JP6201345B2 - Method for producing ITO particles - Google Patents

Description

The present invention relates to a method for producing ITO particles suitable for use in electronic devices that need to electrically bond dissimilar materials such as solar cells, touch panels, and liquid crystal panels. In this specification, ITO refers to indium tin oxide.

  Conventionally, a super straight type thin film solar cell in which a composite film composed of a transparent conductive film and a conductive reflective film is formed on a photoelectric conversion layer as a back electrode by a wet coating method is disclosed (for example, see Patent Document 1). An ITO particle is shown as one of the conductive oxide fine particles contained in the composition for forming the transparent conductive film. The ITO particles are prepared by mixing an aqueous alkaline solution with a mixed aqueous solution of indium compound and tin compound to produce a coprecipitated hydroxide of indium and tin, washing the precipitate with water, discarding the supernatant of the precipitate and indium. It is manufactured by preparing a slurry in which tin hydroxide particles are dispersed, drying the slurry, and firing the dried indium hydroxide tin oxide.

  In consideration of the power generation efficiency of the solar cell, it is desirable that the work function of the ITO particles as the main component of the back electrode is as low as possible. The work function of ITO particles manufactured by the conventional method is 5.33 eV when measured by the Kelvin method, while the work function of the photoelectric conversion layer made of amorphous silicon or polycrystalline silicon, that is, the power generation layer, is determined by the Kelvin method. When measured, it was 4.8 eV, and the difference from the work function of the ITO particles was 0.53 eV. The Kelvin method is a method of measuring a work function of a target sample by measuring a contact potential difference between a sample and a measurement electrode and correcting a metal having a known work function with a reference electrode. As the reference electrode, gold having a known work function, a natural oxide film, and a stable surface is generally used.

  Patent Document 2 describes that the work function of a transparent electrode generally formed of ITO is 4.5 to 5.1 eV, and in this example, it is provided on one side of ITO having a film thickness of 150 nm. It is described that it is a glass substrate with ITO. The ITO transparent conductive film provided on this glass substrate is usually formed by a sputtering method, and its work function is measured by ultraviolet photoelectron spectroscopy (UPS), and the difference from the Si work function of 4.05 eV is 0.45. Since it is ˜1.05 eV, when measured by the Kelvin method, the work function of the ITO transparent conductive film formed by the sputtering method is estimated to be 5.25 to 5.95 eV.

JP2009-088489A (summary, paragraph [0042]) JP 2006-351721 A (paragraphs [0024] and [0034])

  The work function range of ITO particles produced by firing dried indium water tin oxide by the conventional method is more than 5.3 eV and not more than 5.4 eV (measured value by Kelvin method). It is easy to cause a work function difference between the back electrode of the solar cell and the power generation layer, and this difference forms an energy barrier at the interface of the ITO particles, which makes it difficult to improve the power generation efficiency of the solar cell. there were. Specifically, when different types of materials are electrically bonded, a potential barrier is formed at the bonding interface (called a Schottky barrier) when the work function difference between the two materials is 0.5 eV or more. When this is formed, it becomes a barrier when electrons propagate, and the interface becomes a high resistance layer. When ITO particles are used for the back electrode of a solar cell, the power generation efficiency of the solar cell is reduced when the interface between ITO and Si becomes high resistance.

The object of the present invention is to reduce the energy barrier at the interface between the ITO particles and the power generation layer when the ITO particles are used for the back electrode of the solar cell, thereby improving the power generation efficiency of the solar cell. It is in providing the method of manufacturing . Another object of the present invention is to provide a transparent conductive film formed of an ITO conductive film paint containing the ITO particles, so that a work function difference between the power generation layer and the back electrode mainly composed of the ITO particles is obtained. It is providing the manufacturing method of the solar cell which can improve the electric power generation efficiency of a solar cell by reducing this.

