Structural Engineering of Luminogens with High Emission Efficiency Both in Solution and in the Solid State.

Area of Science:

• Organic electronics
• Photophysics
• Materials science

Background:

• Developing organic luminogens with high emission efficiency in both solution and solid states is challenging due to aggregation-caused quenching (ACQ) or aggregation-induced emission (AIE).
• Existing organic emitters often suffer from reduced performance in condensed phases due to intermolecular interactions.

Purpose of the Study:

• To design and synthesize novel organic emitters that overcome the limitations of ACQ and AIE.
• To achieve high emission efficiency in both dilute solution and solid-state conditions.

Main Methods:

• Integration of planar and distorted molecular structures within a donor-acceptor-pi-donor-acceptor (DAπAD) framework.
• Incorporation of long alkyl side chains to modulate intermolecular interactions and solid-state packing.
• Utilizing a linear diphenyl-diacetylene core and cyanostilbene units to control electronic properties and molecular conformation.

Main Results:

• Achieved strong emission in dilute solution with quantum yields up to 98.2% due to the planar excited state facilitated by the diphenyl-diacetylene core and charge transfer.
• Demonstrated strong solid-state emission with quantum yields up to 60.7% by restricting molecular vibration/rotation through distorted cyanostilbene units and mitigating π-π stacking quenching with alkyl chains.

Conclusions:

• Successfully developed DAπAD type emitters that exhibit high emission efficiency in both solution and solid states.
• The molecular design effectively balances planarity for solution emission and controlled distortion/intermolecular interactions for solid-state emission.
• This strategy offers a promising pathway for designing advanced organic light-emitting materials.