KR20120003637A - Solar cell and method for fabricating the same - Google Patents

Abstract

PURPOSE: A solar battery and a manufacturing method thereof are provided to arrange an anti-reflection coating structure by successively laminating a plurality of thin films with different refractive indices, thereby minimizing a surface reflection rate. CONSTITUTION: An n-type semiconductor layer(203) is arranged on a first conductive type substrate(201). A first, second, and third anti-reflection films(204,205,206) are successively laminated on the n-type semiconductor layer. A front surface electrode(207) is arranged in a shape penetrating the first, second, and third anti-reflection films. The front surface electrode is arranged in a structure touching the n-type semiconductor layer. A rear surface electrode(208) is arranged on the rear surface of the substrate.

Description

Solar cell and its manufacturing method {Solar cell and method for fabricating the same}

The present invention relates to a solar cell and a method for manufacturing the same, and more particularly, to a solar cell and a method for manufacturing the same, which can reduce the carrier recombination rate while minimizing surface reflectance by combining thin films having different refractive indices.

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 105 is disposed above the n-type semiconductor layer 102 and below the p-type semiconductor layer, respectively. ) And a back electrode 106 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.

Meanwhile, an anti-reflection film 104 is provided on the n-type semiconductor layer 102 to minimize surface reflection. In general, the anti-reflection film 104 is formed of a single layer of SiN _x material. When the anti-reflection film of such a single layer structure is applied, the surface reflectance does not meet expectations, and the carrier in the anti-reflection film is n-type. There is a problem of recombination by moving to the semiconductor layer 102.

The present invention has been made to solve the above problems, to provide a solar cell and a method of manufacturing the same that can reduce the carrier recombination rate while minimizing the surface reflectance by combining a thin film having a different refractive index. have.

The solar cell according to the present invention for achieving the above object comprises a first conductive crystalline silicon substrate having a second conductive semiconductor layer to form a pn junction structure and the first, sequentially stacked on the semiconductor layer, And a second and third antireflection film, wherein the first antireflection film is formed of silicon nitride, the second antireflection film is formed of silicon oxynitride, and the third antireflection film is formed of silicon oxide.

A solar cell manufacturing method according to the present invention comprises the steps of preparing a crystalline silicon substrate of the first conductivity type, the step of forming a second conductive semiconductor layer on the substrate and a second refractive index on the semiconductor layer And sequentially stacking first, second and third antireflection films, wherein the first antireflection film is formed of silicon nitride, the second antireflection film is formed of silicon oxynitride, and the third antireflection film is formed of silicon oxide It is characterized by.

The refractive index decreases in the order of the first, second and third antireflection films, the refractive index of the first antireflection film is 1.9 to 2.5, the refractive index of the second antireflection film is 1.45 to 1.9, and the refractive index of the third antireflection film May be 0.5 to 1.45.

The step of sequentially stacking the first, second and third anti-reflection film having different refractive indices on the semiconductor layer may include supplying SiH ₄ and NH ₃ gas into the chamber to form a first anti-reflection film on the semiconductor layer. A second process of forming a second anti-reflection film made of a silicon oxynitride film on the silicon nitride film by supplying SiH ₄ , NH ₃ and N ₂ O gas into the chamber in a state in which the silicon nitride film is formed; And a third step of supplying SiH ₄ and N ₂ O gas into the chamber to form a third antireflection film made of a silicon oxide film on the silicon oxynitride film.

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

By sequentially stacking a plurality of thin films having different refractive indices to form an anti-reflection film structure, the surface reflectance can be minimized and the solar cell can be effectively protected from the external environment.

1 is a cross-sectional view of a solar cell according to the prior art.
2 is a cross-sectional view of a solar cell according to an embodiment of the present invention.
3A to 3F are flowcharts illustrating a method of manufacturing a solar cell according to an embodiment of the present invention.

Hereinafter, a solar cell and a method of manufacturing the same according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

First, referring to a structure of a solar cell according to an embodiment of the present invention, as shown in FIG. 2, a crystalline silicon substrate 201 of a first conductivity type is provided. Here, the first conductivity type may be p type or n type, the second conductivity type described later is the opposite of the first conductivity type, in the following description, the first conductivity type is p type, the second conductivity type is n type On the basis of

The second conductive semiconductor layer 203, that is, the n-type semiconductor layer 203 is provided on the first conductive substrate 201. In addition, first, second and third anti-reflection films 204, 205 and 206 are sequentially stacked on the n-type semiconductor layer 203. In the first, second and third anti-reflection films 204, 205 and 206, the refractive index is in the order of the first, second and third anti-reflection films 204, 205 and 206. The antireflection film 204 preferably has a refractive index of 1.9 to 2.5, the second antireflection film 205 is 1.45 to 1.9, and the third antireflection film 206 is 0.5 to 1.45. In addition, the first antireflection film 204 is a silicon nitride film (SiN _x ), the second antireflection film 205 is a silicon oxynitride film (SiON), and the third antireflection film 206 is a silicon oxide film (SiO _x ). It can be configured, the thickness of each anti-reflection film can be adjusted to have the above refractive index.

Meanwhile, the front electrode 207 is provided to penetrate the first to third antireflection films 204, 205 and 206, and the first to third antireflection films 204, 205 and 206 are provided. The front electrode 207 penetrates the n-type semiconductor layer 203 and has a structure in contact with the n-type semiconductor layer 203. In addition, a rear electrode 208 is provided on the rear surface of the substrate 201.

Next, a method of manufacturing a solar cell according to an embodiment of the present invention will be described.

