Photo functional metal oxide porous films with enhanced performance and a low cost film fabrication

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Titanium dioxide was applied for photocatalyst and dye sensitized solar cells (DSSCs). A new coating technique of titanium dioxide thin films was developed in a liquid phase included titanyl nitrate. Applications of the titanium dioxide thin films are mainly studied for DSSCs. In order to lead to best cell performance, it is necessary to optimize the interface between photo sensitive materials such as titanium dioxide and transparent conductive oxides (TCO). In this report, fluorine doped tin dioxide(FTO)films were employed as the TCO films. Many problems of the interface were discussed by using polycrystalline FTO films with different preferred crystalline orientations. The compact titanium dioxide films were prepared on these FTO films, and profiles of fluorine and chlorine concentration in the interface were elucidated by SIMS analyses. The performance of DSSCs with these interfaces was estimated on AM1.5 and 100mW/cm2. On the basis of the interface analyses, it was found that the FTO films needed to be free of excess chlorine of interstitial sites and extremely preferred crystalline orientations. Moreover, FTO films on texture glass substrates with high surface roughness and tandem type cells with FTO middle layer were fabricated for enhanced cell performance. It was found that the liquid phase deposition was one of useful methods to fit the compact titanium dioxide films to the higher roughness surfaces. The leaked currents of the DSSCs were depressed as a result of the deposition of the compact films. The liquid phase deposition is very useful technique.