JP2005310388A - Photoelectric conversion device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make the efficiency of a photoelectric conversion device higher by improving a light energy conversion efficiency and suppressing reaction losses caused by internal energy consumption. <P>SOLUTION: On a translucent substrate 30, a transparent electrode 10 having a large number of projections in an arbitrary uneven shape such as a triangular pyramid and a cylinder on its opposite-side surface is arranged with a diffusion prevention film 60 in-between. The projection formed side surface of the transparent electrode 10 is coated with a light absorption semiconductor layer 20, and a counterelectrode 50 is arranged with a charge transfer layer 40 in-between. Though the specific surface area of an electrode composed of the transparent electrode 10 and the semiconductor layer 20 can be increased by fining and lengthening the projections, and forming them densely, the space factor and the aspect ratio of the projections are set considering the problem of diffusion in the transfer layer 40, etc. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a photoelectric conversion element, and more particularly to a photoelectric conversion element including a transparent electrode and a light absorption layer.

In recent years, problems such as global warming and acid rain due to carbon dioxide generated by using fossil fuels such as oil as energy have been highlighted. Solar cells are attracting attention as a trump card for such global environmental problems. In general, a solar cell has a high power generation cost, and how to reduce the power generation cost is one of the problems.
In view of such problems, wet solar cells have been developed as solar cells with relatively low power generation costs. However, a problem with wet solar cells is that the output power is relatively low, which is due to poor reaction efficiency in the semiconductor layer that performs light absorption and electronic excitation (in some cases, a semiconductor layer carrying a dye on the surface). Is a big cause. Therefore, in a wet solar cell, it is one of the problems to increase the output by improving the reaction efficiency in the semiconductor layer.

By the way, the reaction in the semiconductor layer absorbs light in the layer, and electrons are excited by the absorbed light. And when an electrode is N type, the excited electron flows through a semiconductor layer and a transparent electrode to a counter electrode. When the electrode is P-type, the flow of electrons is reversed.
Therefore, in order to improve the reaction efficiency in the semiconductor layer, the following measures are considered.
-Increase the specific surface area of the semiconductor layer to improve the light absorption efficiency.
・ Efficient excitation of electrons by light.
-Make recombination of excited electrons and holes difficult to occur.

  In a dye-sensitized solar cell, which is a typical wet solar cell, in order to efficiently perform electron excitation by light, a semiconductor layer carrying a dye is used as a semiconductor layer, and light absorption and electron excitation are performed by the dye. The method is taken. When the dye layer supported on the semiconductor is a single molecule, sufficient light absorption cannot be performed. Therefore, the specific surface area is improved about 1000 times using a finely divided semiconductor, and the dye per unit area is increased. A method of increasing the light absorption efficiency by increasing the amount is employed.

In order to improve the light absorption efficiency by increasing the specific surface area of the semiconductor layer, and to improve the electron transfer efficiency and make it difficult for recombination of electrons and holes, the transparent electrode is placed on the surface of the Hausdorff dimension. A photoelectric conversion element having a structure is described in Patent Document 1 below. For the same purpose, Patent Document 2 below discloses a photoelectric conversion device in which an electrode on a semiconductor has a needle-like crystal structure without grain boundaries.
Furthermore, Patent Document 3 below describes a technique for increasing the area of a semiconductor electrode layer by disposing a granular semiconductor crystal on a needle-like crystal.
JP-A-11-260427 JP 2002-356400 A JP 2002-141115 A

In the solar cell using the above-described finely divided semiconductor, the recombination of electrons and holes is caused by a decrease in electron transfer efficiency between the semiconductor particles and between the semiconductor and the transparent electrode as a barrier for electron transfer. Is likely to occur. In addition, when a solid electrolyte is used, the wettability and mass transfer of the electrolyte into the fine gaps between the fine particles become a problem, so that the output is eventually lowered.
In addition, the larger the specific surface area of the semiconductor layer is, the more advantageous for light absorption. However, when the shape is complicated as described in Patent Documents 1 and 2, the manufacturing becomes complicated and the cost increases. In addition, in the wet solar cell, there arises a problem of wettability between the semiconductor layer and the charge transfer layer, and further, mass transfer in the charge transfer layer becomes insufficient, so that the efficiency of the entire battery is rather lowered. There is a tendency.

