JP6021375B2 - Solar cell substrate and solar cell - Google Patents

Description

  Embodiments described herein relate generally to a solar cell substrate and a solar cell.

  Solar cells are attracting attention as natural energy. Conventional solar cells have been mainly silicon solar cells. Silicon-based solar cells have achieved a power generation efficiency of 10% or more. On the other hand, silicon-based solar cells are expensive because they have a variety of vacuum film formation techniques such as silicon crystal growth and sputtering. In order to solve this problem, dye-sensitized solar cells that can make extensive use of paste coating techniques have been studied. In dye-sensitized solar cells, a certain power generation efficiency is obtained by using titanium oxide powder as an electrode material.

  By the way, since a solar cell literally uses sunlight, the amount of power generation changes according to the amount of sunlight. For this reason, when the amount of sunshine changes abruptly, the amount of power generation decreases rapidly. In order to cope with such changes in the amount of sunshine, a solid electricity storage layer such as tungsten oxide is provided on a layer that performs photoelectric conversion such as titanium oxide, thereby imparting an electricity storage function to the dye-sensitized solar cell. It has been proposed.

  However, it is difficult to achieve both power generation efficiency and a power storage function only by providing a power storage layer in a dye-sensitized solar cell. It can be said that it is important to improve the power storage function when considering the effective use of sunlight.

JP 2008-204956 A JP 2009-1335025 A

  The problem to be solved by the present invention is to provide a solar cell substrate capable of improving the power storage function and a solar cell using the solar cell substrate.

According to the embodiment, a solar cell substrate including a semiconductor layer including tungsten oxide powder is provided. The tungsten oxide powder has a first peak in the range of 268 to 274 cm ^−1, a second peak in the range of 630 to 720 cm ⁻¹ and a third peak in the range of 800 to 810 cm ⁻¹ in Raman spectroscopic analysis. The thickness of the semiconductor layer is 1 μm or more and 150 μm or less . The porosity of the semiconductor layer is 20 vol% or more and 80 vol% or less. The average BET surface area of the tungsten oxide powder is 15 m ² / g or more and 150 m ² / g or less. The average size of the voids in the semiconductor layer is 5 nm or more and 20 nm or less.

  Moreover, according to the embodiment, a solar cell including this solar cell substrate, a dye, a counter electrode, and an electrolyte composition is provided. The dye is supported on the semiconductor layer of the solar cell substrate. The electrolyte composition is filled between the semiconductor layer and the counter electrode.

It is sectional drawing which shows the solar cell of embodiment. It is a chart which shows the Raman spectroscopy analysis result of the tungsten oxide powder used for embodiment.

  Hereinafter, embodiments will be described with reference to the drawings.

(First embodiment)
According to the first embodiment, a solar cell substrate including a semiconductor layer is provided. The semiconductor layer includes a tungsten oxide powder, and the tungsten oxide powder has a first peak in the range of 268 to 274 cm ^−1, a second peak in the range of 630 to 720 cm ^{−1 and} a range of 800 to 810 cm ⁻¹ in Raman spectroscopy. Has a third peak. The semiconductor layer has a thickness of 1 μm or more and a porosity of 20 vol% or more and 80 vol% or less.

  The substrate can be used as a semiconductor electrode (photoelectrode) of the dye-sensitized solar cell by supporting the dye on the tungsten oxide powder. Examples of the dye include a ruthenium-tris transition metal complex, a ruthenium-bis transition metal complex, an osmium-tris transition metal complex, an osmium-bis transition metal complex, and a ruthenium-cis-diaqua-bipyridyl complex. , Phthalocyanine and porphyrin. There can be one or more dyes.

  When the tungsten oxide powder has the first peak, the second peak, and the third peak, the power storage function of the tungsten oxide powder can be enhanced. However, even when the tungsten oxide powder having the first to third peaks is used, if the thickness of the semiconductor layer is less than 1 μm or the porosity of the semiconductor layer is less than 20 vol%, the dye and electrolyte in the semiconductor layer Since the amount of the dye and the amount of the electrolyte composition when the composition is held are insufficient, it is difficult to improve the power storage performance of the solar cell. Moreover, even if the thickness of the semiconductor layer is 1 μm or more, those having a porosity exceeding 80 vol% are inferior in both power generation performance and power storage performance of the solar cell because the amount of tungsten oxide powder is insufficient. The tungsten oxide powder having the first to third peaks, the semiconductor layer thickness is 1 μm or more, and the porosity is in the range of 20 to 80 vol%. Therefore, it is possible to realize a solar cell excellent in both power generation performance and power storage performance.

