JP2014090093A - Tandem type organic thin-film solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic solar cell, with suppressed performance variation, highly efficient, highly durable, and low cost.SOLUTION: The tandem type organic thin-film solar cell includes on a substrate: a first electrode; a first organic thin-film solar cell of a coating type containing a low molecule material; an intermediate layer of an evaporation type containing a low molecule material; a second organic thin-film solar cell of an evaporation type containing a low molecule material; and a second electrode in this order.

Description

  The present invention relates to a tandem organic thin film solar cell and a method for manufacturing the same.

  Organic solar cells (organic thin-film solar cells) provide electrical output with respect to light input, as typified by photodiodes and imaging devices that convert optical signals into electrical signals, and solar cells that convert optical energy into electrical energy. It is a device to show.

In recent years, solar cells have attracted a great deal of attention as a clean energy source against the background of fossil fuel depletion problems and global warming problems, and research and development have been actively conducted.
Conventionally, silicon solar cells represented by single crystal Si, polycrystal Si, amorphous Si, etc. have been put into practical use. However, as the cost and raw material Si shortage problems surface, The demand for next generation solar cells is increasing. Against this background, organic solar cells are attracting much attention as next-generation solar cells next to silicon-based solar cells because they are inexpensive, have low toxicity, and do not have a fear of shortage of raw materials.

In an organic solar cell and an organic solar cell module using the same, high efficiency and low cost are required.
In the organic solar cell element, both holes and electrons are separated and generated from excitons generated by light irradiation. Therefore, high efficiency in the organic solar cell can be realized by suppressing deactivation of excitons in the photoactive photoelectric conversion layer and effectively performing charge separation.

Controlling exciton diffusion without exciton recombination is very important in increasing the efficiency of organic solar cells.
The diffusion distance of excitons can be increased by using a perfect single crystal in terms of structure and chemical purity, but it is impossible to use a single crystal organic material for general purposes.

  Instead of increasing the exciton diffusion distance, it has been proposed to reduce the average distance to the pn interface that results in charge separation. By introducing an i layer (mixed layer of p and n materials) or a bulk heterostructure, the photogenerated excitons only have to reach the pn interface by diffusing a very short distance, and the conversion efficiency is improved. It has been found to improve.

In addition, in organic solar cells using polymer materials as well as low molecular materials, using conductive polymers as p materials and soluble _C60 derivatives as n materials, they are mixed and heat-treated for microphase separation. Research on so-called bulk heterostructures, in which conversion efficiency is improved by inducing heterointerfaces by induction, is mainly performed.

As other measures for improving the characteristics of the organic solar cell, other approaches include the following.
Multi-junction is conceivable as a measure for improving the conversion efficiency of the organic solar cell. Multi-junction has been studied with Si or compound semiconductors. In consideration of cost, so-called tandem formation in which two single cells of top and bottom are stacked via an intermediate layer is being studied by each company.

  For example, the polymer (coating) / polymer (coating) type described in Patent Document 1 or the like, or low molecules (deposition) represented by Patent Document 2 / Low molecular (vapor deposition) type.

JP-T-2006-527490 JP 2009-188409 A

In the polymer (coating) / polymer (coating) type, no suitable intermediate layer that can prevent dissolution in the lower layer has been found. In particular, there are reports on cells of several mm square level, but there are no reports on examples of cells or modules whose size has been increased. Moreover, it is difficult to design the molecule of the p-material on the long wavelength side in the low molecule (evaporation) / low molecule (evaporation) type.
That is, for practical use, a material with high efficiency and low cost and sufficiently suppressed performance variation and its manufacturing process have not yet been determined.
An object of the present invention is to provide an organic solar cell with high efficiency, high durability, and low cost, in which performance variations are suppressed.

