JP5732162B2 - Photoelectric conversion element and manufacturing method thereof - Google Patents

Description

  The present invention relates to a photoelectric conversion element and a manufacturing method thereof.

  As one means for improving the efficiency of the solar cell, a method of converting incident sunlight into a form more suitable for photoelectric conversion can be considered. For example, there is a method of increasing carrier excitation by generating an enhanced electric field by plasmon resonance using a nanostructure. Plasmon resonance is a phenomenon in which collective vibration waves of electrons are generated on a metal surface, and it is known that an enhanced electromagnetic field generated thereby activates carrier generation.

  For example, Patent Document 1 proposes a solar cell that absorbs light using surface plasmons by using a metal nanostructure as a main component of the photosensitive layer.

WO2007 / 118815

  However, there is a demand for further improving the photoelectric conversion efficiency of the photoelectric conversion element.

  An object of the present invention is to obtain a photoelectric conversion element having high efficiency for increasing carrier excitation by an enhanced electric field.

The photoelectric conversion element according to the present invention is a photoelectric conversion element including a photoelectric conversion layer formed of two electrode layers and two or more semiconductor layers stacked between the two electrode layers, A porous thin film made of metal sandwiched between two of the two, wherein the porous thin film has a plurality of openings penetrating the metal thin film, and an average area per opening is 80 nm ² The thickness is in the range of 0.8 μm ² or less, and the thickness of the porous thin film is in the range of 2 nm to 200 nm.

Alternatively, the photoelectric conversion element according to the present invention is a photoelectric conversion element including a photoelectric conversion layer formed of two electrode layers and two or more semiconductor layers stacked between the two electrode layers, and the semiconductor Including a layer having a plurality of metal microscopic bodies sandwiched between two of the layers, and the average volume per one microscopic area is in the range of 4 nm ^{3 to} 0.52 μm ³ and adjacent to each other The average distance between the two microscopic objects is 1 nm or more and 1 μm or less.

  The manufacturing method of the photoelectric conversion element by this invention is a manufacturing method of the photoelectric conversion element of any one of Claim 1 or 2, Comprising: The process of forming an at least 1 semiconductor layer, On the said semiconductor layer A step of forming a metal thin film layer, a step of preparing a stamper having a fine concavo-convex pattern corresponding to the opening on the surface, a step of transferring a resist pattern to the at least part of the metal thin film layer using the stamper, The method includes a step of forming a pattern on the metal thin film layer using the resist pattern as an etching mask, and a step of forming at least one semiconductor layer on the metal thin film on which the pattern is formed.

  ADVANTAGE OF THE INVENTION According to this invention, the photoelectric conversion element with the high efficiency which increases carrier excitation by an augmented electric field can be provided.

1 is a schematic view of a solar cell according to an embodiment of the invention. The conceptual diagram for demonstrating the operation | movement principle of the solar cell which is one Embodiment of this invention. The schematic of the metal microstructure of the solar cell which is one Embodiment of this invention. The figure which shows the simulation result of the electric field enhancement effect. The figure which shows the simulation result of the electric field enhancement effect. The figure which shows the simulation result of the electric field enhancement effect. The schematic diagram explaining the density of a microstructure. The conceptual diagram for demonstrating the manufacturing method of the solar cell by one Embodiment of this invention. The conceptual diagram for demonstrating the manufacturing method of the solar cell by one Embodiment of this invention. The conceptual diagram for demonstrating the manufacturing method of the solar cell by one Embodiment of this invention. The conceptual diagram for demonstrating the manufacturing method of the solar cell by one Embodiment of this invention. The conceptual diagram for demonstrating the manufacturing method of the solar cell by one Embodiment of this invention. The conceptual diagram for demonstrating the manufacturing method of the solar cell by one Embodiment of this invention. The conceptual diagram for demonstrating the manufacturing method of the solar cell by one Embodiment of this invention. The conceptual diagram for demonstrating the manufacturing method of the solar cell by one Embodiment of this invention. The conceptual diagram for demonstrating the manufacturing method of the solar cell by one Embodiment of this invention. The conceptual diagram for demonstrating the manufacturing method of the solar cell by one Embodiment of this invention.

