JP2007048590A - Dye-sensitized solar cell, its photoelectrode substrate, and manufacturing method of photoelectrode substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dye-sensitized solar cell capable of preventing degradation of power generation characteristics of the dye-sensitized solar cell by preventing reverse electron movement from a transparent electrode membrane to a semiconductor layer of a photoelectrode substrate of the solar cell, its photoelectrode substrate, and a manufacturing method of the photoelectrode substrate. <P>SOLUTION: The photoelectrode substrate 2 of a dye-sensitized solar cell 1 has an electrolyte 4 sealed between the photoelectrode substrate 2 and an opposed electrode of an opposed electrode substrate 3. A metal membrane 7 consisting of titanium is formed on a transparent electrode membrane 6 formed on the surface of a substrate member 5, and a porous semiconductor electrode membrane 8 is formed on this metal membrane 7, and a sensitized dye is adsorbed to or carried on this semiconductor electrode membrane 8. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a dye-sensitized solar cell, a photoelectrode substrate thereof, and a method of manufacturing the photoelectrode substrate, and more particularly, a dye-sensitized type in which an electrolyte is sealed between a photoelectrode substrate and a counter electrode of the counter electrode substrate. The present invention relates to a solar cell, a photoelectrode substrate thereof, and a method of manufacturing the photoelectrode substrate.

  In recent years, from the viewpoint of environmental problems, solar cells that convert light energy into electrical energy have attracted attention, and in particular, dye-sensitized solar cells have attracted attention because they can reduce manufacturing costs. Conventional dye-sensitized solar cells were poor in practicality due to low photoelectric conversion efficiency. Recently, a large amount of dye is adsorbed by making the semiconductor electrode porous to increase the surface area. In addition, a technique for improving photoelectric conversion efficiency has been developed (for example, see Patent Document 1).

  As schematically shown in FIG. 6, a dye-sensitized solar cell using such a technique includes a photoelectrode substrate 102, a counter electrode substrate 103, and an electrolytic solution 104 enclosed therebetween. A dye-sensitized solar cell 101 is known. The photoelectrode substrate 102 of the dye-sensitized solar cell 101 includes a substrate member 105, a transparent electrode film 106 formed on the surface 105 a of the substrate member 105, and titanium oxide formed on the transparent electrode film 106. The porous semiconductor electrode film 108 is made up of, and a dye is adsorbed to the porous semiconductor electrode film 108. The porous semiconductor electrode film 108 is formed by applying a suspension containing semiconductor particles on the transparent electrode film 106, drying it, and baking it. On the other hand, the counter electrode substrate 103 of the dye-sensitized solar cell 101 includes a counter substrate member 110 and a counter electrode 111 formed by coating the counter substrate member 110 with a catalyst such as platinum. . A substrate member 105 and a counter substrate member 110 are disposed so that the counter electrode 111 and the porous semiconductor electrode film 108 are opposed to each other with a predetermined interval, and an electrolyte solution is interposed between the counter electrode 111 and the porous semiconductor electrode film 108. 104 is enclosed, and the dye-sensitized solar cell 101 is configured. In this dye-sensitized solar cell 101, the dye molecules adsorbed on the surface of the porous semiconductor electrode film 108 absorb light, inject electrons into the semiconductor, and the porous semiconductor electrode film 108 side becomes a negative electrode. It is designed to generate electricity.

JP-T-5-504023 (first page, FIG. 1)

  However, in the conventional dye-sensitized solar cell 101 described above, electrons move from the porous semiconductor electrode film 108 to the transparent electrode film 106 by diffusion, so that reverse electron transfer from the transparent electrode film 106 to the semiconductor layer occurs. At the same time, the residence time of electrons in the porous semiconductor electrode film 108 becomes longer, and the probability of recombination between the electrons and the dye increases. As a result, the power generation characteristics of the dye-sensitized large intestine battery 101 There is a problem that decreases.

  Therefore, in view of such conventional problems, the present invention prevents back-electron transfer from the transparent electrode film of the photoelectrode substrate of the dye-sensitized solar cell to the semiconductor layer, and generates power in the dye-sensitized solar cell. An object of the present invention is to provide a dye-sensitized solar cell, a photoelectrode substrate thereof, and a method for producing the photoelectrode substrate, which can prevent deterioration of characteristics.

