JP2015056421A - Method for manufacturing photoelectric conversion element, and electrode for light water electrolysis - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a method for manufacturing a photoelectric conversion element that has a high photoelectric conversion efficiency; and an electrode for light water electrolysis, which is utilized for hydrogen production through water electrolysis.SOLUTION: A method for manufacturing a photoelectric conversion element includes: a first step of forming a Cu-Zn-Sn-based metal layered film including a Cu film, an Sn film and a Zn film, using an electrodeposition method on a substrate; a second step of annealing the Cu-Zn-Sn-based metal layered film to form a Cu-Zn-Sn-based metal alloy precursor; and a third step of sulfurizing the Cu-Zn-Sn-based metal alloy precursor to form a CZTS film. The CZTS film formed through the third step has a surface having a surface roughness of 0.5 μm or less.

Description

The present invention is method of manufacturing a photoelectric conversion element constituting the photoelectric conversion layer in CZTS _(Cu 2 ZnSnS ₄₎ and relates to an optical water for electrolysis having the CZTS manufactured by the manufacturing method _(Cu 2 ZnSnS ₄₎ film, In particular, the present invention relates to a method for producing a photoelectric conversion element having high photoelectric conversion efficiency and a photo-water splitting electrode used for decomposing water to generate hydrogen.

Currently, research on solar cells is actively conducted. A solar cell has a laminated structure in which a semiconductor photoelectric conversion layer that generates current by light absorption is sandwiched between a back electrode and a transparent electrode.
A photoelectric conversion layer using chalcopyrite-based CuInSe ₂ (CIS) or Cu (In, Ga) Se ₂ (hereinafter also simply referred to as CIGS) has been studied. A solar cell using the CIGS film as a photoelectric conversion layer (hereinafter referred to as a CIGS solar cell) has been studied actively because it has a relatively high efficiency and a high light absorptance, and can be thinned.

  However, since CIGS solar cells use rare metals of In and Ga, copper (Cu), zinc (Zn), tin (Sn), sulfur (S), selenium (Se) (hereinafter simply referred to as CZTS) is used. The one used is being studied. CZTS does not use rare metals, and Sn and Zn are abundant and much cheaper than In and the like.

Non-Patent Document 1 describes a Cu ₂ ZnSnS ₄ solar cell using an electrodeposited method. In the Cu ₂ ZnSnS ₄ solar cell of Non-Patent Document 1, a conversion efficiency of 7.3% is obtained.
Further, the _Cu 2 ZnSnS ₄ solar cell of the non-patent document 1, as described _below, to produce a photoelectric conversion layer of Cu 2 ZnSnS ₄ (light absorbing layer).
First, a Cu / Zn / Sn or Cu / Sn / Zn metal laminate is produced by electroplating. Then, in order to generate a homogeneous Cu, Zn alloy, Cu, Sn alloy, low temperature annealing (soft annealing) is performed at a temperature of 210 ° C. to 350 ° C. in an N ₂ atmosphere. Then, annealing is performed at a temperature of 550 ° C. to 590 ° C. in a sulfur atmosphere for 5 to 15 minutes. Thereby, it is said that it is completely converted into a high single crystalline Cu ₂ ZnSnS ₄ phase, and a photoelectric conversion layer of Cu ₂ ZnSnS ₄ is obtained.

Adv. Energy. Mater. , 2012,2,253-259

The Cu ₂ ZnSnS ₄ solar cell described in Non-Patent Document 1 has a problem that the efficiency is not sufficient. For this reason, when the photoelectric conversion layer of Cu ₂ ZnSnS ₄ is used for decomposing water to generate hydrogen, there is a problem that hydrogen cannot be generated efficiently.

  An object of the present invention is to provide a method for producing a photoelectric conversion element with high photoelectric conversion efficiency and an optical water splitting electrode used for decomposing water and generating hydrogen by solving the problems based on the conventional technology. There is to do.

In order to achieve the above object, a first aspect of the present invention is a first aspect in which a Cu—Zn—Sn-based metal multilayer film including a Cu film, a Sn film, and a Zn film is formed on a substrate by an electrodeposition method. A second step of annealing the Cu-Zn-Sn-based metal multilayer film to form a Cu-Zn-Sn-based metal alloy precursor, and sulfiding the Cu-Zn-Sn-based metal alloy precursor; And a third step of forming a CZTS film, and the CZTS film formed in the third step has a surface roughness of 0.5 μm or less. It is to provide.
In the present invention, the surface roughness is an arithmetic average obtained by measuring surface irregularities in a measurement range of 200 μm × 284.7 μm out of the surface to be measured, and measuring the irregularities in the measurement range. It is roughness. The above arithmetic average roughness is calculated based on JIS B0601: 2001. For this reason, the detailed description of the calculation method of arithmetic average roughness is abbreviate | omitted. Thus, the surface roughness of the present invention is an extension of JIS B0601: 2001. In the present invention, the unevenness in the measurement range can be measured in a non-contact manner using, for example, a laser microscope. As a laser microscope, for example, KEYENCE shape measurement laser microscope VK-9700 (trade name) can be used.

