(618x) Synthesis of Anisotropic Porous Titanium Dioxide Thin Films by Using Scaffolds of Magnetically Aligned Microparticles

The motivation of this research project is to develop a simple, low-cost method to make titanium dioxide (TiO2) thin films with improved mechanical and electrical properties for use in dye-sensitized solar cells (DSSC). The aim is to make films with mechanical integrity, high porosity, and the ability to conduct electrons in a direction perpendicular to the substrate. The innovation is that we utilized magnetic particles to make anisotropic films of TiO2. First super-paramagnetic nanoparticles were embedded in ~0.5 micrometer polymer microspheres. In the presence of an external magnetic field, the particles form chain-like structures and, when on a surface, they form miniature pillars.  Sol-gel chemistry was performed to deposit TiO2 around the polymer microspheres.  Upon heating at sufficiently high temperature, the polymer was burned off, and the microstructure of the remaining TiO2 was almost uni-directional.  The chemical process at the various steps was measured with reflectance infrared spectroscopy.  To ascertain the uniformity and amount of cracks, these thin films were imaged with scanning electron microscopy as well as atomic force microscopy.  The porosity of the TiO2 was determined with nitrogen absorption techniques.  We expect that this method will result in DSSC’s that can produce larger amounts of electrical power than those made with nanopowders.