[4]Rhombene: Solution-Phase Synthesis and Application in Distributed Feedback Lasers With Emission Beyond 830 nm

Area of Science:

• Organic electronics
• Materials science
• Laser technology

Background:

• Graphene-like molecules with zigzag edges are promising gain materials for organic lasers.
• Rhombenes, a type of molecular graphene, are suitable for near-infrared (NIR) lasers due to small energy gaps.
• Synthesizing large rhombenes for emission beyond 800 nm in solution is challenging.

Purpose of the Study:

• To develop a straightforward synthesis for aryl-substituted [4]rhombene derivatives.
• To investigate the optical properties and laser performance of the synthesized [4]rhombene derivative.
• To enable NIR organic lasers emitting beyond 800 nm.

Main Methods:

• Synthesis of aryl-substituted [4]rhombene ([4]RB-Ar) via intramolecular radical-radical coupling and Bi(OTf)3-mediated cyclization.
• Structural confirmation using X-ray crystallographic analysis.
• Optical characterization including amplified spontaneous emission (ASE) measurements and laser performance evaluation in thin films and solution-processed distributed feedback (DFB) lasers.

Main Results:

• Aryl-substituted [4]rhombene ([4]RB-Ar) was successfully synthesized and structurally characterized.
• Theoretical calculations confirmed aromatic sextet localization along the molecule's long axis.
• The material exhibited narrow ASE around 834 nm in polystyrene thin films and tunable narrow emissions (830–844 nm) in solution-processed DFB lasers.

Conclusions:

• The developed synthesis provides a viable route to large-size rhombenes for NIR organic lasers.
• [4]RB-Ar serves as an effective gain material for NIR lasers emitting beyond 800 nm.
• This work advances the development of solution-processable organic lasers in the NIR region.