JP2001223374A - Manufacturing method for chalcopyrite-based solar battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a manufacturing method for a chalcopyrite-based solar battery wherein any complex large equipment is not required and the chalcopyrite layer of an excellent quality can be formed by a small number of manufacturing processes in a comparably short time with a low cost. SOLUTION: The chalcopyrite-based solar battery is formed by first and second processes. In the first process, a copper substrate 11 having a formed copper film on its surface is so contacted with a fused In or the mixture of the fused In and a fused Ga as to form a CuIn reaction layer or a CuInGa reaction layer on the surface of the copper substrate 11. In the second process, the CuIn layer or the CuInGa layer formed on the surface of the copper substrate 11 is so contacted with one of a fused Se and the mixture of the fused Se and a fused S as to form the chalcopyrite layer 13 on the surface of the copper substrate 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a chalcopyrite-based solar cell, and to easily form a chalcopyrite layer in the chalcopyrite-based solar cell at low cost.

[0002]

2. Description of the Related Art As a solar cell, a chalcopyrite solar cell having a high conversion efficiency from sunlight to electricity is known. FIG. 2 shows an example of a typical structure of the chalcopyrite-based solar cell. In this chalcopyrite-based solar cell 10, a metal electrode 2 made of Mo or the like is formed on a substrate 1, and a chalcopyrite layer 3, which is an absorption layer, a buffer layer 4 made of CdS or the like, is formed on the metal electrode 2. Zn
Window layer 5 made of O or the like, transparent electrode 6 made of IT0 or the like
Are sequentially formed, and an electrode 7 made of aluminum or the like is provided thereon.

As the substrate 1, a substrate having sufficient heat resistance is used throughout the manufacturing process of the solar cell 10. However, since it is inexpensive and has excellent strength and dimensional stability, soda lime glass or the like is used. Often used. As the metal electrode 2 on the absorption layer side, as in this example, a Mo film is used to prevent a reaction between the substrate 1 and the chalcopyrite layer 3 and to obtain a highly efficient solar cell. Often.

Further, the chalcopyrite layer _{3, Cu (In X Ga (1} -X)) (Se Y S (1-Y)) 2, (x =
0-1 and Y = 0-1), and has the most important effect on the power generation efficiency of the solar cell. Such a C
The chalcopyrite layer 3 made of IGS includes In, Ga,
A vacuum evaporation method using each component of Se and S as an evaporation source, or a sputtering method using a target material composed of a part or all of these components, or a mixture of the vacuum evaporation method and the sputtering method It is formed by a process or the like.

In the formation of the chalcopyrite layer 3, in order to improve the absorptivity, Se or S component which easily escapes during film formation is increased to a stoichiometric ratio and incorporated into the chalcopyrite layer 3. Further, it is necessary to grow the crystals of the chalcopyrite compound in the chalcopyrite layer 3 to a sufficient size (up to about several 10 ^-6 m). For this purpose, the formed chalcopyrite layer 3
In a vapor atmosphere containing Se or S, for example, H
Heat treatment (for example, 550 ° C. × 1 hour) is often performed in ₂ Se gas or H ₂ S gas, or in heated steam of solid Se or solid S. Such a heat treatment is called a selenization treatment or a sulfidation treatment. The buffer layer 4, the window layer 5, and the transparent electrode 6 are sequentially formed on the chalcopyrite layer 3 thus formed by a solution deposition method, a sputtering method, or the like.

[0006]

The chalcopyrite layer 3 in the chalcopyrite-based solar cell 10 as described above.
As described above, a vacuum evaporation method, a sputtering method, or the like is used for the formation of the film. In these film formation methods, an apparatus for installing an evaporation source or a target, and an apparatus for installing the substrate 1 are used. The number of the devices is relatively large, and all the devices are housed in a vacuum vessel capable of evacuating. Therefore, the size of the entire device is increased, and these devices are expensive. However, since the film forming speed is slow and the film forming takes a long time, there is a problem that the production cost of the product eventually increases. Further, as described above, in the conventional method, it is necessary to perform a selenization treatment or a sulfidation treatment in order to increase the absorption rate of the chalcopyrite layer 3.

