JP6359525B2 - Solar power module - Google Patents

Description

  Embodiments described below generally relate to photovoltaic modules.

  Solar cells that generate power using sunlight are attracting attention as clean electrical energy devices. As a solar cell, a solar cell including a single crystal silicon substrate or a polycrystalline silicon substrate is mainly used because of its excellent power generation efficiency. In order to reduce the cost, the use of a thin-film amorphous silicon solar cell including a thinned silicon substrate has been studied.

  Further, compound semiconductor solar cells using gallium, arsenic, phosphorus, germanium, indium, or the like have been proposed as solar cells other than silicon. The above-mentioned silicon-based solar cells and compound semiconductor-based solar cells have a problem that they cannot be spread as expected because they are expensive due to the large size of the silicon substrate that receives sunlight and the complexity of the compound synthesis process. It was.

Therefore, in recent years, solar cells including a metal silicide layer as a semiconductor layer have been studied. For example, a solar cell having a β-FeSi ₂ layer as a semiconductor layer has been proposed. Metal silicides such as iron silicide can produce both single crystals and polycrystals, and are expected to be lower in cost than silicon solar cells. In addition, metal silicide solar cells are expected as solar cells having higher power generation efficiency than silicon solar cells because they generate power by sensing infrared rays that are not used in silicon solar cells.

  However, metal silicide solar cells are not commercialized at present and are in the research stage. This is because stable power generation efficiency is not obtained. In addition, since the output of the metal silicide solar cell varies depending on the intensity of received light, there is anxiety about the use as a single power source.

JP 2011-198941 A

  The problem to be solved by the present invention is to provide a solar power generation module having a metal silicide layer and having high power generation efficiency. Another object of the present invention is to provide a solar power generation module that enables stable power supply that is resistant to changes in light intensity, that is, changes in the amount of sunlight.

The solar power generation module according to the embodiment includes a polycrystalline metal silicide layer as a power generation layer. The polycrystalline metal silicide layer has a p-type polycrystalline barium silicide layer and an n-type polycrystalline barium silicide layer in contact with the p-type polycrystalline barium silicide layer. The average crystal grain size of the p-type polycrystalline barium silicide layer is equal to or greater than the film thickness of the p-type polycrystalline barium silicide layer. The average crystal grain size of the n-type polycrystalline barium silicide layer is equal to or greater than the film thickness of the n-type polycrystalline barium silicide layer. The average crystal grain size of each of the p-type polycrystalline barium silicide layer and the n-type polycrystalline barium silicide layer is 0.01 μm or more and 3 μm or less.

It is a schematic diagram which shows the structural example of a solar power generation module. It is a schematic diagram which shows the structural example of a polycrystalline metal silicide layer. It is a schematic diagram which shows the structural example of a pn junction type polycrystalline metal silicide layer. It is a schematic diagram which shows the structural example of a Schottky type polycrystalline metal silicide layer. It is a schematic diagram which shows the structural example of a solar power generation module. It is a schematic diagram which shows the structural example of an electrical storage mechanism part. It is a schematic diagram which shows the output characteristic example of a solar power generation module.

  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.

  FIG. 1 is a schematic diagram illustrating a structural example of the photovoltaic power generation module 1 according to the first embodiment. The photovoltaic power generation module 1 includes a polycrystalline metal silicide layer 2 provided on a substrate 5, a surface electrode portion 4 provided on the surface side (sunlight receiving surface side) of the polycrystalline metal silicide layer 2, a polycrystalline And an electrode layer 3 provided on the back side of the metal silicide layer 2 (opposite side of the sunlight receiving surface).

  The polycrystalline metal silicide layer 2 has a function of receiving sunlight and generating electric power. In the photovoltaic power generation module 1, electricity generated by the polycrystalline metal silicide layer 2 using the surface electrode portion 4 and the electrode layer 3 can be taken out to the outside. At this time, the polycrystalline metal silicide layer 2 has a function as a power generation layer.

  The average crystal grain size A (μm) and the film thickness B (μm) of the polycrystalline metal silicide layer 2 satisfy A ≧ B. That is, the average crystal grain size A of the polycrystalline metal silicide layer 2 is not less than the film thickness B of the polycrystalline metal silicide layer 2 (A ≧ B).

  In the polycrystalline metal silicide layer 2, each crystal particle contributes to power generation. The electricity generated by the metal silicide crystal particles is taken out through the surface electrode portion 4 and the electrode layer 3 as described above. That is, electricity flows in the thickness direction of the polycrystalline metal silicide layer 2. When electricity flows through the polycrystalline metal silicide layer 2, the grain boundaries between the metal silicide crystal particles become trap sites. The grain boundary trap site serves as an internal resistance that hinders carrier conduction. For this reason, if there is a grain boundary trap site, it becomes difficult to take out the electricity generated by the polycrystalline metal silicide layer 2, and as a result, the power generation efficiency tends to be lowered.

  In the photovoltaic module 1, the average crystal grain size A of the polycrystalline metal silicide layer 2 is set to be not less than the film thickness B of the polycrystalline metal silicide layer 2 (A ≧ B), so that the thickness direction of the polycrystalline metal silicide layer 2 is increased. In contrast, the number of grain boundaries can be reduced (including zero). At this time, it is most preferable that there is no grain boundary of the metal silicide crystal grains so as to cross the thickness direction of the polycrystalline metal silicide layer 2.

  An example of a method for measuring the average crystal grain size A and the film thickness B of the polycrystalline metal silicide layer 2 will be described. First, an enlarged photograph of an arbitrary cross section in the thickness direction of the polycrystalline metal silicide layer 2 is acquired. The maximum diameter of each individual metal silicide crystal particle in the obtained enlarged photograph is defined as the crystal particle diameter of the crystal particle, and the average crystal grain diameter (maximum diameter) of any 30 metal silicide crystal particles is the average crystal grain diameter. A. Moreover, in the acquired enlarged photograph, the thickness of arbitrary 10 places is measured and the average value of the measured thickness of 10 places is set to the film thickness B. The magnification of the enlarged photograph is such a magnification that the grain boundary between the metal silicide crystal grains can be seen. Further, when not all of the 30 metal silicide crystal particles are included in one photograph (one field of view), a plurality of enlarged photographs are used so that the photograph images are continuous.

  FIG. 2 is a schematic diagram showing a structural example of the polycrystalline metal silicide layer 2. In FIG. 2, the film thickness B of the polycrystalline metal silicide layer 2 is shown. FIG. 2 is a schematic diagram showing a state in which five metal silicide crystal particles are arranged as an example. The shape of the grain boundary between the metal silicide crystal grains is not particularly limited, and may be, for example, linear or curved. The particle diameter of each metal silicide crystal particle is the maximum diameter of each metal silicide crystal particle shown in the enlarged photograph. At this time, the particle diameters of the metal silicide crystal particles shown in FIG. 2 are a particle diameter A1, a particle diameter A2, a particle diameter A3, a particle diameter A4, and a particle diameter A5, respectively.

