WO2009113450A1

WO2009113450A1 - Photovoltaic device, active layer material, and manufacturing method for photovoltaic device

Info

Publication number: WO2009113450A1
Application number: PCT/JP2009/054246
Authority: WO
Inventors: 山本　修平; 北澤　大輔; 塚本　遵
Original assignee: 東レ株式会社
Priority date: 2008-03-12
Filing date: 2009-03-06
Publication date: 2009-09-17
Also published as: TW201001775A; JPWO2009113450A1

Abstract

Provided is a photovoltaic device that improves the photoelectric conversion efficiency of various organic semiconductors. The photovoltaic device comprises: a first electrode and a second electrode, one or both of which are light-permeable; and an active layer, comprising an electron-donating organic semiconductor (A) and/or an electron-accepting organic semiconductor (B), sandwiched between the first electrode and the second electrode. The first electrode and the second electrode include a fluorous compound (C) therebetween, said fluorous compound existing locally either in proximity to the surface boundary between the first electrode and the active layer, or in proximity to the surface boundary of the second electrode and the active layer.

Description

Photovoltaic element, active layer material and method for producing photovoltaic element

The present invention relates to a photovoltaic device, an active layer material, and a method for manufacturing a photovoltaic device.

Solar cells are attracting attention as environmentally friendly electrical energy sources. At present, inorganic materials such as single crystal silicon, polycrystalline silicon, amorphous silicon, and compound semiconductors are used as semiconductor materials for photovoltaic elements of solar cells. However, solar cells manufactured using inorganic semiconductors have not been widely used in ordinary households because of high costs compared with power generation methods such as thermal power generation and nuclear power generation. The high cost factor is mainly in the process of forming the semiconductor thin film under vacuum and high temperature. Therefore, in order to simplify the manufacturing process, an organic solar cell using an organic semiconductor such as a conjugated polymer or an organic crystal or an organic dye as a semiconductor material has been studied. In such an organic solar cell, a semiconductor material can be manufactured by a coating method, so that the manufacturing process can be simplified.

However, conventional organic solar cells using organic semiconductors such as conjugated polymers have not yet been put into practical use because of lower photoelectric conversion efficiency than conventional solar cells using inorganic semiconductors. The following two points are mainly cited as the reason why the photoelectric conversion efficiency of an organic solar cell using a conventional conjugated polymer is low. First, it is easy to form a bound state called exciton in which electrons and holes generated by incident light are difficult to separate. Second, since traps for capturing carriers (electrons and holes) are easily formed, the generated carriers are easily captured by the traps, and the mobility of carriers is low. That is, a semiconductor material generally requires a high mobility μ for a carrier of the material, but a conjugated polymer has a problem that the mobility μ is lower than that of a conventional inorganic crystal semiconductor or amorphous silicon.

For this reason, a means for efficiently separating the generated electrons and holes from the exciton, and suppression of carrier scattering and trapping of carriers between the amorphous region of the conjugated polymer and the conjugated polymer chain are suppressed. Finding a means for improving mobility is the key to putting solar cells made of organic semiconductor materials into practical use.

The photovoltaic devices based on organic semiconductors known so far can be generally classified into the following device configurations at present. A Schottky type that joins an electron-donating organic material (p-type organic semiconductor) and a metal having a low work function, and an electron-accepting organic material (n-type organic semiconductor) and an electron-donating organic material (p-type organic semiconductor). Heterojunction type. These photovoltaic elements have low photoelectric conversion efficiency because only the organic layer (about several molecular layers) at the junction contributes to photocurrent generation.

Therefore, as one method for improving photoelectric conversion efficiency, an electron-accepting organic material (n-type organic semiconductor) and an electron-donating organic material (p-type organic semiconductor) are mixed to increase the area of the pn junction surface that causes photoelectric conversion. The bulk heterojunction type (for example, refer nonpatent literature 1) made is proposed. For example, the conjugated polymer used as the electron donating organic material (p-type organic semiconductor), a conductive polymer having semiconductor properties of n-type as the electron accepting organic material, using fullerene or a carbon nanotube, such as C ₆₀ Photoelectric conversion materials have been proposed (see, for example, Non-Patent Document 2 and Patent Documents 1 and 2). Moreover, it is disclosed that photoelectric conversion efficiency is further improved by adding alkanedithiol to the photoelectric conversion material (see, for example, Non-Patent Document 3).

Furthermore, in order to improve the photoelectric conversion efficiency, the interface state between the active layer containing the electron-accepting organic material (n-type organic semiconductor) and the electron-donating organic material (p-type organic semiconductor) and the electrode is important. Electric charges (holes and electrons) photoelectrically converted in the active layer are moved to the first electrode and the second electrode sandwiching the active layer by the internal electric field, respectively, and taken out to the external circuit. At that time, if there is a resistance such as an energy barrier or contact failure at the interface between the active layer and the electrode, the charge extraction efficiency is lowered, so that the photoelectric conversion efficiency is also lowered. Therefore, in general, in order to improve the interface state between the active layer and the electrode, a composite electrode having a buffer layer on the side in contact with the active layer is used. For the hole extraction buffer layer, a conductive polymer such as polyethylene dioxythiophene: polystyrene sulfonate (PEDOT: PSS) is preferably used (for example, see Non-Patent Document 4), and for the electron extraction buffer layer, lithium fluoride or Alkali metals, alkaline earth metals, polyethylene oxide, and the like are preferably used (see, for example, Non-Patent Document 5).

Further, regarding an organic semiconductor solution, a liquid composition including an organic semiconductor containing a high molecular weight component, an organic solvent that is a good solvent for the organic semiconductor, and an organic solvent that is a poor solvent for the organic semiconductor is disclosed (for example, Patent Document 3). To 4).
"Nature", 1995, 376, 498-500 "Applied Physics Letters," (USA), 2002, 80, 112-114. "Nature Materials", 2007, Vol. 6, pp. 497-500 "Applied Physics Letters" (USA), 2001, 79, 126-128, "Advanced Materials" (USA), 2007, 19, 1825-1838, JP 2003-347565 A JP 2004-165474 A US Patent Application Publication No. 2007/173578 US Patent Application Publication No. 2008/265214

However, according to the knowledge of the present inventors, the effect of improving the photoelectric conversion efficiency by alkanedithiol varies depending on the type of organic semiconductor, so that the effect is not sufficient depending on the type of organic semiconductor used. Further, merely providing a hole extraction buffer layer using a conductive polymer cannot sufficiently improve the interface between the active layer and the electrode, and the photoelectric conversion efficiency is insufficient. Furthermore, it has been difficult to obtain a photovoltaic device having sufficient photoelectric conversion efficiency even when the techniques described in Patent Documents 3 to 4 are used. Accordingly, an object of the present invention is to provide a photovoltaic device having improved photoelectric conversion efficiency for various organic semiconductors mainly by improving the interface state between the active layer and the electrode.

The present invention relates to a first electrode and a second electrode, at least one of which is light transmissive, at least (A) an electron donating organic semiconductor sandwiched between the first electrode and the second electrode, and (B) an electron accepting. A photovoltaic device having an active layer containing a conductive organic semiconductor, comprising (C) a fluorous compound between the first electrode and the second electrode, wherein the (C) fluorous compound comprises the first electrode and the The photovoltaic element is located near the interface with the active layer or near the interface between the second electrode and the active layer.

According to the present invention, a photovoltaic device with high photoelectric conversion efficiency can be provided.

