Narrow Results

Dust and other environmentally suspended particles deposited on the solar panels reduce the sunlight to photovoltaic cells, reducing the total energy outcome. A dust-reflecting coating keeps a cleaner surface, thus enhancing light absorption and improving the overall energy outcome. This study synthesized the sol–gel of SiO₂, MgF₂, and TiO₂ and made the coating on the glass substrate by SiO${}_2+{\mathrm{\text{MgF}}}_2$, SiO${}_2+{\mathrm{\text{TiO}}}_2$, and MgF${}_2+{\mathrm{\text{SiO}}}_2+{\mathrm{\text{TiO}}}_2$ using sol–gel dip coating and spin coating method. Coatings that occurred on the glass sample surfaces were identified by using FTIR analysis. Five of the above six coatings made using different mixtures have increased transmittance than pure glass, while one SiO${}_2+{\mathrm{\text{MgF}}}_2$ spin coating reduced the transmittance. The minimum water contact angle of 37.69^∘ was found on the SiO${}_2+{\mathrm{\text{TiO}}}_2$ spin-coated surface, and the maximum contact angle was 72.10^∘ on the MgF₂ dip-coated surface. This shows that the self-cleaning properties in SiO${}_2+{\mathrm{\text{TiO}}}_2$ spin-coated surfaces are maximum and minimum in MgF₂ dip-coated surfaces. The angle found by the test shows that spin coating is a better technique than dip coating for hydrophilic surface coating. This was due to the more homogenous coating on the spin-coated sample surfaces. There was less accumulation of dust found on the coated surfaces compared to non-coated glass sample surfaces.

New Julolidine substituted phthalocyanine dyes developed in this work exhibit being cost-effective and simple to produce. FTIR, MALDI-TOF, UV-visible, and NMR analysis verified the structural properties of the dyes. The dyes did not clump and were soluble in a wide range of organic solvents. The dyes ZnPc, NiPc, CoPc and CuPc are completely transparent in solution. The dye’s thermal stability and transmittance were measured using thermogravimetric analysis (TGA) and UV-visible spectroscopy. Among the other produced dyes, ZnPc (17%) spin-coated films had the lowest light scattering process and the maximum transmittance (83%) in the blue area. Finally, the combined results revealed that ZnPc dye might be employed as an LCD color filter.

In this study ZnO thin film was fabricated by sol-gel spin coating method on glass substrate. X-ray reflectivity (XRR) and its optimization by simulated annealing (SA) technique have been used for characterization and extracting physical parameters of the film. The model independent information was needed to establish data analyzing process for XRR before optimization process. This independent information was extracted from wavelet transform of Fresnel reflectivity normalized XRR. This transformation yields thickness of each coated layer. This information was a keynote for constructing optimization process. Specular XRR optimization yielded structural parameters such as thickness, roughness of surface and interface and electron density profile of the film. Acceptable agreement exists between results obtained from wavelet transformation and XRR fitting.

Organic inorganic-based perovskites solar cells (PSCs) are quite prominent as next generation solar cells as they exhibit excellent properties as well as high power conversion efficiency. In spite of the high cost, interfacial recombinations and instability in ambient environment limit their commercialization. Herein, TiO₂-based compact layer (c-TiO₂) with different thicknesses is employed (<50nm) to study the charge transportation at interface and recombination in PSCs fabricated under high humid conditions (R${}_{\text{H}}\sim$ 80%). The thickness of CL was varied from 7nm to 35nm and was optimized by changing the precursor concentration as well as spinning speed. The prepared c-TiO₂ and the mesoporous layer of TiO₂ (m-TiO₂) were thoroughly characterized using Raman spectroscopy, UV-Vis, cyclic voltammetry and electrochemical techniques. Furthermore, CuSCN was used as hole transporting layer (HTL) in PSCs owing to ease of handling and nominal cost. The optimized PSC is found to show that the power conversion efficiency (PCE) improved by 50% on varying the thickness of CL and is stable even under high humid conditions. The elevated performance of PSCs is ascribed to the appropriate thickness of CL which resulted in improved charge transportation and reduced electron hole recombinations.