The first aspect of the present invention is to irradiate ultraviolet rays while stirring a slurry of indium tin hydroxide, which is a coprecipitate of indium and tin, and dry the slurry-like indium tin hydroxide after irradiation. Baked and pulverized aggregates formed by this baking to produce ITO powder, impregnated by putting this ITO powder in a surface treatment liquid, and then heated, based on gold, Kelvin method This is a method for producing ITO particles characterized by having a work function in the range of 4.8 to 5.3 eV when measured repeatedly.
The second aspect of the present invention, the indium tin hydroxide slurry is co-precipitate of indium and tin by spraying the N ₂ gas in circulation is gasified by ultrasonic, the indium tin hydroxide This is a method for producing ITO particles having a work function in the range of 4.8 to 5.3 eV when repeatedly measured by the Kelvin method on the basis of gold by thermally decomposing the product.
The third aspect of the present invention, after drying the slurry of indium tin hydroxide is coprecipitate Lee indium and tin and baking, the ITO powder was ground formed aggregates by this calcination The ITO powder prepared and further pulverized with this ITO powder was impregnated in a surface treatment solution, and then heated, so that when measured repeatedly with the Kelvin method based on gold, 4.8-5. It is a method for producing ITO particles having a work function in the range of 3 eV.
A fourth aspect of the present invention is a method for producing an ITO conductive film paint from ITO particles produced by the method according to any one of the first to third aspects.
A fifth aspect of the present invention is a method for forming a transparent conductive film using the ITO conductive film paint according to the fourth aspect .
Furthermore, a sixth aspect of the present invention is a method for manufacturing a solar cell having a transparent conductive film formed by the method of the fifth aspect .

Since the ITO particles produced by the methods of the first to third aspects of the present invention have a work function in the range of 4.8 to 5.3 eV lower than the conventional 5.33 eV when measured by the Kelvin method, When used for the back electrode of a solar cell, the energy barrier at the interface between the ITO particles and the power generation layer can be reduced, thereby improving the power generation efficiency of the solar cell.
The manufacturing method of the solar cell of the 6th viewpoint of this invention has a transparent conductive film formed with the ITO electrically conductive film coating material containing ITO particle | grains, Between a power generation layer and the back surface electrode which has ITO particle | grains as a main component. The power generation efficiency of the solar cell can be improved by reducing the difference in the work functions.

It is a figure which shows the relationship between the work function of each ITO particle of Examples 1-6 and Comparative Example 1, and the curve factor calculated from the thin film photovoltaic cell produced using each ITO particle for a back surface electrode.

Next, the form for implementing this invention is demonstrated. The present invention is a method for producing ITO particles having a work function in the range of 4.8 to 5.3 eV, which is lower than the conventional 5.33 eV when measured by the Kelvin method. A work function of 4.8 eV is the minimum value that can be reached with current technology. When it exceeds 5.3 eV, when used for the back electrode of the solar cell, an energy barrier at the interface between the ITO particles and the power generation layer is likely to be formed, and thus the power generation efficiency of the solar cell cannot be improved. . Since the work function of ITO is larger than that of Si at the interface between ITO and Si, it is necessary to lower the work function of ITO in order to reduce the work function difference between ITO and Si. As a method for lowering the work function of ITO, there are firstly a method of increasing the carrier concentration of ITO and secondly a method of modifying the surface of ITO particles. Based on this idea, the present inventors have found three manufacturing method of lowering the work function below. The first manufacturing method promotes the homogenization of the solid solution of In and Sn by irradiating the hydroxide in a state in which In and Sn are heterogeneously mixed in the particles immediately after generation with ultraviolet rays. As a result, the work function of the ITO particles can be lowered by increasing the carrier concentration of the ITO particles and suppressing the segregation of SnO 2 on the ITO surface. In the second production method, the atomized hydroxide slurry is poured into a heated furnace and rapidly heated and pyrolyzed to suppress the segregation of SnO2 on the ITO surface, and the reduction. By increasing the carrier concentration of the ITO particles by heating in the atmosphere, the work function of the ITO particles can be lowered. The third method of preparation is changed by heating under atmosphere, by increasing the carrier concentration of the ITO particles, it is possible to lower the work function of the ITO particles.

