JPH06163961A - Organic colar cell - Google Patents

Abstract

PURPOSE:To improve the photoelectric conversion efficiency of an organic solar cell, by forming a photoconductive layer containing charge generating pigment and charge transfer material, between two electrodes in an organic solar cell, and using compound expressed by a specified formula as the charge generating pigment. CONSTITUTION:An organic solar cell is provided with a substrate 1, an electrode 2, a photoconductive layer 3, and a transparent counter electrode 4. Material which forms a Schottky junction with the photoconductive layer 3 is used as the material of the electrode 2 and the transparent electrode 4. The photoconductive layer 3 contains binder resin, charge generating pigment, and charge transfer pigment. As the charge generating pigment, compound expressed by a specific formula is used. In the formula, R<1>, R<2> are identical or different and show hydrogen atom, or halogen atom, or alkyl group which may have substituent, or aromatic group which may have substituent, (m) and (n) show integers of 0-2, and A and B are identical or different and show coupler residue.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an organic solar cell,
More specifically, the present invention relates to a function-separated type organic solar cell using an organic pigment and an organic material.

[0002]

2. Description of the Related Art In an organic solar cell, a pn junction is formed between an inorganic semiconductor such as silicon or germanium and a photoconductive layer made of an organic dye, or a metal and an organic dye are combined to emit light energy. It is converted into electric energy. The photoconductive layer is, for example, an organic photoconductor made of a synthetic dye or pigment such as chlorophyll, a conductive polymer material such as polyacetylene, or a composite material thereof, by a vacuum deposition method, a casting method, a dipping method, or the like. It is formed of a thin film.

The organic solar cell using the organic photoconductor or the organic semiconductor as described above is more economical than the conventional inorganic solar cell in which a pn junction is formed in a single crystal of an inorganic semiconductor such as silicon or germanium. In recent years, it has attracted attention as a solar cell for consumer use because it has advantages such as excellent heat resistance and easy manufacture. For example, JP-A 1-21
No. 5070 discloses a photoconductive layer in which an organic charge generating pigment and an organic charge transporting dye are dispersed in a binder resin,
An organic solar cell formed by being arranged between two electrodes is disclosed.

In this organic solar cell, a bisazo pigment or a phthalocyanine pigment is used as the charge generating pigment. As the charge transport dye, organic compounds such as pyrazoline-based, hydrazone-based, oxazole-based, trianolmethane-based, and polyarylalkanes are used. In this organic solar cell, a Schottky junction is formed between the electrode and the photoconductive layer containing the organic charge generating pigment. Therefore, when the organic charge generating pigment is irradiated with light, carrier pairs are generated in the Schottky barrier portion. Among the carrier pairs, holes are injected into the organic charge transport dye in the photoconductive layer, holes move in the dye, and electrons move in the pigment according to the potential difference of the Schottky junction.

Therefore, according to the organic solar cell disclosed in Japanese Unexamined Patent Publication No. 1-215070, it is said that an inexpensive organic solar cell having high photoelectric conversion efficiency and high continuous use stability can be obtained.

[0006]

However, in the organic solar cell using the pigment as described above, the amount of generated carriers cannot be said to be sufficient and the photoelectric conversion efficiency is insufficient. The present invention has been made to solve the above problems,
Its purpose is to provide an organic solar cell having a high photoelectric conversion rate.

[0007]

The organic solar cell of the present invention is an organic solar cell in which a photoconductive layer containing a charge generating pigment and a charge transport material is provided between two electrodes, The charge generating pigment is a compound represented by the following general formula (1), and thereby the above object is achieved.

[0008]

[Chemical 2]

(In the formula, R1 and R2 are the same or different and each represents a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, or an aromatic group which may have a substituent. , M and n each independently represent an integer of 0 to 2, and A and B are the same or different and each represents a coupler residue.)

