JP2015201522A - Photoelectric conversion element and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric conversion element excellent in energy conversion efficiency and productivity; and provide a manufacturing method of the photoelectric conversion element.SOLUTION: A photoelectric conversion element comprises: a conductive first electrode layer 1; a light absorption layer 2 which is provided on the first electrode layer 1 and includes a metal chalcogenide semiconductor containing a chalcogen element selected form sulfur and/or selenium; a buffer layer 3 which is provided on the light absorption layer 2 and includes a semiconductor having polarity different from that of the light absorption layer 2; and a second electrode layer 4 provided on the buffer layer 3. The metal chalcogenide semiconductor has a spherical or substantially spherical shape. At an interface between the light absorption layer 2 and the buffer layer 3, the light absorption layer 2 has an uneven rough surface. The buffer layer 3 does not contact the first electrode layer 1.

Description

  The present invention relates to a photoelectric conversion element and a manufacturing method thereof, and more particularly to a photoelectric conversion element excellent in energy conversion efficiency and productivity and a manufacturing method thereof.

  In recent years, in order to solve environmental problems and resource problems, photoelectric conversion elements that convert light energy and electric energy, particularly solar cells, have been actively developed. Conventionally, in the field of solar cells, a method of using crystalline silicon as a light-absorbing semiconductor has been mainstream, but silicon is inferior in light absorption characteristics, so that it is necessary to increase the film thickness. Therefore, rapid development of solar cells using metal chalcogenide semiconductors such as CIGS (copper-indium, gallium-sulfur, selenium) and CZTS (copper-zinc-tin-sulfur, selenium), which have excellent light absorption characteristics It is being advanced.

Such a compound semiconductor thin film type photoelectric conversion element and a light absorption layer of a solar cell comprising the compound semiconductor are manufactured by forming a metal thin film by a sputtering method, followed by firing in an atmosphere of hydrogen sulfide or hydrogen selenide. In general, it is manufactured by a method in which constituent metal elements are vapor-deposited simultaneously on a heating substrate.
Further, for the purpose of improving energy conversion efficiency by balancing power generation decrease due to carrier recombination during power generation and current increase due to light utilization efficiency improvement, for example, Patent Document 1 discloses Cu _x (Al, In , Ga) _y Te _1-xy , a technology for controlling the roughness of the pn interface of a solar cell using a Te telluride semiconductor in a specific range represented by 10 to 100 nm is disclosed in Patent Document 2. There has been proposed a method for improving scribing suitability by using a substrate having an uneven surface.

  On the other hand, for the purpose of improving productivity and the like, various methods for applying a solution to produce a light absorption layer have been proposed (Non-Patent Document 1). In such a method of applying a solution, it is important to realize the growth of crystal particles. In Patent Document 3, particles of metal selenide prepared in advance are mixed and applied onto a substrate, and a hydrogen atmosphere A technique for promoting the growth of crystal grains is disclosed by applying a selenium-containing solution again after firing in, and firing in a hydrogen atmosphere. Similarly, Patent Document 4 discloses a technique in which nanoparticles prepared in advance are coated on a substrate and fired in an Se atmosphere.

Furthermore, Patent Document 5 discloses a technique for forming a light absorption layer by fixing large micron-scale particles produced in advance with an organic binder.
As an example of realizing high energy conversion efficiency using a coating method, for example, Non-Patent Document 2 uses a method of producing a light absorption layer by repeating spin coating using a raw material such as metal selenide using hydrazine as a solvent. Although disclosed, it has the disadvantage that it has an explosive property of hydrazine and generates dangerous gas such as phosgene by thermal decomposition, which requires safety measures in the manufacturing process and is inferior in productivity.

  Therefore, a coating method using a relatively safe solvent has been studied, and Non-Patent Document 3 discloses a method of coating with ethanol or the like as a solvent for selenization, but high performance is more easily realized than sulfide. Despite the use of selenides, the energy conversion efficiency is not sufficient, and the preparation of the coating liquid takes several days, which has the problem of poor productivity. In such a situation, Non-Patent Document 4 discloses a method of spraying water on a heating substrate using water as a solvent and sulfiding, but the energy conversion efficiency is insufficient.

JP 2012-233502 A JP 2007-201304 A JP 2010-129648 A Special table 2012-515708 gazette JP 2011-204825 A

European Journal of Inorganic Chemistry, 2010, 17-28 Progress in Photovoltaics: Research and Applications, 2013, 21, 82-87 Progress in Photovoltaics: Research and Applications, 2012, 20, 526-533 Catalysis Science and Technology, 2013, 3, 1849-1854

However, in Patent Document _{1, Cu x (Al, In} , Ga) y Te 1-x-y in the roughness of the pn interface between the solar cell using a Te telluride semiconductor particular range of 10nm represented Although a technique for controlling to 100 nm or less is disclosed, it is a technique using a semiconductor different from the present invention, and uses a light absorption layer including a metal chalcogenide semiconductor containing a chalcogen element selected from sulfur and / or selenium. Not.

Moreover, although the method of patent document 2 uses the board | substrate which provided the unevenness | corrugation to the surface and improves scribing suitability, it utilizes the shape of the substantially spherical metal chalcogenide semiconductor of this invention, and an unevenness | corrugation on the surface. The manufacturing process is complicated, unlike the case of imparting.
In addition, in Patent Document 3, particles of a metal selenide produced in advance are mixed and applied onto a substrate, fired in a hydrogen atmosphere, then coated again with a selenium-containing solution and fired in a hydrogen atmosphere. Although a technique for promoting particle growth is disclosed, what is an optical absorption layer produced by spraying an aqueous solution containing the metal chalcogenide semiconductor raw material of the present invention a plurality of times on a heated first electrode layer? In contrast, the process is complicated and the particle growth is not sufficient.

  Moreover, the thing of patent document 4 is the same as patent document 3 mentioned above, but the technique of apply | coating the nanoparticle manufactured beforehand on a base material and baking in Se atmosphere is disclosed, but the metal chalcogenide semiconductor of this invention is disclosed. Unlike the light absorption layer produced by spraying the aqueous solution containing the raw material a plurality of times on the heated first electrode layer, the process is complicated and the columnar crystal is different from the substantially spherical shape of the present invention. Therefore, high energy conversion efficiency is not realized.

In addition, the technique of Patent Document 5 discloses a technique for forming a light absorption layer by fixing large particles of micron scale produced in advance with an organic binder, but unlike the light absorption layer of the present invention, It is essential to join the particles with an organic substance, and the organic substance is mixed in the light absorption layer, so that the durability is not sufficient.
This invention is made | formed in view of such a problem, The place made into the objective is to provide the photoelectric conversion element excellent in energy conversion efficiency and productivity, and its manufacturing method.

  As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention have provided a light absorption layer made of a metal chalcogenide semiconductor provided on the first electrode layer and containing a chalcogen element selected from sulfur and / or selenium. A photoelectric conversion element comprising a buffer layer made of a semiconductor having a polarity different from that of the light absorption layer and a second electrode layer provided on the buffer layer, the metal chalcogenide semiconductor Has a substantially spherical shape, and at the interface between the light absorption layer and the buffer layer, the light absorption layer has an irregular rough surface in a specific range, and the buffer layer is not in contact with the first electrode layer. A photoelectric conversion element having excellent energy conversion efficiency is obtained, and moreover, the light absorption layer contains at least one water-soluble metal salt containing a metal constituting a metal chalcogenide semiconductor, and sulfur. An aqueous solution containing a metal chalcogenide semiconductor raw material containing one or more water-soluble chalcogen-containing organic compounds containing a chalcogen element selected from selenium and / or selenium is applied to the heated first electrode layer a plurality of times. After spraying, it discovered that an effect became more remarkable when it baked and manufactured in the gas atmosphere containing the chalcogen element selected from sulfur and / or selenium, and it came to this invention.

  The present invention has been made to achieve the above-described object, and the invention according to claim 1 includes a conductive first electrode layer (1) and the first electrode layer (1). A light absorption layer (2) comprising a metal chalcogenide semiconductor containing a chalcogen element selected from sulfur and / or selenium, and provided on the light absorption layer (2), the light absorption layer (2 ) And a second electrode layer (4) provided on the buffer layer (3), wherein the metal chalcogenide semiconductor is , Having a substantially spherical shape, and at the interface between the light absorption layer (2) and the buffer layer (3), the light absorption layer (2) has an uneven rough surface of 20 nm to 400 nm, The buffer layer (3) is in contact with the first electrode layer (1). A photoelectric conversion element characterized in that no.

The invention according to claim 2 is the invention according to claim 1, wherein the metal chalcogenide semiconductor contains copper.
The invention according to claim 3 is the invention according to claim 2, wherein the metal chalcogenide semiconductor further contains indium and / or gallium.
The invention according to claim 4 is the invention according to claim 1, 2 or 3, wherein the light absorption layer (2) contains one or more water-soluble substances containing a metal constituting the metal chalcogenide semiconductor. The first electrode in which an aqueous solution containing a metal chalcogenide semiconductor material containing a metal salt and one or more water-soluble chalcogen-containing organic compounds containing a chalcogen element selected from sulfur and / or selenium is heated. It is formed by spraying a plurality of times on the layer (1).

  The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the light absorption layer (2) contains one or more water-soluble substances containing a metal constituting the metal chalcogenide semiconductor. A heated aqueous solution containing a metal chalcogenide semiconductor raw material containing a metallic metal salt and at least one water-soluble chalcogen-containing organic compound containing a chalcogen element selected from sulfur and / or selenium. After spraying a plurality of times on the electrode layer (1), it is formed by firing in a gas atmosphere containing a chalcogen element selected from sulfur and / or selenium and having an oxygen partial pressure of 1 Pa or less. .

The invention according to claim 6 is the invention according to any one of claims 1 to 5, wherein the buffer layer (3) is formed by a chemical bath deposition method.
The invention according to claim 7 is the invention according to any one of claims 1 to 6, wherein any one of the first and second electrode layers (1, 4) is the light absorption layer ( 2) It is characterized by being translucent in order to introduce light.

  The invention according to claim 8 is the method for manufacturing a photoelectric conversion element according to any one of claims 1 to 7, wherein the light absorption layer includes a metal chalcogenide semiconductor on the first electrode layer (1). (1) includes a laminated structure formed by laminating (2), heating the first electrode layer (1), and containing the metal constituting the metal chalcogenide semiconductor on the first electrode layer (1) Multiple times an aqueous solution containing a metal chalcogenide semiconductor raw material containing one or more water-soluble metal salts and one or more water-soluble chalcogen-containing organic compounds containing a chalcogen element selected from sulfur and / or selenium A first step of spraying to form a precursor of the light absorbing layer (2), and firing the precursor of the light absorbing layer (2) in the first step to form the light absorbing layer (2) And a second step of .

