The effects of hydroxyl-free polystyrene buffer layer on electrical performance of pentacene-based thin-film transistors with high-k oxide gate dielectric

We have investigated the effects of hydroxyl-free polystyrene (PS) as buffer layer on pentacene-based low-voltage organic thin-film transistors (OTFTs). The PS buffer layer is formed on the HfO2 layer evaporated on Si substrate by spin-coating method prior to pentacene deposition, existence of which results in a dramatic increase of field effect mobility from 0.09 to 0.59 cm2/Vs and negligible hysteresis. The improved mobility and hysteresis of the OTFTs can be attributed to the formation of smooth and nonpolar hydroxyl-free PS/HfO2 gate dielectric surface. The PS insulator buffer layer can also effectively reduce gate leakage current by more than 70%. The results demonstrate that using appropriate polymer buffer layer is favorable to improve the performance of the OTFTs operating at low voltages with high mobility and good electrical stability.