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

Abstract

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 D-5(0) -> F-7(2) 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 = similar to 0.69, y = similar to 0.30) fall within the red color region. The J-O parameters (Omega(2), Omega(4)) were calculated following the emission spectra of Eu3+-doped samples and the intensity parameters (Omega(2)>Omega(4)), 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 (beta(R)) & experimental (beta(exp))), stimulated emission cross-section (sigma(E)(p)), gain bandwidth (sigma(E)(p) x lambda(eff)), and optical gain (sigma(E)(P) x tau(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 sigma(E)(P) = 19.684 x 10(-21) cm(2), beta(exp) = 0.759, tau(exp) = 1.325 m s, minimum non-radiative relaxation, W-NR = 296/s, and 60.78% of quantum efficiency (eta) for 1.0 mol% Eu3+-doped glass for D-5(0) -> F-7(2) transition indicates its promising features for red light-emitting optical devices and also as a red component in WLEDs.