JP2003078149A - Method for manufacturing photovoltaic element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a photovoltaic element having a higher efficiency and high reliability, by depositing an amorphous silicon or a microcrystal silicon of a photoelectric conversion layer without deteriorating light transmission characteristics of a transparent conductive film, when a silicon is deposited on the conductive film made of an oxide to form the conversion layer. SOLUTION: The method for manufacturing the photovoltaic element comprises the steps of forming an extra-thin film made of the amorphous silicon layer or the microcrystal silicon at an initial time of depositing the silicon on the transparent conductive film, and thereafter forming the photoelectric conversion layer.

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 highly efficient photovoltaic element without deteriorating the light transmittance of a transparent conductive film made of an oxide. The photovoltaic element is used for a solar cell or the like.

[0002]

2. Description of the Related Art Thin film solar cells are conventionally manufactured by using amorphous silicon (hereinafter referred to as a-Si), CdTe, CuInSe.
It is known to use 2 or the like. Among them, a-Si is thin and can be manufactured at a relatively low temperature. This a
A PECVD method (plasma CVD method) using silane or hydrogen as a raw material is widely used as a method for forming a -Si solar cell, and ITO is formed on a transparent substrate such as glass or plastic.
A on a substrate on which a transparent conductive film such as SnO2 or SnO2 is deposited.
A method of depositing a photoelectric conversion layer made of —Si is often used.

However, in such a film formation of a-Si by PECVD, a reaction occurs in a reducing atmosphere due to hydrogen radicals, so that the surface of the transparent oxide conductive film such as ITO or SnO 2 is reduced and metal rich. It is known that a film is deposited and the visible light transmittance is reduced. It is considered that this reduces the amount of light that reaches the photoelectric conversion layer made of a-Si or microcrystalline silicon, resulting in a decrease in conversion efficiency.

Therefore, if the transparent conductive film can be protected without creating a reducing atmosphere at the initial stage of deposition of a-Si or microcrystalline silicon which is the photoelectric conversion layer, the visible light transmittance will not be lowered and the conversion efficiency will be lowered. Can escape.

[0005]

In forming the above-mentioned transparent conductive film protective layer, a method is adopted in which a reducing atmosphere is not used.
-Si or microcrystalline silicon must be made. Further, if the a-Si layer becomes thicker, light is absorbed there, and the amount of light reaching the photoelectric conversion layer decreases, so that it is required to be deposited extremely thinly. Therefore, the present invention provides a method for producing a photoelectric conversion element having higher efficiency and higher reliability by depositing a-Si or microcrystalline silicon that is a photoelectric conversion layer without deteriorating the light transmission characteristics of the transparent conductive film. The purpose is to do.

[0006]

The present invention has been made to solve the above problems, and the invention according to claim 1 is
A method for producing a photovoltaic element, characterized in that an ultrathin film made of an amorphous silicon layer or microcrystalline silicon is formed on a transparent conductive film at the initial stage of depositing silicon, and then a photoelectric conversion layer is formed. .

According to a second aspect of the present invention, in the method of manufacturing a photovoltaic element according to the first aspect, the ultrathin film made of the amorphous silicon layer or microcrystalline silicon is formed by means of physical vapor deposition (PVD). It is characterized by forming a film.

The invention according to claim 3 is the method for producing a photovoltaic element according to claim 1 or 2, wherein the transparent conductive film is made of an oxide having a specific resistance of 5 × 10 −4 Ωcm or less. It is characterized by

According to a fourth aspect of the present invention, in the method of manufacturing a photovoltaic element according to any one of the first to third aspects, an ultrathin film made of the amorphous silicon layer or microcrystalline silicon and photoelectric conversion are provided. The feature is that layers are formed continuously without exposure to the atmosphere.

According to a fifth aspect of the present invention, in the method of manufacturing a photovoltaic element according to any one of the first to fourth aspects, the photoelectric conversion layer is formed by means of plasma CVD method. Characterize things.

According to a sixth aspect of the present invention, in the method of manufacturing a photovoltaic element according to any one of the first to fifth aspects, the ultrathin film made of the amorphous silicon layer or microcrystalline silicon is B It is characterized by comprising any one of doped amorphous silicon, B-doped microcrystalline silicon, amorphous silicon carbide, microcrystalline silicon carbide, B-doped amorphous silicon carbide, and B-doped microcrystalline silicon carbide.

