JP5249825B2 - Organic solar cells - Google Patents

Description

  The present invention relates to an organic solar cell.

  With the development of industry, the amount of energy used has increased dramatically, and research and development of new clean energy sources that have a low environmental impact on the earth and are economical and have high performance are being carried out in various places. Here, solar cells are attracting attention as a new energy source because they use sunlight that can be said to be infinite.

  Here, most of the solar cells currently in practical use are inorganic silicon solar cells using single crystal silicon, polycrystalline silicon, or amorphous silicon. However, inorganic silicon solar cells have the disadvantages that their manufacturing process is complicated and expensive, so they have not been widely used in general households. In order to eliminate such drawbacks, research on organic solar cells (organic power generation elements) using organic materials, which can reduce costs and increase the area by a simple process, has been actively conducted.

  As an example, it is announced that a dye-sensitized solar cell based on a photochemical reaction using porous titanium oxide, ruthenium dye, iodine and iodine ion has a high conversion efficiency of 10%, which is a kind of organic solar cell. (See Non-Patent Document 1).

  In addition, organic thin-film solar cells, which are different types of organic solar cells from dye-sensitized solar cells, are also formed by vapor-depositing electron-donating semiconductors and electron-withdrawing semiconductors, which are low-molecular materials, by vacuum evaporation. It has been reported that a conversion efficiency of 3.6% was obtained in an organic thin film solar cell provided with a power generation layer having a double hetero structure between a positive electrode and a negative electrode as a pair of electrodes. (Refer nonpatent literature 2).

  In addition, as a material for the power generation layer in the organic solar cell, not only a low-molecular material but also a study of using a polymer material (polymer) is in progress. This is because when the material of the power generation layer is a low-molecular material, it is necessary to form the power generation layer by vacuum deposition, whereas when the material of the power generation layer is a polymer material, the power generation layer is applied and printed. This is because it can be formed using technology, and the manufacturing cost can be reduced.

  As an organic solar cell using a polymer material, an organic thin-film solar cell having a mixed layer of a conjugated polymer and a fullerene derivative as a power generation layer has recently been reported to have obtained a conversion efficiency of 5.5%. (See Non-Patent Document 3), various institutes have been devised and studied to obtain highly efficient organic thin-film solar cells.

  However, since the organic thin film solar cell uses the same structure and material as the organic EL element (organic electroluminescence element), there is a problem in durability in practical use.

  As means for improving the durability of the organic thin-film solar cell, for example, a technique has been reported that suppresses deterioration of characteristics due to light irradiation by removing oxygen and moisture (see Non-Patent Documents 4 and 5).

Christophe J Barbe, et, al, `` Nanocrystalline Titanium Oxide Electrodes for Photovoltaic Application '', J. Am. Ceram. Soc., 80, 1997, p. 3157-3171 P.Peumans, et, al, `` Very-high-efficiency double-heterostructure copper phthalocyanine / C60 photovoltaic cells '', APPLIED PHYSICS LETTERS, VOLUME 79, NUMBER 1,2001, p.126-128 J.PEET, et, al, `` Efficiency enhancement in low-bandgap polymer solar cells by processing with alkane dithiols '', nature materials, VOL 6,2007, p.497-500 Kenji Kawano, el, al, `` Degradation of organic solar cells due to air exposure '', Solar Energy Materials & Solar cells. 90, 2006, p. 3520-3530 H. Neugebauer et, al, `` Stability and photodegradation mechanisms of conjugated polymer / fullerene plastic solar cells '', Solar Energy Materials & Solar cells.61,2000, p.35-42

  By the way, in order to put an organic thin film solar cell into practical use, it is necessary to efficiently convert light into electricity and maintain its characteristics for a long time. However, even if oxygen and moisture are removed by applying the techniques disclosed in Non-Patent Documents 4 and 5 in order to improve the durability of the organic solar battery, the deterioration of characteristics gradually proceeds.

  The present invention has been made in view of the above reasons, and an object of the present invention is to provide an organic solar cell capable of extending the life.

  The invention of claim 1 is an organic solar cell comprising an organic solar cell element having a mixed layer of an electron-donating semiconductor and an electron-withdrawing semiconductor between a pair of electrodes, and the charge accumulated in the mixed layer is reduced. A heating means capable of heating the mixed layer so as to be discharged out of the mixed layer is provided.

