Silver nanoparticles(AgNPs) with well-distributed sizes were prepared by magnetron sputtering on slides and crystalline silicon(c-Si) solar cell following by annealing at different temperatures. The morphologies,optical and photovoltaic performance were investigated in detail. The spectroscopic result shows that two resonance peaks resulting from coupling effect among neighboring particles are difficult to obtain by other chemical methods.The photovoltaic performances reveal that the solar cells decorated with AgNPs significantly are degraded, including a maximal decrease of 20.4 % in short-circuit density and 53.9 % in energy conversion efficiency. The lowest efficiency achieved is 5.85 % for c-Si solar cells with AgNPs annealed at 500 ℃. The deterioration should result from the synergetic effect of the intrinsic absorption of single particle and coupling absorption between neighboring particles.
Using the oxidation method from vanadium metal thin films by magnetron sputtering, under the fixed annealing parameters of temperature(400 ℃) and oxygen pressure(103 Pa), we fabricated a series of vanadium dioxide thin films through the change of annealing durations or substrates(quartz glass or AZOcovered glass). Characterization of the thermochromic properties together with the X-ray diffraction(XRD) and field emission scanning electron microscopy(FE-SEM) indicates that appropriate annealing duration is a key factor to obtain pure VO2 films and AZO-covered glass is more suitable to obtain the VO2 films with high visible transmittance, good crystallinity and larger near-infrared switching efficiencies(maximum 34% at 2000 nm) compared with the substrate of quartz glass. However, VO2 films on quartz glass exhibit narrower loop(7 ℃) with smart reversible response to temperature. Depth profile XPS spectra further indicate that for the films fabricated on quartz glass from thicker V metal films, the existence of low valence vanadium oxides is inevitable and leads to a lower transmittance in the region of visible light.
A lithium ion conductive solid electrolyte, L2O-Al2O3-TiO2-SiO2-P2O5 glass with NASICON-type structure have been synthesized and transformed into glass-ceramic through thermal-treatment at various temperatures from 700 to 1 000 ℃ for 12 h. The differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and complex impedance techniques were employed to characterize the samples. The experimental results indicated that the capability of glass forming in this system is superior to that of L2O-Al2O3-TiO2-P2O5. The glass has an amorphous structure and resultant glass-ceramic mainly consisting of LiTi2(PO4)3 phases. Impurity phases AlPO4, TiO2, TiP2O7 and unidentified phase were observed. With the enhanced heat-treatment temperature, grain grew gradually and lithium ion conductivity of glass-ceramics increased accordingly, the related impedance semicircles were depressed gradually and even disappeared, which could be analytically explained by the coordinate action of the 'Constant phase element' (CPE) model and the 'Concept of Mismatch and Relaxation' model (CMR). When the sample is devitrified at 1 000 ℃, the maximum room temperature lithium ion conductivity comes up to 4.1×10-4 S/cm, which is suitable for the application as an electrolyte of all-solid-state lithium batteries.
Mono-disperse silver nanoparticles with tunable morphologies have been fabricated by reducing AgNO3 in the presence of N-dimethylformamide (DMF) and larger molecular weight poly(vinylpyrrolidone)(PVP). By adjusting the reaction temperature, the conversion of the morphology can be easily and effectively controlled. The crystal structures and growth mechanism of mono-disperse silver nanoparticles were studied by using TEM, HR-TEM, FFT, XRD and UV-Vis spectra data. The results show that the morphologies of nanoparticles with spherical shape can be adjusted to a truncated triangle/hexagon along with the change of reaction temperature from 80 to 120 ℃. It is found that the shape transformation from sphere to truncated triangle is caused by the difference in surface energy and the selective adsorption of PVP on silver atom.
