JP2008053042A - Pigment sensitized solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dye-sensitized solar cell capable of converting incident light into electric energy by efficiently absorbing (utilizing) it. <P>SOLUTION: The dye-sensitized solar cell 1 has a first anode 10 having a first sensitizing dye 24 and a second anode 30 having a second sensitizing dye 44 different from the first sensitizing dye arranged separated in front and rear direction. A cathode 50 (typically mesh electrode) is arranged between both anodes 10, 30. By these electrodes 10, 30, 50, a solar cell 1 in which two sub cells 6, 7 connected electrically in parallel are superposed in front and rear is formed. Thereby, light L2 which has transmitted through the first anode 10 is introduced efficiently into the second anode 30 and furthermore, energy can be taken out from the light L2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a dye-sensitized solar cell, and more particularly to a dye-sensitized solar cell that can efficiently absorb incident light by effectively using a plurality of sensitizing dyes.

  Gretzel cell type (wet) dye-sensitized solar cells (hereinafter sometimes simply referred to as “dye-sensitized solar cells”) are more resource-intensive than other solar cells (for example, silicon-based solar cells). It has features such as few restrictions, reduction in manufacturing cost, and theoretical conversion efficiency exceeding silicon-based solar cells. However, the conversion efficiency of the dye-sensitized solar cell actually obtained is lower than that of a single crystal silicon solar cell or the like, and further higher efficiency is demanded. Patent Documents 1 to 3 can be cited as prior art documents relating to dye-sensitized solar cells.

Japanese Patent Laid-Open No. 1-220380 JP 2006-024574 A JP 2006-066215

The configuration and operation of a typical conventional dye-sensitized solar cell will be described with reference to FIG. The dye-sensitized solar cell 100 shown in FIG. 5 is roughly composed of an anode 110 and a cathode 150, and an electrolyte 160 filled therebetween. The anode 110 includes a glass substrate 112, a transparent conductive layer 114 formed on the inner surface (side facing the cathode 150) of the glass substrate, and further includes a dye layer 120 formed on the conductive layer. The dye layer 120 has a configuration in which a sensitizing dye 124 such as a ruthenium complex is held on a porous film 122 formed using nano-sized titanium oxide particles. The cathode 150 includes a glass substrate 152, and a conductive layer 154 and a platinum film 156 formed in order on the inner side (side facing the anode 110). The anode 110 and the cathode 150 are electrically connected by a conductive path 170 including a load 172. When the solar cell 100 having such a configuration is irradiated with light from the anode 110 side, the sensitizing dye 124 is excited by the incident light, and electrons are transferred from the dye to the titanium oxide (n-type semiconductor) conductor constituting the porous film 122. (E ⁻ ) is injected. The electrons reach the cathode 150 from the anode 110 via the conductive path (external circuit) 170. The sensitizing dye 124 in an oxidized state by donating electrons to titanium oxide receives electrons from ions contained in the electrolyte 160 and returns to the neutral state. As a result, the ions lose electrons and enter an oxidized state, but return to the original oxidation number by receiving electrons from the cathode 150. By repeating such a cycle, light energy is converted into electric energy (current).

  Each of the above sensitizing dyes has a specific light absorption characteristic (absorption spectrum), and in the light absorption characteristic, light having a wavelength with a high extinction coefficient is well absorbed, whereas light having a wavelength with a low extinction coefficient is not so absorbed (use efficiency is low). Low). Therefore, it is considered that a dye-sensitized solar cell capable of absorbing (utilizing) light in a wider wavelength range can be constructed by using a plurality of sensitizing dyes having different light absorption characteristics. However, in the solar cell 100 having a conventional configuration (see FIG. 5), simply holding a mixture of a plurality of dyes in the porous titanium oxide layer 122 as the sensitizing dye 124 does not necessarily improve the efficiency of the battery. This is presumably because energy transfer occurs between the dyes in a state where a plurality of dyes are mixed.

  In addition, when the solar cell 100 (see FIG. 5) having a conventional structure is irradiated with light having a wide wavelength range such as sunlight, the wavelength at which the sensitizing dye 124 included in the anode 110 of the battery exhibits a high extinction coefficient. Is absorbed well, and the sensitizing dye 124 can be excited to send electrons to the cathode 150 (electrical energy is taken out). However, the sensitizing dye 124 has a wavelength with a low extinction coefficient. The dye layer 120 is transmitted without being absorbed by the light. If electric energy can be further extracted from such transmitted light, it is considered that higher performance (short-circuit current density, conversion efficiency, etc.) can be realized.

  However, when the configuration of the anode 110 in the conventional solar cell 100 is changed to a configuration in which a dye layer having a different sensitizing dye is simply laminated on the dye layer 120 having the sensitizing dye 124, the laminated dyes are stacked. The thickness of the entire layer (laminate) may be too large. For this reason, disappearance due to recombination of electrons easily occurs, and sufficient performance improvement is not realized, or rather the performance deteriorates. In order to avoid such an event, if the thickness of the entire laminate is limited to the same level as that of the conventional dye layer 120, the thickness of the individual dye layers constituting the laminate is reduced. The light cannot be fully utilized (absorbed).

  Therefore, the present invention provides a dye-sensitized solar cell that can absorb (utilize) incident light more efficiently and convert it into electric energy by effectively using a plurality of sensitizing dyes. One purpose.

  The present inventor has a plurality of anodes arranged to be separated in the front-rear direction with respect to the incident direction of light, and a dye sensitization having a configuration in which a dye layer having different sensitizing dyes is divided into these anodes. According to the solar cell, the present invention was completed by finding that incident light can be efficiently absorbed by effectively using the sensitizing dye held in each dye layer.

  That is, one dye-sensitized solar cell according to the present invention is a Gretzel cell type (wet) dye-sensitized solar cell, and includes a first dye layer that holds a first sensitizing dye. Including the anode. The first anode may be one that exhibits translucency (translucent anode). The solar cell also includes a second anode that includes a second dye layer that retains a second sensitizing dye. The second sensitizing dye is typically a dye different from the first sensitizing dye. The second anode is disposed behind the first anode with respect to the light incident direction. The second anode is disposed so that the first dye layer and the second dye layer substantially overlap each other when viewed from the incident direction of the light. The solar cell also includes a cathode disposed between the first anode and the second anode as viewed from the light incident direction. The cathode may be one that exhibits translucency (a translucent cathode). The cathode is electrically connected to the first anode and the second anode. The solar cell further includes an electrolyte filled between the first anode, the second anode, and the cathode.

  In the solar cell having such a configuration, two subcells stacked in the front-rear direction with respect to the light incident direction and electrically connected in parallel to each other between each of the first anode and the second anode and the cathode. (That is, the first subcell including the first anode and the cathode and positioned in front of the light incident direction, and the first subcell including the second anode and the cathode and the first subcell with respect to the light incident direction. A second subcell located on the rear side of the subcell) is configured. Typically, the cathode is shared by the two subcells. By making the two subcells stacked in this way (arranged in tandem), the light transmitted through the first dye layer (light not absorbed by the first dye layer) is efficiently transferred to the second dye layer. It can be introduced well and absorbed efficiently in the second dye layer. That is, energy can be further extracted from the transmitted light by exciting the second sensitizing dye using light transmitted through the first dye layer having the first sensitizing dye. The second dye layer is not directly laminated on the first dye layer, but is formed on the second anode arranged at a distance from the first anode having the first dye layer. ing. For this reason, the sensitizing dye currently hold | maintained at each pigment | dye layer can be utilized efficiently, and the light of the wavelength range according to the light absorption characteristic of this pigment | dye can be absorbed more appropriately. Therefore, according to the solar cell disclosed here, better energy conversion efficiency can be realized as compared with the solar cell having no configuration of the second anode.

