JP2006086056A - Dye-sensitized solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dye-sensitized solar cell having high power generation efficiency in the dye-sensitized solar cell having an oxide semiconductor layer formed in a porous state by integrating fine particles in an optical electrode. <P>SOLUTION: The oxide semiconductor layer 25 emitting electrons by irradiating incident light has a first porous layer 26 formed by integrating first semiconductor particles 26a having a particle size of 1-5 nm, a second porous layer 27 formed by integrating second semiconductor particles 27a having particle diameter larger than the first semiconductor particles on the first porous layer 26, and sensitized dyes 28 adsorbed on the surfaces of the first porous layer 26 and the second porous layer 27, and exciting by absorbing the incident light U. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a dye-sensitized solar cell having a photoelectrode having an oxide semiconductor layer in which fine particles are accumulated and formed into a porous shape, and particularly relates to a dye-sensitized solar cell with high power generation efficiency.

  First, as a first conventional technique for improving the power generation efficiency of a dye-sensitized solar cell (hereinafter sometimes simply referred to as a battery), the following may be mentioned. That is, this is a technique for reducing the particle size of the semiconductor particles constituting the oxide semiconductor layer of the photoelectrode on which incident light is incident and increasing the specific surface area of the oxide semiconductor layer. Thereby, since the amount of the sensitizing dye adsorbed on the surface of the oxide semiconductor layer can be increased, the density of the adsorbed sensitizing dye in the unit thickness of the oxide semiconductor layer can be increased. Therefore, the incident light incident on the photoelectrode excites many sensitizing dyes in the process of going straight, so that highly efficient conversion of electric energy is achieved.

Next, as a second conventional technique for improving the power generation efficiency of the dye-sensitized solar cell, for example, techniques disclosed in Patent Documents 1 and 2 are disclosed.
According to these conventional techniques, the oxide semiconductor layer is configured by laminating a plurality of porous layers having different particle diameters of fine particles. The incident light is confined using the scattering effect inside the porous layer and the reflection effect at the interface between the adjacent porous layers, so that the light energy is converted into electric energy with high efficiency.
JP 2002-352868 A JP-A-10-255863

  However, in the first prior art, if the particle size of the semiconductor particles is reduced, the gap between the semiconductor particles is also reduced, and diffusion of ions moving through the gap in the electrolytic solution is suppressed. Therefore, even if the sensitizing dye is excited by absorbing incident light, electrons are not donated from the ions, so that the dye and the electrons in the semiconductor are recombined. For this reason, if the particle size of the semiconductor particles constituting the oxide semiconductor layer is too small, the power generation efficiency of the battery is reduced.

Further, in the second prior art, in order to sufficiently exhibit the above-described incident light scattering effect, it is required that the particle diameter of the fine particles is the wavelength level of the incident light, that is, several hundred nm or more. Such a scattering effect cannot be expected when the oxide semiconductor layer is composed of at least a porous layer made of fine particles having a particle diameter of 10 nm or less.
Further, in order to sufficiently exhibit the reflection effect at the interface described above, it is necessary to provide a plurality of interfaces, and for this purpose, it is necessary to configure the oxide semiconductor layer by increasing the number of porous layers to be stacked. .

As described above, in the second prior art, in order to sufficiently exhibit the scattering effect and the reflection effect described above, the oxide semiconductor layer is formed by laminating a porous layer composed of fine particles having a large particle diameter over a plurality of layers. Need to be configured. Further, in order to ensure a certain density of the sensitizing dye in the layer thickness direction of the oxide semiconductor layer, it is inevitable that the layer thickness becomes large. As a result, the distance between the electrodes is widened, the loss of carriers injected into the semiconductor is increased, and the travel of ions reciprocating from the sensitizing dye to the counter electrode in the electrolytic solution is lengthened to increase the internal resistance of the battery. As a result, satisfactory power generation efficiency may not be achieved.
As described above, the conventional power generation efficiency of the dye-sensitized solar cell has a limit in the power generation efficiency that can be reached.

  Then, this invention makes it the problem which should be solved to make the power generation efficiency of a dye-sensitized solar cell reach a still higher level.

