Systematic studies on electronic structures of CuInSe 2 and the other chalcopyrite related compounds by first principles calculations

Abstract

We have systematically studied electronic structure of chalcopyrite-type CuInSe 2 and the other chalcopyrite compounds, ABX 2 (A = Cu, Ag; B = In, Ga, Al; X= Se, S). First-principles calculations were performed within a density functional theory with the generalized gradient approximation (GGA), using a planewave pseudopotential method. Valence band maximum (VBM) of CuBX 2 is an antibonding state of Cu 3d and Se 4p (S 3p), while conduction band minimum (CBM) is also an antibonding state derived from B ns and Se 4p (S 3p). Theoretical band gap increases at the order of In, Ga, Al and the values of sulfides, CuBS 2 were larger than those of the corresponding selenides, CuBSe 2. In present study, we found that the lowest unoccupied ns orbital of B atom in the conduction band shift up to higher energy. Therefore, the band gaps of CuBSe 2 (CuBS 2) increase at the order of In, Ga, Al with shifting of ns orbital for B atom. © 2006 WILEY-VCH Verlag GmbH & Co. KGaA.