  Furthermore, in the above-described photoelectric conversion devices of Patent Documents 2 and 3, since the contact problem between the transparent electrode and the charge transfer layer is not taken into consideration, there is a possibility that they contact each other. When such contact occurs, electrons that have moved to the transparent electrode directly react with ions that are undergoing charge transfer, and as a result, sufficient battery efficiency may not be obtained. In addition, when the specific surface area is improved up to about 1000 times, which is the same as that of the current dye-sensitized solar cell, with a needle-shaped crystal semiconductor, the crystal having a cross-sectional area of nano-order is made to a length of micron order, etc. A high aspect ratio is required. Therefore, it becomes difficult to manufacture, and the moving distance of electrons in the semiconductor layer becomes long, and the probability of recombination of electrons and holes increases.

  The present invention has been made in view of the above-described problems of the conventional example, and its purpose is to reduce the reaction loss due to light energy conversion efficiency and internal energy consumption in a photoelectric conversion device including a transparent electrode and a light absorption layer. By suppressing it, the efficiency of the photoelectric conversion device is improved.

In order to achieve the above object, the present invention is a photoelectric conversion element comprising:
A transparent electrode formed on a light-transmitting substrate;
A light-absorbing semiconductor layer covering the surface of the transparent electrode;
A charge transfer layer in contact with the light absorbing semiconductor layer;
In a photoelectric conversion element having a counter electrode in contact with the charge transfer layer,
The transparent electrode has an arbitrary uneven shape on at least a part of the surface opposite to the substrate,
The light-absorbing semiconductor layer provides a photoelectric conversion element characterized by covering the surface of the transparent electrode along the uneven shape of the transparent electrode.

  In the above-described photoelectric conversion element according to the present invention, it is preferable that the transparent electrode has a protrusion formed by an uneven shape, and the protrusion is hollow. The charge transfer layer is preferably composed of an electrolyte containing charge transport carriers.

  In the above-described photoelectric conversion element according to the present invention, the light absorption semiconductor layer is composed of a semiconductor having a band gap of about 1.5 eV, and crystal growth in one direction with few grain boundaries in the carrier movement direction. The thin film semiconductor is preferably used. The light absorbing semiconductor layer may be set to about 1.5 eV by widening the band gap by making the semiconductor nanostructured. Furthermore, it is preferable that at least a part of the light-absorbing semiconductor layer has a whisker structure. Furthermore, it is preferable that a dye is supported on the surface of the light-absorbing semiconductor layer in contact with the charge transfer layer.

  In the above-described photoelectric conversion element according to the present invention, the counter electrode has a concavo-convex shape symmetrical to the concavo-convex shape of the transparent electrode, whereby the thickness of the charge transfer layer between the light-absorbing semiconductor layer and the counter electrode is almost equal. It is preferable to be configured uniformly. Further, a PN junction is preferably formed between the light absorbing semiconductor layer and the charge transfer layer.

The present invention is configured as described above. Since the transparent electrode has a three-dimensional structure having a plurality of protrusions, that is, a three-dimensional structure, the specific surface area is large and the light absorption efficiency is excellent. Therefore, incident light can be efficiently converted into electric energy. Further, since the semiconductor layer is coated on the transparent electrode having a three-dimensional structure, the electron transfer distance in the semiconductor is short, the recombination of electrons is difficult to occur, and the charge transfer from the semiconductor layer to the charge transfer layer and It is possible to suppress the movement of electrons in the charge transfer layer.
Thereby, the energy conversion efficiency of a photoelectric conversion element can be improved.

Before describing the embodiments of the present invention, the point of focus related to the present invention will be described.
As described above, in order to improve the efficiency of the photoelectric conversion element, it is essential to improve the reaction efficiency in the semiconductor layer, that is, the energy conversion efficiency. One method is to improve the light absorption efficiency, and in order to realize this, it is conceivable to increase the specific surface area by making the electrode uneven. In order to increase the specific surface area, it is desirable that the unevenness is large and has a complicated shape. However, if the unevenness is too large, the electron transfer distance in the semiconductor layer becomes long and the electric resistance increases, and the excitation increases. The rate of recombination of electrons and holes will increase. If the shape is too complicated, wettability with the charge transfer layer and material diffusion in the charge transfer layer become a problem. All of these lead to a decrease in efficiency.

