JP6230051B2 - Coordination polymer thin film and method for producing thin film solar cell comprising the same - Google Patents

Description

  The present invention relates to a coordination polymer thin film having a polymer structure composed of a metal ion and a bridging ligand, and a method for producing a thin film solar cell including the coordination polymer thin film.

  Coordination polymers with a polymer structure consisting of metal ions and bridging ligands are new inorganic / organic composite polymer materials that combine the properties of metal ions and flexible organic molecules, such as porous materials and catalysts. Has been applied. It is also possible to give the coordination polymer properties such as conductivity and ferroelectricity.

  For example, Patent Document 1 discloses a thin film solar cell in which a particulate coordination polymer is incorporated into two or more types of organic semiconductors that form a bulk heterostructure.

  Patent Document 2 discloses a coordination polymer composed of a derivative of dithiocarbamic acid, a chlorine ion, and a copper ion and exhibiting ferroelectricity.

International Publication No. 2012-117860 JP 2007-230880 A

  By the way, as is generally known, the performance can be improved by using a thinned conductor or ferroelectric for a solar cell or a memory element.

  However, for example, it is difficult to make a coordination polymer thin film for the following reasons. That is, wet methods such as vacuum deposition require heating, and are generally not suitable for thinning a polymer. In addition, due to the presence of alkyl groups, polymers often dissolve in organic solvents while maintaining their polymer structure, but coordination polymers have low solubility in many organic solvents, such as spin coating. Thinning by a wet method is also difficult.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a simple method for producing a coordination polymer thin film.

  As a result of diligent studies to solve the above problems, the present inventors have found that a coordination polymer is induced by inducing self-assembly in a solution in which a metal ion and a bridging ligand are present in a suitable ratio. It was found that a thin film was formed. The present invention is based on this new knowledge.

That is, the present invention is a method for producing a coordination polymer thin film comprising repeating units of one or more kinds of metal ions and one or more kinds of bridging ligands,
Preparing a solution containing the metal ion and a bridging ligand in a solvent containing a polar solvent capable of coordinating to at least one of the metal ions;
Applying the prepared solution onto a substrate to evaporate the solvent and inducing self-assembly of metal ions and bridging ligands,
The step of preparing the solution is characterized by preparing a solution in which the metal ions and the bridging ligand are present in a ratio suitable for self-assembly.

  According to the present invention, a simple method for producing a coordination polymer thin film is realized by self-organization of a metal ion and a bridging ligand.

It is a schematic diagram which shows an example of the thin film solar cell provided with the coordination polymer thin film manufactured according to embodiment of this invention. It is a schematic diagram which shows the three-dimensional structure of coordination polymer P1. It is a schematic diagram which shows the three-dimensional structure of coordination polymer P2. It is a schematic diagram which shows the three-dimensional structure of coordination polymer P7. It is a schematic diagram which shows the three-dimensional structure of coordination polymer P8. It is a schematic diagram which shows the three-dimensional structure of coordination polymer P9. It is a schematic diagram which shows the three-dimensional structure of coordination polymer P10. It is a schematic diagram which shows the three-dimensional structure of coordination polymer P11. It is a schematic diagram which shows the three-dimensional structure of coordination polymer P12. It is a schematic diagram which shows the three-dimensional structure of coordination polymer P13. It is a schematic diagram which shows the three-dimensional structure of coordination polymer P15. (A) It is a schematic diagram which shows the two-dimensional sheet structure of coordination polymer P16, (b) It is a schematic diagram which shows the ferrocenium ion taken in between two-dimensional sheets. (A) It is the schematic diagram which looked at the two-dimensional sheet structure of coordination polymer P17 from the side, (b) It is the schematic diagram which looked at the structure from the top. It is a graph which shows the result of the UV-Vis-NIR spectrum measurement with respect to coordination polymer P8 and the mononuclear complex C6. (A) The optical microscope photograph of the thin film of coordination polymer P8 produced on the glass substrate is shown, (b) The laser microscope photograph of a part of the square enclosure of (a) is shown. It is a graph which shows the result of the UV-Vis-NIR spectrum measurement with respect to the thin film of the coordination polymer P8 produced by changing the quantity which dripped a solution. (A) It is a graph which shows the measurement result of the powder X-ray diffraction performed with respect to the thin film of produced coordination polymer P8, (b) The single crystal performed with respect to the produced single crystal of coordination polymer P8 It is a graph which shows the measurement result of X-ray diffraction. (A) It is a graph which shows the measurement result of the powder X-ray diffraction performed with respect to the thin film of produced coordination polymer P15, (b) The single crystal performed with respect to the produced single crystal of coordination polymer P15 It is a graph which shows the measurement result of X-ray diffraction. It is a graph which shows the result of the UV-Vis-NIR spectrum measurement performed with respect to the produced thin film (a) and single crystal (b) of coordination polymer P15. It is a graph which shows the measurement result of the powder X-ray diffraction performed before and after annealing with respect to the produced thin film of coordination polymer P8. It is a graph which shows the result of the UV-Vis-NIR spectrum measurement performed before and after annealing with respect to the produced thin film of coordination polymer P8.

  Hereinafter, the manufacturing method of the coordination polymer thin film which concerns on embodiment of this invention is demonstrated.

First, a single crystal of a coordination polymer is prepared (step S1).
“Coordination polymer” refers to a polymer having a one-dimensional structure, a two-dimensional structure, or a three-dimensional structure in which a metal complex in which a ligand of an organic compound is bonded around a metal ion. In other words, the coordination polymer includes a repeating unit of one type or two or more types of metal ions and one type or two or more types of bridging ligands.

  Further, the coordination polymer may contain a crosslinking agent component other than the ligand, for example, a halide ion, which crosslinks each unit of the complex, if necessary. Therefore, the “coordinating polymer” includes those having a repeating structure crosslinked by the crosslinking agent component.

  Furthermore, for example, when the coordination polymer skeleton is charged, a cation or anion such as a ferrocenium ion or an ammonium ion may enter between the coordination polymer skeletons so as to cancel the charge. Good.