The present invention has been made in view of the above circumstances and provides a method capable of easily forming the chalcopyrite layer 3. More specifically, the present invention does not require a complicated or large-sized apparatus, has a small number of manufacturing steps, and is relatively simple. An object of the present invention is to provide a method for manufacturing a chalcopyrite-based solar cell that can form a high-quality chalcopyrite layer in a short time and at a low cost.

[0008]

According to the method for manufacturing a chalcopyrite-based solar cell of the present invention, a substrate having a copper film formed on its surface is brought into contact with molten In or a mixture of molten In and molten Ga to form a substrate. CuIn reaction layer or Cu on the copper substrate surface
A first step of forming an InGa reaction layer, and forming a CuIn layer or CuInGa layer formed on the
e, a chalcopyrite layer is formed by a second step of forming a chalcopyrite layer on the substrate surface by contacting with any of molten S or a mixture of molten Se and molten S. At this time, it is preferable to repeat the first step and the second step in this order twice or more to form a chalcopyrite layer.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to embodiments. The method for manufacturing a solar cell of the present invention uses a substrate having a copper film formed on its surface, and forms a chalcopyrite layer on the substrate by contacting a melt of each metal that is a component of chalcopyrite. It is characterized by forming. FIG. 1 shows an example of a solar cell manufactured by the method for manufacturing a solar cell of the present invention. The present invention is characterized by a method of manufacturing a chalcopyrite layer formed on a copper substrate 11 (described later) in a solar cell 20, and the other configuration is the same as that of the conventional solar cell 10 shown in FIG. Since it has, we omit the explanation about these things,
These components will be described with the same reference numerals as those in FIG.

In a solar cell 20 shown in FIG. 1, a chalcopyrite layer 13 is formed on a substrate having a copper film formed on a surface thereof (a copper substrate 11 described later).
A buffer layer 4, a window layer 5, a transparent electrode 6, and an electrode 7 are sequentially formed thereon. Hereinafter, a method for forming the chalcopyrite layer 13 in the method for manufacturing the solar cell 20 will be described. Chalcopyrite layer 13, as described _{above, Cu (In X Ga (1} -X)) (Se Y S (1-Y)) 2, (x =
0, 1, Y = 0-1).

In the method of forming the chalcopyrite layer 13, first, a copper substrate 11 having a copper film formed on the surface is used as the substrate. As the copper substrate 11, a Mo film and a copper film are sequentially formed on a substrate made of copper, such as a copper plate or a copper foil, or a substrate made of a non-copper saw dime glass, by a known film forming method. Is used. Copper substrate 1
In the case where a substrate made of copper such as a copper plate or a copper foil is used for 1, these can also be used as electrodes in the solar cell 20, so that the step of forming an electrode such as a Mo film can be omitted. Further, it is preferable that such a copper substrate 11 be subjected to a surface treatment such as a mirror surface treatment or an ultrasonic cleaning in order to sufficiently remove oxides, oils and the like attached to the surface.

Next, the surface of the copper substrate 11 is immersed in an In bath or a paste of In is applied to the copper substrate 1.
After coating at a desired position, the copper substrate 11 is heated to the melting point of In (1
57 ° C.) or more, so that the C
u and molten In, and Cu and I
An n reaction layer (referred to as a CI layer) is formed. The contact time at this time is preferably 1 minute or more. (First step)

Next, the surface of the copper substrate 11 on which the reaction layer of Cu and In is formed is immersed in a molten bath of Se, or a paste of Se is applied to a desired position on the copper substrate 11. Is heated above the melting point of Se (195 to 221 ° C.) to bring the Cu / In compound on the surface of the copper substrate 11 into contact with the molten Se.
A reaction layer of the / In compound and Se (referred to as a CIS layer) is formed. The contact time at this time is preferably 10 minutes or more. (2nd process)

As described above, the chalcopyrite layer 1 (hereinafter abbreviated as CIS layer) composed of a reaction layer of Cu, In and Se on the copper substrate 11 by the first step and the second step.
3 can be formed. In addition, in the first step, the reaction can be performed by adding Ga to In. In this case, the surface of the copper substrate 11 is immersed in a molten bath in which molten Ga is added to molten In, or G is added to the In paste.
After applying the mixed paste to which the paste a is added to a desired position on the copper substrate 11, the melting points of In and Ga (157
° C) or more to bring Cu and In and Ga on the surface of the copper substrate 11 into contact with each other.
And a Ga reaction layer (referred to as a CIG layer). The contact time at this time is preferably 1 minute or more.

