JP2010141307A - Method for manufacturing thin-film solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a thin-film solar cell with a low manufacturing cost, which can reliably and sufficiently diffuse an alkali metal to a light absorbing layer. <P>SOLUTION: The method for manufacturing a thin-film solar cell including a light absorbing layer 3 between a first electrode layer 2 and a second electrode layer 5 includes: a step of producing a light absorbing layer solution including Cu, In, and an alkali metal as elements; a step of producing a precursor by applying and drying the light absorbing layer solution on the first electrode layer; a step of heat-treating the precursor under a reduction atmosphere, and forming the light absorbing layer 3 including Cu, In, and the alkali metal as elements, on the first electrode layer 2; and a step of forming the second electrode layer 5 on the light absorbing layer 3. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a thin film solar cell having a light absorption layer between a pair of electrode layers.

  FIG. 1 shows a basic structure of a general thin film solar cell. As shown in FIG. 1, the thin-film solar cell has a first electrode layer 2 made of, for example, Mo formed on a substrate 1 made of soda lime glass, for example, and is formed on the first electrode layer 2. A light absorption layer 3 made of a compound semiconductor thin film is formed, and a transparent second electrode layer 5 made of ZnO or the like is formed on the light absorption layer 3 through a buffer layer 4 made of ZnS, CdS, or the like. .

As the light absorption layer 3 made of a compound semiconductor, a compound semiconductor thin film made of Cu (In, Ga) Se ₂ is used as one capable of obtaining high energy conversion efficiency.

  Conventionally, the first electrode layer 2, the light absorption layer 3, the buffer layer 4, and the second electrode layer 5 are usually formed by a vapor deposition method or a sputtering method called a dry method.

In such a thin-film solar cell, alkali metal from the substrate 1 made of soda lime glass diffuses into the light absorption layer 3 to grow crystal grains of Cu (In, Ga) Se ₂ , thereby energy conversion efficiency. Can be improved.

Conventionally, a manufacturing method is known in which sodium selenide is deposited on the first electrode layer 2 by vapor deposition, and the light absorption layer 3 is formed thereon by sputtering (see Patent Document 1). Furthermore, a method is also known in which, when Cu (In, Ga) Se ₂ or the like is vapor-deposited, a compound such as Na ₂ Se or Na ₂ S is vapor-deposited at the same time, followed by heat treatment (see Patent Document 2).

  Conventionally, the first electrode layer 2 is formed by a sputtering method, a solution in which an alkali metal is dissolved is applied on the first electrode layer 2 to form an alkali metal layer, and a light absorption layer is formed on the surface by a sputtering method. A method for producing a thin film solar cell in which 3 is formed is also known (see Patent Document 3).

  Furthermore, after forming the 1st electrode layer 2 and the light absorption layer 3 by sputtering method, the solution containing an alkali metal is apply | coated to the light absorption layer 3, an alkali metal layer is formed, and the manufacturing method of heat-processing after this is also known. (See Patent Document 4).

  In such a method for manufacturing a thin film solar cell, the alkali metal in the alkali metal layer diffuses into the light absorption layer 3 during the heat treatment, and crystal grains in the light absorption layer 3 can be grown.

JP-A-8-222750 JP-A-8-102546 JP 2003-282908 A Republished patent publication of WO2005 / 109525

  However, when an alkali metal layer is formed on the first electrode layer 2 by vapor deposition or sputtering as in the manufacturing method of Patent Document 1, the alkali metal layer such as Na has hygroscopicity. There was a problem that the alkali metal layer was exposed to the atmosphere and changed in quality after the layer was formed and before the multilayer precursor was formed, and peeled off from the first electrode layer 2.

  In the production method of Patent Document 2, in addition to the problem that the alkali metal is hygroscopic, there is a problem that the deposition apparatus is enlarged and the equipment cost is increased. Such problems of Patent Documents 1 and 2 are problems peculiar to dry methods such as vapor deposition and sputtering.

  On the other hand, in the production methods of Patent Documents 3 and 4, the problems peculiar to the dry process are solved. However, there is a problem that the diffusion of the alkali metal into the light absorption layer 3 is unstable, and the diffusion state of the alkali metal is easily changed depending on the formation conditions of the alkali metal layer, the heat treatment conditions, and the like.

  An object of the present invention is to provide a method for producing a thin-film solar cell that can reliably and sufficiently diffuse an alkali metal into a light absorption layer and that is inexpensive to produce.

