TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Compositions: Molar ratio of copper salt to indium and gallium salts is 1:0.65-1:0.85. Group consisting of copper salts, indium salts, and gallium salts comprises salts selected from acetates, acetylacetonates, chlorides, bromides, and iodides. Nanoparticles are selected from tert., quat., and quinary chalcogenides of the form CulnwGaxSeySz including doped species and/or alloys. Nanoparticles are nanoparticles which are soluble and dispersible in solvent. Substrate is selected from indium tin oxide (ITO), molybdenum-coated bare glass, and molybdenum-coated soda-lime glass (SLG). At least one buffer layer contains CIGS nanoparticles having stoichiometry different from that of nanoparticles used to formulate the ink. Ratio of copper to indium (Cu/In) is less than or equal to 1. Sulfur-rich atmosphere is provided with hydrogen sulfide (H2S) gas in inert carrier gas. Selenium-rich atmosphere is provided with hydrogen selenide (H2Se) gas in inert carrier gas. The n-type semiconductor layer comprises material selected from cadmium sulfide (CdS), zinc oxysulfide (Zn(O,S)), zinc oxide (ZnO), and zinc sulfide (ZnS). Window layer contains aluminum zinc oxide (AZO) and boron-doped zinc oxide. Window layer contains ITO. Preferred Processes: Method includes cooling reaction solution to 3rd temperature and stirring for 2nd time interval after heating reaction solution to 2nd temperature. Method includes annealing reaction solution at temperature lower than 2nd temperature for 4-24 hours. Nanoparticles are isolated by precipitating nanoparticles from solution by addition of greater than or equal to 1 other solvent. CIGS nanoparticles are prepared by mixing copper salts, indium salts, and gallium salts in solvent at 1st temperature to produce reaction solution, adding organo-chalcogen precursor to reaction solution, heating reaction solution to 1st temperature while stirring for 1st time interval, heating reaction solution to 2nd temperature and adding 2nd chalcogen precursor over 2nd time interval, stirring reaction solution at 2nd temperature for 3rd time interval, cooling reaction solution to 3rd temperature and stirring for 4th time interval, cooling reaction solution to room temperature, and isolating nanoparticles. Photovoltaic device preparation includes performing greater than or equal to 1 film processing step subsequent to step (d) selected from annealing, sintering, selenization, and etching with potassium cyanide (KCN). Steps (b) and (c) are repeated until CIGS film thickness is greater than or equal to 1 mu m. At least one buffer layer is deposited onto substrate and processed prior to deposition of ink. Film is annealed at 1st lower temperature of 250-300 degrees C for 3-7 minutes then subsequently annealed at 2nd higher temperature of 400-430 degrees C for 3-7 minutes. CIGS-based photovoltaic device preparation includes performing greater than or equal to 1 film processing step subsequent to step (d), such has sulfurization process in which CIGS film is annealed in sulfur-rich atmosphere and selenization process in which CIGS film is annealed in selenium-rich atmosphere. Selenization process effects conversion of excess copper in CIGS nanoparticles to copper selenide. Selenization process effects partial conversion of copper indium sulfide (CuInS2) layer to copper indium selenide (CulnSe2). CIGS-based photovoltaic device preparation includes etching CIGS film in KCN solution to selectively remove excess copper selenide and/or copper sulfide phases from CIGS absorber layer. Preferred Conditions: The 1st temperature is room temperature to 100 degrees C. The 2nd temperature which is higher than the 1st temperature is 160-240 degrees C, preferably 120-160 degrees C. The 1st time interval is time sufficient to effect distillation of all volatile by-products. The 3rd time interval is 30 minutes to 2 hours. The 3rd temperature is 80-120 degrees C. The 4th time interval is 3-6 hours. Preferred Parameters: Thickness of buffer layer is less than or equal to 100 nm.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Compositions: Solvent is non-coordinating solvent e.g. 1-octadecene, benzylether, diphenylether, and heat transfer fluid containing hydrogenated terphenyl. Organo-chalcogen precursor is represented by formula R-X-H. Organo-chalcogen precursor is selected from 1-octanethiol, 1-octane selenol, and 1-dodecane selenol. The 2nd chalcogen precursor comprises elemental chalcogen dissolved in coordinating solvent. Coordinating solvent is selected from trioctylphosphine sulfide and trioctylphosphine selenide. Solvent is selected from toluene, alkane, dichloromethane, chloroform, isophorone, anisole, alpha -terpinene, and limonene. Ink further contains 2-5 wt.% oleic acid with respect to total ink formulation. Preferred Parameters: Organo-chalcogen precursor has boiling point of less than or equal to 250 degrees C.R=alkyl or aryl;X=S or Se;w= greater than or equal to 0;x= less than or equal to 1;w+x= less than or equal to 1;y, z= greater than or equal to 0; andy+z=2.