Papers by Keyword: PL Spectroscopy

Abstract: Tungsten Sulfide (WS₂) has been appeared as visible range semi-conductors with having substantial direct band gap. In two-dimensional (2D) transition metal dichalcogenides (TMDC) i.e.WS₂ has been growing research attention over more than the past twenty years in low cost, energy-efficient, adaptable or environment-friendly material, which is crucial part of optoelectronic emission devices. WS₂ semiconductor thin films were grown on glass and Si substrates by using DC sputtering method. During deposition the substrate were kept at temperature of 200°C. The thin films were studied by X-ray diffraction, UV-Vis spectrometry and Spectrofluorometer (FS5). XRD analysis revealed the nature of grown film effected by temperature of substrate results in to be amorphous. Photoluminescence analysis at 532nm and optical study proved the direct to indirect band transition in WS₂.

Abstract: In this work, zinc oxide were synthesized by biological method using Aloe vera plant and the water solution of zinc . The detail characterization of the nanoparticles was carried out on different PH value . The samples were examined with an X-ray diffraction device and the results were almost identical to the JCPDS standard. It was also observed that the size of the particles was affected by the basic and acidic medium in a large way, as the results obtained from the Transmission Electron Microscopy The particle sizes ranged from 5nm to 100nm depending on the change of the PH value.

Abstract: Nanocrystalline NiO has been prepared successfully by chemical precipitation route using nickel nitrate hexahydrate (Ni (NO₃)_{2 ·}6H₂O) and sodium hydroxide (NaOH) aqueous solution at a temperature of 60 ̊C. Their compositional, structural, morphological, thermal and optical properties were studied using energy dispersive analysis of X-rays (EDAX), X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), ultraviolet-visible (UV-Vis) spectroscopy, photoluminescence (PL) spectroscopy and Raman spectroscopy. From XRD pattern we confirmed the face centered cubic (fcc) structure of the synthesized NiO nanoparticles. The selected area electron diffraction (SAED) pattern indicated the same crystalline planes as seen in XRD pattern. TGA indicates good thermal stability of synthesized NiO nanoparticles and the optical absorption spectrum of NiO nanoparticles shows the strong absorption edge at 235nm (4.10eV). PL spectra of NiO nanoparticles shows two wide emission peaks at 420nm (2.95eV) and 440nm (2.82eV) and a strong–broad peak at 460nm (2.70eV) in violet emission band whereas the Raman peak observed at 518cm^-1 shows the Ni-O stretching mode of vibration.

Abstract: A series of glasses with composition of xPbO-(50-x)ZnO-yB₂O₃-(50-y)P₂O₅ with 0 x 50 mol% and 10 y 20 mol% were prepared by melt quenching technique, with 30 minutes pre-heating and 10 minutes for melting. The structural properties of prepared samples were studied using Fourier Transform-Infrared spectroscopy. The glasses were mainly based on PO₂, BOP and BO₃ unit. In order to obtain luminescence properties, another series of sample at composition 20PbO-30ZnO-10B₂O₃-40P₂O₅ doped with Fe²⁺, Ti²⁺, Y²⁺ and Nd²⁺ were prepared. These samples were investigated using Photoluminescence Spectroscopy with different excitation wavelength to compare results. Results showed that with the presence of rare earth and transition metal ions as activator in lead zinc borophosphate glass system give rise to luminescence of visible light.

Abstract: This paper reviews results of studies on different materials and technologies for polycrystalline solar cells conducted at Tallinn University of Technology. Structural properties and defect structure of kesterite CZTS compounds (Cu2ZnSnSe4, Cu2ZnSn(SSe)4) were studied. Influence of selenization parameters of a Zn-Cu-Sn stacked layer on the CZTS layer growth and on the morphology, distribution of elements was analyzed. All the results obtained have been used to optimize the technology of producing solar cell structures in different designs. Cu2ZnSnSe4 and, Cu2ZnSn(SSe)4 based monograin layer solar cells were developed.