Indium-based interface chemical engineering by electrochemistry and atomiclayer deposition for copper indium diselenide solar cells

The key to achieve better Cu(In, Ga)Se-2 (CIGS) cells is through the improv ement of the CIGS/ZnO interface. In this work, we illustrate various approa ches, wet and dry, to engineer that interface with processes that avoid the use of Cd containing compounds. Wet chemical treatments have been performe d so as to test the possibility to improve that interface by surface doping of CIGS. X-ray photoelectron spectroscopy (XPS) and Kelvin probe studies s how that such doping is not achieved in the conditions leading to best devi ces. Rather, the most desirable feature of the surface treatments appears t o be surface passivation. We show that this can be achieved via CIGS surfac e reaction with In(III) ions, leading to 12.5% efficient devices. A well pa ssivated interface can also be achieved directly, using an all dry process, by Atomic Layer Deposition (ALD) of In2S3 buffer layer, yielding to 13.5% efficient devices. The ALD growth of the buffer layers have been studied in situ with the help of a quartz crystal microgravimetry.