Polarons in DPP Polymers – How Glycol Side Chains and Elongated Conjugated Backbone Influence the Formation and Transport

ABSTRACT Understanding polaron formation in conjugated polymers is critical for advancing solid‐state organic electronics. Here, we investigate diketopyrrolopyrrole (DPP)‐based polymers with tailored side chains to elucidate the impact of glycolation on charge transport and polaron formation. We demonstrate that glycol side chains enhance p‐type character and charge carrier density, while backbone elongation improves planarity and mobility. Electrochemical doping using a semicrystalline solid‐state ionic liquid (SSIL) can increase conductivity by four orders of magnitude. In situ field‐dependent Raman spectroscopy probes polaron formation, showing increased π‐electron redistribution in glycolated DPP. Polaron formation of the DPPT‐T conjugated backbone shows a more localised polaron with structural changes to the thiophene donor unit. Backbone elongation results in greater polaron delocalisation with lower reorganisation energy. Finally, ion‐gel gated organic synaptic transistors (IGOSTs) demonstrate significant performance gains for glycolated polymers with gDPPT‐T and gDPPT‐TVT exhibiting strong excitatory post‐synaptic currents. The more facile polaron formation pathway for gDPPT‐TVT offers a significant advantage in the dynamics of ion migration and retention. This work provides molecular‐level insight into the incorporation of glycol side chains to high‐performance conjugated polymers for solid‐state applications.