TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Composition: The solar cell absorber composition or the photovoltaic device further comprises: ligand attached to the compound. Preferred Method: The method (M1) further involves attaching a ligand to a nanoparticle prior to coating. In the method (M1), the ligand and the solvent both comprise pyridine; the nanoparticles are sintered at 200-600 degrees C; and the sintering is done under a selenium atmosphere.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The nanoparticles comprise a compound of formula CuxZnySnz(SaSeb)4, where x/(y+z) is 0.7-1.2; y/z is 0.7-1.5 and a+b is 1. The nanoparticles are sintered. The sintered nanoparticles comprise a compound of formula Cu2ZnSnSe4, Cu2ZnSnS4 and/or Cu2ZnSnSxSe4-l. The Sn(Zn) defect centers are less than the Sn(Cu) defect centers. The nanoparticles comprise a compound having a direct bandgap of 0.7-1.8 eV. The nanoparticles are dispersed in an organic solvent and the dispersion has a viscosity of 1-100 cP.l=0-4.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The ligand contains compound chosen from alkyl phosphine, alkyl phosphine oxide, alkyl phosphonic acid, or alkyl phosphinic acid, alkyl carboxylic acid, pyridine, cyclic ether, amine, hydrazine and alkyl hydrazine (preferably pyridine). EXAMPLE - Copper(II) acetylacetonate (0.52 g), zinc acetate (0.29 g), dihydrate stannous chloride (SnCl2.2H2O) (0.18 g) and sulfur (S) (0.13 g) were added to oleylamine (40 ml) in a flask. The mixture was degassed under vacuum for 2 hours, purged with argon (Ar) for 30 minutes, heated at 280 degrees C for 1 hour, and then cooled to room temperature. The nanocrystals were collected by precipitation with ethanol followed by centrifugation. Pyridine (10 ml) was added to the final precipitation and refluxed for an extended period of time to replace the original ligand oleylamine. The pyridine exchanged nanoparticles were purified by precipitation with hexane and redispersed in pyridine at a desired concentration to form a viscous ink. The band gap of the Cu2ZnSnS4 (CZTS) nanoparticles was estimated to 1-1.5. The average composition of the CZTS nanoparticles was determined. In a method of making nanoparticles various ligands were used to complex with metals during the precipitation process to prevent homogeneous nucleation (precipitation).