Optical properties of solution-processable semiconducting TiOx thin films for solar cell and other applications

The optical properties of solution-processable semiconducting titanium suboxide (TiOx) thin films were investigated as a function of wavelength (350-800 nm) using ellipsometric and optical reflection technique. The variation of refractive index under different thermal annealing conditions (room temperature to 900 °C) was studied. The increase in refractive index with high-temperature thermal annealing process was observed, allowing the opportunity to obtain refractive index values from 1.77 to 2.57 at a wavelength of 600 nm. The x-ray diffraction and atomic force microscopy studies indicate that the index variation is due to the TiOx phase, density, and morphology changes under thermal annealing. The TiOx thin films have applications in organic and inorganic solar cells as well as other optical and photonic devices. We show that TiOx thin films can be used as an effective antireflection layer for Si solar cells.