Stepwise Stiffening Chromophore Strategy Realizes a Series of Ultralong Blue Room-Temperature Phosphorescent Materials.

Ultralong room-temperature phosphorescent (URTP) materials have attracted wide attention in anti-counterfeiting, optoelectronic display, and bio-imaging due to their special optical properties. However, room-temperature blue phosphorescent materials are very scarce during applications because of the need to simultaneously populate and stabilize high-energy excited states. In this work, a stepwise stiffening chromophore strategy is proposed to suppress non-radiative jump by continuously reducing the internal spin of the chromophore, and successfully developing a series of blue phosphorescent materials. Phosphorescence lifetimes of more than 3 s are achieved, with the longest lifetime reaching 5.44 s and lasting more than 70 s in the naked eye. As far as is know, this is the best result that has been reported. By adjusting the chromophore conjugation, multicolor phosphorescences from cyan to green have been realized. In addition, these chromophores exhibit the same excellent optical properties in urea and polyvinyl alcohmance (PVA). Finally, these materials are successfully applied to luminescent displays.