The effect of number of vacuum thermal evaporation cycles to the optoelectronic and morphological properties of ZnO

Zinc oxide (ZnO) is a wide band gap material (~3.37 eV) which has small exciton Bohr radius ~2.34 nm. In dye-sensitized solar cell, ZnO thin film is used as photoelectrode. Light-sensitive organic/ inorganic fluorophores could be adsorbed on the surface of the ZnO film, which later will be sandwiched with electrolyte and a counter electrode. The aim of this paper is to study the effect of number of evaporation cycle to the yielded morphology and size of ZnO building blocks; deposited using one, two, and three cycles of vacuum thermal evaporation technique. The ZnO thin films have been deposited on ITO glass substrate at vacuum pressure of 5 ´ 10-5 Torr, 116 A, and 2.6 V. The morphology of the thin films has been examined under Field Emission Scanning Electron Microscope (FESEM), which showed nanosphere morphology. The morphological observation is supported by a simulation; which calculated based on the crystallographic properties of the synthesized ZnO – characterized by X-ray diffractometer (XRD). Three sets of the ZnO thin films consists of ZnO particles in the range of 8 – 20 nm, 11 – 37 nm, and 6 – 16 nm respectively. According to the optical properties characterized by absorption spectrometer, it has been observed that the band gap of the thin films increased with increasing number of evaporation cycles. The values of the optical bandgap, Eg evaluated from Tauc’s plot, were found in the range between 2.40 eV to 2.60 eV

Effect of ohmic-drop on electrochemical performance of EDLC fabricated from PVA:dextran:NH4I based polymer blend electrolytes

Proton conducting solid polymer blend electrolytes based on poly(vinyl alcohol)(PVA):dextran that were doped with different quantities of ammonium iodide (NH4I) were prepared. The X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) study were carried out to examine the compatibility of NH4I withPVA:dextran polymers. FTIR spectroscopy assessment was used to establish the presence of a complex formation between the PVA:dextran and added salt through the modification and reduction in the intensity of FTIR bands relevant to the functional groups. The field emission scanning electron microscopy (FESEM) examination was used to assess the channels for proton transport. Electrical impedance spectroscopy (EIS) was used to analyse the samples conductivity behaviour. The sample with 20 wt.% of added salt has shown a high DC conductivity which can be employed in electrochemical devices such as EDLC. It is also demonstrated by the transference number (TNM) and linear sweep voltammetry (LSV) that it is appropriate to use the largest conducting sample for electrochemical device. There was electrochemical stability of the electrolyte sample with voltage sweeping linearly to 1.3 V. It is shown by the outcome of cyclic voltammetry (CV) plot that charge storage at the site of electrode-electrolyte is non-Faradiac. A high drop voltage (Vd=IR) is implied by the usual galvanostatic charge-discharge. The equivalent series resistance (Res) increases as a result of the increase in Vd all the way through the charge-discharge cycle. Specific capacitance (Csp) is nearly constant from the foremost cycle to the 100th cycle, with average of 4.2 F/g

Glycerolized Li+ Ion Conducting Chitosan-Based Polymer Electrolyte for Energy Storage EDLC Device Applications with Relatively High Energy Density

In this study, the solution casting method was employed to prepare plasticized polymer electrolytes of chitosan (CS):LiCO2CH3:Glycerol with electrochemical stability (1.8 V). The electrolyte studied in this current work could be established as new materials in the fabrication of EDLC with high specific capacitance and energy density. The system with high dielectric constant was also associated with high DC conductivity (5.19 × 10−4 S/cm). The increase of the amorphous phase upon the addition of glycerol was observed from XRD results. The main charge carrier in the polymer electrolyte was ion as tel (0.044) < tion (0.956). Cyclic voltammetry presented an almost rectangular plot with the absence of a Faradaic peak. Specific capacitance was found to be dependent on the scan rate used. The efficiency of the EDLC was observed to remain constant at 98.8% to 99.5% up to 700 cycles, portraying an excellent cyclability. High values of specific capacitance, energy density, and power density were achieved, such as 132.8 F/g, 18.4 Wh/kg, and 2591 W/kg, respectively. The low equivalent series resistance (ESR) indicated that the EDLC possessed good electrolyte/electrode contact. It was discovered that the power density of the EDLC was affected by ESR