JP5505642B2 - Oxide deposition material - Google Patents

Description

The present invention relates to an oxide vapor deposition material used for producing a transparent conductive film by various vacuum vapor deposition methods such as an electron beam vapor deposition method, an ion plating method, and a high density plasma assisted vapor deposition method, and more particularly to a solar cell. The present invention relates to an improvement in an oxide vapor deposition material for producing a high-quality transparent conductive film having a low resistance and a high transmittance from the visible to the near infrared region, which is useful as a transparent electrode.

  The transparent conductive film has high conductivity and high light transmittance in the visible light region. And taking advantage of this characteristic, the transparent conductive film is used for electrodes of solar cells, liquid crystal display elements, other various light receiving elements, etc., and further, utilizing the reflection / absorption characteristic in the near infrared region, it can be used for automobiles and buildings. It is also used as a heat-reflective film used for window glass, various antistatic films, and a transparent heating element for anti-fogging such as a frozen showcase.

The transparent conductive film generally has tin oxide (SnO ₂ ) containing antimony or fluorine as a dopant, aluminum, gallium, indium, zinc oxide (ZnO) containing tin as a dopant, tin, tungsten or titanium as a dopant. Indium oxide (In ₂ O ₃ ) and the like are widely used. In particular, an indium oxide film containing tin (tin) as a dopant, that is, an In ₂ O ₃ —Sn film, is called an ITO (Indium tin oxide) film, and is widely used because a transparent conductive film with low resistance can be easily obtained. Has been.

  As a method for producing these transparent conductive films, a vacuum deposition method, a sputtering method, or the like is generally used. These methods are effective when using materials with low vapor pressure or when precise film thickness control is required, and are industrially useful because they are very simple to operate. is there. Further, when the vacuum deposition method and the sputtering method are compared, the vacuum deposition method is superior in mass productivity because it can form a film at a higher speed.

By the way, in the vacuum deposition method, in general, in a vacuum of about 10 ⁻³ to 10 ⁻² Pa, a solid or liquid as an evaporation source is heated to be decomposed once into gas molecules and atoms, and then again on the substrate surface. It is a method of condensing as a thin film. Further, although there are various heating methods for the evaporation source, a resistance heating method (RH method) and an electron beam heating method (EB method, electron beam evaporation method) are common. A reactive vapor deposition method is also well known in which vapor deposition is performed while introducing a reactive gas such as O ₂ gas into a film forming chamber (chamber).

In the case of depositing an oxide film such as ITO, the electron beam evaporation method has been used historically. That is, an ITO oxide vapor deposition material (also referred to as an ITO tablet or an ITO pellet) is used as an evaporation source, an O ₂ gas as a reaction gas is introduced into a film forming chamber (chamber), and a thermoelectron generating filament (mainly W When the thermal electrons emitted from the line) are accelerated by an electric field and irradiated onto the ITO oxide vapor deposition material, the irradiated portion becomes locally high in temperature and evaporated to be deposited on the substrate. In addition, it is possible to produce a low-resistance film on a low-temperature substrate by generating plasma using a thermionic emitter or RF discharge and activating evaporates and reactive gases (O ₂ gas etc.) with this plasma. An activated reactive vapor deposition method (ARE method) that can be used is also a useful method for forming an ITO film. Furthermore, recently, it has become clear that a high-density plasma-assisted vapor deposition method (HDPE method) using a plasma gun is also an effective method for forming an ITO film, and has begun to be widely used industrially (see Non-Patent Document 1). . In this method, arc discharge using a plasma generator (plasma gun) is used, but arc discharge is maintained between a cathode built in the plasma gun and a crucible (anode) of an evaporation source. Electrons emitted from the cathode are guided (guided) by a magnetic field and are concentrated and irradiated on the local area of the ITO oxide deposition material charged in the crucible. The evaporated material is evaporated and deposited on the substrate from the portion where the electron beam is irradiated and locally heated. Since the evaporated vapor and the introduced O ₂ gas are activated in this plasma, an ITO film having good electrical characteristics can be produced. Further, as another classification method of these various vacuum deposition methods, those accompanied by ionization of evaporates and reaction gases are collectively referred to as an ion plating method (IP method), and ITO with low resistance and high light transmittance is used. It is effective as a method for obtaining a film (see Non-Patent Document 2).

  By the way, in any type of solar cell to which the transparent conductive film is applied, the transparent conductive film is indispensable for the front side electrode to which light hits, and conventionally, the above-described ITO film or the like has been used. These transparent conductive films are required to have characteristics such as low resistance and high light transmittance of sunlight. Further, as a method for producing these transparent conductive films, vacuum deposition methods such as the above-described ion plating method and high-density plasma assist deposition method are used.

  The oxide deposition material used in the vacuum deposition methods such as the electron beam deposition method, ion plating method, and high density plasma assisted deposition method has a small size (for example, a diameter of 10 to 50 mm and a height of about 10 to 50 mm). Therefore, there is a limit to the amount of film that can be formed with one oxide vapor deposition material. Then, when the consumption amount of the oxide vapor deposition material increases and the remaining amount decreases, the film formation is interrupted, the vacuum film formation chamber is introduced into the atmosphere and replaced with an unused oxide vapor deposition material, and the film is formed. It was necessary to evacuate the chamber again, which caused productivity to deteriorate.

  Therefore, a continuous supply method of the above-mentioned oxide deposition material is cited as an indispensable technique for mass production of transparent conductive films by vacuum deposition methods such as electron beam deposition, ion plating, and high density plasma assisted deposition. One example is described in Non-Patent Document 1. In this continuous supply method, columnar oxide vapor deposition materials are continuously stored inside a cylindrical hearth, and the oxide vapor deposition materials are sequentially extruded while maintaining the height of the sublimation surface constant. It comes to be supplied. And the mass production of the transparent conductive film by a vacuum evaporation method came to be realizable by the continuous supply method of an oxide vapor deposition material.

Regarding the oxide vapor deposition material used as a raw material, Patent Document 1 introduces an ITO vapor deposition material. It is substantially an In ₂ O ₃ —SnO ₂ type particle composed of indium, tin and oxygen, and the volume of one particle is 0.01 to 0.5 cm ³ and the relative density is 55% or more. Further, an ITO vapor deposition material having a bulk density of 2.5 g / cm ³ or less when filled in a container has been proposed. With the above configuration, an ITO evaporation material that can stably form a low-resistance ITO film by electron beam evaporation, has a utilization efficiency of 80% or more, and can be continuously supplied without clogging in the supply machine. Is obtained.

  In addition, as the indium oxide-based transparent conductive film other than ITO, materials having various compositions have been introduced as a raw material by sputtering, that is, as a sputtering target material. For example, Patent Document 2 and Patent Document 3 introduce a technique relating to a cerium-containing indium oxide sputter target material (In-Ce-O) and a transparent conductive film obtained by sputtering from the sputter target material. Yes. And since the indium oxide type transparent conductive film containing cerium introduced in Patent Document 2 has poor reactivity with Ag, the transparent conductive film having high permeability and excellent heat resistance is laminated by stacking with an Ag type ultrathin film. It is introduced that a film can be realized, and Patent Document 3 introduces that a film excellent in etching property can be obtained. Patent Document 4 introduces that a crystalline transparent conductive film (crystalline In—W—O) made of indium oxide containing tungsten is useful for a transparent electrode of a solar cell. Furthermore, the transparent conductive film made of indium oxide containing gadolinium obtained by the pulse laser deposition method has both high conductivity and high transmittance in the visible to near-infrared region and is useful as a transparent electrode for solar cells. It has recently become clear (see Non-Patent Document 3).

  These indium oxide-based transparent conductive films other than ITO have a low resistance and excellent light transmission performance in the visible light region, as well as compared to the ITO films and zinc oxide-based films that have been used conventionally. The light transmission performance in the near-infrared region is excellent, and when such a transparent conductive film is used for the front electrode of the solar cell, the energy of near-infrared light can also be used effectively.

JP-A-8-104978 Japanese Patent No. 3445891 JP 2005-290458 A JP 2004-43851 A

`` Vacuum '', Vol.44, No.4, 2001, p.435-439 "Technology of transparent conductive film", Ohmsha, 1999, p. 205-211 R. K. Gupta et al., “High mobility, transparent, conducting Gd-doped In2O3thin films by pulsed laser deposition”, Thin Solid Films 516 (2008) 3204-3209

  However, there are few technologies relating to oxide vapor deposition materials for stably forming the above-described indium oxide-based transparent conductive films other than ITO by vacuum vapor deposition, and in particular, there has been an increasing worldwide demand for solar cells in recent years. However, there have been very few techniques relating to oxide vapor deposition materials and vapor deposition films that can effectively produce a transparent conductive film useful as a transparent electrode for solar cells by vapor deposition.

