JP2011165963A - Organic dye and organic thin-film solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sensitizing dye material with a wide absorption wavelength range in a new conjugated copolymer oligomer and a conjugated compound having a donor property. <P>SOLUTION: The conjugated copolymer oligomer has a squarylium (SQ) frame and a benzodithiophene (BD) frame as a main chain. The conjugated compound has the squarylium (SQ) frame and the benzodithiophene (BD) frame. A bulk heterojunction type organic thin-film solar cell has a photoelectric conversion layer containing a donor-nature substance and a fullerene derivative (PCBM). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to the provision of squarylium-containing oligomers and squarylium-containing compounds used as bulk heterojunction organic thin-film solar cells in combination with fullerene derivatives as electron acceptors, and the provision of the organic thin-film solar cells. The invention also relates to the provision of an organic dye comprising a squarylium-containing oligomer and a squarylium-containing compound.

  Considering global warming and energy problems, there is an urgent need to develop clean alternative energy at low cost. Among them, solar energy is practically inexhaustible, and various materials are being researched and developed because it is expected to be an alternative energy because it does not place a burden on the environment.

  Solar cells that use solar energy have already entered the stage of practical use, where inorganic photoelectric conversion elements typified by amorphous silicon are used. This inorganic photoelectric conversion element exhibits a photoelectric conversion efficiency as high as several tens of percent and is excellent, but there is a potential for improvement in workability and a problem of silicon resources.

  In order to solve such a problem, a dye-sensitized solar cell in which a porous semiconductor layer on which a photosensitizing dye is adsorbed is provided between a pair of electrodes, at least one of which is transparent, and an electrolyte is injected therein has been developed. However, this solar cell has a problem that the battery case deteriorates with time and the electrolyte injected therein leaks, and further, it is inferior in mass productivity and it is difficult to increase the area of the condensing part.

  As a method not using an electrolytic solution, a bulk heterojunction (BHJ) type (or organic thin film) solar cell has been proposed. Since this solar cell is manufactured using a printing technique, development is awaited because it is inexpensive and can be increased in area, and a lightweight and flexible solar cell can be obtained.

  BHJ-type solar cells ensure a wide contact interface by blending p-type and n-type materials, improve the energy conversion efficiency by promoting rapid exciton dissociation and efficient transport of dissociated charges at the interface There is expected.

  Here, the photoelectric conversion process of the BHJ solar cell consists of (1) exciton generation by light absorption, (2) exciton diffusion, (3) charge generation by exciton dissociation, and (4) charge transport and charge It consists of four stages of integration. In order to realize high power conversion efficiency (η), it is necessary to increase the efficiency of each stage of (1) to (4).

As photoelectric conversion materials for BHJ-type thin film solar cells, poly (3-hexylthiophene) (P3HT) as an electron donor and [6,6] -phenyl-C ₆₁ -butyric acid methyl ester which is a fullerene derivative as an electron acceptor ( A combination with PC ₆₁ BM) is a typical example. The energy conversion efficiency of this P3HT / PCBM system is 5% (W. Ma, C. Yang, X. Gong, K. Lee, AJ Heeger, Adv. Funct. Mater. 2005, 15, 1617-1622).

  In order to realize further improvement in light energy conversion efficiency, it is necessary to increase the efficiency of each step (1) to (4) described above. More specifically, donor polymer molecules and acceptors (fullerene derivatives) are required. ) [1] Improvement of electronic interaction with molecules and [2] Realization of ideal morphology (form) of contact interface is necessary.

  According to BC Thompson et al., The ideal morphology of [2] is that BHJ solar cells are a physical mixture of donor and acceptor materials. Maximization of the contact interface region that promotes efficient transport, and b) an average region size that is commensurate with exciton diffusion length (5-10 nm) that does not result in deactivation due to charge path loss and dissociation charge recombination It is said to be a bicontinuous composition of a donor material and an acceptor material that can satisfy the two requirements (BC Thompson et. Al., Angw. Chem. Int. Ed. 2008, 47, pp.64).

  On the other hand, the mainstream of research aimed at improving the electronic interaction of [1] has been focused on improving donor polymers that replace P3HT. This is because the opinion that fullerene derivatives such as PCBM are the best acceptors has been established among those skilled in the art.

  Two points have been pointed out in improving donor polymers (B. C. Thompson et. Al., Angw. Chem. Int. Ed. 2008, 47, 58-77). One is that the absorption spectrum width of 3PHT is narrow and the effective absorption rate of sunlight is low. The maximum absorption spectrum of the luminous flux of sunlight is about 1.8 ev (700 nm), whereas the bandwidth of 3PHT is Eg = 1.9 ev, and sunlight is only in the range of 350-650 nm, and that range Only about 46% of the available photons can be absorbed. In order to improve this, it is conceivable to expand (shift) the width of the absorption spectrum of the P3HT / PCBM system, that is, to expand the absorption spectrum to the near infrared region. That is, to develop a low-bandwidth donor polymer. The molecular design for this is a donor-acceptor approach. That is, it is a hypothesis that a donor polymer having a low bandwidth can be obtained by alternately introducing a donor structure and an acceptor structure into the donor polymer main chain (HAM van Mullekom et. Al., Mater. Sci. Eng. R2001, 32, 1-40).

  Another point is that the energy conversion efficiency η is proportional to the product of the three factors of open circuit voltage (Voc), short circuit current density (Jsc) and fill factor (FF), and the energy conversion efficiency of P3HT / PCBM system is 5 The reason why it stays at% is that Voc is as low as about 0.6V. To improve this, Voc needs to be increased. Voc is said to be proportional to the difference between the highest occupied orbital (HOMO) of an electron donor polymer and the lowest empty orbital (LUMO) of a fullerene derivative as an electron acceptor (Sharber, MC et. Al., J. Adv. Mater., 2006, 18, 789), is a hypothesis to develop a donor polymer with a deeper HOMO energy level in order to obtain high Voc.

  That is, it is hypothesized that an ideal donor polymer is a polymer having not only a narrow bandwidth but also a deep HOMO level.

  Recently, Luping Yu et al. Proceeded with molecular design of donor polymer based on this hypothetical group, and have thieno [3,4-b] thiophene skeleton as acceptor skeleton and benzodithiophene skeleton as donor skeleton alternately in the main chain. Polymers (PBT1-6) (Formula 1) were synthesized (Luping Yu, et al., J. Am. Chem. Soc., 2009, 131, 7792-7799).

