A high-contrast polymorphic difluoroboron luminogen with efficient RTP and TADF emissions

Area of Science:

• Materials Science
• Organic Chemistry
• Photophysics

Background:

• Development of efficient organic light-emitting materials is crucial for advanced display and lighting technologies.
• Tuning emission colors and properties through molecular design remains a key challenge.

Purpose of the Study:

• To report a novel N,S-chelated four-coordinated difluoroboron-based emitter.
• To investigate the photophysical properties and emission mechanisms of its different crystalline polymorphs.

Main Methods:

• Synthesis of a difluoroboron-based emitter.
• Crystallization to obtain distinct polymorphs.
• Photoluminescence spectroscopy to analyze emission characteristics.
• Single crystal X-ray diffraction for structural analysis.
• Theoretical calculations (e.g., DFT) to understand electronic properties and exciton dynamics.

Main Results:

• Three polymorphs (G, Y, R) exhibiting distinct emission colors were obtained.
• Green and Red crystals displayed thermally activated delayed fluorescence (TADF) at 530 nm and 630 nm, respectively, with a 100 nm spectral shift.
• Yellow crystals showed efficient room temperature phosphorescence (RTP) at 570 nm with a high solid-state quantum yield of 77%.
• Structural analysis revealed different molecular conformations and packing modes correlating with emission properties.

Conclusions:

• Molecular conformation and crystal packing significantly influence photophysical pathways, enabling distinct emission mechanisms (TADF vs. RTP).
• This study presents a versatile difluoroboron platform for achieving high-contrast, multi-color emission through controlled solid-state properties.