JP2019163199A - Reduced heteropolyoxomethalate and production process therefor, coating ink containing said reduced heteropolyoxomethalate, and organic electronic device using same - Google Patents

Abstract

To provide, as a coating-type hole injection material, a reduced heteropolyoxometalate and production process therefor that does not require heat treatment after film formation and can drive organic electronic device at low voltage.SOLUTION: Provided is a reduced heteropolyoxometalate characterized in that the proportion of Mo(V)-derived peaks among molybdenum (Mo) peaks measured by X-ray photoelectron spectroscopy (XPS) is 30% or more. Said reduced heteropolyoxometalate is produced by heating and reducing a heteropolyacid selected from the group consisting of phosphomolybdic acid, silicomolybdic acid, and phosphotungstomolybdic acid.SELECTED DRAWING: None

Description

  The present invention relates to reduced heteropolyoxometalates for organic electronic devices.

  Since the coating type organic EL can be produced by a simple method, it is advantageous in increasing the area and productivity. As a coating-type hole injection material that can stably drive the organic EL element for a long time, a material that is heated in the atmosphere at a high temperature of 200 ° C. or higher is known. For example, in Patent Document 1, a polyoxometalate containing phosphomolybdic acid (FIG. 1) having a Keggin structure is dissolved in water and applied, and then dried by heating at 200 ° C. for 10 minutes. However, an element using this material has a high driving voltage. The present inventors have also found that when a phosphomolybdic acid thin film having a thickness of about 10 nm is heated at a high temperature of 200 ° C. or higher under nitrogen, the driving voltage is significantly reduced (Non-patent Document 1). Since this leads to an increase in running costs such as electricity bills as it is used in industry, a material that can be processed at low temperature is required.

  When the phosphomolybdic acid thin film is heated at a high temperature in an inert atmosphere, molybdenum is reduced from hexavalent to pentavalent. Then, defect levels are generated in the film, and the work function is lowered. It is considered that when the exchange of charges with the adjacent layer using this defect level works effectively, the drive voltage is lowered. It has also been found that the drive voltage decreases as the proportion of molybdenum reduced to pentavalent increases.

  However, 200 ° C. is a high temperature. For example, when a plastic substrate such as a PET substrate is used, there is a problem that the substrate is greatly deformed at a high temperature. Therefore, a material applicable to a plastic substrate or the like is demanded.

JP 2011-23711 A

ACS Appl. Mater. Interfaces, 2016, 8, 20946 (published July 2016)

  The present invention provides a reduced heteropolyoxometalate as a coating-type hole injection material that does not require heat treatment after film formation and that can reduce the driving voltage of an organic electronic device, and a method for producing the same. With the goal.

The present invention comprises the following items.
The reduced heteropolyoxometalate of the present invention is characterized in that the proportion of Mo (V) -derived peaks among molybdenum (Mo) peaks measured by X-ray photoelectron spectroscopy (XPS) is 30% or more. .
The difference in peak top position between the peak derived from Mo (VI) and the peak derived from Mo (V) in the Mo 3d _3/2 binding energy peak obtained by fitting the spectrum measured by XPS, and Mo3d The difference in peak top position between the peak derived from Mo (VI) and the peak derived from Mo (V) in the _5/2 binding energy peak is preferably 1.30 eV or more on average.

The method for producing a reduced heteropolyoxometalate according to the present invention is characterized in that a heteropolyacid is spread and placed on a flat bottom pan and heated. The method for producing a reduced heteropolyoxometalate according to the present invention is characterized in that a solution obtained by dissolving a heteropolyacid in a solvent is dropped into a flat bottom dish in a thin film form and heated.
The heteropolyacid is preferably at least one selected from the group consisting of phosphomolybdic acid, silicomolybdic acid, and phosphotungstomolybdic acid.
The ink of the present invention is characterized by containing the reduced heteropolyoxometalate and an organic solvent.
The organic solvent is preferably an alcohol or a carbonyl group-containing compound.
The organic electronic device of the present invention uses the reduced heteropolyoxometalate.
The organic electronic device is preferably an organic electroluminescence element.

