Open-shell organic semiconductors: an emerging class of materials with novel properties

Organic materials with unpaired electrons along with the discovery of their unique properties have fascinated scientists for over a century. The development of open-shell molecules has recently been rekindled as the result of improved synthetic strategies and spectroscopic techniques. In this focus review, we provide an overview of open-shell polymers and small-molecules organic semiconductors. We review strategies toward molecular magnets or spin-polarized magnetic organic semiconductors that encompasses incorporation of stable radical groups directly into the backbone of organic semiconductors or preparing highly conjugated ladder-type molecules based on open-shell Kekule-type structures to enable efficient spin delocalization along the conjugation length. These novel materials have the potential to make significant societal impacts in the areas of information, energy and human health technologies.