Gel Spin Research Articles

Thermal Annealing Effect on Properties of Nickel Oxide (NiO) Thin Films for Photovoltaic Applications

In this study, the impact of annealing temperature (TA) from room temperature (RT) to 400 °C on the structural, optical and electrical properties of NiO thin films deposited using sol‐ gel spin coating technique on glass substrate is presented. A theoretical approach is also employed to calculate the open circuit voltage (VOC) from the energy band gap (Eg) value, fill factor (FF), short circuit current (ISC), and power conversion efficiency (PCE) of the material for solar cell applications. Crystallinity improvement is observed upon annealing the NiO thin films and the average size of crystallites varies from 28 to 34 nm with a maximum value observed for 300 °C annealed film. The SEM micrographs confirm the nano form of NiO nanoparticles, with particles that are between 73 and 100 nm in size. All the films are semitransparent with transmittance >55% and the thin film annealed at 300 °C exhibited 88% transmittance in the visible region, making it a promising option as a transparent conducting oxide (TCO) in photovoltaic applications. The I–V curves display a non‐linear behaviour for all annealing temperatures. The conductivity increases with an increase in TA and the film annealed at 300 °C shows the highest conductivity.

Effect of holmium on structural and optical properties of sol–gel spin coating-derived cadmium oxide thin films

Effect of holmium on structural and optical properties of sol–gel spin coating-derived cadmium oxide thin films

The microstructure and energy-band structure coupling regulation of Ti-doped seed layer for the NiO electrochromic composite films

Structure regulation and doping modification are important means to enhance the electrochemical and electrochromic performance of anode NiO electrochromic films. How to improve cycle stability is crucial for the application of NiO electrochromic films. In this work, we prepared Ti-doped seed layers with varying precise chemical stoichiometry ratios through the sol–gel spin coating method. Subsequently, NiO composite films were successfully fabricated on these seed layers through a simple hydrothermal process. Notably, among all the samples, the A 1/8 sample exhibits superior electrochromic performance, including a large optical modulation amplitude (69.61 % at 550 nm), faster response time (5.0 and 6.2 s), high coloring efficiency (33.87 cm2/C), and excellent cycle stability (3300 cycles). The seed layer plays a crucial role in preventing direct contact between the electrolyte and the electrode, inducing the growth of self-assembled structures, and enhancing adhesion between the film and the electrode. The Ti-doped seed layer can regulate the composite film microstructure and band structure, impacting the film electrochromic properties. In this work, we demonstrate that the cycle stability of the NiO composite films is improved through dual regulation of structure and doping. The A 1/8 sample exhibits superior cycle stability, attributed to the coupling effect of multi-channel nanostructure, and reduces interface barrier with FTO.

Enhancing Gel Spinning of Ultra-High Molecular Weight Polyethylene: Insights into Rheology and Microstructure

Enhancing Gel Spinning of Ultra-High Molecular Weight Polyethylene: Insights into Rheology and Microstructure

Exploration of electrical conduction mechanisms via modulating sintering period of La0.67Ca0.33MnO3 films in various phase regions

Perovskite manganese oxide films have garnered significant attention due to their unique and diverse physical properties. In this work, La0.67Ca0.33MnO3 (LCMO) films are prepared on LaAlO3 (00l) substrates using the sol−gel spin coating method with varying sintering period (Ps). By optimizing Ps, improvements were observed in the films’ structure, morphology, ionic valence, and temperature−dependent resistivity. The reduction in Mn−O bond length and the increase in Mn−O−Mn bond angle change the degree of MnO6 distortion, resulting in an increased eg bandwidth. As Ps increased, the LCMO films exhibited better crystalline quality. The improved Mn4+/Mn3+ ratio strengthened the double exchange effect, facilitating the carrier hopping of the eg electrons. Analyses of various electrical conduction mechanisms showed that optimized electron scattering behavior, reduced hopping distance, energy and theoretical Curie temperature collectively enhance the temperature coefficient of resistivity (TCR) of LCMO films under optimal Ps. The TCR of the LCMO films reached a maximum value (31.64 % K−1) at Ps = 18 min. These findings offer valuable insights into the main electrical conduction mechanisms in both metallic and semiconducting phases, providing a deeper understanding of the underlying physical processes and offering experimental guidance for optimizing the electrical transport properties of perovskite films.