  According to the present invention, a reduced heteropolyoxometalate containing 30% or more of Mo (V) is used as the hole injecting material, so that the driving voltage is significantly reduced without performing a heating process after film formation. An electronic device, for example, an organic EL element can be manufactured.

FIG. 1 represents the structure of phosphomolybdic acid. 2A is an XPS measurement spectrum of the sample of Comparative Example 1, FIG. 2B is an XPS measurement spectrum of the sample of Comparative Example 3, FIG. 2C is an XPS measurement spectrum of the sample of Example 1, and FIG. (D) represents the XPS measurement spectrum of the sample of Example 2, and FIG. 2 (e) represents the XPS measurement spectrum of the sample of Example 2. FIG. 3 shows the relationship between the current density and voltage characteristics of the hole-only device. FIG. 4 shows the relationship between the current density and voltage characteristics of the organic EL element. FIG. 5 shows the relationship between the current density-voltage characteristics of the solar cell elements of Example 7, Comparative Example 10 and Comparative Example 11 (FIG. 5A), and spectral sensitivity characteristics (external quantum efficiency) at each wavelength (FIG. 5). (B)) is shown. In FIG. 5, TFB / PMA represents the device of Example 7, TFB / PEDOT: PSS represents the device of Comparative Example 10, and PEDOT: PSS represents the device of Comparative Example 11.

Hereinafter, the present invention will be described in detail.
The reduced heteropolyoxometalate of the present invention is characterized in that the proportion of Mo (V) -derived peaks among molybdenum (Mo) peaks measured by X-ray photoelectron spectroscopy (XPS) is 30% or more. .
Here, the heteropolyoxometalate is a compound having a structure in which a polyatom is coordinated to the heteroatom through oxygen, with a heteroatom at the center. In particular, the Keggin type heteropolyoxometalate is oxidized. It is known to be used as a reaction catalyst.
The reduced heteropolyoxometalate of the present invention is a substance having a reduced oxidation number of heteroatoms constituting the heteropolyoxometalate. The reduced heteropolyoxometalate can be obtained by heating a specific heteropolyacid and reducing the oxidation state of a heteroatom, specifically molybdenum, from (+ VI) to (+ V). Such reduction of molybdenum from hexavalent to pentavalent can be seen by changing the color from yellow to blue.

  Specific examples of the heteropolyacid include phosphomolybdic acid, silicomolybdic acid, and phosphotungstomolybdic acid. Of these, phosphomolybdic acid is more preferable from the viewpoints of high solubility in a solvent, charge transportability, and low driving voltage when used in an organic electronic device, and improvement of lifetime. These heteropolyacids are commercially available.

The reduced heteropolyoxometalate may be heated by spreading these heteropolyacids in a flat bottom dish such as a petri dish as a powder, or by dissolving in a solvent to form a thin film on the flat bottom dish. May be. The solvent used for forming the thin film is not limited as long as it can dissolve the heteropolyacid, but since the heteropolyacid has high solubility in a polar solvent, the solvent is preferably highly polar. Specifically, acetonitrile, linear alcohol such as 1-butanol, or the like is used.
The heating temperature is usually 100 to 200 ° C., preferably 200 ° C., and the heating time is usually 60 to 300 minutes, preferably about 180 minutes.

When the constituent elements and electronic state of the reduced heteropolyoxometalate are analyzed by X-ray photoelectron spectroscopy (XPS), the Mo (VI) -derived peak and the Mo (V) -derived peak in the Mo 3d _5/2 binding energy peak are analyzed. The difference between the peak and the position of the peak top is 1.30 eV or more on average, specifically 1.30 eV or more. When the difference between the binding energies of Mo (VI) and Mo (V) is in the above range, the driving voltage of the element can be greatly reduced without requiring heating of the thin film.

