JP5704563B2 - Photoelectric conversion element and solar cell - Google Patents

Description

  The present invention relates to a photoelectric conversion element and a solar cell, and particularly relates to a bulk hetero organic photoelectric conversion element and an organic thin film solar cell including the same.

  Due to the recent rise in fossil energy, a system that can generate electric power directly from natural energy has been demanded. Solar cells using monocrystalline, polycrystalline, or amorphous Si, compound-based solar cells such as GaAs and CIGS, or Dye-sensitized photoelectric conversion elements have been proposed and put into practical use.

  Although these solar cells have a high carrier mobility, it has been a difficult point in the spread that the cost of power generation is higher than the price of electricity generated and transmitted using fossil fuels.

  Photovoltaic conversion element with an electron donor layer (π electron donor layer) and an electron acceptor layer (π electron acceptor layer) provided between a transparent electrode and a counter electrode as a solar cell that costs less than fossil fuel power generation costs Has been proposed (see Non-Patent Document 1).

  However, this solar cell has a low internal quantum efficiency, and a solar cell having higher photoelectric conversion efficiency is demanded.

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

  An object of this invention is to provide the photoelectric conversion element which has high carrier mobility, and the thin film solar cell excellent in the photoelectric conversion efficiency using this element.

  As a result of intensive studies in view of the above problems, the present inventors have found that the phthalocyanine derivative of the general formula (I) has high-speed carrier mobility and is excellent as a π electron donor of a photoelectric conversion element.

That is, this invention provides the following bulk hetero type | mold organic photoelectric conversion elements and the organic thin-film solar cell containing the same.
Item 1. A bulk hetero-type organic photoelectric conversion element comprising a third component added to a system in which an active layer is a mixture of a polythiophene derivative and a C60 derivative in a bulk hetero-type organic photoelectric conversion element.
Item 2. Item 3. The bulk hetero-type organic photoelectric conversion device according to Item 1, wherein the third component is a phthalocyanine derivative.
Item 3. Item 3. The bulk hetero organic photoelectric conversion device according to Item 1, wherein the third component is a liquid crystalline organic semiconductor.
Item 4. Item 3. The bulk hetero-type organic photoelectric conversion device according to any one of Items 1 to 3, wherein the third component is a liquid crystalline phthalocyanine derivative.
Item 5. Item 5. The bulk hetero organic photoelectric conversion element according to any one of Items 1 to 4, wherein the active layer is formed by applying the solution.
Item 6. Item 6. The bulk hetero-type organic photoelectric conversion device according to any one of Items 1 to 5, wherein one of the components constituting the active layer is poly (3-alkylthiophene).
Item 7. Item 7. The bulk hetero-type organic photoelectric conversion device according to any one of Items 1 to 6, wherein one of the components constituting the active layer has a structure having an appropriate substituent in C60.
Item 8. Item 8. The bulk hetero-type organic photoelectric conversion device according to Item 7, wherein the C60 derivative is PCBM.
Item 9. Item 7. The bulk hetero organic photoelectric conversion device according to Item 6, wherein one of the components constituting the active layer is poly (3-hexylthiophene).
Item 10. 3. The bulk hetero-type organic photoelectric device according to item 2, wherein the third component constituting the active layer has an alkyl group at positions 1,4,8,11,15,18,22,25 of the phthalocyanine ring. Conversion element.
Item 11. Item 11. The bulk hetero organic photoelectric conversion device according to Item 10, wherein the alkyl group is a hexyl group.
Item 12. Item 12. An organic thin-film solar cell comprising the bulk hetero-type organic photoelectric conversion device according to any one of Items 1 to 11.

  The bulk hetero type organic photoelectric conversion element of the present invention and the organic thin film solar cell including the same can realize high photoelectric conversion efficiency.

The structure of the produced photoelectric conversion element. Wavelength dispersion of external quantum efficiency (vertical axis%). Current-voltage characteristics (conversion efficiency). The result of XRD in each ratio of P3HT and C6PcH ₂ is shown.

  The active layer of the photoelectric conversion element of the present invention is obtained by adding a third component to a system that is a mixture of a polythiophene derivative and a C60 derivative.

