WO2013094403A1

WO2013094403A1 - Transparent conductive film laminate, method for producing same, thin-film solar cell, and method for producing same

Info

Publication number: WO2013094403A1
Application number: PCT/JP2012/081478
Authority: WO
Inventors: 健太郎曽我部; 山野辺　康徳; 文彦松村
Original assignee: 住友金属鉱山株式会社
Priority date: 2011-12-20
Filing date: 2012-12-05
Publication date: 2013-06-27
Also published as: JP5252066B2; TWI585783B; TW201342397A; JP2013131560A; CN104081534A

Abstract

Provided is a transparent conductive film laminate which exhibits excellent contact properties with an Si layer, exerts an excellent light confinement effect, and is useful as the surface electrode of a solar cell. Also provided are a method for producing said transparent conductive film laminate, a thin-film solar cell, and a method for producing same. The transparent conductive film laminate is formed as a three-layer laminate structure in which an indium oxide transparent conductive film (I) (21) formed on a translucent substrate (1) functions as a base, and a zinc oxide transparent conductive film (II) (22) exhibiting excellent concavo-convex properties and a transparent conductive film (III) (23) having a high work function are formed in said order on the indium oxide transparent conductive film (I) (21).

Description

Transparent conductive film laminate and manufacturing method thereof, thin film solar cell and manufacturing method thereof

The present invention provides a transparent conductive film laminate useful for producing a high-efficiency silicon-based thin film solar cell, excellent in contact with the Si layer, excellent in light confinement effect, and useful as a surface electrode of a solar cell, and The present invention relates to a manufacturing method, a thin film solar cell, and a manufacturing method thereof. This application claims priority on the basis of Japanese Patent Application No. 2011-278748 filed on December 20, 2011 in Japan, and is incorporated herein by reference. Is done.

Transparent conductive films with high conductivity and high transmittance in the visible light region are used for electrodes of solar cells, liquid crystal display elements, and other various light receiving elements, and in addition, heat ray reflection for automobile windows and buildings. It is also used as a transparent heating element for various types of antifogging, such as a film, an antistatic film, and a frozen showcase.

As transparent conductive films, tin oxide (SnO ₂ ) -based, zinc oxide (ZnO) -based, and indium oxide (In ₂ O ₃ ) -based thin films are known. As the tin oxide, those containing antimony as a dopant (ATO) and those containing fluorine as a dopant (FTO) are used.
As the zinc oxide system, those containing aluminum as a dopant (AZO) and those containing gallium as a dopant (GZO) are used.

The transparent conductive film most industrially used is an indium oxide type, and indium oxide containing tin as a dopant is referred to as an ITO (Indium-Tin-Oxide) film. Since it is obtained, it has been used widely.

In recent years, the global environmental problems due to the increase in carbon dioxide and the problem of rising prices of fossil fuels have been highlighted, and thin film solar cells that can be manufactured at a relatively low cost are attracting attention. A thin-film solar cell generally includes a transparent conductive film, one or more semiconductor thin-film photoelectric conversion units, and a back electrode, which are sequentially stacked on a light-transmitting substrate. Since silicon materials are abundant in resources, silicon-based thin-film solar cells using silicon-based thin films for photoelectric conversion units (light absorption layers) are quickly put into practical use, and research and development are expanding actively. Has been.

And the types of silicon-based thin film solar cells are further diversified. In addition to amorphous thin film solar cells using amorphous thin films such as amorphous silicon in the conventional light absorption layer, fine crystalline silicon is mixed in amorphous silicon. A microcrystalline thin film solar cell using the microcrystalline thin film and a crystalline thin film solar cell using a crystalline thin film made of crystalline silicon have been developed, and a hybrid thin film solar cell in which these are laminated has been put into practical use.

Such a photoelectric conversion unit or thin film solar cell has an amorphous photoelectric conversion layer that occupies the main part regardless of whether the p-type and n-type conductive semiconductor layers contained therein are amorphous, crystalline, or microcrystalline. Those having a high quality are referred to as amorphous units or amorphous thin-film solar cells, and those having a crystalline photoelectric conversion layer are referred to as crystalline units or crystalline thin-film solar cells, and the photoelectric conversion layer is microcrystalline. Are called microcrystalline units or microcrystalline thin-film solar cells.

By the way, the transparent conductive film is used for the surface transparent electrode of the thin film solar cell, and in order to effectively confine the light incident from the translucent substrate side in the photoelectric conversion unit, the surface thereof is usually fine. Many irregularities are formed.

Haze rate is an index representing the degree of unevenness of this transparent conductive film. This is equivalent to the light that is transmitted when the light from a specific light source is incident on a transparent substrate with a transparent conductive film divided by the scattered component whose optical path is bent and divided by all components. Measured using a C light source containing Generally, the haze ratio increases as the height difference between the projections and depressions increases, or as the distance between the projections and depressions of the projections and projections increases, and the light incident into the photoelectric conversion unit is effectively confined. The effect is excellent.

Regardless of whether the thin-film solar cell is a thin-film solar cell having a single light absorption layer of amorphous silicon, crystalline silicon, or microcrystalline silicon or the above-described hybrid thin-film solar cell, the transparent conductive film If the haze ratio can be increased and sufficient light confinement can be performed, a high short-circuit current density (Jsc) can be realized, and a thin film solar cell with high conversion efficiency can be manufactured.

For the above purpose, a metal oxide material mainly composed of tin oxide produced by a thermal CVD method is known as a transparent conductive film having a high haze ratio, and is generally used as a transparent electrode of a thin film solar cell.

However, in the film formation method by the thermal CVD method, when a film having a high haze ratio is formed, particularly when a film having a high haze ratio is formed, the characteristics such as the haze ratio and the resistance value and the variation in film thickness are ± 10. It is disadvantageous for forming a film having a large haze ratio as large as about% on a large area. Therefore, the haze ratio of the tin oxide-based transparent conductive film generally used for mass production as a surface electrode of a thin film solar cell is at most 10-13% in order to provide in-plane uniformity. With such a method, the yield is poor, and a film forming method capable of further improvement is required. Here, mass production of the surface electrode film by sputtering advantageous for large area film formation is required.

On the other hand, Non-Patent Document 1 proposes a method of obtaining a transparent conductive film having a surface roughness and having a high haze ratio, mainly composed of zinc oxide, by a sputtering method. This method uses a zinc oxide sintered body target to which ₂ wt% of Al ₂ O ₃ is added and performs sputtering film formation at a high gas pressure of 3 Pa to 12 Pa and a substrate temperature of 200 ° C. to 400 ° C. ing. However, the film is formed by applying a power of DC 80 W to a 6 inch φ target, and the input power density to the target is as extremely low as 0.442 W / cm ² . For this reason, the film formation rate is as extremely low as 14 nm / min or more and 35 nm / min or less and industrially impractical. According to the applicant's experience, when performing DC sputtering film formation using an AZO target, if DC sputtering film formation is performed by increasing the power density applied to the target in order to perform film formation at high speed, arcing (abnormal discharge) ) Occur frequently. When arcing occurs in the production process of a film forming line, a film defect occurs or a film having a predetermined film thickness cannot be obtained, making it impossible to stably manufacture a high-quality transparent conductive film. .

In addition, the uneven film formed under such a high gas pressure has many voids between the unevenness on the outermost surface of the film, and is used as a surface electrode of a thin film solar cell. When the Si layer is formed by the method, there is a problem that defects (cracks, peeling, etc.) occur in the Si layer.

In Non-Patent Document 2, after obtaining a transparent conductive film with zinc oxide as a main component and produced by a conventional sputtering method with small surface irregularities, the surface of the film is etched with acid to make the surface irregular. A method for producing a transparent conductive film having a high haze ratio is disclosed. However, in this method, after a film is manufactured by a sputtering method which is a vacuum process in a dry process, it is dried by performing acid etching in the air, and a semiconductor layer must be formed again by a CVD process in the dry process. There are problems such as complicated processes and high manufacturing costs.

From the above,

Non-Patent Documents

1 and 2 address the problems such as in-plane uniformity and productivity that have been problems when using a tin oxide-based transparent conductive film by a CVD method as a surface electrode film of a thin-film Si-based solar cell. In the formation of a zinc oxide-based transparent conductive film by the sputtering method proposed in the above, problems such as generation of arcing and complicated processes due to a combination of dry and wet processes remain, and mass productivity has not been improved.

The present applicant has proposed a sputter target in which gallium oxide is mixed with zinc oxide as a main component and abnormal discharge is reduced by adding a third element (Ti, Ge, Al, Mg, In, Sn) (patent) Reference 1). Here, the GZO sintered body containing gallium as a dopant is composed of a ZnO phase in which at least one selected from the group consisting of Ga, Ti, Ge, Al, Mg, In, and Sn is dissolved in an amount of 2 wt% or more. It is a main constituent phase, and the other constituent phases are a ZnO phase in which at least one of the above is not dissolved, and an intermediate compound phase represented by ZnGa ₂ O ₄ (spinel phase). In such a GZO target to which a third element such as Al is added, abnormal discharge can be reduced, but it cannot be completely eliminated. If abnormal discharge occurs even once in the continuous film formation line, the product at the time of film formation becomes a defective product, which affects the manufacturing yield.

In order to solve this problem, the present applicant optimizes the content of aluminum and gallium in an oxide sintered body containing zinc oxide as a main component and further containing aluminum and gallium as additive elements. By optimally controlling the type and composition of the crystalline phase produced during firing, especially the composition of the spinel crystalline phase, particles are unlikely to form even when film formation is continued for a long time with a sputtering device, even under high DC power input. A target oxide sintered body that does not cause any abnormal discharge has been proposed (see Patent Document 2).

By using such a zinc oxide-based sintered body, it becomes possible to form a high-quality transparent conductive film having a lower resistance and higher permeability than in the past. Here, the present applicant forms a zinc oxide-based transparent conductive film on the indium oxide-based transparent conductive film using the sputtering target having the above composition, and can be obtained by high-speed film formation only by a sputtering method, and has a high haze. A transparent conductive film having both high efficiency and high conductivity has been proposed (see Patent Document 3).

