Visible to infrared down conversion of Er3+ doped tellurite glass for luminescent solar converters

A series of tellurite glasses having the composition70TeO2–20ZnO–(10-x)Nb2O5 (in mol%) doped with Er3+ ion (x = 0.5, 1.0, 1.5, 2.5, 3, 3.5 and 4 mol% respectively) was synthesized using the melt quenching route. Based on the Raman analysis and Differential Scanning Calorimetry, the produced glasses exhibited low-phonon (772 cm−1) energy and good thermal stability (147 °C), respectively. The X-ray (XR) diffraction proved the amorphous state of the synthesized glasses, which highlights the high quality of the obtained glass materials. The impact of Er2O3 content on the local structure around erbium ions was investigated via Judd-Ofelt theory. Various radiative parameters such as the quality factors (χ), the branching ratios (β), the quantum efficiencies (η) and radiative lifetimes (τR) have been reported and discussed. The Down-conversion (DC) energy-process in the Er3+ ions was analyzed using an excitation wavelength of 488 nm and the different mechanisms involved in the 1.53 µm emission are discussed. The effect of erbium content on the measured lifetime of the 4I13/2state was analyzed according the M. Inokuti and F. Hirayama (I-H) model. For high concentrations of Er2O3 oxide, the obtained results showed an efficient energy transfer between Er3+ ions, which may cause the luminescence quenching and the reduction in radiative parameters of the 4I13/2 → 4I15/2 transition at 1.53 µm. While the addition of Er2O3 oxide at low content up to a concentration of 4.211020 cm−3 showed that this glass possessed high quantum efficiency (91%), large emission cross section of about 9.1 10−21 cm2 and effective bandwidth exceeding 100 nm attributed to the 1.53 µm emission, which makes the proposed tellurite glass highly promising in many photonic applications, especially for the design of luminescent solar concentrators (LSC) for bandgap solar cells in the range of 0.7–0.9 eV.