WO2015186230A1 - Solar cell - Google Patents

Solar cell Download PDF

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Publication number
WO2015186230A1
WO2015186230A1 PCT/JP2014/065012 JP2014065012W WO2015186230A1 WO 2015186230 A1 WO2015186230 A1 WO 2015186230A1 JP 2014065012 W JP2014065012 W JP 2014065012W WO 2015186230 A1 WO2015186230 A1 WO 2015186230A1
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Prior art keywords
dielectric layer
layer
metal
solar battery
battery cell
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PCT/JP2014/065012
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French (fr)
Japanese (ja)
Inventor
裕紀 若菜
敬司 渡邉
長部　太郎
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株式会社日立製作所
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Priority to PCT/JP2014/065012 priority Critical patent/WO2015186230A1/en
Publication of WO2015186230A1 publication Critical patent/WO2015186230A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0216—Coatings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/06—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by at least one potential-jump barrier or surface barrier
    • H01L31/068—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by at least one potential-jump barrier or surface barrier the potential barriers being only of the PN homojunction type, e.g. bulk silicon PN homojunction solar cells or thin film polycrystalline silicon PN homojunction solar cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/547—Monocrystalline silicon PV cells

Definitions

  • the present invention relates to a solar battery cell.
  • a conductor portion is formed on one surface of a p-type semiconductor substrate so as to be distributed in a predetermined pattern, and a silicon liquid material is sealed so as to seal the conductor portion. It is applied and baked to form an i-type semiconductor, and an n-type semiconductor layer and a transparent conductive film to be a light-irradiated surface are formed thereon, and the conductor portion induces surface plasmon resonance and performs photoelectric conversion during light irradiation.
  • Technology is disclosed.
  • Patent Document 2 discloses a pn junction formed by a p-type semiconductor layer and an n-type semiconductor layer, a metal electrode formed in one conductive type semiconductor layer of the pn junction, and a pn junction.
  • the metal electrode is formed by a metal nanoparticle layer composed of metal nanoparticles that cause surface plasmon resonance. The technology formed is disclosed.
  • multi-exciton production has attracted attention as a technology for improving the efficiency of solar cells.
  • multi-exciton generation will be briefly described.
  • the light that can be absorbed by the solar battery cell is light having energy equal to or higher than the band gap of the semiconductor material of the power generation layer. Therefore, surplus energy exceeding the band gap (hereinafter referred to as Eg) Dissipated as heat.
  • Eg surplus energy exceeding the band gap
  • multi-exciton generation is a phenomenon in which electron-hole pairs are further generated by surplus energy when the surplus energy is twice or more Eg. By utilizing this phenomenon, surplus energy that has been dissipated as heat in the past can be converted into electric power, which is expected to increase the efficiency of solar cells.
  • a typical object of the present invention is to provide a solar cell that achieves both improvement in efficiency in the short wavelength region and reduction in reflectance.
  • the solar cell includes a substrate having a pn junction, a metal layer formed on the substrate and having a periodic pattern structure smaller than a wavelength of incident light, and a first layer formed so as to cover the metal layer. And a dielectric layer.
  • the thickness of the first dielectric layer is equal to or less than the thickness ( ⁇ / 4) based on the wavelength of the incident light.
  • a solar cell includes a substrate having a pn junction, an oxide film formed on the substrate, a metal layer formed on the oxide film and having a periodic pattern structure smaller than the wavelength of incident light, And a first dielectric layer formed to cover the metal layer.
  • the thickness of the first dielectric layer is equal to or less than the thickness ( ⁇ / 4) based on the wavelength of the incident light.
  • a typical effect is to provide a solar cell that achieves both improvement in efficiency in the short wavelength region and reduction in reflectance.
  • the photovoltaic cell of Embodiment 1 of this invention is a graph which shows the relationship between the film thickness of a metal layer, and the average reflectance of a short wavelength area. It is sectional drawing which shows the manufacturing method of the photovoltaic cell of Embodiment 1 of this invention. It is sectional drawing which shows the manufacturing method of a photovoltaic cell following FIG. 6A. It is sectional drawing which shows the manufacturing method of a photovoltaic cell following FIG. 6B. It is sectional drawing which shows the metal layer vicinity of the photovoltaic cell of Embodiment 2 of this invention.
  • the photovoltaic cell of Embodiment 2 of this invention is a graph which shows the relationship between the film thickness of an oxide film, and the average reflectance of a short wavelength area. It is a block diagram which shows the solar cell system using the photovoltaic cell of Embodiment 3 of this invention.
  • the constituent elements are not necessarily indispensable unless otherwise specified and apparently essential in principle. Needless to say.
  • the shapes, positional relationships, etc. of the components, etc. when referring to the shapes, positional relationships, etc. of the components, etc., the shapes are substantially the same unless otherwise specified, or otherwise apparent in principle. And the like are included. The same applies to the above numbers and the like (including the number, numerical value, quantity, range, etc.).
  • the solar battery cell according to the embodiment includes a substrate having a pn junction (light receiving layer 1) and a metal layer (metal layer 2) formed on the substrate and having a periodic pattern structure smaller than the wavelength of incident light. And a first dielectric layer (first dielectric layer 3) formed to cover the metal layer. The thickness of the first dielectric layer is equal to or less than the thickness ( ⁇ / 4) based on the wavelength of the incident light.
  • This solar battery cell is an example of the first embodiment.
  • the solar battery cell according to the embodiment is formed by being incident on a substrate having a pn junction (light receiving layer 1), an oxide film (oxide film 9) formed on the substrate, and the oxide film.
  • a metal layer metal layer 2 having a periodic pattern structure smaller than the wavelength of light; and a first dielectric layer (first dielectric layer 3) formed to cover the metal layer.
  • the thickness of the first dielectric layer is equal to or less than the thickness ( ⁇ / 4) based on the wavelength of the incident light.
  • This solar battery cell is an example of the second embodiment.
  • hatching may be omitted even in a cross-sectional view for easy understanding of the drawings. Further, even a top view may be hatched to make the drawing easy to see.
  • the metal nanopattern structure is taken up.
  • the metal nanopattern structure is a periodic pattern structure in which columnar structures having a width smaller than that of incident sunlight (fine) or having a width equivalent to the wavelength of sunlight are periodically arranged on the light receiving layer.
  • the metal layer thickness is 20 nm or less and the pattern width is 300 nm to 500 nm or less, so that it has an aspect ratio close to that of a flat plate, and the columnar direction of the columnar structure Is perpendicular to the light-receiving layer surface.
  • a cylindrical shape (circular when viewed from above) is cited as the metal nanopattern shape, but a different metal nanopattern shape such as a prism may be used.
  • FIG. 1 is a cross-sectional view showing the structure of the solar battery cell of the first embodiment.
  • FIG. 2 is sectional drawing which shows the metal layer vicinity of a photovoltaic cell.
  • the metal layer 2, the first dielectric layer 3, the second dielectric layer 4, and the third dielectric are formed on the light receiving layer 1 made of a substrate having a pn junction.
  • the light-receiving layer 1 has a pn junction composed of a p-type semiconductor layer such as a silicon substrate into which p-type impurities are introduced and an n-type semiconductor layer such as silicon into which n-type impurities are introduced.
  • a nano pattern of a metal layer 2 such as Al or Ag is formed on the light receiving layer 1, and a first dielectric layer 3 is formed so as to cover the metal layer 2,
  • the second dielectric layer 4 is formed on the first dielectric layer 3, and the third dielectric layer 5 is formed on the second dielectric layer 4.
  • the material of the metal layer 2 should just be comprised from at least 1 type of Ag and Al.
  • FIG. 3 is a top view (a top view with respect to the cross-sectional view of FIG. 2) showing the metal pattern 8 of the metal layer 2.
  • FIG. 3 the same hatching as that of the cross-sectional view is given for easy understanding of the correspondence with the cross-sectional view of FIG.
  • metal patterns 8 having a periodic pattern structure smaller than the wavelength of incident sunlight are periodically arranged on the metal layer 2.
  • the combination of the metal layer 2 and the first dielectric layer 3 has a function of generating surface plasmon resonance and increasing the intensity of light of a specific wavelength by a locally enhanced electric field.
  • plasmon refers to a phenomenon in which free electrons in a metal collectively vibrate.
  • Surface plasmon resonance (hereinafter also referred to as plasmon resonance) is a phenomenon in which when light is applied to a metal thin film, light interacts with free electrons in the metal under specific conditions, causing the light reflectance to change.
  • this plasmon resonance generates an electric field that is remarkably enhanced locally (an electric field that is about three orders of magnitude larger than the electric field of incident light).
  • plasmon resonance is caused by light having a wavelength of 300 nm to 500 nm of incident sunlight, and the light in the wavelength region is strengthened and absorbed by the light receiving layer 1.
  • the metal pattern 8 of the metal layer 2 is arranged at an interval a equal to or less than the wavelength for surface plasmon coupling, as shown in FIG. It is necessary to arrange it below the wavelength to be coupled. That is, the arrangement interval a of the metal pattern 8 and the pattern size b of the metal pattern 8 are set to be equal to or smaller than the wavelength of incident sunlight. Further, the relationship between the arrangement interval a and the pattern size b is a> b. In FIG.
  • the pattern size b has a circular width, that is, a diameter dimension.
  • the metal pattern is not circular (cylindrical) but has another shape such as a quadrangle (quadrangular column)
  • the pattern size is the dimension in the width direction. If the arrangement interval a and the pattern size b are longer than the wavelength for surface plasmon coupling, the coupling itself becomes weak, the electric field enhancing effect is lowered, and the efficiency is lowered.
  • FIG. 4 is a graph showing the relationship between the refractive index of the first dielectric layer 3 and the average reflectance in the short wavelength region (light wavelength: 300-500 nm). As shown in FIG. 4, by using the first dielectric layer 3 having a refractive index of 1.8 or more, the light absorption in the short wavelength region is increased and the average reflectance is reduced (here, the average reflectance). 20 or less).
  • FIG. 5 is a graph showing the relationship between the film thickness of the metal layer 2 and the average reflectance in the short wavelength region (light wavelength: 300-500 nm). As shown in FIG.
  • the metal layer 2 needs to have a film thickness of 20 nm or less.
  • the film thickness of the metal layer 2 is more preferably in the range of 5 nm to 20 nm (within this range, the average reflectance is 20 or less).
  • ⁇ Solar cell manufacturing method> 6A, 6B, and 6C are cross-sectional views illustrating the method for manufacturing the solar battery cell of the first embodiment. Each step of the method for manufacturing the solar cell having the above-described structure will be described with reference to FIGS. 6A to 6C.
  • a pn junction is formed on a silicon substrate, and the light receiving layer 1 is formed.
  • a cross-sectional view of the structure after formation is shown in FIG. 6A.
  • the pn junction is manufactured from a p-type semiconductor layer of a silicon substrate into which a p-type impurity is introduced and an n-type semiconductor layer into which an n-type impurity is introduced.
  • Impurity doping to the silicon substrate is formed by, for example, ion implantation, solid phase diffusion, or vapor phase diffusion.
  • the metal layer 2 is formed on the light receiving layer 1 by, for example, a sputtering method or a plating method, and further, a metal pattern 8 is formed on the metal layer 2 by, for example, a wet processing process or a dry processing process.
  • the metal pattern 8 can also be formed using, for example, a nanoimprint method.
  • FIG. 6B A cross-sectional view of the structure after formation is shown in FIG. 6B.
  • the metal layer 2 is composed of at least one material of Ag and Al.
  • the metal pattern 8 formed on the metal layer 2 has a periodic pattern structure smaller than the wavelength of incident sunlight.
  • the first dielectric layer 3, the second dielectric layer 4, and the third dielectric layer 5 are formed in this order by a film forming method such as a CVD method so as to cover the metal layer 2.
  • a film forming method such as a CVD method so as to cover the metal layer 2.
  • FIG. 6C A cross-sectional view of the structure after formation is shown in FIG. 6C.
  • the thickness t1 of the first dielectric layer 3 is set to 1 ⁇ 4 or less of the wavelength ( ⁇ ) of light. That is, the thickness t1 of the first dielectric layer 3 is set to a thickness ( ⁇ / 4) or less based on the wavelength of incident sunlight.
  • the film thickness t2 of the second dielectric layer 4 is set to 1 ⁇ 4 or less of the light wavelength ( ⁇ ) (thickness ( ⁇ / 4) or less based on the wavelength of incident sunlight).
  • the relationship between the film thickness t1 of the first dielectric layer 3, the film thickness t2 of the second dielectric layer 4, and the film thickness t3 of the third dielectric layer 5 is t1 ⁇ t3 and t2 ⁇ t3. is there.
