JP2011187920A - Method for producing compound semiconductor thin film, solar cell, and device for producing compound semiconductor thin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compound semiconductor thin film, such as a CIGS thin film, which is fine, has excellent surface smoothness, and is ideal for use in a solar cell, and which is produced readily at a low cost and with good productivity in a non-vacuum process. <P>SOLUTION: A method for producing the compound semiconductor thin film containing a group IB element, group IIIB element, and group VIB element comprises: a step for preparing an application agent containing a group IB element, group IIIB element, and group VIB element; a step for forming an application film by applying the application agent to a substrate; and a step for baking under pressure in which the application film is heated and sintered while pressure is mechanically applied. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a compound semiconductor thin film, a solar cell, and a compound semiconductor thin film manufacturing apparatus.

Cu (In, Ga) Se ₂ (hereinafter also referred to as CIGS) has an optimum band gap and high light absorption coefficient for the absorption of sunlight, and therefore is a promising semiconductor as a light absorption layer of a high-efficiency thin film solar cell. It is a thin film forming material. Currently, CIGS thin films used for solar cells are manufactured in Japan, Europe and America using a selenization method or a vapor deposition method. In the selenization method, a metal precursor is formed by sputtering, and the metal precursor is selenized with H ₂ Se gas. In the vapor deposition method, the CIGS light absorption layer is physically vapor-deposited from each constituent element. However, in order to further reduce the cost of CIGS solar cells, a CIGS thin film manufacturing process that does not use vacuum is desired and studied, unlike selenization and vapor deposition (see, for example, Patent Document 1). As a non-vacuum manufacturing process, an ink containing oxide particles is printed on a substrate, and the obtained oxide film is reduced with hydrogen gas to be converted into a metal film, and then selenized with H ₂ Se gas. There is a method of obtaining a CIGS thin film. There is also a method of preparing a CIGS thin film by preparing an ink using CIGS powder, applying the ink by a screen printing method, and then sintering the CIGS powder by heat treatment under normal pressure and in an inert atmosphere (for example, Non-patent document 1). However, the CIGS thin film produced by this method has voids inside, and it is difficult to produce a dense thin film. In addition, a screen mesh mark remains on the film coated with ink by the screen printing method, and it is difficult to obtain a film having a smooth surface. Furthermore, in the sintering process, Se is likely to evaporate from the thin film, and it has been difficult to sinter many CIGS thin films at once under uniform conditions.

Special table 2008-537640

Takahiro Wada, “The Frontiers of Printable Electronics Technology Development-Materials Development and Applied Technology-” Technical Information Association, Inc., January 31, 2008, p. 239-245

  Accordingly, an object of the present invention is to provide a compound semiconductor thin film such as a CIGS thin film which is dense and excellent in surface smoothness and can be suitably used for a solar cell with high productivity and low cost easily in a non-vacuum process. And

  In order to achieve the above object, a method for producing a compound semiconductor thin film of the present invention is a method for producing a compound semiconductor thin film containing a group B element, a group B element, and a group V element, and includes a group B element, a group B element, A step of preparing a coating agent containing a VΙB group element, a step of coating the coating agent on a substrate to form a coating film, and heating and baking the coating film under a mechanically pressurized condition. And a pressure firing step for binding.

  The solar cell of the present invention is a solar cell having a compound semiconductor thin film, wherein the compound semiconductor thin film is manufactured by the method for manufacturing a compound semiconductor thin film of the present invention.

  The compound semiconductor thin film manufacturing apparatus of the present invention is an apparatus used in the compound semiconductor thin film manufacturing method of the present invention, and includes at least a pressing means and a heating means.

  According to the present invention, a compound semiconductor thin film such as a CIGS thin film, which is dense and excellent in surface smoothness and can be suitably used for a solar cell, can be provided easily and at low cost with high productivity in a non-vacuum process.

FIG. 1 is a schematic cross-sectional view showing a method for producing a compound semiconductor thin film of the present invention. FIG. 2 is an X-ray diffraction pattern of the compound semiconductor thin film obtained in Example 1. 3 is a scanning electron microscope (SEM) image of the surface and cross section of the compound semiconductor thin film obtained in Example 1. FIG. FIG. 4 is a graph showing the light transmittance of the compound semiconductor thin film obtained in Example 1. 5 is an SEM image of the surface and cross section of the compound semiconductor thin film obtained in Example 2. FIG. 6 is an SEM image of the surface of the compound semiconductor thin film obtained in Example 3. FIG. FIG. 7 is a schematic cross-sectional view illustrating the method for manufacturing the compound semiconductor in Example 4. FIG. 8 is an SEM image of the surface of the compound semiconductor thin film obtained in Example 4. FIG. 9 is an SEM image of the surface of the compound semiconductor thin film obtained in Example 5. FIG. 10 is an X-ray diffraction pattern of the compound semiconductor thin film obtained in Example 6. FIG. 11 is an SEM image of the surface of the compound semiconductor thin film obtained in Example 6. 12 is an SEM image of the surface and cross section of the compound semiconductor thin film obtained in Comparative Example 1. FIG. FIG. 13 is a schematic diagram showing an example of the configuration of the compound semiconductor thin film manufacturing apparatus of the present invention. FIG. 14 is a schematic cross-sectional view of a device structure of a solar cell having a substrate type structure. FIG. 15 is an SEM image of the surface and cross section of the compound semiconductor thin film obtained in Example 7. FIG. 16 is a graph showing the light transmittance of the compound semiconductor thin film obtained in Example 7. FIG. 17 is an SEM image of the surface and cross section of the compound semiconductor thin film obtained in Example 8. FIG. 18A is a transmission electron microscope (TEM) image of a cross section of the compound semiconductor (CIGS) thin film obtained in Example 8. FIG. FIG. 18B is a chart showing the intensity of characteristic X-rays obtained by analyzing the portion indicated by the arrow in FIG. 18A by energy dispersive X-ray spectroscopy (EDX). FIG. 19A is a TEM image of the microstructure of the interface between the CIGS layer and the Mo layer in the cross section of the compound semiconductor (CIGS) thin film. FIG. 19B is a chart showing the intensity of characteristic X-rays obtained by analyzing the portion indicated by the arrow in FIG. 19A by EDX. FIG. 20A is a photograph of the CIGS solar cell prototyped in Example 8. FIG. FIG. 20B is an SEM image of a cross section of the CIGS solar cell. FIG. 21 is a graph of the characteristics of the CIGS solar cell prototyped in Example 8. FIG. 22 is an SEM image of the surface and cross section of the compound semiconductor thin film obtained in Example 9. FIG. 23 is an SEM image of the surface and cross section of the compound semiconductor thin film obtained in Example 10. 24 is a SEM image of the surface and cross section of the compound semiconductor thin film obtained in Example 11. FIG. FIG. 25A is a graph showing the light transmittance of the compound semiconductor thin film obtained in Example 12. FIG. 25B, 25C and 25D are graphs for obtaining the forbidden band width of the compound semiconductor thin film obtained in Example 12. FIG. FIG. 26 is an X-ray diffraction pattern of the compound semiconductor thin film obtained in Example 13. 27 is an SEM image of the surface and cross section of the compound semiconductor thin film obtained in Example 13. FIG. FIG. 28A is a graph showing the light transmittance of the compound semiconductor thin film obtained in Example 13. FIG. FIG. 28B is a graph for obtaining the forbidden band width of the compound semiconductor thin film obtained in Example 13.

  In the method for producing a compound semiconductor thin film of the present invention, the coating agent containing the ΙB group element, ΙΙΙB group element, and VΙB group element is an element of at least two kinds selected from ΙB group element, ΙΙΙB group element, and V 元素 B group element. It is preferable to use a coating agent containing compound particles containing.

  As a coating agent containing the ΙB group element, お よ び B group element and VΙB group element, a coating agent containing ΙΙΙB group element and VΙB group element, ΙB group element powder, and VΙB group element powder is used. Is also preferable.

  As the coating agent containing the ΙB group element, the ΙΙΙB group element and the VΙB group element, it is also preferable to use a coating agent containing compound particles containing the ΙB group element, the ΙΙΙB group element and the VΙB group element.

  As the compound particles, it is preferable to use compound particles obtained by performing a mechanochemical process.

  In the method for producing a compound semiconductor thin film of the present invention, the group B element is preferably at least one element selected from Cu and Ag.

  In the method for producing a compound semiconductor thin film of the present invention, the group B element is preferably at least one element selected from In, Ga, and Al.

  In the method for producing a compound semiconductor thin film of the present invention, the V 好 ま し い B group element is preferably at least one element selected from S, Se, and Te.

  In the method for producing a compound semiconductor thin film of the present invention, it is preferable that the coating agent further contains Sb.

  In the method for producing a compound semiconductor thin film of the present invention, it is preferable that a drying step of drying the coating film is further performed before the pressure baking step.

  In the method for producing a compound semiconductor thin film of the present invention, it is preferable that a mechanically applied pressure in the pressure firing step is in a range of more than 0 Pa and 100 MPa or less.

  In the method for producing a compound semiconductor thin film of the present invention, it is preferable that the pressure firing step is performed at a temperature within a range of 300 ° C to 650 ° C.

  In the method for producing a compound semiconductor thin film of the present invention, it is preferable that the pressure firing step is performed in an atmosphere having a pressure in the range of normal pressure to 1 MPa.

  In the method for producing a compound semiconductor thin film of the present invention, it is preferable that a heat treatment step of heating in an atmosphere having a pressure in the range of normal pressure to 1 MPa is further performed after the pressure firing step.

  In the method for producing a compound semiconductor thin film of the present invention, the heat treatment step is preferably performed at a temperature higher than the temperature in the pressure firing step.

  In the method for producing a compound semiconductor thin film of the present invention, it is preferable that the step of applying the coating agent on a substrate is performed by screen printing.

  In the method for producing a compound semiconductor thin film of the present invention, it is preferable that in the pressure baking step, pressure baking is performed in a state where a plurality of substrates on which the coating film is formed are stacked.

  It is preferable to provide a spacer between the plurality of stacked substrates and perform pressure firing.

  The spacer is preferably a spacer selected from the group consisting of metal, glass and ceramics.

  In the method for producing a compound semiconductor thin film of the present invention, a group B element and a group VB element can be used in combination in place of or in place of the group B element.

  Next, the present invention will be described in detail. However, the present invention is not limited by the following description.

