A General Approach to Activate Second-Scale Room Temperature Photoluminescence in Organic Small Molecules

Area of Science:

• Materials Science
• Organic Chemistry
• Photophysics

Background:

• Organic small molecules with room-temperature phosphorescence are crucial for advanced applications like sensing and bioimaging.
• Achieving long phosphorescence lifetimes (second-scale) is challenging due to requirements for efficient intersystem crossing and suppressed nonradiative decay pathways.

Purpose of the Study:

• To develop a simple, scalable method for activating long-lived phosphorescence in diverse organic molecules.
• To overcome limitations in current design strategies for long-lifetime phosphorescent materials.

Main Methods:

• Suspending organic chromophores in rigid polymer hosts.
• Annealing the composite materials above the polymer's glass transition temperature to form submicron aggregates.
• Characterizing the photophysical properties of the resulting materials.

Main Results:

• Successfully induced second-scale phosphorescence in various organic molecules using the described method.
• Formation of submicron aggregates effectively suppressed intramolecular motion and nonradiative recombination.
• Minimized triplet-triplet annihilation, a common quenching pathway in larger aggregates.
• Observed evidence of excimer-mediated intersystem crossing enhancing triplet generation in some aggregated systems.

Conclusions:

• The developed approach provides a straightforward and scalable route to long-lived organic phosphors.
• This method bypasses traditional molecular design constraints, accelerating the discovery and development of novel phosphorescent materials.
• The findings pave the way for wider implementation of organic phosphors in sensing, anticounterfeiting, and bioimaging.