JP4937438B2 - Semiconductor for photoelectric conversion, photoelectric conversion element and photovoltaic cell - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a photoelectric conversion semiconductor, a photoelectric conversion element using the same, and a photovoltaic cell comprising the photoelectric conversion element.
[0002]
[Prior art]
As solar cells used for photovoltaic power generation, single crystal silicon solar cells, polycrystalline silicon solar cells, amorphous silicon solar cells, compound solar cells such as cadmium telluride and indium copper selenide have been put into practical use or have been mainly researched and developed. It is targeted. However, the compound solar cell has problems such as high manufacturing cost, difficulty in securing raw materials, and long energy payback time, and the above-mentioned problems need to be overcome in order to spread. On the other hand, many solar cells using organic materials aimed at increasing the area and reducing the cost have been proposed so far.
[0003]
Under such circumstances, “Nature” (Vol. 353, pp. 737-740, 1991) and U.S. Pat. No. 4,927,721 disclose a photoelectric conversion element and a solar cell using semiconductor fine particles sensitized with a dye, and Materials and manufacturing techniques for making this have been disclosed. The battery disclosed in the above-mentioned document is a wet solar battery in which a titanium dioxide porous thin film spectrally sensitized with a ruthenium complex is used as a working electrode, and electrical connection with a counter electrode is performed by an electrolyte solution. The advantage of this solar cell is that an inexpensive oxide semiconductor such as titanium dioxide can be used without being purified with high purity, which is advantageous in that an inexpensive photoelectric conversion element can be realized. However, there is a problem that the conversion efficiency is low. One of the main causes of this problem is that the actual open circuit voltage (Voc) is much lower than the theoretically expected Voc. For example, titanium dioxide is used as a semiconductor fine particle, and (I^-/ I_Three ^-In theory, an open circuit voltage (Voc) of 1 V or higher is expected, but only a low open circuit voltage of about 0.6 V is actually obtained.
[0004]
[Problems to be solved by the invention]
This invention is made | formed in view of the said various problems, Comprising: It aims at providing the semiconductor for photoelectric conversion which shows a high open circuit voltage, the photoelectric conversion element excellent in the photoelectric conversion characteristic, and a photovoltaic cell.
[0005]
[Means for Solving the Problems]
  Means for solving the above-mentioned problems are as follows.
<1> At least on the surface of the semiconductorOne selected from the following compounds 1-1 to 1-8 and 2-1 to 2-11To the compound bound to the surfaceDipping in a solution selected from the following dye compounds R-1 to R-13 or applying the solution to a compound bonded to the surfaceIt is a semiconductor for photoelectric conversion characterized by being mordanted.
[0006]
[Chemical 1]
[Chemical 2]
[Chemical Formula 3]
[0014]
<2> The semiconductor contains at least a metal chalcogenide <1>It is the semiconductor for photoelectric conversion of description.
<3> The semiconductor is a porous semiconductor film comprising semiconductor fine particles formed on a support <1>Or<2> Is a photoelectric conversion semiconductor according to any one of the above.
[0015]
<4A photosensitive layer and a charge transport layer are provided between a pair of electrodes, and the photosensitive layer is from <1> to <3> A photoelectric conversion device comprising the photoelectric conversion semiconductor according to any one of the above.
<5> <4A photovoltaic cell comprising the photoelectric conversion element according to>.
<6> A step of bonding one selected from the following compounds 1-1 to 1-8 and 2-1 to 2-11 to at least the surface of the semiconductor, and a compound bonded to the surface to the following dye compound R-1 Dipping in a kind of solution selected from R-13 or applying the solution to a compound bonded to the surface and mordanting, and a method for producing a semiconductor for photoelectric conversion.
[Formula 4]
[Chemical formula 5]
[Chemical 6]
[0016]
In the photoelectric conversion semiconductor of the present invention, when irradiated with light, the dye fixed on the semiconductor surface by mordanting absorbs light and generates electrons and holes. On the other hand, the semiconductor receives and transmits these electrons (or holes). By sandwiching the photoelectric conversion semiconductor together with a charge transport layer between a pair of electrodes and connecting the electrodes to an external load, electrons or holes collected on one electrode by the semiconductor work, Move from electrode to counter electrode. In the photoelectric conversion semiconductor of the present invention, high sensitizing efficiency is obtained by immobilizing a sensitizing dye on the surface of the semiconductor by mordanting using electrostatic interaction. As a result, a photoelectric conversion element having the photoelectric semiconductor as a photosensitive layer and a photovoltaic cell including the photoelectric conversion element have a high open circuit voltage.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, each of the semiconductor for photoelectric conversion, the photoelectric conversion element, and the photovoltaic cell of the present invention will be described.
[Semiconductor for photoelectric conversion]
  The semiconductor for photoelectric conversion of the present invention has a basic compound and / or a cationic compound on at least the surface of the semiconductor.(One type selected from compounds 1-1 to 1-8 described later)A dye having an anionic group formed by removing protons from the acidic group or acidic group to the compound bonded to the surfaceImmerse in a solution (one selected from the following dye compounds R-1 to R-13) or apply the solution to a compound bound to the surfaceIt is characterized by being mordanted.
[0018]
(A) Semiconductor
There is no particular limitation on the shape and structure of the semiconductor, and the semiconductor may be in the form of a semiconductor substrate composed only of a semiconductor material, or on a conductive support such as a transparent electrode such as ITO glass or a platinum electrode. It may be in the form of a semiconductor layer. When used in the form of the semiconductor layer, the semiconductor layer is preferably in the form of a porous film made of semiconductor fine particles.
[0019]
Examples of the semiconductor include a single semiconductor such as silicon and germanium, a III-V compound semiconductor, a metal chalcogenide (for example, oxide, sulfide, selenide, or a composite thereof), or a compound having a perovskite structure ( For example, strontium titanate, calcium titanate, sodium titanate, barium titanate, potassium niobate, etc.) can be used. Among these, a semiconductor made of a metal chalcogenide is preferable.
[0020]
Examples of the metal chalcogenides include titanium, tin, zinc, iron, tungsten, zirconium, hafnium, strontium, indium, cerium, yttrium, lanthanum, vanadium, niobium or tantalum oxide, cadmium, zinc, lead, silver, antimony or Bismuth sulfide, cadmium or lead selenide, cadmium telluride and the like are preferable. Examples of other compound semiconductors include phosphides such as zinc, gallium, indium, and cadmium, gallium-arsenic or copper-indium selenides, and copper-indium sulfides. Furthermore, M_xO_yS_zOr M¹ _xM² _yO_z(M, M¹And M²Represents a metal element, O represents an oxygen atom, and x, y, and z are preferably semiconductors composed of composites such as the number of combinations in which the valence is neutral.
[0021]
Preferred examples of the semiconductor include Si and TiO.₂, SnO₂, Fe₂O_Three, WO_Three, ZnO, Nb₂O_Five, CdS, ZnS, PbS, Bi₂S_Three, CdSe, CdTe, GaP, InP, GaAs, CuInS₂, CuInSe₂And more preferably TiO₂ZnO, SnO₂, Fe₂O_Three, WO_Three, Nb₂O_Five, CdS, PbS, CdSe, InP, GaAs, CuInS₂Or CuInSe₂And particularly preferably TiO₂Or Nb₂O_FiveAnd most preferably TiO₂It is. TiO₂Is preferably one containing more anatase type crystals, more preferably containing 70% or more, and TiO comprising 100% anatase type crystals.₂Is particularly preferred.
[0022]
The use of a semiconductor doped with a metal is preferable because electronic conductivity in the semiconductor is improved. As a metal to dope, a bivalent or trivalent metal is preferable. In addition, it is preferable to use a semiconductor doped with a monovalent metal because a reverse current can be prevented from flowing from the semiconductor to the charge transport layer (described later).
[0023]
The semiconductor used in the present invention may be single crystal or polycrystal, but polycrystal is preferable from the viewpoint of production cost, securing raw materials, energy payback time, etc., and it is particularly preferable to use in the form of a porous film made of semiconductor fine particles. Moreover, what contains a part amorphous part can also be used.
[0024]
The particle diameter of the semiconductor fine particles is generally on the order of nm to μm, but the average particle diameter of primary particles obtained from the diameter when the projected area is converted into a circle is preferably 5 nm to 200 nm. More preferably, it is 8 nm to 100 nm. In the case where a dispersion liquid is prepared by dispersing the semiconductor fine particles in a solvent and the dispersion liquid is applied to the surface of a conductive support or the like to form a porous semiconductor film, the semiconductor fine particles (2 The average particle size of the secondary particles is preferably 0.01 μm to 30 μm. Two or more types of semiconductor fine particles having different particle size distributions may be mixed and used. In this case, the average particle size of the small particles is preferably 25 nm or less, more preferably 10 nm or less. For the purpose of improving the light capture rate by scattering incident light, it is also preferable to mix semiconductor particles having a large particle diameter, for example, about 100 nm or more and about 300 nm.
