JP2017037876A - Photovoltaic module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photovoltaic module having a metal silicide layer of high generation efficiency.SOLUTION: In a photovoltaic module including a polycrystalline metal silicide layer as a power generation layer, an electrode layer provided on the upper surface or lower surface of the polycrystalline metal silicide layer consists of a GZO electrode, partially or entirely. Preferably, the average grain diameter A (μm) and the thickness B (μm) of the polycrystalline metal silicide layer satisfy a relation; A≥B.SELECTED DRAWING: Figure 1

Description

Embodiments described below generally relate to photovoltaic modules.

Solar cells using sunlight are attracting attention as clean electric energy. As solar cells, those using a single crystal silicon substrate or a polycrystalline silicon substrate are mainly used because of their excellent power generation efficiency. In addition, the use of thin-film amorphous silicon obtained by reducing the thickness of a silicon substrate has been studied for cost reduction. In addition, compound semiconductor solar cells using gallium, arsenic, phosphorus, germanium, indium or the like are also known as non-silicon solar cells. Conventional solar cells have a problem that the cost is high due to the increase in the size of the silicon substrate that receives sunlight and the complexity of the compound synthesis process, and the diffusion of the solar cell does not proceed as expected.
In recent years, solar cells using metal silicide as a semiconductor layer have been studied. For example, JP-A-20
11-198941 (Patent Document 1) discloses a solar cell using a β-FeSi ₂ layer as a semiconductor layer. A metal silicide such as iron silicide can be produced as either a single crystal or a polycrystal, and is expected to be lower in cost than a silicon-based solar cell. In addition, since metal silicide solar cells generate power by sensing infrared rays that are not used in silicon solar cells, there are expectations for higher efficiency than silicon solar cells.
However, solar cells using a metal silicide layer are not commercialized at present and are in the research stage. This is because stable power generation efficiency cannot be obtained. Moreover, since the output of a solar cell using a metal silicide layer fluctuates depending on the intensity of received light, there was anxiety in use as a single power source.
In order to improve this, International Publication No. 2014/171146 (Patent Document 2)
Then, it is proposed to control the relationship between the film thickness of the metal silicide layer and the average crystal grain size.

JP 2011-198941 A International Publication No. 2014/171146

As shown in Patent Document 2, the power generation efficiency is improved by making the average crystal grain size larger than the film thickness of the metal silicide layer. On the other hand, the power generation efficiency is around 2%. Therefore, further improvement in power generation efficiency is required.
The problem to be solved by the present invention is to provide a photovoltaic power generation module using a metal silicide layer with good power generation efficiency.

A photovoltaic power generation module according to an embodiment is a photovoltaic power generation module including a polycrystalline metal silicide layer as a power generation layer, wherein a part or all of the electrode layers provided on the upper surface or the lower surface of the polycrystalline metal silicide layer are GZO electrodes. It is characterized by comprising.

It is a schematic diagram for illustrating a solar power generation module. It is a schematic diagram for illustrating another photovoltaic power generation module. It is a schematic diagram for illustrating a polycrystalline metal silicide layer. It is a schematic diagram for illustrating a pn junction type polycrystalline metal silicide layer. It is a schematic diagram for illustrating a Schottky type polycrystalline metal silicide layer.

Hereinafter, embodiments will be illustrated with reference to the drawings. In addition, in each drawing, the same code | symbol is attached | subjected to the same component and detailed description is abbreviate | omitted suitably.
Drawing 1 is a mimetic diagram for illustrating the photovoltaic power generation module concerning an embodiment.
In the figure, 1 is a photovoltaic power generation module according to the embodiment, 2 is a polycrystalline metal silicide layer, 3 is a lower electrode layer, 4 is an upper electrode layer, and 5 is a substrate.
An upper surface electrode layer 4 is provided on the front surface side (sunlight receiving surface side) of the polycrystalline metal silicide layer 2, and a lower surface electrode layer 3 is provided on the back surface side (the side opposite to the sunlight receiving surface). The polycrystalline metal silicide layer has a function of receiving sunlight and generating electric power, and electricity generated by the polycrystalline metal silicide layer using the upper electrode layer 4 and the lower electrode layer 3 can be taken out to the outside. Therefore, the polycrystalline metal silicide layer is a power generation layer.

The photovoltaic power generation module according to the embodiment is characterized in that part or all of the electrode layer provided on the upper surface or the lower surface of the polycrystalline metal silicide layer is formed of a GZO electrode.
This indicates that a part or all of the lower electrode layer 3 or the upper electrode layer 4 is made of a GZO electrode.
GZO is zinc oxide (ZnO) doped with Ga (gallium). G
The ZO electrode is a kind of transparent electrode. Light is transmitted because it is a transparent electrode. Therefore, it can be used for both the upper electrode layer and the lower electrode layer.
The GZO electrode is a material that hardly reacts with the metal silicide layer. I as a transparent electrode
There are TO and AZO. As metal silicide, FeSi ₂ and BaS are used as will be described later.
i ₂ may be mentioned. These metal silicides are easily oxidized. Power generation efficiency decreases due to oxidation of metal silicide. It has been found that when an ITO electrode is provided on the metal silicide layer, oxygen in the ITO electrode reacts with the metal silicide to oxidize the metal silicide. Since the metal silicide layer is oxidized, the power generation efficiency is not further improved. A
A similar oxidation phenomenon occurred with respect to the ZO electrode.

