Band gap control via tuning of inversion degree in CdIn2S4 spinel

Based on theoretical arguments, we propose a possible route for controlling the band-gap in the promising photovoltaic material CdIn₂S₄. Our ab initio calculations show that the experimental degree of inversion in this spinel (fraction of tetrahedral sites occupied by In) corresponds approximately to the equilibrium value given by the minimum of the theoretical inversion free energy at a typical synthesis temperature. Modification of this temperature, or of the cooling rate after synthesis, is then expected to change the inversion degree, which in turn sensitively tunes the electronic band-gap of the solid, as shown here by screened hybrid functional calculations.