JP6733455B2 - Photoelectric conversion element, solar cell and solar cell module - Google Patents

Description

The present invention relates to a photoelectric conversion element, a solar cell, and a solar cell module.

In recent years, electronic devices using organic semiconductors, particularly organic thin film solar cells (OPV), have been actively studied. Organic thin-film solar cells generally have a structure in which an active layer is formed between a pair of electrodes and the electrodes. An example of adding nanoparticles has been reported.
For example, Patent Document 1 includes an organic thin film layer containing a first organic compound having a dye capable of absorbing light, a second organic compound having an electron accepting property, and inorganic nanoparticles. Examples of organic thin-film solar cells are described. Furthermore, Non-Patent Document 1 describes an example of producing an organic solar cell using a coating liquid containing P3HT, PCBM, and zinc oxide.

JP, 2009-158730, A

Solar Energy Materials & Solar Cells 134. (2015) 291-297

Assuming that the organic thin-film solar cell is used outdoors, not only conversion efficiency, but also high light resistance with little decrease in photoelectric conversion efficiency with respect to light is required. However, according to the study by the present inventors, it has been found that it may be difficult to achieve high light resistance with the organic thin film solar cells described in Patent Document 1 and Non-Patent Document 1.
The present invention is to solve the above problems, and an object of the present invention is to provide a photoelectric conversion element, a solar cell, and a solar cell module having high light resistance with less deterioration of photoelectric conversion efficiency even when exposed to light for a long time. And

As a result of intensive studies made by the present inventors in view of the above-mentioned circumstances, they have found that the inorganic nanoparticles are appropriately dispersed in the active layer to achieve the above object, and have accomplished the present invention. That is, the gist of the present invention is as follows.

[1] At least a pair of electrodes and an active layer between the pair of electrodes are provided on the element substrate,
The active layer contains a p-type organic semiconductor compound, an n-type semiconductor compound, and inorganic nanoparticles, and the presence of the inorganic nanoparticles at a depth of 1/3 of the active layer from the upper interface of the active layer. Amount M ₁ , the amount of inorganic nanoparticles present from a depth of 1/3 of the active layer to a depth of 2/3 of the active layer is M ₂ , and a depth of 2/3 of the active layer to the depth of the active layer. the abundance of the inorganic nanoparticles in depth up to the lower side surface when the _{M 3, M} 1 / _{M 2} and _M 3 / _{M 2} is state, and are 0.7 to 1.3, respectively, wherein The number density of the inorganic nanoparticles in the cross section of the active layer is 25/μm ²
The photoelectric conversion device characterized der Rukoto 500 / [mu] m ² or less.
[ 2 ] At least a pair of electrodes and an active layer between the pair of electrodes are provided on the element substrate,
The active layer contains a p-type organic semiconductor compound, an n-type semiconductor compound, and inorganic nanoparticles.
And the amount of inorganic nanoparticles present at a depth of 1/3 of the active layer from the upper interface of the active layer.
M ₁ , the presence of inorganic nanoparticles from a depth of 1/3 of the active layer to a depth of 2/3 of the active layer
The amount of M ₂ is the inorganic at a depth of 2/3 of the active layer to the lower interface of the active layer.
When the amount of nanoparticles is M ₃ , M ₁ /M ₂ and M ₃ /M ₂ are each 0.7 or more.
Upper 1.3 or less, and the major axis length is 10 nm with respect to the total number of the inorganic nanoparticles in the active layer.
The photoelectric conversion element, wherein the proportion of more than 100nm or less of the inorganic nanoparticles is 70% or more.
[ 3 ] At least a pair of electrodes and an active layer between the pair of electrodes are provided on the element substrate,
The active layer contains a p-type organic semiconductor compound, an n-type semiconductor compound, and inorganic nanoparticles.
And the amount of inorganic nanoparticles present at a depth of 1/3 of the active layer from the upper interface of the active layer.
M ₁ , the presence of inorganic nanoparticles from a depth of 1/3 of the active layer to a depth of 2/3 of the active layer
The amount of M ₂ is the inorganic at a depth of 2/3 of the active layer to the lower interface of the active layer.
When the amount of nanoparticles is M ₃ , M ₁ /M ₂ and M ₃ /M ₂ are each 0.7 or more.
And the above 1.3 or less, the photoelectric conversion element, wherein the energy difference of the conduction band bottom of the LUMO energy level and the inorganic nanoparticles of the n-type semiconductor compound is less than 1.0 eV.
[ 4 ] The inorganic nanoparticles are zinc oxide or titanium oxide [1] to [ 3 ]
] The photoelectric conversion element in any one of these.
[ 5 ] A solar cell having the photoelectric conversion element according to any one of [1] to [ 4 ].
[ 6 ] A solar cell module having the solar cell according to [ 5 ].

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a photoelectric conversion element, a solar cell, and a solar cell module having a high light resistance, in which the photoelectric conversion efficiency is less likely to decrease even when exposed to light for a long time.

It is sectional drawing which shows the structure of the photoelectric conversion element as one Embodiment of this invention typically. It is sectional drawing which shows the structure of the solar cell as one Embodiment of this invention typically. It is sectional drawing which shows the structure of the solar cell module as one Embodiment of this invention typically.

Embodiments of the present invention will be described in detail below. The description of the constituent elements described below is an example (representative example) of the embodiment of the present invention, and the present invention is not specified to these contents unless the gist thereof is exceeded.

The photoelectric conversion element according to the present invention has at least a pair of electrodes and an active layer between the pair of electrodes on the element substrate.

As shown in FIG. 1, one embodiment of the photoelectric conversion element according to the present invention is such that a lower electrode 101, a lower buffer layer 102, an active layer 103, an upper buffer layer 104, and an upper electrode are provided on an element substrate 106. 105 has a layered structure formed in sequence. In the present invention, the lower electrode means an electrode stacked on the element substrate 106 side, and the upper electrode means an electrode stacked above the lower electrode when the element substrate 106 is the bottom. .. In the present invention, the lower electrode 101 and the upper electrode 105 may be collectively referred to as a pair of electrodes. Further, the lower buffer layer 102 and the upper buffer layer 104 are not essential structures and may be provided arbitrarily, and may have only one of the lower buffer layer 102 and the upper buffer layer 104. Further, the photoelectric conversion element may optionally have another layer other than the above. Hereinafter, each constituent member of the photoelectric conversion element will be described.

<1-1. Element substrate 106>

Each layer forming the photoelectric conversion element 107 is usually formed on the element substrate 106 that serves as a support. There is no particular limitation on the material of the element substrate 106. Suitable examples of the material of the element substrate 106 include quartz, glass, an inorganic material such as sapphire or titania, and a flexible substrate. Specific examples of the flexible substrate include, but are not limited to, polyethylene terephthalate, polyethylene naphthalate, polyether sulfone, polyimide, nylon, polystyrene, polyvinyl alcohol, ethylene vinyl alcohol copolymer, fluororesin film, vinyl chloride. Or a polyolefin such as polyethylene; an organic material (resin base material) such as cellulose, polyvinylidene chloride, aramid, polyphenylene sulfide, polyurethane, polycarbonate, polyarylate, polynorbornene or epoxy resin; paper material such as paper or synthetic paper; stainless steel, Examples of the composite material include a metal foil such as titanium or aluminum whose surface is coated or laminated in order to impart insulation.

The thickness of the element substrate 106 is not particularly limited, but is usually 5 μm or more, preferably 20 μm or more, while it is usually 20 mm or less, preferably 10 mm or less. It is preferable that the film thickness of the element substrate is 5 μm or more because the possibility of insufficient strength of the photoelectric conversion element is reduced.

In the solar cell, when the element substrate 106 side is the light receiving surface, the element substrate 106 preferably has a light-transmitting property. In the present invention, having translucency means having a visible light transmittance of 40% or more. Note that the visible light transmittance of the element substrate 106 is preferably 70% or more because more light can reach the active layer 103. The visible light transmittance of the element substrate 106 can be measured by the method defined in JIS R3106. On the other hand, in the solar cell, when the upper electrode 105 side of the photoelectric conversion element 107 is used as the light receiving surface, the element substrate 106 may or may not have a light-transmitting property. However, when a solar cell is installed in a window or the like, it is preferable to use a see-through type solar cell, and in this case, it is preferable that the element substrate 106 has translucency regardless of the light receiving surface.