  The present invention is characterized in that a compound semiconductor thin film such as CIGS containing a group B element, a group B element and a group VB element, which has been conventionally performed by a vacuum process, is manufactured by a non-vacuum process. In the non-vacuum process, a coating agent containing a group B element, a group B element, and a group V element is prepared, and this coating agent is applied to a substrate, heated, and sintered to form a group B element and group B. A compound semiconductor thin film containing an element and a VΙB group element is manufactured. And when heating and sintering, it is a great feature that pressure firing is performed in a state where mechanical pressure is applied.

  The group B element is preferably at least one element selected from Cu and Ag. The element can be appropriately selected according to the design value of the band gap required for the compound semiconductor thin film. For example, when Ag is used, the band gap can be widened.

  The group B element is preferably at least one element selected from In, Ga, and Al. For example, when Ga or Al is used, the band gap can be widened. In the case of a compound semiconductor thin film containing Cu as a group B element and In as a group B element, the ideal element ratio of Cu / In in the thin film is 0.95 to 0.7. However, since excessive Cu can be easily removed by etching with an aqueous KCN solution after forming a thin film, the ratio of excess Cu may be used. The ratio may be about 0.95 to 0.4.

  The VΙB group element is preferably at least one element selected from S, Se and Te. Sulfur (S) is used in the production of a compound semiconductor thin film in a vacuum process, but since it has a high vapor pressure, it is preferably contained as a main component of the process for producing the thin film by conventional heating and sintering. There wasn't. However, in the production method of the present invention, since the heat sintering is performed under pressure, the high vapor pressure is not a big problem. Since the presence of sulfur can be expected to improve the characteristics of CIGS grain boundaries, it is also preferable to use it as a small amount of additive.

The compound particles containing at least two kinds of elements selected from the group B elements, group B elements, and group V elements include compound particles containing group B elements and group V elements, group B elements, and group elements V and B. Compound particles can be used. The coating agent used in the present invention may be a mixture of particles containing two types of elements and group element powders not included in the particles, or particles containing at least two types of elements. May be prepared so as to contain all of the group B element, the group B element, and the group V element. The compound particles containing the group B element and the group V group B are preferably CuSe. When using the ΙΙΙB group element and a compound particle comprising VΙB group elements _{(In 1-X Ga X)} 2 Se 3, by reaction with _{CuSe, Cu (In 1-X} Ga X) easily getting Se ₂ Can do. Conventionally, Cu ₂ Se and Ag ₂ Se that have been used hardly react with compound particles containing a group B element and a group V element in a short time even when heated. On the other hand, in the case of CuSe, it decomposes into liquid phase Se containing a high concentration of Cu and a small amount of Cu _2-Z Se (solid) at 523 ° C. or higher. This Cu ₂ -Z Se exists in the form of a non-stoichiometric compound in which Z can take a value of about 0 to 0.2. The generated Se in the liquid phase reacts actively with the compound particles containing the ΙΙΙB group element and the VΙB group element. Although Cu _2-Z Se produced at the same time inhibits the reaction, Cu _2-Z Se can be dissolved in the Se melt by adding a slight excess of Se to the reaction system. -Se melt is obtained. A homogeneous Cu—Se melt is preferable because the above reaction can proceed well.

In the above, as the coating agent containing the group B element, group B element and group V element, the coating agent containing compound particles containing group B element and group V element, group B element powder, and group group V powder. Is preferably used. Furthermore, it is more preferable that the compound particle containing a ΙΙΙB group element and a VΙB group element is a ΙΙΙB ₂ VΙB ₃ group compound. For example, in the crystal structure of CuInSe ₂ , according to recent theoretical calculations by the inventors, it has been found that the Cu—Se bond is much weaker than the In—Se bond. Therefore, when a CuInSe ₂ thin film is produced by the vapor deposition method, first, an In ₂ Se ₃ thin film is produced, Cu and Se are diffused in the thin film, and the orientation of the In ₂ Se ₃ thin film is changed. CuInSe ₂ thin film is obtained. Also in the method for producing a compound semiconductor thin film of the present invention, a high-quality thin film is obtained by using a coating agent containing a compound particle containing a Group B element and a Group V element, a Group B element powder, and a Group V element powder. Can be obtained. Compound particles containing the ΙΙΙB group element and VΙB group elements _is preferably at least one selected from _{(In 1-X Ga X)} 2 Se 3 and _{(In 1-X Ga X)} Se. When (In _1-X Ga _X ) Se is used, the Se amount is smaller than when (In _1-X Ga _X ) ₂ Se ₃ is used. Therefore, in order to obtain the same composition ratio as in the case of using (In _1-X Ga _X ) ₂ Se ₃ , 0.5 mol of Se is added to ₁ mol of (In _1-X Ga _X ) Se. Further, X in the chemical formula, which is a Ga / (In + Ga) ratio in the compound semiconductor thin film, is preferably in the range of 0 to 0.6, and more preferably in the range of 0.2 to 0.4. . When a compound semiconductor thin film is used as a solar cell, the band gap is most preferably about 1.4 eV. From the viewpoint of the band gap, it is preferable that Ga is contained in an amount of about 0.6, but from the viewpoint of conversion efficiency, it is more preferably in the range of 0.2 to 0.4.

  As the particle diameter of the compound particles reacts with the compound particles to produce a target compound semiconductor, the smaller the particle diameter, the higher the reactivity and the more desirable. The particle diameter is preferably 1 μm or less, and more preferably 0.1 μm or less.

  The compound particles may be prepared as a compound particle containing a group B element and a group VB element, or a compound particle containing a group B element and a group VB element, but each elemental element is prepared in a desired ratio. Each compound particle can also be obtained by a mechanochemical process using a mixture of the above. By using this method, it becomes easy to freely design the composition of the compound particles.

  When mechanical energy such as impact, shear, shear stress, and friction is applied to a finely divided material in the process of pulverizing the material, a part of the mechanical energy is accumulated in the fine particle, thereby increasing the activity and reactivity of the material particle. . The process of synthesizing composite particles by utilizing the phenomenon that the particles having increased activity and reaction cause a chemical reaction with surrounding substances is called a mechanochemical process. The mechanochemical process is characterized by high energy efficiency, high productivity and short cycle time.

  In the present invention, as a means for performing a mechanochemical process, a sufficient machine is sufficient for a mechanochemical reaction to obtain CuSe or (In, Ga) -Se compound from each of Cu, Se, In, and Ga. The apparatus is not particularly limited as long as it is a device capable of applying a dynamic energy. Examples of the apparatus include a planetary ball mill, a ball mill, a jet mill, an attritor mill, a rod mill, a roll mill, and a crusher mill. Among these, a planetary ball mill capable of obtaining an impact several times the gravitational acceleration is preferable.

  The said ball mill grind | pulverizes a to-be-processed substance with many spheres. Specifically, there are a rolling ball mill, a planetary ball mill, a vibrating ball mill, and the like that pulverize a material to be treated by a sphere (ball) using mechanical energy such as rotational force, planetary motion, and vibration. The material of the ball is not particularly limited, but zirconia, alumina, silicon nitride, tungsten carbide, agate and the like are preferable from the viewpoint of contamination with impurities.

  In the present invention, the number of rotations of the ball mill, the size of the container, and the diameter and amount of the balls used when performing the mechanochemical process are not particularly limited as long as the reaction can be promoted.

  The content ratio of the ΙB group element, the ΙB group element, and the VΙB group element in the coating agent is preferably added in such a ratio that the composition of the target compound semiconductor thin film is obtained. When an element such as Se that easily volatilizes from a compound is contained in the heating (baking) step after coating, it is also preferable that the element alone is excessively mixed in advance in the coating agent. Alternatively, it is preferable that a single element of the element that is likely to volatilize coexist in the reaction vessel because the element can be prevented from volatilizing from the thin film during firing.

  It is also preferable that the coating agent contains a solvent. The solvent may be an aqueous solvent or a non-aqueous solvent such as an organic solvent. Organic solvents include acrylates, alcohols (butyl, ethyl, isopropyl or methyl), aldehydes, benzene, dibromomethane, chloroform, dichloromethane, dichloroethane, trichloroethane, cyclo compounds (eg, cyclopentanone, cyclohexanone), esters (eg, butyl) Acetate, ethyl acetate), ether, glycol (ethylene glycol, propylene glycol, etc.), hexane, heptane, aliphatic hydrocarbon, aromatic hydrocarbon, ketone (eg, acetone, methyl ethyl ketone, methyl isobutyl ketone), natural oil, terpene, There are terpinol and toluene. When the coating agent is applied to the substrate by a method such as screen printing, a solvent having a high boiling point and high viscosity such as terpineol or ethylene glycol monophenyl ether is preferable from the viewpoint of coating property and workability during coating. . Although the aqueous solvent has a small environmental load, it has a drawback that the surface tension is relatively larger than that of the organic solvent, and repelling is likely to occur when it is applied to a substrate. In order to improve the coating property to the substrate, the surface tension of the coating agent may be reduced by adding a surfactant. The amount of the solvent added may be adjusted so as to be in the optimum viscosity range according to the coating method of the coating agent.

  For the coating agent, pigments, fillers, dispersants, plasticizers, UV absorbers, surfactants, binders, emulsifiers, antifoaming agents, desiccants, and leveling may be used as long as they do not impair performance. An agent, corrosion inhibitor, antioxidant, thixotropic agent, etc. may be added. These additives may be used alone or in combination of two or more. In addition, since the adhesiveness with a board | substrate can be improved by adding NaF to the said coating agent, it is preferable.

  It is preferable that the coating agent further contains Sb. Sb is considered to act as a sintering aid, and it was found that the addition of the CIGS thin film promotes the sintering, and a denser thin film is obtained. Although the addition amount of Sb can be set in a range in which the performance of the obtained compound semiconductor can be maintained, it is preferably about 0.25 to 5 mol%. Within this range, a dense thin film can be obtained as the amount of Sb added increases.

  The coating agent can be prepared by means similar to the means for performing a mechanochemical process, such as a ball mill. When the desired coating agent has a low viscosity, it can also be obtained by stirring without using a ball mill or the like. When using a means for pulverizing the material to be treated such as the ball mill, generally, the particle size of the particles in the coating agent can be reduced by increasing the pulverization time (stirring time). In the coating agent preparation step in the present invention, the pulverization time is preferably in the range of 30 minutes to 24 hours, and can be appropriately set according to the desired physical properties of the coating agent.

  Examples of methods for applying the coating agent to the substrate include screen printing methods, phantom coating methods, die coating methods, spin coating methods, spray coating methods, gravure coating methods, roll coating methods, and bar coating methods. Can be used.

