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  Demling, A.; Keller, J.; Wilks, R. G.; Hägglund, C.; Edoff, M.; Bär, M.: How ALD Settings May Affect the Chemical Structure of the (Zn_1–xSn_x)O_y/Wide-Gap (Ag,Cu)GaSe₂ Thin-Film Solar Cell Interface. ACS Applied Materials & Interfaces 18 (2026), p. 6180–6190

10.1021/acsami.5c21162
Open Access Version

Abstract:
In this work, the effect of different atomic layer deposition (ALD) settings on the interface formation between ALD-grown (Zn1–xSnx)Oy (ZTO) buffers with varying [Sn]/([Sn]+[Zn]) composition and wide-band gap silver-alloyed CuGaSe2 (ACGSe) absorbers is investigated using X-ray fluorescence, transmission electron microscopy, and synchrotron-based soft and hard X-ray photoelectron spectroscopy. For buffer layers prepared in an industry-scale ALD reactor, we discover the formation of an interlayer best described by a mixture of ZnO with a minor (<10%) amount of Ga2O3, which is not present in similar layer stacks prepared in a lab-scale R&D-type ALD reactor. In addition, we show that ZTO/ACGSe-based solar cells containing such an interlayer have significantly lower fill factors compared to their counterparts without this interlayer, suggesting the presence of an electron transport barrier at the front contact.