High Energy Transfer Efficiency in Photoluminescence of (Ce~(3+), Tb~(3+))-Codoped NaCl Green Phosphor

摘要

(Ce~(3+), Tb~(3+))-codoped NaCl phosphor was synthesized from an aqueous solution of NaCl-CeCl_3-TbCl_3. 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 (Ce~(3+), Tb~(3+))-codoped NaCl phosphor showed a strong Tb~(3+)-related emission in the 480-690 nm spectral region, together with a very weak Ce~(3+)-related emission at ~400 nm. The Tb~(3+)-related emission intensity in the codoped phosphor was enhanced more than 500 times compared to the Tb~(3+) singly doped phosphor. The enhanced emission intensity in the codoped phosphor could be attributed to an efficient energy transfer from Ce~(3+) to Tb~(3+). The maximum transfer efficiency was found to be η ~ 95% for the phosphor synthesized at a solution of NaCl: CeCl_3 : TbCl_3 = 1 : 0.1 : 0.01 in molar ratio. The PL decay times were ~20 ns and ~0.4-1 ms for the Ce~(3+) and Tb~(3+) emissions, respectively. The temperature dependence of the Tb~(3+)-related emission intensity yielded quenching energies of ~50 meV and ~0.40 eV below and above ~300 K, respectively.