KR101428841B1

KR101428841B1 - Solar-cell comprising back-side electrode with grid structure

Info

Publication number: KR101428841B1
Application number: KR1020110073762A
Authority: KR
Inventors: 송희은; 백태현; 이정철; 강기환; 유권종
Original assignee: 한국에너지기술연구원
Priority date: 2011-07-25
Filing date: 2011-07-25
Publication date: 2014-08-14
Also published as: KR20130012495A

Abstract

A solar cell including a back electrode of a grid structure is provided.
According to an embodiment of the present invention, the solar cell includes a solar cell substrate; An emitter layer formed on the front surface of the solar cell substrate; An antireflection film formed on the emitter layer; A front electrode formed on the antireflection film and in contact with the emitter layer; And a rear electrode formed on a rear surface of the solar cell substrate, wherein the rear electrode is a grid pattern in which a horizontal line and a vertical line cross each other. The solar cell according to the present invention includes a substrate portion Voids) in the high-temperature heat treatment process can be effectively solved through the grid-shaped rear electrode structure. In addition, the amount of aluminum used for the rear electrode can be reduced to reduce the manufacturing cost of the solar cell.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a solar cell comprising a back electrode of a grid structure,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell including a rear electrode of a grid structure, and more particularly, to a solar cell including a grid structure of a rear electrode, To a solar cell including a backside electrode that effectively solves the substrate bowing problem in the process.

In recent years, the spread of solar cells has been rapidly spreading due to various reasons such as pollution, simplicity of facilities, improvement of durability, etc. Thus, various methods for manufacturing solar cells having high efficiency and high mass productivity can be studied have.

Fig. 1 shows a manufacturing process of a solar cell in which a back surface electric field is formed by using aluminum paste (Al paste).

First, a doping process for forming an emitter is performed on the solar cell substrate 10 having completed the sawing damage etching process and the texturing process shown in FIG. 1A, The emitter layer 12 is formed. Then, as shown in FIG. 1C, an antireflection film 14 is formed on the emitter layer 12 to prevent reflection of sunlight to increase efficiency.

Then, the rear electrode 16 is printed and dried on the rear surface of the solar cell substrate 10 using aluminum paste (Fig. 1D), and the front electrode 18 is printed on the front surface of the solar cell substrate 10 Dried (Fig. 1E). In this case, the printing and drying methods of the rear electrode 16 and the front electrode 18 may be performed in reverse order. Thereafter, the solar cell substrate 10 is subjected to a high-temperature heat treatment process (co-firing) at a temperature of 700 to 900 ° C. for several minutes to several tens of minutes

. The high temperature heat treatment process is performed to form a back electric field on the rear surface of the solar cell substrate 10 and allow the front electrode 18 to be well bonded to the emitter layer 14. [ When the high-temperature heat treatment is performed, a rear electric field 20 is formed between the solar cell substrate 10 and the rear electrode 16 as an impurity layer due to diffusion of aluminum atoms. A state in which the rear electric field 20 is formed is shown in FIG. When the back electric field 20 is formed on the solar cell substrate 10 in this order, the collection efficiency of the generated carriers in the rear electric field 20 is improved.

However, the solar cell manufactured by the above-described conventional method has the following problems.

First, the production cost of the solar cell is increased due to the use of the relatively expensive aluminum paste when forming the rear electric field (20) of the solar cell, so that the price competitiveness is weakened.

In addition, in order to reduce the manufacturing cost of solar cells and improve the efficiency, the substrate thickness is continuously lowered. As the thickness of the substrate becomes thinner and thinner, bowing, which is a substrate bending shape due to the difference in thermal expansion coefficient of aluminum (Al) And the risk of damaging the solar cell in the modularization process, which is a post-process, increases.

Therefore, a problem to be solved by the present invention is to provide a solar cell capable of effectively solving the problem of bending of a substrate caused in a high-temperature heat treatment process.

In order to solve the above problems, the present invention provides a solar cell substrate comprising: a solar cell substrate; An emitter layer formed on the front surface of the solar cell substrate; An antireflection film formed on the emitter layer; A front electrode formed on the antireflection film and in contact with the emitter layer; And a rear electrode formed on a rear surface of the solar cell substrate, wherein the rear electrode is a grid pattern in which a horizontal line and a vertical line cross each other.

