JPWO2012157524A1 - Substrate with transparent conductive film and dye-sensitized solar cell - Google Patents

Abstract

By improving the heat resistance and oxidation resistance of a conductive layer, a substrate with a transparent conductive film having high conductivity and transparency even after a heat treatment step is provided. The transparent conductive film 15 of the substrate 10 with the transparent conductive film in which the transparent conductive film 15 is formed on the transparent substrate 11 includes the base layer 12, the conductive layer 13, and the oxidation-resistant protective layer 14 that are sequentially stacked from the substrate 11 side. doing. The oxidation-resistant protective layer 14 is made of a conductive material containing tin oxide, the conductive layer 13 is made of a metal oxide, and the base layer 12 has an oxide generation energy higher than that of the material constituting the conductive layer 13. It is made of an oxide that is small and lacks oxygen more than its chemical equivalent.

Description

  The present invention relates to a substrate with a transparent conductive film and a dye-sensitized solar cell, and more particularly to a substrate with a transparent conductive film and a dye-sensitized solar cell with high conductivity and transparency.

  Conventionally, as an electrode of a display device, a sensor or a solar cell, a transparent conductive film formed of an oxide obtained by adding other elements to indium (In), zinc (Zn), tin (Sn), etc. on a transparent substrate is provided. (Hereinafter referred to as “a substrate with a transparent conductive film”) is used. Among transparent conductive films, a transparent conductive film made of an oxide of indium (In) -tin (Sn) (ITO, Indium Tin Oxide) has a relatively low resistance, a high light transmittance in the visible region, and Since it is easy to etch, it is used in many electronic display devices.

  Among the various devices described above, particularly in the solar cell field, in order to improve energy conversion efficiency, the electrical resistance value of the transparent conductive film is small (that is, excellent conductivity) and the optical transmittance is high (that is, transparency). Excellent).

And since it passes through the process of heating (baking) a board | substrate with a transparent conductive film at the time of manufacture of a solar cell, as a factor which influences the electroconductivity and transparency of a transparent conductive film, the heat resistance and oxidation resistance of a transparent conductive film There is a need for technology to improve the performance.
As an example of the heating temperature, in the manufacturing process of the Si-based solar cell, after forming a transparent conductive film on the substrate, it goes through an element manufacturing process for forming a compound semiconductor layer having high photoelectric conversion efficiency. The film forming temperature needs to be about 400 ° C., and in the manufacturing process of the dye-sensitized solar cell, it needs to be about 500 ° C., which is higher than that of the Si solar cell.

  However, when the transparent conductive film made of ITO or the like is exposed to high temperature, oxygen in the atmosphere is bonded to a part of the oxygen deficient structure (vacancies), and the oxygen deficient structure acting as a carrier decreases. As a result of the carrier concentration being reduced, the conductivity of the transparent conductive film is reduced.

  Patent Document 1 considers the reduction of the oxygen deficient structure caused by heating the transparent conductive film, and on the surface side of the transparent conductive film (that is, the side exposed to the atmosphere) when forming the transparent conductive film. A technique for forming oxygen-deficient indium oxide on a substrate is disclosed. Thus, in the transparent conductive film, the surface side is mainly oxidized when heat-treated by making the surface side oxygen-deficient compared to the substrate side, thereby providing a transparent conductive film having high conductivity. can do.

  Patent Document 2 discloses a technique for forming a transparent conductive film by forming a tin oxide-based film having an oxygen (gas) barrier property (particularly a tin oxide film containing antimony: ATO film) on an ITO film. ing. Thus, by forming a film having a high oxygen barrier property on the ITO film, a transparent conductive film having high oxidation resistance and chemical resistance can be obtained.

Japanese Patent Laid-Open No. 5-81943 Japanese Patent Laid-Open No. 2005-19205

In the technique disclosed in Patent Document 1, the vicinity of the surface of the transparent conductive film is preferentially oxidized during the heat treatment (firing) step by previously setting the surface vicinity of the transparent conductive film to an oxygen-deficient composition. Therefore, the oxygen deficient structure near the substrate does not decrease. On the other hand, in the vicinity of the surface, the number of oxygen-deficient structures increases and enters an optimum range, and deterioration of conductivity and transparency can be suppressed.
However, the technique disclosed in Patent Document 1 has an oxygen-deficient composition in the vicinity of the transparent conductive film surface so that an oxygen-deficient structure is a desirable number after heat treatment. It is difficult to control the amount, and it is difficult to ensure high conductivity and transparency in a transparent conductive film with a certain quality.

  In the technique disclosed in Patent Document 2, a tin oxide-based film (mainly an ATO film) having an oxygen barrier property is formed on an ITO film, thereby forming a transparent conductive film having high oxidation resistance, that is, a conductive film. A high transparent conductive film can be formed. However, the conductivity and transparency of the ATO film are not high as compared with the ITO film, and as a result, the conductivity and transparency of the entire transparent conductive film are lowered. Moreover, in order to ensure oxygen barrier property, the thickness of the ATO film must be increased, and the transparency of the transparent conductive film is further impaired.

The present invention has been made in view of the above problems, and its purpose is to improve the heat resistance and oxidation resistance of the conductive layer, thereby providing high conductivity and transparency even after the heat treatment step. The object is to provide a substrate with a transparent conductive film.
Moreover, the other object of this invention is to provide the dye-sensitized solar cell provided with high energy conversion efficiency by improving the electroconductivity and transparency of a transparent conductive film.

  According to the substrate with a transparent conductive film of the present invention, the subject is a substrate with a transparent conductive film in which a transparent conductive film is formed on a transparent substrate, and the transparent conductive film is laminated in order from the substrate side. A base layer, a conductive layer, and an oxidation-resistant protective layer, the oxidation-resistant protective layer is made of a conductive material containing tin oxide, the conductive layer is made of a metal oxide, and the base layer is This is solved by the fact that the oxide generation energy is lower than that of the material constituting the conductive layer and the oxide is insufficient in oxygen than the chemical equivalent.

Thus, the substrate with a transparent conductive film of the present invention includes not only an oxidation-resistant protective layer whose main material is tin oxide but also a base layer on the conductive layer. And, since the base layer has a lower oxide generation energy than the material constituting the conductive layer and is composed of an oxygen-deficient oxide than the chemical equivalent, even if the substrate with the transparent conductive film is heated, Since oxygen is absorbed, oxidation of the conductive layer is prevented and heat resistance is improved. That is, since the constituent material of the underlayer has a lower oxide generation energy than the constituent material of the conductive layer and has an oxygen-deficient structure, the underlayer is preferentially oxidized, thereby heat treatment (firing). ) Is prevented from being oxidized, and heat resistance can be improved.
As a result of the oxidation of the base layer in preference to the conductive layer, the substrate with a conductive film of the present invention retains oxygen vacancies in the conductive layer because the conductive layer is hardly oxidized when heat-treated. Therefore, even when the substrate with a transparent conductive film is heated, oxygen vacancies in the conductive layer are maintained, so that high conductivity and transparency can be provided without impairing conductivity and transparency.

At this time, it is preferable that the underlayer is made of a material represented by a chemical formula SiO _x (where X is a stoichiometric ratio and 1.2 <X <1.8).
Since SiO _x is a material having a relatively small oxide generation energy, the oxide generation energy is smaller than that of a general metal oxide constituting the conductive layer. Therefore, when the material constituting the underlayer is the above substance, the underlayer is more easily oxidized when the substrate with the transparent conductive film is heat-treated.
In addition, since silicon oxide has higher optical transmittance than other materials (that is, high transparency), the transparency of the substrate with a transparent conductive film is not lowered.
Furthermore, by setting the value of X indicating the stoichiometric ratio within the above range, the underlayer becomes more transparent and easily oxidized. Therefore, by forming the base layer made of the above material, it is possible to give a high antioxidation effect to the conductive layer and to obtain a transparent conductive film having high transparency.

