In order to investigate the role of sodium in CuInSe2 absorber layer, the formation energy of sodium induced point defects and bound defects in CuInSe2 were calculated using first principles calculations within the super-cell approximation approach. Neutral defect NaCu and acceptor defect NaIn were found to form easily, which explains the enhanced p-type conductivity of CuInSe2 by sodium incorporation. More than that, sodium induced defects were energetically favourable to form bound defects with intrinsic defects (i.e. VCu, Cui, InCu and VSe), which was responsible for the increased range of composition. The contour plot of total valence charge density suggested the chemical bonding between NaIn and Se atoms was stronger than that of Nai and NaCu.

Roles of Sodium Induced Defects in CuInSe2 by First Principles Calculation. X.Sun, F.Jiang, J.Feng: Computational Materials Science, 2009, 47[1], 31-4