Thesis (Bachelor of Science in Applied Physics & Electronics)
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listelement.badge.dso-type Item , Design and development of CsSnI3 solar cell using SCAPS-1D simulation(BRAC University, 2024-08) Haque, Md. Firoze H.; Rahman, Muhammad Lutfor; Department of Mathematics and Natural Sciences"Solar cells are popular because they offer a clean, renewable way to produce elec- tricity from sunlight without harming the environment. Recently, lead-based per- ovskites have been used in the absorber layer in the construction of solar cells due to their ability to absorb light, high carrier mobility, and tunable band gap. However, lead is known to be toxic, posing safety challenges for the environment. To address this problem, extensive research is being conducted to find alternatives, such as de- veloping safer lead-free perovskites. This study proposes a model for a lead-free solar cell consisting of a cesium tin io- dide perovskite in the absorber layer. A simulation was conducted using SCAPS-1D software, which allows users to create a model and analyze its various properties. Indium Tin Oxide (ITO) was chosen as the transparent conducting layer. [6,6]- Phenyl-C61-butyric acid methyl ester (PCBM), an organic compound, was chosen as the electron transport layer (ETL), and Copper Iron Tin Sulfide (CFTS) was used for the hole transport layer (HTL). Cesium Tin Iodide (CsSnI3) was used as the absorber layer, which was sandwiched between the ETL and HTL. Lastly, gold (Au) was used to serve as contacts between the layers. Once the device was modeled, several parameters, such as the thickness of each layer, doping concentrations, electron affinities, and temperatures, were varied to study their impact on power conversion efficiency (PCE), fill factor (FF), open- circuit voltage (Voc), and short-circuit current (Isc). The simulation indicated that the maximum obtained power conversion efficiency stood at 26.9% for this device at a temperature of 298 K by optimizing these param- eters. The results demonstrate that the device is a promising alternative to both the current market-available solar cells and lead-based perovskite solar cells."listelement.badge.dso-type Item , Measurement and analysis of temperature dependent resistance of 𝑳𝒊𝒙𝑪𝒖0.5𝒁𝒏𝟎.𝟓−𝟐𝒙𝑭𝒆𝟐+𝒙𝑶4(BRAC University, 2023) Jajayare, MD.Jabar Al; Haque, Md.Firoze H.; Rahman, Muhammad Lutfor; Department of Mathematics and Natural SciencesThe DC electrical property of 𝑳𝒊𝒙𝑪𝒖0.5𝒁𝒏𝟎.𝟓−𝟐𝒙𝑭𝒆𝟐+𝒙𝑶4 (x=0.00, x=0.05, 0.10) samples prepared by solid state reaction method was investigated. The samples were calcined at 800℃ and sintered at 1000℃ and 1050℃ respectively in air for 5 hours. The samples were placed in an electric oven and the corresponding resistance and temperature measurement were taken using 2 probe method by keithley 2450 and 6517b respectively. The resistance was found to decrease as the value of x increased and also increasing temperature showed semiconductor behaviour of the sampleslistelement.badge.dso-type Item , Ion acoustic wave in relativistic magnetized quantum plasma with positive ions, negative ions, electrons and stationary dust particles(BRAC University, 2022-07) Sarker, Md. Nasim; Hasan, M M; Department of Mathematics and Natural SciencesThe propagation of the ion acoustic (IA) solitary waves (SWs) in a degenerate quantum plasma with external magnetic field (containing magnetized positive and negative ions, unmagnetized quantum electrons with stationary charged dust particles) have been theoretically investigated. The Reductive Perturbation method is adopted to derive the Korteweg-de Varies (K-dV), the modified K-dV (mK-dV) and mixed mK-dV (mmK-dV) equations. The stationary solutions of K-dV, mK-dV and mmK-dV are shown and analyzed numerically to study the basic characteristics of IASWs that are commonly formed in degenerate quantum plasmas. Main process of the propagation of waves through oscillation in plasma is investigated graphically. The basic properties (phase speed, width, amplitude) of IASWs are found to be significantly modified by the effects of number densities of the plasma particles, mass of the ions, relativistically degenerate electrons , external magnetic field and charge state of the dust particles. The outcomes from this conceptual analysis can be significant for understanding the layout and prominence of the solitary structures in astrophysical compact objects. Besides that the data from this research can be used for developing advanced concepts related to plasma physics in future.listelement.badge.dso-type Item , Influence of 𝑳𝒊+ Substitution on Magnetic and Electrical Properties of 𝑳𝒊𝒙𝑪𝒖𝟎.