First-Principles Study of Diffusion of Cu and In Atoms in CuInSe2

Cu and In diffusion in Cu-poor CuInSe2 (CIS) with a Cu vacancy have been investigated by first-principles calculations with the generalized gradient approximation. The activation energies and migration pathways are obtained by means of the combination of linear and quadratic synchronous transit (LST/QST) methods and nudged elastic band (NEB) method. The activation energy of Cu migration was 1.06 eV, which is 0.44 eV lower than that of the moving Cu atom located at the center of octahedral site and 0.17 eV lower than that of the moving Cu atom located at center of tetrahedral site. In the transition state, the moving Cu atom is located at the point between the center of the octahedral site and Se atom, which is saddle point of electrostatic potential. The activation energy of In migration (1.70 eV) is much higher than that of Cu migration. The In atom at Cu site (In-Cu) in Cu-poor CIS is scarcely to occur at room temperature. (C) 2013 The Japan Society of Applied Physics