JP2015064944A - Method of manufacturing light incident side electrode of dye-sensitized photoelectric conversion element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a light incident side electrode of a dye-sensitized photoelectric conversion element at a low cost and with stability.SOLUTION: A plurality of semiconductor fine particle groups having different average grain diameters are prepared (S1). Each of the plurality of semiconductor fine particle groups is individually mixed in dispersion media to form a plurality of colloids (S2). A pair of electrodes one of which consists of a transparent substrate having a transparent conductive film are inserted into the colloid of the semiconductor fine particle group having the minimum average grain diameter, and a current is applied between the electrodes to perform electrophoresis (S3). During the electrophoresis, the colloids of the remaining semiconductor fine particle groups are added by a predetermined amount at a predetermined time interval, in an ascending order of the average grain diameter, and thereby, semiconductor fine particles are laminated on the transparent conductive film of the transparent substrate (S4). The transparent substrate on which the semiconductor fine particles are laminated is subjected to heat treatment (S5). A semiconductor fine particle layer on the transparent substrate is made adsorb dye (S6).

Description

  The present invention relates to a method for producing a light-incident side electrode of a dye-sensitized photoelectric conversion element, particularly a dye-sensitized solar cell.

In recent years, dye-sensitized solar cells have attracted attention as new solar cells that can replace silicon-based solar cells.
A dye-sensitized solar cell is usually a transparent substrate having a transparent conductive film, a light incident side electrode formed on the transparent substrate and having a porous semiconductor layer adsorbing the dye, and a porous surface of the light incident side electrode. It is comprised from the counter electrode arrange | positioned facing a semiconductor layer, and the electrolyte solution layer hold | maintained between the light-incidence side electrode and the counter electrode.

  Then, light enters from the transparent substrate side (light incident surface) of the light incident side electrode, and when the incident light reaches the porous semiconductor layer, it is absorbed by the dye and the electrons in the dye molecule are excited. Since the energy level of the excited electrons is on the negative side of the Fermi level of the semiconductor fine particles constituting the porous semiconductor layer, the excited electrons are injected into the semiconductor fine particles. On the other hand, the dye is in an oxidized state. The electrons injected into the semiconductor fine particles move in the porous semiconductor layer, reach the transparent conductive film of the light incident side electrode, and then reach the counter electrode through the external circuit. At the counter electrode, a reduction reaction of the redox species occurs at the interface with the electrolytic solution, and the electrons reaching the counter electrode are transferred to ions in the electrolyte. The ions that have passed the electrons move through the electrolyte to the porous semiconductor layer, and reduce the dye in the oxidized state. Then, by repeating this series of processes, electric energy is extracted from light energy such as sunlight.

  In this case, in order to increase the photoelectric conversion efficiency of the dye-sensitized solar cell, it is important to increase the absorption efficiency of incident light by the dye in the porous semiconductor layer. There has been proposed a light incident side electrode configured such that the porous semiconductor layer of the electrode has a multilayer structure and the average particle diameter of the semiconductor fine particles gradually increases for each layer as the distance from the light incident surface side increases (for example, Patent Documents). 1 and 2).

  According to the light incident side electrode, light scattering is suppressed in the layer of semiconductor fine particles having a small average particle diameter located on the light incident surface side, while the semiconductor having a large average particle diameter located on the side far from the light incident surface. When light is scattered in the fine particle layer, incident light is efficiently absorbed by the dye, and as a result, the efficiency of photoelectric conversion of the dye-sensitized solar cell is increased.

  However, in this prior art, a porous semiconductor layer having a multilayer structure is formed by applying a plurality of colloidal solutions prepared in advance, each having a different average particle diameter, on a substrate in order of decreasing average particle diameter. Each time coating is performed, the obtained coating film is dried and then baked in a temperature range of 50 to 800 ° C. for about 10 seconds to 12 hours. For this reason, when obtaining a porous semiconductor layer having a multilayer structure of three or more layers, there is a problem that it takes time and the production cost also increases. In addition, in coating, it is not easy to form a coating having a uniform thickness over a large area and on a curved surface. Therefore, it is difficult to produce a large size electrode or an electrode that is not flat. It was.

JP 2002-352868 A JP 2003-217688 A

  Therefore, the subject of this invention is providing the method which can manufacture the light-incidence side electrode of a dye-sensitized photoelectric conversion element cheaply and stably.