  The average crystal grain size A of the polycrystalline metal silicide layer 2 is preferably 0.01 μm or more (10 nm or more). When the average crystal grain size A is less than 10 nm, it is difficult to control the average crystal grain size A and the film thickness B of the polycrystalline metal silicide layer 2 so that the crystal grain size is too small and A ≧ B. There is. The upper limit of the average crystal grain size A is not particularly limited, but is preferably 3 μm or less, for example. If the average crystal grain size A exceeds 3 μm, it may be difficult to produce a uniform crystal. Furthermore, the average crystal grain size A is more preferably 0.05 to 1.2 μm (50 to 1200 nm).

  The film thickness B of the polycrystalline metal silicide layer 2 is preferably 1 μm or less. When the film thickness B exceeds 1 μm, it may be difficult to produce a homogeneous crystal. Moreover, even if it is a case exceeding 1 micrometer, there exists a possibility that electric power generation efficiency may not improve.

  The metal silicide contained in the polycrystalline metal silicide layer 2 is preferably at least one selected from the group consisting of, for example, β-iron silicide, barium silicide, magnesium silicide, chromium silicide, and rhenium silicide.

The β-iron silicide is preferably β-FeSi ₂ . 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 FeSi ₂ , it can be used as iron silicide even if it is slightly deviated (the range in which the atomic ratio of Fe and Si is 1: 2 by rounding off the first digit of the decimal point).

  When β-iron silicide is used, the solar power generation module 1 includes, for example, a p-type β-iron silicide layer and an n-type β-iron silicide layer provided so as to be in contact with the p-type β-iron silicide layer. A pn junction structure, a Schottky structure, a MIS (Metal Insulator Semiconductor) structure, or a MOS (Metal Oxide Semiconductor) structure may be used. When comparing the pn junction type structure and the Schottky type structure, the Schottky type structure is preferable. With a Schottky structure, it is not necessary to use two types of metal silicides, p-type and n-type, unlike the pn junction structure, so that the cost can be reduced. If necessary, the polycrystalline metal silicide layer 2 may be doped with impurities.

The carrier density of p-type β-FeSi ₂ is preferably 1 × 10 ¹⁴ to 1 × 10 ²¹ cm ⁻³ , and the carrier density of n-type β-FeSi ₂ is 1 × 10 ¹⁴ to 1 × 10 ²¹ cm ^−3. It is preferable that The carrier density of the Schottky β-FeSi ₂ is preferably 1 × 10 ¹⁴ to 1 × 10 ¹⁸ cm ⁻³ . Furthermore, the carrier density is more preferably 1 × 10 ¹⁶ cm ⁻³ or less for any β-FeSi ₂ . By reducing the carrier density, the power generation efficiency is improved. 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 a numerical value smaller than 1 × 10 ¹⁶ cm ⁻³ , such as a multiplier of 1 × 10 ¹⁶ cm ⁻³ or 1 × 10 ¹⁴ cm ^−3. Show.

Barium silicide is preferably a BaSi _2. In addition to BaSi ₂ , examples of barium silicide include BaSi, and BaSi ₂ has the highest power generation efficiency. If the stoichiometry approximates to BaSi ₂ , it can be used as barium silicide even if the composition ratio is slightly deviated. When barium silicide is used, the photovoltaic module 1 includes a pn junction structure, a Schottky structure, a MIS structure, or a p-type barium silicide layer and an n-type barium silicide layer in contact with the p-type barium silicide layer. It may have a MOS type structure. If necessary, the polycrystalline metal silicide layer 2 may be doped with impurities.

Preferably the carrier density of the p-type BaSi ₂ is ^{1 × 10 14 ~1 × 10 21} cm -3, that the carrier density of the n-type BaSi ₂ is ^{1 × 10 14 ~1 × 10 21} cm -3 preferable. The carrier density of Schottky BaSi ₂ is preferably 1 × 10 ¹⁴ to 1 × 10 ¹⁸ cm ⁻³ . Furthermore, the carrier density is more preferably 1 × 10 ¹⁷ cm ⁻³ or less for any BaSi ₂ . By reducing the carrier density, the power generation efficiency is improved. The improvement in power generation efficiency indicates that the carrier density is 1 × 10 ¹⁷ cm ⁻³ or less. Note that the carrier density of 1 × ¹⁰ 17 ^{cm -3,} a number lower than 1 × ¹⁰ 17 ^{cm -3} as a multiplier of 1 × ¹⁰ 17 ^{cm -3} and equal to or 1 × ¹⁰ 15 ^{cm -3} Show.

Since β-FeSi ₂ has a band gap Eg of about 0.85 eV and is a direct transition type, β-FeSi ₂ has high absorption efficiency with respect to light having a wavelength of 1500 nm or less. BaSi ₂ has a band gap Eg of about 1.4 eV and is an indirect transition type, and therefore has high absorption efficiency for wavelengths of 950 nm and below. By using β-FeSi ₂ or BaSi ₂ for the polycrystalline metal silicide layer 2, infrared light having a wavelength of 1500 nm or less or 950 nm or less can be used for power generation, and power generation can be performed for a long time even in units of one day. . Moreover, since the absorption coefficient of β-FeSi ₂ and BaSi ₂ is as high as 100 to 1000 times that of Si, the film thickness of the polycrystalline metal silicide layer 2 containing β-FeSi ₂ and BaSi ₂ is set to the same power generation efficiency. It can also be made as thin as about 1/100 to 1/1000 of the Si solar cell layer.

The structure of the photovoltaic module 1 includes a first polycrystalline metal silicide layer having a β-FeSi ₂ layer and a second polycrystalline metal having a BaSi ₂ layer provided on the first polycrystalline metal silicide layer. A tandem structure including a silicide layer may be used. The BaSi ₂ layer has high absorption efficiency at a wavelength of 950 nm or less. In other words, light exceeding the wavelength of 950 nm is likely to be transmitted. On the other hand, since the β-FeSi ₂ layer has high absorption efficiency at a wavelength of 1500 nm or less, the light transmitted through the BaSi ₂ layer can be used for power generation by using the β-FeSi ₂ layer. In the case of a tandem structure, it is preferable to use a light-transmitting electrode layer as the back electrode of the second polycrystalline metal silicide layer.

The magnesium silicide is preferably Mg ₂ Si, the chromium silicide is preferably CrSi ₂ , and the rhenium silicide is preferably ReSi ₂ . In addition, even if it is a material whose atomic ratio deviates from BaSi ₂ , Mg ₂ Si, CrSi ₂ , or ReSi ₂ , if the atomic ratio falls within this range by rounding off the first decimal place, it should be used as each metal silicide. Can do. Even when Mg ₂ Si, CrSi ₂ , or ReSi ₂ is used as the metal silicide, the carrier density is preferably 1 × 10 ¹⁷ cm ⁻³ or less as in the case of BaSi ₂ .