According to the present invention, the organic solar cell is provided with the heating means for heating the mixed layer so as to discharge the charges accumulated in the mixed layer to the outside of the mixed layer. The electric charge accumulated in the element can contribute to power generation, and the characteristics of the organic solar cell element are restored by releasing the electric charge, so that the lifetime can be extended .
The invention according to claim 2 is the invention according to claim 1, wherein the substrate, the organic solar cell element formed on one surface side of the substrate, and the organic solar cell element are formed on the one surface side so as to cover the organic solar cell element. The surface protective layer is provided.

The invention according to claim 3 is the heating element according to claim 1 or 2 , wherein the heating means is provided outside the organic solar cell element and generates heat when energized to heat the mixed layer by heat transfer. It is characterized by being.

  According to this invention, it is possible to equalize the temperature of the mixed layer when the mixed layer is heated.

The invention of claim 4 is the invention of claim 1 or 2 , wherein at least one of the pair of electrodes is a resistor, and the resistor constitutes the heating means.

  According to this invention, it is not necessary to provide the heating means separately from the organic solar cell element, and the cost can be reduced.

According to a fifth aspect of the present invention, in the first or second aspect of the invention, at least one of the pair of electrodes is a metal electrode, and the heating means is provided outside the organic solar cell element and energized. It consists of a coil for induction heating a metal electrode.

  According to this invention, the incident light to the organic solar cell element can be prevented from being blocked by the heating means.

  In the invention of claim 1, by heating the mixed layer by the heating means, the charge accumulated in the solar cell element can contribute to power generation, and the characteristics of the solar cell element can be improved by releasing the charge. Since it can be recovered, there is an effect that the life can be extended.

The organic solar cell of Embodiment 1 is shown, (a) is a schematic sectional drawing, (b) is a schematic front view. It is characteristic explanatory drawing same as the above. It is characteristic explanatory drawing same as the above. It is characteristic explanatory drawing same as the above. The organic solar cell of Embodiment 2 is shown, (a) is a schematic sectional drawing, (b) is a schematic front view. The organic solar cell of Embodiment 3 is shown, (a) is a schematic sectional drawing, (b) is a schematic front view. The organic solar cell of Embodiment 4 is shown, (a) is a schematic sectional drawing, (b) is a schematic front view. 6 is a schematic cross-sectional view showing an organic solar battery according to Embodiment 5. FIG.

(Embodiment 1)
As shown in FIG. 1, the organic solar cell of the present embodiment includes a substrate 1 having a rectangular shape in plan view (in the illustrated example, a rectangular shape in plan view), and one surface side of the substrate 1 (upper surface side in FIG. And the surface protective layer 3 formed on the one surface side of the substrate 1 so as to cover the organic solar cell element 2.

  The organic solar cell element 2 includes a positive electrode 21 formed on the one surface side of the substrate 1, a hole transport layer 22 formed on the positive electrode 21, and sunlight formed on the hole transport layer 22. A mixed layer 23 that is a power generation layer (photoelectric conversion layer) that absorbs and generates electric power, an electron transport layer 24 formed on the mixed layer 23, and a negative electrode 25 formed on the electron transport layer 24 are provided. . In the present embodiment, the positive electrode 21 and the negative electrode 25 constitute a pair of electrodes.

  The above-described organic solar cell uses a light-transmitting substrate as the substrate 1 and the positive electrode 21 is formed of a transparent electrode. The other surface of the substrate 1 is a light incident surface for sunlight (external light).

  The translucent substrate that constitutes the substrate 1 is not limited to a colorless and transparent substrate, and may be one that is slightly colored. Here, a glass substrate such as a soda lime glass substrate or a non-alkali glass substrate is used as the translucent substrate constituting the substrate 1, but is not limited to a glass substrate, for example, polyester, polyolefin, polyamide resin, epoxy A plastic film or a plastic substrate formed of a resin, a fluorine-based resin, or the like may be used. Here, the glass substrate may be ground glass. Further, the substrate 1 may be provided with light diffusibility by containing particles, powder, bubbles, or the like having a refractive index different from that of the base material of the substrate 1 in the substrate 1. Moreover, when not providing the board | substrate 1 in the light-incidence surface side of the organic solar cell element 2, the material of the board | substrate 1 etc. are not specifically limited, What is necessary is just what can support the organic solar cell element 2. FIG.

