JP5225570B2 - Electrode substrate manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing of an electrode substrate used for a photoelectric conversion element having a permeable transparent conductive substrate.

  With the development of thin film formation technology, it is known that a new function can be added by coating only the surface of a certain material with a thin film of a different material. As an example, a resin film that is lightweight by laminating a film on an optical component such as a lens and adding an antireflection function, or laminating a thin film with a high gas barrier property on a resin substrate with a low gas barrier property A technique for adding a gas barrier function while having the above characteristics is known.

  In addition, thin film formation techniques are used for various applications such as the production of transparent electrodes in the production of electronic devices such as liquid crystal displays (LCDs) and the formation of light emitter layers in the production of light-emitting diodes. Known thin film forming techniques include sputtering, vacuum deposition, ion plating, CVD, and spray pyrolysis.

  In general, it is known that in order to form a high-quality film with high crystallinity, it is better to perform film formation at a higher temperature than at a low temperature, or heat treatment at a high temperature after film formation, For example, a typical indium-tin oxide film as a transparent conductive film is formed at about 250 ° C. (see, for example, Patent Document 1).

  In particular, in applications where transparency is required, glass is often used as a base material, but application to resin base materials such as plastics is required because of demands for weight reduction and the like. However, since resin base materials such as plastics have low heat resistance and are not suitable for film formation at high temperatures, a method for improving the crystallinity at low temperatures and forming a low resistance film has been devised (for example, , Patent Document 2 and Patent Document 3).

However, when a thin film with a smaller coefficient of thermal expansion is formed on a substrate with a large coefficient of thermal expansion, such as a plastic substrate, there is a problem with the heat resistance of the film after film formation due to the difference in coefficient of thermal expansion between the substrate and the film Will occur. Specifically, since the expansion of the base material due to heat is larger than that of the film, tensile stress acts on the film to cause damage such as cracks, resulting in various deteriorations in characteristics. For example, in the case of a laminate in which a transparent conductive film is formed on a glass substrate, the thermal expansion coefficient of the film and the base material is almost the same. When a film was formed on a plastic substrate having a higher coefficient, the transparent conductive film could not follow the thermal expansion of the base material, causing cracks, resulting in an increase in resistance, which is an important characteristic.
JP 2003-323818 A JP 2005-56771 A JP 1999-279756 A

The present invention has been proposed in view of such a conventional situation, and is not limited to the difference in thermal expansion coefficient between the transparent conductive film and the substrate, and damage such as cracks in the transparent conductive film caused by any deformation. The first object is to provide a method for producing a transparent conductive substrate that is suppressed and excellent in heat resistance, chemical resistance, press resistance and the like.
Further, the present invention is an electrode substrate for a photoelectric conversion element using a transparent conductive substrate, which is not limited to the difference in thermal expansion coefficient between the transparent conductive film and the base material, and cracks in the transparent conductive film, etc. It is a second object of the present invention to provide a method for producing an electrode substrate used for a photoelectric conversion element having a transparent conductive substrate that is excellent in heat resistance, chemical resistance, press resistance and the like.

The method for producing an electrode substrate according to claim 1 of the present invention comprises a first electrode substrate having a porous oxide semiconductor layer carrying a sensitizing dye and functioning as a window electrode, and at least a part of the electrolyte layer. A second electrode substrate disposed opposite to the first electrode substrate, wherein at least one of the first electrode substrate and the second electrode substrate includes a base material made of resin and one surface of the base material A method for producing an electrode substrate used in a photoelectric conversion element having a transparent conductive substrate in which a transparent conductive film made of a metal oxide is disposed on the substrate, wherein the substrate is heated and expanded, Maintaining the stretched state, forming the transparent conductive film on one surface of the substrate while maintaining the stretched state, releasing the stretched state, and applying compressive stress to the transparent conductive film; The surface of the transparent conductive film has a porous oxide semi-conductor. A step of applying a paste containing a body, and a step of firing the paste, wherein the stretch ratio of the base material in the stretched state is 0.08% or more and 1% or less in at least one direction. And the temperature of the substrate in the heating is 100 ° C. or more and the softening point temperature of the substrate or less .

  In the present invention, when a transparent conductive film is formed on a base material having a coefficient of thermal expansion greatly different from that of a transparent conductive film, such as a resin base material, the base material is expanded by a method such as heating. By applying compressive stress after the film formation, the transparent conductive film can follow the expansion of the base material. Thereby, not only the difference in the thermal expansion coefficient of a transparent conductive film and a base material but damage, such as a crack of a transparent conductive film resulting from every deformation | transformation, can be suppressed. As a result, a method for producing a transparent conductive substrate excellent in heat resistance, chemical resistance, press resistance and the like can be provided.

