Non-conjugated Radical Polymers as Transparent Conductors in Organic Electronic Devices

Radical polymers are an emerging class of organic electronic materials that are composed of a non-conjugated macromolecular backbone and with stable open-shell moieties present on their pendant groups. However, their utilization in solid-state organic electronic devices has been limited due to the commonly-held belief that this lack of conjugation impedes their ability to conduct charge effectively in the solid state. Through a combination of experiment and computation we alter this archetype, and we demonstrate that pristine (i.e., not doped) radical polymers are able to achieve relatively high electrical conductivity values (i.e., > 20 S m^-1) near room temperature through appropriate polymer processing. This places our radical polymer electrical conductivity on par with many common commercial grades of doped conjugated polymers. Moreover, the non-conjugated macromolecular backbones of radical polymers allow for high optical transparency values to be achieved across the visible spectrum. As such, we demonstrate how these macromolecules are successfully incorporated as transparent conducting thin films in organic photovoltaic cells, perovskite solar cells, and electrochromic modules in order to improve the performance and lifetime of these next-generation optoelectronic devices.