A BHJ solar cell was fabricated by combining this PBT with the fullerene derivative PC ₆₁ BM (Formula 2) as an acceptor, and its performance was examined. As a result, the 3-position substituent X of the thieno [3,4-b] thiophene, which is the acceptor skeleton in the PBT polymer, is a negative fluorine atom, and the 2-position substituent is a carboxylic acid octyl ester group (PBT4 ), Energy conversion efficiency η = 5.91-6.1%, Voc = 0.74 v, Jsc = 13.0 mA / cm ² when the 4-position and 8-position substituents of benzodithiophene which is a donor skeleton are 2-ethylhexyloxy groups FF = 61.4% (Y. Liang, L. Yu et. Al., J. Am. Chem. Soc. 2009, 131, 7792-7799). From the viewpoint of electron interaction and morphology, molecular design of donor polymer will be a rare example of success.

In addition, J. Hou et al. Proceeded further with Luping Yu et al. To further reduce the HOMO level of the donor polymer PBT by the substitution of the 2-position substituent of thieno [3,4-b] thiophene, which is an acceptor skeleton. A donor polymer (PBT-K) (formula 3) was synthesized in which the carboxylic acid octyl ester group was changed to a 2-ethylhexylcarbonyl group, which is a more electron-attracting ketone group. A BHJ type solar cell was created by combining with the fullerene derivative PC61BM (Formula 2) as an acceptor, and high performance of energy conversion efficiency η = 6.3%, Voc = 0.70v, Jsc = 14.7 mA / cm ² , FF = 64% (Jianhui Hou et. Al., J. Am. Chem. Soc. 2009, 131, 15586-15587).

  On the other hand, in place of PBT, development of a donor polymer having as a constituent unit a squarylium compound that is used as a photoconductive material or an electron donor for a photoreceptor and is known as an electron donor has been attempted. Ajayaghosh et al. Obtained π-conjugated polymers 4a to 4g (Formula 4) having a squarylium skeleton by condensing a stilbene-type dipyryl monomer with 2 equivalents of squalic acid (Lucjan Strekowski, Heterocyclic Polymethine Dyes: Synthesis, Properties and Applications). , Springer; 1st edition (2008/8/27), pp. 167). This polymer shows a wide absorption band in the visible to near-infrared region and is a low-bandwidth photoconductive material, but it is mentioned whether it has a donor property that can replace PBT in BHJ solar cells. Not.

  In addition, Nakasumi et al. Generated intramolecular electron transfer from a photoexcited squarylium compound to a fullerene group by binding a fullerene derivative, which is a kind of electron acceptor, to the terminal of a squarylium compound, which is a kind of electron donor. Have proposed a compound (Formula 5) that can maintain a long-lived charge separation state (Japanese Patent Laid-Open No. 2007-67074). The fluorescence emission spectrum of a chloroform solution (5.0 μmol concentration) of this compound shows an absorption band at λmax = 650 nm, indicating that it is a low-bandwidth photoconductive material. This kind of new material is expected to provide a foothold for the development of new organic solar cells.

JP 2007-67074 A

W. Ma, C. Yang, X. Gong, K. Lee, A. J. Heeger, Adv. Funct. Mater. 2005, 15, 1617-1622. B. C. Thompson et. Al., Angw. Chem. Int. Ed. 2008, 47, pp. 64. B. C. Thompson et. Al., Angw. Chem. Int. Ed. 2008, 47, pp. 58-77. H. A. M. van Mullekom et. Al., Mater. Sci. Eng. R2001, 32, 1-40. Sharber, M. C. et.al., J. Adv. Mater., 2006, 18, 789. Y. Liang, Luping Yu, et al., J. Am. Chem. Soc., 2009, 131, 7792-7799. Jianhui Hou et.al., J. Am. Chem. Soc. 2009, 131, 15586-15587. Lucjan Strekowski, Heterocyclic Polymethine Dyes: Synthesis, Properties and Applications, Springer; 1st ed., (2008/8/27), pp. 167

An object of the present invention is to provide a novel donor-conjugated compound in order to overcome the limitations of conventional bulk heterojunction organic thin-film solar cells. Another object of the present invention is to provide a conjugated compound having a narrow band gap and a wide absorption wavelength region in order to achieve more effective use of sunlight.

As a result of diligent research to solve the above problems, the present inventor has developed a novel conjugated copolymer oligomer and conjugated compound having an electron donor property as a material having a narrow band gap and a wide absorption wavelength region. The headline and the present invention were completed.

（式中、Ｒ_１、Ｒ_２はそれぞれ独立に、炭素数１〜１６の炭化水素基を表し、Ｒ_３、Ｒ_４はそれぞれ独立に、炭素数１〜１６の炭化水素基、炭素数１〜１６の炭化水素基が少なくとも１つ置換しているアミノ基、炭素数１〜１６の炭化水素基で置換されていてもよいオキシ基又は水素原子を表し、＊印は１価の結合点、＊＊印は２価の結合点を表し、ｎは１〜１０の整数であり、Ｐは式Ｎ５又はＮ６：

（式中、Ｒ_７、Ｒ_１３はそれぞれ独立に炭素数１〜１６の炭化水素基を表し、Ｒ_５、Ｒ_６、Ｒ_８〜Ｒ_１０、Ｒ_１１、Ｒ_１２、Ｒ_１４〜Ｒ_１６はそれぞれ独立に、炭素数１〜１６の炭化水素基、炭素数１〜１６の炭化水素基が少なくとも１つ置換しているアミノ基、炭素数１〜１６の炭化水素基で置換されていてもよいオキシ基又は水素原子を表し、＊印は１価の結合点を表す。）で表される含窒素複素環を表し、Ｑは式Ｎ５′又はＮ６′：

（式中、Ｒ_７′、Ｒ_１３′はそれぞれ独立に炭素数１〜１６の炭化水素基を表し、Ｒ_５′、Ｒ_６′、Ｒ_８′〜Ｒ_１０′、Ｒ_１１′、Ｒ_１２′、Ｒ_１４′〜Ｒ_１６′はそれぞれ独立に、炭素数１〜１６の炭化水素基、炭素数１〜１６の炭化水素基が少なくとも１つ置換しているアミノ基、炭素数１〜１６の炭化水素基で置換されていてもよいオキシ基又は水素原子を表し、＊印は１価の結合点、＊＊印は２価の結合点を表す。）で表される含窒素複素環を表す。）で表わされる、スクアリウム（ＳＱ）骨格及びベンゾジチオフェン（ＢＤ）骨格を主鎖に有してなる。 That is, the conjugated copolymer oligomer provided by the present invention has a general formula A:

