Three-photon absorption cross-section enhancement in two symmetrical fluorene-based molecules.

Area of Science:

• Materials Science
• Photochemistry
• Organic Electronics

Background:

• Fluorene-based molecules are explored for nonlinear optical applications.
• Understanding three-photon absorption (3PA) is crucial for advanced optical materials.
• Novel molecular architectures can enhance 3PA properties.

Purpose of the Study:

• To investigate the three-photon absorption effects of two novel symmetrical fluorene-based molecules.
• To analyze the influence of molecular structure on 3PA cross-sections.
• To determine the primary factors governing 3PA in these compounds.

Main Methods:

• Synthesis and characterization of 2D-pi-2D and 2D-D-pi-D-2D fluorene derivatives.
• Experimental measurement of three-photon absorption cross-sections.
• Computational studies using PM3 and ZINDO/S for geometries and electronic excitations.
• Application of a novel fitting method for 3PA coefficient determination.

Main Results:

• Achieved high three-photon absorption cross-sections: (4.74 +/- 0.01) x 10(-76) cm(6) s(2) for 2D-pi-2D and (6.77 +/- 0.02) x 10(-76) cm(6) s(2) for 2D-D-pi-D-2D.
• Demonstrated a strong correlation between molecular structure and 3PA efficiency.
• Identified the transition dipole moment as the most critical factor influencing 3PA.

Conclusions:

• The studied fluorene derivatives exhibit significant three-photon absorption properties.
• Molecular design, particularly the transition dipole moment, is paramount for optimizing 3PA.
• The developed fitting method provides a more accurate determination of the 3PA coefficient.