  For this reason, the manufacturing technology of the sintered compact of a sputtering target has been diverted until now about the oxide vapor deposition material used with a vacuum evaporation method. However, using a conventional oxide vapor deposition material manufactured by such a diversion technique, low resistance and high light can be achieved by various vacuum vapor deposition methods such as electron beam vapor deposition, ion plating, and high density plasma assisted vapor deposition. When manufacturing a transparent conductive film having transparency, it is necessary to introduce a large amount of oxygen gas into a film-forming vacuum chamber during film formation, and thus the following problems arise mainly.

  First, the composition deviation of a transparent conductive film and an oxide vapor deposition material becomes large, and the composition design of a transparent conductive film becomes difficult. This is because, generally, when the amount of oxygen introduced into the film-forming vacuum chamber increases, the difference in composition between the transparent conductive film and the oxide vapor deposition material tends to increase. In the film formation mass production process, the amount of oxygen in the film formation vacuum chamber is likely to fluctuate, and accordingly, the film composition is likely to fluctuate due to the influence thereof, leading to variations in film characteristics.

  In reactive vapor deposition using oxygen gas, when the amount of oxygen increases, not only the density of the film decreases, but also the adhesion of the film to the substrate weakens. This is because if the evaporated metal oxide is oxidized before reaching the substrate, energy is lost, and if the rate of oxidation increases, it becomes difficult to obtain a dense and highly adhesive film with respect to the substrate.

  Furthermore, when a transparent conductive film is formed on a substrate covered with a metal film or organic film whose surface is easily oxidized, if there is a large amount of oxygen gas to the film formation vacuum chamber, the substrate surface will be oxidized before film formation. As a result, high-performance devices cannot be manufactured. This tendency becomes more prominent as the substrate temperature during film formation is higher. For example, when manufacturing a solar cell that converts energy by making light incident from the surface opposite to the substrate, it is necessary to form a transparent conductive film on the PIN element formed of a metal thin film. If a large amount of film is formed, the element is easily damaged and a high-performance device cannot be manufactured. The same applies to the formation of organic thin-film solar cells and top-emission type organic electroluminescence elements. When a transparent conductive film is formed on an organic light-emitting layer, the organic light-emitting layer is oxidized under conditions where a large amount of oxygen is introduced. Therefore, a high-performance element cannot be realized.

The present invention has been made paying attention to such problems, and the problem is that the main component is indium oxide to which gadolinium is added, and low resistance is achieved even if the amount of oxygen introduced during film formation is small. Then, it is providing the oxide vapor deposition material which can manufacture stably the transparent conductive film which has a high light transmittance not only in a visible region but in a near infrared region.

That is, the invention according to claim 1
In oxide vapor deposition materials,
It is composed of a sintered body containing indium oxide as a main component and containing gadolinium, and the gdolinium content is 0.001 to 0.070 in terms of Gd / In atomic ratio, and the L ^* value in the CIE1976 color system is 60. ~ 94,
The invention according to claim 2
In the oxide vapor deposition material according to the invention of claim 1,
The gadolinium content is 0.030 to 0.050 in terms of Gd / In atomic ratio.

The oxide vapor deposition material according to the present invention is composed of a sintered body containing indium oxide as a main component and containing gadolinium, the gadolinium content is 0.001 to 0.070 in terms of Gd / In atomic ratio, and the CIE 1976 table. The L ^* value in the color system is 60 to 94.

And since the oxide vapor deposition material which concerns on this invention whose L ^* value in a CIE1976 colorimetric system is 60-94 has the optimal oxygen amount, film-forming vacuum is applied by applying this oxide vapor deposition material. Even if the amount of oxygen gas introduced into the tank is small, it becomes possible to produce a transparent conductive film having a low resistance and a high permeability in the visible to near infrared region by the vacuum deposition method, and the oxygen gas to the film forming vacuum tank Since the introduction amount of the material is small, it is possible to reduce the difference in composition between the film and the oxide vapor deposition material, and it is easy not only to obtain the target film composition but also to reduce the fluctuation of the film composition and the characteristic during mass production. It becomes possible. In addition, since film formation with a small amount of oxygen gas introduced into the film formation vacuum chamber can reduce damage to the substrate due to oxygen gas, a high-performance device can be realized. In particular, a high-performance film useful for solar cells can be stably produced without damaging the substrate.

  In addition, by applying the oxide vapor deposition material according to the present invention, it is possible to produce a transparent conductive film exhibiting high conductivity while exhibiting high light transmittance not only in the visible region but also in the near infrared region by a vacuum deposition method. It becomes.

Explanatory drawing which shows schematic structure of the silicon-type solar cell using the transparent conductive film to which the oxide vapor deposition material which concerns on this invention was applied as an electrode layer. Explanatory drawing which shows schematic structure of the compound thin film type solar cell which used the electrode layer comprised by the transparent conductive film to which the oxide vapor deposition material which concerns on this invention was applied for the glass substrate side. Explanatory drawing which shows schematic structure of the compound thin film type solar cell which used the electrode layer comprised by the transparent conductive film to which the oxide vapor deposition material which concerns on this invention was applied on the opposite side to a glass substrate.

  Hereinafter, embodiments of the present invention will be described in detail.

(1) Oxide vapor deposition material The oxide vapor deposition material of the present invention has a composition in which indium oxide is a main component and gadolinium is contained in a Gd / In atomic ratio of 0.001 to 0.070. . And since the composition of the transparent conductive film manufactured by the vacuum evaporation method using the oxide vapor deposition material of the present invention is very close to the composition of the oxide vapor deposition material, the film composition to be manufactured is also composed mainly of indium oxide. And it becomes a composition which the composition of gadolinium contains only in the ratio of 0.001-0.070. The reason why gadolinium is contained in the above ratio is that the mobility of the indium oxide film can be increased. When the film composition, that is, the gadolinium content (Gd / In atomic ratio) of the oxide vapor deposition material composition is less than 0.001, the effect of increasing the mobility is small and a low resistance film cannot be obtained. On the other hand, if it exceeds 0.070, the amount of gadolinium in the film is too large, and neutral impurity scattering at the time of electron transfer increases, so that the mobility is lowered and a low resistance film cannot be obtained. Furthermore, the more preferable content of gadolinium for exhibiting higher mobility to obtain a low resistance film is 0.030 to 0.050 in terms of the Gd / In atomic ratio.

  By the way, the transparent conductive film containing indium oxide as a main component is an n-type semiconductor, but an appropriate oxygen deficiency is required in order to exhibit high conductivity and high light transmittance. That is, when the amount of oxygen in the film is large and the amount of oxygen vacancies is small, even if it contains a dopant, it does not exhibit conductivity. In order to exhibit conductivity, it is necessary to introduce oxygen vacancies into the film. However, if the amount of oxygen vacancies is too large, light absorption of visible light increases, which causes coloring. Therefore, the film needs to have an optimal oxygen deficiency. Oxygen in the film is supplied not only from the oxide vapor deposition material as a raw material but also by oxygen gas introduced into the film formation vacuum chamber during film formation being taken into the film. And if there is little supply from an oxide vapor deposition material, it is necessary to increase the amount of oxygen gas introduced into the film-forming vacuum chamber, but as described above, the amount of oxygen gas introduced into the film-forming vacuum chamber is increased. Problems arise. Therefore, an oxide vapor deposition material having an optimal oxygen amount is useful.

And, the oxide vapor deposition material according to the present invention is characterized in that it is defined by the L ^* value in the CIE 1976 color system. Here, the CIE 1976 color system is a color space recommended by the CIE (International Commission on Illumination) in 1976. Color, lightness L ^* and black Manet ticks indices a ^*, since those expressed in coordinates on a uniform color space of b ^*, are abbreviated as CIELAB. ^{L *} is showing the lightness ^{indicates black,} the diffuse color of white in the L * = 100 in ^L * = 0. Further, a ^* is a negative value for green, a positive value for magenta, b ^* is a negative value for blue, and a positive value for yellow.

And it is preferable that the color of the sintered body surface and the inside of the sintered body of the oxide vapor deposition material according to the present invention defined by the L ^* value in the CIE 1976 color system is the same, but it is temporarily different between the outermost surface and the inside. In the present invention, the L ^* value is determined for the inside of the sintered body.