[0010]

[Function] When the photoconductive layer of the organic solar cell is irradiated with light,
A charge is generated in the charge generation pigment in the photoconductive layer, electrons move to the positive electrode, and holes are injected into the charge transport dye, and move to the negative electrode via the charge transport dye. Here, the disazo compound represented by the formula (1) used as the charge generating pigment in the present invention is described in JP-A 1-21.
The charge generation ability is superior to that of the charge generation pigment disclosed in Japanese Patent No. 5070. Therefore, by containing this disazo compound as a charge generating material in the photoconductive layer, the amount of photocarriers generated is increased, so that an organic solar cell having excellent photoelectric conversion efficiency can be obtained.

[0011]

[Preferable embodiment]

<< Structure of Solar Cell >> The organic solar cell according to the present invention can have a configuration as shown in FIG. 1, for example. This organic solar cell A has a substrate 1, an electrode 2, a photoconductive layer 3 and a transparent counter electrode 4 which are sequentially laminated on the substrate 1.

In this structure, light is emitted from the transparent electrode 4 side, but when the substrate 1 and the electrode 2 are translucent, the light may be emitted from the substrate 1 side. In that case, the transparent electrode 4 may be non-translucent. In this structure, an undercoat layer may be provided on the substrate 1 in order to improve the adhesion between the electrode 2 and the substrate 1. As the material of the substrate 1, a metal such as aluminum or stainless steel,
Paper, plastic, etc. can be used.

As a material for the electrode 2 and the transparent electrode 4, any material can be used as long as it forms a Schottky junction with the photoconductive layer 3. For example, metals such as aluminum, copper, stainless steel; polyacetylene,
A conductive polymer such as polypyrrole; a quaternary ammonium salt dissolved in the polymer; an oxide such as SnO2 or ITO can be used. However, when translucency is required, it is necessary to use a semitransparent thin film of metal, a transparent conductive oxide, or the like.

The electrodes 2 and 4 are formed, for example, by vacuum deposition or sputtering. The photoconductive layer 3 generally contains a binder resin, a charge generating pigment, and a charge transport dye. << Charge Generating Pigment >> As the charge generating pigment contained in the photoconductive layer 3, a compound represented by the following general formula (1) is used.

[0015]

[Chemical 3]

(In the formula, R1 and R2 are the same or different and each represents a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, or an aromatic group which may have a substituent. , M and n each independently represent an integer of 0 to 2, and A and B are the same or different and represent a coupler residue.) Examples of the alkyl group include methyl, ethyl, propyl, isopropyl, butyl and isobutyl. And lower alkyl groups having 1 to 6 carbon atoms such as pentyl and hexyl.

Specific examples of the above-mentioned coupler residues A and B include the groups (a) to (f) shown below. Specific examples of the charge generation pigment include the following formula (A
The compounds shown in 1) to (A8) are exemplified.

[0018]

[Chemical 4]

[0019]

[Chemical 5]

[0020]

[Chemical 6]

[0021]

[Chemical 7]

[0022]

[Chemical 8]

[0023]

[Chemical 9]

[0024]

[Chemical 10]

[0025]

[Chemical 11]

[0026]

[Chemical 12]

[0027]

[Chemical 13]

[0028]

[Chemical 14]

Since the charge generation pigment represented by the above general formula (1) has a diphenoquinone skeleton as a central skeleton of the disazo pigment, the molecular polarization of excited π electrons in the molecule is in an efficient state and is large. It is considered that the charge generation efficiency is increased as a result of the fact that the stacking property between molecules is improved by having the π electron plane.