The Cu—Zn—Sn-based metal multilayer film formed in the first step preferably has a surface roughness of 0.1 μm or less.
Further, the Cu—Zn—Sn-based metal laminated film is preferably laminated in the order of the Cu film, the Sn film, and the Zn film from the substrate side.

  A second aspect of the present invention is an optical water splitting electrode, which has a CZTS film produced using the method for producing a photoelectric conversion element of the first aspect of the present invention. An electrode for water splitting is provided.

  According to the present invention, a photoelectric conversion element having a high photoelectric conversion efficiency using CZTS for a photoelectric conversion layer is obtained by an electrolytic deposition method (electrodeposition method) that is low in cost and can be expanded to a large area. be able to. In addition, it is possible to obtain a photohydrolysis electrode with high hydrogen generation efficiency.

(A)-(d) is a typical perspective view which shows the manufacturing method of the photoelectric conversion element of embodiment of this invention in process order. (A)-(d) is a typical perspective view which shows the manufacturing method of the photoelectric conversion element of embodiment of this invention in process order. It is a typical sectional view showing an electrode for water splitting.

Below, based on suitable embodiment shown in an accompanying drawing, the manufacturing method of the photoelectric conversion element of the present invention, and the electrode for photo-water splitting are explained in detail.
Drawing 1 (a)-(d) is a typical perspective view showing a manufacturing method of a photoelectric conversion element of an embodiment of the present invention in order of a process. FIGS. 2A to 2D are schematic perspective views showing, in the order of steps, the manufacturing method of the photoelectric conversion element of the embodiment of the present invention from the next step of FIG.

In the method for manufacturing a photoelectric conversion element of this embodiment, a CZTS film is formed as a photoelectric conversion element layer of the photoelectric conversion element.
As a configuration of the photoelectric conversion element 40 (see FIG. 2D), the back electrode 12 is formed on the substrate 10, and the CZTS film 24 functioning as a photoelectric conversion layer is formed on the back electrode 12. Yes. A buffer layer 26, a window layer 28 and a transparent electrode 30 are formed on the CZTS film 24 in this order. A bus line 32 is formed on the transparent electrode 30.
In the photoelectric conversion element 40, current is generated by photoelectric conversion in the CZTS film 24 by light incident from the transparent electrode 30 side, and current is extracted to the outside through the bus line 32.
Hereinafter, the manufacturing method of the photoelectric conversion element 40 of this embodiment is demonstrated concretely.

As shown in FIG. 1A, first, a substrate 10 having a back electrode 12 formed on a front surface 10a is prepared. The substrate 10 is made of glass, for example. The back electrode 12 is made of, for example, Mo and is formed by a sputtering method.
Next, as shown in FIG. 1B, a Cu layer 14 is formed on the surface 12a of the back electrode 12 by, for example, an electrodeposition method. For forming the Cu layer 14, for example, the substrate 10 with the back electrode 12 is used as a working electrode, a platinum foil is used as a counter electrode, Ag / AgCl is used as a reference electrode, and a mixed solution of CuSO ₄ , trisodium citrate and citric acid. Is used.

Next, as shown in FIG. 1C, the Sn layer 16 is formed on the surface 14a of the Cu layer 14 by, for example, an electrodeposition method. In order to form the Sn layer 16, for example, the substrate 10 on which the Cu layer 14 is formed is used as a working electrode, a platinum foil is used as a counter electrode, Ag / AgCl is used as a reference electrode, Sn (SO ₃ CH ₃ ) ₂ , CH A mixed solution of ₃ SO ₃ H and n-dodecyl-N, N-dimethylglycine (DDMG) is used.

Next, as shown in FIG. 1D, a Zn layer 18 is formed on the surface 16a of the Sn layer 16 by, for example, an electrodeposition method. Thereby, a Cu—Zn—Sn-based metal multilayer film 20 (hereinafter referred to as a metal multilayer film 20) is formed.
For forming the Zn layer 18, for example, the substrate 10 on which the Sn layer 16 is formed is used as a working electrode, a platinum foil is used as a counter electrode, Ag / AgCl is used as a reference electrode, ZnSO ₄ , K ₂ SO ₄ , and pH 3 Use a mixed solution of buffers.

