TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - The substrate comprises a metal foil substrate, a glass substrate, a ceramic substrate, aluminum foil and a polymer substrate. The bulk precursor layer is formed by depositing Cu, Zn, Sn and at least one of S and Se all together onto the substrate using solution coating, evaporation, electrochemical deposition, or sputtering. The bulk precursor layer is formed by depositing a stack of layers on the substrate, where each of the layers contains at least one of the Cu, the Zn, the Sn and the at least one of S and Se, and where each of the layers is deposited using solution coating, evaporation, electrochemical deposition or sputtering. The bulk precursor layer is formed by the steps of: forming a solution or dispersion comprising Cu, Zn, Sn and least one of S and Se in a solvent; and depositing the solution or dispersion on the substrate. The solution is deposited on the substrate using a solution coating process selected from spin coating, dip coating, doctor blading, curtain coating, slide coating, spraying, slit casting, meniscus coating, screen printing, inkjet printing, pad printing, flexography, and gravure printing. The bulk precursor layer is formed on the substrate to a thickness of 100 nanometers to about 5 micrometers. The capping layer is formed on the bulk precursor layer by the steps of: dissolving at least one of Sn, S and Se in a solvent to form an ink; and depositing the ink on the bulk precursor layer to form the capping layer. The ink is deposited on the bulk precursor layer using a solution coating process selected from spin coating, dip coating, doctor blading, curtain coating, slide coating, spraying, slit casting, meniscus coating, screen printing, inkjet printing, pad printing, flexography, and gravure printing. The capping layer comprises only one of S and Se. The bulk precursor layer and the capping layer are annealed in an environment containing at least one of nitrogen, argon, helium, hydrogen, forming gas, S vapor, Se vapor, Sn vapor, water vapor and oxygen vapor.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - The solvent is selected from hydrazine and hydrazine-water mixtures, with hydrazine content of 0.1-99.9%.