According to the present invention, the following tandem organic thin film solar cell and the like are provided.
1. On a substrate, a first electrode, a coating type first organic thin film solar cell containing a low molecular material, a vapor deposition type intermediate layer containing a low molecular material, and a vapor deposition type second organic thin film containing a low molecular material A tandem organic thin-film solar battery including a solar battery cell and a second electrode in this order.
2. 2. The tandem organic thin film solar cell according to 1, wherein the molecular weight of the low molecular weight material contained in the first organic thin film solar cell is 5,000 or less.
3. The tandem organic thin film solar cell according to 1 or 2, wherein the number of repeating units of the low molecular weight material contained in the first organic thin film solar cell is 10 or less.
4). The tandem organic thin film solar cell according to any one of 1 to 3, wherein the first organic thin film solar cell includes 0.01% to 0.1% of an organic solvent.
5. A coating step of forming a first organic thin-film solar cell containing a low-molecular material by a coating method in a nitrogen atmosphere or an atmosphere having a moisture concentration of 100 ppm or less on a substrate on which an electrode is formed; and 1 × 10 ⁻³ The manufacturing method of the tandem-type organic thin-film solar cell in any one of 1-4 containing the vapor deposition process of forming an intermediate | middle layer and a 2nd organic thin-film solar cell by vapor deposition method below Pa.
6). Immediately after forming the first organic thin film solar cell, the organic solvent remaining in the first organic thin film solar cell is removed during the formation of the intermediate layer, and the content in the first organic thin film solar cell The manufacturing method of the tandem-type organic thin-film solar cell of 5 with which becomes 0.1% or less.

  According to the present invention, it is possible to provide an organic solar battery with high efficiency, high durability, and low cost, in which performance variation is suppressed.

It is a figure which shows one Embodiment of the organic thin film solar cell of this invention.

  The organic thin film solar cell of the present invention is a tandem type, and a first electrode (lower electrode), a coating type first organic thin film solar cell including a low molecular material, and a vapor deposition type including a low molecular material on a substrate. The intermediate layer, the vapor deposition type second organic thin film solar cell containing the low molecular material, and the second electrode (upper electrode) are included in this order.

By using a low molecular material (no molecular weight distribution) for the first and second organic thin film solar cells and the intermediate layer, the organic thin film solar cell of the present invention is excellent in performance reproducibility, that is, there is little variation in performance. High productivity. Moreover, it is excellent in durability by using a low molecular material for the said layer.
In the tandem organic thin film solar cell of the present invention, the first organic thin film solar cell is a coating type, and the second organic thin film solar cell is a vapor deposition type. That is, high efficiency can be achieved. Specifically, the first organic thin film solar cell can absorb longer wavelength sunlight, and the second organic thin film solar cell can absorb shorter wavelength sunlight.

The first organic thin-film solar battery cell used in the present invention is formed by a coating method and usually consists of one layer. By using the coating method, the manufacturing cost can be kept low. In addition, when the first organic thin-film solar battery cell is formed of a mixed material (bulk heterojunction (BHJ)), which will be described later, by a drying process after coating, etc., an unstable nanostructure (PN junction) Can be stabilized, and durability can be further enhanced.
As the coating method, a known method can be used, and specifically, as described later.

The first organic thin film solar cell preferably has an organic solvent content of 0.1% or less, more preferably 0.05% or less. The organic solvent content is usually 0.01% or more.
The organic solvent content can be measured with a precision electronic balance.

The molecular weight of the low molecular weight material used for the first organic thin film solar cell is preferably 5,000 or less, and more preferably 2,000 or less. The molecular weight is measured with a mass spectrometer such as TOF-MASS (Time of Flight Mass Spectrometry).
Moreover, when the said low molecular material consists of a repeating unit, Preferably, the number of repeating units is 10 or less, More preferably, it is 5 or less.

The low-molecular material used for the first organic thin-film solar cell is usually a p-material, preferably a p-material that absorbs longer wavelength sunlight. As low molecular weight materials, NATURE MATERIALS vol. 11, p44 (2012).
When used for the first organic thin film solar cell, a bulk heterojunction (BHJ) of a low molecular weight p material and a low molecular weight n material (for example, PC60BM, PC70BM, etc. which are fullerene derivatives) is preferable.

The intermediate layer used in the present invention is produced by a vapor deposition method.
Examples of the intermediate layer include an intermediate electrode, a p-type or n-type doping layer, or a laminate in which both are stacked.

The material of the intermediate electrode is not particularly limited, and materials for forming a positive electrode and a negative electrode, which will be described later, can be used. Preferably, Pt and Au, Ca, Mg, Ni, Cu, Zn, Pd, Ag, Cd, Mo, V, Ti, In, and Sn metals and oxides, and one or more selected from binary metal systems such as Mg: Ag, Mg: In, and Al: Li.
Examples of the oxides of Ca, Mg, Ni, Cu, Zn, Pd, Ag, Cd, Mo, V, Ti, In, and Sn include, for example, MoO ₃ , VO, ZnO, TiO, TiO ₂ , In ₂ O ₃ , SnO ₂ and _V 2 _{O 5} and the like.
The intermediate electrode is more preferably a layer made of silver, a layer made of an alloy or a laminated film of silver and molybdenum oxide (MoO ₃ ), a layer made of gold and calcium, or a layer made of molybdenum oxide (MoO ₃ ).

