Photoluminescence and photocurrent characteristics of Eu2+ activated MAl2O4 (M = Ba, Ca, Sr) phosphors

Photoluminescence and photocurrent characteristics of Eu2+ activated MAl2O4 ( M = Ba, Ca, Sr) phosphors during and after Ultraviolet ray and visible light irradiation have been investigated. The photoluminescence (PL) and the photocurrent ( PC) of the phosphors, in order to elucidate the relationship between the PL and the PC, were measured simultaneously on the same samples within a specially designed measuring box. Composition effects, such as a presence of Dy3+ as a co-activator and Al-rich composition on the PL and PC characteristics have been investigated. Also, sensing characteristics on UV and visual light have been tested. The simultaneous measurement of PL and PC on the same sample clearly indicated that the presence of co-activator and vacant site, namely Al-rich composition, acted as a hole trap; the introduction of co-activator and vacant site decreased the PC and increased the PL during and after UV and visible light irradiation, whose PC was much lower than that of MAl2O4 with only Eu2+ as an activator. The electrical intensity affected on the PL characteristics after UV and visual light irradiation( afterglow); with increasing in the electrical intensity, the afterglow lasted more longer and intensively. The PC of MAl2O4 showed a good proportional relationship to UV and visible light intensity. Especially, SrAl2O4 showed an excellent linearity within 1-5 mW/cm(2), but showed somewhat delayed response and hysterisis as seen in CdS photoelectric cell.