The surface roughness of the surface 20a of the metal laminated film 20 is preferably 0.1 μm or less. By setting the surface roughness of the surface 20a of the metal laminated film 20 to 0.1 μm or less, the conversion efficiency of the photoelectric conversion element 40 finally obtained can be adjusted together with the definition of the surface roughness of the surface 24a of the CZTS film 24 described later. Can be high.
Here, the regulation and calculation method of the surface roughness of the surface 20a of the metal laminated film 20 is as described for the surface roughness of the present invention, and a detailed description thereof will be omitted. For example, when a laser microscope is used to measure the surface roughness of the surface 20a of the metal laminated film 20, it can be measured in a non-contact manner, and the surface roughness can be measured in-line.

Next, the pre-annealing process is performed on the metal laminated film 20 shown in FIG. 1D at a temperature of 200 ° C. to 400 ° C. for 10 minutes or more under a reduced pressure of 0.01 Pa to 0.5 Pa, for example. Do. Thereby, the metal laminated film 20 is alloyed to form a Cu—Zn—Sn-based metal alloy precursor 22 (hereinafter referred to as the precursor 22) as shown in FIG.
Note that the pre-annealing treatment does not have to be an atmosphere under reduced pressure as long as it is a nitrogen atmosphere or an argon atmosphere, and may be a normal pressure or higher pressure.

Next, the precursor 22 is subjected to sulfiding treatment under a sulfur atmosphere at a temperature of 400 ° C. to 620 ° C. for 3 to 60 minutes. As a result, a CZTS film 24 is formed from the precursor 22 as shown in FIG. The CZTS film 24 is a photoelectric conversion layer.
At this time, the surface roughness of the surface 24a of the CZTS film 24 is 0.5 μm or less.
Note that the definition and measurement method of the surface roughness of the surface 24a of the CZTS film 24 are as described for the surface roughness of the present invention, and a detailed description thereof will be omitted. For example, when a laser microscope is used for measuring the surface roughness of the surface 24a of the CZTS film 24, the surface roughness can be measured in-line.

Next, for example, a potassium cyanide aqueous solution or a hydrochloric acid aqueous solution treatment is performed on the CZTS film 24. Thereafter, as shown in FIG. 2C, a buffer layer 26 is formed on the surface 24a of the CZTS film 24 by, for example, chemical bath deposition (hereinafter referred to as CBD method). The buffer layer 26 is made of CdS, for example. The buffer layer 26 and the CZTS film 24 form a pn junction.
Next, as shown in FIG. 2D, the window layer 28 is formed on the surface 26a of the buffer layer 26 by RF sputtering, for example. The window layer 28 is formed on the buffer layer 26 in order to suppress a parallel resistance component generated at the pn junction. The window layer 28 is composed of a high-resistance insulating film made of, for example, i-ZnO.

Next, a transparent electrode 30 that is paired with the back electrode 12 is formed on the front surface 28a of the window layer 28 by, for example, a vapor deposition method such as an electron beam evaporation method, a sputtering method, or a CVD method, or a coating method. The transparent electrode 30 is made of, for example, ITO.
Then, a rectangular bus line 32 is formed on a part of the surface 30a of the transparent electrode 30 by, for example, vapor deposition, sputtering, CVD, or the like. Thereby, the photoelectric conversion element 40 is formed.
The bus line 32 is made of aluminum, for example. The bus line 32 is an electrode for taking out the current generated in the photoelectric conversion layer 24 from the transparent electrode 30. For this reason, the bus line 32 may not be provided.
In addition, the conveyance method in the manufacturing method of the photoelectric conversion element 40 may be a roll-to-roll method or a single wafer method, and the conveyance method can be appropriately selected according to the flexibility of the substrate 10 or the like.

  It is known that when the metal laminated film 20 is annealed for a long time, Sn loss occurs and a composition shift occurs, resulting in a decrease in photoelectric conversion efficiency of the CZTS film 24 after sulfidation. For this reason, in general, in order to make the metal laminated film 20 into an alloy, annealing is not performed for a necessary time or more. However, in the present invention, Sn omission or the like was not confirmed even after long-time annealing longer than the time necessary for making the metal laminated film 20 into an alloy. Here, although it is known that recombination that causes carriers to disappear and is no longer used for photoelectric conversion occurs at the interface, recombination at the interface can be suppressed by reducing the interface. By setting the surface roughness Ra of the surface 24a of the CZTS film 24 after sulfidation to 0.5 μm or less, the interface between the CZTS film 24 and the buffer layer 26 can be reduced, and the characteristics of the photoelectric conversion element 40 are improved. . As a result, high conversion efficiency is obtained for the photoelectric conversion element 40. Thus, the conversion efficiency of the finally obtained photoelectric conversion element 40 can be increased by setting the surface roughness of the surface 24a of the CZTS film 24 to 0.5 μm or less. In addition, it exists in the tendency for the conversion efficiency of the photoelectric conversion element 40 finally obtained to become high, so that surface roughness Ra is small. The improvement of the characteristics of the photoelectric conversion element will be described in detail later.

