Improving the phosphorescence properties of doped materials through the heavy atom effect of the hosts

Abstract

Using a host–guest doping strategy to construct materials with excellent phosphorescence properties has important practical significance, and designing guests with strong luminescence properties to enhance the phosphorescence activity of doped systems is a commonly used method. However, enhancing phosphorescence performance through hosts is often overlooked. Herein, a doped system was constructed by selecting five compounds containing Group 15 elements (triphenylamine, triphenylphosphine, triphenylarsine, triphenylstibine, and triphenylbismuthine) as the hosts, and triphenylamine derivatives as the guests. The luminescence intensity of the doped materials is significantly enhanced by the external heavy atom effect of the hosts, and the phosphorescence quantum efficiency gradually increases from 5.2–5.6% in triphenylbismuthine-based doped materials to 22.8–26.0% in triphenylbismuth-based doped materials. Theoretical calculations show that heavy atoms significantly enhance the SOC of the hosts, thereby inducing an increase in the phosphorescence intensity of the doped materials. In addition, the single crystal structure and XRD analyses of the hosts further demonstrated that heavy atoms give the host a larger spatial volume and good deformability, allowing for better encapsulation of guest molecules. Finally, the doped materials can be effectively used for in vivo subcutaneous afterglow imaging in mice, demonstrating good imaging performance.