The Zn(S,O,OH)/ZnMgO buffer in thin‐film Cu(In,Ga)(Se,S) 2 ‐based solar cells part II: Magnetron sputtering of the ZnMgO buffer layer for in‐line co‐evaporated Cu(In,Ga)Se 2 solar cells

A ZnS/Zn 1‐x Mg x O buffer combination was developed to replace the CdS/i‐ZnO layers in in‐line co‐evaporated Cu(In,Ga)Se 2 (CIGS)‐based solar cells. The ZnS was deposited by the chemical bath deposition (CBD) technique and the Zn 1‐x Mg x O layer by RF magnetron sputtering from ceramic targets. The [Mg]/([Mg] + [Zn]) ratio in the target was varied between x = 0·0 and 0·4. The composition, the crystal structure, and the optical properties of the resulting layers were analyzed. Small laboratory cells and 10 × 10 cm 2 modules were realized with high reproducibility and enhanced stability. The transmission is improved in the wavelength region between 330 and 550 nm for the ZnS/Zn 1‐x Mg x O layers. Therefore, a large gain in the short‐circuit current density up to 12% was obtained, which resulted in higher conversion efficiencies up to 9% relative as compared to cells with the CdS/i‐ZnO buffer system. Peak efficiencies of 18% with small laboratory cells and 15·2% with 10 × 10 cm 2 mini‐modules were demonstrated. Copyright © 2009 John Wiley & Sons, Ltd.