Poly(3-hexylthiophene) revisited - Influence of film deposition on the electrochemical behaviour and energy levels

In this article we highlight the importance of film deposition conditions on the electrochemical behaviour of the work horse of the organic electronics community, namely poly(3-hexylthiophene) (P3HT). While a huge number of publications have dealt with the influence of morphology on optical, electronic and opto-electronic properties, the effect on the electrochemical response has been less addressed. Electrochemistry is often only used as convenient tool in this community to determine the energy levels or more specifically the HOMO level of P3HT. This is performed by measuring oxidation onset potentials and introducing correction factors which relate the electrochemical with the Fermi scale. Here we want to stress out that this procedure should be performed with great care in order to get meaningful data. We demonstrate that film deposition conditions can strongly alter the oxidation behaviour of the polymers which makes the determination of the oxidation onset potentials and energy levels very difficult. We compare state-of-the-art of electropolymerisation and solution deposition of chemically synthesized polymers of defined regioregularity with our own expertise on deposition and controlling crystallisation in films. (C) 2018 Elsevier Ltd. All rights reserved.