JP2014056767A - Method for producing transparent conductive film and method for manufacturing photoelectric conversion element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a transparent conductive film, which is capable of enhancing electrical conductivity of a transparent conductive film by a relatively simple process.SOLUTION: The method for producing a transparent conductive film of the present invention comprises the steps of: sequentially forming a first transparent conductive layer containing tin oxide and a second transparent conductive layer containing zinc oxide on at least one surface of a transparent substrate; and heat-treating the transparent substrate on which the first transparent conductive layer and the second transparent conductive layer have been formed, at a temperature of 200 to 300°C inclusive.

Description

  The present invention relates to a method for producing a transparent conductive film and a method for producing a photoelectric conversion element, and is suitable for a method for producing a transparent conductive film having high electrical conductivity and a method for producing a photoelectric conversion element.

Transparent conductive films are used in various fields such as solar cell substrates, display substrates, and touch panel substrates. The transparent conductive film is required to have high electrical conductivity and high transmittance at the temperature (for example, room temperature) to be used. In order to achieve high electrical conductivity, it is a guideline to achieve high carrier density and high mobility. On the other hand, in order to realize high transmittance in the visible light region, it is necessary to form the transparent conductive film with a material having a band gap energy of 3.0 eV or more. In order to satisfy these requirements, In ₂ O ₃ , SnO _2, ZnO or the like is mainly used as a material for the transparent conductive film. When a very small amount of additive is added to these materials, the carrier density is further increased, so that the electrical conductivity can be further increased.

JP-A-6-28932

J. R. Bellingham, W. A. Phillips and C. J. Adkins, J. Mater. Sci. Lett., 11, 263-265 (1992)

  However, in the above-described method of increasing the carrier density of the transparent conductive film by adding a small amount of additive, the transparent conductive film has a wavelength longer than the wavelength corresponding to the plasma frequency of the carrier as the carrier density increases. Light (for example, near-infrared light) is reflected (Non-Patent Document 1). Therefore, if such a transparent conductive film is used in a device (for example, a solar cell) that also wants to capture light in the near infrared region, it becomes a factor of deteriorating the characteristics of the device. That is, in the method of increasing the carrier density of the transparent conductive film by adding an additive, there is a trade-off relationship between electrical conductivity and transmittance. Therefore, a method for further increasing the electrical conductivity without reducing the transmittance of the transparent conductive film is required.

  For example, Patent Document 1 and the like describe the following as a method for further increasing the electrical conductivity without decreasing the transmittance of the transparent conductive film. First, a crystal nucleation layer having a thickness of 3 to 30 nm is coated on the organic resin surface as a first layer. Next, crystal nuclei are grown by annealing the crystal nucleation layer in a reduced pressure atmosphere. Subsequently, a low resistance layer is coated as a second layer on the crystal nucleation layer. The low resistance layer thus formed is a layer having a large crystal grain size even when formed at a low temperature. Accordingly, the number of crystal grain boundaries is reduced, and the scattering of conduction electrons at the crystal grain boundaries is reduced. Therefore, the mobility of conduction electrons in the film is increased, and the electrical resistivity of the film is decreased.

  When heat treatment is performed in an oxygen-free atmosphere, carrier density increases due to the generation of oxygen defects, and thus electrical conductivity increases. However, as described above, when the carrier density increases, the transparent conductive film reflects light having a wavelength longer than the wavelength corresponding to the plasma frequency of the carrier (for example, light in the near infrared region). Therefore, the transmittance is reduced. On the other hand, when heat treatment is performed in an atmosphere in which oxygen exists, oxygen is taken into the transparent conductive film, and oxygen defects are reduced. As a result, the carrier density decreases and the electrical conductivity decreases. That is, the method of heat-treating the transparent conductive film also has a trade-off relationship between electrical conductivity and transmittance.

  In order to realize an oxygen-free atmosphere, an expensive vacuum device is required. Therefore, the manufacturing cost of the transparent conductive film is increased.

  The present invention has been made to solve the above-described problems, and the object of the present invention is to provide a method for producing a transparent conductive film capable of increasing the electrical conductivity of the transparent conductive film by a relatively simple method. And a method for producing a photoelectric conversion element including the transparent conductive film.

