Photoluminescence-Based Judd-Ofelt Studies, Quantum Efficiency and DFT Analysis of the Eu3+-Doped Pb3Bi(PO4)3 Phosphor Prepared by the Combustion Technique for Orange-Red Solid-State Lighting Applications.

Abstract

The Eu3+-activated Pb3Bi(PO4)3 phosphors were synthesized for the first time by the energy-efficient combustion technique, and their structural and luminescence properties were investigated for orange-red solid-state lighting applications. X-ray diffraction analysis with Rietveld refinement confirmed the phase-pure cubic structure (space group I-43d), while the SEM images revealed a highly porous, agglomerated morphology. Under 394-nm excitation, the phosphors exhibited characteristic Eu3+ emissions at 592, 615, 658 and 705 nm, dominated by the hypersensitive 5D0 → 7F2 electric-dipole transition at 615 nm. The photoluminescence intensity, asymmetry ratio (R = 1.418), Judd-Ofelt intensity parameters (Ω2 = 2.226 × 10-20 cm2, Ω4 = 1.849 × 10-20 cm2), radiative lifetime (τR = 3852 μs) and experimental lifetime (τ = 3592 μs) were found to be optimum at 0.5 mol% Eu3+, yielding a quantum efficiency of 93.2%. The main emission's chromaticity coordinates were determined to be high colour purity. The CIE chromaticity coordinates of (0.586, 0.412) and (0.680, 0.319) colour purity of about 97.23% and 97.56% and dominant wavelengths of 592 and 615 nm confirm the nearly saturated orange-red emission. The DFT-derived electron-density map corroborates the Judd-Ofelt parameters. These results establish the combustion-synthesized Pb3Bi(PO4)3:Eu3+ phosphor as a promising candidate for near-UV-pumped orange-red solid-state lighting.