According to an experiment by the inventors, when the L ^* value inside the oxide vapor deposition material is 60 to 94, high conductivity and high transmittance in the visible to near infrared region even if the amount of oxygen introduced into the deposition vacuum chamber is small. Can be obtained. Also, the whitish color has a higher L ^* value, while the darker the color, the lower the L ^* value. The L ^* value of the oxide vapor deposition material is considered to have a correlation with the amount of oxygen contained in the oxide vapor deposition material. The larger the L ^* value, the greater the amount of oxygen contained, and the smaller the L ^* value. It is considered that the oxygen content is small. The present inventor has changed manufacturing conditions, was experimented to produce a transparent conductive film by a vacuum deposition method using an oxide evaporation materials of various L ^* values, as L ^* value is large, during the film formation The optimum amount of oxygen to be introduced into (the amount of oxygen for obtaining a low resistance and high transparency film) was small. This is because the larger the L ^* value, the greater the amount of oxygen supplied from the oxide vapor deposition material itself. Further, the difference in composition between the film and the oxide vapor deposition material tends to increase as the amount of oxygen introduced increases. Therefore, the larger the L ^* value, the smaller the composition difference.

The oxide vapor deposition material according to the present invention has conductivity, and the conductivity of the oxide vapor deposition material depends on the oxygen content, but also on the density, the crystal grain size, and the gadolinium dopant efficiency. Therefore, the conductivity and L ^* value of the oxide vapor deposition material do not correspond one to one.

The oxide deposition material according to the present invention containing indium oxide as a main component and containing gadolinium generates evaporated particles mainly in the form of In ₂ O _3-x and Gd ₂ O _3-x during vacuum deposition. Then, oxygen is absorbed while reacting with oxygen in the chamber, and reaches the substrate to form a film. Further, when the evaporated particles reach the substrate and deposit on the substrate, the energy becomes a driving source for mass transfer, contributing to densification of the film and enhancement of adhesion to the substrate. Since the smaller the L ^* value of the oxide vapor deposition material, the less oxygen in the oxide vapor deposition material, the greater the oxygen deficiency of the evaporated particles, so that a large amount of oxygen is introduced into the vacuum chamber before reaching the substrate. It is necessary to increase the rate of oxidation reaction. However, since the evaporated particles consume energy by being oxidized during the flight, it is difficult to obtain a dense film having high adhesion to the substrate in the reactive film in which a large amount of oxygen is introduced. On the contrary, the reactive vapor deposition film forming the oxygen gas to be introduced as much as possible is easier to obtain a highly adherent and high density film, and the oxide vapor deposition material of the present invention can realize this.

Here, when the L ^* value is less than 60, the amount of oxygen in the oxide vapor deposition material is too small, so the optimum amount of oxygen introduced into the film formation vacuum chamber for obtaining a film with low resistance and high transparency. This is not preferable because not only the compositional difference between the film and the oxide vapor deposition material increases, but also problems such as increased damage to the substrate occur during film formation. On the other hand, if the L ^* value exceeds 94, the amount of oxygen contained in the oxide deposition material is too large, so that too much oxygen is supplied from the oxide deposition material to the film, resulting in an optimal oxygen deficiency. It is impossible to obtain a highly conductive film.

By the way, as described above, JP 2005-290458 A (Patent Document 3) introduces a sputtering target of an indium oxide sintered body containing cerium, but according to the manufacturing method described in Patent Document 3. When an indium oxide sintered body containing gadolinium is produced, the L ^* value of the indium oxide sintered body containing gadolinium is a low value of 35 to 55. Therefore, when such a sintered body is used as an oxide vapor deposition material, it is necessary to increase the amount of oxygen introduced into a film formation vacuum chamber for obtaining an optimum film, and thus the above-described problem occurs. Therefore, the object of the present invention has not been achieved.

Here, the oxide sintered body for vapor deposition (oxide vapor deposition material) of the present invention having the L ^* value of 60 to 94 cannot be produced by a conventional technique for producing a sputtering target. An oxide vapor deposition material having an appropriate amount of oxygen (or oxygen deficiency) suitable for use in mass production by a vacuum vapor deposition method can be produced by the following method.

  That is, an oxide sintered body containing indium oxide as a main component and containing gadolinium is obtained by using indium oxide and gadolinium oxide powders as raw materials, mixing and molding these to form a green compact, and firing it at a high temperature. Then, it can be produced by reaction and sintering. Each powder of indium oxide and gadolinium oxide is not special, and may be a conventionally used raw material for an oxide sintered body. Moreover, the average particle diameter of the powder used is 1.5 micrometers or less, Preferably it is 0.1-1.1 micrometers.

  A ball mill mixing method is used as a general raw material powder mixing method for manufacturing the oxide sintered body, but it is also effective in manufacturing the sintered body of the present invention. A ball mill is a device that makes a fine mixed powder by grinding and mixing materials by putting hard balls (ball diameter 1 to 5 mm) such as ceramics (mainly zirconia) and material powder into a container and rotating them. It is. Ball mills (grinding media) include steel, stainless steel, nylon, etc. as can bodies, and alumina, magnetic material, natural silica, rubber, urethane, etc. are used as linings. There are wet and dry pulverization methods such as alumina balls with alumina as the main component, natural silica, nylon balls with iron core, zirconia balls, etc., for mixing and pulverizing raw material powder to obtain a sintered body Widely used.

  Further, as a method other than the ball mill mixing, a bead mill method or a jet mill method is also effective. In particular, it is very effective when a raw material having a large average particle diameter is used or when it is necessary to pulverize and mix in a short time. In the bead mill method, 70-90% of beads (crushed media, bead diameter: 0.005-3 mm) are filled in a container called a vessel, and the rotation axis at the center of the vessel is set at a peripheral speed of 7-15 m / sec. Giving motion to the beads by rotating. Here, a slurry in which a material to be crushed, such as raw material powder, is mixed with a liquid is fed by a pump and finely pulverized and dispersed by colliding beads. In the case of a bead mill, efficiency can be improved by reducing the bead diameter according to the object to be crushed. In general, a bead mill can achieve pulverization and mixing at an acceleration close to 1,000 times that of a ball mill. The bead mill with such a structure is called by various names. For example, sand grinder, aquamizer, attritor, pearl mill, avex mill, ultra visco mill, dyno mill, agitator mill, coball mill, spike mill, SC mill Etc. are known, and any of them can be used in the present invention. In addition, the jet mill is a method in which high-pressure air or steam injected from a nozzle at around the sonic velocity is collided with an object to be crushed such as raw material powder as an ultra-high speed jet, and pulverized into fine particles by impact between particles. .

  As described above, first, indium oxide powder and gadolinium oxide powder are put into a ball mill pot at a desired ratio, and mixed powder is prepared by dry or wet mixing. And in order to obtain the oxide sintered compact of this invention, it prepares so that content of an indium and gadolinium may be 0.001-0.070 by Gd / In atomic ratio about the mixture ratio of the said raw material powder. To do.

  A slurry is produced by adding water and an organic substance such as a dispersing agent / binder to the mixed powder thus prepared. The viscosity of the slurry is preferably 150 to 5000 cP, more preferably 400 to 3000 cP.

  Next, the obtained slurry and beads are placed in a bead mill container and processed. Examples of the bead material include zirconia and alumina. Zirconia is preferable in terms of wear resistance. The diameter of the beads is preferably 1 to 3 mm from the viewpoint of grinding efficiency. The number of passes may be one, but it is preferably two or more, and a sufficient effect can be obtained by five or less. Moreover, as processing time, Preferably it is 10 hours or less, More preferably, it is 4 to 8 hours.

  By performing such a treatment, the pulverization and mixing of the indium oxide powder and the gadolinium oxide powder in the slurry are improved.

Next, it shape | molds using the slurry processed in this way. As the molding method, either a cast molding method or a press molding method can be employed. When cast molding is performed, the obtained slurry is injected into a casting mold to produce a molded body. The time from bead mill treatment to casting is preferably within 10 hours. It is because it can prevent that the slurry obtained by doing in this way shows thixotropic property. Moreover, when performing press molding, binders, such as polyvinyl alcohol, are added to the obtained slurry, moisture adjustment is performed as needed, and it is dried with a spray dryer etc. and granulated. The obtained granulated powder is filled in a metal mold of a predetermined size, and thereafter, uniaxial pressure molding is performed at a pressure of 100 to 1000 kg / cm ² using a press machine to obtain a molded body. The thickness of the molded body at this time is preferably set to a thickness capable of obtaining a sintered body having a predetermined size in consideration of shrinkage caused by the subsequent firing step.

  When manufacturing an oxide sintered compact using the molded object produced from the above-mentioned mixed powder, it is preferable to manufacture by an atmospheric pressure sintering method with low manufacturing cost. When an oxide sintered body is obtained by firing by this normal pressure sintering method, it is as follows.