  • the relationship between the refractive index n1 of the first dielectric layer 3, the refractive index n2 of the second dielectric layer 4, and the refractive index n3 of the third dielectric layer 5 is n3 ⁇ n2 ⁇ n1. is there. If the refractive index is reversed, the total amount of light reaching the light receiving layer 1 is reduced. Since the antireflection effect appears by using at least two kinds of dielectric layers, if necessary, two dielectric layers of the first dielectric layer 3 and the second dielectric layer 4 are used. Also good. Alternatively, three or more dielectric layers may be used. As for the material of the dielectric layer, the same effect can be obtained as long as it is a transparent dielectric material satisfying the above relationship (film thickness, reflectance).
  • SiN x is used for the first dielectric layer 3
  • SiON is used for the second dielectric layer 4
  • SiO 2 is used for the third dielectric layer 5.
  • a third dielectric layer 5 is preferably 1.45 or less in refractive index.
  • the front surface electrode 6 and the back surface electrode 7 are formed, and the front surface electrode 6 and the back surface electrode 7 are connected to the light receiving layer 1, whereby the solar battery cell shown in FIG. 1 can be obtained.
  • annealing may be performed in a nitrogen atmosphere and a hydrogen atmosphere when forming each layer.
  • the combination of the patterned metal layer 2 and the first dielectric layer 3 formed so as to cover the metal layer 2 corresponds to surface plasmon resonance in incident sunlight.
  • plasmon resonance occurs, and the electric field in the vicinity of the metal layer 2 is remarkably enhanced locally, improving the absorption efficiency of the light receiving layer 1.
  • an antireflection effect can be obtained at the same time. As a result, the effect of improving the conversion efficiency of the solar battery cell can be obtained by increasing the efficiency in the short wavelength region.
  • this technique can be applied to solar cells that utilize highly efficient multi-exciton generation, and the efficiency can be improved by multi-excitons in the short wavelength region. Therefore, according to the first embodiment, it is possible to provide a solar battery cell that achieves both efficiency improvement and reflectance reduction in the short wavelength region.
  • FIG. 7 is a cross-sectional view showing the vicinity of the metal layer of the solar battery cell according to the second embodiment.
  • an oxide film 9, a metal layer 2, a first dielectric layer 3, a second dielectric layer 4, and a first dielectric layer are formed on a light receiving layer 1 made of a substrate having a pn junction.
  • 3 is a solar battery cell in which three dielectric layers 5 are formed. The difference from the first embodiment is that an oxide film 9 is inserted between the light receiving layer 1 and the metal layer 2.
  • the light-receiving layer 1 has a pn junction composed of a p-type semiconductor layer such as a silicon substrate into which p-type impurities are introduced and an n-type semiconductor layer such as silicon into which n-type impurities are introduced.
  • a p-type semiconductor layer such as a silicon substrate into which p-type impurities are introduced
  • an oxide film 9 is formed on the light receiving layer 1 by thermal oxidation, and a nano pattern of the metal layer 2 such as Al or Ag is formed on the oxide film 9.
  • a first dielectric layer 3 is formed so as to cover the layer 2, a second dielectric layer 4 is formed on the first dielectric layer 3, and a third dielectric layer 4 is formed on the second dielectric layer 4.
  • the body layer 5 is formed.
  • the oxide film 9 is formed by thermally oxidizing the silicon surface.
  • the thickness of the oxide film 9 will be described with reference to FIG.
  • FIG. 8 is a graph showing the relationship between the thickness of the oxide film 9 and the average reflectance (light wavelength: 300-500 nm) in the short wavelength region.
  • the thickness of the oxide film 9 is preferably 20 nm or less because the surface plasmon coupling tends to weaken and reflectivity increases as the film thickness increases.
  • plasmon resonance is generated by light having a wavelength of 300 nm to 500 nm of incident sunlight, and the light in the wavelength region is strengthened and absorbed by the light receiving layer 1. I am doing so.
  • the metal pattern 8 of the metal layer 2 is arranged at an interval a which is not more than the wavelength for surface plasmon coupling, and the pattern size b is also arranged to be not more than the wavelength for surface plasmon coupling. It will be necessary. If the arrangement interval a and the pattern size b are longer than the wavelength for surface plasmon coupling, the coupling itself becomes weak, the electric field enhancing effect is lowered, and the efficiency is lowered.
  • the refractive index of the first dielectric layer 3 is It becomes important. As in the first embodiment, by using the first dielectric layer 3 having a refractive index of 1.8 or more, light absorption in the short wavelength region increases, and the reflectance can be reduced.
  • the metal layer 2 and the first dielectric layer 3 patterned in a periodic pattern structure smaller than the wavelength of incident sunlight are combined with the second dielectric layer 4 and the third dielectric layer 5. Therefore, the antireflection effect is enhanced.
  • the metal layer 2 functions as a reflection layer when the film thickness is increased.
  • the metal layer 2 has a film thickness of 20 nm in order to simultaneously enhance the antireflection effect. It is as follows.
  • the first dielectric layer 3, the second dielectric layer 4, and the third dielectric layer 5 are arranged in this order so as to cover the metal layer 2, for example. It is formed by a film forming method such as a CVD method.
  • the thickness t1 of the first dielectric layer 3 is set to 1 ⁇ 4 or less of the wavelength ( ⁇ ) of light. If the film thickness of the first dielectric layer 3 is 1 ⁇ 4 or more of the wavelength of light, the reflectance in the short wavelength region increases due to optical interference, causing a reduction in efficiency. Further, the film thickness t2 of the second dielectric layer 4 is set to 1 ⁇ 4 or less of the wavelength ( ⁇ ) of light.
  • the relationship between the film thickness t1 of the first dielectric layer 3, the film thickness t2 of the second dielectric layer 4, and the film thickness t3 of the third dielectric layer 5 is t1 ⁇ t3 and t2 ⁇ t3. is there.
  • the relationship between the refractive index n1 of the first dielectric layer 3, the refractive index n2 of the second dielectric layer 4, and the refractive index n3 of the third dielectric layer 5 is n3 ⁇ n2 ⁇ n1. is there. If the refractive index is reversed, the total amount of light reaching the light receiving layer 1 is reduced. Since the antireflection effect appears by using at least two types of dielectric layers, two or more dielectric layers may be used as necessary. As for the material of the dielectric layer, the same effect can be obtained as long as it is a transparent dielectric material satisfying the above relationship. For example, SiN x is used for the first dielectric layer 3, SiON is used for the second dielectric layer 4, and SiO 2 is used for the third dielectric layer 5.
  • the third dielectric layer 5 preferably has a refractive index of 1.45 or less.
  • the solar cell can be obtained by forming the front electrode 6 and the back electrode 7 and connecting the front electrode 6 and the back electrode 7 to the light receiving layer 1. If necessary, annealing may be performed in a nitrogen atmosphere and a hydrogen atmosphere when forming each layer.
  • a combination of the patterned metal layer 2 and the first dielectric layer 3 formed so as to cover the metal layer 2 allows light corresponding to surface plasmon resonance in incident sunlight.
  • plasmon resonance occurs, and the electric field in the vicinity of the metal layer 2 is remarkably enhanced locally, thereby improving the absorption efficiency of the light receiving layer 1.
  • an antireflection effect can be obtained at the same time.
  • the effect of improving the conversion efficiency of the solar battery cell can be obtained by increasing the efficiency in the short wavelength region.
  • this technique can be applied to solar cells that utilize highly efficient multi-exciton generation, and the efficiency can be improved by multi-excitons in the short wavelength region. Therefore, according to the second embodiment, it is possible to provide a solar battery cell that achieves both efficiency improvement and reflectance reduction in the short wavelength region.
  • the oxide film 9 by inserting the oxide film 9, the trap level density on the silicon surface can be suppressed, so that the efficiency in the short wavelength region can be further improved.
  • Embodiment 3 will be described with reference to FIG.
  • the third embodiment is an example of a solar battery system using the solar battery cells described in the first and second embodiments.
  • FIG. 9 is a configuration diagram showing a solar battery system using the solar battery cell according to the third embodiment.
  • the third embodiment is a solar battery system using the solar battery cells of the first and second embodiments.
  • the solar cell system includes a solar cell panel 11, a connection box 12, a current collection box 13, a power conditioner 14, and a transformer 15.
  • Solar cell panel 11 is a solar cell panel in which a plurality of solar cells described in the first and second embodiments are arranged. This solar cell panel 11 is a panel that generates electric power by sunlight.
  • the connection box 12 is a connection box that transmits the electric power generated by the solar cell panel 11 to the current collection box 13.
  • the current collection box 13 is a current collection box that collects the electric power transmitted from the connection box 12 and transmits it to the power conditioner 14.
  • the power conditioner 14 is a converter that converts the electric power transmitted from the current collection box 13 from direct current to alternating current and transmits the electric power to the transformer 15.
  • the transformer 15 is a transformer that transforms the voltage of the AC power transmitted from the power conditioner 14 and transmits it to the commercial power system 16.
  • three power conditioners 14 and a current collection box 13 are connected to one transformer 15 connected to the commercial power system 16. Further, a three-system connection box 12 and a solar cell panel 11 are connected to each one-system power conditioner 14 and current collection box 13.
  • the electric power generated by the solar cell panel 11 is transmitted to the connection box 12 and collected by the current collection box 13. Thereafter, the power conditioner 14 converts the current from direct current to alternating current, transforms the voltage together with the transformer 15, and connects to the commercial power system 16.
  • the said structure is a structural example of the mega solar system with many panel numbers especially in a solar cell system. In the case of a residential system with a relatively small number of panels, it is directly connected to the power conditioner 14 from the connection box 12.
  • the solar cell system of Embodiment 3 can be realized.
  • the solar cell system according to the third embodiment it is possible to increase the efficiency of solar power generation by taking advantage of the effect of the solar cell structure.
  • This invention has the following characteristics as a manufacturing method of a photovoltaic cell. (1) a first step of forming a substrate having a pn junction; A second step of forming a metal layer having a periodic pattern structure smaller than the wavelength of incident light on the substrate; A third step of forming a first dielectric layer so as to cover the metal layer; Have In the third step, the method of manufacturing a solar battery cell, wherein the thickness of the first dielectric layer is set to a thickness ( ⁇ / 4) or less based on the wavelength of the incident light.
  • the second step includes a step of forming a metal pattern of the periodic pattern structure as the metal layer,
  • the arrangement interval a of the metal pattern and the pattern size b of the metal pattern are set to be equal to or less than the wavelength of the incident light,
  • the manufacturing method of the photovoltaic cell which makes the relationship of the arrangement
  • the material of the metal layer is composed of at least one of Ag and Al, The manufacturing method of the photovoltaic cell which makes the film thickness of the said metal layer 5 nm or more and 20 nm or less.
  • a method for manufacturing a solar battery cell wherein the refractive index of the first dielectric layer is 1.8 or more.
  • the film thickness t2 of the second dielectric layer is set to a thickness ( ⁇ / 4) or less based on the wavelength of the incident light, A method for manufacturing a solar battery cell, wherein a relationship between a film thickness t3 of the third dielectric layer and a film thickness t2 of the second dielectric layer satisfies t3> t2.
  • a first step of forming a substrate having a pn junction A second step of forming an oxide film on the substrate; A third step of forming a metal layer having a periodic pattern structure smaller than the wavelength of incident light on the oxide film; A fourth step of forming a first dielectric layer so as to cover the metal layer; Have In the fourth step, the method of manufacturing a solar battery cell, wherein the thickness of the first dielectric layer is set to a thickness ( ⁇ / 4) or less based on the wavelength of the incident light.
  • the manufacturing method of the photovoltaic cell which sets the film thickness of the said oxide film to 20 nm or less.
  • the third step includes a step of forming a metal pattern of the periodic pattern structure as the metal layer, The arrangement interval a of the metal pattern and the pattern size b of the metal pattern are set to be equal to or less than the wavelength of the incident light, The manufacturing method of the photovoltaic cell which makes the relationship of the arrangement
  • the material of the metal layer is composed of at least one of Ag and Al, The manufacturing method of the photovoltaic cell which makes the film thickness of the said metal layer 5 nm or more and 20 nm or less.
  • the film thickness t2 of the second dielectric layer is set to a thickness ( ⁇ / 4) or less based on the wavelength of the incident light, A method for manufacturing a solar battery cell, wherein a relationship between a film thickness t3 of the third dielectric layer and a film thickness t2 of the second dielectric layer satisfies t3> t2.
  • This invention has the following characteristics as a solar cell system.
  • (21) a solar panel in which a plurality of solar cells are arranged;
  • a power conditioner that converts electric power generated by the solar cell panel from direct current to alternating current;
  • a transformer that transforms AC power converted by the power conditioner and outputs the transformed power to the power system;
  • the solar battery cell is a substrate having a pn junction;
  • Have The thickness of the first dielectric layer is a solar cell system having a thickness ( ⁇ / 4) or less based on the wavelength of the incident light.
