Warm to cool tunable ultra-stable white light emissions from carbon dots -Tb3+ - Eu3+ doped silica

Abstract

Development of ultra-stable, solid-state, cost-effective phosphors for white light emitting devices with high color rendition is in high demand. In this work, we prepared carbon quantum dots (CQDs) by a hydrothermal method with an average size ranging from 2 to 8 nm which exhibits low toxicity. Optical analysis confirmed the influence of both Cu2+ and Fe3+ ions and the excitation-dependent fluorescence of CQDs are effectively quenched by addition of Fe3+ ions. The excitation dependent emission property of CQDs and degradation resistant blue emission of CQDs-silica are utilized to construct CQDs-Europium–Terbium doped silica matrices for stable multi-colour emissions upon different excitation wavelengths. Optimized composition of CQDs with Terbium and Europium ions produced white light emissions under UV exposure of 370–393 nm. Continuous tuning from warm white emission to cool white emission with moderate CRI is achieved by varying the concentration of CQDs. The ultra-stable white emissions which last long for a year, reveals the potential WLED applications of these solid-state luminescent materials.