  In this embodiment, when forming the metal laminated film 20, the Cu layer 14, the Sn layer 16, and the Zn layer 18 are formed in this order from the substrate 10 side. The stacking order is preferably Cu layer 14, Sn layer 16 and Zn layer 18 from the substrate 10 side, but the stacking order is not particularly limited. The stacking order is, for example, the order of Cu layer, Zn layer and Sn layer, or Cu layer, Sn layer, Cu layer and Zn layer from the substrate 10 side.

  In the photoelectric conversion element 40, the substrate 10 is not particularly limited as long as it is an insulating substrate that is usually used as a substrate for a photoelectric conversion element or a solar cell. As the substrate 10, for example, a soda lime glass substrate, a ceramic substrate, a resin substrate, or the like can be used. Further, as the substrate 10, a substrate in which an insulating layer is formed on a metal substrate can be used. This metal substrate is, for example, a metal substrate such as an Al substrate or a SUS substrate, or a composite metal substrate such as a composite Al substrate made of a composite material of an Al base and another metal base such as SUS. Furthermore, as the substrate 10, a metal substrate with an insulating film in which an anodized film formed by anodizing the surface is used as an insulating layer on the surface of an Al substrate or the like can also be used.

  The thickness of the substrate 10 is not particularly limited as long as sufficient strength can be ensured according to the size of the photoelectric conversion element 40, the forming material of the substrate 10, the presence or absence of flexibility of the substrate 10, and the like. The thickness of the substrate 10 is preferably 0.02 to 10 mm, for example. In addition, the board | substrate 10 is flat form, for example, The shape, a magnitude | size, etc. are suitably determined according to the magnitude | size etc. of the photoelectric conversion element 40 applied.

  The back electrode 12 is made of, for example, a metal such as Mo, Al, Cu, Cr, W, Ni, Ta, Fe, Co, or a combination of these metals. The back electrode 12 may have a single-layer structure or a laminated structure such as a two-layer structure. The back electrode 12 is preferably composed of Mo. The back electrode 12 preferably has a thickness of about 200 nm to 1000 nm (1 μm).

  The CZTS film 24 forms a pn junction with the CZTS film 24 side being P-type and the buffer layer 26 side being N-type at the interface with the buffer layer 26, and is transmitted through the transparent electrode 30, the window layer 28, and the buffer layer 26. It is a layer that absorbs light that has arrived and generates holes on the p side and electrons on the n side, and has a photoelectric conversion function.

The buffer layer 26 is formed to form a pn junction with the CZTS film 24 and to protect the CZTS film 24 from damage that occurs when the transparent electrode 30 is formed.
In addition to CdS, the buffer layer 26 is made of ZnS, Zn (S, O) and / or Zn (S, O, OH), SnS, Sn (S, O) and / or Sn (S, O, OH), InS. , In (S, O) and / or In (S, O, OH) and the like, preferably containing a metal sulfide containing at least one metal element selected from the group consisting of Cd, Zn, Sn, In. . The thickness of the buffer layer 26 is preferably 10 nm to 2 μm, and more preferably 15 to 200 nm. For example, the CBD method is used to form the buffer layer 26.

  The window layer 28 is formed on the buffer layer 26 in order to suppress a parallel resistance component generated at the pn junction, and is configured by a high-resistance insulating film made of the above-described i-ZnO or the like. The window layer 28 is formed by, for example, a sputtering method. In particular, it is preferable to form a window layer 28 made of a high resistance film such as ZnO between the buffer layer 26 such as CBD-CdS and the transparent electrode 30 such as ZnO: Al. Note that the window layer 28 is not necessarily provided.

The transparent electrode 30 has translucency, takes light into the CZTS film 24, and functions as an electrode through which a current generated by the CZTS film 24 flows in a pair with the back electrode 12. The transparent electrode 30 is made of, for example, IMO (In ₂ O ₃ to which Mo is added), ZnO doped with Al, B, Ga, In, or the like, or ITO. The transparent electrode 30 may have a single layer structure or a laminated structure such as a two-layer structure. The film thickness of the transparent electrode 30 is, for example, 50 nm to 2 μm.
In addition, the formation method of the transparent electrode 30 is not specifically limited, It can form by vapor phase film-forming methods, such as an electron beam vapor deposition method, a sputtering method, and CVD method, or the apply | coating method. Further, an antireflection film made of MgF ₂ or the like may be formed on the surface 30 a of the transparent electrode 30.

