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We report on the anisotropic optical properties of single-crystal tin monosulfide (SnS). The components e a , e b , and e c of the pseudodielectric-function tensor hei ¼ he 1 i þ ihe 2 i spectra are taken from 0.73 to 6.45 eV by spectroscopic ellipsometry. The measured hei spectra are in a good agreement with the results of the calculated dielectric response from hybrid density functional theory. The hei spectra show the direct band-gap onset and a total of eight above-band-gap optical structures that are associated with the interband-transition critical points (CPs). We obtain accurate CP energies by fitting analytic CP expressions to second-energy-derivatives of the hei data. Their probable electronic origins and implications for photovoltaic applications are discussed. V C 2014 AIP Publishing LLC. [http://dx.

The effects of pH and ultraviolet (UV) light with ligated formic acid on mesoporous TiO2 were characterized by transmission Fourier transform infrared (FTIR) spectroscopy and compared with adsorbed formate complexes. Surface-modified anatase thin films were prepared from acidic aqueous nanoparticulate anatase suspensions diluted with methanol and ethanol. Bands assigned to carboxylic acid groups displayed unique bonding character in the ligated formic acid on the anatase surface. For increased proton concentrations in the films, separation in -COO stretching bands (delta nu) for formic acid increased (increase in frequency for nuC=O and decrease in frequency for nuC-O). With UV exposure, surface-bound organics were rapidly removed by photocatalytic oxidation at 40 degrees C and 40% relative humidity (RH). In addition, the delta nu of the formic acid bands decreased as organics were mineralized to carbonates and CO2 with UV light. Aqueous formic acid adsorption experiments showed a distinctly different bonding environment lacking carbonate, and the delta nu for the carboxylic groups indicated a bridging bidentate coordination. The delta nu of the bands increased with increasing proton concentration, with both bands shifting to higher wavenumbers. The shifts may be ascribed to the influence of protonation on surface charge and the effect of that charge on the electronegativity of carboxylate groups bound to the surface. As alcohols are used in the mesoporous TiO2 solar cell preparation, implications of these surface modifications to dye-sensitized photovoltaics are discussed.

Solar farm suitability in remote areas will involve a multi-criteria evaluation (MCE) process, particularly well suited for the geographic information system (GIS) environment. Photovoltaic (PV) solar farm criteria were evaluated for an island-based case region having complex topographic and regulatory criteria, along with high demand for low-carbon local electricity production: Ulleung Island, Korea. Constraint variables that identified areas forbidden to PV farm development were consolidated into a single binary constraint layer (e.g., environmental regulation, ecological protection, future land use). Six factor variables were selected as influential on-site suitability within the geospatial database to seek out increased annual average power performance and reduced potential investment costs, forming new criteria layers for site suitability: solar irradiation, sunshine hours, average temperature in summer, proximity to transmission line, proximity to roads, and slope. Each factor variable was normalized via a fuzzy membership function (FMF) and parameter setting based on the local characteristics and criteria for a fixed axis PV system. Representative weighting of the relative importance for each factor variable was assigned via pairwise comparison completed by experts. A suitability index (SI) with six factor variables was derived using a weighted fuzzy summation method. Sensitivity analysis was conducted to assess four different SI based on the development scenarios (i.e., the combination of factors being considered). From the resulting map, three highly suitable regions were suggested and validated by comparison with satellite images to confirm the candidate sites for solar farm development. The GIS-MCE method proposed can also be applicable widely to other PV solar farm site selection projects with appropriate adaption for local variables.