If this manufacturing method is used, the productivity can be improved by the process of only the sputtering method as compared with the conventional method, and the in-plane uniformity of the obtained film can be improved, and it can be applied to the manufacture of a solar cell with high conversion efficiency. However, since the transparent conductive film obtained by this method is also an uneven film formed under high gas pressure as in Non-Patent Document 1, there are voids between the unevenness on the outermost surface of the film, There is a problem in that the yield is reduced because of the possibility of inducing defects in the Si layer formed on the transparent conductive film by the CVD method. There is a need for a transparent conductive film applicable to solar cells that achieve higher conversion efficiency without impairing electrode quality such as transparency and mass productivity.

Japanese Patent Laid-Open No. 10-306367 JP 2008-110911 A International Publication No. 2010/104111

In view of the situation as described above, the present invention is obtained only by a mass-productive and advantageous sputtering method that is useful in manufacturing a high-efficiency silicon-based thin film solar cell, and has no complicated voids in the outermost surface structure. Therefore, it is possible to prevent a decrease in the yield of solar cell manufacturing, improve the contactability with the Si layer, and provide a transparent conductive film laminate excellent in light confinement effect, a manufacturing method thereof, and a thin film solar cell and a manufacturing method thereof The purpose is to do.

In order to solve the problems of the prior art, the present inventors have conducted intensive research and studied various transparent conductive film materials as transparent conductive films for surface transparent electrodes of thin film solar cells. Transparent structure in which a transparent conductive film (I) is used as a base, a zinc oxide-based transparent conductive film (II) composed of large crystal grains is formed thereon, and an oxide-based transparent conductive film (III) is further laminated It has been found that the conductive film laminate prevents the generation of defects in the Si power generation layer as the surface electrode of the thin-film solar cell, improves the contact property with the Si layer, and has an excellent light confinement effect. It came to complete.

That is, the transparent conductive film laminate according to the present invention includes an indium oxide-based transparent conductive film (I) having a thickness of 50 nm to 600 nm formed on a light-transmitting substrate, and the indium oxide-based transparent conductive film ( I) The zinc oxide-based transparent conductive film (II) formed on the zinc oxide-based transparent conductive film (II) having a thickness of 200 nm to 1,000 nm and the film thickness formed on the zinc oxide-based transparent conductive film (II) of 5 nm to 200 nm And a certain oxide-based transparent conductive film (III).

Moreover, the manufacturing method of the transparent conductive film laminated body which concerns on this invention forms the indium oxide type transparent conductive film (I) whose film thickness is 50 nm or more and 600 nm or less on a translucent substrate by sputtering method. A film-forming step, and a second film-forming step of forming a zinc oxide-based transparent conductive film (II) having a thickness of 200 nm or more and 1000 nm or less on the indium oxide-based transparent conductive film (I) by sputtering. And a third film-forming step of forming an oxide-based transparent conductive film (III) having a thickness of 5 nm to 200 nm on the zinc oxide-based transparent conductive film (II) by a sputtering method. Features.

Moreover, the thin film solar cell according to the present invention is the thin film solar cell in which a transparent conductive film laminate, a photoelectric conversion layer unit, and a back electrode layer are sequentially formed on a translucent substrate. The body is formed of the indium oxide-based transparent conductive film (I) having a thickness of 50 nm or more and 600 nm or less formed on the translucent substrate, and the thickness of the indium oxide-based transparent conductive film (I). Zinc oxide-based transparent conductive film (II) having a thickness of 200 nm to 1000 nm and an oxide-based transparent conductive film (III) having a thickness of 5 nm to 200 nm formed on the zinc oxide-based transparent conductive film (II) ).

Moreover, the manufacturing method of the thin film solar cell which concerns on this invention is a manufacturing method of the thin film solar cell which forms a transparent conductive film laminated body, a photoelectric converting layer unit, and a back surface electrode layer in order on a translucent board | substrate, A first film forming step of forming an indium oxide-based transparent conductive film (I) having a thickness of 50 nm to 600 nm on the light-transmitting substrate by a sputtering method; and the indium oxide-based transparent conductive film (I) A second film forming step of forming a zinc oxide-based transparent conductive film (II) having a film thickness of 200 nm or more and 1000 nm or less by sputtering, and sputtering on the zinc oxide-based transparent conductive film (II) And a third film formation step of forming an oxide-based transparent conductive film (III) having a film thickness of 5 nm to 200 nm by a method.

According to the present invention, on the indium oxide-based transparent conductive film (I), the zinc oxide-based transparent conductive film (II) having a thickness of 200 nm to 1000 nm and the transparent conductive having a thickness of 5 nm to 200 nm. By laminating the film (III), there is no space between the irregularities on the outermost surface, a film characteristic with a haze ratio of 8% or more and a surface resistance of 25Ω / □ or less is obtained, and an Si layer that is a power generation layer of a solar cell Therefore, it is possible to provide a transparent conductive film laminate that is effective in preventing the occurrence of defects and has an excellent light confinement effect.

Moreover, since the transparent conductive film laminate according to the present invention can be produced only by a sputtering method, it is not only excellent in conductivity and the like for a surface transparent electrode of a thin film solar cell, but also by a conventional thermal CVD method. Cost reduction is possible compared to a transparent conductive film. Therefore, since a highly efficient silicon-based thin film solar cell can be provided at a low cost by a simple process, it is extremely useful industrially.

FIG. 1 is a graph showing the relationship between the contents of aluminum and gallium in the zinc oxide-based transparent conductive film (II). FIG. 2 is a cross-sectional view illustrating a configuration example of a thin film solar cell using an amorphous silicon thin film as a photoelectric conversion unit. FIG. 3 is a cross-sectional view showing a configuration example of a hybrid thin film solar cell in which an amorphous silicon thin film and a crystalline silicon thin film are stacked as a photoelectric conversion unit. FIG. 4 is a surface SEM photograph of the transparent conductive thin film.

Hereinafter, embodiments of the present invention (hereinafter referred to as “present embodiments”) will be described in detail in the following order with reference to the drawings.
1. 1. Transparent conductive film laminate 1-1. Indium oxide-based transparent conductive film (I)
1-2. Zinc oxide based transparent conductive film (II)
1-3. Oxide-based transparent conductive film (III)
1-4. 1. Properties of transparent conductive film laminate 2. Method for producing transparent conductive film laminate 2-1. Film formation of indium oxide based transparent conductive film (I) 2-2. Formation of zinc oxide based transparent conductive film (II) 2-3. 2. Formation of oxide-based transparent conductive film (III) Thin film solar cell and manufacturing method thereof

<1. Transparent conductive film laminate>
The transparent conductive film laminate according to the present embodiment is based on an indium oxide-based transparent conductive film (I) formed on a light-transmitting substrate, and a zinc oxide-based transparent conductive film excellent in unevenness thereon. (II) and then a three-layer laminated structure in which an oxide-based transparent conductive film (III) is sequentially formed. By adopting this laminated structure, the haze ratio is high, the so-called light confinement effect is excellent, and the resistance is low. In addition, since defects in the Si layer, which is a photoelectric conversion layer of the thin film solar cell, can be prevented, it is very useful as a surface electrode material for a thin film solar cell. Furthermore, the transparent conductive film laminate according to the present embodiment can be manufactured only by the sputtering method and has high productivity.

<1-1. Indium oxide-based transparent conductive film (I)>
The film thickness of the indium oxide-based transparent conductive film (I) formed on the translucent substrate is 50 nm or more and 600 nm or less. When the film thickness of the indium oxide-based transparent conductive film (I) is in the range of 50 nm or more and 600 nm or less, good transmittance, haze ratio, and surface resistance can be obtained. A more preferable film thickness of the indium oxide-based transparent conductive film (I) is 300 nm or more and 500 nm or less.

The indium oxide-based transparent conductive film (I) is a crystal film containing indium oxide as a main component and one or more metal elements selected from Sn, Ti, W, Mo, Zr, Ce, or Ga. A crystal film in which an additive element of Sn, Ti, W, Mo, Zr, Ce, or Ga is contained in indium oxide is useful because of its excellent conductivity. In particular, when an element of Ti, W, Mo, Zr, Ce, or Ga is included, a film with high mobility can be obtained. Therefore, since the resistance is reduced without increasing the carrier concentration, a low resistance film having a high transmittance in the visible region to the near infrared region can be realized.

Further, when the indium oxide-based transparent conductive film (I) contains Sn containing indium oxide as a main component, the content ratio is preferably 15 atomic% or less in terms of the Sn / (In + Sn) atomic ratio. Moreover, when it contains Ti, it is preferable that the content rate is 5.5 atomic% or less in Ti / (In + Ti) atomic ratio. Moreover, when it contains W, it is preferable that the content rate is 4.3 atomic% or less in W / (In + W) atomic ratio. Moreover, when it contains Zr, it is preferable that the content rate is 6.5 atomic% or less by Zr / (In + Zr) atomic ratio. Moreover, when it contains Mo, it is preferable that the content rate is 6.7 atomic% or less by Mo / (In + Mo) atomic number ratio. Moreover, when it contains Ce, it is preferable that the content rate is 6.5 atomic% or less by Ce / (In + Ce) atomic ratio. Moreover, when it contains Ga, it is preferable that the content rate is 6.5 atomic% or less by Ga / (In + Ga) atomic ratio. If the content exceeds this range, the resistance becomes high, which is not useful.

Among such indium oxide based transparent conductive films (I), an ITO film containing Sn as a dopant and an ITiO film containing Ti as a dopant are preferably used in the present embodiment.

<1-2. Zinc Oxide Transparent Conductive Film (II)>
The film thickness of the zinc oxide-based transparent conductive film (II) is 200 nm or more and 1000 nm or less. When the film thickness is less than 200 nm, it is difficult to obtain a high haze ratio. When the film thickness exceeds 1000 nm, characteristics such as the haze ratio can be maintained, but it is disadvantageous in terms of permeability and productivity. In addition, if the proposed manufacturing method is used, a sufficient haze ratio can be obtained with a film thickness of 1000 nm or less. A more preferable film thickness of the zinc oxide-based transparent conductive film (II) is 300 nm or more and 600 nm or less.

