WO2012093702A1

WO2012093702A1 - Transparent electroconductive film laminate and method for manufacturing same, as well as thin-film solar cell and method for manufacturing same

Info

Publication number: WO2012093702A1
Application number: PCT/JP2012/050124
Authority: WO
Inventors: 阿部　能之; 健太郎曽我部; 山野辺　康徳
Original assignee: 住友金属鉱山株式会社
Priority date: 2011-01-05
Filing date: 2012-01-05
Publication date: 2012-07-12
Also published as: TW201243869A; JP2012142499A

Abstract

Provided are a transparent electroconductive film laminate having excellent resistance to hydrogen reduction and excellent light confinement effect, and a method for manufacturing this laminate, as well as a thin-film solar cell and a method for manufacturing the same. A three-layer laminated structure is provided in which an indium oxide transparent electroconductive film (I) formed on a translucent substrate is used as a foundation on which are formed, in sequence, a zinc oxide transparent electroconductive film (II) for protecting the indium oxide transparent electroconductive film, and a zinc oxide transparent electroconductive film (III) having excellent concavo-convex properties.

Description

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

The present invention is useful for producing a high-efficiency silicon-based thin film solar cell, and is a transparent conductive film laminate excellent in hydrogen reduction resistance and excellent in light confinement effect, a method for producing the same, and a thin film solar cell and the same It relates to a manufacturing method. This application claims priority on the basis of Japanese Patent Application No. 2011-000777 filed on January 5, 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.

The photoelectric conversion unit formed on the surface of the transparent conductive film is generally manufactured using a high-frequency plasma CVD method, and as a source gas used at this time, a silicon-containing gas such as SiH ₄ or Si ₂ H ₆ , or those A mixture of the above gas and H ₂ is used. Further, as a dopant gas for forming a p-type or n-type layer in the photoelectric conversion _unit, B 2 _H 6, PH ₃ or the like is preferably used. As formation conditions, the substrate temperature is 100 ° C. or more and 250 ° C. or less (however, the amorphous p-type silicon carbide layer 3p is 180 ° C. or less), the pressure is 30 Pa or more and 1500 Pa or less, and the high frequency power density is 0.01 W / cm ² or more and 0.5 W / cm ² or less is preferably used.

Thus, when manufacturing the photoelectric conversion unit, if the formation temperature is increased, the reduction of the metal oxide is promoted by the existing hydrogen, and in the case of the transparent conductive film mainly composed of tin oxide, the hydrogen reduction is performed. There is a loss of transparency. If such a transparent conductive film with poor transparency is used, a thin film solar cell with high conversion efficiency cannot be realized.

Similarly, the transparent conductive film mainly composed of indium oxide also loses transparency due to this hydrogen reduction. In particular, when an indium oxide-based transparent conductive film is used, the transparency is impaired as the film is blackened by hydrogen reduction, so that it is very difficult to use it as a surface electrode of a thin film solar cell.

As a method for preventing reduction of a transparent conductive film containing tin oxide as a main component by hydrogen, Non Patent Literature 1 discloses a reduction resistance on a transparent conductive film made of tin oxide having a high degree of unevenness formed by a thermal CVD method. A method of forming a thin zinc oxide film having a good thickness by sputtering is proposed. Since zinc oxide has a strong bond between zinc and oxygen and is excellent in resistance to hydrogen reduction, the transparency of the transparent conductive film can be kept high by adopting the above structure.

However, in order to obtain the transparent conductive film having the above-described structure, it is necessary to form a film by combining two kinds of methods. Moreover, about the method of manufacturing all the laminated films of a tin oxide type transparent conductive film and a zinc oxide type transparent conductive film by sputtering method, a highly transparent tin oxide type transparent conductive film cannot be manufactured by sputtering method, etc. It is said that it is impossible to realize for the reason.

On the other hand, Non-Patent Document 2 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.

In Non-Patent Document 3, after obtaining a transparent conductive film with zinc oxide as a main component and produced by a conventional sputtering method and having 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.

Among zinc oxide-based transparent conductive film materials, those related to AZO containing aluminum as a dopant are used to produce an AZO transparent conductive film that is C-axis oriented by DC magnetron sputtering using a target that is mainly composed of zinc oxide and mixed with aluminum oxide. Has been proposed (see Patent Document 1). In this case, arcing (abnormal discharge) frequently occurs when DC sputtering film formation is performed by increasing the power density applied to the target in order to perform film formation at high speed. 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. .

Therefore, 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). (See Patent Document 2). 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). With such a GZO target to which a third element such as Al is added, abnormal discharge as described in Patent Document 1 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 3).

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. However, in recent years, a solar cell with higher conversion efficiency has been demanded, and a high-quality transparent conductive film that can be used therefor is required.

Japanese Patent Laid-Open No. 62-12201 Japanese Patent Laid-Open No. 10-306367 JP 2008-110911 A

In view of the situation as described above, the present invention is useful for producing a high-efficiency silicon-based thin film solar cell, and is a transparent conductive film laminate excellent in hydrogen reduction resistance and excellent in light confinement effect, and its production It is an object of the present invention to provide a method, and a thin film solar cell and a method for manufacturing the same.

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. An indium oxide-based transparent conductive film having low hydrogen reduction resistance is formed by forming a dense crystalline zinc oxide-based transparent conductive film (II) having c-axis orientation on the transparent conductive film (I) as a base. (I) It is possible to protect the entire surface, and further, by forming the zinc oxide-based transparent conductive film (III) composed of large crystal grains on the zinc oxide-based transparent conductive film (II), the light confinement effect In addition, the present inventors have found that the structure is excellent, and have completed the present invention.

That is, in the method for producing a transparent conductive film laminate according to the present invention, the c-axis inclination angle of the hexagonal crystal is formed on the indium oxide-based transparent conductive film (I) formed on the light-transmitting substrate by sputtering. A first film-forming step of forming a zinc oxide-based transparent conductive film (II) having a thickness of 10 ° or less and a film thickness of 10 nm or more and 200 nm or less with respect to a direction perpendicular to the translucent substrate surface; A second film forming step of forming a zinc oxide-based transparent conductive film (III) having a film thickness of 400 nm or more and 1600 nm or less on the transparent conductive film (II) by a sputtering method, and the surface roughness (Ra ) Is 35.0 nm or more, and a transparent conductive film laminate having a surface resistance of 25 Ω / □ or less is produced.

The transparent conductive film laminate according to the present invention includes an indium oxide-based transparent conductive film (I) formed on a translucent substrate and a hexagonal crystal formed on the indium oxide-based transparent conductive film (I). A zinc oxide-based transparent conductive film (II) in which the c-axis tilt angle of the crystal-based crystal is 10 ° or less with respect to the direction perpendicular to the light-transmitting substrate surface, and the film thickness is 10 nm or more and 200 nm or less; (II) a zinc oxide-based transparent conductive film (III) having a film thickness of 400 nm or more and 1600 nm or less formed thereon, a surface roughness (Ra) of 35.0 nm or more, and a surface resistance of 25Ω / □ or less. It is characterized by being.

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, On the indium oxide-based transparent conductive film (I) formed on the translucent substrate, the c-axis tilt angle of the hexagonal crystal is 10 ° or less with respect to the direction perpendicular to the translucent substrate surface by sputtering. The film thickness is 10 nm or more and 200 nm or less, and a film thickness is formed by sputtering on the zinc oxide-based transparent conductive film (II) and the zinc oxide-based transparent conductive film (II). A second film formation step of forming a zinc oxide-based transparent conductive film (III) having a thickness of 400 nm or more and 1600 nm or less, and a surface roughness (Ra) of 35.0 nm or more on the translucent substrate. Resistance is 25Ω / □ or less A transparent conductive film laminate is formed.

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 indium oxide-based transparent conductive film (I) formed on the translucent substrate and the hexagonal crystal c-axis tilt angle formed on the indium oxide-based transparent conductive film (I) Zinc oxide-based transparent conductive film (II) having a thickness of 10 ° or less and a film thickness of 10 nm or more and 200 nm or less with respect to the direction perpendicular to the translucent substrate surface, and a film formed on the zinc oxide-based transparent conductive film (II) And a zinc oxide-based transparent conductive film (III) having a thickness of 400 nm or more and 1600 nm or less, having a surface roughness (Ra) of 35.0 nm or more and a surface resistance of 25Ω / □ or less.

According to the present invention, on the indium oxide-based transparent conductive film (I), the c-axis tilt angle of the hexagonal crystal is 10 ° or less with respect to the direction perpendicular to the translucent substrate surface, and the film thickness is 10 nm or more and 200 nm. By laminating the zinc oxide-based transparent conductive film (II) and the zinc oxide-based transparent conductive film (III) having a film thickness of 10 nm or more and 200 nm or less, the surface roughness (Ra) is 35.0 nm or more, A film having a surface resistance of 25Ω / □ or less can be obtained, a transparent conductive film laminate having excellent hydrogen reduction resistance and excellent light confinement effect can be provided.