The inventors of the present invention are that the metal microstructure included in the semiconductor layer is a minute body, and the volume of each minute body is in a range of 520 nm ³ or more and 6.5 × 10 ⁻² μm ³ or less. It has been found that when the average distance between two adjacent micro objects is 100 nm or more and 1 μm or less, an electric field enhancement effect is obtained and the conversion efficiency of the photoelectric conversion element is improved.

  The details of the present invention will be described below with reference to the illustrated embodiments.

  First, the principle of the present invention will be described in detail using a solar cell which is one of photoelectric conversion elements. Here, the solar cell according to an embodiment of the present invention is photoelectrically converted between the light irradiation surface electrode 10 and the back surface electrode 20 facing the light irradiation surface electrode 10 as shown in the cross-sectional view on the left side of FIG. It has a layer 60. The photoelectric conversion layer 60 includes a semiconductor layer 30 and a layer (electric field enhancement layer) 40 having a metallic microstructure 50 sandwiched between the semiconductor layers 30.

  Whether the porous thin film is used as the fine structure 50 or the fine structure is used, the cross section can be expressed as shown in the left side of FIG. When a porous thin film is used, the opening is filled with the semiconductor layer 30. When the minute bodies are used, the space between the minute bodies is filled with the semiconductor layer 30.

  When sunlight L enters the semiconductor layer 30 from the light irradiation surface electrode 10 side surface (light receiving surface), the incident sunlight L generates electrons 70 and hole 71 pairs in the photoelectric conversion layer 60, A current flows through the electrodes (light irradiation surface electrode 10 and back surface electrode 20).

  The right side of FIG. 1 shows an energy band diagram at a corresponding position in the structure of the solar cell on the left side of FIG. In the energy band diagram, an electron 70 / hole 71 pair is generated by light absorption, and a current flows by carrier movement. In FIG. 1, the flow of electrons is indicated by arrows 72.

In the photoelectric conversion layer 60, a range in which electrons 70 and hole 71 pairs are generated by light absorption and carriers can be effectively recovered is referred to as a photoactive layer 31. The photoactive layer 31 includes a region where the built-in electric field V _bi shown in the energy band diagram exists. For example, the photoactive layer 31 in the pn junction is a portion including a depletion layer and an extension of a minority carrier diffusion length from the end of the depletion layer. Alternatively, the photoactive layer 31 in the pin junction is an i layer. A region of the photoelectric conversion layer 60 other than the photoactive layer 31 is referred to as a bulk semiconductor layer 32. That is, the semiconductor layer 30 is a layer including the photoactive layer 31 and the bulk semiconductor 32. In the case of FIG. 1, at least a part of the electric field enhancement layer 40 is included in the photoactive layer 31. Further, in the semiconductor layer 30, a part near the electric field enhancement layer 40 is the photoactive layer 31, and the other part is the bulk semiconductor layer 32.

  A feature of the solar cell according to one embodiment of the present invention is that the photoelectric conversion layer 60 includes the electric field enhancement layer 40 provided with the fine structure 50 described above.

(principle)
As described above, the present inventors have made it possible to generate a larger amount of current than the current corresponding to the amount of light propagated to the semiconductor layer 30 by making the solar cell as shown in FIG. Found.

  FIG. 2 is a conceptual diagram for explaining the operation principle. FIG. 2 is an enlarged cross-sectional view showing a part of the microstructure 50 of FIG. The above phenomenon is considered to be due to the following mechanism. First, it is known that when the metal microstructure 50 included in the electric field enhancement layer 40 is irradiated with light L, surface plasmon excitation occurs when the size of the microstructure 50 is about the wavelength of incident light. It has been. That is, as shown in FIG. 2A, when the electric field enhancement layer 40 is irradiated with the light L, the free electrons of the fine structure 50 vibrate perpendicularly to the traveling direction of the light L (V direction). The free electrons are more likely to vibrate on the side irradiated with light (701). The free electrons of the microstructure 50 on the opposite side (702) to the side irradiated with light are unlikely to vibrate because electromagnetic waves cannot enter. This phenomenon is called the skin effect, and the thickness at which electromagnetic waves can penetrate into the metal is called the skin thickness T.

