JPWO2013151142A1 - Organic photoelectric conversion device and solar cell using the same - Google Patents

Abstract

An organic photoelectric conversion element having excellent photoelectric conversion efficiency and exhibiting sufficient durability and a solar cell using the same are provided. An organic photoelectric conversion element having a first electrode, a bulk heterojunction photoelectric conversion layer, a hole transport layer, and a second electrode in this order, wherein the first electrode is an ultraviolet light A work structure of the first electrode, comprising: a nanostructure having a work function measured by photoelectron spectroscopy greater than 4.3 eV; and a surface modifying molecule having a dipole moment and adsorbed on the surface of the nano structure. Is 0.2 eV or more smaller than the work function of the nanostructure and 0.7 eV or less smaller than the work function of the hole transport layer. [Selection] Figure 4

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-mentioned problem of power generation cost can be solved. Furthermore, the bulk heterojunction organic photoelectric conversion element is different from the conventional production of silicon photoelectric conversion elements, compound photoelectric conversion elements, dye-sensitized photoelectric conversion elements, etc. Since it is not essential, it is expected that it can be formed on an inexpensive and 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.

In order to improve the photoelectric conversion efficiency of the bulk heterojunction type organic photoelectric conversion element, a method of increasing the film thickness of the power generation layer can be considered in order to obtain a sufficient amount of light absorption. However, when the thickness of the power generation layer is increased, carriers such as holes or electrons generated in the power generation layer are recombined in the power generation layer before reaching the electrodes and the charge transport layer, and thus it is difficult to recover the carriers. . Therefore, the film thickness of the power generation layer cannot be increased, and there is a trade-off between the power generation layer thickness in the short circuit current density (J _SC ) and the fill factor (FF) as element performance.

  As a countermeasure against the above problem, a structure in which a monomolecular layer self-adsorbed on the surface of a nanopillar connected to a substrate and an active layer is formed on the monomolecular layer (for example, Patent Document 1) A technique using a charge extraction structure using a composite (for example, Patent Document 2) in which a conjugated compound is adsorbed on metal particles having an aspect ratio of 1.5 or more has been proposed.

  On the other hand, in bulk heterojunction organic photoelectric conversion elements, the reason why sufficient durability against heat and light is not obtained is, for example, general organic electronic devices such as organic thin film transistors (OTFTs) and organic light emitting diodes (OLEDs). Similarly, the photoelectric conversion element has a problem that it is easily affected by oxygen and moisture. Therefore, when 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 such as a barrier film or a glass plate.

However, even when sealed with a barrier member, trace amounts of moisture and oxygen that are mixed in during the manufacturing process and remain as they are, and trace amounts of moisture and oxygen that pass through the barrier member are unavoidable. Exists. Generally, a material with a small work function (shallow) is selected as the cathode or hole blocking layer on the electron extraction side, and thus continuous light irradiation was performed in the presence of a small amount of moisture and oxygen. In such a case, the short circuit current density (J _SC ) and fill factor (FF) are attenuated due to the influence of moisture and oxygen, and the lifetime of the device is remarkably shortened.

  As a countermeasure against the above problems, for example, a technique for improving stability by light irradiation by using a layer made of titanium oxide that is stable to moisture and oxygen as a hole block layer (hereinafter also referred to as “electron transport layer”). (For example, patent document 3) and the trial which improves the lifetime of an element by using the material whose glass transition temperature is 80 degreeC or more for a hole block layer are proposed (for example, patent document 4).

US Patent Application Publication No. 2011/108102 JP 2010-261102 A US Patent Application Publication No. 2011/056747 JP 2011-176305 A

A. Heeger et al. , Nature Mat. , Vol. 6 (2007), p497

However, as a result of investigations by the present inventors, it has been found that it is difficult to achieve both sufficient photoelectric conversion efficiency and durability even with the technique described in the above document. That is, in the techniques disclosed in Patent Document 1 and Patent Document 2, since the material covering the surfaces of the nanopillars and nanoparticles included in the layers constituting the element has a bulky structure, There are areas where the material cannot be sufficiently covered. As a result, it was found that a sufficient fill factor could not be obtained due to a leak current generated from the region, and the photoelectric conversion efficiency of the device was lowered. Moreover, the photoelectric conversion element which has the said structure using a nano pillar and a nanoparticle has the problem that durability with respect to a heat | fever or light is inadequate. When the photoelectric conversion element having the above-described configuration is driven by continuous light irradiation, a large level mismatch occurs at the interface between the material of the photoelectric conversion layer and the material and electrode constituting the nanopillar or nanoparticle. As a result, it was found that charges are accumulated near the interface, the level mismatch is promoted by the shift of the vacuum level, the short-circuit current density (J _SC ) is attenuated, and the lifetime of the device is remarkably shortened. This level mismatch was insufficient in the durability of the photoelectric conversion element even with the techniques described in Patent Documents 1 to 4.

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

  As a result of intensive studies aimed at solving the above-mentioned problems, the present inventors have found that the above-described object can be achieved by the following constitution, and have led to the disclosure of the present invention.

  That is, an organic photoelectric conversion element having a first electrode, a bulk heterojunction photoelectric conversion layer, a hole transport layer, and a second electrode in this order, wherein the first electrode is an ultraviolet photoelectron. A nanostructure having a work function measured by spectroscopy of greater than 4.3 eV, and a surface modifying molecule having a dipole moment and adsorbed on the surface of the nanostructure, the work of the first electrode The function is an organic photoelectric conversion element that is smaller than the work function of the nanostructure by 0.2 eV or more and smaller than the work function of the hole transport layer by 0.7 eV or more.

1 is a schematic cross-sectional view schematically illustrating an organic photoelectric conversion element according to an embodiment of the present invention. It is the cross-sectional schematic which represented the organic photoelectric conversion element based on 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 based on other embodiment of this invention. It is the elements on larger scale of the 1st electrode of the organic photoelectric conversion element based on one Embodiment of this invention. It is the cross-sectional schematic which represented the organic photoelectric conversion element based on further another embodiment of this invention typically. It is the cross-sectional schematic which represented typically the organic photoelectric conversion element based on other one Embodiment of this invention. It is the cross-sectional schematic which represented typically the organic photoelectric conversion element provided with the tandem-type photoelectric conversion layer based on other one Embodiment of this invention. It is the schematic diagram which showed the relationship between the dipole moment of a surface coating molecule | numerator, and the work function of Ag at the time of coat | covering a surface coating molecule | numerator when a nanostructure is silver (Ag).

  Embodiments of the present invention will be described below. In this specification, “work function” is defined as the minimum energy required to extract one electron from the surface of a substance to the vacuum level, and generally has a large work function (deep). The material has a property that it is difficult to be oxidized, and a material having a small work function (shallow) is easily oxidized. In this specification, the work function is measured by an ultraviolet photoelectron spectrum spectrometer (UPS method).

The “dipole moment” indicates the product of a vector from a negative charge to a positive charge and the magnitude of the charge. Specifically, the vector and size can be obtained from calculation by the density functional (DFT) method. In the present invention, the dipole moment in a state of being bonded to one silver (Ag) atom as the metal species to be adsorbed was determined. The calculation program is Gaussian 03, the organic part is B3LYP / 6-31G ^{* as} the basis function, and the metal part is B3LYP / SDD.

Furthermore, “X to Y” indicating a range means “X or more and Y or less”. further,
“Transparent” means to exhibit a transmittance of 80% or more for visible light of 380 to 800 nm.

  The present invention is an organic photoelectric conversion element having a first electrode, a bulk heterojunction type photoelectric conversion layer, a hole transport layer, and a second electrode in this order, wherein the first electrode comprises: A nanostructure having a work function measured by ultraviolet photoelectron spectroscopy of greater than 4.3 eV, and a surface-modifying molecule having a dipole moment and adsorbed on the surface of the nanostructure, the first electrode The organic photoelectric conversion element has a work function smaller than the work function of the nanostructure by 0.2 eV or more and 0.7 eV or less than the work function of the hole transport layer.

  In other words, according to the present invention, the first electrode has a nanostructure having a level whose work function measured by ultraviolet photoelectron spectroscopy is deeper than 4.3 eV, a dipole moment, and the nanostructure. The work function of the first electrode is at a level shallower by 0.2 eV or more than the work function of the nanostructure, and the work of the hole transport layer is It is an organic photoelectric conversion element having a level shallower by 0.7 eV or more than the function.

  As described above, the first electrode has a structure in which the surface modification molecule having a dipole moment is adsorbed to the nanostructure, thereby having excellent photoelectric conversion efficiency and driving the photoelectric conversion element by continuous light irradiation. In this case, a photoelectric conversion element with improved durability can be obtained. Although the mechanism is not clear, the present inventors presume as follows. Note that the present invention is not limited to the following estimation.

  That is, with the above configuration, it is considered important to control so that no level mismatch occurs at the interface between the electrode having the nanostructure and the power generation layer.

  Generally, in order to reduce the level mismatch as described above, the work function is small (shallow) such as alkali metal, alkaline earth metal, or a metal belonging to these metals, and chloride, fluoride, etc. A metal species (specifically, calcium, lithium, cesium, or a compound containing these) is used as an electrode material or a hole block material. However, since the metal species having a small work function is unstable with respect to moisture and oxygen, it is easily affected by water and oxygen, and as a result, the life of the element, that is, the durability cannot be improved. On the other hand, in the present invention, as the material constituting the first electrode, an electrode member having excellent stability, that is, a nanostructure having a core material made of a material having a high work function is used. By covering nanostructures with a large work function with surface-modifying molecules having a child moment, the apparent work function can be shifted by the vacuum level shift of the interface between the electrode and the organic substance, resulting in a small work function. A small work function side electrode can be made stable with respect to water and oxygen.

  In the present invention, a nanostructure having a work function larger than 4.3 eV is used in order to maintain the stability of the nanostructure against water and oxygen. When the work function is 4.3 eV or less, the stability of the electrode against water and oxygen is not sufficient, which is not preferable.

  In addition, in order to drive stably by light irradiation, it is necessary that the interface level mismatch does not fluctuate even during continuous driving. Therefore, in the present invention, the work function of the first electrode is controlled to be at least 0.2 eV or less as compared with the work function of the nanostructure by the surface modification molecule coating.

Further, in order to obtain a sufficient open circuit voltage (V _oc ) in principle in the organic photoelectric conversion element, a sufficient potential difference is set between the work function of the hole transport layer and the work function of the first electrode, that is, the cathode. In the present invention, it has a potential difference of at least 0.7 eV or more. If the potential difference is smaller than 0.7 eV, a practical open circuit voltage (V _oc ) cannot be obtained, which is not preferable.

In general, V _oc greater than the potential difference between both electrodes (or both charge transport layers) cannot be obtained, and “the potential difference formed at the pn interface of the power generation layer (generally, the p-type semiconductor A relationship of “−0.3 eV ≧ open circuit voltage (V _oc )” (referred to as a difference in LUMO of a HOMO-n type semiconductor) is obtained empirically (for example, Adv. Mater. 2006, 18, 789-794). See). Therefore, it is necessary to have a sufficient potential difference between the work function on the hole transport layer side and the work function on the first electrode side in order to convert to maximum energy.

  Furthermore, since the built-in electric field strength (E) is proportional to the potential difference (V) and inversely proportional to the film thickness (d), the carrier density inside the power generation layer is substantially uniform by widening the potential difference between the electrodes. In order to reduce the film thickness dependency and improve the conversion efficiency, the advantage of widening the potential difference between the two electrodes can be obtained.

  Hereinafter, the organic photoelectric conversion element 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 only to the following embodiments. . In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may differ from the actual ratios.

<Configuration of organic photoelectric conversion element>
Hereinafter, the configuration of the organic photoelectric conversion element of the present invention will be described with reference to FIGS. 1 to 3. The electrode through which holes mainly flow is referred to as “anode”, and the electrode through which electrons mainly flow is referred to as “cathode”. Called.

[One Embodiment]
FIG. 1 is a schematic cross-sectional view schematically showing an organic photoelectric conversion element according to an embodiment of the present invention. Specifically, the organic photoelectric conversion element 10 of FIG. 1 includes a cathode 11, an electron transport layer 27, a photoelectric conversion layer 14, a hole transport layer 26, and a second electrode as a first electrode on a substrate 25. As the anode 12 is laminated in this order. As will be described later, when the surface modifying molecule has a sufficient hole blocking action, the electron transport layer 27 may not be provided.

  When the organic photoelectric conversion element 10 shown in FIG. 1 is operated, light is irradiated from the substrate 25 side. Although the structure of the cathode 11 provided in this embodiment will be described in detail below, it is preferable that the irradiated light has high transparency so that the irradiated light can easily reach the photoelectric conversion layer 14. The light irradiated from the substrate 25 side reaches the photoelectric conversion layer 14 through the transparent cathode 11 and the electron transport layer 27.

  In FIG. 1, light incident from the cathode 11 through the substrate 25 is absorbed by the electron acceptor or the electron donor in the photoelectric conversion layer 14, electrons move from the electron donor to the electron acceptor, and holes and electrons are absorbed. Pair (charge separation state) is formed.

  In the case where the generated electric charges have different internal electric fields, for example, when the work functions of the anode 12 and the cathode 11 are different, the electrons pass between the electron acceptors and the holes pass between the electron donors due to the potential difference between the anode 12 and the cathode 11. Each is carried to a different electrode and the photocurrent is detected.

  The hole transport layer 26 is formed of a material having a high hole mobility, and has a function of efficiently transporting holes generated at the pn junction interface of the photoelectric conversion layer 14 to the anode 12. . On the other hand, the electron transport layer 27 is formed of a material having high electron mobility, and has a function of efficiently transporting electrons generated at the pn junction interface of the photoelectric conversion layer 14 to the cathode 11.

[Other embodiments]
FIG. 2 is a schematic cross-sectional view schematically showing an organic photoelectric conversion device according to another embodiment of the present invention. 2, the anode 12 and the cathode 11 are disposed at opposite positions as compared with the organic photoelectric conversion element 10 of FIG. 1, and the hole transport layer 26, the electron transport layer 27, Are different in that they are arranged at the opposite positions. That is, the organic photoelectric conversion element 20 of FIG. 2 has a configuration in which the anode 12, the hole transport layer 26, the photoelectric conversion layer 14, the electron transport layer 27, and the cathode 11 are laminated on the substrate 25 in this order. ing. By having such a configuration, electrons generated at the pn junction interface of the photoelectric conversion layer 14 are transported to the cathode 11 through the electron transport layer 27, and holes are transported to the anode 12 through the hole transport layer 26. Transported.

[Still another embodiment]
FIG. 3 is a schematic cross-sectional view schematically illustrating an organic photoelectric conversion element including a tandem (multi-junction type) photoelectric conversion layer according to still another embodiment of the present invention. Compared to the organic photoelectric conversion element 20 in FIG. 2, the organic photoelectric conversion element 30 in FIG. 3 replaces the photoelectric conversion layer 14 with the first photoelectric conversion layer 14 a, the second photoelectric conversion layer 14 b, and these The difference is that a stacked body with the charge recombination layer 38 interposed between the two photoelectric conversion layers 14a and 14b is disposed. In the tandem organic photoelectric conversion element 30 shown in FIG. 3, photoelectric conversion materials (p-type organic semiconductor and n-type organic semiconductor) having different absorption wavelengths are used for the first photoelectric conversion layer 14a and the second photoelectric conversion layer 14b, respectively. By using this, light in a wider wavelength range can be efficiently converted into electricity.

  Hereinafter, each component of the organic photoelectric conversion element according to the present invention will be described in detail.

<First electrode>
Hereinafter, the structure of the cathode 11 which is the first electrode of the present invention will be described with reference to FIGS.

  The first electrode of the present invention includes a nanostructure 2 having a work function larger than 4.3 eV and a surface modifying molecule 3 having a dipole moment and adsorbed on the surface of the nanostructure 2. . 4 (a) and 4 (b), for convenience, the surface modification molecule 3 is illustrated as a film. However, as will be described in detail below, each of the surface modification molecules 3 is an individual molecule. Adsorbed on the nanostructure 2. As a general concept, a molecular self-adsorption film (SAM film) is formed.

  In addition, the first electrode can be mainly composed of the nanostructure 2 (or 2 ′) and the surface modification molecule 3, but in addition to these, in addition to these, ITO (indium tin oxide), AZO ( A thin film made of a transparent conductive material such as aluminum zinc oxide), that is, a transparent conductive film 1 as an auxiliary electrode is formed in advance, and a nanostructure 2 (or 2 ′) is formed on the transparent conductive film 1 Also good.

  Further, the surface modifying molecule 3 has a hole blocking action and can also function as an electron transporting layer.

  Furthermore, the first electrode of the present invention includes not only the above-described elements, but also 0.2 eV or less smaller than the work function of the nanostructure described in detail below, and smaller than the work function of the hole transport layer. 0.7 eV or more is small. That is, the work function difference between the first electrode and the nanostructure is 0.2 eV or more, and the work function difference between the first electrode and the hole transport layer is 0.7 eV or more.

[Nanostructure]
In this specification, the “nanostructure” included in the first electrode indicates the maximum height difference (Rpv) due to unevenness formed on the surface using nanometers (nm) as a unit of length. The maximum height difference (Rpv) is preferably 50 to 1000 nm, more preferably 70 to 200 nm, and particularly preferably 90 to 150 nm. In the present specification, the maximum height difference (Rpv) is measured according to JIS B 0601: 2001.

  The nanostructure 2 (or 2 ′) is an aggregate of microstructures 2a (or 2a ′) whose major axis is on the scale of several to several tens of nm. Examples of the microstructures 2a (or 2a ′) include, for example, Nanowires 2a (nanofibers), nanoparticle 2a ′, nanorods, nanopillars, nanobelts, nanoribbons, nanoporous structures, and the like can be preferably used. Among these, when forming the first electrode by a coating method, it is preferable to use the nanowire 2a and the nanoparticle 2a 'because the film forming process is simple. Furthermore, since these microstructures have interfacial resistance, it is particularly preferable to use the nanowire 2a for the purpose of making the interface as small as possible.

  The thickness of the nanostructure is preferably about 50 to 1000 nm in order to ensure conductivity that can function as an electrode of the organic photoelectric conversion element.

  Examples of the material for the nanostructure include metals, metal oxides, inorganic materials such as metal nitrides, organic polymers, and the like, and a conductive material is particularly preferable. Examples of the conductive material include organic substances coated with metal, inorganic substances coated with metal, conductive metal oxides, metals, and the like. In order to impart sufficient conductivity to the nanostructure, it is particularly preferable to form the nanostructure with a metal.

  In order to give sufficient conductivity to the nanostructure, the metal forming the nanostructure of the present invention is platinum (Pt: 6.3 eV), gold (Au: 5.1 eV), silver (Ag: 4.3 eV). ), Copper (Cu: 4.7 eV), iron (Fe: 4.5 eV), tin (Sn: 4.4 eV), cobalt (Co: 5.0 eV), chromium (Cr: 4.5 eV), nickel (Ni : 5.0 eV), molybdenum (Mo: 4.4 eV), tungsten (W: 4.5 eV), zinc (Zn: 4.3 eV), tantalum (Ta: 4.25 eV), indium (In), tellurium (Te ), Rhenium (Re), germanium (Ge), or the like, or a combination of two or more of these. The numerical values in parentheses indicate the work function of each metal, but the work functions of the above-mentioned metal species are general literature values (reference values), and the film forming method and process, the uneven structure of the present application (nanostructure) ) May change depending on the process of forming. In the present invention, both the conductivity and the stability of the first electrode can be achieved, and the work function of the nanostructure is only required to be greater than 4.3 eV, which is always exactly the same as the literature value described in parentheses above. Do not mean. In such a case, it is preferable to clean the surface by a known method. For example, a plasma etching method, cleaning by sputtering, an ablation method using an excimer lamp, a laser, or the like can be preferably used.

  Among the above metals, it is preferable to include a noble metal such as platinum, gold and silver and at least one metal belonging to the group consisting of copper, iron, tin, cobalt, chromium, nickel, molybdenum, tungsten and zinc. In particular, platinum, gold, silver, copper, cobalt, chromium, iridium, nickel, palladium, molybdenum, tungsten, and zinc having a work function of 4.3 eV or more are preferable. Among these, it is preferable to include at least one selected from the group consisting of gold, silver, copper, tungsten and zinc, which is a metal having a large work function and being particularly stable against oxidation. From the viewpoint of conductivity and the adsorptivity of the surface-modifying molecules described later, it is more preferable to contain at least silver. Further, in order to achieve both conductivity and stability (sulfurization and oxidation resistance of the nanostructure and resistance to magnesium), silver and at least one metal belonging to a noble metal other than silver may be included.

(Nanowire)
In the present invention, a nanowire as a microstructure used to form a nanostructure has a shape whose length is sufficiently longer than a diameter (thickness). Examples of the shape of the nanowire include a hollow tube shape, a wire shape, and a fiber shape.

  The nanowire according to the present invention is considered to function as an auxiliary to the electrode by forming a three-dimensional carrier path network when the nanowires contact each other in the organic film. Accordingly, a longer nanowire is preferable because it is advantageous for forming a conductive network. As the metal nanowire according to the present invention, in order to form a long conductive path with one metal nanowire, the average length is preferably 3 μm or more, more preferably 4 to 500 μm, and particularly preferably 5 to 300 μm. It is preferable that In addition, the relative standard deviation of the length is preferably 40% or less.