<1-2. Pair of electrodes (101, 105)>
As described above, the photoelectric conversion element according to the present invention has the pair of electrodes including the lower electrode 101 and the upper electrode 105. Note that one of the pair of electrodes is a cathode having a function of collecting electrons generated in the active layer 103, and the other electrode has a function of collecting holes generated in the active layer 103. It has an anode. When the lower electrode 101 serves as a cathode, the upper electrode 105 serves as an anode, and when the lower electrode 101 serves as an anode, the upper electrode 105 serves as a cathode.

The material for forming the lower electrode 101 and the upper electrode 105 is not particularly limited and may be nickel oxide, tin oxide, indium oxide, indium tin oxide (ITO), indium-zirconium oxide (IZO), titanium oxide, indium oxide or zinc oxide. Metal oxides such as; metal such as gold, platinum, silver, copper, iron, tin, zinc, aluminum, indium, chromium, lithium, sodium, potassium, cesium, calcium, magnesium or cobalt or alloys thereof. Among the above, the anode is preferably formed of a material having a relatively large work function, and the cathode is preferably formed of a material having a relatively small work function. Note that when the photoelectric conversion element has the lower buffer layer 102 and/or the upper buffer layer 104, the lower electrode 101 and the upper electrode 105 may be formed using the same material by adjusting these buffer layer materials. it can.

The lower electrode 101 and the upper electrode 105 may each have a single layer structure or a laminated structure.

Further, at least one of the pair of electrodes preferably has a light-transmitting property. For example, when the element substrate 106 side is used as a sunlight receiving surface, the lower electrode 101 preferably has a light-transmitting property, and the upper electrode 105 may have a light-transmitting property. It does not have to have the property. When the upper electrode 105 side is used as a sunlight receiving surface, the upper electrode 105 preferably has a light-transmitting property, and the lower electrode 101 may have a light-transmitting property. It does not have to have optical properties. Note that when the photoelectric conversion element is a see-through type, it is preferable that both the lower electrode 101 and the upper electrode 105 have a light-transmitting property.

When the electrode has a light-transmitting property, the metal oxide as described above may be used to form the electrode. Further, it may have a structure in which a layer containing a metal oxide and a thin metal layer are laminated.

The film thickness of the lower electrode 101 and the upper electrode 105 is not particularly limited, but is usually 5 nm or more, preferably 10 nm or more, more preferably 20 nm or more, while it is usually 2 μm or less, preferably 1 μm or less, more preferably It is 500 nm or less.

The sheet resistance of the electrode is not particularly limited, but is usually 0.1 Ω/□ or more, on the other hand, 1000 Ω/□ or less, preferably 500 Ω/□ or less, more preferably 100 Ω/□ or less.

The method of forming the lower electrode 101 and the upper electrode 105 is not particularly limited and can be formed by a known method according to the material used. For example, a vacuum film forming method such as a vapor deposition method or a sputtering method; or a wet coating method in which an ink containing nanoparticles or a precursor is applied to form a film.

<1-3. Active layer 103>
The active layer 103 is a bulk hetero type mixed layer containing a p-type organic semiconductor compound, an n-type semiconductor compound, and inorganic nanoparticles. As described above, when the active layer 103 absorbs light, electrons and holes are generated at the interface between the p-type organic semiconductor compound and the n-type semiconductor compound, and these charges are extracted from each electrode.

The p-type organic semiconductor compound is not particularly limited, and examples thereof include a p-type low molecular weight organic semiconductor compound and a p-type organic semiconductor polymer. Among them, a p-type semiconductor polymer having an energy band gap of 1.0 eV or more and 1.8 eV or less is preferable.

Specifically, the p-type semiconductor polymer is preferably a semiconductor polymer obtained by copolymerizing two or more kinds of monomer units, and specifically, a π-electron conjugated unit containing an acceptor constitutional unit and a donor constitutional unit. It is preferably a polymer.

In the present invention, the donor constitutional unit (D) is a constitutional unit having a small ionization potential and a strong tendency to donate electrons. Specifically, the donor constitutional unit is more ionized than the acceptor constitutional unit (A). It is a structural unit with a small potential and electron affinity. That is, in the present invention, the donor constitutional unit (D) is a constitutional unit having a higher HOMO energy level and a higher LUMO energy level than the acceptor constitutional unit (A). The HOMO energy level and LUMO energy level of the acceptor constitutional unit and the donor constitutional unit are measured by photoelectron yield spectroscopy (PYS), ultraviolet photoelectron spectroscopy (UPS), inverse photoelectron spectroscopy (IPES), and cyclic voltammetry. It can be estimated experimentally by, for example, or it can be calculated by quantum chemical calculation such as molecular orbital method (MO method) and density half-function method (DFT method). When the HOMO energy level and the LUMO energy level of the acceptor constitutional unit and the donor constitutional unit are calculated, the terminal portion of each constitutional unit is replaced with a hydrogen atom.

The acceptor constitutional unit (A) and the donor constitutional unit (D) are not particularly limited, but may have a substituent, such as an aromatic hydrocarbon group, an aromatic heterocyclic group or an aliphatic heterocyclic group. Are listed. In addition, these groups may be monocyclic or may be condensed polycyclic. The substituent is not particularly limited, and any substituent can be selected according to the improvement of the solubility of the p-type semiconductor polymer and the adjustment of the absorption wavelength. Examples thereof include an aliphatic hydrocarbon group, an alkoxy group, an alkylcarbonyl group, an alkoxycarbonyl group, an alkylthio group, an aliphatic heterocyclic group, an aromatic hydrocarbon group, an aromatic heterocyclic group and a halogen atom. These substituents may further have a substituent. Among them, the acceptor constitutional unit (A) and the donor constitutional unit (D) are each preferably an aromatic heterocyclic group which may have a substituent.

Specific examples of the acceptor constitutional unit (A) and the donor constitutional unit (D) include, but are not limited to, imidothiophene unit, naphthobisthiadiazole unit, benzothiadiazole unit, dithienosilole unit, benzodithiophene unit, Examples include dithienothiophene units, dithienopyrrole units, thienothiophene units, or diketopyrrolopyrrole units. The acceptor constitutional unit and the donor constitutional unit can be selected in consideration of the HOMO energy level and LUMO energy level of these groups.

More specific examples of the p-type semiconductor polymer include polythiophene-thienothiophene copolymers described in Nature Materials, 2006, 5, 328 and polythiophene-diketopyrrolopyrroles described in WO 2008/000664. Copolymer, Adv. Mater. , 2007, 4160, a polythiophene-thiazolothiazole copolymer, a polythiophene copolymer such as PCPDTBT described in Nature Materials, 2007, 6, 497, an imidothiophene described in International Publication No. 2011/028827 pamphlet. And a copolymer of thienothiophene and benzodithiophene described in International Publication No. 2011/011545 pamphlet, and the like. Further, conjugated polymer compounds described in WO 2013/180243 Pamphlet, International Publication No. 2013/065855 Pamphlet and the like are also included. Further, derivatives of these polymers and polymers that can be synthesized by combining the monomers listed here can be used as well. Substituents of these polymers and monomers can be appropriately selected in order to control the solubility, crystallinity, film formability, HOMO energy level, LUMO energy level and the like.

Among the above, as a preferable form of the p-type semiconductor copolymer, an imidothiophene unit which may have a substituent as an acceptor constitutional unit and a dithienosilole unit which may have a substituent as a donor constitutional unit are preferable. And a naphthobisthiadiazole unit which may have a substituent as an acceptor constitutional unit, and a benzodithiophene unit which may have a substituent as a donor constitutional unit. The π-electron conjugated polymer which has.