The invention according to claim 9 is the compound according to claim 8, wherein the one or more water-soluble chalcogen-containing organic compounds containing the chalcogen element used in the first step are compounds containing sulfur. And firing in the second step is performed in a gas atmosphere containing selenium and having an oxygen partial pressure of 1 Pa or less.
The invention according to claim 10 is the invention according to claim 8 or 9, wherein the precursor in the first step is a metal chalcogenide semiconductor, and the precursor in the second step is fired. In the interface between the light absorption layer (2) and the buffer layer (3), a rough surface having an irregular shape of 20 nm to 400 nm is formed in the light absorption layer (2).

  According to an eleventh aspect of the present invention, there is provided a conductive first electrode layer (1) and a chalcogen element selected from sulfur and / or selenium provided on the first electrode layer (1). A light absorption layer (2) containing a metal chalcogenide semiconductor, a buffer layer (3) provided on the light absorption layer (2) and containing a semiconductor having a polarity different from that of the light absorption layer (2), and the buffer A method for manufacturing a photoelectric conversion element comprising a second electrode layer (4) provided on a layer (3), the step of forming a substantially spherical shape in the metal chalcogenide semiconductor, and the light absorption layer (2) and a step of forming an uneven rough surface having a roughness of 20 nm or more and 400 nm or less on the light absorption layer (2) at the interface between the buffer layer (3), and the buffer layer (3) It is not in contact with the first electrode layer (1).

The invention according to claim 12 is the invention according to claim 11, wherein the metal chalcogenide semiconductor contains copper.
The invention according to claim 13 is the invention according to claim 12, wherein the metal chalcogenide semiconductor further contains indium and / or gallium.

  The invention according to claim 14 is the invention according to claim 11, 12 or 13, wherein the light absorption layer (2) contains one or more water-soluble substances containing a metal constituting the metal chalcogenide semiconductor. The first electrode in which an aqueous solution containing a metal chalcogenide semiconductor material containing a metal salt and one or more water-soluble chalcogen-containing organic compounds containing a chalcogen element selected from sulfur and / or selenium is heated. It is formed by spraying a plurality of times on the layer (1).

  The invention according to claim 15 is the invention according to any one of claims 11 to 14, wherein the light absorption layer (2) contains one or more water-soluble substances containing a metal constituting the metal chalcogenide semiconductor. A heated aqueous solution containing a metal chalcogenide semiconductor raw material containing a metallic metal salt and at least one water-soluble chalcogen-containing organic compound containing a chalcogen element selected from sulfur and / or selenium. It is characterized by being formed by spraying a plurality of times on the electrode layer (1), followed by firing in a gas atmosphere containing a chalcogen element selected from sulfur and / or selenium and having an oxygen partial pressure of 1 Pa or less.

The invention according to claim 16 is the invention according to any one of claims 11 to 15, wherein the buffer layer (3) is formed by a chemical bath deposition method.
The invention according to claim 17 is the invention according to any one of claims 11 to 16, wherein any one of the first and second electrode layers (1, 4) is the light absorption layer ( 2) It is characterized by being translucent in order to introduce light.

  ADVANTAGE OF THE INVENTION According to this invention, the photoelectric conversion element of the outstanding energy conversion efficiency is obtained by having the light absorption layer and buffer layer which have a structure of a specific range. Furthermore, a photoelectric conversion element having high energy photoelectric conversion efficiency can be easily manufactured.

It is a block diagram for demonstrating embodiment of the photoelectric conversion element which concerns on this invention. It is a figure which shows the process drawing for demonstrating the manufacturing method of the photoelectric conversion element which concerns on this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Embodiment]
FIG. 1 is a configuration diagram for explaining an embodiment of a photoelectric conversion element according to the present invention. In the figure, reference numeral 1 denotes a first electrode layer, 2 denotes a light absorption layer, 3 denotes a buffer layer, and 4 denotes a second electrode layer.
The photoelectric conversion element of the present invention includes a conductive first electrode layer 1 and a metal chalcogenide semiconductor provided on the first electrode layer 1 and containing a chalcogen element selected from sulfur and / or selenium. A light absorption layer 2, a buffer layer 3 provided on the light absorption layer 2 and including a semiconductor having a polarity different from that of the light absorption layer 2, and a second electrode layer 4 provided on the buffer layer 3 are provided. It is a photoelectric conversion element.

The metal chalcogenide semiconductor has a spherical or substantially spherical shape, and the light absorbing layer 2 has an uneven rough surface of 20 nm to 400 nm at the interface between the light absorbing layer 2 and the buffer layer 3, and the buffer layer 3 is not in contact with the first electrode layer 1.
The metal chalcogenide semiconductor contains copper. The metal chalcogenide semiconductor contains indium and / or gallium.

The light absorption layer 2 contains one or more water-soluble metal salts containing a metal constituting the metal chalcogenide semiconductor and one or more water-soluble chalcogens containing a chalcogen element selected from sulfur and / or selenium. An aqueous solution containing a metal chalcogenide semiconductor material containing an organic compound is sprayed on the heated first electrode layer 1 a plurality of times.
The light absorption layer 2 contains one or more water-soluble metal salts containing a metal constituting the metal chalcogenide semiconductor and one or more water-soluble chalcogens containing a chalcogen element selected from sulfur and / or selenium. An aqueous solution containing a metal chalcogenide semiconductor material containing an organic compound is sprayed a plurality of times on the heated first electrode layer 1, and then contains a chalcogen element selected from sulfur and / or selenium, and oxygen It is formed by firing in a gas atmosphere with a partial pressure of 1 Pa or less.

The buffer layer 3 is formed by a chemical bath deposition method. In addition, one of the first and second electrode layers 1 and 4 is translucent in order to introduce light into the light absorption layer 2.
Hereafter, each component which comprises the photoelectric conversion element of this invention is demonstrated sequentially.
First, the electrode layer will be described.
The electrode layers in the present invention are paired so as to sandwich the light absorption layer 2 and the buffer layer 3, the light absorption layer 2 side being the first electrode layer 1, and the buffer layer 3 side being the second electrode layer. 4 is provided. The first and second electrode layers 1 and 4 form a pair of positive and negative electrodes in the photoelectric conversion element of the present invention.

The material constituting the first and second electrode layers 1 and 4 is not particularly limited as long as it is conductive, but one of them is translucent to introduce light into the light absorption layer 2 of the present invention. is there.
Further, the conductivity in the present invention means a material having a sheet resistance of 1 kΩ / □ or less, preferably 100Ω / □ or less, more preferably 50Ω / □ or less.
Specifically, gold, silver, copper, platinum, aluminum, iron, titanium, molybdenum, tungsten, tantalum, niobium, nickel and alloys thereof, zinc doped with aluminum (AZO), and gallium are doped. Zinc oxide materials such as zinc oxide (GZO), zinc oxide doped with indium and gallium (IGZO), indium oxide materials represented by indium oxide doped with tin (ITO), tin oxide doped with fluorine (FTO) ), Oxide semiconductors such as tin oxide materials such as tin oxide doped with antimony (ATO) and tin oxide doped with phosphorus (PTO), and carbon materials represented by carbon black.

As described above, the first electrode layer 1 and the second electrode layer 4 in the present invention form a pair, and at least one of them has a light-transmitting property. Therefore, a combination of a metal material and an oxide semiconductor is preferably used. It is done.
When a metal is used for the electrode layer, as described later, the light absorption layer 2 of the present invention is made of a metal chalcogenide semiconductor containing a chalcogen element selected from sulfur and / or selenium. In particular, molybdenum, tungsten, tantalum, niobium and alloys thereof are preferable, and molybdenum and tantalum are more preferable from the viewpoint of workability, and molybdenum is more preferable. In particular, when metals are used as the first electrode layer 1 that is in direct contact with the light absorption layer, a material having low corrosivity when contacted with these sulfur and selenium is preferably selected.

In the case where an oxide semiconductor is used for the electrode layer, an oxide semiconductor electrode has a light-transmitting function, and thus a material having a good balance between conductivity and light-transmitting property is preferably used.
Here, translucency means that light can be led in and out according to the sensitivity wavelength of the light absorption layer 2 of the present invention. In the present invention, light having a wavelength of 550 nm is used as a representative value of visible light. The measured light transmittance is 50% or more, preferably 60% or more, more preferably 70% or more. In addition, since it is preferable that the light transmittance is higher in the photoelectric conversion element because the efficiency of light reception and emission is higher, the upper limit is not limited and is 100% or less.

  The material used for the translucent electrode in the present invention is not particularly limited. Specifically, zinc oxide doped with aluminum (AZO), zinc oxide doped with gallium (GZO), and indium oxide doped with tin ( ITO) and fluorine-doped tin oxide (FTO) are preferred. Furthermore, when these materials are used as the first electrode layer, heat resistance and chemical resistance may be required, and therefore, tin oxide (FTO) doped with fluorine is preferably used.

On the other hand, in order to use it as the second electrode layer 4, zinc oxide doped with aluminum (AZO), zinc oxide doped with gallium (GZO) from the viewpoint that it is manufactured at a relatively low temperature and easily obtains high conductivity. ), Tin-doped indium oxide (ITO) is preferably used.
Moreover, the 1st electrode layer 1 in this invention may be formed on the board | substrate which supports it. The board | substrate in this invention is not specifically limited, What is necessary is just to select according to the use of the photoelectric conversion element of this invention.

  Specifically, various resin substrates such as polyethylene terephthalate, polyethylene naphthalate and polyimide, various glass substrates such as soda lime glass, alkali-free glass and quartz glass, various ceramic substrates such as zinc oxide, sapphire and zirconium, gold and silver Examples thereof include various metals such as copper, platinum, aluminum, iron, titanium, molybdenum, tungsten, tantalum, niobium and nickel, metal substrates of these alloys, and various semiconductor substrates such as silicon and gallium arsenide.

