TW201429025A - Organic thin film solar cell - Google Patents

Abstract

An object of the present invention is to provide an organic thin film solar cell material having high charge mobility, solvent solubility, oxidation stability, and good film forming properties, and an organic thin film solar cell using the same. The solution of the present invention is to use an organic thin film solar cell material represented by the following general formula (1) in an n-type semiconductor in an organic thin film solar cell having at least a positive electrode, a p-type semiconductor layer, an n-type semiconductor layer, and a negative electrode. Layer of organic thin film solar cells. In the formula, L is a divalent linking group selected from an ethylene diyl group, an acetylene diyl group, or an aromatic group. □

Description

Organic thin film solar cell

The present invention relates to an organic thin film solar cell obtained using a novel organic thin film solar cell material.

In general, in semiconductor devices using inorganic semiconductor materials, in the formation of thin films, high-temperature processes and high-vacuum processes are necessary. Since a high-temperature process is required, it is impossible to form a film on a plastic substrate or the like, and it is difficult to impart flexibility or light weight to a product incorporating a semiconductor element. Moreover, since a high vacuum process is required, it is difficult to increase the area and cost of a product incorporating a semiconductor element.

Therefore, in recent years, research has been conducted on an organic semiconductor device (for example, an organic electroluminescence (organic EL) device, an organic thin film transistor device, or an organic thin film solar cell) using an organic semiconductor material as an organic electronic component. Compared with inorganic semiconductor materials, these organic semiconductor materials are significantly reduced in process temperature of the fabrication apparatus, making it possible to form on a plastic substrate or the like. Further, by using an organic semiconductor material having an improved solubility in a solvent and having good film formability, a coating method without a vacuum process is required, for example, a film is formed using an inkjet device or the like. As a result, it has been expected that the use of a semiconductor element based on an inorganic semiconductor material is difficult to achieve a large area and a low cost. As described above, compared with inorganic semiconductor materials, organic semiconductor materials are advantageous for large-area, flexible, lightweight, low-cost, etc., and applications for organic semiconductor products that produce such characteristics are, for example, expected to be information labels. Applications such as large-area sensors such as electronic artificial skin sheets or sheet-type scanners, displays such as liquid crystal displays, electronic papers, solar cells, and organic EL panels.

On the other hand, solar cells are the background of the problem of the depletion of fossil fuels or the problem of global warming. The green energy source that can be used as a solution strategy has been attracting attention in recent years and is actively conducting research and development. The principle of driving a solar cell is to convert an optical signal into an electrical signal by using a semiconductor material. Up to now, as an inorganic semiconductor material, a lanthanide solar cell such as a single crystal ruthenium, a polycrystalline ruthenium or an amorphous ruthenium has been put into practical use. . However, since the lanthanide solar cells are high in price or insufficient in raw materials, development of next generation solar cells is expected. In order to obtain an inorganic semiconductor material such as ruthenium, it is necessary to have a high vacuum and a high temperature process, and this is the reason why the price of the solar cell is so high. Therefore, in place of a lanthanide semiconductor, an organic thin film solar cell using an organic semiconductor has been attracting attention as a solar cell of the next generation, and various studies are being conducted.

At the beginning, organic thin film solar cells have been studied for single-layer films such as anthocyanin pigments, but since they have been found to be p-type by n-type semiconductor layers and transport holes formed by n-semiconductor materials for transporting electrons. Multilayer film of p-type semiconductor layer formed by semiconductor material, improving light After inputting the conversion efficiency (photoelectric conversion efficiency) of the power output, the multilayer film has become the mainstream. The materials used in the beginning of the multilayer film research were copper phthalocyanine (CuPc) as a p-type semiconductor material and quinone imine (PTCBI) as an n-type semiconductor material. On the other hand, an organic thin film solar cell using a polymer is mixed and heat-treated by using a conductive polymer as a p-type semiconductor material and a fullerene (C60) derivative as an n-type semiconductor material. Inducing microlayer separation increases the heterogeneous interface, and the photoelectric conversion efficiency is improved, that is, the so-called bulk hetero structure is mainly studied. The material system that has been used herein is mainly a poly-3-hexylthiophene (P3HT) as a p-type semiconductor material and a C60 derivative (PCBM) as an n-type semiconductor material.

