KR101061991B1 - Solar cell back electrode and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a solar cell back electrode and a method of manufacturing the same.

The present invention provides a solar cell back electrode formed by heat-treating a paste, wherein the paste includes an aluminum powder and an organic binder having a weight ratio of 1: 1.5 to 1: 2.0, and 10 to 30 weight based on the total weight of the aluminum powder. It consists of Cryolite (%) is included. The method for manufacturing a solar cell back electrode according to the present invention includes preparing a material for preparing a critter, an aluminum powder and an organic binder (S100), an aluminum powder and an organic binder having a weight ratio of 1: 1.5 to 1: 2.0, and A paste forming step of forming a paste by mixing 10 to 30% by weight of cryolite with respect to the total weight of the aluminum powder; and (S200), a back electrode using the screen printing process. Electrode molding step of forming a shape (S300), and the heat treatment step (S400) of manufacturing the back electrode by heat-treating the paste of the back electrode shape. According to such a configuration, since the heat treatment is possible at a low firing temperature, there is an advantage in that the electrical cost is improved as well as manufacturing cost is reduced.

Solar cell, back electrode, aluminum, cryolite, electrical resistance

Description

Back electrode for solar cell and manufacturing method thereof {A Hole transporting layer for Solar cell and method for manufacturing et al}

1 is a process flowchart showing a method for manufacturing a solar cell back electrode according to the present invention.

2A is a surface photograph of a first comparative example of the present invention.

Figure 2b is a surface photograph of a second comparative example for the present invention.

2C is a surface photograph of a third comparative example of the present invention.

Figure 2d is a surface photograph of the fourth comparison to the present invention.

3 is a graph showing the surface resistance of the first to fourth comparative examples for the present invention.

Figure 4 is an enlarged photo showing the surface of the back electrode prepared according to the first embodiment in the method for manufacturing a back electrode for a solar cell according to the present invention.

5 is an enlarged photograph of a surface of a back electrode manufactured according to a second embodiment in a method of manufacturing a back electrode for a solar cell according to the present invention;

6 is an enlarged photograph of a surface of a back electrode manufactured according to a third embodiment in a method of manufacturing a back electrode for a solar cell according to the present invention;

Figure 7 is an enlarged photo showing the surface of the back electrode prepared according to the fourth embodiment in the method for manufacturing a back electrode for a solar cell according to the present invention.

8 is an enlarged photograph of a surface of a back electrode manufactured according to a fifth embodiment in a method of manufacturing a back electrode for a solar cell according to the present invention;

9 is an enlarged photograph of a surface of a back electrode manufactured according to a sixth embodiment in a method of manufacturing a back electrode for a solar cell according to the present invention;

10 is a table comparing the surface resistance values of the third comparative example and the first to sixth embodiments in the method for manufacturing a solar cell back electrode according to the present invention.

Explanation of symbols on the main parts of the drawings

S100. Material preparation step S200. Paste Formation Step

S300. Electrode forming step S400. Heat treatment step

The present invention relates to a solar cell back electrode and a method of manufacturing the same, and more particularly, by adding a predetermined amount of cryolite to the rear electrode paste to enable heat treatment at a low temperature, the solar cell back surface having high electrical properties at low production costs It relates to an electrode and a method of manufacturing the same.

Recently, the spread of solar cells is rapidly spreading due to various reasons such as pollution-free, convenience of equipment, and durability improvement. Accordingly, various methods of manufacturing solar cells with high mass production while improving efficiency of solar cells have been studied. .

The electrode formation of the conventional silicon solar cell was formed by printing a paste containing a conductive metal powder, a glass frit, and an organic vehicle on a silicon substrate, and drying and baking to form an electrode.

At this time, the firing temperature is performed at 800 to 100 ° C. higher than the melting point of 660 ° C. due to the oxide film formed on the surface of the aluminum powder.

That is, the aluminum electrode through heat treatment increases the electrical conductivity by partially opening the oxide film of aluminum at high temperature and melting the aluminum inside to flow out to cover the oxide film surface with pure aluminum, and the oxide film formed on the outer surface of the aluminum powder is 900 ° C or higher. This is because cracking may occur only when heat treatment is performed at a temperature.

Accordingly, a lot of researches have been conducted on a technology for reducing the production cost and mass production in manufacturing an aluminum electrode so that firing can be performed at a high temperature in a short time.

