Organic adhesive for aluminum paste of silicon solar cells and preparation method thereof

Abstract

The invention provides organic adhesive for the aluminum paste of silicon solar cells and a preparation method thereof. The organic adhesive comprises the following components by the weight part: 23% of ethyl cellulose, 1% to 5% of cellulose acetate butyrate, 88% to 94% of organic solvent, 0.2% to 1% of wetting dispersant and 1% to 3% of defoamer with the total amount being 100%. The preparation method comprises the following steps: putting the components into a reaction kettle; heating the components up to the temperature of 120 to 140 DEG C while stirring at the speed of 60 to 80 RPM and holding at a constant temperature for 2 to 4 hours to ensure that the components in the reaction kettle can be evenly stirred and subjected to complete reaction; and cooling the reactant and filtering the reactant with mesh to obtain the final product of the organic adhesive. The aluminum paste prepared from the organic adhesive has the advantages that the dispersibility or the suspensibility thereof is high, the aluminum paste does not laminate or precipitate after long-time storage and the aluminum paste can be uniformly coated so that the solid powder in the dried aluminum powder has the advantages of high adhesive strength and low stress generated on silicon chips.

Description

technical field [0001] The invention relates to crystalline silicon solar cells, in particular to an organic binder for aluminum paste of silicon solar cells and a preparation method thereof. The organic binder exists as a carrier or a dispersion medium in the aluminum paste, endows the paste with suitable fluid properties, can fully wet the aluminum powder and the inorganic binder powder in the aluminum paste, and can be miscible with other additives. Background technique [0002] In the preparation process of crystalline silicon solar cells, the aluminum paste is printed on the back of the silicon wafer, and after sintering, an aluminum back electric field electrode is formed on the back of the silicon wafer of the solar cell, which can reduce the contact resistance and improve the photoelectric conversion efficiency of the cell. [0003] The aluminum paste is composed of aluminum powder, an organic binder, glass powder as an inorganic binder, additives and the like. Amon...

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Problems solved by technology

[0006] 1. The organic binder in the prepared aluminum paste can make the aluminum powder layer and the silicon chip have a certain bonding strength after drying, but the aluminum paste prepared by the organic adhesive is more brittle after drying (before sintering) Strong, large shrinkage rate, easy to add stress to the silicon wafer, resulting in silicon wafer fragmentation, reducing the yield; at the same time, due to its brittleness, the formed aluminum paste film shrinks and the adhesion to the silicon substrate decreases instead. Its bond strength is 4th grade, and the aluminum film will be partially peeled off when it is wiped.

[0007] 2. The dispersion and suspension effect of the above-mentioned organic binder is also not good. After long-term storage of the aluminum paste, the layered settlement of the powder sometimes occurs, and the stability of the aluminum paste is not good, resulting in solidification everywhere on the silicon wafer after screen printing. If the content is inconsistent, the uniformity and continuity of the formed back field electrode is not good, which affects the photoelectric conversion efficiency

[0008] 3. The above-mentioned organic binders often produce more air bubbles during the grinding and stirring process for preparing aluminum paste, resulting in poor film density during printing

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