At this time, it is preferable that the conductive layer is made of indium oxide (ITO) containing tin, and the oxidation-resistant protective layer is made of tin oxide to which at least one of niobium, tantalum, and antimony is added.
Thus, a conductive layer is provided with high electroconductivity and transparency by comprising a conductive layer with ITO. Therefore, a substrate with a transparent conductive film provided with a conductive layer made of ITO can have high conductivity and transparency. However, since ITO has the property of being easily oxidized due to heat treatment and lowering its conductivity, it is not only provided with a base layer, but also by forming an oxidation-resistant protective layer with the above-mentioned material having gas barrier properties, the ITO film is oxidized. It becomes difficult to be done. As a result, the conductivity and transparency of the conductive layer (ITO film) are kept high, and the substrate with a transparent conductive film having good conductivity and transparency as the entire transparent conductive film can be obtained.

Furthermore, at this time, it is preferable that the oxidation-resistant protective layer is made of tin oxide (ATO) to which antimony is added.
As described above, when the oxidation-resistant protective layer is made of ATO having a high gas barrier property, the conductive layer provided below the oxidation-resistant protective layer is further hardly oxidized. In addition, ATO has particularly high conductivity among materials having high gas barrier properties, and the conductivity is improved by heat treatment at 400 ° C. to 500 ° C., so that the conductivity of the transparent conductive film can be improved.
In addition, since antimony has some toxicity, it is possible to select the oxidation-resistant protective layer as tin oxide to which at least one of niobium and tantalum is added in consideration of the environment. When the oxidation-resistant protective layer is composed of tin oxide to which at least one of niobium and tantalum is added, it is slightly inferior to ATO in terms of conductivity and transparency, but is almost equivalent to the case of using ATO in terms of oxidation resistance. The effect of

At this time, it is preferable that a titanium oxide (TiO ₂ ) film is further provided on the surface of the oxidation-resistant protective layer on the side opposite to the conductive layer.
Thus, the heat resistance of a transparent conductive film can further be improved by providing a titanium oxide film on the surface of the oxidation-resistant protective layer on the side opposite to the conductive layer.

In addition, it is preferable that the thickness of the oxidation-resistant protective layer is in a range of 200 to 1000 mm and the thickness of the base layer is in a range of 100 to 500 mm.
In this way, by setting the thickness of the underlayer made of SiO _x to 100 to 500 mm, the underlayer can provide an effect of suppressing oxidation of the conductive layer, and thus it is not necessary to increase the thickness of the oxidation-resistant protective layer. And the oxidation of a conductive layer can be suppressed by the thickness of the oxidation protective layer which consists of an ATO film | membrane being 200-1000 mm. Thus, since it is not necessary to thicken the oxidation-resistant protective layer, the oxidation resistance of the transparent conductive film is ensured without lowering the transparency due to the formation of the thick oxidation-resistant protective layer. Conductivity and transparency can be set to practically appropriate values.

  Furthermore, according to the dye-sensitized solar cell of the present invention, the problem is that the first conductive substrate, the second conductive substrate disposed opposite to the first conductive substrate, A porous semiconductor layer formed on the surface of the first conductive substrate on the second conductive substrate side and adsorbing a dye, and between the porous semiconductor layer and the second conductive substrate The electrolyte is formed, and the first conductive substrate is solved by being the substrate with a transparent conductive film according to any one of claims 1 to 6.

  Thus, not only the oxidation-resistant protective layer but also a base layer, and a substrate with a transparent conductive film having a configuration in which the base layer is preferentially oxidized compared to the conductive layer is an electrode of a dye-sensitized solar cell. By using as, in the electrode of a dye-sensitized solar cell, electroconductivity and transparency can be improved. As a result, since the electrode has a small electric resistance value and a high optical transmittance, the energy conversion efficiency of the dye-sensitized solar cell can be improved.

The substrate with a transparent conductive film of the present invention includes a base layer that is more easily oxidized than the conductive layer in the transparent conductive film, whereby oxidation of the conductive layer is prevented and heat resistance is improved. And, by improving the oxidation resistance and heat resistance of the conductive layer, it prevents the decrease in conductivity and transparency due to the decrease of oxygen deficiency in the conductive layer, and high conductivity and transparency even after the heat treatment step The board | substrate with a transparent conductive film provided with can be provided.
Moreover, since the electroconductivity and transparency of the transparent conductive film with which an electrode is equipped improve, a dye-sensitized solar cell with high energy conversion efficiency can be provided.

It is a schematic sectional drawing of the board | substrate with a transparent conductive film which concerns on one Embodiment of this invention. It is a graph which shows the relationship between the oxygen amount at the time of film-forming of the base layer of the board | substrate with a transparent conductive film which concerns on one Embodiment of this invention, and the resistance value change rate of a transparent conductive film. It is a graph which shows the relationship between the oxygen amount at the time of film-forming of the base layer of the board | substrate with a transparent conductive film which concerns on one Embodiment of this invention, and the optical transmittance of a transparent conductive film. Is a graph showing the relationship between the O / Si ratio of SiO _x constituting the deposition time oxygen content and the underlayer of the transparent conductive film-attached substrate of the underlying layer according to an embodiment of the present invention. It is a graph which shows the relationship between the film thickness of the base layer of the board | substrate with a transparent conductive film which concerns on one Embodiment of this invention, and the resistance value of a transparent conductive film. It is a graph which shows the relationship between the film thickness of the base layer of the board | substrate with a transparent conductive film which concerns on one Embodiment of this invention, and the resistance value change rate of a transparent conductive film. It is a graph which shows the relationship between the film thickness of the base layer of the board | substrate with a transparent conductive film which concerns on one Embodiment of this invention, and the optical transmittance of a transparent conductive film. It is a schematic sectional drawing of the board | substrate with a transparent conductive film which concerns on other embodiment of this invention. It is a schematic sectional drawing of the dye-sensitized solar cell which concerns on one Embodiment of this invention. It is a graph which shows the relationship (JV characteristic) of the current density and output voltage of the dye-sensitized solar cell which concerns on one Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the members, materials, configurations, and the like described below do not limit the present invention, and various modifications can be made in accordance with the spirit of the present invention. Hereinafter, the optical transmittance is described only as “transmittance”.
1 to 7 relate to a substrate with a transparent conductive film according to an embodiment of the present invention, FIG. 1 is a schematic sectional view of the substrate with a transparent conductive film, and FIG. FIG. 3 is a graph showing the relationship between the resistance value change rate of the transparent conductive film, FIG. 3 is a graph showing the relationship between the amount of oxygen during film formation of the underlying layer and the optical transmittance of the transparent conductive film, and FIG. FIG. 5 is a graph showing the relationship between the amount of oxygen during film formation and the O / Si ratio of SiO _x constituting the underlayer, FIG. 5 is a graph showing the relationship between the film thickness of the underlayer and the resistance value of the transparent conductive film, and FIG. Is a graph showing the relationship between the thickness of the underlying layer and the resistance change rate of the transparent conductive film, and FIG. 7 is a graph showing the relationship between the thickness of the underlying layer and the optical transmittance of the transparent conductive film.
FIG. 8 relates to a substrate with a transparent conductive film according to another embodiment of the present invention, and is a schematic sectional view of the substrate with a transparent conductive film.
9 and 10 relate to a dye-sensitized solar cell according to an embodiment of the present invention, FIG. 9 is a schematic cross-sectional view, and FIG. 10 is a relationship between current density and output voltage (J− It is a graph which shows a V characteristic.

<< Configuration of Substrate with Conductive Film 10 >>
Based on FIGS. 1-7, the board | substrate 10 with a transparent conductive film of this embodiment is demonstrated.
As shown in FIG. 1, the substrate 10 with a transparent conductive film according to the present embodiment is formed by forming a transparent conductive film 15 on a transparent substrate 11, and the transparent conductive film 15 is arranged in order from the substrate 11 side. It has a ground layer 12, a conductive layer 13, and an oxidation-resistant protective layer 14. That is, a transparent conductive film 15 formed by sequentially laminating a base layer 12, a conductive layer 13, and an oxidation-resistant protective layer 14 on a substrate 11 is provided.

