WO2012060280A1 - Metal oxide semiconductor particle dispersion - Google Patents

Abstract

Disclosed are: a metal oxide semiconductor particle dispersion containing an amine compound, an organic titanate having an alkoxy group and/or a diketonate group, titanium oxide particles, and a solvent; a metal oxide semiconductor electrode including an electroconductive base material and a film formed on the electroconductive base material by using said metal oxide semiconductor particle dispersion; and a photoelectric conversion element including said metal oxide semiconductor electrode, a sensitizing dye, an electrolyte, and an electroconductive opposing electrode.

Description

Metal oxide semiconductor particle dispersion

The present invention relates to a metal oxide semiconductor particle dispersion suitably used for producing a photoelectric conversion element, a metal oxide semiconductor electrode using the same, and a photoelectric conversion element.

In solar power generation, single crystal silicon solar cells, polycrystalline silicon solar cells, amorphous silicon solar cells, and compound solar cells such as cadmium telluride and indium copper selenide have been put into practical use or are subject to research and development. Therefore, it is necessary to overcome problems such as manufacturing cost, securing raw materials, and long energy payback time. On the other hand, many solar cells using organic materials aimed at increasing the area and price have been proposed so far, but have the problems of low conversion efficiency and poor durability.

Under such circumstances, a photoelectric conversion electrode and a photoelectric conversion cell using a semiconductor microporous body sensitized with a dye, and a material and a manufacturing technique for producing the photoelectric conversion electrode have been disclosed (Patent Document 1 and Non-Patent Document). Reference 1). The proposed battery is a dye-sensitized photoelectric conversion cell comprising a titanium oxide porous layer spectrally sensitized with a sensitizing dye such as a ruthenium complex as a working electrode, an electrolyte mainly composed of iodine, and a counter electrode. . The first advantage of this method is that an inexpensive photoelectric conversion element can be provided because an inexpensive oxide semiconductor such as titanium oxide is used. The second advantage is that the ruthenium complex used is widely used in the visible light range. Since it has absorption, a relatively high conversion efficiency is obtained.

In order to produce a dye-sensitized photoelectric conversion cell having high conversion efficiency, a method of using a titanium oxide sol by hydrothermal synthesis for the titanium oxide porous layer is often used, but this has many manufacturing problems. . The production method by hydrothermal synthesis requires a high temperature and high pressure condition near 200 ° C in an aqueous solvent using an autoclave, so there are problems in mass production, reproducibility of quality, safety during production, cost, etc. have. Further, since the titanium oxide content ratio to the aqueous solvent in the autoclave is not a low concentration of less than 10%, fine particles are not formed, and a concentration step is also required for use as a paste. Moreover, even if concentration is performed, the titanium oxide content ratio remains around 20% in order to maintain the film forming viscosity, and it is necessary to perform printing a plurality of times in order to obtain a photoelectric conversion electrode with good performance. Etc., productivity was reduced.

In order to overcome such problems, a technique of mixing titanium oxide fine particles and a titanium oxide precursor (Patent Document 2) and a technique of treating titanium dioxide and polyvinyl butyral resin with two rolls (Patent Document 3) have been proposed. ing. However, since the dispersed particles are not miniaturized and the photoelectric conversion characteristics are inferior as compared with the above-described hydrothermal synthesis method, it has been difficult to provide a photoelectric conversion electrode with good performance at low cost. Furthermore, a technique of adding a metal atom complex alone to disperse titanium oxide particles has been proposed, but further improvement has been desired (Patent Document 4).

US Pat. No. 4,927,721 JP 2002-75477 A JP 2007-115602 A JP 2005-203360 A

An object of the present invention is to improve the performance of a metal oxide semiconductor electrode produced from a relatively inexpensive material. Furthermore, it is to provide a high-performance photoelectric conversion element at low cost by using the same electrode. The problem to be solved by the present invention is to provide a dispersion having a low viscosity even at a high titanium oxide concentration by improving the dispersibility of titanium oxide. Furthermore, it is to provide an electrode and a photoelectric conversion element having high photoelectric conversion efficiency using the dispersion.

The present invention relates to a metal oxide semiconductor particle dispersion comprising an amine compound, an organic titanate having at least one of an alkoxy group and a diketonate group, and a solvent.
The present invention also relates to a metal oxide semiconductor electrode comprising a conductive substrate and a film formed on the conductive substrate using the metal oxide semiconductor particle dispersion according to the present invention.
Furthermore, this invention relates to the photoelectric conversion element which comprises the said metal oxide semiconductor electrode, a sensitizing dye, electrolyte, and a conductive counter electrode.

In the present invention, since dispersion particles can be made fine even in a dispersion process under a mild condition using a relatively inexpensive material, the concentration of titanium oxide particles in the metal oxide semiconductor particle dispersion can be increased. , The stability of the dispersion can be increased. As a result, a metal oxide semiconductor electrode and a photoelectric conversion element that are inexpensive and have excellent photoelectric conversion performance using the metal oxide semiconductor particle dispersion can be provided.

The metal oxide semiconductor particle dispersion according to the present invention is also referred to as a treated metal oxide semiconductor particle dispersion, that is, a titanium oxide dispersion (in the following description, also simply referred to as “dispersion”). This dispersion exhibits an excellent function by using an organic titanate such as a metal atom complex and an amine compound as a dispersion treatment agent and dispersing titanium oxide particles in a solvent. Here, the dispersion treatment agent refers to an auxiliary agent that helps the dispersion of the metal oxide semiconductor particles in the solvent and promotes the dispersion, and can also be referred to as a dispersion agent.

1. Metal oxide semiconductor particle dispersion (titanium oxide particles)
Titanium oxide (titanium dioxide) particles have relatively low material costs, are available in various particle sizes, have stable characteristics and are easy to handle, and have hydroxyl groups on the crystal surface. It is most useful as a photoelectric conversion material for dye-sensitized solar cells, because it has strong absorption of dyes and has little absorption in the visible range and does not interfere with sunlight absorption of sensitizing dyes. is there. In addition, the rutile type (tetragonal high temperature type), anatase type (tetragonal low temperature type), and brookite type (orthorhombic type) are known as crystal structures, but the anatase type (tetragonal low temperature type) is the most suitable. It is.
The primary particle diameter of titanium oxide is not particularly limited, but the average primary particle diameter is preferably 3 to 40 nm. If the average primary particle size is smaller than 3 nm, the voids in the film are remarkably reduced, which may cause problems such as the dye solution not permeating. On the other hand, if it exceeds 40 nm, the specific surface area may not be sufficiently increased. The average primary particle diameter here can be determined as follows. That is, 100 arbitrary particles are selected from an image obtained by photographing titanium oxide particles with a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and the average value of the minor axis diameter and major axis diameter of each particle is calculated. The particle diameter (d) is assumed. Each particle is regarded as a sphere having a particle size (d), and the volume (V) of each particle is determined. This operation is performed for 100 particles, and the value calculated using the following formula (A) is taken as the average primary particle diameter.
Formula (A): MV = Σ (V · d) / Σ (V)

(Organic titanate)
The organic titanate is a component that can be adsorbed on the surface of metal oxide semiconductor particles used in the metal oxide semiconductor particle dispersion, that is, titanium oxide particles, and can function as a dispersion treatment agent for achieving good dispersion. Furthermore, after this dispersion is applied to a conductive substrate to form an electrode layer, it is a component that can provide high adhesion and conversion efficiency even after firing or non-firing.

The organic titanate is an alkoxytitanium or organic titanium chelate (metal atom complex) having a structure containing a Ti—O—C bond formed by Ti (IV) and an alcoholic hydroxyl group and / or a diketonate group.

That is, the organic titanate is preferably a metal atom complex having a partial structure represented by the following general formula (1a).
General formula (1a)

In the formula, R ₁ to R ₃ each independently represent a hydrogen atom or a monovalent substituent. The arrow indicates a coordinate bond or ionic bond from the oxygen atom to Ti. Dashed lines indicate delocalized bonds in the diketonate compound structure. n is an integer of 0 to 4 and represents the coordination number of the diketato compound.
In the above formula (1a), n is preferably an integer of 1 to 3.

