We report solution processed high-k dielectric films with excellent insulating quality (leakage current densities ∼10⁻⁸ A cm⁻² at 2 MV cm⁻¹), tunable dielectric constant (4.7–6.7) and high flexibility. The effects of incorporating different concentrations of barium zirconate (BZ) nanoparticles into poly-4-vinylphenol (PVP) gate dielectrics for flexible organic thin film transistors (OTFTs) were systematically studied. The effect of dielectric composition on the mobilities (μ), threshold voltages (V_T), on/off ratios and subthreshold swings (S) has been discussed. The morphologies of dielectric and semiconductor films were investigated and shown to correlate closely with device performances. Two kinds of unipolar inverters based on these transistors have been fabricated and characterized. The depleted load inverter showed large signal gain and sharp switching. The electrical properties under various compressive and tensile strains evidenced the high mechanical stability of the dielectric films, hence the transistors and inverters. These findings will be of value for printable electronic devices on flexible substrates.