JP2006032636A - Organic solar cell and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic solar cell for improving photoelectric conversion efficiency and simplifying manufacturing. <P>SOLUTION: This organic solar cell is formed with a photoelectric conversion layer 107 having bulk a heterojunction formed of at least a first organic material 103 and a second organic material 104, and a pair of electrodes 102 and 105 by which the photoelectric conversion layer 107 is interposed. At least either the first organic material 103 or the second organic material 104 of the photoelectric conversion layer 107 is constituted as a conductive polymer, and one end of the conductive polymer is chemically connected to one electrode 102. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an organic solar cell, and more particularly to a solar cell using charge separation by bulk heterojunction using different organic materials and a method for manufacturing the solar cell.

Solar cells using organic semiconductors are versatile, have low toxicity, good workability and productivity, can be reduced in cost by mass production, are easily flexible, and have a wide range of use. It has excellent features.
Two main types of organic solar cells are currently being studied. One is a pn-junction organic solar cell in which different organic materials are sequentially stacked on the substrate, imitating the inorganic solar cell system, and the other is a mixture of two organic materials that take advantage of the unique properties of organic materials. It is a bulk heterojunction type organic solar cell formed into a film.

Since bulk heterojunction organic solar cells are mixed with different organic materials, the junction area between the two organic materials is wide, and the region where charges are separated is also wide.
A solar cell using a mixed film of poly [(2-methoxy-5- (2′ethylhexyloxy) 1-4-phenylenevinylene], a fullerene derivative of polyphenylene vinylene which is a conductive polymer (US Pat. No. 5,331,183) Description (Patent Document 1)) and poly [(2-methoxy-5- (2′ethylhexyloxy) 1-4-phenylenevinylene] and poly [2-methoxy-5- (2′-ethylhexyloxy)] Of 1,4- (1-cyanovinylene) phenylene] (G. Yu and AJ Heeger, Appl. Phys. Lett. Vol. 78, p4510 (non-patent document 1)) Such a bulk heterojunction solar cell has also been proposed.

  However, in the bulk heterojunction solar cell, carriers separated by charge in the photoelectric conversion layer move to the electrode through an intermolecular hopping process, so it is difficult for the carrier to reach the electrode, and it reaches the electrode. There is a high probability of being deactivated before. Further, the contact resistance between the physically contacting organic layer and the electrode is large. From the above, there is a problem that the energy conversion efficiency is low.

US Pat. No. 5,331,183 G. Yu and A.J. J. et al. Heeger, Appl. Phys. Lett. Vol. 78, p4510

  This invention is made | formed in view of said problem, and makes it a subject to provide the organic solar cell which enables the improvement of photoelectric conversion efficiency, and easy manufacture, and its manufacturing method.

According to the present invention, it comprises a photoelectric conversion layer having a bulk heterojunction formed of at least a first organic material and a second organic material, and a pair of electrodes sandwiching the photoelectric conversion layer, the photoelectric conversion layer comprising An organic solar cell in which at least one of the first organic material and the second organic material is a conductive polymer, and the conductive polymer is chemically bonded to one of the pair of electrodes. Is provided.
According to another aspect, the present invention includes a step (a) of forming a first electrode on a substrate, and a conductive polymer having a functional group at a terminal at a surface functional group of the first electrode. A step (b) of chemically bonding the functional groups of the first organic material to form a film of the first organic material; and a second organic material in contact with the first organic material to form a first organic material A method for producing an organic solar cell, comprising: a step (c) of forming a photoelectric conversion layer in a state where a material and the second organic material are mixed; and a step (d) of forming a second electrode on the photoelectric conversion layer. Or
A step (a) of forming a first electrode on a first substrate; and the first organic material comprising a conductive polymer having a first functional group at a terminal at a first surface functional group of the first electrode. A step (b) for chemically bonding one functional group, a step (e) for forming a second electrode on the second substrate, and a second functional group at the end of the second surface functional group of the second electrode. A step (f) of chemically bonding the second functional group of the second organic material made of a conductive polymer having a step, and a step (g) of bonding the first substrate and the second substrate. A step (h) of sealing between the first substrate and the second substrate except for a part, and a step of injecting a solvent into the photoelectric conversion layer from an unsealed portion between the first substrate and the second substrate There is provided a method for producing an organic solar cell, comprising (i) and a step (j) for volatilizing the solvent from a functional layer.

