WO2014020988A1 - Organic thin-film solar cell and method for producing same - Google Patents

Organic thin-film solar cell and method for producing same Download PDF

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WO2014020988A1
WO2014020988A1 PCT/JP2013/065580 JP2013065580W WO2014020988A1 WO 2014020988 A1 WO2014020988 A1 WO 2014020988A1 JP 2013065580 W JP2013065580 W JP 2013065580W WO 2014020988 A1 WO2014020988 A1 WO 2014020988A1
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layer
bulk heterojunction
organic semiconductor
type organic
solar cell
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French (fr)
Japanese (ja)
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優 永井
郵司 吉田
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富士電機株式会社
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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K30/00—Organic devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation
    • H10K30/30—Organic devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation comprising bulk heterojunctions, e.g. interpenetrating networks of donor and acceptor material domains
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K30/00—Organic devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation
    • H10K30/50—Photovoltaic [PV] devices
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
    • H10K85/10—Organic polymers or oligomers
    • H10K85/111—Organic polymers or oligomers comprising aromatic, heteroaromatic, or aryl chains, e.g. polyaniline, polyphenylene or polyphenylene vinylene
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
    • H10K85/10—Organic polymers or oligomers
    • H10K85/111—Organic polymers or oligomers comprising aromatic, heteroaromatic, or aryl chains, e.g. polyaniline, polyphenylene or polyphenylene vinylene
    • H10K85/113—Heteroaromatic compounds comprising sulfur or selene, e.g. polythiophene
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
    • H10K85/40—Organosilicon compounds, e.g. TIPS pentacene
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/549—Organic PV cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present invention relates to an organic thin film solar cell including a bulk heterojunction layer and a method for manufacturing the same.
  • a bulk heterojunction type organic thin film solar cell in which a bulk heterojunction layer is formed between a transparent electrode layer and a counter electrode layer as one of thin film solar cells using an organic material (hereinafter referred to as an organic thin film solar cell). (See Non-Patent Document 1).
  • a bulk heterojunction type organic thin film solar cell is formed by applying a coating liquid containing a p-type organic semiconductor, an n-type organic semiconductor, and an organic solvent on one electrode layer. It is manufactured by forming a bulk heterojunction layer.
  • the first requirement is related to the domain size.
  • the bulk heterojunction layer absorbs light, excitons are generated in the domain, and the excitons diffuse into the domain and reach the pn interface, and then are separated into free charges.
  • the exciton diffusion length in the bulk heterojunction layer is small and is 10 to 20 nm.
  • the domain size is larger than this diffusion length, free charges are not generated because excitons are deactivated before reaching the pn interface. Therefore, it is ideal that the domain size is 10 nm or less.
  • the second requirement is related to the connection structure between domains.
  • the domains In the bulk heterojunction layer, it is considered that holes conduct through a domain of a p-type material and electrons conduct through a domain of an n-type material. Therefore, in a situation where the domains are separated from each other, even if free charge is generated, it cannot be conducted to the electrode. Under these circumstances, it is ideal that the domains are in contact with each other to form a percolation structure.
  • the structure of the bulk heterojunction layer 1 is that the domain 1a has a size smaller than the diffusion length of excitons and the domain 1a is an electrode as shown in FIG. What has the percolation structure connected to a few is ideal.
  • an object of the present invention is to provide an organic thin-film solar cell with excellent power generation performance by optimizing the structure of the bulk heterojunction layer. Moreover, it is providing the manufacturing method for it.
  • the present inventors have shown that the structure that has been considered to be ideal as the structure of the bulk heterojunction layer shown in FIG. 4 is not necessarily preferable for solar cell performance, and the short circuit current is reduced. Found that it is likely to bring
  • the organic thin-film solar cell of the present invention includes a bulk heterojunction layer in which a domain of a p-type organic semiconductor and a domain of an n-type organic semiconductor are phase-separated, and either directly on the one side of the bulk heterojunction layer
  • An organic thin-film solar cell comprising an anode disposed via a layer and a cathode disposed directly or via another layer on the other side of the bulk heterojunction layer,
  • domains of a p-type organic semiconductor having an average diameter of 1 nm or more and 30 nm or less are dispersed, and a percolation structure in which the domains of the p-type organic semiconductor are connected to connect both electrodes is formed. It is characterized by not.
  • the domain of the p-type organic semiconductor has a substantially spherical shape and is dispersed in the bulk heterojunction layer.
  • the p-type organic semiconductor is an amorphous material and the n-type semiconductor is a fullerene derivative.
  • a hole blocking layer is preferably inserted between the bulk heterojunction layer and the cathode.
  • the manufacturing method of the organic thin-film solar cell of the present invention includes a step of forming a first electrode layer on a substrate, and a p-type organic semiconductor on the first electrode layer directly or via another layer. a step of applying a coating solution containing an n-type organic semiconductor and an organic solvent to form a coating film; a step of forming a second electrode layer on the coating film directly or via another layer; A step of heat-treating the coating film at 50 ° C. or more and 140 ° C. or less for 10 minutes or more and 30 minutes or less after forming the second electrode layer.
  • the short-circuit current, the open-circuit voltage, and the fill factor are improved, and high energy conversion efficiency can be realized.
  • the coating liquid containing a p-type organic semiconductor, an n-type organic semiconductor, and an organic solvent on the 1st electrode layer directly or through another layer After forming a coating film, a second electrode layer is formed on the coating film directly or via another layer, and then the coating film is formed at 50 ° C. or more and 140 ° C. or less for 10 minutes or more and 30 minutes.
  • the domain of the p-type organic semiconductor having an average diameter of 1 nm or more and 30 nm or less is dispersed, and the domain of the p-type organic semiconductor is connected to form a percolation structure that connects the electrodes.
  • An organic thin film solar cell having a bulk heterojunction layer that is not formed can be manufactured.
  • FIG. 4 is a cross-sectional projection view of a bulk heterojunction layer of Test Example 1.
  • FIG. 6 is a cross-sectional projection view of a bulk heterojunction layer of Test Example 2.
  • FIG. It is the schematic of the bulk heterojunction layer considered conventionally ideal.
  • the organic thin film solar cell shown in FIG. 1 is formed by sequentially laminating a first electrode layer 12, a bulk heterojunction layer 13, and a second electrode layer 14 on a substrate 11.
  • the substrate 11 is not particularly limited.
  • an insulating plastic film substrate such as a polyimide film, a polyethylene terephthalate film, a polyethylene naphthalate film, a polyethersulfone film, an acrylic film, an aramid film, a glass substrate, a stainless steel substrate, or the like can be used.
  • substrate is distribute
  • FIG. Examples of the electrode material of the electrode layer disposed on the light incident side include transparent conductive oxides such as ITO (indium oxide + tin oxide), ZnO, TiO 2 , SnO 2 , and IZO (indium oxide + zinc oxide).
  • Examples of the electrode material of the electrode layer disposed on the non-light-receiving side include metals such as Al, Mg, Ca, and alloys thereof.
  • the bulk heterojunction layer 13 has a structure in which a domain 13a of a p-type organic semiconductor and a domain 13b of an n-type organic semiconductor are phase-separated.
  • the p-type organic semiconductor domains 13a having an average diameter of 1 nm to 30 nm are dispersed almost uniformly in the bulk heterojunction layer 13, and the p-type organic semiconductor domains 13a The percolation structure by 13a is not formed.
  • an organic thin-film solar cell capable of realizing high energy conversion efficiency with improved short-circuit current, open-circuit voltage, and fill factor. Can do. The reason for this is not known in detail, but is probably because some of the holes generated at the pn interface are conducted to the n-type organic semiconductor domain in addition to the p-type organic semiconductor domain. It is assumed.
  • the domain size of the domain 13a of the p-type organic semiconductor is an average diameter of 1 nm or more and 30 nm or less.
  • the average diameter is more preferably 1 nm or more and 20 nm or less, and particularly preferably 1 nm or more and 10 nm or less. If the domain size exceeds 30 nm, excitons are deactivated before reaching the pn interface, and free charges are hardly generated. Further, if the domain size is too small, the number of absorbed photons per unit film thickness tends to decrease and the short circuit current tends to decrease, so the lower limit is 1 nm.
  • the shape of the domain 13a of the p-type organic semiconductor is preferably substantially spherical. If it is substantially spherical, the internal electric field generated in the film thickness direction efficiently acts on the pn interface, and the charge separation efficiency is increased.
  • phase separation structure of the bulk heterojunction layer 13 is prepared by using Scanning Transmission Electron Microscope (STEM), Electron Energy Loss SpectroEL, Spectral Spectroscopy, etc. This can be confirmed by observing the image.