  Further, in the present invention, when forming a transparent conductive film on a substrate made of resin, the substrate is expanded by a method such as heating, and a compressive stress is applied after the film formation, thereby expanding the substrate. The transparent conductive film can follow. Thereby, not only the difference in the thermal expansion coefficient of a transparent conductive film and a base material but damage, such as a crack of a transparent conductive film resulting from every deformation | transformation, can be suppressed. As a result, the manufacturing method of the electrode substrate used for the photoelectric conversion element which has a transparent conductive substrate excellent in heat resistance, chemical resistance, press resistance, etc. can be provided. The photoelectric conversion element using such an electrode substrate can suppress the characteristic deterioration (for example, a photoelectric conversion characteristic fall etc.) resulting from the said mechanical characteristic fall, and, as a result, was excellent in durability It becomes.

  Hereinafter, an embodiment of a transparent conductive substrate and a photoelectric conversion element according to the present invention will be described with reference to the drawings.

FIG. 1 is a schematic cross-sectional view showing an embodiment of a transparent conductive substrate according to the present invention.
The transparent conductive substrate 10 is generally composed of a transparent base material 11 and a transparent conductive film 12 formed on one surface 11a thereof.

  As the transparent base material 11, a substrate made of a light-transmitting resin is used, and any material such as polyethylene terephthalate, polycarbonate, polyethersulfone, etc., which is usually used as a transparent base material for photoelectric conversion elements, can be used. Can do. The transparent substrate 11 is appropriately selected from these in consideration of resistance to the electrolytic solution. Moreover, as a transparent base material 11, the board | substrate which is excellent in the light transmittance as much as possible is preferable on a use, and the board | substrate whose transmittance | permeability is 90% or more is more preferable.

The transparent conductive film 12 is a thin film formed on one surface 11a in order to impart conductivity to the transparent substrate 11. In the present invention, the transparent conductive film 12 is preferably a thin film made of a conductive metal oxide in order to obtain a structure that does not significantly impair the transparency of the transparent conductive substrate.
Examples of the conductive metal oxide that forms the transparent conductive film 12 include tin-added indium oxide (ITO), fluorine-added tin oxide (FTO), and tin oxide (SnO ₂ ). Among these, ITO and FTO are preferable from the viewpoint of having both high transparency and low resistance.

  Further, as the transparent conductive film 12, a single layer film made only of ITO, a laminated film in which a film made of ITO is laminated on a film made of ITO, or a film made of FTO is laminated on a film made of ITO. The laminated film is a preferable configuration. By adopting such a configuration, it is possible to configure a transparent conductive substrate with a small amount of light absorption in the visible range and a low resistance.

Next, the manufacturing method of the transparent conductive substrate of this embodiment is demonstrated.
A transparent conductive film 12 made of a metal oxide is formed so as to cover one surface 11a of the transparent base material 11 made of resin, and the transparent conductive substrate 10 is produced.
At this time, in the present invention, the step of holding the transparent substrate 11 in the stretched state, the step of forming the transparent conductive film 12 on one surface of the transparent substrate 11 while maintaining the stretched state, and the stretching state are released. And applying a compressive stress to the transparent conductive film 12.

  When forming the transparent conductive film 12 having a smaller thermal expansion coefficient on the transparent base material 11 made of a material having a large thermal expansion coefficient such as a resin, the film is formed in a state in which the transparent base material 11 is previously stretched. Thus, even if the base material expands due to temperature or the like after film formation, the transparent conductive film 12 can follow the thermal expansion of the transparent base material 11, and damage to the transparent conductive film 12 can be suppressed. Thereby, the heat resistance of the transparent conductive film 12 and the transparent conductive substrate 10 can be improved.

The degree to which the transparent substrate 11 is stretched in advance is preferably the same as or higher than the degree to which it is expanded or stretched by heating or the like in a post-process or use environment. Even if it is less than that, the effect can be obtained, but the degree is small.
Specifically, the stretching ratio of the transparent substrate 11 in the stretched state is preferably 0.08% or more and 1% or less with respect to at least one direction. By setting the stretching ratio of the transparent substrate 11 to 0.08% or more, mechanical strength such as press resistance can be improved. On the other hand, if the film is stretched too much, warping occurs when it is released. Therefore, it is preferably about 0.3% or less in consideration of the subsequent use, but the transparent base material 11 is restored with respect to heat resistance and chemical resistance. If it is within the range (1% or less), there is no problem.

