JP2013089684A - Organic photoelectric conversion element and solar cell using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic photoelectric conversion element which is excellent in durability and is capable of exhibiting sufficient photoelectric conversion efficiency, and a solar cell using the same.SOLUTION: The organic photoelectric conversion element includes: a first electrode; a second electrode; a hole transport layer containing a metal oxide and a bulk-heterojunction photoelectric conversion layer which are arranged between the first electrode and the second electrode; and a self-assembled monolayer arranged between the hole transport layer and the photoelectric conversion layer.

Description

  The present invention relates to an organic photoelectric conversion element and a solar cell using the same.

  In recent years, in order to cope with global warming, reduction of carbon dioxide emissions has been strongly desired. In addition, fossil fuels such as oil, coal, and natural gas are expected to be depleted in the near future, and there is an urgent need to secure an earth-friendly energy resource to replace them. Therefore, development of power generation technology using sunlight, wind power, geothermal heat, nuclear power, and the like has been actively performed, and solar power generation is particularly attracting attention because of its high safety.

  In solar power generation, light energy is directly converted into electric power using a photoelectric conversion element utilizing the photovoltaic effect. Generally, a photoelectric conversion element has a structure in which a photoelectric conversion layer (light absorption layer) is sandwiched between a pair of electrodes, and light energy is converted into electric energy in the photoelectric conversion layer. The photoelectric conversion element is a silicon-based photoelectric conversion element using single-crystal / polycrystalline / amorphous Si, GaAs, CIGS (copper (Cu), indium (In), depending on the material used for the photoelectric conversion layer and the form of the element. Compound-based photoelectric conversion elements using a compound semiconductor such as gallium (Ga) and selenium (Se)), dye-sensitized photoelectric conversion elements (Gretzel cells), and the like have been proposed and put to practical use.

  However, the power generation cost when these solar cells are used is still higher than the cost when generating and transmitting power using fossil fuels, which hinders the spread of solar power generation. In addition, since heavy glass must be used for the substrate, reinforcement work is required when it is installed on a roof or the like, which has also contributed to a rise in power generation costs.

  As a technique for reducing power generation costs in solar power generation, a mixture of an electron-donating organic compound (p-type organic semiconductor) and an electron-accepting organic compound (n-type organic semiconductor) between a transparent electrode and a counter electrode A bulk heterojunction type photoelectric conversion element is proposed (see, for example, Non-Patent Document 1).

  Bulk heterojunction organic photoelectric conversion elements are lightweight and flexible, and are expected to be applied to various products. In addition, since the structure is relatively simple and a photoelectric conversion layer can be formed by applying a p-type organic semiconductor and an n-type organic semiconductor, it is suitable for mass production and contributes to the early diffusion of solar cells due to cost reduction. It is thought to do. More specifically, in a bulk heterojunction organic photoelectric conversion element, a metal layer or a metal oxide layer constituting electrodes (anode and cathode) can be formed by a vapor deposition method, but other layers are coated. It can be formed using a process. Therefore, it is expected that the production of the bulk heterojunction photoelectric conversion element can be performed at high speed and at low cost, and it is considered that there is a possibility that the above-described problem of power generation cost can be solved. Furthermore, unlike the manufacture of conventional silicon-based photoelectric conversion elements, compound-based photoelectric conversion elements, dye-sensitized photoelectric conversion elements, etc., it does not necessarily involve a manufacturing process at a temperature higher than 160 ° C. It is expected that it can be formed on a lightweight plastic substrate.

  However, it cannot be said that the organic photoelectric conversion element has sufficient photoelectric conversion efficiency and durability against heat and light compared to other types of photoelectric conversion elements.

  For example, an organic photoelectric conversion element has a problem that it is easily affected by oxygen and moisture, as in a general organic electronic device (for example, an organic thin film transistor (OTFT) or an organic light emitting diode (OLED)). If oxygen or moisture enters the element, the element deteriorates and the lifetime of the element is shortened. Therefore, it is necessary to prevent such penetration by using a barrier member (for example, a barrier film or a glass plate). .

However, even when sealed with a barrier member, a minute amount of moisture and oxygen mixed in during production and a minute amount of moisture and oxygen that permeate the barrier member inevitably exist in the device. To do. Thus, when continuous light irradiation is performed in the presence of a minute amount of moisture, PEDOT: PSS (poly (3,4-ethylenedithiothiophene): poly (styreneenesulfonate), which is mainly used as a hole transport layer material. ) And the like, or the morphology of the bulk heterojunction layer (photoelectric conversion layer) formed by the p-type semiconductor material and the n-type semiconductor material changes, thereby causing a short circuit current density (J _SC ) is attenuated, and the lifetime of the device is remarkably shortened.

As countermeasures against these problems, for example, by using an oxide semiconductor layer such as molybdenum oxide (MoO ₃ ) instead of PEDOT: PSS used as a hole transport material, stability in storage in a dark place is improved. Techniques to do this have been proposed. Furthermore, when a metal oxide such as MoO ₃ is used, the film can be formed with an extremely thin film and can exhibit the desired function. Therefore, the resistance of the layer itself can be lowered as compared with the conventional PEDOT: PSS. Therefore, the technology is indispensable for improving the efficiency of the element (for example, Non-Patent Document 2, Patent Document 1, etc.).

  In addition, a technique for forming a self-assembled monolayer (SAM) between a metal oxide layer and a photoelectric conversion layer has been reported as an efficiency improvement technique using an oxide semiconductor. It has succeeded in adjusting the vacuum level by forming SAM on the metal oxide layer and obtaining higher Voc (for example, Non-Patent Document 3).

JP 2008-91381 A

A. Heeger et al. , Nature Mat. , Vol. 6 (2007), p497 Adv. Mater. 2011, 23, 2226-2230 J. et al. Appl. Phys. 101, 114503 (2007)

However, as a result of investigations by the present inventors, it has been found that sufficient durability and photoelectric conversion efficiency cannot be obtained even with the technique described in the above document. That is, according to the techniques described in Non-Patent Document 2 and Patent Document 1, when a photoelectric conversion element is driven by continuous light irradiation, a large level mismatch occurs at the interface between the oxide semiconductor and the organic layer. It has been found that short circuit current density (J _SC ) decays due to the occurrence of, and the lifetime of the device is significantly shortened. Non-Patent Document 3 does not describe any decrease in the lifetime of the device under continuous light irradiation due to this level mismatch. Furthermore, the occurrence of a large level mismatch at the interface due to this interface mismatch is normal. The metal oxide used on the hole transport layer side is more conspicuous, and the non-patent document 3 does not solve these problems.

  This invention is made | formed in view of the said subject, It aims at providing the organic photoelectric conversion element which is excellent in durability, and can exhibit sufficient photoelectric conversion efficiency, and a solar cell using the same. .

  The present inventors have intensively studied to solve the above problems. As a result, by having a self-assembled monolayer between the hole transport layer made of a metal oxide and the photoelectric conversion layer, it is durable even when the photoelectric conversion element is driven by continuous light irradiation. The present invention has been completed by finding that it has excellent performance and exhibits sufficient photoelectric conversion efficiency.

  That is, the present invention relates to a first electrode, a second electrode, a hole transport layer including a metal oxide disposed between the first electrode and the second electrode, and a bulk heterojunction photoelectric conversion. It is an organic photoelectric conversion element which has a layer and the self-organization monomolecular layer arrange | positioned between the said positive hole transport layer and the said photoelectric converting layer.

  ADVANTAGE OF THE INVENTION According to this invention, the solar cell using the organic photoelectric conversion element which is excellent in durability, and can exhibit sufficient photoelectric conversion efficiency, and the organic photoelectric conversion element can be provided.

It is a figure which illustrates typically the effect of the organic photoelectric conversion element of the present invention. It is the cross-sectional schematic which represented the organic photoelectric conversion element by one Embodiment of this invention typically. It is the cross-sectional schematic which represented the organic photoelectric conversion element by other embodiment of this invention typically. It is the cross-sectional schematic which represented typically the organic photoelectric conversion element provided with the tandem-type photoelectric conversion layer by other embodiment of this invention.