  • STEM Scanning Transmission Electron Microscope
  • Electron Energy Loss SpectroEL Electron Energy Loss SpectroEL
  • Spectral Spectroscopy etc. This can be confirmed by observing the image.
  • any organic material having an electron donating property can be used.
  • compounds such as thiophene, phenylene vinylene, thienylene vinylene, carbazole, vinyl carbazole, pyrrole, isothiaphene and heptadiene, and the above compounds having a hydroxyl group, an alkyl group, an amino group, a methyl group, a nitro group, a halogen group, etc.
  • Examples include, but are not limited to, polymers of derivatives. These may be used alone or in combination of two or more.
  • compounds of the following formulas (1) to (14) can be mentioned as an example.
  • n is preferably 5 to 150, more preferably 10 to 100.
  • the compounds represented by the formulas (1) and (6) are crystalline compounds. Further, the compounds represented by the formulas (7) to (14) are amorphous (non-crystalline).
  • the p-type organic semiconductor may be crystalline or amorphous (amorphous). Since the crystalline organic semiconductor material has high domain elasticity, the domain 13a of the p-type organic semiconductor as shown in FIG. 1 is dispersed almost uniformly in the bulk heterojunction layer 13, and the domain of the p-type organic semiconductor is obtained. It is easy to adopt the bulk heterojunction layer 13 having a structure in which the percolation structure by 13a is not formed. Therefore, a crystalline material is particularly preferably used for the p-type organic semiconductor. The degree of stereoregularity of the p-type organic semiconductor is not questioned.
  • the weight average molecular weight of the p-type organic semiconductor depends on the material used and cannot be generally mentioned, but is preferably 2,000 to 150,000.
  • any organic material having an electron accepting property can be used.
  • examples thereof include fullerene derivatives and perylene derivatives.
  • fullerene derivatives are particularly preferable because electron transfer from the p-type organic semiconductor is particularly fast.
  • Preferred examples of the fullerene derivative include a fullerene C 60 derivative, a fullerene C 70 derivative, and a fullerene C 80 derivative.
  • PCBM Phenyl-C 61 -Butyric-Acid -Methyl Ester
  • bis-PCBM Bisadduct-Phenyl-C 61 -Butyric- Acid-Methyl Ester
  • the first electrode layer 12 and the second electrode layer 14 are directly formed on both sides of the bulk heterojunction layer 13.
  • a hole blocking layer may be formed between the electrode layer serving as a cathode of the layer 14 and the bulk heterojunction layer 13. According to this aspect, hole-electron recombination in the vicinity of the cathode can be suppressed, rectification is improved, and short-circuit current is improved.
  • the hole blocking layer is not particularly limited as long as it has a hole blocking effect.
  • Examples thereof include a lithium fluoride (LiF) film, a Bathocupline (BCP) film, a TiO x film, a TiO 2 film, and a ZnO nanoparticle.
  • the film thickness of the hole blocking layer is preferably from 0.1 nm to 1.0 nm, and more preferably from 0.3 nm to 0.5 nm.
  • the thickness is less than 0.1 nm, the hole blocking effect cannot be sufficiently obtained.
  • the thickness exceeds 1.0 nm, the insulating property becomes high and charge injection tends to be inhibited.
  • a hole transport layer may be formed between the electrode layer serving as an anode and the bulk heterojunction layer 13 among the first electrode layer 12 and the second electrode layer 14. According to this aspect, the injection of charge from the bulk heterojunction layer 13 to the anode can be promoted, the rectification is improved, and the short-circuit current is improved.
  • hole transport layer examples include poly (3,4-ethylenediothiophene / poly (styrene sulfate) (PEDOT / PSS).
  • the first electrode layer 12 is formed on the substrate 11.
  • a method for forming the first electrode layer 12 is not particularly limited, and a conventionally known method such as a sputtering method, a CVD method, or a spray film forming method can be used.
  • the organic solvent has sufficient solubility with respect to the p-type organic semiconductor and the n-type organic semiconductor.
  • the solvent volatilizes immediately after application of the coating solution, and phase separation between the p-type organic semiconductor and the n-type organic semiconductor cannot proceed sufficiently.
  • the present inventors have found that if the phase separation is insufficient, the domains of the p-type organic semiconductor are connected to each other and a percolation structure is easily formed. Therefore, it is desirable that the organic solvent has a high boiling point above a certain level.
  • the organic solvent is preferably 100 ° C. or higher and 300 ° C. or lower, and more preferably 120 ° C.
  • organic solvent examples include chlorobenzene (boiling point: 131 ° C.), anisole (boiling point: 154 ° C.), 1,2-dichlorobenzene (boiling point: 181 ° C.), 1,2,3-trichlorobenzene (boiling point: 221). ° C) and the like.
  • 70 mass% or more and 99.9 mass% or less are preferable, and, as for content of the organic solvent in a coating liquid, 80 mass% or more and 99 mass% or less are more preferable.
  • content of the organic solvent in a coating liquid 80 mass% or more and 99 mass% or less are more preferable.
  • the content of the organic solvent is less than 70% by mass, organic semiconductors as solutes tend to aggregate together, and phase separation tends not to occur.
  • the content exceeds 99.9% by mass the viscosity of the solution decreases. It becomes difficult to form a coating film having an appropriate film thickness by applying the coating liquid.
  • the coating liquid can contain additives such as an antioxidant, a compatibilizing agent and a crystallization accelerator as long as the physical properties are not impaired.
  • the coating liquid is preferably applied in an inert gas atmosphere with a humidity of 0.01% or less, such as dry nitrogen or dry argon.
  • a humidity of 0.01% or less such as dry nitrogen or dry argon.
  • the coating method of the coating liquid is not particularly limited, and conventionally known methods such as spin coating, dip coating, spray coating, ink jet printing, and screen printing can be used.
  • the second electrode layer 14 is formed directly or via another layer such as a hole blocking layer or a hole transporting layer on the coating film formed by applying the coating liquid.
  • a method for forming the second electrode layer 14 is not particularly limited, and a conventionally known method such as a sputtering method, a CVD method, or a spray film forming method can be used.
  • the coating film is heat-processed and the bulk heterojunction layer 13 is formed, and an organic thin-film solar cell is manufactured.
  • the coating film is heated at a temperature of 140 ° C. or lower, and the detailed reason is not clear, but the heating temperature corresponds to the metastable region of the phase diagram.
  • the phase separation between the p-type organic semiconductor and the n-type organic semiconductor is sufficiently advanced, the domains of the p-type organic semiconductor having an average diameter of 1 nm to 30 nm are dispersed, and the p-type organic semiconductor Organic thin-film solar cells having a bulk heterojunction layer in which the percolation structure that connects the two domains and connects the two electrodes are not formed can be manufactured. If the heat treatment is performed at a temperature of 150 ° C.
  • the domains of the p-type organic semiconductor are connected to form a percolation structure that connects the two electrodes.
  • the reason for this is considered to be that the heating temperature corresponds to the spinodal region of the phase diagram.
  • thermo treatment method There is no particular limitation on the heat treatment method.
  • a method using a hot plate can be used.
  • the heat treatment is performed so that the coating film is 50 ° C. or more and 140 ° C. or less and is performed for 10 minutes or more and 30 minutes or less.
  • the temperature is preferably 100 ° C. or higher and 140 ° C. or lower.
  • the heating time is preferably 10 minutes or more and 20 minutes or less.
  • the temperature is lower than 50 ° C., the phase separation does not reach an equilibrium structure, and the phase separation hardly occurs.
  • the temperature exceeds 140 ° C. it becomes easy to form a percolation structure in which the domains of the p-type organic semiconductor are connected to connect the two electrodes.
  • the heating time is less than 10 minutes, the phase separation does not reach an equilibrium structure, and phase separation hardly occurs. Moreover, the phase separation structure no longer changes even if it continues for 30 minutes or more.
  • a glass substrate on which a first electrode layer (ITO) was formed was prepared, and the surface was dry-cleaned with oxygen plasma. Then, the said coating liquid was apply
  • the rotation condition was 2000 rpm ⁇ 120 seconds. Application was performed in a glove box filled with dry nitrogen.
  • the substrate is put back into the glove box and subjected to heat treatment (130 ° C. ⁇ 15 minutes) using a hot plate to form a bulk heterojunction layer.
  • An organic thin film solar cell was manufactured.