The reduced heteropolyoxometalate exhibits a blue color derived from Mo ⁵⁺ . In order to maintain the reduced state even when the reduced heteropolyoxometalate forms a hole injection layer of the organic EL device described later, a solution obtained by dissolving the reduced heteropolyoxometalate in water or an organic solvent can also be used. Must be blue. Such an organic solvent is not limited as long as it is a solvent that can completely dissolve the reduced heteropolyoxometalate into a uniform solution and can be removed in the film formation process. -Linear alcohols such as propanol, 1-butanol, 1-pentanol and 1-hexanol, tetrahydrofuran (THF), methyl ethyl ketone (MEK), cyclohexanone, and esters such as butyl acetate, ethyl benzoate and butyl benzoate It is done. Of these, 1-butanol and MEK are more preferably used.

The ink of the present invention is a solution in which reduced heteropolyoxometalate is dissolved in the above organic solvent, and is used as an ink for forming a hole injection layer of an organic electronic device.
In addition, you may add additives, such as binder resin which does not become a hole trap, and a coating property improving agent, to the said ink as needed.

  The organic electronic device of the present invention uses the reduced heteropolyoxometalate. That is, the organic electronic device of the present invention, particularly the organic EL element, has a thin film coated with the reduced heteropolyoxometalate as a hole injection material.

  Examples of the method for applying the reduced heteropolyoxometalate include a dipping method, a spin coating method, a transfer printing method, a roll coating method, a brush coating method, an ink jet method, a spray method, and a slit coating method. Among these, the spin coat method is preferably used in that the film thickness can be easily adjusted by a coating method using a rotational centrifugal force.

  After application, the solvent is heated to room temperature to about 100 ° C. using a hot plate or an oven, for example, at room temperature under an inert gas such as air, nitrogen, or vacuum, or as necessary. Evaporate. Thereby, a uniform thin film can be formed. That is, in the present invention, by using the reduced heteropolyoxometalate, it is possible to manufacture an element with a greatly reduced driving voltage without heating to 200 ° C. as in the prior art after film formation.

  The film thickness of the thin film thus formed is usually 0.1 to 200 nm, preferably 0.5 to 50 nm, more preferably 1.0 to 15 nm. The film thickness can be adjusted by changing the concentration of the reduced heteropolyoxometalate in the ink or changing the coating amount.

  The organic electronic device of the present invention, specifically, the organic EL device, includes a step of forming a film by coating and laminating the hole injection layer on the anode as described above and then drying from room temperature to 100 ° C. It can be produced by a method. In the present invention, since the hole injection layer can be formed by a low-temperature process, it can be suitably applied to element fabrication using a flexible substrate such as a PET substrate, which is not applicable to a high-temperature heat treatment step.

  The layer structure of the organic EL element is a structure in which at least one light emitting layer is laminated between a pair of electrodes via an intermediate layer including a charge generation layer. For example, anode / hole injection layer / hole transport Examples of the layer structure include layer / light emitting layer / electron transport layer / electron injection layer / cathode. Specifically, it can be configured as shown in the following examples. The layer structure may further include a hole transport light emitting layer, an electron transport light emitting layer, and the like.

  The film forming material used for the constituent layer of the organic EL element can be appropriately selected from known materials, and may be either a low molecular weight type or a high molecular weight type. The film thickness of each constituent layer of the organic EL element is appropriately determined according to the situation in consideration of the adaptability between the layers and the required total layer thickness, but is usually in the range of 0.5 nm to 5 μm. Is within.

  The electrode may be a known material and configuration and is not limited. For example, a so-called ITO substrate is generally used in which a transparent conductive thin film is formed on a transparent substrate made of glass or polymer, and an indium tin oxide (ITO) electrode is formed as an anode on the glass substrate. In addition, since high-temperature heating is not required, a flexible substrate or the like can be suitably applied. On the other hand, the cathode is composed of a metal, alloy, or conductive compound having a small work function (4 eV or less) such as Al.

