JP2014056739A - Dye-sensitized solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dye-sensitized solar cell which can inhibit short-circuit current and decrease in open-circuit voltage which are caused by an exposed part of electrodes to which metal oxide semiconductors adhere thereby to improve conversion efficiency; and further make it easy to procure materials even when production is increased thereby to decrease manufacturing cost.SOLUTION: A dye-sensitized solar cell comprises electrodes to which dye-adsorbed metal oxide semiconductors adhere in which a barely exposed part of the electrodes where the metal oxide semiconductor does not adhere is covered with an insulating film. The electrodes are net-like electrodes. The insulation film is an inorganic compound having at least one of alumina and silica. The insulating film is an organic compound which is an electrodeposition paint.

Description

  The present invention relates to a dye-sensitized solar cell obtained by adsorbing a dye to an electrode. More specifically, the present invention relates to a dye-sensitized solar cell in which an insulating film is coated on a part of an electrode to which a metal oxide semiconductor adheres.

  Regarding the dye-sensitized solar cell, a research group of Gratzel et al. Announced a solar energy conversion efficiency of 7.1% in 1991 (Non-patent Document 1), and in 1993 the group announced a conversion efficiency of 10%. In particular, it has become a technology that attracts worldwide attention (Non-Patent Document 2).

  The structure of the dye-sensitized solar cell announced by Gratzel et al. Is provided with an indium / tin based transparent conductive layer on the inside of a glass plate or transparent plastic sheet, and fine metal oxide such as titanium dioxide in the transparent conductive layer. A redox body such as an iodine solution is filled between an electrode in which a semiconductor is fixed and a dye such as a ruthenium compound is adsorbed on the metal oxide semiconductor and a counter electrode such as platinum or carbon.

  Since materials such as platinum, indium, and ruthenium used for the positive electrode and the negative electrode in the dye-sensitized solar cell are rare and expensive, in order for the dye-sensitized solar cell to spread, the electrode is inexpensive. It was a problem to be manufactured. For this reason, attempts have been made to manufacture electrodes at low cost.

  For example, in Patent Document 1, in order to provide a dye-sensitized solar cell that is inexpensive and has high conversion efficiency using a simple manufacturing method, a metal mesh electrode having a lattice-like network made of a material such as platinum is used as a positive electrode. The dye-sensitized solar cell used is disclosed.

  Further, in Patent Document 2, in order to provide a high-quality dye-sensitized solar cell that is easy to manufacture and hardly causes poor connection, a mesh-like metal electrode is transparent for the purpose of improving the conductivity of the negative electrode transparent electrode. A dye-sensitized solar cell having an electrode layer integrated with an electrode is disclosed.

JP 2006-156214 A JP 2011-243556 A

B. O'regan, M.M. Graetzel, Nature (London, United Kingdom), 353, 737 (1991) M.M. K. Nazeeruddin, a. Kay, I.D. Rodicio, R.C. Humphry-Baker, E .; Mueller, P.M. Liska, N .; Vlachopoulos, M.M. Graetzel, Journal of the American Chemical Society, 115, 6382 (1993)

  However, as in Patent Document 1, when light is transmitted using a mesh electrode for the positive electrode and light is irradiated to the negative electrode having a metal oxide semiconductor through the electrolyte layer, part of the light is blocked by the electrolyte layer. The light applied to the dye-sensitized solar cell has not been fully utilized.

  In addition, as in Patent Document 2, even if a network electrode is used for the negative electrode, it is an auxiliary to the transparent electrode, and the transparent electrode made of ITO or the like in which tin is added to indium oxide is used. If the production is expanded, it becomes difficult to procure materials, and the cost of the dye-sensitized solar cell increases.

  When a mesh electrode is used for the negative electrode, it is difficult to adhere the metal oxide semiconductor to be adhered so as to completely cover the mesh electrode, and the metal oxide semiconductor is locally peeled off to form a mesh electrode. In the dye-sensitized solar cell, the potential difference between the negative electrode and the positive electrode is small, and a current in the reverse direction flows from the exposed portion. Get smaller. As a result, the photoelectric conversion efficiency may be lowered.

  Furthermore, in the first place, not only the mesh electrode disclosed in Patent Document 1 and Patent Document 2, but also a plate-like electrode, a metal oxide semiconductor such as titanium oxide is not present in a state where defects such as micro holes exist. It is difficult to adhere, or it is peeled off during drying or sintering of the attached metal oxide semiconductor, and an exposed portion is exposed on a part of the electrode. This exposed portion has a problem that the short-circuit current and the open-circuit voltage of the dye-sensitized solar cell are low, and further, the conversion efficiency is low.