In the second step, the copper substrate 11
The surface is immersed in a molten bath in which S is added to Se, or a mixed paste of the paste of Se and the paste of S is
After being applied to a desired position on the copper substrate 11, the Cu / In compound on the surface of the copper substrate 11 and the molten S
e, by contacting the molten S with Cu / I
A reaction layer (CIS layer or CIGS layer) of n (or Cu / InGa) and Se and S can be formed. The contact time at this time is preferably 10 minutes or more.

In the method of forming the chalcopyrite layer 13 of this embodiment, as described above, in the first step (including the case where Ga is added) and the second step (including the case where S is added), the copper substrate The chalcopyrite layer 13 such as a CIS layer or a CIGS layer can be formed depending on the composition of the solution to be brought into contact with the layer 11. The order of these steps is
As in this example, it is preferable to perform the first step and the second step in this order. With this configuration, in the second step, excess Se or Se and S are supplied, so that the above-described selenization treatment and sulfidation treatment become unnecessary. Note that the second step (including the case where S is added) and the first step (including the case where Ga is added) can be performed in this order. In this case, the formed chalcopyrite layer 13 is formed. Se or S is liable to be deficient, and the selenization treatment described above after the formation,
Sulfidation treatment may be required.

In the method of forming the chalcopyrite layer 13, it is preferable to repeat the first step and the second step two or more times, preferably two or three times, in this order. By doing so, the Cu / (In + Ga) ratio in the formed chalcopyrite layer 13 is set to 0.9 to 1.
It can be a slight In-rich state of about 0,
The power generation efficiency of the solar cell can be increased. When the first step and the second step are performed only once, the Cu / (In + Ga) ratio in the formed chalcopyrite layer 13 is 1
As described above, the state often becomes a Cu-rich state, and the power generation efficiency of the solar cell is inferior to that obtained by repeating the first and second steps two to three times. This is because In in the CuIn compound formed on the copper substrate 11 in the first step,
30-40 at% of compounds having a composition such as δ phase or η phase
It is thought that it is to occupy.

Further, in this example, the first step,
Although the chalcopyrite layer 13 was formed in the second step, the molten alloy of In, Ga, Se, and S reacted with Cu on the copper substrate 11 to combine the two steps into one step. However, in this case, In ₂ Se ₃ (melting point 900 ° C.) is contained in the reaction bath.
During the reaction, it is necessary to heat the reaction bath to a temperature at which these components are dissolved. During the heating, Se and S in the bath evaporate due to high vapor pressure, and the reaction bath is heated. Since the management of the molten bath becomes difficult, for example, the Se and S concentrations of the chalcopyrite layer 13 are reduced,
As described above, it is preferable to perform the process in two steps.

In such a method of forming the chalcopyrite layer 13, a good chalcopyrite layer 13 having a high absorptivity can be obtained without using a large number of apparatuses as used in the conventional sputtering method, and using a large apparatus. And can be easily formed. Further, the film forming time of the chalcopyrite layer 13 can be shortened by several steps as compared with the conventional method. Therefore, a film can be formed at low cost. The method for manufacturing a chalcopyrite-based solar cell of the present invention has a method for forming such a chalcopyrite layer 13. Therefore, a highly efficient solar cell can be obtained in a shorter time and at lower cost than the conventional method. In the description of the method for manufacturing a chalcopyrite-based solar cell of the present invention, a solar cell having the structure shown in FIG. 1 is shown, but the present invention is not limited to this. Can be used.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments. An oxygen-free copper plate having a thickness of 0.5 mm, a width of 10 mm, and a length of 25 mm was used for the copper substrate 11, and the treated surface was treated before treatment in order to sufficiently remove oxides, oils, and the like. Polishing was performed until a mirror surface was obtained, and ultrasonic cleaning was performed in acetone. Next, the chalcopyrite layer 13 was formed on the surface of the copper substrate 11 under the conditions (samples 1 to 5) shown in Table 1, and each chalcopyrite layer 13 was evaluated. The results are shown in Table 1. In the evaluation of the chalcopyrite layer 13, the crystal structure was determined by an X diffraction pattern, and the composition was determined by Auger electron spectroscopy.
+ Ga) ratio was calculated.