  For example, as shown in FIGS. 1A and 1B of Japanese Patent Application Laid-Open No. 2011-165790, the photoelectric conversion element 40 is electrically connected in series on one substrate 10 to form a solar cell. May be. In this case, for example, in the solar cell, the back electrode 12, the CZTS film 24, the buffer layer 26, the window layer 28, and the transparent electrode 30 are stacked, and the first groove portion that penetrates only the back electrode 12, CZTS A second groove portion that penetrates the film 24 and the buffer layer 26 and a third groove portion that penetrates the CZTS film 24, the buffer layer 26, and the transparent electrode 30 are formed. Thereby, the some photoelectric conversion element 40 is electrically connected in series on a board | substrate, and makes a solar cell.

Next, a description will be given of an optical water splitting electrode used for decomposing water to generate hydrogen. FIG. 3 is a schematic cross-sectional view showing an electrode for water splitting.
The CZTS film 24 formed by the manufacturing method of the present embodiment can be used for an electrode for water photolysis.
As shown in FIG. 3, the water splitting electrode 50 is laminated on the collector electrode 52 in the order of a p-type semiconductor film 54 and an n-type semiconductor film 56, and a reaction promoter is formed on a surface 56 a of the n-type semiconductor film 56. 58 is formed.
The CZTS film 24 described above is used for the p-type semiconductor film 54. The buffer layer 26 described above is used for the n-type semiconductor film 56. For this reason, the detailed description is abbreviate | omitted.
As for the p-type semiconductor film 54, the surface roughness of the surface 54a is 0.5 μm or less as in the case of the CZTS film 24 described above. As a result, the interface between the p-type semiconductor film 54 and the n-type semiconductor film 56 can be reduced, and recombination that can no longer be used for photo-hydrogen conversion due to disappearance of carriers is suppressed, thereby decomposing water. Efficiency can be increased.

The collector electrode 52 is not particularly limited as long as it has conductivity and is electrochemically durable, but from the viewpoint of heat resistance, for example, Fe, Cu, Al, Ni, Metal materials such as SUS, Ti, Ta, Mo, Au, and Pt are preferable. In addition, an insulating material such as glass can be used as a substrate, and the substrate can be used as a collecting electrode 52 with a conductive layer coated thereon. In this case, the metal material can be used for the conductive layer.
As the insulating material used for the substrate, quartz, soda lime glass, or the like can be used.
The shape of the collecting electrode 52 is not particularly limited, but it is preferable to use a sheet-like one having a thickness of about 1 μm to 1 mm. Further, the thickness of the conductive layer formed on the surface of the insulating material is preferably 100 nm to 10 μm.

Examples of the reaction co-catalyst 58 include Pt, Pd, Ru, Ni, Fe, etc. In addition to this, for example, NiO, RuO ₂ , IrO ₂ , Rh ₂ O ₃ , Cr—Rh composite oxide, Examples thereof include core-shell type Rh / Cr ₂ O ₃ , Pt / Cr ₂ O ₃ , NiS, MoS ₂ , and NiMoS.
The formation method of the reaction co-catalyst 58 is not particularly limited, and can be formed by a photo-deposition method, a sputtering method, an impregnation method, or the like.

The photo-water splitting electrode 50 can be manufactured, for example, as follows.
First, as the collector electrode 52, for example, a soda lime glass plate on which a Mo film is formed by sputtering is prepared.
Next, a CZTS film is formed as a p-type semiconductor film 54 on the collector electrode 52, that is, on the Mo film. Since the method of forming this CZTS film is as described above, its detailed description is omitted.
Next, for example, a CdS film is formed on the p-type semiconductor film 54 as the n-type semiconductor film 56. Since the method for forming this CdS film is as described above, its detailed description is omitted. As described above, the surface roughness of the surface 54a of the p-type semiconductor film 54 is 0.5 μm or less. Also in the p-type semiconductor film 54, the surface roughness of the surface of the metal laminated film is preferably 0.1 μm or less in the step of forming the CZTS film.
Next, as the reaction promoter 58, a Pt promoter is supported on the surface 56a of the n-type semiconductor film 56 by, for example, a photo-deposition method. In this way, the photo-water splitting electrode 50 can be manufactured.

  In the water splitting method using the photo-water splitting electrode 50, the photo-water splitting electrode 50 is immersed in an electrolytic solution and irradiated with light, whereby water can be decomposed to generate hydrogen. The pH of the electrolytic solution is preferably 7 or more and 13 or less from the viewpoint of efficiently performing a water splitting reaction. Conventionally, water decomposition using a photocatalytic electrode is often carried out in a strong acid aqueous solution as shown in J. Kaneshiro et al. Solar Energy Materials & Solar Cells 94 (2010) 12-16. However, from the viewpoint of onset potential and electrode stability, the electrolyte is preferably weakly alkaline.

