KR20130064656A - Method of fabricating solar cell - Google Patents

Abstract

PURPOSE: A method for fabricating a solar cell is provided to improve the electrical and optical characteristics of the solar cell by reducing the generation of stress due to the expansion of a volume. CONSTITUTION: A back electrode layer(200) is formed on a support substrate(100). A precursor(30) of a light absorption layer is formed on the back electrode layer. A diffusion groove(32) is formed in the precursor. The diffusion groove exposes the upper surface of the back electrode layer. A selenization process is performed on the precursor.

Description

Manufacturing method of solar cell {METHOD OF FABRICATING SOLAR CELL}

The embodiment relates to a method of manufacturing a solar cell.

A manufacturing method of a solar cell for solar power generation is as follows. First, a substrate is provided, a back electrode layer is formed on the substrate, and patterned by a laser to form a plurality of back electrodes.

Thereafter, a light absorbing layer, a buffer layer, and a high resistance buffer layer are sequentially formed on the back electrodes. In order to form the light absorbing layer, various methods such as a method of forming a light absorbing layer while simultaneously or separately evaporating copper, indium, gallium, and selenium have been used.

Thereafter, a buffer layer containing cadmium sulfide (CdS) is formed on the light absorbing layer by a sputtering process. Thereafter, a high resistance buffer layer including zinc oxide (ZnO) is formed on the buffer layer by a sputtering process. Thereafter, a groove pattern may be formed in the light absorbing layer, the buffer layer, and the high resistance buffer layer.

Thereafter, a transparent conductive material is stacked on the high resistance buffer layer, and the groove pattern is filled with the transparent conductive material. Thereafter, a groove pattern is formed in the transparent electrode layer, and a plurality of solar cells may be formed. The transparent electrodes and the back electrodes are misaligned with each other, and the transparent electrodes and the back electrodes are electrically connected to each other by the connection wirings. Accordingly, a plurality of solar cells can be electrically connected in series with each other.

As such, in order to convert sunlight into electrical energy, various types of photovoltaic devices may be manufactured and used. Such a photovoltaic device is disclosed in Patent Publication No. 10-2008-0088744 and the like.

Meanwhile, in the process of forming the light absorbing layer on the back electrode layer in such a solar cell, the adhesion between the back electrode layer and the light absorbing layer may be lowered, thereby causing an electrical shunt path and an electrical loss. In addition, there is a problem that the stress may increase due to volume expansion while the light absorbing layer is formed.

The embodiment can provide a solar cell having improved reliability.

A method of manufacturing a solar cell according to an embodiment includes forming a back electrode layer on a support substrate; Forming a precursor of a light absorbing layer on the back electrode layer; Forming a diffusion groove in the precursor; And selenization of the precursor.

A method of manufacturing a solar cell according to an embodiment includes a step of selenization, and in the step of selenization, selenium (Se) may be diffused along a diffusion groove formed in the precursor. Accordingly, the selenium may be easily diffused through the diffusion groove. In addition, during the selenium diffusion, it is possible to reduce the generation of stress due to volume expansion. That is, the selenium reacts uniformly, and stress generation can be reduced, thereby improving interface bonding between the back electrode layer and the light absorbing layer. Therefore, the electrical and optical characteristics of the solar cell can be improved.

1 to 5 are cross-sectional views illustrating a method of manufacturing another solar cell according to an embodiment.

In the description of embodiments, each layer, region, pattern, or structure may be “on” or “under” the substrate, each layer, region, pad, or pattern. Substrate formed in ”includes all formed directly or through another layer. Criteria for the top / bottom or bottom / bottom of each layer will be described with reference to the drawings.

The thickness or the size of each layer (film), region, pattern or structure in the drawings may be modified for clarity and convenience of explanation, and thus does not entirely reflect the actual size.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 to 5, a method of manufacturing a solar cell according to an embodiment will be described in detail. 1 to 5 are cross-sectional views illustrating a method of manufacturing another solar cell according to an embodiment.

First, referring to FIG. 1, a metal such as molybdenum is deposited on a support substrate 100 by a sputtering process, and a back electrode layer 200 is formed. The rear electrode layer 200 may be formed by two processes having different process conditions.

An additional layer such as a diffusion barrier may be interposed between the support substrate 100 and the back electrode layer 200.

Subsequently, the precursor 30 of the light absorbing layer is formed on the back electrode layer 200. The precursor 30 of the light absorbing layer may be formed by a sputtering process or an evaporation method.

The precursor 30 of the light absorbing layer may be formed by, for example, a stacked precursor 30 film having a predetermined composition ratio consisting of a copper-gallium alloy layer and an indium layer. It may also be formed by a sputtering process using a copper target, an indium target, and a gallium target. Therefore, the precursor 30 of the light absorbing layer may be made of constituent elements of copper, indium and gallium.

