From a blue to white to yellow emitter: a hexanuclear copper iodide nanocluster

Area of Science:

• Materials Science
• Inorganic Chemistry
• Photochemistry

Background:

• Copper(i) halide nanoclusters are gaining attention for their emissive properties, particularly thermally activated delayed fluorescence (TADF).
• However, reports on TADF in copper(i) halide nanoclusters remain scarce.

Purpose of the Study:

• To synthesize and characterize a novel hexanuclear copper(i) iodide cluster with a tridentate N^P^N ligand.
• To investigate its photophysical properties, including emission characteristics and potential applications.

Main Methods:

• Synthesis of the hexanuclear copper(i) iodide cluster [Cu6I6(ppda)2] using a specific N^P^N ligand (ppda).
• Characterization of the cluster's structure and coordination environment.
• Photoluminescence spectroscopy to determine emission spectra, quantum yields (ΦPL), and lifetimes (τ).
• Fabrication and testing of a solution-processed, nondoped device.

Main Results:

• The synthesized [Cu6I6(ppda)2] complex features six four-coordinate copper atoms (four CuPNI2 and two CuI4 units).
• It exhibits intense white emission in the powder state at room temperature (λmax = 535 nm, ΦPL = 0.36, τ = 4.4 μs).
• Emission color is tunable from blue to white to yellow across different states (crystal, powder, film).
• The emission mechanism involves a combination of metal-to-ligand charge transfer (MLCT) and ligand-to-ligand charge transfer (XLCT) transitions.
• A fabricated device showed stable yellow emission (CIE: (0.43, 0.51)).
• The complex demonstrated good thermal stability and reasonable photocatalytic H2 evolution activity under visible light.

Conclusions:

• The novel [Cu6I6(ppda)2] cluster is a promising material for tunable emission and photocatalysis.
• Its unique structure and properties contribute to the development of advanced functional materials.
• This work expands the scope of TADF materials based on copper(i) halide nanoclusters.