JP2017183464A - Compound thin-film solar battery, and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a photoelectric conversion efficiency of a CZTS compound thin-film solar battery.SOLUTION: A compound thin-film solar battery 100 according to the present invention comprises: a substrate 101; a first electrode layer 102 provided on the substrate 101; a light-absorbing layer 103 provided on the first electrode layer 102 and made of a p-type semiconductor; a buffer layer 104 provided on the light-absorbing layer 103 and made of an n-type semiconductor; and a second electrode layer 107 provided on the buffer layer 104. The p-type semiconductor includes at least one element of sulfur and selenium, copper, zinc and tin. The compound thin-film solar battery further comprises a halogenated tin reaction layer on a face of the light-absorbing layer 103 on the side of the buffer layer 104.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a compound thin film solar cell.

The compound thin film solar cell in which the light absorption layer contains at least one of Cu ₂ ZnSnS ₄ , Cu ₂ ZnSnSe ₄ , and Cu ₂ ZnSn (S, Se) ₄ is called a CZTS-based compound thin film solar cell. The CZTS-based compound thin-film solar cell uses CuInGaSe ₂ as a light absorption layer, and does not use rare metals such as In as compared to CIGS solar cells that are already industrially produced. Therefore, the cost can be reduced. For this reason, CZTS-based compound thin film solar cells are attracting a great deal of attention as next-generation solar cells and are actively researched and developed.

  As a method for producing a CZTS-based compound thin film solar cell, for example, Patent Document 1 proposes a method of performing heat treatment by sputtering Cu—Zn—Sn. However, since this method is a vacuum process, it cannot be said that it is inexpensive in terms of the manufacturing process.

  A manufacturing method using a non-vacuum process is superior to a manufacturing method using a vacuum process in that an expensive vacuum apparatus is not required. As a manufacturing method using this non-vacuum process, a hydrazine method is well known (see Patent Document 2). However, hydrazine is a toxic and explosive solvent. Therefore, the hydrazine method requires various measures for preventing environmental pollution and ensuring safety in industrial production.

JP 2010-215497 A US Patent Application Publication No. 2011/0097496

  An alternative to the hydrazine method is a nanoparticle coating method. In the nanoparticle coating method, first, nanoparticles composed of a CZTS-based semiconductor are prepared, then a coating film containing the nanoparticles is formed on a substrate, and then the coating film is subjected to heat treatment to sinter the nanoparticles. It is a method to tie. This method is excellent in that no hydrazine is used. However, the photoelectric conversion efficiency of the CZTS-based compound thin film solar cell obtained by this method is currently lower than the theoretical value. For practical application of CZTS-based compound thin film solar cells, improvement of photoelectric conversion efficiency is the most important issue.

  The present invention has been made in view of the above circumstances, and an object thereof is to make it possible to improve the photoelectric conversion efficiency of a CZTS-based compound thin film solar cell.

  According to a first aspect of the present invention, a substrate, a first electrode layer provided on the substrate, a light absorption layer provided on the first electrode layer and made of a p-type semiconductor, and the light absorption layer A buffer layer made of an n-type semiconductor, and a second electrode layer provided on the buffer layer, wherein the p-type semiconductor comprises at least one element of sulfur and selenium, copper, There is provided a compound thin film solar cell comprising zinc and tin, and having a tin halide reaction layer on a surface of the light absorption layer on the buffer layer side.

  According to the second aspect of the present invention, a light absorption layer made of a p-type semiconductor containing at least one of copper, zinc, tin, sulfur and selenium is formed on a first electrode layer provided on a substrate. Forming a tin halide reaction layer on the light absorption layer, forming a buffer layer made of an n-type semiconductor on the surface-modified light absorption layer, and on the buffer layer And a step of forming a second electrode layer. A method of manufacturing a compound thin film solar cell is provided.

When the above surface modification is performed, foreign phases such as CuSe ₂ and ZnS and foreign substances are removed from the surface of the light absorption layer, thereby reducing defects and recombination in the pn junction. Therefore, according to the present invention, it is possible to improve the photoelectric conversion efficiency of the CZTS compound thin film solar cell.

Sectional drawing which shows schematically the compound thin film solar cell which concerns on embodiment of this invention.

Embodiments of the present invention will be described below with reference to the drawings.
A compound thin film solar cell 100 shown in FIG. 1 includes a substrate 101 and a back electrode 102, a light absorption layer 103, a buffer layer 104, an i layer 105, an n layer 106, and a surface electrode 107, which are sequentially provided thereon. Contains.

