TW201618319A - Conductive aid for fabrication process of solar cell, and conductive paste using the conductive aid - Google Patents

Abstract

The present invention provides a conductive aid for fabrication process of solar cell, and conductive paste using the conductive aid. The conductive aid comprises conductive carbon material, solvent, dispersing agent, and de-foaming agent. The component ratio of conductive carbon material is 1 wt.% to 20 wt.%, the component ratio of solvent is 58 wt.% to 99 wt.%, the component ratio of dispersing agent is 0.1 wt.% to 20 wt.%, and the component ratio of de-foaming agent is less than 2 wt.%, wherein the conductive carbon material is carbon nanotube or graphene. Because of using the conductive carbon material, the conductive aid and the conductive paste are provided with the characteristics of high electrical conductivity, stable structure, and low cost. When producing the conductive paste, the ratio of conductive silver powder body can be decreased so as to reduce the required cost.

Description

Conductive auxiliaries for solar cell process and conductive paste using the same

The invention relates to a chemical material used for a solar cell, in particular to a conductive auxiliary agent for a solar cell process and a conductive paste using the same.

Energy is generally divided into exhaustive energy and renewable energy. However, crude oil, natural gas, coal and uranium, which are commonly used today, are limited in terms of mineral resources, so they are exhausted energy, and their consumption rate is much faster than their regeneration rate, so they are depleted. Once the performance source is exhausted, it will not be able to extract more available reserves for future use, making the world face a crisis of energy shortage. Moreover, the carbon dioxide emitted by burning exhausted energy will increase global carbon dioxide emissions. The negative greenhouse effect caused by carbon dioxide has a serious impact on the earth's climate and ecology, so all countries in the world are actively looking for alternative raw materials. At present, the main renewable energy sources include solar energy, hydropower, wind power and biomass energy. Because solar energy is non-polluting, available everywhere, and inexhaustible, and solar energy devices are safe and easy to install, they are the most renewable energy sources. A high-profile industry.

The most common solar cell currently on the market is a polycrystalline silicon solar cell, the structure of which comprises a polycrystalline germanium semiconductor used as a battery and a conductive paste used as an electrode, and the function of the conductive paste is used to collect the electrical energy generated by the solar cell. Transfer to the outside of the battery. Conductive paste plays a key role in the conversion efficiency of solar modules, enabling solar cells to achieve higher conversion efficiencies.

The conductive paste for solar cells includes three kinds of aluminum paste, silver paste and silver aluminum paste. The silver paste is mainly used as the front electrode of the solar cell, the aluminum paste is used as the back electrode and the electric field to increase the battery conversion efficiency, and the silver aluminum paste is applied. The back of the solar cell serves as a wire for the module string.

However, since metal is a consumable material, its stock in nature will continue to decrease as the amount of use and time increases, and its price will continue to rise as the stock decreases.

In the cost structure of solar cells, the slurry is the most important material affecting the cost of solar cells except for the silicon wafer. It is estimated that the conductive paste accounts for about 10% of the cost of the battery, and with the price of polycrystalline germanium falling, the future conductive paste accounts for The proportion of battery cost is getting higher and higher. Therefore, how to reduce the cost of conductive paste and improve the conductivity of conductive paste has become a topic faced by the solar cell industry today.

The main object of the present invention is to reduce the process cost required for solar cells.

In order to achieve the above object, the present invention provides a conductive auxiliary agent for a solar cell process, comprising a conductive carbon material, a solvent, a dispersing agent and an antifoaming agent, wherein the conductive carbon material has a composition ratio of 1 wt.%. Between 20 wt.%, and the conductive carbon material is selected from the group consisting of carbon nanotubes, graphene and combinations thereof, and the composition ratio of the solvent is between 58 wt.% and 99 wt.%. The component ratio of the dispersant is between 0.1 wt.% and 20 wt.%, and the proportion of the antifoaming agent is <2 wt.%.

In order to achieve the above object, the present invention further provides a conductive paste for a solar cell process, comprising the above-mentioned conductive auxiliary agent for solar cell process, a curing resin, a conductive silver powder, and a glass powder. a thixotropic agent and a wetting agent, the proportion of the conductive auxiliary agent is between 1 wt.% and 30 wt.%, and the proportion of the curing resin is between 3 wt.% and 10 wt.%. The composition ratio of the conductive silver powder is between 50 wt.% and 90 wt.%, and the composition ratio of the glass powder is between 0.5 wt.% and 5 wt.%, the composition of the thixotropic agent. The ratio is between 0.5 wt.% and 5 wt.%, and the composition ratio of the wetting agent is between 0.5 wt.% and 5 wt.%.

