Mohammad Jahangir Alam

Optical and electrical properties of transparent conductive ITO thin films deposited by sol–gel process

Indium tin oxide (ITO) thin films have been deposited onto quartz glass substrates by a sol–gel process. The starting solution was prepared by mixing indium chloride dissolved in acetylacetone and tin chloride dissolved in ethanol. 0–20% by weight Sn-doped indium oxide (ITO) films were prepared by heat-treatment at above 400°C. The electrical, optical and structural properties of ITO thin films were investigated. The thickness of ITO film was measured by ellipsometer. The electrical resistivity was measured by using four-point probe method. The ITO thin films containing 10 wt.% Sn showed the minimum resistivity of ρ=1.5×10−3 Ω-cm. The spectral transmittance of ITO thin films was measured in the wavelength range from 275 to 900 nm by a UV-vis spectrometer. The film has high transmittance above 80% and has an absorption edge at 300 nm. X-Ray diffraction measurements employing CuKα radiation were performed to determine the crystallinity of the ITO films which showed that the ITO films were polycrystalline with a cubic bixbyite structure. XRD results show that a single phase is detected for In-Sn oxide and X-ray photoelectron spectroscopy (XPS) results show that a single valence state and chemical bonding state is observed for In and Sn in In-Sn oxides. Therefore, we can say that Sn is incorporated into the In2O3 structure substitutionally.

Preparation and properties of transparent conductive aluminum-doped zinc oxide thin films by sol–gel process

Highly conductive and transparent aluminum-doped zinc oxide thin films have been prepared from the solution of zinc acetate and aluminum nitrate in ethanol by the sol–gel process. The effect of changing the aluminum-to-zinc ratio from 0 to 5 at. % and annealing temperature from 0 °C to 700 °C in air has been investigated. The resistivities of thin films were measured as a function of annealing temperature and also as a function of aluminum dopant concentration in the solution. As-deposited films have high resistivity and high optical transmission. Annealing of the as-deposited films in air leads to a substantial reduction in resistivity. The films have a minimum value of resistivity of 1.5×10−4 Ω cm for 0.8 at. % aluminum-doped zinc oxide and a maximum transmission of about 91% when deposited on glass substrates. X-ray diffraction measurements employing Cu Kα radiation were performed to determine the crystallinity of the ZnO:Al films which showed that the films were polycrystalline with a hexagonal struct...

Power factor improvement by pulse width modulated switched single capacitor

Reactive power is recognized as an essential factor in the design and good operation of power system. Real and reactive power on a transmission line in an integrated network is governed by the line impedance, voltage magnitudes, the angle of differences at the line ends, and the role the line plays in maintaining network stability under dynamic contingencies. Reactive power compensation or control is essential part in a power system to minimize power transmission loss, to maximize power transmission capability, and to maintain the system voltage within desired level. In this paper a new method is proposed which improves the power factor automatically of varying lagging loads to unity, using one single large shunt capacitor instead of using a bank of switching capacitors. Basically, this control scheme is a static power factor correction method by continuous voltage or current control of a capacitor. In this work the voltage across the capacitor is being changed by a bi-directional switch to control the magnitude of compensating capacitor current and thereby attaining unity power factor. This system incorporates high-speed insulated gate bipolar transistor switching technology. The gate signal of the switching devices is generated by using a compact and commercially available IC chip SG1524B. The scheme is simple in this sense that it uses only one static bi-directional switch controlled by an electronic control circuit that uses only analog ICs and some discrete digital components.

Cuk topology based power factor correction and output voltage regulation of AC-DC converter

This paper focuses on the analysis of a power factor correction (PFC) converter using close loop Cuk topology. Regardless of the input line voltage and output load variations, input current drawn by the buck or buck-boost converter is always discontinuous. The Boost converter suffers from high voltage stresses across the power electronic devices. The input current in Cuk converter is comparable to boost converters input current. In this paper output voltage is controlled by inner current and outer voltage control loop along with power factor correction (PFC). It shows less input current THD (less than 5%), nearly unity power factor and better output voltage regulation of AC-DC converter under variable input voltage and output load. Small signal model analysis is presented for obtaining frequency response of the control loop. The MATLAB Simulink programming environment is used as a simulation tool.

An innovative Energy Neutral Home system for rural areas of Bangladesh

Nowadays, Power crisis is one of the greatest problems of Bangladesh. Most of the electricity produced in Bangladesh is based on non-renewable energy resources. The reserve of Natural resources or non-renewable energy sources such as: fossil fuels, oil, natural gas etc are limited. So this is the time to search such a system where the residential areas of Bangladesh become Energy Neutral. This paper demonstrates such a system in which an Energy Neutral Home (ENH) is designed and implemented for rural areas of Bangladesh. The designed system is able to meet the energy requirement with renewable energy resources without taking any electricity from grid. In this research, biogas is used as primary renewable energy source for the generation of electricity.

Design and analysis the characteristics of a cost-effective polymer based bulk heterojunction tandem solar cell

In this paper, a device model that describes the current-voltage characteristics of polymer:fullerene bulk heterojunction solar cell has been developed. Two organic PV cells of two different materials are cascaded together to form a tandem organic solar cell. In the design, PPV is implemented as the top cell and P3HT:PCBM blend is used as bottom cell. The simulation has been carried out using Silvaco ATLAS software. The power curve is also derived. Furthermore, the ideal efficiency and the Fill Factor of the tandem cell have been predicted from the curve. The stability of the model is ensured by introducing a thin buffer layer of ZnO coated on top of the solar cell.