  The upper limit value of the thickness of the semiconductor layer is desirably 150 μm or less. Thereby, the light transmittance of a semiconductor layer can be made favorable.

  A more preferable range of the porosity is 40 vol% or more and 70 vol% or less.

  The average size of the voids in the semiconductor layer is preferably 5 nm or more. Thereby, the uniformity of distribution of the dye and the electrolyte composition when the dye and the electrolyte composition are held in the semiconductor layer can be increased. A more preferable range of the average size is 7 nm or more and 20 nm or less.

It is desirable that the BET specific surface area of the tungsten oxide powder is 15 m ² / g or more on average. Thereby, the pigment | dye carrying amount of tungsten oxide powder can be raised. Further, the upper limit of the BET specific surface area can be an average of 150 m ² / g or less.

It is desirable that a film is formed on at least a part of the surface of the tungsten oxide powder. The material for forming the coating includes inorganic substances such as metal oxides and metal nitrides, organic substances, and the like. Preferred materials are Y ₂ O ₃ , TiO ₂ , ZnO, SnO ₂ , ZrO ₂ , MgO, Al ₂ O ₃ , CeO ₂ , Bi ₂ O ₃ , Mn ₃ O ₄ , Tm ₂ O ₃ , Ta ₂ O ₅ , It is at least one selected from the group consisting of Nb ₂ O ₅ , La ₂ O ₃ and ITO. By forming a film on at least a part of the surface of the tungsten oxide powder, the adsorptivity of the dye can be improved, and the effect of reducing the reverse electron transfer by improving the electron mobility can be obtained. . In addition, when a metal oxide is used for the coating material, oxygen vacancies in tungsten oxide can be reduced.

  The tungsten oxide powder is manufactured, for example, by the following method. First, a plasma process is performed. Tungsten oxide particles having an average particle size of 10 μm or less, preferably 1 to 5 μm, are prepared as the tungsten oxide coarse powder. When the average particle diameter of the coarse powder exceeds 10 μm, it is difficult to uniformly put it into the plasma flame. On the other hand, when the average particle size is as small as less than 1 μm, it is difficult to prepare coarse powder, which causes an increase in cost.

  Further, as the plasma flame, it is preferable to use a high-temperature flame having a center temperature of 8000 ° C. or higher, more preferably 10,000 ° C. or higher. Fine tungsten oxide particles can be obtained by heat treatment in an oxygen-containing atmosphere such as air using a high-temperature plasma flame. Moreover, it is preferable that the tungsten oxide particles jumped out of the plasma flame after being put into the plasma flame are subjected to a rapid cooling step of 1000 ° C./s or more over a distance of 1 m or more. The target tungsten oxide particles can be obtained by introducing a high-temperature plasma flame and performing a predetermined quenching step.

Next, a heat treatment step is performed. The heat treatment step is a step of heating the tungsten oxide particles (as-plasma powder) obtained in the plasma step at a predetermined temperature for a predetermined time in an oxidizing atmosphere. the as-plasma powder and to a lot of defects on the surface, the ratio of W and O with WO ₃ is 1: less than 3 (W _x O _y, such that y / x <3) some tungsten oxide May include. By adding a heat treatment step to this, surface defects are reduced and the proportion of WO ₃ in tungsten oxide is set to 99% or more. Furthermore, the crystal structure and particle size of the obtained tungsten oxide particles can be controlled by the conditions of the heat treatment.

  A specific heat treatment temperature (maximum temperature in the heat treatment step) is preferably from 300 ° C. to 1000 ° C., and preferably from 450 ° C. to 600 ° C. The heat treatment time (holding time at the maximum temperature) is preferably 10 minutes or longer, and preferably 2 hours or longer and 60 hours or shorter. This is because the surface is oxidized slowly in a temperature range where the reaction rate is low in order to reduce defects inside the particle surface. At high temperatures, where the reaction rate is high, the heat treatment time is short, and there is an advantage in process costs. However, the as-plasma powder is not heated evenly, the crystal structure and particle size after heat treatment become uneven, and the particle surface It is not preferable because defects remain inside. In particular, those exceeding 1000 ° C. are not preferable because the tungsten oxide particles cause rapid grain growth.