  The method for producing a transparent conductive film of the present invention includes a step of forming a first transparent conductive layer containing tin oxide and a second transparent conductive layer containing zinc oxide on at least one surface of a transparent substrate, And a step of heat-treating the transparent substrate on which the transparent conductive layer and the second transparent conductive layer are formed at a temperature of 200 ° C. or higher and 300 ° C. or lower.

  The method for producing a photoelectric conversion element of the present invention includes a step of forming a first transparent conductive layer containing tin oxide and a second transparent conductive layer containing zinc oxide on at least one surface of a transparent substrate, A step of performing a heat treatment on the transparent substrate on which the transparent conductive layer and the second transparent conductive layer are formed at a temperature of 200 ° C. or more and 300 ° C. or less, and a photoelectric conversion on the transparent conductive film produced by performing the heat treatment Forming a layer and a back electrode.

Step, 1 × 10 preferably includes a step of performing heat treatment at 1 × 10 ⁷ Pa pressure equal to or smaller than ^-8 Pa or more, 1 × 10 ^-8 Pa or more 1 × 10 ⁷ Pa or less of the oxygen partial pressure of performing heat treatment It is preferable to include a step of performing a heat treatment.

  In the method for producing a transparent conductive film of the present invention, a transparent conductive film having high electrical conductivity can be produced by a relatively simple method. In the method for producing a photoelectric conversion element of the present invention, a photoelectric conversion element provided with a transparent conductive film having high electrical conductivity can be provided by a relatively simple method.

It is sectional drawing which shows typically an example of a structure of the transparent conductive film of this invention. It is a flowchart which shows an example of the manufacturing method of the transparent conductive film of this invention in order of a process. It is a flowchart which shows an example of the manufacturing method of the photoelectric conversion element of this invention in order of a process. It is a flowchart which shows the manufacturing method of the transparent conductive film of Example 1 in order of a process. 2 is a cross-sectional view schematically showing a configuration of a transparent conductive film manufactured in Example 1. FIG. It is a graph which shows the relationship between heat processing temperature and the sheet resistance value of a transparent conductive film.

  Hereinafter, the manufacturing method of the transparent conductive film of this invention and the manufacturing method of a photoelectric conversion element are demonstrated using drawing. In the drawings of the present invention, the same reference numerals represent the same or corresponding parts. In addition, dimensional relationships such as length, width, thickness, and depth are changed as appropriate for clarity and simplification of the drawings, and do not represent actual dimensional relationships.

[Configuration of transparent conductive film]
FIG. 1 is a cross-sectional view schematically showing an example of the configuration of the transparent conductive film of the present invention. The transparent conductive film 4 shown in FIG. 1 is configured by alternately forming the first transparent conductive layer 2 and the second transparent conductive layer 3 on one surface of the transparent substrate 1. The transparent conductive film 4 may be formed by alternately forming the first transparent conductive layer 2 and the second transparent conductive layer 3 on both surfaces of the transparent substrate 1. Further, either the first transparent conductive layer 2 or the second transparent conductive layer 3 may be in contact with the transparent base material 1 or may be farthest from the transparent base material 1.

[Method for producing transparent conductive film]
FIG. 2 is a flowchart showing an example of the method for producing a transparent conductive film of the present invention in the order of steps. The transparent conductive film manufacturing method shown in FIG. 2 includes a transparent conductive film forming step S101 and a heat treatment step S102.

<Formation of transparent conductive film>
In the transparent conductive film forming step S <b> 101, the first transparent conductive layer 2 and the second transparent conductive layer 3 are alternately formed on one surface of the transparent substrate 1. Thereby, the transparent conductive film 4 is formed.

  The transparent substrate 1 is particularly limited as long as it is excellent in light transmittance and can structurally support the first transparent conductive layer 2 and the second transparent conductive layer 3 formed on the transparent substrate 1. Not. For example, as the transparent substrate 1, a substrate made of a light-transmitting resin having heat resistance such as polyimide and polyvinyl, a glass plate, or a layer in which a layer made of a light-transmitting resin and a layer made of glass are laminated, etc. Can be used as appropriate. Moreover, it is preferable that the thickness of the transparent base material 1 is 50 micrometers-10 mm.