On the other hand, the oxidation phenomenon is suppressed in the GZO electrode. For this reason, the polycrystalline metal silicide layer is hardly oxidized, and the power generation efficiency is improved. When oxygen enters the crystal grain boundary of the polycrystalline metal silicide layer, the grain boundary trap phenomenon increases. Therefore, the GZO electrode is effective for those using a polycrystalline metal silicon layer.
FIG. 2 illustrates another photovoltaic power generation module. The numbers in the figure are the same as in FIG. FIG. 2 shows a structure in which the upper electrode layer 4 is provided on the entire surface of the metal silicide layer 2. For this reason, the upper surface electrode layer 4 is provided on the entire upper surface of the metal silicide layer 2 and the lower surface electrode layer 3 is provided on the entire lower surface. At this time, by using at least one of the upper electrode layer 4 or the lower electrode layer 3 as a GZO electrode, the metal silicide layer 2 can be prevented from being deteriorated by oxidation. Moreover, it is preferable that both the upper surface electrode layer 4 and the lower surface electrode layer 3 are GZO electrodes. Further, by covering the upper and lower surfaces of the metal silicide layer 2 with the electrode layer, the metal silicide layer 2 can be prevented from being oxidized by being exposed to the outside air.

In the photovoltaic power generation module, it is preferable that the relationship between the average crystal grain size A (μm) and the film thickness B (μm) of the polycrystalline metal silicide layer satisfies A ≧ B. That is, the average crystal grain size of the polycrystalline metal silicide layer is larger than the film thickness. In polycrystalline metal silicide, individual crystal particles contribute to power generation. The electricity generated by the metal silicide crystal particles is taken out through the upper electrode layer 4 and the lower electrode layer 3 as described above. That means
Electricity flows in the thickness direction of the metal silicide layer. When electricity flows through the metal silicide layer 2, the grain boundary between the metal silicide crystal particles becomes a trap site. The grain boundary trap site becomes an internal resistance that impedes carrier conduction, and the electricity generated by the metal silicide layer cannot be taken out efficiently, resulting in a decrease in power generation efficiency. Therefore, by setting the average crystal grain size A (μm) ≧ film thickness B (μm), the number of grain boundaries in the thickness direction of the metal silicide layer can be reduced (including zero). For this reason, the state where there is no grain boundary between the metal silicide crystal grains in the thickness direction of the metal silicide layer is most preferable. In addition, the measuring method of the average crystal grain size A (μm) and the film thickness B (μm) of the metal silicide layer is as follows:
First, an enlarged photograph of an arbitrary cross section in the thickness direction of the metal silicide layer is measured. The maximum diameter of the individual crystal grains shown there is taken as the grain diameter, and the average value of any 30 grains is taken as the average crystal grain diameter A (μm). As for the film thickness, an enlarged photograph of the cross section is taken in the same manner, the thicknesses at arbitrary 10 locations are measured, and the average value is defined as the film thickness B (μm). The enlarged photograph is enlarged to such an extent that the grain boundary between crystal grains can be seen. In addition, when not all 30 grains are included in one photograph (one field of view), a plurality of continuous enlarged photographs are used.

FIG. 3 shows a schematic diagram of a polycrystalline metal silicide layer. In the figure, 2 is a polycrystalline metal silicide layer. B is the thickness of the metal silicide layer. FIG. 3 schematically shows a state in which five crystal grains are arranged. The grain boundary between crystal grains is not particularly limited, such as a straight line or a curved line. Further, as shown in FIG. 3, the individual particle diameters of the metal silicide crystal particles are the maximum diameters of the crystal particles appearing there, so that A1, A2, A3, A4, and A5 are the particle diameters, respectively. . This operation is performed 30 grains, and the average value is obtained.

The average crystal grain size A (μm) of the polycrystalline metal silicide layer is 0.01 μm or more (10 n
m or more). If the average crystal grain size is less than 10 nm, the crystal size is too small and it may be difficult to control A ≧ B. The upper limit of the average crystal grain size is not particularly limited, but is preferably 3 μm or less. If the average crystal grain size exceeds 3 μm, it may be difficult to produce a uniform crystal. The average crystal grain size is preferably 0.
It is 05-1.2 micrometers (50-1200 nm).
In addition, the polycrystalline metal silicide layer preferably has a film thickness B (μm) of 1 μm or less.
Further, if the film thickness exceeds 1 μm, it may be difficult to produce a homogeneous crystal.
Moreover, even if it exceeds 1 μm, there is a possibility that no more power generation efficiency can be obtained.

The metal silicide is preferably one of β-iron silicide, barium silicide, magnesium silicide, chromium silicide, or rhenium silicide. Also,
The β-iron silicide layer is preferably a β-FeSi ₂ layer. The barium silicide is preferably a BaSi ₂ layer.
The iron silicide, FeSi besides FeSi _2, Fe 3 _Si, but like _Fe 5 Si ₃ and the like, FeSi ₂ is good and most power generation efficiency. If the stoichiometry approximates to FeSi ₂ , it can be used even if it is slightly deviated (a range in which the atomic ratio of Fe and Si is 1: 2 by rounding off the first digit of the decimal point). Magnesium silicide is preferably Mg ₂ Si, chromium silicide is preferably CrSi ₂ , and rhenium silicide is preferably ReSi ₂ . BaSi ₂ ,
For Mg ₂ Si, CrSi ₂ , and ReSi _2, it is sufficient that the first decimal place is rounded off and the atomic ratio falls within this range.

Further, a pn junction type structure in which a p-type β-iron silicide layer and an n-type β-iron silicide layer are in contact structure, or a Schottky type structure, MIS (metal-thin insulator).
-Semi-conductor-type structure, MOS (metal-oxide-semic)
Any structure of an inductor type. Moreover, you may dope impurities etc. as needed.
In addition, p-type β-FeSi ₂ has a carrier density of 1 × 10 ¹⁴ to 1 × 10 ²¹ cm ⁻³ , n
The type β-FeSi ₂ preferably has a carrier density of 1 × 10 ¹⁴ to 1 × 10 ²¹ cm ⁻³ and the Schottky type β-FeSi ₂ preferably has a carrier density of 1 × 10 ¹⁴ to 1 × 10 ¹⁸ cm ^−3. . In any β-FeSi ₂ , the carrier density is preferably 1 × 10 ¹⁶ cm ⁻³ or less. The power generation efficiency is improved by reducing the carrier density. In other words, that the power generation efficiency is improved indicates that the carrier density is 1 × 10 ¹⁶ cm ⁻³ or less. The carrier density of 1 × 10 ¹⁶ cm ⁻³ or less is 1 × 10
A numerical value with a small multiplier such as ¹⁴ cm ⁻³ is shown.

