“Structural disorder and electrical conduction in polymers”
Organic semiconductors are candidates for use in next-generation thin film electronics for applications ranging from displays to energy conversion devices, such as solar cells and thermoelectrics. Controlling the electrical doping of semiconducting polymers presents an important challenge towards achieving these goals. Intrinsic semiconducting polymers are low dielectric constant materials, whereas heavily doped materials are effectively organic salts. Understanding this transition between the two states is complex because of the disordered microstructure in polymers. We will discuss our work to understand how doping occurs in semiconducting polymers and its implications for thermoelectric energy conversion. Examination of semicrystalline polymers across length scales using synchrotron-based X-ray scattering methods reveals that the ordering of domains plays the largest factor in electrical transport. In-situ experiments reveal how doping occurs within the amorphous and ordered domains in semiconducting polymers. Recent models to explain the connection between electrical conductivity and thermopower in disordered systems will be discussed. The implications of this behavior for improvement of the thermoelectric properties of polymers will be discussed.