The first sensitizing dye and the second sensitizing dye may be two kinds of dyes arbitrarily selected from various dyes known as sensitizing dyes that can be used in the anode of a dye-sensitized solar cell. . In one preferred embodiment of the solar cell disclosed herein, one of the first sensitizing dye and the second sensitizing dye is an N ₃ die and the other is a black die. This combination of the N ₃ die and the black die is an example of a combination of sensitizing dyes that can efficiently absorb light in a wider wavelength range by complementing each other's light absorption characteristics (absorption spectrum). For example, an N ₃ die can be preferably used as the first sensitizing dye, and a black die can be used as the second sensitizing dye.

In a preferred embodiment of the solar cell disclosed herein, the thickness of each of the first dye layer and the second dye layer is approximately 20 μm or less (typically approximately 3 μm to 20 μm). As described above, when the thickness of the dye layer is excessively increased, the output characteristics (for example, the short-circuit current density J _sc ) may be reduced due to the contribution of electron recombination. By setting each individual dye layer to the above thickness, electrons generated from the sensitizing dye retained in each dye layer can be efficiently used (for example, taken out to an external circuit). The total thickness of the first dye layer and the second dye layer is preferably in the range of about 10 to 40 μm, for example. If the total thickness is too small, it may be difficult to obtain sufficient conversion efficiency. On the other hand, if the total thickness is too large, the thickness of at least one of the dye layers becomes too large, and the output characteristics (for example, the short-circuit current density J _sc ) can be reduced due to the contribution of electron recombination.

  As the cathode, a conductive mesh member can be preferably used from the viewpoint of ensuring translucency and increasing the contact efficiency with the electrolyte. For example, it is preferable to use a mesh made of a conductive metal (such as platinum) or a woven or non-woven fabric made of conductive fibers (such as platinum wire or carbon fiber).

  In a preferred aspect of the solar cell disclosed herein, the second anode includes a light reflecting metal film (metal reflecting film) on the rear side (back side) with respect to the light incident direction. Of the second anode, it is preferable that at least a portion on the incident direction side (front side or incident side) of the metal film has translucency. According to such a configuration, light that has once passed through the second dye layer (not absorbed) is reflected by the metal film and enters the second dye layer again, whereby the light excites the second sensitizing dye. Increase the chances (absorbed). This makes it possible to absorb incident light more efficiently and convert it into electrical energy.

  In another preferred embodiment of the solar cell disclosed herein, the first sensitizing dye is applied to a porous layer in which the first dye layer is obtained by firing titanium oxide particles having an average particle diameter of about 10 to 40 nm. It is held. In addition, the second dye layer holds the second sensitizing dye in a porous layer formed by firing titanium oxide particles having an average particle size of about 100 to 1000 nm. According to such a configuration, the first dye layer has high transparency by using titanium oxide particles having an average particle size of about 10 to 40 nm, and scattering of incident light (reflecting component, that is, going out of the cell) In other words, a porous layer can be formed. On the other hand, with respect to the second dye layer, light scattering is caused by using (relatively large) titanium oxide particles having an average particle size of about 100 to 1000 nm, thereby improving the short circuit current density (and thus improving the conversion efficiency). Can be achieved. Therefore, by using titanium oxide particles having the above average particle diameter in the first dye layer and the second dye layer, incident light can be absorbed (utilized) more efficiently and converted into electric energy.

The first dye layer is obtained by holding a first sensitizing dye in a porous layer having a specific surface area of approximately 60 to 80 m ² / g obtained by firing titanium oxide particles having an average particle diameter of approximately 15 to 25 nm. obtain. In such a porous layer, about 5 × 10 ⁻⁸ mol or more per 1 cm ² area of the porous layer (typically about 5 × 10 ⁻⁸ mol / cm ² to about 30 × 10 ⁻⁸ mol / cm ^2). ) Of the first sensitizing dye may be retained. The first dye layer having such a configuration transmits incident light by the first sensitizing dye of the first dye layer and transmits light that has not been absorbed by the first dye layer (second dye layer). It is preferable because of its excellent balance with performance.

  Another dye-sensitized solar cell disclosed herein is a Gretzel cell type dye-sensitized solar cell, and includes a plurality of anodes having a dye layer in which a sensitizing dye is held. Typically, the sensitizing dyes held in each dye layer of the plurality of anodes are different from each other. The solar cell also includes a cathode that is electrically connected to the plurality of anodes. Furthermore, an electrolyte filled between the plurality of anodes and the cathode is included. Here, the plurality of anodes are disposed at a distance from each other in the light incident direction. The plurality of anodes are arranged so that the dye layers of the anodes overlap each other when viewed from the incident direction. Of the plurality of anodes and the cathodes, at least the anode and the cathode disposed on the incident side (front side) than the anode disposed on the rearmost side with respect to the light incident direction are both translucent. Have.

  In the solar cell having such a configuration, a plurality of subcells are formed between each of the plurality of anodes and the cathode so as to be stacked back and forth in the light incident direction and electrically connected in parallel to each other. The plurality of subcells may share the cathode. In this way, by adopting a configuration in which a plurality of subcells are stacked (arranged in tandem), light transmitted through the dye layer of the anode disposed on the relatively front side (incident side) among the plurality of anodes (the The light that has not been absorbed by the dye layer can be efficiently introduced into the dye layer of another anode arranged on the rear side and absorbed by the dye layer. That is, energy can be further extracted from the transmitted light by exciting the sensitizing dye of the rear anode using light transmitted through the dye layer of the front anode. In the configuration of the solar cell, a plurality of dye layers holding different sensitizing dyes are not directly laminated, but are provided on each of a plurality of anodes arranged at intervals in the front and rear. For this reason, the sensitizing dye currently hold | maintained at each pigment | dye layer can be utilized efficiently, and the light of the wavelength range according to the light absorption characteristic of this pigment | dye can be absorbed more appropriately. Therefore, according to the solar cell disclosed herein, better energy conversion efficiency can be realized as compared with the solar cell having no configuration of the rear anode.

In one preferred embodiment, the thickness of each of the dye layers is about 20 μm or less (typically about 3 μm to 20 μm). Thereby, the electrons generated from the sensitizing dye held in each dye layer can be efficiently used. In another preferred embodiment, the total thickness of the dye layers of the plurality of anodes is about 10 μm or more (for example, about 10 μm to 100 μm). If the total thickness is too thick, raw material costs and manufacturing costs may increase for the energy obtained.
In still another preferred embodiment, the cathode has translucency, and at least one of the anodes is disposed on the front side and the rear side of the cathode as viewed from the incident direction of the light. Of the plurality of anodes, the anode located on the rearmost side in the light incident direction may include a metal film for light reflection on the rear side (back side) with respect to the light incident direction. Of the anode, it is preferable that at least a portion on the incident direction side (front side) of the metal film has translucency.
The invention disclosed in this specification further includes the following.