<Operation> a on the transparent conductive film in the present invention
Since the method of depositing —Si or microcrystalline silicon does not expose the transparent conductive film to a reducing atmosphere, it suppresses a phenomenon in which the transmittance of visible light decreases due to metal deposition due to a decrease in the degree of oxidation of the transparent conductive film. In addition, since the film thickness of a-Si or microcrystalline silicon by the PVD method is very thin, PVD
When a photoelectric conversion layer is deposited by the CVD method in a hydrogen plasma atmosphere after the film is deposited by the method, the surface modification causes a defect in a-Si, and the photoelectric conversion efficiency is not reduced.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1A is a sectional view showing an example of the structure of a photovoltaic element obtained by the method for producing a photovoltaic element of the present invention. FIG. 1B is a cross-sectional view showing an example of the steps of the method for manufacturing a photoelectric conversion element of the present invention and the main part of the apparatus. The photovoltaic element obtained by the method for producing a photoelectric conversion element of the present invention comprises a transparent conductive film 2, an a-Si layer 3, and a photoelectric conversion layer, which are sequentially made of ITO on a transparent insulating substrate 1 made of transparent glass. 4 is a photovoltaic element having a structure in which a lower electrode layer 5 is laminated.

An ultra-thin film of a-Si or microcrystalline silicon is deposited by the PVD method on a base material having a transparent conductive film formed on a transparent insulating substrate without creating a reducing atmosphere.
After that, by forming a photoelectric conversion layer by PECVD method, PE
It is characterized by suppressing a decrease in the transmittance of the transparent conductive film in the reducing atmosphere of CVD. The PVD method used here is any one of EB vapor deposition, ion plating method and magnetron sputtering method, and is preferably the ion plating method using a cluster ion beam. Further, the film thickness is an ultrathin film having a thickness of about 5Å to 20Å.

Further, as the photoelectric conversion layer, any of amorphous silicon, amorphous silicon carbide, microcrystalline silicon and microcrystalline silicon carbide is used for the B-doped layer, and amorphous silicon, microcrystalline silicon, amorphous silicon germanium, and intrinsic silicon are used for the intrinsic layer. Either microcrystalline silicon germanium or silicon carbide is used, and PE is used for each film forming method.
The CVD method is used to promote the improvement of the electrical characteristics of the ultra-thin film of a-Si or microcrystalline silicon produced by the PVD method.

Next, a method for manufacturing the photoelectric conversion element of the present invention will be described. As shown in FIG. 1B, after setting the substrate 10 on which the transparent conductive film is deposited in the preliminary exhaust chamber 11, the preliminary exhaust chamber 11 is exhausted to 10 −5 Pa or less, and the substrate is transferred to the PVD chamber 12. In the PVD chamber 12, a transparent conductive film protective layer (B-doped a-Si layer) is deposited by the EB vapor deposition method. After that, the substrate is transferred to the CVD chamber 13 and PECV
The photoelectric conversion layer is formed by the D method. By the method for producing a photoelectric conversion element of the present invention described above, the transparent conductive film protective layer 3 and the photoelectric conversion layer 4 can be continuously produced without exposure to the air, and impurities such as water and oxygen at the interface between both layers can be formed. Prevents mixture and prevents deterioration of photoelectric conversion efficiency.

Although the transparent glass substrate is used as the transparent insulating substrate 1 described above, it goes without saying that a transparent insulating substrate made of a flexible film substrate can also be used. Moreover, not only EB vapor deposition as PVD method,
An ion plating method or a magnetron sputtering method can also be applied. In particular, when the a-Si layer is formed by an ion plating method using a cluster ion beam, the transparent conductive film layer 2 is hardly damaged, and the light transmittance and the electrical conductivity are reduced. It is possible to form the protective layer 3 that does not deteriorate the properties.

[0018]

EXAMPLES A method of manufacturing the photovoltaic element of the present invention will be specifically described below with reference to FIG.

<Example 1> A transparent conductive film 2 made of ITO was deposited on a transparent insulating substrate 1 made of transparent glass by a sputtering method to give a light irradiation side electrode. IT
The specific resistance of O was 4.1 × 10 −4 Ωcm, and the visible light transmittance was about 80% on average. On top of that, EB
The a-Si layer 3 was deposited by the vapor deposition method. Regarding the deposition conditions in the EB vapor deposition, first, the degree of vacuum was set to 5 × 10 −5 Pa or less, the substrate temperature was set to 100 ° C., and the target was irradiated with EB. After the target silicon was sufficiently heated, the shutter was opened to start vapor deposition. The deposition rate and time are 5 Å / sec for 5 seconds, and after the deposition, PECV without opening to the atmosphere.
The photoelectric conversion layer 4 was deposited by D. The silicon target used for vapor deposition is a B-doped wafer with a specific resistance of 100 Ωcm placed in a crucible and melted by EB. Further, on the a-Si layer 3, B-doped a-Si is 30 nm, intrinsic a-Si is 300 nm, and P-doped a-Si is 20 nm as a photoelectric conversion layer 4 by PECVD.
Each was deposited, and Ag was further deposited as the lower electrode layer 5 by a vapor deposition method. The photoelectric conversion characteristics (open circuit voltage Voc, short-circuit current density Jsc, photoelectric conversion efficiency η) of the obtained photoelectric conversion element were set to AM1.5 pseudo sunlight (100 mW / cm).
Using 2), the photovoltaic element was evaluated under the conditions of a temperature of 25 ° C. and a humidity of 50%. The results are shown in Table 1.