Moreover, since this transparent conductive film laminated body can be manufactured only by the sputtering method, it is not only excellent in conductivity etc. for a surface transparent electrode of a thin film solar cell, but also by a conventional transparent conductive film by a thermal CVD method. As a result, the cost can be reduced. 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 a zinc oxide-based transparent conductive film. 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 obtained by the production method of the present invention. FIG. 5 is a cross-sectional SEM photograph of the transparent conductive thin film obtained by the production method of the present invention.

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. Zinc 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 zinc 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 the indium oxide-based transparent conductive film is protected thereon. It has a three-layer laminated structure in which a zinc oxide-based transparent conductive film (II) and then a zinc oxide-based transparent conductive film (III) excellent in unevenness are sequentially formed. By adopting this laminated structure, it is possible to protect the indium oxide-based transparent conductive film (I) which is excellent in conductivity but inferior in hydrogen reduction resistance, and therefore has excellent hydrogen reduction resistance and transparency of the transparent conductive film. In addition, the conductivity can be kept high. Moreover, such a transparent conductive film laminated body has a high haze ratio, is excellent in so-called light confinement effect, has low resistance, and is very useful as a surface electrode material for thin film solar cells. 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 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.

In the case where Sn is mainly contained in indium oxide, 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 tin as a dopant and an ITiO film containing titanium as a dopant are preferably used in the present embodiment.

The film thickness of the indium oxide-based transparent conductive film (I) is not particularly limited, but is preferably 50 nm or more and 600 nm or less, more preferably 300 nm or more and 500 nm or less.

<1-2. Zinc Oxide Transparent Conductive Film (II)>
In the zinc oxide-based transparent conductive film (II), the c-axis tilt angle of the hexagonal crystal is 10 ° or less with respect to the direction perpendicular to the translucent substrate surface. When the c-axis tilt angle exceeds 10 °, the crystal grains become large, voids are formed between the grains, and the underlying indium oxide-based transparent conductive film (I) is exposed. On the other hand, when the c-axis tilt angle is 10 ° or less, the crystal grains are small, and it is possible to prevent the underlying indium oxide-based transparent conductive film (I) from being exposed by voids formed between the grains. .

The film thickness of the zinc oxide-based transparent conductive film (II) is 10 nm or more and 200 nm or less. When the film thickness is less than 10 nm, it is difficult to completely cover the indium oxide-based transparent conductive film (I). When the film thickness exceeds 200 nm, the transparency and productivity are lowered.

Further, the zinc oxide-based transparent conductive film (II) may contain any additive element as long as zinc oxide is a main component (90% or more by weight), and may contain no additive element. Since this zinc oxide-based transparent conductive film (II) mainly protects the indium oxide-based transparent conductive film (I), its composition is not greatly limited, but an additive element that contributes to the conductivity of the oxide film As for it, it is preferable that 1 or more types of additional metal elements chosen from aluminum or gallium are included.

Specifically, the main component is zinc oxide, and one or more additive metal elements selected from aluminum or gallium are included, and the aluminum content and the gallium content are within the range represented by the following formula (1). It is preferable that it exists in.

-[Al] + 0.30 ≦ [Ga] ≦ −1.92 × [Al] +6.10 (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). Gallium content.)

When the content of aluminum and gallium in the zinc oxide-based transparent conductive film (II) exceeds or falls below the region (A) defined by the formula (1) as shown in FIG. There is a possibility that the conductivity becomes insufficient to the extent that the high conductivity is impaired. Moreover, since the conductivity of the target used having the same composition becomes insufficient, the film formation rate becomes slow, which is not preferable for production.

<1-3. Zinc Oxide Transparent Conductive Film (III)>
The film thickness of the zinc oxide-based transparent conductive film (III) is 400 nm or more and 1600 nm or less. When the film thickness is less than 400 nm, it is difficult to obtain sufficient surface roughness (Ra) and haze ratio, and when the film thickness exceeds 1600 nm, the permeability and productivity are lowered. The film thickness of the zinc oxide-based transparent conductive film (III) is more preferably 700 nm or more and 1400 nm or less.

Further, in the zinc oxide-based transparent conductive film (III), it is preferable to use zinc oxide containing one or more additive metal elements selected from aluminum or gallium as an additive element contributing to the conductivity of the oxide film.

Specifically, as disclosed in International Publication No. 2010/104111, zinc oxide is the main component, and one or more additive metal elements selected from aluminum or gallium are included. The content of is preferably in the range represented by the following formula (2).

-[Al] + 0.30 ≦ [Ga] ≦ −2.68 × [Al] +1.74 (2)
(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). Gallium content.)

When the content of aluminum and gallium in the zinc oxide-based transparent conductive film (III) exceeds the range of the region (B) defined by the formula (2) as shown in FIG. 1, the silicon-based material formed thereon Aluminum and gallium easily diffuse into the thin film, making it difficult to realize a silicon-based thin film solar cell with excellent characteristics. Also, in terms of productivity, when the aluminum and gallium contents in the film are larger than the range defined by the formula (2), 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. On the other hand, when it is less than the range defined by the formula (2), the conductivity becomes insufficient.

The zinc oxide-based transparent conductive films (II) and (III) include other elements (for example, indium, titanium, germanium, silicon, tungsten, molybdenum, iridium, ruthenium, zinc, aluminum, gallium and oxygen). Rhenium, cerium, magnesium, silicon, fluorine, etc.) may be contained within a range not impairing the object of the present invention.

Moreover, it is desirable that the zinc oxide-based transparent conductive films (II) and (III) are within the range represented by the above formula (2). Thereby, the same sputtering target can be used for film-forming of a zinc oxide type transparent conductive film (II) and a zinc oxide type transparent conductive film (III), and productivity can be improved.

<1-4. Characteristics of transparent conductive film laminate>
In the transparent conductive film laminates (I) to (III) according to the present embodiment, the film thickness is not particularly limited and depends on the composition of the material, but the indium oxide-based transparent conductive film (I ) Is from 50 nm to 500 nm, particularly preferably from 100 nm to 300 nm, and the zinc oxide-based transparent conductive film (III) is from 400 nm to 1600 nm, particularly preferably from 700 nm to 1400 nm. The thickness of the zinc oxide-based transparent conductive film (II) is preferably a film pressure that can completely cover the surface of the indium oxide-based transparent conductive film (I), but the productivity and the transmittance are deteriorated. 200 nm or less is preferable. The above film thickness is satisfied, and the total film thickness as the transparent conductive film laminate of the present invention is preferably 450 nm to 2300 nm, particularly preferably 800 nm to 1700 nm.

Moreover, the surface roughness (Ra) of the transparent conductive film laminate is 35.0 nm or more. When the surface roughness (Ra) is less than 35.0 nm, a zinc oxide-based transparent conductive film (III) having a high haze ratio cannot be obtained, and when the silicon-based thin film solar cell is produced, the light confinement effect is inferior. High conversion efficiency cannot be realized. In order to provide a sufficient light confinement effect, the surface roughness (Ra) is preferably as large as possible at 35.0 nm or more.

However, if the surface roughness (Ra) of the zinc oxide-based transparent conductive film (III) exceeds 70 nm, it affects the growth of the silicon-based thin film formed on the zinc oxide-based transparent conductive film (III), and the zinc oxide-based transparent conductive film (III) This is not preferable because a gap is generated at the interface between the transparent conductive film (III) and the silicon-based thin film, the contact property is deteriorated, and the solar cell characteristics are deteriorated.

Moreover, the surface resistance of the transparent conductive film laminate is 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 transparent conductive film laminate, the smaller the power loss at the surface electrode portion, and therefore, a high efficiency 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 electrode is 25Ω / □ or less, a solar cell of at least 5 cm □ can be realized, but if it is 20Ω / □ or less, a solar cell of at least 8 cm □ can be realized, and if it is 13Ω / □ or less, at least If the 15 cm □ cell is 10 Ω / □ or less, at least 17 cm □ cell can be realized, and if it is 8 Ω / □ or less, at least 20 cm □ cell can be realized without considering the influence of power loss at the surface electrode. Solar cells with a small cell area need to be connected by metal wiring, which not only reduces the amount of power generated per unit area of a single module made by connecting cells due to factors such as increased cell spacing. This is not preferable because of problems such as an increase in manufacturing cost per cell area.

Further, the haze ratio of the transparent conductive film laminate is preferably 8% or more, more preferably 12% or more, still more preferably 16% or more, and most preferably 20% or more. 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. Furthermore, it is effective to use a surface electrode having a haze ratio of 20% or more in order to realize a conversion efficiency of 15% or more in the same evaluation. In a highly efficient tandem silicon thin film solar cell, a surface electrode having a haze ratio of 20% or more is particularly useful. In the transparent conductive film laminate according to the present embodiment, the above-described zinc oxide-based transparent conductive films (II) and (III) are stacked in addition to the indium oxide-based transparent conductive film (I) inserted in the base. By doing so, a high haze rate can be realized.