  Therefore, in the present invention, in the dye-sensitized solar cell, it is possible to suppress a decrease in short-circuit current and open-circuit voltage due to the exposed portion of the electrode to which the metal oxide semiconductor is attached, and to improve the conversion efficiency. It is an object of the present invention to provide a dye-sensitized solar cell that can easily procure materials even when production is expanded and can reduce manufacturing costs.

  (1) That is, the present invention includes an electrode to which a metal oxide semiconductor adsorbing a dye is attached, and the exposed portion of the electrode that is not attached to the metal oxide semiconductor is exposed by an insulating film. It is a dye-sensitized solar cell characterized by being coated.

  (2) The dye-sensitized solar cell according to (1), wherein the electrode is a mesh electrode.

  (3) The dye-sensitized solar cell according to (1) or (2), wherein the insulating film is an inorganic compound having at least one of alumina and silica.

  (4) The dye-sensitized solar cell according to (1) or (2), wherein the insulating film is an organic compound that is an electrodeposition paint.

  According to the present invention, in a dye-sensitized solar cell, it is possible to suppress a decrease in short-circuit current and open-circuit voltage due to an exposed portion of an electrode to which a metal oxide semiconductor is attached, and to improve conversion efficiency. Even if production is expanded, the procurement of materials is easy, and the manufacturing cost can be reduced.

Schematic sectional view of a preferred form of the dye-sensitized solar cell of the present invention

  Hereinafter, embodiments related to the present invention will be described in detail. In addition, the expression showing a range includes the upper limit and the lower limit.

  The negative electrode of the dye-sensitized solar cell is obtained by applying a solution in which a metal oxide semiconductor having a particle diameter of 1 to 100 nm is dispersed on a conductive flat or network electrode, removing the solvent by heating, and further increasing the temperature. The layered metal oxide semiconductor having a film thickness of 10 to 100 μm is formed on the plate-like electrode or mesh electrode by heating to the plate-like electrode or mesh-like electrode exposed without forming the layered metal oxide semiconductor. The exposed part is covered with an insulating film, and the metal oxide semiconductor layer is immersed in a solution containing the dye, and after removing the solvent, the dye is adsorbed to the layered metal oxide semiconductor by removing the solvent. Produced.

The flat electrode is a plate having a rectangular shape, a square shape, a circular shape, an elliptical shape, or the like using a conductive material, and can conduct electrons from a metal oxide semiconductor. . This flat electrode is preferably transparent, but even if it is opaque, it is desirable that the metal oxide semiconductor adsorbing the dye adheres to the side irradiated with light and that the electrolyte is in contact with the electrode. Because it can operate, it can be made of various materials such as various types of stainless steel and copper. Even if the production of dye-sensitized solar cells is expanded, it is easy to procure materials and reduce manufacturing costs. it can.

  The conductive mesh electrode has a plurality of polygonal or circular holes such as a triangle, a quadrangle, and a hexagon using a conductive material, and can conduct electrons from a metal oxide semiconductor. it can. By eliminating the need for the electrode itself to be transparent by making the electrode mesh like this, it is not a rare and expensive material such as indium, but can be composed of general-purpose materials such as various stainless steels and copper, Even if the production of dye-sensitized solar cells is expanded, the procurement of materials is easy, and the manufacturing cost can be reduced.

  The thickness of the flat electrode or mesh electrode is preferably in the range of 0.1 μm to 1 mm. This is because when the thickness of the plate-like electrode or the mesh-like electrode exceeds the above range, the mass of the dye-sensitized solar cell becomes heavy, which hinders physical distribution and construction, and increases the manufacturing cost. Moreover, when the thickness of the said flat electrode or mesh electrode is less than the said range, it is because the said flat electrode or mesh electrode may not fully fulfill | perform the function as an electrode.

  The ratio of the openings of the mesh electrode is preferably in the range of 10% to 99%. This is because, when the ratio of the openings of the mesh electrode is less than the above range, it interferes with the passage of iodine ions through the openings, and as a result, the current is reduced, thereby reducing the conversion efficiency. Further, when the ratio of the openings of the mesh electrode exceeds the above range, most of the light passes through the openings, and the conversion efficiency is lowered.

  The line width of the mesh electrode and the gap between the mesh electrodes are appropriately selected according to the shape of the dye-sensitized solar cell to be used. The line width of the mesh electrode is 1 μm to 3 mm is preferable, 5 μm to 1 mm is more preferable, and 10 μm to 100 μm is most preferable. The mesh spacing of the mesh electrode is preferably 5 μm to 1000 μm, more preferably 10 μm to 500 μm, and most preferably 20 μm to 300 μm.