[0025]
Two or more kinds of semiconductor fine particles made of different materials may be mixed and used. When two or more kinds of semiconductor fine particles are mixed and used, at least one kind is TiO.₂, ZnO, Nb₂O_FiveAnd SrTiO₂It is preferable that any one of the semiconductor fine particles is selected from the group consisting of SnO₂, Fe₂O_ThreeAnd WO_ThreeAny one of the semiconductor fine particles selected from the above is preferable. A more preferred combination is ZnO and SnO.₂, ZnO and WO_ThreeOr ZnO, SnO₂And WO_ThreeAnd the like. When two or more kinds of semiconductor fine particles are mixed and used, their particle sizes may be different. In particular, a combination in which the particle size of the semiconductor fine particles mentioned as the first type is large and the particle size of the second and subsequent types of semiconductor fine particles combined with the first type of semiconductor fine particles is small is preferable. Further, when semiconductor fine particles made of different materials and having different sizes are used in combination, a combination in which the average particle size of large semiconductor fine particles is 100 nm or more and the average particle size of small semiconductor fine particles is 15 nm or less Is preferred.
[0026]
As the method for producing the semiconductor fine particles, “Science of Sol-Gel Method” (Sakuo Sakuna, Agne Jofusha, 1998) and “Thin Film Coating Technology by Sol-Gel Method” (Technical Information Association, 1995) ), “Synthesis of Monodispersed Particles by New Synthetic Gel-Sol Method and Size Control” (by Tadao Sugimoto), and Materia, Vol. 35, No. 9, 1012 ～ The gel-sol method described on page 1018 (1996) is preferred. In addition, a method of producing an oxide by hydrolyzing a chloride developed by Degussa in an oxyhydrogen salt is also preferable.
[0027]
When the semiconductor fine particles are titanium oxide, the sol-gel method, the gel-sol method, and the high-temperature hydrolysis method in oxyhydrogen salt of chloride are preferable, but further, “Titanium oxide properties and applied technology” ( The sulfuric acid method and the chlorine method described in Kiyono Manabu, Gihodo Publishing, 1997) can also be used. Further, as the sol-gel method, the method described in Journal of American Ceramic Society, Vol. 80, No. 12, pp. 3157-3171 (1997) or the chemistry of Burnside et al. , Vol. 10, No. 9, pages 2419-2425 are also preferred.
[0028]
(B) Cationic compound and / or basic compound
  A cationic compound and / or a basic compound is bonded to at least the surface of the semiconductor. The cationic compound and the basic compound have a function as a so-called mordant for linking the semiconductor surface and the dye (hereinafter, the cationic compound and / or the basic compound may be referred to as “mordant linking compound”). By modifying the surface of the semiconductor with the mordanting linking compound, a site where the dye can act can be formed on the surface of the semiconductor. Therefore, the mordanting linking compound is a compound that can be combined with the semiconductor used and also has a function of acting on the pigment used as the mordanting dye and immobilizing it on the semiconductor surface.
  In particular, in the present invention, the cationic compound and / or basic compound refers to the compounds 1-1 to 1-8 and 2-1 to 2-8 described later.
  The mordant linking compound is preferably a colorless compound that does not absorb in the visible region. It is preferable that the mordanting linking compound is a compound that does not absorb in the visible part, because a decrease in efficiency (filter effect) caused by the mordanting linking compound absorbing light can be prevented.
[0029]
The mordant linking compound is preferably a compound represented by the following general formula (1) or (2).
[0030]
[Chemical 7]
[0031]
In the general formula (1), Z¹Is its conjugate acid (HZ¹(+) -H represents a basic substituent having a pKa of 3 or more and 20 or less. Preferably, the conjugate acid has a pKa of 4 or more and 15 or less, more preferably 5 or more and 12 or less. Z¹Specific examples thereof include, for example, pyridyl group, imidazolyl group, triethylamino group, morpholyl and guanidyl group. However, Z¹Preferably does not contain a dye chromophore (does not absorb in the visible region).
[0032]
In the general formula (1), B¹Represents a divalent linking group and p¹Represents 0 or 1. p¹Z is 0¹Is directly M¹Combine with. B¹As, for example, an alkylene group, an arylene group, -O-, -S-, -N (R)-(R is a hydrogen atom or an alkyl group), -CO- or -SO₂-Or a divalent linking group formed by combining two or more of these.
[0033]
In the general formula (1), M¹Represents Si, Ti, Al, Ge or Sn, and is preferably Si.
[0034]
In the general formula (1), X¹Represents an alkoxy group (for example, methoxy, ethoxy and the like), an aryloxy group (for example, phenyloxy), a halogen atom (for example, a chlorine atom), a hydroxyl group or a hydrogen atom. Among these, an alkoxy group is preferable.
[0035]
In the general formula (1), m¹Represents an integer from 1 to 3 and n¹Is X¹Is M¹Represents the number that can be substituted, and is usually 2 to 3. m¹Z is 2 or more¹, B¹, X¹, P¹And n¹These two or more combinations may be the same or different.
[0036]
In the general formula (2), Z²Represents an atomic group having a cation. The atomic group preferably contains a nitrogen cation, a phosphorus cation, an oxygen cation, a sulfur cation or a carbon cation, and preferably contains at least one of a nitrogen cation or a phosphorus cation. Most preferably. Z¹Examples thereof include quaternary ammonium cations, pyridinium cations, imidazolium cations, morpholium cations, and guanidinium cations. However, Z²Preferably does not contain a dye chromophore (does not absorb in the visible region).
[0037]
In the general formula (2), A represents an anion, and q represents Z.²Represents the number required to make the cation charge of A equal to the anion charge of A. Examples of A include halide ions (Cl^-, Br^-, I^-Etc.), SCN^-, BF_Four ^-, PF₆ ^-, ClO_Four ^-, (CF_ThreeSO₂)₂N^-, (CF_ThreeCF₂SO₂)₂N^-, CF_ThreeSO_Three ^-, CF_ThreeCOO^-, Ph_FourB^-And (CF_ThreeSO₂)_ThreeC^-Etc. are preferred.
[0038]
In the general formula (2), B², M²And X²Is B in the general formula (1)¹, M¹And X¹Are synonymous with each other. In the general formula (2), p²Represents 0 or 1. p²Z is 0²Is directly M²Combine with. In the general formula (2), m²Represents an integer from 1 to 3 and n²Is X²Is M²Represents the number that can be substituted, and is usually 2 to 3.
[0039]
Each of the compounds represented by the general formula (1) or (2) is X¹And X²All or a part of is bonded to the bonding site of the semiconductor and bonded to the semiconductor. When there are multiple reactive sites in the molecule (m¹And m²Are all 2 or 3), all of the sites may be bonded to the semiconductor, or a part of the sites may be bonded to the semiconductor.
[0040]
Preferred specific examples of the compound represented by the general formula (1) (Exemplary compounds 1-1 to 8) and preferred specific examples of the compound represented by the general formula (2) (Exemplary compounds 2-1 to 11) Although shown below, this invention is not limited to these.
[0041]
[Chemical 8]
[0042]
[Chemical 9]
[0043]
[Chemical Formula 10]
[0044]
The semiconductor to which the mordant linking compound is bonded preferably has at least a surface having a structure represented by the following general formula (4) or (5).
[0045]
Embedded image
[0046]
In the general formulas (4) and (5), P_scRepresents a semiconductor, and O represents an oxygen atom. The oxygen atom may be a semiconductor-derived atom, an atom derived from the mordant linking compound, or an atom derived from a solvent or other reagent used in both reactions. In the general formulas (4) and (5), Z¹, Z², B¹, B², P¹, P², M¹, M², M¹, M², A and q are respectively synonymous with those in the general formulas (1) and (2).
[0047]
(C) Dye
  The semiconductor for photoelectric conversion of the present invention is obtained by mordanting the surface of a semiconductor with a dye. The dye is electrostatically interacted with the mordant linking compound (for example, a compound represented by the general formula (1) or (2)) bonded to a semiconductor, fixed, and mordanted. The dye has an anionic group formed by removing a proton from an acidic group or an acidic group capable of forming an ionic bond with the mordant linking compound. When the cationic compound is used as the mordant linking compound, the dye having the anionic group is used as the dye, and when the basic compound is used as the mordanting linking compound, the acidic group is used as the dye. The pigment | dye which has is used.
  In particular, in the present invention, the dye having an acidic group or an anionic group formed by removing a proton from the acidic group refers to dye compounds R-1 to R-13 described later.
[0048]
As said pigment | dye, the compound represented by following General formula (3) is preferable.
[0049]
Embedded image
[0050]
In the general formula (3), Dye represents a dye residue. The dye residue refers to a residue having a chromophore obtained by removing any substituent or r hydrogen atoms from a dye compound having a chromophore.
[0051]
In the general formula (3), Y represents an anionic group formed by removing a proton from an acidic group or an acidic group. When Y represents an acidic group, Y is CH_ThreeAn acidic group having a pKa of −2 or more and 16 or less is preferable, and an acidic group having −2 or more and 10 or less is more preferable. Specifically, —COOH group, —OH group, —SO_ThreeH group, -P (O) (OH)₂Group and -OP (O) (OH)₂Groups and the like. Among them, -COOH group, -P (O) (OH)₂Group or -OP (O) (OH)₂The group is particularly preferred. In the general formula (3), when Dye is a polymethine dye and the methine chain forms a squarylium ring or a croconium ring, the squarylium ring or the croconium ring may be an acidic group. When Y represents the anionic group, Y is preferably an anionic group formed by removing a proton from the acidic group mentioned as a preferred example of the acidic group. When Y is an anionic group, Y can have a cation necessary to neutralize its charge. Examples of the cations include alkali metal cations, quaternary ammonium cations, and cations obtained by quaternizing nitrogen-containing aromatic rings such as pyridinium cations and imidazolium cations.
