Functionalising the gate dielectric of organic field-effect transistors with self-assembled monolayers: effect of molecular electronic structure on device performance

The performance of organic field-effect transistors (OFETs) is determined by the semiconductor/dielectric interface. In this work, we report the functionalization of an OFET dielectric with a novel electroactive self-assembled monolayer (SAM) based on a polychlorotriphenylmethyl (PTM) radical derivative and its alpha H non electroactive counterpart. The influence of these SAMs on p- and n-type OFETs is explored. We observe that differences in the accessibility of the electronic energy levels of the PTM derivatives has a significant impact on the device performance. Both SAMs are hydrophobic, which lead to smoother pentacene films. In addition, the radical electroactive SAMs act as p-dopant in pentacene transistors and as charge trap in fullerene C-60 OFETs. This approach can be useful for fabricating organic electronic devices with tailored properties.