The barium silicide layer is preferably a BaSi ₂ layer. In addition to BaSi ₂ , examples of barium silicide include BaSi, and BaSi ₂ has the highest power generation efficiency. If the stoichiometry approximates BaSi ₂ , it can be used even if it is slightly deviated. The p-type barium silicide layer and the n-type barium silicide layer have a contact structure.
n-junction structure or Schottky structure, MIS (metal-thin insul)
antor-semiconductor type structure, MOS (metal-oxide-s)
Any of the structure of the semiconductor) type may be used. Moreover, you may dope impurities etc. as needed.
In addition, p-type BaSi2 has a carrier density of 1 × 10 ¹⁴ to 1 × 10 ²¹ cm ⁻³ and n-type B.
aSi ₂ has a carrier density of 1 × 10 ¹⁴ to 1 × 10 ²¹ cm ⁻³ and a Schottky BaS.
i ₂ preferably has a carrier density of 1 × 10 ¹⁴ to 1 × 10 ¹⁸ cm ⁻³ . The carrier density is preferably 1 × 10 ¹⁷ cm ⁻³ or less for any BaSi ₂ . The power generation efficiency is improved by reducing the carrier density. In other words, that the power generation efficiency is improved indicates that the carrier density is 1 × 10 ¹⁷ cm ⁻³ or less. Similarly, even if it is another metal silicide (Mg ₂ Si, CrSi ₂ , ReSi ₂ ), the carrier density is preferably 1 × 10 ¹⁷ cm ⁻³ or less. In addition,
The carrier density of 1 × 10 ¹⁷ cm ⁻³ or less indicates a numerical value with a small multiplier such as 1 × 10 ¹⁵ cm ⁻³ .

Since β-FeSi ₂ has a band gap Eg of about 0.85 eV and is a direct transition type, it has a high absorption efficiency for wavelengths of 1500 nm or less. Further, BaSi ₂ has a high band gap Eg of about 1.4 eV and an indirect transition type, and therefore has high absorption efficiency for wavelengths of 950 nm or less. Since infrared rays of 1500 nm or less or 950 nm or less can be used for power generation, it is possible to generate power for a long time even when viewed on a daily basis. Β
-FeSi ₂ and BaSi ₂ have an absorption coefficient as high as 100 to 1000 times that of Si, so that the film thickness can be reduced to about 1/100 to 1/1000 of the Si solar cell layer when the efficiency is the same. .

Note that the pn junction type and the Schottky type are preferably Schottky types. In the case of the Schottky type, it is not necessary to prepare two types of metal silicides of the p-type and the n-type unlike the pn junction type, so that the cost can be reduced.
FIG. 4 shows a schematic diagram of a photovoltaic power generation module having a pn junction type polycrystalline metal silicide layer and FIG. 5 having a Schottky type polycrystalline metal silicide layer. In the figure, 2 is a polycrystalline metal silicide layer, 2-1 is a p-type polycrystalline metal silicide layer, 2-2 is an n-type polycrystalline metal silicide layer, 2-
3 is a depletion layer, 3 is a lower electrode layer, and 4 is an upper electrode layer.
FIG. 4 is a schematic diagram of a photovoltaic power generation module having a pn junction type polycrystalline metal silicide layer. Although FIG. 4 illustrates the structure in which the p-type is provided on the upper electrode layer side and the n-type is provided on the lower electrode layer side, the p-type and n-type may be reversed. As shown in FIG. 4, when charge is applied to the pn junction structure, a depletion layer 2-3 is formed between the p-type layer 2-1 and the n-type layer 2-2. Due to the presence of the depletion layer, an electric double layer is formed, and electricity can be extracted.

FIG. 5 is a schematic diagram of a photovoltaic power generation module having a Schottky polycrystalline metal silicide layer. The polycrystalline metal silicide layer 2 in FIG. 5 may be either the p-type layer 2-1 or the n-type layer 2-2. The Schottky type is a junction that exhibits a rectifying action between a metal and a semiconductor. In addition, a depletion layer is formed by contact between the metal and the semiconductor. In this case, the metal is the upper electrode layer 4 or the lower electrode layer 3. The semiconductor is a polycrystalline metal silicide layer.
The pn junction type mainly has a structure in which current is supplied using minority carriers, whereas the Schottky type has a structure in which current is mainly supplied using majority carriers. Therefore, a photovoltaic power generation module that is superior in high-speed operation in the Schottky type can be manufactured. The p-type fabrication can be exemplified by a method of doping one selected from Group 3B of the periodic table. The group 3B of the periodic table includes B (boron), Al (aluminum), Ga (gallium), and In (indium).
, Tl (thallium). In addition, n-type fabrication can be exemplified by a method of doping one selected from Group 5B of the periodic table. The group 5B of the periodic table is N (nitrogen), P (phosphorus), As (arsenic), Sb (antimony), and Bi (bismuth).