Next, referring to FIG. 2, diffusion grooves 32 are formed in the precursor 30. The diffusion groove 32 exposes an upper surface of the back electrode layer 200. The area of the diffusion groove 32 may be 30% to 50% of the area of the precursor 30. When selenization of the precursor 30 later through the diffusion groove 32, selenium (Se) can be smoothly diffused. When the area of the diffusion groove 32 is less than 30% of the area of the precursor 30, the effect that the selenium is easily diffused may be insignificant. In addition, when the area of the diffusion groove 32 exceeds 50% of the area of the precursor 30, the area of the precursor 30 may be relatively small. The diffusion groove 32 may be formed by scraping the precursor 30 with a pin. However, the embodiment is not limited thereto, and various methods for forming the diffusion groove 32 may be used.

On the other hand, after the step of forming the back electrode layer 200 further comprises the step of forming a through groove (not shown, the same below) to expose the top surface of the support substrate 100 in the back electrode layer 200 The diffusion groove 32 may be spaced apart from the through groove. That is, the diffusion groove 32 and the through groove may be offset. The through groove exposes the top surface of the support substrate 100, and the back electrode layer 200 is divided into a plurality of back electrodes by the through groove. Since the diffusion groove 32 is spaced apart from the through groove, the upper surface of the support substrate 100 may be prevented from being directly exposed to the selenium.

Next, referring to FIGS. 3 and 4, the precursor 30 may be subjected to selenization. In the metal precursor 30 film, a light absorption layer 300 of a copper-indium-gallium selenide system (Cu (In, Ga) Se 2; CIGS system) is formed by a selenization process.

Here, the selenization process refers to a process of heat treatment at low temperature in an atmosphere made of selenium and / or sulfur-containing gas.

Alternatively, the CIS-based or CIG-based optical absorption layer 300 can be formed by using only a copper target and an indium target, or by a sputtering process and a selenization process using a copper target and a gallium target.

The selenization may be performed along the diffusion groove 32. That is, in the selenization step, selenium (Se) 40 may be diffused along the diffusion groove 32. Accordingly, the selenium 40 may be easily diffused through the diffusion groove 32. In addition, it is possible to reduce the generation of stress due to volume expansion when the selenium 40 diffusion. That is, the selenium 40 may react uniformly and reduce stress generation, thereby improving interface bonding between the back electrode layer 200 and the light absorbing layer. Therefore, the electrical and optical characteristics of the solar cell can be improved.

Subsequently, referring to FIG. 5, a buffer layer 400 is formed on the light absorbing layer 300. Here, cadmium sulfide is deposited by a sputtering process or a chemical bath deposit (CBD) or the like, and the buffer layer 400 is formed.

Thereafter, zinc oxide may be deposited on the buffer layer 400 by a sputtering process, and the high resistance buffer layer 500 may be formed.

The buffer layer 400 and the high resistance buffer layer 500 are deposited to a low thickness. For example, the thickness of the buffer layer 400 and the high resistance buffer layer 500 is about 1 nm to about 80 nm.

Subsequently, the front electrode layer 600 is formed on the high resistance buffer layer 500. The front electrode layer 600 may be formed by depositing a transparent conductive material such as zinc oxide doped with aluminum on the high resistance buffer layer 500 by a sputtering process.

The features, structures, effects and the like described in the foregoing embodiments are included in at least one embodiment of the present invention and are not necessarily limited to one embodiment. In addition, the features, structures, effects, and the like illustrated in the embodiments may be combined or modified with respect to other embodiments by those skilled in the art to which the embodiments belong. Therefore, it should be understood that the present invention is not limited to these combinations and modifications.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be construed as limiting the scope of the present invention. It can be seen that various modifications and applications are possible. For example, each component specifically shown in the embodiments may be modified. It is to be understood that the present invention may be embodied in many other specific forms without departing from the spirit or essential characteristics thereof.

Claims (7)

Forming a back electrode layer on the support substrate;
Forming a precursor of a light absorbing layer on the back electrode layer;
Forming a diffusion groove in the precursor; And
The method of manufacturing a solar cell comprising the selenization (Selenization). The method of claim 1,
The diffusion groove is a method of manufacturing a solar cell to expose the top surface of the back electrode layer. The method of claim 1,
The area of the diffusion groove is a solar cell manufacturing method of 30% to 50% of the area of the precursor. The method of claim 1,
Forming the diffusion groove is a method of manufacturing a solar cell scraping the precursor with a pin (pin). The method of claim 1,
The selenization step is a solar cell manufacturing method is performed along the diffusion groove. The method of claim 1,
In the selenization step, the selenium (Se) is diffused along the diffusion groove manufacturing method of a solar cell. The method of claim 1,
And forming a through groove exposing the top surface of the support substrate on the back electrode layer after forming the back electrode layer, wherein the diffusion groove is spaced apart from the through groove.

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