Direct white-light emitting room-temperature-phosphorescence thin films with tunable two-color polarized emission through orientational hydrogen-bonding layer-by-layer assembly

Molecule-based room-temperature-phosphorescence (RTP) materials have received much attention recently. For future optical displays and image applications, the development of ordered RTP thin films is highly important, but the fabrication of such RTP films is much more difficult than that of RTP crystals, and examples are still quite limited. In this work, we confirm that the direct layer-by-layer assembly of a small RTP molecule (DBT) and polyvinyl alcohol (PVA) can be achieved based on hydrogen bonding interaction. The films not only exhibit tunable RTP light-emitting colors upon UV photostimulation at 254 nm and 365 nm, but also exhibit direct white-light-emitting polarized phosphorescence due to the ordered micro/nanostructure of the RTP films. Moreover, the highly enhanced RTP quantum yields and lifetimes upon increasing assembly cycles can be assigned to the strong Fermi coupling between DBT and PVA in the films. It is anticipated that the incorporation of other RTP molecules in flexible polymers based on the ordered LBL assembly can be utilized to fabricate a range of new smart RTP film materials.