  A single crystal of this coordination polymer can be produced by a known method such as mixing a complex containing a bridging ligand and a metal compound (metal salt) in an organic solvent. Thereby, a single crystal of a coordination polymer composed of repeating units of one type or two or more types of metal ions and one type or two or more types of bridging ligands is produced.

  As will be described in detail in the Examples section, when, for example, bromine ions or iodine ions are used as the cross-linking agent component, a mononuclear complex is first prepared, and then the mononuclear complex is mixed with the bromine ion compound or iodine ion compound. To produce a coordination polymer. Specifically, for example, a mononuclear complex in which hexamethylene dithiocarbamic acid is coordinated to a copper ion using a copper salt and hexamethylene dithiocarbamic acid is prepared, and then the produced mononuclear complex and copper bromide are combined. Made by mixing in an organic solvent. Of course, you may use a ready-made thing as a mononuclear complex.

  The “bulk state coordination polymer” in the claims refers to a coordination polymer that is not in the form of a thin film. In addition to the single crystal of the coordination polymer produced in this step S1, polycrystal, Any form such as amorphous may be used.

  As a metal ion constituting the coordination polymer, for example, an ion of an element selected from transition metal elements can be used.

  As the bridging ligand, a sulfur-containing compound, a nitrogen-containing compound, an oxygen-containing compound, a phosphorus-containing compound, or the like can be used. Examples of the sulfur-containing compound include dithiooxalate, tetrathiooxalate, and a ligand having a dithiocarboxylic acid substituent. Examples of nitrogen-containing compounds include pyrazine, bipyridine, ligands having an imidazole skeleton, and the like. Examples of oxygen-containing compounds include oxalate, chloranilate, 2,5-dihydroxy-1,4-benzoquinone, benzenedicarboxylate, catechol and the like. Examples of the phosphorus-containing compound include triphenylphosphine, diphenylphosphinoethane, diphenylphosphinopropane, 1,1'-bis (diphenylphosphino) ferrocene and the like.

Next, a mixed solvent containing a polar solvent capable of coordinating to at least one of the metal ions constituting the coordination polymer prepared in step S1 and a nonpolar solvent is prepared (step S2).
As the polar solvent, any solvent that coordinates relatively weakly to the metal ion can be used. For example, acetonitrile, propionitrile, benzonitrile, butyronitrile, tetrahydrofuran, methanol, ethanol, propanol, acetone and the like which are polar solvents having a nitrile group can be used, and acetonitrile has been found to be particularly preferable. Nitrile groups have been found to be compatible with monovalent copper ions. For example, in the coordination polymer P8: [Cu ₇ ^I Cu ^II Br ₇ (nBu ₂ -dtc) ₂ ] _n described in the examples, nBu ₂ -dtc ⁻ which is an ion of a dithiocarbamic acid derivative is a divalent copper ion. To chelate. Therefore, when the coordination polymer P8 is dissolved in a solvent containing acetonitrile or the like, the nitrile group is not coordinated to the divalent copper ion, but is relatively weakly coordinated to the monovalent copper ion. It is thought that there is.

Nonpolar solvents can be used chloroform, toluene, dichloromethane, benzene, carbon tetrachloride, dichloroethane, trichloroethane, tetrachloroethane, chlorobenzene, etc. dichlorobenzene, a known non-polar organic solvents.

Here, when a mixed solvent having a small ratio of the nonpolar solvent to the polar solvent or containing no nonpolar solvent is used, the coordination ability from the polar solvent to the metal ion is reduced when the coordination polymer is dissolved. Since it becomes too high, self-organization may be hindered. In such a case, it is preferable to use a mixed solvent in which a polar solvent and a nonpolar solvent are mixed at a suitable ratio.
Further, for example, in the case of a coordination polymer having a dithiocarbamic acid derivative ion as a ligand, it is difficult to dissolve in a highly polar solvent due to the presence of an alkyl group. Therefore, it is preferable to determine the mixing ratio of the polar solvent and the nonpolar solvent in consideration of the solubility of the coordination polymer.

Next, the single crystal of the coordination polymer prepared in step S1 is dissolved in the mixed solvent prepared in step S2 (step S3).
At this time, the temperature of the mixed solvent is preferably set to about 20 ° C. to about 30 ° C. In the mixed solvent, it is considered that the metal ion coordinated with the polar solvent and the bridging ligand exist in a separated form.

Next, the solution prepared in step S3 is applied on the substrate to evaporate the mixed solvent (step S4).
Step S4 can be performed, for example, under atmospheric pressure at a standard environmental temperature (about 25 ° C.), but may be performed under a different atmosphere such as nitrogen. By this step S4, self-organization of the metal ions present in the solution and the bridging ligand is induced, and a thin film is produced on the substrate.

  As the “substrate”, a substrate having a size, material, and shape suitable for the application of the coordination polymer thin film can be used, and a flexible substrate or a curved substrate may be used. Further, the “base material” in the claims is a base material on which a coordination polymer thin film can be formed, and is not limited to the “substrate”. For example, a material provided on the substrate Layers are also included in the “substrate”.

  Application of the solution and film formation can be performed by a known method, for example, spin coating, dip coating, electrostatic spraying, ink jet, roll-to-roll, nanoimprint, or screen printing.

The thickness of the thin film can be controlled by changing the amount of solution applied onto the substrate. For example, in the case of spin coating, the thickness of the thin film can be controlled by adjusting the rotation speed, rotation time, atmosphere (evaporation speed), and the like of the stage. The same applies to other coating methods. Furthermore, it has been found that a thicker film can be formed by applying a solution on a preheated substrate.
In this specification, according to a general definition, for example, a thin film having a thickness of several μm or less is referred to as a “thin film”. However, as described above, the thickness of the film can be controlled and the thickness is several tens of μm or more. Of course, it is possible to produce a so-called thick film.

  Here, in order to self-assemble the metal ion and the bridging ligand constituting the coordination polymer to construct the polymer structure of the coordination polymer again, the metal ion and the bridging ligand It is necessary to prepare a solution present in the mixed solvent at a ratio suitable for self-assembly. “Ratio” refers to the particle number ratio (molar ratio). This state is easily realized by dissolving a single crystal of a coordination polymer in a mixed solvent.

