JPH06188444A - Manufacture of film solar cell - Google Patents

Abstract

PURPOSE:To prevent the swelling of volume in the vicinity of a substrate by penetrating gas-form group V1 element and also, suppress the production of V1 compounds on the surface of a substrate by keeping the area near to the substrate of an initial film containing the group V1 element. CONSTITUTION:A lower electrode 2 is formed on a glass substrate 1 by the sputterning of Mo, Cr, or the like, and then a Cu-In-Se mixed film 3 is formed at 200 deg.C in substrate temperature by a triple simultaneous evoparation method. Then, a Cu-In mixe film 4 is formed. Next, processing it for about one hour at approximately 400 deg.C in substrate temperature in atmosphere including S, for example, in the gas containing H2Se deluted with Ar by about 3-15% forms a CuInSe2 film 5 by the reaction of Se being thermally decomposed from H2Se. For this CuInSe2 film 5, the adhesive strength of the interface with the lower electrode 2 on the substrate 1 is favorable. Hereby, the efficiency of a solar cell can be improved sharply.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a thin film solar cell in which light energy such as sunlight is converted into electric energy by bonding with a chalcopyrite type ternary semiconductor compound thin film.

[0002]

2. Description of the Related Art I-III-VI₂Tribe chalcopyrite type three
Original compound thin film, especially CuInSe₂, CuInS ₂, AgInSe₂, Ag
InS₂Has an optical gap of 1.0 to 1.8 eV,
It is expected to be used as a photoelectric conversion element. These days
Thin film solar cell device
It is attracting more attention as a material. Below this type of solar cell
To form chalcopyrite-type ternary compound thin films at room temperature
About the method, CuInSe₂The conventional technology is explained by taking
To do.

As a film forming method of a CuInSe ₂ thin film, a ternary simultaneous vapor deposition method, a selenization method, etc. are known. In the selenization method, after forming a Cu / In laminated film on a substrate at room temperature, Substrate temperature 400 ~ 550 ℃ in Se diluted with Ar, for example 3 ~ 15
This is a method of forming a CuInSe ₂ thin film having a large grain size of about 3 μm by treating it in a gas containing% H ₂ Se for several hours. When the VI group element is S, the treatment is performed in an S atmosphere.

[0004]

When processing in H ₂ Se in the process of the selenization method as described above, Se gas invades the surface of the substrate, and Se compounds such as, for example, Se compounds on the surface of the substrate during the temperature rising process. MoSe ₂ is generated on the Mo electrode layer on the surface of the substrate. This Se compound has a high resistance, and the form factor of the manufactured solar cell (F
F) will be lowered. Moreover, since Se enters the Cu / In laminated film and reacts with it, volume expansion occurs, and the adhesive force at the substrate / CuInSe ₂ thin film interface is weakened, and there is a problem in industrialization such as large area.

Next, the Cu-In-Se mixed film was formed into H _{2 in the same} manner as above.
When treated in Se, the problem of the substrate / CuInSe ₂ thin film interface does not occur, but since it reacts with Se in the film during the temperature rising process, a CuInSe ₂ thin film is formed at a relatively low temperature, and the grain size is about 1
It did not grow further up to about μm, and the efficiency of the manufactured solar cell was low. An object of the present invention is to provide a method for producing a thin film solar cell having a chalcopyrite type compound thin film having a large grain size, which is formed without forming a group VI element compound on the substrate surface.

[0006]

In order to achieve the above object, in a method for producing a thin film solar cell having a group I-III-VI ₂ chalcopyrite type ternary compound thin film on a substrate, a periodic pattern is formed on the substrate. After forming an initial film consisting of the group I element and the group III element and containing the group VI element only on the substrate side, the treatment is performed in the group VI element atmosphere. Then, it is effective that the amount of the group VI element contained in the initial film is equal to or less than the sum of the amount of the group I element and the amount of the group III element. The initial film may be a laminated film of each element or a mixed film. Furthermore, it is effective that the substrate temperature during the initial film formation is 400 ° C. or lower.

[0007]

[Function] By including the group VI element in the vicinity of the substrate of the initial film, the volume expansion of the invading gaseous group VI element in the vicinity of the substrate is prevented, and during the temperature rising process Since the -III-VI ₂ group compound is formed, the generation of the VI group compound on the substrate surface is suppressed. Further, suppressing the substrate temperature at the time of forming the initial film to 400 ° C. or lower enhances the effect of suppressing volume expansion and compound formation in the vicinity of the substrate. Also III
Since the group element is present only near the substrate, the formed film surface reacts with the gas group VI element at a high substrate temperature to cause I-II.
A group I-VI compound is formed, and a large grain size can be grown.

