WO2012176817A1 - Base having transparent conductive oxide film - Google Patents

Base having transparent conductive oxide film Download PDF

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Publication number
WO2012176817A1
WO2012176817A1 PCT/JP2012/065775 JP2012065775W WO2012176817A1 WO 2012176817 A1 WO2012176817 A1 WO 2012176817A1 JP 2012065775 W JP2012065775 W JP 2012065775W WO 2012176817 A1 WO2012176817 A1 WO 2012176817A1
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Prior art keywords
film
transparent conductive
conductive oxide
oxide film
substrate
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PCT/JP2012/065775
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French (fr)
Japanese (ja)
Inventor
誠二 東
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旭硝子株式会社
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Publication of WO2012176817A1 publication Critical patent/WO2012176817A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0224—Electrodes
    • H01L31/022408—Electrodes for devices characterised by at least one potential jump barrier or surface barrier
    • H01L31/022425—Electrodes for devices characterised by at least one potential jump barrier or surface barrier for solar cells

Definitions

  • the present invention relates to a substrate with a transparent conductive oxide film.
  • the substrate with a transparent conductive oxide film of the present invention is suitable as a substrate with a transparent conductive oxide film for a photoelectric conversion element such as a solar cell.
  • Thin film solar cells that are photoelectric conversion elements include amorphous silicon (a-Si) type and polycrystalline silicon type depending on the type of photoelectric conversion layer.
  • a-Si amorphous silicon
  • polycrystalline silicon type depending on the type of photoelectric conversion layer.
  • the incident light side is transparent.
  • a transparent conductive oxide film is used as the electrode layer.
  • This transparent conductive oxide film is required to have low resistance and high transparency and high light scattering performance in order to increase photoelectric conversion efficiency.
  • Patent Document 1 discloses a fluorine-doped SnO 2 film containing 0.0001 to 0.04 (molar ratio) of fluorine with respect to SnO 2 and having a conductive electron density of 5 ⁇ 10 19 to 4 ⁇ 10 20 cm ⁇ 3. This fluorine-doped SnO 2 film is said to be highly transparent with little absorption of the film and high durability against active hydrogen species.
  • a thin film solar cell has a structure in which a transparent electrode layer, a photoelectric conversion layer, and a back electrode are formed in this order on a substrate such as a glass substrate.
  • a transparent electrode layer In a thin film solar cell, light is reflected at the interface between the transparent electrode layer and the photoelectric conversion layer due to the difference in refractive index between the transparent electrode layer and the photoelectric conversion layer (for example, about 9% reflection). ), The amount of light introduced into the photoelectric conversion layer is reduced, and as a result, the short-circuit current (J SC ) is reduced and the photoelectric conversion efficiency (E ff ) can be kept low.
  • Patent Document 2 there is translucency between the transparent electrode layer and the semiconductor layer (photoelectric conversion layer), and the value of the refractive index thereof is the transparent electrode layer and the semiconductor.
  • the light is smoothly introduced into the semiconductor layer (photoelectric conversion layer).
  • the refractive index adjustment layer is made of titanium oxide TiO 2 (2-X) containing oxygen defects (where X is 0.4 or less), thereby imparting conductivity to the refractive index adjustment layer. is doing. Further, instead of giving oxygen defects to titanium oxide TiO 2 constituting the refractive index adjustment layer, by mixing 20% or less of titanium and a metal having a different valence, such as tantalum (Ta) or barium (Ba), It is said that the same effect as giving oxygen defects can be exhibited.
  • a metal having a different valence such as tantalum (Ta) or barium (Ba
  • films were formed on the transparent electrode layer of titanium oxide system is to hydrogen plasma, the property of having a strong reduction resistance than a tin oxide film (SnO 2 film), thermal or plasma during the photoelectric conversion layer formed It is also known to have a function as a protective layer for protecting the transparent conductive oxide film, which is a transparent electrode layer, from impact.
  • an atmospheric pressure CVD method is preferably used as a means for forming these films because the apparatus cost is low and the film formation speed is high. Even when a titanium oxide film as described above is formed as the refractive index adjusting layer, the atmospheric pressure CVD method is preferably used for the same reason.
  • a fluorine-doped SnO 2 film is formed as a transparent conductive oxide film
  • a titanium oxide-based film is formed as a refractive index adjusting layer or a protective layer on the transparent conductive oxide film
  • a Schottky barrier is formed at the interface between a transparent conductive oxide film (fluorine-doped SnO 2 film) and a titanium oxide-based film, so that an ohmic contact cannot be achieved. I found.
  • the present invention provides a substrate with a transparent conductive oxide film in which an overcoat film is formed on a transparent conductive oxide film. Forming a stable transparent conductive oxide film even at the time of film formation, and achieving ohmic contact at the interface between the transparent conductive oxide film and the overcoat film, the fill factor when creating a photoelectric conversion element ( The object is to suppress the decrease in FF) and achieve good photoelectric conversion efficiency (E ff ).
  • the present invention provides a substrate with a transparent conductive oxide film in which a transparent conductive oxide film and an overcoat film are formed in this order on a substrate, the transparent conductive oxide film
  • the oxide film contains tin oxide (SnO 2 ) as a main component, contains fluorine, and the ratio of fluorine at the interface in contact with at least the overcoat film of the transparent conductive oxide film is such that fluorine is tin oxide (SnO 2 ).
  • the overcoat film contains 0.0001 to 0.09 (molar ratio)
  • the overcoat film contains titanium oxide (TiO 2 ) as a main component, tin oxide, and Sn / (Sn + Ti in the overcoat film).
  • a substrate with a transparent conductive oxide film characterized in that the molar ratio is 0.05 or more and less than 0.5.
  • the Sn / (Sn + Ti) molar ratio in the overcoat film is preferably 0.07 or more and 0.3 or less.
  • the overcoat film preferably has a thickness of 10 nm to 100 nm.
  • the thickness of the overcoat film is particularly preferably from 30 nm to 50 nm.
  • the present invention includes a step of forming a transparent conductive oxide film containing tin oxide (SnO 2 ) as a main component and containing fluorine on a substrate, and titanium oxide (TiO 2) on the transparent conductive oxide film.
  • a step of forming an overcoat film containing tin oxide as a main component, and a method for producing a substrate with a transparent conductive oxide film In the step of forming the transparent conductive oxide film, the content ratio of fluorine in at least the layer in contact with the overcoat film of the transparent conductive oxide film is set to 0. 0 with respect to tin oxide (SnO 2 ).
  • the step of forming the overcoat film includes a step of making the Sn / (Sn + Ti) molar ratio in the overcoat film to be 0.05 or more and less than 0.5, and the overcoat film includes:
  • a method for producing a substrate with a transparent conductive oxide film comprising a step of forming the substrate on the transparent conductive oxide film heated to 450 ° C. or higher by atmospheric pressure CVD.
  • ohmic contact can be achieved at the interface between the transparent conductive oxide film and the overcoat film.
  • the fall of the fill factor (FF) at the time of producing a photoelectric conversion element can be suppressed, and favorable photoelectric conversion efficiency ( Eff ) can be achieved.
  • an overcoat film is formed on the transparent conductive oxide film.
  • the refractive index of the overcoat film is within the range where the refractive index of the transparent conductive oxide film and the refractive index of the photoelectric conversion layer are the upper limit and the lower limit, respectively, it functions as a refractive index adjustment layer and is transparent.
  • the substrate with a transparent conductive oxide film of the present invention has a structure in which a transparent conductive oxide film and an overcoat film are formed in this order on the substrate.
  • a transparent conductive oxide film and an overcoat film are formed in this order on the substrate.
  • the substrate used for the substrate with a transparent conductive oxide film of the present invention is not necessarily flat and plate-like, and may be curved or atypical.
  • the substrate include a glass substrate, a ceramic substrate, a plastic substrate, and a metal substrate.
  • the substrate is preferably a transparent substrate excellent in translucency, and a glass substrate is preferable from the viewpoint of strength and heat resistance.
  • a transparent glass plate made of colorless and transparent soda lime silicate glass, aluminosilicate glass, borate glass, lithium aluminosilicate glass, quartz glass, borosilicate glass substrate, non-alkali glass substrate, and other various glasses. Can do.
  • the thickness of the glass substrate is preferably 0.2 to 6.0 mm. Within this range, the strength of the glass substrate is high and the transmittance is high.
  • the substrate preferably has a high average transmittance in the wavelength region of 350 to 800 nm, for example, a transmittance of 80% or more. Moreover, it is desirable that it is sufficiently insulating and has high chemical and physical durability.
  • an alkali barrier layer such as a silicon oxide film, an aluminum oxide film, or a zirconium oxide film may be provided on the glass substrate surface.
  • the alkali barrier layer formed on the soda lime glass substrate is a SiO 2 film, a mixed oxide film of SiO 2 and SnO 2 , a multilayer film in which a SiO 2 film and another oxide film are laminated, etc.
  • the film thickness (total film thickness in the case of a multilayer film) is preferably 20 to 100 nm. When the film thickness is within this range, reflection and absorption of transmitted light from the glass substrate can be controlled.
  • Examples of the multilayer film include films in which a TiO 2 film and a SiO 2 film are sequentially laminated on a soda lime glass substrate, and the film thicknesses are preferably 10 to 20 nm and 10 to 40 nm, respectively.
  • the thickness of the alkali barrier layer is preferably 30 to 60 nm.
  • the transparent conductive oxide film is a fluorine-doped SnO 2 film in which at least a portion in contact with the overcoat film contains 0.0001 to 0.09 (molar ratio) of fluorine with respect to tin oxide (SnO 2 ). Therefore, it may be a transparent conductive oxide film having a single layer structure in which only the fluorine-doped SnO 2 film is formed on the substrate. Further, it may be a transparent conductive oxide film having a structure in which a plurality of oxide films are laminated on a substrate as described in International Publication WO2003 / 036657 and International Publication WO2010 / 016468. However, in this case, the portion in contact with the overcoat film, that is, the outermost layer is required to be the fluorine-doped SnO 2 film.
  • the oxide film constituting the transparent conductive oxide film (transparent conductive oxide having a laminated structure)
  • transparent conductive oxide having a laminated structure all oxide films constituting the laminated structure are required to be transparent in the visible light region.
  • the transparent conductive oxide film at least a layer in contact with the overcoat film (in the case of a transparent conductive oxide film having a single layer structure, the transparent conductive oxide film itself, or a transparent conductive oxide film having a laminated structure) In some cases, the outermost layer) is further required to have conductivity.
  • the transparent conductive oxide film at least a layer in contact with the overcoat film is a fluorine-doped SnO 2 film containing 0.0001 to 0.09 (molar ratio) of fluorine with respect to SnO 2 of fluorine.
  • the conductive electron density is improved, and the range is suitable as a substrate for a photoelectric conversion element such as a solar cell.
  • the conductive electron density of the transparent conductive oxide film is in the range of 5 ⁇ 10 19 to 4 ⁇ 10 20 cm ⁇ 3 , and 1.5 ⁇ A range of 10 20 to 3.0 ⁇ 10 20 cm ⁇ 3 is more preferable. Within this range, the film absorbs less light, is highly transparent, and has high durability against active hydrogen species. Therefore, the photoelectric conversion layer is formed on the substrate with the transparent conductive oxide film of the present invention. Transparency is not impaired even by hydrogen plasma irradiation generally used.
  • an oxide film constituting a transparent conductive oxide film (in the case of a transparent conductive oxide film having a laminated structure, all oxide films constituting the laminated structure)
  • the refractive index is preferably 1.8 to 2.2 at a wavelength of 400 to 800 nm, and more preferably 1.9 to 2.1.
  • the sheet resistance of the transparent conductive oxide film is preferably 8 to 20 ⁇ / ⁇ , and more preferably 8 to 12 ⁇ / ⁇ .
  • the sheet resistance of the transparent conductive oxide film having a single layer structure satisfies the above range.
  • the sheet resistance of the entire transparent conductive oxide film having the laminated structure satisfies the above range.
  • the thickness of the fluorine-doped SnO 2 film forming the transparent conductive oxide film having a single layer structure is 300 to 2000 nm. Is preferably 450 to 1450 nm, and more preferably 600 to 1000 nm.
  • the film thickness of the fluorine-doped SnO 2 film forming the surface layer is 300 to 1800 nm. It is preferably 400 to 1000 nm, more preferably 450 to 900 nm.
  • the film thickness of the entire laminated structure is preferably 350 to 2000 nm, more preferably 450 to 1450 nm, and even more preferably 600 to 1200 nm.
  • the oxide film constituting the transparent conductive oxide film (transparent conductive oxide having a laminated structure)
  • all oxide films constituting the laminated structure are preferably formed by an atmospheric pressure CVD method because the apparatus cost is low and the film forming speed is high.
  • the atmospheric pressure CVD method a stable conductive oxide film can be formed even at a high temperature of 450 ° C. or higher.
  • the procedure for forming an oxide film by the atmospheric pressure CVD method differs depending on the composition and shape of the oxide film to be formed.
  • the substrate was heated to the (glass substrate) 540 ° C., tin tetrachloride, water and hydrogen fluoride sprayed simultaneously, atmospheric pressure CVD method By carrying out, a fluorine-doped SnO 2 film can be formed on the substrate.
  • the overcoat film is mainly composed of titanium oxide (TiO 2 ) and contains tin oxide, and the Sn / (Sn + Ti) molar ratio in the overcoat film is 0.05 or more and less than 0.5. is there.
  • the Sn / (Sn + Ti) molar ratio in the overcoat film in the present invention can be determined, for example, by the following procedure.
