Unusual Effect of Cerium Codoping on Stokes and Anti-Stokes Luminescence of BiOCl:Er 3+ Crystal

Effect of cerium codoping on Stokes or anti-Stokes luminescence of BiOCl:Er ³⁺ crystals, which were controlled by a special photon avalanche (PA) mechanism under 980-nm excitation, was investigated. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis indicate that Ce ³⁺ ions were successfully doped into BiOCl lattices. However, in PA photoluminescence behaviors, the doped Ce ³⁺ ions did not present efficient resonant energy transfer (ET) processes between the Er ³⁺ ions as generally reported. As a result, the intensity of visible PA upconversion emission and 1.54 $mutext{m}$ downshifting near-infrared (NIR) emission of Er ³⁺ ions shows the same concentration dependence of cerium dopants. This phenomenon can be understood by the influence of cerium dopant content on the magnitude of internal electric field in layered BiOCl crystals, which may play a more important role on the upconversion (UC) and NIR luminescence of Er ³⁺ than the traditional ET between rare-earth (RE) ions. The results of our work may offer a different understanding for the method to control the emissions of RE ions.