Sectional drawing which shows the one aspect | mode of a tandem type photovoltaic device. Sectional drawing which shows the other one aspect | mode of the photovoltaic device of this invention. PEDOT: In-air photoelectron spectroscopy measurement results when a fluorous compound was applied on the PSS layer. The TOF-SIMS analysis result of Example 1. The TOF-SIMS analysis result of the comparative example 1. The TOF-SIMS analysis result of Example 2. The TOF-SIMS analysis result of Example 3 The TOF-SIMS analysis result of Example 4 The TOF-SIMS analysis result of the comparative example 4. The TOF-SIMS analysis result of Example 5. The TOF-SIMS analysis result of Example 6. The TOF-SIMS analysis result of Example 7. The TOF-SIMS analysis result of Example 8. The TOF-SIMS analysis result of Example 9. The TOF-SIMS analysis result of Example 10. The TOF-SIMS analysis result of Example 11. The TOF-SIMS analysis result of Example 12. The TOF-SIMS analysis result of Example 13 The TOF-SIMS analysis result of Example 14 The TOF-SIMS analysis result of Example 15 The TOF-SIMS analysis result of Example 16

Explanation of symbols

1 Substrate 2 Hole Extraction Electrode 3 First Active Layer 4 First Charge Recombination Layer 5 Second Active Layer 6 Second Charge Recombination Layer 7 Third Active Layer 8 Electron Extraction Electrode 9 Substrate 10 First Electrode 11 Fluorous Compound Localized region 12 Active layer 13 Second electrode

The photovoltaic element of the present invention comprises at least one of a first electrode and a second electrode having light transparency, at least (A) an electron-donating organic semiconductor sandwiched between the first electrode and the second electrode, and (B) It has an active layer containing an electron-accepting organic semiconductor. (C) a fluorous compound is included between the first electrode and the second electrode, and the (C) fluorous compound is near the interface between the first electrode and the active layer, or the second electrode and the second electrode. It is characterized by being localized in the vicinity of the interface with the active layer. One of the first electrode and the second electrode is a hole extraction electrode, and the other is an electron extraction electrode. The electrode on the side where the fluorous compound is localized is preferably a hole extraction electrode. In general, as the hole extraction electrode, a composite electrode having a hole extraction buffer layer is used in order to improve the hole extraction efficiency at the interface between the active layer and the hole extraction electrode. The buffer layer can change the work function of the electrode, reduce the energy barrier at the interface between the active layer and the hole extraction electrode, and improve the hole extraction efficiency. In addition, a method for controlling the state of the energy level at the interface by chemically modifying the electrode surface with a silane coupling agent or the like has been studied. As a result of intensive studies on methods for improving the energy state at the interface, the present inventors have improved the photoelectric conversion efficiency by localizing the fluorous compound in the vicinity of the interface between the hole extraction electrode and the active layer. I found out that I can do it. Fluorous compounds with strong electron-withdrawing properties localized at the interface promote photoelectric conversion by promoting polarization between the fluorous compound and the electrode, reducing the interfacial energy barrier between the electrode and the active layer, and improving the hole extraction efficiency It is estimated that the efficiency is improved. The improvement of the photoelectric conversion efficiency according to the present invention is effective in the combination of various electrodes, electron donating organic semiconductors, electron accepting organic semiconductors, and fluorous compounds.

Hereinafter, the photovoltaic element of the present invention will be described with examples. The photovoltaic element of the present invention has a first electrode and a second electrode (that is, a hole extraction electrode and an electron extraction electrode), and at least one of these has light transparency. Between the two electrodes, there is an active layer containing at least (A) an electron-donating organic semiconductor and (B) an electron-accepting organic semiconductor described later. The active layer may contain a surfactant, a binder resin, a filler and the like as long as the object of the present invention is not impaired. The photovoltaic device of the present invention includes (C) a fluorous compound between the first electrode and the second electrode. The fluoro compound is localized in the vicinity of the interface between the first electrode and the active layer or in the vicinity of the interface between the second electrode and the active layer. Alternatively, it may be contained in the active layer. In the case of a tandem photovoltaic element, the charge recombination layer functions as both a hole extraction electrode and an electron extraction electrode. From the one electrode (or charge recombination layer) to the other electrode (or charge recombination layer) sandwiching only one active layer is the photovoltaic element in the present invention.

FIG. 1 is a cross-sectional view showing one embodiment of a tandem photovoltaic element. A hole extraction electrode 2, a first active layer 3, a first charge recombination layer 4, a second active layer 5, a second charge recombination layer 6, a third active layer 7, and an electron extraction electrode 8 are formed on the substrate 1. In this order. In this case, the hole extraction electrode 2, the first active layer 3, and the first charge recombination layer 4 are regarded as one photovoltaic element of the present invention. Further, the first charge recombination layer 4, the second active layer 5, and the second charge recombination layer 6 are also regarded as one photovoltaic device of the present invention, and the second charge recombination layer 6, the third active layer. 7 and the electron extraction electrode 8 are also regarded as one photovoltaic element of the present invention. Therefore, not only the interface between the hole extraction electrode and the first active layer, but also the interface between the first charge recombination layer and the second active layer, or the vicinity of the interface between the second charge recombination layer and the third active layer. The case where the fluoro compound is localized in the photovoltaic element is also included in the photovoltaic device of the present invention.

FIG. 2 is a cross-sectional view showing another embodiment of the photovoltaic element of the present invention. A first electrode 10, an active layer 12, and a second electrode 13 are provided on the substrate 9 in this order, and a localized region 11 of a fluorous compound exists in the vicinity of the interface between the first electrode 10 and the active layer 12.

As the substrate 1, a substrate on which an electrode or an active layer can be stacked can be selected and used. For example, films made by any method from inorganic materials such as alkali-free glass and quartz glass, organic materials such as polyester, polycarbonate, polyolefin, polyamide, polyimide, polyphenylene sulfide, polyparaxylene, epoxy resin and fluorine resin A board can be used. When light is incident from the substrate 1 side, the light transmittance of the substrate is preferably 60-100%. Here, the light transmittance is
[Transmission light intensity (W / m ² ) / incident light intensity (W / m ² )] × 100 (%)
The value given by.

In the photovoltaic device of the present invention, the first electrode or the second electrode has optical transparency. It is sufficient that at least one of them has optical transparency, and both of them may have optical transparency. Here, having optical transparency means that incident light reaches the active layer and an electromotive force is generated. That is, when the light transmittance exceeds 0%, it is said to have light transmittance. The light-transmitting electrode preferably has a light transmittance of 60 to 100% in all wavelength regions of 400 nm to 900 nm. Further, the thickness of the light-transmitting electrode is not limited as long as sufficient conductivity is obtained and varies depending on the material, but is preferably 20 nm to 300 nm. In addition, the electrode which does not have a light transmittance should just be electroconductive, and thickness is not specifically limited, either.

As the electrode material, it is preferable to use a conductive material having a high work function for the hole extraction electrode and a conductive material having a low work function for the other electron extraction electrode.

