BEHAVIOR OF SPRAYED CDS PHOTOELECTRODES ETCHED WITH AMMONIA SOLUTION

The behaviour of two CdS films of respectively 0.6 and 2.00 mu m thickness etched with ammonia solution is reported. The film surface treatment applied is optimised when the wetting of the sample into this solution takes 6-7 h. The CdS/(Sx-2/S-2) interface properties are unchanged with the treated films at least till the optimised point. The equilibrium potential of the redox couple is kept at -0.72 V/SCE. The flat-band potential value obtained is -1.50 V/SCE with the two samples, before the treatment and at the optimised stage. The improvement in the photocurrent property is similar with the two samples till this very point. The dissolution rate of the material from this point onwards depends upon the initial film thickness. The process involved has two steps. The first corresponds to a levelling of the film surface that certainly increases the electrochemical surface area and then explains the photocurrent improvement. The second leads to the destruction of the film surface and then leads to the decrease of this very film property.