JP2014022569A - Photoelectric conversion element and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric conversion element including a light absorption layer that can be deposited at a low cost by a spray thermal decomposition method, and having a sufficient conversion efficiency, and to provide a manufacturing method of such a photoelectric conversion element.SOLUTION: A photoelectric conversion element 10 includes a light absorption layer containing CuBiSas a main component, and having a thickness from 20 nm to 10 μm. Preferably, the light absorption layer is obtained by a spray thermal decomposition method. The light absorption layer is a p-type semiconductor layer 5, and includes an n-type semiconductor layer 3 composed of a transparent semiconductor material and laminated on one side of the p-type semiconductor layer 5.

Description

The present invention relates to a photoelectric conversion element including a light absorption layer containing Cu ₃ BiS ₃ as a main component and a manufacturing method thereof.

The photoelectric conversion element is an element that converts light such as sunlight or room light into electricity, and is used as an optical sensor such as a photodiode or a phototransistor or a solar cell. As materials used for these photoelectric conversion elements, silicon crystal semiconductors, cuprous oxide (Cu ₂ O), and the like are known for optical sensor applications, and crystalline silicon wafers, amorphous silicon thin films, Gallium arsenide (GaAs) has been put into practical use. In order to manufacture these photoelectric conversion elements, expensive single crystal manufacturing equipment, semiconductor manufacturing equipment, and the like are usually required. For example, silicon crystals and GaAs crystals are relatively expensive materials because a high-purity single crystal is manufactured, a wafer is processed, and precise high-temperature heat treatment is performed. In addition, the amorphous silicon thin film is formed by using a chemical vapor deposition (CVD) method, and at this time, since a silane gas that is a special material gas is used, a large facility is required.

On the other hand, a photoelectric conversion element using a new photoelectric conversion material replacing each of the conventional materials has been proposed. For example, a method for producing a photovoltaic device using a compound semiconductor containing cadmium sulfide or cadmium telluride (see Japanese Patent Laid-Open No. 1-168073), a light absorption layer of a CIS type thin film solar cell made of Cu (InGa) Se ₂ Production method (see JP-A-2006-186114), photoelectric device using a sulfide-based compound semiconductor containing Cu-Zn-Sn-S as a light absorption layer (JP-A 2009-26891 and JP-A 2009-135316) No. gazette) has been proposed. As a method for depositing these various materials, a chemical vapor deposition (CVD) method and a physical vapor deposition (PVD) method are generally used. However, in the CVD method, the type of film that can be formed is limited by the reactivity of the source gas. In addition, in the PVD method such as the vapor deposition method or the sputtering method, a vacuum film forming apparatus is necessary, which increases the cost. Therefore, it is conceivable to use film forming means in a non-vacuum process such as a spin coating method, a coating method, and a printing method. However, the spin coating method and the coating method have many restrictions on materials, such as not reacting with the solvent and the coating liquid being required to have an appropriate viscosity. In the printing method, it is necessary to use a material that can be sintered by heat treatment.

  As described above, in various film forming methods, materials that can be used are limited, and it has been studied to form a photoelectric conversion material by spray pyrolysis. This spray pyrolysis method prepares a raw material solution in which metal chlorides, nitrates, acetates, oxides, etc. are dissolved in an organic solvent such as water or ethanol, and sprays it on a heated substrate with a hot plate. It is said that the thin film can be formed at low cost. As a method for producing a photoelectric conversion element using a spray pyrolysis method, a method for forming an FTO film for a dye-sensitized solar cell or a mixed layer of an oxide semiconductor is formed (see JP 2009-158388 A). A method (see JP 2009-87573 A) has been proposed. Thus, although a method for forming an oxide film using a spray pyrolysis method has been proposed, research on forming a material suitable as a light absorption layer by a spray pyrolysis method has been sufficiently advanced. Not in.

Japanese Unexamined Patent Publication No. 1-168073 JP 2006-186114 A JP 2009-26891 A JP 2009-135316 A JP 2009-158388 A JP 2009-87573 A

  The present invention has been made based on the above circumstances, and includes a photoelectric conversion element having a light absorption layer that can be formed at low cost by a spray pyrolysis method and having sufficient conversion efficiency, and such An object of the present invention is to provide a method for manufacturing a photoelectric conversion element.

As a result of intensive studies on materials for light absorption layers of photoelectric conversion elements that can be formed by spray pyrolysis, the inventors have found that a light absorption layer can be formed by spray pyrolysis according to Cu ₃ BiS _3. The headline, the present invention has been completed.

