Organic Phosphorescence Lasing Based on a Thermally Activated Delayed Fluorescence Emitter

Organic phosphorescence materials provide an opportunity
to use
triplets for lasing. However, population inversion based on phosphorescence
is hard to establish, owing to low luminescent quantum efficiency
and intensive optical loss. By comparison, thermally activated delayed
fluorescence emitters exhibit excellent optical gain with the aid
of the reverse intersystem crossing (RISC) process. In this work,
we designed a multifunctional gain material, not only serving as a
thermally activated delayed fluorescence (TADF) emitter with excellent
optical gain but also working as a phosphorescence source with high
utilization of triplets. The lone pair of electrons in oxygen substitutions
promotes a fast spin-flip and high delayed fluorescence quantum yield
(ΦDF = 55%), enabling TADF amplified spontaneous
emissions (ASE) of CH2Cl2 solution. Single-crystalline
nanowires of H-aggregates effectively lower triplet energy levels
with high phosphorescence quantum yield (ΦP = 27%),
demonstrating Fabry–Perot mode phosphorescence lasing at 630
nm.