Strategies for High-Performance Solid-State Triplet-Triplet-Annihilation-Based Photon Upconversion.

Area of Science:

• Materials Science
• Photochemistry
• Optoelectronics

Background:

• Photon upconversion via triplet-triplet annihilation (TTA) shows high efficiency in solutions and polymer matrices.
• Solid-state TTA performance is significantly lower, hindering integration into devices.
• Understanding solid-state loss mechanisms is crucial for improving TTA efficiency.

Purpose of the Study:

• Investigate solid-state loss mechanisms in green-to-blue TTA upconversion.
• Develop strategies to mitigate identified loss pathways.
• Demonstrate a high-efficiency, dry-processed solid-state TTA system.

Main Methods:

• Identified three key solid-state loss mechanisms: energy back transfer, sensitizer aggregation, and triplet-charge annihilation.
• Developed strategies to reduce energy back transfer and sensitizer aggregation.
• Fabricated a completely dry-processed solid-state TTA device.

Main Results:

• Achieved a solid-state TTA upconversion efficiency of approximately 2.5% at 238 mW cm⁻² excitation intensity.
• Demonstrated a dry-processed system comparable to solution-processed systems.
• Successfully mitigated energy back transfer and sensitizer aggregation.

Conclusions:

• The developed strategies offer a pathway to enhance solid-state TTA performance.
• This work enables solvent-damage-sensitive applications requiring efficient solid-state upconversion.
• The findings are generalizable to other TTA upconversion systems.