Solution-processed high-k ZrTiOx dielectric films achieve a k value and capacitance of 53 and 467 nF cm−2, and a low leakage current of 4 × 10−8 A cm−2 with polymer modification. High-performance organic thin film transistors with a carrier mobility of 0.58 cm2 V−1 s−1, and a low operating voltage of 6 V were realized with ZrTiOx dielectric films.