JP2012243423A - Conductive substrate, method for manufacturing conductive substrate, solar cell and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive substrate having no problem on specific resistance thereof, having no surface unevenness causing problems in laminating other functional layers, and further easy in manufacture.SOLUTION: A conductive substrate includes: a porous layer having a plurality of pores extending three-dimensionally; and a transparent conductive layer formed on the porous layer. In the conductive substrate, metal is filled into at least a part of the pores of the porous layer, and the metal is brought into contact with the transparent conductive layer on a surface of the porous layer.

Description

  The present invention relates to a conductive substrate and a method for manufacturing the same, and further to a solar cell and a display device using the conductive substrate.

  Transparent display layers such as ITO and IZO are used in various display devices such as liquid crystal display devices and organic EL display devices, and solar cells.

However, the specific resistance of these transparent conductive layers is 10 ⁻⁴ to 10 ⁻³ Ω · cm, which is about 1000 times the specific resistance of metals such as silver and gold. Therefore, when it is going to respond to the request | requirement of the enlargement with respect to various display apparatuses and solar cells in recent years, the loss by the resistance of the said transparent conductive layer becomes a big problem.

  In order to solve such a problem, an auxiliary electrode made of a mesh-like metal is provided on the front or back surface of the transparent conductive layer (see Patent Document 1). However, when an auxiliary electrode made of a mesh-like metal is provided, the surface has irregularities corresponding to the thickness of the auxiliary electrode, and there is a concern that various functional layers laminated thereon may be adversely affected. The

  Patent Document 2 discloses a technique in which a concave groove is provided on the surface of a transparent conductive layer and a metal is filled in the concave groove in order to solve the problem of unevenness that occurs when a so-called auxiliary electrode is provided. .

JP 2003-203681 A Japanese Patent No. 4479287

  According to the technique disclosed in Patent Document 2, the surface of the transparent conductive layer can be flattened while supplementing the conductivity of the transparent conductive layer with a so-called auxiliary electrode. However, a concave groove is formed in the transparent conductive layer of the μm order. Then, it is difficult to fill the concave groove with metal, and the manufacturing process becomes complicated, resulting in high costs.

  In addition, organic thin film solar cells and organic EL display devices may be required to have flexibility, but in such a case, it is difficult to form a concave groove in the flexible transparent conductive layer by etching or the like.

  The present invention has been made in such a situation, the specific resistance does not become a problem even when the size is increased, and there is no surface unevenness that becomes a problem in stacking other functional layers, In addition to providing a conductive substrate and a method for manufacturing the same that are easy to manufacture, a main object is to provide a solar cell and a display device using the conductive substrate.

  1st invention for solving the said subject contains the porous layer which has the several hole extended in three dimensions, and the transparent conductive layer formed on the said porous layer, At least of the said porous layer Some of the holes are filled with metal, and the metal is a conductive substrate in contact with the transparent conductive layer on the surface of the porous layer.

  Further, in the above invention, in the porous layer, a hole not filled with metal is filled with a resin, and the resin is in contact with the transparent conductive layer on the surface of the porous layer. Also good.

  A second invention for solving the above-mentioned problem is to prepare a porous layer having a plurality of pores extending three-dimensionally, filling the pores appearing on the surface of the porous layer with a metal, and then porous A transparent conductive layer is formed on the surface of the layer.

  In the above invention, the transparent conductive layer may be formed by a vapor deposition method.

  A third invention for solving the above-mentioned problem is a solar cell having two conductive substrates facing each other and a photoelectric conversion layer provided between the two conductive substrates, and at least one of the two conductive substrates. One conductive substrate includes a porous layer having a plurality of pores extending in three dimensions, and a transparent conductive layer formed on the porous layer, and at least some of the pores of the porous layer include A metal is filled, and the metal is in contact with the transparent conductive layer on the surface of the porous layer.

  A fourth invention for solving the above-described problem is a display device having two conductive substrates facing each other and a light emitting layer provided therebetween, and at least one of the two conductive substrates. The conductive substrate includes a porous layer having a plurality of pores extending in three dimensions, and a transparent conductive layer formed on the porous layer, and at least some of the pores of the porous layer include a metal. The metal is in contact with the transparent conductive layer on the surface of the porous layer.