  • (22) a solar cell panel in which a plurality of solar cells are arranged;
  • a power conditioner that converts electric power generated by the solar cell panel from direct current to alternating current;
  • a transformer that transforms AC power converted by the power conditioner and outputs the transformed power to the power system;
  • the solar battery cell is a substrate having a pn junction;
  • the thickness of the first dielectric layer is a solar cell system having a thickness ( ⁇ / 4) or less based on the wavelength of the incident light.

Abstract

According to an embodiment of the present invention, a solar cell has: a light receiving layer (1) formed of a substrate having a pn junction; a metal layer (2), which is formed on the light receiving layer (1), and which has a periodic pattern structure that is smaller than the wavelength of light to be inputted; and a first dielectric material layer (3) that is formed to cover the metal layer (2). The film thickness of the first dielectric material layer (3) is equal to or less than a thickness (λ/4) based on the wavelength of the light to be inputted. With such solar cell structure, the solar cell achieving both efficiency improvement and reflectance reduction of a short wavelength region at one time can be provided.

Description

太陽電池セルSolar cells
　本発明は、太陽電池セルに関する。 The present invention relates to a solar battery cell.
　例えば、特許文献１には、ｐ型半導体基板の一方面上にそれぞれが分離する所定のパターンで分布するように導電体部位が形成され、導電体部位を封止するようにシリコン液体系材料を塗布し焼成してｉ型半導体を形成し、その上層にｎ型半導体層及び光照射面となる透明導電膜を形成し、光照射時には導電体部位が表面プラズモン共鳴を誘起して光電変換を行う技術が開示されている。 For example, in Patent Document 1, a conductor portion is formed on one surface of a p-type semiconductor substrate so as to be distributed in a predetermined pattern, and a silicon liquid material is sealed so as to seal the conductor portion. It is applied and baked to form an i-type semiconductor, and an n-type semiconductor layer and a transparent conductive film to be a light-irradiated surface are formed thereon, and the conductor portion induces surface plasmon resonance and performs photoelectric conversion during light irradiation. Technology is disclosed.
　また、特許文献２には、ｐ型半導体層とｎ型半導体層とによって形成されるｐｎ接合体と、ｐｎ接合体の一方の導電型の半導体層に形成される金属電極と、ｐｎ接合体の他方の導電型の半導体層に形成される透明電極層とを備える光電変換素子が基板上に形成された太陽電池において、金属電極は、表面プラズモン共鳴を生じる金属ナノ粒子からなる金属ナノ粒子層によって形成される技術が開示されている。 Patent Document 2 discloses a pn junction formed by a p-type semiconductor layer and an n-type semiconductor layer, a metal electrode formed in one conductive type semiconductor layer of the pn junction, and a pn junction. In a solar cell in which a photoelectric conversion element including a transparent electrode layer formed on the other conductive type semiconductor layer is formed on a substrate, the metal electrode is formed by a metal nanoparticle layer composed of metal nanoparticles that cause surface plasmon resonance. The technology formed is disclosed.
　また、太陽電池セルを高効率化する技術として、マルチエキシトン生成が注目されている。以下、マルチエキシトン生成について簡単に述べる。太陽電池セルが吸収できる光は、発電層の半導体材料のバンドギャップ以上のエネルギーを有する光であるため、バンドギャップ（以下、Ｅｇと記す）を上回る余剰エネルギーは、一般的な太陽電池セルでは、熱として散逸される。これに対して、マルチエキシトン生成とは、余剰エネルギーがＥｇの２倍以上である場合に、余剰エネルギーによって、さらに電子正孔対が生成されるという現象である。この現象を利用することで、従来は熱として散逸されていた余剰エネルギーを電力に変換することが可能となり、太陽電池セルの高効率化が可能と期待されている。 Also, multi-exciton production has attracted attention as a technology for improving the efficiency of solar cells. Hereinafter, multi-exciton generation will be briefly described. The light that can be absorbed by the solar battery cell is light having energy equal to or higher than the band gap of the semiconductor material of the power generation layer. Therefore, surplus energy exceeding the band gap (hereinafter referred to as Eg) Dissipated as heat. On the other hand, multi-exciton generation is a phenomenon in which electron-hole pairs are further generated by surplus energy when the surplus energy is twice or more Eg. By utilizing this phenomenon, surplus energy that has been dissipated as heat in the past can be converted into electric power, which is expected to increase the efficiency of solar cells.
特開２０１０－２２５７９８号公報JP 2010-225798 A 特開２００９－２４６０２５号公報JP 2009-246025 A
　前記特許文献１に記載の構成では、ｐ型半導体層とｎ型半導体層の間に導電体部位が配置されているため、５００ｎｍ以下の短波長の光が導電体部位とカップリングすることが無く、電場増強効果を得ることが難しい。また、導電体部位がｉ型半導体内に配置しているため、短波長の光の反射率を低減する効果を有さない。 In the configuration described in Patent Document 1, since the conductor portion is disposed between the p-type semiconductor layer and the n-type semiconductor layer, light having a short wavelength of 500 nm or less is not coupled to the conductor portion. It is difficult to obtain an electric field enhancement effect. In addition, since the conductor portion is disposed in the i-type semiconductor, it does not have an effect of reducing the reflectance of light having a short wavelength.
　また、前記特許文献２に記載の構成では、金属ナノ粒子層上に、ｐ型半導体層とｎ型半導体層とによって形成されるｐｎ接合体を形成しているため、受光部に相当するｐｎ接合体内に多くの欠陥準位が存在し、変換効率の低下を引き起こすことが考えられる。また、受光部の表面近傍のみで吸収する短波長領域の光は、有効に利用することができない。 In the configuration described in Patent Document 2, since a pn junction formed by a p-type semiconductor layer and an n-type semiconductor layer is formed on the metal nanoparticle layer, a pn junction corresponding to the light receiving portion is formed. Many defect levels exist in the body, which may cause a decrease in conversion efficiency. Further, light in a short wavelength region that is absorbed only in the vicinity of the surface of the light receiving unit cannot be used effectively.
　そのため、太陽電池セルの高効率化技術となる、マルチエキシトン生成を実現しようとした場合、光のエネルギーが高い短波長の光を有効に利用できるセル構造にする必要がある。例えば、従来のテクスチャ構造やナノピラー構造などの反射防止構造では、受光層を加工するため、多くのダメージが表面に残っているので、短波長領域の効率が低い。また、アモルファスシリコンを用いた太陽電池セルもまた、短波長領域の効率が低いことが知られている。 Therefore, when trying to realize multi-exciton generation, which is a technology for improving the efficiency of solar cells, it is necessary to have a cell structure that can effectively use short-wavelength light with high light energy. For example, in an antireflection structure such as a conventional texture structure or nanopillar structure, since the light receiving layer is processed, a lot of damage remains on the surface, so the efficiency in the short wavelength region is low. Also, it is known that solar cells using amorphous silicon have low efficiency in the short wavelength region.
　本発明の代表的な目的は、短波長領域の効率向上と反射率低減を両立する太陽電池セルを提供することである。 A typical object of the present invention is to provide a solar cell that achieves both improvement in efficiency in the short wavelength region and reduction in reflectance.
　本発明の前記ならびにその他の目的と新規な特徴は、本明細書の記述および添付図面から明らかになるであろう。 The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.
　本願において開示される発明のうち、代表的なものの概要を簡単に説明すれば、下記の通りである。 Of the inventions disclosed in this application, the outline of typical ones will be briefly described as follows.
　（１）太陽電池セルは、ｐｎ接合を有する基板と、前記基板上に形成され、入射する光の波長より小さい周期パターン構造を有する金属層と、前記金属層を覆うように形成された第１の誘電体層と、を有する。そして、前記第１の誘電体層の膜厚は、前記入射する光の波長に基づいた厚さ（λ／４）以下である。 (1) The solar cell includes a substrate having a pn junction, a metal layer formed on the substrate and having a periodic pattern structure smaller than a wavelength of incident light, and a first layer formed so as to cover the metal layer. And a dielectric layer. The thickness of the first dielectric layer is equal to or less than the thickness (λ / 4) based on the wavelength of the incident light.
　（２）太陽電池セルは、ｐｎ接合を有する基板と、前記基板上に形成された酸化膜と、前記酸化膜上に形成され、入射する光の波長より小さい周期パターン構造を有する金属層と、前記金属層を覆うように形成された第１の誘電体層と、を有する。そして、前記第１の誘電体層の膜厚は、前記入射する光の波長に基づいた厚さ（λ／４）以下である。 (2) A solar cell includes a substrate having a pn junction, an oxide film formed on the substrate, a metal layer formed on the oxide film and having a periodic pattern structure smaller than the wavelength of incident light, And a first dielectric layer formed to cover the metal layer. The thickness of the first dielectric layer is equal to or less than the thickness (λ / 4) based on the wavelength of the incident light.
　本願において開示される発明のうち、代表的なものによって得られる効果を簡単に説明すれば、以下の通りである。 The effects obtained by typical ones of the inventions disclosed in this application will be briefly described as follows.
　代表的な効果は、短波長領域の効率向上と反射率低減を両立する太陽電池セルを提供することができる。 A typical effect is to provide a solar cell that achieves both improvement in efficiency in the short wavelength region and reduction in reflectance.
本発明の実施の形態１の太陽電池セルの構造を示す断面図である。It is sectional drawing which shows the structure of the photovoltaic cell of Embodiment 1 of this invention. 本発明の実施の形態１の太陽電池セルの金属層近傍を示す断面図である。It is sectional drawing which shows the metal layer vicinity of the photovoltaic cell of Embodiment 1 of this invention. 本発明の実施の形態１の太陽電池セルにおいて、金属層の金属パターンを示す上面図である。In the photovoltaic cell of Embodiment 1 of this invention, it is a top view which shows the metal pattern of a metal layer. 本発明の実施の形態１の太陽電池セルにおいて、第１の誘電体層の屈折率と短波長領域の平均反射率との関係を示すグラフである。In the photovoltaic cell of Embodiment 1 of this invention, it is a graph which shows the relationship between the refractive index of a 1st dielectric material layer, and the average reflectance of a short wavelength area | region. 本発明の実施の形態１の太陽電池セルにおいて、金属層の膜厚と短波長領域の平均反射率との関係を示すグラフである。In the photovoltaic cell of Embodiment 1 of this invention, it is a graph which shows the relationship between the film thickness of a metal layer, and the average reflectance of a short wavelength area. 本発明の実施の形態１の太陽電池セルの製造方法を示す断面図である。It is sectional drawing which shows the manufacturing method of the photovoltaic cell of Embodiment 1 of this invention. 図６Ａに続く、太陽電池セルの製造方法を示す断面図である。It is sectional drawing which shows the manufacturing method of a photovoltaic cell following FIG. 6A. 図６Ｂに続く、太陽電池セルの製造方法を示す断面図である。It is sectional drawing which shows the manufacturing method of a photovoltaic cell following FIG. 6B. 本発明の実施の形態２の太陽電池セルの金属層近傍を示す断面図である。It is sectional drawing which shows the metal layer vicinity of the photovoltaic cell of Embodiment 2 of this invention. 本発明の実施の形態２の太陽電池セルにおいて、酸化膜の膜厚と短波長領域の平均反射率との関係を示すグラフである。In the photovoltaic cell of Embodiment 2 of this invention, it is a graph which shows the relationship between the film thickness of an oxide film, and the average reflectance of a short wavelength area. 本発明の実施の形態３の太陽電池セルを用いた太陽電池システムを示す構成図である。It is a block diagram which shows the solar cell system using the photovoltaic cell of Embodiment 3 of this invention.
　以下の実施の形態においては便宜上その必要があるときは、複数のセクションまたは実施の形態に分割して説明するが、特に明示した場合を除き、それらは互いに無関係なものではなく、一方は他方の一部または全部の変形例、応用例、詳細説明、補足説明等の関係にある。また、以下の実施の形態において、要素の数等（個数、数値、量、範囲等を含む）に言及する場合、特に明示した場合および原理的に明らかに特定の数に限定される場合等を除き、その特定の数に限定されるものではなく、特定の数以上でも以下でもよい。 In the following embodiment, when it is necessary for the sake of convenience, the description will be divided into a plurality of sections or embodiments. However, unless otherwise specified, they are not irrelevant, and one is the other. Some or all of the modifications, application examples, detailed explanations, supplementary explanations, and the like are related. Further, in the following embodiments, when referring to the number of elements (including the number, numerical value, quantity, range, etc.), especially when clearly indicated and when clearly limited to a specific number in principle, etc. Except, it is not limited to the specific number, and may be more or less than the specific number.