The zinc oxide-based transparent conductive film (II) may not contain an additive element, but may contain an additive element such as aluminum or gallium for the purpose of imparting conductivity to the oxide film.

Specifically, as shown in FIG. 1, when zinc oxide is a main component and one or more additive metal elements selected from aluminum or gallium are included, the aluminum content and the gallium content are expressed by the following formulas: It is preferable that it exists in the range shown by (1).
[Al] ≦ [Ga] ≦ −2.68 × [Al] +1.74 (1)
(However, [Al] is the aluminum content expressed by the atomic ratio (%) of Al / (Zn + Al), while [Ga] is expressed by the atomic ratio (%) of Ga / (Zn + Ga). (Al) ≧ Al and [Ga] ≧ 0.)

When the content of aluminum and gallium in the zinc oxide-based transparent conductive film (II) exceeds the range defined by the formula (1), a transparent conductive film with large surface irregularities and a high haze ratio is produced at high speed by the sputtering method. It becomes difficult to do.

Unlike the zinc oxide-based transparent conductive film disclosed in International Publication No. 2010/104111, the zinc oxide-based transparent conductive film (II) in the present embodiment includes a case where no additive element is included. When the additive element is not included, there is a concern that the conductivity may be insufficient, but the presence of the indium oxide-based transparent conductive film (I) as a base film, and the zinc oxide-based transparent conductive film (II) By laminating the following oxide-based transparent conductive film (III) between the Si layer and the Si layer, the electrical contact property between the transparent conductive film laminate and the Si layer is improved, which is useful.

In addition to zinc, aluminum, gallium and oxygen, the zinc oxide based transparent conductive film (II) includes other elements (for example, indium, titanium, germanium, silicon, tungsten, molybdenum, iridium, ruthenium, rhenium, cerium, (Magnesium, silicon, fluorine, etc.) may be contained as long as the object of the present invention is not impaired.

<1-3. Oxide transparent conductive film (III)>
The film thickness of the oxide-based transparent conductive film (III) is 5 nm or more and 200 nm or less. When the film thickness is less than 5 nm, a situation occurs in which the surface coating on the zinc oxide-based transparent conductive film (II) becomes insufficient, and the generation of defects in the Si layer formed thereon cannot be prevented. On the other hand, if the film thickness exceeds 200 nm, not only the permeability is lowered but also the unevenness is impaired, leading to a reduction in haze rate and a reduction in productivity.

The oxide-based transparent conductive film (III) is a metal oxide and contains one or more elements selected from Mg, Al, Si, Ti, Zn, Ga, In, Sn, W, and Ce. Is preferred. Thus, the oxide-based transparent conductive film (III) can function as an electrode for extracting holes as a contact layer with the Si photoelectric conversion layer, and has a high work function (φ = 4.5 eV to 5.5 eV). Is obtained. Even in this case, if the film thickness is less than 5 nm, a stable high work function cannot be obtained.

Here, the composition of the oxide-based transparent conductive film (III) is not limited as long as it is a combination of the above elements. A transparent conductive oxide mainly composed of In ₂ O ₃ or ZnO is preferable from the viewpoint of transparency and conductivity including work function.

Specific examples of the oxide-based transparent conductive film (III) include, for example, gallium / aluminum-doped zinc oxide (GAZO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), and magnesium-doped zinc oxide (ZMgO). Silicon doped zinc oxide (SZO), tin doped zinc oxide (ZTO), titanium / tin doped indium oxide (ITiTO), gallium doped indium oxide (IGO), cerium doped indium oxide (ICO), tungsten doped indium oxide (IWO), etc. Can be mentioned.

In general, In ₂ O ₃ oxides are concerned about hydrogen plasma resistance, but if the film thickness is 200 nm or less as defined in this proposal, the influence of hydrogen plasma is very small, and the surface electrode It is a level that is safe to use. In particular, according to the knowledge of the present inventors, indium oxide added with Ga has a result that the decrease in transmittance due to hydrogen plasma is smaller than that of fluorine-doped tin oxide (FTO).

However, when the oxide-based transparent conductive film (III) is a thin film having a thickness of 10 nm or less, the oxide-based transparent conductive film (III) is mainly composed of zinc oxide and Mg in view of hydrogen plasma resistance. It is preferable to contain one or more elements selected from Al, Si, Ga, Sn, and W.

<1-4. Characteristics of transparent conductive film laminate>
In the transparent conductive film laminate according to the present embodiment, the film thickness of the indium oxide-based transparent conductive film (I) is 50 nm to 600 nm and the thickness of the zinc oxide-based transparent conductive film (II) is 200 nm to 1000 nm. It is. The film thickness of the indium oxide-based transparent conductive film (I) is more preferably 300 nm to 500 n, and the film thickness of the zinc oxide-based transparent conductive film (II) is 300 nm to 600 nm.

The thickness of the oxide-based transparent conductive film (III) is 5 nm or more and 200 nm or less. When the thickness of the oxide-based transparent conductive film (III) is less than 5 nm, it becomes difficult to completely cover the surface of the zinc oxide-based transparent conductive film (II), and the generation of defects in the Si layer cannot be prevented. On the other hand, when the thickness of the oxide-based transparent conductive film (III) exceeds 200 nm, there is a possibility that the productivity is lowered and the characteristics are deteriorated.

The total film thickness of the indium oxide-based transparent conductive film (I), the zinc oxide-based transparent conductive film (II), and the oxide-based transparent conductive film (III) is not particularly limited as long as the above-described film thickness is satisfied. However, it is preferably from 355 nm to 1800 nm, particularly from 600 nm to 1500 nm, depending on the composition of the material.

Further, the work function of the oxide-based transparent conductive film (III) which is the outermost surface is preferably 4.5 eV or more. When the work function is less than 4.5 eV, the role as an electrode for extracting holes from the p-type Si layer cannot be functioned, and as a result, the conversion efficiency is lowered. In order to achieve sufficient extraction of holes, the work function needs to be 4.5 eV or more on the outermost surface of the transparent conductive film laminate, and more preferably 5.0 eV or more.

The surface resistance of the oxide-based transparent conductive film (III) is preferably 25Ω / □ or less. When the surface resistance exceeds 25Ω / □, when used as a surface electrode of a solar cell, power loss at the surface electrode increases, and a highly efficient solar cell cannot be realized. Since the transparent conductive film laminate according to the present embodiment has the laminated structure as described above, the surface resistance can be 25 Ω / □ or less. The surface resistance of the transparent conductive film laminate according to the present embodiment is preferably 20Ω / □ or less, more preferably 13Ω / □ or less, still more preferably 10Ω / □ or less, and most preferably 8Ω / □ or less.

The lower the surface resistance of the oxide-based transparent conductive film (III), the smaller the power loss at the surface electrode portion, so that a highly efficient solar cell can be realized even with a large cell area. Conversely, if the surface resistance of the surface electrode is high, the power loss at the surface electrode increases to a level that cannot be ignored if the cell of the solar battery is large. It is necessary to increase the area by wiring the cells.

If the surface resistance is 25Ω / □ or less, a solar cell of at least 5 cm □ can be realized, and if it is 20Ω / □ or less, a solar cell of at least 8 cm □ can be realized. Furthermore, if it is 13Ω / □ or less, a cell of at least 15cm □ can be realized, if it is 10Ω / □ or less, a cell of at least 17cm □ can be realized, and if it is 8Ω / □ or less, a cell of at least 20cm □ can be realized. realizable.

Since solar cells with a large cell area do not need to be connected by metal wiring, the cell spacing can be reduced. Therefore, when cells are connected to produce a module, not only the amount of power generation per unit area of one module is increased, but also the manufacturing cost per area of the cell can be reduced. Further, by reducing the surface resistance as described above, it becomes possible to ignore the influence of the power loss at the surface electrode.

The haze ratio of the surface of the oxide-based transparent conductive film (III) is preferably 8% or more, more preferably 12% or more, still more preferably 16% or more, and most preferably 20% or more. is there. In a standard thin film silicon solar cell having a single structure, a haze ratio of 12% or more is indispensable in order to achieve a conversion efficiency of 10% or more. In order to realize a conversion efficiency of 12% or more in the same evaluation, it is effective to use a surface electrode having a haze ratio of 16% or more. The transparent conductive film laminate according to the present embodiment includes the above-described zinc oxide-based transparent conductive film (II) and oxide transparent conductive film in addition to the indium oxide-based transparent conductive film (I) inserted in the base. By laminating (III), a high haze ratio can be realized.

As described above, the transparent conductive film laminate according to the present embodiment is not only excellent in the light confinement effect, but also the oxide-based transparent conductive film (III) improves the voids between the irregularities of the film surface structure, Generation of defects in the Si layer can be prevented. Moreover, since it has a high work function of 4.5 eV or more on the surface of the oxide transparent conductive film (III), it becomes possible to smoothly extract holes from the Si layer as an electrode.

In addition, the transparent conductive film laminate according to the present embodiment has a low haze ratio and excellent conductivity, particularly from the viewpoint of defects in the Si layer and hole transport, and has a wavelength of 380 nm. The light energy of sunlight including from the visible light of 1200 nm or less to the near infrared can be converted into electrical energy very effectively. Therefore, it is very useful as a surface electrode application of a high efficiency solar cell.

<2. Manufacturing method of transparent conductive film laminate>
The manufacturing method of the transparent conductive film laminate according to the present embodiment is a first method in which an indium oxide-based transparent conductive film (I) having a thickness of 50 nm to 600 nm is formed on a light-transmitting substrate by a sputtering method. A film-forming step, and a second film-forming step of forming a zinc oxide-based transparent conductive film (II) having a thickness of 200 nm or more and 1000 nm or less on the indium oxide-based transparent conductive film (I) by a sputtering method; And a third film-forming step of forming an oxide-based transparent conductive film (III) having a thickness of 5 nm to 200 nm on the zinc oxide-based transparent conductive film (II) by a sputtering method.