The p-type semiconductor polymer may have two or more acceptor constitutional units, and may similarly have two or more donor constitutional units. Further, the p-type semiconductor polymer may have a group capable of functioning as a spacer, in addition to the acceptor constituent unit and the donor constituent unit. The group that can function as a spacer is not particularly limited, but examples thereof include a thienyl group even if it has a substituent.

The n-type semiconductor compound is not particularly limited, but specifically, fullerene; fullerene compound; quinolinol derivative metal complex represented by 8-hydroxyquinoline aluminum; naphthalenetetracarboxylic acid diimide or perylenetetracarboxylic acid diimide, etc. Condensed ring tetracarboxylic acid diimides; perylene diimide derivative, terpyridine metal complex, tropolone metal complex, flavonol metal complex, perinone derivative, benzimidazole derivative, benzoxazole derivative, thiazole derivative, benzthiazole derivative, benzothiadiazole derivative, oxadiazole Derivatives, thiadiazole derivatives, triazole derivatives, aldazine derivatives, bisstyryl derivatives, pyrazine derivatives, phenanthroline derivatives, quinoxaline derivatives, benzoquinoline derivatives, bipyridine derivatives, borane derivatives; of condensed polycyclic aromatic hydrocarbons such as anthracene, pyrene, naphthacene or pentacene Full fluoride; single-walled carbon nanotubes, n-type polymers (n-type polymer semiconductor materials), and the like.

Among these, the n-type semiconductor compound is a fullerene, a fullerene compound, a borane derivative, a thiazole derivative, a benzothiazole derivative, a benzothiadiazole derivative, an N-alkyl-substituted naphthalenetetracarboxylic acid diimide, or an N-alkyl-substituted perylenediimide derivative. Alternatively, an n-type polymer semiconductor material is preferable, a fullerene, a fullerene compound, an N-alkyl-substituted perylene diimide derivative, an N-alkyl-substituted naphthalene tetracarboxylic acid diimide or an n-type polymer semiconductor compound is more preferable, and a fullerene compound is Particularly preferred. The fullerene compound is not particularly limited, but those described in known documents such as International Publication No. 2011/016430 or Japanese Patent Laid-Open No. 2012-191194 can be used. Among the fullerene compounds, PC61BM or PC71BM is preferable. One of the above compounds may be used, or a mixture of a plurality of compounds may be used.

The ratio of the n-type semiconductor compound to the p-type organic semiconductor compound in the active layer 103 is not particularly limited, but is preferably 100 parts by mass or more, and 150 parts by mass or more in order to promote charge separation. More preferably, on the other hand, it is preferably 400 parts by mass or less, and particularly preferably 350 parts by mass or less.

The active layer 103 contains inorganic nanoparticles, as described above. In the present invention, the inorganic nanoparticles are preferably present in the active layer 103 in a reasonably uniform manner. Specifically, the presence amount of the inorganic nanoparticles at the depth of 1/3 of the active layer from the upper interface of the active layer is M ₁ , and from the depth of 1/3 of the active layer to 2/3 of the active layer. When the abundance of the inorganic nanoparticles at the depth of M ₂ is M ₂ and the abundance of the inorganic nanoparticles at the depth from the 2/3 depth of the active layer to the lower side interface of the active layer is M ₃ , , M ₁ /M ₂ and M ₃ /M ₂ are each preferably 0.7 or more and 1.3 or less. The abundance of the inorganic nanoparticles is determined by, for example, X-ray photoelectron spectroscopy (XPS) analysis. In particular, in the present invention, the abundance ratios M ₁ /M ₂ and M ₃ /M ₂ of inorganic nanoparticles are obtained by performing X-ray photoelectron spectroscopy (XPS) analysis in the depth direction while performing Ar sputtering. It can be calculated from the profile. Specifically, for M ₁ /M ₂ , the composition distribution can be obtained from the spectral peak intensity obtained by X-ray photoelectron spectroscopy (XPS) analysis, and (1/3 depth direction from the upper interface of the active layer). In the above, the profile area derived from the inorganic nanoparticles)/(the profile area derived from the inorganic nanoparticles from the depth of 1/3 of the active layer to the depth of 2/3 of the active layer) can be calculated. Similarly, M ₃ /M ₂ is derived from the inorganic nanoparticles (from the depth of 2/3 of the active layer to the lower interface of the active layer) in the spectral peak obtained by X-ray photoelectron spectroscopy (XPS) analysis. Profile area)/(profile area derived from inorganic nanoparticles at a depth of 1/3 of the active layer to a depth of 2/3 of the active layer).

In addition, as described later, in order to further improve the light resistance of the photoelectric conversion element, M ₁ /M ₂ is more preferably 0.8 or more, particularly preferably 0.9 or more, while It is more preferably 1.2 or less, and particularly preferably 1.1 or less.

Similarly, as described later, in order to further improve the light resistance of the photoelectric conversion element, M ₃ /M ₂ is more preferably 0.8 or more, particularly preferably 0.9 or more, while It is more preferably 1.2 or less, and particularly preferably 1.1 or less.

Further, there is no particular limitation, but (M ₁ /M ₂ )/(M ₃ /M ₂ ) is 0.7 or more in order to further improve the light resistance of the photoelectric conversion element as described later. Is more preferable, 0.8 or more is more preferable, 0.9 or more is particularly preferable, while 1.3 or less is preferable, 1.2 or less is more preferable, and 1. It is particularly preferably 1 or less.

Conventionally, as described in JP-A-2009-158730 or Solar Energy Materials & Solar cells 134(2015) 291-297, an attempt has been made to contain a zinc oxide nanoparticle or the like by providing a concentration gradient in the active layer. Came.

For example, in Japanese Unexamined Patent Publication No. 2009-158730, after forming a layer containing P3HT and PCBM, an active layer is formed by applying a coating liquid containing P3HT, PCBM, and titanium oxide nanoparticles. It is described to do. The active layer thus formed has a concentration distribution in the normal direction consisting of the plane of the positive electrode or the negative electrode, and since titanium oxide nanoparticles are present, the short-circuit current density increases and It is described that it contributes to high efficiency of the battery.
In Solar Energy Materials & Solar cells 134(2015) 291-297, a zinc oxide layer is deposited on the lower electrode by directly applying a coating solution containing P3HT, PCBM, and zinc oxide on the lower electrode. However, it is described that a mixed layer of P3HT and PCBM is formed thereon. That is, in the case of the method described in Solar Energy Materials & Solar cells 134(2015) 291-297, a region having a high zinc oxide concentration exists under the active layer.

However, according to the study by the present inventors, the gradient of the inorganic nanoparticles in the active layer is reduced as much as possible, and the inorganic nanoparticles are present in a reasonably uniform manner, whereby the light resistance of the photoelectric conversion element is surprisingly improved. There was found. Although this mechanism is not clear, it is thought to be due to the following reasons.

For example, in the known Advanced Energy Materials 4 (2014) 1300693, a conventional organic thin-film solar cell containing PCBM in the active layer and no inorganic nanoparticles contains PCBM when exposed to light. It is mentioned that the dimer of is produced. When PCBM dimers are generated, electron mobility is lowered due to causes such as trap formation, morphology change, and energy level disorder, and charge recombination in the active layer increases, resulting in organic thin film solar cells. It is described that the conversion efficiency of the battery is reduced. That is, in the conventional organic solar cell, when the photoelectric conversion element is exposed to light, the electron mobility of the n-type semiconductor compound is reduced due to the influence of the change in the morphology of the active layer, and as a result, the conversion efficiency is reduced. Is a concern.

On the other hand, as in the present invention, the appropriate morphology is formed by the inorganic nanoparticles being present in the active layer 103 in an appropriate and uniform manner. Therefore, even if the active layer is exposed to light and the electron mobility of the n-type semiconductor compound is reduced, the inorganic nanoparticles function as an electron transport path, and thus the reduction in conversion efficiency due to photodegradation of the photoelectric conversion element is suppressed. It is considered possible.

