Further studies on dc electroluminescent phosphors

Direct current electroluminescent (dcel) powder phosphors in the zinc sulphide: manganese, copper, system can now be readily prepared giving a luminance of 250 ft lamberts at 100 V and 5 mA cm −2 . Under continuous constant voltage operation at 100 V, the luminance falls to 100 ft lamberts in about 5 hours, and subsequently to 50 ft lamberts in about 25 hours. With constant power input a luminance of 100 ft lamberts has been maintained for a period of 400 hours. dcel has also been obtained in zinc selenide: manganese, copper powder phosphors. In addition to the yellow/orange emission due to manganese, green dcel emission has been observed in erbium activated zinc sulphide.