Effect of Post-annealing Temperature on Microstructural, Morphological and Optical Properties of Sol–gel Spin Coated Cu Doped SnO2 Thin Films

Effect of Post-annealing Temperature on Microstructural, Morphological and Optical Properties of Sol–gel Spin Coated Cu Doped SnO2 Thin Films

Effect of Al doping on the structural, optical and photocatalytic properties of sol-gel spin-coated NiO thin films

Nanostructured NiO thin films are renowned for their catalytic activity and potential for degradation of industrial effluents. In this study, Al-doped NiO (Ni1-xAlxO with x = 0, 0.02, 0.04, 0.06, and 0.08) thin films were synthesized by sol–gel spin coating, and the influence of Al doping on their physical properties, surface morphology, optical band gap, and photo-catalytic performance was investigated. X-ray diffraction (XRD) analysis confirmed the high crystallinity of the thin films and revealed a pronounced doping effect on parameters such as crystallite size, microstrain, and dislocation density. Scanning electron microscopy (SEM) revealed the formation of spherical nanoparticles with particle sizes ranging from 26 nm to 11 nm. The elemental composition was verified through energy-dispersive x-ray (EDX) analysis. The optical bandgap of the prepared films was determined through UV-visible spectroscopy. The Ni0.98Al0.02O films exhibited the lowest PL intensity, indicating a reduced recombination rate. To assess the photo-degradation capability of the prepared thin film catalysts, industrial effluent Indigo Carmine was employed as a test compound. The Ni0.98Al0.02O sample demonstrated the highest degradation efficiency, achieving about 96% degradation within 2 h of UV–vis light irradiation. Furthermore, the degradation followed pseudo-first-order kinetics.

Effect of Spin Speed on the Physical Characteristics of CuO Films Synthesized by Sol–Gel Spin Coating for H2S Gas Sensing

Effect of Spin Speed on the Physical Characteristics of CuO Films Synthesized by Sol–Gel Spin Coating for H2S Gas Sensing

DEVELOPING HIGH-PERFORMANCE LOW-TEMPERATURE CO2 GAS SENSORS BASED ON NANOSTRUCTURED CO3O4 THIN FILMS: A SOL–GEL APPROACH AND THE ROLE OF ANNEALING

In this study, we synthesized Co3O4 thin films using a sol–gel spin coating method and investigated the effect of heat treatment on their carbon dioxide (CO2) gas sensing properties. To optimize their crystallinity and enhance their CO2 sensitivity, the thin films were annealed at temperatures ranging from 400∘C to 550∘C. We characterized the morphological, structural, electrical, and optical properties of the Co3O4 thin films to gain insights into their behavior in the low operating temperature range (OTR). Our X-ray diffraction (XRD) analysis revealed that all the thin films exhibited a cubic structure, with improved crystallinity observed at higher annealing temperatures. We observed a decrease in band edges in the optical transmittance spectra of the thin films as the annealing temperature increased, indicating a redshift in the absorption edge. Notably, the highest electrical conductivity was observed for the sample annealed at 550∘C, suggesting enhanced crystallinity and improved CO2 gas sensitivity. These findings provide valuable insights into the optimization of Co3O4 thin films for CO2 gas sensing applications.

Dry gel spinning of fungal hydrogels for the development of renewable yarns from food waste

