Open Access Publications from the University of California

## Understanding Charge Transport in Polymers for Thermoelectric Applications

• Author(s): Glaudell, Anne
The effort is two fold: to assess the viability of high-mobility semiconducting polymers for thermoelectric applications, and to gain a deeper understanding of the underlying transport mechanism that governs electronic, thermoelectric, and optical properties. First, we evaluate the thermoelectric properties of a consistent set of polythiophenes varying the dopant molecule and method. By comparing the electronic and thermoelectric properties studied here and the many existing OTE compounds in the literature, we demonstrate that a general relationship between electrical conductivity $\sigma$ and thermopower $\alpha$, $\alpha\propto\sigma^{-1/4}$, emerges over a large range of conductivity, polymers, and doping schemes. This empirical relationship can function as an approximate metric for assessing new materials as well as to guide improvements in thermoelectric performance in organics. Next, the temperature-dependent electronic and thermoelectric transport properties of the well-studied high-mobility polymer poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno-