Reducing the contact resistance in organic thin-film transistors by introducing a PEDOT:PSS hole-injection layer

We coated gold electrodes with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) in order to reduce the contact resistance in pentacene organic field-effect transistors (OFETs). The crystallinity of the pentacene layers on the gold electrodes was found to increase upon coating the substrates with PEDOT:PSS, whereas the hole-injection barrier between the organic semiconductor and the metal electrode decreased from 0.85 to 0.14 eV. The increased crystallinity and reduced hole-injection barrier resulted in a significant reduction of the contact resistance in the pentacene OFETs, thus leading to an improvement of the field-effect mobility of the devices (from 0.031 to 0.218 cm2/Vs).