Eu³⁺-doped fluoro-telluroborate glasses as red-emitting components for W-LEDs application

From 0.1 up to 2.5 mol% Eu³⁺-doped fluro-telluroborate glasses as red light-emitting components for white-light-emitting diodes (WLEDs) were investigated. Non-periodicity in the atomic arrangements was studied through the XRD pattern. The photoluminescence (PL) spectra were recorded under blue light (464 nm) excitation and analyzed. All the PL spectra exhibit an intense peak at 612 nm for ⁵D₀ → ⁷F₂ transition, revealing their red photoemission. Optimal PL emissions were achieved for 1.0 mol% Eu³⁺-doped sample. The CIE chromaticity coordinates for all the glasses (x = ~0.69, y = ~0.30) fall within the red color region. The J‒O parameters (Ω₂, Ω₄) were calculated following the emission spectra of Eu³⁺-doped samples and the intensity parameters (Ω₂>Ω₄), as well as the high asymmetry ratio (R/O), indicate the low ionicity in all the studied glasses. Using the J-O parameters, several radiative features like total emission transition probability (A_T), branching ratios (radiative (β_R) & experimental (β_exp)), stimulated emission cross-section (σ_P ^E), gain bandwidth (σ_P ^E × λ_eff), and optical gain (σ_P ^E × τ_rad) were evaluated. All the luminescence decay curves fit well to non-exponential function and decay times were decreased at Eu³⁺ concentration >0.5 mol%. The evaluated σ_P ^E = 19.684 × 10⁻²¹ cm², β_exp = 0.759, τ_exp = 1.325 m s, minimum non-radiative relaxation, W_NR = 296/s, and 60.78% of quantum efficiency (η) for 1.0 mol% Eu³⁺-doped glass for ⁵D₀ → ⁷F₂ transition indicates its promising features for red light-emitting optical devices and also as a red component in WLEDs.