Korean Patent Application Publication No. 10-2008-0099407 discloses a "solar cell electrode forming paste." This conventional technique is to ensure that the mechanical strength and adhesion is excellent and the warpage phenomenon after firing can be suppressed.

However, since the preferred temperature range of the firing is limited to 850 to 900 ° C., thermal defects may eventually occur, resulting in a gap between the substrate and the electrode.

An object of the present invention is to solve the problems of the prior art as described above, by adding a certain amount of cryolite to the paste for manufacturing the rear electrode to enable the aluminum oxide film to crack even if the heat treatment at a low temperature, high electrical properties at low production costs. The present invention provides a solar cell back electrode and a method of manufacturing the same.

The present invention provides a solar cell back electrode formed by heat-treating a paste, wherein the paste includes an aluminum powder and an organic binder having a weight ratio of 1: 1.5 to 1: 2.0, and 10 to 30 weight based on the total weight of the aluminum powder. Characterized by comprising a cryolite (Cryolite) included in%.

The solar cell back electrode is characterized in that the heat treatment in the temperature range of 660 to 800 ℃.

The solar cell back electrode has a surface resistance of 31.16 mPa / sq or less.

The method for manufacturing a solar cell back electrode according to the present invention includes a material preparation step of preparing a cryolite, which is a paste material, an aluminum powder and an organic binder, and a weight ratio of 1: 1.5 to 1: 2.0. A paste forming step of forming a paste by mixing an aluminum powder and an organic binder having 10 wt% to 30 wt% of a cryolite with respect to the total weight of the aluminum powder, and using a screen printing process on the paste. And forming a back electrode by heat-treating the paste of the back electrode shape.

The heat treatment step is characterized in that the heat treatment of the paste in the temperature range of 660 to 800 ℃.

The heat treatment step is characterized in that the aluminum is applied to the outside of the oxide film formed on the outer surface of the aluminum powder.

The heat treatment step is characterized in that a process of removing the portion of the oxide film formed on the outer surface of the aluminum powder so that the aluminum melted in the oxide film flows to the outside of the oxide film.

According to such a configuration, since the heat treatment is possible at a low firing temperature, there is an advantage in that the electrical cost is improved as well as manufacturing cost is reduced.

Hereinafter, a method of manufacturing a solar cell back electrode according to the present invention will be described with reference to FIG. 1.

1 is a process flowchart showing a method of manufacturing a solar cell back electrode according to the present invention.

As shown in the drawing, the method for manufacturing a solar cell back electrode according to the present invention is performed by heat-treating a paste made by mixing a tens of micro-sized aluminum powder and an organic binder with cryolite which is a main component of the present invention.

That is, in the present invention, a material preparation step (S100) of preparing a cryolite, an aluminum powder, and an organic binder, a paste forming step (S200) of mixing the cryolite, an aluminum powder, and an organic binder to form a paste, and the paste The electrode forming step (S300) of forming a back electrode shape by using a screen printing process, and the heat treatment step (S400) of manufacturing a back electrode by heat-treating the paste of the back electrode shape.
In more detail, the paste includes an aluminum powder and an organic binder having a weight ratio of 1: 1.5 to 1: 2.0, and a cryolite included in an amount of 10 to 30% by weight based on the total weight of the aluminum powder. do.

The creoliite serves to remove at least a portion of the oxide film formed on the outer surface of the aluminum powder at a lower temperature than the heat treatment step (S400), and is compared with the total weight of the aluminum powder by the embodiment to be described below. 10% by weight or more, and preferably added to 30% by weight or less based on the total weight of the aluminum powder to ensure the content of aluminum.

It is proved by the following experiment that the cryolite is not expected to improve the electrical properties of the electrode when added in excess of the upper limit of 30% by weight.

The cryolite, aluminum powder and organic binder prepared in the material preparation step (S100) are mixed and pasted through the paste forming step (S200), and the paste has a shape of a back electrode through an electrode forming step (S300). The screen is printed.

Thereafter, the back electrode of the paste state is completed as a back electrode through a heat treatment step (S400).

At this time, the heat treatment step (S400) is carried out in a temperature range of 660 to 800 ℃.

That is, the heat treatment step (S400) is a process for applying aluminum to the outside of the oxide film formed on the outer surface of the aluminum powder, the oxide film is at least a part is removed by the creoliite, 660 ℃ is the melting point of aluminum, so the oxide film is removed The molten aluminum flows out of the oxide film through the portion of the oxide film.

