Polymer Thermoelectrics: Opportunities And Challenges

The inherent low thermal conductivity of polymeric materials along with their capability for nonconventional processability, light weight, and flexibility makes them potential candidates for low-power thermoelectrical applications. However, it requires the improvement of both Seebeck coefficient and electrical conductivity simultaneously. This Perspective addresses some of the concepts in the literature to achieve this by considering the intricacies and interconnectivities of different thermoelectric parameters. Especially, the applicability of the Wiedemann-Franz rule as well as DOS engineering by blending two semiconductors, valid in inorganics, is reviewed for polymeric systems. One of the biggest advantages of polymeric semiconductors is that their thermal conductivity is mostly phononic (lattice thermal conductivity) and remains low with increasing charge carrier concentrations, as needed for TE applications. The momentum in polymer synthetic strategies has to be coupled with the studies on doping efficiency and doping mechanisms to overcome the bottlenecks in polymeric thermoelectrics. We recommend for a paradigm shift toward low dopant ratios with high doping efficiencies and for DOS engineering to separate the Fermi level and transport level to achieve high absolute Seebeck coefficients in polymers.