  In order to solve the above-mentioned problems, according to the present invention, there is provided a method for producing a light incident side electrode of a dye-sensitized photoelectric conversion element, comprising: (1) preparing a plurality of semiconductor fine particle groups having different average particle diameters; (2) a step of forming a plurality of colloids by individually mixing each of the plurality of semiconductor fine particle groups in a dispersion medium; and (3) an average particle size of the plurality of semiconductor fine particle groups being the smallest. A colloid of a group of semiconductor fine particles is contained in a container, a pair of electrodes, at least one of which is a transparent substrate having a transparent conductive film, is inserted into the colloid, and the transparent substrate having the transparent conductive film is interposed between the pair of electrodes. (4) during the electrophoresis, the remaining colloids of the semiconductor fine particle groups are predetermined at predetermined time intervals in order from the smallest average particle diameter. Adding a semiconductor fine particle on the transparent conductive film of the transparent substrate on the cathode side by adding, and (5) removing the transparent substrate on which the semiconductor fine particle has been laminated from the container and performing a heat treatment, 6) There is provided a production method characterized by comprising a step of adsorbing a dye to a semiconductor fine particle layer on the transparent substrate after the heat treatment.

  In the above production method, preferably, in the step (4), the colloid is added by continuously adding the colloid to be added at a constant addition rate over a predetermined time.

  According to the production method of the present invention, a transparent substrate having a transparent conductive film, a semiconductor fine particle layer formed on the transparent conductive film of the transparent substrate, and a dye adsorbed on the semiconductor fine particle layer, Thus, the light incident side electrode is manufactured such that the proportion of the semiconductor fine particles having a larger particle diameter gradually increases as the semiconductor fine particle layer moves away from the transparent substrate.

  According to another preferred embodiment of the present invention, each of the plurality of semiconductor fine particle groups is formed from semiconductor fine particles having different crystal structures, and in step (6), the adsorption of the dye to the semiconductor fine particle layer is performed. A dye suitable for the semiconductor fine particle group is prepared for each of the semiconductor fine particle groups, and a solution of the dye compatible with the semiconductor fine particle group having the smallest average particle diameter is contained in a second container. A pair of electrodes having the transparent substrate as one electrode is inserted, and a current is passed between the pair of electrodes to perform electrophoresis. During this electrophoresis, each solution of the remaining dye is average particle size. Is carried out by adsorbing the dye to the semiconductor fine particle layer on the transparent substrate by adding a predetermined amount at predetermined time intervals in order from the one that is suitable for the semiconductor fine particle group having a small size.

  And according to this manufacturing method, the transparent substrate having a transparent conductive film, a semiconductor fine particle layer formed on the transparent conductive film of the transparent substrate, and a dye adsorbed on the semiconductor fine particle layer, As the semiconductor fine particle layer moves away from the transparent substrate, the proportion of the semiconductor fine particles having a large particle diameter gradually increases, and the crystal structure of the semiconductor fine particles gradually changes corresponding to the transition of the particle diameter. The light incident side electrode is manufactured by adsorbing the semiconductor fine particle layer with a dye suitable for the crystal structure of the semiconductor fine particle.

According to still another preferred embodiment of the present invention, the plurality of semiconductor fine particle groups are formed of different types of semiconductors.
According to another preferred embodiment of the present invention, each of the plurality of semiconductor fine particle groups is formed from titanium oxide.

  According to the present invention, the semiconductor fine particle layer of the light incident side electrode of the dye-sensitized photoelectric conversion element is formed by electrophoresis, and this electrophoresis is performed in advance. Starting from the colloid of the semiconductor fine particle group having the smallest average particle diameter, the remaining semiconductor fine particle group is added to this colloid in order of increasing average particle diameter. In the layer, a structure in which the proportion of semiconductor fine particles having a larger particle diameter gradually increases as the distance from the transparent substrate increases.

  With this structure of the semiconductor fine particle layer, the transmittance in the semiconductor fine particle layer of light incident from the transparent substrate side (light incident surface) decreases as the distance from the transparent substrate increases, and the incident light is farthest from the transparent substrate. When it reaches the end of the semiconductor fine particle layer, it attenuates moderately. Thus, incident light can be efficiently collected by the semiconductor fine particle layer.