  • the beam diameter is set to 100 ⁇ m, and a transparent conductive oxide film ( The composition analysis is performed up to the interface with the fluorine-doped SnO 2 film, and the average value can be obtained as a calculated value.
  • XPS scanning X-ray photoelectron spectrometer
  • the titanium oxide-based film has translucency, and the refractive index values thereof are the upper and lower limits of the refractive indexes of the transparent conductive oxide film and the photoelectric conversion layer, respectively. Therefore, it functions as a refractive index adjusting layer that adjusts the difference in refractive index between them.
  • the titanium oxide film is superior in reduction resistance against hydrogen plasma as compared with a tin oxide film (SnO 2 film). It also has a function as a protective layer for protecting the transparent conductive oxide film.
  • titanium oxide (TiO 2 ) is insulative
  • Patent Document 2 discloses a film made of titanium oxide TiO 2 (2-X) containing oxygen defects (where X is 0.4 or less), or titanium oxide TiO 2. 2 titanium and a different valence metals, such as tantalum Ta or barium Ba was imparted conductivity by a film of a mixture of 20% or less.
  • titanium oxide-based films and tin oxide (SnO 2 ) -based transparent conductive oxide films such as fluorine-doped SnO 2 films are not suitable for work function matching. There is a problem that a barrier is formed and ohmic contact cannot be achieved.
  • the overcoat film is composed mainly of titanium oxide (TiO 2 ) and tin oxide, and Sn / (Sn + Ti) in the overcoat film
  • TiO 2 titanium oxide
  • Sn / (Sn + Ti) in the overcoat film
  • the overcoat film is preferably formed by the atmospheric pressure CVD method similar to the transparent conductive oxide film. By forming by the atmospheric pressure CVD method, a stable conductive oxide film can be formed even at a high temperature of 450 ° C. or higher.
  • tin oxide having good conductivity in the overcoat film of the present invention is tin oxide (SnO (2-X) ) having oxygen defects (where X is 0.4 or less).
  • X is set to 0.4 or less, that is, the oxygen defect ratio is set to 20% or less in order to suppress an increase in light absorption in the overcoat film.
  • fluorine SnO 2 (hereinafter doped, fluorine SnO 2 which is doped; referred to as "SnO 2 F" ).
  • the fluorine dope amount is less than 1.0 in terms of the molar ratio of F / Ti in the raw material during the overcoat film formation (molar ratio in the raw material).
  • the fluorine doping amount is 1.0 or more in the molar ratio of F / Ti in the raw material at the time of overcoat film formation (molar ratio in the raw material)
  • the etching action by fluorine during the formation of the overcoat film As a result, the transparent conductive oxide film may be damaged.
  • the conductivity of the transparent conductive oxide film is deteriorated, and the photoelectric conversion efficiency ( E ff ) may decrease.
  • the fluorine doping amount is 1.0 or more in terms of the F / Ti molar ratio in the raw material during overcoat film formation, the overcoat film itself is also subjected to an etching action by fluorine, and as a result, the overcoat film is formed.
  • the fluorine doping amount is preferably 0.0001 to 0.5, more preferably 0.001 to 0.3 in terms of F / Ti molar ratio in the raw material at the time of overcoat film formation. More preferably, it is 001 to 0.25.
  • tin oxide is SnO 2 ; F, good conductivity can be obtained even if a large amount of oxygen is mixed in the raw material. For this reason, air can be used for the dilution gas of a raw material, and low-cost film-forming can be performed.
  • the carbon component content in the film is reduced and the transparency tends to be improved, which is preferable from the viewpoint of improving the transmittance.
  • tin oxide preferably SnO 2 -X or “SnO 2 ; F”
  • TiO 2 film which is the main component of the overcoat film.
  • the function required for the overcoat film that is, it has translucency, functions as a refractive index adjusting layer, and exhibits good electrical conductivity
  • the work function matching with the transparent conductive oxide film is improved, and ohmic contact can be achieved.
  • the TiO 2 is present in a molar ratio of 50% or more as a main component.
  • the overcoat layer only TiO 2
  • they tend to TiO 2 crystal grains increases, the outermost surface of the overcoat film of the TiO 2 crystals A sharp edge portion due to the shape of the grain is formed. Thereby, a defect is generated in the photoelectric conversion layer formed on the substrate.
  • tin oxide is present in the TiO 2 film, which is the main component of the overcoat film, the crystal grains of TiO 2 become small and a sharp edge portion is not formed on the outermost surface of the film. Thereby, the effect which reduces the defect in the photoelectric converting layer formed on a base
  • substrate can also be anticipated.
  • the Sn / (Sn + Ti) molar ratio in the overcoat film is 0.05 or more and less than 0.5. Is preferred. In addition, it is preferable that the Sn / (Sn + Ti) molar ratio in the overcoat film is 0.05 or more from the viewpoint of improving conductivity and securing good contact resistance.
  • the Sn / (Sn + Ti) molar ratio in the overcoat film is less than 0.05, the effect of developing conductivity by tin oxide is low, and the contact resistance between the overcoat film and the transparent conductive oxide film increases. Achieving ohmic contact becomes difficult.
  • the refractive index of the overcoat film will be low and the effect as a refractive index adjusting layer will be weak, and it may not be possible to obtain a good antireflection effect. Is not preferable.
  • the Sn / (Sn + Ti) molar ratio is 0.5 or more, the Sn ratio in the overcoat film increases, and tin oxide is unevenly present in the TiO 2 film, which is the main component of the overcoat film. This is not preferable.
  • the Sn / (Sn + Ti) molar ratio in the overcoat film is preferably 0.07 or more and 0.3 or less from the viewpoint of improving conductivity, ensuring good ohmic contact, and adjusting the refractive index.
  • the film thickness of the overcoat film is 10 nm or more and 100 nm or less, which suppresses deterioration of the transparent conductive oxide film due to heat or plasma impact during the formation of the photoelectric conversion layer. It is preferable to exhibit the function required for the overcoat film.
  • the film thickness of the overcoat film is preferably 10 nm or more and 100 nm or less, and more preferably 30 nm or more and 50 nm or less in order to exhibit the function as the refractive index adjustment layer.
  • the refractive index of the overcoat film is preferably 2.1 to 2.7 at a wavelength of 400 to 800 nm, and preferably 2.2 to 2.5. More preferred. As described above, the refractive index of the transparent conductive oxide film covered with the overcoat film is preferably 1.8 to 2.2 at a wavelength of 400 to 800 nm, and more preferably 1.9 to 2. 1 is preferred. On the other hand, when manufacturing a photoelectric conversion element using the substrate with a transparent conductive oxide film of the present invention, the refractive index of the photoelectric conversion element formed on the overcoat film depends on the structure and material of the photoelectric conversion element.
  • the wavelength is in the range of 2.8 to 4.5 at a wavelength of 400 to 800 nm. If the refractive index of the overcoat film is within the above range, the refractive index of the transparent conductive oxide film and the refractive index of the photoelectric conversion layer are within the upper and lower limits, respectively. In addition, the reflection of light caused by the difference in refractive index between the transparent conductive oxide film and the photoelectric conversion layer is suppressed, and the light introduction efficiency into the photoelectric conversion layer is improved.
  • Tin oxide, tin oxide having an oxygen deficiency (SnO (2-X), (where, X is 0.4 or less)), the and, SnO 2 doped with fluorine; of ( "SnO 2 F")
  • the overcoat film is preferably formed by an atmospheric pressure CVD method because the apparatus cost is low and the film formation speed is high.
  • the procedure for forming the overcoat film by the atmospheric pressure CVD method is the composition of the overcoat film to be formed, specifically, the kind of tin oxide (SnO (2-X) or “SnO” described above) contained in the overcoat film. 2 ; F ”).
  • an overcoat film is formed by the following procedure.
  • a tin-containing compound for example, an organic tin compound or an inorganic tin compound such as tin tetrachloride, monobutyltrichlorotin, dimethyldichlorotin, or tetramethyltin
  • a titanium-containing compound for example, an organic titanium compound or an inorganic titanium compound such as tetrachlorotitanium, titanium tetraisopropoxysite, titanium tetraethoxide, or titanium tetramethoxide
  • the main component is titanium oxide, and the proportion of the above range as tin oxide
  • An overcoat film containing SnO 2 (2-X) can be formed.
  • oxygen, water vapor, alcohols such as methanol, ethanol and isopropanol, and diols such as ⁇ -diketonate may be mixed in the tin raw material and titanium raw material as additives.
  • the tin raw material and the titanium raw material may be premixed before spraying, or may be mixed on a spraying base from separate nozzles.
  • the additives may be premixed with the tin raw material and the titanium raw material, or may be separately mixed on the sprayed substrate.
  • tin oxide As tin oxide; if containing "SnO 2 F", to form an overcoat film by the following procedure.
  • the raw material As the raw material, the same tin raw material and titanium raw material as described above in the case of containing SnO 2 (2-X) as tin oxide are vaporized.
  • a fluorine-containing compound for example, an inorganic fluorine compound such as hydrofluoric acid, trifluoroacetic acid, trifluoronitride, or fluorocarbons, or an organic fluorine compound
  • the vaporized fluorine-containing compound is mixed with the vaporized tin raw material and titanium raw material.
  • the overcoat film containing titanium oxide as the main component and tin oxide containing “SnO 2 ; F” by spraying onto the transparent conductive oxide film on the substrate heated to 450 ° C. or higher as before. Can be formed.
  • trifluoroacetic acid or hydrofluoric acid is preferably used as a fluorine raw material from the viewpoint of cost, and trifluoroacetic acid is used to control the fluorine doping amount. It is more preferable from the nature.
  • Example 1 A soda-lime glass substrate (300 mm ⁇ 300 mm ⁇ 3.9 mm) on which an antireflection film in which a TiO 2 film and a SiO 2 film are laminated is used as a substrate, and the reflection on the substrate is performed by atmospheric pressure CVD.
  • a fluorine-doped SnO 2 film was formed as a transparent conductive oxide film on the prevention film.
  • the procedure for forming the fluorine-doped SnO 2 film by the atmospheric pressure CVD method is as follows. A soda-lime glass substrate heated to 550 ° C.
  • an overcoat film containing titanium oxide as a main component and “SnO 2 ; F” as tin oxide is formed on the fluorine-doped SnO 2 film by an atmospheric pressure CVD method.
  • a substrate with a conductive oxide film was obtained.
  • the procedure for forming the overcoat film by the atmospheric pressure CVD method is as follows. Monobutyltrichlorotin was used as a tin raw material, and titanium tetraisopropoxysite was used as a titanium raw material, each was heated in a heating bubbling tank, and bubbling was performed using dry nitrogen, and a predetermined amount of the raw material was taken out as a vapor together with a bubbling gas.
  • trifluoroacetic acid is heated as a fluorine raw material in a heated bubbling tank, and dry nitrogen is used for bubbling to adjust the trifluoroacetic acid / titanium tetraisopropoxysite ratio to 0.2 in terms of molar ratio.
  • These source gases are mixed with oxygen gas and sprayed onto the surface of the substrate heated to 550 ° C. on which the fluorine-doped SnO 2 film is formed, so that titanium oxide is the main component on the fluorine-doped SnO 2 film, and tin oxide is used.
  • An overcoat film containing “SnO 2 ; F” was formed. About the formed overcoat film
  • the determination coefficient R 2 of the least square method is a value represented by the following equation with respect to (x i , y i ) where x is the voltage of measured data and y is the current.
  • y a is an average value of y i
  • f i is an estimated value of y with respect to x i obtained by the least square fitting formula.
  • the photoelectric conversion element was produced by forming a photoelectric converting layer and a back surface electrode layer with the following procedures.
  • a part of the substrate with a transparent conductive oxide film is cut out, and a pin type amorphous is formed thereon. A silicon film was formed.
  • the current-voltage curve (IV curve) of the produced photoelectric conversion element was measured, and from this, the short-circuit current (J SC ), open-circuit voltage (V oc ), fill factor (FF), and photoelectric conversion efficiency (E ff ) were measured. Calculated. The measurement was performed using a solar simulator (CE-24 type solar simulator manufactured by Opto Research). The irradiation light spectrum of the solar simulator at the time of IV measurement was AM (air mass) 1.5, and the light intensity was 100 (mW / cm 2 ). . The electrode of the photoelectric conversion element having an area of 6.25 mm 2 was used.
  • the photoelectric conversion element was prepared in the same procedure as described above for the evaluation standard sample in which the overcoat film was not formed. Carried out. J SC , V oc , FF, and E ff in the table below are ratios based on the numerical values of the evaluation reference samples. The results are shown in the table below.
  • Examples 2--7 The same procedure as in Example 1 was performed except that the thickness of the overcoat film and the Sn / (Sn + Ti) molar ratio were changed to the values shown in the following table.
  • the substrate with a transparent conductive oxide film of the present invention ohmic contact can be achieved at the interface between the transparent conductive oxide film and the overcoat film. A decrease in the factor (FF) can be suppressed, and good photoelectric conversion efficiency (E ff ) can be achieved.
  • the substrate with a transparent conductive oxide film of the present invention is useful as a conductive substrate for a thin film solar cell. It should be noted that the entire contents of the specification, claims and abstract of Japanese Patent Application No. 2011-136069 filed on June 20, 2011 are incorporated herein as the disclosure of the present invention.