  In the present invention, by forming a plurality of protrusions made of the same material as the electrode on the surface of the transparent electrode, the specific surface area of the electrode is increased to improve the reaction efficiency, and the shape of the protrusion is relatively simple. By adopting a simple shape, problems such as wettability with the charge transfer layer, deterioration of mass transfer in the layer, and manufacturing complexity are solved.

Embodiments suitable for the photoelectric conversion element of the present invention will be described below with reference to the drawings.
(A)-(D) of FIG. 1 is typical sectional drawing which shows embodiment of the transparent electrode 10 employable for the wet photoelectric conversion element which concerns on this invention, In the figure, 11 is a flat transparent electrode (Hereinafter referred to as “flat plate portion”) and 12 are a plurality of transparent electrodes (hereinafter referred to as “protrusion portions”) extending in a protruding shape from the flat plate portion 11. The flat plate portion 11 and the protruding portion 12 are made of the same material, and thereby, the transparent electrode 10 of one photoelectric conversion element is formed.
The shape of the projecting portion 12 is, for example, a cone, an elliptical cone, a polygonal pyramid ((A) in FIG. 1), a columnar shape such as a cylinder, an elliptical column, or a polygonal column ((B) to (D) in FIG. 1). It is a relatively simple shape. You may form in the shape of a hollow pipe. Even if the electrode is transparent, the amount of light absorption increases as the thickness of the electrode is increased and the thickness is increased. Therefore, it is possible to keep light absorption to a minimum by making the protrusion 12 into a hollow pipe shape.

Note that all the protrusions 12 included in one photoelectric conversion element do not necessarily have the same shape, and a plurality of protrusions 12 may be mixed as long as the shape is relatively simple. Further, it is not necessary to align all the protrusions 12 with the flat plate part 11 in the same direction, and as shown in FIG. 1D, the plurality of protrusions 12 may extend in different directions, and in the middle. You may touch. Further, as shown in FIG. 1C, the protrusions 12 may be deformed such as being bent in the middle, and may be in contact with each other in the middle.
The protruding portion 12 may be formed as a rod-like body (a bowl-like body) lying on the surface of the flat plate portion 11.

As a material for the transparent electrode 10, indium oxide, tin oxide, zinc oxide, or the like can be used. Also, the concavo-convex shape is formed by a sol-gel method or a coating pyrolysis method and a mold or stamp represented by anodized Al ₂ O _3. The transparent electrode 10 provided with the protrusions 12 can be manufactured by an electrodeposition method, a hydrothermal method, or the like, which is combined with a forming method.
As described above, since the transparent electrode 10 is constituted by the flat plate portion 11 and the plurality of protrusion portions 12 protruding from the flat plate, a semiconductor having a large specific surface area and a small thickness without increasing the electron moving distance. A layer can be obtained, and thus recombination of electrons can be suppressed.

By the way, in the reaction process which occurs in the photoelectric conversion element, in the case of an N-type semiconductor, an excited electron moves from the semiconductor layer to the transparent electrode, and a current flows by flowing from the counter electrode to the charge transfer layer. That is, electrons are
The semiconductor layer → transparent electrode → counter electrode → charge transfer layer → semiconductor layer.
On the other hand, in the case of a P-type semiconductor, electrons are
It moves in the order of semiconductor layer → charge transfer layer → counter electrode → transparent electrode → semiconductor layer.
In the semiconductor layer in contact with the charge transfer layer, since there is a band bending in the semiconductor, in the case of an N-type semiconductor, electrons are transferred from the semiconductor layer to the transparent electrode (which has a lower energy level than electrons). In the case of a type semiconductor, electrons move from the transparent electrode to the semiconductor layer. At this time, if the transparent electrode is in contact with the charge transfer layer, electrons move from the transparent electrode to the charge transfer layer, thereby reducing the reaction efficiency.

