Preparation of aluminum doped zinc oxide films with low resistivity and outstanding transparency by a sol-gel method for potential applications in perovskite solar cell

Highly transparent and conductive aluminum doped zinc oxide (AZO) films were prepared by sol-gel method on the glass substrates. The effects of doping concentration, annealing temperature and facing direction during annealing on the structural, electrical and optical properties of AZO films were studied by performing a series of characterizations including X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, UV-vis spectrophotometry, four-point probe method and Hall effect measurement system. The results showed that the AZO films were wurtzite crystallized with c-axis preferred orientation. A minimum resistivity of 1.8 × 10^{- 3} Ω cm and a transmittance above 90% were obtained for the film doped with 1.5 at.% aluminum, annealed at 510 °C and faced-down in the oven, which was among the best performance of the currently reported works based on sol-gel process. Moreover, energy level analysis revealed that the AZO film has a work function of 4.3 eV, exhibiting great potential in perovskite solar cell applications.