(Substrate 11)
The substrate 11 is a plate-like member, and as the material of the substrate 11, an appropriate material that can form the transparent conductive film 15 on the surface and has transparency to the extent that light is received by the transparent conductive film 15. Selected from. As such a material, for example, a material capable of transmitting a predetermined amount of light such as a glass substrate, a quartz substrate, and an optical crystal substrate is used. Particularly preferred is a non-alkali glass not containing an alkali element such as Na or a quartz substrate having high heat resistance.
In addition, a thin film such as SiO ₂ or TiO ₂ is sputtered on the surface to increase transparency, prevent diffusion of alkali elements such as Na, or improve heat resistance. It may be a substrate formed by a method. Further, these substrates 11 may be plate-shaped or film-shaped.

The transmittance of the substrate 11 is not particularly limited as long as it can transmit light to the transparent conductive film 15, but normally the average transmittance in the wavelength range of 350 to 800 nm is in the range of 10% to 99%. In particular, the range of 60% to 99% is preferable, and the range of 80% to 99% is optimal.
The thickness of the substrate 11 is not particularly limited, but is usually in the range of 100 μm to 5 mm, and particularly preferably in the range of 500 μm to 2 mm.

(Transparent conductive film 15)
The transparent conductive film 15 is a film that is light transmissive and conductive. The transparent conductive film 15 constitutes the negative electrode of the dye-sensitized solar cell 100 described later. As described below, when manufacturing the dye-sensitized solar cell 100 shown in FIG. 9, in the step of forming a porous titania layer on the transparent conductive film 15, a titanium oxide paste is applied on the transparent conductive film 15. Then, baking is performed at 400 to 500 ° C. as a desirable temperature. Therefore, the transparent conductive film 15 is preferably made of a material whose transmittance is not reduced by this baking process and whose resistance is not increased. That is, the transparent conductive film 15 is required to have high conductivity and transparency after being baked at a high temperature. Hereinafter, the configuration of the transparent conductive film 15 of the present embodiment will be described in detail.
The transparent conductive film 15 of the present embodiment is formed by sequentially laminating a base layer 12, a conductive layer 13, and an oxidation-resistant protective layer 14 on a substrate 11.

  The transparent conductive film 15 as a whole has an average transmittance in the range of wavelengths of 350 nm to 800 nm in the range of 10% to 99%, particularly preferably in the range of 60% to 99%, more preferably. Is optimally in the range of 80% to 99%.

(Transparent conductive film 15: conductive layer 13)
The conductive layer 13 is made of a metal oxide having high conductivity and high transparency.
The transmittance of the conductive layer 13 is such that the average transmittance in the wavelength range of 350 nm to 800 nm is in the range of 10% to 99%, particularly in the range of 60% to 99%, and more preferably 80%. It is optimal that it is in the range of 99% or less.

As the metal oxide constituting the conductive layer 13, indium oxide (In ₂ O ₃ ), zinc oxide (ZnO), tin oxide (SnO ₂ ), or a material obtained by adding impurities to these materials can be used.
Examples of the material include, for example, indium oxide containing at least one of tin, germanium, zinc, and gallium, zinc oxide containing at least one of aluminum, gallium, boron, and magnesium, antimony, and fluorine. Added tin oxide can be used.

The content of tin, germanium, zinc, and gallium added to indium oxide is the atomic ratio of these materials to indium (Sn / In, Ge / In, Zn / In, Ga / In) is preferably 0.5 to 20.0%.
Here, the atomic ratio is the ratio of the oxides of each material, and Sn / In should be expressed strictly as Sn oxide / In oxide, but it is based on commonly used abbreviations. Sn / In. The same applies to other materials.
When added in such a ratio, the conductivity and transparency of the film constituting the conductive layer 13 can be maintained well. In addition, when a plurality of types of these materials are added, the total amount of materials to be added is preferably 20.0% or less with respect to indium.

  In addition, the content of aluminum, gallium, boron, and magnesium added to zinc oxide is the atomic ratio of these materials to zinc (Al / Zn, Ga / Zn, B / Zn, Mg / Zn) may be 0.5 to 20.0%. When added in such a ratio, the conductivity and transparency of these materials can be maintained well. Moreover, when adding multiple types of these materials, it is good to make the addition amount of the whole material to add into 20.0% or less with respect to zinc.

Among these materials, ITO with tin added to indium oxide, ATO with tin oxide added with antimony, FTO with fluorine doped tin oxide, AZO with aluminum added to zinc oxide, GZO with zinc oxide added with gallium, etc. Is suitable as a material constituting the conductive layer 13 because of its excellent conductivity and transparency.
In particular, ITO has a high conductivity and transmittance because it appropriately has oxygen vacancies serving as electron channels, and is suitable as a material constituting the conductive layer 13.

  The thickness of the conductive layer 13 is preferably in the range of 200 to 10,000 mm. In such a range, the resistance value of the transparent conductive film 15 can be reduced and the transmittance can be kept high.

(Transparent conductive film 15: Underlayer 12)
A base layer 12 is formed between the substrate 11 and the conductive layer 13. The underlayer 12 is provided together with the oxidation resistant protective layer 14 to prevent oxidation of the conductive layer 13. Therefore, for example, even when the substrate 10 with a transparent conductive film is subjected to a baking process at about 400 to 500 ° C., the underlying layer 12 is preferentially oxidized over the conductive layer 13. The structure can be retained. As a result, the conductive layer 13 can maintain high conductivity and transparency.

  The transmittance of the underlayer 12 is such that the average transmittance in the wavelength range of 350 nm to 800 nm is in the range of 10% to 99%, particularly in the range of 60% to 99%, and more preferably 80%. It is optimal that it is in the range of 99% or less.

  The underlayer 12 is formed of an oxide that has an oxide generation energy lower than that of the material constituting the conductive layer 13 and lacks oxygen more than a chemical equivalent. That is, the material constituting the underlayer 12 is an oxide whose generation energy line shown in the Ellingham diagram is lower than that of the material constituting the conductive layer 13 and has an oxygen deficient structure. Here, the oxide formation energy refers to standard Gibbs energy when an oxide is formed, and is also referred to as oxide formation free energy.

Examples of such a material include silicon oxide (SiO _x ), aluminum oxide (Al _x O _y ), and the like. Since such a material basically has a lower generation energy line in the Ellingham diagram than the metal oxide constituting the conductive layer 13 and has a lower oxide generation energy, for example, a substrate with a transparent conductive film When 10 undergoes a baking process at about 400 to 500 ° C., the underlying layer 12 is oxidized in preference to the conductive layer 13.

The underlayer 12 may be formed of a material represented by the chemical formula SiO _x . Silicon is a material having a low oxide generation energy and is likely to be an oxide. Therefore, by forming the underlayer 12 from SiO _x having an oxygen deficient structure, the underlayer 12 can absorb oxygen and suppress the oxidation of the conductive layer 13.

  X represents a stoichiometric ratio, and is preferably in the range of 1.2 <X <1.8. When the value of X is 1.2 or less, the composition approaches that of SiO, so that the underlayer 12 appears to be colored yellow, and the transparency is lowered. Further, those having X of 1.8 or more are inappropriate because it is difficult to form a film by sputtering or vapor deposition, and therefore it is difficult to form the underlayer 12 with a certain quality.

  The thickness of the underlayer 12 is preferably in the range of 100 to 500 mm. If the thickness is less than 100%, the transmittance is high, but the underlayer 12 cannot sufficiently absorb oxygen, and the transparent conductive film 15 cannot be provided with sufficient oxidation resistance. On the other hand, when the thickness is larger than 500 mm, the underlying layer 12 can sufficiently absorb oxygen and provide the transparent conductive film 15 with sufficient oxidation resistance, but the transmittance decreases.