  For this reason, it is necessary to make the semiconductor which covers a transparent electrode into an integrated structure so that a transparent electrode and a charge transfer layer do not contact directly, (A) and (B) of FIG. 1 is a cross-sectional view of an embodiment of a photoelectric conversion element according to the present invention made in FIG. In FIG. 2, 20 is a light-absorbing semiconductor layer (semiconductor 20) that covers the surface of the transparent electrode 10, 30 is a light-transmitting substrate on which the transparent electrode 10 is formed, and 40 is a charge transfer layer in contact with the semiconductor layer 20. , 50 is a counter electrode in contact with the charge transfer layer 40. The transparent electrode 10 and the semiconductor layer 20 constitute one electrode. Reference numeral 60 denotes a diffusion preventing film disposed between the light transmissive substrate and the transparent electrode. The diffusion preventing film 60 is not essential. In the photoelectric conversion element of the illustrated embodiment, the transparent electrode 10 having the shape structure shown in FIGS. 1A and 1B is used.

In order to increase the specific surface area of the electrode composed of the transparent electrode 10 and the light-absorbing semiconductor layer 20, it can be realized by making the protrusions 12 fine and long and densely formed on the flat plate part 11. However, if the protrusions 12 are formed densely, diffusion in the charge transfer layer 40 becomes a problem.
FIG. 3 is a schematic diagram for explaining such a problem. The density of the electrode composed of the transparent electrode 10 and the light-absorbing semiconductor layer 20 = the space occupancy is represented by S as the surface area (projection of the flat plate portion of the transparent electrode 10). The area can be expressed as follows, where L is the length of the electrode 100.
Space occupancy (%)
= (Volume inside semiconductor layer in S × L space) / (S × L) × 100 (1)

In Formula (1), when the projection part 10 is a cylinder and a cone, the space occupancy can be expressed as follows.
Space occupancy (cylinder)
= Π · α / 4 (2)
Space occupancy (cone)
= Π · α / 12 (3)
Here, α represents the filling rate of the columnar or conical protrusions 12 on the flat plate part 11, and α = 1 when the protrusions 12 are arranged densely without vertical and horizontal gaps.

Using the formulas (2) and (3), α can be changed in increments of 0.1 and the space occupancy can be calculated as shown in Table 1 below.

Table 1
α Space occupancy (cylinder) Space occupancy (cone)
0.1 7.9% 2.6%
0.2 15.7 5.2
0.3 23.6 7.9
0.4 31.4 10.5
0.5 39.3 13.1
0.6 47.1 15.7
0.7 55.0 18.3
0.8 62.8 20.9
0.9 70.7 23.6
1 78.5 26.2

From Table 1 above, in the case of a cylindrical shape, the space occupancy rate (cylindrical) when aligned without vertical and horizontal gaps is 78.5%, so it is considered that the upper limit is preferably about 80%.
In the case of the conical shape, the space occupancy is greatly reduced as compared with the case of the cylindrical shape, and is about 26% even when α = 1, and about 13% when α = 0.5. The larger the space occupancy, the more the specific surface area is improved. However, due to the ease of manufacturing when the conical protrusion 12 is formed, α may be about 0.5. ) Is about 10%. A preferable range is about 20 to 60%.

When a cylindrical shape is used as the protrusion 12, the specific surface area is expressed by the following formula (4).
Specific surface area (cylinder)
= 1 + π · α · A (4)
Here, A is the aspect ratio represented by A = L / 2r, and r is the radius of the cylinder.
The specific surface area (cylinder) calculated by the equation (4) when α = 1 is shown in Table 2 below.

Table 2
Aspect ratio A Specific surface area (Cylinder)
14
10 32
100 315
1000 3143
10000 31417

  The larger the aspect ratio, the larger the specific surface area. However, when the aspect ratio is extremely large, manufacturing becomes difficult, and the distance of electron movement in the transparent electrode 10 increases and the electrical resistance increases. Therefore, a preferable aspect ratio range is 10 to 1000.

