Solution processable nanoparticles as high-k dielectric for organic field effect transistors

The need for low operating voltages in organic field effect transistors (OFETs) is a motivation for the development of low temperature solution processable synthesis of high dielectric constant materials. Specifically, the glycothermal synthesis of barium titanate nanoparticles (size 10-15 nm) is described here. The effect of reaction time, temperature and reactant ratio has been studied. An 85% yield of pure BaTiO₃ was obtained at a temperature of 220 °C and a reaction time of 16 h with the H ₂O:propanol molar ratio fixed at 1:1. A suspension of these nanoparticles in ethanol was then used to fabricate the dielectric layers in OFETs. The roughness of the spun coated layers limited the performance of these transistors. The deposition of an overlayer of sol-gel silica on the nanoparticle films improved the charge transport properties within the pentacene organic thin films by up to two orders of magnitude. The combination of solution processable high dielectric constant BaTiO₃ nanoparticle layer and sol-gel silica is promising for low voltage organic electronics.