Narrow-Band Red-Emitting Phosphors with High Color Purity, Trifling Thermal and Concentration Quenching for Hybrid White LEDs and Li3Y3BaSr(MoO4)8:Sm3+, Eu3+-Based Deep-Red LEDs for Plant Growth Applications.

Trivalent europium-based monochromatic red light-emitting phosphors are an essential component to realize high-performance smart lighting devices; however, the concentration and thermal quenching restrict their usage. Here, we report a series of efficient Eu3+-substituted Li3Y3BaSr(MoO4)8 red-emitting phosphors based on a stratified scheelite structure with negligible concentration and thermal quenching. All of the host and phosphor compositions crystallize in monoclinic crystal structure (space group C2/c). All of the phosphor compositions produce narrow-band red emission (FWHM ∼6 nm), which is highly apparent to the human eyes, and lead to exceptional chromatic saturation of the red spectral window. Concurrently, detailed investigations were carried out to comprehend the concentration and thermal quenching mechanism. Absolute quantum yields as high as 88.5% were obtained for Li3Y0.3Eu2.7BaSr(MoO4)8 phosphor with virtuous thermal stability (at 400 K, retaining 87% of its emission intensity). The light-emitting diodes were constructed by coupling Li3BaSrY0.3Eu2.7(MoO4)8 red phosphor with a near-UV LED chip (395 nm) operated at 20 mA forward bias, and the hybrid white LED (an organic yellow dye + red Li3Y3BaSr(MoO4)8:Eu3+ phosphor integrated with an NUV LED chip) showed a low CCT (6645 K), high CRI (83) values, and CIE values of x = 0.303; y = 0.368, which indicated that the synthesized phosphors can be a suitable red component for white LEDs. In addition, we have systematically investigated the Sm3+ and Sm3+, Eu3+ activation in Li3Y3BaSr(MoO4)8 to display the latent use of the system in plant growth applications and establish that the phosphor exhibits orange red emission with an intense deep-red emission (645 nm (4G5/2 → 6H9/2)). The phytochrome (Pr) absorption spectrum well matched the fabricated deep-red LED (by integrating a NUV LED + Li3Y3BaSr(MoO4)8:Sm3+ and Eu3+ phosphor) spectral lines.

Novel narrow band red emitters based on mixed metal oxides and their application in hybrid white light-emitting diodes.

A series of high-efficiency narrow band red-emitting La2 M2 O9 :Eu3+ (M = Mo/W) phosphors for white LEDs was synthesized using a conventional solid-state reaction method. All the compositions show absorption in the near ultraviolet (UV) light region due to charge transfer from O to M (M = W and Mo). In order to investigate the luminescence quenching effect, the Eu3+ concentration was varied in the La2 M2 O9 lattice. The tungstate analogue had a quantum yield of 46.5%, whereas the molybdate equivalent had a comparatively subordinate value (15.4%). The phosphor could be competently excited by ~395 or 465 nm photons (could be integrated well with a near-UV or blue LED chip) and showed dominant red emission electric-dipole transition (5 D0 →7 F2 ) with sharp spectral lines due to 4f-4f electronic transition of the Eu3+ ion and potential red-emitting colour converters for white LEDs. The red LED was fabricated by integrating the best phosphor composition with a near-UV LED and a white hybrid LED was fabricated by conjugating with a yellow organic dye and a red phosphor with near-UV LEDs. The white hybrid LED showed an excellent colour rendering index (83%), with CIE colour coordinates (0.313, 0.365) and CCT (6280 K).