  As the charge transfer layer 40 shown in FIG. 2, it is preferable to use an electrolyte containing a charge transport carrier. Thereby, the ionized carrier moves in the electrolyte, and exchanges electrons with the electrode by an electrochemical reaction at each electrode. As a representative charge transport carrier that causes such an electrochemical reaction, a redox system (redox pair) reversibly forms a pair in the form of an oxidant and a reductant. Are iodine-iodine compound, bromine-bromine compound, chlorine-chlorine compound, vanadium ion (III) -vanadium ion (II), manganate ion-permanganate ion, iron ion (III) -iron ion (II), Ferricyan compound-ferrocyan compound, copper ion (II)-copper ion (I), ruthenium ion (III)-ruthenium ion (II), cerium ion (IV)-cerium ion (III), tellurium ion (II)-tellurium ion (II), titanium ion (III) -titanium ion (II), thallium ion (III) -thallium ion (I), mercury ion (II) -mercury ion (I), quinone-hydride Quinone, fumaric acid - succinic acid, sodium polysulfide, alkylthiol - alkyl disulfides, can be employed as viologen dyes.

  Solvents for dissolving the redox system include ethylene carbonate, diethyl carbonate, methyl ethyl carbonate, diethyl carbonate, propylene carbonate, acetonitrile, propionitrile, butyronitrile, benzonitrile, ethylenediamine, pyridine, formamide, methylformamide, dimethylformamide , Methylacetamide, dimethylformamide, methylpropionamide, hexamethylphosphortriamide, 1-methyl-2-pyrrolidinone, 1,3-dimethyl-2-imidazolidinone, dimethyl sulfoxide, sulfolane, γ-butyrolactone, ethyl acetate, acetic acid Methyl, diethyl ether, phenol, a climbing solution, etc. can be employed.

  When no redox system or solvent is used, a molten salt of iodide which is an ionic solution can be used. Examples thereof include iodides of heterocyclic nitrogen-containing compounds such as imidazolium salts, pyridinium salts, quaternary ammonium salts, pyrrolidinium salts, pyrazolidium salts, and isothiazolidium salts.

  As the electrolyte, it is also possible to use a solid or solid state in addition to the liquid, and as a polymer compound constituting the solid electrolyte, polyether, polyester, polyolefin, polybutadiene, polysiloxane, polyacrylic acid, polymethacrylic acid, Polystyrene, polystyrene sulfonic acid, polyethylene sulfonic acid, maleic acid copolymer, polyphosphoric acid, polyvinyl pyridine, polyvinyl amine, polyvinyl benzyl trimethyl ammonium, polyethylene glycol, polyvinyl alcohol, polycarbonate, polyvinyl pyrrolidone, polyvinyl methine, polyvinyl acetate, polychlorinated Vinyl, polyvinylidene chloride, polyvinyl fluoride, polyvinylidene fluoride, polyimine, polyglutamic acid, gelatin, carboxymethylcellulose, agar, etc. It is possible to use.

  It is also possible to use an oil gelling agent in order to directly solidify the solvent without using a polymer compound. Examples of oil gelling agents include 1,2,3,4-dibenzylidene-D-sorbitol, 12 hydroxystearic acid, N-lauroyl-L-glutamic acid-α, spin-labeled steroid, dialkylaluminum phosphate, phenolic cyclic oligomer 2,3-bis-n-hexadecyloxyanthracene, cyclic depsipeptide, partially fluorinated derivative, cystine derivative, butyrolactone derivative, urea derivative, vitamin H derivative, cholic acid derivative and the like.

As the light-absorbing semiconductor layer 20, it is preferable to use a semiconductor having a band gap of about 1.5 eV that is excellent in electron excitation efficiency by visible light. As such a semiconductor, Cu ₂ S, FeS ₂ , Mg ₂ Si, Zn ₃ P ₂ , CuInS ₂ , SnS, NiO, or the like can be employed.

  In addition, it is preferable to use a semiconductor in which the grain boundary is reduced in the electron movement direction, such as making the light absorbing semiconductor layer 20 thin and growing a single crystal or a crystal in one direction. By reducing the thickness of the light-absorbing semiconductor layer 20, the electron transfer distance in the semiconductor layer is shortened, and the driving force of electron transfer is improved by steepening the band in the semiconductor. Recombination can be reduced. Furthermore, when the excited electrons move to the transparent electrode, the electrons can be prevented from passing through the crystal grain boundary that is the center of recombination, and this also suppresses recombination. it can.

  Furthermore, it is preferable to make the light-absorbing semiconductor layer 20 into a nanostructure. Since the band gap can be widened by forming the nanostructure, a band gap of less than 1.5 eV can be optimized and used in the vicinity of 1.5 eV. Further, in addition to shortening the electron moving distance in the light-absorbing semiconductor layer 20 and making the band steep, it is possible to greatly reduce the probability of electrons being thinned by defects in the semiconductor that is the center of recombination. Become.

