Fast and efficient room-temperature phosphorescence from metal-free organic molecular liquids

Area of Science:

• Materials Science
• Organic Chemistry
• Photophysics

Background:

• Condensed matter exists in various states, with liquids offering unique flexibility for functional soft materials.
• Achieving efficient room-temperature phosphorescence (RTP) in metal-free organic molecular liquids is challenging due to their inherent properties.
• RTP is a valuable photophysical process with applications in sensing, imaging, and optoelectronics.

Purpose of the Study:

• To design and synthesize novel metal-free organic molecules capable of efficient room-temperature phosphorescence in a liquid state.
• To investigate the photophysical properties, particularly RTP, of these liquid organic materials.
• To establish design principles for creating RTP-active liquid materials by controlling molecular aggregation.

Main Methods:

• Synthesis of thienyl diketones with dimethyloctylsilyl (DMOS) substituents.
• Characterization of photophysical properties including RTP quantum yields and decay kinetics.
• Spectroscopic analysis to understand excited-state dynamics and emission mechanisms.

Main Results:

• Efficient RTP was achieved from solvent-free liquefied thienyl diketones with DMOS substituents.
• High RTP quantum yields were observed, reaching up to 5.6% in air and 25.6% under Argon.
• A large RTP rate constant exceeding 5000 s⁻¹ was measured, indicating efficient phosphorescence emission.
• Suppression of aggregation-caused quenching was demonstrated by introducing two DMOS substituents, enabling monomer emission.

Conclusions:

• Novel metal-free organic liquids exhibiting efficient RTP have been successfully developed.
• The molecular design incorporating DMOS substituents is effective in achieving high RTP performance and preventing aggregation.
• These findings provide a valuable design strategy for future development of RTP-active liquid materials for various applications.