Anti-Stokes Luminescence in Multi-Resonance-Type Thermally-Activated Delayed Fluorescence Molecules

Area of Science:

• Organic molecular systems
• Photophysics
• Energy harvesting

Background:

• Photon-upconversion in organic systems offers potential for energy harvesting by generating higher-energy excitons.
• Photon-upconversion utilizing ambient heat is particularly promising for light-driving cooling systems.
• Few organic molecular systems currently exist for efficient photon-upconversion.

Purpose of the Study:

• To report anti-Stokes photoluminescence (ASPL) from hot-band absorption in multi-resonance-type thermally-activated delayed fluorescence (MR-TADF) molecules.
• To investigate the characteristics of ASPL in novel MR-TADF materials.
• To explore the potential of these materials for applications like light-driving cooling.

Main Methods:

• Synthesis and characterization of a series of MR-TADF molecules.
• Measurement of anti-Stokes photoluminescence (ASPL) and photoluminescence quantum yield (PLQY).
• Analysis of the correlation between activation energy for ASPL and the thermally-activated delayed fluorescence (TADF) process.

Main Results:

• MR-TADF molecules demonstrated significant ASPL with an anti-Stokes shift of approximately 0.1 eV.
• High photoluminescence quantum yields were observed in the solution state.
• The observed anti-Stokes shift correlated with the 1-0 vibrational transition from the ground to the excited singlet state.

Conclusions:

• MR-TADF molecules represent a novel class of materials exhibiting ASPL.
• These findings suggest MR-TADF molecules are suitable for applications requiring energy upconversion, including light-driving cooling systems.
• The study highlights the potential of MR-TADF for advanced photonic and energy applications.