Doped State Engineering in Conjugated Polymers

Doping has long been a central strategy for modulating the performance of organic semiconductors, yet traditional views focusing mainly on carrier density and conductivity are no longer sufficient to account for the complexity of heavily doped systems. Conjugated polymers (CPs), now widely employed in organic thermoelectrics (OTEs) and organic electrochemical transistors (OECTs), exhibit rich electronic and structural transformations upon chemical and electrochemical doping. These doped states critically govern device performance but remain only partially understood. In this Perspective, we provide a detailed explanation of the concept, doped state engineering, in CPs, which emphasizes deliberate control over the charge-transfer processes, structural reorganization, and counterion-CP interactions that accompany doping. We highlight how this framework guides advances in molecular design, doping strategies, and processing methods, and we discuss its potential to accelerate the development of high-performance organic electronic materials and devices.