Efficient Blue Photo- and Electroluminescence from CF₃-Decorated Cu(I) Complexes.

Area of Science:

• Materials Science
• Organic Electronics
• Photochemistry

Background:

• Organometallic complexes of copper(I) are crucial for organic light-emitting diodes (OLEDs).
• Copper(I)-based carbene-metal-amide (CMA) complexes show promise as emitters.
• Development of blue-emitting Cu(I) CMA complexes remains a challenge.

Purpose of the Study:

• To construct novel blue-emitting Cu(I) CMA complexes.
• To investigate the photophysical properties and emission mechanisms.
• To evaluate their performance in vacuum-deposited OLED devices.

Main Methods:

• Synthesis of two blue-emitting Cu(I) CMA complexes, MAC*-Cu-CF3Cz and MAC*-Cu-2CF3Cz, by functionalizing carbazole ligands with CF3 groups.
• Characterization of thermal stability and emission properties.
• Analysis of emission origins using photoluminescence spectroscopy and lifetime measurements in doped films and OLED devices.

Main Results:

• Both synthesized complexes demonstrated high thermal stability and blue emission.
• MAC*-Cu-CF3Cz exhibited thermally activated delayed fluorescence (TADF) from ligand-to-ligand charge transfer states.
• MAC*-Cu-2CF3Cz showed dominant phosphorescence from local triplet excited states.
• MAC*-Cu-CF3Cz achieved a photoluminescence quantum yield of 94%, short emission lifetime of 1.2 μs, and high radiative rates.
• OLEDs fabricated with MAC*-Cu-CF3Cz displayed pure-blue electroluminescence (462 nm) with a high external quantum efficiency of 13.0%.

Conclusions:

• The introduction of CF3 substituents effectively tuned the emission properties of Cu(I) CMA complexes.
• MAC*-Cu-CF3Cz is a highly efficient blue emitter with potential for OLED applications.
• The distinct emission mechanisms highlight the versatility of CMA complexes for color tuning and efficiency enhancement.