Nabin Baran Manik

Photocurrent growth and decay behavior of crystal violet dye-based photoelectrochemical cell in photovoltaic mode

Crystal violet dye-doped photoelectrochemical cells (PEC) show different and unusual behavior in their electrical and optical characteristics. In this work, we have studied the photocurrent growth and decay behavior of crystal violet dye-based solid-state PEC in photovoltaic mode. Photocurrent growth and decay are studied for different intensities of illumination. They follow a power law relationship with time which is of the form Iph ∼ t±α, where Iph is the photocurrent and α is a constant. The positive and negative signs are used to indicate the growth and decay of the photocurrent, respectively. This power law relation is explained by dispersive transport model which was originally developed by Scher and Montrol and subsequently modified by different workers. The constant, α is termed as dispersion parameter, and it is related to the disorder. It is observed that the value of this parameter depends on the intensity of incident illumination. Dependence of this dispersion parameter on incident intensity is studied in this work. Variations of α with intensity for growth and decay have been discussed. In our system, the value of α is 0.325 ± 0.005 for decay whereas, in the growth region, its value varies from 0.55 to 0.33, when intensity varies from minimum to maximum. The value of the disorder parameter, α, decreases as the intensity of illumination increases for growth of current whereas it remains nearly constant for decay of current. This work will be helpful in understanding the charge transport mechanism of dye-based PEC cell.

Effect of Temperature on Electro-Optical Characteristics of Silicon Based p-n Photodiode (VTB8440BH)

To get useful information about the carrier transport mechanism we first measure the current-voltage (I-V) characteristics of a silicon p-n photodiode (VTB8440BH) in the temperature range 350 − 110 K. All semilog I-V curves exhibit three successive linearly dependent regions along with their bias levels which are defined as I, II and III regions, respectively. Regions I and II with different slopes are used to determine the bias dependent ideality factors namely, n1 and n2. The variation of n1 and n2 with temperature shows that with lowering of temperature the tunneling probability gradually increases. Furthermore, these results are used to identify the paramount carrier at different bias levels. Secondly, to acquire knowledge of electron-hole generation rate we measure the variation of photocurrent in the same temperature range. Results show that photocurrent decreases slowly as temperature decreases from 350 to 239 K and it changes sharply below 239 K. The change of photocurrent with temperature is explained in terms of temperature dependence of carrier mobility, lifetime and optical generation rate. Finally, these results will be helpful for precision application of the optoelectronics device in both high and low temperature ambience.

Implementation of Reed Muller Expansion Technique Using Mach-Zehnder Interferometer Based All Optical Reversible Gates

From the last century the reversible logic has formed as an unconventional form of computing. It is relatively very new in the area of extensive applications in low power CMOS, quantum computing, digital signal processing (DSP), nanotechnology, communication, etc. In all-optical domain with the help of Feynman and Toffli gates we represent the implementation of Reed Muller transformation technique for any canonical SOP (sum of product) expression and here also we have introduced their principle of operations and used a theoretical model to complete the task. In the field of ultra-fast all-optical signa processing Mach–Zehnder interferometer (MZI), semiconductor optical amplifier (SOA)-based, has an important function. The different logical (realization of Boolean function) functions can be executed by this method with Feynman and Toffoli gates in the domain of reversible logic-based information processing.

Safranine T dye based photo electrochemical solar cell: Effect of electrodes on device mechanism

We made two photovoltaic devices using blend of Safranine T dye in a thin film of polyvinyl alcohol mixed with solid electrolyte made by PEO and LiClO4, placed between two electrodes, resulting photo electrochemical cell (PEC) structure. One of the cells made of two ITO coated glass plates as electrodes and the other with ITO and Silver. The current voltage relation of the cells has been measured in the dark. Detail analysis of the dark I-V curve shows two distinct regions below and above certain voltage for the second cell unlike to first cell, which has only one region. I- V curve for the cells indicates trap charge limited (TCL) conduction through exponentially distributed traps. Characteristic trap energy (Et) has been calculated for both the cells. Use of dissimilar electrodes increases efficiency up to one order in magnitude than the other. From photovoltaic current growth nature we discussed the charge transport process through these materials using concept of dispersive transport model.