A series of copper doped sulpho-selenide binary solid solutions, giving electroluminescent emission, right from green to red, has been prepared using ZnS and ZnSe in varying proportions. The behaviour of such polycrystalline samples was studied by usual methods in audio-frequency range. While the hydrogen ion acted as the main donor impurity in the entire series, its comparative study was made with chlorine coactivated samples. As regards the electroluminescent emission, while in the case of hydrogen coactivation, it is the transition from donor levels to the copper level that predominates, Cl-coactivation favoured direct transition from conduction band to same fundamental copper level. On frequency variation while the samples with ZnS-ZnSe composition showed marked peak shifts in their respective emission bands, no such effect could be observed in samples with single base.