(1) Gretzel cell type dye-sensitized solar cell element (cell):
A plurality of anodes having a dye layer holding a sensitizing dye, wherein the sensitizing dyes held in each dye layer of the plurality of anodes are different from each other;
A cathode; and
An electrolyte filled between the plurality of anodes and the cathode;
Including
The plurality of anodes are arranged such that the dye layers of the anodes overlap with each other at a distance from the front and back with respect to the incident direction of light, as viewed from the incident direction.
Among the plurality of anodes and the cathodes, at least the anode or the cathode disposed on the incident side with respect to the anode disposed on the rearmost side with respect to the incident direction has a light-transmitting property. element.
Typically, the solar cell element is configured such that the plurality of anodes and the cathode are electrically connected to each other, so that light is incident between each of the plurality of anodes and the cathode. A plurality of subcells stacked in front and back (arranged in tandem) and electrically connected to each other can be configured. The plurality of subcells may share the cathode. The solar electronic device disclosed herein can be preferably used in a state where the plurality of anodes and cathodes are connected in this manner.

(2) The solar cell according to (1), wherein the cathode has translucency, and at least one of the anodes is disposed on the front side and the rear side of the cathode as viewed from the incident direction of the light. element.
(3) Of the plurality of anodes, an anode located on the rearmost side in the light incident direction includes a light reflecting metal film on the rear side with respect to the light incident direction, and at least the metal among the anodes The solar cell element according to (1) or (2), wherein a portion closer to the incident direction than the film has translucency.

(4) A Gretzel cell type dye-sensitized solar cell element (cell):
A translucent first anode comprising a first dye layer carrying a first sensitizing dye;
A second dye layer on which a second sensitizing dye different from the first sensitizing dye is held, the second dye layer being behind the first anode with respect to the light incident direction and the first sensitizing dye as viewed from the incident direction; A second anode arranged such that one dye layer and the second dye layer overlap;
A translucent cathode disposed between the first anode and the second anode as viewed from the direction of incidence of the light; and
An electrolyte filled between the first anode, the second anode and the cathode;
A dye-sensitized solar cell element comprising:
Typically, the solar cell element is configured such that the first anode, the second anode, and the cathode are electrically connected to each other, so that a light is interposed between each of the two anodes and the cathode. Two subcells stacked in tandem (disposed in tandem) with respect to the incident direction of the light source and electrically connected in parallel with each other (that is, the first anode and the cathode are provided on the front side with respect to the incident direction of light) A first subcell positioned, and a second subcell that includes the second anode and the cathode and is positioned on the rear side of the first subcell with respect to the light incident direction. The two subcells may share the cathode. The solar electronic device disclosed herein can be preferably used in a state where the first anode, the second anode, and the cathode are connected in this manner.

  Hereinafter, preferred embodiments of the present invention will be described. Note that matters other than matters specifically mentioned in the present specification and necessary for the implementation of the present invention can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.

One typical configuration example of the dye-sensitized solar cell disclosed herein is schematically shown in FIG.
The dye-sensitized solar cell 1 shown in FIG. 1 roughly includes a first anode 10 disposed on the front side (incident side) with respect to the incident direction of light (the direction from left to right in FIG. 1); The second anode 30 disposed on the rear side (back side) with respect to the incident direction, the cathode 50 disposed between the two anodes 10 and 30, and the filling between the electrodes 10, 30, and 50. And the electrolyte 60 thus formed. That is, the cathode 50 and the electrolyte 60 are sandwiched between the two anodes 10 and 30 disposed on the front and back surfaces.

The first anode 10 includes a transparent substrate 12 and a transparent conductive layer 14 formed on the surface inside the cell of the substrate (on the back side with respect to the light incident direction). The first anode 10 further includes a first dye layer 20 formed on the transparent conductive layer 14. The first dye layer 20 includes a porous layer 22 made of an oxide semiconductor (typically an n-type semiconductor, for example, titanium oxide), and a first sensitizing dye 24 held in the porous layer. Have.
The second anode 30 includes a transparent substrate 32 and a transparent conductive layer 34 formed on the surface of the substrate on the cell inner side (front side with respect to the light incident direction). The second anode 30 further includes a second dye layer 40 formed on the transparent conductive layer 34. The second dye layer 40 includes a porous layer 42 made of an oxide semiconductor (typically an n-type semiconductor, for example, titanium oxide), and a second sensitizing dye 44 held in the porous layer. Have. Here, the first sensitizing dye 24 and the second sensitizing dye 44 are different from each other.

  The first anode 10 and the second anode 30 are arranged so that the region where the first dye layer 20 is provided and the region where the second dye layer 40 is provided overlap each other as viewed from the light incident direction (however, Spaced apart). For example, about 70% or more (more preferably about 90% or more, typically about 100%) of the area of the first dye layer 20 overlaps the region where the second dye layer 40 is provided. preferable. Alternatively, about 70% or more (more preferably about 90% or more, typically about 100%) of the area of the second dye layer 40 overlaps the region where the first dye layer 20 is provided. preferable. With such a configuration, the light transmitted through the first dye layer 20 can be efficiently introduced into the second dye layer 40. Note that the dye-sensitized solar cell 1 shown in FIG. 1 has a metal reflection film (a metal film for light reflection) provided on the rear side of the second anode 30 (the back surface of the transparent substrate 32 in the example shown in FIG. 1). 36 may further be provided. The metal reflecting film 36 is mainly made of a metal such as aluminum (Al), silver (Ag), iron (Fe), nickel (Ni), chromium (Cr), rhodium (Rh), or any of these metals. It can be an alloy as a component. The thickness of the metal reflection film 36 may be about 0.2 to 20 μm, for example. Such a metal reflective film 36 can be produced by applying, for example, a general vacuum deposition method, sputtering method, ion plate method, electrolytic plating method, or the like.

The cathode 50 is a net-like (mesh-like) member made of a conductive metal, and is immersed in an electrolyte 60 filled between the first anode 10 and the second anode 30. As the electrolyte 60, oxidizable and reducible ions (e.g. I ^- / I ₃ ^- redox pair) such as those are dissolved in a suitable solvent.
The cathode 50 is electrically connected to each of the first anode 10 and the second anode 30 via a conductive path (external circuit) 70 including a load 72. As a result, the first subcell 6 is formed between the first anode 10 and the cathode 50, and the second subcell 7 is formed between the second anode 30 and the cathode 50. The 1st subcell 6 and the 2nd subcell 7 are piled up back and forth with respect to the incident direction of light, and are arranged (in tandem). The first subcell 6 and the second subcell 7 share the cathode 50. In addition, since the cathode 50 has a mesh shape, the electrolyte (typically liquid) 60 can go back and forth between the first subcell 6 and the second subcell 7 through the mesh of the cathode 50. Therefore, in the solar cell 1 having the configuration shown in FIG. 2, the electrolyte 60 is shared by the first subcell 6 and the second subcell 7. Note that the electrolyte in the first subcell and the electrolyte in the second subcell may be separated (for example, separated by a cathode).

When the dye-sensitized solar cell 1 having such a structure is irradiated with light L1 from the first anode 10 side (left side in FIG. 1), the first sensitizing dye 24 is excited by the light L1, and the porous layer 22 is formed from the dye. Electrons (e ⁻ ) are injected into the oxide semiconductor to be formed. The electrons reach the cathode 50 via the conductive path (external circuit) 70 from the first anode 10. The first sensitizing dye 24 that is in an oxidized state by giving electrons to the oxide semiconductor receives electrons from a solute ion (for example, I ⁻ ) contained in the electrolyte 60 and returns to the neutral state. As a result, the ions lose electrons and enter an oxidized state (for example, I ₃ ⁻ ). The ions in the oxidation state receive electrons flowing through the conductive path 70 from the cathode 50 and return to the original oxidation number state (for example, I ⁻ ). By repeating such a cycle, electric energy can be extracted from the light L1 irradiated to the battery. Energy conversion by such a cycle is performed by the first subcell 6 located on the front side of the solar cell 1 with respect to the light incident direction.

