JP2008211165A - Composition appropriate for photoelectromotive element, and the photoelectromotive element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectromotive element which has high photoelectric conversion efficiency. <P>SOLUTION: A composition contains a component A which is an electron-donor conjugated polymer compound, a component B which is an electron-acceptor organic semiconductor, a component C which is a good solvent for the components A and B, and a component D which is an amide-based solvent having a specific inductive capacity of 33 or higher at 25°C. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a composition that can be suitably used for forming an active layer of a photovoltaic device, and a photovoltaic device using the composition.

  Solar cells are attracting attention as an environmentally friendly electrical energy source and an influential energy source for increasing energy problems. Currently, inorganic materials such as single crystal silicon, polycrystalline silicon, amorphous silicon, and compound semiconductor are used as semiconductor materials for photovoltaic elements of solar cells. However, solar cells manufactured using inorganic semiconductors have not been widely used in ordinary households because of high costs compared with power generation methods such as thermal power generation and nuclear power generation. The main reason for the high cost is the process in which the semiconductor thin film must be manufactured under vacuum and high temperature. Therefore, organic semiconductor cells using organic semiconductors such as conjugated polymers and organic crystals and organic dyes are being studied as semiconductor materials that are expected to simplify the manufacturing process. In such an organic solar cell, since a semiconductor material can be produced by a coating method, the manufacturing process can be simplified.

  However, conventional organic solar cells typified by conjugated polymers have not yet been put into practical use because of lower photoelectric conversion efficiency than conventional solar cells using inorganic semiconductors. This is mainly due to the fact that a bound state called exciton, in which electrons and holes generated by incident light are difficult to separate, is easily formed, and the generated carriers are easily trapped in the trap, resulting in low carrier mobility.

  For this reason, mobility is achieved by means of successfully separating generated electrons and holes from excitons, and suppressing carrier scattering and trapping of carriers between amorphous regions and conjugated polymer chains of conjugated polymers. Finding a means that can improve the power is the key to putting solar cells made of organic semiconductor materials into practical use.

  The following element structure is known as a conventional photovoltaic element using an organic semiconductor. That is, a Schottky type, an electron-accepting organic material (n-type organic semiconductor) and an electron-donating organic material (p-type organic semiconductor) for joining an electron-donating organic material (p-type organic semiconductor) and a metal having a small work function. Heterojunction type to be joined. These photovoltaic elements have low photoelectric conversion efficiency because only the organic layer (about several molecular layers) at the junction contributes to photocurrent generation.

Therefore, as one method for improving photoelectric conversion efficiency, an electron-accepting organic material (n-type organic semiconductor) and an electron-donating organic material (p-type organic semiconductor) are mixed, and the area of the pn-junction surface that causes photoelectric conversion is reduced. An increased bulk heterojunction type (for example, see Non-Patent Document 1) has been proposed. Use for example, using a conjugated polymer as an electron donating organic material (p-type organic semiconductor), a fullerene or a carbon nanotube, such as other C ₆₀ of the conductive polymer having the semiconductor characteristics of the n-type as the electron accepting organic material Known photoelectric conversion materials are known (see, for example, Non-Patent Document 2, Patent Documents 1 and 2).
Nature 376, pages 498-500, (1995) Applied Physics Letters (USA), 80, 112-114, (2002) JP 2003-347565 A (Claims 1 and 3) JP 2004-165474 A (Claims 1 and 3)

  It is known that an active layer of a bulk heterojunction element can be formed by a coating method using chlorobenzene, dichlorobenzene, chloroform, or the like as a solvent. On the other hand, according to the knowledge of the present inventors, the photoelectric conversion efficiency of the active layer depends not only on the semiconductor material but also on the solvent system. However, no conventionally known solvent system having sufficient photoelectric conversion efficiency has been found. Then, an object of this invention is to provide the composition which gives the active layer with high photoelectric conversion efficiency.

  In order to solve such problems, the present inventors have made extensive studies on solvent systems, and have focused on short-circuit current values and fill factors (FF), which are factors for improving photoelectric conversion efficiency, and have found compositions that have improved these. The present invention has been completed.

  That is, the present invention provides a composition (coating solution) for forming an active layer comprising an electron-donating conjugated compound, an electron-accepting organic semiconductor, and a good solvent for the material, having a relative dielectric constant of 33 or more at 25 ° C. The present invention provides a photovoltaic device in which an active layer is formed using such a composition.

  According to the present invention, a photovoltaic device with high photoelectric conversion efficiency can be provided.