Further, in order to suppress a decrease in conductivity due to photodegradation of the active layer as described below, the number density of the inorganic nanoparticles in the cross section of the active layer is preferably 25 particles/μm ² or more, and 40 particles/μm ² or more. still more preferably [mu] m ² or more, and particularly preferably 60 / [mu] m ² or more. On the other hand, the number density of the inorganic nanoparticles in the cross section of the active layer is 500 in order to secure the area of the pn junction interface of the active layer and suppress the decrease in the amount of charge generation, or to prevent the leakage due to the inorganic nanoparticles. /Μm ² or less is preferable, 300/μm ² or less is more preferable, and 200/μm ² or less is particularly preferable. In the present invention, the number density of the inorganic nanoparticles in the active layer can be estimated by observing an arbitrary cross section of the active layer with a scanning electron microscope. Specifically, in the observed cross section of the active layer, the number density of the inorganic nanoparticles can be estimated from the number of the inorganic nanoparticles existing in the range of 2 μm in the width direction of the active layer. In addition, in the present invention, particles having a distance between adjacent particles of 10 nm or less are collectively regarded as one inorganic nanoparticle.

Further, in order to improve the electron transporting property, it is preferable that the inorganic nanoparticles in the active layer have an appropriate size and are appropriately dispersed without aggregating. Specifically, the ratio of the number of inorganic nanoparticles having a major axis length of 10 nm or more and 100 nm or less to the total number of inorganic nanoparticles in the active layer is preferably 70% or more, more preferably 80% or more. It is preferably 90% or more and particularly preferably. In the present invention, the ratio of the number of inorganic nanoparticles having a major axis length of 10 nm or more and 100 nm or less to the total number of inorganic nanoparticles in the active layer can be estimated by a scanning electron microscope, like the number density of inorganic nanoparticles. it can. Specifically, in the observed cross section of the active layer, it can be estimated from the number of inorganic nanoparticles existing in the range of 2 μm in the width direction of the active layer. The long axis of the inorganic nanoparticles means the longest distance between two points among the line segments formed by connecting two points on the outer edge of the inorganic nanoparticles in the observed cross section.

The compound constituting the inorganic nanoparticles is not particularly limited as long as it is an inorganic nanoparticle having an electron transporting property, but metal oxides such as tin oxide, titanium oxide and zinc oxide; aluminum, gallium, alkali metal, alkaline earth Examples thereof include zinc oxide doped with a group metal and the like; compound semiconductors containing copper, indium, selenium, and the like. Among these, it is preferable to use inorganic nanoparticles having a band at the bottom of the conduction band close to the LUMO energy level of the n-type organic semiconductor compound in the active layer 103, in order to function as an auxiliary of the electron conduction path. .. Specifically, the energy difference between the LUMO energy level of the n-type semiconductor compound and the conduction band bottom of the inorganic nanoparticles is preferably 1.0 eV or less, more preferably 0.7 eV or less, and 0.5 eV. The following is particularly preferable. Specifically, the compounds forming the inorganic nanoparticles include zinc oxide, titanium oxide, gallium nitride, gallium phosphide, indium phosphide, zinc sulfide, zinc selenide, copper (I) oxide, cadmium sulfide, and strontium titanate. Is preferred. The LUMO energy level of the n-type semiconductor compound and the energy level of the bottom of the conduction band of the inorganic nanoparticles can be estimated by known methods.

The ratio of the inorganic nanoparticles in the active layer 103 is preferably 0.5 parts by mass or more, and 1.0 part by mass with respect to the n-type semiconductor in order to form a good morphology and function as an electron transport path. The amount is more preferably at least 2.5 parts by mass, more preferably at least 2.5 parts by mass. On the other hand, if the ratio of the inorganic nanoparticles to the n-type semiconductor compound is too large, the pn junction interface of the active layer 103 is reduced, so that the charge separation is lowered, and further, when the highly conductive inorganic nanoparticles are used, The conversion element tends to leak easily. Therefore, the ratio of the inorganic nanoparticles to the n-type semiconductor compound in the active layer 103 is preferably 20% by mass or less, more preferably 17% by mass or less, and particularly preferably 15% by mass or less. ..

The film thickness of the active layer 103 is not particularly limited, but is usually 5 nm or more, preferably 10 nm or more, more preferably 50 nm or more, more preferably 120 nm or more in order to absorb more light. On the other hand, in order to reduce the series resistance, the thickness of the active layer 103 is usually 600 nm or less, preferably 500 nm or less, more preferably 400 nm or less.

The method for forming the active layer 103 is not particularly limited, but it is preferable to form the active layer 103 by a wet coating method using the composition for forming the active layer. Specifically, by preparing a composition for forming an active layer containing a p-type organic semiconductor compound, an n-type semiconductor compound, inorganic nanoparticles, and a solvent, and applying the composition for forming an active layer. The active layer 103 can be formed.

The coating method can be used any method, for example, spin coating method, inkjet method, doctor blade method, drop casting method, reverse roll coating method, gravure coating method, kiss coating method, roll brushing method, spray coating method, Examples thereof include an air knife coating method, a wire bar bar coating method, a slit die coating method, a pipe doctor method, an impregnation/coating method and a curtain coating method.

Moreover, you may heat-dry after apply|coating the composition for active layer formation. The heating can promote self-assembly of the active layer. The heating temperature is usually 50°C or higher, preferably 80°C or higher, while it is usually 300°C or lower, preferably 280°C or lower, more preferably 250°C or lower. The heating time is usually 1 minute or longer, preferably 3 minutes or longer, while it is usually 3 hours or shorter, preferably 1 hour or shorter.

The solvent contained in the active layer forming composition is not particularly limited as long as it is a solvent capable of dissolving or dispersing the p-type organic semiconductor compound, the n-type semiconductor compound, and the inorganic nanoparticles. For example, aromatic hydrocarbons such as chlorobenzene or orthodichlorobenzene; alicyclic hydrocarbons such as cyclopentane, cyclohexane, methylcyclohexane, cycloheptane, cyclooctane, tetralin or decalin; lower alcohols such as methanol, ethanol or propanol Aliphatic ketones such as acetone, methyl ethyl ketone, cyclopentanone or cyclohexanone; Aromatic ketones such as acetophenone or propiophenone; Esters such as ethyl acetate, butyl acetate or methyl lactate; Chloroform, methylene chloride, dichloroethane, Examples thereof include halogenated hydrocarbons such as trichloroethane and trichloroethylene; ethers such as ethyl ether, tetrahydrofuran or dioxane; and amides such as dimethylformamide or dimethylacetamide.

As the solvent, one kind of solvent may be used alone, or any two or more kinds of solvents may be used in combination at any ratio. When two or more kinds of solvents are used in combination, a low boiling point solvent having a boiling point of 60° C. to 150° C. under normal pressure and a high boiling point solvent having a boiling point of 180° C. to 250° C. under normal pressure are combined. Is preferred. For example, the high boiling point solvent may be tetralin, decalin, acetophenone or the like, and the low boiling point solvent may be toluene, xylene, tetrahydrofuran, ethyl methyl ketone or the like. When a high-boiling solvent and a low-boiling solvent are used in combination as described above, when the active layer is formed, the low-volatility high-boiling solvent is slowly volatilized to promote the organization of the semiconductor compound. , The phase separation structure can be optimized. Further, from the viewpoint of environmental load, it is preferable that the high boiling point solvent and the low boiling point solvent are non-halogenated solvents.

Further, as described above, in order to allow the inorganic nanoparticles to be present in the active layer 103 in a reasonably uniform manner, it is preferable to apply the active layer composition containing a dispersant to form the active layer 103. In particular, since nanoparticles of zinc oxide, titanium oxide, etc. exhibit hydrophilicity, when these particles are dispersed in a nonpolar solvent, it is preferable to carry out surface modification with a dispersant or the like. Alternatively, these particles may be directly modified with an organic chain during particle synthesis. As the dispersant, for example, a dispersant containing a hydroxyl group, a carboxyl group, an amine group or the like is preferably used. Further, by heating and stirring or ultrasonically treating the composition for active layer, the inorganic nanoparticles in the active layer after coating can be appropriately homogenized. Further, by using a bead mill, a jet mill or the like for the active layer composition, the inorganic nanoparticles can be appropriately homogenized in the active layer.