  On the other hand, when the nanowire becomes long, the nanowire is entangled to form an aggregate, which may deteriorate the optical characteristics. The formation of the conductive network and the formation of aggregates are affected by the rigidity and diameter of the nanofibers. Therefore, it is necessary to use the one with the optimal average aspect ratio (aspect ratio = length / diameter) according to the nanofiber used. preferable. As a rough guide, the average aspect ratio is preferably 3 to 50,000, more preferably 5 to 10,000, still more preferably 10 to 1,000, and particularly preferably 100 to 500.

  The average diameter of the nanowire is preferably small from the viewpoint of transparency, while it is preferably large from the viewpoint of conductivity. In the present invention, the average diameter of the nanowire is preferably 5 to 300 nm, more preferably 10 to 200 nm, still more preferably 20 to 150 nm, and particularly preferably 30 to 100 nm. In addition, the relative standard deviation of the diameter is preferably 20% or less. The length and diameter of the nanowire are measured by high-magnification TEM observation, and more specifically, an average value obtained by measuring 500 nanowires by TEM observation is adopted.

  Examples of the material of the nanowire include the above-described inorganic substances and organic substances, and it is particularly preferable that the nanowire has conductivity. Examples of the nanowire having conductivity according to the present invention include metal-coated organic nanofibers and inorganic nanofibers, conductive metal oxide nanofibers, metal nanowires, carbon fibers, and carbon nanotubes.

[Metal nanowires]
Among the microstructures constituting the nanostructure described above, it is particularly preferable to form the nanostructure using metal nanowires.

  In general, the metal nanowire refers to a linear structure having a metal element as a main component. In particular, the metal nanowire in the present invention means a linear structure having a diameter from the atomic scale to the nm scale.

  The metal nanowire material according to the present invention may be used in combination of one or more of the above metal species, and at this time, it is preferable to use silver or zinc (oxide). Furthermore, when two or more kinds of metal elements are included, for example, the metal composition may be different between the surface and the inside of the metal nanowire, or the entire metal nanowire may have the same metal composition as an alloy. Good.

  In the present invention, there are no particular limitations on the means for producing the metal nanowire, and for example, known means such as a liquid phase method and a gas phase method can be used. Moreover, there is no restriction | limiting in particular in a specific manufacturing method, A well-known manufacturing method can be used. In particular, Adv. Mater. , 2002, 14, 833-837 and Chem. Mater. 2002, 14, 4736-4745, the method for producing silver nanowires can easily produce silver nanowires in an aqueous system. Since the electrical conductivity of silver is the largest among metals, it can be particularly preferably used as the metal nanowire according to the present invention.

(Nano pillar)
Nanopillars as microstructures used to form nanostructures are slightly different from nanowires in the ratio of their pillar diameter (diameter) to height, but are basically the same materials as the above nanowires And has an equivalent configuration. The aspect ratio (aspect ratio = height / diameter) is preferably in the same range as the nanowire. (Nanoparticles)
Nanoparticles as microstructures used to form nanostructures preferably have a particle diameter in the range of 5 to 500 nm. Here, “particle diameter” means the diameter when the nanoparticles are spherical, and means the long diameter when the nanoparticles are not spherical. The particle diameter of the nanoparticles is measured by TEM observation at a high magnification, and more specifically, an average value obtained by measuring 500 particles by TEM observation is adopted.

  Examples of the material of the nanoparticles include the above-described inorganic substances and organic substances, and it is particularly preferable that the nanoparticle materials have conductivity. Examples of the conductive nanoparticles according to the present invention include metal-coated organic nanoparticles, inorganic nanoparticles, nanoparticles made of a conductive metal oxide, and metal nanoparticles. In order to give sufficient electrical conductivity to the nanostructure, the metal forming the nanoparticles is preferably at least one selected from the above metal species. Among these, it is particularly preferable to use gold or silver.

  As a method for producing such nanoparticles, particularly metal nanoparticles, metal ions in the liquid phase, such as physical generation methods such as gas evaporation, sputtering, and metal vapor synthesis, colloidal methods, and coprecipitation methods are used. A chemical production method in which metal fine particles are produced by reduction is exemplified, but preferably, the colloidal method disclosed in JP-A-11-76800, JP-A-11-80647, JP-A-2000-239853, etc. By the gas evaporation method described in 2001-254185, JP 2001-53028, JP 2001-35814, JP 2001-35255, JP 2000-124157, JP 2000-123634, etc. It is.

[Surface modifying molecule]
In the present invention, the first electrode has a configuration in which a surface modifying molecule having a dipole moment is adsorbed to the nanostructure. Since the surface modification molecule coats the nanostructure, it has an adsorbing group at the end of the molecule that has adsorptivity to the nanostructure. Examples of adsorbing groups include thiol groups (—SH), methylthio groups (—SCH ₃ ), mercaptothio groups (—S—SH), methyl mercaptothio groups, dithiocarbamate groups (—N—CS ₂ ), xanthate groups. (—O—CS ₂ ), thiocarbonyl group (> C═S), thiocarboxyl group (—C (O) SH), acetylthio group (—SC (O) CH ₃ ), dithiocarboxyl group, sulfide group (— S-), disulfide group (-S-S-), a sulfo group _(-SO 3 H), sulfino group (-SOOH), carboxyl group (-COOH), a phosphono group _{(-P (O) (OH)} 2) And a phosphoric acid group (—PO ₄ H).

  As described above, since the nanostructure preferably has sufficient conductivity, the material of the nanostructure is preferably a metal. Accordingly, among the adsorbing groups, a thiol group, a dithiocarbamate group, a xanthate group, a sulfide group, and a disulfide group that have high adsorptivity to the metal surface and high thermal stability are preferable, and a thiol group and a dithiocarbamate group are more preferable. The surface modifying molecule may have one or a plurality of the above adsorbing groups, or may have a combination of different types. In this specification, “adsorption” means physical adsorption by van der Waals force or chemical adsorption by covalent bond, ionic bond, coordinate bond, hydrogen bond, etc. On the other hand, chemical adsorption in which the surface modifying molecules are strongly adsorbed is preferable.

  For example, when a surface modification molecule is adsorbed on a metal nanostructure composed of metal nanowires, etc., it has an adsorption group such as a thiol group, a methylthio group, a mercaptothio group, a methyl mercaptothio group, a dithiocarbamate group, or an acetylthio group at the end. The compound is adsorbed on the surface of the metal nanostructure by a sulfide bond. Alternatively, the metal nanostructure may be adsorbed from a dimer or multimer of molecules bonded through a disulfide bond.

  The physical properties can be changed by adsorbing the surface modifying molecules to the nanostructure. An example of such a change in physical properties is a change in apparent work function. Examples of such surface-modifying molecules that change the physical properties include, for example, a nitrogen atom, a carbon atom, or sulfur as an adsorbing group that has an adsorptivity to the nanostructure so as to induce a dipole moment in the molecule. A surface modifying molecule having a substituent bonded through an atom is exemplified. In general, the amount of change in work function of a nanostructure to which a surface modifying molecule is adsorbed is proportional to the density at which the surface modifying molecule is adsorbed and the magnitude of the dipole moment of the surface modifying molecule. Therefore, in order to construct a nanostructure having an appropriate work function, it is preferable that the surface modifying molecule has a dipole moment. Although the dipole moment of the surface modifying molecule can be selected as appropriate, in the present invention, in order to form an electrode composed of a nanostructure with reduced influence of moisture and oxygen, it is preferably +1.0 to + 20D, and +1.5 It is more preferable that it is-+ 10D, and it is especially preferable that it is + 3.0-10.0D. Here, the dipole moment in the present invention refers to the dipole moment calculated by the density functional (DFT) method for the molecular structure adsorbed on one silver (Ag) atom via an adsorbing group on the surface modification molecule.

In this way, by adsorbing surface-modified molecules having a dipole moment in the molecule to the nanostructure, the vacuum level is increased, and even nanostructures that originally have a large work function seem to have small work. Since a function can be obtained and a sufficient open-circuit voltage (V _oc ) can be obtained between the first electrode and the second electrode, a metal species resistant to oxidation or the like can be used for the electrode. Therefore, it is preferable. At this time, as the nanostructure for adsorbing the surface-modifying molecules, any of the nanostructures described in the column of the nanostructure may be used. However, from the metal nanostructure made of metal, particularly from metal nanowire or metal nanoparticle. It is preferable to use a metal nanostructure.

  The surface modifying molecule is not particularly limited as long as the above-mentioned dipole moment can be obtained, and a molecule in which an electron donating group or an electron withdrawing group is appropriately introduced can be used. Among them, it is preferable to have an electron donating group bonded to an adsorbing group. That is, it is particularly preferable that the surface modifying molecule has an adsorbing group that adsorbs to form a nanostructure, and an electron donating substituent bonded to the adsorbing group. In the present specification, the “electron-donating group” refers to a substituent having a negative value for Hammett's substituent constant σp. The electron donating group is preferably bonded to the adsorption group of the surface modifying molecule. By having the electron donating group bonded to the adsorbing group, it is easy to appropriately control the magnitude and direction of the dipole moment of the surface modifying molecule. Note that the electron-donating group is not necessarily bonded directly to the adsorbing group, and may be via a substituted or unsubstituted aliphatic group or aromatic group.

  Examples of electron donating groups include hydroxyl groups (or salts thereof), mercapto groups (or salts thereof), alkoxy groups, aryloxy groups, heterocyclic oxy groups, alkylthio groups, arylthio groups, heterocyclic thio groups, amino groups , An alkylamino group, an arylamino group, a heterocyclic amino group, a heterocyclic group in which σp takes a negative value, or a phenyl group substituted with these electron donating groups. The surface modifying molecule may have one or a plurality of the above electron donating groups, or may have a combination of different types.

  As the surface modifying molecule, a derivative such as a dithiocarbamate compound, an alkyldithiocarbamate compound, a phenyldithiocarbamate compound, or a diphenyldithiocarbamate compound as disclosed in European Patent Application No. 2278636 can be used.

  Specific examples of the surface modifying molecule include the following.

In the above formulas (A) to (Q), n is an integer of 0 to 3, X represents N or CH, preferably N, and X ′ independently represents —N═ or —CH═. And preferably represents —NR—, —CR ₂ —, preferably —NR ₂ —, and each R independently represents a hydrogen atom, a methyl group, an ethyl group, or .Y representing the benzyl group -N =, - CH =, or -C _(CH 3) = represents, Z is = N -, = CH-, or = C (CH ₃₎ - represents, EA 'is -OC (O) -, - CO (O) -, - C (O) -, and -SO ₂ - represents, ED 'is -NR' -, - N (R ') C (O) -, - Represents O— or —S—, and R ′ represents a hydrogen atom, a methyl group, an ethyl group, or a benzyl group, and in the above formulas (A) to (Q), EA represents Represents an electron accepting group, ED represents an electron donating group, and when two or more of the same symbols exist in the same compound, each symbol may represent the same or different one.

As an electron-accepting group represented by EA, a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, an iodine atom), —CF ₃ , —CCOOCF ₃ , —SO ₂ CF ₃ , —COCF ₃ , —CHO, —COOCH _{3, -SO 2 CH 3, -SO} 2 NH 2, -COCH 3, include -CN, or -NO _2. Examples of the electron donating group represented by ED include —CH ₃ , —NH ₂ , —NHCH ₃ , —N (CH ₃ ) ₂ , —OH or —OCH ₃ . The substitution position of EA or ED is not particularly limited, but is preferably p-position in the case of ED, and preferably o-position in the case of EA.

  In the formula (K), each R ″ independently represents a hydrogen atom, a linear, branched or cyclic alkyl group having 1 to 20 carbon atoms, and a substituted or non-substituted group having 1 to 20 carbon atoms. Although it represents a substituted aryl group, both do not represent a hydrogen atom.

  With the dithiocarbamate compound, the nanostructure forms the following structure.

M represents a metal atom on the surface of the nanostructure.

The method of adsorbing to the surface of the metal nanostructure through a dithiocarbamate group can be treated with reference to the method described in J. AM. CHEM. SOC. 2005, 127, 7328-7329. Specifically, it can be adsorbed by bringing a primary or secondary amine serving as a precursor and carbon disulfide into contact with the metal nanostructure. More preferably, the precursor is a secondary amine. That is, dithiocarbamic acid (R ₂ NCS ₂ ⁻ ) generated by the reaction represented by the following reaction formula (1) is generated in the presence of a metal nanostructure to adsorb surface adsorbed molecules through dithiocarbamate groups. Can be made.

In the above reaction formula (1), R is not particularly limited, but is selected from, for example, a hydrogen atom, a substituted or unsubstituted aliphatic group, and an aromatic group. In addition, piperazine, piperidine, dialkylamine, phenylamine, diphenylamines and the like can be preferably used as secondary amines represented by R ₂ NH in the above reaction formula (1).

  Among the above formulas (A) to (Q), specific examples of preferable surface modifying molecules include compounds having the following structures. In the present specification, compounds are represented by the following numbers. For example, a compound having the following structure 1 is referred to as “compound 1”. In the following, each compound is adsorbed on a metal. Moreover, the numerical value described on the right side of a compound shows the magnitude | size of the dipole moment of the said compound. For example, in the case of Compound 1, the dipole moment is 1.45D.

  A known synthesis method can be applied to the method for introducing a substituent capable of adsorbing with the nanostructure into the surface modification molecule of the present invention. For example, as a method for substituting the SH group at the end of the aromatic ring, J. et. Org. Chem. EN; 60; 7; 1995; 2082-2091. J. et al. Amer. Chem. Soc. EN; 116; 26; 1994; 11985-11989. , Synthesis; EN; 9; 1983; 751-755. J. et al. Chem. Soc. PerkinTrans. 1; EN; 1987; 187-194. Can be referred to. For the method of making “alkylene-terminated SH” in a compound having a sulfur atom adsorbing with silver at its terminal and having a π-electron system via an alkylene group, Amer. Chem. Soc. 70; 1948; 2439. (Reduction of isothiourea), Chem. Ber. GE; 93; 1960; 2604-2612. (Reaction in which thiourea was allowed to act on terminal alkyl halide), Tetrahedron Lett. EN; 35; 12; 1994; 1837-1840. (Addition to a double bond by a radical reaction in which triphenylsilanethiol is allowed to act on a terminal C═C double bond) can be referred to.

  Poly (3-alkylthiophene) s may be used as other surface modification molecules used in the present invention. More specifically, poly (3-alkylthiophene) having an adsorption group at the 5-position of the terminal thiophene unit represented by the following general formula (1) and the 2-position of the terminal thiophene unit represented by the general formula (2) And poly (3-alkylthiophene) having an adsorbing group.

  In the above general formulas (1) and (2), R represents a substituted or unsubstituted alkyl group having 4 to 15 carbon atoms or an alkoxyalkyl group, and R 'represents a hydrogen atom or an arbitrary substituent. R ″ represents a hydrogen atom, a methyl group, an acetyl group, a mercapto group, or a methyl mercapto group. X represents a divalent linking group. m represents 0 or 1, and n represents an integer of 2 to 500.

  In the general formula (1) or (2), the alkyl group or alkoxyalkyl group having 4 to 15 carbon atoms represented by R is preferably an alkyl group or alkoxyalkyl group having 6 to 10 carbon atoms.

  Examples of the substituent represented by R ′ include a substituted or unsubstituted alkyl group, and a methyl group is preferable.

  X preferably represents an alkylene group or an arylene group, more preferably a methylene group, ethylene or propylene.

m is preferably 0 or 1. n is preferably from 100 to 500, and most preferably from 150 to 300. )
Furthermore, other preferred surface modifying molecules of the present invention include porphyrin derivatives disclosed in JP-A Nos. 2001-253883 and 2008-16834. In the present invention, in order to obtain a porphyrin bonded to the nanostructure, a method of synthesizing a porphyrin monomer having an adsorbing group to the nanostructure by the above-described method can be used.

  A conventionally known method can be used as a method of modifying the nanostructure using the surface modifying molecule. As an example, the surface modification molecule can be adsorbed to the nanostructure by immersing the substrate on which the nanostructure is formed in the solution of the surface modification molecule. At this time, the addition amount of the surface modification molecule is not particularly limited as long as the effect is obtained, but it is preferably 0.1 to 10% by mass with respect to 100% by mass of the metal nanostructure.

[Method for Manufacturing First Electrode]
The means for forming the first electrode having the nanostructure of the present invention may be any known method as long as the effect of the present invention can be obtained, but a preferable example of the production method will be described below. .

(Method II: Method of adsorbing surface-modified molecules after forming nanostructures)
When producing the first electrode, first, a nanostructure is formed on a substrate (or an electron transport layer or a photoelectric conversion layer produced in advance), and then the nanostructure is immersed in a solution of surface modification molecules. A first electrode including a nanostructure having adsorbed surface modifying molecules can be formed. In addition, after being immersed in the solution of the surface modification molecule, a step of washing and drying only with a solvent may be further performed.

  As a method for forming the nanostructure, the above-described micro structure is formed by a wet process such as a vacuum deposition method, a sputtering method, a molecular beam epitaxy method or the like dry process, a spin coating method, a dip method, or a Langmuir-Blodgett method (LB method). A method for accumulating structures is given. It is preferable to use a wet process because it is easy to form a film and can be produced roll-to-roll using an apparatus such as a die coater.

  When using a wet process, it is necessary to disperse the microstructure in the solution, and the concentration thereof is not particularly limited. However, in the case of a dilute solution, the formation of the nanostructure becomes insufficient, so at least 0.01 mass % Or more is preferable. Preferably, it is 0.1-50 mass%, More preferably, it is the range of 0.3-5 mass%. The solvent to be used is not particularly limited as long as it can uniformly disperse the above-mentioned microstructure, but ketones such as acetone, ethers such as diethyl ether and dibutyl ether, methanol, ethanol, ethylene glycol Alcohols such as water, aromatic solvents such as water, toluene, chlorobenzene and dichlorobenzene can be used. In addition, ultrasonic treatment may be performed to uniformly disperse the microstructure in these solvents.

  The solution of the surface modification molecule in which the nanostructure formed according to the above is immersed is prepared by dissolving an appropriate surface modification molecule (or a precursor of the surface modification molecule) in an appropriate solvent. The type of the solvent used is not particularly limited, but may be a nonpolar solvent or a polar solvent as long as the above-described surface modifying molecule can be 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. . At this time, in order to adsorb a sufficient amount of surface modifying molecules to the nanostructure, it is preferably at least 10 to 500 mM.

  The solvent used for the subsequent washing may be the same as or different from that used for the solution, and can be appropriately selected.

  When the first electrode is formed by a coating method, the temperature of the coating surface is not particularly limited, but is preferably 30 to 150 ° C. from the viewpoint of preventing material unevenness due to temperature fluctuations during coating and drying. More preferably, it is 30-100 degreeC, More preferably, it is 50-80 degreeC. Furthermore, there is no restriction | limiting in particular also about the specific form of drying, A conventionally well-known knowledge can be referred suitably.

  In addition, when adopting the configuration in which the first electrode is formed on the substrate, that is, the configuration of the organic photoelectric conversion element 10 according to one embodiment, a transparent conductive film such as ITO is previously formed on the substrate as an auxiliary electrode. In order to avoid unnecessary short circuit between the ITO surface and the semiconductor material of the power generation layer, a block layer (preferably a hole block layer) may be provided as appropriate. Further, an underlayer may be provided so that the nanostructure does not peel from the substrate during the surface treatment, and the underlayer may have a hole blocking property.

(Method I-II: Method of forming a photoelectric conversion layer simultaneously with the first electrode)
In the above-described method II, the method of immersing the solution of the surface modification molecule after forming the nanostructure has been described. The photoelectric conversion layer described in detail below is further formed in the solution of the surface modification molecule. The material to be used may also be dispersed. As the solvent used at this time, a solvent capable of dissolving the surface modifying molecules and sufficiently dispersing the material constituting the photoelectric conversion layer is used.

(Method II-I: Method of applying a mixed solution of nanostructures and surface modifying molecules)
In the above-described method II, a method of separately preparing a solution of a microstructure for forming a nanostructure and a solution of a surface modification molecule and adsorbing the surface modification molecule after forming the nanostructure in advance has been described. Alternatively, the first electrode may be formed by preparing a mixed solution containing both of these. By dispersing the microstructure and the surface modifying molecule in the same solution, the surface modifying molecule is adsorbed to the microstructure in the solution. As the solvent used at this time, a solvent capable of dispersing the microstructure and sufficiently dissolving the surface modifying molecule is used.

  In addition, when forming an organic photoelectric conversion element in order from the cathode side, that is, when preparing the organic photoelectric conversion element 10 which is one embodiment, before applying a mixed solvent of a microstructure and a surface modification molecule, It is preferable to form a transport layer (also referred to as a hole block layer).

(Method II-II: Method of simultaneously forming the photoelectric conversion layer simultaneously with the first electrode)
In the above-described method II-I, the method of forming the first electrode by applying a mixed solution containing a microstructure and a surface modifying molecule has been described, but the photoelectric solution described in detail below is further added to this mixed solution. The material constituting the conversion layer may also be dispersed. As the solvent used at this time, a solvent that can sufficiently disperse the microstructure and the surface modification molecule and can sufficiently disperse the material constituting the photoelectric conversion layer is used.