  As the substrate 101, for example, a glass plate, a metal plate, a metal foil, a plastic film, or the like can be used.

The back electrode 102 is an example of a first electrode layer. The back electrode 102 is made of a metal such as molybdenum (Mo), nickel (Ni), copper (Cu), titanium (Ti), stainless steel, iron (Fe), TiO ₂ (titania), and aluminum (Al). . Further, a carbon-based electrode such as graphite and graphene, or a transparent conductive film such as ITO (Indium Tin Oxide) and ZnO may be used as the back electrode 102.

  In order to improve the adhesion between the back electrode 102 and the light absorption layer 103, the crystal orientation of the back electrode 102 may be oriented in a predetermined direction, or the back electrode 102 may be subjected to a surface treatment. Examples of this surface treatment include plasma treatment and ozone treatment.

  The light absorption layer 103 is a layer made of a p-type compound semiconductor. This p-type compound semiconductor contains Cu, Zn, Sn, and at least one of S and Se. That is, this p-type compound semiconductor is a CZTS semiconductor. The light absorption layer 103 has a reaction layer on the surface on the buffer layer 104 side.

The buffer layer 104 is a layer made of an n-type compound semiconductor. As a material of the buffer layer 104, for example, CdS, Zn (S, O, OH), ZnS, ZnSe, In ₂ S _{3 and the} like can be used.

  The i layer 105 is a layer made of an i-type compound semiconductor. As a material of the i layer 105, for example, a metal oxide such as ZnO can be used.

  The n layer 106 is a layer made of an n-type compound semiconductor. As a material of the n layer 106, for example, ZnO or ITO to which impurities such as Al, Ga, and B are added can be used.

  The surface electrode 107 is an example of a second electrode layer. As a material of the surface electrode 107, for example, a metal such as Al and Ag can be used. Alternatively, as the surface electrode 107, a carbon-based electrode such as graphite and graphene, or a transparent conductive film such as ITO and ZnO may be used.

  An antireflection film may be provided over the n layer 106. The antireflection film suppresses reflection of light, and allows more light to be absorbed by the light absorption layer. As a material for the antireflection film, for example, magnesium fluoride or lithium magnesium can be used. The thickness of the antireflection film may be any thickness as long as the effect can be confirmed, and is preferably 10 nm to 500 nm, more preferably 10 nm to 200 nm.

This compound thin film solar cell 100 is manufactured by the following method, for example.
First, the back electrode 102 is formed on one main surface of the substrate 101. The back electrode 102 is formed on the upper surface of the substrate 101 by using, for example, a sputtering method, a vapor deposition method, or a CVD (Chemical Vapor Deposition) method.

Next, the light absorption layer 103 is formed on the back electrode 102.
Specifically, fine particle ink is applied or printed on the back electrode 102 to form a coating film. Subsequently, this coating film is dried to obtain a precursor layer. Thereafter, the precursor layer is subjected to a heat treatment to sinter the fine particles.

  Examples of the ink application method include a doctor method, a spin coating method, a slit coating method, and a spray method. Examples of the ink printing method include a gravure printing method, a screen printing method, a reverse offset printing method, and a relief printing method.

  The fine particles are composed of elements constituting the light absorption layer 103. The fine particles are, for example, nano-sized particles. The fine particles are produced, for example, by mixing a solution containing a metal salt or a metal complex with a solution containing a chalcogenide salt and reacting a compound contained in the solution.

  As the fine particles, it is preferable to use amorphous fine particles. Amorphous includes amorphous. Since crystalline particles are stable in terms of energy, components constituting the fine particles are difficult to move during heat treatment. Therefore, it is difficult to obtain a highly dense thin film. On the other hand, the amorphous fine particles increase the density of the light absorption layer 103 because the components constituting the fine particles easily move during the heat treatment. When the fine particles are amorphous, the heat treatment of the precursor layer causes crystallization of the fine particles in addition to the sintering of the fine particles.

  It is preferable to add a binder to the fine particles in order to improve leveling properties during coating.

  The added amount of the binder is preferably 5 to 70% by mass with respect to the mass of the fine particles. If the amount of binder added is small, a large amount of cavities may be formed in the light absorption layer 103. Moreover, when a binder is added excessively, the surface roughness of the light absorption layer 103 tends to increase. Most preferably, 20-60 mass% of binder is added.

