JP5528160B2 - Thick film composition for forming precursor film and method for producing chalcopyrite film using the thick film composition - Google Patents

Description

  The present invention is used to form a precursor film containing a group Ib element and a group IIIb element before combining with a group VIb element in a process for producing a chalcopyrite film used for a light absorption layer of a CIS solar cell. To a thick film composition.

  In response to the recent trend of energy saving aimed at preventing global warming and the like, interest in solar power generation using light energy centered on sunlight is increasing. There are various types of solar cells used for solar power generation depending on the form of the element, the material of the light absorption layer, and the like, and research and development of each type is underway.

  Among these, a solar cell using an Ib-IIIb-VIb group compound (CIS compound) called a chalcopyrite type for a light absorption layer is called a CIS solar cell and has attracted attention in recent years. The CIS solar cell is a thin film solar cell, has a feature that less semiconductor material is used for forming the battery and has high energy conversion efficiency, and has already been put to practical use.

  A CIS solar cell has a light absorbing layer composed of a lower electrode made of a molybdenum (Mo) metal film, a chalcopyrite film made of a group Ib-IIIb-VIb compound, a zinc sulfide on a substrate such as soda lime glass. , A buffer layer made of a sulfide such as indium sulfide and cadmium sulfide, and a transparent electrode layer made of a zinc-based material such as zinc oxide are sequentially laminated.

  Examples of the group Ib element include copper (Cu) and silver (Ag), examples of the group IIIb element include indium (In), gallium (Ga), and aluminum (Al), and examples of the group VIb element include selenium (Se). ), Sulfur (S), tellurium (Te), and other chalcogens (sulfur group elements) are typically used. In addition, the indication of Ib group, IIIb group, and VIb group is based on the provisions of the old IUPAC. For reference, in the provisions of the new IUPAC, the Ib group is the 11th group and the IIIb group is the 13th group. , VIb group corresponds to the 16th group respectively.

  Among the manufacturing processes of CIS solar cells having such a structure, the manufacturing process of the chalcopyrite film that constitutes the light absorption layer and greatly influences the energy conversion efficiency of the solar cell is regarded as the most important. However, the formation of the chalcopyrite film is the most difficult process because it is necessary to combine at least two kinds of metal and chalcogen.

  Generally, a chalcopyrite film is formed by forming a precursor film made of an Ib-IIIb group alloy on a lower electrode formed on a substrate by a sputtering process or the like by a sputtering process or the like, and then forming a precursor film. It is obtained by combining a group Ib metal and group IIIb metal and a group VIb element in the film. The compounding step is typically performed by heating the precursor film at a temperature of about 500 ° C. in an atmosphere containing a VIb group element.

  However, the formation of the precursor film by the vacuum process has been pointed out in addition to the cost of the apparatus and various drawbacks. For example, it is required to form the Ib group element and the IIIb group element at a predetermined ratio, but since the film formation speed differs depending on the element, it is necessary to finely control the film formation conditions. In addition, abnormal projections may occur on the surface of the precursor film, which may hinder subsequent formation of the buffer layer. Furthermore, the vacuum process is basically performed not only on the part where the film is to be deposited, but also on the whole, and the target material that is the source of the raw material cannot be used to the end. It has the major drawback of being a low and expensive process.

  For this reason, various manufacturing methods other than the vacuum process have been studied. For example, a typical example is film formation by a plating method such as electrodeposition and a thick film method in which paste or ink is applied.

  Patent Document 1 discloses forming a precursor film of a copper indium alloy from a plating solution containing copper ions and indium ions as a typical example of forming a chalcopyrite film by a plating method. In the plating method, there is a difference in the reduction potential of copper that is group Ib and indium that is group IIIb, and the utilization rate of indium is considerably lower than copper. Therefore, indium contains 50 times more indium than copper. There is a need to make it. In Patent Document 1, citric acid or tartaric acid is added to the plating solution as a countermeasure to improve the utilization rate of indium by 5 to 10 times. However, although the utilization rate of indium is improved as compared with the conventional method, the utilization rate of indium is limited in the plating method, and the efficiency is still low and the cost is high.

  Also, in order to keep the amount of copper and indium deposited at a constant level in a continuous plating process, it is essential to manage the conditions such as the composition of the plating solution, the solution temperature, and the current density. However, it can be said that the cost required for this is not small. As described above, the plating method can be said to be an appropriate means for producing a continuous film without using a vacuum process in order to form a single metal. This is an unsuitable method for film formation.

