Ultrahighly Efficient Narrowband Red Luminescence of Uniquely Distorted Mn4+ Octahedron in the Feldspar-Type LED Phosphor

The mineral structure-inspired discovery of red phosphors has become a research hotspot that can help compensate for the missing red components in cold white light-emitting diodes (WLEDs). Herein, first the feldspar-type structure is utilized to develop narrowband red-emitting CaAl 2 Si 2 O 8 :Mn 4+ /Mn 4+ , Mg 2+ phosphors. Rietveld refinement results confirm the Mn 4+ occupation of the distorted [Ca1O 6 ] octahedron, resulting in a strong nephelauxetic effect, and thus exhibits bright red luminescence with a narrow full width at half maximum (43 nm). Compared with CaAl 2 Si 2 O 8 :Mn 4+ , the fluorescence intensity of CaAl 2 Si 2 O 8 :Mn 4+ , Mg 2+ is further enhanced by up to 210% owing to the decreasing nonradiative decay rate from 2 E g excited state, which weakens the concentration quenching effect resulting from energy migration along the adjacently aggregated Mn 4+ . CaAl 2 Si 2 O 8 :Mn 4+ , Mg 2+ shows preferable thermal stability with an ultrahigh quantum efficiency (90.3%), surpassing other current Mn 4+ -doped oxide phosphors and UCr 4 C 4 -type nitride phosphors. A fabricated prototype WLED obtains ideal warm white light with a low correlated color temperature (3081 K) and a wide color gamut covering 112% of the National Television System Committee standard. Guided by natural mineral-type structural prototypes, this study demonstrates the possibility of designing a uniquely distorted local structure to achieve a superior luminescence performance of Mn 4+ for warm WLEDs.