Comparison of doping mechanism and efficacy between polymers doped by novel Lewis acid dopant BCF and F4-TCNQ

Doping of polymers has been a longstanding area of research in an effort to enhance their electrical properties, yet typically used π-electron acceptors such as F4-TCNQ are limited by solubility and insufficiently deep electron affinity. Alternative dopants based on Lewis acids have attracted attention recently due to promising results on a range of polymers, but the doping mechanism is not yet fully understood. We have studied the Lewis acid dopant BCF with three polymers, using a range of optical techniques and comparing with F4-TCNQ doped samples. Absorption spectroscopy has revealed polaron formation as well as confirming a protonation-based doping mechanism. FTIR spectroscopy has shown to be particularly useful in such protonation-based doping by revealing evidence of the specific protonation site and its effect on the polymer. Finally, pump-probe measurements help to uncover whether different doping mechanisms affect ultrafast charge dynamics and polaron excitation in doped polymers. By pumping and probing the polaron directly, we are able to monitor the excitation and evolution of the polaron within 50 ps of excitation for both dopant types. These results help to further the understanding of a novel type of dopant and test their suitability for use in organic electronics.