  As the substrate on which the coating agent is applied, soda lime glass is preferably used. The soda lime glass contains Na, but the contained Na may diffuse into the compound semiconductor thin film layer formed on the substrate, so that the electrical properties of the compound semiconductor thin film may be positively affected. In particular, it is preferable when the compound semiconductor thin film is used as a solar cell. In the method for producing a compound semiconductor thin film of the present invention, a thin film is formed on a substrate by a coating process, so that the selection range of the substrate can be widened as compared with vapor deposition. In addition to the hard substrate such as soda lime glass, for example, a flexible substrate such as a metal foil or a plastic film can be used. When a flexible substrate is used, it can also be applied to a mass-productive process such as a roll-to-roll method.

  In the method for producing a compound semiconductor thin film of the present invention, the step of applying the coating agent to a substrate to form a coating film, and heating the coating film under pressure under mechanical pressure, the compound semiconductor It is also preferable to include a coating agent drying step between the sintering step. When the coating film is heated to a high temperature in a state where a large amount of solvent is contained, voids may be generated in the film due to evaporation of the solvent all at once. In addition, since the heating is performed in a mechanically pressurized state, the solvent may not be evaporated and may remain in the film. Therefore, it is preferable to provide a step of removing a certain amount of solvent and drying the coating film before the pressure firing step.

  The step of drying the coating film may be, for example, natural drying, air drying by blowing air, heat drying or vacuum drying. Moreover, the method which combined these may be used. The thickness of the coating film is preferably in the range of 10 to 0.1 μm, and more preferably in the range of 3 to 0.3 μm.

  In the press firing process in the present invention, the substrate on which the coating film is formed is sandwiched between press plates from above and below, pressed, and heated in that state (hot pressing), so that the group B element contained in the coating agent In this step, the compound semiconductor thin film is manufactured by sintering the group B element and the group V group B element. This step can be performed using an apparatus including a pressing unit and a heating unit described below.

  In FIG. 13, an example of a structure of the compound semiconductor thin film manufacturing apparatus of this invention is shown. As illustrated, the manufacturing apparatus 130 includes a chamber 131, a heating tank 132, a heater 133, and push rods 134 and 134 'as main components.

  In the chamber 131, a heating tank 132 and a set of push rods 134, 134 'are arranged. The set of push bars 134, 134' is a pressing means in the present invention, and the heating tank 132 has a vertical direction. It is pierced opposite. A heater 133 is installed in the heating tank 132. A vacuum pump or a gas supply means (not shown) may be connected to the chamber 131. By reducing the pressure in the chamber 131 with a vacuum pump and supplying a gas such as nitrogen from the gas supply means into the chamber, the air in the chamber can be replaced. The gas supply means is connected to a gas cylinder, whereby a gas having an appropriate pressure can be supplied into the chamber 131. The heater 133 is a means for controlling the temperature in the heating tank 132. In this example, the heater 133 is installed in the heating tank 132, but is not limited thereto. In an embodiment in which the heater 133 is in the heating tank 132, the heater 133 is preferably a quartz tube heater in which the heater is enclosed in a quartz tube. This is because Se and the like may evaporate from the coating layer due to heating, and the inside of the heating tank may become a Se atmosphere, but when the heater is exposed, Se and the like react with each other. The temperature control means is not limited to a heater, and may be a current heating or a discharge plasma sintering machine.

  In the manufacturing method of the present invention, after the substrate on which the coating film is formed is installed between the pair of push rods 134 and 134 ', the interval between the pair of push rods 134 and 134' is reduced. By moving in the direction, mechanical pressure is applied to the substrate. When applying pressure to the substrate, a pressing plate having the same size as the substrate is prepared so that the entire substrate is pressurized, and the substrate is arranged so as to sandwich the substrate. Is preferred. As the material of the pressing plate, silicon nitride ceramics, alumina, zirconia, or the like can be suitably used. In addition, a second push plate that serves as a cushioning material may be further provided between the push plate and the substrate in order to prevent damage to the substrate. As the second push plate, a graphite sheet, a Teflon (registered trademark) sheet, or the like can be used.

  It is preferable that a spacer is disposed on the surface of the substrate on which the coating film is formed. The spacer is used to prevent the coating film from adhering to the pressing plate. As the spacer, it is preferable to use a material that does not react with an element constituting the compound semiconductor contained in the coating film, hardly transfers the coating film from the substrate, and does not deform excessively by pressurization. As the spacer, metal, glass, ceramics and the like are preferable, and aluminum foil, borosilicate glass and the like can be used. Further, a material that can serve as a spacer may be coated on the surface of the pressing plate.

For example, when producing CuInSe ₂ as a compound semiconductor thin film, the equilibrium reaction proceeds in the following direction due to the evaporation of Se.
2CuInSe ₂ → Cu ₂ Se + In ₂ Se + Se ₂
In the manufacturing method of the present invention, Se is difficult to evaporate in order to press the coated surface, and therefore, the above formula proceeds in the opposite direction (2CuInSe ₂ ← Cu ₂ Se + In ₂ Se + Se ₂ ), which is preferable.

  In the pressure baking process in the present invention, pressure baking can be performed in a state where a plurality of substrates on which the coating film is formed are stacked. In general, the pressure firing process is often low in productivity because it becomes a batch process. However, in the present invention, since a plurality of substrates can be processed simultaneously, the production efficiency is greatly improved. Can be improved. In this case, the spacer may be inserted between the substrates on which a plurality of the coating films are formed.

  The pressurization is preferably in the range where the mechanically applied pressure exceeds 0 Pa and is 100 MPa or less. By applying a pressure within this range, the crystal grains of the compound semiconductor whose surroundings are in a liquid phase by heating are easily bonded to the adjacent crystal grains, so that the grain growth is promoted. In addition, in a state where pressure is applied, reaction sintering and grain growth can be performed in a state where the contact area between the crystal grains and the crystal grains is large, so that a dense thin film can be manufactured. When sintering without pressure in the conventional process, the sintering proceeds in a three-dimensional process, so shrinkage occurs in the vertical and horizontal directions from the state in which the coating film is formed, and dimensional accuracy is obtained. In addition, the thin film had many vacancies and was difficult to be densified. Another problem is that the film is cracked by the contraction of the film in the horizontal direction. The production method of the present invention improves these problems.

  The heating temperature in the pressure firing step is preferably performed at a temperature in the range of 300 ° C to 650 ° C, more preferably in the range of 350 ° C to 550 ° C. The atmosphere is preferably a pressure atmosphere in the range of normal pressure to 1 MPa. In order to minimize the evaporation of Se from the CIGS film after setting the substrate on which the coating film has been formed in the chamber at room temperature and normal pressure, when the pressure baking is performed in a sealed chamber, the temperature As the temperature rises, the atmospheric pressure inside the chamber increases. However, if it exceeds 1 MPa, the specifications required for the material and structure of the device become high, and the practicality is low from the viewpoint of versatility and safety. In the production method of the present invention, the compound semiconductor thin film can be produced under a low temperature condition as compared with the case of sintering without applying pressure. According to the production method of the present invention, crystal grains grow even at a lower heating temperature than in the conventional method.

  After the pressure firing step, it is also preferable to perform a heat treatment step of heating in an atmosphere having a pressure in the range of normal pressure to 1 MPa. By performing the heat treatment step, the characteristics of a solar cell are improved even if the crystal grain size does not change. The heating temperature in the heat treatment step is effective when performed at a temperature higher than the temperature in the heat treatment step, preferably in the range of 400 ° C to 650 ° C, more preferably in the range of 450 ° C to 600 ° C. Is within.

  The heat treatment step is also preferably performed while depositing Se. By performing the heat treatment while depositing Se, the CIGS thin film is prevented from being decomposed, and the characteristics of the solar cell are improved. Also in this case, it is effective when carried out at a temperature higher than the temperature at the heating temperature in the pressure firing step, preferably in the range of 400 ° C to 650 ° C, more preferably in the range of 450 ° C to 600 ° C. Is within.

  In the above, the manufacturing method of the compound semiconductor thin film containing the ΙB group element, the ΙΙΙB group element and the VΙB group element has been described in detail. In the present invention, in addition to or instead of the ΙΙΙB group element, the ΙΙB group element and the ΙVB group. A compound semiconductor thin film can also be manufactured by using it in combination with an element. When a ΙΙB group element and a ΙVB group element are used in combination instead of the ΙΙΙB group element, a compound semiconductor thin film containing a ΙB group element, a ΙΙB group element, a ΙVB group element, and a VΙB group element can be produced. Rare metals such as In and Ga, which are group B elements, have resource limitations. Therefore, In can be used in place of Zn which is a ΙΙB group element and Sn which is a ΙVB group element. Zn can be suitably used as the ΙΙB group element, and Sn or Ge can be suitably used as the ΙVB group element.

  The compound semiconductor thin film produced by the method for producing a compound semiconductor thin film of the present invention can be suitably used for a solar cell. An example of the structure of the solar cell is a substrate type structure. An example of a schematic cross-sectional view of the device structure of a solar cell having a substrate type structure is shown in FIG. A back electrode 142 is provided on a substrate 141, and a light absorption layer 143 made of a compound semiconductor thin film, a buffer layer 144, a transparent electrode 145, and an extraction electrode 146 are formed thereon. For example, soda lime glass is used for the substrate 141, Mo is used for the back electrode 142, ZnO / CdS is used for the buffer layer 144, ZnO: Al or ZnO: B is used for the transparent electrode 145, and Al / Ni is used for the extraction electrode 146. Sunlight enters from the transparent electrode 145 side. An antireflection film 147 may be provided on the transparent electrode 145 as necessary.

  When the compound semiconductor thin film is used for a solar cell, a thickness of the thin film of 1 μm or more is sufficient for absorbing sunlight. Furthermore, by reflecting light on the back surface, the optical path length in the light absorption layer can be increased, and even a thin film of 1 μm or less can sufficiently absorb sunlight. In consideration of use in low-cost solar cells, the thickness of the thin film is desirably 10 μm or less. Moreover, the crystal grain of the CIGS film produced by the vapor deposition method is large, and the grain size has grown to about the film thickness. However, high conversion efficiency may be obtained even if the crystal grain size is not so large. The important point is that the crystal grains are sufficiently sintered and dense.

  Next, examples of the present invention will be described. The present invention is not limited or restricted by the following examples. In addition, various properties and physical properties in each example and each comparative example were measured and evaluated by the following methods.