Moreover, since the transparent conductive film laminate according to the present embodiment protects the indium oxide-based transparent conductive film by the zinc oxide-based transparent conductive film (II) as described above, it is excellent in resistance to hydrogen reduction. Specifically, a decrease in transmittance due to heat treatment in a hydrogen atmosphere at 500 ° C. can be suppressed to 10% or less.

<2. Manufacturing method of transparent conductive film laminate>
In the method for manufacturing a transparent conductive film laminate according to the present embodiment, the c-axis tilt angle of the hexagonal crystal is increased by sputtering on the indium oxide-based transparent conductive film (I) formed on the light-transmitting substrate. A zinc oxide-based transparent conductive film (II) having a thickness of 10 ° or less and a film thickness of 10 nm or more and 200 nm or less with respect to the direction perpendicular to the translucent substrate surface was formed, and on the zinc oxide-based transparent conductive film (II), A zinc oxide-based transparent conductive film (III) having a film thickness of 400 nm or more and 1600 nm or less is formed by a sputtering method.

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)>
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 can obtain a film having a larger surface roughness (Ra) and haze ratio than the second method in which the substrate is heated to form the crystalline film.

<2-2. Formation of Zinc Oxide Transparent Conductive Film (II)>
The oxide sintered compact target used for film formation of the zinc oxide-based transparent conductive film (II) may contain any additive element as long as it contains lead oxide as a main component (90% or more by weight). An additive element may not be contained. Since the zinc oxide-based transparent conductive film (II) mainly plays a role in protecting the indium oxide-based transparent conductive film (I), the composition of the oxide sintered compact target is not greatly limited. It is preferable that the additive element contributing to the property contains one or more additive metal elements selected from aluminum or gallium. 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.

When using a zinc oxide sintered compact target containing one or more additive metal elements selected from aluminum or gallium, the oxide firing in which the contents of aluminum and gallium are within the range represented by the above formula (1). It is preferable to use a ligation target.

If the content of aluminum and gallium in the oxide sintered compact target is within the range specified by the formula (1), the conductivity of the zinc oxide-based transparent conductive film (II) will be sufficient, but the oxidation As the oxide sintered compact target used for forming the zinc-based transparent conductive film (II), the same target as that for forming the zinc oxide-based transparent conductive film (III) can be used. This makes it possible to replace the oxide sintered compact target in the film formation of the zinc oxide-based transparent conductive film (II) and the film formation of the zinc oxide-based transparent conductive film (III), and to contaminate the chamber due to the different target composition. Can be prevented, and productivity can be improved.

This zinc oxide sintered compact target containing one or more additive metal elements selected from aluminum or gallium is prepared by adding and mixing gallium oxide powder and aluminum oxide powder to zinc oxide powder as a raw material powder, The slurry obtained by blending the raw material powder with the aqueous medium can be pulverized and mixed, then the pulverized / mixture is formed, and then the formed body is fired. The detailed manufacturing method is described in Patent Document 3.

Similarly to the formation of the indium oxide-based transparent conductive film (I), the zinc oxide-based transparent conductive film (II) is formed by forming an amorphous film without heating the substrate, and then heat-treating the crystal. A first method for forming a crystalline film and a second method for forming a crystalline film by heating the substrate can be used.

In the first method, an amorphous material is used in which the DC input power density to the sputtering target is 1.66 W / cm ² or more under the condition that the sputtering gas pressure is 0.1 Pa or more and less than 1.0 Pa and the substrate temperature is 100 ° C. or less. After forming as a film, it heat-processes at 200 degreeC or more and 600 degrees C or less, and crystallizes zinc oxide type transparent conductive film (II). In the second method, the DC input power density to the sputtering target is 1.66 W / cm ² or more under the condition that the substrate temperature is 200 ° C. or more and 600 ° C. or less when the sputtering gas pressure is 0.1 Pa or more and less than 1.0 Pa. As a film, a zinc oxide-based transparent conductive film (II) is formed.

In this embodiment mode, neither the first method nor the second method significantly affects the characteristics of the transparent conductive film laminate, but from the viewpoint of productivity, the heat treatment after film formation. The 2nd method which does not need to provide a process is preferable.

In the present embodiment, the zinc oxide-based transparent conductive film (II) is formed under the condition that the sputtering gas pressure is 0.1 Pa or more and less than 1.0 Pa as described above. When the sputtering gas pressure is less than 0.1 Pa, it is difficult to form a crystal film. Further, when the sputtering gas pressure is 1.0 Pa or more, a zinc oxide-based transparent conductive film (II) in which the c-axis tilt angle of the hexagonal crystal is 10 ° or less with respect to the direction perpendicular to the translucent substrate surface is formed. Difficult to do.

Moreover, in this Embodiment, you may introduce | transduce hydrogen gas at the time of film-forming of a zinc oxide type transparent conductive film (II). By introducing hydrogen gas, excess oxygen in the film is dissociated, and conductivity and transmittance can be improved. In this case, it is preferable to use a mixed gas of argon (Ar) and hydrogen (H ₂ ) as a sputtering gas species, and the mixing ratio (molar ratio) is H ₂ / (Ar + H ₂ ) ≦ 0.43. When the mixing ratio (molar ratio) of the mixed gas of argon (Ar) and hydrogen (H ₂ ) used as the sputtering gas species is H ₂ / (Ar + H ₂ )> 0.43, the adhesion of the transparent conductive film to the substrate Or the transparent conductive film becomes too rough and the conductivity deteriorates, making it practically difficult to use as an electrode of a solar cell. In addition, transparency loss due to hydrogen reduction occurs in the indium oxide-based transparent conductive film (I), which is the underlayer, and it becomes very difficult to use as a surface electrode of a thin film solar cell.

<2-3. Formation of Zinc Oxide Transparent Conductive Film (III)>
If the oxide sintered compact target used for the film formation of the zinc oxide-based transparent conductive film (III) is within the range defined by the formula (2), the surface irregularities as described above The zinc oxide-based transparent conductive film (III) having a large haze ratio can be produced at high speed by a sputtering method.

Similarly to the formation of the zinc oxide-based transparent conductive film (II), the zinc oxide-based transparent conductive film (III) is crystallized by forming an amorphous film without heating the substrate and then heat-treating it. A first method for forming a crystalline film and a second method for forming a crystalline film by heating the substrate can be used.

In the first method, an amorphous material is used in which the direct current input power density to the sputtering target is 1.66 W / cm ² or more under the condition that the sputtering gas pressure is 1.0 Pa or more and 15.0 Pa or less and the substrate temperature is 100 ° C. or less. After forming as a film, it heat-processes at 200 degreeC or more and 600 degrees C or less, and crystallizes zinc oxide type transparent conductive film (III). In the second method, the DC input power density to the sputtering target is 1.66 W / cm ² or more under the conditions that the sputtering gas pressure is 1.0 Pa or more and 15.0 Pa or less and the substrate temperature is 200 ° C. or more and 600 ° C. or less. As a film, a zinc oxide-based transparent conductive film (III) is formed.

In the present embodiment, the first method or the second method does not greatly affect the characteristics of the transparent conductive film laminate, but from the viewpoint of productivity, the heat treatment step after film formation is performed. The second method which does not need to be provided is preferable.

Moreover, in this Embodiment, it is preferable to form zinc oxide type transparent conductive film (III) on the conditions whose 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.

Further, in the present embodiment, during the formation of the zinc oxide-based transparent conductive film (III), hydrogen gas is supplied as H ₂ / (Ar + H ₂ ) ≦ 0 in the same manner as when the zinc oxide-based transparent conductive film (II) is formed. .43 may be introduced at a mixing ratio (molar ratio) to dissociate excess oxygen in the film, thereby improving conductivity and transmittance.

Moreover, in this Embodiment, the substrate temperature at the time of film-forming of zinc oxide type transparent conductive film (III) shall be 200 to 600 degreeC similarly to the time of film-forming of zinc oxide type transparent conductive film (II). It is preferable. 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 described above, when the input power to the sputtering target is increased, the film formation rate is increased and the film productivity is improved. However, the above-described characteristics are hardly obtained by the conventional technique. The high-speed film formation here refers to performing sputtering film formation by increasing the input power to the target to 2.76 W / cm ² or more. Thereby, for example, a film formation speed of 90 nm / min or more can be realized in static facing film formation, and a zinc oxide-based transparent conductive film having a large surface roughness and a high haze ratio 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 the present 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 surface roughness (Ra) is 35. A transparent conductive film laminate having a surface irregularity having a surface resistance of 0.0 nm or more and a surface resistance of 25 Ω / □ or less can be produced. In particular, according to the present embodiment, the surface roughness (Ra) and the surface resistance can be realized even with a thin film thickness of 450 nm or more and 1000 nm or less, and the transmittance is improved by reducing the film thickness. .