  • a thin sample (thickness 50 nm) was cut out from the bulk heterojunction layer using Focused Ion Beam (FIB), and transmission observation was performed using Scanning Transmission Electron Microscope (STEM) to examine the phase separation structure. Separately, domain components of the bulk heterojunction layer were confirmed using Electron Energy Loss Spectroscopy (EELS). The results are shown in FIG.
  • the domain (white portion) of the p-type organic semiconductor had a substantially spherical shape with a diameter of 15 ⁇ 5 nm, and was almost uniformly dispersed in the bulk heterojunction layer. Moreover, the percolation structure was not formed.
  • Test Example 2 In Test Example 1, except that the heat treatment condition was changed to 160 ° C. ⁇ 15 minutes, a bulk heterojunction layer was formed in the same manner as in Test Example 1 to produce an organic thin film solar cell.
  • Test Example 3 LiF was deposited on the coating film to form a hole blocking layer (thickness 0.1 nm), and a second electrode layer (Al) was deposited on the hole blocking layer. Next, the substrate was returned to the glove box, and heat treatment (160 ° C. ⁇ 15 minutes) was performed using a hot plate to form a bulk heterojunction layer, thereby manufacturing an organic thin film solar cell.
  • the light receiving cells (2 mm ⁇ 2 mm) of the organic thin film solar cells of Test Examples 1 to 3 were irradiated with simulated sunlight (AM1.5), and the solar cell performance (short circuit current (Jsc), open circuit voltage (Voc)), FF (curve factor), energy conversion efficiency (PCE)) were examined.
  • For irradiation with simulated sunlight OTE-XL manufactured by Spectrometer Co., Ltd. was used.
  • Test Example 1 showed the highest short-circuit current (Jsc). Moreover, also about the open circuit voltage (Voc), FF (fill factor), and energy conversion efficiency (PCE), the test example 1 showed the solar cell performance comparable as the test example 3 which formed the hole block layer.
  • Substrate 12 First electrode layer 13: Bulk heterojunction layer 13a: Domain of p-type organic semiconductor 13b: Domain of n-type organic semiconductor 14: Second electrode layer

Abstract

Provided is an organic thin-film solar cell having excellent power generation performance as a result of optimizing the structure of a bulk heterojunction layer. The organic thin-film solar cell is provided with: a bulk heterojunction layer (13) wherein p-type organic semiconductor domains (13a) and n-type semiconductor domains (13b) are present as separate phases; an anode (12) (or 14) positioned directly on one side of the bulk heterojunction layer (13) or with another layer therebetween; and a cathode anode (14) (or 12) positioned directly on the other side of the bulk heterojunction layer (13) or with another layer therebetween. The bulk heterojunction layer (13) has a structure wherein the p-type organic semiconductor domains (13a), which have an average diameter of 1 nm to 30 nm, are dispersed, and the p-type semiconductor domains (13a) are linked so that a percolation structure connecting both electrodes is not formed.

Description

有機薄膜太陽電池及びその製造方法Organic thin film solar cell and method for producing the same
　本発明は、バルクヘテロ接合層を備えた有機薄膜太陽電池及びその製造方法に関する。 The present invention relates to an organic thin film solar cell including a bulk heterojunction layer and a method for manufacturing the same.
　有機材料を用いた薄膜太陽電池（以下、有機薄膜太陽電池という）の一つとして、透明電極層と対向電極層との間にバルクヘテロ接合層を形成してなる、バルクヘテロ接合型の有機薄膜太陽電池がある（非特許文献１参照）。 A bulk heterojunction type organic thin film solar cell in which a bulk heterojunction layer is formed between a transparent electrode layer and a counter electrode layer as one of thin film solar cells using an organic material (hereinafter referred to as an organic thin film solar cell). (See Non-Patent Document 1).
　バルクヘテロ接合型の有機薄膜太陽電池は、例えば特許文献１に開示されるように、ｐ型有機半導体とｎ型有機半導体と有機溶媒とを含む塗工液を、一方の電極層上に塗布してバルクへテロ接合層を形成することにより製造される。 For example, as disclosed in Patent Document 1, a bulk heterojunction type organic thin film solar cell is formed by applying a coating liquid containing a p-type organic semiconductor, an n-type organic semiconductor, and an organic solvent on one electrode layer. It is manufactured by forming a bulk heterojunction layer.
　バルクヘテロ接合層の構造としては、以下の二つの要件が想定されている。 The following two requirements are assumed for the structure of the bulk heterojunction layer.
　第一の要件は、ドメインサイズに関するものである。バルクヘテロ接合層が光を吸収すると、ドメイン内に励起子が生成され、励起子がドメイン内を拡散してｐｎ界面に到達した後、自由電荷に分離される。バルクヘテロ接合層での励起子の拡散長は小さく、１０～２０ｎｍとされている。ドメインサイズがこの拡散長より大きい場合は、励起子はｐｎ界面に到達する以前に失活してしまうため、自由電荷が生成されない。そのため、ドメインサイズは１０ｎｍ以下であることが理想とされている。 The first requirement is related to the domain size. When the bulk heterojunction layer absorbs light, excitons are generated in the domain, and the excitons diffuse into the domain and reach the pn interface, and then are separated into free charges. The exciton diffusion length in the bulk heterojunction layer is small and is 10 to 20 nm. When the domain size is larger than this diffusion length, free charges are not generated because excitons are deactivated before reaching the pn interface. Therefore, it is ideal that the domain size is 10 nm or less.
　第二の要件は、ドメイン同士の連結構造に関するものである。バルクヘテロ接合層では、正孔はｐ型材料、電子はｎ型材料のドメインを、それぞれ伝導すると考えられる。したがって、ドメインが互いに分離して存在しているような状況では、例え自由電荷が生じたとしても、電極まで伝導してゆくことが出来ない。これらの事情から、ドメイン同士は互いに接触してパーコレーション構造を形成していることが理想とされている。 The second requirement is related to the connection structure between domains. In the bulk heterojunction layer, it is considered that holes conduct through a domain of a p-type material and electrons conduct through a domain of an n-type material. Therefore, in a situation where the domains are separated from each other, even if free charge is generated, it cannot be conducted to the electrode. Under these circumstances, it is ideal that the domains are in contact with each other to form a percolation structure.
　このため、バルクヘテロ接合型の有機薄膜太陽電池においては、バルクヘテロ接合層１の構造として、図４に示されるように、ドメイン１ａが励起子の拡散長より小さなサイズを持ち、かつ、ドメイン１ａが電極２，３まで連結したパーコレーション構造を有するものが理想とされている。 Therefore, in the bulk heterojunction type organic thin film solar cell, the structure of the bulk heterojunction layer 1 is that the domain 1a has a size smaller than the diffusion length of excitons and the domain 1a is an electrode as shown in FIG. What has the percolation structure connected to a few is ideal.
特開２００９－２５２７６８号公報JP 2009-252768 A
　バルクヘテロ接合層の構造を直接観察した研究例は少なく、バルクヘテロ接合層の構造と、太陽電池性能との関係は十分に明らかではなかった。上述したバルクヘテロ接合構造の要件についても、これまでは仮説の域を出なかった。このため、理想的なバルクヘテロ接合構造が必ずしも明確となってはいないために、素子の設計指針を確立出来ていないという状況が続いてきた。 There are few examples of direct observation of the structure of the bulk heterojunction layer, and the relationship between the structure of the bulk heterojunction layer and the solar cell performance was not sufficiently clear. The requirements for the above-described bulk heterojunction structure have not been in the hypothesis so far. For this reason, since the ideal bulk heterojunction structure is not necessarily clarified, the situation that the design guideline of the element has not been established has continued.
　よって、本発明の目的は、バルクヘテロ接合層の構造を最適化して、発電性能に優れた有機薄膜太陽電池を提供することにある。また、そのための製造方法を提供することにある。 Therefore, an object of the present invention is to provide an organic thin-film solar cell with excellent power generation performance by optimizing the structure of the bulk heterojunction layer. Moreover, it is providing the manufacturing method for it.
　本発明者らは、鋭意研究の結果、図４に示される、バルクヘテロ接合層の構造として従来理想的であると考えられてきた構造は、必ずしも太陽電池性能にとって好ましいものではなく、短絡電流の低下をもたらす可能性が高いことを見出した。 As a result of intensive studies, the present inventors have shown that the structure that has been considered to be ideal as the structure of the bulk heterojunction layer shown in FIG. 4 is not necessarily preferable for solar cell performance, and the short circuit current is reduced. Found that it is likely to bring
　そして、ドメイン同士が分離した構造は、従来の仮説に従うと、自由電荷が電極まで伝導してゆくことが出来ないため、好ましくないと考えられていたが、ドメインサイズが適切に制御された限りにおいて、短絡電流、開放電圧、曲線因子が向上して、高いエネルギー変換効率などを実現することが出来ることを見出し、本発明を完成するに至った。 And, according to the conventional hypothesis, the structure in which the domains are separated from each other was considered to be unfavorable because free charge cannot be conducted to the electrode. However, as long as the domain size is appropriately controlled. The inventors have found that the short-circuit current, the open-circuit voltage, and the fill factor can be improved to realize high energy conversion efficiency, and the present invention has been completed.