By forming a film in this way, it has a high haze ratio, an excellent so-called light confinement effect and low resistance, and in addition, it prevents defects in the Si layer that is a photoelectric conversion layer of a thin film solar cell. A transparent conductive film laminate can be obtained. Furthermore, since a transparent conductive film laminated body can be manufactured only by sputtering method, it has high productivity.

Hereinafter, a method for forming each transparent conductive film will be described in detail.

<2-1. Formation of Indium Oxide-Based Transparent Conductive Film (I)>
First, an indium oxide-based transparent conductive film (I) having a thickness of 50 nm to 600 nm is formed on a light-transmitting substrate by a sputtering method. For the formation of the indium oxide-based transparent conductive film (I), an oxide firing mainly composed of indium oxide containing one or more metal elements selected from Sn, Ti, W, Mo, Zr, Ce, or Ga is used. A ligation target is used. Note that when an oxide film is obtained by sputtering using an oxide sintered body target, the composition of the oxide film is the same as that of the target unless a volatile substance is contained.

Among such oxide sintered compact targets, Sn is contained, and the content ratio is 15 atomic% or less in terms of the Sn / (In + Sn) atomic ratio, or Ti is contained, and the content ratio is Ti / Those having an atomic ratio of (In + Ti) of 5.5 atomic% or less are preferably used.

The indium oxide-based transparent conductive film (I) is formed by a first method in which an amorphous film is formed without heating the substrate and then crystallized by heat treatment, and a crystal is formed by heating the substrate. A second method of forming a material film can be used.

In the first method, after forming an amorphous film under the conditions of a substrate temperature of 100 ° C. or less and a sputtering gas pressure of 0.1 or more and less than 1.0 Pa, heat treatment is subsequently performed to 200 ° C. or more and 600 ° C. or less, The amorphous film is crystallized to form an indium oxide-based transparent conductive film. In the second method, the indium oxide-based transparent conductive film is formed as a crystal film under conditions of a substrate temperature of 200 ° C. or more and 600 ° C. or less and a sputtering gas pressure of 0.1 Pa or more and less than 1.0 Pa.

In the present embodiment, it is preferable to use the first method in which an amorphous film is formed without heating the substrate and then crystallized by heat treatment. This is because the first method provides a film having a larger haze ratio than the second method in which the crystalline film is formed by heating the substrate.

<2-2. Formation of Zinc Oxide Transparent Conductive Film (II)>
Next, a zinc oxide-based transparent conductive film (II) having a film thickness of 200 nm or more and 1000 nm or less is formed on the indium oxide-based transparent conductive film (I) by a sputtering method. For the film formation of the zinc oxide-based transparent conductive film (II), an oxide sintered body target containing zinc oxide as a main component is used. Note that when an oxide film is obtained by sputtering using an oxide sintered body target, the composition of the oxide film is the same as that of the target unless a volatile substance is contained.

The oxide sintered compact target for forming the zinc oxide-based transparent conductive film (II) may not contain an additive element, but for the purpose of imparting conductivity to the oxide film, addition of aluminum, gallium or the like It may contain an element.

Specifically, as shown in FIG. 1, when zinc oxide is the main component and one or more additive metal elements selected from aluminum or gallium are included, the aluminum content and the gallium content are expressed by the following formula ( It is preferable that it exists in the range shown by 1).
[Al] ≦ [Ga] ≦ −2.68 × [Al] +1.74 (1)
(However, [Al] is the aluminum content expressed by the atomic ratio (%) of Al / (Zn + Al), while [Ga] is expressed by the atomic ratio (%) of Ga / (Zn + Ga). (Al) ≧ Al and [Ga] ≧ 0.)

When the content of aluminum and gallium in the sputtering target for forming the zinc oxide-based transparent conductive film (II) exceeds the range defined by the formula (1), the transparent conductive film having large surface irregularities and high haze ratio It is difficult to manufacture the film at a high speed by the sputtering method.

In the present embodiment, it is preferable to form the zinc oxide-based transparent conductive film (II) under a condition where the sputtering gas pressure is 1.0 Pa or more and 15.0 Pa or less. When the sputtering gas pressure is less than 1.0 Pa, it is difficult to obtain a film having large surface irregularities, and a film having an Ra value of 35.0 nm or more cannot be obtained. On the other hand, if it exceeds 15.0 Pa, the film formation rate is slow, which is not preferable. For example, in static facing film formation, in order to obtain a film formation rate of 40 nm / min or more by applying high power with a DC input power density of 1.66 W / cm ² or more to the target, the sputtering gas pressure is 15. It is necessary to make it 0 Pa or less.

Moreover, you may introduce | transduce hydrogen gas effective in order to raise a haze rate at the time of film-forming of a zinc oxide type transparent conductive film (II). At this time, the mixing ratio (molar ratio) of hydrogen to be introduced is not particularly limited, but the haze ratio increases as the ratio increases, whereas the transmission ratio decreases as the ratio increases. Therefore, the mixing ratio of hydrogen to be introduced is more preferably set to H ₂ / (Ar + H ₂ ) ≦ 0.43 in consideration of a decrease in transmittance.

In addition, the substrate temperature is preferably set to 200 ° C. or more and 600 ° C. or less when forming the zinc oxide-based transparent conductive film (II). Thereby, the crystallinity of the transparent conductive film is improved, the mobility of carrier electrons is increased, and excellent conductivity can be realized. When the substrate temperature is less than 200 ° C., the growth of film particles is inferior, so that a film having a large Ra value cannot be obtained. In addition, when the substrate temperature exceeds 600 ° C., not only does the problem arise such that the amount of electric power required for heating increases and the manufacturing cost increases, but when the glass substrate is used as the substrate, the softening point is exceeded. This is not preferable because problems such as deterioration of the glass also occur.

In the film formation of the transparent conductive film, when the input power to the sputtering target is increased, the film formation rate is increased and the productivity of the film is improved. When sputtering film formation is performed by increasing the input power to the target to 2.76 W / cm ² or more, for example, a film formation speed of 90 nm / min or more can be realized in static facing film formation, surface irregularities are large, and high haze is achieved. A zinc oxide-based transparent conductive film can be obtained. Also, in the pass-type film formation (transfer film formation) in which the substrate is passed over the target, for example, the film was formed at a similar input power density of 5.1 nm · m / min (transfer speed (m / min)). In the high-speed transport film formation of the obtained film thickness (nm), it is possible to obtain a zinc oxide-based transparent conductive film having excellent surface irregularity and a high haze ratio. In addition, the film-forming speed | rate in this case will not be restrict | limited especially if the objective of this invention can be achieved.

In this embodiment, even if high-speed film formation is attempted by increasing the input power density to the target to 2.760 W / cm ² or more by forming the film under the above-described conditions, the haze ratio is 8% or more, A transparent conductive film laminate having a surface irregularity having a resistance of 25Ω / □ or less can be produced.

<2-3. Formation of oxide-based transparent conductive film (III)>
Next, an oxide-based transparent conductive film (III) having a thickness of 5 nm to 200 nm is formed on the zinc oxide-based transparent conductive film (II) by a sputtering method. The film formation of the oxide transparent conductive film (III) is a metal oxide and contains one or more elements selected from Mg, Al, Si, Ti, Zn, Ga, In, Sn, W, and Ce. An oxide sintered compact target is used. Note that when an oxide film is obtained by sputtering using an oxide sintered body target, the composition of the oxide film is the same as that of the target unless a volatile substance is contained.

Sputtering targets for forming the oxide-based transparent conductive film (III) include gallium / aluminum-doped zinc oxide (GAZO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), and magnesium-doped zinc oxide ( ZMgO), silicon-doped zinc oxide (SZO), tin-doped zinc oxide (ZTO), titanium / tin-doped indium oxide (ITiTO), gallium-doped indium oxide (IGO), cerium-doped indium oxide (ICO), tungsten-doped indium oxide (IWO) Etc.

Moreover, when the film thickness of the oxide-based transparent conductive film (III) is a thin film of 10 nm or less, the sputtering target for forming the oxide-based transparent conductive film (III) is oxidized from the viewpoint of hydrogen plasma resistance. It is preferable that zinc is a main component and contains one or more elements selected from Mg, Al, Si, Ga, Sn, and W.

The film formation of the oxide transparent conductive film (III) includes a first method of forming an amorphous film without heating the substrate, and heating after forming the amorphous film without heating the substrate. A second method of crystallizing by treatment and a third method of forming a crystalline film by heating the substrate can be used.

In the first method, an amorphous film is formed under conditions of a substrate temperature of 100 ° C. or lower and a sputtering gas pressure of 0.1 or higher and lower than 1.0 Pa. In the second method, after the amorphous film is formed by the first method, the amorphous film is crystallized by subsequently performing heat treatment at 200 ° C. or more and 600 ° C. or less to form an oxide transparent conductive film. Is done. In the third method, the oxide-based transparent conductive film is formed as a crystal film under conditions of a substrate temperature of 200 ° C. or more and 600 ° C. or less and a sputtering gas pressure of 0.1 Pa or more and less than 1.0 Pa. In this manufacturing method, it is possible to use all of the first to third methods. However, assuming that the Si layer is heated at a temperature of 200 ° C. or higher, the compound layer is stabilized by crystallization. The second or third method is preferred.

Furthermore, after the formation of the oxide transparent conductive film (III), the surface of the obtained transparent conductive film laminate may be subjected to a surface cleaning treatment using UV / ozone cleaning, plasma processing, or the like. Thereby, a work function improves by removing the contaminating component which remains on the transparent conductive film laminated body surface.

As described above, according to the method for manufacturing the transparent conductive film laminate according to the present embodiment, the oxide-based transparent conductive film (III) having a film thickness of 5 nm to 200 nm is formed, thereby forming the light In addition to being excellent in the confinement effect, it is possible to obtain a transparent conductive film laminate that can improve the voids between the irregularities of the film surface structure and prevent the generation of defects in the Si layer.