(In the formula, R ₁ and R ₂ each independently represent a hydrocarbon group having 1 to 16 carbon atoms; R ₃ and R ₄ each independently represent a hydrocarbon group having 1 to 16 carbon atoms; 16 represents an amino group substituted with at least one hydrocarbon group, an oxy group optionally substituted with a hydrocarbon group having 1 to 16 carbon atoms, or a hydrogen atom, * represents a monovalent bonding point, * * Represents a divalent bonding point, n is an integer of 1 to 10, and P is a formula N5 or N6:

(In formula, R < ₇ >, R < ₁₃ > represents a C1-C16 hydrocarbon group each independently, R < ₅ >, R < ₆ >, R < ₈ > -R < ₁₀ >, R < ₁₁ >, R < ₁₂ >, R < ₁₄ > -R < ₁₆ > is respectively Independently, a hydrocarbon group having 1 to 16 carbon atoms, an amino group in which at least one hydrocarbon group having 1 to 16 carbon atoms is substituted, and an oxy group optionally substituted with a hydrocarbon group having 1 to 16 carbon atoms Represents a group or a hydrogen atom, and * represents a monovalent point of attachment.) Represents a nitrogen-containing heterocyclic ring represented by the formula: N5 ′ or N6 ′:

(In the formula, R ₇ ′ and R ₁₃ ′ each independently represent a hydrocarbon group having 1 to 16 carbon atoms, and R ₅ ′, R ₆ ′, R ₈ ′ to R ₁₀ ′, R ₁₁ ′, R ₁₂ ′ R ₁₄ ′ to R ₁₆ ′ are each independently a hydrocarbon group having 1 to 16 carbon atoms, an amino group substituted with at least one hydrocarbon group having 1 to 16 carbon atoms, or a carbon group having 1 to 16 carbon atoms. It represents an oxy group or a hydrogen atom which may be substituted with a hydrogen group, * represents a monovalent bonding point, and ** represents a divalent bonding point. The main chain has a squalium (SQ) skeleton and a benzodithiophene (BD) skeleton represented by

（式中、Ｒ_１、Ｒ_２、Ｒ_７、Ｒ_７′は上記と同義である。Ｒ_１７、Ｒ_１７′は炭素数１〜１６の炭化水素基、炭素数１〜１６の炭化水素基が少なくとも１つ置換しているアミノ基、炭素数１〜１６の炭化水素基で置換されていてもよいオキシ基又は水素原子を表し、ｍは１〜４の整数である。）で表わされるスクアリウム（ＳＱ）骨格及びベンゾジチオフェン（ＢＤ）骨格を有してなる。 The conjugated compound provided by the present invention has a general formula B (5):

(Wherein R ₁ , R ₂ , R ₇ and R ₇ ′ have the same meanings as above. R ₁₇ and R ₁₇ ′ represent a hydrocarbon group having 1 to 16 carbon atoms and a hydrocarbon group having 1 to 16 carbon atoms. An amino group substituted with at least one, an oxy group optionally substituted with a hydrocarbon group having 1 to 16 carbon atoms or a hydrogen atom, and m is an integer of 1 to 4). SQ) skeleton and benzodithiophene (BD) skeleton.

（式中、Ｒ_１、Ｒ_２、Ｒ_７は上記と同義であり、Ａｒは炭素数１〜１６の炭化水素基、炭素数１〜１６の炭化水素基が少なくとも１つ置換しているアミノ基、又は炭素数１〜１６の炭化水素基で置換されていてもよいアリール基を表し、Ｒ_１８、Ｒ_１８′は炭素数１〜１６の炭化水素基を表す。）で表わされるスクアリウム（ＳＱ）骨格及びベンゾジチオフェン（ＢＤ）骨格を有してなる。 Further conjugated compounds provided by the present invention have the general formula C (5):

(Wherein R ₁ , R ₂ and R ₇ are as defined above, Ar is a hydrocarbon group having 1 to 16 carbon atoms and an amino group substituted with at least one hydrocarbon group having 1 to 16 carbon atoms) Or an aryl group which may be substituted with a hydrocarbon group having 1 to 16 carbon atoms, and R ₁₈ and R ₁₈ ′ represent a hydrocarbon group having 1 to 16 carbon atoms.) It has a skeleton and a benzodithiophene (BD) skeleton.

  The conjugated copolymer oligomer and conjugated compound of the present invention have a squalium (SQ) skeleton and a benzodithiophene (BD) skeleton in the main chain, and the SQ skeleton and BD skeleton are nitrogen-containing heterocyclic conjugated systems. It has a common technical feature on the chemical structure of being linked through.

  The present invention also provides a bulk heterojunction (BHJ) type organic thin film solar cell comprising a photoelectric conversion layer containing the conjugated copolymer oligomer and / or conjugated compound as an electron donor and a fullerene derivative as an electron acceptor. To do.

The present invention also provides an organic dye containing the conjugated copolymer oligomer and / or conjugated compound. The organic dye of the present invention exhibits strong absorption in a wide range from infrared to near infrared over 600 to 800 nm.

  The present invention provides a novel organic dye substance and a wide absorption wavelength region by providing a novel conjugated copolymer oligomer and a conjugated compound having an absorption maximum in the infrared region to the near infrared region. The new organic thin film solar cell material has a new possibility for improving the efficiency of the bulk heterojunction (BHJ) type organic thin film solar cell.