When a p-type or n-type doping layer is used, the molecular weight of the low molecular weight material used for the doping layer is preferably 1,000 or less.
As the p-type or n-type doping layer, a p-type doping layer is preferable. As the p-type doping layer, a hole transporting material (donor material) doped with an acceptor material can be used.

As the donor material, for example, in the case of an organic compound, N, N′-bis (3-tolyl) -N, N′-diphenylbenzidine (mTPD), N, N′-dinaphthyl-N, N′-diphenylbenzidine ( NPD), 4,4 ′, 4 ″ -tris (phenyl-3-tolylamino) triphenylamine (MTDATA) and other amine compounds; phthalocyanine (Pc), copper phthalocyanine (CuPc), zinc phthalocyanine (ZnPc) Phthalocyanines such as titanyl phthalocyanine (TiOPc); porphyrins typified by octaethylporphyrin (OEP), platinum octaethylporphyrin (PtOEP), zinc tetraphenylporphyrin (ZnTPP); and acenes such as anthracene, tetracene and pentacene And a thiophene group etc. In the case of a high molecular compound, main chain conjugated polymers such as polyhexylthiophene (P3HT) and methoxyethylhexyloxyphenylene vinylene (MEHPPV), and side chains represented by polyvinylcarbazole and the like. Type polymers.
These compounds can be used individually by 1 type or in mixture of 2 or more types.

The acceptor material is, for example, an organic compound having an electron-withdrawing substituent, and specifically, a quinoid derivative having an electron-withdrawing substituent, a pyrazine derivative having an electron-withdrawing substituent, and an electron-withdrawing substitution. And arylborane derivatives having a group, imide derivatives having an electron-withdrawing substituent, and the like.
For example, examples of the quinoid derivative include quinodimethane derivatives, thiopyran dioxide derivatives, thioxanthene dioxide derivatives, quinone derivatives, and the like, and examples of electron-withdrawing substituents include fluoro groups and cyano groups. The species can be used alone or as a mixture of two or more species.
Of these, preferred are cyano compounds in which the substituent of the electron-withdrawing group is a cyano group.

The cyano compound that is an acceptor material is preferably a tetracyanoquinodimethane derivative represented by the following formula (1). In the tetracyanoquinodimethane derivative represented by the formula (1), at least one of the four Rs is preferably a cyano group, and more preferably at least two of the four Rs are cyano groups.
(In the formula, each R is independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkyloxy group having 1 to 10 carbon atoms, a dialkylamine group having 2 to 20 carbon atoms, or a cyano group. .)

The second organic thin film solar cell used in the present invention is produced by a vapor deposition method, and preferably has a single layer or a laminated structure of two or more layers. As such a laminated structure, for example, (p layer / n layer), (p layer / i layer (mixed layer of p material and n material) / n layer), (i layer), and the like.
The molecular weight of the low molecular weight material used for the second organic thin film solar cell is preferably 1,000 or less. Examples of the low-molecular material used for the second organic thin-film solar battery include a p-layer material and an n-layer material described later.

  As a vapor deposition method, a known method can be used, and specifically, as described later. By forming the intermediate layer and the subsequent layers by vapor deposition, unlike in the case of laminating the coating layer, consideration for wettability is greatly reduced.

  The cell structure of the organic thin film solar cell of the present invention includes a coating type single cell (first organic thin film solar cell), a vapor deposition type intermediate layer, and a vapor deposition type single cell (second organic) between a pair of electrodes. The structure is not particularly limited as long as it has a structure having a thin film solar battery cell. Specifically, the structure which has the following structure on a board | substrate is mentioned.

