A green light emissive LaSr 2 AlO 5 :Er 3+ nanocrystalline material for solid state lighting: crystal phase refinement and down-conversion photoluminescence with high thermal stability.

The present study reveals the structural and optoelectronic characteristics of a down-converted (DC) green luminous Er 3+ doped LaSr 2 AlO 5 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 LaSr 2 AlO 5 (5.97 eV) and optimized La 0.96 Sr 2 AlO 5 :4 mol% Er 3+ (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 H 9/2 → 4 I 15/2 (406 nm), 2 H 11/2 → 4 I 15/2 (520 nm), 4 S 3/2 → 4 I 15/2 (550 nm), and 4 F 9/ 2 → 4 I 15/2 (665 nm) were revealed by photoluminescence spectroscopy under 377 nm excitation. Above 4 mol% Er 3+ 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 λ ex = 377 nm and λ em = 550 nm, the average lifetime of the excited levels of considered nanomaterials was estimated. The temperature-dependent emission spectra of the La 0.96 Sr 2 AlO 5 :4 mol% Er 3+ 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.