Conductive materials with large work functions include metals such as gold, platinum, chromium and nickel, transparent metal oxides such as indium and tin, and complex metal oxides (indium tin oxide (ITO), indium zinc oxide) Products (IZO) and the like, and conductive polymers are preferably used. More preferably, the hole extraction electrode has a hole extraction buffer layer. The hole extraction buffer layer can form a more suitable interface state for extracting carriers. Furthermore, there is an effect of preventing a short circuit between the electrodes. Materials for forming the hole extraction buffer layer include conductive polymers such as polythiophene-based polymers, poly-p-phenylene vinylene-based polymers, and polyfluorene-based polymers containing dopants, and metal oxides such as molybdenum oxide. Is preferably used. The polythiophene polymer, poly-p-phenylene vinylene polymer, and polyfluorene polymer refer to polymers having a thiophene skeleton, a p-phenylene vinylene skeleton, and a fluorene skeleton in the main chain, respectively. Among these, a conductive polymer containing a dopant is preferable, and a polythiophene polymer containing a dopant is more preferable. More preferred is a polythiophene polymer such as polyethylenedioxythiophene (PEDOT) containing a dopant, particularly a mixture of PEDOT and polystyrene sulfonate (PSS). By using these materials for the hole extraction buffer layer, the fluorous compound can be appropriately adsorbed in the vicinity of the electrode / active layer interface. The hole extraction buffer layer preferably has a thickness of 5 nm to 600 nm, more preferably 30 nm to 600 nm. Examples of the conductive material having a small work function include alkali metals such as lithium, alkaline earth metals such as magnesium and calcium, tin Silver, aluminum, etc. are preferably used. Furthermore, an electrode made of an alloy made of the above metal or a laminate of the above metal is also preferably used. The electron extraction electrode may have an electron extraction buffer layer. As a material for forming the electron extraction buffer layer, metal fluorides such as lithium fluoride and cesium fluoride are preferably used.

Next, the active layer in the photovoltaic device of the present invention will be described. The active layer is sandwiched between the first electrode and the second electrode, and includes at least (A) an electron-donating organic semiconductor and (B) an electron-accepting organic semiconductor described later. For example, a layer composed of a mixture of an electron-donating organic semiconductor and an electron-accepting organic semiconductor, a structure in which a layer composed of an electron-donating organic semiconductor and a layer composed of an electron-accepting organic semiconductor, a layer composed of an electron-donating organic semiconductor, The structure etc. which laminated | stacked the layer which consists of these mixtures between the layers which consist of an electron-accepting organic semiconductor are mentioned. You may contain 2 or more types of electron-donating organic semiconductors or electron-accepting organic semiconductors. In the present invention, the electron donating organic semiconductor and the electron accepting organic semiconductor preferably form a mixed layer. The content ratio of the electron-donating organic semiconductor and the electron-accepting organic semiconductor in the active layer is not particularly limited, but the weight ratio of electron-donating organic semiconductor: electron-accepting organic semiconductor is in the range of 1 to 99:99 to 1. Preferably there is. A more preferred range is 10 to 90:90 to 10, and a further preferred range is 20 to 60:80 to 40. The active layer may have a thickness sufficient for (A) the electron-donating organic semiconductor and (B) the electron-accepting organic semiconductor to generate a photovoltaic force by light absorption. Although it varies depending on the material, a thickness of 10 nm to 1000 nm is preferable, and 50 nm to 500 nm is more preferable. The active layer in the present invention may contain other components such as a surfactant, a binder resin, and a filler as long as the object of the present invention is not impaired.

(A) An electron donating organic semiconductor will not be specifically limited if it is an organic substance which shows a p-type semiconductor characteristic. For example, polythiophene polymer, 2,1,3-benzothiadiazole-thiophene copolymer, quinoxaline-thiophene copolymer, poly-p-phenylene vinylene polymer, poly-p-phenylene polymer, poly Conjugated polymers such as fluorene polymers, polypyrrole polymers, polyaniline polymers, polyacetylene polymers, polythienylene vinylene polymers, 2,1,3-benzothiadiazole-thiophene compounds, H ₂ phthalocyanine (H ₂ Pc), copper phthalocyanine (CuPc), phthalocyanine derivatives such as zinc phthalocyanine (ZnPc), porphyrin derivatives, N, N′-diphenyl-N, N′-di (3-methylphenyl) -4,4′- Diphenyl-1,1′-diamine (TPD), N, N′-dinaphthyl-N, N′-di Triarylamine derivatives such as phenyl-4,4′-diphenyl-1,1′-diamine (NPD), carbazole derivatives such as 4,4′-di (carbazol-9-yl) biphenyl (CBP), oligothiophene derivatives And low molecular organic compounds such as (terthiophene, quarterthiophene, sexithiophene, octithiophene, etc.). Two or more of these may be used. Among them, the above polythiophene polymer, 2,1,3-benzothiadiazole-thiophene copolymer, 2,1,3-benzothiadiazole-thiophene compound, quinoxaline-thiophene copolymer, and poly-p-phenylene A vinylene polymer is preferable in order to obtain higher photoelectric conversion efficiency.

The polythiophene polymer refers to a conjugated polymer having a thiophene skeleton in the main chain, and includes those having a side chain. A polythiophene polymer is preferable in that it is suitable for obtaining a homogeneous thin film and that light having a long wavelength can be used for photoelectric conversion. Specifically, poly-3-alkylthiophene such as poly-3-methylthiophene, poly-3-butylthiophene, poly-3-hexylthiophene, poly-3-octylthiophene, poly-3-decylthiophene, poly- Poly-3-alkoxythiophene such as 3-methoxythiophene, poly-3-ethoxythiophene, poly-3-dodecyloxythiophene, poly-3-methoxy-4-methylthiophene, poly-3-dodecyloxy-4-methylthiophene And poly-3-alkoxy-4-alkylthiophene.

The 2,1,3-benzothiadiazole-thiophene copolymer and the 2,1,3-benzothiadiazole-thiophene compound are a conjugated copolymer having a thiophene skeleton and a benzothiadiazole skeleton in the main chain, or a thiophene skeleton. It refers to a conjugated compound having a benzothiadiazole skeleton as the main skeleton, including those having side chains. Examples thereof include conjugated polymers and conjugated compounds represented by the following general formula (1).

In the general formula (1), R ¹ to R ¹² may be the same or different and each represents hydrogen, an alkyl group, an alkoxy group, an aryl group, a heteroaryl group, or a halogen. W, X, Y and Z may be the same or different and are selected from the group consisting of a single bond, an arylene group, a heteroarylene group, an ethenylene group and an ethynylene group. m is 0 or 1. n represents a range of 1 to 1000.

Here, the alkyl group is, for example, a saturated aliphatic group such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, or a dodecyl group. A hydrocarbon group is shown. The alkyl group may be linear or branched, and may be unsubstituted or substituted. The alkoxy group refers to an aliphatic hydrocarbon group through an ether bond such as a methoxy group, an ethoxy group, a propoxy group, or a butoxy group, and may be unsubstituted or substituted. The aryl group refers to, for example, an aromatic hydrocarbon group such as a phenyl group, a naphthyl group, a biphenyl group, a phenanthryl group, an anthryl group, a terphenyl group, a pyrenyl group, or a fluorenyl group, which is unsubstituted or substituted. It doesn't matter. The heteroaryl group is, for example, thienyl group, furyl group, pyrrolyl group, imidazolyl group, pyrazolyl group, oxazolyl group, pyridyl group, pyrazyl group, pyrimidyl group, quinolinyl group, isoquinolyl group, quinoxalyl group, acridinyl group, carbazolyl group. Heteroaromatic group having an atom other than carbon such as a group, which may be unsubstituted or substituted. Halogen is fluorine, chlorine, bromine or iodine.