In summary, the present invention is characterized in that the conductive auxiliary agent and the conductive paste contain the conductive carbon material, and the carbon nanotubes and graphenes can partially replace the conventional solar energy because of their high electrical conductivity and structural stability. The conductive silver powder conventionally used in the process is convenient for the conductive carbon material, and the material cost is lower than that of the conductive silver powder, so that the required process cost can be reduced, and the desired conductive property can be maintained.

The invention provides a conductive auxiliary agent for a solar cell process and a conductive paste using the conductive auxiliary agent, the conductive auxiliary agent comprises a conductive carbon material, a solvent, a dispersing agent and an antifoaming agent, the conductive carbon material The component ratio is between 1 wt.% and 20 wt.%, and the solvent component ratio is between 58 wt.% and 99 wt.%, and the dispersant is used to uniformly disperse the conductive carbon material in the The proportion of the component of the antifoaming agent is <2 wt.% in the solvent and the proportion of the component is between 0.1 wt.% and 20 wt.%, wherein the conductive carbon material is a carbon nanotube, graphene or two a mixture of people.

In one embodiment of the present invention, the solvent may be selected from the group consisting of alcohols, alcohol esters, terpenes, terpineol, Dibutyl phthalate (DBP), butyl carbitol, turpentine, and ethylene. Alcohol butyl ether, butyl carbitol acetate, ethylene glycol ethyl ether acetate, tributyl citrate, diethylene glycol monobutyl ether acetate, dibutyl phthalate, tributyl phosphate, two A chemical solvent such as Dimethylacetamide (DMAC), dodecyl alcohol ester or tributyl citrate, and a suitable solvent is selected depending on the kind and polarity of the chemical raw material in the conductive paste, and is not limited to the above The dispersing agent may be selected from sodium lauryl sulfate, sodium dodecylbenzenesulfonate or sodium cholate (NaC); and the antifoaming agent may be selected from polyvinyl ketone ketone copolymer or non-foaming agent. Ionic ethoxy perfluoroester surfactant.

In addition, the present invention further provides a conductive paste for use in a solar cell process, which uses the above-mentioned conductive auxiliary agent, in addition to the conductive auxiliary agent, the conductive paste further comprises a curing resin and a conductive silver powder. a glass powder, a thixotropic agent and a wetting agent, the conductive additive has a composition ratio of between 1 wt.% and 30 wt.%, and the curing resin has a composition ratio of 3 wt.%. Between 10 wt.%, the proportion of the conductive silver powder is between 50 wt.% and 90 wt.%, and the proportion of the glass powder is between 0.5 wt.% and 5 wt.%. The composition ratio of the glass powder is between 0.5 wt.% and 5 wt.%, and the composition ratio of the wetting agent is between 0.5 wt.% and 5 wt.%.

In an embodiment of the invention, the conductive silver powder has an average particle diameter (D50) of between 0.5 micrometers and 2 micrometers, and the shape may be spherical or flake, and the average particle diameter of the glass powder is (D50) is between 500 nm and 3 μm, and the glass transition temperature (Glass Transition Temperature, T _g ) of the glass powder is between 350 ° C and 500 ° C, and the curing resin can be selected from ethyl fibers. Or a polymethacrylate or an alkyd resin, the thixotropic agent may be selected from a hydrogenated castor oil derivative or a polyamide wax, and the wetting agent may be selected from the group consisting of cetyl alcohol, stearyl alcohol, and sorbitol trioleic acid. Ester, lecithin or terpineol.

The invention further provides a method for preparing a solar cell using a conductive paste, comprising the following steps:

S1: firstly mixing the conductive carbon material, the solvent, the dispersing agent and the antifoaming agent to form the conductive auxiliary agent, the conductive carbon material having a composition ratio of between 1 wt.% and 20 wt.%, the solvent The proportion of the component is between 58 wt.% and 99 wt.%, the component ratio of the dispersant is between 0.1 wt.% and 20 wt.%, and the component ratio of the antifoaming agent is <2 wt.%. And the conductive carbon material is a carbon nanotube, graphene or a mixture of the two.

S2: mixing the conductive auxiliary agent with the curing resin, the conductive silver powder, the glass powder, the thixotropic agent and the wetting agent to form the conductive paste, wherein the conductive additive has a composition ratio of 1 Between wt.% and 30 wt.%, the composition ratio of the curing resin is between 3 wt.% and 10 wt.%, and the composition ratio of the conductive silver powder is between 50 wt.% and 90 wt. Between %, the composition ratio of the glass powder is between 0.5 wt.% and 5 wt.%, and the composition ratio of the glass powder is between 0.5 wt.% and 5 wt.%, the wetting agent The composition ratio is between 0.5 wt.% and 5 wt.%.

S3: coating the conductive paste on a solar cell substrate to form a solar substrate to be processed.

S4: The solar cell to be processed is subjected to a first sintering process in a sintering furnace, and the atmosphere of the first sintering process is air. The solar substrate to be processed is heated in the sintering furnace to a first sintering temperature, and the first sintering temperature is between 200 ° C and 500 ° C. In the first sintering process, the organic matter in the conductive paste reacts with oxygen to be volatilized and removed.

