Crystal structure and optical characterizations of Titanium-doped Zinc Oxide thin films for organic photovoltaic applications

Thin films of transparent conducting titanium-doped zinc oxide (TZO) were deposited by radio-frequency magnetron sputtering technique using a sintered ceramic target of ZnTiO₃. The structural and optical properties of the thin films were characterized with X-ray diffraction and spectrophotometer. The results show that the polycrystalline TZO thin films consist of the hexagonal crystal structures with c-axis as the preferred growth orientation normal to the substrate, and that the titanium doping level significantly affects the crystal structures and optical properties of the thin films. The TZO film deposited with the titanium content of 3 wt% has the relatively well crystallinity, the largest crystal size and the highest average visible transmittance. Furthermore, the optical constants and optical energy gaps of the thin films were determined by optical characterization method.