  As a result of diligent research to solve the above problems, the present inventor has a porous structure in which an electrolyte is enclosed between the transparent electrode film of the photoelectrode substrate and the counter electrode of the counter electrode substrate to adsorb or carry the sensitizing dye. In the dye-sensitized solar cell in which the semiconductor electrode film is formed on the transparent electrode film, the photoelectrode of the dye-sensitized solar cell is formed by forming the porous semiconductor electrode film on the transparent electrode film through the metal film. It has been found that the reverse electron transfer from the transparent electrode film of the substrate to the semiconductor layer can be prevented, and the power generation characteristics of the dye-sensitized solar cell can be prevented from being lowered, and the present invention has been completed.

  That is, the photoelectrode substrate of the dye-sensitized solar cell according to the present invention includes a substrate member, a transparent electrode film formed on the substrate member, a metal film formed on the transparent electrode film, and the metal film. A porous semiconductor electrode film formed thereon and a sensitizing dye adsorbed or supported on the porous semiconductor electrode film are provided. In the photoelectrode substrate of the dye-sensitized solar cell, the metal film is preferably a film made of titanium or tantalum, the thickness of the metal film is preferably 1 to 100 nm, and the metal film is visible light. The transmittance is preferably 10% or more.

  Further, the dye-sensitized solar cell according to the present invention includes the above-described photoelectrode substrate, a counter electrode substrate provided with a counter electrode disposed to face the porous semiconductor electrode film of the photoelectrode substrate, and the counter electrode It consists of the electrolyte enclosed between the board | substrate and the photoelectrode board | substrate, It is characterized by the above-mentioned.

  Furthermore, the method for producing a photoelectrode substrate of a dye-sensitized solar cell according to the present invention includes a step of forming a transparent electrode film on a substrate member, a step of forming a metal film on the transparent electrode film, and the metal film. The method includes a step of forming a porous semiconductor electrode film thereon and a step of adsorbing or carrying a sensitizing dye on the porous semiconductor electrode film. In the method for producing a photoelectrode substrate of the dye-sensitized solar cell, the metal film is preferably a film made of titanium or tantalum, the metal film is preferably 1 to 100 nm in thickness, and the metal film is visible. It preferably has a transmittance of 10% or more with respect to light.

  According to the present invention, the contact between the metal film made of titanium or the like formed on the transparent electrode film and the porous semiconductor electrode film made of titanium oxide or the like (contact between the metal and the semiconductor) becomes a Schottky contact, and the rectification characteristics Can appear. That is, while electrons are likely to move from the porous semiconductor film to the transparent electrode side, electrons are less likely to move in the opposite direction, thereby preventing reverse electron movement from the transparent electrode film to the semiconductor layer. Thus, the probability of recombination of electrons and dyes can be reduced, and as a result, the power generation efficiency of the solar cell can be improved.

  According to the present invention, it is possible to prevent reverse electron transfer from the transparent electrode film of the photoelectrode substrate of the dye-sensitized solar cell to the semiconductor layer, and to prevent a decrease in power generation characteristics of the dye-sensitized solar cell. A dye-sensitized solar cell and a photoelectrode substrate thereof can be provided.

  Hereinafter, embodiments of a dye-sensitized solar cell, a photoelectrode substrate thereof, and a method of manufacturing the photoelectrode substrate according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 schematically shows an embodiment of a dye-sensitized solar cell according to the present invention. As shown in FIG. 1, the dye-sensitized solar cell 1 of the present embodiment includes a photoelectrode substrate 2, a counter electrode substrate 3, and an electrolyte 4 enclosed between them. The photoelectrode substrate 2 includes a transparent plastic substrate member 5, a transparent electrode film 6 formed on the surface 5a of the substrate member 5, and a metal film 7 made of titanium formed on the transparent electrode film 6. The porous semiconductor electrode film 8 is formed on the metal film 7 and adsorbs and carries the sensitizing dye. On the other hand, the counter electrode substrate 3 includes a plastic counter substrate member 10 and a counter electrode 11 formed on the surface 10 a of the counter substrate member 10. The substrate member 5 and the counter substrate member 10 are made of plastic such as acrylic, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyolefin, polycarbonate (PC).