  The present invention includes a first electrode, a second electrode, a hole transport layer including a metal oxide disposed between the first electrode and the second electrode, and a bulk heterojunction photoelectric conversion layer, And an organic photoelectric conversion element having a self-assembled monolayer disposed between the hole transport layer and the photoelectric conversion layer.

By having a self-assembled monolayer between the hole transport layer and the photoelectric conversion layer, the HOMO levels are more ohmic between the p-type semiconductor and the hole transport layer formed from the inorganic oxide. Even when the photoelectric conversion element is driven by continuous light irradiation, occurrence of a large level mismatch at the interface between the hole transport layer and the photoelectric conversion layer can be reduced. As a result, attenuation of the short circuit current density (J _SC ) can be suppressed, and durability (device lifetime) can be improved.

If this effect is further explained schematically with reference to FIG. 1, a hole transport layer and a photoelectric conversion layer in an organic photoelectric conversion element having no self-assembled monolayer as shown in FIG. At the interface, a large HOMO level mismatch occurs. However, the organic photoelectric conversion device of the present invention as shown in FIG. 1B has a self-organized monomolecular layer, so that the work function of the hole transport layer becomes shallow, and the hole transport layer and the photoelectric conversion Between the layers, the HOMO levels can be more ohmic-connected. This effect can reduce mismatch at the interface even if the HOMO level of the hole transport layer shifts deeply due to continuous light irradiation. As a result, the short-circuit current density (J _SC ) is attenuated. Can be suppressed, and the durability (the lifetime of the element) can be improved.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the technical scope of the present invention should be determined by the description of the scope of claims, and is not limited to the following embodiments. In addition, the dimension ratio of drawing is exaggerated on account of description, and may differ from an actual ratio.

(Configuration of organic photoelectric conversion element)
FIG. 2 is a schematic cross-sectional view schematically showing a normal layer type organic photoelectric conversion element according to an embodiment of the present invention.

  The organic photoelectric conversion element 10 is formed by laminating a first electrode 12, a hole transport layer 17, a photoelectric conversion layer 14, an electron transport layer 18, and a second electrode 13 on a substrate 11 in this order. A self-assembled monolayer 19 is disposed between the hole transport layer 17 and the photoelectric conversion layer 14.

  As one embodiment of the present invention, the substrate 11 and the first electrode 12 are transparent, and light used for photoelectric conversion is irradiated from the substrate 11 side, passes through the first electrode 12 and the hole transport layer 17, It reaches the photoelectric conversion layer 14.

  The photoelectric conversion layer 14 is a layer that converts light energy into electrical energy, and contains a p-type semiconductor material and an n-type semiconductor material.

  The p-type semiconductor material functions relatively as an electron donor (donor), and the n-type semiconductor material functions relatively as an electron acceptor (acceptor).

  Here, the electron donor and the electron acceptor are “an electron donor in which, when light is absorbed, electrons move from the electron donor to the electron acceptor to form a hole-electron pair (charge separation state)”. And an electron acceptor ”, which does not simply donate or accept electrons as in the case of an electrode, but donates or accepts electrons by a photoreaction.

  In FIG. 2, the light incident from the first electrode 12 through the substrate 11 is absorbed by the electron acceptor or the electron donor in the photoelectric conversion layer 14, and electrons move from the electron donor to the electron acceptor. A pair of holes and electrons (charge separation state) is formed.

  The generated electric charge is generated between the electron acceptors due to the internal electric field, for example, when the work functions of the first electrode 12 and the second electrode 13 are different, due to the potential difference between the first electrode 12 and the second electrode 13. And the holes pass between the electron donors and are carried to different electrodes, and a photocurrent is detected.

  In the example of FIG. 2, the work function of the first electrode 12 is larger than the work function of the second electrode 13, so that holes are transported to the first electrode 12 and electrons are transported to the second electrode 13. In this case, the second electrode 13 is made of a metal that has a small work function and is easily oxidized. In this case, the first electrode functions as an anode (anode) and the second electrode functions as a cathode (cathode).

  FIG. 3 is a schematic cross-sectional view schematically showing a reverse layer type organic photoelectric conversion device according to another embodiment of the present invention.

  In FIG. 3, contrary to the case of FIG. 2, the work function of the second electrode 13 is made larger than the work function of the first electrode 12, whereby electrons are transferred to the first electrode 12. The case where it designed so that it might convey to the 2nd electrode 13 was shown. In this case, the electron transport layer 18 is provided between the first electrode 12 and the photoelectric conversion layer 14, the hole transport layer 17 is provided between the photoelectric conversion layer 14 and the second electrode 13, The first electrode functions as a cathode (cathode) and the second electrode functions as an anode (anode). A self-assembled monolayer 19 is disposed between the hole transport layer 17 and the photoelectric conversion layer 14.

  Although not shown in FIGS. 2 and 3, the organic photoelectric conversion element of the present invention may have a layer such as a hole blocking layer, an electron blocking layer, or a smoothing layer.

  Furthermore, it is good also as a tandem-type structure which laminated | stacked such a photoelectric conversion element for the purpose of the improvement of sunlight utilization factor (photoelectric conversion efficiency). FIG. 4 is a schematic cross-sectional view schematically illustrating an organic photoelectric conversion element including a tandem photoelectric conversion layer.

  In the case of the tandem configuration, the first electrode 12, the hole transport layer 17, the first photoelectric conversion layer 14a, and the charge recombination layer 15 are stacked in this order on the substrate 11, and then the second photoelectric conversion layer 14b. By stacking the electron transport layer 18 and then the second electrode 13, a tandem structure can be obtained.

  A self-assembled monolayer 19 is disposed between the hole transport layer 17 and the first photoelectric conversion layer 14a.

  The second photoelectric conversion layer 14b may be a layer that absorbs the same spectrum as the absorption spectrum of the first photoelectric conversion layer 14a, or may be a layer that absorbs a different spectrum, but efficiently emits light in a wider wavelength range. Therefore, the layer preferably absorbs a different spectrum.

  Hereinafter, each structure of the organic photoelectric conversion element which concerns on this invention is demonstrated in detail.

(Hole transport layer)
The hole transport layer is a layer that is located between the anode and the photoelectric conversion layer, and that can transfer holes more efficiently between the photoelectric conversion layer and the electrode. Note that the hole transport layer having a LUMO level shallower than the LUMO level of the n-type semiconductor material used for the photoelectric conversion layer has a rectifying effect that prevents electrons generated in the photoelectric conversion layer from flowing to the anode side. It has an electronic block function. Such a hole transport layer is also called an electron block layer, and it is preferable to use a hole transport layer having such a function.

  The hole transport layer according to the present invention contains a metal oxide.

  Examples of the metal oxide used for the hole transport layer include molybdenum (Mo), vanadium (V), tungsten (W), chromium (Cr), niobium (Nb), rhenium (Re), tantalum (Ta), Zirconium (Zr), hafnium (Hf), scandium (Sc), yttrium (Y), thorium (Tr), manganese (Mn), iron (Fe), ruthenium (Ru), osmium (Os), cobalt (Co), Nickel (Ni), cadmium (Cd), aluminum (Al), gallium (Ga), indium (In), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), antimony (Sb), Examples include bismuth (Bi) or oxides of so-called rare earth elements from lanthanum (La) to lutetium (Lu). From the viewpoint of excellent hole transport ability, an oxide of at least one metal selected from the group consisting of molybdenum (Mo), tungsten (W), vanadium (V), nickel (Ni), and rhenium (Re) Is preferable, and at least one selected from the group consisting of molybdenum trioxide, tungsten trioxide, nickel oxide, and divanadium pentoxide is more preferable. These metal oxides may be used alone or in combination of two or more.

  Although the thickness of a positive hole transport layer does not have a restriction | limiting in particular, Usually, it is 1-1000 nm. From the viewpoint of hole transport properties and hole injection (extraction) properties, the thickness is more preferably 2 to 50 nm, and still more preferably 3 to 20 nm.

  The hole transport layer can be formed by using a general film forming method, for example, a dry process such as a heating vacuum deposition method, an electron beam deposition method, a laser beam deposition method, a sputtering method, a CVD method, an atmospheric pressure plasma method, or a coating method. A wet process such as a method, a plating method, or an electric field forming method can be used. Of these, heating vacuum deposition (Example) is particularly preferred.

