Junction formation at the interface of CdS/CuInxGa(1 −x)Se₂

This is the authors' abstract. We don't add key points for this paper.

The interfacial band alignment and chemical composition at the cadmium sulfide (CdS)/copper indium gallium diselenide (CuIn x Ga 1− x Se 2 : CIGS) heterojunction was investigated by photoelectron spectroscopy. Over the two different interfaces made by either thermal deposition of CdS on a CIGS film or step-by-step etching of a chemical-bath deposited (CBD)-CdS/CIGS film by Ar + ions, the valence band maximum and conduction band minimum were determined using ultraviolet photoelectron spectroscopy and inverse photoemission spectroscopy, respectively. Concurrently, x-ray photoelectron spectroscopy was used to trace chemical changes across the interface. Both interfaces showed a In-rich and Cu-deficient profile. The thermal deposition of CdS on CIGS induces Cd–Cu intermixing and nonstoichiometric CdS formation associated with a strong band bending and high electron injection barrier. However, the CBD-CdS layer shows a rather sharp interface and negligible electron injection barrier in the conduction band, which will show better solar cell characteristics.