Influence of annealing temperature on formation and photoelectric properties of AZO nanosheet-coated FTO-based films

In this work, we reported a direct fabrication of Al-doped zinc oxide (AZO) nanosheets on fluorine-doped tin oxide (FTO)-based substrates using thermal annealing method. Specifically, silver (Ag) and AZO layers were successively deposited on commercial FTO/glass by direct current magnetron sputtering, and then the as-deposited AZO/Ag/FTO films were thermally annealed in a tube furnace to prepare AZO nanosheets. The effects of annealing temperature on the AZO nanosheet morphology and the performance of AZO/Ag/FTO films were investigated by an X-ray diffractometer, a scanning electron microscope, an energy dispersive spectrometer, optical transmittance spectra, reflectance spectra and a digital four-point probe instrument. It was found that a suitable temperature resulted in the formation of AZO nanosheets, which could effectively decrease the reflectance and thus improve the transmittance of the films. Smaller densely-distributed AZO nanosheets were observed on the film annealed at 450 °C, enabling it to have the highest average transmittance of 81.0% and the lowest reflectance of 6.3% in the waveband of 400–800 nm. The results also showed that the film annealed at 450 °C had the highest figure of merit of 2.59 × 10⁻² Ω⁻¹, which was more than four times that of the as-deposited film (0.57 × 10⁻² Ω⁻¹). This work demonstrates the availability of preparing AZO nanosheets by thermal annealing and provides a reference for improving overall photoelectric property of transparent conducting oxide films.