The composition for forming an active layer may be prepared by mixing a solution containing a p-type organic semiconductor compound, a solution containing an n-type semiconductor compound, and a dispersion containing inorganic nanoparticles, and then mixing them. The p-type organic semiconductor compound, the n-type semiconductor compound, and the inorganic nanoparticles may be dissolved or dispersed at the same time in one or more kinds of solvents to prepare them. In addition, an inorganic nanoparticle dispersion liquid containing inorganic nanoparticles and a dispersant is prepared in advance, and the dispersion liquid is added to a liquid containing a p-type organic semiconductor compound and an n-type semiconductor compound to form an active layer composition. It is preferable to prepare the product. A commercially available product may be used as the inorganic nanoparticle dispersion liquid. Examples thereof include ZNT15WT%-G0 (manufactured by CI Kasei), NANOBYKR-3842 (manufactured by BYK Chemie), RTIT15WT%-GO (manufactured by CI Kasei), and the like.

The ratio of each compound in the active layer forming composition is not particularly limited and may be arbitrarily selected according to the desired composition of the active layer 103.

<1-4. Buffer layer (lower buffer layer 102, upper buffer layer 104)>
As described above, the photoelectric conversion element according to this embodiment has the buffer layer between the lower electrode 101 and the active layer 103 and between the upper electrode 105 and the active layer 103, respectively. In the present invention, for convenience, the buffer layer 102 between the lower electrode 101 and the active layer 103 may be referred to as a lower buffer layer, and the buffer layer 104 between the upper electrode 105 and the active layer 103 may be referred to as an upper buffer layer. Sometimes referred to as a layer.

The buffer layers 102 and 104 are hole extraction layers or electron extraction layers. The hole extraction layer is a layer having a function of improving transport efficiency of holes generated in the organic active layer 103, and the electron extraction layer has a function of improving transport efficiency of electrons generated in the organic active layer 103. It is a layer that has. Therefore, the buffer layer between the anode and the active layer is preferably a hole extraction layer, and the buffer layer between the cathode and the active layer is preferably an electron extraction layer. Specifically, when the upper electrode 105 is an anode and the lower electrode 104 is a cathode, it is preferable that the upper buffer layer 104 be a hole extraction layer and the lower buffer layer 102 be an electron extraction layer. When it is a cathode and the lower electrode 104 is an anode, it is preferable that the upper buffer layer 104 is an electron extraction layer and the lower buffer layer 102 is a hole extraction layer.

The lower buffer layer 102 and the upper buffer layer 104 are not essential constituent members and may be provided arbitrarily. Further, it may have only one of the buffer layers. However, in the present invention, the lower buffer layer is preferably the electron extraction layer for the following reasons. In the present invention, the inorganic nanoparticles are dispersed so as to be present in the active layer 103 as uniformly as possible. Generally, since the inorganic nanoparticles have a higher specific gravity than organic substances, coating with good dispersibility is possible. Even if the liquid is used, the number of inorganic nanoparticles existing on the lower buffer layer side and in contact with the lower buffer layer in the organic active layer tends to increase. Therefore, when the lower buffer layer is a hole extraction layer, the inorganic nanoparticles having an electron transporting property may make ohmic contact with the hole extraction layer having a hole extraction function, and as a result, the leakage current It may increase. On the other hand, when the lower buffer layer is an electron extraction layer, ohmic contact is not formed even if the lower buffer layer contacts with the electron transporting inorganic nanoparticles, so that increase of the leak current can be suppressed. For this reason, the lower buffer layer is preferably an electron extraction layer.

The material of the electron extraction layer is not particularly limited as long as it is a material that improves the extraction efficiency of electrons from the active layer 103 to the cathode, and an inorganic compound or an organic compound can be used.

Examples of the inorganic compound include salts of alkali metals such as Li, Na, K, and Cs; n-type semiconductor oxides such as titanium oxide (TiOx) and zinc oxide (ZnO). Among them, the alkali metal salt is preferably a fluoride salt such as LiF, NaF, KF or CsF, and the n-type semiconductor oxide is preferably zinc oxide (ZnO). Although the operating mechanism of such materials is unknown, it is conceivable to reduce the work function of the cathode and increase the voltage applied to the inside of the solar cell element when combined with the cathode made of Al or the like.

Examples of the organic compound include a phosphine compound having a double bond between a phosphorus atom and a Group 16 element such as a triarylphosphine oxide compound; a substituent such as bathocuproine (BCP) or bathophenanthrene (Bphen) A phenanthrene compound in which 1- and 10-positions may be substituted with heteroatoms; a boron compound such as triarylboron; an organometallic such as (8-hydroxyquinolinato)aluminum (Alq3) Oxide; Compound having 1 or 2 ring structure which may have a substituent, such as oxadiazole compound or benzimidazole compound; naphthalenetetracarboxylic acid anhydride (NTCDA) or perylenetetracarboxylic acid anhydride Examples thereof include aromatic compounds having a condensed dicarboxylic acid structure such as dicarboxylic acid anhydrides such as (PTCDA).

The electron extraction layer can be formed by using the compound as described above, but in order to reduce the electron extraction barrier, the electron extraction layer contains the same compound as the compound constituting the inorganic nanoparticles in the active layer. Preferably. For example, when the inorganic nanoparticles are composed of a metal oxide, it is preferable that the electron extraction layer also contains the same metal oxide as the metal oxide forming the inorganic nanoparticles. In this case, the metal oxide contained in the electron extraction layer may be doped with a metal element. In particular, it is preferable that the inorganic nanoparticles are made of zinc oxide and the electron extraction layer contains zinc oxide.

The material of the hole extraction layer is not particularly limited, and is not particularly limited as long as it is a material that can improve the extraction efficiency of holes from the active layer 103 to the anode. Specifically, polythiophene, polypyrrole, polyacetylene, triphenylenediamine, polyaniline, or the like, a conductive polymer doped with sulfonic acid and/or iodine, a polythiophene derivative having a sulfonyl group as a substituent, or a conductive organic material such as arylamine Examples thereof include compounds, metal oxides such as copper oxide, nickel oxide, manganese oxide, molybdenum oxide, vanadium oxide and tungsten oxide, Nafion, and p-type semiconductors described later. Among them, a conductive polymer doped with sulfonic acid is preferable, and more preferably, (3,4-ethylenedioxythiophene)poly(styrenesulfonic acid) obtained by doping polystyrenesulfonic acid in a polythiophene derivative (PEDOT:PSS). Is. Further, a thin film of a metal such as gold, indium, silver or palladium can also be used. The thin film of metal or the like may be formed alone or may be used in combination with the above organic material.

The film thickness of each of the lower buffer layer 102 and the upper buffer layer 104 is usually 0.1 nm or more. On the other hand, it is usually 400 nm or less, preferably 200 nm or less. When the film thickness of each buffer layer is within the above range, electric charges can be easily taken out from the active layer 103, and the photoelectric conversion efficiency can be improved.

There is no limitation on the method of forming the lower buffer layer 102 and the upper buffer layer 104. For example, when a sublimable material is used, it can be formed by a vacuum vapor deposition method or the like. Further, for example, when a material soluble in a solvent is used, it can be formed by a wet coating method such as a spin coating method or an inkjet method.

When the buffer layer is formed by the coating method, the coating liquid may further contain a surfactant. The use of the surfactant suppresses the occurrence of dents due to the adhesion of fine bubbles or foreign matter and/or uneven coating in the drying process. As the surfactant, known surfactants (cationic surfactant, anionic surfactant, nonionic surfactant) can be used. Of these, a silicon-based surfactant, an acetylene diol-based surfactant or a fluorine-based surfactant is preferable. As the surfactant, only one kind may be used, or two or more kinds may be used in optional combination and ratio.

<1-5. Method for manufacturing photoelectric conversion element>
In the photoelectric conversion element 107 having the configuration shown in FIG. 1, the lower electrode 101, the lower buffer layer 102, the active layer 103, the upper buffer layer 104, and the upper electrode are formed on the element substrate 106 according to the method described above for each layer. It can be manufactured by sequentially stacking 105.