  According to the present invention, even when the size is increased, the resistivity does not become a problem, and a conductive substrate that has a flat surface, is easy to manufacture, and is inexpensive can be provided. In addition, a solar cell or a display device using such a conductive substrate can be provided.

It is a schematic sectional drawing of an electroconductive board | substrate. It is a schematic sectional drawing which shows another aspect of an electroconductive board | substrate.

  Hereinafter, a conductive substrate, a method for manufacturing a conductive substrate, and a solar cell and a display device using the conductive substrate of the present invention will be described with reference to the drawings.

<Conductive substrate>
FIG. 1 is a schematic cross-sectional view of a conductive substrate.

  As shown in FIG. 1, the conductive substrate 1 includes a porous layer 2 and a transparent conductive layer 3, and in some cases, may be formed on a support substrate 10 as illustrated. The porous layer 2 has a plurality of holes 4 extending three-dimensionally, and at least a part of the holes 4A is filled with a metal 5, and the metal 5 is a porous layer. 2 is in contact with the transparent conductive layer 3. If reduced, among the plurality of holes 4 in the porous layer 2, at least some of the holes 4A among the holes opened on the surface thereof are filled with the metal 5, By filling the holes 4 </ b> A, the metal is in contact with the transparent conductive layer 3 on the surface of the porous layer 2. According to such a conductive substrate 1, only the transparent conductive layer 3 has a large specific resistance and a large electrical loss. Therefore, the porous layer 2 is filled with a plurality of holes 4A extending three-dimensionally. Since the metal 5 forms an electrical path and functions as a so-called auxiliary electrode, the specific resistance of the entire conductive substrate 1 can be reduced.

  Below, each structure of the electroconductive board | substrate 1 is demonstrated in detail.

<< Porous layer >>
The porous layer 2 has a plurality of holes 4 extending three-dimensionally. By filling the metal 5 in all or a part of the holes located on the surface, a three-dimensional structure is formed by the metal 5. It has a function of forming an electrical path and assisting the transparent conductive layer 3. Therefore, it is necessary to be a porous layer capable of exhibiting such a function. From this point of view, it is preferable that the pores 4 are present uniformly and three-dimensionally at least in the vicinity of the surface.

  Note that “extending in three dimensions” means that the pores 4 extend in various directions in the porous layer 2, in other words, in random directions. Further, “the surface of the porous layer 2” means, as described above, the interface between the porous layer 2 and the transparent conductive layer 3 laminated thereon, and the vicinity thereof, and the holes 4 are formed. It does not mean to include the inside of the hole in the portion. Furthermore, “filling metal” in the holes 4 in the porous layer 2 not only means that the metal is filled without voids according to the volume of the holes 4 but also has some voids. This includes the case where the metal is filled and the case where the metal is filled in a slightly raised state from the opening portion of the hole 4.

  Here, the transparent conductive layer 3 can be sufficiently assisted by setting the surface resistance value of the porous layer 2 in the state filled with the metal 5 to 1 Ω / sq or less. Therefore, the density of the porous layer 2, that is, the porosity and the average pore diameter of the pores 4, it is necessary that the surface resistance value is 1 Ω / sq or less when the metal 5 is filled, Further, even when the metal 5 is filled, the filling may be performed so that the surface resistance value is 1 Ω / sq or less.

  For example, the average pore diameter of the pores 4 of the porous layer 2 is preferably 30 nm or more. If the average hole diameter of the hole 4 is smaller than this value, it may be difficult to fill the hole 4 with metal, and the production yield may be reduced. If the hole 4 is too small, a sufficient electrical path may be provided. This is because it cannot be formed, and the support of the transparent conductive layer 3 may be insufficient. Here, since it is the “average hole diameter”, when attention is paid to each of the holes 4 that randomly extend if reduced in three dimensions, the hole diameter of one hole 4 needs to be always the same up to the tip. The diameter may be different at the place.

In addition, the average hole diameter of the hole 4 is measured by using a fully automatic gas adsorption amount measuring apparatus (AUTOSORB-1-AG, manufactured by Yuasa Ionics Co., Ltd.), using N ₂ gas as a carrier gas, and measuring temperature 77K. Can be sought. When the average pore diameter of the porous member exceeds 200 nm, the average pore diameter can be obtained using a mercury porosimeter (PoreMaster, Yuasa Ionics).