  Examples of the binder include thiol organic substances, selenol organic substances, and alcohols having 10 or more carbon atoms. Moreover, Se particle | grains, S particle | grains, Se compound, S compound, etc. can also be used as a binder. Further, sodium sulfide, sodium selenide, potassium selenide, sodium selenate, thiosulfate, and the like can be used as the binder. Preference is given to thiol organics. Further preferred is thiourea.

  The ink is obtained by dispersing the above-described fine particles in an organic solvent and optionally adding a binder or the like. The organic solvent is not particularly limited, and can be selected from, for example, alcohols, ethers, esters, aliphatic hydrocarbons, alicyclic hydrocarbons, and aromatic hydrocarbons. Preferred organic solvents are alcohols having less than 10 carbon atoms such as methanol, ethanol and butanol, diethyl ether, pentane, hexane, cyclohexane and toluene, with methanol, pyridine, toluene and hexane being particularly preferred.

  As described above, a coating layer made of this ink is formed, and the organic solvent is removed from the coating film to obtain a precursor layer. And the light absorption layer 103 is obtained by heat-processing this precursor layer.

As this heat treatment, rapid thermal annealing (RTA) may be performed in addition to annealing in a heating furnace. The heat treatment atmosphere is, for example, selected from the group consisting of H ₂ S gas, H ₂ Se gas, nitrogen gas, Ar gas, Se vapor, S vapor, hydrogen gas, and a mixed gas of hydrogen gas and inert gas. One or more types can be used.

  The heat treatment temperature is preferably 250 ° C. or higher. In the case where a glass substrate is used as the substrate 101, it is necessary to perform heat treatment at a temperature that the glass substrate can withstand. Specifically, the heat treatment temperature in this case is preferably 650 ° C. or less, and more preferably 600 ° C. or less.

The heat treatment is preferably performed in a container containing a solid containing at least one of S and Se. These may be a single powder or an organic or inorganic compound containing at least one of S and Se. The heat treatment is in a container to do this may be performed while supplying a gas containing S or Se such as H 2 _S and H ₂ Se.

In order to control the S concentration and Se concentration in the film thickness direction of the light absorption layer 103, it is preferable to perform heat treatment under any of the following conditions. The heat treatment atmosphere contains sulfur and selenium at the same time, and the ratio M _Se of the atomic concentration M _Se of selenium in the atmosphere to the total amount of the atomic concentration M _S of sulfur in the atmosphere and the atomic concentration M _Se of selenium in the atmosphere It is desirable that / (M _S + M _Se ) is larger than 0.33 and smaller than 0.66. Alternatively, the heat treatment atmosphere preferably contains H ₂ S and H ₂ Se at the same time, and the ratio M _Se / (M _S + M _Se ) is preferably larger than 0.33 and smaller than 0.66. Alternatively, as the heat treatment, it is preferable to sequentially perform a first heat treatment in a sulfur atmosphere and a second heat treatment in a selenium atmosphere.

  When the treatment is performed under the above conditions, the S concentration change rate in the film thickness direction of the light absorption layer 103 can be controlled to 10% or less, and the Se concentration change rate can be controlled to be within a range of 20% to 50%.

  In the light absorption layer 103, the S concentration change rate in the film thickness direction is within 10%, the Se concentration change rate is in the range of 20% to 50%, and the Se concentration on the buffer layer side is smaller than that on the back electrode side. High is desirable. When the combination of the S concentration profile and the Se concentration profile as described above is employed, the photoelectric conversion efficiency of the compound thin film solar cell 100 can be increased.

  In the light absorption layer 103, it is desirable that the Se concentration on the buffer layer side is higher than that on the back electrode side, and the Se concentration change rate in the film thickness direction is in the range of 10% to 50%. In the light absorption layer 103, when a gradient of Se concentration is generated in the film thickness direction, the band structure is inclined, and as a result, the photoelectric conversion efficiency of the compound thin film solar cell 100 may be improved. However, if the Se concentration change rate is too small, the effect of improving the photoelectric conversion efficiency by the band structure described above cannot be expected. Further, if the Se concentration change rate is excessively large, single Se may be segregated on the surface of the light absorption layer 103 on the buffer layer side. In this case, the bonding between the light absorption layer 103 and the buffer layer 104 is impaired. there is a possibility.