  The present invention is basically configured as described above. As mentioned above, although the manufacturing method of the photoelectric conversion element of this invention and the electrode for optical water splitting were demonstrated in detail, this invention is not limited to the said embodiment, In the range which does not deviate from the main point of this invention, various improvement or change Of course, you may do it.

  Hereinafter, the manufacturing method of the photoelectric conversion element of this invention is demonstrated concretely based on an Example. The present invention is not limited to these examples.

In the present Example, in order to confirm the effect of this invention, the pre-annealing time (minute) was changed and the photoelectric conversion element of the comparative examples 1-5 shown below was manufactured. About each photoelectric conversion element of Comparative Examples 1 to 5, current density-voltage characteristics (IV characteristics) were measured using a pseudo sun of AM (Air mass) 1.5 and 100 mW / cm ² .
From each current density-voltage characteristic of Comparative Examples 1 to 5, the short circuit current density (Jsc), the open circuit voltage (Voc), the fill factor (FF), and the conversion efficiency were determined. The results are shown in Table 1 below together with the pre-annealing time (minutes) and the surface roughness Ra of the surface 24a of the CZTS film 24.

Regarding the surface roughness Ra of the surface 24a of the CZTS film 24, the unevenness in the measurement range of 200 μm × 284.7 μm of the surface 24a of the CZTS film 24 was measured using a laser microscope (Keyence Corporation, Shape Measurement Laser Microscope VK−). 9700 (trade name)), and the arithmetic average roughness in the measurement range was calculated based on JIS B0601: 2001 as described above. This arithmetic average roughness was defined as the surface roughness Ra of the surface 24a of the CZTS film 24.
In Examples 1 to 5, the surface roughness Ra of the surface 24a of the CZTS film 24 was measured after the sulfurization treatment.
About Examples 1-5, the measurement of the surface roughness of the surface 20a of the metal laminated film 20 was also performed. In each of Examples 1 to 5, the surface roughness of the surface 20a of the metal laminated film 20 was 0.067 μm.
In Comparative Example 1, since the pre-annealing treatment is not performed, the surface roughness of the surface 20a of the metal laminated film 20 is measured before the sulfiding treatment, and the surface roughness obtained at this time is measured on the surface of the CZTS film 24. 24a was treated as surface roughness Ra.
Further, the surface roughness of the surface 20a of the metal laminated film 20 of Comparative Example 1 was measured in the same manner as the surface roughness Ra of the surface 24a of the CZTS film 24. For this reason, the detailed description is abbreviate | omitted.

Hereinafter, the manufacturing method of the photoelectric conversion element of Example 1- Example 5 and Comparative Example 1 is demonstrated.
Example 1
In Example 1, the photoelectric conversion element 40 having the configuration shown in FIG. First, a soda lime glass substrate is prepared as the substrate 10.
Next, a Mo film having a thickness of 600 nm is formed as the back electrode 12 on the surface 10a of the substrate 10 by sputtering.
Next, a Cu layer 14 was formed on the Mo film by using an electrodeposition method. The Cu layer 14 is formed by using the substrate 10 with the back electrode 12 as a working electrode, using a platinum foil as a counter electrode, using Ag / AgCl as a reference electrode, 0.05M CuSO ₄ , 0.04M trisodium citrate. And a mixed solution of 0.02M citric acid was used.
Next, the Sn layer 16 was produced on the Cu layer 14 using the electrodeposition method. The Sn layer 16 is formed by using the substrate 10 on which the Cu layer 14 is formed as a working electrode, using a platinum foil as a counter electrode, using Ag / AgCl as a reference electrode, and 0.05M Sn (SO ₃ CH ₃ ) _2. , 1M in _CH 3 _SO 3 H, and 1M of n- dodecyl -N, a mixed solution of N- dimethylglycine (DDMG) was used.

Next, a Zn layer 18 was formed on the Sn layer 16 by using an electrodeposition method to obtain a metal laminated film 20 having a thickness of 1.3 μm. The Zn layer 18 is formed by using the substrate 10 on which the Sn layer 16 is formed as a working electrode, using a platinum foil as a counter electrode, using Ag / AgCl as a reference electrode, 0.1M ZnSO ₄ , 0.5M K A mixed solution of ₂ SO ₄ and pH 3 buffer (HYDRION (registered trademark)) was used.
And the surface roughness of the surface 20a of the metal laminated film 20 is measured in-line using a laser microscope as described above.
Next, a pre-annealing process was performed on the metal laminated film 20 under a reduced pressure of 0.01 Pa to 0.5 Pa at a temperature of 320 ° C. for a pre-annealing time of 10 minutes, thereby forming a precursor 22.
Next, the precursor 22 was subjected to a sulfurization treatment in a sulfur atmosphere at a temperature of 550 ° C. for 15 minutes to form a CZTS film 24. Then, the surface roughness of the surface 24a of the CZTS film 24 is measured in-line using the laser microscope as described above.