  The oxidizing atmosphere may be oxygen, air, an inert gas into which water vapor or oxygen is introduced, water, etc., and the atmospheric pressure may be atmospheric pressure or under pressure. The heating method may be any of heat conduction from atmosphere, radiant heat (electric furnace, etc.), high frequency, microwave, laser and the like.

The semiconductor layer may include at least one second powder selected from the group consisting of metal oxide powder, metal boride powder, metal fluoride powder, carbonate powder, carbon powder, metal carbide powder, and metal powder. desirable. Preferred second powders are Fe, Mn, Co, Ni, Li ₂ O, LiF, Na ₂ O, K ₂ O, MgO, CaO, MnO, MnO ₂ , FeO, Fe ₂ O ₃ , CoO, NiO, Cu _2. It is at least one selected from the group consisting of O, B ₂ O ₃ , SiO ₂ , La ₂ O ₃ , ZrO ₂ , Y ₂ O ₃ , C, LaB ₆ , ITO and ATO. By using an oxide for the second powder, the sinterability of the tungsten oxide particles can be improved, and necking bonding between the tungsten oxide and the transparent electrode and the tungsten oxide particles can be improved. As a result, the physical bonding can be strengthened to improve the component reliability, and the electrical conductivity can be improved by reducing the resistance of the grain boundary to improve the power generation efficiency. In addition, by using a conductor (for example, Fe, Mn, Co, Ni, C, ITO, ATO) as the second powder, the conductivity of the semiconductor layer can be improved, so that the power generation efficiency can be improved. it can.

  The semiconductor layer can be formed on a transparent conductive film on a transparent substrate such as a glass substrate. The transparent conductive film includes ITO, ATO and the like. The thickness of the transparent conductive film can be 10 nm or more and 200 nm or less.

  The method for measuring the film thickness, porosity, and average size of the semiconductor layer is as follows.

(Semiconductor layer thickness)
An enlarged photograph 1 is taken of an arbitrary cross-section corresponding to at least “thickness 1 μm or more × width 10 μm” of the semiconductor layer so that the upper end portion of the semiconductor layer can be seen (magnification 5000 times or more). In the enlarged photograph 1, the thickness of an arbitrary part is measured at three places, and the average value is defined as the film thickness (thickness).

(Porosity of semiconductor layer)
An arbitrary cross-section corresponding to at least “thickness of 1 μm or more × width of 10 μm” at the viewing angle of the semiconductor layer is formed on the upper end of the semiconductor layer (the surface opposite to the surface in contact with the conductive film (in FIG. Take an enlarged photo (magnification of 100,000 times or more) and take an enlarged photo 2 so that the catalytic catalyst layer 2 side) can be seen. It is possible to distinguish the tungsten oxide particles and the voids from the contrast of the enlarged photograph 2. From the enlarged photograph 2, the area of the gap corresponding to “unit area 1 μm × 3 μm” is obtained. When “unit area 1 μm × 3 μm” cannot be photographed in one field of view, photographing is performed a plurality of times until the total becomes “unit area 1 μm × 3 μm”.

(Average size of voids in the semiconductor layer)
The average size of the voids is obtained from the enlarged photograph 2 by the line intercept method. Specifically, an arbitrary straight line (drawing a straight line from an arbitrary end portion of the enlarged photograph 2) is drawn on the enlarged photograph 2, and the number of voids existing on the straight line and the total length are obtained. The total size of the voids / the number of voids is defined as an average size, and this operation is performed on three arbitrary straight lines, and the average value is defined as the average size of the voids.

(Raman spectroscopy)
The Raman spectroscopic analysis is performed by the following method. For the apparatus, PDP-320 manufactured by Photon Desing is used. Measurement conditions are: microscopic Raman, measurement magnification of 100 times, beam diameter of 1 μm or less, light source Ar ⁺ laser (wavelength 514.5 nm), laser power 0.5 mW (at tube), diffraction grating Single 600 gr / mm, cross slit 100 μm , Slit 100 μm, detector CCD / Roper 1340 channel. Under this condition, 100 to 1500 cm ⁻¹ is analyzed. The sample form can be measured as tungsten oxide particles.

