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 La 2 M 2 O 9 :Eu 3+ (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 Eu 3+ concentration was varied in the La 2 M 2 O 9 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 D 0 → 7 F 2 ) with sharp spectral lines due to 4f–4f electronic transition of the Eu 3+ 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).