　すなわち、本発明の有機薄膜太陽電池は、ｐ型有機半導体のドメインとｎ型有機半導体のドメインとが相分離しているバルクヘテロ接合層と、前記バルクヘテロ接合層の一方の面側に直接又は他の層を介して配置された陽極と、前記バルクヘテロ接合層の他方の面側に直接又は他の層を介して配置された陰極とを備えた有機薄膜太陽電池であって、
　前記バルクヘテロ接合層は、平均直径１ｎｍ以上３０ｎｍ以下のｐ型有機半導体のドメインが分散しており、かつ、ｐ型有機半導体のドメインどうしが連結して両電極間を接続するパーコレーション構造が形成されていないことを特徴とする。 That is, the organic thin-film solar cell of the present invention includes a bulk heterojunction layer in which a domain of a p-type organic semiconductor and a domain of an n-type organic semiconductor are phase-separated, and either directly on the one side of the bulk heterojunction layer An organic thin-film solar cell comprising an anode disposed via a layer and a cathode disposed directly or via another layer on the other side of the bulk heterojunction layer,
In the bulk heterojunction layer, domains of a p-type organic semiconductor having an average diameter of 1 nm or more and 30 nm or less are dispersed, and a percolation structure in which the domains of the p-type organic semiconductor are connected to connect both electrodes is formed. It is characterized by not.
　本発明の有機薄膜太陽電池は、前記ｐ型有機半導体のドメインが略球状をなして、前記バルクヘテロ接合層に分散していることが好ましい。 In the organic thin film solar cell of the present invention, it is preferable that the domain of the p-type organic semiconductor has a substantially spherical shape and is dispersed in the bulk heterojunction layer.
　本発明の有機薄膜太陽電池は、前記ｐ型有機半導体がアモルファス性材料であり、前記ｎ型半導体がフラーレン誘導体であることが好ましい。 In the organic thin film solar cell of the present invention, it is preferable that the p-type organic semiconductor is an amorphous material and the n-type semiconductor is a fullerene derivative.
　本発明の有機薄膜太陽電池は、前記バルクヘテロ接合層と前記陰極との間に、正孔ブロック層が挿入されていることが好ましい。 In the organic thin-film solar cell of the present invention, a hole blocking layer is preferably inserted between the bulk heterojunction layer and the cathode.
　また、本発明の有機薄膜太陽電池の製造方法は、基板上に、第１電極層を形成する工程と、前記第１電極層上に、直接又は他の層を介して、ｐ型有機半導体とｎ型有機半導体と有機溶媒とを含む塗工液を塗布して塗膜を形成する工程と、前記塗膜上に、直接又は他の層を介して、第２電極層を形成する工程と、前記第２電極層を形成したのち、前記塗膜を５０℃以上１４０℃以下で、１０分間以上３０分間以下加熱処理する工程とを含むことを特徴とする。 Moreover, the manufacturing method of the organic thin-film solar cell of the present invention includes a step of forming a first electrode layer on a substrate, and a p-type organic semiconductor on the first electrode layer directly or via another layer. a step of applying a coating solution containing an n-type organic semiconductor and an organic solvent to form a coating film; a step of forming a second electrode layer on the coating film directly or via another layer; A step of heat-treating the coating film at 50 ° C. or more and 140 ° C. or less for 10 minutes or more and 30 minutes or less after forming the second electrode layer.
　本発明の有機薄膜太陽電池によれば、短絡電流、開放電圧、曲線因子が向上して、高いエネルギー変換効率を実現できる。 According to the organic thin film solar cell of the present invention, the short-circuit current, the open-circuit voltage, and the fill factor are improved, and high energy conversion efficiency can be realized.
　また、本発明の有機薄膜太陽電池の製造方法によれば、第１電極層上に、直接又は他の層を介して、ｐ型有機半導体とｎ型有機半導体と有機溶媒とを含む塗工液を塗布して塗膜を形成した後、該塗膜上に、直接又は他の層を介して第２電極層を形成し、その後、塗膜を５０℃以上１４０℃以下で、１０分間以上３０分間以下加熱処理することで、平均直径１ｎｍ以上３０ｎｍ以下のｐ型有機半導体のドメインが分散しており、かつ、ｐ型有機半導体のドメインどうしが連結して両電極間を接続するパーコレーション構造が形成されていないバルクヘテロ接合層を備えた有機薄膜太陽電池を製造できる。 Moreover, according to the manufacturing method of the organic thin-film solar cell of this invention, the coating liquid containing a p-type organic semiconductor, an n-type organic semiconductor, and an organic solvent on the 1st electrode layer directly or through another layer. After forming a coating film, a second electrode layer is formed on the coating film directly or via another layer, and then the coating film is formed at 50 ° C. or more and 140 ° C. or less for 10 minutes or more and 30 minutes. By performing the heat treatment for a minute or less, the domain of the p-type organic semiconductor having an average diameter of 1 nm or more and 30 nm or less is dispersed, and the domain of the p-type organic semiconductor is connected to form a percolation structure that connects the electrodes. An organic thin film solar cell having a bulk heterojunction layer that is not formed can be manufactured.
本発明の有機薄膜太陽電池の概略図である。It is the schematic of the organic thin film solar cell of this invention. 試験例１のバルクヘテロ接合層の断面投影図である。4 is a cross-sectional projection view of a bulk heterojunction layer of Test Example 1. FIG. 試験例２のバルクヘテロ接合層の断面投影図である。6 is a cross-sectional projection view of a bulk heterojunction layer of Test Example 2. FIG. 従来理想とされてきたバルクヘテロ接合層の概略図である。It is the schematic of the bulk heterojunction layer considered conventionally ideal.
　本発明の有機薄膜太陽電池について、図１を用いて説明する。 The organic thin film solar cell of the present invention will be described with reference to FIG.
　図１に示す有機薄膜太陽電池は、基板１１上に、第１電極層１２、バルクヘテロ接合層１３、第２電極層１４が順次積層されて形成されている。 The organic thin film solar cell shown in FIG. 1 is formed by sequentially laminating a first electrode layer 12, a bulk heterojunction layer 13, and a second electrode layer 14 on a substrate 11.
　基板１１としては、特に限定されない。例えば、ポリイミドフィルム、ポリエチレンテレフタレートフィルム、ポリエチレンナフタレートフィルム、ポリエーテルスルホンフィルム、アクリルフィルム、アラミドフィルム等の絶縁性プラスチックフィルム基板、ガラス基板、ステンレス基板などを用いることができる。なお、この基板が光入射側に配される場合には、光透過性の材料で構成すべきことはいうまでもない。 The substrate 11 is not particularly limited. For example, an insulating plastic film substrate such as a polyimide film, a polyethylene terephthalate film, a polyethylene naphthalate film, a polyethersulfone film, an acrylic film, an aramid film, a glass substrate, a stainless steel substrate, or the like can be used. In addition, when this board | substrate is distribute | arranged to the light-incidence side, it cannot be overemphasized that it should comprise with a light transmissive material.
　第１電極層１２、第２電極層１４を構成する電極材料としては、特に限定はない。光入射側に配される電極層の電極材料としては、ＩＴＯ（酸化インジウム＋酸化スズ）、ＺｎＯ、ＴｉＯ２、ＳｎＯ２、ＩＺＯ（酸化インジウム＋酸化亜鉛）などの透明導電性酸化物が挙げられる。非受光側に配される電極層の電極材料としては、Ａｌ、Ｍｇ、Ｃａ等の金属あるいはこれらの合金が挙げられる。 There is no limitation in particular as an electrode material which comprises the 1st electrode layer 12 and the 2nd electrode layer 14. FIG. Examples of the electrode material of the electrode layer disposed on the light incident side include transparent conductive oxides such as ITO (indium oxide + tin oxide), ZnO, TiO 2 , SnO 2 , and IZO (indium oxide + zinc oxide). . Examples of the electrode material of the electrode layer disposed on the non-light-receiving side include metals such as Al, Mg, Ca, and alloys thereof.