  Examples of the polythiophene derivative include polythiophene such as poly-3-hexylthiophene (P3HT) and oligomers thereof, or polythiophene having a polymerizable group described in Technical Digest of the International PVSEC-17, Fukuoka, Japan, 2007, P1225, N Material, (2006) vol. 5, p328, polythiophene-thienothiophene copolymer, WO2008 / 000664, polythiophene-diketopyrrolopyrrole copolymer, Adv Mater, 2007 p4160, polythiophene-thiazolothiazole copolymer, Nature Mat. vol. 6 (2007), p497, and a polythiophene copolymer such as PCPDTBT. A preferred polythiophene derivative is poly-3-hexylthiophene (P3HT).

  C60 or its derivatives include fullerene 60, [6,6] -phenyl C61-butyric acid methyl ester (PCBM), [6,6] -phenyl C61-butyric acid-nbutyl ester (PCBnB), [6 , 6] -phenyl C61-butyric acid-isobutyl ester (PCBiB), [6,6] -phenyl C61-butyric acid-n-hexyl ester (PCBH), Adv. Mater. , Vol. 20 (2008), p2116, etc., aminated fullerenes such as JP-A 2006-199674, metallocene fullerenes such as JP-A 2008-130889, and cyclics such as US Pat. No. 7,329,709. Examples include fullerene derivatives having a substituent and having improved solubility, such as fullerene having an ether group.

  The third component may be one or more of a π electron donor and a π electron acceptor. Examples of the π-electron donor include anthracene, tetracene, pentacene, hexacene, heptacene, chrysene, picene, fluorene, pyrene, peropyrene, perylene, terylene, quaterylene, coronene, obalene, circumcamanthracene, bisanthene, xethrene, heptazesulene, pyranthrene, violanthene. , Compounds such as isoviolanthene, cacobiphenyl, anthradithiophene, porphyrin, copper phthalocyanine, tetrathiafulvalene (TTF) -tetracyanoquinodimethane (TCNQ) complex, bisethylenetetrathiafulvalene (BEDTTTTF) -perchloric acid Examples include complexes, and condensed polycyclic aromatic compounds such as derivatives and precursors thereof or derivatives thereof. Examples of the derivative include substituents described in International Publication No. 03/16599, International Publication No. 03/28125, US Pat. No. 6,690,029, Japanese Patent Application Laid-Open No. 2004-107216, and the like. A pentacene derivative described in U.S. Patent Application Publication No. 2003/136964 and the like; Amer. Chem. Soc. , Vol127. No. 14.4986, J. MoI. Amer. Chem. Soc. , Vol. 123, p9482; Amer. Chem. Soc. , Vol. 130 (2008), no. 9, 2706 etc. substituted acene-based compounds substituted with a trialkylsilylethynyl group, polypyrrole and oligomers thereof, polyaniline, polyphenylene and oligomers thereof, polyphenylene vinylene and oligomers thereof, polythienylene vinylene and oligomers thereof, polyacetylene, polydiacetylene , Conjugated polymers such as polysilane and polygermane, α-sexual thiophene α, ω-dihexyl-α-sexual thiophene, α, ω-dihexyl-α-kinkethiophene, α, ω-bis ( And oligomers such as 3-butoxypropyl) -α-sexithiophene.

  π electron acceptors include fullerenes other than C60 derivatives, octaazaporphyrin, π electron donor perfluoro products (perfluoropentacene, perfluorophthalocyanine, etc.), naphthalene tetracarboxylic anhydride, naphthalene tetracarboxylic diimide, perylene tetracarboxylic Polymers containing aromatic carboxylic acid anhydrides such as acid anhydrides and perylenetetracarboxylic acid diimides and imidized products thereof as skeletons, such as fullerene C70, fullerene C76, fullerene C78, fullerene C84, fullerene C240, fullerene C540, mixed Fullerenes, fullerene nanotubes, multi-walled nanotubes, single-walled nanotubes, nanohorns (conical), etc., and some of them are hydrogen atoms, halogen atoms, substituted or unsubstituted alkyl , An alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, a cycloalkyl group, a silyl group, an ether group, a thioether group, an amino group, and a fullerene derivatives substituted by silyl group.

  As the third component, a liquid crystalline organic semiconductor is preferable.

  A preferred third component is phthalocyanine or a derivative thereof, and a liquid crystalline phthalocyanine derivative is more preferred.