  In order to solve the above problems, the dye-sensitized solar cell according to claim 1 is a dye-sensitized solar cell including a transparent electrode layer, an oxide semiconductor layer, an electrolytic solution, and a counter electrode. A first porous layer in which first semiconductor particles having a particle size of 1 to 5 nm are accumulated, a second porous layer having a particle size larger than that of the first semiconductor particles, a first porous layer, and a second porous layer A sensitizing dye adsorbed on the surface of the quality layer is provided as a means for solving the problem.

  According to the dye-sensitized solar cell according to claim 1, the first porous layer through which the incident light that is transmitted through the transparent electrode layer and irradiated on the oxide semiconductor layer first passes is the first semiconductor particle. Has a sufficiently large specific surface area even though the layer thickness is small. For this reason, a large amount of sensitizing dye can be adsorbed on the narrow portion of the oxide semiconductor layer that is in contact with the transparent electrode layer, that is, the inner surface of the first porous layer. Even if these large amounts of sensitizing dye absorb and absorb incident light and inject electrons into the semiconductor, the first porous layer is sufficiently thin so that the ions in the electrolyte are excited. Since the electrons can be moved immediately in the vicinity of the sensitizing dye to donate electrons, the sensitizing dye and the electrons in the first porous layer are not recombined. Then, a part of the incident light that has passed through the first porous layer without being completely absorbed by the light passes through the second porous layer to excite the sensitizing dye adsorbed on the surface. Then absorbed. By the way, since the particle size of the second semiconductor particles constituting the second porous layer is 10 to 100 nm, it can be said that a sufficient gap necessary for ion diffusion is secured. For this reason, even if the layer thickness of the second porous layer is large, the movement of ions that travel back and forth between the first porous layer and the counter electrode via the electrolytic solution is not hindered.

  Therefore, the sensitizing dye excited by the incident light passing therethrough does not recombine with electrons in the porous layer regardless of whether it is adsorbed on the surface of the first porous layer or the second porous layer. Before bonding, electrons can be donated from ions in the electrolyte. In addition, the first porous layer has a high density of sensitizing dyes although the layer thickness is thin, so that most of the light energy is absorbed when the incident light passes through the first porous layer. . The incident light that passes through the first porous layer and enters the second porous layer has already attenuated its optical energy considerably. Therefore, the light energy of the incident light is absorbed by the second porous layer. Can be sufficiently absorbed. Therefore, the thickness of the oxide semiconductor layer as a whole can be reduced, so that the interval between the transparent electrode layer and the counter electrode can be reduced, and the internal resistance of the battery can be reduced.

  Next, in the invention of the dye-sensitized solar cell according to claim 2, the layer thickness of the first porous layer is 0.5 to 5 μm, and the layer thickness of the second porous layer is 2 It is ˜50 μm.

  According to the dye-sensitized solar cell of claim 2, most of the light energy of the incident light can be absorbed by the first porous layer, and ions in the electrolytic solution are contained in the first porous layer. It is possible to reach the sensitizing dye that has been excited by penetrating into the substrate before electrons recombine. A part of the incident light passing through the first porous layer is absorbed in the process of passing through the second porous layer.

  Since the present invention can absorb light energy of incident light with high efficiency in a dye-sensitized solar cell having an oxide semiconductor layer in which a fine particle is accumulated and formed into a porous shape, the photoelectric conversion efficiency is high. Achieved.

  Hereinafter, embodiments of the dye-sensitized solar cell of the present invention will be described with reference to the drawings. FIG. 1 is a side sectional view showing a dye-sensitized solar cell 10 according to this embodiment. FIG. 2 is an enlarged view showing a portion indicated by an arrow A in FIG.

  As shown in FIG. 1, the dye-sensitized solar cell 10 includes a photoelectrode 20 on which incident light U is incident, a counter electrode 40, and spacers 50 a that form a sealed space interposed therebetween. 50b and the electrolytic solution 30 filled in this space. And the dye-sensitized solar cell 10 converts the light energy of the incident light U irradiated into electric energy, and supplies electric power to the external load 60 connected to the photoelectrode 20 and the counter electrode 40.