𝟓𝒁𝒏𝟎.𝟓−𝟐𝒙𝑭𝒆𝟐+𝒙𝑶𝟒(BRAC University, 2018) Mustafa, Anjum; Hossain, A.K.M Akhter; Department of Mathematics and Natural SciencesStructural, AC magnetic and electrical properties of 𝐿𝑖𝑥𝐶𝑢0.5𝑍𝑛0.5−2𝑥𝐹𝑒2+𝑥𝑂4 (x=0.00, x=0.05, 0.10) have been investigated which were prepared by solid state reaction method. Various chemical compositions were calcined at 800 C and samples of these compositions were sintered at 950, 1000, 1050 and 1100 C in air for 5 hours. The X-ray diffraction analysis, SEM (Scanning Electron Microscopy) and EDS (Energy Dispersive Spectroscopy) results were performed on the samples sintered at 1000 C. X-ray diffraction pattern confirms the formation of single phase cubic spinel structure and the lattice parameter decreases with the increase of 𝐿𝑖+ content obeying Vegard’s law. EDS report showed the homogeneous distribution of elements in the samples. The bulk density, permeability and permittivity decreases with the 𝐿𝑖+ substitution. At high frequency it is found that the permeability is almost stable but the permittivity falls with the 𝐿𝑖+ substitution.listelement.badge.dso-type Item , Influence of Mn Substitution on Structural and AC magnetic properties of (Ni0.4Cu0.15Zn0.45)1-xMnxFe2O4 with x=0.00, 0.15(BRAC University, 2017) Shara, Afrin Jahan; Hossain, Dr. A.K.M Akther; Department of Mathematics and Natural SciencesStructural and AC magnetic properties of (Ni0.4Cu0.15Zn0.45)1-xMnxFe2O4 (x=0.00 and 0.15) have been investigated which were prepared by solid state reaction method. Various chemical compositions were calcined at 9500C and samples of these compositions were sintered at 1100, 1150 and 12000C in air for 5 hours. The X-ray diffraction analysis, SEM (Scanning Electron Microscopy) and EDS (Energy Dispersive Spectroscopy) results were performed on the samples sintered at 11000C. X-ray diffraction pattern confirms the formation of single phase spinel structure and the lattice parameter increased with Mn2+. The compositions showed a decrease in bulk and theoretical density with increase of Mn2+ content that can be explained by the atomic weights of the doped and substituted elements. It is also observed that porosity increases, while gain size decreases with increasing of Mn2+ content. EDS report showed the homogeneous distribution of elements in the samples. The real part of permeability is always higher for all temperatures when Mn is absent from the compositions. With content increment, real and imaginary part of permeability decreased. Natural resonance frequency is noticed to be decreased with rising temperature for a particular value of x. It increased with increasing Mn2+ content.listelement.badge.dso-type Item , Structural and AC magnetic properties of (Ni0.4Cu0.15Zn0.45)1-xMnxFe2O4(x=0.30, 0.45) due to Mn substitution(BRAC University, 2017) Mridula, Zarrin Tasnim; Hossain, Dr. A.K.M Akther; Department of Mathematics and Natural SciencesStructural and magnetic properties of (Ni0.4Cu0.15Zn0.45)1-xMnxFe2O4 ferrites(x=0.3, x=0.45) were investigated and it was prepared by solid state reaction methods. Various chemical compositions were calcined at 950C, and samples prepared from these compositions were sintered at 1100C in air for 5 hours. The X-ray diffraction analysis, SEM and EDS results were performed for the samples sintered at 1100C temperature. X-ray diffraction pattern confirms the formation of single phase spinel structure and the lattice parameter which resulted in increasing with the increase of Mn2+. The compositions show a decrease in bulk and theoretical density with increase of Mn2+ that can be explained by the atomic weights of the doped and substituted elements. It is also observed that porosity increases, while gain size decreases with increasing of Mn content. EDS report shows the homogeneous distribution of elements in the samples. The permeability curves have shown a quite variation while being sintered at different temperatures. However, the real part is always higher for