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Abstract

In a base having a transparent conductive oxide film, wherein an overcoat film is provided on the transparent conductive oxide film, an ohmic contact is established at the interface between the transparent conductive oxide film and the overcoat film. A base having a transparent conductive oxide film, wherein a transparent conductive oxide film is formed on a base and an overcoat film is formed on the transparent conductive oxide film respectively by an atmospheric pressure CVD method. The base having a transparent conductive oxide film is characterized in that: the transparent conductive oxide film is composed of a fluorine-doped SnO2 film, which contains fluorine at a molar ratio of 0.0001-0.09 relative to the tin oxide (SnO2), in at least a portion that is in contact with the overcoat film; the overcoat film is mainly composed of titanium oxide (TiO2) and contains tin oxide; and the Sn/(Sn + Ti) molar ratio in the overcoat film is 0.05 or more but less than 0.5.

Description

透明導電性酸化物膜付き基体Substrate with transparent conductive oxide film
　本発明は、透明導電性酸化物膜付き基体に関する。本発明の透明導電性酸化物膜付き基体は、太陽電池のような光電変換素子用の透明導電性酸化物膜付き基体として好適である。 The present invention relates to a substrate with a transparent conductive oxide film. The substrate with a transparent conductive oxide film of the present invention is suitable as a substrate with a transparent conductive oxide film for a photoelectric conversion element such as a solar cell.
　光電変換素子である薄膜系太陽電池には光電変換層の種類によりアモルファスシリコン（ａ－Ｓｉ）系、多結晶シリコン系などがあるが、これらの薄膜シリコン系太陽電池では、その入射光側の透明電極層として透明導電性酸化物膜が使用される。この透明導電性酸化物膜は、光電変換効率を高めるために低抵抗・高透明であり、かつ光散乱性能が大きいことが要求される。特許文献１には、フッ素をＳｎＯ2に対して、０.０００１～０．０４（モル比）含み、導電電子密度が５×１０１９～４×１０２０ｃｍ-3であるフッ素ドープＳｎＯ2膜が記載されており、このフッ素ドープＳｎＯ2膜は、膜の吸収量が少なく高透明で、かつ活性水素種に対して高い耐久性があるとされている。 Thin film solar cells that are photoelectric conversion elements include amorphous silicon (a-Si) type and polycrystalline silicon type depending on the type of photoelectric conversion layer. In these thin film silicon type solar cells, the incident light side is transparent. A transparent conductive oxide film is used as the electrode layer. This transparent conductive oxide film is required to have low resistance and high transparency and high light scattering performance in order to increase photoelectric conversion efficiency. Patent Document 1 discloses a fluorine-doped SnO 2 film containing 0.0001 to 0.04 (molar ratio) of fluorine with respect to SnO 2 and having a conductive electron density of 5 × 10 19 to 4 × 10 20 cm −3. This fluorine-doped SnO 2 film is said to be highly transparent with little absorption of the film and high durability against active hydrogen species.
　薄膜系太陽電池は、ガラス基板等の基体上に、透明電極層、光電変換層、および、裏面電極がこの順に形成された構造を有する。
　薄膜系太陽電池では、透明電極層と、光電変換層と、の間で屈折率が異なることにより、透明電極層と光電変換層との界面で光が反射されてしまい（例えば、９％程度反射される。）、光電変換層内に導入される光量が減少し、その結果、短絡電流（ＪSC）が減少し光電変換効率（Ｅff）が低く抑えられるという問題があった。 A thin film solar cell has a structure in which a transparent electrode layer, a photoelectric conversion layer, and a back electrode are formed in this order on a substrate such as a glass substrate.
In a thin film solar cell, light is reflected at the interface between the transparent electrode layer and the photoelectric conversion layer due to the difference in refractive index between the transparent electrode layer and the photoelectric conversion layer (for example, about 9% reflection). ), The amount of light introduced into the photoelectric conversion layer is reduced, and as a result, the short-circuit current (J SC ) is reduced and the photoelectric conversion efficiency (E ff ) can be kept low.
　このような問題を解決するため、特許文献２では、透明電極層と、半導体層（光電変換層）と、の間に透光性を有し、その屈折率の値が、透明電極層および半導体層（光電変換層）の屈折率をそれぞれ上限及び下限とする範囲内にある屈折率調整層を設けることにより、透明電極層と半導体層（光電変換層）との屈折率の差に起因する光の反射を少なくし、半導体層（光電変換層）への光の導入が円滑に行われるようにしている。 In order to solve such a problem, in Patent Document 2, there is translucency between the transparent electrode layer and the semiconductor layer (photoelectric conversion layer), and the value of the refractive index thereof is the transparent electrode layer and the semiconductor. Light resulting from a difference in refractive index between the transparent electrode layer and the semiconductor layer (photoelectric conversion layer) by providing a refractive index adjustment layer within the range where the refractive index of the layer (photoelectric conversion layer) is an upper limit and a lower limit, respectively. Thus, the light is smoothly introduced into the semiconductor layer (photoelectric conversion layer).
　特許文献２では、屈折率調整層を、酸素欠陥を含む酸化チタンＴｉＯ（２－Ｘ）（但しＸは０．４以下）から成るものとすることにより、該屈折率調整層に導電性を付与している。また、屈折率調整層を構成する酸化チタンＴｉＯ２に酸素欠陥を持たせる代わりに、チタンと価数の異なる金属、例えばタンタル（Ｔａ）又はバリウム（Ｂａ）を２０％以下混合することによっても、酸素欠陥を持たせるのと同等の効果を発揮することができるとしている。 In Patent Document 2, the refractive index adjustment layer is made of titanium oxide TiO 2 (2-X) containing oxygen defects (where X is 0.4 or less), thereby imparting conductivity to the refractive index adjustment layer. is doing. Further, instead of giving oxygen defects to titanium oxide TiO 2 constituting the refractive index adjustment layer, by mixing 20% or less of titanium and a metal having a different valence, such as tantalum (Ta) or barium (Ba), It is said that the same effect as giving oxygen defects can be exhibited.
　また、透明電極層上に形成した酸化チタン系の膜は、水素プラズマに対し、酸化錫膜（ＳｎＯ2膜）よりも強い耐還元性を有するという特性により、光電変換層形成時における熱やプラズマ衝撃から、透明電極層である透明導電性酸化物膜を保護するための保護層としての機能も有することが知られている。 Further, films were formed on the transparent electrode layer of titanium oxide system is to hydrogen plasma, the property of having a strong reduction resistance than a tin oxide film (SnO 2 film), thermal or plasma during the photoelectric conversion layer formed It is also known to have a function as a protective layer for protecting the transparent conductive oxide film, which is a transparent electrode layer, from impact.
　透明導電性酸化物膜として、フッ素ドープＳｎＯ2膜を形成する場合、これらの膜の形成手段として常圧ＣＶＤ法が、装置コストが低いこと、成膜速度が速い等の理由から好ましく用いられる。
　屈折率調整層として、上述するような酸化チタン系の膜を形成する場合も、同様の理由から常圧ＣＶＤ法が好ましく用いられる。 When forming a fluorine-doped SnO 2 film as the transparent conductive oxide film, an atmospheric pressure CVD method is preferably used as a means for forming these films because the apparatus cost is low and the film formation speed is high.
Even when a titanium oxide film as described above is formed as the refractive index adjusting layer, the atmospheric pressure CVD method is preferably used for the same reason.
日本特開２００９－１３５０９６号公報Japanese Unexamined Patent Publication No. 2009-133506 日本特許第２９３９７８０号明細書Japanese Patent No. 2,939,780
　しかしながら、透明導電性酸化物膜として、フッ素ドープＳｎＯ2膜を形成し、該透明導電性酸化物膜上に、屈折率調整層あるいは保護層として、酸化チタン系の膜を形成した場合、半導体である透明導電性酸化物膜（フッ素ドープＳｎＯ2膜）と、酸化チタン系の膜と、の界面部分にショットキー障壁（Ｓｃｈｏｔｔｋｙ　ｂａｒｒｉｅｒ）が形成されて、オーミック接触（Ｏｈｏｍｉｃ　ｃｏｎｔａｃｔ）を達成できなくなることを見出した。透明導電性酸化物膜と酸化チタン系の膜との界面にオーミック接触が達成できなくなる部分があると、その界面での接触抵抗が上昇し、光電変換素子を作成した場合に、電池特性のうち、フィルファクター（ＦＦ）が低下し、光電変換効率（Ｅff）が低下する。
　更に酸化チタン系膜をＣＶＤ法で形成する場合、実用上の成膜速度を得るには基体温度４５０℃以上の高温で成膜する必要があるが、このような高温成膜条件では酸化チタンの酸化度のコントロールが難しく、安定した導電性酸化物膜が得にくいという問題がある。このような導電性能が良好でない透明導電性酸化物膜を用いて光電変換素子を作成した場合、高抵抗により電池特性の内、フィルファクター（ＦＦ：Ｆｉｌｌ　ｆａｃｔｏｒ）が低下し良好な光電変換効率（Ｅff）を達成することができない。 However, when a fluorine-doped SnO 2 film is formed as a transparent conductive oxide film, and a titanium oxide-based film is formed as a refractive index adjusting layer or a protective layer on the transparent conductive oxide film, A Schottky barrier is formed at the interface between a transparent conductive oxide film (fluorine-doped SnO 2 film) and a titanium oxide-based film, so that an ohmic contact cannot be achieved. I found. If there is a part where the ohmic contact cannot be achieved at the interface between the transparent conductive oxide film and the titanium oxide film, the contact resistance at the interface increases, and when a photoelectric conversion element is created, , The fill factor (FF) decreases, and the photoelectric conversion efficiency (E ff ) decreases.
Furthermore, when a titanium oxide film is formed by the CVD method, it is necessary to form the substrate at a high temperature of 450 ° C. or higher in order to obtain a practical film formation rate. There is a problem that it is difficult to control the degree of oxidation and it is difficult to obtain a stable conductive oxide film. When a photoelectric conversion element is formed using such a transparent conductive oxide film having poor conductivity, the fill factor (FF) of the battery characteristics is reduced due to high resistance, and the photoelectric conversion efficiency ( E ff ) cannot be achieved.
　上記した従来技術の問題点を解決するため、本発明は、透明導電性酸化物膜上にオーバーコート膜が形成された透明導電性酸化物膜付基体において、基体温度で４５０℃以上の高温成膜時でも安定した透明導電性酸化物膜を形成し、透明導電性酸化物膜と、オーバーコート膜と、の界面でオーミック接触を達成することにより、光電変換素子を作成した際のフィルファクター（ＦＦ）の低下を抑制し、良好な光電変換効率（Ｅff）を達成することを目的とする。 In order to solve the above-described problems of the prior art, the present invention provides a substrate with a transparent conductive oxide film in which an overcoat film is formed on a transparent conductive oxide film. Forming a stable transparent conductive oxide film even at the time of film formation, and achieving ohmic contact at the interface between the transparent conductive oxide film and the overcoat film, the fill factor when creating a photoelectric conversion element ( The object is to suppress the decrease in FF) and achieve good photoelectric conversion efficiency (E ff ).
　上記した目的を達成するため、本発明は、基体上に、透明導電性酸化物膜、および、オーバーコート膜がこの順に形成された透明導電性酸化物膜付基体であって、前記透明導電性酸化物膜は酸化スズ（ＳｎＯ2）を主成分とし、フッ素を含有し、前記透明導電性酸化物膜の少なくとも前記オーバーコート膜と接する界面のフッ素の比率が、フッ素を酸化スズ（ＳｎＯ2）に対して、０．０００１～０．０９（モル比）含み、前記オーバーコート膜が、酸化チタン（ＴｉＯ2）を主成分とし、酸化スズを含有し、前記オーバーコート膜中のＳｎ／（Ｓｎ＋Ｔｉ）モル比が０．０５以上０．５未満であることを特徴とする透明導電性酸化物膜付基体を提供する。
　本発明の透明導電性酸化物膜付基体において、前記オーバーコート膜中のＳｎ／（Ｓｎ＋Ｔｉ）モル比が、０．０７以上０．３以下であることが好ましい。 In order to achieve the above object, the present invention provides a substrate with a transparent conductive oxide film in which a transparent conductive oxide film and an overcoat film are formed in this order on a substrate, the transparent conductive oxide film The oxide film contains tin oxide (SnO 2 ) as a main component, contains fluorine, and the ratio of fluorine at the interface in contact with at least the overcoat film of the transparent conductive oxide film is such that fluorine is tin oxide (SnO 2 ). In contrast, the overcoat film contains 0.0001 to 0.09 (molar ratio), the overcoat film contains titanium oxide (TiO 2 ) as a main component, tin oxide, and Sn / (Sn + Ti in the overcoat film). ) A substrate with a transparent conductive oxide film, characterized in that the molar ratio is 0.05 or more and less than 0.5.
In the substrate with a transparent conductive oxide film of the present invention, the Sn / (Sn + Ti) molar ratio in the overcoat film is preferably 0.07 or more and 0.3 or less.