Thus, in the organic thin film solar cell, the material of each layer has not progressed from the beginning, so a phthalocyanine derivative, a quinone imine derivative, and a C60 derivative are still used. Accordingly, the photoelectric conversion efficiency should be improved, and in place of these conventional materials, development of novel materials is eagerly desired. In general, p-type and n-type semiconductor materials which are preferred for organic thin film solar cells require atmospheric stability or high charge mobility characteristics and high light absorption characteristics in the visible light region. In order to absorb in the visible light region of the organic compound, it is known that the long wavelength is increased by the maximum absorption wavelength of the π-electron conjugated structure. However, if the molecular weight of the expanded conjugated system is excessively increased, the solubility in the solvent is lowered to make the purification difficult, and the sublimation temperature is raised to make it difficult to sublimate and purify. Therefore, research has been conducted to improve the efficiency by increasing the wavelength of the absorption wavelength while suppressing a certain molecular weight. Moreover, the improvement of atmospheric stability or the improvement of the charge transport barrier by the control of the highest occupied orbital energy level and the lowest empty orbital energy level of the semiconductor material has been reviewed, and the expansion of the π -conjugated structure of the semiconductor material is improved. Charge transfer characteristics. As a result, a polyacene is developed as a p-type semiconductor material (see Patent Documents 1 to 3 and Non-Patent Documents 1 and 2). On the other hand, although the above review has progressed in the development of n-type semiconductor materials, the results are limited to quinone derivatives or C60 derivatives, and the development of novel derivatives has not been completed. Furthermore, the result is not to give a satisfactory conversion efficiency (see Patent Documents 4 to 5 and Non-Patent Documents 1 to 2). On the other hand, the development of n-type semiconductor materials for the purpose of utilizing in the field of organic electro-crystals is almost centered on quinone derivatives or C60 derivatives, and recently, diphenyls having electron-attracting groups have been reported. The ethylene derivative exhibits a high charge mobility characteristic, but the possibility of the organic thin film solar cell of this derivative is not known (refer to Patent Document 6).

[Previous Technical Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2007-335760

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2008-34764

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2008-91380

[Patent Document 4] WO2007/093643

[Patent Document 5] WO2007/129768

[Patent Document 6] WO2010/101224

[Non-Patent Document 1] Chemical Engineering, Vol. 56, No. 3, pp206~210 (2011)

[Non-Patent Document 2] Polymer Reviews, Vol. 48, pp423~431 (2008)

[Summary of the Invention]

The present invention has an object of providing an organic thin film solar cell using an organic thin film solar cell material which solves the problems of the prior art as described above.

As a result of intensive studies, the present inventors have found that an organic thin film solar cell exhibiting high conversion efficiency is obtained by using the compound of the general formula (1) in an n-type semiconductor layer of an organic thin film solar cell, and completed the present invention.

The present invention relates to an organic thin film solar cell characterized by being an organic thin film solar cell having at least a positive electrode, a p-type semiconductor layer, an n-type semiconductor layer, and a negative electrode, and an organic thin film solar energy represented by the following general formula (1) The battery material is used in an n-type semiconductor layer.

Wherein L represents a divalent linking group selected from the group consisting of substituted or unsubstituted ethylene diyl, acetylene diyl, and substituted or unsubstituted aromatic groups, and R ¹ represents a carbon number of 2 a fluorenyl group of ~12, a cyano group, or a fluorine-substituted alkyl group having 1 to 12 carbon atoms, and R ² represents a halogen atom, a cyano group, or a fluorenyl group having 2 to 12 carbon atoms. m and n independently represent an integer of 1 to 5, and when m and n are 2 or more, L and R ¹ may be the same or different.

In the above general formula (1), it is preferred that m is 1 to 4, n is 1, or R ² is a cyano group. Further, in the above general formula (1), L is selected from the group consisting of a substituted or unsubstituted ethylene diyl group or a benzene, naphthalene, anthracene, thiophene, thienothiophene, furan, pyrrole and thiazole. The substituted or unsubstituted aromatic group is preferred.