[Photoelectric conversion layer]
The photoelectric conversion layer has a function of converting light energy into electric energy using the photovoltaic effect. The photoelectric conversion layer contains a p-type organic semiconductor material and an n-type organic semiconductor material as a photoelectric conversion material. When light is absorbed by these photoelectric conversion materials, excitons are generated, which are separated into holes and electrons at the pn junction interface.

  The p-type organic semiconductor material used for the photoelectric conversion layer preferably contains a p-type conjugated polymer. This p-type conjugated polymer is a copolymer having an electron donating group (donor unit) and an electron withdrawing group (acceptor unit) in the main chain. More specifically, the p-type conjugated polymer has a structure in which donor units and acceptor units are alternately arranged. Thus, by arranging the donor unit and the acceptor unit alternately, the absorption region of the p-type organic semiconductor can be expanded to a long wavelength region. That is, since the p-type conjugated polymer can absorb light in a long wavelength region (for example, 700 to 1000 nm) in addition to the absorption region (for example, 400 to 700 nm) of the conventional p-type organic semiconductor, It becomes possible to efficiently absorb radiant energy over a wide range of the optical spectrum.

  The donor unit that can be included in the p-type conjugated polymer is a unit in which the LUMO level or the HOMO level is shallower than a hydrocarbon aromatic ring (benzene, naphthalene, anthracene, etc.) having the same number of π electrons. If there is, it can be used without restriction. For example, a unit including a thiophene ring, a furan ring, a pyrrole ring, a hetero 5-membered ring such as cyclopentadiene or silacyclopentadiene, and a condensed ring thereof.

  Specific examples include fluorene, silafluorene, carbazole, dithienocyclopentadiene, dithienosylcyclopentadiene, dithienopyrrole, and benzodithiophene.

  The donor unit preferably has a structure represented by the following chemical formula 1.

In the formula, Z ₁ represents a carbon atom, a silicon atom, or germanium,
Each R ₁ independently represents a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted fluorinated alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted carbon group having 3 to 30 carbon atoms, or An unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, a substituted or unsubstituted heteroaryl group having 1 to 20 carbon atoms, or a substituted or unsubstituted group having 1 to 20 carbon atoms And two R _{1 's} may be bonded to each other to form a ring. R ₁ may be different from each other.

  A structure represented by the following chemical formula 2 is also suitable as the donor unit.

In the formula, each R ₂ independently represents a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, or 1 to 20 carbon atoms. Represents a substituted or unsubstituted alkyl ester group. R ₂ may be different from each other.

The alkyl group having 1 to 20 carbon atoms in R ₁ and R ₂ is a linear or branched alkyl group having 1 to 20 carbon atoms. Specifically, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, isopentyl group, neopentyl group, 1, 2-dimethylpropyl group, n-hexyl group, 1,3-dimethylbutyl group, 1-isopropylpropyl group, 1,2-dimethylbutyl group, n-heptyl group, 1,4-dimethylpentyl group, 2-methyl- 1-isopropylpropyl group, 1-ethyl-3-methylbutyl group, n-octyl group, 2-ethylhexyl group, 3-methyl-1-isopropylbutyl group, 2-methyl-1-isopropyl group, 1-t-butyl- Examples include 2-methylpropyl group, n-nonyl group, 3,5,5-trimethylhexyl group, n-decyl group, n-dodecyl group and the like.

Examples of the cycloalkyl group having 3 to 30 carbon atoms in R ₁ include a cyclopentyl group, a cyclohexyl group, a norbornyl group, and an adamantyl group.

Examples of the aryl group having 6 to 30 carbon atoms in R ₁ include phenyl group, phenethyl group, o-, m- or p-tolyl group, 2,3- or 2,4-xylyl group, mesityl group, and naphthyl group. Etc.

Examples of the heteroaryl group having 6 to 30 carbon atoms in R ₁ include a pyrrole group, a furan group, a thiophenyl group, a pyridyl group, and a pyrimidyl group.

Examples of the alkylsilyl group having 1 to 20 carbon atoms in R ₁ include a trimethylsilyl group, a triethylsilyl group, a triisopropylsilyl group, and a tert-butyldimethylsilyl group.

Examples of the alkoxy group having 1 to 20 carbon atoms in R ₂ include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, a 2-ethylhexyloxy group, and an octyloxy group. And linear, branched or cyclic alkoxy groups.

Examples of the alkyl ester group having 1 to 20 carbon atoms in R ₂ include a methyl ester group, an ethyl ester group, an n-propyl ester group, an i-propyl ester group, an n-butyl ester group, a 2-methylpropyl ester group, Examples include 1-methylpropyl group, t-butyl ester group, pentyl ester group, hexyl ester group, heptyl ester group, octyl ester group, nonyl ester group, decyl ester group, undecyl ester group, dodecyl ester group and the like.

In the above chemical formula 1 and chemical formula 2, as an optional substituent in the alkyl group, fluorinated alkyl group, cycloalkyl group, aryl group, heteroaryl group, alkylsilyl group, alkoxy group, or alkyl ester group, For example, halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom), acyl group, alkyl group, phenyl group, alkoxy group, halogenated alkyl group, halogenated alkoxy group, nitro group, amino group, alkylamino group, Alkylcarbonylamino group, arylamino group, arylcarbonylamino group, carbonyl group, alkoxycarbonyl group, alkylaminocarbonyl group, alkoxysulfonyl group, alkylthio group, carbamoyl group, aryloxycarbonyl group, oxyalkyl ether group, Such as amino group are exemplified, but not limited thereto. As the substituent, a group different from the skeleton group used as R ₁ and R ₂ is used.

  The donor unit represented by the above chemical formulas 1 and 2 has a solubility imparted by a substituent while the thiophene structure having a high mobility is condensed to have a large π-conjugated plane. Since such a donor unit is excellent in both solubility and mobility, the photoelectric conversion efficiency can be further improved.

  On the other hand, acceptor units that can be included in the p-type conjugated polymer include, for example, quinoxaline skeleton, pyrazinoquinoxaline skeleton, benzothiadiazole skeleton, benzooxadiazole skeleton, benzoselenadiazole skeleton, benzotriazole skeleton, pyrido Thiadiazole skeleton, thienopyrazine skeleton, phthalimide skeleton, 3,4-thiophenedicarboxylic acid imide skeleton, isoindigo skeleton, thienothiophene skeleton, diketopyrrolopyrrole skeleton, 4-acyl-thieno [3,4-b] thiophene skeleton, pyrazolo [ 5,1-c] [1,2,4] triazole skeleton and the like. In addition, the donor unit or acceptor unit contained in the p-type conjugated polymer of this embodiment may be used alone or in combination of two or more.

  In the present embodiment, preferable p-type conjugated polymers include Nature Material, (2006) vol. 5, p328, polythiophene-thienothiophene copolymer, polythiophene-diketopyrrolopyrrole copolymer described in WO08 / 000664, Adv. Mater. , 2007, p4160, a polythiophene-thiazolothiazole copolymer, Nature Mat. vol. 6 (2007), p497, and polythiophene copolymers such as PCDTBT (polythiophene-carbazole-benzothiadiazole copolymer). Of these, PCDTBT is more preferable.

  The molecular weight of the p-type conjugated polymer is not particularly limited, but the number average molecular weight is preferably 5,000 to 500,000, more preferably 10,000 to 100,000, and 15,000. More preferably, it is -50,000. When the number average molecular weight is 5,000 or more, the effect of improving the fill factor becomes more remarkable. On the other hand, when the number average molecular weight is 500,000 or less, the solubility of the p-type conjugated polymer is improved, so that productivity can be increased. In addition, in this specification, the value measured by gel permeation chromatography (GPC) is employ | adopted for a number average molecular weight.

