Magnetic Resonance Studies of Highly Doped Polymeric Semiconductors

Doped organic semiconductors have proved attractive for future device applications such as thermoelectrics, bioelectronics and spintronics. At low doping levels, coulombic trapping of intercalated counter ions is believed to limit charge transport while at high doping levels conductivity is limited by disorder in the material.¹ However, a more detailed understanding of the couplings between the charge/spin carrying polarons of these materials and their environment remains sought after. Work has been done to understand such interactions in undoped materials by means of field induced Electron Spin Resonance (ESR) and has yielded valuable insight into the intimate couplings between charge, spin and structural dynamics.² Here, we extend that work to the study of systems systematically doped in-situ by means of an electrochemical transistor architecture and investigate the effects of interactions between polarons and with the counterions as function of temperature and varying doping levels. We complement the ESR measurements with Nuclear Magnetic Resonance (NMR) characterisation which has been shown to be a powerful technique for characterising ion dynamics in polymeric semiconductors.³ We therefore use NMR to understand ionic motion and interactions in these systems and explore how they could impact the electronic properties of the material.<br/><br/><i>References </i><br/>1. I. Jacobs et al., <i>Journal of the American Chemical Society</i>, doi:10.1021/jacs.1c10651.<br/>2. S. Schott et al., <i>Nature Physics</i>, doi:10.1038/s41567-019-0538-0.<br/>3. D. Lyu <i>et al.</i>, <i>Nature Materials, </i>doi: 10.1038/s41563-023-01524-1.