The Effect of Oxygen in [Sigam]3(114) CulnSe sub(2) Grain Boundary

Using density functional theory calculation, we show that oxygen (O) exhibits an interesting effect in CuInSe2. The Se atoms with dangling bonds in a Se-rich [Sigam]3 (114) grain boundary (GB) create deep gap states due to strong interaction between Se atoms. However, when such a Se atom is substituted by an O atom, due to their smaller atomic size and stronger electronegativity, the deep gap states are shifted to lower energy regions close or even below the top of the valence band, which is beneficial to CuInSe2 solar cell.