FIG. 1 shows a schematic diagram of a bulk heterojunction (BHJ) type organic thin film solar cell (see Example 4). FIG. 2 shows the ¹ H-NMR spectrum of conjugated copolymer oligomer A (5) -C ₁₂ (300 Hz, CDCl ₃ , 25 ° C.). Figure 3 shows a conjugated copolymer oligomer A (5) MALDI-TOF MS spectrum of -C ₁₂ (matrix-assisted laser desorption ionization time-of-flight mass spectrometer) ((Matrix CHCA). Figure 4 shows the IPCE (photoelectric conversion efficiency) spectrum of conjugated copolymer oligomer A (5) _{-C 12.}

  The conjugated copolymer oligomer represented by the general formula A of the present invention or the conjugated compound represented by the general formula B (5) or the general formula C (5) includes a squarylium skeleton and a benzodithiophene skeleton in the main chain skeleton. It has a common chemical structural feature. And a nitrogen-containing heterocycle represented by P and Q between the squarylium (SQ) skeleton and the benzodithiophene (BD) skeleton, the nitrogen-containing heterocycle having an indole skeleton and / or a quinoline skeleton. A large π-electron conjugated system is formed as a whole molecule. For this reason, it is estimated that the bandwidth between the highest occupied molecular orbital (HOMO) and the lowest unoccupied orbital (LUMO) is reduced, but the present invention is not bound by the theory, and as a result, the infrared region to the near red Strong absorption maximum in the outer region. In that respect, it is a substance that falls into the category of organic dyes.

  The degree of polymerization n of the conjugated copolymer oligomer represented by Formula A may be in the range of 1-10. When n is 11 or more, since the molecular weight is high, the solubility in a solvent is lowered, and it may be difficult to form a thin film by a coating method such as spin coating. Taking into account mechanical properties such as the spread of the conjugated system, the solubility in the solvent, and the strength and flexibility of the resulting thin film, the degree of polymerization n is preferably in the range of 2-8, more preferably in the range of 2-5. Is preferred.

P in the general formula A represents a nitrogen-containing heterocyclic ring which is an indole derivative or a quinoline derivative represented by the formula N5 or N6, and is a single bond with a squarylium skeleton and a benzodithiophene skeleton respectively by two monovalent points of attachment To form a conjugated system, Q represents a nitrogen-containing heterocycle which is an indole derivative or a quinoline derivative represented by N5 ′ or N6 ′, a divalent bonding point indicated by ** and a monovalent value indicated by * A conjugated system is formed by forming a single bond and a double bond with the squarylium skeleton and the benzodithiophene skeleton, respectively, according to the bonding points.
The substituents R ₁ and R ₂ in the general formula A represent a hydrocarbon group having 1 to 16 carbon atoms, specifically, an alkyl group having 1 to 16 carbon atoms, an alkenyl group having 2 to 16 carbon atoms, and 5 carbon atoms. Represents a ˜16 alkyl group and an aryl group having 6 to 16 carbon atoms.
Examples of the alkyl group include methyl group, ethyl group, propyl group, butyl group, hexyl group, pentyl group, octyl group, 2-ethylhexyl group, dodecyl group and the like. Examples of alkenyl groups include vinyl and allyl groups. Examples of the cycloalkyl group include a cyclopentyl group and a cyclohexyl group. Examples of the aryl group include a phenyl group and a naphthyl group.

R ₇ , R ₁₃ , R ₇ ′ and R ₁₃ ′ in the formulas N5, N6, N5 ′ and N6 ′ each independently represent a hydrocarbon group having 1 to 16 carbon atoms, specifically, 1 to 16 carbon atoms. An alkyl group having 2 to 16 carbon atoms, a cycloalkyl group having 5 to 16 carbon atoms, and an aryl group having 6 to 16 carbon atoms.
Examples of the alkyl group include methyl group, ethyl group, propyl group, butyl group, hexyl group, pentyl group, octyl group, 2-ethylhexyl group, dodecyl group and the like. Examples of alkenyl groups include vinyl and allyl groups. Examples of the cycloalkyl group include a cyclopentyl group and a cyclohexyl group. Examples of the aryl group include a phenyl group and a naphthyl group.

Wherein N5, N6, N5 ', N6 ' R 5 _{in, R 6, R 8 ~R 10} , R 11, R 12, R 14 ~R 16, R 5 ', R 6', R 8 '~R 10 ′, R ₁₁ ′, R ₁₂ ′, R ₁₄ ′ to R ₁₆ ′ are each independently an amino group substituted with at least one hydrocarbon group having 1 to 16 carbon atoms or a hydrocarbon group having 1 to 16 carbon atoms. Group, an oxy group which may be substituted with a hydrocarbon group having 1 to 16 carbon atoms or a hydrogen atom.
Specific examples of the hydrocarbon group having 1 to 16 carbon atoms include an alkyl group having 1 to 16 carbon atoms, an alkenyl group having 2 to 16 carbon atoms, a cycloalkyl group having 5 to 16 carbon atoms, and 6 to 16 carbon atoms. Represents an aryl group. Examples of the alkyl group include methyl group, ethyl group, propyl group, butyl group, hexyl group, pentyl group, octyl group, 2-ethylhexyl group, dodecyl group and the like. Examples of alkenyl groups include vinyl and allyl groups. Examples of the cycloalkyl group include a cyclopentyl group and a cyclohexyl group. Examples of the aryl group include a phenyl group and a naphthyl group.
Examples of the amino group substituted with at least one hydrocarbon group having 1 to 16 carbon atoms include propylamino group, butylamino group, hexylamino group, octylamino group, 2-ethylhexylamino group, and dodecylamino group. Amino group containing a chain or branched alkyl group; linear or branched alkyl group such as dimethylamino group, diethylamino group, dipropylamino group, methylethylamino group, methylhexylamino group, methyloctylamino group, etc. An amino group including: an aromatic amino group such as a phenylamino group or a naphthylamino group; an aralkylamino group such as a benzylamino group; a diaromatic amino group such as a diphenylamino group or a dinaphthylamino group; Diaralkylamino groups and the like can be mentioned.
Examples of oxy groups to which a hydrocarbon group may be bonded include linear or branched propyloxy groups, butyloxy groups, hexyloxy groups, octyloxy groups, 2-ethylhexyloxy groups, dodecyloxy groups, and the like. Examples thereof include an alkyloxy group containing an alkyl group, an aromatic oxy group such as a phenyloxy group and a naphthyloxy group, and an aralkyloxy group such as a benzyloxy group.