  The method for producing a thin film solar cell according to the present invention is a method for producing a thin film solar cell having a light absorption layer between a first electrode layer and a second electrode layer, wherein Cu, III-B group metal and alkali metal are used as elements. A step of preparing a light absorption layer solution containing, a step of preparing a precursor by applying the light absorption layer solution on the first electrode layer and drying, and heat-treating the precursor in a reducing atmosphere, Forming the light absorption layer containing Cu, III-B group metal and alkali metal as elements on the first electrode layer; and forming the second electrode layer on the light absorption layer. It is characterized by comprising.

  In the method for producing a thin-film solar cell of the present invention, a light absorption layer solution containing Cu, III-B group metal and alkali metal as elements is prepared, and this light absorption layer solution is applied on the electrode layer and dried. Since the light absorption layer was formed by heat treatment in a reducing atmosphere, the alkali metal was dissolved together with the Cu and III-B metal in the light absorption layer solution, and the alkali metal was dissolved in the light absorption layer solution. Since it is uniformly dispersed, the diffusion of the alkali metal into the light absorption layer can be reliably and sufficiently performed by applying the light absorption layer solution and drying.

  As a result, the crystal grains constituting the light absorption layer can be uniformly and sufficiently grown by alkali metal during heat treatment, and there is no unevenness of grain growth depending on the location, and energy conversion efficiency for each product. Can be controlled almost the same, which can improve the manufacturing yield.

  Also, using a light absorbing layer solution containing Cu, III-B group metal and alkali metal, this light absorbing layer solution is applied and dried to prepare a precursor, which is then heat-treated to prepare a light absorbing layer Therefore, unlike the conventional method, the vapor deposition method or the sputtering method is not used to form the light absorption layer or the alkali metal layer, so that the manufacturing process can be simplified, and expensive gas, equipment, or the like is used. Therefore, the manufacturing cost can be reduced.

  In the method for producing a thin-film solar cell of the present invention, the reducing atmosphere is an atmosphere containing Se, and the heat absorption layer contains Cu, III-B metal, Se, and an alkali metal as elements by heat treatment. It is characterized by forming. In such a manufacturing method, a light-absorbing layer is selenized by heat-treating a precursor containing Cu, a group III-B metal and an alkali metal in an atmosphere containing Se, and Cu, a group III-B metal, Se And a light absorption layer containing an alkali metal can be formed, grain growth by the alkali metal element can be further promoted, and energy conversion efficiency can be further improved.

  Furthermore, in the method for producing a thin-film solar cell of the present invention, the light absorption layer solution contains Se as an element, and the light absorption containing Cu, III-B group metal, Se, and an alkali metal as an element by heat treatment. A layer is formed. In such a production method, Cu, a group III-B metal, Se, and an alkali metal are contained in the precursor, so that grain growth by heat treatment in a reducing atmosphere can be further promoted, and energy conversion efficiency can be further improved. .

  In the method for manufacturing a thin-film solar battery of the present invention, the light absorption layer solution is prepared by preparing a solution containing Cu, a solution containing a group III-B metal, and a solution containing an alkali metal, and mixing these solutions. It is characterized by being manufactured.

  In such a manufacturing method, a solution containing Cu, a solution containing a group III-B metal, and a solution containing an alkali metal are prepared and mixed, so that Cu, In, and the alkali metal can be uniformly dissolved, Since there is no uneven mixing of the metal and uniform dispersion mixing is possible, uniform crystal growth can be realized to further improve the uniformity of film formation, and the crystal grain size can be further increased.

  Furthermore, in the method for manufacturing a thin-film solar battery according to the present invention, the reducing atmosphere is an atmosphere from which moisture has been removed. In such a manufacturing method, since heat treatment is performed in a reducing atmosphere from which moisture has been removed, alkali metal in the light absorption layer can be prevented from absorbing moisture, and alteration of the light absorption layer can be suppressed.

  Furthermore, in the method for producing a thin-film solar battery according to the present invention, the light absorption layer solution includes a raw material containing Cu as an element and a group III-B metal in a solvent containing a chalcogen element-containing organic compound and a Lewis basic organic solvent. It is characterized by dissolving a raw material and a raw material containing an alkali metal.

  In such a production method, the chalcogen element-containing organic compound and the Lewis basic organic solvent can form a stable complex with Cu, a group III-B metal and an alkali metal, and the raw material can be dissolved at a high concentration. Therefore, it is possible to increase the viscosity of the light absorption layer solution and form a good precursor that is thick and has a uniform distribution of raw materials.