On the other hand, part of the incident light L1 passes through the first anode 10 (light L2), and further passes through the cathode 50 and enters the second dye layer 40. The second sensitizing dye 44 is excited by the light L2, and electrons (e ⁻ ) are injected from the dye into the oxide semiconductor constituting the porous layer. The subsequent process is the same as that of the first anode 10. That is, the second sensitizing dye 44 in the oxidized state receives electrons from the solute of the electrolyte 60 and returns to the neutral state. The solute that has been oxidized by giving electrons to the second sensitizing dye 24 receives electrons from the cathode 50 and returns to its original oxidation number. Energy conversion by such a cycle is performed by the second subcell 7 located on the rear side (back side) of the solar cell 1 with respect to the light incident direction. By repeating the cycle, electric energy can be further extracted in the second subcell 7 from the light L2 that could not be used in the first anode 10 (first subcell 6).

  In the battery 1 having the metal reflective film 36, at least a part of the light L3 transmitted through the second anode 30 is reflected by the metal reflective film 36, and the reflected light L4 is again reflected by the second dye layer 40. It can be returned to. By exciting the second sensitizing dye 44 with the light L4, it is possible to further extract electric energy from the light L3 that was not available (transmitted) when first incident on the first anode 10 and the second anode 30. it can.

The solar cell 1 having such a structure can be constructed using various conventionally known materials as long as the function (photoelectric conversion function) can be appropriately exhibited.
For example, as the transparent substrates 12 and 32, those having translucency and having appropriate physical strength and chemical stability with respect to the electrolyte can be appropriately selected and used. For example, various substrates known as those that can be used for transparent electrodes of conventional solar cells (typically dye-sensitized solar cells) can be used without particular limitation. In a preferred embodiment, a glass substrate is used as each of the transparent substrates 12 and 32. The transparent substrate 12 used for the first anode 10 and the transparent substrate 32 used for the second anode 30 may be the same (same type) transparent substrate or different transparent substrates.
In this specification, “translucent” means simulated sunlight (typically AM (air mass) 1.5, light quantity 100 mW / cm ² ) obtained by sunlight or a solar simulator, unless otherwise specified. Of light) is a property of transmitting at least a part (a part of the intensity, a part of the wavelength region, or both of them).

The transparent conductive layer 14 provided on the surface of the transparent substrate 12 and the transparent conductive layer 34 provided on the surface of the transparent substrate 32 may be the same as the transparent conductive layer provided in the anode of the conventional solar cell. Preferable examples of the transparent conductive layer 14 include an indium-tin oxide (ITO) film, a fluorine-doped tin oxide (hereinafter sometimes referred to as “F: SnO ₂ ”) film, and the like. . The transparent conductive layer 14 included in the first anode 10 and the transparent conductive layer 34 included in the second anode 30 may be made of the same (same type) material or different materials. In addition, since the conductive glass substrate in which such a transparent conductive layer was formed on the glass substrate is marketed, you may construct | assemble a solar cell using this.

In a preferred embodiment, the porous layer 22 constituting the first dye layer 20 and the porous layer 42 constituting the second dye layer 40 are formed using fine particles of an oxide semiconductor (typically an n-type semiconductor). It is a formed layer. For example, the oxide may be titanium oxide (TiO ₂ ), zinc oxide (ZnO), barium titanate (BaTiO ₃ ), tungsten oxide (WO ₃ ), or the like. These oxides may be complex oxides of these oxides, or complex oxides of these oxides and other oxides. The average particle diameter of the fine particles may be, for example, in the range of about 10 nm to 1000 nm. In a preferred embodiment, the porous layer 22 is a porous layer formed using fine particles of titanium oxide (typically anatase-type titanium oxide). For example, titanium oxide fine particles having an average particle diameter of about 10 nm to 40 nm (more preferably about 15 to 25 nm, for example, about 20 nm) can be used. It is preferable to prepare the first dye layer by using titanium oxide fine particles having such an average particle diameter. Further, for example, titanium oxide fine particles having an average particle diameter of about 100 nm to 1000 nm (more preferably about 200 to 600 nm, for example, about 400 nm) can be used. It is preferable to produce the second dye layer using titanium oxide fine particles having such an average particle diameter.

  As a method of forming the porous layer 22 on the transparent conductive layer 14 using such oxide semiconductor fine particles, various conventionally known methods in the field of dye-sensitized solar cells can be appropriately employed. For example, a liquid composition in which the particles are dispersed in an appropriate medium is prepared, and the composition is applied onto the transparent conductive layer 14 by a wet process such as a squeegee method, a doctor blade method, a spin coating method, or a screen printing method. And a method of heating (baking) to an appropriate temperature (approximately 400 to 500 ° C., typically about 450 ° C. can be preferably employed in the case of titanium oxide fine particles) after drying as necessary. It can preferably be employed.

As the first sensitizing dye 24 and the second sensitizing dye 44, various kinds known to be used for an electrode (typically an anode) of a dye-sensitized solar cell and exhibit a photosensitizing function. A pigment | dye can be selected suitably. Examples of such a dye include ruthenium metal complexes such as a ruthenium polypyridyl complex (N ₃ dye, black dye, etc.), a ruthenium phenanthroline complex, and a quinoline-based ruthenium complex. A dye having a functional group in the molecule such as a carboxylic acid group, a carboxylic anhydride group, a sulfonic acid group, and an alkoxy group that can form a chemical bond between the complex and an oxide semiconductor (typically TiO ₂ ). Is preferred.

As the first sensitizing dye (the dye contained in the dye layer disposed on the foremost side with respect to the incident direction of light), a dye exhibiting an absorption spectrum that can absorb sunlight well can be preferably employed. On the other hand, as the second sensitizing dye, (1) showing an absorption spectrum capable of absorbing sunlight well, and / or (2) light transmitted through the first dye layer and the electrolyte (more generalized, A dye satisfying at least one of the absorption spectrum that can well absorb the incident light (light reaching the second dye layer) can be preferably employed. An example of a combination of a first sensitizing dye and a second sensitizing dye that can be preferably employed from such a viewpoint includes a combination of an N ₃ dye and a black die. The N ₃ dye may be the first sensitizing dye and the black dye may be the second sensitizing dye, the black dye may be the first sensitizing dye and the N ₃ dye may be the second sensitizing dye. More favorable results can be achieved with a solar cell using an N ₃ dye as the first sensitizing dye and a black die as the second sensitizing dye.

  As a technique for holding the sensitizing dye in the porous layer (typically, the porous titanium oxide layer), a conventional dye sensitization including a single anode holding the sensitizing dye in the porous titanium oxide layer is used. Various methods similar to those used when the sensitizing dye is held in the porous titanium oxide layer in a solar cell can be appropriately employed. For example, a method including impregnating the porous layer with a solution obtained by dissolving a sensitizing dye in an appropriate solvent and drying the impregnated sensitizing dye solution (removing the solvent) is adopted. obtain. When the oxide semiconductor fine particles are heated in the process of forming the porous layer as described above, the porous layer is heated at a stage where the temperature of the porous layer is moderately lowered (for example, to about 150 to 250 ° C.) after the heating. The layer may be immersed in the sensitizing dye solution. As a result, the sensitizing dye solution can be well distributed to each part of the porous layer, and a dye layer in which more sensitizing dye is retained can be formed. Such a method can be preferably applied to the production of the first dye layer and the second dye layer.