The composition of the present invention comprises an A component, an electron donating conjugated compound, a B component, an electron accepting organic semiconductor C component, a good solvent for the A component, the B component, and a D component. An amide solvent having a relative dielectric constant of 33 or more at 25 ° C including.

  The electron donating conjugated compound of component A used in the present invention is not particularly limited as long as it is a conjugated compound exhibiting p-type semiconductor characteristics. For example, polythiophene polymer, poly-p-phenylene vinylene polymer, poly -Conjugated polymers such as p-phenylene polymers, polyfluorene polymers, polypyrrole polymers, polyaniline polymers, polyacetylene polymers, polythienylene vinylene polymers, compounds containing benzothiadiazole, etc. Can be mentioned. Here, the XX polymer indicates a polymer having a XX structure skeleton, and includes a polymer in which at least a part thereof is substituted and a polymer having a side chain. For example, examples of the poly-p-phenylene vinylene polymer include poly-p-phenylene vinylene and a polymer having a side chain on the poly-p-phenylene vinylene. Two or more of these may be used. The degree of polymerization of the electron donating conjugated polymer is not particularly limited, but is preferably 5 or more and 500 or less from the viewpoint of solubility in a solvent.

  Among the electron donating conjugated compounds, a compound containing a polythiophene polymer or benzothiadiazole is preferable in that light having a long wavelength can be used for photoelectric conversion.

  The polythiophene polymer is a conjugated polymer having a polythiophene structure skeleton or a structure having a side chain attached thereto. Specifically, poly-3-alkylthiophene such as poly-3-methylthiophene, poly-3-butylthiophene, poly-3-hexylthiophene, poly-3-octylthiophene, poly-3-decylthiophene, and poly-3 -Methoxythiophene, poly-3-ethoxythiophene, poly-3-alkoxythiophene such as poly-3-dodecyloxythiophene, poly-3-methoxy-4-methylthiophene, poly-3-dodecyloxy-4-methylthiophene, etc. Of poly-3-alkoxy-4-alkylthiophene. Among these, poly-3-hexylthiophene is more preferable. Poly-3-hexylthiophene is suitable for obtaining a homogeneous film and can use long-wavelength light for photoelectric conversion.

  Among the compounds containing benzothiadiazole, a compound represented by the following general formula (1) is more preferable. Such a compound is suitable for obtaining a homogeneous film, and long wavelength light can be used for photoelectric conversion.

R ^{1 to} R ¹² may be the same or different and each represents hydrogen, an alkyl group, an alkoxy group, an aryl group, or a heteroaryl group. Each m is independently 1 or 2, and n represents a range of 1 or more and 1000 or less. Here, the alkyl group is, for example, a saturated aliphatic carbonization such as methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group. It is a hydrogen group and may be linear or branched. Further, the alkoxy group represents an aliphatic hydrocarbon group via an ether bond such as a methoxy group, an ethoxy group, a propoxy group, or a butoxy group, and the aliphatic hydrocarbon group may be unsubstituted or substituted. The aryl group refers to an aromatic hydrocarbon group such as a phenyl group, a naphthyl group, a biphenyl group, a phenanthryl group, an anthryl group, a terphenyl group, a pyrenyl group, or a fluorenyl group, which is unsubstituted or substituted. It doesn't matter. The heteroaryl group includes, for example, thienyl group, furyl group, pyrrolyl group, imidazolyl group, pyrazolyl group, oxazolyl group, pyridyl group, pyrazyl group, pyrimidyl group, quinolinyl group, isoquinolyl group, quinoxalyl group, acridinyl group, carbazolyl group. Heteroaromatic groups having atoms other than carbon, such as, may be unsubstituted or substituted.

  The electron-accepting organic semiconductor of component B used in the present invention is not particularly limited as long as it is an organic material exhibiting n-type semiconductor characteristics. For example, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 3,4, 9,10-perylenetetracarboxylic dianhydride, N, N′-dioctyl-3,4,9,10-naphthyltetracarboxydiimide, oxazole derivative (2- (4-biphenylyl) -5- (4-t-butyl) Phenyl) -1,3,4-oxadiazole, 2,5-di (1-naphthyl) -1,3,4-oxadiazole, etc.), triazole derivatives (3- (4-biphenylyl) -4-phenyl -5- (4-t-butylphenyl) -1,2,4-triazole, etc.), phenanthroline derivatives, fullerene derivatives, carbon nanotu And a derivative (CN-PPV) in which a cyano group is introduced into a poly-p-phenylene vinylene polymer. Two or more of these may be used. A fullerene derivative is preferably used because it is an n-type semiconductor that is stable and has high carrier mobility.