  In one embodiment of the conjugated copolymer oligomer in the present invention, the general formula A is, for example, the general formula A (5) or A (6):

（式中、Ｒ_１、Ｒ_２、Ｒ_７、Ｒ_１３、Ｒ_７′、Ｒ_１３′、Ｒ_３〜Ｒ_６、Ｒ_８〜Ｒ_１２、Ｒ_１４〜Ｒ_１６、Ｒ_３′〜Ｒ_６′、Ｒ_８′〜Ｒ_１２′、Ｒ_１４′〜Ｒ_１６′及びｎは上記と同義である。）であるオリゴマーであってよく、また、別の実施態様において、一般式Ａ（５）‐１：

(In the formula, R ₁ , R ₂ , R ₇ , R ₁₃ , R ₇ ′, R ₁₃ ′, R _{3 to} R ₆ , R _{8 to} R ₁₂ , R _{14 to} R ₁₆ , R ₃ ′ to R ₆ ′, R ₈ ′ to R ₁₂ ′, R ₁₄ ′ to R ₁₆ ′ and n are as defined above.), And in another embodiment, in the general formula A (5) -1:

（式中、Ｒ_１、Ｒ_２、Ｒ_７、Ｒ_７′及びｎは上記と同義である。）であるオリゴマーであってよい。

(Wherein R ₁ , R ₂ , R ₇ , R ₇ ′ and n are as defined above).

In another embodiment of the conjugated copolymer oligomer of the present invention, R ₁ , R ₂ , R ₇ , R ₇ ′ of A (5) -1 is a C ₁₂ H ₂₅ group represented by the following formula A (5 ) _{-C 12:}

（式中、ｎは上記と同義である。）で表されるオリゴマーであってよい。

(Wherein n is as defined above).

In the conjugated compound of the present invention, examples of the embodiment in the general formula B (5) are as follows: R ₁ , R ₂ , R ₇ , R ₇ ′ are C ₁₂ H ₂₅ groups, and R ₁₇ , R ₁₇ ′ are hydrogen Formula B (5) -1 which is an atom:

で表わされる化合物であってよい。

The compound represented by these may be sufficient.

で表わされる化合物であってよい。 An example of another embodiment of the conjugated compound of the present invention is as follows. In general formula C (5), R ₁ and R ₂ are C ₁₂ H ₂₅ groups, R ₇ is a butyl group, and Ar group is 4- Formula C (5) -1 which is an aminophenyl group and R ₁₈ and R ₁₈ ′ are butyl groups:

The compound represented by these may be sufficient.

The conjugated copolymer oligomer and conjugated compound having a squalium (SQ) skeleton and a benzodithiophene (BD) skeleton of the present invention include, for example, an organotin derivative of benzodithiophene and a leaving group such as halogen. The Stille coupling reaction with the squarylium-based dye can be synthesized as a key reaction. This reaction is usually performed in an aprotic solvent such as DMF, using a catalyst composed of tetrakistriphenylphosphine palladium (Pd (PPh ₃ ) ₄ ) and cuprous halide (CuX).

As a specific example, a conjugated system by a Stille coupling reaction between a ditrimethyltin derivative (BD-Sn) of benzodithiophene having a dialkoxy group and a bisindole squarylium diiodo derivative (INSQIN-I) which is a symmetric derivative of squarylium A synthetic reaction formula of the polymer oligomer (A (5) -C ₁₂ ) is shown in the following formula (I).

Here, the conjugated oligomer A (5) -C ₁₂ has, as its limiting structure, for example between the squarylium skeleton indole skeleton of its ends, a resonance structure between the following formula (I) and (I ') Can be represented. Of course, the whole oligomer can be expressed as a limit structure between a wider range of resonance structural formulas including a benzodithiophene skeleton.

  Similarly, conjugated compounds (B (5) -1 and C (5) -1) can also be synthesized according to a Stille coupling reaction (formula (II)) using a palladium catalyst.

The starting material in each of the above reaction formulas can be produced by a known method.
For example, as a method for synthesizing BD-Sn, the following reaction examples can be given: ^7-8 :

7) Y. Liang, Y. Wu, D. Feng, S.-T. Tsai, H.-J. Son, G. Li, L. Yu, J. Am. Chem. Soc. 2009, 131, 56- 57;
8) Y. Liang, D. Feng, Y. Wu, S.-T. Tsai, G. Li, C. Ray, L. Yu, J. Am. Chem. Soc. 2009, 131, 7792-7799.)

Examples of the method for synthesizing the symmetric derivative INSQIN-I of squarylium include the following reaction examples ^4-6 :

4) KY Law, Chem. Rev. 1993, 93, 449;
5) S. Yagi, Y. Hyodo, S. Matsumoto, N. Takahashi, H. Kono, H. Nakazumi, J. Chem. Soc., Perkin Trans., 2000, 1, 599;
6) Grehard Kobmehl, Chem. Ber., 1986, 119, 3198)

Examples of the method for synthesizing the asymmetric derivative of squarylium SQIN-C include the following reaction examples ^4-6 :

  The conjugated copolymer oligomer or conjugated compound having a squalium (SQ) skeleton and a benzodithiophene (BD) skeleton of the present invention is a low band gap compound having an absorption maximum in the infrared to near infrared region. An excellent photoelectric conversion element can be configured by photoexcitation.

A bulk heterojunction organic thin-film solar cell can be constructed using these conjugated copolymer oligomers or conjugated compounds as electron donors and fullerene derivatives as electron acceptors. Examples of fullerene derivatives include [6,6] -phenyl-C ₆₁ -butyric acid methyl ester (PCBM or PC ₆₁ BM) and [6,6] -phenyl-C ₇₁ -butyric acid methyl ester (PC ₇₁ BM). Can be used.

  FIG. 1 shows a schematic diagram as an example of a bulk heterojunction (BHJ) type organic thin film solar cell. The layer structure of the BHJ type organic thin film solar cell in FIG. 1 is as follows: (1) glass substrate layer, (2) transparent electrode layer (ITO (indium tin oxide) as cathode), FTO (fluorine doped) Tin oxide)), (3) hole transfer layer (PEDOT / PSS: polyethylenedioxyorthothiophene / polystyrenesulfonic acid aggregate, etc.), (4) photoelectric conversion layer, (5) electron transfer layer (LiF, etc.) and (6) It consists of an anode layer (such as Al).

  The photoelectric conversion layer (4) contains the conjugated copolymer oligomer or conjugated compound of the present invention as an electron donor component and a fullerene derivative as an electron acceptor component. In the photoelectric conversion layer, the donor component electrons are excited from HOMO to LUMO by sunlight to generate donor excitons. The excited electrons of the donor exciton are transferred to LUMO of the acceptor fullerene derivative by diffusion to generate an acceptor radical anion charge carrier and a donor radical cation charge carrier to generate charge separation.