  On the other hand, the thick film method includes a metal component to be added to the paste, and is applied in a wet state to a predetermined place by printing or the like, and then subjected to heat treatment in an atmosphere containing a VIb group element to form a chalcopyrite film. It is to form. Since the metal component to be formed is determined by the amount added to the paste, the component ratio contained in the film of the group Ib element and the group IIIb element can be easily controlled. It can be said that it is suitable for film formation. Since it can be applied only to a desired portion without using a vacuum process, it is advantageous in terms of cost such as material efficiency.

  In Patent Document 2, one or both of copper and silver and one or both of indium oxide and gallium oxide are deposited individually or simultaneously, and then heat-treated in a reducing gas atmosphere containing one or both of selenium and sulfur. Thus, it is disclosed to form a chalcopyrite film. This document suggests that when depositing indium oxide or gallium oxide, a dip coating method using ink can be used in addition to the vapor deposition method and the sputtering method. However, means other than the dip coating method such as the vapor deposition method are used for the deposition of the group Ib, and it cannot be said to be a complete ink method.

  In Patent Document 3, an oxide is used as a material of a group IIIb element in order to enable synthesis of a chalcopyrite compound having a uniform composition, and as a method for forming an oxide layer, for example, a metal of a group Ib element and It has been suggested that a predetermined amount of each of Group IIIb element oxide powders is pulverized and mixed by a wet process to produce a paste, and a film is formed on the substrate using a technique such as screen printing. However, no concrete demonstration has been made.

  Also in Patent Document 4, for the purpose of making the composition of the chalcopyrite film uniform, the precursor film is printed with a composite oxide of a group Ib element and a group IIIb element or a paste of powders of these individual oxides. The precursor film thus obtained is heat-treated in a reducing atmosphere containing a VIb group element or an atmosphere containing a reducing VIb group compound. In this technique, a precursor film is formed on a substrate by screen printing. However, the preparation of the paste is described only when the oxide powder is mixed with polyethylene glycol, and the composition is not described in detail. Further, the Ib group element, the IIIb group element, and the composite oxide need to be specially prepared for this application, which is disadvantageous in terms of cost.

  Patent Document 5 also uses Ib group element and IIIb group element oxide particles processed into ink, and is applied by a method such as cup coating, dried, and heated in a reducing atmosphere to obtain Ib. It is disclosed to form a precursor film made of an alloy of a group element and a group IIIb element. More specifically, screen printing technology is used for pasty source materials, and spray, brush, roller or pad, gravure printing, stamp printing, doctor blading if the source material is ink or paint. Alternatively, it is described that various known wet deposition techniques such as cup coating, ink lighting and curtain coating can be used. In the embodiment, a mixed powder of copper oxide and indium oxide is added with water and a dispersant, pulverized and mixed with a ball mill, ink is prepared, and the ink is coated on the substrate by cup coating.

  In the techniques of Patent Documents 4 and 5, it is shown that oxides of group Ib elements and group IIIb elements preferably having a size of 2 to 3 μm or less are used as raw materials, which is advantageous in terms of cost. However, the thick film method involves a film forming process of applying a thick film composition made of ink or paste, drying, and heating, and it is necessary to fully consider all these processes. However, these techniques are not considered in consideration of an application or printing process which is an important process in the following points. That is, in Patent Document 4, a mixture of only oxide powder and polyethylene glycol is used, but with this composition, the powder settles within a few days after mixing, and a paste having a stable viscosity cannot be obtained. Moreover, in patent document 5, although it is a mixture of oxide powder, water, and a dispersing agent, if a dispersing agent is appropriate, it can prevent about the sedimentation of powder like patent document 4, but water is used. Therefore, this volatilization occurs during storage and use, and the viscosity of the paste is remarkably increased, so that it is not practical.

  Patent Document 6 proposes printing a paste made of indium selenide powder, selenium powder, copper chloride powder, and a binder on a lower electrode using a screen. This is a method in which a film is heated and selenized in a vacuum, an inert gas atmosphere, or a gas obtained by mixing a reducing gas in an inert gas after paste printing. Examples of the binder include propylene glycol and ethylene glycol, but other binders can be used unless they are contrary to the purpose. This technique is characteristic in that the selenium component is preliminarily contained in the paste, but indium selenide powder, which is one of the raw materials, has no other general use and needs to be specially manufactured. It is disadvantageous in terms of cost.

  In Patent Document 7, in order to form a chalcopyrite film, a colloidal suspension of metal chalcogenide nanoparticles composed of copper, indium, gallium, and selenium is deposited on a substrate. In this technology, the melting point of the metal chalcogenide is very high, and the particles having an average particle diameter of 10 to 30 nm cannot be formed by sintering between the particles by heating at a temperature that the glass substrate can withstand. Thus, a chalcopyrite film can be formed by heat treatment at a temperature of 300 ° C. or lower by dramatically lowering the melting point. However, this technique also requires a special production of chalcogenide nanoparticles, resulting in high costs, and the colloidal suspension of nanoparticles generally lacks liquid stability and has a problem in storage stability.

