D.S. Dalavi

Efficient electrochromic performance of nanoparticulate WO3 thin films

This report highlights the suitability of electrodeposited nanoparticulate-WO3 (NP-WO3) electrodes for transmissive electrochromic devices (ECDs). The WO3 electrodes in the form of thin films are composed of 10–20 nm nanoparticles. An electrochromic (EC) device of dimensions 5 × 4 cm2 fabricated using NP-WO3 showed an Li insertion coefficient (x) of 0.43, which resulted in highest photopic transmittance modulation (88.51%), better Li-ion diffusion coefficient (∼3.16 × 10−9 cm2 s−1), fast electrochromic response time (5.2 s for coloration and 3.7 for bleaching) and excellent coloration efficiency (∼137 cm2 C−1). On reduction of WO3, the CIELAB 1931 2° color space coordinates show the transition from colorless to the deep blue state (Y = 97, a* = −1.93, b* = 0.46 and Y = 10, a* = 1.57, b* = −41.01) with steady decrease in relative luminance.

An Mn Doped Polyaniline Electrode for Electrochemical Supercapacitor

Undoped and Mn doped Polyaniline (PANI) thin films were deposited on stainless steel substrates by sonochemical method. Films deposition was done using dip coating technique. To study the Mn doping effect on the specific capacitance of PANI, concentration of Mn was varied from 0.4 to 1.6 wt %. The Fourier Transform-IR (FT-IR) and Raman spectroscopy techniques have been used for the phase identification and determination of the Mn in the PANI films. Surface morphology was examined by using Field Emission Scanning Electron Microscopy (FESEM) which showed nanofiber aggregate structure of undoped PANI and porous and well distributed nanofibers for the doped PANI. The supercapacitive behavior of the electrodes was tested in three electrode system with 1.0 M H 2 SO 4 electrolyte by using cyclic voltammetry. The specific capacitance value increases from 285 to 474 F g ―1 as the Mn concentration was increased. This work demonstrates a simple strategy of improving specific capacitance of the polymer and hence may be adopted easily for other dopants also. Thus the work will open a new avenue for designing low cost high performance devices for better supercapcitors.

Electrochromic properties of dandelion flower like nickel oxide thin films

This report highlights a one pot, surfactantless, template free approach to grow novel dandelion flower like nickel oxide (NiO) thin films composed of nano-flakes with a highly porous structure. Good transmittance modulation, fast response time and excellent coloration efficiency make them a potential electrode material for electrochromic devices.

Electro-optical properties of copper phthalocyanines (CuPc) vacuum deposited thin films

Copper phthalocyanine (CuPc) thin films grown on glass substrates by the vacuum deposition method were investigated using photo absorption–transmission as well as photoreflectance spectroscopy with respect to different thickness. The surface morphology was investigated using scanning electron microscopy (SEM). Structural properties were studied by grazing angle XRD diffraction. The vibrational studies were carried out using Fourier transform infrared spectroscopy (FT-IR). The wettability was studied using a contact angle meter.

Effect of annealing on microstructural and optoelectronic properties of nanocrystalline TiO2 thin films

In this study, semi-transparent nanostructured titanium oxide (TiO2) thin films have been prepared by sol–gel technique. The titanium isopropoxide was used as a source of TiO2 and methanol as a solvent and heat treated at 60°C. The as prepared powder was sintered at various temperatures in the range of 400–700°C and has been deposited onto a glass substrate using spin coating technique. The effect of annealing temperature on structural, morphological, electrical and optical properties was studied by using X-ray diffraction (XRD), high resolution transmittance electron microscopy (HRTEM), atomic force microscopy (AFM), scanning electron microscopy (SEM), dc resistivity measurement and optical absorption studies. The XRD measurements confirmed that the films grown by this technique have good crystalline nature with tetragonal-mixed anatase and rutile phases and a homogeneous surface. The HRTEM image of TiO2 thin film (annealed at 700°C) showed grains of about 50–60 nm in size with aggregation of 10–15 nm crystallites. Electron diffraction pattern shows that the TiO2 films exhibited a tetragonal structure. SEM images showed that the nanoparticles are fine and varies with annealing temperature. The optical band gap energy decreases with increasing annealing temperature. This means that the optical quality of TiO2 films is improved by annealing. The dc electrical conductivity lies in the range of 10−6 to 10−5 Ω cm−1 and it decreases by the order of 10 with increase in annealing temperature from 400°C to 700°C. It is observed that the sample Ti700°C has a smooth and flat texture suitable for different optoelectronic applications.