  Therefore, when the thickness of the underlayer 12 is in the above range, the effect of suppressing the oxidation of the conductive layer 13 can be sufficiently obtained by being provided in combination with the oxidation-resistant protective layer 14.

(Transparent conductive film 15: oxidation-resistant protective layer 14)
On the other hand, an oxidation-resistant protective layer 14 is laminated on the surface of the conductive layer 13 opposite to the base layer 12. The oxidation-resistant protective layer 14 is a film having light permeability and conductivity, and further having an oxygen (gas) barrier property.
The transmittance of the oxidation-resistant protective layer 14 is such that the average transmittance in the wavelength range of 350 nm to 800 nm is in the range of 10% to 99%, particularly preferably in the range of 60% to 99%, and more preferably. It is optimal to be in the range of 80% or more and 99% or less.

  The oxidation-resistant protective layer 14 is preferably composed of tin oxide containing tin oxide as a main component and at least one of niobium, tantalum, and antimony added. Further, the oxidation-resistant protective layer 14 may be composed of tin oxide that does not contain the additive. The content of niobium, tantalum, and antimony added to tin oxide, when adding one of these, the atomic ratio of these materials to tin (Nb / Sn, Ta / Sn, Sb / Sn) Is preferably 0.5 to 20.0%. When added in such a ratio, the conductivity and transparency of the film constituting the oxidation-resistant protective layer 14 can be maintained well. Moreover, when adding multiple types of these materials, it is good to make the addition amount of the whole material to add into 20.0% or less with respect to tin.

Among the above materials, tin oxide (ATO) to which antimony is added is particularly suitable as a material constituting the oxidation-resistant protective layer 14 because it has a good gas barrier property and high conductivity and transparency.
However, since antimony has some toxicity, its use may not be preferred due to environmental considerations. Although tin oxide (described as SnO _x ) to which niobium or tantalum or both are added is slightly inferior in resistance value and transmittance as compared with ATO, as described later, in the oxidation-resistant protective layer 14 of the present embodiment. When used, the oxidation resistance shows almost the same performance as ATO, and this point can also be said to be an effect derived from the structure described in the claims.

The thickness of the oxidation-resistant protective layer 14 is preferably in the range of 200 to 1000 mm. If it is smaller than 200 mm, the transmittance is high but sufficient oxidation resistance cannot be obtained. If it is larger than 1000 mm, the oxidation resistance is improved, but the transmittance is lowered.
Therefore, when the thickness of the oxidation-resistant protective layer 14 is in the above range, the effect of suppressing the oxidation of the conductive layer 13 can be sufficiently obtained by being provided in combination with the base layer 12. In addition, since the oxidation of the conductive layer 13 is also suppressed by the base layer 12, it is not necessary to increase the thickness of the oxidation-resistant protective layer 14. Therefore, since the transparency of the oxidation-resistant protective layer 14 can be ensured, as a result, the transparency as the transparent conductive film 15 can be improved.

(Titanium oxide film 16)
A titanium oxide film 16 may further be provided on the surface of the oxidation-resistant protective layer 14 on the side opposite to the conductive layer 13 as shown in FIG. The titanium oxide film 16 is a titanium oxide thin film that is formed by a technique such as sputtering, vacuum deposition, or ion plating, and has a denser structure than porous titanium oxide.
By laminating the titanium oxide film 16 on the surface of the oxidation-resistant protective layer 14 opposite to the conductive layer 13, the heat resistance of the transparent conductive film 15 can be further improved by a synergistic effect with the base layer 12. That is, by providing the base layer 12, the oxidation-resistant protective layer 14, and the titanium oxide film 16, the conductive layer 13 is prevented from being oxidized even when the substrate 10 with the transparent conductive film undergoes a baking step. The transparent conductive film 15 can maintain high conductivity and transparency.

  Further, in a general dye-sensitized battery, a porous titanium oxide layer is formed on a transparent conductive film of a substrate with a transparent conductive film, but in this embodiment, it has a denser structure than porous titanium oxide. By providing the titanium oxide film 16 on the transparent conductive film 15, dark current flowing from the transparent conductive film 15 side to the titanium oxide film 16 side can be suppressed. Therefore, according to the substrate 10 with a transparent conductive film provided with the titanium oxide film 16 of the present embodiment, the electrical characteristics of the dye-sensitized solar cell 100 can be improved.

  In the dye-sensitized solar cell 100, each of the films constituting the transparent conductive film 15 (the base layer 12, the conductive layer 13, and the oxidation-resistant protective layer 14) has a substantially rectangular opening so as to form a substantially rectangular negative electrode pattern. It is formed using a plurality of formed masks. In addition, as a method for forming the transparent conductive film 15 on the surface of the substrate 11, a known film forming technique such as a sputtering method, a vacuum deposition method, an ion plating method, or the like can be used.

<< Configuration of Dye-Sensitized Solar Cell 100 >>
Next, the structure of the dye-sensitized solar cell 100 provided with the board | substrate 10 with a transparent conductive film is demonstrated. In the following, a single cell will be described as an example, but it is needless to say that a plurality of cells may be connected in series or in parallel.
As shown in FIG. 9, the dye-sensitized solar cell 100 includes a substrate 10 with a transparent conductive film as a first conductive substrate 110, and further a second electrode at a position facing the first conductive substrate 110. A conductive substrate 120 is provided. For the sake of explanation, FIG. 9 shows an enlarged thickness of each layer of the substrate 10 with a transparent conductive film.
And between the 1st conductive substrate 110 and the 2nd conductive substrate 120, the porous semiconductor layer 17a formed in the 1st conductive substrate 110 side, the porous semiconductor layer 17a, and the 2nd And an electrolyte 17b formed between the conductive substrate 120 and the conductive substrate 120. In addition, the code | symbol 17c of FIG. 9 is a sealing material, 17d is a catalyst layer.

(Dye-sensitized solar cell 100: first conductive substrate 110 and second conductive substrate 120)
The substrate 10 with a transparent conductive film is provided as a first conductive substrate 110, and is disposed with the surface on which the transparent conductive film 15 is formed facing the second conductive substrate 120 side. A conductive wire 30 as a lead wire is connected to the conductive layer 13 constituting the first conductive substrate 110.

The second conductive substrate 120 is a plate-like member having the electrode layer 22 formed on the surface. The material of the substrate 21 constituting the second conductive substrate 120 can be selected from the same transparent material as that of the substrate 11.
However, unlike the substrate 11, the substrate 21 is not necessarily on the side that captures light, and thus does not necessarily need to be formed of a transparent material, and may be formed of a material with poor light transmission. Examples of such materials include various ceramics such as oxide ceramics and nitride ceramics.
The thickness of the substrate 21 is not particularly limited, but is usually in the range of 100 μm to 5 mm, and particularly preferably in the range of 500 μm to 2 mm. The substrate 21 may be plate-shaped or film-shaped.

  The electrode layer 22 formed on the substrate 21 is an electrode formed in a film shape with a conductive material. For the electrode layer 22, a conductive metal or carbon, the same material as that described for the conductive layer 13 of the transparent conductive film 15, or the like is used. A transparent conductive film is used when the electrode layer 22 is used in a portion that needs to transmit light. On the other hand, when it is not necessary to transmit light in the electrode layer 22, a metal film such as Al, Pt, Pd, Au, or a carbon film is used as the electrode layer 22.

  FIG. 9 shows the configuration of the dye-sensitized solar cell 100 including the catalyst layer 17d. In order to increase the photoelectric conversion efficiency, the electrode layer 22 has a catalytic action and is excellent in resistance to the electrolyte 17b. Pt, Pd, Au or the like is preferably used. A conductive wire 40 as a lead wire is connected to the electrode layer 22 for connection to an external load. Thus, since the electrode layer 22 has both a catalytic function and a function as a collecting electrode, it is not necessary to separately provide a collecting electrode, and the configuration of the battery can be simplified.

