High-quality spray-deposited fluorine-doped tin oxide: effect of film thickness on structural, morphological, electrical, and optical properties

High-quality fluorine-doped tin oxide (FTO) thin films were deposited using a low-cost homemade spray pyrolysis apparatus and the effect of film thickness on structural, morphological, electrical, and optical properties were investigated. As the thickness increases, the carrier concentration remains almost unchanged (~ 2.6 × 1020 cm−3). However, as a result of grain size increase, mobility enhanced considerably (from 19.1 to 40.1 cm2 V−1 s−1), which can be a convincing explanation for resistivity reduction (from 12.0 × 10–4 Ω cm to 6.00 × 10–4 Ω cm). As expected, the FTO thin films were highly transparent in the visible region and naturally decreased by increasing the thickness. The band-gap value of the spray-deposited FTO thin films was estimated, with results showing a gradual reduction with increasing thickness. The figure of merit was calculated for the prepared FTO thin film and an outstanding value of 9.77 × 10–3 Ω−1 corresponding to an average transmittance of 78.60 (400–900 nm) and sheet resistance of 9.21 Ω/sq was achieved.