<Second electrode>
The organic photoelectric conversion element of the present invention requires a second electrode which is an electrode facing the first electrode. The second electrode formed to face the first electrode that is the cathode functions as an anode.

  The material used for the second electrode is not particularly limited as long as the photoelectric conversion element is driven, and an electrode material that can be used in this technical field can be appropriately employed. In particular, the second electrode is preferably made of a material having a relatively large work function compared to the first electrode, and conversely, the first electrode contains a surface modifying molecule as described above. Thus, a relatively small work function is obtained. Note that in the case where a charge transport layer (a hole transport layer or an electron transport layer) is present, it functions sufficiently as a photoelectric conversion element even in a form other than the above.

  Further, the microscopic shape of the material constituting the second electrode is not particularly limited, and can be used in the shape of nanowire, nanoparticle, thin film or the like. Furthermore, the electrode may be configured by laminating two or more layers made of different materials.

  The sheet resistance of the first electrode and the second electrode is not particularly limited, but is preferably several hundred Ω / □ or less, more preferably 50Ω / □ or less, and further preferably 15Ω / □ or less. The lower limit of the sheet resistance of the first electrode and the second electrode is not particularly limited, but usually 0.01Ω / □ or more, preferably 0.1Ω / □ or more to obtain the effect of the present invention. Can do. Here, the sheet resistances of the first electrode and the second electrode may be the same or different. The thickness of the second electrode is also not particularly limited and varies depending on the material, but is usually 10 to 1000 nm, preferably 100 to 200 nm, and is appropriately set by those skilled in the art from the viewpoint of light transmittance or resistance. Can be done. Here, the film thicknesses of the first electrode and the second electrode may be the same or different.

[One Embodiment]
In the organic photoelectric conversion element 10 shown in FIG. 1, the cathode 11 that is the first electrode is formed on the substrate 25 side where light enters, that is, the surface of the substrate 25, and the opposite side, that is, the farthest position from the substrate 25. An anode 12 as a second electrode is formed. Therefore, as described above, the cathode 11 shown in FIG. 1 has a relatively low apparent work function as compared with the anode 12 and a highly transparent structure. On the other hand, the anode 12 is preferably made of an electrode material having a relatively large work function as compared with the cathode 11 and usually having low translucency.

In the organic photoelectric conversion element 10 of FIG. 1, examples of the electrode material used for the second electrode include metals such as gold, platinum, silver, nickel, molybdenum, tungsten, and copper; indium tin oxide (ITO) And transparent conductive metal oxides such as aluminum zinc oxide (AZO), SnO ₂ and ZnO; and carbon materials such as metal nanowires and carbon nanotubes. Alternatively, a conductive polymer may be used as the electrode material for the second electrode. Examples of the conductive polymer that can be used for the second electrode include PEDOT: PSS, polypyrrole, polyaniline, polythiophene, polythienylene vinylene, polyazulene, polyisothianaphthene, polycarbazole, polyacetylene, polyphenylene, polyphenylene vinylene, and polyacene. , Polyphenylacetylene, polydiacetylene, polynaphthalene and derivatives thereof. These electrode materials may be used alone or as a mixture of two or more materials.

  In addition, among these materials, in particular, by using a metal, light incident from the first electrode side and transmitted without being absorbed by the photoelectric conversion layer is reflected by the second electrode and reused for photoelectric conversion. It is possible to improve the photoelectric conversion efficiency.

[Other embodiments]
In the organic photoelectric conversion elements 20 and 30 of FIGS. 2 and 3, the anode 12 as the second electrode is formed so as to be in contact with the surface of the substrate 25. Therefore, in the case of FIG. 2 and FIG. 3 in which the second electrode is formed on the light incident side, the second electrode needs to have translucency, and thus a transparent electrode is produced. An electrode having translucency may be referred to as a “transparent electrode”, and an electrode having low translucency may be referred to as a “counter electrode”. In the case of the form of FIG. 2 and FIG. 3, the 2nd electrode is a transparent electrode with translucency normally, and a 1st electrode is a counter electrode with low translucency.

  In the organic photoelectric conversion elements 20 and 30 shown in FIGS. 2 and 3 described above, the second electrode has a relatively large work function compared to the first electrode, and is made of a transparent electrode material. preferable.

As described above, in the organic photoelectric conversion elements 20 and 30 shown in FIGS. 2 and 3, examples of the electrode material used for the second electrode that is a transparent electrode include metals such as gold, silver, and platinum; Examples thereof include transparent conductive metal oxides such as oxide (ITO), aluminum zinc oxide (AZO), SnO ₂ and ZnO; carbon materials such as metal nanowires and carbon nanotubes. Alternatively, a conductive polymer may be used as the electrode material for the second electrode. Examples of the conductive polymer that can be used for the second electrode include PEDOT: PSS, polypyrrole, polyaniline, polythiophene, polythienylene vinylene, polyazulene, polyisothianaphthene, polycarbazole, polyacetylene, polyphenylene, polyphenylene vinylene, and polyacene. , Polyphenylacetylene, polydiacetylene, polynaphthalene and derivatives thereof. These electrode materials may be used alone or as a mixture of two or more materials.

(Auxiliary electrode)
When forming the first electrode and / or the second electrode, an auxiliary electrode may be produced. Examples of auxiliary electrode materials include gold, silver, copper, iron, nickel, chromium, aluminum, or alloys thereof (for example, aluminum alloys), metal compounds such as silver compounds, indium tin oxide (ITO), aluminum zinc An auxiliary electrode (also referred to as a grid electrode or a bus line electrode) may be manufactured using a transparent conductive metal oxide such as oxide (AZO), SnO ₂ , or ZnO. After producing the auxiliary electrode, a transparent electrode can be obtained by providing the conductive polymer film exemplified above. By providing the auxiliary electrode in this way, it is possible to suppress the reduction of the fill factor (FF) that occurs when the element has a large area.

  The shape of the auxiliary electrode is not particularly limited, but for example, the conductive portion has a stripe shape, a mesh shape, or a random mesh shape. There are no particular limitations on the method of forming the stripe-shaped or mesh-shaped auxiliary electrode with the conductive portion, and a conventionally known method can be used. For example, a metal layer can be formed on the entire surface of the substrate and can be formed by a known photolithography method. Specifically, a method of forming a conductor layer on the entire surface of the substrate using one or more physical or chemical forming methods such as vapor deposition, sputtering, plating, etc., or a metal foil on the substrate with an adhesive After the lamination, it can be processed into a desired stripe shape or mesh shape by a method of etching using a known photolithography method. As another method, a method of printing an ink containing metal fine particles in a desired shape by various printing methods such as screen printing, flexographic printing, gravure printing, and an ink jet method, and various printing methods similar to plating catalyst ink As another method, a method of applying a silver salt photographic technique can be used after coating in a desired shape. Among these methods, the method of printing ink containing metal fine particles in a desired shape by various printing methods can be manufactured in a simple process, so that it is possible to reduce the entrainment of foreign matters that may cause leakage at the time of manufacture. Since the ink is used only at the portions, the liquid loss is small, which is most preferable.

  In addition, the sheet resistance when the auxiliary electrode is provided is preferably 0.001 to 20Ω / □, more preferably 0.01 to 10Ω / □, and particularly preferably 0.5 to 8Ω / □. . In this case, the sheet resistance is determined by the shape (line width, height, pitch, shape) of the auxiliary electrode, and even if a material having higher resistance than the auxiliary electrode is used, the resistance of the window portion is hardly affected.

<Hole transport layer>
The organic photoelectric conversion element of this embodiment essentially includes a hole transport layer. The hole transport layer has a function of transporting holes and a property of extremely small ability to transport electrons (for example, 1/10 or less of the mobility of holes). The hole transport layer is provided between the photoelectric conversion layer and the anode and prevents recombination of electrons and holes by blocking the movement of electrons while transporting holes to the anode. Can do. Therefore, in this specification, a positive hole injection layer, an electronic block layer, etc. are also included in the concept of a positive hole transport layer.

  The hole transport material used for the hole transport layer is not particularly limited, and any material that can be used in this technical field can be appropriately employed. For example, a conductive polymer, a low molecular organic semiconductor, a metal oxide, and the like. Can be preferably used.

  The conductive polymer preferably used in the present invention is not particularly limited, but preferably comprises a π-conjugated polymer and a polyanion. Such a polymer can be easily produced by subjecting a precursor monomer forming a π-conjugated polymer to chemical oxidative polymerization in the presence of an appropriate oxidizing agent, an oxidation catalyst, and a polyanion described later.

  Examples of the π-conjugated polymer that can be used in the present invention include polythiophenes (including basic polythiophenes, the same applies hereinafter), polypyrroles, polyindoles, polycarbazoles, polyanilines, polyacetylenes, polyfurans, and polyparaffins. A chain conductive polymer of phenylene vinylenes, polyazulenes, polyparaphenylenes, polyparaphenylene sulfides, polyisothianaphthenes, polythiazyl compounds can be used. Of these, polythiophenes and polyanilines are preferable from the viewpoints of conductivity, transparency, stability, and the like. Furthermore, polyethylenedioxythiophenes are preferable.

  The polyanion preferably used in the present invention is not particularly limited, but it is more preferable to have a sulfo group as the anionic group. Specific examples of polyanions include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyacrylic acid ethyl sulfonic acid, polyacrylic acid butyl sulfonic acid, poly-2-acrylamido-2-methylpropane sulfonic acid, polyisoprene sulfone. An acid etc. are mentioned. These homopolymers may be sufficient and 2 or more types of copolymers may be sufficient.

  Moreover, the polyanion which has a fluorine (F) in a compound may be sufficient. Specifically, Nafion (made by Dupont) containing a perfluorosulfonic acid group, Flemion (made by Asahi Glass Co., Ltd.) made of perfluoro vinyl ether containing a carboxylic acid group, and the like can be mentioned.

  As the conductive polymer, known materials and commercially available materials can be preferably used. For example, PEDOT: PSS such as trade name Clevios (registered trademark) -P manufactured by Heraeus Co., Ltd., and fluorine-based polyanions (Nafion ( Registered trademark)), or a fluorine-based polyanion-added structure as disclosed in JP-A-2006-225658, polythienothiophenes described in European Patent No. 1647566, and sulfonated polythiophene described in JP-A-2010-206146 , Polyaniline and its doping materials, cyan compounds described in WO 2006/019270 pamphlet, etc., Aldrich as PEDOT-PASS 483095, 560598, Nagase Chemtex from Denatron (registered trademark) It is commercially available as Leeds. Polyaniline is commercially available from Nissan Chemical as the ORMECON (registered trademark) series. In the present invention, such an agent can also be preferably used.

  Also, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, and pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives Further, stilbene derivatives, silazane derivatives, aniline copolymers, conductive polymer oligomers, particularly thiophene oligomers, and the like can also be used.

  In addition to these, porphyrin compounds, aromatic tertiary amine compounds, styrylamine compounds, and the like can be used, and among these, aromatic tertiary amine compounds are preferably used. In some cases, the hole transport layer may be formed using an inorganic compound such as p-type-Si, p-type-SiC, nickel oxide, molybdenum oxide, vanadium oxide, or tungsten oxide.

  Furthermore, a polymer material in which a structural unit contained in the above compound is introduced into a polymer chain, or a polymer material having the above compound as the main chain of the polymer can also be used as a hole transport material. JP-A-11-251067, J. Org. Huang et. al. , Applied Physics Letters, 80 (2002), p. A hole transport material made of a p-type organic semiconductor compound as described in 139 can also be used. Furthermore, a hole transport material with high p property doped with impurities can be used. For example, JP-A-4-297076, JP-A-2000-196140, JP-A-2001-102175, J. Pat. Appl. Phys. , 95, 5773 (2004), Appl. Phys. Let. , 98, 073311 (2011), and the like.

Furthermore, examples of the organic semiconductor material include a metal complex of an 8-quinolinol derivative, a phthalocyanine derivative, and a polyfluorene derivative. Among these, the metal complex of the 8-quinolinol derivative is not particularly limited, and examples thereof include tris (8-quinolinol) aluminum (Alq ₃ ), tris (5,7-dichloro-8-quinolinol) aluminum, tris (5,5). 7-dibromo-8-quinolinol) aluminum, tris (2-methyl-8-quinolinol) aluminum, tris (5-methyl-8-quinolinol) aluminum, bis (8-quinolinol) zinc (Znq), etc., and their metals Examples include metal complexes in which the central metal of the complex is replaced with In, Mg, Cu, Ca, Sn, Ga, or Pb. In addition, the phthalocyanine derivative is not particularly limited, but, for example, one in which the central metal of phthalocyanine contains Cu, Sn, Si, Zn, Al, or the like. Also, those having a side chain structure that is covalently or coordinately bonded to these central metals. Examples thereof include phthalocyanine chloroaluminum, phthalocyanine alkylsilane, metal-free and metal phthalocyanine, or those having a terminal substituted with an alkyl group, a sulfonic acid group, a halogen group, or the like. The polyfluorene derivative is not particularly limited, and examples thereof include polydioctylfluorene-butylphenyldiphenylamine (commonly referred to as TFB) described in APPLIED PHYSICS LETTERS 96, 063303 2010, FIG. 4a and FIG. Examples include the fluorene derivative described in 4b.

  In addition, these hole transport materials may be used individually by 1 type, and may use together or dope 2 or more types. It is also possible to form a hole transport layer by laminating two or more layers made of each material.

  The thickness of the hole transport layer made of such a conductive polymer or organic semiconductor compound is not particularly limited, but is usually 1 to 2000 nm. From the viewpoint of further improving 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.

In general, the conductivity of the hole transport layer is preferably as high as possible. However, if the conductivity is too high, the ability to prevent electrons from moving may be reduced, and rectification may be reduced. Therefore, the conductivity of the hole transport layer is preferably 10 ⁻⁵ to 1 S / cm, and more preferably 10 ⁻⁴ to 10 ⁻² S / cm.

  As a hole transport layer which can be preferably used in the present invention, it is preferable that a metal oxide is mainly used as a main component. Here, the “main component” means that the proportion of the metal oxide in the total amount of 100 mass% of the constituent materials of the hole transport layer is 50 mass% or more. However, the ratio of the metal material to the total amount of 100% by mass of the constituent materials of the metal oxide layer is preferably 60% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass or more. Yes, most preferably 100% by weight.

Metal oxides used for the metal oxide layer (including some nonmetallic materials) include molybdenum (Mo), vanadium (V), tungsten (W), chromium (Cr), niobium (Nb), tantalum ( Ta), titanium (Ti), zirconium (Zr), hafnium (Hf), scandium (Sc), yttrium (Y), thorium (Tr), manganese (Mn), iron (Fe), ruthenium (Ru), osmium ( Os), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), cadmium (Cd), aluminum (Al), gallium (Ga), indium (In), silicon (Si), germanium ( Ge), tin (Sn), lead (Pb), antimony (Sb), bismuth (Bi) or lanthanum (La) to lutetium (Lu) Oxides of rare earth elements and the like that. Among these, metal oxides such as molybdenum trioxide (MoO ₃ ), nickel oxide (NiO), tungsten trioxide (WO ₃ ), and vanadium pentoxide (V ₂ O ₅ ) are used from the viewpoint of excellent hole transport ability. In particular, molybdenum trioxide, tungsten trioxide, and divanadium pentoxide are particularly preferable. These inorganic oxides may be used alone or in combination of two or more or may be used by doping the above-described conductive polymer or organic semiconductor material.

  The thickness of the hole transport layer made of a metal oxide is not particularly limited, but is preferably about 3 to 20 nm, more preferably about 5 to 15 nm, from the viewpoint of photoelectric conversion efficiency and durability.

  The hole transport layer can be formed by using a general film forming method, for example, vacuum deposition method, heating vacuum deposition method, electron beam deposition method, laser beam deposition method, sputtering method, CVD method, atmospheric pressure plasma method, etc. A wet process such as a dry process, a coating method, a plating method, or an electric field forming method can be used. Among the coating methods, a direct patterning method using a printing technique, for example, an ink jet printing method can be preferably used.

In addition, the hole transport layer material that can be used in the present invention has an energy level for transporting holes (mainly coincident with the work function and the HOMO level) in the range of 4.8 eV to 6.5 eV. Is preferred. More preferably, it is 5.0 eV-6.0 eV, Most preferably, it is 5.2 eV-5.7 eV. If it is larger than 4.8 eV, a sufficient open circuit voltage (V _oc ) of the element can be obtained.

<Photoelectric conversion layer>
[n-type organic semiconductor and p-type organic semiconductor]
The photoelectric conversion layer has a function of converting light energy into electric energy using the photovoltaic effect. 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 used for the photoelectric conversion layer of this embodiment is not particularly limited as long as it is a donor (electron donating) organic compound, and materials that can be used in this technical field can be appropriately adopted. Among such compounds, as the condensed polycyclic aromatic low molecular weight compound, for example, anthracene, tetracene, pentacene, hexacene, heptacene, chrysene, picene, fluorene, pyrene, peropyrene, perylene, terylene, quaterylene, coronene, ovalene, Compounds such as circumanthracene, bisanthene, bisanthene, heptazethrene, pyranthrene, violanthene, isoviolanthene, cacobiphenyl, anthradithiophene, porphyrin, copper phthalocyanine, tetrathiafulvalene (TTF) -tetracyanoquinodimethane (TCNQ) complex, Examples include bisethylenedithiotetrathiafulvalene (BEDTTTF) -perchloric acid complex, and derivatives and precursors thereof.

  Examples of the derivative having the above-mentioned condensed polycycle include WO 03/16599 pamphlet, WO 03/28125 pamphlet, US Pat. No. 6,690,029, JP 2004-107216 A. A pentacene derivative having a substituent described in JP-A No. 2003-136964, a pentacene precursor described in US Patent Application Publication No. 2003/136964, and the like; Amer. Chem. Soc. , Vol127. No. 14.4986, J. Am. Amer. Chem. Soc. , Vol. 123, p9482; Amer. Chem. Soc. , Vol. 130 (2008), no. 9, acene-based compounds substituted with a trialkylsilylethynyl group described in 2706 and the like.

  As the conjugated polymer, for example, a polythiophene such as poly-3-hexylthiophene (P3HT) and its oligomer, or a polymerizable group described in Technical Digest of the International PVSEC-17, Fukuoka, Japan, 2007, P1225. Polythiophene, Nature Material, (2006) vol. 5, p328, a polythiophene-thienothiophene copolymer, a polythiophene-diketopyrrolopyrrole copolymer described in WO2008 / 000664, and a polythiophene-thiazolothiazole copolymer described in Adv Mater, 2007p4160 , Nature Mat. vol. 6 (2007), p497, a polythiophene copolymer such as PCPDTBT, Adv. Mater. , Vol. 19, (2007) p2295, polythiophene-carbazole-benzothiadiazole copolymer (PCDTBT), APPLPHYSLETT, 98, (2011) thiazolothiazole copolymer described in p043301, Macromolecules 2009, 42, p1610-1618 Σ-conjugate such as vinyl group-substituted polyhexylthiophene (P3HNT), polypyrrole and its oligomer, polyaniline, polyphenylene and its oligomer, polyphenylene vinylene and its oligomer, polythienylene vinylene and its oligomer, polyacetylene, polydiacetylene, polysilane, polygermane, etc. And polymer materials such as polymer.

  In addition, oligomeric materials instead of polymer materials include thiophene hexamer α-sexual thiophene α, ω-dihexyl-α-sexual thiophene, α, ω-dihexyl-α-kinkethiophene, α, ω-bis (3 Oligomers such as -butoxypropyl) -α-sexithiophene can be preferably used.

  Among these compounds, compounds that have high solubility in organic solvents to the extent that solution processing is possible, can form a crystalline thin film after drying, and can achieve high mobility are preferable. More preferably, it is a compound (a compound capable of forming an appropriate phase separation structure) having appropriate compatibility with a fullerene derivative which is an n-type organic semiconductor material described later.

  In addition, when an electron transport layer or a hole blocking layer is further formed on a bulk heterojunction layer by a solution process, it can be easily laminated if it can be further applied on a layer once applied. However, if a layer is further laminated by a solution process on a layer that is usually made of a material having good solubility, there is a problem in that it cannot be laminated because the underlying layer is dissolved. Therefore, a material that can be insolubilized after application by a solution process is preferable.

  Examples of such a material include materials that can be insolubilized by polymerizing and crosslinking the coating film after coating, such as polythiophene having a polymerizable group described in Technical Digest of the International PVSEC-17, Fukuoka, Japan, 2007, P1225. Or by applying energy such as heat as described in U.S. Patent Application Publication No. 2003/136964, Japanese Patent Application Laid-Open No. 2008-16834, and the like, the soluble substituent reacts to become insoluble (pigmentation). ) Materials can be mentioned.

