Construction of full-color room-temperature afterglow materials using dicyanomethylene-4H-pyrans based on an alkene conjugated bridge as the third component

Abstract

Although the alkene bond as a connecting unit is widely used to construct D–π–A luminescent molecules, room-temperature afterglow (RTA) systems containing this kind of molecule are extremely rare. In this work, a series of multi-component doped RTA materials were prepared using polyvinylpyrrolidone as the host, 2-(4-chlorophenyl)-1-(4-(diphenylamino)phenyl)ethan-1-one as the guest, dicyanomethylene-4H-pyrans with an alkene bond bridge as the third component, and RhB and Cy5 as the fourth component. Two-component materials emit bright cyan room-temperature phosphorescence; three-component materials emit yellow-green, orange, and red afterglows, respectively; and four-component doped materials further exhibit afterglow at 740 nm in the near-infrared region. The RTA emissions of three-component and four-component materials have been shown to be delayed fluorescence, which is caused by the phosphorescence of the second component transitioning from the triplet state to the singlet state and thus the domino-type Förster resonance energy transfer of S₁–S₁ between different luminescent molecules. The results reveal that using dicyanomethylene-4H-pyrans as the third component can lead to full-color afterglow emissions. This work gives a possible development direction for the construction of RTA materials using D–π–A fluorescent molecules.