Next, the light absorption layer of the present invention will be described.
The light absorption layer 2 of the present invention comprises a metal chalcogenide semiconductor containing a chalcogen element selected from sulfur and / or selenium. Such a semiconductor has a direct transition type electron transition characteristic, and therefore, high efficiency of light receiving and emitting of the photoelectric conversion element is increased.
Specifically, ZnS, CdS, FeS, Fe ₂ S ₃ , FeS ₂ , MoS, MoS ₂ , CuS, Cu ₂ S, Ag ₂ S, Al ₂ S ₃ , Ga ₂ S ₃ , In ₂ S ₃ , SnS , SnS ₂ , PbS, Sb ₂ S ₃ , Bi ₂ S ₃ and other metal sulfides, ZnSe, CdSe, FeSe, Fe ₂ Se ₃ , FeSe ₂ , MoSe, MoSe ₂ , CuSe, Cu ₂ Se, Ag ₂ Se , Al ₂ Se ₃ , Ga ₂ Se ₃ , In ₂ Se ₃ , SnSe, SnSe ₂ , PbSe, Sb ₂ Se ₃ , Bi ₂ Se ₃ and other metal selenides, such as (Cd _(1-x) , There are mixed crystal compounds in which a part of a metal element is substituted, such as Zn _x ) Se (0 <x <1).

Further, mixed crystal compounds in which a part of the chalcogen element is substituted, such as Zn (S _(1-x) , Se _x ) (0 <x <1), CuInS ₂ , CuGaS ₂ , Ag ₈ SnS ₆ , Ternary metal chalcogenide semiconductors such as Ag ₄ Sn ₃ S ₈ , CuInSe ₂ , CuGaSe ₂ , Ag ₈ SnSe ₆ , Ag ₄ Sn ₃ Se ₈ , Cu (In _(1-x) , Ga _x ) S ₂ (0 <x <1) or _{Cu (in (1-x)} , Ga x) (S (1-y), Se y) 2 (0 <x, y <1) of the three-component metal chalcogenide semiconductor such as the There are mixed crystal compounds in which some elements are substituted.

Further, quaternary compounds such as Cu ₂ ZnSnS ₄ , Cu ₂ ZnGeS ₄ , Ag ₂ ZnSnS ₄ , Ag ₂ FeSnS ₄ , Cu ₂ ZnSnSe ₄ , Cu ₂ ZnGeSe ₄ , Ag ₂ ZnSnSe ₄ , Ag ₂ FeSnSe ₄ metal such as Cu ₂ ZnSnS ₄ , (Cu _(1-x) , Ag _x ) ZnSnS ₄ (0 <x <1), Cu ₂ ZnSn (S _(1-x) , Se _x ) ₄ (0 <x <1), (Cu _{(1- x)} , Ag _x ) ZnSn (S _(1-y) , Se _y ) ₄ (0 <x, y <1) mixed crystal compounds in which some elements of quaternary metal chalcogenide semiconductors are substituted Etc. can be exemplified.

Especially, when using the light-receiving element typified by a solar cell photoelectric conversion element of the present _{invention, CuS, Cu 2 S, CuSe} , Cu 2 Se, CuInS 2, CuGaS 2, CuInSe 2, CuGaSe 2, Cu 2 ZnSnS 4 Metal chalcogenide semiconductors containing Cu, such as Cu ₂ ZnGeS ₄ , Cu ₂ ZnSnSe ₄ , Cu ₂ ZnGeSe ₄ , and mixed crystal compounds thereof, are preferably used as semiconductors having high photoelectric conversion performance.

  That is, a chalcogenide semiconductor containing copper is likely to become a p-type semiconductor due to the hybrid of orbits of copper and chalcogen elements. In such a p-type semiconductor containing copper, the diffusion of carriers generated by electron transition is an n-type semiconductor. This is because the crystal quality of the chalcogenide semiconductor becomes more important because it is slower than the above. Accordingly, the chalcogenide semiconductor of the present invention is preferably a chalcogenide semiconductor containing copper as a metal element and containing sulfur and / or selenium as a chalcogen element because the photoelectric conversion performance is improved.

In particular, when the chalcogenide semiconductor of the present invention is a chalcogenide semiconductor containing, in addition to copper, an element selected from indium and / or gallium as a metal element and containing sulfur and / or selenium as a chalcogen element. It is preferable because photoelectric conversion performance can be obtained.
The metal chalcogenide semiconductor contained in the light absorption layer 2 of the present invention has a substantially spherical shape. The term “substantially spherical” in the present invention means that an electron microscope is used to observe the cross section of the photoelectric conversion element, and the ratio of the domain having the longest to shortest ratio of the chalcogenide semiconductor domain of 1.3 or less is more than 50%. say.

That is, by having such a shape, as will be described later, a light absorption layer having an appropriate rough surface can be easily obtained.
The size of the metal chalcogenide semiconductor domain in the present invention is not particularly limited, but if it is too small, the power generation characteristics may be lowered. Therefore, the average size is preferably 100 nm or more, more preferably 150 nm or more, and still more preferably 200 nm or more. As for the upper limit, if it is too large, electrons generated by absorbing light in the metal chalcogenide semiconductor domain cannot flow to the electrode layer, so that it is preferably 3000 nm or less, more preferably 2000 nm or less, and even more preferably 1500 nm or less. is there.

  At the interface between the light absorption layer 2 and the buffer layer 3 to be described later, the light absorption layer 2 has an uneven rough surface of 20 nm to 400 nm. Since the light absorbing layer 2 has an uneven rough surface, the penetration of light into the light absorbing layer 2 is promoted and the pn junction interface to which an internal electric field is applied increases, so that the electromotive current increases, but the unevenness is large. If too large, the area of the pn junction interface increases and recombination increases, so the electromotive force decreases.

  Therefore, the unevenness of the light absorption layer 2 at the interface between the light absorption layer 2 and the buffer layer 3 of the present invention is 20 nm or more and 400 nm or less, and the effect of increasing the electromotive current becomes more remarkable, so the lower limit is more preferably 50 nm or more. More preferably, it is 80 nm or more, and most preferably 110 nm or more. Further, the upper limit is more preferably 400 nm or less, and even more preferably 300 nm or less, because voltage drop due to recombination may become significant or the thickness of the light absorption layer in the recess may be insufficient.

  Since the light absorption layer 2 of the present invention has a feature that a high photocurrent is easily obtained even with a high carrier concentration and a thin film thickness, as will be described later, it is generated by absorbing light when the film thickness becomes too thick. It may be difficult to extract electrons. Therefore, in the interface between the light absorption layer 2 and the buffer layer 3 to be described later, when the light absorption layer 2 has an appropriate rough surface having a roughness of 20 nm to 400 nm, the electromotive voltage does not decrease at the pn junction interface where an internal electric field is applied. Increasing in range works effectively.

In the present invention, the uneven rough surface of the light absorption layer 2 at the interface between the light absorption layer 2 and the buffer layer 3 is obtained by observing the photoelectric conversion element with an electron microscope from the cross-sectional direction, The difference between the maximum value and the minimum value is the rough surface of the light absorption layer 2 at the interface between the light absorption layer 2 and the buffer layer 3.
In the photoelectric conversion element of the present invention, it is necessary that the buffer layer 3 is not in contact with the first electrode layer 1. That is, in the present invention, the buffer layer 3 includes a semiconductor having a polarity different from that of the light absorption layer 2 in contact with the first electrode layer 1, and the second electrode layer 4 that forms a pair of the first electrode layer 1 and the positive and negative electrodes. This is because when the buffer layer 3 is in contact with the first electrode layer 1, the buffer layer 3 is short-circuited or the electromotive voltage is reduced.

Such contact between the buffer layer 3 and the first electrode layer 1 specifies the location of each layer by electron microscope observation and energy dispersive X-ray spectroscopy (EDX method) from the cross-sectional direction of the photoelectric conversion element. Can be confirmed.
In the photoelectric conversion element of the present invention, the light absorption layer 2 includes one or more water-soluble metal salts containing a metal constituting the metal chalcogenide semiconductor and one kind containing a chalcogen element selected from sulfur and / or selenium. It is preferable that the aqueous solution containing the metal chalcogenide semiconductor raw material containing the water-soluble chalcogen-containing organic compound is sprayed on the heated first electrode layer 1 a plurality of times.

  That is, one or more water-soluble chalcogens containing one or more water-soluble metal salts containing a metal constituting a metal chalcogenide semiconductor and a chalcogen element selected from sulfur and / or selenium on a heated electrode layer. When the light-absorbing layer 2 is produced by spraying a solution containing a metal chalcogenide semiconductor raw material containing a containing organic compound, crystal nuclei of the metal chalcogenide semiconductor of the present invention are generated on the heated electrode layer. This is because a metal chalcogenide semiconductor having such a substantially spherical shape can be easily obtained.

The solution sprayed onto the heated electrode layer is preferably an aqueous solution using an aqueous medium as a solvent because of concerns such as ignition that will be described later. Further, by spraying a plurality of times, a photoelectric conversion element in which the buffer layer 3 is not in contact with the first electrode layer 1 can be easily obtained. Moreover, by spraying in multiple times, it is selected from CuInS ₂ , CuGaS ₂ , CuInSe ₂ and CuGaSe ₂ called CIGS, which is one of the preferred compositions as the light absorption layer 2 of the photoelectric conversion element of the present invention. In the case of using a mixed crystal compound of a compound, a photoelectric conversion element having a composition gradient between the first electrode layer 1 and the second electrode layer 4 and having both a high power generation current and a high power generation voltage Is obtained.

In the present invention, the metal chalcogenide semiconductor raw material is one or more water-soluble metal salts containing a metal constituting the metal chalcogenide semiconductor and one or more water-soluble metals containing a chalcogen element selected from sulfur and / or selenium. It contains a chalcogen-containing organic compound and is used as an aqueous solution by dissolving in an aqueous medium.
In the present invention, water-soluble means to dissolve 0.0001 mol% or more, preferably 0.001 mol% or more, in an aqueous medium containing 50 vol% or more of water. That is, if the solubility of one or more water-soluble metal salts containing a metal constituting the metal chalcogenide semiconductor of the present invention or a water-soluble chalcogen-containing organic compound in an aqueous medium is low, the aqueous medium This is because the ratio of the above increases, and much energy is required for volatilization of the aqueous medium.

  In the present invention, the aqueous medium is not particularly limited as long as it contains water in the above-mentioned range. Water and alcohols such as methanol, ethanol and propanol, ketones such as acetone and methyl ethyl ketone, and amine compounds such as trimethylamine, triethylamine and ethanolamine , A mixed solvent with an organic solvent such as dimethylformamide and dimethylsulfoxide can be used.

Note that, when an organic solvent is mixed in the aqueous medium, there is a high risk of ignition when using the coating composition of the present invention. Therefore, water is preferably contained in an amount of 70% by volume, more preferably 90% by volume or more. The solvent and the most preferred aqueous medium is water.
In such an aqueous medium, a water-soluble metal salt described later and a water-soluble chalcogen-containing organic compound are dissolved independently or mixed to prepare an aqueous solution.