  Patent Document 8 also describes a method for producing ink composed of nanoparticles and a method for forming a chalcopyrite film formed therefrom. In this technique, the nanoparticles are not metal chalcogenides, group VIb elements are added alone, and after applying inks containing group Ib and group IIIb nanoparticles and even group VIb elements, heating is performed in an appropriate atmosphere. As a result, a chalcopyrite film is formed. However, ink using nanoparticles similarly has problems in cost and storage stability.

  As described above, methods for manufacturing a chalcopyrite film or a precursor film that is a precursor thereof by various thick film methods have been proposed. In the thick film method using ink or paste, there is no problem with the combination of the Ib group element and the IIIb group element, which is the biggest problem in the vacuum method and the plating method. In the thick film method, it is most difficult to form a film from particles, and various techniques have been devised in each technique. However, the use of complex oxides, chalcogenide particles, and nanoparticles is disadvantageous in terms of cost because a special raw material needs to be prepared only for this application.

  On the other hand, although it is disclosed to use an oxide having a particle size that is generally distributed as a raw material for the group Ib element and the group IIIb element, an important coating process is considered for the composition of these pastes. Since it is not a thing, the actual situation is that it is not fully capable of continuous printing in coating processes such as printing.

Japanese Patent No. 3011319 Japanese Patent No. 3095182 JP-A-5-326997 Japanese Patent No. 3091599 Japanese Patent No. 4303363 JP-A-10-229208 Japanese Patent No. 4279455 Special table 2008-537640

  An object of the present invention is to provide a thick film composition for forming a precursor film which is a precursor of a chalcopyrite film, which is inexpensive and has excellent printability.

  The present inventors diligently studied from the viewpoint of providing a thick film composition for forming a precursor film, which is a precursor of a chalcopyrite film, at a low cost, and completed the present invention.

  That is, the present invention relates to a thick film composition for forming a precursor film that is a precursor of a chalcopyrite film. The thick film composition of the present invention is basically composed of an inorganic component and an organic component. In particular, the thick film composition of the present invention has, as its inorganic component, at least one Ib group element powder selected from copper, copper oxide, silver and silver oxide, and at least one selected from indium oxide and gallium oxide. It is constituted by an inorganic powder composed of a seed group IIIb element powder, and the average particle size of the group Ib element powder and the group IIIb element inorganic powder is 0.1 μm or more and 10 μm or less. is there.

  The thick film composition of the present invention is characterized in that the organic component is composed of an organic vehicle composed of an organic resin and an organic solvent having a boiling point of 180 ° C. or higher and 350 ° C. or lower.

  Furthermore, in the thick film composition of the present invention, by regulating the content of the organic vehicle, the viscosity of the thick film composition is 10 Pa · s or more and 190 Pa · s or less. In addition, the said viscosity uses the rotational viscosity meter HBT type made from Brookfield, SC4-6 as a container which puts a thick film composition, SC4-14 as a rotor, respectively, rotational speed: 10 rpm, ambient temperature : Value measured at 25 ± 2 ° C. Moreover, it is preferable that content of this organic vehicle is 20 mass% or more and 70 mass% or less.

  In the thick film composition of the present invention, the molar ratio of the group Ib element to the group IIIb element is preferably 1.0: 1.0 or more and less than 1.5: 1.0. Moreover, in the thick film composition of this invention, it is not prevented that an appropriate organic additive and / or an inorganic additive are included other than said inorganic component and organic component.

  The thick film composition of the present invention is applied on the lower electrode formed on the substrate, dried at a temperature of 100 to 300 ° C., heated at a temperature of 300 to 650 ° C. in a reducing atmosphere, and thickened. Removing the organic solvent and the organic resin in the film composition, and forming a precursor film made of an alloy of a group Ib element and a group IIIb element, and then the group Ib element and group IIIb element in the precursor film; A chalcopyrite film containing an Ib-IIIb-VI group compound can be formed at a low cost by combining the VIb group elements.

  In addition, it is preferable to perform the said application | coating by screen printing.

  By using the thick film composition of the present invention, a chalcopyrite film can be produced at low cost by the thick film method without preparing a special raw material for manufacturing a chalcopyrite film, such as composite compounds, chalcogenide compound particles, and nanoparticles. Can be formed.