A specific method for producing ITO particles for lowering the work function of the ITO particles will be described below. However, the method for producing ITO particles of the present invention is not limited to these three methods.

(1) First Production Method A trivalent indium compound and a divalent or tetravalent tin compound are precipitated in a solution in the presence of an alkali to form a coprecipitated hydroxide of indium and tin. At this time, by adjusting the pH of the solution to 4.0 to 9.3, preferably pH 6.0 to 8.0, and the liquid temperature to 5 ° C. or higher, preferably 10 ° C. to 80 ° C. Co-precipitated hydroxide can be precipitated. In order to adjust the liquid property during the reaction to pH 4.0 to 9.3, for example, a mixed aqueous solution of indium trichloride (InCl ₃ ) and tin dichloride (SnCl ₂ · 2H ₂ O) is used. It is preferable that the alkaline aqueous solution is simultaneously dropped into water to adjust the pH range. Alternatively, the above mixed solution is dropped into an alkaline aqueous solution. As the alkaline aqueous solution, ammonia (NH ₃ ) water, ammonium hydrogen carbonate (NH ₄ HCO ₃ ) water, or the like is used.

After the coprecipitated indium tin hydroxide is formed, the precipitate is washed with pure water and washed until the supernatant has a resistivity of 5000 Ω · cm or more, preferably 50000 Ω · cm or more. If the resistivity of the supernatant liquid is lower than 5000 Ω · cm, impurities such as chlorine are not sufficiently removed, and high-purity indium tin oxide powder cannot be obtained. Discard the supernatant of the precipitate with a resistivity of 5000 Ω · cm or more, make it into a slurry with high viscosity, and irradiate with ultraviolet rays in the range of 126 to 365 nm for 1 to 50 hours while stirring this slurry. To do. If the wavelength of ultraviolet rays is less than the lower limit value, a general-purpose ultraviolet irradiation device cannot be used, and if the upper limit value is exceeded, the ultraviolet absorption of the precipitate is poor and the effect of irradiating ultraviolet rays cannot be obtained. If the irradiation time is less than the lower limit value, the precipitate does not absorb much ultraviolet light, and the effect of irradiating the ultraviolet light cannot be obtained, and even if the upper limit value is irradiated, the effect cannot be obtained.
After irradiation with ultraviolet rays, the slurry-like indium tin hydroxide is dried in the atmosphere, preferably in an inert gas atmosphere such as nitrogen or argon, in the range of 100 to 200 ° C. for 2 to 24 hours, and then in the atmosphere 250 to Bake at 800 ° C. for 0.5-6 hours. Aggregates formed by this firing are pulverized using a hammer mill, a ball mill, or the like, and ITO particles are obtained. The ITO particles were impregnated with a solution obtained by mixing 50 to 95 parts by mass of absolute ethanol and 5 to 50 parts by mass of distilled water, and then placed in a glass petri dish in a nitrogen gas atmosphere in the range of 200 to 400 ° C. When heated for 0.5 to 5 hours, the ITO particles of the present invention are obtained. The work function of the ITO particles can be controlled by changing the irradiation time of the ultraviolet rays.