According to the organic solar cell of the present invention, since the conductive polymer forming the photoelectric conversion layer and the electrode are chemically bonded, the carriers generated in the photoelectric conversion layer move smoothly to the electrode. In addition, the contact resistance between the conductive polymer and the electrode can be reduced. Therefore, while having a large charge separation region, the carrier extraction efficiency is also increased, and the photoelectric conversion efficiency is improved.
According to the method for manufacturing an organic solar cell of the present invention, at least one of the first organic material and the second organic material is a conductive polymer, and the terminal of the conductive polymer is chemically connected to one electrode. Organic solar cells having bulk heterojunctions that are bonded together can be easily produced.
According to another method for manufacturing an organic solar cell of the present invention, both the first organic material and the second organic material are conductive polymers, and one terminal of the conductive polymer is connected to one electrode. An organic solar cell having a bulk heterojunction that is chemically bonded and the terminal of the other conductive polymer is chemically bonded to the other electrode can be easily manufactured.

[Description of Organic Solar Cell Configuration]
The present invention includes organic solar cells having the configurations of the following first and second embodiments.
(Embodiment 1)
A photoelectric conversion layer having a bulk heterojunction formed from a first organic material and a second organic material, and a pair of electrodes sandwiching the photoelectric conversion layer, wherein the first organic material is a conductive polymer One end of this conductive polymer is chemically bonded to one electrode. In this case, a configuration in which a substrate is provided on each of the outer surfaces of the pair of electrodes may be used, or a configuration in which a substrate is provided only on one electrode side (the electrode side chemically bonded to the conductive polymer) may be used.
(Embodiment 2)
A photoelectric conversion layer having a bulk heterojunction formed from a first organic material and a second organic material, and a pair of electrodes sandwiching the photoelectric conversion layer, the photoelectric conversion layer including a first organic material and a second organic material Is a conductive polymer, one end of one conductive polymer is chemically bonded to one electrode, and one end of the other conductive polymer is chemically bonded to the other electrode. In this case, it is set as the structure which each provided the board | substrate in the outer surface side of a pair of electrode.

Here, in the organic solar cell of the present invention, “a photoelectric conversion layer having a bulk heterojunction” means a photoelectric conversion layer formed by contacting (for example, mixing) different kinds of organic materials.
In the present invention, “chemical bond” between the conductive polymer and the electrode is a state in which the conductive polymer and the electrode are bonded not by physical contact but by π bond or σ bond. Means. For example, a state in which the conductive polymer and the electrode are bonded by silicon atoms and oxygen atoms can be cited as the chemical bond.

  In the present invention, the occupation area ratio of the conductive polymer chemically bonded to the electrode to the electrode is preferably 30 to 70%, and more preferably 45 to 65%. Here, the occupied area ratio means that when the surface functional groups of the electrode are formed most densely, the state in which all the conductive polymers are bonded to the functional groups is defined as 100%. Means. If this occupied area ratio exceeds 70%, when forming a bulk heterojunction with the other organic material, the density of the conductive polymer on the side of the chemically bonded electrode becomes too high, so that It becomes difficult to form a uniform mixed state, and the area for charge separation is reduced. On the other hand, if the chemical bonding rate is less than 30%, it becomes difficult for carriers to move between the conductive polymer and the electrode. Furthermore, when the chemical bond rate is extremely large and small, the mixing balance of the two organic materials is deteriorated, and the region for charge separation is reduced. Therefore, the chemical bonding rate is preferably 30 to 70%.

In the photoelectric conversion layer of the present invention, the different first organic material and second organic material forming the bulk heterojunction may be made of an organic material soluble in the same solvent. In this way, a good photoelectric conversion layer having a wide junction area and a wide charge separation region can be obtained by uniformly mixing different kinds of first and second organic materials.
Hereinafter, each component of the organic solar cell of this invention is demonstrated.

<Board>
The substrate is not limited by the material and thickness as long as the electrode can be held on the surface. Therefore, the substrate may be in the form of a plate or a film, and materials such as metals such as aluminum and stainless steel, alloys, plastics such as polycarbonate and polyester can be used. Moreover, glass, transparent plastic, etc. can be used as a light transmissive material. Here, the light-transmitting property in the present invention means a property of transmitting light in a predetermined wavelength region used in an organic solar cell, for example, visible region with high efficiency (80% or more).

<Material for photoelectric conversion layer>
As for the organic material that forms a conductive polymer and a bulk heterojunction with the conductive polymer, the former is an electron-accepting organic material, and the latter is an electron-donating organic material.
An electron-accepting organic material is a π-electron compound with a wide conjugated system, a charge carrier is an electron, a material that exhibits stable n-type semiconductor characteristics in air, and a chemical bond with an electrode. There is no particular limitation as long as it has a substituent.
On the other hand, the electron-donating organic material is not particularly limited as long as it is a π-electron compound having a conjugated system and charge carriers are holes, and a material exhibiting stable p-type semiconductor characteristics in air. Absent.
In addition, when one is a conductive polymer, the other can be a conductive polymer or a low molecule. In this case, when one is an electron donor, the other may be an electron acceptor. However, if the electron-accepting organic material is a low molecule, the electron-donating organic material is preferably a conductive polymer.
Hereinafter, specific materials for the photoelectric conversion layer will be described.