[0008]

EXAMPLES Examples of the present invention in producing CuInSe ₂ thin film solar cells will be described below. 1 (a) to 1 (d) show a manufacturing process of a CuInSe ₂ thin film solar cell according to an embodiment of the present invention, in which Mo, Cr, etc. are sputtered on a glass substrate 1 [(a) in the same figure]. Lower electrode 2 with a thickness of about 1 μm
After the formation of [FIG. 2 (b)], the Cu—In—Se mixed film 3 is formed at a substrate temperature of 200 ° C. by the ternary simultaneous vapor deposition method. At this time, for example, Cu / In = 0.95 and Se / (Cu + In) = 1 or less are controlled. Further, the Cu-In-Se film 3 is provided only in the vicinity of the substrate, and for example, Cu corresponding to the Cu film having a thickness of about 0.2 μm is evaporated and In corresponding to the In film having a thickness of about 0.465 μm is evaporated. When evaporating, close the shutter of the Se evaporation source at the time when Cu corresponding to a thickness of 0.1 μm or less is evaporated,
Then, a Cu-In mixed film 4 is formed [FIG. Next, an atmosphere containing Se, for example, H ₂ Se diluted with Ar is added to 3
When treated in a gas containing about 15% at a substrate temperature of about 400 ° C for about 1 hour, it reacts with Se pyrolyzed from H ₂ Se.
A CuInSe ₂ thin film 5 is formed [(d) in the figure].

CuInSe ₂ thin film 5 formed by this method
Has a good adhesive force at the interface with the lower electrode 2 on the substrate 1, and has a particle size of about 3 μm, which is larger than about 1 μm of the CuInSe ₂ thin film obtained from the Cu—In—Se mixed film of the conventional method and is a good film. was gotten. In addition, the lines 21 and 22 in FIG.
CuInSe ₂ thin film obtained by the conventional method without containing
The open circuit voltage V _OC and the conversion efficiency E _ff of the solar cell prototyped using are shown. The solar cell using CuInSe ₂ thin film of this method has a high open circuit voltage and a good conversion efficiency of 12% or more.

As another method, as for the Cu / In laminated film, Se is simultaneously formed at the time of Cu formation, and the Cu film thickness is about 1 /
After the supply of Se was stopped at around 2, Cu was formed to a specified film thickness, then
In may be formed. Line 23, 24 in FIG. 2, a solar cell using the CuInSe ₂ thin film thus obtained, simply open the solar cell using the CuInSe ₂ thin film obtained by the conventional method selenide a Cu / In stacked film The voltage and conversion efficiency are shown for comparison. In addition, the AgInSe ₂ selenide method, CuInS _2, AgInS
_The same effect can be obtained when the film of _{2 is formed} by the sulfurization method.

[0011]

INDUSTRIAL APPLICABILITY I-III containing a Group VI element only near the substrate
By heat-treating the element laminated film and the mixed film in an atmosphere containing Se, it is possible to prevent the volume expansion near the substrate, and the I-III-VI ₂ group compound is formed early only in the vicinity of the substrate during the temperature rising process. Therefore, the production of the group VI element compound can be suppressed. Further, since the group VI element exists only near the substrate, the film surface can be grown to a large particle size by reaction with a gaseous group VI element, for example, Se thermally decomposed from H ₂ Se, and the efficiency of the solar cell is increased. Can be improved.

[Brief description of drawings]

FIG. 1 shows a CuInSe ₂ film forming process in one embodiment of the present invention.
Sectional views shown in order from (a) to (d)

FIG. 2 is a film formed by an embodiment of the present invention and a conventional method.
Comparative diagram of characteristics of solar cell with CuInSe ₂ thin film

[Explanation of symbols]

1 Glass substrate 2 Lower electrode 3 Cu-In-Se mixed film 4 Cu-In mixed film 5 CuInSe ₂ film

Claims (5)

[Claims] 1. A method of manufacturing a thin film solar cell having a group I-III-VI chalcopyrite ternary compound thin film on a substrate, comprising a group I element and a group III element of the periodic table, and a group VI element only on the substrate side. A method for manufacturing a thin-film solar cell, comprising: treating the substrate in an atmosphere of a Group VI element after forming an initial film containing Al. 2. The method for producing a thin film solar cell according to claim 1, wherein the amount of the group VI element contained in the initial film is not more than the sum of the amount of the group I element and the amount of the group III element. 3. The method for producing a thin film solar cell according to claim 1, wherein the initial film is a laminated film of each element. 4. The method for producing a thin film solar cell according to claim 1, wherein the initial film is a mixed film of each element. 5. The method for producing a thin film solar cell according to claim 1, wherein the substrate temperature during the initial film formation is 400 ° C. or lower.