(1) Lower electrode / first organic thin film solar cell / intermediate layer / second organic thin film solar cell (p layer / n layer) / upper electrode (2) lower electrode / first organic thin film solar cell / Intermediate layer / second organic thin film solar cell (p layer / i layer (mixed layer of p and n materials) / n layer) / upper electrode (3) lower electrode / first organic thin film solar cell / Intermediate layer / second organic thin film solar cell (i layer) / upper electrode

Moreover, you may provide a buffer layer between an electrode and an organic layer as needed. A configuration in which a buffer layer is provided in the above configuration is exemplified below.
(4) Lower electrode / buffer layer / first organic thin film solar cell / intermediate layer / buffer layer / second organic thin film solar cell (p layer / n layer) / buffer layer / upper electrode (5) lower electrode / Buffer layer / first organic thin film solar cell / intermediate layer / buffer layer / second organic thin film solar cell (p layer / i layer / n layer) / buffer layer / upper electrode

In addition, the first and second organic thin-film solar cells can be reversed. An example of the reverse configuration will be described below.
(6) Lower electrode / buffer layer / first organic thin film solar cell / intermediate layer / buffer layer / second organic thin film solar cell (n layer / p layer) / buffer layer / upper electrode (7) lower electrode / Buffer layer / first organic thin film solar cell / intermediate layer / buffer layer / second organic thin film solar cell (n layer / i layer / p layer) / buffer layer / upper electrode

  Either or both of the lower electrode and the upper electrode are transparent electrodes. When taking in light from the lower electrode side, the lower electrode is transparent and the substrate is also transparent.

  Further, the material constituting the first organic thin film solar cell and the second organic thin film solar cell is configured to complement the absorption spectrum as layers having different absorption spectra, and has a structure capable of absorbing a wide solar spectrum. It is preferable to do.

Hereinafter, each component will be briefly described.
1. p-layer, n-layer, i-layer The p-layer is a layer that transports holes, and the material used as the p-layer is not particularly limited, but is preferably a compound having a function as an electron-donating material, and the movement of holes A high degree of material is preferred. Because it is a functional layer that absorbs sunlight and contributes to power generation,
It is preferable to strongly absorb sunlight.
For example, N, N′-bis (3-tolyl) -N, N′-diphenylbenzidine (mTPD), N, N′-dinaphthyl-N, N′-diphenylbenzidine (NPD), 4,4 ′, 4 ′ Amine compounds represented by '-tris (phenyl-3-tolylamino) triphenylamine (MTDATA), etc., phthalocyanine (Pc), copper phthalocyanine (CuPc), zinc phthalocyanine (ZnPc), titanyl phthalocyanine (TiOPc), boron phthalocyanine ( Subphycline complexes such as phthalocyanine complexes such as SubPc), naphthalocyanine complexes, benzoporphyrin (BP), octaethylporphyrin (OEP), platinum octaethylporphyrin (PtOEP), zinc tetraphenylporphyrin (ZnTPP), and thienoacenes Be mentioned . Moreover, if it is a high molecular compound using the application | coating process by a solution, main chain type conjugated polymers, such as methoxyethyl hexyloxy phenylene vinylene (MEHPPV), polyhexyl thiophene (P3HT), cyclopentadithiophene-benzothiadiazole (PCPDTBT) And side chain polymers represented by polyvinylcarbazole and the like.
The p layer may be crystalline or amorphous, but is preferably crystalline. However, if the crystallinity is too strong, it may not be possible to form a thin film, such as white turbidity.

The n layer is a layer that transports electrons, and the material used for the n layer is not particularly limited, but a compound having a function as an electron accepting material is preferable.
For _example, a fullerene or fullerene derivatives such as C _{60, C 70,} carbon nanotube, perylene derivatives, polycyclic quinone, quinacridone, the polymeric CN- poly (phenylene - vinylene), MEH-CN-PPV, -CN group or CF ₃ group-containing polymers, their -CF ₃ substituted polymers, poly (fluorene) derivatives and the like can be mentioned. Of these, fullerenes and fullerene derivatives are particularly preferable.
Moreover, an inorganic compound may be sufficient. Specifically, doped semiconductors and compound semiconductors such as n-Si, GaAs, CdS, PbS, CdSe, InP, Nb ₂ O ₅ , WO ₃ , Fe ₂ O ₃ , titanium dioxide (TiO ₂ ), and titanium monoxide (TiO), titanium oxides such as dititanium trioxide (Ti ₂ O ₃ ), and conductive oxides such as zinc oxide (ZnO) and tin oxide (SnO ₂ ), and one or two of them A combination of the above may also be used.

The i layer is a mixed layer of an electron donating material and an electron accepting material. The kind of electron donating material and electron accepting material is not particularly limited.
The material used for the p layer is preferable for the electron donating material, and the material used for the n layer is preferable for the electron accepting material.
The i layer can be formed by co-evaporating an electron donating material and an electron accepting material. At this time, the mixing ratio of the electron donating material is 1% by weight to 99% by weight.

