A lighting device is presented. The lighting device includes an LED light source; and a red/far-red emitting phosphor radiationally coupled to the LED light source, wherein the red/far-red emitting phosphor comprises a host material activated with an activator ion, and wherein the activator ion comprises at least one of Sm.sup.2+ and Mn.sup.2+. Numerous other aspects are provided.

The present disclosure discloses a blue fluorescent powder for a three primary color warm white LED and a preparation method thereof. SrCO.sub.3, NH.sub.4Cl, H.sub.3BO.sub.3, Eu.sub.2O.sub.3, and NH.sub.4H.sub.2PO.sub.4 function as raw materials to obtain a chemical formula of a blue fluorescent powder Sr.sub.(2-x)Eu.sub.x(BO.sub.3).sub.y(PO.sub.4).sub.(1-y)Cl in a reducing atmosphere by a solid-state sintering method, wherein 0.001≤x≤0.1 and 0.001≤y≤0.5. The blue fluorescent powder is mixed with CaAlSiN.sub.3:Eu.sup.2+ red fluorescent powder and (SrBa).sub.2SiO.sub.4:Eu.sup.2+ green fluorescent powder at a certain proportion to emit warm white light with a light efficiency and a color rendering index under a violet light excitation. An application prospect is wide.

The present disclosure discloses a blue fluorescent powder for a three primary color warm white LED and a preparation method thereof. SrCO.sub.3, NH.sub.4Cl, H.sub.3BO.sub.3, Eu.sub.2O.sub.3, and NH.sub.4H.sub.2PO.sub.4 function as raw materials to obtain a chemical formula of a blue fluorescent powder Sr.sub.(2-x)Eu.sub.x(BO.sub.3).sub.y(PO.sub.4).sub.(1-y)Cl in a reducing atmosphere by a solid-state sintering method, wherein 0.001x0.1 and 0.001y0.5. The blue fluorescent powder is mixed with CaAlSiN.sub.3:Eu.sup.2+ red fluorescent powder and (SrBa).sub.2SiO.sub.4:Eu.sup.2+ green fluorescent powder at a certain proportion to emit warm white light with a light efficiency and a color rendering index under a violet light excitation. An application prospect is wide.

A lighting device is presented. The lighting device includes an LED light source; and a red/far-red emitting phosphor radiationally coupled to the LED light source, wherein the red/far-red emitting phosphor comprises a host material activated with an activator ion, and wherein the activator ion comprises at least one of Sm.sup.2+ and Mn.sup.2+. Numerous other aspects are provided.

Lanthanide double perovskite nanocrystals are described. The nanocrystals display high energy luminescence, making them useful in a variety of light-emitting materials and devices. Methods of preparing the lanthanide double perovskite nanocrystals using a hot injection method are also described.