The first transparent conductive layer 2 and the second transparent conductive layer 3 are preferably made of a known material as the material of the transparent conductive layer, and are preferably made of different materials. For example, the first transparent conductive layer 2 is preferably made of tin oxide (SnO ₂ ), zinc oxide (ZnO), indium tin oxide (ITO), or the like. The second transparent conductive layer 3 is preferably made of a material different from the first transparent conductive layer 2 among tin oxide (SnO ₂ ), zinc oxide (ZnO), indium tin oxide (ITO), and the like. More preferably, the first transparent conductive layer 2 contains tin oxide and the second transparent conductive layer 3 contains zinc oxide. Thereby, in the heat treatment step S102 described later, a conductive layer excellent in conductivity is formed at the interface between the first transparent conductive layer 2 and the second transparent conductive layer 3. Therefore, the transparent conductive film 4 having high electrical conductivity can be manufactured.

The 1st transparent conductive layer 2 and the 2nd transparent conductive layer 3 may contain a trace amount impurity in the range which does not inhibit the effect of this invention other than the well-known material of the transparent conductive layer mentioned above. For example, the film containing tin oxide may contain a trace amount (for example, 1 × 10 ²² atoms / cm ³ or less) of fluorine or antimony. The film containing zinc oxide may contain a small amount (for example, 1 × 10 ²² atoms / cm ³ or less) of indium, gallium, aluminum, boron, or the like.

  The thicknesses of the first transparent conductive layer 2 and the second transparent conductive layer 3 are preferably set as appropriate depending on the intended electrical conductivity, transmittance, material cost, etc., but are preferably 20 nm to 5 μm. .

  The number of layers of each of the first transparent conductive layer 2 and the second transparent conductive layer 3 is not particularly limited. However, in the heat treatment step S <b> 102 described later, a conductive layer having excellent conductivity is formed at the interface between the first transparent conductive layer 2 and the second transparent conductive layer 3. Therefore, if the number of layers of each of the first transparent conductive layer 2 and the second transparent conductive layer 3 is large, the number of interfaces between the first transparent conductive layer 2 and the second transparent conductive layer 3 increases. The transparent conductive film 4 having conductivity can be manufactured. Therefore, it is preferable that the first transparent conductive layer 2 and the second transparent conductive layer 3 have a larger number of layers. For example, when the thickness of the transparent conductive film 4 is 10 μm, the total number of layers of the first transparent conductive layer 2 and the second transparent conductive layer 3 is preferably 2 or more and 500 or less.

  Each formation method of the 1st transparent conductive layer 2 and the 2nd transparent conductive layer 3 is not specifically limited. Examples of methods for forming the first transparent conductive layer 2 and the second transparent conductive layer 3 include sputtering, atmospheric pressure CVD (Chemical Vapor Deposition), reduced pressure CVD, MOCVD (Metal Organic Chemical Vapor Deposition), A known film formation method such as an electron beam evaporation method, a sol-gel method, an electrodeposition method, or a spray method can be appropriately selected.

For example, when a zinc oxide film is formed by sputtering, a target that can form a zinc oxide film under the following conditions using a commercially available product such as a sputtering apparatus (manufactured by Hirano Kotone Co., Ltd.): ZnO
Gas: Ar
Gas pressure: 4.0 mTorr
Power applied to the target: 1.5 kW.

  A substrate with a transparent conductive layer in which the first transparent conductive layer 2 is formed on one surface of the transparent substrate 1 (for example, product name: Asahi-U manufactured by Asahi Glass) can be used. In this case, the second transparent conductive layer 3 may be formed on the first transparent conductive layer 2 of the substrate with a transparent conductive layer. Alternatively, the transparent conductive film 4 may be formed by alternately forming the first transparent conductive layer 2 and the second transparent conductive layer 3 on both surfaces of the transparent substrate 1. Alternatively, the transparent conductive film 4 may be formed by alternately forming the second transparent conductive layer 3 and the first transparent conductive layer 2 on at least one surface of the transparent substrate 1.

