Abstract
π-Conjugated radical cations, open-shell species carrying a positive charge, serve as charge carriers in p-type organic semiconductors, underpinning the operation of various organic electronic devices. Although they are traditionally perceived as highly reactive and challenging to isolate under ambient conditions, recent advances in electronic and steric stabilization have enabled the isolation and full characterization of a number of robust π-conjugated radical cations. This review provides a comprehensive overview of fully characterized π-conjugated radical cations, with particular emphasis on species identified via single-crystal X-ray crystallography within the last two decades. We highlight structural features and stabilization strategies that enable ambient stability, and explore structure-property relationships critical to their application in organic electronic materials, indicating the potential to enhance material stability and improve device performance. Based on this analysis, we assess the current state of the field and outline promising future directions.