First, the obtained molded body is heated at a temperature of 300 to 500 ° C. for about 5 to 20 hours to perform a binder removal treatment. Thereafter, sintering is performed by raising the temperature, but the rate of temperature rise is 150 ° C./hour or less, preferably 100 ° C./hour or less, more preferably 80 ° C., in order to effectively release internal vacancies to the outside. / Hour or less. The sintering temperature is 1150 to 1300 ° C, preferably 1200 to 1250 ° C, and the sintering time is 1 to 20 hours, preferably 2 to 5 hours. It is important that the binder removal process to the sintering process be performed by introducing oxygen into the furnace at a rate of 5 liters / minute or more per 0.1 m ^{3 of} the furnace volume. The reason why oxygen is introduced in the sintering step is to prevent the sintered body from dissociating oxygen at 1150 ° C. or higher and easily proceeding to an excessive reduction state. The dissociation of oxygen becomes more severe as the firing temperature becomes higher, and oxygen vacancies are more likely to occur on the surface side than the center of the sintered body. Therefore, when firing is performed at a temperature exceeding 1300 ° C., unevenness in the oxygen deficiency concentration in the sintered body tends to occur. If the oxygen deficiency concentration unevenness is large, the oxygen deficiency concentration unevenness may not be eliminated not only in the outermost surface of the sintered body but also in the sintered body in the subsequent oxygen adjusting step, which is not preferable. Moreover, if the firing temperature is less than 1150 ° C., the temperature is too low and the sintering is poor, and a sintered body with sufficient strength cannot be obtained.

  After sintering, an oxygen content adjusting step of the sintered body is performed. It is important that the oxygen amount adjusting step is performed at a heating temperature of 900 to 1100 ° C., preferably 950 to 1050 ° C., and the heating time is 10 hours or more. Cooling to the heating temperature in the oxygen amount adjusting step is performed while continuing the introduction of oxygen, and the temperature is decreased at a temperature decreasing rate of 0.1 to 20 ° C./min, preferably 2 to 10 ° C./min.

In the process of adjusting the amount of oxygen in the sintered body, it is particularly important to control the atmosphere in the furnace, and the gas introduced into the furnace has a mixing ratio (volume ratio) of oxygen and argon of O ₂ / Ar = 40/60 to 90/10. Therefore, it is important to control the flow rate within a range of 5 liters / minute or more per 0.1 m ^{3 of} the furnace volume. By precisely adjusting the temperature, atmosphere, and time, a sintered body having the L ^* value defined in the present invention, which is useful when used as an oxide deposition material, can be obtained.

When the heating temperature in the oxygen amount adjusting step is less than 900 ° C., the oxygen dissociation / adsorption reaction is slow, and it takes time for uniform reduction treatment to the inside of the sintered body. If it is performed at a temperature, the dissociation of oxygen is too intense, and an optimal reduction treatment in the above atmosphere becomes impossible. Further, if the heating temperature in the oxygen amount adjusting step is less than 10 hours, it is not preferable because uniform reduction treatment cannot be performed to the inside of the sintered body. Further, if the mixing ratio (O ₂ / Ar) of the gas introduced into the furnace is less than 40/60, the reduction due to the dissociation of oxygen becomes too dominant, and the sintered body has an L ^* value of less than 60. Therefore, it is not preferable. On the contrary, if the mixing ratio of the gas introduced into the furnace (O ₂ / Ar) exceeds 90/10, the oxidation becomes too dominant and the L ^* value exceeds 94, which is not preferable. .

  In order to obtain the oxide vapor deposition material of the present invention, as described above, annealing treatment is performed in a gas atmosphere in which oxygen gas is precisely diluted with argon gas, that is, in an atmosphere in which the amount of oxygen is precisely controlled. It is important that the atmosphere gas is not necessarily a mixed gas of oxygen and argon. For example, it is effective to use other inert gas such as helium or nitrogen instead of argon. Further, even when the atmosphere is used instead of argon, it is effective if the oxygen content is precisely and constantly controlled in the entire mixed gas. However, it is not effective to introduce oxygen gas into a furnace fired in the atmosphere as in the prior art because the oxygen content of the atmosphere in the furnace cannot be precisely controlled. As proposed in the present invention, an oxide vapor deposition material having an optimal reduced state is obtained by introducing a mixed gas with an inert gas whose oxygen gas content is precisely controlled to fill the furnace. Can be obtained.

  And after finishing an oxygen amount adjustment process, it can cool to room temperature at 10 degree-C / min, and can take out from a furnace at room temperature. The obtained sintered body can be processed into a predetermined dimension by grinding or the like to obtain an oxide vapor deposition material. Also, considering the shrinkage rate of sintering, if a molded body having a predetermined size after firing is used, it can be used as an oxide deposition material without performing grinding after sintering. it can.

By the way, it is known that the hot press method is effective as a method for obtaining a high-density sintered body as one of the methods for producing a sputtering target. However, when the hot pressing method is applied to the material of the present invention, only a sintered body having an L ^* value of 40 or less and an excessively strong reducing property can be obtained. With such a sintered body, the object of the present invention cannot be achieved.

  In addition, the oxide vapor deposition material of the present invention can be used, for example, in the form of a cylindrical tablet or pellet having a diameter of 10 to 50 mm and a height of 10 to 50 mm. Such a sintered body is pulverized. It can also be used in the form of granules of about 1 to 10 mm.

  In addition, the oxide vapor deposition material according to the present invention has the characteristics of the present invention even if, for example, tin, tungsten, molybdenum, zinc, titanium, yttrium, etc. are contained as elements other than indium, gadolinium, and oxygen. Is allowed on condition that it will not be damaged. However, among metal ions, when the vapor pressure of the oxide is extremely higher than the vapor pressure of indium oxide or gadolinium oxide, it is difficult to evaporate by various vacuum deposition methods, so it is preferable not to contain it. For example, metals such as aluminum, titanium, and silicon have vapor pressures of these oxides that are extremely high compared to indium oxide and gadolinium oxide. Therefore, when they are included in an oxide deposition material, they vaporize together with indium oxide and gadolinium oxide. It becomes difficult to make it. For this reason, it must remain in the oxide vapor deposition material to increase the concentration, and ultimately it should not be contained because it adversely affects the evaporation of indium oxide and gadolinium oxide.

  Further, in the oxide vapor deposition material according to the present invention, it may be formed of only an indium oxide phase in which gadolinium is replaced with indium sites, or an indium oxide phase in which gadolinium is replaced with indium sites and a gadolinium oxide phase are mixed. The form may be sufficient and the oxide compound phase of gadolinium and indium may be mixed in them.

  And when applying the oxide vapor deposition material of the present invention to produce a transparent conductive film by various vacuum vapor deposition methods, the oxygen content in the oxide vapor deposition material is optimally adjusted. Even if the amount of oxygen introduced is small, an optimal oxygen deficient transparent conductive film can be obtained. Therefore, there is an advantage that the compositional difference between the transparent conductive film and the oxide vapor deposition material is small, and it is difficult to be affected by the characteristic variation accompanying the variation of the oxygen introduction amount.

(2) Transparent conductive film It is composed of a sintered body containing indium oxide as a main component and containing gadolinium, and the gadolinium content is 0.001 to 0.070 in terms of Gd / In atomic ratio, and L in the CIE1976 color system. ^* Indium oxide containing gadolinium by applying the oxide deposition material according to the present invention having a value of 60 to 94 and various vacuum deposition methods such as an electron beam deposition method, an ion plating method and a high density plasma assisted deposition method. The crystal film can be manufactured.

By using a crystal film, high mobility can be exhibited when gadolinium is substituted and dissolved in the indium sites of indium oxide. The crystal film can be obtained by heating the substrate being formed to 180 ° C. or higher, but can also be obtained by annealing the film obtained by non-heated film formation without heating the substrate at 180 ° C. or higher. it can.

And since the said crystalline transparent conductive film can be manufactured from the oxide vapor deposition material of this invention which can make a composition difference of a film | membrane and an oxide vapor deposition material small, it is 0.001-0.070 by Gd / In atomic ratio. This is an indium oxide film containing gadolinium. When the gadolinium content (Gd / In atomic ratio) of the film is less than 0.001, the effect of increasing the mobility is small and a low resistance film cannot be obtained. On the other hand, if it exceeds 0.070, the amount of gadolinium in the film is so large that neutral impurity scattering during electron transfer becomes large, and the mobility is lowered and a low resistance film cannot be obtained. A more preferable content of gadolinium for obtaining a transparent conductive film with higher mobility is 0.030 to 0.050 in terms of the Gd / In atomic ratio. With such a composition range, a transparent conductive film having a hole mobility of 65 cm ² / V · s or more and a specific resistance of 5 × 10 ⁻⁴ Ωcm or less can be realized. Moreover, since the transparent conductive film in which the gadolinium content is 0.030 to 0.050 in terms of the Gd / In atomic ratio has a low carrier concentration, the average transmittance of the film itself at a wavelength of 400 to 1200 nm is 85% or more. And very high.