  The semiconductor layer is formed by, for example, a method described below. A paste containing tungsten oxide particles is prepared. The paste includes tungsten oxide particles, a binder, and a solvent. When tungsten oxide particles (including additives when additives are added), binder, and solvent are combined to 100 wt%, tungsten oxide particles (including additives and coating) are 5 to 50 wt%, and binders are 3 to 3 wt%. The range is preferably 30 wt%. The binder is preferably an organic binder having a thermal decomposition rate of 99.0% or more at 500 ° C. If it can be thermally decomposed at a temperature of 500 ° C. or lower, the glass substrate or the like can be prevented from being damaged. Examples of such a binder include ethyl cellulose and polyethylene glycol. Examples of the solvent include alcohol, organic solvent, pure water and the like. Of these, alcohol solvents are preferred.

The mixing in the paste preparation is preferably performed by mixing a binder and a solvent, stirring them, and then adding tungsten oxide particles to them and stirring them. When the tungsten oxide particles and the binder are added to the solvent at once, a paste with many aggregates tends to be formed. Further, when the tungsten oxide particles are fine particles having a BET specific surface area of 5 m ² / g or more, it is necessary to sufficiently stir.

  Moreover, it is preferable that the viscosity of a paste is the range of 800-10000 cps at room temperature (25 degreeC). The semiconductor layer is formed, for example, by applying a paste containing tungsten oxide by a screen printing method or the like and baking at a temperature of 500 ° C. or lower. It is effective to print the film several times until the required thickness is reached. Moreover, when the binder amount is set in the above range, the porosity is easily adjusted to a range of 20 to 80 vol%. In addition, the firing temperature is set in the range of 200 to 500 ° C. so as not to damage the substrate such as the glass substrate. Further, if the binder is thermally decomposed at once by increasing the temperature rising rate to 100 ° C./h or more, the average size of the voids is easily set to 5 nm or more.

According to a first embodiment of a solar battery substrate as described above, in the Raman spectroscopic analysis, the first peak in the range of 268～274Cm ^-1, the second peaks and 800~810cm the range of 630~720cm ^{-1 - 1} includes a tungsten oxide powder having a third peak in the range of ¹ , a semiconductor layer having a thickness of 1 μm or more and a porosity of 20 vol% or more and 80 vol% or less. Since the dye carrying ability and the electrolyte composition holding ability of the layer can be increased, a solar cell excellent in both power generation performance and power storage performance can be realized.

(Second Embodiment)
According to 2nd Embodiment, the solar cell (dye sensitized solar cell) containing the board | substrate for solar cells which concerns on 1st Embodiment, a pigment | dye, a counter electrode, and an electrolyte composition is provided. The dye is supported on the semiconductor layer of the solar cell substrate. A substrate for a solar cell on which a dye is supported is called a semiconductor electrode (photoelectrode). The electrolyte composition is accommodated between the semiconductor layer and the counter electrode.

  The counter electrode includes a transparent substrate such as a glass substrate, a conductive film on the transparent substrate, and a conductive catalyst layer formed on the conductive film. The conductive catalyst layer includes, for example, a platinum (Pt) layer. The conductive film includes a transparent conductive film such as ITO or ATO. The thickness of the conductive film can be greater than or equal to 10 nm and less than or equal to 200 nm. The conductive film is not limited to a transparent conductive film, and may be a conductive film.

  The electrolyte composition includes a reversible redox couple and a supporting electrolyte.

The reversible redox _couple can be supplied from, for example, a mixture of iodine (I ₂ ) and iodide, iodide, bromide, hydroquinone, TCNQ complex, and the like. In particular, a redox pair consisting of I ⁻ and I ₃ ⁻ supplied from a mixture of iodine and iodide is preferable. The redox couple desirably exhibits a redox potential that is 0.1 to 0.6 V lower than the oxidation potential of the dye. In the redox pair showing a redox potential 0.1 to 0.6 V lower than the oxidation potential of the dye, for example, a reducing species such as I ⁻ can receive holes from the oxidized dye. By containing such a redox pair in the electrolyte, the speed of charge transport between the semiconductor electrode and the counter electrode can be increased, and the open-circuit voltage can be increased.

The supporting electrolyte imparts a power storage function, and for example, a lithium salt is used. Examples of the lithium salt include lithium halide, lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, LiN (SO ₂ Rf) ₂ .LiC (SO ₂ Rf) ₃ (where Rf = CF ₃ , C ₂ F ₅ ) and LiBOB (lithium bisoxalate borate). These lithium salts can be used alone or in combination of two or more. Lithium iodide is desirable because it can supply iodine and lithium ions.