When this is shown by the whole structure, it is preferable to use the compound shown by the following general formula (1b) as organic titanate.
General formula (1b)

In the formula, R ₁ to R ₃ each independently represent a hydrogen atom or a monovalent substituent. The arrow indicates a coordinate bond or ionic bond from the oxygen atom to Ti. Dashed lines indicate delocalized bonds in the diketonate compound structure. n is an integer of 0 to 4 and represents the coordination number of the diketato compound. R represents an alkoxy group. p represents an integer of 0 to 4. O represents an oxygen atom. q represents an integer of 0 or 1. When q is 0, p + n = 4. When q is 1, p + n = 2.

In the following description, the organic titanate is also referred to as a metal atom complex, and the compound represented by the general formula (1a) or (1b) is also referred to as “metal atom complex (1)”.
The metal atom complex (1) may contain a plurality of ligands. An example including a plurality of ligands is shown as a compound in which any two or more of p, q, and n are not 0 in the general formula (1b).
More specifically, the compounds shown in Table 8-1 and Table 8-2 used in Examples described later are preferable examples of the metal atom complex (1). In the table, “Ti (acac) 4” is a compound of p = 0, q = 0, n = 4 in the general formula (1b), and “Ti (OnBu) 4” and “Ti (OiPr) 4” are , P = 4, q = 0, n = 0, “Ti (acac) 2 (OnBu) 2”, “Ti (acac) 2 (OiPr) 2”, “Ti (L 2) 2 (OnBu)” 2 ”and“ Ti (L4) 2 (OiPr) 2 ”are compounds of p = 2, q = 0, n = 2, and“ Ti (L3) (OiPr) 3 ”and“ Ti (L5) (OiPr) ) 3 ”is a compound with p = 1, q = 0, n = 3, and“ Ti═O (L1) 2 ”and“ Ti═O (L2) 2 ”are p = 0, q = 1, It is a compound of n = 2.

In the above formula (1b), the alkoxy group is preferably an alkoxy group having 1 to 20 carbon atoms, more preferably an alkoxy group having 1 to 8 carbon atoms, such as a methoxy group, an ethoxy group, or a diisopropoxy group. Most preferred is a propoxy group or a butoxy group such as an n-butoxy group.

In the above formulas (1a) and (1b), typical examples of the monovalent substituent include a halogen group, an alkyl group, an aryl group, a heterocyclic group, an alkoxy group, an alkylthio group, an arylthio group, a nitro group, and a cyano group. Group, thiocyanic acid group, isothiocyanic acid group, amino group, monoalkylamino group, dialkylamino group, aryloxy group, monoarylamino group, diarylamino group, alkylcarbonyl group or alkenylcarbonyl group (acyl group), alkylcarbonyloxy Groups, alkenylcarbonyloxy groups, arylcarbonyl groups, sulfonic acid amide groups, sulfonic acid ester groups, phthalimidomethyl groups, and the like, but are not limited thereto. The following exemplary compounds are not limited to these.

Examples of the halogen group include fluorine, chlorine, bromine and iodine.

Examples of the alkyl group include methyl group, ethyl group, propyl group, isopropyl group, butyl group, sec-butyl group, tert-butyl group, pentyl group, isopentyl group, neopentyl group, tert-pentyl group, hexyl group, isohexyl group, Heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl Groups and the like. *

Aryl groups include phenyl, biphenylyl, terphenylyl, quarterphenylyl, o-, m-, and p-tolyl, xylyl, o-, m-, and p-cumenyl, mesityl, pentalenyl Group, indenyl group, naphthyl group, binaphthalenyl group, turnaphthalenyl group, quarternaphthalenyl group, azulenyl group, heptaenyl group, biphenylenyl group, indacenyl group, fluoranthenyl group, acenaphthylenyl group, aceanthrylenyl group, phenenyl group, fluorenyl group , Anthryl group, bianthracenyl group, teranthracenyl group, quarteranthracenyl group, anthraquinolyl group, phenanthryl group, triphenylenyl group, pyrenyl group, chrysenyl group, naphthacenyl group, preadenyl group, picenyl group, perylene Group, pentaphenyl group, pentacenyl group, tetraphenylenyl les group, hexaphenyl group, hexacenyl group, rubicenyl group, coronenyl groups, trinaphthylenyl groups, heptacenyl groups, pyranthrenyl groups, ovalenyl group and the like.

Heterocyclic groups include thienyl group, benzo [b] thienyl group, naphtho [2,3-b] thienyl group, thiantenyl group, furyl group, pyranyl group, isobenzofuranyl group, chromenyl group, xanthenyl group, phenoxathi Inyl, 2H-pyrrolyl, pyrrolyl, imidazolyl, pyrazolyl, pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, indolizinyl, isoindolyl, 3H-indolyl, indolyl, 1H-indazolyl, purinyl Group, 4H-quinolidinyl group, isoquinolyl group, quinolyl group, phthalazinyl group, naphthyridinyl group, quinoxanilyl group, quinazolinyl group, cinnolinyl group, pteridinyl group, 4aH-carbazolyl group, carbazolyl group, β-carbolinyl group, phenanthridinyl group, Acridinyl Perimidinyl group, phenanthrolinyl group, phenazinyl group, phenalsadinyl group, isothiazolyl group, phenothiazinyl group, isoxazolyl group, furazanyl group, phenoxazinyl group, isochromanyl group, chromanyl group, pyrrolidinyl group, pyrrolinyl group, imidazolidinyl group, imidazolinyl group, Examples include pyrazolidinyl group, pyrazolinyl group, piperidyl group, piperazinyl group, indolinyl group, isoindolinyl group, quinuclidinyl group, morpholinyl group and the like.

Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, an isopropoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, a pentyloxy group, a hexyloxy group, and an isopentyloxy group. .

Examples of the alkylthio group include a methylthio group, an ethylthio group, a propylthio group, a butylthio group, an isopropylthio group, an isobutylthio group, a sec-butylthio group, a tert-butylthio group, a pentylthio group, a hexylthio group, and an isopentylthio group.

Examples of the arylthio group include a phenylthio group, a 1-naphthylthio group, a 2-naphthylthio group, a 9-anthrylthio group, and a 9-phenanthrylthio group.

Monoalkylamino groups include methylamino, ethylamino, propylamino, butylamino, pentylamino, hexylamino, heptylamino, octylamino, nonylamino, decylamino, dodecylamino, octadecyl Amino group, isopropylamino group, isobutylamino group, isopentylamino group, sec-butylamino group, tert-butylamino group, sec-pentylamino group, tert-pentylamino group, tert-octylamino group, neopentylamino group , Cyclopropylamino group, cyclobutylamino group, cyclopentylamino group, cyclohexylamino group, cycloheptylamino group, cyclooctylamino group, cyclododecylamino group, 1-adamantamino group, 2-adamantamino group Etc. The.

Dialkylamino group includes dimethylamino group, diethylamino group, dipropylamino group, dibutylamino group, dipentylamino group, dihexylamino group, diheptylamino group, dioctylamino group, dinonylamino group, didecylamino group, didodecylamino group, Dioctadecylamino group, diisopropylamino group, diisobutylamino group, diisopentylamino group, methylethylamino group, methylpropylamino group, methylbutylamino group, methylisobutylamino group, cyclopropylamino group, pyrrolidino group, piperidino group, And piperazino group.

Aryloxy groups include phenyloxy, biphenylyloxy, terphenylyloxy, quarterphenylyloxy, o-, m-, and p-tolyloxy, xylyloxy, o-, m-, and p -Cumenyloxy group, mesityloxy group, pentarenyloxy group, indenyloxy group, naphthyloxy group, binaphthalenyloxy group, turnaphthalenyloxy group, quarternaphthalenyloxy group, azulenyloxy group, heptalenyloxy Group, biphenylenyloxy group, indacenyloxy group, fluoranthenyloxy group, acenaphthylenyloxy group, aseantrirenyloxy group, phenalenyloxy group, fluorenyloxy group, anthryloxy group, Bianthracenyloxy group, teranthracenyloxy group, -Anthracenyloxy group, anthraquinolyloxy group, phenanthryloxy group, triphenylenyloxy group, pyrenyloxy group, chrysenyloxy group, naphthacenyloxy group, preadenyloxy group, picenyloxy group, perylenyloxy group, penta Phenyloxy group, pentacenyloxy group, tetraphenylenyloxy group, hexaphenyloxy group, hexacenyloxy group, rubicenyloxy group, coronenyloxy group, trinaphthylenyloxy group, heptaphenyloxy group, heptacene Examples include a nyloxy group, a pyrantrenyloxy group, and an oberenyloxy group.