According to the present invention, it is possible to freely change the particle size transition of the semiconductor fine particles in the semiconductor fine particle layer simply by controlling the mixing ratio of the semiconductor particle groups in the colloid during electrophoresis. There is no need to repeat drying and firing for each layer to form a multilayer structure as in the case of using the coating method, and therefore, the light incident side electrode of the photoelectric conversion element can be manufactured in a shorter time and at lower cost. .
Furthermore, in the present invention, since the semiconductor fine particle layer is formed on the transparent substrate by electrophoresis, even a large-sized electrode or an electrode having a shape other than a flat plate shape can be stably manufactured.

It is a flowchart of the manufacturing method of the incident side electrode of the dye-sensitized photoelectric conversion element by one Example of this invention. (A) is the schematic explaining the electrophoresis process of the manufacturing method shown in FIG. 1, (B) is the dye-sensitized type | mold using the light-incidence side electrode produced with the manufacturing method shown in FIG. It is sectional drawing which shows the structural example of a solar cell. It is a cross-sectional SEM image of one example of the light-incidence side electrode produced with the manufacturing method shown in FIG. (A) is a graph which shows the prediction value of the mixing ratio of the semiconductor fine particle in the colloid during the electrophoresis of each Example, (B) is incident light collection of the light incident side electrode of each Example. It is a graph which shows light wavelength dependence. (A) is a graph which shows the current density-voltage characteristic of the dye-sensitized solar cell using the light incident side electrode of each Example, (B) is the light incident side electrode of an Example, and a comparative example. It is a graph which shows the current density-voltage characteristic of the dye-sensitized solar cell which respectively used the light-incidence side electrode.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a flowchart for explaining a method of manufacturing a light incident side electrode of a dye-sensitized photoelectric conversion device according to one embodiment of the present invention.
Referring to FIG. 1, according to the present invention, first, a plurality of semiconductor fine particle groups having different average particle diameters are prepared (step S1 in FIG. 1). In this case, in order to make the particle diameter uniform for each semiconductor fine particle group, a classification method is usually used. In addition, each of the plurality of semiconductor fine particle groups may be formed of different types of semiconductors, or each of the plurality of semiconductor fine particle groups may be formed of the same type of semiconductor such as titanium oxide. .

Next, each of the plurality of semiconductor fine particle groups is individually mixed in the dispersion medium to form a plurality of colloids (step S2 in FIG. 1).
Then, as shown in FIG. 2A, the colloid 2 of the semiconductor fine particle group having the smallest average particle diameter among the plurality of semiconductor fine particle groups is accommodated in the container 1, and at least one of the colloids 2 is transparent conductive. A pair of electrodes 3 and 4 made of a transparent substrate 3 having a film 3a is inserted, and an electric current is passed between the pair of electrodes 3 and 4 so that the transparent substrate 3 having a transparent conductive film 3a becomes a cathode. Electrophoresis is performed (step S3 in FIG. 1).

During this electrophoresis, the remaining colloids of the semiconductor fine particle groups are added in a predetermined amount at predetermined time intervals in order from the one having the smallest average particle diameter, and thereby on the transparent conductive film 3a of the transparent substrate 3 on the cathode side. The semiconductor fine particles are laminated to form a porous semiconductor fine particle layer (step S4 in FIG. 1).
In this case, the colloid is preferably added by continuously adding the colloid to be added at a constant addition rate over a predetermined time.

Thereafter, the transparent substrate 3 on which the semiconductor fine particles are laminated is taken out from the container 1 and heat-treated (Step S5 in FIG. 1), and the dye is adsorbed on the semiconductor fine-particle layer on the transparent substrate after the heat treatment (Step S6 in FIG. 1). ).
The adsorption of the dye to the semiconductor fine particle layer is usually performed using an immersion method.
However, when each of a plurality of semiconductor fine particle groups is formed of semiconductor fine particles having different crystal structures, the energy level also differs if the crystal structure is different. Therefore, a suitable dye is adsorbed for each crystal structure. It is preferable to make it.

  Therefore, when each of the plurality of semiconductor fine particle groups is formed of semiconductor fine particles having different crystal structures, a dye suitable for the semiconductor fine particle group is prepared for each semiconductor fine particle group. Then, a solution of a dye compatible with the semiconductor fine particle group having the smallest average particle diameter is accommodated in the second container, and a pair of the transparent substrate having the semiconductor fine particle layer in the dye solution is used as one electrode. Electrophoresis is performed by inserting an electrode and passing a current between a pair of electrodes. During this electrophoresis, each remaining dye solution is determined in order from the one that matches the group of semiconductor fine particles having a small average particle diameter. The dye is adsorbed to the semiconductor fine particle layer on the transparent substrate by adding a predetermined amount at the time interval.

