Achieving High‐Performance Organic Long Persistent Luminescence Materials via Manipulation of Radical Cation Stability

Abstract Organic long persistent luminescence (OLPL) materials, with their hour‐long afterglow, hold great promise across numerous applications, yet their performance lags behind that of inorganic counterparts. A deeper understanding of the underlying photophysical mechanisms, particularly the effective control of radical intermediates, is essential for developing high‐performance OLPL materials; while systematic studies on the intrinsic stability of radical intermediates and their impact on OLPL performance remain scarce. Here biphenyl groups is introduced into a luminophore‐matrix‐donor three‐component OLPL system. By varying substituents at the ortho‐position of the biphenyl groups, the stability of radical cations is systematically modulated, and their influence on OLPL properties is investigated. Combined experimental results and theoretical calculations reveal that increased flexibility of the biphenyl bond and adjustable conformations lead to higher stability of radical cations, thereby significantly enhancing OLPL performance. Based on this understanding, a luminophore with two biphenyl groups is designed to successfully achieve remarkable afterglow brightness close to inorganic Sr 2 Al 14 O 25 /Eu 2+ , Dy 3+ materials. Furthermore, these OLPL materials exhibit time‐encoded afterglow properties and promising applications in advanced anti‐counterfeiting, as well as background‐independent bioimaging functions. This work not only provides a novel strategy for constructing high‐performance OLPL materials but also lays a foundation for their widespread application in various fields.