Effect of CIGS Layer Thickness and Bandgap on the Efficiency of Thin-Film Copper Indium Gallium Selenide (CIGS) Solar Cells Using GPVDM

This study explores how CIGS absorber layer thickness and bandgap influenced the efficiency of Copper Indium Gallium Selenide (CIGS) thin-film solar cells through simulations carried out using the General-Purpose Photovoltaic Device Model (GPVDM). The unique properties of CIGS, including its tunable energy bandgap, are highlighted for optimal alignment with the solar spectrum. Through sets of simulations, optimal values are determined for thickness and bandgap. Results indicate an optimal thickness range (1.2 to 1.3 µm), striking a balance between absorption and recombination losses. Furthermore, an optimal bandgap range (between 1.261 eV and 1.596 eV) was identified, aligning photon absorption and energy losses for maximal efficiency. These findings underscore the nuanced optimization required for effective solar cell design, with implications for the advancement of renewable energy technologies.

Analytical solutions of the null-geodesics in Ellis-Bronnikov wormhole spacetime via exp(-\Phi(\xi))-expansion method

    In this article, we use the so-called  exp(-\Phi(\xi))-expansion method to obtain some specific classes of one-parameter exact solutions of null-geodesics in the Ellis- Bronnikov wormhole metric. In the first stage of this method, the nonlinear PDE is converted into a nonlinear ordinary derivative equation (ODE) of polynomial form. Therefore, if we initially have a nonlinear ODE of polynomial form, sometimes its solutions can be obtained using the procedure of the exp(-\Phi(\xi))-expansion method. In our paper, this method allows us to obtain some exact analytical solutions to null-geodesic equations in the Ellis-Bronnikov wormhole metric, expressed in the elementary functions

The Impact of Sintering Temperature on the Microstructure and Electrical Characteristics of Varistor Ceramics Containing V2O5-doped ZnO-Bi2O3-Sb2O3 and MnO2 Additives

Abstract: This study explores the enhancement of ZnO varistor ceramics as voltage surge protectors for electronic components by incorporating various metal oxides, including Bi2O3, as varistor-forming agents. The investigation focuses on the impact of V2O5 doping in ZnO-Bi2O3-Sb2O3-MnO2 varistor ceramics to achieve maximum nonlinearity and low leakage current. A mixture of powdered materials (98.1 mol% ZnO, 0.7 mol% Bi2O3, 0.3 mol% Sb2O3, 0.7 mol% MnO2, and x mol% V2O5) underwent a 24-hour ball milling process, followed by drying and grounding. The resulting powder was uniaxially pressed into 10 mm diameter, 1 cm thick disks, and then sintered at 1240 °C for 4 hours, with a heating and cooling rate of 5°C/min for all compositions. Electrical and microstructural properties were examined for varying V2O5 doping levels (x = 0.0 to 0.6 mol%) in ZnO-Bi2O3-Sb2O3 and MnO2 varistor ceramics. The maximum barrier height observed was 0.68 eV, corresponding to the highest nonlinearity coefficient of 11.25. Minimal leakage current, approximately 1×10-4 mA/cm2, was observed for doping levels of 0, 0.08, 0.20, 0.40, and 0.60 mol%. The highest relative density of the prepared ceramics was 91.31% and 87.23% for ceramics with 0.2 and 0.4 mol% content of doping, respectively, this approached the theoretical density of ZnO (5.78 g/cm3). Microstructural features were examined using SEM attached with EDX. The XRD patterns revealed primary phases of ZnO, with secondary phases including ZnSb2O4, Zn7Sb2O12, MnVO3, BiVO4, and Zn3(V4)2 polymorphs

Naturally Occurring Radioactive Concentrations and the Associated Cancer risks from Tailings by Kaolin Mining in Katsina, Nigeria