  The formation method of each of the above layers may be a dry process such as a vapor deposition method or a sputtering method. However, the present invention has an advantage in that it can be formed by a coating process, and a spin coating method, an ink jet method, a casting method. Wet processes such as a method, a dip coating method, a bar coating method, a blade coating method, a roll coating method, a gravure coating method, a flexographic printing method, a spray coating method, and a method using a nanoparticle dispersion can be suitably applied.

EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not restrict | limited by the following Example.
(Preparation of reduced phosphomolybdic acid)

[Preparation Example 1]
12 Molybdo (VI) phosphate n-hydrate (manufactured by Kanto Chemical Co., Ltd.) (hereinafter referred to as “phosphomolybdate n-hydrate” or “PMA”) was spread on a petri dish and heated in an oven at 200 ° C. A sample 1 was obtained by baking for 3 hours. The phosphomolybdic acid n-hydrate powder was yellow but turned blue after heating.

[Preparation Example 2]
Phosphormolybdic acid n-hydrate powder is dissolved in acetonitrile at a concentration of 1 g / mL, dropped onto a petri dish, spin-coated at 1000 rpm for 30 seconds, spread on the petri dish, and then exposed to fluorescent light in the oven. Sample 2 was obtained by scraping the powder that was baked at 200 ° C. for 3 hours and turned blue-black in a petri dish.

[Preparation Example 3]
Sample 3 was obtained in the same manner as in Preparation Example 2 except that the solvent was changed from acetonitrile to n-butanol in Preparation Example 2. Similarly to sample 2, sample 3 also turned blue-black after heating.

[Preparation of reduced phosphomolybdic acid ink]
Various solvents were added to Sample 2 obtained in Preparation Example 2 so that the concentration of Sample 2 was 10 mg / mL.
The results are shown in Table 1. Sample 2 was confirmed to dissolve well in water, linear alcohol and methyl ethyl ketone.

[Evaluation of reduced phosphomolybdic acid by X-ray photoelectron spectroscopy (XPS)]
XPS measurement of samples 1 to 3 was performed, and the ratio of Mo (V) and the peak top position of the molybdenum (Mo) peak were examined. The apparatus used was a Theta Probe manufactured by Thermo Fisher Scientific Co., Ltd., using AlKα as a light source, and X-rays were monochromatized using a spectroscopic crystal. The path energy of the analyzer that determines the resolution of the peak was 50 eV. The peak position derived from C1s was set to 285.0 eV, and the energy axis (horizontal axis) was corrected.

[Comparative Example 1]
PMA powder that was not subjected to reduction treatment was dissolved in 1-butanol and formed into a film with a thickness of 30 nm by spin coating, and then XPS measurement was performed without heat treatment.

[Comparative Example 2]
The PMA powder not subjected to reduction treatment was dissolved in 1-butanol, formed into a film of 30 nm by spin coating, and subjected to heat treatment at 100 ° C. for 10 minutes in a nitrogen atmosphere, and then XPS measurement was performed.

[Comparative Example 3]
The PMA powder not subjected to the reduction treatment was dissolved in 1-butanol, formed into a film of 30 nm by spin coating, and subjected to a heat treatment at 200 ° C. for 10 minutes in a nitrogen atmosphere, and then XPS measurement was performed.

[Example 1]
Sample 1 obtained in Preparation Example 1 was dissolved in 1-butanol and formed into a film with a thickness of 30 nm by spin coating, and then XPS measurement was performed without heat treatment.

[Example 2]
Sample 2 obtained in Preparation Example 2 was dissolved in 1-butanol and formed into a film with a thickness of 30 nm by spin coating, and then XPS measurement was performed without heat treatment.

[Example 3]
Sample 3 obtained in Preparation Example 3 was dissolved in 1-butanol and formed into a film with a thickness of 30 nm by spin coating, and then XPS measurement was performed without heat treatment.

[Example 4]
Sample 3 obtained in Preparation Example 3 was dissolved in 1-butanol, spin-coated to a thickness of 30 nm, subjected to heat treatment at 100 ° C. for 10 minutes in a nitrogen atmosphere, and then XPS measurement was performed.