  A preferred phthalocyanine derivative is a phthalocyanine derivative represented by the general formula (I).

(In the formula, R is independently a C ₂ -C ₁₈ linear or branched alkyl group, a C ₂ -C ₁₈ linear or branched alkenyl group, a C ₂ -C ₁₈ linear or A branched alkynyl group, a C _{2 to} C ₁₈ linear or branched alkoxy group, and a C _{2 to} C ₁₈ linear or branched alkylthio group.)

C ₂ -C ₁₈ alkyl includes ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, straight-chain or _C 2 -C ₁₈ alkyl group having a branched such as octadecyl, preferably include _C 2 -C ₇ alkyl group, preferably n- pentyl, n-Hexyl. When R is n-pentyl, n-hexyl or n-heptyl, the compound of the general formula (I) exhibits liquid crystallinity.

C ₂ -C ₁₈ alkenyl includes vinyl, n-propenyl, isopropenyl, n-butenyl, isobutenyl, sec-butenyl, tert-butenyl, n-pentenyl, n-hexenyl, n-heptenyl, octenyl, nonenyl, decenyl , undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, heptadecenyl, straight-chain or _C 2 -C ₁₈ alkenyl group having a branched such as octadecenyl, and the like, preferably a _C 2 -C ₇ alkenyl group.

The alkynyl of C ₂ -C _18, Asechiniru, n- propargyl, n- butynyl, sec- butynyl, n- pentynyl, n- hexynyl, n- heptynyl, octynyl, nonynyl, decynyl, undecynyl, dodecynyl, tridecynyl, tetradecynyl, Examples thereof include linear or branched C _{2 to} C ₁₈ alkynyl groups such as pentadecynyl, hexadecynyl, heptadecynyl and octadecynyl, preferably C _{2 to} C ₇ alkynyl groups.

Examples of C ₂ -C ₁₈ alkoxy include a group represented by —O— (C ₂ -C ₁₈ alkyl), preferably n-propoxy, isopropoxy, n-butyloxy, isobutyloxy, sec-butyloxy. Tert-butyloxy, n-pentyloxy, n-hexyloxy, n-heptyloxy, octyloxy, nonyloxy, decyloxy, undecyloxy, dodecyloxy, tridecyloxy, tetradecyloxy, pentadecyloxy, hexadecyloxy, A linear or branched C ₂ -C ₁₈ alkoxy group such as heptadecyloxy, octadecyloxy, etc., preferably a C ₂ -C ₇ alkoxy group is exemplified, and n-pentyloxy and n-hexyloxy are preferred.

The alkylthio of the C ₂ -C _18, -S- groups represented by include (C ₂ -C ₁₈ alkyl), preferably ethylthio, n- propylthio, isopropylthio, n- butylthio, isobutylthio, sec -Butylthio, tert-butylthio, n-pentylthio, n-hexylthio, n-heptylthio, octylthio, nonylthio, decylthio, undecylthio, dodecylthio, tridecylthio, tetradecylthio, pentadecylthio, hexadecylthio, heptadecylthio, octadecylthio, etc. A branched C _{2 to} C ₁₈ alkylthio group, preferably a C _{2 to} C ₇ alkylthio group, may be mentioned, and n-pentylthio and n-hexylthio are preferable.

  In the general formula (I), all eight R groups may be the same, or two or more substituents may be present in one compound (for example, four are hexyl groups and four are pentyl groups). Compound).

  Preferred phthalocyanine derivatives are compounds having an alkyl group at the 1,4,8,11,15,18,22,25 position of the phthalocyanine ring.

  The compound of general formula (I) is a well-known compound, can be synthesize | combined by a well-known method, for example, can be synthesize | combined according to the following scheme 1.

(R is as defined above)

  In the above dicyano compound, if two R groups are different (for example, pentyl group and hexyl group), or if two or more kinds of dicyano compounds having different R are used as raw materials, R in the general formula (I) is two or more kinds. A compound can be obtained.