In the organic solar cell of the present invention, the compound represented by the above general formula (1) may be used alone as the charge generating pigment, or may be used in combination with other conventionally known charge generating pigments. You can also The charge generating pigment used in combination is preferably one having a good absorption of sunlight or visible light, and the one which functions as an electron acceptor for the organic charge transporting dye used in combination is preferable. For example, selenium, selenium-tellurium, selenium-arsenic, amorphous silicon, pyrylium salts, thiopyrylium pigments, phthalocyanine compounds, ansanthuron compounds, anthanthrone pigments, perylene compounds, dibenzpyrenequinone pigments, pyratron pigments, trisazo pigments. , Bisazo pigments, azo compounds, disazo compounds, indigo compounds, thioindigo compounds, triphenylmethane compounds, slene compounds, toluidine compounds, pyrazoline compounds, quinacdrine compounds, pyrrolopyrrole compounds, asymmetric quinocyanines, quinocyanines , Polycyclic condensed dyes, porphyrin dyes and the like can be used.

These charge generating pigments may be used alone or in combination of two or more. These charge-generating organic pigments can be formed into fine particles having an appropriate crystal form by heating and stirring the milling dispersion liquid. << Charge Transport Material >> As the charge transport material used in the present invention, a material known per se can be used. As the conventionally known charge transport material, various electron-withdrawing compounds and electron-donating compounds can be used.

Examples of the electron-withdrawing compound include:
Diphenoquinone derivatives such as 2,6-dimethyl-2 ′, 6′-ditert-dibutyldiphenoquinone, malononitrile, thiopyran compounds, tetracyanoethylene,
2,4,8-trinitrothioxanthone, 3,4,5,
Examples thereof include 7-tetranitro-9-fluorenone, dinitrobenzene, dinitroanthracene, dinitroacridine, nitroanthraquinone, dinitroanthraquinone, succinic anhydride, maleic anhydride and dibromomaleic anhydride.

As the electron donating compound, 2,5
-Oxadiazole compounds such as di (4-methylaminophenyl) and 1,3,4-oxadiazole, 9- (4
-Styryl compounds such as diethylaminostyryl) anthracene, carbazole compounds such as polyvinylcarbazole, pyrazoline compounds such as 1-phenyl-3- (p-dimethylaminophenyl) pyrazoline, hydrazone compounds, triphenylamine compounds, indole compounds Examples thereof include nitrogen-containing cyclic compounds such as compounds, oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, and triazole compounds, and condensed polycyclic compounds.

These charge transport materials may be used alone or in combination of two or more. When a charge transporting material having film-forming property such as polyvinylcarbazole is used,
The binder resin is not always necessary. Among these charge transport materials, it is particularly preferable to use hydrazone compounds, triphenylamine compounds, stilbene compounds and the like. << Binder Resin >> Examples of the binder resin forming the photoconductive layer 3 include styrene-based polymers, styrene-butadiene copolymers, styrene-acrylonitrile copolymers, styrene-maleic acid copolymers, and acrylic copolymers. , Styrene-acrylic acid copolymer, polyethylene,
Ethylene-vinyl acetate copolymer, chlorinated polyethylene,
Heat of polyvinyl chloride, polypropylene, vinyl chloride-vinyl acetate copolymer, polyester, polyamide, alkyd resin, polycarbonate, polyarylate, polysulfone, diallyl phthalate resin, ketone resin, polyvinyl butyral resin, polyether resin, polyurethane resin, etc. Plastic resin, silicone resin, epoxy resin, phenol resin, urea resin, melamine resin, other cross-linkable thermosetting resin, and epoxy acrylate,
Examples thereof include photo-curable resins such as urethane-acrylate. These binder resins can be used alone or in combination of two or more.