  On the other hand, the n-type organic semiconductor used for the photoelectric conversion layer of this embodiment 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 may be appropriately adopted. it can. Such compounds include, for example, fullerenes, carbon nanotubes, octaazaporphyrins, and the like perfluoro compounds in which the hydrogen atoms of the p-type organic semiconductor are substituted with fluorine atoms (for example, perfluoropentacene and perfluorophthalocyanine), naphthalene, etc. Examples thereof include aromatic carboxylic acid anhydrides such as tetracarboxylic acid anhydride, naphthalenetetracarboxylic acid diimide, perylenetetracarboxylic acid anhydride, and perylenetetracarboxylic acid diimide, and polymer compounds containing the 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 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 or PC ₆₀ BM), [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 this embodiment, the n-type organic semiconductor may be used alone or in combination of two or more.

  The junction form of the p-type organic semiconductor and the n-type organic semiconductor in the photoelectric conversion layer of this embodiment is a bulk heterojunction (that is, the photoelectric conversion layer is a bulk heterojunction photoelectric conversion layer). Here, the “bulk heterojunction” is formed by applying a mixture of a p-type organic semiconductor and an n-type organic semiconductor, and the domain of the p-type organic semiconductor and the n-type organic semiconductor are formed in this single layer. The domain has a microphase separation structure. Therefore, in a bulk heterojunction, many pn junction interfaces exist throughout the layer as compared to a planar heterojunction. 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. For these reasons, the junction between the p-type organic semiconductor and the n-type organic semiconductor in the photoelectric conversion layer of this embodiment is preferably a bulk heterojunction.

  The bulk heterojunction layer is formed of a single layer (i layer) in which a normal p-type organic semiconductor material and an n-type organic semiconductor layer are mixed, and the i layer is made of a p-type organic semiconductor. In some cases, it has a three-layer structure (p-i-n structure) sandwiched between a p layer and an n layer made of an n-type organic semiconductor. Such a pin structure has higher rectification of holes and electrons, reduces loss due to recombination of charge-separated holes and electrons, and can achieve higher photoelectric conversion efficiency. .

  In the present invention, the mixing ratio of the p-type organic semiconductor and the n-type organic semiconductor contained in the photoelectric conversion layer is preferably in the range of 2: 8 to 8: 2, more preferably 4: 6 to 6: 4. Range. The thickness (dry film thickness) of the photoelectric conversion layer is not particularly limited, but is preferably ˜1,000 nm, more preferably 100 to 600 nm.

<Electron transport layer>
The organic photoelectric conversion element of the present invention may include an electron transport layer as necessary. In addition, when the surface modification molecule contained in the first electrode has a sufficient hole blocking function, it is not always necessary to separately form the electron transport layer.

  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. The electron transport layer has a property of transporting electrons and having a remarkably small ability to transport holes. The electron transport layer is provided between the photoelectric conversion layer and the cathode, and prevents the recombination of electrons and holes by blocking the movement of holes while transporting electrons to the cathode. it can. Therefore, in this specification, an electron injection layer, a hole block layer, an exciton block layer, and the like are also included in the concept of the electron transport layer.

  There is no restriction | limiting in particular in the electron transport material used for an electron carrying layer, The material which can be used in this technical field can be employ | adopted suitably. Examples include nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, carbodiimides, fluorenylidenemethane derivatives, anthraquinodimethane and anthrone derivatives, oxadiazole derivatives, and the like. In addition, in the above oxadiazole derivative, a thiadiazole derivative in which the oxygen atom of the oxadiazole ring is substituted with a sulfur atom, and a quinoxaline derivative having a quinoxaline ring known as an electron-withdrawing group can also be used as an electron transport material. Furthermore, a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain can also be used.

In addition, metal complexes of 8-quinolinol derivatives such as tris (8-quinolinol) aluminum (Alq ₃ ), tris (5,7-dichloro-8-quinolinol) aluminum, tris (5,7-dibromo-8-quinolinol) Aluminum, tris (2-methyl-8-quinolinol) aluminum, tris (5-methyl-8-quinolinol) aluminum, bis (8-quinolinol) zinc (Znq), etc., and the central metals of these metal complexes are In, Mg A metal complex substituted with Cu, Ca, Sn, Ga or Pb can also be used as an electron transporting material. In addition, metal-free or metal phthalocyanine, or those having terminal ends substituted with an alkyl group or a sulfonic acid group can be preferably used as the electron transporting material. As with the hole transport layer described above, an inorganic semiconductor such as n-type-Si or n-type-SiC, or an inorganic oxide having n-type conductivity (such as titanium oxide or zinc oxide) should be used as an electron transport material. Can do.

  A material species that forms an interface dipole by bonding a dipole material to an electrode and improves charge extraction, for example, 3- (2-aminoethyl) aminopropyltrimethoxy described in WO2008 / 134492 Silane (AEAP-TMOS) etc. can be mentioned as a material of an electron carrying layer.

  Further, as the electron transport layer, an electron transport layer having a high n property doped with impurities can be used. Examples thereof include JP-A-4-297076, JP-A-10-270172, JP-A-2000-196140, JP-A-2001-102175, J. Pat. Appl. Phys. 95, 5773 (2004), and the like.

  Specific examples include N, N′-bis (3-methylphenyl)-(1,1′-biphenyl) -4,4′-diamine (TPD) and 4,4′-bis [N- (naphthyl)- Aromatic diamine compounds such as N-phenyl-amino] biphenyl (α-NPD) and derivatives thereof, oxazole, oxadiazole, triazole, imidazole, imidazolone, stilbene derivative, pyrazoline derivative, tetrahydroimidazole, polyarylalkane, butadiene, 4 , 4 ', 4 "-tris (N- (3-methylphenyl) N-phenylamino) triphenylamine (m-MTDATA), porphine, tetraphenylporphine copper, phthalocyanine, copper phthalocyanine, titanium phthalocyanine oxide, etc. , Triazole derivatives, oxa Zazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, annealed amine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, silazane derivatives, etc. In the polymer material, polymers such as phenylene vinylene, fluorene, carbazole, indole, pyrene, pyrrole, picoline, thiophene, acetylene, diacetylene, and derivatives thereof can be preferably used.

  The thickness of the electron transport layer is not particularly limited, but is usually 1 to 2000 nm. From the viewpoint of further improving 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, more preferably 200 nm or less, and further preferably 50 nm or less.

<Charge recombination layer; intermediate electrode>
In a tandem (multijunction type) organic photoelectric conversion element having two or more photoelectric conversion layers as shown in FIG. 3, a charge recombination layer (intermediate electrode) is formed between the photoelectric conversion layers.

  The material used for the charge recombination layer (intermediate electrode) is not particularly limited as long as it is a material having both conductivity and translucency. Examples of the electrode material described above include ITO, AZO, FTO, and titanium oxide. Transparent metal oxides, metals such as Ag, Al, and Au, carbon materials such as carbon nanoparticles and carbon nanowires, conductive polymers such as PEDOT: PSS, polyaniline, and the like can be used. These materials may be used alone or in combination of two or more. It is also possible to form a charge recombination layer by laminating two or more layers made of each material. In addition, the hole transport layer and the electron transport layer described above also have a combination that works as an intermediate electrode (charge recombination layer) by stacking them in an appropriate combination. With such a configuration, the charge recombination layer (intermediate layer) Electrode) It is preferable because the step of forming one layer can be omitted.

The electric conductivity of the charge recombination layer is preferably high from the viewpoint of obtaining high conversion efficiency. Specifically, it is preferably 5 to 50,000 S / cm, and preferably 100 to 10,000 S / cm. Is more preferable. The thickness of the charge recombination layer is not particularly limited, but is preferably 1 to 1000 nm, and preferably 5 to 50 nm. By setting the thickness to 1 nm or more, the film surface can be smoothed. On the other hand, by setting the thickness to 1000 nm or less, it is possible to reduce the decrease in the short-circuit current density J _sc (mA / cm ² ).

<Board>
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.

  When light that is photoelectrically converted enters from the substrate side, the substrate is preferably a member that can transmit the light that is photoelectrically converted, that is, a member that is transparent to the wavelength of the light to be photoelectrically converted. As the substrate, for example, a glass substrate, a resin substrate and the like are preferably mentioned, but it is desirable to use a transparent resin film from the viewpoint of light weight and flexibility.

  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 to a transparent resin film according to the present invention. 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 the configuration of the organic photoelectric conversion element of the present invention, in addition to the above-described members (each layer), various intermediate layers may be included in the element for the purpose of improving photoelectric conversion efficiency and improving the lifetime of the element. Good.

  Examples of the intermediate layer include an exciton block layer, a UV absorption layer, a light reflection layer, a wavelength conversion layer, and a smoothing layer. Further, a layer such as a silane coupling agent may be provided in order to make the metal oxide fine particles unevenly distributed in the upper layer more stable. Further, a metal oxide layer may be laminated adjacent to the photoelectric conversion layer of the present invention.

  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. Examples of the optical functional layer include a light condensing layer such as an antireflection film and a microlens array, and a light diffusion layer that can scatter light reflected by the cathode and enter the power generation layer again.

  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 for 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 is smaller than this, the effect of diffraction is generated and colored.

  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.

<Method for producing organic photoelectric conversion element>
There is no restriction | limiting in particular in the manufacturing method of the organic photoelectric conversion element of the above-mentioned this form, It can manufacture by referring a conventionally well-known method suitably. Hereinafter, the manufacturing method of the organic photoelectric conversion element shown in FIG. 1 will be described as an example, and a preferable manufacturing method of the organic photoelectric conversion element of this embodiment will be described. However, each process in the manufacturing method can be applied not only to the organic photoelectric conversion element of FIG. 1 but also to the organic photoelectric conversion element shown in FIG. 2 and the tandem type manufacturing as shown in FIG.

  The manufacturing method of the organic photoelectric conversion element of this form forms the photoelectric conversion layer containing the process of forming the cathode which is a 1st electrode, and a p-type organic-semiconductor material and an n-type organic-semiconductor material on the said cathode. And a step of forming an anode as a second electrode on the photoelectric conversion layer. Hereinafter, each process of the manufacturing method of the organic photoelectric conversion element of this form is demonstrated in detail.

  In the manufacturing method of this embodiment (one embodiment of FIG. 1), first, a cathode is formed. In addition, you may perform the process of forming an auxiliary electrode by a transparent conductive film etc. as needed before the process of forming a cathode. Examples of the method for forming the cathode include the methods described as the methods II to II-II in the above-mentioned [Method for producing first electrode], but are not particularly limited. Any method can be used as long as it can form the first electrode having a structure in which a surface modifying molecule having a dipole moment is adsorbed to the nanostructure.

  After forming the cathode by the above method, an electron transport layer may be formed on the cathode as necessary. The means for forming the electron transport layer may be either a dry process such as a vapor deposition method or a wet process such as a solution coating method, but from the viewpoint of ease of film formation, a solution coating method is preferred. In the case of forming an electron transport layer using a solution coating method, a solution obtained by dissolving and dispersing the above-described electron transport material in a suitable solvent is coated on the cathode using a suitable coating method and dried. That's fine. The coating methods used for the solution coating method include cast method, spin coating method, blade coating method, wire bar coating method, gravure coating method, spray coating method, dipping (dipping) coating method, bead coating method, air knife coating method. Ordinary methods such as curtain coating method, inkjet method, screen printing method, letterpress printing method, intaglio printing method, offset printing method, flexographic printing method, Langmuir-Blodgett method (LB method), etc. Can do. Among these, it is particularly preferable to use a spin coating method or a blade coating method because the film can be easily formed.

  In addition, although the solid content concentration of the solution used for the coating method may vary depending on the coating method and the film thickness, it is preferably 0.5 to 15% by mass, more preferably 1 to 10% by mass.

  The temperature of the coating solution and / or the coating surface during coating is not particularly limited, but is preferably 30 to 180 ° C. from the viewpoint of preventing precipitation and unevenness due to temperature fluctuations during coating and drying. Preferably it is 50-160 degreeC. Furthermore, there is no restriction | limiting in particular also about the specific form of drying, A conventionally well-known knowledge can be referred suitably. An example of drying (heat treatment) conditions is exemplified by conditions of about 90 to 180 ° C. and about 5 to 90 minutes. Examples of the apparatus used for drying include a hot plate, hot air drying, an infrared heater, a microwave, and a vacuum dryer. Of course, other drying apparatuses can be used.

  Next, a photoelectric conversion layer including a p-type organic semiconductor and an n-type organic semiconductor is formed on the cathode or the electron transport layer formed as described above. A specific method for forming the photoelectric conversion layer is not particularly limited, but preferably, a solution in which a p-type organic semiconductor and an n-type organic semiconductor are dissolved or dispersed in an appropriate solvent, respectively or collectively. Then, it may be applied on the cathode using an appropriate application method (the specific form is as described above) and dried. After that, it is preferable to perform heating in order to cause removal of residual solvent, moisture, gas, and improvement of mobility and absorption absorption by crystallization of the semiconductor material. When annealing is performed at a predetermined temperature during the manufacturing process, a part of the particles is microscopically aggregated or crystallized and the photoelectric conversion layer can have an appropriate phase separation structure. As a result, the mobility of holes and electrons (carriers) in the photoelectric conversion layer is improved, and high efficiency can be obtained. In this way, the p-type organic semiconductor and the n-type organic semiconductor are uniformly mixed, and a bulk heterojunction organic photoelectric conversion element can be obtained.

  On the other hand, in the case of forming a photoelectric conversion layer (for example, a p-i-n structure) composed of a plurality of layers having different mixing ratios of a p-type organic semiconductor and an n-type organic semiconductor, the layer is applied after applying one layer. It can be formed by insolubilizing (pigmenting) and then applying another layer.

  In the case of forming a photoelectric conversion layer containing polyalkyleneimine, for example, a solution in which p-type organic semiconductor and / or n-type organic semiconductor, polyalkyleneimine and polyalkyleneimine are dissolved and dispersed in an appropriate solvent is prepared and applied. , Dry.

  The step of forming the photoelectric conversion layer is preferably performed in a glove box under a nitrogen atmosphere so as not to be exposed to oxygen or moisture. Thus, by performing in a nitrogen atmosphere, it is possible to prevent the p-type organic semiconductor from being deteriorated by oxygen or moisture in the air, and to increase the durability of the element.

  Next, a hole transport layer is formed on the photoelectric conversion layer. The hole transport layer is formed using a vapor deposition method or a solution coating method, preferably a vapor deposition method (for example, a vacuum vapor deposition method). In addition, it is preferable to perform the process of forming the said positive hole transport layer within the glove box of nitrogen atmosphere similarly to the process of forming the said photoelectric converting layer. As described above, by performing in a nitrogen atmosphere, the hole transport layer can be prevented from being deteriorated by oxygen or moisture in the air, and the durability of the element can be improved.

  Thereafter, an anode as a second electrode is formed on the hole transport layer formed as described above. The means for forming the anode is not particularly limited and may be either a vapor deposition method or a solution coating method, but a vapor deposition method (for example, a vacuum vapor deposition method) is preferably used. In addition, it is preferable to perform the process of forming the said anode in the glove box in nitrogen atmosphere similarly to the process of forming the said photoelectric converting layer.

  Furthermore, when layers other than the various layers described above are included, a step for forming these layers can be appropriately added by using a solution coating method, a vapor deposition method, or the like.

<Patterning>
The electrodes (cathode / anode), photoelectric conversion layer, hole transport layer, electron transport layer, and the like can be patterned as necessary. The patterning method is not particularly limited, and a known method can be appropriately applied. For example, when patterning soluble materials used in bulk heterojunction type photoelectric conversion layers, hole transport layers, electron transport layers, etc., only unnecessary portions may be wiped after the entire surface of die coating, dip coating, etc. Alternatively, patterning may be performed by ablation using a carbonic acid laser or the like after film formation, by direct scraping with a scriber, or by direct patterning at the time of coating using a method such as an inkjet method or screen printing. . On the other hand, in the case of insoluble materials used in electrodes, etc., vacuum deposition method, vacuum sputtering method, plasma CVD method, screen printing method using ink in which fine particles of electrode material are dispersed, gravure printing method, ink jet method, etc. Various printing methods, and known methods such as etching or lift-off of the deposited film can be used. Alternatively, the pattern may be formed by transferring a pattern formed on another substrate.

<Sealing>
Moreover, the organic photoelectric conversion element of this embodiment can be sealed as necessary in order to prevent deterioration due to oxygen, moisture, and the like in the environment. There is no restriction | limiting in particular in the method of sealing, It can carry out by the well-known method used with an organic photoelectric conversion element, an organic electroluminescent element, etc. For example, (1) a method of sealing by bonding a cap made of aluminum or glass with an adhesive; (2) a plastic film on which a gas barrier layer such as aluminum, silicon oxide, aluminum oxide or the like is formed and organic photoelectric conversion (3) A method of spin-coating an organic polymer material (polyvinyl alcohol, etc.) having a high gas barrier property; (4) An inorganic thin film (silicon oxide, aluminum oxide, etc.) having a high gas barrier property Alternatively, a method of depositing an organic film (parylene or the like) under vacuum; and (5) a method of laminating these in a composite manner may be mentioned.

  Furthermore, the organic photoelectric conversion element of this embodiment may have a configuration in which the entire element is sealed with two substrates with a barrier from the viewpoint of improving energy conversion efficiency and element lifetime, and preferably includes a moisture getter, an oxygen getter, and the like. It is more preferable that the configuration is as described above.

<Uses of organic photoelectric conversion elements>
According to the other form of this invention, the solar cell which has the organic photoelectric conversion element which concerns on the above-mentioned embodiment, and the organic photoelectric conversion element obtained by the said manufacturing method is provided. Since the organic photoelectric conversion element of this form has the outstanding photoelectric conversion efficiency and durability, it can be used suitably for the solar cell which uses this as an electric power generation element.

  Moreover, according to the further another form of this invention, the optical sensor array by which the organic photoelectric conversion element mentioned above is arranged in the array form is provided. That is, the organic photoelectric conversion element of this embodiment can also be used as an optical sensor array that converts an image projected on the optical sensor array into an electrical signal using the photoelectric conversion function.

<Other manufacturing method of organic photoelectric conversion element (especially photoelectric conversion layer)>
In this application, the method of using the nanostructure which consists of an inorganic substance as a preferable method of manufacturing an organic photoelectric conversion element especially the photoelectric converting layer is also provided. Specifically, in the formation of the photoelectric conversion layer of the organic photoelectric conversion element, the manufacturing method uses two photoelectric conversion layer forming solutions, and at least one of the photoelectric conversion layer forming solutions is a nanostructure made of an inorganic substance. It includes the body. The photoelectric conversion layer obtained by such a manufacturing method contains the nanostructure which consists of inorganic substances. By including an inorganic nanostructure in the photoelectric conversion layer in this manner, the mobility of carriers in the photoelectric conversion layer can be dramatically improved, and the charges generated in the photoelectric conversion layer can be recombined. Therefore, it is possible to efficiently extract charges from the electrodes. When the film thickness is increased in order to increase the light absorption efficiency, the Rsh deterioration (FF decrease) and Jsc decrease due to carrier deactivation due to an increase in charge recombination are particularly significant. On the other hand, according to the present invention, the improvement in charge transportability by the addition of nanostructures suppresses the decrease in FF particularly when the film thickness is increased, and the improvement in Jsc due to the increase in the amount of light absorption. An effect is also acquired and element performance improves.

  Furthermore, by using two solutions for forming a photoelectric conversion layer, a layer including a nanostructure can be formed so as to segregate on an electrode to which charges are transported. Thereby, the effect of nanostructure addition can be improved more. In addition, it is possible to form a film so that nanostructures that enhance the transportability of electrons and holes are unevenly distributed on the respective electrodes, so that more selective charge can be taken out.

  FIG. 5 is a schematic cross-sectional view schematically illustrating an organic photoelectric conversion element according to an embodiment of the present manufacturing method. In the organic photoelectric conversion element 10 ′ of FIG. 5, the cathode (first electrode) 11 and the anode (second electrode) 12 are in opposite positions as compared with the organic photoelectric conversion element 20 ′ of FIG. The hole transport layer 26 and the electron transport layer 27 are disposed at opposite positions. That is, the organic photoelectric conversion element 10 ′ of FIG. 5 has a cathode (first electrode) 11, an electron transport layer 27, a second photoelectric conversion layer 14b, a first photoelectric conversion layer 14a, and holes on a substrate 25. The transport layer 26 and the anode (second electrode) 12 are stacked in this order. With this configuration, when light is incident from the substrate 25 side, electrons generated at the pn junction interface of the photoelectric conversion layer 14 are transported to the cathode 11 through the electron transport layer 27, and the positive holes are positive. It is transported to the anode 12 through the hole transport layer 26. Moreover, the 1st photoelectric converting layer 14a is formed with the 1st photoelectric converting layer formation solution, and the 2nd photoelectric converting layer 14b is formed with the 2nd photoelectric converting layer forming solution. At least one of the first photoelectric conversion layer 14a and the second photoelectric conversion layer 14b contains a nanostructure in the photoelectric conversion layer. In FIG. 5, the first photoelectric conversion layer 14 a and the second photoelectric conversion layer 14 b are described as two layers having interfaces, but the first photoelectric conversion layer forming solution and the second photoelectric conversion layer 14 When the film is formed with the photoelectric conversion layer forming solution, the interface between the two layers does not appear clearly, and the photoelectric conversion layer 14 may be composed of one layer. However, the present application includes such a form.

