Structural, electrical and optical properties of aluminum doped zinc oxide spin coated films made using different coating sols

Transparent conducting aluminum doped zinc oxide Al:ZnO (AZO) layers have been deposited by spin coating on glass substrates using two different sols, 1-propanolic solution of Zinc and Aluminum salts (conventional sol) and a suspension of already crystalline AZO nanoparticles redispersed in 1-propanol. The coatings have been sintered in air at 600 °C for 15 min. and then post annealed in a reducing atmosphere at 400 °C for 90 min. The influence of the aluminum content in the coating sol (sol-gel layer) and in the redispersed nanoparticles (nanoparticulare suspension layer) on the optical properties and electrical resistivity have been investigated. A single step spin coated thin layer is obtained, so that multilayers coating have been used to lower the obtained sheet resistance. The visible transmission of both types of layers is high (T> 80%). The influence of the sintering temperature and the optimum doping concentration are investigated. Seven layers synthesized with Al/Zn = 1 mol.% and submitted to reducing treatment in forming gas (N2:H2= 92:8) exhibited a sheet resistanceR= 0.42 k (ρ = 7.9× 10–3Ω· cm) with an average transmittance of 80% at 550 nm for layer deposited from conventional sol and 36 k (ρ = 2.5× 10–1Ω· cm) for nanoparticles suspension layer.