In the present invention, one or more water-soluble metal salts containing a metal constituting the metal chalcogenide semiconductor are halide salts such as fluoride, chloride, bromide, iodide, etc. of the metal constituting the chalcogenide semiconductor described above. Inorganic compound salts such as nitrates, sulfates and phosphates, and organic compound salts typified by acetates, which have the above-mentioned water-solubility.
Specifically, fluoride, chloride of metals such as magnesium, calcium, strontium, barium, zinc, cadmium, iron, nickel, molybdenum, copper, silver, aluminum, gallium, indium, tin, lead, antimony, bismuth, Examples thereof include halide salts such as bromide and iodide, inorganic compound salts such as nitrate, sulfate and phosphate, and organic compound salts typified by acetate.

  Among them, halide salts such as fluoride, chloride, bromide, iodide, and nitrate are excluded by decomposition or the like on the heated first electrode layer 1 when the metal chalcogenide semiconductor raw material of the present invention is sprayed. It is preferably used since the volume of the anion component to be produced is small. That is, because the volume of the anion component to be excluded is small, it is difficult for pore defects of the light absorption layer 2 to occur, and the buffer layer 3 of the present invention is difficult to contact the first electrode layer 1.

The water-soluble chalcogen-containing organic compound in the present invention is a compound containing one or more carbon elements and one or more chalcogen elements selected from sulfur and selenium and exhibiting the above-described water-solubility. .
Specifically, organic compounds having a chalcogenic group such as sulfonic acid and selenonic acid, sulfoxide, organic compounds having a chalcogenoxide group of selenoxide group, organic compounds having a chalcogenol group such as thiol and selenol, thioketone, selenoketone, etc. Examples include organic compounds having a chalcogenoketone group.

Of these, organic compounds having a chalcogenol group such as thiol and selenol, and organic compounds having a chalcogenoketone group such as thioketone and selenoketone are preferably used.
That is, since the water-soluble chalcogen-containing organic compound in the present invention has a function of supplying a chalcogen element to the metal chalcogenide semiconductor of the present invention, an aqueous solution of the metal chalcogenide semiconductor raw material of the present invention is applied onto the first electrode layer 1. However, it is necessary to decompose and release the chalcogen element when energy such as heating is applied, but organic compounds having a chalcogen acid group and organic compounds having a chalcogenoxide group have a strong bond between oxygen and the chalcogen element. This is because the function of releasing the chalcogen element may be inferior.

More specifically, thiourea, thioacetamide, N-methylthiourea, N-allylthiourea, N, N′-dimethylthiourea, N, N′-diethylthiourea, tetramethylthiourea, selenourea, N-methylselenourea, N , N′-dimethylselenourea, 1-hexanethiol, octane-1-thiol and the like.
Among these, sulfur-containing organic compounds selected from thiols and thioketones are preferable as the water-soluble chalcogen-containing organic compounds of the present invention because they do not require safety measures and are easy to handle. Furthermore, thioketones are preferably used because of their high water solubility.

  Such metal chalcogenide semiconductors containing sulfur as a chalcogen element often have inferior semiconductor physical properties compared to metal chalcogenide semiconductors containing selenium as a chalcogen element, but as described later, the metal chalcogenide of the present invention After the semiconductor aqueous solution is sprayed on the first electrode layer 1, the chalcogen element can be replaced by firing in an atmosphere containing the chalcogen element. In such a case, in particular, the safety of the metal chalcogenide semiconductor raw material Since importance is attached to the property, sulfur-containing organic compounds selected from thiols and thioketones are preferably used.

  On the other hand, when the metal chalcogenide semiconductor of the present invention contains selenium as a chalcogen element, excellent semiconductor physical properties can be easily obtained. For this reason, when the metal chalcogenide semiconductor of the present invention is sprayed on the first electrode layer 1 and firing is not performed to replace the chalcogen element, selenium-containing organic compounds are preferred as the water-soluble chalcogen-containing organic compounds of the present invention. Used.

The ratio of the water-soluble metal salt to the water-soluble chalcogen-containing organic compound in the chalcogenide semiconductor raw material of the present invention is not particularly limited, and is on the first electrode layer 1 heated using the metal chalcogenide semiconductor raw material aqueous solution of the present invention. What is necessary is just to obtain the target metal chalcogenide semiconductor after spraying.
That is, even when the mixing ratio of the metal salt and chalcogen-containing organic compound in the metal chalcogenide semiconductor raw material deviates from the stoichiometric ratio of the target metal chalcogenide semiconductor, the unreacted components are washed and energy such as heating is used. Furthermore, after the metal chalcogenide semiconductor raw material of the present invention is sprayed, the chalcogen element may be added or replaced by firing in an atmosphere containing the chalcogen element. This is possible.

  On the other hand, when there are too many unreacted components, the uniformity of the film | membrane manufactured by spraying the aqueous solution of the metal chalcogenide semiconductor raw material of this invention on the heated 1st electrode layer 1 several times may fall. Therefore, the ratio of the water-soluble metal salt to the water-soluble chalcogen-containing organic compound is preferably 10 or less, more preferably 5 or less, still more preferably 2 or less, relative to the stoichiometric ratio of the target metal chalcogenide semiconductor. Most preferably, it is 1 or less.

  Regarding the lower limit, when the water-soluble chalcogen-containing organic compound is sprayed with an aqueous solution of a metal chalcogenide semiconductor raw material, there is an effect of improving the stability of the aqueous solution in the case of a mixed solution with a metal salt, or the first electrode layer Is decomposed by heating when sprayed on 1, and is widely accepted compared to the upper limit, preferably 0.01 or more, more preferably 0.02 or more, more preferably 0.05 or more, most preferably It is 0.1 or more.

  As described above, in the present invention, the light absorption layer 2 is manufactured by spraying the aqueous solution containing the metal chalcogenide semiconductor raw material of the present invention a plurality of times on the heated first electrode layer 1. It is preferable. The film containing the metal chalcogenide semiconductor formed on the first electrode layer 1 in this way does not generate hole-like defects, and the buffer layer 3 and the first electrode layer 1 in the photoelectric conversion element of the present invention. No contact occurs.

  That is, in the aqueous solution of the metal chalcogenide semiconductor raw material of the present invention, the water-soluble metal salt generally has a counter ion that dissociates ions in water, and this counter ion is desorbed and converted into a metal chalcogenide semiconductor. If the desorption of the counter ions is performed with a film fixed by coating, the film becomes porous and the uniformity may be insufficient. Therefore, this desorption is performed on the heated first electrode layer 1. This is because hole defects are less likely to occur.

  In addition, as described above, the water-soluble chalcogen-containing organic compound has a function of supplying a chalcogen element to the metal chalcogenide semiconductor of the present invention, so that organic components other than the chalcogen element may be detached. If a film fixed by coating is used, the film becomes porous and the uniformity may be insufficient. Therefore, by performing this desorption on the heated first electrode layer 1, pore defects It is because it becomes difficult to generate | occur | produce.

Further, by forming a film containing the metal chalcogenide semiconductor on the first electrode layer 1 by spraying an aqueous solution of the metal chalcogenide semiconductor raw material of the present invention, the aqueous medium of the present invention easily volatilizes in situ, and the first Hole defects in a film containing a metal chalcogenide semiconductor on one electrode layer 1 are reduced.
And in the photoelectric conversion element containing the light absorption layer 2 of this invention manufactured by repeating the operation in multiple times, high energy conversion efficiency is realizable, without the buffer layer 3 contacting the 1st electrode layer 1. FIG. .

In the present invention, the temperature for heating the first electrode layer 1 is not particularly limited, and is appropriately selected depending on the reactivity of the chalcogenide semiconductor raw material of the present invention and the heat-resistant temperature of the substrate.
For example, when thiourea, which is suitably used as a water-soluble chalcogen-containing organic compound, is used as one chalcogenide semiconductor raw material, thiourea has a function of decomposing at around 240 ° C. to release sulfur, and therefore a preferable temperature for heating a substrate. Is 240 ° C. or higher, more preferably 270 ° C. or higher. Furthermore, considering that the heated substrate is somewhat cooled with the aqueous medium of the present invention, the temperature is more preferably 300 ° C. or higher. Further, when used in an atmosphere containing oxygen typified by an air atmosphere, thiourea may ignite, and therefore, preferably 430 ° C. or less, more preferably 400 ° C. or less is suitable as a temperature for heating the substrate. It is.

  Since the light absorption layer 2 of the present invention improves the crystal quality of the metal chalcogenide semiconductor, it can be formed by spraying on the heated first electrode layer 1 and then applying energy such as heat, plasma, or microwave. preferable. Such energy can be applied in an atmosphere according to the purpose, such as in the air, in a non-reactive gas atmosphere, in a gas atmosphere containing a chalcogen element selected from sulfur and / or selenium, or in a vacuum atmosphere. However, it is preferable to carry out in a gas atmosphere containing a chalcogen element selected from sulfur and / or selenium.

That is, when energy is applied to the metal chalcogenide semiconductor, desorption of the chalcogen element occurs, and the electrical physical properties of the semiconductor may deteriorate.
In addition, when energy is applied to the metal chalcogenide semiconductor in a gas atmosphere containing a chalcogen element selected from sulfur and / or selenium, it is preferably performed in an atmosphere having an oxygen partial pressure of 1 Pa or less. That is, when the oxygen partial pressure is high, the chalcogen element selected from sulfur and / or selenium is not only oxidized but also the crystal growth of the metal chalcogenide semiconductor may be inhibited.

The lower limit of the oxygen partial pressure is not particularly limited, and it is preferable that the oxygen partial pressure is low. However, in order to achieve a low oxygen partial pressure, the apparatus may become large and productivity may decrease. , Preferably it is 100 nPa or more.
When such energy application is performed, it is simple and preferable that heating equipment represented by an electric furnace is heated. The heating temperature at that time is not particularly limited, and may be appropriately set according to the physical properties of the metal chalcogenide semiconductor. However, from the viewpoint of crystal growth, a higher temperature is preferable, preferably 300 ° C. or higher, more preferably 350 ° C. or higher. More preferably, it is 400 ° C. or higher, most preferably 450 ° C. or higher. Although it does not specifically limit about an upper limit, The heat resistance temperature or less of the board | substrate which supports the 1st electrode layer 1 and the 1st electrode layer 1 is preferable.