　本発明の透明導電性酸化物膜付基体において、前記オーバーコート膜の膜厚が１０ｎｍ以上１００ｎｍ以下であることが好ましい。
　本発明は、オーバーコート膜の膜厚は、３０ｎｍ以上５０ｎｍ以下が特に好ましい。
　本発明は、基体上に、酸化スズ（ＳｎＯ2）を主成分とし、フッ素を含有する透明導電性酸化物膜を形成するステップと、前記透明導電性酸化物膜上に、酸化チタン（ＴｉＯ2）を主成分とし、酸化スズを含有するオーバーコート膜を形成するステップとを、有する透明導電性酸化物膜付基体の製造方法であって、
　前記透明導電性酸化物膜を形成するステップは、前記透明導電性酸化物膜の少なくとも前記オーバーコート膜と接する層のフッ素の含有比率が、フッ素を酸化スズ（ＳｎＯ2）に対して、０．０００１～０．０９（モル比）となるように作製する工程を有し、
　前記オーバーコート膜を形成するステップは、前記オーバーコート膜中のＳｎ／（Ｓｎ＋Ｔｉ）モル比が０．０５以上０．５未満となるように作製する工程を有し、かつ前記オーバーコート膜は、常圧ＣＶＤにより、４５０℃以上に加熱された基体の前記透明導電性酸化物膜上に形成する工程を有することを特徴とする透明導電性酸化物膜付基体の製造方法を提供する。 In the substrate with a transparent conductive oxide film of the present invention, the overcoat film preferably has a thickness of 10 nm to 100 nm.
In the present invention, the thickness of the overcoat film is particularly preferably from 30 nm to 50 nm.
The present invention includes a step of forming a transparent conductive oxide film containing tin oxide (SnO 2 ) as a main component and containing fluorine on a substrate, and titanium oxide (TiO 2) on the transparent conductive oxide film. A step of forming an overcoat film containing tin oxide as a main component, and a method for producing a substrate with a transparent conductive oxide film,
In the step of forming the transparent conductive oxide film, the content ratio of fluorine in at least the layer in contact with the overcoat film of the transparent conductive oxide film is set to 0. 0 with respect to tin oxide (SnO 2 ). Having a step of manufacturing so as to be 0001 to 0.09 (molar ratio),
The step of forming the overcoat film includes a step of making the Sn / (Sn + Ti) molar ratio in the overcoat film to be 0.05 or more and less than 0.5, and the overcoat film includes: There is provided a method for producing a substrate with a transparent conductive oxide film, comprising a step of forming the substrate on the transparent conductive oxide film heated to 450 ° C. or higher by atmospheric pressure CVD.
　本発明の透明導電性酸化物膜付基体では、透明導電性酸化物膜と、オーバーコート膜との界面でオーミック接触を達成することができる。これにより、光電変換素子を作成した際のフィルファクター（ＦＦ）の低下を抑制し、良好な光電変換効率（Ｅff）を達成することができる。 In the substrate with a transparent conductive oxide film of the present invention, ohmic contact can be achieved at the interface between the transparent conductive oxide film and the overcoat film. Thereby, the fall of the fill factor (FF) at the time of producing a photoelectric conversion element can be suppressed, and favorable photoelectric conversion efficiency ( Eff ) can be achieved.
　また、本発明の透明導電性酸化物膜付基体では、透明導電性酸化物膜上にオーバーコート膜が形成されているため、該透明導電性酸化物膜付基体を用いて太陽電池のような光電変換素子を製造する場合に、光電変換層形成時における熱やプラズマ衝撃による透明導電性酸化物膜の劣化が抑制されると期待できる。
　また、オーバーコート膜の屈折率が、透明導電性酸化物膜の屈折率、および、光電変換層の屈折率をそれぞれ上限及び下限とする範囲内にあるため、屈折率調整層として機能し、透明導電性酸化物膜と、光電変換層と、の屈折率の差に起因する光の反射が抑制され、光電変換層への光の導入効率が向上していると期待できる。
　また、オーバーコート膜が波長４００～１０００ｎｍの領域における光線の吸収が少ないことも期待でき、光電変換層への光の導入効率の向上に寄与する。
　上記した数値範囲を示す「～」とは、その前後に記載された数値を下限値および上限値として含む意味で使用され、特段の定めがない限り、以下本明細書において「～」は、同様の意味をもって使用される。 Further, in the substrate with a transparent conductive oxide film of the present invention, an overcoat film is formed on the transparent conductive oxide film. When manufacturing a photoelectric conversion element, it can be expected that the deterioration of the transparent conductive oxide film due to heat and plasma impact during formation of the photoelectric conversion layer is suppressed.
In addition, since the refractive index of the overcoat film is within the range where the refractive index of the transparent conductive oxide film and the refractive index of the photoelectric conversion layer are the upper limit and the lower limit, respectively, it functions as a refractive index adjustment layer and is transparent. It can be expected that light reflection caused by the difference in refractive index between the conductive oxide film and the photoelectric conversion layer is suppressed, and the efficiency of introducing light into the photoelectric conversion layer is improved.
In addition, it can be expected that the overcoat film absorbs less light in the wavelength region of 400 to 1000 nm, which contributes to the improvement of light introduction efficiency into the photoelectric conversion layer.
The term “to” indicating the above numerical range is used in the sense that the numerical values described before and after it are used as the lower limit value and the upper limit value, and unless otherwise specified, “to” is the same hereinafter. Used with meaning.
　以下、本発明の一態様の明導電性酸化物膜付基体について説明する。 Hereinafter, the substrate with a bright conductive oxide film according to one embodiment of the present invention will be described.
　本発明の透明導電性酸化物膜付き基体は、基体上に、透明導電性酸化物膜、および、オーバーコート膜がこの順に形成された構造を有する。本発明の透明導電性酸化物膜付き基体の個々の構成について、以下に説明する。 The substrate with a transparent conductive oxide film of the present invention has a structure in which a transparent conductive oxide film and an overcoat film are formed in this order on the substrate. Each structure of the base | substrate with a transparent conductive oxide film of this invention is demonstrated below.
＜基体＞
　本発明の透明導電性酸化物膜付き基体に用いられる基体は、必ずしも平面で板状である必要はなく、曲面でも異型状でもよい。該基体としては、ガラス基体、セラミックス基体、プラスチック基体、金属基体などが挙げられる。該基体は透光性に優れた透明の基体であることが好ましく、ガラス基板であることが強度および耐熱性の点から好ましい。ガラス基板としては、無色透明なソーダライムシリケートガラス、アルミノシリケートガラス、ボレートガラス、リチウムアルミノシリケートガラス、石英ガラス、ホウ珪酸ガラス基板、無アルカリガラス基板、その他の各種ガラスからなる透明ガラス板を用いることができる。
　太陽電池のような光電変換素子用の基体に用いる場合、ガラス基板の厚さは０. ２～６. ０ｍｍであることが好ましい。この範囲であると、ガラス基板の強度が強く、透過率が高い。また基体は、３５０～８００ｎｍの波長領域において高い平均透過率、例えば８０％以上の透過率を有することが好ましい。また、十分絶縁性で、かつ化学的、物理的耐久性が高いことが望ましい。
　なお、ソーダライムシリケートガラスなどのナトリウムを含有するガラスからなるガラス基板、または低アルカリ含有ガラスからなるガラス基板の場合には、ガラス基板上に形成される透明導電性酸化物膜へのアルカリ成分の拡散を最小限にするために、酸化ケイ素膜、酸化アルミニウム膜、酸化ジルコニウム膜などのアルカリバリア層をガラス基板面に施してもよい。
　また、ガラス基板の表面に、ガラス基板の表面と、その上に設けられる層との屈折率の差異を軽減するための屈折率調整層をさらに有していてもよい。 <Substrate>
The substrate used for the substrate with a transparent conductive oxide film of the present invention is not necessarily flat and plate-like, and may be curved or atypical. Examples of the substrate include a glass substrate, a ceramic substrate, a plastic substrate, and a metal substrate. The substrate is preferably a transparent substrate excellent in translucency, and a glass substrate is preferable from the viewpoint of strength and heat resistance. As a glass substrate, use a transparent glass plate made of colorless and transparent soda lime silicate glass, aluminosilicate glass, borate glass, lithium aluminosilicate glass, quartz glass, borosilicate glass substrate, non-alkali glass substrate, and other various glasses. Can do.
When used for a substrate for a photoelectric conversion element such as a solar cell, the thickness of the glass substrate is preferably 0.2 to 6.0 mm. Within this range, the strength of the glass substrate is high and the transmittance is high. The substrate preferably has a high average transmittance in the wavelength region of 350 to 800 nm, for example, a transmittance of 80% or more. Moreover, it is desirable that it is sufficiently insulating and has high chemical and physical durability.
In addition, in the case of a glass substrate made of glass containing sodium such as soda lime silicate glass or a glass substrate made of low alkali-containing glass, the alkali component to the transparent conductive oxide film formed on the glass substrate In order to minimize diffusion, an alkali barrier layer such as a silicon oxide film, an aluminum oxide film, or a zirconium oxide film may be provided on the glass substrate surface.
Moreover, you may further have the refractive index adjustment layer for reducing the difference in the refractive index of the surface of a glass substrate, and the layer provided on it on the surface of a glass substrate.
　ソーダライムガラス基板上に形成するアルカリバリア層は、ＳｉＯ2膜や、ＳｉＯ2とＳｎＯ2との混合酸化物膜や、ＳｉＯ2膜と他の酸化物膜とを積層した多層膜などであり、その膜厚（多層膜の場合は合計膜厚）は２０～１００ｎｍであることが好ましい。膜厚がこの範囲であると、ガラス基板からの透過光の反射および吸収を制御することができる。多層膜の例としては、ソーダライムガラス基板上にＴｉＯ2膜とＳｉＯ2膜とを順次積層した膜が挙げられ、膜厚はそれぞれ１０～２０ｎｍ、１０～４０ｎｍであることが好ましい。特に、該アルカリバリア層の膜厚は、３０～６０ｎｍであることが好ましい。 The alkali barrier layer formed on the soda lime glass substrate is a SiO 2 film, a mixed oxide film of SiO 2 and SnO 2 , a multilayer film in which a SiO 2 film and another oxide film are laminated, etc. The film thickness (total film thickness in the case of a multilayer film) is preferably 20 to 100 nm. When the film thickness is within this range, reflection and absorption of transmitted light from the glass substrate can be controlled. Examples of the multilayer film include films in which a TiO 2 film and a SiO 2 film are sequentially laminated on a soda lime glass substrate, and the film thicknesses are preferably 10 to 20 nm and 10 to 40 nm, respectively. In particular, the thickness of the alkali barrier layer is preferably 30 to 60 nm.
＜透明導電性酸化物膜＞
　透明導電性酸化物膜は、少なくともオーバーコート膜と接する部分が、フッ素を酸化スズ（ＳｎＯ2）に対して、０．０００１～０．０９（モル比）含むフッ素ドープＳｎＯ2膜である。
　したがって、基体上に上記のフッ素ドープＳｎＯ2膜のみが形成された単層構造の透明導電性酸化物膜であってもよい。
　また、国際公開ＷＯ２００３／０３６６５７号や国際公開ＷＯ２０１０／０１６４６８号に記載されているような、基体上に複数の酸化物膜が積層した構造の透明導電性酸化物膜であってもよい。但し、この場合、オーバーコート膜と接する部分、つまり、最表層が、上記のフッ素ドープＳｎＯ2膜であることが求められる。 <Transparent conductive oxide film>
The transparent conductive oxide film is a fluorine-doped SnO 2 film in which at least a portion in contact with the overcoat film contains 0.0001 to 0.09 (molar ratio) of fluorine with respect to tin oxide (SnO 2 ).
Therefore, it may be a transparent conductive oxide film having a single layer structure in which only the fluorine-doped SnO 2 film is formed on the substrate.
Further, it may be a transparent conductive oxide film having a structure in which a plurality of oxide films are laminated on a substrate as described in International Publication WO2003 / 036657 and International Publication WO2010 / 016468. However, in this case, the portion in contact with the overcoat film, that is, the outermost layer is required to be the fluorine-doped SnO 2 film.
　上述した単層構造の透明導電性酸化物膜、および、積層構造の透明導電性酸化物膜のいずれにおいても、透明導電性酸化物膜を構成する酸化物膜（積層構造の透明導電性酸化物膜の場合は、積層構造を構成する全ての酸化物膜）は、可視光域で透明であることが求められる。透明導電性酸化物膜のうち、少なくともオーバーコート膜と接する層（単層構造の透明導電性酸化物膜の場合は透明導電性酸化物膜自体、積層された構造の透明導電性酸化物膜の場合は最表層）については、さらに導電性を有していることが求められる。
　透明導電性酸化物膜のうち、少なくともオーバーコート膜と接する層を、フッ素をＳｎＯ2に対して、フッ素を０．０００１～０．０９（モル比）含むフッ素ドープＳｎＯ2膜とすることにより、導電電子密度が向上し、太陽電池のような光電変換素子用の基体として好適な範囲となる。 In any of the above-described transparent conductive oxide film having a single layer structure and transparent conductive oxide film having a laminated structure, the oxide film constituting the transparent conductive oxide film (transparent conductive oxide having a laminated structure) In the case of a film, all oxide films constituting the laminated structure are required to be transparent in the visible light region. Of the transparent conductive oxide film, at least a layer in contact with the overcoat film (in the case of a transparent conductive oxide film having a single layer structure, the transparent conductive oxide film itself, or a transparent conductive oxide film having a laminated structure) In some cases, the outermost layer) is further required to have conductivity.
Of the transparent conductive oxide film, at least a layer in contact with the overcoat film is a fluorine-doped SnO 2 film containing 0.0001 to 0.09 (molar ratio) of fluorine with respect to SnO 2 of fluorine. The conductive electron density is improved, and the range is suitable as a substrate for a photoelectric conversion element such as a solar cell.