As described above, zinc oxide is the main component, one or more selected from aluminum or gallium is included as an additive metal element, and the aluminum content [Al] and the gallium content [Ga] are within a specific range. By forming a certain zinc oxide-based transparent conductive film (III), high-speed film formation is possible only by a sputtering method, surface roughness (Ra) is 35.0 nm or more, surface resistance is 25 Ω / □ or less, A transparent conductive film laminate excellent in the light confinement effect can be obtained. Further, when the zinc oxide-based transparent conductive film is formed on the indium oxide-based transparent conductive film (I), a layer (II) obtained by sputtering under a low gas pressure condition and a layer (II) obtained by sputtering under a high gas pressure condition ( By sequentially laminating III), the low gas pressure layer (II) can protect all over the indium oxide-based transparent conductive film (I) with low hydrogen reduction resistance, and has excellent hydrogen reduction resistance, light A structure having an excellent confinement effect can be obtained.

Moreover, since a transparent conductive film laminated body can be manufactured only by sputtering method, it is not only excellent in electroconductivity etc. for the surface transparent electrode of a thin film solar cell, but the transparent conductive film by the conventional thermal CVD method and In comparison, the cost can be reduced. 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.

In addition, this transparent conductive film laminate is particularly excellent in hydrogen reduction resistance, has a high haze ratio and excellent conductivity, and includes sunlight ranging from visible light to near infrared light having a wavelength of 380 nm to 1200 nm. Can be converted into electrical energy very effectively. Therefore, it is very useful as a surface electrode application of a high efficiency solar cell.

<3. Thin Film Solar Cell and Method for Producing the Same>
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 a zinc oxide type 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 the 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 interface layer 33 shown in FIG. 2 or on the n-type silicon 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. In the method for manufacturing a 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 indium oxide-based transparent conductive film is protected thereon. By forming a transparent conductive film laminate having a three-layer laminated structure in which a zinc oxide-based transparent conductive film (II) and then a zinc oxide-based transparent conductive film (III) excellent in unevenness are successively formed, A low-resistance transparent conductive film for a surface transparent electrode of a thin film 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 and parallel line transmittance, and the total light reflectance and parallel light reflectance of the transparent conductive film laminate were 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. The surface roughness (Ra) of the film was measured in an area of 5 μm × 5 μm using an atomic force microscope (manufactured by Digital Instruments, NS-III, D5000 system).

(6) The hydrogen reduction resistance of the transparent conductive film laminate was evaluated by investigating changes in the transmittance of the transparent conductive film laminate before and after heat treatment in a hydrogen atmosphere at 500 ° C. Here, the transmittance was an average transmittance at a wavelength of 300 to 1200 nm.

(7) The orientation of the zinc oxide-based transparent conductive film (II) is evaluated by the pole figure by X-ray diffraction measurement (manufactured by PANalytical, XPPro Pro MPD), and the c-axis in the film crystal is perpendicular to the substrate. It was evaluated how many times it was inclined against.

[Example 1] GAZO / GAZO / ITO
Transparent structure with large surface irregularities in the structure in which two types of zinc oxide-based transparent conductive films (II) and (III) having different characteristics are formed on the tin-containing indium oxide-based transparent conductive film (I) by the following procedure. A conductive film laminate was produced by a sputtering method.

[Example 1: Preparation of indium oxide-based transparent conductive film (I)]
First, an indium oxide-based transparent conductive film (I) serving as a base was formed 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), Sn / (In + Sn) was 5 .30 atomic% or less. The results are shown in Table 2. 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 400 ° C., and then DC input power 300 W (target input power density = 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 pre-sputtering for 10 minutes to clean the target surface, sputtering film formation is performed while the substrate is stationary immediately above the center of the target, and a 300 nm-thick indium oxide transparent conductive film is formed on the substrate. did.

[Example 1: Preparation of zinc oxide-based transparent conductive film (II)]
Next, on the indium oxide-based transparent conductive film (I) under the conditions shown in Table 1, using a zinc oxide-based sintered target (made by Sumitomo Metal Mining Co., Ltd.) containing aluminum and gallium as additive elements, A zinc oxide-based transparent conductive film (II) was formed. The composition of the target was quantitatively analyzed by ICP emission spectroscopic analysis (manufactured by Seiko Instruments Inc., SPS4000). As a result, Al / (Zn + Al) was 0.30 atomic% and Ga / (Zn + Ga) was 0.30 atomic%. It was. Table 2 shows the measurement results. 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 (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 introduced into the chamber. The gas pressure was 0.3 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 right above the center of the target, forming a 150 nm-thick zinc oxide transparent conductive film (II) Then, a transparent conductive film laminate was obtained.

[Example 1: Preparation of zinc oxide-based transparent conductive film (III)]
Finally, on the zinc oxide-based transparent conductive film (II) under the conditions shown in Table 1, using a zinc oxide-based sintered target (made by Sumitomo Metal Mining Co., Ltd.) containing aluminum and gallium as additive elements, the surface A zinc oxide-based transparent conductive film (III) having large irregularities was formed. The composition of the target was 0.30 atomic% for Al / (Zn + Al) and 0.30 atomic% for Ga / (Zn + Ga), as in the zinc oxide-based transparent conductive film (II) (Table 2). 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 (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 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 for cleaning the target surface, sputtering film formation was performed while the substrate was left still directly above the center of the target to form a 700 nm-thick zinc oxide transparent conductive film (III) Then, a transparent conductive film laminate was obtained.

The film thickness and resistance value of the obtained transparent conductive thin film laminate were measured by the methods (1) and (3). Further, the total light transmittance and parallel line transmittance of the transparent conductive thin film laminate, the total light reflectance and parallel light reflectance, the haze ratio of the film, and the surface roughness Ra of the above (4) and (5) Measured by the method. In addition, as an evaluation of hydrogen reduction resistance of the obtained transparent conductive film laminate, an average transmittance (300 nm to 1200 nm) was measured before and after heat treatment in a hydrogen atmosphere by the method (6). Moreover, about the cross section of the zinc oxide type transparent conductive film (II), c-axis inclination evaluation by X-ray diffraction measurement was performed by the method of said (7).

Table 3 shows the characteristic evaluation results of the obtained transparent conductive film laminate. The film thickness of the transparent conductive film laminate was 1150 nm. The surface roughness Ra value measured with an atomic force microscope was as high as 39.1 nm, and the haze ratio was as high as 10.3%. The surface resistance was 12.0Ω / □, indicating high conductivity. The c-axis tilt angle of the hexagonal crystal of the zinc oxide-based transparent conductive film (II) was 5 ° with respect to the direction perpendicular to the translucent substrate surface. Furthermore, the transmittance | permeability of the obtained transparent conductive film laminated body was 0%, and the fall was not seen at all before and after heat processing in hydrogen atmosphere. Therefore, it was confirmed that a transparent conductive film laminate having excellent hydrogen reduction resistance and a high haze ratio and a low resistance value can be obtained at high speed.

FIG. 4 shows a surface SEM photograph of the transparent conductive thin film, and FIG. 5 shows a cross-sectional SEM photograph of the transparent conductive thin film. From the surface SEM photograph shown in FIG. 4, it can be seen that a rough surface with large crystal grains is obtained. Moreover, it can be seen from the cross-sectional SEM photograph shown in FIG. 5 that the zinc oxide-based transparent conductive film (II) on the indium oxide-based transparent conductive film (I) has small crystal grains and is densely formed.

[Examples 2 to 5: GAZO / GAZO / ITO]
Regarding the indium oxide-based transparent conductive film (I), the zinc oxide-based transparent conductive film (II), and the zinc 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 laminate and the zinc oxide-based transparent conductive film (II) was carried out using the same items and methods as in Example 1.

Table 3 shows the characteristic evaluation results of the transparent conductive film laminates of Examples 2 to 5. The film thicknesses of the transparent conductive film laminate were 950 nm (Example 2), 2150 nm (Example 3), 1100 nm (Example 4), and 2300 nm (Example 5), respectively. The surface roughness Ra values measured with an atomic force microscope were 35.5 nm (Example 2), 47.1 nm (Example 3), 36.0 nm (Example 4), and 48.5 nm (Example 5), respectively. And haze ratios of 8.5% (Example 2), 13.1% (Example 3), 9.1% (Example 4), and 14.2% (Example 5), respectively. It was high. The surface resistances were 12.6Ω / □ (Example 2), 5.3Ω / □ (Example 3), 11.0Ω / □ (Example 4), 5.1Ω / □ (Example 5), respectively. And showed high conductivity.