The top electrode layer 4 is preferably an electrode material that transmits light having a wavelength of 1500 nm or less. Examples of such a material include transparent electrode materials such as GZO, ITO, ATO, and AZO. Further, the surface electrode layer 4 may be formed at one or more places on the polycrystalline metal silicide layer 2.
Further, after a nitride film is provided on the polycrystalline metal silicide layer 2, a transparent electrode material may be formed thereon. The nitride film has an effect of a protective film that prevents oxidation and moisture absorption of the polycrystalline metal silicide layer 2. The nitride film is preferably a silicon nitride film. Further, the silicon nitride film is selected from Si _x N _y , Si _x N _y O _z , Si _x N _y O _z H _α , and Si _x N _y H _α 1
Species are preferred. Note that x, y, z, and α are atomic ratios, 0 <x ≦ 3.0, 0 <y ≦ 4.0.
0 ≦ z ≦ 1.0 and 0 ≦ α ≦ 0.1. The nitride film thickness is 10n
m or less, more preferably 5 nm or less. Many nitride films are insulating (low conductivity).
If the film thickness exceeds 10 nm, electricity may not flow. 10 nm or less, or 5
By using a thin film of nm or less, a tunnel effect is obtained, so that there is no influence on conduction. The minimum thickness of the nitride film is not particularly limited as long as it functions as a protective film, but is preferably 2 nm or more.
Examples of the nitride film include film formation methods such as sputtering, CVD, and direct nitridation (a method of nitriding metal silicide). Further, when each film forming method is performed, Si _x N _y O _z , Si _x N _y O _z H _α , and Si _x N _y H _α are formed by adding oxygen or hydrogen to the atmosphere during film formation. be able to.
Further, an antireflection film or a glass substrate may be provided on the upper surface electrode layer 4 and the polycrystalline metal silicide layer 2 as necessary.

A lower electrode layer 3 and a substrate 5 are formed on the back side of the polycrystalline metal silicide layer 2. The lower electrode layer 3 may be any material having conductivity, such as metal materials (including alloys) such as Pt, Ag, Al, and Cu, conductive nitrides such as LaB ₆ and TiN, and nickel silicide (
Examples thereof include metal silicides such as NiSi ₂ ) and cobalt silicide (CoSi). β
When -FeSi ₂ is used, NiSi ₂ is preferably used. NiSi ₂ is β-F
an electrode material serving as a template for controlling the crystal orientation of the eSi _2.
Moreover, when using an alloy as the lower surface electrode layer 3, an Al alloy is used. Examples of the Al alloy include an Al-rare earth alloy such as an AlNd alloy. The rare earth content in the Al-rare earth alloy is preferably 10 at% or less.
The lower electrode layer 3 is preferably a heat resistant material. As will be described later, it is preferable to perform heat treatment when the polycrystalline metal silicide layer 2 is formed. For this reason, it is preferable that the lower surface electrode layer 3 is a material having heat resistance. As a heat resistant material, NiSi
₂ , AlNd alloy, LaB ₆ , TiN. By using a heat-resistant electrode material, the formation yield of the electrode layer is improved. In particular, when the lower electrode layer 3 does not require translucency, these heat-resistant materials are preferable.
As the electrode layer 3, it is preferable to perform work function matching of the polycrystalline metal silicide layer. Specifically, the electrode layer of the p-type polycrystalline metal silicide layer is preferably lower than the work function of the p-type polycrystalline metal silicide layer. The electrode layer of the n-type polycrystalline metal silicide layer is preferably higher than the work function of the n-type polycrystalline metal silicide layer. By performing such matching, rectification characteristics can be imparted between the polycrystalline metal silicide layer and the electrode layer. The rectification characteristic is a characteristic that facilitates current flow in a certain direction. By providing the rectification characteristic, the power generation efficiency is improved.
Further, an insulating layer may be partially provided between the metal silicide layer 2 and the electrode layer 3 as necessary.
Examples of the substrate 5 include a glass substrate, an insulating ceramic substrate, and a metal substrate.
In the case of a metal substrate, an insulating layer is provided to ensure insulation from the outside.
If it is the above photovoltaic power generation modules, a photovoltaic power generation module with good power generation efficiency can be provided.

Here, the manufacturing method of a photovoltaic power generation module is demonstrated. As long as it has the said structure regarding this embodiment, a manufacturing method will not be specifically limited, The following method is mentioned as a method for obtaining efficiently.
First, the substrate 5 is prepared. If necessary, the surface of the substrate 5 is cleaned. In the case of washing, a sufficient drying process is performed.
Next, the lower electrode layer 3 is formed. The lower electrode layer 3 is formed by forming the components constituting the electrode layer using a film forming method such as a sputtering method. The thickness of the lower electrode layer 3 is arbitrary, but 10 nm
The above is preferable.
Further, when a metal silicide such as NiSi ₂ is used as the lower electrode layer 3, NiSi
Examples include a method using _two targets and a method using both a Ni target (metal target) and a Si target. In the case of the method using both the Ni target and the Si target, the Ni target and the Si target may be either simultaneous sputtering or alternate sputtering. Further, after the sputtering, it is preferable to react the NiSi ₂ by heat treatment. The heat treatment conditions are preferably 300 to 700 ° C. and 30 seconds to 5 minutes in an inert atmosphere such as nitrogen. If heat treatment is performed at a high temperature exceeding 700 ° C. or for a long time exceeding 5 minutes, the substrate 5 or the like may be distorted. The purity of NiSi ₂ is 99.9 wt% or more, and further 99.
It is preferable that it is 999 wt% or more. NiSi ₂ may be either a polycrystalline film or a single crystal film. In the case of a polycrystalline film, it is preferable that the average crystal grain size is large. NiSi ₂
By increasing the average crystal grain size of the underlying layer, the average crystal grain size of the polycrystalline metal silicide layer 2 formed thereon can be increased. The same effect can be obtained even if the base layer is a single crystal film.