  A method for bringing the transparent base material 11 into a stretched state is not particularly limited, but for example, expansion due to mechanical pulling or thermal expansion due to heating or the like can be considered. In particular, the method by heating is considered to be an effective method because the transparent substrate 11 can be uniformly expanded without difficulty. Moreover, a uniform stretched state can be easily maintained.

  Specifically, when the transparent conductive film 12 is formed by a sputtering method, a vapor deposition method, or the like, the transparent substrate 11 is heated and thermally expanded in advance. The heating temperature at this time needs to be several tens of degrees lower than the heat resistant temperature of the transparent base material 11 and may be higher than the heat resistant temperature of the transparent conductive substrate 10 required after film formation. is important. Even if the film formation temperature is lower than the heat resistance temperature required after film formation, the heat resistance is improved, but the effect is small. When the transparent conductive substrate 10 is used for a photoelectric conversion element or the like, heat resistance at least at 100 ° C. or higher is required. In this case, the film forming temperature at 100 ° C. or higher and below the softening point of the substrate is required. desirable.

  That is, it is preferable that the transparent substrate 11 in the stretched state is subjected to a heat treatment, and the temperature of the transparent substrate 11 in the heat treatment is set to 100 ° C. or more and not more than the softening point temperature of the transparent substrate 11. By setting it within this range, the transparent conductive film 12 with little variation in resistance value can be formed without causing irreversible deformation of the substrate itself.

  The transparent conductive film 12 and the transparent conductive substrate 10 having high heat resistance are formed by forming the transparent conductive film 12 by sputtering or the like in a state where the transparent base material 11 is heated and thermally expanded. In addition to the above, the film forming method includes a DC magnetron sputtering method, an RF magnetron sputtering method, an EB vapor deposition method, and the like. The heating atmosphere is not particularly limited, but when there is film quality deterioration due to oxidation or the like, it is preferably performed in a low oxygen atmosphere or in a vacuum.

  The transparent conductive substrate 10 thus obtained allows the transparent conductive film to follow the thermal expansion of the transparent base material 11, and is not limited to the difference in the thermal expansion coefficient between the transparent conductive film 12 and the transparent base material 11. Generation | occurrence | production of damages, such as a crack of the transparent conductive film 12, resulting from every deformation | transformation can be suppressed. As a result, a method for producing a transparent conductive substrate excellent in heat resistance, chemical resistance, press resistance and the like can be provided.

FIG. 2 is a schematic cross-sectional view showing one embodiment of the photoelectric conversion element according to the present invention.
In FIG. 2, 10 is a transparent conductive substrate, 11 is a transparent substrate, 12 is a transparent conductive film, 13 is a porous oxide semiconductor layer, 14 is a working electrode, 15 is an electrolyte layer, 16 is another substrate, Reference numeral 17 denotes a conductive film, 18 denotes a counter electrode, 19 denotes a sealing member, and 30 denotes a dye-sensitized photoelectric conversion element.
This photoelectric conversion element 30 is generally configured by a working electrode 14, a counter electrode 18, and an electrolyte layer 15 made of an electrolyte enclosed between them.

The working electrode 14 is formed on one surface of the transparent conductive film 12 constituting the transparent conductive substrate 10 and is composed of a porous oxide semiconductor layer 13 carrying a sensitizing dye.
The counter electrode 18 is composed of another base material 16 and a conductive film 17 formed on this one surface.
In the photoelectric conversion element 30, a laminated body in which the electrolyte layer 15 is sandwiched between the working electrode 14 and the counter electrode 18 is bonded and integrated by a sealing member 19 to function as a photoelectric conversion element.

The porous oxide semiconductor layer 13 is provided on the transparent conductive film 12, and a sensitizing dye is supported on the surface thereof. The semiconductor for forming the porous oxide semiconductor layer 13 is not particularly limited, and any semiconductor can be used as long as it is generally used for forming a porous oxide semiconductor for a photoelectric conversion element. As such a semiconductor, for example, titanium oxide (TiO ₂ ), tin oxide (SnO ₂ ), tungsten oxide (WO ₃ ), zinc oxide (ZnO), niobium oxide (Nb ₂ O ₅ ), or the like can be used. .

