RF sputtered back contacts for CdTe/CdS thin film solar cells

Abstract

One of the critical issues associated with the fabrication of thin film CdTe/CdS solar cells is the formation of a stable, low-resistance back contact. This paper reports on the formation of a back contact to CdTe cells using RF sputtering of a Cu/sub x/Te target. The cells used in this study are of the commonly used superstrate configuration glass/SnO/sub 2//CdS/CdTe. The back contact was formed by depositing a thin Cu/sub x/Te film by RF sputtering followed by the deposition of a metal. The devices were characterized using I-V, C-V, and spectral response measurements. Fill factors in excess of 70% have been obtained using the Cu/sub x/Te/metal contact. The best device measured at the National Renewable Energy Laboratory exhibited a conversion efficiency of 14.9%.