  FIG. 3 is a schematic diagram showing a structural example of a photovoltaic power generation module having a pn junction structure. The photovoltaic power generation module shown in FIG. 3 includes a polycrystalline metal silicide layer 2, a surface electrode portion 4 provided on the surface side (sunlight receiving surface side) of the polycrystalline metal silicide layer 2, and the polycrystalline metal silicide layer 2. Electrode layer 3 provided on the back surface side (opposite side of the sunlight receiving surface). Furthermore, the polycrystalline metal silicide layer 2 includes a p-type polycrystalline metal silicide layer 2a provided on the surface electrode portion 4 side, and an n-type polycrystalline metal silicide layer 2b provided on the electrode layer 3 (back surface electrode) side. It comprises. The arrangement of the p-type polycrystalline metal silicide layer 2a and the n-type polycrystalline metal silicide layer 2b may be reversed. As shown in FIG. 3, when an electric charge is applied to a photovoltaic power generation module having a pn junction structure, a depletion layer 2c is formed between the p-type polycrystalline metal silicide layer 2a and the n-type polycrystalline metal silicide layer 2b. Due to the presence of the depletion layer 2 c, the polycrystalline metal silicide layer 2 becomes an electric double layer, and electricity can be extracted from the polycrystalline metal silicide layer 2. The electrode layer 3 may be formed on the substrate 5 as in FIG.

  FIG. 4 is a schematic diagram showing a structural example of a photovoltaic power generation module having a Schottky structure. The photovoltaic power generation module shown in FIG. 4 includes a polycrystalline metal silicide layer 2, a surface electrode portion 4 provided on the surface side (sunlight receiving surface side) of the polycrystalline metal silicide layer 2, and the polycrystalline metal silicide layer 2. Electrode layer 3 provided on the back surface side (opposite side of the sunlight receiving surface). At this time, the polycrystalline metal silicide layer 2 may be either the p-type polycrystalline metal silicide layer 2a or the n-type polycrystalline metal silicide layer 2b. In general, a Schottky structure is a junction structure that exhibits a rectifying action between a metal and a semiconductor. The depletion layer is formed by contact between a metal and a semiconductor. In the case of the photovoltaic module having the Schottky structure shown in FIG. 4, the metal is the surface electrode portion 4 or the electrode layer 3. The semiconductor is p-type polycrystalline metal silicide layer 2a or n-type polycrystalline metal silicide layer 2b. The electrode layer 3 may be formed on the substrate 5 as in FIG.

  The pn junction structure is a structure in which current is mainly flowed using minority carriers, whereas the Schottky structure is a structure in which current is mainly flowed using majority carriers. For this reason, the solar power generation module in which the Schottky structure is superior in high-speed operability can be manufactured.

  As an example of a method for producing the p-type polycrystalline metal silicide layer 2a, a method of adding at least one element selected from Group 13 of the periodic table to the polycrystalline metal silicide layer can be used. Examples of the elements belonging to Group 13 of the periodic table include B (boron), Al (aluminum), Ga (gallium), In (indium), and Tl (thallium). As an example of a method for producing the n-type polycrystalline metal silicide layer 2b, a method of adding at least one element selected from Group 15 of the periodic table to the polycrystalline metal silicide layer can be used. Examples of the elements belonging to Group 15 of the periodic table include N (nitrogen), P (phosphorus), As (arsenic), Sb (antimony), Bi (bismuth), and the like. The p-type polycrystalline metal silicide layer 2a and the n-type polycrystalline metal silicide layer 2b can also be produced by controlling the composition of the polycrystalline metal silicide layer.

  The surface electrode portion 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 ITO (Indium Tin Oxide: ITO), ATO (Antimony Tin Oxide: ATO), and AZO (Aluminum Zinc Oxide: AZO). One or more surface electrode portions 4 may be formed on the polycrystalline metal silicide layer 2. An antireflection film or a glass substrate may be provided on the surface electrode portion 4 and the polycrystalline metal silicide layer 2.

After forming a nitride film on the polycrystalline metal silicide layer 2, a transparent electrode may be formed thereon. The nitride film functions as a protective film that prevents oxidation and moisture absorption of the polycrystalline metal silicide layer 2. A silicon nitride film is preferably used as the nitride film. As the silicon nitride film, it is preferable to use a nitride film of one material selected from SiN _x , SiN _x O _y , SiN _x O _y H _z , and SiN _x H _z . In this case, x, y and z are atomic ratios when the atomic weight of Si is 1, x is a number satisfying 0 <x ≦ 2.0, y is a number satisfying 0 ≦ y ≦ 1.0, z Is preferably a number satisfying 0 ≦ z ≦ 0.1.

  The thickness of the nitride film is preferably 10 nm or less, more preferably 5 nm or less. Nitride films are often insulative (low conductivity), and if the film thickness exceeds 10 nm, electricity may not flow. By using a thin film of 10 nm or less, and further 5 nm or less, the tunnel effect is obtained, so there is no influence on conduction. If the nitride film functions as a protective film, the thickness of the nitride film is not particularly limited, but is preferably 2 nm or more, for example.

Examples of methods for forming the nitride film include film formation methods such as sputtering, chemical vapor deposition (CVD), and direct nitridation (a method for nitriding metal silicide). Further, when each film forming method is used, a nitride film of SiN _x O _y , SiN _x O _y H _z , or SiN _x H _z can be formed by including oxygen or hydrogen in the atmosphere during film formation. .

The electrode layer 3 may be any material having conductivity, and examples of materials applicable to the electrode layer 3 include metal materials (including alloys) such as Pt, Ag, Al, and Cu, and conductivity such as LaB ₆ and TiN. Examples thereof include metal silicides such as nitride, nickel silicide (NiSi ₂ ), and cobalt silicide (CoSi). The thickness of the electrode layer 3 is arbitrary, but is preferably 10 nm or more. When β-FeSi ₂ is used as the polycrystalline metal silicide layer 2, NiSi ₂ is preferably used as the electrode layer 3. NiSi ₂ is an electrode material that also functions as a template for controlling the crystal orientation of β-FeSi ₂ .

  When an alloy is used as the electrode layer 3, an alloy applicable to the electrode layer 3 is an Al alloy. Examples of the Al alloy include an Al-rare earth alloy such as an AlNd alloy. The rare earth element content in the Al-rare earth alloy is preferably 10 atomic% or less. An insulating layer may be partially provided between the polycrystalline metal silicide layer 2 and the electrode layer 3 as necessary.

The electrode layer 3 is preferably a material having heat resistance. This is because, as will be described later, it is preferable to perform heat treatment when the polycrystalline metal silicide layer 2 is formed. Examples of the material having heat resistance include NiSi ₂ , AlNd alloy, LaB ₆ , and TiN. The yield in forming the electrode layer 3 is improved by using an electrode material having heat resistance.