(Surface shape observation)
The surface of the compound semiconductor thin film was observed using a scanning electron microscope (manufactured by Keyence Corporation, trade name “Real Surface Microscope VE-9800SP2199”).

(Crystal structure analysis)
The compound semiconductor thin film was analyzed using an X-ray diffractometer (manufactured by Rigaku Corporation, trade name “automatic X-ray diffractometer RINT2400”). Using a Cu target, X-rays were generated at a tube voltage of 40 kV and a tube current of 100 mA. The measurement was performed by the 2θ / θ method.

(Light transmittance)
The compound semiconductor thin film formed on the glass substrate is measured for absorption spectrum using a multi-channel spectrometer (trade name “Multi-channel spectrometer PMA-12” manufactured by Hamamatsu Photonics Co., Ltd.), and light transmittance is calculated. Went. As the light detection element, an InGaAs linear image sensor C10028-01 having a sensitivity wavelength range of 900 nm to 1650 nm was used.

[Example 1]
(Preparation of raw material powder)
After weighing the element powders Cu, In, Ga, Se so as to have a ratio of Cu _1.02 (In _1-X Ga _X ) Se _2.1 (X = 0.005, 0.1, 0.2), Thereto was added 0.5 mol% of NaF (Cu _1.02 (In _1-X Ga _X ) Se _2.1 corresponds to 0.005 mol with respect to 1 mol). 20 g of powder weighed in a 45 cc container made of zirconia for a planetary ball mill (trade name “Planet type ball mill premium line P-7” manufactured by Fritsch) and 40 g of 3 mm diameter zirconia cobblestone were placed at 800 rpm in a nitrogen atmosphere. For 20 minutes. By agitation, it occurs mechanochemical _reaction, powder based on _{Cu (In 1-X Ga X} ) Se 2 (CIGS) was obtained. Here, there are three levels of X = 0.005, 0.1, and 0.2. It was confirmed by powder X-ray diffraction that the main component of the obtained powder was CIGS having a chalcopyrite type crystal structure and good crystallinity.

(Preparation of coating agent)
Add 4 ml of ethylene glycol monophenyl ether to each of the zirconia containers containing the above-mentioned CIGS as a main component, make the container a nitrogen atmosphere, and stir at 700 rpm for 120 minutes to obtain three types of inks as coating agents. It was.

(Application)
As a substrate, 5 cm □ soda lime glass (thickness 2 mm) was prepared. The obtained ink was applied by screen printing (400 mesh) to form a coating layer.

(Dry)
The substrate on which the coating layer was formed was dried at 145 ° C. for 7 minutes in a nitrogen atmosphere.

(Pressurized firing)
As shown in the schematic cross-sectional view of FIG. 1, using the compound semiconductor thin film manufacturing apparatus of the present invention, the dried substrate was pressure fired as follows, and the coated film was sintered to produce a CIGS thin film. The substrate 2 on which the CIGS coating film 1 was formed was placed on the pressing plate 5. Then, the spacer 3 was placed in direct contact with the CIGS coating film 1, and a push plate 5 'was placed thereon. The two pressing plates 5 and 5 ′ were sintered while being mechanically pressed by a pair of pressing rods 4 and 4 ′. The spacer 3 was an aluminum foil (thickness 7 μm), the push rods 4 and 4 ′ were cylindrical zirconia ceramics having a diameter of 40 mm, and the push plates 5 and 5 ′ were 60 mm square silicon nitride ceramic plates. Using such an apparatus, under a nitrogen atmosphere at 450 ° C. with a mechanical pressure of 2 MPa applied, pressure firing was performed for 30 minutes to obtain a sintered CIGS thin film. Heating was started at normal pressure in a nitrogen atmosphere after the chamber was sealed, and when the temperature reached 200 ° C., mechanical pressure (press) was applied with a pressing plate. After heating to a predetermined 450 ° C. in a pressurized state and holding at 450 ° C. for 30 minutes, the pressure on the pressing plate was released and the pressure was returned to normal pressure. After cooling to room temperature, the chamber was opened and the sintered substrate with a thin film was taken out.

(Thin film characteristics)
Three types of CIGS thin films (X = 0.005, 0.1, 0.2) obtained in Example 1 were analyzed by X-ray diffraction (XRD). The obtained X-ray diffraction pattern is shown in FIG. These X-ray diffraction patterns basically correspond to the X-ray diffraction patterns obtained by simulation based on the crystal structure analysis data (ICSD: Inorganic Crystal Structure Database # 70051) of CuInSe ₂ , and a CIGS thin film having a chalcopyrite structure is synthesized. I found out. From this X-ray diffraction pattern, the CIGS thin film of the present example is a single phase that does not contain impurities, and as the X increases, the diffraction peak shifts to the high angle side, and the solid solution amount of Ga increases. Can be confirmed.

  Excess Se is believed to evaporate during the sintering process. Therefore, it is necessary to adjust the amount of Se added excessively according to conditions. In general, when the firing temperature is high, Se transpiration is severe, and the optimum amount of excess Se also increases. Moreover, Cu added excessively reacts with Se to form CuSe, which is considered to work as a sintering aid for CIGS. CuSe remains in the CIGS thin film as Cu—Se impurities after firing. This Cu—Se impurity can be easily removed by etching with an aqueous KCN solution.

  The surface and cross-sectional microstructure of the obtained thin film were observed with a scanning electron microscope (SEM). Those photographs are shown in FIG. From these photographs, CIGS crystal grain growth and densification are recognized, and it can be confirmed that a dense CIGS thin film can be obtained by the method of this example. In particular, the surface of the thin film is very smooth.

The light absorption spectrum of the CIGS thin film produced in Example 1 was measured in the wavelength range of 900 nm to 1600 nm. In FIG. 4, the graph of the light transmittance of the produced CIGS thin film is shown. This figure shows that the shortest wavelength of the light which permeate | transmits a CIGS thin film shifts to the short wavelength side with increase of X (Ga solid solution amount). This is because the forbidden band width of the CIGS thin film becomes wider as the amount of Ga dissolved increases, and the absorption edge of the CIGS thin film shifts to the short wavelength side. The forbidden band width of the CIGS thin film obtained based on this light transmittance is as follows: X = 0.005, Eg = 1.00 eV, X = 0.1, Eg = 1.06 eV, X = 0.2, Eg = 1.10 eV. These values are consistent with literature values.

[Example 2]
(Preparation of raw material powder)
The element powders Cu, In, Ga, and Se were weighed so as to have a ratio of Cu _1.02 (In _0.995 Ga _0.005 ) Se _2.1 , and then 0.5 mol% of NaF was added thereto. In the same manner as in Example 1, 20 g of the weighed powder and 40 g of 3 mm diameter zirconia cobblestone were placed in a zirconia 45 cc container for a planetary ball mill, and stirred at 800 rpm for 20 minutes in a nitrogen atmosphere. By stirring, a mechanochemical reaction occurred, and a powder containing Cu (In _0.995 Ga _0.005 ) Se ₂ as a main component was obtained.

(Preparation of coating agent)
4 ml of ethylene glycol monophenyl ether was added to a container made of zirconia containing the raw material powder containing Cu (In _0.995 Ga _0.005 ) Se ₂ as a main component, and the mixture was stirred and applied under the same conditions as in Example 1. An ink as an agent was obtained.

(Application)
As a substrate, 5 cm □ soda lime glass (thickness 2 mm) was prepared. The obtained ink was applied by screen printing under the same conditions as in Example 1 to form a coating layer.

(Dry)
The substrate on which the coating layer was formed was dried under the same conditions as in Example 1.

(Pressurized firing)
Sintering was performed in the same manner as in Example 1 except that the sintering conditions were four levels of 400 ° C. × 30 minutes, 450 ° C. × 30 minutes, 450 ° C. × 60 minutes, and 500 ° C. × 10 minutes. A CIGS thin film was obtained.

(Thin film characteristics)
The surface and cross-sectional microstructures of the four types of CIGS thin films obtained above were observed with an SEM. These photographs are shown in FIG. As shown in FIG. 5, the CIGS thin film of this example showed crystal grain growth and densification, and it was confirmed that a dense CIGS thin film was obtained by the method of this example.

[Example 3]
(Preparation of raw material powder and coating agent)
In the same manner as in Example 2, a powder containing Cu (In _0.995 Ga _0.005 ) Se ₂ as a main component was obtained, and an ink as a coating agent was prepared.

(Coating and drying)
A substrate was prepared by forming a Mo electrode on 5 cm square soda lime glass (thickness 2 mm). The obtained ink was applied to the substrate under the same conditions as in Example 1 to form a coating layer, and then the substrate on which the coating layer was formed was dried under the same conditions as in Example 1.

(Pressurized firing)
As the spacer, two types of aluminum foil (thickness: 7 μm) and borosilicate glass plate (thickness: 2 mm) similar to those in Example 1 were used, respectively. A sintered CIGS thin film was obtained.

(Heat treatment)
The sintered CIGS thin films obtained by the pressure firing were each heat-treated at 550 ° C. for 10 minutes in a nitrogen atmosphere. At this time, the substrate was put in a petri dish made of quartz glass, and Se was put in the petri dish.

(Etching process)
Each of the heat-treated CIGS thin films was immersed in a 10 wt% KCN aqueous solution at room temperature for 3 minutes to dissolve and remove Cu—Se impurities.

(Membrane characteristics)
The surface microstructure of the CIGS thin film in each state after the pressure firing, after the heat treatment, and after the etching treatment was observed with an SEM. These photographs are shown in FIG. From these photographs, crystal grain growth and densification were observed in all samples. The heat treatment after sintering by pressure firing was an effective means for evaporating excess Se and improving the crystallinity of the CIGS thin film, crystal grain growth and densification. It can also be seen that the Cu—Se impurities (the part surrounded by a circle in the photograph of FIG. 6) observed on the CIGS thin film surface after the heat treatment can be removed by the etching process.

[Example 4]
(Preparation of raw material powder)
After weighing the element powders Cu, In, Ga, Se so as to have a ratio of Cu _1.02 (In _1-X Ga _X ) Se _2.1 (X = 0.05, 0.1, 0.2), in the same manner as in example 1 _to obtain a powder mainly composed of _{Cu (in 1-X Ga X} ) Se 2. Here, there are three levels of X = 0.005, 0.1, and 0.2.