  As a method for forming the porous oxide semiconductor layer 13, for example, a dispersion obtained by dispersing commercially available oxide semiconductor fine particles in a desired dispersion medium, or a colloidal solution that can be prepared by a sol-gel method is used as necessary. After adding the desired additives, after applying by a known application method such as screen printing method, ink jet printing method, roll coating method, doctor blade method, spray coating method, etc., heat treatment is performed to form voids and make it porous The method to do can be applied.

  As the sensitizing dye, a ruthenium complex containing a bipyridine structure or a terpyridine structure as a ligand, a metal-containing complex such as porphyrin or phthalocyanine, or an organic dye such as eosin, rhodamine or merocyanine can be applied. Therefore, those exhibiting behavior suitable for the intended use and the semiconductor used can be selected without particular limitation.

  The electrolyte layer 15 is formed by impregnating a porous oxide semiconductor layer 13 with an electrolytic solution, or after impregnating the porous oxide semiconductor layer 13 with an electrolytic solution, the electrolytic solution is applied to an appropriate gel. Gelled (pseudo-solidified) using an agent and formed integrally with the porous oxide semiconductor layer 13, or a gel electrolyte containing an ionic liquid, oxide semiconductor particles, and conductive particles Is used.

As said electrolyte solution, what melt | dissolved electrolyte components, such as an iodine, iodide ion, and tertiary butyl pyridine, in organic solvents, such as ethylene carbonate and methoxyacetonitrile, is used.
Examples of the gelling agent used for gelling the electrolytic solution include polyvinylidene fluoride, a polyethylene oxide derivative, and an amino acid derivative.

The ionic liquid is not particularly limited, and examples thereof include room temperature molten salts that are liquid at room temperature and have a quaternized compound having a nitrogen atom as a cation.
Examples of the cation of the room temperature molten salt include quaternized imidazolium derivatives, quaternized pyridinium derivatives, and quaternized ammonium derivatives.
Examples of the anion of the room temperature molten salt include BF ₄ ⁻ , PF ₆ ⁻ , F (HF) _n ⁻ , bistrifluoromethylsulfonylimide [N (CF ₃ SO ₂ ) ₂ ⁻ ], iodide ions, and the like.
Specific examples of the ionic liquid include salts composed of quaternized imidazolium-based cations and iodide ions or bistrifluoromethylsulfonylimide ions.

The oxide semiconductor particles are not particularly limited in terms of the type and particle size of the substance, but those that are excellent in miscibility with an electrolytic solution mainly composed of an ionic liquid and that gel the electrolytic solution are used. In addition, the oxide semiconductor particles are required to have excellent chemical stability against other coexisting components contained in the electrolyte without reducing the conductivity of the electrolyte. In particular, even when the electrolyte contains a redox pair such as iodine / iodide ions or bromine / bromide ions, the oxide semiconductor particles are preferably those that do not deteriorate due to an oxidation reaction.
Examples of such oxide semiconductor particles include TiO ₂ , SiO ₂ , SnO ₂ , WO ₃ , ZnO, Nb ₂ O ₅ , In ₂ O ₃ , ZrO ₂ , Ta ₂ O ₅ , La ₂ O ₃ , SrTiO ₃ , One or a mixture of two or more selected from the group consisting of Y ₂ O ₃ , Ho ₂ O ₃ , Bi ₂ O ₃ , CeO ₂ , and Al ₂ O ₃ is preferable. Titanium dioxide fine particles (nanoparticles), silicon dioxide Is particularly preferred. The average particle diameter of the titanium dioxide or silicon dioxide is preferably about 2 nm to 1000 nm.

As the conductive fine particles, conductive particles such as a conductor and a semiconductor are used. The range of the specific resistance of the conductive particles is preferably 1.0 × 10 ⁻² Ω · cm or less, and more preferably 1.0 × 10 ⁻³ Ω · cm or less. Further, the type and particle size of the conductive particles are not particularly limited, and those that are excellent in miscibility with an electrolytic solution mainly composed of an ionic liquid and that gel this electrolytic solution are used. Furthermore, it is necessary that the oxide film (insulating film) or the like is not formed in the electrolyte to lower the conductivity, and that the chemical stability against other coexisting components contained in the electrolyte is excellent. In particular, even when the electrolyte contains an oxidation / reduction pair such as iodine / iodide ion or bromine / bromide ion, an electrolyte that does not deteriorate due to oxidation reaction is preferable.
Examples of such conductive fine particles include those composed mainly of carbon, and specific examples include particles such as carbon nanotubes, carbon fibers, and carbon black. All methods for producing these substances are known, and commercially available products can also be used.

