Quantifying the Energetics of Ion Injection into Mixed Ionic/Electronic Conductors*

Organic electrochemical transistors (OECTs) rely on the electrochemical doping of an organic semiconductor to modulate the conductivity of the channel. This doping process requires electronic charge injection into the polymer from the metal contacts, as well as charge compensation by an ion provided by the electrolyte. Numerous factors have been shown to affect the ease and speed of ion injection including polymer side chain, polymer crystallinity, ion type, pH, solvent, etc. Here we use kinetics derived from temperature dependent spectroelectrochemistry measurements to extract the activation energy of ion injection into a polymer semiconductor. We compare the energetics of injection in a variety of different polymers, salts, and solvents to quantify the contribution of each of the factors controlling ion injection. A deeper understanding of the relative importance of each factor will help with future design of mixed ionic/electronic conductors.