The monoarylamino group includes N-arylamino group, anilino group, 1-naphthylamino group, 2-naphthylamino group, o-toluidino group, m-toluidino group, p-toluidino group, 2-biphenylamino group, 3 -Biphenylamino group, 4-biphenylamino group, 1-fluoreneamino group, 2-fluoreneamino group, 2-thiazoleamino group, p-terphenylamino group and the like.

Examples of the diarylamino group include a diarylamino group, a diphenylamino group, a ditolylamino group, an N-phenyl-1-naphthylamino group, and an N-phenyl-2-naphthylamino group.

Examples of the alkylcarbonyl group or alkenylcarbonyl group include formyl group, acetyl group, propionyl group, butyryl group, isobutyryl group, valeryl group, isovaleryl group, pivaloyl group, lauroyl group, myristoyl group, palmitoyl group, stearoyl group, cyclopentylcarbonyl group, Examples include cyclohexylcarbonyl group, acryloyl group, methacryloyl group, crotonoyl group, isocrotonoyl group, oleoyl group and the like.
Examples of the alkylcarbonyloxy group or alkenylcarbonyloxy group include groups derived from the above alkylcarbonyl group or alkenylcarbonyl group.

As the arylcarbonyl group, benzoyl group, 2-methylbenzoyl group, 4-methoxybenzoyl group, 1-naphthoyl group, 2-naphthoyl group, cinnamoyl group, 3-furoyl group, 2-thenoyl group, nicotinoyl group, isonicotinoyl group, Examples thereof include 9-anthroyl group and 5-naphthacenoyl group.
Examples of the sulfonate group include a methoxysulfonyl group, an ethoxysulfonyl group, a butoxysulfonyl group, and a phenoxysulfonyl group.

The monovalent substituent may be further substituted. In this case, examples of the group that further substitutes the monovalent substituent include the monovalent substituent described above or a group having a double bond.

Here, examples of the group having a double bond include a vinyl group, an allyl group, a 2-methylallyl group, a crotyl group, an isocrotyl group, a crotonoyl group, an isocrotonoyl group, a (meth) acryloyl group, and a (meth) acryloxy group. .
In particular, R ₁ to R ₃ are preferably selected from a hydrogen atom, a substituted or unsubstituted alkyl group, and a substituted or unsubstituted alkoxy group. The number of carbon atoms of the alkyl group or alkoxy group is not particularly limited, but is preferably 1 to 10, and particularly preferably 1 to 4. The substituent is preferably a halogen group, and particularly preferably fluorine.

These metal atom complexes together with the amine compound described later function as a dispersion treatment agent in the same solvent, thereby making a paste or dispersion solution, that is, a metal oxide semiconductor particle dispersion together with titanium oxide particles. After this dispersion is formed, it is sintered by heating to form a titanium oxide porous layer, and by further connecting a sensitizing dye, photoelectric conversion up to the visible light and / or near infrared light region is possible. Become. The presence of the metal atom complex further improves the adhesion after film formation.
In order for the surface of the titanium oxide porous layer to be sensitized by the sensitizing dye, it is desirable that the conduction band exists at a position where electrons are easily received from the photoexcitation order of the sensitizing dye.
In the present invention, the metal atom complex can be selected from a plurality of types and combined.

By bringing titanium oxide particles into contact with these metal atom complexes, the metal atom complexes are adsorbed on the surface of the titanium oxide particles to form a titanium oxide particle-metal atom complex complex. It is considered that a new similar metal oxide layer is formed. The newly formed metal oxide layer promotes the bonding between titanium oxide particles and facilitates the movement of electrons between the particles, so that the metal oxide semiconductor electrode has a relatively high performance even in a low-temperature firing process. It is thought that can be obtained.

These metal atom complexes can be purchased from Amax Co., Ltd., but can also be obtained by reacting, for example, a halide of an inorganic element with alcohols, carboxylic acids, free beta diketones, and the like.

(Amine compound)
The amine compound in the present invention is a compound having at least a primary amino group, a secondary amino group, or a tertiary amino group in the molecule. For example,
Such as ethylamine, n-propylamine, isopropylamine, t-butylamine, sec-butylamine, hexylamine, 2-ethylhexylamine, 2-ethylhexyloxypropylamine, 3-ethoxypropylamine, dodecylamine, stearylamine, allylamine, aniline, etc. Primary amine compounds;
Diethylamine, di-n-butylamine, diisopropylamine, diisobutylamine, di-2-ethylhexylamine, dioctylamine, dilaurylamine, diallylamine, iminobispropylamine, methylaminopropylamine, N-methylethanolamine, aminoethylethanolamine, Secondary amine compounds such as diphenylamine, 2,4-dimethyldiphenylamine, 3-methoxydiphenylamine, 4-isopropoxydiphenylamine, 3-hydroxydiphenylamine, 3,3′-dihydroxydiphenylamine, piperidine;
Triethylamine, tributylamine, trihexylamine, triallylamine, 3-diethylaminopropylamine, dibutylaminopropylamine, tetramethylethylenediamine, triethylenediamine, tri-n-octylamine, dimethylaminopropylamine, N, N-dimethylethanolamine, Triethanolamine, N, N-diethylethanolamine, N-methyl-N, N-diethanolamine, N, N-dibutylethanolamine, triphenylamine, 4-methyltriphenylamine, 4,4-dimethyltriphenylamine, Tertiary amine compounds such as diphenylethylamine, diphenylbenzylamine, N, N-diphenyl-p-anisidine;
Pyridine, 2-picoline, pyrazine, 2-pyridinemethanol, pyrrolidine, 1,4-bis (3-aminopropyl) piperazine, 1- (2-hydroxyethyl) piperazine, 2-pipecoline, 1,5,7-triaza Bicyclo [4.4.0] dec-5-ene, 7-methyl-1,5,7-triazabicyclo [4.4.0] dec-5-ene, 1,8-diazabicyclo [5.4. 0] undec-7-ene, 6-dibutylamino-1,8-diazabicyclo [5.4.0] undec-7-ene, 1,5-diazabicyclo [4.3.0] non-5-ene, etc. Examples thereof include, but are not limited to, cyclic amine compounds.

Preferably, an amine compound represented by the following general formula (2) can be used.
General formula (2)

In the formula, each of R ₄ to R ₆ independently represents a hydrogen atom, an unsubstituted or substituted alkyl group, an unsubstituted or substituted alkoxy group, an unsubstituted or substituted aryl group, unsubstituted or An alkylcarbonyl group having a substituent is represented.

Examples of the alkyl group, alkoxy group, aryl group, and alkylcarbonyl group in R ₄ to R ₆ include the same groups as those represented by R ₁ to R ₃ in the metal atom complex (1).
When R ₄ to R ₆ are substituted with a substituent, they may be substituted with one or more substituents, and bonded to any carbon atom on which R ₄ to R ₆ are not bonded to N. ing. Examples of the substituent include a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, an aryloxy group, an amino group, for example, an alkylamino group such as a monoalkylamino group and a dialkylamino group, an alkylcarbonyl group, and a hydroxy group. It is done. The alkyl group, alkoxy group, aryl group, aryloxy group, monoalkylamino group, dialkylamino group, and alkylcarbonyl group mentioned here are those represented by R ₁ to R ₃ in the metal atom complex (1). Similar groups can be mentioned. Moreover, these substituents may be further substituted.

The amine compound represented by the general formula (2) is not particularly limited, but a compound in which at least one of R ₄ to R ₆ is an alkyl group substituted with a hydroxy group is preferable.

Examples of the alkyl group substituted with a hydroxy group include hydroxymethyl group, hydroxyethyl group, hydroxypropyl group, hydroxyisopropyl group, hydroxy-n-butyl group, hydroxyisobutyl group, hydroxy-sec-butyl group, hydroxy-tert- Butyl, hydroxy-n-amyl, hydroxy-sec-amyl, hydroxy-tert-amyl, hydroxyisoamyl, hydroxy-n-hexyl, hydroxycyclohexyl, hydroxy-n-heptyl, hydroxy-n- Octyl group, hydroxy-2-ethylhexyl group, hydroxynonyl group, hydroxyisononyl group, hydroxydecyl group, hydroxyisodecyl group, hydroxyundecyl group, hydroxylauryl group, hydroxytridecyl group Hydroxy isotridecyl group, hydroxy myristyl group, hydroxy cetyl group, hydroxy isocetyl group, hydroxy stearyl group, there are hydroxy isostearyl group, especially a hydroxyethyl group are preferable.

