KR20080105268A - Method of forming passivation layer of solar cell, method of preparing solar cell and solar cell - Google Patents

Abstract

A passivation layer formation method of the solar battery and the manufacturing method of the solar battery and the solar battery are provided to improve the quantum efficiency of the solar battery using the ISSG oxidation manner. A passivation layer formation method of a solar battery comprises the following steps; the step for supplying the silicon substrate into the furnace; the step for injecting the oxygen gas and hydrogen gas into the furnace; the step for forming the oxide film on the surface of the silicon substrate while maintaining the pressure of 1~50torr, and the temperature of 850~950‹C.

Description

Method of forming solar cell, method of manufacturing solar cell and solar cell {Method of forming passivation layer of solar cell, method of preparing solar cell and solar cell}

The following drawings attached to this specification are illustrative of preferred embodiments of the present invention, and together with the detailed description of the invention to serve to further understand the technical spirit of the present invention, the present invention is a matter described in such drawings It should not be construed as limited to.

1 is a schematic diagram showing the basic structure of a solar cell.

2 to 6 are views for explaining the solar cell manufacturing method of the present invention.

The present invention relates to a method for forming a passivation layer of a solar cell, a method for manufacturing a solar cell, and a solar cell. More particularly, the present invention is performed at a low temperature, so that the film quality of the passivation layer can be improved without causing deterioration of physical properties such as thickening of the emitter layer. The present invention relates to a method for forming a floating layer of a solar cell, a method for manufacturing a solar cell, and a solar cell.

Recently, as the prediction of depletion of existing energy resources such as oil and coal is expected, interest in alternative energy to replace them is increasing. Among them, solar cells are particularly attracting attention because they are rich in energy resources and have no problems with environmental pollution. Solar cells include solar cells that generate steam for rotating turbines using solar heat, and solar cells that convert photons into electrical energy using the properties of semiconductors. Refers to photovoltaic cells (hereinafter referred to as solar cells).

Referring to FIG. 1 showing the basic structure of a solar cell, a solar cell has a junction structure of a p-type semiconductor 101 and an n-type semiconductor 102 like a diode, and when light is incident on the solar cell, Interaction with the materials that make up the semiconductor causes electrons with negative charge and electrons to escape, creating holes with positive charge, and as they move, current flows. This is called a photovoltaic effect. Among the p-type 101 and n-type semiconductors 102 constituting the solar cell, electrons are directed toward the n-type semiconductor 102 and holes are p-type semiconductors ( Pulled toward 101 and moved to the electrodes 103 and 104 bonded to the n-type semiconductor 101 and the p-type semiconductor 102, respectively, and when the electrodes 103 and 104 are connected by wires, electricity flows. Can get

In general, the output characteristics of such a solar cell have a total light energy (S ×) incident on the solar cell at a maximum value Pm of the product Ip × Vp of the output current Ip and the output voltage Vp on the output current voltage curve obtained using the solar simulator. I: S is evaluated based on the conversion efficiency η, which is a value obtained by dividing the device area and I is the intensity of light irradiated to the solar cell.

In order to improve the conversion efficiency of the solar cell, it is necessary to lower the reflectance of the solar cell to sunlight, reduce the degree of recombination of carriers, and lower the resistance of the semiconductor substrate and the electrode. Research on solar cells is largely underway.

The passivation layer formed on the surface of the silicon wafer during solar cell manufacture is to improve the photoelectric conversion efficiency of the solar cell by preventing carriers (electrons or holes) generated in the p-n junction of the silicon wafer from recombining.

Such a method of forming the passivation layer is a dry oxidation method (dry oxidztion), there is no impurities in the oxide film formed through this, the SiO ₂ / Si interface characteristics are good, it is currently used most commonly. However, dry oxidation should proceed at a high temperature of 1000 ° C. or higher. At this high temperature, the efficiency of the solar cell is inferior due to the thickening of the emitter layer or the occurrence of defects.

Wet oxidation has been developed as a method of forming a passivation layer at low temperature due to the above-described problems of dry oxidation, but the passivation layer formed by the wet oxidation method has poor film quality and thus cannot play a role as a passivation layer. There is.

Therefore, efforts to solve the above-mentioned problems of the formation of the passivation layer of the solar cell have been steadily made in the related field, and the present invention has been made under such a technical background.

