Temperature-Stable TCO Layer, Method for Production and Application

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This invention relates to a temperature-stable transparent conductive oxide (TCO) layer, specifically doped zinc oxide (ZnO:Al), which can maintain its optical transparency and electrical conductivity even after being subjected to high-temperature processing (above 450°C). The invention achieves this by applying a transparent, conductive protective layer containing at least one Group IV element (such as silicon) to the surface of the TCO layer. This protective layer is formed via a process involving coating and heating at controlled temperatures, thus preventing property deterioration during further high-temperature processing.

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• Manufacture of thin-film solar cells (such as CIS, CdTe, polycrystalline silicon) that require high-temperature steps where conventional ZnO:Al TCO layers would degrade.
• Production of advanced energy-efficient glass products, such as architectural or display glass with integrated transparent electrodes that must endure high processing temperatures.
• Fabrication of semiconductor devices and sensors using TCO layers that must retain functional properties after high-temperature treatments.
• Development of highly conductive and transparent coatings for optoelectronic devices that are processed at elevated temperatures.
• Enabling new processes for polycrystalline silicon thin-film production by using the protective layer as a seed layer for orderly crystal growth.

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• Ensures the stability of optical and electrical properties of TCO layers during post-deposition high-temperature processes.
• Enables the use of cost-effective, low-temperature deposition methods for ZnO:Al, followed by safe high-temperature processing, thus reducing manufacturing costs.
• Extends the range of applications for TCO-coated materials, especially in high-efficiency thin-film solar cells and advanced glazing products.
• Can improve or maintain device performance, such as solar cell efficiency, by preventing degradation due to heat exposure.
• Allows the integration of TCO layers into new device structures and fabrication processes previously not possible due to temperature limitations.

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Patent Abstract

Transparent conductive oxide (TCO) layers of doped zinc oxide (ZnO:Al) are used for example in the thin-film photovoltaic field and are expected to exhibit the highest possible optical transparency and electrical conductivity, which however change significantly as a result of subsequent thermal treatments, thus up until now limiting the use of said TCO layers. The invention therefore provides a TCO layer of doped zinc oxide (ZnO:Al) for integration into layer systems with processing at temperatures in excess of a temperature TP, at which the unprotected TCO layer exhibits changes in the optical and electrical characteristics, comprising a transparent, conductive protective layer (SS) on the surface designated for processing. Said protective layer is created by bringing the TCO layer into contact with a material composition containing at least one element (Si) of the fourth main group of the periodic table and by subsequent heating at a temperature TA lying below the temperature TP, before the TCO layer is subjected to processing at temperatures in excess of the temperature TP. The protective layer (SS) of the invention thus permits a significant expansion of the area of application, in particular thin-film solar cells or commercial glasses with oxide layers (TCO) can now be produced as contact layers or protective layers.