  FIG. 6 is a schematic cross-sectional view schematically showing an organic photoelectric conversion device according to another embodiment of the present manufacturing method. Specifically, the organic photoelectric conversion element 20 ′ of FIG. 6 includes an anode (second electrode) 12, a hole transport layer 26, a first photoelectric conversion layer 14a, and a second photoelectric conversion layer on a substrate 25. 14b, the electron carrying layer 27, and the cathode (1st electrode) 11 are laminated | stacked in this order. That is, the anode (second electrode) 12 and the cathode (first electrode) 11 are disposed at opposite positions as compared with the organic photoelectric conversion element 10 ′ of FIG. 5 described above, and the hole transport layer. 26 and the electron transport layer 27 are different in the opposite positions. The first photoelectric conversion layer 14a and the second photoelectric conversion layer 14b constitute the photoelectric conversion layer 14. The first photoelectric conversion layer is disposed on the anode (second electrode) 12 side, and the second photoelectric conversion layer is disposed on the cathode (first electrode) 11 side. The first photoelectric conversion layer 14a is formed of a first photoelectric conversion layer forming solution, and the second photoelectric conversion layer 14 is formed of a second photoelectric conversion layer forming solution. At least one of the first photoelectric conversion layer 14a and the second photoelectric conversion layer 14b contains a nanostructure in the photoelectric conversion layer. In FIG. 6, the first photoelectric conversion layer 14 a and the second photoelectric conversion layer 14 b are described as two layers having interfaces, but the first photoelectric conversion layer forming solution and the second photoelectric conversion layer 14 When the film is formed with the photoelectric conversion layer forming solution, the interface between the two layers does not appear clearly, and the photoelectric conversion layer 14 may be composed of one layer. However, the present application includes such a form.

  When the organic photoelectric conversion element 10 shown in FIG. 6 is operated, light is irradiated from the substrate 25 side. In the present embodiment, the anode 12 is made of a transparent electrode material (for example, ITO) so that the irradiated light reaches the photoelectric conversion layer 14. The light irradiated from the substrate 25 side reaches the photoelectric conversion layer 14 through the transparent anode 12 and the hole transport layer 26.

  In FIG. 1, light incident from the anode 12 through the substrate 25 is absorbed by the electron acceptor or the electron donor in the photoelectric conversion layer 14, electrons move from the electron donor to the electron acceptor, and holes and electrons are absorbed. Pair (charge separation state) is formed.

  When the generated electric charges have different internal electric fields, for example, when the work functions of the anode 12 and the cathode 11 are different, the potential difference between the anode 12 and the cathode 11 causes the electrons and holes to be carried to different electrodes, respectively, and a photocurrent is detected. The At this time, the first photoelectric conversion layer 14a on the anode (second electrode) 12 side includes a nanostructure excellent in electron donating property and hole transporting property (high hole mobility), or the cathode It is preferable that the second photoelectric conversion layer 14b on the (first electrode) 11 side includes a nanostructure excellent in electron accepting property and electron transporting property (high in electron mobility). In such a form, electrons pass between nanostructures having excellent electron accepting properties and electron transport properties (high electron mobility), and holes have excellent electron donating properties and hole transport properties (positive). It passes between nanostructures (with high hole mobility) and can be efficiently transported to different electrodes.

  The hole transport layer 26 is formed of a material having a high hole mobility, and the holes generated at the pn junction interface of the photoelectric conversion layer 14 and transported by the nanostructure are more efficiently anode 12. It is responsible for transporting to On the other hand, the electron transport layer 27 is formed of a material having high electron mobility, and is generated at the pn junction interface of the photoelectric conversion layer 14 and efficiently transports the electrons transported by the nanostructure to the cathode 11. It has a function.

  FIG. 7 is a schematic cross-sectional view schematically illustrating an organic photoelectric conversion element including a tandem (multi-junction type) photoelectric conversion layer according to another embodiment of the present invention. The organic photoelectric conversion element 30 ′ in FIG. 7 has a configuration in which the first cell and the second cell are connected in parallel or in series in the intermediate layer 38, and the photoelectric conversion layer of the organic photoelectric conversion element 20 ′ in FIG. Instead of 14, the first cell includes a photoelectric conversion layer 36a, and the second cell includes a photoelectric conversion layer 36b. At this time, the intermediate layer 38 becomes a charge extraction electrode when the first cell and the second cell are connected in parallel, and becomes a charge recombination electrode when they are connected in series. In the present embodiment, the photoelectric conversion layer 36a includes a first photoelectric conversion layer 14a and a second photoelectric conversion layer 14b. And at least one layer of the 1st photoelectric converting layer 14a and the 2nd photoelectric converting layer 14b contains the nanostructure in the photoelectric converting layer. In FIG. 7, the first photoelectric conversion layer 14 a and the second photoelectric conversion layer 14 b are described as two layers in which an interface is formed, but the first photoelectric conversion layer forming solution and the second photoelectric conversion layer 14 When the film is formed with the solution for forming a photoelectric conversion layer, the interface between the two layers does not appear clearly, and the photoelectric conversion layer 36a may be composed of one layer, but the present application includes such a form.

  In the tandem organic photoelectric conversion element 30 ′ shown in FIG. 7, photoelectric conversion materials (p-type organic semiconductors and p-type organic semiconductors) having different absorption wavelengths are respectively formed in the photoelectric conversion layer 36a of the first cell and the photoelectric conversion layer 36b of the second cell. By using an n-type organic semiconductor), light in a wider wavelength range can be efficiently converted into electricity.

[Method for producing organic photoelectric conversion element]
An organic photoelectric conversion element manufacturing method according to the present invention is an organic photoelectric conversion element having a photoelectric conversion layer containing a p-type organic semiconductor material and an n-type organic semiconductor material between a first electrode and a second electrode. It is a manufacturing method, Comprising: The process which forms the said photoelectric converting layer using the 1st solution for photoelectric conversion layer formation and the 2nd solution for photoelectric conversion layer formation, The said 1st solution for photoelectric conversion layer formation And at least one of the said 2nd solution for photoelectric conversion layer formation contains the nanostructure which consists of inorganic substances, It is a manufacturing method of the organic photoelectric conversion element characterized by the above-mentioned. By applying two photoelectric conversion layers including the nanostructure in at least one layer, a photoelectric conversion layer in which the nanostructure is unevenly distributed in the direction of the upper or lower electrode can be formed. As described above, even when two photoelectric conversion layer forming solutions are used, a photoelectric conversion layer formed from a single layer may be obtained without making the interface clear.

  The production method of the present invention preferably uses (1) a step of forming an electrode on a transparent substrate, and (2) a first photoelectric conversion layer forming solution and a second photoelectric conversion layer forming solution. A step of forming a photoelectric conversion layer, and (3) a step of forming an electrode on the photoelectric conversion layer. If necessary, a step of forming a hole transport layer and / or a step of forming an electron transport layer are included.

  Taking the method for producing an organic photoelectric conversion element shown in FIG. 5 as an example, a preferred embodiment of the method for producing an organic photoelectric conversion element will be described below. However, each process in the manufacturing method can be applied not only to the organic photoelectric conversion element of FIG. 5 but also to the organic photoelectric conversion element shown in FIG. 6 and the tandem type manufacturing as shown in FIG.

  One embodiment of the method for producing the organic photoelectric conversion element shown in FIG. 5 includes (1) a step of forming a cathode (first electrode) on a transparent substrate, and (2) a first photoelectric conversion layer forming solution and a first step. A step of forming a photoelectric conversion layer using the photoelectric conversion layer forming solution of 2, and a step of forming an anode (second electrode) on the photoelectric conversion layer. Hereinafter, each process of the manufacturing method of the organic photoelectric conversion element of this form is demonstrated in detail.

(1) Step of forming cathode First, a substrate is prepared, and a cathode is formed on the substrate. The substrate will be described later.

  The method of forming the cathode is not particularly limited, but is easy to operate and can be produced by roll-to-roll using a device such as a die coater. Preferably, the method is a method of applying and drying. Besides this, a commercially available thin film electrode material may be used as it is.

  After forming the cathode as described above, an electron transport layer may be formed on the cathode as necessary. The means for forming the electron transport layer may be either vapor deposition or solution coating, but is preferably solution coating. In the case of forming an electron transport layer using a solution coating method, a solution obtained by dissolving and dispersing the above-described electron transport material in a suitable solvent is coated on the cathode using a suitable coating method and dried. That's fine. The coating methods used for the solution coating method include cast method, spin coating method, blade coating method, wire bar coating method, gravure coating method, spray coating method, dipping (dipping) coating method, bead coating method, air knife coating method. Ordinary methods such as a curtain coating method, an ink jet method, a screen printing method, a relief printing method, an intaglio printing method, an offset printing method, a flexographic printing method, and a Langmuir-Blodgett (LB) method can be used. Among these, it is particularly preferable to use a spin coating method or a blade coating method. In addition, although the solid content concentration of the solution used for the coating method may vary depending on the coating method and the film thickness, it is preferably 0.5 to 15% by mass, more preferably 1 to 10% by mass. Further, the temperature of the coating liquid and / or the coating surface during coating is not particularly limited, but is preferably 30 to 150 ° C. from the viewpoint of preventing precipitation and unevenness due to temperature fluctuations during coating and drying. More preferably, it is 50-120 degreeC. Furthermore, there is no restriction | limiting in particular also about the specific form of drying, A conventionally well-known knowledge can be referred suitably. An example of the drying (heat treatment) condition is exemplified by a temperature of about 90 to 150 ° C. and a condition of about 5 to 60 minutes. Examples of the apparatus used for drying include a hot plate, hot air drying, an infrared heater, a microwave, and a vacuum dryer. Of course, other drying apparatuses can be used.

(2) Step of forming the bulk heterojunction photoelectric conversion layer using the first photoelectric conversion layer forming solution and the second photoelectric conversion layer forming solution Subsequently, on the cathode or electron transport layer formed above A photoelectric conversion layer including a p-type organic semiconductor and an n-type organic semiconductor is formed. At this time, in the present invention, two types of photoelectric conversion layer solutions (first photoelectric conversion layer forming solution and second photoelectric conversion layer forming solution) are used.

  And at least one of the said 1st solution for photoelectric conversion layer formation and the 2nd solution for photoelectric conversion layer formation, Preferably both contain the nanostructure which consists of an inorganic substance.

  In this embodiment, after apply | coating the 2nd solution for photoelectric conversion layer formation on the cathode or electron carrying layer formed above, the 1st solution for photoelectric conversion layer formation is apply | coated.

  Since the first photoelectric conversion layer forming solution is formed on the anode side, it contains the second electrode (anode) when it contains a nanostructure excellent in electron donating property and hole transporting property (high hole mobility). ) Is preferable because the movement of the holes to) is performed smoothly. In addition, since the second photoelectric conversion layer forming solution is formed on the cathode side, the first electrode (with the electron mobility and high electron mobility) including the first electrode ( This is preferable because electrons move smoothly to the cathode. When both the first photoelectric conversion layer forming solution and the second photoelectric conversion forming solution include a nanostructure, the nanostructure included in the first photoelectric conversion layer forming solution is a second photoelectric conversion formation. It is preferably more electron transport than the nanostructure contained in the solution for use. In addition, the nanostructure as used herein includes a nanostructure covered with a surface.

  That is, whether the nanostructure is contained in the first or second photoelectric conversion layer forming solution is determined in consideration of the charge transport property of the nanostructure. In general, the charge transport property of the nanostructure is considered by using the mobility of each carrier as an index. When the nanostructure contained in the photoelectric conversion layer has semiconductor characteristics, those having n-type semiconductor characteristics generally have high electron mobility, and those having p-type semiconductor characteristics generally have high hole mobility. is there. In the case where the nanostructure has characteristics of a so-called conductor such as a metal, it has high transportability for both electrons and holes. In that case, the HOMO level of the p-type semiconductor constituting the photoelectric conversion layer or It is determined by matching with the LUMO level of the n-type semiconductor material. That is, a metal nanostructure with a deep WF (work function) is generally excellent in matching with the HOMO level of a p-type semiconductor, and therefore generally functions as a hole transport property. However, as disclosed in the present invention, even if the nanostructure has a deep WF, if the surface level is adjusted so as to match the n-type LUMO level by surface treatment with a dipole material or the like, It becomes electron transport property because it becomes excellent in transport property.

  The first photoelectric conversion layer forming solution preferably contains at least one of a nanostructure made of metal, a nanostructure made of carbon, or a nanostructure formed by coating with a surface modifying molecule. In this case, the nanostructure formed by coating with the surface modifying molecules preferably has a hole transporting property. More preferably, the 1st solution for photoelectric conversion layer formation contains the nanostructure which consists of metals. The nanostructure made of metal is a conductor, but considering the work function, the hole transportability is strong. Therefore, it is considered that the nanostructure is preferably included in the first solution for forming a photoelectric conversion layer.

  The second photoelectric conversion layer forming solution preferably contains at least one of a metal oxide nanostructure or a nanostructure formed by coating with a surface modifying molecule. In this case, the nanostructure formed by coating with the surface modification molecules preferably has an electron transporting property.

  Furthermore, as a preferred embodiment, either one of the first or second photoelectric conversion layer forming solution includes a nanostructure formed by adsorbing surface modifying molecules. A nanostructure formed by adsorption of a surface modifying molecule is preferable because the surface modifying molecule can improve charge characteristics.

  In still another preferred embodiment, the first photoelectric conversion layer forming solution includes a nanostructure made of metal, and the second photoelectric conversion layer forming solution is an oxide nanostructure made of metal, or the surface It includes nanostructures coated with modifying molecules. With such a form, the charge is efficiently transferred, and the photoelectric conversion efficiency is very good even when the thickness of the photoelectric conversion layer is increased. As a more preferable embodiment, the first photoelectric conversion layer forming solution contains a nanostructure made of metal, and the second photoelectric conversion layer forming solution is made of a metal covered with a surface modifying molecule. including.

  Details of the nanostructure will be described later.

  A coating method is not particularly limited, but a solution coating method is preferable. When a photoelectric conversion layer is formed by using a solution coating method, a solution in which a p-type organic semiconductor and an n-type organic semiconductor, or in some cases, nanostructures are dissolved or dispersed in an appropriate solvent. May be coated on the cathode or the electron transport layer using an appropriate coating method and dried. Examples of the coating method used for the solution coating method include those described in the section (1) above.

  As a method of applying the first photoelectric conversion layer forming solution and the second photoelectric conversion layer forming solution in a multilayer manner, sequential coating or simultaneous coating may be used, but the photoelectric conversion layer may be formed by simultaneous coating. preferable. Simultaneous coating means a method of forming a plurality of coating liquids constituting different layers by supplying them simultaneously to the coating apparatus from the stage of the coating process. Therefore, it is different from the sequential multi-layer coating method in which wet coating is sequentially performed in a plurality of times. Preferably, a photoelectric conversion layer including a single p-type semiconductor, an n-type semiconductor, and a nanostructure can be formed by simultaneously applying and drying two or more layers by a blade coating method. The simultaneous application of the photoelectric conversion layer is preferable because the photoelectric conversion efficiency is improved as compared with the sequential application. This is because the lower layer fullerene is selectively dissolved by the upper layer solvent, and it is possible to suppress the decrease in performance due to the increase in the fullerene domain in the process of laminating and drying the second layer. It is done.

  As the solvent used in the first and second photoelectric conversion layer forming solutions, a solvent capable of dissolving both the p-type semiconductor material and the n-type semiconductor material is preferable. As such a solvent, for example, aromatic solvents such as toluene, xylene and tetralin, and halogen solvents such as chloroform, dichloroethane, chlorobenzene, dichlorobenzene and trichlorobenzene are preferable. In addition, Nature Mat. , Vol. 6 (2007), p497, a poor solvent (octanedithiol, diiodooctane, etc.) that enhances the crystallinity of the p-type material may be further added in an amount of 0.1 to 5% by mass.

  The total concentration of the p-type semiconductor material and the n-type semiconductor material in the first and second photoelectric conversion layer forming solutions varies depending on the desired film thickness and the film forming method, but about 1 in the spin coating method and the blade coating method. It is preferable to set it as -4 mass%, More preferably, it is 1.5-3 mass%. Further, the concentration of the nanostructure in the first and second photoelectric conversion layer forming solutions is 0.01 to 20% by mass with respect to a total of 100% by mass of the p-type semiconductor material and the n-type semiconductor material. Is preferable, and it is more preferable that it is 0.1-5 mass%.

  The coating thicknesses of the first and second photoelectric conversion layer forming solutions are appropriately set, but are preferably dry film thicknesses: first photoelectric conversion layer: second photoelectric conversion layer = 1: 0. It can apply | coat so that it may become 5-5.

  Although the drying is performed after the application of the first and second photoelectric conversion layer forming solutions, the method described above can be appropriately used for the drying process. Heating is preferably performed in order to cause removal of residual solvent, moisture, and gas, and improvement in mobility and absorption of long waves by crystallization of the semiconductor material. When annealing is performed at a predetermined temperature during the manufacturing process, a part of the particles is microscopically aggregated or crystallized and the photoelectric conversion layer can have an appropriate phase separation structure. As a result, the mobility of holes and electrons (carriers) in the photoelectric conversion layer is improved, and high efficiency can be obtained. If the time until the drying becomes longer in the drying process, the nanostructure may diffuse before the photoelectric conversion layer is dried when it is desired to make the nanostructure unevenly distributed on the upper electrode side, which is not preferable. As drying time of a photoelectric converting layer, 1 second-10 minutes are preferable, and 1 second-5 minutes are more preferable. Thus, it can be set as a bulk heterojunction type organic photoelectric conversion element.

  The step of forming the photoelectric conversion layer can be performed in a glove box under a nitrogen atmosphere so as not to be exposed to oxygen or moisture. As described above, since the p-type organic semiconductor can be prevented from being deteriorated by oxygen or moisture in the atmosphere by performing in a nitrogen atmosphere, and the durability of the element can be increased, it can be used as appropriate.

(3) Step of forming an anode on the photoelectric conversion layer Next, an anode is formed on the photoelectric conversion layer formed above. The means for forming the anode is not particularly limited and may be either a vapor deposition method or a solution coating method, but a vapor deposition method (for example, a vacuum vapor deposition method) is preferably used. In addition, when providing a positive hole transport layer between a photoelectric converting layer and an anode, a positive hole transport layer is formed using a vapor deposition method or a solution coating method, Preferably a solution coating method. In addition, it is preferable to perform the process of forming the said positive hole transport layer within the glove box of nitrogen atmosphere similarly to the process of forming the said photoelectric converting layer. Thus, by performing in a nitrogen atmosphere, deterioration of the photoelectric conversion layer due to oxygen or moisture in the air can be prevented, and the durability of the element can be improved.

  Furthermore, when layers other than the various layers described above are included, a step for forming these layers can be appropriately added by using a solution coating method, a vapor deposition method, or the like.

  The electrodes (cathode / anode), photoelectric conversion layer, hole transport layer, electron transport layer, and the like can be patterned as necessary. The patterning method is not particularly limited, and a known method can be appropriately applied. For example, when patterning soluble materials used in bulk heterojunction type photoelectric conversion layers, hole transport layers, electron transport layers, etc., only unnecessary portions may be wiped after the entire surface of die coating, dip coating, etc. Alternatively, patterning may be performed by ablation using a carbonic acid laser or the like after film formation, by direct scraping with a scriber, or by direct patterning at the time of coating using a method such as an inkjet method or screen printing. . On the other hand, in the case of insoluble materials used in electrodes, etc., vacuum deposition method, vacuum sputtering method, plasma CVD method, screen printing method using ink in which fine particles of electrode material are dispersed, gravure printing method, ink jet method, etc. Various printing methods, and known methods such as etching or lift-off of the deposited film can be used. Alternatively, the pattern may be formed by transferring a pattern formed on another substrate.

  Moreover, the organic photoelectric conversion element of this embodiment can be sealed as necessary in order to prevent deterioration due to oxygen, moisture, and the like in the environment. There is no restriction | limiting in particular in the method of sealing, It can carry out by the well-known method used with an organic photoelectric conversion element, an organic electroluminescent element, etc. For example, (1) a method of sealing by bonding a cap made of aluminum or glass with an adhesive; (2) a plastic film on which a gas barrier layer such as aluminum, silicon oxide, aluminum oxide or the like is formed and organic photoelectric conversion (3) A method of spin-coating an organic polymer material (polyvinyl alcohol, etc.) having a high gas barrier property; (4) An inorganic thin film (silicon oxide, aluminum oxide, etc.) having a high gas barrier property Alternatively, a method of depositing an organic film (parylene or the like) under vacuum; and (5) a method of laminating these in a composite manner may be mentioned.

  Moreover, in the manufacture of an organic photoelectric conversion element, a sealing step is included as necessary in order to prevent deterioration due to oxygen and moisture in the environment.

  There is no restriction | limiting in particular in the sealing method, It can carry out by the well-known method used with an organic photoelectric conversion element, an organic electroluminescent element, etc. For example, (1) a method of sealing by bonding a cap made of aluminum or glass with an adhesive; (2) a plastic film on which a gas barrier layer such as aluminum, silicon oxide, or aluminum oxide is formed, and organic photoelectric conversion (3) A method of spin-coating an organic polymer material (polyvinyl alcohol, etc.) having a high gas barrier property; (4) An inorganic thin film (silicon oxide, aluminum oxide, etc.) having a high gas barrier property Alternatively, a method of depositing an organic film (parylene or the like) under vacuum; and (5) a method of laminating these in a composite manner may be mentioned.