[0052]
In the general formula (3), r represents an integer of 1 to 6. When r is 2 or more, 2 or more Y may be the same or different.
[0053]
The dye is preferably a metal complex dye, a phthalocyanine-based dye, or a methine dye, and more preferably a metal complex dye or a methine dye. Two or more kinds of the dyes can be mixed, and when two or more kinds are mixed, the kind and the ratio of the dyes to be mixed can be arbitrarily selected.
[0054]
Hereinafter, the preferred dye will be described more specifically.
(A) Metal complex dye
As the metal complex dye, metal phthalocyanine dyes, metal porphyrin dyes and ruthenium complex dyes are preferable, and ruthenium complex dyes are particularly preferable. Examples of the ruthenium complex dye include, for example, U.S. Pat. Nos. 4,927,721, 4,684,537, 5,084,365, 5,350,644, 5,463,057, 5,525,440, and JP-A-7-249790, JP-T-10- Examples thereof include dyes described in JP-A-504512, International Patent No. 98/50393, JP-A No. 2000-26487, and the like.
[0055]
Furthermore, the ruthenium complex dye is preferably a compound represented by the following general formula (6).
General formula (6)
(A¹)_tRu (Ba)_u(Bb)_v(Bc)_w
In the general formula (6), A¹Represents a mono- or bidentate ligand. A¹Is Cl, SCN, H₂It is preferably a ligand selected from the group consisting of O, Br, I, CN, NCO, SeCN, β-diketones, oxalic acid and dithiocarbamic acid derivatives. When t is 2 or more, 2 or more A¹May be the same or different. In the general formula (6), Ba, Bb, and Bc each independently represent a ligand represented by any of the following formulas (B-1) to (B-10). t represents an integer of 0 to 3, u, v and w each represents 0 or 1, and the coordination is performed so that the ruthenium complex represented by the general formula (6) is a hexacoordination complex. They are combined as appropriate according to the type of child.
[0056]
Embedded image
[0057]
In the formulas (B-1) to (B-10), R^aRepresents a hydrogen atom or a substituent. R^aAs the substituent represented by, for example, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted aralkyl group having 7 to 12 carbon atoms, or a substitution having 6 to 12 carbon atoms Alternatively, an unsubstituted aryl group or an anionic group formed by removing a proton from the above-described acidic group or acidic group can be used. R^aThe substituent represented by may be further substituted with another substituent, and examples of the other substituent include the above-mentioned acidic group or an anionic group formed by removing a proton from the acidic group. The alkyl group and the alkyl part of the aralkyl group may be linear or branched. In addition, the aryl group and the aryl part of the aralkyl group may be monocyclic or polycyclic (fused ring, ring assembly). )
[0058]
In the general formula (6), Ba, BB, and Bc may be the same or different. However, the compound represented by the general formula (6) has at least one anionic group formed by removing a proton from the acidic group or acidic group described above.
[0059]
Preferred specific examples (Exemplary Compounds R-1 to R-17) of the organometallic complex dye are shown below, but the dye used in the present invention is not limited to the following specific examples.
[0060]
Embedded image
[0061]
Embedded image
[0062]
(B) Methine dye
Examples of the methine dye include polymethine dyes such as a cyanine dye, a merocyanine dye, and a squarylium dye. The methine dye has at least one anionic group formed by removing protons from the acidic group or acidic group. Preferred examples of the methine dye include JP-A-11-35836, JP-A-11-67285, JP-A-11-86916, JP-A-11-97725, JP-A-11-158395, and JP-A-11-163378. And dyes described in JP-A-11-214730, JP-A-11-214731 and JP-A-11-238905, and European Patents 892411 and 911841.
[0063]
Preferred specific examples (Exemplary Compounds M-1 to M-8) of the methine dye are shown below, but the dye used in the present invention is not limited to the following specific examples.
[0064]
Embedded image
[0065]
Embedded image
[0066]
(D) Manufacturing method of the semiconductor for photoelectric conversions of this invention
The semiconductor for photoelectric conversion of the present invention comprises a step of bonding a basic compound and / or a cationic compound to at least the surface of the semiconductor, and an anionic property formed by removing protons from the acidic group or acidic group to the compound bonded to the surface It can be produced by a process of mordanting with a dye having a group. The bonding of the mordant linking compound to the semiconductor surface and the mordanting of the dye to the mordant linking compound bonded to the surface may be performed directly on a semiconductor substrate made of a semiconductor or on a support (especially conductive). You may carry out with the form of the semiconductor layer (preferably porous membrane) formed by apply | coating the coating liquid containing the said semiconductor fine particle on a support body. In the form of a semiconductor layer formed on the support, the mordant linking compound is bonded and the mordant linking compound bonded to the surface is mordanted with the dye of the resulting semiconductor for photoelectric conversion. The photoelectric conversion characteristics are improved and the operation is easy, which is preferable.
[0067]
Hereinafter, each step will be described.
(A) A step of bonding a mordant linking compound to a semiconductor surface
The mordanting linking compound (preferably the compound represented by the general formula (1) or (2)) is brought into contact with at least a solution containing the mordanting linking compound on the surface of the semiconductor, and is heated as desired. Can be bonded to the surface of the semiconductor. The solution can be brought into contact with the surface by, for example, a method of immersing a semiconductor in the solution or a method of applying the solution to the surface of the semiconductor. The immersion is preferably performed at room temperature for 5 hours to 5 days. Moreover, when the immersion is performed by heating the solution, the immersion is preferably performed for 1 to 24 hours. When the semiconductor is in the form of a semiconductor layer formed on a support, the support can be immersed in the solution, and the solution can be applied on the semiconductor layer. The reaction between the semiconductor and the mordant linking compound may be performed at room temperature or by heating. In order to increase the reaction amount between the semiconductor and the mordant linking compound, it is preferable to heat-treat the semiconductor before the reaction. In order to avoid water adsorbing on the surface of the semiconductor fine particles after the heat treatment, it is preferable to maintain the temperature at 40 to 80 ° C. without returning to room temperature and to react the mordanting linking compound quickly.
[0068]
The solvent used for the preparation of the solution containing the mordanting linking compound can be appropriately selected according to the solubility of the mordanting linking compound. For example, alcohols (methanol, ethanol, t-butanol, benzyl alcohol, etc.), nitriles (acetonitrile, propionitrile, 3-methoxypropionitrile, etc.), nitromethane, halogenated hydrocarbons (dichloromethane, dichloroethane, chloroform, chlorobenzene) Etc.), ethers (diethyl ether, tetrahydrofuran, etc.), dimethyl sulfoxide, amides (N, N-dimethylformamide, N, N-dimethylacetamide, etc.), N-methylpyrrolidone, 1,3-dimethylimidazolidinone , 3-methyloxazolidinone, esters (ethyl acetate, butyl acetate, etc.), carbonates (diethyl carbonate, ethylene carbonate, propylene carbonate, etc.), ketones (acetone, 2-butanone, cyclohexanone, etc.), hydrocarbons (hexyl) Sun, petroleum ether, benzene, toluene, etc.) and mixed solvents thereof. Preferred are hydrocarbons, nitriles, halogenated hydrocarbons and ethers.
[0069]
(B) Mordant process with pigment
The semiconductor to which the mordanting linking compound is bonded (including the semiconductor layer formed on the support) is immersed in the dye solution, or the dye solution is bonded to the surface of the semiconductor (the mordanting linking compound is bonded). The semiconductor can be mordanted with the dye by applying to the surface. In the former case, an immersion method, a dip method, a roller method, an air knife method, or the like can be used. In the immersion method, the dye may be adsorbed at room temperature, or may be performed by heating and refluxing as described in JP-A-7-249790. As the latter application method, a wire bar method, a slide hopper method, an extrusion method, a curtain method, a spin method, a spray method, or the like can be used.
[0070]
As the solvent used for preparing the dye solution, for example, alcohols (methanol, ethanol, t-butanol, benzyl alcohol, etc.), nitriles (acetonitrile, propionitrile, 3-methoxypropio, etc.) are preferable. Nitrile, etc.), nitromethane, halogenated hydrocarbons (dichloromethane, dichloroethane, chloroform, chlorobenzene, etc.), ethers (diethyl ether, tetrahydrofuran, etc.), dimethyl sulfoxide, amides (N, N-dimethylformamide, N, N-dimethyla) Cetamide, etc.), N-methylpyrrolidone, 1,3-dimethylimidazolidinone, 3-methyloxazolidinone, esters (ethyl acetate, butyl acetate, etc.), carbonates (diethyl carbonate, ethylene carbonate, propylene carbonate, etc.), Ton class (acetone, 2-butanone, cyclohexanone), hydrocarbons (hexane, petroleum ether, benzene, toluene, etc.) or mixed solvents thereof.