As shown in FIG. 1, the photoelectrode 20 includes a transparent electrode layer 21 composed of a transparent substrate 22 and a conductive light transmission film 23, and an oxide semiconductor layer 25 composed of a first porous layer 26 and a second porous layer 27. It consists of.
Among these, the transparent electrode layer 21 transmits the incident incident light U without being attenuated in its light energy, and transmits the electrons emitted from the oxide semiconductor layer 25 to the external load 60 by connection. It has a function.
The transparent electrode layer 21 has a plate shape with a plate thickness of 0.1 to 1 mm, and a conductive light-transmitting film 23 with a film thickness of 2.5 to 10 μm is provided on one side of a transparent substrate 22 made of glass or plastic. It is formed by coating by a known method.

  By the way, the conductive light transmission film 23 has electrical conductivity, is excellent in transparency to incident light U, and adhesion to the transparent substrate 22, and is made of ITO (Indium-Tin-Oxide). Is preferably used. The conductive light transmission film 23 is not limited to ITO, and a transparent conductive film such as IZO or ZnO can be used.

  The oxide semiconductor layer 25 is provided in contact with the conductive light transmission film 23 side of the transparent electrode layer 21, and emits electrons to the conductive light transmission film 23 when irradiated with incident light U. . In the oxide semiconductor layer 25, the narrow portion in contact with the transparent electrode layer 21 is composed of the first porous layer 26, and the second porous layer 27 is laminated on the first porous layer 26. Thus, the main surface is provided to face the counter electrode 40.

As shown in FIG. 2, the first porous layer 26 is accumulated with first semiconductor particles 26 a of TiO ₂ (hereinafter referred to as titania) having a particle diameter in the range of 1 to 5 nm, preferably 2 to 4 nm. A porous layer having a layer thickness of 0.5 to 5 μm, desirably 2 to 4 μm is formed.

  The second porous layer 27 has a larger particle size than the first semiconductor particles 26a, preferably 10 to 100 nm, more preferably 20 to 50 nm. Is a porous film having a layer thickness of 2 to 50 μm, preferably 5 to 20 μm.

  The first semiconductor particles 26a and the second semiconductor particles 27a having the particle diameter ranges determined as described above are the main components constituting the first porous layer 26 and the second porous layer 27, respectively. The case where a particle having a particle size deviating from these ranges is not excluded. The second porous layer 27 is a semiconductor particle having a particle diameter smaller than that of the second semiconductor particle 27a (for example, the first semiconductor particle 26a) to an extent that does not hinder the movement of ions for the purpose of increasing the specific surface area. May be included.

  As described above, the oxide semiconductor layer 25 includes the first porous layer 26 and the second porous layer 27, so that the oxide semiconductor layer 25 has a narrow portion in contact with the transparent electrode layer 21. The specific surface area of the (first porous layer 26) can be relatively increased, and the adsorption density of the sensitizing dye 28 in this portion can be improved.

  Furthermore, if the first semiconductor particles 26a constituting the first porous layer 26 are titania, it is known that extremely fine titania particles having a particle diameter of 1 to 5 nm are likely to aggregate and form a lump. Yes. The titania fine particles formed into such a lump are densely filled with nano-sized anatase-type titania microcrystals to form a titania microcrystal aggregate in which the crystal faces of each microcrystal are in direct contact with each other. For this reason, in the 1st porous layer 26, an electron movement will be rapidly performed through a titania layer, and it will contribute to the high efficiency of a battery.

Further, there is a certain gap between the above-mentioned titania fine particles, and observation by TEM shows that the size of the lump is about 10 to 15 nm and the gap is 3 to 5 nm. ing. The size of the gap is large enough to allow the diffusion of iodine ions and I ₃ ⁻ ions, which will be described later. Accordingly, the small particle size of the first semiconductor particles 26a means that the movement of ions in the first porous layer 26 includes that the first porous layer 26 is a thin film of 0.5 to 5 μm and the ion diffusion distance is short. It does not become a factor to inhibit. Note that the time required for diffusion is proportional to the square of the diffusion distance. For example, when the diffusion distance becomes 1/100, the diffusion time becomes 1/10000.

On the other hand, in the second porous layer 27, the gap formed by the second semiconductor particles 27a, 27a... Within the above-described particle diameter range is sufficient for rapid diffusion of iodine ions and I ₃ ⁻ ions. It can be said that it is secured in size. For this reason, the ion which moves inside the 2nd porous layer 27 in the direction of the 1st porous layer 26, or moves in the direction of the counter electrode 40 is not prevented.

