JP2013091712A - Conjugated polymer compound and organic photoelectric conversion element using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the film making property of a layer including a conjugated polymer compound, and to provide a means to achieve the enough photoelectric conversion efficiency.SOLUTION: The conjugated polymer compound has a partial structure of the chemical formula 1 that has a 5th place and/or 6th place fluorine atom or chlorine atom of a benzimidazole backbone. In the formula, Rand Rare each independently hydrogen, (un)substituted 1-20C alkyl, 1-20C fluorinated alkyl, 3-20C cycloalkyl, 3-20C fluorinated cycloalkoxy, 1-20C alkoxy, 1-20C fluorinated alkoxy, 1-20C fluorinated alkylthio, 6-30C aryl, 6-30C fluorinated aryl, 4-20 heteroaryl, 4-20 fluorinated heteroaryl, and Rand Rmay bond mutually to form a ring; and Xand Xare each independently hydrogen, fluorine or chlorine, wherein at least one of Xand Xdenotes fluorine or chlorine.

Description

  The present invention relates to a conjugated polymer compound and an organic photoelectric conversion device using the same. More specifically, the present invention relates to a technique for improving the photoelectric conversion efficiency of an organic photoelectric conversion element.

  In recent years, in order to cope with global warming, reduction of carbon dioxide emissions has been strongly desired. In addition, fossil fuels such as oil, coal, and natural gas are expected to be depleted in the near future, and there is an urgent need to secure alternative earth-friendly energy resources. Therefore, development of power generation technology using sunlight, wind power, geothermal energy, nuclear power, and the like has been actively carried out. Among them, solar power generation is particularly attracting attention because of its high safety.

  In solar power generation, light energy is directly converted into electric power using a photoelectric conversion element utilizing the photovoltaic effect. Generally, a photoelectric conversion element has a structure in which a photoelectric conversion layer (light absorption layer) is sandwiched between a pair of electrodes, and light energy is converted into electric energy in the photoelectric conversion layer. The photoelectric conversion element is a silicon-based photoelectric conversion element using single-crystal / polycrystalline / amorphous Si, GaAs, CIGS (copper (Cu), indium (In), depending on the material used for the photoelectric conversion layer and the form of the element. Compound-based photoelectric conversion elements using a compound semiconductor such as gallium (Ga) and selenium (Se)), dye-sensitized photoelectric conversion elements (Gretzel cells), and the like have been proposed and put to practical use.

  However, the power generation cost when these solar cells are used is still higher than the cost when generating and transmitting power using fossil fuels, which hinders the spread of solar power generation. In addition, since heavy glass must be used for the substrate, reinforcement work is required when it is installed on a roof or the like, which has also contributed to the increase in power generation costs.

  As a technique for reducing power generation costs in solar power generation, a mixture of an electron-donating organic compound (p-type organic semiconductor) and an electron-accepting organic compound (n-type organic semiconductor) between a transparent electrode and a counter electrode A bulk heterojunction type photoelectric conversion element including a photoelectric conversion layer has been proposed, and in 2007, a photoelectric conversion efficiency exceeding 5% was reported (Non-patent Document 1). % Can be achieved (Non-Patent Document 2).

  Bulk heterojunction organic photoelectric conversion elements are lightweight and flexible, and are expected to be applied to various products. In addition, since the structure is relatively simple and a photoelectric conversion layer can be formed by applying a p-type organic semiconductor and an n-type organic semiconductor, cost reduction can be expected by mass production on a roll-to-roll basis. It is thought to contribute to the early dissemination of More specifically, in the bulk heterojunction organic photoelectric conversion element, the electrodes (anode and cathode), the metal oxide layer constituting the hole transport layer, and the like can be formed by a method other than the coating process (for example, vacuum deposition method). Etc.). On the other hand, other layers can be formed using a coating process. Therefore, it is expected that the production of the bulk heterojunction photoelectric conversion element can be performed at high speed and at low cost, and it is considered that there is a possibility that the above-described problem of power generation cost can be solved. Further, unlike the production of conventional silicon-based photoelectric conversion elements, compound-based photoelectric conversion elements, dye-sensitized photoelectric conversion elements, etc., it does not necessarily involve a manufacturing process at a temperature higher than 160 ° C. It is expected that it can be formed on a lightweight plastic substrate.

  However, the organic photoelectric conversion element is still not sufficient in photoelectric conversion efficiency and durability against heat and light as compared with other types of photoelectric conversion elements. Accordingly, various improvements have been made in order to improve photoelectric conversion efficiency and durability. In particular, for the purpose of improving durability, for example, each layer is laminated in the reverse order of a normal organic photoelectric conversion element, electrons are taken out from the transparent electrode side, and holes are taken from the stable metal electrode side having a deep work function. A so-called reverse layer type organic photoelectric conversion element to be taken out has been proposed (Patent Document 1).

  Such a reverse layer type organic photoelectric conversion element has a configuration in which a hole transport layer composed of a conductive polymer having inferior optical transparency exists between a counter electrode (cathode) and a photoelectric conversion layer. In general, the counter electrode (cathode) is made of a metal material, but the light reflected by the counter electrode cannot be efficiently reused in the photoelectric conversion layer due to the presence of the hole transport layer having low light transmittance. Therefore, the reverse layer type is a disadvantageous configuration from the viewpoint of utilization of light (Non-Patent Document 3). In order to obtain sufficient photoelectric conversion efficiency in the reverse layer type element, it is necessary to increase the film thickness of the photoelectric conversion layer (for example, 150 nm or more), but the photoelectric conversion materials known so far are: When the film thickness of the photoelectric conversion layer is small (less than 100 nm), good photoelectric conversion efficiency can be achieved, but when the film thickness is large (100 nm or more), the fill factor (FF) decreases, and the desired photoelectric conversion efficiency is obtained. It had the problem that it was not possible.

  On the other hand, recently, by using a polymer having a fluorinated benzotriazole group (Non-Patent Document 4) or a polymer having a fluorinated benzothiadiazole group (Non-Patent Document 5) as a photoelectric conversion material, It has been reported that even when the thickness is about 200 nm, a photoelectric conversion efficiency of 7% or more can be achieved.

JP 2009-146981 A JP 2010-111649 A

A. Heeger et al. , Nature Mat. , Vol. 6 (2007), p497 Christoph J. et al. Brabec et al. , Adv. Mater. 2006, 18, p789 Appl. Phys. Lett. , 98, 043301 (2011) J. et al. Am. Chem. Soc. , 2011, 133 (12), p4625 Angew. Chem. Int. Ed. , 2011, 50, p1

  However, it has been found that when the photoelectric conversion material described in Non-Patent Document 4 or 5 is used for a reverse layer type element, desired photoelectric conversion efficiency cannot be obtained. Furthermore, it has been found that a new problem occurs that it is difficult to form a hole transport layer on the surface of the photoelectric conversion layer. That is, in the manufacturing process of the reverse layer type element, a hole transport material such as PEDOT: PSS dissolved in an aqueous solvent is usually applied to the surface of the photoelectric conversion layer, and the coating film is dried to thereby form a hole transport layer. However, since the photoelectric conversion material described in Non-Patent Document 4 or 5 has a property of easily repelling the coating film, it is difficult to form the hole transport layer uniformly. This is considered to be caused by a decrease in the surface energy of the polymer by containing fluorine, and improvement has been demanded.

  Therefore, the present invention provides a conjugated polymer compound for use in an organic photoelectric conversion element in order to improve the film forming property of a layer adjacent to the layer containing the conjugated polymer compound and achieve sufficient photoelectric conversion efficiency. It aims at providing the means of.

  In order to solve the above problems, the present inventors have conducted intensive research. Then, by using a conjugated polymer compound having a specific partial structure having a fluorine atom or a chlorine atom at the 5-position and / or 6-position of the benzimidazole skeleton, a charge transport layer (for example, a hole) adjacent to the photoelectric conversion layer is used. The film forming property of the transport layer) was significantly improved and sufficient photoelectric conversion efficiency was obtained, and the present invention was completed.

  That is, the conjugated polymer compound of the present invention is characterized in that it contains at least one partial structure represented by the following chemical formula 1.

In the formula, each of R ¹ and R ² independently represents a hydrogen atom; a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a fluorinated alkyl group having 1 to 20 carbon atoms, or a carbon atom. A cycloalkyl group having 3 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a fluorinated alkoxy group having 1 to 20 carbon atoms, and 1 to 20 carbon atoms A fluorinated alkylthio group, an aryl group having 6 to 30 carbon atoms, a fluorinated aryl group having 6 to 30 carbon atoms, a heteroaryl group having 4 to 20 carbon atoms, or a fluorinated heterocycle having 4 to 20 carbon atoms R ¹ and R ² may be bonded to each other to form a ring;
X ¹ and X ² each independently represent a hydrogen atom, a fluorine atom, or a chlorine atom (provided that at least one of X ¹ and X ² represents a fluorine atom or a chlorine atom).

  ADVANTAGE OF THE INVENTION According to this invention, in the conjugated polymer compound used with an organic photoelectric conversion element, the film forming property of the layer adjacent to the layer containing the said conjugated polymer compound is improved, and sufficient photoelectric conversion efficiency is achieved. It becomes possible.

It is the cross-sectional schematic which represented typically the normal layer type organic photoelectric conversion element based on one Embodiment of this invention. It is the cross-sectional schematic which represented typically the reverse layer type organic photoelectric conversion element based on other one Embodiment of this invention. It is the cross-sectional schematic which represented typically the organic photoelectric conversion element provided with the tandem-type photoelectric conversion layer based on other one Embodiment of this invention.

  Hereinafter, preferred embodiments of the present invention will be described. One embodiment of the present invention relates to a conjugated polymer compound having a specific partial structure having a fluorine atom or a chlorine atom at the 5-position and / or the 6-position of a benzimidazole skeleton. That is, the conjugated polymer compound of this embodiment is characterized in that it contains at least one partial structure represented by the following chemical formula 1.

In the formula, each of R ¹ and R ² independently represents a hydrogen atom; a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a fluorinated alkyl group having 1 to 20 carbon atoms, or a carbon atom. A cycloalkyl group having 3 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms, and a fluorine group having 6 to 30 carbon atoms. An aryl group, a heteroaryl group having 4 to 20 carbon atoms, or a fluorinated heteroaryl group having 4 to 20 carbon atoms.

  The alkyl group having 1 to 20 carbon atoms is not particularly limited. For example, a methyl group, an ethyl group, an isopropyl group, a tert-butyl group, an n-octyl group, an n-decyl group, an n-hexadecyl group, Examples include 2-ethylhexyl group and 2-hexyldecyl group. Among these, from the viewpoint of improving solubility, an alkyl group having 1 to 12 carbon atoms is preferable, and an alkyl group having 1 to 8 carbon atoms is more preferable.