  In the general formula (I), a compound having 4 to 5 carbon atoms in R has a crystalline phase, and a compound having 6 or more has an intermediate phase. Of these, from the viewpoint of developing the intermediate phase and expanding its temperature range, the eight Rs are preferably composed of two or more different linear or branched hydrocarbon groups. Here, the intermediate phase is a general term for a phase state having a certain molecular orientation order located between the crystalline phase and the amorphous phase, and includes a nematic liquid crystal phase, a smectic liquid crystal phase, a plastic crystal, and a discotic columnar liquid crystal. This refers to a molecular aggregation state such as a phase, a cholesteric liquid crystal phase, or an optically isotropic liquid crystal (cubic phase) phase. Such a mesophase-forming compound is advantageous in terms of device fabrication because it has two advantages of a large area uniformity of the film obtained by its spontaneous orientation and a molecular orientation mode convenient for carrier movement.

  The phthalocyanine derivative represented by the general formula (I) has high carrier mobility for both holes and electrons as a π-electron donor of the photoelectric conversion element.

  Some of the phthalocyanine derivatives represented by the general formula (I) express an intermediate phase in addition to high carrier mobility. Such a compound is soluble in an organic solvent and should be subjected to appropriate alignment treatment. Thus, self-organization can be promoted and it can be preferably used for a photoelectric conversion element.

  The photoelectric conversion element or the thin film solar cell of the present invention may contain π electron donors other than the above phthalocyanine derivatives in any combination as long as the performance is not deteriorated.

  FIG. 1 is a cross-sectional view showing an example of a photoelectric conversion element for a thin film solar cell.

  The photoelectric conversion element has a transparent electrode (ITO transparent electrode in FIG. 1), a hole transport layer (PEDOT: PSS in FIG. 1), a photoelectric conversion unit (in FIG. 1) on one side of a substrate (quartz substrate in FIG. 1). P3HT: C6PcH2: PCBM), an electron transport layer (LiF in FIG. 1), and a negative electrode (Al electrode in FIG. 1) are sequentially laminated.

  A board | substrate is a member holding the transparent electrode, photoelectric conversion part, and counter electrode (negative electrode) which were laminated | stacked one by one. In this embodiment of FIG. 1, since the photoelectrically converted light is incident from the substrate side, the substrate can transmit the photoelectrically converted light, that is, with respect to the wavelength of the light to be photoelectrically converted. Transparent member. For example, a glass substrate or a resin substrate is used as the substrate. This substrate is not essential. For example, an organic photoelectric conversion element may be configured by forming a transparent electrode and a counter electrode on both surfaces of the photoelectric conversion unit.

  The photoelectric conversion part is a layer that converts light energy into electric energy, and is preferably composed of a composition in which a π electron donor and a π electron acceptor are uniformly mixed in a gel or a polymer. The polymer or gel preferably has a polymerizable functional group, and the photoelectric conversion part may be constituted by polymerizing the polymerizable functional group in the liquid crystal phase of the compound (I).

  The π electron donor functions as an electron donor (donor), and the π electron acceptor functions as an electron acceptor. Here, the π-electron donor and the π-electron acceptor are “an electron donor that forms a hole-electron pair (charge-separated state) when electrons are transferred from the electron donor to the electron acceptor when light is absorbed. And an electron acceptor ”, which does not simply donate or accept electrons like an electrode, but donates or accepts electrons by a photoreaction.

  In FIG. 1, light incident from the transparent electrode through the substrate is absorbed by the π electron acceptor or π electron donor of the photoelectric conversion unit, electrons move from the π electron donor to the π electron acceptor, and holes and electrons are A pair (charge separation state) is formed. Due to the internal electric field, for example, when the work function of the transparent electrode and the counter electrode is different, due to the potential difference between the transparent electrode and the counter electrode, electrons pass between the π electron acceptors, and holes pass between the π electron donors. Each is carried to a different electrode and the photocurrent is detected. For example, when the work function of the transparent electrode is larger than the work function of the counter electrode, electrons are transported to the transparent electrode and holes are transported to the counter electrode. If the magnitude of the work function is reversed, electrons and holes are transported in the opposite direction. Moreover, the transport direction of electrons and holes can be controlled by applying a potential between the transparent electrode and the counter electrode.

  Although not shown in FIG. 1, other layers such as a hole blocking layer, an electron blocking layer, an electron injection layer, a hole injection layer, or a smoothing layer may be included.