　バルクヘテロ接合層１３は、ｐ型有機半導体のドメイン１３ａと、ｎ型有機半導体のドメイン１３ｂとが相分離した構造をなしている。そして、本発明においては、図１に示すように、平均直径１ｎｍ以上３０ｎｍ以下のｐ型有機半導体のドメイン１３ａが、バルクヘテロ接合層１３中にほぼ均一に分散しており、ｐ型有機半導体のドメイン１３ａによるパーコレーション構造が形成されていないことが特徴である。 The bulk heterojunction layer 13 has a structure in which a domain 13a of a p-type organic semiconductor and a domain 13b of an n-type organic semiconductor are phase-separated. In the present invention, as shown in FIG. 1, the p-type organic semiconductor domains 13a having an average diameter of 1 nm to 30 nm are dispersed almost uniformly in the bulk heterojunction layer 13, and the p-type organic semiconductor domains 13a The percolation structure by 13a is not formed.
　バルクヘテロ接合層１３がこのような構造をなすことで、後述する実施例に示すように、短絡電流、開放電圧、曲線因子が向上して、高いエネルギー変換効率を実現できる有機薄膜太陽電池とすることができる。この理由は、詳細には分からないが、おそらく、ｐｎ界面で生じた正孔の一部が、ｐ型有機半導体のドメインに加えて、ｎ型有機半導体のドメインにも伝導しているためであると想定される。 By forming such a structure of the bulk heterojunction layer 13, as shown in an example described later, an organic thin-film solar cell capable of realizing high energy conversion efficiency with improved short-circuit current, open-circuit voltage, and fill factor. Can do. The reason for this is not known in detail, but is probably because some of the holes generated at the pn interface are conducted to the n-type organic semiconductor domain in addition to the p-type organic semiconductor domain. It is assumed.
　ｐ型有機半導体のドメイン１３ａのドメインサイズは、平均直径１ｎｍ以上３０ｎｍ以下である。その平均直径は、１ｎｍ以上２０ｎｍ以下がより好ましく、１ｎｍ以上１０ｎｍ以下が特に好ましい。ドメインサイズが３０ｎｍを超えると、励起子がｐｎ界面に到達する以前に失活して自由電荷が生成され難くなる。また、ドメインサイズが小さすぎると単位膜厚あたりの吸収フォトン数が少なくなって、短絡電流が低下する傾向にあるので、その下限は１ｎｍである。 The domain size of the domain 13a of the p-type organic semiconductor is an average diameter of 1 nm or more and 30 nm or less. The average diameter is more preferably 1 nm or more and 20 nm or less, and particularly preferably 1 nm or more and 10 nm or less. If the domain size exceeds 30 nm, excitons are deactivated before reaching the pn interface, and free charges are hardly generated. Further, if the domain size is too small, the number of absorbed photons per unit film thickness tends to decrease and the short circuit current tends to decrease, so the lower limit is 1 nm.
　ｐ型有機半導体のドメイン１３ａの形状は、略球状が好ましい。略球状であれば膜厚方向に生じる内部電場が効率良くｐｎ界面に作用して、電荷分離効率が高まる。 The shape of the domain 13a of the p-type organic semiconductor is preferably substantially spherical. If it is substantially spherical, the internal electric field generated in the film thickness direction efficiently acts on the pn interface, and the charge separation efficiency is increased.
　なお、バルクヘテロ接合層１３の相分離構造は、Ｆｏｃｕｓｅｄ　Ｉｏｎ　Ｂｅａｍ（ＦＩＢ）を用いて薄片サンプルを作製したのちに、Ｓｃａｎｎｉｎｇ　Ｔｒａｎｓｍｉｓｓｉｏｎ　Ｅｌｅｃｔｒｏｎ　Ｍｉｃｒｏｓｃｏｐｅ（ＳＴＥＭ）、Ｅｌｅｃｔｒｏｎ　Ｅｎｅｒｇｙ　Ｌｏｓｓ　Ｓｐｅｃｔｒｏｓｃｏｐｙ（ＥＥＬＳ）等を用いて、透過像を観察することで確認できる。 In addition, the phase separation structure of the bulk heterojunction layer 13 is prepared by using Scanning Transmission Electron Microscope (STEM), Electron Energy Loss SpectroEL, Spectral Spectroscopy, etc. This can be confirmed by observing the image.
　バルクヘテロ接合層１３を構成するｐ型有機半導体としては、電子供与性を有する任意の有機材料を用いることができる。例えば、チオフェン、フェニレンビニレン、チエニレンビニレン、カルバゾール、ビニルカルバゾール、ピロール、イソチアナフェンおよびヘプタジエンなどの化合物、ならびに水酸基、アルキル基、アミノ基、メチル基、ニトロ基およびハロゲン基などを有する上記化合物の誘導体の重合体が挙げられるが、これらには限定されない。これらは、単独で用いてもよいし、二種以上を組み合わせて用いてもよい。例えば、下記式（１）～（１４）の化合物が一例として挙げられる。 As the p-type organic semiconductor constituting the bulk heterojunction layer 13, any organic material having an electron donating property can be used. For example, compounds such as thiophene, phenylene vinylene, thienylene vinylene, carbazole, vinyl carbazole, pyrrole, isothiaphene and heptadiene, and the above compounds having a hydroxyl group, an alkyl group, an amino group, a methyl group, a nitro group, a halogen group, etc. Examples include, but are not limited to, polymers of derivatives. These may be used alone or in combination of two or more. For example, compounds of the following formulas (1) to (14) can be mentioned as an example.
Figure JPOXMLDOC01-appb-C000001
Figure JPOXMLDOC01-appb-C000001
Figure JPOXMLDOC01-appb-C000002
Figure JPOXMLDOC01-appb-C000002
Figure JPOXMLDOC01-appb-C000003
Figure JPOXMLDOC01-appb-C000003
Figure JPOXMLDOC01-appb-C000004
Figure JPOXMLDOC01-appb-C000004
Figure JPOXMLDOC01-appb-C000005
Figure JPOXMLDOC01-appb-C000005
　上記式（１）～（１４）におけるｎは５～１５０が好ましく、１０～１００がより好ましい。 In the above formulas (1) to (14), n is preferably 5 to 150, more preferably 10 to 100.
　上記化合物のうち、式（１）、（６）で表される化合物は、結晶性の化合物である。また、式（７）～（１４）で表される化合物は、アモルファス性（非晶性）である。ｐ型有機半導体は、結晶性でもアモルファス性（非晶性）であってもよい。結晶性の有機半導体材料は、ドメインの弾性が高いために、図１に示すような、ｐ型有機半導体のドメイン１３ａが、バルクヘテロ接合層１３中にほぼ均一に分散し、ｐ型有機半導体のドメイン１３ａによるパーコレーション構造が形成されていない構造のバルクヘテロ接合層１３を採り易い。そのため、ｐ型有機半導体は、結晶性の材料が特に好ましく用いられる。また、ｐ型有機半導体の立体規則性の程度については問われない。 Among the above compounds, the compounds represented by the formulas (1) and (6) are crystalline compounds. Further, the compounds represented by the formulas (7) to (14) are amorphous (non-crystalline). The p-type organic semiconductor may be crystalline or amorphous (amorphous). Since the crystalline organic semiconductor material has high domain elasticity, the domain 13a of the p-type organic semiconductor as shown in FIG. 1 is dispersed almost uniformly in the bulk heterojunction layer 13, and the domain of the p-type organic semiconductor is obtained. It is easy to adopt the bulk heterojunction layer 13 having a structure in which the percolation structure by 13a is not formed. Therefore, a crystalline material is particularly preferably used for the p-type organic semiconductor. The degree of stereoregularity of the p-type organic semiconductor is not questioned.
　ｐ型有機半導体の重量平均分子量は、用いる材料にも依存し、一概には言及出来ないが、２，０００～１５０，０００が望ましい。 The weight average molecular weight of the p-type organic semiconductor depends on the material used and cannot be generally mentioned, but is preferably 2,000 to 150,000.