  Examples of electron-accepting materials include oligomers and polymers having pyridine and its derivatives as a skeleton, oligomers and polymers having quinoline and its derivatives as a skeleton, ladder polymers using benzophenanthrolines and derivatives thereof, and polymers such as cyanopolyphenylene vinylene. Small molecules such as fluorinated metal-free phthalocyanines, fluorinated metal phthalocyanines and derivatives thereof, perylene and derivatives thereof, naphthalene derivatives, bathocuproine and derivatives thereof can be used.

  As electron donating materials, oligomers and polymers having thiophene and its derivatives in the skeleton, oligomers and polymers having phenylene vinylene and its derivatives in the skeleton, oligomers and polymers having thienylene vinylene and its derivatives in the skeleton, vinyl carbazole and its derivatives Oligomers and polymers with skeletons, oligomers and polymers with pyrrole and its derivatives as skeletons, oligomers and polymers with acetylene and its derivatives as skeletons, oligomers and polymers with isothiaphene and its derivatives as skeletons, heptadiene and its derivatives Polymers such as oligomers and polymers having a skeleton, metal-free phthalocyanines, metal phthalocyanines and their derivatives, diamines, phenyldiamines and their derivatives, penta Acenes and derivatives thereof, porphyrin, tetramethylporphyrin, tetraphenylporphyrin, diazotetrabenzporphyrin, monoazotetrabenzporphyrin, diazotetrabenzporphyrin, triazotetrabenzporphyrin, octaethylporphyrin, octaalkylthioporphyrazine, octa Low molecules such as metal-free porphyrins such as alkylaminoporphyrazine, hemiporphyrazine and chlorophyll, metalloporphyrins and derivatives thereof, quinone dyes such as cyanine dyes, merocyanates, benzoquinones and naphthoquinones can be used. As the central metal of metal phthalocyanine and metal porphyrin, magnesium, zinc, copper, silver, aluminum, silicon, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, tin, platinum, lead and other metals, metal oxides, Metal halides are used.

<Material of electrode>
The following materials can be used for one electrode and the other electrode (hereinafter sometimes referred to as a counter electrode). At least one of the electrode or the counter electrode sandwiching the photoelectric conversion layer has light transmittance.
As the material of one electrode, in order to form ohmic contact with the electron-accepting organic material, it is preferable to select a metal material having a small work function such as aluminum or indium, and when the electrode is on the light receiving surface side In order to reduce the thickness of these metal materials (10 to 20 nm), such as tin-doped indium oxide (ITO), fluorine-doped tin oxide, or the like having light transmittance is used. it can.
In addition, as a material for the counter electrode, in order to form an ohmic contact with the electron donating organic material, it is preferable to select a metal material having a high work function such as gold or platinum. In some cases, these metal materials are thinned to a thickness allowing light transmission (10 to 20 nm), or light-transmitting, for example, tin-doped indium oxide (ITO), fluorine-doped tin oxide, or the like is used. be able to.

(Description of manufacturing method of organic solar cell)
The method for manufacturing an organic solar cell according to Embodiment 1 of the present invention includes a step (a) of forming a first electrode on a substrate and a first organic material made of a conductive polymer on the surface of the first electrode. A photoelectric conversion layer having a bulk heterojunction formed by bringing the second organic material into contact with the first organic material and mixing the first organic material and the second organic material. (C) and (d) forming a second electrode on the photoelectric conversion layer.

  Moreover, the manufacturing method of the organic solar cell of the said Embodiment 2 of this invention WHEREIN: The process (a) which forms a 1st electrode on a 1st board | substrate, and the 1st which consists of a conductive polymer on the said 1st electrode surface. A step (b) of chemically bonding an organic material; a step (e) of forming a second electrode on the second substrate; and a second organic material made of a conductive polymer on the surface of the second electrode. A step (f) for bonding to the substrate, a step (g) for bonding the first substrate and the second substrate, and a step (h) for sealing the bonded first substrate and the second substrate except for a part. And a step (i) of injecting a solvent into the photoelectric conversion layer from an unsealed portion between the first substrate and the second substrate, and a step (j) of volatilizing the solvent from the photoelectric conversion layer.

  In the method for manufacturing the organic solar cell according to Embodiments 1 and 2, the chemical adsorption method is preferable as a method for chemically bonding the organic material to the electrode. If the chemical adsorption method is used, the amount of the conductive polymer adsorbed on the substrate can be easily controlled by the reaction time and / or reaction temperature. Therefore, it is possible to form a bulk heterojunction in which a mixed state of different organic materials is good, that is, different organic materials are mixed uniformly in a well-balanced manner and a large region for charge separation can be secured.