[0071]
The total amount of the dye adsorbed to the semiconductor is preferably 0.01 to 1 mmol per gram of semiconductor. When the semiconductor for photoelectric conversion of the present invention is used as a porous semiconductor layer of a photosensitive layer of a photoelectric conversion element described later, the unit area of the electrode (1 m²) Is preferably adsorbed in an amount of 0.01 to 100 mmol. When the amount of the dye adsorbed is less than the range, the sensitizing effect may be insufficient. On the other hand, when the amount of the dye adsorbed is larger than the range, the dye that is not immobilized on the surface of the semiconductor floats. In some cases, the sensitization effect may be reduced. It is preferable that the amount of the dye adsorbed be within the above range since the sensitizing effect of the dye in the semiconductor can be sufficiently obtained without causing the above problem. In addition, when mordanting a dye on the surface of a semiconductor, it is preferable to add a colorless compound to the dye and cause it to act on the semiconductor because interactions such as aggregation between the dyes can be reduced. As the colorless compound, compounds having surface active properties and structures are effective, and examples thereof include steroid compounds having a carboxyl group (for example, chenodeoxycholic acid) and sulfonates.
[0072]
The dye not immobilized on the semiconductor surface is preferably removed by washing immediately after the mordanting treatment. Cleaning is preferably performed using, for example, a wet cleaning tank and using an organic solvent such as a polar solvent such as acetonitrile or an alcohol solvent. Moreover, after mordanting with the said pigment | dye, you may process the surface of a semiconductor using amines. Preferable amines include pyridine, 4-t-butylpyridine and polyvinylpyridine. When these are liquids, they may be used as they are, or may be used after being dissolved in an organic solvent.
[0073]
The semiconductor for photoelectric conversion of this invention can be used suitably for a photoelectric conversion element.
[0074]
[Photoelectric conversion element]
An example of the photoelectric conversion element of the present invention is shown in FIG. In the photoelectric conversion element of FIG. 1, the semiconductor for photoelectric conversion of the present invention is used in the form of a porous semiconductor layer included in the photosensitive layer. The photoelectric conversion element 10 is formed by sequentially laminating a conductive layer 12, an undercoat layer 14, a photosensitive layer 16, a charge transport layer 18, and a counter electrode conductive layer 20. The photosensitive layer 16 includes a semiconductor layer 24 sensitized by the dye d and a charge transport material t. The semiconductor layer 24 is a porous layer made of semiconductor fine particles s, and voids are formed between the semiconductor fine particles s, and the charge transport material t penetrates into the voids. The charge transport material t is composed of the same components as the material used for the charge transport layer 18. A substrate 26 is disposed under the conductive layer 12, and a substrate 28 is disposed under the counter electrode conductive layer 20. The substrates 26 and 28 are for imparting strength to the photoelectric conversion element, and may not be provided. Further, at the boundary of each layer, for example, the boundary between the conductive layer 12 and the photosensitive layer 16, the boundary between the photosensitive layer 16 and the charge transport layer 18, the boundary between the charge transport layer 18 and the counter electrode conductive layer 20, etc. The constituent components may be diffusively mixed with each other. Note that light may enter the photoelectric conversion element 10 from either or both, and the light-transmitting conductive layer 12 and the substrate 26 and / or the counter electrode conductive layer 20 and the substrate 28 may transmit light. It can comprise from the material which has.
[0075]
Next, the operation of the photoelectric conversion element 10 will be described. The case where the semiconductor fine particles s are n-type will be described.
When light enters the photoelectric conversion element 10, the incident light reaches the photosensitive layer 16 and is absorbed by the dye d or the like to generate an excited dye d. The excited dye d or the like passes high-energy electrons to the conduction band of the semiconductor fine particles s and becomes an oxidant itself. The electrons transferred to the conduction band reach the conductive layer 12 through the network of semiconductor fine particles s. Therefore, the conductive layer 12 has a negative potential with respect to the counter electrode conductive layer 20. In an embodiment in which the photoelectric conversion element 10 is used for a photovoltaic cell, when the photovoltaic cell is connected to an external circuit, electrons in the conductive layer 12 reach the counter electrode conductive layer 20 while working in the external circuit. The electrons are the components of this electrolyte (eg I^-) And reduced product (for example, I_Three ^-) Reduces and restores the oxidized form of the dye d. By continuing to irradiate light, a series of reactions occur and electricity can be taken out.
[0076]
Hereinafter, materials that can be used for each layer and a method for forming the same will be described in detail. In the following, the term “conductive support” includes both the conductive layer 12 and the conductive layer 12 and an optional substrate 26, and the term “counter electrode” refers to only the counter electrode conductive layer 20. And the counter electrode conductive layer 20 and the substrate 26 optionally provided.
[0077]
(A) Conductive support
The conductive support is composed of a single layer of a conductive layer or two layers of a conductive layer and a substrate. In the former case, a material that can maintain sufficient strength and sealability is used as the conductive layer. For example, a metal material (platinum, gold, silver, copper, zinc, titanium, aluminum, or an alloy containing these) Can be used. In the latter case, a substrate having a conductive layer containing a conductive agent on the photosensitive layer side can be used. Preferred conductive agents include metals (eg, platinum, gold, silver, copper, zinc, titanium, aluminum, indium, etc., or alloys containing these), carbon or conductive metal oxides (indium-tin composite oxide, tin oxide with fluorine Or those doped with antimony). The thickness of the conductive layer is preferably about 0.02 to 10 μm.
[0078]
The conductive support preferably has a lower surface resistance. The range of the surface resistance is preferably 50Ω / □ or less, more preferably 20Ω / □ or less.
[0079]
When irradiating light from the conductive support side, the conductive support is preferably substantially transparent. Substantially transparent means that the light transmittance is 10% or more, preferably 50% or more, and particularly preferably 80% or more.
[0080]
The transparent conductive support is preferably formed by applying or vapor-depositing a transparent conductive layer made of a conductive metal oxide on the surface of a transparent substrate such as glass or plastic. A preferable transparent conductive layer is fluorine dioxide or antimony-doped tin dioxide or indium-tin oxide (ITO). As the transparent substrate, a transparent polymer film can be used in addition to a glass substrate such as soda glass which is advantageous in terms of low cost and strength, alkali-free glass which is not affected by alkali elution. Examples of the material for the transparent polymer film include tetraacetyl cellulose (TAC), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), syndiotactic polyester (SPS), polyphenylene sulfide (PPS), polycarbonate (PC), poly Examples include arylate (PAr), polysulfone (PSF), polyester sulfone (PES), polyetherimide (PEI), cyclic polyolefin, and brominated phenoxy. In order to ensure sufficient transparency, the amount of conductive metal oxide applied is 1 m of glass or plastic support.²It is preferable to be 0.01 to 100 g per unit.
[0081]
It is preferable to use a metal lead for the purpose of reducing the resistance of the conductive support. The material of the metal lead is preferably a metal such as platinum, gold, nickel, titanium, aluminum, copper, or silver. The metal lead can be installed on the substrate by vapor deposition or sputtering, and a conductive layer made of conductive tin oxide or ITO film is preferably provided thereon. The decrease in the amount of incident light due to the installation of the metal lead is preferably within 10%, more preferably 1 to 5%.
[0082]
(B) Photosensitive layer
The photosensitive layer contains the semiconductor for photoelectric conversion of the present invention. The photosensitive layer has a function of absorbing light and performing charge separation to generate electrons and holes. The photoelectric conversion semiconductor of the present invention is a dye-sensitized semiconductor, and light absorption and generation of electrons and holes thereby occur mainly in the dye, and the semiconductor plays a role of receiving and transmitting these electrons (or holes). Take on. The semiconductor used in the present invention is preferably an n-type semiconductor in which conductor electrons become carriers under photoexcitation and give an anode current.
[0083]
Since the mordanting of the semiconductor material and the sensitizing dye has been described above, a method for forming a semiconductor layer on the conductive support will be described here.
The semiconductor layer is preferably a porous layer made of semiconductor fine particles. The porous semiconductor layer can be formed by coating a coating liquid containing semiconductor fine particles on a conductive support. The coating liquid may be a dispersion liquid in which semiconductor fine particles are dispersed in a suitable dispersion medium, or a colloidal solution dissolved in a suitable solvent to form a colloid. In addition to applying the coating solution on the conductive support, it can be formed by using the sol-gel method described above. In consideration of mass production of photoelectric conversion elements, physical properties of the semiconductor fine particle dispersion, flexibility of the conductive support, and the like, a wet film forming method is relatively advantageous. Typical examples of the wet film forming method include a coating method, a printing method, an electrolytic deposition method, and an electrodeposition method. Also, a method of oxidizing metal, a method of depositing in a liquid phase from a metal solution by ligand exchange (LPD method), a method of vapor deposition by sputtering, a CVD method, or a metal that thermally decomposes on a heated substrate An SPD method in which a metal oxide is formed by spraying an oxide precursor can also be used.
[0084]
In addition to the sol-gel method, semiconductor fine particle dispersions can be prepared by grinding in a mortar, pulverizing using a mill, or dispersing as fine particles in a solvent when synthesizing a semiconductor. And a method of using it as it is.
[0085]
Examples of the solvent for the dispersion medium or colloidal solution include water or various organic solvents (for example, methanol, ethanol, isopropyl alcohol, dichloromethane, acetone, acetonitrile, ethyl acetate, etc.). When dispersing, if necessary, for example, a polymer such as polyethylene glycol, a surfactant, an acid, a chelating agent, or the like may be used as a dispersion aid. By changing the molecular weight of polyethylene glycol, the viscosity of the dispersion can be adjusted, and a semiconductor layer that is difficult to peel off can be formed and the porosity of the semiconductor layer can be controlled. Therefore, it is preferable to add polyethylene glycol.
