Chalcopyrite CuIn1- xGaxSe2 (CIGS; x < 0.3) nanoparticles were synthesized by reacting CuCl, InCl3, GaCl3 and Se in oleyl amine over 250 degrees C. Depending on the reaction temperature and duration, the obtained nanoparticles had sizes of less than 100 nm and different chemical compositions. Because the atomic percentage of Se decreased with increasing reaction time, the proportion of Se and Ga content also changed. Furthermore, the lattice parameters, a and c, changed with increasing reaction temperature and time. Lastly, the bandgap energies of the CIGS films coated on glass plates were similar to 0.98 eV and did not significantly change with increasing heat- treatment temperature. (C) 2013 Elsevier B.V. All rights reserved.