all temperatures when Mn is absent from the composition. With each content increment, real part of permeability decreases with x=0.3 to x=0.45 at 1100, 1150 and 12000C. Natural resonance frequency is noticed to be decreased with temperature rising, although it rises with increasing Mn content.listelement.badge.dso-type Item , Designing and performance evaluation of a solar water pumping system(BRAC University, 2016-01) Haque, Aynus Tazwar; Kaiser, Dr. M. Shamim; Department of Mathematics and Natural SciencesThis study includes the detailed designing of solar water pumping system and its performance evaluation. Water pumping system is an ancient procedure and many methods have been established. Human energy, animal power, hydro power, wind, solar and fossil fuels for small generators are all used as power source, above all PV system is chosen because it is durable ecofriendly and long lasting. As Bangladesh is at semitropical region so sunlight is available for that PV system is perfect for generating power for pumping. A good sizing is important for having more efficient system. A flowrate equation related with input power of the PV system has been established based on 1st affinity law, 2nd affinity law, and efficiency law and power equation. With the help of equation, the input power and the Flowrate has been analyzed, based on that analyzation the sizing can be assumed more accurately and increased the efficiency. Thus the performance of the systems has evaluated.listelement.badge.dso-type Item , Computational study of electronic transport property of a quantum dot in a single electron transistor(BRAC University, 2017-06) Noor, Lamisha; Haque, Dr. Md. Firoze H.; Department of Mathematics and Natural SciencesMicroscopic object’s conductance behaviours are totally different from those of the macroscopic ones and cannot be understood, let alone deciphered using classical approach. Nanoscale systems’ electron transport is not diffusive and has different carrier transport mechanism based on the contact type. Quantum dots are artificial atoms with the fascinating possibility of exploring their atomic states by applying current and voltage to them. They can be used to make single electron transistors where the quantum dot is kept separated from the source, drain and gate terminal by tunnel barriers. Quantum tunnelling causes current to flow when specific electrochemical potential requirements are met which can be achieved by varying the gate voltage. During this a phenomenon called Coulomb blockade is observed which is basically the appearance of oscillations in the conductance as a function of gate voltage. This is unique because it can only be observed for quantum dots and not in bulk materials. The conductance of the single electron transistor also varies with the temperature. All these characteristic behaviours can be deduced by carefully constructing and solving the rate equations. The acquired equations were then simulated using Python programs to plot the graphs for current versus voltage, differential conductance versus voltage, differential conductance versus temperature and maximum conductance versus temperature. The achieved graphs clearly depict how the current and the differential conductance are related to different source drain voltage at different gate voltages. The discrete conductance peak indicates different atomic states. Furthermore, it also outlines the fact that differential conductance depends on temperature and its value decreases as the temperature increases.listelement.badge.dso-type Item , Localized surface plasmon resonance based nanocube-nanosphere dimer biosensor(BRAC University, 2017-06) Ahmed, Arik Rafiquddin; Das, Avijit; Department of Mathematics and Natural SciencesFor this paper, the Localized Surface Plasmon Resonance (LSPR) properties of bimetallic nanoparticles in the shape of a nanocube-nanosphere and consisting of Drude metals was analysed. The refractive index based plasmonic bio-sensing with nanocube-nanosphere dimers was studied through the illumination of a broadband beam at normal. The power absorption curves and electric field graphs for different material combinations between the nanocube and nanosphere were analysed to select the best material combination, which was found as silver nanocube-silver nanosphere. Using that