[0021]

[Table 1]

Hereinafter, the prototype samples 1 to 5 were evaluated. (Sample 1) Sample 1 was obtained by immersing the surface of the copper substrate 11 once in the molten In bath and once in the molten Se bath for 10 minutes, and as a result, the surface of the copper substrate 11 was 0.3 μm thick. The chalcopyrite layer 13 was formed, and it was demonstrated that the chalcopyrite layer was easily formed by this method. However, the Cu / In ratio was 1.4, and the composition of Cu was excessive.

(Sample 2) Sample 2 is obtained by increasing the contact time to the molten In bath from the conditions of Sample 1 to 5 minutes.
As a result, the thickness of the chalcopyrite layer 13 was increased to 1.2 μm, but the Cu / In ratio was 1.2, and the composition of Cu was excessive. (Sample 3) Sample 3 is obtained by increasing the number of immersion treatments to three times from the conditions of Sample 1. As a result, the Cu / In ratio was reduced to 0.9, and a slightly In-rich chalcopyrite layer 13 could be formed. This indicates that Cu / In of the chalcopyrite layer 13 can be controlled by adjusting the number of treatments.

(Sample 4) Sample 4 is obtained by changing the immersion in the molten In bath to the immersion in a 10 at% molten Ga bath from the conditions of the prototype sample 3, but the copper substrate 11 has chalcopyrite. The layer 13 was formed, and a Cu / (In + Ga) ratio of 1.0 was obtained. (Sample 5) Sample 5 was further melted Se from the conditions of Sample 4.
The immersion in the bath was changed to the immersion in molten S. As a result, even in this case, the chalcopyrite layer 13 can be formed on the copper substrate 11 and Cu / (In + G
a) The target stoichiometric ratio of 0.9 was obtained.

Although the results are not shown in Table 1, the Se or S concentrations of these samples 1 to 5 are as follows:
It satisfied the stoichiometric ratio. From the above results, there are relatively many devices such as the conventional vacuum evaporation method and sputtering method,
It was found that the formation of the chalcopyrite layer 13, which was difficult without using a large-sized apparatus, can be easily performed by the method for manufacturing a chalcopyrite-based solar cell of the present invention.

[0026]

As described above, according to the method for manufacturing a chalcopyrite-based solar cell of the present invention, a substrate having a copper film formed on its surface is brought into contact with molten In or a mixture of molten In and molten Ga, A CuIn reaction layer or C
a first step of forming a uInGa reaction layer, and forming a CuIn layer or CuInGa layer formed on the
e, the chalcopyrite layer is formed on the substrate surface by being brought into contact with either the molten S or a mixture of the molten Se and the molten S. Therefore, the number of devices is small, and a short time can be achieved without using a large device. A chalcopyrite solar cell can be manufactured easily in a short time and at low cost.
By repeating the first step and the second step in this order at least twice, a chalcopyrite-based solar cell having a chalcopyrite layer having a high absorption rate can be manufactured.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one structural example of a chalcopyrite solar cell.

FIG. 2 is a cross-sectional view showing one structural example of a chalcopyrite-based solar cell manufactured by the method for manufacturing a chalcopyrite-based solar cell of the present invention.

[Explanation of symbols]

 Reference Signs List 11 copper substrate 13 chalcopyrite layer 4 buffer layer 5 window layer 6 transparent electrode 7 electrode 20 chalcopyrite solar cell

Claims (2)

[Claims] 1. A substrate having a copper film formed on its surface is melted
n or a mixture of molten In and molten Ga,
A first step of forming a CuIn reaction layer or a CuInGa reaction layer on the substrate surface; and a CuIn layer or CuInGa formed on the substrate.
Forming a chalcopyrite layer by a second step of forming a chalcopyrite layer on a substrate surface by bringing the layer into contact with either molten Se, molten S or a mixture of molten Se and molten S. Manufacturing method of pyrite solar cell. 2. The first and second steps are performed in this order,
2. The method for manufacturing a chalcopyrite-based solar cell according to claim 1, wherein the chalcopyrite layer is formed by repeating at least two times.