  Alternatively, a solution of a metal compound (metal salt) dissolved in a polar solvent and a cross-linking ligand dissolved in a non-polar solvent is prepared, and the metal ion and the cross-linking ligand are in a ratio suitable for these self-organizations. Mixed solutions may also be prepared. At this time, the “ratio suitable for self-assembly” is not limited to a strict ratio between the metal ions constituting the coordination polymer and the bridging ligand, and a slight deviation is allowed.

Further, after the coordination polymer thin film is formed on the substrate, the thin film may be heated together with the substrate (step S5).
Thereby, the smoothness of a board | substrate, electroconductivity, etc. can be improved. This is presumably because the crystallinity of the coordination polymer thin film increases. The heating temperature can be, for example, about 50 ° C. to about 150 ° C. in the case of the coordination polymer exemplified in this specification.

  The coordination polymer thin film produced as described above can be used as, for example, a porous solid catalyst. Further, by selecting a metal ion or a bridging ligand, it is possible to control the conductivity (insulation), semiconductor characteristics, dielectric properties (ferroelectricity, paraelectricity), etc. of the coordination polymer. Therefore, applications of coordination polymer thin films are envisioned for lithium ion battery electrodes, thin film solar cell semiconductor layers, organic transistor semiconductor layers and insulating films, capacitor dielectrics, and the like. A ferroelectric memory with a capacitor is also envisaged. In addition, it is considered that the ferroelectricity in the coordination polymer is manifested by cooperative displacement of metal ions embedded in the coordination polymer skeleton.

  For example, the thin film solar cell 10 shown in FIG. 1 can be manufactured as follows. That is, the coordination polymer thin film 3 as a p-type semiconductor layer is provided on the substrate 1 on which the electrode 2 is formed according to the method according to the present embodiment. Next, according to the method (solution application) according to the present embodiment, a coordination polymer thin film 4 as an n-type semiconductor layer is provided on the coordination polymer thin film 3 (base material), and an electrode 5 is formed thereon. Form. For example, the electrode 2 is ITO (indium tin oxide) or FTO (fluorine-doped tin oxide), and the substrate 1 is, for example, a glass substrate. A commercially available substrate 1 on which the electrode 2 is formed may be used. The electrode 5 is, for example, aluminum and can be formed by vacuum deposition. Contrary to the above method, the coordination polymer thin films 4 and 3 and the electrode 2 may be provided on the electrode 5.

  Whether the prepared coordination polymer functions as a p-type semiconductor or an n-type semiconductor can be determined by a known method, for example, by examining the output characteristics of a field effect transistor using the coordination polymer as a channel layer. Can be determined. With this method, it has been confirmed that the coordination polymer p8 functions as a p-type semiconductor. In Table 1, it can be considered that a high LUMO value functions as an n-type semiconductor, and a low LUMO value functions as a p-type semiconductor.

  The structure of the thin-film solar cell is not limited to the so-called pn junction type shown in FIG. 1, but may be a so-called Schottky type in which a p-type semiconductor layer is sandwiched between electrodes 2 and 5. Further, a structure in which a thin film made of a plurality of kinds of coordination polymers prepared by mixing a p-type semiconductor and an n-type semiconductor is sandwiched between the electrodes 2 and 5 may be used. Also, a so-called p-i-n bulk heterojunction structure may be used.

  Further, a buffer layer may be interposed between the electrodes 2 and 5 and the coordination polymer thin films 3 and 4, respectively. The buffer layer on the electrode 2 side is, for example, a PEDOT-PSS film, and can be formed by applying poly (3,4-ethylenedioxythiophene) added with polystyrene sulfonic acid by spin coating. The buffer layer on the electrode 5 side is, for example, a TiO 2 layer, and can be formed by applying an ethanol solution of Ti alkoxide by spin coating.

One of the coordination polymer thin films 3 and 4 may function as an n-type or p-type semiconductor, and may be substituted with a compound conventionally used in a thin film solar cell.
Examples of such compounds include fullerene, fullerene derivatives, oligothiophene, oligothiophene derivatives, polythiophene, polythiophene derivatives, phthalocyanines, phthalocyanine derivatives, metal phthalocyanines, metal phthalocyanine derivatives, polyphenylene, polyphenylene derivatives, polyphenylene vinylene, polyphenylene vinylene derivatives, polyvinyl Carbazole, polyvinylcarbazole derivative, polysilane, polysilane derivative, polyfluorene, polyfluorene derivative, pentacene, pentacene derivative, anthracene, anthracene derivative, rubrene, rubrene derivative, perylene, perylene derivative, tetracyanoquinodimethane, tetracyanoquinodimethane derivative Tetrathiafulvalene, tetrathiafulvalene derivatives, Sajiazoru, and an oxadiazole derivative. Among these compounds, since higher conversion efficiency can be expressed, 1- (3-methoxycarbonyl) propyl-1-phenyl- [6,6] -C61 (PCBM) and poly-3-hexylthiophene It is preferable to use (P3HT).

  Further, it is preferable to use ions of so-called Group 8 and Group 1B elements such as Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Os, Ir, Pt, and Au as metal ions. In particular, there is an advantage that electrons can be delocalized in the entire coordination polymer by using Cu and coordinating the exemplified bridging ligand described above. In addition, it is also possible to express the characteristics of each metal ion by using a plurality of different metal ions in combination. For example, by using metal ions with heavy atom effects such as platinum ions and iridium ions together with copper ions, in addition to the delocalization effect of electrons that copper ions have, the excitation life extension effect that platinum ions and iridium ions have It can be demonstrated.

Further, as a bridging ligand, an ion of a dithiocarboxylic acid derivative represented by the following chemical formula ₁ (R ₁ is an aliphatic hydrocarbon group, a substituted aliphatic hydrocarbon group, an aromatic hydrocarbon group, a substituted aromatic carbon group. It is preferable to use a hydrogen group, a heterocyclic group or a substituted heterocyclic group.