Although there is no restriction | limiting in particular as said C1-C20 fluorinated alkyl group, For example, the group by which at least 1 of the hydrogen atom contained in the alkyl group illustrated above was substituted by the fluorine atom is mentioned. Among these, from the viewpoint of achieving a higher V _oc (deep HOMO level), the carbon atom closest to the bonding site of the alkyl group exemplified above with the benzimidazole skeleton (ie, the carbon atom at the 1st position in the alkyl group) It is preferable that only a group substituted with a fluorine atom. Specifically, fluoromethyl group, 1-fluoroethyl group, 1-fluoropropyl group, 1-fluorobutyl group, 1-fluorooctyl group, 1-fluorodecyl group, 1-fluorohexadecyl group, 1-fluoro- Monofluoroalkyl groups such as 2-ethylhexyl group and 1-fluoro-2-hexyldecyl group; difluoromethyl group, 1,1-difluoroethyl group, 1,1-difluoropropyl group, 1,1-difluorobutyl group, 1 , 1-difluorooctyl group, 1,1-difluorodecyl group, 1,1-difluorohexadecyl group, 1,1-difluoro-2-ethylhexyl group, 1,1-difluoro-2-hexyldecyl group, etc. Group; a trifluoroalkyl group such as a trifluoromethyl group, and the like. Moreover, it is preferable that it is a C1-C3 fluorinated alkyl group from a viewpoint of maintaining the applicability | paintability of an upper layer. Such a number of carbon atoms is sufficiently shorter than other soluble groups (substituents for imparting solubility generally use C6 or more) and have little influence on the upper layer coating property. It is. Of these, a trifluoromethyl group having 1 carbon atom is more preferable.

In general, a conjugated polymer compound having a fluorine atom easily repels a polar solvent because the surface energy of the polymer is lowered by the fluorine atom. However, according to a conjugated polymer compound of the present embodiment, for example, even when introducing a fluorinated alkyl group in R ¹ and R ^2, and was introduced fluorine atom in X ¹ and X ^2, the polar solvent It is difficult to be repelled, and the film forming property of the upper layer can be sufficiently maintained. The reason why such characteristics are obtained is not certain, but the present inventors speculate that it is due to the polarity of the benzimidazole structure itself.

  Although there is no restriction | limiting in particular as said C3-C20 cycloalkyl group, For example, a cyclopropyl group, a cyclopentyl group, a cyclohexyl group, a norbornyl group, an adamantyl group etc. are mentioned. Among these, a cycloalkyl group having 4 to 8 carbon atoms is preferable from the viewpoint of improving solubility.

The fluorinated cycloalkyl group having 3 to 20 carbon atoms is not particularly limited, and examples thereof include a group in which at least one hydrogen atom contained in the cycloalkyl group exemplified above is substituted with a fluorine atom. . Among these, from the viewpoint of achieving higher V _oc (deep HOMO level), it is preferable that all the hydrogen atoms contained in the cycloalkyl group exemplified above are groups substituted with fluorine atoms. It is also preferable to adjust the number and position to an appropriate number and position (for example, only the carbon atom closest to the bonding site with the benzimidazole skeleton is substituted with a fluorine atom). Moreover, it is preferable that it is a C4-C8 fluorinated cycloalkyl group from a viewpoint of improving solubility.

  The alkoxy group having 1 to 20 carbon atoms is not particularly limited, and examples thereof include methoxy group, ethoxy group, isopropoxy group, tert-butoxy group, n-octyloxy group, n-decyloxy group, and n-hexa. A decyloxy group, 2-ethylhexyloxy group, 2-hexyldecyloxy group, etc. are mentioned.

  The fluorinated alkoxy group having 1 to 20 carbon atoms (fluorinated alkyloxy group) is not particularly limited, but for example, a group in which an oxygen atom is bonded to the root of the fluorinated alkyl group exemplified above. Can be mentioned. Among these, from the viewpoint of achieving a higher Voc (deep HOMO level), it is preferable that all the hydrogen atoms contained in the alkyl chain exemplified above are groups substituted with fluorine atoms. It is also preferable to adjust the number and position to an appropriate number and position (for example, only the carbon atom closest to the bonding site with the benzimidazole skeleton is substituted with a fluorine atom).

  The fluorinated alkylthio group having 1 to 20 carbon atoms is not particularly limited, and examples thereof include a group in which an oxygen atom is bonded to the base of the fluorinated alkyl group exemplified above. Among these, from the viewpoint of achieving a higher Voc (deep HOMO level), it is preferable that all the hydrogen atoms contained in the alkyl chain exemplified above are groups substituted with fluorine atoms. It is also preferable to adjust the number and position to an appropriate number and position (for example, only the carbon atom closest to the bonding site with the benzimidazole skeleton is substituted with a fluorine atom).

  The aryl group having 6 to 30 carbon atoms is not particularly limited, and examples thereof include non-condensed hydrocarbon groups such as a phenyl group, a biphenyl group, and a terphenyl group; a pentarenyl group, an indenyl group, a naphthyl group, an azulenyl group, Heptalenyl group, biphenylenyl group, fluorenyl group, acenaphthylenyl group, preadenyl group, acenaphthenyl group, phenalenyl group, phenanthryl group, anthryl group, fluoranthenyl group, acephenanthrenyl group, aceanthrylenyl group, triphenylenyl group, pyrenyl group , Condensed polycyclic hydrocarbon groups such as a chrycenyl group and a naphthacenyl group.

The fluorinated aryl group having 6 to 30 carbon atoms is not particularly limited, and examples thereof include a group in which at least one hydrogen atom contained in the aryl group exemplified above is substituted with a fluorine atom. Among these, from the viewpoint of achieving higher V _oc (deep HOMO level), it is preferable that all the hydrogen atoms contained in the aryl group exemplified above are groups substituted with fluorine atoms. It is also preferable to adjust the number and position to an appropriate number (for example, only the carbon atom closest to the binding site with the benzimidazole skeleton is substituted with a fluorine atom).

  The heteroaryl group having 1 to 20 carbon atoms is not particularly limited. For example, pyridyl group, pyrimidyl group, pyrazinyl group, triazinyl group, furanyl group, pyrrolyl group, thiophenyl group (thienyl group), quinolyl group, Furyl group, piperidyl group, coumarinyl group, silafluorenyl group, benzofuranyl group, benzimidazolyl group, benzoxazolyl group, benzthiazolyl group, dibenzofuranyl group, benzothiophenyl group, dibenzothiophenyl group, indolyl group, carbazolyl group, pyrazolyl Group, imidazolyl group, oxazolyl group, isoxazolyl group, thiazolyl group, indazolyl group, benzothiazolyl group, pyridazinyl group, cinnolyl group, quinazolyl group, quinoxalyl group, phthalazinyl group, phthalazine dionyl group, phthalamidyl group, Romonyl, naphtholactamyl, quinolonyl, naphthalidinyl, benzimidazolonyl, benzoxazolonyl, benzothiazolonyl, benzothiazothionyl, quinazolonyl, quinoxalonyl, phthalazonyl, dioxopyrimidinyl Group, pyridonyl group, isoquinolonyl group, isoquinolinyl group, isothiazolyl group, benzisoxazolyl group, benzisothiazolyl group, indazironyl group, acridinyl group, acridonyl group, quinazoline dionyl group, quinoxaline dionyl group, benzoxazine dionyl Group, benzoxazinonyl group, naphthalimidyl group, dithienocyclopentadienyl group, dithienosylcyclopentadienyl group, dithienopyrrolyl group, benzodithiophenyl group and the like.

The fluorinated heteroaryl group having 1 to 20 carbon atoms is not particularly limited, and examples thereof include a group in which at least one hydrogen atom contained in the heteroaryl group exemplified above is substituted with a fluorine atom. . Among these, from the viewpoint of achieving higher V _oc (deep HOMO level), it is preferable that all of the hydrogen atoms contained in the heteroaryl group exemplified above are groups substituted with fluorine atoms. It is also preferable to adjust the number and position to an appropriate number and position (for example, only the carbon atom closest to the bonding site with the benzimidazole skeleton is substituted with a fluorine atom).

The substituent optionally present in R ¹ and R ² is not particularly limited, and examples thereof include an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, an acyl group, and an alkoxycarbonyl group. Group, amino group, alkoxy group, cycloalkyloxy group, aryloxy group, aryloxycarbonyl group, acyloxy group, acylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfonylamino group, sulfamoyl group, carbamoyl group, alkylthio Group, arylthio group, silyl group, sulfonyl group, sulfinyl group, ureido group, phosphoric acid amide group, halogen atom, hydroxyl group, mercapto group, cyano group, sulfo group, carboxyl group, nitro group, hydroxamic acid group, sulfi group It can be exemplified group, a hydrazino group, and an imino group.

In Non-Patent Document 2, as a requirement for a conjugated polymer compound that is expected to have high photoelectric conversion efficiency, the LUMO level is shallower by about 0.3 eV than an n-type organic semiconductor material (for example, fullerene derivative), that is, It is preferable to have a LUMO level of about −4.0 eV. In order to obtain a conjugated polymer compound having such a deep HOMO / LUMO level, R ¹ and / or R ² may be the above-described fluorinated alkyl group, the above-described alkyl group, cycloalkyl group, or aryl group. Or at least one hydrogen atom of the heteroaryl group is preferably substituted with an electron withdrawing group. That is, R ¹ and / or R ² is a fluorinated alkyl group having 1 to 20 carbon atoms, a fluorinated alkoxy group having 1 to 20 carbon atoms, a fluorinated alkylthio group having 1 to 20 carbon atoms, or the following chemical formula: The group represented by 2 is preferable.

In the formula, L represents an alkylene group having 1 to 20 carbon atoms, a cycloalkylene group having 3 to 20 carbon atoms, an arylene group having 3 to 20 carbon atoms, or a heteroarylene group having 3 to 20 carbon atoms, Represent. Among these, from the viewpoint of achieving higher V _oc (deep HOMO level), L is preferably an arylene group having 3 to 20 carbon atoms or a heteroarylene group having 3 to 20 carbon atoms.

  The alkylene group having 1 to 20 carbon atoms is not particularly limited, and examples thereof include a group in which one hydrogen atom is removed from the groups exemplified in the description of the alkyl group having 1 to 20 carbon atoms. It is done. Similarly, the cycloalkylene group having 3 to 20 carbon atoms, the arylene group having 3 to 20 carbon atoms, or the heteroarylene group having 3 to 20 carbon atoms is not particularly limited. One hydrogen atom is removed from the groups exemplified in the description of 20 cycloalkyl groups, alkoxy groups having 1 to 20 carbon atoms, aryl groups having 6 to 30 carbon atoms, and heteroaryl groups having 4 to 20 carbon atoms. The group which consists of.