Specifically, for example, when a quartz glass substrate is used, 1000 ° C. or lower is preferable, when a soda lime glass substrate is used, 600 ° C. or lower is preferable, and when a polyimide substrate is used, 450 ° C. or lower is preferable.
Accordingly, in the present invention, the light absorption layer 2 includes at least one water-soluble metal salt containing a metal constituting the metal chalcogenide semiconductor and at least one water-soluble metal containing a chalcogen element selected from sulfur and / or selenium. An aqueous solution containing a metal chalcogenide semiconductor material containing an organic chalcogen-containing organic compound is sprayed a plurality of times on the heated first electrode layer 1, and then contains a chalcogen element selected from sulfur and / or selenium, And it is preferable that it was manufactured by baking in the gas atmosphere of oxygen partial pressure 1Pa or less.

Examples of the gas atmosphere containing a chalcogen element selected from sulfur and / or selenium include hydrogen sulfide, hydrogen selenide, carbon disulfide vapor, sulfur element vapor, selenium element vapor, and mixtures thereof. Examples of the atmosphere include elemental sulfur vapor, selenium elemental vapor, or a mixture thereof.
In other words, elemental vapor, selenium elemental vapor, and mixtures of these elements are suitable for producing chalcogenide semiconductors with high purity and no by-products because they are vapors of simple elements. This is because the excess can be easily removed by cooling and is excellent in productivity.

  The film thickness of the light absorption layer 2 in the present invention is not particularly limited and can be appropriately selected according to physical properties such as light absorption characteristics and mobility of the chalcogenide semiconductor of the present invention and the intended use of the photoelectric conversion element of the present invention. If it is thick, the efficiency of extracting electrons generated by light irradiation may be reduced, so that it is preferably 5 microns or less, more preferably 3 microns or less, and even more preferably 2 microns or less.

Regarding the lower limit, if it is too thin, the uniformity of the metal chalcogenide semiconductor may be reduced or light absorption may be insufficient, so it is preferably 0.1 microns or more, more preferably 0.3 microns. More preferably, it is 0.5 microns or more.
Next, the buffer layer of the present invention will be described.
The buffer layer 3 in the present invention is provided on the light absorption layer 2 and includes a semiconductor having a polarity different from that of the light absorption layer 2. The light absorption layer 2 and the buffer layer 3 are sandwiched between the first electrode layer 1 and the second electrode layer 4. With such a structure, the photoelectric conversion element of the present invention functions as a power generation element.

In the present invention, the buffer layer 3 is not particularly limited as long as it is a semiconductor in the above-described range, and may be an organic material or an inorganic material.
For example, a metal chalcogenide semiconductor forming the light absorbing layer 2 of the present invention, when a mixed crystal compound of a compound selected from the called CIGS CuInS _2, CuGaS _2, CuInSe _2, CuGaSe _2, generally, the light-absorbing Layer 2 is often a p-type semiconductor. In that case, the buffer layer 3 needs to be an n-type semiconductor, and various materials such as CdS, ZnS, In ₂ S ₃ , ZnO, (Zn _x , Mg _(1-x) ) O, and mixed crystal compounds thereof. Or the material which laminated | stacked them etc. is used preferably.

  The buffer layer 3 of the present invention may be formed by a solution method typified by a chemical bath deposition method, or may be formed by using a vacuum film formation method such as a sputtering method or a vacuum evaporation method. Those formed by a deposition method are preferred. That is, the buffer layer formed by the chemical bath deposition method is less likely to cause damage such as defects in the metal chalcogenide semiconductor film of the present invention, and can easily realize excellent photoelectric conversion performance.

Next, the manufacturing method of the photoelectric conversion element of this invention is demonstrated.
The method for producing a photoelectric conversion element of the present invention includes a first electrode layer 1 provided on a substrate, and a chalcogen element provided on the first electrode layer 1 and selected from sulfur and / or selenium. A light absorption layer 2 including a metal chalcogenide semiconductor, a buffer layer 3 provided on the light absorption layer 2 and including a semiconductor having a polarity different from that of the light absorption layer 2, and a second layer provided on the buffer layer 3. It is a manufacturing method of the photoelectric conversion element provided with the electrode layer 4 of this.

A step of forming a substantially spherical shape in the metal chalcogenide semiconductor, and a step of forming an uneven rough surface of 20 nm or more and 400 nm or less in the light absorption layer 2 at the interface between the light absorption layer 2 and the buffer layer 3; The buffer layer 3 is formed so as not to contact the first electrode layer 1.
The metal chalcogenide semiconductor contains copper. The metal chalcogenide semiconductor further contains indium and / or gallium.

The light absorption layer 2 contains one or more water-soluble metal salts containing a metal constituting the metal chalcogenide semiconductor and one or more water-soluble chalcogens containing a chalcogen element selected from sulfur and / or selenium. An aqueous solution containing a metal chalcogenide semiconductor raw material containing an organic compound is formed by spraying the heated first electrode layer 1 a plurality of times.
The light absorption layer 2 contains one or more water-soluble metal salts containing a metal constituting the metal chalcogenide semiconductor and one or more water-soluble chalcogens containing a chalcogen element selected from sulfur and / or selenium. An aqueous solution containing a metal chalcogenide semiconductor material containing an organic compound is sprayed a plurality of times on the heated first electrode layer 1, and then contains a chalcogen element selected from sulfur and / or selenium, and oxygen It is formed by firing in a gas atmosphere with a partial pressure of 1 Pa or less.

The buffer layer 3 is formed by a chemical bath deposition method. In addition, one of the first and second electrode layers 1 and 4 is translucent in order to introduce light into the light absorption layer 2.
FIG. 2 is a view showing process drawings for explaining a method for producing a photoelectric conversion element according to the present invention.
The method for manufacturing a photoelectric conversion element of the present invention includes a stacked structure formed by stacking a light absorption layer 2 containing a metal chalcogenide semiconductor on the first electrode layer 1. It has the 1st process of forming the precursor of a light absorption layer (2), and the 2nd process of baking a precursor and forming a light absorption layer (2).

  In the first step, the first electrode layer 1 is heated, and on the first electrode layer 1, one or more water-soluble metal salts containing a metal constituting a metal chalcogenide semiconductor, sulfur and / or An aqueous solution containing a metal chalcogenide semiconductor raw material containing one or more water-soluble chalcogen-containing organic compounds containing a chalcogen element selected from selenium is sprayed a plurality of times to form a precursor of the light absorption layer 2.

In the second step, the light absorption layer 2 is formed by firing the precursor of the light absorption layer 2 in the first step.
In addition, the one or more water-soluble chalcogen-containing organic compounds containing the chalcogen element used in the first step are compounds containing sulfur, and the baking in the second step includes selenium and oxygen partial pressure. It is performed in a gas atmosphere of 1 Pa or less.

Further, the precursor in the first step has a substantially spherical shape and is a metal chalcogenide semiconductor, and the light absorption layer is formed at the interface between the light absorption layer 2 and the buffer layer 3 by firing the precursor in the second step. 2 is formed with a rough surface having an irregular shape of 20 nm or more and 400 nm or less.
That is, as described above, the photoelectric conversion element of the present invention is provided on the first electrode layer 1 and the first electrode layer 1, and includes a metal chalcogenide containing a chalcogen element selected from sulfur and / or selenium. A light absorption layer 2 including a semiconductor, a buffer layer 3 provided on the light absorption layer 2 and including a semiconductor having a polarity different from that of the light absorption layer 2, and a second electrode layer 4 provided on the buffer layer 3 It is a photoelectric conversion element provided with.

  The metal chalcogenide semiconductor has a substantially spherical shape, and at the interface between the light absorption layer 2 and the buffer layer 3, the light absorption layer 2 has an uneven rough surface of 20 nm to 400 nm, and the buffer layer 3 is If it has the structure which is not in contact with the 1st electrode layer 1, the manufacturing method will not be specifically limited, The photoelectric conversion element of this invention heats the 1st electrode layer 1, and 1st electrode One or more water-soluble metal salts containing a metal constituting the metal chalcogenide semiconductor and one or more water-soluble chalcogen-containing organic compounds containing a chalcogen element selected from sulfur and / or selenium on the layer 1 A first step of spraying an aqueous solution containing a metal chalcogenide semiconductor raw material containing a plurality of times to form a precursor of the light absorption layer 2, and firing the precursor of the light absorption layer 2 to form a light absorption layer With the second step It is suitably produced Te.

That is, by manufacturing in this way, a photoelectric conversion element having the characteristics of the present invention can be easily obtained.
The 1st process of the preferable manufacturing method of the photoelectric conversion element of this invention is demonstrated.
In the 1st process in the manufacturing method of the photoelectric conversion element of this invention, the 1st electrode layer 1 is heated and the 1st or more types of water solution containing the metal which comprises a metal chalcogenide semiconductor on the 1st electrode layer 1 are included. Light-absorbing layer by spraying an aqueous solution containing a metal chalcogenide semiconductor material containing a metallic metal salt and one or more water-soluble chalcogen-containing organic compounds containing a chalcogen element selected from sulfur and / or selenium multiple times 2 precursors are formed.

That is, one or more water-soluble chalcogens containing one or more water-soluble metal salts containing a metal constituting a metal chalcogenide semiconductor and a chalcogen element selected from sulfur and / or selenium on a heated electrode layer. When the light-absorbing layer 2 is produced by spraying a solution containing a metal chalcogenide semiconductor material containing an organic compound, crystal nuclei that are precursors of the metal chalcogenide semiconductor of the present invention are formed on the heated electrode layer Therefore, a metal chalcogenide semiconductor having a substantially spherical shape as described above can be easily obtained. The solution sprayed onto the heated electrode layer is preferably an aqueous solution using an aqueous medium as a solvent because of concerns such as ignition that will be described later. Further, by spraying a plurality of times, a photoelectric conversion element in which no hole-like defect is generated and the above-described buffer layer 3 is not in contact with the first electrode layer 1 can be easily obtained. Moreover, by spraying in multiple times, it is selected from CuInS ₂ , CuGaS ₂ , CuInSe ₂ and CuGaSe ₂ called CIGS, which is one of the preferred compositions as the light absorption layer 2 of the photoelectric conversion element of the present invention. In the case of using a mixed crystal compound of the above compound, the composition of the light absorption layer 2 can be inclined, and a photoelectric conversion element having a high power generation current and a high power generation voltage can be obtained.