In a preferred embodiment, at least one (preferably both) of the first dye layer and the second dye layer is a dye layer (typically a dye layer having a structure in which a sensitizing dye is held in a porous titanium oxide layer). ) is a dye layer sensitizing dye is retained in the area of 1 cm ² per approximately 5 × 10 ^-8 mol or more (e.g., about ^{5 × 10 -8 mol / cm 2} ~30 × 10 -8 mol / cm 2) of the. About 10 × 10 ⁻⁸ mol / cm ² or more (for example, about 10 × 10 ⁻⁸ mol / cm ² to 30 × 10 ⁻⁸ mol / cm ² ) of the sensitizing dye was retained per 1 cm ² of the area of the dye layer. A dye layer is more preferable. It is preferable that the sensitizing dye retention amount per 1 cm ² of area of the first dye layer is in the above range.
Further, the amount of the sensitizing dye held per volume of 1 cm ^{3 of} the dye layer (typically a dye layer having a structure in which the sensitizing dye is held in the porous titanium oxide layer) is about 3 × 10 ^−5. A dye layer having a mol / cm ³ or more (for example, about 3 × 10 ⁻⁵ mol / cm ³ to 50 × 10 ⁻⁵ mol / cm ³ ) is preferable, and 10 × 10 ⁻⁵ mol / cm ³ or more (for example, about 10 ×). 10 ⁻⁵ mol / cm ³ to 50 × 10 ⁻⁵ mol / cm ³ , typically about 10 × 10 ⁻⁵ mol / cm ³ to 30 × 10 ⁻⁵ mol / cm ³ ) are more preferable. . It is preferable that at least the sensitizing dye retention amount per 1 cm ³ of the volume of the first dye layer is in the above range.

In general, when the amount of the sensitizing dye retained per unit area of the dye layer increases, the number of sensitizing dye molecules excited by light incident on the dye layer increases, so that more current is supplied to the dye layer. Can be taken out from. In order to increase the amount of the sensitizing dye, it is effective to increase the specific surface area of the porous layer. Therefore, if the specific surface area of the porous layer is approximately the same, the amount of the sensitizing dye that can be held in the porous layer tends to increase as the thickness of the porous layer increases. However, when the thickness of the dye layer is excessively increased as described above, the electrons extracted from the sensitizing dye disappear due to recombination, so that the current density extracted to the external circuit can be reduced. Therefore, when the relationship between the thickness of the dye layer and the short-circuit current density (J _sc ) of the cell having the dye layer on the anode is examined under the same conditions, in general, (a) the thickness of the dye layer is While the thickness of the porous layer increases while the thickness is relatively small, the value of the short-circuit current density increases. (B) When the thickness of the dye layer becomes larger, the increase in the value of the short-circuit current density becomes dull. When the thickness of the dye layer is further increased, the value of the short-circuit current density is approximately the same even if the thickness of the dye layer is increased, and (d) when the thickness of the dye layer is further increased, the thickness of the dye layer is increased. There is a tendency for the short circuit current density to decrease as it increases.

Therefore, it is preferable that the thickness of the first dye layer and the second dye layer is set to a certain degree so that the thickness of the dye layer and the short-circuit current density are in the relationship (a), (b) or (c). . For example, it is preferable that the thickness of each of the first dye layer and the second dye layer is about 25 μm or less (typically about 3 μm to 25 μm, more preferably 3 μm to 20 μm, for example, 5 μm to 20 μm). In particular, the thickness of the first dye layer disposed in front of the second dye layer with respect to the incident direction of light is such that the thickness of the dye layer and the short-circuit current density are in the relationship (a) or (b). It is preferable to have a certain thickness. For example, the thickness of the first dye layer is preferably about 20 μm or less (typically 3 μm to 20 μm, more preferably about 3 μm to 15 μm, for example 5 μm to 15 μm).
The total thickness of the first dye layer and the second dye layer can be set in a range of about 10 to 40 μm, for example. The total thickness may be in the range of approximately 15-30 μm.

The cathode constituting the dye-sensitized battery disclosed herein is not particularly limited as long as it can provide translucency and conductivity. For example, a conductive mesh member can be preferably used from the viewpoint of ensuring translucency and conductivity and increasing the contact efficiency with the electrolyte (reducing internal resistance). For example, a mesh made of conductive metal (platinum (Pt), copper (Cu), silver (Ag), gold (Au), etc.), woven fabric or non-woven fabric made of conductive fibers (platinum wire, carbon fiber, etc.), etc. Use is preferred. In addition, a member in which a conductive metal (platinum or the like) is thinly attached to the surface of a woven or nonwoven fabric made of carbon fiber, glass fiber, synthetic resin fiber, or the like by a technique such as sputtering or plating can be used.
Although the thickness of the cathode is not particularly limited, it is not preferable to excessively increase the thickness of the cathode in consideration of translucency and the entire size (thickness) of the solar cell. Usually, it is appropriate to set the thickness of the cathode to about 5 μm to 1000 μm (for example, about 30 μm to 300 μm). When viewed from the light incident direction (typically, the thickness direction of the cathode), the ratio of the opening area of the holes penetrating the cathode to the area of the entire cathode is at least about 25% (more preferably 40% or more). ) Is preferable.

As the electrolyte, various electrolytes known as those that can be used for the electrolyte of a dye-sensitized solar cell can be appropriately selected and used. For example, an oxidation-reduction pair (redox couple) such as iodine (I ⁻ / I ₃ ⁻ ) or bromine (Br ⁻ / Br ₃ ⁻ ) as a solute is dissolved in a suitable solvent A common redox electrolyte can be preferably used. As said solvent, organic solvents, such as nitrile type (for example, acetonitrile), carbonate type (for example, ethylene carbonate, propylene carbonate), or these mixed solvents can be used preferably.

  In the above, the solar cell having the structure schematically shown in FIGS. 1 and 2, that is, two anodes (first anode and second anode) having different sensitizing dyes are arranged before and after the light-transmitting cathode. Although the dye-sensitized solar cell having the arranged configuration has been described, a plurality of anodes spaced apart from each other in the light incident direction are provided, and dye layers having different sensitizing dyes are provided on the plurality of anodes. The idea of the present invention of arranging separately can also be realized in other modes.