As the other base material 16, a metal plate, a synthetic resin plate, or the like is used because it is not necessary to have the same material as the transparent base material 11, or particularly need to have light transmittance.
The conductive film 17 is a thin film made of metal, carbon, a conductive polymer, or the like formed on one surface of the other base material 16 in order to impart conductivity. As the conductive film 17, for example, a layer of carbon, platinum, or the like, which has been heat-treated after vapor deposition, sputtering, and application of chloroplatinic acid is preferably used, but is not particularly limited as long as it functions as an electrode. Absent.

  The sealing member 19 is not particularly limited as long as it has excellent adhesion to the transparent base material forming the transparent conductive substrate 10 and the other base material 16 forming the counter electrode 18. For example, a carboxylic acid group is included in the molecular chain. Adhesives made of a thermoplastic resin having the above are desirable, and specific examples include Hi Milan (manufactured by Mitsui DuPont Polychemical Co., Ltd.), Binnel (manufactured by Mitsui DuPont Polychemical Co., Ltd.), and the like.

Next, the manufacturing method of the photoelectric conversion element 30 of this embodiment is demonstrated.
First, the transparent conductive film 12 made of a metal oxide is formed so as to cover the one surface 11a of the transparent base material 11 made of resin, and the transparent conductive substrate 10 is produced.
At this time, in the present invention, the step of holding the transparent base material 11 in a stretched state, the step of forming the transparent conductive film 12 on one surface of the transparent base material 11 while maintaining the stretched state, and the stretched state include And a step of applying a compressive stress to the transparent conductive film 12.

  As described above, when the transparent conductive film 12 having a smaller thermal expansion coefficient is formed on the transparent base material 11 made of a material having a large thermal expansion coefficient such as a resin, the transparent base material 11 is previously stretched. By forming the film, the transparent conductive film 12 can follow the expansion of the transparent substrate 11 even if the substrate expands due to temperature or the like after the film formation. Thereby, damage to the transparent conductive film 12 can be suppressed. As a result, mechanical properties such as heat resistance, chemical resistance, and press resistance of the transparent conductive film 12 and the transparent conductive substrate 10 can be improved.

Next, the porous oxide semiconductor layer 13 is formed so as to cover the transparent conductive film 12. The formation of the porous oxide semiconductor layer 13 mainly includes a coating process and a drying / firing process.
The coating process is a process in which, for example, a paste of TiO ₂ colloid obtained by mixing TiO ₂ powder and a surfactant at a predetermined ratio is applied to the surface of the transparent conductive film 12 that has been made hydrophilic. At this time, as a coating method, a pressing means is used so that the applied colloid maintains a uniform thickness while pressing the colloid on the transparent conductive film 12 using a pressing means (for example, a glass rod). A method of moving on the transparent conductive film 12 is exemplified.

  The drying / firing process includes, for example, a method in which the coated colloid is allowed to stand at room temperature for approximately 30 minutes in the atmosphere, and then dried, and then fired at a temperature of 150 ° C. for approximately 30 minutes using an electric furnace. It is done.

Next, the dye is supported on the porous oxide semiconductor layer 13 formed by the coating process and the drying / firing process.
As the dye solution for supporting the dye, for example, a solution prepared by adding an extremely small amount of N719 powder to a solvent of acetonitrile and t-butanol in a volume ratio of 1: 1 is prepared in advance.
The porous oxide semiconductor layer 13 that has been separately heated in an electric furnace at about 120 to 150 ° C. is immersed in a dye solvent placed in a petri dish-like container, and immersed in a dark place for a whole day and night (approximately 20 hours). To do. Thereafter, the porous oxide semiconductor layer 13 taken out from the dye solution is washed using a mixed solution of acetonitrile and t-butanol.
Through the above-described steps, a working electrode 14 (also referred to as a window electrode) obtained by providing a porous oxide semiconductor layer 13 made of a dye-supported TiO ₂ thin film on a transparent substrate is obtained.
Thus, the electrode substrate obtained can suppress generation | occurrence | production of damages, such as a crack of a transparent conductive film resulting from the difference in the thermal expansion coefficient of a transparent conductive film and a base material. Thereby, mechanical properties such as heat resistance, chemical resistance (electrolytic solution), and press resistance are improved.

  On the other hand, a counter electrode 18 formed by forming a conductive film 17 made of, for example, platinum by an evaporation method or the like is provided on one surface of another base material (not necessarily transparent). The counter electrode 18 is provided with at least one hole penetrating in the thickness direction. This hole is an inlet for injecting an electrolyte solution to be described later.

