Oxygen-Tolerant Near-Infrared Organic Long-Persistent Luminescent Copolymers

Organic materials exhibiting long-lasting emission in the near infrared are expected to have applications in bio-imaging and other areas. Although room temperature phosphorescence and thermally activated delayed fluorescence display long-lived emission of approximately one minute, organic long-persistent luminescence (OLPL) systems with a similar emission mechanism to inorganic persistent emitters can emit for several hours at room temperature. In particular OLPL with a hole-diffusion mechanism can function even in the presence of oxygen. However, ionic materials lack long-term stability in neutral organic host owing to aggregation and phase separation. In this study, we synthesized polymers with stable near-infrared persistent luminescence at room temperature via the copolymerization of electron donors and acceptors. The copolymers exhibit long-persistent luminescence (LPL) at temperatures below the glass transition temperature and can be excited by approximately the entire range of visible light. LPL properties and spectra can be controlled by the dopant. Polymers exhibiting near-infrared (NIR) long-persistent luminescence (LPL) consisting of a carbazole donor and a small amount of ionic acceptor have been realized. The polymer exhibits LPL without dopants and has higher phase stability than small molecule mixtures. The LPL can be observed even in air and at high temperatures below the glass transition temperature.**+image