In the method for producing an organic solar cell, when the conductive polymer is chemically bonded to the electrode, the surface of the electrode may be subjected to a hydrophilic treatment (pretreatment). In this case, by setting the terminal group of the conductive polymer to a chlorosilyl group or a chlorosilane group, the terminal group of the conductive polymer can be chemically bonded to a hydroxyl group or the like on the electrode surface by a π bond and / or a σ bond.
Hereinafter, an organic solar cell as an embodiment of the present invention and a manufacturing method thereof will be described in detail with reference to the drawings. The present invention is not limited to the embodiment.

(Method for Manufacturing Organic Solar Cell of Embodiment 1)
1A and 1B are explanatory views for explaining a schematic configuration of an organic solar cell according to Embodiment 1 of the present invention. FIG. 1A is an enlarged cross-sectional view, and FIG. It is a figure which shows a typical coupling state.

  As shown in FIG. 1 (a), the organic solar cell of the present invention is a conductive material that is a substrate 101, a first electrode 102, and a first organic material whose one end is chemically bonded to the first electrode 102. The photoelectric conversion layer 107 made of the second organic material 104 that forms a bulk heterojunction with the polymer 103 and the conductive polymer 103, and the counter electrode 105 are sequentially stacked. Here, when light is irradiated from the substrate side, the substrate 101 and the first electrode 102 are formed of a light-transmitting material. On the other hand, when light is irradiated from the counter electrode side, the counter electrode 105 is formed of a light transmissive material.

  As shown in FIG. 1B, the chemical bond between the conductive polymer 103 and the electrode 102 is not physical contact, but the electrode 102 and the conductive polymer 103 are bonded by π bond or σ bond. It is in a connected state. For example, the conductive polymer 103 and the electrode 102 are bonded by silicon atoms (Si) and oxygen atoms (O).

<Manufacturing method 1>
The organic solar cell of Embodiment 1 is produced by the following manufacturing method 1, for example. First, the electrode 102 is formed on the substrate 101. The electrode 102 can be formed as a thin film having a thickness of about 5 to 200 nm by a method such as vacuum deposition, ion sputtering, or chemical vapor deposition.
After the electrode 102 is formed over the substrate 101, the surface of the electrode 102 is preferably washed. For example, the substrate 101 is immersed in an organic solvent such as isopropyl alcohol, acetone, or chloroform, and impurities are removed by washing the electrode surface with ultrasonic waves.

Next, when the photoelectric conversion layer 107 that forms a bulk heterojunction between the conductive polymer 103 and the organic material 104 is manufactured, first, a process of chemically bonding the conductive polymer 103 to the surface of the electrode 102 is performed. .
As a method of chemically bonding the electrode 102 and the conductive polymer 103, for example, the following chemical adsorption method is used. The chemical adsorption method is a method in which organic molecules are chemically adsorbed on the substrate surface by bringing the organic molecules into contact with the substrate surface.
First, the surface of the electrode 102 is hydrophilized. The method for hydrophilization treatment is not particularly limited. For example, the surface hydrophilization treatment is performed by immersing the substrate in hydrofluoric acid. Alternatively, it can be hydrophilized by oxygen plasma.
After the electrode 102 is subjected to a surface hydrophilization treatment, it is bonded to a terminal substituent of the conductive polymer 103 and a hydroxyl group formed by the surface hydrophilization treatment. When the conductive polymer 103 is brought into contact with the surface of the substrate 101, active hydrogen on the surface of the substrate 101 reacts with a substituent group modified at the terminal of the conductive polymer 103 to form a chemical bond.
In the chemisorption method described above, pairs of a substituent modified at the terminal of the conductive polymer 103 and a functional group modifying the surface of the electrode 102 include —COOH and —NH ₂ , —COOH and —OH, —Cl For example, a combination of —OH, —Si (OCH ₃ ) ₃ , —OH, and the like is given.

In addition, when the density of the conductive polymer 103 with respect to the area of the electrode 102 is high (occupied area ratio exceeds 70%), when the bulk heterojunction is formed, the mixed state with the other organic material 104 is uniformly formed. It becomes difficult. Also, when the density is high and low, the mixed state of the two conductive polymers 103 and the organic material 104 is biased, and an effective charge separation interface cannot be formed. For this reason, it is preferable that the conductive polymer 103 occupies about 30 to 70% of the surface of the electrode 102. The occupied area ratio can be estimated from the absorbance, and the occupied area ratio can be estimated from 100% absorbance. Specifically, when all the functional groups on the substrate are bonded, they are saturated even if they are reacted further. The absorbance in that state can be estimated as 100%.
Further, as described above, in order to make the occupation area ratio about 30 to 70%, the reaction temperature and / or the reaction time when the terminal group of the conductive polymer 103 and the substituent that modifies the surface of the electrode 102 react with each other. The reaction time can be controlled. This will be described in detail later.

