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)Se2 Solar Cells

A ZnS/Zn1-xMgxO 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 Zn1-xMgxO 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 X 10 cut 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/Zn1-xMgxO layers. Therefore, a large gain in the short-circuit current density tip to 12% was obtained, which resulted in higher conversion efficiencies tip 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 x 10 cm(2) mini-modules were demonstrated. Copyright (C) 2009 John Wiley & Sons, Ltd.