  As a more preferable configuration, the photoelectric conversion portion may be a three-layer configuration in which a composition layer including a π electron donor and a π electron acceptor is sandwiched between a layer composed of a π electron donor alone and a layer composed of a π electron acceptor alone. . By adopting such a three-layer structure, the rectifying property of holes and electrons is further increased, loss due to recombination of charge-separated holes and electrons is reduced, and higher photoelectric conversion efficiency can be obtained. .

  Furthermore, it is good also as a tandem-type structure which laminated | stacked such a photoelectric conversion element for the purpose of the improvement of sunlight utilization factor (photoelectric conversion efficiency). In the case of the tandem type configuration, after laminating the transparent electrode and the first photoelectric conversion unit ′ sequentially on the substrate, laminating the charge recombination layer, laminating the second photoelectric conversion unit and then the counter electrode, A tandem configuration can be adopted. The second photoelectric conversion unit may be a layer that absorbs the same spectrum as the absorption spectrum of the first photoelectric conversion unit or may be a layer that absorbs a different spectrum, but is preferably a layer that absorbs a different spectrum.

  In the general formula (1), R is a linear or branched alkyl group having 2 to 7 carbon atoms, preferably 4 to 6 carbon atoms.

  It is preferable to dispose a hole transport layer between the photoelectric conversion part of the present invention and the transparent electrode (anode) because it is possible to more efficiently take out the charges generated in the photoelectric conversion part. Examples of the material constituting the hole transport layer include aromatic cyclic acid anhydrides represented by NTCDA for low molecular compounds, and poly (3,4-ethylenedioxy) for high molecular compounds. ) Thiophene; known conductive polymers represented by the following polystyrene sulfonate (PEDOT: PSS), polyaniline; camphorsulfonic acid (PANI: CSA), and the like.

  Further, a buffer layer may be inserted on one side or both sides of the photoelectric conversion unit in order to prevent the excitons from diffusing to the electrode and deactivating. The functioning as the exciton blocking layer in this way is effective for increasing the efficiency. As a preferable material in the case where the buffer layer has a role as an exciton blocking layer, for example, a well-known material for a hole barrier layer or a material for an electron barrier layer for organic electroluminescence (organic EL) applications may be used. A material preferably used as the hole blocking layer is a compound having a sufficiently high ionization potential, and a material preferably used as the electron blocking layer is a compound having a sufficiently low electron affinity. Specific examples of the hole blocking layer material on the cathode side include bathocuproin (BCP) and bathophenanthroline (BPhen).

  The photoelectric conversion element of the present invention is preferable because the charge generated in the photoelectric conversion unit can be taken out more efficiently by forming an electron transport layer between the photoelectric conversion unit and the counter electrode (cathode). . The means for forming these layers may be either a vacuum deposition method or a solution coating method, but is preferably a solution coating method.

  For the purpose of improving energy conversion efficiency and improving the lifetime of the element, a structure having various intermediate layers in the element may be employed. Examples of the intermediate layer include a hole block layer, an electron block layer, a hole injection layer, an electron injection layer, an exciton block layer, a UV absorption layer, a light reflection layer, and a wavelength conversion layer.

In the transparent electrode of the present invention, the cathode and the anode are not particularly limited and can be selected depending on the element structure, but it is generally used as an anode. In the present invention, the anode means an electrode for extracting holes. For example, when used as an anode, it is preferably an electrode that transmits light of 380 to 800 nm. As the material, for example, transparent conductive metal oxides such as indium tin oxide (ITO), SnO ₂ and ZnO, metal thin films such as gold, silver and platinum, metal nanowires and carbon nanotubes can be used. Also, a conductive material selected from the group consisting of polypyrrole, polyaniline, polythiophene, polythienylene vinylene, polyazulene, polyisothianaphthene, polycarbazole, polyacetylene, polyphenylene, polyphenylene vinylene, polyacene, polyphenylacetylene, polydiacetylene and polynaphthalene. A functional polymer can also be used. A plurality of these conductive compounds can be combined to form a transparent electrode.