More specifically, the step of chemically bonding the conductive polymer 103 to the electrode 102 will be described. In this step, the substrate 101 with the electrode is immersed in a solution obtained by dissolving the conductive polymer 103 with a solvent. Heat at 60 to 130 ° C. (preferably 90 to 110 ° C.) for 15 to 90 minutes (preferably 30 to 60 minutes). As a result, the terminal groups of the conductive polymer 103 react with the substituents on the surface of the electrode 102, and the chemical bonding rate is about 30 to 70% by controlling the reaction temperature and / or reaction time within the above range. The conductive polymer 103 is chemically bonded to the electrode 102. For example, when the terminal group of the conductive polymer 103 is —Si (OCH ₃ ) ₃ and the substituent on the surface of the electrode 102 is —OH, the conductive polymer 103 and the electrode 102 are formed as shown in FIG. It is chemically π-bonded and / or σ-bonded through silicon atoms and oxygen atoms.
Thereafter, the substrate is pulled up from the solution and dried by heating at 50 to 150 ° C. for 30 to 90 minutes.

Next, a solution obtained by dissolving the organic material 104 in a solvent is applied onto the conductive polymer 103 film on the substrate 101 by spin coating. Alternatively, the substrate 101 may be immersed in the solution.
At this time, it is preferable that both the conductive polymer 103 and the organic material 104 before bonding are dissolved in a solvent from the viewpoint that both molecules can be mixed uniformly. Here, examples of the solvent used for spin coating include alcohols (methanol, ethanol, t-butanol, benzyl alcohol, etc.), nitriles (acetonitrile, propionitrile, 3-methoxypropionitrile, etc.), nitromethane, and the like. Halogenated hydrocarbons (dichloromethane, dichloroethane, chloroform, chlorobenzene, etc.), ethers (diethyl ether, tetrahydrofuran, etc.), dimethyl sulfoxide, amides (N, N-dimethylformamide, N, N-dimethylacetamide, etc.), N-methylpyrrolidone, 1,3-dimethylimidazolidinone, 3-methyloxazolidinone, esters (ethyl acetate, butyl acetate, etc.), carbonates (diethyl carbonate, ethylene carbonate, propylene carbonate, etc.), ketones (acetone, - butanone, cyclohexanone), hydrocarbons (hexane, petroleum ether, benzene, toluene, etc.), but mixtures of these solvents, but are not limited thereto.

Thereafter, the substrate is pulled up from the solution, and baked at 100 to 250 ° C. for 30 to 60 minutes to be dried.
The film thickness of the photoelectric conversion layer 107 thus formed is preferably about 50 to 2000 nm, and more preferably 100 to 500 nm. If the film thickness is less than 50 nm, an electrical short circuit is caused and no photoelectric conversion characteristics are exhibited. If the film thickness is more than 2000 nm, the light transmittance is lowered and the electric resistance of the film is increased, thereby reducing the photocurrent.

Next, the counter electrode 105 is formed with a thickness of about 100 to 150 nm on the surface of the photoelectric conversion layer 107. Specific examples of the forming method include vacuum deposition, ion sputtering, and chemical vapor deposition. In this way, an organic solar cell as shown in FIG.
Note that the photoelectric conversion layer and the electrode are preferably produced in vacuum or in an inert gas such as nitrogen in order to prevent photooxidation. Furthermore, it is more preferable to carry out all the steps without exposing them to the atmosphere.

(Method for Producing Organic Solar Cell of Embodiment 2)
FIG. 2 is an enlarged cross-sectional view for explaining a schematic configuration of the organic solar battery as the second embodiment of the present invention. The organic solar cell includes a first substrate 201, a first electrode 202, a first conductive polymer 203 whose one end is chemically bonded to the first electrode 202, a first conductive polymer 203, The organic material 204 that forms a bulk heterojunction and is chemically bonded to the second electrode 205, the second electrode 205, and the second substrate 206 are stacked in this order. Here, when light is irradiated from the first substrate 201 side, the first substrate 201 and the first electrode 202 are formed of a light-transmitting material. On the other hand, when light is irradiated from the second substrate 206 side, the second substrate 206 and the first electrode 206 are formed of a light transmissive material.