Specific examples of the fullerene derivative include unsubstituted ones such as C ₆₀ , C ₇₀ , C ₇₆ , C ₇₈ , C ₈₂ , C ₈₄ , C ₉₀ , and C ₉₄ , and [6,6] -phenyl C61 Rick acid methyl ester ([6,6] -C61-PCBM), [5,6] -phenyl C61 butyric acid methyl ester, [6,6] -phenyl C61 butyric acid hexyl ester, [6,6]- Examples thereof include substituted derivatives such as phenyl C61 butyric acid dodecyl ester and [6,6] -phenyl C71 butyric acid methyl ester.

  In the present invention, any of the above fullerene derivatives can be used, but [6,6] -C61-PCBM is more preferably used from the viewpoint of solubility in an organic solvent.

  The contents of the electron donating conjugated compound of component A and the electron accepting organic semiconductor of component B are not particularly limited as long as both component A and component B are dissolved in the composition according to the present invention. The weight fraction of the B component is preferably in the range of A component: B component = 1 to 99:99 to 1, more preferably in the range of 20 to 80:80 to 20. However, at any weight fraction, the sum of the weights of the A component and the B component is preferably 0.1 to 3.0 parts by weight with respect to 100 parts by weight of the sum of the C and D components described later. More preferably, it is 0.5 to 2.0 parts by weight.

  The good solvent for the A component and B component used for the C component in the present invention is not particularly limited as long as it provides a uniform solution as the composition of the present invention (however, the amide solvent of the D component described later is Although it does not correspond to this C component, it is desirable to use those having a solubility at 25 ° C. of 5 mg / mL or more for each of the A component and the B component. Examples thereof include toluene, xylene, acetone, ethyl acetate, tetrahydrofuran, dichloromethane, chloroform, dichloroethane, chlorobenzene, dichlorobenzene, and trichlorobenzene. Two or more of these may be used. Among the good solvents, chlorobenzene, dichlorobenzene, and chloroform having higher solubility of the A component and the B component are preferably used. Chlorobenzene and dichlorobenzene having the highest solubility of the A component and the B component are more preferably used. This is because when these solvents are used as the C component, a uniform coating solution can be obtained even if the content of the D component described later is increased.

  The composition of the present invention is characterized by containing an amide solvent having a relative dielectric constant of 33 or more at 25 ° C. for the D component. By containing such a component, the short circuit current value and FF value of the photovoltaic element can be improved. It is considered that the amide solvent contributes to making the structure of the active layer a layer separation structure suitable for charge transport. Furthermore, the short-circuit current value and the FF value can be improved by setting the relative dielectric constant to 33 or more. If the relative dielectric constant is less than 33, such an effect cannot be obtained. This is presumably because the active layer is unlikely to have the layer separation structure described above. Preferably they are 33 or more and 40 or less.

  Examples of the amide solvent having a relative dielectric constant at 25 ° C. of D component used in the present invention of 33 or more include acetamide, dimethylacetamide, dimethylformamide, dimethylimidazolidinone and the like. Two or more of these may be used. Preferably, dimethylformamide and dimethylimidazolidinone, which are amide solvents having a relative dielectric constant of 33 to 40, are used. Although content of D component will not be specifically limited if a uniform solution is given as a composition of this invention, Preferably it is 0.1-20 volume parts with respect to 100 volume parts of the sum of C component and D component. More preferably, it is 3 to 10 parts by volume. If it is 0.1 volume part or more, the said effect is fully acquired. On the other hand, if it is 20 volume parts or less, a uniform composition can be produced easily.

  The composition of the present invention may contain other components such as a surfactant, a binder resin, and a filler, in addition to the above components A to D, as long as the object of the present invention is not impaired.

  Next, the photovoltaic element of the present invention will be described with an example.

  The photovoltaic element has an active layer sandwiched between a first electrode and a second electrode (that is, a positive electrode and a cathode), at least one of which is light transmissive.

  FIG. 1 is a cross-sectional view showing one embodiment of a photovoltaic element in the present invention. On the substrate 1, a positive electrode 2, an active layer 3, and a negative electrode are provided in this order. The active layer 3 is a layer obtained by applying and drying the composition of the present invention.

A substrate 1 shown in FIG. 1 is a substrate on which an electrode material and an organic semiconductor layer can be laminated, for example, an inorganic material such as alkali-free glass or quartz glass, polyester, polycarbonate, polyolefin, polyamide, depending on the type and application of the photoelectric conversion material. Films and plates produced by an arbitrary method from organic materials such as polyimide, polyphenylene sulfide, polyparaxylene, epoxy resin and fluorine resin can be used. When light is incident from the substrate 1 side and used, the light transmittance of the substrate is preferably 60 to 100%. Here, in the present invention, the light transmittance is
[Transmission light intensity (W / m ² ) / incident light intensity (W / m ² )] × 100 (%)
The value given by.