In addition, the c-axis tilt angles of the hexagonal crystals of the zinc oxide-based transparent conductive films (II) of Examples 2 to 5 are 8 ° (Example 2) and 8 respectively with respect to the direction perpendicular to the translucent substrate surface. ° (Example 3), 4 ° (Example 4), and 5 ° (Example 5). Further, the transmittances of the transparent conductive film laminates of Examples 2 to 5 were all 0%, and no decrease was observed before and after the heat treatment in a hydrogen atmosphere. Therefore, it was confirmed that a transparent conductive film laminate having excellent hydrogen reduction resistance and a high haze ratio and a low resistance value can be obtained at high speed.

[Examples 6 to 9: GAZO / GAZO / ITO]
A transparent conductive film laminate was prepared by replacing the tin-containing indium oxide-based transparent conductive film (I) used for the base film in Examples 2 to 5 with a titanium-containing indium oxide-based transparent conductive film (ITO). At this time, the underlying indium oxide-based transparent conductive film (I) was produced under the conditions shown in Table 1.

The composition of the target used for the preparation of the underlying indium oxide-based transparent conductive film (I) was 0.50 atomic% in terms of Ti / (In + Ti) when quantitatively analyzed by ICP emission spectroscopic analysis (manufactured by Seiko Instruments Inc., SPS4000). It was the following. Table 2 shows the measurement results. Moreover, the purity of the target was 99.999%, and the size was 6 inches (Φ) × 5 mm (thickness).

Film formation is performed by the apparatus used in Example 1, and the type of cathode is the same. A Corning 7059 glass substrate having a thickness of 1.1 mm was attached to the opposing surface of the 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 400 ° C., and then DC input power 300 W (target input power density = 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 kept still immediately above the center of the target, and an indium oxide-based transparent conductive film having a film thickness of 50 nm and 500 was formed on the substrate. Formed.

Next, zinc oxide-based transparent conductive films (II) and (III) are formed on the prepared base film (I) under the same conditions as in Examples 2 to 5 shown in Table 1, and a transparent conductive film stack is formed. Got the body.

Table 3 shows the characteristic evaluation results of the transparent conductive film laminates of Examples 6 to 9. The compositions of the transparent conductive films (I) to (III) of Examples 6 to 9 were almost the same as the composition of the target. The film thicknesses of the transparent conductive film laminates of Examples 6 to 9 were 950 nm (Example 6), 2150 nm (Example 7), 1100 nm (Example 8), and 2300 nm (Example 9), respectively. The surface roughness Ra values measured with an atomic force microscope were 36.3 nm (Example 6), 49.0 nm (Example 7), 38.1 nm (Example 8), and 49.6 nm (Example 9), respectively. And haze ratios of 9.0% (Example 6), 14.5% (Example 7), 9.9% (Example 8), and 15.0% (Example 9), respectively. It was high. The surface resistances were 12.1Ω / □ (Example 6), 5.3Ω / □ (Example 7), 9.8Ω / □ (Example 8), 5.0Ω / □ (Example 9), respectively. And showed high conductivity.

Further, the c-axis tilt angles of the hexagonal crystals of the zinc oxide-based transparent conductive films (II) of Examples 6 to 9 were 10 ° (Example 6) and 8 respectively with respect to the direction perpendicular to the translucent substrate surface. ° (Example 7), 2 ° (Example 8) and 4 ° (Example 9). Further, the transmittances of the transparent conductive film laminates of Examples 6 to 9 were all 0%, and no decrease was observed before and after the heat treatment in a hydrogen atmosphere. Therefore, it was confirmed that a transparent conductive film laminate having excellent hydrogen reduction resistance and a high haze ratio and a low resistance value can be obtained at high speed.

[Examples 10 to 13: AZO / AZO / ITO]
Using the indium oxide-based transparent conductive film (I) in Examples 2 to 5 as a base, the zinc oxide-based transparent conductive films (II) and (III) are formed on the base film under the conditions shown in Table 1, and the transparent conductive film laminate is formed. Produced. The characteristics evaluation of the produced transparent conductive film laminate and the zinc oxide-based transparent conductive film (II) was carried out using the same items and methods as in Example 1.

[Examples 10 to 13: Production of zinc oxide-based transparent conductive film (II)]
The composition of the target used for forming the zinc oxide-based transparent conductive film (II) was quantitatively analyzed by ICP emission spectroscopic analysis (manufactured by Seiko Instruments Inc., SPS4000). As a result, Al / (Zn + Al) was 0.30 atomic%. there were. Table 2 shows the measurement results. The purity of each target was 99.999%, and the size of the target was 6 inches (Φ) × 5 mm (thickness).

The film formation of the zinc oxide-based transparent conductive film (II) is performed by the apparatus used in Example 1, and the type of the cathode is the same. A Corning 7059 glass substrate having a thickness of 1.1 mm was attached to the opposing surface of the 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.

Next, 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, and the gas pressure is 0.5 Pa. It was. 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 for cleaning the target surface, sputtering film formation was carried out while the substrate was still directly above the center of the target, and each film thickness was changed as shown in Table 1 to oxidize. A zinc-based transparent conductive film (II) was formed to obtain a transparent conductive film laminate.

[Examples 10 to 13: Production of zinc oxide-based transparent conductive film (III)]
Finally, on the zinc oxide-based transparent conductive film, a zinc oxide-based transparent conductive film (III) having large surface irregularities is obtained using a zinc oxide-based sintered target (made by Sumitomo Metal Mining Co., Ltd.) containing aluminum as an additive element. ) Was formed. The composition of the target was 0.30 atomic% in Al / (Zn + Al) as in the case of the zinc oxide-based transparent conductive film (II) (Table 2). The purity of each target is 99.999%, and the size of the target is 6 inches (Φ) × 5 mm (thickness).

In forming the zinc oxide-based 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 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 for cleaning the target surface, sputtering film formation was carried out while the substrate was still directly above the target center, and each film thickness was changed as shown in Table 1 to oxidize the target surface. A zinc-based transparent conductive film (III) was formed to obtain a transparent conductive film laminate.

Table 3 shows the characteristic evaluation results of the transparent conductive film laminates of Examples 10 to 13. The film thicknesses of the transparent conductive film laminates of Examples 10 to 13 were 950 nm (Example 10), 2150 nm (Example 11), 1100 nm (Example 12), and 2300 nm (Example 13), respectively. The surface roughness Ra values measured with an atomic force microscope are 35.3 nm (Example 10), 46.3 nm (Example 11), 35.4 nm (Example 12), and 48.5 nm (Example 13), respectively. And haze ratios of 8.5% (Example 10), 12.8% (Example 11), 8.2% (Example 12), and 14.0% (Example 13), respectively. It was high. The surface resistances were 15.3Ω / □ (Example 10), 7.0Ω / □ (Example 11), 11.7Ω / □ (Example 12), 7.0Ω / □ (Example 13), respectively. And showed high conductivity.

Further, the c-axis tilt angles of the hexagonal crystals of the zinc oxide-based transparent conductive film (II) of Examples 10 to 13 were 9 ° (Example 10) with respect to the direction perpendicular to the translucent substrate surface, respectively. 7 ° (Example 11), 5 ° (Example 12), and 3 ° (Example 13). Further, the transmittances of the transparent conductive film laminates of Examples 10 to 13 were all 0%, and no decrease was observed before and after the heat treatment in a hydrogen atmosphere. Therefore, it was confirmed that a transparent conductive film laminate having excellent hydrogen reduction resistance and a high haze ratio and a low resistance value can be obtained at high speed.

[Examples 14 to 17: AZO / AZO / ITO]
As shown in Tables 1 and 2, as the indium oxide-based transparent conductive film (I), the indium oxide-based transparent conductive film (ITO) containing titanium in Examples 6 to 9 is used as a base, and a zinc oxide-based transparent conductive film is formed thereon. As transparent conductive films (II) and (III), a zinc oxide-based transparent conductive film (AZO) containing aluminum in Examples 10 to 13 was formed to produce a transparent conductive film laminate. The characteristics evaluation of the produced transparent conductive film laminated body was implemented by the same item and method as Example 1.

Table 3 shows the characteristic evaluation results of the transparent conductive film laminates of Examples 14 to 17. The film thicknesses of the transparent conductive film laminates of Examples 14 to 17 were 950 nm (Example 14), 2150 nm (Example 15), 1100 nm (Example 16), and 2300 nm (Example 17), respectively. The surface roughness Ra values measured with an atomic force microscope were 36.0 nm (Example 14), 47.0 nm (Example 15), 37.0 nm (Example 16), and 48.4 nm (Example 17), respectively. And haze ratios of 8.8% (Example 14), 12.7% (Example 15), 9.1% (Example 16), and 14.0% (Example 17), respectively. It was high. The surface resistances were 14.9Ω / □ (Example 14), 6.7Ω / □ (Example 15), 11.3Ω / □ (Example 16), and 6.9Ω / □ (Example 17), respectively. And showed high conductivity.