In addition, since a transparent conductive film laminate can be produced only by sputtering, it is not only excellent in conductivity etc. for the surface transparent electrode of thin film solar cells, but also compared with conventional conductive films using thermal CVD. Cost reduction is possible. Therefore, since a highly efficient silicon-based thin film solar cell can be provided at a low cost by a simple process, it is extremely useful industrially.

<3. Thin Film Solar Cell and Manufacturing Method Thereof>
In the thin film solar cell according to the present embodiment, a transparent conductive film laminate, a photoelectric conversion layer unit, and a back electrode layer are sequentially formed on a translucent substrate.

The thin film solar cell according to the present embodiment is a photoelectric conversion element using the above-described transparent conductive film laminate as an electrode. The structure of the solar cell element is not particularly limited, and includes a PN junction type in which a p-type semiconductor and an n-type semiconductor are stacked, a PIN junction type in which an insulating layer (I layer) is interposed between the p-type semiconductor and the n-type semiconductor, and the like. Can be mentioned.

Thin film solar cells are roughly classified according to the type of semiconductor. Silicon solar cells using a silicon-based semiconductor thin film such as microcrystalline silicon and / or amorphous silicon as a photoelectric conversion element, CuInSe-based or Cu (In, Ga) Se-based , Ag (In, Ga) Se, CuInS, Cu (In, Ga) S, Ag (In, Ga) S and their solid solutions, GaAs, CdTe, and other compound semiconductor thin films Although it is classified into a compound thin film solar cell used as a photoelectric conversion element, and a dye-sensitized solar cell using an organic dye (also referred to as a Gretzel cell solar cell), the solar cell according to the present embodiment is In any case, high efficiency can be realized by using the above-described transparent conductive film laminate as an electrode. In particular, in a silicon-based solar cell and a compound thin-film solar cell, a transparent conductive film is indispensable for an electrode on which sunlight is incident (light receiving unit side, front side), and the transparent conductive film lamination according to the present embodiment By using the body, high conversion efficiency characteristics can be exhibited.

The p-type and n-type conductive semiconductor layers in the photoelectric conversion unit serve to generate an internal electric field in the photoelectric conversion unit. The value of the open circuit voltage (Voc), which is one of the important characteristics of the thin film solar cell, depends on the magnitude of the internal electric field. The i-type layer is a substantially intrinsic semiconductor layer and occupies most of the thickness of the photoelectric conversion unit. The photoelectric conversion action mainly occurs in this i-type layer. Therefore, the i-type layer is usually called an i-type photoelectric conversion layer or simply a photoelectric conversion layer. The photoelectric conversion layer is not limited to an intrinsic semiconductor layer, and may be a layer doped with a small amount of p-type or n-type as long as loss of light absorbed by a doped impurity (dopant) does not become a problem. .

FIG. 2 is a diagram showing an example of the structure of a silicon-based amorphous thin film solar cell. In addition to amorphous thin film solar cells, silicon thin film solar cells that use silicon thin films for photoelectric conversion units (light absorption layers) include microcrystalline thin film solar cells and crystalline thin film solar cells. Laminated hybrid thin film solar cells have also been put into practical use. In addition, as above-mentioned, in the photoelectric conversion unit or thin film solar cell, when the photoelectric conversion layer which occupies the principal part is amorphous, it is called the amorphous unit or the amorphous thin film solar cell. A crystalline photoelectric conversion layer is called a crystalline unit or a crystalline thin film solar cell. Furthermore, the one having a microcrystalline photoelectric conversion layer is referred to as a microcrystalline unit or a crystalline thin film solar cell.

As a method for improving the conversion efficiency of such a thin film solar cell, there is a method of stacking two or more photoelectric conversion units into a tandem solar cell. For example, in this method, a front unit including a photoelectric conversion layer having a large band gap is disposed on the light incident side of the thin film solar cell, and a rear unit including a photoelectric conversion layer having a small band gap is sequentially disposed behind the front unit. . Thereby, photoelectric conversion is enabled over the wide wavelength range of incident light, and the conversion efficiency as the whole solar cell can be improved. Among these tandem solar cells, those in which an amorphous photoelectric conversion unit and a crystalline or microcrystalline photoelectric conversion unit are stacked are called hybrid thin film solar cells.

FIG. 3 is a diagram showing an example of the structure of a hybrid thin film solar cell. In a hybrid thin-film solar cell, for example, the wavelength range of light that can be photoelectrically converted by i-type amorphous silicon is up to about 800 nm on the long wavelength side, but i-type crystalline or microcrystalline silicon is longer than that. Light up to a wavelength of about 1150 nm can be photoelectrically converted.

Next, the configuration of the thin-film solar cell according to the present embodiment will be described more specifically with reference to FIGS. 2 and 3, on the translucent substrate 1, the transparent conductive film 21 which is the above-described indium oxide-based transparent conductive film (I), the transparent conductive film 22 which is the zinc oxide-based transparent conductive film (II), The transparent conductive film laminated body 2 which consists of the transparent conductive film 23 which is an oxide transparent conductive film (III) is formed.

As the translucent substrate 1, a plate-like member or a sheet-like member made of glass, transparent resin or the like is used. An amorphous photoelectric conversion unit 3 is formed on the transparent conductive film laminate 2. The amorphous photoelectric conversion unit 3 includes an amorphous p-type silicon carbide layer 31, a non-doped amorphous i-type silicon photoelectric conversion layer 32, and an n-type silicon-based interface layer 33. The amorphous p-type silicon carbide layer 31 is formed at a substrate temperature of 180 ° C. or lower in order to prevent a decrease in transmittance due to reduction of the transparent conductive film stack 2.

In the hybrid thin film solar cell shown in FIG. 3, the crystalline photoelectric conversion unit 4 is formed on the amorphous photoelectric conversion unit 3. The crystalline photoelectric conversion unit 4 includes a crystalline p-type silicon layer 41, a crystalline i-type silicon photoelectric conversion layer 42, and a crystalline n-type silicon layer 43. A high frequency plasma CVD method is suitable for forming the amorphous photoelectric conversion unit 3 and the crystalline photoelectric conversion unit 4 (hereinafter, both units are simply referred to as “photoelectric conversion unit”). As conditions for forming the photoelectric conversion unit, the substrate temperature is 100 ° C. or higher and 250 ° C. or lower (however, the amorphous p-type silicon carbide layer 31 is 180 ° C. or lower), the pressure is 30 Pa or higher and 1500 Pa or lower, and the high frequency power density is 0.01 W / cm. ² or more and 0.5 W / cm ² or less are preferably used. As a raw material gas used for forming the photoelectric conversion unit, a silicon-containing gas such as SiH ₄ or Si ₂ H ₆ or a mixture of these gases and H ₂ is used. As a dopant gas for forming the p-type or n-type layer in the photoelectric conversion unit, B ₂ H ₆ or PH ₃ is preferably used.

The back electrode 5 is formed on the n-type silicon-based interface layer 33 shown in FIG. 2 or on the n-type silicon-based interface layer 43 shown in FIG. The back electrode 5 includes a transparent reflective layer 51 and a back reflective layer 52. The transparent reflective layer 51 is preferably made of a metal oxide such as ZnO or ITO. For the back reflective layer 52, it is preferable to use Ag, Al, or an alloy thereof.

In forming the back electrode 5, a method such as sputtering or vapor deposition is preferably used. The back electrode 5 has a thickness of usually 0.5 μm to 5 μm, preferably 1 μm to 3 μm. After the back surface electrode 5 is formed, the solar cell is completed by heating to near atmospheric pressure at an atmospheric temperature equal to or higher than the formation temperature of the amorphous p-type silicon carbide layer 31. As the gas used in the heating atmosphere, air, nitrogen, a mixture of nitrogen and oxygen, or the like is preferably used. Moreover, the vicinity of atmospheric pressure generally indicates a range of 0.5 atm or more and 1.5 atm or less.

As described above, according to the method for manufacturing a thin-film solar cell according to the present embodiment, it is possible to provide a silicon-based thin-film solar cell using the transparent conductive film laminate 2 as an electrode. Moreover, in the manufacturing method of the thin film solar cell according to the present embodiment, the indium oxide-based transparent conductive film (I) formed on the light-transmitting substrate is used as a base, and the zinc oxide-based excellent in unevenness is formed thereon. A thin film capable of achieving high conversion efficiency by forming a transparent conductive film (II) and then a transparent conductive film laminate having a three-layer structure in which an oxide transparent conductive film (III) having a high work function is sequentially formed. A transparent conductive film for a surface transparent electrode of a solar cell can be obtained. Furthermore, the transparent conductive film laminate can be provided at a lower cost than a transparent conductive film formed by a conventional thermal CVD method. The method for manufacturing a thin-film solar cell according to the present embodiment is extremely useful industrially because a highly efficient silicon-based thin-film solar cell can be provided at a low cost by a simple process.

FIG. 3 shows the structure of the hybrid thin film solar cell. However, the number of photoelectric conversion units is not necessarily two, but an amorphous or crystalline single structure, a stacked solar cell structure having three or more layers. It may be.

Hereinafter, examples of the transparent conductive film having a three-layer structure according to the present invention will be described in comparison with comparative examples. In addition, this invention is not limited by this Example.

[Evaluation]
(1) The film thickness was measured by the following procedure. Before forming a film, apply a part of the substrate with oil-based magic ink, wipe the magic with ethanol after film formation, and form a film-free part. It was determined by measuring with a shape measuring instrument (Alpha-Step IQ manufactured by KLA Tencor).

(2) The target used for the production of the transparent conductive film was quantitatively analyzed by ICP emission spectroscopic analysis (manufactured by Seiko Instruments Inc., SPS4000).

(3) The resistance value of the transparent conductive thin film was measured by a four-probe method using a resistivity meter Loresta EP (Dia Instruments MCP-T360 type).

(4) The total light transmittance at a wavelength of 400 to 1200 nm of the transparent conductive film laminate was measured with a spectrophotometer (U-4000 manufactured by Hitachi, Ltd.).