Next, a patterning process is performed on the lower electrode layer 3 as necessary. Examples of the patterning process include a method of performing an etching process by applying an etching resist or placing a mask material in a place where a pattern (wiring) is desired to be left.
Next, a step of providing a metal silicide layer is performed. When the metal silicide layer is provided, the metal silicide layer is formed using a film formation method such as a sputtering method. The thickness of the metal silicide layer is 0.01 μm
m (10 nm) or more is preferable.
Further, when forming a β-FeSi ₂ layer, a method of sputtering an FeSi ₂ target,
A method using both an Fe target and a Si target is mentioned. In the case of the method using both the Fe target and the Si target, the Fe target and the Si target may be either simultaneous sputtering or alternate sputtering. Also, after sputtering, heat treatment is performed and Fe
It is preferable to react with Si ₂ . The heat treatment conditions are preferably 300 to 900 ° C. and 30 seconds to 1 hour in an inert atmosphere or a reducing atmosphere. Nitrogen gas, argon gas, etc. are mentioned as inert atmosphere. Moreover, as reducing atmosphere, nitrogen gas containing hydrogen, etc. are mentioned. Further, if heat treatment is performed at a high temperature exceeding 900 ° C. or for a long time exceeding 1 hour, the substrate 5 or the like may be distorted. When metal silicide (NiSi ₂ or CoSi) is used as the lower electrode layer 3, the heat treatment temperature can be set to 500 ° C. or lower. This is because the metal silicide serves as a template for forming the β-FeSi ₂ layer. The heat treatment temperature for forming the β-FeSi ₂ layer is 500 ° C.
The following is desirable because damage to the substrate, particularly the glass substrate can be reduced. Further, the average crystal grain size of the β-FeSi ₂ layer can be controlled by heat treatment after sputtering.

Further, in order to obtain a homogeneous β-FeSi ₂ layer, a method of performing a heat treatment after alternately sputtering an Fe target and a Si target is preferable. Fe film 0.5 ~ 5nm, Si film 1 ~
A range of 10 nm is set, Fe film / Si film is set as one set, and laminated films are alternately formed until a target film thickness is obtained, and heat treatment is performed. Due to the heat treatment, the Fe film and the Si film react to produce polycrystalline β-
FeSi ₂ layer. When the Fe film and the Si film are alternately laminated, the atomic ratio of Si and Fe is Fe: Si = 1: 1.5 to 2.5, and further the atomic ratio Fe: Si = 1: 2.0 to 2 .5 is preferable. By setting the atomic ratio of Fe and Si to 1: 2.0 to 2.5, a uniform β-FeSi ₂ layer is easily formed. When it becomes a homogeneous β-FeSi ₂ layer, the resistivity is 4 × 1.
0 ⁴ Ωcm or more. In particular, by making the range Fe: Si = 1: 2.1 to 2.4,
The resistivity can be 1 × 10 ⁵ Ωcm or more. High sheet resistance means that
It shows that a uniform β-FeSi ₂ layer is obtained with few portions of metal Fe or metal Si having low resistance values.

In addition, the purity of the sputtering target to be used is 99.9 wt% or more, even 99.999 wt% or more, regardless of which method is a method of sputtering an FeSi ₂ target or a method using both an Fe target and an Si target. High purity is preferable.
Further, the sputtering process is preferably performed in a vacuum or in an inert atmosphere. By performing the process in a vacuum or in an inert atmosphere, impurities can be prevented from being mixed during the sputtering process. Further, 1 × 10 ⁻³ Pa or less is preferable in vacuum, and argon gas is preferable in an inert atmosphere. Further, a heating atmosphere may be used during the sputtering process.
The sheet resistance value is measured on the surface of the β-FeSi ₂ layer by the 4-probe method. The formation of a homogeneous β-FeSi ₂ layer can also be confirmed by the XRD method. When the resulting beta-FeSi ₂ layer was subjected to XRD analysis (2θ), β-FeSi ₂ in the specific (202
) / (220) plane peak at 28-30 °, (004) / (040) plane peak, (42
2) The peak of the plane and the peak of the (133) plane are detected between 42 and 58 °. Also,(
202) / (220) plane is preferably the strongest peak. Homogeneous β-
When it is FeSi ₂ , the peak of metal Fe or metal Si is not detected when XRD analysis is performed.

In addition, when heat treatment is performed to obtain a homogeneous β-FeSi ₂ layer, the infrared absorption characteristic is 630.
An absorption edge can be provided at 0-6500 cm ⁻¹ . Also, the Fe film and the Si film as described above are alternately sputtered and subjected to heat treatment to form β-FeSi.
_{In the case where two} layers are formed, the temperature dependence of the sheet resistance is good. When the sheet resistance temperature dependency is Arrhenius plot (Arrhenios plot), the one with “resistivity of 8 × 10 ⁴ Ωcm, Ea = 0.142 eV” at 298 K (25 ° C.) is “200 K (−73 ° C.)” Resistivity 3.6 × 10 ⁵ Ωcm, Ea = 0.123 eV ”, 90K (−183 ° C.)“ Resistivity 3.6 × 10 ⁶ Ωcm, Ea = 0.0926 eV ”, 50 K (−223 ° C.) Resistivity 2 × 10 ⁷ Ωcm, Ea = 0.0395 eV ”. An excellent resistivity even in a low temperature region indicates that the carrier density is 1 × 10 ¹⁸ cm ⁻³ or less.
For this reason, the method of laminating Fe films and Si films alternately and reacting with β-FeSi ₂ by heat treatment provides a homogeneous β-FeSi ₂ layer. Also, by preparing the heat treatment conditions,
The relationship between the average crystal grain size A (μm) and the film thickness B (μm) of the polycrystalline metal silicide layer can also satisfy A ≧ B.