As the amine compound containing a hydroxyethyl group, an amine compound represented by the following general formula (3) can be preferably used.
General formula (3)

In the amine compound, R ₇ and R ₈ each independently represent a hydrogen atom, an unsubstituted or substituted alkyl group, an unsubstituted or substituted aryl group, an unsubstituted or substituted alkylcarbonyl group. To express.

Examples of the alkyl group and aryl group in R ₇ and R ₈ include the same groups as those represented by R ₁ to R ₃ in the metal atom complex (1).
When R ₇ and R ₈ are substituted with a substituent, they may be substituted with one or more substituents and bonded to any carbon atom on R ₇ and R ₈ where N is not bonded. ing. Examples of the substituent groups include the same groups as the substituents may include the R _{4 ~} R ₆ described above, these substituents may be further substituted.

In a preferred embodiment, R ₇ and R _{8 in} the general formula (3) are methyl groups.
In another preferred embodiment, R ₇ and R _{8 in} the general formula (3) are hydroxyethyl groups.
That is, the amine compound represented by the general formula (3) is not particularly limited, but N, N-dimethylethanolamine and triethanolamine are preferable.

In another preferred embodiment, the amine compound is a nitrogen-containing aromatic heterocyclic compound which may have a substituent. That is, it is also preferable to use a nitrogen-containing aromatic heterocyclic compound as the amine compound. Here, the nitrogen-containing aromatic heterocyclic compound refers to a compound having a nitrogen atom represented by pyridine, pyrazine, or pyrimidine as a constituent atom of the aromatic ring.

Furthermore, it is also preferable to use an amine compound represented by the following general formula (4) as the nitrogen-containing aromatic heterocyclic compound.
General formula (4)

In the general formula (4), R ₉ to R ₁₃ each independently represent a hydrogen atom, an unsubstituted or substituted alkyl group, an unsubstituted or substituted alkoxy group, an unsubstituted or substituted alkylamino A group, an unsubstituted or substituted aryl group, an unsubstituted or substituted alkylcarbonyl group, an amino group, a hydroxy group, an N-alkylcarbamoyl group, and an alkoxycarbonyl group;

Examples of the alkyl group, alkoxy group, alkylamino group, aryl group, and alkylcarbonyl group in R ₉ to R ₁₃ include the same groups as those represented by R ₁ to R ₃ in the metal atom complex (1). Can do. Examples of the N-alkylcarbamoyl group include an N-methylcarbamoyl group. Examples of the alkoxycarbonyl group include a methoxycarbonyl group.

When R ₉ to R ₁₃ are substituted with a substituent, they may be substituted with one or more substituents and bonded to any carbon atom on R ₉ to R ₁₃ to which N is not bonded. ing. Examples of the substituent include the same groups as the substituents that R ₄ to R ₆ can contain, and these substituents may be further substituted.

The amine compound represented by the general formula (4) is not particularly limited, but a compound in which R ₉ to R ₁₃ are all hydrogen atoms is preferable.

In the present invention, a plurality of types of amine compounds can be selected and combined.
In the present invention, the amine compound is considered not to be a ligand of the metal atom complex but to be adsorbed on the surface of the titanium oxide particles, and is considered to exhibit a dispersion effect by being adsorbed. Various amine compounds are completely or partially dissolved in a solvent, and titanium oxide particles are added and mixed in the solution, so that it is considered that the adsorption of amine compounds on the surface of titanium oxide particles proceeds. And it seems that wetting with respect to the solvent of the titanium oxide particle surface is promoted by the polarity of the amine compound adsorbed on the surface of the titanium oxide particle, and the aggregation of the titanium oxide particles is easy to be solved. Furthermore, by using the above metal atom complex in combination, the dispersion proceeds with a synergistic effect, so that not only the dispersion treatment is performed by adding the metal atom complex alone, but the stability of the dispersion state is increased, It is also possible to increase the concentration of titanium oxide particles in the dispersion.
That is, titanium oxide particles can be favorably dispersed at a high concentration by using a metal atom complex and an amine compound in combination. Here, the improvement of the dispersibility of the titanium oxide particles improves the photoelectric conversion efficiency. Increasing the concentration of the dispersion makes it possible to increase the film thickness of the metal oxide semiconductor electrode and to improve the photoelectric conversion efficiency by increasing the film thickness.

The above metal atom complex and amine compound are contained in the dispersion as a dispersion treatment agent, and both are in a range of 0.01% by weight to 100% by weight with respect to the entire titanium oxide particles before treatment. That is, it is preferably used in the range of 0.0001 to 1 with respect to the weight 1 of titanium oxide particles to be blended. In order to sufficiently exhibit effects such as improvement in dispersibility by the treatment of the metal atom complex and amine compound and improvement in conversion efficiency by low-temperature firing, the amount is preferably 0.01% by weight or more. On the other hand, when the amount exceeds 100% by weight, these dispersion treatment agents become excessive with respect to the treatment of the surface of the metal oxide semiconductor, so that the dispersion treatment agent present alone in the dispersion increases and adheres during film formation. It may be undesirable in terms of deteriorating film quality, such as a decrease in properties. When the weight of the titanium oxide particles is 1, the total of the metal atom complex and the amine compound is more preferably 0.001 or more, still more preferably 0.01 or more, and most preferably 0.1 or more, more preferably Is used in an amount of 0.8 or less, more preferably 0.6 or less, and most preferably 0.4 or less.

The amine compound may be used in the range of 0.1 to 30% by weight with respect to the entire metal atom complex, that is, in the range of 0.001 to 0.3 with respect to the weight 1 of the metal atom complex to be blended. preferable. In order to sufficiently exhibit effects such as improvement of dispersibility by the amine compound and increase in concentration of the titanium oxide particles, the blending amount is preferably 0.1% by weight or more. On the other hand, if the amount of the amine compound relative to the metal atom complex is too large, a large amount of the amine compound adheres to the surface of the titanium oxide particles, so that the conduction band level of the titanium oxide semiconductor electrode after film formation changes or the electron trap is In some cases, such as formation may occur, so the content is preferably 30% by weight or less. The amine compound is preferably used in an amount of 0.005 or more, more preferably 0.01 or more, most preferably 0.03 or more, more preferably 0.25 or less, and more preferably 0.005 or more, with the weight of the metal atom complex being 1. Preferably it is used in an amount of 0.2 or less, most preferably 0.16 or less.

(solvent)
Solvents that can be used to prepare the metal oxide semiconductor particle dispersion include alcohol solvents such as ethanol, isopropyl alcohol, benzyl alcohol, and terpineol; nitrile solvents such as acetonitrile and propionitrile; chloroform, dichloromethane, chlorobenzene, and the like Halogen solvents; ether solvents such as diethyl ether and tetrahydrofuran; ester solvents such as ethyl acetate and butyl acetate; ketone solvents such as acetone, methyl ethyl ketone, cyclohexanone and isophorone; carbonate solvents such as diethyl carbonate and propylene carbonate; Hydrocarbon solvents such as hexane, octane, toluene, xylene; dimethylformamide, dimethylacetamide, dimethylsulfoxide, 1,3-dimethylimidazolinone, N-methyl Pyrrolidone, water, etc. can be used, but are not limited thereto. Two or more kinds of solvents may be mixed and used.

From the viewpoint of the influence of the volatile components after film formation on the environment, it is more desirable to use an alcohol solvent alone or in combination with another solvent. In order to prevent hydrolysis of the dispersion treatment agent, the water content in the solvent used is preferably 10% by weight or less, preferably 5% by weight or less, more preferably 1% by weight or less. . The water content in the solvent can be measured by, for example, a moisture meter such as a Karl Fischer moisture meter MKC-610 manufactured by Kyoto Electronics Industry Co., Ltd. Further, when this dispersion is used for measuring screen printing or the like, it is desirable that the boiling point of the solvent is higher than 100 ° C., because plate drying is less likely to occur.
As the alcohol solvent, in addition to the above, an alcohol having 1 to 30 carbon atoms is preferably used, an alcohol having 4 to 10 carbon atoms is more preferably used, and an alcohol having 6 to 8 carbon atoms is further used. preferable. The alcohol is preferably an aliphatic alcohol, preferably a linear alcohol, and preferably a monoalcohol. It is also preferable to use these alcohol solvents mixed with a ketone solvent such as isophorone (terpene monoketone).