  The material of the flat electrode or the mesh electrode is not particularly limited as long as it is a conductive material. Specifically, copper, aluminum, titanium, chromium, tungsten, molybdenum, platinum, tantalum, Examples include niobium, zirconium, zinc, carbon, various stainless steels, and alloys thereof, and titanium, chromium, tungsten, various stainless steels, and alloys thereof are preferable. Note that the flat electrode or the mesh electrode may have flexibility.

The metal oxide semiconductor is formed by aggregating a plurality of metal oxide semiconductors having a particle shape or the like in which transition between band gaps occurs. The shape of each metal oxide semiconductor is not limited to a spherical shape, and may be any shape such as a rod shape, a needle shape, or a cone shape. Examples of the material of the metal oxide semiconductor include TiSrO ₃ , BaTiO ₃ , TiO ₂ , Nb ₂ O ₅ , MgO, ZnO, WO ₃ , Bi ₂ O ₃ , CdS, CdSe, CdTe, In ₂ O _3. Various metal oxide semiconductors such as SnO ₂ are used. Of these, TiO ₂ is preferably used to improve photoelectric conversion efficiency. When TiO ₂ is used, the anatase type is more preferable as the crystal structure than the rutile type.

  As a method for adhering the metal oxide semiconductor to the plate-like electrode or mesh electrode, the plate-like electrode or mesh electrode is immersed in a dispersion solution of a metal oxide semiconductor having a particle shape or the like, and then a lifting solvent is used. A method of repeating the drying step once or a plurality of times and then sintering at 300 to 500 ° C. is preferable. Alternatively, the metal oxide semiconductor may be attached to the plate electrode or network electrode by a method comprising a step of immersing the plate electrode or network electrode in a metal alkoxide such as titanium isopropoxide and hydrolyzing the metal alkoxide. good.

  The film thickness of the metal oxide semiconductor is preferably 0.1 μm to 200 μm, more preferably 0.5 μm to 100 μm, and most preferably 1 to 50 μm. Conversion efficiency can be improved as the film thickness of a metal oxide semiconductor is this range.

  Even if the metal oxide semiconductor is attached to the flat electrode or the mesh electrode, the metal oxide semiconductor is difficult to adhere due to the shape of the mesh electrode, or the metal oxide semiconductor is Although it adheres and peels off during drying and sintering, an exposed portion in which a part of the mesh electrode is exposed is generated. This exposed portion reduces the short-circuit current and open-circuit voltage of the dye-sensitized solar cell and further reduces the conversion efficiency. In order to improve this, in the dye-sensitized solar cell of the present invention, the exposed portion is insulated. Cover with a film.

  The insulating film is made of an inorganic compound, an organic compound, or a composite thereof having extremely low conductivity, and is a member that protects the exposed portion with a predetermined film thickness. As an inorganic compound used for the insulating film, it is preferable to use a single metal oxide or a combination of a plurality of highly insulating metal oxides such as alumina and silica. Moreover, as an organic compound used for the insulating film, a highly insulating paint, particularly an electrodeposition paint is preferable. When these materials are used for coating, the adhesion to the exposed portion of the plate-like or mesh-like electrode is good and the insulation can be maintained, so that the short-circuit current and the open-circuit voltage of the dye-sensitized solar cell are improved, and further the conversion efficiency Can be improved. In particular, when an electrodeposition paint is used, only the exposed portion of the flat electrode or the mesh electrode can be selectively and reliably covered.

  The film thickness of the insulating film is preferably 0.1 μm to 200 μm, more preferably 0.5 μm to 100 μm, and most preferably 1 to 50 μm. When the film thickness of the insulating film is within this range, the exposed portion of the flat electrode or the mesh electrode can be reliably insulated, and the metal oxide semiconductor is not excessively covered. Does not reduce conversion efficiency.

  The above dye functions as a sensitizing dye that absorbs a specific wavelength of sunlight and enters an excited state, and injects electrons into the metal oxide semiconductor to which the dye adsorbs. And as a metal contained in a pigment | dye, transition metals, such as ruthenium, osmium, iron, copper, platinum, cobalt, rhenium, chromium, are used.

