The structure of the Cu2S layer of Cu2S/CdS thin-film solar cells

Abstract

Techniques have been developed for separating the Cu2S layer from Cu2S/CdS thin-film solar cells by slowly dissolving away the CdS. Free-standing Cu2S layers, cemented-down Cu2S layers, Cu2S layers exposed after potting and cross sectioning, and replicas of Cu2S layers have been prepared and examined in the scanning electron microscope. The Cu2S morphology so disclosed is a complex composite of a conformal coating of the upper surface of the texture-etched CdS film and more or less vertical penetrations into the CdS film along grain boundaries. The texture etch of the CdS film opens deep [about (10–15) ×10−4 cm] etch pits from which a substantial portion of the Cu2S penetration into grain boundaries occurs. The thickness of the Cu2S layer of conventional CdS thin-film solar cells is about 1000 Å, though the thickness of some of the deeper penetrations may be less than 500 Å.