<Manufacturing method 2-1>
Next, the manufacturing method 2-1 of the organic solar cell of this Embodiment 2 is demonstrated.
First, the first electrode 202 is formed on the first substrate 201. As a formation method thereof, a method such as vapor deposition, ion sputtering, or chemical vapor deposition can be used, and the first electrode 202 having a thin film thickness of about 5 to 200 nm can be formed.
After cleaning the substrate, as in the first embodiment, the surface of the first electrode 202 is subjected to a hydrophilic treatment, and the first conductive polymer 203 is chemically bonded to the first electrode 202 to thereby perform the first conductivity. A film of the conductive polymer 203 is formed and then dried.

  Next, similarly to the first substrate 201 side, a second electrode 205 having a thickness of about 5 to 200 nm is formed on the second substrate 206. After the second substrate 206 is washed, the surface of the second electrode 205 is made hydrophilic. The second conductive polymer 204 is chemically bonded to the second electrode 205 to form a film of the second conductive polymer 204, and then dried.

  Next, a laminate of the first substrate 201 / first electrode 202 / first conductive polymer 203 film and a laminate of the second substrate 206 / second electrode 205 / second conductive polymer 204 film are formed. In use, a bulk heterojunction of the first conductive polymer 203 and the second conductive polymer 204 is formed as follows. First, the first substrate 201 and the second substrate 206 are physically bonded together with the first conductive polymer 203 film and the second conductive polymer 204 film in contact with each other. Thereafter, sealing is performed except for a part of the periphery between the first and second substrates 201 and 206. A thermoplastic resin can be used as the sealing material. Thereafter, a solvent is injected from a portion not sealed between the film of the first conductive polymer 203 and the film of the second conductive polymer 204. As the solvent, it is preferable to use a solvent in which both the first conductive polymer 203 and the second conductive polymer 204 are soluble, as in the first embodiment. After 10 to 10 minutes have passed since the solvent injection, the solvent is removed from between the electrodes by heating and dried to form the photoelectric conversion layer 207, thereby obtaining an organic solar cell.

<Manufacturing method 2-2>
Moreover, the solar cell of Embodiment 2 can also be produced by the following production method 2-2. In this case, the surface of each electrode is hydrophilized as in Embodiment 1, but the first electrode 202 and the second electrode 205 are treated so as to have different functional groups. That is, a reaction of a pair of a substituent modified at the terminal of the first conductive polymer 203 and a substituent modifying the first electrode 202, a substituent modified at the terminal of the second conductive polymer 204, and A pair reaction with a substituent that modifies the second electrode 205 is performed, and there is no particular limitation as long as the pair does not react with each other between different pairs. Examples of pairs in which the reaction is performed include combinations of —COOH and —NH ₂ , —COOH and —OH, —Cl and —OH, —Si (OCH ₃ ) ₃ and —OH, and the like. For example, as a combination of functional groups in which the first conductive polymer does not react with the second electrode and the second conductive polymer does not react with the first electrode, the first electrode is -COOH and the second electrode is As the —OH, a combination in which the first conductive polymer is —NH ₂ and the second conductive polymer is —Si (OCH ₃ ) ₃ can be mentioned.

Subsequently, the first electrode 202 of the first substrate 201 and the second electrode 205 of the second substrate 206 are opposed to each other, and a support (for example, plastic) is used to maintain a certain gap between the first and second electrodes 202 and 205. Insulators such as glass) are disposed at the corners between the electrodes, for example. As a processing method, the method shown in the first embodiment is used. Subsequently, as in the manufacturing method 2-1, the outer periphery between the first and second substrates 201 and 206 is sealed except for a part.
Thereafter, a mixed solution of the first conductive polymer 203 and the second conductive polymer 204 is sealed in the gap between the electrodes, and the first conductive polymer 203 is inserted into the first electrode 202 and the second conductive polymer 203. Are reacted with the second electrode 204 at a chemical bonding rate of 30 to 70%. Thereafter, the solvent between the electrodes is dried to form the photoelectric conversion layer 207, thereby obtaining an organic solar cell.

  In the production methods 2-1 and 2-2, the photoelectric conversion layer and the electrode are preferably produced in vacuum or in an inert gas such as nitrogen in order to prevent photooxidation. Furthermore, it is more preferable to carry out all the steps without exposing them to the atmosphere.

Example 1
An ITO (indium tin oxide) electrode was formed on a quartz substrate by sputtering. Next, the quartz substrate coated with ITO was cut into a size of 25 × 25 mm. Thereafter, the electrode was etched using hydrochloric acid for patterning. The substrate was ultrasonically washed with chloroform for 20 minutes, and then washed with a mixed solution of acetone and ethanol for 20 minutes. After exposing the clean surface by ashing with oxygen plasma, the ITO surface was hydrophilized by hydroxylating the oxygen radical surface by immersing in ultrapure water for 10 minutes.