The counter electrode of the present invention is not particularly limited to a cathode and an anode, and can be selected depending on the element structure, but is usually used as a cathode. In the present invention, the cathode means an electrode for taking out electrons. For example, when used as a cathode, the counter electrode may be a single layer of a conductive material, but in addition to a conductive material, a resin that holds these may be used in combination. The counter electrode may be a single layer of a conductive material, but in addition to a conductive material, a resin that holds these may be used in combination. As the conductive material of the counter electrode, a material having a small work function (4 eV or less) metal, alloy, electrically conductive compound and a mixture thereof is used. Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al ₂ O ₃ ) Mixtures, indium, lithium / aluminum mixtures, rare earth metals and the like. Among these, from the viewpoint of electron extraction performance and durability against oxidation, etc., a mixture of these metals and a second metal which is a stable metal having a larger work function value than this, for example, a magnesium / silver mixture, magnesium / Aluminum mixtures, magnesium / indium mixtures, aluminum / aluminum oxide (Al ₂ O ₃ ) mixtures, lithium / aluminum mixtures, aluminum and the like are preferred. The counter electrode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. The film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm.

  If a metal material is used as the conductive material of the counter electrode, the light coming to the counter electrode side is reflected and reflected to the first electrode side, and this light can be reused and is absorbed again by the photoelectric conversion layer, and more photoelectric conversion efficiency Is preferable. The counter electrode may be a metal (eg, gold, silver, copper, platinum, rhodium, ruthenium, aluminum, magnesium, indium, etc.), carbon nanoparticle, nanowire, or nanostructure. A dispersion is preferable because a transparent and highly conductive counter electrode can be formed by a coating method.

  Moreover, when making the counter electrode side light-transmitting, for example, after forming a conductive material suitable for the counter electrode such as aluminum and aluminum alloy, silver and silver compound in a thin film thickness of about 1 to 20 nm, By providing a film of the conductive light transmissive material mentioned in the description of the transparent electrode, a light transmissive counter electrode can be obtained.

  In addition, the intermediate electrode material required when the photoelectric conversion element has a tandem configuration is preferably a layer using a compound having both transparency and conductivity. Transparent metal oxides such as ITO, AZO, FTO and titanium oxide, very thin metal layers such as Ag, Al and Au, or layers containing nanoparticles / nanowires, conductive polymer materials such as PEDOT: PSS and polyaniline Etc.) can be used.

  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, polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) modified polyester, polyethylene (PE) resin film, polypropylene (PP) resin film, polystyrene resin film, polyolefin resins such as cyclic olefin resin Film, vinyl resin film such as polyvinyl chloride, polyvinylidene chloride, polyether ether ketone (PEEK) resin film, polysulfone (PSF) resin film, polyether sulfone (PES) resin film, polycarbonate (PC) resin film, A polyamide resin film, a polyimide resin film, an acrylic resin film, a triacetyl cellulose (TAC) resin film, and the like can be given. If the resin film transmittance of 80% or more at ~800nm), 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, and biaxially stretched. More preferred are polyethylene terephthalate films and biaxially stretched polyethylene naphthalate films.

  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.

  In order to suppress permeation of oxygen and water vapor, a barrier coat layer may be formed in advance on the transparent substrate.

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

  Various known antireflection layers can be provided as the antireflection layer. For example, when the transparent resin film is a biaxially stretched polyethylene terephthalate film, the refractive index of the easy adhesion layer adjacent to the film is 1.57. It is more preferable to set it to ˜1.63 because the interface reflection between the film substrate and the easy adhesion layer can be reduced and the transmittance can be improved. The method 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 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.

  As a method for forming a photoelectric conversion part in which a π electron acceptor (C60 derivative, third component) and a π electron donor (polythiophene derivative, third component) are mixed, and a transport layer / electrode, a vapor deposition method or a coating method is used. Examples include a printing method (including a casting method and a spin coating method). Although there is no restriction | limiting in the coating method used in this case, For example, a spin coat method, the casting method from a solution, a dip coat method, a blade coat method, a wire bar coat method, a gravure coat method, a spray coat method etc. are mentioned. Patterning can also be performed by a printing method such as an inkjet method, a screen printing method, a relief printing method, an intaglio printing method, an offset printing method, or a flexographic printing method. Solvents that dissolve the π electron acceptor (C60 derivative, third component) and π electron donor (polythiophene derivative, third component) include halogens such as chloroform, methylene chloride, carbon tetrachloride, and 1,2-dichloroethane. Solvents, aromatic hydrocarbons such as benzene, toluene and xylene, heteroaromatic compounds such as pyridine, alcohols such as methanol, ethanol, propanol and butanol, esters such as ethyl acetate, ethers such as THF, diethyl ether and diisopropyl ether, Examples include acetone, ketones such as methyl ethyl ketone, dioxane, DMF, DMSO, and the like. These solvents can be used alone or in combination of two or more.