  The dye-sensitized solar cell 1 having the above-described structure can be manufactured as follows.

  First, in a vacuum apparatus in which argon gas and a small amount of oxygen gas are introduced (not shown), sputtering treatment is performed using indium tin oxide (hereinafter referred to as “ITO”) as a target material and plasma generated by high frequency discharge. As a result, a transparent electrode film 6 made of ITO is formed on the surface 5a of the transparent plastic substrate member 5 of the photoelectrode substrate 2 as shown in FIG. 2A.

  Next, the substrate member 5 on which the transparent electrode film 6 is formed is put in a vacuum apparatus together with titanium as a target material, argon gas is introduced into the vacuum apparatus, and sputtering is performed using plasma generated by high frequency discharge. A metal film 7 made of titanium is formed on the transparent electrode film 6 as shown in FIG. 2B. By continuously performing the titanium film forming operation in the vacuum apparatus, a barrier layer such as an impurity is not generated at the interface between the transparent electrode film 6 and the metal film 7, and the metal film 7 is placed on the transparent electrode film 6. It can be formed by laminating. The metal film 7 may be formed by vapor deposition or ion plating instead of sputtering.

Next, as shown in FIG. 2C, after a porous semiconductor electrode film 8 made of titanium dioxide (TiO ₂ ) is formed on the metal film 7 by a firing method, the photoelectric conversion function is applied to the porous semiconductor electrode film 8. A sensitizing dye (for example, a ruthenium complex) having benzene is adsorbed and supported. Thus, the photoelectrode substrate 2 is formed by sequentially laminating the transparent electrode film 6, the metal film 7, and the porous semiconductor electrode film 8 that adsorbs and carries the sensitizing dye on the surface 5 a of the substrate member 5. It is formed by. The porous semiconductor electrode film 8 may be formed by an electrodeposition method or a hydrothermal treatment method instead of the firing method.

  On the other hand, by coating the counter electrode 11 made of platinum on the surface 10a of the counter substrate member 10, the counter electrode substrate 3 having the platinum counter electrode 11 on the surface 10a of the counter substrate member 10 as shown in FIG. Form. Note that graphite may be used as the counter electrode 11 instead of platinum.

  The porous semiconductor electrode film 8 of the photoelectrode substrate 2 thus formed and the counter electrode 11 of the counter electrode substrate 3 are arranged so as to face each other, and the electrolyte is interposed between the porous semiconductor electrode film 8 and the counter electrode 11. 4 is enclosed, and the dye-sensitized solar cell 1 of the present embodiment is completed (see FIG. 1). In addition, as the electrolyte 4, a redox electrolyte solution containing an oxidation-reduction pair such as an iodine-iodine compound or a bromine-bromine compound can be usually used.

In the dye-sensitized solar cell 1 formed in this way, when sunlight is incident on the photoelectrode substrate 2 from the outside, the sensitizing dye adsorbed and supported on the porous semiconductor film 8 is excited, and the electrons are grounded. Transition from state to excited state. The excited electrons of the sensitizing dye are injected into the conduction band of TiO ₂ constituting the porous semiconductor electrode film 8 and move to the transparent electrode film 6 via the metal film 7 made of titanium. This transparent electrode film 6 to the counter electrode 11 via an external circuit (not shown). The electrons that have moved to the counter electrode 11 reduce triiodide ions in the electrolyte 4 to iodide ions (when a redox electrolyte containing an iodine-iodine compound is used as the electrolyte 4). This reduced iodide ion is oxidized again by the sensitizing dye and returns electrons to the sensitizing dye. Electric energy is extracted by repeating such an action.

  In the dye-sensitized solar cell 1 of the present embodiment as described above, the contact between the metal film 7 made of titanium and the porous semiconductor electrode film 8 formed on the transparent electrode film 6 is a Schottky contact. Shows rectification characteristics. That is, while electrons easily move from the porous semiconductor electrode film 8 to the transparent electrode film 6 side, electrons do not easily move in the opposite direction, and thus the reverse from the transparent electrode film 6 to the semiconductor layer. The probability of recombination of electrons and dyes can be reduced by preventing electron transfer.

