Cation-Exchange Doping of n-Type Conjugated Polymers Entailing Glycolated Side Chains

Improving the doping efficiency of n-type conjugated polymers is a significant challenge in the field. However, the limited availability of dopants and methods for doping result in the electrical performance of n-type materials lagging behind that of p-type materials. In this study, we introduce a novel method for n-doping called cation-exchange doping, which enhances the doping levels of n-type polymers that incorporate glycolated side chains. We selected two n-type conjugated polymers to undergo cation-exchange doping using the direct dopant tetrakis(dimethylamino)ethylene (TDAE), along with three cations Li+, 1-ethyl-3-methylimidazolium, and tributylmethylphosphonium. All of these doped materials demonstrate improved thermoelectric performance and achieve deeper doping levels compared with doping with TDAE alone. The two polymers exhibit distinct electrical properties and thermoelectric performance related to cations, highlighting the importance of counterion engineering in optimizing the outcomes of cation-exchange doping. This can be explained by the cation-mediated density of states and electrical conductivity resulting from electrochemical doping. This research demonstrates a universal method for cation-exchange doping in n-type polymer semiconductors and offers new insights into understanding the interaction between polymers and counterions in organic electronics.