Downconverted significant luminescence enhancement and structural confinement of a dichromatic nanophosphor for potential applications in NUV-triggered cool pc-WLEDs

Abstract

Trivalent rare-earth ions activated phosphor-converted near ultraviolet (NUV) triggered white light-emitting diodes (WLEDs) are nowadays being explored as a prominent light source, in the field of lighting. Herein, we prepared a sequence of single-phase Gd2O3:Dy3+,Li+nanophosphor via chemical co-precipitation techniques for the applications in cool pc-WLEDs. To examine the crystal structure, luminescent characteristics, and potential applications of WLEDs, a systematic and comprehensive analysis was conducted. This study extensively investigated the effect of Li+ on the Gd2O3:Dy3+white-emitting nanophosphor. The phase purity and crystal structure of nanophosphors were characterized via powder X-ray diffraction (XRD) analysis. Rietveld refinement clearly quantified that the Gd2O3 host possesses two non-equivalent cationic sites that are coordinated sixfold. The interior morphology and elemental composition were illustrated by high-resolution transmission electron microscopy (HR-TEM) and energy dispersive spectroscopy (EDS). These nanophosphors effectively exhibit dichromatic significant photoluminescence (PL) emission bands of Dy3+ ion for blue and yellow color at 486 and 574 nm, while triggered in the NUV range. The blending of blue and yellow color lights yields a broad spectrum of light that appears white color to the human eye. Besides, it has been observed that the incorporation of Li+ significantly enhances the PL-emission intensity. The critical distance between Gd3+ and Dy3+ was determined, and it showed that the electric multipolar interaction was responsible for the energy transfer quenching mechanism. The colorimetric performance reveals that the CIE coordinates fall within the white region of the color space and that the correlated color temperature (CCT) is substantially higher than 4000 K. The lowest color purity (CP) was found to be 4.0% for x = 2 at.%Li+ ion concentration under excitation wavelength 350 nm. These findings suggest that the prepared nanophosphors are a suitable candidate for application in NUV-triggered cool-WLEDs.