　さらに、以下の実施の形態において、その構成要素（要素ステップ等も含む）は、特に明示した場合および原理的に明らかに必須であると考えられる場合等を除き、必ずしも必須のものではないことは言うまでもない。同様に、以下の実施の形態において、構成要素等の形状、位置関係等に言及するときは、特に明示した場合および原理的に明らかにそうでないと考えられる場合等を除き、実質的にその形状等に近似または類似するもの等を含むものとする。このことは、上記数等（個数、数値、量、範囲等を含む）についても同様である。 Further, in the following embodiments, the constituent elements (including element steps and the like) are not necessarily indispensable unless otherwise specified and apparently essential in principle. Needless to say. Similarly, in the following embodiments, when referring to the shapes, positional relationships, etc. of the components, etc., the shapes are substantially the same unless otherwise specified, or otherwise apparent in principle. And the like are included. The same applies to the above numbers and the like (including the number, numerical value, quantity, range, etc.).
　［本発明の実施の形態の概要］
　まず、本発明の実施の形態の概要について説明する。本実施の形態の概要では、一例として、括弧内に実施の形態の対応する構成要素、符号等を付して説明する。 [Outline of Embodiment of the Present Invention]
First, an outline of an embodiment of the present invention will be described. In the outline of the present embodiment, as an example, the description will be given with parentheses corresponding constituent elements, reference numerals and the like in parentheses.
　（１）実施の形態の太陽電池セルは、ｐｎ接合を有する基板（受光層１）と、前記基板上に形成され、入射する光の波長より小さい周期パターン構造を有する金属層（金属層２）と、前記金属層を覆うように形成された第１の誘電体層（第１の誘電体層３）と、を有する。そして、前記第１の誘電体層の膜厚は、前記入射する光の波長に基づいた厚さ（λ／４）以下である。この太陽電池セルは、実施の形態１の例である。 (1) The solar battery cell according to the embodiment includes a substrate having a pn junction (light receiving layer 1) and a metal layer (metal layer 2) formed on the substrate and having a periodic pattern structure smaller than the wavelength of incident light. And a first dielectric layer (first dielectric layer 3) formed to cover the metal layer. The thickness of the first dielectric layer is equal to or less than the thickness (λ / 4) based on the wavelength of the incident light. This solar battery cell is an example of the first embodiment.
　（２）実施の形態の太陽電池セルは、ｐｎ接合を有する基板（受光層１）と、前記基板上に形成された酸化膜（酸化膜９）と、前記酸化膜上に形成され、入射する光の波長より小さい周期パターン構造を有する金属層（金属層２）と、前記金属層を覆うように形成された第１の誘電体層（第１の誘電体層３）と、を有する。そして、前記第１の誘電体層の膜厚は、前記入射する光の波長に基づいた厚さ（λ／４）以下である。この太陽電池セルは、実施の形態２の例である。 (2) The solar battery cell according to the embodiment is formed by being incident on a substrate having a pn junction (light receiving layer 1), an oxide film (oxide film 9) formed on the substrate, and the oxide film. A metal layer (metal layer 2) having a periodic pattern structure smaller than the wavelength of light; and a first dielectric layer (first dielectric layer 3) formed to cover the metal layer. The thickness of the first dielectric layer is equal to or less than the thickness (λ / 4) based on the wavelength of the incident light. This solar battery cell is an example of the second embodiment.
　以下、上述した本発明の実施の形態の概要に基づいた実施の形態を図面に基づいて詳細に説明する。以下の説明は本発明の内容の具体例を示すものであり、本発明がこれらの説明に限定されるものではなく、本明細書に開示される技術的思想の範囲内において当業者による様々な変更および修正が可能である。また、実施の形態を説明するための全図において、同一の部材には原則として同一の符号を付し、その繰り返しの説明は省略する場合がある。 Hereinafter, an embodiment based on the outline of the embodiment of the present invention described above will be described in detail based on the drawings. The following description shows specific examples of the contents of the present invention, and the present invention is not limited to these descriptions. Various modifications by those skilled in the art are within the scope of the technical idea disclosed in this specification. Changes and modifications are possible. In all the drawings for explaining the embodiments, the same members are denoted by the same reference symbols in principle, and the repeated description thereof may be omitted.
　また、実施の形態で用いる図面においては、断面図であっても図面を見易くするためにハッチングを省略する場合もある。また、上面図であっても図面を見易くするためにハッチングを付す場合もある。 In the drawings used in the embodiments, hatching may be omitted even in a cross-sectional view for easy understanding of the drawings. Further, even a top view may be hatched to make the drawing easy to see.
　［実施の形態１］
　実施の形態１について、図１～図６を用いて説明する。 [Embodiment 1]
The first embodiment will be described with reference to FIGS.
　本実施の形態では、金属ナノパターン構造を取り上げる。金属ナノパターン構造とは、入射する太陽光の波長より小さい（微細）、または太陽光の波長と同等な幅を有する柱状構造が、受光層上に周期的に配列された周期パターン構造である。また、反射防止も考慮した構成であるため、金属層の膜厚が２０ｎｍ以下、かつパターン幅が３００ｎｍから５００ｎｍ以下であることから、平板に近いアスペクト比を有し、当該柱状構造の柱軸方向は受光層面と垂直である。以下の実施の形態では、金属ナノパターン形状として円柱（上面から見ると円形）を挙げているが、角柱など、異なる金属ナノパターン形状であってもよい。 In this embodiment, the metal nanopattern structure is taken up. The metal nanopattern structure is a periodic pattern structure in which columnar structures having a width smaller than that of incident sunlight (fine) or having a width equivalent to the wavelength of sunlight are periodically arranged on the light receiving layer. In addition, since it is configured to prevent reflection, the metal layer thickness is 20 nm or less and the pattern width is 300 nm to 500 nm or less, so that it has an aspect ratio close to that of a flat plate, and the columnar direction of the columnar structure Is perpendicular to the light-receiving layer surface. In the following embodiment, a cylindrical shape (circular when viewed from above) is cited as the metal nanopattern shape, but a different metal nanopattern shape such as a prism may be used.
　＜太陽電池セルの構造＞
　図１は、本実施の形態１の太陽電池セルの構造を示す断面図である。また、図２は、太陽電池セルの金属層近傍を示す断面図である。本実施の形態１の太陽電池セルは、ｐｎ接合を有する基板からなる受光層１上に、金属層２、第１の誘電体層３、第２の誘電体層４、および第３の誘電体層５が形成された太陽電池セルであり、電極として、表面電極６と裏面電極７を有する。 <Solar cell structure>
FIG. 1 is a cross-sectional view showing the structure of the solar battery cell of the first embodiment. Moreover, FIG. 2 is sectional drawing which shows the metal layer vicinity of a photovoltaic cell. In the solar cell of the first embodiment, the metal layer 2, the first dielectric layer 3, the second dielectric layer 4, and the third dielectric are formed on the light receiving layer 1 made of a substrate having a pn junction. A solar battery cell in which the layer 5 is formed, and has a front electrode 6 and a back electrode 7 as electrodes.
　受光層１は、ｐ型の不純物を導入したシリコン基板などのｐ型半導体層と、ｎ型の不純物を導入したシリコンなどのｎ型半導体層とからなるｐｎ接合を有している。本実施の形態による太陽電池セルは、受光層１上に、ＡｌやＡｇなどの金属層２のナノパターンが形成され、この金属層２を覆うように第１の誘電体層３が形成され、第１の誘電体層３上に第２の誘電体層４が形成され、第２の誘電体層４上に第３の誘電体層５が形成された構成を有する。金属層２の材質は、ＡｇおよびＡｌの少なくとも１種類から構成されていれば良い。 The light-receiving layer 1 has a pn junction composed of a p-type semiconductor layer such as a silicon substrate into which p-type impurities are introduced and an n-type semiconductor layer such as silicon into which n-type impurities are introduced. In the solar battery cell according to the present embodiment, a nano pattern of a metal layer 2 such as Al or Ag is formed on the light receiving layer 1, and a first dielectric layer 3 is formed so as to cover the metal layer 2, The second dielectric layer 4 is formed on the first dielectric layer 3, and the third dielectric layer 5 is formed on the second dielectric layer 4. The material of the metal layer 2 should just be comprised from at least 1 type of Ag and Al.
　ここで、金属層２のナノパターンについて、図３を用いて説明する。図３は、金属層２の金属パターン８を示す上面図（図２の断面図に対する上面図）である。図３の上面図では、図２の断面図との対応関係を分かり易くするために断面図と同じハッチングを付している。図３に示すように、金属層２には、入射する太陽光の波長より小さい周期パターン構造の金属パターン８を周期的に配置する。金属層２と第１の誘電体層３との組み合わせにより、表面プラズモン共鳴を発生させ、局所的に増強された電場により、ある特定の波長の光の強度を増加させる機能を有する。ここで、プラズモンとは、金属中の自由電子が集団的に振動する現象のことを言う。また、表面プラズモン共鳴（以下、プラズモン共鳴とも記す）とは、金属の薄膜に光を照射すると特定の条件で金属中の自由電子と光が相互作用し、光の反射率が変化する現象のことを言う。このプラズモン共鳴では、局所的に著しく増強された電場（入射光の電場に対して３桁程度大きな電場）を発生することが知られている。 Here, the nano pattern of the metal layer 2 will be described with reference to FIG. FIG. 3 is a top view (a top view with respect to the cross-sectional view of FIG. 2) showing the metal pattern 8 of the metal layer 2. In the top view of FIG. 3, the same hatching as that of the cross-sectional view is given for easy understanding of the correspondence with the cross-sectional view of FIG. As shown in FIG. 3, metal patterns 8 having a periodic pattern structure smaller than the wavelength of incident sunlight are periodically arranged on the metal layer 2. The combination of the metal layer 2 and the first dielectric layer 3 has a function of generating surface plasmon resonance and increasing the intensity of light of a specific wavelength by a locally enhanced electric field. Here, plasmon refers to a phenomenon in which free electrons in a metal collectively vibrate. Surface plasmon resonance (hereinafter also referred to as plasmon resonance) is a phenomenon in which when light is applied to a metal thin film, light interacts with free electrons in the metal under specific conditions, causing the light reflectance to change. Say. It is known that this plasmon resonance generates an electric field that is remarkably enhanced locally (an electric field that is about three orders of magnitude larger than the electric field of incident light).
　本実施の形態１では、入射した太陽光の３００ｎｍから５００ｎｍの波長の光でプラズモン共鳴を生じさせ、上記の波長域の光を強めて受光層１で吸収するようにしている。表面プラズモン共鳴による受光層１の吸収を高めるには、金属層２の金属パターン８を、図３に示すように、表面プラズモンカップリングする波長以下の間隔ａで配置し、パターンサイズｂも表面プラズモンカップリングする波長以下に配置することが必要となる。すなわち、金属パターン８の配置間隔ａおよび金属パターン８のパターンサイズｂは、入射する太陽光の波長以下とする。さらに、配置間隔ａとパターンサイズｂとの関係を、ａ＞ｂとする。図３では、金属パターン８は円形であるので、パターンサイズｂは、円形の幅、すなわち直径の寸法となる。なお、金属パターンが円形（円柱）ではなく、例えば四角形（四角柱）などの他の形状の場合は、パターンサイズは幅方向の寸法となる。もし、配置間隔ａやパターンサイズｂを表面プラズモンカップリングする波長以上にすると、カップリングそのものが弱くなり、電場増強効果が低下し、効率低下を引き起こす。 In the first embodiment, plasmon resonance is caused by light having a wavelength of 300 nm to 500 nm of incident sunlight, and the light in the wavelength region is strengthened and absorbed by the light receiving layer 1. In order to enhance the absorption of the light-receiving layer 1 due to surface plasmon resonance, the metal pattern 8 of the metal layer 2 is arranged at an interval a equal to or less than the wavelength for surface plasmon coupling, as shown in FIG. It is necessary to arrange it below the wavelength to be coupled. That is, the arrangement interval a of the metal pattern 8 and the pattern size b of the metal pattern 8 are set to be equal to or smaller than the wavelength of incident sunlight. Further, the relationship between the arrangement interval a and the pattern size b is a> b. In FIG. 3, since the metal pattern 8 is circular, the pattern size b has a circular width, that is, a diameter dimension. When the metal pattern is not circular (cylindrical) but has another shape such as a quadrangle (quadrangular column), the pattern size is the dimension in the width direction. If the arrangement interval a and the pattern size b are longer than the wavelength for surface plasmon coupling, the coupling itself becomes weak, the electric field enhancing effect is lowered, and the efficiency is lowered.