  Moreover, since the porous layer 2 assists the transparent conductive layer 3, it is preferable that the porous layer 2 itself is also transparent. In the first place, the transparent conductive layer 3 is a part that is required to be transparent in solar cells and various display devices, specifically as a light receiving surface side electrode in solar cells and as a display surface side electrode in various display devices. This is because it is often used.

  The transparency of the porous layer 2 is not particularly limited and can be appropriately adopted as long as it can be practically used. For example, it is preferably 80% or more.

  The present invention is not particularly limited with respect to the thickness of the porous layer 2 and can be appropriately designed in consideration of the above-described transparency and conductivity, that is, the formation of an electrical path. 10-50 micrometers is especially preferable.

  The material of the porous layer 2 is not particularly limited as long as it is a material that can satisfy the above-described various conditions and can exhibit the above-described effects. Appropriate for the manufacturing method of itself and the manufacturing method of the conductive substrate 1 and considering transparency, heat resistance, mechanical strength, adhesion to the mating material used together with the conductive substrate, etc. You can choose. Specific examples include cellulose resins, polyvinyl resins, vinyl resins, acrylic resins, olefin resins, urethane resins, epoxy resins, phenoxy resins, and the like. Among these, a polyvinyl acetal resin belonging to the polyvinyl resin, more specifically, a polyvinyl butyral resin may be used. The resin is excellent in film-forming properties, adhesiveness to the coated surface, and further soluble in alcohol. Therefore, it is easily available because it is widely used as a binder resin in the paint and ink fields. This is because, from the nature, the porous layer 2 can be easily produced by a production method in which a good solvent and a poor solvent are mixed.

  A method for producing such a porous layer 2 itself is not particularly limited, and a method capable of producing the porous layer 2 having the configuration and performance described above may be appropriately employed. For example, a method of forming a porous layer by mixing a good solvent and a poor solvent to form a coating solution for forming a porous layer, applying this onto a substrate, and then drying, or the good solvent and the poor solvent Instead of this, a method using a high-boiling solvent and a low-boiling solvent can be mentioned. Moreover, you may use the method of mixing a foaming agent in resin and forming a porous layer by making it foam. Furthermore, a porous layer is formed by mixing a resin that dissolves in a predetermined solvent and a resin that does not dissolve, applying and drying the resin, and then dissolving only the “soluble resin” using the predetermined solvent. You may use the method to do.

<< Metal >>
As described above, all or a part of the holes 4 located on the surface of the porous layer 2 are filled with the metal 5. The metal 5 functions as a so-called auxiliary electrode by contacting the transparent conductive layer 3 formed on the surface of the porous layer 2.

  The material of the metal 5 is not particularly limited, and may be appropriately adopted as long as it can be filled in the holes 4 formed on the surface of the porous layer 2 and can function as an auxiliary electrode. Is possible. Specifically, for example, aluminum (Al), gold (Au), silver (Ag), cobalt (Co), nickel (Ni), platinum (Pt), copper (Cu), titanium (Ti), aluminum alloy, Mention may be made of conductive metals such as titanium alloys and nickel-chromium alloys (Ni-Cr). Among the conductive metals described above, those having a relatively low electrical resistance value are preferred. Examples of such a conductive metal include Al, Au, Ag, and Cu.

  As described above, the metal 5 does not necessarily need to fill all the holes 4 located on the surface of the porous layer 2, and there may be holes that are not filled with the metal 5 as shown in FIG. 1. However, as described above, the surface of the porous layer 2 in a state where the metal 5 is filled, for example, to the extent that the porous layer 2 as a whole forms an electrical path with the metal 5 and functions as an auxiliary electrode. It is necessary to be filled so that the resistance value is 1 Ω / sq or less.

  The method for filling the holes 5 of the porous layer 2 with the metal 5 is not particularly limited, and can be appropriately selected depending on the type of the metal 5 and the like. For example, when filling the metal 5, paste-like metal nanoparticles may be used. In this case, the paste is applied to the surface of the porous layer 2, and after removing excess components such as a spatula, it is dried. Thus, the metal can be filled into the holes 4 of the porous layer 2.