Copper phthalocyanine (CuPc) is synthesized chemically and used for making CuPc thin films using spin coating technique. Films were prepared from trifluroacetic acid (TFA) and chlorobenzene mixed solution on the glass substrate. Spin coated films of unsubstituted CuPc films were heat annealed at 150°C for 2 h duration and were used to study NO₂ gas sensing characteristics. α-phase of CuPc is noted by UV-visible absorption spectra. IR spectra of undoped CuPc films and doped CuPc films with NO₂ revealed that, doping of nitrogen dioxide modifies and deletes some of the bands. The effect of NO₂ at various concentrations from 50 ppm to 500 ppm in atmospheric air at room temperature on the electrical conductivity of CuPc films was studied. Sensitivity, response time and repeatability of the CuPc sensor were discussed in this paper.

In this work, electrochemical double layer supercapacitors were fabricated using multiwalled carbon nanotube (MWCNT) composite microfilm as electrode. To improve the electrochemical properties, MWCNTs were functionalized with −COOH by acid treatments. CNT/PVA films have been deposited on different current collectors by spin coating to drastically enhance the electrode performance. Electrode fabrication involved various stages preparing of the CNT composite, and coating of the CNT/PVA paste on different substrates which also served as current collector. Al, Ni and graphite were used and compared as current collectors. The surface morphology of the fabricated electrodes was investigated with scanning electrode microscopy (SEM). Overall cell performance was evaluated with a multi-channel potentiostat/galvanostat analyzer. Each supercapacitor cell was subjected to charge–discharge cycling study at different current rates from 0.2Ag${}^{-1}$ to 1Ag${}^{-1}$. The results showed that graphite-based electrodes offer advantages of significantly higher conductivity and superior capacitive behavior compared to thin film electrodes formed on Ni and Al current collectors. The specific capacitance of graphite based electrode is found to be 29Fg${}^{-1}$.

ZnO thin films were prepared on silica glass substrates by a sol–gel spin coating technique. The thickness of the films was about 200 nm. At 370 nm in the ultraviolet region, there is a sharp absorption edge that corresponds to the ZnO intrinsic band gap of 3.30 eV. The structural properties of the films were examined by X-ray diffraction, which demonstrates that the ZnO films were c-axis oriented. From the infrared spectrum, we conclude that ZnO was deposited on silica glass substrates through a high temperature process at 700°C.

Highly transparent ZnO thin films were deposited on glass substrates by using a simple and inexpensive multi-step sol–gel spin coating process. This research investigated the effects of annealing temperature in the range from 350–600°C on the microstructure, surface morphology and optical properties of thin films by using XRD, SEM and transmittance spectra. The XRD results showed that the c-axis orientation of ZnO thin films was improved with the increase of annealing temperature. The grain size increases from 16.6–19.7 nm with the increase in temperature. The transmittance spectra indicated that the transmittance and direct optical band gap Eg of the films showed a decreased trend with annealing temperature. It is found that the tensile stress exist in the films, which decreases with the increase in annealing temperature up to 500°C, on further increasing the annealing temperature up to 600°C, the stress in the film changes from tensile to compressive nature.

The effect of substrate on the crystalline phase and morphology of the poly (vinylidene fluoride) (PVDF) thin film has been investigated. The solution of PVDF/Hexamethyl phosphoramide (HMPA) was deposited on four different substrates, namely, silicon (Si), glass (SiO₂), indium tin oxide (ITO) coated glass and silver (Ag) coated glass respectively by using the spin coating technique. The crystalline structure was investigated using X-ray diffraction (XRD) and Fourier transform infrared (FTIR) techniques. The morphology was determined using scanning electron microscopy (SEM). XRD demonstrated that the structure of PVDF thin films on each substrate is $\beta$-phase with different orientations of the molecular chains. FTIR results confirmed XRD that the samples contain $\beta$-phase. SEM shows spherulites structure, which is rough and porous, besides, the size of spherulites and the porosity are different for each sample. The size of spherulites is in average diameter range (1–6$\mu$m) and this range is attributed to the $\beta$-phase. The nucleation process of $\beta$-phase on the various substrates attributed either to the match of polymer-substrate or to the electrostatic interaction. Among the substrates used, the ITO substrate exhibited a greater tendency for $\beta$-phase formation.