Further, the positive electrode 21 is an electrode for efficiently collecting holes generated in the mixed layer 23, and the material of the positive electrode 21 is ITO, but is not limited to ITO. It is preferable to use a metal, an alloy, an electrically conductive compound, or a mixture thereof having a large work function. It is preferable to use one. Examples of the material of the positive electrode 2 include a conductive high polymer doped with a metal such as gold, a conductive polymer such as CuI, ITO, SnO ₂ , ZnO, IZO, PEDOT, polyaniline, and an arbitrary acceptor. Examples thereof include conductive light transmissive materials such as molecules and carbon nanotubes. Here, the positive electrode 21 may be formed on the one surface side of the substrate 1 by a vacuum deposition method, a sputtering method, a coating method, or the like. Here, in order to allow sunlight to pass through the positive electrode 21 and enter the mixed layer 23 as in this embodiment, the light transmittance of the positive electrode 2 is preferably set to 70% or more. Furthermore, the positive electrode 21 preferably has a sheet resistance of several hundred Ω / □ or less, and particularly preferably 100 Ω / □ or less. Here, the film thickness of the positive electrode 21 may be appropriately set according to the characteristics of the positive electrode 21, such as light transmittance, sheet resistance, etc., and varies depending on the material of the positive electrode 21, but is 500 nm or less, preferably 10 What is necessary is just to set suitably in the range of -200 nm.

The negative electrode 25 is an electrode for efficiently collecting electrons generated in the mixed layer 23. As a material of the negative electrode 25, a metal, an alloy, an electrically conductive compound having a small work function, and a mixture thereof are used. Preferably, a material having a work function of 1.9 eV or more and 5 eV or less is used so that the difference from the LUMO (Lowest Unoccupied Molecular Orbital) level does not become too large. Examples of the material of the negative electrode 25 include alkali metals, alkali metal halides, alkali metal oxides, alkaline earth metals, rare earths, and alloys of these with other metals such as sodium and sodium. -Potassium alloy, lithium, magnesium, magnesium-silver mixture, magnesium-indium mixture, aluminum-lithium alloy, Al / LiF mixture, etc. can be mentioned. Also, aluminum, a mixture of Al and Al ₂ O ₃ and the like can be used. The negative electrode 25 has at least one layer made of a material having a work function of 5 eV or less on the base film, using a thin film made of an alkali metal oxide, an alkali metal halide, or a metal oxide as the base film. These thin films may be laminated. As such a negative electrode 25, for example, a laminated film of a thin film made of alkali metal and a thin film made of Al, a thin film made of an alkali metal halide, a thin film made of alkaline earth metal, and a thin film made of Al are laminated. Examples thereof include a laminated film of an ultra-thin film made of Al ₂ O ₃ (here, a thin film having a thickness of 10 μm or less capable of flowing electrons by tunnel injection) and a thin film made of Al. The negative electrode 25 described above may be formed on the one surface side of the substrate 1 by vacuum deposition, sputtering, coating, or the like.

  In addition, as the electron-donating semiconductor of the organic compound used for the mixed layer 23, poly (3-hexylthiophene) (hereinafter abbreviated as P3HT), which is a kind of conductive polymer material, is employed. For example, phthalocyanine pigments, indigo, thioindigo pigments, quinacridone pigments, merocyanine compounds, cyanine compounds, squalium compounds, polycyclic aromatic compounds, charge transfer agents used in organic electrophotographic photoreceptors, electric Examples thereof include conductive organic charge transfer complexes, and other conductive polymer materials. However, the conductive organic charge transfer complexes are not limited to these as long as they are soluble in a solvent.

  Examples of the above phthalocyanine pigments include divalent pigments such as Cu, Zn, Co, Ni, Pb, Pt, Fe, and Mg, metal-free phthalocyanine, aluminum chlorophthalocyanine, indium chlorophthalocyanine, and gallium chlorophthalocyanine. Examples include, but are not limited to, trivalent metal phthalocyanine coordinated with a halogen atom, and other phthalocyanine coordinated with oxygen such as baanadyl phthalocyanine and titanyl phthalocyanine.

  Examples of the polycyclic aromatic compound include anthracene, tetracene, pentacene, and derivatives thereof, but are not particularly limited thereto.

  Examples of the charge transfer agent include, but are not limited to, hydrazone compounds, pyrazoline compounds, triphenylmethane compounds, and triphenylamine compounds.

  Examples of the electroconductive organic charge transfer complex include, but are not limited to, tetrathiofulvalene and tetraphenyltetrathioflavalene.

  In addition to P3HT described above, conductive polymer materials that donate electrons include poly (3-alkylthiophene), polyparaphenylene vinylene derivatives, polyfluorene derivatives, thiophene polymers, conductive polymer oligomers, and the like. Although what is soluble in an organic solvent is mentioned, it is not limited to these.

