Enhanced and adjustable photoresponse performance in Bi4Ti3O12/TiO2 bilayer films

Bi4Ti3O12/TiO2 bilayer films were synthesized on general fluorine-doped tin oxide glass (FTO) substrates adopting a simple solution coating processing. The Bi4Ti3O12 film with different thickness was first prepared on FTO substrates, and then TiO2 layer with different thickness was spin-coated on the Bi4Ti3O12 layer, to obtain different Bi4Ti3O12/TiO2 bilayer films with almost the same total thickness. The morphology and crystal structure of Bi4Ti3O12/TiO2 bilayer films were characterized and analyzed by scanning electron microscopy and X-ray diffraction. The enhanced photoresponse was observed in bilayer films compared with the single-phase films of Bi4Ti3O12 or TiO2. Besides, it was also observed that the photoresponse of the bilayer films could drastically be adjusted by applied bias voltage and ferroelectric polarization states. The reasons for the above phenomena were also investigated.