First, as shown in FIG. 3A, a crystalline silicon substrate 201 of a first conductivity type (eg, p-type) is prepared, and irregularities 202 are formed on an upper surface of the p-type silicon substrate 201. The texturing process proceeds as much as possible. The texturing process is for maximizing light absorption on the surface of the substrate 201 and may be performed using a dry etching method such as wet etching or reactive ion etching.

In the state where the texturing process is completed, as shown in FIG. 3B, a diffusion process is performed to form an n-type semiconductor layer 203. Specifically, the silicon substrate 201 is provided in a chamber, and a gas (for example, POCl ₃ ) containing a second conductivity type impurity ion, that is, an n-type impurity ion, is supplied into the chamber to form phosphorus (P) ions. Diffusion is allowed into the substrate 201. As a result, the n-type semiconductor layer 203 is formed at a predetermined depth along the periphery of the substrate 201.

With the n-type semiconductor layer 203 formed on the entire surface of the substrate 201, the first, second and third anti-reflection films 204, 205, and 206 are sequentially formed on the n-type semiconductor layer 203. To form. The first, second and third anti-reflection films 204, 205 and 206 may be continuously formed in the same chamber through plasma enhanced chemical vapor deposition (PECVD).

Specifically, when SiH ₄ and NH ₃ gas are supplied into the chamber under a predetermined process condition while the substrate 201 is mounted in the chamber, a silicon nitride film (SiN _x ), that is, a first, is formed on the n-type semiconductor layer 203. An antireflection film 204 is formed (see FIG. 3C). In a state in which the silicon nitride film is formed to have a predetermined thickness, supplying a gas containing oxygen (O ₂ ), for example, N ₂ O gas into the chamber while reducing the supply amount of the NH ₃ gas, provides a second anti-reflection film on the silicon nitride film. A silicon oxynitride film (SiON) constituting 205 is formed (see FIG. 3D). At this time, SiH ₄ gas is continuously supplied. Finally, when the supply of the NH ₃ gas is stopped and the N ₂ O gas and the SiH ₄ gas are supplied into the chamber while the silicon oxynitride film is formed to have a predetermined thickness, a third anti-reflection film 206 is formed on the silicon oxynitride film. A silicon oxide film (SiO _x ) is formed (see FIG. 3E).

Formation thicknesses of the silicon nitride film (SiN _x ), the silicon oxynitride film (SiON), and the silicon oxide film (SiO _x ) constituting the first, second and third anti-reflection films 204, 205 and 206, respectively. Can be adjusted by controlling the supply amount of the process gas, and the formation thickness of each thin film is designed in consideration of the refractive index. That is, the thickness of the first anti-reflection film 204 should be adjusted to have a refractive index of 1.9 to 2.5, the second anti-reflection film 205 to 1.45 to 1.9, and the third anti-reflection film 206 to have a refractive index of 0.5 to 1.45. .

In the state where the first to third anti-reflection films 204, 205, and 206 are sequentially formed on the n-type semiconductor layer 203, the third anti-reflection film 206 and the substrate on the entire surface of the substrate 201 are provided. After the conductive material is coated on the back surface through a screen printing method or the like, the firing process is performed to form the front electrode 207 and the rear electrode 208 as shown in FIG. 3F. The manufacturing method of the solar cell according to the embodiment is completed.

201: substrate 202: irregularities
203: n-type semiconductor layer 204: first antireflection film
205: second antireflection film 206: third antireflection film
207: front electrode 208: rear electrode

Claims (6)

Preparing a crystalline silicon substrate of a first conductivity type;
Forming a second conductive semiconductor layer on the substrate; And
Sequentially stacking first, second and third anti-reflection films having different refractive indices on the semiconductor layer,
The first anti-reflection film is a silicon nitride film, the second anti-reflection film is a silicon oxynitride film, the third anti-reflection film is a manufacturing method of a solar cell, characterized in that the silicon oxide film.
The method of claim 1, wherein the refractive index decreases in the order of the first, second, and third anti-reflection films.
The method of claim 1, wherein the refractive index of the first anti-reflection film is 1.9 to 2.5, the refractive index of the second anti-reflection film is 1.45 to 1.9, and the refractive index of the third anti-reflection film is 0.5 to 1.45. Way.
The method of claim 1, wherein sequentially stacking the first, second, and third antireflection films having different refractive indices on the semiconductor layer include:
A first step of supplying SiH ₄ and NH ₃ gas into the chamber to form a first antireflection film made of a silicon nitride film on the semiconductor layer;
A second process of supplying SiH ₄ , NH ₃ and N ₂ O gas into the chamber in the state where the silicon nitride film is formed to form a second anti-reflection film comprising a silicon oxynitride film on the silicon nitride film;
And a third step of supplying SiH ₄ and N ₂ O gas into the chamber to form a third antireflection film comprising a silicon oxide film on the silicon oxynitride film.
A first conductivity type crystalline silicon substrate having a second conductivity type semiconductor layer to form a pn junction structure; And
It comprises a first, second and third anti-reflection film sequentially stacked on the semiconductor layer,
The first anti-reflection film is a silicon nitride film, the second anti-reflection film is a silicon oxynitride film, the third anti-reflection film is a solar cell, characterized in that the silicon oxide film.
The solar cell of claim 5, wherein the refractive index of the first antireflection film is 1.9 to 2.5, the refractive index of the second antireflection film is 1.45 to 1.9, and the refractive index of the third antireflection film is 0.5 to 1.45.

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