Among the above-mentioned ions of the chemical formula 1, the ions of the dithiocarbamic acid derivative represented by the chemical formula 2 below (R ₂ and R ₃ may be the same or different aliphatic hydrocarbon group, substituted aliphatic hydrocarbon group, aromatic carbonization. It is preferable to use a hydrogen group, a substituted aromatic hydrocarbon group, a heterocyclic group or a substituted heterocyclic group.

R ₂ and R ₃ preferably have 1 to 50 carbon atoms, and more preferably 1 to 30 carbon atoms.

Specific examples of R ₁ include an aliphatic hydrocarbon group, a substituted aliphatic hydrocarbon group, an aromatic hydrocarbon group, a substituted aromatic hydrocarbon group, a heterocyclic group, and a substituted heterocyclic group represented by the following chemical formula 3 Is mentioned.

  As described above, the coordination polymer may include a halide ion that crosslinks metal ions in addition to the metal ion and the ligand. Among them, it is preferable to use bromine ions or iodine ions in terms of improving the delocalization effect of electrons. By using such crosslinker components, the HOMO (highest occupied orbit) and LUMO (lowest empty orbit) orbital of each component forms an energy band, improving the transport properties of the generated electrons and holes. Can be made. For example, as shown in chemical formula 4 below, a mononuclear complex using copper ions as metal ions and hexamethylenedithiocarbamic acid as a ligand is used as bromine ions or iodine ions (X in chemical formula 4). By crosslinking, an energy band is formed by overlapping each orbit and high carrier transport characteristics can be realized.

  For example, when a coordination polymer thin film is used as a semiconductor layer of an organic transistor or the like, it is preferable to use an element such as Cu, Ni, or Fe among the transition metal elements as the metal ion.

  When used in the exemplified applications, the molecular weight and the number of repeating units (n) of the coordination polymer are not particularly limited, and are appropriately set according to the organic semiconductor used. The number of repeating units is preferably 100 or more. In addition, about the upper limit of molecular weight and the number of repeating units (n), it can set suitably in the range which does not have trouble in use.

(Example)
Next, a method for producing a coordination polymer thin film according to an embodiment of the present invention will be specifically described with reference to the following examples. The following examples are merely examples of the present invention and do not limit the technical scope of the present invention.

[Preparation of mononuclear complex]
First, a method for producing the mononuclear complexes C1 to C8 will be described.

(Mononuclear complex C1: Cu (Pip-dtc) ₂ )
First, 10 mmol of piperidine was added to 100 ml of a methanol solution in which 10 mmol of sodium hydroxide was dissolved, and further 10 mmol of carbon disulfide was reacted. Next, a solution obtained by dissolving 5 mmol of copper chloride dihydrate in 100 ml of methanol was added to this solution, and the mixture was stirred and reacted for 5 minutes. The resulting precipitate was collected by filtration, dissolved in 200 ml of chloroform, 200 ml of methanol was added to the solution, and the mixture was concentrated under reduced pressure to about 100 ml. Further, 200 ml of methanol was added and concentrated under reduced pressure to about 50 ml. The obtained microcrystals were collected by suction filtration, washed with a small amount of ether and dried to give a mononuclear complex C1: Cu (Pip -Dtc) ₂ was obtained.

(Mononuclear complex C2: Cu (Hm-dtc) ₂ )
The mononuclear complex C2: Cu (Hm-dtc) ₂ shown in the following chemical formula 6 is obtained in the same manner as the mononuclear complex C1 except that hexamethyleneimine is used instead of piperidine used for the production of the mononuclear complex C1. It was.

(Mononuclear complex C3: Cu (Pyr-dtc) ₂ )
The mononuclear complex C3: Cu (Pyr-dtc) ₂ shown below was obtained in the same manner as the mononuclear complex C1 except that pyrrolidine was used instead of piperidine used for the production of the mononuclear complex C1.

(Mononuclear complex C4: Cu (Ocm-dtc) ₂ )
A mononuclear complex C4: Cu (Ocm-dtc) _{2 shown} in the following chemical formula 8 is obtained in the same manner as the mononuclear complex C1 except that octamethyleneimine is used instead of piperidine used for the production of the mononuclear complex C1. It was.

(Mononuclear complex _{C5: Cu (nPr 2 -dtc)} 2)
The mononuclear complex C5: Cu (nPr ₂ -dtc) _{2 shown} in the following chemical formula 9 is obtained in the same manner as the mononuclear complex C1 except that dipropylamine is used instead of piperidine used for the production of the mononuclear complex C1. Obtained.

(Mononuclear complex C6: Cu (nBu ₂ -dtc) ₂ )
The mononuclear complex C6: Cu (nBu ₂ -dtc) ₂ shown below is obtained in the same manner as the mononuclear complex C1, except that dibutylamine is used instead of piperidine used for the production of the mononuclear complex C1. It was.

(Mononuclear complex C7: Ni (Hm-dtc) ₂ )
First, 10 mmol of piperidine was added to 100 ml of a methanol solution in which 10 mmol of sodium hydroxide was dissolved, and further 10 mmol of carbon disulfide was reacted. Next, a solution obtained by dissolving 5 mmol of nickel chloride hexahydrate in 100 ml of methanol was added to this solution, and the mixture was stirred for 5 minutes to be reacted. The resulting precipitate was collected by filtration, dissolved in 200 ml of chloroform, 200 ml of methanol was added to the solution, and the mixture was concentrated under reduced pressure to about 100 ml. After adding 200 ml of methanol and concentrating under reduced pressure to about 50 ml, the resulting microcrystals were collected by suction filtration, washed with a small amount of ether and dried to give a mononuclear complex C7: Ni (Hm -Dtc) ₂ was obtained.

(Mononuclear complex C8: Cu (Pen ₂ -dtc) ₂ )
First, 10 mmol of dipentylamine was added to 100 ml of a methanol solution in which 10 mmol of potassium hydroxide was dissolved, and 10 mmol of carbon disulfide was further reacted. Next, a solution obtained by dissolving 5 mmol of copper chloride dihydrate in 100 ml of methanol was added to this solution, and the mixture was stirred and reacted for 5 minutes. The resulting precipitate was collected by filtration, dissolved in 200 ml of chloroform, 200 ml of methanol was added to the solution, and the mixture was concentrated under reduced pressure to about 100 ml. Further, 200 ml of methanol was added and concentrated under reduced pressure to about 50 ml, and the resulting microcrystals were collected by suction filtration, washed with a small amount of ether and dried to give a mononuclear complex C8: Cu (Pen -Dtc) ₂ was obtained.

