In Situ Fabrication of Flexible, Thermally Stable, Large-Area, Strongly Luminescent Copper Nanocluster/Polymer Composite Films

Composite polymer films incorporating luminescent copper nanoclusters are conveniently fabricated by solution processing of a precursor mixture of polyvinylpyrrolidone, poly(vinyl alcohol), a Cu²⁺ salt, and glutathione in water. The formation of Cu nanoclusters takes place through chemical reactions of the precursors in a hydrogel network, whose dehydration during the subsequent aging process leads to aggregation-induced emission enhancement. Large-area (25 cm × 32 cm), flexible, transparent, thermally stable, bright-orange-emitting films are realized, with the photoluminescence quantum yield reaching 30%. The emission of the films is attributed to a phosphorescence mechanism, taking place through ligand-to-metal charge transfer followed by a radiative relaxation over a triplet state. Cu-nanocluster-based composite films are employed as a light-emitting layer for down-conversion orange light-emitting diodes.