  Furthermore, in the method for producing a thin-film solar cell according to the present invention, the light absorption layer solution is formed by directly dissolving Cu or a group III-B metal in the state of a single metal or an alloy thereof in the solvent. And

  Note that Cu or III-B metal is directly dissolved in the solvent in the state of a single metal because the Cu or III-B metal is dissolved in the solvent directly in the state of a single metal. It means being done. In addition, Cu or III-B metal is directly dissolved in the solvent in the state of the alloy because the alloy of Cu and III-B metal or the alloy of III-B metal is included in the solvent. Directly dissolved in the solvent.

  In such a production method, Cu or III-B group metal is directly dissolved without being converted into an organometallic compound or metal salt, so that impurities other than the components constituting the light absorption layer are contained in the light absorption layer solution. It can suppress favorably remaining. Moreover, the conversion to an organometallic compound or a metal salt is unnecessary, and the process can be simplified.

  According to the method of manufacturing a thin film solar cell of the present invention, the alkali metal is dissolved together with Cu and In in the light absorption layer solution, and the alkali metal is uniformly dispersed in the light absorption layer solution. By applying and drying the layer solution, it is possible to reliably and sufficiently diffuse the alkali metal into the light absorption layer. Thereby, the energy conversion efficiency for every product can be controlled to be substantially the same, and the production yield can be improved. Further, unlike the conventional method, the vapor deposition method or the sputtering method is not used for the formation of the light absorption layer or the alkali metal layer, so that the manufacturing process can be simplified, and it is necessary to use an expensive gas or apparatus. Therefore, the manufacturing cost can be reduced.

It is sectional drawing which shows an example of a thin film solar cell.

  The thin film solar cell produced by the manufacturing method of the present invention is a thin film solar cell having a light absorption layer between a pair of electrode layers. For example, as shown in FIG. A layer 2 is formed, a light absorption layer 3 made of a compound semiconductor thin film is formed on the first electrode layer 2, and a transparent second electrode layer 5 is formed on the light absorption layer 3 via a buffer layer 4. ing.

  As the substrate 1, for example, a soda lime glass substrate, a metal substrate such as Mo or SUS, a resin substrate such as polyimide, or the like can be used. A first electrode layer 2 is formed on the substrate 1, and a light absorption layer 3 is formed on the first electrode layer 2. A second electrode layer 5 is formed on the light absorption layer 3 via the buffer layer 4, and the light absorption layer 3 is sandwiched between the first electrode layer 2 and the second electrode layer 5. 1, a thin film solar cell having a light absorption layer 3 between the second electrode layers 2 and 5 is configured.

  In addition, although the example which laminated | stacked the board | substrate 1, the 1st electrode layer 2, the light absorption layer 3, the buffer layer 4, and the 2nd electrode layer 5 was demonstrated sequentially, in this invention, a pair of 1st, 2nd electrode layer 2, As long as the light absorption layer 3 is provided between the layers 5, various intermediate layers may be formed between the layers. Further, the present invention may be of a type that does not have the substrate 1, in other words, a type in which the first electrode layer 2 functions as a substrate.

As the light absorption layer 3 made of a compound semiconductor, a compound semiconductor made of a chalcopyrite structure is used so that high energy conversion efficiency can be obtained. As a compound semiconductor having a chalcopyrite structure, an I-III-VI group compound semiconductor is used, and examples thereof include CuInSe ₂ and Cu (In, Ga) Se ₂ . The I-III-VI group compound semiconductor is a compound semiconductor composed of a group IB (also referred to as group 11) element, a group III-B (also referred to as group 13) element and a group VI-B (also referred to as group 16) element. It is.

The manufacturing method of the thin film solar cell of this invention is demonstrated. First, for example, a substrate 1 made of soda lime glass is prepared. A first electrode layer 2 is formed on the substrate 1. The first electrode layer 2 is made of any electrode material selected from molybdenum (Mo), tungsten (W), chromium (Cr), polysilicon (SiO ₂ ), metal silicide, aluminum (Al), and the like. desirable. The first electrode layer 2 can be formed by a vapor deposition method, a sputtering method, a coating method, or the like.