(2) Second manufacturing method After discarding the supernatant of the precipitate, which is the indium tin coprecipitated hydroxide obtained by the first manufacturing method, to obtain slurry-like indium tin hydroxide, the longitudinal direction of the tube In a state where N ₂ gas which is a carrier gas is circulated inside a tubular furnace heated in the range of 250 to 800 ° C., the slurry-like indium tin hydroxide is added at a frequency exceeding 40 kHz to 2 MHz. spraying N ₂ gas in circulation is gasified by waves. When the ultrasonic frequency is less than the lower limit, the droplets containing atomized indium tin hydroxide are large, and the content of indium tin hydroxide in the droplet is large. There is a problem of sintering and coarsening, and when the upper limit is exceeded, there is a problem that the efficiency of atomization deteriorates. Thereby, indium tin hydroxide is thermally decomposed in the tubular furnace, and the ITO particles of the present invention are obtained from the outlet of the tubular furnace. The work function of the ITO particles can be controlled by changing the gas flow rate and the furnace temperature.

( 3 ) Third production method After removing the supernatant of the precipitate, which is the indium tin coprecipitated hydroxide obtained by the first method, to obtain slurry-like indium tin hydroxide, this indium tin hydroxide The product is dried in the atmosphere, preferably in an inert gas atmosphere such as nitrogen or argon, in the range of 100 to 200 ° C. for 2 to 24 hours, and then fired in the range of 250 to 800 ° C. for 0.5 to 6 hours. . Aggregates formed by this firing are pulverized using a hammer mill, a ball mill, or the like, and ITO particles are obtained. The ITO particles are pulverized using a jet mill so that the average particle diameter is in the range of 5 to 15 nm. Thereafter, in the same manner as in the first method, the ITO particles are impregnated with a solution obtained by mixing absolute ethanol and distilled water, then placed in a glass petri dish and heated in a nitrogen gas atmosphere. Is obtained. The work function of the ITO particles can be controlled by changing the time and temperature of the treatment.
In addition, the average particle diameter of ITO particle | grains in this specification means the average particle diameter based on number distribution. In the present invention, the average diameter is 200.

  Next, examples of the present invention will be described in detail together with comparative examples.

<Example 1>
First, 50 mL of an indium chloride (InCl ₃ ) aqueous solution containing 18 g of In metal and 0.36 g of tin dichloride (SnCl ₂ .2H ₂ O) are mixed, and this mixed aqueous solution and an aqueous ammonia (NH 3) solution are added to 500 mL of water. At the same time, the solution was added dropwise to adjust the pH to 7. The reaction was carried out for 30 minutes with the liquid temperature at 30 ° C. The generated precipitate of indium tin coprecipitated hydroxide was repeatedly washed with ion-exchanged water using an inclined exchange. When the resistivity of the supernatant liquid reached 50,000 Ω · cm or more, the supernatant liquid of the precipitate was discarded, and the slurry was stirred into a high-viscosity slurry. The deep UV type was selected using 9), and ultraviolet rays were irradiated for 5 hours so that the central illuminance of the irradiated liquid surface was 50 mW / cm ² or more. Thereafter, the slurry-like indium tin hydroxide was dried in the atmosphere at 110 ° C. overnight, then baked in the atmosphere at 550 ° C. for 3 hours, and the aggregate was pulverized and loosened to obtain about 25 g of ITO powder. 25 g of this ITO powder was impregnated in a mixed liquid of absolute ethanol and distilled water (mixing ratio was 5 parts by mass of distilled water with respect to 95 parts by mass of ethanol), and then placed in a glass petri dish under a nitrogen gas atmosphere. The ITO particles of the present invention were obtained by heating at 0 ° C. for 2 hours.

<Example 2>
The ITO particles of the present invention were obtained in the same manner as in Example 1 except that the condensing mirror for irradiating the indium tin coprecipitated hydroxide slurry of Example 1 with ultraviolet rays was set to the standard type.