[Preparation of single crystal of coordination polymer]
Next, a method for producing single crystals of coordination polymers P1 to P17 will be described. A single crystal of a coordination polymer is produced by the following method, but any type of coordination polymer such as polycrystalline or amorphous may be produced.

(Coordination polymer P1: [Cu ₅ I ₃ (Pip-dtc) ₄ ] _n )
Mononuclear complex C1: 0.1 mmol of Cu (Pip-dtc) ₂ was dissolved in 20 ml of chloroform, 0.1 mmol of copper iodide was dissolved in a mixed solvent of 10 ml of propionitrile and 10 ml of acetone, and then each solution was dissolved. By mixing and allowing to stand at room temperature for 2 days, a black single crystal of the coordination polymer P1: [Cu ₅ I ₃ (Pip-dtc) ₄ ] _n was produced. The three-dimensional structure obtained from the structural analysis of the coordination polymer P1 is shown in FIG. In this three-dimensional structure, a mononuclear complex Cu (Pip-dtc) ₂ is bonded to both sides of a copper (I) iodide complex having a one-dimensional ladder structure.

(Coordination polymer P2: [Cu ₃ Br ₂ (Hm-dtc) ₂ (CH ₃ CN) ₂ ] _n )
Mononuclear complex C2: 0.1 mmol of Cu (Hm-dtc) ₂ was dissolved in 20 ml of chloroform, and 0.2 mmol of copper bromide was dissolved in a mixed solvent of 3 ml of acetonitrile and 17 ml of acetone, and then the respective solutions were mixed. A black single crystal of the coordination polymer P2: [Cu ₃ Br ₂ (Hm-dtc) ₂ (CH ₃ CN) ₂ ] _n was produced by allowing it to stand at room temperature for 1 day. The three-dimensional structure obtained from the structural analysis of the coordination polymer P2 is shown in FIG.

(Coordination polymer P3: [Cu ₃ I ₂ (Hm-dtc) ₂ (CH ₃ CN) ₂ ] _n )
Mononuclear complex C2: 0.1 mmol of Cu (Hm-dtc) ₂ was dissolved in 20 ml of chloroform, and 0.2 mmol of copper iodide was dissolved in a mixed solvent of 10 ml of acetonitrile and 10 ml of acetone, and then the respective solutions were mixed. A black single crystal of the coordination polymer P3: [Cu ₃ I ₂ (Hm-dtc) ₂ (CH ₃ CN) ₂ ] _n was produced by allowing it to stand at room temperature for 1 day.

(Coordination polymer P4: {[Cu ₆ Br ₄ (Pyr-dtc) ₄ ] CHCl ₃ } _n )
Mononuclear complex C3: 0.1 mmol of Cu (Pyr-dtc) ₂ is dissolved in 20 ml of chloroform, 0.4 mmol of CuBrS (CH ₃ ) ₂ is dissolved in 10 ml of acetonitrile, diluted with 10 ml of acetone, and then dissolved. The liquids were mixed and allowed to stand at room temperature for 1 day, whereby a black single crystal of the coordination polymer P4: {[Cu ₆ Br ₄ (Pyr-dtc) ₄ ] CHCl ₃ } _n was produced.

(Coordination polymer P5: [Cu ₃ Br ₂ (Ocm-dtc) ₂ ] _n )
Mononuclear complex C4: 0.1 mmol of Cu (Ocm-dtc) ₂ was dissolved in 20 ml of chloroform, and 0.2 mmol of copper (I) dimethyl sulfide complex was dissolved in a mixed solvent of 4 ml of acetonitrile and 16 ml of acetone. Were mixed and allowed to stand at room temperature for 3 days to produce a black single crystal of coordination polymer P5: [Cu ₃ Br ₂ (Ocm-dtc) ₂ ] _n shown in Chemical Formula 13 below.

(Coordination polymer P6: [Cu ₃ I ₂ (Ocm-dtc) ₂ ] _n )
Mononuclear complex C4: 0.1 mmol of Cu (Ocm-dtc) ₂ is dissolved in 20 ml of chloroform, and 0.2 mmol of copper (I) iodide is dissolved in a mixed solvent of 10 ml of acetonitrile and 10 ml of acetone, and then each solution. Were mixed and allowed to stand at room temperature for 3 days, thereby producing a black single crystal of coordination polymer P6: [Cu ₃ I ₂ (Ocm-dtc) ₂ ] _n shown in Chemical Formula 14 below.

(Coordination polymer P7: [Cu ₇ Cl ₇ (nPr ₂ -dtc) ₂ ] _n )
Mononuclear complex C5: 0.1 mmol of Cu (nPr ₂ -dtc) ₂ is dissolved in 20 ml of chloroform, 0.4 mmol of copper chloride dihydrate is dissolved in a mixed solvent of 20 ml of acetone, and then each solution is mixed. Then, a black single crystal of the coordination polymer P7: [Cu ₇ Cl ₇ (nPr ₂ -dtc) ₂ ] _n was produced by leaving it to stand at room temperature for 1 day.

(Coordination polymer _{P8: [Cu 8 Br 7 (} nBu 2 -dtc) 2] n)
Mononuclear complex C6: 0.1 mmol of Cu (nBu ₂ -dtc) ₂ was dissolved in 20 ml of chloroform, 0.2 mol of copper bromide was dissolved in a few drops of water, dissolved in 20 ml of acetone, and then dissolved. The liquids were mixed and allowed to stand at room temperature for 1 day, thereby producing a black single crystal of the coordination polymer P8: [Cu ₈ Br ₇ (nBu ₂ -dtc) ₂ ] _n .