  Furthermore, from the viewpoint of improving energy conversion efficiency and device life, the entire device may be sealed with two substrates with a barrier, and a structure in which a moisture getter, an oxygen getter, and the like are enclosed is more preferable.

  Hereinafter, the organic photoelectric conversion element in the manufacturing method and the nanostructure used in the organic photoelectric conversion element obtained by the manufacturing method will be described in detail. In addition, about the structural material of other components (an electrode, a positive hole transport layer, an electron carrying layer, etc.), since the form mentioned above can be used similarly, detailed description is abbreviate | omitted here.

[Nanostructure]
In the present invention, when the photoelectric conversion layer is a bulk heterojunction type including a p-type semiconductor and an n-type semiconductor, a nanostructure is further included separately from the p-type semiconductor and the n-type semiconductor. This nanostructure may be the above-described “nanostructure having a work function larger than 4.3 eV measured by ultraviolet photoelectron spectroscopy” as included in the first electrode, or any other nanostructure However, it is preferably a “nanostructure having a work function measured by ultraviolet photoelectron spectroscopy greater than 4.3 eV”.

  As the nanostructure, for example, nanoparticles (nanorods, nanopillars, etc.), nanofibers (nanowires), and nanoporouss can be preferably used. Here, the nanostructure refers to a substance having an average particle size of primary particles measured with a transmission electron microscope (TEM) in the nano order (less than 1,000 nm, preferably 1 to 900 nm). The average particle size is the average particle size of 100 structures. The particle diameter indicates a diameter in the case of a spherical shape or nanowire, and a short diameter in the case of a rod shape. Among these, since the film forming process is simple, it is more preferable to use nanoparticles, nanowires, or the like.

  The material constituting the nanostructure is not particularly limited, and examples thereof include metals, metal nitrides, metal oxides, and carbon. In particular, nanostructures used in the present invention include metal nanostructures (hereinafter also referred to as metal nanostructures), metal oxide nanostructures (hereinafter also referred to as metal oxide nanostructures), Alternatively, it is preferably a nanostructure made of carbon (hereinafter also referred to as carbon nanostructure).

  Metals or metal oxides include platinum, gold, silver, nickel, chromium, copper, iron, tin, titanium, tantalum, indium, cobalt, palladium, tellurium, rhenium, iridium, aluminum, ruthenium, germanium, molybdenum, tungsten, Examples thereof include metals such as zinc, alloys thereof, and metal oxides thereof. In particular, platinum, gold, silver, copper, cobalt, nickel, molybdenum, nickel oxide, molybdenum oxide, titanium oxide, zinc oxide, and tin oxide are preferable from the viewpoint of excellent charge transportability.

  As above-mentioned, a metal is mentioned as a suitable form of the nanostructure contained in the 1st solution for photoelectric conversion layer formation. From the viewpoint of excellent charge transportability, the metal is preferably platinum (Pt), gold (Au), silver (Ag), copper (Cu), cobalt (Co), nickel (Ni), or molybdenum (Mo). It is preferable to contain gold (Au), silver (Ag), or copper (Cu). Moreover, as a suitable form of the nanostructure contained in the solution for forming the second photoelectric conversion layer, a metal oxide is exemplified, and nickel oxide, molybdenum oxide, titanium oxide, zinc oxide, and tin oxide are preferable. .

  Examples of the nanoparticles include fine particles such as metals, inorganic oxides, and inorganic nitrides. Nanoparticles are produced by reducing metal ions in the liquid phase, such as physical production methods such as gas evaporation, sputtering, and metal vapor synthesis, colloidal methods, and coprecipitation methods. A chemical production method can be mentioned, but a liquid phase synthesis method is preferred from the viewpoint of controlling the particle size and facilitating dispersion in a solution.

  The preferred particle size of the nanoparticles is 10 to 200 nm, more preferably 30 to 100 nm. It is presumed that when the particle size is 10 nm or more, the nanoparticles are in contact with each other in the photoelectric conversion layer, so that the charge transport property is further improved. Moreover, it is more preferable that the particle size is 200 nm or less because the photoelectric conversion layer is covered with the nanoparticles, and performance degradation such as leakage is suppressed.

  A nanowire (hereinafter also referred to as “conductive fiber”) is conductive and has a length that is sufficiently longer than its diameter (thickness), and a metal element as a main component. It refers to a linear structure. Here, nanowire means a linear structure having a diameter of nm scale. The nanowires are in contact with each other in the photoelectric conversion layer to form a three-dimensional carrier path network, and the charge is transported through the inside to reach the electrode. ing. Accordingly, a longer nanowire is preferable because it is advantageous for forming a conductive network. On the other hand, when the nanowire becomes long, the nanowire is entangled to form an aggregate, which may deteriorate the optical characteristics. Since the rigidity and diameter of the nanowire influence the formation of the conductive network and the formation of aggregates, it is preferable to use the one having the optimum average aspect ratio (aspect = length / diameter) according to the nanowire to be used. . As the nanowire, from the viewpoint of forming a long conductive path with one metal nanowire and suppressing aggregation, the average length is preferably 3 μm or more, more preferably 3 to 500 μm, particularly 3 It is preferable that it is -300 micrometers. In addition, the relative standard deviation of the length is preferably 40% or less. Moreover, it is preferable that an average diameter is small from a transparency viewpoint, On the other hand, the larger one is preferable from an electroconductive viewpoint. The average diameter of the nanowire is preferably 1 to 300 nm, more preferably 10 to 300 nm, and even more preferably 30 to 200 nm. In addition, the relative standard deviation of the diameter is preferably 20% or less. The average aspect ratio is preferably 10 to 10,000.

  Examples of the shape include a hollow tube shape, a wire shape, and a fiber shape, such as inorganic nanofibers coated with metal, conductive metal oxide nanofibers, metal nanowires, carbon fibers, and carbon nanotubes. In the present invention, a nanowire having a thickness of 100 nm or less is preferable from the viewpoint of transparency. Moreover, since electroconductivity is also satisfied, a metal nanowire and a carbon nanotube are more preferable, and a metal nanowire is further more preferable from a photoelectric conversion efficiency improving.

  There is no restriction | limiting in particular as a metal composition of metal nanowire, Although it can comprise from the 1 type or several metal of a noble metal element and a base metal element, it is a noble metal (For example, gold | metal | money, platinum, silver, palladium, rhodium, iridium, ruthenium) , Osmium, etc.) and at least one metal belonging to the group consisting of iron, cobalt, copper, and tin, and preferably includes gold (Au), silver (Ag), or copper (Cu) from the viewpoint of conductivity. It is more preferable that it contains at least silver. Moreover, in order to make electroconductivity and stability (sulfurization and oxidation resistance of metal nanowire, and resistance to magnetization) compatible, silver and at least one metal belonging to a noble metal other than silver can also be included. When the metal nanowire according to the present invention contains two or more kinds of metal elements, for example, the metal composition may be different between the surface and the inside of the metal nanowire, and the entire metal nanowire has the same metal composition. You may do it.

  In the present invention, the nanowire production means is not particularly limited, and for example, known means such as a liquid phase method and a gas phase method can be used. Moreover, modification | denaturation etc. of the surface substituent for making it disperse | distribute in a photoelectric converting layer solution can also be performed suitably.

[Surface modifying molecule]
In the present invention, the nanostructure may be coated with a surface modifying molecule. Since the surface modification molecule coats the nanostructure, it has an adsorbing group at the end of the molecule that has adsorptivity to the nanostructure. Examples of the adsorbing group include a thiol group (—SH), a methylthio group (—SCH ₃ ), a mercaptothio group (—S—SH), a methyl mercaptothio group, a dithiocarbamate group (—CS ₂ ), a thiocarbonyl group ( > C = S), thiocarboxyl group (—C (O) SH), acetylthio group (—SC (O) CH ₃ ), dithiocarboxyl group, sulfide group (—S—), disulfide group (—S—S—) ), Sulfo group (—SO ₃ H), sulfino group (—SOOH), carboxyl group (—COOH), phosphono group (—P (O) (OH) ₂ ), phosphoric acid group (—PO ₄ H). . Among these, a thiol group, a dicarbamate group, and a sulfide group that have high adsorptivity to a metal surface and high thermal stability are preferable. The surface modifying molecule may have one or a plurality of the above adsorbing groups, or may have a combination of different types. In this specification, “adsorption” means physical adsorption by van der Waals force or chemical adsorption by covalent bond, ionic bond, coordination bond, hydrogen bond, etc. On the other hand, chemical adsorption in which the surface modifying molecules are strongly adsorbed is preferable.

  For example, when a surface modification molecule is adsorbed to a metal nanostructure such as silver nanowire, it has an adsorption group such as a thiol group, methylthio group, mercaptothio group, methyl mercaptothio group, dithiocarbamate group, acetylthio group at the end. Is adsorbed on the surface of the metal nanostructure by a sulfide bond. Alternatively, the metal nanostructure may be adsorbed from a dimer or multimer of molecules bonded through a disulfide bond.

  The physical properties of the nanostructure can also be changed by the surface modifying molecule. Examples of changes in physical properties include changes in charge transport properties. Examples of such surface-modifying molecules that change the physical properties include, for example, a nitrogen atom, a carbon atom, or sulfur as an adsorbing group that has an adsorptivity to the nanostructure so as to induce a dipole moment in the molecule. A surface modifying molecule having a substituent bonded through an atom is exemplified. Thus, by adsorbing surface-modified molecules having a dipole moment in the molecule to the nanostructure, the vacuum level of the nanostructure changes, the connection with the semiconductor in the photoelectric conversion layer improves, and the fill factor Is preferable. When it is intended to improve the connection between the nanostructure and the p-type semiconductor, a dipole material having an electron-withdrawing group (electron-accepting group) is coated to improve the connection with the n-type semiconductor. It is preferred to coat a dipole material having a donating group. In this case, the dipole moment +-is reversed.

  In general, the vacuum level of a nanostructure to which a surface modifying molecule is adsorbed is proportional to the density at which the surface modifying molecule is adsorbed and the magnitude of the dipole moment of the surface modifying molecule. Therefore, in order to constitute a nanostructure having an appropriate vacuum level, it is preferable that the surface modifying molecule has a dipole moment. The dipole moment is preferably 0.5 to 10 in absolute value, and particularly preferably 1 to 6.

  The “dipole moment” indicates a product of a vector from a negative charge to a positive charge and the magnitude of the charge. Specifically, the vector and size can be obtained from calculation by the density functional (DFT) method. In the present invention, the dipole moment in a state of being bonded to one silver (Ag) atom as the metal species to be adsorbed was determined. The calculation program is Gaussian 03, the organic part is B3LYP / 6-31G * as the basis function, and the metal part is B3LYP / SDD.

  The dipole moment of the surface coating molecule correlates with the work function. FIG. 8 is a diagram showing the correlation between the surface modification molecules used in the examples and the work function. Since the current heterojunction photoelectric conversion layer has an LUMO of about 4.1 eV, the electrode preferably has a value equal to or smaller than 4.1 eV. A molecule having a dipole moment of 3.0D or more has a work function shallower than 4.1 eV when coated with Ag. Therefore, since the electron transport property of the photoelectric conversion layer can be improved, the nanostructure coated with such a surface coating molecule (for example, the nanostructure coated with the compound g in Examples) is used as the cathode. It is preferable to be included in the second photoelectric conversion layer forming solution on the side. On the other hand, a molecule having a dipole moment of less than 3.0D can improve the hole transport property of the photoelectric conversion layer, and thus a nanostructure (for example, in the examples) coated with such a surface coating molecule. The nanostructure coated with the compound e) may be included in the first photoelectric conversion layer forming solution.

  As the nanostructure for adsorbing the surface modifying molecule, any of the nanostructures described in the column of the nanostructure may be used, but it is preferable to use a metal nanostructure made of a metal.

  As described above, in order to improve the connection with the n-type semiconductor, the surface modifying molecule preferably has an electron donating group. In the present specification, the “electron-donating group” refers to a substituent having a negative value for Hammett's substituent constant σp.

  The electron donating group is preferably bonded to the adsorption group of the surface modifying molecule. By having the electron donating group bonded to the adsorbing group, it is easy to appropriately control the magnitude and direction of the dipole moment of the surface modifying molecule. Note that the electron-donating group is not necessarily bonded directly to the adsorbing group, and may be via a substituted or unsubstituted aliphatic group or aromatic group.

Examples of electron donating groups include alkyl groups having 1 to 20 carbon atoms, preferably 1 to 12 carbon atoms, hydroxyl groups (or salts thereof), mercapto groups (or salts thereof), and 1 to 20 carbon atoms. , Preferably an alkoxy group having 1 to 12 carbon atoms (for example, methoxy group, ethoxy group), aryloxy group, heterocyclic oxy group, alkylthio group, arylthio group, heterocyclic thio group, amino group, 1 to 1 carbon atom 20, preferably an alkylamino group having 1 to 12 carbon atoms (for example, —NHCH ₃ , —N (CH ₃ ) ₂ ) arylamino group, heterocyclic amino group, heterocyclic group in which σp takes a negative value, or these And a phenyl group substituted with an electron donating group. The surface modifying molecule may have one or a plurality of the above electron donating groups, or may have a combination of different types.

Further, as described above, in order to improve the connection with the p-type semiconductor, the surface modification molecule preferably has an electron accepting group. In the present specification, the “electron-accepting group” refers to a substituent having a positive value for Hammett's substituent constant σp. As an electron-accepting group, a phenyl group, a triazine group, a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, an iodine atom), —CF ₃ , —CCOOCF ₃ , —SO ₂ CF ₃ , —COCF ₃ , —CHO, —COOCH ₃ , —SO ₂ CH ₃ , —SO ₂ NH ₂ , —COCH ₃ , —CN or —NO ₂ may be mentioned.

  As the surface modifying molecule, a dithiocarbamate compound as disclosed in European Patent Application Publication No. 2278636, a compound represented by the following formula (I), or the like can be used.

  Specific examples of the surface modifying molecule include the following.

In the above formulas (A) to (G), n is an integer of 0 to 3, X represents N or CH, preferably N, Y represents N, CH, or C (CH ₃ ), Z represents N, CH, or C (CH ₃ ), X ′ independently represents N or CH, EA ′ represents OCO, CO (O), C (O), and SO ₂ , ED 'Represents NR' (wherein R 'represents a hydrogen atom, a methyl group, an ethyl group, or a benzyl group), O, or S. In the above formulas (A) to (G) and (I), EA represents an electron accepting group, and ED represents an electron donating group. In the formulas (A) to (G), when two or more same symbols exist in the same compound, each symbol may represent the same or different one.

As an electron-accepting group represented by EA, a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, an iodine atom), —CF ₃ , —CCOOCF ₃ , —SO ₂ CF ₃ , —COCF ₃ , —CHO, —COOCH _{3, -SO 2 CH 3, -SO} 2 NH 2, -COCH 3, include -CN, or -NO _2. Examples of the electron donating group represented by ED include —NH ₂ , —NHCH ₃ , —N (CH ₃ ) ₂ , —OH or —OCH ₃ . The substitution position of EA or ED is not particularly limited, but is preferably p-position.

  In the formula (H), R ″ each independently represents a hydrogen atom, a linear, branched or cyclic alkyl group having 1 to 20 carbon atoms, preferably 1 to 12 carbon atoms. It does not represent a hydrogen atom.

  Specific examples include the following compounds a to l.

  The dithiocarbamate compound forms the following structure with the nanostructure.

  In the above formula, M represents a nanostructure.

When adsorbing on the surface of the metal nanostructure via a dithiocarbamate group, the precursor amine and carbon disulfide may be adsorbed by contacting the metal nanostructure. That is, dithiocarbamic acid (R ₂ NCS ₂ ⁻ ) generated by the reaction represented by the following reaction formula (1) is generated in the presence of a metal nanostructure to adsorb surface adsorbed molecules through dithiocarbamate groups. Can be made.

  In the above reaction formula (1), R is not particularly limited, but is selected from, for example, a hydrogen atom, a substituted or unsubstituted aliphatic group, and an aromatic group.

  A conventionally known method can be used as a method of modifying the nanostructure using the surface modifying molecule. As an example, after surface-protecting the nanostructure using polyvinyl alcohol or the like, a surface-modifying molecule is added to the surface-protected nanostructure, and the precipitate obtained by centrifugation is resuspended in water. can get. At this time, the addition amount of the surface modification molecule is not particularly limited as long as the effect is obtained, but is preferably 0.01 to 1% by mass with respect to 100% by mass of the metal nanostructure.

  As other surface modification molecules, poly (3-alkylthiophenes) as disclosed in JP 2010-251592 A may be used. More specifically, poly (3-alkylthiophene) having an adsorption group at the 5-position of the terminal thiophene unit represented by the following general formula (1) and the 2-position of the terminal thiophene unit represented by the general formula (2) And poly (3-alkylthiophene) having an adsorbing group.

In general formula (1) or (2), R represents an optionally substituted alkyl group or alkoxyalkyl group having 4 to 15 carbon atoms, and R ′ may have a hydrogen atom or a substituent. A good alkyl group having 1 to 20 carbon atoms is represented. R ^〃 represents a hydrogen atom, a methyl group, an acetyl group, a mercapto group or a methyl mercapto group. X represents a divalent linking group. m represents 0 or 1, and n represents an integer of 2 to 500.

  In the general formula (1) or (2), the alkyl group or alkoxyalkyl group having 4 to 15 carbon atoms represented by R is preferably an alkyl group or alkoxyalkyl group having 6 to 10 carbon atoms.

  The substituent represented by R ′ is preferably a methyl group.

  X preferably represents an alkylene group or an arylene group, more preferably a methylene group, ethylene or propylene.

  m is preferably 0 or 1. n is preferably from 100 to 500, and most preferably from 150 to 300.

  A known synthesis method can be applied to the method for introducing an adsorbing group capable of adsorbing the poly (3-alkylthiophene) s to the nanostructure with the nano conjugate. For example, as a method for producing an SH group at the end of an aromatic ring, J. et al. Org. Chem. EN; 60; 7; 1995; 2082-2091. J. et al. Amer. Chem. Soc. EN; 116; 26; 1994; 11985-11989. , Synthesis; EN; 9; 1983; 751-755. J. et al. Chem. Soc. PerkinTrans. 1; EN; 1987; 187-194. Can be referred to. A method of making “alkylene terminal SH” in a pattern of π electron system with an alkylene group sandwiched between the terminal S and J. Amer. Chem. Soc. 70; 1948; 2439. (Reduction of isothiourea), Chem. Ber. GE; 93; 1960; 2604-2612. (Reaction in which thiourea was allowed to act on terminal alkyl halide), Tetrahedron Lett. EN; 35; 12; 1994; 1837-1840. (Addition to a double bond by a radical reaction in which triphenylsilanethiol is allowed to act on a terminal C═C double bond) can be referred to.

  Examples of other surface modifying molecules include porphyrin derivatives disclosed in Japanese Patent Application Laid-Open Nos. 2001-253883 and 2008-16834. In order to obtain porphyrin bonded to the nanostructure, a method of synthesizing a porphyrin monomer having an adsorbing group to the nanostructure by the above-described method can be used.

  In addition, according to preferable embodiment in this manufacturing method, the following characteristics are prescribed | regulated.

  The formation of the photoelectric conversion layer is preferably performed by simultaneously coating and forming the first photoelectric conversion layer forming solution and the second photoelectric conversion layer forming solution.

  The nanostructure is preferably a nanostructure made of metal, metal oxide, or carbon.

  The first solution for forming a photoelectric conversion layer includes at least one of a nanostructure made of metal, a nanostructure made of carbon, or a nanostructure formed by coating a surface modifying molecule, and / or It is preferable that the solution for forming a photoelectric conversion layer contains at least one of a metal oxide nanostructure or a nanostructure formed by coating with a surface modification molecule. At this time, it is more preferable that the first photoelectric conversion layer forming solution contains a nanostructure made of metal. Moreover, it is preferable that the said metal contains at least 1 sort (s) selected from the group which consists of Au, Ag, and Cu.

  It is preferable that either one of the first or second photoelectric conversion layer forming solution includes a nanostructure formed by coating with a surface modification molecule.

  The first photoelectric conversion layer forming solution includes a nanostructure made of metal, and the second photoelectric conversion layer forming solution is an oxide nanostructure made of metal or a nanostructure formed by coating with a surface modifying molecule It is also preferred to include a body. At this time, it is more preferable that the second solution for forming a photoelectric conversion layer includes a nanostructure made of a metal coated with a surface modifying molecule.

  The effects of the present invention will be described using the following examples and comparative examples. However, the technical scope of the present invention is not limited only to the following examples.

<Preparation of p-type semiconductor material (KP115)>
As a p-type semiconductor material, a thiazolothiazole copolymer (KP115) was synthesized according to the method described in APPHPHYSLETT, 98, (2011) p043301. The number average molecular weight of the following KP115 was 43,000.

<Preparation of surface modification molecule>
The compounds and precursors used in the following examples and comparative examples were synthesized according to a known synthesis method or commercially available.