Next, a CdS film having a thickness of 100 nm is formed as the buffer layer 26 on the surface 24a of the CZTS film 24 by using the CBD method. Thereafter, an i-ZnO film having a thickness of 80 nm is formed as the window layer 28 by using an RF sputtering method.
Next, an ITO film having a thickness of 420 nm is formed as the transparent electrode 30 on the surface 28a of the window layer 28 by RF sputtering.
Next, an Al bus line 32 is formed on a part of the surface 30a of the transparent electrode 30 by vapor deposition.

(Example 2)
In Example 2, as compared with Example 1, a photoelectric conversion element was manufactured in the same process as in Example 1 except that the pre-annealing treatment was performed at a temperature of 320 ° C. for 20 minutes. For this reason, detailed description of Example 2 is omitted.
(Example 3)
In Example 3, as compared with Example 1, a photoelectric conversion element was produced in the same process as Example 1 except that the pre-annealing treatment was performed at a temperature of 320 ° C. for 40 minutes. For this reason, detailed description of Example 3 is omitted.

Example 4
In Example 4, as compared with Example 1, a photoelectric conversion element was manufactured in the same process as Example 1 except that the pre-annealing treatment was performed at a temperature of 320 ° C. for 80 minutes. For this reason, detailed description of Example 4 is omitted.
(Example 5)
In Example 5, a photoelectric conversion element was manufactured in the same process as in Example 1 except that the pre-annealing treatment was performed at a temperature of 320 ° C. and a pre-annealing time of 150 minutes as compared with Example 1. For this reason, detailed description of Example 5 is omitted.
(Comparative Example 1)
In Comparative Example 1, as compared with Example 1, the CZTS film 24 was formed by performing a sulfurization treatment at a temperature of 550 ° C. for 15 minutes without performing a pre-annealing treatment, and as described above. A photoelectric conversion element was manufactured in the same process as in Example 1 except that the surface roughness of the surface 20a of the metal laminated film 20 was measured in-line using a laser microscope, and this was changed to the surface roughness Ra. For this reason, the detailed description of the comparative example 1 is abbreviate | omitted. In addition, the surface roughness of the surface 20a of the metal laminated film 20 was 0.067 μm.

  As shown in Table 1 above, Example 1 to Example 5 subjected to the pre-annealing treatment had a surface roughness Ra of the CZTS film of 0.5 μm or less as compared with Comparative Example 1 where the pre-annealing treatment was not performed. Improved conversion efficiency. Moreover, in Example 1- Example 5, if the surface roughness Ra of a CZTS film | membrane becomes small, conversion efficiency will improve.

In this example, using the CZTS films of Examples 1 to 5 and Comparative Example 1 of the first example, the electrodes for photo-water splitting of Examples 10 to 14 and Comparative Example 10 shown below are produced. did.
Each electrode for water splitting is irradiated with light using a pseudo sun of AM (Air mass) 1.5, 100 mW / cm ² , and the current density-voltage characteristics (hereinafter referred to as IV characteristics) are used as an electrolyte solution. Measured in. For this the I-V characteristic, and adapting the following formula, a value that is a maximum value and with H ₂ efficiency with respect to the applied voltage V.
Incidentally, _{H 2} efficiency of Examples 10 to 14 and Comparative Example 10 are shown in relative values with a value of 1 _{H 2} efficiency of Example 10. The results are shown in the column of H ₂ efficiency (relative value) in Table 2 below.
In the measurement of IV characteristics, an Ag / AgCl electrode was used as a reference electrode (reversible hydrogen electrode, RHE), a Pt wire was used as a counter electrode, and 0.1 M of 0.1 M adjusted to pH 9.5 using NaOH as an electrolyte solution. Na ₂ SO ₄ was used.