2. Upper electrode, lower electrode The material of the upper electrode and the lower electrode is not particularly limited, and a known conductive material can be used. For example, a metal such as tin-doped indium oxide (ITO), gold (Au), osmium (Os), palladium (Pd) can be used as the electrode connected to the p layer, and silver as the electrode connected to the n layer. Metals such as (Ag), aluminum (Al), indium (In), calcium (Ca), platinum (Pt), lithium (Li) and the like, and binary metal systems such as Mg: Ag, Mg: In and Al: Li, Furthermore, the electrode example material connected with the said p layer can be used.
In order to obtain highly efficient photoelectric conversion characteristics, for example, in the case of an organic thin film solar cell, it is desirable that at least one surface of the solar cell be sufficiently transparent to the sunlight spectrum. The transparent electrode is formed using a known conductive material so as to ensure a predetermined translucency by a method such as vapor deposition or sputtering. The light transmittance of the electrode on the light receiving surface is preferably 10% or more. In a preferred configuration of the pair of electrode configurations, one of the electrode portions includes a metal having a high work function, and the other includes a metal having a low work function.

3. Buffer Layer A preferred compound for the buffer layer is preferably a compound having sufficiently high carrier mobility so that the short-circuit current does not decrease even when the film thickness is increased. For example, if it is a low molecular compound, the aromatic cyclic acid anhydride represented by NTCDA shown below etc. will be mentioned, and if it is a high molecular compound, poly (3,4-ethylenedioxy) thiophene: polystyrene sulfonate (PEDOT: PSS), polyaniline: camphorsulfonic acid (PANI: CSA), and other known conductive polymers.

  In addition, the buffer layer may have a role of preventing excitons from diffusing to the electrodes and deactivating. Inserting a buffer layer as an exciton blocking layer in this way is effective for increasing efficiency. The exciton blocking layer can be inserted on either the positive electrode side or the negative electrode side, or both can be inserted simultaneously. In this case, examples of a preferable material for the exciton blocking layer include a hole barrier layer material or an electron barrier layer material known for use in organic electroluminescence device. A preferable material for the hole blocking layer is a compound having a sufficiently large ionization potential, and a preferable material for the electron blocking layer is a compound having a sufficiently small electron affinity. Specifically, bathocuproin (BCP), bathophenanthroline (BPhen), and the like, which are well-known materials for organic electroluminescence device applications, can be cited as the hole blocking layer material on the negative electrode side.

Furthermore, you may use the inorganic semiconductor compound illustrated as said electron-accepting material for a buffer layer. As the p-type inorganic semiconductor compound, CdTe, p-Si, SiC, GaAs, WO ₃ or the like can be used.

4). Substrate The substrate preferably has mechanical and thermal strength and transparency. For example, there are a glass substrate and a transparent resin film. Transparent resin films include polyethylene, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polypropylene, polystyrene, polymethyl methacrylate, polyvinyl chloride, polyvinyl alcohol, polyvinyl butyral, nylon, polyether ether ketone. , Polysulfone, polyethersulfone, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, polyvinyl fluoride, tetrafluoroethylene-ethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polychlorotrifluoroethylene, Polyvinylidene fluoride, polyester, polycarbonate, polyurethane, polyimide, polyetherimide, polyimide, polypropylene, etc. That.

  The thickness of each layer is not particularly limited, but is set to an appropriate thickness. Since it is generally known that the exciton diffusion length of an organic thin film is short, if the film thickness is too thick, the exciton is deactivated before reaching the heterointerface, resulting in low photoelectric conversion efficiency. If the film thickness is too thin, pinholes and the like are generated, so that sufficient diode characteristics cannot be obtained, resulting in a decrease in conversion efficiency. The normal film thickness is suitably in the range of 1 nm to 10 μm, but more preferably in the range of 5 nm to 0.2 μm.

Then, the manufacturing method of the organic thin film solar cell of this invention is demonstrated.
The manufacturing method of the present invention includes a coating step of forming a first organic thin-film solar cell by a coating method on a substrate on which a lower electrode (first electrode) is formed, and an intermediate layer and a second organic thin-film solar. A vapor deposition step of forming the battery cell by a vapor deposition method is included. Specifically, the first electrode is formed on the substrate, the first organic thin film solar cell is applied and formed, the intermediate layer and the second organic thin film solar cell are deposited, and the second electrode Form.