That is, the invention made to solve the above problems is
It includes Cu ₃ BiS ₃ as a main component, a photoelectric conversion element comprising a light-absorbing layer thickness is 20nm or more 10μm or less.

According to the photoelectric conversion element, since a layer having a predetermined thickness mainly composed of Cu ₃ BiS ₃ is provided as the light absorption layer, sufficient conversion efficiency can be exhibited. In addition, since Cu ₃ BiS ₃ can be formed by spray pyrolysis, the photoelectric conversion element can be manufactured at low cost.

  The light absorption layer is preferably obtained by a spray pyrolysis method. By obtaining the light absorption layer by the spray pyrolysis method, the photoelectric conversion element can be manufactured at low cost.

  The atomic ratio (Bi / Cu) of Bi to Cu in the light absorption layer is 0.25 to 0.35, and the atomic ratio (Bi / S) of Bi to S is 0.25 to 0.4. It is good to be. By setting the atomic ratio of Cu, Bi and S in the above range, the function as a light absorption layer can be enhanced.

  The light absorption layer is a p-type semiconductor layer, and is preferably provided with an n-type semiconductor layer which is laminated on one surface side of the p-type semiconductor layer and made of a transparent semiconductor material. When the photoelectric conversion element has such a structure, it can be suitably used as a pn junction solar cell or the like.

The transparent semiconductor material is preferably at least one selected from the group consisting of TiO ₂ , ZnO, SnO ₂ and In ₂ O ₃ . These materials can function as an n-type semiconductor, have sufficient transparency, and can also function as an electron transport layer. Moreover, since these materials can be formed into a film by a spray pyrolysis method, manufacturing cost can be suppressed.

  It is preferable to provide a short-circuit prevention layer disposed between the p-type semiconductor layer and the n-type semiconductor layer. By providing the short-circuit prevention layer in this way, occurrence of a short circuit in the photoelectric conversion element can be prevented.

The main component of the short-circuit prevention layer is preferably In ₂ S ₃ . In ₂ S ₃ can be formed by spray pyrolysis, and is excellent in film formability. In addition, since In ₂ S ₃ functions as an n-type semiconductor, power generation efficiency can be further increased.

  A pair of electrodes connected to the p-type semiconductor layer and the n-type semiconductor layer may be provided. By providing the electrode in this way, the usability of the photoelectric conversion element can be increased.

Another invention made to solve the above problems is as follows:
A step of forming a light absorption layer by spray pyrolysis,
This is a method for manufacturing a photoelectric conversion element, in which the light absorption layer contains Cu ₃ BiS ₃ as a main component and has a thickness of 20 nm to 10 μm.

According to the manufacturing method, since the light absorption layer containing Cu ₃ BiS ₃ as a main component is formed by the spray pyrolysis method, the manufacturing cost of the photoelectric conversion element can be reduced.

The light absorption layer is a p-type semiconductor layer;
It is preferable to further include a step of forming an n-type semiconductor layer by a spray pyrolysis method and a step of forming a short-circuit prevention layer by a spray pyrolysis method.

  Thus, by forming all three layers of the p-type semiconductor layer, the n-type semiconductor layer, and the short-circuit prevention layer by the spray pyrolysis method, the manufacturing cost can be further reduced.

As described above, the photoelectric conversion element of the present invention can be manufactured at low cost because the light absorption layer is composed of a layer having Cu ₃ BiS ₃ having a predetermined thickness as a main component, and has sufficient conversion efficiency. It can be demonstrated. Moreover, the manufacturing method of the photoelectric conversion element of this invention can manufacture the photoelectric conversion element which has sufficient conversion efficiency at low cost. Therefore, the said photoelectric conversion element and this manufacturing method can be used suitably for a solar cell, an optical sensor, and these manufacture.

Typical sectional drawing which shows one Embodiment of the photoelectric conversion element of this invention X-ray diffraction spectrum of Cu ₃ BiS ₃ film obtained in Production Example 1 X-ray diffraction spectrum of the TiO ₂ film obtained in Production Example 2 X-ray diffraction spectrum of the ZnO film obtained in Production Example 3 X-ray diffraction spectrum of SnO ₂ film obtained in Production Example 4 X-ray diffraction spectrum of In ₂ O ₃ film obtained in Production Example 5 X-ray diffraction spectrum of In ₂ S ₃ film obtained in Production Example 6

  Hereinafter, embodiments of the photoelectric conversion element and the manufacturing method of the present invention will be described in detail with reference to the drawings as appropriate.