  Here, when the particle diameter of the first semiconductor particle 26a is 1 nm or less, which is the lower limit, the gel in which the sensitizing dye 28 is dispersed penetrates the inner surface of the oxide semiconductor layer 25 when the photoelectrode 20 described later is formed. However, the gap between the first semiconductor particles 26 a, 26 a... Is too narrow and the diffusion of the sensitizing dye 28 becomes insufficient, so that the sensitizing dye 28 can be sufficiently adsorbed on the inner surface of the first porous layer 26. Can not. When the particle size of the first semiconductor particles 26a is 5 nm or more, which is the upper limit, the specific surface area of the narrow portion in contact with the transparent electrode layer 21 of the oxide semiconductor layer 25 is reduced, and the density of the sensitizing dye 28 to be adsorbed is reduced. The desired photoelectric conversion efficiency cannot be obtained due to the decrease.

  Further, when the particle size of the second semiconductor particles 27a is 10 nm or less, which is the lower limit, the moving speed of ions moving through the electrolytic solution 30 that has penetrated into the second porous layer 27 is slowed, and the internal resistance of the battery is increased. I will let you. Furthermore, when the particle size of the second semiconductor particles 27a exceeds the upper limit of 100 nm, the specific surface area of the second porous layer 27 is reduced. Therefore, in order to obtain a desired photoelectric conversion efficiency, the layer of the second porous layer 27 The thickness must be increased, and as a result, the electrode interval between the transparent electrode layer 21 and the counter electrode 40 is increased, and the internal resistance of the battery is increased.

  Here, the lower limit of the layer thickness of the first porous layer 26 is 0.5 μm because it is the minimum thickness formed by one film formation process when the photoelectrode 20 described later is formed. . If the upper limit of the thickness of the first porous layer 26 is 5 μm or more, the moving speed of ions moving through the electrolyte 30 that has penetrated into the first porous layer 26 is extremely slow. It takes time for ions to move to the vicinity of the boundary with 21. For this reason, even if the incident light U is absorbed and excited, the sensitizing dye 28 that does not receive the donation of electrons and recombines with the electrons in the first porous layer 26 increases, and the desired photoelectric conversion is achieved. Conversion efficiency cannot be obtained.

  Further, the lower limit of the layer thickness of the second porous layer 27 is 2 μm or less because it is the minimum thickness formed by one film formation process when the photoelectrode 20 described later is formed. When the thickness of the second porous layer 27 exceeds the upper limit of 50 μm, the electrode spacing between the transparent electrode layer 21 and the counter electrode 40 increases, increasing the internal resistance of the battery, and the desired photoelectric conversion efficiency cannot be obtained. .

In the present embodiment, the compound constituting the first semiconductor particle 26a and the second semiconductor particle 27a is titania (TiO ₂ ). However, electrons are efficiently injected from the sensitizing dye 28, and light energy is used. The compound is not particularly limited as long as it is a compound that can be efficiently converted into electric energy.
Therefore, the compounds constituting the oxide semiconductor layer 25 (first semiconductor particles 26a, second semiconductor particles 27a) are, for example, tin oxide (SnO ₂ ), zinc oxide (ZnO) in addition to titania (TiO ₂ ). Niobium oxide (Nb ₂ O ₅ ), indium oxide (In ₂ O ₃ ), zirconium oxide (ZrO ₂ ), lanthanum oxide (La ₂ O ₃ ), tantalum oxide (Ta ₂ O ₅ ), strontium titanate (SrTiO ₃₎ ), Barium titanate (BaTiO ₃ ), and the like.

The sensitizing dye 28 is adsorbed in the form of a monomolecular layer on the inner surface of the oxide semiconductor layer 25, that is, on the surfaces of the first semiconductor particles 26a and the second semiconductor particles 27a constituting the oxide semiconductor layer 25. Of the sensitizing dyes 28 adsorbed in this manner, only the sensitizing dye 28 that directly chemically bonds to the inner surface of the oxide semiconductor layer 25 exhibits a sensitizing action.
This sensitizing action absorbs the light energy of the incident light U, and the sensitizing dye 28 is excited to an energy about 0.2 eV higher than the level of the conductor of the compound (titania) constituting the oxide semiconductor layer 25. Thus, electrons are injected from the sensitizing dye 28 into the oxide semiconductor layer 25.