  For example, in the configuration shown in FIG. 1, the first anode, the second anode, and the cathode are arranged in order of “(incident side) first anode / cathode / second anode (back side)” from the light incident side. However, for example, the arrangement of these electrodes may be “(incident side) first anode / second anode / cathode (back side)”. Here, each of the first anode and the second anode has a first dye layer and a second dye layer in which different sensitizing dyes are held, and the first anode and the second anode are spaced apart from each other in the light incident direction. Yes. The cathode is electrically connected to the first anode and the second anode. Thus, a first subcell is formed between the first anode and the cathode, and a second subcell is formed between the second anode and the cathode. The first subcell and the second subcell share the cathode and are electrically connected in parallel, and are stacked in the front-rear direction with respect to the light incident direction. Note that the portion of the first subcell on the rear side of the second anode overlaps with the second subcell. In the dye-sensitized solar cell having such a configuration, a cathode having a platinum film provided on a conductive glass substrate having a transparent conductive film (ITO or the like) on the surface can be preferably used as the cathode. Further, the second anode constituting the solar cell has one or more through holes through which the electrolyte can flow in order to ensure charge transfer via the electrolyte between the first anode and the cathode. Can be a thing. The dye layer of the second anode may be provided on the back side (cathode side) of the transparent substrate constituting the second anode, or may be provided on the front side (first cathode side or incident side). It may be provided on both sides. Usually, it is preferable to use a second anode having a dye layer on at least the back side (cathode side).

  Furthermore, as another aspect, it is good also as a structure provided with three or more anodes (1st anode, 2nd anode, 3rd anode ...) which have mutually different sensitizing dyes and are arrange | positioned back and forth. For example, the plurality of anodes and cathodes are arranged in the order of “(incident side) first anode / second anode / third anode / cathode (back side)” from the light incident side, or “ (Incident side) first anode / second anode / cathode / third anode (back side) ”, etc.

  Several examples relating to the present invention will be described below, but the present invention is not intended to be limited to those shown in the examples.

<Example 1: cell and a N ₃ sensitized anode and BD sensitized anode>
[Preparation of N ₃ -sensitized anode (A)]
A conductive glass substrate (width 10 mm, length 25 mm, thickness 1.1 mm) having a fluorine-doped tin oxide (F: SnO ₂ ) film on the surface as a conductive layer was prepared. On a conductive layer of the glass substrate, a paste-like composition containing anatase-type titanium oxide particles having a diameter of 20 nm (Catalyst Kasei Kogyo Co., Ltd., trade name “PST-18NR” was used) was square of 5 mm × 5 mm. It was applied to the shape range. After drying the substrate coated with the composition, the temperature was raised from room temperature to 450 ° C. in an air atmosphere over 30 minutes, and the TiO ₂ film was baked by maintaining the same temperature for 30 minutes. Thereafter, the substrate was allowed to cool to 200 ° C., where N ₃ dye (Ru (4,4′-dicarboxy-2,2′bipyridine) ₂ (NCS) ₂ ) ethanol as a sensitizing dye was used. It was immersed in the solution to adsorb the N ₃ dye on the TiO ₂ film. In this way, N ₃ dye-adsorbed TiO ₂ layer (dye layer) in the range of 5mm × 5mm conductive glass substrate to obtain a formed N ₃ sensitization anode (A). The N ₃ dye-adsorbed TiO ₂ film had a thickness of 6 μm and a specific surface area of 72 m ² / g. The N ₃ dye adsorption amount per unit area was 8.8 × 10 ⁻⁸ mol / cm ² .

[Production of BD-sensitized anode (a)]
A point where black dye (BD) was adsorbed instead of N ₃ dye as a sensitizing dye (this adsorption was performed using BD tetrabutylammonium salt ([Ru (4,4 ', 4 "-tricarboxy-2,2': 6 , 2 "-terpyridine) (NCS) ₃ ] ^3- [(C ₄ H ₉ ) ₄ N] ⁺ ₃ ) ethanol solution)), and a TiO ₂ film with a thickness of about 10 μm is formed The BD-adsorbed TiO ₂ film (dye layer) having a thickness of 11 μm on the conductive glass substrate was prepared in the same manner as the production of the N ₃ sensitized anode (A) except that the coating thickness of the paste-like composition was adjusted. BD sensitized anode (a) having a size of 5 mm × 5 mm was obtained. The specific surface area of the BD adsorption TiO ₂ film was N ₃ comparable to the dye-adsorbed TiO ₂ film of the N ₃ sensitization anode (A). Further, the BD adsorption amount per unit area was 12.0 × 10 ⁻⁸ mol / cm ² .

[Build cell]
The N ₃ sensitized anode (A) is used as a first anode (an anode disposed on the front side with respect to the light incident direction), and the BD sensitized anode (a) is used as a second anode (with respect to the incident direction). 2), a cell having a configuration schematically shown in FIG. 2 was constructed. As the cathode, platinum mesh with a thickness of 70 μm (product of High Purity Chemical Laboratory Co., Ltd., 100 mesh Pt wire mesh made of woven platinum wire. Square meshes are formed continuously in the vertical and horizontal directions at a pitch of about 200 μm. Used). The light transmittance of the mesh when irradiated with simulated sunlight of AM 1.5 and light quantity 100 mW / cm ² from the thickness direction of the platinum mesh is about 50%.

As shown in FIG. 2, a first anode (N ₃ sensitized anode (A)) 10 and a second anode (BD sensitized anode (a) are sandwiched between spacers 62 and 64 on both sides of a cathode (platinum mesh) 50. )) 30 was placed. The first anode 10 and the second anode 30 have the dye layers 20 and 40 inside (facing each other), and the position of the dye layer 20 and the position of the dye layer 40 when viewed from the light incident direction (cell thickness direction). And are arranged so as to match (overlap). As the spacers 62 and 64, a polytetrafluoroethylene film having a thickness of 50 μm formed with holes corresponding to the size (planar shape) of the dye layers 20 and 40 was used.
Then, the electrolytic solution 60 was injected into the space between the anodes 10 and 30. The electrolyte 60 includes 0.1 M lithium iodide (LiI), 0.05 M iodine (I ₂ ), 0.5 M 4-tert-butylpyridine and 0.5 M tetrabutylammonium iodide (( An acetonitrile solution containing C ₄ H ₉ ) ₄ NI) was used. In this way, a cell 1 having an overall thickness of about 2.37 mm was constructed. The cell 1 includes a first subcell 6 formed between the first anode 10 and the cathode 50 and a second subcell 7 formed between the second anode 30 and the cathode 50 with respect to the incident direction of light. And stacked in front and back (in tandem). The cathode 50 and the electrolyte 60 are shared by the first subcell 6 and the second subcell 7.

[Evaluation of output characteristics]
By electrically connecting the first anode 10 and the second anode 30 of the cell 1 obtained above with the cathode 50, the first subcell 6 and the second subcell 7 are electrically connected in parallel (FIG. 1). reference). Then, using a solar simulator from the first anode 10 side (left side in FIG. 2) (using Ushio Electric Co., Ltd. product, model name “Module X”), simulated sunlight with AM 1.5 and light quantity of 100 mW / cm ² was used. Irradiation was performed, and current-voltage characteristics were measured with a source meter (a Keithley product, model name “Model 2400” was used). From the obtained current-voltage curve, the short circuit current density (J _sc ), the open circuit voltage (V _oc ), the fill factor (FF) and the energy conversion efficiency (η) of the cell were calculated. As a result, the short-circuit current density (Jsc) of the cell according to this example is 11.5 mA / cm ² , the open circuit voltage (V _oc ) is 0.70 V, the fill factor (FF) is 0.49, and the energy conversion efficiency ( η) was 4.0%.

