KR20120026700A - Method for fabricating solar cell - Google Patents

Abstract

PURPOSE: A method for fabricating a solar cell is provided to improve the conductivity of a metal electrode by using silver or tin without a glass frit as a metal paste material. CONSTITUTION: A crystalline silicon substrate having a semiconductor layer thereon is prepared(S401). An organic pattern layer is formed in the top of the substrate(S402). A silicon oxide film is formed in the top of the substrate to perform heat treatment(S403). A reflection barrier layer is formed over the substrate including the organic pattern layer and the silicon oxide film(S404). An organic pattern layer is removed(S405). A metal paste is coated to remove the organic pattern layer(S406).

Description

Solar cell manufacturing method {Method for fabricating solar cell}

The present invention relates to a method for manufacturing a solar cell, and more particularly, to a method for manufacturing a solar cell using selective deposition of a silicon nitride (SiN _x ) antireflection film using an organic paste and a metal paste printing containing no glass frit. .

A solar cell is a key element of photovoltaic power generation that converts sunlight directly into electricity, and is basically a diode composed of a p-n junction.

In the process of converting sunlight into electricity by solar cells, when solar light is incident on the pn junction of solar cells, electron-hole pairs are generated, and electrons move to n layers and holes move to p layers by the electric field. Photovoltaic power is generated between the pn junctions, and when a load or a system is connected to both ends of the solar cell, current flows to generate power.

On the other hand, solar cells are classified into various types according to the material and the shape of the light absorption layer, which is a pn junction layer. Examples of the light absorption layer include silicon (Si). And a thin film type for forming a light absorption layer by depositing silicon in a thin film form.

The structure of the substrate type of the silicon-based solar cell is as follows. As shown in FIG. 1, an n-type semiconductor layer 102 is provided on the p-type semiconductor layer 101, and the front electrode 104 is disposed above the n-type semiconductor layer 102 and below the p-type semiconductor layer, respectively. ) And a rear electrode 105 is provided. In this case, the p-type semiconductor layer 101 and the n-type semiconductor layer 102 is implemented in one substrate, the lower portion of the substrate is a p-type semiconductor layer 101, the upper portion of the substrate is an n-type semiconductor layer 102 In general, an n-type semiconductor layer 102 is formed by implanting and diffusing n-type impurity ions into an upper layer of a p-type silicon substrate in a state where a p-type silicon substrate is prepared. In addition, an anti-reflection film 103 is provided on the n-type semiconductor layer 102 to minimize surface reflection.

Such silicon-based solar cells are manufactured through processes such as preparation of a p-type silicon substrate, surface texturing (formation of irregularities) on the silicon substrate, implantation and diffusion of n-type impurity ions, lamination of an antireflection film, and formation of front and rear electrodes. In this case, the process of forming the n-type semiconductor layer 102 by implanting and diffusing n-type impurity ions is described in detail. The phosphoric acid solution is coated on a p-type silicon substrate, and (P) is diffused into the p-type silicon substrate so that the n-type semiconductor layer 120 is formed.

In the conventional general solar cell manufacturing process, as shown in FIG. 2, after forming the anti-reflection film 103 on the surface, the paste 104 containing metal and glass frit (glass particles) is printed on the surface and fired to form an electrode. To form. The glass frit can penetrate the silicon nitride (SiN _x ) antireflection film at high temperature and contact the n-type semiconductor layer 102 of the silicon substrate to form an electrode.

However, referring to FIG. 3, in the firing process of the electrode, the glass frit should be formed by penetrating only to the n + doping layer, as shown on the left side. As can be seen, the glass frit penetrates into the p-type semiconductor layer 101 of the silicon substrate to reduce the shunt resistance of the solar cell, thereby causing the electrons to go out to be dissipated inside the solar cell. The result is a rapid drop in light conversion efficiency.

In addition, when firing at a lower temperature than a proper temperature or for a short time, as shown on the rightmost side of FIG. 3, the glass frit does not sufficiently penetrate the silicon nitride (SiN _x ) antireflection film, thereby forming an electrode. Increasing the series resistance of the battery likewise leads to a rapid drop in light conversion efficiency.

In addition, since the metal paste inevitably contains glass frit, the conductivity of the metal paste is reduced, and this also acts as a factor of increasing the series resistance of the solar cell, which in turn lowers the efficiency of the solar cell as a whole.