(Coordination polymer P9: [Cu ₃ Br ₂ (Pip-dtc) ₂ (CH ₃ CN) ₂ ] _n )
Mononuclear complex C1: 0.1 mmol of Cu (Pip-dtc) ₂ is dissolved in 20 ml of chloroform, and 0.2 mmol of monovalent copper bromide is dissolved in a mixed solvent of 4 ml of acetonitrile and 16 ml of acetone, and then each solution. Were mixed and allowed to stand at room temperature for 1 day, thereby producing a black single crystal of the coordination polymer P9: [Cu ₃ Br ₂ (Pip-dtc) ₂ (CH ₃ CN) ₂ ] _n . The three-dimensional structure obtained from the structural analysis of the coordination polymer P9 is shown in FIG.

(Coordination polymer P10: [Cu ₃ I ₂ (Pip-dtc) ₂ (CH ₃ CN) ₂ ] _n )
Mononuclear complex C1: 0.1 mmol of Cu (Pip-dtc) ₂ is dissolved in 20 ml of chloroform, and 0.1 mmol of monovalent copper iodide is dissolved in a mixed solvent of 10 ml of acetonitrile and 10 ml of acetone, and then each solution. Were mixed and allowed to stand at room temperature for 1 day to prepare a coordination polymer P10: [Cu ₃ I ₂ (Pip-dtc) ₂ (CH ₃ CN) ₂ ] _n black single crystal. The three-dimensional structure obtained from the structural analysis of the coordination polymer P10 is shown in FIG.

(Coordination polymer P11: [Cu ₂ NiBr ₂ (Hm-dtc) ₂ (CH ₃ CN) ₂ ] _n )
Mononuclear complex C7: 0.1 mmol of Ni (Hm-dtc) ₂ is dissolved in 20 ml of chloroform, and 0.2 mmol of monovalent copper bromide is dissolved in a mixed solvent of 10 ml of acetonitrile and 10 ml of acetone, and then each solution. Were mixed and allowed to stand at room temperature for 1 day, to produce a black single crystal of the coordination polymer P11: [Cu ₂ NiBr ₂ (Hm-dtc) ₂ (CH ₃ CN) ₂ ] _n . The three-dimensional structure obtained from the structural analysis of the coordination polymer P11 is shown in FIG.

(Coordination polymer P12: [Cu ₂ NiI ₂ (Hm-dtc) ₂ (CH ₃ CN) ₂ ] _n )
Mononuclear complex C7: Ni (Hm-dtc) ₂ 0.1 mmol was dissolved in chloroform 20 ml, monovalent copper iodide 0.1 mmol was dissolved in a mixed solvent of acetonitrile 10 ml and acetone 10 ml, and then each solution. Were mixed and allowed to stand at room temperature for 1 day, thereby producing a black single crystal of the coordination polymer P12: [Cu ₂ NiI ₂ (Hm-dtc) ₂ (CH ₃ CN) ₂ ] _n . The three-dimensional structure obtained from the structural analysis of the coordination polymer P12 is shown in FIG.

(Coordination polymer P13: [Cu ₂ NiBr ₂ (Hm-dtc) ₂ ] _n )
Mononuclear complex C7: 0.3 mmol of Ni (Hm-dtc) ₂ was dissolved in 20 ml of chloroform, 0.2 mmol of divalent copper bromide was dissolved in a few drops of water, and then dissolved in a mixed solvent of 20 ml of acetone. Thereafter, the respective dissolved solutions were mixed and allowed to stand at room temperature for 1 day to prepare black block crystals of the coordination polymer P13: [Cu ₂ NiBr ₂ (Hm-dtc) ₂ ] _n . The three-dimensional structure obtained from the structural analysis of the coordination polymer P13 is shown in FIG.

(Coordination polymer P14: [Cu (dahex-dtc)] _n )
After dissolving 20 mmol of potassium hydroxide in about 500 ml of methanol solvent, mononuclear complex N, N′-diethyl-1,6-diaminohexane (Tokyo Chemical Industry Co., Ltd.) 10 mmol, carbon disulfide 20 mmol, copper chloride 10 mmol of dihydrate was added in order to obtain a brown precipitate. The brown precipitate was subjected to suction filtration, and then dissolved in about 500 ml of chloroform and filtered. Thereafter, a certain amount of chloroform was blown off using an evaporator and then diffused with a large amount of hexane to prepare a brown precipitate of the coordination polymer P14: [Cu (dahex-dtc)] _{n shown in} the following chemical formula 15. .

(Coordination polymer P15: [Cu ₂₁ Br ₂₀ (Pen ₂ -dtc) ₆ ] _n )
Mononuclear complex C8: Cu (Pen ₂ -dtc) ₂ 0.3 mmol was dissolved in 20 ml of chloroform, and 1.0 mmol of divalent copper bromide was dissolved in a mixed solvent of 10 drops of water and 20 ml of acetone. The solution is mixed, hexane is added from above, and the mixture is allowed to stand at room temperature for 1 day, thereby producing a black plate-like crystal of coordination polymer P15: [Cu ₂₁ Br ₂₀ (Pen ₂ -dtc) ₆ ] _n. did.

(Coordination polymer P16: {Fc ₂ [Cu ₆ Br ₈ ]} _n )
Mononuclear complex ferrocene (Fc = Fe (C ₅ H ₅ ) ₂ ) (manufactured by Wako Pure Chemical Industries, Ltd.) as a guest molecule in an acetone solution (20 ml) of divalent copper bromide 0.2 mmol prepared with a small amount of water A mixture of 0.2 mmol was diffused with hexane, allowed to stand for 5 days in a dark place at 40 ° C. and diffused, and the black acicular crystals of the coordination polymer P16: {Fc ₂ [Cu ₆ Br ₈ ]} _n Was made.
A two-dimensional sheet structure obtained from the structural analysis of the coordination polymer P16 is shown in FIG. Moreover, the schematic diagram of the ferrocenium ion taken in between two-dimensional sheets is shown in FIG.12 (b).