The arylene group represents a divalent (two bonding sites) aryl group, which may be unsubstituted or substituted. Preferable specific examples of the arylene group include the divalent groups described above as preferable examples of the aryl group. The heteroarylene group refers to a divalent heteroaryl group, which may be unsubstituted or substituted. Preferable specific examples of the heteroarylene group include the divalent groups described above as preferable examples of the heteroaryl group. The ethenylene group represents a trans-C═C-double bond or a cis-C═C-double bond, which may be unsubstituted or substituted. The ethynylene group is a —C≡C-triple bond.

Specific examples of the 2,1,3-benzothiadiazole-thiophene copolymer or 2,1,3-benzothiadiazole-thiophene compound include the following structures. In the following formula, n represents a range of 1 to 1000.

The quinoxaline-thiophene copolymer refers to a conjugated copolymer having a thiophene skeleton and a quinoxaline skeleton in the main chain. Specific examples of the quinoxaline-thiophene copolymer include the following structures. In the following formula, n represents a range of 1 to 1000.

The poly-p-phenylene vinylene polymer refers to a conjugated polymer having a p-phenylene vinylene skeleton in the main chain, and includes those having a side chain. Specifically, poly [2-methoxy-5- (2-ethylhexyloxy) -1,4-phenylenevinylene], poly [2-methoxy-5- (3 ′, 7′-dimethyloctyloxy) -1, 4-phenylene vinylene] and the like.

(B) The electron-accepting organic semiconductor is not particularly limited as long as it is an organic substance exhibiting n-type semiconductor characteristics. For example, 1,4,5,8-naphthalene tetracarboxylic dianhydride, 3,4,9,10-perylene tetracarboxylic dianhydride, N, N′-dioctyl-3,4,9,10-naphthyl tetracarboxy Diimide, oxazole derivative (2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole, 2,5-di (1-naphthyl) -1,3,4 -Oxadiazole, etc.), triazole derivatives (3- (4-biphenylyl) -4-phenyl-5- (4-t-butylphenyl) -1,2,4-triazole, etc.), phenanthroline derivatives, fullerene derivatives, carbon Nanotubes, derivatives in which a cyano group is introduced into a poly-p-phenylene vinylene polymer (CN-PPV), etc. It is. Two or more of these may be used. A fullerene derivative is preferably used because it is an n-type semiconductor that is stable and has high carrier mobility.

Specific examples of the fullerene derivative include unsubstituted ones such as C ₆₀ , C ₇₀ , C ₇₆ , C ₇₈ , C ₈₂ , C ₈₄ , C ₉₀ , C ₉₄ , and [6,6] -phenyl C61 Rick acid methyl ester ([6,6] -C61-PCBM, or [60] PCBM), [5,6] -phenyl C61 butyric acid methyl ester, [6,6] -phenyl C61 butyric acid hexyl ester, Examples thereof include substituted derivatives such as [6,6] -phenyl C61 butyric acid dodecyl ester and phenyl C71 butyric acid methyl ester ([70] PCBM). Among these, [70] PCBM is more preferable.

Next, the (C) fluorous compound in the photovoltaic device of the present invention will be described. (C) The fluoro compound refers to a compound containing fluorine. The fluoro compound may be in the state of gas, liquid, or solid at normal temperature and pressure, but is preferably liquid or solid at normal pressure for ease of handling. A fluoro compound that is liquid at normal temperature and pressure is called a fluorous solvent, and a fluoro compound that is solid at normal temperature and pressure is called a solid fluoro compound.

Examples of the fluorous solvent include benzotrifluoride, 2-fluorobenzotrifluoride, 3-fluorobenzotrifluoride, 4-fluorobenzotrifluoride, perfluorotoluene, hexafluorobenzene, fluorobenzene, pentafluorobenzene, 1,2, 4-trifluorobenzene, 1,2,5-trifluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,1,1,3,3,3-hexa Fluoro-2-propanol, perfluorodecalin, 2H, 3H-decafluoropentane, perfluorononane, perfluorooctane, perfluoroheptane, perfluorohexane, tetradecafluoro-2-methylpentane, perfluoro (1,3-dimethyl Cyclohexane), perfluoromethylcyclohexane, perfluoro triallylamine, perfluorotributylamine, etc. perfluoro triethylamine. Examples of the solid fluorous compound include 1H, 1H, 2H, 2H-heptadecafluoro-1-decanol, 1H, 1H-pentadecafluoro-1-octanol, 2,2,3,3,4,4,5, Examples include 5,6,6,7,7-dodecafluoro-1,8-octanediol and 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol. Two or more of these may be contained. In the present invention, it is preferable that the fluorous compound does not contain a highly reactive and hygroscopic carboxylic acid.

(C) The fluoro compound is localized in the vicinity of the interface between the first electrode or the second electrode and the active layer to such an extent that the insulating property of the fluoro compound is negligible, that is, does not hinder the movement of charges from the active layer to the electrode. Preferably it is. Among (C) fluorous compounds, a fluorous solvent is preferred because most of it is volatilized and removed except for the amount necessary to achieve the effects of the present invention.

In the photovoltaic device of the present invention, (C) the fluorous compound is localized in the vicinity of the interface between the first electrode and the active layer or in the vicinity of the interface between the second electrode and the active layer. It is characterized by. Here, localizing near the interface means, for example, the interface between the hole extraction electrode and the active layer. (1) When the hole extraction electrode does not have a hole extraction buffer layer, a fluorous compound film The distribution width in the thickness direction is (active layer film thickness + hole extraction electrode film thickness) / 2 or less, and the maximum content position of the fluorous compound is active from the interface between the active layer and the hole extraction electrode to the active layer side. It means that it is within the range of 40% of the layer thickness or within the range of 40% of the electrode thickness from the interface between the active layer and the hole extraction electrode to the hole extraction electrode side. Further, (2) when the hole extraction electrode has a hole extraction buffer layer, the distribution width in the film thickness direction of the fluorous compound is (active layer film thickness + hole extraction buffer layer film thickness) / 2 or less, and the fluorous The position where the maximum content of the compound is within 40% of the active layer thickness from the interface between the active layer and the hole extraction buffer layer to the active layer side, or from the interface between the active layer and the hole extraction buffer layer. It means that it is in the range of 40% or less of the hole extraction buffer layer thickness on the extraction buffer layer side. The distribution width referred to here is the width of the position where the content of the fluorous compound is reduced to 50%, assuming that the amount at the maximum content position of the fluorous compound is 100%.

The localization of the fluorous compound is carried out by using the method described in Applied Surface Science 2004, Vol. 231-232, pages 353-356, in the first electrode or the second electrode and the inside of the active layer. Can be observed by time-of-flight secondary ion mass spectrometry (TOF-SIMS). First, a sample including an active layer and an electrode is cut obliquely over several μm or more to expose the inside of the film. Next, TOF-SIMS analysis is performed on the exposed portions of the oblique cut surface corresponding to the respective film thicknesses. By plotting the signal intensities of the sample constituents obtained by TOF-SIMS analysis against the corresponding film thicknesses, the distribution in the thickness direction of each constituent of the sample can be examined. In order to know the distribution of the (C) fluorous compound in this distribution in the film thickness direction, it is only necessary to pay attention to the secondary ions derived from the fluorous compound and plot the signal intensity against the corresponding film thickness. Examples of secondary ions derived from the fluorous compound include fluorine negative ions (F ⁻ , mass number 19) and fluorocarbon ions, depending on the type of fluorous compound used.