The working electrode 14 is disposed so that the porous oxide semiconductor layer 13 made of a dye-supported TiO ₂ thin film is located above, and the counter electrode 18 is disposed so that the porous oxide semiconductor layer 13 and the conductive film 17 face each other. A laminated body is formed by being provided over the working electrode 14. Thereafter, the side part of the laminate, that is, the vicinity of the outer periphery where the working electrode 14 and the counter electrode 18 overlap each other is sealed with a sealing member 19 made of, for example, High Milan (Mitsui DuPont Polychemical Co., Ltd.) or Binell (Mitsui DuPont Polychemical Co., Ltd.). Stop.

  After the sealing member 19 is solidified, the electrolyte solution is injected from the inlet provided in the counter electrode 18 into the gap of the laminate, that is, the space surrounded by the working electrode 14, the counter electrode 18, and the sealing member 19. Thereby, the dye-sensitized photoelectric conversion element 30 is formed.

  The photoelectric conversion element 30 thus obtained uses the transparent conductive substrate 10 with improved mechanical properties such as heat resistance, chemical resistance (for example, electrolytic solution), press resistance, and the like in the working electrode 14. Therefore, it is possible to suppress the characteristic deterioration (for example, the increase of the resistance value and the decrease of the photoelectric conversion characteristic) due to the deterioration of the mechanical characteristics, and as a result, the durability is excellent.

  The transparent conductive substrate and the photoelectric conversion element of the present invention have been described above. However, the present invention is not limited to the above example, and can be appropriately changed as necessary.

FIG. 3 shows a film forming apparatus by sputtering used in this example.
The film forming apparatus 50 includes a support unit 52, a heating unit 53 provided facing the outer surface of the support unit 52, a first cathode 54, a second cathode 55, a surface, and a chamber 51. And a processing device 56.
The support means 52 is a carousel-type base material, which has a substantially octagonal prism shape in FIG. 3, and a base material that is an object to be processed is attached to the outer peripheral side surface portion. The support means 52 is rotated at a constant rotation speed in the direction of the arrow in the figure during film formation by a built-in rotation mechanism (not shown).
The heating device 53 heats the base material in order to form a thin film while heating and holding the base material at a predetermined temperature. The heating device 53 is, for example, an infrared lamp heater.

The first cathode (ITO target) 54 is provided to face the outer surface portion of the support means, and the target is sputtered to form an ITO thin film on one surface of the object to be processed. In this apparatus, an RF cathode is usually used instead of film formation by DC sputtering.
The second cathode (TO target) 55 is provided to face the outer surface portion of the support means, and forms a TO thin film on one surface of the substrate by sputtering the target.
The surface treatment device 56 performs surface treatment such as plasma cleaning on the formed thin film.
The chamber 51 is evacuated by a vacuum exhaust device (not shown).

In the case of forming a film using such a film forming apparatus 50, first, a base material that is an object to be processed is placed on the outer surface portion of the support means 52.
Thereafter, the inside of the chamber 51 is evacuated by a vacuum exhaust device.
Prior to film formation, the surface temperature of the substrate is raised in advance using a heating device (infrared lamp heater) 52.
An ITO film is formed on one surface of the substrate by sputtering while introducing a plasma gas into the chamber 51 and rotating the support means 52 at a constant rotation speed.

That is, in this film forming apparatus 50, the carousel type support means 52 provided with the base material rotates at a constant rotation speed in the plasma space where the first cathode (ITO target) 54 is RF-sputtered. In passing, an extremely thin ITO film is formed on the substrate. Next, the film is passed through a high vacuum for about 3 to 4 times as long as the actual film formation time, and is reheated by the heating device 52 before the next film formation. By repeating this process, a plurality of ultrathin ITO films are stacked to form a thick ITO film.
For example, the support means 52 rotates once in 12 seconds, and film formation is performed at 350 μm / min.

A transparent conductive substrate was produced using the film forming apparatus as described above.
Example 1
As the transparent substrate, a 188 μm thick polyethylene naphthalate (PEN) substrate (linear expansion coefficient: about 20 × 10 ⁻⁶ / K) was used.
The substrate was set in a sputtering chamber and evacuated. A batch type carousel type sputtering apparatus was used as the sputtering apparatus. Prior to film formation, the surface temperature of the PEN substrate was raised to 150 ° C. in advance using an infrared lamp heater installed in the sputtering chamber. Argon is used as a plasma gas for sputtering, and an ITO film (linear expansion coefficient: about 7.2 ×) is formed on one surface of the substrate by sputtering while rotating the carousel under a vacuum of 7 × 10 ⁻³ Torr. 10 ⁻⁶ / K) to form a transparent conductive substrate.
The film forming conditions at this time are shown in Table 1.