<Photoelectric conversion element>
The photoelectric conversion element 10 of FIG. 1 is a thin film type, and includes a transparent substrate 1, a transparent electrode layer 2, an n-type semiconductor layer 3, a short-circuit prevention layer 4, a p-type semiconductor layer 5 (light absorption layer), and an electrode layer 6. These are layer structures formed by laminating in this order.

  The transparent substrate 1 is formed from a transparent material. As a material of the transparent substrate 1, for example, glass such as alkali silicate glass, non-alkali glass and quartz glass, synthetic resin such as acrylic resin and PET, and the like can be used. Among these, glass is preferable from the viewpoints of strength and thermal stability. The glass is preferably chemically or thermally strengthened.

  Although it does not specifically limit as thickness of the transparent substrate 1, Usually, it is about 0.1 mm or more and 10 mm or less. The transparent substrate 1 may be a flexible substrate made of, for example, a synthetic resin and thin.

The transparent electrode layer 2 is laminated on the surface of the transparent substrate 1. The transparent electrode layer 2 has conductivity and is formed from a transparent material. Examples of the material of the transparent electrode layer 2 include metals such as In ₂ O ₃ : Sn (ITO), SnO ₂ : Sb, SnO ₂ : F (FTO), ZnO: Al, ZnO: F, and Cd ₂ SnO _4. Oxides can be mentioned. The thickness of the transparent electrode layer 2 is not particularly limited, and can be, for example, 100 nm or more and 10 μm or less.

  A lead wire 7a is electrically connected to a part of the surface of the transparent electrode layer 2 (a portion where the n-type semiconductor layer 3 is not laminated) via a conductive bonding member 8a. As the conductive bonding member 8a, indium solder, silver paste, or the like can be used.

  The n-type semiconductor layer 3 is laminated on the surface of the transparent electrode layer 2. The n-type semiconductor layer 3 is formed from a transparent n-type semiconductor material. In the photoelectric conversion element 10, the n-type semiconductor layer 3 is transparent as described above, so that light can be incident from the transparent substrate 1 side and the incident light can reach the p-type semiconductor layer 5.

The specific material of the n-type semiconductor layer 3 is preferably at least one selected from the group consisting of TiO ₂ , ZnO, SnO ₂ and In ₂ O ₃ . These materials can function as an n-type semiconductor, have sufficient transparency, and can also function as an electron transport layer. Moreover, since these materials can be formed into a film by a spray pyrolysis method, manufacturing cost can be suppressed. The n-type semiconductor layer 3 may contain other components as long as the function and transparency as an n-type semiconductor are not impaired.

  The thickness (average thickness) of the n-type semiconductor layer 3 is preferably 10 nm or more and 10 μm or less, and more preferably 100 nm or more and 1 μm or less. When the thickness of the n-type semiconductor layer 3 is less than the above lower limit, the desired range may not be completely covered, and conversion efficiency may be reduced. Conversely, when the thickness exceeds the above upper limit, there is a possibility that the resistance may be increased or the light transmittance may be reduced.

  The short-circuit prevention layer 4 is laminated on the surface of the n-type semiconductor layer 3. Since the photoelectric conversion element 10 includes the short-circuit prevention layer 4 as described above, occurrence of a short-circuit and suppression of recombination of electrons and holes generated in the n-type semiconductor layer 3 and the p-type semiconductor layer 5 can be suppressed. Conversion efficiency can be increased. In particular, when the n-type semiconductor layer 3 is formed by a spray pyrolysis method, it is heated at a high temperature, so that pinholes and cracks are likely to occur during subsequent cooling. Thus, when a pinhole or a crack arises, if there is no short circuit prevention layer 4, the p-type semiconductor layer 5 will contact the transparent electrode layer 2, and a short circuit will arise. Therefore, this short circuit can be prevented by providing the short circuit prevention layer 4.

The material for forming the short-circuit prevention layer 4 is not particularly limited, and can be appropriately set according to the characteristics of each material for forming the n-type semiconductor layer 3 and the p-type semiconductor layer 5. ₂ S ₃ is preferred. In ₂ S ₃ can be formed by spray pyrolysis, forms a film following the surface shape of the n-type semiconductor layer 3, and is excellent in film formability. In addition, since In ₂ S ₃ functions as an n-type semiconductor, power generation efficiency can be further increased. The content of the _{an In} 2 _{S 3} in the short-circuit preventing layer 4 is preferably 90 mass% or more to 100 mass% or less, more preferably at least 99 wt%, more preferably at least 99.9 mass%.