  When determining the material of the electrode layer 3, it is preferable to match the work function of the polycrystalline metal silicide layer 2. Specifically, the work function of the electrode in contact with the p-type polycrystalline metal silicide layer 2a is preferably lower than the work function of the p-type polycrystalline metal silicide layer 2a. The work function of the electrode in contact with n-type polycrystalline metal silicide layer 2b is preferably higher than the work function of n-type polycrystalline metal silicide layer 2b. By performing such matching, rectification characteristics can be imparted between the polycrystalline metal silicide layer 2 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.

For example, when the p-type polycrystalline metal silicide layer 2a is a p-type BaSi ₂ layer, it is preferable to select an electrode material based on the work function 4.7, and the n-type polycrystalline metal silicide layer 2b is an n-type BaSi ₂ layer. If the p-type polycrystalline metal silicide layer 2a is a p-type β-FeSi ₂ layer, it is preferable to select the electrode material based on the work function 3.3. The electrode material is preferably selected. When the n-type polycrystalline metal silicide layer 2b is an n-type β-FeSi ₂ layer, the electrode material is preferably selected based on the work function 4.8. The unit of work function is eV.

  As the substrate 5, a glass substrate, an insulating ceramic substrate, a metal substrate, or the like can be used. In the case of a metal substrate, it may have an insulating surface made of an insulating layer.

  In the solar power generation module in the first embodiment, power generation efficiency can be improved. Here, the manufacturing method of a 1st photovoltaic power generation module is demonstrated. Although the manufacturing method of the solar power generation module of this embodiment will not be specifically limited if it has the said structure, The following method is mentioned as a method for obtaining a solar power generation module efficiently.

  First, the substrate 5 is prepared. At this time, the surface of the substrate 5 is cleaned as necessary. If washed, perform the drying process sufficiently. Next, the electrode layer 3 is formed. For example, the electrode layer 3 can be formed by a film forming method such as sputtering using a material applicable to the electrode layer 3.

For example, when a metal silicide such as NiSi ₂ is used for the electrode layer 3, sputtering using a NiSi ₂ target, sputtering using both a Ni target and a Si target, and the like can be applied. In the case of sputtering using both the Ni target and the Si target, either sputtering using the Ni target and the Si target at the same time or sputtering using them alternately may be used. At this time, a heat treatment is performed after sputtering to react the film formed by the sputtering to form a NiSi ₂ layer.

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 may be distorted. The purity of NiSi ₂ formed is preferably 99.9% by mass or more, and more preferably 99.999% by mass or more.

The NiSi ₂ layer may be either a polycrystalline film or a single crystal film. In the case of a polycrystalline film, the NiSi ₂ layer preferably has a large average crystal grain size. By increasing the average crystal grain size of the underlying layer such as the NiSi ₂ 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 electrode layer 3 as necessary. Examples of the patterning process include a method in which a resist or a mask material is disposed at a place where a pattern (wiring) is desired to be left and an etching process is performed.

  Next, a polycrystalline metal silicide layer 2 is formed. For example, the polycrystalline metal silicide layer 2 can be formed using a film forming method such as sputtering. The thickness of the polycrystalline metal silicide layer 2 is preferably 0.01 μm (10 nm) or more.

When forming a beta-FeSi ₂ layer as a polycrystalline metal silicide layer 2, FeSi ₂ method of performing sputtering using a target, β-FeSi ₂ layer by using a method of performing sputtering using both Fe target and a Si target Can be formed. In the case of sputtering using both the Fe target and the Si target, either sputtering using the Fe target and the Si target at the same time or sputtering using them alternately may be used. At this time, FeSi ₂ is formed by reacting the film formed by sputtering after heat treatment.

  The heat treatment conditions are preferably 300 to 900 ° C. and 30 seconds to 1 hour in an inert atmosphere or a reducing atmosphere. Examples of the inert atmosphere include a nitrogen gas atmosphere and an argon gas atmosphere. Examples of the reducing atmosphere include a nitrogen gas atmosphere containing hydrogen. 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 electrode layer 3, the heat treatment temperature can be set to 500 ° C. or less. This is because the metal silicide serves as a template for forming the β-FeSi ₂ layer. In addition, it is desirable that the heat treatment temperature for forming the β-FeSi ₂ layer be 500 ° C. or lower because damage to the substrate, particularly the glass substrate can be reduced. Further, the average crystal grain size A of the β-FeSi ₂ layer can be controlled by heat treatment after sputtering.

In order to obtain a homogeneous β-FeSi ₂ layer, it is preferable to perform heat treatment after performing sputtering using an Fe target and an Si target alternately. The Fe film is in the range of 0.5 to 5 nm, the Si film is in the range of 1 to 10 nm, the Fe film and the Si film are formed while being alternately stacked until the desired film thickness is obtained, and heat treatment is performed. By the heat treatment, the Fe film and the Si film react to form a 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 Fe: Si = 1: 2.0 to 2.5. It is preferable that 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.

The resistivity of the homogeneous β-FeSi ₂ layer formed by the above process is 4 × 10 ⁴ Ωcm or more. In particular, the resistivity of the β-FeSi ₂ layer can be set to 1 × 10 ⁵ Ωcm or more by setting the atomic ratio of Fe and Si to the range of Fe: Si = 1: 2.1 to 2.4. A high sheet resistance value indicates that there are few portions of Fe simple substance or Si simple substance having a low resistance value, and a homogeneous β-FeSi ₂ layer is obtained.

The purity of the sputtering target to be used is 99.9% by mass or more, regardless of the method of sputtering using an FeSi ₂ target or the method of sputtering using both an Fe target and an Si target. Preferably has a high purity of 99.999% by mass or more.

Sputtering is preferably performed in a vacuum atmosphere or an inert atmosphere. By performing sputtering in a vacuum atmosphere or an inert atmosphere, contamination of impurities during sputtering can be prevented. The vacuum atmosphere is preferably a vacuum atmosphere of 1 × 10 ⁻³ Pa or less, and the inert atmosphere is preferably an argon gas atmosphere. Moreover, it is good also as a heating atmosphere during sputtering.

The sheet resistance value is measured on the β-FeSi ₂ layer surface by the four-probe method. Whether or not a homogeneous β-FeSi ₂ layer is formed can also be confirmed by X-ray diffraction (XRD) analysis. When XRD analysis (2θ) was performed on the obtained β-FeSi ₂ layer, the peak of (202) / (220) plane of β-FeSi ₂ and (004) / (040 The peak of the (422) plane and the peak of the (133) plane are detected between 42 and 58 °. In addition, it is preferable that the peak of (202) / (220) plane becomes the strongest peak. Moreover, if it is homogeneous β-FeSi ₂ , the peak of simple Fe or simple Si is not detected when XRD analysis is performed.

The homogeneous β-FeSi ₂ layer obtained by the heat treatment has an absorption edge at 6300 to 6500 cm ⁻¹ as infrared absorption characteristics. In addition, a β-FeSi ₂ layer formed by alternately forming an Fe film and a Si film by sputtering and reacting the Fe film and the Si film by heat treatment has a high temperature dependence of the sheet resistance.

