JP2928033B2 - Manufacturing method of thin film solar cell - Google Patents

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 thin-film solar cell in which light energy such as sunlight is converted into electric energy by bonding using a chalcopyrite-type ternary semiconductor compound thin film.

[0002]

_2. Description of the Related Art X has the formula XYZ ₂ and X is Ag or
Chalcopyrite-type ternary compound thin film in which Cu and Y are In or Ga and Z is Se or S, particularly CuInSe ₂ and CuInS
₂ , AgInSe ₂ and AgInS ₂ have an optical gap of 1.0 to 1.8.
It is in the range of eV and is expected to be used as an optical conversion element. In recent years, with the development of thin film formation technology for these materials,
These substances as thin-film solar cell element materials are receiving more and more attention and are being studied by many research institutions. Hereinafter, taking a CuInSe ₂ has progressed most studied example is described prior art. FIG. 2 is a cross-sectional view of a part of a conventional solar cell using a CuInSe ₂ thin film. In the figure, thickness 1 ~
On a 4 mm glass substrate 1, a metal electrode 2 made of molybdenum (Mo) having a thickness of 0.2 to 2 μm is formed. The semiconductor layer is a CuInSe ₂ layer having a thickness of ₂ to 4 μm as a p-type semiconductor layer.
A thin film 3, a cadmium sulfide (CdS) thin film 4 having a thickness of 250 to 500 .mu.m as an n-type semiconductor layer and a thickness of 2 to 4 .mu.m which is an n-type semiconductor layer having a wide band gap and serving as a window layer;
m of zinc oxide (ZnO) thin film 5. Aluminum is deposited on layer 5 by sputtering, evaporation or plating.
A metal electrode 6 made of (Al) is provided. CuInSe ₂
As a general method of forming a thin film, there is a ternary simultaneous vapor deposition method. In the ternary simultaneous evaporation method, each element of Ci, In, and Se is simultaneously evaporated from three crucibles on a substrate to form a CuInSe ₂ film.

[0003]

When a CuInSe ₂ thin film is formed on a substrate by a ternary co-evaporation method, a substrate temperature of 400 to 400 ° C.
The film is formed at about 550 ° C., and when the substrate is cooled after the film is formed, each crucible is cooled simultaneously. Therefore, during the cooling of the substrate, the substrate is cooled in a high vacuum. With such a method, CuInSe ₂
Se is desorbed from the film surface, CuInSe ₂ making semiconductor junction
As a result, the surface of the thin film becomes insufficient for Se, and it is difficult to perform good bonding. Therefore, it is difficult to obtain a solar cell with high conversion efficiency. Alternatively, it is necessary to perform annealing at a substrate temperature of about 200 ° C. in an oxygen atmosphere after the formation of the solar cell in order to fill O ₂ after Se desorption. The same problem also occurred when CuInSe ₂ was formed by a sputtering method.

An object of the present invention is to solve the above-mentioned problems and to provide a method for manufacturing a thin-film solar cell having a chalcopyrite-type compound thin film of the formula XYZ ₂ in which the Z element is not deficient on the surface.

[0005]

To achieve the above object, according to the solution to ## according to the present invention, has the formula XYZ _2, X is silver or copper, Y is indium or gallium, Z is a selenium or sulfur in the method for manufacturing a thin-film solar cells using a chalcopyrite-type ternary compound thin film on the active layer, after XYZ ₂ thin film deposition, which is treated with an atmosphere containing Z, when the process of the XYZ ₂ thin film deposition The heated deposition target substrate is cooled in an atmosphere containing Z.
Here, the XYZ ₂ thin film deposition, X, Y, Z each steam supply, to apply the three-way simultaneous evaporation method in which evaporation is performed by heating the film formation substrate, cooling the substrate after XYZ ₂ thin film deposition At times, it is effective to stop the supply of the X and Y vapors and supply only the Z vapor. In addition, it is preferable that the process in the atmosphere containing Z be stopped at a time when the temperature of the substrate to be cooled is 250 ° C. or higher. Incidentally, after XYZ ₂ thin film deposition Z is selenium, treating in an atmosphere containing selenium, after XYZ ₂ thin film deposition Z is selenium, it is effective to treatment in an atmosphere containing sulfur.