Further, a hole transport layer may be provided between the positive electrode 2 and the active layer 3. As a material for forming the hole transport layer, conductive polymers such as polythiophene polymers, poly-p-phenylene vinylene polymers, polyfluorene polymers, phthalocyanine derivatives (H ₂ Pc, CuPc, ZnPc, etc.) ), Low molecular organic compounds exhibiting p-type semiconductor properties such as porphyrin derivatives are preferably used. In particular, polyethylenedioxythiophene (PEDOT), which is a polythiophene polymer, or PEDOT to which polystyrene sulfonate (PSS) is added is preferably used. The thickness of the hole transport layer is preferably 5 nm to 600 nm, more preferably 30 nm to 600 nm.

  In the photovoltaic device of the present invention, the first electrode and the second electrode, that is, either the positive electrode 2 or the negative electrode 4 in the case of FIG. Here, the phrase “being light transmissive” means that the light has such light transmittance that incident light reaches the active layer 3 and an electromotive force is generated. That is, when the light transmittance exceeds 0%, it is said that there is light transmittance. The electrode having light transmittance preferably has a light transmittance of 60 to 100%. Here, the light transmittance refers to the transmittance for white light. Further, the thickness of the light-transmitting electrode is not limited as long as sufficient conductivity is obtained and varies depending on the material, but is preferably 20 nm to 300 nm. In addition, in the electrode which does not have a light transmittance, it is enough if there is electroconductivity, and thickness is not specifically limited, either.

  As materials used for the electrodes, it is preferable to use a conductive material having a high work function for one electrode and a conductive material having a low work function for the other electrode. In this case, an electrode using a conductive material having a large work function is a positive electrode. In addition to metals such as gold, platinum, chromium and nickel, conductive materials having a large work function include transparent metal oxides such as indium and tin, composite metal oxides (indium tin oxide (ITO), indium Zinc oxide (IZO) or the like is preferably used. Here, the conductive material used for the positive electrode 2 is preferably one that is in ohmic contact with the active layer 3. Furthermore, when a hole transport layer is used, it is preferable that the conductive material used for the positive electrode 2 is in ohmic contact with the active layer 3 or the hole transport layer (when a hole transport layer is provided).

  An electrode using a conductive material having a low work function is the negative electrode 4, and as the conductive material having a low work function, an alkali metal or alkaline earth metal, specifically lithium, magnesium, or calcium is used. . Tin, silver, and aluminum are also preferably used. Furthermore, an electrode made of an alloy made of the above metal or a laminate of the above metal is also preferably used. Further, it is possible to improve the extraction current by providing an electron transport layer between the negative electrode 4 and the active layer 3 or introducing a metal fluoride or the like at the interface between the electron transport layer and the negative electrode 4. Here, the conductive material used for the negative electrode 4 is preferably an ohmic junction with the active layer 3 or the electron transport layer (when an electron transport layer is provided).

  Next, an example is given and demonstrated about the manufacturing process of the photovoltaic device of this invention. A transparent electrode such as ITO (corresponding to a positive electrode in this case) is formed on the substrate by sputtering or the like. Next, the composition concerning this invention is apply | coated and dried on this transparent electrode, and an active layer is formed.

  In the composition of the present invention, for example, an electron donating conjugated compound of component A and an electron accepting organic semiconductor of component B are added to a good solvent of component C, and a method such as heating, stirring, or ultrasonic irradiation is used. It is obtained by dissolving to make a solution, and then adding an amide solvent of component D.

  For the formation of the active layer, any method such as spin coating, blade coating, slit die coating, screen printing coating, bar coater coating, mold coating, printing transfer method, dip-up method, ink jet method, spray method, etc. should be used. The coating method may be selected according to the properties of the coating film to be obtained, such as coating thickness control and orientation control. For example, in order to obtain a uniform coating film having a thickness of 5 to 200 nm, spin coating is performed with a coating solution in which the sum of the weights of the component A and component B is 0.5 to 3 parts by weight with respect to 100 parts by weight of a good solvent. What is necessary is just to produce by a method. Next, in order to remove the solvent from the formed coating film, the film is dried under reduced pressure or under an inert gas atmosphere (nitrogen or argon atmosphere). Further, the annealing treatment may be performed under reduced pressure or in an inert gas atmosphere. A preferable temperature for the annealing treatment is 50 ° C to 300 ° C, more preferably 70 ° C to 200 ° C. Further, by performing the annealing treatment, the effective area where the stacked layers permeate and contact each other at the interface increases, and the short-circuit current can be increased. This annealing treatment may be performed after the formation of the negative electrode.

