Controlling contact resistance in top-gate polythiophene-based field-effect transistors by molecular engineering

Marta Tello...et al.We report on an effective control of source–drain contact resistance by insertion of a self-assembled monolayer at the metal/semiconductor interface in top-gate staggered polymer field-effect transistors fabricated with poly(2,5-bis(3-tetradecylthiophene-2-yl)thieno[3,2- b]thiophene) (pBTTT). The device performance can be dramatically improved by introducing a fluorinated alkyl-thiol, 1H, 1H, 2H, 2H-perflourodecanethiol (PFDT) on the gold source–drain contacts. The PFDT-induced interface dipole and hydrophobic surface enables both a favourable shift of work function lowering the hole injection barrier via dipole alignment and a large crystal growth of pBTTT film with a unique lamellar morphology near to the contact. The optimized device with PFDT-modified gold contact plus OTS-treated substrate exhibits a high field-effect mobility above 0.4 cm2 V−1 s−1 and low contact resistance of 0.45 M at the gate voltage of −60 V.This work was supported by the Engineering and Physical Sciences Research Council (EPSRC) and Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2010- 0023180).Peer reviewe