  Thus, according to the present invention, the semiconductor fine particle layer of the light incident side electrode of the dye-sensitized photoelectric conversion element is formed by electrophoresis, and this electrophoresis is performed in advance by a plurality of semiconductors having different average particle diameters. Starting from the colloid of the semiconductor fine particle group having the smallest average particle size among the fine particle groups, the remaining semiconductor fine particle group is added to this colloid in order of increasing average particle size, so that the semiconductor fine particle layer of the light incident side electrode In the layer, the proportion of the semiconductor fine particles having a larger particle diameter gradually increases as the distance from the transparent substrate increases.

  Thereby, the transmittance of the light entering the semiconductor fine particle layer from the transparent substrate side (light incident surface) decreases as the distance from the transparent substrate increases, and the incident light reaches the end of the semiconductor fine particle layer farthest from the transparent substrate. When it reaches, it attenuates moderately. Thereby, incident light can be efficiently collected by the semiconductor fine particle layer.

  According to the present invention, it is possible to freely change the particle size transition of the semiconductor fine particles in the semiconductor fine particle layer simply by controlling the mixing ratio of the semiconductor particle groups in the colloid during electrophoresis. Unlike the case where the coating method is used, it is not necessary to repeat drying and baking for each layer when forming the multilayer structure, and thus the light incident side electrode of the photoelectric conversion element can be manufactured in a shorter time and at lower cost. In addition, in the present invention, since the semiconductor fine particle layer is formed on the transparent substrate by electrophoresis, even a large-sized electrode or an electrode having a shape other than a flat plate shape can be stably manufactured.

Next, a verification experiment was conducted in order to examine the effects of the present invention. The contents of the experiment are as follows.
Example 1
(I) Formation of TiO ₂ nanoparticles Tetraisopropyl orthotitanate (TIPT) as a titanate alkoxide and acetylacetone (ACAC) as an organic solvent were mixed at a molar ratio of 1: 1 to form a TIPT solution. Next, 0.1 mol of laurylamine hydrochloride (LAHC) aqueous solution as a water-soluble surfactant was mixed with this TIPT solution at a molar ratio of 4: 1 to cause precipitation.
Then, the mixture is stirred in a thermostatic chamber at 40 ° C. for 3 to 5 days with a magnetic stirrer to dissolve all precipitates, and then the hydrolysis and polycondensation reactions are allowed to proceed at 80 ° C. TiO ₂ ) nanoparticles were formed (synthesized).

(Ii) Particle classification The formed TiO ₂ nanoparticles are dispersed in a dispersion medium (2-propanol) and sealed in a centrifuge tube, and then centrifuged at 10,000 rpm to precipitate coarse particles having a large particle size. Removed. Subsequently, the remaining supernatant was separated and precipitated at a higher speed of 13,500 rpm to obtain a TiO ₂ nanoparticle group (average particle diameter = 5 nm) having a uniform particle diameter.
Also, commercially available P25 fine particles (manufactured by Degussa) are dispersed in water, sealed in a centrifuge tube, and centrifuged as before to obtain a P25 fine particle group (average particle size = 50 nm) having a uniform particle size. It was.

(Iii) Colloid formation-Colloid A
The TiO ₂ fine particle group (average particle size = 5 nm) obtained by classification is added to ethanol so that the concentration becomes 0.40 Vol%, stirred with a magnetic stirrer for 5 minutes, irradiated with ultrasonic waves for 5 minutes, and then magnetized again. The mixture was stirred with a stirrer for 5 minutes to prepare colloid A.
・ Colloid B
The P25 fine particle group (average particle size = 50 nm) obtained by classification is added to ethanol so as to have a concentration of 1.0 Vol%, and diffusion for 5 minutes with a magnetic stirrer and ultrasonic irradiation for 5 minutes are repeated. Colloid B was prepared.