  On the other hand, the metal 5 may be filled by a screen printing method using a screen plate corresponding to the hole 4 to be filled with the metal 5, and further, in the same manner, a gravure printing method, an offset printing method, a flexographic printing method. The metal 5 can also be filled by various printing methods such as a printing method.

<< Transparent conductive layer >>
As shown in FIG. 1, the transparent conductive layer 3 is formed on the surface of the porous layer 2 on the side where the holes 4 filled with the metal 5 exist, and the conductive layer 3 is in contact with the metal 5 by contacting the metal 5. It is a layer that improves the properties. The transparent conductive layer 3 is not particularly limited, and a transparent conductive layer that has been conventionally used in solar cells and various display devices, so-called transparent electrodes, can be used as appropriate. According to the present invention, it can be said that any transparent conductive layer can be used due to the effect of the porous layer 2 described above.

  Specifically, for example, In—Zn—O (IZO), In—Sn—O (ITO), ZnO—Al, Zn—Sn—O, and the like can be given.

  The total light transmittance of the transparent conductive layer 3 is preferably 85% or more, more preferably 90% or more, and particularly preferably 92% or more. When the total light transmittance of the transparent conductive layer 3 is in the above range, the transparent conductive layer 3 can sufficiently transmit light. For example, when used in a solar cell, light is transmitted through the photoelectric conversion layer. It is because it can absorb efficiently.

  The total light transmittance is a value measured using an SM color computer (model number: SM-C) manufactured by Suga Test Instruments Co., Ltd. in the visible light region.

  The sheet resistance of the transparent conductive layer 3 is preferably 20Ω / sq or less, more preferably 10Ω / sq or less, and particularly preferably 5Ω / sq or less. If the sheet resistance is larger than the above range, for example, when used in a solar cell, there is a possibility that charges generated in the photoelectric conversion layer cannot be sufficiently transmitted to an external circuit.

  In addition, the said sheet resistance is measured based on JIS R1637 (Resistance test method of fine ceramics thin film: Measurement method by 4 probe method) using a surface resistance meter (Loresta MCP: Four-terminal probe) manufactured by Mitsubishi Chemical Corporation. It is the value.

  The transparent conductive layer 3 may be a single layer or may be laminated using different materials.

  The thickness of the transparent conductive layer 3 is preferably in the range of 0.1 nm to 500 nm in the case of a single layer, and the total thickness of the transparent conductive layer 3 in the case of being composed of a plurality of layers. It is preferable to be within a range of ˜300 nm. This is because if the thickness is less than the above range, the sheet resistance of the transparent conductive layer 3 becomes too large. On the other hand, if the thickness is larger than the above range, the total light transmittance may be lowered.

  The transparent conductive layer 3 may be formed on the entire surface of the porous layer 2 or may be formed in a pattern.

  Moreover, as a formation method of the transparent conductive layer 3, the formation method of a general electrode can be used, Although it does not specifically limit, For example, a vapor deposition method etc. are employable. According to the vapor deposition method, even when the hole 4 not filled with the metal 5 exists on the surface of the porous layer 2, the transparent conductive layer 3 is embedded while filling the hole 4 with the resin to be the transparent conductive layer 3. Since it can laminate | stack and form, it is preferable at the point which can planarize the surface of the transparent conductive layer 3 finally.

<Support substrate>
The support substrate 10 is a substrate for supporting the conductive substrate 1 and is not particularly limited as long as it can perform the function. However, the conductive substrate 1 is required to be transparent as described above. Since it is often used in the situation, it is preferable that the support substrate 10 is transparent. For example, polyethylene terephthalate resin (PET), polypropylene resin (PP), polyethylene naphthalate resin (PEN), polycarbonate A transparent resin film such as resin (PC) is preferred. This is because such a transparent resin film is excellent in workability, has features such as reduction in manufacturing cost, weight reduction, and resistance to cracking, and can be applied to a curved surface, thereby expanding the applicability to various applications.

  The thickness of the support substrate 10 is not particularly limited, but is, for example, about 10 μm to 500 μm, and a particularly preferable thickness is 50 μm to 300 μm.

<Another embodiment of conductive substrate>
FIG. 2 is a schematic cross-sectional view showing another embodiment of the conductive substrate.

