using a cost-effective chemical bath deposition technique. The structural properties of the chemically synthesized SnS1−x Sex thin films were analyzed by means of the X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM). The XRD results demonstrate that all the chemically synthesized SnS1−x Sex thin films are polycrystalline and displayed an orthorhombic phase corresponding to the different compositions. The compositional elements of the SnS1−x Sex thin films were investigated via an energy dispersive X-ray analysis (EDAX). The optical study on the SnS1−x Sex thin films displayed that the chemically deposited SnS1−x Sex films exhibited a direct allowed optical transition and by increasing the Se content the magnitudes of the direct bandgap were decreased from 1.41–1.23 eV while the Urbach energy was increased. The effect of composition on the skin depth δ, absorption coefficient α, linear refractive index n and the static refractive index no of the SnS1−x Sex thin films was studied. Additionally, the results displayed that there is an improvement in the magnitudes of the nonlinear refractive index n2, optical conductivity, third-order nonlinear optical susceptibility $$\chi^{\left( 3 \right)}$$ and the electrical conductivity of the SnS1−x Sex thin films occurred by increasing the selenium content.

Zinc Vacancy - Hydrogen Complexes as Major defects in ZnO nanowires Grown by Chemical Bath Deposition

Abstract: Crystal defects in unintentionally doped ZnO nanowires grown by chemical bath deposition (CBD) play a capital role on their optical and electrical properties, governing the performances of many nan...