(Iv) Lamination of semiconductor fine particles by electrophoresis 40 cc of colloid A is put in a container, and in colloid A, an ITO substrate (manufactured by Furuuchi Chemical, 10Ω / cm ² ) as an anode and an aluminum plate (purity 99.99% as an anode) ) Was inserted, and the ITO substrate surface was perpendicular to the colloidal liquid surface, and the ITO substrate and the aluminum plate were arranged parallel to each other.
Then, while supplying a constant current (0.1 A / cm) between the electrode plates, electrophoresis is performed only with colloid A for 60 seconds from the start of current supply, and then (after 60 seconds have elapsed from the start of current supply), After colloid B is added to colloid A at a dropping rate of 6.24 × 10 ⁻² cc / sec for 300 seconds, the current supply is stopped to terminate electrophoresis, and a semiconductor fine particle layer having a thickness of 7.2 μm on the substrate Were laminated.
(V) Dye adsorption N719 (Cis-di (thiocyanate) bis (2,2'-bipyridy 1-4,4'-di-carboxy-late)-ruthenium (II) bis-tetra-butylammonium) as a sensitizing dye A ruthenium metal complex dye called “I” was dissolved in ethanol so as to have a concentration of 3.0 × 10 ⁻⁴ M to prepare a dye dispersion solution.
And after taking out the board | substrate which laminated | stacked the semiconductor fine particle layer and heat-processing, it is made to adsorb | suck a pigment | dye in a semiconductor fine particle layer by immersing in this pigment dispersion solution in the state which maintained the temperature of the solution at 40 degreeC for 24 hours. Thus, a light incident side electrode of the photoelectric conversion element was produced.

(Example 2)
Electrophoresis was performed in the same manner as in Example 1 at a colloid B dropping rate of 4.16 × 10 ⁻² cc / sec, and a semiconductor fine particle layer having a thickness of 4 μm was laminated on the substrate. Thus, the light incident side electrode of the photoelectric conversion element was produced by adsorbing the dye in the semiconductor fine particle layer.
(Example 3)
Electrophoresis was performed in the same manner as in Example 1 at a colloid B dropping rate of 2.08 × 10 ⁻² cc / sec, and a semiconductor fine particle layer having a thickness of 5 μm was laminated on the substrate. Thus, the light incident side electrode of the photoelectric conversion element was produced by adsorbing the dye in the semiconductor fine particle layer.

FIG. 4A is a graph showing a predicted value of a change in the mixing ratio of TiO ₂ nanoparticles and P25 fine particles in the container with the passage of time during electrophoresis in each of Examples 1 to 3. In FIG. 4A, X, Y, and Z show the graphs of Example 1, Example 2, and Example 3, respectively.

(Comparative Example 1)
A colloid obtained by mixing the TiO ₂ nanoparticle group having an average particle diameter of 5 nm obtained by classification in Example 1 and the P25 fine particle group having an average particle diameter of 50 nm at a mass ratio of 1: 1 is formed, and the colloid is formed in the colloid. Electrophoresis is performed by inserting a pair of electrodes similar to those in Example 1, and a semiconductor fine particle layer having a thickness of 7.2 μm is laminated on the transparent conductive film of the transparent substrate, and Example 1 is placed in the semiconductor fine particle layer. In the same manner as described above, the light incident side electrode of the photoelectric conversion element was produced by adsorbing the dye.
(Comparative Example 2)
Using a P25 fine particle group having an average particle diameter of 50 nm obtained by classification in Example 1, a colloid was formed in the same manner as in Experiment 1, and a pair of electrodes similar to those in Experiment 1 were inserted into this colloid for electrophoresis. Then, a semiconductor fine particle layer having a thickness of 7.2 μm is laminated on the transparent conductive film of the transparent substrate, and the dye is adsorbed in the semiconductor fine particle layer in the same manner as in Example 1, thereby allowing light incident on the photoelectric conversion element. A side electrode was produced.

[Experiment 1]
The cross section of the light incident side electrode of Example 1 was observed by SEM (scanning electron microscope). FIG. 3 shows this SEM image, (A) is an image of the entire cross section, and (B) to (E) are regions (1) to (4) in (A), respectively. It is an enlarged image of.
In FIG. 3A, a region (1) is a region formed by electrophoresis only with colloid A before colloid B is dropped. From FIG. 3B, this region contains TiO _2. It can be seen that only nanoparticles are laminated.
In FIG. 3 (A), region (2) is a region formed immediately after the start of colloid B dripping, and from FIG. 3 (C), from this layer, a layer of P25 fine particles is formed from a layer of TiO ₂ nanoparticles. It can be seen that a transition portion to the layer is formed.
In FIG. 3A, the region (3) is a region formed at an intermediate point of colloid B dropping, the region (4) is a region formed immediately before the end of electrophoresis, and FIG. 3 (D) and (E) show that the proportion of P25 fine particles increases as the colloid B dropping time elapses.

