Papers by Keyword: Bandgap

Abstract: The use of innovative engineering materials, such as conducting polymers or surfactants, in thin films has shifted the focus of solar cell production from rare elements towards low-cost, abundant, and non-toxic alternatives. This research aims to synthesize and characterize an enhanced, low-cost Copper Zinc Tin Sulfide (CZTS) material for solar cell applications using Cetyltrimethylammonium Bromide (CTAB) as a surfactant through the chemical bath deposition (CBD) process. The precursor solution for film growth was prepared from the sources of copper sulfate, zinc sulfate, tin chloride, thiacetamides, and CTAB in a volume ratio of 2:2:2:2:1. CTAB was employed as a capping agent to improve the optical, morphological, and solid-state properties of the CZTS films. Following deposition, the samples were annealed for one hour period at a temperature of 200°C. The deposited films were analyzed using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Raman Spectroscopy. SEM analysis revealed a dense structure with extremely small nanopores and compacted grains, suggesting that the presence of CTAB in the film enhanced the morphology and improved the conductivity of the CZTS film. Optical properties are assessed using a 756S UV-VIS-NIR Spectrophotometer, and the results demonstrated low absorbance, reflectance, and transmittance. Bandgap values of 1.34 eV, 1.38 eV, and 1.48 eV were obtained, closely matching the 1.45 eV value of pure CZTS. The addition of the polymer significantly increased electrical conductivity, as evidenced by the well-formed particle structure observed in XRD and SEM images.

Abstract: It has been demonstrated that thin films of fluorine-doped Bi₂O₃ can be prepared using sol-gel spin coating. An X-ray diffraction (XRD) and energy dispersive analysis were used to examine samples. Using a sol-gel spin-coating technique, different electrolytes and sweep rates were used in the study to characterize fluorine-doped Bi₂O₃ films. In the results of the studies, it was extensively examined whether these films could be used in the fabrication of electrochromic devices. The enhanced properties of fluorine doped samples are due to their increased separation efficiency and strong oxidation potential. For two hours, the samples were exposed to temperatures ranging from 350 °C to 450 °C. F:Bi₂O₃ films have been the subject of an intercalation and deintercalation investigation. Therefore, H₂SO₄ and KCl are used to intercalate H+ and K+ ions in PC electrolytes. Sharp transmittance peaks at the band's edge in a spectrum with good crystallinity signify interfering patterns. Band assignment 3482 cm^-1, stretching vibration of carbohydrate, C-OH, 2432 cm^-1 asymmetric stretching vibration, 1625 cm^-1 unconjugated C=O stretching vibration, and 1383 cm^-1 bending vibration of C-H are among the numerous assignments in Fourier transform infrared spectroscopy. Additionally, 1101 cm^-1 are vibrations of hydroxyl groups and 625 cm^-1 are metallic bond vibrations of F:Bi₂O₃. The surface roughness of F:Bi₂O₃ films was found to have significantly improved. It is probable that a sol-gel spin coating process at 200 °C produced dense, irregularly shaped Bi₂O₃ grains. The thermodynamic characteristics of the corrosion process for Bi in concentrated sulfuric acid solution were studied. These parameters were Ea (activation energy), H (enthalpy change), and S (entropy change).

Abstract: The aging of the precipitate product is a crucial stage in forming particles using the precipitation method. In this study, the aging time in atmospheric ambient was investigated for its impact on the formation and properties of zinc oxide particles. The zinc oxide particles were synthesized using an ultrasound-assisted precipitation method. The diffraction pattern confirmed the crystallinity and crystallite size of zinc oxide decreases with increasing aging time. The UV-Vis absorption spectrum analysis revealed that 24 hours of aging resulting zinc oxide with a bandgap close to that bulk zinc oxide band gap energy. The scanning electron microscope image showed an alteration of zinc oxide morphology from rod to flake-like particle as the aging time. The crystallinity, morphology, and optical properties of zinc oxide particles are significantly affected by aging time. The results suggested that aging time in the ultrasound-assisted precipitation method can be used to engineer the suitable properties of zinc oxide particles for its application.

Abstract: In this work, we elucidate the opto-electronic properties of pure zinc oxide and copper- doped zinc oxide nanoparticles prepared via the sol-gel method. Here, the main objective is to study the impact of copper doping on the crystalline structure of ZnO and to explore the composition dependent variations in opto-electronic properties. Synthesized ZnO nanoparticles were characterized by SEM, FTIR, UV–vis-nir, and Raman Spectroscopy. The structural and opto-electronic properties are further correlated using UV-vis-nir and high-resolution X- ray diffractometer data analysis. The size of synthesized nanoparticles are found in the range of 9.2 nm to 95.5 nm. Bandgaps are found both in the visible range (2.72 eV – 2.96 eV) as well as in the infrared regions (1.54 eV-1.58 eV). The transmittance of copper doped ZnO nanoparticles increases with increase in the doping concentrations.