  Although it does not specifically limit as thickness (average thickness) of the short circuit prevention layer 4, 10 nm or more and 200 nm or less are preferable. By setting the thickness of the short-circuit prevention layer 4 in the above range, both high power generation efficiency and prevention of short-circuit occurrence can be achieved. When this thickness is less than the above lower limit, there is a possibility that a pinhole is generated in the short-circuit prevention layer 4 itself and the effect of preventing the occurrence of a short-circuit is lowered. On the contrary, if the thickness exceeds the upper limit, the light absorption amount and resistance by the short-circuit prevention layer 4 are increased, which may reduce the power generation efficiency.

The p-type semiconductor layer 5 is laminated on the surface of the short-circuit prevention layer 4. The p-type semiconductor layer 5 is a light absorption layer containing Cu ₃ BiS ₃ as a main component. As described above, since Cu ₃ BiS ₃ can be formed by spray pyrolysis, it can be manufactured at low cost. The p-type semiconductor layer 5 may contain other components as long as the function as a p-type semiconductor is not impaired. The content of Cu ₃ BiS ₃ in the p-type semiconductor layer 5 is preferably 90% by mass or more and 100% by mass or less, more preferably 99% by mass or more, and further preferably 99.9% by mass or more.

  The atomic ratio (Bi / Cu) of Bi to Cu in the p-type semiconductor layer 5 is preferably 0.25 or more and 0.35 or less. Further, the atomic ratio (Bi / S) of Bi to S in this layer 5 is preferably 0.25 or more and 0.4 or less. In the p-type semiconductor layer 5, by setting the atomic ratio of Cu, Bi, and S in the above range, functions such as light absorption and conversion efficiency can be enhanced.

  The thickness (average thickness) of the p-type semiconductor layer 5 is 20 nm or more and 10 μm or less, and preferably 30 nm or more and 8 μm or less. By setting the thickness of the p-type semiconductor layer 5 within the above range, sufficient conversion efficiency can be exhibited. When this thickness is less than the above lower limit, the amount of light absorption is reduced, or defects are easily generated in the film, so that a sufficient electromotive force cannot be obtained. On the contrary, when this thickness exceeds the upper limit, peeling occurs, resistance increases, and electromotive force decreases.

  A method for forming the p-type semiconductor layer 5 is not particularly limited, but it is preferably obtained by a spray pyrolysis method. By obtaining the p-type semiconductor layer 5 by spray pyrolysis, the photoelectric conversion element can be manufactured at low cost.

  The electrode layer 6 is laminated on the surface of the p-type semiconductor layer 5 in a thin film shape. The material for forming the electrode layer 6 is not particularly limited as long as it has conductivity, but metals such as Pt, Al, Au, Cu, Ti, Ni, graphite, and the like can be used. Further, the thickness (average thickness) of the electrode layer 6 is not particularly limited, but may be, for example, 10 nm or more and 1 μm or less.

  A lead wire 7b is electrically connected to the surface of the electrode layer 6 via a conductive bonding member 8b. As the conductive bonding member 8b, indium solder, silver paste, or the like can be used.

  According to the photoelectric conversion element 10, when light such as sunlight is irradiated from the transparent substrate 1 side, a potential difference is generated between the n-type semiconductor layer 3 and the p-type semiconductor layer 5, and light is converted into electric power. can do. This electric power is output from a pair of electrodes (transparent electrode layer 2 and electrode layer 6) connected to the n-type semiconductor layer 3 and the p-type semiconductor layer 5, respectively.

<Method for producing photoelectric conversion element>
The manufacturing method of the photoelectric conversion element 10 is not particularly limited and can be obtained by sequentially laminating each layer.
(1) A step of forming an n-type semiconductor layer 3 on the surface of the transparent electrode layer 2 by spray pyrolysis,
(2) a step of forming a short-circuit prevention layer 4 on the surface of the n-type semiconductor layer 3 by spray pyrolysis, and (3) a p-type semiconductor layer 5 (light) on the surface of the short-circuit prevention layer 4 by spray pyrolysis. It can obtain suitably by the manufacturing method which has the process of forming an absorption layer. Hereinafter, each step will be described in detail.

