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.

Anodic Cu2S and CuS nanorod and nanowall arrays: preparation, properties and application in CO2 photoreduction

“…There has also been a resumption of interest in CuS as an unconventional superconductor. 16,17 Copper sulfides have potential applications in photovoltaics, [18][19][20] photocatalytic water-splitting, 21 field emitters, 22 non-volatile memories, 23 biosensors, 24 optical limiters, 25 photothermal cancer cell ablation 26 and lithium ion batteries 27,28 due to favorable optical, electrical and superionic properties. Copper deficiency and nanostructured morphology render adjustable band-gaps of the p-type Cu 2 S semiconductor materials between 1.2 and 2.0 eV, and therefore enable tunable properties.…”

An Electrochemical Barrier Process for Inhibiting p ‐ Cu x S Grain Boundary Growth in Thin Film CdS Solar Cells

“…The CdS film is initially texturized by etching in hot HC1 solution which modifies normally a smooth topostructure into pyramidal hills-and-valleys in order to incur an increase in solar absorbance due to light piping effect, on the one hand, and to enhance the effective junction area for higher current collection, on the other (2). A serious problem associated with such processed cells is the occurrence of deep and narrow CuxS growth intrusions along grain boundaries, thus rendering the junction interface highly anisotropic and corrugated (3,4). This inherent characteristic feature is caused by the inhomogeneous diffusion kinetics, where in one case, the Cu * ions in the aqueous CuC] bath diffuse over the exposed pyramidal grain tops through a slower surface diffusion process and replace Cd ~ ions to form CuxS, and in the other, an accelerated Cu~S growth occurs in the grain boundaries and other defects in the CdS owing to a much more rapid volume diffusion of reacting Cu * ions (5).…”