  In the light absorption layer 103, the ratio of the sum of the atomic concentration of S and the atomic concentration of Se to the sum of the atomic concentration of Cu, the atomic concentration of Zn, and the atomic concentration of Sn is 1 to 1.3. desirable. When this ratio is too small, holes are easily formed in the light absorption layer 103 due to insufficient Se or S, and the performance of the semiconductor is impaired. If this ratio is too large, single Se or S may segregate on the side surface of the buffer layer of the light absorption layer 103, and the pn junction between the light absorption layer 103 and the buffer layer 104 may be impaired.

The thickness of the light absorption layer 103 can be, for example, about 0.3 to 10 μm. The thickness of the light absorption layer 103 is preferably 1 to 3 μm.
Here, the nanoparticle coating method is described as a method for forming the light absorption layer 103, but the light absorption layer 103 may be formed by other methods.

  The light absorption layer 103 is provided with a tin halide reaction layer on the surface on the buffer layer side. When this reaction layer is present, the photoelectric conversion efficiency of the compound thin film solar cell 100 can be improved. The reason for this will be described below.

On the surface of the light absorption layer 103 after sintering, a CZTS-based semiconductor (a semiconductor composed of at least one of Cu ₂ ZnSnS ₄ , Cu ₂ ZnSnSe ₄ , and Cu ₂ ZnSn (S, Se) ₄ ), which is a main component thereof, is formed. As well as by-products, hetero-phases, foreign substances, etc. generated by the reaction of at least one of Cu, Zn, Sn 2, Se 2, and S with an element present in the atmosphere or sintering atmosphere Exists. These cause defects and recombination in the pn junction, which causes a decrease in photoelectric conversion efficiency. In particular, when these are present on the surface of the light absorption layer 103 on the buffer layer side, the photoelectric conversion efficiency is remarkably lowered.

  The present inventors tried to modify the surface of the light absorption layer 103 in order to reduce these effects. Specifically, the surface of the light absorption layer 103 formed by the heat treatment was immersed in a tin halide solution. As a result, it was possible to reduce the influence of Cu, Zn, or Sn-based by-products or heterogeneous phases, particularly copper selenide, zinc sulfide, and metal oxides on photoelectric conversion efficiency.

  Although not intended to be limiting, among tin halides, tin chloride is particularly preferred. In order to increase the effect of reducing zinc sulfide that is remarkably scattered on the surface of the light absorption layer 103, zinc halide may be further added to the tin halide solution. Among zinc halides, zinc chloride is particularly preferably used. On the contrary, when heterogeneous phases such as copper sulfide and copper selenide are scattered, copper halide may be added. Of the copper halides, copper chloride is particularly preferably used.

A sulfurizing agent may be further added to the tin halide solution. The band gap depends on the constituent _elements, the band gap of Cu 2 ZnSnS ₄ is about 1.5 _eV, the band gap of Cu 2 ZnSnSe ₄ is said to be about 1.0 eV. Therefore, by further adding a sulfiding agent to the tin halide solution, for example, the band gap can be finely controlled in the region near the buffer layer 104 in the light absorption layer 103. Although not intended to be limiting, thiourea and thioacetamide are preferably used as sulfurizing agents.

  The concentration of tin halide in the solution is preferably 0.0001 to 0.1M, more preferably 0.001 to 0.01M. As for the density | concentration of the thiourea in the said solution, 0.001-10M is desirable, More preferably, it is 0.01-1M. The concentration of zinc halide in the above solution is preferably 0.0001 to 0.1M, more preferably 0.001 to 0.01M.

  The solvent used in the above solution may be any solvent that can dissolve tin halide, and is preferably water, methanol, or ethanol.

  The pH of the solution may be any value as long as surface modification proceeds. Although not intended to be limiting, the pH of the solution is preferably pH 0.5-5.

  Even if all of the by-products, foreign phases, and foreign substances contained in the light absorption layer 103 are not replaced, the above-described effects are exhibited if the reaction layer is formed in a region from the surface to a depth of 300 nm, for example. As a result, the pn junction is improved. Preferably, a region from the buffer layer side to a depth of at least 100 nm is effective.