In addition, as the electron-withdrawing semiconductor used in the mixed layer 23, [6,6] -phenyl C61-butyric acid methyl ester (hereinafter abbreviated as PCBM), which is a fullerene derivative, is employed. limited without, for example, a particle size of compound and semiconductor nanocrystals of about 1 nm~100 nm, C ₆₀ and C ₇₀ low molecular weight material or a conductive polymer material made of a fullerene derivative containing the higher fullerenes such as, C _84, Carbon nanotubes can also be used. Here, the shape of the compound semiconductor nanocrystal is not particularly limited, and may be rod-shaped, spherical, or tetrapod-shaped. Specific materials for the compound semiconductor nanocrystal include III-V group compound semiconductors such as InP, InAs, GaP, and GaAs, II-VI group compound semiconductors such as CdSe, CdS, CdTe, and ZnS, ZnO, SiO ₂ , and TiO _2. Examples thereof include oxide semiconductors such as Al ₂ O ₃ , CuInSe ₂ , and CuInS, but are not particularly limited thereto. The mixed layer 23 may have a large number of rod-shaped compound semiconductor nanocrystals arranged at intervals of 200 nm or less in contact with the electron transport layer 24, but this interval is not particularly limited. .

  The electron-donating semiconductor and the electron-withdrawing semiconductor of the mixed layer 23 are not limited to either a high molecular material or a low molecular material, and either one may be adopted.

  Moreover, as a material of the above-mentioned hole transport layer 22 interposed between the positive electrode 21 and the mixed layer 23, polyethylenedioide thiophene: polystyrene sulfonate (PEDOT: PSS) is adopted. It has the ability to transport holes, has a hole transfer effect from the mixed layer 4, has an excellent hole transfer effect with respect to the positive electrode 21, and blocks electrons. Compounds having excellent characteristics and excellent thin film forming ability. Specifically, for example, phthalocyanine derivatives, naphthalocyanine derivatives, porphyrin derivatives, N, N′-bis (3-methylphenyl)-(1,1′-biphenyl) -4,4′-diamine (TPD) and 4 , 4′-bis [N- (naphthyl) -N-phenyl-amino] biphenyl (α-NPD) and the like, oxazole, oxadiazole, triazole, imidazole, imidazolone, stilbene derivative, pyrazoline derivative, tetrahydro Imidazole, polyarylalkane, butadiene, 4,4 ′, 4 ″ -tris (N- (3-methylphenyl) N-phenylamino) triphenylamine (m-MTDATA), and polyvinylcarbazole, polysilane, aminopyridine derivative, Polyethylene geoside thiophene (PEDO) However, the present invention is not limited to these materials, and examples thereof include molybdenum trioxide, vanadium pentoxide, tungsten trioxide, and rhenium oxide having hole transport properties. Inorganic oxides and inorganic oxides such as p-type semiconductors such as nickel oxide and copper oxide can also be used, and even inorganic materials can be used without limitation as long as they have hole transportability can do.

Examples of the material of the electron transport layer 24 interposed between the negative electrode 25 and the mixed layer 23 include bathocuproin, bathophenanthroline, and derivatives thereof, TPBi, silole compound, triazole compound, tris (8- Hydroxyquinolinato) aluminum complex, bis (4-methyl-8-quinolinato) aluminum complex, oxadiazole compound, distyrylarylene derivative, silole compound, TPBI (2,2 ′, 2 ″-(1,3,3) 5-benzenetolyl) tris- [1-phenyl-1H-benzimidazole]) and the like, but any material having an electron transporting property may be used, and the material is not particularly limited thereto. the materials, compounds and semiconductor nanocrystals mentioned as the material of the mixed layer 23, C ₆₀ and C _70, C _84, etc. Low molecular materials made of fullerene derivatives containing higher-order fullerenes, conductive polymers, carbon nanotubes, and the like can also be used, and any electron transporting material can be used without particular limitation. Thus, the material used for the electron transport layer 24 is preferably a material having an electron mobility of 10 ⁻⁶ cm ² / Vs or more, and more preferably a material having 10 ⁻⁵ cm ² / Vs or more.