　なお、太陽電池のような光電変換素子用の基体の場合、透明導電性酸化物膜の導電電子密度が５×１０19～４×１０20ｃｍ-3の範囲であれば好ましく、１．５×１０20～３．０×１０20ｃｍ-3の範囲であればより好ましい。この範囲であれば、膜の光吸収量が少なく、高透明で、かつ活性水素種に対して高い耐久性があるので、本発明の透明導電性酸化物膜付基体に光電変換層を形成する際に一般に用いられる水素プラズマ照射によっても、透明性は損なわれない。 In the case of a substrate for a photoelectric conversion element such as a solar cell, it is preferable that the conductive electron density of the transparent conductive oxide film is in the range of 5 × 10 19 to 4 × 10 20 cm −3 , and 1.5 × A range of 10 20 to 3.0 × 10 20 cm −3 is more preferable. Within this range, the film absorbs less light, is highly transparent, and has high durability against active hydrogen species. Therefore, the photoelectric conversion layer is formed on the substrate with the transparent conductive oxide film of the present invention. Transparency is not impaired even by hydrogen plasma irradiation generally used.
　なお、可視光域で高透過であるためには、透明導電性酸化物膜を構成する酸化物膜（積層構造の透明導電性酸化物膜の場合、積層構造を構成する全ての酸化物膜）の屈折率は、波長４００～８００ｎｍにおいて、１．８～２．２であることが好ましく、さらに、１．９～２．１であるのが好ましい。 In order to achieve high transmission in the visible light region, an oxide film constituting a transparent conductive oxide film (in the case of a transparent conductive oxide film having a laminated structure, all oxide films constituting the laminated structure) The refractive index is preferably 1.8 to 2.2 at a wavelength of 400 to 800 nm, and more preferably 1.9 to 2.1.
　導電性に関して、透明導電性酸化物膜のシート抵抗が８～２０Ω／□であることが好ましく、より好ましくは８～１２Ω／□である。なお、上述した単層構造の透明導電性酸化物膜の場合、単層構造の透明導電性酸化物膜のシート抵抗が上記範囲を満たす。上述した積層構造の透明導電性酸化物膜の場合、積層構造の透明導電性酸化物膜全体のシート抵抗が上記範囲を満たす。 Regarding the conductivity, the sheet resistance of the transparent conductive oxide film is preferably 8 to 20Ω / □, and more preferably 8 to 12Ω / □. In the case of the transparent conductive oxide film having a single layer structure described above, the sheet resistance of the transparent conductive oxide film having a single layer structure satisfies the above range. In the case of the transparent conductive oxide film having the laminated structure described above, the sheet resistance of the entire transparent conductive oxide film having the laminated structure satisfies the above range.
　透明導電性酸化物膜が、上述した単層構造の透明導電性酸化物膜の場合、単層構造の透明導電性酸化物膜をなすフッ素ドープＳｎＯ2膜の膜厚が３００～２０００ｎｍであることが好ましく、４５０～１４５０ｎｍであることがより好ましく、６００～１０００ｎｍであることがさらに好ましい。
　一方、透明導電性酸化物膜が、上述した積層構造の透明導電性酸化物膜の場合、表層（基板から一番離れた層である）をなすフッ素ドープＳｎＯ2膜の膜厚が３００～１８００ｎｍであることが好ましく、４００～１０００ｎｍであることがより好ましく、４５０～９００ｎｍであることがさらに好ましい。積層構造全体としての膜厚が３５０～２０００ｎｍであることが好ましく、４５０～１４５０ｎｍであることがより好ましく、６００～１２００ｎｍであることがさらに好ましい。 When the transparent conductive oxide film is the above-described transparent conductive oxide film having a single layer structure, the thickness of the fluorine-doped SnO 2 film forming the transparent conductive oxide film having a single layer structure is 300 to 2000 nm. Is preferably 450 to 1450 nm, and more preferably 600 to 1000 nm.
On the other hand, when the transparent conductive oxide film is the above-described transparent conductive oxide film having a laminated structure, the film thickness of the fluorine-doped SnO 2 film forming the surface layer (the layer farthest from the substrate) is 300 to 1800 nm. It is preferably 400 to 1000 nm, more preferably 450 to 900 nm. The film thickness of the entire laminated structure is preferably 350 to 2000 nm, more preferably 450 to 1450 nm, and even more preferably 600 to 1200 nm.
　上述した単層構造の透明導電性酸化物膜、および、積層構造の透明導電性酸化物膜のいずれにおいても、透明導電性酸化物膜を構成する酸化物膜（積層構造の透明導電性酸化物膜の場合は、積層構造を構成する全ての酸化物膜）は、装置コストが低いこと、成膜速度が速い等の理由から常圧ＣＶＤ法により形成されることが好ましい。また、前記常圧ＣＶＤ法では、４５０℃以上の高温成膜時でも安定した導電性酸化物膜を形成することができる。
　常圧ＣＶＤ法により酸化物膜の形成手順は、形成する酸化物膜の組成や形状によって異なるが、上述した単層構造の透明導電性酸化物膜を形成する場合、つまり、基体上にフッ素ドープＳｎＯ2膜を形成する場合について、具体的な手順の一例を挙げると、基体（ガラス基板）を５４０℃に加熱し、四塩化錫、水、およびフッ化水素を同時に吹き付け、常圧ＣＶＤ法を実施することにより、フッ素ドープＳｎＯ2膜を基体上に形成することができる。 In any of the above-described transparent conductive oxide film having a single layer structure and transparent conductive oxide film having a laminated structure, the oxide film constituting the transparent conductive oxide film (transparent conductive oxide having a laminated structure) In the case of a film, all oxide films constituting the laminated structure are preferably formed by an atmospheric pressure CVD method because the apparatus cost is low and the film forming speed is high. In the atmospheric pressure CVD method, a stable conductive oxide film can be formed even at a high temperature of 450 ° C. or higher.
The procedure for forming an oxide film by the atmospheric pressure CVD method differs depending on the composition and shape of the oxide film to be formed. However, when forming the above-described single-layer transparent conductive oxide film, that is, fluorine doping on the substrate. for the case of forming a SnO 2 film, an example and a specific procedure, the substrate was heated to the (glass substrate) 540 ° C., tin tetrachloride, water and hydrogen fluoride sprayed simultaneously, atmospheric pressure CVD method By carrying out, a fluorine-doped SnO 2 film can be formed on the substrate.
＜オーバーコート膜＞
　オーバーコート膜は、酸化チタン（ＴｉＯ2）を主成分とし、酸化スズを含有するものであり、かつ、当該オーバーコート膜中のＳｎ／（Ｓｎ＋Ｔｉ）モル比が０．０５以上０．５未満である。
　本発明に於けるオーバーコート膜中のＳｎ／（Ｓｎ＋Ｔｉ）モル比は、例えば、以下の手順で求めることができる。
　走査型Ｘ線光電子分光装置（ＸＰＳ）（ＰＨＩ　４５００　ＶｅｒｓａＰｒｏｂｅ（製品名）、アルバック・ファイ株式会社製）を用いてビーム径を１００μｍとし、膜表面からＡｒスパッタリングを行いながら透明導電性酸化物膜（フッ素ドープＳｎＯ2膜）との界面まで組成分析を行い、その平均値を計算した値として求めることができる。 <Overcoat film>
The overcoat film is mainly composed of titanium oxide (TiO 2 ) and contains tin oxide, and the Sn / (Sn + Ti) molar ratio in the overcoat film is 0.05 or more and less than 0.5. is there.
The Sn / (Sn + Ti) molar ratio in the overcoat film in the present invention can be determined, for example, by the following procedure.
Using a scanning X-ray photoelectron spectrometer (XPS) (PHI 4500 VersaProbe (product name), ULVAC-PHI Co., Ltd.), the beam diameter is set to 100 μm, and a transparent conductive oxide film ( The composition analysis is performed up to the interface with the fluorine-doped SnO 2 film, and the average value can be obtained as a calculated value.
　特許文献２にも記載されているように、酸化チタン系の膜は透光性を有し、その屈折率の値が透明導電性酸化物膜および光電変換層の屈折率をそれぞれ上限及び下限とする範囲内とすることができるため、これらの間の屈折率の差を調整する屈折率調整層として機能する。
　また、酸化チタン系の膜は、酸化錫膜（ＳｎＯ2膜）と比較して水素プラズマに対する耐還元性が優れているという特性により、光電変換層形成時における熱やプラズマ衝撃から、透明電極層である透明導電性酸化物膜を保護するための保護層としての機能も有する。
　しかしながら、酸化チタン（ＴｉＯ2）は絶縁性であるため、特許文献２では、酸素欠陥を含む酸化チタンＴｉＯ（２－Ｘ）（但しＸは０．４以下）からなる膜、あるいは、酸化チタンＴｉＯ2にチタンと価数の異なる金属、例えばタンタルＴａ又はバリウムＢａを２０％以下混合した膜とすることで導電性を付与していた。 As described in Patent Document 2, the titanium oxide-based film has translucency, and the refractive index values thereof are the upper and lower limits of the refractive indexes of the transparent conductive oxide film and the photoelectric conversion layer, respectively. Therefore, it functions as a refractive index adjusting layer that adjusts the difference in refractive index between them.
In addition, the titanium oxide film is superior in reduction resistance against hydrogen plasma as compared with a tin oxide film (SnO 2 film). It also has a function as a protective layer for protecting the transparent conductive oxide film.
However, since titanium oxide (TiO 2 ) is insulative, Patent Document 2 discloses a film made of titanium oxide TiO 2 (2-X) containing oxygen defects (where X is 0.4 or less), or titanium oxide TiO 2. 2 titanium and a different valence metals, such as tantalum Ta or barium Ba was imparted conductivity by a film of a mixture of 20% or less.
　これらの酸化チタン系の膜と、フッ素ドープＳｎＯ2膜のような酸化錫（ＳｎＯ2）系の透明導電性酸化物膜と、は仕事関数のマッチングが適当ではないため、接触界面部分にショットキー障壁が形成されて、オーミック接触を達成できなくなるという問題がある。 These titanium oxide-based films and tin oxide (SnO 2 ) -based transparent conductive oxide films such as fluorine-doped SnO 2 films are not suitable for work function matching. There is a problem that a barrier is formed and ohmic contact cannot be achieved.
　本発明の透明導電性酸化物膜付基体では、オーバーコート膜を、酸化チタン（ＴｉＯ2）を主成分とし、酸化スズを含有するものとし、かつ、当該オーバーコート膜中のＳｎ／（Ｓｎ＋Ｔｉ）モル比が０．０５以上、好ましくは０．０５以上０．５未満であるものとすることにより、透明導電性酸化物膜との仕事関数のマッチングを改善し、オーミック接触を達成する。これにより、光電変換素子を作成した際のフィルファクター（ＦＦ）の低下を抑制し、良好な光電変換効率（Ｅff）を達成することができる。
　なお、酸化スズ自身は導電性を有するが、導電性の良い（すなわち、抵抗値の低い）酸化スズからなるものがより好ましい。
　また、オーバーコート膜は、透明導電性酸化物膜と同様の常圧ＣＶＤ法で形成することが好ましい。常圧ＣＶＤ法で形成することで、４５０℃以上の高温成膜時でも安定した導電性酸化物膜を形成することができる。 In the substrate with a transparent conductive oxide film of the present invention, the overcoat film is composed mainly of titanium oxide (TiO 2 ) and tin oxide, and Sn / (Sn + Ti) in the overcoat film By making the molar ratio 0.05 or more, preferably 0.05 or more and less than 0.5, the matching of the work function with the transparent conductive oxide film is improved and ohmic contact is achieved. Thereby, the fall of the fill factor (FF) at the time of producing a photoelectric conversion element can be suppressed, and favorable photoelectric conversion efficiency ( Eff ) can be achieved.
In addition, although tin oxide itself has electroconductivity, what consists of tin oxide with favorable electroconductivity (namely, resistance value is low) is more preferable.
The overcoat film is preferably formed by the atmospheric pressure CVD method similar to the transparent conductive oxide film. By forming by the atmospheric pressure CVD method, a stable conductive oxide film can be formed even at a high temperature of 450 ° C. or higher.
　本発明のオーバーコート膜における好ましい導電性の良い酸化スズの具体例の一つは、酸素欠陥を有する酸化スズ（ＳｎＯ（２－Ｘ））（但し、Ｘは０．４以下）である。ここで、Ｘの値を０．４以下、つまり、酸素欠陥の割合を２０％以下としたのは、オーバーコート膜での光の吸収が増大するのを抑制するためである。これにより、本発明の透明導電性酸化物膜付基体を用いて光電変換素子を作成した際に、光電変換層への光の入射量が確保される。 One specific example of tin oxide having good conductivity in the overcoat film of the present invention is tin oxide (SnO (2-X) ) having oxygen defects (where X is 0.4 or less). Here, the value of X is set to 0.4 or less, that is, the oxygen defect ratio is set to 20% or less in order to suppress an increase in light absorption in the overcoat film. Thereby, when a photoelectric conversion element is produced using the substrate with a transparent conductive oxide film of the present invention, the amount of light incident on the photoelectric conversion layer is ensured.
