Browsing by Subject "Carrier separation"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item Open Access Laser induced sponge-like Si in Si-rich oxides for photovoltaics(Optical Society of American (OSA), 2013) Gundogdu, S.; Sungur Ozen, E.; Hübner, R.; Heinig, K.H.; Aydınlı, AtillaWe show that a sponge-like structure of interconnected Si nanowires embedded in a dielectric matrix can be obtained by laser annealing of silicon rich oxides (SRO). Due to quantum confinement, the large bandgap displayed by these percolated nanostructures can be utilized as a tandem stage in 3rd generation thin-film solar cells. Well passivated by the SiO2 dielectric matrix, they are expected to overcome the difficulty of carrier separation encountered in the case of isolated crystalline quantum dots. In this study PECVD grown SRO were irradiated by a cw Ar+ laser. Raman spectroscopy has been used to assess the crystallinity of the Si nanostructures and thus to optimize the annealing conditions as dwell times and power densities. In addition, Si plasmon imaging in the transmission electron microscope was applied to identify the sponge-like structure of phase-separated silicon. © 2013 Optical Society of America.Item Open Access Rational synthesis of Na and S co-catalyst TiO2-based nanofibers: presence of surface-layered TiS3 shell grains and sulfur-induced defects for efficient visible-light driven photocatalysis(Royal Society of Chemistry, 2017) Ranjith, K. S.; Uyar, TamerSurface-modified TiO2 nanofibers (NFs) with tunable visible-light photoactive catalysts were synthesised through electrospinning, followed by a sulfidation process. The utilization of sodium-based sulfidation precursors effectively led to the diffusion and integration of sulfur impurities into TiO2, modifying its band function. The optical band function of the sulfur-modified TiO2 NFs can be easily manipulated from 3.17 eV to 2.28 eV through surface modification, due to the creation of oxygen vacancies through the sulfidation process. Sulfidating TiO2 NFs introduces Ti-S-based nanograins and oxygen vacancies on the surface that favor the TiO2-TiS3 core-shell interface. These defect states extend the photocatalytic activity of the TiO2 NFs under visible irradiation and improve effective carrier separation and the production of reactive oxygen species. The surface oxygen vacancies and the Ti-S-based surface nanograins serve as charge traps and act as adsorption sites, improving the carrier mobility and avoiding charge recombination. The diffused S-modified TiO2 NFs exhibit a degradation rate of 0.0365 cm-1 for RhB dye solution, which is 4.8 times higher than that of pristine TiO2 NFs under visible irradiation. By benefiting from the sulfur states and oxygen vacancies, with a narrowed band gap of 2.3 eV, these nanofibers serve as suitable localized states for effective carrier separation.