(1) n-type semiconductor layer forming step In this step, the n-type semiconductor layer 3 is formed on the surface of the transparent electrode layer 2 laminated on the surface of the transparent substrate 1 by spray pyrolysis. Under the present circumstances, as a laminated body of the transparent substrate 1 and the transparent electrode layer 2, a commercially available glass substrate with a transparent electrode layer (film | membrane) etc. can be used. The surface of the transparent electrode layer 2 is preferably previously subjected to cleaning with a neutral detergent or the like, ultrasonic cleaning with pure water or the like.

  As a raw material solution used in the spray pyrolysis method of this step, a solution obtained by dissolving a solute such as metal chloride, nitrate, acetate, oxide in an organic solvent such as water or alcohol such as ethanol or propanol is used. be able to. The solute may be appropriately selected according to the material forming the n-type semiconductor layer 3.

When the n-type semiconductor layer 3 is formed of TiO ₂ as the raw material solution, for example, an alcohol solution of titanium (IV) bisacetylacetylate diisopropoxide is formed, and the n-type semiconductor layer 3 is formed of ZnO. For example, when an aqueous solution of zinc nitrate is formed of the n-type semiconductor layer 3 with SnO ₂ , for example, an aqueous solution of tin chloride and hydrogen chloride is formed with an n-type semiconductor layer 3 of In ₂ O ₃ , for example, An aqueous solution of indium chloride can be used.

  By spraying such a raw material solution on the surface of the heated transparent electrode layer 2, a chemical reaction (oxidation) proceeds, and extra components such as a solvent are volatilized to obtain a layer made of each oxide. it can. The heating method is not particularly limited, and a hot plate or the like may be used. The temperature at the time of heating (the temperature of the surface of the transparent electrode layer 2) depends on the type of the raw material solution used and is, for example, about 300 ° C. or more and 500 ° C. or less. Moreover, the said spraying can be performed using the well-known sprayer normally used when performing a spray pyrolysis method.

  Note that the raw material solution may be sprayed in a state where a part of the surface of the transparent electrode layer 2 is masked in order to secure an electrode extraction place.

(2) Short-circuit preventing layer forming step In this step, the short-circuit preventing layer 4 is formed on the surface of the n-type semiconductor layer 3 obtained in the step (1) by a spray pyrolysis method.

What is necessary is just to select the raw material solution used for the spray pyrolysis method of this process suitably according to the material which forms the short circuit prevention layer 4. FIG. For example, when the short-circuit prevention layer 4 is formed of In ₂ S ₃ , a mixed aqueous solution of indium chloride and thiourea can be used. In this case, the content ratio (mass ratio) of indium chloride and thiourea is preferably 1: 1 or more and 3: 1 or less.

  By spraying such a raw material solution onto the surface of the heated n-type semiconductor layer 3, the short-circuit prevention layer 4 can be formed. In addition, when using the mixed aqueous solution of the said indium chloride and thiourea, as heating temperature (temperature of the n-type semiconductor layer 3 surface), it can be 200 degreeC or more and 300 degrees C or less, for example. The means for heating and spraying is the same as in step (1).

(3) p-type semiconductor layer forming step In this step, the p-type semiconductor layer 5 is formed on the surface of the short-circuit preventing layer 4 obtained in the step (2) by spray pyrolysis.

The raw material solution used in the spray pyrolysis method of this step includes a salt containing copper (copper chloride, copper nitrate, copper acetate, etc.), a salt containing bismuth (bismuth chloride, bismuth acetate, etc.) and a sulfur source (thiourea, An aqueous solution or an alcohol solution containing sodium sulfate, sulfur, etc.) as a solute can be used. By using such a raw material solution, on the surface of the heated short-circuit prevention layer 4, the solvent and other unnecessary components evaporate, and a chemical reaction between sulfur and the metal component proceeds, and sulfide (Cu ₃ BiS ₃ ). Is formed.

  Among these, an aqueous solution containing copper chloride, bismuth chloride and thiourea is preferable as a solute. When preparing such a raw material solution, first, a solution A is prepared by dissolving copper chloride and thiourea in pure water, and a solution B is prepared by dissolving bismuth chloride in hydrochloric acid. It is preferable to mix B into a raw material solution. By doing in this way, a raw material solution can be obtained, without producing a precipitate. A raw material solution containing precipitates is not preferable because it hinders spraying using a sprayer. For example, when copper chloride, bismuth chloride and thiourea are dissolved in pure water, a yellowish white precipitate is generated. Further, yellowish white turbidity also occurs when a solution A in which copper chloride and thiourea are dissolved in pure water and a solution B ′ in which bismuth nitrate is dissolved in an acidic solution are mixed.