[Experiment 2]
For each light incident side electrode of Example 1, Example 2, and Example 3, the dependency of the light collection efficiency on the incident light wavelength was measured.
The measurement results are shown in the graph of FIG. In FIG. 4B, X, Y, and Z show the graphs of Example 1, Example 2, and Example 3, respectively.
From the graph of FIG. 4B, it was found that the light collection efficiency is improved over the entire wavelength of incident light as the thickness of the semiconductor fine particle layer of the light incident side electrode increases.

[Experiment 3]
Using the light incident side electrode of Example 1, a dye-sensitized solar cell was produced. FIG. 2B schematically shows the structure of the manufactured solar cell.
Referring to FIG. 2B, first, an opening of 5.0 mm × 5.0 mm is formed as a spacer 6 on the semiconductor fine particle layer 5a on which the dye of the light incident side electrode 5 of Example 1 is adsorbed. A 50 μm-thick Hi Milan (registered trademark) plate having 6 a was placed, and the electrolyte solution 7 was injected into the opening 6 a of the spacer 6. Incidentally, the electrolyte solution 7, using 3-Methoxy-propionitrile as a solvent, to which 0.1M of LiI, 0.005 M to _{I 2, DMPII (1-propyl} -2,3 dimethylimidazolium iodide) to 0.6M, TBP (4-tert-butylpyridine) added with 0.5M.

Then, an ITO glass electrode 8 sputtered with platinum was placed on the spacer 6 and the two electrodes 5 and 8 were sandwiched and fixed from outside (not shown) by a binder clip to obtain a solar cell.
The solar simulator (SAN-EI ELECTRIC, XES-40S1) calibrated as a standard light source on the light incident surface of the dye-sensitized solar cell (surface opposite to the semiconductor fine particle layer of the light incident side electrode) Light was irradiated and the current density-voltage characteristics of the solar cell were measured.

Using the light incident side electrode of Example 2 instead of the light incident side electrode of Example 1, a dye-sensitized solar cell was produced in the same manner as in Example 1, and the obtained dye-sensitized solar cell was The current density-voltage characteristics were measured in the same manner as in Example 1.
A dye-sensitized solar cell was prepared in the same manner as in Example 1, using the light-incident side electrode of Example 3 instead of the light-incident side electrode of Example 1, and the resulting dye-sensitized solar cell The current density-voltage characteristics of the battery were measured in the same manner as in Example 1.

These measurement results are shown in the graph of FIG. In FIG. 5A, X, Y, and Z show the graphs of Example 1, Example 2, and Example 3, respectively.
From the graph of FIG. 5A, it was found that a larger short circuit current density can be obtained as the thickness of the semiconductor fine particle layer of the light incident side electrode increases.

[Experiment 4]
Using the light incident side electrode of Comparative Example 1 instead of the light incident side electrode of Example 1, a dye sensitized solar cell was produced in the same manner as in Example 1, and the obtained dye sensitized solar cell was The current density-voltage characteristics were measured in the same manner as in Example 1.
A dye-sensitized solar cell was prepared in the same manner as in Example 1 using the light-incident side electrode of Comparative Example 2 instead of the light-incident side electrode of Example 1, and the resulting dye-sensitized solar cell The current density-voltage characteristics of the battery were measured in the same manner as in Example 1.

These measurement results are shown in the graph of FIG. In FIG. 5B, C ₁ and C ₂ indicate graphs of Comparative Example 1 and Comparative Example 2, respectively. In addition, the graph X in FIG.5 (B) reproduces the graph X of Example 1 shown in FIG.5 (A) for the comparison.
From the graph of FIG. 5B, it was found that the short-circuit current density increased in the order of Example 1, Comparative Example 1, and Comparative Example 2.

  In Example 1, the semiconductor fine particle layer has a structure in which the proportion of the semiconductor fine particles having a larger particle diameter gradually increases as the distance from the transparent substrate in the layer increases. The transmittance decreases as the distance from the transparent substrate decreases, and when the incident light reaches the end of the semiconductor particle layer farthest from the transparent substrate, it is moderately attenuated, so that the incident light is efficiently transmitted to the semiconductor particle layer. In contrast, in Comparative Example 1 and Comparative Example 2, it is considered that the incident light was not appropriately attenuated in the semiconductor fine particle layer and was not sufficiently collected by this layer.

