A cluster-based phosphor against thermal quenching via dynamic metallic bonding

Abstract

The effect of dynamic chemical bonding on material properties has long been the subject of intensive investigation in the fields of chemistry and materials. Especially, the dynamic metallic bonding is uncommon because the intermetallic electronic interaction may respond to external stimuli, which potentially builds the synergistic coupling among many physical properties. Herein, we experimentally investigate a dynamic Cu‒Cu bonding interaction that dictates the thermal quenching effect of photoluminescence (PL) in a high-efficiency metal-halide cluster-based phosphor. The weakening of Cu−Cu bonding in such a phosphor system enables the release of bonding electrons from Cu(I) 3d-orbital and hence sustains the PL efficiency at high temperatures (up to 100 oC). The temperature-dependent structural, NMR and EPR measurements reveal a reversible transition from diamagnetic Cu(I) to paramagnetic Cu(II) species. The white light-emitting diodes (LEDs) incorporating the thermally stable phosphor show a rapid brightness rise even at a high bias current (1,000 mA) with color rendering index as high as 90, comparable to the commercial phosphor-based prototype LEDs (e.g., YAG:Ce3+). This work establishes a novel prototype of cluster-based phosphor featuring dynamic metallic bonding, which paves the way for exploration of phosphor-converted LEDs against thermal quenching.