S5: performing a second sintering process on the solar substrate to be processed in the sintering furnace, wherein the atmosphere of the second sintering process is a vacuum environment. The solar substrate to be processed is heated in the sintering furnace to a second sintering temperature, and the second sintering temperature is between 500 ° C and 1000 ° C. In the second sintering process, since the second sintering temperature is higher than the glass transition temperature of the glass powder of the conductive paste, the glass powder starts to melt, thereby causing the conductive silver powder in the conductive paste. And the conductive carbon material is fused to form a conductive path.

In summary, the present invention has the following features:

1. Since the conductive auxiliary agent and the conductive paste contain the conductive carbon material, and the carbon nanotubes and the graphene have the characteristics of high electrical conductivity and structural stability, the conductive silver which is conventionally used in the conventional solar energy process can be partially replaced. The powder is convenient for the conductive carbon material, and the material cost is lower than that of the conductive silver powder, so that the required process cost can be reduced and the desired electrical conductivity can be maintained.

2. By the difference in temperature and environment between the first sintering process and the second sintering process, the conductive carbon material is prevented from decomposing in a high temperature sintering process in an atmospheric environment.

Therefore, the present invention is highly progressive and conforms to the requirements of the invention patent application, and the application is filed according to law, and the praying office grants the patent as soon as possible.

The present invention has been described in detail above, but the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the scope of the invention. That is, the equivalent changes and modifications made by the scope of the present application should remain within the scope of the patent of the present invention.

S1 ~ S5‧‧‧ steps

FIG. 1 is a flow chart showing the steps of a solar cell process of the present invention.

S1~S5‧‧‧Steps

Claims (11)

A conductive additive for a solar cell process, comprising: a conductive carbon material having a composition ratio of between 1 wt.% and 20 wt.%, wherein the conductive carbon material is selected from the group consisting of nano carbon a group consisting of a tube, a graphene, and a combination thereof; a solvent having a composition ratio of between 58 wt.% and 99 wt.%; a dispersant having a composition ratio of 0.1 wt. Between % and 20 wt.%; and an antifoaming agent, the proportion of the antifoaming agent is <2 wt.%. The conductive auxiliary agent for solar cell process according to claim 1, wherein the solvent is selected from the group consisting of alcohols, alcohol esters, terpenes, terpineol, dibutyl phthalate, butyl card. Alcohol, turpentine, ethylene glycol butyl ether, butyl carbitol acetate, ethylene glycol ethyl ether acetate, tributyl citrate, diethylene glycol monobutyl ether acetate, dibutyl phthalate a group consisting of tributyl phosphate, dimethylacetamide, dodecyl alcohol ester and tributyl citrate. The conductive auxiliary agent for solar cell process according to claim 1, wherein the dispersing agent is selected from the group consisting of sodium lauryl sulfate, sodium dodecylbenzenesulfonate and bile salts. . The conductive auxiliary agent for solar cell process according to claim 1, wherein the antifoaming agent is selected from the group consisting of a polyvinyl ketone ketone copolymer or a nonionic ethoxy perfluoroester surfactant. A conductive paste for a solar cell process comprises: a conductive additive for a solar cell process as described in claim 1, wherein the conductive additive has a composition ratio of from 1 wt.% to 30 wt. Between %; a curing resin, the composition ratio of the curing resin is between 3 wt.% and 10 wt.%; a conductive silver powder, the conductive silver powder has a composition ratio of 50 wt.% Between 90 wt.%; a glass powder, the composition ratio of the glass powder is from 0.5 wt.% to 5 wt.%; a thixotropic agent, the proportion of the thixotropic agent is between 0.5 wt.% Between 5 wt.%; and a wetting agent, the composition ratio of the wetting agent is between 0.5 wt.% and 5 wt.%. The conductive paste for solar cell process according to claim 5, wherein the conductive silver powder has an average particle diameter of from 0.5 μm to 2 μm. The conductive paste for solar cell process according to claim 5, wherein the conductive silver powder has a spherical shape or a sheet shape. The conductive paste for solar cell process according to claim 5, wherein the glass powder has an average particle diameter of from 500 nm to 3 μm. The conductive paste for solar cell process according to claim 5, wherein the curing resin is selected from the group consisting of ethyl cellulose, polymethacrylate, and alkyd resin. The conductive paste for solar cell process according to claim 5, wherein the thixotropic agent is selected from the group consisting of hydrogenated castor oil derivatives and polyamide waxes. The conductive paste for solar cell process according to claim 5, wherein the wetting agent is selected from the group consisting of cetyl alcohol, stearyl alcohol, sorbitan trioleate, lecithin, and terpineol. The group that makes up.