  The sensitizing dye 28 used in the present invention is, for example, a ruthenium complex, particularly a ruthenium bipyridine complex, a metal complex or an organic compound such as phthalocyanine, cyanine, merocyanine, porphyrin, chlorophyll, pyrene, methylene blue, thionine, xanthene, coumarin, and rhodamine. Dyes as well as their derivatives can be used.

  By the way, since the incident light U cannot be completely absorbed by a single layer of the monomolecular layer of the sensitizing dye 28, the incident light U is on the traveling path in order to improve the absorption efficiency of the incident light U. In addition, it is necessary to prevent the incident light U from penetrating the monomolecular layer in multiple layers. For this purpose, the specific surface area of the oxide semiconductor layer 25 may be increased, and it is effective to reduce the particle diameter of the constituent semiconductor particles or increase the thickness of the oxide semiconductor layer 25. However, when the thickness of the oxide semiconductor layer 25 is increased, the distance between the transparent electrode layer 21 and the counter electrode 40 is increased, the internal resistance of the battery is increased, and this may cause a decrease in photoelectric conversion efficiency. As stated.

The electrolyte 30 is not particularly limited as long as it contains ions capable of donating electrons to the sensitizing dye 28 after excitation that has injected electrons into the first and second semiconductor particles 26a and 27a. An iodine electrolyte solution 30 containing I ⁻ / I ₃ ⁻ is preferably used. In addition, using electrolytes such as Br ⁻ / Br ₃ ⁻ and quinone / hydroquinone dissolved in electrochemically inert solvents (and mixed solvents thereof) such as acetonitrile, propylene carbonate, and ethylene carbonate Also good.

  The counter electrode 40 is formed by coating one surface of the fixed plate 42 with a conductive film 41 made of a platinum material or the like. The counter electrode 40 and the photoelectrode 20 are opposed to each other at a predetermined interval with the surfaces of the conductive film 41 and the oxide semiconductor layer 25 facing inward, and the formed internal space is sealed. The spacers 50a and 50b are provided in the peripheral portion.

  Next, the operation principle of the dye-sensitized solar cell 10 according to this embodiment will be described with reference to FIG. First, when the incident light U is incident on the photoelectrode 20 of the dye-sensitized solar cell 10, the incident light U is not absorbed by the transparent electrode layer 21 but is almost transmitted and reaches the oxide semiconductor layer 25. When the incident light U hits the sensitizing dye 28 adsorbed on the surface of the first porous layer 26 in contact with the conductive light transmitting film 23, the sensitizing dye 28 is part of the light energy of the incident light U. Is absorbed and excited. When this excitation reaches an energy of about 0.2 V higher than the level of the conductor of the first semiconductor particle 26a, electrons are injected from the sensitizing dye 28 into the first semiconductor particle 26a.

Further, the incident light U travels inside the first porous layer 26 and sequentially excites the sensitizing dye 28 adsorbed on the inner surface of the first porous layer 26 to convert electrons into the first semiconductor particles. Inject into 26a. Since the injected electrons form a titania microcrystal aggregate in which the crystal planes of the microcrystals are in direct contact with each other as described above, the first semiconductor particles 26a form the conductive light-transmitting film 23 very quickly. Will be led to. For this reason, the sensitizing dye 28 adsorbed on the surface of the first porous layer 26 can improve the speed of the excitation operation with respect to the incident light U incident one after another. The injected electrons are injected into the titania layer and guided to the conductive light transmission film 23.
In this way, most of the incident light is converted from light energy to electric energy in the process of traveling inside the first porous layer 26, so that the incident light reaches the interface with the second porous layer 27. Most of the light energy will be lost.

  By the way, when the sensitizing dye 28 absorbs the incident light U and is excited, if it is left as it is, the injected electrons are recombined with the sensitizing dye 28 and the injected electrons are deactivated. . Therefore, before such electron recombination occurs in the sensitizing dye 28, ions in the electrolyte solution 30 surrounding it must move to donate electrons.

