Heavily fluorine-doped tin dioxide films were deposited by spray pyrolysis using a high precursor concentration. The effect of film thickness was studied in the range 80-1230 nm. The films were polycrystalline and preferentially oriented along [200]. The grain size, carrier mobility mu, carrier concentration N and resistivity reached similar to 230 nm, 35 cm(2)/V s. 6 x 10(20) cm(-3) and 3 x 10(-4) Omega cm, respectively, for 1000 nm films. An unusual 'direct and linear' mu-N dependence revealed the importance of the structural properties. The 1000 nm thick films possessed an average visible transmittance similar to 81 % and a reflectance similar to 66% at 2500 nm. The electro-optical properties revealed their excellent quality as a TCO material. (C) 2009 Elsevier B.V. All rights reserved.