(3) Solar cell
Solar cell is a photoelectric conversion element that has use of the transparent conductive film as an electrode. The structure of the solar cell element is not particularly limited, and includes a PN junction type in which a p-type semiconductor and an n-type semiconductor are stacked, a PIN junction type in which an insulating layer (I layer) is interposed between the p-type semiconductor and the n-type semiconductor, and the like. Can be mentioned.

Solar cells are broadly classified according to the type of semiconductor. Solar cells using silicon-based semiconductors such as single crystal silicon, polycrystalline silicon, and amorphous silicon as photoelectric conversion elements, CuInSe systems, and Cu (In, Ga) Se systems , Ag (In, Ga) Se, CuInS, Cu (In, Ga) S, Ag (In, Ga) S and their solid solutions, GaAs, CdTe, and other compound semiconductor thin films It is classified into a compound thin film solar cell used as a photoelectric conversion element and a dye-sensitized solar cell using an organic dye (also referred to as a Gretzel cell solar cell). Efficiency can be realized. In particular, in a solar cell using amorphous silicon or a compound thin film solar cell, a transparent conductive film is indispensable for the electrode on which sunlight is incident (light receiving part side, front side), and the transparent conductive film is used. Can exhibit high conversion efficiency characteristics.

  When the silicon solar cell is outlined, the PN junction type solar cell element uses, for example, a monocrystalline or polycrystalline silicon substrate having a thickness of about 0.2 to 0.5 mm and a size of about 180 mm square. A PN junction in which a P layer containing a large amount of P-type impurities such as boron and an N layer containing a large amount of N-type impurities such as phosphorus are in contact with each other is formed inside the silicon substrate.

In place of the silicon substrate, a glass plate, a resin plate, a transparent substrate such as a resin film also Ru is used. In this case , after forming the transparent conductive film as an electrode on the substrate, amorphous or polycrystalline silicon is laminated and classified as a thin film silicon solar cell.

  Amorphous silicon is a PIN junction in which an insulating layer (I layer) is interposed between PN junctions. That is, as shown in FIG. 1, on a glass substrate 1, a front side (light receiving part side) transparent electrode film 2, a p-type amorphous silicon film or a hydrogenated amorphous silicon carbide film 3, and an amorphous silicon film containing no impurities 4, an n-type amorphous silicon film 5, a back-side transparent electrode film (contact improvement layer) 6, and a back-side metal electrode, that is, a back-side electrode 7. The p-type amorphous silicon film or hydrogenated amorphous silicon carbide film 3, the amorphous silicon film 4 containing no impurities, and the n-type amorphous silicon film 5 are usually formed by plasma CVD. These amorphous silicon film and hydrogenated amorphous silicon film may contain germanium, carbon, nitrogen, tin or the like in order to control the light absorption wavelength.

In addition, a thin film solar cell using a silicon thin film has a photoelectric conversion layer including a silicon thin film (that is, a PIN junction layer) formed of an amorphous silicon thin film, a film formed of a microcrystalline silicon thin film, amorphous silicon It is classified into a layer (tandem type thin film photoelectric conversion layer) composed of a laminate of a photoelectric conversion layer composed of a thin film and a photoelectric conversion layer composed of a microcrystalline silicon thin film. There is also a solar cell in which the number of stacked photoelectric conversion layers is three or more . Other, a photoelectric conversion layer of a single-crystal silicon plate or polycrystalline silicon plate, there shall have a photoelectric conversion layer of the hybrid type in which the thin-film photoelectric conversion layers are stacked.

  Next, the compound thin film solar cell will be described. A solar cell using a compound thin film is usually composed of a heterojunction of a compound semiconductor thin film (n-type semiconductor intermediate layer) having a wide band gap and a compound semiconductor (p-type semiconductor light absorbing layer) having a narrow band gap. ing. The general structure is: front electrode (transparent conductive film) / window layer / intermediate layer / light absorption layer / back electrode (metal or transparent conductive film).

Specifically, as shown in FIG. 2, on a glass substrate 12, a transparent electrode film 11 made of the transparent conductive film , a window layer 10, a semiconductor intermediate layer 9, and a p-type semiconductor light absorption layer. 8 and the back electrode 7 are laminated. Also, in FIG. 3, a glass substrate 12 is formed with a lower electrode, that is, a back electrode 13, a p-type semiconductor light absorption layer 8, a semiconductor intermediate layer 9, a window layer 10, and the transparent conductive film. A transparent electrode film 11 is laminated. In any structure, the transparent electrode film 11 side is the incident direction of sunlight.

The substrate is not particularly limited depending on the material such as glass, resin, metal, ceramic, etc., and may be transparent or non-transparent, but a transparent substrate is preferable. In the case of a resin, those having various shapes such as a plate shape and a film can be used. In the case of metals, examples include stainless steel and aluminum, and examples of ceramics include alumina, zinc oxide, carbon, silicon nitride, and silicon carbide. As oxides other than alumina and zinc oxide, oxides selected from Ga, Y, In, La, Si, Ti, Ge, Zr, Sn, Nb or Ta may be used. Examples of these oxides include Ga ₂ O ₃ , Y ₂ O ₃ , In ₂ O ₃ , La ₂ O ₃ , SiO ₂ , TiO ₂ , GeO ₂ , ZrO ₂ , SnO ₂ , Nb ₂ O ₅ , Ta ₂ O _{5 and the} like can be mentioned. In this specification, these glass, resin, and ceramic substrates are referred to as non-metallic substrates. It is desirable that the surface of the substrate is provided with a mountain-shaped unevenness on at least one side, and is roughened by etching or the like so as to easily reflect incident sunlight.

  Further, as the back electrodes 7 and 13, conductive electrode materials such as Mo, Ag, Au, Al, Ti, Pd, Ni, and alloys thereof are used, and any of Mo, Ag, Au, or Al is preferable. . Usually, the thickness is 0.5 to 5 μm, preferably 1 to 3 μm. The forming means is not particularly limited, and for example, a direct current magnetron sputtering method, a vacuum deposition method, a CVD method, or the like can be used.

As the p-type semiconductor constituting the light absorption layer 8, CuInSe ₂ , CuInS ₂ , CuGaSe ₂ , CuGaSe ₂ , AgInSe ₂ , AgInS ₂ , AgGaSe ₂ , AgGaS _2, and their solid solutions and CdTe can be used. is there. The conditions required to obtain higher energy conversion efficiency are the optimal optical design to obtain more photocurrent, high quality heterojunction without carrier recombination at the interface or especially the absorbing layer and It is to make a thin film. Usually, the thickness is 1 to 5 μm, preferably 2 to 3 μm. The forming means is not particularly limited, and for example, a vacuum deposition method, a CVD method, or the like can be used. Further, the high-quality heterointerface has a deep relationship with the combination of the intermediate layer / absorbing layer, and is a CdS / CdTe system, CdS / CuInSe ₂ system, CdS / Cu (In, Ga) Se ₂ system, CdS / Ag (In, Ga). ) Heterojunctions useful in Se ₂ systems and the like can be obtained.

In order to increase the efficiency of the solar cell, a semiconductor having a wider band gap, for example, CdS, CdZnS, or the like is used as a semiconductor thin film constituting the intermediate layer 9. These semiconductor thin films can improve sensitivity of short wavelengths in sunlight. Usually, the thickness is 10 to 200 nm, preferably 30 to 100 nm. The means for forming the intermediate layer 9 is not particularly limited. In the case of a CdS thin film, it is formed by a solution deposition method using a mixed solution of CdI ₂ , NH ₄ Cl ₂ , NH ₃ and thiourea. Further, on the incident light side of CdS or (Cd, Zn) S which is the intermediate layer 9, a semiconductor having a larger band gap than these thin films can be disposed as the window layer 10. Thereby, it becomes a high-performance solar cell with high reproducibility. The window layer 10 is composed of a thin film having a conductivity similar to that of a CdS thin film, such as a ZnO or (Zn, Mg) O thin film, and is usually 50 to 300 nm, preferably 100 to 200 nm thick. The window layer 10 is not particularly limited as a means for forming, but is formed by a direct current magnetron sputtering method using a target such as ZnO and Ar as a sputtering gas.

The solar cell uses a transparent conductive film formed by applying the oxide vapor deposition material of the present invention to an electrode (front surface and / or back surface) on which the sunlight enters in a compound thin film solar cell. In addition, since the transparent conductive film has lower resistance and higher transmittance than the conventional transparent conductive film, high conversion efficiency can be realized.

  By the way, in any type of solar cell element described above, a bus bar electrode and a finger electrode are formed on the light receiving surface (front surface) side and the back surface side by a screen printing method using a silver paste, respectively. The electrode surface is solder coated over almost the entire surface in order to facilitate its protection and connection tab attachment. When the solar cell element is a silicon substrate, a transparent protective material such as a glass plate, a resin plate, or a resin film is provided on the light receiving surface side.