  Lithium ions ionized from the lithium salt are used for charge / discharge reactions at the semiconductor electrode. If the content of the lithium salt in the electrolyte composition is in the range of 0.01 mol / L or more and 3 mol / L or less, without depositing from the electrolyte solution between the semiconductor electrode and the counter electrode and shorting internally, A sufficient effect can be obtained. The content of the lithium salt in the electrolyte composition is more preferably 0.02 mol / L to 2 mol / L, and particularly preferably 0.03 mol / L to 1 mol / L.

  It is desirable that the electrolyte composition further contains an iodide. Examples of iodides include alkali metal iodides, iodides of organic compounds, and molten salts of iodides. Examples of the molten salt of iodide include iodides of heterocyclic nitrogen-containing compounds such as imidazolium salts, pyridinium salts, quaternary ammonium salts, pyrrolidinium salts, pyrazolidium salts, isothiazolidinium salts, and isoxazolidinium salts. Can be used.

  Examples of the molten salt of iodide include 1,1-dimethylimidazolium iodide, 1-methyl-3-ethylimidazolium iodide, 1-methyl-3-pentylimidazolium iodide, 1-methyl-3- Isopentyl imidazolium iodide, 1-methyl-3-hexylimidazolium iodide, 1-methyl-3-isohexyl (branched) imidazolium iodide, 1-methyl-3-ethylimidazolium iodide, 1, 2 -Dimethyl-3-propylimidazole iodide, 1-ethyl-3-isopropylimidazolium iodide, 1-propyl-3-propylimidazolium iodide, pyrrolidinium iodide and the like can be mentioned. Such a molten salt of iodide can be used alone or in combination of two or more. Moreover, it is preferable that the content is about 0.005 mol / L or more and 7 mol / L or less in electrolyte solution. By setting this range, high ionic conductivity can be obtained.

  The electrolyte composition preferably contains iodine in a range of 0.01 mol / L to 3 mol / L. Iodine is mixed with iodide in the electrolyte composition and acts as a reversible redox pair. By setting the iodine content to 0.01 mol / L or more, the oxidized form of the redox couple becomes sufficient, and the charge can be transported sufficiently. Moreover, light can be efficiently given to a semiconductor layer by setting it as 3 mol / L or less. The iodine content is more preferably 0.03 mol / L or more and 1.0 mol / L or less.

  The electrolyte composition may be either liquid or gel, and can contain an organic solvent. By containing the organic solvent, the viscosity of the electrolyte composition can be further reduced, so that it can easily penetrate into the semiconductor electrode. Examples of the organic solvent that can be used include cyclic carbonates such as ethylene carbonate (EC) and propylene carbonate (PC); chain carbonates such as dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate; γ-butyrolactone, acetonitrile, Examples include methyl propionate and ethyl propionate. Furthermore, cyclic ethers such as tetrahydrofuran and 2-methyltetrahydrofuran; chain ethers such as dimethoxyethane and diethoxyethane; nitrile solvents such as acetonitrile, propionitrile, glutaronitrile, and methoxypropionitrile It is done. These organic solvents can be used alone or as a mixture of two or more. The content of the organic solvent is not particularly limited, but is preferably 80% by weight or less, and more preferably 0% by weight or more and 30% by weight or less in the electrolyte composition.

  An example of the solar cell of the second embodiment is shown in FIG. The dye-sensitized solar cell shown in FIG. 1 includes a semiconductor electrode (photoelectrode), a counter electrode, and an electrolyte composition 3. The semiconductor electrode (photoelectrode) includes a glass substrate 6, a transparent conductive film 7 formed on the glass substrate 6, and a semiconductor layer 1 formed on the transparent conductive film 7. The semiconductor layer 1 includes tungsten oxide particles 4 and a dye 5 supported on the surface of the tungsten oxide particles 4. The counter electrode includes a glass substrate 8, a transparent conductive film 9 on the glass substrate 8, and a conductive catalyst layer 2 formed on the transparent conductive film 9. The space between the semiconductor electrode and the counter electrode is sealed with a sealing resin 10. The electrolyte composition 3 is made of, for example, an electrolytic solution. The electrolyte composition 3 is impregnated in the semiconductor layer 1 and is filled in a space between the semiconductor layer 1 and the conductive catalyst layer 2.