  The inventors of the present invention have made various studies from the viewpoint of providing a thick film composition that is inexpensive and excellent in printability, and has reached the present invention.

  First, in the thick film composition as a material for forming the chalcopyrite film, it is the inorganic powder that determines the price thereof, so that the powder was examined. As a result, for the inorganic component, at least one powder selected from copper, copper oxide, silver and silver oxide as a group Ib element, and at least selected from indium oxide and gallium oxide as a group IIIb element The knowledge that a uniform precursor film can be formed at a low cost by constituting with one kind of powder was obtained.

  Copper is used in large quantities as a metal powder in thick film compositions used for capacitor and printed circuit board electrode materials, and as an oxide powder in raw materials for catalysts and plating solutions. Silver is widely used as a metal powder as a thick film composition used for resistors, electrode materials for solar cells and the like, and as a silver oxide powder as a raw material for battery materials. Of course, since silver is an expensive material compared to copper, it is desirable to use copper powder or copper oxide powder.

  In addition, at least one powder selected from indium oxide and gallium oxide is used as the group IIIb element constituting the thick film composition. Indium and gallium have a very low melting point and it is very difficult to obtain a metal powder, and the use of the metal powder increases the cost. It is distributed in large quantities as the main raw material.

  These raw materials are generally marketed as powders having a particle size of 0.05 μm or more, and enable production of a very inexpensive thick film composition which is the object of the present invention.

  A thickness of 1 to 8 μm is required for the precursor film as a precursor of the chalcopyrite film. For this reason, the added inorganic powder needs to have an average particle diameter of 10 μm or less, preferably 5 μm or less. In the case of particles having an average particle size exceeding 10 μm, practical surface flatness is lacked in film formation of 8 μm or less. On the other hand, when the average particle size is less than 0.1 μm, the printability of the thick film composition is deteriorated and lacks practicality, and the particle size is generally not commercially available, resulting in an increase in cost. Therefore, in the present invention, an inorganic powder having an average particle size of 0.1 μm or more is used. Although the particle size can be measured by various methods, in the present invention, a laser diffraction type particle size distribution measuring device is used. The average particle diameter is based on D50, which is the median value of the number distribution obtained by this measurement.

  In the thick film composition of the present invention, the molar ratio of the group Ib element to the group IIIb element is preferably 1.0: 1.0 or more and less than 1.5: 1.0. Chalcopyrite is a compound in which a group Ib element and a group IIIb element are combined with a group VIb element at a molar ratio of 1: 1. Usually, the molar ratio of the group Ib element to the group IIIb element is 1: 1, but the molar ratio of the group Ib element to the group IIIb element in the chalcopyrite film finally used as a solar cell is 0.6. : 1.0 or more and less than 1.0: 1.0.

  Here, in order to promote crystal growth for chalcogenizing the precursor film, it is preferable that the composition of the precursor film is excessive with an Ib group element. For this reason, it is preferable that the molar ratio of the Ib group element and the IIIb group element is 1.0: 1.0 or more and less than 1.5: 1.0. When the precursor film formed by this blending is chalcogenized, a compound composed of two excess components of the group Ib element and selenium is deposited on the film surface. Residue of this phase needs to be removed because it adversely affects the characteristics of the solar cell, but this phase can usually be easily removed by immersing in a 1-10 mass% KCN solution for several minutes. Is possible. In this case, after removing this phase, the molar ratio of the Ib group element to the IIIb group element is preferably blended in the above film (0.6: 1.0 or more, 1.0: 1.0 The chalcopyrite film having better crystallinity can be obtained than in the case where the film is formed by a lesser method.

  A component for making an inorganic component made of inorganic powder into a paste is an organic vehicle composed of an organic resin and an organic solvent. Among these organic components, the organic resin plays a role of adjusting the viscosity of the thick film composition to be suitable for printing and fixing the thick film composition so that the powder is not scattered in the drying step after printing. In addition, it is desirable that the organic resin disappears and does not remain in the formed precursor film in heating in a reducing atmosphere for the purpose of reducing inorganic oxide to metal after printing and drying.

Examples of the organic resin include cellulose polymers such as ethyl cellulose and nitrocellulose, vinyl polymers such as poly-α-methylstyrene and polystyrene, and acrylic polymers such as polymethyl methacrylate and polybutyl methacrylate. However, in order to disappear by heating in a reducing atmosphere, a heat-decomposable vinyl polymer or acrylic polymer is preferable. On the other hand, when the printability is insufficient with these alone, addition of a cellulose-based polymer is effective. As will be described later, the types and addition amounts of these organic resins are arbitrarily selected so that the viscosity of the resulting thick film composition falls within an appropriate range, and the addition amount also depends on the type of the selected organic resin. However, the organic resin as a whole preferably has a content in the range of 1.0 to 8.0% by mass in the organic vehicle .