In addition, the molten aluminum flowing out of the oxide film is applied to the outer surface of the oxide film and cured, thereby lowering the surface resistance of the rear electrode to improve electrical characteristics.

In addition, since the paste having the shape of the back electrode heat-treated in the heat treatment step (S400) is capable of removing the oxide film even at a relatively low temperature of 800 ° C. by the cryolite, there is no need to heat-treat it with a high heat exceeding 800 ° C.

Hereinafter, a comparative example of the present invention will be described with reference to FIGS. 2A to 3.

2A to 2D are surface photographs of Comparative Examples 1 to 4 according to the present invention, and FIG. 3 is a graph showing surface resistance and specific resistance values of Comparative Examples 1 to 4 according to the present invention.

2A to 2D illustrate a rear electrode formed by heat-treating a paste including only aluminum powder and an organic binder, without containing any cryoolite, which is a main component of the present invention, and manufactured with different heat treatment temperatures.

That is, Figure 2a is a heat treatment at a temperature of 600 ℃, Figure 2b is 700 ℃, Figure 2c is a 800 ℃, Figure 2d is a heat treatment at 900 ℃ is an electron micrograph of the rear electrode.

As shown in these photographs, it can be seen that as the heat treatment temperature increases, the roughness of the surface of the aluminum powder increases, which causes defects in the oxide film formed on the surface as the heat treatment temperature increases, causing the molten aluminum inside to flow out of the oxide film surface. It appears to have occurred by coating it.

And, it can be seen that the roughness of the surface increases as the amount of molten aluminum flowed out of the oxide film increases.

And, when the heat treatment at 600 ℃ lower than the melting point of aluminum 660 ℃ exhibited a very high surface resistance of 709mPa / sq. On the other hand, when the heat treatment temperature is carried out at 700 ℃, 800 ℃, 900 ℃ as shown in Figure 3 226.20mΩ / sq, 49.48mΩ / sq, 27.00mΩ / sq to confirm that the electrical properties improve as the heat treatment temperature increases Could.

It can be seen that the aluminum melted inside due to the high temperature heat treatment is coated on the outside of the oxide film, and in order to improve the electrical properties of the aluminum electrode, it is possible to remove the oxide film on the surface of the aluminum powder at a relatively low temperature. This would be desirable.

Hereinafter, preferred embodiments of the present invention will be described with reference to FIGS. 4 to 9.

4 to 9 are enlarged photographs showing the surface of the back electrode manufactured according to the first to sixth embodiments in the method for manufacturing a back electrode for a solar cell according to the present invention, and FIG. 10 is a third comparative example. It is a graph comparing the surface resistance values of the first to sixth embodiments.

[First Embodiment]

As a composition of a paste for preparing a rear electrode, the powder includes aluminum powder, organic binder, and 5% by weight of creoliite based on the total weight of the aluminum powder. In the heat treatment step (S400), 10% of hydrogen-nitrogen mixed gas is mixed. Heat treatment at a temperature of 800 ℃ in the atmosphere to prepare a back electrode of FIG.

As shown in the drawing, the removal of the oxide film on the surface of the aluminum powder did not occur smoothly, and the added creoliite remained on the surface of the powder. As shown in FIG. 10, the electrical characteristics were also compared with those of the rear electrode of the comparative example without the creoliite added. It can be seen that the electrical resistance is high.

[Second Embodiment]

As a composition of a paste for preparing a rear electrode, the aluminum powder, the organic binder, and 10 wt% of creoliite based on the total weight of the aluminum powder, and the hydrogen-nitrogen mixed gas is mixed with 10% in the heat treatment step (S400). In the atmosphere at room temperature to 800 ℃ to prepare a rear electrode of FIG.

As shown in the figure, the surface of the aluminum powder can be seen that the roughness is increased compared to the comparative examples, the surface resistance of the rear electrode is 49.54 mPa / sq it can be seen that compared with the third comparative example.

[Third Embodiment]

As a composition of a paste for preparing a rear electrode, the powder includes aluminum powder, organic binder, and 15% by weight of creole based on the total weight of the aluminum powder, and in the heat treatment step (S400), hydrogen 10% -nitrogen 90% mixed gas. Heat treatment at a temperature of 800 ℃ in the atmosphere to prepare a back electrode of FIG.

As shown in the figure, the surface of the aluminum powder was found to have a higher roughness when compared with the comparative examples, but when compared with the second embodiment, a large change in roughness could not be confirmed. However, the surface resistance value of the formed rear electrode showed the lowest 31.16 mPa / sq among the examples as shown in FIG.