　また、金属層２の金属パターン８以外に、短波長から可視領域で表面プラズモン共鳴を生じさせ、受光層１での光吸収を増大させるためには、第１の誘電体層３の屈折率が重要となる。これを、図４を用いて説明する。図４は、第１の誘電体層３の屈折率と短波長領域の平均反射率（光の波長：３００－５００ｎｍ）との関係を示すグラフである。図４に示すように、１．８以上の屈折率を有する第１の誘電体層３にすることで、短波長領域の光吸収が増加し、平均反射率を低減（ここでは、平均反射率が２０以下）させることができる。 In addition to the metal pattern 8 of the metal layer 2, in order to cause surface plasmon resonance from a short wavelength to a visible region and increase light absorption in the light receiving layer 1, the refractive index of the first dielectric layer 3 is It becomes important. This will be described with reference to FIG. FIG. 4 is a graph showing the relationship between the refractive index of the first dielectric layer 3 and the average reflectance in the short wavelength region (light wavelength: 300-500 nm). As shown in FIG. 4, by using the first dielectric layer 3 having a refractive index of 1.8 or more, the light absorption in the short wavelength region is increased and the average reflectance is reduced (here, the average reflectance). 20 or less).
　また、入射する太陽光の波長より小さい周期パターン構造にパターン化された金属層２と第１の誘電体層３は、第２の誘電体層４と第３の誘電体層５とを組み合わせることで、反射防止効果を高めている。ここで、金属層２は、膜厚が厚くなると金属反射層として機能することが知られており、本実施の形態１では反射防止効果も同時に高めるため、金属層２の膜厚を２０ｎｍ以下としている。図５は、金属層２の膜厚と短波長領域の平均反射率（光の波長：３００－５００ｎｍ）との関係を示すグラフである。図５に示すように、金属層２の膜厚が２０ｎｍ以上になると、金属層２の光の透過率が著しく低下することで平均反射率が増加している。また、金属層２の膜厚が５ｎｍ以下になると、３００ｎｍから５００ｎｍの波長域の表面プラズモン共鳴を発生させる効果が弱くなり、平均反射率が増加している。そのため，表面プラズモン共鳴による光吸収効果と反射防止を両立するには、金属層２の膜厚を２０ｎｍ以下にする必要がある。より好ましい金属層２の膜厚は、５ｎｍから２０ｎｍの範囲（この範囲内では、平均反射率が２０以下）である。 Further, the metal layer 2 and the first dielectric layer 3 patterned in a periodic pattern structure smaller than the wavelength of incident sunlight are combined with the second dielectric layer 4 and the third dielectric layer 5. Therefore, the antireflection effect is enhanced. Here, it is known that the metal layer 2 functions as a metal reflection layer when the film thickness is increased. In the first embodiment, the antireflection effect is enhanced at the same time, so that the film thickness of the metal layer 2 is set to 20 nm or less. Yes. FIG. 5 is a graph showing the relationship between the film thickness of the metal layer 2 and the average reflectance in the short wavelength region (light wavelength: 300-500 nm). As shown in FIG. 5, when the thickness of the metal layer 2 is 20 nm or more, the light transmittance of the metal layer 2 is remarkably lowered, so that the average reflectance is increased. Moreover, when the film thickness of the metal layer 2 is 5 nm or less, the effect of generating surface plasmon resonance in the wavelength region of 300 nm to 500 nm is weakened, and the average reflectance is increased. Therefore, in order to achieve both the light absorption effect by surface plasmon resonance and the antireflection, the metal layer 2 needs to have a film thickness of 20 nm or less. The film thickness of the metal layer 2 is more preferably in the range of 5 nm to 20 nm (within this range, the average reflectance is 20 or less).
　従来の光閉じ込め技術としては、受光層１をテクスチャ構造やナノピラー構造に加工したものを用いるものが知られている。しかしながら、受光層１を加工することにより、表面層にダメージが入り、短波長領域の発電効率を著しく低下させることも知られている。本実施の形態１では、テクスチャ構造の受光層１上に形成することで、ある程度、反射防止の効果は向上する。また、短波長領域の更なる効率向上には、受光層１の表面をできる限り低ダメージで形成することが必要となる。図１の構造の太陽電池セルでは、短波長領域の効率向上が可能である。 As a conventional optical confinement technique, one using a light-receiving layer 1 processed into a texture structure or a nanopillar structure is known. However, it is also known that processing the light-receiving layer 1 damages the surface layer and significantly reduces the power generation efficiency in the short wavelength region. In the first embodiment, the antireflection effect is improved to some extent by being formed on the light-receiving layer 1 having a texture structure. In order to further improve the efficiency in the short wavelength region, it is necessary to form the surface of the light receiving layer 1 with as little damage as possible. In the solar cell having the structure of FIG. 1, the efficiency in the short wavelength region can be improved.
　＜太陽電池セルの製造方法＞
　図６Ａ、図６Ｂ、図６Ｃは、本実施の形態１の太陽電池セルの製造方法を示す断面図である。図６Ａ～図６Ｃを用いて、上述した構造の太陽電池セルの製造方法の各工程について説明する。 <Solar cell manufacturing method>
6A, 6B, and 6C are cross-sectional views illustrating the method for manufacturing the solar battery cell of the first embodiment. Each step of the method for manufacturing the solar cell having the above-described structure will be described with reference to FIGS. 6A to 6C.
　まず、シリコン基板にｐｎ接合を作製し、受光層１を形成する。形成後の構造の断面図を図６Ａに示す。ｐｎ接合の作製は、例えば、ｐ型の不純物を導入したシリコン基板のｐ型半導体層と、ｎ型の不純物を導入したｎ型半導体層とから作製する。シリコン基板への不純物ドープは、例えば、イオン打ち込み法、固相拡散法、気相拡散法などによって形成する。 First, a pn junction is formed on a silicon substrate, and the light receiving layer 1 is formed. A cross-sectional view of the structure after formation is shown in FIG. 6A. For example, the pn junction is manufactured from a p-type semiconductor layer of a silicon substrate into which a p-type impurity is introduced and an n-type semiconductor layer into which an n-type impurity is introduced. Impurity doping to the silicon substrate is formed by, for example, ion implantation, solid phase diffusion, or vapor phase diffusion.
　その後、受光層１上に、金属層２を、例えばスパッタ法やめっき法で形成し、さらに、例えばウェット加工プロセスもしくはドライ加工プロセスにより、金属層２に金属パターン８を形成する。その他に、例えばナノインプリント法を用いて金属パターン８を形成することもできる。形成後の構造の断面図を図６Ｂに示す。金属層２は、ＡｇおよびＡｌの少なくとも１種類の材料から構成される。金属層２に形成する金属パターン８は、入射する太陽光の波長より小さい周期パターン構造にする。 Thereafter, the metal layer 2 is formed on the light receiving layer 1 by, for example, a sputtering method or a plating method, and further, a metal pattern 8 is formed on the metal layer 2 by, for example, a wet processing process or a dry processing process. In addition, the metal pattern 8 can also be formed using, for example, a nanoimprint method. A cross-sectional view of the structure after formation is shown in FIG. 6B. The metal layer 2 is composed of at least one material of Ag and Al. The metal pattern 8 formed on the metal layer 2 has a periodic pattern structure smaller than the wavelength of incident sunlight.
　次に、金属層２上を覆うように、第１の誘電体層３、第２の誘電体層４、第３の誘電体層５を、この順で、例えばＣＶＤ法などの成膜法によって形成する。形成後の構造の断面図を図６Ｃに示す。この時の第１の誘電体層３の膜厚ｔ１は、光の波長（λ）の１／４以下にする。すなわち、第１の誘電体層３の膜厚ｔ１は、入射する太陽光の波長に基づいた厚さ（λ／４）以下にする。例えば、太陽光の波長が３００ｎｍの場合、第１の誘電体層３の膜厚ｔ１は３００／４＝７５ｎｍとなり、また、太陽光の波長が５００ｎｍの場合、第１の誘電体層３の膜厚ｔ１は５００／４＝１２５ｎｍとなる。もし、第１の誘電体層３の膜厚が光の波長の１／４以上になると、光学干渉により、短波長領域の反射率が増大し、効率低下を引き起こす。また、第２の誘電体層４の膜厚ｔ２を、光の波長（λ）の１／４以下（入射する太陽光の波長に基づいた厚さ（λ／４）以下）にする。第１の誘電体層３の膜厚ｔ１と、第２の誘電体層４の膜厚ｔ２と、第３の誘電体層５の膜厚ｔ３との関係は、ｔ１＜ｔ３、ｔ２＜ｔ３である。 Next, the first dielectric layer 3, the second dielectric layer 4, and the third dielectric layer 5 are formed in this order by a film forming method such as a CVD method so as to cover the metal layer 2. Form. A cross-sectional view of the structure after formation is shown in FIG. 6C. At this time, the thickness t1 of the first dielectric layer 3 is set to ¼ or less of the wavelength (λ) of light. That is, the thickness t1 of the first dielectric layer 3 is set to a thickness (λ / 4) or less based on the wavelength of incident sunlight. For example, when the wavelength of sunlight is 300 nm, the film thickness t1 of the first dielectric layer 3 is 300/4 = 75 nm, and when the wavelength of sunlight is 500 nm, the film of the first dielectric layer 3 The thickness t1 is 500/4 = 125 nm. If the film thickness of the first dielectric layer 3 is ¼ or more of the wavelength of light, the reflectance in the short wavelength region increases due to optical interference, causing a reduction in efficiency. The film thickness t2 of the second dielectric layer 4 is set to ¼ or less of the light wavelength (λ) (thickness (λ / 4) or less based on the wavelength of incident sunlight). The relationship between the film thickness t1 of the first dielectric layer 3, the film thickness t2 of the second dielectric layer 4, and the film thickness t3 of the third dielectric layer 5 is t1 <t3 and t2 <t3. is there.
　また、第１の誘電体層３の屈折率ｎ１と、第２の誘電体層４の屈折率ｎ２と、第３の誘電体層５の屈折率ｎ３との関係は、ｎ３＜ｎ２＜ｎ１である。もし、屈折率の大小が反転すると、受光層１に到達する光の総量が低下する。反射防止効果は、最低２種類の誘電体層を用いることで現れるため、必要に応じて、第１の誘電体層３と第２の誘電体層４との２層の誘電体層を用いても良い。もしくは、３層以上の誘電体層を用いても良い。また、誘電体層の材料については、上記の関係（膜厚、反射率）を満たす透明誘電材料であれば、同様な効果を得ることが可能である。例えば、第１の誘電体層３にＳｉＮＸ、第２の誘電体層４にＳｉＯＮ、第３の誘電体層５にＳｉＯ２を用いる。ここで、第２の誘電体層４にＳｉＯ２を用いた場合、第３の誘電体層５は、１．４５以下の屈折率が好ましい。 The relationship between the refractive index n1 of the first dielectric layer 3, the refractive index n2 of the second dielectric layer 4, and the refractive index n3 of the third dielectric layer 5 is n3 <n2 <n1. is there. If the refractive index is reversed, the total amount of light reaching the light receiving layer 1 is reduced. Since the antireflection effect appears by using at least two kinds of dielectric layers, if necessary, two dielectric layers of the first dielectric layer 3 and the second dielectric layer 4 are used. Also good. Alternatively, three or more dielectric layers may be used. As for the material of the dielectric layer, the same effect can be obtained as long as it is a transparent dielectric material satisfying the above relationship (film thickness, reflectance). For example, SiN x is used for the first dielectric layer 3, SiON is used for the second dielectric layer 4, and SiO 2 is used for the third dielectric layer 5. In the case of using the SiO 2 in the second dielectric layer 4, a third dielectric layer 5 is preferably 1.45 or less in refractive index.
　最後に、表面電極６と裏面電極７とを形成して、表面電極６および裏面電極７を受光層１と接続することにより、図１に示した太陽電池セルを得ることができる。また、必要に応じて、各層の形成時に、窒素雰囲気中および水素雰囲気中でのアニールを施しても良い。 Finally, the front surface electrode 6 and the back surface electrode 7 are formed, and the front surface electrode 6 and the back surface electrode 7 are connected to the light receiving layer 1, whereby the solar battery cell shown in FIG. 1 can be obtained. If necessary, annealing may be performed in a nitrogen atmosphere and a hydrogen atmosphere when forming each layer.
