KR20080092583A - Single crystal silicon solar cell and pattern of the front electrode of single crystal silicon solar cell - Google Patents

Abstract

A single crystal silicon solar cell and a pattern of a front electrode of the single crystal silicon solar cell are provided to improve a fill factor to secure excellent conversion efficiency by implementing low lateral series resistance for electron mobility. A p-n structure is comprised of a first conductive type silicon substrate(201), a second conductive type conductive layer(202), and a p-n junction. The second conductive type conductive layer has a conductive type opposite to the silicon substrate. The p-n junction is formed on an interface between the silicon substrate and the second conductive type conductive layer. An anti-reflective coating(205) is formed on the second conductive type conductive layer. A front electrode(203) includes two or more finger lines and a bus bar that electrically connect the finger lines. The front electrode is formed on the anti-reflective coating and passes through the anti reflective coating. The front electrode is connected to the second conductive type conductive layer. The finger line of the front electrode is vertical or parallel with respect to a direction of a silicon crystal of the silicon substrate. A back electrode(204) is formed at an opposite side of the front electrode with the silicon substrate. The back electrode is connected to the silicon substrate.

Description

Single crystal silicon solar cell and pattern of the front electrode of single crystal silicon 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 is a view schematically showing a cross section of a single crystal silicon solar cell according to an embodiment of the present invention.

3 shows a crystal structure of silicon.

4 to 6 are diagrams showing states of <100>, <110>, and <111> directions of silicon crystals, respectively.

7 and 8 are diagrams schematically showing the front electrode pattern of the present invention.

The present invention relates to a single crystal silicon solar cell, and more particularly, to a single crystal silicon solar cell having excellent photoelectric conversion efficiency by reducing the transfer resistance of a carrier by improving the structure of a silicon substrate and a front electrode.

Recently, as the prediction of depletion of existing energy sources such as oil and coal is increasing, 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. X I: S is the device area, I is the conversion efficiency η divided by the intensity of light irradiated to the solar cell. Studies on solar cells improve such conversion efficiency in addition to lowering the manufacturing cost of the solar cell. In order to improve the conversion efficiency of the solar cell, it is necessary to increase 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.

The technical problem to be achieved by the present invention is to improve the conversion efficiency of the single crystal silicon solar cell by improving the structure of the silicon substrate and the front electrode to lower the transfer resistance of the carrier, the single crystal silicon solar cell that can achieve this technical problem It is an object of the present invention to provide a.

In order to achieve the technical problem to be achieved by the present invention, the present invention provides a first conductive silicon substrate, a second conductive conductive layer having an opposite conductivity type to the silicon substrate, and between the silicon substrate and the second conductive conductive layer. A pn structure consisting of a pn junction formed at an interface; An antireflection film formed on the second conductivity type conductive layer; And at least two finger lines and a bus bar for electrically connecting the finger lines, wherein the finger lines are formed on the anti-reflection film and are connected to the second conductive type conductive layer while penetrating the anti-reflection film. A front electrode formed perpendicular or parallel to the <110> direction of the crystal; And a back electrode formed on the opposite side of the front electrode with the silicon substrate interposed therebetween to be connected to the silicon substrate.

As the silicon substrate, a p-type silicon substrate may be typically used.

The anti-reflection film may typically be formed of silicon nitride, and thus, the anti-reflection film including silicon nitride may be typically formed by plasma chemical vapor deposition, chemical vapor deposition, or sputtering.

The solar cell may further include a passivation layer between the anti-reflection film and the second conductivity type conductive layer, and the passivation layer may typically include silicon oxide.

The finger line and the bus bar of the front electrode may typically be made of silver and glass frit, and the back electrode may be made of aluminum and glass frit.

The BSF layer may be formed on the silicon substrate to a predetermined depth from a surface where the silicon substrate contacts the rear electrode.

In another aspect, the present invention, in the front electrode pattern of a single crystal silicon solar cell, the finger line of the front electrode is formed perpendicular to or parallel to the <110> direction of the silicon crystal constituting the silicon substrate. It provides a front electrode pattern of.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings to assist in understanding the present invention.

The inventors of the present invention find that the scattering degree due to the silicon lattice varies depending on the crystal direction of silicon in the silicon substrate in the single crystal silicon solar cell, and there is a difference in resistance value with respect to the current. By properly adjusting the pattern of the front electrode finger line in relation to the crystal direction, the present invention has been completed.

2 is a view schematically showing a cross section of a single crystal silicon solar cell according to an embodiment of the present invention.

As shown in FIG. 2, the single crystal silicon solar cell of the present invention includes a first conductive silicon substrate 201, a second conductive conductive layer 202, an antireflection film 205, a front electrode 203, and a rear electrode. 204.

When the second conductive layer layer 202 having a different conductivity type is formed on the silicon substrate 201, a p-n junction is formed, thereby forming a p-n structure. Both the p-type and n-type silicon substrates may be used as the silicon substrate 201, among which the p-type silicon substrate has a long lifetime and mobility of minority carriers (in the case of p-type electrons are minority carriers). Most preferably used. 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 second conductive conductive layer 202 and the pn junction forming step may be performed in various ways, typically including a dopant capable of placing a silicon substrate in a diffusion furnace and forming a second conductive conductive layer 202. There is a method of heating a diffusion furnace after injecting a gas, and a method of applying a composition containing a dopant to one surface of a semiconductor substrate and placing it in the diffusion furnace and heating it. In the former method, since the second conductivity type conductive layer 202 is formed on the entire surface of the silicon substrate, an edge isolation process is performed to cut the side edge portion of the silicon substrate. Through this, the electrical connection between the front electrode 203 and the rear electrode 204 can be prevented.