<Production of organic photoelectric conversion element>
[Comparative Example 1-1] Production of Organic Photoelectric Conversion Element SC-101 A 150 nm thick indium tin oxide (ITO) transparent conductive film deposited on a glass substrate (sheet resistance: 10Ω / □) is used as a photolithography technique. And an auxiliary electrode (transparent electrode) were formed by patterning to a width of 20 mm using wet etching using hydrochloric acid. The auxiliary electrode on which the pattern is formed is ultrasonically cleaned using a mixture of a surfactant and ultrapure water, then ultrasonically cleaned using ultrapure water, dried with nitrogen blow, and finally cleaned with ultraviolet ozone. went. Next, in order to form a layer corresponding to the first electrode having a function as an electron transport layer, a ZnO precursor solution is spun onto the transparent electrode on the substrate on which the auxiliary electrode (transparent electrode) is formed. It was coated (rotation speed 4000 rpm, rotation time 180 seconds) and wiped off in a predetermined pattern. And the layer which consists of a ZnO film | membrane with a film thickness of about 40 nm was formed by heat-processing this at 250 degreeC for 10 minute (s) in air. The Rpv of the surface of the ZnO film measured according to JIS B 0601: 2001 was 20 nm.

  The ZnO precursor solution was prepared by the following method (sol-gel method). The precursor solution was dissolved in 2-methoxyethanol containing 0.5M zinc acetate dihydrate (Sigma-Aldrich) and 0.5M ethanolamine (Tokyo Chemical Industry).

  The work function of the obtained ZnO film was measured by the UPS method (ESCALab200R and UPS-1 manufactured by Vacuum Generators) and found to be 4.48 eV.

  Thereafter, the substrate was placed in a glove box (dew point <−80 ° C., oxygen <1 ppm), and film formation was performed in a nitrogen atmosphere.

To form the photoelectric conversion layer, o- dichlorobenzene, and KP115 synthesized _{above, PC} 60 BM (manufactured by Frontier Carbon Corporation, E100H: 6,6-phenyl _{-C 61} - butyric acid methyl ester) and 1: A solution A was prepared by dissolving what was mixed at 1 (mass ratio) at a rate of 3.0% by mass. This was formed into a film on the electron transport layer using a blade coater so that the dry film thickness was about 250 nm, thereby forming a photoelectric conversion layer.

  Thereafter, in order to form a hole transport layer, polystyrenesulfonic acid was used for a PEDOT: PSS (Clevios (registered trademark) P4083, manufactured by Heraeus) dispersion (solid content: about 3% by mass) composed of a conductive polymer and a polyanion. Solution B containing 0.1 wt% sodium (Polynas (registered trademark) PS-1, manufactured by Tosoh Organic Chemical Co., Ltd.) and 20 wt% isopropanol was prepared. The obtained solution B was filtered with a 0.45 μm PVDF filter, applied onto the photoelectric conversion layer with a blade coater so as to have a dry film thickness of about 100 nm, and dried. After wiping to a predetermined size, the film was further heated at 120 ° C. for 10 minutes to form a hole transport layer.

  In addition, it was 5.1 eV when the work function of the positive hole transport layer was measured by UPS method similarly to the work function of the said ZnO film | membrane.

Next, the substrate on which the series of functional layers is formed is moved into a vacuum deposition apparatus chamber, and the inside of the vacuum deposition apparatus is depressurized to 1 × 10 ⁻⁴ Pa or less. A second electrode was formed by laminating 100 nm at 1.0 nm / second. The obtained organic photoelectric conversion element is moved to a nitrogen chamber and sealed using a sealing cavity glass and an epoxy-based UV curable resin (manufactured by Nagase Chemtech, epoxy resin for semiconductor sealing). An organic photoelectric conversion element SC-101 having a size of about 5 mm × 20 mm was completed.

  A single film was prepared for each of the materials constituting the first electrode and the hole transport layer, and the work function was measured in the same manner as the above work function measurement method. In addition, for the organic photoelectric conversion elements of the following examples and comparative examples, the work function of the first electrode (in the comparative example, a layer corresponding to the first electrode), the first electrode (in the comparative example, the first When the surface modification molecule is contained in the layer corresponding to 1 electrode), the work function shift amount due to the adsorption of the surface modification molecule (compared with the work function of the nanostructure on which the surface modification molecule is not adsorbed) Table 1 below shows the results of the work function difference between the first electrode (in the comparative example, the layer corresponding to the first electrode) and the hole transport layer. . Table 1 also shows the value of the maximum height difference (Rpv) on the surface of the first electrode (a layer corresponding to the first electrode in the comparative example) measured according to JIS B 0601: 2001. .

[Comparative Example 1-2] Production of Organic Photoelectric Conversion Device SC-102 ZnO was prepared by the following CBD method (chemical bath deposition method) on a substrate on which a layer made of ZnO prepared in the same manner as Comparative Example 1-1 was formed. Nano pillars were formed, and a layer corresponding to the first electrode was formed.

  A solution prepared by adding a 0.01N NaOH aqueous solution dropwise to an aqueous solution containing 0.02M zinc sulfate heptahydrate and 0.6M ammonium chloride to adjust the pH to 12 was prepared. Subsequently, the prepared liquid was kept at 60 ° C., and the substrate on which the prepared ZnO layer was formed was immersed and treated for 12 hours. When the formed nano pillars of ZnO were observed with an SEM, the pillar diameter was 10 to 20 nm and the pillar height was about 80 nm. Rpv was 120 nm.

  Each layer was formed like SC-101 of the comparative example 1 except having the structure which has the ZnO nanopillar obtained as mentioned above, and obtained organic photoelectric conversion element SC-102.

  The work function of the nanostructure composed of ZnO nanopillars measured in the same manner as described above was 4.45 eV.

[Example 1-1] Preparation of organic photoelectric conversion element SC-103 In the preparation of organic photoelectric conversion element SC-102, after forming ZnO nanopillars, p-methoxybenzoic acid (compound 101, dipole) was further used as a surface modification molecule. Moment: + 3.25D) was coated, and an organic photoelectric conversion element SC-103 was obtained in the same manner as SC-102 except that the first electrode was formed.

  The surface-modifying molecule was adsorbed by dissolving p-methoxybenzoic acid (Compound 101) in methanol (solvent) to a concentration of 50 mM and immersing it in a previously formed ZnO layer for 2 hours. After adsorbing, it was washed with methanol and dried with dry air. Furthermore, it was made to dry for 10 minutes on a 120 degreeC hotplate.

[Comparative Example 1-3] Production of Organic Photoelectric Conversion Element SC-104 In the production of organic photoelectric conversion element SC-101, a layer corresponding to the first electrode was formed on the ITO film in place of the ITO and ZnO layers. Further, an organic photoelectric conversion element SC-104 was obtained in the same manner as SC-101 except that an Ag film was laminated to form a layer corresponding to the first electrode. More specifically, after the substrate is moved into the vacuum deposition apparatus chamber and the inside of the vacuum deposition apparatus is depressurized to 1 × 10 ⁻⁴ Pa or less, Ag metal is deposited at a deposition rate of 0.1 to 0.5 nm / second. A layer corresponding to the first electrode was formed by stacking 4 nm. The work function of the Ag film was measured by the method described above and found to be 4.48 eV.

[Comparative Example 1-4] Preparation of Organic Photoelectric Conversion Device SC-105 In the preparation of the organic photoelectric conversion device SC-104, instead of forming the layer corresponding to the first electrode with only ITO and Ag, surface modification molecules were further formed. Organic photoelectric conversion element SC-105 was obtained in the same manner as SC-104, except that (compound 13; dipole moment: + 3.85D) was coated.

  The surface-modifying molecule is prepared by dissolving a precursor of compound 13 (piperidine derivative) and carbon disulfide in ethanol, a precursor concentration of 50 mM, a carbon disulfide concentration of 50 mM, and a substrate provided with a pre-formed Ag film. The compound 13 was adsorbed by immersion for 60 minutes.

[Comparative Example 1-5] Production of Organic Photoelectric Conversion Device SC-106 In production of the organic photoelectric conversion device SC-104, an Ag film was laminated on the ITO film in order to form a layer corresponding to the first electrode. Thereafter, an organic photoelectric conversion element SC-106 was obtained in the same manner as SC-104, except that Ag particles were further deposited to produce a nanostructure made of Ag particles and used as the first electrode.

As the Ag particles, EMSC 60 (Ag colloid, 60 nm diameter) purchased from British Biocell International was used. Ag particles are concentrated using an ultrafiltration membrane and then dispersed in a water / ethanol mixture to prepare an Ag particle dispersion (Ag particle content 0.4 mass%). The basis weight of Ag particles is 50 mg. / M ² was applied to a glass substrate using an applicator and dried under nitrogen at 120 ° C. for 10 minutes to form a layer made of Ag particles having a thickness of 80 nm, thereby producing a first electrode. .

[Example 1-2] Preparation of organic photoelectric conversion element SC-107 In preparation of organic photoelectric conversion element SC-106, instead of forming a nanostructure made of ITO and Ag particles as the first electrode, surface modification was further performed. Organic photoelectric conversion element SC-107 was obtained in the same manner as SC-106, except that the molecule (compound 13) was coated.

  The surface modifying molecules were adsorbed on the nanostructures made of Ag particles in the same manner as SC-105.

[Comparative Example 1-6] Production of Organic Photoelectric Conversion Device SC-108 In the production of organic photoelectric conversion device SC-106, instead of producing a nanostructure made of Ag particles and forming a layer corresponding to the first electrode, Organic photoelectric conversion element SC-108 was obtained in the same manner as SC-106 except that a layer corresponding to the first electrode was formed using Au particles.

As the Au particles, EMGC60 (Au colloid, 60 nm diameter) purchased from British Biocell International was used. Silver particles are concentrated using an ultrafiltration membrane, and then dispersed in a water / ethanol mixture to prepare an Au particle dispersion (Au particle content: 0.8% by mass). The basis weight of Au particles is 100 mg. / M ² was applied to a glass substrate using an applicator, dried under nitrogen at 120 ° C. for 10 minutes to form a layer made of Au having a thickness of 80 nm, and a first electrode was produced.

[Example 1-3] Preparation of organic photoelectric conversion element SC-109 In preparation of the organic photoelectric conversion element SC-108, instead of forming the first electrode with only nanostructures made of Au particles, surface modification molecules were further formed. Organic photoelectric conversion element SC-109 was obtained in the same manner as SC-108 except that (compound 13) was coated.

  In addition, the surface modification molecule | numerator was made to adsorb | suck to the nanostructure which consists of Au particle | grains like SC-105.

[Comparative Example 1-7] Production of Organic Photoelectric Conversion Device SC-110 In production of the organic photoelectric conversion device SC-106, an Ag film was laminated on the ITO film, and then Ag nanowires were further deposited to form Ag nanowires. Organic photoelectric conversion element SC-110 was obtained in the same manner as SC-106 except that a nanostructure made of a wire was prepared to be a layer corresponding to the first electrode.

  In addition, Ag nanowire was deposited according to the following procedures.

(Preparation of dispersion 1)
Ag nanowires are described in Adv. Mater. , 2002, 14, 833 to 837, after preparing Ag nanowires having an average diameter of 75 nm and an average length of 10 μm, and filtering and washing the Ag nanowires using an ultrafiltration membrane Then, it was re-dispersed in ethanol to prepare an Ag nanowire dispersion (Ag nanowire content: 5% by mass).

  The ITO-deposited film substrate was cleaned in the order of ultrasonic cleaning with a surfactant and ultrapure water, followed by ultrasonic cleaning with ultrapure water, dried with nitrogen blow, and finally subjected to ultraviolet ozone cleaning.

On the ITO deposited film substrate, the dispersion 1 was applied and dried using an applicator so that the basis weight of Ag nanowires was 80 mg / m ² , thereby producing a first electrode.

[Comparative Example 1-8] Production of Organic Photoelectric Conversion Device SC-111 In the production of the organic photoelectric conversion device SC-110, only a nanostructure composed of ITO, an Ag film, and Ag nanowires was used as the layer corresponding to the first electrode. An organic photoelectric conversion device SC-111 was obtained in the same manner as SC-110 except that the surface modification molecule (1-butanethiol; dipole moment: + 2.05D) was further coated instead of the above.

  The surface modifying molecule was adsorbed by dissolving 1-butanethiol in methanol (solvent) to a concentration of 50 mM and immersing in the Ag nanostructure formed above for 60 minutes.

[Comparative Example 1-9] Production of Organic Photoelectric Conversion Device SC-112 In production of the organic photoelectric conversion device SC-111, the surface modification molecule was changed to Compound 4 (dipole moment: -2.89D). Organic photoelectric conversion element SC-112 was obtained in the same manner as -111.

  In addition, the surface modification molecule | numerator was made to adsorb | suck to the nanostructure which consists of Ag nanowire like SC-105. Moreover, the work function shift amount in Table 1 being a negative value indicates that the work function of the layer corresponding to the first electrode is increased by adsorbing the surface modifying molecules (SC-110). And comparison).

[Comparative Example 1-10] Preparation of Organic Photoelectric Conversion Element SC-114 In the preparation of organic photoelectric conversion element SC-111, the surface modification molecule was changed to Compound 2 (dipole moment: + 1.91D). In the same manner as in 111, an organic photoelectric conversion element SC-114 was obtained.

[Example 1-4] Preparation of organic photoelectric conversion element SC-115 In the preparation of organic photoelectric conversion element SC-111, the surface modification molecule was changed to compound 19 (dipole moment: + 3.30D). In the same manner as in 111, an organic photoelectric conversion element SC-115 was obtained.

[Example 1-5] Preparation of organic photoelectric conversion element SC-116 In the preparation of organic photoelectric conversion element SC-111, the surface modification molecule was changed to compound 13 (dipole moment: + 3.85D). In the same manner as in 111, an organic photoelectric conversion element SC-116 was obtained.

[Example 1-6] Preparation of organic photoelectric conversion element SC-117 In the preparation of organic photoelectric conversion element SC-111, the surface modification molecule was changed to compound 21 (dipole moment: + 6.39D). In the same manner as in 111, an organic photoelectric conversion element SC-117 was obtained.

[Example 1-7] Preparation of organic photoelectric conversion element SC-118 In the preparation of organic photoelectric conversion element SC-111, the surface modification molecule was changed to compound 55 (dipole moment: + 3.06D). In the same manner as in 111, an organic photoelectric conversion element SC-118 was obtained.

[Example 1-8] Preparation of organic photoelectric conversion element SC-119 In preparation of organic photoelectric conversion element SC-111, the surface modification molecule was changed to p-methoxybenzenethiol (compound 102, dipole moment: + 3.05D). Except that, organic photoelectric conversion element SC-119 was obtained in the same manner as SC-111.

<Evaluation of conversion efficiency>
About the photoelectric conversion element produced in the said Examples 1-1 to 1-8 and Comparative Examples 1-1 to 1-10, the light of the intensity | strength of 100 mW / cm < ² > of a solar simulator (AM1.5G filter) is irradiated, and it is effective. A mask having an area of 1 cm ² is overlaid on the light receiving portion, and a short-circuit current density J _sc [mA / cm ² ], an open circuit voltage V _oc [V], and a fill factor FF are formed on the same element. Each light receiving part was measured and the average value was obtained. Moreover, photoelectric conversion efficiency (eta) (%) was calculated | required according to Formula (1) from the calculated | required short circuit current density Jsc, the open circuit voltage Voc, and the fill factor FF. Here, it shows that energy conversion efficiency (photoelectric conversion efficiency) is so favorable that the number of photoelectric conversion efficiency (eta) (%) is large.

[Evaluation]
Table 1 shows relative values when the photoelectric conversion efficiency η of Comparative Example 1-1 (SC-101) produced above is set to 100 for the light conversion efficiency η of each Example and Comparative Example.

<Evaluation of photothermal stability>
A photoelectric conversion element manufactured by the above placed 85 ° C. on a hot plate 2 using a wavelength type white LED (Toshiba small SMD) light source, a short-circuit current density J _sc measured in the evaluation of the photoelectric conversion efficiency The light amount of the LED was adjusted so as to be approximately the same value (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, and the ratio [%] of J _sc after light irradiation to the initial J _sc was obtained. The results of Examples and Comparative Examples are shown in Table 1.

[Evaluation]
A: The ratio of J _sc after light irradiation to the initial J _sc is 90% or more. ○: The ratio of J _sc after light irradiation to the initial J _sc is 80% or more and less than 90%. Δ: J after light irradiation to the initial J _sc . The ratio of _sc is 70% or more and less than 80% x: The ratio of J _sc after light irradiation to the initial J _sc is less than 70%

The organic photoelectric conversion elements of the examples are obtained by adsorbing surface-modifying molecules having a dipole moment on nanostructures having a work function larger than 4.3 eV. As is apparent from Table 1 above, with this configuration, the first work function is smaller than the nanostructure by a work function of 0.2 eV or more and 0. 0 than the work function of the hole transport layer. It can be seen that the photoelectric conversion element including the first electrode shifted so as to be smaller than 7 eV has high photoelectric conversion efficiency, and a stable element with little decrease in J _sc due to light irradiation is obtained. Furthermore, when a compound in which an electron-donating substituent is bonded to an adsorbing group is used as the surface modifying molecule, the work function of the first electrode can be particularly greatly shifted, and a practical potential difference between the electrodes can be achieved. Can do.

  Conversely, the organic photoelectric conversion element (Comparative Examples 1-5, 1-6, and 1-7) including the first electrode that has the nanostructure and does not have the surface modification molecule, and the first electrode The organic photoelectric conversion element (Comparative Example 1-8) including the first electrode containing the surface-adsorbed molecules that cannot shift the work function to an appropriate size cannot improve both the conversion efficiency and the light stability. It has been shown.

<Preparation of normal layer type organic photoelectric conversion element>
[Comparative Example 2-1] Production of Organic Photoelectric Conversion Device SC-201 An organic photoelectric conversion device described in Japanese Patent No. 4188389 was produced as follows.

(Formation of transparent electrode)
A first 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. The electrode was formed. The patterned first electrode (anode) is cleaned in the order of ultrasonic cleaning with surfactant and ultrapure water, followed by ultrasonic cleaning with ultrapure water, dried with nitrogen blow, and finally UV ozone cleaning. It was.

(Formation of hole transport layer)
Next, PEDOT-PSS (CLEVIOS (registered trademark) P VP AI 4083, manufactured by Helios Co., Ltd., conductivity 1 × 10 ⁻³ S / cm) made of a conductive polymer and a polyanion is 3.0 as a hole transport layer. An isopropanol solution containing by mass% was prepared, and the substrate was applied and dried using a blade coater whose temperature was adjusted to 65 ° C. so that the dry film thickness was about 30 nm. Thereafter, heat treatment was carried out with warm air of 120 ° C. for 20 seconds to form a hole transport layer on the first electrode.

(Formation of photoelectric conversion layer)
Subsequently, MET-PPV (methoxyphenylene vinylene) and CN-PPV (poly (cyanophenylene-vinylene)) ("CN-PPV") are added to o-dichlorobenzene at 7: 3 (mass ratio), 3: 7. What was mixed by (mass ratio) was dissolved in the ratio of 3.0 mass%, and the solution A (1st solution for photoelectric conversion layer formation) and the solution B (2nd solution for photoelectric conversion layer formation) were prepared, respectively. did. After forming the solution A to a dry film thickness of 50 nm by an inkjet method, the solution B is formed to a dry film thickness of 50 nm, and photoelectric conversion is performed so that the total film thickness is 100 nm. A layer was formed.

  The formed photoelectric conversion layer was patterned in a predetermined pattern by wiping.

(Formation of buffer layer and second electrode)
Next, the board | substrate which formed the film to the said photoelectric converting layer was installed in the vacuum evaporation system. Then, the element was set so that the shadow mask with a width of 10 mm was orthogonal to the transparent electrode, and the inside of the vacuum deposition apparatus was depressurized to 10 ⁻³ Pa or less, and then LiF 0.6 nm at a deposition rate of 0.05 nm / second, then A buffer layer and a second electrode (cathode) were formed by depositing Al at a deposition rate of 2 nm / sec.

(Sealing of organic photoelectric conversion elements)
The obtained organic photoelectric conversion element was moved to a nitrogen chamber, and sandwiched between ^two 3M Ultra Barrier Solar Film UBL-9L (water vapor transmission rate <5 × 10 ⁻⁴ g / m ² / d), UV After sealing using a curable resin (manufactured by Nagase ChemteX Corporation, UV RESIN XNR5570-B1), it is taken out into the atmosphere, the light receiving part is about 10 × 10 mm in size, and the film thickness of the photoelectric conversion layer is 100 nm. Organic photoelectric conversion element SC-201 was produced.

  Further, in the formation of the photoelectric conversion layer, the first photoelectric conversion layer forming solution and the second photoelectric conversion layer forming solution are formed by 150 nm each, so that the total film thickness becomes 300 nm. An organic photoelectric conversion element SC-201 having a photoelectric conversion layer thickness of 300 nm was prepared in the same manner as described above except that the film was formed.

[Comparative Example 2-2] Production of Organic Photoelectric Conversion Device SC-202 The formation of the hole transport layer was performed in the same manner as SC-201.