  The organic solvent is a component for imparting appropriate printability to the thick film composition. For the application of the thick film composition, a transfer method such as a screen printing method, a roll coater, or a gravure printing can be used, but in any case, the thick film composition is kept at room temperature in the atmosphere for a minimum of several hours. Things will be exposed. In order to form a coating film having a constant coating thickness and no defects, the viscosity of the thick film composition needs to be stable during this period. In addition, in order to stabilize the film formation from the beginning to the end of the production, it is necessary that the viscosity of the thick film composition is stable after the production until it is used up. Therefore, the present inventor considered the volatility at normal temperature as the main factor determining the stability of viscosity, and examined the volatility of various organic solvents at normal temperature. As a result, they obtained knowledge that volatility at room temperature can be ignored by using an organic solvent having a boiling point of 180 ° C. or higher.

  That is, the organic solvent must have a boiling point of 180 ° C. or higher, preferably 200 ° C. or higher, and the organic resin can be dissolved. In the case of a solvent having a low boiling point such as water or methyl alcohol, the volatilization of the solvent is large during continuous printing, the viscosity increases accordingly, and the printability is greatly deteriorated. Specifically, when printed on a predetermined pattern, blurring or sagging may occur. However, the material with such curling or sagging cannot be made into a product, resulting in a decrease in yield. Become. On the other hand, when the boiling point is too high, there arises a problem that drying is insufficient in the drying step after printing. From this viewpoint, an organic solvent having a boiling point of 350 ° C. or lower, preferably 300 ° C. or lower is preferable. Typical examples of such solvents include turpentine oil, butyl carbitol acetate, terpineol, 2- (4-methylcyclohexane-1-yl) propan-2-ol, di-n-butyl phthalate, ethylene glycol, Examples include diethylene glycol, triethylene glycol, propylene glycol, and methoxybutyl acetate. The addition amount of the organic solvent is also arbitrarily selected according to the type so that the viscosity of the resulting thick film composition is in an appropriate range. It is preferable to make it content in the range of 25-65 mass% in a thing.

  In the thick film method, by increasing the content of the organic vehicle in the ink and paste to be used, it is possible to thin the film after drying and heating even by application with the same thickness. In this case, as the content of the same organic vehicle increases, the viscosity of the thick film composition decreases, but this viscosity changes the type of organic resin and the content of organic solvent in the organic vehicle. It is possible to make adjustments.

  By the way, when using a thick film composition for the electrode material for solar cells, application | coating needs to be performed at once with the magnitude | size of this panel. If a coating defect such as a blur or a pinhole occurs in a very thin coating film of about 10 μm, these cause a significant deterioration in the light conversion efficiency of the entire panel. For this reason, the viscosity of the thick film composition is a very important characteristic. As a result of making various thick film compositions having different viscosities and investigating the frequency of occurrence of defects after coating, it was found that a composition having a viscosity of 190 Pa · s or less is good. A viscosity of 10 Pa · s or less is not preferable because the thick film composition starts to drip around the pattern to be printed. Preferably, it is in the range of 30 to 150 Pa · s after the production.

  Here, since the thick film composition generally has thixotropy, its viscosity is affected by measurement conditions. Even if the same fluid is measured, if the measurement conditions are changed, the viscosity value will also be different. The viscosity in this specification is a rotational viscometer HBT type manufactured by Brookfield, SC4-6 is used as a container for the thick film composition, SC4-14 is used as a rotor, rotation speed: 10 rpm, ambient temperature : Value measured under conditions of 25 ± 2 ° C.

  Thus, by changing the type of organic resin and the content of the organic solvent in the organic vehicle, the viscosity is adjusted so as to improve the printability of the thick film composition to 10 Pa · s or more and 190 Pa · s or less. Is possible. However, there is a limit to the adjustment method based on the viscosity of the thick film composition. That is, the thickness of the precursor film is 1 μm to 8 μm, which is the thinnest film formed by the thick film method. In order to form a final film within this thickness range, the amount of the organic vehicle in the thick film composition needs to be in the range of 20% by mass to 70% by mass. When the amount of the organic vehicle exceeds 70% by mass, the thixotropy of the thick film composition essential for printability is lowered and printability is deteriorated. On the other hand, when it is less than 20% by mass, the viscosity of the thick film composition increases, and in order to prevent this, adjustment to reduce the amount of the organic resin in the organic vehicle is necessary, but substantially no organic resin can be added. Only a thick film composition having poor printability can be obtained.

