SnO2)

We report the fabrication and testing of dye sensitized solar cells (DSSC) based on tin oxide (SnO 2) particles of average size ~20 nm. Fluorine-doped tin oxide (FTO) conducting glass substrates were treated with TiO x or TiCl 4 precursor solutions to create a blocking layer before tape casting the SnO 2 mesoporous anode. In addition, SnO 2 photoelectrodes were treated with the same precursor solutions to deposit a TiO 2 passivating layer covering the SnO 2 particles. We found that the modification enhances the short circuit current, open-circuit voltage and fill factor, leading to nearly 2-fold increase in power conversion efficiency, from 1.48% without any treatment, to 2.85% achieved with TiCl 4 treatment. The superior photovoltaic performance of the DSSCs assembled with modified photoanode is attributed to enhanced electron lifetime and suppression of electron recombination to the electrolyte, as confirmed by electrochemical impedance spectroscopy (EIS) carried out under dark condition. These results indicate that modification of the FTO and SnO 2 anode by titania can play a major role in maximizing the photo conversion efficiency.

Urchin-like SnO 2 microspheres have been grown for use as photoanodes in dye-sensitized solar cells (DSSCs). We observed that a thin layer coating of TiO 2 on urchin-like SnO 2 microsphere photoanodes greatly enhanced dye loading capability and light scattering ability, and achieved comparable solar cell performance even at half the thickness of a typical nanocrystalline TiO 2 photoanode. In addition, this photoanode only required attaching ~55% of the amount of dye for efficient light harvesting compared to one based on nanocrystalline TiO 2. Longer decay of transient photovoltage and higher charge recombination resistance evidenced from electrochemical impedance spectroscopy of the devices based on TiO 2 coated urchin-like SnO 2 revealed slower recombination rates of electrons as a result of the thin blocking layer of TiO 2 coated on urchin-like SnO 2. TiO 2 coated urchin-like SnO 2 showed the highest value (76.1 ms) of electron lifetime (τ) compared to 2.4 ms for bare urchin-like SnO 2 and 14.9 ms for nanocrystalline TiO 2. TiO 2 coated SnO 2 showed greatly enhanced open circuit voltage (V oc), short-circuit current density (J sc) and fill factor (FF) leading to a four-fold increase in efficiency increase compared to bare SnO 2. Although TiO 2 coated urchin-like SnO 2 showed slightly lower cell efficiency than nanocrystalline TiO 2 , it only used a half thickness of photoanode and saved ~45% of the amount of dye for efficient light harvesting compared to normal nanocrystalline TiO 2 .

Because of its electrically conducting properties combined with excellent thermal stability and transparency throughout the visible spectrum, tin oxide (SnO2) is extremely attractive as a transparent conducting material for applications in low-emission window coatings and solar cells, as well as in lithium-ion batteries and gas sensors. It is also an important catalyst and catalyst support for oxidation reactions. Here, we describe a novel nonaqueous sol−gel synthesis approach to produce tin oxide nanoparticles (NPs) with a low NP size dispersion. The success of this method lies in the nonhydrolytic pathway that involves the reaction between tin chloride and an oxygen donor, 1-hexanol, without the need for a surfactant or subsequent thermal treatment. This one-pot procedure is carried out at relatively low temperatures in the 160−260 °C range, compatible with coating processes on flexible plastic supports. The NP size distribution, shape, and dislocation density were studied by powder X-ray powder diffraction analyzed using the method of whole powder pattern modeling, as well as high-resolution transmission electron microscopy. The SnO2 NPs were determined to have particle sizes between 3.4 and 7.7 nm. The reaction products were characterized using liquid-state 13 C and 1 H nuclear magnetic resonance (NMR) that confirmed the formation of dihexyl ether and 1-chlorohexane. The NPs were studied by a combination of 13 C, 1 H, and 119 Sn solid-state NMR as well as Fourier transform infrared (FTIR) and Raman spectroscopy. The 13 C SSNMR, FTIR, and Raman data showed the presence of organic species derived from the 1-hexanol reactant remaining within the samples. The optical absorption, studied using UV−visible spectroscopy, indicated that the band gap (Eg) shifted systematically to lower energy with decreasing NP sizes. This unusual result could be due to mechanical strains present within the smallest NPs perhaps associated with the organic ligands decorating the NP surface. As the size increased, we observed a correlation with an increased density of screw dislocations present within the NPs that could indicate relaxation of the stress. We suggest that this could provide a useful method for band gap control within SnO2 NPs in the absence of chemical dopants.

The SnO 2 and In 2 O 3 powder mixed with different ratio and heated at 900 0 C about 5 hrs and then this powder is used to prepared thick films by a screen-printing technique on glass substrate. The NH 3 gas sensing properties, particularly the rate of response of SnO 2-In 2 O 3 sensors are studied at room temperature. SEM and EDAX analysis showed that crystallite size is small (86.43 nm) for 65SnO 2-45In 2 O 3 composition. The Sensitivity increases drastically as the expose of NH 3 gas for 65SnO 2-45In 2 O 3 sample. This sample is found to be better sensing material as regards to other in all respect.

A full characterization of phase separation and the competition between phases is necessary for a comprehensive understanding of strongly correlated electron materials, such as under-doped high-temperature superconductors 1,2 , complex oxide heterojunctions 3 , spinels 4,5 , multiferroics 6,7 , rare-earth ferroelectric manganites 8 and mixed-valence manganites in which phase competition is the dominant mechanism governing the insulator-metal (IM) transition and the associated colossal magnetoresistance effect 9-11 . Thin films of strongly correlated electron materials are often grown epitaxially on planar substrates and typically have anisotropic properties that are usually not captured by edge-mounted four-terminal electrical measurements, which are primarily sensitive to inplane conduction paths. We present an experimental study of anisotropic transport in phase-separated manganite thin films by using an unconventional arrangement of contact electrodes that enables the simultaneous determination of colossal magnetoresistance associated with d.c. transport parallel to the film substrate and colossal magnetocapacitance associated with a.c. transport in the perpendicular direction. We distinguish two distinct direction-dependent IM transitions and find a dielectric response that collapses onto a scale-invariant dependence over a large range of frequency, temperature and magnetic field.

A dual layer Benzocyclobutene (BCB) polymer with tailored refractive index values is successfully fabricated using different curing processes, forming a platform for integrated optical devices. The dual layer BCB polymer could potentially solve the high index contrast issue associated with existing glass-polymer structure, which require sub-micron precision when producing single-mode waveguides. Although the two BCB layers display similar physical properties, they have significantly different optical and chemical characteristics. The different curing processes for the undercladding and core layers led to these differences. Single mode waveguides fabricated via photolithography were also demonstrated with an average propagation loss of 2 dB/cm.