  Further, as the material of the surface protective layer 3 described above, a material having a gas barrier property may be employed. For example, a fluorine-based compound, a fluorine-based polymer, other organic molecules, a polymer material, or the like may be employed. Here, the surface protective layer 3 may be formed on the one surface side of the substrate 1 by a vapor deposition method, a sputtering method, a CVD method, a plasma polymerization method, or the like, or a solution of a polymer material as in a spin coating method. It can also be formed by a method of applying an ultraviolet ray or heat after applying by a different application method, or other methods. Further, the surface protective layer 3 may be constituted by a laminated film of an insulating film made of a general-purpose polymer and a metal film such as an Al film having gas barrier properties and an insulating film made of a general-purpose polymer. Each insulating film may be formed by a coating method, and the metal film may be formed by a method capable of forming a highly dense metal film such as a sputtering method. Further, the surface protective layer 3 can be formed of a film-like or plate-like structure having light permeability and gas barrier properties. In the former case, the surface protective layer 3 is formed on the one surface of the substrate 1 by a vacuum laminating method, for example. What is necessary is just to adhere a peripheral part to the said one surface of the board | substrate 1 with sealing agents (adhesive agent), such as an ultraviolet curable resin, for example. When the surface protective layer 3 having such light transmittance is employed, if the negative electrode 25 is formed of a transparent electrode, sunlight can be incident on the mixed layer 23 through the surface protective layer 3 and the negative electrode 25. Therefore, it is not always necessary to configure the substrate 1 with a translucent substrate, and it is not necessary to configure the positive electrode 21 with a transparent electrode. In addition, when making sunlight inject into the mixed layer 23 from the surface protective layer 3 side, it is preferable that the light transmittance of the surface protective layer 3 shall be 70% or more.

  Moreover, in the organic solar cell of this embodiment, the external connection electrode 21a electrically connected to the positive electrode 21 and the external connection electrode 25a electrically connected to the negative electrode 25 on the one surface of the substrate 1. Is formed on the side surface of the organic solar cell element 2 on the one surface side of the substrate 1 to electrically insulate the positive electrode 21 from the connection portion between the negative electrode 25 and the external connection electrode 25a. An insulating film 4 is formed.

  Further, in the configuration shown in FIG. 1, the organic solar cell element 2 includes the hole transport layer 22 and the electron transport layer 24, and the positive electrode 21 / hole transport layer 22 / mixed layer 23 / electron transport layer 24 / Although it has the layer structure of the negative electrode 25, the layer structure of the organic solar cell element 2 is not particularly limited as long as the mixed layer 23 is provided at least between the positive electrode layer 21 and the negative electrode 25. For example, the layer structure of the positive electrode 21 / power generation layer 23 / negative electrode 25 may be used, the layer structure of the positive electrode 21 / hole transport layer 22 / mixed layer 23 / negative electrode 25, or the positive electrode 21 / mixed layer. The layer structure of 23 / electron transport layer 24 / negative electrode 25 may be used.

  By the way, as a result of earnest research, the inventor of the present application has determined a specific temperature that is determined according to the material of the mixed layer 23 after the characteristics (conversion efficiency) of the above-described organic solar cell element 2 are reduced by light irradiation. It was found that the characteristics of the organic solar cell element 2 were recovered by heating at, and the charge accumulated in the mixed layer 23 was taken out by light irradiation.

  Therefore, the organic solar cell of the present embodiment includes a heating unit 8 that can heat the mixed layer 23 so that the charge accumulated in the mixed layer 23 is released to the outside of the mixed layer 23. Here, the heating means 8 is composed of a heating element composed of a silicon rubber heater that generates heat when energized, and is provided on the surface protective layer 3 in contact with the surface protective layer 3. Therefore, the heating means 8 is arrange | positioned so that the organic solar cell element 2 may be heated by heat transfer.

  Hereinafter, the above knowledge will be described with reference to FIGS.

  FIGS. 2-4 is the result of having measured the characteristic about the organic solar cell of the following Examples 1-5.

  In the organic solar cells of Examples 1 to 5, the substrate 1 was a glass substrate and the positive electrode 21 was an ITO film, and the hole transport layer 22 was formed on the one surface side of the substrate 1 on which the positive electrode 21 was formed. In forming the hole transport layer 22, the material of the hole transport layer 22 was PEDOT: PSS (manufactured by Starck), and the film thickness of the hole transport layer 22 was 40 nm. Here, as a pretreatment when forming the hole transport layer 22, ultrasonic cleaning is performed for 10 minutes each with acetone, isopropyl alcohol, semi-clean, and ultrapure water, followed by cleaning with vapor of isopropyl alcohol. Then, a surface cleaning treatment with atmospheric pressure plasma was performed for 3 minutes.