  When using an aqueous solution containing copper chloride, bismuth chloride and thiourea, the amount ratio (mass ratio) of these is preferably 40 parts by weight or more and 80 parts by weight or less of bismuth chloride with respect to 100 parts by weight of copper chloride. 55 parts by mass or more and 65 parts by mass or less are more preferable. Moreover, 150 mass parts or more and 250 mass parts or less are preferable with respect to 100 mass parts of copper chloride, and 210 mass parts or more and 230 mass parts or less are more preferable. By setting it as such usage-amount ratio, the atomic ratio of Cu, Bi, and S in the p-type semiconductor layer 5 becomes a favorable range, and functions such as light absorption and conversion efficiency can be enhanced.

  In addition, although it does not specifically limit as solid content concentration of this raw material solution, For example, it can be 1 mass% or more and 5 mass% or less. By doing in this way, the controllability etc. in the case of spraying can be improved.

  In addition, as temperature (heating temperature) of the surface of the short circuit prevention layer 4 in the case of spraying, 250 degreeC or more and 350 degrees C or less are preferable. The means for heating and spraying is the same as in step (1).

  Thus, by forming all three layers of the n-type semiconductor layer 3, the short-circuit prevention layer 4, and the p-type semiconductor layer 5 by the spray pyrolysis method, the photoelectric conversion element 10 can be obtained while suppressing the manufacturing cost. it can.

<Other embodiments>
The photoelectric conversion element and the manufacturing method thereof of the present invention are not limited to the above embodiment. As the photoelectric conversion element, for example a Cu ₃ BiS ₃ donor is added to the light-absorbing layer containing as a main component, or may be made to function as an n-type semiconductor layer. In addition, the short-circuit prevention layer may not be provided, and In ₂ S ₃ used as the short-circuit prevention layer in the above embodiment also functions as an n-type semiconductor, and can also be used as an n-type semiconductor layer.

  In addition, the n-type semiconductor layer, the p-type semiconductor layer, and the short-circuit prevention layer can be formed by means other than spray pyrolysis. Examples of other means include a sputtering method and a vapor deposition method. Furthermore, the formation order may be reversed from the p-type semiconductor layer.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

<Production Example 1: Production of Cu ₃ BiS ₃ Film by Spray Pyrolysis Method>
In 15 cc of pure water, 0.15 g of copper chloride and 0.33 g of thiourea were dissolved. Next, 0.09 g of bismuth chloride was dissolved in 5 cc of 1N hydrochloric acid, and then both were mixed to obtain a raw material solution for spraying. On the other hand, the glass (5 cm square) used as a board | substrate was heated at 300 degreeC with the hotplate. Next, the raw material solution was transferred to a glass sprayer. Then, the raw material solution was sprayed toward the substrate from the tip of the spray nozzle by flowing compressed air (0.2 MPa) to the spray nozzle using an air pump. By doing in this way, the thin film of 200 nm was formed per 10 cc of raw material solutions.

When the structure of the obtained thin film was examined by X-ray diffraction, it was a sulfide having a composition of Cu ₃ BiS ₃ (see FIG. 2). Further, when the resistance of this thin film was measured, it was 3 MΩ. In addition, the transmittance and reflectance were measured using a spectrometer, the absorptance was calculated from these, and the optical band gap was estimated from this. The band gap was 1.5 eV, and it was found to have a good band gap as a light absorption layer of a solar cell (photoelectric conversion element).

<Production Example 2: Production of TiO ₂ film by spray pyrolysis method>
Titanium (IV) bis-acetylacetonate-diisopropoxide: 7 cc of a 75% 2-propanol solution was mixed with 43 cc of ethanol to obtain a raw material solution. This raw material solution was sprayed on a glass substrate heated to 450 ° C. with a hot plate to obtain a thin film. When the structure of the obtained thin film was examined by X-ray diffraction, it was confirmed that a TiO ₂ film was formed (see FIG. 3).

<Production Example 3: Production of ZnO film by spray pyrolysis>
0.24 g of zinc nitrate was dissolved in 30 cc of pure water to obtain a raw material solution. This raw material solution was sprayed onto a glass substrate heated to 400 ° C. to obtain a thin film. When the structure of the obtained thin film was examined by X-ray diffraction, it was confirmed that a ZnO film was formed (see FIG. 4).