<Heat treatment>
In the heat treatment step S102, the formed transparent conductive film 4 is heat treated at a temperature of 200 ° C. or higher and 300 ° C. or lower. Thereby, the electrical conductivity of the transparent conductive film 4 increases. The reason is considered as follows. When the heat treatment is performed, metal atoms contained in the first transparent conductive layer 2 diffuse into the second transparent conductive layer 3, or metal atoms contained in the second transparent conductive layer 3 diffuse into the first transparent conductive layer 2. To do. Thereby, a conductive layer having excellent conductivity is formed at the interface between the first transparent conductive layer 2 and the second transparent conductive layer 3. Therefore, it is possible to manufacture the transparent conductive film 4 having a higher electrical conductivity than that of a single layer transparent conductive film.

  For example, when the first transparent conductive layer 2 is made of tin oxide and the second transparent conductive layer 3 is made of zinc oxide, tin contained in the first transparent conductive layer 2 diffuses into the second transparent conductive layer 3. Alternatively, zinc contained in the second transparent conductive layer 3 diffuses into the first transparent conductive layer 2. Thereby, a conductive layer having excellent conductivity is formed at the interface between the first transparent conductive layer 2 and the second transparent conductive layer 3.

  On the other hand, when an ITO (Indium Tin Oxide) layer and a zinc oxide layer are sequentially formed on at least one surface of the transparent substrate, the concentration of tin that is an ITO donor when tin diffuses from the ITO layer to the zinc oxide layer Becomes lower. Therefore, the electrical conductivity of the ITO layer is reduced. Also, even if zinc diffuses from the zinc oxide film to the ITO film, the zinc does not act as a donor in the ITO film, so that the electrical conductivity of the ITO layer is reduced due to the diffusion of tin into the zinc oxide layer. It is difficult to prevent. For these reasons, if the ITO layer and the zinc oxide layer are sequentially formed on at least one surface of the transparent substrate and then heat treatment is performed, the electrical conductivity of the ITO layer is lowered.

  Moreover, since tin is a base material in the tin oxide layer, the tin concentration in the tin oxide layer reaches several tens of percent. On the other hand, the tin concentration in the ITO layer is about 10% at most. Therefore, even if an ITO layer and a zinc oxide layer are sequentially formed on at least one surface of the transparent substrate and then heat treatment is performed, a sufficient amount of tin diffuses to the interface between the ITO layer and the zinc oxide layer is sufficiently secured. Therefore, a conductive layer having excellent conductivity may not be formed at the interface between the ITO layer and the zinc oxide layer. From the above, in order to produce the transparent conductive film 4 having high electrical conductivity, rather than sequentially forming an ITO layer and a zinc oxide layer on at least one surface of the transparent substrate and performing a heat treatment, It is preferable to heat-treat after forming a tin oxide layer and a zinc oxide layer in order on at least one surface of the transparent substrate.

  If the heat treatment temperature for the formed transparent conductive film 4 (hereinafter simply referred to as “heat treatment temperature”) is less than 200 ° C., atoms contained in the first transparent conductive layer 2 are difficult to diffuse into the second transparent conductive layer 3. In some cases, atoms contained in the second transparent conductive layer 3 are difficult to diffuse into the first transparent conductive layer 2. Therefore, there is a possibility that a conductive layer having excellent conductivity may not be formed at the interface between the first transparent conductive layer 2 and the second transparent conductive layer 3, and the transparent conductive film 4 having high electrical conductivity may not be manufactured. When the heat treatment temperature exceeds 300 ° C., oxygen contained in the atmosphere during the heat treatment may fill oxygen defects in the first transparent conductive layer 2 or the second transparent conductive layer 3. For this reason, a transparent conductive film having high electrical conductivity may not be produced. From the above, the heat treatment temperature is preferably 200 ° C. or higher and 300 ° C. or lower, and more preferably 240 ° C. or higher and 280 ° C. or lower. If the heat treatment temperature is 240 ° C. or higher and 280 ° C. or lower, atoms contained in the first transparent conductive layer 2 are sufficiently diffused into the second transparent conductive layer 3, and atoms contained in the second transparent conductive layer 3 are first transparent. It diffuses sufficiently into the conductive layer 2. Therefore, a conductive layer having excellent conductivity is formed at the interface between the first transparent conductive layer 2 and the second transparent conductive layer 3. In addition, it is possible to suppress oxygen contained in the atmosphere during the heat treatment from filling oxygen defects in the first transparent conductive layer 2 and the second transparent conductive layer 3. Therefore, the transparent conductive film 4 having very high electric conductivity can be manufactured.