  The surface modification of the light absorption layer 103 may be performed while stirring the tin halide solution with a stirrer bar or the like. The treatment time for surface modification may be any time as long as the effect of reducing the heterogeneous phase can be confirmed, but is preferably 0.1 second to 72 hours, more preferably 0.1 second to 24 hours. More preferably 0.1 seconds to 3 hours. In the reaction, heat or vibration may be applied to enhance the treatment effect, and the reaction temperature is from -10 ° C to 100 ° C, more preferably from 10 ° C to 80 ° C.

  Note that after this treatment, a halide such as a chlorine-based compound may remain on the surface of the light absorption layer 103. In order to remove this, if necessary, the surface of the light absorption layer 103 on the buffer layer side is further heat-treated, or water, an inorganic acid, an organic acid, an alkali solution, or ethanol, acetone, glycerin, It can also be treated with an organic solvent such as an ether. Halides such as zinc chloride produced by the reaction can be easily removed because they are soluble in, for example, alcohol, acetone, glycerin, or ether solvents.

  Next, the buffer layer 104 is formed over the light absorption layer 103. The buffer layer 104 can be formed using, for example, a CBD (chemical bath deposition) method, a MOCVD (Metal Organic Chemical Vapor Deposition) method, an ALD (Atomic Layer Deposition) method, or the like.

  Next, the i layer 105 is formed over the buffer layer 104. The i layer 105 can be formed using, for example, an MOCVD method or a sputtering method.

  Further, the n layer 106 is formed on the i layer 105. The n layer 106 is formed using, for example, the MOCVD method or the sputtering method.

Thereafter, the surface electrode 107 is formed on the n layer 106. The surface electrode 107 is formed using, for example, a sputtering method, a vapor deposition method, a CVD (chemical vapor deposition) method, or the like.
As described above, the compound thin film solar cell 100 shown in FIG. 1 is obtained.

As described above, in the present embodiment, the above reaction layer is formed. Thereby, foreign phases and foreign matters such as CuSe ₂ and ZnS are removed from the surface of the light absorption layer 103, and as a result, defects and recombination in the pn junction are reduced. Therefore, according to this embodiment, the photoelectric conversion efficiency of the compound thin film solar cell 100 can be improved.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to this Example.

Example 1
The compound thin film solar cell 100 shown in FIG. 1 was manufactured by the following method.

(Manufacture of Cu-Zn-Sn-Se ink)
CuI, ZnI ₂ , and SnI ₄ were dissolved in pyridine so that the molar ratio of Cu, Zn, and Sn was 1.8: 1.1: 1 to prepare a first solution. Further, Na ₂ Se was dissolved in methanol to prepare a second solution.

  The 1st solution and the 2nd solution were mixed and the liquid mixture whose molar ratio of Cu, Zn, Sn, and Se was 1.8: 1.1: 1: 4 was obtained. This mixed solution was reacted at 0 ° C. in an inert gas atmosphere to produce Cu—Zn—Sn—Se fine particles.

  Cu-Zn-Sn-Se fine particles were separated from the reaction solution by filtration and washed with methanol. Thereafter, the obtained Cu—Zn—Sn—Se fine particles and thiourea were mixed so that the mass ratio of the Cu—Zn—Sn—Se fine particles to thiourea was 3: 2. Then, pyridine and methanol were further added to this mixture to obtain a Cu—Zn—Sn—Se ink having a solid content of 6.5% by mass.

(Formation of back electrode 102)
Soda lime glass was prepared as the substrate 101, and a back electrode 102 made of a Mo layer was formed on one main surface thereof by sputtering.

(Formation of the light absorption layer 103)
On the back electrode 102, Cu—Zn—Sn—Se ink was applied by a spray method. Next, the back electrode 102 and the substrate 101 on which the coating film was formed were put into an oven, and the coating film was heated to 250 ° C. Thereby, the solvent contained in the coating film was evaporated to obtain a precursor layer. Thereafter, the substrate 101 on which the back electrode 102 and the precursor layer were formed was put in a case containing 16 mg of sulfur and 40 mg of selenium, and heat-treated at 600 ° C. for 20 minutes in a nitrogen atmosphere. As a result, a light absorption layer 103 having a thickness of about 2 μm was obtained.

(Surface modification of the light absorption layer 103)
The substrate 101 on which the back electrode 102 and the light absorption layer 103 were formed was immersed in an aqueous solution containing tin chloride at a concentration of 10% by mass and left at room temperature for 1 hour. Thereafter, the substrate 101 was pulled up from the solution and dried.

