TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: In the method, 5-30 vol.% of 1-5C alcohol is added to the metal complex solution. Preferred Components: At least one metal or metal compound is copper element, zinc element, gallium element, indium element, germanium element, tin element, copper metal, copper hydroxide, copper sulfide, copper selenide, cupric oxide, cuprous oxide, silver oxide, silver sulfide, zinc metal, zinc selenide, zinc oxide, zinc hydroxide, indium selenide, indium oxide, indium sulfide, gallium oxide, tin metal, tin sulfide, tin selenide (SnSe), tin selenide (SnSe2), tin oxide or germanium oxide. EXAMPLE - 383 mg of Metal copper and 1903.2 mg of selenium were stirred in 10 ml of dimethyl sulfoxide (DMSO) for 3 days in the presence of 2 equivalents of hydrazine relative to the copper metal. Then, the remaining hydrazine was removed by flowing nitrogen, followed by concentration. The obtained concentrated solution was subjected to filtration using a 0.2 mu m PTFE filter, thus obtaining a hydrazine-coordinated copper-selenium complex/DMSO solution (solution-A). 356 mg of Metal tin and 711 mg of selenium were stirred in 5 ml of hydrazine for 3 days. Then, the remaining hydrazine was removed by flowing nitrogen, thus obtaining a crude product. The crude product was extracted with DMSO (at 80 degrees C, for 1 hour), followed by filtering the extract using a 0.2 mu m PTFE filter. Subsequently, isopropanol (IPA) was added and stirred, thus precipitating a dark-red product. Then, supernatant was removed, and the precipitate was washed with IPA and dried, thus obtaining a dark-yellow hydrazine-coordinated tin-selenium complex (solution-B).460 mg of Zinc selenide and 1588 mg of selenium were stirred in 8 ml of DMSO at room temperature for 1 week in the presence of 3 equivalents of hydrazine relative to zinc selenide. Then, the remaining hydrazine was removed by flowing nitrogen, thus obtaining a reaction intermediate solution. Subsequently, the reaction intermediate solution was extracted with DMSO or under heated conditions i.e. at 80 degrees C for 1 hour. Then, the extracted liquid was subjected to filtration using a 0.2 mu m PTFE filter, followed by concentration under reduced pressure. The obtained concentrated solution was filtered, thus obtaining a hydrazine-coordinated zinc precursor solution (solution-C). 322.8 mg of Selenium was added to 255.4 mg of sodium selenide and stirred in 10 ml of DMSO for 1 week, thus obtaining a homogeneous black solution (solution-D). 2.132 ml of Solution-A, 3.184 ml of the solution-B, and 25 ml of the solution-C were mixed together, and then the resulting solution was distilled to concentrate the solution to a desired concentration, followed by addition of 0.054 ml of the solution-D, thus preparing a copper zinc tin sulfur and selenium (CZTS)/DMSO precursor solution. To the obtained CZTS/DMSO precursor solution 0.1 vol.% of ethanol was added, thus obtaining the coating solution for forming a CZTS layer.