  In the dye-sensitized solar cell 1 of the present embodiment, the above-described rectification characteristics can be improved by increasing the thickness of the metal film 7 made of titanium in the thickness of the thin film region. However, if the metal film 7 is thickened, the ratio of the metal film 7 that reflects and absorbs incident light increases, and the amount of light transmitted through the metal film 7 decreases, so the amount of light for photoelectric conversion decreases. Therefore, the thickness of the metal film 7 is set so that the metal film 7 is appropriately thinned to increase the above-described effect of preventing reverse electron transfer than the effect of reducing the light amount for photoelectric conversion, and consequently increase the conversion efficiency. It is preferable to adjust the thickness. Thus, in order to increase the effect of preventing reverse electron transfer more than the effect of reducing the amount of light for photoelectric conversion, the thickness of the metal film 7 is preferably 1 to 100 nm, and preferably 2 to 20 nm. More preferably, it is most preferably 3 to 10 nm. Moreover, it is preferable that the metal film 7 has a transmittance of 10% or more with respect to visible light. Even when the effect of reducing the amount of light for photoelectric conversion is greater than the effect of preventing reverse electron movement, it is possible to realize a solar cell having a metallic color in appearance and use the solar cell as a mirror.

  In the dye-sensitized solar cell 1 of the present embodiment, the substrate member 5 and the counter substrate member 10 are formed of a plastic material, but may be formed of glass.

  Further, in the dye-sensitized solar cell 1 according to the present embodiment, since the sunlight is incident from the substrate member 5 side, the substrate member 5 is formed of a transparent plastic material excellent in light transmittance. The substrate member 10 is not necessarily formed of a plastic material having excellent light transmittance. However, when sunlight is incident from the counter substrate member 10 side, it is necessary to form the counter substrate member 10 from a plastic material having excellent light transmittance and to make the counter electrode 11 transparent. In this way, when sunlight is incident from the counter substrate member 10 side, a material having poor light transmittance may be used for the substrate member 5 and the transparent electrode film 6.

  Moreover, in the dye-sensitized solar cell 1 of the present embodiment, the metal film 7 made of titanium is used, but the same effect can be obtained even if a metal film made of tantalum is used. These two metals not only have a Schottky contact with the porous semiconductor electrode film, but also have high corrosion resistance and are not corroded by iodine ions in the electrolyte.

  Hereinafter, examples of the dye-sensitized solar cell, the photoelectrode substrate thereof, and the method for producing the photoelectrode substrate according to the present invention will be described in detail.

[Example 1]
First, a substrate member with ITO in which a transparent electrode film (ITO film) 6 made of ITO is formed on the surface of a substrate member 5 made of polyethylene naphthalate (PEN) (having a rectangular planar shape with a side length of 5 cm) A plate member having a thickness of 125 μm and an electric resistance value of 10Ω / □ was prepared (see FIG. 2A). This substrate member with ITO is put in a vacuum apparatus together with titanium as a target material, argon gas is introduced into the vacuum apparatus at 50 sccm, and plasma generated on the surface of the target material by high frequency discharge (13.56 MHz, 400 W). Was used for 60 seconds to form a metal film (titanium film) 7 of titanium having a thickness of 10 nm on the ITO film 6 (see FIG. 2B).

  Next, after applying a titania coating paste for low temperature film formation to a thickness of 50 μm on the titanium film 7, the porous semiconductor electrode having a film thickness of 5 μm is heated on the titanium film 7 by heating at 150 ° C. for 5 minutes. A film 8 was formed (see FIG. 2C), and then a ruthenium complex dye was adsorbed on the porous semiconductor electrode film 8. In this way, the titanium film 7 is formed on the ITO film 6, and the photoelectrode substrate 2 formed by laminating the porous semiconductor electrode film 8 on which the sensitizing dye is adsorbed and supported on the titanium film 7 is formed. Produced.

