JP2815719B2 - 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 of manufacturing a thin film solar cell having a junction using a group I-III-VI compound semiconductor formed on a metal electrode.

[0002]

2. Description of the Related Art I-III-VI compound semiconductors, for example,
Copper indium diselenide (CuInSe _Two), Copper indium
Sulfide (CuInS_Two), Silver indium diselenide
(AgInSe_Two) Indicates that the optical band gap is in the range of 1.0 to 1.8 eV.
Light that is different from silicon with a band gap of 1.7 eV
Can be obtained with
Use is expected. In recent years, with the development of thin film formation technology,
These materials as thin film solar cell element materials
Attention has been paid. For example, CuInSe_TwoIs the optical band
The gap is about 1 eV, has a direct transition type band structure, and p
And n-type conductivity. In addition, band gap 2.4e
The lattice mismatch with CdS of V is also about 1%.
-Type CuInSe using p-type CdS as window layer material_TwoHeterojunction of
The development of thin-film solar cells having a combination is underway. CuIn
Se_TwoElectrodes for Heterojunction Thin Film Solar Cells Including Thin Film Layers
And CuInSe_TwoGallium improves adhesion to thin film layers
To increase the processing temperature in the photovoltaic device manufacturing process.
Making this possible is known from Japanese Patent Application Laid-Open No. 2-94669.
You. FIG. 2 shows one of the thin-film solar cells described in the above publication.
Is a cross-sectional view of a portion, on the glass substrate 1 having a thickness of 1 to 4 mm,
Metal electrode layer 2 made of molybdenum (Mo) of 0.2 to 2 μm
Is formed. The semiconductor layer has a thickness of 1 as a p-type semiconductor layer.
~ 3μm CuInSe_TwoThin film layer 4, thickness as n-type semiconductor layer
Cadmium sulfide (CdS) thin film layer 5 of 250 to 500 お よ び
Conductive with wide bandgap, n-type as window layer
1.5-3.5 μm thick zinc oxide (ZnO), which is a semiconductor layer
It is composed of a thin film layer 6. Metal electrode layer 2 and CuInSe_TwoWith thin film layer 4
The gallium (G
a) is formed. On top of layer 6
Aluminum (A
1) is formed.

Here, a thin film layer 3 containing gallium (Ga) is used.
Is obtained by magnetron sputtering of a copper gallium alloy having 17 atomic% of gallium on the metal electrode layer 2.
It is formed to a thickness of 2000-3000mm. CuInSe ₂ thin film layer 4
Is formed on the thin film layer 3 by a magnetron sputtering method, followed by forming a thin film of indium (In) having a thickness of 3000 to 4000 ° and then heating in a selenium (Se) atmosphere. That is, in a heating furnace filled with a gas containing 12% H ₂ Se diluted with nitrogen gas, a metal electrode layer 2, a gallium-containing layer 3, and indium (I
n) First, the glass substrate 1 on which the thin film layer is formed
By heating for 5 to 20 minutes and then at 450 ° C. for 30 minutes, a CuInSe ₂ thin film layer 4 is obtained. Thus CuIn
Se ₂ is a thin film layer 3 formed by heating in a selenium (Se) atmosphere.
Formed by the interdiffusion of indium and selenium with copper in

It is described that in the above-described manufacturing process, by providing the layer 3 containing gallium, the adhesion between the molybdenum layer and the CuInSe ₂ thin film layer 4 is improved. That is, the molybdenum metal layer 2 on the glass substrate 1 and the
When the adhesion to the CuInSe ₂ thin film layer 4 is not always sufficient, the CuInSe ₂ thin film layer may wrinkle, warp or peel off. As a result, the processing temperature in the manufacturing process of the thin film solar cell can be increased, and the conversion efficiency is improved.

[0005]

According to the above prior art, the effect of improving the adhesion at the interface can be obtained by providing a layer containing gallium near the molybdenum metal electrode layer. However, in the conventional technique, a CuInSe ₂ thin film layer is obtained by heating a layer containing gallium and copper and an indium thin film layer formed by sputtering in a selenium atmosphere. For this reason, gallium diffuses into the CuInSe ₂ thin film layer due to the heating history, and the gallium concentration at and near the interface on the molybdenum metal electrode layer is reduced, so that there is a disadvantage that sufficient adhesion without peeling cannot be obtained.