(Preparation of coating agent)
The _{Cu (In 1-X Ga X} ) zirconia container of Se ₂ containing the raw material powder whose main component, except that by adding each 4.5ml ethylene glycol monophenyl ether, stirred under the same conditions as in Example 1 As a result, three types of inks as coating agents were obtained.

(Coating and drying)
A substrate was prepared by forming a Mo electrode on 5 cm square soda lime glass (thickness 2 mm). The obtained ink was applied to the substrate under the same conditions as in Example 1 and dried to form a coating layer, and then the substrate on which the coating layer was formed was dried under the same conditions as in Example 1.

(Pressurized firing)
As shown in FIG. 7, the three substrates coated with the three kinds of inks were simultaneously fired under pressure, and the coating layer was sintered to produce a CIGS thin film. The substrate 12 on which the CIGS coating film 11 was formed was disposed on the pressing plate 5 via the second pressing plate 6. The spacer 13 was placed in direct contact with the CIGS coating film 11. The intermediate pressing plate 17 was placed on the spacer 13 and the substrate 22 on which the CIGS coating film 21 was formed was disposed. Further, the spacer 23 was placed in direct contact with the CIGS coating film 21. An intermediate pressing plate 27 was placed on the spacer 23, and a substrate 32 on which a CIGS coating film 31 was formed was disposed. The spacer 33 was placed in direct contact with the CIGS coating film 31, and the intermediate push plate 37, the second push plate 6 ′, and the push plate 5 ′ were placed in this order. The two pressing plates 5 and 5 ′ were sintered while being mechanically pressed by a pair of pressing rods 4 and 4 ′. Aluminum spacers (thickness 7 μm) were used as the spacers 13, 23 and 33, cylindrical zirconia ceramics having a diameter of 40 mm were used as the push rods 4 and 4 ′, and 50 mm square silicon nitride ceramic plates were used as the push plates 5 and 5 ′. The second pressing plates 6 and 6 ′ provided on the pressing surface side of the pressing plates 5 and 5 ′ serve as a cushioning material between the pressing plate and the substrate. Here, graphite sheets ( A thickness of 0.4 mm) was used. As the intermediate pressing plates 17, 27 and 37, borosilicate glass plates (thickness 2 mm) were used. The substrate was set as shown in FIG. 7, and the sintered CIGS thin film was obtained by pressurizing and firing for 30 minutes in a nitrogen atmosphere at 450 ° C. with a mechanical pressure of 2 MPa. Heating was started at normal pressure in a nitrogen atmosphere after the chamber was sealed, and when the temperature reached 200 ° C., mechanical pressure (press) was applied with a pressing plate. After heating to a predetermined 450 ° C. in a pressurized state and holding at 450 ° C. for 30 minutes, the pressure on the pressing plate was released and the pressure was returned to normal pressure. After cooling to room temperature, the chamber was opened and the sintered substrate with a thin film was taken out.

(Heat treatment)
The sintered CIGS thin films obtained by the pressure firing were each heat-treated at 550 ° C. for 10 minutes in a nitrogen atmosphere. At this time, the substrate was put in a petri dish made of quartz glass, and Se was put in the petri dish.

(Etching process)
Each of the heat-treated CIGS thin films was immersed in a 10 wt% KCN aqueous solution at room temperature for 3 minutes to dissolve and remove Cu—Se impurities.

(Membrane characteristics)
The surface microstructure of the obtained film was observed by SEM. These photographs are shown in FIG. From these photographs, CIGS crystal grain growth and densification were observed, and it was confirmed that a dense CIGS thin film was obtained by the method of this example. In particular, the surface of the film is very smooth. In this example, a plurality of CIGS thin films are pressure-fired at a time, but the surface is very smooth and dense as in the case of processing one by one as shown in Examples 1 to 3. A CIGS thin film could be produced.

(Prototype solar cell)
Using these CIGS thin films, a solar cell having an Al / n-ZnO: B / i-ZnO / CdS / CIGS / Mo / soda lime glass structure having a structure as shown in FIG. The solar cell was produced by the following process.
(1) A CdS buffer layer 144a is formed on the CIGS thin film 143 by a solution growth (CBD) method using cadmium sulfate CdSO ₄ .
(2) The i-ZnO layer 144b and the ZnO: B (B-doped ZnO) window layer 145 are deposited by metal organic chemical vapor deposition (MOCVD). Diethyl zinc (Zn (C ₂ H ₅ ) ₂ ) is used as a raw material for Zn, and pure water (H ₂ O) is used as an oxidizing agent. Further, diborane (B ₂ H ₆ ) diluted with 1% hydrogen was used as the n-type doping gas.
(3) A comb-shaped Al electrode 146 was formed by a vacuum deposition method.
The CIGS solar cells of this example, which were experimentally produced by this process, all showed solar cell characteristics, and it was confirmed that the present invention was effective for producing a thin film of a compound semiconductor for solar cells.

[Example 5]
(Preparation of raw material powder)
The element powders Cu, In, Ga, and Se have a stoichiometric ratio of Cu _{1 + Y} (In _0.995 Ga _0.005 ) Se _2.1 (Y = 0.01, 0.00, −0.005). Then, in the same manner as in Example 1, a raw material powder containing Cu (In _0.995 Ga _0.005 ) Se ₂ as a main component was obtained.

(Preparation of coating agent)
Under the same conditions as in Example 1, except that 4.5 ml of ethylene glycol monophenyl ether was added to a container made of zirconia containing the raw material powder mainly containing Cu (In _0.995 Ga _0.005 ) Se _2. The mixture was stirred to obtain three types of inks as coating agents.

(Coating and drying)
A substrate was prepared by forming a Mo electrode on 5 cm square soda lime glass (thickness 2 mm). The obtained ink was applied to the substrate under the same conditions as in Example 1 to form a coating layer, and then the substrate on which the coating layer was formed was dried under the same conditions as in Example 1.

(Pressurized firing)
In the same manner as in Example 4, these substrates were simultaneously fired under pressure, and the coating layer was sintered to produce a CIGS thin film. The conditions for pressure firing are the same as in Example 4.

(Heat treatment)
The sintered CIGS thin films obtained by the pressure firing were each heat-treated at 600 ° C. for 10 minutes in a nitrogen atmosphere. At this time, the substrate was put in a petri dish made of quartz glass, and Se was put in the petri dish.

(Etching process)
Each of the heat-treated CIGS thin films was immersed in a 10 wt% KCN aqueous solution for 3 minutes to dissolve and remove Cu—Se impurities.

(Membrane characteristics)
The surface microstructure of the obtained film was observed by SEM. Those photographs are shown in FIG. Compared with the comparative example, densification was observed in any CIGS thin film. In particular, it can be seen that a CIGS thin film having a composition with a large Y value has a dense microstructure and large crystal grains.

[Example 6]
(Preparation of CuSe powder)
Cu powder and Se powder were weighed at a molar ratio of 1: 1. 100 g of powder weighed in an 80 cc container made of zirconia for a planetary ball mill (product name “Planet Ball Mill P-5 / 2” manufactured by Fritsch) and 200 g of 3 mm diameter zirconia cobblestone are put into a nitrogen atmosphere. And stirred at 370 rpm for 120 minutes. By stirring, a mechanochemical reaction occurred and CuSe powder was obtained. It was confirmed by powder X-ray diffraction that the obtained CuSe was a highly crystalline CuSe.

_{((In 1-X Ga X} ) 2 Se 3 powder preparation of)
In powder, Ga powder and Se powder were weighed at a molar ratio of (2-2X): 2X: 3. Here, there are three types of X = 0.005, 0.1, and 0.2. A powder weighed in a 45 cc container made of zirconia for a planetary ball mill (trade name “Planet type ball mill premium line P-7” manufactured by Fritsch Co., Ltd.) and 40 g of 3 mm diameter zirconia cobblestone were placed. The filling amount of the powder in the container was adjusted to 20 g by adding CuSe during the preparation of the coating agent. They were stirred at 800 rpm for 20 minutes under a nitrogen atmosphere to obtain a powder having a composition ratio of (In _1-X Ga _X ) ₂ Se ₃ .

(Preparation of coating agent)
In a container made of zirconia used for preparation of the powder having the composition ratio of (In _1-X Ga _X ) ₂ Se ₃ , the ratio of Cu _1.02 (In _1-X Ga _X ) Se _2.51 is set. CuSe powder was added. Furthermore, 0.5 mol% of NaF (corresponding to 0.005 mol with respect to 1 mol of Cu _1.02 (In _1-X Ga _X ) Se ₂ ) was added thereto. Further, 7 ml of terpineol was added as a solvent, the inside of the container was placed in a nitrogen atmosphere, and the mixture was stirred at 500 rpm for 120 minutes to obtain an ink as a coating agent.

(Application)
As a substrate, 5 cm □ soda lime glass (thickness 2 mm) was prepared. The obtained ink was applied by screen printing (400 mesh) to form a coating layer.

(Dry)
The substrate on which the coating layer was formed was dried at 145 ° C. for 5 minutes in a nitrogen atmosphere.

(Pressurized firing)
In the same manner as in Example 4, these substrates were simultaneously fired under pressure, and the coating layer was sintered to produce a CIGS thin film. The conditions for pressure firing are the same as in Example 4.

(Heat treatment)
The sintered CIGS thin films obtained by the pressure firing were each heat-treated at 600 ° C. for 10 minutes in a nitrogen atmosphere. At this time, the substrate was put in a petri dish made of quartz glass, and Se was put in the petri dish.

(Membrane characteristics)
Three types of CIGS thin films (X = 0.005, 0.1, 0.2) obtained in Example 6 were subjected to XRD analysis. The results are shown in FIG. The X-ray diffraction pattern coincides with the X-ray diffraction pattern obtained by simulation based on crystal structure analysis data (ICSD: Inorganic Crystal Structure Database # 70051), and it was found that a CIGS thin film having a chalcopyrite structure was synthesized. From this X-ray diffraction pattern, as in Example 1, the CIGS thin film of this example is a single phase containing no impurities, the diffraction peak shifts to the high angle side as X increases, It can be confirmed that the amount of solid solution increases. Moreover, the surface microstructure of the obtained thin film was observed with SEM. The result is shown in FIG. From these SEM photographs, it can be seen that crystal grain growth and densification are observed in any sample.