<Example 3>
50 mL of indium chloride (InCl ₃ ) aqueous solution containing 18 g of In metal and 0.6 g of tin dichloride (SnCl ₂ .2H ₂ O) are mixed, and this mixed aqueous solution and aqueous ammonia (NH ₃ ) solution are simultaneously added to 500 mL of water. It was dripped and adjusted to pH7. The reaction was carried out for 30 minutes with the liquid temperature at 30 ° C. The generated precipitate of indium tin coprecipitated hydroxide was repeatedly washed with ion-exchanged water using an inclined exchange. When the resistivity of the supernatant liquid became 50000 Ω · cm or more, the supernatant liquid of the precipitate was discarded to obtain slurry-like indium tin hydroxide. This slurry was diluted with absolute ethanol so that the solid content was 1.0%, and the inside of the tubular furnace, which was placed with the longitudinal direction of the tube vertical, was sufficiently replaced with nitrogen, and then heated to 600 ° C., In a state where the carrier gas, N ₂ gas, was circulated inside the tubular furnace, slurry-like indium tin hydroxide was atomized with 100 kHz ultrasonic waves and sprayed onto the circulating N ₂ gas. At this time, the flow rate of the circulating gas was set to 0.5 m / s. Thereby, indium tin hydroxide was thermally decomposed in the tubular furnace, and ITO particles of the present invention were obtained from the outlet of the tubular furnace.

<Example 4>
After discarding the supernatant of the precipitate, which is the indium tin coprecipitated hydroxide obtained in Example 2, to obtain slurry-like indium tin hydroxide, the indium tin hydroxide was removed from the atmosphere, preferably nitrogen or Indium tin hydroxide powder dried in the range of 100 to 200 ° C. for 15 hours under an inert gas atmosphere such as argon was obtained. A dispersion solution in which this indium tin hydroxide powder is ultrasonically dispersed in ethanol at a solid content of 1.0% is put in a quartz glass container, and is expanded by a magnetic stirrer, while being oscillated by a Nd: YAG laser at 266 nm. Laser light was irradiated. The intensity of the laser beam was 100 mJ (100 mJ / pulse) per pulse, the pulse width of the laser beam was 20 ns, the peak value (peak power) was 100 MW, and the laser oscillation frequency (pulse period) was 30 Hz. The solution in which the ITO nanopowder obtained after the laser irradiation was dispersed was solid-liquid separated and dried to obtain ITO particles of the present invention.

<Example 5>
After discarding the supernatant of the precipitate, which is the indium tin coprecipitated hydroxide obtained in Example 2, to obtain slurry-like indium tin hydroxide, the indium tin hydroxide was removed at 110 ° C. in the atmosphere at 15 ° C. After drying for an hour, it was calcined at 600 ° C. for 3 hours in the atmosphere. Aggregates formed by this firing were pulverized and loosened using a hammer mill, ball mill, or the like to obtain ITO particles. The ITO particles are pulverized using a jet mill so that the average particle diameter is in the range of 5 to 15 nm. Thereafter, in the same manner as in the first method, the ITO particles were impregnated in a mixed liquid of absolute ethanol and distilled water, and then placed in a glass petri dish and heated at 400 ° C. for 5 hours in a nitrogen gas atmosphere. Thus, ITO particles of the present invention were obtained.

<Example 6>
In the production method of Example 5, the ITO particles of the present invention were obtained in the same manner as in Example 5 except that the heating condition was changed to 250 ° C. for 1 hour.

<Comparative Example 1>
In metal: 200 g was added to 600 cm ³ of 12N-HCl and completely dissolved to prepare an indium chloride solution. 33 g of a 60 mass% aqueous solution of SnCl ₄ was added to this indium chloride solution to prepare a mixed solution of InCl ₃ —SnCl ₄ (Sn / In ratio: 0.05). Next, 550 g of ammonium carbonate was dissolved in ion-exchanged water to prepare a liquid amount: 4.5 dm 3 and a temperature: 30 ° C. The total amount of InCl ₃ —SnCl ₄ liquid was added dropwise to the aqueous ammonia carbonate solution while stirring for about 20 minutes to form a coprecipitate, which was further stirred for 30 minutes. At this time, the final pH of the reaction solution was 4.5. The coprecipitate was collected, dehydrated with a centrifuge, and subjected to centrifugal filtration while adding ion-exchanged water and washing. When the specific resistance of the filtrate reached 5000 Ω · cm or more, the centrifugal filtration was terminated. Next, the coprecipitate was dried overnight at 100 ° C., then thermally decomposed at 600 ° C. for 3 hours, and pulverized to obtain 213 g of indium tin oxide powder of Comparative Example 1.

