Recent advances in Mn 4+ -doped fluoride narrow-band red-emitting phosphors

White lighting emitting diodes (WLEDs) are considered as next generation solid-state lighting source, show great potential for lighting and displays application, because of their superior properties of energy saving, environment-friendliness and long lifetime. To date, the most popular commercial WLEDs are constructed by the combination of blue light emitting InGaN chip and yellow phosphor Y 3 Al 5 O 12 :Ce 3+ (YAG). However, owing to the inherent deficiency of red emission from YAG:Ce 3+ , the well-established strategy suffers from a low color rendering index (CRI, Ra <80) and high correlated color temperature (CCT>4000 K), which makes it inappropriate for applications in indoor lighting or backlighting in liquid-crystal display (LCD). To solve this problem, a suitable extra red emitting phosphor should be added into the aforementioned design. Currently, narrow-band Mn 4+ -activated fluorides have gained considerable attention due to their superiorities of sharp line emission, high luminescence efficiency, good thermal stability, high color purity, and solution-availability, which are highly important to the application for WLEDs. Here in this review, we overview the recent development of Mn 4+ doped fluoride red phosphors, especially focusing on the investigations on crystal structure, synthetic approaches, optical properties and promising application for WLEDs. Afterwards, the existing challenges and future developments have been proposed pointedly.