In general, in order to prevent a decrease in electrical conductivity of the transparent conductive film due to oxidation, it is preferable to perform the heat treatment with the oxygen partial pressure as low as possible. In addition, when heat treatment is performed under high vacuum, oxygen defects in the transparent conductive film increase, and the electrical conductivity increases. Therefore, in general, the pressure during the heat treatment is preferably as low as possible. However, in the present invention, a conductive layer excellent in conductivity is formed at the interface between the first transparent conductive layer 2 and the second transparent conductive layer 3 by heat treatment, and as a result, the transparent conductive film 4 having high electrical conductivity. Is manufactured. Therefore, the electrical conductivity of the transparent conductive film 4 is not affected by the atmospheric pressure or the oxygen partial pressure during the heat treatment. Therefore, in the heat treatment step S102, 1 × 10 ^-8 Pa or more and 1 × able to perform heat treatment in the following under pressure 10 ⁷ Pa, the heat treatment at 1 × 10 ^-8 Pa or more and 1 × 10 ⁷ Pa or less of the oxygen partial pressure Can be performed.

  The heat treatment is preferably performed at a set heat treatment temperature for 10 minutes or more, and more preferably from 20 minutes to 100 minutes. If the heat treatment time is less than 10 minutes, atoms contained in the first transparent conductive layer 2 may not diffuse into the second transparent conductive layer 3, and atoms contained in the second transparent conductive layer 3 may not be diffused into the first transparent conductive layer 3. 2 may not diffuse. Therefore, there is a possibility that a conductive layer having excellent conductivity may not be formed at the interface between the first transparent conductive layer 2 and the second transparent conductive layer 3, and the transparent conductive film 4 having high electrical conductivity may not be manufactured. When the heat treatment time exceeds 100 minutes, the production time of the transparent conductive film 4 is prolonged, and thus mass production of devices (for example, solar cells) including the transparent conductive film 4 may not be achieved.

  It is preferable to perform a heat treatment in the heat treatment step S102 by appropriately selecting a known apparatus or equipment. For example, a commercial product such as a constant temperature dryer (manufactured by Yamato Scientific Co., Ltd., product number: DR-22) can be suitably used. In addition, in heat processing process S102, the necessity of rapid heating, rapid cooling, slow heating, or slow cooling is not ask | required.

  The transparent conductive film 4 manufactured according to the present invention can be suitably used as a substrate included in a photoelectric conversion element. FIG. 3 is a flowchart showing an example of the method for producing a photoelectric conversion element of the present invention in the order of steps. The photoelectric conversion element manufacturing method shown in FIG. 3 includes a photoelectric conversion layer formation step S201 and a back electrode formation step S202 in addition to the transparent conductive film formation step S101 and the heat treatment step S102.

<Formation of photoelectric conversion layer>
In the photoelectric conversion layer forming step S201, the photoelectric conversion layer is formed on the transparent conductive film 4 manufactured by the heat treatment step S102 shown in FIG. As a material of the photoelectric conversion layer, for example, a silicon-based material (amorphous, microcrystalline, or polycrystalline), a CIGS-based material, a II-VI group-based material, a dye-sensitized metal oxide material, or the like can be used.

  The formation method in particular of a photoelectric converting layer is not restrict | limited, A well-known method can be suitably combined as needed as a forming method of a photoelectric converting layer. For example, when forming a photoelectric conversion layer made of amorphous silicon, a photoelectric conversion layer is used under the following conditions using a commercially available product such as a plasma CVD apparatus (for example, ACV-T440L type manufactured by Shinko Seiki Co., Ltd.). Can be formed.

(Example of conditions for forming a p-type amorphous silicon layer (thickness: 10 nm))
Material gas and the raw material gas flow rate: SiH ₄ (flow rate 6 sccm), CH ₄ (flow rate 10 sccm), H ₂ (flow rate 22 sccm), H ₂ (including the B ₂ H ₆ 0.1% by volume, flow rate 18 sccm)
Pressure: 30Pa
Substrate temperature: 180 ° C
Distance between electrodes: 40mm
Electric power: 70W.