  As shown in FIG. 2, in the porous layer 2 constituting the conductive substrate 1, resin 6 is filled in the holes 4 </ b> B that are open on the surface where the transparent conductive layer 3 is formed but are not filled with the metal 5. It may be. By filling the resin 6 in the holes 4B not filled with the metal 5 in this way, the surface of the transparent conductive layer 3 can be kept flat when the transparent conductive layer 3 is formed. This is particularly effective when the transparent conductive layer 3 is formed by coating or the like.

  The resin 6 is not particularly limited as long as the hole 4B can be filled, but is preferably transparent. For example, the same resin as the porous layer 2, that is, a cellulose resin, a polyvinyl resin, Examples thereof include vinyl resins, acrylic resins, olefin resins, urethane resins, epoxy resins, and phenoxy resins.

  Also, the filling method of the resin 6 is not particularly limited, and as in the case of the metal 5, various printing methods such as a method of applying the paste-like resin 6 and then drying it, and a screen printing method can be used.

<Solar cell>
The conductive substrate 1 described above is, for example, a solar cell having two conductive substrates facing each other and a photoelectric conversion layer provided between the conductive substrates, and at least one of the two conductive substrates is conductive. It can be suitably used as a conductive substrate.

<Display device>
The conductive substrate 1 described above is a display device having two conductive substrates opposed to each other and a light emitting layer provided therebetween, and at least one of the two conductive substrates. It can also be suitably used as a conductive substrate.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

Example 1
10 g of polyvinyl butyral resin (manufactured by Denki Kagaku Kogyo Co., Ltd .: 6000 C), 90 g of methanol as a good solvent, and 23.5 g of ion-exchanged water as a poor solvent were prepared, and polyvinyl butyral resin and ion-exchanged water were added to methanol. It added, stirring, and obtained the coating liquid for porous layer formation. Next, this coating solution was applied to the entire surface of one side of a PEN film substrate having an outer size of 50 mm square and a film thickness of 125 μm with a comma coater so that the film thickness after drying was 35 μm. The coating film was dried at 50 ° C. for 1 minute, and further dried at 100 ° C. for 1 minute to obtain a PEN film substrate on which a porous layer was formed. Next, a silver nanoparticle paste (manufactured by Mitsuboshi Belting Co., Ltd .: MDot-SLP) is pattern-coated by screen printing on the PEN film substrate on which the porous layer is formed, and the pores of the porous layer are formed. After partially filling the silver nanoparticle paste, it was dried at 120 ° C. for 30 minutes. Next, acrylic resin was subjected to pattern coating by screen printing in the holes of the porous layer that were not filled with the silver nanoparticle paste, thereby filling the holes with the acrylic resin. Next, an ITO layer having a thickness of 150 nm and a surface resistance value of 60 Ω / sq was formed by sputtering to obtain a conductive substrate of Example 1 of the present application.

(Comparative Example 1)
20 nm thick by sputtering method (film forming pressure: 0.1 Pa, film forming power: 180 W, time: 3 minutes / 12 minutes / 3 minutes) on the entire surface of one side of a PEN film substrate having an outer size of 50 mm square and a film thickness of 125 μm. Ni / Cu / Ni was laminated at / 300 nm / 20 nm. A dry film resist (manufactured by Asahi Kasei Corporation, Sunfort AQ-1558, negative type) is laminated on the entire surface of the Ni / Cu / Ni film at a lamination pressure of 0.4 kgf / cm ² and a temperature of 120 ° C. The desired shape was transferred onto the dry film resist by performing UV irradiation through the photomask. Thereafter, the unexposed portion of the resist was removed in a 0.5 wt% sodium carbonate aqueous solution to form a resist image having a desired shape. The exposed Ni / Cu / Ni film was etched with a ferric chloride solution (45 Baume) at a liquid temperature of 50 ° C. using the resist image as a mask. The time required for etching the Ni / Cu / Ni film was 3 seconds. Thereafter, the resist was removed at a liquid temperature of 50 ° C. using a 2 wt% sodium hydroxide solution to form a Ni / Cu / Ni metal mesh having a predetermined opening. Next, an ITO layer having a thickness of 150 nm and a surface resistance value of 60 Ω / sq was formed by sputtering to obtain a conductive substrate of Comparative Example 1.