　＜実施の形態１の効果＞
　以上説明した本実施の形態１によれば、パターン化した金属層２とそれを覆うように形成した第１の誘電体層３との組み合わせにより、入射した太陽光のうちの表面プラズモン共鳴に相当する光について、プラズモン共鳴が生じ、金属層２付近の電場が局所的に著しく増強され、受光層１の吸収効率を向上させる。また、パターン化した金属層２と複数の誘電体層３，４，５とを組み合わせることで、反射防止効果も同時に得られる。その結果、短波長領域の効率を高めることで、太陽電池セルの変換効率を改善する効果を得ることができる。また、高効率に有効なマルチエキシトン生成を利用した太陽電池セルにこの技術を適用し、短波長領域でのマルチエキシトンによる効率向上が可能となる。従って、本実施の形態１によれば、短波長領域の効率向上と反射率低減を両立する太陽電池セルを提供することができる。 <Effect of Embodiment 1>
According to the first embodiment described above, the combination of the patterned metal layer 2 and the first dielectric layer 3 formed so as to cover the metal layer 2 corresponds to surface plasmon resonance in incident sunlight. As for the light to be emitted, plasmon resonance occurs, and the electric field in the vicinity of the metal layer 2 is remarkably enhanced locally, improving the absorption efficiency of the light receiving layer 1. Further, by combining the patterned metal layer 2 and the plurality of dielectric layers 3, 4, 5, an antireflection effect can be obtained at the same time. As a result, the effect of improving the conversion efficiency of the solar battery cell can be obtained by increasing the efficiency in the short wavelength region. In addition, this technique can be applied to solar cells that utilize highly efficient multi-exciton generation, and the efficiency can be improved by multi-excitons in the short wavelength region. Therefore, according to the first embodiment, it is possible to provide a solar battery cell that achieves both efficiency improvement and reflectance reduction in the short wavelength region.
　［実施の形態２］
　実施の形態２について、図７～図８を用いて説明する。本実施の形態２では、前記実施の形態１と違う点を主に説明する。 [Embodiment 2]
The second embodiment will be described with reference to FIGS. In the second embodiment, differences from the first embodiment will be mainly described.
　＜太陽電池セルの構造、および製造方法＞
　図７は、本実施の形態２の太陽電池セルの金属層近傍を示す断面図である。本実施の形態２の太陽電池セルは、ｐｎ接合を有する基板からなる受光層１上に、酸化膜９、金属層２、第１の誘電体層３、第２の誘電体層４、および第３の誘電体層５が形成された太陽電池セルである。前記実施の形態１との違いは、受光層１と金属層２との間に酸化膜９を挿入した点である。 <Structure of Solar Cell and Manufacturing Method>
FIG. 7 is a cross-sectional view showing the vicinity of the metal layer of the solar battery cell according to the second embodiment. In the solar cell of the second embodiment, an oxide film 9, a metal layer 2, a first dielectric layer 3, a second dielectric layer 4, and a first dielectric layer are formed on a light receiving layer 1 made of a substrate having a pn junction. 3 is a solar battery cell in which three dielectric layers 5 are formed. The difference from the first embodiment is that an oxide film 9 is inserted between the light receiving layer 1 and the metal layer 2.
　受光層１は、ｐ型の不純物を導入したシリコン基板などのｐ型半導体層と、ｎ型の不純物を導入したシリコンなどのｎ型半導体層とからなるｐｎ接合を有している。本実施の形態２による太陽電池セルは、受光層１上に、熱酸化により酸化膜９が形成され、この酸化膜９上にＡｌやＡｇなどの金属層２のナノパターンが形成され、この金属層２を覆うように第１の誘電体層３が形成され、第１の誘電体層３上に第２の誘電体層４が形成され、第２の誘電体層４上に第３の誘電体層５が形成された構成を有する。 The light-receiving layer 1 has a pn junction composed of a p-type semiconductor layer such as a silicon substrate into which p-type impurities are introduced and an n-type semiconductor layer such as silicon into which n-type impurities are introduced. In the solar battery cell according to the second embodiment, an oxide film 9 is formed on the light receiving layer 1 by thermal oxidation, and a nano pattern of the metal layer 2 such as Al or Ag is formed on the oxide film 9. A first dielectric layer 3 is formed so as to cover the layer 2, a second dielectric layer 4 is formed on the first dielectric layer 3, and a third dielectric layer 4 is formed on the second dielectric layer 4. The body layer 5 is formed.
　ここで、酸化膜９は、シリコン表面を熱酸化することで形成する。この酸化膜９の膜厚について、図８を用いて説明する。図８は、酸化膜９の膜厚と短波長領域の平均反射率（光の波長：３００－５００ｎｍ）との関係を示すグラフである。図８に示すように、酸化膜９の厚みは、膜厚が厚いほど、表面プラズモンカップリングが弱まり、反射率が増加する傾向を有するため、２０ｎｍ以下が好ましい。この酸化膜９を挿入することで、シリコン表面のトラップ準位密度を抑制できるため、短波長領域の効率向上が可能となる。 Here, the oxide film 9 is formed by thermally oxidizing the silicon surface. The thickness of the oxide film 9 will be described with reference to FIG. FIG. 8 is a graph showing the relationship between the thickness of the oxide film 9 and the average reflectance (light wavelength: 300-500 nm) in the short wavelength region. As shown in FIG. 8, the thickness of the oxide film 9 is preferably 20 nm or less because the surface plasmon coupling tends to weaken and reflectivity increases as the film thickness increases. By inserting this oxide film 9, the trap level density on the silicon surface can be suppressed, so that the efficiency in the short wavelength region can be improved.
　本実施の形態２では、前記実施の形態１と同様に、入射した太陽光の３００ｎｍから５００ｎｍの波長の光でプラズモン共鳴を生じさせ、上記の波長域の光を強めて受光層１で吸収するようにしている。表面プラズモンによる受光層１の吸収を高めるには、金属層２の金属パターン８を、表面プラズモンカップリングする波長以下の間隔ａで配置し、パターンサイズｂも表面プラズモンカップリングする波長以下に配置することが必要となる。もし、配置間隔ａやパターンサイズｂを表面プラズモンカップリングする波長以上にすると、カップリングそのものが弱くなり、電場増強効果が低下し、効率低下を引き起こす。 In the second embodiment, as in the first embodiment, plasmon resonance is generated by light having a wavelength of 300 nm to 500 nm of incident sunlight, and the light in the wavelength region is strengthened and absorbed by the light receiving layer 1. I am doing so. In order to enhance the absorption of the light receiving layer 1 by the surface plasmon, the metal pattern 8 of the metal layer 2 is arranged at an interval a which is not more than the wavelength for surface plasmon coupling, and the pattern size b is also arranged to be not more than the wavelength for surface plasmon coupling. It will be necessary. If the arrangement interval a and the pattern size b are longer than the wavelength for surface plasmon coupling, the coupling itself becomes weak, the electric field enhancing effect is lowered, and the efficiency is lowered.
　また、金属層２の金属パターン８以外に、短波長から可視領域で表面プラズモン共鳴を生じさせ、受光層１での光吸収を増大させるためには、第１の誘電体層３の屈折率が重要となる。前記実施の形態１と同様に、１．８以上の屈折率を有する第１の誘電体層３にすることで、短波長領域の光吸収が増加し、反射率を低減させることができる。 In addition to the metal pattern 8 of the metal layer 2, in order to cause surface plasmon resonance from a short wavelength to a visible region and increase light absorption in the light receiving layer 1, the refractive index of the first dielectric layer 3 is It becomes important. As in the first embodiment, by using the first dielectric layer 3 having a refractive index of 1.8 or more, light absorption in the short wavelength region increases, and the reflectance can be reduced.
　また、入射する太陽光の波長より小さい周期パターン構造にパターン化された金属層２と第１の誘電体層３は、第２の誘電体層４と第３の誘電体層５とを組み合わせることで、反射防止効果を高めている。ここで、金属層２は、膜厚が厚くなると反射層として機能することが知られており、前記実施の形態１と同様に、反射防止効果を同時に高めるため、金属層２の膜厚を２０ｎｍ以下としている。 Further, the metal layer 2 and the first dielectric layer 3 patterned in a periodic pattern structure smaller than the wavelength of incident sunlight are combined with the second dielectric layer 4 and the third dielectric layer 5. Therefore, the antireflection effect is enhanced. Here, it is known that the metal layer 2 functions as a reflection layer when the film thickness is increased. Similarly to the first embodiment, the metal layer 2 has a film thickness of 20 nm in order to simultaneously enhance the antireflection effect. It is as follows.
　また、前記実施の形態１と同様に、金属層２上を覆うように、第１の誘電体層３、第２の誘電体層４、第３の誘電体層５を、この順で、例えばＣＶＤ法などの成膜法によって形成する。この時の第１の誘電体層３の膜厚ｔ１は、光の波長（λ）の１／４以下にする。もし、第１の誘電体層３の膜厚が光の波長の１／４以上になると、光学干渉により、短波長領域の反射率が増大し、効率低下を引き起こす。また、第２の誘電体層４の膜厚ｔ２を、光の波長（λ）の１／４以下にする。第１の誘電体層３の膜厚ｔ１と、第２の誘電体層４の膜厚ｔ２と、第３の誘電体層５の膜厚ｔ３との関係は、ｔ１＜ｔ３、ｔ２＜ｔ３である。 Similarly to the first embodiment, the first dielectric layer 3, the second dielectric layer 4, and the third dielectric layer 5 are arranged in this order so as to cover the metal layer 2, for example. It is formed by a film forming method such as a CVD method. At this time, the thickness t1 of the first dielectric layer 3 is set to ¼ or less of the wavelength (λ) of light. If the film thickness of the first dielectric layer 3 is ¼ or more of the wavelength of light, the reflectance in the short wavelength region increases due to optical interference, causing a reduction in efficiency. Further, the film thickness t2 of the second dielectric layer 4 is set to ¼ or less of the wavelength (λ) of light. The relationship between the film thickness t1 of the first dielectric layer 3, the film thickness t2 of the second dielectric layer 4, and the film thickness t3 of the third dielectric layer 5 is t1 <t3 and t2 <t3. is there.
　また、第１の誘電体層３の屈折率ｎ１と、第２の誘電体層４の屈折率ｎ２と、第３の誘電体層５の屈折率ｎ３との関係は、ｎ３＜ｎ２＜ｎ１である。もし、屈折率の大小が反転すると、受光層１に到達する光の総量が低下する。反射防止効果は、最低２種類の誘電体層を用いることで現れるため、必要に応じて、２層もしくは３層以上の誘電体層を用いても良い。また、誘電体層の材料については、上記の関係を満たす透明誘電材料であれば、同様な効果を得ることが可能である。例えば、第１の誘電体層３にＳｉＮＸ、第２の誘電体層４にＳｉＯＮ、第３の誘電体層５にＳｉＯ２を用いる。ここで、第２の誘電体層にＳｉＯ２を用いた場合、第３の誘電体層５は、１．４５以下の屈折率が好ましい。 The relationship between the refractive index n1 of the first dielectric layer 3, the refractive index n2 of the second dielectric layer 4, and the refractive index n3 of the third dielectric layer 5 is n3 <n2 <n1. is there. If the refractive index is reversed, the total amount of light reaching the light receiving layer 1 is reduced. Since the antireflection effect appears by using at least two types of dielectric layers, two or more dielectric layers may be used as necessary. As for the material of the dielectric layer, the same effect can be obtained as long as it is a transparent dielectric material satisfying the above relationship. For example, SiN x is used for the first dielectric layer 3, SiON is used for the second dielectric layer 4, and SiO 2 is used for the third dielectric layer 5. Here, when SiO 2 is used for the second dielectric layer, the third dielectric layer 5 preferably has a refractive index of 1.45 or less.
　最後に、表面電極６と裏面電極７とを形成して、表面電極６および裏面電極７を受光層１と接続することにより、太陽電池セルを得ることができる。また、必要に応じて、各層の形成時に、窒素雰囲気中および水素雰囲気中でのアニールを施しても良い。 Finally, the solar cell can be obtained by forming the front electrode 6 and the back electrode 7 and connecting the front electrode 6 and the back electrode 7 to the light receiving layer 1. If necessary, annealing may be performed in a nitrogen atmosphere and a hydrogen atmosphere when forming each layer.
