Interface chemistry between the sputter Zn1 xMgxO buffer and the Cu In,Ga S,Se 2 absorber

Sputtered Zn1 xMgxO buffer layers can replace both i ZnO and CdS in n ZnO i ZnO CdS Cu In,Ga S,Se 2 Mo glass CIGSSe solar cells, opening a completely dry route to thin film solar cells. We used surface sensitive photoelectron spectroscopy PES and x ray excited Auger electron spectroscopy XAES , both on very thin buffer layers allowing the detection of absorber signals through the cover layer and on CIGSSe surfaces that had been sputter coated with 50 nm of Zn1 xMgxO and were subsequently etched to remove the sputter layer and expose the absorber surface. We found a dependence of the Mg Zn ratio on the layer thickness of Zn1 xMgxO with Mg rich initial layers and a decreasing Mg Zn ratio with increasing layer thickness. After removal of the Zn1 xMgxO layer with acetic acid we found residual Zn but no Mg on the absorber surface. The Zn containing interface species was analyzed by XAES and PES and the obtained values of the modified Auger parameter agree with Zinc in an S or Se environment. Keywords buffer layer, sputtering, photoelectron spectroscop