High dielectric constant fluorinated polymer film gate electrets for organic field effect transistors

The high dielectric constant of dipolar charge electrets makes these materials attractive as gate dielectric in organic field effect transistors (OFET). Additionally, dipole electrets may even provide functionalities to such devices, like permanently polarized gate dielectrics for nonvolatile memories as well as pyro- or piezoelectric OFETs. Organic thin film transistors in top-contact geometry with pentacene as semiconductor and double layers of a ferroelectric polymer electret poly(vinylidene-fluoride tetrafluoroethylene hexafluoropropylene) and the polymer poly(vinyl cinnamate) as gate dielectric are shown. The electret is a terpolymer of vinylidene fluoride, trifluoroethylene and hexafluoropropylene with a high dielectric constant ε=10 at 1 MHz. The transistors show large intrinsic field effect mobility´s in the range of μ_i=1 cm²/Vs and a large ratio of on- to off-current of about 10⁵. The use of strongly polar high-k polymer gate dielectrics seems promising for applications of organic field effect transistors as non-volatile memory elements and in organic sensor systems.