  The electrode layer 22 is formed using a mask or the like in which an opening having an appropriate size is formed. In addition, as a method for forming the electrode layer 22 on the surface of the substrate 21, a known film forming technique such as a sputtering method, a vacuum evaporation method, an ion plating method, or the like can be used.

(Dye-sensitized solar cell 100: porous semiconductor layer 17a)
The porous semiconductor layer 17a is obtained by adsorbing a dye (dye sensitizer) to metal oxide semiconductor fine particles. The metal oxide semiconductor fine particles used for the porous semiconductor layer 17a are not particularly limited as long as they are made of a metal oxide having semiconductor characteristics. Examples of the metal oxide used for the porous semiconductor layer 17a include TiO ₂ , ZnO, SnO ₂ , ZrO ₂ , Al ₂ O ₃ , Ta ₂ O, Nb ₂ O _{5 and the} like. Among these, it is preferable to use TiO ₂ because it is particularly excellent in semiconductor characteristics.

The porous semiconductor layer 17a made of TiO ₂ is prepared by mixing titanium oxide powder with a binder to form a paste, applying this fired paste onto the titanium oxide film 16 formed on the transparent conductive film 15, and firing it. It is formed. The firing temperature may be 100 ° C. or higher, but it is preferably fired at 400 ° C. or higher in order to improve the sinterability between the titanium oxide particles and increase the photoelectric conversion efficiency.

  As the binder of the baked paste, an organic solvent, an acidic solution, or the like can be used. The crystal structure of titanium oxide constituting the porous semiconductor layer 17a is preferably an anatase type. Moreover, in order to have a favorable solar cell characteristic, it is preferable that the porous semiconductor layer 17a has a pore structure including many small holes.

  A dye is adsorbed on a part of the porous semiconductor layer 17a. As the dye, a dye that can efficiently absorb sunlight, that is, a dye having an absorption band from the near ultraviolet region to the near infrared region centering on the visible region is used. The dye is dissolved in a solvent such as alcohol, and the first conductive substrate 110 formed up to the porous semiconductor layer 17a is immersed in the dye, thereby being adsorbed on the pores of the porous semiconductor layer 17a.

Examples of such a dye include an organic dye and a metal complex dye. Examples of organic dyes include acridine, azo, indigo, quinone, coumarin, merocyanine, and phenylxanthene dyes. Examples of the metal complex dye include a ruthenium bipyridine dye and a ruthenium terpyridine dye which are ruthenium complexes. Among these, a Ru complex [RuL ₂ (NSC) ₂ ] (where L = 4,4′-dicboxy-2) that can efficiently move electrons to the porous semiconductor layer 17a when excited by light. , 2′-bypyridine) or the like.

(Dye-sensitized solar cell 100: electrolyte 17b)
An electrolyte 17b is provided on the surface side of the porous semiconductor layer 17a.
As the material of the electrolyte 17b, a material that can supply electrons to the dye contained in the porous semiconductor layer 17a and receive electrons by the electrode layer 22 is used. The electrolyte 17b may be solid or liquid, and is not particularly limited as long as it is a material used as an electrolyte for a general dye-sensitized solar cell. Specific examples of such materials include an electrolytic solution in which lithium iodide and metallic iodine are dissolved in polyethylene glycol, and an electrolytic solution in which acetonitrile and ethylene carbonate are mixed.

(Dye-sensitized solar cell 100: sealing material 17c)
Between the first conductive substrate 110 and the second conductive substrate 120, a sealing material 17c for partitioning the cells of each dye-sensitized solar cell 100 is formed. The sealing material 17c is a member for partitioning the entire outer peripheral portion of the plurality of cells, and is also a member that separates the cells. In the space partitioned by the sealing material 17c, the porous semiconductor layer 17a and the electrolyte 17b in which the dye is adsorbed are held.
As the material of the sealing material 17c, resin, glass, or the like can be used. Specific examples of the resin include an epoxy resin and a urethane resin.

(Dye-sensitized solar cell 100: catalyst layer 17d)
A catalyst layer 17d is provided on the upper layer of the electrode layer 22 on the second conductive substrate 120 side. The catalyst layer 17d is provided to promote the oxidation-reduction reaction, and Pt, Pd, Au, C or the like is used as a material constituting the catalyst layer 17d.

  Note that the substrate 10 with a transparent conductive film can be used as the second conductive substrate 120. In this case, the catalyst layer 17d is formed on the second conductive substrate 120. As the catalyst layer 17d, for example, platinum chloride is used when forming a Pt film. However, due to the corrosive nature of platinum chloride, it is difficult to form a Pt film directly on the transparent conductive film 15, and the quality is also high. descend. Therefore, by forming the titanium oxide film 16 on the transparent conductive film 15 of the transparent conductive film moon substrate 10, the transparent conductive film 15 can be protected from the corrosiveness of platinum chloride, and the Pt film and the transparent conductive film 15 are protected. The film quality can be kept good.

<< Example >>
Hereinafter, the board | substrate 10 with a transparent conductive film and the dye-sensitized solar cell 100 of this invention are demonstrated based on an Example.

[Example 1: Configuration of transparent conductive film 15]
As shown in FIG. 1, the substrate 10 with a transparent conductive film of Example 1 has only a transparent conductive film 15 on a substrate 11.

(Example 1-i: Effect of the underlayer 12)
In the substrate 10 with a transparent conductive film, Examples 1-1 to 1-3 provided with the foundation layer 12 were compared with Comparative Examples 1 to 5 not provided with the foundation layer 12, and the effect of the foundation layer 12 was examined. In Examples 1-3-1 and Example 1-3-2, the amount of oxygen during the formation of the undercoat layer 12 (SiO _x film) is different, the oxygen flow rate of Example 1-3-1 Is 30 cc, and the oxygen flow rate of Example 1-3-2 is 35 cc.

The board | substrate 10 with a transparent conductive film of Examples 1-1 to 1-3 was created as follows.
First, an SiO _x film as an underlayer 12 was formed on a glass substrate as the substrate 11 at a film formation temperature of 300 ° C. by a sputtering method. At this time, unless otherwise specified, the amount of oxygen was adjusted so that X was about 1.62. Specifically, the flow rate was 45 cc, and the flow rate ratio between oxygen gas and inert gas was adjusted to be O ₂ / Ar + O ₂ = 0.07.
Next, an ITO (Sn / In = 10/90) film as the conductive layer 13 was formed on the SiO _x film by a sputtering method at a film formation temperature of 300 ° C.
Furthermore, an ATO (Sb / Sn = 2.5 / 97.5) film as an oxidation-resistant protective layer 14 was formed on the ITO film at a film formation temperature of 300 ° C. by a sputtering method. The thickness of each film is as shown in Table 1.
And the board | substrate 10 with a transparent conductive film produced as mentioned above was put into the electric furnace, and was heat-processed at 500 degreeC or 600 degreeC for 1 hour in air | atmosphere. Area resistance (hereinafter referred to as “resistance value”), average transmittance (hereinafter referred to as “transmittance”), resistance value and transmission of the transparent conductive film before and after the heat treatment Table 1 shows the rate of change before and after the heat treatment.

  The sheet resistance was measured using a Loresta GP manufactured by Mitsubishi Chemical Analytech. The transmittance was measured with a Hitachi Electronic Recording Spectrometer (U-4100), and the reference was measured as air. Unless otherwise specified, measurements according to the following examples were also measured with the same apparatus.

Comparative Examples 1 to 5 form a transparent conductive film on the glass substrate 11 that does not include either the base layer 12, the oxidation-resistant protective layer 14, or both, as compared to Examples 1-1 to 1-3. It is a thing. The oxidation-resistant protective layer 14 is based on an ATO (Sb / Sn = 2.5 / 97.5) film, and only one example (Comparative Example 2-2) includes tin oxide containing tantalum and niobium (SnO _x , Ta / Nb). /Sn=2.0/0.5/97.5) membrane was used.

