Control of electronic structure in (Cu, Ag)(Ga, In)Se2 for high efficiency solar cells

Abstract

Abstract A three-dimensional (3D) band-gap energy (E g) map was constructed for a (Cu1−y Ag y )(Ga x In1−x )Se2 (CAGISe) system. This system’s E g increases monotonically from CuInSe2 (CISe) as the ratios of both Ga/(Ga+In) [GGI], x, and Ag/(Cu+Ag) [ACA], y, increase. Furthermore, the energy levels of the VB maximum (VBM) and the conduction band minimum (CBM) were also mapped in 3D. In this CAGISe system, there is no significant change in VBM, whereas CBM does show an increase as the GGI ratio increases. However, as the ACA ratio increases, there is a decrease in VBM level but no significant change in CBM. The substitution effects of Ga for In and Ag for Cu in CISe are discussed on the basis of “principles of orbital interaction.”