<Production Example 4: Production of SnO ₂ film by spray pyrolysis method>
30 cc of pure water was mixed with 0.17 g of tin chloride and 1 cc of 1 N hydrochloric acid to obtain a raw material solution. This raw material solution was sprayed on a glass substrate heated to 400 ° C. to obtain a thin film. When the structure of the obtained thin film was examined by X-ray diffraction, it was confirmed that a SnO ₂ film was formed (see FIG. 5).

<Production Example 5: Production of In ₂ O ₃ film by spray pyrolysis>
0.25 g of indium chloride was dissolved in 30 cc of pure water to obtain a raw material solution. This raw material solution was sprayed on a glass substrate heated to 400 ° C. to obtain a thin film. When the structure of the obtained thin film was examined by X-ray diffraction, it was confirmed that an In ₂ O ₃ film was formed (see FIG. 6).

<Production Example 6: Production of In ₂ S ₃ film by spray pyrolysis>
A raw material solution was obtained by dissolving 0.1 g of indium chloride and 0.05 g of thiourea in 30 cc of pure water. This raw material solution was sprayed onto a glass substrate heated to 250 ° C. to obtain a thin film. When the structure of the obtained thin film was examined by X-ray diffraction, it was confirmed that an In ₂ S ₃ film was formed (see FIG. 7).

<Example 1>
A commercially available glass substrate with a transparent conductive layer (Pilkinton TEC15: FTO glass) was cut into 2 cm square, then washed with a neutral detergent, and further ultrasonically washed with pure water. The substrate was placed on a hot plate with the FTO surface facing up and heated to a desired temperature. For electrode removal, a small glass piece of 5 mm × 2 cm was placed on the upper end of the FTO to provide a place where the spray raw material solution was not sprayed.

First, a TiO ₂ film (n-type semiconductor layer) was formed by spray pyrolysis. Specifically, titanium (IV) bis-acetylacetonate diisopropoxide: 7 cc of a 75% 2-propanol solution was mixed with 43 cc of ethanol to prepare a raw material solution for a TiO ₂ film. This raw material solution was transferred to a glass spray device and a spray nozzle was attached. Next, the raw material solution was sprayed toward the FTO substrate glass heated to 400 ° C. with a hot plate. Spraying was performed by flowing compressed air (0.2 MPa) through the spray nozzle using an air pump. Such a raw material solution was sprayed on the substrate from the spray nozzle tip be in the to obtain a TiO ₂ film (n-type semiconductor layer).

Next, an In ₂ S ₃ film (short-circuit prevention layer) was formed by spray pyrolysis. Specifically, 0.1 g of indium chloride and 0.05 g of thiourea were dissolved in 30 cc of pure water to prepare a raw material solution, and film formation was performed at 300 ° C.

Next, a Cu ₃ BiS ₃ film (p-type semiconductor layer) was formed by spray pyrolysis. Specifically, 0.15 g of copper chloride and 0.33 g of thiourea were dissolved in 15 cc of pure water to obtain a solution A. Next, 0.09 g of bismuth chloride was dissolved in 5 cc of 1N hydrochloric acid to obtain a solution B. Solution A and solution B were mixed to obtain a raw material solution. Spray film formation was performed using this raw material solution. The substrate was heated to 300 ° C. After the film formation, the temperature of the hot plate was lowered and the substrate was taken out after the temperature became low. When the thickness of the Cu ₃ BiS ₃ film was measured with a stylus type film thickness meter, it was 1200 nm. In addition, this thickness was measured in arbitrary 5 places, and it was set as the average value.

Thereafter, using a commercially available carbon paste, a 10 mm square carbon electrode layer was formed on the surface of the Cu ₃ BiS ₃ film by printing. Further, a graphite sheet was attached to a copper lead wire, and the carbon electrode and the copper lead wire were attached with a tape. On the other hand, lead wires were attached to the FTO surface (counter electrode of the carbon electrode) with indium solder. Thus, the photoelectric conversion element of Example 1 was obtained.

<Example 2>
A photoelectric conversion element of Example 2 was obtained in the same manner as in Example 1 except that the n-type semiconductor layer was changed to a ZnO film. Specifically, in the formation of the n-type semiconductor layer, 0.24 g of zinc nitrate was dissolved in 30 cc of pure water to obtain a raw material solution, which was sprayed onto a substrate heated to 400 ° C.

<Example 3>
A photoelectric conversion element of Example 3 was obtained in the same manner as in Example 1 except that the n-type semiconductor layer was a SnO ₂ film. Specifically, in the formation of the n-type semiconductor layer, 0.17 g of tin chloride and 1 cc of 1 N hydrochloric acid were mixed with 30 cc of pure water to obtain a raw material solution, which was sprayed on a substrate heated to 400 ° C.