[Comparative example]
In the same manner as in Example 1, preparation of a raw material powder having a composition of Cu _1.02 (In _0.995 Ga _0.005 ) Se _2.1 , preparation of a coating agent, coating, and drying were performed. The SEM image of the surface of the film after drying and the cross-sectional microstructure is shown in FIG. From this figure, it can be seen that the CIGS thin film at the stage after drying is an aggregate of very fine particles. The dried thin film was heat-treated at 450 ° C. for 30 minutes in a nitrogen atmosphere without mechanical pressurization using the same apparatus as in Example 1. The SEM image of the surface and cross-sectional microstructure of the CIGS thin film after heat treatment is also shown in FIG. From these figures, it can be seen that when heat treatment is performed without mechanical pressurization, the material is hardly densified.

[Example 7]
(Preparation of raw material powder)
The element powders Cu, In, Ga, and Se were weighed so as to have a ratio of Cu _1.02 (In _0.995 Ga _0.005 ) Se _2.1 , and then 0.5 mol% of NaF was added thereto. In the same manner as in Example 1, 20 g of the weighed powder and 40 g of 1 mm diameter zirconia cobblestone were placed in a zirconia 45 cc container for a planetary ball mill, and stirred at 800 rpm for 20 minutes in a nitrogen atmosphere. By stirring, a mechanochemical reaction occurred, and a powder containing Cu (In _0.995 Ga _0.005 ) Se ₂ as a main component was obtained.

(Preparation of coating agent)
8 ml of ethylene glycol monophenyl ether is added to a container made of zirconia containing the raw material powder containing Cu (In _0.995 Ga _0.005 ) Se ₂ as a main component, and the inside of the container is placed in a nitrogen atmosphere, and at 700 rpm for a predetermined time. Was stirred. The stirring time was three levels of 2 hours, 5 hours, and 10 hours, and three types of inks as coating agents were obtained. Here, in general, increasing the pulverization (stirring) time decreases the particle size of the powder and increases the surface area, so that the viscosity of the ink increases. Therefore, 0.5 ml of the solvent was added to the ink whose stirring time was 10 hours in order to obtain a viscosity suitable for screen printing.

(Application)
As a substrate, 5 cm □ soda lime glass (thickness 2 mm) was prepared. The obtained ink was applied by screen printing (500 mesh) to form an application layer.

(Dry)
The substrate on which the coating layer was formed was dried under the same conditions as in Example 1.

(Pressurized firing)
Under pressure and firing under the same conditions as in Example 1, a sintered CIGS thin film was obtained.

(Thin film characteristics)
The surface and cross-sectional microstructures of the three types of CIGS thin films obtained above were observed with an SEM. Those photographs are shown in FIG. As shown in FIG. 15, in the CIGS thin film of this example, crystal grain growth and densification were observed, and it was confirmed that a dense CIGS thin film was obtained by the method of this example. The thickness of the CIGS thin film obtained was 2.3 μm for the ink using the stirring time of 2 hours, 1.3 μm for the ink using the stirring time of 5 hours, and the stirring time of 10 hours. The one using ink was 0.8 μm.

  The near infrared light absorption spectrum of the CIGS thin film produced in Example 7 was measured in the wavelength range of 900 nm to 1600 nm. In FIG. 16, the graph of the light transmittance of the produced CIGS thin film is shown. From this figure, it can be seen that the ink stirring time is increased, the CIGS film thickness is decreased, and the transmittance of light having a wavelength of 1200 nm or more is increased. Thus, even in the manufacturing method of this embodiment using screen printing, the CIGS film having the same thickness as the CIGS film prepared by the vapor deposition method can be obtained by devising the ink adjustment process and the screen to be used. Can be produced.

[Example 8]
(Preparation of raw material powder)
The element powders Cu, In, Ga, and Se were weighed so as to have a ratio of Cu _1.02 (In _0.995 Ga _0.005 ) Se _2.1 , and then 0.5 mol% of NaF was added thereto. In the same manner as in Example 1, 20 g of the weighed powder and 40 g of 1 mm diameter zirconia cobblestone were placed in a zirconia 45 cc container for a planetary ball mill, and stirred at 800 rpm for 20 minutes in a nitrogen atmosphere. By stirring, a mechanochemical reaction occurred, and a powder containing Cu (In _0.995 Ga _0.005 ) Se ₂ as a main component was obtained.

(Preparation of coating agent)
9 ml of ethylene glycol monophenyl ether is added to a container made of zirconia containing the raw material powder containing Cu (In _0.995 Ga _0.005 ) Se ₂ as a main component, and the inside of the container is put in a nitrogen atmosphere, at 700 rpm for 10 hours. By stirring, an ink as a coating agent was obtained.

(Application)
A substrate was prepared by forming a Mo electrode on 5 cm square soda lime glass (thickness 2 mm). The obtained ink was applied by screen printing (500 mesh) to form an application layer.

(Dry)
The substrate on which the coating layer was formed was dried under the same conditions as in Example 1.

(Pressurized firing)
Under pressure and firing under the same conditions as in Example 1, a sintered CIGS thin film was obtained.

(Heat treatment)
The sintered CIGS thin film obtained by the pressure firing was heat-treated at 600 ° C. for 10 minutes in a nitrogen atmosphere. At this time, the substrate was put in a petri dish made of quartz glass, and Se was put in the petri dish.

(Etching process)
The heat-treated CIGS thin film was immersed in a 10 wt% KCN aqueous solution at room temperature for 3 minutes to dissolve and remove Cu—Se impurities.

(Membrane characteristics)
The surface and cross-sectional microstructure of the obtained CIGS film were observed with an SEM. Those photographs are shown in FIG. From these photographs, CIGS crystal grain growth and densification were observed, and it was confirmed that a dense CIGS thin film having a thickness of about 2 μm was obtained by the method of this example.

  In order to examine in detail the microstructure of the obtained CIGS film, the cross-sectional microstructure was observed with a transmission electron microscope (TEM). First, in order to observe the cross-sectional microstructure with a TEM, a thin piece sample was prepared. First, in order to protect the outermost surface of the sample, a carbon film is coated with a high vacuum deposition apparatus, and a tungsten film is coated with an FIB processing apparatus. Then, a designated portion is extracted by a microsampling method and is subjected to FIB (Focused Ion Beam) processing. Thinned. Thereafter, the FIB damage layer was removed by ion milling. The apparatus used was a focused ion beam processing apparatus (manufactured by Hitachi, Ltd., “FB-2100”) and an ion milling apparatus (manufactured by GATAN, “PIPS Model-691” (with cold stage)). Next, the obtained flake sample was observed with a field emission transmission electron microscope (“JEM-2010F” manufactured by JEOL Ltd.) under an acceleration voltage of 200 kV. FIG. 18A shows a cross-sectional microstructure of the CIGS film of this example, which was observed with a transmission electron microscope.

  Further, the chemical composition of the point P1 near the center of the CIGS film, indicated by an arrow in FIG. 18A, was analyzed by energy dispersive X-ray spectroscopy (EDX). The apparatus used is a Noran EDX analyzer “Vantage”. The analysis result is shown in FIG. When the atomic ratio of Cu: In: Ga: Se was determined from the intensity of the characteristic X-ray, it was 23.2: 25.6: 0.1: 51.1, and the chemical composition of the target CIGS film (Cu: It was found to be very close to (In + Ga): Se = 25: 25: 50).

Next, FIG. 19A shows a microstructure in which the vicinity of the interface between the CIGS layer and the Mo layer of the CIGS film is further enlarged and observed by TEM. As is clear from FIG. 19A, an interface layer is formed between the CIGS layer and the Mo layer. The chemical composition at the point P2 indicated by the arrow in FIG. 19A was analyzed by EDX in the same manner as the point P1. The analysis result is shown in FIG. From the interface layer, it can be seen that only Mo and Se are detected while only noise levels of Cu and In are detected. When the atomic ratio of Mo: Se was calculated from the intensity of the characteristic X-ray, it was 64.9: 35.1 and was very close to the chemical composition of MoSe ₂ (Mo: Se = 66.7: 33.3). I understood. Thus, in the present embodiment, it was confirmed that the MoSe ₂ is generated in the vicinity of the interface between the CIGS layer and the Mo layer. It is presumed that MoSe ₂ of the interface layer was generated by a reaction between CIGS and Mo during the sintering and heat treatment processes. In the deposition method, the interface between the CIGS layer and the Mo layer, MoSe ₂ is produced, MoSe ₂ of this interface is known to contribute to improvement in characteristics of the CIGS solar cells (e.g., Jpn. J. Appl.Phys., Vol.35 (1996) pp.L1253-L1256).

(Prototype solar cell)
Using this CIGS thin film, a solar cell having an Al / n-ZnO: B / i-ZnO / CdS / CIGS / Mo / soda lime glass structure having a structure as shown in FIG. Prototype. FIG. 20A shows a photograph of the CIGS solar cell of this example. FIG. 20B shows the microstructure of the fracture surface of the CIGS solar cell of this example observed with a scanning electron microscope. It is observed that a ZnO layer is formed on the CIGS light absorption layer. Since the thickness of the CdS layer is 0.1 μm or less, it cannot be identified from this photograph.

(Characteristic evaluation of solar cells)
The characteristics of the solar cell prototyped above were evaluated. Measurement conditions were standard measurement conditions (Standard Test Condition: STC): spectrum: AM1.5, illuminance of incident light: 100 mW / cm ² , and the temperature was kept at about 25 ° C. The IV characteristic of the solar cell was performed by a four-terminal method. The area of one solar battery cell is 0.2 cm ² . The solar cell characteristics of this cell are shown in FIG. In FIG. 20A, the circled cell showed the highest conversion efficiency. The characteristics are: conversion efficiency (η): 3.2%, open circuit voltage (V _oc ): 284.2 mV, short circuit current (J _sc ): 26.2 mA / cm ² , fill factor (FF): It was 42.9%.

[Example 9]
(Preparation of raw material powder)
The ratio of elemental powder Cu, In, Ga, Se to Cu _1.00 (In _0.995 Ga _0.005 ) Se _2.1 and Cu _0.95 (In _0.995 Ga _0.005 ) Se _2.1 After weighing each so, 0.5 mol% of NaF and 2 mol% of Sb powder were added thereto. The Sb powder acts as a sintering aid and can control crystal growth. In the same manner as in Example 1, 20 g of the weighed powder and 40 g of 1 mm diameter zirconia cobblestone were placed in a zirconia 45 cc container for a planetary ball mill, and stirred at 800 rpm for 20 minutes in a nitrogen atmosphere. By stirring, a mechanochemical reaction occurred, and a powder containing Cu (In _0.995 Ga _0.005 ) Se ₂ as a main component was obtained.