  Next, the light absorption layer 3 is formed on the first electrode layer 2. First, a light absorption layer solution for forming the light absorption layer 3 is prepared. This light absorption layer solution is a solution in which Cu, a Group III-B metal and an alkali metal are dissolved, and includes a Cu, a Group III-B metal and an alkali metal, and a nitrogen-containing solvent. Note that the group III-B metal is a group III-B (also referred to as group 13) metal such as Ga or In. The group III-B metal may be one element or two or more elements. The light absorption layer solution is desirably a solution in which Cu, In, Ga, and an alkali metal are dissolved. Furthermore, a solution in which Cu, In, Ga, Se, and an alkali metal are dissolved is desirable. Hereinafter, the case where the light absorption layer solution contains Cu, In, Ga, and an alkali metal will be described.

  As the nitrogen-containing solvent, for example, at least one of ammonia, hydrazine, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, ethanolamine, allylamine, ethanolamine, diethanolamine, triethanolamine, and aniline should be used. Can do.

  The light absorption layer solution is constituted by dissolving a copper compound, an indium compound, a gallium compound, and an alkali metal compound in the nitrogen-containing solvent described above. Examples of the copper compound include copper, copper selenide, and copper sulfide. Examples of the indium compound include indium, indium selenide, and indium sulfide. Examples of the gallium compound include gallium, gallium selenide, and sulfide. Gallium is used. In addition, although copper is not a copper compound, in this specification, copper was described as a copper compound for convenience. The same applies to indium in an indium compound and gallium in a gallium compound.

  As the alkali metal compound, at least one of an organic acid alkali metal salt, an organic alkali metal salt, and an alkali metal selenide salt can be used.

As the organic acid alkali metal salt, lithium acetate (CH ₃ COOLi), sodium acetate (CH ₃ COONa), potassium acetate (CH ₃ COOK), or the like is preferably used. As the organic alkali metal salt, methyl lithium, methyl sodium, methyl potassium, ethyl lithium, ethyl sodium, ethyl potassium and the like can be used. As the alkali metal selenide, lithium selenide (Li ₂ Se), sodium selenide (Na ₂ Se), or potassium selenide (K ₂ Se) can be used. Lithium sulfide (Li ₂ S), lithium telluride (Li ₂ Te), sodium sulfide (Na ₂ S), sodium telluride (Na ₂ Te), potassium sulfide (K ₂ S), potassium telluride (K ₂ Te) Can also be used.

  The light absorption layer solution includes, for example, a solution in which a copper compound is dissolved in a nitrogen-containing solvent, a solution in which an indium compound is dissolved in a nitrogen-containing solvent, a solution in which a gallium compound is dissolved in a nitrogen-containing solvent, and a nitrogen-containing solution of the alkali metal compound. It can be produced by mixing four types of solutions dissolved in a solvent. Thereby, the light absorption layer solution which Cu, In, Ga, and the alkali metal melt | dissolved uniformly in the organic solvent can be prepared.

  As the alkali metal compound, an organic acid alkali metal salt, an organic alkali metal salt, an alkali metal selenide, or the like is used, and the alkali metal can be uniformly dispersed and mixed by dissolving it in an organic solvent. Furthermore, it is desirable to use the same type of organic solvent in which Cu, In, and Ga are dissolved as the organic solvent in which the alkali metal compound is dissolved. Thereby, the solution in which the alkali metal is dissolved can be easily mixed with the solution containing Cu, In and Ga, and the problem of reprecipitation at the time of mixing can be eliminated.

  The light absorption layer solution is a solution containing at least one of an organic acid alkali metal salt, an organic alkali metal salt and an alkali selenide salt in an organic solvent, added to one solution containing Cu, In and Ga. It can also be produced by mixing.

  And this light absorption layer solution is apply | coated on the 1st electrode layer 2 of the above-mentioned board | substrate 1, it dries and produces a precursor, This precursor is heat-processed in a reducing atmosphere, on the 1st electrode layer 2, The light absorption layer 3 can be formed. The thickness of the light absorption layer 3 is, for example, 1.0 to 2.5 μm.

  The application of the light absorption layer solution onto the first electrode layer 2 is desirably performed using a spin coater, screen printing, dipping, spraying, a die coater, or the like. Drying is desirably performed in a reducing atmosphere. The temperature at the time of drying is 50-300 degreeC, for example.

  The light absorption layer solution includes organic solvents or ligands such as C, H, and N that are bonded to Cu, In, and Ga, and C, H, and N that are not bonded to Cu, In, and Ga. However, the precursor obtained by drying is composed of a combination of C, H, N, etc. and Cu, In, Ga.

