Toward Ultra-Broadband Absorption and High Quantum Efficiency Red Emission via Fluoride Single Crystals with Heavy Mn4+ Doping

Abstract

Owing to the avoidance of device reabsorption and improvement in the color rendering index (CRI), Mn4+-activated fluorides have potential applications in full-spectrum lighting. However, it is still challenging to improve the external quantum efficiency (EQE) and adapt it to the excitation of violet-light chips used for increasing the CRI and reducing the blue-light hazard. Here, red-light single crystals Rb2Si1−xMnxF6 (RSMF) with an ultrahigh optimal Mn4+ content of 32.4 mol% are obtained through structural and morphological design. Breaking through the limitation of low quenching concentration (<10 mol%) of Mn4+-activated fluorides, the as-grown heavy Mn4+-doped RSMF crystal not only exhibits a record EQE of 80.2% but also has a broad excitation band of full width at half maxima = 86 nm, which can be efficiently excited by both blue (460 nm) and violet (437 nm) light. The white light-emitting diodes fabricated by violet/blue dual-chips, commercial green phosphor, and the optimized RSMF crystal can realize a high luminous efficacy of 161.8 lm W−1 and high CRI of Ra = 95.5. Additionally, laser diode devices with high luminous flux of 198.2 lm are also presented. This study provides new insights into heavy Mn4+-doped materials and promotes the application of full-spectrum lighting.