Different molar concentrations (0.05-0.2 M) of vanadium pentoxide nanoparticles were synthesized with and without polyvinylpyrrolidone (PVP) using hydrothermal method. The growth mechanism with different molar concentrations as well as the effect of PVP on the structural, optical, and electrical properties have been investigated. The size of the particles was measured from transmission electron microscopy (TEM) and x-ray diffraction spectroscopy (XRD). Optical properties were analyzed through photoluminescence and absorption measurement. The electrical transport properties were analyzed by impedance spectroscopy and Van der Pauw method. From impedance measurements, dominance of grain boundary resistance over grain resistance was observed. The resistivity also decreased with increasing molar concentrations of nanoparticles with and without PVP. The highest temperature coefficient of resistance (TCR) value of À 2.33 %/K with the lowest resistivity of 0.02 Ω. cm for V 2 O 5 nanoparticle of 0.2 M concentration without using PVP was observed. Therefore, such V 2 O 5 nanoparticles are a potential material for microbolometer applications.
Iron doped ZnO (Fe-ZnO) nanoparticles were synthesized using two techniques that are economical as well as scalable to yield tunable properties of nanoparticles for facilitating down conversion in an absorbing layer of a solar cell. To evaluate the suitability of Fe-ZnO nanoparticles prepared by two deposition methods, we present a comparison of optical, electrical, and structural properties of Fe-ZnO using several experimental techniques. Structural properties were analyzed using transmission electron microscopy and x-ray diffraction spectroscopy (XRD) with Rietveld analysis for extracting information on compositional variations with Fe doping. The chemical composition of nanoparticles was analyzed through X-ray photoelectron spectroscopy (XPS). The optical properties of nanoparticles were studied using photoluminescence and UV-Vis absorption spectroscopy. In addition, fluorescence lifetime measurement was also performed to study the changes in an exponential decay of lifetimes. The electrical transport properties of Fe-ZnO were analyzed by impedance spectroscopy. Our studies indicate that ethanol as a solvent in a microwave method would produce smaller nanoparticles up to the size of 11 nm. In contrast, the precipitation method produces secondary phases of Fe2O3 beyond 5% doping. In addition, our studies show that the optical and electrical properties of resulting Fe-ZnO nanoparticles depend on the particle sizes and the synthesis techniques used. These new results provide insight into the role of solvents in fabricating Fe-ZnO nanoparticles by precipitation and microwave methods for photovoltaic and other applications.
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