  By the way, there is a concern that the first porous layer 26 has a large ion diffusion resistance and a low moving speed due to the fineness of the first semiconductor particles 26a, 26a,. However, as described above, the ions move immediately through the gaps formed by the aggregation of the fine particles of the first semiconductor particles 26a, 26a..., So that they immediately reach the excited sensitizing dye 28. Can donate electrons. Furthermore, since the first porous layer 26 is configured to have a thin layer thickness at the surface layer portion in contact with the transparent electrode layer 21, even when the sensitizing dye 28 is excited in a large amount, it recombines with the injected electrons. Before, ions can be distributed to the sensitizing dye 28. Thereby, most of a large amount of electrons injected into the titania layer from the sensitizing dye 28 excited on the inner surface of the first porous layer 26 is guided to the conductive light transmission film 23 without recombination. .

  Then, the incident light U that has entered the second porous layer 27 through the first porous layer 26 has absorbed the sensitizing dye 28 adsorbed on the inner surface of the second porous layer 27 by the same process as described above. Excited and injected with electrons. The second porous layer 27 is large in the size of the second semiconductor particles 27a, 27a, etc. that form the second porous layer 27, so that the gap through which the electrolytic solution 30 permeates is wide and ions can move freely. Therefore, naturally, not only for the sensitizing dye 28 adsorbed on the inner surface of the second porous layer 27, but also for the sensitizing dye 28 adsorbed on the inner surface of the first porous layer 26, Does not hinder the movement of ions to donate.

  Then, the ions oxidized by donating electrons to the sensitizing dye 28 adsorbed on the inner surface of the oxide semiconductor layer 25 are now directed toward the opposite counter electrode 40 in the first and second porous layers. It moves through the electrolytic solution 30 penetrating into the gaps 26 and 27. When the oxidized ions reach the counter electrode 40, they are reduced by accepting electrons from the conductive film 41. In this manner, the oxidation / reduction reaction is repeated by many reciprocations between the sensitizing dye 28 adsorbed on the inner surface of the oxide semiconductor layer 25 and the counter electrode 40 in the electrolyte 30. As a result, a potential gradient is generated between the photoelectrode 20 and the counter electrode 40. When the conductive light transmission film 23 and the conductive film 41 are short-circuited via the external load 60, electric power is supplied to the external load 60.

  As described above, in the dye-sensitized solar cell according to the present invention, since the first porous layer 26 is formed by the extremely fine first semiconductor particles 26a, the density of the sensitizing dye 28 in the thickness direction of the layer is low. Improved, excellent conductivity of injected electrons in the first porous layer 26, and excellent mobility of ions passing between the electrodes (electrolytic solution 30 filled between the photoelectrode 20 and the counter electrode 40). The internal resistance of the battery can be reduced by narrowing the interval, and high photoelectric conversion efficiency is achieved.

Below, an Example is shown and the detail of preparation of the photosensitized solar cell which concerns on this invention is demonstrated.
(Preparation of the first titania gel used as the raw material of the first porous layer 26)
First, an aqueous solution containing 10 wt% of triblock copolymer F127 from BASF: HO— (CH ₂ CH ₂ O) ₁₀₆ — (CH ₂ C (CH) ₃ H ₂ O) ₇₀ — (CH ₂ CH ₂ O) ₁₀₆ H made. Specifically, 0.2 g of 2 M hydrochloric acid was added to 30 ml of distilled water, and 3 g of F127 was dissolved therein.
Next, the titanium alkoxide tetraisopropyl orthotitanate (TIPT) and acetylacetone (ACA) to be the first semiconductor particles 26a were mixed at a molar ratio of 1: 1. Specifically, 3.4 g TIPT and 1.2 g ACA were mixed.
Then, an aqueous solution of F127 prepared as described above and a mixed solution of TIPT and ACA were mixed at 40 ° C. and stirred for 24 hours to obtain a transparent liquid. The liquid that became transparent was allowed to stand for 3 days in an air constant temperature bath at 80 ° C. for 3 days to gel the liquid, thereby obtaining a first titania gel.

(Preparation of the second titania gel used as the raw material of the second porous layer 27)
In the first titania gel, Degussa P-25 (Nippon Aerosil Co., Ltd.) as the second semiconductor particles 27a is mixed so as to be 8 wt% and 11 wt%, and stirred at room temperature for 24 hours, so that the two different concentrations are uniform. Second titania gels (8 wt%) and (11 wt%) were obtained.