From the results in Table 1, the comparison is made with reference to Examples 1-1 and 1-2 and Comparative Examples 2-1 and 2-2. In Examples 1-1 and 1-2, the transparent conductive film 15 includes the SiO _x film as the base layer 12. In Comparative Example 2-1, only the ITO film as the conductive layer 13 and the ATO film as the oxidation-resistant protective layer 14 are used. In Comparative Example 2-2, the ITO film as the conductive layer 13 and the SnO as the oxidation-resistant protective layer 14 are used. Only the _x film is formed with the same thickness as in Examples 1-1 and 1-2.
In Examples 1-1 and 1-2, compared to Comparative Examples 2-1 and 2-2, the thickness of the SiO _x film is increased with respect to the resistance value, although there is no particular difference regarding the transmittance. As a result, the resistance value after firing became extremely small, and the rate of change before and after firing was close to 1, indicating that the resistance value hardly changed before and after firing. Similar results were obtained when compared with reference to Examples 1-3-1, 1-3-2 and Comparative Example 4.

In addition, when Comparative Examples 1, 2-1, 2-2, and 3 are compared, it can be seen that the resistance value decreases as the thickness of the ATO film or SnO _x film as the oxidation-resistant protective layer 14 increases. However, in the case where only the ATO film is provided as in Comparative Example 2-1, for example, the resistance value of the transparent conductive film 15 is compared with the case where the underlayer 12 is provided as in Example 1-2. It is shown that the rate of change is large. The same applies to Comparative Example 2-2 including only the SnO _x film. In Comparative Example 5 that includes only the SiO _x film as the underlayer 12 and does not include the oxidation-resistant protective layer 14, the resistance value and the rate of change are large, so that the oxidation resistance of the transparent conductive film 15 is increased. In order to improve, it was shown that it is necessary to provide both the underlayer 12 and the oxidation-resistant protective layer 14.

  As described above, the transparent conductive film 15 including the base layer 12 and the oxidation-resistant protective layer 14 has a low resistance value and a substantially constant transmittance even after the baking treatment. In general, the conductive layer 13 is oxidized and the conductivity is lowered by performing the baking treatment. In this example, since the base layer 12 and the oxidation-resistant protective layer 14 are provided, the oxidation of the conductive layer 13 is suppressed. As a result, even after the firing step, the resistance value of the transparent conductive film 15 does not decrease. This is because the base layer 12 is composed of an oxide having an oxide generation energy smaller than that of the conductive layer 13 and an oxygen-deficient oxide than the chemical equivalent. In other words, the base layer 12 is preferentially oxidized over the conductive layer 13 during the firing step.

Furthermore, according to Examples 1-1 to 1-3, it was found that the thicker the SiO _x film and the ATO film, the smaller the resistance value of the transparent conductive film 15 and the closer the rate of change before and after firing. However, the transmittance (transparency) of the transparent conductive film 15 decreased as the thickness of each film increased.

(Example 1-ii: thickness and composition of oxidation-resistant protective layer 14)
In Examples 1-4 to 1-7, the transparent conductive film 15 was created by changing the thickness of the oxidation-resistant protective layer 14 while keeping the thickness of the base layer 12 and the conductive layer 13 constant. Those employing an ATO film as the oxidation-resistant protective layer 14 are represented by -1 at the end of each example number, and those employing an SnO _x film are represented by -2. In addition, the transparent conductive film 15 was created on the conditions similar to Examples 1-1 to 1-3 except the thickness of each layer. Table 2 shows the resistance value, transmittance, and change rate before and after firing for each example.

As shown in Table 2, the thickness of the ATO film or SnO _x film as the oxidation-resistant protective layer 14 was changed between 200 and 500 mm, and the resistance value and transmittance of each transparent conductive film 15 were measured. Also in this case, it was shown that the resistance value of the transparent conductive film 15 after the baking treatment becomes smaller as the film thickness becomes larger. Further, the thicker the film, the smaller the change rate of the resistance value before and after firing, and the result was that the oxidation resistance of the transparent conductive film 15 was improved. Furthermore, when the thickness of the ATO film or SnO _x film exceeds a certain value (see Examples 1-6-1 and 2, 1-7-1 and 2), the resistance value after firing is higher than that before firing. And the rate of change was smaller than 1.

  On the other hand, as the film thickness of the oxidation-resistant protective layer 14 increased, the rate of change before and after firing was substantially constant, but the transmittance decreased. Accordingly, since the resistance value and the transmittance are in a trade-off relationship, the thickness of the oxidation-resistant protective layer 14 is set to an appropriate size in consideration of the relationship between the structure and thickness of the underlayer 12 described below. I found it necessary to do.

It was also found that sufficient oxidation resistance can be imparted to the transparent conductive film 15 even when SnO _x is used as the material for the oxidation-resistant protective layer 14 as well as ATO. As can be seen from the comparison of Example Nos. -1 and -2, when the SnO _x film is formed as the oxidation-resistant protective layer 14, the transmittance is slightly lower than when the ATO film is formed, but SnO _x It was shown that sufficient oxidation resistance can be obtained even with an _x film.

(Example 1-iii: Composition of base layer 12)
Next, an appropriate value of X in the SiO _x film as the underlayer 12 was examined. In Examples 1-8 to 1-15, the transparent conductive film 15 was formed by changing the amount of oxygen at the time of forming the SiO _x film. In Examples 1-8 and 1-9, and Examples 1-10 to 1-15, the thicknesses of the conductive layer 13 and the oxidation-resistant protective layer 14 and the firing conditions were changed. Table 3 shows the resistance value, transmittance, and change rate before and after firing for each of these examples.

Furthermore, figure and the amount of oxygen during the formation of the SiO _x film, the relationship between the resistance value change rate of the transparent conductive film 15 in FIG. 2, and the amount of oxygen during the formation of the SiO _x film, the relationship between the transmittance 3 shows.
From FIG. 2, the smaller the amount of oxygen during film formation, that is, the smaller the oxygen content in the SiO _x film and the smaller the value of X, the smaller the change rate of the resistance value of the transparent conductive film 15. Although the oxidation resistance of 15 was shown to be high, the effect was saturated when the amount of oxygen was around 30 cc. Further, it was shown that even when the amount of oxygen was increased from about 60 cc, the rate of change in resistance value did not change greatly and did not increase.

On the other hand, as shown in FIG. 3, the smaller the amount of oxygen at the time of film formation, that is, the smaller the oxygen content in the SiO _x film and the smaller the value of X, the lower the transmittance of the transparent conductive film 15 and the transparency. It has been shown to decline. In order to use the substrate 10 with a transparent conductive film for various devices such as the dye-sensitized solar cell 100, the transparent conductive film 15 desirably has a transmittance of about 80% after firing. It is appropriate that the amount of oxygen during the formation of the SiO _x film is more than 30 cc. If this amount of oxygen is less than, for composition ratios SiO _x film is close to SiO, become SiO _x film is visually colored yellow, transparency decreases.
Therefore, in view of the resistance value and the transmittance, it was shown that the amount of oxygen at the time of forming the SiO _x film should be more than 30 cc.

Next, a film forming time of the oxygen amount of SiO _x film, the relationship between the composition ratio of the SiO _x film, shown in FIG. Than 4, if increasing the amount of oxygen during the formation of the SiO _x film, the amount of oxygen in the SiO _x film is also X also increases with increasing, if reducing the amount of oxygen during the formation of the SiO _x film, It is shown that the amount of oxygen in the SiO _x film also decreases and X decreases. However, when the amount of oxygen exceeds 50-60 cc, the amount of oxygen in the SiOx film is saturated and the value of X is about 1.8. Therefore, also in FIGS. 2 and 3, the resistance value change rate and the transmittance are expected to be substantially constant when the oxygen amount is about 60 cc or more.

Then, based on FIG. 4, the lower limit value and the upper limit value of X of the SiO _x film will be considered.
2 and 3 indicate that the amount of oxygen during film formation should be greater than 30 cc. Therefore, considering FIG. 4 together, the value of X in the SiO _x film is X = 1.2. It is preferable to be larger than.
On the other hand, as shown in FIG. 4, when the amount of oxygen formed in the SiO _x film is about 60 cc or more, the amount of oxygen in the SiO _x film is saturated, so that it is difficult to form a SiO _x film with X = 1.8 or more. To be judged. Therefore, the value of X is preferably smaller than 1.8.

