Utilizing morpholine for purely organic room temperature phosphors

In this article, morpholine, a non-conjugated heterocycle, is embedded into π system to construct single-component organic room temperature phosphorescence (RTP) luminogens. The effect of morpholine on intermolecular interaction, crystal packing modes, and RTP performance is investigated systematically. The experimental and theoretical calculation results illustrate the versatility of morpholine in promoting the n-π* transition and intensifying the intermolecular interactions, which not only enhances the generation of triplet excitons, but also suppresses the nonradiative decay of triplet excitons. Impressively, TMPh containing three morpholine units shows an ultralong lifetime of 1.03 s and a visible afterglow up to 10 s. The unique dual delayed emission and long afterglow property allow potential application of morpholine derivatives in data encryption, and the time-dependent color change of afterglow emission is realized after removing the excitation source, providing a high-level data security. This article provides a new perspective for the design of purely organic RTP system without utilization of metal, or even any heavy atoms.