Ho3+activated Ca0.5Y1.90-xO3 green-emitting nanophosphors for solid state lightening

Abstract

This paper presents a series of Ho3+activated Ca0.5Y1.90-xO3 green-emitting nanophosphors using the facile solution combustion method. X-ray diffraction (XRD) and Transmission electron microscope (TEM) confirm the phase purity, structural morphology with cubic phase, and irregular shape particle with the average particle size of 21 nm. Diffuse reflectance spectra of the recorded and band gap estimated by Tauc's equation which is 5.78 eV, 4.90 eV for direct and indirect band gaps for 2 mol% of Ho3+, respectively. Under the excitation of 448 nm wavelength (5I8 → 3G6), the doped samples display characteristic emission of Ho3+ ions correspond to 5S2 → 5I8 (at 551 nm) transition, which fall in a strong green region. The optimal concentration for Ho3+ doping is found as 2 mol%, after this quenching of photoluminescence (PL) intensity occurred and this is accredited due to dipole-dipole interaction. The proposed nanophosphor also displays the good thermal stability with activation energy of 0.23 eV. The nanophosphor confirms the excellent color purity (98%), CRI (98.36%), and CCT value (5724 K). With this, nanophosphor also exhibits good quantum efficiency of 81.1% under the 448 nm excitation wavelength. These results direct that the Ho3+activated Ca0.5Y1.90-xO3 nanophosphor may have potential applicability for green-emitting LEDs, display device and optoelectronic applications.