  The spectra obtained in Comparative Examples 1 to 3 and Examples 1 to 4 and the results obtained by fitting are shown in FIG.

From the low binding energy side, there are four spectra corresponding to Mo 3d _5/2 Mo (V) peak and Mo (VI) peak, and Mo3d _3/2 Mo (V) peak and Mo (VI) peak. There was a peak component. Each peak area was weighted with a sensitivity factor to determine the ratio of the valence of Mo. The ratio of Mo (V) was 24% in Comparative Example 3 heated at 200 ° C., whereas In Examples 1-4, it turned out that 32% or more has a high ratio. Patent Document 1 describes a heteropolyoxometalate mixed with Mo (V), but its Mo (V) ratio is as low as 15%. Looking at the results of the hole-only device, which will be described later, it can be seen that the drive voltage of the device is high at a ratio of 15%, but the drive voltage drastically decreases when the ratio is higher. Therefore, it is very important to increase the Mo (V) ratio beyond 15%.

Moreover, in this invention, the space | interval of the peak derived from Mo (VI) and Mo (V) of _{Mo3d3 / 2} and Mo3d5 _{/ 2} was large. In the case of Comparative Example 3 heated at 200 ° C. after being formed on a thin film, it was 1.17 eV, whereas reduced phosphomolybdic acid heated in advance at 200 ° C. according to the present invention was applied to form a film. All have a large interval of 1.30 eV or more. Therefore, the peak is divided into four. This shows that what is obtained by the present invention is essentially different from a sample heated after a known thin film.

[Preparation of hole-only devices]
In order to evaluate the hole injection characteristics, devices of ITO (130 nm) / hole injection layer (10 nm) / α-NPD (90 nm) / MoO ₃ (5 nm) / Al (100 nm) were fabricated. Here, the hole injection layer was as follows. The hole injection layer was formed by spin coating, and α-NPD, MoO ₃ , and Al were formed by vapor deposition.

[Comparative Example 4]
PMA powder not subjected to reduction treatment was dissolved in acetonitrile, and a film was formed to 10 nm by spin coating. Thereafter, no heat treatment was performed.

[Comparative Example 5]
PMA powder not subjected to reduction treatment was dissolved in acetonitrile, and a film was formed to 10 nm by spin coating. Thereafter, heat treatment was performed at 100 ° C. for 10 minutes in a nitrogen atmosphere.

[Comparative Example 6]
PMA powder not subjected to reduction treatment was dissolved in acetonitrile, and a film was formed to 10 nm by spin coating. Thereafter, heat treatment was performed at 200 ° C. for 10 minutes in a nitrogen atmosphere.

[Example 5]
Sample 2 obtained in Preparation Example 2 was dissolved in 1-butanol and formed into a film of 10 nm by spin coating. Thereafter, no heat treatment was performed.

The current density-voltage characteristics of the element are shown in FIG. Table 3 shows the voltage at 20 mA / cm ² .

  The comparative example was not driven at a low voltage unless heated at a high temperature of 200 ° C. after the thin film was formed. On the other hand, the thing of Example 5 which was not heated after thin film film formation showed the driving voltage significantly lower than the thing of the comparative example 4 which was not heated after thin film film formation similarly. This indicates that the effect of reducing phosphomolybdic acid is exerted. The driving voltage was almost the same as that of Comparative Example 6 heated at 200 ° C. after the thin film was formed. As is clear from the above, the reduced phosphomolybdic acid of the present invention showed higher hole injection characteristics than the conventional phosphomolybdic acid. Therefore, the same effect can be expected in an organic electroluminescence element using the thin film. Although it is not known to what extent it should be reduced to Mo (V), it can be said that a Mo (V) ratio of 15% or more is necessary because Comparative Example 5 had a high driving voltage.

