Effects of the polymeric dielectric on OTFT performances

Three polymers have been tested as gate dielectric in pentacene-OTFTs: polyimide, polystyrene and commercial photoresist. The electrical characterizations revealed a gate leakage current and the effects of source and drain contact barriers both responsible of the non-crossing of the curves into the I S -V DS diagram origin. An electrical model have been proposed taking into account the gate leakage current and the V DS shift by inserting two gate-diodes and a voltage source. The model has allowed to estimate the correct values of the channel mobility and the device voltage threshold.