Synthesis of anatase(core)/rutile(shell) nanostructured TiO2 thin films by magnetron sputtering methods for dye-sensitized solar cell applications

Currently, anatase-rutile core-shell structures are accepted as highly efficient building blocks for TiO2 based catalysts or photo-electrodes used in dye-sensitized solar cells (DSSCs). Basically, a thin layer of rutile covering the core anatase pillar would improve the performance of DSSCs by retarding the charge recombination at the semiconductor/sensitizer/electrolyte interfaces. In this work, we report on the synthesis of core-shell nanostructured TiO2 thin films using reactive magnetron sputtering at a glancing angle modulating the power applying mode. First, pure anatase well-separated pillars are synthesized using the DC mode, and then, in a second step, high-pulse peak power is applied to the Ti target (high power impulse magnetron sputtering – HiPIMS) resulting in the covering of the anatase columns by a thin layer of rutile. The latter technique is well-known to increase the kinetic energy of the species striking the surface of the growing film which is a key parameter to successfully obtain the...