Structural and optical properties of AZO/TiO2 heterostructures thin film on ITO substrates for solar cell application.

The X-ray diffraction (X-RD) and UV-Vis spectrophotometer have been performed to investigate the structural and optical properties of the AZO/TiO2 hetero-structures using sol-gel spin coating. The AZO/TiO2 samples were arranged by zinc acetate dehydrates (Zn(CH3COO)2.2H2O) and titania nanopowders as a main chemical compound. To prepare the AZO films, the precursor of (Zn(CH3COO)2.2H2O) was dissolved into the ethanol. Aluminum chloride (AlCl3) and triethanolamine (TEA) as a dopant source and a stabilizer, respectively, were added into the solution. For titanium dioxide (TiO2) films, the TiO2 nanopowders used as a precursor were dissolved into ethanol, yielding TiO2 sol-gel. We first deposited the AZO films onto ITO substrates followed by TiO2 on the top surface of AZO films using the spin coating technique. The AZO/TiO2/ITO hetero-structures thin films were calcined at temperatures of 5000C for 1 hour. From X-RD results, the X-RD peaks in AZO/TiO2 films are seen at the reflection plane of (100), (103), (110), and (103) that represented ZnO films, while TiO2 diffraction peaks were seen at the plane of (110) that corresponded to TiO2 is anatase phase. The change of the phase anatase to rutile phase structures was not observed in TiO2 films after annealing at 600oC.