Determining factor of MoSe2 formation in Cu(In,Ga)Se2 solar Cells

Abstract The MoSe 2 layers, as a necessary interface layer in Cu(In,Ga)Se 2 /Mo for high-efficiency Cu(In,Ga)Se 2 solar cells, were observed to form in the Mo and CIGS/Mo films during the selenization process. In order to reveal the determining factor of MoSe 2 , the correlation of MoSe 2 thickness with the Mo sputtering pressure was investigated. The MoSe 2 thickness increased with decreasing the sputtering pressure. Furthermore, the dependence of MoSe 2 thickness on the deposition time of SiO 2 layer and the characterizations of X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy demonstrate that the formation of Na 2 Se x compounds plays a determining role for the formation of MoSe 2 layer. The illuminated I – V characterization showed that the high series resistance of the CIGS solar cell was induced by too thick MoSe 2 layer. The significant deterioration of efficiency was observed because of the peeling-off of the absorber layer from Mo layer when the MoSe 2 layer was too thin.