A thin film field-effect transistor structure has been used to study the field-effect mobility in thin films of poly(3-alkylthiophenes) or quinquethiophene on discontinuous metal films of gold or copper. The field-effect was always p-type, but the mobilities were typically lower than in the reference samples without metal islands. The results seem to imply that the limiting step in the transport is polaronic hopping in the interisland gap of the polymer/oligomer film.
Paloheimo, J., Stubb, H., & Grönberg, L. (1993). Field-effect transport in conjugated polymers/oligomers between metal islands. Synthetic Metals, 57(1), 4198-4203. https://doi.org/10.1016/0379-6779(93)90581-G