When the temperature dependence of the sheet resistance in the β-FeSi ₂ layer is represented by an Arrhenius plot (Arrhenios Plot), when “resistivity is 8 × 10 ⁴ Ωcm, Ea = 0.142 eV” at 298 K (25 ° C.), At 200K (−73 ° C.), “resistivity is 3.6 × 10 ⁵ Ωcm, Ea = 0.123 eV”, and at 90K (−183 ° C.), “resistivity is 3.6 × 10 ⁶ Ωcm, Ea = 0. 0926 eV ”, and“ resistivity is 2 × 10 ⁷ Ωcm, Ea = 0.0395 eV ”at 50 K (−223 ° C.). The fact that excellent resistivity is exhibited even in a low temperature region as described above indicates that the carrier density is 1 × 10 ¹⁸ cm ⁻³ or less.

For this reason, a uniform β-FeSi ₂ layer can be obtained by alternately stacking Fe films and Si films and generating a β-FeSi ₂ layer by heat treatment. Further, by adjusting the heat treatment conditions, the average crystal grain size A of the polycrystalline metal silicide layer 2 can be set to a film thickness B or more (A ≧ B).

In the case of forming a BaSi ₂ layer as the polycrystalline metal silicide layer 2, a method of forming the BaSi ₂ layer by performing sputtering using a barium silicide target can be mentioned. Examples of the barium silicide target include a BaSi ₂ target _{and a} BaSi target. 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.

Sputtering is preferably performed in a vacuum atmosphere or an inert atmosphere. By performing sputtering in a vacuum atmosphere or an inert atmosphere, a BaSi ₂ layer can be formed while suppressing oxidation. The vacuum atmosphere is preferably a vacuum atmosphere of 1 × 10 ⁻³ Pa or less. The inert atmosphere is preferably an inert atmosphere such as nitrogen or argon. Note that a heating atmosphere may be used during the sputtering process.

In the sputtering step, heat treatment may be performed after forming a BaSi ₂ layer using a BaSi ₂ target. Also, in the sputtering process, a sputtering target in which the composition ratio of Ba and Si is changed, such as a BaSi ₂ target and a BaSi target, is prepared, and sputtering is performed alternately to form a laminated film of an Si film and an Fe film, and sputtering is performed. Thereafter, a BaSi ₂ layer may be formed by reacting the Si film and the Fe film by heat treatment.

The heat treatment conditions are preferably 300 to 900 ° C. and 30 seconds to 1 hour in a vacuum atmosphere, an inert atmosphere or a reducing atmosphere. 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 atmosphere, it is preferable that a vacuum atmosphere is 1 * 10 < ^-3 > Pa or less. The inert atmosphere is preferably a nitrogen atmosphere, an argon atmosphere, or the like. The reducing atmosphere is preferably a nitrogen atmosphere containing hydrogen.

When metal silicide (NiSi ₂ or CoSi) is used as the electrode layer 3, the heat treatment temperature can be set to 500 ° C. or less. 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 lower because damage to the substrate 5, particularly the glass substrate can be reduced. The average crystal grain size A 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 electrode layer 3 may be either a polycrystal or a single crystal. In the case of a polycrystal, it is desirable that the average crystal grain size be as large as possible. When the polycrystalline metal silicide layer 2 is provided on the electrode layer 3 having a large average crystal grain size, the average crystal grain size A (μm) and the film thickness B (μm) of the polycrystalline metal silicide layer 2 easily satisfy A ≧ B. Become. When metal silicide is used as the electrode layer 3, a multilayer electrode structure in which the electrode layer 3 is a base layer and a metal electrode or the like is provided thereunder may be employed.

  When the patterning process of the electrode layer 3 is performed as described above, it is performed after a resist or a mask material is disposed in a place where the 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, the polycrystalline metal silicide layer 2 can be formed by combining sputtering and heat treatment. In order for the average crystal grain size A (μm) and the film thickness B (μm) of the polycrystalline metal silicide layer 2 to satisfy A ≧ B, the polycrystalline metal silicide layer 2 is subjected to heat treatment to grow grains. It is valid. This heat treatment is preferably performed at 300 to 900 ° C. for 30 seconds to 1 hour. Note that the heat treatment may be performed together with the heat treatment after performing sputtering using the Fe target and the Si target simultaneously or sputtering using the target alternately. Note that with the Schottky structure, since the heat treatment temperature can be set to 500 ° C. or lower, damage to the substrate 5 can be reduced.

  Next, the process of providing the surface electrode part 4 is performed. When a transparent electrode such as ITO or ATO is used as the surface electrode portion 4, an ITO film or ATO film is formed by sputtering using an ITO target or an ATO target. Thereafter, as shown in FIG. 1, when the surface electrode portion 4 is partially provided on the polycrystalline metal silicide layer 2, sputtering may be performed by placing a resist or a mask material. After forming the surface electrode part 4, if necessary, an antireflection film may be formed on the surface electrode part 4, or the surface electrode part 4 and a transparent substrate such as a glass substrate may be bonded together. Further, the surface electrode portion 4 may be bonded to a transparent substrate provided in advance.

  Next, the photovoltaic power generation module (second photovoltaic power generation module) according to the second embodiment will be described. FIG. 5 is a schematic diagram showing a structural example of the second photovoltaic power generation module. The solar power generation module 6 shown in FIG. 5 includes the substrate 5 of the solar power generation module according to the first embodiment, and a power storage mechanism unit 11 provided on the back side thereof. Moreover, the solar power generation module 6 includes the polycrystalline metal silicide layer 2, the electrode layer 3, and the surface electrode portion 4 provided on the surface side of the substrate 5 as in the solar power generation module in the first embodiment. In addition, about the same component as the solar power generation module which concerns on 1st Embodiment, description of the solar power generation module which concerns on 1st Embodiment can be used suitably.

  The power storage mechanism 11 has a function of storing part or all of the power supplied from the polycrystalline metal silicide layer 2. The power storage mechanism unit 11 is connected to the surface electrode unit 4 and the electrode layer 3 by wiring (not shown) or the like. FIG. 6 is a schematic diagram showing a structural example of the power storage mechanism unit 11. The power storage mechanism unit 11 illustrated in FIG. 6 includes an electrode unit 12 (corresponding to an example of a first electrode unit), an electrode unit 13 (corresponding to an example of a second electrode unit), a sealing unit 14, and a power storage unit 15. , An electrolytic solution 16, a protection unit 17, and a reduction unit 18. In addition, the outer periphery of the electrical storage mechanism part 11 is covered with the insulating member (not shown).

The electrode portion 12 has a plate shape and is formed using a conductive material. The electrode part 12 contains metals, such as aluminum, copper, stainless steel, platinum, for example. The electrode portion 13 has a plate shape and is provided to face the electrode portion 12. The electrode portion 13 is formed using a conductive material. The electrode part 13 contains metals, such as aluminum, copper, stainless steel, platinum, for example. In addition, the electrode part 12 and the electrode part 13 can also be formed using the same material, and the electrode part 12 and the electrode part 13 can also be formed using different materials. Further, as the electrode portion 12 and the electrode portion 13, for example ITO, IZO (Indium Zinc Oxide) , FTO (Fluorine Tin Oxide), may be a material made of SnO 2, InO _3.