In the chemical formula 2, EWG represents a fluorinated alkyl group having 1 to 20 carbon atoms, an alkylcarbonyl group having 2 to 20 carbon atoms (acyl group; —COR), or an alkylcarbonyloxy having 2 to 20 carbon atoms. Group (acyloxy group; —OCOR), alkyloxycarbonyl group having 2 to 20 carbon atoms (—COOR), alkylcarbonylamino group having 2 to 40 carbon atoms (acylamino group; —NHCOR, —N (COR) ₂ ) , An alkylaminocarbonyl group having 2 to 40 carbon atoms (—CONHR, —CONR ₂ ), a cyano group, a nitro group, an alkylsulfinyl group having 1 to 20 carbon atoms (—S (O) R), a sulfo group (— SO ₃ H), an alkylsulfonyloxy group having a carbon number of 1~20 (-OSO ₂ R), aminosulfonyl group _{(-SO 2} NH 2) It represents at least one electron withdrawing group is selected from that group.

  The fluorinated alkyl group having 1 to 20 carbon atoms is not particularly limited, and examples thereof include perfluoromethyl group, perfluoroethyl group, perfluoroisopropyl group, perfluoro tert-butyl group, and perfluoro n-octyl. Group, perfluoro n-decyl group, perfluoro n-hexadecyl group, perfluoro 2-ethylhexyl group, perfluoro 2-hexyldecyl group and the like.

The alkylcarbonyl group (acyl group) having 2 to 20 carbon atoms is not particularly limited, and examples thereof include acetyl, propionyl, butyryl, isobutyryl, tert-butyryl, pentanoyl, valeryl, and isovaleryl. Group, pivaloyl group, hexanoyl group, heptanoyl group, octanoyl group, decanoyl group, dodecanoyl group, hexadecanoyl group, octadecanoyl group, cyclohexylcarbonyl group, 2-ethylhexylcarbonyl group, 2-hexyldecylcarbonyl group, etc. .

  The alkylcarbonyloxy group having 2 to 20 carbon atoms (acyloxy group) is not particularly limited. For example, acetyloxy group, propionyloxy group, butyryloxy group, isobutyryloxy group, tert-butyryloxy group, penta Noyloxy, valeryloxy, isovaleryloxy, pivaloyloxy, hexanoyloxy, heptanoyloxy, octanoyloxy, decanoyloxy, dodecanoyloxy, hexadecanoyloxy, octadecanoyl Examples thereof include an oxy group, a cyclohexylcarbonyloxy group, a 2-ethylhexylcarbonyloxy group, and a 2-hexyldecylcarbonyloxy group.

  The alkyloxycarbonyl group having 2 to 20 carbon atoms is not particularly limited, and examples thereof include a methyloxycarbonyl group, an ethyloxycarbonyl group, an isopropyloxycarbonyl group, a tert-butyloxycarbonyl group, and an n-octyloxycarbonyl group. Group, n-decyloxycarbonyl group, n-hexadecyloxycarbonyl group, 2-ethylhexyloxycarbonyl group, 2-hexyldecyloxycarbonyl group and the like.

  The alkylcarbonylamino group (acylamino group) having 2 to 40 carbon atoms is not particularly limited. For example, (di) acetylamino group, (di) propionylamino group, (di) butyrylamino group, (di) Isobutyrylamino group, (di) tert-butyrylamino group, (di) pentanoylamino group, (di) valerylamino group, (di) isovalerylamino group, (di) pivaloylamino group, (di) hexanoylamino group , (Di) heptanoylamino group, (di) octanoylamino group, (di) decanoylamino group, (di) dodecanoylamino group, (di) hexadecanoylamino group, (di) octadecanoylamino group (Di) cyclohexanecarbonylamino group, (di) 2-ethylhexylcarbonylamino group, (di) 2-hexyldecylcarbonyl An amino group.

  The alkylaminocarbonyl group having 2 to 40 carbon atoms is not particularly limited. For example, (di) methylaminocarbonyl group, (di) ethylaminocarbonyl group, (di) isopropylaminocarbonyl group, (di) tert-butylaminocarbonyl group, (di) n-octylaminocarbonyl group, (di) n-decylaminocarbonyl group, (di) n-hexadecylaminocarbonyl group, (di) 2-ethylhexylaminocarbonyl group, (di ) 2-hexyldecylaminocarbonyl group and the like.

  The alkyl group contained in the alkylsulfinyl group having 1 to 20 carbon atoms or the alkylsulfonyloxy group having 1 to 20 carbon atoms is not particularly limited, and examples thereof include a methyl group, an ethyl group, an isopropyl group, and tert- A butyl group, n-octyl group, n-decyl group, n-hexadecyl group, 2-ethylhexyl group, 2-hexyldecyl group and the like can be mentioned.

  Of these, the EWG is preferably a fluorinated alkyl group having 1 to 3 carbon atoms. By including such a fluorinated alkyl group that is a strong electron-withdrawing group, a conjugated polymer compound having the above-mentioned preferable HOMO / LUMO levels can be obtained. Moreover, even when the hole transport layer is formed by a coating method on the photoelectric conversion layer containing the conjugated polymer compound by setting the chain length of the fluorinated alkyl group to a certain value or less, the hole transport material An aqueous coating solution containing can be made difficult to be repelled on the photoelectric conversion layer.

R ¹ and R ² may be bonded to each other to form a ring. As an example, forms such as A04, A07, and A16 of the following chemical formula 3 may be mentioned. Thus, when R ¹ and R ² are bonded to each other to form a ring, high planarity can be maintained as a whole of the conjugated polymer compound.

Note that R ¹ and R ² contained in one partial structure may be the same or different from each other, but it is possible to achieve higher V _oc (deep HOMO level) and upper layer coatability. From the viewpoint, it is preferable that one is an alkyl group and the other is a fluorinated alkyl group or a group represented by Formula 2. In addition, the conjugated polymer compound of the present embodiment includes one or more partial structures represented by the above chemical formula 1, but a plurality of R ¹ present when two or more partial structures are present, R ² may be the same as or different from each other.

In the above chemical formula 1, X ¹ and X ² each independently represent a hydrogen atom, a fluorine atom, or a chlorine atom. However, at least one of X ¹ and X ² represents a fluorine atom or a chlorine atom. As described above, a conjugated polymer compound having a deeper HOMO / LUMO level can be obtained by having an electron-attracting fluorine atom or chlorine atom at the 5-position and / or the 6-position of the benzimidazole skeleton. it can. Therefore, it is possible to achieve excellent photoelectric conversion efficiency and photooxidation stability by using such a conjugated polymer compound for an organic photoelectric conversion element. Also, if both X ¹ and X ² is a fluorine atom, more preferably both X ¹ and X ² is a chlorine atom, more preferably both X ¹ and X ² are fluorine atoms. When both X ¹ and X ² are fluorine atoms, or both X ¹ and X ² are chlorine atoms, the symmetry of the partial structure represented by Chemical Formula 1 is improved, and the crystal of the conjugated polymer compound Can increase the sex. Furthermore, when both X ¹ and X ² are fluorine atoms, the steric hindrance with the adjacent unit is small compared to the case where both X ¹ and X ² are chlorine atoms. High planarity can be maintained as a whole, whereby the crystallinity of the conjugated polymer compound can be enhanced. As a result, the carrier mobility is improved, so that the photoelectric conversion efficiency can be further improved.

  Hereinafter, preferred forms of the partial structure represented by Chemical Formula 3 will be exemplified.

  Since the partial structure represented by the chemical formula 1 as described above has a fluorine atom or a chlorine atom at the 5-position and / or the 6-position of the benzimidazole skeleton, the conjugated polymer compound having a deep HOMO / LUMO level can do. In addition, by including a partial structure having high planarity as described above, the stacking ability of the conjugated polymer compound can be improved, and the carrier mobility can be improved. Therefore, by forming a photoelectric conversion layer using the conjugated polymer compound of this embodiment, it is possible to achieve photoelectric conversion efficiency superior to that of the conventional organic photoelectric conversion element. In particular, when the photoelectric conversion layer is thickened, the photoelectric conversion efficiency tends to decrease because the extraction efficiency of carriers (holes / electrons) generally decreases. However, according to the partial structure, the photoelectric conversion layer is thickened. Even if it exists, it becomes possible to maintain a high photoelectric conversion efficiency. In addition, the deep HOMO / LUMO level due to the partial structure also has the effect of improving the open-circuit voltage and the photo-oxidation stability. Furthermore, in general, when a fluorine atom is introduced into a partial structure, the affinity with various solvents tends to decrease. However, when a fluorine atom is introduced into the benzimidazole skeleton as in the present embodiment, Affinity can be maintained.

  Generally, a partial structure (unit) in which the LUMO level or the HOMO level is deeper than a hydrocarbon aromatic ring (benzene, naphthalene, anthracene, etc.) having the same number of π electrons as in the partial structure represented by Chemical Formula 1. Is called “acceptor unit”. On the other hand, a partial structure (unit) whose LUMO level or HOMO level is shallower than a hydrocarbon aromatic ring (benzene, naphthalene, anthracene, etc.) having the same number of π electrons is called a “donor unit”. The conjugated polymer compound of this embodiment may be (1) a conjugated polymer compound consisting only of an acceptor unit as long as it contains at least one partial structure represented by Chemical Formula 1, or (2) It may be a conjugated polymer compound in which an acceptor unit and a donor unit group including one or more donor units are alternately arranged. Among these, in order to efficiently absorb radiant energy over a wide range of the solar spectrum, the conjugated polymer compound of the latter (2) is preferable. This is because the absorption region can be expanded to a long wavelength region by alternately arranging the acceptor unit and the donor unit group. Therefore, such a conjugated polymer compound can absorb light in a long wavelength region (for example, 700 to 1000 nm) in addition to the absorption region (for example, 400 to 700 nm) of a conventional p-type organic semiconductor. Become.

  Note that the acceptor unit included in the conjugated polymer compound of this embodiment may include another partial structure (a structure having an electron withdrawing property) as long as it includes the partial structure represented by Chemical Formula 1. . However, in order to achieve higher photoelectric conversion efficiency, it is preferable that the proportion of the partial structure represented by Chemical Formula 1 is larger in the acceptor unit included in the conjugated polymer compound. Specifically, the number of partial structures represented by Chemical Formula 1 is preferably 50% or more and 70% or more with respect to the total number of acceptor units contained in the conjugated polymer compound. Is more preferably 90% or more, particularly preferably 95% or more, and most preferably 100%.

  The donor unit included in the group of donor units that can be included in the conjugated polymer compound of this embodiment includes a LUMO level or a HOMO rather than a hydrocarbon aromatic ring (benzene, naphthalene, anthracene, etc.) having the same number of π electrons. Any unit that has a shallow level can be used without restriction. For example, a unit including a thiophene ring, a furan ring, a pyrrole ring, a hetero 5-membered ring such as cyclopentadiene, silacyclopentadiene, and a condensed ring thereof.

