Self-assembled dipoles of o-carborane on gate oxide tuning charge carriers in organic field effect transistors

Molecules of 12-o-carboranyldodecylphosphonic acid form a novel self-assembled monolayer (SAM) on alumina, which can effectively tune charge carriers in organic field effect transistors (OFETs) with the assembled dipoles of o-carborane at the semiconductor–dielectric interface. This SAM has not only realized p-channel OFETs of pentacene with both low threshold voltage and high field effect mobility (up to 5.2 cm² V⁻¹ s⁻¹), but also enabled ambipolar charge transport in the solution-processed thin films of a chlorinated tetraazapentacene, which is a typical n-type organic semiconductor. As measured with Kelvin probe force microscopy, the SAM of CBPA has a surface electrostatic potential of −0.40 ± 0.10 V versus gold, which is in agreement with the observed shift of threshold voltage in the OFETs.