  When a photoelectric conversion layer is composed of two components of a fullerene derivative and a conjugated copolymer oligomer or conjugated compound, the blending ratio of the two is not limited, but usually a fullerene derivative: a conjugated copolymer oligomer or Conjugated compound (weight ratio) = 1: 0.1 to 1:10, preferably 1: 0.5 to 1: 5, more preferably 1: 0.6 to 1: 2, more preferably 1. : It may be in the range of 0.8 to 1.2. In addition to the fullerene derivative, the conjugated copolymer oligomer, or the conjugated compound, the photoelectric conversion layer may further include other conductive materials or dyes having a photoelectric conversion action.

The method for forming the photoelectric conversion layer is not particularly limited. For example, a solution in which a mixture of a fullerene derivative and a conjugated copolymer oligomer or a conjugated compound is dissolved in a solvent is placed on the hole transfer layer on the transparent electrode. Examples thereof include a method of coating or a method of vacuum-depositing a mixture of a fullerene derivative and a conjugated copolymer oligomer or a conjugated compound. Among these, the method of apply | coating is preferable.
As the solvent in the coating method, toluene, chloroform, chlorobenzene or orthodichlorobenzene can be usually used, and chloroform, chlorobenzene or orthodichlorobenzene is preferable.
Although the method of apply | coating is not specifically limited, For example, methods, such as spin coating, inkjet printing, and roller casting, are mentioned. Of these, spin coating is preferred.

  Although the thickness of a photoelectric converting layer is not limited, Usually, it is 10-500 nm, Preferably it is 50-300 nm, More preferably, it is about 100-200 nm.

  For example, ITO (indium tin oxide) or FTO (fluorine-doped tin oxide) is preferable as the transparent electrode (2) as the cathode, and ITO is particularly preferable. The thickness of the transparent electrode layer is not limited, but may be about 1 to 1000 nm, preferably 5 to 500 nm, more preferably about 10 to 300 nm. Formation of a transparent electrode layer can be performed by methods, such as vacuum evaporation and ion sputtering, for example.

  The hole transport layer (3) is a material having hole transport properties such as polyethylenedioxyorthothiophene (PEDOT) / polystyrene sulfonic acid (PSS) aggregates (PEDOT / PSS), and the HOMO energy level is vacuum. There is no particular limitation as long as the level is lower than that of the transparent electrode as compared with the level. The method of forming the hole transfer layer is not limited, but, for example, it is formed by spin coating a PEDOT / PSS aqueous dispersion such as a commercially available 1.3 wt% aqueous dispersion (Aldrich) on the transparent electrode layer. Can do. The thickness of the hole transport layer is not limited, but may be about 10 to 300 nm, preferably about 20 to 200 nm, more preferably about 30 to 100 nm.

  The electron transfer layer (5) can be made of a material having a small work function such as lithium fluoride (LiF), calcium, lithium, or magnesium. For example, LiF is preferable. The thickness of the electron transfer layer is not limited, but may be generally 1 to 300 nm, preferably 5 to 200 nm, more preferably about 10 to 100 nm. The electron transfer layer can be formed by, for example, a method such as vacuum deposition or ion sputtering.

  Aluminum (Al), indium (In), or the like, which is a material having a small work function, can be used for the anode layer (6). Although the thickness of an anode layer is not limited, Usually, it may be 1-300 nm, Preferably it is 5-200 nm, More preferably, it may be about 10-100 nm. The anode layer can be formed by a method such as vacuum deposition or ion sputtering, for example.

The photoelectric conversion efficiency (η) of the BHJ type organic thin film solar cell is calculated by the formulas (1) and (2) based on the schematic diagram of FIG.
η ＝ Pout / Pin = [FF (Jsc) (Voc)] / Pin (1)
FF = [(Jm) (Vm)] / [(Jsc) (Voc)] (2)
Here, Pout: output, Pin: input, FF: fill factor, Jsc: short-circuit current density, Voc: open circuit voltage, Jm: current at the maximum output point, Vm: voltage at the maximum output point.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1 "Synthesis of conjugated copolymer oligomer A (5) -C _12"
According to the following reaction formula (I), the squarylium skeleton and benzodithiophene skeleton both conjugated copolymer oligomer A (5) a -C _12, Stille cross-coupling reaction of the corresponding iodide element and the tin derivative (I) Was synthesized as follows.

Under nitrogen atmosphere, bistrimethyltin derivative of benzodithiophene (BD-Sn) with squarylium dye INSQIN-I ^4-6 (30 mg, 3.1 × 10 ^-2 mmol) and dialkoxy group in a two-necked eggplant type flask ^7,8 (24 mg, 3.1 × 10 ⁻² mmol), tetrakistriphenylphosphine palladium (0) (1.5 mg, 1.3 × 10 ⁻³ mmol), copper (I) iodide (0.3 mg, 1.4 × 10 ⁻³ mmol) was added, DMF (0.125 mL) and toluene (0.500 mL) were added, and the mixture was stirred at 50 ° C. for 21 hours. After evaporating the solvent under reduced pressure, the residue was purified by column chromatography (SiO ₂ column, developing solvent chloroform). Dissolved further resulting solid in chloroform, reprecipitated with methanol as a poor solvent, to obtain a conjugated copolymer oligomer A (5) -C ₁₂ as the target compound at a recovery rate of 47%. ^The molecular structure was confirmed by ¹ H-NMR (FIG. 2), and the formation of oligomers was confirmed by MALDI-TOF MS (Matrix Assisted Laser Desorption / Ionization Time-of-Flight Mass Spectrometer) (FIG. 3).
The starting material squarylium dye INSQIN-I was synthesized according to the description in the above-mentioned documents 4) to 6), and the bistrimethyltin derivative (BD-Sn) of benzodithiophene was synthesized from the documents 7) and 8). Synthesized according to the description.

