TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The nitrogen-containing reducing agent having a standard reduction potential is less than the standard reduction potential of selenium. The nitrogen-containing reducing agent is hydrazine. The copper salt is copper chloride, copper bromide, copper iodide, copper acetate, copper formate, copper nitrate, and/or copper trifluoromethanesulfonate. The liquid precursor comprises a copper concentration of 0.08-0.10 M. The deposited solid precursor comprises elemental selenium. The copper and selenium are present in a molar ratio of 1:3.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: The method further comprises the step of separating any precipitate formed during the combining step. In the method-1, the deposited solid precursor is a thin film, and the temperature is at least 50 degrees C, preferably 50-275 degrees C. The separation step is carried out using a process consisting of filtration, and/or centrifugation. The deposited solid precursor is copper selenide at least substantially in the form of CuSe2. In the method-1, the step of applying is implemented through a process consisting of drop coating, dip coating, spin coating, spraying, brushing, air brushing, ink jet application, stamping, printing, pouring, wiping, smearing, spray deposition, and/or slot coating. Preferred Components: The first and second solvents are primary amines, secondary amines, and/or glycols, preferably ethylene diamine. The first and second solvents are ethylene diamine, pyridine, ethanolamine, diethylene triamine, and/or ethylene glycol. The deposited solid precursor is characterized by an X-ray diffraction pattern as given in the figure of specification. The hydrazine-free solvent comprises solvent comprising glycols, and/or amines. EXAMPLE - Selenium powder (2.38 g) and ethylene diamine (40 ml) were placed in a flask under a nitrogen atmosphere to form a selenium in ethylene diamine solution, and anhydrous hydrazine (0.160 g) was added to the solution. The resulting red solution was added over a 45 minutes for a period to a stirred solution of copper formate (1.54 g) in pyridine (40 ml) to produce a dark red solution containing a small amount of solid precipitate. The precipitate was removed by filtration and the composition of the precursor solution was measured. The precursor composition was comprised of copper (25.4%) and selenium (74.6%).