The present invention was devised to solve the above-mentioned problems of the prior art, and an object of the present invention is to improve the film quality of the passivation layer and is performed at a low temperature, so that it does not deteriorate other physical properties of the solar cell. The present invention provides a method for manufacturing a solar cell including the same and a solar cell manufactured using the same.

In order to achieve the technical problem to be achieved by the present invention, the present invention, (a1) the step of injecting a silicon substrate into the furnace (furnace) and (a2) injecting oxygen gas and hydrogen gas into the furnace, the furnace 1 ~ 50torr It maintains at a pressure of 850 ~ 950 ℃ provides a method for forming a passivation layer of a solar cell comprising the step of forming an oxide film on the surface of the silicon substrate.

The oxidation step is preferably performed for 10 minutes to 1 hour.

The present invention also provides (b1) forming an emitter layer of a conductivity type opposite to that of the silicon substrate on the silicon substrate (b2) injecting a silicon substrate on which the emitter layer is formed into a furnace, followed by oxygen gas and hydrogen in the furnace. Injecting a gas and maintaining the furnace at a pressure of 1 to 50 torr and a temperature of 850 to 950 ° C. to form a passivation layer on the surface of the silicon substrate (b3) forming an antireflection film on the passivation layer formed on the emitter layer. (S4) forming a front electrode to penetrate the passivation layer and the antireflection film and to be connected to the emitter layer (S5) to be connected to the silicon substrate through a passivation layer formed on a surface opposite to the surface on which the emitter layer of the silicon substrate is formed It provides a method of manufacturing a solar cell comprising the step of forming a back electrode.

The silicon substrate may be representatively used as a p-type silicon substrate, and the anti-reflection film may be typically formed of silicon nitride, and the anti-reflection film forming step is typically plasma chemical vapor deposition (PECVD) or chemical vapor phase. The step (b4) may typically be performed by applying a front electrode forming paste onto an antireflection film according to a predetermined pattern, followed by heat treatment. The step (b5) may be performed. The back electrode forming paste may be applied to a passivation layer formed on a surface opposite to the surface on which the emitter layer of the silicon substrate is formed according to a predetermined pattern, and then heat-treated. Further, in the steps (b4) and (b5), the front electrode forming paste is coated on the antireflection film according to a predetermined pattern, and the back electrode forming paste is formed on the surface on which the emitter layer of the silicon substrate is formed according to the predetermined pattern. It can be carried out by applying on the passivation layer formed on the opposite side and then simultaneously heat-treating.

The present invention also provides a solar cell manufactured using the solar cell manufacturing method.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings to assist in understanding the present invention. The antifreeze layer forming method of the solar cell of the present invention employs an in-situ steam generation (ISSG) oxidation method to solve the problems of the conventional dry oxidation and wet oxidation methods. Such a method for forming a passivation layer of the present invention includes (a1) injecting a silicon substrate into a furnace and (a2) injecting oxygen gas and hydrogen gas into the furnace, and applying the furnace at a pressure of 1 to 50 torr, 850 to 950. Maintaining at a temperature of about 0 ° C. to form an oxide film on the surface of the silicon substrate.

In the method of forming the antifreeze layer, the furnace can inject a specific gas and block other gases, and can be used without particular limitation as long as it can control the temperature and pressure therein. The silicon substrate to be put into the furnace has undergone an emitter layer forming process, and a silicon substrate having a p-n junction is used.

The formation of the oxide film (SiO ₂ ) is performed under a pressure of 1 to 50 torr and a temperature of 850 to 950 ° C., and oxygen (O ₂ ) and hydrogen (H ₂ ) gases injected into the furnace are H ₂ O on the surface of the silicon substrate. Gas, O radicals and OH radicals are made and the formed radicals react with the silicon substrate to form an oxide film on the silicon substrate. The reaction is as follows.

1) Scheme 1: O and OH radical formation

H ₂ + O _2- > H ₂ O + O + OH

    2) Scheme 2: Oxide film formation by generated radicals

Si (wafer) + 2O-> SiO ₂

Si (wafer) + 2OH-> SiO ₂ + H ₂

      All remaining gases are released to the outside.

