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

摘要

A ZnS/Zn_(1-x)Mg_xO 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_xO 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 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_xO layers. Therefore, a large gain in the short-circuit current density up to 12 percent was obtained, which resulted in higher conversion efficiencies up to 9 percent relative as compared to cells with the CdS/i-ZnO buffer system. Peak efficiencies of 18 percent with small laboratory cells and 15.2 percent with 10 X10 cm~2 mini-modules were demonstrated.