Oligomer A (5) -C analysis of UV-Vis spectra and ¹ H NMR of ₁₂ are shown in position under:
Oligomer A (5) -C ₁₂ : UV-Vis spectrum (CHCl ₃ ): λ _max : 696 nm,
(ε = 5.82 × 10 ⁵ M ^-1 cm ^-1 ). [ ¹ H NMR (300 Hz)] (CDCl ₃ : δ) 0.84 to 0.96 (m, 12H), 1.11 to 1.41 (m, 40H) 1.74 to 2.01 (m, 24H) 3.86 to 4.14 (m, 4H), 4.28 to 4.42 (m, 4H), 5.93 to 6.09 (m, 2H), 6.71 to 6.78 (m, 1H), 6.98 to 7.11 (m, 2H), 7.58-7.78 (m, 5H).

  From FIG. 3, it was found that the oligomer was a mixture having a BD / SQ ratio of 1/1, 2/1, 1/2, 2/2, 3/2, 2/3, and 3/3. . That is, an oligomer having a distribution of n = 1 to 3 was obtained. Λmax in the chloroform solution of this oligomer was 696 nm.

Examples 2 and 3 “Synthesis of Conjugated Compounds B (5) -1 and C (5) -1”
Conjugated compounds B (5) -1 and C (5) -1 having both a squarylium skeleton and a benzodithiophene skeleton are subjected to the following reaction formula (II) by a Stille cross-coupling reaction between the corresponding iodine form and a tin derivative. Was synthesized according to

Under nitrogen substitution, 25 mg (4.0 × 10 ⁻² mmol) of the compound BD-Sn ^7,8 , 10 mg (1.3 × 10 ⁻² mmol) of the compound SQIN-B ^4-6 , tetrakistriphenylphosphine palladium (0) (0.5 mg, 0.43 × 10 ⁻³ mmol) and copper iodide (I) (0.1 mg, 0.53 × 10 ⁻³ mmol) were added, DMF (1.0 mL) was added, and the mixture was stirred at 50 ° C. for 48 hours. After the solvent was distilled off under reduced pressure, the residue was purified by column chromatography (SiO ₂ column, developing solvent ethyl acetate / hexane = 2/1 (v / v)). Further, the obtained solid was dissolved in chloroform and recrystallized using hexane as a poor solvent to obtain the target compound B (5) -1 in a yield of 28%. Similarly, the compound C (5) -1 was obtained in 69% yield from the squarylium dye SQIN-C ^4-6 .
The starting material BD-Sn was synthesized according to the descriptions in the above-mentioned documents 7) and 8), and SQIN-B was synthesized according to the descriptions in the above-mentioned documents 4) to 6).

The results of MALDI TOF-MS and ¹ H NMR analysis of Compound B (5) -1 are shown below:
B (5) -1: MALDI TOF-MS (positive): Calcd for C ₉₂ H ₁₁₈ N ₄ O ₆ S ₂ [B (5) -1] ⁺ : m / z = 1438.9. Found: m / z = 1439.0 [ ¹ H NMR (300 Hz)] (CDCl ₃ : δ) 0.80 to 1.08 (m, 24H), 1.15 to 1.98 (m, 48H), 3.39 (m, 8H), 4.11 (m, 4H), 4.36 ( m, 4H), 6.15 (s, 2H), 6.64 (m, 4H), 7.16 (m, 2H), 7.61-7.78 (m, 6H), 8.26 (m, 4H).

Compound C (5) -1: UV-Vis spectrum, MALDI TOF-MS and ¹ H NMR analysis results are shown below:
C (5) -1: UV-Vis spectrum (CHCl ₃ ): λ _max : 674 nm
(ε = 1.97 × 10 ⁵ M ^-1 cm ^-1 ). MALDI TOF-MS (positive): Calcd for C ₁₂₆ H ₁₇₈ N ₄ O ₆ S ₂ [C (5) -1 + H ⁺ ] ⁺ : m / z = 1908.3. Found: m / z = 1908.0. [ ¹ H NMR (300 Hz)] (CDCl ₃ : δ) 0.76 to 0.86 (m, 18H), 1.11 to 1.41 (m, 66H) 1.68 to 1.93 (m, 38H) 3.85 to 4.00 (m, 8H), 4.25 to 4.31 (t, J = 6.1 Hz, 4H), 5.89 to 5.96 (m, 4H), 6.94 (d, J = 8 Hz, 4H), 7.10 (t, J = 7.2 Hz, 2H), 7.25 (t, J = 7.2 Hz, 2H), 7.31 (d, J = 7.2 Hz, 2H), 7.57 (s, 2H), 7.59 to 7.65 (m, 4H).

Example 4 “Preparation of BHJ-type organic thin-film solar cells (see FIG. 1) and measurement of solar cell characteristics”
An ITO substrate in which an ITO layer as a transparent electrode layer (2) is formed on a glass substrate layer (1) is etched into an H-shape. First, a conductive polymer PEDOT-PSS (hole transfer layer (3)) A solution of Nagase ChemteX, Denatron P NHC) was applied onto an ITO substrate (Geomatic, ~ 10 Ω / cm ² ) by spin coating (rotation speed 7000 rpm, time 60 s) and baked at 110 ° C for 60 minutes did. Next, the synthesized oligomer A (5) _{-C 12} or Compound B (5) -1 or C (5) -1 and 50:50 (weight ratio) of the fullerene derivative PC ₆₁ BM chlorobenzene solution or chloroform solution of a mixture Was applied to the PEDOT-PSS film by spin coating (rotation speed 1000 rpm, time 100 s), baked at 110 ° C. for 60 minutes or left at room temperature to form a photoelectric conversion layer (4), and then fluorinated. Lithium (electron transfer layer (5)) and aluminum (anode layer (6)) were vacuum-deposited (about 10 ⁻⁶ Torr) to obtain a BHJ type organic thin film solar cell (FIG. 1).
For the characteristics of the organic thin-film solar cell with an irradiation area of 0.16 cm ² produced in this way, the maximum value of each conversion efficiency is measured from the IV measurement using the spectral sensitivity measuring device CEP-2000 (manufactured by Spectrometer). did. The shape factor and conversion efficiency under irradiation of simulated sunlight at AM 1.5 and 100 mW / cm ² were measured. The obtained results are shown in Table 1. The Figure 4 shows the IPCE (photoelectric conversion efficiency spectra) of the oligomer A (5) _{-C 12.}

The photoelectric conversion efficiency (η) of the BHJ-type organic thin film solar cell in Table 1 was calculated by the formulas (1) and (2).
η ＝ Pout / Pin = [FF (Jsc) (Voc)] / Pin (1)
FF = [(Jm) (Vm)] / [(Jsc) (Voc)] (2)
Here, Pout: output, Pin: input, FF: fill factor, Jsc: short-circuit current density, Voc: open circuit voltage, Jm: current at the maximum output point, Vm: voltage at the maximum output point.