Further, in the above general formula (1), R ¹ is preferably a fluorenyl group having 2 to 6 carbon atoms, a cyano group or a fluorine-substituted alkyl group having 1 to 6 carbon atoms, R ² is a cyano group, and m and n are An integer from 1 to 5. Further, in the above general formula (1), R ¹ is preferably a fluorine-substituted alkyl group having 1 to 3 carbon atoms, R ² is a cyano group, and m and n are integers of 1 to 2.

The material of the n-type semiconductor layer used in the organic thin film solar cell of the present invention has a conjugated structure diffused in the entire molecular structure, and its molecular orbital also diffuses throughout the molecular structure. The three-dimensional structure is characterized by high planarity, which makes the encapsulation between the molecules tight, and the result is a high charge mobility characteristic. Further, since it has characteristics such as high stability to air or moisture, when this material is used for an organic thin film solar cell, an organic thin film solar cell exhibiting a high conversion efficiency is made possible, and its technical value is extremely large.

7‧‧‧Substrate

8‧‧‧ positive

9‧‧‧p-type semiconductor layer

10‧‧‧n type organic semiconductor material layer

11‧‧‧negative

12‧‧‧ Mixed layer of p-type semiconductor layer and n-type semiconductor layer

Fig. 1 is a cross-sectional view showing a structural example of an organic thin film solar cell.

Fig. 2 is a cross-sectional view showing another structural example of an organic thin film solar cell.

The material used for the n-type semiconductor layer of the organic thin film solar cell of the present invention is a compound represented by the general formula (1).

In the general formula (1), L represents a divalent linking group, and is a substituted or unsubstituted ethylenediyl group, an acetylenediyl group, or a substituted or unsubstituted aromatic group. The equivalent is an ethylene diyl, substituted or unsubstituted aromatic group.

When L is a substituted or unsubstituted aromatic group, the aromatic group may be an aromatic hydrocarbon group, a condensed aromatic hydrocarbon group, an aromatic heterocyclic group or a condensed aromatic heterocyclic group. The aromatic group is preferably in the range of 3 to 30 carbon atoms, and more preferably in the range of 3 to 18 carbon atoms. Specific examples of the unsubstituted aromatic group include benzene, naphthalene, phenanthrene, anthracene, pyrene, anthracene, and the like. (chrysene), thick pentacene, brown , thick tetraphenyl, triphenylene, picene, thiophene, furan, pyrrole, pyrazole, imidazole, triazole, oxazole, thiazole, thiadiazole, pyridine, pyrimidine, triazine, pyrazine, hydrazine, Anthraquinone, carbazole, benzothiophene, benzofuran, thienothiophene, Thiazolothiazole, dibenzothiophene, dibenzofuran, dithienothiophene, benzimidazole, benzoxazole, anthraquinone An aromatic compound such as Benzo-thieno benzothiophene, dibenzobenzofuran, acridine or quinoline removes two hydrogen atoms to form a divalent group. Preferably, a divalent group derived from the removal of two hydrogens from benzene, naphthalene, anthracene, thiophene, thienothiophene, furan, pyrrole or thiazole is mentioned.

The acetylene diyl group, the ethylene diyl group, and the aromatic group may have a substituent, and the substituent thereof is not particularly limited, although the performance of the solar cell material is not particularly limited, but the total number of substituents is preferably 0 to 4, more preferably 0~2. Preferred examples of the ethylene diyl group include a halogen atom such as fluorine, chlorine or bromine, an alkyl group having 1 to 12 carbon atoms, a fluorine-substituted alkyl group having 1 to 12 carbon atoms, and an alkoxycarbonyl group having 2 to 12 carbon atoms. , a fluorenyl group having 2 to 12 carbon atoms, a fluorinated fluorenyl group having 2 to 12 carbon atoms, an alkylsulfonyl group having 1 to 12 carbon atoms, an alkoxysulfonyl group having 1 to 12 carbon atoms, and a carbon number of 1~ A fluorinated alkylsulfonyl group of 12, an alkylaminocarbonyl group having 2 to 12 carbon atoms, a fluorinated alkylaminocarbonyl group having 2 to 12 carbon atoms, a nitro group, a cyano group or the like. More preferably, it is a halogen atom such as fluorine, chlorine or bromine, an alkyl group having 1 to 12 carbon atoms, a fluorine-substituted alkyl group having 1 to 12 carbon atoms, a fluorenyl group having 2 to 12 carbon atoms, and a fluorinated fluorene having 2 to 12 carbon atoms. A group, an alkylsulfonyl group having 1 to 12 carbon atoms, a fluorinated alkylsulfonyl group having 1 to 12 carbon atoms, a nitro group, and a cyano group.