Next, a method for manufacturing the photovoltaic device of the present invention will be described. (C) The following two methods are mainly given as a method for localizing the fluoro compound near the interface between the first electrode and the active layer, or near the interface between the second electrode and the active layer. It is done. That is, (1) a method of pretreating an electrode with a fluoro compound, and (2) a method of forming an active layer using an active layer material containing a fluoro compound described later. You may combine both methods.

First, the manufacturing method of the photovoltaic element of the present invention using the method (1) will be described with an example.
(A) A transparent electrode such as ITO (in this case, corresponding to a hole extraction electrode) is formed on the substrate. A sputtering method is generally used for forming the transparent electrode.
(B) After forming the hole extraction electrode on the substrate by the method described in (a), the hole extraction electrode is pretreated with a fluorous compound. When the hole extraction electrode has a hole extraction buffer layer, the hole extraction buffer layer may be pretreated.
(C) An active layer is formed on the transparent electrode by vacuum deposition or coating / drying of the active layer material. Examples of the coating method of the active layer material include spin coating, blade coating, slit die coating, screen printing coating, bar coater coating, mold coating, printing transfer method, dip pulling method, ink jet method, and spray method. it can. What is necessary is just to select the application | coating method according to the coating-film characteristic to obtain, such as thickness adjustment of an active layer, or orientation control. For example, in order to obtain a homogeneous active layer having a thickness of 5 to 200 nm, the sum of the weights of (A) electron-donating organic semiconductor and (B) electron-accepting organic semiconductor is (D) 5 in 1 mL of solvent described later. It is preferable to form an active layer by a spin coating method using an active layer material prepared to be ˜30 mg.
(D) Next, when the active layer material contains a solvent, it is preferably dried under reduced pressure or in an inert gas atmosphere (nitrogen or argon atmosphere) to remove the solvent from the coating film.
(E) Next, a metal electrode such as Al (corresponding to an electron extraction electrode in this case) is formed on the active layer. Generally, a vapor deposition method or a sputtering method is used for forming the metal electrode.

In addition, an active layer is formed on the electron extraction electrode by the method corresponding to the above (a) to (d), and a hole extraction electrode pretreated with the fluorous compound is laminated thereon to thereby positively convert the fluorous compound. It can be localized near the interface between the hole extraction electrode and the active layer.

The method for pretreating the electrode with a fluorous compound is not particularly limited as long as the electrode is in direct contact with the fluorous compound. For example, a method of applying a solution containing a fluorous compound on the electrode, or a method of applying an electrode to the fluorous compound The method of exposing to steam. Examples of the method for applying the solution containing the fluorous compound include spin coating, blade coating, slit die coating, screen printing, bar coater coating, dip-up method, ink jet method, and spray method.

FIG. 3 shows a fluorous solvent (hexafluorobenzene (HFB): melting point 5 ° C., boiling point 81 ° C.) or solid fluorous compound solution on a PEDOT: PSS film corresponding to a hole extraction buffer layer formed by coating and drying on glass. Atmospheric photoelectron spectrometer (AC-2) when (1H, 1H, 2H, 2H-heptadecafluoro-1-decanol (HDFD: melting point 46 ° C.) chlorobenzene solution (0.2 g / L)) is spin-coated It is a measurement result by. The irradiation light energy at the point where the base line and the approximate straight line intersect becomes the work function. It is observed that the work function of PEDOT: PSS is changed by pretreatment with a fluorous compound. This suggests that there is a polarization between the fluorous compound deposited on PEDOT: PSS and PEDOT: PSS. Since a change in work function is observed even in a highly volatile fluorous solvent, it is presumed that a strong adsorption action is acting between the fluorous compound and PEDOT: PSS.

Next, an example is given and demonstrated about the manufacturing method of the photovoltaic element of this invention using the method of said (2).
(A) A transparent electrode such as ITO (in this case, corresponding to a hole extraction electrode) is formed on the substrate. A sputtering method is generally used for forming the transparent electrode.
(B) On the transparent electrode, an active layer material described later is applied and dried to form an active layer. Examples of the method for applying the active layer material include the methods exemplified in the method (1).
(C) Next, the solvent is removed from the coating film by drying preferably under reduced pressure or under an inert gas atmosphere (nitrogen or argon atmosphere).
(D) Next, a metal electrode such as Al (corresponding to an electron extraction electrode in this case) is formed on the active layer. Generally, a vapor deposition method or a sputtering method is used for forming the metal electrode.

The active layer material in the above method is an organic semiconductor composition containing the (A) electron donating organic semiconductor, the (B) electron accepting organic semiconductor, the (C) fluorous compound, and (D) a solvent. Even when such an active layer material is used, (C) a fluorous compound in the vicinity of the interface between the first electrode and the active layer, or in the vicinity of the interface between the second electrode and the active layer, as in (1) above. Can be localized. After the formation of the active layer, (C) the fluorous compound concentrates and remains in the vicinity of the interface between the active layer and the electrode, thereby reducing the energy barrier at the interface and improving the extraction efficiency of holes and electrons. The photoelectric conversion efficiency of the photovoltaic element can be improved.

As an organic semiconductor composition for forming an active layer of a bulk heterojunction photovoltaic device, those containing an electron donating organic semiconductor, an electron accepting organic semiconductor, and a solvent have been studied so far. According to the knowledge of the present inventors, the photoelectric conversion efficiency depends not only on the organic semiconductor but also on the solvent system. According to the present invention, by using an active layer formed from an active layer material containing (C) a fluoro compound, photoelectric conversion efficiency can be improved when various organic semiconductors are used. This photoelectric conversion efficiency improvement effect is considered to be mainly due to the above-described energy barrier reduction effect at the interface. Further, it is considered that (C) the fluorous compound has a fluorine atom with a strong electron-withdrawing property, so that the carrier path in the active layer has a network structure advantageous for charge extraction by interacting with the organic semiconductor.

(A) The electron-donating organic semiconductor, (B) the electron-accepting organic semiconductor, and (C) the fluorous compound may be those exemplified above for the photovoltaic device. The solvent (D) is not particularly limited as long as the active layer material is a uniform solution except for the fluorous solvent. For example, toluene, xylene, acetone, ethyl acetate, tetrahydrofuran, dichloromethane, chloroform, dichloroethane, chlorobenzene, dichlorobenzene, trichlorobenzene and the like can be mentioned. Among these, the (A) electron-donating organic semiconductor and (B) electron-accepting organic semiconductor each preferably have a solubility at 25 ° C. of 5 mg / mL or more. As such a highly soluble solvent, chlorobenzene, dichlorobenzene, and chloroform are preferable.

In the active layer material of the present invention, the contents of (A) electron-donating organic semiconductor and (B) electron-accepting organic semiconductor are not particularly limited, but the weight fraction of electron-donating organic semiconductor: electron-accepting organic semiconductor is The range of 1 to 99:99 to 1 is preferable. A more preferred range is 10 to 90:90 to 10, and a further preferred range is 20 to 60:80 to 40. The content of the (C) fluorous compound is not particularly limited as long as the active layer material of the present invention is in a uniform solution. Preferably, the weight fraction of the fluorous compound: solvent is 0.01 to 30. Is preferably in the range of 99.99 to 70, more preferably 0.4 to 4: 99.6 to 96. On the other hand, the volume fraction of the fluorous compound: solvent is preferably in the range of 0.01-20: 99.99-80, more preferably 0.1-2: 99.9-98. (C) By making content of a fluorous compound into the said range, the fluorous compound localized in the interface vicinity can reduce an interface energy barrier moderately.

