Spectroscopic characterisation of alternate current electroluminescent devices based on ZnS-Cu

The present study is focused on the spectroscopic properties of ac powder electroluminescent lamps, in which the electroluminescent materials are based on ZnS-Cu, in order to understand the mechanisms of the electroluminescence and improve their performances. To this purpose ad hoc sets of devices have been built and their performances have been evaluated by comparing spectroscopic measurements performed by changing alternatively the applied frequency and the voltage. The emission wavelength of these devices (i.e. the color of the lamps) is found to be strictly related to the applied frequency, while the voltage mainly determines the intensity of the emission. (C) 2002 Elsevier Science B.V. All rights reserved.