The dye-sensitized solar cell 1 using the photoelectrode substrate 2 thus produced was irradiated with pseudo-sunlight having a light irradiation energy of 10 mW / cm ² using a solar simulator, and a battery characteristic test was performed. Further, as a comparative example, the conventional dye-sensitized solar cell 101 shown in FIG. 6 is manufactured so as to have the same configuration except that the configuration of the photoelectrode substrate 102 is different from the configuration of the photoelectrode substrate 2, and the same battery A characteristic test was conducted. The results are shown in FIGS. 3 and 4 and Table 1. FIG. 3 shows a comparison of the experimental results on the current-voltage characteristics of the dye-sensitized solar cell 1 of this example and the dye-sensitized solar cell 101 of the comparative example, and FIG. 4 shows this example. Current flowing when a voltage is applied between the photoelectrode substrates 2 and 102 and the counter electrode substrates 3 and 103 in a state where the dye-sensitized solar cell 1 and the dye-sensitized solar cell 101 of the comparative example are not irradiated with light. Is shown. In Table 1, Isc is a current (short-circuit current) flowing between both terminals when the output terminal of the dye-sensitized solar cell is short-circuited, and Voc is when the output terminal of the dye-sensitized solar cell is opened. Voltage between both terminals (open voltage), f. f. Is a value obtained by dividing the maximum output Pmax (= Imax · Vmax) by the product of the open-circuit voltage Voc and the current density Jsc (short-circuit current Isc per 1 cm ² ) (fill factor) ff = Pmax / Voc · Jsc ), Η represents a value (conversion efficiency) expressed as a percentage by multiplying 100 by a value obtained by dividing the maximum output Pmax by the irradiation light quantity (W) (per 1 cm ² ).

  As shown in FIG. 3 and Table 1, in the dye-sensitized solar cell 1 of this example, compared to the dye-sensitized solar cell 101 of the comparative example, the influence of reflection and absorption of incident light by the titanium film 7 Although the short-circuit current is reduced by about 10%, the fill factor is remarkably improved to about 1.4 times. As a result, the conversion efficiency is 1.3 times or more. The difference in performance between the dye-sensitized solar cell 1 of this example and the dye-sensitized solar cell 101 of the comparative example is due to the rectification characteristics caused by the titanium film 7 of the photoelectrode substrate 2 of this example. It is considered a thing. Also, from FIG. 4, in the dye-sensitized solar cell 1 of this example, no current flows with respect to the reverse voltage, whereas in the dye-sensitized solar cell 101 of the comparative example, the reverse direction. It can be seen that current flows with respect to the voltage of. This is because the titanium film 7 exists between the titanium oxide film as the porous semiconductor electrode film 8 and the ITO film as the transparent electrode film 6 so that the contact between the titanium oxide film and the titanium film becomes Schottky contact. It is thought that this is to show the rectification characteristics. On the other hand, in the photoelectrode substrate 102 of the comparative example, it is considered that the reverse electron transfer from the transparent electrode film 106 to the semiconductor layer cannot be prevented, so that current flows in the reverse direction.

[Example 2]
A dye-sensitized solar cell was prepared in the same manner as in Example 1 except that the thickness of the titanium film 7 was changed to 5 nm, and the same battery characteristic test as in Example 1 was performed. The results are shown in FIG. As shown in FIG. 3 and Table 1, in the dye-sensitized solar cell 1 of this example, the titanium film 7 is thinner than that of Example 1, so that the incident light from the titanium film 7 is smaller than that of Example 1. The effect of reflection and absorption is reduced, the short circuit current is increased, and the fill factor is improved to about 1.3 times that of the comparative example, so that the conversion efficiency is about 1.7 times that of the comparative example. Yes.

[Example 3]
A dye-sensitized solar cell 1 was produced in the same manner as in Example 1 except that a tantalum film having a thickness of 5 nm was formed as the metal film 7, and the same battery characteristic test as in Example 1 was performed. The results are shown in FIG. In addition, FIG. 5 has shown and compared the experimental result about the current-voltage characteristic of the dye-sensitized solar cell 1 of a present Example, and the dye-sensitized solar cell 101 of a comparative example.