In the case of forming a BaSi ₂ layer include a method of sputtering a barium silicide target. Examples of the barium silicide target include BaSi ₂ and BaSi. In addition, oxidation and moisture absorption after opening to the atmosphere can be prevented by continuously forming a nitride film (protective film) after forming the BaSi ₂ layer. Moreover, it can form into a film, suppressing oxidation by performing a sputtering process in a vacuum or inert atmosphere. The vacuum atmosphere is preferably 1 × 10 ⁻³ Pa or less. The inert atmosphere is nitrogen,
Argon or the like is preferable. Further, a heating atmosphere may be used during the sputtering process.
In addition, the sputtering process may use a method of performing heat treatment after forming a film using a BaSi ₂ target. In the sputtering process, a sputtering target with different composition ratios of Ba and Si, such as BaSi ₂ and BaSi, is prepared, and alternately laminated and sputtered. After sputtering, heat treatment is performed to react with BaSi _2. May be. As heat treatment conditions, in vacuum, in an inert atmosphere or in a reducing atmosphere, 300 to 900 ° C., 30 seconds to
One hour is preferred. If heat treatment is performed at a high temperature exceeding 900 ° C. or for a long time exceeding 1 hour, the substrate 5 or the like may be distorted. Moreover, when heat-processing in a vacuum, it is preferable that a vacuum atmosphere is 1 * 10 < ^-3 > Pa or less. The inert atmosphere is preferably nitrogen or argon. Examples of the reducing atmosphere include a nitrogen atmosphere containing hydrogen.

In the case of forming a BaSi ₂ layers, by a vacuum deposition method, and a method of co-evaporation of barium and silicon. In the vacuum deposition method, since a high-purity deposition source can be used, BaS
Impurities in the i ₂ layer can be reduced. The purity of the deposition source of barium and silicon is 99w respectively.
t% or more is preferable. Furthermore, a high purity of 99.9 wt% or more is desirable. B
After forming the aSi ₂ layer, a nitride film (protective film) is continuously formed to prevent oxidation and moisture absorption after opening to the atmosphere.
Further, it can be prevented. Moreover, it can form into a film, suppressing oxidation by performing a co-evaporation process in a vacuum. The vacuum atmosphere is preferably 1 × 10 ⁻⁴ Pa or less. A heating atmosphere may be used during the co-evaporation step.
In the co-evaporation step, BaSi ₂ is deposited using a barium and silicon deposition source,
A method of performing heat treatment may be used. In the co-evaporation step, barium and silicon vapor deposition sources may be alternately stacked and vapor deposited, followed by heat treatment and reaction with BaSi ₂ . The heat treatment conditions are 300 to 900 ° C. under vacuum, in an inert atmosphere or in a reducing atmosphere.
30 seconds to 1 hour is preferable. If heat treatment is performed at a high temperature exceeding 900 ° C. or for a long time exceeding 1 hour, the substrate 5 or the like may be distorted. Moreover, when heat-processing in a vacuum, it is preferable that a vacuum atmosphere is 1 * 10 < ^-3 > Pa or less. The inert atmosphere is nitrogen,
Argon or the like is preferable. Examples of the reducing atmosphere include a nitrogen atmosphere containing hydrogen.
When metal silicide (NiSi ₂ or CoSi) is used as the lower electrode layer 3, the heat treatment temperature can be set to 500 ° C. or lower. This is because the metal silicide serves as a template for forming the BaSi ₂ layer. Further, it is desirable that the heat treatment temperature for forming the BaSi ₂ layer can be 500 ° C. or less because damage to the substrate, particularly the glass substrate can be reduced. Further, the average crystal grain size of the BaSi ₂ layer can be controlled by heat treatment after sputtering.
When metal silicide (NiSi ₂ or CoSi) is used as the electrode layer 3, the metal silicide electrode layer may be either a polycrystal or a single crystal.

In addition, when making a polycrystal, the average crystal grain size is desirably as large as possible. When the polycrystalline metal silicide layer 2 is provided on the metal silicide electrode layer 3 having a large average crystal grain size, the relationship between the average crystal grain size A (μm) and the film thickness B (μm) easily satisfies A ≧ B.
When metal silicide is used as the lower electrode layer 3, the metal silicide electrode layer 3
May be a multi-layer electrode structure in which a base electrode is provided and a metal electrode or the like is provided thereunder.
Further, when the patterning process of the lower electrode layer 3 is performed as described above, it is performed after a resist or a mask material is arranged in a place where the lower electrode layer 3 is not provided.
Further, in the case of a laminated structure such as a pn junction type, a step of doping impurities is performed.

As described above, a polycrystalline metal silicide layer is formed by combining sputtering and heat treatment. The relationship between the average crystal grain size A (μm) and the film thickness B (μm) of the polycrystalline metal silicide layer is A
In order to satisfy ≧ B, it is effective to perform grain growth by applying heat treatment to the polycrystalline metal silicide layer. This heat treatment is preferably 300 to 900 ° C. and 30 seconds to 1 hour. Further, this heat treatment may be performed together with the heat treatment after simultaneous sputtering or alternate sputtering of the Fe target and the Si target.
Further, if the Schottky structure is used, the heat treatment temperature can be set to 500 ° C. or lower, so that damage to the substrate 5 can be reduced.

Next, the process of providing the upper surface electrode layer 4 is performed. When a transparent electrode such as GZO, ITO or ATO is used, the upper electrode layer is preferably formed by a sputtering method using a GZO target, ITO target or ATO target.
As shown in FIG. 1, when the upper surface electrode portion 4 is partially provided on the metal silicide layer 2, sputtering is performed with a resist or mask material disposed. Also, FIG.
As described above, when the upper surface electrode layer 4 is provided on the entire surface of the metal silicide layer 2, sputtering is performed with a resist or mask material disposed around the metal silicide layer 2.
Moreover, it is preferable that at least one part or all of the upper surface electrode layer 4 is a GZO electrode. The GZO electrode is preferable because it is a material that hardly reacts with the metal silicide layer.
Moreover, after forming the upper surface electrode layer 4, if necessary, an antireflection film may be formed or bonded to a transparent substrate such as a glass substrate. Alternatively, the upper electrode layer 6 may be bonded to a transparent substrate provided in advance.