[0006]

[Action] XYZ_TwoChalcopyrite type compound thin film deposition
Later, if the treatment is performed in a Z atmosphere, Z desorption is prevented.
Alternatively, replenishment of the desorbed Z is performed, and X having no Z deficiency on the surface is obtained.
YZ _TwoA thin film is completely formed. Chalcopyrite compound
Thing is CuInSe_TwoAt this time, if the film is treated in an S atmosphere after the film formation,
The forbidden band width only on the film surface can be changed,
The efficiency of the solar cell is improved.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to manufacture a solar cell having the structure shown in FIG. 2, CuInSe was formed on a glass substrate 1 having a Mo layer 2 formed on the surface.
_{(2) The} thin film 3 was formed by a ternary simultaneous vapor deposition method using a vapor deposition apparatus provided with a Cu, In, and Se evaporation source capable of closing an opening by a shutter. FIG. 1 shows the film forming profile, in which the temperature of the substrate and each evaporation source is increased, and at the time A when the substrate temperature exceeds a predetermined temperature of 550 ° C., the shutter of each evaporation source is opened, and then the deposition is performed for 40 minutes. When reaching the point B after the film time, the shutters of the evaporation source of Cu and the evaporation source of In were closed, but the shutter of the evaporation source of Se was kept open. Then, the heater of the substrate was turned off to cool the substrate. As a result, desorption of Se during cooling of the substrate could be prevented. When the substrate temperature reached 300 ° C. at about 20 minutes C, the shutter of the evaporation source of Se was closed. in this case,
If the supply of Se is continued until the substrate temperature becomes too low, then Se becomes excessive, and the excess Se degrades the solar cell characteristics. In order to prevent this, the supply of Se should be 30 higher than the melting point of Se.
The excess of Se was prevented by stopping the supply at about 0 ° C.
Since the melting point of Se is 217 ° C,
Supply needs to be stopped.

As a result of trial production of a solar cell using the CuInSe ₂ thin film obtained in this example as an active layer, a conversion efficiency of 10% or more was shown immediately after the production. In addition, even if annealing was performed in an oxygen atmosphere, the characteristics were hardly changed, indicating that annealing in an oxygen atmosphere was unnecessary. As described above, when Se is supplied when the substrate temperature after film formation is cooled, desorption of Se is suppressed, and a good film can be obtained.

In another embodiment, a substrate on which a CuInSe ₂ thin film is formed by a conventional vapor deposition method or sputtering method is H
_The substrate is kept at 600 ° C. for 30 minutes in an atmosphere of ₂ Se, and then the substrate is cooled. When the temperature reaches about 300 ° C., the supply of H ₂ Se is stopped.
₂ atmosphere. This compensated for the Se removed, and the same effect was obtained. The effect can be obtained by heating the substrate in a Se atmosphere at a temperature higher than the temperature at the time of film formation, but it cannot be increased to a temperature exceeding 600 ° C. in view of the heat resistance of the substrate or the film thereon. Further, if the processing is performed in an S atmosphere such as H ₂ S instead of the Se atmosphere, S enters the defect portion where Se is desorbed, and the forbidden band width only on the film surface can be changed. Higher efficiency can also be expected.

[0010]

According to the present invention, a chalcopyrite-type ternary compound thin film having the chemical formula XYZ ₂ , wherein X is silver or copper, Y is indium or gallium, and Z is selenium or sulfur, is used for the active layer. In the method of manufacturing a thin film solar cell, after the XYZ ₂ thin film is formed, when the substrate temperature is cooled,
By maintaining the Z atmosphere, Z desorption from the film surface is prevented. According to this method, defects and the like on the surface of the CIS thin film of the solar cell can be suppressed, and a good junction can be formed.
The efficiency of the solar cell is improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a change in a film formation rate of each element and a change in a substrate temperature in a CuInSe ₂ film formation process according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a CuInSe ₂ thin film solar cell manufactured according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Metal electrode 3 CuInSe ₂ thin film 4 CdS thin film 5 ZnO thin film 6 Metal electrode

Claims (5)

(57) [Claims] 1. A method for manufacturing a thin film solar cell using a chalcopyrite type ternary compound thin film having the chemical formula XYZ ₂ , wherein X is silver or copper, Y is indium or gallium, and Z is selenium or sulfur, as an active layer. In, XYZ
After ₂ thin film deposition, which is treated with an atmosphere containing Z, characterized in that the processing target substrate heated during the XYZ ₂ thin film deposition, and shall be cooled in an atmosphere containing Z Of manufacturing a thin film solar cell. 2. The XYZ ₂ thin film is formed by applying a ternary simultaneous vapor deposition method in which vapors of X, Y, and Z are supplied to heat the substrate on which the XYZ ₂ thin film is formed. When cooling
2. The method according to claim 1, wherein the supply of the X and Y vapors is stopped and only the Z vapor is supplied. 3. The method for manufacturing a thin-film solar cell according to claim 1, wherein the treatment in the atmosphere containing Z is stopped when the temperature of the substrate to be cooled is 250 ° C. or higher. 4. The method for producing a thin-film solar cell according to claim 1, wherein after forming an XYZ ₂ thin film in which Z is selenium, the film is treated in an atmosphere containing selenium. 5. The method for producing a thin-film solar cell according to claim 1, wherein after forming the XYZ ₂ thin film wherein Z is selenium, the film is treated in an atmosphere containing sulfur.