[Production of organic EL element]
ITO (130 nm) / hole injection layer (10 nm) / α-NPD (90 nm) / CBP: 8 wt% Ir (ppy) ₃ (30 nm) / BAlq (10 nm) / Alq3 (40 nm) / Liq (1 nm) / Al ( 100 nm) was produced.

  The hole injection layer was formed by spin coating as shown in Comparative Examples 7 and 8 and Example 6. The other layers were formed by vapor deposition.

[Comparative Example 7]
PMA powder not subjected to reduction treatment was dissolved in acetonitrile, and a film was formed to 10 nm by spin coating. Thereafter, no heat treatment was performed.

[Comparative Example 8]
PMA powder not subjected to reduction treatment was dissolved in acetonitrile, and a film was formed to 10 nm by spin coating. Thereafter, heat treatment was performed at 200 ° C. for 10 minutes in a nitrogen atmosphere.

[Example 6]
Sample 2 obtained in Preparation Example 2 was dissolved in 1-butanol and formed into a film of 10 nm by spin coating. Thereafter, no heat treatment was performed.

FIG. 4 shows the current density-voltage characteristics of the element. Table 4 shows the voltage at 20 mA / cm ² .

  As in the case of the hole-only device, the reduced phosphomolybdic acid of the present invention, which was not heated after the thin film was formed, had a driving voltage significantly lower than that of Comparative Example 7, The driving voltage was as low as that of Comparative Example 8 in which the acid was heated at 200 ° C. In other words, it can be said that the reduced phosphomolybdic acid was successfully synthesized without the need for post-treatment after thin film formation.

[Example 7]
ITO (150 nm) / TFB (1 nm) / reduced PMA (1 nm) / CH ₃ NH ₃ PbI ₃ (500 nm) / C ₇₀ (30 nm) / B4PyMPM (4 nm) / Ag (80 nm) perovskite solar cell element Was prepared by the following procedure.
First, a 3 mm wide ITO / glass substrate with ITO patterned in stripes was washed with detergent and pure water, dried in an oven at 65 ° C. overnight, and then surface-treated with a UV-ozone apparatus for 10 minutes. It was. A TFB p-xylene solution (0.2 mg / ml) was spin-coated thereon as a hole injection layer. Next, a 1-butanol solution (1 mg / ml) of PMA subjected to reduction treatment was spin-coated. After lightly washing the film-formed surface with DMF, a solution of CH ₃ NH ₃ I and PbI ₂ in N, N-dimethylformamide (DMF) is spin-coated, and chlorobenzene is dropped on the surface immediately after spin coating. A highly crystalline CH ₃ NH ₃ PbI ₃ perovskite film was formed. Thereafter, the substrate was moved to a vacuum evaporation apparatus, an electron transport layer, the C ₇₀ and B4PyMPM turn, it was formed by vacuum deposition. Finally, a metal shadow mask with a stripe width of 3 mm was set, and Ag was deposited by vacuum evaporation. The obtained solar cell element was sealed by adhering a glass sealing cap with an adhesive, and then the element characteristics were evaluated by a solar cell characteristic measuring apparatus manufactured by Spectrometer Co., Ltd.

[Comparative Example 9]
A device was fabricated in the same manner as in Example 7 without using PMA. The element structure is ITO (150 nm) / TFB (1 nm) / CH ₃ NH ₃ PbI ₃ (500 nm) / C ₇₀ (30 nm) / B4PyMPM (4 nm) / Ag (80 nm).
The device characteristics were evaluated in the same manner as in Example 7.

[Comparative Example 10]
A device was fabricated in the same manner as in Example 7 using PEDOT: PSS instead of PMA. The element structure is ITO (150 nm) / TFB (1 nm) / PEDOT: PSS (40 nm) / CH ₃ NH ₃ PbI ₃ (500 nm) / C ₇₀ (30 nm) / B4PyMPM (4 nm) / Ag (80 nm).
The device characteristics were evaluated in the same manner as in Example 7.