  Specific examples include thiophene, thienothiophene, bithiophene, fluorene, silafluorene, carbazole, dithienocyclopentadiene, dithienosilacyclopentadiene, dithienopyrrole, and benzodithiophene. Among these units, it is preferable to have a thiophene structure capable of imparting high mobility, and thus, the photoelectric conversion efficiency can be further improved. Moreover, the solubility and crystallinity are improved by substituting the hydrogen atom couple | bonded with the atom which comprises a ring structure with a C1-C20 linear or branched alkyl group, an alkoxy group, etc. It is also possible.

  Hereinafter, preferred forms of the donor unit will be exemplified.

  In the donor unit represented by Chemical Formula 4, each R independently represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. Specific examples of the alkyl group include a methyl group, an ethyl group, an isopropyl group, a tert-butyl group, an n-octyl group, an n-decyl group, an n-hexadecyl group, a 2-ethylhexyl group, and a 2-hexyldecyl group. Can be mentioned.

  In this embodiment, the donor unit group is not particularly limited as long as it includes one or more donor units, and may be composed of only one donor unit, or two or more donor units are connected. It may be. Preferably, the donor unit group has a structure in which a first donor unit, a second donor unit, and a third donor unit are linearly connected in this order. At this time, the first donor unit and the third donor unit located at both ends of the donor unit group are adjacent to the acceptor unit. In other words, the conjugated polymer compound has a structure in which an acceptor unit and a second donor unit are connected via a first donor unit or a third donor unit.

  In the donor unit group, each of the first donor unit and the third donor unit located at both ends independently includes at least one partial structure represented by the following chemical formula 5, and is located in the middle. The second donor unit preferably does not contain the partial structure.

In the formula, R ³ and R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.

  Thus, the crystallinity of the conjugated polymer compound can be improved by introducing the partial structure represented by Chemical Formula 5 between the acceptor unit and the second donor unit. As a result, the carrier mobility is improved, so that the photoelectric conversion efficiency can be further improved.

In the partial structure represented by Chemical Formula 5, at least one of R ³ and R ⁴ is preferably independently a linear alkyl group having 1 to 20 carbon atoms.

  Among these, from the viewpoint of improving the crystallinity of the conjugated polymer compound and improving the mobility of the carrier; or from the viewpoint of improving the solubility of the monomer when producing the conjugated polymer compound, the number of carbon atoms is A relatively large linear alkyl group is preferred. Specifically, a linear alkyl group having 8 to 20 carbon atoms such as an n-octyl group, an n-decyl group, and an n-undecyl group is preferable. By introducing a linear alkyl group having 8 to 20 carbon atoms, it is possible to improve the solubility of the monomer when producing a conjugated polymer compound, so that a polymer having a large molecular weight can be obtained. By increasing the molecular weight of the conjugated polymer compound in this manner, a preferable morphology can be provided in the bulk heterojunction type photoelectric conversion layer, so that the photoelectric conversion efficiency can be further improved. In addition, since the solubility of the entire conjugated polymer compound can be improved, it is possible to provide sufficient solubility for forming a photoelectric conversion layer by a coating method, and a relatively thick (100 nm or more) photoelectric film can be provided. Even the conversion layer can be easily formed. Moreover, there is an effect that the crystallinity of the compound is increased by using a so-called fastener effect in which alkyl chains try to pack each other, and higher photoelectric conversion efficiency can be obtained. In addition, the fall of a short circuit current value can be prevented by making the carbon atom number of a linear alkyl group into 20 or less. On the other hand, in order to efficiently charge-separate the generated excitons, a linear alkyl group having a relatively small number of carbon atoms is preferable. Specifically, a methyl group, an ethyl group, an n-propyl group, n It is preferably a straight-chain alkyl group having 1 to 7 carbon atoms such as -butyl group, n-pentyl group, n-hexyl group, and n-heptyl group.

As a more preferable embodiment, at least one of R ³ and R ⁴ in one partial structure out of the partial structure included in the first donor unit and the partial structure included in the third donor unit is the number of carbon atoms Examples include a straight-chain alkyl group having 6 to 20 and R ³ and R ⁴ in the other partial structure being a hydrogen atom or a straight-chain alkyl group having 1 to 5 carbon atoms. Thus, a partial structure having a linear alkyl group having a relatively small number of carbon atoms and a partial structure having a linear alkyl group having a relatively large number of carbon atoms coexist in one conjugated polymer compound. As a result, it is possible to improve both carrier mobility, monomer solubility, and charge separation efficiency.

  Below, the preferable form of a donor property unit group is shown below. In the following chemical formula 6, “D-II” represents an arbitrary second donor unit.

  Further, the donor unit group may have the following structure in which the first to fifth donor units are sequentially connected in a straight chain in this order.

  The molecular weight of the conjugated polymer compound of this embodiment is not particularly limited, but preferably has an appropriate molecular weight in order to give morphology to the conjugated polymer compound. On the other hand, if the molecular weight is too high, the solubility may be lowered. Specifically, the number average molecular weight of the conjugated polymer compound is preferably 10,000 to 100,000, more preferably 15,000 to 70,000, and even more preferably 25,000 to 50,000. A low molecular compound (for example, fullerene derivative) used as an n-type organic semiconductor is widely used in constituting a bulk heterojunction type photoelectric conversion layer, but a conjugated polymer compound used as a p-type organic semiconductor When the molecular weight is within the above range, a microphase separation structure is formed well, and a carrier path for carrying holes and electrons generated at the pn junction interface is easily formed. The number average molecular weight in the present specification can be measured by gel permeation chromatography (GPC; standard material polystyrene) as described in Examples described later.

  In the present embodiment, the combination of the acceptor unit exemplified above and the donor unit is not particularly limited, and a conjugated polymer compound is appropriately combined with any acceptor unit and any donor unit. Can be synthesized and used. In the examples described later, conjugated polymer compounds having the combinations shown in Table 1 and Chemical Formula 7 below were synthesized and their performance was evaluated, but the technical scope of the present invention was limited to these examples only. Not.

<Organic photoelectric conversion element>
As described above, since the conjugated polymer compound according to the present invention can exhibit sufficient photoelectric conversion efficiency, it can be suitably used for an organic photoelectric conversion element. That is, according to another embodiment of the present invention, the first electrode, the second electrode, the n-type organic semiconductor and the p-type organic semiconductor that are present between the first electrode and the second electrode An organic photoelectric conversion element including the above-described conjugated polymer compound of the present invention is provided.

  Hereinafter, the present embodiment will be described with reference to the accompanying drawings. However, the technical scope of the present invention should be determined by the description of the scope of claims, and is not limited to the following embodiments. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may be different from the actual ratios.

  FIG. 1 is a schematic cross-sectional view schematically showing a normal layer type organic photoelectric conversion element according to an embodiment of the present invention. Specifically, the organic photoelectric conversion element 10 of FIG. 1 has a configuration in which an anode 11, a hole transport layer 26, a photoelectric conversion layer 14, an electron transport layer 27, and a cathode 12 are laminated in this order on a substrate 25. Have The substrate 25 is a member that is arbitrarily provided mainly for facilitating the formation of the anode 11 thereon by a coating method.

  When the organic photoelectric conversion element 10 shown in FIG. 1 is operated, light is irradiated from the substrate 25 side. In the present embodiment, the anode 11 is made of a transparent electrode material (for example, ITO) so that the irradiated light reaches the photoelectric conversion layer 14. The light irradiated from the substrate 25 side reaches the photoelectric conversion layer 14 through the transparent anode 11 and the hole transport layer 26.

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

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

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

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

  FIG. 3 is a schematic cross-sectional view schematically illustrating an organic photoelectric conversion element including a tandem (multi-junction type) photoelectric conversion layer according to another embodiment of the present invention. Compared with the organic photoelectric conversion element 10 in FIG. 1, the organic photoelectric conversion element 30 in FIG. 3 replaces the photoelectric conversion layer 14 with a first photoelectric conversion layer 14 a, a second photoelectric conversion layer 14 b, and these The difference is that a stacked body with a charge recombination layer 38 interposed between two photoelectric conversion layers is disposed. In the tandem organic photoelectric conversion element 30 shown in FIG. 3, photoelectric conversion materials (p-type organic semiconductor and n-type organic semiconductor) having different absorption wavelengths are used for the first photoelectric conversion layer 14a and the second photoelectric conversion layer 14b, respectively. By using this, light in a wider wavelength range can be efficiently converted into electricity.

  Hereinafter, each structure of the organic photoelectric conversion element which concerns on this invention is demonstrated in detail.

[electrode]
The organic photoelectric conversion element of this embodiment essentially includes a first electrode and a second electrode. The first electrode and the second electrode each function as an anode or a cathode. In the present specification, “first” and “second” are terms for distinguishing functions as an anode or a cathode. Therefore, the first electrode may function as an anode and the second electrode may function as a cathode. Conversely, the first electrode may function as a cathode and the second electrode may function as an anode. is there. As described above, the carriers (holes / electrons) generated in the photoelectric conversion layer 14 drift between the electrodes, and the holes reach the anode 12 and the electrons reach the cathode 16. In the present invention, an electrode through which holes mainly flow is called an anode, and an electrode through which electrons mainly flow is called a cathode. Moreover, when taking a tandem structure, a tandem structure can be achieved by using a charge recombination layer (intermediate electrode). Furthermore, from the functional aspect of whether or not the electrode has translucency, the translucent electrode is sometimes referred to as a transparent electrode, and the non-translucent electrode is sometimes referred to as a counter electrode. In the case of a normal layer configuration, the anode is usually a transparent electrode having a light transmitting property, and the cathode is a counter electrode having no light transmitting property.

  The material used for the electrode of this embodiment is not particularly limited as long as it is driven as a photoelectric conversion element, and an electrode material that can be used in this technical field can be appropriately employed. In particular, the anode is preferably composed of a material having a relatively large work function compared to the cathode, and conversely, the cathode is composed of a material having a relatively small work function compared to the anode. Is preferred.

  The anode 11 in the normal layer type organic photoelectric conversion element 10 shown in FIG. 1 is preferably composed of a transparent electrode material having a relatively large work function and capable of transmitting light of 380 to 800 nm. . On the other hand, the cathode 12 has a relatively small work function (for example, 4 eV or less), and can usually be composed of an electrode material having low translucency.

In such a normal layer type organic photoelectric conversion element 10, examples of electrode materials used for the anode (transparent electrode) include metals such as gold, silver, and platinum; indium tin oxide (ITO), SnO _2. And transparent conductive metal oxides such as ZnO; carbon materials such as metal nanowires and carbon nanotubes. It is also possible to use a conductive polymer as the anode electrode material. Examples of conductive polymers that can be used for the anode include PEDOT: PSS, polypyrrole, polyaniline, polythiophene, polythienylene vinylene, polyazulene, polyisothianaphthene, polycarbazole, polyacetylene, polyphenylene, polyphenylene vinylene, polyacene, polyphenyl. Examples include acetylene, polydiacetylene, polynaphthalene, and derivatives thereof. These electrode materials may be used alone or as a mixture of two or more materials. It is also possible to form an electrode by laminating two or more layers made of each material.