　本発明のオーバーコート膜における好ましい導電性の良い酸化スズの具体例の別の一つは、フッ素がドープされたＳｎＯ2（以下、フッ素がドープされたＳｎＯ2を「ＳｎＯ2；Ｆ」とも表記する。）である。但し、フッ素ドープ量は、オーバーコート成膜時の原料中のＦ／Ｔｉのモル比（原料中のモル比）で１．０未満である。ここで、フッ素ドープ量がオーバーコート成膜時の原料中のＦ／Ｔｉのモル比（原料中のモル比）で１．０以上であると、オーバーコート膜の形成時において、フッ素によるエッチング作用により透明導電性酸化物膜がダメージを受けるおそれがある。フッ素によるエッチング作用により透明導電性酸化物膜がダメージを受けると、透明導電性酸化物膜の導電性が劣化し、太陽電池のような光電変換素子を基体上に作製したときに光電変換効率（Ｅff）が低下するおそれがある。これは、フッ素によるエッチング作用が、透明導電性酸化物膜の酸化錫結晶の粒界部分に起こるため、結晶粒間の導電性が低下するためである。
　また、フッ素ドープ量がオーバーコート成膜時の原料中のＦ／Ｔｉのモル比で１．０以上であると、オーバーコート膜自体もフッ素によるエッチング作用を受け、その結果、オーバーコート膜の成膜速度が低下する、膜の緻密性が低下しオーバーコート膜の導電性が低下するといった問題が生じるおそれがある。
　フッ素ドープ量は、オーバーコート成膜時の原料中のＦ／Ｔｉのモル比で０．０００１～０．５であることが好ましく、０．００１～０．３であることがより好ましく、０．００１～０．２５であることがさらに好ましい。 One alternative embodiment of the preferred good conductivity tin oxide in the overcoat layer of the present invention, fluorine SnO 2 (hereinafter doped, fluorine SnO 2 which is doped; referred to as "SnO 2 F" ). However, the fluorine dope amount is less than 1.0 in terms of the molar ratio of F / Ti in the raw material during the overcoat film formation (molar ratio in the raw material). Here, when the fluorine doping amount is 1.0 or more in the molar ratio of F / Ti in the raw material at the time of overcoat film formation (molar ratio in the raw material), the etching action by fluorine during the formation of the overcoat film As a result, the transparent conductive oxide film may be damaged. When the transparent conductive oxide film is damaged by the etching action by fluorine, the conductivity of the transparent conductive oxide film is deteriorated, and the photoelectric conversion efficiency ( E ff ) may decrease. This is because the etching action by fluorine occurs at the grain boundary portion of the tin oxide crystal of the transparent conductive oxide film, so that the conductivity between crystal grains decreases.
In addition, when the fluorine doping amount is 1.0 or more in terms of the F / Ti molar ratio in the raw material during overcoat film formation, the overcoat film itself is also subjected to an etching action by fluorine, and as a result, the overcoat film is formed. There is a possibility that problems such as a decrease in film speed, a decrease in film density, and a decrease in conductivity of the overcoat film may occur.
The fluorine doping amount is preferably 0.0001 to 0.5, more preferably 0.001 to 0.3 in terms of F / Ti molar ratio in the raw material at the time of overcoat film formation. More preferably, it is 001 to 0.25.
　なお、酸化錫がＳｎＯ2；Ｆである場合、原料中に多量の酸素が混合されていても良好な導電性を得ることができる。このため、原料の希釈ガスに空気を用いることができ、低コスト成膜が可能となる。また、原料中に多量の酸素が入った条件で成膜すると膜中の炭素成分の含有量が少なくなり、透明性が向上する傾向があるので、透過率の向上面からも好ましい。 When tin oxide is SnO 2 ; F, good conductivity can be obtained even if a large amount of oxygen is mixed in the raw material. For this reason, air can be used for the dilution gas of a raw material, and low-cost film-forming can be performed. In addition, when a film is formed under a condition in which a large amount of oxygen is contained in the raw material, the carbon component content in the film is reduced and the transparency tends to be improved, which is preferable from the viewpoint of improving the transmittance.
　本発明におけるオーバーコート膜では、オーバーコート膜の主成分であるＴｉＯ2膜中に、酸化スズ（好ましい例として、ＳｎＯ２－Ｘ、あるいは、「ＳｎＯ2；Ｆ」）が存在することにより、上述したオーバーコート膜に要求される機能（すなわち、透光性を有し、屈折率調整層としての機能を発揮し、良好な電気導電性を示す）が好ましく発揮される。また、透明導電性酸化物膜との仕事関数のマッチングが改善され、オーミック接触を達成することができる。なお、ＴｉＯ2が主成分とはモル比で５０％以上存在することをさす。
　また、ＴｉＯ2のみでオーバーコート膜を形成した場合、オーバーコート膜中にＴｉＯ2のみが存在するため、ＴｉＯ2の結晶粒が大きくなる傾向があり、オーバーコート膜の最表面にＴｉＯ2の結晶粒の形状による鋭いエッジ部分が形成される。これにより、基体上に形成される光電変換層に欠陥を生じる。これに対し、オーバーコート膜の主成分であるＴｉＯ2膜中に、酸化スズが存在する場合、ＴｉＯ2の結晶粒は小さくなり、膜の最表面に鋭いエッジ部分が形成されなくなる。これにより、基体上に形成される光電変換層での欠陥を軽減する効果も期待できる。 In the overcoat film according to the present invention, tin oxide (preferably SnO 2 -X or “SnO 2 ; F”) is present in the TiO 2 film which is the main component of the overcoat film. The function required for the overcoat film (that is, it has translucency, functions as a refractive index adjusting layer, and exhibits good electrical conductivity) is preferably exhibited. In addition, the work function matching with the transparent conductive oxide film is improved, and ohmic contact can be achieved. Incidentally, refers to the TiO 2 is present in a molar ratio of 50% or more as a main component.
Also, when forming the overcoat layer only TiO 2, since only TiO 2 is present in the overcoat film, they tend to TiO 2 crystal grains increases, the outermost surface of the overcoat film of the TiO 2 crystals A sharp edge portion due to the shape of the grain is formed. Thereby, a defect is generated in the photoelectric conversion layer formed on the substrate. On the other hand, when tin oxide is present in the TiO 2 film, which is the main component of the overcoat film, the crystal grains of TiO 2 become small and a sharp edge portion is not formed on the outermost surface of the film. Thereby, the effect which reduces the defect in the photoelectric converting layer formed on a base | substrate can also be anticipated.
　上述した基体上に形成される光電変換層での欠陥を軽減する効果を発揮するためには、オーバーコート膜中のＳｎ／（Ｓｎ＋Ｔｉ）モル比が、０．０５以上０．５未満であることが好ましい。
　また、オーバーコート膜中のＳｎ／（Ｓｎ＋Ｔｉ）モル比が０．０５以上であることは、導電性の向上、良好な接触抵抗の確保の点でも好ましい。
　オーバーコート膜中のＳｎ／（Ｓｎ＋Ｔｉ）モル比が０．０５未満であると、酸化スズによる導電性発現効果が低く、オーバーコート膜と透明導電性酸化物膜との間の接触抵抗が大きくなり、オーミック接触の達成が困難になる。
　Ｓｎ／（Ｓｎ＋Ｔｉ）モル比が０．５以上であると、オーバーコート膜の屈折率が低くなり屈折率調整層としての効果が弱くなり、良好な反射防止効果を得ることができなくなるおそれがあり、好ましくない。また、Ｓｎ／（Ｓｎ＋Ｔｉ）モル比が０．５以上であると、オーバーコート膜中のＳｎの比率が高くなり、オーバーコート膜の主成分であるＴｉＯ2膜中に酸化スズが不均一に存在するおそれがあり、好ましくない。 In order to exhibit the effect of reducing defects in the photoelectric conversion layer formed on the substrate, the Sn / (Sn + Ti) molar ratio in the overcoat film is 0.05 or more and less than 0.5. Is preferred.
In addition, it is preferable that the Sn / (Sn + Ti) molar ratio in the overcoat film is 0.05 or more from the viewpoint of improving conductivity and securing good contact resistance.
When the Sn / (Sn + Ti) molar ratio in the overcoat film is less than 0.05, the effect of developing conductivity by tin oxide is low, and the contact resistance between the overcoat film and the transparent conductive oxide film increases. Achieving ohmic contact becomes difficult.
If the Sn / (Sn + Ti) molar ratio is 0.5 or more, the refractive index of the overcoat film will be low and the effect as a refractive index adjusting layer will be weak, and it may not be possible to obtain a good antireflection effect. Is not preferable. In addition, when the Sn / (Sn + Ti) molar ratio is 0.5 or more, the Sn ratio in the overcoat film increases, and tin oxide is unevenly present in the TiO 2 film, which is the main component of the overcoat film. This is not preferable.
　オーバーコート膜中のＳｎ／（Ｓｎ＋Ｔｉ）モル比は、０．０７以上０．３以下であることが、導電性の向上、良好なオーミック接触の確保および屈折率調整の両立の点から好ましい。 The Sn / (Sn + Ti) molar ratio in the overcoat film is preferably 0.07 or more and 0.3 or less from the viewpoint of improving conductivity, ensuring good ohmic contact, and adjusting the refractive index.
　本発明の透明導電性酸化物膜付基体において、オーバーコート膜の膜厚が１０ｎｍ以上１００ｎｍ以下であることが、光電変換層形成時における熱やプラズマ衝撃による透明導電性酸化物膜の劣化を抑制するという、オーバーコート膜に要求される機能を発揮するうえで好ましい。
　オーバーコート膜に要求される機能のうち、屈折率調整層としての機能を発揮するためには、オーバーコート膜の膜厚は、１０ｎｍ以上１００ｎｍ以下が好ましく、３０ｎｍ以上５０ｎｍ以下好ましい。 In the substrate with a transparent conductive oxide film of the present invention, the film thickness of the overcoat film is 10 nm or more and 100 nm or less, which suppresses deterioration of the transparent conductive oxide film due to heat or plasma impact during the formation of the photoelectric conversion layer. It is preferable to exhibit the function required for the overcoat film.
Of the functions required for the overcoat film, the film thickness of the overcoat film is preferably 10 nm or more and 100 nm or less, and more preferably 30 nm or more and 50 nm or less in order to exhibit the function as the refractive index adjustment layer.
　屈折率調整層としての機能を発揮するため、オーバーコート膜の屈折率は、波長４００～８００ｎｍにおいて、２．１～２．７であることが好ましく、２．２～２．５であることがより好ましい。
　上述したように、オーバーコート膜で被覆される透明導電性酸化物膜の屈折率は、波長４００～８００ｎｍにおいて、１.８～２.２であることが好ましく、さらに、１.９～２.１であるのが好ましい。
　一方、本発明の透明導電性酸化物膜付基体を用いて光電変換素子を製造する際に、オーバーコート膜上に形成される光電変換素子の屈折率は、光電変換素子の構造や材質によっても異なるが、いずれの場合においても、波長４００～８００ｎｍにおいて、２．８～４．５の範囲内である。
　オーバーコート膜の屈折率が上記の範囲であれば、透明導電性酸化物膜の屈折率および光電変換層の屈折率をそれぞれ上限および下限とする範囲内となるため、屈折率調整層として機能し、透明導電性酸化物膜と、光電変換層と、の屈折率の差に起因する光の反射を抑制し、光電変換層への光の導入効率が向上する。 In order to exhibit the function as a refractive index adjusting layer, the refractive index of the overcoat film is preferably 2.1 to 2.7 at a wavelength of 400 to 800 nm, and preferably 2.2 to 2.5. More preferred.
As described above, the refractive index of the transparent conductive oxide film covered with the overcoat film is preferably 1.8 to 2.2 at a wavelength of 400 to 800 nm, and more preferably 1.9 to 2. 1 is preferred.
On the other hand, when manufacturing a photoelectric conversion element using the substrate with a transparent conductive oxide film of the present invention, the refractive index of the photoelectric conversion element formed on the overcoat film depends on the structure and material of the photoelectric conversion element. Although different, in any case, the wavelength is in the range of 2.8 to 4.5 at a wavelength of 400 to 800 nm.
If the refractive index of the overcoat film is within the above range, the refractive index of the transparent conductive oxide film and the refractive index of the photoelectric conversion layer are within the upper and lower limits, respectively. In addition, the reflection of light caused by the difference in refractive index between the transparent conductive oxide film and the photoelectric conversion layer is suppressed, and the light introduction efficiency into the photoelectric conversion layer is improved.
　酸化スズが、酸素欠陥を有する酸化スズ（ＳｎＯ（２－Ｘ）、（但し、Ｘは０．４以下））の場合、および、フッ素がドープされたＳｎＯ2（「ＳｎＯ2；Ｆ」）の場合のいずれにおいても、オーバーコート膜は、装置コストが低いこと、成膜速度が速い等の理由から常圧ＣＶＤ法により形成されるのが好ましい。 Tin oxide, tin oxide having an oxygen deficiency (SnO (2-X), (where, X is 0.4 or less)), the and, SnO 2 doped with fluorine; of ( "SnO 2 F") In any case, the overcoat film is preferably formed by an atmospheric pressure CVD method because the apparatus cost is low and the film formation speed is high.
　常圧ＣＶＤ法によるオーバーコート膜の形成手順は、形成するオーバーコート膜の組成、具体的には、オーバーコート膜に含まれる前記した酸化スズの種類（ＳｎＯ（２－Ｘ）、または、「ＳｎＯ2；Ｆ」）によって異なる。 The procedure for forming the overcoat film by the atmospheric pressure CVD method is the composition of the overcoat film to be formed, specifically, the kind of tin oxide (SnO (2-X) or “SnO” described above) contained in the overcoat film. 2 ; F ”).