In addition to the above components, the active layer material of the present invention may contain other components such as a surfactant, a binder resin, and a filler as long as the object of the present invention is not impaired. The active layer material of the present invention is prepared by, for example, adding (A) an electron-donating conjugated polymer and (B) an electron-accepting organic semiconductor to (D) a solvent to which (C) a fluorous compound is added, and heating, stirring, It is obtained by dissolving using a method such as ultrasonic irradiation.

Hereinafter, the present invention will be described more specifically based on examples. In addition, this invention is not limited to the following Example. Of the compounds used in the examples and the like, those using abbreviations are shown below.
Isc: short-circuit current density Voc: open circuit voltage η: photoelectric conversion efficiency ITO: indium tin oxide PEDOT: polyethylene dioxythiophene PSS: polystyrene sulfonate A-1: compound represented by the chemical formula (5)

A-2: Compound represented by chemical formula (6) A-3: Compound represented by chemical formula (7) A-4: Compound represented by chemical formula (8) A-5: Represented by chemical formula (9) Compound A-6: Compound represented by chemical formula (10) A-7: Compound represented by chemical formula (11)

MEH-PPV: poly [2-methoxy-5- (2-ethylhexyloxy) -1,4-phenylenevinylene]
P3HT: poly-3-hexylthiophene [70] PCBM: phenyl C71 butyric acid methyl ester [60] PCBM: [6,6] -phenyl C61 butyric acid methyl ester BTF: benzotrifluoride (melting point: -29 ° C, Boiling point: 102 ° C)
HFP: 1,1,1,3,3,3-hexafluoro-2-propanol (melting point: −4 ° C., boiling point: 59 ° C.)
HFB: hexafluorobenzene (melting point: 5 ° C, boiling point: 81 ° C)
PFT: Perfluorotoluene (melting point: -70 ° C, boiling point: 104 ° C)
PFD: Perfluorodecalin (melting point: −10 ° C., boiling point: 142 ° C.)
HDFD: 1H, 1H, 2H, 2H-heptadecafluoro-1-decanol (melting point: 46 ° C.)
ODT: 1,8-octanedithiol CB: Chlorobenzene CF: Chloroform Note that the above compounds A-1 to A-5 and A-7 are the Advanced Functional Materials 2005, 15, 1545-1552. It was synthesized by the method described on page. A-6 was synthesized by the method described in Advanced Functional Materials 2007, Vol. 17, pp. 3836-3842.

The photoelectric conversion efficiency in each example / comparative example was determined by the following equation.
η (%) = Isc (mA / cm ² ) × Voc (V) × FF / irradiation light intensity (mW / cm ² ) × 100
FF = JVmax / (Isc (mA / cm ² ) × Voc (V))
JVmax (mW / cm ² ) is a value of the product of the current density and the applied voltage at the point where the product of the current density and the applied voltage is maximum between the applied voltage of 0 V and the open circuit voltage.

Example 1
0.1 mg of CB solvent containing 1.1% by weight of BTF obtained by mixing 1% by volume of BTF and 99% by volume of CB was obtained by adding 0.6 mg of A-1 and [70] PCBM (manufactured by Solene) of 2.4 mg. In addition to the sample bottle, the solution A was obtained by irradiating with ultrasonic waves for 30 minutes in an ultrasonic cleaner (US-2 manufactured by Iuchi Seieido Co., Ltd., output 120 W).

A glass substrate having an ITO transparent conductive layer of 125 nm deposited as a positive electrode deposited by sputtering was cut into 38 mm × 46 mm, and then ITO was patterned into a 38 mm × 13 mm rectangular shape by photolithography. The light transmittance of the obtained substrate was measured with a Hitachi spectrophotometer U-3010. As a result, it was 85% or more in all wavelength regions from 400 nm to 900 nm. The substrate was subjected to ultrasonic cleaning with an alkali cleaning solution (“Semico Clean” EL56, manufactured by Furuuchi Chemical Co., Ltd.) for 10 minutes, and then cleaned with ultrapure water. After UV / ozone treatment of this substrate for 30 minutes, a PEDOT: PSS aqueous solution (0.8% by weight of PEDOT, 0.5% by weight of PSS) to be a hole extraction buffer layer was formed on the substrate to a thickness of 60 nm by spin coating. Filmed. After heating and drying at 200 ° C. for 5 minutes using a hot plate, the above solution A was dropped on the PEDOT: PSS layer, and an active layer having a thickness of 100 nm was formed by spin coating. Thereafter, the substrate and the electron extraction electrode mask are installed in a vacuum deposition apparatus, the vacuum in the apparatus is exhausted to 1 × 10 ⁻³ Pa or less, and an aluminum layer that becomes an electron extraction electrode is formed by resistance heating. Was deposited to a thickness of 80 nm. The extraction electrodes were taken out from the upper and lower electrodes of the produced device, and a photovoltaic device having an area where the band-like ITO layer and the aluminum layer overlap each other was 5 mm × 5 mm was produced.

The upper and lower electrodes of the photovoltaic device thus produced were connected to a picoammeter / voltage source 4140B manufactured by Hewlett-Packard Co., and white light (AM1.5; 100 mW / cm from the ITO layer side in the atmosphere). ² ), and the current value was measured when the applied voltage was changed from -1V to + 2V. The photoelectric conversion efficiency (η) calculated from the obtained result was 2.6%.

A sample (ITO / PEDOT: PSS / active layer) before forming the electron extraction electrode was cut obliquely with a diamond blade, and the result of TOF-SIMS analysis on the cut surface is shown in FIG. The vertical axis represents the detected intensity of secondary ions, and the horizontal axis represents the distance of the oblique cutting surface. 0 on the horizontal axis corresponds to the edge of the cutting surface, that is, the outermost surface of the active layer. C ₇₀ ⁻ ions are derived from [70] PCBM in the active layer, C ₈ H ₇ SO ₃ ⁻ ions are derived from PSS in the hole extraction buffer layer, and F ⁻ ions are derived from BTF. It can be seen that BTF is localized at the interface between the active layer and the hole extraction buffer layer.

Comparative Example 1
A uniform solution B was obtained in the same manner as in Example 1 except that the CB solvent containing 1.1% by weight of BTF was replaced with CB. A photovoltaic device was prepared using the solution B in the same manner as in Example 1, and the current-voltage characteristics were measured. The photoelectric conversion efficiency at this time was 2.2%. The result of the TOF-SIMS analysis performed in the same manner as in Example 1 is shown in FIG.

Comparative Example 2
A uniform solution C was obtained in the same manner as in Example 1 except that BTF was replaced with ODT. A photovoltaic device was produced using the solution C in the same manner as in Example 1, and the current-voltage characteristics were measured. The photoelectric conversion efficiency at this time was 0.4%.

Comparative Example 3
A uniform solution D was obtained in the same manner as in Example 1 except that BTF was replaced with toluene. A photovoltaic device was prepared using the solution D in the same manner as in Example 1, and the current-voltage characteristics were measured. The photoelectric conversion efficiency at this time was 2.2%.