Moreover, the 1st electrode layer in this invention has electroconductivity. The conductivity in the present invention means a material having a sheet resistance of 1 kΩ / □ or less, preferably 100Ω / □ or less, more preferably 50Ω / □ or less.
Specifically, gold, silver, copper, platinum, aluminum, iron, titanium, molybdenum, tungsten, tantalum, niobium, nickel and alloys thereof, zinc doped with aluminum (AZO), and gallium are doped. Zinc oxide materials such as zinc oxide (GZO), zinc oxide doped with indium and gallium (IGZO), indium oxide materials represented by indium oxide doped with tin (ITO), tin oxide doped with fluorine (FTO) ), Oxide semiconductors such as tin oxide materials such as tin oxide doped with antimony (ATO) and tin oxide doped with phosphorus (PTO), and carbon materials represented by carbon black.

  Among these, in the second step of the present invention, as described later, since it is preferable to fire in a gas atmosphere containing sulfur and selenium, those having low corrosiveness when contacting with sulfur and selenium are preferable, Specifically, molybdenum, tungsten, tantalum, niobium and alloys thereof are preferable. From the viewpoint of workability, molybdenum and tantalum are more preferable, and molybdenum is more preferable.

In the present invention, in the case where an oxide semiconductor is used for the electrode layer, an oxide semiconductor electrode has a light-transmitting function, and thus a material having a balance between conductivity and light-transmitting property is preferably used.
Translucency means that light can be led in and out in accordance with the sensitivity wavelength of the light absorption layer 2 of the present invention. In the present invention, light was measured using light having a wavelength of 550 nm as a representative value of visible light. The light transmittance means 50% or more, preferably 60% or more, more preferably 70% or more. In addition, since light generation efficiency becomes so high that a light transmittance is high in a photoelectric conversion element, since it is preferable, about an upper limit, it is not limited and is 100% or less.

  The material used for the light-transmitting electrode in the present invention is not particularly limited. Specifically, zinc oxide doped with aluminum (AZO), zinc oxide doped with gallium (GZO), indium oxide doped with tin ( ITO) and fluorine-doped tin oxide (FTO) are preferred. Furthermore, when these materials are used as the first electrode layer 1, heat resistance and chemical resistance may be required, and therefore, tin oxide (FTO) doped with fluorine is preferably used.

On the other hand, in order to use it as the second electrode layer 4, zinc oxide doped with aluminum (AZO), zinc oxide doped with gallium (GZO) from the viewpoint that it is manufactured at a relatively low temperature and easily obtains high conductivity. ), Tin-doped indium oxide (ITO) is preferably used.
Moreover, the 1st electrode layer 1 in this invention may be formed on the board | substrate which supports it. The board | substrate in this invention is not specifically limited, What is necessary is just to select according to the use of the photoelectric conversion element of this invention.

  Specifically, various resin substrates such as polyethylene terephthalate, polyethylene naphthalate and polyimide, various glass substrates such as soda lime glass, alkali-free glass and quartz glass, various ceramic substrates such as zinc oxide, sapphire and zirconium, gold and silver Examples thereof include various metals such as copper, platinum, aluminum, iron, titanium, molybdenum, tungsten, tantalum, niobium and nickel, metal substrates of these alloys, and various semiconductor substrates such as silicon and gallium arsenide.

  Among these, when fired in a gas atmosphere containing sulfur or selenium in the second step, a material that can be heated to maintain its shape and is not highly reactive is preferable, and a heat resistant resin substrate typified by polyimide. Various glass substrates such as soda lime glass, alkali-free glass, and quartz glass, and various metal substrates of iron, titanium, molybdenum, tungsten, tantalum, niobium, and alloys thereof are preferable.

In the present invention, the metal chalcogenide semiconductor raw material is one or more water-soluble metal salts containing a metal constituting the metal chalcogenide semiconductor and one or more water-soluble metals containing a chalcogen element selected from sulfur and / or selenium. Contains a chalcogen-containing organic compound and is sprayed as an aqueous solution.
In the present invention, water-soluble means to dissolve 0.0001 mol% or more, preferably 0.001 mol% or more, in an aqueous medium containing 50 vol% or more of water. That is, if the solubility of one or more water-soluble metal salts containing a metal constituting the metal chalcogenide semiconductor of the present invention or a water-soluble chalcogen-containing organic compound in an aqueous medium is low, the aqueous medium This is because the ratio of the above increases, and much energy is required for volatilization of the aqueous medium.

  In the present invention, the aqueous medium is not particularly limited as long as it contains water in the above-mentioned range. Water and alcohols such as methanol, ethanol and propanol, ketones such as acetone and methyl ethyl ketone, and amine compounds such as trimethylamine, triethylamine and ethanolamine , A mixed solvent with an organic solvent such as dimethylformamide and dimethylsulfoxide can be used.

Note that, when an organic solvent is mixed in the aqueous medium, there is a high risk of ignition when using the coating composition of the present invention. Therefore, water is preferably contained in an amount of 70% by volume, more preferably 90% by volume or more. The solvent and the most preferred aqueous medium is water.
In such an aqueous medium, a water-soluble metal salt described later and a water-soluble chalcogen-containing organic compound are dissolved independently or mixed to prepare an aqueous solution.

In the present invention, one or more water-soluble metal salts containing a metal constituting the metal chalcogenide semiconductor are halide salts such as fluoride, chloride, bromide, iodide, etc. of the metal constituting the chalcogenide semiconductor described above. Inorganic compound salts such as nitrates, sulfates and phosphates, and organic compound salts typified by acetates, which have the above-mentioned water-solubility.
Specifically, fluoride, chloride of metals such as magnesium, calcium, strontium, barium, zinc, cadmium, iron, nickel, molybdenum, copper, silver, aluminum, gallium, indium, tin, lead, antimony, bismuth, Examples thereof include halide salts such as bromide and iodide, inorganic compound salts such as nitrate, sulfate and phosphate, and organic compound salts typified by acetate.

  Among them, halide salts such as fluoride, chloride, bromide, iodide, and nitrate are excluded by decomposition or the like on the heated first electrode layer 1 when the metal chalcogenide semiconductor raw material of the present invention is sprayed. It is preferably used since the volume of the anion component to be produced is small. That is, a small volume of the anion component to be excluded is preferable because pore defects in the light absorption layer are hardly generated.

In the present invention, the water-soluble chalcogen-containing organic compound is a compound containing one or more carbon elements and one or more chalcogen elements selected from sulfur and selenium and exhibiting the above-described water-solubility. .
Specifically, organic compounds having a chalcogenic group such as sulfonic acid and selenonic acid, sulfoxide, organic compounds having a chalcogenoxide group of selenoxide group, organic compounds having a chalcogenol group such as thiol and selenol, thioketone, selenoketone, etc. Examples include organic compounds having a chalcogenoketone group.

Of these, organic compounds having a chalcogenol group such as thiol and selenol, and organic compounds having a chalcogenoketone group such as thioketone and selenoketone are preferably used.
That is, in the present invention, the water-soluble chalcogen-containing organic compound has a function of supplying a chalcogen element to the metal chalcogenide semiconductor of the present invention. Therefore, an aqueous solution of the metal chalcogenide semiconductor raw material of the present invention is applied onto the first electrode layer 1. However, it is necessary to decompose and release the chalcogen element when energy such as heating is applied, but organic compounds having a chalcogen acid group and organic compounds having a chalcogenoxide group have a strong bond between oxygen and the chalcogen element. This is because the function of releasing the chalcogen element may be inferior.

More specifically, thiourea, thioacetamide, N-methylthiourea, N-allylthiourea, N, N′-dimethylthiourea, N, N′-diethylthiourea, tetramethylthiourea, selenourea, N-methylselenourea, N , N′-dimethylselenourea, 1-hexanethiol, octane-1-thiol and the like.
Among these, sulfur-containing organic compounds selected from thiols and thioketones are preferred as the water-soluble chalcogen-containing organic compounds of the present invention because they do not require safety measures and are easy to handle. Furthermore, thioketones are preferably used because of their high water solubility.

  Such metal chalcogenide semiconductors containing sulfur as a chalcogen element often have inferior semiconductor physical properties compared to metal chalcogenide semiconductors containing selenium as a chalcogen element, but as described below, the metal chalcogenide semiconductor of the present invention. After the semiconductor aqueous solution is sprayed on the first electrode layer 1, the chalcogen element can be replaced by firing in an atmosphere containing the chalcogen element. In such a case, in particular, the safety of the metal chalcogenide semiconductor raw material Since importance is attached to the property, sulfur-containing organic compounds selected from thiols and thioketones are preferably used.

  The ratio of the water-soluble metal salt to the water-soluble chalcogen-containing organic compound in the chalcogenide semiconductor raw material of the present invention is not particularly limited, and is on the first electrode layer 1 heated using the metal chalcogenide semiconductor raw material aqueous solution of the present invention. What is necessary is just to obtain the target metal chalcogenide semiconductor after spraying. That is, even when the mixing ratio of the metal salt and chalcogen-containing organic compound in the metal chalcogenide semiconductor raw material deviates from the stoichiometric ratio of the target metal chalcogenide semiconductor, the unreacted components are washed and energy such as heating In addition, by performing the second step in a sulfur or selenium gas atmosphere, the chalcogen element is added or replaced by firing in an atmosphere containing the chalcogen element. It is also possible to do.

  On the other hand, when there are too many unreacted components, the uniformity of the film | membrane manufactured by spraying the aqueous solution of the metal chalcogenide semiconductor raw material of this invention on the heated 1st electrode layer 1 several times may fall. Therefore, the ratio of the water-soluble metal salt to the water-soluble chalcogen-containing organic compound is preferably 10 or less, more preferably 5 or less, still more preferably 2 or less, relative to the stoichiometric ratio of the target metal chalcogenide semiconductor. Most preferably, it is 1 or less.

  Regarding the lower limit, when the water-soluble chalcogen-containing organic compound is sprayed with an aqueous solution of a metal chalcogenide semiconductor raw material, it has an effect of improving the stability of the aqueous solution when mixed with a metal salt, or the first electrode. Since it decomposes by heating when sprayed on the layer 1, it is widely accepted compared to the upper limit, preferably 0.01 or more, more preferably 0.02 or more, still more preferably 0.05 or more, most preferably Is 0.1 or more.

In the first step of the present invention, it is necessary to spray the aqueous solution containing the metal chalcogenide semiconductor raw material a plurality of times on the heated first electrode layer 1.
That is, in the aqueous solution of the metal chalcogenide semiconductor raw material of the present invention, the water-soluble metal salt generally has a counter ion that dissociates ions in water, and this counter ion is desorbed and converted into a metal chalcogenide semiconductor. If the desorption of the counter ions is performed with a film fixed by coating, the film becomes porous and the uniformity may be insufficient. Therefore, this desorption is performed on the heated first electrode layer 1. This is because hole defects are less likely to occur.