The ethylene diradical system is represented by -CH=CH-. The acetylene diradical system is represented by -C≡C-. The H group of the ethylene diradical is obtained by substituting the above substituent.

In the general formula (1), R ¹ represents a fluorenyl group having 2 to 12 carbon atoms, a cyano group, or a fluorine-substituted alkyl group having 1 to 12 carbon atoms. The fluorenyl group having 2 to 12 carbon atoms may have fluorine as a substituent. Preferably, it is a cyano group, a fluorine-substituted alkyl group having 1 to 6 carbon atoms, or a fluorenyl group having 2 to 6 carbon atoms, more preferably a fluorine-substituted alkyl group having 1 to 3 carbon atoms.

In the general formula (1), R ² represents a halogen atom, a fluorenyl group having 2 to 12 carbon atoms, or a cyano group. Examples of the halogen atom include fluorine, chlorine, and bromine. The fluorenyl group having 2 to 12 carbon atoms may have fluorine as a substituent. It is preferably a cyano group and a fluorenyl group having 2 to 12 carbon atoms, more preferably a cyano group.

In the general formula (1), m and n represent an integer of 1 to 5. Preferably, m is an integer from 1 to 4, and n is preferably 1. When m and n are 2 or more, m or n of L or R ¹ may be the same or different from each other.

A better organic thin film solar cell material used for the n-type semiconductor layer of the organic thin film solar cell is a general formula (1), and R ¹ is a fluorenyl group having 2 to 6 carbon atoms, a cyano group, or a fluorine having 1 to 6 carbon atoms. Substituting an alkyl group, R ² is a cyano group, and m and n are compounds having an integer of from 1 to 5. More preferably, R ¹ is a fluorine-substituted alkyl group having 1 to 3 carbon atoms, R ² is a cyano group, and m and n are a compound of an integer of 1 to 2.

The specific examples of the compound represented by the general formula (1) are shown below, but the compounds of the present invention are not limited thereto.

The compound represented by the general formula (1) is a reaction scheme of the following formula, which can be subjected to a Kernevenagel reaction by reacting an aromatic substituted active methylene compound with a dialdehyde in the presence of a basic catalyst (Knoevenagel Condensation reaction).

In the formula, L, R ¹ , R ² , m, and n have the same meanings as in the general formula (1).

Moreover, the compound represented by the general formula (1) can be produced by the production method described in Patent Document 6. When the compound described in Patent Document 6 is contained in the compound represented by the general formula (1), the compounds are also used as the organic thin film solar cell material used in the n-type semiconductor layer of the organic thin film solar cell of the present invention.

The structure of the organic thin film solar cell of the present invention will be described with reference to the drawings, but the structure of the organic thin film solar cell of the present invention is not limited to any of the figures.

1 and 2 are cross-sectional views showing a structural example of a general organic thin film solar cell used in the present invention. In Fig. 1, each indicates that 7 is a substrate, 8 is a positive electrode, 9 is a p-type semiconductor layer, 10 is an n-type semiconductor layer, and 11 is a negative electrode. Further, in Fig. 2, 7, 8, and 11 are the same as those in Fig. 1, and 12 is a mixed layer of a p-type semiconductor layer and an n-type semiconductor layer.

