Improving Color Quality of Nanowire White Light-Emitting Diodes with Mn⁴⁺ Doped Fluoride Nanosheets

A two-dimensional nanostructured fluoride red-emitting phosphor with an excellent quantum yield of ~91% is studied for cost-effective and high-color quality nanowire white light-emitting diodes (WLEDs). K₂TiF₆:Mn⁴⁺ phosphors are synthesized via an emulsification method using surfactants as sodium dodecyl sulphonate and oleic acid. The K₂TiF₆:Mn⁴⁺ phosphors in ultra-thin and nanosheet crystals are observed via scanning electron microscopy and high-resolution transmission electron microscopy. The surfactants are found to play a key role in inhibition of KTFM crystal growth process and stabilization of Mn⁴⁺ ions doping into the K₂TiF₆ host. The prepared phosphors exhibited intensive red emission at approximately 632 nm and excellent thermal stability in the range of 300-500 K upon 460 nm light excitation. Moreover, the K₂TiF₆:Mn⁴⁺ nanosheets were integrated on InGaN/AlGaN nanowire WLEDs for color quality study. The results show that the nanowire WLEDs with red-emitting phosphor exhibit unprecedentedly high color rendering index ~96.4, and correlated color temperature ~4450 K.