  In forming the mixed layer 23, P3HT (manufactured by Merck, regioregular type) is used as the electron donating semiconductor, and PCBM (manufactured by Solenne), which is a fullerene derivative, is used as the electron withdrawing semiconductor (hole donating semiconductor). P3HT and PCBM were dissolved in a mixed solvent in which 1,2-dichlorobenzene and chloroform were mixed at a volume ratio of 6: 4 at a mass ratio of 1: 2 to 1: 0.2. Then, the substrate 1 on which the positive electrode 21 and the hole transport layer 22 are formed is transferred to a glove box having a dew point of −76 ° C. or less and an oxygen of 1 ppm or less in a dry nitrogen atmosphere, and P3HT and PCBM are placed on the hole transport layer 22. A solution dissolved in a mixed solvent was spin-coated to form a mixed layer 23 having a thickness of 200 nm. Here, the mass ratio of P3HT and PCBM is 1: 2 in Example 1, 1: 1 in Example 2, 1: 0.7 in Example 3, and 1: 0.4 in Example 4. In Example 5, it was set to 1: 0.2.

  In forming the negative electrode 25, the negative electrode 25 made of an Al film having a film thickness of 100 nm was formed by vacuum deposition.

  Next, the substrate 1 on which the positive electrode 21, the hole transport layer 22, the mixed layer 23, and the negative electrode 25 were formed was transported to a glove box in a dry nitrogen atmosphere having a dew point of −76 ° C. or less without being exposed to the air. On the other hand, a getter kneaded with calcium oxide as a water-absorbing material is affixed to a glass sealing plate with an adhesive, and a sealing agent made of UV curable resin is applied to the outer periphery of the sealing plate in advance. In the box, the surface protection layer 3 which consists of a sealing board which is a plate-shaped structure was formed by sticking a sealing board on the board | substrate 1 with the sealing compound, and hardening a sealing compound with UV.

  Further, as the heating means 8, a silicon rubber heater (manufactured by ASONE Co., Ltd.) was provided in contact with the surface protective layer 3.

In the above-described FIGS. 2A to 2C, the organic solar cells of Examples 1 to 5 are irradiated with simulated solar light having an air mass of 1.5 G and 100 mW / cm ^{2 on} the other surface of the substrate 1. FIG. 2 shows the result of measuring the change over time of the conversion efficiency of the element 2, and it can be seen from FIG. 2 that the conversion efficiency decreases as the elapsed time from the start of irradiation increases in all of Examples 1-5. . The conversion efficiencies in FIG. 2 and FIG. 3 are values normalized by assuming that the conversion efficiency at the start of irradiation is 1 in each of Examples 1 to 5.

Moreover, the above-mentioned (i) to (ii) in FIG. 3 irradiate the other surface of the substrate 1 with pseudo-sunlight of air mass 1.5G and 100 mW / cm ² for the organic solar cells of Examples 1 to 8, respectively. FIG. 3 shows the results of measuring the conversion efficiency before and after heating when the organic solar cell was heated to 150 ° C. after irradiation for a period of time. From FIG. 3, after heating at 150 ° C. (“ It can be seen that the conversion efficiency of “after” is higher than that before heating (“front” on the horizontal axis in FIG. 3), and that the conversion efficiency at the start of irradiation is restored. In heating the organic solar cell, the organic solar cell was placed in a metal chamber having a cylinder provided with a heater around it, and the heater was heated to 150 ° C. at a rate of temperature increase of 10 ° C./min.

4A and 4B, the organic solar cells of Examples 1 to 5 were irradiated with simulated solar light with an air mass of 1.5 G and 100 mW / cm ^{2 on} the other surface of the substrate 1 and 8 respectively. The graph shows the change in current density when each organic solar cell was heated from −73 ° C. (200 K) to 150 ° C. (423 K) at a rate of temperature increase of 10 ° C./min after time irradiation. Here, the current density was obtained by dividing the output current of the organic solar cell element 2 by the plane area (power generation area) of the region overlapping the positive electrode 21 and the negative electrode 25 in the mixed layer 23 in the organic solar cell element 2. Value.

  In the organic solar cells of Examples 1 to 5, in which the mixed layer 23 is formed using P3HT and PCBM, the conversion efficiency is improved by irradiating the organic solar cell with pseudo sunlight for 8 hours. Even after the decrease, it is presumed that most of the charges accumulated in the mixed layer 23 are taken out by heating to 150 ° C.