Further, the thickness of the transparent conductive film constituting the electrode is not particularly limited and is preferably 150 to 1500 nm, particularly preferably 200 to 900 nm, although it depends on the composition of the material. And since the said transparent conductive film is low resistance and has the high transmittance | permeability of the sunlight which contains visible light of a wavelength of 400 nm-1200 nm to near infrared rays, it converts sunlight light energy into electrical energy very effectively. Can do.

In addition to the solar cell, the transparent conductive film is also useful as a transparent electrode of a light detection element, a touch panel, a flat panel display (LCD, PDP, EL, etc.), and a light emitting device (LED, LD, etc.). For example, in the case of a photodetection element, it includes a structure in which a glass electrode, a transparent electrode on the light incident side, a photodetection material layer such as infrared rays, and a back electrode are laminated. The photo-sensitive material layer for detecting infrared rays is a type using a semiconductor material based on Ge or InGeAs [photodiode (PD) or avalanche photodiode (APD)], sulfide of an alkaline earth metal element Alternatively, there is a type that uses a material in which one or more elements selected from Eu, Ce, Mn, and Cu and one or more elements selected from Sm, Bi, and Pb are added to the selenide. In addition, an APD using a laminate of amorphous silicon germanium and amorphous silicon is also known, and any of them can be used.

  Examples of the present invention will be specifically described below.

[Examples 1 to 4]
Preparation of oxide vapor deposition material In ₂ O ₃ powder having an average particle diameter of 0.8 μm and Gd ₂ O ₃ powder having an average particle diameter of 1 μm are used as raw material powders. These In ₂ O ₃ powder and Gd ₂ O _{The three} powders were prepared in such a ratio that the atomic ratio of Gd / In was 0.030, put into a resin pot, and mixed by a wet ball mill. At this time, hard ZrO ₂ balls were used, and the mixing time was 20 hours.

  After mixing, the slurry was taken out, and a polyvinyl alcohol binder was added to the resulting slurry, which was dried with a spray dryer or the like and granulated.

Using this granulated material, uniaxial pressure molding was performed at a pressure of 1 ton / cm ² to obtain a cylindrical shaped body having a diameter of 30 mm and a thickness of 40 mm.

  Next, the obtained molded body was sintered as follows.

That is, after debinding treatment of the molded body by heating for about 10 hours at 300 ° C. in the atmosphere in the sintering furnace, oxygen is supplied at a rate of 5 liters / minute per 0.1 m ^{3 of} the furnace volume. In the atmosphere to be introduced, the temperature was increased at a rate of 1 ° C./min and sintered at 1250 ° C. for 2 hours (atmospheric pressure sintering method). At this time, the temperature was lowered to 1000 ° C. at a rate of 10 ° C./min while introducing oxygen during cooling after sintering.

  Next, the introduced gas is switched to a mixed gas of oxygen and argon, heated and held at 1000 ° C. for 15 hours (hereinafter, this step is referred to as a sintered body oxygen content adjusting step), and then the temperature is lowered to room temperature at 10 ° C./min. did.

And the oxide sintered compact (oxide vapor deposition material) of various L ^* value was able to be obtained by changing the mixing ratio of oxygen of the said mixed gas, and argon.

  That is, the oxide vapor deposition material according to Example 1 is manufactured under the condition that the oxygen gas / argon gas flow rate ratio (that is, the volume ratio) is “40/60”, and the oxide vapor deposition material according to Example 2 has the above volume ratio. Manufactured under the condition of “60/40”, the oxide vapor deposition material according to Example 3 is produced under the condition that the volume ratio is “80/20”, and the oxide vapor deposition material according to Example 4 has the above volume. It is manufactured under the condition of the ratio “90/10”.

In addition, it was 4.3-5.0 g / cm < ³ > when the volume was calculated by measuring the volume and weight of the obtained oxide sintered compact (oxide vapor deposition material). Moreover, when the average value of 100 crystal grain diameters in an oxide sintered compact was calculated | required from the observation with the scanning electron microscope of the fracture surface of the said oxide sintered compact, all were 2-7 micrometers. Further, the specific resistance was calculated by measuring the surface resistance with respect to the electron beam irradiated surface of the oxide sintered body with a four-end needle method resistivity meter, and it was 1 kΩcm or less. Furthermore, composition analysis was performed on all oxide sintered bodies by ICP emission analysis, and it was found that they had a charged composition. Further, when the L ^* value in the CIE1976 color system was measured for the sintered body surface and the inside of the sintered body using a color difference meter (Spectroguide manufactured by BYK-Gardner GmbH, E-6834), almost the same value was obtained. showed that.

Table 1 shows the oxygen gas / argon gas flow rate ratio (that is, the volume ratio) of the mixed gas introduced in the sintered body oxygen content adjusting step and the L ^* value of the obtained oxide sintered body (oxide vapor deposition material). .

[Preparation of transparent conductive film, evaluation of film characteristics, evaluation of film formation]
(1) A magnetic field deflection type electron beam evaporation apparatus was used for the production of the transparent conductive film.
The evacuation system is composed of a low evacuation system using a rotary pump and a high evacuation system using a cryopump, and can evacuate up to 5 × 10 ⁻⁵ Pa. The electron beam is generated by heating the filament, accelerated by an electric field applied between the cathode and anode, bent in the magnetic field of a permanent magnet, and then irradiated onto an oxide deposition material installed in a tungsten crucible. The The intensity of the electron beam can be adjusted by changing the voltage applied to the filament. Further, the irradiation position of the beam can be changed by changing the acceleration voltage between the cathode and the anode.

  Film formation was performed under the following conditions.

Ar gas and O ₂ gas were introduced into the vacuum chamber to maintain the pressure at 1.5 × 10 ⁻² Pa. At this time, the characteristics of the transparent conductive film obtained by changing the mixing ratio of Ar gas and O ₂ gas introduced into the vacuum chamber were evaluated. A columnar oxide vapor deposition material of Examples 1 to 4 was placed upright on a tungsten crucible, and the central portion of the circular surface of the oxide vapor deposition material was irradiated with an electron beam on a Corning 7059 glass substrate having a thickness of 1.1 mm. A transparent conductive film having a thickness of 200 nm was formed on the substrate. The set voltage of the electron gun was 9 kV, the current value was 150 mA, and the substrate was heated to 250 ° C.

(2) The characteristics of the obtained thin film (transparent conductive film) were evaluated by the following procedure.
First, the surface resistance of the thin film (transparent conductive film) was measured with a four-end needle method resistivity meter Loresta EP (manufactured by Dia Instruments, MCP-T360 type), and the film thickness of the thin film (transparent conductive film) was contacted. The specific resistance was calculated by evaluating the difference in level between the non-deposited portion and the deposited portion using a type surface roughness meter (manufactured by Tencor). Moreover, the carrier concentration and the hole mobility at room temperature of the film | membrane by the Van der Pauw method were measured using the Hall effect measuring apparatus (Toyo Technica ResiTest).

Next, the transmittance [T _{L + B} (%)] of the film (glass substrate B with film L) including the glass substrate is measured with a spectrophotometer (manufactured by Hitachi, Ltd., U-4000), and measured by the same method. From the transmittance [T _B (%)] of only the glass substrate (glass substrate B), the transmittance of the film itself was calculated as [T _{L + B} ÷ T _B ] × 100 (%).

  The crystallinity of the film was evaluated by X-ray diffraction measurement. As the X-ray diffractometer, X'Pert PROMPD (manufactured by PANalytical) was used, the measurement conditions were wide-area measurement, CuKα rays were used, and measurement was performed at a voltage of 45 kV and a current of 40 mA. The film crystallinity was evaluated from the presence or absence of an X-ray diffraction peak. This result is also shown in the “film crystallinity” column of Table 1.

  Next, the composition of the film (Gd / In atomic ratio) was measured by ICP emission spectrometry. Further, the adhesion of the film to the substrate was evaluated based on JIS C0021. The evaluation was good (strong) when there was no film peeling, and was insufficient (weak) when there was film peeling. These results are also shown in the columns of “Gd / In atomic ratio” and “Adhesive force of film to substrate” in Table 1.

The specific resistance and transmittance of each thin film (transparent conductive film) depended on the mixing ratio of Ar gas and O ₂ gas introduced into the film forming vacuum chamber during film forming. The mixing ratio of O ₂ gas [O ₂ / (Ar + O ₂ ) (%)] was changed from 0 to 50% in increments of 1%, and the mixing ratio of O ₂ gas showing the lowest specific resistance was determined as the optimum oxygen mixing amount As determined. The results are shown in the “optimum oxygen mixing amount” column of Table 1.

  A thin film (transparent conductive film) produced with an oxygen amount smaller than the optimum oxygen mixing amount was not only poor in conductivity but also low in the visible region. The thin film (transparent conductive film) produced with the optimum oxygen mixing amount not only has good conductivity, but also has high transmittance in the visible to near infrared.

