The influence of gate dielectrics on a high-mobility n-type conjugated polymer in organic thin-film transistors

Organic thin-film transistors based on a high mobility n-type semiconductor poly{[n,n9-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,59-(2,29-bithiophene)} P(NDI2OD-T2) and different polymer gate dielectrics are fabricated. The average electron mobility decreases from 0.76 to 0.08 cm²/Vs with the increase of the gate dielectric constant from 2.6 to 7.8. The P(NDI2OD-T2) film shows unconventional face-on molecular packing, which results in short distances and pronounced interactions between electrons and gate dielectric. Therefore, the decrease of the electron mobility with the increasing dielectric constant is attributed to the Fröhlich polaron effect for the interaction between electrons in the channel and ionic polarization cloud in the gate dielectric.