  In addition, you may include other p-type organic-semiconductor materials other than the p-type conjugated polymer mentioned above. Examples of such other p-type organic semiconductor materials include triarylamine compounds, benzidine compounds, pyrazoline compounds, styrylamine compounds, hydrazone compounds, triphenylmethane compounds, carbazole compounds, polysilane compounds, thiophene compounds, phthalocyanine compounds, Cyanine compounds, merocyanine compounds, oxonol compounds, polyamine compounds, indole compounds, pyrrole compounds, pyrazole compounds, polyarylene compounds, condensed aromatic carbocyclic compounds (naphthalene derivatives, anthracene derivatives, phenanthrene derivatives, tetracene derivatives, pyrene derivatives, perylene derivatives, Fluoranthene derivatives) and metal complexes having a nitrogen-containing heterocyclic compound as a ligand. However, from the viewpoint of remarkably expressing the effects of the present invention, the mass ratio of the p-type conjugated polymer in the p-type organic semiconductor material contained in the photoelectric conversion layer is preferably 5% by mass or more, More preferably, it is 10 mass% or more, More preferably, it is 50 mass% or more, Especially preferably, it is 90 mass% or more, Most preferably, it is 100 mass%.

  The band gap of the p-type organic semiconductor material contained in the photoelectric conversion layer is preferably 1.8 eV or less, and more preferably 1.6 to 1.1 eV. When the band gap is 1.8 eV or less, sunlight can be widely absorbed. On the other hand, when the band gap is 1.1 eV or more, the open circuit voltage Voc (V) is easily generated, and the conversion efficiency can be improved. In addition, p-type organic semiconductors may be used alone or in combination of two or more.

  On the other hand, the n-type organic semiconductor material used for the photoelectric conversion layer is not particularly limited as long as it is an acceptor (electron-accepting) organic compound, and a material that can be used in this technical field can be appropriately employed. As such a compound, for example, a perfluoro product in which a hydrogen atom of the p-type organic semiconductor material is substituted with a fluorine atom, such as fullerene, carbon nanotube, and octaazaporphyrin (for example, perfluoropentacene or perfluorophthalocyanine), Examples thereof include aromatic carboxylic acid anhydrides such as naphthalenetetracarboxylic acid anhydride, naphthalenetetracarboxylic acid diimide, perylenetetracarboxylic acid anhydride, and perylenetetracarboxylic acid diimide, and polymer compounds containing an imidized product thereof as a skeleton.

  Of these, fullerenes, carbon nanotubes, or derivatives thereof are preferably used from the viewpoint that charge separation can be efficiently performed with a p-type organic semiconductor material at high speed (up to 50 fs). More specifically, fullerene C60, fullerene C70, fullerene C76, fullerene C78, fullerene C84, fullerene C240, fullerene C540, mixed fullerene, fullerene nanotube, multi-walled carbon nanotube, single-walled carbon nanotube, carbon nanohorn (conical type), etc. , And some of these are hydrogen atoms, halogen atoms (fluorine atoms, chlorine atoms, bromine atoms, iodine atoms), substituted or unsubstituted alkyl groups, alkenyl groups, alkynyl groups, aryl groups, heteroaryl groups, And a fullerene derivative substituted with a cycloalkyl group, a silyl group, an ether group, a thioether group, an amino group, or the like.

  In particular, [6,6] -phenyl C61-butyric acid methyl ester (abbreviation PCBM), [6,6] -phenyl C61-butyric acid-nbutyl ester (PCBnB), [6,6] -phenyl C61- Butyric acid-isobutyl ester (PCBiB), [6,6] -phenyl C61-butyric acid-n hexyl ester (PCBH), [6,6] -phenyl C71-butyric acid methyl ester (abbreviation PC71BM), Adv . Mater. , Vol. 20 (2008), p2116, aminated fullerene described in JP-A 2006-199674, metallocene fullerene described in JP-A 2008-130889, US Pat. No. 7,329,709 It is preferable to use a fullerene derivative whose solubility is improved by a substituent, such as fullerene having a cyclic ether group described in the specification. In addition, n-type organic-semiconductor material may be used individually by 1 type, and may use 2 or more types together.

  The junction form of the p-type organic semiconductor and the n-type organic semiconductor in the photoelectric conversion layer according to the present invention is a bulk heterojunction (bulk heterojunction). A bulk heterojunction (bulk heterojunction) is formed by applying a mixture of a p-type organic semiconductor and an n-type organic semiconductor. In this single layer, a domain of the p-type organic semiconductor and a domain of the n-type organic semiconductor are formed. And have a microphase separation structure. Therefore, in a bulk heterojunction, as compared with a planar heterojunction, many pn junction interfaces exist throughout the layer. Therefore, most of the excitons generated by light absorption can reach the pn junction interface, and the efficiency leading to charge separation can be increased.

  The mixing ratio of the p-type organic semiconductor material and the n-type organic semiconductor material contained in the photoelectric conversion layer is preferably in the range of 2: 8 to 8: 2, more preferably in the range of 4: 6 to 6: 4. It is. Moreover, the film thickness of a photoelectric converting layer becomes like this. Preferably it is 50-400 nm, More preferably, it is 80-300 nm.

(Self-assembled monolayer)
The organic photoelectric conversion device of the present invention has a self-assembled monolayer between the hole transport layer and the photoelectric conversion layer.

  The self-assembled monolayer is a layer obtained by adsorbing an organic compound, particularly an organic compound having an adsorbing group, onto an inorganic material through the adsorbing group. In the adsorption mechanism, since only a monomolecular layer is formed in a self-organized state between the organic compound and the inorganic material, a self-assembled monolayer or a self-assembled monolayer (SAM, It is called Self-Assembled Monolayer.

  The organic compound that forms such a self-assembled monolayer is generally a surface of an inorganic material such as a functional group (adsorbing group) capable of binding to an inorganic material and an electron-donating group or electron-withdrawing group on the opposite side. A functional group (terminal group) that modifies the surface properties (controlling the surface energy), and a linking group such as an aromatic group or a linear or branched carbon chain that connects these functional groups. In addition, such organic compounds are also preferably used in the self-assembled monolayer according to the present invention.

  Examples of the adsorption group include a thiol group (—SH), a phosphonic acid group (—PO (OH) 2), a carboxyl group (—COOH), a carbonyl chloride group (—COCl), a carbonyl bromide group (—COBr), A chlorosilane group (-SiCl), a bromosilane group (-SiBr), an alkoxysilane group (-SiOR), etc. are mentioned.

Examples of the terminal group include an alkyl group, an amino group (—NR ₂ ), a hydroxy group (—OH), an alkoxy group (—OR) such as a methoxy group and an ethoxy group, an aryloxy group such as a phenoxy group, and trifluoro Examples thereof include an electron donating group such as a methyl group (—CF ₃ ), a phenocenyl group, a quinonyl group, and a porphinyl group.

  Examples of the aromatic group include a phenylene group. As said carbon chain, a C3-C10 linear or branched alkylene group etc. are mentioned, for example.

  Specific examples of the organic compound forming the self-assembled monolayer according to the present invention include, for example, linking groups such as benzoic acid, 4-methylbenzoic acid, 4-methoxybenzoic acid, and 4-aminobenzoic acid. Compounds having an aromatic group; octyltrimethoxysilane, octadecyltrimethoxysilane, octyltriethoxysilane, octadecyltriethoxysilane, octyltrichlorosilane, octadecyltrichlorosilane, phenethyltrimethoxysilane, phenoxyoctadecyltrimethoxysilane, phenyltriethoxysilane , Phenethyltriethoxysilane, phenoxyoctadecyltriethoxysilane, phenethyltrichlorosilane, phenoxyoctadecyltrichlorosilane, aminopropyltrimethoxysilane, aminopropyltrie Xysilane, aminopropyltrichlorosilane, perfluorooctylethyltrimethoxysilane, perfluorooctylethyltriethoxysilane, perfluorooctylethyltrichlorosilane, 10-amido-1-decanethiol, 16-amino-1-hexadecanethiol, 18- Examples thereof include compounds having a carbon chain as a linking group such as amino-1-octadecanethiol.

  The adsorbing group is preferably a carboxyl group from the viewpoint of film forming properties on the metal oxide.

  In addition, the terminal group can form an electron donor from the viewpoint of forming a dipole in a direction in which the energy level of the photoelectric conversion layer and the energy level of the metal oxide (hole transport layer) are more ohmicly connected. Preferably an amino group or a methoxy group.

  The electron donating group is preferably oriented on the photoelectric conversion layer side, and the adsorbing group is preferably oriented on the hole transport layer side. With such an orientation, a dipole in a direction in which the energy level of the photoelectric conversion layer and the energy level of the metal oxide (hole transport layer) are more ohmicly connected can be formed, and the effect of the present invention can be achieved. Further improve.