(3) Using the oxide vapor deposition materials of Examples 1 to 4, the optimum oxygen mixing amount, the specific resistance of the film at that time, and the visible region (wavelength 400 to 800 nm) when performing the above-described film formation evaluation The average transmittance of the film itself in the near infrared region (wavelength 800-1200 nm) was determined.

  These evaluation results are shown in the “specific resistance” and “transmittance of the membrane itself” columns of Table 1, respectively.

  In the film formation using the oxide vapor deposition materials of Examples 1 to 4, the optimum oxygen mixing amount to be introduced into the film formation vacuum chamber in order to obtain the transparent conductive film having the lowest resistance and high permeability was very small. This is because each oxide vapor deposition material contained an optimal amount of oxygen. In addition, the film produced at the optimum oxygen mixing amount showed the same composition as the oxide vapor deposition material, and not only showed a very low specific resistance, but also showed a high transmittance in the visible to infrared region. Further, it was confirmed that the film was a crystal film of indium oxide having a bixbyite structure, and the adhesion to the substrate was strong, which was practically sufficient.

  Furthermore, the set voltage of the electron gun was 9 kV, and the current value was 150 mA. The oxide vapor deposition material after electron beam irradiation for 60 minutes was observed, and it was visually observed whether the oxide vapor deposition material was cracked or cracked (oxide vapor deposition material durability test). Even if it used continuously for the oxide vapor deposition material of Examples 1-4, a crack did not generate | occur | produce (evaluation of "no crack").

  Such a transparent conductive film can be said to be very useful as a transparent electrode of a solar cell.

[Comparative Examples 1-2]
In Examples 1 to 4, oxide sintered bodies were manufactured by changing only the mixing ratio of the introduced gas in the sintered body oxygen content adjusting step. That is, in Comparative Example 1, the O ₂ / Ar flow rate ratio was 30/70, and in Comparative Example 2, it was 100/0. About the obtained sintered compact, the density, the specific resistance, the crystal grain size, and the composition were evaluated in the same manner, but were equivalent to those of Examples 1 to 4. The obtained oxide sintered body had the same surface color and internal color, and when its L ^* value was measured, it showed the values shown in Table 1.

Next, as in Examples 1 to 4, film formation evaluation was performed.
The results are also shown in Table 1 above.

Comparative Example 1 is an oxide vapor deposition material having an L ^* value that is smaller than the specified range (60 to 94) of the present invention (55), compared to the oxide vapor deposition materials of Examples 1 to 4. The optimum oxygen mixing amount at the time of filming was large (16). As for the characteristics of the membrane at the optimum oxygen mixing amount, the transmittance was the same as in Examples 1 to 4, but the specific resistance was slightly higher. This is probably because the compositional deviation of the film was large. Furthermore, the film of Comparative Example 1 had weaker adhesion to the substrate than Examples 1-4. This is probably because the film was formed by introducing a large amount of oxygen during film formation. Such an oxide vapor-deposited material has a large compositional deviation in the resulting film, and thus it is difficult to design the film composition. Further, since it is necessary to introduce a large amount of oxygen into the film formation vacuum chamber, when used in the mass production process of film formation, variations in composition and characteristics increase due to the influence of oxygen concentration variation in the vacuum chamber. Therefore, it is confirmed that the oxide vapor deposition material of Comparative Example 1 is not suitable for film formation mass production.

Moreover, the comparative example 2 is an example of the oxide vapor deposition material in which L ^* value showed the value (98) larger than the prescription | regulation range of this invention. The optimum oxygen mixing amount at the time of film formation was 0%, but the specific resistance of the film was higher than those in Examples 1 to 4. This is presumably because the amount of oxygen supplied from the oxide vapor deposition material to the film was too large and the amount of oxygen in the film was large, so that the optimum amount of oxygen deficiency could not be introduced. Therefore, it is confirmed that even if a film is formed using such an oxide vapor deposition material, a film exhibiting high conductivity inherent in the composition of the vapor deposition material cannot be obtained.

[Comparative Example 3]
Next, an indium oxide sintered body containing gadolinium was manufactured according to the sputtering target sintered body manufacturing technique introduced in JP-A-2005-290458 (Patent Document 3).

First, an In ₂ O ₃ powder having an average particle diameter of 0.8 μm and a Gd ₂ O ₃ powder having an average particle diameter of 1 μm are used as raw material powders, and the Ind ratio is adjusted so that the Gd / In atomic ratio is 0.030. ₂ O ₃ powder and Gd ₂ O ₃ powder were prepared and placed in a resin pot and mixed by a wet ball mill. At this time, hard ZrO ₂ balls were used, and the mixing time was 20 hours. After mixing, the slurry was taken out, filtered, dried and granulated. And using the obtained granulated powder, the pressure of 3 t / cm < ² > was added and it shape | molded with the cold isostatic press.

The obtained compact was put in a sintering furnace, oxygen was introduced at a rate of 5 liters / minute per 0.1 m ^{3 of} the furnace volume, and an atmosphere was created, and sintering was performed at 1450 ° C. for 8 hours. At this time, the temperature was increased up to 1000 ° C. at 1 ° C./min and 1000 to 1450 ° C. at 2 ° C./min. Thereafter, oxygen introduction was stopped, and the temperature was decreased from 1450 to 1300 ° C. at 5 ° C./min. And in the atmosphere which introduce | transduces argon gas in the ratio of 10 liters / min per furnace internal volume 0.1m < ³ >, after holding 1300 degreeC for 3 hours, it stood to cool.

The obtained sintered body was processed into a cylindrical shape having a diameter of 30 mm and a thickness of 40 mm. The density of the sintered body was 6.6 g / cm ³ and the specific resistance was 1.1 mΩcm. The crystal grain size was 10 to 15 μm, and the composition was almost the same as the charged composition. The surface and internal color of the obtained sintered body were equivalent, and its L ^* value was measured. As a result, it was very low (49) as shown in Table 1. This indicates that the amount of oxygen in the oxide vapor deposition material is very small.

Moreover, film-forming evaluation was implemented similarly to Examples 1-4.
The results are also shown in Table 1 above.

Comparative Example 3 shows a value (49) in which the L ^* value is significantly smaller than the specified range (60 to 94) of the present invention. Compared with the oxide vapor deposition materials of Examples 1 to 4 having the same composition, the optimum oxygen mixing amount during film formation is very large (35). As for the characteristics of the membrane at the optimum oxygen mixing amount, the transmittance was the same as in Examples 1 to 4, but the specific resistance was high. This is probably because the compositional deviation of the film was large. Furthermore, the film of Comparative Example 3 was weaker in adhesion to the substrate than in Examples 1 to 4. This is probably because the film was formed by introducing a large amount of oxygen during film formation. Such an oxide vapor deposition material is difficult to design the film composition because the composition deviation of the obtained film is large. Further, since it is necessary to introduce a large amount of oxygen into the film formation vacuum chamber, when used in the mass production process of film formation, variations in composition and characteristics increase due to the influence of oxygen concentration variation in the vacuum chamber. Moreover, when the oxide vapor deposition material durability test was performed on the same conditions as Examples 1-4, the oxide vapor deposition material after continuous film-forming had a crack (evaluation of "crack"). When film formation is continuously performed using such an oxide vapor deposition material having cracks, problems such as large fluctuations in the film formation speed occur and stable film formation cannot be achieved.

  Therefore, it was confirmed that the oxide vapor deposition material of Comparative Example 3 is not suitable for mass production of films.

[Examples 5 to 8]
When preparing the In ₂ O ₃ powder and the Gd ₂ O ₃ powder, it was carried out including the conditions for adjusting the oxygen content of the sintered body, except that the ratio was such that the Gd / In atomic ratio was 0.050. Under the same conditions as in Examples 1 to 4, oxide sintered bodies (oxide vapor deposition materials) of Examples 5 to 8 were produced.

  That is, the oxide vapor deposition material according to Example 5 is manufactured under the condition that the oxygen gas / argon gas flow ratio (that is, the volume ratio) is “40/60”, and the oxide vapor deposition material according to Example 6 has the above volume ratio. Manufactured under the condition of “60/40”, the oxide vapor deposition material according to Example 7 is produced under the condition where the volume ratio is “80/20”, and the oxide vapor deposition material according to Example 8 has the above volume. It is manufactured under the condition of the ratio “90/10”.

And about the obtained oxide sintered compact (oxide vapor deposition material) of Examples 5-8, when density, specific resistance, crystal grain size, and composition were evaluated similarly, all were equivalent to Examples 1-4. Met. Moreover, the surface and internal color of the obtained oxide sintered body were equivalent. The results of measuring the L ^* values are shown in Table 1 above.

