Solvent-Induced Self-Assembly of Copper Nanoclusters for White Light Emitting Diodes

As a type of luminescent material, copper nanoclusters (Cu NCs) are widely concerned because of their low cost, nontoxicity, and outstanding biocompatibility. However, research studies on the preparation of hydrophobic Cu NCs with high quantum yield can be improved. In this work, we first synthesized atomically precise triphenylphosphine (PPh3)-capped Cu NCs (Cu4–NCs). Second, we adopted solvent engineering strategies to trigger the self-assembly of Cu4–NCs into the assembly with branched structures, thereby achieving aggregation-induced emission (AIE), thermally activated delayed fluorescence (TADF), and a high absolute quantum yield of 67.05%. Moreover, we performed structural characterization and optical analysis, which revealed that the high compactness of the assembly enhances the cuprophilic interaction and suppresses the intramolecular vibration and rotation of the Cu4–NCs ligand, protecting the Cu core from singlet oxygen quenching. These properties lead to the emergence of TADF and AIE. By mixing the as-assembled Cu4–NCs with commercial phosphors, a white light emitting diode prototype can be fabricated. This research demonstrates that TADF emission and the robust luminescence structure of the Cu4–NCs assembly provide them a high application value and extend the research opportunities for metal NCs in optical devices.