The heat treatment is desirably performed in a reducing atmosphere. _{Thus, CuInSe 2, Cu (In,} Ga) light-absorbing layer consisting of Se _2, etc. can be obtained. In particular, any one of a nitrogen atmosphere, a forming gas atmosphere, and a hydrogen atmosphere is desirable. The reducing atmosphere during the heat treatment is preferably a reducing atmosphere in which moisture is removed through a hygroscopic agent. The hygroscopic agent is not particularly limited as long as it can remove moisture, but a molecular sieve or the like is preferably used. The heat treatment temperature is set to 400 ° C. to 600 ° C., for example.

After the formation of the light absorption layer 3, it is desirable to remove the high resistance layer made of Cu ₂ Se or the like on the surface by etching with a KCN aqueous solution.

Thereafter, an n-type buffer layer 4 for heterojunction is formed on the light absorption layer 3. CdS, ZnS, ZnSe, ZnMgO, ZnS / ZnMgO, ZnO, InS, InSe, In (OH) ₃ , ZnInSe, ZnInS, ZnSSe, CuI, Mg Materials such as OH) ₂ are used. These can be produced by immersing a substrate formed up to the light absorption layer by a dip coating method, a CBD method (solution growth method) or the like in an aqueous solution to deposit fine particles.

  Next, a transparent second electrode layer 5 made of ITO or ZnO is formed on the buffer layer 4. This second electrode layer can be formed by sputtering, spraying or coating. The thickness of the buffer layer 4 is, for example, 10 to 200 nm, and the thickness of the second electrode layer 5 is, for example, 0.5 to 3.0 μm.

  In the method for producing a thin film solar cell of the present invention, an alkali metal is dissolved together with Cu and III-B metals in the light absorption layer solution, and the light of the alkali metal is coated and dried. Diffusion into the absorption layer can be performed reliably and sufficiently. Therefore, during heat treatment, the particles constituting the light absorption layer 3 can be grown uniformly with alkali metal, and there is no grain growth unevenness depending on the location, and the energy conversion efficiency for each product is almost the same. Can be controlled, thereby improving the production yield.

  In addition, since a light absorption layer solution containing Cu, III-B group metal and alkali metal is prepared, applied and heat-treated to prepare the light absorption layer 3, Since an evaporation method or a sputtering method is not used for forming the alkali metal layer, the manufacturing process can be simplified, and an expensive gas or apparatus is not used, so that the manufacturing cost can be reduced.

  In the above example, the light absorption layer 3 made of Cu, In, Ga, and an alkali metal has been described. However, in the present invention, when heat treatment is performed, Se is contained in the atmosphere and heat treatment is performed in a selenization atmosphere. Se can be contained in the absorption layer 3, whereby it is possible to further promote grain growth by the alkali metal. Moreover, S can be contained in the light absorption layer 3 by containing S in the atmosphere.

  Furthermore, by including not only Cu, In, Ga, and an alkali metal but also Se in the light absorption layer solution, Se can be included in the light absorption layer 3. It becomes possible to further promote grain growth. Se is composed of a selenium compound dissolved in the above nitrogen-containing solvent. Examples of the selenium compound include selenium and selenium sulfide, which are mixed with a solution of Cu, In, Ga, and an alkali metal. It can produce using a light absorption layer solution. Further, by using copper selenide as the copper compound, indium selenide as the indium compound, gallium selenide as the gallium compound, or alkali metal selenide as the alkali metal compound, Se can be contained in the light absorption layer. it can.

  In the above example, the metal chalcogenide such as copper selenide is dissolved in a nitrogen-containing solvent and this solution is applied and baked. However, copper, indium, gallium, selenium, and sulfur are contained in one molecule. Nitrogen-containing compounds such as ammonia, hydrazine, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, ethanolamine, allylamine, ethanolamine, diethanolamine, triethanolamine, aniline, pyridine, Furthermore, alcohols such as methanol, ethanol, propanol, butanol, terpineol, propylene glycol, and acetone, acetonitrile, toluene, xylene, etc. There.

  Further, the light absorption layer solution includes a raw material containing Cu as an element, a raw material containing a Group III-B metal, and an alkali in a solvent containing a chalcogen element-containing organic compound and a Lewis basic organic solvent (hereinafter referred to as a mixed solvent S). It is preferable to dissolve a raw material containing a metal. Thereby, the chalcogen element-containing organic compound and the Lewis basic organic solvent can form a stable complex with Cu, III-B group metal and alkali metal, and the raw material can be dissolved at a high concentration. Therefore, it is possible to increase the viscosity of the light absorption layer solution and form a good precursor that is thick and has a uniform distribution of raw materials.