(Preparation of coating agent)
8 ml of ethylene glycol monophenyl ether was added to each of the two zirconia containers containing the raw material powder containing Cu (In _0.995 Ga _0.005 ) Se ₂ as a main component, and the inside of the container was made into a nitrogen atmosphere, and 700 rpm Were stirred for 5 hours to obtain two types of inks.

(Application)
As a substrate, 5 cm □ soda lime glass (thickness 2 mm) was prepared. The obtained two types of inks were applied by screen printing (500 mesh) to form an application layer.

(Dry)
The substrate on which the coating layer was formed was dried under the same conditions as in Example 1.

(Pressurized firing)
The sintered CIGS thin film was obtained by simultaneous pressure firing under the same conditions as in Example 4 except that the number of substrates was two.

(Heat treatment)
The sintered CIGS thin films obtained by the pressure firing were each heat-treated at 600 ° C. for 10 minutes in a nitrogen atmosphere. At this time, the substrate was put in a petri dish made of quartz glass, and Se was put in the petri dish.

(Thin film characteristics)
The surface and cross-sectional microstructures of the two types of CIGS thin films obtained above were observed with an SEM. Those photographs are shown in FIG. As shown in FIG. 22, crystal growth and densification were observed in the CIGS thin film of this example, and it was confirmed that a dense CIGS thin film was obtained by the method of this example. A solar cell having an Al / n-ZnO: B / i-ZnO / CdS / CIGS / Mo / soda lime glass structure having the structure shown in FIG. As a result, the solar cell characteristics were confirmed, and it was confirmed that the dense CIGS thin film produced by the method of this example was useful as a light absorption layer of the solar cell.

[Example 10]
(Preparation of (In _0.995 Ga _0.005 ) ₂ Se ₃ powder)
In the same manner as in Example 6, In powder, Ga powder and Se powder were weighed at a molar ratio of 1.99: 0.01: 3. The powder weighed in a 45 cc container made of zirconia for a planetary ball mill and 40 g of 1 mm diameter zirconia cobblestone were placed. The filling amount of the powder in the container was adjusted to 20 g by adding Cu powder and Se powder when preparing the coating agent. They were stirred at 800 rpm for 20 minutes under a nitrogen atmosphere to obtain a powder having a composition ratio of (In _0.995 Ga _0.005 ) ₂ Se ₃ . Similarly, a total of 4 pots having such a composition ratio of (In _0.995 Ga _0.005 ) ₂ Se ₃ were prepared.

(Preparation of coating agent)
Cu _0.95 (In _0.995 Ga _0.005 ) Se _{2 was added} to each of the four zirconia containers containing powders having a composition ratio of (In _0.995 Ga _0.005 ) ₂ Se _3. Cu powder and Se powder were added to a ratio of _.10 . Furthermore, 0.5 mol% of NaF (Cu _0.95 (In _0.995 Ga _0.005 ) Se _2.10 corresponds to 0.005 mol with respect to 1 mol) was added thereto. In three of the four pots, 0.25 mol%, 1.0 mol%, and 2.0 mol% (Cu _0.95 (In _0.995 Ga _0.005 ) Se) were used as sintering aids, respectively. _2.10 corresponds to 0.0025, 0.01, and 0.02 per 1 mol), and Sb was not added to the remaining one. Furthermore, 9 ml of terpineol as a solvent was added to these four types of pots, and the inside of the container was placed in a nitrogen atmosphere and stirred at 700 rpm for 5 hours to obtain an ink as a coating agent.

(Application)
As a substrate, 5 cm □ soda lime glass (thickness 2 mm) was prepared. The obtained ink was applied by screen printing (500 mesh) to form an application layer.

(Dry)
The substrate on which the coating layer was formed was dried at 110 ° C. for 5 minutes in a nitrogen atmosphere.

(Pressurized firing)
These substrates were simultaneously fired under pressure in the same manner as in Example 4 except that the number of substrates was four, and the coating layer was sintered to produce a CIGS thin film. The conditions for pressure firing are the same as in Example 4.

(Membrane characteristics)
The four types of CIGS thin films obtained in Example 10 (addition amounts of Sb of 0.25 mol%, 1.0 mol%, 2.0 mol%, and Sb were not added) were subjected to XRD analysis. The X-ray diffraction pattern coincides with the X-ray diffraction pattern obtained by simulation based on crystal structure analysis data (ICSD: Inorganic Crystal Structure Database # 70051), and it was found that a CIGS thin film having a chalcopyrite structure was synthesized. From this X-ray diffraction pattern, it was confirmed that the CIGS thin film of this example was a single phase containing no impurities, as in the case of Example 1. Moreover, the surface microstructure of the obtained thin film was observed with SEM. The result is shown in FIG. From these SEM photographs, sufficient densification is observed without adding Sb as a sintering aid, but by adding Sb as a sintering aid, the densification becomes more dense as the amount added increases. It turns out that it is promoted.

[Example 11]
(Preparation of (In _0.995 Ga _0.005 ) ₂ Se ₃ and (In _0.9 Ga _0.1 ) ₂ Se ₃ powder)
In powder, Ga powder and Se powder were weighed in a molar ratio of 1.99: 0.01: 3 and 1.80: 0.20: 3. The powder weighed in a 45 cc container made of zirconia for a planetary ball mill and 40 g of 1 mm diameter zirconia cobblestone were placed. The filling amount of the powder in the container was adjusted to 20 g by adding Cu powder and Se powder during the preparation of the coating agent. They are stirred at 800 rpm for 20 minutes in a nitrogen atmosphere to obtain a powder having a composition ratio of (In _0.995 Ga _0.005 ) ₂ Se ₃ and (In _0.9 Ga _0.1 ) ₂ Se _3. It was.

(Preparation of coating agent)
In the zirconia container used for the preparation of the powder having the composition ratio of (In _0.995 Ga _0.005 ) ₂ Se ₃ and (In _0.9 Ga _0.1 ) ₂ Se ₃ , Cu _0.9 ( Cu powder and Se powder were added so as to have a ratio of In _0.995 Ga _0.005 ) Se _2.10 to Cu _0.9 (In _0.9 Ga _0.1 ) Se _2.10 . Furthermore, 0.5 mol% of NaF was added to them (Cu _0.9 (In _0.995 Ga _0.005 ) Se _2.10 and Cu _0.9 (In _0.9 Ga _0.1 ) Se _2.10 ). Equivalent to 0.005 mol per 1 mol). In the two pots, 2 mol% (Cu _0.9 (In _0.995 Ga _0.005 ) Se _2.10 and Cu _0.9 (In _0.9 Ga _0.1 ) Se were used as sintering aids. _2.10 corresponds to 0.02 mol per 1 mol). Furthermore, 9 ml of terpineol was added to these pots as a solvent, and the inside of the container was placed in a nitrogen atmosphere and stirred at 700 rpm for 5 hours to obtain ink as a coating agent.

(Application)
As a substrate, 5 cm □ soda lime glass (thickness 2 mm) was prepared. The obtained ink was applied by screen printing (500 mesh) to form an application layer.

(Dry)
The substrate on which the coating layer was formed was dried at 110 ° C. for 5 minutes in a nitrogen atmosphere.

(Pressurized firing)
In the same manner as in Example 4, these substrates were simultaneously fired under pressure, and the coating layer was sintered to produce a CIGS thin film. The conditions for pressure firing are the same as in Example 4.

(Membrane characteristics)
Two types of CIGS thin films obtained in Example 11 were subjected to XRD analysis. The X-ray diffraction pattern basically matches the X-ray diffraction pattern obtained by simulation based on crystal structure analysis data (ICSD: Inorganic Crystal Structure Database # 70051), and a CIGS thin film having a chalcopyrite structure is synthesized. all right. From this X-ray diffraction pattern, it was confirmed that the CIGS thin film of this example was a single phase containing no impurities, as in the case of Example 1. Moreover, the surface microstructure of the obtained thin film was observed with SEM. The result is shown in FIG. From these SEM photographs, it can be seen that crystal grain growth and densification are observed in any sample. A solar cell having an Al / n-ZnO: B / i-ZnO / CdS / CIGS / Mo / soda lime glass structure having the structure shown in FIG. As a prototype, the solar cell characteristics were confirmed, and it was found that a dense CIGS thin film produced by the method of this example was useful as a light absorption layer of a solar cell.

[Example 12]
(Preparation of raw material powder)
After weighing element powders Cu, In, Se, Te to a ratio of Cu _1.02 In (Se _1-X Te _X ) _2.1 (X = 0.0, 0.3, 0.5), in the same manner as in example 1 to obtain a powder mainly composed of _{CuIn (Se 1-X Te X} ) 2. Here, the three levels of X = 0.0, 0.3, and 0.5.

(Preparation of coating agent)
Entered zirconia containers starting powder whose main component is the _{CuIn (Se 1-X Te X} ) 2, except that by adding each 13ml ethylene glycol monophenyl ether, and stirred under the same conditions as in Example 1, the coating Three types of inks were obtained.

(Application)
As a substrate, 5 cm □ soda lime glass (thickness 2 mm) was prepared. The obtained ink was applied by screen printing (500 mesh) to form an application layer.

(Dry)
The substrate on which the coating layer was formed was dried at 145 ° C. for 7 minutes in a nitrogen atmosphere.

(Pressurized firing)
In the same manner as in Example 4, these substrates were simultaneously fired under pressure, and the coating layer was sintered to produce a CuIn (Se _1-X Te _X ) ₂ thin film. The conditions for pressure firing are the same as in Example 4.

(Heat treatment)
The sintered CuIn (Se _1-X Te _X ) ₂ thin films obtained by the pressure firing were each heat-treated at 550 ° C. for 10 minutes in a nitrogen atmosphere. At this time, the substrate was put in a petri dish made of quartz glass, and Se was put in the petri dish.

(Membrane characteristics)
Fabricated _CuIn the _(Se 1-X _{Te X)} near-infrared absorption spectrum of ₂ thin film, the wavelength is measured in the range of 900Nm～1600nm. FIG. 25A shows a graph of the light transmittance of the prepared CuIn (Se _1-X Te _X ) ₂ thin film. _{Thus, CuIn (Se 1-X Te} X) dense Makugae be even ₂ thin film, it can be seen that the absorption edge of light with increasing amount of solid solution Te is shifted to the long wavelength side. In order to obtain the forbidden band width of the CuIn (Se _1-X Te _X ) ₂ thin film from this transmission spectrum, (αhν) ² plots with respect to hν assuming a direct transition semiconductor are shown in FIGS. ) And (d). From FIG. 25B, the forbidden band width of the CuIn (Se _1-X Te _X ) ₂ thin film is 0.98 eV when X = 0.0, and 0.90 eV when X = 0.3 from FIG. 25C. It can be seen from (d) that at X = 0.5, it is 0.88 eV.