Such dyes include cis-dithiocyano bis (4,4′-dicarboxy-2,2′-bipyridine) ruthenium; Ru (dcbpy) ₂ (NCS) ₂ ; -Bis (2,2'-bipyridyl-4-carboxylate-4'-carboxylic acid) -ruthenium; N719, Ru (tctpy) ₂ (NCS) ₃ ; N714, Ru (dmypy) (dcbpyH) I, Ru (c H)) ruthenium-bipyridine complexes such as ₂ (NCS) ₂ , cis-Ru (dcbiqH) ₂ (NCS) ₂ (TBA) ₂ , cis-dithiocyanobi s (4,4′-dicarboxy-2,2′-bipyridine) osmium; osmium-bipyridine-based complexes such as Os (dcbpy) ₂ (NCS) ₂ , cis-dithiocyano bis (4,4′-dicarboxy-2,2 '-Bipyridine) iron; iron-bipyridine complexes such as Fe (dcbpy) ₂ (NCS) ₂ , copper-phenanthroline systems such as bis (2,9-di (4-carboxy) diphenyl-1,10-phenanthroline) copper Complexes, platinum-quinoxaline complexes such as Pt (dcbpy) ₂ (L) ₂ [L: quinoxaline-2,3-dithiolate], rhenium-pyridine complexes such as Re (bpy) (CO) ₃ (ina), etc. Cited .

  A molecule that has a functional group (imidazolyl group, carboxyl group, phosphone group, etc.) that binds to a metal oxide semiconductor, does not cause desorption as a result of bonding, and can suppress exposure of the electrode surface as a result of adsorption. Can be used as an additive. Specific examples include phosphonic acids having a long-chain alkyl group such as tert-butylpyridine, 1-methoxybenzimidazole, and decanephosphoric acid.

  When producing a dye-sensitized solar cell, the positive electrode that is the counter electrode can be any conductive material as long as it is a conductive material. If a conductive layer is installed on the side facing the surface, it can be used. However, it is preferable to use an electrochemically stable substance for the counter electrode. Specific examples include platinum, platinum black, carbon, various stainless steels, and conductive polymers. The positive electrode may be a transparent or opaque substrate such as a quartz glass substrate on which a film of the above substance is formed, or a platinum substrate. In addition, the light that has passed through the openings that are the openings of the mesh electrode and the electrolyte does not originally contribute to photoelectric conversion. Irradiation to the attached metal oxide semiconductor can contribute to photoelectric conversion. Therefore, the positive electrode is preferably one that reflects light.

  The electrolyte is used for receiving electrons from the positive electrode and reducing the oxidized dye, and has a liquid, gel, or solid form. As the electrolyte, a solute such as an iodine-iodide salt (such as lithium iodide, sodium iodide, tetrabutylammonium iodide) that is a redox chemical species, a polar solvent that does not easily volatilize, such as acetonitrile or ionic liquid, or It can be obtained by dissolving or dispersing in a gel or solid polymer material.

  In addition, on the outer surface side of the flat electrode or mesh electrode, that is, on the side opposite to the electrolyte side, a thin glass plate, polycarbonate film, hard It is preferable to provide a protective layer using a transparent material that transmits sunlight, such as a coated PET film.

  Hereinafter, one embodiment of the present invention will be described in detail. In addition, this invention is not limited to the following embodiment.

Example 1
1. An anatase-type titanium oxide fine particle having a particle diameter of several nanometers to several tens of nanometers was dispersed and dissolved in a mixed liquid composed of ethylene glycol, acetylacetone, and water to prepare a 10 wt% titanium oxide dispersion. This titanium oxide dispersion was immersed in a mesh-like electrode 1 of SUS306, which is a mesh-like and austenitic stainless steel, under a condition of 25 ° C. for 3 seconds, and then dried at 120 ° C. for 3 minutes. This dipping and drying operation was repeated 5 times to attach titanium oxide to the mesh electrode 1. Further, sintering was performed at 450 ° C. for 30 minutes to form a layered metal oxide semiconductor 2 made of titanium oxide having a thickness of 15 μm.

  Next, a mesh electrode 1 to which the metal oxide semiconductor 2 is attached and a mesh SUS306 as a counter electrode are coated with an electrodeposition paint containing a modified polyamide-imide resin (“INSURED 4000” manufactured by Nippon Paint Co., Ltd.). ) And applying a voltage of 24 V for 30 seconds using the mesh electrode 1 with the metal oxide semiconductor 2 attached thereto as a cathode to insulate the exposed portion 11 of the mesh electrode with the metal oxide semiconductor attached thereto. Was coated with a functional film 4.