　バルクヘテロ接合層を構成するｎ型有機半導体としては、電子受容性を有する任意の有機材料を用いることができる。例えば、フラーレン誘導体、ペリレン誘導体等が挙げられる。なかでも、フラーレン誘導体は、ｐ型有機半導体からの電子移動が取り分け早いので、特に好ましい。フラーレン誘導体としては、フラーレンＣ６０の誘導体、フラーレンＣ７０の誘導体、フラーレンＣ８０の誘導体等が好ましく挙げられる。具体的な一例としては、Ｐｈｅｎｙｌ－Ｃ６１－Ｂｕｔｙｒｉｃ－Ａｃｉｄ－Ｍｅｔｈｙｌ　Ｅｓｔｅｒ（ＰＣＢＭ）、Ｂｉｓａｄｄｕｃｔ－Ｐｈｅｎｙｌ－Ｃ６１－Ｂｕｔｙｒｉｃ－Ａｃｉｄ－Ｍｅｔｈｙｌ　Ｅｓｔｅｒ（ｂｉｓ－ＰＣＢＭ）等が挙げられる。 As the n-type organic semiconductor constituting the bulk heterojunction layer, any organic material having an electron accepting property can be used. Examples thereof include fullerene derivatives and perylene derivatives. Among these, fullerene derivatives are particularly preferable because electron transfer from the p-type organic semiconductor is particularly fast. Preferred examples of the fullerene derivative include a fullerene C 60 derivative, a fullerene C 70 derivative, and a fullerene C 80 derivative. As a specific example, Phenyl-C 61 -Butyric-Acid -Methyl Ester (PCBM), or the like Bisadduct-Phenyl-C 61 -Butyric- Acid-Methyl Ester (bis-PCBM) and the like.
　図１に示す実施形態の有機薄膜太陽電池は、バルクヘテロ接合層１３の両側に、第１電極層１２、第２電極層１４がそれぞれ直接形成されているが、第１電極層１２及び第２電極層１４のうち、陰極となる電極層と、バルクヘテロ接合層１３との間に、正孔ブロック層が形成されていてもよい。この態様によれば、陰極近傍における正孔―電子の再結合を抑制でき、整流性が改善されて短絡電流が向上する。 In the organic thin film solar cell of the embodiment shown in FIG. 1, the first electrode layer 12 and the second electrode layer 14 are directly formed on both sides of the bulk heterojunction layer 13. A hole blocking layer may be formed between the electrode layer serving as a cathode of the layer 14 and the bulk heterojunction layer 13. According to this aspect, hole-electron recombination in the vicinity of the cathode can be suppressed, rectification is improved, and short-circuit current is improved.
　正孔ブロック層としては、正孔のブロック効果があるものであれば良く、特に限定はない。例えば、フッ化リチウム（ＬｉＦ）膜、Ｂａｔｈｏｃｕｐｒｏｉｎｅ（ＢＣＰ）膜、ＴｉＯｘ膜、ＴｉＯ２膜、ＺｎＯナノパーティクルなどが挙げられる。 The hole blocking layer is not particularly limited as long as it has a hole blocking effect. Examples thereof include a lithium fluoride (LiF) film, a Bathocupline (BCP) film, a TiO x film, a TiO 2 film, and a ZnO nanoparticle.
　正孔ブロック層の膜厚は、０．１ｎｍ以上１．０ｎｍ以下が好ましく、０．３ｎｍ以上０．５ｎｍ以下がより好ましい。０．１ｎｍ未満であると、正孔のブロック効果が十分に得られない。１．０ｎｍを超えると、絶縁性が高くなって、電荷注入が阻害される傾向にある。 The film thickness of the hole blocking layer is preferably from 0.1 nm to 1.0 nm, and more preferably from 0.3 nm to 0.5 nm. When the thickness is less than 0.1 nm, the hole blocking effect cannot be sufficiently obtained. When the thickness exceeds 1.0 nm, the insulating property becomes high and charge injection tends to be inhibited.
　また、第１電極層１２及び第２電極層１４のうち、陽極となる電極層と、バルクヘテロ接合層１３との間に、正孔輸送層が形成されていてもよい。この態様によれば、バルクヘテロ接合層１３から陽極への電荷の注入を促進でき、整流性が改善されて短絡電流が向上する。 Further, a hole transport layer may be formed between the electrode layer serving as an anode and the bulk heterojunction layer 13 among the first electrode layer 12 and the second electrode layer 14. According to this aspect, the injection of charge from the bulk heterojunction layer 13 to the anode can be promoted, the rectification is improved, and the short-circuit current is improved.
　正孔輸送層としては、ｐｏｌｙ（３，４－ｅｔｈｙｌｅｎｅｄｉｏｘｙｔｈｉｏｐｈｅｎｅ／ｐｏｌｙ（ｓｔｙｒｅｎｅ　ｓｕｌｆｏｎａｔｅ）（ＰＥＤＯＴ／ＰＳＳ）等が挙げられる。 Examples of the hole transport layer include poly (3,4-ethylenediothiophene / poly (styrene sulfate) (PEDOT / PSS).
　次に、本発明の有機薄膜太陽電池の製造方法について説明する。 Next, a method for producing the organic thin film solar cell of the present invention will be described.
　まず、基板１１上に、第１電極層１２を形成する。第１電極層１２の形成方法としては、特に限定は無く、スパッタ法、ＣＶＤ法、スプレー成膜法等、従来公知の方法を用いることができる。 First, the first electrode layer 12 is formed on the substrate 11. A method for forming the first electrode layer 12 is not particularly limited, and a conventionally known method such as a sputtering method, a CVD method, or a spray film forming method can be used.
　次に、第１電極層１２上に、直接又は、正孔ブロック層、正孔輸送層等の他の層を介して、ｐ型有機半導体とｎ型有機半導体と有機溶媒とを含む塗工液を塗布し、塗膜を形成する。 Next, a coating liquid containing a p-type organic semiconductor, an n-type organic semiconductor, and an organic solvent on the first electrode layer 12 directly or via another layer such as a hole blocking layer or a hole transporting layer. Is applied to form a coating film.
　塗工液中におけるｐ型有機半導体とｎ型有機半導体との混合割合は、モル比で、ｐ型有機半導体：ｎ型有機半導体＝１：０．５～７が好ましく、１：０．７～３がより好ましい。混合割合が上記範囲内であれば、電子と正孔がバランス良く輸送されるため、高いＦＦ値を得ることが出来る。 The mixing ratio of the p-type organic semiconductor and the n-type organic semiconductor in the coating liquid is preferably a molar ratio of p-type organic semiconductor: n-type organic semiconductor = 1: 0.5-7, 1: 0.7- 3 is more preferable. If the mixing ratio is within the above range, electrons and holes are transported in a well-balanced manner, so that a high FF value can be obtained.
　有機溶媒は、ｐ型有機半導体及びｎ型有機半導体に対して、十分な溶解性を持つものであることが望ましい。また、有機溶媒の沸点があまり低いと、塗工液の塗布後直ちに溶媒が揮発してしまい、ｐ型有機半導体とｎ型有機半導体の相分離が十分に進行することが出来ない。本発明者らは、研究の結果、相分離の進行が不十分であると、ｐ型有機半導体のドメインどうしが互いに連結して、パーコレーション構造が形成され易くなることを見出した。そのため、有機溶媒は、一定以上の高い沸点を持つものであることが望ましく、具体的には１００℃以上３００℃以下が好ましく、１２０℃以上２５０℃以下がより好ましい。有機溶媒の好ましい具体例としては、クロロベンゼン（沸点：１３１℃）、アニソール（沸点：１５４℃）、１，２－ジクロロベンゼン（沸点：１８１℃）、１，２，３－トリクロロベンゼン（沸点：２２１℃）等が挙げられる。 It is desirable that the organic solvent has sufficient solubility with respect to the p-type organic semiconductor and the n-type organic semiconductor. On the other hand, if the boiling point of the organic solvent is too low, the solvent volatilizes immediately after application of the coating solution, and phase separation between the p-type organic semiconductor and the n-type organic semiconductor cannot proceed sufficiently. As a result of research, the present inventors have found that if the phase separation is insufficient, the domains of the p-type organic semiconductor are connected to each other and a percolation structure is easily formed. Therefore, it is desirable that the organic solvent has a high boiling point above a certain level. Specifically, the organic solvent is preferably 100 ° C. or higher and 300 ° C. or lower, and more preferably 120 ° C. or higher and 250 ° C. or lower. Preferred examples of the organic solvent include chlorobenzene (boiling point: 131 ° C.), anisole (boiling point: 154 ° C.), 1,2-dichlorobenzene (boiling point: 181 ° C.), 1,2,3-trichlorobenzene (boiling point: 221). ° C) and the like.
　塗工液中における有機溶媒の含有量は、７０質量％以上９９．９質量％以下が好ましく、８０質量％以上９９質量％以下がより好ましい。有機溶媒の含有量が７０質量％未満であると、溶質である有機半導体同士が凝集して、相分離が生じ難くなる傾向があり、９９．９質量％を超えると溶液の粘度が低下して、塗工液の塗布により適切な膜厚を有する塗膜を形成し難くなる。 70 mass% or more and 99.9 mass% or less are preferable, and, as for content of the organic solvent in a coating liquid, 80 mass% or more and 99 mass% or less are more preferable. When the content of the organic solvent is less than 70% by mass, organic semiconductors as solutes tend to aggregate together, and phase separation tends not to occur. When the content exceeds 99.9% by mass, the viscosity of the solution decreases. It becomes difficult to form a coating film having an appropriate film thickness by applying the coating liquid.
