Thin film solar cell based on Cu(In,Ga)Se2 contain a thin, chemically deposited (CBD), cadmium sulfide (CdS) buffer layer. For environmental and industrial reasons, its replacement by a Cd-free material deposited under vacuum is among the challenges of the research community. In this work, co-sputtered (PVD)Zn(O,S) thin films have been studied as an alternative buffer layer. The properties of these layers have been compared to an optimized (CBD)Zn(O,S) reference. It is observed that the deposition technique has a strong impact on the optical and structural properties of the films for a given composition. As a result, the electrical behavior of the corresponding devices is also affected. The electrical characterization of (CBD)Zn(O,S)-buffered solar cells has shown that the absorber and the window layers properties strongly influence the performance of the cells. These progress together with the understanding of Zn(O,S) films properties makes it possible the realization of 16 % efficiency stable devices with a (CBD)Zn(O,S) buffer layer. Meanwhile, the tuning of the sulfur content has lead to the control of the conduction band offset in CIGSe/(PVD)Zn(O,S) devices and the achievement of similar Jsc than the one of (CBD)Zn(O,S)-buffered devices. Although the present structure of the (PVD)Zn(O,S) buffer layer is not suitable to obtain comparable Voc, these results offer many research perspectives in hetero-interface for a better understanding of Cu(In,Ga)Se2-based solar cells.