SUMMARY OF THE INVENTION An object of the present invention is to prevent gallium, which is placed in the vicinity of a metal electrode of an I-III-VI compound semiconductor layer, from being diffused by heating to improve adhesion to a metal electrode, thereby preventing sound from being peeled off. It is an object of the present invention to provide a method of manufacturing a thin-film solar cell in which excellent adhesion is performed.

[0007]

In order to achieve the above object, the present invention provides a thin-film solar cell in which a gallium-containing layer is interposed on a side of a group I-III-VI compound semiconductor layer close to a metal electrode layer. In the manufacturing method, after forming a gallium-containing layer on the metal electrode layer, a sulfur film is applied on the surface of the layer, and then a heat treatment is performed on the film to form a sulfur film.
A group III-VI compound semiconductor layer is formed.
The group I-III-VI compound is copper indium diselenide (CuInSe ₂ ), a copper gallium layer is formed on the metal electrode layer, and a sulfur-containing solution is brought into contact with the surface of the copper gallium layer to contact the sulfur. It is effective to form a film, then laminate at least an indium layer on the film, and heat in an atmosphere containing selenium to form a CuInSe ₂ layer. Further, it is also effective to laminate a copper layer in addition to the indium layer on the copper gallium layer having a sulfur coating on the surface. It is also effective that the solution containing sulfur is an ammonium polysulfide solution.

[0008]

After forming a layer containing gallium, a sulfur (S) film is deposited on the surface, so that a thin film consisting of several atomic layers of sulfur is formed on the surface of the layer containing gallium. Due to the presence of the sulfur coating, diffusion of gallium due to a heat treatment in a later step is prevented, and gallium remains at and near the interface on the metal electrode layer, so that sufficient adhesion without peeling can be obtained.

[0009]

FIG. 1 is a cross-sectional view of a Cu manufactured according to an embodiment of the present invention.
InSe_TwoPart of solar cell including heterojunction using thin film layer
2 and the same parts as those in FIG.
Have been. In the figure, on a glass substrate 1 having a thickness of 1 mm
The metal electrode layer 2 made of molybdenum (Mo) with a thickness of 2 μm
It is formed. The semiconductor layer formed thereon is a p-type semiconductor.
CuInSe with a body layer thickness of 2 μm_TwoOf the thin film layer 4 and the n-type semiconductor layer
Cadmium sulfide (CdS) thin film layer 5 with a thickness of 400 mm
3 μm thick n-type semiconductor layer as a window layer also serving as an extreme layer
m of zinc oxide (ZnO) thin film layer 6. On the ZnO layer 6
Has a strip-shaped metal electrode layer 7 made of aluminum (Al).
Has been established. Metal electrode layer 2 and CuInSe _TwoBetween thin film layer 4
3,000 mm thick thin film layer 3 made of copper-gallium
And a sulfur coating 8 are formed.

In such a structure, first, the molybdenum electrode layer 2 is formed by sputtering, and
The thin film layer 3 made of copper-gallium is formed by sputtering a copper gallium alloy having gallium of atomic%. Subsequently, the film is immersed in an ammonium polysulfide solution and left at 50 ° C. for 3 hours to form a sulfur coating 8 on the surface of the thin film layer 3. Here, ammonium polysulfide has the chemical formula ((NH ₄ ) ₂
S _x , x> 1) Sulfur-rich ammonium sulfide which can be represented by the following formula: By dipping in the ammonium polysulfide solution, a coating 8 containing sulfur as a main component and having a thickness of about 10 nm is formed on the surface of the copper gallium layer 3. According to the Auger electron spectroscopy analysis, it was confirmed that the sulfur in the ammonium polysulfide was adsorbed on the copper gallium surface and remained as a thin film composed of several atomic layers of sulfur.

[0011] Again, the thickness of 2000 mm by sputtering
A copper (Cu) thin film layer and a 4400 mm thick indium (In) thin film layer are continuously formed, and a CuInSe ₂ thin film layer 4 is formed by selenization. As a selenization method, a glass substrate 1 on which a thin film layer is formed is heated at 500 ° C. for 30 minutes in a heating furnace filled with a nitrogen gas containing 12% H ₂ Se to obtain Cu.
Obtain an InSe ₂ thin film layer. Finally, an aluminum electrode layer 7 is formed by sputtering and patterning.