  Here, the organic solar cell of the present embodiment includes the heating unit 8 that heats the mixed layer 23 so as to release the charge accumulated in the mixed layer 23 to the outside of the mixed layer 23. By heating the mixed layer 23, the electric charge accumulated in the organic solar cell element 2 can contribute to power generation, and the characteristics (conversion efficiency) of the organic solar cell element 2 are restored by releasing the electric charge. Therefore, the service life can be extended.

  Here, the heating temperature by the heating means 8 is optimal near the glass transition temperature (Tg) of the organic compound used in the mixed layer 23. For example, when the organic compound is P3HT, 140 to 170 ° C. is preferable. As can be seen from FIG. 4, 150 ° C., which is the glass transition temperature of PH3T, is particularly preferable. Here, when the heating temperature is lower than 140 ° C., the thermal energy given to the mixed layer 23 is insufficient, and the current due to the electric charge accumulated in the mixed layer 23 is sufficiently taken out of the organic solar cell element 2. Since the charge remains in the organic solar cell element 2, the conversion efficiency of the organic solar cell element 2 does not recover to substantially the same conversion efficiency as the initial conversion efficiency. Moreover, when heating temperature is too high, destruction of an organic material will arise and a characteristic will be reduced.

Alternatively, at least one of the positive electrode 21 and the negative electrode 25 may be used as a resistor, and the resistor may be energized, and the mixed layer 23 may be heated by heat generated by the resistor due to the energization. Here, in order to configure the resistor, a low resistance made of a material having a work function necessary for power generation of the organic solar cell element 2 (for example, ITO for the positive electrode 21 and Al for the negative electrode 25). A layer may be combined with a high resistance layer made of a material having a higher resistance than the low resistance layer (for example, an oxide semiconductor such as SnO ₂ or a metal having a relatively high resistance). In this case, for example, a high resistance layer made of, for example, a SnO ₂ film may be formed in, for example, a stripe shape in a portion that does not block external light to the mixed layer 23, or may be formed in an extremely fine grid shape. The blocking of extraneous light may be minimized. As described above, if at least one of the positive electrode 21 and the negative electrode 25 that are a pair of electrodes is a resistor, and the resistor constitutes the heating means 8, the heating means 8 is replaced with the organic solar cell element 2. There is no need to provide it separately, and the cost can be reduced.

  In this embodiment, only the positive electrode 21 is a transparent electrode, but only the negative electrode 25 or both the positive electrode 21 and the negative electrode 25 are transparent electrodes, and the planar shape of the heating means 8 is a frame shape. In addition, the surface protective layer 3 may be formed of a translucent material.

(Embodiment 2)
The basic configuration of the organic solar cell of the present embodiment is substantially the same as that of the first embodiment. As shown in FIG. 5, the heating means 8 made of a heating element is disposed in contact with the other surface of the substrate 1 and is organic. It is different in that it is formed in a frame shape surrounding the projection area of the solar cell element 2. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 1, and description is abbreviate | omitted.

  Thus, in the organic solar cell of the present embodiment, the heating means 8 is arranged in contact with the other surface of the substrate 1 and is formed in a frame shape surrounding the projection region of the organic solar cell element 2. A decrease in the amount of power generation due to a decrease in the power generation area of the organic solar cell element 2 can be prevented. Here, the heating means 8 should just be provided in the part which does not block the external light introduce | transduced into the mixed layer 23, and the position provided is not specifically limited.

As the heating element constituting the heating means 8, the same silicon rubber heater as that of the first embodiment may be used, or it may be constituted by an SnO ₂ film appropriately patterned so as to surround the projection region. Heat may be generated by energizing the _two films.

  In this embodiment, only the positive electrode 21 is used as a transparent electrode. However, the surface protective layer 3 is formed of a translucent material using only the negative electrode 25 or both the positive electrode 21 and the negative electrode 25 as transparent electrodes. You may make it do.

(Embodiment 3)
The basic configuration of the solar cell of the present embodiment is substantially the same as that of the first embodiment, and is different in that the heating means 8 is provided between the substrate 1 and the positive electrode 21 as shown in FIG. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 1, and description is abbreviate | omitted.

  In the present embodiment, as the heating means 8, for example, a base material made of a translucent material with a linear heater embedded therein may be used, or a metal thin film having translucency may be used. Alternatively, the material may be selected so that each of the negative electrode 25 and the surface protective layer 3 has translucency.