DESCRIPTION OF SYMBOLS 1 Container 2 Colloid 3 Transparent substrate 3a Transparent electrically conductive film 4 Electrode 5 Light incident side electrode 5a Semiconductor fine particle layer 6 which the pigment | dye was adsorbed 6 Spacer 6a Opening part 7 Electrolyte solution 8 Electrode

Claims (9)

A method for producing a light incident side electrode of a dye-sensitized photoelectric conversion element,
(1) preparing a plurality of semiconductor fine particle groups having different average particle diameters;
(2) forming a plurality of colloids by individually mixing each of the plurality of semiconductor fine particle groups in a dispersion medium;
(3) A colloid of a semiconductor fine particle group having a minimum average particle diameter among the plurality of semiconductor fine particle groups is accommodated in a container, and a pair of electrodes, at least one of which is a transparent substrate having a transparent conductive film, in the colloid. Inserting and conducting electrophoresis by passing a current between the pair of electrodes so that the transparent substrate having the transparent conductive film serves as a cathode; and
(4) A transparent conductive film of the transparent substrate on the cathode side is added during the electrophoresis by adding a predetermined amount of the colloid of the remaining semiconductor fine particle group in order from the smallest average particle size at a predetermined time interval. Laminating semiconductor fine particles thereon,
(5) removing the transparent substrate on which the semiconductor fine particles are laminated from the container and performing a heat treatment;
(6) A method comprising adsorbing a dye on a semiconductor fine particle layer on the transparent substrate after the heat treatment.   In the step (4), the colloid is added by continuously adding the colloid to be added at a constant addition rate over a predetermined time. Each of the plurality of semiconductor fine particle groups is formed from semiconductor fine particles having different crystal structures,
In the step (6), for the adsorption of the dye to the semiconductor fine particle layer, a dye suitable for the semiconductor fine particle group is prepared for each semiconductor fine particle group, and the dye suitable for the semiconductor fine particle group having the smallest average particle diameter is prepared. In a second container, a pair of electrodes having the transparent substrate as one electrode is inserted into the dye solution, and an electric current is passed between the pair of electrodes to perform electrophoresis. During electrophoresis, each solution of the remaining dye is added to the semiconductor fine particle layer on the transparent substrate by adding a predetermined amount at predetermined time intervals in order from the one that matches the semiconductor fine particle group having a small average particle diameter. The method according to claim 1 or 2, wherein the method is performed by adsorbing a dye.   The manufacturing method according to any one of claims 1 to 3, wherein each of the plurality of semiconductor fine particle groups is formed of a different type of semiconductor.   The manufacturing method according to claim 1, wherein each of the plurality of semiconductor fine particle groups is made of titanium oxide. A light incident side electrode of a dye-sensitized photoelectric conversion element manufactured by the manufacturing method according to claim 1 or 2,
A transparent substrate having a transparent conductive film;
A semiconductor fine particle layer formed on the transparent conductive film of the transparent substrate;
A dye adsorbed on the semiconductor fine particle layer,
The light incident side electrode, wherein the semiconductor fine particle layer is configured so that a ratio of semiconductor fine particles having a large particle diameter gradually increases as the distance from the transparent substrate increases. A light incident side electrode of a dye-sensitized photoelectric conversion element manufactured by the manufacturing method according to claim 3,
A transparent substrate having a transparent conductive film;
A semiconductor fine particle layer formed on the transparent conductive film of the transparent substrate;
A dye adsorbed on the semiconductor fine particle layer,
As the semiconductor fine particle layer moves away from the transparent substrate, the proportion of the semiconductor fine particles having a large particle size gradually increases, and the crystal structure of the semiconductor fine particles gradually changes corresponding to the transition of the particle size, Further, the light incident side electrode, wherein the semiconductor fine particle layer is adsorbed with a dye suitable for a crystal structure of the semiconductor fine particle.   8. The light incident side electrode according to claim 6, wherein each of the plurality of semiconductor fine particle groups is made of a different type of semiconductor.   8. The light incident side electrode according to claim 6, wherein each of the plurality of semiconductor fine particle groups is made of titanium oxide.