  At least a part of the light absorbing semiconductor layer 20 may have a whisker structure 21 as shown in FIG. By making the surface of the semiconductor layer 20 a whisker structure 21, the specific surface area can be dramatically increased. At this time, the probability of the occurrence of electron recombination can be greatly reduced by using a substantially complete crystal whisker structure.

As shown in FIG. 5, the dye 22 may be supported on the surface of the light absorption semiconductor layer 20. For example, the semiconductor layer 20 is formed of TiO ₂ , ZnO or the like, and a metal complex dye or an organic dye is supported on the surface. Ru-based dyes are often used as metal complex dyes, including phenanthroline dyes, quinoline dyes, β-diketonate complex dyes, or Ru (II), Os (II), Fe (II), Re (I), Cu ( And polypyridyl ligand transition metal complexes such as I). Organic dyes include polymethine dyes such as cyanine and merocyanine, xanthene dyes such as mercurochrome, rose bengal and eosin Y, porphyrin complexes, triphenylmethane, acridine, coumarin, phthalocyanine, oxazine and indico. Various dyes can be mentioned.

In the above-described photoelectric conversion element, it is preferable to use a semiconductor having a type opposite to that of the light absorption semiconductor layer 20 as the charge transfer layer 40. Thereby, a PN junction is formed between the light absorption semiconductor layer 20 and the charge transfer layer 40. A polymer semiconductor can be used for the charge transfer layer 40.
When not using the electrolyte can be used inorganic hole transport material, for example, as a Cu-based compound semiconductor, (CuI, CuBr, CuSCN, CuInSe 2, CuGaSe 2, Cu 2 O, CuS, CuGaS 2, CuInS ₂ and can be employed polyaniline, polypyrrole, polythiophene, phthalocyanine and the like.

  Moreover, in the above-described photoelectric conversion element, the counter electrode 50 may be three-dimensional like the transparent electrode 10 as shown in FIG. That is, the counter electrode 50 includes a flat plate portion 51 and a plurality of protrusions 52 protruding from the flat plate portion 51. The protrusions 52 are positioned so as to enter between the protrusions 12 (+ semiconductor layer 20) of the transparent electrode 10. Due to the three-dimensionalization of the transparent electrode 10, the diffusion distance in the charge transfer layer becomes longer and the charge transfer resistance increases in the recesses between the adjacent protrusions 12. Such an increase in charge transfer resistance can be suppressed because the thickness of the charge transfer layer in each part can be made substantially constant by making the counter electrode 50 three-dimensional as shown in FIG.

The electrodes of the above-described photoelectric conversion element according to the present invention, that is, the transparent electrode 10 and the light-absorbing semiconductor layer 20 were manufactured by the following process using commercially available TiO ₂ particles, a dye, an iodine solution, and the like.
A transparent electrode 10 having a three-dimensional structure using a nanowire structure with a diameter of about 200 nm and a length of about 60 μm as a protrusion 12 and a light-transmitting substrate 30 made of flat glass by using anodized Al ₂ O ₃ as a template by a sol-gel method. Formed on top. The filling factor of the wire was α = about 0.8, the space occupation ratio was about 60%, and the specific surface area was about 750 times.
Next, the transparent electrode 10 is dipped in a semi-pasty solution containing TiO ₂ particles and dried, and then heat treated at 450 ° C. to form the TiO ₂ particles on the surface of the transparent electrode 10, An electrode coated with the light absorbing semiconductor layer 20 was formed.
And the electrode was immersed in the solution containing a ruthenium pigment | dye, and the pigment | dye was made to adsorb | suck to the surface.

An actual machine test in which an electrode on a light-transmitting substrate 30 manufactured by the above process is sandwiched and fixed with glass whose surface is baked with a conductive film, an iodine solution is used as an electrolyte, and a current is measured by irradiating visible light. went. For comparison, a flat electrode having a two-dimensional structure, that is, a transparent electrode was coated on a flat glass, and TiO ₂ was baked by the same method to prepare a battery, and current was measured.
As a result, in the photoelectric conversion element according to the present invention, although there was some variation depending on the cell, a current about 1.5 times as large as that using a plate electrode was observed, and the photoelectric conversion efficiency was improved. .

