Improvement of the poly-3-hexylthiophene transistor performance using small molecule contact functionalization

We demonstrate an approach to improve poly-3-hexylthiophene field effect transistors by modifying the gold contacts with monolayer thick pentacenequinone (PQ) or naphthalene (NL). The effective contact resistance is reduced by a factor of two and sixteen for interlayers of PQ and NL, respectively. The observation is attributed to different injection barriers at the metal-organic interface caused by the functionalization and to an additional tunneling barrier enhancing the on/off ratios. This barrier yields to activation energies of 37 meV (NL) and 104 meV (PQ) below 190 K, which are smaller than without functionalization, 117 meV.