　塗工液には、酸化防止剤、相溶化剤、結晶化促進剤等の添加剤を、物性を損なわない範囲で含有できる。 The coating liquid can contain additives such as an antioxidant, a compatibilizing agent and a crystallization accelerator as long as the physical properties are not impaired.
　塗工液の塗布は、乾燥窒素、乾燥アルゴン等の湿度０．０１％以下の不活性ガス雰囲気下で行うことが好ましい。酸素や水分の存在下で塗膜を形成すると、これらの成分が塗膜中に残存して、高分子材料を劣化させる恐れがある。 The coating liquid is preferably applied in an inert gas atmosphere with a humidity of 0.01% or less, such as dry nitrogen or dry argon. When a coating film is formed in the presence of oxygen or moisture, these components may remain in the coating film and deteriorate the polymer material.
　塗工液の塗布方法は、特に限定はなく、スピン塗布、ディップ塗布、スプレー塗布、インクジェット印刷、スクリーン印刷など従来公知の方法を用いることができる。 The coating method of the coating liquid is not particularly limited, and conventionally known methods such as spin coating, dip coating, spray coating, ink jet printing, and screen printing can be used.
　次に、上記塗工液を塗布して形成した塗膜上に、直接又は、正孔ブロック層、正孔輸送層等の他の層を介して、第２電極層１４を形成する。第２電極層１４の形成方法としては、特に限定は無く、スパッタ法、ＣＶＤ法、スプレー成膜法等、従来公知の方法を用いることができる。 Next, the second electrode layer 14 is formed directly or via another layer such as a hole blocking layer or a hole transporting layer on the coating film formed by applying the coating liquid. A method for forming the second electrode layer 14 is not particularly limited, and a conventionally known method such as a sputtering method, a CVD method, or a spray film forming method can be used.
　そして、本発明では、塗膜上に第２電極層１４を形成した後、塗膜を加熱処理してバルクヘテロ接合層１３を形成し、有機薄膜太陽電池を製造する。 And in this invention, after forming the 2nd electrode layer 14 on a coating film, the coating film is heat-processed and the bulk heterojunction layer 13 is formed, and an organic thin-film solar cell is manufactured.
　第２電極層１４を形成した後、塗膜を１４０℃以下の温度で加熱処理することで、詳細な理由は定かではないが、該加熱温度が相図の準安定領域に対応していると推定される理由により、ｐ型有機半導体とｎ型有機半導体との相分離が十分に進行し、平均直径１ｎｍ以上３０ｎｍ以下のｐ型有機半導体のドメインが分散しており、かつ、ｐ型有機半導体のドメインどうしが連結して両電極間を接続するパーコレーション構造が形成されていないバルクヘテロ接合層を備えた有機薄膜太陽電池を製造できる。なお、第２電極層１４を形成する前に、１５０℃以上の温度で加熱処理すると、ｐ型有機半導体のドメインどうしが連結して、両電極間を接続するパーコレーション構造が形成される。この理由は、該加熱温度が相図のスピノーダル領域に対応していることによるものと考えられる。 After the second electrode layer 14 is formed, the coating film is heated at a temperature of 140 ° C. or lower, and the detailed reason is not clear, but the heating temperature corresponds to the metastable region of the phase diagram. For the reason presumed, the phase separation between the p-type organic semiconductor and the n-type organic semiconductor is sufficiently advanced, the domains of the p-type organic semiconductor having an average diameter of 1 nm to 30 nm are dispersed, and the p-type organic semiconductor Organic thin-film solar cells having a bulk heterojunction layer in which the percolation structure that connects the two domains and connects the two electrodes are not formed can be manufactured. If the heat treatment is performed at a temperature of 150 ° C. or higher before the second electrode layer 14 is formed, the domains of the p-type organic semiconductor are connected to form a percolation structure that connects the two electrodes. The reason for this is considered to be that the heating temperature corresponds to the spinodal region of the phase diagram.
　加熱処理方法としては、特に限定は無い。例えば、ホットプレートを用いる方法等が挙げられる。 There is no particular limitation on the heat treatment method. For example, a method using a hot plate can be used.
　加熱処理は、塗膜が５０℃以上１４０℃以下になるように加熱し、１０分間以上３０分間以下行う。温度は１００℃以上１４０℃以下が好ましい。加熱時間は１０分間以上２０分間以下が好ましい。温度が５０℃未満であると、相分離が平衡構造に到達せず、相分離が生じ難い。また、温度が１４０℃を超えると、ｐ型有機半導体のドメインどうしが連結して両電極間を接続するパーコレーション構造が形成され易くなる。また、加熱時間が１０分未満であると相分離が平衡構造に到達せず、相分離が生じ難い。また、３０分以上続けても相分離構造はもはや変化しない。 The heat treatment is performed so that the coating film is 50 ° C. or more and 140 ° C. or less and is performed for 10 minutes or more and 30 minutes or less. The temperature is preferably 100 ° C. or higher and 140 ° C. or lower. The heating time is preferably 10 minutes or more and 20 minutes or less. When the temperature is lower than 50 ° C., the phase separation does not reach an equilibrium structure, and the phase separation hardly occurs. On the other hand, when the temperature exceeds 140 ° C., it becomes easy to form a percolation structure in which the domains of the p-type organic semiconductor are connected to connect the two electrodes. If the heating time is less than 10 minutes, the phase separation does not reach an equilibrium structure, and phase separation hardly occurs. Moreover, the phase separation structure no longer changes even if it continues for 30 minutes or more.
　（試験例１）
　ｐ型有機半導体としてポリ３－ヘキシルチオフェン（Ｐ３ＨＴ）を２０ｍｇと、ｎ型有機半導体としてＰｈｅｎｙｌ－Ｃ６１－Ｂｕｔｙｒｉｃ－Ａｃｉｄ－Ｍｅｔｈｙｌ　Ｅｓｔｅｒ（ＰＣＢＭ）を１４ｍｇ採取し、溶媒クロロベンゼン（沸点１３１℃）１ｍＬに溶解させて、２０時間攪拌し、塗工液を調製した。 (Test Example 1)
20 mg of poly-3-hexylthiophene (P3HT) as a p-type organic semiconductor and 14 mg of Phenyl-C 61 -Butyric-Acyl-Methyl Ester (PCBM) as an n-type organic semiconductor were sampled into 1 mL of a solvent chlorobenzene (boiling point 131 ° C.). It was dissolved and stirred for 20 hours to prepare a coating solution.
　第１電極層（ＩＴＯ）の形成されたガラス基板を用意して、酸素プラズマで表面をドライ洗浄した。その後、スピンコーターを用いて基板上に上記塗工液を塗布し、塗膜を形成した。回転条件は２０００ｒｐｍ×１２０秒とした。塗布は乾燥窒素が封入されたグローブボックス内で行った。 A glass substrate on which a first electrode layer (ITO) was formed was prepared, and the surface was dry-cleaned with oxygen plasma. Then, the said coating liquid was apply | coated on the board | substrate using the spin coater, and the coating film was formed. The rotation condition was 2000 rpm × 120 seconds. Application was performed in a glove box filled with dry nitrogen.
　次に、塗膜上に、第２電極層（Ａｌ）を蒸着形成した後に、基板をグローブボックス内に戻し、ホットプレートを用いて加熱処理（１３０℃×１５分）を施してバルクヘテロ接合層を形成し、有機薄膜太陽電池を製造した。 Next, after depositing and forming the second electrode layer (Al) on the coating film, the substrate is put back into the glove box and subjected to heat treatment (130 ° C. × 15 minutes) using a hot plate to form a bulk heterojunction layer. An organic thin film solar cell was manufactured.
　Ｆｏｃｕｓｅｄ　Ｉｏｎ　Ｂｅａｍ（ＦＩＢ）を用いて、バルクヘテロ接合層から薄片サンプル（厚み５０ｎｍ）を切り出し、Ｓｃａｎｎｉｎｇ　Ｔｒａｎｓｍｉｓｓｉｏｎ　Ｅｌｅｃｔｒｏｎ　Ｍｉｃｒｏｓｃｏｐｅ（ＳＴＥＭ）を用いて透過観察を行い、相分離構造を調べた。別に、Ｅｌｅｃｔｒｏｎ　Ｅｎｅｒｇｙ　Ｌｏｓｓ　Ｓｐｅｃｔｒｏｓｃｏｐｙ（ＥＥＬＳ）を用いてバルクヘテロ接合層のドメインの成分を確認した。結果を図２に記す。 A thin sample (thickness 50 nm) was cut out from the bulk heterojunction layer using Focused Ion Beam (FIB), and transmission observation was performed using Scanning Transmission Electron Microscope (STEM) to examine the phase separation structure. Separately, domain components of the bulk heterojunction layer were confirmed using Electron Energy Loss Spectroscopy (EELS). The results are shown in FIG.
