A Highly Efficient Red-Emitting Ruthenium Complex with 3,5-Difluorophenyl Substituents

Area of Science:

• Materials Science
• Organic Chemistry
• Photochemistry

Background:

• Ruthenium complexes are widely investigated for their photophysical properties.
• Organic light-emitting diodes (OLEDs) require efficient phosphorescent emitters.
• Fluorinated organic ligands can tune the electronic and optical properties of metal complexes.

Purpose of the Study:

• To synthesize and characterize novel 3,5-difluorophenyl-substituted ruthenium complexes.
• To investigate the impact of these substituents on photophysical, electrochemical, and electroluminescent properties.
• To evaluate the performance of these complexes as emitters in single-layer devices.

Main Methods:

• Synthesis of five ruthenium complexes with varying bipyridine and phenanthroline ligands.
• Photophysical characterization including emission spectra and lifetimes.
• Electrochemical measurements (cyclic voltammetry).
• Fabrication and testing of single-layer electroluminescent devices.
• Density Functional Theory (DFT) calculations.

Main Results:

• The synthesized ruthenium complexes exhibit orange-red phosphorescence (605–638 nm).
• Introduction of 3,5-difluorophenyl groups causes a redshift in emission and extends π-conjugation.
• DFT calculations indicate the lowest unoccupied molecular orbital is localized on the fluorinated ligand.
• Single-layer devices fabricated with these complexes show high luminescence.
• The optimized device based on Ru-Fdpp achieved a luminous efficiency of 4.19 cd A⁻¹ and power efficiency of 1.46 lm W⁻¹.

Conclusions:

• 3,5-difluorophenyl substitution effectively tunes the emission properties of ruthenium complexes.
• These fluorinated ruthenium complexes are promising candidates for efficient phosphorescent emitters in OLEDs.
• The study demonstrates the potential for developing high-performance single-layer luminescent devices.