(Example of conditions for forming i-type amorphous silicon layer (thickness: 300 nm))
Source gas and source gas flow rate: SiH ₄ (flow rate is 20 sccm), H ₂ (flow rate is 50 sccm)
Pressure: 30Pa
Substrate temperature: 200 ° C
Distance between electrodes: 45mm
Electric power: 35W.

(Example of conditions for forming an n-type amorphous silicon layer (thickness: 20 nm))
Source gas and source gas flow rate: SiH ₄ (flow rate is 20 sccm), H ₂ (flow rate is 25 sccm), H ₂ (containing 0.2 vol% of PH ₃ , flow rate is 25 sccm)
Pressure: 30Pa
Substrate temperature: 200 ° C
Distance between electrodes: 45mm
Electric power: 35W.

<Formation of back electrode>
In the back electrode forming step S202, a back electrode is formed on the photoelectric conversion layer. The material for the back electrode is not particularly limited. For example, a back electrode made of zinc oxide or silver can be formed on the photoelectric conversion layer made of amorphous silicon.

  The method for forming the back electrode is not particularly limited, and known methods for forming the back electrode can be appropriately combined as necessary. For example, when a back electrode made of zinc oxide and silver is formed, it can be formed by a sputtering method, and is oxidized under the following conditions using a commercially available product such as a sputtering apparatus (manufactured by Hirano Kotone Co., Ltd.). A back electrode formed by laminating a zinc film and a silver film can be formed.

(Example of conditions for forming a zinc oxide film (thickness: 80 nm))
Target: ZnO
Gas: Ar
Gas pressure: 4.0 mTorr
Power applied to the target: 1.5 kW.

(Example of conditions for forming a silver film (thickness: 120 nm))
Target: Ag
Gas: Ar
Gas pressure: 20.0 mTorr
Power applied to the target: 2.0 kW.

  The photoelectric conversion element thus manufactured includes the transparent conductive film 4 manufactured by the heat treatment step S102 shown in FIG. Therefore, the photoelectric conversion element manufacturing method shown in FIG. 3 can provide a photoelectric conversion element including a transparent conductive film having high electrical conductivity by a relatively simple method.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

<Example 1>
In Example 1, the transparent conductive film shown in FIG. 5 was manufactured according to the flowchart shown in FIG. FIG. 4 is a flowchart showing the method of manufacturing the transparent conductive film of this example in the order of steps. FIG. 5 is a cross-sectional view schematically showing the configuration of the transparent conductive film produced in this example.

  First, in step S301, a substrate with a transparent conductive layer (for example, product name: Asahi-U, manufactured by Asahi Glass Co., Ltd.) on which a tin oxide layer 12 is formed on a glass substrate 11 was prepared. Here, the tin oxide layer 12 contained fluorine as an impurity and had a thickness of 1000 nm.

Next, in step S302, a film forming process was performed for 3 minutes under the following conditions using a sputtering apparatus (manufactured by Hirano Kotone Co., Ltd.). Thereby, the target in which the zinc oxide layer 13 (thickness 50 nm) was formed on the tin oxide layer 12: ZnO
Gas: Ar
Gas pressure: 4.0 mTorr
Power applied to the target: 1.5 kW.

Subsequently, in step S303, the substrate with the transparent conductive layer on which the zinc oxide layer 13 was formed was heat-treated using a constant temperature dryer (manufactured by Yamato Kagaku Co., Ltd., product number: DR-22). Specifically, heat treatment was performed for 60 minutes while changing the heat treatment temperature within a range of 200 ° C. or more and 300 ° C. or less while flowing N ₂ at 10 L / min under atmospheric pressure. Thus, the transparent conductive film 14 was manufactured. The sheet resistance value of the produced transparent conductive film 14 was measured using a sheet resistance measuring device (manufactured by Napson Corporation, product number: RT-8A / RG-8). The result is shown in FIG. FIG. 6 is a graph showing the relationship between the heat treatment temperature and the sheet resistance value of the transparent conductive film.