Example 2
Examples were used except that a CB solvent containing 0.5% by weight of BTF obtained by mixing 0.5% by volume of BTF and 99.5% by volume of CB was used instead of the CB solvent containing 1.1% by weight of BTF. In the same manner as in Example 1, a uniform solution E was obtained. A photovoltaic device was produced using the solution E in the same manner as in Example 1, and the current-voltage characteristics were measured. The photoelectric conversion efficiency at this time was 2.5%. The results of TOF-SIMS analysis performed in the same manner as in Example 1 are shown in FIG. It can be seen that BTF is localized at the interface between the active layer and the hole extraction buffer layer.

Example 3
Example except that CB solvent containing 0.7% by weight of HFB obtained by mixing 0.5% by volume of HFB and 99.5% by volume of CB was used instead of CB solvent containing 1.1% by weight of BTF. In the same manner as in Example 1, a uniform solution F was obtained. A photovoltaic device was prepared using the solution F in the same manner as in Example 1, and the current-voltage characteristics were measured. The photoelectric conversion efficiency at this time was 2.4%. The result of the TOF-SIMS analysis performed in the same manner as in Example 1 is shown in FIG. It can be seen that HFB is localized at the interface between the active layer and the hole extraction buffer layer.

Example 4
Instead of the CB solvent containing 1.1% by weight of BTF, a CB solvent containing 1.4% by weight of HFP obtained by mixing 1% by volume of HFP and 99% by volume of CB was used in the same manner as in Example 1. And uniform solution G was obtained. A photovoltaic device was produced using the solution G in the same manner as in Example 1, and the current-voltage characteristics were measured. The photoelectric conversion efficiency at this time was 2.4%. The result of the TOF-SIMS analysis performed in the same manner as in Example 1 is shown in FIG. It can be seen that HFP is localized at the interface between the active layer and the hole extraction buffer layer.

Comparative Example 4
A uniform solution H was obtained in the same manner as in Example 1 except that a CB solvent containing 7.2% by weight of HFP was used instead of the CB solvent containing 1.1% by weight of BTF. A photovoltaic device was produced using the solution H in the same manner as in Example 1, and the current-voltage characteristics were measured. The photoelectric conversion efficiency at this time was 1.8%. The result of the TOF-SIMS analysis performed in the same manner as in Example 1 is shown in FIG.

Example 5
Instead of the CB solvent containing 1.1% by weight of BTF, a CB solvent containing 1.5% by weight of PFT obtained by mixing 1% by volume of PFT and 99% by volume of CB was used in the same manner as in Example 1. And uniform solution I was obtained. A photovoltaic device was prepared in the same manner as in Example 1 using Solution I, and the current-voltage characteristics were measured. The photoelectric conversion efficiency at this time was 2.5%. The results of TOF-SIMS analysis performed in the same manner as in Example 1 are shown in FIG. It can be seen that PTF is localized at the interface between the active layer and the hole extraction buffer layer.

Example 6
Example except that CB solvent containing 0.2% by weight of PFD obtained by mixing 0.1% by volume of PFD and 99.9% by volume of CB was used instead of CB solvent containing 1.1% by weight of BTF. In the same manner as in Example 1, a uniform solution J was obtained. A photovoltaic device was prepared using the solution J in the same manner as in Example 1, and the current-voltage characteristics were measured. The photoelectric conversion efficiency at this time was 2.5%. The result of the TOF-SIMS analysis performed in the same manner as in Example 1 is shown in FIG. It can be seen that the PTD is localized at the interface between the active layer and the hole extraction buffer layer.

Example 7
A uniform solution K was obtained in the same manner as in Example 4 except that A-2 was used instead of A-1. A photovoltaic device was prepared using the solution K in the same manner as in Example 1, and the current-voltage characteristics were measured. The photoelectric conversion efficiency at this time was 1.7%. The result of the TOF-SIMS analysis performed in the same manner as in Example 1 is shown in FIG. It can be seen that HFP is localized at the interface between the active layer and the hole extraction buffer layer.

Comparative Example 5
A uniform solution L was obtained in the same manner as in Example 7 except that CB was used instead of the CB solvent containing 1.4% by weight of HFP. A photovoltaic device was prepared using the solution L in the same manner as in Example 1, and the current-voltage characteristics were measured. The photoelectric conversion efficiency at this time was 1.5%.

Example 8
A uniform solution M was obtained in the same manner as in Example 4 except that A-3 was used instead of A-1. A photovoltaic device was produced using the solution M in the same manner as in Example 1, and the current-voltage characteristics were measured. The photoelectric conversion efficiency at this time was 2.3%. The results of TOF-SIMS analysis performed in the same manner as in Example 1 are shown in FIG. It can be seen that HFP is localized at the interface between the active layer and the hole extraction buffer layer.

Comparative Example 6
A uniform solution N was obtained in the same manner as in Example 8 except that CB was used instead of the CB solvent containing 1.4% by weight of HFP. A photovoltaic device was prepared using the solution N in the same manner as in Example 1, and the current-voltage characteristics were measured. The photoelectric conversion efficiency at this time was 2.2%.

Example 9
A-4 was used instead of A-1, and a CB containing 1.5% by weight of HFB obtained by mixing 1% by volume of HFB and 99% by volume of CB instead of a CB solvent containing 1.1% by weight of BTF. A uniform solution O was obtained in the same manner as in Example 1 except that the solvent was used. A photovoltaic device was produced using the solution O in the same manner as in Example 1, and the current-voltage characteristics were measured. The photoelectric conversion efficiency at this time was 2.6%. The result of the TOF-SIMS analysis performed in the same manner as in Example 1 is shown in FIG. It can be seen that HFB is localized at the interface between the active layer and the hole extraction buffer layer.

Comparative Example 7
A uniform solution P was obtained in the same manner as in Example 9 except that CB was used instead of the CB solvent containing 1.5% by weight of HFB. A photovoltaic device was produced using the solution P in the same manner as in Example 1, and the current-voltage characteristics were measured. The photoelectric conversion efficiency at this time was 2.3%.

Example 10
Example except that CB solvent containing 0.1% by weight of HFP obtained by mixing 0.1% by volume of HFP and 99.9% by volume of CB was used instead of CB solvent containing 1.5% by weight of HFB In the same manner as in Example 9, a uniform solution Q was obtained. A photovoltaic device was produced using the solution Q in the same manner as in Example 1, and the current-voltage characteristics were measured. The photoelectric conversion efficiency at this time was 2.6%. The result of the TOF-SIMS analysis performed in the same manner as in Example 1 is shown in FIG. It can be seen that HFP is localized at the interface between the active layer and the hole extraction buffer layer.

Example 11
A uniform solution R was obtained in the same manner as in Example 1 except that A-1 was replaced with MEH-PPV (Aldrich). A photovoltaic device was produced using the solution R in the same manner as in Example 1, and the current-voltage characteristics were measured. The photoelectric conversion efficiency at this time was 1.2%. FIG. 16 shows the results of TOF-SIMS analysis performed in the same manner as in Example 1. It can be seen that BTF is localized at the interface between the active layer and the hole extraction buffer layer.

Comparative Example 8
A uniform solution S was obtained in the same manner as in Example 11 except that the CB solvent containing 1.1% by weight of BTF was replaced with CB. A photovoltaic device was produced using the solution S in the same manner as in Example 1, and the current-voltage characteristics were measured. The photoelectric conversion efficiency at this time was 1.1%.