In the dye-sensitized solar cell, when light is incident from the glass substrate 6 side, the dye 5 is first excited by absorbing incident light, and the excited dye 5 delivers electrons to the semiconductor electrode, and the electrolyte composition 3. Photoelectric conversion (power generation) is carried out by passing the hole to. The flow of electrons during the power generation reaction is indicated by arrows in FIG. On the other hand, in the electricity storage reaction, ions (for example, Li ⁺ ) ionized from the supporting electrolyte in the electrolyte composition 3 are electrochemically reduced on the surfaces of the tungsten oxide particles 4. In such a dye-sensitized solar cell, when the light irradiation is stopped and exposed to darkness, the power generation reaction stops, but an electromotive force is generated due to the difference in the electrode potential between the anode and the cathode. Since a discharge reaction in which electrons accumulated in tungsten oxide flow to the outside occurs, the dye-sensitized solar cell can have a power storage function.

  In addition, the Raman spectroscopic analysis of the tungsten oxide powder contained in the solar cell of the second embodiment is performed as follows. First, the sealing part on the side surface of the solar cell is destroyed, and the electrolytic solution is removed. Next, the glass substrate on the counter electrode side is removed, and the semiconductor layer is exposed. The tungsten oxide particle layer is cut from the semiconductor layer and washed with pure water, alcohol, or an organic solvent to remove the dye. The tungsten oxide particles from which the dye has been removed are subjected to Raman spectroscopic analysis. The measurement method of Raman spectroscopic analysis is as described in the first embodiment.

According to the solar cell of the second embodiment described above, since the semiconductor electrode (photoelectrode) including the solar cell substrate according to the first embodiment is used, both the power generation performance and the power storage performance are excellent. For example, it is possible to achieve excellent performance such that the power generation efficiency is 1% or more and the power storage function is 100 C / m ² or more.

  Hereinafter, embodiments will be described with reference to the drawings.

(Examples 1-15 and Comparative Examples 1-3)
First, tungsten oxide (WO ₃ ) powders 1 to 3 were synthesized by the following method.

(Synthesis of tungsten oxide (WO ₃ ) powder 1)
Plasma treatment was performed by putting a coarse powder of tungsten oxide having an average particle diameter of 3 μm into a plasma flame having a center temperature of 10,000 ° C. Next, the tungsten oxide jumped out of the plasma flame is subjected to rapid cooling at a distance of 1 m or more at 1000 ° C./s or more, thereby obtaining tungsten oxide (WO) having an average particle diameter of 10 nm converted from a BET specific surface area (average 83 m ² / g). ₃ ) Powder 1 (Sample 1) was prepared.

(Synthesis of tungsten oxide (WO ₃ ) powder 2)
After plasma treatment under the same conditions as WO ₃ powder 1, heat treatment was performed at 450 ° C. for 50 hours, and tungsten oxide (WO ₃ ) powder 2 having an average particle diameter of 15 nm converted from a BET specific surface area (average 56 m ² / g) ( Sample 2) was prepared.

(Synthesis of tungsten oxide (WO ₃ ) powder 3)
After plasma treatment under the same conditions as WO ₃ powder 1, heat treatment is performed at 600 ° C. for 1 hour, and tungsten oxide (WO ₃ ) powder 3 having an average particle diameter of 20 nm converted from a BET specific surface area (average 42 m ² / g) ( Sample 3) was prepared.

The obtained samples 1 to 3 are subjected to Raman spectroscopic analysis under the conditions described in the first embodiment, and the obtained chart is shown in FIG. In the chart of FIG. 2, the horizontal axis is Raman shift (cm ⁻¹ ), and the vertical axis is intensity (CPS). As apparent from FIG. 2, the sample 1 were those first peak at 269cm ^-1, the second peak and 801cm ^-1 to 695cm ^-1 with a third peak. Sample 2 were those first peak at 272cm ^-1, the second peak and 805cm ^-1 to 712 cm ^-1 having a third peak. Sample three was the first peak to 273cm ^-1, the second peak and 807cm ^-1 to 717cm ^-1 with a third peak. Therefore, tungsten oxide (WO ₃₎ powder 1-3, the first peak in the range of 268～274Cm ^-1, a third peak in the range of the second peak and 800～810Cm ^-1 in the range of 630～720Cm ^-1 I had it.