  Next, a metal electrode such as Al (corresponding to a negative electrode in this case) is formed on the active layer by vapor deposition or sputtering.

  When a hole transport layer is provided between the positive electrode and the active layer, a desired p-type organic semiconductor material (such as PEDOT) is applied on the positive electrode by spin coating, bar coating, blade casting, or the like. Then, the solvent is removed using a vacuum thermostat or a hot plate to form a hole transport layer. In the case of using a low molecular organic material such as a phthalocyanine derivative or a porphyrin derivative, a vapor deposition method using a vacuum vapor deposition machine can be applied. The electron transport layer can be provided in the same manner.

  The photovoltaic element of the present invention can be applied to various photoelectric conversion devices using a photoelectric conversion function, an optical rectification function, and the like. For example, it is useful for photovoltaic cells (such as solar cells), photovoltaic elements, electronic elements (such as optical sensors, optical switches, phototransistors), optical recording materials (such as optical memories), and the like.

Hereinafter, the present invention will be described more specifically based on examples. In addition, this invention is not limited to the following Example. Of the compounds used in the examples and the like, those using abbreviations are shown below.
ITO: Indium tin oxide PEDOT: Polyethylenedioxythiophene PSS: Polystyrene sulfonate P3HT: Poly (3-hexylthiophene)
C60-PCBM: [6,6] -phenyl C61 butyric acid methyl ester C70-PCBM: [6,6] -phenyl C71 butyric acid methyl ester DMF: dimethylformamide (dielectric constant 37)
NMP: N-methylpyrrolidone (dielectric constant 32)
DMI: Dimethylimidazolidinone (dielectric constant 38)
GBL: γ-butyrolactone (relative permittivity 42).

Comparative Example 1
Add 1.5 mg of P3HT (Aldrich, regioregular, polymerization degree 120) and 1.5 mg of C60-PCBM (American Dye Source) into a sample bottle containing 0.2 mL of chlorobenzene, and perform ultrasonic cleaning. A uniform solution A was prepared by irradiating with ultrasonic waves for 30 minutes in a machine (US-2 manufactured by Iuchi Seieido Co., Ltd., output 120 W). That is, chlorobenzene is a good solvent for P3HT and C60-PCBM. In all of the examples and comparative examples described below, uniform solutions were obtained.

  A glass substrate on which an ITO transparent conductive layer serving as a positive electrode having a thickness of 120 nm was deposited by sputtering was cut into 38 mm × 46 mm, and then ITO was patterned into a 38 mm × 13 mm rectangular shape by photolithography. The light transmittance of the obtained substrate measured using white light was 85%. The substrate was subjected to ultrasonic cleaning with an alkali cleaning solution (“Semico Clean” EL56, manufactured by Furuuchi Chemical Co., Ltd.) for 10 minutes, and then cleaned with ultrapure water. After this substrate was UV / ozone treated for 30 minutes, a PEDOT: PSS aqueous solution (PEDOT 0.8 wt%, PSS 0.5 wt%) serving as a hole transport layer was formed on the substrate to a thickness of 100 nm by spin coating. did. After heating and drying at 200 ° C. for 5 minutes using a hot plate, the above solution A was dropped on the PEDOT: PSS layer, and an active layer having a thickness of 100 nm was formed by spin coating. Thereafter, the substrate and the mask for the cathode are placed in a vacuum deposition apparatus, and the degree of vacuum in the apparatus is evacuated to 1 × 10 −3 Pa or less. Vapor deposited. The extraction electrodes were taken out from the upper and lower electrodes of the produced device, and a photovoltaic device having an area where the band-like ITO layer and the aluminum layer overlap each other was 5 mm × 5 mm was produced.

The photovoltaic element thus fabricated was placed in a shield box, and the upper and lower electrodes were connected to a Hewlett-Packard Picoammeter / Voltage source 4140B, and the applied voltage was -2V under reduced pressure (100 Pa). The dark current value was measured when the voltage was changed from +2 to + 2V. Next, white light (100 mW / cm ² ) was irradiated from the ITO layer side, and the current value when the applied voltage was changed from −2 V to +2 V was measured. Examples 1 and 2 and Comparative Example 2 were evaluated based on the element characteristics at this time.

Here, FF is obtained by the following equation. All FFs in the following examples and comparative examples were calculated by the same method.
FF = JVmax / (short circuit current density × open voltage)
However, JVmax is a value of the product of the current density and the applied voltage at the point where the product of the current density and the applied voltage becomes maximum when the applied voltage is from 0 V to the open circuit voltage.