Moreover, the transparent electrode 10 which has the three-dimensional structure of the photoelectric conversion element which concerns on this invention was formed with the following processes using the stamper.
Indium propoxide and tin butoxide were weighed so that In / Sn = 1: 0.05, and triethanolamine was added in an equimolar amount with indium, which was dissolved in propanol to obtain a uniform solution.
To this, 10 wt% of indium propoxide was added to cellulose to obtain a raw material solution. This solution was dip-coated on a substrate and dried to form a gel film, and a stamper was pressed to make the surface uneven. Next, this was baked at 500 ° C. for 30 minutes. A film of the transparent electrode 10 having a slightly yellowish three-dimensional structure was formed.
As a result of XRD analysis of the transparent electrode 10 thus formed, it was confirmed that indium oxide (In ₂ O ₃ ) was generated. The conductivity was 0.8 Ωcm, and the light transmittance was 80% or more in the visible light region of 400 nm or more. Therefore, sufficient electrical conductivity and light transmittance could be achieved.

It is typical sectional drawing for demonstrating the structure of the transparent electrode of the three-dimensional structure used for the photoelectric conversion element which concerns on this invention. It is typical sectional drawing for demonstrating the structure of the photoelectric conversion element which concerns on this invention. It is a figure for demonstrating the space occupation rate of the electrode which consists of a transparent electrode and a light absorption semiconductor layer in the photoelectric conversion element which concerns on this invention. It is typical sectional drawing for demonstrating the structure of the photoelectric conversion element at the time of setting the light absorption semiconductor surface based on this invention to the whisker structure. It is typical sectional drawing for demonstrating the structure of the photoelectric conversion element at the time of making the pigment | dye carry | support on the surface of the light absorption semiconductor layer based on this invention. It is typical sectional drawing for demonstrating the structure of the photoelectric conversion element at the time of making a counter electrode into a three-dimensional structure based on this invention.

Claims (10)

A photoelectric conversion element,
A transparent electrode formed on a light-transmitting substrate;
A light-absorbing semiconductor layer covering the surface of the transparent electrode;
A charge transfer layer in contact with the light absorbing semiconductor layer;
In a photoelectric conversion element having a counter electrode in contact with the charge transfer layer,
The transparent electrode has an arbitrary uneven shape on at least a part of the surface opposite to the substrate,
The photoelectric conversion element characterized by the light absorption semiconductor layer covering the surface of a transparent electrode along the uneven | corrugated shape of a transparent electrode. 2. The photoelectric conversion element according to claim 1, wherein the transparent electrode has a protrusion formed in an uneven shape, and the protrusion is hollow. 3. The photoelectric conversion element according to claim 1, wherein the charge transfer layer is composed of an electrolyte containing a charge transport carrier. 4. The photoelectric conversion element according to claim 1, wherein the light absorption semiconductor layer is made of a semiconductor having a band gap of about 1.5 eV. 5. The photoelectric conversion element according to claim 1, wherein the light absorption semiconductor layer is formed of a single crystal or a thin film semiconductor that is crystal-grown in one direction with few grain boundaries in the carrier movement direction. Photoelectric conversion element. 5. The photoelectric conversion device according to claim 1, wherein the light absorption semiconductor layer is set to about 1.5 eV by widening a band gap by forming the semiconductor into a nanostructure. element. 5. The photoelectric conversion element according to claim 1, wherein at least a part of the light absorption semiconductor layer has a whisker structure. The photoelectric conversion element according to claim 1, further comprising a dye supported on a surface of the light-absorbing semiconductor layer that is in contact with the charge transfer layer. 9. The photoelectric conversion element according to claim 1, wherein the counter electrode has a concavo-convex shape symmetrical to the concavo-convex shape of the transparent electrode, whereby a charge transfer layer between the light-absorbing semiconductor layer and the counter electrode is formed. A photoelectric conversion element having a substantially uniform thickness. 10. The photoelectric conversion element according to claim 1, wherein a PN junction is formed between the light absorbing semiconductor layer and the charge transfer layer.

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