The substrate of the organic thin film solar cell is not particularly limited, and for example, a conventionally known one can be used. It is preferable to use a glass substrate or a transparent resin film which has mechanical and thermal strength and has transparency. Examples of the transparent resin film include polyethylene, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polypropylene, polystyrene, polymethyl methacrylate, polyvinyl chloride, polyvinyl alcohol, and polyethylene. Butyral, nylon, polyetheretherketone, polyfluorene, polyether oxime, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, poly Fluorine, tetrafluoroethylene-ethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polychlorotrifluoroethylene, polyvinylidene fluoride, polyester, polycarbonate, polyurethane, polyimine , polyether phthalimide, polyimine, polypropylene and the like.

As the electrode material, a conductive material having a large work function is used for the electrode on one side, and a conductive material having a small work function is preferably used for the electrode on the other side. An electrode using a conductive material having a large work function is defined as a positive electrode. As a conductive material having a large work function, in addition to metals such as gold, platinum, chromium, and nickel, it is preferable to use a metal oxide such as indium or tin having transparency, and a composite metal oxide (indium tin oxide (ITO)). , indium zinc oxide (IZO), etc.). Here, the conductive material used for the positive electrode is preferably an ohmic contact with the organic semiconductor layer. Further, when a hole transport layer to be described later is used, the conductive material used for the positive electrode is preferably in ohmic contact with the hole transport layer.

An electrode using a conductive material having a small work function is defined as a negative electrode, and as the conductive material having a small work function, an alkali metal or an alkaline earth metal is used, specifically, lithium, magnesium, and calcium. Further, tin or silver or aluminum is preferably used. Further, it is preferable to use an alloy formed of the above-described metal or an electrode made of the above-described metal laminate. Further, by introducing a metal fluoride such as lithium fluoride or cesium fluoride at the interface between the negative electrode and the electron transporting layer, the discharge current can be increased. Here, the conductive material used for the negative electrode is preferably in ohmic contact with the organic semiconductor layer. Further, when an electron transport layer to be described later is used, the conductive material used for the negative electrode is preferably in ohmic contact with the electron transport layer.

-n type semiconductor layer -

The n-type semiconductor layer is formed using an organic thin film solar cell material (also referred to as an organic thin film solar cell material of the present invention) represented by the general formula (1). As the n-type semiconductor layer, one type or two or more types of the organic thin film solar cell materials of the general formula (1) can be used. Further, in addition to the organic thin film solar cell material of the general formula (1), other n-type organic semiconductor materials may be used in combination.

Examples of other n-type organic semiconductor materials include 1,4,5,8-naphthalenetetracarboxylic acid dianhydride (NTCDA), 3,4,9,10-decanetetracarboxylic acid dianhydride (PTCDA), and 3. 4,9,10-nonanedicarboxylic acid dibenzimidazole (PTCBI), N,N'-dioctyl-3,4,9,10-naphthyltetracarboxydiimide (PTCDI-C8H), 2 -(4-biphenyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole (PBD), 2,5-di(1-naphthyl)-1,3 , an oxazole derivative such as 4-oxadiazole (BND), 3-(4-biphenyl)-4-phenyl-5-(4-t-butylphenyl)-1,2,4- a triazole derivative such as triazole (TAZ), a phenanthroline derivative, a phosphine oxide derivative, or a fullerene compound (initially C60, C70, C76, C78, C82, C84, C90, C94 unsubstituted, And [6,6]-phenyl C61 butyric acid methyl ester ([6,6]-PCBM), [5,6]-phenyl C61 butyric acid methyl ester ([5,6]-PCBM), [6, 6]-phenyl C61 butyrate hexyl ester ([6,6]-PCBH), [6,6]-phenyl C61 butyrate dodecyl ester ([6,6]-PCBD), phenyl C71 butyrate Ester (PC70BM), phenyl C85 methyl butyrate (PC84BM), etc., carbon nanotubes (CNT), and the like.