　＜実施の形態２の効果＞
　本実施の形態２によれば、パターン化した金属層２とそれを覆うように形成した第１の誘電体層３との組み合わせにより、入射した太陽光のうちの表面プラズモン共鳴に相当する光について、プラズモン共鳴が生じ、金属層２付近の電場が局所的に著しく増強され、受光層１の吸収効率を向上させる。また、パターン化した金属層２と複数の誘電体層３，４，５とを組み合わせることで、反射防止効果も同時に得られる。その結果、短波長領域の効率を高めることで、太陽電池セルの変換効率を改善する効果を得ることができる。また、高効率に有効なマルチエキシトン生成を利用した太陽電池セルにこの技術を適用し、短波長領域でのマルチエキシトンによる効率向上が可能となる。従って、本実施の形態２によれば、短波長領域の効率向上と反射率低減を両立する太陽電池セルを提供することができる。特に、本実施の形態２では、酸化膜９を挿入することで、シリコン表面のトラップ準位密度を抑制できるため、より一層、短波長領域の効率向上が可能となる。 <Effect of Embodiment 2>
According to the second embodiment, a combination of the patterned metal layer 2 and the first dielectric layer 3 formed so as to cover the metal layer 2 allows light corresponding to surface plasmon resonance in incident sunlight. As a result, plasmon resonance occurs, and the electric field in the vicinity of the metal layer 2 is remarkably enhanced locally, thereby improving the absorption efficiency of the light receiving layer 1. Further, by combining the patterned metal layer 2 and the plurality of dielectric layers 3, 4, 5, an antireflection effect can be obtained at the same time. As a result, the effect of improving the conversion efficiency of the solar battery cell can be obtained by increasing the efficiency in the short wavelength region. In addition, this technique can be applied to solar cells that utilize highly efficient multi-exciton generation, and the efficiency can be improved by multi-excitons in the short wavelength region. Therefore, according to the second embodiment, it is possible to provide a solar battery cell that achieves both efficiency improvement and reflectance reduction in the short wavelength region. In particular, in the second embodiment, by inserting the oxide film 9, the trap level density on the silicon surface can be suppressed, so that the efficiency in the short wavelength region can be further improved.
　［実施の形態３］
　実施の形態３について、図９を用いて説明する。本実施の形態３は、前記実施の形態１および２で説明した太陽電池セルを用いた太陽電池システムの例である。 [Embodiment 3]
Embodiment 3 will be described with reference to FIG. The third embodiment is an example of a solar battery system using the solar battery cells described in the first and second embodiments.
　＜太陽電池システム＞
　図９は、本実施の形態３の太陽電池セルを用いた太陽電池システムを示す構成図である。本実施の形態３は、前記実施の形態１および２の太陽電池セルを用いた太陽電池システムである。太陽電池システムは、太陽電池パネル１１と、接続箱１２と、集電箱１３と、パワーコンディショナー１４と、変圧器１５とを有する。 <Solar cell system>
FIG. 9 is a configuration diagram showing a solar battery system using the solar battery cell according to the third embodiment. The third embodiment is a solar battery system using the solar battery cells of the first and second embodiments. The solar cell system includes a solar cell panel 11, a connection box 12, a current collection box 13, a power conditioner 14, and a transformer 15.
　太陽電池パネル１１は、前記実施の形態１および２で説明した太陽電池セルを複数配置した太陽電池パネルである。この太陽電池パネル１１は、太陽光により電力を発電するパネルである。接続箱１２は、太陽電池パネル１１により発電された電力を集電箱１３へ送電する接続箱である。集電箱１３は、接続箱１２から送電されてきた電力を集約してパワーコンディショナー１４へ送電する集電箱である。パワーコンディショナー１４は、集電箱１３から送電されてきた電力を直流から交流へ変換して変圧器１５へ送電する変換器である。変圧器１５は、パワーコンディショナー１４から送電されてきた交流電力の電圧を変圧して商用電力系統１６へ送電する変圧器である。 Solar cell panel 11 is a solar cell panel in which a plurality of solar cells described in the first and second embodiments are arranged. This solar cell panel 11 is a panel that generates electric power by sunlight. The connection box 12 is a connection box that transmits the electric power generated by the solar cell panel 11 to the current collection box 13. The current collection box 13 is a current collection box that collects the electric power transmitted from the connection box 12 and transmits it to the power conditioner 14. The power conditioner 14 is a converter that converts the electric power transmitted from the current collection box 13 from direct current to alternating current and transmits the electric power to the transformer 15. The transformer 15 is a transformer that transforms the voltage of the AC power transmitted from the power conditioner 14 and transmits it to the commercial power system 16.
　図９の例では、商用電力系統１６に接続される１つの変圧器１５に対して、３系統のパワーコンディショナー１４および集電箱１３が接続されている。さらに、各１系統のパワーコンディショナー１４および集電箱１３に対して、３系統の接続箱１２および太陽電池パネル１１が接続されている。 In the example of FIG. 9, three power conditioners 14 and a current collection box 13 are connected to one transformer 15 connected to the commercial power system 16. Further, a three-system connection box 12 and a solar cell panel 11 are connected to each one-system power conditioner 14 and current collection box 13.
　本実施の形態３の太陽電池システムにおいて、太陽電池パネル１１で発電された電力は、接続箱１２へと送電され、集電箱１３で集約される。その後、パワーコンディショナー１４で、直流から交流へと変換され、纏めて変圧器１５で電圧を変圧し、商用電力系統１６に接続される。なお、上記構成は、太陽電池システムの中でも、特に、パネル枚数の多いメガソーラーシステムの構成例である。パネル枚数の比較的少ない住宅用システムの場合には、接続箱１２から直接、パワーコンディショナー１４へと接続される。 In the solar cell system of the third embodiment, the electric power generated by the solar cell panel 11 is transmitted to the connection box 12 and collected by the current collection box 13. Thereafter, the power conditioner 14 converts the current from direct current to alternating current, transforms the voltage together with the transformer 15, and connects to the commercial power system 16. In addition, the said structure is a structural example of the mega solar system with many panel numbers especially in a solar cell system. In the case of a residential system with a relatively small number of panels, it is directly connected to the power conditioner 14 from the connection box 12.
　以上のようにして、本実施の形態３の太陽電池システムを実現することができる。本実施の形態３の太陽電池システムでは、太陽電池セルの構造による効果を活かして、太陽光発電の高効率化が可能となる。 As described above, the solar cell system of Embodiment 3 can be realized. In the solar cell system according to the third embodiment, it is possible to increase the efficiency of solar power generation by taking advantage of the effect of the solar cell structure.
　［付記］
　（Ａ）本発明は、太陽電池セルの製造方法として、以下の特徴を有する。
（１）ｐｎ接合を有する基板を形成する第１工程と、
　前記基板上に、入射する光の波長より小さい周期パターン構造を有する金属層を形成する第２工程と、
　前記金属層を覆うように第１の誘電体層を形成する第３工程と、
　を有し、
　前記第３工程では、前記第１の誘電体層の膜厚を、前記入射する光の波長に基づいた厚さ（λ／４）以下にする、太陽電池セルの製造方法。
（２）前記（１）記載の太陽電池セルの製造方法において、
　前記第２工程では、前記金属層として、前記周期パターン構造の金属パターンを形成する工程を含み、
　前記金属パターンの配置間隔ａおよび前記金属パターンのパターンサイズｂを、前記入射する光の波長以下にし、
　前記金属パターンの配置間隔ａと前記金属パターンのパターンサイズｂとの関係を、ａ＞ｂにする、太陽電池セルの製造方法。
（３）前記（１）記載の太陽電池セルの製造方法において、
　前記金属層の材質は、ＡｇおよびＡｌの少なくとも１種類から構成され、
　前記金属層の膜厚を、５ｎｍ以上、かつ、２０ｎｍ以下にする、太陽電池セルの製造方法。
（４）前記（１）記載の太陽電池セルの製造方法において、
　前記第１の誘電体層の屈折率を、１．８以上にする、太陽電池セルの製造方法。
（５）前記（４）記載の太陽電池セルの製造方法において、
　前記第１の誘電体層上に、第２の誘電体層と第３の誘電体層とをこの順で、少なくとも１層以上積層して形成する第４工程を有し、
　前記第１の誘電体層の屈折率ｎ１と前記第２の誘電体層の屈折率ｎ２と前記第３の誘電体層の屈折率ｎ３との関係を、ｎ１＞ｎ２＞ｎ３にする、太陽電池セルの製造方法。
（６）前記（１）記載の太陽電池セルの製造方法において、
　前記第２の誘電体層の膜厚ｔ２を、前記入射する光の波長に基づいた厚さ（λ／４）以下にし、
　前記第３の誘電体層の膜厚ｔ３と前記第２の誘電体層の膜厚ｔ２との関係を、ｔ３＞ｔ２にする、太陽電池セルの製造方法。
（７）ｐｎ接合を有する基板を形成する第１工程と、
　前記基板上に酸化膜を形成する第２工程と、
　前記酸化膜上に、入射する光の波長より小さい周期パターン構造を有する金属層を形成する第３工程と、
　前記金属層を覆うように第１の誘電体層を形成する第４工程と、
　を有し、
　前記第４工程では、前記第１の誘電体層の膜厚を、前記入射する光の波長に基づいた厚さ（λ／４）以下にする、太陽電池セルの製造方法。
（８）前記（７）記載の太陽電池セルの製造方法において、
　前記酸化膜の膜厚を、２０ｎｍ以下にする、太陽電池セルの製造方法。
（９）前記（７）記載の太陽電池セルの製造方法において、
　前記第３工程では、前記金属層として、前記周期パターン構造の金属パターンを形成する工程を含み、
　前記金属パターンの配置間隔ａおよび前記金属パターンのパターンサイズｂを、前記入射する光の波長以下にし、
　前記金属パターンの配置間隔ａと前記金属パターンのパターンサイズｂとの関係を、ａ＞ｂにする、太陽電池セルの製造方法。
（１０）前記（７）記載の太陽電池セルの製造方法において、
　前記金属層の材質は、ＡｇおよびＡｌの少なくとも１種類から構成され、
　前記金属層の膜厚を、５ｎｍ以上、かつ、２０ｎｍ以下にする、太陽電池セルの製造方法。
（１１）前記（７）記載の太陽電池セルの製造方法において、
　前記第１の誘電体層の屈折率を、１．８以上にする、太陽電池セルの製造方法。
（１２）前記（１１）記載の太陽電池セルの製造方法において、
　前記第１の誘電体層上に、第２の誘電体層と第３の誘電体層とをこの順で、少なくとも１層以上積層して形成する第５工程を有し、
　前記第１の誘電体層の屈折率ｎ１と前記第２の誘電体層の屈折率ｎ２と前記第３の誘電体層の屈折率ｎ３との関係を、ｎ１＞ｎ２＞ｎ３にする、太陽電池セルの製造方法。
（１３）前記（７）記載の太陽電池セルの製造方法において、
　前記第２の誘電体層の膜厚ｔ２を、前記入射する光の波長に基づいた厚さ（λ／４）以下にし、
　前記第３の誘電体層の膜厚ｔ３と前記第２の誘電体層の膜厚ｔ２との関係を、ｔ３＞ｔ２にする、太陽電池セルの製造方法。 [Appendix]
(A) This invention has the following characteristics as a manufacturing method of a photovoltaic cell.
(1) a first step of forming a substrate having a pn junction;
A second step of forming a metal layer having a periodic pattern structure smaller than the wavelength of incident light on the substrate;
A third step of forming a first dielectric layer so as to cover the metal layer;
Have
In the third step, the method of manufacturing a solar battery cell, wherein the thickness of the first dielectric layer is set to a thickness (λ / 4) or less based on the wavelength of the incident light.
(2) In the method for producing a solar battery cell according to (1),
The second step includes a step of forming a metal pattern of the periodic pattern structure as the metal layer,
The arrangement interval a of the metal pattern and the pattern size b of the metal pattern are set to be equal to or less than the wavelength of the incident light,
The manufacturing method of the photovoltaic cell which makes the relationship of the arrangement | positioning space | interval a of the said metal pattern, and the pattern size b of the said metal pattern a> b.
(3) In the method for producing a solar battery cell according to (1),
The material of the metal layer is composed of at least one of Ag and Al,
The manufacturing method of the photovoltaic cell which makes the film thickness of the said metal layer 5 nm or more and 20 nm or less.
(4) In the method for producing a solar battery cell according to (1),
A method for manufacturing a solar battery cell, wherein the refractive index of the first dielectric layer is 1.8 or more.
(5) In the method for manufacturing a solar battery cell according to (4),
A fourth step of forming at least one layer of a second dielectric layer and a third dielectric layer in this order on the first dielectric layer;
A solar cell in which the relationship between the refractive index n1 of the first dielectric layer, the refractive index n2 of the second dielectric layer, and the refractive index n3 of the third dielectric layer satisfies n1>n2> n3. Cell manufacturing method.
(6) In the method for producing a solar battery cell according to (1),
The film thickness t2 of the second dielectric layer is set to a thickness (λ / 4) or less based on the wavelength of the incident light,
A method for manufacturing a solar battery cell, wherein a relationship between a film thickness t3 of the third dielectric layer and a film thickness t2 of the second dielectric layer satisfies t3> t2.
(7) a first step of forming a substrate having a pn junction;
A second step of forming an oxide film on the substrate;
A third step of forming a metal layer having a periodic pattern structure smaller than the wavelength of incident light on the oxide film;
A fourth step of forming a first dielectric layer so as to cover the metal layer;
Have
In the fourth step, the method of manufacturing a solar battery cell, wherein the thickness of the first dielectric layer is set to a thickness (λ / 4) or less based on the wavelength of the incident light.