[Measurement of work function of ITO particles]
The work function of each ITO particle obtained in Examples 1 to 4 and Comparative Example 1 was measured by the following method. First, the ITO particles are put into a flat dish-shaped stainless steel particle holder having a diameter of 10 mm and a depth of 1 mm, and then the ITO particles are compressed using a slide glass so that the ITO particles do not collapse, and the packing density is 2 to 3 g / cm. ^The particle holder was filled so as to be ³ . This was dried in a dryer at 60 ° C. for 1 hour or longer to remove moisture adsorbed from the ITO particles. The moisture content was 0.8%. The compressed body of ITO particles was taken out from the particle holder, allowed to cool at room temperature for 5 minutes, and the contact potential difference was measured within 5 minutes. The measurement is performed using a gold-plated chip with a Kelvin probe (manufactured by KP Technology; model SKP 020), and the 50 times integration is repeated 3 times, and the average value of the contact potential difference with the gold plated on the chip is measured. The sum of the average value of the contact potential difference and the gold work function (5.10 eV) was used as the work function of the ITO particles. The results are shown in Table 1 below.

[Production of ITO transparent conductive film]
20 g of each ITO particle obtained in Examples 1 to 4 and Comparative Example 1 was distilled water (0.020 g), triethylene glycol-di-2-ethylhexanoate [3G] (23.8 g), absolute ethanol (2.1 g), phosphoric acid polyester (1.0 g), 2-ethylhexanoic acid (2.0 g), and 2,4-pentanedione (0.5 g) were mixed and dispersed. The prepared dispersion was diluted with absolute ethanol until the content of ITO particles as a solid content was 10% by mass. The diluted dispersion was applied to a quartz glass plate by spin coating to form a film, and an ITO transparent conductive film having a thickness of 0.2 μm was obtained.

[Manufacture of conductive film paint, transparent conductive film and solar cell]
An ITO conductive film paint was prepared from each ITO particle obtained in Examples 1 to 6 and Comparative Example 1, and this paint was applied onto the photoelectric conversion layer of the super straight type thin film solar cell, that is, the power generation layer, by a wet coating method. A transparent conductive film was formed. This solar cell was composed of another transparent conductive film made of FTO (fluorine-doped SnO ₂ ), a photoelectric conversion layer (power generation layer), the transparent conductive film, and a conductive reflective film on a transparent glass substrate. A back electrode was formed on the top.

  The conductive film paint was prepared by the following method. That is, 1.0% by mass of each ITO particle obtained in Examples 1 to 6 and Comparative Example 1, 0.2% by mass of a siloxane polymer obtained by hydrolyzing ethyl silicate as a binder, and the following formula ( 0.01% by mass of the organic coupling agent shown in 1) was added, and ethanol was added as a dispersion medium to make the whole 100% by mass. A conductive film coating material was prepared by dispersing ITO particles in the mixture by operating this mill for 2 hours using a dyno mill (horizontal bead mill) and zirconia beads having a diameter of 0.3 mm.

  Next, the conductive film coating is applied onto the power generation layer thus formed by spin coating so that the film thickness after baking is 80 nm, and the coating film is baked at 200 ° C. for 30 minutes to form a transparent conductive film on the back side. Formed. The film thickness after firing was measured by a photograph of the cross section taken by SEM. The ratio of ITO particles / binder in the transparent conductive film on the back side obtained by firing was 2/1 in the ratio of ITO particles / binder. The firing temperature was determined by measuring four temperatures at the corners of a 10 cm square glass substrate, and setting the average value within ± 5 ° C. of the set temperature (200 ° C.).