[0020]

[Table 1]

<Comparative Example 1> Next, for comparison with Example 1, a photovoltaic element having a B-doped a-Si layer 3 serving as a transparent conductive film protective layer formed by PECVD was produced.
The manufacturing conditions of this photovoltaic element were the same as in Example 1 except for the a-Si layer 3. The B-doped a-Si layer in this photovoltaic element was formed under the same film-forming conditions as those for the B-doped layer of the photoelectric conversion layer 4 in Example 1, and the B-doped a-Si layer was formed.
The thickness of the entire -Si layer was set to 32 nm, which is almost the same as in Example 1. The photoelectric conversion characteristics of the photoelectric conversion element obtained in Comparative Example 1 were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0022]

[Table 2]

From these, Voc and fill factor FF are not so different, but in the photovoltaic element in which the transparent conductive film protective layer 3 of the present invention is manufactured by the PVD method, the decrease in Jsc due to the decrease in the transmittance of the ITO film can be suppressed. I understand that.

[0024]

EFFECTS OF THE INVENTION According to the inventions of claims 1 and 2, even when the transparent conductive film layer is deteriorated in light transmissivity due to a reducing atmosphere during formation of the photoelectric conversion layer after the transparent conductive film is formed, It is possible to provide a highly efficient photovoltaic element without deteriorating the light transmittance by protecting the photovoltaic element. Further, according to the invention of claim 4, it is possible to provide a highly efficient photovoltaic element by preventing impurities such as water and oxygen from being mixed in the photoelectric conversion layer and preventing deterioration of photoelectric conversion characteristics. Further, according to the invention of claim 5, an a-Si layer or a microcrystalline silicon layer having good electric conductivity is provided by the defect modification action of the a-Si layer made of PVD which is a transparent conductive film protective layer. It is possible to
The photovoltaic element obtained by the method for producing a photovoltaic element of the present invention is used for a solar cell or the like.

[Brief description of drawings]

FIG. 1A is a cross-sectional view showing an example of the configuration of a photovoltaic element obtained by the method for producing a photovoltaic element of the present invention. (B) is sectional drawing which showed an example of the manufacturing process of the photoelectric conversion element of this invention, and the principal part of an apparatus.

[Explanation of symbols]

1. Transparent insulating substrate 2 ... Transparent conductive film 3 ... a-Si layer for protecting transparent conductive film 4 ... Photoelectric conversion layer 5 ... Lower metal electrode layer 10 ... Substrate 11 ... Exhaust chamber 12 ... PVD deposition chamber 13 ... CVD film forming chamber 14 ... Preliminary exhaust chamber

Claims (6)

[Claims] 1. A photovoltaic device, comprising: forming an amorphous thin film or an ultrathin film of microcrystalline silicon on a transparent conductive film at an initial stage of depositing silicon, and then forming a photoelectric conversion layer. Of manufacturing. 2. The method of manufacturing a photovoltaic element according to claim 1, wherein the ultrathin film made of the amorphous silicon layer or microcrystalline silicon is formed by means of physical vapor deposition (PVD). . 3. The method for producing a photovoltaic element according to claim 1, wherein the transparent conductive film is made of an oxide having a specific resistance of 5 × 10 −4 Ωcm or less. 4. The ultrathin film made of the amorphous silicon layer or microcrystalline silicon and the photoelectric conversion layer are continuously formed without exposure to the atmosphere. A method for manufacturing the photovoltaic element according to 1. 5. The method of manufacturing a photovoltaic element according to claim 1, wherein the photoelectric conversion layer is formed by using a plasma CVD method. 6. An ultrathin film comprising the amorphous silicon layer or microcrystalline silicon is B-doped amorphous silicon, B-doped microcrystalline silicon, amorphous silicon carbide, microcrystalline silicon carbide, B-doped amorphous silicon carbide, B-doped microcrystalline silicon. 6. The method for producing a photovoltaic element according to claim 1, wherein the photovoltaic element is made of any one of carbides.