Photoluminescence properties and energy-level diagrams in (Ce3+, Tb3+)-codoped KCl green phosphor

KCl:Ce3+, Tb3+ green phosphor was synthesized from an aqueous solution of KCl-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 KCl:Ce3+, Tb3+ phosphor showed a strong Tb3+-related emission in the 480-700 nm spectral region. The Tb3+-related emission intensity in the codoped phosphor was enhanced more than 300 times compared to that in the Tb3+ singly doped phosphor. This enhancement in the PL intensity could be attributed to an efficient energy transfer from Ce3+ to Tb3+ in the KCl host. The maximum transfer efficiency was η ~92% for the sample synthesized at a solution of KCl:CeCl3:TbCl3=1:0.01:0.05 in molar ratio. The (Ce3+, Tb3+) concentration dependences of the Ce3+- and Tb3+-emission decay times were determined. The temperature dependence of the Tb3+-related emission intensity was also measured and analyzed from T=20-450 K.