(5) The haze ratio of the film was evaluated with a haze meter (HM-150 manufactured by Murakami Color Research Laboratory Co., Ltd.) based on JIS standard K7136.

(6) The work function of the transparent conductive film laminate was measured with an atmospheric photoelectron spectrometer (manufactured by Riken Keiki Co., Ltd., AC-2).

(7) The surface texture of the transparent conductive film laminate was observed with a scanning electron microscope (SEM, ULTRA55 manufactured by Carl Zeiss).

(8) The Si layer laminated on the transparent conductive film laminate is subjected to cross-sectional observation with a scanning electron microscope (SEM, Carl Zeiss ULTRA55) to determine whether defects such as cracks and peeling exist. went. Specifically, for each sample, cross sections were observed at 10 points at intervals of 20 mm or more in the length direction of the substrate, and the presence or absence of defects was determined.

Example 1 GAZO / GAZO / ITO
Transparent conductive film laminate with a large surface irregularity having a structure in which a zinc oxide-based transparent conductive film (II) and an oxide-based transparent conductive film (III) are formed on an indium oxide-based transparent conductive film (I) by the following procedure Was prepared by sputtering.

[Example 1: Preparation of indium oxide-based transparent conductive film (I)]
First, an indium oxide-based transparent conductive film (I) as a base was formed on a light-transmitting substrate under the conditions shown in Table 1. When the composition of the target (manufactured by Sumitomo Metal Mining Co., Ltd.) used for the production of the underlying indium oxide-based transparent conductive film was quantitatively analyzed by ICP emission spectroscopic analysis (manufactured by Seiko Instruments Inc., SPS4000), Ti / (In + Ti) was 0. .50 atomic% or less. Moreover, the purity of the target was 99.999%, and the size was 6 inches (Φ) × 5 mm (thickness).

This sputtering target is applied to a cathode for a ferromagnetic target of a DC magnetron sputtering apparatus (SPF503K manufactured by Tokki Co., Ltd.) (maximum horizontal magnetic field strength at a position 1 cm away from the target surface is about 80 kA / m (1 kG)). A Corning 7059 glass substrate having a thickness of 1.1 mm was attached to the opposite surface of the sputtering target. The average light transmittance of the Corning 7059 glass substrate itself in the visible light wavelength region is 92%. The distance between the sputtering target and the substrate was 50 mm.

When the degree of vacuum in the chamber reaches 2 × 10 ⁻⁴ Pa or less, 6 vol. Ar gas mixed with ₂ % O ₂ gas was introduced into the chamber to a gas pressure of 0.6 Pa, the substrate was heated to 300 ° C., and then DC input power 300 W (input power density to target = DC input power) ÷ Target surface area = 300 W ÷ 181 cm ² = 1.660 W / cm ² ) was introduced between the target and the substrate to generate DC plasma. After performing pre-sputtering for 10 minutes for cleaning the target surface, sputtering film formation was carried out while the substrate was left stationary immediately above the center of the target, and an indium oxide-based transparent conductive film (I) having a film thickness of 300 nm was formed on the substrate. Formed on top.

[Example 1: Preparation of zinc oxide-based transparent conductive film (II)]
Next, on the indium oxide-based transparent conductive film (I), a zinc oxide-based sintered body target (manufactured by Sumitomo Metal Mining Co., Ltd.) containing aluminum and gallium as additive elements is used. A transparent conductive film (II) was formed. The composition of the target was 0.30 atomic% for Al / (Zn + Al) and 0.30 atomic% for Ga / (Zn + Ga).
The purity of each target was 99.999%, and the target size was 6 inches (Φ) × 5 mm (thickness).

In forming the zinc oxide-based transparent conductive film (II), the inside of the chamber is evacuated, and when the degree of vacuum reaches 2 × 10 ⁻⁴ Pa or less, Ar gas having a purity of 99.9999 mass% is placed in the chamber. The gas pressure was 4.0 Pa. The substrate temperature was set to 400 ° C., and DC input power of 400 W (input power density to target = DC input power ÷ target surface area = 400 W ÷ 181 cm ² = 2.210 W / cm ² ) was input between the target and the substrate, Plasma was generated. After pre-sputtering for 10 minutes to clean the target surface, sputtering film formation was carried out with the substrate still immediately above the center of the target to form a 400 nm-thick zinc oxide transparent conductive film (II) Then, a transparent conductive film laminate was obtained.

[Example 1: Production of oxide-based transparent conductive film (III)]
Finally, a zinc oxide based sintered target (made by Sumitomo Metal Mining Co., Ltd.) containing aluminum and gallium as additive elements was used on the zinc oxide based transparent conductive film (II) under the conditions shown in Tables 1 and 2. Thus, an oxide-based transparent conductive film (III) was formed. The composition of the target was 2.00 atomic% for Al / (Zn + Al) and 2.00 atomic% for Ga / (Zn + Ga). The purity of each target was 99.999%, and the target size was 6 inches (Φ) × 5 mm (thickness).

In forming the transparent conductive film (III), the inside of the chamber is evacuated, and when the degree of vacuum reaches 2 × 10 ⁻⁴ Pa or less, Ar gas having a purity of 99.9999 mass% is introduced into the chamber. The gas pressure was 0.3 Pa. The substrate temperature is set to 300 ° C., and DC input power of 400 W (input power density to target = DC input power ÷ target surface area = 400 W ÷ 181 cm ² = 2.210 W / cm ² ) is input between the target and the substrate, Plasma was generated. After pre-sputtering for 10 minutes to clean the target surface, sputtering film formation was performed while the substrate was left just above the center of the target to form an oxide-based transparent conductive film (III) with a film thickness of 50 nm. Then, a transparent conductive film laminate was obtained.

[Comparative Example 1] GAZO / ITO
The transparent conductive film was prepared in the same manner as in Example 1 except that the indium oxide-based transparent conductive film (I) and the zinc oxide-based transparent conductive film (II) were prepared and the oxide-based transparent conductive film (III) was not formed. A film laminate was obtained.

[Characteristic Evaluation: Example 1, Comparative Example 1]
The film thickness and resistance value of the transparent conductive thin film laminates of Example 1 and Comparative Example 1 were measured by the methods (1) and (3). Further, the total light transmittance and the haze ratio of the transparent conductive thin film laminate at a wavelength of 400 to 1200 nm were measured by the methods (4) and (5). Moreover, the work function of the obtained transparent conductive film laminated body outermost surface was measured by the method of said (6).

As shown in Table 3, the film thickness of the transparent conductive film laminate of Example 1 was 750 nm. The total light transmittance at a wavelength of 400 to 1200 nm was 80.8%, and the haze ratio was as high as 20.3%. The surface resistance was 9.9Ω / □, indicating high conductivity. Moreover, the work function of the transparent conductive film laminated body outermost surface is 4.8 eV, and it can obtain the transparent conductive film laminated body which has a target high work function, and has a high haze rate and a low resistance value at high speed. It was confirmed that it was possible.

The film thickness of the transparent conductive film laminate of Comparative Example 1 was 700 nm. The total light transmittance at a wavelength of 400 to 1200 nm was 81.0%, and the haze ratio was 19.6%. The surface resistance was 10.1Ω / □. Moreover, the work function of the transparent conductive film laminated body outermost surface was 4.7 eV.

FIG. 4 shows a surface SEM photograph of the transparent conductive thin film after the formation of the zinc oxide-based transparent conductive film (II). On the zinc oxide-based transparent conductive film (II), there is a steep recess as shown in the circle of FIG. In Example 1, the oxide-based transparent conductive film (III) is formed on the zinc oxide-based transparent conductive film (II), and such a steep recess is eliminated. On the other hand, in Comparative Example 1, since the oxide-based transparent conductive film (III) is not formed, the Si layer is laminated on the steep concave portion.

On each transparent conductive film laminate of Example 1 and Comparative Example 1, a Si layer was formed by the CVD method, and the Si layer was observed. As a result, although no defect was present in Example 1, cracks and partial peeling occurred in the Si layer in Comparative Example 1. Therefore, it was found that the three-layer structure including the oxide-based transparent conductive film (III) as in Example 1 is effective for preventing defects in the Si layer.

[Examples 2 to 7, Comparative Examples 2 to 6: GAZO / GAZO / ITO]
For the indium oxide-based transparent conductive film (I), the zinc oxide-based transparent conductive film (II) and the oxide-based transparent conductive film (III) shown in Example 1, the respective film thicknesses are set as shown in Tables 1 and 2. It changed and produced the transparent conductive film laminated body. Other film forming conditions were the same as in Example 1. The characteristics evaluation of the produced transparent conductive film laminated body was implemented by the same item and method as Example 1.

[Characteristic evaluation: Examples 2 to 7, Comparative examples 2 to 6]
In Table 3, the characteristic evaluation result of the obtained transparent conductive film laminated body is shown. In Comparative Example 2 in which the thickness of the zinc oxide-based transparent conductive film (II) was 150 nm, the crystal grains did not grow sufficiently to obtain a sufficiently high haze ratio, and the haze ratio was as low as 7.0%. It was.

Further, Comparative Example 3 in which the film thickness of the oxide-based transparent conductive film (III) is 3 nm does not sufficiently cover the surface gap of the zinc oxide-based transparent conductive film (II), and the Si layer is laminated. As a result, cracks in the Si layer occurred. On the other hand, in Comparative Example 4 in which the thickness of the oxide-based transparent conductive film (III) was 230 nm, the total light transmittance was as low as 74.8%.

Next, in Comparative Example 5 in which the film thickness of the indium oxide-based transparent conductive film (I) was 30 nm, the conductivity was not sufficient, and the sheet resistance value as the obtained transparent conductive film laminate was 30.1Ω / □. It was high. On the other hand, in Comparative Example 6 in which the film thickness of the indium oxide-based transparent conductive film (I) was 700 nm, the total light transmittance was as low as 73.8%.

