Pressure-shortened delayed fluorescence lifetime of solid-state thermally activated delayed fluorescent 4CzIPN: the...

Area of Science:

• Materials Science
• Organic Chemistry
• Photophysics

Background:

• Mechanochromic luminescence in thermally activated delayed fluorescence (TADF) molecules is a developing field for multifunctional materials.
• Systematic design and control over TADF molecule versatility remain challenging.

Purpose of the Study:

• To investigate the effect of pressure on the photophysical properties of 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene crystals.
• To explore the relationship between molecular conformation, pressure, and luminescence characteristics.
• To develop strategies for controlling delayed fluorescence lifetime in TADF materials.

Main Methods:

• Crystallization of 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene.
• Application of hydrostatic pressure to the crystalline samples.
• Spectroscopic analysis (luminescence) under varying pressure conditions.
• Computational analysis of molecular conformation and electronic structure (HOMO/LUMO overlap).

Main Results:

• A continuous shortening of delayed fluorescence lifetime with increasing pressure was observed.
• Pressure-induced emission enhancement and multicolor emission (green to red) at high pressures were detected.
• Planarization of molecular conformation and increased HOMO/LUMO overlap were correlated with lifetime shortening.
• Formation of new intermolecular interactions contributed to pressure-induced emission changes.

Conclusions:

• The study demonstrates a novel method to shorten the delayed fluorescence lifetime of TADF molecules through mechanical pressure.
• Pressure-induced conformational changes and electronic interactions offer a route to tune luminescence properties.
• Findings provide valuable insights for designing efficient TADF-based organic light-emitting diodes (OLEDs) with reduced efficiency roll-off.