The synthesis of versatile, and non-toxic precursors for ambient-air deposition of semiconducting metal-oxide thin films by spray pyrolysis is reported. The resulting thin films yield stable and reproducible performance in thin-film transistors. The precursors are based on reactions of metal salts and an organic ammonium source in water. The precursor preparation is highly versatile with respect to low-level handling requirements (i.e. in air) and miscibility for the synthesis of customized mixed metal oxides. The precursor solutions are deposited by spray pyrolysis and integrated into bottom-gate test structures with staggered source and drain contacts. Indium-zinc oxide thin films deposited from a precursorwith an [In]/[Zn] ratio of 3:1 exhibit an on-off current ratio of 10(6) with a calculated saturation mobility of 14.1 cm(2) V-1 s(-1) +/- 1.1 cm(2) V-1 s(-1) at a drain voltage of 40 V. The demonstrated route to non-toxicmolecular precursors for low-temperature thin-film processing in ambient atmosphere benefits from low cost of educts, environmentally friendly solvents, minimized health risk when compared to nanoparticle processing, and an excellent performance for electronic applications. (C) 2013 Elsevier B. V. All rights reserved.