From the above, it is preferable that the value of X is 1.2 <X <1.8 depending on the relationship between the amount of oxygen at the time of forming the SiO _x film and the resistance value and transmittance of the transparent conductive film 15.
The value of X is a value obtained by XPS analysis (X-ray Photoelectron Spectroscopy). JPS-9000MC manufactured by JEOL Ltd. was used for XPS measurement, MgKα as the X-ray source, X-ray output 10 KV × 10 mA, irradiation time and number of times 100 ms × 4, measurement step 0.1 eV, measurement area φ = 6.0 mm I went there.

(Example 1-iv: thickness of the underlayer 12)
Next, an appropriate film thickness of the SiO _x film as the underlayer 12 was examined. In Examples 1-16 to 1-18, the transparent conductive film 15 was formed by changing the film thickness of the SiO _x film, respectively. In addition, as an example without the SiO _x film, the result of Comparative Example 3 was compared. Table 4 shows the resistance value before and after firing, the rate of change in resistance value, the transmittance, the reflectance, and the absorptance for each example and comparative example. In Examples 1-16 to 1-18 and Comparative Example 3, in order to compare the effect of the thickness of the SiO _x film, the ATO film as the oxidation-resistant protective layer 14 is sufficiently thick, and the gas barrier property is ensured. Conditions.

Further, in FIG. 5 and the film thickness of the SiO _x film, the relationship between the resistance value of the transparent conductive film 15, the film thickness of the SiO _x film, in FIG. 6 the relationship between the resistance value change rate, film SiO _x film The relationship between the thickness and the transmittance is shown in FIG. The dotted lines in FIGS. 5 to 7 indicate that the thickness of the SiO _x film is 100 mm.

5 that after the deposition, the resistance value before firing of the transparent conductive film 15 is substantially constant, although not dependent on the thickness of the SiO _x film, the resistance value after firing, the film thickness of the SiO _x film is large As it became, it was greatly reduced. When the film thickness of the SiO _x film was 100 mm, the resistance value decreased rapidly. Therefore, the film thickness of the SiO _x film is preferably 100 mm or more. From FIG. 6, the rate of change in the resistance value of the transparent conductive film 15 was close to 1 when the film thickness of the SiO _x film was 100 mm or more. From this point, the film thickness of the SiO _x film was 100 mm. The above is preferable. Further, from FIG. 7, even if the thickness of the SiO _x film was made thinner than 100 mm, the transmittance was not improved, so that the thickness of the SiO _x film was made smaller than 100 mm for the purpose of improving the transmittance. However, it became clear that it was not effective.

From the above, it has been shown that the thickness of the SiO _x film is preferably 100 mm or more in consideration of both the resistance value and the transmittance. Further, as shown in Examples 1-3-1 and 1-3-2 of Table 1 in the section of Example 1-i, the film thickness of the ATO film was changed to Examples 1-16 to 1-18. When the thickness of the SiO _x film was 500 mm, a sufficient transmittance of about 80% was obtained. In addition, the transparent conductive film 15 of Examples 1-3-1 and 1-3-2 has a resistance value as low as about 5Ω / Sq, and sufficient conductivity was obtained. Both sex can be satisfied.

From the above, it was shown that the thickness of the SiO _x film is preferably in the range of 100 to 500 mm.
On the other hand, when the SiO _x film as the underlayer 12 has a thickness range of 100 to 500 mm, the ATO film as the oxidation-resistant protective layer 14 from Tables 1 to 4 shown in the sections of Examples 1-i to 1-iv. The film thickness is preferably 200 to 1000 mm.
Sufficient oxidation resistance can be obtained by setting the thickness ranges of the SiO _x film and the ATO film to 100 to 500 mm, respectively. If the film thickness of the SiO _x film is larger than 500 mm and the film thickness of the ATO film is larger than 1000 mm, the oxidation resistance of the transparent conductive film 15 is improved, but the transmittance is lowered. Therefore, by setting the film thickness of the SiO _x film as the underlayer 12 to 100 to 500 mm and the film thickness of the ATO film to 200 to 1000 mm, both the conductivity and transparency of the transparent conductive film 15 are good. A practical resistance value and transmittance can be provided.

[Example 2: Effect of titanium oxide film 16]
The substrate 10 with a transparent conductive film of Example 2 is provided with a transparent conductive film 15 and a titanium oxide film 16 on a substrate 11 as shown in FIG.
In the substrate 10 with a transparent conductive film of Examples 2-1 to 2-4, a SiO _x film, an ITO film, and an ATO film were formed on the glass substrate 11 in the same manner as in Examples 1-1 to 1-3. Thereafter, a titanium oxide film 16 was further formed on the ATO film at a film formation temperature of 300 ° C. by sputtering. The thickness of the titanium oxide film 16 was 80 mm in all of Examples 2-1 to 2-4.
Then, the substrate 10 with a transparent conductive film was put in an electric furnace and heat-treated at 500 ° C. for 1 hour in the atmosphere.
In Comparative Example 2-2, a titanium oxide film 16 was formed on Comparative Example 2-1 in Table 1 shown in Example 1-i above. In Comparative Example 2-2, the thickness of the ITO film and the ATO film is the same as that of Comparative Example 2-1.
Table 5 shows resistance values, transmittances, and change rates before and after firing for Examples 2-1 to 2-4 and Comparative Example 2-2.

In Example 2-4 and Comparative Example 2-2, the ITO film thickness and the ATO film thickness are formed to be equal to each other. When Example 2-4 and Comparative Example 2-2 are compared, Example 2-4 having the SiO _x film as the underlayer 12 is after firing as compared with Comparative Example 2-2 having no SiO _x film. The resistance value of the film was extremely small, and the rate of change of the resistance value before and after firing was close to 1. Thus, it was shown that the oxidation resistance was further improved by providing the titanium oxide film 16. Moreover, although the transmittance | permeability fell a little in Example 2-4 compared with Comparative Example 2-2, the practical transmittance | permeability was hold | maintained.
As a general tendency, if the thickness of the titanium oxide film 16 is too large, the transmittance of the transparent conductive film 15 is lowered. Since oxidation resistance and transmittance are in a trade-off relationship with each other, it is necessary to form the titanium oxide film 16 with such a thickness that both values are good.

  Further, from Examples 2-1 to 2-4, the rate of change in resistance value before and after firing is a value smaller than 1, and the resistance value after firing is smaller than that before firing. It has been found that the provision of the titanium film 16 can further improve the conductivity of the transparent conductive film 15.

[Example 3: Battery characteristics of dye-sensitized solar cell 100]
In Example 3, the dye-sensitized solar cell 100 in which the substrate 10 with the transparent conductive film of FIG. 8 described in Example 2 and including the titanium oxide film 16 was used as the first conductive substrate 110. Will be described.
In Examples 3-1 to 3-4, the dye-sensitized battery 100 was formed by the following steps.
A titanium oxide paste was further applied onto the titanium oxide film 16 (film thickness: 80 mm) of the substrate 10 with a transparent conductive film, and then fired at 500 ° C. to form a porous semiconductor layer 17a (thickness: 50000 mm). Further, a dye solution in which the sensitizing dye is dissolved at a concentration of 0.3 mmol / l is prepared in an organic solvent having the ability to dissolve the sensitizing dye, and the substrate 10 provided with the porous semiconductor layer 17a is immersed for 3 hours. Thus, a monomolecular film of a sensitizing dye was chemically adsorbed on the surface of the porous semiconductor layer 17a. Furthermore, an electrolyte 17b containing imidazolium iodide and iodine as main components, platinum 1000 と し て as a catalyst layer 17d, and ITO as the second conductive substrate 120 were further laminated to form a dye-sensitized solar cell 100.

