Universal Scaling of DC Conductivity with Dielectric Interfacial Polarization in Conjugated Polymers

Abstract

Understanding the intricate relationship between conductivity and polymer film microstructure is paramount to designing and developing high-performance conjugated-polymer-based electronic devices. Conjugated polymers are typically semicrystalline, and their films comprise both highly crystalline and amorphous regions with significant disparity between the conductivity of these regions. However, traditional conductivity measurements under steady-state conditions overlook the presence of the amorphous phase, offering an incomplete perspective on charge transport. Here, by employing isothermal dielectric measurements, we reveal that the amorphous phase plays a pivotal role and dominates the electrical conductivity at temperatures more pertinent to practical applications, while the crystalline fraction takes precedence at temperatures below room temperature. The conductivity mismatch between the amorphous and crystalline phases yields the Maxwell-Wagner-Sillars interfacial polarization (MWS-IP) effect. Here we demonstrated that the existence of MWS-IP ensues a universal scaling between the electrical conductivity, the relaxation time and the dielectric relaxation strength, for various conjugated polymers and their blends. Shedding light on the contribution of the amorphous phase in the conductivity of conjugated polymers can lead to the development of new polymers for applications in electronic devices with improved performance at operationally relevant temperatures.