(Embodiment 4)
The basic configuration of the organic solar cell of the present embodiment is substantially the same as that of the first embodiment. As shown in FIG. 7, the heating means 8 is provided outside the organic solar cell element 2 and energized so that the metal electrode. The negative electrode 25 is made of a coil for induction heating. That is, the mixed layer 23 is heated by induction heating of the negative electrode 25 made of a metal electrode. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 1, and description is abbreviate | omitted.

  Here, the coil which comprises the heating means 8 differs in the point currently formed in the coil-shaped shape surrounding the projection area | region of the organic solar cell element 2 on the said other surface of the board | substrate 1. FIG. Here, copper is used as the material of the heating means 8, but any metal that can be induction-heated may be used, and the material is not particularly limited to copper.

  Therefore, also in the organic solar battery of this embodiment, it is possible to prevent the incident light to the organic solar battery element 2 from being blocked by the heating means 8. In the present embodiment, only the negative electrode 25 is configured by a metal electrode, but at least one of the positive electrode 21 and the negative electrode 25 may be a metal electrode, and when both are configured by a metal electrode, It is necessary to set the film thickness so that at least one of them has translucency, or to pattern so that the portion that blocks the extraneous light to the mixed layer 23 is reduced.

(Embodiment 5)
The basic configuration of the organic solar cell of the present embodiment is substantially the same as that of the first embodiment. As shown in FIG. 8, the heating means 8 is configured by an infrared absorbing sheet fixed to the other surface of the substrate 1. Is different. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 1, and description is abbreviate | omitted.

  Thus, in the organic solar cell of the present embodiment, the organic solar cell element 2 efficiently absorbs infrared rays that hardly contribute to power generation in the organic solar cell element 2 by the infrared absorbing sheet that is the heating means 8 and converts it into heat. Since 2 can be heated, there is no need to energize the heating means 8 and the running cost can be reduced.

  In each of the above embodiments, the heating means 8 for releasing the charge accumulated in the mixed layer 23 of the organic solar cell element 2 to the outside includes the positive electrode 21, the hole transport layer 22, and the organic solar cell element 2. By applying thermal energy to the mixed layer 23, the electron transport layer 24, and the negative electrode 25, the thermal vibration of each of the positive electrode 21, the hole transport layer 22, the mixed layer 23, the electron transport layer 24, and the negative electrode 25 is amplified, The charge captured and accumulated in the mixed layer 23 is taken out. As a means for taking out the charge accumulated in the mixed layer 23, a positive electrode 21 constituting the organic solar cell element 2, a hole transport layer 22, Energy corresponding to a difference in work function or electron affinity between the materials of the mixed layer 23, the electron transport layer 24, and the negative electrode 25, or between the electron donating semiconductor and the electron withdrawing semiconductor forming the mixed layer 23. Outside It can be taken out charges that are trapped in the organic solar cell element in a two by giving the. As an emitting means for releasing the charge of the mixed layer 23 to the outside by applying such energy from the outside, for example, irradiation with light having a wavelength corresponding to the above-described difference in work function or electron affinity can be cited. The energy in this case is preferably 0.5 to 1.0 eV, more preferably 0.6 to 0.9 eV (that is, the light wavelength is preferably 1240 to 2480 nm, 1370). A wavelength of ˜2070 nm is more preferred).

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Organic solar cell element 3 Surface protective layer 8 Heating means 21 Positive electrode (electrode)
22 hole transport layer 23 mixed layer 24 electron transport layer 25 negative electrode (electrode)

Claims (5)

  An organic solar cell including an organic solar cell element having a mixed layer of an electron-donating semiconductor and an electron-withdrawing semiconductor between a pair of electrodes so as to discharge charges accumulated in the mixed layer to the outside of the mixed layer An organic solar cell comprising a heating means capable of heating the mixed layer. A substrate, the organic solar cell element formed on one surface side of the substrate, and a surface protective layer formed on the one surface side of the substrate so as to cover the organic solar cell element. Item 10. An organic solar cell according to Item 1. Said heating means, according to claim 1 or 2 Symbol placement of organic solar and this and features exothermed to a heating element to heat the mixed layer by heat transfer by being energized is provided outside of the organic solar cell device battery. At least one of a resistor, according to claim 1 or 2 Symbol placement organic solar cells, characterized in that the resistor constitute the heating means of the pair of electrodes. The at least one of the pair of electrodes is a metal electrode, and the heating unit includes a coil that is provided outside the organic solar cell element and that inductively heats the metal electrode when energized. The organic solar cell according to 1 or 2.

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