  Various small amounts of additives can be added to the thick film composition of the present invention. There are organic additives that are effective to improve coatability. Examples of such an organic additive include an organic additive having a carboxyester structure having a lipophilic group selected from a stearyl group, a lauryl group, a myristyl group, a palmityl group, and an oleyl group and a polyethylene glycol moiety. The addition improves the wettability of the powder to the solvent and improves the stability of the viscosity of the thick film composition. In this case, the organic additive may be added directly to the thick film composition, or may be added in the form of adhering to the powder surface in the powder production process. can get. The addition amount of the organic additive is desirably 3% by mass or less, usually 1% by mass or less in the thick film composition.

  Furthermore, the addition of inorganic additives may be effective for improving the light conversion efficiency. It is well known that potassium, sodium, etc. are effective elements for this purpose. These inorganic additives can be added to the thick film composition of the present invention in the form of oxide powder, carbonate powder, or nitrate powder. The addition amount of the inorganic additive is desirably 0.5% by mass or less, usually 0.1% by mass or less in the thick film composition.

  Regarding the addition of the organic vehicle, it is possible to add the organic resin and the organic solvent separately in the manufacturing process of the thick film composition, but in order to make the composition in the product more uniform, the thick film composition Before adding to a thing, it is desirable to make the organic resin into the state melt | dissolved in the organic solvent at the temperature of 50-80 degreeC.

  Equipment for producing various inks and pastes can be used to produce thick film compositions. For example, a roll mill, an attritor, a ball mill, a bead mill and the like can be given as such equipment.

  A method for forming a chalcopyrite film from a precursor film using the thick film composition formed as described above will be described. A soda lime glass substrate is generally used as the substrate of the CIS solar cell. A molybdenum film to be a lower electrode is formed on this substrate. This film is formed in a rectangular shape with a thickness of about 1 μm by a vacuum process such as sputtering. The thick film composition of the present invention is applied thereon. As a coating method, it is possible to adopt a method applicable to a thick film method such as a screen printing method and a transfer method. It is also necessary to be thin, and the screen printing method is most suitable for this purpose.

  The screen mask used in the screen printing method is generally a 200-400 mesh stainless steel mesh with an emulsion having a thickness of 5-20 μm. The thick film composition is printed with a printing thickness of 8 to 15 μm on the glass substrate on which the molybdenum film is formed. The organic solvent component is volatilized by drying at a temperature of 100 to 300 ° C. for several minutes to several tens of minutes. Then, it puts into the heating furnace for reduction. The atmosphere in the heating furnace is replaced with nitrogen or argon gas containing 1% by volume or more of hydrogen, and heated at a temperature of 300 to 650 ° C. for 10 minutes or more to eliminate the organic resin component and thick film composition An inorganic oxide in the material is reduced to a metal to form a precursor film made of an inorganic component.

At this time, the precursor film is preferably in an alloy state of an Ib group element and an IIIb group element. Next, this precursor film and a VIb group element (chalcogen) such as selenium, sulfur, and tellurium are combined to form a desired chalcopyrite film. In the supply of the VIb group element, the VIb group element is generally contained in the atmosphere during the heat treatment for compounding. Specifically, a mixed gas obtained by mixing a VIb group element-containing gas such as H ₂ S or H ₂ Se and an inert gas is supplied into the furnace. The heating temperature is 300 to 650 ° C., which is the same as the reduction treatment, and it is necessary to heat for 15 minutes or more.

  When an excessive amount of the lb group element is added, after the heat treatment, an undesired compound phase composed of the lb group element and the VIb group element formed by this heat treatment is immersed in the KCN solution for several minutes. It is necessary to remove it.

  In general, a chalcopyrite film can be obtained from the thick film composition in this manner, but the process described above is a general process and is not limited to this process. For example, after forming a precursor film by the thick film method using the thick film composition of the present invention, a VIb group element is deposited on the precursor film, and a lid is formed on the precursor film on which the VIb group element is deposited. Place the lid on which the VIb group element is deposited on one surface on the precursor film so that the precursor film and the VIb group element are in contact with each other. The technique proposed by the present inventor can be used.

Example 1
Copper powder for thick film conductive paste having an average particle diameter (D50) of 0.5 μm (Mitsui Metal Mining Co., Ltd., Cu1030Y): 18.3% by mass, average particle diameter being in the range of 1 to 3 μm Indium oxide powder for transparent electrode (manufactured by Asia Physical Materials Co., Ltd.): 31.8% by mass, organic vehicle: 49.9% by mass, mixed with a roll mill, and pasted into a thick film composition. Obtained. The metal molar ratio of copper and indium was 1.3: 1.0. As the organic vehicle, an organic resin, ethyl cellulose: 2.3% by mass, and polymethyl methacrylate: 0.7% by mass, and an organic solvent, 2- (4-methylcyclohexane-1-yl) propane- 2-ol (boiling point: 210 ° C.): 97 mass% dissolved in 50 ° C. was used.