  The chalcogen element-containing organic compound is an organic compound containing a chalcogen element. The chalcogen element refers to S, Se, or Te among VI-B group elements. When the chalcogen element is S, examples of the chalcogen element-containing organic compound include thiol, sulfide, disulfide, thiophene, sulfoxide, sulfone, thioketone, sulfonic acid, sulfonic acid ester, and sulfonic acid amide. Preferably, thiol, sulfide, disulfide and the like are preferable from the viewpoint that a metal solution can be favorably produced by forming a complex with a metal. In particular, those having a phenyl group are preferred from the viewpoint of enhancing the coating property. As what has such a phenyl group, thiophenol, diphenyl sulfide, etc. and derivatives thereof are mentioned, for example.

  When the chalcogen element is Se, examples of the chalcogen element-containing organic compound include selenol, selenide, diselenide, selenoxide, and selenone. Preferably, from the viewpoint that a metal solution can be satisfactorily formed by forming a complex with a metal, serer, selenide, diselenide and the like are preferable. In particular, those having a phenyl group are preferred from the viewpoint of enhancing the coating property. Examples of those having such a phenyl group include phenyl selenol, phenyl selenide, diphenyl diselenide and the like and derivatives thereof.

  When the chalcogen element is Te, examples of the chalcogen element-containing organic compound include tellurol, telluride, ditelluride, and the like.

  A Lewis basic organic solvent is an organic solvent that can be a Lewis base with respect to Cu and III-B group metals. Examples of the Lewis basic organic solvent include pyridine, aniline, triphenylphosphine, and derivatives thereof. In particular, those having a boiling point of 100 ° C. or higher are preferable from the viewpoint of improving the coating property.

  The mixed solvent S is preferably a combination that becomes liquid at room temperature from the viewpoint of handleability. The number of moles of the chalcogen element-containing organic compound is preferably 0.1 to 10 times the number of moles of the Lewis basic organic solvent. Thereby, Cu or III-B group metal which is a raw material for forming the light absorption layer 3 can form a chemical bond such as a coordinate bond well with the chalcogen element-containing organic compound and the Lewis basic organic solvent. A high concentration light absorption layer solution can be obtained.

  As a method for preparing a light absorption layer solution by dissolving Cu or a group III-B metal in the mixed solvent S, the Cu or group III-B metal is directly dissolved in the mixed solvent S in a single metal state, Alternatively, it is preferable to directly dissolve an alloy of Cu and a group III-B metal or an alloy of group III-B metals in the mixed solvent S. In such a manufacturing method, Cu or III-B group metal is directly dissolved without being converted into an organometallic compound or metal salt, so that impurities other than the components constituting the light absorption layer 3 are contained in the light absorption layer solution. Can be suppressed satisfactorily. Moreover, the conversion to an organometallic compound or a metal salt is unnecessary, and the process can be simplified.

  The group III-B metal may be one element or two or more elements. In the case of two or more elements, a method for preparing a solution by dissolving a group III-B metal in the mixed solvent S is to mix a mixture of two or more group III-B metals into the mixed solvent S at a time. It may be dissolved. Alternatively, the group III-B metal of each element may be dissolved in the mixed solvent S and then mixed.

  Se or Se compound may be dissolved in the mixed solvent S as a raw material for constituting the light absorption layer 3. In the case of using the mixed solvent S, it is preferable because the Se simple metal can be directly dissolved, so that it is possible to satisfactorily suppress the components other than the elements constituting the light absorption layer 3 from remaining. In addition, you may perform supply of Se or Se compound by making the gas containing Se or Se compound contact the precursor obtained by apply | coating a light absorption layer solution. The element Se element may be an S element.

  Hereinafter, although the example and the comparative example are given and the manufacturing method of the thin film solar cell of this invention is demonstrated in detail, this invention is not limited only to a following example.

0.206 g (1 mmol) of copper selenide (Cu ₂ Se) as the copper compound, 0.467 g (1 mmol) of indium selenide (In ₂ Se ₃ ) as the indium compound, and gallium selenide (Ga ₂ Se ₃ as the gallium compound) ) Was dissolved in 30 ml of pyridine to prepare three types of solutions in which Cu ₂ Se, In ₂ Se ₃ and Ga ₂ Se ₃ were dissolved. In the three types of solutions, Cu, In, or Ga was dissolved in pyridine.

Furthermore, as an alkali metal salt, sodium acetate and 2.3 × 10 ⁻⁵ g in terms of metal were dissolved in 5 ml of pyridine to prepare a solution in which Na was dissolved in pyridine.