A solvent is used in the binder resin to disperse the organic charge generating pigment in the form of particles to uniformly dissolve the organic charge transporting dye. Various organic solvents can be used as the solvent. For example, alcohols such as methanol, ethanol, isopropanol and butanol, aliphatic hydrocarbons such as n-hexane, octane and cyclohexane, aromatic hydrocarbons such as benzene, toluene and xylene, dichloromethane, dichloroethane, carbon tetrachloride and chlorobenzene. Halogenated hydrocarbons such as dimethyl ether, diethyl ether, tetrahydrofuran,
Examples thereof include ethers such as ethylene glycol dimethyl ether and diethylene glycol dimethyl ether, ketones such as acetone, methyl ethyl ketone and cyclohexanone, esters such as ethyl acetate and methyl acetate, dimethylformaldehyde, dimethylformamide and dimethyl sulfoxide. These solvents may be used alone or in combination of two or more. << Preparation of Organic Solar Cell >> The above organic pigment, organic dye, binder resin and above solvent are used to prepare a coating solution using a method such as homogenizer, ultrasonic wave, ball mill, sand mill, attritor, roll mill, paint shaker, and casting. The photoconductive layer 3 is formed on the electrode 2 by laminating or dipping.

The photoconductive layer 3 may contain various additives in order to improve carrier generation, injection and transport properties. For example, diphenyl, diphenyl chloride, terphenyl, halonaphthoquinones, dibutyl phthalate, dimethyl glycol phthalate, dioctyl phthalate, triphenyl phosphoric acid, methyl naphthalene,
Acetylnaphthalene, benzophenone, chlorinated paraffin, dilauryl thiopropionate, 3,5-dinitrosalicylic acid, various fluorocarbons and the like can be mentioned.

Further, a surfactant, a leveling agent or the like may be used in order to improve the dispersibility and dyeing property of the charge transport dye or the charge generating pigment. Here, the charge generating pigment is 2 to 20 parts by weight, particularly 3 to 15 parts by weight, and the phenylenediamine compound represented by the general formula (1) is 40 to 200 parts by weight with respect to 100 parts by weight of the binder resin. And particularly preferably 50 to 150 parts by weight. The thickness of the photoconductive layer is preferably 0.1 to 2 μm, and more preferably about 0.5 μm.

[0038]

The present invention will be described in detail below with reference to examples and comparative examples. (1) Synthesis of Disazo Compound 1 To 96 ml of 10% hydrochloric acid, 7.96 g (0.023 mol) of a diamine compound represented by the following formula (A): Was maintained at -1 ° C. Then, 3.54 g (0.051 mol) of sodium nitrite dissolved in 10 ml of water was added dropwise in an ice-water bath over 30 minutes, and the mixture was further stirred for 1 hour and then left to cool. Then, 20% of 42% hydrogen borofluoride was added thereto, and the generated crystals were filtered, washed with ethanol and dried to obtain 1.02 g (0.002 g) of tetrazonium fluoroborate.
mol) and a coupler represented by the following formula (B) 1.06
g (0.004 mol) dissolved in 100 ml of N, N-dimethylformamide (DMF), and 0.35 g (0.0043 mol) of sodium acetate dissolved in 5 ml of water was kept at 17 to 21 ° C. Was added dropwise over 5 minutes. Then, after stirring for 3 hours, the formed precipitate was filtered and washed 5 times with 200 ml of DMF. Then, it was washed twice with water and dried under reduced pressure to give 1.41 g of a disazo pigment.
(Yield 81.0%) was obtained.

From the elemental analysis results of the obtained compound, it was confirmed that the following formula (C) was obtained. Elemental analysis value: Calculated value (%) as C56H38N8O6 C: 73.19 H: 4.17 N: 12.19 Analysis value (%) C: 73.39 H: 4.57 N: 11.89

[0040]

[Chemical 15]

[0041]

[Chemical 16]

[0042]

[Chemical 17]

(2) Synthesis of Disazo Compound 2 A disazo compound (D) was obtained in the same manner as in Synthesis 1, except that p-cresol was used as the coupler. When the elemental analysis of the same compound was performed, the following results were obtained. Elemental analysis value: Calculated as C36H28N6O4 (%) C: 71.04 H: 4.64 N: 1
3.81 Found (%) C: 71.21 H: 4.47 N: 1
3.77

[0044]

[Chemical 18]