(8) In the method for producing a solar battery cell according to (7),
The manufacturing method of the photovoltaic cell which sets the film thickness of the said oxide film to 20 nm or less.
(9) In the method for producing a solar battery cell according to (7),
The third step includes a step of forming a metal pattern of the periodic pattern structure as the metal layer,
The arrangement interval a of the metal pattern and the pattern size b of the metal pattern are set to be equal to or less than the wavelength of the incident light,
The manufacturing method of the photovoltaic cell which makes the relationship of the arrangement | positioning space | interval a of the said metal pattern, and the pattern size b of the said metal pattern a> b.
(10) In the method for producing a solar battery cell according to (7),
The material of the metal layer is composed of at least one of Ag and Al,
The manufacturing method of the photovoltaic cell which makes the film thickness of the said metal layer 5 nm or more and 20 nm or less.
(11) In the method for producing a solar battery cell according to (7),
A method for manufacturing a solar battery cell, wherein the refractive index of the first dielectric layer is 1.8 or more.
(12) In the method for producing a solar battery cell according to (11),
A fifth step of stacking at least one second dielectric layer and a third dielectric layer in this order on the first dielectric layer; and
A solar cell in which the relationship between the refractive index n1 of the first dielectric layer, the refractive index n2 of the second dielectric layer, and the refractive index n3 of the third dielectric layer satisfies n1>n2> n3. Cell manufacturing method.
(13) In the method for producing a solar battery cell according to (7),
The film thickness t2 of the second dielectric layer is set to a thickness (λ / 4) or less based on the wavelength of the incident light,
A method for manufacturing a solar battery cell, wherein a relationship between a film thickness t3 of the third dielectric layer and a film thickness t2 of the second dielectric layer satisfies t3> t2.
　（Ｂ）本発明は、太陽電池システムとして、以下の特徴を有する。
（２１）太陽電池セルを複数配置した太陽電池パネルと、
　前記太陽電池パネルで発電された電力を直流から交流へ変換するパワーコンディショナーと、
　前記パワーコンディショナーで変換された交流電力を変圧して電力系統へ出力する変圧器と、
　を有し、
　前記太陽電池セルは、
　ｐｎ接合を有する基板と、
　前記基板上に形成され、入射する光の波長より小さい周期パターン構造を有する金属層と、
　前記金属層を覆うように形成された第１の誘電体層と、
　を有し、
　前記第１の誘電体層の膜厚は、前記入射する光の波長に基づいた厚さ（λ／４）以下である、太陽電池システム。
（２２）太陽電池セルを複数配置した太陽電池パネルと、
　前記太陽電池パネルで発電された電力を直流から交流へ変換するパワーコンディショナーと、
　前記パワーコンディショナーで変換された交流電力を変圧して電力系統へ出力する変圧器と、
　を有し、
　前記太陽電池セルは、
　ｐｎ接合を有する基板と、
　前記基板上に形成された酸化膜と、
　前記酸化膜上に形成され、入射する光の波長より小さい周期パターン構造を有する金属層と、
　前記金属層を覆うように形成された第１の誘電体層と、
　を有し、
　前記第１の誘電体層の膜厚は、前記入射する光の波長に基づいた厚さ（λ／４）以下である、太陽電池システム。 (B) This invention has the following characteristics as a solar cell system.
(21) a solar panel in which a plurality of solar cells are arranged;
A power conditioner that converts electric power generated by the solar cell panel from direct current to alternating current;
A transformer that transforms AC power converted by the power conditioner and outputs the transformed power to the power system;
Have
The solar battery cell is
a substrate having a pn junction;
A metal layer formed on the substrate and having a periodic pattern structure smaller than the wavelength of incident light;
A first dielectric layer formed to cover the metal layer;
Have
The thickness of the first dielectric layer is a solar cell system having a thickness (λ / 4) or less based on the wavelength of the incident light.
(22) a solar cell panel in which a plurality of solar cells are arranged;
A power conditioner that converts electric power generated by the solar cell panel from direct current to alternating current;
A transformer that transforms AC power converted by the power conditioner and outputs the transformed power to the power system;
Have
The solar battery cell is
a substrate having a pn junction;
An oxide film formed on the substrate;
A metal layer formed on the oxide film and having a periodic pattern structure smaller than the wavelength of incident light;
A first dielectric layer formed to cover the metal layer;
Have
The thickness of the first dielectric layer is a solar cell system having a thickness (λ / 4) or less based on the wavelength of the incident light.
　以上、本発明者によってなされた発明をその実施の形態に基づき具体的に説明したが、本発明は前記実施の形態に限定されるものではなく、その要旨を逸脱しない範囲で種々変更可能であることは言うまでもない。 As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.
１…受光層
２…金属層
３…第１の誘電体層
４…第２の誘電体層
５…第３の誘電体層
６…表面電極
７…裏面電極
８…金属パターン
９…酸化膜
  DESCRIPTION OF SYMBOLS 1 ... Light reception layer 2 ... Metal layer 3 ... 1st dielectric material layer 4 ... 2nd dielectric material layer 5 ... 3rd dielectric material layer 6 ... Front surface electrode 7 ... Back surface electrode 8 ... Metal pattern 9 ... Oxide film

Claims (13)

  1. 　ｐｎ接合を有する基板と、
    　前記基板上に形成され、入射する光の波長より小さい周期パターン構造を有する金属層と、
    　前記金属層を覆うように形成された第１の誘電体層と、
    　を有し、
    　前記第１の誘電体層の膜厚は、前記入射する光の波長に基づいた厚さ（λ／４）以下である、太陽電池セル。     a substrate having a pn junction;
    A metal layer formed on the substrate and having a periodic pattern structure smaller than the wavelength of incident light;
    A first dielectric layer formed to cover the metal layer;
    Have
    The solar battery cell, wherein the first dielectric layer has a thickness (λ / 4) or less based on the wavelength of the incident light.
  2. 　請求項１記載の太陽電池セルにおいて、
    　前記金属層は、前記周期パターン構造の金属パターンを有し、
    　前記金属パターンの配置間隔ａおよび前記金属パターンのパターンサイズｂは、前記入射する光の波長以下であり、
    　前記金属パターンの配置間隔ａと前記金属パターンのパターンサイズｂとの関係は、ａ＞ｂである、太陽電池セル。     The solar battery cell according to claim 1,
    The metal layer has a metal pattern of the periodic pattern structure,
    The arrangement interval a of the metal pattern and the pattern size b of the metal pattern are not more than the wavelength of the incident light,
    The relationship between the arrangement interval a of the metal pattern and the pattern size b of the metal pattern is a solar battery cell in which a> b.
  3. 　請求項１記載の太陽電池セルにおいて、
    　前記金属層の材質は、ＡｇおよびＡｌの少なくとも１種類から構成され、
    　前記金属層の膜厚は、５ｎｍ以上、かつ、２０ｎｍ以下である、太陽電池セル。     The solar battery cell according to claim 1,
    The material of the metal layer is composed of at least one of Ag and Al,
    The film thickness of the said metal layer is a solar cell which is 5 nm or more and 20 nm or less.
  4. 　請求項１記載の太陽電池セルにおいて、
    　前記第１の誘電体層の屈折率は、１．８以上である、太陽電池セル。     The solar battery cell according to claim 1,
    The solar cell, wherein the refractive index of the first dielectric layer is 1.8 or more.
  5. 　請求項４記載の太陽電池セルにおいて、
    　前記第１の誘電体層上に、第２の誘電体層と第３の誘電体層とをこの順で、少なくとも１層以上積層して形成され、
    　前記第１の誘電体層の屈折率ｎ１と前記第２の誘電体層の屈折率ｎ２と前記第３の誘電体層の屈折率ｎ３との関係は、ｎ１＞ｎ２＞ｎ３である、太陽電池セル。     The solar battery cell according to claim 4,
    On the first dielectric layer, a second dielectric layer and a third dielectric layer are formed in this order by laminating at least one layer,
    The relationship between the refractive index n1 of the first dielectric layer, the refractive index n2 of the second dielectric layer, and the refractive index n3 of the third dielectric layer is n1>n2> n3. cell.
  6. 　請求項１記載の太陽電池セルにおいて、
    　前記第２の誘電体層の膜厚ｔ２は、前記入射する光の波長に基づいた厚さ（λ／４）以下であり、
    　前記第３の誘電体層の膜厚ｔ３と前記第２の誘電体層の膜厚ｔ２との関係は、ｔ３＞ｔ２である、太陽電池セル。     The solar battery cell according to claim 1,
    The film thickness t2 of the second dielectric layer is equal to or less than the thickness (λ / 4) based on the wavelength of the incident light,
    The solar cell in which the relationship between the film thickness t3 of the third dielectric layer and the film thickness t2 of the second dielectric layer is t3> t2.
  7. 　ｐｎ接合を有する基板と、
    　前記基板上に形成された酸化膜と、
    　前記酸化膜上に形成され、入射する光の波長より小さい周期パターン構造を有する金属層と、
    　前記金属層を覆うように形成された第１の誘電体層と、
    　を有し、
    　前記第１の誘電体層の膜厚は、前記入射する光の波長に基づいた厚さ（λ／４）以下である、太陽電池セル。     a substrate having a pn junction;
    An oxide film formed on the substrate;
    A metal layer formed on the oxide film and having a periodic pattern structure smaller than the wavelength of incident light;
    A first dielectric layer formed to cover the metal layer;
    Have
    The solar battery cell, wherein the first dielectric layer has a thickness (λ / 4) or less based on the wavelength of the incident light.
  8. 　請求項７記載の太陽電池セルにおいて、
    　前記酸化膜の膜厚は、２０ｎｍ以下である、太陽電池セル。     The solar battery cell according to claim 7, wherein
    The solar battery cell, wherein the oxide film has a thickness of 20 nm or less.
  9. 　請求項７記載の太陽電池セルにおいて、
    　前記金属層は、前記周期パターン構造の金属パターンを有し、
    　前記金属パターンの配置間隔ａおよび前記金属パターンのパターンサイズｂは、前記入射する光の波長以下であり、
    　前記金属パターンの配置間隔ａと前記金属パターンのパターンサイズｂとの関係は、ａ＞ｂである、太陽電池セル。     The solar battery cell according to claim 7, wherein
    The metal layer has a metal pattern of the periodic pattern structure,
    The arrangement interval a of the metal pattern and the pattern size b of the metal pattern are not more than the wavelength of the incident light,
    The relationship between the arrangement interval a of the metal pattern and the pattern size b of the metal pattern is a solar battery cell in which a> b.
  10. 　請求項７記載の太陽電池セルにおいて、
    　前記金属層の材質は、ＡｇおよびＡｌの少なくとも１種類から構成され、
    　前記金属層の膜厚は、５ｎｍ以上、かつ、２０ｎｍ以下である、太陽電池セル。     The solar battery cell according to claim 7, wherein
    The material of the metal layer is composed of at least one of Ag and Al,
    The film thickness of the said metal layer is a solar cell which is 5 nm or more and 20 nm or less.
  11. 　請求項７記載の太陽電池セルにおいて、
    　前記第１の誘電体層の屈折率は、１．８以上である、太陽電池セル。     The solar battery cell according to claim 7, wherein
    The solar cell, wherein the refractive index of the first dielectric layer is 1.8 or more.
  12. 　請求項１１記載の太陽電池セルにおいて、
    　前記第１の誘電体層上に、第２の誘電体層と第３の誘電体層とをこの順で、少なくとも１層以上積層して形成され、
    　前記第１の誘電体層の屈折率ｎ１と前記第２の誘電体層の屈折率ｎ２と前記第３の誘電体層の屈折率ｎ３との関係は、ｎ１＞ｎ２＞ｎ３である、太陽電池セル。     The solar battery cell according to claim 11,
    On the first dielectric layer, a second dielectric layer and a third dielectric layer are formed in this order by laminating at least one layer,
    The relationship between the refractive index n1 of the first dielectric layer, the refractive index n2 of the second dielectric layer, and the refractive index n3 of the third dielectric layer is n1>n2> n3. cell.
  13. 　請求項７記載の太陽電池セルにおいて、
    　前記第２の誘電体層の膜厚ｔ２は、前記入射する光の波長に基づいた厚さ（λ／４）以下であり、
    　前記第３の誘電体層の膜厚ｔ３と前記第２の誘電体層の膜厚ｔ２との関係は、ｔ３＞ｔ２である、太陽電池セル。
          The solar battery cell according to claim 7, wherein
    The film thickness t2 of the second dielectric layer is equal to or less than the thickness (λ / 4) based on the wavelength of the incident light,
    The solar cell in which the relationship between the film thickness t3 of the third dielectric layer and the film thickness t2 of the second dielectric layer is t3> t2.
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