Further, the c-axis tilt angles of the hexagonal crystals of the zinc oxide based transparent conductive films (II) of Examples 14 to 17 were 10 ° with respect to the direction perpendicular to the translucent substrate surface (Example 14), They were 10 ° (Example 15), 5 ° (Example 16), and 3 ° (Example 17). Furthermore, the transmittances of the transparent conductive film laminates of Examples 14 to 17 were all 0%, and no decrease was observed before and after the heat treatment in a hydrogen atmosphere. Therefore, it was confirmed that a transparent conductive film laminate having excellent hydrogen reduction resistance and a high haze ratio and a low resistance value can be obtained at high speed.

[Examples 18 to 21: GZO / GZO / ITO]
As shown in Tables 1 and 2, as the indium oxide-based transparent conductive film (I), the zinc oxide-based transparent conductive film (II), (III) having the ITO film in Examples 2 to 5 as a base and containing gallium thereon. To form a transparent conductive film laminate. The characteristics evaluation of the produced transparent conductive film laminate and the zinc oxide-based transparent conductive film (II) was carried out using the same items and methods as in Example 1.

[Examples 18 to 21: Production of zinc oxide-based transparent conductive film (II)]
The composition of the target used for forming the zinc oxide-based transparent conductive film (II) was quantitatively analyzed by ICP emission spectroscopic analysis (manufactured by Seiko Instruments Inc., SPS4000). As a result, Ga / (Zn + Ga) was 0.87 atomic%. there were. Table 2 shows the measurement results. The purity of each target was 99.999%, and the size of the target was 6 inches (Φ) × 5 mm (thickness).

[Examples 18 to 21: Production of zinc oxide-based transparent conductive film (III)]
Finally, on the zinc oxide-based transparent conductive film (II), using a zinc oxide-based sintered target (made by Sumitomo Metal Mining Co., Ltd.) containing gallium as an additive element, a zinc oxide-based transparent with large surface irregularities A conductive film (III) was formed. The composition of the target was 0.87 atomic% in terms of Ga / (Zn + Ga), similar to the zinc oxide-based transparent conductive film (II). The purity of each target was 99.999%, and the size of the target was 6 inches (Φ) × 5 mm (thickness).

Table 3 shows the characteristic evaluation results of the transparent conductive film laminates of Examples 18 to 21. The film thicknesses of the transparent conductive film laminates of Examples 18 to 21 were 950 nm (Example 18), 2150 nm (Example 19), 1100 nm (Example 20), and 2300 nm (Example 21), respectively. The surface roughness Ra values measured with an atomic force microscope were 35.8 nm (Example 18), 47.1 nm (Example 19), 38.0 nm (Example 20), and 49.3 nm (Example 21), respectively. And haze ratios of 9.0% (Example 18), 12.9% (Example 19), 10.0% (Example 20), and 14.9% (Example 21), respectively. It was high. The surface resistances were 12.0Ω / □ (Example 18), 5.7Ω / □ (Example 19), 10.5Ω / □ (Example 20), 5.1Ω / □ (Example 21), respectively. And showed high conductivity.

The c-axis tilt angles of the hexagonal crystals of the zinc oxide-based transparent conductive films (II) of Examples 18 to 21 were 8 ° with respect to the direction perpendicular to the translucent substrate surface (Example 18), They were 9 ° (Example 19), 4 ° (Example 20), and 4 ° (Example 21). Furthermore, the transmittances of the transparent conductive film laminates of Examples 18 to 21 were all 0%, and no decrease was observed before and after the heat treatment in a hydrogen atmosphere. Therefore, it was confirmed that a transparent conductive film laminate having excellent hydrogen reduction resistance and a high haze ratio and a low resistance value can be obtained at high speed.

[Examples 22 to 25: GZO / GZO / ITO]
As shown in Tables 1 and 2, as the indium oxide-based transparent conductive film (I), an ITiO film containing titanium in Examples 6 to 9 was used as a base, and a zinc oxide-based transparent conductive film (II), ( As III), a GZO film containing gallium in Examples 18 to 21 was formed to produce a transparent conductive film laminate. The characteristics evaluation of the produced transparent conductive film laminate and the zinc oxide-based transparent conductive film (II) was carried out using the same items and methods as in Example 1.

Table 3 shows the characteristic evaluation results of the transparent conductive film laminates of Examples 22 to 25. The film thicknesses of the transparent conductive film laminates of Examples 22 to 25 were 950 nm (Example 22), 2150 nm (Example 23), 1100 nm (Example 24), and 2300 nm (Example 25), respectively. The surface roughness Ra values measured with an atomic force microscope were 36.9 nm (Example 22), 49.1 nm (Example 23), 38.5 nm (Example 24), and 51.0 nm (Example 25), respectively. And haze ratios of 9.5% (Example 22), 14.0% (Example 23), 10.0% (Example 24), and 16.2% (Example 25), respectively. It was high. The surface resistances were 11.4Ω / □ (Example 22), 5.2Ω / □ (Example 23), 10.2Ω / □ (Example 24), 4.9Ω / □ (Example 25), respectively. And showed high conductivity.

The c-axis tilt angles of the hexagonal crystals of the zinc oxide-based transparent conductive films (II) of Examples 22 to 25 were 9 ° (Example 22) with respect to the direction perpendicular to the translucent substrate surface, respectively. 7 ° (Example 23), 3 ° (Example 24), and 3 ° (Example 25). Further, the transmittances of the transparent conductive film laminates of Examples 22 to 25 were all 0%, and no decrease was observed before and after the heat treatment in a hydrogen atmosphere. Therefore, it was confirmed that a transparent conductive film laminate having excellent hydrogen reduction resistance and a high haze ratio and a low resistance value can be obtained at high speed.

[Comparative Example 1: GAZO / ITO]
As shown in Tables 1 and 2, a transparent conductive film laminate in which a zinc oxide-based transparent conductive film (III) is formed on an indium oxide-based transparent conductive film (I) without inserting a zinc oxide-based transparent conductive film (II) A transparent conductive film laminate was produced in the same manner as in Example 6 except that. The characteristics evaluation of the produced transparent conductive film laminated body was implemented by the same item and method as Example 1.

Table 3 shows the characteristic evaluation results of the obtained transparent conductive film laminate. The film thickness of the obtained transparent conductive film was 900 nm, the surface roughness Ra value measured with an atomic force microscope was as high as 36.0 nm, and the haze ratio was as high as 8.5%. However, the transmittance of the obtained transparent conductive film laminate was greatly reduced from 75.2% to 35.7% by performing heat treatment in a hydrogen atmosphere. This is because the zinc oxide-based transparent conductive film (III) on the surface is very rough and the surface of the indium oxide-based transparent conductive film (I), which is the underlying layer, is not completely protected. This is thought to be because the oxygen was dissociated by hydrogen. Accordingly, when the indium oxide-based transparent conductive film (I) is not protected by the zinc oxide-based transparent conductive film (II), only a transparent conductive film laminate having extremely low hydrogen reduction resistance can be obtained, which is not useful. confirmed.

[Comparative Example 2: GAZO / ITO]
As shown in Tables 1 and 2, a transparent conductive film laminate in which a zinc oxide-based transparent conductive film (III) is formed on an indium oxide-based transparent conductive film (I) without inserting a zinc oxide-based transparent conductive film (II) A transparent conductive film laminate was produced in the same manner as in Example 14 except that. The characteristics evaluation of the produced transparent conductive film laminated body was implemented by the same item and method as Example 1.

Table 3 shows the characteristic evaluation results of the obtained transparent conductive film laminate. The film thickness of the obtained transparent conductive film was 900 nm, the surface roughness Ra value measured with an atomic force microscope was as high as 35.0 nm, and the haze ratio was as high as 8.2%. However, the transmittance of the obtained transparent conductive film laminate was greatly reduced from 76.5% to 40.3% by performing heat treatment in a hydrogen atmosphere. This is presumably because, as in Comparative Example 1, the surface protection of the zinc oxide-based transparent conductive film (III) was insufficient, and oxygen in the indium oxide-based transparent conductive film was dissociated. Therefore, as in Comparative Example 1, when the indium oxide-based transparent conductive film (I) is not protected by the zinc oxide-based transparent conductive film (II), the hydrogen reduction resistance is very low and useful as an electrode of a solar cell. Not confirmed.

[Comparative Example 3: GAZO / ITO]
As shown in Tables 1 and 2, a transparent conductive film laminate in which a zinc oxide-based transparent conductive film (III) is formed on an indium oxide-based transparent conductive film (I) without inserting a zinc oxide-based transparent conductive film (II) A transparent conductive film laminate was produced in the same manner as in Example 22 except that. The characteristics evaluation of the produced transparent conductive film laminated body was implemented by the same item and method as Example 1.