  Further, an Ag nano ink in which an Ag colloid having an average particle size of 0.03 μm is dispersed in an ethanol solvent so as to have a film thickness after firing of 200 nm by spin coating on the transparent conductive film on the back side. The coating film was baked at 200 ° C. for 30 minutes to form a reflective electrode film on the back side. Thereby, a multi-junction thin film silicon solar cell for evaluation was obtained.

[Calculation of optimum operating point and fill factor of solar cell]
A lead wire is wired on the substrate after the line processing of the solar cell of the multi-junction thin film silicon solar cell for evaluation obtained by the above-described method, and using a solar simulator and a digital source meter, AM: 1.5, An IV (current-voltage) curve was obtained when light of 100 mW / cm ² was irradiated. While the maximum power V _m × I _{m is obtained by} setting the voltage at the optimum operating point in this curve as V _m and the current as I _m , the open circuit voltage VOC which is the maximum value of the voltage of this curve and the short circuit current I which is the maximum value of the current seek _SC, was calculated fill factor from _{(V m × I m) /} (V OC × I SC). This curve factor is shown in Table 1 and FIG.

[Calculation of conversion efficiency of solar cell power generation layer]
Furthermore, the JV (current density-voltage) curve was calculated | required by remove | dividing the electric current value (I) in the obtained IV (current-voltage) curve by the surface area of a thin film photovoltaic cell. In this JV curve, the output in the area when the area of the rectangle drawn by connecting the origin and the point on the JV curve with the voltage axis and the current density axis as two sides is maximized. The maximum power density (mW / cm ² ) was set, and [maximum power density (mW / cm ² )] / [100 (mW / cm ² )] × 100 was defined as the conversion efficiency of the power generation layer. Table 1 shows the conversion efficiency of the power generation layer of the solar cell used in the transparent conductive film containing the ITO particles of Examples 1 to 6 and Comparative Example 1.

<Evaluation>
As is clear from Table 1, the ITO particle work function of Comparative Example 1 was 5.33 eV, whereas the ITO particles of Examples 1 to 6 had a work function of 4 ITO particles. It was possible to control within the range of .80 to 5.30. Further, as is clear from Table 1 and FIG. 1, the performance as a solar cell was higher in the curve factors of Examples 1 to 6 than in Comparative Example 1, and was found to be excellent in conversion efficiency.

Claims (6)

  The indium tin hydroxide slurry, which is a co-precipitate of indium and tin, is irradiated with ultraviolet rays, and after the irradiation, the slurry-like indium tin hydroxide is dried and fired. The agglomerates were pulverized to produce an ITO powder. The ITO powder was impregnated in a surface treatment solution, and then heated, so that when measured repeatedly with the Kelvin method based on gold, 4.8 to A method for producing ITO particles having a work function in the range of 5.3 eV. Indium tin hydroxide slurry is co-precipitate of indium and tin by spraying the N ₂ gas in circulation is gasified by ultrasonic, the indium tin hydroxide by pyrolysis, a gold A method for producing ITO particles having a work function in the range of 4.8 to 5.3 eV when repeatedly measured by the Kelvin method as a reference.   The slurry of indium tin hydroxide, which is a coprecipitate of indium and tin, was dried and then fired, and the aggregate formed by this firing was pulverized to produce an ITO powder, and this ITO powder was further pulverized This ITO powder is impregnated in a surface treatment solution, and then heated to produce ITO particles having a work function in the range of 4.8 to 5.3 eV when repeatedly measured by the Kelvin method with gold as a reference. How to manufacture. Method for producing an ITO conductive coating of ITO particles prepared by the method according to any one of claims 1 to 3. The method to form a transparent conductive film using the ITO electrically conductive film coating material manufactured by the method of Claim 4 . The manufacturing method of the solar cell which has a transparent conductive film formed by the method of Claim 5 .

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