Optical characteristics and Judd–Ofelt analysis of novel red phosphors Rb5La(MoO4)4:Eu3+ for plant-cultivation LEDs, w-LEDs, and latent fingerprint detection

A range of red-emitting Rb₅La(MoO₄)₄:xEu³⁺ phosphors with varying dopant concentrations (x = 0.05–1.00 mol) were prepared through high-temperature solid-state methods. Comprehensive characterization through X-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence spectroscopy analysis demonstrated its outstanding performance. Excitation at 395 nm wavelengths induced four distinct radiative transitions from the ⁵D₀ level to ⁷F₁ (591 nm), ⁷F₂ (616 nm), ⁷F₃ (657 nm), and ⁷F₄ (707 nm) levels. The Judd-Ofelt parameters (Ω₂, Ω₄) of Rb₅La(MoO₄)₄:Eu³⁺ phosphors were determined from the emission spectrum, confirming that Eu³⁺ occupies asymmetric positions within the crystal lattice of Rb₅La(MoO₄)₄. The luminescence intensity reached its maximum at 0.60 mol doping concentration, beyond which the interaction of the nearest-neighbor ions led to concentration quenching. Notably, all synthesized phosphors demonstrated exceptional color purity exceeding 99.8 %. The Rb₅La(MoO₄)₄:0.60Eu³⁺ is accompanied by an impressive internal quantum yield of 60.22 % and an activation energy (E_a) of 0.28 eV. The developed red-emission LED device showed remarkable spectral overlap with photosynthetic pigments such as chlorophyll b, phycocyanin, and phytochrome red P_R, which can provide supplementary light for plants in both the red (600–700 nm) wavelength range. A white light-emitting (w-LED) diode constructed with this phosphor exhibited a correlated color temperature (CCT) of 5407 K and a color rendering index (CRI, R_a) value of 90. The phosphor demonstrates fingerprint visualization capabilities, particularly in resolving Level I–III ridge details on multicolor substrates. Based on the above findings, Rb₅La(MoO₄)₄:Eu³⁺ phosphors hold considerable potential for applications in plant cultivation LEDs, w-LEDs, and fingerprint detection.