Visible-Light-Excitable Sky-Blue TADF-Type Organic Afterglow

Blue afterglow emitters contribute one of the three primary afterglow colors and can be used to generate other afterglow colors via energy transfer. Statistics shows that although there are examples of blue afterglow emitters with high afterglow efficiency and long afterglow lifetime, such emitters require ultraviolet-B excitation to switch on their afterglow properties. Here, we fabricate visible-light-excitable sky-blue thermally activated delayed fluorescent (TADF)-type organic afterglow materials via a dopant-matrix strategy, where TADF represents thermally activated delayed fluorescence. Luminescent difluoroboron beta-diketonate (BF(2)bdk) dopants were synthesized by our cascade reaction. Upon doping into rigid organic matrices, the resultant BF2bdk-matrix materials exhibit sky-blue ambient afterglow, which can be excited by ultraviolet-A, 405 nm purple, or 420 nm blue light. The materials possess afterglow lifetimes of several hundred milliseconds and an afterglow efficiency of up to 72.9%. Because of the singlet nature, the sky-blue TADF afterglow emitters can serve as efficient donors for energy transfer to produce afterglow materials with other colors.