Bright bluish-green emitting Cu(I) complexes exhibiting efficient thermally activated delayed fluorescence

Area of Science:

• Inorganic Chemistry
• Materials Science
• Photophysics

Background:

• Copper(I) complexes are explored for their luminescent properties.
• Developing efficient emitters for optoelectronic devices is crucial.
• Thermally Activated Delayed Fluorescence (TADF) offers a pathway to high quantum efficiency.

Purpose of the Study:

• Synthesize and characterize novel copper(I) complexes.
• Investigate their photoluminescence and emission mechanisms.
• Explore the influence of ligand structure on emissive properties.

Main Methods:

• Synthesis and characterization of three Cu(I) complexes: [Cu(tBupzmpy)(POP)]BF4, [Cu(Phpzmpy)(POP)]BF4, and [Cu(Adpzmpy)(POP)]BF4.
• Photoluminescence spectroscopy at room temperature.
• Temperature-dependent studies of spectroscopic properties and emission decay.
• Theoretical calculations (DFT) to understand excited states.

Main Results:

• All three complexes exhibit strong bluish-green photoluminescence in the solid state.
• High quantum yields (91%, 71%, 77%) and long lifetimes (13.4-34.1 μs) were observed.
• Efficient TADF emission was confirmed, originating from metal-to-ligand charge transfer (MLCT) and ligand-to-ligand charge transfer (LLCT) states.
• Ligand modification effectively tuned the emission characteristics.

Conclusions:

• The synthesized Cu(I) complexes are efficient TADF emitters.
• The emission mechanism involves MLCT and LLCT transitions.
• Steric and electronic tuning of diimine ligands provides a strategy for optimizing luminescent properties of Cu(I) complexes.