  The method for forming the self-assembled monolayer is not particularly limited, and examples thereof include dry processes such as vacuum deposition, sputtering, molecular beam epitaxy, spin coating (Examples), dip method, Langmuir-Blodgett. A wet process such as a method (LB method) may be mentioned. From the viewpoint of ease of film formation, a wet process is preferable.

  When the wet process is used, the concentration of the organic compound in the solution is not particularly limited. However, in the case of a dilute solution, formation of a monomolecular layer is insufficient, and in the case of a concentrated solution, a second layer is formed. Therefore, it is preferably 0.5 to 5 mM. After applying a solution containing a compound that forms a self-assembled monolayer, the excess self-assembled monolayer can be removed by coating (rinsing) with a solvent alone. The solvent in this case may be the same as or different from that used for the solution, and can be appropriately selected. The type of the solvent is not particularly limited, and may be a nonpolar solvent or a polar solvent as long as the organic compound is dissolved. Examples include n-hexane, diethyl ether, tetrahydrofuran, dichloromethane, chloroform, carbon tetrachloride, 1,2-dichloroethane, benzene, toluene, xylene, acetone, methanol, ethanol, ethoxyethanol, 2-propanol, water, and the like. .

〔electrode〕
Although the organic photoelectric conversion element of the present invention has the first electrode and the second electrode, when the tandem configuration is adopted, the tandem configuration can be achieved by using the intermediate electrode.

  In the present invention, the first electrode is preferably a transparent electrode.

  “Transparent” means that the light transmittance is 50% or more.

  The light transmittance is in the visible light wavelength range measured by a method in accordance with “Testing method of total light transmittance of plastic-transparent material” of JIS K 7361-1: 1997 (corresponding to ISO 13468-1: 1996). The total light transmittance.

  In the organic photoelectric conversion element of the present invention, the reverse layer type is preferable from the viewpoint of durability. Therefore, the first electrode is preferably a transparent cathode (cathode), and the second electrode is an anode (anode). It is preferable that

  Hereinafter, the electrode of the reverse layer type organic photoelectric conversion element which is a preferred embodiment will be described. Note that a light-transmitting electrode is also referred to as a transparent electrode, and an electrode having a low light-transmitting property is also referred to as a counter electrode.

[First electrode]
Examples of the material used for the first electrode (transparent electrode) of the present invention include indium tin oxide (ITO), AZO (aluminum doped zinc oxide), FTO (fluorine doped tin oxide), SnO ₂ , ZnO, and oxidation. Transparent metal oxides such as titanium, metals such as Ag, Al, Au, and Pt, metal nanowires, nanowires such as carbon nanotubes and nanoparticles, conductive polymer materials such as PEDOT: PSS, polyaniline, and the like can be used.

  Also selected from the group consisting of derivatives of polypyrrole, polyaniline, polythiophene, polythienylene vinylene, polyazulene, polyisothianaphthene, polycarbazole, polyacetylene, polyphenylene, polyphenylene vinylene, polyacene, polyphenylacetylene, polydiacetylene and polynaphthalene. Conductive polymers can also be used. Further, a plurality of these conductive compounds can be combined to form a cathode.

[Second electrode]
The second electrode may be a single layer of a conductive material, but in addition to a conductive material, a resin that holds these may be used in combination.

  Since the work function of the transparent electrode, which is the cathode, is approximately −5.0 to −4.0 eV, the built-in potential is necessary for the carriers generated in the bulk heterojunction photoelectric conversion layer to diffuse and reach each electrode. That is, it is preferable that the work function difference between the anode and the cathode is as large as possible.

  Therefore, as an anode conductive material, a material having a work function (4 eV or less) metal, alloy, electrically conductive compound, and a mixture thereof as an electrode material is used. Specific examples of such an electrode material include gold, silver (Example), copper, platinum, rhodium, indium, nickel, palladium and the like. Among these, silver (Example) is most preferable from the viewpoint of hole extraction performance, light reflectance, and durability against oxidation and the like.

  The first electrode and the second electrode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. The film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm (Example: first electrode 150 nm, second electrode 200 nm).

  Further, when making the anode side light-transmitting, for example, a conductive material suitable for the anode such as aluminum and aluminum alloy, silver and silver compound is formed in a thin film thickness of about 1 to 20 nm, and then conductive light is used. By providing a film of a transmissive material, a light transmissive anode can be obtained.

  In the above description, preferred materials for the second electrode material for making a so-called reverse layer type element, which is advantageous for improving the durability, have been described. However, the so-called normal layer type (the first electrode is an anode and the second electrode is a cathode) ), The work function relationship between the first electrode and the second electrode may be reversed as described above. However, the types of substantially transparent electrodes are limited, and the work functions are compared. In many cases, a deep layer organic thin film solar cell can be obtained by using a metal having a shallow work function (less than −4.0 eV) on the second electrode side. Examples of such metals include aluminum, calcium, magnesium, lithium, sodium, potassium, and the like. In general, aluminum having high reflectivity and high conductivity is used. Further, the second electrode may be a transparent electrode. “Transparent” has the same meaning as described above for the first electrode.

[Charge recombination layer; intermediate electrode]
In addition, the material of the charge recombination layer (intermediate electrode) required in the case of the tandem configuration as shown in FIG. 3 is preferably a layer using a compound having both transparency and conductivity. Materials used (transparent metal oxides such as ITO, AZO, FTO, SnO ₂ , ZnO, and titanium oxide, metals such as Ag, Al, Au, and Pt, metal nanowires, nanowires and nanoparticles such as carbon nanotubes, PEDOT, etc. : Conductive polymer materials such as PSS and polyaniline).

  In addition, in the hole transport layer and the electron transport layer described above, there is also a combination that works as an intermediate electrode (charge recombination layer) by appropriately combining and laminating. Is preferable.

(Electron transport layer)
The organic photoelectric conversion element of the present invention may include an electron transport layer as necessary.

  The electron transport layer is a layer that is located between the cathode and the photoelectric conversion layer and that can more efficiently transfer electrons between the photoelectric conversion layer and the electrode.

  It is preferable that the electron transport layer has a metal compound and has a shallow work function and is polymerized. The work function in the electron transport layer refers to the HOMO-LUMO level of the electron transport layer itself. When the work function of the adjacent electrode is changed by stacking the electron transport layer of a very thin film like a monomolecular film, the electrode Is specified as the work function of the electron transport layer.

As the electron transport layer, octaazaporphyrin, p-type semiconductor perfluoro compounds (perfluoropentacene, perfluorophthalocyanine, etc.), carboline compounds described in WO 04/095889 pamphlet, and the like can be used. In addition, the electron transport layer having a HOMO level deeper than the HOMO level of the p-type semiconductor material used for the photoelectric conversion layer has a rectifying effect so that holes generated in the photoelectric conversion layer do not flow to the cathode side. It has a hole blocking function. More preferably, a material deeper than the HOMO level of the n-type semiconductor is used as the electron transport layer. From the viewpoint of blocking holes, it is preferable to use a compound having a hole mobility lower than 10 ⁻⁶ . Moreover, it is preferable to use a compound with high electron mobility from the characteristic of transporting electrons. More preferably, it is a compound having an electron mobility of 10 ⁻⁴ or more.

  Examples of such materials include phenanthrene compounds such as bathocuproine, n-type semiconductor materials such as naphthalenetetracarboxylic acid anhydride, naphthalenetetracarboxylic acid diimide, perylenetetracarboxylic acid anhydride, and perylenetetracarboxylic acid diimide, International Publication No. 08. An amine compound such as the amine-based silane coupling agent described in the / 134492 pamphlet and n-type inorganic oxides such as titanium oxide (TiOX), zinc oxide, and gallium oxide can be used. Moreover, the layer which consists of a n-type semiconductor material single-piece | unit used for the photoelectric converting layer can also be used.

  The means for forming these layers may be either a vacuum deposition method or a solution coating method, but is preferably a solution coating method.

  The thickness of the electron transport layer is not particularly limited, but is usually 1 to 2000 nm. From the viewpoint of enhancing the leak prevention effect, the thickness is preferably 5 nm or more. Further, from the viewpoint of maintaining high transmittance and low resistance, the thickness is preferably 1000 nm or less, and more preferably 200 nm or less.