[Fourth Embodiment]

As a composition of a paste for preparing a back electrode, the aluminum powder, the organic binder, and 20 wt% of creoliite based on the total weight of the aluminum powder, and in the heat treatment step (S400), hydrogen 10% -nitrogen 90% mixed gas Heat treatment at a temperature of 800 ℃ in the atmosphere to prepare a back electrode of FIG.

As shown in the figure, the roughness of the surface of the aluminum powder was increased in comparison with the comparative examples, and the large roughness change could not be confirmed in comparison with the second and third embodiments. However, the surface resistance of the rear electrode was 47.48 mPa / sq, which was somewhat lower than the result of the third embodiment as shown in FIG.

[Example 5]

As a composition of a paste for preparing a rear electrode, the powder includes aluminum powder, an organic binder, and 30% by weight of creoliite based on the total weight of the aluminum powder, and in the heat treatment step (S400), hydrogen 10% -nitrogen 90% mixed gas. Heat treatment at a temperature of 800 ℃ in the atmosphere to prepare a back electrode of FIG.

As shown in FIG. 8, the surface of the aluminum powder was found to have a higher roughness when compared with the comparative examples, but a large roughness change could not be confirmed when compared with the second, third, and fourth examples. However, the surface resistance value of the formed rear electrode was 61.62 mPa / sq as shown in FIG.

[Sixth Embodiment]

As a composition of a paste for manufacturing a back electrode, the powder includes aluminum powder, organic binder, and 50% by weight of creoliite based on the total weight of the aluminum powder, and in the heat treatment step (S400), hydrogen 10% -nitrogen 90% mixed gas. Heat treatment at a temperature of 800 ℃ in the atmosphere to prepare the back electrode of FIG.

As shown in FIG. 9, the surface of the aluminum powder was found to have increased roughness when compared with the comparative examples, but when compared with the second, third, fourth, and fifth embodiments, a large change in roughness could not be confirmed. The surface resistance of was 99.22mΩ / sq.

This result shows that the electrical properties of the rear electrode is improved when the paste contains more than 10% by weight of creoliite based on the total weight of the aluminum powder. In order to maintain the aluminum content of the rear electrode at a certain level, The light is preferably added at 30% by weight or less based on the total weight of the aluminum powder.

The scope of the present invention is not limited to the above-described embodiments, and many other modifications based on the present invention will be possible to those skilled in the art within the scope of the present invention.

 In the present invention, the rear electrode is manufactured by performing a heat treatment at a low temperature of 660 to 800 ℃ by adding a predetermined amount of cryolite to the paste for preparing the rear electrode.

Therefore, thermal defects are minimized due to heat treatment at a relatively low temperature, and electrical characteristics are improved.

In addition, there is an advantage that the manufacturing cost is reduced.

Claims (7)

In the solar cell back electrode formed by heat treatment of the paste, The paste, Aluminum powder and organic binder having a weight ratio of 1: 1.5 to 1: 2.0, Back electrode for a solar cell, characterized in that it comprises a cryolite (Cryolite) contained in 10 to 30% by weight based on the total weight of the aluminum powder. The method of claim 1, wherein the solar cell back electrode, Solar cell back electrode, characterized in that the heat treatment in the temperature range of 660 to 800 ℃. The method of claim 2, wherein the solar cell back electrode, A solar cell back electrode having a surface resistance of 31.16 mPa / sq or less. A material preparation step of preparing a cryolite, which is a paste material, an aluminum powder and an organic binder, Paste forming step of forming a paste by mixing an aluminum powder and an organic binder having a weight ratio of 1: 1.5 to 1: 2.0, and 10 to 30% by weight of cryolite based on the total weight of the aluminum powder. Wow, An electrode forming step of forming the paste into a shape of a back electrode by using a screen printing process; And a heat treatment step of manufacturing a back electrode by heat-treating the back electrode paste. The method of claim 4, wherein the heat treatment step, Method of manufacturing a back electrode for a solar cell, characterized in that the process of heat-treating the paste in the temperature range of 660 to 800 ℃. The method of claim 5, wherein the heat treatment step, The method of manufacturing a solar cell back electrode, characterized in that the aluminum coating process on the outside of the oxide film formed on the outer surface of the aluminum powder. The method of claim 5, wherein the heat treatment step, And removing the part of the oxide film formed on the outer surface of the aluminum powder so that aluminum melted in the oxide film flows out of the oxide film.

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