Hydrogen Bonding as a Tool to Control Chain Structure of PEDOT: Electrochemical Synthesis in the Presence of Different Electrolytes

The current knowledge about the presence of cation radicals in organic semiconductors is connected with oxidized constitutional units and their interaction with counterions. In this work, we have shown that the formation of cation radicals in poly(3,4-ethylenedioxythiophene) is induced by intermolecular electrostatic interactions, particularly by hydrogen-bond formation between formic acid and polymer. Raman, XPS, UV-vis, and EPR spectroscopies were used to prove that by using the simplest carboxylic acid, which can form hydrogen bonding, it is possible to form localized cation radicals. Moreover, it was shown that by replacing formic acid with o-phosphoric acid, it is possible to obtain delocalized cation radicals. The gained new understanding how to tune the formation and nature of cation radicals in organic semiconductors can be used in the design of organic electronics.