NOVELTY - Depositing a buffer layer having at least one sulfide of cadmium, indium, magnesium, zinc or tin on a copper indium selenide/sulfide (CIS) absorber layer comprises: (a) providing a solar cell slug; (b) treating the solar cell slug with an aqueous alkaline adsorber solution, at least one salt, a metal comprising cadmium, indium, magnesium, tin or zinc; (c) rinsing the solar cell slug with an aqueous alkaline rinsing solution; (d) treating the solar cell slug with an aqueous solution of a sulfur-donating substance; and (e) optionally multiple cyclic repeating of the steps (b)-(d).    USE - The method is useful for depositing a buffer layer (1) on a thin film CIS solar cell and manufacturing a copper indium selenide/sulfide thin film solar cell.    ADVANTAGE - The method: provides no mixing of the cation and sulfur-containing reactant, formation of a uniform buffer layer; uses less toxic metals and hence it is environment friendly; and requires less time for completion.    DETAILED DESCRIPTION - Depositing a buffer layer having at least one sulfide of cadmium, indium, magnesium, zinc or tin on a copper indium selenide/sulfide (CIS) absorber layer of a CIS-thin layer solar cell comprises providing a solar cell slug having a substrate deposited on a CIS-absorber layer; treating the solar cell slug at 30-90 degrees C with an aqueous alkaline adsorber solution, at least one salt, a metal comprising cadmium, indium, magnesium, tin or zinc of concentration 1-50 mmol/l; rinsing the solar cell slug with an aqueous alkaline rinsing solution; treating the solar cell slug at 30-90 degrees C with an aqueous solution of a sulfur-donating substance having a concentration of 30-120 mmol/l; and optionally multiple cyclic repeating of the steps (b)-(d) until full development of the buffer layer. An INDEPENDENT CLAIM is also included for the CIS thin layer solar cell prepared by the above method.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic representation of the structure of the solar cell.    Buffer layer (1)    Window layer (2a)    Intrinsic window layer (2b)    Chalcogen precursor layer (4a)    Metallic precursor layer (4b)