Further, it is preferable to provide an antioxidant film on the side surface of the metal silicide layer 2 so that the metal silicide layer 2 is not oxidized.

(Example)
(Examples 1-2, Comparative Example 1)
A NiSi ₂ layer (thickness 20 nm) was provided as a bottom electrode layer on the glass substrate. NiS
The i ₂ layer was formed by alternately sputtering a Ni target and a Si target to form a laminated film in which a large number of Ni / Si layers were alternately laminated. Thereafter, the NiSi ₂ layer was reacted by heat treatment at 500 ° C. for 1 minute in a nitrogen atmosphere. The Ni target or Si target has a purity of 99.9.
The wt% was used.
Next, a β-FeSi ₂ layer (thickness 300 nm) was formed on the NiSi ₂ layer. β-FeS
The i ₂ layer was formed by alternately sputtering an Fe target and a Si target to form a laminated film in which a large number of Fe films / Si films were alternately laminated. In Examples 1 and 2, the film thickness of the Fe film is set to 1 to 1.
The film thickness of 3 nm and the Si film was alternately stacked in the range of 5 to 10 nm. In Example 1, the atomic ratio is Fe: Si = 1: 2.1, and in Example 2, the atomic ratio is Fe: Si = 1: 2.3. The Fe target and the Si target were 99.9 wt% in purity. Thereafter, the relationship between the average crystal grain size and the film thickness was controlled by heat treatment under the conditions shown in Table 1.

A surface electrode layer made of GZO was provided on the β-FeSi ₂ layer. The GZO surface electrode layer was formed by sputtering a GZO target. Comparative Example 1 is the same as Example 1.
The upper electrode layer is changed to an ITO electrode.
In Example 1, a GZO electrode was provided on the half of the top surface of the β-FeSi ₂ layer. Example 2
A GZO electrode was provided on the entire top surface of the β-FeSi ₂ layer.
By such a method, a photovoltaic power generation module having a Schottky structure was produced. The average crystal grain size of the β-FeSi ₂ layer was determined for the obtained photovoltaic power generation module. The average crystal grain size was measured by cutting the β-FeSi ₂ layer in the thickness direction, taking an enlarged photograph of the cross section, and calculating the average value of 30 grains having the maximum diameter of each crystal grain. In addition, the β-FeSi ₂ layer is changed to XR.
As a result of D analysis, only the peak of β-FeSi ₂ crystal was detected, and the peaks of metal Fe and metal Si were not detected.

Regarding the photovoltaic power generation modules according to Examples 1 and 2 and Comparative Example 1, the power generation efficiency was obtained.
The method of measuring the power generation efficiency is the solar spectrum (emission intensity 30W / m ² , color temperature 5700K)
The power generation efficiency was obtained by irradiating with LED illumination light having an approximate emission spectrum at 12:00 noon. The results are shown in Table 2.

As can be seen from the table, the photovoltaic power generation module according to the example had good efficiency. This is G
This is because the ZO electrode hardly reacts with the metal silicide layer. Further, since the average crystal grain size A ≧ film thickness B, the grain boundary trap side is reduced.

(Examples 3 to 4, Comparative Example 2)
An AlNd alloy electrode layer (thickness 50 nm) was provided on the SiO ₂ substrate. As the AlNd alloy, an Al-1 at% Nd alloy was used.
Next, a BaSi ₂ layer (thickness 300 nm) was formed on the AlNd electrode layer. The BaSi ₂ layer was formed by sputtering a BaSi ₂ target and then continuously forming a silicon nitride film layer (thickness 3 nm). The sputtering process was performed in a heated atmosphere at 300 ° C. in an Ar atmosphere of 0.2 Pa. A BaSi ₂ target having a purity of 99 wt% was used.
Thereafter, the relationship between the average crystal grain size and the film thickness was controlled by heat treatment under the conditions shown in Table 3.
An upper electrode layer made of GZO was provided on the BaSi ₂ layer. The GZO upper surface electrode layer was formed by sputtering a GZO target.
Moreover, the comparative example 2 changes the upper surface electrode layer of Example 3 into the AZO electrode.
In Example 3, a GZO electrode was provided on half of the upper surface of the BaSi ₂ layer. Example 4 is Ba
A GZO electrode was provided on the entire upper surface of the Si ₂ layer.
By such a method, a photovoltaic power generation module having a Schottky structure was produced. The average crystal grain size of the BaSi ₂ layer was determined for the obtained photovoltaic power generation module. The average crystal grain size was measured by cutting the BaSi ₂ layer in the thickness direction, taking an enlarged photograph of the cross section, and obtaining the average value of 30 grains of the maximum diameter of each crystal grain.

Regarding the photovoltaic power generation modules according to Examples 3 to 4 and Comparative Example 2, the power generation efficiency was obtained.
The method for measuring the power generation efficiency is the same as that in Example 1. The results are shown in Table 4.

As can be seen from the table, the photovoltaic power generation module according to the example had good efficiency. This is G
This is because the ZO electrode hardly reacts with the metal silicide layer. Further, since the average crystal grain size A ≧ film thickness B, the grain boundary trap side is reduced.