Next, as shown in Table 1, WO ₃ powders 1 to 3 alone, WO ₃ powders 1 to ₃ coated with Y ₂ O ₃ or CeO ₂ , second powder (MgO, Y ₂ O ₃ , C) mixed and TiO ₂ powder were prepared as particles constituting the semiconductor layer (hereinafter referred to as semiconductor particles).

(Preparation of dye-sensitized solar cell substrate)
A battery electrode material paste is prepared by mixing 6.4 g of a binder (EC-100FTP manufactured by Nisshin Kasei Co., Ltd.) and 20 g of an alcohol solvent with respect to 3.6 g of each of the semiconductor particles of Examples 1 to 15 and Comparative Example 1. did. A glass substrate having a thickness of 1.1 mm and a sheet resistance of 5Ω / □ was used, and one side of the glass substrate was covered with a transparent conductive film (ITO). The paste was printed on the transparent conductive film of the glass substrate by a screen printing method and baked at 400 to 480 ° C. for 30 to 60 minutes. Thus, dye-sensitized solar cell substrates of Examples 1 to 15 and Comparative Example 1 were obtained.

  As for Comparative Example 2, the dye-sensitized solar of Comparative Example 2 was changed in the same manner as in Example except that the paste composition was changed to 9 g of the semiconductor particles of Comparative Example 2, 1 g of the binder and 20 g of the alcohol solvent. A battery substrate was obtained.

  For Comparative Example 3, the dye composition of Comparative Example 3 was the same as that of Example 3 except that the paste composition was changed to 1 g of the semiconductor particles of Comparative Example 3, 9 g of the binder, and 20 g of the alcohol solvent. A battery substrate was obtained.

The film thickness, porosity and void average size of the semiconductor layers of the dye-sensitized solar cell substrates of the obtained Examples and Comparative Examples were measured by the method described in the first embodiment, and the results are shown in Table 2 below. Show.

  Using the obtained dye-sensitized solar cell substrates of Examples and Comparative Examples, dye-sensitized solar cells were obtained by the following method. As a dye adsorption process, the photoelectrode was produced by immersing the semiconductor layer of the board | substrate for dye-sensitized solar cells of an Example and a comparative example at room temperature for 48 hours. The dye solution is a ruthenium complex (cis-bis (thiocyanato) -N, N-bis (2,2′-dipyridyl-4,4′-dicarboxylic acid) -ruthenium (II) dihydrate of N719 (manufactured by Sigma-Aldrich) ) 0.3 mM dissolved in a mixed solvent of acetonitrile and t-butyl alcohol (volume ratio 1: 1) was used. As the counter electrode, a glass substrate with a transparent conductive film and having platinum sputtered to a thickness of 80 nm was used.

A spacer resin having a thickness of 60 μm was disposed so as to open four electrolyte composition injection holes and surrounding the periphery of the photoelectrode, and a counter electrode heated to 110 ° C. was bonded thereto. The electrolyte composition (electrolytic solution) was injected with a syringe from the electrolyte composition injection port, and the injection port was sealed with a two-component curable resin. The composition of the electrolytic solution was 0.5M (mol) lithium iodide, 0.05M iodine, 0.58M t-butylpyridine, EtMeIm (CN) ₂ (1-ethyl-3-methylimidazolium) 0.6M in acetonitrile solvent. What was dissolved was used. A dye-sensitized solar cell was produced by this process.

  As the characteristics of the produced dye-sensitized solar cell, power generation efficiency and power storage function were measured. The results are shown in Table 3.

<Measurement conditions>
The produced dye-sensitized solar cell was irradiated with light having an intensity of 1 kW / m ² (AM1.5 solar simulator), and the photoelectric conversion efficiency (power generation efficiency) was measured.

Next, this dye-sensitized solar cell was connected to a resistor of 510Ω, and the change in current during light irradiation and light interruption was measured. As the light source, light having an intensity of 1 kW / m ² (AM1.5 solar simulator) was used. In order to confirm the power storage effect, after standing for 20 seconds in a dark place and confirming that the amount of power generation became zero, light irradiation was performed for 20 seconds, and then the light was blocked. From the maximum current value at the time of light irradiation, the discharge capacity until the current value became 0 mA / cm ² after light interruption was determined. The obtained discharge capacity (C / m ² ) is shown in Table 3 as a power storage function.