[Transparent substrate]
The organic photoelectric conversion element of the present invention may include a substrate as necessary. The substrate has a role as a member to be coated with a coating solution when the electrode is formed by a coating method. The substrate is a transparent substrate, but “transparent” has the same meaning as described above for the first electrode.

  Suitable examples of the substrate include a glass substrate and a resin substrate. There is no restriction | limiting in particular in the transparent resin film which can be preferably used as a transparent substrate by this invention, The material, a shape, a structure, thickness, etc. can be suitably selected from well-known things.

  For example, polyolefins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyester resin film such as modified polyester, polyethylene (PE) resin film, polypropylene (PP) resin film, polystyrene resin film, cyclic olefin resin, etc. Resin films, vinyl resin films such as polyvinyl chloride and polyvinylidene chloride, polyether ether ketone (PEEK) resin films, polysulfone (PSF) resin films, polyether sulfone (PES) resin films, polycarbonate (PC) resin films , Polyamide resin film, polyimide resin film, acrylic resin film, triacetyl cellulose (TAC) resin film, and the like. If the resin film transmittance of 80% or more in from zero to eight hundred nanomolar), can be preferably applied.

  Among these, from the viewpoint of transparency, heat resistance, ease of handling, strength and cost, it is preferably a biaxially stretched polyethylene terephthalate film, a biaxially stretched polyethylene naphthalate film, a polyethersulfone film, or a polycarbonate film. More preferred are a stretched polyethylene terephthalate film and a biaxially stretched polyethylene naphthalate film.

  The transparent substrate used in the present invention can be subjected to a surface treatment or an easy adhesion layer in order to ensure the wettability and adhesiveness of the coating solution. A conventionally well-known technique can be used about a surface treatment or an easily bonding layer. For example, the surface treatment includes surface activation treatment such as corona discharge treatment, flame treatment, ultraviolet treatment, high frequency treatment, glow discharge treatment, active plasma treatment, and laser treatment. Examples of the easy adhesion layer include polyester, polyamide, polyurethane, vinyl copolymer, butadiene copolymer, acrylic copolymer, vinylidene copolymer, and epoxy copolymer.

  For the purpose of suppressing the permeation of oxygen and water vapor, a barrier coat layer may be formed in advance on the transparent substrate, or a hard coat layer may be formed in advance on the opposite side to which the transparent conductive layer is transferred. Good.

[Other layers]
As a structure of the organic photoelectric conversion element of this invention, it is good also as a structure which has various intermediate | middle layers in an element for the purpose of the improvement of a photoelectric conversion efficiency, and the improvement of element lifetime.

  Examples of the intermediate layer include a hole block layer, an electron block layer, a hole injection layer, an electron injection layer, an exciton block layer, a UV absorption layer, a light reflection layer, and a wavelength conversion layer.

  Moreover, the organic photoelectric conversion element of this invention may have various optical function layers for the purpose of more efficient light reception of sunlight. As the optical functional layer, for example, a light condensing layer such as an antireflection film or a microlens array, a light diffusing layer that can scatter the light reflected by the cathode and enter the power generation layer again may be provided. .

  Various known antireflection layers can be provided as the antireflection layer. For example, when the transparent resin film is a biaxially stretched polyethylene terephthalate film, the refractive index of the easy adhesion layer adjacent to the film is 1.57. It is more preferable to set it to ˜1.63 because the interface reflection between the film substrate and the easy adhesion layer can be reduced and the transmittance can be improved. The method of adjusting the refractive index can be carried out by appropriately adjusting the ratio of the oxide sol having a relatively high refractive index such as tin oxide sol or cerium oxide sol and the binder resin. The easy adhesion layer may be a single layer, but may be composed of two or more layers in order to improve adhesion.

  As the condensing layer, for example, it is processed so as to provide a structure on the microlens array on the sunlight receiving side of the support substrate, or the amount of light received from a specific direction is increased by combining with a so-called condensing sheet. Conversely, the incident angle dependency of sunlight can be reduced.

  As an example of the microlens array, quadrangular pyramids having a side of 30 μm and an apex angle of 90 degrees are two-dimensionally arranged on the light extraction side of the substrate. One side is preferably 10 to 100 μm. If it becomes smaller than this, the effect of diffraction will generate | occur | produce and color, and if too large, thickness will become thick and is not preferable.

  Examples of the light scattering layer include various antiglare layers, layers in which nanoparticles or nanowires such as metals or various inorganic oxides are dispersed in a colorless and transparent polymer, and the like.

[Patterning]
The method and process for patterning each electrode, photoelectric conversion layer, hole transport layer, electron transport layer and the like according to the present invention are not particularly limited, and known methods can be appropriately applied.

  If it is a soluble material such as a photoelectric conversion layer and an electron transport layer, only unnecessary portions may be wiped after the entire surface of die coating, dip coating, spin coating, blade coating, etc., or a method such as an inkjet method or screen printing is used. Then, direct patterning may be performed at the time of application.

  In the case of an insoluble material such as an electrode material, the electrode can be subjected to mask vapor deposition during vacuum deposition or patterned by a known method such as etching or lift-off. Alternatively, the pattern may be formed by transferring a pattern formed on another substrate.

[Solar cell]
Since the said organic photoelectric conversion element has the outstanding photoelectric conversion efficiency and durability, it can be used suitably for a solar cell.

  The solar cell of the present invention comprises the above-described organic photoelectric conversion element, has a structure in which optimum design and circuit design are performed for sunlight, and optimum photoelectric conversion is performed when sunlight is used as a light source. .

  That is, the photoelectric conversion layer has a structure that can be irradiated with sunlight, and when the solar cell of the present invention is configured, the photoelectric conversion layer and each electrode are housed in a case and sealed, Alternatively, it is preferable to seal them entirely with resin.

  As a sealing method, since the produced organic photoelectric conversion element is not deteriorated by oxygen, moisture, etc. in the environment, it is preferable to seal not only the organic photoelectric conversion element but also an organic electroluminescence element by a known method. .

  For example, a method of sealing a cap made of aluminum or glass by bonding with an adhesive, a plastic film on which a gas barrier layer such as aluminum, silicon oxide, or aluminum oxide is formed and an organic photoelectric conversion element are pasted with an adhesive. Method, spin coating of organic polymer material with high gas barrier property (polyvinyl alcohol, etc.), inorganic thin film with high gas barrier property (silicon oxide, aluminum oxide, etc.) or organic film (parylene etc.) are deposited under vacuum. Examples thereof include a method and a method of laminating these in a composite manner.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.
is not.

[Preparation of p-type semiconductor material (PCDTBT)]
As a p-type semiconductor material, a polythiophene-carbazole-benzothiadiazole copolymer (PCDTBT) is disclosed in Adv. Mater. , Vol. 19, (2007) p2295. The obtained polymer was purified by Soxhlet extraction to obtain PCDTBT having a number average molecular weight (Mn): 35,000 and PDI: 2.0.

[Preparation of Self-Assembled Monolayer (SAM Layer) Formation Solutions A to E]
Benzoic acid (compound A), 10-amido-1-dodecanthiol (compound B), 4-methylbenzoic acid (compound C), 4-aminobenzoic acid (compound D), and 4-methoxybenzoic acid (compound E) Were dissolved in ethanol at a concentration of 1 mM, and stirred at room temperature for 1 day to prepare solutions A to E for forming a self-assembled monolayer (hereinafter also simply referred to as SAM layer).

(Comparative Example 1)
[Production of Organic Photoelectric Conversion Element SC-101]
An indium tin oxide (ITO) transparent conductive film deposited on a glass substrate with a thickness of 150 nm (sheet resistance 12 Ω / □) is patterned to a width of 10 mm using a normal photolithography technique and wet etching, and the first An electrode was formed. The patterned first electrode was washed in the order of ultrasonic cleaning with a surfactant and ultrapure water, followed by ultrasonic cleaning with ultrapure water, dried by nitrogen blowing, and finally subjected to ultraviolet ozone cleaning.

The substrate is moved and set in the vacuum deposition apparatus, and after reducing the pressure in the vacuum deposition apparatus to 1 × 10 ⁻³ Pa or less, 5 nm of molybdenum trioxide (MoO ₃ ) is laminated at a deposition rate of 0.03 nm / second. A hole transport layer was formed.

