We had experienced such coloration issues with: CS(NH2)2 , when we were obliged to provide S element to a spray pyrolysis precursor solution.

After hudreds of experiments, we discovered that if we replace our CHLORINE salts (CuCl2 &  ZnCl2), by SULFATES (CuSO4 & ZnSO4), ammoniacal ions coloration issues wre minimized.

Try this, and inform us about the outcome.

sincerely 

For the preparation of such thin layers by spray technique, you can use an aqueous solution containing a mixture of zinc chloride and copper chloride at low concentration (less than 10-2M) to this solution you add the thiourea (SC(NH2)2), the thiourea to zinc molar ratio should be between 3 and 4 to avoid the formation of the corresponding oxides. The spray temperature should not exceed 300 ° C and try to maintain a low flow rate to ensure evaporation of the solvent

Tank you very much prof. Karem Boubaker and prof. A. Boukhachem for your answers which we need. We will tel you the results. Kind regards.

Dissolution of Cu(tu)xCly complexes is limited. Clear solution you will be able to prepare at 2-4 mmol concentration of CuCl2 and precursor molar ratio Cu-S of 1-3 or 1-4. Solutions will be stable up to 30 min.

 Dear Svetlana Polivtseva .

Thank you very much for your answer which indicate that the mix solutions will be unstable after 30 min. and we must prepared the films during this time. 

Best bregards.

Dear H. Omran,

Have you ever checked the pH of the solution? You may adjust the pH of the solution to prevent milky colour.

All the best.

Dear Erkan Aydin 

Thank you very much for your answer , what is the proper PH value which prevent the solution milky color.