[Example 13]
(Preparation of raw material powder)
Conducted after weighing element powders Cu, Zn, Sn, Se to a ratio of Cu _2.04 ZnSnSe _4.2 (equivalent to Cu _1.02 (Zn _0.5 Sn _0.5 ) Se _2.1 ) In the same manner as in Example 1, a powder containing Cu ₂ ZnSnSe ₄ as a main component was obtained.

(Preparation of coating agent)
An ink as a coating agent was obtained by stirring under the same conditions as in Example 1 except that 13 ml of ethylene glycol monophenyl ether was added to a container made of zirconia containing the raw material powder containing Cu ₂ ZnSnSe ₄ as a main component. .

(Application)
As a substrate, 5 cm □ soda lime glass (thickness 2 mm) was prepared. The obtained ink was applied by screen printing (500 mesh) to form an application layer.

(Dry)
The substrate on which the coating layer was formed was dried at 145 ° C. for 7 minutes in a nitrogen atmosphere.

(Pressurized firing)
In the same manner as in Example 1, the coating layer was sintered to prepare a Cu ₂ ZnSnSe ₄ thin film. The conditions for pressure firing are the same as in Example 1.

(Thin film characteristics)
The Cu ₂ ZnSnSe ₄ thin film obtained in Example 13 was analyzed by X-ray diffraction (XRD). The obtained X-ray diffraction pattern is shown in FIG. This X-ray diffraction pattern basically coincides with the X-ray diffraction pattern obtained by simulation based on the crystal structure analysis data (ICSD: Inorganic Crystal Structure Database # 95007) of Cu ₂ ZnSnSe ₄ shown below, and the Cu ₂ ZnSnSe ₄ thin film Was found to be synthesized. From this X-ray diffraction pattern, it can be confirmed that the Cu ₂ ZnSnSe ₄ thin film of this example is a single phase containing no impurities.

The surface and cross-sectional microstructure of the obtained thin film were observed with a scanning electron microscope (SEM). Those photographs are shown in FIG. From these photographs, growth of crystal grains and densification of Cu ₂ ZnSnSe ₄ are recognized, and it can be confirmed that a dense Cu ₂ ZnSnSe ₄ thin film can be obtained by the method of this example.

The near-infrared light absorption spectrum of the prepared Cu ₂ ZnSnSe ₄ thin film was measured in a wavelength range of 900 nm to 1600 nm. FIG. 28 (a) shows a graph of the light transmittance of the prepared Cu ₂ ZnSnSe ₄ thin film. FIG. 28B shows a diagram in which (αhν) ^{2 is} plotted against hν, assuming a direct transition semiconductor, in order to obtain the forbidden band width of the Cu ₂ ZnSnSe ₄ thin film from this transmission spectrum. FIG. 28B shows that the forbidden band width of the Cu ₂ ZnSnSe ₄ thin film is 1.05 eV.

[Example 14]
(Preparation of raw material powder)
After weighing the element powders Cu, Ag, Ga, Se to a ratio of (Cu _1-X Ag _X ) GaSe _2.1 (X = 0.2, 0.8), the same as in Example 1, A powder containing (Cu _1-X Ag _X ) GaSe ₂ as a main component was obtained. Here, two levels of X = 0.2 and 0.8.

(Preparation of coating agent)
Except for adding 8 ml of ethylene glycol monophenyl ether to a silicon nitride container containing a raw material powder mainly composed of (Cu _1-X Ag _X ) GaSe ₂ and using a silicon nitride boulder having a diameter of 3 mm, The mixture was stirred under the same conditions as in Example 1 to obtain two types of inks as coating agents.

(Application)
As a substrate, 5 cm □ soda lime glass (thickness 2 mm) was prepared. The obtained ink was applied by screen printing (500 mesh) to form an application layer.

(Dry)
The substrate on which the coating layer was formed was dried at 145 ° C. for 7 minutes in a nitrogen atmosphere.

(Pressurized firing)
In the same manner as in Example 4, these substrates were simultaneously fired under pressure, and the coating layer was sintered to produce a (Cu _1-X Ag _X ) GaSe ₂ thin film. The conditions for pressure firing are the same as in Example 4.

(Heat treatment)
The sintered (Cu _1-X Ag _X ) GaSe ₂ thin films obtained by the pressure firing were each heat-treated at 600 ° C. for 10 minutes in a nitrogen atmosphere. At this time, the substrate was put in a petri dish made of quartz glass, and Se was put in the petri dish.

(Membrane characteristics)
Since according to this example dense _{(Cu 1-X Ag X)} GaSe 2 thin film could be produced, ultraviolet resulting membrane - visible - the infrared absorption spectrum, the wavelength is measured in the range of 350Nm～1600nm. As bandgap of AgGaSe ₂ bandgap at 1.68eV of CuGaSe ₂ it is expected because it is 1.80 eV, towards the solute intensive X = 0.8 of the membrane of Ag is X = It has been found that the absorption edge has a shorter wavelength than the 0.2 film, and that the forbidden band width is slightly increased due to the solid solution of Ag.

  According to the method for producing a compound semiconductor thin film of the present invention, the compound semiconductor thin film can be easily provided at a low cost by a non-vacuum process. This manufacturing method enables material application under normal pressure, reduces capital investment in the manufacturing equipment, and reduces the amount of material used. Manufacturing that can greatly reduce costs in the manufacturing process of solar cell modules It is applicable as a method. The obtained compound semiconductor thin film can be applied to a wide range of uses such as solar cells.

DESCRIPTION OF SYMBOLS 1 CIGS coating film 2 Substrate 3 Spacer 4, 4 'Push bar 5, 5' Push plate 6, 6 'Second push plate (graphite sheet)
11, 21, 31 CIGS coating film 12, 22, 32 Substrate 13, 23, 33 Spacer 17, 27, 37 Intermediate pressing plate 130 Compound semiconductor thin film manufacturing apparatus 131 Chamber 132 Heating tank 133 Heater 134, 134 'Push rod 141 Substrate 142 Back surface Electrode 143 Light absorption layer 144 Buffer layer 145 Transparent electrode 146 Extraction electrode 147 Antireflection layer

Claims (22)

A method for producing a compound semiconductor thin film containing a group B element, a group B element, and a group V element, and a step of preparing a coating agent containing the group B element, the group B element, and the group V element,
Applying the coating agent to a substrate to form a coating film;
A method for producing a compound semiconductor thin film, comprising: a pressure firing step in which the coating film is heated and sintered under a condition where mechanical pressure is applied. As a coating agent containing the ΙB group element, ΙΙΙB group element and VΙB group element,
The manufacturing method of the compound semiconductor thin film of Claim 1 using the coating agent containing the compound particle | grains containing the element of the at least 2 sorts of group chosen from the ΙB group element, the ΙΙΙB group element, and the VΙB group element. As a coating agent containing the ΙB group element, ΙΙΙB group element and VΙB group element,
The manufacturing method of the compound semiconductor thin film of Claim 1 or 2 using the coating agent containing the compound particle | grains containing the ΙΙΙB group element and the VΙB group element, the ΙB group element powder, and the VΙB group element powder. As a coating agent containing the ΙB group element, ΙΙΙB group element and VΙB group element,
The manufacturing method of the compound semiconductor thin film of Claim 1 or 2 using the coating agent containing the compound particle | grain containing a ΙB group element, a ΙΙΙB group element, and a VΙB group element. The method for producing a compound semiconductor thin film according to claim 2, wherein compound particles obtained by performing a mechanochemical process are used as the compound particles. The method for producing a compound semiconductor thin film according to claim 1, wherein the group B element is at least one element selected from Cu and Ag. The method for producing a compound semiconductor thin film according to any one of claims 1 to 6, wherein the group B element is at least one element selected from In, Ga, and Al. The method for producing a compound semiconductor thin film according to any one of claims 1 to 7, wherein the VΙB group element is at least one element selected from S, Se, and Te. The method for producing a compound semiconductor thin film according to claim 1, wherein the coating agent further contains Sb. Furthermore, the manufacturing method of the compound semiconductor thin film as described in any one of Claim 1 to 9 which performs the drying process which dries the said coating film before the said pressurization baking process. The method for producing a compound semiconductor thin film according to any one of claims 1 to 10, wherein a pressure applied mechanically in the pressure firing step is in a range of more than 0 Pa and 100 MPa or less. The manufacturing method of the compound semiconductor thin film as described in any one of Claim 1 to 11 with which the said pressurization baking process is performed at the temperature within the range of 300 to 650 degreeC. The manufacturing method of the compound semiconductor thin film as described in any one of Claim 1 to 12 with which the said pressurization baking process is performed in the atmosphere of the pressure of the range of normal pressure to 1 MPa. The method for producing a compound semiconductor thin film according to any one of claims 1 to 13, wherein a heat treatment step of heating in an atmosphere having a pressure in a range of normal pressure to 1 MPa is further performed after the pressure firing step. The method for producing a compound semiconductor thin film according to claim 14, wherein the heat treatment step is performed at a temperature higher than a temperature in the pressure firing step. The method for producing a compound semiconductor thin film according to any one of claims 1 to 15, wherein the step of applying the coating agent to the substrate is performed by screen printing. The method for producing a compound semiconductor thin film according to any one of claims 1 to 16, wherein, in the pressure firing step, pressure firing is performed in a state where a plurality of substrates on which the coating film is formed are stacked. The method for producing a compound semiconductor thin film according to claim 17, wherein a spacer is provided between the plurality of stacked substrates and pressure firing is performed. The method for producing a compound semiconductor thin film according to claim 18, wherein a spacer selected from the group consisting of metal, glass and ceramics is used as the spacer. The method for producing a compound semiconductor thin film according to any one of claims 1 to 19, wherein a combination of a group B element and a group VB element is used in addition to or instead of the group B element. A solar cell having a compound semiconductor thin film,
The solar cell, wherein the compound semiconductor thin film is manufactured by the method for manufacturing a compound semiconductor thin film according to any one of claims 1 to 20. 21. An apparatus for manufacturing a compound semiconductor thin film according to any one of claims 1 to 20, comprising at least a pressing means and a heating means.