  Next, the substrate was moved into the glove box (oxygen concentration 10 ppm, dew point temperature −80 degrees). Prepare a solution in which 0.6% by mass of PCDTBT, which is a p-type organic semiconductor material, and 1.2% by mass of PC71BM, which is an n-type organic semiconductor material, is mixed with o-dichlorobenzene. , Stir while heating to 100 ° C. in an oven (60 minutes) to dissolve PCPDTBT and PC71BM, and then apply a blade coater so that the dry film thickness is about 100 nm while filtering through a 0.20 μm filter. And dried at 80 ° C. for 2 minutes to form a photoelectric conversion layer.

Next, a 150 mM TiO _X precursor solution was spin-coated on the transparent electrode (rotation speed 5000 rpm, rotation time 60 seconds), and wiped off in a predetermined pattern. And after leaving this in the air for 2 hours to hydrolyze the TiO _X precursor, an electron transport layer composed of a TiO _X layer having a thickness of about 10 nm was formed by heat treatment at 150 ° C. for 1 hour. .

The 150 mM TiO _X precursor solution was prepared by the following method (sol-gel method). In a 100 mL three-necked flask, 12.5 mL of 2-methoxyethanol and 6.25 mmol of titanium tetraisopropoxide were placed and cooled in an ice bath for 10 minutes. Next, 12.5 mmol of acetylacetone was slowly added and stirred in an ice bath for 10 minutes. Next, this mixed solution was heated at 80 ° C. for 2 hours and then refluxed for 1 hour. This was cooled to room temperature (25 ° C.) and adjusted to a concentration of 150 mM using 2-methoxyethanol to obtain a TiO _X precursor solution. The above steps were all performed in a nitrogen atmosphere.

Next, 200 nm of Ag metal was laminated at a deposition rate of 0.5 nm / second to form a second electrode. The obtained laminate was moved to a nitrogen chamber and sandwiched between ^two relief printing transparent barrier films GX (water vapor transmission rate 0.05 g / m ² / d), and UV curable resin (Nagase ChemteX Corporation). Manufactured, manufactured by UV RESIN XNR5570-B1) and then taken out into the atmosphere to obtain an organic photoelectric conversion element SC-101 having a light receiving portion of about 10 × 10 mm size for comparison.

(Comparative Example 2)
[Preparation of Organic Photoelectric Conversion Element SC-102: Comparative Example 2]
In the production of the organic photoelectric conversion element SC-101, the same procedure as for SC-101 was performed except that 5 nm of MoO ₃ was laminated and 5 nm of divanadium pentoxide (V ₂ O ₅ ) was laminated to form a hole transport layer. Organic photoelectric conversion element SC-102 was obtained.

Example 1
[Production of Organic Photoelectric Conversion Element SC-103]
A substrate prepared by a method similar to the method for manufacturing the organic photoelectric conversion element SC-101 was laminated by depositing 5 nm of nickel oxide (NiO) at a deposition rate of 0.03 nm / second by a pulse laser deposition method to form a hole transport layer. Next, the substrate is moved into the glove box (oxygen concentration 10 ppm, dew point temperature −80 ° C.), the SAM forming solution E prepared above is spin-coated at 2000 rpm, and then ethanol alone is spin-coated at 2000 rpm and rinsed. Thus, the SAM layer E was formed on NiO.

  Thereafter, an organic photoelectric conversion element SC-103 was obtained in the same manner as the organic photoelectric conversion element SC-101.

(Example 2)
[Production of Organic Photoelectric Conversion Element SC-104]
The substrate prepared by the same method as the manufacturing method of the organic photoelectric conversion element SC-101 is moved and set in a vacuum deposition apparatus, and the inside of the vacuum deposition apparatus is depressurized to 1 × 10 ⁻³ Pa or less, and then the deposition rate. A hole transport layer was formed by laminating 5 nm of MoO ₃ at 0.03 nm / second. Next, the substrate is moved into the glove box (oxygen concentration 10 ppm, dew point temperature −80 ° C.), the SAM-forming solution A prepared above is spin-coated at 2000 rpm, and then only ethanol is spin-coated at 2000 rpm for rinsing. Thus, the SAM layer A was formed on the MoO ₃ .

  Thereafter, an organic photoelectric conversion element SC-104 was obtained in the same manner as the organic photoelectric conversion element SC-101.

(Example 3)
[Production of Organic Photoelectric Conversion Element SC-105]
The substrate prepared by the same method as the manufacturing method of the organic photoelectric conversion element SC-101 is moved and set in a vacuum deposition apparatus, and the inside of the vacuum deposition apparatus is depressurized to 1 × 10 ⁻³ Pa or less, and then the deposition rate. A hole transport layer was formed by laminating 5 nm of MoO ₃ at 0.03 nm / second. Next, the substrate is moved into the glove box (oxygen concentration 10 ppm, dew point temperature −80 ° C.), the SAM-forming solution B prepared above is spin-coated at 2000 rpm, and then ethanol alone is spin-coated at 2000 rpm and rinsed. Thus, the SAM layer B was formed on the MoO ₃ .

  Thereafter, an organic photoelectric conversion element SC-105 was obtained in the same manner as the organic photoelectric conversion element SC-101.

Example 4
[Production of Organic Photoelectric Conversion Element SC-106]
The substrate prepared by the same method as the manufacturing method of the organic photoelectric conversion element SC-101 is moved and set in a vacuum deposition apparatus, and the inside of the vacuum deposition apparatus is depressurized to 1 × 10 ⁻³ Pa or less, and then the deposition rate. A hole transport layer was formed by laminating 5 nm of MoO ₃ at 0.03 nm / second. Next, the substrate is moved into the glove box (oxygen concentration 10 ppm, dew point temperature −80 ° C.), the SAM-forming solution C prepared above is spin-coated at 2000 rpm, and then ethanol alone is spin-coated at 2000 rpm and rinsed. Thus, the SAM layer C was formed on the MoO ₃ .

  Thereafter, an organic photoelectric conversion element SC-106 was obtained in the same manner as the organic photoelectric conversion element SC-101.

(Example 5)
[Production of Organic Photoelectric Conversion Element SC-107]
The substrate prepared by the same method as the manufacturing method of the organic photoelectric conversion element SC-101 is moved and set in a vacuum deposition apparatus, and the inside of the vacuum deposition apparatus is depressurized to 1 × 10 ⁻³ Pa or less, and then the deposition rate. A hole transport layer was formed by laminating 5 nm of MoO ₃ at 0.03 nm / second. Next, the substrate is moved into the glove box (oxygen concentration 10 ppm, dew point temperature −80 ° C.), the SAM-forming solution D prepared above is spin-coated at 2000 rpm, and then ethanol alone is spin-coated at 2000 rpm for rinsing. Thus, the SAM layer D was formed on the MoO ₃ .

  Thereafter, an organic photoelectric conversion element SC-107 was obtained in the same manner as the organic photoelectric conversion element SC-101.

(Example 6)
[Production of Organic Photoelectric Conversion Element SC-108]
The substrate prepared by the same method as the manufacturing method of the organic photoelectric conversion element SC-101 is moved and set in a vacuum deposition apparatus, and the inside of the vacuum deposition apparatus is depressurized to 1 × 10 ⁻³ Pa or less, and then the deposition rate. V ₂ O ₅ was deposited in a thickness of 5 nm at 0.03 nm / second to form a hole transport layer. Next, the substrate is moved into the glove box (oxygen concentration 10 ppm, dew point temperature −80 ° C.), the SAM forming solution E prepared above is spin-coated at 2000 rpm, and then ethanol alone is spin-coated at 2000 rpm and rinsed. Thus, the SAM layer E was formed on V ₂ O ₅ .

  Thereafter, an organic photoelectric conversion element SC-108 was obtained in the same manner as the organic photoelectric conversion element SC-101.