(Create dispersion)
The metal oxide semiconductor particle dispersion is produced, for example, by dispersing titanium oxide particles, a metal atom complex, and an amine compound in a solvent, and mixing a binder component with the dispersion as necessary. Can do. The order of addition of each component is not limited to this. Further, if necessary, a solvent may be further added during or after mixing. For example, zirconia beads are used for the dispersion treatment, and the dispersion treatment is generally performed by a paint shaker or a mill, but is not limited thereto.

The titanium oxide is preferably used in an amount of 25% by weight or more, more preferably 30% by weight or more, and still more preferably 40% by weight or more based on the entire dispersion. If it is less than 25% by weight, it may be unfavorable in that overprinting is required to form a film having a thickness of several microns to tens of microns, which is optimal for a metal oxide semiconductor electrode. From the viewpoint of facilitating dispersibility, titanium oxide is preferably used in the dispersion in an amount of 75% by weight or less, more preferably 70% by weight or less, and still more preferably 60% by weight or less.

The amine compound is preferably used in an amount of 0.01% by weight or more, more preferably 0.1% by weight or more, and further preferably 0.2% by weight or more, preferably 5% by weight or less based on the entire dispersion. More preferably, it is used in an amount of 3% by weight or less, more preferably 1.5% by weight or less.
The metal atom complex (1) is preferably used in an amount of 1% by weight or more, more preferably 3% by weight or more, and still more preferably 5% by weight or more, preferably 20% by weight or less, more preferably based on the whole dispersion. Is used in an amount of 10% by weight or less.
The solvent is used in an amount of preferably 20% by weight or more, more preferably 30% by weight or more, and further preferably 40% by weight or more, preferably 70% by weight or less, more preferably 60% by weight or less, based on the entire dispersion. Used in the amount of.

The target viscosity of the dispersion (value at 25 ° C. using an ultrasonic vibration viscometer manufactured by Yamaichi Electronics Co., Ltd.) varies depending on the film forming method using this. For example, the standard is about 0.001 to 1000 mPa · s for a film forming method using squeegee, and about 0.1 to 350 mPa · s for a film forming method using screen printing. Absent. The dispersion using the inkjet printing method is preferably 0.02 mPa · s or less, but is not limited thereto. The viscosity can be adjusted by changing the amount ratio of the titanium oxide particles, the metal atom complex, and the amine compound solution, changing the degree of dispersion, or adding an appropriate amount of a thickening component such as a binder resin. *

Examples of the binder resin added as an optional component include cellulose, polyethylene glycol, acrylic, urethane, polyol, polyethylene, polyamide, and the like. It is not restricted to these as long as the characteristic as a metal oxide semiconductor electrode after a film is acquired. When blending a binder resin, it is preferably used in the range of 0.1 wt% or more and less than 60 wt% in the dispersion, and more preferably used in a range of 0.1 wt% or more and less than 20 wt%. preferable. Moreover, you may mix | blend binder resin in 0.1 weight% or more and less than 10 weight% of range. If it is less than 0.1% by weight, it may be unfavorable in that the effect of changing the viscosity or improving the film formability is not recognized. On the other hand, if it is 60% by weight or more, it may be unfavorable in that the viscosity as a dispersion is excessively increased or film formation becomes difficult. Furthermore, the dispersion can contain additives as required. Various additives can be added for the purpose of improving the properties of the dispersion, such as storage stability, drying properties, substrate adhesion, and film formation suitability.

2. Metal Oxide Semiconductor Electrode A metal oxide semiconductor electrode according to the present invention is obtained by forming a metal oxide semiconductor particle dispersion into a film, and includes a conductive substrate and the conductive material using the dispersion. A film formed on the substrate. For example, the metal oxide semiconductor particle dispersion is applied on a conductive substrate, and then dried or sintered. As a method of applying the dispersion onto the conductive substrate, a spin coater application method, a screen printing method, an application method using a squeegee, a dipping method, a spraying method, a roller method, and the like are used. Absent.
After the applied dispersion is dried or baked, volatile components in the dispersion are removed, and a film made of the dispersion or a metal oxide porous body is formed on the conductive substrate.

(Conductive substrate)
The conductive base material on which the metal oxide semiconductor particle dispersion is applied is not particularly limited, but a conductive film is formed on the surface of a non-conductive base body, or the base material itself has conductivity. If it is. Specifically, a metal oxide layer having good conductivity and transparency such as ITO (indium-tin oxide), tin oxide (including those doped with fluorine), zinc oxide, etc. was laminated on the surface. It may be a transparent substrate, a metal such as Ti (titanium) that does not react with the electrolyte described later, an oxide having a conductive layer formed on the surface, or a carbon material.
The transparent substrate used for the electrode having a conductive surface is not particularly limited as long as it is a material that absorbs less light from the visible to the near infrared region of sunlight. Glass substrates such as quartz, ordinary glass, BK7, lead glass, polyethylene terephthalate, polyethylene naphthalate, polyimide, polyester, polyethylene, polycarbonate, polyvinyl butyrate, polypropylene, tetraacetylcellulose, syndioctane polystyrene, polyphenylene sulfide, polyarylate Resin base materials such as polysulfone, polyester sulfone, polyetherimide, cyclic polyolefin, brominated phenoxy, and vinyl chloride can be used. However, in constituting the photoelectric conversion element, at least one of the conductive base material on which the metal oxide semiconductor particle dispersion is applied and the conductive counter electrode described later is a transparent conductive base material having light transmittance. Therefore, at least one is preferably a transparent substrate having a transparent conductive film formed on the surface.

When producing a metal oxide semiconductor electrode, as a drying or firing condition, for example, a method of applying thermal energy for 1 hour at a temperature of 400 ° C. to 500 ° C. is generally used. If it is the drying or baking method which has adhesiveness and can obtain a favorable electromotive force at the time of sunlight irradiation, it will not be restricted to this.

In particular, when the conductive base material is a resin, the metal oxide semiconductor particle dispersion of the present invention has a good electromotive force even under heating conditions of 250 ° C. or lower, further 200 ° C. or lower, at which a resin having low heat resistance does not melt. It is possible to give

A metal oxide semiconductor electrode in which a film using a metal oxide semiconductor particle dispersion is formed on a resin substrate with a transparent conductive film can provide high conversion efficiency even in a drying treatment at room temperature to 250 ° C., Furthermore, before, during or after heating, metal oxide semiconductor electrode is subjected to pressure treatment, ultrasonic welding treatment, microwave irradiation treatment, ultraviolet light irradiation treatment, ozone treatment, flash annealing treatment, laser annealing treatment, discharge plasma sintering treatment. Alternatively, by adding an additional process such as an excimer lamp process, conversion efficiency, film adhesion, and the like can be increased. When the electrode is irradiated with ultraviolet light simultaneously with heating, the organic component on the particle surface is effectively reduced. In this case, the conversion efficiency is higher as the temperature by heating is higher. Similarly, UV-ozone treatment can reduce organic substances and improve conversion efficiency.

The film thickness (thickness after drying or firing) of the dispersion or metal oxide porous layer formed on the conductive substrate is preferably 3 μm or more from the viewpoint of obtaining effective conversion efficiency. From the viewpoint of film formability, it is preferably 50 μm or less. If the film thickness is too large, it will be difficult to create such as cracking or peeling during film formation, and the distance between the metal oxide porous body surface layer and the conductive surface will increase, and the generated charge will be effectively transmitted to the conductive surface. Therefore, it becomes difficult to obtain good conversion efficiency. This film thickness is more preferably 5 μm or more, further preferably 7 μm or more, more preferably 30 μm or less, and further preferably 20 μm or less.

