Engineered interface using a hydroxyl group-free polymeric buffer layer onto a TiO ₂ nanocomposite film for improving the electrical properties in a low-voltage operated organic transistor

We demonstrate the effect of engineered interfaces by introducing different classes of polymeric buffer layers onto a titanium oxide (TiO ₂) nanocomposite film on the density of interfacial trap sites and corresponding mobility in low-voltage-operated organic field-effect transistors. The organic field-effect transistors were fabricated using pentacene as an organic semiconductor layer and a high dielectric TiO ₂ nanocomposite film for low-voltage operation stacked with two different kinds of thin polymers, one of which is hydroxyl group-existing polyvinyl phenol and the other is hydroxyl group-free polyvinyl cinnamate. By using the hydroxyl group-free buffer layer, the interfacial trap density is found to be much decreased than that for the hydroxyl group-existing buffer layer. In addition, the mobility for the polyvinyl cinnamate used case, shows significantly increased value by at least one of magnitude compared to the case of no buffer layer. It is found that a hydroxyl group-free polymeric layer produces a more effective surface, which leads to high electrical properties and less electrochemical traps at the interface in the organic devices.