<Comparative Example 1>
In Comparative Example 1, after the zinc oxide layer was formed on the tin oxide layer, the heat treatment temperature was changed within the range of 20 ° C. or higher and lower than 200 ° C. and higher than 300 ° C. and within the range of 400 ° C. or lower to perform heat treatment. A transparent conductive film was produced according to the method described in Example 1 above. Then, the relationship between the heat treatment temperature and the sheet resistance value of the transparent conductive film was examined according to the method described in Example 1 above. The result is shown in FIG.

<Comparative example 2>
In Comparative Example 2, except that the heat treatment temperature was changed in the range of 20 ° C. or more and 400 ° C. or less for the tin oxide layer (thickness 1000 nm) formed on the glass substrate, except that the heat treatment was performed. Produced a transparent conductive film according to the method described in Example 1 above. Then, the relationship between the heat treatment temperature and the sheet resistance value of the transparent conductive film was examined according to the method described in Example 1 above. The result is shown in FIG.

<Comparative Example 3>
In Comparative Example 3, the method described in Example 1 was used except that a heat treatment was performed at a temperature shown in FIG. 6 on a glass substrate on which a zinc oxide layer (thickness: 1000 nm) was formed. Therefore, a transparent conductive film was manufactured. Then, the relationship between the heat treatment temperature and the sheet resistance value of the transparent conductive film was examined according to the method described in Example 1 above. The result is shown in FIG.

  As shown in FIG. 6, in Example 1, the sheet resistance value of the transparent conductive film was lower than that in Comparative Example 1. The reason is that in Example 1, the heat treatment temperature is 200 ° C. or more and 300 ° C. or less, whereas in Comparative Example 1, the heat treatment temperature is less than 200 ° C. or more than 300 ° C.

  Moreover, in Example 1, compared with the comparative example 2 and the comparative example 3, the sheet resistance value of the transparent conductive film fell. The reason is that in Example 1, there is an interface between the tin oxide layer and the zinc oxide layer, whereas in Comparative Example 2 and Comparative Example 3, there is no interface between the tin oxide layer and the zinc oxide layer. Can be mentioned.

  From the above, it was found that when a tin oxide layer and a zinc oxide layer are sequentially formed on a glass substrate and then heat-treated at a temperature of 200 ° C. to 300 ° C., a transparent conductive film having high electrical conductivity can be produced. .

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Base material, 2 1st transparent conductive layer, 3rd 2nd transparent conductive layer, 4,14 Transparent conductive film, 11 Glass substrate, 12 Tin oxide layer, 13 Zinc oxide layer.

Claims (6)

Forming a first transparent conductive layer containing tin oxide and a second transparent conductive layer containing zinc oxide on at least one surface of the transparent substrate;
And a step of heat-treating the transparent substrate on which the first transparent conductive layer and the second transparent conductive layer are formed at a temperature of 200 ° C. or higher and 300 ° C. or lower. The method for producing a transparent conductive film according to claim 1, wherein the step of performing the heat treatment includes a step of performing a heat treatment under a pressure of 1 × 10 ⁻⁸ Pa to 1 × 10 ⁷ Pa. The method for producing a transparent conductive film according to claim 1, wherein the step of performing the heat treatment includes a step of performing a heat treatment under an oxygen partial pressure of 1 × 10 ⁻⁸ Pa to 1 × 10 ⁷ Pa. Forming a first transparent conductive layer containing tin oxide and a second transparent conductive layer containing zinc oxide on at least one surface of the transparent substrate;
Performing a heat treatment at a temperature of 200 ° C. or higher and 300 ° C. or lower on the transparent substrate on which the first transparent conductive layer and the second transparent conductive layer are formed;
The manufacturing method of a photoelectric conversion element provided with the process of forming a photoelectric converting layer and a back surface electrode on the transparent conductive film manufactured by performing the said heat processing. 5. The method for manufacturing a photoelectric conversion element according to claim 4, wherein the step of performing the heat treatment includes a step of performing a heat treatment under a pressure of 1 × 10 ⁻⁸ Pa or more and 1 × 10 ⁷ Pa or less. 5. The method for manufacturing a photoelectric conversion element according to claim 4, wherein the step of performing the heat treatment includes a step of performing a heat treatment under an oxygen partial pressure of 1 × 10 ⁻⁸ Pa to 1 × 10 ⁷ Pa. 5.

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