Tunable Triplet-Mediated Multicolor Lasing from Nondoped Organic TADF Microcrystals

Area of Science:

• Materials Science
• Organic Electronics
• Photonics

Background:

• Thermally Activated Delayed Fluorescent (TADF) emitters are crucial for organic light-emitting diodes and laser diodes due to high exciton utilization and reduced triplet losses.
• Direct observation of lasing emission from nondoped TADF microcrystals remains an underexplored area.

Purpose of the Study:

• To demonstrate multicolor lasing from nondoped TADF microcrystals.
• To investigate the role of singlet regeneration in enabling thermally activated lasing.
• To explore the structure-property relationships for TADF gain materials.

Main Methods:

• Fabrication of three-color (green, yellow, red) nondoped TADF microcrystals with controlled geometries.
• Temperature-dependent dynamic analyses to study exciton dynamics and population inversion.
• Systematic investigation of the relationship between molecular structure and triplet-harvesting capability in single-crystalline TADF emitters.

Main Results:

• Successful demonstration of three-color microlasers from nondoped TADF microcrystals.
• Evidence that regenerated singlets from reverse intersystem crossing at room temperature facilitate population inversion.
• Reduced optical losses from triplet absorption/annihilation due to efficient singlet regeneration, leading to thermally activated lasing.
• Established correlations between molecular structure and triplet-harvesting efficiency in TADF materials.

Conclusions:

• Nondoped TADF microcrystals can achieve efficient thermally activated lasing.
• Singlet regeneration is a key mechanism for achieving population inversion and optical gain in TADF lasers.
• The findings provide a rational design strategy for pure TADF gain materials and guidance for high-performance organic solid-state lasers.