After stacking the lower electrode 101 and the upper electrode 105, the photoelectric conversion element is usually heated to 50° C. or higher, preferably 80° C. or higher, while usually 300° C. or lower, preferably 280° C. or lower, more preferably 250° C. or lower. It is preferable to heat (this step is called an annealing treatment step).

Performing the annealing process at a temperature of 50° C. or higher improves the adhesion between the layers of the photoelectric conversion element, for example, the adhesion between the lower buffer layer 102 and the lower electrode 101 and/or the lower buffer layer 102 and the active layer 103. This is preferable because the effect of By improving the adhesiveness between the layers, the thermal stability and durability of the photoelectric conversion element can be improved. Also, the annealing process may promote self-assembly of the active layer. It is preferable to set the temperature of the annealing treatment step to 300° C. or lower because the organic compound in the active layer 103 is less likely to be thermally decomposed. In the annealing process, stepwise heating may be performed within the above temperature range.

The heating time is usually 1 minute or longer, preferably 3 minutes or longer, while it is usually 3 hours or shorter, preferably 1 hour or shorter. It is preferable to terminate the annealing treatment step when the open circuit voltage, the short circuit current and the fill factor, which are the parameters of the solar cell performance, become constant. In addition, the annealing treatment step is preferably performed under normal pressure and in an inert gas atmosphere.

As a method of heating, the photoelectric conversion element may be placed on a heat source such as a hot plate, or the photoelectric conversion element may be placed in a heating atmosphere such as an oven. The heating may be performed in a batch system or a continuous system.

Each layer constituting the photoelectric conversion element according to the present invention is not particularly limited and can be formed by a sheet-to-sheet (sheet-fed) method or a roll-to-roll method.

<2. Solar cell>
The photoelectric conversion element according to the above-described embodiment is preferably used as a solar cell element, particularly a see-through type organic thin-film solar cell solar cell element. The solar cell may have a configuration other than the photoelectric conversion element as shown in FIG.

FIG. 2 is a cross-sectional view schematically showing the configuration of the thin film solar cell as one embodiment of the present invention. As shown in FIG. 2, the thin-film solar cell 14 of the present embodiment includes a weather-resistant protective film 1, an ultraviolet ray blocking film 2, a gas barrier film 3, a getter material film 4, a sealing material 5, and photoelectric conversion. The element 6, the sealing material 7, the getter material film 8, the gas barrier film 9, and the back sheet 10 are provided in this order. Then, in the thin-film solar cell, light is normally irradiated from the side (lower side in the drawing) on which the weather resistant protective film 1 is formed, and the photoelectric conversion element 6 generates power. The thin-film solar cell does not have to have all of these constituent members, and each constituent member may be arbitrarily selected and provided.

There is no particular limitation on these constituent members constituting the thin-film solar cell and the manufacturing method thereof, and well-known techniques can be used. For example, those described in publicly known documents such as International Publication No. 2011/016430 or Japanese Patent Laid-Open No. 2012-191194 can be used.

The use of the solar cell according to the present invention, particularly the above-mentioned thin-film solar cell 14 is not particularly limited and can be used for any application. For example, solar cells for building materials, solar cells for automobiles, solar cells for space machines, solar cells for home appliances, solar cells for mobile phones, solar cells for toys, and the like.

The solar cell according to the present invention, particularly the thin-film solar cell, may be used as it is, or may be used as a solar cell module by installing the solar cell on a substrate, for example. For example, as shown in FIG. 3, a solar cell module 13 having a thin film solar cell 14 on a base material 12 can be installed and used at a place of use. A well-known technique can be used for the base material 12, and for example, those described in International Publication No. 2011/016430 or Japanese Patent Laid-Open No. 2012-191194 can be used. For example, when a plate material for building materials is used as the base material 12, a solar cell panel can be manufactured as the solar cell module 13 by providing the thin film solar cell 14 on the surface of the plate material.

The embodiments of the present invention will be described below with reference to examples, but the present invention is not limited to these as long as the gist thereof is not exceeded. The items described in this example were measured by the following methods.

(Measurement method of weight average molecular weight and number average molecular weight)
The polystyrene-equivalent weight average molecular weight (Mw) and number average molecular weight (Mn) were determined by gel permeation chromatography (GPC). Molecular weight distribution (PDI) represents Mw/Mn.

The gel permeation chromatography (GPC) measurement was performed under the following conditions.
Column: Polymer Laboratories GPC column (PLgel MIXED-B 10 μm, inner diameter 7.5 mm, length 30 cm) used by connecting two in series Pump: LC-10AT (manufactured by Shimadzu Corporation) Oven: CTO-10A (Shimadzu Manufacturing) (Made by the company)
Detector: Differential refractive index detector (RID-10A manufactured by Shimadzu Corporation) and UV-vis detector (SPD-10A manufactured by Shimadzu Corporation)
Sample: 1 μL of a solution prepared by dissolving 1 mg of sample in chloroform (200 mg)
Mobile phase: Chloroform Flow rate: 1.0 mL/min
Analysis: LC-Solution (manufactured by Shimadzu Corporation)

(Evaluation of photoelectric conversion element)
A 4 mm square metal mask is attached to the photoelectric conversion element, a solar simulator with an air mass (AM) of 1.5 G and an irradiance of 100 mW/cm 2 is used as an irradiation light source, and an ITO electrode and silver are used with a source meter (Kathley, 2400 type). The current-voltage characteristics between the electrodes were measured. From this measurement result, the open circuit voltage Voc (V), the short circuit current density Jsc (mA/cm2), the form factor FF, and the photoelectric conversion efficiency PCE (%) were calculated.

Here, the open circuit voltage Voc is a voltage value when the current value is 0 (mA/cm2), and the short circuit current density Jsc is a current density when the voltage value is 0 (V). The form factor FF is a factor representing the internal resistance, and is represented by the following equation when the maximum output is Pmax.
FF = Pmax/(Voc x Jsc)
Further, the photoelectric conversion efficiency PCE is given by the following equation when the incident energy is Pin.
PCE=(Pmax/Pin)×100
= (Voc x Jsc x FF/Pin) x 100

<Synthesis Example 1: Synthesis of Copolymer 1>

In a 50 mL two-necked eggplant flask under a nitrogen atmosphere, 1,3-dibromo-5-(n-octyl was obtained as a monomer by referring to the method described in a known document (Organic Letters 2004, 6,3381-3384). )-4H-thieno[3,4-c]pyrrole-4,6-(5H)-dione (Compound B1: imidothiophene dibromide), 350 mg, 0.826 mmol), known literature (Polymer, 1990, 31, 1379). -1383), 4,4'-didodecyl-5,5'-bis(trimethylstannyl)-2,2'-bithiophene (Compound C1) (342 mg, 0.413 mmol), and WO2013/ 4,4-bis(2-ethylhexyl)-2,6-bis(trimethyltin)-dithieno[3,2-b:2',3'-d]silole obtained by referring to the method described in 180243. (Compound A1) (308 mg, 0.413 mmol) was added, and tetrakis(triphenylphosphine)palladium(0) (28.6 mg, 3 mol%) and triphenylphosphine-containing heterogeneous palladium complex catalyst Pd-EnCatTPP30 (Aldrich Co.) were added. (37.2 mg, 3 mol%), toluene (24 mL), and N,N-dimethylformamide (6 mL) were added, and the mixture was stirred at 90°C for 1 hour and subsequently at 100°C for 10 hours. The reaction solution was diluted 4 times with toluene and further heated and stirred at 100° C. for 0.5 hours, and then, as terminal treatment, trimethyl(phenyl)tin (0.036 mL) was added and heated and stirred at 100° C. for 5 hours. Bromobenzene (8 mL) was further added, and the mixture was heated with stirring at 100° C. for 2 hours, the reaction solution was poured into methanol, and the deposited precipitate was collected by filtration. The obtained solid was dissolved in chloroform, diamine silica gel (manufactured by Fuji Silysia Chemical Ltd.) was added, and the mixture was stirred at room temperature for 1 hour and passed through a short column of acidic silica gel. The solution was concentrated, recrystallized with chloroform/ethyl acetate as a solvent, and the deposited precipitate was separated by filtration to obtain the target Copolymer 1 in a yield of 74%. The weight average molecular weight Mw of the obtained copolymer 1 was 37,000 and the PDI was 2.1.