In one embodiment of the present invention,

In one embodiment of the present invention, the ratio of the substrate exposed through the rear electrode of the grid pattern is 10 to 20%.

In an embodiment of the present invention, the horizontal line and the vertical line intersect at right angles.

The present invention relates to a solar cell substrate; An emitter layer formed on the front surface of the solar cell substrate; A front electrode including a bus electrode and a finger electrode parallel to each other, the bus electrode having a width wider than the finger electrode; And a rear electrode formed on a rear surface of the solar cell substrate, wherein the rear electrode is a grid pattern, and the line forming the grid pattern includes a first line having a relatively wide width and a second line And a solar cell.

In one embodiment of the present invention, the back electrode is aluminum, and the substrate ratio exposed through the back electrode of the grid pattern is 10 to 20%.

In an embodiment of the present invention, the first line and the second line are perpendicular to each other, and the first lines are plural and are spaced apart from each other in parallel.

The solar cell according to the present invention can effectively solve the substrate bowing problem in a high-temperature heat treatment process through a grid-shaped rear electrode structure including a partially exposed substrate portion (void). In addition, the amount of aluminum used for the rear electrode can be reduced to reduce the manufacturing cost of the solar cell.

FIG. 1 shows a manufacturing process of a solar cell in which a rear surface electric field is formed by using aluminum paste (Al paste).
2 and 3 are a cross-sectional view and a bottom view, respectively, of a solar cell according to an embodiment of the present invention.
4 to 6 are photographs of a surface electrode pattern in which the exposure ratio (void ratio) of the back surface of the substrate is 9.5%, 15.5% and 21.5%.
7 is a plan view of a front electrode of a solar cell according to an embodiment of the present invention.
8 is a plan view of a rear electrode according to another embodiment of the present invention.
FIG. 9 is a plan view of a substrate after a front electrode and a rear electrode are coupled according to an embodiment of the present invention. FIG.

Hereinafter, the present invention will be described in detail with reference to the drawings. The following embodiments are provided by way of example so that those skilled in the art can fully understand the spirit of the present invention. Therefore, the present invention is not limited to the embodiments described below, but may be embodied in other forms. In the drawings, the width, length, thickness, etc. of components may be exaggerated for convenience. Like reference numerals designate like elements throughout the specification.

In order to solve the above-described problems of the prior art, the present invention forms a grid structure in which a rear electrode of a solar cell formed on the rear surface of a substrate crosses a horizontal line and a vertical line. Accordingly, the back surface of the substrate is exposed between the horizontal line and the vertical line, and the exposed portion is hereinafter referred to as a void. The present invention reduces the physical deformation force of the silicon substrate due to the rear electrode despite the difference in thermal expansion coefficient between the rear electrode and the silicon substrate through the rear electrode having the void structure.

2 and 3 are a cross-sectional view and a bottom view, respectively, of a solar cell according to an embodiment of the present invention.

2 and 3, a solar cell according to the present invention includes a solar cell substrate 101; An emitter layer 102 formed on the front surface of the solar cell substrate; An anti-reflection film 103 on the emitter layer 102; A front electrode 104 contacting the emitter layer; And a rear electrode 105 formed on the rear surface of the solar cell substrate. At this time, the rear electrode 105 according to the present invention does not cover the entire rear surface of the substrate but forms a so-called grid structure in which the horizontal line 105a and the vertical line 105b cross each other.

In particular, the present invention disperses the thermal expansion direction of the rear electrode such as aluminum occurring in a high-temperature environment through the grid structure in the lateral direction and the longitudinal direction, thereby minimizing the deformation force applied to the substrate by deformation of the rear electrode . In one embodiment of the present invention, the back electrode 104 is aluminum, but the scope of the present invention is not limited thereto.

Figs. 4 to 6 are photographs of a rear electrode pattern in which the exposure ratio (void ratio) of the back surface of the substrate is 9.5%, 15.5%, and 21.5%. Here, the exposure ratio of the back surface of the substrate means the area of the substrate exposed to the outside through the back electrode among the whole substrate area.

The present inventors have found that the degree of bending of an actual substrate varies depending on the exposure ratio of the back surface of the substrate. Table 1 below shows experimental results on the degree of substrate bending according to the exposure ratio of the substrate.