Example 12
A-1 (0.6 mg) is replaced with P3HT (0.75 mg), [70] PCBM (2.4 mg) is replaced with [60] PCBM (0.75 mg), and a CB solvent containing 1.1 wt% BTF A uniform solution T was obtained in the same manner as in Example 1 except that a CF solvent containing 0.8% by weight of BTF obtained by mixing 1% by volume of BTF and 99% by volume of CF was used. A photovoltaic device was prepared in the same manner as in Example 1 except that the solution T was heat-treated at 110 ° C. for 30 minutes after the aluminum layer was deposited, and current-voltage characteristics were measured. The photoelectric conversion efficiency at this time was 3.1%. The result of the TOF-SIMS analysis performed in the same manner as in Example 1 is shown in FIG. It can be seen that BTF is localized at the interface between the active layer and the hole extraction buffer layer.

Comparative Example 9
A uniform solution U was obtained in the same manner as in Example 12 except that the CF solvent containing 0.8% by weight of BTF was replaced with CF. Using the solution U, a photovoltaic device was produced in the same manner as in Example 1, and the current-voltage characteristics were measured. The photoelectric conversion efficiency at this time was 2.9%.

Example 13
A uniform solution V was obtained in the same manner as in Example 1, except that A-1 was replaced with A-5 and CB was used instead of the CB solvent containing 1.1% by weight of BTF. In addition, a photovoltaic device was fabricated in the same manner as in Example 1 except that after the PEDOT: PSS layer was formed and BTF was spin-coated thereon and then the active layer was formed using the solution V, a photovoltaic device was produced. Characteristics were measured. The photoelectric conversion efficiency at this time was 1.8%. FIG. 18 shows the result of the TOF-SIMS analysis performed in the same manner as in Example 1. It can be seen that BTF is localized at the interface between the active layer and the hole extraction buffer layer.

Comparative Example 10
A uniform solution W was obtained in the same manner as in Example 1, except that A-1 was replaced with A-5, and CB was used instead of the CB solvent containing 1.1% by weight of BTF. A photovoltaic device was produced using the solution W in the same manner as in Example 1, and the current-voltage characteristics were measured. The photoelectric conversion efficiency at this time was 1.7%.

Example 14
A-1 was replaced with A-6, [70] PCBM was replaced with [60] PCBM, and CB was used instead of the CB solvent containing 1.1% by weight of BTF. Solution X was obtained. In addition, the PEDOT: PSS layer was formed, and then an HDFD solution (0.2 g / L, chlorobenzene solvent) was spin-coated thereon, and then an active layer was formed using the solution X. A photovoltaic device was fabricated and current-voltage characteristics were measured. The photoelectric conversion efficiency at this time was 2.1%. The results of TOF-SIMS analysis performed in the same manner as in Example 1 are shown in FIG. It can be seen that HDFD is localized at the interface between the active layer and the hole extraction buffer layer.

Comparative Example 11
A uniform solution Y as in Example 1, except that A-1 was replaced with A-6, [70] PCBM was replaced with [60] PCBM, and CB solvent containing 1.1 wt% BTF was replaced with CB. Got. A photovoltaic device was prepared using the solution Y in the same manner as in Example 1, and the current-voltage characteristics were measured. The photoelectric conversion efficiency at this time was 1.9%.

Example 15
A uniform solution Z was obtained in the same manner as in Example 1 except that A-1 was replaced with A-7. Using the solution Z, a photovoltaic device was produced in the same manner as in Example 1, and the current-voltage characteristics were measured. The photoelectric conversion efficiency at this time was 2.9%. The result of the TOF-SIMS analysis performed in the same manner as in Example 1 is shown in FIG. It can be seen that BTF is localized at the interface between the active layer and the hole extraction buffer layer.

Comparative Example 12
A uniform solution AA was obtained in the same manner as in Example 15 except that the CB solvent containing 1.1% by weight of BTF was replaced with CB. A photovoltaic device was produced using the solution AA in the same manner as in Example 1, and the current-voltage characteristics were measured. The photoelectric conversion efficiency at this time was 2.6%.

Example 16
A uniform solution AB was obtained in the same manner as in Example 1, except that A-1 was replaced with P3HT and CB was used in place of the CB solvent containing 1.1% by weight of BTF. Further, after forming the PEDOT: PSS layer, the HDFD solution (0.2 g / L, chlorobenzene solvent) was spin-coated thereon, and then the active layer was formed using the solution AB. A photovoltaic device was fabricated and current-voltage characteristics were measured. The photoelectric conversion efficiency at this time was 2.3%. The result of the TOF-SIMS analysis performed in the same manner as in Example 1 is shown in FIG. It can be seen that HDFD is localized at the interface between the active layer and the hole extraction buffer layer.

Comparative Example 13
A uniform solution AC was obtained in the same manner as in Example 1, except that A-1 was replaced with P3HT, and CB was used instead of the CB solvent containing 1.1% by weight of BTF. A photovoltaic device was prepared using the solution AC in the same manner as in Example 1, and the current-voltage characteristics were measured. The photoelectric conversion efficiency at this time was 2.1%.

Tables 1 and 2 show the compositions and evaluation results of the examples and comparative examples. Examples 1 to 6 are compared with Comparative Examples 1 to 4, Example 7 is compared with Comparative Example 5, Example 8 is compared with Comparative Example 6, and Examples 9 to 10 are compared. Is compared with Comparative Example 7, Example 11 is compared with Comparative Example 8, Example 12 is compared with Comparative Example 9, and Example 13 is compared with Comparative Example 10. Example 14 can improve photoelectric conversion efficiency according to the present invention by comparing Example 14 with Comparative Example 11, Example 15 by comparing with Comparative Example 12, and Example 16 by comparing with Comparative Example 13. I understand.

The photovoltaic element of the present invention can be applied to various photoelectric conversion devices using a photoelectric conversion function, an optical rectification function, and the like. For example, it is useful for photovoltaic cells (such as solar cells), electronic elements (such as optical sensors, optical switches, and phototransistors), optical recording materials (such as optical memories), and the like.

Claims

A first electrode and a second electrode, at least one of which is light transmissive, and at least (A) an electron-donating organic semiconductor and (B) an electron-accepting organic semiconductor sandwiched between the first electrode and the second electrode A photovoltaic device having an active layer comprising: (C) a fluorous compound between the first electrode and the second electrode, wherein the (C) fluorous compound is formed between the first electrode and the active layer. A photovoltaic element localized near an interface or near an interface between the second electrode and the active layer.
An active layer material for forming an active layer of the photovoltaic device according to claim 1, wherein (A) an electron donating organic semiconductor, (B) an electron accepting organic semiconductor, (C) a fluorous compound and ( D) Active layer material containing solvent.
The active layer material according to claim 2, wherein the (C) fluorous compound is a fluorous solvent.
The photovoltaic device according to claim 1, wherein the (C) fluorous compound is a fluorous solvent.
5. The photovoltaic element according to claim 1, wherein, of the first electrode and the second electrode, the electrode in which the (C) fluoro compound is localized in the vicinity of the interface with the active layer contains a conductive polymer. 6. .
The photovoltaic element according to claim 5, wherein the conductive polymer is a polymer having a thiophene skeleton in the main chain.
The photovoltaic element according to claim 5, wherein the conductive polymer contains polyethylene dioxythiophene.
At least (1) a step of treating the first electrode or the second electrode with (C) a fluorous compound, and (2) an active layer containing at least (A) an electron-donating organic semiconductor and (B) an electron-accepting organic semiconductor The manufacturing method of the photovoltaic element of Claim 1 including the process of laminating | stacking the electrode processed with the said (C) fluorous compound.