  In the photoelectric conversion element of the present invention, the polythiophene derivative and the third component preferably have a fine crystal structure. When an active layer is formed by a printing method or a coating method, a photoelectric conversion element having high photoelectric conversion efficiency can be obtained by adjusting the solubility in a solvent, the evaporation rate of the solvent, the compatibility of the components to be blended, and the like. .

  After vapor deposition, coating or printing, it is preferable to perform heating in order to cause removal of residual solvent, moisture and gas, and improvement of mobility and absorption of long wave by crystallization of the semiconductor material. When annealing is performed at a predetermined temperature during the manufacturing process, a part of the material is microscopically promoted to agglomerate or crystallize, and an appropriate phase separation structure can be obtained. As a result, carrier mobility is improved and high efficiency can be obtained.

  The photoelectric conversion unit may be composed of a single layer in which a π electron acceptor and a π electron donor are uniformly mixed, or may be composed of a plurality of layers in which the mixing ratio of the π electron acceptor and the π electron donor is changed. Good. In this case, it can be formed by using a material that can be insolubilized after coating as described above.

  The photoelectric conversion part can be formed by dispersing a π electron donor and a π electron acceptor in a gel or a polymer. Examples of the polymerizable functional group include a group having a carbon-carbon double bond (for example, vinyl, allyl, acrylate, methacrylate).

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these Examples.

Example 1
A polymer conductive film (PEDOT: PSS) was spin-coated on a quartz substrate patterned with a 2 mm wide ITO transparent electrode (3000 rpm, 60 sec), 10 mg P3HT, 3 mg C6PcH ₂ , 10 mg of PCBM prepared by stirring in 1 ml of chloroform with an ultrasonic washer was spin-coated onto a PEDOT: PSS layer (500 rpm, 60 sec). A LiF buffer layer and an Al electrode were formed thereon by vacuum deposition through a 2 mm wide mask pattern. The effective area of the device was 2 × 2 mm ² .

The device produced by mixing C6PcH2 into the organic active layer by this method was excited with a spectral xenon lamp light, and the external quantum efficiency was measured at room temperature and in vacuum. No photocurrent was obtained with the device not mixed with C6PcH2. In addition, a significant improvement in photocurrent was obtained in the 650 to 800 nm wavelength region. An external quantum efficiency of 45% was obtained at 730 nm, the absorption peak of C6PcH2. Furthermore, under simulated sunlight (AM1.5, 100 mW / cm ² ) irradiation, the conversion efficiency was measured at room temperature and in vacuum using a solar simulator, and the light absorption wavelength range was expanded by mixing C6PcH2. As a result, the short-circuit photocurrent was increased by 1.4 times and the conversion efficiency was improved from 2.3% to 3.0% (FIGS. 2 and 3).

Example 2
Spin 10 mg of P3HT, C6PcH ₂ (1 mg, 2 mg, 3 mg, 4 mg, 5 mg, 6 mg), 10 mg of PCBM in 1 ml of chloroform with an ultrasonic cleaner and spin on the PEDOT: PSS layer A film was formed by coating (500 rpm, 60 sec), and X-ray diffraction data were measured. The results are shown in FIG. It was revealed that the number of diffraction peaks was high and P3HT and C6PcH2 coexisted under the conditions of P3HT: C6PcH ₂ = 10: 3.

Claims (3)

In the bulk hetero organic photoelectric conversion element, the active layer is a mixture of a polythiophene derivative and a C60 derivative and a third component is added to the system .
The polythiophene derivative is poly (3-hexylthiophene),
C60 derivative is PCBM,
The third component is a liquid crystalline phthalocyanine derivative having the general formula (I)

(Wherein the eight R groups are all identical C ₆ -C ₁₀ straight chain alkyl groups)
A bulk hetero-type organic photoelectric conversion element, which is a phthalocyanine derivative represented by: The bulk hetero organic photoelectric conversion device according to claim 1, wherein the alkyl group is a hexyl group. The organic thin-film solar cell containing the bulk hetero organic photoelectric conversion element of Claim 1 or 2.

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