  In addition, as described above, the water-soluble chalcogen-containing organic compound has a function of supplying a chalcogen element to the metal chalcogenide semiconductor of the present invention, so that organic components other than the chalcogen element may be detached. If a film fixed by coating is used, the film becomes porous and the uniformity may be insufficient. Therefore, by performing this desorption on the heated first electrode layer 1, pore defects It is because it becomes difficult to generate | occur | produce.

Further, by forming a film containing the metal chalcogenide semiconductor on the first electrode layer 1 by spraying an aqueous solution of the metal chalcogenide semiconductor raw material of the present invention, the aqueous medium of the present invention easily volatilizes in situ, and the first Hole defects in a film containing a metal chalcogenide semiconductor on one electrode layer 1 are reduced.
The hole defect is eliminated by repeating the operation a plurality of times.

In the present invention, the temperature for heating the first electrode layer 1 is not particularly limited, and is appropriately selected depending on the reactivity of the chalcogenide semiconductor raw material of the present invention and the heat-resistant temperature of the substrate.
For example, when thiourea, which is suitably used as a water-soluble chalcogen-containing organic compound, is used as one chalcogenide semiconductor raw material, thiourea has a function of decomposing at around 240 ° C. to release sulfur, and therefore a preferable temperature for heating a substrate. Is 240 ° C. or higher, more preferably 270 ° C. or higher. Furthermore, considering that the heated substrate is somewhat cooled with the aqueous medium of the present invention, the temperature is more preferably 300 ° C. or higher. Further, when used in an atmosphere containing oxygen typified by an air atmosphere, thiourea may ignite, and therefore, preferably 430 ° C. or less, more preferably 400 ° C. or less is suitable as a temperature for heating the substrate. It is.

In the second step of the present invention, for the purpose of crystal quality of the metal chalcogenide semiconductor, it is fired after being formed by spraying on the heated first electrode layer 1.
Such firing can be performed in an atmosphere according to the purpose, such as in the air, in a non-reactive gas atmosphere, in a gas atmosphere containing a chalcogen element selected from sulfur and / or selenium, or in a vacuum atmosphere. Is preferably performed in a gas atmosphere containing a chalcogen element selected from sulfur and / or selenium. That is, when a metal chalcogenide semiconductor is baked in an environment that does not contain a chalcogen element selected from sulfur and / or selenium, the chalcogen element may be detached and the electrical properties of the semiconductor may be reduced.

  The firing temperature is not particularly limited and may be appropriately set according to the physical properties of the metal chalcogenide semiconductor. However, from the viewpoint of crystal growth, a higher temperature is preferable, preferably 300 ° C. or higher, more preferably 350 ° C. or higher. Preferably it is 400 degreeC or more, Most preferably, it is 450 degreeC or more. Although it does not specifically limit about an upper limit, The heat resistance temperature or less of the board | substrate which supports the 1st electrode layer 1 and the 1st electrode layer 1 is preferable.

Specifically, for example, when a quartz glass substrate is used, 1000 ° C. or lower is preferable, when a soda lime glass substrate is used, 600 ° C. or lower is preferable, and when a polyimide substrate is used, 450 ° C. or lower is preferable.
Examples of the gas atmosphere containing a chalcogen element selected from sulfur and / or selenium include hydrogen sulfide, hydrogen selenide, carbon disulfide vapor, sulfur element vapor, selenium element vapor, and mixtures thereof. Examples of the atmosphere include elemental sulfur vapor, selenium elemental vapor, or a mixture thereof.

In other words, elemental vapor, selenium elemental vapor, and mixtures of these elements are suitable for producing chalcogenide semiconductors with high purity and no by-products because they are vapors of simple elements. This is because the excess can be easily removed by cooling and is excellent in productivity.
Moreover, when baking a metal chalcogenide semiconductor in the gas atmosphere containing the chalcogen element selected from sulfur and / or selenium, it is preferable to carry out in the atmosphere of oxygen partial pressure 1Pa or less. That is, when the oxygen partial pressure is high, the chalcogen element selected from sulfur and / or selenium is not only oxidized but also the crystal growth of the metal chalcogenide semiconductor may be inhibited.

The lower limit of the oxygen partial pressure is not particularly limited, and it is preferable that the oxygen partial pressure is low.However, in order to achieve a low oxygen partial pressure, the apparatus may become large and productivity may be reduced. , 100 nPa or more.
Moreover, in this invention, it is preferable to perform baking of a 2nd process in the gas atmosphere containing selenium. That is, as described above, when the metal chalcogenide semiconductor contains a large amount of selenium as a chalcogen element, the semiconductor physical properties are excellent as compared with a case where it contains a large amount of sulfur. By doing in this way, when the sulfur-containing organic compounds selected from the thiol and thioketone excellent in productivity as described above are used as the water-soluble chalcogen-containing organic compound used in the first step of the present invention. Even if it exists, the metal chalcogenide semiconductor excellent in the semiconductor physical property can be obtained by replacing most of the sulfur with selenium.

  Therefore, the photoelectric conversion element of the present invention heats the first electrode layer 1, and on the first electrode layer 1, one or more water-soluble metal salts containing a metal constituting the metal chalcogenide semiconductor, and sulfur A first step of forming a precursor of the light absorption layer 2 by spraying an aqueous solution containing a metal chalcogenide semiconductor raw material containing at least one water-soluble chalcogen-containing organic compound containing a plurality of times, and a light absorption layer The second precursor is baked in a gas atmosphere containing selenium and having an oxygen partial pressure of 1 Pa or less to produce the light absorption layer 2 more suitably.

Further, as described above, the gas atmosphere containing selenium is preferably vapor of selenium.
On the light absorption layer 2 manufactured in this manner, the buffer layer 3 and the second electrode layer 4 described in the photoelectric conversion element can be formed to manufacture the photoelectric conversion element.
In such a case, as described in the photoelectric conversion element, the buffer layer 3 is a semiconductor having a polarity different from that of the light absorption layer 2, and either the second electrode layer 4 or the first electrode layer is used. One side has translucency.

Next, the use of the photoelectric conversion element of the present invention will be described.
The photoelectric conversion element of the present invention has a function of converting light energy into electric energy. Therefore, it is used as a light receiving element such as a photocatalytic electrode, a photosensor, or a solar cell that generates light by applying light energy. In addition, the photoelectric conversion element of the present invention is also characterized in that it can be easily manufactured in a large area, and is suitably used as a solar cell. Furthermore, since light can be emitted when electric energy is applied to the photoelectric conversion element of the present invention, it can be used as a light-emitting element.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely using an Example and a comparative example, this invention is not limited to these technical scopes.

The measuring method used in the present invention is as follows.
<Transmission electron microscope measurement, energy dispersive X-ray spectroscopy measurement>
Using a focused ion beam apparatus FB-2100 manufactured by Hitachi High-Technologies Corporation, a sample section was prepared at an acceleration voltage of 40 kV, and using a scanning transmission electron microscope HD-2300A model manufactured by Hitachi High-Technologies Corporation. A transmission electron microscope image was observed. Further, energy dispersive X-ray spectroscopy measurement was performed using an EDAX Genesis type manufactured by Ametech Corporation. Observation and measurement were performed under the condition of an acceleration voltage of 200 kV.

<Crystal structure>
Using an X-ray diffractometer Ultima-IV manufactured by Rigaku Corporation, Cu was used as a target, an excitation voltage was 40 kV, an excitation current was 40 mA, and an operation axis was 2θ / θ. A high-speed one-dimensional X-ray detector D / teX Ultra was used as the detector.

<Power generation characteristics>
Using an optical microscope, calculate the area of the photoelectric conversion element, and then irradiate the photoelectric conversion element with about 100 mW / cm ² of pseudo-sunlight using a solar simulator (manufactured by Wacom Denso Co., Ltd.). Using a meter (Agilent Technologies B2902A type), current-voltage characteristics were measured, and short-circuit current density (Jsc), open-circuit voltage value (Voc), fill factor (FF), and energy conversion efficiency were determined. .

<Preparation of aqueous metal chalcogenide semiconductor material solution>
An aqueous solution A1 prepared by weighing and mixing Cu (NO ₃ ) ₂ .3H ₂ O and In (NO ₃ ) ₃ .3H ₂ O as metal chalcogenide semiconductor raw materials to a concentration of 0.18 / 0.20 mol / L was prepared. . Separately, a 1.6 mol / L aqueous solution B1 of thiourea was prepared. Next, the aqueous solution A and the aqueous solution B were mixed at a volume ratio of 1: 1 to prepare an aqueous solution C1 to be used for spraying.

<Production of photoelectric conversion element>
On a hot plate set at 330 ° C., a conductive substrate in which 1 μm thick molybdenum was deposited as a first electrode layer on 1 mm thick soda lime glass was set so that the molybdenum was on the surface side, The operation of spraying the aqueous solution C1 at a rate of 2 mL / min for 1 minute was performed three times to spray a total of 6 mL of the aqueous solution. When this sample was analyzed by an X-ray diffraction method, low crystalline CuInS ₂ was formed.

Next, the obtained substrate was put into a tube made of borosilicate glass, and then 10 mg of sulfur was put into the same tube. Then, the oxygen partial pressure was kept at a vacuum of about 0.4 Pa, and the product made of borosilicate glass was used. The other side of the tube was sealed, and the inside of the tube was kept in a vacuum state. Next, this tube was heated at 600 ° C. for 10 minutes using an electric furnace to form a p-type CuInS ₂ light absorption layer.
Next, 70.5 mL of water was heated to 60 ° C., then an aqueous cadmium sulfate solution prepared by dissolving 0.13 g of 3CdSO ₄ .8H ₂ O powder in water to 10.5 mL was added, and 28% ammonia water was further added. 19 mL was added. When this aqueous solution reached 60 ° C., the substrate having the light absorption layer and the first electrode layer was immersed in this aqueous solution, and 0.845 g of thiourea was further added and stirred for 60 minutes at 60 ° C. An n-type CdS buffer layer was prepared.
Furthermore, a photoelectric conversion element was manufactured by depositing about 300 nm of tin-doped indium oxide (ITO) as an electrode using a sputtering apparatus. The sheet resistance of the tin-doped indium oxide electrode was about 30Ω / □.