On the other hand, in the normal layer type organic photoelectric conversion element, as an electrode material used for the cathode (counter electrode), a metal, an alloy, an electron conductive compound, and a mixture thereof can be used. Specifically, 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 ) mixture, indium, Examples include lithium / aluminum mixtures and rare earth metals. Of these, a mixture of a first metal having a low work function and a second metal, which is a metal having a larger work function and more stable than the first metal, from the viewpoint of electron extraction performance and durability against oxidation, etc. For example, it is preferable to use a magnesium / silver mixture, a magnesium / aluminum mixture, a magnesium / indium mixture, an aluminum / aluminum oxide (Al ₂ O ₃ ) mixture, a lithium / aluminum mixture, aluminum which is a stable metal, or the like. In addition, it is also preferable to use a metal among these materials, so that light that is incident from the first electrode side and transmitted without being absorbed by the photoelectric conversion layer is reflected by the second electrode and is regenerated for photoelectric conversion. The photoelectric conversion efficiency can be improved. These electrode materials may be used alone or as a mixture of two or more materials. It is also possible to form an electrode by laminating two or more layers made of each material. The thickness of the cathode (counter electrode) is not particularly limited, but is usually 10 nm to 5 μm, preferably 50 to 200 nm.

  In the reverse layer type organic photoelectric conversion element shown in FIG. 2, the cathode 12 is located on the substrate 25 side on which light is incident, and the anode 11 is located on the opposite side. Therefore, the anode 11 in the reverse layer type shown in FIG. 2 is preferably composed of an electrode material having a relatively large work function and usually low translucency. On the other hand, the cathode 12 has a relatively small work function and is made of a transparent electrode material.

  In the reverse layer type organic photoelectric conversion element, examples of the electrode material used for the cathode (transparent electrode) include metals such as gold, silver, copper, platinum, rhodium, ruthenium, aluminum, magnesium, and indium, metal compounds, And carbon materials such as carbon nanoparticles, carbon nanowires, and carbon nanostructures. These electrode materials may be used alone or as a mixture of two or more materials. It is also possible to form an electrode by laminating two or more layers made of each material. Among these, it is preferable to use carbon nanowires because a transparent and highly conductive cathode can be formed by a coating method. In addition, when a metal material is used, an auxiliary electrode having a thickness of about 1 to 20 nm is formed on the side facing the anode (counter electrode) using, for example, aluminum, an aluminum alloy, silver, a silver compound, or the like. Then, a cathode (transparent electrode) can be obtained by providing a conductive polymer film exemplified as the anode (transparent electrode) material of the above-mentioned normal layer type organic photoelectric conversion element.

  On the other hand, in the reverse layer type organic photoelectric conversion element, the electrode material used for the anode (counter electrode) is preferably an electrode material having a relatively higher work function than the cathode (transparent electrode). For example, the anode (counter electrode) may be formed using a metal material such as silver, nickel, molybdenum, gold, platinum, tungsten, and copper.

As described above, in the present invention, the organic photoelectric conversion element having the reverse layer structure of FIG. 2 in which a material that hardly deteriorates due to oxygen, moisture, or the like can be used for both the anode and the cathode is preferable. Examples of preferable anode / cathode combinations in the reverse layer configuration include, for example, 1) first electrode (cathode) ITO, second electrode (anode) silver 2) first electrode (cathode) PEDOT: PSS, second Electrode (anode) silver 3) first electrode (cathode) ITO, second electrode (anode) copper 4) first electrode (cathode) PEDOT: PSS, second electrode (anode) gold 5) first Electrode (cathode) ITO, second electrode (anode) PEDOT: PSS
Etc.

[Photoelectric conversion layer]
The photoelectric conversion layer has a function of converting light energy into electric energy using the photovoltaic effect. The organic photoelectric conversion element of this embodiment is characterized in that the photoelectric conversion layer essentially includes the n-type organic semiconductor and the conjugated polymer compound of the present invention as a p-type organic semiconductor. When light is absorbed by these photoelectric conversion materials, excitons are generated, which are separated into holes and electrons at the pn junction interface.

  The photoelectric conversion layer of this embodiment essentially contains the above-described conjugated polymer compound of the present invention, and may contain other p-type organic semiconductor materials as necessary. An example of another p-type organic semiconductor material is shown below.

  Examples of the condensed polycyclic aromatic low molecular weight compound include anthracene, tetracene, pentacene, hexacene, heptacene, chrysene, picene, fluorene, pyrene, peropyrene, perylene, terylene, quaterylene, coronene, ovalene, thacumanthracene, bisanthene, zeslene. , Heptazethrene, pyranthrene, violanthene, isoviolanthene, cacobiphenyl, anthradithiophene, etc., porphyrin, copper phthalocyanine, tetrathiafulvalene (TTF) -tetracyanoquinodimethane (TCNQ) complex, bisethylenedithiotetrathiafulvalene (BEDTTTTF) -perchloric acid complex, and derivatives and precursors thereof.

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

  As the conjugated polymer, for example, a polythiophene such as poly-3-hexylthiophene (P3HT) and an oligomer thereof, or a technical group described in Technical Digest of the International PVSEC-17, Fukuoka, Japan, 2007, P1225. Polythiophene, Nature Material, (2006) vol. 5, p328, a polythiophene-thienothiophene copolymer described in WO2008 / 000664, a polythiophene-diketopyrrolopyrrole copolymer described in WO2008 / 000664, a polythiophene-thiazolothiazole copolymer described in Adv Mater, 2007p4160, Nature Mat. vol. 6 (2007), p497 described in PCPDTBT, etc., polypyrrole and its oligomer, polyaniline, polyphenylene and its oligomer, polyphenylene vinylene and its oligomer, polythienylene vinylene and its oligomer, polyacetylene, polydiacetylene, Examples thereof include polymer materials such as σ-conjugated polymers such as polysilane and polygermane.

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

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

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

  Examples of such materials include materials that can be insolubilized by polymerizing the coating film after coating, such as polythiophene having a polymerizable group described in Technical Digest of the International PVSEC-17, Fukuoka, Japan, 2007, P1225. Or a material in which soluble substituents react and become insoluble (pigmented) by applying energy such as heat, as described in US Patent Application Publication No. 2003/136964, and Japanese Patent Application Laid-Open No. 2008-16834 And so on.

  In addition, as long as the p-type organic semiconductor contained in the photoelectric converting layer of this form contains the above-mentioned conjugated polymer compound, the content of the other p-type organic semiconductor material is not particularly limited. However, in order to achieve higher photoelectric conversion efficiency, with respect to the total amount of the p-type organic semiconductor included in the photoelectric conversion layer (when two or more photoelectric conversion layers are included, the total amount in all layers), The larger the proportion of the conjugated polymer compound described above, the better. Specifically, the ratio of the conjugated polymer compound to the total amount of the p-type organic semiconductor is preferably 50% by mass or more, more preferably 70% by mass or more, and 90% by mass or more. More preferably, it is particularly preferably 95% by mass or more, and most preferably 100% by mass.

  On the other hand, the n-type organic semiconductor used in the photoelectric conversion layer of the present embodiment is not particularly limited as long as it is an organic compound that is acceptor (electron-accepting) with respect to the p-type organic semiconductor, and is used in this technical field. The material which can be used can be employ | adopted suitably. Such a compound may be a compound deeper by 0.2 to 0.5 eV or more than the LUMO level of the p-type organic semiconductor. For example, the p-type organic such as fullerene, carbon nanotube, octaazaporphyrin, etc. Perfluoro compounds (for example, perfluoropentacene and perfluorophthalocyanine) in which hydrogen atoms of a semiconductor are substituted with fluorine atoms, naphthalene tetracarboxylic acid anhydride, naphthalene tetracarboxylic acid diimide, perylene tetracarboxylic acid anhydride, perylene tetracarboxylic acid Examples thereof include aromatic carboxylic acid anhydrides such as diimide and polymer compounds containing the imidized product thereof as a skeleton.

  Of these, fullerenes, carbon nanotubes, or derivatives thereof are preferably used from the viewpoint that charge separation can be efficiently performed with a p-type organic semiconductor at high speed (up to 50 fs). More specifically, fullerene C60, fullerene C70, fullerene C76, fullerene C78, fullerene C84, fullerene C240, fullerene C540, mixed fullerene, fullerene nanotube, multi-walled carbon nanotube, single-walled carbon nanotube, carbon nanohorn (conical type), etc. , And some of these are hydrogen atoms, halogen atoms (fluorine atoms, chlorine atoms, bromine atoms, iodine atoms), substituted or unsubstituted alkyl groups, alkenyl groups, alkynyl groups, aryl groups, heteroaryl groups, And a fullerene derivative substituted with a cycloalkyl group, a silyl group, an ether group, a thioether group, an amino group, or the like.

  In particular, [6,6] -phenyl C61-butyric acid methyl ester (abbreviation PCBM), [6,6] -phenyl C61-butyric acid-nbutyl ester (PCBnB), [6,6] -phenyl C61- Butyric acid-isobutyl ester (PCBiB), [6,6] -phenyl C61-butyric acid-n hexyl ester (PCBH), [6,6] -phenyl C71-butyric acid methyl ester (abbreviation PC71BM), Adv . Mater. , Vol. 20 (2008), p2116, aminated fullerene described in JP-A 2006-199674, metallocene fullerene described in JP-A 2008-130889, US Pat. No. 7,329,709 It is preferable to use a fullerene derivative whose solubility is improved by a substituent, such as fullerene having a cyclic ether group described in the specification. In this embodiment, the n-type organic semiconductor may be used alone or in combination of two or more.

  There is no particular limitation on the junction form of the p-type organic semiconductor and the n-type organic semiconductor in the photoelectric conversion layer of this embodiment, and it may be a planar heterojunction or a bulk heterojunction (bulk heterojunction). Good. A planar heterojunction is a junction in which a p-type organic semiconductor layer containing a p-type organic semiconductor and an n-type organic semiconductor layer containing an n-type organic semiconductor are stacked, and the surface where these two layers contact is the pn junction interface. It is a form. On the other hand, a bulk heterojunction is formed by applying a mixture of a p-type organic semiconductor and an n-type organic semiconductor. In this single layer, a domain of the p-type organic semiconductor and a domain of the n-type organic semiconductor are formed. It has a microphase separation structure. Therefore, in a bulk heterojunction, many pn junction interfaces exist throughout the layer as compared to a planar heterojunction. Therefore, most of the excitons generated by light absorption can reach the pn junction interface, and the efficiency leading to charge separation can be increased. For these reasons, the junction between the p-type organic semiconductor and the n-type organic semiconductor in the photoelectric conversion layer of this embodiment is preferably a bulk heterojunction.