(Example 7)
[Production of Organic Photoelectric Conversion Element SC-109]
The substrate prepared by the same method as the manufacturing method of the organic photoelectric conversion element SC-101 is moved and set in a vacuum deposition apparatus, and the inside of the vacuum deposition apparatus is depressurized to 1 × 10 ⁻³ Pa or less, and then the deposition rate. A hole transport layer was formed by laminating tungsten trioxide (WO ₃ ) at a thickness of 5 nm at 0.03 nm / second. Next, the substrate is moved into the glove box (oxygen concentration 10 ppm, dew point temperature −80 ° C.), the SAM forming solution E prepared above is spin-coated at 2000 rpm, and then ethanol alone is spin-coated at 2000 rpm and rinsed. Thus, the SAM layer E was formed on the WO ₃ .

  Thereafter, an organic photoelectric conversion element SC-109 was obtained in the same manner as the organic photoelectric conversion element SC-101.

(Comparative Example 3)
[Production of Organic Photoelectric Conversion Element SC-201]
A 150 mM TiO _X precursor solution is spin-coated on a transparent electrode (a rotational speed of 5000 rpm, a rotational time of 60 seconds) on a substrate prepared in the same manner as the manufacturing method of the organic photoelectric conversion element SC-101. Wiped off. And after leaving this in the air for 2 hours to hydrolyze the TiO _X precursor, an electron transport layer composed of a TiO _X layer having a thickness of about 10 nm was formed by heat treatment at 150 ° C. for 1 hour. .

Next, the substrate was moved into the glove box (oxygen concentration 10 ppm, dew point temperature −80 degrees). Prepare a solution in which 0.6% by mass of PCDTBT, which is a p-type organic semiconductor material, and 1.2% by mass of PC71BM, which is an n-type organic semiconductor material, is mixed with o-dichlorobenzene. Stir while heating to 100 ° C. in an oven (60 minutes) to dissolve PCDTBT and PC71BM, and then apply a blade coater so that the dry film thickness is about 100 nm while filtering through a 0.20 μm filter. The resultant was applied and dried at 80 ° C. for 2 minutes to form a photoelectric conversion layer. After moving and setting in a vacuum deposition apparatus, the inside of the vacuum deposition apparatus was depressurized to 1 × 10 ⁻³ Pa or less, and then 5 nm of MoO ₃ was laminated at a deposition rate of 0.03 nm / second to form a hole transport layer. .

Next, 200 nm of Ag metal was laminated at a deposition rate of 0.5 nm / second to form a second electrode. The obtained laminate was moved to a nitrogen chamber and sandwiched between ^two relief printing transparent barrier films GX (water vapor transmission rate 0.05 g / m ² / d), and UV curable resin (Nagase ChemteX Corporation). Manufactured, manufactured by UV RESIN XNR5570-B1) and then taken out into the atmosphere to obtain an organic photoelectric conversion element SC-201 in which the light receiving part has a comparison of about 10 × 10 mm size.

(Comparative Example 4)
[Production of Organic Photoelectric Conversion Element SC-202]
A 150 mM TiO _X precursor solution is spin-coated on a transparent electrode (a rotational speed of 5000 rpm, a rotational time of 60 seconds) on a substrate prepared in the same manner as the manufacturing method of the organic photoelectric conversion element SC-101. Wiped off. And after leaving this in the air for 2 hours to hydrolyze the TiO _X precursor, an electron transport layer composed of a TiO _X layer having a thickness of about 10 nm was formed by heat treatment at 150 ° C. for 1 hour. . Next, the substrate is moved into the glove box (oxygen concentration 10 ppm, dew point temperature −80 ° C.), the SAM forming solution E prepared above is spin-coated at 2000 rpm, and then ethanol alone is spin-coated at 2000 rpm and rinsed. Thus, the SAM layer E was formed on the TiO _X.

Next, the substrate was moved into the glove box (oxygen concentration 10 ppm, dew point temperature −80 degrees). Prepare a solution in which 0.6% by mass of PCDTBT, which is a p-type organic semiconductor material, and 1.2% by mass of PC71BM, which is an n-type organic semiconductor material, is mixed with o-dichlorobenzene. Stir while heating to 100 ° C. in an oven (60 minutes) to dissolve PCDTBT and PC71BM, and then apply a blade coater so that the dry film thickness is about 100 nm while filtering through a 0.20 μm filter. The resultant was applied and dried at 80 ° C. for 2 minutes to form a photoelectric conversion layer. After moving and setting in a vacuum deposition apparatus, the inside of the vacuum deposition apparatus was depressurized to 1 × 10 ⁻³ Pa or less, and then 5 nm of MoO ₃ was laminated at a deposition rate of 0.03 nm / second to form a hole transport layer. .

Next, 200 nm of Ag metal was laminated at a deposition rate of 0.5 nm / second to form a second electrode. The obtained laminate was moved to a nitrogen chamber and sandwiched between ^two relief printing transparent barrier films GX (water vapor transmission rate 0.05 g / m ² / d), and UV curable resin (Nagase ChemteX Corporation). Manufactured, manufactured by UV RESIN XNR5570-B1) and then taken out into the atmosphere to obtain an organic photoelectric conversion element SC-202 having a light receiving portion of about 10 × 10 mm size for comparison.

<Evaluation of initial photoelectric conversion efficiency>
About the organic photoelectric conversion element produced above, the solar simulator (AM1.5G filter) is irradiated with light having an intensity of 100 mW / cm ² , a mask with an effective area of 1 cm ² is superimposed on the light receiving part, and the IV characteristics are obtained. By evaluating, the short circuit current density J _sc [mA / cm ² ], the open circuit voltage V _oc [V], and the fill factor FF were measured, and the initial photoelectric conversion efficiency η was calculated from the following formula 1. The evaluation results are shown in Table 1.

<Evaluation of light stability>
The organic photoelectric conversion element prepared above is placed on a hot plate at 85 ° C., and a short wavelength current density J measured in the evaluation of the initial photoelectric conversion efficiency is performed using a two-wavelength type white LED (Toshiba small SMD) as a light source. The light quantity of the LED was adjusted so as to be approximately the same value as _sc (about 1 Sun), and the light was irradiated for 1000 hours. The short-circuit current density J _sc after light irradiation, was measured according to the measurement method in the evaluation of the photoelectric conversion efficiency, the ratio of J _sc after the deterioration to the initial J _sc (retention) was determined [%]. The evaluation results are shown in Table 1.

  As apparent from Table 1 above, the SAM layer was formed on the hole transport layer made of a metal oxide and the interface between the photoelectric conversion layer and the hole transport layer was adjusted. It can be seen that a stable element with little decrease is obtained. Even if a metal oxide is used for the hole blocking layer (electron transport layer), there is almost no deterioration of Jsc as long as the interface on the hole transport layer side is adjusted.

  On the contrary, in the case where the interface is adjusted with the SAM layer only on the hole blocking layer side (Comparative Example 4), the same Jsc degradation occurs as in the case where the adjustment is not performed with the SAM layer. It can be seen that it is essential to adjust the interface with the SAM layer on the side.

10, 20, 30 organic photoelectric conversion element,
11 substrate,
12 first electrode;
13 second electrode,
14 photoelectric conversion layer,
14a 1st photoelectric conversion layer,
14b second photoelectric conversion layer,
15 charge recombination layer,
17 hole transport layer,
18 electron transport layer,
19 Self-assembled monolayer.

Claims (7)

The first electrode,
The second electrode,
A hole transport layer including a metal oxide and a bulk heterojunction type photoelectric conversion layer disposed between the first electrode and the second electrode, and the hole transport layer and the photoelectric conversion layer A self-assembled monolayer placed between,
An organic photoelectric conversion element.   The hole transport layer includes an oxide of at least one metal selected from the group consisting of molybdenum (Mo), tungsten (W), vanadium (V), nickel (Ni), and rhenium (Re). Item 10. The organic photoelectric conversion device according to Item 1.   The organic photoelectric conversion element according to claim 1 or 2, wherein the compound forming the self-assembled monolayer has an electron donating group and an adsorbing group.   The organic photoelectric conversion element according to claim 3, wherein the electron donating group is an amino group or a methoxy group.   The organic photoelectric conversion element according to claim 3 or 4, wherein the adsorption group is a carboxyl group.   The organic photoelectric conversion element according to any one of claims 3 to 5, wherein the electron donating group is oriented toward the photoelectric conversion layer, and the adsorbing group is oriented toward the hole transport layer.   The solar cell which has an organic photoelectric conversion element of any one of Claims 1-6.

Images