Next, in the production of the photoelectric conversion layer, poly [2-methoxy-5- (2′-ethylhexyloxy) -1,4 whose end is modified with a chlorosilyl group is used as an electron donating material which is the first organic material. -Phenylene vinylene] (hereinafter referred to as MEH-PPV), [6,6] -phenylene C ₆₁ -butyric acid ester that is a derivative of fullerene (C ₆₀ ) as an electron-accepting material that is the second organic material ( (Hereinafter referred to as PCBM).
In addition, MEH-PPV used the product made from Aldrich (average molecular weight 125000). PCBM is also published in Journal of Applied Physics- May 1, 1999-Volume 85, Issue 9, pp. Although it produced by the method of 6866-6872, a commercial item (for example, Frontier Carbon company make) may be used.

Next, MEH-PPV whose end was modified with a chlorosilyl group was chemically bonded to the hydrophilic ITO surface. In the bonding method, the ITO-coated substrate is immersed in a 2 wt% xylene solution of MEH-PPV whose end is modified with a chlorosilyl group, heated at 100 ° C. for 40 minutes, and the ITO electrode and MEH-PPV are chemically bonded. Combined.
Next, a chloroform solution of PCBM was prepared. The concentration of PCBM was approximately 2 wt%. This prepared solution was spin-coated on a MEH-PPV film chemically bonded onto the ITO surface. After spin coating, chloroform was volatilized to form a photoelectric conversion layer. The film thickness of the photoelectric conversion layer was about 1000 nm.
After producing the photoelectric conversion layer, a mask capable of forming a 2 × 25 mm pattern is formed on the photoelectric conversion layer formed on the ITO quartz substrate, and the degree of vacuum is about 4.0 with the mask attached. An Al electrode was formed by vacuum deposition at × 10 ⁻⁴ Pa, and then the mask was removed to obtain an organic solar cell.

All the characteristics of the organic solar cell of Example 1 thus obtained were measured in air. As the light source, white light from a 150 W halogen tungsten lamp condensed on an organic solar cell was used. The light intensity measured with an optical power meter was 100 mW / cm ² . In order to obtain the photoelectric conversion efficiency, the current-voltage characteristic was measured with an electrometer (type 236 manufactured by KEITHLEY) while applying voltage, and the current value was recorded in a computer through a GP-IB interface. Solar cell characteristics such as open electromotive force (V _oc ), short-circuit photocurrent density (J _sc ), fill factor (FF), and photoelectric conversion efficiency (η) were determined from this current-voltage curve.
Here, the fill factor is a ratio of FF = (maximum output that can be actually taken out by the operation of the organic solar cell / output of J _sc × V _oc watt that can be taken out if the organic solar cell is ideally operated). This is the value given. Further, the photoelectric conversion efficiency is given by η (%) = (electric output that can be taken out / incident light energy) × 100.
The measurement results of fill factor (FF) and photoelectric conversion efficiency (η) are shown in Table 1.

(Comparative Example 1)
In Example 1, the photoelectric conversion element of Comparative Example 1 was produced in the same manner as in Example 1 except that the method for producing the photoelectric conversion layer was changed as follows.
A chloroform mixed solution obtained by mixing a 2 wt% MEH-PPV chloroform solution and a PCBM 2 wt% chloroform solution in a weight ratio of 1: 1 without performing the hydrophilization treatment on the ITO electrode surface performed in Example 1. Spin coated on the ITO surface. After spin coating, chloroform was volatilized. The film thickness of the photoelectric conversion layer was about 1000 nm.
The method of measuring the characteristics of the organic solar cell of Comparative Example 1 obtained in this way was the same as that of Example 1, and the measurement results are shown in Table 1.

(Example 2)
An ITO (indium tin oxide) electrode was formed on a quartz substrate by sputtering. Next, the quartz substrate coated with ITO was cut into a size of 25 × 25 mm. Thereafter, the electrode was etched using hydrochloric acid for patterning. The substrate was ultrasonically washed with chloroform for 20 minutes, and then washed with a mixed solution of acetone and ethanol for 20 minutes. Furthermore, another quartz substrate was cut into a size of 25 × 25 mm, and an Al electrode was produced by vacuum deposition at a vacuum degree of about 4.0 × 10 ⁻⁴ Pa with a mask attached.

A clean surface was exposed to each electrode of the two substrates by ashing with oxygen plasma, and then immersed in ultrapure water for 10 minutes to hydroxylate the oxygen radical surface and perform a hydrophilic treatment.
After hydrophilization treatment, MEH-PPV and ITO electrode modified with chlorosilane groups at the ends and poly [2-methoxy-5- (2′-ethylhexyloxy) -1,4- modified with chlorsilane groups at the ends (1-Cyanovinylene) phenylene] (hereinafter referred to as CN-PPV) and an Al electrode were each chemically bonded in the same manner as in Example 1.
In addition, CN-PPV used the Aldrich company make (average molecular weight 86000).

