Achieving Long-Wavelength Electroluminescence Using Two-Coordinate Gold(I) Complexes: Overcoming the Energy Gap Law

Area of Science:

• Materials Science
• Chemistry
• Physics

Background:

• Two-coordinate coinage metal complexes are promising for efficient organic light-emitting devices (OLEDs).
• Achieving efficient long-wavelength electroluminescence from these complexes is challenging.
• Existing Au(I) complex emitters face limitations in low-energy emission regions.

Purpose of the Study:

• Investigate molecular design strategies to enhance photoluminescence quantum yield (Φ) in Au(I) complex emitters.
• Develop two-coordinate Au(I) complexes for efficient long-wavelength and near-infrared emission.
• Understand the photophysical mechanisms governing emission efficiency.

Main Methods:

• Synthesized a series of two-coordinate Au(I) complexes by varying amido ligands.
• Measured photoluminescence peak wavelengths and photoluminescence quantum yields (Φ).
• Performed quantum chemical calculations and photophysical analyses.

Main Results:

• Developed Au(I) complexes with photoluminescence peak wavelengths spanning 533-750 nm.
• Achieved Φ values up to 10% in the near-infrared emission region.
• Demonstrated that radiative control overcomes the energy gap law, enhanced by increased overlap of hole and electron distributions (Sr(r)).
• Found Sr(r) increases with the distance between the hole-distribution centroid and the amido ligand's nitrogen atom.
• Fabricated multilayer OLEDs with improved performance beyond previous coinage metal complex devices.

Conclusions:

• Molecular design of two-coordinate Au(I) complexes with amido ligands enables efficient long-wavelength and near-infrared electroluminescence.
• Radiative control, influenced by excited-state charge distribution overlap, is key to overcoming the energy gap law.
• These findings pave the way for advanced OLEDs with tailored emission properties.