<Synthesis Example 2: Synthesis of Copolymer 2>
In a 50 mL two-necked eggplant flask under a nitrogen atmosphere, 3,7-di(2-bromo-3-dodecylthiophene- was obtained as a monomer by referring to the method described in U.S. Patent Application Publication No. 2012/0227812. 5-yl)-naphtho[1,2-c:5,6-c]bis[1,2,5]thiadiazole (60.0 mg, 0.066 mmol), obtained by referring to the method described in Patent 5698371. 4,8-bis-[5-(2-hexyldecyl)-thiophen-2-yl]-2,6-bis(trimethylstannyl)-benzo[1,2-b:4,5-b'] Synthesis was performed using dithiophene (74.7 mg, 0.067 mmol) to obtain a copolymer 2 containing a structural unit represented by the following formula. The weight average molecular weight Mw of 2 of the obtained copolymer was 120,000 and the PDI was 5.5.

<Preparation of active layer forming composition>
(Preparation of active layer-forming composition 1)
A copolymer 1 obtained as a synthetic example 1 as a p-type organic semiconductor compound and a mixture of PC61BM (phenyl C61 butyric acid methyl ester) and PC71BM (phenyl C71 butyric acid methyl ester), which are fullerene compounds as n-type semiconductor compounds, have a mass ratio of The mixture was mixed at a ratio of 1:2. In addition, PC61BM and PC71BM were manufactured with reference to Journal of Organic Chemistry, 1995, 60, 532. This mixture was mixed in a mixed solvent of toluene and tetralin (volume ratio 9:1) in a nitrogen atmosphere so that the solid content concentration was 4% by mass to prepare a solution in which the mixture was well dissolved. Furthermore, a dispersion liquid containing a zinc oxide nanoparticle having an average primary particle diameter of 15 nm ZNT15WT%-G0 (manufactured by CI Kasei Co., Ltd.) was diluted with toluene to prepare a dispersion liquid in which the zinc oxide nanoparticle was 4% by mass with respect to the mixture. Was added to. The obtained solution was stirred and mixed on a hot stirrer at a temperature of 80° C. for 1 hour. The solution after stirring and mixing was filtered with a 1 μm polytetrafluoroethylene (PTFE) filter to obtain an active layer forming composition 1. The LUMO energy level of a mixture of PC61BM (phenyl C61 butyric acid methyl ester) and PC71BM (phenyl C71 butyric acid methyl ester), which are n-type semiconductor compounds, measured by cyclic voltammetry was -3.8 eV.

(Preparation of active layer forming composition 2)
Instead of ZNT15WT%-G0 (manufactured by SI Kasei Co., Ltd.), zinc oxide nanoparticles having an average primary particle size of 100 nm or less (544-906 manufactured by Sigma-Aldrich) have a zinc oxide nanoparticle ratio of 4 mass% based on the solid content. An active layer forming composition 2 was prepared in the same manner as the active layer forming composition 1 except that the above components were added. The energy of the bottom of the conduction band of zinc oxide is -4.0 eV.

(Preparation of active layer forming composition 3)
Instead of ZNT15WT%-G0 (manufactured by SI Kasei Co., Ltd.), zinc oxide nanoparticles having an average primary particle size of 15 nm (manufactured by Kanto Denka Kogyo Co., Ltd.) were added so that the ratio of zinc oxide nanoparticles to solid content was 4% by mass. Except for the above, active layer forming composition 3 was prepared in the same manner as active layer forming composition 1.

(Preparation of active layer-forming composition 4)
An active layer forming composition 4 was prepared in the same manner as the active layer forming composition 1 except that ZNT15WT%-G0 (manufactured by CI Kasei Co., Ltd.) was not added.

(Preparation of active layer forming composition 5)
As the p-type semiconductor compound, the copolymer 2 obtained in Synthesis Example 2 was used instead of the copolymer 1, and the titanium oxide dispersion RTIT 15WT%-G0 was used instead of ZNT15WT%-G0 (manufactured by CI Kasei). An active layer-forming composition 5 was prepared in the same manner as the active layer-forming composition 1 except that (CI Chemicals) was used. The energy of the bottom of the conduction band of titanium oxide is -4.2 eV.

(Preparation of active layer forming composition 6)
An active layer forming composition 6 was prepared in the same manner as the active layer forming composition 5 except that RTIT 15WT%-G0 (manufactured by CI Kasei Co., Ltd.) was not added.

<Example 1: Production and evaluation of solar cell module 1>
A PEN substrate on which a transparent conductive film made of indium tin oxide (ITO)/Ag/indium tin oxide (ITO) was patterned was ultrasonically cleaned with acetone, then ultrasonically cleaned with isopropanol, and then blown with nitrogen. Dried and UV-ozone treated.

500 mg of zinc acrylate (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 7.77 g of ethanol (manufactured by Wako Pure Chemical Industries, Ltd.), and this solution was stirred for 1 hour. After that, this solution was applied onto the PEN substrate that had been subjected to the above treatment with a wire bar. By heating this PEN substrate at 150° C. for 5 minutes, a zinc oxide-containing layer was formed as an electron extraction layer.

The active layer-forming composition 1 prepared as described above was applied onto the substrate having the electron extraction layer formed thereon by a wire bar to form an active layer. Then, the substrate was heated at 140 degrees for 5 minutes.

Further, the PEDOT:PSS dispersion liquid was applied onto the active layer with a wire bar to form a hole extraction layer. Then, the substrate was heated at 150 degrees for 10 minutes.

After forming the hole extraction layer, an IZO film having a thickness of 30 nm as a transparent electrode layer, a silver film having a thickness of 8 nm, and an IZO film having a thickness of 40 nm are sequentially formed by vacuum sputtering to produce a photoelectric conversion element 1 having a size of 5 mm×8.5 mm. did.

Next, SiO ₂ was sputtered on one surface of a polyethylene terephthalate substrate having a thickness of 0.05 mm as a barrier layer to form a barrier film. Subsequently, _two laminated bodies in which an olefin resin having a thickness of 0.05 mm was laminated as a sealing layer on the SiO ₂ formation surface of the produced barrier film were produced. Next, the laminated body and the photoelectric conversion element 1 are stacked in this order from the bottom to form a barrier layer, a sealing layer, a photoelectric conversion element 1, a sealing layer, and a barrier layer, and a vacuum laminator (NPC Manufactured by NLM-270×400). First, the inside of the laminator is held under reduced pressure for 15 minutes, then the laminated body is held at 140° C. for 15 minutes while being pressure-bonded at atmospheric pressure, and immediately thereafter, the solar cell module is cooled down to room temperature. 1 was produced.

The solar cell characteristics of the solar cell module 1 thus manufactured were evaluated by measuring the current-voltage characteristics as described above. Further, in order to evaluate the light resistance of the solar cell module 1, exposure was performed for 40 hours using a solar simulator having an air mass (AM) of 1.5 G and an irradiance of 100 mW/cm 2 as an irradiation light source, and photoelectric conversion efficiency after exposure and before exposure The ratio (maintenance rate) of photoelectric conversion efficiency was obtained. The results obtained are shown in Table 1.
In order to investigate the distribution of zinc oxide nanoparticles in the active layer of the photoelectric conversion element 1, the above-mentioned X-ray photoelectron spectroscopy (XPS) analysis was performed. Al-Kα was used as the X-ray source, and the depth direction distribution of zinc oxide nanoparticles was determined from the peak derived from Zn2p3/2. From the profile of the distribution in the depth direction, M ₁ /M ₂ and M ₃ /M ₂ were calculated by the method described above. The results obtained are shown in Table 1.
Next, after the cross section of the photoelectric conversion element 1 was processed by a cross section polisher (made by JEOL Ltd.), a working distance of 2.4 mm, an acceleration voltage of 2 kV and a magnification of 50,000 were obtained by a scanning electron microscope (made by Carl Zeiss, Ultra55). A backscattered electron image was obtained by multiplying the number of zinc oxide nanoparticles in the cross section of the active layer and the abundance of zinc oxide nanoparticles having a major axis length of 10 nm or more and 100 nm or less with respect to the total number of zinc oxide nanoparticles. Specifically, in the observed cross section of the active layer, from the number of zinc oxide nanoparticles present in the width direction of the active layer to the range of 2 μm, the number density of zinc oxide nanoparticles and the oxidation of the major axis length of 10 nm or more and 100 nm or less. The abundance of zinc nanoparticles was determined. The results obtained are shown in Table 1.