The aim of this work is to study the solution concentration effect on the SnO₂ thin film properties, which were deposited on glass substrates by spin coating technique and annealed for one hour at 500${}^{\circ }$C. X-ray diffraction (XRD) spectra show that the films deposited at various solution concentrations (0.5mol/L, 0.7mol/L and 1mol/L) are polycrystalline with a tetragonal rutile type. Grains have two preferred orientations along the directions (110) and (101) corresponding to 2$\theta$ equal to 26.74${}^{\circ }$ and 34.11${}^{\circ }$, respectively. We have also noted that the grain size changes between 109nm and 178nm. However, the film coated at 10 deposition cycles and 0.7mol/L solution concentration has a minimum arithmetic average roughness of 0.376 nm. The optical transmittance of the films in the visible spectrum was in the range of 77–84% and the optical band gap gradually decreases with the decrease of the solution concentration from 4.11eV to 3.56eV.

Cobalt-doped ZnO films were grown on the glass substrates using sol–gel/spin-coating technique to investigate the effect of annealing on the structural and magnetic properties. The X-ray diffraction (XRD) patterns of the Co-doped ZnO films are dominated by the (002) peak, suggesting an up-standing array of ZnO structure hexagonal (wurtzite) with a good crystalline quality, however, the secondary phases of Co₃O₄ and Co are present in the samples. With the annealing temperature increased, the secondary phases tend to disappear completely and the intensity of the (002) peak increased, indicating a high crystallinity of the samples. For the ZnO majority phase, the lattice constant ($c)$ decreases (from 5.232 $\mathrm{\text{Å}}$ to 5.224 $\mathrm{\text{Å}}$), while the crystallite size increases (from 22.040nm to 24.018nm) as the annealing temperature varies from 380^∘C to 600^∘C. Significant changes in the dislocation density ($\delta )$, strain $({\epsilon }_c)$ and stress $({\sigma }_c)$ of the Co-doped ZnO films were also observed, by increasing the annealing temperature. All samples display a ferromagnetic behavior with variations in the saturation magnetization ($M_s=1.31\times 10^{-5}$, $1.19\times 10^{-5}$ and $1.15\times 10^{-5}$ emu/cm${}^3)$ and coercive field ($H_c=82$, 104 and 75 Oe) for the temperatures of 380^∘C, 500^∘C and 600^∘C, respectively. The magnetic behavior of Co-doped ZnO films confirms the exchange interaction between the local spin moments produced by the oxygen vacancy. In addition, the ferromagnetic existence of the samples (380^∘C, 500^∘C and 600^∘C) can be attributed to certain nanoparticles or to the binding of Co${}^{+2}$ ions at the Zn${}^{+2}$ location in the ZnO lattice. Finally, it appears that the ferromagnetism at room temperature found in these films, is consistent with endogenous defects (oxygen vacancies) and magnetic ions insertion along the same lines.

The structural and optical characteristics of polyvinyl alcohol (PVA) doped with different concentration of Nd₂O₃ nanoparticles to use an active media for polymer laser were studied. The PVA polymer was considered as the host and Nd₂O₃ nanoparticles as the active element. The media as a thin film was prepared using spin coating technique. Structural properties of layers were investigated by X-ray diffraction (XRD) pattern and atomic force microscope (AFM) technique. The effect of the concentrations of the neodymium source on the optical properties of Nd₂O₃/PVA thin films was investigated through UV-Vis absorption spectroscopy and their optical band gap was evaluated. Also, the FTIR and fluorescence spectra of the samples were detected. The fluorescence spectra of films showed that the maximum wavelength occurred at 568nm with no significant shift.

Thin films of metal phthalocyanines (M: Co, Zn, Ni) substituted with four 3,5-bis(2${}^{\prime }$,3${}^{\prime }$,4${}^{\prime }$,5${}^{\prime }$,6${}^{\prime }$-pentafluorobenzyloxy)benzyloxy groups have been prepared by the spin-coating technique. Optical properties and surface morphology of the thin films of metallophthalocyanines have been investigated as a function of organic solvents of acetone, chloroform, tetrahydrofuran, dimethylformamide and dimethylsulfoxide. Results show that optical properties and surface morphology of the prepared films depend on the type of organic solvent used.