3. Photoelectric Conversion Element A photoelectric conversion element according to the present invention includes the metal oxide semiconductor electrode, a sensitizing dye (sensitizing dye for photoelectric conversion), an electrolyte, and a conductive counter electrode. In the metal oxide semiconductor electrode, the sensitizing dye is adsorbed on the surface of the film (or the metal oxide porous body) (this is also referred to as a photoelectric conversion electrode), and the photoelectric conversion is performed by combining the conductive counter electrode via the electrolyte. An element is formed.

(Sensitizing dye)
A sensitizing dye, that is, a sensitizing dye for photoelectric conversion, has a role of absorbing light in a wavelength region where the metal oxide semiconductor electrode cannot be photoelectrically converted and injecting excited electrons into the valence band of the metal oxide semiconductor. ing. Ruthenium dyes (N719 dye, etc.) that can be obtained from Solaronics, etc. are typical examples, but there are concerns about resource depletion and cost in terms of using rare elements, and in recent years there have been organic sensitizing dyes that replace them. Many have been developed. Coumarin-based, cyanine-based, rhodanine-based, squarylium-based, diketopyrrolopyrrole-based, phenylene vinylene-based, fluorene-based dyes, merocyanine-based dyes, and the like fall under this, and these can also be used as sensitizing dyes in the present invention. Some of these organic dyes exhibit bright red or blue color, and there is an advantage that they can be selected and used according to the use in which design properties are emphasized. Among these organic dyes, merocyanine dyes manufactured by Mitsubishi Paper Industries are well known, and D77, D102, D131, D149, D358 and the like can be obtained from the company. As the sensitizing dye for photoelectric conversion, two or more kinds of dyes may be mixed and used.

The sensitizing dye can be adhered to the surface of the electrode film (or metal oxide porous body) by dissolving it in an arbitrary solvent and immersing the metal oxide semiconductor electrode in the solution.
The solvent for preparing the sensitizing dye solution needs to be a solvent that can dissolve the sensitizing dye and mediate dye adsorption on the metal oxide layer. In order to dissolve the sensitizing dye, it may be heated as necessary, or a solubilizing agent may be added and insoluble matter may be filtered. Solvents include alcohol solvents such as ethanol, isopropyl alcohol and benzyl alcohol; nitrile solvents such as acetonitrile and propionitrile; halogen solvents such as chloroform, dichloromethane and chlorobenzene; ether solvents such as diethyl ether and tetrahydrofuran; acetic acid Ester solvents such as ethyl and butyl acetate; ketone solvents such as acetone, methyl ethyl ketone and cyclohexanone; carbonate solvents such as diethyl carbonate and propylene carbonate; hydrocarbon solvents such as hexane, octane, toluene and xylene; dimethylformamide, Dimethylacetamide, dimethylsulfoxide, 1,3-dimethylimidazolinone, N-methylpyrrolidone, water and the like can be used, but are not limited thereto. Two or more kinds of solvents may be mixed and used.

(Photoelectric conversion electrode)
The photoelectric conversion electrode includes a conductive substrate, a film (or a metal oxide porous body) formed on the conductive substrate using the metal oxide semiconductor particle dispersion, and, for example, as described above. A sensitizing dye adsorbed on the surface of the membrane (or porous metal oxide).

(Electrolyte and electrolyte layer)
The electrolyte provided in contact with these electrodes between the metal oxide semiconductor electrode and the conductive counter electrode is preferably provided as an electrolyte layer. The electrolyte layer is preferably composed of an electrolyte, a medium, and an additive. As the electrolyte, I ₂ and an iodide (LiI Examples, NaI, KI, CsI, MgI 2, CaI 2, CuI, tetraalkylammonium iodide, pyridinium iodide, imidazolium iodide, etc.) mixtures, and Br ₂ A mixture of bromide (for example, LiBr), a molten salt described in Inorg. Chem. 1996, 35, 1168-1178, and the like can be used, but this is not a limitation. Among these, an electrolyte in which LiI, pyridinium iodide, imidazolium iodide, or the like is mixed as a combination of I ₂ and iodide is preferable, but is not limited to this combination.
The preferable electrolyte concentration is I ₂ in the medium is 0.01 M or more and 0.5 M or less, and the iodide mixture is 0.1 M or more and 15 M or less.

The medium used for the electrolyte layer is preferably a compound that can exhibit good ionic conductivity. Examples of the solution medium include ether compounds such as dioxane and diethyl ether; chain ethers such as ethylene glycol dialkyl ether, propylene glycol dialkyl ether, polyethylene glycol dialkyl ether, and polypropylene glycol dialkyl ether; methanol, ethanol, ethylene glycol monoalkyl Alcohols such as ether, propylene glycol monoalkyl ether, polyethylene glycol monoalkyl ether, polypropylene glycol monoalkyl ether; polyhydric alcohols such as ethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, glycerin; acetonitrile, glutarodinitrile, Methoxyacetonitrile, propioni Lil, nitrile compounds such as benzonitrile, ethylene carbonate, carbonate compounds such as propylene carbonate; heterocyclic compounds such as 3-methyl-2-oxazolidinone; dimethyl sulfoxide, can be used aprotic polar substances such as sulfolane, water, and the like.

A polymer may be included for the purpose of using a solid (including gel) medium. In this case, a polymer such as polyacrylonitrile or polyvinylidene fluoride is added to the solution-like medium, or a polyfunctional monomer having an ethylenically unsaturated group is polymerized in the solution-like medium, so that the medium is solid. Can be.

As the electrolyte layer, 2,2 ′, 7,7′-tetrakis (N, N-di-p-methoxyphenylamine) 9, 9 described in Nature, Vol. 395, 8 Oct. 1998, p583-585 is also used. A hole transport material such as' -spirobifluorene can be used.

An additive that functions to improve the electrical output of the photoelectric conversion element or improve the durability can be added to the electrolyte layer. Examples of additives that improve electrical output include 4-t-butylpyridine, 2-picoline, 2,6-lutidine, and cyclodextrin. Examples of additives that improve durability include MgI.

(Conductive counter electrode)
The conductive counter electrode functions as a positive electrode of the photoelectric conversion element. The conductive material used for the counter electrode is metal (for example, platinum, gold, silver, copper, aluminum, rhodium, indium, etc.), metal oxide (ITO (indium-tin oxide), FTO ((fluorine-doped tin oxide)) , Zinc oxide, etc.), or carbon.

(Assembly of photoelectric conversion element)
A photoelectric conversion cell is formed by combining the photoelectric conversion electrode and the conductive counter electrode via an electrolyte or an electrolyte layer. If necessary, sealing is performed around the photoelectric conversion cell in order to prevent leakage or volatilization of the electrolyte or the electrolyte layer. For sealing, a thermoplastic resin, a photocurable resin, glass frit, or the like can be used as a sealing material. The photoelectric conversion cell is formed by connecting small-area photoelectric conversion cells as necessary. By combining the photoelectric conversion cells in series, the electromotive voltage can be increased.

EXAMPLES Hereinafter, although this invention is demonstrated in more detail based on an Example, this invention is not limited to an Example. The water content of the solvent used was less than 1% by weight at the reagent level. In the examples, “part” means “part by weight” and “%” means “% by weight”. acac represents an acetylacetonate residue (—OC (CH ₃ ) CH ₂ C (CH ₃ ) O).

(1) Examples 1-122 and Comparative Example 1
In 50.75 parts of 1-hexanol, titanium oxide acetylacetonate (TiO (acac) ₂ ) (in general formula (1b), p = 0, q = 1, n as a metal atom complex represented by general formula (1b) = 2) 8 parts, amine compound 1.25 parts, Ishihara Sangyo Co., Ltd. titanium oxide ST-01 (average particle size 7 nm) 40 parts, mixed with zirconia beads, dispersed using a paint shaker A metal oxide semiconductor particle dispersion was obtained. For the viscosity, an ultrasonic vibration viscometer manufactured by Yamaichi Electronics Co., Ltd. was used, and the value at 25 ° C. was used. Tables 1 to 5 show the amine compounds used as the dispersant and the viscosity of the dispersion. As Comparative Example 1, the viscosity of a dispersion obtained by carrying out a dispersion treatment using 52 parts of 1-hexanol without using an amine compound is also shown.