[0086]
The application method is disclosed in Japanese Patent Publication No. 58-4589 as a roller method, a dip method, etc. as an application system, an air knife method, a blade method, etc. as a metering system, and the application and metering can be made the same part. The wire bar method, the slide hopper method, the extrusion method, the curtain method and the like described in US Pat. Nos. 2,681,294, 2,761,419, and 2,761791 are preferred. Moreover, a spin method and a spray method are also preferable as a general purpose machine. As the wet printing method, intaglio, rubber plate, screen printing and the like are preferred, including the three major printing methods of letterpress, offset and gravure. From these, a preferred film forming method is selected according to the liquid viscosity and the wet thickness.
[0087]
The semiconductor layer may be a single layer or a multilayer structure. For example, a dispersion of semiconductor fine particles having different particle diameters can be applied in multiple layers, or a coating liquid containing different types of semiconductor fine particles (or different binders and additives) can be applied in multiple layers. Multi-layer coating is also effective when the film thickness is insufficient with a single coating.
[0088]
In general, as the thickness of the semiconductor layer (same as the thickness of the photosensitive layer) increases, the amount of dye per unit projected area increases, so the light capture rate increases. However, the diffusion distance of the generated electrons increases, resulting in charge recombination. Loss also increases. Therefore, the preferable thickness of the semiconductor layer is 0.1 to 100 μm. When using the said photoelectric conversion element for a photovoltaic cell, 1-30 micrometers is preferable and, as for the thickness of a semiconductor layer, 2-25 micrometers is more preferable. Semiconductor fine particle support 1m²The applied amount per hit is preferably 0.5 to 100 g, and more preferably 3 to 50 g.
[0089]
After applying the coating liquid containing semiconductor fine particles on the conductive support, the semiconductor fine particles are brought into electronic contact with each other, and heat treatment is performed in order to improve coating film strength and adhesion to the support. It is preferable to do this. The range of preferable heating temperature is 40 ° C. or higher and 700 ° C. or lower, and more preferably 100 ° C. or higher and 600 ° C. or lower. The heating time is about 10 minutes to 10 hours. When using a support having a low melting point or softening point such as a polymer film, high temperature treatment is not preferable because it causes deterioration of the support. Moreover, it is preferable that it is as low temperature as possible (for example, 50 to 350 degreeC) also from a viewpoint of cost. The temperature can be lowered by heat treatment in the presence of small semiconductor fine particles of 5 nm or less, mineral acids, and metal oxide precursors, and irradiation with ultraviolet rays, infrared rays, microwaves, electric fields, and ultrasonic waves must be applied. Can also be performed. At the same time, for the purpose of removing unnecessary organic substances and the like, it is preferable to use a combination of heating, decompression, oxygen plasma treatment, pure water cleaning, solvent cleaning, gas cleaning and the like in addition to the above irradiation and application.
[0090]
After the heat treatment, for example, chemical plating using titanium tetrachloride aqueous solution or titanium trichloride to increase the surface area of the semiconductor fine particles, increase the purity in the vicinity of the semiconductor fine particles, and increase the efficiency of electron injection from the dye into the semiconductor fine particles. You may perform the electrochemical plating process using aqueous solution. In order to prevent a reverse current from flowing from the semiconductor fine particles to the charge transport layer, it is also effective to adsorb an organic substance having a low electron conductivity other than the dye on the particle surface. As an organic substance to adsorb | suck, the thing which has a hydrophobic group is preferable.
[0091]
The porous semiconductor layer preferably has a large surface area so that a large amount of dye can be adsorbed. The surface area of the semiconductor layer is preferably 10 times or more with respect to the projected area, and more preferably 100 times or more. This upper limit is not particularly limited, but is usually about 1000 times.
[0092]
The thus formed semiconductor layer is bonded to at least the surface of the mordant linking compound by the above-described method, and then the dye is allowed to act on the mordanting linking compound by the above-described method to sensitize and dye the dye. A semiconductor layer can be formed.
[0093]
(C) Charge transport layer
The charge transport layer is a layer containing a charge transport material having a function of replenishing electrons to an oxidant of a dye produced by absorbing light. As an example of a typical charge transport material that can be used in the present invention, as an ion transport material, a solution (electrolytic solution) in which redox pair ions are dissolved, and a polymer matrix gel are impregnated with a redox pair solution. Examples include so-called gel electrolytes, molten salt electrolytes containing redox counterions, and solid electrolytes. In addition to a charge transport material that involves ions, an electron transport material or a hole transport material can also be used as a charge transport material that involves carrier movement in a solid. These charge transport materials can be used in combination.
[0094]
It is particularly preferable to use the molten salt electrolyte as the charge transport material because both photoelectric conversion efficiency and durability can be achieved. The molten salt electrolyte is a liquid electrolyte at room temperature or an electrolyte having a low melting point. For example, WO95 / 18456, JP-A-8-259543, Electrochemistry, Vol. 65, No. 11, page 923 (1997). And the like, known electrolytes such as pyridinium salts, imidazolium salts, and triazolium salts. A molten salt electrolyte that is liquid at 100 ° C. or lower, particularly near room temperature, is preferred.
[0095]
Examples of the molten salt electrolyte that can be preferably used include compounds represented by any one of the following general formulas (Ya), (Yb), and (Yc).
[0096]
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[0097]
In the general formula (Ya), Q_y1Represents an atomic group capable of forming a 5- or 6-membered aromatic cation with a nitrogen atom. Q_y1Is preferably composed of at least one atom selected from the group consisting of carbon atom, hydrogen atom, nitrogen atom, oxygen atom and sulfur atom. Q_y1The five-membered ring formed by is preferably an oxazole ring, thiazole ring, imidazole ring, pyrazole ring, isoxazole ring, thiadiazole ring, oxadiazole ring, triazole ring, indole ring or pyrrole ring, A thiazole ring or an imidazole ring is more preferable, and an oxazole ring or an imidazole ring is particularly preferable. Q_y1The 6-membered ring formed by is preferably a pyridine ring, pyrimidine ring, pyridazine ring, pyrazine ring or triazine ring, more preferably a pyridine ring.
[0098]
In the general formula (Yb), A_y1Represents a nitrogen atom or a phosphorus atom.
[0099]
In the general formulas (Ya), (Yb) and (Yc), R_y1~ R_y6Each independently represents a substituted or unsubstituted alkyl group (preferably having 1 to 24 carbon atoms, which may be linear or branched or cyclic, such as methyl group, ethyl Group, propyl group, isopropyl group, pentyl group, hexyl group, octyl group, 2-ethylhexyl group, t-octyl group, decyl group, dodecyl group, tetradecyl group, 2-hexyldecyl group, octadecyl group, cyclohexyl group, cyclopentyl group Or a substituted or unsubstituted alkenyl group (preferably having 2 to 24 carbon atoms, which may be linear or branched, such as a vinyl group or an allyl group), more preferably An alkyl group having 2 to 18 carbon atoms or an alkenyl group having 2 to 18 carbon atoms is preferable, and an alkyl group having 2 to 6 carbon atoms is particularly preferable.
[0100]
In the general formula (Yb), R_y1~ R_y4Two or more of them are connected to each other_y1May form a non-aromatic ring containing R in the general formula (Yc)_y1~ R_y6Two or more of them may be connected to each other to form a ring structure.
[0101]
In the general formulas (Ya), (Yb) and (Yc), Q_y1And R_y1~ R_y6May have a substituent, and preferable examples of the substituent include a halogen atom (F, Cl, Br, I, etc.), a cyano group, an alkoxy group (methoxy group, ethoxy group, methoxyethoxy group, methoxyethoxy group). Ethoxy groups, etc.), aryloxy groups (phenoxy groups, etc.), alkylthio groups (methylthio groups, ethylthio groups, etc.), alkoxycarbonyl groups (ethoxycarbonyl groups, etc.), carbonate groups (ethoxycarbonyloxy groups, etc.), acyl groups (acetyl groups) , Propionyl group, benzoyl group etc.), sulfonyl group (methanesulfonyl group, benzenesulfonyl group etc.), acyloxy group (acetoxy group, benzoyloxy group etc.), sulfonyloxy group (methanesulfonyloxy group, toluenesulfonyloxy group etc.), Phosphonyl group (diethylphosphonyl group, etc.), amino Groups (acetylamino group, benzoylamino group, etc.), carbamoyl groups (N, N-dimethylcarbamoyl group, etc.), alkyl groups (methyl group, ethyl group, propyl group, isopropyl group, cyclopropyl group, butyl group, 2-carboxy group) Ethyl group, benzyl group etc.), aryl group (phenyl group, toluyl group etc.), heterocyclic group (pyridyl group, imidazolyl group, furanyl group etc.), alkenyl group (vinyl group, 1-propenyl group etc.), silyl group and A silyloxy group etc. are mentioned.