Next, a substrate having an ITO electrode bonded with MEH-PPV and a substrate having an Al electrode bonded with CN-PPV were bonded together. After pasting, it was sealed with an adhesive or the like except for a part. Chloroform was injected into the unsealed part. After injecting and stirring, chloroform was volatilized and dried while applying pressure to the substrate. The film thickness of the photoelectric conversion layer thus formed was about 1000 nm.
The measurement method of the characteristics of the organic solar cell of Example 2 obtained in this way was the same as that of Example 1, and the measurement results are shown in Table 1.

(Comparative Example 2)
In Example 1, a photoelectric conversion element of Comparative Example 2 was produced in the same manner as in Example 1 except that the method for producing the photoelectric conversion layer was changed as follows.
The chloroform mixed solution which mixed the chloroform solution of concentration 2wt% of MEH-PPV and the concentration of 2wt% of CN-PPV by the weight ratio of 1: 1 without performing the hydrophilization treatment of the ITO electrode surface performed in Example 1. Was spin coated on the ITO surface. After spin coating, chloroform was volatilized. The film thickness of the photoelectric conversion layer was about 1000 nm.
Thus, the measuring method of the characteristic of the organic solar cell of the comparative example 2 obtained was the same as that of Example 1, and the measurement result was shown in Table 1.

  From Table 1, it was found that Examples 1 and 2 had better fill factor (FF) and photoelectric conversion efficiency (η) than Comparative Examples 1 and 2.

  The organic solar cell of the present invention can be used for power generation systems for outdoor and indoor use, and is particularly suitable as a solar cell for mobile devices.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing for demonstrating schematic structure of the organic solar cell as Embodiment 1 of this invention, Comprising: (a) is an expanded sectional view, (b) is the chemical coupling | bonding of a conductive polymer and an electrode. It is a figure which shows a state. It is an expanded section for demonstrating schematic structure of the organic solar cell as Embodiment 2 of this invention.

Explanation of symbols

101 Substrate 102 Electrode 103 Conductive polymer (first organic material)
104 Organic material (second organic material)
105 Counter electrode 107, 207 Photoelectric conversion layer 201 First substrate 202 First electrode 203 First conductive polymer (first organic material)
204 Second conductive polymer (second organic material)
205 Second electrode 206 Second substrate

Claims (7)

A photoelectric conversion layer having a bulk heterojunction formed from at least a first organic material and a second organic material, and a pair of electrodes sandwiching the photoelectric conversion layer;
In the photoelectric conversion layer, at least one of the first organic material and the second organic material is a conductive polymer, and the conductive polymer is chemically coupled to one of the pair of electrodes. An organic solar cell characterized by being bonded.   The organic solar cell according to claim 1, wherein the occupation area ratio of the conductive polymer chemically bonded to the electrode to the electrode is 30 to 70%.   The organic solar cell according to claim 1 or 2, wherein the first organic material and the second organic material are organic materials soluble in the same solvent.   The organic solar cell according to any one of claims 1 to 3, wherein the chemical bond is a π bond and / or a σ bond. Forming a first electrode on the substrate (a);
A step of chemically bonding the functional group of the first organic material made of a conductive polymer having a functional group at a terminal to the surface functional group of the first electrode to form a film of the first organic material ( b) and
A step (c) of forming a photoelectric conversion layer in a state where the first organic material and the second organic material are mixed by bringing the second organic material into contact with the first organic material;
The manufacturing method of the organic solar cell characterized by including the process (d) which forms a 2nd electrode on the said photoelectric converting layer. Forming a first electrode on the first substrate (a);
(B) chemically bonding the first functional group of the first organic material made of a conductive polymer having a first functional group at the end to the first surface functional group of the first electrode;
Forming a second electrode on the second substrate (e);
(F) chemically bonding the second functional group of the second organic material made of a conductive polymer having a second functional group at the end to the second surface functional group of the second electrode;
A step (g) of bonding the first substrate and the second substrate;
A step (h) of sealing a portion between the bonded first substrate and second substrate except for a part thereof;
Injecting a solvent into the photoelectric conversion layer from an unsealed portion between the first substrate and the second substrate (i);
The manufacturing method of the organic solar cell characterized by including the process (j) which volatilizes the said solvent from a photoelectric converting layer.   The method for producing an organic solar cell according to claim 5 or 6, wherein the chemical bonding method is a chemical adsorption method.

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