As described above, the oligomer A (5) -C ₁₂ and Compound B (5) -1, C ( 5) In any -1 also, the photocurrent is observed, functions as a photoelectric conversion active layer these compounds with PCBM is doing. Further, the absorption maxima of the oligomer A (5) -C ₁₂ in a thin film state is observed at 726 nm, oligomer A (5) in real IPCE spectrum -C ₁₂ is in the near infrared wavelength region of 700-800 nm The conversion efficiency has reached 1.31% (Table 1 and FIG. 4).
Further, even in the compound C (5) -1, the absorption maximum value in a thin film state is 717 nm, and the actual IPCE spectrum is also photoelectrically converted in a long wavelength region of 700 nm or more.

  The synthesized conjugated copolymer oligomer and conjugated compound both acted as electron donors and exhibited good solar cell characteristics. Furthermore, photoelectric conversion could be achieved even in the near-infrared region, which cannot be fully used with existing bulk heterojunction solar cells represented by P3HT / PCBM. Therefore, the conjugated copolymer oligomer and the conjugated compound developed in the present invention are both effective as a photoelectric conversion layer of an organic thin film solar cell and operate in the near-infrared region that has not been used so far. Expanded the possibilities.

Claims (10)

General formula A:

(In the formula, R ₁ and R ₂ each independently represent a hydrocarbon group having 1 to 16 carbon atoms; R ₃ and R ₄ each independently represent a hydrocarbon group having 1 to 16 carbon atoms; 16 represents an amino group substituted with at least one hydrocarbon group, an oxy group optionally substituted with a hydrocarbon group having 1 to 16 carbon atoms, or a hydrogen atom, * represents a monovalent bonding point, * * Represents a divalent bonding point, n is an integer of 1 to 10, and P is a formula N5 or N6:

(In formula, R < ₇ >, R < ₁₃ > represents a C1-C16 hydrocarbon group each independently, R < ₅ >, R < ₆ >, R < ₈ > -R < ₁₀ >, R < ₁₁ >, R < ₁₂ >, R < ₁₄ > -R < ₁₆ > is respectively Independently, a hydrocarbon group having 1 to 16 carbon atoms, an amino group in which at least one hydrocarbon group having 1 to 16 carbon atoms is substituted, and an oxy group optionally substituted with a hydrocarbon group having 1 to 16 carbon atoms Represents a group or a hydrogen atom, and * represents a monovalent point of attachment.) Represents a nitrogen-containing heterocyclic ring represented by the formula: N5 ′ or N6 ′:

(In the formula, R ₇ ′ and R ₁₃ ′ each independently represent a hydrocarbon group having 1 to 16 carbon atoms, and R ₅ ′, R ₆ ′, R ₈ ′ to R ₁₀ ′, R ₁₁ ′, R ₁₂ ′ R ₁₄ ′ to R ₁₆ ′ are each independently a hydrocarbon group having 1 to 16 carbon atoms, an amino group substituted with at least one hydrocarbon group having 1 to 16 carbon atoms, or a carbon group having 1 to 16 carbon atoms. It represents an oxy group or a hydrogen atom which may be substituted with a hydrogen group, * represents a monovalent bonding point, and ** represents a divalent bonding point. And a conjugated copolymer oligomer having a squalium skeleton and a benzodithiophene skeleton in the main chain. The general formula A is the general formula A (5) or A (6):

(In the formula, R ₁ , R ₂ , R ₇ , R ₁₃ , R ₇ ′, R ₁₃ ′, R _{3 to} R ₆ , R _{8 to} R ₁₂ , R _{14 to} R ₁₆ , R ₃ ′ to R ₆ ′, _{R 8 '~R 12', R} 14 '~R 16' and n are as defined above.) the oligomer according to claim 1. The general formula A (5) is represented by the general formula A (5) -1:

The oligomer according to claim 2, wherein R ₁ , R ₂ , R ₇ , R ₇ 'and n are as defined above. Formula B (5):

(Wherein R ₁ , R ₂ , R ₇ and R ₇ ′ have the same meanings as above. R ₁₇ and R ₁₇ ′ represent a hydrocarbon group having 1 to 16 carbon atoms and a hydrocarbon group having 1 to 16 carbon atoms. An at least one substituted amino group, an oxy group which may be substituted with a hydrocarbon group having 1 to 16 carbon atoms, or a hydrogen atom, and m is an integer of 1 to 4.) And a conjugated compound having a benzodithiophene skeleton. Formula B (5) _-1 in which R ₁ , R ₂ , R ₇ , R ₇ ′ is a C ₁₂ H ₂₅ group and R ₁₇ , R ₁₇ ′ is a hydrogen atom in the general formula B (5):

The compound of Claim 4 represented by these. Formula C (5):

(Wherein R ₁ , R ₂ and R ₇ are as defined above, Ar is a hydrocarbon group having 1 to 16 carbon atoms and an amino group substituted with at least one hydrocarbon group having 1 to 16 carbon atoms) Or an aryl group which may be substituted with a hydrocarbon group having 1 to 16 carbon atoms, and R ₁₈ and R ₁₈ ′ represent a hydrocarbon group having 1 to 16 carbon atoms.) A conjugated compound having a dithiophene skeleton. In the general formula C (5), R ₁ and R ₂ are C ₁₂ H ₂₅ groups, R ₇ is a butyl group, Ar group is a 4-aminophenyl group, and R ₁₈ and R ₁₈ ′ are butyl. Formula C (5) -1 being a group:

The compound of Claim 6 represented by these.   It has a photoelectric conversion layer containing the oligomer according to at least one of claims 1 to 3 and / or the compound according to at least one of claims 4 to 7 as an electron donor and a fullerene derivative as an electron acceptor. Bulk heterojunction organic thin film solar cell. The solar cell according to claim 8, wherein the fullerene derivative is [6,6] -phenyl-C ₆₁ -butyric acid methyl ester (PC ₆₁ BM).   An organic dye comprising the oligomer according to at least one of claims 1 to 3 or the compound according to at least one of claims 4 to 7.

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