FTIR, EPMA, Auger, and XPS analysis of impurity precipitates in CdS films

Impurities in cadmium sulfide (CdS) films are a concern in the fabrication of copper (indium, gallium) diselenide (CIGS) and cadmium telluride (CdTe) photovoltaic devices. Films of CdS grown using chemical bath deposition (CBD) generally yield better devices than purer CdS films grown using vacuum deposition techniques, despite the higher impurity concentrations typically observed in the CBD CdS films. In this work, we present Fourier transform infrared (FTIR), Auger, electron microprobe (EPMA), X-ray photoelectron spectroscopic (XPS), and secondary ion mass spectroscopic (SIMS) analyses of the impurities in CBD CdS films, and show that these differ as a function of substrate type and film deposition conditions. We also show that some of these impurities exist as 10² micron-scale precipitates