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

  In the present invention, the mixing ratio of the p-type organic semiconductor and the n-type organic semiconductor contained in the photoelectric conversion layer is preferably in the range of 2: 8 to 8: 2, more preferably 3.3: 6.7. It is the range of -5: 5. Moreover, the film thickness of one photoelectric conversion layer is preferably 50 to 400 nm, more preferably 80 to 300 nm, and particularly preferably 100 to 200 nm. In general, from the viewpoint of absorbing more light, it is preferable that the thickness of the photoelectric conversion layer is larger. However, as the film thickness increases, the extraction efficiency of carriers (holes / electrons) decreases, so the photoelectric conversion efficiency decreases. Tend to. However, when a photoelectric conversion layer is formed using the conjugated polymer compound of the present embodiment described above as a p-type organic semiconductor material, a film having a thickness of 100 nm or more is formed as compared with a photoelectric conversion layer using a conventional p-type organic semiconductor material. Even when the thickness is increased, the extraction efficiency of carriers (holes / electrons) is unlikely to decrease, so that high photoelectric conversion efficiency can be maintained.

(substrate)
The organic photoelectric conversion element of the present invention may include a substrate as necessary. The substrate has a role as a member to be coated with a coating solution when the electrode is formed by a coating method.

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

  There is no restriction | limiting in particular in the transparent resin film which can be preferably used as a transparent substrate by this invention, The material, a shape, a structure, thickness, etc. can be suitably selected from well-known things. For example, polyolefins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyester resin film such as modified polyester, polyethylene (PE) resin film, polypropylene (PP) resin film, polystyrene resin film, cyclic olefin resin, etc. Resin films, vinyl resin films such as polyvinyl chloride and polyvinylidene chloride, polyether ether ketone (PEEK) resin films, polysulfone (PSF) resin films, polyether sulfone (PES) resin films, polycarbonate (PC) resin films , Polyamide resin film, polyimide resin film, acrylic resin film, triacetyl cellulose (TAC) resin film, and the like. If the resin film transmittance of 80% or more in from zero to eight hundred nanomolar), can be preferably applied to a transparent resin film according to the present invention. Among these, from the viewpoint of transparency, heat resistance, ease of handling, strength and cost, it is preferably a biaxially stretched polyethylene terephthalate film, a biaxially stretched polyethylene naphthalate film, a polyethersulfone film, or a polycarbonate film. More preferred are a stretched polyethylene terephthalate film and a biaxially stretched polyethylene naphthalate film.

  The transparent substrate used in the present invention can be subjected to a surface treatment or an easy adhesion layer in order to ensure the wettability and adhesiveness of the coating solution. A conventionally well-known technique can be used about a surface treatment or an easily bonding layer. For example, the surface treatment includes surface activation treatment such as corona discharge treatment, flame treatment, ultraviolet treatment, high frequency treatment, glow discharge treatment, active plasma treatment, and laser treatment. Examples of the easy adhesion layer include polyester, polyamide, polyurethane, vinyl copolymer, butadiene copolymer, acrylic copolymer, vinylidene copolymer, and epoxy copolymer.

  For the purpose of suppressing the permeation of oxygen and water vapor, a barrier coat layer may be formed in advance on the transparent substrate, or a hard coat layer may be formed in advance on the opposite side to which the transparent conductive layer is transferred. Good.

(Hole transport layer)
The organic photoelectric conversion element of this form can contain a positive hole transport layer as needed. The hole transport layer has a function of transporting holes and a property of extremely small ability to transport electrons (for example, 1/10 or less of the mobility of holes). The hole transport layer is provided between the photoelectric conversion layer and the anode and prevents recombination of electrons and holes by blocking the movement of electrons while transporting holes to the anode. Can do.

  There is no restriction | limiting in particular in the hole transport material used for a hole transport layer, The material which can be used in this technical field can be employ | adopted suitably. As an example, for example, PEDOT: PSS such as product name BaytronP manufactured by Clevios, polythienothiophenes described in European Patent No. 1647566, sulfonated polythiophenes described in JP 2010-206146, polyaniline, and the like The dope material, cyan compounds described in International Publication No. 2006/019270 pamphlet and the like can be mentioned.

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

  Besides these, a porphyrin compound, an aromatic tertiary amine compound, a styrylamine compound, and the like can be used, and among these, it is preferable to use an aromatic tertiary amine compound. In some cases, the hole transport layer may be formed using an inorganic compound such as a metal oxide such as molybdenum, vanadium, or tungsten, or a mixture thereof.

  Furthermore, a polymer material in which a structural unit contained in the above compound is introduced into a polymer chain, or a polymer material having the above compound as the main chain of the polymer can also be used as a hole transport material. JP-A-11-251067, J. Org. Huang et. al. , Applied Physics Letters, 80 (2002), p. A p-type hole transport material as described in 139 can also be used. Furthermore, a hole transport material with high p property doped with impurities can be used. For example, JP-A-4-297076, JP-A-2000-196140, JP-A-2001-102175, J. Pat. Appl. Phys. 95, 5773 (2004), and the like. In addition, these hole transport materials may be used individually by 1 type, and may use 2 or more types together. It is also possible to form a hole transport layer by laminating two or more layers made of each material.

  The thickness of the hole transport layer is not particularly limited, but is usually 1 to 2000 nm. From the viewpoint of further improving the leak prevention effect, the thickness is preferably 5 nm or more. Further, from the viewpoint of maintaining high transmittance and low resistance, the thickness is preferably 1000 nm or less, and more preferably 200 nm or less.

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

(Electron transport layer)
The organic photoelectric conversion element of this form can contain an electron carrying layer as needed. The electron transport layer has a property of transporting electrons and having a remarkably small ability to transport holes. The electron transport layer is provided between the photoelectric conversion layer and the cathode, and prevents the recombination of electrons and holes by blocking the movement of holes while transporting electrons to the cathode. it can.

  There is no restriction | limiting in particular in the electron transport material used for an electron carrying layer, The material which can be used in this technical field can be employ | adopted suitably. For example, octaazaporphyrin, a perfluoro body of a p-type organic semiconductor (perfluoropentacene, perfluorophthalocyanine, etc.) can be used. Similarly, it is more than the HOMO level of a p-type organic semiconductor used in a photoelectric conversion layer. The electron transport layer having a deep HOMO level is provided with a hole blocking function having a rectifying effect so that holes generated in the photoelectric conversion layer do not flow to the cathode side. Therefore, more preferably, a material deeper than the HOMO level of the n-type organic semiconductor is used as the electron transport material. Examples of such electron transport materials include phenanthrene compounds such as bathocuproine, n-type organic semiconductors such as naphthalenetetracarboxylic anhydride, naphthalenetetracarboxylic acid diimide, perylenetetracarboxylic acid anhydride, perylenetetracarboxylic acid diimide, and oxidation. N-type inorganic oxides such as titanium, zinc oxide, and gallium oxide, and alkali metal compounds such as lithium fluoride, sodium fluoride, and cesium fluoride can be used. Moreover, the layer which consists of a n-type organic semiconductor single-piece | unit used for the photoelectric converting layer can also be used. In addition, these electron transport materials may be used individually by 1 type, and may use 2 or more types together. It is also possible to form an electron transport layer by stacking two or more layers made of each material.

  As described above, in the case of an inverted layer type element that is advantageous from the viewpoint of durability, the photoelectric conversion layer is formed after the electron transport layer is formed on the first electrode. A compound that is insoluble in the coating liquid to be contained is preferred as the electron transport material. From such a viewpoint, the electron transport material is preferably an inorganic substance such as titanium oxide or zinc oxide, and a crosslinkable organic substance such as polyethyleneimine or an aminosilane coupling agent described in International Publication No. 2008-134492. Among them, it is preferable to use an aminosilane coupling agent.

  The thickness of the electron transport layer is not particularly limited, but is usually 1 to 2000 nm. From the viewpoint of further improving the leak prevention effect, the thickness is preferably 5 nm or more. Further, from the viewpoint of maintaining high transmittance and low resistance, the thickness is preferably 100 nm or less, and more preferably 20 nm or less.

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

  The material used for the charge recombination layer (intermediate electrode) is not particularly limited as long as it is a material having both conductivity and translucency, and examples thereof include ITO, AZO, FTO, and titanium oxide exemplified above. Transparent metal oxides, metals such as Ag, Al, and Au, carbon materials such as carbon nanoparticles and carbon nanowires, and conductive polymers such as PEDOT: PSS and polyaniline can be used. These materials may be used alone or in combination of two or more. It is also possible to form a charge recombination layer by laminating two or more layers made of each material.

The electric conductivity of the charge recombination layer is preferably high from the viewpoint of obtaining high conversion efficiency. Specifically, it is preferably 5 to 50000 S / cm, more preferably 100 to 10,000 S / cm. preferable. The thickness of the charge recombination layer is not particularly limited, but is preferably 1 to 1000 nm, and preferably 5 to 50 nm. By setting the thickness to 1 nm or more, the film surface can be smoothed. On the other hand, by setting the thickness to 1000 nm or less, it is possible to reduce the decrease in the short-circuit current density J _sc (mA / cm ² ).

(Other layers)
The organic photoelectric conversion device of this embodiment may further include other members (other layers) in addition to the above-described members (each layer) in order to improve photoelectric conversion efficiency and improve the lifetime of the device. . Examples of other members include 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. Further, a layer such as a silane coupling agent may be provided in order to make the metal oxide fine particles unevenly distributed in the upper layer more stable. Further, a metal oxide layer may be laminated adjacent to the photoelectric conversion layer of the present invention.

  Moreover, the organic photoelectric conversion element of this invention may have various optical function layers for the purpose of more efficient light reception of sunlight. Examples of the optical functional layer include a light condensing layer such as an antireflection film and a microlens array, and a light diffusion layer that can scatter light reflected by the cathode and enter the power generation layer again.

  Various known antireflection layers can be provided as the antireflection layer. For example, when the transparent resin film is a biaxially stretched polyethylene terephthalate film, the refractive index of the easy adhesion layer adjacent to the film is 1.57. It is more preferable to set it to ˜1.63 because the interface reflection between the film substrate and the easy adhesion layer can be reduced and the transmittance can be improved. The method for adjusting the refractive index can be carried out by appropriately adjusting the ratio of the oxide sol having a relatively high refractive index such as tin oxide sol or cerium oxide sol and the binder resin. The easy adhesion layer may be a single layer, but may be composed of two or more layers in order to improve adhesion.

  As the condensing layer, for example, it is processed so as to provide a structure on the microlens array on the sunlight receiving side of the support substrate, or the amount of light received from a specific direction is increased by combining with a so-called condensing sheet. Conversely, the incident angle dependency of sunlight can be reduced.

  As an example of the microlens array, quadrangular pyramids having a side of 30 μm and an apex angle of 90 degrees are two-dimensionally arranged on the light extraction side of the substrate. One side is preferably 10 to 100 μm. If it becomes smaller than this, the effect of diffraction will generate | occur | produce and color, and if too large, thickness will become thick and is not preferable.

