Facile synthesis, novel structure, and tunable luminescence properties of K6Bi13(PO4)15:Dy3+,Eu3+ phosphors for ultraviolet converted white light-emitting diodes

Abstract

A variety of novel Dy3+/Eu3+ mono- and co-doped K6Bi13(PO4)15 (KBPO) luminescent materials have been fabricated by a simple solid-state method for the first time. Both experimental studies and theoretical calculations verify that the K6Bi13(PO4)15 crystals are suitable to be utilized as host materials for the lanthanide activator ions. The XRD, EDS, and XPS results reveal that the Dy3+ and Eu3+ have been effectively incorporated into the KBPO host matrix and do not damage the structure of KBPO. The Dy3+ or Eu3+ mono-doped phosphors display the characteristic spectral patterns of the activator ions upon UV excitation whereas an energy transfer between Dy3+ and Eu3+ occurs which helps to obtain the tunable luminescence of the KBPO:Dy3+,Eu3+ phosphors. The emission colors of the KBPO:Dy3+,Eu3+ regularly shift from green-blue, through white, and finally toward yellow and orange-red by varying the activator doping concentrations under a fixed excitation wavelength. Interestingly, the single-phase white light emitting phosphors with CIE chromaticity coordinates of (0.3122, 0.3106) and (0.3602, 0.3246) are obtained by doping appropriate concentrations of Dy3+ and Eu3+, which match well with the standard white light illuminate of (0.333, 0.333). Moreover, the annealing conditions are optimized and the luminescent mechanisms and temperature-dependent luminescence performance are systematically investigated. Finally, the WLEDs device prepared by KBPO:Dy3+,Eu3+ phosphor and UV chip displays a dazzling white light with favorable CIE (Commission Internationale de I'Eclairage 1931 chromaticity) coordinates, color rendering index (Ra), correlated color temperature (CCT), and thermal stability, which provides direct evidence that the as-prepared inorganic luminescent materials may have prospects as an eminent single-phase white light emitting materials for white light-emitting diodes (WLEDs) and optoelectronic devices.