<Evaluation of photoelectric conversion element>
When the power generation characteristics of the photoelectric conversion element were evaluated, energy conversion was performed at a short-circuit current density (Jsc) of 19.4 mA / cm ² , an open circuit voltage (Voc) of 0.62 V, and a fill factor (FF) of 51%. Efficiency: 6.1%.
In addition, when evaluated using transmission electron microscope-energy dispersive X-ray spectroscopy measurement, CuInS _{2 of the} light absorption layer is substantially spherical, its average particle size is 350 nm, and the light absorption layer 2 and the buffer layer 3 The unevenness of the interface was 200 nm. Further, contact between CdS constituting the buffer layer 3 and molybdenum of the first electrode layer 1 was not observed.

<Preparation of aqueous metal chalcogenide semiconductor material solution>
0.18 / 0 Cu (NO ₃ ) ₂ .3H ₂ O, In (NO ₃ ) ₃ .3H ₂ O, Ga (NO ₃ ) ₃ .nH ₂ O (n = 7 to 9) as metal chalcogenide semiconductor raw materials The aqueous solution A2 weighed and prepared was adjusted to a concentration of 12 / 0.08 mol / L. At this time, n of Ga (NO ₃ ) ₃ .nH ₂ O (n = 7 to 9) was calculated as 8 and weighed. Separately, a 1.6 mol / L aqueous solution B1 of thiourea was prepared. Next, the aqueous solution A2 and the aqueous solution B2 were mixed at a volume ratio of 1: 1 to prepare an aqueous solution C2 to be used for spraying.

<Production of photoelectric conversion element>
Change the aqueous solution to be sprayed to C2, change to 10 mg of sulfur, put 5 mg of selenium into a tube sealed with one side made of borosilicate glass, seal the tube in a vacuum atmosphere with an oxygen partial pressure of about 0.01 Pa, A photoelectric conversion element was produced in the same manner as in Example 1 except that the light absorption layer was produced in the same manner as in Example 1 except that heating with an electric furnace was set at 560 ° C. for 10 minutes. The composition of the light absorption layer was Cu (In, Ga) (S, Se) ₂ .

<Evaluation of photoelectric conversion element>
When the power generation characteristics of the photoelectric conversion element were evaluated, energy conversion was performed at a short circuit current density (Jsc): 36.6 mA / cm ² , an open circuit voltage (Voc): 0.64 V, and a fill factor (FF): 36%. Efficiency: 8.5%.
Moreover, when evaluated using transmission electron microscope-energy dispersive X-ray spectroscopy measurement, Cu (In, Ga) (S, Se) ₂ of the light absorption layer ₂ is substantially spherical, and its average particle size is At 200 nm, the unevenness at the interface between the light absorption layer 2 and the buffer layer 3 was 110 nm. Further, contact between CdS constituting the buffer layer 3 and molybdenum of the first electrode layer 1 was not observed.

[Comparative Example 1]
When the photoelectric conversion element was produced and evaluated in the same manner as in Example 1 except that the film formation by spraying was performed by continuously spraying 4 mL without dividing the film into three times, the power generation characteristics of the photoelectric conversion element were evaluated. Short-circuit current density (Jsc): 22.0 mA / cm ² , open-circuit voltage (Voc): 0.52 V, fill factor (FF): 46%, and energy conversion efficiency: 5.2%.
Further, when evaluated using transmission electron microscope-energy dispersive X-ray spectroscopy measurement, CuInS ₂ of the light absorption layer ₂ is substantially spherical, its average particle diameter is 200 nm, and the light absorption layer and the buffer layer The unevenness of the interface was 500 nm, and CdS constituting the buffer layer 3 and molybdenum of the first electrode layer 1 were in partial contact.

[Comparative Example 2]
A photoelectric conversion element was produced and evaluated in the same manner as in Example 1 except that the light absorption layer was produced in the same manner as in Example 2 except that the tube was sealed in a vacuum atmosphere having an oxygen partial pressure of about 4 Pa. The composition of the light absorption layer was Cu (In, Ga) (S, Se) ₂ . When the power generation characteristics of the photoelectric conversion element were evaluated, energy conversion was performed at a short circuit current density (Jsc): 1.4 mA / cm ² , an open circuit voltage (Voc): 0.15 V, and a fill factor (FF): 31%. Efficiency: 0.063%.

Moreover, when evaluated using transmission electron microscope-energy dispersive X-ray spectroscopy measurement, Cu (In, Ga) (S, Se) ₂ of the light absorption layer ₂ is substantially spherical, and its average particle size is At 80 nm, the unevenness at the interface between the light absorption layer 2 and the buffer layer 3 was 10 nm, and CdS constituting the buffer layer 3 and molybdenum in the first electrode layer 1 were not in partial contact.

[Comparative Example 3]
A photoelectric conversion element was produced and evaluated in the same manner as in Example 2 except that selenium was not baked in the vapor atmosphere. As a result of X-ray diffraction measurement, Cu (In, Ga) (S, Se) ₂ was formed, the crystallite size was 0.004 μm, and partial peeling occurred during the formation of the buffer layer, and no power was generated.

  The photoelectric conversion element of the present invention has high energy conversion efficiency, can be easily manufactured, and is particularly suitable as a solar cell.

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

Claims (17)

A conductive first electrode layer, a light absorption layer provided on the first electrode layer and including a metal chalcogenide semiconductor containing a chalcogen element selected from sulfur and / or selenium, and the light absorption layer A photoelectric conversion element comprising: a buffer layer including a semiconductor having a polarity different from that of the light absorption layer; and a second electrode layer provided on the buffer layer,
The metal chalcogenide semiconductor has a substantially spherical shape;
At the interface between the light absorption layer and the buffer layer, the light absorption layer has a rough surface with an uneven shape of 20 nm to 400 nm,
The photoelectric conversion element is characterized in that the buffer layer is not in contact with the first electrode layer.   The photoelectric conversion element according to claim 1, wherein the metal chalcogenide semiconductor contains copper.   The photoelectric conversion device according to claim 2, wherein the metal chalcogenide semiconductor further contains indium and / or gallium.   The light absorption layer contains one or more water-soluble metal salts containing a metal constituting the metal chalcogenide semiconductor and one or more water-soluble chalcogen-containing organics containing a chalcogen element selected from sulfur and / or selenium. An aqueous solution containing a metal chalcogenide semiconductor material containing a compound is formed by spraying a plurality of times on the heated first electrode layer (1). The photoelectric conversion element as described in 2.   The light absorption layer contains one or more water-soluble metal salts containing a metal constituting the metal chalcogenide semiconductor and one or more water-soluble chalcogen-containing organics containing a chalcogen element selected from sulfur and / or selenium. An aqueous solution containing a metal chalcogenide semiconductor material containing a compound is sprayed a plurality of times on the heated first electrode layer, and then contains a chalcogen element selected from sulfur and / or selenium, and has an oxygen content. The photoelectric conversion element according to claim 1, wherein the photoelectric conversion element is formed by firing in a gas atmosphere having a pressure of 1 Pa or less.   The photoelectric conversion element according to claim 1, wherein the buffer layer is formed by a chemical bath deposition method.   7. The photoelectric conversion element according to claim 1, wherein one of the first electrode layer and the second electrode layer is translucent in order to introduce light into the light absorption layer. . It is a manufacturing method of the photoelectric conversion element according to any one of claims 1 to 7,
Including a laminated structure formed by laminating a light absorption layer including a metal chalcogenide semiconductor on the first electrode layer;
A chalcogen selected from one or more water-soluble metal salts containing a metal constituting the metal chalcogenide semiconductor and sulfur and / or selenium on the first electrode layer by heating the first electrode layer A first step of spraying an aqueous solution containing a metal chalcogenide semiconductor raw material containing at least one water-soluble chalcogen-containing organic compound containing an element a plurality of times to form a precursor of a light absorption layer;
And a second step of forming the light absorption layer by firing the precursor of the light absorption layer in the first step.   The one or more water-soluble chalcogen-containing organic compounds containing the chalcogen element used in the first step are compounds containing sulfur, and the baking in the second step includes selenium and oxygen partial pressure The method for producing a photoelectric conversion element according to claim 8, wherein the process is performed in a gas atmosphere of 1 Pa or less.   The precursor in the first step is a metal chalcogenide semiconductor, and firing of the precursor in the second step causes the light absorption layer to be 20 nm to 400 nm in the interface between the light absorption layer and the buffer layer. A method for producing a photoelectric conversion element according to claim 8, wherein a rough surface having an uneven shape is formed. A conductive first electrode layer, a light absorption layer provided on the first electrode layer and including a metal chalcogenide semiconductor containing a chalcogen element selected from sulfur and / or selenium, and the light absorption layer A photoelectric conversion element comprising: a buffer layer including a semiconductor having a polarity different from that of the light absorption layer; and a second electrode layer provided on the buffer layer,
Forming a substantially spherical shape in the metal chalcogenide semiconductor;
Forming an uneven rough surface of 20 nm to 400 nm in the light absorption layer at the interface between the light absorption layer and the buffer layer;
The method for manufacturing a photoelectric conversion element, wherein the buffer layer is not in contact with the first electrode layer.   The method for producing a photoelectric conversion element according to claim 11, wherein the metal chalcogenide semiconductor contains copper.   The method for producing a photoelectric conversion element according to claim 12, wherein the metal chalcogenide semiconductor further contains indium and / or gallium.   The light absorption layer contains one or more water-soluble metal salts containing a metal constituting the metal chalcogenide semiconductor and one or more water-soluble chalcogen-containing organics containing a chalcogen element selected from sulfur and / or selenium. 14. The photoelectric device according to claim 11, wherein an aqueous solution containing a metal chalcogenide semiconductor raw material containing a compound is sprayed a plurality of times on the heated first electrode layer. A method for manufacturing a conversion element.   The light absorption layer contains one or more water-soluble metal salts containing a metal constituting the metal chalcogenide semiconductor and one or more water-soluble chalcogen-containing organics containing a chalcogen element selected from sulfur and / or selenium. An aqueous solution containing a metal chalcogenide semiconductor material containing a compound is sprayed a plurality of times on the heated first electrode layer, and then contains a chalcogen element selected from sulfur and / or selenium, and has an oxygen content. The method for producing a photoelectric conversion element according to claim 11, wherein the photoelectric conversion element is formed by firing in a gas atmosphere having a pressure of 1 Pa or less.   The method for manufacturing a photoelectric conversion element according to claim 11, wherein the buffer layer is formed by a chemical bath deposition method.   17. The photoelectric conversion element according to claim 11, wherein one of the first electrode layer and the second electrode layer is translucent in order to introduce light into the light absorption layer. Method.

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