Copper-Iodide Hybrid Clusters with Partial Distortion Enable High-Performance Full-Visible-Spectrum White-Light-Emitting Diodes.

Abstract

Phosphor-converted white-light-emitting diodes (pc-WLEDs) have become increasingly prevalent artificial light sources. Currently, multicomponent phosphors are commonly used for pc-WLEDs, but they often suffer from issues of undesirable reabsorption and unstable emission colors. The potential alternative for pc-WLEDs is a single-component white phosphor that covers the broad visible spectrum with desirable low thermal quenching and efficient luminescence, which is still scarce. To address this challenge, we design a unique single-component white phosphor based on Cu4I4(4-(tert-butyl)-2-(diphenylphosphaneyl)pyridine)2 (Cu4I4(NP-tBu)2) hybrid clusters, which exhibits ultrabroad dual emission from 400 to 800 nm and a high photoluminescence quantum yield of 97% under 320 nm light excitation. Based on time-resolved fluorescence spectroscopy and theoretical model analysis of our Cu4I4 series clusters, we hypothesize that the dual emission comes from the coexistence of two triplet states caused by partial cluster distortion under light excitation. The Cu4I4(NP-tBu)2 cluster's high structural stability also endows consistent spectral performance and low thermal quenching up to 240 °C. Thus, the fabricated pc-WLED using Cu4I4(NP-tBu)2 white phosphor exhibits a maximum efficiency of 63.4 lm/W and maintains a high color rendering index of ∼88 during 1000 h of continuous operation. Our results highlight a new strategy of low-cost and high-performance copper-iodide cluster-based single-component white phosphors for high-quality pc-WLEDs.