Impedance Changes Induced by Photoconductive Effect in ZnS:Cu, Cl Phosphors

Abstract

The photoconductivity of ZnS:Cu, Cl phosphors having green or blue emission is indirectly estimated from the capacitance changes induced by light. Under the irradiation of 365 mµ the photoconductive effect is remarkable in the green phosphors and is very small in the blue phosphors. This indicates that the electronic transition emitting green fluorescence is accompanied by a photoconductive process but the transition emitting blue fluorescence is not. In order to interprete the experimental results, three models are proposed for the emission mechanism in ZnS:Cu, Cl phosphors. An infrared photoconductive effect at 1.25 µ induced by previous irradiation of 365 mµ is observed with the green phosphors.