Abstract: This research investigated the Hydrogen doping of the single-walled carbon nanotube (HCNT) with encapsulated cellulose, (C₆H₁₀O₅)₂, and provide theoretical predictions on the properties of the resulting complex system. After full structural optimization, two different bond lengths and angles in the HCNT and (C₆H₁₀O₅)₂/HCNT system were calculated. Further, it was found that substitutional H atoms acted as charge acceptors and drove necessary rearrangements in the valence region. The (C₆H₁₀O₅)₂ caused some peaks at the valence band mainly caused by the p orbitals of the oxygen atoms. A bandgap decrease has been observed for the (C₆H₁₀O₅)₂/HCNT system. The results are consistent with the previous works which demonstrated the possibility of band gap engineering in CNTs.

Abstract: Axion is the dark particle introduced to the quantum chromodynamics to solve the strong CP-problem. Because of its dark nature, there are many indirect evidences, but axion itself have not been registered till now. In the paper, we report the observation of dark axion-like particles formed by the polariton coupling in the resonant microcavity of a globular photonic crystal. To overcome the very small cross-section, we use the Bose-Einstein condensation of polaritons into the nearest-to-the-surface microcavity of an opal-like globular photonic crystal. This way, the synchronicity conditions are met and all polaritons have the same wavefunction to be coupled. Moreover, the giant density of states of a Bose-condensate makes polariton coupling not only allowed but stimulated. At the experiment, we observe “Light Shining through a Wall” Primakoff effect which proves dark particles. The additional spectral peak at the unitary polariton line of a maximal transparency of a crystal allows to differ bipolaritons from other particles. The results can be used not only to generate dark particles at a lab, but also to get a laboratory source of an optical-frequency gravitational waves.

Abstract: Lousy odor is severe pollution in natural rubber processing industries and the air pollution treatment by using photocatalytic decomposition method has not much known. This study aims to explore the photocatalyst preparation and characterization of Fe doped ZnO immobilized on fiberglass cloth. Fe doped ZnO was prepared both with and without co-precipitation agent of NaOH. Both methods confirmed the metal existence and gave crystallite catalyst particles with mean diameters of 50 nm according to XRD characterization methods. SEM-EDS analysis showed Fe-ZnO particles prepared without co-precipitation were less aggregated particles than those made with the other method. EDS data identified the elemental composition of Zn, Fe, and O, and the fiberglass cloth composition, including Si and Mg. In the co-preparation method, sodium was always existed along with Fe and ZnO. DR-UV analysis showed the bandgap of Fe-ZnO was 3.20 and 3.22 eV without and with co-precipitation methods, respectively. TEM analysis of the catalyst slurry shows all particles were agglomerated in both preparations. Spherical-like particles existed non-precipitation method, and a spherical- and rod particle shapes were detected in co-precipitation preparation. The non-co-precipitation process was a preparable step in immobilization of the Fe-ZnO particles onto fiberglass cloth

Abstract: A facile doping method utilizing inexpensive raw materials was proposed to achieve variation in optical bandgap and UV-visible light absorption property of MoS₂ nanosheets. Carbon-assistant heating with degreasing cotton has demonstrated the development of carbon-doped MoS₂ nanosheets with enhanced rich defects. The results obtained shown that modified MoS₂ nanosheets with the lateral width of ~600 nm are exhibited shift of the intensively blue peaks of photo-luminescence (PL) comparing to those MoS₂ nanosheets with a lateral dimension of larger than 1 μm. Optical bandgap of the carbon-doped MoS₂ nanosheets was found to be broader than that of the pure MoS₂ nanosheets and the prepared samples also exhibited a broadband UV-visible light absorption property.

Abstract: A novel one pot synthesis approach in oleic acid medium was employed to obtain monophasic ZnSe quantum dots (QD) of average size 3.7nm. The QDs were well crystalline in hexagonal phase as revealed by x-ray diffraction and high resolution transmission electron microscopy (HRTEM) studies. The ZnSe QDs exhibit sharp emission peak in the blue (465nm) with 385picosecond fluorescence decay time. The theoretical band gap corresponding to 3.7nm ZnSe QDs matched well with the measured 3.11eV band gap of synthesized QDs which thus showed quantum confinement effect.

Abstract: A theoretical model of electron tunneling current in a p-n junction based on strained armchair graphenenanoribbons (AGNRs) is developed. The effects of strain to the energy dispersion relation and the band gap of AGNR are formulated under the extended tight binding method. The electron transmittance was derived by utilizing the transfer matrix method. The calculated transmittance was then used to obtain the tunneling current by employing the Landauer formula with Gauss Quadrature computation method. The effects of strain to the energy band gap, AGNR width, and tunneling current are studied thoroughly.