<Example 2: Cell comprising N ₃ sensitized anode and BD sensitized anode>
A 6 μm thick N ₃ dye-adsorbed TiO ₂ film (dye layer) is formed in a range of 5 mm × 5 mm on a conductive glass substrate by the same procedure as the production of the N ₃ -sensitized anode (A) according to Example 1 above. N ₃ sensitized anode (B) was obtained. Further, except that the coating thickness of the paste-like composition was adjusted so that a TiO ₂ film having a thickness of about 10 μm was formed, the same as the production of the BD sensitized anode (a) according to Example 1 above, A BD-sensitized anode (b) in which a BD-adsorbed TiO ₂ film (dye layer) having a thickness of 10 μm was formed in a range of 5 mm × 5 mm on a glass substrate was obtained.
A cell was prepared in the same manner as in Example 1 except that the N ₃ sensitized anode (B) was used for the first anode (front side) and the BD sensitized anode (b) was used for the second anode (back side). It was constructed and its output characteristics were evaluated. As a result, the short-circuit current density (J _sc ) of the cell according to this example was 7.3 mA / cm ² , and the conversion efficiency (η) was 3.9%. Further, when the output characteristic of only the first anode (first subcell) was evaluated by blocking the conductive path connecting the second anode and the cathode, the short-circuit current density (J _sc ) of 4.6 mA / cm. ² and the conversion efficiency (η) was 3.1%. On the other hand, when the output characteristic of only the second anode (second subcell) was evaluated by cutting off the conductive path connecting the first anode and the cathode, the short-circuit current density (J _sc ) was 2.2 mA / cm ² and the conversion efficiency was (Η) 0.9%.

Here, the relationship between the thickness of the TiO ₂ film and the adsorption amount of the N ₃ dye was examined in the case where the N ₃ dye was adsorbed on the TiO ₂ film by the same method as the production of the N ₃ sensitized anode (A). The results will be described. The study, the case and the TiO ₂ particles used the same TiO ₂ particles as used in Example 1 was performed in the case of using a different TiO ₂ particles properties.

That is, using the same titanium oxide particles (trade name “PST-18NR”) as used in Example 1, on the conductive glass substrate by the same method as the production of the N ₃ sensitized anode (A). A plurality of samples having an N ₃ dye-adsorbing TiO ₂ film (dye layer) was prepared. At this time, by adjusting the application amount of the paste composition, the thickness of the dye layer of each sample was varied in the range of about 3 to 15 μm. The specific surface areas of the dye layers formed using these PST-18NRs were all about 72 m ² / g.
In addition, a paste-like composition containing titanium oxide particles having a diameter of 30 nm (Degussa product, trade name “AWROXIDE (trademark) TiO ₂ P25”. This may also be referred to as “P25” hereinafter). A plurality of samples having an N ₃ dye-adsorbing TiO ₂ film (dye layer) on a conductive glass substrate were prepared in the same manner as in the preparation of the N ₃ sensitized anode (A). At this time, the thickness of the dye layer of each sample was varied in the range of about 6 to 20 μm by adjusting the coating amount of the paste composition. The specific surface area of the dye layer formed using P25 was about 49 to 50 m ² / g.

The amount of N ₃ dye adsorbed on these samples (dye adsorption amount) was measured. The measurement was performed by immersing each sample in a 0.1M aqueous potassium hydroxide solution to desorb the dye, and then determining the dye concentration of the aqueous potassium hydroxide solution by a colorimetric method.
FIG. 3 shows the result of plotting the amount of N ₃ dye adsorbed on the dye layer of each sample (dye adsorption amount [mol / cm ² ]) against the thickness of the dye layer. In FIG. 3, the plots indicated by white circles are data relating to samples using PST-18NR as titanium oxide particles, and the plots indicated by black circles are data relating to samples using P25 as titanium oxide particles. As can be seen from this figure, regardless of which titanium oxide particles are used, there is a generally proportional relationship between the dye layer thickness (film thickness) and the dye adsorption amount for each type of titanium oxide. It was. In addition, a sample using PST-18NR having a smaller average particle diameter (which can form a dye layer having a larger specific surface area) has more dye at a comparable film thickness than a sample using P25. It can be seen that it can be adsorbed.

<Example 3: cell and a BD-sensitized anode and N ₃ sensitization anode>
The cell produced in Example 2 was irradiated with the simulated sunlight from the BD-sensitized anode (b) side of the cell, and the output characteristics of the cell were measured. That is, in the cell evaluated here, the BD sensitized anode (b) is used as the first anode (front side) and the N ₃ sensitized anode (B) is used as the second anode (back side). As a result, the short-circuit current density (J _sc ) of the cell according to this example was 6.5 mA / cm ² and the conversion efficiency (η) was 2.9%. Further, when the output characteristics of only the first anode were evaluated by blocking the conductive path connecting the second anode and the cathode, the short-circuit current density (J _sc ) of 6.2 mA / cm ² and the conversion efficiency ( η) 2.6%. On the other hand, when the output characteristic of only the second anode was evaluated by cutting off the conductive path connecting the first anode and the cathode, the short-circuit current density (J _sc ) 0.7 mA / cm ² , the conversion efficiency (η) 0. It was 5%.

  The output characteristics measured for the cells according to Example 2 and Example 3 are shown together in Table 1 together with the schematic configurations of the first anode and the second anode of the cell according to each example. This table also shows the output characteristics obtained by using only the first anode and only the second anode for the cells according to Example 2 and Example 3.

As shown in Table 1, the short-circuit current density and conversion efficiency obtained using the individual anodes, and the short-circuit current density and conversion efficiency obtained using the two anodes, the first anode and the second anode, Additivity was observed between them. That is, the short-circuit current density of the cell according to Example 2 is the short-circuit current density when only the first anode is used among the two anodes of the cell and the short-circuit current density when only the second anode is used. Almost consistent with the sum. In addition, the conversion efficiency of the cell according to Example 2 was almost the same as the sum of the efficiency when only the first anode was used and the efficiency when only the second anode was used among the two anodes of the cell. . Similarly, the short-circuit current density and the conversion efficiency of the cell according to Example 3 were almost the same as the sum of the measured value when only the first anode was used and the measured value when only the second anode was used. In addition, the short circuit current density and conversion efficiency which were measured using only the first anode for the cell according to Example 2 were measured on the first anode (N ₃ sensitized anode (B)) according to Example 2 and the conductive glass substrate. The short-circuit current density and the conversion efficiency of the cell (without the second anode) filled with the electrolyte between the cathode having the platinum film and the conversion efficiency were comparable. These results support that inconvenience (for example, the performance of the first anode is greatly reduced) caused by the configuration having the second anode in addition to the first anode is not particularly recognized. . Moreover, the performance (photoelectric conversion performance) obtained by the second anode (second subcell) can effectively contribute to the performance improvement of the entire cell as an addition to the performance obtained by the first anode (first subcell). I support that.

<Example 4: cells with N ₃ sensitization anode>
Except that the coating thickness of the paste-like composition was adjusted so that a TiO ₂ film having a thickness of about 15 μm was formed, a thickness was formed on the conductive glass substrate in the same manner as the preparation of the N ₃ sensitized anode (A). Thus, an N ₃ sensitized anode (C) in which an N ₃ adsorption TiO ₂ film (dye layer) of 14.9 μm was formed in a range of 5 mm × 5 mm was obtained. Also, a cathode having a structure in which a platinum film was provided on a conductive glass substrate having an ITO film on the surface was prepared. The N ₃ sensitized anode (C) and the cathode are opposed to each other with a polytetrafluoroethylene film having a thickness of 50 μm (holes having a shape corresponding to the dye layer) as spacers. The same electrolyte as used in 1-3 was filled. In this way, a cell having the N ₃ sensitized anode (C) as a single anode (having no component corresponding to the second anode) was constructed. When the output characteristics of the cell were evaluated in the same manner as in Example 1, the short-circuit current density (J _sc ) was 10.1 mA / cm ² , the open circuit voltage (V _oc ) was 0.74 V, and the fill factor (FF) was 0. The energy conversion efficiency (η) was 4.2%.