Optical coherence tomography (OCT) has been widely applied to the diagnosis of eye diseases during the past two decades. However, valid evaluation methods are still not available for the clinical OCT devices. In order to assess the axial resolution of the OCT system, standard model eyes with micro-scale multilayer structure have been designed and manufactured in this study. Mimicking a natural human eye, proper Titanium dioxide (TiO₂) materials of particles with different concentrations were selected by testing the scattering coefficient of PDMS phantoms. The artificial retinas with multilayer films were fabricated with the thicknesses from 9.5 to 30 micrometers using spin coating technology. Subsequently, standard OCT model eyes were accomplished by embedding the retina phantoms into the artificial frames of eyes. For ease of measurement processing, a series of model eyes were prepared, and each contained films with three kinds of thicknesses. Considering the traceability and accuracy of the key parameters of the standard model eyes, the thicknesses of multilayer structures were verified using Thickness Monitoring System. Through the experiment with three different OCT devices, it demonstrated the model eyes fabricated in this study can provide an effective evaluation method for the axial resolution of an ophthalmic OCT device.

We report on the growth and characterization of undoped indium nitride (InN) thin films grown on a silicon substrate. The InN thin films were grown on aluminium nitride (AlN) template with gallium nitride (GaN) nucleation layer using a relatively simple and low-cost sol–gel spin coating method. The crystalline structure and optical properties of the deposited films were investigated. X-ray diffraction and Raman results revealed that InN thin films with wurtzite structure were successfully grown. For InN thin film grown on a substrate with the GaN nucleation layer, its strain and dislocation density are lower than that of the substrate with the AlN nucleation layer. From the ultra-violet-visible diffuse reflectance spectrum analysis, the energy bandgap of the InN thin films with the GaN layer was 1.70 eV. The potential application of the sol–gel spin-coated InN thin films was also explored. Metal–semiconductor–metal (MSM) infrared (IR) photodetectors were fabricated by depositing the platinum contacts using two interdigitated electrodes metal mask on the samples. The finding shows that the device demonstrates good sensitivity and repeatability towards IR excitation at a wavelength of 808 nm. The photodetector characteristics at dark and photocurrent conditions such as Schottky barrier height (SBH) and ideality factor are determined. Upon exposure to the IR source at 3V applied bias, InN/AlN/Si device configuration displays rapid rise time of 0.85 s and decay time of 0.78 s, while InN/GaN/AlNSi demonstrates slow rise time of 7.45 s and decay time of 13.75 s.

Thin films of iron (Fe)-doped titanium dioxide (Fe:TiO${}_2)$ were prepared by sol–gel spin coating technique and further calcined at 450${}^{\circ }$C. The structural and optical properties of Fe-doped TiO₂ thin films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet–visible spectroscopy (UV–vis) and atomic force microscopic (AFM) techniques. The XRD results confirm the nanostructured TiO₂ thin films having crystalline nature with anatase phase. The characterization results show that the calcined thin films having high crystallinity and the effect of iron substitution lead to decreased crystallinity. The SEM investigations of Fe-doped TiO₂ films also gave evidence that the films were continuous spherical shaped particles with a nanometric range of grain size and film was porous in nature. AFM analysis establishes that the uniformity of the TiO₂ thin film with average roughness values. The optical measurements show that the films having high transparency in the visible region and the optical band gap energy of Fe-doped TiO₂ film with iron (Fe) decrease with increase in iron content. These important requirements for the Fe:TiO₂ films are to be used as window layers in solar cells.

Thin films of metal phthalocyanines (M: Co, Zn, Ni) substituted with four 3,5-bis(2′,3′,4′,5′,6′-pentafluorobenzyloxy)benzyloxy groups have been prepared by the spin-coating technique. Optical properties and surface morphology of the thin films of metallophthalocyanines have been investigated as a function of organic solvents of acetone, chloroform, tetrahydrofuran, dimethylformamide and dimethylsulfoxide. Results show that optical properties and surface morphology of the prepared films depend on the type of organic solvent used.