(Example 2 to Example 5)
The film formation was performed in the same manner as in Example 1 except that the film formation temperature was 50 ° C. (Example 2), 80 ° C. (Example 3), 100 ° C. (Example 4), and 120 ° C. (Example 5). And a transparent conductive substrate was produced.

(Example 6 to Example 10)
Polyethylene terephthalate (PET) (Example 6), polycarbonate (PC) (Example 7), polyarylate (PAR) (Example 8), polycycloolefin (PCO) (Example 9), polymethyl Except for using methacrylate (PMMA) (Example 10), film formation was performed in the same manner as in Example 1 to produce a transparent conductive substrate.

(Example 11)
After forming an ITO film on the PEN substrate in the same manner as in Example 1, a TO (tin oxide) film was laminated and formed in the same manner while the substrate was heated to produce a transparent conductive substrate.

(Comparative Examples 1 to 6)
The film forming temperature was room temperature (24 ° C.), and the base material was polyethylene naphthalate (PEN) (Comparative Example 1), polyethylene terephthalate (PET) (Comparative Example 2), polycarbonate (PC) (Comparative Example 3), polyarylate (PAR) (Comparative Example 4), polycycloolefin (PCO) (Comparative Example 5), polymethyl methacrylate (PMMA) (Comparative Example 6) was used, and film formation was performed in the same manner as in Example 1, A transparent conductive substrate was produced.

(Comparative Example 7 to Comparative Example 8)
Using soda glass as the base material, the film formation temperature was set to room temperature (Comparative Example 7) and 120 ° C. (Comparative Example 8), and the film formation was performed in the same manner as in Example 1 to produce a transparent conductive substrate. did.

The XRD analysis result of the transparent conductive film formed on the soda glass substrate as described above is shown in FIG. Here, the temperature shown on the right side of each spectrum in FIG. 4 represents the heating temperature of the substrate.
As is apparent from FIG. 4, when the substrate heating temperature is 160 ° C. or lower, a strong diffraction peak is hardly observed at a specific 2θ, so that it is found that the ITO film is hardly crystallized. In this example, since oxygen is not introduced as the plasma gas, it is in an oxygen deficient state and the carrier concentration is higher than usual.

Moreover, about the obtained transparent conductive substrate, heat resistance, chemical resistance, press resistance, and total light transmittance were evaluated. Each evaluation condition is described below.
The heat resistance is a measured value of specific resistance after 5 cycles of heating at 150 ° C. for 1 hour.
Chemical resistance is a measured value of specific resistance after being immersed in ethanol and acetonitrile for 13 hours at 40 ° C., respectively.
In addition, the press resistance was evaluated by determining that the specific resistance increased by 10% or more after pressing at 100 MPa for 1 minute at room temperature, and that the others were defective (x mark), and the others were good (◯ mark).
These evaluation results are shown in Table 2 together with the linear expansion coefficient of the substrate.

  As is clear from Table 2, in Comparative Examples 1 to 5 in which the transparent conductive film was formed at room temperature, the resistance value was significantly increased after heating or after chemical immersion. This is presumably because damage such as cracks has occurred in the transparent conductive film. Also, good results have not been obtained in press resistance.

  On the other hand, in the Example which formed the transparent conductive film in the state which heated the base material and was thermally expanded, the raise of a resistance value becomes small after a heating or chemical | medical immersion. Also, good results have been obtained in press resistance. In particular, it can be seen that particularly good results are obtained when the heating temperature of the substrate is 100 ° C. or higher and the expansion coefficient (stretching rate) of the substrate is 0.08% or higher.

For example, when the substrate is expanded in advance by heating and a film having a larger linear expansion coefficient than that of the substrate is formed thereon, a compressive stress is applied when the film is cooled to room temperature after film formation. Since it is extremely difficult to measure a specific value of compressive stress with a highly elastic material such as a resin substrate, the film formation conditions are determined using the linear expansion coefficients of the substrate and the film as indices. And simple. The difference (Δ1) in the expansion coefficient (stretch ratio) at this time is generally expressed by the following equation (1). Here, β _TF represents the linear expansion coefficient of the film, β _SUB represents the linear expansion coefficient of the substrate, T _DEP represents the film forming temperature, and T _RT represents the room temperature.

