NaKLaNbO5:Eu3+: A highly efficient and thermally stable orange-red emitting phosphor for white light-emitting diodes

Abstract

The development of an appropriate blue-light-excitable red-emitting phosphor is of great importance for blue-emitting InGaN chip based white light-emitting diodes (w-LEDs). In this work, we attempted to synthesize a series of Eu3+ doped NaKLaNbO5 phosphors by solid-state reaction method. The successful preparation of the as-expected micron-size phosphor samples was testified through the characterizations of X-ray diffraction (XRD) along with Rietveld refinement, scanning electron microscope (SEM), energy dispersive X-ray (EDX) spectrum as well as elemental mapping. The photoluminescence properties of the as-prepared phosphor including excitation/emission spectra, decay lifetime, quantum efficiency, as well as the thermal stability of luminescence were investigated in detail. Upon excitation with blue light (464 nm), the phosphor KNaLa0.8Eu0.2NbO5 with optimized composition presented orange-red emission due to the dominant 5D0→7F2 transition of Eu3+ at 606 nm, which was with high color purity, high quantum efficiency, and excellent thermal stability. Finally, by employing NaKLa0.8Eu0.2NbO5 phosphor as orange-red component, a white LED device with appropriate correlated color temperature (CCT) of 5712 K, and high color rendering index (CRI) of 83.2 was fabricated. The results above showed certain potential of NaKLaNbO5:Eu3+ phosphor as possible orange-red component for blue-emitting InGaN chip based w-LEDs.