Progress in Conducting Polymers: Synthesis, Stability, and Ionic/Electronic Transport Properties

Conducting polymers (CPs) have garnered immense interest since the discovery of polyacetylene, bridging the gap between traditional plastics and metals by combining the processability and mechanical flexibility of organic polymers with the electrical conductivity of semiconductors or metals. The evolution of CPs, especially the progress in solution-processable CPs, has facilitated the development of cost-effective, large-area, and flexible electronic and optoelectronic devices. This review provides a comprehensive overview of the fundamental and applied aspects of CPs, encompassing their synthesis, doping, stability, fundamental conduction mechanisms, and some applications. It discusses the critical role of doping, with an exploration of p-type (oxidative) and n-type (reductive) doping processes, dopant types, and innovative strategies like photo-induced doping. Furthermore, the review highlights the environmental and operational stability of CPs and introduces strategies to enhance their durability. Finally, the intricate conduction mechanisms in CPs, involving charge carriers such as polarons and bipolarons, the movement of counter-ions, and their transport through intrachain and interchain pathways, are discussed, elucidating the factors that influence conductivity and applications. This review aims to provide a thorough understanding of the current state and future perspectives in the development of CPs.