Example 1
A uniform solution B was prepared by adding 0.1 mL of a chlorobenzene solution containing 30 volume percent of DMF to the solution A and irradiating with ultrasonic waves for 10 minutes. A photoelectric conversion element was produced in the same manner as in Comparative Example 1 except that the active layer was formed using the solution B instead of the solution A, and current-voltage characteristics were measured. At this time, the short-circuit current value (the value of the current density when the applied voltage was 0 V) and the fill factor (FF) value increased by 1.9 times and 1.4 times, respectively, as compared with Comparative Example 1. The dark current value at 0.7 V increased 220 times that of Comparative Example 1.

Comparative Example 2
A photoelectric conversion element was produced in the same manner as in Example 1 except that NMP was used instead of DMF, and current-voltage characteristics were measured. In this case, no photovoltaic was observed.

Example 2
A photoelectric conversion element was produced in the same manner as in Example 1 except that DMI was used instead of DMF, and current-voltage characteristics were measured. At this time, the short circuit current value and the FF value increased 1.7 times and 1.1 times, respectively, as compared with Comparative Example 1. The dark current value at 0.7 V increased 640 times.

Comparative Example 3
A photoelectric conversion element was produced in the same manner as in Comparative Example 1 except that the solution A was prepared using chloroform instead of chlorobenzene, and current-voltage characteristics were measured. Example 3 and Comparative Examples 4 and 5 were evaluated based on the element characteristics at this time.

Example 3
Solution A was prepared using 0.1 mL of chloroform as C component instead of 0.2 mL of chlorobenzene, and DMI was used as D component instead of DMF, and 0.15 mL of chloroform solution containing 5 volume percent of D component was added to Solution A. A photoelectric conversion element was produced in the same manner as in Example 1 except that the solution B was mixed to prepare a current-voltage characteristic. Incidentally, the content of the D component was 3 parts by volume with respect to 100 parts by volume of the C component. At this time, the short circuit current value and the FF value increased by 1.02 times and 1.3 times, respectively, with respect to Comparative Example 3. did. The dark current value at 0.7 V increased 21 times.

Comparative Example 4
A photoelectric conversion element was produced in the same manner as in Example 3 except that NMP was used instead of DMI, and current-voltage characteristics were measured. At this time, the short-circuit current value and the FF value decreased by 0.008 times and 0.5 times, respectively, as compared with Comparative Example 3.

Comparative Example 5
A photoelectric conversion element was produced in the same manner as in Example 3 except that GBL was used in place of DMI, and current-voltage characteristics were measured. At this time, the short-circuit current value and the FF value decreased by 0.001 times and 0.38 times as compared with Comparative Example 3, respectively.

Comparative Example 6
An active layer was formed using 0.8 mg of BT instead of 1.5 mg of P3HT and 3.2 mg of C70-PCBM instead of 1.5 mg of C60-PCBM, and 40 volume percent of 2-propanol was added to the PEDOT: PSS aqueous solution. A photoelectric conversion element was produced in the same manner as in Comparative Example 1 except that a 60 nm PEDOT: PSS layer was formed using the prepared solution, and current-voltage characteristics were measured. Example 4 was evaluated based on the element characteristics at this time. BT was synthesized by the following method.

  5. Dissolve 5.2 g of 3-n-hexylthiophene (manufactured by Tokyo Chemical Industry Co., Ltd.) in 50 ml of dimethylformamide (manufactured by Wako Pure Chemical Industries, Ltd.), and N-bromosuccinimide (manufactured by Wako Pure Chemical Industries, Ltd.) 5 g was added, and the mixture was stirred at room temperature for 3 hours under a nitrogen atmosphere. 100 ml of water and 100 ml of ethyl acetate were added to the resulting solution, and the organic layer was separated, washed 3 times with 100 ml of water, and dried over magnesium sulfate. From the obtained solution, the solvent was distilled off under reduced pressure using a rotary evaporator to obtain 7.9 g of 2-bromo-3-n-hexylthiophene.

  7.9 g of the above 2-bromo-3-n-hexylthiophene was dissolved in 50 ml of tetrahydrofuran (manufactured by Wako Pure Chemical Industries, Ltd.) and cooled to -80 ° C. Add 22 ml of n-butyllithium 1.6M hexane solution (manufactured by Wako Pure Chemical Industries, Ltd.), stir for 2 hours, raise the temperature to −50 ° C., and add 3.3 ml of dimethylformamide (manufactured by Wako Pure Chemical Industries, Ltd.). added. The mixture was warmed to room temperature and stirred for 5 hours under a nitrogen atmosphere. To the obtained solution, 100 ml of ethyl acetate and 100 ml of saturated aqueous ammonium chloride solution were added, and the organic layer was separated, washed three times with 100 ml of water, and dried over magnesium sulfate. From the obtained solution, the solvent was distilled off under reduced pressure using a rotary evaporator to obtain 6.3 g of 2-formyl-3-n-hexylthiophene.

