Quaternary Culn(S1-xSex)2 Nanocrystals: Facile Heating-Up Synthesis, Band Gap Tuning, and Gram-Scale Production

Tetragonal chalcopyrite Culn(S1-xSex)(2) (0 <= x <= 1) nanocrystals were synthesized by reacting a mixture of CuCl, InCl3, S, and Se in the presence of oleylamine at 265 degrees C. The S/Se composition ratio in the CuIn(S1-xSex)(2) could be tuned across the entire composition range of x from 0 to 1 by modulating the S/Se reactant mole ratio. The tetragonal lattice constants, that is, a and c, increase linearly with the increase of Se content, following Vegard's law. The band gap energies of CuIn(S1-xSex)(2) nanoaystals could be tuned in the range between 0.98 and 1.46 eV and change nonlinearly with respect to x, deriving a bowing parameter of 0.17 eV. In addition, the method developed in this study was scalable to achieve gram-scale production of stoichiometry-controlled CuIn(S1-xSex)(2) and CuIn1-xGaxSe2 nanocrystals.