<Example 4>
A photoelectric conversion element of Example 4 was obtained in the same manner as in Example 1 except that the n-type semiconductor layer was changed to an In ₂ O ₃ film. Specifically, in the formation of the n-type semiconductor layer, 0.25 g of indium chloride was dissolved in 30 cc of pure water to obtain a raw material solution, which was sprayed onto a substrate heated to 400 ° C.

<Example 5>
Example 1 except that an In ₂ S ₃ film (short-circuit prevention layer) was not formed, and a Cu ₃ BiS ₃ film (p-type semiconductor layer) was formed directly on the surface of the TiO ₂ film (n-type semiconductor layer). The photoelectric conversion element of Example 5 was obtained by the same operation.

<Example 6>
A photoelectric conversion element of Example 6 was obtained in the same manner as in Example 1 except that the TiO ₂ film was not formed and an In ₂ S ₃ film was formed on the FTO surface. In the photoelectric conversion element of Example 6, the In ₂ S ₃ film functions as an n-type semiconductor layer.

<Examples 7-8 and Comparative Examples 1-2>
Photoelectric conversion elements of Examples 7 to 8 and Comparative Examples 1 to 2 were obtained in the same manner as in Example 1 except that the Cu ₃ BiS ₃ film (p-type semiconductor layer) had a thickness shown in Table 2.

<Evaluation>
A pair of lead wires provided in the obtained photoelectric conversion element was connected to a tester. The photoelectric conversion element was irradiated with light having a color temperature of 4500 K and an illuminance of 100,000 LUX (using Urban Act manufactured by Iwasaki Electric Co., Ltd.) from the substrate side, and the photovoltaic power and short-circuit current of the photovoltaic element were measured. The measurement results are shown in Tables 1 and 2.

In Comparative Example 2, peeling of the p-type semiconductor layer (Cu ₃ BiS ₃ film) occurred.

  It turns out that the photoelectric conversion element obtained in each Example functions as a solar cell. In particular, it can be seen that the photoelectric conversion elements of Examples 1-4, 7 and 8 provided with the short-circuit prevention layer have high photoelectric conversion efficiency.

  The photoelectric conversion element of this invention and this manufacturing method can be used suitably for a solar cell, an optical sensor, and these manufacture.

DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Transparent electrode layer 3 N-type semiconductor layer 4 Short-circuit prevention layer 5 P-type semiconductor layer 6 Electrode layer 7a, 7b Lead wire 8a, 8b Conductive joining member 10 Photoelectric conversion element

Claims (10)

Cu ₃ comprises BiS ₃ as a main component, a photoelectric conversion element comprising a light-absorbing layer thickness is 20nm or more 10μm or less.   The photoelectric conversion element according to claim 1, wherein the light absorption layer is obtained by a spray pyrolysis method.   The atomic ratio (Bi / Cu) of Bi to Cu in the light absorption layer is 0.25 to 0.35, and the atomic ratio (Bi / S) of Bi to S is 0.25 to 0.4. The photoelectric conversion element according to claim 1 or 2. The light absorption layer is a p-type semiconductor layer;
4. The photoelectric conversion element according to claim 1, comprising an n-type semiconductor layer made of a transparent semiconductor material and laminated on one surface side of the p-type semiconductor layer. The photoelectric conversion element according to claim 4, wherein the transparent semiconductor material is at least one selected from the group consisting of TiO ₂ , ZnO, SnO ₂ and In ₂ O ₃ .   The photoelectric conversion element according to claim 4, further comprising a short-circuit prevention layer disposed between the p-type semiconductor layer and the n-type semiconductor layer. The photoelectric conversion element according to claim 6, wherein a main component of the short-circuit prevention layer is In ₂ S ₃ .   The photoelectric conversion element according to any one of claims 4 to 7, further comprising a pair of electrodes connected to the p-type semiconductor layer and the n-type semiconductor layer, respectively. A step of forming a light absorption layer by spray pyrolysis,
The light absorbing _layer, Cu 3 includes BiS ₃ as a main component, method for manufacturing the film thickness is 20nm or more 10μm or less photoelectric conversion element. The light absorption layer is a p-type semiconductor layer;
The method for producing a photoelectric conversion element according to claim 9, further comprising: a step of forming an n-type semiconductor layer by a spray pyrolysis method; and a step of forming a short-circuit prevention layer by a spray pyrolysis method.

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