Moisture induced surface polarization in a poly(4-vinyl phenol) dielectric in an organic thin-film transistor

Surface polarization in a poly(4-vinyl phenol) (PVP) dielectric induced by water molecules has been qualitatively investigated in pentacene thin-film transistors. The magnitudes of drain currents from devices with PVP dielectrics subject to specific surface treatments increased with humidity, whereas the opposite responses were observed from device with SiO2 dielectrics. The increase in drain current is attributed to the accumulation of extra charge carriers induced by the surface polarization in addition to that by the vertical electric field. Such polarization effects should be carefully considered in characterizing organic and polymer thin-film transistors, particularly those with polymeric gate insulators.