Table 1

Examples 1 to 23 are obtained by preparing a metal oxide semiconductor particle dispersion using the compound represented by the general formula (3) as an amine compound and measuring the viscosity. It can be seen that the viscosity of the dispersions of Examples 1 to 23 is lower than that of Comparative Example 1. In Comparative Example 1, gelation occurred and the viscosity became too high, and measurement with the viscometer used was not possible. Since the upper limit of measurement of this viscometer is 350 mPa · s, it is confirmed with a viscometer for high viscosity measurement (Brookfield Analog Viscometer HBT for high viscosity, manufactured by Brookfield) that can measure up to about 64,000 Pa · s. As a result, it was found that the viscosity was higher than 100 Pa · s.

Table 2

In Examples 24 to 42, metal oxide semiconductor particle dispersions were produced using compounds in which at least one of R ₄ to R _{6 in} the general formula (2) is an alkyl group substituted with a hydroxy group as an amine compound. The viscosity was measured. It can be seen that the viscosity of the dispersions of Examples 24 to 42 is lower than that of Comparative Example 1.

Table 3

Examples 43 to 63 are obtained by preparing a metal oxide semiconductor particle dispersion using the compound of the general formula (2) as an amine compound and measuring the viscosity. Compared with Comparative Example 1, it can be seen that the dispersions of Examples 43 to 63 have lower viscosities.

Table 4

Examples 64 to 84 were prepared by preparing metal oxide semiconductor particle dispersions using the compound group of the general formula (4) as amine compounds and measuring the viscosity. Compared to Comparative Example 1, it can be seen that the dispersions of Examples 64-84 have lower viscosities.

Table 5

Examples 85 to 122 are prepared by preparing a metal oxide semiconductor particle dispersion using a nitrogen-containing aromatic heterocyclic compound which may have a substituent as an amine compound, and measuring the viscosity. Compared with Comparative Example 1, it can be seen that the dispersions of Examples 85 to 122 have lower viscosities.

From the results of Examples 1 to 122 and Comparative Example 1, it was found that when an amine compound was used, the viscosity of the dispersion decreased, and the amine compound functions as a dispersant. The effect of decreasing the viscosity is a compound in which at least one of R ₄ to R _{6 in} the general formula (2) is an alkyl group substituted with a hydroxy group, or a nitrogen-containing compound that may have a substituent. The case where an aromatic heterocyclic compound was used was large, and the case where a compound represented by general formula (3) or a compound represented by general formula (4) was used was particularly large.

As described above, since the dispersibility of titanium oxide was improved by using an amine compound, the viscosity of the metal oxide semiconductor particle dispersion was lower than that of Comparative Example 1. Thereby, the titanium oxide concentration in the dispersion can be increased. In the present invention, the amine compound is a compound in which at least one of R ₄ to R _{6 in} the general formula (2) is an alkyl group substituted with a hydroxy group, or may contain a substituent. It turns out that a nitrogen aromatic heterocyclic compound is suitable. Furthermore, it turns out that the compound shown by General formula (3) or the compound shown by General formula (4) is more suitable among those compound groups.

(2) Example 123
(Preparation of screen printing paste)
44.75 parts of 1-octanol, 9 parts of titanium acetyl oxide acetonate (TiO (acac) ₂ ) as a metal atom complex, 1.25 parts of the amine compound described in Example 3, titanium oxide ST— manufactured by Ishihara Sangyo Co., Ltd. 45 parts of 01 (average particle diameter 7 nm) was added, mixed with zirconia beads, and dispersed using a paint shaker to obtain a metal oxide semiconductor particle dispersion. The viscosity of the dispersion was measured with an ultrasonic vibration viscometer manufactured by Yamaichi Electronics Co., Ltd. and found to be 82.4 mPa · s. Thereafter, 14.81 parts of ethyl cellulose (N-4 manufactured by Hercules Co., Ltd.) and 14.81 parts of 1-octanol were dissolved and kneaded into 70.37 parts of the dispersion to prepare a screen printing paste. The viscosity after the preparation was 210 Pa · s at 25 ° C. and 0.3 rpm when measured with a cone plate type (E type) TV22 viscometer manufactured by Toki Sangyo Co., Ltd.

(Production of metal oxide semiconductor electrode)
The above screen printing paste was applied onto a glass substrate with an FTO film (type UT CO manufactured by Asahi Glass Co., Ltd.) using a stainless steel mesh screen (# 180) having a 1 cm square pattern, dried, and then 470 By baking at 1 ° C. for 1 hour to form a film, a metal oxide semiconductor electrode having a 1 cm square metal oxide porous body formed on a conductive transparent substrate was obtained. The film thickness of the porous metal oxide was measured using a stylus type surface shape measuring device DEKTAK6M manufactured by Veeco, and found to be 9.4 μm.

(Adsorption of sensitizing dye)
Sensitizing dye (Ru complex; manufactured by Solaronics: N719) 3 × 10 ⁻⁴ M was dissolved in a 1: 1 mixture of t-butyl alcohol and acetonitrile, and the insoluble matter was removed with a membrane filter. The metal oxide semiconductor electrode was immersed in this dye solution and allowed to stand at 40 ° C. for 2 hours. The colored electrode surface was washed with the solvent used and then dried to obtain a photoelectric conversion electrode on which the sensitizing dye was adsorbed.

(Preparation of electrolyte solution)
An electrolyte solution was obtained according to the following formulation.
Solvent 3-methoxyacetonitrile LiI: 0.1M
I ₂ : 0.05M
4-t-butylpyridine: 0.5M
1-propyl-2,3-dimethylimidazolium iodide: 0.6M

(Assembly of photoelectric conversion element)
As the conductive counter electrode, a platinum layer having a thickness of 200 nm was formed by sputtering on a conductive layer of a glass substrate with an FTO film (type UTCO manufactured by Asahi Glass Co., Ltd.). In addition, as a resin film spacer, a “High Milan” film (25 μm thickness) made by Mitsui DuPont Polychemical Co., Ltd. is prepared, the photoelectric conversion electrode and the conductive counter electrode are opposed to each other via a spacer, and the above electrolyte solution is contained inside Was filled to form an electrolytic solution layer, thereby completing a photoelectric conversion element.

(Measurement of conversion efficiency)
Combined with a solar simulator (# 8116) manufactured by ORIEL and an air mass filter, the light quantity is adjusted to 1-SUN with a light meter to obtain a light source for measurement, and a test sample of a photoelectric conversion element is irradiated with light, and 2400 manufactured by KEITHLEY The IV curve characteristics were measured using a type source meter. The conversion efficiency η was calculated by the following equation using Voc (open circuit voltage value), Jsc (short circuit current value), and FF (fill factor value) obtained from the IV curve characteristic measurement.

As a result, Voc = 0.72 V, Jsc = 15.73 mA / cm ² , FF = 0.64, and η = 7.25% were obtained.

(3) Examples 124 to 133 and Comparative Examples 2 and 3
The same procedure as in Example 123, except that the metal oxide semiconductor electrode was produced by changing the type of amine compound as a dispersion aid, the composition of the metal oxide semiconductor particle dispersion, and the preparation composition of the screen printing paste. The performance of the photoelectric conversion element was measured. The amine compound used, the composition of the dispersion, and the viscosity (value at 25 ° C. using an ultrasonic vibration viscometer manufactured by Yamaichi Electronics Co., Ltd.) are shown in Table 6, and the paste preparation (composition) and viscosity (Toki Table 7 shows the film thickness and photoelectric conversion efficiency of the metal oxide semiconductor electrode measured with a cone plate type (E type) TV22 viscometer manufactured by Sangyo Co., Ltd., measured at 25 ° C.). For reference, Example 123 is also shown in the table.

In Table 7, the prescription index Resin / TiO ₂ is the ratio of the weight of ethyl cellulose (N-4 manufactured by Hercules Co.) to the weight of titanium oxide in the metal oxide semiconductor particle dispersion used for preparing the paste (= ( Ethyl cellulose weight / titanium oxide weight) × 100).

