In this work, first principle calculations of Cu_2ZnSnS_4 (CZTS), Cu_2ZnGeS_4 (CZGS) and Cu_2ZnSiS_4 (CZSS) are performed to highlight the impact of the cationic substitution on the structural, electronic and optical properties of kesterite compounds. Direct bandgaps are reported with values of 1.32, 1.89 and 3.06 eV respectively for CZTS, CZGS... Show more