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

Abstract

AbstractOwing 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.