(Example 2)
A conductive polymer paste (poly- (3,4-ethylenedioxythiophene) / polystyrene sulfonic acid dispersion) was formed on the conductive substrate of Example 1 by spin coating, and then 10 ° C. at 10 ° C. It was dried for minutes to form a buffer layer. Next, polythiophene (P3HT: poly (3-hexylthiophene-2,5-diyl), manufactured by Aldrich) and C60PCBM ([6,6] -phenyl-C61-butylic acid methyl ester, manufactured by Nano-C) were bromo. It was dissolved in benzene to prepare a coating solution for a photoelectric conversion layer having a solid content concentration of 1.4 wt%. Subsequently, after applying the coating liquid for photoelectric conversion layers on the said buffer layer by the spin coat method, it was dried at 100 degreeC for 10 minute (s), and the photoelectric converting layer was formed. Next, calcium and aluminum were formed on the photoelectric conversion layer by a vacuum deposition method to form a metal electrode, and an organic thin film solar cell of Example 2 of the present application was obtained.

(Comparative Example 2)
Using the conductive substrate of Comparative Example 1, an organic solar cell of Comparative Example 2 was obtained in the same manner as in Example 2.

(Evaluation)
The surface resistance values and the maximum surface steps of the conductive substrates of Example 1 and Comparative Example 1 were evaluated. The results are shown in Table 1 below.

  In the measurement of the surface resistance value, a surface resistance meter (Loresta MCP: four-terminal probe) manufactured by Mitsubishi Chemical Corporation was used, and JIS R1637 (low-efficiency test method for fine ceramic thin film: measurement method using a four-probe method) ) Measured based on. . The measurement of the maximum surface level difference is a value obtained by measuring an area of 100 μm × 100 μm in a tapping mode using a probe microscope (Nanopics 1000) manufactured by SII Nano Technology.

  From the above, it can be seen that the conductive substrate of Example 1 of the present application is useful for organic thin-film solar cells and the like because it has a lower surface resistance value and smaller surface step than the conductive substrate of Comparative Example 1. It was.

Moreover, about the organic thin-film solar cell of Example 2 and Comparative Example 2, 100 mW / cm < ² >, A.E. M.M. The solar cell performance was evaluated under the condition of 1.5G. The results are shown in Table 2 below.

  From the above, it was found that the organic thin film solar cell of Example 2 of the present application using the conductive substrate of the present application was superior to the organic thin film solar cell of Comparative Example 2 in conversion efficiency.

DESCRIPTION OF SYMBOLS 1 ... Conductive substrate 2 ... Porous layer 3 ... Transparent conductive layer 4 ... Hole 5 ... Metal 6 ... Resin 10 ... Support substrate

Claims (6)

A porous layer having a plurality of pores extending in three dimensions, and a transparent conductive layer formed on the porous layer,
At least a part of the pores of the porous layer is filled with metal, and the metal is in contact with the transparent conductive layer on the surface of the porous layer.   The porous layer is filled with a resin in a hole not filled with metal, and the resin is in contact with the transparent conductive layer on the surface of the porous layer. The conductive substrate according to 1. Prepare a porous layer with multiple pores extending in three dimensions,
Fill the pores appearing on the surface of the porous layer with metal,
Then, a transparent conductive layer is formed on the surface of a porous layer, The manufacturing method of the conductive substrate characterized by the above-mentioned.   The method for producing a conductive substrate according to claim 3, wherein the transparent conductive layer is formed by a vapor deposition method. A solar cell having two conductive substrates facing each other and a photoelectric conversion layer provided therebetween,
At least one of the two conductive substrates is:
A porous layer having a plurality of pores extending in three dimensions, and a transparent conductive layer formed on the porous layer,
At least a part of the pores of the porous layer is filled with metal, and the metal is in contact with the transparent conductive layer on the surface of the porous layer. A display device having two conductive substrates facing each other and a light emitting layer provided therebetween,
At least one of the two conductive substrates is:
A porous layer having a plurality of pores extending in three dimensions, and a transparent conductive layer formed on the porous layer,
At least a part of the pores of the porous layer is filled with metal, and the metal is in contact with the transparent conductive layer on the surface of the porous layer.

Images