[0102]
The compound represented by the general formula (Ya), (Yb) or (Yc) is Q_y1Or R_y1~ R_y6A multimer may be formed via
[0103]
The compound represented by the general formula (Ya), (Yb) or (Yc) may be used alone or in combination of two or more as a charge transport material. Also, it can be used in combination with a molten salt in which the iodine anion is replaced with another anion. Anions that replace iodine anions include halide ions (Cl^-, Br^-Etc.), SCN^-, BF_Four ^-, PF₆ ^-, ClO_Four ^-, (CF_ThreeSO₂)₂N^-, (CF_ThreeCF₂SO₂)₂N^-, CH_ThreeSO_Three ^-, CF_ThreeSO_Three ^-, CF_ThreeCOO^-, Ph_FourB^-, (CF_ThreeSO₂)_ThreeC^-Etc. are mentioned as preferred examples, and SCN^-, CF_ThreeSO_Three ^-, CF_ThreeCOO^-, (CF_ThreeSO₂)₂N^-Or BF_Four ^-It is more preferable that In addition, other iodine salts such as LiI and CF_ThreeCOOLi, CF_ThreeAlkali metal salts such as COONa, LiSCN, and NaSCN can also be added. The addition amount of the alkali metal salt is preferably about 0.02 to 2% by mass, and more preferably 0.1 to 1% by mass.
[0104]
Specific examples of the molten salt preferably used as the charge transport material in the present invention are listed below, but are not limited thereto.
[0105]
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[0106]
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[0107]
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[0108]
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[0109]
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[0110]
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[0111]
The molten salt electrolyte is preferably in a molten state at room temperature, and preferably does not use a solvent. Although the solvent described later may be added, the content of the molten salt is preferably 50% by mass or more, and particularly preferably 90% by mass or more with respect to the entire electrolyte composition. Moreover, it is preferable that 50 mass% or more of a salt is an iodine salt.
[0112]
It is preferable to add iodine to the electrolyte composition. In this case, the content of iodine is preferably 0.1 to 20% by mass, and 0.5 to 5% by mass with respect to the entire electrolyte composition. It is more preferable that
[0113]
When an electrolytic solution is used as the charge transport material, the electrolytic solution is preferably composed of an electrolyte, a solvent, and an additive. The electrolyte is I₂And iodide (LiI, NaI, KI, CsI, CaI as iodides)₂Metal iodides such as tetraalkylammonium iodide, pyridinium iodide, imidazolium iodide and the like quaternary ammonium compounds such as iodine salts), Br₂And bromide combinations (LiBr, NaBr, KBr, CsBr, CaBr as bromides)₂In addition to metal bromides such as tetraalkylammonium bromide and pyridinium bromide bromides, etc.), metal complexes such as ferrocyanate-ferricyanate and ferrocene-ferricinium ions, sodium polysulfide, Sulfur compounds such as alkylthiol-alkyldisulfides, viologen dyes, hydroquinone-quinones, and the like can be used. I among them₂An electrolyte that combines an iodine salt of a quaternary ammonium compound such as LiI, pyridinium iodide, and imidazolium iodide is preferable. The electrolytes described above may be used in combination.
[0114]
The electrolyte concentration in the electrolytic solution is preferably 0.1 M (mol / L) or more and 10 M (mol / L) or less, and preferably 0.2 M (mol / L) or more and 4 M (mol / L) or less. More preferred. Moreover, the preferable addition density | concentration of an iodine in the case of adding an iodine to electrolyte solution is 0.01 M (mol / L) or more and 0.5 M (mol / L) or less.
[0115]
The solvent used in the electrolytic solution is desirably a compound having a low viscosity and improving ion mobility, or having a high dielectric constant and an effective carrier concentration, thereby exhibiting excellent ion conductivity. Examples of such a solvent include carbonate compounds such as ethylene carbonate and propylene carbonate, heterocyclic compounds such as 3-methyl-2-oxazolidinone, ether compounds such as dioxane and diethyl ether, ethylene glycol dialkyl ether, propylene glycol dialkyl ether, and polyethylene. Chain ethers such as glycol dialkyl ether and polypropylene glycol dialkyl ether, alcohols such as methanol, ethanol, ethylene glycol monoalkyl ether, propylene glycol monoalkyl ether, polyethylene glycol monoalkyl ether, polypropylene glycol monoalkyl ether, ethylene glycol, Propylene glycol, polyethylene glycol, polyp Examples include polyhydric alcohols such as pyrene glycol and glycerol, nitrile compounds such as acetonitrile, glutarodinitrile, methoxyacetonitrile, propionitrile, and benzonitrile, aprotic polar substances such as dimethyl sulfoxide and sulfolane, and water. Can also be used in combination.
[0116]
In the present invention, J. Org. Am. Ceram. Soc. , 80 (12) 3157-3171 (1997), basic compounds such as tert-butylpyridine, 2-picoline, and 2,6-lutidine are added to the aforementioned molten salt electrolyte and electrolyte. It is preferable. A preferable concentration range when adding a basic compound is 0.05 M (mol / L) or more and 2 M (mol / L) or less.
[0117]
The gel electrolyte that can be used as the charge transporting material is gelled (solid) by using the above-described molten salt electrolyte or electrolytic solution by polymer addition, oil gelling agent addition, polymerization including polyfunctional monomers, polymer crosslinking reaction, or the like. Can be produced. In the case of gelation by polymer addition, compounds described in “Polymer Electrolyte Revues-1 and 2” (JR MacCallum and CA Vincent co-edit, ELSEVIER APPLIED SCIENCE) can be used. In particular, polyacrylonitrile and polyvinylidene fluoride can be preferably used. In the case of gelation by adding an oil gelling agent, J. Org. Chem Soc. Japan, Ind. Chem. Sec. 46, 779 (1943); Am. Chem. Soc. 111, 5542 (1989), J. Am. Chem. Soc. Chem. Com mun. , 1993, 390, Angew. Chem. Int. Ed. Engl. , 35, 1949 (1996), Chem. Lett. , 1996, 885, J. et al. Chm. Soc. Chem. Commun. , 1997, 545 can be used, but preferred compounds are those having an amide structure in the molecular structure. An example of gelling the electrolytic solution is described in JP-A-11-185863, and an example of gelling the molten salt electrolyte is described in JP-A-2000-58140, which can also be applied to the present invention.
[0118]
Further, when the electrolyte is gelled by a polymer crosslinking reaction, it is desirable to use a polymer containing a crosslinkable reactive group and a crosslinking agent in combination. In this case, preferred crosslinkable reactive groups are amino groups and nitrogen-containing heterocycles (eg, pyridine ring, imidazole ring, thiazole ring, oxazole ring, triazole ring, morpholine ring, piperidine ring, piperazine ring, etc.) Preferred cross-linking agents are bifunctional or higher reagents capable of electrophilic reaction with nitrogen atoms (for example, alkyl halides, halogenated aralkyls, sulfonic acid esters, acid anhydrides, acid chlorides, isocyanates, α, β-unsaturated). A sulfonyl group, an α, β-unsaturated carbonyl group, an α, β-unsaturated nitrile group, etc.), and the crosslinking techniques described in JP-A Nos. 2000-17076 and 2000-86724 are also applicable.
[0119]
As the charge transport material, in the present invention, instead of an ion conductive electrolyte such as a molten salt, a solid hole transport material that is organic or inorganic or a combination of both can be used. Examples of the organic hole transport material include J.I. Hagen et al. , Synthetic Metal 89 (1997) 215-220, Nature, Vol. 395, 8 Oct. 1998, p 583-585 and WO 97/10617, JP 59-194393, JP 5-234681, U.S. Pat. No. 4,923,774, JP 4-308688, U.S. Pat. 764,625, JP-A-3-269084, JP-A-4-129271, JP-A-4-175395, JP-A-4-264189, JP-A-4-290851, JP-A-4-364153. No. 5, JP-A-5-25473, JP-A-5-239455, JP-A-5-320634, JP-A-6-1972, JP-A-7-138562, JP-A-7-252474. Aromatic amines disclosed in JP-A-11-144773, etc., JP-A-11-149821, JP-A-11 No. 148,067, can be preferably used a triphenylene derivatives described in JP-like of JP-A-11-176489. Also, Adv. Mater. 1997, 9, N0.7, p557, Angew. Chem. Int. Ed. Engl. 1995, 34, no. 3, p303-307, JACS, Vol120, N0.4, 1998, p664-672, and the like. Murakoshi et al. Chem. Lett. 1997, p471, polyacetylene and its derivatives described in “Handbook of Organic Conductives and Polymers Vol. 1, 2, 3, 4” (by NALWA, published by WILEY), poly (p-phenylene) and Conductive polymers such as derivatives thereof, poly (p-phenylene vinylene) and derivatives thereof, polythienylene vinylene and derivatives thereof, polythiophene and derivatives thereof, polyaniline and derivatives thereof, polytoluidine and derivatives thereof can be preferably used. .
[0120]
For hole transport materials, see Nature, Vol. 395, 8 Oct. As described in 1998, p583-585, a compound containing a cation radical such as tris (4-bromophenyl) aminium hexachloroantimonate is added to control the dopant level. In order to perform potential control (space charge layer compensation), Li [(CF_ThreeSO₂)₂N] may be added.
