Silicon nitride films as the diffusion barriers for flexible CIGS thin film solar cells

Impurity diffusion from the flexible metal substrate into CIGS absorption layer can remarkably reduce cell performance comparing with conventional glass substrate. A diffusion barrier layer lying between the metal substrate and Mo backcontact layer is required to prevent this spread of impurities. In this paper, a set of Si3+xN4-x barrier layers are grown on stainless steel sheets and alloy foils by the magnetron sputtering under different conditions. The morphological, structural and electrical properties of the samples are characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and I-V measurements. Our results indirectly support good blocking effect of Si3+xN4-x barrier to the metal impurities from the stainless steel substrate.