  The electrode part 12 and the electrode part 13 are provided on a substrate (not shown). Examples of the substrate include a glass substrate and an insulated metal substrate. As the substrate, the above-described substrate 5 may be used. That is, the structure of the solar power generation module 6 may be a structure including the power storage mechanism unit 11 arranged directly on the substrate 5.

  The electrode unit 13 provided on the power storage unit 15 side serves as a negative electrode. Moreover, the electrode part 12 which opposes the electrode part 13 turns into a positive electrode. The sealing part 14 is provided between the electrode part 12 and the electrode part 13 and seals the peripheral part of the electrode part 12 and the peripheral part of the electrode part 13. That is, the sealing unit 14 is provided so as to surround the inside of the power storage mechanism unit 11 along the periphery of the electrode unit 12 and the electrode unit 13, and the power storage mechanism is formed by joining the electrode unit 12 side and the electrode unit 13 side. The inside of the part 11 is sealed. Further, the thickness of the sealing portion 14 is not particularly limited, but is preferably in the range of 1.5 to 30 times the thickness of the power storage portion 15. Since the thickness of the sealing part 14 becomes a space for filling the electrolyte solution 16, the sealing part 14 should have a thickness within a predetermined range. If it is less than 1.5 times, the electricity stored in the electricity storage unit 15 is likely to be released, and if it exceeds 30 times, it is difficult to take out the electricity stored in the electricity storage unit 15.

  The sealing part 14 seals between the electrode part 12 and the electrode part 13. The sealing unit 14 may include a glass material. The sealing portion 14 can be formed using, for example, a glass frit that is made into a paste by mixing powder glass, a binder such as an acrylic resin, an organic solvent, or the like. Examples of the powder glass material include vanadate glass and bismuth oxide glass. In this case, the glass frit in the form of paste can be applied to the portion to be sealed and baked to form the sealing portion 14. Then, by heating the sealing part 14, the sealing part 14 can be melted and the power storage mechanism part 11 can be sealed. For example, the power storage mechanism 11 can be sealed by irradiating the formed sealing portion 14 with laser light and melting the portion of the sealing portion 14 irradiated with the laser light. In addition, the material applicable to the sealing part 14 is not limited to a glass material. For example, the sealing part 14 may contain a resin material. For example, the power storage mechanism unit 11 may have a structure in which the sealing unit 14 includes a resin material and is bonded to the electrode unit 12 and the electrode unit 13.

The power storage unit 15 is provided inside the sealing unit 14 and on the surface of the electrode unit 13 facing the electrode unit 12. The power storage unit 15 is provided on the electrode unit 13 via the protection unit 17. The power storage unit 15 is formed of a material having a power storage property. The power storage unit 15 includes, for example, WO ₃ (tungsten oxide). The power storage unit 15 may have a porous structure. The porosity of the porous structure is preferably in the range of 20 to 80% by volume. As tungsten oxide, it is preferable to use tungsten oxide particles having an average particle diameter of 1 to 1000 nm, more preferably 1 to 100 nm. In addition, a metal film, a metal oxide film, or the like may be provided on the surface of the tungsten oxide particles in order to improve power storage performance.

If the power storage unit 15 has a porous structure, the contact area with the electrolytic solution 16 can be increased. Therefore, the power storage with respect to the power storage unit 15 can be facilitated. The thickness of the power storage unit 15 can be about 30 μm, for example. Alternatively, the power storage unit 15 may be formed by laminating WO ₃ particles having a diameter of about 20 nm to a thickness of about 30 μm. Moreover, the thickness of the electrical storage part 15 will not be specifically limited if it can have an electrical storage function, However, 1 micrometer or more, Furthermore, 1 micrometer-100 micrometers are preferable.

  The electrolytic solution 16 is provided inside the sealing portion 14. That is, the electrolytic solution 16 is filled in a space surrounded by the electrode part 12, the electrode part 13, and the sealing part 14. As the electrolytic solution 16, for example, an electrolytic solution containing iodine can be used. Moreover, as the electrolytic solution 16, for example, an electrolytic solution in which lithium iodide and iodine are dissolved in a solvent such as acetonitrile can be used. The concentration of lithium iodide is preferably in the range of 0.5 to 5 mol / L, and the concentration of iodine is preferably in the range of 0.01 to 5 mol / L.

  The protection unit 17 has a film shape and is provided between the power storage unit 15 and the electrode unit 13. The protection part 17 is provided so as to cover the surface of the electrode part 13 defined by the sealing part 14. The protection part 17 is provided to prevent the electrode part 13 from being corroded by the electrolytic solution 16. The protection part 17 is formed using a material having conductivity and chemical resistance against the electrolytic solution 16. The protection unit 17 includes, for example, carbon or platinum. The thickness of the protection part 17 is preferably about 100 nm, for example. In addition, when forming the electrode part 13 using the material which has chemical resistance with respect to the electrolyte solution 16, the protection part 17 does not necessarily need to be provided.

The reducing part 18 has a film shape and is provided so as to cover the surface of the electrode part 12 defined by the sealing part 14. The reducing unit 18 is provided to reduce ions contained in the electrolytic solution 16. For example, the reducing unit 18 reduces I ₃ ⁻ ions (triiodide ions) contained in the electrolytic solution 16 to I ⁻ ions (iodide ions). Therefore, the reducing portion 18 is formed using a material that takes into consideration conductivity, chemical resistance to the electrolytic solution 16, and reduction of ions contained in the electrolytic solution 16. The reducing unit 18 includes, for example, carbon or platinum. The thickness of the reducing unit 18 is preferably about 80 nm, for example.

With such a power storage mechanism unit 11, part or all of the power generated by the polycrystalline metal silicide layer 2 can be stored efficiently. Moreover, such a power storage mechanism 11 a storage capacity 1000 C-/ ^{m 2} or more, further it is also possible to 10000C / ^{m 2} or more.

  Next, output characteristics of the solar power generation module (solar power generation module 6) in the second embodiment will be described. FIG. 7 is a schematic diagram showing output characteristics of the photovoltaic power generation module according to the second embodiment.

  In FIG. 7, the vertical axis represents the voltage of power supplied by the solar power generation module 6, and the horizontal axis represents time. The photovoltaic power generation module 6 is exposed to sunlight and supplies a constant voltage. When the amount of sunshine decreases due to changes in the weather, etc., the power generated by the polycrystalline metal silicide layer 2 decreases. At this time, when the voltage drops to a certain voltage (ΔV1), electric power is supplied from the power storage mechanism 11. Electric power is supplied according to the electric power (electric storage capacity) stored in the electric storage mechanism 11. Switching to a commercial power source or the like may be performed until the voltage from the power storage mechanism unit 11 drops to a constant voltage (ΔV2). Thus, unlike the case where power is generated by a solar cell alone, it is possible to improve the problem that the power supply becomes unstable as the amount of sunlight changes.