Table 3 shows the characteristic evaluation results of the obtained transparent conductive film laminate. The film thickness of the obtained transparent conductive film was 900 nm, the surface roughness Ra value measured with an atomic force microscope was as high as 35.5 nm, and the haze ratio was as high as 8.8%. However, the transmittance of the obtained transparent conductive film laminate was greatly reduced from 71.3% to 32.1% by performing heat treatment in a hydrogen atmosphere. This is presumably because, as in Comparative Example 1, the surface protection of the zinc oxide-based transparent conductive film (III) was insufficient, and oxygen in the indium oxide-based transparent conductive film was dissociated. Therefore, as in Comparative Example 1, when the indium oxide-based transparent conductive film (I) is not protected by the zinc oxide-based transparent conductive film (II), the hydrogen reduction resistance is very low and useful as an electrode of a solar cell. Not confirmed.

[Comparative Examples 4, 5: GAZO / GAZO / ITO]
As shown in Tables 1 and 2, the zinc oxide sintered compact target composition containing aluminum used when forming the zinc oxide-based transparent conductive film (III) was changed to a composition deviating from the above-described formula (1). A transparent conductive film laminate was produced in the same manner as Example 14 except for the above. As a target used for the zinc oxide-based transparent conductive film (III), in Comparative Example 4, the composition is 0.40 atomic% for Al / (Zn + Al) and 1.00 atomic% for Ga / (Zn + Ga). Was used. In Comparative Example 5, Al / (Zn + Al) was 0.10 atomic% and Ga / (Zn + Ga) was 0.10 atomic%. The characteristics evaluation of the produced transparent conductive film laminate and the zinc oxide-based transparent conductive film (II) was carried out using the same items and methods as in Example 1.

As shown in Table 3, the characteristics of the obtained films were 0% in the transmittance change before and after the heat treatment in the hydrogen atmosphere in all the films of Comparative Examples 1 and 2, and no decrease was observed. . Further, the c-axis tilt angles of the hexagonal crystals of the zinc oxide-based transparent conductive films (II) of Comparative Examples 1 and 2 were 8 ° (Comparative Example 4) and 9 respectively with respect to the vertical direction of the translucent substrate surface. ° (Comparative Example 5).

Although the film of Comparative Example 4 had good conductivity, unlike Example 14, the film had a low Ra value and a low haze ratio. Therefore, it was found that the light confinement effect is insufficient, so that it cannot be used as a surface transparent electrode of a highly efficient solar cell. Moreover, although the film | membrane of the comparative example 5 has high Ra value and a haze rate, since surface resistance is too high, it is not useful as an electrode of a solar cell.

[Examples 26 to 28, Comparative Examples 6 and 7: GAZO / GAZO / ITO]
As shown in Tables 1 and 2, the gas pressures when forming the zinc oxide-based transparent conductive film (III) were 0.5 Pa (Comparative Example 6), 1.0 Pa (Example 26), 10.5 Pa ( Example 27) A transparent conductive film laminate was produced in the same manner as in Example 6 except that the pressure was changed to 15.0 Pa (Example 28) and 20.0 Pa (Comparative Example 7). The characteristics evaluation of the produced transparent conductive film laminate and the zinc oxide-based transparent conductive film (II) was carried out using the same items and methods as in Example 1.

As shown in Table 3, as the characteristics of the obtained film, the Ra value and the haze ratio increased as the gas pressure during film formation increased. The film of Comparative Example 6 has a low haze ratio and a weak light confinement effect, and cannot be used as a surface transparent electrode of a highly efficient solar cell. In Comparative Example 7, the film formation rate at the time of production was very slow and the productivity was poor, and the obtained film had a high haze ratio but a high surface resistance, and the adhesion of the film to the substrate was weak. It is easy to peel off and cannot be used as a device electrode.

On the other hand, the transparent conductive film laminates of Examples 26 to 28 not only have low surface resistance, but also have a sufficiently high haze ratio of 8% or more and high film adhesion. In addition, the c-axis tilt angle of the hexagonal crystal of the zinc oxide-based transparent conductive film (II) is 8 (Example 26) and 10 ° (Example 27) with respect to the direction perpendicular to the translucent substrate surface, respectively. 8 ° (Example 28). Further, in the transparent conductive film laminates of Examples 26 to 28, the transmittance change was 0% before and after the heat treatment in a hydrogen atmosphere in all the films, and no reduction was observed. It was confirmed that it can be used as a surface transparent electrode of a battery.

[Examples 29 and 30, Comparative Examples 8 and 9: GAZO / GAZO / ITO]
As shown in Tables 1 and 2, the substrate temperatures for forming the zinc oxide-based transparent conductive film (III) were 150 ° C. (Comparative Example 8), 200 ° C. (Example 29), and 550 ° C. (Example 30), respectively. ), 610 ° C. (Comparative Example 9), a transparent conductive film laminate was produced in the same manner as in Example 6. The characteristics evaluation of the produced transparent conductive film laminate and the zinc oxide-based transparent conductive film (II) was carried out using the same items and methods as in Example 1.

As shown in Table 3, the characteristics of the obtained film were such that the Ra value and the haze ratio increased as the substrate temperature increased, but the surface resistance also increased. The film of Comparative Example 8 is sufficiently low in surface resistance, but has a low haze ratio and a weak light confinement effect, and cannot be used as a surface transparent electrode of a highly efficient solar cell. In Comparative Example 9, the film formation rate at the time of production is very slow and the productivity is poor, and the obtained film also has a high haze ratio but a high surface resistance, so it cannot be used as a surface transparent electrode of a solar cell. .

On the other hand, the transparent conductive film laminates of Examples 29 and 30 not only have a low surface resistance but also a sufficiently high haze ratio of 8% or more. The c-axis tilt angles of the hexagonal crystal of the zinc oxide-based transparent conductive film (II) are 10 (Example 29) and 9 ° (Example 30) with respect to the direction perpendicular to the translucent substrate surface, respectively. Met. Furthermore, in the transparent conductive film laminates of Examples 29 and 30, the transmittance change was 0% before and after the heat treatment in a hydrogen atmosphere in all the films, and no reduction was observed. It is useful as a surface transparent electrode of a battery.

[Examples 31 to 33, Comparative Example 10: GAZO / GAZO / ITO]
As shown in Tables 1 and 2, the indium oxide-based transparent conductive film (I) in Examples 6 to 9 is used as a base, and a hydrogen (H ₂ ) gas is provided thereon in a molar ratio of H ₂ / (Ar + H ₂ ). , 0.01 (Example 31), 0.25 (Example 32), 0.43 (Example 33), and 0.50 atomic% (Comparative Example 10). Zinc oxide-based transparent conductive films (II) and (III) were formed in the same manner as in Examples 6 to 9 except that the film thickness of (III) was changed to 400 nm, to prepare a transparent conductive film laminate. The characteristics evaluation of the produced transparent conductive film laminate and the zinc oxide-based transparent conductive film (II) was carried out using the same items and methods as in Example 1.

As shown in Table 3, the characteristics of the obtained film tended to increase the Ra value and haze ratio as the H ₂ ratio of the film forming gas increased, but also increase the surface resistance. The film of Comparative Example 10 has a high Ra value and a high haze ratio, but cannot be used as an electrode of a solar cell because the surface resistance is too high. Further, the film of Comparative Example 10 also had problems such as extremely weak adhesion to the substrate.

On the other hand, the transparent conductive film laminates of Examples 31 to 33 not only have low surface resistance, but also have a sufficiently high haze ratio of 8% or more and high film adhesion. The c-axis tilt angles of the hexagonal crystal of the zinc oxide-based transparent conductive film (II) are 5 (Example 31) and 8 ° (Example 32), respectively, with respect to the direction perpendicular to the translucent substrate surface. 10 ° (Example 33). Furthermore, since the transparent conductive film laminates of Examples 31 to 33 did not show any decrease in the transmittance before and after the heat treatment in a hydrogen atmosphere, they are useful as surface transparent electrodes for high-efficiency solar cells.

[Example 34, Comparative Examples 11 and 12: GAZO / GAZO / ITO]
As shown in Tables 1 and 2, the gas pressures when forming the zinc oxide-based transparent conductive film (II) were 0.8 Pa (Example 34), 1.0 Pa (Comparative Example 11), and 2.0 Pa (2.0 Pa, respectively). A transparent conductive film laminate was produced in the same manner as in Example 6 except that Comparative Example 12) was used. The characteristics evaluation of the produced transparent conductive film laminate and the zinc oxide-based transparent conductive film (II) was carried out using the same items and methods as in Example 1.

As shown in Table 3, the characteristics of the obtained films were 0% in the transmittance before and after the heat treatment in the hydrogen atmosphere in all the films, and no decrease was observed. The Ra value increased as the gas pressure increased. In addition, the transmittance of the transparent conductive film laminate obtained in Example 34 was slightly decreased by 7.6% from 74.3% to 66.7% by performing the heat treatment in a hydrogen atmosphere. It was.

