Quantifying the Effects of Inhomogeneity and Doping on the Electronic Contribution to Thermal Conductivity in Semiconducting Polymers

Abstract Quantifying contributions to thermal conductivity from electrons and atomic vibrations in doped semiconducting polymers is important for heat transfer. Several studies report Lorenz numbers ( L ) that are larger than the Sommerfeld limit ( L 0 ), counterintuitively implying that charge carriers in semiconducting polymers carry more heat than those in metals. Alternatively, this phenomenon can be explained by recognizing that semiconducting polymers often contain insulating and conducting domains. Microstructures can lead to misinterpretation of the effective Lorenz number ( L eff ) observed macroscopically. Herein, effective medium theory (EMT) shows that inhomogeneity can result in macroscopic measurements where L eff ≠ L 0 , even when each component exhibits L 0 at the microscopic level. The authors then extend the semi‐localized transport (SLoT) model to explain the origins of the large L eff values, validating with the prototypical poly(3,4‐ethylenedioxythiophene) system. This electro‐thermal extension of the SLoT model (ET‐SLoT) improves the ability to engineer the electronic contribution to thermal conductivity of semiconducting polymers.