High Energy Transfer Efficiency in Photoluminescence of (Ce3+, Tb3+)-Codoped NaCl Green Phosphor

Abstract

(Ce3+, Tb3+)-codoped NaCl phosphor was synthesized from an aqueous solution of NaCl–CeCl3–TbCl3. The synthesized phosphor was investigated using X-ray diffraction analysis, electron probe microanalysis, diffuse reflectance measurements, photoluminescence (PL) analysis, PL excitation spectroscopy, and PL decay measurements. The (Ce3+, Tb3+)-codoped NaCl phosphor showed a strong Tb3+-related emission in the 480–690 nm spectral region, together with a very weak Ce3+-related emission at ∼400 nm. The Tb3+-related emission intensity in the codoped phosphor was enhanced more than 500 times compared to the Tb3+ singly doped phosphor. The enhanced emission intensity in the codoped phosphor could be attributed to an efficient energy transfer from Ce3+ to Tb3+. The maximum transfer efficiency was found to be η ∼ 95% for the phosphor synthesized at a solution of NaCl : CeCl3 : TbCl3 = 1 : 0.1 : 0.01 in molar ratio. The PL decay times were ∼20 ns and ∼0.4–1 ms for the Ce3+ and Tb3+ emissions, respectively. The temperature dependence of the Tb3+-related emission intensity yielded quenching energies of ∼50 meV and ∼0.40 eV below and above ∼300 K, respectively.