(Formation of photoelectric conversion layer)
As a p-type semiconductor material, Adv. Mater. , Vol. 19, (2007), p2295, and a polythiophene-carbazole-benzothiadiazole copolymer (PCDTBT) was synthesized.

A mixture of PCDTBT and PC ₆₀ BM synthesized above at a ratio of 7: 3 (mass ratio) and 3: 7 (mass ratio) was dissolved in o-dichlorobenzene at a ratio of 3.0 mass%, and each solution C (First solution for forming a photoelectric conversion layer) and Solution D (second solution for forming a photoelectric conversion layer) were prepared.

  Two blades are continuously arranged on the coater set at 80 ° C., and the solution C is formed on the blade formed on the lower layer (the front side with respect to the traveling direction), and the film formed on the upper layer (the traveling direction). On the other hand, the solution D was set on the blade on the rear side, and coating film formation was performed at a coating speed of 10 mm / s to form a photoelectric conversion layer having a dry film thickness of 100 nm.

  Thereafter, a buffer layer and a second electrode were formed in the same manner as SC-201, and sealing was performed to produce an organic photoelectric conversion element SC-202 having a photoelectric conversion layer thickness of 100 nm.

  Further, in the formation of the photoelectric conversion layer, the coating speed of the solutions C and D was changed to 40 mm / s, and the photoelectric conversion layer was formed in the same manner as above except that a photoelectric conversion layer having a dry film thickness of 300 nm was formed. An organic photoelectric conversion element SC-202 having a film thickness of 300 nm was produced.

[Comparative Example 2-3] Production of Organic Photoelectric Conversion Device SC-203 The formation of the hole transport layer was performed in the same manner as SC-201.

(Formation of photoelectric conversion layer)
Angew, Chem, Int, Ed. (2011), 50, 5519-5523, PVP-protected Au nanoparticles were prepared. The obtained Au nanoparticles had a truncated octahedral structure, and the particle size was 70 nm ± 10 nm.

in o- dichlorobenzene, and PCDTBT synthesized in Comparative Example _{2, PC} 60 BM 5: 5 Au nanoparticles prepared above solution was stirred overnight (mass ratio) was added 5 wt% 10 minutes ultrasonic Solution E prepared by dispersing was prepared.

  A blade was placed on the coater, and coating of the solution E was performed at a coating speed of 20 mm / s to form a photoelectric conversion layer having a dry film thickness of 100 nm.

  Thereafter, a buffer layer and a second electrode were formed in the same manner as SC-201, and sealing was performed to produce an organic photoelectric conversion element SC-203 having a photoelectric conversion layer thickness of 100 nm.

  Further, in the formation of the photoelectric conversion layer, the film thickness of the photoelectric conversion layer was changed by the same method as above except that the coating speed of the solution E was changed to 60 mm / s and the photoelectric conversion layer having a dry film thickness of 300 nm was formed. Produced an organic photoelectric conversion element SC-203 having a thickness of 300 nm.

[Example 2-1] Production of organic photoelectric conversion element SC-204 After applying the first photoelectric conversion layer forming solution by the blade method, the second photoelectric conversion layer forming solution was applied by sequential application. Except for the above, SC-204 having a dry film thickness of the photoelectric conversion layer of 100 nm and 300 nm was prepared in the same manner as SC-202, respectively.

When forming the photoelectric conversion layer, the PCDTBT synthesized in Comparative Example 2-2 and PC ₆₀ BM are stirred at 5: 5 (mass ratio) all day and night on the lower layer side (first photoelectric conversion layer). A solution E (first photoelectric conversion layer forming solution) prepared by adding 5% by mass of Au nanoparticles prepared in Comparative Example 2-3 to 100% by mass of the prepared solution and ultrasonically dispersing for 10 minutes. The upper layer side (second photoelectric conversion layer) uses the solution PCDTBT and the solution G (second photoelectric conversion layer forming solution) prepared by stirring the PC ₆₀ BM at 5: 5 (mass ratio) all day and night. did.

[Example 2-2] Preparation of organic photoelectric conversion element SC-205 CARBON. (2012) With reference to 40-46, carbon nanotubes (ODA-CNT) whose surface was modified with octadecylamine were prepared. The obtained ODA-CNT had an average diameter of 2 nm and an average length of about 55 μm.

  SC-205 having a dry thickness of the photoelectric conversion layer of 100 nm and 300 nm was prepared by the same method as SC-202, respectively.

When forming the photoelectric conversion layer, on the lower layer side (first photoelectric conversion layer), PCDTBT and PC ₆₀ BM synthesized in the above Comparative Example 2-2 were mixed with o-dichlorobenzene at 5: 5 (mass). The solution F (for the formation of the first photoelectric conversion layer) prepared by adding 0.2% by mass of ODA-CNT prepared previously to 100% by mass of the solution and agitating ultrasonically for 10 minutes. Solution G) was prepared by stirring PCDTBT and PC ₆₀ BM at 5: 5 (mass ratio) all day and night on the upper layer side (second photoelectric conversion layer) (second photoelectric conversion layer forming solution). It was used.

[Example 2-3] Production of organic photoelectric conversion element SC-206 SC-206 having a dry film thickness of 100 nm and 300 nm of the photoelectric conversion layer was produced in the same manner as SC-202.

When the photoelectric conversion layer is formed, the lower layer side is the solution G (first photoelectric conversion layer forming solution), and the upper layer side is PCDTBT and PC ₆₀ BM synthesized in o-dichlorobenzene in Comparative Example 2 above. 5: 5 (mass ratio) of 5% by mass of toluene-dispersed TiO ₂ nanoparticles (CAI Kasei Co., Ltd., average particle size 50 nm) was added to 100% by mass of the solution and stirred for 10 minutes. A solution H (second solution for forming a photoelectric conversion layer) prepared by dispersing was used.

[Example 2-4] Preparation of organic photoelectric conversion element SC-207 Chem, Mater. (2002), 14, 4736-4745, PVP-protected Ag nanowires (AgNW) were prepared. The obtained AgNW had an average diameter of 30 to 40 nm and an average length of about 50 μm.

SC-207 having a dry thickness of the photoelectric conversion layer of 100 nm and 300 nm was prepared by the same method as SC-202, respectively. When forming the photoelectric conversion layer, on the lower layer side, a solution prepared by stirring PCDTBT synthesized in the above Comparative Example 2-2 in the above Comparative Example 2-2 and PC ₆₀ BM at 5: 5 (mass ratio) all day and night is used. Solution I (first photoelectric conversion layer forming solution) prepared by adding 20% by mass of the prepared AgNW to 100% by mass of the solution and ultrasonically dispersing for 10 minutes. Photoelectric conversion layer forming solution) was used.

[Example 2-5] Preparation of organic photoelectric conversion element SC-208 Angew, Chem, Int, Ed. (2011), 50, 5519-5523, PVP-protected Au nanoparticles were prepared. The obtained Au nanoparticles had a truncated octahedral structure, and the particle size was 70 nm ± 10 nm.

  After adding 10 equivalents of compound g to the PVP-protected Au nanoparticles prepared above and stirring for 10 minutes, the precipitate obtained by centrifuging at 5000 rpm for 20 minutes was redispersed in ultrapure water, and compound g Coated Au nanoparticles were obtained.

PCDTBT synthesized in o-dichlorobenzene in the above Comparative Example 2-2 and PC ₆₀ BM were stirred overnight at 5: 5 (mass ratio) with compound g-coated Au nanoparticles at 5% by mass with respect to 100% by mass of the solution. Solution J was prepared by adding and ultrasonically dispersing for 10 minutes.

  SC-108 with a dry film thickness of the photoelectric conversion layer of 100 nm and 300 nm was prepared by the same method as SC-202, respectively. When forming the photoelectric conversion layer, the solution G (first photoelectric conversion layer forming solution) was used on the lower layer side, and the solution J (second photoelectric conversion layer forming solution) was used on the upper layer side.

[Example 2-6] Production of organic photoelectric conversion element SC-209 To PVP-protected AgNW prepared in Example 2-4, 10 equivalents of compound j was added and stirred for 10 minutes, followed by centrifugation at 5000 rpm for 20 minutes. The precipitate thus obtained was redispersed in ultrapure water to obtain compound j-coated AgNW.

Compound j-coated AgNW was 0.2% by mass with respect to 100% by mass of the solution in PCDTBT synthesized in o-dichlorobenzene and PC 60BM synthesized in Comparative Example 2-2 and PC ₆₀ BM at 5: 5 (mass ratio). The solution K was prepared by adding and ultrasonically dispersing for 10 minutes.

  SC-209 having a dry thickness of the photoelectric conversion layer of 100 nm and 300 nm was prepared by the same method as SC-202, respectively. When forming the photoelectric conversion layer, the solution G (first photoelectric conversion layer forming solution) was used on the lower layer side, and the solution K (second photoelectric conversion layer forming solution) was used on the upper layer side.

[Example 2-7] Production of organic photoelectric conversion device SC-210 To PVP-protected Au nanoparticles prepared in Example 2-5, 10 equivalents of compound e was added and stirred for 10 minutes, and then centrifuged at 5000 rpm for 20 minutes. The precipitate obtained by performing the above was redispersed in ultrapure water to obtain Compound e-coated Au nanoparticles.

Compound e-coated Au nanoparticles were added to a solution obtained by stirring PCDTBT synthesized in o-dichlorobenzene in the above Comparative Example 2-2 and PC ₆₀ BM at 5: 5 (mass ratio) overnight for 5% by mass with respect to 100% by mass of the solution. The solution L was prepared by adding and ultrasonically dispersing for 10 minutes.

  SC-210 having a dry thickness of the photoelectric conversion layer of 100 nm and 300 nm was prepared by the same method as SC-202, respectively. When forming the photoelectric conversion layer, the solution L (first photoelectric conversion layer forming solution) was used on the lower layer side, and the solution G (second photoelectric conversion layer forming solution) was used on the upper layer side.

[Example 2-8] Production of organic photoelectric conversion element SC-211 Toluene was added to a solution in which PCDTBT synthesized in the above Comparative Example 2-2 and PC ₆₀ BM were stirred in o-dichlorobenzene at 5: 5 (mass ratio) overnight. Dispersed ZnO nanoparticles (manufactured by C-I Kasei Co., Ltd., average particle size 60 nm) were added at 5% by mass with respect to 100% by mass of the solution, and ultrasonically dispersed for 10 minutes to prepare Solution M.

  SC-211 having a dry thickness of the photoelectric conversion layer of 100 nm and 300 nm was prepared in the same manner as SC-202, respectively. When forming the photoelectric conversion layer, the solution E (first photoelectric conversion layer forming solution) was used on the lower layer side, and the solution M (second photoelectric conversion layer forming solution) was used on the upper layer side.

[Example 2-9] Production of organic photoelectric conversion element SC-212 SC-212 having a dry film thickness of 100 nm and 300 nm was produced by the same method as SC-202, respectively. When forming the photoelectric conversion layer, the solution E (first photoelectric conversion layer forming solution) was used on the lower layer side, and the solution H (second photoelectric conversion layer forming solution) was used on the upper layer side.

[Example 2-10] Production of organic photoelectric conversion element SC-213 SC-213 having a dry film thickness of 100 nm and 300 nm of the photoelectric conversion layer was produced in the same manner as SC-202. When forming the photoelectric conversion layer, the solution I (first photoelectric conversion layer forming solution) was used on the lower layer side, and the solution J (second photoelectric conversion layer forming solution) was used on the upper layer side.

[Example 2-11] Production of organic photoelectric conversion element SC-214 To PVP-protected Au nanoparticles prepared in Example 2-5, 10 equivalents of compound k was added and stirred for 10 minutes, and then centrifuged at 5000 rpm for 20 minutes. The precipitate obtained by performing the above was redispersed in ultrapure water to obtain compound k-coated Au nanoparticles.

Compound k-coated Au nanoparticles were added in an amount of 5% by mass to 100% by mass of the solution in PCDTBT and PC ₆₀ BM synthesized in Comparative Example 2 above in o-dichlorobenzene at 5: 5 (mass ratio). Solution N was prepared by ultrasonic dispersion for 10 minutes.

  SC-214 having a dry film thickness of the photoelectric conversion layer of 100 nm and 300 nm was prepared in the same manner as SC-202, respectively. When forming the photoelectric conversion layer, the solution E (first photoelectric conversion layer forming solution) was used on the lower layer side, and the solution N (second photoelectric conversion layer forming solution) was used on the upper layer side.

<Evaluation of conversion efficiency>
About the photoelectric conversion element produced in the said Examples 2-1 to 2-11 and Comparative Examples 2-1 to 2-3, the short circuit current density _Jsc [mA / cm < ² >] and the open circuit voltage V were carried out by the method similar to the above. _oc [V] and fill factor (fill factor) FF were measured and the average value was determined. Moreover, photoelectric conversion efficiency (eta) (%) was calculated | required according to the said Formula (1) from the calculated | required short circuit current density Jsc, the open circuit voltage Voc, and the fill factor FF.

  Tables 2 and 3 show the layer configurations and results of the above Examples and Comparative Examples.

  In the table, PCE is an abbreviation for Power Conversion Efficiency and refers to photoelectric conversion efficiency.

<Preparation of reverse layer type organic photoelectric conversion element>
[Comparative Example 2-4] Preparation of Organic Photoelectric Conversion Element SC-301 (Formation of Transparent Electrode)
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. The electrode (cathode) was formed. The patterned second electrode was washed in the order of ultrasonic cleaning with a surfactant and ultrapure water, followed by ultrasonic cleaning with ultrapure water, dried with nitrogen blow, and finally subjected to ultraviolet ozone cleaning.

(Formation of electron transport layer)
On this second electrode, a 0.05 mass% methoxyethanol solution of 3- (2-aminoethyl) -aminopropyltrimethoxysilane manufactured by Aldrich was used with a blade coater so that the dry film thickness was about 5 nm. And dried. Thereafter, a heat treatment was performed at 120 ° C. for 1 minute on a hot plate to form an electron transport layer.

(Formation of photoelectric conversion layer)
Two blades are continuously arranged on the coater set at 80 ° C., the solution D (second photoelectric conversion layer forming solution) is formed on the blade formed on the lower layer, and the film formed on the upper layer. A solution C (first solution for forming a photoelectric conversion layer) was set on the blade, and a coating film was formed at a coating speed of 10 mm / s to form a photoelectric conversion layer having a dry film thickness of 100 nm.

(Formation of hole transport layer)
After completion of drying of the photoelectric conversion layer, it is taken out again into the atmosphere, and then, as a hole transport layer, PEDOT-PSS (CLEVIOS (registered trademark) PVP AI 4083, manufactured by Helios Co., Ltd. (1 × 10 ⁻³ S / cm) was diluted with an equal amount of isopropanol, and applied and dried using a blade coater so that the dry film thickness was about 30 nm. Then, it heat-processed for 20 second with 90 degreeC warm air, and formed the positive hole transport layer (organic material layer) which consists of organic substance.

Next, the element was set so that the shadow mask with a width of 10 mm was orthogonal to the transparent electrode, the inside of the vacuum deposition apparatus was depressurized to 1 × 10 ⁻³ Pa or less, and then Ag metal was deposited at a deposition rate of 0.5 nm / second. A first electrode (anode) was formed by laminating 200 nm. The obtained laminate was moved to a nitrogen chamber and sandwiched between UBF-9L (water vapor transmission rate 5.0 × 10 ⁻⁴ g / m ² / d) manufactured by Sumitomo 3M Co., Ltd., and UV curable resin (Nagase Chem) After sealing using Tex Co., Ltd. UV RESIN XNR5570-B1), it was taken out into the atmosphere to obtain an organic photoelectric conversion element SC-301 having a light receiving portion of about 10 × 10 mm size.

  Further, in the formation of the photoelectric conversion layer, the first photoelectric conversion layer forming solution and the second photoelectric conversion layer forming solution are formed by 150 nm each, so that the total film thickness becomes 300 nm. An organic photoelectric conversion element SC-301 having a photoelectric conversion layer thickness of 300 nm was produced in the same manner as described above except that was formed.

[Comparative Example 2-5] Preparation of Organic Photoelectric Conversion Element SC-302 The process was the same as SC-301 until the formation of the electron transport layer.

(Formation of photoelectric conversion layer)
A squeegee was placed on the coater, and coating of the solution E was performed at a coating speed of 20 mm / s to form a photoelectric conversion layer having a dry film thickness of 100 nm.

  Thereafter, a hole transport layer and a second electrode were formed and sealed in the same manner as SC-201, and an organic photoelectric conversion element SC-302 having a photoelectric conversion layer thickness of 100 nm was produced.

  Further, in the formation of the photoelectric conversion layer, the film thickness of the photoelectric conversion layer was changed by the same method as above except that the coating speed of the solution E was changed to 60 mm / s and the photoelectric conversion layer having a dry film thickness of 300 nm was formed. Produced an organic photoelectric conversion element SC-302 having a thickness of 300 nm.

[Example 2-12] Production of organic photoelectric conversion element SC-303 SC-303 having a dry film thickness of 100 nm and 300 nm of the photoelectric conversion layer was produced in the same manner as SC-301. When forming the photoelectric conversion layer, the solution G (second photoelectric conversion layer forming solution) was used on the lower layer side, and the solution E (first photoelectric conversion layer forming solution) was used on the upper layer side.

[Example 2-13] Production of organic photoelectric conversion element SC-304 SC-304 having a dry film thickness of 100 nm and 300 nm was produced by the same method as SC-301, respectively. When forming the photoelectric conversion layer, the solution K (second photoelectric conversion layer forming solution) was used on the lower layer side, and the solution G (first photoelectric conversion layer forming solution) was used on the upper layer side.

[Example 2-14] Production of organic photoelectric conversion element SC-305 SC-305 having a dry film thickness of 100 nm and 300 nm of the photoelectric conversion layer was produced in the same manner as SC-301. When forming the photoelectric conversion layer, the solution G (second photoelectric conversion layer forming solution) was used on the lower layer side, and the solution L (first photoelectric conversion layer forming solution) was used on the upper layer side.

[Example 2-15] Production of organic photoelectric conversion element SC-306 SC-306 having a dry thickness of 100 nm and 300 nm of the photoelectric conversion layer was produced in the same manner as SC-202. When forming the photoelectric conversion layer, the solution J (second photoelectric conversion layer forming solution) was used on the lower layer side, and the solution I (first photoelectric conversion layer forming solution) was used on the upper layer side.

[Example 2-16] Production of organic photoelectric conversion element SC-307 SC-307 having a dry thickness of 100 nm and 300 nm of the photoelectric conversion layer was produced in the same manner as SC-202. When forming the photoelectric conversion layer, the solution N (second photoelectric conversion layer forming solution) was used on the lower layer side, and the solution E (first photoelectric conversion layer forming solution) was used on the upper layer side.

  Tables 4 and 5 show the layer configurations and the conversion efficiency evaluation results of the above examples and comparative examples.

  From the above results, the organic photoelectric conversion elements of Examples were organic photoelectric conversion elements having high FF and Jsc and excellent photoelectric conversion efficiency. Further, when the organic photoelectric conversion layer was made thicker, the decrease in FF was small and Jsc was improved, so that an organic photoelectric conversion element excellent in photoelectric conversion efficiency was obtained. Moreover, it was a photoelectric conversion element with high photoelectric conversion efficiency irrespective of a layer structure.

10, 20, 30 organic photoelectric conversion element,
1 transparent conductive film,
2,2 'nanostructure,
2a microstructure (nanowire),
2a 'microstructure (nanoparticle),
3 surface modifying molecules,
11 cathode (first electrode),
12 Anode (second electrode),
14 photoelectric conversion layer,
14a 1st photoelectric conversion layer,
14b second photoelectric conversion layer,
25 substrates,
26 hole transport layer,
27 electron transport layer,
38 Charge recombination layer (intermediate layer).

Claims (7)

An organic photoelectric conversion element having a first electrode, a bulk heterojunction photoelectric conversion layer, a hole transport layer, and a second electrode in this order,
The first electrode includes a nanostructure having a work function larger than 4.3 eV measured by ultraviolet photoelectron spectroscopy, and a surface modifying molecule having a dipole moment and adsorbed on the surface of the nanostructure. Including
The organic photoelectric conversion element, wherein a work function of the first electrode is 0.2 eV or more smaller than a work function of the nanostructure and 0.7 eV or less smaller than a work function of the hole transport layer.   The organic photoelectric conversion element according to claim 1, wherein the nanostructure is made of metal nanowires or metal nanoparticles.   The organic photoelectric conversion element according to claim 1 or 2, wherein the metal forming the nanostructure includes at least one selected from the group consisting of Au, Ag, Cu, W, and Zn.   The said surface modification molecule | numerator has the adsorption group adsorb | sucked to the metal which forms the said nanostructure, and the electron-donating substituent couple | bonded with this adsorption group of any one of Claims 1-3. Organic photoelectric conversion element. The surface modification molecule has an -SH group or -CS ₂ groups, organic photoelectric conversion device according to any one of claims 1-4.   The organic photoelectric conversion element according to any one of claims 1 to 5, wherein a dipole moment of the surface modification molecule is + 3.0D to + 10.0D.   The solar cell which has an organic photoelectric conversion element of any one of Claims 1-6.