Moreover, the power generation of the polycrystalline metal silicide layer 2 can be stabilized by increasing the power storage capacity of the power storage mechanism 11 to 1000 C / m ² or more. For example, when the power generation efficiency target of the polycrystalline metal silicide layer 2 is set to 5%, the power generation can be stabilized by supplying electric power less than 5% from the power storage mechanism unit 11.

(Examples 1 and 2 and Comparative Example 1)
A NiSi ₂ layer (thickness 20 nm) was provided on a glass substrate. In forming the NiSi ₂ layer, sputtering was performed by alternately using the Ni target and the Si target, and a plurality of Ni films / Si films were alternately stacked to form a stacked film. Thereafter, heat treatment was performed in a nitrogen atmosphere at 500 ° C. for 1 minute to form a NiSi ₂ layer. The purity of the Ni target or Si target was 99.9% by mass.

Next, a β-FeSi ₂ layer (thickness 300 nm) was formed on the NiSi ₂ layer. In the formation of the β-FeSi ₂ layer, sputtering was performed by alternately using the Fe target and the Si target, and the Fe film and the Si film were alternately stacked a plurality of times. In Example 1, Example 2, and Comparative Example 1, the film thickness of the Fe film was set to 1 to 3 nm, and the film thickness of the Si film was set to the range of 5 to 10 nm. In Example 1, the atomic ratio of Fe and Si was set to Fe: Si = 1: 2.1, and in Example 2 and Comparative Example 1, Fe: Si = 1: 2.3. The purity of the Fe target and the Si target was 99.9% by mass. Thereafter, heat treatment was performed under the conditions shown in Table 1 to react the Fe film and the Si film to obtain a β-FeSi ₂ layer. Next, a surface electrode portion made of ITO was provided on the β-FeSi ₂ layer. In forming the ITO surface electrode portion, the ITO target was sputtered to form an ITO film.

A photovoltaic power generation module having a Schottky structure was produced by the above method. The average crystal grain size A and film thickness B of the β-FeSi ₂ layer were determined for the obtained solar power generation module. The measuring method of the average crystal grain size A and the film thickness B in the examples is as shown in the above embodiment. Further, as a result of XRD analysis to beta-FeSi ₂ layer, only detected peaks of beta-FeSi ₂ crystals, Fe alone and Si single peak was detected.

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

  As can be seen from Table 2, the power generation efficiency of the solar power generation modules according to Example 1 and Example 2 was higher than the power generation efficiency of the solar power generation module according to Comparative Example 1. This is because in Example 1 and Example 2, the average grain size A ≧ film thickness B, so that the grain boundary trap side was reduced.

(Examples 3 and 4 and 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 atomic% Nd alloy was used. Next, a BaSi ₂ layer (thickness 300 nm) was formed on the AlNd alloy electrode layer. In the formation of the BaSi ₂ layer, sputtering was performed using a BaSi ₂ target, and then a silicon nitride layer (thickness 3 nm) was continuously formed. In addition, the sputtering process was performed in a 300 degreeC heating atmosphere in the vacuum of 1 * 10 < ^-3 > Pa or less. Moreover, the purity of the BaSi ₂ target was 99.99% by mass. Thereafter, heat treatment was performed under the conditions shown in Table 3. Next, a surface electrode portion made of AZO was provided on the BaSi ₂ layer. In the formation of the AZO surface electrode portion, an AZO film was formed by sputtering an AZO target.

By such a method, a photovoltaic power generation module having a Schottky structure was produced. With respect to the obtained photovoltaic power generation module, the average crystal grain size A and the film thickness B of the BaSi ₂ layer were determined by the measurement method described above.

  Furthermore, 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 Table 4, the power generation efficiency of the solar power generation modules according to Example 3 and Examples 3 and 4 was higher than the power generation efficiency of the solar power generation module according to Comparative Example 2. This is because in Example 3 and Example 4, since the average crystal grain size A ≧ film thickness B, the grain boundary trap side was reduced.

(Examples 5 to 9)
A NiSi ₂ layer (thickness 20 nm) was provided on a glass substrate. In forming the NiSi ₂ layer, sputtering was performed by alternately using the Ni target and the Si target to form a laminated film in which a plurality of Ni films / Si films were alternately laminated. Thereafter, heat treatment was performed in a nitrogen atmosphere at 500 ° C. for 1 minute to react the Ni film and the Si film to obtain a NiSi ₂ layer. The purity of the Ni target and the Si target was 99.99% by mass.

Next, a β-FeSi ₂ layer was formed on the NiSi ₂ layer. In the formation of the β-FeSi ₂ layer, sputtering was performed by alternately using the Fe target and the Si target, and the Fe film and the Si film were alternately stacked a plurality of times. In Examples 5 to 9, the film thickness of the Fe film was in the range of 1 to 3 nm, and the film thickness of the Si film was in the range of 5 to 10 nm. In Examples 5 to 9, the atomic ratio of Fe to Si was set to Fe: Si = 1: 2.25. The purity of the Fe target and the Si target was 99.99% by mass. Moreover, the sputtering process was performed in a vacuum of 1 × 10 ⁻³ Pa or less. Thereafter, heat treatment was performed under the conditions shown in Table 5. Next, a surface electrode portion made of ITO was provided on the β-FeSi ₂ layer. In the formation of the ITO surface electrode part, the ITO target was sputtered to form an ITO film.

By such a method, a photovoltaic power generation module having a Schottky structure was produced. The average crystal grain size A and film thickness B of the β-FeSi ₂ layer were determined for the obtained solar power generation module. Further, as a result of XRD analysis to beta-FeSi ₂ layer, only detected peaks of beta-FeSi ₂ crystals, Fe alone and Si single peak was detected.

  Regarding the photovoltaic power generation modules according to Examples 5 to 9, 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 Table 6, the power generation efficiency of the solar power generation modules according to Examples 5 to 9 was high. This is because the grain boundary trap side is reduced because the average crystal grain size A ≧ film thickness B. As described above, the power generation efficiencies of the solar power generation modules according to Examples 5 to 9 were all 2% or more.

(Examples 10 and 11, Comparative Example 3)
A NiSi ₂ layer (thickness 20 nm) was provided on a glass substrate. The formation of the NiSi ₂ layer was performed by alternately using the Ni target and the Si target, and the Ni film and the Si film were alternately stacked a plurality of times. Thereafter, heat treatment was performed in a nitrogen atmosphere at 500 ° C. for 1 minute to react the Ni film and the Si film to form a NiSi ₂ layer. The purity of the Ni target and the Si target was 99.99% by mass.