　酸化スズとして、前述したＳｎＯ（２－Ｘ）を含有する場合、以下の手順でオーバーコート膜を形成する。
　スズ原料としてスズを含有する化合物（例えば四塩化錫、モノブチルトリクロロスズ、ジメチルジクロロスズ、テトラメチルスズなどの有機スズ化合物または無機スズ化合物）をバブリング法または気化器を使い気化する。同様に、チタン原料としてチタンを含有する化合物（例えばテトラクロロチタン、チタンテトライソプロポキサイト、チタンテトラエトキサイト、チタンテトラメトキサイトなどの有機チタン化合物または無機チタン化合物）を気化する。これら気化したガスを混合し窒素ガスを搬送ガスとして、４５０℃以上に加熱した基体の上の透明導電性酸化物膜に吹き付けることにより、酸化チタンを主成分とし、酸化スズとして、上記範囲の割合で含有するＳｎＯ（２－Ｘ）を含有するオーバーコート膜を形成することができる。
　このときスズ原料、チタン原料中に酸素、水蒸気、メタノール、エタノール、イソプロパノールなどのアルコール類、βジケトネートなどのジオール類を添加物として混合しても良い。また、スズ原料、チタン原料は吹き付ける前に予備混合してもよく、別々のノズルから吹き付け基体上で混合しても良い。添加物についても、スズ原料、チタン原料に予備混合しても良く、別々に吹き付け基体上で混合しても良い。 When tin oxide (2-X) is contained as tin oxide, an overcoat film is formed by the following procedure.
A tin-containing compound (for example, an organic tin compound or an inorganic tin compound such as tin tetrachloride, monobutyltrichlorotin, dimethyldichlorotin, or tetramethyltin) is vaporized using a bubbling method or a vaporizer. Similarly, a titanium-containing compound (for example, an organic titanium compound or an inorganic titanium compound such as tetrachlorotitanium, titanium tetraisopropoxysite, titanium tetraethoxide, or titanium tetramethoxide) is vaporized. By mixing these vaporized gases and using nitrogen gas as a carrier gas and spraying it on the transparent conductive oxide film on the substrate heated to 450 ° C. or higher, the main component is titanium oxide, and the proportion of the above range as tin oxide An overcoat film containing SnO 2 (2-X) can be formed.
At this time, oxygen, water vapor, alcohols such as methanol, ethanol and isopropanol, and diols such as β-diketonate may be mixed in the tin raw material and titanium raw material as additives. Further, the tin raw material and the titanium raw material may be premixed before spraying, or may be mixed on a spraying base from separate nozzles. The additives may be premixed with the tin raw material and the titanium raw material, or may be separately mixed on the sprayed substrate.
　酸化スズとして、「ＳｎＯ2；Ｆ」を含有する場合、以下の手順でオーバーコート膜を形成する。
　原料としては、酸化スズとしてＳｎＯ（２－Ｘ）を含有する場合に説明した上述したものと同様のスズ原料、チタン原料を気化する。これらに加えて、フッ素原料としてフッ素を含有する化合物（例えばフッ酸、トリフルオロ酢酸、トリフルオロナイトライド、フルオロカーボン類などの無機フッ素化合物、または有機フッ素化合物）を気化する。この気化したフッ素を含有する化合物と前記した気化したスズ原料およびチタン原料と混合する。そして、先と同様に４５０℃以上に加熱した基体の上の透明導電性酸化物膜に吹き付けることにより、酸化チタンを主成分とし、酸化スズとして、「ＳｎＯ2；Ｆ」を含有するオーバーコート膜を形成することができる。 As tin oxide; if containing "SnO 2 F", to form an overcoat film by the following procedure.
As the raw material, the same tin raw material and titanium raw material as described above in the case of containing SnO 2 (2-X) as tin oxide are vaporized. In addition to these, a fluorine-containing compound (for example, an inorganic fluorine compound such as hydrofluoric acid, trifluoroacetic acid, trifluoronitride, or fluorocarbons, or an organic fluorine compound) is vaporized as a fluorine raw material. The vaporized fluorine-containing compound is mixed with the vaporized tin raw material and titanium raw material. The overcoat film containing titanium oxide as the main component and tin oxide containing “SnO 2 ; F” by spraying onto the transparent conductive oxide film on the substrate heated to 450 ° C. or higher as before. Can be formed.
　上記のいずれの場合においても、スズ原料、チタン原料として、有機化合物を用いると、成膜中の微粉発生を抑制することが可能であり、上述したオーバーコート膜を形成するうえで好ましい。
　また、スズ原料として、モノブチルトリクロロスズを用いることが、オーバーコート膜中のＳｎＯ2量を容易に制御できる点から好ましい。また、チタン原料として、チタンテトライソプロポキシサイトを用いることが気化のしやすさ、原料価格面、粉抑制面から好ましい。また、酸化スズとして、「ＳｎＯ2；Ｆ」を含有する場合は、フッ素原料として、トリフルオロ酢酸またはフッ酸を用いることが価格面から好ましく、トリフルオロ酢酸を用いることがフッ素のドープ量の制御性からより好ましい。 In any of the above cases, when an organic compound is used as the tin raw material and the titanium raw material, generation of fine powder during film formation can be suppressed, which is preferable in forming the above-described overcoat film.
Further, it is preferable to use monobutyltrichlorotin as a tin raw material from the viewpoint that the amount of SnO 2 in the overcoat film can be easily controlled. Moreover, it is preferable to use titanium tetraisopropoxysite as a titanium raw material from the viewpoint of easiness of vaporization, raw material price, and powder suppression. Further, when “SnO 2 ; F” is contained as tin oxide, trifluoroacetic acid or hydrofluoric acid is preferably used as a fluorine raw material from the viewpoint of cost, and trifluoroacetic acid is used to control the fluorine doping amount. It is more preferable from the nature.
　以下、実施例により本発明を詳述するが、本発明はこれらの実施例に限定されるものではない。
　実施例では以下に示す手順で透明導電性酸化物膜付き基体を作製し、オーバーコート膜の比抵抗、オーミック特性、および、該透明導電性酸化物膜付き基体を用いて作製した光電変換素子の光電変換特性を評価した。
　なお、以下に示す例１～７のうち、例１～５が実施例、例６～７が比較例である。 EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these Examples.
In the examples, a substrate with a transparent conductive oxide film was prepared according to the following procedure, and the specific resistance of the overcoat film, ohmic characteristics, and the photoelectric conversion element manufactured using the substrate with the transparent conductive oxide film Photoelectric conversion characteristics were evaluated.
Of Examples 1 to 7 shown below, Examples 1 to 5 are Examples, and Examples 6 to 7 are Comparative Examples.
（例１）
　基体として、ＴｉＯ2膜とＳｉＯ2膜とを積層した反射防止膜が形成されたソーダライムガラス基板（３００ｍｍ×３００ｍｍ×３．９ｍｍ）を使用し、常圧ＣＶＤ法によって、該基体上の前記反射防止膜上に透明導電性酸化物膜として、フッ素ドープＳｎＯ2膜を形成した。常圧ＣＶＤ法によるフッ素ドープＳｎＯ2膜の形成手順は以下の通りである。
　ソーダライムガラス基板を電気ヒーターで５５０℃まで昇温したものに、四塩化錫、水蒸気、およびフッ酸をノズルから吹き付け、膜厚７００ｎｍのフッ素ドープＳｎＯ2膜を形成した。
　形成したフッ素ドープＳｎＯ2膜について、シート抵抗を直流４探針法で測定したところ、シート抵抗は９Ω/□であった。また、フッ素ドープＳｎＯ2膜のフッ素比率を二次イオン質量分析計（ＳＩＭＳ）で測定したところ０．０６（モル比）であった。
　なお、後述する評価基準のサンプルは、上記の手順で基体上にフッ素ドープＳｎＯ2膜を形成したサンプルを評価した値である。 (Example 1)
A soda-lime glass substrate (300 mm × 300 mm × 3.9 mm) on which an antireflection film in which a TiO 2 film and a SiO 2 film are laminated is used as a substrate, and the reflection on the substrate is performed by atmospheric pressure CVD. A fluorine-doped SnO 2 film was formed as a transparent conductive oxide film on the prevention film. The procedure for forming the fluorine-doped SnO 2 film by the atmospheric pressure CVD method is as follows.
A soda-lime glass substrate heated to 550 ° C. with an electric heater was sprayed with tin tetrachloride, water vapor, and hydrofluoric acid from a nozzle to form a 700 nm-thick fluorine-doped SnO 2 film.
With respect to the formed fluorine-doped SnO 2 film, the sheet resistance was measured by a direct current four-probe method, and the sheet resistance was 9Ω / □. Was also fluorine-doped SnO 2 film of fluorine ratio was measured with a secondary ion mass spectrometer (SIMS) 0.06 (molar ratio).
Incidentally, the sample criteria which will be described later, a value obtained by evaluating the sample to form a fluorine-doped SnO 2 film on the substrate as described above.
　次に、常圧ＣＶＤ法によって、フッ素ドープＳｎＯ2膜上に、酸化チタンを主成分とし、酸化スズとして、「ＳｎＯ2；Ｆ」を含有するオーバーコート膜を形成して、本発明の透明導電性酸化物膜付基体を得た。
　常圧ＣＶＤ法によるオーバーコート膜の形成手順は以下の通りである。
　スズ原料としてモノブチルトリクロロスズを、チタン原料としてチタンテトライソプロポキサイトを用い、それぞれ加熱バブリングタンクで加熱し、乾燥窒素を用いてバブリングを行い、所定量の原料をバブリングガスと共に蒸気として取り出した。また、フッ素原料としてトリフルオロ酢酸を同様に加熱バブリングタンクで加熱し、乾燥窒素を用いてバブリングを行い、トリフルオロ酢酸／チタンテトライソプロポキサイトの比率がモル比で０．２となるように調整し供給した。これらの原料ガスを酸素ガスと混合し、５５０℃に加熱した基板のフッ素ドープＳｎＯ2膜が形成された面に吹き付けることにより、フッ素ドープＳｎＯ2膜上に酸化チタンを主成分とし、酸化スズとして、「ＳｎＯ2；Ｆ」を含有するオーバーコート膜を形成した。
　形成したオーバーコート膜について、膜中のＳｎ／（Ｓｎ＋Ｔｉ）モル比、膜厚、比抵抗、および、オーミック性を以下の手順で測定した。 Next, an overcoat film containing titanium oxide as a main component and “SnO 2 ; F” as tin oxide is formed on the fluorine-doped SnO 2 film by an atmospheric pressure CVD method. A substrate with a conductive oxide film was obtained.
The procedure for forming the overcoat film by the atmospheric pressure CVD method is as follows.
Monobutyltrichlorotin was used as a tin raw material, and titanium tetraisopropoxysite was used as a titanium raw material, each was heated in a heating bubbling tank, and bubbling was performed using dry nitrogen, and a predetermined amount of the raw material was taken out as a vapor together with a bubbling gas. Similarly, trifluoroacetic acid is heated as a fluorine raw material in a heated bubbling tank, and dry nitrogen is used for bubbling to adjust the trifluoroacetic acid / titanium tetraisopropoxysite ratio to 0.2 in terms of molar ratio. Supplied. These source gases are mixed with oxygen gas and sprayed onto the surface of the substrate heated to 550 ° C. on which the fluorine-doped SnO 2 film is formed, so that titanium oxide is the main component on the fluorine-doped SnO 2 film, and tin oxide is used. , An overcoat film containing “SnO 2 ; F” was formed.
About the formed overcoat film | membrane, Sn / (Sn + Ti) molar ratio, film thickness, specific resistance, and ohmic property in a film | membrane were measured in the following procedures.
［Ｓｎ／（Ｓｎ＋Ｔｉ）モル比］
　走査型Ｘ線光電子分光装置（ＸＰＳ）（ＰＨＩ　４５００　ＶｅｒｓａＰｒｏｂｅ（製品名）、アルバック・ファイ株式会社製）を用いてビーム径を１００μｍとし、オーバーコート膜の表面からＡｒスパッタリングを行いながらフッ素ドープＳｎＯ2膜との界面まで組成分析を行い、その平均値を計算した。 [Sn / (Sn + Ti) molar ratio]
Using a scanning X-ray photoelectron spectrometer (XPS) (PHI 4500 VersaProbe (product name), ULVAC-PHI Co., Ltd.), the beam diameter is set to 100 μm, and fluorine-doped SnO 2 while performing Ar sputtering from the surface of the overcoat film. The composition analysis was performed up to the interface with the film, and the average value was calculated.
［膜厚］
　オーバーコート膜の一部をエッチングし、フッ素ドープＳｎＯ2膜との段差を段差計（Ｖｅｅｃｏ社製　触針式表面形状測定器Ｄｅｋｔａｋ）で測定した。
　比抵抗：直流４探針法により測定した。 [Film thickness]
A part of the overcoat film was etched, and the level difference from the fluorine-doped SnO 2 film was measured with a level difference meter (stylus type surface shape measuring device Dektak manufactured by Veeco).
Specific resistance: Measured by a direct current 4-probe method.
［オーミック性］
　１ｃｍ角に試料を切断し、これをＡｃｃｅｎｔ　Ｏｐｔｉｃａｌ　Ｔｅｃｈｎｏｌｏｇｉｅｓ社製ホール効果測定器ＨＬ５４５０ＰＣ，ＨＬ５５８０ＰＣシステムにセットし、金メッキプローブを試料の４角に正確に接触させ、電圧値が－１Ｖから１Ｖの範囲で電流―電圧曲線を測定し、この曲線を最小２乗法を用いて直線近似した際の決定係数Ｒ2を求め、Ｒ2が０．９９以上であるとき良好なオーミック接触をしていると判断した。最小２乗法の決定係数Ｒ2とは、実測データの電圧をｘ、電流をｙとした時の（ｘi，ｙi)について、下記式で表わされる値である。
Figure JPOXMLDOC01-appb-M000001
 　上記式中、ｙaはｙiの平均値であり、ｆiは最小二乗フィット式で求めたｘiに対するｙの推算値である。 [Omic]
Cut the sample into 1 cm square, set it on the Hall Effect Measuring Instruments HL5450PC and HL5580PC systems manufactured by Accent Optical Technologies, and bring the gold plating probe into contact with the four corners of the sample accurately, with a voltage value in the range of -1V to 1V. A current-voltage curve was measured, and a determination coefficient R 2 was obtained when the curve was linearly approximated using the least square method. When R 2 was 0.99 or more, it was determined that a good ohmic contact was made. . The determination coefficient R 2 of the least square method is a value represented by the following equation with respect to (x i , y i ) where x is the voltage of measured data and y is the current.
