Full color-emitting (Y,Tb,Eu)NbO4 nanophosphors: calcination-assisted hydrothermal synthesis, energy interaction, and application in deep UV chip-based WLEDs†
Phosphor-converted white light-emitting diodes (pc-WLEDs) integrated with deep UV chips and single-component white light-emitting phosphors have attracted widespread research interest recently. (Y,Tb,Eu)NbO4 nanophosphors with full-color emission properties were achieved in this work by a facile calcination-assisted hydrothermal method, and the elaborately designed white light-emitting (Y0.988Tb0.010Eu0.002)NbO4 phosphor was successfully applied to a 275 nm chip excited pc-WLED with a relatively low correlated color temperature (CCT) of 5517 K and a high color-rendering index (CRI) of 86.7. Through a comprehensive characterization by XRD, elemental analysis, FE-SEM, TEM, TG, FT-IR, UV-vis, and optical spectroscopy, the YNbO4 nanophosphor with optimal PL properties was evidenced to be obtainable through calcining the hydrothermally crystallized precursor at 1000 °C. The quenching concentrations of Tb3+ and Eu3+ in YNbO4 were determined to be ∼4 and 5 at%, respectively, and the efficiency of the NbO43− → Tb3+ energy transfer was calculated to be ∼47.93%. Upon excitation at 260 nm, the ternary (Y,Tb,Eu)NbO4 phosphor simultaneously displays blue NbO43−, green Tb3+, and red Eu3+ emissions. Benefiting from the NbO43− → Tb3+ → Eu3+ energy transfer, full color emission was achieved via adjusting the Tb3+ and Eu3+ concentrations in (Y,Tb,Eu)NbO4. The white light-emitting (Y0.988Tb0.010Eu0.002)NbO4 phosphor with color coordinates of (0.336, 0.334) can maintain its emission color and ∼67% of its overall emission intensity at 150 °C, indicating that the phosphor is highly promising for application in deep UV chip-based pc-WLEDs.