Therefore, the transparent conductive film laminates as in Comparative Examples 2 to 6 are not useful for the surface transparent electrode of the thin film solar cell. In the transparent conductive film laminates in Examples 2 to 7, it was confirmed that no defects in the Si layer were generated because there were no complicated voids in the surface structure. Moreover, since it has a high haze rate and a low resistance value, it was confirmed that it was useful for the surface transparent electrode of a thin film solar cell.

Example 8 AZO / AZO / ITO
As shown in Tables 1 and 2, as in Example 1, except that the zinc oxide-based transparent conductive film (II) and the oxide-based transparent conductive film (III) in Example 1 were aluminum-containing zinc oxide (AZO). A transparent conductive film laminate was prepared according to the items and conditions. The composition of the target used for producing the zinc oxide-based transparent conductive film (II) and the oxide transparent conductive film (III) was quantitatively analyzed by ICP emission spectroscopic analysis (manufactured by Seiko Instruments Inc., SPS4000). Zn + Al) was 0.50 atomic% or less. Moreover, the purity of the target was 99.999%, and the size was 6 inches (Φ) × 5 mm (thickness).

[Comparative Example 7] AZO / ITO
As shown in Tables 1 and 2, a transparent conductive film laminate was produced in the same manner as in Example 8 except that the oxide-based transparent conductive film (III) in Example 8 was not formed.

[Characteristic Evaluation: Example 8, Comparative Example 7]
In Table 3, the characteristic evaluation result of the transparent conductive film laminated body of Example 8 and Comparative Example 7 is shown. The characteristics of the transparent conductive thin film laminate were measured by the same items and methods as in Example 1. The film thickness of the transparent conductive film laminate of Example 8 was 750 nm. The total light transmittance at a wavelength of 400 to 1200 nm was 81.0%, and the haze ratio was as high as 16.8%. The surface resistance was 11.4Ω / □, indicating high conductivity. Moreover, the work function of the transparent conductive film laminated body outermost surface is 4.5 eV, and it can obtain the transparent conductive film laminated body which has a target high work function, and has a high haze rate and a low resistance value at high speed. It was confirmed that it was possible.

The film thickness of the transparent conductive film laminate of Comparative Example 7 was 700 nm. The total light transmittance at a wavelength of 400 to 1200 nm was 81.2%, and the haze ratio was 17.0%. The surface resistance was 11.5Ω / □. Moreover, the work function of the transparent conductive film laminated body outermost surface was 4.6 eV.

Next, the Si layer was formed by the CVD method on the transparent conductive film laminate obtained in Example 8 and Comparative Example 7, and observed. As a result, although no defect was present in Example 8, cracks and partial peeling occurred in the Si layer in Comparative Example 7. Therefore, it was found that the three-layer structure including the oxide-based transparent conductive film (III) is effective for preventing defects in the Si layer.

Example 9 GZO / GZO / ITO
As shown in Tables 1 and 2, except that the zinc oxide-based transparent conductive film (II) and the oxide-based transparent conductive film (III) in Example 1 were zinc oxide containing gallium, A transparent conductive film laminate was produced under the conditions. The composition of the target used for the production of the zinc oxide-based transparent conductive film (II) and the oxide transparent conductive film (III) was quantitatively analyzed by ICP emission spectroscopic analysis (manufactured by Seiko Instruments Inc., SPS4000). Ga + Al) was 0.50 atomic% or less. Moreover, the purity of the target was 99.999%, and the size was 6 inches (Φ) × 5 mm (thickness).

[Comparative Example 8] GZO / ITO
As shown in Tables 1 and 2, a transparent conductive film laminate was produced in the same manner as in Example 9 except that the oxide-based transparent conductive film (III) in Example 9 was not formed.

[Characteristic Evaluation: Example 9, Comparative Example 8]
In Table 3, the characteristic evaluation result of the transparent conductive film laminated body of Example 9 and Comparative Example 8 is shown. The characteristics of the transparent conductive thin film laminate were measured by the same items and methods as in Example 1. The film thickness of the transparent conductive film laminate of Example 9 was 750 nm. The total light transmittance at a wavelength of 400 to 1200 nm was 80.2%, and the haze ratio was as high as 19.9%. The surface resistance was 9.5Ω / □, indicating high conductivity. In addition, the work function of the outermost surface of the transparent conductive film laminate is 4.7 eV, and a transparent conductive film laminate having a target high work function, a high haze ratio, and a low resistance value can be obtained at high speed. It was confirmed that it was possible.

The film thickness of the transparent conductive film laminate of Comparative Example 8 was 700 nm. The total light transmittance at a wavelength of 400 to 1200 nm was 80.3%, and the haze ratio was as high as 20.3%. The surface resistance was 9.2Ω / □. Moreover, the work function of the transparent conductive film laminated body outermost surface was 4.7 eV.

Next, an Si layer was formed by CVD on the transparent conductive film laminate obtained in Example 9 and Comparative Example 8, and observed. As a result, although no defect was present in Example 9, cracks and partial peeling occurred in the Si layer in Comparative Example 8. Therefore, it was found that the three-layer structure including the oxide-based transparent conductive film (III) is effective for preventing defects in the Si layer.

[Examples 10 to 16, Comparative Examples 9 to 11]
As shown in Tables 1 and 2, the oxide-based transparent conductive film (III) in Example 1 was 3.00 atomic% (Example 10: ZMgO) in Mg / (Zn + Mg) and 3 in Si / (Zn + Si), respectively. 0.000 atomic% (Example 11: SZO), Sn / (Zn + Sn) at 6.00 atomic% (Example 12: ZTO), Ti / (In + Ti) at 2.00 atomic% and Sn / (In + Sn) at 0 0.05 atomic% (Example 13: ITiTO), Ga / (In + Ga) at 15.0 atomic% (Example 14: IGO), Ce / (In + Ce) at 10.0 atomic% (Example 15: ICO), Example 1 except that W / (In + W) was 1.00 atomic% (Example 16: IWO), V ₂ O ₅ (Comparative Example 9), Al (Comparative Example 10), and Ni (Comparative Example 11). Make a transparent conductive film laminate using the same items and conditions as Made.

[Characteristic Evaluation: Examples 10 to 16, Comparative Examples 9 to 11]
Table 3 shows the characteristic evaluation results of the transparent conductive film laminates of Examples 10 to 16 and Comparative Examples 9 to 11. The characteristics of the transparent conductive thin film laminate were measured by the same items and methods as in Example 1. The transparent conductive film laminate of Comparative Example 9 in which the composition of the oxide-based transparent conductive film (III) was V ₂ O ₅ had a surface work function as good as 5.4 eV, but the film could be confirmed with the naked eye. The total light transmittance was very low at 70.4%. In addition, the transparent conductive film laminates of Comparative Example 10 and Comparative Example 11 in which the composition of the oxide-based transparent conductive film (III) is a metal film have a reflectance due to carrier scattering unique to the metal film as compared with the oxide film. As a result, the total light transmittance was very low at 67.3% (Comparative Example 10) and 68.2% (Comparative Example 11), respectively.

Therefore, the transparent conductive film laminates as in Comparative Examples 9 to 11 are not useful for the surface transparent electrode of the thin film solar cell. In the transparent conductive film laminates in Examples 10 to 16, since no complicated voids exist in the surface structure, it was confirmed that Si layer defects do not occur. Moreover, since it has a high haze rate and a low resistance value, it was confirmed that it was useful for the surface transparent electrode of a thin film solar cell.

[Examples 17 to 21]
As shown in Tables 1 and 2, the indium oxide-based transparent conductive film (I) in Example 1 was 1.00 atomic% (Example 17) in terms of W / (In + W) and 1.00 in terms of Mo / (In + Mo), respectively. Atomic% (Example 18), Zr / (In + Zr) at 1.00 atomic% (Example 19), Ce / (In + Ce) at 10.0 atomic% (Example 20), Ga / (In + Ga) at 15. A transparent conductive film laminate was produced under the same items and conditions as in Example 1 except that the content was 0 atomic% (Example 21).

[Characteristic evaluation: Examples 17 to 21]
Table 3 shows the characteristic evaluation results of the transparent conductive film laminates of Examples 17 to 21. The characteristics of the transparent conductive thin film laminate were measured by the same items and methods as in Example 1. In the transparent conductive film laminates in Examples 17 to 21, since no complicated voids exist in the surface structure, it was confirmed that Si layer defects do not occur. Moreover, since it has a high haze rate and a low resistance value, it was confirmed that it was useful for the surface transparent electrode of a thin film solar cell.

[Examples 22 to 25] GAZO / GAZO / ITOO
As shown in Tables 1 and 2, the indium oxide-based transparent conductive film (I) in Example 1 is used as a base, and hydrogen (H ₂ ) gas is further added thereon in a molar ratio of H ₂ / (Ar + H ₂ ). .01 (Example 22), 0.25 (Example 23), 0.43 (Example 24), and 0.50 atomic% (Example 25) were introduced and the film thickness was changed to 300 nm. A zinc oxide-based transparent conductive film (II) was formed in the same manner as in Example 1 to produce a transparent conductive film laminate.

[Characteristic evaluation: Examples 22 to 25]
Table 3 shows the characteristic evaluation results of the transparent conductive film laminates of Examples 22 to 25. The characteristics evaluation of the transparent conductive film laminate was carried out using the same items and methods as in Example 1. Regarding the film characteristics of the transparent conductive film laminate, although the haze ratio and the surface resistance tend to increase as the H ₂ ratio of the film forming gas increases, the transparent conductive film laminates of Examples 22 to 25 The haze rate was not only sufficiently high at 8% or more, but also the surface resistance was as low as 25Ω / □ or less. In addition, it was confirmed that no defects in the Si layer were generated due to the absence of complex voids in the surface structure of the transparent conductive film laminate due to the lamination of the oxide-based transparent conductive film (III). Moreover, since it has a high haze rate and a low resistance value, it was confirmed that it was useful for the surface transparent electrode of a thin film solar cell.