On the other hand, the transmittance of the transparent conductive film laminate obtained in Comparative Example 11 was reduced by 10% or more from 73.9% to 61.5%. Moreover, the transmittance | permeability of the transparent conductive film laminated body obtained by the comparative example 12 was seen from 73.0% to 48.5%, and the big fall was seen. Since the zinc oxide-based transparent conductive film (II) on the surface formed in Comparative Examples 11 and 12 is a rough film lacking in denseness, the surface of the indium oxide-based transparent conductive film (I) that is the underlying layer This is considered to be because oxygen in the indium oxide-based transparent conductive film was dissociated by hydrogen. Therefore, when obtaining a zinc oxide-based transparent conductive film (II) under the high sputtering gas pressure conditions as in Comparative Examples 11 and 12, only a transparent conductive film laminate having extremely low hydrogen reduction resistance can be obtained, which is not useful. Was confirmed.

[Examples 35 and 36: GAZO / GAZO / ITO]
As shown in Tables 1 and 2, when forming the indium oxide-based transparent conductive film (I) (Example 35) or forming the zinc oxide-based transparent conductive film (II) (Example 36), A transparent conductive film laminate was produced in the same manner as in Example 6 except that an amorphous film was formed at room temperature without heating the substrate and then heat treatment was performed at 350 ° C. Characteristic evaluation of the obtained film was performed in the same manner as in Example 1.

As shown in Table 3, the transparent conductive film laminate of Example 35 had an increased haze ratio compared to the film of Example 6 in which the substrate heating film formation was performed on the indium oxide-based transparent conductive film (I). . Furthermore, the transmittances of the transparent conductive film laminates of Examples 35 and 36 are both 0% before and after heat treatment in a hydrogen atmosphere, excellent in hydrogen reduction resistance, high haze rate and low resistance value. It was confirmed that the transparent conductive film laminated body having it can be obtained at high speed.

[Example 37: GAZO / GAZO / ITO]
As shown in Tables 1 and 2, a transparent conductive film laminate was produced in the same manner as in Example 6 except that the composition of the zinc oxide-based transparent conductive film (II) was changed. Characteristic evaluation of the obtained film was performed in the same manner as in Example 1.

As shown in Table 3, the resistance value of the transparent conductive film laminate of Example 37 was lower than that of the film of Example 6. Further, the transmittance of the transparent conductive film laminate of Example 37 was 0% before and after heat treatment in a hydrogen atmosphere, had excellent hydrogen reduction resistance, and had a high haze ratio and a low resistance value. It was confirmed that the film laminate can be obtained at high speed.

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. Zinc oxide-based transparent conductive film (III)

Claims

On the indium oxide-based transparent conductive film (I) formed on the translucent substrate, the c-axis tilt angle of the hexagonal crystal is 10 ° or less with respect to the direction perpendicular to the translucent substrate surface by sputtering. A first film forming step of forming a zinc oxide-based transparent conductive film (II) having a thickness of 10 nm to 200 nm;
A second film-forming step of forming a zinc oxide-based transparent conductive film (III) having a film thickness of 400 nm or more and 1600 nm or less on the zinc oxide-based transparent conductive film (II) by a sputtering method;
A method for producing a transparent conductive film laminate, comprising producing a transparent conductive film laminate having a surface roughness (Ra) of 35.0 nm or more and a surface resistance of 25 Ω / □ or less.
The sputtering target for forming the zinc oxide-based transparent conductive film (II) contains zinc oxide as a main component and includes one or more additive metal elements selected from aluminum or gallium. The manufacturing method of the transparent conductive film laminated body of description.
The sputtering target for forming the zinc oxide-based transparent conductive film (II) and the zinc oxide-based transparent conductive film (III) is composed of zinc oxide as a main component and one or more additive metal elements selected from aluminum or gallium 2. The method for producing a transparent conductive film laminate according to claim 1, wherein the content is in a range represented by the following formula (1).
-[Al] + 0.30 ≦ [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). Gallium content.)
In the first film forming step, the sputtering gas pressure is set to 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 1 to 3, wherein in the second film formation step, a sputtering gas pressure is set to 1.0 Pa or more and 15.0 Pa or less.
In the first film formation step and the second film formation step, a mixing ratio of a mixed gas of argon and hydrogen is set to H 2 / (Ar + H 2 ) ≦ 0.43 as a sputtering gas species. The method for producing a transparent conductive film laminate according to any one of claims 1 to 4.
In the first film forming step, the DC input power density to the sputtering target is 1.66 W / cm 2 or more under the condition that the substrate temperature is 100 ° C. or less when the sputtering gas pressure is 0.1 Pa or more and less than 1.0 Pa. 4. The zinc oxide-based transparent conductive film (II) is crystallized by heat treatment at 200 ° C. or more and 600 ° C. or less after being formed as an amorphous film. The manufacturing method of the transparent conductive film laminated body of description.
In the first film-forming step, the DC input power density to the sputtering target is 1.66 W / cm under the condition that the substrate temperature is 200 ° C. or more and 600 ° C. or less when the sputtering gas pressure is 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 1 to 3, wherein the zinc oxide-based transparent conductive film (II) is formed into two or more.
In the second film forming step, the DC input power density to the sputtering target is 1.66 W / cm under the conditions of sputtering gas pressure of 1.0 Pa to 15.0 Pa and substrate temperature of 200 ° C. to 600 ° C. The method for producing a transparent conductive film laminate according to claim 6, wherein the film is formed at a high speed as 2 or more.
After the indium oxide-based transparent conductive film (I) is formed as an amorphous film under the conditions of 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, the temperature is 200 ° C. or more and 600 ° C. or less. The method for producing a transparent conductive film laminate according to claim 1, wherein the transparent conductive film laminate is crystallized on the translucent substrate by heat treatment.
The indium oxide-based transparent conductive film (I) is formed as a crystal film 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 manufacturing method of the transparent conductive film laminated body of Claim 1 characterized by these.
An indium oxide-based transparent conductive film (I) formed on a light-transmitting substrate;
The c-axis tilt angle of the hexagonal crystal formed on the indium oxide-based transparent conductive film (I) is 10 ° or less with respect to the direction perpendicular to the translucent substrate surface, and the film thickness is 10 nm or more and 200 nm or less. A zinc oxide-based transparent conductive film (II);
A zinc oxide-based transparent conductive film (III) having a thickness of 400 nm or more and 1600 nm or less formed on the zinc oxide-based transparent conductive film (II),
A transparent conductive film laminate having a surface roughness (Ra) of 35.0 nm or more and a surface resistance of 25 Ω / □ or less.
The transparent conductive film laminate according to claim 11, wherein 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. .
The zinc oxide-based transparent conductive film (II) and the zinc oxide-based transparent conductive film (III) contain zinc oxide as a main component and include one or more additive metal elements selected from aluminum or gallium, and the content thereof is It is in the range shown by following formula (1), The transparent conductive film laminated body of Claim 11 characterized by the above-mentioned.
-[Al] + 0.30 ≦ [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). Gallium content.)
The transparent conductive film laminate according to any one of claims 11 to 13, wherein a decrease in transmittance due to heat treatment in a hydrogen atmosphere at 500 ° C is 10% or less.
The transparent conductive film laminate according to any one of claims 11 to 13, wherein a haze ratio is 8% 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 11 to 13.
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. The transparent conductive film laminate according to any one of 11 to 13.
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 11 to 13.
In the method for producing 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 this order on a light-transmitting substrate.
On the indium oxide-based transparent conductive film (I) formed on the translucent substrate, the c-axis tilt angle of the hexagonal crystal is 10 ° or less with respect to the direction perpendicular to the translucent substrate surface by sputtering. A first film forming step of forming a zinc oxide-based transparent conductive film (II) having a thickness of 10 nm to 200 nm,
A second film-forming step of forming a zinc oxide-based transparent conductive film (III) having a film thickness of 400 nm or more and 1600 nm or less on the zinc oxide-based transparent conductive film (II) by a sputtering method;
A method for producing a thin-film solar cell, comprising forming a transparent conductive film laminate having a surface roughness (Ra) of 35.0 nm or more and a surface resistance of 25 Ω / □ or less on the translucent substrate.
In a 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 transparent conductive film laminate is
An indium oxide-based transparent conductive film (I) formed on the translucent substrate;
The c-axis tilt angle of the hexagonal crystal formed on the indium oxide-based transparent conductive film (I) is 10 ° or less with respect to the direction perpendicular to the translucent substrate surface, and the film thickness is 10 nm or more and 200 nm or less. A zinc oxide-based transparent conductive film (II);
A zinc oxide-based transparent conductive film (III) having a thickness of 400 nm or more and 1600 nm or less formed on the zinc oxide-based transparent conductive film (II),
A thin film solar cell having a surface roughness (Ra) of 35.0 nm or more and a surface resistance of 25 Ω / □ or less.