Moreover, film-forming evaluation was implemented similarly to Examples 1-4.
The results are also shown in Table 1 above.

  In the film formation using the oxide vapor deposition materials of Examples 5 to 8, the optimum oxygen mixing amount to be introduced into the film formation vacuum chamber in order to obtain the transparent conductive film having the lowest resistance and the high permeability is as described in Examples 1 to 8. Like 4 it was very little. This is because the optimum amount of oxygen was contained in the oxide vapor deposition material. In addition, the film produced at the optimum oxygen mixing amount showed the same composition as the oxide vapor deposition material, and not only showed a very low specific resistance, but also showed a high transmittance in the visible to infrared region. In addition, all the films were indium oxide bixbite crystal structures, and the adhesion of the films to the substrate was strong and practically sufficient. Furthermore, even if the oxide vapor deposition material of Examples 5-8 was used continuously, a crack did not generate | occur | produce.

  Such a transparent conductive film can be said to be very useful as a transparent electrode of a solar cell.

[Comparative Examples 4 to 5]
In Comparative Examples 1 and ₂ , oxidation was performed under the same conditions as in Comparative Examples 1 and 2, except that the atomic ratio of Gd / In in preparing In ₂ O ₃ powder and Gd ₂ O ₃ powder was 0.050. A material vapor deposition material was produced. That is, the conditions for adjusting the amount of oxygen in the sintered body were 30/70 in the O ₂ / Ar flow ratio in Comparative Example 4 and 100/0 in Comparative Example 5. About the obtained sintered compact, although the density, specific resistance, crystal grain size, and composition were evaluated similarly, it was equivalent to Examples 5-8. Further, the surface and the internal color of the obtained sintered body were the same, and when the L ^* value was measured, the values shown in Table 1 were shown.

Next, as in Examples 1 to 4, film formation evaluation was performed.
The results are also shown in Table 1.

Comparative Example 4 is an oxide vapor deposition material having an L ^* value that is smaller than the specified range of the present invention (56). Compared with the case where the oxide vapor deposition materials of Examples 5 to 8 are used, film formation is performed. There was a lot of optimal oxygen mixing amount at the time. As for the characteristics of the membrane at the optimum oxygen mixing amount, the transmittance was almost the same as in Examples 5 to 8, but the specific resistance was slightly higher. This is probably because the composition deviation of the film is large and gadolinium is excessively contained in the film. Furthermore, the film of Comparative Example 4 had weaker adhesion to the substrate than Examples 5-8. The reason for such a large compositional deviation and low adhesion is that the film was formed by introducing a large amount of oxygen during film formation. Such an oxide vapor deposition material is difficult to design the film composition because the composition deviation of the obtained film is large. In addition, since it is necessary to introduce a large amount of oxygen into the film formation vacuum chamber, when used in the mass production process of film formation, the composition and characteristics are significantly susceptible to variations due to the influence of oxygen concentration variation in the vacuum chamber. . Therefore, it was confirmed that the oxide vapor deposition material of Comparative Example 4 is also unsuitable for film production.

Moreover, the comparative example 5 is an example of the oxide vapor deposition material in which L ^* value showed the value (98) larger than the prescription | regulation range of this invention. The optimum oxygen mixing amount at the time of film formation was 0%, but the specific resistance of the film was higher than those in Examples 5-8. This is presumably because the oxygen supplied from the oxide deposition material to the film was too much and the amount of oxygen in the film was so large that the optimum amount of oxygen deficiency could not be introduced. Therefore, it is confirmed that even if a film is formed using such an oxide vapor deposition material, a film exhibiting high conductivity inherent in the composition of the oxide vapor deposition material cannot be obtained.

[Comparative Example 6]
In Comparative Example 3, the oxide vapor deposition material was formed under the same conditions as in Comparative Example 3 except that the atomic ratio of Gd / In when preparing In ₂ O ₃ powder and Gd ₂ O ₃ powder was 0.050. Produced. The obtained sintered body was similarly evaluated in terms of density, specific resistance, crystal grain size, and composition, and was equivalent to Comparative Example 3. Further, the surface and the internal color of the obtained sintered body were equivalent, and the L ^* value was measured, and the values shown in Table 1 were shown.

Next, as in Examples 1 to 4, film formation evaluation was performed.
The results are also shown in Table 1.

Comparative Example 6 also shows a value (48) in which the L ^* value is significantly smaller than the specified range of the present invention. Compared with the oxide vapor deposition materials of Examples 5 to 8 having the same composition, the optimum oxygen mixing amount during film formation is very large (40). As for the characteristics of the membrane at the optimum oxygen mixing amount, the transmittance was the same as in Examples 5 to 8, but the specific resistance was high. This is probably because the compositional deviation of the film was large. Furthermore, the film of Comparative Example 6 had weaker adhesion to the substrate than Examples 5-8. This is because the film was formed by introducing a large amount of oxygen during film formation. Such an oxide vapor deposition material is difficult to design the film composition because the composition deviation of the obtained film is large. Further, since it is necessary to introduce a large amount of oxygen into the film formation vacuum chamber, when used in the mass production process of film formation, variations in composition and characteristics increase due to the influence of oxygen concentration variation in the vacuum chamber. Moreover, when the oxide vapor deposition material durability test was performed on the same conditions as Examples 1-4, the oxide vapor deposition material after continuous film-forming had a crack (evaluation of "crack"). When film formation is continuously performed using such an oxide vapor deposition material having cracks, problems such as large fluctuations in the film formation speed occur and stable film formation cannot be achieved.

  From the above, it is confirmed that the oxide vapor deposition material of Comparative Example 6 is also unsuitable for film formation mass production.

[Examples 9 to 13]
The blending ratio when blending In ₂ O ₃ powder and Gd ₂ O ₃ powder is 0.001 (Example 9), 0.005 (Example 10), 0.010 (implementation) in terms of the Gd / In atomic ratio. Ex. 11), 0.060 (Example 12), and 0.070 (Example 13), except that the conditions were the same as in Example 2 (that is, the oxygen gas / argon gas flow rate ratio was “60”. / 40 "conditions) oxide sintered bodies (oxide vapor deposition materials) of Examples 9 to 13 were produced.

And about the obtained oxide sintered compact (oxide vapor deposition material) of Examples 9-13, when the density, specific resistance, crystal grain size, and composition were evaluated similarly, all were equivalent to Example 2. It was. Moreover, the surface and internal color of the obtained oxide sintered body were equivalent. The results of measuring the L ^* values are shown in Table 1 above.

Moreover, film-forming evaluation was implemented similarly to Examples 1-4.
The results are also shown in Table 1 above.

  In the film formation using the oxide vapor deposition materials of Examples 9 to 13, the optimum oxygen mixing amount to be introduced into the film formation vacuum chamber in order to obtain the transparent conductive film having the lowest resistance and the high permeability is as described in Examples 1 to 3. Like 4 it was very little. This is because the optimum amount of oxygen was contained in the oxide vapor deposition material. In addition, the film produced at the optimum oxygen mixing amount showed the same composition as the oxide vapor deposition material, and not only showed a very low specific resistance, but also showed a high transmittance in the visible to infrared region. Further, it was confirmed that all the films were indium oxide bixbite type crystal structures, and the adhesion of the films to the substrate was strong and practically sufficient. Moreover, although the oxide vapor deposition material durability test was done on the conditions similar to Examples 1-4, the oxide vapor deposition material of Examples 9-13 did not generate | occur | produce a crack even if it used continuously.

  Such a transparent conductive film can be said to be very useful as a transparent electrode of a solar cell.

  By applying the oxide vapor deposition material according to the present invention, it becomes possible to produce a transparent conductive film exhibiting high conductivity while exhibiting high light transmittance not only in the visible region but also in the near infrared region by a vacuum deposition method. Therefore, it has the industrial applicability utilized as an oxide vapor deposition material for forming the transparent electrode of various solar cells.

DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Front side (light-receiving part side) Transparent electrode film 3 P-type amorphous silicon film or hydrogenated amorphous silicon carbide film 4 Amorphous silicon film not containing impurities 5 N-type amorphous silicon film 6 Back side transparent electrode film (contact improvement layer)
7 Back side metal electrode (back side electrode)
8 Light absorption layer 9 Semiconductor intermediate layer 10 Window layer 11 Transparent electrode film 12 Glass substrate 13 Lower electrode

Claims (2)

It is composed of a sintered body containing indium oxide as a main component and containing gadolinium, and the gdolinium content is 0.001 to 0.070 in terms of Gd / In atomic ratio, and the L ^* value in the CIE1976 color system is 60. It is -94, The oxide vapor deposition material characterized by the above-mentioned.   2. The oxide vapor deposition material according to claim 1, wherein the gadolinium content is 0.030 to 0.050 in terms of a Gd / In atomic ratio.

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