TECHNOLOGY FOCUS - ELECTRONICS - Preferred Device: The device further comprises an electrically conductive layer on the substrate.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: In the method, the conditions comprise a temperature of -50 degrees C to 300 degrees C (preferably 15-250 degrees C). In the method (M2) and (M3), the conditions comprise a temperature of 20-300 degrees C. The metal-chalcogenide nanoparticles are isolated using centrifugation or filtration. In the method (M3), the ink is deposited on the substrate using spin-coating, dip-coating, doctor blading, curtain coating, slide coating, spraying, slit casting, meniscus coating, screen printing, ink jet printing, pad printing, flexographic printing or gravure printing. The metal-chalcogenide layer is heat treated at a temperature of 200-800 (preferably 400-600) degrees C. Preferred Components: The chalcogen element is selected from sulfur (S), selenium (Se) and tellurium (Te). The reducing agent has a carbon content of less than 2 atomic percent, and a metal content of less than 100 parts per million (ppm). The reducing agent contains at least one of the functional groups BH3 and BH4. The reducing agent is ammonia borane. The metal source (S1) is selected from elemental Cu, elemental Zn, elemental Sn, elemental Ge, elemental In, elemental Fe, elemental Ga, copper chloride, copper bromide, copper fluoride, copper iodide, zinc chloride, zinc bromide, zinc fluoride, zinc iodide, tin chloride, tin bromide, tin iodide, indium chloride, germanium chloride, gallium chloride, indium fluoride, indium bromide, indium iodide, iron chloride, iron bromide, copper acetate, zinc acetate, tin acetate, iron acetate, indium acetate, copper nitrate, zinc nitrate, tin nitrate, iron nitrate, indium nitrate, copper sulfate, zinc sulfate, tin sulfate, iron sulfate, indium sulfate, copper sulfide (CuS), Cu2S, copper selenide (CuSe), Cu2Se, Cu2SnS3, Cu4SnS4, Cu2SnSe3, CuInS2, CuInSe2, CuGaSe2, Cu(In,Ga)Se2, Cu(In,Ga)(S,Se)2, tin sulfide (SnS), SnS2, tin selenide (SnSe), SnSe2, zinc sulfide (ZnS), zinc selenide (ZnSe), Cu2ZnSnS4, Cu2ZnSnSe4, Cu2ZnSn(S,Se)4, iron sulfide (FeS), iron selenide (FeS2), copper acetylacetonate, zinc acetylacetonate, tin(II) phthalocyanine and iron pentacarbonyl. The metal source (S2) comprises a Cu source, a Sn source and a Zn source. The metal source (S2) is selected from elemental Cu, elemental Zn, elemental Sn, copper chloride, copper fluoride, copper bromide, copper iodide, zinc bromide, zinc fluoride, zinc chloride, zinc iodide, tin chloride, tin bromide, tin iodide, copper acetate, zinc acetate, tin acetate, copper nitrate, zinc nitrate, tin nitrate, copper sulfate, zinc sulfate, tin sulfate, CuS, Cu2S, CuSe, Cu2Se, Cu2SnS3, Cu4SnS4, Cu2SnSe3, ZnS, ZnSe, SnS, SnS2, SnSe, SnSe2, Cu2ZnSnS4, Cu2ZnSnSe4, and Cu2ZnSn(S,Se)4.    TECHNOLOGY FOCUS - METALLURGY - Preferred Components: The metal source (S1) is selected from Cu-Sn alloys, Cu-Zn alloys, Zn-Sn alloy, Cu-Al alloys, Cu-Ni alloys, Cu-In alloys, and In-Ga alloys. The metal source (S2) is selected from Cu-Zn alloys, Zn-Sn alloys, and Cu-Sn alloys.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The liquid medium (L1) comprises a solvent selected from water, ammonium hydroxide, ammonium hydroxide-water mixtures, alcohols, ethers, glycols, aldehydes, ketones, alkanes, amines, dimethylsulfoxide (DMSO), cyclic compounds and halogenated organic compounds. The liquid medium (L2) comprises the chalcogen-containing solution prepared according to the method (M1). EXAMPLE - A selenium (Se) powder (1.98 g) and ammonia borane (NH3BH3) (0.4 g), were mixed with ethylene glycol (CH2OH)2 (4 ml). The mixture was slowly heated to 80-100 degrees C under vigorous stirring on a hot plate. A red solution was formed after releasing a large amount of gas (possibly H2), as indicated by bubbling during the heat treatment. Then ammonia hydroxide (200-500 mu l) was used to accelerate the dissolving process, and to obtain chalcogen-containing solution.