The molybdenum layer 2 obtained by the above manufacturing method
In the Auger analysis of the upper copper gallium layer 3 and the CuInSe ₂ thin film layer 4, gallium was detected only in the copper-gallium layer 3, but not in the CuInSe ₂ thin film layer 4.
This is due to the presence of the sulfur coating 8 on the copper gallium layer 3,
This shows that gallium is prevented from diffusing into the CuInSe ₂ thin film layer 4.

Further, in the thin-film solar cell obtained by using the above-mentioned manufacturing method, no wrinkle, peeling or the like was observed in the CuInSe ₂ thin film. The fact that peeling does not occur even by heating at 500 ° C. in the selenization step indicates that the adhesion between the CuInSe ₂ thin film and the molybdenum layer in this example is good. And CuInSe
₂ is generated by the interdiffusion of copper, indium and selenium in the selenization process, so heating at a higher temperature enables a high-quality film to be obtained in a short time, improving solar cell characteristics and reducing manufacturing time. It means that it can be shortened.

The thin-film solar cell obtained according to the present embodiment exhibited an improvement in conversion efficiency of about 5% as compared with the solar cell according to the prior art. This is mainly due to an increase in release voltage (V _OC ), that is, an increase from about 0.43 volts in the prior art to about 0.48 volts, which results in improved adhesion and higher heat treatment temperature in the selenization process. This is due to the fact that

In the above embodiment, an alloy of gallium and copper was used, and a layer of pure copper was further formed. However, it is necessary to increase the thickness of the copper gallium layer and supply sufficient copper for forming CuInSe ₂ therefrom. If possible, only the indium thin film layer may be laminated without forming the pure copper thin film layer. Further, the layer containing gallium may contain not only copper but also indium. The present invention can be implemented in a thin film is not limited to the solar cell, thin film solar cell having an I-III -VI compound semiconductor thin film layer is a metal electrode in contact with one surface using CuInSe _2.

[0016]

According to the present invention, a layer containing gallium is provided on a metal electrode, a sulfur film is formed on the layer, and then a group I-III-VI compound semiconductor thin film layer is laminated. Gallium was prevented from diffusing into the semiconductor thin film layer during the heat treatment in the subsequent step, and the effect of improving the adhesiveness of the semiconductor thin film layer by containing gallium near the interface with the metal electrode layer could be maintained. Thus, for example, CuIn
The heat treatment temperature of selenization for obtaining a Se ₂ thin film can be raised to 500 ° C. without causing separation from the metal electrode layer, and selenization can be performed in a short time. It has become possible to obtain a group VI compound semiconductor thin film layer. For this reason, the conversion efficiency of the thin-film solar cell was improved.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view of a thin-film solar cell according to one embodiment of the present invention.

FIG. 2 is a partial cross-sectional view of a conventional thin-film solar cell.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Metal electrode layer 3 Copper gallium thin film layer 4 CuInSe ₂ thin film layer 5 CdS thin film layer 6 ZnO thin film layer 7 Al layer 8 Sulfur coating

Claims (4)

(57) [Claims] In a method of manufacturing a thin-film solar cell in which a gallium-containing layer is interposed on a side of a group I-III-VI compound semiconductor layer near a metal electrode layer, after forming a gallium-containing layer on the metal electrode layer, , Applying a sulfur coating on the surface of the layer,
Next, I-II is performed on the film by a process including a heat treatment.
A method for manufacturing a thin-film solar cell, comprising forming an I-VI compound semiconductor layer. 2. The group I-III-VI compound is copper indium diselenide, a copper gallium layer is formed on a metal electrode layer, and a sulfur-containing solution is brought into contact with the surface of the copper gallium layer to form a sulfur coating. The method for producing a thin-film solar cell according to claim 1, wherein after forming at least an indium layer on the coating, heating is performed in an atmosphere containing selenium to form a copper indium tin selenide layer. 3. The method for manufacturing a thin-film solar cell according to claim 2, wherein a copper layer is laminated in addition to the indium layer on the copper gallium layer having a surface coated with a sulfur film. 4. The method according to claim 2, wherein the solution containing sulfur is an ammonium polysulfide solution.