TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The metal chalcogenides comprise: at least one of copper, indium, gallium, zinc, tin, sodium, potassium, aluminum and phosphorus; indium selenide and copper sulfide; and at least one of copper selenide, copper telluride, indium sulfide, indium telluride, cadmium telluride, cadmium selenide, cadmium sulfide, gallium sulfide and gallium selenide. The solvent is hydrazine. The alkali metal or alkali metal compound comprises at least one of lithium, sodium (preferred), potassium, rubidium, carbons and francium. The alkali metal or alkali metal compound comprises an alkali metal salt, preferably at least one of carbonate, hydroxide or chalcogenide derivative alkali metal compound. The substructure is a complex substructure comprising layers of materials. The complex substructure includes at least one semiconductor sub-device, where the method produces a tandem semiconductor device that has at least two tandem semiconductor sub-devices. Preferred Method: The method-I further comprises: preparing a third precursor solution comprising a second metal chalcogenide dissolved in a third solvent prior to the combining; and combining the third precursor solution with at least one of the first and second precursor solutions prior to the combining or during the combining. The first, second and third solvents are substantially the same solvents. The method-II further comprises: bringing the substructure substantially to a predetermined temperature such that volatile components of the layer of the precursor solution evaporates and/or migrates from the layer as the layer of precursor solution becomes the semiconductor layer; and additional processing subsequent to the forming the layer of the precursor solution on the substructure. EXAMPLE - Sodium (1 mmol) or sodium selenide was placed in a screw cap glass vial to form sodium solution, then a hydrazine solution (0.5 ml) was added dropwise with a micropipette to the vial containing the (Na). The hydrazine was observed to react violently upon contact with sodium, indicated by fuming, followed by vigorous bubbling, once the bubbling subsided, an additional hydrazine (1.5 ml) was added to the vial. In another two separate vials, indium selenide and copper sulfide solutions were prepared by mixing indium selenide (1 mmol) in hydrazine (4 ml). The initially dark solution gradually turned into a transparent viscous oil-like solution after few days of continuous stirring. For copper sulfide precursor, copper sulfide (1 mmol) and sulfur (2 mmol) were mixed in hydrazine (4 ml). The initially blackish-yellow colored solution gradually became a transparent yellow solution after several days of continuous stirring. After both metal chalcogenides had completely dissolved, both mixtures were filtered to remove any insoluble species to form precursor solution comprising the indium selenide, copper sulfide, and sodium-solutions in various ratios.