Effect of lithium ion addition on afterglow time of green-emitting Ce3+ and Pr3+ codoped CaS phosphor by black light irradiation

This paper reports the effect of lithium ion addition on the afterglow time of green-emitting Ce3+ and Pr3+ codoped CaS phosphor by black light irradiation. CaS:Ce3+, Pr3+, irradiated with black light, emitted in the green region and showed afterglow. The afterglow time of CaS:Ce3+, Pr3+ was relatively short (about 10 min). When a Li+ invades the free space in a CaS crystal lattice, new cation vacancy is formed for the charge compensation in the Ca2+ site. The afterglow intensity of CaS:Ce3+, Pr3+, with Li+ incorporated in the host, increased to three times that of the original sample (CaS:Ce3+, Pr3+). The afterglow time of CaS:Ce3+, Pr3+, with Li+ incorporated was extended to 40 min.