The present invention has been made to solve the above problems, and relates to a method for manufacturing a solar cell using a selective deposition of silicon nitride (SiN _x ) antireflection film using an organic paste and metal paste printing containing no glass frit. will be.

In accordance with another aspect of the present invention, there is provided a method of manufacturing a solar cell, including preparing a crystalline silicon substrate having a semiconductor layer on a surface thereof, forming an organic pattern layer on the substrate, and heat treating the substrate. Forming a silicon oxide film on the substrate while solidifying the organic pattern layer, forming an antireflection film on the entire surface of the substrate including the organic pattern layer and the silicon oxide film, and removing the organic pattern layer. And applying a metal paste to a position where the organic pattern layer is removed.

The anti-reflection film may include silicon nitride (SiN _x ).

The organic pattern layer may be removed using an organic solvent.

The metal paste may include silver (Ag) or tin (Sn).

The forming of the organic pattern layer on the substrate may be performed by laminating an organic paste using a method of screen printing, gravure offset, photolithography, or aerosol.

The height of the organic pattern layer may be 5 micrometers (μm) to 100 micrometers (μm).

The anti-reflection film may be formed on the entire surface of the substrate including the organic pattern layer and the silicon oxide layer using plasma enhanced chemical vapor deposition (PECVD) or low pressure chemical vapor deposition (LPCVD).

The antireflection film may have a thickness of 30 nanometers (nm) to 120 nanometers (nm).

The manufacturing method of the solar cell according to the present invention has the following effects.

The electrode forming process is facilitated because it is possible at a wide range of temperatures and times. In addition, since the metal paste does not contain glass frit, conductivity is improved. In addition, the surface passivation effect is increased due to the addition of the SiO _x film. In addition, the series resistance decreases due to the wide contact between the metal forming the electrode and the silicon substrate.

1 is a cross-sectional view showing a structure of a substrate type of a conventional silicon solar cell.
2 is a cross-sectional view showing a process of forming a metal electrode in the conventional solar cell manufacturing method.
3 is a view showing an example in which a glass frit is in contact with a silicon substrate to form a metal electrode in a conventional solar cell manufacturing method.
4 is a flowchart illustrating a method of manufacturing a solar cell according to the present invention.
5A to 5F are cross-sectional views illustrating a method of manufacturing a solar cell according to the present invention.

Hereinafter, a method of forming a metal electrode of a solar cell according to an embodiment of the present invention will be described with reference to the drawings. 4 is a flowchart illustrating a method of manufacturing a solar cell according to the present invention, and FIGS. 5A to 5F are cross-sectional views illustrating a method of forming a metal electrode of the solar cell according to the present invention.

First, as shown in FIGS. 4 and 5A, a crystalline silicon substrate having a semiconductor layer 202 on its surface is prepared (S401). The lower portion of the silicon substrate may be a p-type crystalline silicon substrate 201, and the semiconductor layer 202 may be an n-type upper portion of the p-type silicon substrate 201 in a state where the p-type silicon substrate 201 is prepared. N-type semiconductor layer 202 formed by implanting and diffusing impurity ions.

4 and 5b, an organic pattern layer 100 is formed on the substrate (S402). The forming of the organic pattern layer 100 on the substrate may be performed by laminating organic pastes using a method of screen printing, gravure offset, photo-lithography, and aerosol. Can be. In this case, the height of the organic pattern layer 100 may be formed to be at least several micrometers (μm) to about 100 micrometers (μm).

Thereafter, as shown in FIGS. 4 and 5C, the substrate is heat-treated to solidify the organic pattern layer 100. In addition, a silicon oxide film (SiO _x ) 203 is formed on the substrate by the heat treatment (S403). In this process, a mask layer is formed on a portion where the organic pattern layer 100 is printed, and a silicon oxide film (SiO _x ) 203 is additionally formed on a portion where the organic pattern layer 100 is not printed. . The silicon oxide film 203 manufactured through the heat treatment induces a passivation effect on the surface of the substrate to improve the efficiency of the solar cell.

