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

Transparent conductive FTO, ATO and ITO films were synthesized by spray pyr olysis technique on flat 12 x 12 cm borosilicate glass substrates at 500-55 0 degrees C and investigated with respect to their electrical and optical p roperties. The resistivity of sprayed ITO films decreases with the thicknes s down to 3.0 x 10(-4) Omega cm (300 nm). The optical transmission in the v isible range is 80% and the near IR reflection up to 96% for thicknesses la rger than 300 nm. A reducing treatment at 400 degrees C in forming gas stil l decreases the resistivity by a factor of two. Bending of the coated glass es in air at 650 degrees C for 1.5 h increases the resistivity of the coati ngs 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 a t 400 degrees C leads to a drastic decrease of resistivity in both cases by a factor of 5-7 with resulting value rho = 2-3 x 10(-4) Omega cm. ATO laye rs have lower visible transmission (70-75%) due to stronger absorption and a higher resistivity (rho = 1 X 10(-3) 12 cm). Spray pyrolyzed FTO coatings have a resistivity rho = 5 x 10(-3) Omega cm for film thicknesses >350 nm. (C) 1999 Elsevier Science S.A. All rights reserved.