The anti-reflection film 205 is for lowering the reflectance of sunlight and is formed on the second conductivity type conductive layer 202 formed on the silicon substrate 201. The anti-reflection film 205 may be formed by a method typically selected from the group consisting of plasma chemical vapor deposition (PECVD), chemical vapor deposition (CVD), and sputtering.

A passivation layer (not shown) may be further formed between the anti-reflection film 205 and the second conductivity type conductive layer 202, and the passivation layer may typically include silicon oxide.

The front electrode 203 includes two or more finger lines and a bus bar electrically connecting the finger lines, and is formed on the anti-reflection film 205 and penetrates the anti-reflection film 205 to form a second conductivity type. It is connected to the conductive layer 202.

In the present invention, the pattern of the finger line is formed in consideration of the crystal structure of silicon. 3 is a diagram illustrating a crystal structure of silicon, and FIGS. 4 to 6 are diagrams illustrating states of <100>, <110>, and <111> directions of silicon crystals, respectively. Since the silicon substrate 201 is formed so that the upper and lower surfaces of the substrate are perpendicular to the <100> direction of the silicon crystal, the influence of the lattice on the carrier movement in the direction perpendicular to the upper and lower surfaces of the silicon substrate 201 is independent of the pattern of the electrode. same. However, when the carrier reaches the second conductivity type conductive layer 202 and moves to the electrode, i.e., in the direction parallel to the upper and lower surfaces of the substrate, the scattering degree of the carrier by the lattice varies depending on the electrode formation direction. .

Accordingly, the present invention reduces the lateral series resistance between the finger and the finger by forming the finger line of the front electrode 203 perpendicular or parallel to the <110> direction of the silicon crystal. ) To improve the efficiency of the single crystal silicon solar cell.

7 and 8 are diagrams schematically illustrating the front electrode pattern of the present invention. FIG. 7 illustrates a case in which the side surface of the silicon substrate 305 is formed to be perpendicular to the <100> direction of the silicon crystal. The case where the side surface of the substrate 305 is formed to be perpendicular to the <110> direction of the silicon crystal. As shown in FIGS. 7 and 8, even if the side surface of the silicon substrate 305 is in any positional relationship with the silicon crystal direction, the finger line 301 of the front electrode is formed perpendicular or parallel to the <110> direction of the silicon crystal. The bus bar 303 is formed to electrically connect the finger line 301.

The back electrode 204 is formed to be connected to the silicon substrate 201 on the opposite side to the front electrode 203 with the silicon substrate 201 interposed therebetween.

The finger line 301 and the bus bar 303 of the front electrode 203 may typically include silver and glass frit, and the back electrode 204 typically includes aluminum and glass frit. Can be.

The front electrode 203 and the back electrode 204 may be formed by, for example, applying a paste for forming an electrode according to a predetermined pattern and then performing heat treatment. Through the heat treatment, the front electrode 203 penetrates through the anti-reflection film 205 and is connected to the second conductive type conductive layer 202 (punch throuth), and the silicon substrate 201 is formed on the silicon substrate 201 at the rear side. A back surface field (BSF) layer 206 is formed from a surface in contact with the electrode 204 to a predetermined depth. Since the order of forming the front electrode 203 and the forming of the back electrode 204 is not limited, any of them may be performed first, and it is also possible to heat-treat simultaneously after applying the respective pastes.

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 single crystal silicon solar cell of the present invention, the finger line of the front electrode is formed on the silicon substrate so as to be perpendicular or parallel to the <110> direction of the silicon crystal, so that the lateral series resistance to the movement of electrons is low, so FF It shows an excellent conversion efficiency by improving the fill factor.

Claims (10)

A p-n structure comprising a first conductivity type silicon substrate, a second conductivity type conductive layer having an opposite conductivity type to the silicon substrate, and a p-n junction formed at an interface between the silicon substrate and the second conductivity type conductive layer; An antireflection film formed on the second conductivity type conductive layer; And at least two finger lines and a bus bar for electrically connecting the finger lines, wherein the finger lines are formed on the anti-reflection film and are connected to the second conductive type conductive layer while penetrating the anti-reflection film. A front electrode formed perpendicular or parallel to the <110> direction of the crystal; And And a back electrode formed on the opposite side of the front electrode with the silicon substrate interposed therebetween to be connected to the silicon substrate. The method of claim 1, The silicon substrate is a single crystal silicon solar cell, characterized in that the p-type silicon substrate. The method of claim 1, The anti-reflection film is a single crystal silicon solar cell, characterized in that made of silicon nitride. The method of claim 3, The anti-reflection film is a single crystal silicon solar cell, characterized in that formed by plasma chemical vapor deposition, chemical vapor deposition or sputtering. The method of claim 1, Single crystal silicon solar cell further comprises a passivation layer between the anti-reflection film and the second conductive type conductive layer. The method of claim 5, Single passivation silicon solar cell, characterized in that the passivation layer comprises a silicon oxide. The method of claim 1, The finger line and the bus bar of the front electrode include silver and glass frit. The method of claim 1, The back electrode is a single crystal silicon solar cell, characterized in that made of aluminum and glass frit. The method of claim 1, The silicon substrate is a single crystal silicon solar cell, characterized in that the BSF layer is formed from a surface in which the silicon substrate is in contact with the back electrode to a predetermined depth. In the front electrode pattern of a single crystal silicon solar cell, The front electrode pattern of the single crystal silicon solar cell, characterized in that the finger line of the front electrode is formed perpendicular to or parallel to the <110> direction of the silicon crystal constituting the silicon substrate.

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