Experiments on Electroluminescence

Abstract

A summary of recent observations of the properties of ZnS: Cu: Pb and ZnS: Cu: Pb: Mn electroluminescent phosphors is reported. The experiments include studies of the optical and electrical response of these phosphors dispersed in "Lucite" to sudden changes in a constant applied field, as well as microscopic studies of the luminescence of individual particles. Both green and yellow phosphors were studied. The most important results observed primarily on green phosphors are the following: Slow changes are found to take place in a phosphor in any given constant electric field, but a steady state is finally approached. A sudden departure from this state produced by changing the applied field will in general produce very little light compared to that produced on returning promptly to the conditions under which the steady state was established. Further, the luminescence in alternating electric fields of individual grains is extremely inhomogeneous, being restricted to small "pinpoints" or "spots" very much smaller than the individual particles. The spots studied luminesced only once per cycle.