This research was carried out to assess the health hazards associated with environmental radioactivity around Kankara and Dutsinma Kaolin mining sites Katsina State; Nine (09) Kaolin samples were collected randomly from the mining sites for the study. The radioactivity analysis was done experimentally using NaI(Ti) gamma spectrometer at Center for energy research and training, Ahmadu Bello University Zaria. The health hazards were evaluated using numerous radiological, Statistical and USEPA models.The hazard indices were found to be below the USEPA threshold limit for non-carcinogenic risks of 1.0 indicating that the exposed population ages are unlikely to experience any adverse non-carcinogenic risks. The radiological parameters obtained are 226Ra, 238U, 232Th and 40K of NORMs (Naturally Occurring Radioactive Materials) with activity concentration of 100.889, 0.129 and 224.040 (Bq-kg-1) in the soil samples, at the studied area. Absorbed dose rate in air (D) measured in nGyh-1 at 1 meter above the ground, was calculated from the mean radioactivity concentrations and obtained as 77.575 while the total annual effective dose (AED) in mSv/y had average value of 0.099 in soil. The values obtained for external and internal radiological hazard indices Hext and Hint are 0.471 and 0.741 in soil; which were lower than the UNSCEAR recommended limit of unity. Finally, the overall excess lifetime cancer risk due to NORMs were 5.63E-06 and 4.15E-06 for adults and children respectively in whole population indicating that a maximum of 6 adults per 1 million may be affected while a maximum of 4 children per 1 million may be affected. These values were within the USEPA threshold of 1E-04

Modal interpretation of Quantum mechanics provides the framework for the Description of physical reality

AbstractThe question whether the quantum description of physical reality may be considered complete remains a challenge among a number of physicists even today. These challenges have their origins from the quantum measurement problem.This paper tries to address this problem by focusing on the quantum logical perspective and particularly on how modal interpretation of quantum mechanics leads to the contextual description of physical reality. It argues that in classical mechanics any composite system can be completely described by the state of its parts. But in quantum mechanics the composite system can be in the entangled state and therefore cannot be described by giving a pure state for each subsystem.By using the modal interpretation of quantum mechanics, we are led to the description of reality that cannot be postulated rather to the reality in postulation. Reality in postulation is contextual. In this sense transition from postulation of reality to reality in postulation is analogously similar to transition from Boolean structure to non – Boolean structure of the universe, from the localized systems to non – localized systems

Fabrication and Characterization of Electrospin PAni/Fe3O4/PVA Nanofiber Composites for Telecommunication Engineering

The synthesis of conducting polymers has made it possible for the research community on their applications toward microwave absorption for telecommunication engineering. Polyaniline has been one such conducting polymer whose synthesis does not require any special equipment or precautions. Such conductive polymer generally, show highly reversible redox behaviour with a noticeable chemical memory and hence have been considered as prominent new materials for the fabrication nanofibers that could be used many applications particularly for telecommunication engineering. The current work presents a successful fabrication of Polyaniline/Magnetite/Poly(vinylalcohol) (PAni/Fe3O4/PVA) nanofibers composites using electrospinning methods.  Field Emission Scanning Electron Microscope (FESEM) was employed to investigate the composites nanofiber’s morphology and TEM was also used to confirmed the present of Fe3O4 nanoparticles in the composites nanofiber, where the nanofibers diameter were investigated and found to be approximately 141 nm as estimated by image-J computer software analysis. Fourier-Transformation Infrared Spectroscopy (FTIR) study confirmed the presence of both Fe3O4 nanoparticles and PAni in the nanofiber structure. The X-ray diffraction (XRD) pattern of Fe3O4 nanoparticles and PAni/Fe3O4/PVA nanofiber materials shows the characteristic behaviour of both amorphose and crystalline phase by indication the peaks at 2? = 23.12o, 24.14o and 35.13o in the prepared materials.

First-Principle Study on Lead-Free Perovskite for Optoelectrical Applications

The research into new types of light harvesters for solar cells is driven by the need to increase their efficiency and make them more reliable. One promising material for replacing the dye-molecule light harvesters is the Organometallic perovskite; the most popular among them is methyl ammonium lead iodide, CH3NH3PbI3. Although methyl ammonium lead iodide, (CH3NH3PbI3) has proven to be an effective photovoltaic material, there remains a huge concern about the toxicity of lead.  An investigation into the possible replacement of lead (Pb) with Germanium (Ge), Silicon (Si), and Tin (Sn) in CH3NH3PbI3 was carried out. Before this investigation, structure building, parameter optimization, determination of the best exchange functional, k-grid convergence test, and determination of equilibrium lattice constant and geometry relaxation were carried out for the first set of materials. Visualization for Electronic and Structural Analysis (VESTA) and Avogadro software were used for the structure building while FHI-aims code was used to simulate these Perovskites materials. The BLYP (a parameterization of GGA) exchange functional gave the minimum single-point energy at a minimum run time for all the structures. The lattice constants obtained using Phonopy (with zero-point energy) are 5.894, 5.907, 6.248, 5.950, and 6.049 ? for CH3NH3GeBr3, CH3NH3GeI3, CH3NH3PbI3, CH3NH3SiI3, and CH3NH3SnI3 respectively. The energy band gap calculated for the second set of materials: CH3NH3GeI3, CH3NH3PbI3, CH3NH3SiI3, CH3NH3SnI3, and CH3NH3GeBr3 at their respective equilibrium lattice constants are 1.606, 1.513, 1.804, 1.051 and 1.925 eV respectively. These calculated band gap values were compared with reported theoretical and experimental values. There is a close agreement in calculated lattice constants and bandgaps with reported theoretical and experimental values. Dielectric constants, refractive index extinction coefficient, absorption coefficient, reflectivity, and optical conductivity of these materials were also determined. The optical properties obtained show that Sn and Ge are a good choice for the replacement of Pb; also, the optical properties obtained indicate that these materials have other possible applications in areas other than photovoltaic technology