Rear electrode
Pattern type Full application 9.5%
Boyd 15.5%
Boyd 21.5%
Boyd Degree of bending 12.18 mm 11.22 mm 8.85 mm 7.00 mm

Referring to the above results, it can be seen that the degree of bending of the substrate decreases as the substrate exposure ratio of the grid type back electrode according to the present invention increases. In particular, when the void ratio exceeds 10%, it is found that the effect of the sudden substrate bending problem is improved, and the effect of improving the substrate bending problem is not clear when 15.5% or 21.5% have. Therefore, in the present invention, the ratio of the substrate exposed through the grid-type rear electrode is preferably 10% or more and 20% or less. If the amount is less than the above range, the effect of improving the substrate warping in the high temperature heat treatment step is insignificant. The present inventors have also found that a front electrode formed on a front surface of the substrate is composed of a bus electrode having a relatively wide width and a finger electrode having a narrow width, Respectively.

7 is a plan view of a front electrode of a solar cell according to an embodiment of the present invention.

7, the front electrodes 104 are spaced apart from each other by a predetermined distance and include a plurality of bus electrodes 104a parallel to each other and finger electrodes 104b vertically crossing the bus electrodes, and the bus electrodes 104a Has a wider width than the finger electrode 104b, since it functions as a passage for collecting formed electrons. In this case, a problem of warpage of the substrate occurs along the bus line 104a having a wide width in the high-temperature heat treatment process.

Accordingly, in the present invention, the width of one line (first line) of the grid structure of the rear electrode is made wider than the width of another line (second line) And the direction perpendicular to the line 104a.

8 is a plan view of a rear electrode according to another embodiment of the present invention.

8, the rear electrode according to the present invention forms a grid structure, but the lines forming the grid structure do not all have the same width, but the first line 106a having a wider width and the narrower width Two lines 106b, and the first lines are spaced apart in a direction parallel to each other.

FIG. 9 is a plan view of a substrate after a front electrode and a rear electrode are coupled according to an embodiment of the present invention. FIG.

Referring to FIG. 9, the bus electrode 104a on the front surface of the substrate and the first line 106a forming the wider width of the grid-shaped rear electrodes are perpendicular to each other. As a result, the deforming forces predominantly acting in one direction of the substrate are dispersed by the front electrode and the rear electrode crossing each other, and as a result, the problem of substrate warping caused by the high-temperature heat treatment can be effectively improved.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. It will be understood that the present invention can be changed.

Claims

Solar cell substrate;
An emitter layer formed on the front surface of the solar cell substrate;
An antireflection film formed on the emitter layer;
A front electrode formed on the antireflection film and contacting the emitter layer; And
And a rear electrode formed on a rear surface of the solar cell substrate,
Wherein the front electrode includes a plurality of bus electrodes parallel to each other and a finger electrode disposed to cross the plurality of bus electrodes, the bus electrode having a wider width than the finger electrode,
The back electrode has a grid pattern in a state including a first line having a relatively wide width and a second line narrower than the first line,
And the bus electrode and the first line cross each other at right angles.

The method according to claim 1,
Wherein the back electrode is aluminum.

The method according to claim 1,
Wherein a ratio of the substrate exposed through the rear electrode of the grid pattern is 10 to 20%.

The method according to claim 1,
Wherein the first line and the second line are perpendicular to each other.

Solar cell substrate;
An emitter layer formed on the front surface of the solar cell substrate;
A front electrode having a width larger than that of the finger electrode, the front electrode including a plurality of bus electrodes parallel to the emitter layer and arranged to cross the plurality of bus electrodes, wherein the bus electrodes are wider than the finger electrodes; And
And a rear electrode formed on a rear surface of the solar cell substrate, wherein the rear electrode is a grid pattern, and the line forming the grid pattern includes a first line having a relatively wide width and a second line narrower than the first line &Lt; / RTI &
And the bus electrode and the first line cross each other at right angles.

6. The method of claim 5,
Wherein the back electrode is aluminum.

6. The method of claim 5,
Wherein a ratio of the substrate exposed through the rear electrode of the grid pattern is 10 to 20%.

6. The method of claim 5,
Wherein the first line and the second line are perpendicular to each other.

9. The method of claim 8,
Wherein the first lines are plural and are spaced apart in parallel with each other.