Photoluminescence lifetime stability studies of β‐diketonate europium complexes based phenanthroline derivatives in poly(methyl methacrylate) films oleh Othmane Essahili, Dr. Mouad Ouafi, Asst. Prof. Dr. Mohamed Ilsouk, Dr. Omar Lakbita, Dr. Carine Duhayon, Dr. Lhassane Mahi, Assoc. Prof. Dr. Omar Moudam