  Thereafter, each of the three types of solutions in which Cu, In and Ga are dissolved in pyridine and a solution in which Na is dissolved in pyridine are mixed, and a light absorption layer solution in which Cu, In, Ga and Na are dissolved in an organic solvent. Was made.

  This light absorption layer solution was formed into a thin film on the first electrode layer made of Mo of the soda lime glass substrate by spray pyrolysis. The thin film was applied to the first electrode layer by spraying the light absorption layer solution using nitrogen gas as a carrier gas in the glove box. At the time of coating, the soda lime glass substrate was heated to 110 ° C. with a hot plate, and the light absorption layer solution was sprayed for 10 minutes to form a thin film and dried.

  After the thin film was formed, heat treatment was performed in an atmosphere of hydrogen gas that passed through the molecular sieve. The heat treatment was performed by rapidly raising the temperature to 525 ° C. in 5 minutes and holding at 525 ° C. for 1 hour, followed by natural cooling to produce a light absorption layer made of a compound semiconductor thin film having a thickness of 2 μm. Thereafter, cadmium acetate and thiourea were dissolved in ammonia, and the substrate was immersed therein to form a buffer layer made of CdS having a thickness of 50 nm on the compound semiconductor thin film. Further, a transparent second electrode made of an Al-doped zinc oxide film was formed on the buffer layer by sputtering. Finally, an aluminum electrode (extraction electrode) was formed by vapor deposition to produce a thin film solar cell.

  When the cross section of the thin film solar cell was observed with a scanning electron microscope (SEM), the average particle diameter of the particles constituting the light absorption layer was 1.5 μm. The average particle size was determined by measuring the length of the light absorption layer in the thickness direction of the crystal particles appearing in the SEM photograph of 30,000 times, and obtaining the average value thereof.

Similarly, using potassium acetate and lithium acetate instead of sodium acetate, respectively, and using a solution obtained by dissolving 6.9 × 10 ⁻⁵ g and 39.0 × 10 ⁻⁵ g in metal conversion in 5 ml of pyridine, respectively. When a thin-film solar cell was produced in the same manner as described above, the average particle sizes of the crystal particles constituting the light absorption layer were 1.5 μm and 1.0 μm, respectively.

Furthermore, when the amount of sodium acetate was changed and a solution in which 2.3 × 10 ⁻⁶ g in terms of metal was dissolved in 5 ml of pyridine was used to produce a thin-film solar battery cell, crystals constituting the light absorption layer The average particle size of the particles was 1.3 μm.

  As a comparative example, when a thin-film solar cell was produced in the same manner as described above using a light absorption layer solution containing Na, Cu, In, and Ga dissolved in an organic solvent, the average particle diameter of the light absorption layer was It was 0.2 μm.

  Therefore, according to the manufacturing method of the present invention, by forming a light absorption layer using a light absorption layer solution in which Cu, In, Ga and an alkali metal are dissolved in an organic solvent, diffusion of the alkali metal into the light absorption layer is achieved. It can be reliably and sufficiently carried out, and it can be seen that the particles constituting the light absorption layer can be grown with an alkali metal during heat treatment, thereby improving the energy conversion efficiency.

0.206 g (1 mmol) of copper selenide (Cu ₂ Se) as the copper compound, 0.467 g (1 mmol) of indium selenide (In ₂ Se ₃ ) as the indium compound, and gallium selenide (Ga ₂ Se ₃ as the gallium compound) ) was dissolved 0.236g of (1 mmol) respectively hydrazine 30 _ml, to prepare a Cu ₂ Se, 3 kinds of _{solutions in 2 Se 3, Ga 2 Se} 3 is dissolved. In each solution, Cu, In, or Ga was dissolved in hydrazine.

Further, sodium acetate as an alkali metal salt and 2.3 × 10 ⁻⁵ g in terms of metal were dissolved in 5 ml of hydrazine to prepare a solution in which Na was dissolved in hydrazine.

  Thereafter, each solution in which Cu, In, Ga was dissolved in hydrazine and a solution in which Na was dissolved in hydrazine were mixed to prepare a light absorption layer solution in which Cu, In, Ga, and Na were dissolved in hydrazine.

  Using this light absorption layer solution, a thin film solar cell was produced in the same manner as in Example 1, and the cross section of the thin film solar cell was observed with an SEM, and the average particle diameter of the particles constituting the light absorption layer Was 1.2 μm, and the average particle size was larger than that of the comparative example using the light absorbing layer solution containing no alkali metal.

