Enhanced anti-reductive properties of nano-flower shaped morphological TiO2/FTO bilayer films for a-Si based solar cells

Titanium dioxide (TiO2)/fluorine-doped tin dioxide (FTO) bilayer films were deposited on glass substrates by spray pyrolysis. The effects of hydrogen plasma exposure on structure, morphology and optical properties of the films were studied. The distribution of elements in the double layer film was investigated by glow discharge spectrometer. The results indicate that the TiO2 film provides effective protection of the underlying FTO film from the bombardment with hydrogen ions and radicals. Without the TiO2 protective layer, SnO2 will be reduced to sub-oxidized SnO and metallic Sn by hydrogen ions and radicals with increasing the exposure time. In addition, the TiO2/FTO film presents a nano-flower shaped appearance due to the small particles (TiO2) agglomerated on the surface of large particles (SnO2), the novel textured morphology is preferred for improving light scattering and haze of the film. A high haze value of 36.7% was obtained when the approximate thickness of the prepared TiO2 layer is 213 nm. This work may provide an alternative for improving performance of a-Si based solar cells.