Copper indium gallium diselenide thin film solar cell back electrode and preparation method thereof

Abstract

The present invention discloses a copper indium gallium diselenide (CIGS) thin film solar cell back electrode. The back electrode comprises a substrate, a metal conduction layer, a barrier layer, an Na alloy layer and an external protection conduction layer arranged in order from down to up; the barrier layer is transition metal nitride or nitric oxide; the Na alloy layer is formed by Na and another alloy element, and the Na content in the Na alloy layer is 2-10% molar ratio; the thickness of the Na alloy layer is 20-50 nm; magnetron sputtering is employed to perform deposition of each structure layer in order on the substrate for completing preparation; the Na alloy layer is taken as an Na diffusion source to provide Na required by crystal growth for the CIGS absorption layer, the barrier layer can prevent the Na from diffusion to the direction of the substrate and also prevent the impurities in the substrate from diffusion to the CIGS absorption layer to realize the accurate control of Na, and the barrier layer prevents selenium element in the deposition process from diffusion to the metal conduction layer so as to avoid reaction between the selenium and the metal conduction layer and ensure the stability of the metal conduction layer in the growth process of the CIGS absorption layer.

Description

technical field [0001] The invention relates to the technical field of thin film solar cells, in particular to a back electrode of a copper indium gallium selenium thin film solar cell with precisely controlled sodium diffusion and a preparation method thereof. Background technique [0002] In the existing solar cell technology, copper indium gallium selenide (CIGS for short) thin-film solar cell has high photoelectric conversion rate, good low-light performance, and low cost. It can be formed on a hard substrate such as glass to make a rigid Components can also be made into flexible components on flexible substrates, such as stainless steel, aluminum and high-temperature-resistant polymer materials, and are most suitable for use in building integrated photovoltaics (BIPV). It has attracted people's attention and is a very Development potential of solar cell technology. [0003] The theoretical maximum efficiency of CIGS thin-film solar cells is 33%, but the highest efficie...

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Problems solved by technology

When the substrate is soda-lime glass, during the high-temperature selenization process after depositing the copper indium gallium metal prefabricated layer or the high-temperature co-deposition process of the four elements of CIGS, the sodium in the glass diffuses through the back electrode and enters the CIGS absorber layer , but due to the large sodium content in soda-lime glass and the variation of sodium content in different glass substrates, the uncertainty of the total amount of sodium diffused into the CIGS layer will eventually lead to the uncertainty of the CIGS crystal structure, affecting the CIGS thin film The photoelectric conversion rate of the battery. When the substrate material is stainless steel or high-temperature-resistant polymer materials, an external Na diffusion source is required. In order to accurately control the amount of sodium and add an external Na diffusion source, the researchers deposited a certain thickness of Na on the surface of the back electrode. The NaF method establishes the Na diffusion source and controls the total amount of sodium, but the method of depositing NaF on the surface of the back electrode as a diffusion source is likely to cause a decrease in the binding force between the absorber layer and the back electrode, which will affect the subsequent processing of the battery. Therefore, the precise control of Na during the preparation of CIGS solar cells is one of the key technologies for the preparation of high-efficiency CIGS thin-film solar cells.

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