All-aluminum back surface field aluminum paste for crystalline silicon solar cell and preparation method thereof
The invention discloses an all-aluminum back surface field aluminum paste for a crystalline silicon solar cell and a preparation method thereof. The all-aluminum back surface field paste mainly comprises 60-70% aluminum powder, 5-10% nanometer metal oily solution, 1-10% inorganic binder, 10-20% organic binder, 5-30% organic solvent and 1-5% accessory ingredient. According to the aluminum paste prepared by the present invention, the back surface preparing process of an all-aluminum back surface field can be implemented preferably; moreover, the paste has great adhesive force, is easy to be better adhered to silver paste printed afterwards; meanwhile, the paste can be in good contact with a silicon chip through the nanometer metal oily solution added into the paste, the aluminum back surface is prevented from falling off, and good ohm contact can be formed, so that the photoelectric conversion efficiency is increased, and the economic benefits of enterprises are increased.
1. A preparation method of an all aluminum back surface field aluminum paste for a crystalline silicon solar cell, comprising the following steps:
(1) preparation of inorganic binder: adding low melting point glass powder and high melting point glass powder according to a mass percentage of 1:1-2:1 into a blender mixer to mix evenly, loading the mixture into a porcelain crucible, drying for 2h in a drying oven under 160° C., then placing the mixture into a high temperature furnace to smelt for 1.5h under 500° C., performing cold-extraction on the mixture, then drying, pulverizing and screening the mixture to obtain inorganic binder;
(2) preparation of organic binder: mixing resin and organic binder according to a mass percentage of 1:1-1:4, then pouring the mixture in a dispersion machine to disperse for 30˜60 min to obtain transparent and even organic binder after the mixture is dispersed and dissolved, wherein the resin is one or several of rosin, styrax, phenolic resin, polyvinyl chloride resin, amber, shellac, polyester resin, polyamide resin and epoxy resin;
(3) preparation of aluminum paste: weighing 60-70% aluminum powder, 5-10% nanometer metal oily solution, 1-10% inorganic binder, 10-20% organic binder, 5-30% organic solvent and 1-10% accessory ingredient by total weight of the aluminum paste, and mixing evenly through the dispersion machine; and
(4) preparation of finished product: grinding the aluminum paste mixed in step (3) through a three-roll grinder to 16˜20 μm to obtain the all-aluminum back surface field aluminum paste.
2. The preparation method according to claim 1 , wherein the all-aluminum back surface field aluminum paste obtained in the step (4) comprises:
60-70% aluminum powder;
5-10% nanometer metal oily solution;
1-10% inorganic binder;
10-20% organic binder;
5-30% organic solvent; and
1-5% accessory ingredient;
wherein the total mass percentage of the components thereof is 100%.
3. The preparation method according to claim 2 , wherein the aluminum powder is spherical aluminum powder has an average particle size of 0.8-10 μm, a purity greater than 99.8% and a span of 2.0-4.0.
4. The preparation method according to claim 3 , wherein the nanometer metal oily solution has an average particle size of 50-100 nm, and an oily solution thereof is one or two of terpineol and butyl carbitol.
5. The preparation method according to claim 2 , wherein the nanometer metal oily solution is an oily solution comprising one or several of nanometer aluminum, tin, aluminum-tin and aluminum-silicate, and having a purity greater than 99%.
6. The preparation method according to claim 2 , wherein the inorganic binder is core-shell glass powder which is mainly obtained by mixing low melting point glass powder and high melting point glass powder according to a mass percentage of 1:1-2:1, and then heating and smelting, performing cold-extraction, pulverizing and screening, wherein a shell structure of the inorganic binder is the low melting point glass powder, and a core structure is the high melting point glass powder.
7. The preparation method according to claim 6 , wherein the low melting point glass powder is a bismuth-series mixture and has a melting point of 350-450° C., the high melting point glass powder is a zinc-series mixture and has a melting point of 550-650° C., and the inorganic binder has a melting point of 480-530° C.
8. The preparation method according to claim 2 , wherein the inorganic binder has a particle size D50 of 2-2.5 μm and a particle size span (D90+D10)/D50 of 2-3, and has an effect of fractional melting assistance.
9. The preparation method according to claim 2 , wherein the accessory ingredient is a reducing accessory ingredient, which is one or several of activated carbon, nanocarbon and conductive carbon, and can prevent the paste from being oxidized too rapidly.
10. The preparation method according to claim 2 , wherein the organic binder is mainly mixed by resin and organic binder according to a mass percentage of 1:1-1:4, the viscosity of the organic binder obtained after being mixed and dispersed is 180-900 dpa·s, and the resin is one or several of rosin, styrax, phenolic resin, polyvinyl chloride resin, amber, shellac, polyester resin, polyamide resin and epoxy resin.