η _ABPE = (I × V _RHE / P) × 100
I: Photocurrent density (mA / cm ² )
V: Applied voltage (V vs RHE (reversible hydrogen electrode))
P: Incident irradiation intensity (100 mW / cm ² )

Hereinafter, the manufacturing method of the electrode for optical water splitting of Examples 10-14 and Comparative Example 10 will be described.
(Example 10)
In Example 10, a soda lime glass substrate on which a Mo film was formed by sputtering was used as a collector electrode. The CZTS film 24 of Example 5 of the first example is formed as a p-type semiconductor film 54 on the Mo film of the collector electrode, and a 100 nm thick CdS film (buffer) is formed thereon as an n-type semiconductor film 56. Layer 26) was formed. Pt particles were formed on the surface 56a of the n-type semiconductor film 56 by electrodeposition as a reaction promoter.
The electrodeposition method for Pt particles was performed as follows.
In the electrodeposition method of Pt particles, an Ag / AgCl electrode is used as a reference electrode, a Pt wire is used as a counter electrode, 0.1 M Na ₂ SO ₄ adjusted to pH 9.5 using NaOH and 10 μM hexachloroplatinic acid (H ₂ In the electrolyte solution of PtCl ₆ ), the above-mentioned CdS film (buffer layer 26) is immersed, and the Ag / AgCl electrode is controlled to −1 V to 0 V, while AM (Air mass) 1.5, Light irradiation of 100 mW / cm ² was performed, and Pt photodeposition was performed. The electrodeposition was terminated when the observed photocathode current value was saturated.
In addition, since the manufacturing method of the CZTS film | membrane 24 and the CdS film | membrane is as above-mentioned, detailed description is abbreviate | omitted.

(Example 11)
Example 11 is similar to Example 10 except that the CZTS film 24 of Example 4 of the first example is formed as the p-type semiconductor film 54. A decomposition electrode was produced. Therefore, detailed description of the eleventh embodiment is omitted.
(Example 12)
Example 12 is similar to Example 10 except that the CZTS film 24 of Example 3 of the first example is formed as the p-type semiconductor film 54. A decomposition electrode was produced. Therefore, detailed description of the twelfth embodiment is omitted.

(Example 13)
Example 13 is similar to Example 10 except that the CZTS film 24 of Example 2 of the first example is formed as the p-type semiconductor film 54. A decomposition electrode was produced. Therefore, detailed description of the thirteenth embodiment is omitted.
(Example 14)
Example 14 is similar to Example 10 except that the CZTS film 24 of Example 1 of the first example is formed as the p-type semiconductor film 54. A decomposition electrode was produced. For this reason, detailed description of Example 14 is omitted.

(Comparative Example 10)
Example 14 is similar to Example 10 except that the CZTS film 24 of Comparative Example 1 of the first example is formed as the p-type semiconductor film 54. A decomposition electrode was produced. For this reason, the detailed description of the comparative example 10 is abbreviate | omitted.

As shown in Table 2 above, the surface roughness Ra of the p-type semiconductor film (CZTS film) is 10 to 14 in which the surface roughness Ra of the p-type semiconductor film (CZTS film) is 0.5 μm or less. H ₂ efficiency (relative value) is higher than that of Comparative Example 10 having a thickness exceeding 0.5 μm. In Examples 10 to 14, the H ₂ efficiency (relative value) is improved when the surface roughness Ra of the p-type semiconductor film (CZTS film) is reduced. This coincides with the tendency that the conversion efficiency is improved when the surface roughness Ra of the CZTS film in the first embodiment is reduced.

DESCRIPTION OF SYMBOLS 10 Board | substrate 12 Back electrode 14 Cu layer 16 Sn layer 18 Zn layer 20 Cu-Zn-Sn type metal laminated film (metal laminated film)
22 Cu—Zn—Sn-based metal alloy precursor (precursor)
24 CZTS film 26 Buffer layer 28 Window layer 30 Transparent electrode 32 Bus line 40 Photoelectric conversion element 50 Electrode for water splitting 52 Collector electrode 54 P-type semiconductor film 56 N-type semiconductor film 58 Reaction promoter

Claims (4)

A first step of forming a Cu-Zn-Sn-based metal laminated film including a Cu film, a Sn film, and a Zn film on a substrate by an electrodeposition method;
A second step of annealing the Cu-Zn-Sn-based metal multilayer film to form a Cu-Zn-Sn-based metal alloy precursor;
A third step of sulfiding the Cu-Zn-Sn based metal alloy precursor to form a CZTS film,
The method of manufacturing a photoelectric conversion element, wherein the CZTS film formed in the third step has a surface roughness of 0.5 μm or less.   2. The method for manufacturing a photoelectric conversion element according to claim 1, wherein the Cu—Zn—Sn-based metal multilayer film formed in the first step has a surface roughness of 0.1 μm or less.   The said Cu-Zn-Sn type metal laminated film is a manufacturing method of the photoelectric conversion element of Claim 1 or 2 laminated | stacked in order of the said Cu film | membrane, the said Sn film | membrane, and the said Zn film | membrane from the said substrate side. An electrode for water photolysis,
A CZTS film produced by using the method for producing a photoelectric conversion element according to claim 1, wherein the photo-water splitting electrode is characterized in that it has a CZTS film.

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