Comparison of spray pyrolyzed FTO, ATO and ITO coatings for flat and bent glass substrates

Abstract

Transparent conductive FTO, ATO and ITO films were synthesized by spray pyrolysis technique on flat 12×12 cm borosilicate glass substrates at 500–550°C and investigated with respect to their electrical and optical properties. The resistivity of sprayed ITO films decreases with the thickness down to 3.0×10−4 Ω cm (300 nm). The optical transmission in the visible range is 80% and the near IR reflection up to 96% for thicknesses larger than 300 nm. A reducing treatment at 400°C in forming gas still decreases the resistivity by a factor of two. Bending of the coated glasses in air at 650°C for 1.5 h increases the resistivity of the coatings on the tensile side of the substrate by a factor of 3–4 and by a factor 2 on the compressed side. A subsequent reducing treatment in forming gas at 400°C leads to a drastic decrease of resistivity in both cases by a factor of 5–7 with resulting value ρ=2–3×10−4 Ω cm. ATO layers have lower visible transmission (70–75%) due to stronger absorption and a higher resistivity (ρ=1×10−3 Ω cm). Spray pyrolyzed FTO coatings have a resistivity ρ=5×10−3 Ω cm for film thicknesses >350 nm.