BackgroundRenewable materials made using environmentally friendly processes are in high demand as a solution to reduce the pollution created by the fashion industry. In recent years, there has been a growing trend in research on renewable materials focused on bio-based materials derived from fungi.ResultsRecently, fungal cell wall material of a chitosan producing fungus has been wet spun to monofilaments. This paper presents a modification for the fungal monofilament spinning process, by the development of a benign method, dry gel spinning, to produce continuous monofilaments and twisted multifilament yarns, from fungal cell wall, that can be used in textile applications. The fungal biomass of Rhizopus delemar, grown using bread waste as a substrate, was subjected to alkali treatment with a dilute sodium hydroxide solution to isolate alkali-insoluble material (AIM), which mainly consists of the fungal cell wall. The treatment of AIM with dilute lactic acid resulted in hydrogel formation. The morphology of the hydrogels was pH dependent, and they exhibited shear thinning viscoelastic behavior. Dry gel spinning of the fungal hydrogels was first conducted using a simple lab-scale syringe pump to inject the hydrogels through a needle to form a monofilament, which was directly placed on a rotating receiver and left to dry at room temperature. The resulting monofilament was used to make twisted multifilament yarns. The process was then improved by incorporating a heated chamber for the quicker drying of the monofilaments (at 30⁰C). Finally, the spinning process was scaled up using a twin-screw microcompounder instead of the syringe pump. The monofilaments were several meters long and reached a tensile strength of 63 MPa with a % elongation at break of 14. When spinning was performed in the heated chamber, the tensile strength increased to 80 MPa and further increased to 103 MPa when a micro-compounder was used for spinning.ConclusionThe developed dry gel spinning method shows promising results in scalability and demonstrates the potential for renewable material production using fungi. This novel approach produces materials with mechanical properties comparable to those of conventional textile fibers.

Conductive and optically transparent sol–gel spin coated Al3+ and Sn4+ doped ZnO nano-crystalline thin-films

Conductive and optically transparent sol–gel spin coated Al3+ and Sn4+ doped ZnO nano-crystalline thin-films

Investigation of kesterite to stannite phase transition and band gap engineering in Cu2Zn1-xCoxSnS4 thin films prepared by sol-gel spin coating

In this study, the Cu2Zn1-xCoxSnS4 (CZn1-xCoxTS) films with partial cation substitution of cobalt are synthetized by sol gel spin coating, followed by sulfurization treatment. The incorporation of cobalt cation in the CZTS crystalline lattice as well as the phase transition from kesterite to stannite were confirmed by the X-ray diffraction (XRD) and Raman spectroscopy data. The XRD pattern shows peak-shifting toward higher 2θ by increasing the Co concentration, indicating a decrease in lattice parameters. The red shift of Raman peaks by increasing x from 0 to 0.6, confirms the phase transition. The CZn1-xCoxTS morphology was observed by scanning electron microscopy, showing large grain size as x increases and a good distribution of elements for all films. X-ray photoelectron spectroscopy was employed to study the valence of cations/anions and to probe the chemical bonds. The optical band gap showed a parabolic behavior versus the molar ratio Co/(Co + Zn), this deviation from Vegard’s law being induced by the difference in electronegativity between cobalt and zinc. The pure CZTS has a band gap of 1.47 eV, while for CZn0.6Co0.4TS the gap is 1.17 eV, which indicates that the incorporation of cobalt cation produces a red-shift of the band to band transition energy.

Synthesis of ZnO/CZTS Hetero-Structure Junction by Sol–Gel Spin Coating Technique

Pertaining to the optimal band alignment of ZnO and CZTS, the heterostructure was fabricated with CZTS as the absorber layer and ZnO being the buffer layer coated on the FTO glass for photovoltaic application. Both the layers were deposited by using sol–gel spin coating technique. The results revealed the polycrystalline nature of both ZnO and CZTS films with distinct phase formations, with ZnO exhibiting prominent diffraction peaks at 31.77, 34.31, 36.20, 47.47, and 56.59° corresponding to (100), (002), (101), (102), and (110) planes, while CZTS showed diffraction peaks at (112), (220), and (312) planes. ZnO thin films demonstrated high optical transmittance (∼90%) and exhibited a wide band gap of 3.24 eV, while CZTS demonstrated a band gap of 1.44 eV. AFM images showed smooth surfaces with favorable topography for both films. Hall effect measurements indicated differences in electrical properties of the two films. Raman spectroscopy revealed vibrational energy patterns in both films. Additionally, current–voltage (I-V) characteristics revealed the electrical behavior of the ZnO/CZTS heterojunction, shedding light on its diode characteristics under both dark and illuminated conditions. With CZTS’s ideal band gap of 1.44 eV, sunlight is easily absorbed, and ZnO’s high electron mobility makes it an effective layer for electron transport. As a result, power conversion efficiency can be improved.

