Dear Husnain, did you try include any heating process. Sintering can also assist in good film formation. Concerning the deposition method, it is very hard (but feasible) to control get a quality film of CZTS, you may also try other techniques such as PVD, CBD. I am sceptical about the dispersion (suspension) of  precursors with your solvents. Good luck

Such questions set incorrectly

you can reduce the molar concentration of salts.

change the order of metal salts added in the solvent. add the tin salt firstly