X-ray photoemission analysis of CS treated polycrystalline 2 Cu In,Ga/Se2

Device-grade polycrystalline thin-film Cu In0.5Ga0.5.Se2 was treated with CS2 to determine the resulting microscopic surface compositionrmorphology. Scanning electron microscopy SEM. was used to evaluate the resultant surface morphology. Angle-integrated high-resolution photoemission measurements on the valence band Cu 3d.electronic structure and In 4drGa 3d, Se 3d and S 2p core lines were used to evaluate the chemistry of the CS2 treated surface. Results show that the surface has been planarized by the highly reactive CS2 treatment and that S has been incorporated at the surface, possibly creating a wider bandgap Cu In1yxGax. Se1yySy.2 surface layer. The purpose of this investigation is to find an environmentally safe replacement for the toxic CdS overlayer commonly used for heterojunction devices without sacrificing overall device performance and reliability. q1999 Elsevier Science B.V. All rights reserved