Then, on the NiSi ₂ layer to form an n-type beta-FeSi ₂ layer was formed a p-type beta-FeSi ₂ layer further thereon. In the formation of the n-type and p-type β-FeSi ₂ layers, sputtering was performed by alternately using the Fe target and the Si target, and the Fe film and the Si film were alternately laminated a plurality of times. In Examples 10 and 11 and Comparative Example 3, the thickness of the Fe film was in the range of 1 to 3 nm, and the thickness of the Si film was in the range of 5 to 10 nm. In Examples 10 and 11 and Comparative Example 3, the atomic ratio of Fe and Si was set to Fe: Si = 1: 2.25. Note that the purity of the Fe target and the Si target was 99.99 mass%. The sputtering process was performed in a vacuum of 1 × 10 ⁻³ Pa or less. Thereafter, heat treatment was performed under the conditions shown in Table 7 to react the Fe film and the Si film to obtain a β-FeSi ₂ layer. The n-type and p-type were prepared by doping impurities into the FeSi ₂ layer.

Next, a surface electrode portion made of ITO was formed on the β-FeSi ₂ layer. In forming the ITO surface electrode portion, the ITO target was sputtered to form an ITO film. Thereby, a pn junction type polycrystalline β-FeSi ₂ photovoltaic power generation module was produced. The average crystal grain size A and film thickness B of the β-FeSi ₂ layer were determined for the obtained solar power generation module.

  Regarding the solar power generation modules according to Examples 10 and 11 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 8.

  As can be seen from Table 8, the power generation efficiency of the solar power generation modules according to Examples 10 and 11 was higher than the power generation efficiency of the solar power generation module according to Comparative Example 3. This is because the grain boundary trap side is reduced because the average crystal grain size A ≧ film thickness B. As described above, it has been found that the power generation efficiency can be increased also for the pn junction type.

(Examples 12 to 14, Comparative Example 4)
In Examples 12 to 14 and Comparative Example 4, a LaB ₆ electrode layer (thickness 50 nm) was provided on the SiO ₂ substrate. Next, n-type BaSi ₂ layer on the electrode layer to form a p-type BaSi ₂ layer thereon. Next, in Example 12 and Example 14, a silicon nitride layer (thickness 3 nm) was continuously formed on the p-type BaSi ₂ layer (Example 13 and Comparative Example 4 have no silicon nitride layer). In addition, the sputtering process was performed in a 300 degreeC heating atmosphere in the vacuum of 1 * 10 < ^-3 > Pa or less. Moreover, the purity of the BaSi ₂ target was 99.9% by mass. Thereafter, heat treatment was performed under the conditions shown in Table 9.

Next, a surface electrode portion made of AZO was provided on the BaSi ₂ layer. In the formation of the AZO surface electrode portion, an AZO film was formed by sputtering an AZO target. A photovoltaic power generation module having a pn junction structure was produced by the above method. For the obtained photovoltaic power generation module, the average crystal grain size A and the film thickness B of the BaSi ₂ layer were determined.

  Regarding the photovoltaic power generation modules according to Examples 12 to 14 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 10.

  As can be seen from Table 10, the power generation efficiency of the solar power generation modules according to Examples 12 to 14 was higher than the power generation efficiency of the solar power generation module according to Comparative Example 4. This is because the grain boundary trap side is reduced because the average crystal grain size A ≧ film thickness B. Thus, it has been found that high power generation efficiency can be obtained even for the pn junction type.

(Examples 1A, 2A)
5 is obtained by joining the power storage mechanism portion shown in FIG. 5 to the back surface of the substrate of the photovoltaic power generation module according to Embodiments 1 and 2 and providing the power storage mechanism portion on the back surface of Embodiment 1. The back surface of 2 was provided with a power storage mechanism portion as Example 2A. When the output characteristics were examined, the behavior shown in FIG. 7 was shown. From this, it can be seen that the photovoltaic power generation modules according to Example 1A and Example 2A are resistant to changes in the amount of sunlight. In addition, regarding Examples 3 to 14, the output characteristics of the photovoltaic power generation module obtained by unitizing with the power storage mechanism portion showed behavior as shown in FIG.

  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 various omissions, replacements, changes, and the like can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and equivalents thereof. Further, the above-described embodiments can be implemented in combination with each other.

Claims (9)

A photovoltaic power generation module comprising a polycrystalline metal silicide layer as a power generation layer,
The polycrystalline metal silicide layer has a p-type polycrystalline barium silicide layer and an n-type polycrystalline barium silicide layer in contact with the p-type polycrystalline barium silicide layer,
The average crystal grain size of the p-type polycrystalline barium silicide layer is on the membrane Atsu以 of the p-type polycrystalline barium silicide layer,
The average crystal grain size of the n-type polycrystalline barium silicide layer is not less than the film thickness of the n-type polycrystalline barium silicide layer,
The photovoltaic module in which the average crystal grain size of each of the p-type polycrystalline barium silicide layer and the n-type polycrystalline barium silicide layer is 0.01 μm or more and 3 μm or less 2. The photovoltaic module according to claim 1, wherein the average crystal grain size of each of the p-type polycrystalline barium silicide layer and the n-type polycrystalline barium silicide layer is 0.05 μm or more and 1.2 μm or less. 3. The photovoltaic module according to claim 1, wherein each of the film thicknesses of the p-type polycrystalline barium silicide layer and the n-type polycrystalline barium silicide layer is 1 μm or less. The p-type polycrystalline barium silicide layer further includes at least one element selected from the group consisting of boron, aluminum, gallium, indium, and thallium,
  4. The sun according to claim 1, wherein the n-type polycrystalline barium silicide layer further includes at least one element selected from the group consisting of nitrogen, phosphorus, arsenic, antimony, and bismuth. Photovoltaic module. 5. The photovoltaic power generation module according to claim 1, wherein each of the p-type polycrystalline barium silicide layer and the n-type polycrystalline barium silicide layer contains BaSi ₂ . Each carrier density of the p-type polycrystalline barium silicide layer and the n-type polycrystalline barium silicide layer, 1 × is 10 ¹⁸ cm ^-3 or less, according to any one of claims 1 to 5 Solar power module. Further comprising an electrode layer in contact with at least one of the p-type polycrystalline barium silicide layer and the n-type polycrystalline barium silicide layer,
The photovoltaic module according to any one of claims 1 to 6, wherein the electrode layer is made of polycrystalline metal silicide. The solar power generation module according to any one of claims 1 to 7 , further comprising a power storage mechanism unit that stores part or all of the power supplied from the polycrystalline metal silicide layer. The power storage mechanism is
A first electrode part;
A second electrode part;
A sealing portion that seals between the first electrode portion and the second electrode portion;
A power storage unit provided inside the sealing unit;
An electrolyte filled in a space surrounded by the first electrode portion, the second electrode portion, and the sealing portion;
A protection unit provided between the power storage unit and the first electrode unit;
A reducing part provided to cover the surface of the second electrode part inside the sealing part;
The solar power generation module according to claim 8 , comprising:

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