Mechanical Insights into Aggregation-Induced Delayed Fluorescence Materials with Anti-Kasha Behavior

Area of Science:

• Organic Electronics
• Materials Science
• Photophysics

Background:

• Aggregation-induced delayed fluorescence (AIDF) materials enhance electroluminescence efficiency and reduce roll-off in organic light-emitting diodes (OLEDs).
• A comprehensive understanding of the underlying mechanisms is crucial for the advancement and application of AIDF materials.

Purpose of the Study:

• To design and investigate novel AIDF materials incorporating benzoyl as an electron acceptor and phenoxazine/fluorene derivatives as electron donors.
• To elucidate the mechanism behind the enhanced fluorescence and delayed emission in aggregated states.
• To explore the potential of these materials in high-performance, non-doped OLEDs.

Main Methods:

• Synthesis of novel organic materials with specific electron donor-acceptor structures.
• Spectroscopic analysis (fluorescence, delayed fluorescence) to characterize photophysical properties in solution and aggregated states.
• Experimental and theoretical investigations (e.g., DFT calculations) to understand the excited-state dynamics and mechanism of AIDF.
• Fabrication and characterization of non-doped OLED devices using the synthesized materials.

Main Results:

• The synthesized AIDF materials exhibit significantly enhanced fluorescence and a pronounced delayed component upon aggregation.
• Experimental and theoretical studies confirm that AIDF arises from suppressed internal conversion and promoted intersystem crossing in the solid state.
• Theoretical calculations reveal an anti-Kasha behavior, where efficient solid-state delayed fluorescence originates from higher energy excited states (S₂) rather than the lowest (S₁).

Conclusions:

• The developed AIDF materials demonstrate excellent solid-state emission properties due to suppressed non-radiative decay pathways.
• The observed anti-Kasha behavior provides new mechanistic insights into efficient delayed fluorescence in organic materials.
• These AIDF materials offer high exciton utilization, leading to superb performance in non-doped OLEDs, paving the way for next-generation lighting and display technologies.