  In Comparative Example 2-3, a porous semiconductor layer 17a made of titanium oxide is formed on Comparative Example 2-2 in Table 5 shown in the section of Example 2 above. In Comparative Example 2-3, the thickness of the ITO film, the ATO film, the titanium oxide film 16, and the thickness of the porous semiconductor layer 17a are the same as those in Comparative Example 2-2.

FIG. 9 shows a dye-sensitized solar cell 100 having a structure in which a substrate 10 with a transparent conductive film is disposed as a first conductive substrate 110 on the upper side and light is transmitted from above. In Table 6, the battery performance of the dye-sensitized solar cell 100 and the transmittance when the porous semiconductor layer 17a made of titanium oxide is provided on the transparent conductive film 15 of the substrate 10 with the transparent conductive film, that is, The transmittances of the underlayer 12, the conductive layer 13, the oxidation-resistant protective layer 14, the titanium oxide film 16, and the porous semiconductor layer 17a are shown.
Note that “Pmax” in Table 6 is the maximum output point, and indicates the amount of power generation at the point of maximum output on the JV characteristic graph shown in FIG.
Further, the battery performance shown in Table 6 and the JV characteristics shown in FIG. 10 are measured at AM 1.5 defined by JIS, irradiance Xe lamp 100 mW / cm ² , and module temperature 25 ° C.
Table 6 also shows FF (Fill Factor). FF is defined by FF = (Vmax · Imax) / (Voc · Isc), where Vmax and Imax are the voltage value at the point where the power value is maximum in the current-voltage curve, and It is a current value, Voc is an open circuit voltage, and Isc is a short circuit current. And it shows that the internal loss of the dye-sensitized solar cell 100 is so small that FF is large, and its performance is excellent.

From Table 6, when Example 3-4 provided with the SiO _x film as the underlayer 12 is compared with Comparative Example 2-3 not provided with the underlayer 12, the transmittance as the substrate 10 with the transparent conductive film is slightly lowered. However, it is shown that the battery performance (particularly, Pmax, FF, conversion efficiency) of the dye-sensitized solar cell 100 is improved.

Also, from the JV characteristic graph of FIG. 10, Examples 3-1 to 3-4 including the SiO _x film as the underlayer 12 are more preferable than Comparative Example 2-3 including no underlayer 12. It has been shown that the battery characteristics are very good.

As described above, the transparent conductive film 15 of the substrate 10 with the transparent conductive film is provided with the base layer 12, the conductive layer 13, and the oxidation-resistant protective layer 14 from the substrate 11 side. It was found that the oxidation resistance of the film 15 was improved. As a result, it was found that even when the baking process was performed, the conductivity of the conductive layer 13 was not impaired and the transparency was ensured.
Furthermore, it was found that the oxidation resistance of the transparent conductive film 15 can be further improved by laminating the titanium oxide film 16. As described above, since the substrate 10 with a transparent conductive film of this example has good conductivity and transparency, the battery characteristics can be dramatically improved particularly when used as an electrode of the dye-sensitized solar cell 100. I understood.

DESCRIPTION OF SYMBOLS 10 Substrate with transparent conductive film 11, 21 Substrate 12 Underlayer 13 Conductive layer 14 Antioxidation protective layer 15 Transparent conductive film 16 Titanium oxide film 17a Porous semiconductor layer 17b Electrolyte 17c Sealing material 17d Catalyst layer 22 Electrode layer 30, 40 Dye-sensitized solar cell 110 First conductive substrate 120 Second conductive substrate

Examples of such a dye include an organic dye and a metal complex dye. Examples of organic dyes include acridine, azo, indigo, quinone, coumarin, merocyanine, and phenylxanthene dyes. Examples of the metal complex dye include a ruthenium bipyridine dye and a ruthenium terpyridine dye which are ruthenium complexes. Among these, a Ru complex [RuL ₂ (NSC) ₂ ] (where L = 4,4′-dicboxy-2) that can efficiently move electrons to the porous semiconductor layer 17a when excited by light. , 2′-b i pyridine) or the like.

Note that the substrate 10 with a transparent conductive film can be used as the second conductive substrate 120. In this case, the catalyst layer 17d is formed on the second conductive substrate 120. As the catalyst layer 17d, for example, platinum chloride is used when forming a Pt film. However, due to the corrosive nature of platinum chloride, it is difficult to form a Pt film directly on the transparent conductive film 15, and the quality is also high. descend. Therefore, by forming a titanium oxide film 16 on the transparent conductive film 15 of the transparent conductive film-attached substrate 10, it is possible to protect the transparent conductive film 15 from corrosion of chloroplatinic, Pt film and the transparent conductive film 15 The film quality can be kept good.

[Example 3: Battery characteristics of dye-sensitized solar cell 100]
In Example 3, the dye-sensitized solar cell 100 in which the substrate 10 with the transparent conductive film of FIG. 8 described in Example 2 and including the titanium oxide film 16 was used as the first conductive substrate 110. Will be described.
In Examples 3-1 to 3-4, the dye-sensitized solar cell 100 is formed by the following steps.
A titanium oxide paste was further applied onto the titanium oxide film 16 (film thickness: 80 mm) of the substrate 10 with a transparent conductive film, and then fired at 500 ° C. to form a porous semiconductor layer 17a (thickness: 50000 mm). Further, a dye solution in which the sensitizing dye is dissolved at a concentration of 0.3 mmol / l is prepared in an organic solvent having the ability to dissolve the sensitizing dye, and the substrate 10 provided with the porous semiconductor layer 17a is immersed for 3 hours. Thus, the second conductive substrate is formed by using, as a catalyst layer 17d, an electrolyte 17b mainly composed of imidazolium iodide and iodine in which a monomolecular film of a sensitizing dye is chemically adsorbed on the surface of the porous semiconductor layer 17a, and platinum 1000Å. The dye-sensitized solar cell 100 was obtained by further laminating ITO as 120.

Claims (8)

A substrate with a transparent conductive film in which a transparent conductive film is formed on a transparent substrate,
The transparent conductive film has an underlayer, a conductive layer, and an oxidation-resistant protective layer laminated in order from the substrate side,
The oxidation-resistant protective layer is made of a conductive material containing tin oxide,
The conductive layer is made of a metal oxide,
The substrate with a transparent conductive film, characterized in that the underlayer is made of an oxide having an oxide generation energy smaller than that of the material constituting the conductive layer and oxygen deficient in chemical equivalent. 2. The underlayer is made of a material represented by a chemical formula SiO _x (where X is a stoichiometric ratio, and 1.2 <X <1.8). The board | substrate with a transparent conductive film of description. The conductive layer is made of indium oxide (ITO) containing tin,
The substrate with a transparent conductive film according to claim 2, wherein the oxidation-resistant protective layer is made of tin oxide to which at least one of niobium, tantalum, and antimony is added.   4. The substrate with a transparent conductive film according to claim 3, wherein the oxidation-resistant protective layer is made of tin oxide (ATO) to which antimony is added.   4. The substrate with a transparent conductive film according to claim 3, wherein the oxidation-resistant protective layer is made of tin oxide to which at least one of niobium and tantalum is added. The substrate with a transparent conductive film according to claim 4, further comprising a titanium oxide (TiO ₂ ) film on a surface of the oxidation-resistant protective layer on the side opposite to the conductive layer. The oxidation-resistant protective layer has a thickness in the range of 200 to 1000 mm,
The substrate with a transparent conductive film according to any one of claims 4 to 6, wherein the thickness of the underlayer is in a range of 100 to 500 mm. A first conductive substrate;
A second conductive substrate disposed opposite to the first conductive substrate;
A porous semiconductor layer formed on the surface of the first conductive substrate on the second conductive substrate side and adsorbing a dye;
An electrolyte formed between the porous semiconductor layer and the second conductive substrate,
The dye-sensitized solar cell, wherein the first conductive substrate is a substrate with a transparent conductive film according to any one of claims 1 to 7.

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