A compound semiconductor thin film made of Cu, In, Ga, and Se was formed using a single source precursor. As a copper-indium-selenium alloy complex, [{P (C ₆ H ₅ ) ₃ } ₂ Cu (Se-C ₆ H ₅ ) ₂ In (Se-C ₆ H ₅ ) ₂ ]
As a copper-gallium-selenium alloy complex, [{P (C ₆ H ₅ ) ₃ } ₂ Cu (Se-C ₆ H ₅ ) ₂ Ga (Se-C ₆ H ₅ ) ₂ ]
Was used.

  9.2 g of a copper-indium-selenium alloy complex and 3.8 g of a copper-gallium-selenium alloy complex were each dissolved in 20 ml of pyridine and stirred for 1 hour to prepare respective pyridine solutions. Thereafter, the respective solutions were mixed and stirred at room temperature for 5 hours to prepare a solution containing copper, indium, gallium, and selenium.

Subsequently, sodium acetate was dissolved in 5 ml of pyridine and stirred to prepare a uniform solution. A solution containing copper, indium, gallium, and selenium and a solution in which sodium was dissolved were mixed, stirred for 1 hour, and mixed to prepare a light absorption layer solution. The addition amount of sodium was in terms of a metal 2.3 × ¹⁰ -5 g, and 2.3 × ^{10 -6} g.

  This light absorption layer solution was formed into a thin film using a die coater in a glove box in which nitrogen gas was flowed. This was heated on a hot plate at 150 ° C. for 1 minute to volatilize the pyridine remaining in the thin film.

  After drying, heat treatment was performed in an atmosphere of hydrogen gas that passed through the molecular sieve. The heat treatment conditions were a rapid temperature increase to 525 ° C. in 5 minutes, a heat treatment at 525 ° C. for 1 hour, natural cooling, and a light absorption layer made of a compound semiconductor thin film having a thickness of 2 μm was produced. After the heat treatment, cadmium acetate and thiourea were dissolved in ammonia, the substrate was immersed in this, and a CdS buffer layer was formed on the light absorption layer. Furthermore, an Al-doped zinc oxide film was formed on the buffer layer by sputtering. Finally, an aluminum electrode was formed by vapor deposition to produce a solar battery cell.

  When the cross section of the thin film solar cell was observed with an SEM, the average particle diameters of the crystal particles constituting the light absorption layer were 1.5 μm and 1.3 μm, respectively.

DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... 1st electrode layer 3 ... Light absorption layer 4 ... Buffer layer 5 ... 2nd electrode layer

Claims (7)

  A process for producing a thin-film solar cell having a light absorption layer between a first electrode layer and a second electrode layer, wherein a light absorption layer solution containing Cu, III-B group metal and alkali metal as an element is prepared And a step of producing a precursor by applying the light absorption layer solution on the first electrode layer and drying, and heat-treating the precursor in a reducing atmosphere to form an element on the first electrode layer as an element. A method of manufacturing a thin-film solar cell, comprising: forming the light absorption layer containing Cu, In, and an alkali metal; and forming the second electrode layer on the light absorption layer.   2. The reducing atmosphere is an atmosphere containing Se, and the light absorption layer containing Cu, III-B group metal, Se and alkali metal as elements is formed by heat treatment. Of thin film solar cell.   The light absorption layer solution contains Se as an element, and heat treatment is performed to form the light absorption layer containing Cu, III-B group metal, Se, and an alkali metal as elements. The manufacturing method of the thin film solar cell of description.   The light absorption layer solution is prepared by preparing a solution containing Cu, a solution containing a group III-B metal, and a solution containing an alkali metal, and mixing these solutions. The manufacturing method of the thin film solar cell in any one of 1-3.   The method for producing a thin-film solar cell according to claim 1, wherein the reducing atmosphere is an atmosphere from which moisture has been removed.   The light absorption layer solution is obtained by dissolving a raw material containing Cu as an element, a raw material containing a group III-B metal, and a raw material containing an alkali metal in a solvent containing a chalcogen element-containing organic compound and a Lewis basic organic solvent. A method for producing a thin-film solar cell according to any one of claims 1 to 5.   7. The method of manufacturing a thin film solar cell according to claim 6, wherein the light absorption layer solution is obtained by directly dissolving Cu or a group III-B metal in the solvent in the state of a single metal or an alloy thereof. .

Images