Showing papers by "Muhammad Hassan Sayyad published in 2017"

Sensing Properties of Cobalt-Phthalocyanine-Based Multipurpose Sensor

Abstract: Cobalt phthalocyanine (CoPc), an organic semiconductor, has been introduced as an active sensing layer in a surface-type multipurpose sensor owing to its stability, low fabrication cost, and multifunctional sensitivity. The capacitance of the sensor was recorded to increase 26.7-fold for a change in relative humidity (RH) from 0% to 92.3%, 12.6-fold for a change in illumination from 11.5 lx to 23,000 lx, and 5.2-fold for a change in temperature from 27°C to 187°C. The morphology of the active thin film of the sensor was analyzed by atomic force microscopy, revealing a rough surface favorable for moisture absorption and light harvesting. The CoPc film was amorphous in nature according to x-ray diffraction analysis. By virtue of its response to humidity, light, and temperature, this represents an attractive approach for cost-effective environmental sensing applications.

Photovoltaic performance and impedance spectroscopy of a purely organic dye and most common metallic dye based dye-sensitized solar cells

Abstract: In this work, performances of an organic electron donor–π-bridge–electron acceptor (D–π–A) type RK1 dye and the most common metallic N719 dye based dye-sensitized solar cells (DSSCs) were compared. To gain insight into the behavior of these devices, current–voltage and impedance spectroscopic measurements were performed. From the current–voltage data, the parameters of cells including open-circuit voltage, short-circuit current, fill factor, solar energy-to-electricity conversion efficiency, series resistance, shunt resistance, and ideality factor were extracted. The RK1 based cell showed higher photovoltage, higher short-circuit current, solar energy-to-electricity conversion efficiency, higher shunt resistance and ideality factor. Using the Mott-Schottky plots, electrical properties of the cells were investigated and lower electron concentration was found for the RK1-DSSC. This high performance can be attributed to the higher absorption coefficient of the RK1 dye and relatively higher induced positive band-shift of the conduction band edge of the TiO2 semiconductor. The trends of the recombination resistance and the chemical capacitance as observed in the measured impedance spectra have also confirmed high photovoltaic performance of the RK1 based cell. Impedance spectra of the devices were observed both voltage and frequency dependent. At low frequencies, significant contribution of trap states was observed.

Effect of Temperature and Humidity on Electrical Properties of Organic Orange Dye Complex Films

Abstract: In this study the effect of temperature and humidity on electrical properties of organic orange dye (OD) complex with vinyl-ethynyl-trimethyl-piperidole (VETP) have been examined. Thin films of OD (C 17 H 17 N 5 O 2 ) and VETP (C 12 H 19 NO) complex were deposited from 10 wt.% (5 wt.% of each matter) solution in mixture of distilled water (80%) and spirit. The films were grown at room temperature under normal gravity conditions, i.e. , 1 g and in a spin coater at an angular speed of 300 RPM. The Cu/OD-VETP/Cu surface type samples were fabricated and their low frequency (10 Hz) AC electric characteristics were evaluated for the temperature range 30-95 В°C at ambient humidity of 45-80%. It was observed that at normal conditions the conductivity of the samples is temperature dependent and shows semi-conductive behavior with activation energy of 0.55 eV. It was found that with increase in humidity the resistance of the samples decreases and at humidity values equal to 60-70% the irreversible transition from semi-conductive to conductive state takes place. It is supposed that in the former state the conductive matrix is formed due to incorporation of the water molecules into OD-VETP complex.

The Photo-Electrical Behavior of n-Si and p-Si/Orange Dye/ Conductive Glass Cells

Abstract: The photo-electrical behavior of n-Si/orange dye/conductive glass and p-Si/orange dye/conductive glass sandwich type cells were investigated. In these cells crystal silicon of n-type and p-type and conductive glass (CG) electrodes were employed and the aqueous solution of organic dye (OD) was used as an electrolyte in the distilled water. Under filament lamp illumination, photo-induced open-circuit voltage and shortcircuit current exponentially dropped with time for the n-Si/orange dye/CG cell. In the p-Si/orange dye/CG cell, the photovoltaic effect was not observed. The n-Si/OD/CG cell showed high photo-electrical response under illumination. In the light-voltage/current conversion, these cells behaved as a differentiator and exhibited charge-storage properties.