  Examples of the light scattering layer include various antiglare layers, layers in which nanoparticles or nanowires such as metals or various inorganic oxides are dispersed in a colorless and transparent polymer, and the like.

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

  The manufacturing method of the organic photoelectric conversion element of this embodiment includes a step of forming a cathode, a step of forming a photoelectric conversion layer including a p-type organic semiconductor material and an n-type organic semiconductor material on the cathode, and the photoelectric conversion. Forming an anode on the layer. Hereinafter, each process of the manufacturing method of the organic photoelectric conversion element of this form is demonstrated in detail.

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

  After forming the cathode as described above, an electron transport layer may be formed on the cathode as necessary. The means for forming the electron transport layer may be either vapor deposition or solution coating, but is preferably solution coating. In the case of forming an electron transport layer using a solution coating method, a solution obtained by dissolving and dispersing the above-described electron transport material in a suitable solvent is coated on the cathode using a suitable coating method and dried. That's fine. The coating methods used for the solution coating method include cast method, spin coating method, blade coating method, wire bar coating method, gravure coating method, spray coating method, dipping (dipping) coating method, bead coating method, air knife coating method. Ordinary methods such as a curtain coating method, an ink jet method, a screen printing method, a relief printing method, an intaglio printing method, an offset printing method, a flexographic printing method, and a Langmuir-Blodgett (LB) method can be used. Among these, it is particularly preferable to use a blade coating method. In addition, although the solid content concentration of the solution used for the coating method may vary depending on the coating method and the film thickness, it is preferably 1 to 15% by mass, more preferably 1.5 to 10% by mass. In addition, the temperature of the coating liquid and / or the coating surface during coating is not particularly limited, but is preferably 30 to 120 ° C. from the viewpoint of preventing precipitation and unevenness due to temperature fluctuations during coating and drying. More preferably, it is 50-110 degreeC. Furthermore, there is no restriction | limiting in particular also about the specific form of drying, A conventionally well-known knowledge can be referred suitably. An example of the drying condition is exemplified by a temperature of about 90 to 140 ° C. and a period of several minutes to several tens of minutes. Examples of the apparatus used for drying include hot air drying, an infrared heater, a microwave, and a vacuum dryer. Of course, it is possible to use other drying apparatuses.

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

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

  Note that the steps after the step of forming the photoelectric conversion layer are preferably performed in a glove box under a nitrogen atmosphere so as not to be exposed to oxygen or moisture. Thus, by performing in a nitrogen atmosphere, it is possible to prevent the p-type organic semiconductor from being deteriorated by oxygen or moisture in the air, and to increase the durability of the element. Specifically, the concentration of oxygen and moisture in the glove box is preferably 1000 ppm or less, and more preferably 100 ppm or less. Most preferably, it is 10 ppm or less.

  Next, an anode is formed on the photoelectric conversion layer formed above. The means for forming the anode is not particularly limited and may be either a vapor deposition method or a solution coating method, but a vapor deposition method (for example, a vacuum vapor deposition method) is preferably used. In addition, when providing a positive hole transport layer between a photoelectric converting layer and an anode, a positive hole transport layer is formed using a vapor deposition method or a solution coating method, Preferably a solution coating method. In addition, it is preferable to perform the process of forming the said positive hole transport layer within the glove box of nitrogen atmosphere similarly to the process of forming the said photoelectric converting layer. Thus, by performing in a nitrogen atmosphere, deterioration of the photoelectric conversion layer due to oxygen or moisture in the air can be prevented, and the durability of the element can be improved. In addition, since the conjugated polymer compound according to the present invention has a benzimidazole skeleton, it has a high solvent affinity even when a fluorine atom and / or a chlorine atom is introduced. Therefore, when forming the hole transport layer using the solution coating method, it is possible to effectively prevent the coating solution containing the hole transport material from being repelled on the surface of the photoelectric conversion layer. The film property can be improved.

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

  The electrodes (cathode / anode), photoelectric conversion layer, hole transport layer, electron transport layer, and the like can be patterned as necessary. The patterning method is not particularly limited, and a known method can be appropriately applied. For example, when patterning soluble materials used in bulk heterojunction type photoelectric conversion layers, hole transport layers, electron transport layers, etc., even if only unnecessary portions are wiped off after the entire surface of die coating, dip coating, etc. Alternatively, direct patterning may be performed at the time of application using a method such as an inkjet method or screen printing. On the other hand, in the case of an insoluble material used for an electrode or the like, mask deposition can be performed at the time of deposition by vacuum deposition, or patterning can be performed by a known method such as etching or lift-off. Alternatively, the pattern may be formed by transferring a pattern formed on another substrate.

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

<Uses of organic photoelectric conversion elements>
According to the other form of this invention, the solar cell which has the organic photoelectric conversion element obtained by the organic photoelectric conversion element which concerns on the above-mentioned 1st form, and the manufacturing method which concerns on a 2nd form is provided. Since the organic photoelectric conversion element of this form has the outstanding photoelectric conversion efficiency and durability, it can be used suitably for the solar cell which uses this as an electric power generation element.

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

  The effect of this invention is demonstrated using a following example and a comparative example. However, the technical scope of the present invention is not limited only to the following examples.

<Synthesis of conjugated polymer compound>
[Synthesis of Compound A01]

(Synthesis of Compound b)
Compound a is Angelwandte Chemie International E
Synthesized with reference to volume 50, Issue 13, p2995-2998.

  8.4 g of compound a was taken in a 200 ml three-necked flask purged with nitrogen, dissolved in 100 ml of methanol, and cooled on ice. 7.6 g of sodium borohydride was added to the resulting solution, and the mixture was stirred at room temperature (25 ° C., the same applies hereinafter) for 24 hours. Insoluble matters were filtered off from the reaction solution, the mother liquor was concentrated under reduced pressure, and then purified by silica column chromatography to obtain 4.0 g of compound b.

(Synthesis of Compound c)
Compounds c and A01 are described in J. Mater. Chem. , 2010, 20, and p6517.

2.6 g of compound b, 20 ml of acetone, 2.0 ml of acetic acid, and 20 ml of tetrahydrofuran (THF) were added and refluxed at 70 ° C. for 5 hours. After allowing to cool, ethyl acetate was added and washed with water. The organic layer was extracted and dried over magnesium sulfate, and then the solvent was distilled off. The brown oil component was purified by silica gel column chromatography (eluent: toluene) to obtain 900 mg of yellow needle crystals (yield 38%). _{NMR (CDCl 3); 4.02ppm,} br (NH), 2.16ppm, s (CH 3).

(Synthesis of Compound A01)
900 mg of compound c, 20 ml of THF, and 3.5 g of manganese oxide were added, and the mixture was stirred at room temperature for 5 hours. After manganese oxide was filtered off, the solvent was distilled off, and the resulting orange oil component was purified using silica gel column chromatography and a preparative GPC device LC-91xxNEXT (toluene solvent) manufactured by Japan Analytical Industry. 420 mg of crystals were obtained (47% yield). In the mass spectrum (negative mode), 433 peaks were confirmed to confirm the structure. _{NMR (CDCl 3); 1.62ppm,} s (CH 3).

  [Synthesis of Compound 103]

  Bis- (5,5'-trimethylstannyl) -3,3'-di- (2-ethylhexyl) -silylene-2,2'-dithiophene is described in JP-T-2010-507233 and Adv. Mater. , 2010, p-E63 was synthesized with reference.

  217 mg (0.5 mmol) of the compound A01 and 372 mg of bis- (5,5′-trimethylstannyl) -3,3′-di- (2-ethylhexyl) -silylene-2,2′-dithiophene (0. 5 mmol) was dissolved in 20 ml of anhydrous toluene. After purging the solution with nitrogen, 12.55 mg (0.014 mmol) of tris (dibenzylideneacetone) dipalladium (0) and 28.80 mg (0.110 mmol) of triphenylphosphine were added. The solution was purged with nitrogen for an additional 15 minutes. Thereafter, the solution was heated to 110 to 120 ° C. and reacted for 40 hours. Furthermore, in order to perform an end cap, 2-tributyltin thiophene (11 mg, 0.03 mmol) was added and refluxed for 10 hours. Further 2-bromothiophene (10 mg, 0.06 mmol) was added and refluxed for 10 hours. After completion of the reaction, the solvent was distilled off, and the resulting residue was washed with methanol (50 ml × 3), and then washed with acetone (3 × 50 ml).

  The recovered polymer product was extracted with Soxhlet extraction using heptane, chloroform, and then orthodichlorobenzene, and then reprecipitated in methanol to give 150 mg of pure polymer (Mn = 29000) (Compound 103) To obtain an organic photoelectric conversion element 103 of the present invention. In addition, the extraction component from chloroform is Mn = 14000, and was used for the organic photoelectric conversion element 104 of the present invention.

[Synthesis of Compound A11]
Synthesis was performed in the same manner as Compound A01, except that acetone used in the synthesis of Compound c was changed to 1,1,1-trifluorobutanone, and Compound A11 was obtained in a yield of 440 mg. In the mass spectrum (negative mode), a peak of 501 was confirmed and the structure was confirmed.

[Synthesis of Compound 105]
In the synthesis of Compound 103, polymerization was carried out in the same manner except that Compound A11 was used in an amount of 251 mg instead of Compound A01, and 140 mg of polymer was obtained at a Mn = 35000 from the Soxhlet extract component of orthodichlorobenzene.

(Synthesis of Compound d)
J. et al. Am. Chem. Soc. , 2008, 130 (25), pp7812, 5.5 g (20 mmol) of 2-bromo-3- (2-ethylhexyl) thiophene dissolved in 100 ml of dehydrated tetrahydrofuran, cooled to −78 ° C., and n- 12.5 ml (20 mmol) of 1.6 M hexane solution of butyllithium was added dropwise and stirred for 1 hour, then 25 ml (25 mmol) of 1.0 M hexane solution of trimethyltin chloride was added dropwise, and the mixture was further stirred for 1 hour, and the temperature was brought to room temperature. The resulting mixture was stirred for 3 hours.

  After completion of the reaction, brine and ethyl acetate were added and washed, and the organic layer was extracted and dried over magnesium sulfate, and then the solvent was distilled off. The obtained oil component was dissolved in hexane: triethylamine = 9: 1 and purified through silica gel previously immersed in triethylamine to obtain 7.0 g of light yellow compound d (yield 97%).

(Synthesis of Compound e)
800 mg of compound d, 500 mg of compound A11, and 120 mg of tetrakis (triphenylphosphine) palladium were dissolved in 20 ml of toluene and refluxed at 120 ° C. for 3 hours under nitrogen. After completion of the reaction, the reaction solution was directly purified by silica gel column chromatography to obtain 600 mg of orange oil compound e (yield 94%).

