NOVELTY - Production of layered stack (3) having copper-zinc-tin sulfide/selenide compound semiconductor (6) involves providing substrate (2), depositing barrier layer (4), electrode layer (5), primary precursor layer and secondary precursor layer, supplying process gas during annealing of precursor layers, and depositing elemental sodium on precursor layers. The compound semiconductor (6) is produced in such manner that sodium content at primary boundary face (11) is maximal and continuously decreases towards secondary boundary face (12) to be minimal at secondary boundary face (12).    USE - Production of layered stack used for manufacture of thin-film solar cell (claimed).    ADVANTAGE - The thin-film solar cell having improved conversion efficiency is economically manufactured using the layered stack.    DETAILED DESCRIPTION - Production of layered stack (3) having a copper-zinc-tin sulfide/selenide (Cu2ZnSn(S,Se)4) compound semiconductor (6) involves providing substrate (2), depositing barrier layer (4) containing material to inhibit diffusion of alkali metal on the substrate, depositing electrode layer (5) on barrier layer, depositing primary precursor layer containing metal copper, zinc and tin, depositing secondary precursor layer containing chalcogen(s) chosen from sulfur and selenium on primary precursor layer, annealing the precursor layers to crystallize the compound semiconductor, supplying process gas(es) during annealing of the precursor layers, and depositing elemental sodium and/or sodium-containing compound on precursor layers and/or electrode layer before, after or during annealing of precursor layers. The compound semiconductor (6) is produced in such manner that sodium content at primary boundary face (11) is maximal and continuously decreases towards secondary boundary face (12) to be minimal at secondary boundary face (12), sodium content at primary boundary face (11) is minimal and continuously increases towards secondary boundary face (12) to be maximal at secondary boundary face (12), sodium content at primary boundary face (11) has a primary maximum, decreases towards secondary boundary face (12) to minimum, and increases towards secondary boundary face (12) to secondary maximum, or sodium content at primary boundary face (11) has primary minimum, increases towards secondary boundary face (12) to maximum, and decreases towards secondary boundary face (12) to secondary minimum, or produced in such manner that sulfur content at primary boundary face (11) is maximal and continuously decreases towards secondary boundary face (12) to minimal at secondary boundary face (12), sulfur content at primary boundary face (11) is minimal and continuously increases towards secondary boundary face (12) to maximal at secondary boundary face (12), sulfur content at primary boundary face (11) has primary maximum, decreases towards secondary boundary face (12) to minimum, and increases towards secondary boundary face (12) to secondary maximum, or sulfur content at primary boundary face (11) has primary minimum, increases towards secondary boundary face (12) to maximum, and decreases towards secondary boundary face (12) to secondary minimum. When sulfur or selenium is contained in secondary precursor layer, other chalcogen and/or compound containing the other chalcogen is contained in process gas. When sulfur and selenium are contained in secondary precursor layer, sulfur and/or selenium and/or a compound containing sulfur and/or a compound containing selenium is contained in process gas. The primary boundary face (11) is more distanced from substrate (2) than secondary boundary face (12). An INDEPENDENT CLAIM is included for manufacture of thin-film solar cell (1).    DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional view of the thin-film solar cell manufactured using the layered stack.    Solar cell (1)    Substrate (2)    Layered stack (3)    Barrier layers (4,7)    Back-electrode layer (5)    Compound semiconductor (6)    Primary boundary face (11)    Secondary boundary face (12)