Biodiesel production from castor oil and analysis of its physical properties

Biodiesel is a biodegradable, renewable energy and efficient substitution fuel which can fulfill energy security needs without sacrificing engine performance. Biodiesel fuels were prepared from vegetable oil of castor beans and its physical properties such as viscosity, flash point and pour point were studied. The crude castor oil was purified and trans-esterified. Transesterification reaction is most widely used method for biodiesel production, in which the triglycerides in the oil reacts with monohydric alcohol. 200 ml of the castor oil was measured and pre-heated to 70 oC using hot magnet stirrer with thermometer. 1.5 ml citric acid was added to the heated oil sample and continuously stirred for 15 minutes at 70 oC. 4g of 8 % KOH was then added to the oil and continuously heated and stirred for 15 minutes at 70 oC. The mixture was then transferred to the vacuum oven where it was heated at 85 oC for 30 minutes. Similarly, 2g of silicon reagent was added while it was being heated and stirred. after 30 minutes the temperature was increased to 85 oC and 4g of activated carbon was added to each 100 ml of the oil sample, heated and stirred for 30 minutes and the mixture was separated using filter paper. At 30, 60 and 90 oC, the viscosity of crude, purified and transesterified castor oil were found to be (64, 52, 50 mpa.s), (47, 43, 37 mpa.s) and (38, 35 and 30 mpa.s) respectively. This shows that, trans-esterified castor oil has viscosities within similar range with the crude biodiesel oil for all the varying temperatures, indicating that viscosity is major reason why oils and fats are trans-esterified to biodiesel

Observation of multiplex photon by ICCD

The image intensifier is a revolutionary device that allows direct observation of the particle nature of photons. This outstanding instrument can simultaneously detect the presence and position of photons, which has greatly improved the study of interference at the photon level. However, this instrument can not measure the energy or wavelength of the photon, so even if multiple photons are detected at the same location, it is still detected as one. We found that the histogram of the ratio of the total light intensity to the peak value of the individual fluorescence images obtained by the image intensifier splits into two peaks. We show that this peak splitting occurs with a high probability near the bright line of the interference fringes and can be explained by the continuous photon incidence

Influence of leakage current density on the stability of Sb2O3 doped ZnO-V2O5-Bi2O3-MnO2 based varistor ceramics during the DC and thermal stress

This study investigated the influence of DC-thermal stress on the stability of Sb2O3 doped ZnO–V2O5–Bi2O3–MnO2 based varistor ceramics from 0 to 1 mol%. The materials were processed using a conventional solid-state technique. The samples were characterized using XRD, SEM, and EDX techniques. The use of XRD and EDX analyses related to those cited in the literature confirmed the presence of Zn7Sb2O12, MnVO4, BiVO4, and Zn3(VO4)2 polymorphs as the secondary phase including ZnO hexagonal wurtzite structure and MnO2 as a primary phase. The EDX analyses reveal the presence of the Zn7Sb2O12 spinel phase located at the triple point junctions, nodal point, and embedded in ZnO bulk grains. Henceforth, the results showed that Sb2O3 dopingcan improve the stability of the varistor ceramics, particularly in the phase formation of Zn7Sb2O12. This contributed to good stability of Sb2O3 doped ZVBM varistor ceramics in terms of degradation rate coefficient of 2.02x10-7 mA h1/2 which was accompanied by low leakage current density around -67%, largest barrier height of 1.54%, breakdown field of 69.83% and ? around 72.94%