(3) Synthesis of Disazo Compound (3) A disazo compound (E) was obtained in the same manner as in Synthesis 1 except that 4-hydroxyindoline was used as a coupler. When the elemental analysis of the same compound was performed, the following results were obtained. Elemental analysis value: Calculated value (%) as C30H24N10O4 C: 61.22 H: 4.11 N: 2
3.80 Measured value (%) C: 61.48 H: 4.00 N: 2
3.66

[0046]

[Chemical 19]

(4) Synthesis of Disazo Compound 4 A disazo compound (G) was obtained in the same manner as in Synthesis (1) except that (F) was used as the diamine. When the elemental analysis of the same compound was performed, the following results were obtained. Elemental analysis value: C52 H34 N8 O6 calculated value (%) C: 72.05 H: 3.95 N: 1
2.93 Found (%) C: 72.33 H: 3.76 N: 1
2.87

[0048]

[Chemical 20]

(5) Synthesis of Disazo Compound 5 A disazo compound (H) was obtained in the same manner as in Synthesis (1) except that 0.002 mol of (B) and 0.002 mol of p-cresol were used as couplers.

[0050]

[Chemical 21]

(Examples 1 to 5 and Comparative Example 1) 100 m
An aluminum electrode (light transmittance: 70%) having a thickness of 500 nm was vacuum-deposited on a glass plate of m × 100 mm. Next, as the organic charge generating pigment and the organic charge transporting dye, 10 parts by weight of each of the compounds shown in Table 1 was mixed with 10 parts by weight of polyvinyl butyral resin (Eslec BM-1, manufactured by Sekisui Chemical Co., Ltd.) and 50 parts by weight of cyclohexanone. And diameter 1mm
It was mixed and dispersed for 24 hours by a ball mill using the glass beads of. Using the spin coating method, the obtained dispersion liquid,
It was applied on the aluminum electrode and dried at 100 ° C. for 30 minutes to form a photoconductive layer having a thickness of 0.5 μm.

A 20 mm × 20 mm gold electrode was vapor-deposited thereon to a thickness of 2000 Å. An organic solar cell was obtained by the above steps. (Evaluation Test) Open circuit voltage VOC (V), short circuit current ISC (mA) and maximum photoelectric conversion efficiency EMAX (%) when adding 1 kΩ of the organic solar cells obtained in Examples 1 to 5 and Comparative Example 1. Was measured under the following conditions.

Light source: Tungsten lamp Light intensity: 200 lux The test results are also shown in Table 1. The chemical structural formulas (I) of the organic dyes shown in Table 1 and the structural formulas (J) of the organic pigments used in Comparative Examples are shown below.

[0054]

[Table 1]

[0055]

[Chemical formula 22]

[0056]

[Chemical formula 23]

From these test results, the organic solar cells of the present invention were found to have an open circuit voltage VOC
(V), short circuit current ISC (mA) and 1
The maximum photoelectric conversion efficiency EMAX (%) when kΩ is added shows a better value than that of the conventional organic solar cell. Further, compared with the conventional organic solar cell, it has excellent stability against light, so that stable characteristics can be obtained during continuous use.

[0058]

As is apparent from the above description, according to the present invention, an organic solar cell having excellent photoelectric conversion efficiency and stable characteristics during continuous use can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an organic solar cell that is an embodiment of the present invention.

[Explanation of reference symbols] 1 substrate 2 electrode 3 photoconductive layer 4 transparent electrode

Claims (1)

[Claims] 1. An organic solar cell in which a photoconductive layer containing a charge generating pigment and a charge transporting material is provided between two electrodes, wherein the charge generating pigment has the following general formula (1): An organic solar cell which is a compound represented. [Chemical 1] (In the formula, R 1 and R 2 are the same or different and each represents a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, or an aromatic group which may have a substituent, m, n independently represents an integer of 0 to 2, and A and B
Are the same or different and represent a coupler residue. )