Figure JPOXMLDOC01-appb-M000001
 In the above formula, y a is an average value of y i , and f i is an estimated value of y with respect to x i obtained by the least square fitting formula.
　上記の手順で得られた透明導電性酸化物膜付基体について、以下の手順で光電変換層および裏面電極層を形成することによって、光電変換素子を作製した。
［光電変換素子の作製］
　上記の手順で得られた透明導電性酸化物膜付基体を用いた光電変換素子の光電変換効率を調べるため、透明導電性酸化物膜付基体の一部を切り出し、その上にｐｉｎ型のアモルファスシリコン膜を形成した。ｐ層としてａ－ＳｉＣ：Ｂ層（２０ｎｍ）、ｉ層としてａ－Ｓｉ：Ｈ層（３５０ｎｍ）、ｎ層としてａ－Ｓｉ：Ｐ層（４０ｎｍ）を、それぞれＳｉＨ4／ＣＨ4／Ｈ2／Ｂ2Ｈ6、ＳｉＨ4／Ｈ2、及びＳｉＨ4／Ｈ2／ＰＨ3を原料として用いて、この順にプラズマＣＶＤ法により形成した。この後、ＧａをドープしたＺｎＯ層を２０ｎｍ形成した後、Ａｌ電極をスパッタリング法により形成することで光電変換素子を作製した。光電変換素子部分の大きさは５ｍｍ角である。
［光電変換素子の特性評価方法］
　作製した光電変換素子の電流－電圧曲線（ＩＶカーブ）を測定し、これより短絡電流（ＪSC）、開放電圧（Ｖoc）、フィルファクター（ＦＦ）、および、光電変換効率（Ｅff）を計算した。測定はソーラーシュミレータ（オプトリサーチ社製ＣＥ－２４型ソーラーシュミレータ）を用い、ＩＶ測定時におけるソーラーシミュレータの照射光スペクトルをＡＭ（エアマス）１．５、光強度を１００（ｍＷ／ｃｍ2）とした。また、光電変換素子の電極には面積が６．２５ｍｍ2のものを用いた。
　また、上記の手順で基体上にフッ素ドープＳｎＯ2膜を形成した後、オーバーコート膜を形成しなかった評価基準のサンプルについても、上記と同様の手順で光電変化素子を作製し、特性評価を実施した。下記表におけるＪSC、Ｖoc、ＦＦ、および、Ｅffは評価基準サンプルの数値を基準した比である。
　結果を下記表に示す。 About the base | substrate with a transparent conductive oxide film obtained by said procedure, the photoelectric conversion element was produced by forming a photoelectric converting layer and a back surface electrode layer with the following procedures.
[Production of photoelectric conversion element]
In order to investigate the photoelectric conversion efficiency of the photoelectric conversion element using the substrate with a transparent conductive oxide film obtained by the above procedure, a part of the substrate with a transparent conductive oxide film is cut out, and a pin type amorphous is formed thereon. A silicon film was formed. An a-SiC: B layer (20 nm) as the p layer, an a-Si: H layer (350 nm) as the i layer, and an a-Si: P layer (40 nm) as the n layer, SiH 4 / CH 4 / H 2 / B 2 H 6 , SiH 4 / H 2 , and SiH 4 / H 2 / PH 3 were used as raw materials and were formed in this order by plasma CVD. Thereafter, a ZnO layer doped with Ga was formed to a thickness of 20 nm, and then an Al electrode was formed by a sputtering method to produce a photoelectric conversion element. The size of the photoelectric conversion element portion is 5 mm square.
[Method for evaluating characteristics of photoelectric conversion element]
The current-voltage curve (IV curve) of the produced photoelectric conversion element was measured, and from this, the short-circuit current (J SC ), open-circuit voltage (V oc ), fill factor (FF), and photoelectric conversion efficiency (E ff ) were measured. Calculated. The measurement was performed using a solar simulator (CE-24 type solar simulator manufactured by Opto Research). The irradiation light spectrum of the solar simulator at the time of IV measurement was AM (air mass) 1.5, and the light intensity was 100 (mW / cm 2 ). . The electrode of the photoelectric conversion element having an area of 6.25 mm 2 was used.
In addition, after forming the fluorine-doped SnO 2 film on the substrate according to the above procedure, the photoelectric conversion element was prepared in the same procedure as described above for the evaluation standard sample in which the overcoat film was not formed. Carried out. J SC , V oc , FF, and E ff in the table below are ratios based on the numerical values of the evaluation reference samples.
The results are shown in the table below.
（例２～７）
　オーバーコート膜の膜厚およびＳｎ／（Ｓｎ＋Ｔｉ）モル比を下記表に示す数値に変えた以外は、例１と同様の手順を実施した。 (Examples 2-7)
The same procedure as in Example 1 was performed except that the thickness of the overcoat film and the Sn / (Sn + Ti) molar ratio were changed to the values shown in the following table.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　表から明らかなように、膜中のＳｎ／（Ｓｎ＋Ｔｉ）モル比が０．０５以上の場合、良好なオーミック性が得られた。また、膜中のＳｎ／（Ｓｎ＋Ｔｉ）モル比が０．０５以上の組成のオーバーコート膜を形成した場合、膜中のＳｎ／（Ｓｎ＋Ｔｉ）モル比が０．０５未満の例６，７に比較して、光電変換素子のＦＦが同程度か、高い値となっており、オーバーコート膜の形成によるＪSCの増加分がそのまま光電変換効率（Ｅff）の向上につながっている。
　また、例６，７からわかるようにＳｎ／（Ｓｎ＋Ｔｉ）モル比が０．０５より低い場合、良好なオーミック性が得られなかった。また、オーバーコート膜を形成しなかった場合に比較して光電変換素子のＦＦが大きく低下し、ＪSCは向上するものの光電変換効率（Ｅff）は低下傾向であることがわかる。 As is clear from the table, when the Sn / (Sn + Ti) molar ratio in the film was 0.05 or more, good ohmic properties were obtained. Further, when an overcoat film having a composition of Sn / (Sn + Ti) molar ratio in the film of 0.05 or more is formed, it is compared with Examples 6 and 7 in which the Sn / (Sn + Ti) molar ratio in the film is less than 0.05. Thus, the FF of the photoelectric conversion element is similar or high, and the increase in J SC due to the formation of the overcoat film directly leads to the improvement of the photoelectric conversion efficiency (E ff ).
As can be seen from Examples 6 and 7, when the Sn / (Sn + Ti) molar ratio was lower than 0.05, good ohmic properties could not be obtained. Also, FF of the photoelectric conversion element is greatly reduced as compared with the case of not forming the overcoat film, J SC is a photoelectric conversion efficiency of which is improved (E ff) is found to be on the decline.
　本発明の透明導電性酸化物膜付基体よれば、透明導電性酸化物膜と、オーバーコート膜との界面でオーミック接触を達成することができ、これにより、光電変換素子を作成した際のフィルファクター（ＦＦ）の低下を抑制し、良好な光電変換効率（Ｅff）を達成することができる。本発明の透明導電性酸化物膜付基体は、薄膜系太陽電池用の導電性基板として有用である。
　なお、２０１１年６月２０日に出願された日本特許出願２０１１－１３６０６９号の明細書、特許請求の範囲および要約書の全内容をここに引用し、本発明の開示として取り入れるものである。 According to the substrate with a transparent conductive oxide film of the present invention, ohmic contact can be achieved at the interface between the transparent conductive oxide film and the overcoat film. A decrease in the factor (FF) can be suppressed, and good photoelectric conversion efficiency (E ff ) can be achieved. The substrate with a transparent conductive oxide film of the present invention is useful as a conductive substrate for a thin film solar cell.
It should be noted that the entire contents of the specification, claims and abstract of Japanese Patent Application No. 2011-136069 filed on June 20, 2011 are incorporated herein as the disclosure of the present invention.

Claims (7)

  1. 　基体上に、透明導電性酸化物膜、および、オーバーコート膜がこの順に形成された透明導電性酸化物膜付基体であって、
    　前記透明導電性酸化物膜は酸化スズ（ＳｎＯ2）を主成分であり、フッ素を含有し、
    　前記酸化スズは、少なくとも１層以上の層からなり、前記透明導電性酸化物膜の少なくとも前記オーバーコート膜と接する層のフッ素の含有比率が、フッ素を酸化スズ（ＳｎＯ2）に対して、０．０００１～０．０９（モル比）であり、
    　前記オーバーコート膜が、酸化チタン（ＴｉＯ2）を主成分とし、酸化スズを含有し、前記オーバーコート膜中のＳｎ／（Ｓｎ＋Ｔｉ）モル比が０．０５以上０．５未満であることを特徴とする透明導電性酸化物膜付基体。     A transparent conductive oxide film and a substrate with a transparent conductive oxide film in which an overcoat film is formed in this order on a substrate,
    The transparent conductive oxide film is mainly composed of tin oxide (SnO 2 ), contains fluorine,
    The tin oxide is composed of at least one layer, and the content ratio of fluorine in at least the layer in contact with the overcoat film of the transparent conductive oxide film is 0 with respect to tin oxide (SnO 2 ). 0.0001 to 0.09 (molar ratio),
    The overcoat film is mainly composed of titanium oxide (TiO 2 ), contains tin oxide, and the Sn / (Sn + Ti) molar ratio in the overcoat film is 0.05 or more and less than 0.5. A substrate with a transparent conductive oxide film.
  2. 　前記オーバーコート膜中のＳｎ／（Ｓｎ＋Ｔｉ）モル比が０．０７以上０．３以下である、請求項１に記載の透明導電性酸化物膜付基体。 2. The substrate with a transparent conductive oxide film according to claim 1, wherein a Sn / (Sn + Ti) molar ratio in the overcoat film is 0.07 or more and 0.3 or less.
  3. 　前記オーバーコート膜の膜厚が１０ｎｍ以上１００ｎｍ以下である請求項１又は２に記載の透明導電性酸化物膜付基体。 The substrate with a transparent conductive oxide film according to claim 1 or 2, wherein the overcoat film has a thickness of 10 nm to 100 nm.
  4. 　前記オーバーコート膜の膜厚が３０ｎｍ以上５０ｎｍ以下である請求項１～３のいずれか１項に記載の透明導電性酸化物膜付基体。 The substrate with a transparent conductive oxide film according to any one of claims 1 to 3, wherein the overcoat film has a thickness of 30 nm to 50 nm.
  5. 　前記オーバーコート膜に含有される酸化スズは、ＳｎＯ（２－Ｘ）（但し、Ｘは０．４以下）である請求項１～３のいずれか１項に記載の透明導電性酸化物膜付基体。 Tin oxide contained in the overcoat film, SnO (2-X) (where, X is 0.4 or less) transparent conductive oxide with membrane according to any one of claims 1 to 3, which is Substrate.
  6. 　請求項１～５のいずれか１項に記載の透明導電性酸化物膜付基体を用いた太陽電池。 A solar cell using the substrate with a transparent conductive oxide film according to any one of claims 1 to 5.
  7. 　基体上に、酸化スズ（ＳｎＯ2）を主成分とし、フッ素を含有する透明導電性酸化物膜を形成するステップと、前記透明導電性酸化物膜上に、酸化チタン（ＴｉＯ2）を主成分とし、酸化スズを含有するオーバーコート膜を形成するステップとを、有する透明導電性酸化物膜付基体の製造方法であって、
    　前記透明導電性酸化物膜を形成するステップは、前記透明導電性酸化物膜の少なくとも前記オーバーコート膜と接する層のフッ素の含有比率が、フッ素を酸化スズ（ＳｎＯ2）に対して、０．０００１～０．０９（モル比）となるように作製する工程を有し、
    　前記オーバーコート膜を形成するステップは、前記オーバーコート膜中のＳｎ／（Ｓｎ＋Ｔｉ）モル比が０．０５以上０．５未満となるように作製する工程を有し、かつ前記オーバーコート膜は、常圧ＣＶＤにより、４５０℃以上に加熱された基体の前記透明導電性酸化物膜上に形成する工程を有することを特徴とする透明導電性酸化物膜付基体の製造方法。     Forming a transparent conductive oxide film containing tin oxide (SnO 2 ) as a main component on a substrate and containing fluorine; and titanium oxide (TiO 2 ) as a main component on the transparent conductive oxide film. And forming an overcoat film containing tin oxide, and a method for producing a substrate with a transparent conductive oxide film,
    In the step of forming the transparent conductive oxide film, the content ratio of fluorine in at least the layer in contact with the overcoat film of the transparent conductive oxide film is set to 0. 0 with respect to tin oxide (SnO 2 ). Having a step of manufacturing so as to be 0001 to 0.09 (molar ratio),
    The step of forming the overcoat film includes a step of making the Sn / (Sn + Ti) molar ratio in the overcoat film to be 0.05 or more and less than 0.5, and the overcoat film includes: A method for producing a substrate with a transparent conductive oxide film, comprising a step of forming the substrate on the transparent conductive oxide film of the substrate heated to 450 ° C. or higher by atmospheric pressure CVD.
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