If the upper limit of the pressure range is exceeded, there is a problem in that no radical is formed. If the lower limit is exceeded, the growth rate of the oxide film is lowered and the thickness of the emitter layer becomes thick due to an increase in process time. In addition, when the upper limit of the temperature range is exceeded, the thickness of the emitter layer becomes thicker, and when the lower limit is not reached, there is a problem that the oxide film does not grow or the film quality deteriorates.

The oxide film forming step is preferably carried out for 10 minutes to 1 hour. If it is less than 10 minutes, the thickness of the formed oxide film is thin and cannot function as a passivation layer. There is a problem that interferes with the function of the solar anti-reflection film formed thereon, and the emitter layer becomes thicker.

The solar cell manufacturing method of the present invention includes a passivation layer forming method as described above. Hereinafter, the solar cell manufacturing method of the present invention will be described with reference to FIGS. 2 to 6.

According to the solar cell manufacturing method of the present invention, prior to the formation of the passivation layer 203, the step of forming the emitter layer 202 of the opposite conductivity type to the silicon substrate on the silicon substrate. The emitter layer 202 is formed to form a p-n junction between the emitter layer 202 and the layer 201 having a conventional conductivity type of the silicon substrate.

As the silicon substrate, both p-type and n-type may be used, and among the p-type silicon substrates, the lifetime and mobility of the minority carrier are large (the electron is the minority carrier in the case of the p-type), and may be most preferably used. have. The p-type silicon substrate is typically doped with group III elements such as B, Ga, and In, and the n-type conductive layer is formed by doping the p-type silicon substrate with group 5 elements such as P, As, and Sb. A junction can be formed.

The step of forming the emitter layer 202 may be performed in various ways. Typically, a silicon substrate is placed in a diffusion furnace, a gas containing a dopant capable of forming the emitter layer 202 is injected, and then the diffusion furnace is heated. There is a method and a method of applying a composition containing a dopant on one side of the semiconductor substrate and putting it in the diffusion furnace and heating. In the former method, since the emitter layer 202 is formed on the entire surface of the silicon substrate, the emitter layer 202 is subjected to an edge isolation process to cut off the side edge portion of the silicon substrate. Through this, the electrical connection between the front electrode 205 and the back electrode 206 can be prevented.

Next, the passivation layer 203 is formed on the surface of the silicon substrate on which the emitter layer 202 is formed in the manner described above.

After the passivation layer 203 is formed, an anti-reflection film 204 is formed on the passivation layer 203 formed on the emitter layer 202. The anti-reflection film 204 is formed to lower the reflectance to sunlight, and may be typically including silicon nitride, and is typically made of plasma chemical vapor deposition (PECVD), chemical vapor deposition (CVD) and sputtering. It can be formed by a method selected from the group

Next, the front electrode 205 is formed to penetrate the passivation layer 203 and the anti-reflection film 204 and be connected to the emitter layer 202, and is opposite to the surface on which the emitter layer 202 of the silicon substrate is formed. The back electrode 206 is formed to pass through the passivation layer 203 formed on the surface and to be connected to the silicon substrate 201.

Step (b4) may be typically performed by applying a front electrode forming paste on the antireflection film 204 according to a predetermined pattern and then heat treating the front electrode 205 through the heat treatment. And penetrate through the passivation layer 203 and the emitter layer 202. The step (b5) may be performed by applying a back electrode forming paste on a passivation layer 203 formed on a surface opposite to a surface on which the emitter layer 202 of the silicon substrate is formed according to a predetermined pattern, and then thermally treating the paste. The back electrode 206 penetrates through the passivation layer 203 and is connected to the silicon substrate by heat treatment, and a portion of the back electrode 206 that contacts the back electrode 206 of the silicon substrate is doped with an electrode forming material to form a BSF layer 207. ) Is formed. The front electrode 205 and the back electrode 206 pass through the passivation layer 203 and the antireflection film 204 by the heat treatment because the glass frit added to the paste etches the passivation layer 203 and the antireflection film 204. to be.

A silver electrode is typically used as the front electrode 205 because the silver electrode is excellent in electrical conductivity, and an aluminum electrode is typically used as the back electrode 206, which not only has excellent conductivity but also silicon. Because of good affinity with the bond is good. In addition, when the p-type silicon substrate is used as the trivalent element, the aluminum electrode can increase efficiency by forming a p + layer, that is, a BSF layer on the silicon substrate, so that carriers can be collected without disappearing from the surface.