  About the obtained thick film composition, the paste viscosity was measured 1 day after manufacture. The measurement was performed using an HBT type rotational viscometer (manufactured by Brookfield), SC4-6 as a container for storing the thick film composition, and SC4-14 as a rotor, respectively, rotation speed: 10 rpm, ambient temperature: 25 ° C. It measured on condition of this. Moreover, in order to evaluate the change with time of the viscosity of the thick film composition, 20 g of the thick film composition was stored in a plastic container at room temperature for 1 month, and the paste viscosity was similarly measured after the passage. The thick film composition of Example 1 had a viscosity of 95 Pa · s on the first day after production and 104 Pa · s on the first month after production. That is, the viscosity change was about 10%, and it was confirmed that the change was sufficiently suppressed to a practical range.

  Next, a coating test was carried out using the thick film composition stored at room temperature for one week after production. Application was carried out by screen printing. A stainless steel screen of 325 mesh and an emulsion thickness of 5 μm (manufactured by Tokyo Process Service Co., Ltd.) was used. As the substrate, soda lime glass (manufactured by Matsunami Glass Industrial Co., Ltd.) having a 25 mm square and a thickness of 1 mm was used, and a thick film composition paste was printed on the substrate in a 20 mm square rectangular pattern. Printing was performed continuously for 100 sheets, and continuous printability was evaluated from observation of the printed state of the 100th sheet. As the failure mode, a blur and a pattern sag that are not printed in a predetermined pattern were evaluated, and determination was made based on the presence or absence of these. The pattern sagging was determined as “present” when sagging 1 mm or more from the edge of the predetermined rectangular pattern. In the thick film composition of Example 1, neither sag nor pattern sagging occurred.

The substrate after printing was passed through a belt drying furnace at a peak temperature of 250 ° C. to dry the solvent component. Next, the tube was put in a tube furnace and once evacuated by a rotary pump, a 3% by volume hydrogen and 97% by volume nitrogen forming gas was flowed at a flow rate of 30 ml per minute. The temperature was raised to 550 ° C. over 30 minutes, held for 30 minutes, and then cooled. When the X-ray diffraction measurement was performed on the sample taken out using an X-ray diffractometer (manufactured by Rigaku Corporation), the oxide was reduced and a precursor film made of Cu ₁₁ In ₉ alloy and In was formed. confirmed. No oxide diffraction peaks were observed. The film thickness was 1.6 μm. Thereafter, the sample was again placed in a tubular furnace and evacuated, and then a forming gas containing 3% by volume of hydrogen selenide and 97% by volume of nitrogen was flowed at a flow rate of 50 ml. The temperature was raised to 600 ° C. over 30 minutes, held for 1 hour, and cooled in the furnace. After removal, the obtained film was immersed in a 4% by weight KCN solution for 5 minutes to remove the Cu ₂ Se phase formed from excess Cu. Again, analysis was performed by X-ray diffraction. A strong peak of CuInSe ₂ was observed, and other peaks were not observed. This indicated that a good CIS chalcopyrite film was formed.

(Comparative Example 1)
Except that the organic solvent in the organic vehicle was changed to butyl cellosolve (boiling point: 171 ° C.) having a boiling point lower than 180 ° C., a thick film composition paste was prototyped in the same manner as in Example 1, Viscosity stability and printability were evaluated. The viscosity of 1 day after production was 113 Pa · s, but the viscosity of 1 month after production was 178 Pa · s, an increase of about 60%. In the initial printability test after production, no problem was obtained, but this change in viscosity is a major factor causing changes in the coating film thickness, making it difficult to print stably over time. Is shown.

(Comparative Example 2)
As an organic vehicle, ethyl cellulose: 9.0% by mass and polymethyl methacrylate: 1.0% by mass, which are organic resins, and 2- (4-methylcyclohexane-1-yl) propane-2, which is an organic solvent, are used. -All (boiling point: 210 ° C): A thick film composition paste was produced in the same manner as in Example 1 except that 90% by mass dissolved at 50 ° C was used. The viscosity stability and printability were evaluated. The viscosity of one day after production was 200 Pa · s, and the viscosity in January after production was 216 Pa · s. Since a solvent with a low boiling point is used, the change in viscosity over time is small and good, but in a printability test one week after production, the printed film does not reach 50 sheets continuously, and the printed film is blurred. In addition, it was confirmed that a predetermined pattern could not be applied uniformly, causing problems in printability.