Enhanced optical performance of solar cell using hydrophobic SnO2/TEOS/MTMS antireflection coating

AbstractAnti‐reflection coatings have potential usage in photovoltaic solar cells, sensors, and display devices to reduce reflectance, glare and enhance light transmission. ARC was developed to increase more efficiency of solar cell cover glasses, by depositing SnO2/TEOS/MTMS coating using the sol–gel spin coating technique. The coating showed a maximum transmittance of 92.70% at 399 nm wavelength with an average refractive index of 1.42. The transmittance of the antireflective film was increased by 2.29% than the bare glass substrate. The surface morphology of the coatings was investigated using FESEM analysis. The mechanical stability of the coating was evaluated using ASTM standard D 3363–05 pencil scratch test, and it demonstrated good performance against 3H hardness pencil. The efficiency of solar cells has been increased by 1.56% after depositing with single layer SnO2/TEOS/MTMS film. Moreover, the coating maintains the solar cell's performance even during dust exposure, because of its self‐cleaning ability with water contact angle of 94°. Thus, the Anti‐reflection coating can be applied to enhance the efficiency of photovoltaic system.

Impact of oxygen vacancies on enhanced NO2 gas sensing performance of lithium doped Co:ZnO thin films

This article explored the influence of lithium on cobalt-doped ZnO thin films fabricated via the sol–gel spin coating technique for NO2 gas sensing applications. The abundance of oxygen vacancies in ZnO can be proven by scanning electron microscopy, four-probe Hall measurements, photoluminescence spectroscopy, UV-visible spectroscopy, and x-ray photoelectron spectroscopy. The presence of lithium plays a crucial role in generating more oxygen vacancies in Co-doped ZnO was discussed. Among the fabricated samples, (Li-Co) co-doped ZnO exhibits better sensitivity (2940.17%), selectivity, repeatability, and stability (after 90 days) toward 75 ppm NO2 gas.

Exploring the spectroscopic and I‑V‑T characteristics advancements of cadmium zinc tungsten phosphate diode

This research accomplished the growth of cadmium zinc tungsten phosphate (CZWP) thin films on both glass and p-Si substrates, employing the sol–gel spin coating method. The sol–gel technique offers a versatile and controlled approach for fabricating nanomaterials with tailored properties. The structural and morphological analyses, conducted through XRD and FE-SEM, provided comprehensive insights into the nature of the films. The optical properties, absorbance behavior, energy gap, refractive indices, dielectric, conductivity, and electronegativity, underwent meticulous examination through UV–Vis spectroscopy. The X-ray diffraction analysis of the zinc cadmium tungsten phosphate diode reveals diffraction lines indicative of a nanostructure featuring a monoclinic-phase Zn2P2O7 and Cd3P6O28. Furthermore, SEM analysis confirms a nanoporous morphology with a nanograpes-like structure in the successful crystalline structure of the cadmium zinc tungsten phosphate nanostructure. The optical absorption studies, covering a wavelength range from 190 to 1500 nm, unveiled both direct and indirect energy band gaps, measuring 4.14 and 3.77 eV, respectively. A rigorous analysis of the I-V-T characteristics for the CZNP/p-Si junction in dark mode led to the identification of key parameters, including the transport ideality factor, barrier height, and series resistance.

Improved electrical transport properties of La0.7Ca0.3−xKxMnO3 (0.0 ≤ x ≤ 0.3) films grown on La0.3Sr0.7Al0.65Ta0.35O3 (00l) substrates by sol–gel spin coating method

Herein, La0.7Ca0.3−xKxMnO3 (LCKMO) films with highly oriented growth were prepared on La0.3Sr0.7Al0.65Ta0.35O3 (00l) substrates by sol–gel spin coating method. Comprehensive analysis of microstructure, surface morphology, ion valence, and electrical transport properties of LCKMO films indicates that the substitution of K+ ions for Ca2+ ions increased the ratio of Mn4+/(Mn3+ + Mn4+), narrowed the one electron bandwidth, and enhanced double exchange mechanism and electron–lattice coupling. Moreover, the doping of K+ ions induced the dense and uniform conical-structured growth of grains on the surface of the films. Results demonstrated that at x = 0.1, LCKMO film exhibited the maximum TCR of 17.84% K−1 at 253.07 K, which was 31.76% higher than that of previously reported La1−x−yCaxKyMnO3 ceramic with the highest TCR. Further theoretical insights into the effects of Ca/K co-doping on electrical transport properties were supplemented.