As can be seen from Table 3, the dye-sensitized solar cells according to the examples had a power generation efficiency of 1% or more, a power storage function of 100 C / m ² or more, and excellent power generation efficiency and power storage function. In contrast, in the solar cell of Comparative Example 1, although the power generation efficiency was higher than that of the example, the power storage function was zero. On the other hand, in the solar cells of Comparative Examples 2 and 3, both the power generation efficiency and the power storage function were inferior to the Examples.

Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.
Hereinafter, the invention described in the scope of the claims of the present application will be appended.
[1] In the Raman spectroscopic analysis comprises a tungsten oxide powder having a third peak in the range of the second peak and 800～810Cm ^-1 first peak in the range of 268～274Cm ^-1, in the range of 630～720Cm ^-1 A solar cell substrate comprising a semiconductor layer having a thickness of 1 μm or more and a porosity of 20 vol% or more and 80 vol% or less.
[2] The solar cell substrate according to [1 ], wherein the tungsten oxide powder has an average BET surface area of 15 m ² / g or more.
[3] The solar cell substrate according to any one of [1] to [2], wherein the semiconductor layer has a thickness of 1 μm or more and 150 μm or less.
[4] The solar cell substrate according to any one of [1] to [3], wherein a film is formed on at least a part of the surface of the tungsten oxide powder.
[5] The semiconductor layer is at least one second powder selected from the group consisting of metal oxide powder, metal boride powder, metal fluoride powder, carbonate powder, carbon powder, metal carbide powder, and metal powder. The solar cell substrate according to any one of [1] to [4], wherein
[6] The solar cell substrate according to any one of [1] to [5], wherein an average size of voids in the semiconductor layer is 5 nm or more.
[7] A substrate for a solar cell according to any one of [1] to [6], a dye carried on the semiconductor layer of the substrate for a solar cell, a counter electrode, the semiconductor layer, and the counter electrode. A solar cell comprising an electrolyte composition filled in between.
[8] The solar cell according to [7], wherein the power generation efficiency is 1% or more.
[9] The solar cell according to any one of [7] to [8], wherein the power storage function is 100 C / m ² or more.

  DESCRIPTION OF SYMBOLS 1 ... Semiconductor layer, 2 ... Electroconductive catalyst layer, 3 ... Electrolyte composition, 4 ... Tungsten oxide particle, 5 ... Dye, 6 ... Glass substrate, 7 ... Transparent electrically conductive film, 8 ... Glass substrate, 9 ... Transparent electrically conductive film, 10: Sealing resin.

Claims (9)

In Raman spectroscopic analysis, it comprises a tungsten oxide powder having a third peak first peak in the range of 268～274Cm ^-1, in the range of the second peak and 800～810Cm ^-1 in the range of 630～720Cm ^-1, the oxidation The average BET surface area of the tungsten powder is 15 m ² / g or more and 150 m ² / g or less, the thickness is 1 μm or more and 150 μm or less , the porosity is 20 vol% or more and 80 vol% or less , and the average size of the voids is 5 nm or more and 20 nm. The board | substrate for solar cells characterized by including the following semiconductor layers. The solar cell substrate according to claim 1, wherein an average size of the voids is in a range of 7 nm to 20 nm . 3. The solar cell substrate according to claim 1 , further comprising a pigment supported on a surface of the tungsten oxide powder . 4.   The solar cell substrate according to claim 1, wherein a film is formed on at least a part of the surface of the tungsten oxide powder.   The semiconductor layer includes at least one second powder selected from the group consisting of metal oxide powder, metal boride powder, metal fluoride powder, carbonate powder, carbon powder, metal carbide powder, and metal powder. The solar cell substrate according to any one of claims 1 to 4, wherein: The solar cell substrate according to any one of claims 1 to 5 ,
A dye carried on the semiconductor layer of the solar cell substrate;
A counter electrode;
A solar cell comprising an electrolyte composition filled between the semiconductor layer and the counter electrode. The solar cell according to claim 6, wherein the power generation efficiency is 1% or more. The solar cell according to any one of claims 6 to 7, wherein a power storage function is 100 C / m ² or more. 9. The solar cell according to claim 6 , wherein the power generation efficiency is 1% or more and the power storage function is 100 C / m ² or more .

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