Next, as shown in FIGS. 4 and 5D, an antireflection film 204 is formed on the entire surface of the substrate including the organic pattern layer 203 and the silicon oxide film 203 (S404). The anti-reflection film 204 may include silicon nitride (SiN _x ). The anti-reflection film 204 may be formed on the entire surface of the substrate including the organic pattern layer 203 and the silicon oxide layer 203 by using plasma plasma enhanced chemical vapor deposition (PECVD) or low pressure chemical vapor deposition (LPCVD). This can be done. In this case, the thickness of the silicon nitride layer 204 may be about 30 nanometers (nm) to about 120 nanometers (nm). Meanwhile, since the thickness of the dried organic pattern layer 100 is several tens of micrometers (μm), a difference in thickness may fly up to 1000 times. Therefore, the silicon nitride is printed in the region where the organic pattern layer 100 is printed. The layer 204 is not completely deposited on the organic pattern layer 100.

Thereafter, as illustrated in FIGS. 4 and 5E, the organic pattern layer 100 is removed (S405). The organic pattern layer may be removed using an organic solvent. When the organic pattern layer 100 is removed using an organic solvent, only the organic pattern layer 100 is removed while the silicon nitride layer 204 and the silicon oxide layer 203 are not dissolved in an organic solvent. That is, in the previous step, the portion where the organic pattern layer 100 is not stacked leaves the silicon nitride layer 204 and the silicon oxide layer 203, and the portion where the pattern is formed by stacking the organic pattern layer 100 is As the organic pattern layer 100 is removed, the n-type semiconductor layer 202 is exposed to the outside.

As such, as shown in FIGS. 4 and 5F, the metal paste 205 is coated on the silicon substrate on which the silicon nitride layer 204 is selectively deposited (S406). The applied metal paste 205 is then dried. The metal paste 205 is printed at a position where the organic paste pattern layer 100 is removed. The metal paste 205 may be dried at a low temperature using a metal paste 205 that does not contain glass frit. In this way, the metal paste 205 is formed at the position where the organic paste pattern layer 100 is removed, thereby completing the metal electrode. The metal paste 205 may include silver (Ag) or tin (Sn). By using silver (Ag) or tin (Sn) that does not contain the glass frit as a material of the metal paste, a metal electrode having improved electrical conductivity may be formed.

The solar cell manufactured by the above method is characterized in that the conductivity of the metal electrode is improved because the glass paste is not contained in the metal paste. In addition, the surface passivation effect is increased due to the addition of the silicon oxide layer. Since the electrode forming process is possible at a wide range of temperature and time, it is easy to manufacture, and the series resistance of the solar cell can be reduced due to the wide contact between the electrode metal and the silicon substrate.

201: silicon substrate 202: semiconductor layer
203: silicon oxide film 204: antireflection film (silicon nitride layer)
205: Metal Paste

Claims (8)

Preparing a crystalline silicon substrate having a semiconductor layer on its surface;
Forming an organic pattern layer on the substrate;
Heat treating the substrate to solidify the organic pattern layer and to form a silicon oxide film on the substrate;
Forming an anti-reflection film on the entire surface of the substrate including the organic pattern layer and the silicon oxide film;
Removing the organic pattern layer; And
A method of manufacturing a solar cell comprising applying a metal paste to a position where the organic pattern layer is removed. The method of claim 1,
The anti-reflection film is a solar cell manufacturing method comprising silicon nitride (SiN _x ). The method of claim 1,
The organic pattern layer is a solar cell manufacturing method, characterized in that removed using an organic solvent. The method of claim 1,
The metal paste is a solar cell manufacturing method comprising silver (Ag) or tin (Sn). The method of claim 1,
Forming an organic pattern layer on the substrate
A method of manufacturing a solar cell, characterized by laminating an organic paste using a method of screen printing, gravure offset, photolithography, or aerosol. The method of claim 1,
The height of the organic pattern layer is a manufacturing method of a solar cell, characterized in that 5 micrometers (μm) to 100 micrometers (μm). The method of claim 1,
Forming an anti-reflection film on the entire surface of the substrate including the organic pattern layer and the silicon oxide film
A method of manufacturing a solar cell, characterized by using plasma enhanced chemical vapor deposition (PECVD) or low pressure chemical vapor deposition (LPCVD). The method of claim 1,
The anti-reflection film has a thickness of 30 nanometers (nm) to 120 nanometers (nm).

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