TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The capping agent is Lewis base or electron pair-donor group or group that can be converted into electron pair-donor group. The film includes a first layer comprising nanoparticles, and a second layer comprising binary semiconductor, chalcogen source, and/or sodium-containing material. The chalcogen source comprises chalcogen particles and/or binary chalcogenide particles. The sodium-containing material is sodium salt of deprotonated acid, sodium hydroxide, and/or sodium sulfide. Preferred Process: Individual metal salts and/or complexes of copper, zinc and tin are separately added in sequence to a mixture of solvent and first capping agent to form reaction mixture, followed by addition of chalogen precursor to the reaction mixture. The process includes reacting the mixture with second capping agent having greater volatility than the first capping agent; or recovering nanoparticle from the reaction mixture and reacting the nanoparticle with second capping agent. Film formation further includes heating the film in inert atmosphere or in atmosphere comprising selenium vapor, sulfur vapor, hydrogen, hydrogen sulfide, and/or hydrogen selenide; and contacting the film with second capping agent. Preferred Properties: The nanoparticle has longest dimension of 1-1000 nm and/or kesterite structure. The capping agent has boiling point of less than 150 degrees C at ambient pressure. The second capping agent has boiling point of less than 200 degrees C at ambient pressure. Preferred Ratio: The molar ratio of copper, zinc, tin and chalcogen is 2:1:1:4, or the molar ratio of copper to zinc+tin is less than 1, or the molar ratio of zinc to tin is greater than 1.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The capping agent is organic molecule having nitrogen-, oxygen-, sulfur-, or phosphorus-based functional group. The sodium-containing material may be sodium salt of deprotonated alcohol and/or sodium acetate. The ink further comprises binder(s) or surfactant(s), preferably decomposable binder, decomposable surfactant, cleavable surfactant, and/or surfactant with boiling point of less than 250 degrees C. EXAMPLE - A solution of zinc chloride (80 mg) in oleylamine (10 ml) and a solution of tin (II) chloride (102 mg) in oleylamine (10 ml) were mixed in a flask that was previously degassed and heated to 110 degrees C under argon atmosphere. After 5 minutes of stirring, a solution of cuprous chloride (77 mg) oleylamine (10 ml) was added, and the resulting solution was stirred for additional 5 minutes. A solution of sulfur (163 mg) of dissolved in oleylamine (10 ml) at 100 degrees C was added, and the reaction temperature was increased to 230 degrees C at 10 degrees C/minute. After reaching 230 degrees C, the system was maintained at this temperature for 10 minutes and heating was turned off. The reaction was cooled naturally with stirring, followed by addition of ethanol (80) ml. The particles were collected via centrifugation and decanting solvent. The presence of kesterite structure was determined by X-ray diffraction.