  When the difference in expansion coefficient (stretch ratio) is calculated from the various resin substrates listed in Table 2 and the value of the linear expansion coefficient of indium oxide, which is a film material, using the formula (1), for example, when a PEN substrate is used When the substrate was previously expanded under the temperature condition where the difference in expansion rate (stretching rate) was 0.08% or more, film formation was improved. When a PC substrate having a larger linear expansion coefficient is used, press resistance is similarly maintained even when the film is expanded to 0.65%. In the expansion by heating, the substrate cannot be heated to a temperature higher than the heat resistant temperature of the substrate. Therefore, if the difference in expansion coefficient (stretching ratio) is substantially expanded within a range of 1% or less, the above press resistance can be obtained. In addition, it is possible to expand the substrate to a difference in expansion coefficient (stretching ratio) of 1% or more by a method other than heating, but there is a possibility that the irreversible plastic deformation of the substrate may occur, and the expansion coefficient (stretching) is as small as possible. Since it is desirable to have a difference in the ratio), it is substantially meaningless to expand it further.

Conversely, the difference (Δ2) in the expansion coefficient (stretching ratio) between the substrate and the film when the film formed on the various resin substrates is heated to the heat resistance test temperature is expressed by the following equation (2). Here, β _TF represents the linear expansion coefficient of the film, β _SUB represents the linear expansion coefficient of the substrate, T _DEP represents the film formation temperature, and T _TEST represents the test temperature.

  When heated to such a heat resistance test temperature, tensile stress acts on the film, and if the difference in expansion coefficient (stretch ratio) is large, the film will break. Similarly, when the difference in expansion coefficient (stretching ratio) is calculated using the formula (1), for example, when a PEN substrate is used, the substrate is used under a temperature condition where the difference in expansion coefficient (stretching ratio) is 0.08% or more. When the film was expanded in advance, the difference in expansion coefficient (stretching ratio) calculated from equation (2) was less than 0.07%, and no increase in resistance value was observed in the 150 ° C. heat resistance test. . When a PC substrate having a larger linear expansion coefficient is used, the heat resistance is similarly maintained even when the film is expanded to 0.65%. In the expansion by heating, the substrate cannot be heated to a temperature higher than the heat resistant temperature of the substrate. Therefore, if the difference in expansion coefficient (stretching ratio) is substantially expanded within a range of 1% or less, the above heat resistance can be obtained. In addition, it is possible to expand the substrate to a difference in expansion coefficient (stretching ratio) of 1% or more by a method other than heating, but there is a possibility that the irreversible plastic deformation of the substrate may occur, and the expansion coefficient (stretching) is as small as possible. Since it is desirable to have a difference in the ratio), it is substantially meaningless to expand it further.

  The present invention is applicable to a transparent conductive substrate and a photoelectric conversion element provided with the transparent conductive substrate.

It is a schematic sectional drawing which shows an example of the transparent conductive substrate which concerns on this invention. It is a schematic sectional drawing which shows an example of the photoelectric conversion element which concerns on this invention. It is a schematic plan view which shows the structure of the sputter film deposition apparatus used in the Example. It is a figure which shows the XRD measurement result of the transparent conductive film formed in the Example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Transparent conductive substrate, 11 Transparent base material, 12 Transparent electrically conductive film, 13 Porous oxide semiconductor layer, 14 Working electrode (window electrode), 15 Electrolyte layer, 16 Other base materials, 17 Conductive film, 18 Counter electrode, 19 Sealing member, 30 photoelectric conversion element.

Claims (1)

A first electrode substrate having a porous oxide semiconductor layer carrying a sensitizing dye and functioning as a window electrode; and a first electrode substrate disposed at least partially opposite the first electrode substrate with an electrolyte layer interposed therebetween. A transparent conductive film comprising a base material made of a resin and a transparent conductive film made of a metal oxide on one surface of the base material. An electrode substrate manufacturing method used for a photoelectric conversion element having a conductive substrate,
Maintaining the substrate in a stretched state by heating and expanding the substrate; and
Forming the transparent conductive film on one surface of the substrate while maintaining the stretched state;
Releasing the stretched state and applying a compressive stress to the transparent conductive film;
Applying a paste containing a porous oxide semiconductor to the surface of the transparent conductive film;
Baking the paste, and
In the stretched state, the stretching ratio of the base material is 0.08% or more and 1% or less with respect to at least one direction,
The method for producing an electrode substrate, wherein the temperature of the base material in the heating is set to 100 ° C. or higher and not higher than a softening point temperature of the base material .

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