<Example 5: Cell with BD sensitized anode>
Similar to the production of the BD sensitized anode (a) except that the coating thickness of the paste-like composition was adjusted so that a TiO ₂ film having a thickness of about 15 μm was formed, the thickness was formed on the conductive glass substrate. A BD-sensitized anode (c) in which a 13.5 μm BD-adsorbed TiO ₂ film (dye layer) was formed in a range of 5 mm × 5 mm was obtained. A cell comprising the BD sensitized anode (c) as a single anode in the same manner as in Example 4 except that the BD sensitized anode (c) was used instead of the N ₃ sensitized anode (C). It was constructed. When the output characteristics of the cell were evaluated in the same manner as in Example 1, the short-circuit current density (J _sc ) was 6.1 mA / cm ² , the open circuit voltage (V _oc ) was 0.68 V, and the fill factor (FF) was 0. The energy conversion efficiency (η) was 2.5%.

<Example 6: N ₃ cells with -BD mixture sensitized anode>
The above N ₃ except that the coating thickness of the paste-like composition was adjusted so that a TiO ₂ film having a thickness of about 15 μm was formed and a mixture of N ₃ dye and black die was adsorbed as a sensitizing dye. Similar to the production of the sensitized anode (A), an N ₃ -BD mixed dye adsorbing TiO ₂ film (dye layer) having a thickness of 16.2 μm formed on a conductive glass substrate in a range of 5 mm × 5 mm _{A 3-} BD mixed dye-sensitized anode was obtained. The adsorption was performed using a solution containing N ₃ dye and black dye at a mass ratio of 1: 1. Except using anode sensitization the N ₃ -BD dye mixture in place of N ₃ sensitization anode (C) is in the same manner as in Example 4, a single anode the N ₃ -BD mixed dye sensitized anode A cell was prepared as When the output characteristics of the cell were evaluated in the same manner as in Example 1, the short-circuit current density (J _sc ) was 4.1 mA / cm ² , the open circuit voltage (V _oc ) was 0.69 V, and the fill factor (FF) was 0. The energy conversion efficiency (η) was 1.7%.

  The output characteristics measured for the cells according to Example 1 and Examples 4 to 6 are shown together in Table 2 together with the schematic configuration of the cells according to each example. Moreover, the current-voltage curve measured about the cell which concerns on Example 1 and Examples 4-6 is shown in FIG.

As shown in Table 2 and FIG. 4, a cell according to Example 1 (a first subcell having an N ₃ sensitized anode (A) and a second subcell having a BD sensitized anode (a) are stacked in this order, and According to the present invention, when the thickness of the first dye layer is 6 μm, the dye layer is more than twice (14.9 μm) thick at the position corresponding to the first dye layer. A short-circuit current density and conversion efficiency comparable to those of the cell according to Example 4 in which is arranged. This result shows that, for example, according to the cell in which the N ₃ sensitized anode (A) in the cell configuration according to Example 1 is replaced with the N ₃ sensitized anode (C) used in Example 4, the performance greatly exceeds the characteristics of Example 4. (Short-circuit current density, conversion efficiency, etc.) can be realized.

Further, the cells according to Example 3 shown in Table 1 (the first subcell having the BD sensitized anode (b) and the second subcell having the N ₃ sensitized anode (B) are stacked in this order and are electrically As can be seen from a comparison between the characteristics of the cell according to Example 5 in Table 2 and the cell according to Example 3, the thickness of the first dye layer is 10 μm. Further, the short-circuit current density and the conversion efficiency exceeding that of the cell according to Example 5 in which the thick dye layer (13.5 μm) was arranged at the position corresponding to the first dye layer were obtained. This result is, for example, much higher than the characteristics of Example 5 in the cell having the configuration in which the BD sensitized anode (b) in the cell configuration according to Example 3 is replaced with the BD sensitized anode (c) used in Example 5. It shows that performance (short circuit current density, conversion efficiency, etc.) can be realized.
Note that the performance (short circuit current density, conversion efficiency, etc.) of the cell according to Example 6 in which the N ₃ dye and BD are held in a mixed state in one dye layer is the same as that of the first anode and the first dye layer. It was clearly inferior to the cells according to Examples 1 to 3 provided separately on the two anodes.

It is typical explanatory drawing which shows the structure and operation | movement of a dye-sensitized solar cell which concern on one embodiment. It is a schematic diagram which shows the structure of the cell which concerns on Examples 1-3. It is a graph which shows the relationship between the thickness of a pigment | dye layer, and pigment | dye adsorption amount. It is a chart which shows the current-voltage characteristic of the cell which concerns on Example 1 and Examples 4-6. It is typical explanatory drawing which shows the structure and operation | movement of the conventional dye-sensitized solar cell.

Explanation of symbols

1: Dye-sensitized solar cell (cell)
10: First anode 20: First dye layer 24: First sensitizing dye 30: Second anode 40: Second dye layer 44: Second sensitizing dye 50: Cathode 60: Electrolyte 70: Conductive path

Claims (9)

A Gretzel cell type dye-sensitized solar cell:
A translucent first anode comprising a first dye layer carrying a first sensitizing dye;
A second dye layer on which a second sensitizing dye different from the first sensitizing dye is held; the first dye layer being behind the first anode with respect to the light incident direction and viewed from the incident direction; A second anode arranged such that the dye layer and the second dye layer overlap;
A translucent cathode disposed between the first anode and the second anode as viewed from the direction of incidence of the light and electrically connected to the anode; and
An electrolyte filled between the first anode, the second anode and the cathode;
A dye-sensitized solar cell comprising: 2. The solar cell according to claim 1, wherein one of the first sensitizing dye and the second sensitizing dye is an N ₃ dye and the other is a black die. The solar cell according to claim 2, wherein the first sensitizing dye is an N ₃ dye and the second sensitizing dye is a black die.   4. The solar cell according to claim 1, wherein each of the first dye layer and the second dye layer has a thickness of 20 μm or less.   The solar cell according to claim 4, wherein the total thickness of the first dye layer and the second dye layer is 10 to 40 μm.   The solar cell according to any one of claims 1 to 5, wherein the cathode is a mesh member having conductivity.   The second anode includes a metal film for light reflection on the rear side with respect to the incident direction of the light, and at least a portion on the incident direction side of the metal film has translucency. The solar cell as described in any one of these. The first dye layer is obtained by holding the first sensitizing dye in a porous layer formed by firing titanium oxide particles having an average particle diameter of 10 to 40 nm.
The said 2nd pigment | dye layer hold | maintains said 2nd sensitizing pigment | dye to the porous layer formed by baking the titanium oxide particle with an average particle diameter of 100-1000 nm, Any one of Claim 1 to 7 The solar cell as described in. The first dye layer is a porous layer having a specific surface area of 60 to 80 m ² / g obtained by firing titanium oxide particles having an average particle diameter of 15 to 25 nm, and 5 × 10 ⁻⁸ mol or more per 1 cm ² of the porous layer. The solar cell according to any one of claims 1 to 8, wherein the first dye is retained.

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