By using an amine compound, the dispersibility of the metal oxide semiconductor particle dispersion can be improved, and the titanium oxide concentration in the dispersion can be improved. After the paste is prepared, the metal oxide semiconductor electrode produced by screen printing is used. The film thickness can be increased. Thereby, since the specific surface area of a metal oxide semiconductor electrode increases and more sensitizing dyes can be adsorbed, the photoelectric conversion efficiency can be increased. On the other hand, as shown in Comparative Example 2, a metal oxide semiconductor electrode prepared by screen printing after preparing a dispersion without using an amine compound and preparing a paste has a sufficient film thickness (titanium oxide). Since the dispersion state of the titanium oxide particles is insufficient because the concentration is high), the photoelectric conversion performance was low. In addition, as shown in Comparative Example 3, in order to make the dispersion state of the titanium oxide particles sufficient without using an amine compound, the metal oxide semiconductor particle dispersion produced by reducing the titanium oxide concentration was used as a paste. After preparation, the film thickness of the metal oxide semiconductor electrode produced by screen printing was low, and high photoelectric conversion performance could not be achieved.

(4) Examples 134 to 144
When producing the metal oxide semiconductor particle dispersion, a metal oxide semiconductor electrode was produced in the same manner as in Example 123 except that the kind of the metal atom complex to be added was changed, and the performance of the photoelectric conversion element was measured. Viscosity of added metal atom complex, metal oxide semiconductor particle dispersion (value at 25 ° C. using an ultrasonic vibration viscometer manufactured by Yamaichi Electronics Co., Ltd.), film thickness of metal oxide semiconductor electrode, photoelectric conversion efficiency Is shown in Table 8.

Table 8

From Table 8, it can be seen that the effect of the present invention is sufficiently achieved even if the type of the metal atom complex (organic titanate) is changed.

In Table 8, iPr represents an isopropyl group, and nBu represents a normal butyl group.
In Table 8, the ligand of the metal atom complex represented by the general formula (1a) or (1b) is represented by the following general formula (5). In this case, acac and L1 to L5 are represented in Table 9.

General formula (5)

(An arrow indicates a coordinate bond or an ionic bond from an oxygen atom to a metal atom. A broken line indicates a delocalized bond in the structure of the diketonate compound.)

As described above, when preparing a metal oxide semiconductor particle dispersion, the dispersibility can be improved by using a metal atom complex and an amine compound in combination as a dispersion treatment agent and dispersing titanium oxide particles in a solvent. In addition, it is possible to increase the titanium oxide concentration in the dispersion and thus increase the film thickness of the metal oxide semiconductor electrode. An increase in the thickness of the metal oxide semiconductor electrode leads to the development of good photoelectric conversion performance and a reduction in the number of printings during electrode production.

(5) Examples 145 to 161
50.75 parts of 1-hexanol, 8 parts of titanium oxide acetylacetonate (TiO (acac) ₂ ), 1.25 parts of amine compound, and titanium oxide ST-01 (average particle diameter 7 nm) manufactured by Ishihara Sangyo Co., Ltd. In addition, the mixture was mixed with zirconia beads and dispersed using a paint shaker to obtain a metal oxide semiconductor particle dispersion. For the viscosity, an ultrasonic vibration viscometer manufactured by Yamaichi Electronics Co., Ltd. was used, and the value at 25 ° C. was used. Table 10 shows the amine compounds used as the dispersant and the viscosity of the dispersion.
Examples 145 to 152 are examples using an amine compound of the general formula (2), Examples 153 to 154 are examples using an amine compound of the general formula (3), and Examples 155 to 161 are those of the general formula (4). ) Examples using amine compounds are shown.

Table 10

As described above, since the dispersibility of titanium oxide was improved by using an amine compound, the viscosity of the metal oxide semiconductor particle dispersion was lower than that of Comparative Example 1. Thereby, the titanium oxide concentration in the dispersion can be increased.

(6) Examples 161 to 183
Except that the metal oxide semiconductor electrode was produced by changing the type of amine compound as a dispersion aid, the composition of the metal oxide semiconductor particle dispersion, and the composition of the paste for screen printing, the same procedure as in Example 123 was performed. The performance of the conversion element was measured. Table 11 shows the amine compound used, the composition of the dispersion, and the viscosity (value at 25 ° C. using an ultrasonic vibration viscometer manufactured by Yamaichi Electronics Co., Ltd.). Table 12 shows the film thickness and photoelectric conversion efficiency of the metal oxide semiconductor electrode measured by a cone plate type (E type) TV22 viscometer manufactured by a company, measured at 25 ° C.).

Table 11

In Table 12, the prescription index Resin / TiO ₂ is the same as the weight ratio in Table 7.
By using an amine compound, the dispersibility of the metal oxide semiconductor particle dispersion can be improved, and the titanium oxide concentration in the dispersion can be improved. After the paste is prepared, the metal oxide semiconductor electrode manufactured by screen printing is used. The film thickness can be increased. As a result, the specific surface area of the metal oxide semiconductor electrode increases and more sensitizing dyes can be adsorbed, so that the photoelectric conversion efficiency can be increased.

The disclosure of the present application is related to the subject matter described in Japanese Patent Application No. 2010-247994 filed on Nov. 5, 2010, the entire disclosure of which is incorporated herein by reference.
It should be noted that various modifications and changes may be made to the above-described embodiments without departing from the novel and advantageous features of the present invention other than those already described. Accordingly, all such modifications and changes are intended to be included within the scope of the appended claims.

Claims (12)

1. A metal oxide semiconductor particle dispersion comprising an amine compound, an organic titanate having at least one of an alkoxy group and a diketonate group, and a solvent.
2. The metal oxide semiconductor particle dispersion according to claim 1, wherein the amine compound is a compound represented by the following general formula (2).
   General formula (2)
   

   

   
   
   [Wherein R ₄ to R ₆ are each independently a hydrogen atom, an unsubstituted or substituted alkyl group, an unsubstituted or substituted alkoxy group, an unsubstituted or substituted aryl group, or unsubstituted. Alternatively, it represents an alkylcarbonyl group having a substituent. ]
3. The metal oxide semiconductor particle dispersion according to claim 2, wherein at least one of R ₄ to R ₆ is an alkyl group substituted with a hydroxy group.
4. The metal oxide semiconductor particle dispersion according to claim 2, wherein the amine compound is a compound represented by the general formula (3).
   General formula (3)
   

   

   
   
   [Wherein, R ₇ and R ₈ each independently represent a hydrogen atom, an unsubstituted or substituted alkyl group, an unsubstituted or substituted aryl group, or an unsubstituted or substituted alkylcarbonyl group. ]
5. The metal oxide semiconductor particle dispersion according to claim 4, wherein R ₇ and R ₈ are methyl groups.
6. The metal oxide semiconductor particle dispersion according to claim 4, wherein R ₇ and R ₈ are hydroxyethyl groups.
7. The metal oxide semiconductor particle dispersion according to claim 1, wherein the amine compound is a nitrogen-containing aromatic heterocyclic compound which may have a substituent.
8. The metal oxide semiconductor particle dispersion according to claim 7, wherein the amine compound is a compound represented by the general formula (4).
   General formula (4)
   

   

   
   
   (Wherein R ₉ to R ₁₃ are each independently a hydrogen atom, an unsubstituted or substituted alkyl group, an unsubstituted or substituted alkoxy group, an unsubstituted or substituted alkylamino group, (Represents a substituted or substituted aryl group, unsubstituted or substituted alkylcarbonyl group, amino group, hydroxy group, N-alkylcarbamoyl group, and alkoxycarbonyl group.)
9. The metal oxide semiconductor particle dispersion according to claim 8, wherein R ₉ to R ₁₃ are all hydrogen atoms.
10. The metal oxide semiconductor particle dispersion according to claim 1, wherein the organic titanate is a compound represented by the following general formula (1b).
    General formula (1b)
    

    

    
    (In the formula, R ₁ to R ₃ each independently represents a hydrogen atom or a monovalent substituent. An arrow represents a coordinate bond or an ionic bond from an oxygen atom to Ti. N represents an integer of 0 to 4 and represents the coordination number of the diketonate compound, R represents an alkoxy group, p represents an integer of 0 to 4, and O represents an oxygen atom. Q represents an integer of 0 or 1. When q is 0, p + n = 4. When q is 1, p + n = 2.)
11. A conductive substrate;
    A film formed on the conductive substrate using the metal oxide semiconductor particle dispersion according to any one of claims 1 to 10,
    A metal oxide semiconductor electrode comprising:
12. A photoelectric conversion device comprising the metal oxide semiconductor electrode according to claim 11, a sensitizing dye, an electrolyte, and a conductive counter electrode.