The effect of lithium on structural and luminescence performance of tunable light-emitting nanophosphors for white LEDs

Abstract

Li⁺ incorporated tunable Y₂O₃:Eu³⁺ red-emitting nanophosphors were synthesized using a wet chemical method. The effect of Li⁺ on structural and luminescence properties of the nanophosphors were studied in detail. The structural results exhibited that nanophosphors have a body-centered cubic (I) phase with point group symmetry m. No additional impurity peaks were observed within the range of the XRD pattern due to the Li⁺ ion. FTIR spectra reveal the formation of the pure and crystalline structure of the nanophosphors. TEM results show the prepared nanophosphors were highly crystalline and polycrystalline in nature. PL studies show the highly enhanced emission band due to the flux effect, greatly improved crystallinity caused by the Li⁺ ion, and the different excitation wavelengths. The most intense luminescence band was observed at 612 nm for red emission ascribed to the ⁵D₀ → ⁷F₂ transition of Eu³⁺ ion upon 254, 393, and 465 nm excitations in the C_3i and C₂ symmetry site of Y₂O₃ respectively. The highly enhanced emission band was observed under excitation at 254 nm and is 6.9 and 3.67 times higher than the emission band excited at 393 and 466 nm, respectively. The average lifetime also varies with different concentrations of Li⁺ ions. The chromaticity color coordinates, CCT values, were tuned in the red region of the color space. Hence, the results indicate that the prepared nanophosphor can be used as a red component to construct the white light for light-emitting diode applications.