In addition to Ag, you can also try Indium, Antimony and Bismuth. These elements have been found to increase the conductivity in glassy Se and Se-Te. They may be effective in CdSe films also.
I agree with the previous opinions. You can improve the electrical conductivity of cadmium selenide (CdSe) films you can add any metal element (ordinary metal or transition metal element) such as Ag, In, Sn, Bi, Zn, Sn, .... But the most suitable one is zinc element where it has the same valence an Cd and Se.