  6.3 g of the above 2-formyl-3-n-hexylthiophene and 3.8 g of 1,4-bis (diethylphosphinoylmethyl) benzene (Tokyo Chemical Industry Co., Ltd.) were added to tetrahydrofuran (Wako Pure Chemical Industries, Ltd.). Manufactured) and dissolved in 100 ml. A suspension obtained by suspending 6.0 g of t-butoxy potassium (manufactured by Tokyo Chemical Industry Co., Ltd.) in 100 ml of tetrahydrofuran (manufactured by Wako Pure Chemical Industries, Ltd.) was dropped, and the mixture was stirred at 70 ° C. for 9 hours in a nitrogen atmosphere. did. To the resulting solution were added 100 ml of dichloromethane and 100 ml of saturated brine, and the organic layer was separated. The organic layer was washed 3 times with 100 ml of water and dried over magnesium sulfate. The resulting solution was purified by column chromatography (filler: silica gel, eluent: dichloromethane / hexane) and 2 g of 1,4-bis (1- (3-n-hexyl-2-thienyl) ethene-2- Il) benzene was obtained.

  The above 2 g of thienylene vinylene was dissolved in 30 ml of tetrahydrofuran (manufactured by Wako Pure Chemical Industries, Ltd.) and cooled to -80 ° C. 22 ml of n-butyllithium 1.6M hexane solution (manufactured by Wako Pure Chemical Industries, Ltd.) was added, stirred for 4 hours, heated to −50 ° C. and 2-isopropoxy-4,4,5,5-tetramethyl 1.7 g of -1,3,2-dioxaborolane (manufactured by Wako Pure Chemical Industries, Ltd.) was added. The mixture was warmed to room temperature and stirred for 12 hours under a nitrogen atmosphere. To the resulting solution, 200 ml of dichloromethane and 100 ml of water were added, and the organic layer was separated. The organic layer was washed 3 times with 100 ml of water and dried over magnesium sulfate. The resulting solution was purified by column chromatography (filler: silica gel, eluent: dichloromethane / hexane) to give 1- (1- (3-n-hexyl-5-pinacolatoboronyl-2-thienyl) ethene- There were obtained 1.3 g of 2-yl) -4- (1- (3-n-hexyl-2-thienyl) ethen-2-yl) benzene.

  3 g of 3-n-hexylthiophene (manufactured by Tokyo Chemical Industry Co., Ltd.) was dissolved in 40 ml of tetrahydrofuran (manufactured by Wako Pure Chemical Industries, Ltd.) and cooled to -80 ° C. Add 12 ml of n-butyllithium 1.6M hexane solution (manufactured by Wako Pure Chemical Industries, Ltd.), stir for 2 hours, raise the temperature to −60 ° C., and 2-isopropoxy-4,4,5,5-tetramethyl. 5.5 g of -1,3,2-dioxaborolane (manufactured by Wako Pure Chemical Industries, Ltd.) was added. The mixture was warmed to room temperature and stirred for 4 hours under a nitrogen atmosphere. To the resulting solution were added 100 ml of dichloromethane and 100 ml of saturated brine, and the organic layer was separated. The organic layer was washed 3 times with 100 ml of water and dried over magnesium sulfate. From the obtained solution, the solvent was distilled off under reduced pressure using a rotary evaporator to obtain 4.6 g of 5-pinacolatoboronyl-3-n-hexylthiophene.

  6.4 g of the above 5-pinacolatoboronyl-3-n-hexylthiophene and 2.1 g of 4,7-dibromo-2,1,3-benzothiadiazole of Synthesis Example 1 were dissolved in 100 ml of toluene. 30 ml of ethanol, 30 ml of 2M aqueous sodium carbonate solution and 0.15 g of tetrakis (triphenylphosphine) palladium (0) (manufactured by Tokyo Chemical Industry Co., Ltd.) were added thereto, and the mixture was stirred at 110 ° C. for 13 hours in a nitrogen atmosphere. 100 ml of ethyl acetate and 100 ml of water were added to the resulting solution, and the organic layer was separated. From the obtained solution, the solvent was distilled off under reduced pressure using a rotary evaporator to obtain 5.8 g of 4,7-bis (4-n-hexylthienyl) -2,1,3-benzothiadiazole.