Enhancement of Minority Carrier Lifetime of Fe Contaminated Boron-Phosphorus Compensated p-Type SoG Silicon

The paper presents the way that colour can serve solving the problem of calibration points indexing in a camera geometrical calibration process. We propose a technique in which indexes of calibration points in a black-and-white chessboard are represented as sets of colour regions in the neighbourhood of calibration points. We provide some general rules for designing a colour calibration chessboard and provide a method of calibration image analysis. We show that this approach leads to obtaining better results than in the case of widely used methods employing information about already indexed points to compute indexes. We also report constraints concerning the technique. Nowadays we are witnessing an increasing need for camera geometrical calibration systems. They are vital for such applications as 3D modelling, 3D reconstruction, assembly control systems, etc. Wherever possible, calibration objects placed in the scene are used in a camera geometrical calibration process. This approach significantly increases accuracy of calibration results and makes the calibration data extraction process easier and universal. There are many geometrical camera calibration techniques for a known calibration scene [1]. A great number of them use as an input calibration points which are localised and indexed in the scene. In this paper we propose the technique of calibration points indexing which uses a colour chessboard. The presented technique was developed by solving problems we encountered during experiments with our earlier methods of camera calibration scene analysis [2]-[3]. In particular, the proposed technique increases the number of indexed points points in case of local lack of calibration points detection. At the beginning of the paper we present a way of designing a chessboard pattern. Then we describe a calibration point indexing method, and finally we show experimental results. A black-and-white chessboard is widely used in order to obtain sub-pixel accuracy of calibration points localisation [1]. Calibration points are defined as corners of chessboard squares. Assuming the availability of rough localisation of these points, the points can be indexed. Noting that differences in distances between neighbouring points in calibration scene images differ slightly, one of the local searching methods can be employed (e.g. [2]). Methods of this type search for a calibration point to be indexed, using a window of a certain size. The position of the window is determined by a vector representing the distance between two previously indexed points in the same row or column. However, experiments show that this approach has its disadvantages, as described below. * E-mail: A.Nowakowski@ire.pw.edu.pl Firstly, there is a danger of omitting some points during indexing in case of local lack of calibration points detection in a neighbourhood (e.g. caused by the presence of non-homogeneous light in the calibration scene). A particularly unfavourable situation is when the local lack of detection effects in the appearance of separated regions of detected calibration points. It is worth saying that such situations are likely to happen for calibration points situated near image borders. Such points are very important for the analysis of optical nonlinearities, and a lack of them can significantly influence the accuracy of distortion modelling. Secondly, such methods may give wrong results in the case of optical distortion with strong nonlinearities when getting information about the neighbouring index is not an easy task. Beside this, the methods are very sensitive to a single false localisation of a calibration point. Such a single false localisation can even result in false indexing of a big set of calibration points. To avoid the above-mentioned problems, we propose using a black-and-white chessboard which contains the coded index of a calibration point in the form of colour squares situated in the nearest neighbourhood of each point. The index of a certain calibration point is determined by colours of four nearest neighbouring squares (Fig.1). An order of squares in such foursome is important. Because the size of a colour square is determined only by the possibility of correct colour detection, the size of a colour square can be smaller than the size of a black or white square. The larger size of a black or white square is determined by the requirements of the exact localisation step which follows the indexing of calibration points [3]. In this step, edge information is extracted from a blackand-white chessboard. This edge information needs larger Artur Nowakowski, Wladyslaw Skarbek Institute of Radioelectronics, Warsaw University of Technology, Nowowiejska 15/19, 00-665 Warszawa, A.Nowakowski@ire.pw.edu.pl Received February 10, 2009; accepted March 27, 2009; published March 31, 2009 http://www.photonics.pl/PLP

Correlation of Fe-Rich Defect Centre and Minority Carrier Lifetime in p-Type Multicrystalline Silicon

A comparative study has been made to analyze the impact of interstitial iron in minority carrier lifetime of multicrystalline silicon (mc-Si). It is shown that iron plays a negative role and is considered very detrimental for minority carrier recombination lifetime. The analytical results of this study are aligned with the spatially resolved imaging analysis of iron rich mc-Si.

Input switched single phase SEPIC controlled rectifier with improved performances

DC power conditioning and processing is an essential challenge now a days. Rectifiers having bridge structures are considered to be nonlinear as they draw non sinusoidal current from line. This distorted current causes several problems related to power quality. In this paper, a new configuration of single phase single switch controlled rectifier using SEPIC topology is proposed. The input current of the proposed configuration is chopped at high frequency using a semiconductor switch to get step up/step down AC to DC conversion, instead of using conventional converters. The proposed circuit is compared with conventional one under same load and operating conditions. The proposed circuit shows better performance i.e. higher power factor at input side and lower distortion (THD) of input current than conventional one. The efficiency of proposed converter is also high. No other control circuitry is required to achieve these advantages.

Input switched high performance single phase single switch Ćuk AC-DC converter

Single phase full wave bridge rectifier draws non sinusoidal current from a sinusoidal voltage source which causes low performance of the rectifier. Switching mode regulators are used to improve the shape of current and power factor of the input side. In this paper a different type of single phase single switch AC-DC converter using Ćuk topology is reported. Input current is chopped in this converter at high frequency during both cycles by a single switch to get step up/step down conversion. Comparison is made between reported and conventional circuit under same load and operating conditions. This proposed circuit shows better performance. The efficiency of this converter is also high. Any other control scheme is not required to achieve these advantages.