combination, the gap between the nanocube and nanosphere was varied to find out the optimal gap, which was found as 1 nm. Taking that gap and material combination, the physical dimensions of the nanocube and nanosphere were varied and the best nanocube-nanosphere size was selected which was a nanocube of side length 20 nm and a nanosphere of radius 12.5 nm. The refractive index sensitivity was analysed in terms of different dielectric media. The sensitivity of the nanocube-nanosphere was also calculated in the presence of Lysozyme (Lys), Human Serum Albumin (HSA), Human gamma-immunoglobulin (IgG) and Human Fibrinogen (Fb) protein samples. Therefore, a comparative analysis was done to highlight how well the dimer performed as a biosensor in certain conditions. All of these processes were simulated using the software FDTD solutions by Lumerical.listelement.badge.dso-type Item , Interface application development of an electrometer using LabVIEW programming to study current-voltage characteristics of semiconductor devices(BRAC University, 2017-02) Karim, Khondker Jeaul; H. Haque, Firoze; Department of Mathematics and Natural SciencesA transistor is an electrical device made of semiconductor material that is used for operations such as amplification and switching of electronic signals and electrical power. Transistors, such as Bipolar Junction Transistor (BJT) and Metal-Oxide Semiconductor Field-Effect Transistor (MOSFET), are used extensively in electrical circuits in applications for a diverse range of electrical devices and systems from mobile phones to computers. In order for a transistor to be used effectively and perform functions as amplifiers and switches, it is important to know its electrical properties and operational specifications as it needs to be adaptable to the circuit’s current/voltage limits and other operating conditions. An electrometer, which is in fact a specialized measuring instrument with numerous applications, can be used to measure the current readings of a transistor subjected to different levels of voltages. For the electrometer to function most efficiently, an application is made using LabVIEW software which allows for its remote access to accomplish functions such as conducting a voltage sweep (applying incremental voltages after short delays and recording the current). This simultaneously decreases the data acquisition time drastically and eliminates the factor of human error completely while taking readings, as the electrometer is software-controlled. Such an application, coupled with the electrometer itself,promotes an efficient way of making a voltage sweep and displaying a graph of the input and output from the data obtained simultaneously. This enables the characterization of the transistors and the data can be used to identify whether the transistor, with its own specifications and boundaries, can be used in a particular system or circuit.listelement.badge.dso-type Item , Simulation of high energy cosmic ray showers using CORSIKA(BRAC University, 2016-01) Salam, Mohammed Shadman; Momen, Mohammed Arshad; Department of Mathematics and Natural Scienceslistelement.badge.dso-type Item , The vela pulsar and its behavioural variance(BRAC University, 2015-01) Tonima, Masuda Akter; Ahmed, Professor Mofiz Uddin; Department of Mathematics and Natural SciencesThis study includes detailed exploration of Vela pulsar magnetosphere and glitches—including recent studies that compare Vela pulsar with other pulsars such as: PSR B0329+54, an optical pulsar (the Crab pulsar, PSR B0531+21), an old millisecond pulsar (PSR J0437-4715) and the 2nd fastest known pulsar (PSR B1937+21). The explored energy band shows γ-ray to be the strongest in emission.Its helical structure and magneto-dynamic instability give further insight to this. Exploration of the magnetosphere shows the effect of pair production and gap on Lorentz factor that is balanced between electric and radiation reaction force—and how that is affected within a boundary. We further explore the magnetosphere in terms of X-ray field, curvature radiation-outside the gap, electric structure, γ-ray spectrum and spectral dependence on the curvature of field line to understand Vela pulsar better. This, we combine with Gvaramadze’s study to prove the relationship of the pulsar velocity with distance.