  5.8 g of the above 4,7-bis (4-n-hexylthienyl) -2,1,3-benzothiadiazole is dissolved in 3 ml of dimethylformamide (manufactured by Wako Pure Chemical Industries, Ltd.), and N-bromosuccinimide (( 3.5 g of Wako Pure Chemical Industries, Ltd.) was added, and the mixture was stirred at room temperature for 2 hours under a nitrogen atmosphere. 100 ml of water and 100 ml of ethyl acetate were added to the resulting solution, and the organic layer was separated. The organic layer was washed 3 times with 100 ml of water and then dried over magnesium sulfate. The resulting solution was purified by column chromatography (filler: silica gel, eluent: dichloromethane / hexane), and 4,7-bis ((4-n-hexyl-5-bromo) -thienyl) -2,1, 1.6 g of 3-benzothiadiazole was obtained.

1- (1- (3-n-hexyl-5-pinacolatoboronyl-2-thienyl) ethen-2-yl) -4- (1- (3-n-hexyl-2-thienyl) ethene- 2-yl) benzene (0.25 g) and the above 4,7-bis ((4-n-hexyl-5-bromo) 2-thienyl) -2,1,3-benzothiadiazole (0.11 g) were dissolved in 20 ml of toluene. . 10 ml of ethanol, 15 ml of 2M aqueous sodium carbonate solution, and 11 mg of tetrakis (triphenylphosphine) palladium (0) (manufactured by Tokyo Chemical Industry Co., Ltd.) were added thereto, followed by stirring at 110 ° C. for 12 hours in a nitrogen atmosphere. 100 ml of ethyl acetate and 100 ml of water were added to the resulting solution, and the organic layer was separated. The resulting solution was purified by column chromatography (filler: silica gel, eluent: dichloromethane / hexane) to obtain 0.17 g of BT represented by the following formula.
¹ H-NMR (CDCl ₂ , ppm): 7.93 (s, 2H), 7.75 (s, 2H), 7.44 (m, 8H), 7.28 (d, 2H), 7.22 (D, 2H), 7.10 (d, 2H), 7.00 (m, 2H), 6.83 (m, 6H) 2.86 (m, 4H) 2.69 (m, 8H) 73 (m, 4H), 1.63 (m, 8H), 1.34 (m, 36H), 0.93 (m, 18H).

Example 4
In place of P3HT 1.5 mg, BT 0.8 mg and C60-PCBM 1.5 mg are replaced with C70-PCBM 3.2 mg. These are dissolved in 0.2 mL of a chloroform solution containing 1 volume percent of DMF, and Solution B is dissolved. A photoelectric conversion element was prepared in exactly the same manner as in Example 1 except that a 60 nm PEDOT: PSS layer was formed using a solution obtained by adding 40 volume percent of 2-propanol to a PEDOT: PSS aqueous solution. -Voltage characteristics were measured. At this time, the short circuit current value and the FF value increased 1.1 times and 1.1 times, respectively. The dark current value at 1.5V increased 1.7 times.

  The results of the above examples and comparative examples are shown in Table 1.

  As shown in the examples and comparative examples, when the D component is included, the short circuit current value and the FF increase, so the effect of the present invention is clear. This is considered to be because the active layer has a layer separation structure suitable for charge transport by the addition of the D component.

Sectional drawing which showed the one aspect | mode of the photovoltaic device of this invention.

Explanation of symbols

1 Substrate 2 Positive electrode 3 Active layer 4 Negative electrode

Claims (6)

A component Electron-donating conjugated compound B component Electron-accepting organic semiconductor C component A composition comprising the A component, a good solvent for the B component, and a D component, an amide solvent having a relative dielectric constant of 33 or more at 25 ° C. The composition according to claim 1, wherein the component A is a compound containing a polythiophene polymer or benzothiadiazole. The composition of Claim 2 in which the said A component contains the compound represented by following General formula (1).

(R ^{1 to} R ¹² may be the same or different and each represents hydrogen, an alkyl group, an alkoxy group, or an aryl group. M is each independently 1 or 2, and n represents a range of 1 or more and 1000 or less. ) The composition according to any one of claims 1 to 3, wherein the component B is a fullerene derivative. The composition according to any one of claims 1 to 4, wherein the component C is at least one selected from the group consisting of chlorobenzene, dichlorobenzene, and chloroform. An active layer obtained by applying and drying the composition according to any one of claims 1 to 5 has a structure in which at least one of the active layers is sandwiched between a first electrode and a second electrode having light transmittance. Photovoltaic element having.

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