  The coating process is usually performed in a nitrogen atmosphere or an atmosphere adjusted to a water concentration of 100 ppm or less. The moisture concentration is preferably 10 ppm or less.

  As the coating method, a known wet film forming method such as spin coating, dip coating, casting, roll coating, flow coating, and ink jet can be applied.

  In the wet film forming method, a low molecular material is dissolved or dispersed in an appropriate organic solvent to prepare a solution to form a thin film, and any solvent can be used as the solvent. For example, halogenated hydrocarbon solvents such as dichloromethane, dichloroethane, chloroform, carbon tetrachloride, tetrachloroethane, trichloroethane, chlorobenzene, dichlorobenzene, chlorotoluene, ether solvents such as dibutyl ether, tetrahydrofuran, dioxane, anisole, methanol, Alcohol solvents such as ethanol, propanol, butanol, pentanol, hexanol, cyclohexanol, methyl cellosolve, ethyl cellosolve, ethylene glycol, hydrocarbon solvents such as benzene, toluene, xylene, ethylbenzene, hexane, octane, decane, tetralin, Examples include ester solvents such as ethyl acetate, butyl acetate, and amyl acetate. Of these, hydrocarbon solvents or ether solvents are preferable. These solvents may be used alone or in combination. In addition, the solvent which can be used is not limited to these.

  A 1st organic thin film photovoltaic cell can be formed by drying after application | coating (drying process).

Next, an intermediate | middle layer and a 2nd organic thin film photovoltaic cell are formed by a vapor deposition process. The vapor deposition is usually performed at 1 × 10 ⁻³ Pa or less, preferably 1 × 10 ⁻⁴ Pa.

  Vapor deposition is performed after the substrate on which the first organic thin-film solar cells are formed is transported to, for example, a vacuum chamber and the vacuum chamber is depressurized to the above pressure (decompression step). The solvent contained in the coating layer (first organic thin-film solar battery cell) can be dried and removed. That is, the decompression step can be combined with the drying step of the coating layer without providing a drying step after coating.

In this case, a small amount (for example, 1% or less) of organic solvent remains in the coating layer immediately after forming the coating layer, but the organic solvent content of the coating layer after the decompression step, that is, when the intermediate layer is formed. Is preferably 0.1% or less, more preferably 0.05% or less.
The organic solvent content of the coating layer is measured with a precision electronic balance.

As a vapor deposition method, a known resistance heating method can be used. The resistance heating method is a method in which a metal boat or crucible is filled with a material and heated to sublimate the material to form a film.
Specifically, a deposition source is placed on a boat made of molybdenum (Mo), tungsten (W), carbon (C), etc., and heated by applying voltage, or alumina (Al ₂ O ₃ ), aluminum nitride ( A method of heating in a crucible such as AlN) and heating with a heater can be used.
The material and shape of a metal boat or crucible used as a deposition source are not limited.

  In the production method of the present invention, a method for forming a layer other than the above-mentioned layers is not particularly limited, and a dry film forming method such as vacuum deposition, sputtering, plasma, ion plating, spin coating, dip coating, casting, roll coating, Wet film formation methods such as flow coating and ink jet can be applied.

Next, an example of the manufacturing method of the organic thin film solar cell of this invention is demonstrated, referring FIG.
The glass substrate 10 with an ITO transparent electrode having a thickness of 25 mm × 75 mm × 0.7 mm is subjected to ultrasonic cleaning in isopropyl alcohol for 5 minutes and then UV ozone cleaning for 15 minutes.

  A film of PEDOT: PSS is formed on the substrate 10 with a spin coater in the atmosphere so as to have a film thickness of 30 nm. Then, it dries on a hot plate heated to 140 ° C., removes the solvent, and forms the p buffer layer 20. Further, patterning is performed by a wiping mechanism soaked with dichloromethane so that the extraction pattern of the upper electrode does not get in the way.

  Separately from the above, in a glove box with a residual moisture and oxygen concentration of 0.1 ppm or less, the purity is sufficiently increased by column purification or the like (for example, 99.9% or more). The material (p material) and PC60BM (n material) are mixed at a weight ratio of 1: 4 to prepare a 4 wt% solution (BHJ (bulk heterojunction) layer coating material) with an organic solvent such as chlorobenzene.

