A green light emissive LaSr2AlO5:Er3+ nanocrystalline material for solid state lighting: crystal phase refinement and down-conversion photoluminescence with high thermal stability
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Date
2024-09
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Abstract
The present study reveals the structural and optoelectronic characteristics of a down-converted (DC) green
luminous Er3+ doped LaSr2AlO5 phosphor that was produced by employing an efficient and reliable gel combustion process assisted with urea as a fuel. Using Rietveld refinement of diffraction data, the crystal
structure and phase formation were examined. The surface morphology and elemental configuration of
the phosphor were analyzed via TEM and EDX spectroscopy, respectively. The band gap of LaSr2AlO5
(5.97 eV) and optimized La0.96Sr2AlO5:4 mol% Er3+ (5.51 eV) classify the optimized sample as a direct
band-gap material. The PL peaks located in the visible range corresponding to transitions 2
H9/2 / 4
I15/2
(406 nm), 2
H11/2 / 4
I15/2 (520 nm), 4
S3/2 / 4
I15/2 (550 nm), and 4
F9/ 2 / 4
I15/2 (665 nm) were revealed
by photoluminescence spectroscopy under 377 nm excitation. Above 4 mol% Er3+ doping, concentration
quenching was observed, which was controlled by the quadrupole–quadrupole interaction. Based on the
findings of the double exponential fitting of lifetime curves acquired from the emission spectra at lex =
377 nm and lem = 550 nm, the average lifetime of the excited levels of considered nanomaterials was
estimated. The temperature-dependent emission spectra of the La0.96Sr2AlO5:4 mol% Er3+ sample were
collected in the range 298–498 K. The considered phosphor was found to have a high thermal stability
as evidenced by the luminous intensity being sustained at 74.29% at 498 K compared to the intensity at
ambient temperature (298 K) with an activation energy of 0.1453 eV. The calculated color purity and
superb chromaticity coordinates indicates that the phosphors have a high degree of color purity, which
further supports its applicability as a green component in solid-state lighting.