Process control of vacuum-deposited CdS for the fabrication of reproducible 8% efficient solar cells

Abstract

As part of the research and development effort, a device fabrication line was established whose mission was to reproducibly fabricate large area (10 cm2) CuxS/CdS solar cells of greater than 8% average conversion efficiency. This goal was accomplished mainly by the careful monitoring and control of the CdS deposition process. Material properties which influence cell performance, such as back contact reflection, CdS resistivity, and deposition rate, were monitored and controlled via temperature control. Photoluminescence of the CdS and resistivity of CuxS layers formed on the CdS were used to electronically characterize the films prepared and served as tools in observing changes in the deposition process and cell performance. The reproducibility of the process was confirmed by a 2-month qualifying run in which an average conversion efficiency of greater than 8% was achieved and maintained.