Strategic Insights into Semiconducting Polymer Thermoelectrics by Leveraging Molecular Structures and Chemical Doping

Thermoelectric (TE) materials can realize the direct transformation between heat and electricity, thereby facilitating the recycling of waste heat. Semiconducting π-conjugated polymers (π-CPs) have been largely explored as organic TE materials thanks to the facile molecular tunability of their electronic properties, their room-temperature solution-processability, their intrinsic low thermal conductivity, and their outstanding mechanical flexibility. In this Focus Review, we describe two key strategieschemical doping and structural tailoringin polymeric TEs for strengthening TE power factors of π-CPs. First, the doping mechanisms are unraveled by a sequential process of charge transfer and free carrier release, followed by the introduction of various doping methods for enhancing the chemical doping. Second, the design principles for polymeric structures including the π-backbone and side-chain engineering are presented. Third, supplementary strategies such as polymer chain alignment and construction of polymer blends are identified. Finally, the existing prime obstacles to future development are discussed and an outlook on feasible solutions to resolving them is provided.