(Comparative Example 3)
A thick film composition paste was made in the same manner as in Example 1 except that the organic solvent in the organic vehicle was changed to ethylene glycol isopropyl ether (boiling point: 143 ° C.). And the printability was evaluated. Although the viscosity of one day after production was 120 Pa · s, the viscosity one month after production increased to 187 Pa · s. Although there was no problem in the initial printability test after production, this change in viscosity is a major factor that causes a change in the coating film thickness, making it difficult to print stably over time.

(Example 2)
Cuprous oxide powder for pigments (manufactured by Furukawa Chemicals Co., Ltd.) having an average particle diameter in the range of 2.0 to 4.0 μm: 19.3 mass%, transparent having an average particle diameter in the range of 1 to 3 μm Indium oxide powder for electrodes (manufactured by Asian Physical Materials Co., Ltd.): 23.8% by mass, and gallium oxide powder having an average particle size of 2.2 μm (manufactured by Asian Physical Materials Co., Ltd.): 6.9% by mass The same organic vehicle as used in Example 1 was blended in an amount of 50% by mass to obtain a thick film composition paste. The metal molar ratio of copper, indium and gallium was 1.1: 0.7: 0.3. The resulting paste was evaluated for viscosity stability and printability in the same manner as in Example 1.

The thick film composition of Example 2 has a viscosity of 128 Pa · s on the first day after manufacture, and 136 Pa · s on the first day after manufacture. Small and good printability. As in Example 1, the obtained film was dried to obtain a precursor film, subjected to a heat treatment in the same selenium-containing atmosphere, and the excess Cu ₂ Se phase was removed, thereby forming a chalcopyrite film. Formed. As a result of the X-ray diffraction measurement, the precursor film was observed to have two phases of Cu ₉ (InGa) ₄ and In, and the chalcopyrite film was observed to have only a single phase of CuInGaSe ₂ , demonstrating that a good CIGS chalcopyrite film was formed. It was done.

  For each example and comparative example, the boiling point of the organic solvent used, the molar ratio of the lb group element to the lb group element in the inorganic component, the organic vehicle content in the thick film composition, and the thick film composition as an evaluation result The changes over time in the viscosity of the product (one day after production and one month after production) and the printability of the thick film composition (presence of sag and pattern sag) are shown respectively.

  In particular, the present invention makes it possible to form a chalcopyrite film used as a light absorption film of a CIS solar cell at a low cost, and it can be said that the contribution to the manufacturing field of solar cells is great.

Claims (4)

A thick film composition for forming a chalcopyrite film,
The inorganic component is at least one selected from copper, copper oxide, silver and silver oxide, and is selected from group Ib element powder having an average particle size of 0.1 μm or more and 10 μm or less, indium oxide and gallium oxide. is at least one that, an average particle diameter of 0.1μm or more, ing from the IIIb group element powder is 10μm or less, comprising an inorganic powder,
As an organic component, an organic vehicle composed of an organic resin and an organic solvent having a boiling point of 180 ° C. or higher and 350 ° C. or lower is contained in the thick film composition in an amount of 20% by mass or more and 70% by mass or less .
The content of the organic resin in the organic vehicle is 1.0 to 8.0% by mass,
Using a Brookfield rotational viscometer model HBT, using SC4-6 as the container for the thick film composition and SC4-14 as the rotor, under conditions of a rotational speed of 10 rpm and an ambient temperature of 25 ± 2 ° C. The thick film composition is characterized by having a viscosity of 10 Pa · s or more and 190 Pa · s or less. The content of the group Ib element powder and the group IIIb element powder is 1.0: 1.0 or more and less than 1.5: 1.0 in terms of a molar ratio of the group Ib element and the group IIIb element. 2. The thick film composition according to 1. The thick film composition according to claim 1 or 2 is applied on a lower electrode formed on a substrate, dried at a temperature of 100 to 300 ° C, and at a temperature of 300 to 650 ° C in a reducing atmosphere. Heating to remove the organic solvent and the organic resin in the thick film composition, and forming a precursor film made of an alloy of a group Ib element and a group IIIb element, and then the group Ib element in the precursor film and A method for producing a chalcopyrite film, comprising combining a group IIIb element and a group VIb element to form a chalcopyrite film containing an Ib-IIIb-VI group compound.   The manufacturing method of the chalcopyrite film | membrane of Claim 3 which performs the said application | coating by screen printing.