(Examples 5-6, Comparative Example 3)
A NiSi ₂ layer (thickness 20 nm) was provided as a bottom electrode layer on the glass substrate. Ni
The Si ₂ layer was formed by alternately sputtering a Ni target and a Si target to form a laminated film in which a large number of Ni / Si layers were alternately laminated. Thereafter, the NiSi ₂ layer was reacted by heat treatment at 500 ° C. for 1 minute in a nitrogen atmosphere. The Ni target and the Si target have a purity of 99.
99% by weight was used.
A NiSi ₂ layer on, n-type beta-FeSi ₂ layer, further provided with a p-type beta-FeSi ₂ layer thereon. The n-type and p-type β-FeSi ₂ layers were formed by alternately sputtering an Fe target and a Si target to form a laminated film in which a large number of Fe films / Si films were alternately laminated. Example 5
In No. 6, the film thickness of the Fe film was alternately laminated in the range of 1 to 3 nm and the film thickness of the Si film was 5 to 10 nm.
In Examples 5 to 6, the atomic ratio was set to Fe: Si = 1: 2.25. Fe
A target and a Si target having a purity of 99.99 wt% were used. Moreover, the sputtering process was performed in a vacuum of 1 × 10 ⁻³ Pa or less. Thereafter, the relationship between the average crystal grain size and the film thickness was controlled by heat treatment under the conditions shown in Table 5. The n-type and p-type were manufactured by impurity doping.
A top electrode layer made of GZO was provided on the β-FeSi ₂ layer. The GZO bottom electrode layer was formed by sputtering a GZO target. Comparative Example 3 is the same as Example 5.
The upper electrode layer is changed to an ITO electrode.
In Example 5, a GZO electrode was provided on the upper half of the β-FeSi ₂ layer. Example 6
A GZO electrode was provided on the entire top surface of the β-FeSi ₂ layer. As a result, a pn junction type polycrystalline β-
A FeSi ₂ photovoltaic module was produced.

Regarding the photovoltaic power generation modules according to Examples 5 to 6 and Comparative Example 3, the power generation efficiency was obtained. The method for measuring the power generation efficiency is the same as that in Example 1. The results are shown in Table 6.

As can be seen from the table, the photovoltaic power generation module according to the example had good efficiency. This is GZ
This is because the reaction of the O electrode with the metal silicide layer is suppressed. Further, the average crystal grain size A
This is because the grain boundary trap side is reduced because of the film thickness B. Thus, it was found that the pn junction type is also effective.

(Examples 7 to 8, Comparative Example 4)
On the SiO ₂ substrate, a LaB ₆ electrode layer (thickness 50 nm) was provided as a bottom electrode layer. Then LaB ₆ electrode layers n-type BaSi ₂ layers on, to form a p-type BaSi ₂ layer thereon. The sputtering process was performed in a heated atmosphere at 300 ° C. in an Ar atmosphere of 0.2 Pa. Ba
A Si ₂ target having a purity of 99 wt% was used.
Thereafter, the relationship between the average crystal grain size and the film thickness was controlled by heat treatment under the conditions shown in Table 7.
An upper electrode layer made of GZO was provided on the BaSi ₂ layer. The GZO upper surface electrode layer was formed by sputtering a GZO target.
In Comparative Example 4, the upper electrode layer of Example 7 is changed to an AZO electrode.
In Example 7, a GZO electrode was provided on half of the upper surface of the BaSi ₂ layer. Example 8 is Ba
A GZO electrode was provided on the entire upper surface of the Si ₂ layer. By such a method, a photovoltaic power generation module having a pn junction type structure was produced.

Regarding the solar power generation modules according to Examples 7 to 8 and Comparative Example 4, the power generation efficiency was obtained. The method for measuring the power generation efficiency is the same as that in Example 1. The results are shown in Table 8.

As can be seen from the table, the photovoltaic power generation module according to the example had good efficiency. This is GZ
This is because the reaction of the O electrode with the metal silicide layer is suppressed. Further, the average crystal grain size A
This is because the grain boundary trap side is reduced because of the film thickness B. Thus, it was found that the pn junction type is also effective.

As mentioned above, although several embodiment of this invention was illustrated, these embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and without departing from the spirit of the invention,
Various omissions, replacements, changes, etc. can be made. These embodiments and their variations are
The invention is included in the scope and gist of the invention, and is included in the invention described in the claims and the equivalent scope thereof. Further, the above-described embodiments can be implemented in combination with each other.

DESCRIPTION OF SYMBOLS 1 ... Solar power generation module 2 which concerns on embodiment ... Polycrystalline metal silicide layer 2-1 ... P-type polycrystalline metal silicide layer 2-2 ... N-type polycrystalline metal silicide layer 2-3 ... Depletion layer 3 ... Top electrode layer 4 ... bottom electrode layer 5 ... substrate

Claims (9)

A photovoltaic power generation module having a polycrystalline metal silicide layer as a power generation layer, wherein a part or all of the electrode layers provided on the upper surface or the lower surface of the polycrystalline metal silicide layer are made of GZO electrodes. module. The photovoltaic power generation module according to claim 1, wherein a GZO electrode layer is provided on at least one of the upper surface and the lower surface of the polycrystalline metal silicide layer. 3. The sun according to claim 1, wherein a relationship between an average crystal grain size A (μm) and a film thickness B (μm) of the polycrystalline metal silicide layer satisfies A ≧ B. Photovoltaic module. The photovoltaic module according to any one of claims 1 to 3, wherein the polycrystalline metal silicide layer has an average crystal grain size A (µm) of 0.01 µm or more. The film thickness B (μm) of the polycrystalline metal silicide layer is 1 μm or less.
The photovoltaic power generation module according to any one of claims 4 to 4. The photovoltaic module according to any one of claims 1 to 5, wherein the metal silicide is one kind of β-iron silicide or barium silicide. The photovoltaic module according to claim 6, wherein the β-iron silicide layer is a β-FeSi ₂ layer. The photovoltaic module according to claim 6, wherein the barium silicide is a BaSi ₂ layer. The photovoltaic power generation module according to any one of claims 1 to 6, wherein the photovoltaic power generation module is a Schottky type.

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