表５に示す通り、還元処理を行ったＰＭＡを用いた太陽電池素子は、１７．９％と最も高い効率を示し、得られた開放電圧が高いことから電圧ロスが少なく、優れた特性を示すことが分かった。
太陽電池の電流−電圧特性、及び、各波長における分光感度特性を図５に示す。実施例７をＴＦＢ／ＰＭＡ、比較例１０をＴＦＢ／ＰＥＤＯＴ：ＰＳＳ、比較例１１をＰＥＤＯＴ：ＰＳＳとして示した。いずれも、ＰＭＡを用いた太陽電池素子の特性が最も高く、優れた電子デバイスを提供することが分かった。 [Comparative Example 11]
A device was fabricated in the same manner as in Example 7 using only PEDOT: PSS instead of TFB / PMA. The element structure is ITO (150 nm) / PEDOT: PSS (40 nm) / CH ₃ NH ₃ PbI ₃ (500 nm) / C ₇₀ (30 nm) / B4PyMPM (4 nm) / Ag (80 nm).
The device characteristics were evaluated in the same manner as in Example 7.
[Solar cell characteristics evaluation results]
The solar cell characteristics of the elements of Example 7, Comparative Example 9, Comparative Example 10, and Comparative Example 11 were evaluated. Among these, in the device of Comparative Example 9, when the CH ₃ NH ₃ PbI ₃ solution was spin-coated on the TFB layer, a phenomenon that the surface of the TFB layer repels the solution, and the uniform CH ₃ NH ₃ PbI was generated. _Three layers could not be formed, and as a result, an element showing solar cell characteristics could not be obtained. Accordingly, the elements of Example 7, Comparative Example 10, and Comparative Example 11 were able to evaluate the solar cell characteristics. The element characteristics are as follows.

As shown in Table 5, the solar cell element using the PMA subjected to the reduction treatment has the highest efficiency of 17.9%, and since the obtained open voltage is high, the voltage loss is small and excellent characteristics are exhibited. I understood that.
FIG. 5 shows the current-voltage characteristics of the solar cell and the spectral sensitivity characteristics at each wavelength. Example 7 was shown as TFB / PMA, Comparative Example 10 as TFB / PEDOT: PSS, and Comparative Example 11 as PEDOT: PSS. In any case, it was found that the solar cell element using PMA has the highest characteristics and provides an excellent electronic device.

Claims (10)

  A reduced heteropolyoxometalate characterized in that the proportion of Mo (V) -derived peaks among molybdenum (Mo) peaks measured by X-ray photoelectron spectroscopy (XPS) is 30% or more. Obtained by fitting the spectrum measured by XPS,
The difference in peak top position between the Mo (VI) -derived peak and the Mo (V) -derived peak in the Mo 3d _3/2 binding energy peak;
The difference in peak top positions between the Mo (VI) -derived peak and the Mo (V) -derived peak in the Mo 3d _5/2 binding energy peak is 1.30 eV or more on average, respectively. 2. The reduced heteropolyoxometalate according to 1.   A method for producing a reduced heteropolyoxometalate, comprising spreading a heteropolyacid on a flat bottom plate and heating the plate.   A method for producing a reduced heteropolyoxometalate, wherein a solution obtained by dissolving a heteropolyacid in a solvent is dropped into a flat bottom dish in a thin film form and heated.   The reduced heteropolyoxometalate according to claim 3 or 4, wherein the heteropolyacid is at least one selected from the group consisting of phosphomolybdic acid, silicomolybdic acid, and phosphotungstomolybdic acid.   An ink comprising the reduced heteropolyoxometalate according to claim 1 and an organic solvent or water.   The ink according to claim 6, wherein the organic solvent is alcohol, a carbonyl group-containing compound, or tetrahydrofuran.   An organic electronic device using the reduced heteropolyoxometalate according to claim 1.   It is an organic electroluminescent element, The organic electronic device of Claim 8 characterized by the above-mentioned.   The organic electronic device according to claim 8, wherein the organic electronic device is a solar cell element.

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