Eu3+ activated non-crystalline BaTiO3 ultra-thin film phosphor with high purity, tailored red emission from n-UV excitation for WLEDs applications

As an alternative WLED red phosphor, BaTiO ₃ sol-gel based ultra-thin films were doped with various mol% of Eu ³⁺ and annealed at 500 °C. The films were amorphous with short range ordered structure as seen via XRD and Raman analysis. Photoluminescence (PL) emission spectra enabled the determination of Eu ³⁺ location asymmetry in the host via Judd-Ofelt (J-O) theory, from which Ω 2 = 9.37 × 10 − 20 c m 2 and Ω 4 = 1.55 × 10 − 20 c m 2 were derived, proving that the Eu ³⁺ ions were non-centrosymmetrically located. This enhanced the Eu ^{3+ 5}D ₀ → ⁷F ₂ electric-dipole transition at 614.0 nm with the strongest emission from 30 mol% doping. 395 nm excited intense and narrow red spectral profiles which exhibited excellent colour coordinates ( x = 0.657, y = 0.342), quantum efficiency (25.7% at a film thickness of ∼380 nm), and colour purity of (92.0%) whereby the red to orange ratio ( R : O) enables colour tailoring with 5 mol% to 30 mol% Eu ³⁺doping. This facilitates flexible control over the colour output, ensuring that it can be easily tailored to meet specific application requirements. The aforementioned results indicate that the red-emitting Eu ³⁺ activated amorphous BaTiO ₃ ultra-thin film phosphors exhibit promising potential for application in n-UV excited WLEDs as a red phosphor with a branching ratio β 0 → 2 = 81.43 % making it a potential candidate for red laser materials too.