(Creation of photoelectrode 20)
A sheet tape of 2 Ω / □ is applied to the ITO transparent conductive film (Indium-Tin Oxide) (manufactured by Geomat Co.) with a predetermined width, and the first titania gel is placed on the empty part. A thin film is obtained by stretching with a glass rod and baking at 450 ° C. for 10 minutes after drying. This process is repeated twice to obtain the first porous layer 26. Next, in the same manner, on the first porous layer 26, a second titania gel (8 wt%) is applied using cello tape (registered trademark) as a spacer, and dried, followed by baking at 450 ° C. for 10 minutes. The second porous layer 27 was obtained by repeating the step of applying the second titania gel (11 wt%) and baking it at 450 ° C. for 10 minutes after drying. In addition, a single layer of titania nanorods with a diameter of 100 nm and a length of 300 nm was applied for the purpose of scattering and reflecting incident light. Thereafter, the oxide semiconductor layer 25 was finally formed by baking at 450 ° C. for 1 hour. Thus, the created oxide semiconductor layer 25 includes a first porous layer composed of the first semiconductor particles 26a having a particle diameter of 2 to 5 nm, Degussa P-25, and the first semiconductor particles 26a. The second porous layer is composed of the mixed particles, and has a layer thickness of 25 μm as a whole.
After the firing of the oxide semiconductor layer 25 is completed, the prepared oxide semiconductor layer 25 is immersed in an ethanol solution of ruthenium dye N719 having a concentration of 3 × 10 ⁻⁴ M for 20 hours, and the sensitizing dye 28 is adsorbed on the inner surface thereof. It was.

(Preparation of dye-sensitized solar cell 10)
The counter electrode 40 in which platinum was vapor-deposited on an ITO transparent conductive film and the photoelectrode 20 were superposed so as to face each other, and the electrolyte solution 30 was filled between the electrodes to constitute the dye-sensitized solar cell 10. The cell size is 5 mm × 5 mm, and the electrolyte 30 is 0.6 M DMPII (1,2-Dimethyl-3-propylimidazoliumiodide) 0.1 M LiI, 0.05 M I2 and 0.5 M TBP (tert-butylpyridine) in Acetonitrile. The dissolved one was used.

(Measurement result)
Incident light U was irradiated from the photoelectrode 20 side, and the performance of the dye-sensitized solar cell 10 was measured. As the incident light U, pseudo-sunlight (100 mW / cm ² ) manufactured by Oriel was used, and a current-voltage curve was measured with a potentiostat manufactured by Hokuto Denko. As a result, the measurement results of a short-circuit current density of 20.14 mA, an open-circuit voltage of 0.756 V, a fill factor of 0.679, and a photoelectric conversion efficiency of 10.34% were obtained.

It is side surface sectional drawing which shows the dye-sensitized solar cell which concerns on this embodiment. It is an enlarged view which shows the A arrow view part in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Dye-sensitized solar cell 20 Photoelectrode 21 Transparent electrode layer 22 Transparent substrate 23 Conductive light transmission film 25 Oxide semiconductor layer 26 First porous layer 26a First semiconductor particle 27 Second porous layer 27a Second semiconductor particle 28 Sensitizing dye 30 Electrolyte 40 Counter electrode 50a, 50b Spacer 60 External load U Incident light

Claims (2)

An oxide semiconductor layer that emits electrons to an adjacent transparent electrode layer when irradiated with incident light; and
An electrolyte that donates electrons to the oxide semiconductor layer to be immersed;
In the dye-sensitized solar cell, which is provided so as to face the transparent electrode layer and to be in contact with the electrolytic solution and have conductivity,
The oxide semiconductor layer is
A first porous layer in which first semiconductor particles having a particle size of 1 to 5 nm are accumulated on the transparent electrode layer;
A second porous layer containing second semiconductor particles having a particle size larger than the first semiconductor particles;
A dye-sensitized solar cell comprising: a sensitizing dye that is adsorbed on the surfaces of the first porous layer and the second porous layer and absorbs and excites the incident light.   2. The dye-sensitized sun according to claim 1, wherein the first porous layer has a thickness of 0.5 to 5 μm, and the second porous layer has a thickness of 2 to 50 μm. battery.

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