Self-assembled monolayers mediated charge injection for high performance bottom-contact poly(3,3′′′-didodecylquaterthiophene) thin-film transistors

Device performance of bottom-contact poly(3,3′′′-didodecylquaterthiophene) (PQT-12) thin-film transistors (TFTs) was significantly improved via surface-modification of Au source-drain (S-D) electrodes with 1-decanethiol and 1H,1H,2H,2H-perfluorodecanethiol self-assembled monolayers (SAMs). By improving the PQT-12 morphology and modulating the Schottky barrier at electrode/PQT-12 contacts, the thiol SAMs chemisorbed onto Au surfaces can improve the charge carrier injection at electrode/PQT-12 contacts and result in dramatic enhancements in device mobilities. Device mobilities up to 0.09 and 0.19 cm² V^-1 s^-1 were obtained in high performance bottom-contact PQT-12 TFTs with 1-decanethiol and 1H,1H,2H,2H-perfluorodecanethiol SAMs surface-modified Au S-D electrodes, compared with 0.015 cm² V^-1 s^-1 in PQT-12 TFTs with bare Au electrodes. This work may provide a simple path to the fabrication of high performance, low-cost, and solution-processable bottom-contact OTFTs using fine lithography technology.