Method for Producing a (001)-Textured Crystal Layer from a Photoactive Superlattice Semiconductor on a Metallically Conductive Layer with the Involvement of a Metal Promoter

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This invention provides improved processes for creating (001)-textured, photoactive crystalline layers from layered chalcogenide semiconductors (such as WS2 or MoS2) on a chemically resistant, electrically conductive metal layer, using a metal promoter. Two main methods are disclosed: (1) inactivating grain boundary diffusion in the metal contact (by saturation with a promoter or oxygen) before forming the semiconductor layer, and (2) partially converting a precursor metal layer into a crystalline semiconductor (chalcogenization), leaving part of the metal as a cost-effective back contact. These methods allow high-quality semiconductor layers to be grown on cheaper metal substrates, overcoming previous limitations and making the process suitable for thin-film solar cells.

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• Production of thin-film solar cells using chalcogenide semiconductor absorber layers with low-cost metal back contacts
• Manufacture of large-area photovoltaic panels where cost and scalability are important
• Fabrication of high-performance optoelectronic devices that require layered semiconductor materials on conductive substrates
• Development of flexible or roll-to-roll processed solar modules using metallic foils as substrates
• Creation of electronic or sensor devices that benefit from high-quality (001)-textured layered chalcogenide films on metals

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• Enables growth of high-quality, (001)-textured chalcogenide semiconductor layers on inexpensive, commercially available metal substrates (not restricted to costly or highly processed materials)
• Reduces manufacturing costs for thin-film solar cells by allowing use of lower-grade metal foils as back contacts
• Improves electronic properties of the semiconductor/metal interface by minimizing detrimental diffusion and defect formation
• Enhances the efficiency of solar cells due to optimized crystal orientation and fewer recombination centers
• Scalable to industry-level production, including roll-to-roll processes for large-area devices
• Flexible process parameters and materials choices (e.g., various metals, promoters, and chalcogenides) increase applicability across multiple device architectures

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Patent Abstract

Layered semiconductors have a significantly higher absorption coefficient for visible light than silicon and are therefore of particular interest as absorber materials in thin-film solar cells. In the presence of a metal promoter, (OO1)-textured crystal layers having two-dimensional crystal growth parallel to the basal plane can presently only be produced by epitaxial growth in sufficient quality on isolator or extremely expensive metal substrates or layers. According to the invention, in a first alternative method (FIG. 4E) the grain boundaries acting as diffusion paths in the polycrystalline metal conductive layer (02) are inactivated by a saturation material, preferably a metal promoter or oxygen. The metal conductive layer (09) to be saturated can thus have any surface quality. As a second alternative method (FIG. 6C), indirect crystallization of the layered semiconductor layer, with partial chalcogenization, of a precursor metal layer (10) suited for producing layered semiconductors is proposed, wherein a thin precursor metal layer (11) is not converted and thus - including the saturated metal layer (09) - can be used as a cost-effective rear contact in a thin-film solar cell.