[0121]
A p-type inorganic compound semiconductor can be used as the inorganic hole transport material. The p-type inorganic compound semiconductor for this purpose preferably has a band gap of 2 eV or more, and more preferably 2.5 eV or more. Also, the ionization potential of the p-type inorganic compound semiconductor needs to be smaller than the ionization potential of the dye-adsorbing electrode from the condition that the holes of the dye can be reduced. Although the preferable range of the ionization potential of the p-type inorganic compound semiconductor varies depending on the dye used, it is generally preferably 4.5 eV or more and 5.5 eV or less, and more preferably 4.7 eV or more and 5.3 eV or less. . A preferred p-type inorganic compound semiconductor is a compound semiconductor containing monovalent copper. Examples of the compound semiconductor containing monovalent copper include CuI, CuSCN, and CuInSe.₂, Cu (In, Ga) Se₂, CuGaSe₂, Cu₂O, CuS, CuGaS₂, CuInS₂, CuAlSe₂Etc. Among these, CuI and CuSCN are preferable, and CuI is most preferable. Other p-type inorganic compound semiconductors include GaP, NiO, CoO, FeO, and Bi.₂O_Three, MoO₂, Cr₂O_ThreeEtc. can be used.
[0122]
In the photoelectric conversion element of the present invention, the charge transport material can be permeated into the voids of the semiconductor layer simultaneously with the formation of the charge transport layer. The charge transport layer can be formed, for example, by sandwiching a counter electrode on the photosensitive layer and injecting a liquid charge transport material into the gap. As another forming method, there is a method in which a charge transport material is formed directly on the photosensitive layer by coating or the like (the counter electrode is applied thereafter). In the former method, the charge transport material is sandwiched between the photosensitive layer and the counter electrode by a normal pressure process utilizing capillary action due to immersion or the like, or the gas phase in the gap is replaced with a liquid phase at a pressure lower than normal pressure. A vacuum process is available. In the latter method, when a liquid charge transport material is used, a counter electrode can be provided without being dried and a liquid leakage preventing measure for the edge portion can be taken. In the case where a gel electrolyte is used as the charge transport material, there is a method in which the gel electrolyte is applied in a wet manner and solidified by a method such as polymerization. In that case, a counter electrode can be provided after drying and solidification. As a method for applying a wet organic hole transporting material or a gel electrolyte in addition to the electrolytic solution, the same methods as described in the above-described formation of the semiconductor layer and dye mordanting can be used.
[0123]
In the case of a solid electrolyte or a solid hole transport material, a charge transport layer can be formed by a dry film forming process such as a vacuum deposition method or a CVD method, and then a counter electrode can be provided. The organic hole transport material can be introduced into the electrode by techniques such as vacuum deposition, casting, coating, spin coating, dipping, electrolytic polymerization, and photoelectrolytic polymerization. Also in the case of an inorganic solid compound, it can be introduced into the electrode by techniques such as casting, coating, spin coating, dipping, electrolytic deposition, and electroless plating.
[0124]
(D) Counter electrode
Similar to the conductive support, the counter electrode may have a single-layer structure made of a conductive material, or may be composed of a counter electrode conductive layer and a support substrate. As the conductive material used for the counter electrode conductive layer, metal (for example, platinum, gold, silver, copper, aluminum, magnesium, indium, etc.), carbon, or conductive metal oxide (indium-tin composite oxide, fluorine-doped tin oxide, etc.) ). Among these, platinum, gold, silver, copper, aluminum, and magnesium can be preferably used as the counter electrode layer. An example of a preferable supporting substrate for the counter electrode is glass or plastic, and the above-described conductive agent is applied or vapor-deposited on the glass or plastic. The thickness of the counter electrode conductive layer is not particularly limited, but is preferably 3 nm to 10 μm. The lower the surface resistance of the counter electrode layer, the better. The range of the surface resistance is preferably 50Ω / □ or less, and more preferably 20Ω / □ or less.
[0125]
In order for light to be incident from one or both of the conductive support and the counter electrode and to reach the photosensitive layer, at least one of the conductive support and the counter electrode may be substantially transparent. . From the viewpoint of improving the power generation efficiency, it is preferable that the conductive support is transparent and light is incident from the conductive support side. In this case, the counter electrode preferably has a property of reflecting light. As the counter electrode, glass or plastic on which a metal or conductive oxide is deposited, or a metal thin film can be used.
[0126]
The counter electrode may be formed by directly applying, plating, or vapor-depositing (PVD, CVD) a conductive material on the charge transport layer, or attaching the conductive layer side of the substrate having the conductive layer. As in the case of the conductive support, it is preferable to use a metal lead for the purpose of reducing the resistance of the counter electrode, particularly when the counter electrode is transparent. In addition, the preferable material and installation method of the metal lead, the decrease in the amount of incident light due to the metal lead installation, and the like are the same as in the case of the conductive support.
[0127]
(E) Other layers
In order to prevent a short circuit between the counter electrode and the conductive support, a dense semiconductor thin film layer is preferably provided as an undercoat layer between the conductive support and the photosensitive layer in advance. This is particularly effective when an electron transport material or a hole transport material is used for the transport layer. The material for the undercoat layer is preferably TiO.₂, SnO₂, Fe₂O_Three, WO_Three, ZnO, Nb₂O_FiveAnd a more preferred material is TiO₂It is. The undercoat layer may be, for example, Electrochimi. In addition to the spray pyrolysis method described in Acta 40, 643-352 (1995), it can be applied by sputtering or the like. The undercoat layer preferably has a thickness of 5 to 1000 nm, more preferably 10 to 500 nm.
[0128]
In addition, a functional layer such as a protective layer or an antireflection layer may be provided on the conductive support that acts as the electrode and on one or both outer surfaces of the counter electrode, between the conductive layer and the substrate, or in the middle of the substrate. . For forming these functional layers, a coating method, a vapor deposition method, a bonding method, or the like can be used depending on the material.
[0129]
As described above, the internal structure of the photoelectric conversion element of the present invention can have various forms depending on the purpose. If divided roughly into two, there are a structure in which light can be incident from both surfaces and a structure in which light can be incident from only one surface. 2 to 9 illustrate the internal structure of a photoelectric conversion element that can be preferably applied to the present invention. 2 to 9, the same members as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted. When the conductive layer 12 and the substrate 26 are light transmissive, the conductive layer 12 ′ and the substrate 26 ′ are used, respectively. When the counter electrode conductive layer 20 and the substrate 28 are light transmissive, the conductive layer 12 ′ and the substrate 28 are used. 'And.
[0130]
In the photoelectric conversion element 10a of FIG. 2, the photosensitive layer 16 and the charge transport layer 18 are interposed between the transparent conductive layer 12 ′ and the transparent counter electrode conductive layer 20 ′, and light enters from both sides. It has a structure.
The photoelectric conversion element 10b of FIG. 3 is provided with a metal lead 30 on a transparent substrate 26 ′, a transparent conductive layer 12 ′, and an undercoat layer 14, a photosensitive layer 16, a charge transport layer 18, and a counter electrode conductive layer 20. In this order, a support substrate 28 is further disposed, and light is incident from the transparent conductive layer 12 ′ side.
4 includes a conductive layer 12, an undercoat layer 14, a photosensitive layer 16, a charge transport layer 18 and a transparent counter electrode conductive layer 20 ′ on a support substrate 26, and a metal lead 30 provided in part. The transparent substrate 28 ′ is arranged with the metal lead 30 side inward, and has a structure in which light is incident from the counter electrode conductive layer 20 ′ side.
[0131]
The photoelectric conversion element 10d in FIG. 5 is provided with a part of the metal lead 30 on the transparent substrate 26 ′, further provided with the transparent conductive layer 12 ′, the undercoat layer 14, the photosensitive layer 16, the charge transport layer 18, and the transparent counter electrode conductive layer 20. 'Is provided in this order, and a transparent substrate 28' provided with a part of the metal leads 30 is provided thereon, and light is incident from both sides.
The photoelectric conversion element 10e of FIG. 6 includes a transparent conductive layer 12 ′, an undercoat layer 14, a photosensitive layer 16, a charge transport layer 18, and a counter electrode conductive layer 20 on a transparent substrate 26 ′, and a support substrate 28 disposed thereon. In this structure, light is incident from the conductive layer 12 ′ side.
7 includes a conductive layer 12, an undercoat layer 14, a photosensitive layer 16, a charge transport layer 18, and a transparent counter electrode conductive layer 20 ′ on a support substrate 26, and a transparent substrate 28 ′ disposed thereon. In this structure, light is incident from the counter conductive layer 20 ′ side.
[0132]
8 includes a transparent conductive layer 12 ′, an undercoat layer 14, a photosensitive layer 16, a charge transport layer 18, and a transparent counter electrode conductive layer 20 ′ on a transparent substrate 26 ′, and further a transparent substrate on the transparent substrate 26 ′. 28 'is arranged, and light is incident from both sides.
In the photoelectric conversion element 10h of FIG. 9, the conductive layer 12 is provided on the support substrate 26, the undercoat layer 14, the photosensitive layer 16, and the solid charge transport layer 18 ′ are provided, and a part of the counter conductive layer 20 ′ is provided thereon. '(Or metal lead 30), and has a structure in which light enters from the counter electrode 20' 'side.
[0133]
The photoelectric conversion element of the present invention can be applied to a photovoltaic cell and an optical sensor. When applied to a photovoltaic cell and an optical sensor, the structure is the same as that of the photoelectric conversion element described above. A photocell is manufactured for the purpose of generating electrical work by connecting to an external load (power generation), and a photosensor is manufactured for the purpose of sensing optical information.