Then, as the dye 3, a structure in which the protons of the two carboxyl groups of the ruthenium dye N719 [cis-dithiocyanobis (4,4′-dicboxy-2,2′-bipyridine) ruthenium are substituted with tetra n-butylammonium. 3.57 mg was dissolved in 10 mL of absolute ethanol to prepare a dye adsorption solution having a concentration of 3 × 10 ⁻⁴ mol / L. In this solution, the mesh stainless steel to which the titanium oxide was attached was immersed overnight, and the dye 3 was adsorbed on the titanium oxide.

2. Preparation of dye-sensitized solar cell 1.97 g of 1-propyl-3-methylimidazolium iodide (PMII), 81.5 mg of iodine, and 0.49 g of polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP) were added with 20 mL of acetone. It melt | dissolved by ultrasonically treating for 1 hour, The gel-like electrolyte solution was produced. Then, 2 mL of this electrolyte solution is dropped onto a plate-like stainless steel plate having no mesh as a counter electrode 6, and a mesh electrode to which the layered metal oxide semiconductor 2 adsorbing the above-mentioned dye is attached before the charge solution is dried. 1 was placed on the electrolyte solution to which 1 was dropped, and the top was covered with a protective layer 8 made of a slide glass. The slide glass and the stainless steel plate of the positive electrode were sandwiched between clips, and the solvent of the electrolyte solution was volatilized to become the electrolyte 5 to prepare a dye-sensitized solar cell.

(Example 2)
A network electrode 1 having a layered metal oxide semiconductor 2 attached thereto was prepared in the same manner as in Example 1, and after adsorbing the ruthenium dye N719, 2-propanol was added to 76.7 mg of aluminum isopropoxide. By immersing the mesh electrode 1 with the metal oxide semiconductor 2 adsorbed to the dye for 15 minutes in an aluminum isopropoxide solution adjusted to 15 mM in a total volume of 25 mL and performing alumina coating on the surface, the above dye is obtained. A negative electrode was fabricated by covering the exposed portion 11 of the mesh electrode 1 to which the layered metal oxide semiconductor 2 adsorbing the metal adhering. In the same manner as in Example 1, a dye-sensitized solar cell was produced using this negative electrode.

(Comparative Example 1)
Similarly to Example 1, a network electrode 1 having a layered metal oxide semiconductor 2 adhered thereto was prepared, and the negative electrode was prepared by adsorbing the dye 3 which is the ruthenium dye N719. In addition, when the negative electrode produced with the optical microscope was observed, the exposed part 11 which was exposed by the magnitude | size of 10 micrometers-40 micrometers among the mesh-like electrode to which the said metal oxide semiconductor 2 adhered was scattered. In the same manner as in Example 1, a dye-sensitized solar cell was produced using this negative electrode.

  The mesh electrode 1 that is the negative electrode of the dye-sensitized solar cell obtained in Examples 1 and 2 and Comparative Example 1 and the counter electrode 6 that is the positive electrode are connected by a lead wire 7, and a xenon lamp light source (“PF-” manufactured by PerkinElmer) 300BF "), current-voltage characteristics were measured respectively. From the obtained current-voltage curve, the short-circuit current, open-circuit voltage, and photoelectric conversion efficiency of the battery were calculated.

  Table 1 shows a list of performances of the dye-sensitized solar cells produced using the negative electrode.

  From the results of Table 1, in Examples 1 and 2, since the exposed portion 11 where a part of the mesh electrode 1 used for the negative electrode is exposed is covered, the short circuit current and the open circuit are more open than in the comparative example 1 that is not covered. It has been found that the voltage is improved and, as a result, the conversion efficiency is also improved. In particular, in Example 1, it was found that the exposed portion 11 of the mesh electrode 1 could be selectively and reliably covered, so that the conversion efficiency could be greatly improved.

DESCRIPTION OF SYMBOLS 1 ... Mesh electrode 11 ... Exposed part 2 ... Metal oxide semiconductor 3 ... Dye 4 ... Insulating film 5 ... Electrolyte 6 ... Counter electrode 7 ... Lead wire 8 ... ..Protective layer

Claims (4)

Comprising an electrode to which a metal oxide semiconductor adsorbing a dye is attached;
The dye-sensitized solar cell, wherein an exposed portion of the electrode where the metal oxide semiconductor is not attached and is exposed is covered with an insulating film. The dye-sensitized solar cell according to claim 1, wherein the electrode is a mesh electrode. The dye-sensitized solar cell according to claim 1 or 2, wherein the insulating film is an inorganic compound having at least one of alumina and silica. The dye-sensitized solar cell according to claim 1, wherein the insulating film is an organic compound that is an electrodeposition paint.

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