-p type semiconductor layer -

The p-type semiconductor layer uses one or more p-type organic semiconductor materials. For example, examples of the well-known p-type organic semiconductor material include a polythiophene-based polymer, a benzothiadiazole-thiophene-based derivative, a benzothiadiazole-thiophene-based copolymer, and a poly-p-phenylene-extended ethylene. Base polymer, poly-p-phenylene polymer, polyfluorene polymer, polypyrrole polymer, polyaniline polymer, polyacetylene polymer, polythiophene vinylene polymer, etc. a conjugated polymer or a phthalocyanine derivative such as H2 phthalocyanine (H2Pc), copper phthalocyanine (CuPc) or zinc phthalocyanine (ZnPc), a purple derivative, N,N'-diphenyl-N, N'-bis(3-methylphenyl)-4,4'-diphenyl-1,1'-diamine (TPD), N,N'-dinaphthyl-N,N'-diphenyl a triarylamine derivative such as -4,4'-diphenyl-1,1'-diamine (NPD) or a carbazole such as 4,4'-bis(carbazol-9-yl)biphenyl (CBP) A low molecular organic compound such as a derivative or an oligothiophene derivative (trithiophene, tetrathiophene, hexathiophene, octathiophene, etc.).

The other n-type organic semiconductor material or p-type organic semiconductor material may be a known compound, or may be a novel compound found in a novel n-type organic semiconductor material or a p-type organic semiconductor material.

Moreover, it is preferable to mix the n-type organic semiconductor material and the p-type organic semiconductor material formed by the organic thin film solar cell material of the present invention. In this case, the p-type organic semiconductor material and the n-type organic semiconductor material are preferably phased. Separation. The size of the phase separation structure is not particularly limited, but is usually 1 nm or more and 50 nm or less. Layer When the p-type organic semiconductor material and the n-type organic semiconductor material are combined, it is preferable that a layer having a p-type organic semiconductor material exhibiting p-type semiconductor characteristics is a positive electrode side, and a layer having an n-type organic semiconductor material exhibiting n-type semiconductor characteristics is Negative side. The organic semiconductor layer is preferably 5 nm to 500 nm thick, more preferably 30 nm to 300 nm. When laminating, the layer containing the n-type organic material of the present invention preferably has a thickness of from 1 nm to 400 nm, more preferably from 15 nm to 150 nm.

In the organic thin film solar cell of the present invention, a hole transport layer may be provided between the positive electrode and the p-type semiconductor layer. As a material for forming the hole transport layer, a conductive polymer such as a polythiophene polymer, a poly-p-phenylene vinyl polymer or a polyfluorene polymer, or a phthalocyanine derivative is preferably used. A low molecular organic compound exhibiting p-type semiconductor characteristics such as H2Pc, CuPc, ZnPc, etc., or a purple derivative. In particular, polyethylene dioxythiophene (PEDOT) using polythiophene-based polymer or polystyrene sulfonate (PSS) added to PEDOT is preferred. The hole transport layer preferably has a thickness of 5 nm to 600 nm, more preferably 30 nm to 200 nm.

Further, in the organic thin film solar cell of the present invention, an electron transport layer may be provided between the n-type semiconductor layer and the negative electrode. The material for forming the electron transport layer is not particularly limited, but an organic thin film solar cell material as shown in the general formula (1) or the above-described n-type organic semiconductor material (NTCDA, PTCDA, PTCDI-) is preferably used. An organic material having N-type semiconductor characteristics of C8H, an oxazole derivative, a triazole derivative, a phenanthroline derivative, a phosphine oxide derivative, a fullerene compound, CNT, CN-PPV, or the like. The electron transport layer preferably has a thickness of 5 nm to 600 nm, more preferably 30nm~200nm.

Further, the organic thin film solar cell of the present invention can form an in-line bonding by laminating (serializing) two or more organic semiconductor layers through one or more intermediate electrodes. For example, a laminated structure of a substrate/positive electrode/first p-type semiconductor layer/first n-type semiconductor layer/intermediate electrode/second p-type semiconductor layer/second n-type semiconductor layer/negative electrode can be cited. By performing such lamination, the open voltage can be increased. Further, the hole transporting layer may be provided between the positive electrode and the first p-type semiconductor layer and between the intermediate electrode and the second p-type semiconductor layer, and may be between the first n-type semiconductor layer and the intermediate electrode, and The electron transport layer described above is provided between the 2 n-type semiconductor layer and the negative electrode.