[Examples 26 to 29] GAZO / GAZO / ITOO
As shown in Tables 1 and 2, when forming the indium oxide-based transparent conductive film (I) (Example 26), forming the zinc oxide-based transparent conductive film (II) (Example 27), or oxidizing, respectively. Example 1 except that when the physical transparent conductive film (III) was formed (Example 28), the substrate was not heated and an amorphous film was formed at room temperature, followed by heat treatment at 300 ° C. In the same manner, a transparent conductive film laminate was produced. In addition, in Example 29, when forming the oxide-based transparent conductive film (III), an amorphous film was formed at room temperature without heating the substrate, and no heat treatment was performed. In the same manner as in Example 1, a transparent conductive film laminate was produced.

[Characteristic evaluation: Examples 26 to 29]
Table 3 shows the characteristic evaluation results of the transparent conductive film laminates of Examples 26 to 29. The characteristics of the transparent conductive thin film laminate were measured by the same items and methods as in Example 1. In the transparent conductive film laminates in Examples 26 to 29, it was confirmed that no defects in the Si layer were generated because there were no complicated voids in the surface structure. Moreover, since it has a high haze rate and a low resistance value, it was confirmed that it was useful for the surface transparent electrode of a thin film solar cell.

DESCRIPTION OF SYMBOLS 1 Translucent board | substrate, 2 Transparent conductive film laminated body, 3 Amorphous photoelectric conversion unit, 4 Crystalline photoelectric conversion unit, 5 Back electrode, 21 Indium oxide type transparent conductive film (I), 22 Zinc oxide type transparent conductive film (II), 23 oxide-based transparent conductive film (III)

Claims

An indium oxide-based transparent conductive film (I) having a thickness of 50 nm or more and 600 nm or less formed on a light-transmitting substrate;
A zinc oxide-based transparent conductive film (II) having a thickness of 200 nm to 1000 nm formed on the indium oxide-based transparent conductive film (I);
A transparent conductive film laminate comprising: an oxide-based transparent conductive film (III) formed on the zinc oxide-based transparent conductive film (II) and having a thickness of 5 nm to 200 nm.
The oxide-based transparent conductive film (III) is a metal oxide and contains one or more elements selected from Mg, Al, Si, Ti, Zn, Ga, In, Sn, W, and Ce. The transparent conductive film laminate according to claim 1, wherein
The oxide-based transparent conductive film (III) is made of gallium / aluminum doped zinc oxide, aluminum doped zinc oxide, gallium doped zinc oxide, magnesium doped zinc oxide, silicon doped zinc oxide, tin doped zinc oxide, titanium / tin doped indium oxide, gallium. 2. The transparent conductive film laminate according to claim 1, comprising one kind selected from doped indium oxide, cerium-doped indium oxide, and tungsten-doped indium oxide.
The oxide-based transparent conductive film (III) contains zinc oxide as a main component and contains one or more elements selected from Mg, Al, Si, Ga, Sn, and W. The transparent conductive film laminated body as described in.
The surface of the oxide-based transparent conductive film (III) has a work function of 4.5 eV or more, a total light transmittance at a wavelength of 400 nm to 1200 nm of 75.0% or more, a haze ratio of 8% or more, and a surface resistance of 25Ω. The transparent conductive film laminate according to any one of Claims 1 to 4, wherein the transparent conductive film laminate is / □ or less.
The zinc oxide-based transparent conductive film (II) contains zinc oxide as a main component and contains one or more additive metal elements selected from aluminum or gallium within a range represented by the following formula (1). The transparent conductive film laminate according to any one of claims 1 to 4.
[Al] ≦ [Ga] ≦ −2.68 × [Al] +1.74 (1)
(However, [Al] is the aluminum content expressed by the atomic ratio (%) of Al / (Zn + Al), and [Ga] is the gallium expressed by the atomic ratio (%) of Ga / (Zn + Ga). And [Al] ≧ 0, [Ga] ≧ 0.)
The transparent conductive film laminate according to any one of claims 1 to 6, wherein a work function of the surface of the oxide-based transparent conductive film (III) is 5.0 eV or more.
The indium oxide-based transparent conductive film (I) is a crystalline film containing indium oxide as a main component and containing one or more metal elements selected from Sn, Ti, W, Mo, Zr, Ce or Ga. The transparent conductive film laminate according to any one of claims 1 to 7.
The indium oxide-based transparent conductive film (I) contains indium oxide as a main component and contains Sn, and the content ratio is 15 atomic% or less in terms of the Sn / (In + Sn) atomic ratio. 8. The transparent conductive film laminate according to any one of 1 to 7.
The indium oxide-based transparent conductive film (I) contains indium oxide as a main component and contains Ti, and the content ratio is 5.5 atomic% or less in terms of Ti / (In + Ti) atomic ratio. The transparent conductive film laminate according to any one of claims 1 to 7.
A first film forming step of forming an indium oxide-based transparent conductive film (I) having a thickness of 50 nm or more and 600 nm or less on a light-transmitting substrate by a sputtering method;
A second film-forming step of forming a zinc oxide-based transparent conductive film (II) having a thickness of 200 nm or more and 1000 nm or less on the indium oxide-based transparent conductive film (I) by a sputtering method;
A transparent conductive film comprising: a third film-forming step of forming an oxide-based transparent conductive film (III) having a thickness of 5 nm to 200 nm on the zinc oxide-based transparent conductive film (II) by a sputtering method. A manufacturing method of a layered product.
The sputtering target for forming the oxide-based transparent conductive film (III) is a metal oxide, and one or more selected from Mg, Al, Si, Ti, Zn, Ga, In, Sn, W, and Ce The process for producing a transparent conductive film laminate according to claim 11, comprising:
Sputtering targets for forming the oxide-based transparent conductive film (III) are gallium / aluminum-doped zinc oxide, aluminum-doped zinc oxide, gallium-doped zinc oxide, magnesium-doped zinc oxide, silicon-doped zinc oxide, tin-doped zinc oxide, The method for producing a transparent conductive film laminate according to claim 11, comprising one kind selected from titanium / tin-doped indium oxide, gallium-doped indium oxide, cerium-doped indium oxide, and tungsten-doped indium oxide.
A sputtering target for forming the oxide-based transparent conductive film (III) contains zinc oxide as a main component and contains one or more elements selected from Mg, Al, Si, Ga, Sn, and W. The manufacturing method of the transparent conductive film laminated body of Claim 11 characterized by these.
The surface of the oxide-based transparent conductive film (III) has a work function of 4.5 eV or more, a total light transmittance at a wavelength of 400 nm to 1200 nm of 75.0% or more, a haze ratio of 8% or more, and a surface resistance of 25Ω. The method for producing a transparent conductive film laminate according to any one of claims 11 to 14, wherein:
A range in which the sputtering target for forming the zinc oxide-based transparent conductive film (II) includes zinc oxide as a main component and one or more additive metal elements selected from aluminum or gallium is represented by the following formula (1): The method for producing a transparent conductive film laminate according to any one of claims 11 to 15, wherein the transparent conductive film laminate is contained.
[Al] ≦ [Ga] ≦ −2.68 × [Al] +1.74 (1)
(However, [Al] is the aluminum content expressed by the atomic ratio (%) of Al / (Zn + Al), and [Ga] is the gallium expressed by the atomic ratio (%) of Ga / (Zn + Ga). And [Al] ≧ 0, [Ga] ≧ 0.)
In the second film forming step, the mixing ratio of a mixed gas of argon and hydrogen as a sputtering gas species is set to H 2 / (Ar + H 2 ) ≦ 0.43. The manufacturing method of the transparent conductive film laminated body of 1 item | term.
In the first film formation step, the sputtering gas pressure is set to 0.1 Pa or more and less than 1.0 Pa, and in the second film formation step, the sputtering gas pressure is set to 1.0 Pa or more and 15.0 Pa or less, The method for producing a transparent conductive film laminate according to any one of claims 11 to 17, wherein in the film forming step, a sputtering gas pressure is set to 0.1 Pa or more and less than 1.0 Pa.
After the indium oxide-based transparent conductive film (I) is formed as an amorphous film at a substrate temperature of 100 ° C. or less and a sputtering gas pressure of 0.1 Pa or more and less than 1.0 Pa in the first film forming step, 19. The method for producing a transparent conductive film laminate according to claim 11, wherein the transparent conductive film laminate is heat-treated at 200 ° C. or more and 600 ° C. or less and crystallized on the translucent substrate.
In the first film forming step, the indium oxide-based transparent conductive film (I) is formed on the translucent substrate under the conditions of a substrate temperature of 200 ° C. or more and 600 ° C. or less and a sputtering gas pressure of 0.1 Pa or more and less than 1.0 Pa. The method for producing a transparent conductive film laminate according to any one of claims 11 to 18, wherein the transparent conductive film laminate is formed as a crystal film.
In a thin film solar cell in which a transparent conductive film laminate, a photoelectric conversion layer unit, and a back electrode layer are formed in order on a light-transmitting substrate,
The transparent conductive film laminate is
An indium oxide-based transparent conductive film (I) having a thickness of 50 nm to 600 nm formed on the light-transmitting substrate;
A zinc oxide-based transparent conductive film (II) having a thickness of 200 nm to 1000 nm formed on the indium oxide-based transparent conductive film (I);
A thin film solar cell comprising: an oxide-based transparent conductive film (III) formed on the zinc oxide-based transparent conductive film (II) and having a thickness of 5 nm to 200 nm.
In the method for manufacturing a thin-film solar cell in which a transparent conductive film laminate, a photoelectric conversion layer unit, and a back electrode layer are formed in order on a light-transmitting substrate,
A first film forming step of forming an indium oxide-based transparent conductive film (I) having a thickness of 50 nm or more and 600 nm or less on the translucent substrate by a sputtering method;
A second film-forming step of forming a zinc oxide-based transparent conductive film (II) having a thickness of 200 nm or more and 1000 nm or less on the indium oxide-based transparent conductive film (I) by a sputtering method;
And a third film forming step of forming an oxide-based transparent conductive film (III) having a thickness of 5 nm to 200 nm on the zinc oxide-based transparent conductive film (II) by a sputtering method. A method for producing a thin-film solar cell.