Optical response and temperature shielding coatings using tri-layer structure composed of titania/silica/titania

The fabrication of metamaterials with inspiration from nature paved the door for the creation of revolutionary passive and active devices. Butterfly wings are one of them, and their multilayered structure motivated nanotechnologists, physicists, and other optoelectronic and photonic engineers to develop photonic crystals, dielectric reflectors, and Bragg reflectors for use in visible light communication, solar cells, and other photonic and optoelectronic applications. We report the sol–gel spin coating of a dielectric reflector on the glass substrate, an optical passive component consisting of titania and silica thin films for infrared radiation reflection. Individual thin films of titania and silica on glass substrates were studied using an x-ray diffractometer, which indicated anatase of titania and the amorphous nature of silica at a Bragg angle of 25° with a sharp and wide peak, respectively. The multilayer structure of titania/silica/titania was further investigated using Fourier transform infrared spectroscopy, which revealed the presence of Ti–O–Ti and Si–O–Si vibrational bonds at wavenumbers 546 and 973 cm−1, respectively, as well as the presence of Ti–O–Si vibrational bond at 1100 cm−1. The thickness of the multilayer titania/silica/titania was measured using a cross-sectional field emission scanning electron microscope (FESEM) and found to be 160/240/160 nm, respectively. Finally, reflection investigation on the multilayer structure using ultraviolet–visible–near-infrared spectroscopy validated the reflection of the infrared spectrum area by around 70% and showed to be beneficial for temperature shielding applications on glass furnishings.

Impact of Mg‐doping on morphology, structure, optical properties, and enhancing photocatalytic performance of ZnO thin films, prepared by sol–gel spin‐coated method

AbstractThin films of pure and Mg‐doped ZnO (MZO) were successfully fabricated on glass substrates by sol–gel spin coating method. Microstructure, surface morphology, elemental composition, optical analysis, and Mg doping effect on the photocatalytic performance of the thin films have been measured by XRD, SEM, EDS, and UV–Vis, respectively. XRD analysis showed that ZnO and MZO thin films have a hexagonal wurtzite structure, and the intensity of the (0 0 2) peak moved from higher to lower angle and right to left with rising Mg‐dopant concentration, and crystallinity was enhanced with doping, whereas micro‐strain and dislocation density dropped. SEM analysis found that ZnO had spherical and agglomerated structures, and the increased size of the grains was observed with increasing doping. The optical analysis demonstrated that the band gaps increased as the dopant percentage increased. Methylene blue, a dye pollutant, examined the thin films’ photocatalytic performance. It was demonstrated that the addition of the Mg to the ZnO lattices increased the absorption of the hydroxyl ions at the surface of the thin film and hence acted as a trap site, leading to a decrease in the electron–hole pair and consequently enhancing the photodegradation.

UV photodetectors based on W-doped ZnO thin films

W-doped ZnO thin films deposited on Si substrates with (100) orientation by sol–gel spin coating method at temperature 500 °C. W/Zn atomic ratio varies from 0% to 4%. Then, the UV detection performance analysis of p–n heterojunction UV photodetectors based on W-doped ZnO/Si is analyzed. The current–voltage curves of W-doped ZnO/Si are investigated in dark and exhibit diode-like rectifying behavior. Among doped ZnO/Si, sample with atomic ratio of W/Zn = 2% is the best candidate to study photodetector characteristics in UV range. The resulting device exhibits a rectification ratio RR of 5587 at ±5 V, a higher responsivity of 3.84 A W−1 and a photosensitivity value of 34 at 365 nm under 0.5 mW cm−2. The experimental findings reveal that the UV detection performance of the heterojunction-based photodetectors strongly dependent on the properties of metal oxide layer. The main goal of this work is to investigate the effect of W doping on the performance of ZnO/Si based photodetectors. Based on our results, it is observed that 2 at% of W dopant is the optimum amount of doping for high performance photodetector of ZnO:W/Si heterojunction thanks to the suppressed recombination ratio and enhanced carrier separation properties in the depletion zone.