The material for the intermediate electrode used herein is preferably one having high conductivity, and examples thereof include metals such as gold, platinum, chromium, nickel, lithium, magnesium, calcium, tin, silver, aluminum, etc., or transparent. a metal oxide such as indium or tin, a composite metal oxide (indium tin oxide (ITO), indium zinc oxide (IZO), etc.), an alloy formed of the above metal or a laminate of the above metals , polyethylene dioxythiophene (PEDOT) or PEDOT added polystyrene sulfonate (PSS), and the like. Although the intermediate electrode is preferably light-transmitting, even if the material having a low light transmittance is thin, the film thickness can be reduced to ensure sufficient light transmittance.

For the formation of p-type and n-type semiconductor layers, spin coating, knife coating, slot die coating, screen printing coating, bar coating, stencil coating, printing transfer method, and impregnation method can be used. , any method such as inkjet method, spray method, vacuum evaporation method, etc., to select film thickness control or alignment control The method of forming the characteristics of the organic semiconductor layer may be used.

The organic thin film solar cell material of the present invention has high charge mobility, solvent solubility, oxidation stability, and good film forming properties, and the organic thin film solar cell using the same also exhibits high characteristics.

[Examples]

The present invention is not limited by the examples, and the present invention is not limited thereto, and may be embodied in various forms without departing from the spirit and scope of the invention. Further, the compound number corresponds to the number attached to the above chemical formula.

Synthesis Example 1

The compound (100) was synthesized in accordance with the following reaction formula.

To a 500 ml three-necked flask under nitrogen atmosphere, 1.7 g (10 mmol) of 2,5-difluoro-terephthalaldehyde, 3.7 g (20 mmol) of 4-trifluoromethylphenylacetonitrile, and ethanol (100 ml) were stirred at room temperature. . Thereto, a solution of 68 mg (1 mmol) of sodium ethoxide in ethanol (10 ml) was added dropwise over 5 minutes. After the dropwise addition, the mixture was further stirred for 2 hours, and then the reaction solution was ice-cooled. After 1 hour, the reaction solution was filtered. The obtained crystal is methanol After washing with 10 ml, it was dried under reduced pressure (18 hours) at 50 ° C to obtain 4.8 g of a yellow solid compound (100).

Example 1

An organic thin film solar cell having the structure shown in Fig. 2 was prepared, and the characteristics of the organic thin film solar cell material of the present invention were evaluated. First, the glass substrate of the patterned ITO electrode (100 nm) was ultrasonically washed in isopropyl alcohol and dried. Further, in order to remove the organic pollutants on the surface of the ITO electrode, UV ozone treatment is performed. Next, it was applied onto an ITO substrate by rotating (4000 rpm, 30 seconds) PEDOT (3,4-ethylenedioxythiophene)/PSS (polystyrenesulfonic acid) aqueous solution (trade name: Baytron P (standard)). After drying at 120 ° C for 1 hour, P3HT (poly(3-hexylthiophene), Regioregular, Mw ~ 87000, Aldrich) (0.5% by weight) was used as a p-type material, and the organic film of the present invention as an n-type material was used. The solar cell material compound (100) (0.5% by weight) was dissolved in tetrahydrofuran, and the organic semiconductor layer was formed by spinning (1000 rpm, 30 seconds). The film thickness of the organic photoelectric conversion layer obtained by the stylus type film thickness meter was 83 nm. On the organic semiconductor layer of the p-type material and the n-type material thus obtained, the thickness of LiF was 6 nm and the thickness of aluminum was 80 nm by vacuum deposition to form a metal electrode, which became an organic thin film solar cell.

Thus the effective area that are intended 0.04cm ² of the organic thin film solar cell, arising from the irradiation of a solar simulator as a light source (1.5G air mass spectrum, the irradiation intensity of 100mW / cm ²⁾ to evaluate suspected sunlight characteristics thereof ( Open voltage, short circuit current density, form factor, conversion efficiency). Here, the open voltage is a voltage between the positive and negative electrodes of the solar cell in an unloaded state. The short-circuit current density is a value obtained by dividing a current (short-circuit current) between a positive electrode and a negative electrode of a solar cell by an effective light-receiving area. The shape factor is the product of the current value and the voltage value at the operating point at which the maximum output power is applied, divided by the value of the product of the open voltage value and the short-circuit current, preferably closer to one. The conversion efficiency is obtained by multiplying the open voltage with the short-circuit current density and the shape factor, and is preferably larger.

