Tuning Thermal Transport in Chain‐Oriented Conducting Polymers for Enhanced Thermoelectric Efficiency: A Computational Study

Thermoelectric polymers should be electron‐crystal and phonon‐glass to efficiently interconvert heat and electricity. Herein, by using molecular dynamics simulations, it is demonstrated that engineering phonon transport in conducting polymers by tailoring its degree of polymerization can effectively improve the energy conversion efficiency. This is based on the separated length scales that charge carriers and phonons travel along the polymer backbone. By tuning the chain length and the crystallinity of chain‐oriented poly(3,4‐ethylenedioxythiophene) fibers, a dramatic decrease of the axial thermal conductivity to 0.97 W m−1 K−1 has been observed in rationally designed polymer fibers with the crystallinity of 0.49 and the relative molecular weight of 5600. The dimensionless thermoelectric figure of merit at 298 K has been enhanced to 0.48, which is approximately one order of magnitude higher than that in crystalline polymers. Tuning degrees of polymerization and crystallinity of conducting polymers have been demonstrated, by using molecular dynamics simulations, as effective strategies to engineer thermal transport along the polymer backbone for achieving a high zT. The essential reason behind this is the separation of length scales for charge carriers and phonons travelling along the polymer backbone.