Enhancement of Long-Persistence by Ce Co-Doping in CaS:Eu[sup 2+], Tm[sup 3+] Red Phosphor

, , , , , , , and , , phosphors samples were prepared using a solid state chemical reaction method. Emission and excitation spectra of (peak emission observed at ) and (peak emission observed at ) were investigated. Neither singly doped sample nor and codoped sample had a long afterglow. , showed some afterglow with a short persistence. By incorporation of , an efficient energy transfer from to was found at a low doping concentration 0.1%. Emission intensity of was enhanced by 20%. Enhancement of long persistence of afterglow emission was achieved by co-doping in , as a durable sensitizer. For the triply doped , , it was found that the persistence time was 22% longer than that of , .