<Comparative Example 1: Preparation and evaluation of solar cell module 2>
A solar cell module 2 was prepared and evaluated in the same manner as in Example 1 except that the active layer forming composition 2 was used in place of the active layer forming composition 1. The results obtained are shown in Table 1.

<Comparative Example 2: Preparation and evaluation of solar cell module 3>
A solar cell module 3 was prepared and evaluated in the same manner as in Example 1 except that the active layer forming composition 3 was used in place of the active layer forming composition 1. The results obtained are shown in Table 1.
<Comparative Example 3: Preparation and evaluation of solar cell module 4>
A solar cell module 4 was prepared and evaluated in the same manner as in Example 1 except that the active layer forming composition 4 was used in place of the active layer forming composition 1. The results obtained are shown in Table 1.
<Comparative Example 4: Preparation and evaluation of solar cell module 5>
In the same manner as in Example 1, a zinc oxide containing layer was formed as an electron extraction layer on a PEN substrate on which a transparent conductive film made of indium tin oxide (ITO)/Ag/indium tin oxide (ITO) was patterned. A film was formed. A dispersion liquid ZNT15WT%-G0 (manufactured by CI Kasei Co., Ltd.) containing zinc oxide nanoparticles having an average primary particle diameter of 15 nm was diluted to have a zinc oxide nanoparticle content of 4% by mass and applied thereto with a wire bar. The substrate was heated at 140 degrees for 10 minutes. Then, the solar cell was formed in the same manner as in Example 1 except that the active layer-forming composition 4 was used instead of the active layer-forming composition 1 on the substrate to form the active layer by two-step coating. The battery module 4 was produced and evaluated. The results obtained are shown in Table 1.

<Example 2: Fabrication and evaluation of solar cell module 6>
A solar cell module 2 was produced and evaluated in the same manner as in Example 1 except that the active layer forming composition 5 was used in place of the active layer forming composition 1. Regarding the evaluation of the light resistance of the solar cell module 6, the light resistance was evaluated by exposing it for 120 hours. The results obtained are shown in Table 1.

<Comparative Example 5: Production and evaluation of solar cell module 7>
A solar cell module 2 was prepared and evaluated in the same manner as in Example 2 except that the active layer forming composition 6 was used in place of the active layer forming composition 5.

From the results of Table 1, the solar cell module according to Example 1 in which the zinc oxide nanoparticles are present in a reasonably uniform manner as compared with the solar cell module according to Comparative Example 3 in which the zinc oxide nanoparticles are not contained in the active layer. It can be confirmed that the decrease in conversion efficiency is small even after 40 hours of light irradiation. On the other hand, also in the solar cell modules according to Comparative Examples 1 and 2, the zinc oxide nanoparticles were contained in the active layer, but the conversion efficiency was significantly reduced after 40 hours of light irradiation. This is because in the active layer, the particles agglomerate to form inorganic nanoparticles of more than 100 nm, and the inorganic nanoparticles do not uniformly exist, so the inorganic nanoparticles function properly as a conductive path. It is considered that the cause was that there was no In addition, in the solar cell module according to Comparative Example 4, since many inorganic nanoparticles existed on the electron extraction layer side and a concentration gradient was formed, the inorganic nanoparticles did not function properly as a conductive path, and thus 40 hours It is probable that the conversion efficiency afterward was significantly reduced. Further, regarding the solar cell modules according to Example 2 and Comparative Example 5 in which the copolymer 2 is used as the p-type semiconductor compound, the solar cell module according to Example 2 in which the titanium oxide nanoparticles are appropriately and uniformly dispersed in the active layer. It can be seen that the maintenance rate of the conversion efficiency after exposure after 120 hours is higher than the maintenance rate of the conversion efficiency after exposure of the solar cell module according to Comparative Example 5 after 120 hours.
From the above results, as in the present invention, it is possible to provide a photoelectric conversion element having high light resistance with little decrease in conversion efficiency after light irradiation due to the reasonably uniformly dispersed inorganic nanoparticles in the active layer. I understand.

101 Lower Electrode 102 Lower Buffer Layer 103 Active Layer 104 Upper Buffer Layer 105 Upper Electrode 106 Element Substrate 107 Photoelectric Conversion Element 1 Weatherproof Protective Film 2 UV Cut Film 3,9 Gas Barrier Film 4,8 Getter Material Film 5,7 Sealing Material 6 Solar Cell Element 10 Back Sheet 12 Base Material 13 Solar Cell Module 14 Thin Film Solar Cell

Claims (6)

On the element substrate, at least a pair of electrodes, and an active layer between the pair of electrodes,
The active layer contains a p-type organic semiconductor compound, an n-type semiconductor compound, and inorganic nanoparticles,
The presence amount of the inorganic nanoparticles at the depth of 1/3 of the active layer from the upper interface of the active layer is M ₁ , and the inorganic amount at the depth of 1/3 of the active layer to the depth of 2/3 of the active layer is inorganic. When the abundance of the nanoparticles is M ₂ , and the abundance of the inorganic nanoparticles at the depth from the 2/3 depth of the active layer to the lower side interface of the active layer is M ₃ , M ₁ /M ₂ and _M 3 / _{M 2} is, der 0.7 to 1.3, respectively is, the number density of the inorganic nanoparticles in the cross section of the active layer is 25 / [mu] m ² or more
The photoelectric conversion element of the upper 500 / [mu] m ^2, characterized in der Rukoto below. On the element substrate, at least a pair of electrodes, and an active layer between the pair of electrodes,
The active layer contains a p-type organic semiconductor compound, an n-type semiconductor compound, and inorganic nanoparticles.
Have,
The amount of inorganic nanoparticles present at a depth of 1/3 of the active layer from the upper interface of the active layer was measured.
M ₁ , abundance of inorganic nanoparticles from a depth of 1/3 of the active layer to a depth of 2/3 of the active layer
M ₂ is the inorganic layer at a depth from the depth of 2/3 of the active layer to the lower interface of the active layer.
M ₁ /M ₂ and M ₃ /M ₂ are 0.7 or more, respectively , when the abundance of the nanoparticles is M _3.
Is 1.3 or less, the photoelectric conversion element wherein the proportion of the major axis to the inorganic nanoparticle total number less 100nm or 10nm inorganic nanoparticles of the active layer is 70% or more. On the element substrate, at least a pair of electrodes, and an active layer between the pair of electrodes,
The active layer contains a p-type organic semiconductor compound, an n-type semiconductor compound, and inorganic nanoparticles.
Have,
The amount of inorganic nanoparticles present at a depth of 1/3 of the active layer from the upper interface of the active layer was measured.
M ₁ , abundance of inorganic nanoparticles from a depth of 1/3 of the active layer to a depth of 2/3 of the active layer
M ₂ is the inorganic layer at a depth from the depth of 2/3 of the active layer to the lower interface of the active layer.
M ₁ /M ₂ and M ₃ /M ₂ are 0.7 or more, respectively , when the abundance of the nanoparticles is M _3.
It is 1.3 or less, the photoelectric conversion element, wherein the energy difference of the conduction band bottom of the LUMO energy level and the inorganic nanoparticles of the n-type semiconductor compound is less than 1.0 eV. The photoelectric conversion device according to any one of claims 1 to 3, wherein the inorganic nanoparticles are zinc oxide or titanium oxide. Solar cell having a photoelectric conversion element according to any one of claims 1-4. A solar cell module comprising the solar cell according to claim 5 .

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