The order of forming the front electrode 205 and the back electrode 206 is not limited, and any electrode may be formed first. In the forming of the front electrode 205 and forming the back electrode 206, the front electrode forming paste is coated on the anti-reflection film 204 according to a predetermined pattern, and the back electrode forming paste is formed according to the predetermined pattern. It can also be carried out by applying on the passivation layer 203 formed on the surface opposite to the surface where the emitter layer 202 of the silicon substrate is formed, and then simultaneously heat-treating.

The solar cell manufactured using the passivation layer forming method and the solar cell manufacturing method as described above is excellent in the film quality characteristics of the passivation layer 203, there is no deterioration factor such as the increase in thickness of the emitter layer 202 and the occurrence of defects, It shows an improved photoelectric conversion efficiency.

The terms or words used in this specification and claims should not be construed as being limited to the common or dictionary meanings, and the inventors can appropriately define the concept of terms in order to best describe their invention. Based on the principle, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention.

Therefore, the exemplary embodiments described herein are only exemplary embodiments of the present invention and do not represent all of the technical ideas of the present invention, and various equivalents and modifications that may substitute them at the time of the present application may be used. It should be understood that there may be.

According to the method for forming a passivation layer of the solar cell of the present invention, by using the ISSG oxidation method, the process proceeds at a low temperature, and there is no deterioration in characteristics due to the thickening of the emitter layer or the occurrence of defects, and the film quality of the passivation layer formed is excellent. This can improve the photoelectric conversion efficiency of the solar cell.

Claims (10)

(a1) injecting a silicon substrate into a furnace, and (a2) injecting oxygen gas and hydrogen gas into the furnace, and maintaining the furnace at a pressure of 1 to 50 torr and a temperature of 850 to 950 ° C. to form an oxide film on the surface of the silicon substrate. Passive layer formation method of a solar cell. The method of claim 1, The oxide film forming step is a passivation layer forming method of a solar cell, characterized in that for 10 minutes to 1 hour. (b1) forming an emitter layer of a conductivity type opposite to that of the silicon substrate on the silicon substrate; (b2) After the silicon substrate on which the emitter layer is formed is introduced into the furnace, oxygen gas and hydrogen gas are injected into the furnace, and the furnace is maintained at a pressure of 1 to 50 torr and a temperature of 850 to 950 ° C. Forming a passivation layer on the surface of the (b3) forming an anti-reflection film on the passivation layer formed on the emitter layer (S4) forming a front electrode to penetrate the passivation layer and the anti-reflection film and to be connected to the emitter layer (S5) A method of manufacturing a solar cell comprising the step of forming a back electrode to pass through the passivation layer formed on the surface opposite to the emitter layer formed on the silicon substrate and connected to the silicon substrate. The method of claim 3, The silicon substrate is a manufacturing method of a solar cell, characterized in that the p-type silicon substrate. The method of claim 3, The anti-reflection film is a solar cell manufacturing method characterized in that it comprises a silicon nitride. The method of claim 3, The step (b3) is a manufacturing method of a solar cell, characterized in that carried out by a method selected from the group consisting of plasma chemical vapor deposition (PECVD), chemical vapor deposition (CVD) and sputtering. The method of claim 3, The step (b4) is a method for manufacturing a solar cell, characterized in that the front electrode forming paste is applied on the antireflection film according to a predetermined pattern, followed by heat treatment. The method of claim 3, The step (b5) is a method of manufacturing a solar cell, characterized in that by applying a back electrode forming paste on a passivation layer formed on the surface opposite to the surface on which the emitter layer of the silicon substrate is formed according to a predetermined pattern, and then heat treatment. . The method of claim 3, In the steps (b4) and (b5), the front electrode forming paste is coated on the antireflection film according to a predetermined pattern, and the back electrode forming paste is formed on the opposite side to the surface on which the emitter layer of the silicon substrate is formed according to the predetermined pattern. The method of manufacturing a solar cell, characterized in that the coating is performed on a passivation layer formed on the substrate, and then subjected to heat treatment at the same time. A solar cell, which is manufactured using the method for manufacturing a solar cell according to any one of claims 3 to 9.

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