Te/Cu bi-layer: A low-resistance back contact buffer for thin film CdS/CdTe solar cells

A buffer layer based on a Te/Cu bi-layer useful for forming ohmic contact to p-CdTe has been developed for application in CdS/CdTe solar cells. The bi-layer buffer was prepared by vapor deposition and a thermal annealing (similar to 200 degrees C) was required for activation. Enhanced efficiency and stability were obtained by optimizing the Cu/Te compositions and the thermal activation conditions. Characterization by XRD, XPS, and PL indicates that under the thermal activation conditions Cu diffuses rapidly in the Te without forming CuxTe compounds. The enhanced stability can be attributed to the mediation of Cu diffusion into CdTe by the Te layer. The Te/Cu buffers are particularly useful for the fabrication of ultrathin CdS/CdTe solar cells. (C) 2014 Elsevier B.V. All rights reserved.