(Formation of buffer layer 104)
A mixture containing 0.0015 M cadmium sulfate (CdSO ₄ ), 0.0075 M thiourea (NH ₂ CSNH ₂ ), and 1.5 M ammonium hydroxide (NH ₄ OH) was heated to 67 ° C. A buffer layer 104 made of CdS having a thickness of 100 nm was formed on the light absorption layer 103 by immersing the substrate 101 on which the back electrode 102 and the light absorption layer 103 were formed in this liquid mixture.

(Formation of i layer 105)
An i layer 105 made of ZnO having a thickness of 50 nm was formed on the buffer layer 104 by MOCVD using diethyl zinc and water as raw materials.

(Formation of n layer 106)
An n layer 106 made of ZnO: B having a thickness of 1 μm was formed on the i layer 105 by MOCVD using diethyl zinc, water, and diborane as raw materials.

(Formation of surface electrode 107)
A surface electrode 107 made of Al having a thickness of 0.3 μm was formed on the n layer 106 by vapor deposition.
As described above, the CZTS-based compound thin film solar cell of Example 1 was obtained.

(Example 2)
The same procedure as in Example 1 except that instead of the tin chloride solution, the reaction layer was formed using an aqueous solution containing tin chloride and thiourea at concentrations of 10% by mass and 0.1M, respectively. A CZTS-based compound thin film solar cell was prepared.

(Comparative Example 1)
A CZTS-based compound thin film solar cell was produced in the same procedure as in Example 1 except that the reaction layer was not formed.

Each compound thin-film solar cell manufactured in Examples 1 and 2 and Comparative Example 1 was evaluated using a standard solar simulator (light intensity: 100 mW / cm ² , air mass: 1.5).
The results are shown in Table 1.

  As shown in Table 1, the compound thin film solar cells of Examples 1 and 2 achieved photoelectric conversion efficiency superior to that of the compound thin film solar cell of Comparative Example 1. Moreover, the compound thin film solar cell of Example 2 achieved the photoelectric conversion efficiency superior to the compound thin film solar cell of Example 1.

  DESCRIPTION OF SYMBOLS 100 ... Compound thin film solar cell; 101 ... Glass substrate; 102 ... Back electrode; 103 ... Light absorption layer; 104 ... Buffer layer; 105 ... i layer;

Claims (10)

A substrate,
A first electrode layer provided on the substrate;
A light absorption layer provided on the first electrode layer and made of a p-type semiconductor;
A buffer layer formed on the light absorption layer and made of an n-type semiconductor;
A second electrode layer provided on the buffer layer,
The p-type semiconductor includes at least one element of sulfur and selenium, copper, zinc, and tin,
A compound thin film solar cell comprising a tin halide reaction layer on a surface of the light absorption layer on the buffer layer side.   The light absorption layer is formed by using an ink containing at least one element of sulfur and selenium, particles containing copper, zinc, and tin, and an organic solvent in which the particles are dispersed. The compound thin film solar cell according to claim 1.   3. The compound thin-film solar cell according to claim 1, further comprising a reaction layer of tin halide and a sulfurizing agent on a surface of the light absorption layer on the buffer layer side.   3. The compound thin-film solar cell according to claim 1, further comprising a reaction layer of tin halide and zinc halide on a surface of the light absorption layer on the buffer layer side.   3. The compound thin film solar cell according to claim 1, wherein a surface of the light absorption layer on the buffer layer side includes a reaction layer of tin halide, a sulfurizing agent, and zinc halide. Forming a light absorption layer made of a p-type semiconductor containing copper, zinc, tin, and at least one of sulfur and selenium on a first electrode layer provided on a substrate;
Providing the light-absorbing layer with a tin halide reaction layer;
Forming a buffer layer made of an n-type semiconductor on the surface-modified light absorption layer;
And a step of forming a second electrode layer on the buffer layer.   The light absorption layer is formed using an ink containing particles containing at least one element of sulfur and selenium, copper, zinc, and tin, and an organic solvent in which the particles are dispersed. A method for producing a compound thin film solar cell according to claim 6.   The method for producing a compound thin-film solar cell according to claim 6 or 7, wherein tin halide and a sulfiding agent are used for the reaction layer.   The method for producing a compound thin-film solar cell according to claim 6 or 7, wherein tin halide and zinc halide are used for the reaction layer. The method for producing a compound thin-film solar cell according to claim 6 or 7, wherein tin halide, a sulfurizing agent, and zinc halide are used for the reaction layer.