(Coordination polymer P17: [TTF (Cu ₂ Br ₄ )] _n )
A solution obtained by adding 0.4 mmol of a mononuclear complex ferrocene (manufactured by Wako Pure Chemical Industries, Ltd.) as a guest molecule to an acetone solution (20 ml) of divalent copper bromide 0.4 mmol prepared with a small amount of water, and tetrathiafulvalene (TTF = C ₆ H ₄ S ₄ ) 0.1 mmol of acetone solution (30 ml) was mixed and allowed to stand in the dark so that the coordination polymer P17: [TTF (Cu ₂ Br ₄ )] _n black Columnar crystals were produced.
FIG. 13A shows a two-dimensional sheet structure (viewed from the side) obtained from the structural analysis of the coordination polymer P17, and FIG. 13B shows a view of the structure viewed from above.

[Evaluation of single crystal of prepared coordination polymer]
HOMO (eV), LUMO (eV), electrical conductivity σ (S / cm) / activation energy Ea (eV) were measured for the single crystals of coordination polymers P1 to P17 produced as described above (HOMO). For LUMO, only coordination polymers P1 to P14). The measurement results are shown in Table 1 below. In the lower column of “Chemical Formula”, the valences of metal ions are shown separately.
HOMO and LUMO were measured using a UV-Vis-NIR (ultraviolet visible near infrared) spectrophotometer (U-4100 manufactured by HITACHI).

Next, coordination polymers _{P8: [Cu 8 Br 7 (} nBu 2 -dtc) 2] n, coordination polymer _{P15: [Cu 21 Br 20 (} Pen 2 -dtc) 6] n, coordination polymer P16 : {Fc ₂ [Cu ₆ Br ₈ ]} _n was measured for relative dielectric constant using an impedance analyzer (6440B manufactured by Wayne Kerr Electronics) (frequency: 1 kHz).
The measurement results were 1.2 × 10 ⁴ (335K), 2.6 × 10 ⁵ (300K), and 7.3 × 10 ⁵ (300K), respectively, and very large values of relative dielectric constant were measured.

FIG. 14 shows a coordination polymer P8: [Cu ₈ Br ₇ (nBu ₂ -dtc) ₂ ] _n (chain line), a mononuclear complex C6: Cu (nBu ₂ -dtc) ₂ constituting the coordination polymer P8. It is a graph which shows the result of the UV-Vis-NIR spectrum measurement with respect to (solid line).
The horizontal axis of the graph represents the absorption wavelength (nm), and the vertical axis represents the absorbance (Abs). The same applies to graphs showing the results of other UV-Vis-NIR spectrum measurements. FIG. 14 shows a spectrum after Kubelka-Munk conversion (the same applies to FIG. 19B).

Here, the spectrum is divided into an ultraviolet region having a wavelength shorter than about 400 nm, a visible light region having a wavelength of about 400 nm to about 800 nm, and a near infrared region having a wavelength longer than about 800 nm. Referring to FIG. 14, in the spectrum profile of the coordination polymer P8, it can be seen that the absorbance from the visible light region to the near infrared region increases with respect to the spectrum of the mononuclear complex C6. This change in profile is thought to be due to the fact that the absorption of light has shifted to the longer wavelength side due to the formation of a band structure with the coordination polymer P8.
Such a difference in the absorption spectrum profile between the mononuclear complex and the coordination polymer is also measured in other coordination polymers.

  The excellent properties of the coordination polymer (single crystal) described so far are also exhibited in the thin film of the coordination polymer.

[Preparation of coordination polymer thin film]
Next, a method for producing a thin film of coordination polymers P8 and P15 will be described. The thin film was produced under the atmospheric pressure of the standard environmental temperature.

(Coordination polymer P8: [Cu ₈ Br ₇ (nBu ₂ -dtc) ₂ ] _n thin film)
When 0.0148 g (0.01 mmol) of the coordination polymer P8 single crystal was dissolved in a mixed solvent of 9 ml of chloroform and 1 ml of acetonitrile (chloroform: acetonitrile = 9: 1) and filtered, a yellow solution was obtained. Obtained. On a glass substrate having dimensions of 2 cm × 2.5 cm, 30 drops (1 drop: 8 μl) of a yellow solution was directly dropped (applied) and allowed to stand for several minutes until dried. Thereby, a blue (blue-black) film was obtained.

(Coordination polymer P15: [Cu ₂₁ Br ₂₀ (Pen ₂ -dtc) ₆ ] _n thin film)
When 0.0144 g (0.0033 mmol) of the coordination polymer P15 single crystal was dissolved in a mixed solvent of chloroform 9.5 ml and acetonitrile 0.5 ml (chloroform: acetonitrile = 19: 1) and filtered, A yellow solution was obtained. On a glass substrate having dimensions of 2 cm × 2.5 cm, 30 drops of a yellow solution were directly dropped (applied) and allowed to stand for several minutes until dried. Thereby, a blue (blue-black) film was obtained.

  In addition, if the solution is dropped on the substrate with impurities, the properties and roughness of the thin film are affected. Therefore, in the above embodiment, the single crystal is dissolved in the mixed solvent and then filtered to reliably remove impurities.

[Evaluation of produced coordination polymer thin film]
FIG. 15A shows an optical micrograph of a thin film of coordination polymer P8 produced on a glass substrate. FIG. 15B shows a laser micrograph of a part of the square box in FIG.
In the portion where the color in the square box in FIG. 15A is light, a part of the thin film is scraped to expose the surface of the substrate, and the thin film is the highest in the portion using a laser microscope (VK-X100 manufactured by Keyence Corporation). The height difference between the position and the surface of the substrate was measured. The height difference (film thickness) was measured to be 0.2 μm. Therefore, it can be said that the produced film is sufficiently thin.

Next, the UV-Vis-NIR spectrum was measured with respect to the thin film of the coordination polymer P8 produced by dripping 10 drops, 30 drops, and 50 drops of the yellow solution on the glass substrate. A graph of the measurement results is shown in FIG.
The dotted line, the solid line, and the chain line in FIG. 16 show the measurement results when only 10 drops, 30 drops, and 50 drops of the solution were dropped.