　図２に示されるように、このバルクヘテロ接合層は、ｐ型有機半導体のドメイン（白色部位）が直径１５±５ｎｍの略球状をなしており、バルクヘテロ接合層にほぼ均一に分散していた。また、パーコレーション構造が形成されていなかった。 As shown in FIG. 2, in this bulk heterojunction layer, the domain (white portion) of the p-type organic semiconductor had a substantially spherical shape with a diameter of 15 ± 5 nm, and was almost uniformly dispersed in the bulk heterojunction layer. Moreover, the percolation structure was not formed.
　（試験例２）
　試験例１において、加熱処理条件を１６０℃×１５分に変更した以外は、試験例１と同様にしてバルクヘテロ接合層を形成し、有機薄膜太陽電池を製造した。 (Test Example 2)
In Test Example 1, except that the heat treatment condition was changed to 160 ° C. × 15 minutes, a bulk heterojunction layer was formed in the same manner as in Test Example 1 to produce an organic thin film solar cell.
　得られた有機薄膜太陽電池について、試験例１と同様にしてＦＩＢ、ＳＴＥＭ，及びＥＥＬＳを用い、バルクヘテロ接合層の相分離構造を調べた。結果を図３に記す。 For the obtained organic thin film solar cell, the phase separation structure of the bulk heterojunction layer was examined using FIB, STEM, and EELS in the same manner as in Test Example 1. The results are shown in FIG.
　図３に示されるように、より高温で加熱処理して形成したバルクヘテロ接合層は、ｐ型有機半導体のドメイン（白色部位）どうしが連結しており、両電極間を接続するパーコレーション構造が形成されていた。 As shown in FIG. 3, in the bulk heterojunction layer formed by heat treatment at a higher temperature, the domains (white portions) of the p-type organic semiconductor are connected to each other, and a percolation structure that connects the two electrodes is formed. It was.
　（試験例３）
　試験例１において、塗膜上にＬｉＦを蒸着して正孔ブロック層（厚み０．１ｎｍ）を形成し、その正孔ブロック層上に第２電極層（Ａｌ）を蒸着形成した。次いで、基板をグローブボックス内に戻し、ホットプレートを用いて加熱処理（１６０℃×１５分）を施してバルクヘテロ接合層を形成し、有機薄膜太陽電池を製造した。 (Test Example 3)
In Test Example 1, LiF was deposited on the coating film to form a hole blocking layer (thickness 0.1 nm), and a second electrode layer (Al) was deposited on the hole blocking layer. Next, the substrate was returned to the glove box, and heat treatment (160 ° C. × 15 minutes) was performed using a hot plate to form a bulk heterojunction layer, thereby manufacturing an organic thin film solar cell.
　試験例１～３の有機機薄膜太陽電池の受光セル（２ｍｍ×２ｍｍ）に、擬似太陽光（ＡＭ１．５）を照射して、太陽電池性能（短絡電流（Ｊｓｃ）、開放電圧（Ｖｏｃ）、ＦＦ（曲線因子）、エネルギー変換効率（ＰＣＥ））を調べた。擬似太陽光の照射には、分光計器製ＯＴＥ－ＸＬを用いた。電流密度と電圧の測定には、ＫＥＩＴＨＬＥＹ製２４００を用いた。表１に、結果をまとめて記す。 The light receiving cells (2 mm × 2 mm) of the organic thin film solar cells of Test Examples 1 to 3 were irradiated with simulated sunlight (AM1.5), and the solar cell performance (short circuit current (Jsc), open circuit voltage (Voc)), FF (curve factor), energy conversion efficiency (PCE)) were examined. For irradiation with simulated sunlight, OTE-XL manufactured by Spectrometer Co., Ltd. was used. For measurement of current density and voltage, 2400 made by KEITHLEY was used. Table 1 summarizes the results.
Figure JPOXMLDOC01-appb-T000006
Figure JPOXMLDOC01-appb-T000006
　表１に示すように、試験例１は最も高い短絡電流（Ｊｓｃ）を示した。また、開放電圧（Ｖｏｃ）、ＦＦ（曲線因子）、エネルギー変換効率（ＰＣＥ）についても、試験例１は、正孔ブロック層を形成した試験例３と同程度の太陽電池性能を示した。 As shown in Table 1, Test Example 1 showed the highest short-circuit current (Jsc). Moreover, also about the open circuit voltage (Voc), FF (fill factor), and energy conversion efficiency (PCE), the test example 1 showed the solar cell performance comparable as the test example 3 which formed the hole block layer.
１１：基板
１２：第１電極層
１３：バルクヘテロ接合層
１３ａ：ｐ型有機半導体のドメイン
１３ｂ：ｎ型有機半導体のドメイン
１４：第２電極層 11: Substrate 12: First electrode layer 13: Bulk heterojunction layer 13a: Domain of p-type organic semiconductor 13b: Domain of n-type organic semiconductor 14: Second electrode layer

Claims (5)

  1. 　ｐ型有機半導体のドメインとｎ型有機半導体のドメインとが相分離しているバルクヘテロ接合層と、前記バルクヘテロ接合層の一方の面側に直接又は他の層を介して配置された陽極と、前記バルクヘテロ接合層の他方の面側に直接又は他の層を介して配置された陰極とを備えた有機薄膜太陽電池であって、
    　前記バルクヘテロ接合層は、平均直径１ｎｍ以上３０ｎｍ以下のｐ型有機半導体のドメインが分散しており、かつ、ｐ型有機半導体のドメインどうしが連結して両電極間を接続するパーコレーション構造が形成されていないことを特徴とする有機薄膜太陽電池。     a bulk heterojunction layer in which a domain of a p-type organic semiconductor and a domain of an n-type organic semiconductor are phase-separated; an anode disposed directly on one side of the bulk heterojunction layer or via another layer; An organic thin-film solar cell comprising a cathode disposed directly or via another layer on the other side of the bulk heterojunction layer,
    In the bulk heterojunction layer, domains of a p-type organic semiconductor having an average diameter of 1 nm or more and 30 nm or less are dispersed, and a percolation structure in which the domains of the p-type organic semiconductor are connected to connect both electrodes is formed. Organic thin-film solar cell characterized by not having.
  2. 　前記ｐ型有機半導体のドメインが略球状をなして、前記バルクヘテロ接合層に分散している、請求項１に記載の有機薄膜太陽電池。 The organic thin-film solar cell according to claim 1, wherein the domains of the p-type organic semiconductor have a substantially spherical shape and are dispersed in the bulk heterojunction layer.
  3. 　前記ｐ型有機半導体がアモルファス性材料であり、前記ｎ型半導体がフラーレン誘導体である、請求項１に記載の有機薄膜太陽電池。 The organic thin-film solar cell according to claim 1, wherein the p-type organic semiconductor is an amorphous material and the n-type semiconductor is a fullerene derivative.
  4. 　前記バルクヘテロ接合層と前記陰極との間に、正孔ブロック層が挿入されている、請求項１に記載の有機薄膜太陽電池。 The organic thin-film solar cell according to claim 1, wherein a hole blocking layer is inserted between the bulk heterojunction layer and the cathode.
  5. 　基板上に、第１電極層を形成する工程と、
    　前記第１電極層上に、直接又は他の層を介して、ｐ型有機半導体とｎ型有機半導体と有機溶媒とを含む塗工液を塗布して塗膜を形成する工程と、
    　前記塗膜上に、直接又は他の層を介して、第２電極層を形成する工程と、
    　前記第２電極層を形成したのち、前記塗膜を５０℃以上１４０℃以下で、１０分間以上３０分間以下加熱処理する工程とを含むことを特徴とする有機薄膜太陽電池の製造方法。     Forming a first electrode layer on the substrate;
    A step of applying a coating liquid containing a p-type organic semiconductor, an n-type organic semiconductor, and an organic solvent directly or via another layer on the first electrode layer to form a coating film;
    Forming the second electrode layer on the coating film directly or via another layer;
    And a step of heat-treating the coating film at 50 to 140 ° C. for 10 to 30 minutes after forming the second electrode layer.
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