(Synthesis of Compound f)
600 mg of compound e and 356 mg of N-bromosuccinimide were dissolved in 20 ml of tetrahydrofuran and refluxed at 60 ° C. for 5 hours under nitrogen. After completion of the reaction, brine and ethyl acetate were added and washed, and the organic layer was extracted and dried over magnesium sulfate, and then the solvent was distilled off. The obtained oil component was purified by silica gel column chromatography to obtain 670 mg of orange oil compound f (yield 89%).

  [Synthesis of Compound 106]

  In the synthesis of Compound 103, 251 mg of Compound A11 instead of Compound A01, bis- (5,5′-trimethylstannyl) -3,3′-di- (2-ethylhexyl) -silylene-2,2′-dithiophene 1,5-bis (trimethyltin) -4,8-bis (2-ethylhexyloxy) -benzo [1,2-b: 4,5-b ′] dithiophene (J. Am. Chem. Soc., 2009, 131 (22), synthesized with reference to pp7792) Polymerization was carried out in the same manner except that the amount was changed to 386 mg.

  200 mg of polymer was obtained with Mn = 34000 from Soxhlet extract component of orthodichlorobenzene.

  [Synthesis of Compound 107]

  In the synthesis of Compound 103, 126 mg of Compound A11 instead of Compound A01, bis- (5,5′-trimethylstannyl) -3,3′-di- (2-ethylhexyl) -silylene-2,2′-dithiophene Was carried out in the same manner except that the compound g was changed to 325 mg of the compound g (synthesized with reference to Macromolecules 2011, 44, 6245).

  110 mg of polymer was obtained with Mn = 41000 from Soxhlet extract component of orthodichlorobenzene.

  Compounds 101, 102, and 104 (especially A25, A27, and A01) can be easily synthesized with reference to the synthesis of compound 103 described above.

<Preparation of reverse layer type organic photoelectric conversion element>
With reference to the description of International Publication No. 2008-134492 Panfoot, a reverse layer type organic photoelectric conversion device was produced as follows.

[Comparative Example 1]
An indium tin oxide (ITO) transparent conductive film deposited with a thickness of 150 nm as a first electrode (cathode) on a PET substrate (sheet resistance 12 Ω / square) is 10 mm wide using ordinary photolithography technology and wet etching. To form a first electrode. The patterned first electrode was cleaned in the order of ultrasonic cleaning with a surfactant and ultrapure water, followed by ultrasonic cleaning with ultrapure water, dried with nitrogen blow, and finally subjected to ultraviolet ozone cleaning. After this, the substrate was brought into the glove box and operated under a nitrogen atmosphere.

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

  Next, 0.8% by mass of Comparative Compound 1 (synthesized based on Non-Patent Document 3), which is a p-type organic semiconductor material, is added to o-dichlorobenzene, and PC61BM (nanospectra E100H made by Frontier Carbon) is an n-type organic semiconductor material. ) Was mixed at 1.6% by mass (p-type organic semiconductor material: n-type organic semiconductor material = 33: 67 (mass ratio)), and dissolved by stirring all day and night while heating to 110 ° C. in an oven. Then, it apply | coated using the blade coater which hold | maintained the substrate temperature at 80 degreeC so that the dry film thickness might be set to about 200 nm, and it dried at 80 degreeC as it was for 2 minutes, and formed the photoelectric converting layer into a film.

After the drying of the photoelectric conversion layer is completed, it is taken out again into the atmosphere, and then, as a hole transport layer, PEDOT-PSS (CLEVIOS (registered trademark) PVP AI 4083, manufactured by Helios Co., Ltd., conductivity, composed of a conductive polymer and a polyanion. (1 × 10 ⁻³ S / cm) was diluted with an equal amount of isopropanol, and applied and dried using a blade coater so that the dry film thickness was about 30 nm. Then, it heat-processed for 20 second with 90 degreeC warm air, and formed the positive hole transport layer (organic material layer) which consists of organic substance. The temperature and humidity of the atmosphere at the time of application were 23 ° C. and 65%.

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

  In addition, after forming the photoelectric conversion layer, the hole transport layer was formed in the glove box as it was without taking it out from the glove box (GB) under nitrogen atmosphere (oxygen concentration 10 ppm, dew point temperature −80 ° C.). Except for this, the reverse layer type organic photoelectric conversion element 1 ′ was produced in the same manner.

[Comparative Examples 2-3]
In the formation of the photoelectric conversion layer, a reverse layer type organic photoelectric conversion element was produced in the same manner as in Comparative Example 1 except that Comparative Compounds 2 to 3 were used as p-type organic semiconductors.

[Examples 2 to 8]
In the formation of the photoelectric conversion layer, an inverted layer type organic photoelectric conversion element was produced in the same manner as in Comparative Example 1 except that the compounds 102 to 107 were used as p-type organic semiconductors.

<Evaluation of reverse layer type organic photoelectric conversion element>
(Evaluation of open circuit voltage, fill factor, and photoelectric conversion efficiency)
The organic photoelectric conversion element was sealed with an epoxy resin and a glass cap, respectively. A solar simulator (AM1.5G filter) is used to irradiate light with an intensity of 100 mW / cm ² , a mask with an effective area of 1 cm ² is overlaid on the light receiving part, and IV characteristics are evaluated, thereby short-circuit current density J _sc (mA / cm ² ), open circuit voltage V _oc (V), and fill factor FF were measured. From the obtained values of J _sc , V _oc and FF, photoelectric conversion efficiency η [%] was calculated according to the following formula 1. The results are shown in Table 2.

(Evaluation of film forming property of hole transport layer on photoelectric conversion layer)
About the said Examples 1-8 and Comparative Examples 1-3, preparation of the reverse layer type organic photoelectric conversion element was tried 5 times, respectively. And when apply | coating a positive hole transport layer on a photoelectric converting layer, the hydrophilic solvent contained in the dispersion liquid of organic solvent type | system | group PEDOT: PSS on a photoelectric converting layer is favorable, and is not repelled on a photoelectric converting layer. The film forming property was evaluated by the number of times the hole transport layer was formed. The results are shown in Table 2.

(Durability evaluation)
The organic photoelectric conversion elements obtained in Examples 1 to 8 and Comparative Examples 1 to 3 were stored in a container maintained at a temperature of 80 ° C. and a humidity of 80%, and taken out periodically to measure IV characteristics. Assuming that the photoelectric conversion efficiency was 100, the time when the initial efficiency was reduced to 80% was evaluated as LT80 [time]. It means that durability is so favorable that the value of LT80 is large. The results are shown in Table 2.

  From the results of Table 2, it was shown that the examples using the conjugated polymer compound of the present invention have better coating properties of the hole transport layer and higher photoelectric conversion efficiency than the comparative examples. .

  As for the durability evaluation of the device, the durability was remarkably improved as compared with the comparative example in each of the examples in which the hole transport layer was formed in the atmosphere and in the glove box.

  Furthermore, the example in which the hole transport layer is formed in a glove box with less oxygen and moisture improves the photoelectric conversion efficiency and the durability of the device further than the example in which the hole transport layer is formed in the atmosphere. It was shown that. On the other hand, in Comparative Examples 2 and 3, when the hole transport layer was applied in the glove box, the hydrophilic solvent was repelled and film formation was extremely difficult.

10, 20, 30 organic photoelectric conversion element,
11 Anode,
12 cathode,
14 photoelectric conversion layer,
14a 1st photoelectric conversion layer,
14b second photoelectric conversion layer,
25 substrates,
26 hole transport layer,
27 electron transport layer,
38 Charge recombination layer.

Claims (11)

A conjugated polymer compound comprising at least one partial structure represented by the following chemical formula 1;
In the formula, each of R ¹ and R ² independently represents a hydrogen atom; a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a fluorinated alkyl group having 1 to 20 carbon atoms, or a carbon atom. A cycloalkyl group having 3 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a fluorinated alkoxy group having 1 to 20 carbon atoms, and 1 to 20 carbon atoms A fluorinated alkylthio group, an aryl group having 6 to 30 carbon atoms, a fluorinated aryl group having 6 to 30 carbon atoms, a heteroaryl group having 4 to 20 carbon atoms, or a fluorinated heterocycle having 4 to 20 carbon atoms R ¹ and R ² may be bonded to each other to form a ring;
X ¹ and X ² each independently represent a hydrogen atom, a fluorine atom, or a chlorine atom (provided that at least one of X ¹ and X ² represents a fluorine atom or a chlorine atom). The conjugated polymer compound according to claim 1, wherein at least one of X ¹ and X ² represents a fluorine atom. The conjugated polymer compound according to claim 2, wherein both X ¹ and X ² represent a fluorine atom. At least one of the R ¹ and R ² is the fluorinated alkyl group having 1 to 20 carbon atoms, the fluorinated alkoxy group having 1 to 20 carbon atoms, the fluorinated alkylthio group having 1 to 20 carbon atoms, or the following The conjugated polymer compound according to any one of claims 1 to 3, which represents a group represented by Chemical Formula 2;
In the formula, L represents an alkylene group having 1 to 20 carbon atoms, an arylene group having 3 to 20 carbon atoms, or a heteroarylene group having 3 to 20 carbon atoms,
EWG is a fluorinated alkyl group having 1 to 20 carbon atoms, an alkylcarbonyl group having 2 to 20 carbon atoms, an alkylcarbonyloxy group having 2 to 20 carbon atoms, an alkyloxycarbonyl group having 2 to 20 carbon atoms, Alkylcarbonylamino group having 2 to 40 carbon atoms, alkylaminocarbonyl group having 2 to 40 carbon atoms, cyano group, nitro group, alkylsulfinyl group having 1 to 20 carbon atoms, sulfo group, 1 to 20 carbon atoms Represents at least one electron-withdrawing group selected from the group consisting of an alkylsulfonyloxy group and an aminosulfonyl group. 5. The conjugated polymer compound according to claim 1, wherein at least one of R ¹ and R ² represents the fluorinated alkyl group having 1 to 3 carbon atoms. An acceptor unit and a donor unit group including one or more donor units are alternately combined,
The conjugated polymer compound according to claim 1, wherein each of the acceptor units independently includes at least one partial structure represented by Chemical Formula 1. The conjugated polymer compound according to claim 6, wherein each of the donor units independently includes at least one partial structure represented by the following D1 to D18;
In the formula, each R independently represents an alkyl group having 1 to 20 carbon atoms. The conjugated polymer compound according to claim 6, wherein the donor unit includes a partial structure represented by D17 below.
A first electrode;
A second electrode;
A photoelectric conversion layer including an n-type organic semiconductor and a p-type organic semiconductor, which exists between the first electrode and the second electrode;
Including
The said p-type organic semiconductor is an organic photoelectric conversion element containing the conjugated polymer compound of any one of Claims 1-8. The first electrode is a transparent electrode;
The second electrode is a counter electrode;
The organic photoelectric conversion element according to claim 9, further comprising a hole transport layer between the photoelectric conversion layer and the second electrode.   The solar cell containing the organic photoelectric conversion element of Claim 9 or 10.