First, as shown in the graph of FIG. 14, the mononuclear complex and the single crystal of the coordination polymer have greatly different absorption spectrum profiles. Comparing the absorption spectrum (chain line) of the coordination polymer in FIG. 14 with FIG. 16, it can be seen that the absorbance is minimal at a wavelength of about 450 nm. Therefore, it can be said that the coordination polymer skeleton is regenerated in the produced thin film.
Further, it can be seen from FIG. 16 that as the amount of the solution to be dropped increases, the absorbance increases, that is, the film thickness of the thin film increases.

Next, FIG. 17A is a graph showing the results of measurement of powder X-ray diffraction performed on the prepared coordination polymer P8 thin film. FIG. 17B is a graph showing the measurement results of single crystal X-ray diffraction (Laue method) performed on the single crystal of the prepared coordination polymer P8. X-ray diffraction was measured using Rigaku R-AXIS RAPID-F.
In each graph, the horizontal axis represents the diffraction angle 2θ (deg), and the vertical axis represents the diffraction intensity (no unit). The same applies to graphs showing measurement results of other powder X-ray diffraction and single crystal X-ray diffraction. In FIG. 17A, as in FIG. 17B, a peak was measured when the diffraction angle 2θ was around 5 °. Since the diffraction angle 2θ corresponds to the interplanar spacing of the crystal, it can be seen that in the prepared coordination polymer thin film, a sheet structure similar to that of the produced coordination polymer single crystal is regenerated.

Next, FIG. 18A is a graph showing the results of measurement of powder X-ray diffraction performed on the prepared coordination polymer P15 thin film. FIG. 18B is a graph showing the measurement results of single crystal X-ray diffraction performed on the single crystal of the produced coordination polymer P15.
In FIG. 18A, as in FIG. 18B, a peak was measured when the diffraction angle 2θ was around 5 °. It can be seen that the sheet structure is regenerated in the case of the coordination polymer P15 as in the case of the coordination polymer P8.

FIG. 19 is a graph showing the results of UV-Vis-NIR spectrum measurements performed on the prepared coordination polymer P15 thin film (a) and single crystal (b).
Comparing FIGS. 19A and 19B, it can be seen that the absorbance is minimum at a wavelength of about 450 nm. Therefore, it can be said that the coordination polymer skeleton is regenerated in the produced thin film.

[Evaluation of coordination polymer thin film after annealing]
Next, the coordinating polymer thin film shown in FIG. 15 was placed on a hot plate heated to 100 ° C. together with the substrate and heated for 10 minutes (annealing).

20 and 21 are graphs showing the results of powder X-ray diffraction and UV-Vis-NIR spectrum measurements performed before and after annealing on the prepared coordination polymer P8 thin film. The solid line shows the measurement result before annealing, and the dotted line shows the measurement result after annealing.
Referring to FIG. 20, it can be seen that the peak of diffraction angle 2θ near 5 ° is greatly increased by annealing. On the other hand, referring to FIG. 21, although the spectrum profile does not change greatly, it can be seen that the absorbance slightly increases from the visible light region to the near infrared region.

  From the measurement results shown in FIGS. 20 and 21, it is considered that the crystallinity of the coordination polymer thin film is increased by annealing. Thereby, improvement in conductivity is expected.

  Although the evaluation of the thin film of the coordination polymer P8 or P15 has been described with reference to FIGS. 16 to 21, these evaluations also apply to the thin films of other coordination polymers.

  According to the method described above, a solution in which a metal ion and a bridging ligand are dissolved in a ratio suitable for self-assembly can be prepared by dissolving a single crystal of a coordination polymer in a mixed solvent. Thus, a coordination polymer thin film can be easily produced.

  In the above description, the method for producing a coordination polymer thin film produced using a mononuclear complex was taken as an example, but the present invention is also applied to the production of a coordination polymer thin film produced using a polynuclear complex. Needless to say, you can.

  As described above, according to the present invention, a coordination polymer thin film can be easily manufactured. As described above, such as a thin film solar cell, an organic transistor, a ferroelectric capacitor, and a ferroelectric memory. It may be suitably used in the technical field.

1 Substrate (base material)
2,5 electrode 3,4 coordination polymer thin film 10 thin film solar cell

Claims (8)

A method for producing a coordination polymer thin film comprising repeating units of one or more metal ions and one or more bridging ligands,
Preparing a solution in which the metal ion and a bridging ligand are present in a solvent containing a polar solvent capable of coordinating to at least one of the metal ions;
Applying the prepared solution onto a substrate to evaporate the solvent and inducing self-assembly of metal ions and bridging ligands,
In the step of preparing a solution, the method comprises preparing a solution in which a metal ion and a bridging ligand are present in a ratio suitable for self-assembly. Further comprising preparing a bulk coordination polymer;
The method according to claim 1, wherein in the step of preparing the solution, the solution is prepared by dissolving a bulk coordination polymer in a solvent containing the polar solvent. The bridging ligand of the coordination polymer has the following formula:
(R ₁ represents an aliphatic hydrocarbon group, a substituted aliphatic hydrocarbon group, an aromatic hydrocarbon group, a substituted aromatic hydrocarbon group, a heterocyclic group or a substituted heterocyclic group) The method according to claim 1, wherein the method comprises the following ions. The bridging ligand of the coordination polymer has the following formula:
(R ₂ and R ₃ represent the same or different aliphatic hydrocarbon group, substituted aliphatic hydrocarbon group, aromatic hydrocarbon group, substituted aromatic hydrocarbon group, heterocyclic group or substituted heterocyclic group) The method according to claim 1, comprising an ion of a dithiocarbamic acid derivative.   The method according to claim 1, further comprising a step of heating the coordination polymer together with the substrate after the step of inducing self-assembly.   The method according to claim 1, wherein a solvent containing a nonpolar solvent is used as the solvent containing the polar solvent in the step of preparing the solution.   The method according to claim 1, wherein a nitrile group-containing compound is used as the polar solvent in the step of preparing the solution. A method for producing a thin-film solar cell comprising a substrate on which an electrode is formed and a semiconductor layer provided on the electrode side of the substrate,
A method of providing a thin film of coordination polymer as a semiconductor layer using the method according to claim 1.