  The substrate 10 on which the p buffer layer 20 is formed is put into the glove box where the BHJ layer coating material is prepared, and the BHJ layer coating material is coated on the p buffer layer 20 with a spin coater so that the film thickness is 60 nm. Then, a low molecular coating layer (first organic thin film solar cell 30) is formed. As with the p buffer layer 20, the excess portion is completely wiped off with dichloromethane.

  Next, the board | substrate 10 which laminated | stacked the 1st organic thin film photovoltaic cell 30 is conveyed from a glove box to a vapor deposition apparatus. The vapor deposition device is connected to the glove box via a gate valve. The vapor deposition device is vented to atmospheric pressure with high-purity nitrogen of S level or higher, and then the gate valve is opened to the vapor deposition device in a nitrogen atmosphere. Transport.

Then, after closing the gate valve, the vapor deposition apparatus is evacuated to 1 × 10 ⁻⁴ Pa. At this time, it is confirmed that the signal level in the quadrupole mass spectrometer indicating the presence of the residual solvent and the hydrocarbon having a molecular weight of 15 to 100 is the same level as the normal operation state before the substrate introduction. Further, patterning is performed using a vapor deposition mask so as to be the same film formation region as that of the first organic thin film solar battery cell 30.

On the first organic thin-film solar battery cell 30 from which the solvent has been removed, 5 nm of Ca is formed as an electron transport layer to form an n buffer layer 42, and 20% of MoO ₃ is stacked to form a p buffer layer 44. Intermediate electrode. Further, patterning is performed using a vapor deposition mask in the same manner as described above.
After the degree of vacuum is stabilized, a 100 膜厚 film thickness adjusting layer (p-type doping layer) 46 (NPV01: NPV07) is formed by the same organic film mask pattern as above, and the intermediate layer 40 is formed.

Subsequently, the p layer 62, i layer 64 and the n layer 66 is formed using _{C 70} as a NPV03, n material p material, to produce a pin-type element (second organic thin film solar cell 60). Subsequently, 10 nm bathocuproin (BCP) is formed thereon by resistance heating vapor deposition at 1 Å / s to form a buffer layer 70. Finally, metal Al is continuously deposited as a counter electrode 80 with a film thickness of 100 nm to obtain the organic thin film solar cell 1.

The material of each said layer is shown below.

  The tandem organic thin-film solar cell of the present invention can be used as a power source or auxiliary power source for various devices such as watches, mobile phones, and mobile personal computers, and electrical appliances. Combined with a rechargeable battery with a charging function, it can be used in the dark, and the application can be expanded.

DESCRIPTION OF SYMBOLS 1 Tandem type organic thin film solar cell 10 Substrate 20 p buffer layer 30 1st organic solar cell 40 Intermediate layer 42 n buffer layer 44 p buffer layer 46 Film thickness adjustment layer 60 2nd organic solar cell 62 p layer 64 i layer 66 n layer 70 buffer layer 80 electrode

Claims (6)

  On a substrate, a first electrode, a coating type first organic thin film solar cell containing a low molecular material, a vapor deposition type intermediate layer containing a low molecular material, and a vapor deposition type second organic thin film containing a low molecular material A tandem organic thin-film solar battery including a solar battery cell and a second electrode in this order.   2. The tandem organic thin film solar cell according to claim 1, wherein the molecular weight of the low molecular weight material contained in the first organic thin film solar cell is 5,000 or less.   The tandem organic thin film solar cell according to claim 1 or 2, wherein the number of repeating units of the low molecular weight material contained in the first organic thin film solar cell is 10 or less.   The tandem organic thin film solar cell according to any one of claims 1 to 3, wherein the first organic thin film solar cell includes 0.01% to 0.1% of an organic solvent. A coating step of forming a first organic thin-film solar cell containing a low-molecular material by a coating method in a nitrogen atmosphere or an atmosphere having a moisture concentration of 100 ppm or less on a substrate on which an electrode is formed; and 1 × 10 ⁻³ The manufacturing method of the tandem-type organic thin-film solar cell in any one of Claims 1-4 including the vapor deposition process of forming an intermediate | middle layer and a 2nd organic thin-film solar cell by vapor deposition method below Pa.   Immediately after forming the first organic thin film solar cell, the organic solvent remaining in the first organic thin film solar cell is removed during the formation of the intermediate layer, and the content in the first organic thin film solar cell The manufacturing method of the tandem-type organic thin-film solar cell of Claim 5 which becomes 0.1% or less.