  As shown in FIG. 5 and Table 1, in the dye-sensitized solar cell 1 of this example, compared to the dye-sensitized solar cell 101 of the comparative example, a short circuit occurred due to the influence of reflection and absorption of incident light of the tantalum film. Although the current is reduced by about 30%, the fill factor is remarkably improved to 1.4 times or more, and as a result, the conversion efficiency is improved.

  A plurality of dye-sensitized solar cells each having a photoelectrode substrate according to the present invention are connected in series, or a plurality of solar cell arrays connected in series are connected in parallel to form a dye-sensitized solar cell assembly. If desired, the desired electrical energy can be obtained. In addition, a mirror type dye-sensitized solar cell can be produced.

It is sectional drawing which shows typically embodiment of the dye-sensitized solar cell by this invention. It is sectional drawing explaining the manufacturing process of the photoelectrode substrate of the dye-sensitized solar cell shown in FIG. It is sectional drawing explaining the manufacturing process of the photoelectrode substrate of the dye-sensitized solar cell shown in FIG. It is sectional drawing explaining the manufacturing process of the photoelectrode substrate of the dye-sensitized solar cell shown in FIG. It is a figure which compares and shows the experimental result about the current-voltage characteristic of the dye-sensitized solar cell of Example 1 and 2 and the dye-sensitized solar cell of a comparative example. It is a figure which compares and shows the performance of the dye-sensitized solar cell of Example 1, and the dye-sensitized solar cell of a comparative example, and is the electric current which flows when a voltage is applied between a photoelectrode substrate and a counter electrode substrate FIG. It is a figure which compares and shows the experimental result about the current-voltage characteristic of the dye-sensitized solar cell of Example 2, and the dye-sensitized solar cell of a comparative example. It is sectional drawing which shows the conventional dye-sensitized solar cell typically.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Dye-sensitized solar cell, 2 ... Photoelectrode substrate, 3 ... Counter electrode substrate, 4 ... Electrolyte, 5 ... Substrate member, 6 ... Transparent electrode film (ITO film), 7 ... Metal film, 8 ... Porous semiconductor Electrode film, 10 ... counter substrate member, 11 ... counter electrode

Claims (11)

A substrate member, a transparent electrode film formed on the substrate member, a metal film formed on the transparent electrode film, a porous semiconductor electrode film formed on the metal film, and the porous semiconductor electrode A photoelectrode substrate for a dye-sensitized solar cell, comprising a sensitizing dye adsorbed or supported on a film. The photoelectrode substrate for a dye-sensitized solar cell according to claim 1, wherein the metal film is a film made of titanium. The photoelectrode substrate for a dye-sensitized solar cell according to claim 1, wherein the metal film is a film made of tantalum. The photoelectrode substrate for a dye-sensitized solar cell according to any one of claims 1 to 3, wherein the metal film has a thickness of 1 to 100 nm. 5. The photoelectrode substrate for a dye-sensitized solar cell according to claim 1, wherein the metal film has a transmittance of 10% or more with respect to visible light. A photoelectrode substrate according to any one of claims 1 to 5, a counter electrode substrate comprising a counter electrode disposed to face the porous semiconductor electrode film of the photoelectrode substrate, the counter electrode substrate and the light A dye-sensitized solar cell comprising an electrolyte sealed between electrode substrates. A step of forming a transparent electrode film on the substrate member; a step of forming a metal film on the transparent electrode film; a step of forming a porous semiconductor electrode film on the metal film; and A method for producing a photoelectrode substrate of a dye-sensitized solar cell, comprising a step of adsorbing or carrying a sensitizing dye. The method for producing a photoelectrode substrate of a dye-sensitized solar cell according to claim 7, wherein the metal film is a film made of titanium. The method for producing a photoelectrode substrate of a dye-sensitized solar cell according to claim 7, wherein the metal film is a film made of tantalum. The method for producing a photoelectrode substrate of a dye-sensitized solar cell according to any one of claims 7 to 9, wherein the metal film has a thickness of 1 to 100 nm. The method for producing a photoelectrode substrate for a dye-sensitized solar cell according to any one of claims 7 to 10, wherein the metal film has a transmittance of 10% or more with respect to visible light.

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