[0134]
(Photo battery)
The photovoltaic cell of the present invention uses the photoelectric conversion element of the present invention and is configured to cause the photoelectric conversion element to work with an external load. Among the photovoltaic cells, the case where the charge transport material is mainly composed of an ion transport material is particularly called a photoelectrochemical cell, and the case where the main purpose is power generation by sunlight is called a solar cell. In order to prevent deterioration of components and volatilization of the contents of the photovoltaic cell, it is preferable to seal the side surface with a polymer or an adhesive. A known circuit can be used as the external circuit itself connected to the conductive support and the counter electrode via leads.
[0135]
When the photoelectric conversion element of the present invention is applied to a solar cell, the structure inside the cell is basically the same as the structure of the photoelectric conversion element described above. In addition, the solar cell of the present invention can basically have the same module structure as a conventional solar cell module. The solar cell module generally has a structure in which cells are provided on a support substrate such as metal or ceramic, the cell is covered with a filling resin or protective glass, and light is taken in from the opposite side of the support substrate. . A transparent material such as tempered glass may be used for the support substrate, and a cell may be formed thereon to take light from the transparent support substrate side. Specifically, a module structure called a super straight type, a substrate type, a potting type, a substrate integrated module structure used in an amorphous silicon solar cell, and the like are known. Depending on the environment, these module structures can be selected as appropriate. Specifically, it is preferable to adopt the structure and aspect described in the specification of Japanese Patent Application No. 11-8457.
[0136]
【Example】
Hereinafter, the present invention will be described in more detail with reference to specific examples, but the present invention is not limited thereto.
[Example 1]
(A) TiO₂Preparation of dispersion
In a 200 ml stainless steel container with an inner volume of Teflon coating, titanium dioxide fine particles (Nippon Aerosil Co., Ltd., Degussa P-25) 15 g, water 45 g, dispersant (Aldrich Triton X-100) 1 g, diameter 30 g of 0.5 mm zirconia beads (manufactured by Nikkato Co., Ltd.) was added, and dispersion treatment was performed at 1500 rpm for 2 hours using a sand grinder mill (manufactured by Imex). Zirconia beads were removed from the obtained dispersion by filtration. The average particle diameter of the titanium dioxide fine particles in the obtained dispersion was 2.5 μm. The particle size was measured with a master sizer manufactured by MALVERN.
[0137]
(B) TiO₂Electrode fabrication
A glass rod is placed on the conductive surface side of a conductive glass having a tin oxide layer doped with fluorine (TCO glass-U manufactured by Asahi Glass Co., Ltd. cut into a size of 20 mm × 20 mm, surface resistance of about 30Ω / □). Used to apply the dispersion. The coating amount of semiconductor fine particles is 20 g / m²It was. At that time, adhesive tape was applied to a part of the conductive surface side (3 mm from the end) to form a spacer, and glass was arranged so that the adhesive tape came to both ends, and eight sheets were applied at a time. After application, the adhesive tape was peeled off and air-dried at room temperature for 1 day. Next, this glass is put into an electric furnace (Yamato Scientific Co., Ltd. muffle furnace FP-32 type), baked at 450 ° C. for 30 minutes, allowed to cool, and TiO 2.₂An electrode was obtained.
[0138]
(C) Mordant with pigment
The electrode prepared in (B) was immersed in a 10% toluene solution of the mordant linking compound (Exemplary Compound 2-1) for 3 days, washed with toluene, and dried under reduced pressure. Next, this electrode was combined with an ethanol solution of dye (Exemplary Compound R-1) (3 × 10^-FourAfter being immersed in 3 mol / l) for 3 hours, it was washed with ethanol and dried naturally.
[0139]
(D) Production of photovoltaic cell
Dye-sensitized TiO prepared as described above₂An electrode substrate and a comparative electrode substrate (20 mm × 20 mm) were overlaid with platinum-deposited glass having the same size. Next, the electrolyte composition is soaked into the gap between the two glasses by utilizing capillary action, and the electrolyte is made of TiO 2.₂A photoelectric conversion element having the same configuration as that shown in FIG. That is, a conductive support layer made of conductive glass (with a conductive layer 12 'formed on a transparent glass substrate 26'), dye-sensitized TiO₂The photosensitive layer 16, the charge transport layer 18, the counter electrode conductive layer 20 made of platinum, and the transparent substrate 28 ′ made of glass were laminated in this order, and then sealed with an epoxy sealant to produce a photovoltaic cell.
[0140]
[Examples 2 to 8]
A photovoltaic cell was produced in the same manner as in Example 1 except that the mordant linking compound, the dye, and the electrolyte composition (charge transporting material) were changed to the materials shown in Table 1 below. However, when the viscosity of the electrolyte composition is high and it is difficult to impregnate the electrolyte composition using capillary action, the electrolyte composition is heated to 50 ° C.₂After coating on the electrode, this electrode was placed under reduced pressure, and after the electrolyte composition sufficiently permeated and the air in the electrode escaped, platinum-deposited glass (counter electrode) was overlaid to similarly produce photovoltaic cells.
[0141]
[Comparative Examples 1 and 2]
In the step (C) of Example 1, a mordant linking compound was not used and TiO was used.₂The conductive electrode is an ethanol solution of a dye (Exemplary Compound R-1) (3 × 10^-FourIn the same manner as in Example 1, except that the sample was immersed in (mol / l) for 3 hours, washed with ethanol, and naturally dried, photovoltaic cells were produced using the materials shown in Table 1.
[0142]
The photoelectric conversion efficiencies of the obtained photovoltaic cells of Examples 1 to 8 and Comparative Examples 1 and 2 were measured. Specifically, first, light from a 500 W xenon lamp (manufactured by USHIO ELECTRIC CO., LTD.) Is passed through an AM1.5 filter (manufactured by Oriel) and a sharp cut filter (Kenko L-42) so that no ultraviolet rays are included. Simulated sunlight was generated. The intensity of this light is 100 mW / cm²Met. Each simulated photovoltaic cell was irradiated with this simulated sunlight at 25 ° C., and the generated electricity was measured with a current-voltage measuring device (Keutley SMU238 type). The open circuit voltage (Voc) of each photovoltaic cell thus obtained is shown in Table 1 below.
[0143]
[Table 1]
[0144]
From the results shown in Table 1, the open-circuit voltage of the photovoltaic cell of the example was higher than that of the comparative example in both cases where a material containing a solvent was used as the charge transport material and when a material containing no solvent was used. I understand that it is expensive.
[0145]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to provide a photoelectric conversion semiconductor exhibiting a high open circuit voltage, and a photoelectric conversion element and a photovoltaic cell excellent in photoelectric conversion characteristics.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional view showing the structure of a preferred photoelectric conversion element of the present invention.
FIG. 2 is a partial cross-sectional view showing the structure of a preferred photoelectric conversion element of the present invention.
FIG. 3 is a partial cross-sectional view showing the structure of a preferred photoelectric conversion element of the present invention.
FIG. 4 is a partial cross-sectional view showing the structure of a preferred photoelectric conversion element of the present invention.
FIG. 5 is a partial cross-sectional view showing the structure of a preferred photoelectric conversion element of the present invention.
FIG. 6 is a partial cross-sectional view showing the structure of a preferred photoelectric conversion element of the present invention.
FIG. 7 is a partial cross-sectional view showing the structure of a preferred photoelectric conversion element of the present invention.
FIG. 8 is a partial cross-sectional view showing the structure of a preferred photoelectric conversion element of the present invention.
FIG. 9 is a partial cross-sectional view showing a structure of a preferable photoelectric conversion element of the present invention.
[Explanation of symbols]
10, 10a to 10h ... photoelectric conversion element
12 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Conductive layer
12 '... Transparent conductive layer
14 ..... Undercoat layer
16 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Photosensitive layer
18 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Charge transport layer
18 '..... charge transport layer made of solid
20 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Counter conductive layer
20 '... transparent conductive layer
20 ″ ······················
24 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Semiconductor layer
26 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Board
26 '............ Transparent substrate
28 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Board
28 '... Transparent substrate
30 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Metal lead
s ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Semiconductor fine particles
d ... Dye
t ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Charge transport material

Claims (6)

A compound selected from the following compounds 1-1 to 1-8 and 2-1 to 2-11 is bonded to at least the surface of the semiconductor, and the compound bonded to the surface is converted from the following dye compounds R-1 to R-13. A semiconductor for photoelectric conversion, which is formed by immersing in a selected solution or applying the solution to a compound bonded to the surface and mordanting.
The semiconductor for photoelectric conversion according to claim 1, wherein the semiconductor contains at least a metal chalcogenide. The semiconductor is composed of semiconductor fine particles formed on the support porous semiconductor film photoelectric conversion semiconductor according to claim 1 or 2. A photoelectric conversion element comprising a photosensitive layer and a charge transport layer between a pair of electrodes, wherein the photosensitive layer includes the semiconductor for photoelectric conversion according to any one of claims 1 to 3 . A photovoltaic cell comprising the photoelectric conversion element according to claim 4 . The step of bonding one selected from the following compounds 1-1 to 1-8 and 2-1 to 2-11 to at least the surface of the semiconductor, and the compounds bonded to the surface are the following dye compounds R-1 to R-13 Dipping in a kind of solution selected from or applying the solution to a compound bonded to the surface and mordanting, a method for producing a semiconductor for photoelectric conversion.