Controlling charge injection by self-assembled monolayers in bottom-gate and top-gate organic field-effect transistors

We investigate the modulation of the charge injection in organic field-effect transistors with self-assembled monolayers (SAMs) using both a bottom-gate and a top-gate geometry. The current modulation by using SAMs is more pronounced in the top-gate geometry due to the better defined upper surface of the bottom source and drain electrodes. By modifying Ag electrodes with a perfluorinated monolayer an injection barrier as high as 1.6 eV into poly(9,9-dioctylfluorene) can be surmounted, enabling the measurement of the saturated field-effect mobility of 6 × 10−5 cm2 V−1 s−1.