As a result of the evaluation, an excellent value of an open voltage of 0.68 V, a short-circuit current density of 8.4 mA/cm ² , a shape factor of 0.62, and a conversion efficiency of 3.5% was obtained.

Synthesis Example 2

In Example 1, except that the substituted 2,5-difluoro-terephthalaldehyde was changed to terephthalaldehyde, the same operation was carried out to obtain 3.8 g of a yellow solid compound (500).

Synthesis Example 3

In Example 1, except that 2,5-difluoro-terephthalaldehyde was used instead of 2,2'-bisthiophene-5,5'-dialdehyde, the same operation was carried out to obtain 4.2 g of yellow. Solid compound (200).

Synthesis Example 4

In Example 1, in addition to replacing 2,5-difluoro-terephthalaldehyde In the same manner as 2,6-thienothiophene dialdehyde, 4.5 g of an orange solid compound (300) was obtained by the same operation.

Synthesis Example 5

In Example 1, except that 2,5-difluoro-terephthalaldehyde was used instead of 2,5-thiophenedialdehyde, the same operation was carried out to obtain 4.5 g of an orange solid compound (201).

Synthesis Example 6

In Example 1, except that the substituted 2,5-difluoro-terephthalaldehyde was changed to 4,4'-biphenyldialdehyde, the same operation was carried out to obtain 4.9 g of a compound as a white solid ( 501).

Example 2~6

In Example 2, the same procedure was carried out except that the compound (500) was used instead of the compound (500), (200), (300), (201), or (501). The results are shown in Table 1.

Comparative example 1

In Example 2, the evaluation of the obtained organic thin film solar cell was carried out except that the substitution compound (100) was changed to the same operation as [6, 6]-PCBM. The result was an open voltage of 0.6 V, a short-circuit current density of 5.3 mA/cm ² , a shape factor of 0.45, and a conversion efficiency of 1.4%.

As described above, by comparing Example 2 with Comparative Example 1, it is understood that the structure represented by the general formula (1) has a high characteristic as an organic thin film solar cell material.

7‧‧‧Substrate

8‧‧‧ positive

9‧‧‧p-type semiconductor layer

10‧‧‧n type organic semiconductor material layer

11‧‧‧negative

Claims (7)

An organic thin film solar cell characterized in that an organic thin film solar cell having the following general formula (1) is used in an organic thin film solar cell having at least a positive electrode, a p-type semiconductor layer, an n-type semiconductor layer, and a negative electrode; N-type semiconductor layer; Here, L represents a divalent linking group selected from a group of a free substituted or unsubstituted ethylene diyl group, an acetylene diyl group, and a substituted or unsubstituted aromatic group, and R ¹ represents a carbon number of 2 ~12 fluorenyl, cyano, or a fluorine-substituted alkyl group having 1 to 12 carbon atoms; R ² represents a halogen atom, a cyano group, or a fluorenyl group having 2 to 12 carbon atoms, and m and n independently represent an integer of 1 to 5 When m and n are 2 or more, L and R ¹ may be the same or different. The organic thin film solar cell of claim 1, wherein m is an integer of 1 to 4. The organic thin film solar cell of claim 1, wherein n is 1. The organic thin film solar cell of claim 1, wherein R ² is a cyano group. An organic thin film solar cell according to claim 1, wherein L is a hydrogen atom removed from a substituted or unsubstituted ethylenediyl group, or a benzene, naphthalene, anthracene, thiophene, thienothiophene, furan, pyrrole or thiazole Replace or not Substituted aromatic group. The organic thin film solar cell of claim 1, wherein R ¹ is a fluorenyl group having 2 to 6 carbon atoms, a cyano group, or a fluorine-substituted alkyl group having 1 to 6 carbon atoms, R ² is a cyano group, and m and n are 1~. An integer of 5. The organic thin film solar cell of claim 6, wherein R ¹ is a fluorine-substituted alkyl group having 1 to 3 carbon atoms, and m and n are integers of 1 to 2.