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The application of a thin, compact layer of TiO 2 on the conductive glass substrate in a dye-sensitized solar cell can prevent short-circuits in the solar cell and, therefore, prevent the back transfer of electrons by blocking direct contact between the electrolyte and the conductive substrate. In this work, it has been found that compact films of TiO 2 , produced by a sol-gel method and applied by dip-coating, increased the short-circuit current and efficiency of the solar cells. As the number of TiO 2 coatings increased, the solar cell efficiency increased, due to the film becoming thicker and more smooth and uniform.

We have examined the potential energy hypersurfaces for the carbon-rich phases of carbon nitride, CN and C 3 N, and discovered low-energy structures different from those reported previously. Trends in the preferred local bonding environments have been analyzed as a function of nitrogen content. For each composition, several structures with similar energies were found, but they have very different equilibrium volumes; the structure produced during synthesis will strongly depend on the preparation conditions. When low densities are favored, conjugated planar-ring structures with sp 2 hybridized carbon are most likely to be formed. These structures are similar to those suggested as potential photocatalytic materials. At high pressures, the preferred structures contain three-coordinate nitrogen and sp 3 hybridized carbon, including the ␤-InS structure, which we predict to be the thermodynamically preferred structure for CN under positive hydrostatic pressures. This structure has a moderately high bulk modulus with a lower formation energy than ␤-C 3 N 4 and so should be more easily synthesized.