  FIG. 2B is a diagram schematically representing a moment when light is incident on the metal microstructure 50 and the electrons are oscillating. On the upper surface side A (the side irradiated with light) of the end portion of the fine structure 50, a portion 703 where electrons are dense and a portion 704 where electrons are sparse are generated due to vibration of free electrons. On the other hand, on the lower surface side B (the side opposite to the side irradiated with light), free electrons do not vibrate, so that the density of electrons does not occur. Therefore, a relative free electron density difference occurs between the upper surface side A (703, 704) and the lower surface side B (705, 706) at the end of the fine structure 50 (the density difference between 703 and 705, and 704). 706 density difference).

  As a result, as shown in FIG. 2C, a local alternating electric field (local electric field) E <b> 1 that vibrates parallel to the traveling direction of the light L (H direction) is generated in the vicinity of the end of the fine structure 50. The localized electric field E1 generated at this time is several hundred times as large as the electric field generated by the incident light L, and this enhanced electric field (E1) promotes the generation of the electron 70 / hole 71 pair. Here, the end portion of the fine structure 50 is a boundary between the fine structure 50 and the semiconductor layer 30 in the electric field enhancement layer 40, and vibration is not generated when free electrons of the fine structure 50 are vibrated by incident light. Refers to a continuous point. In the following, the local electric field and the enhanced electric field are used as consent.

  However, this local electric field E1 is non-propagating and spreads only to the dimension of the fine structure 50. Therefore, when the fine structure 50 capable of generating the localized electric field E1 is outside the semiconductor layer 30, even if the localized electric field E1 is generated, it can contribute only to carrier generation on the surface of the semiconductor layer 30. In the present invention, the local electric field E1 can be effectively used for carrier generation by providing the microstructure 50 having a shape that increases carrier excitation by an enhanced electric field inside the semiconductor.

(Definition of metal microstructures)
Here, the structure of the metal microstructure 50 is a porous thin film 501, for example, as shown in FIGS. 3 (a), 3 (b) and 3 (c). A porous membrane structure having a plurality of openings is provided. 3A is a perspective view of the porous thin film 501, and FIGS. 3B and 3C are top views.

  Alternatively, the structure of the metal microstructure 50 includes the minute body 510, for example, the minute sphere 502 (FIG. 3D), the minute column 503 (FIG. 3E), or the minute cone 504 (FIG. 3 (f)).

  A structure as shown in FIGS. 3A, 3B, and 3C is referred to as a porous thin film 501, and a structure as shown in FIGS. 3D, 3E, and 3F is referred to as a minute body 510. .

(Preferred metal microstructure structure)
Here, a state of a strong local electric field generated in the vicinity of the end of the fine structure 50 is shown. As an example, an Al porous thin film 501 will be described. FIG. 4 (a) shows an optical model that has been simulated by the Finite Difference Time Domain (FDTD) method, and FIG. 4 (b) shows the result.

  The structure assumed in the simulation is the structure of the Al porous thin film 501 sandwiched between the Si layers 30. The thickness d of the Al porous thin film 501 is 30 nm, the opening of the porous thin film 501 is circular and the diameter l is 140 nm, and the width (metal width between openings) r of the metal part sandwiched between the openings of the porous thin film 501 is 60 nm. A certain structure was assumed. The opening is filled with Si forming the semiconductor layer 30 to form the electric field enhancement layer 40. FIG. 4A shows a cross section (xz plane) perpendicular to the electric field enhancement layer 40 in the assumed structure. Here, the inter-opening metal width r and the opening diameter l of the porous thin film 501 are components perpendicular to the traveling direction of the incident light L. The thickness d of the porous thin film 501 is a component parallel to the traveling direction of the incident light L.

  FIG. 4B shows the Ez electric field strength in the xz plane when incident light L (λ = 1000 nm, traveling direction z) is given to the above structure. From the simulation results, it can be seen that the Ez electric field is enhanced near the end of the opening of the Al porous thin film 501, and a localized electric field LE is generated.

  FIG. 5 assumes an optical model similar to FIG. 4 (FIG. 5A), and calculates the FDTD when the metal width r between the openings of the Al porous thin film 501 and the opening diameter l of the Al porous thin film 501 are changed. It is a result. FIG. 5A shows the optical model and the observation point D. FIG. 5B shows the relationship between the metal width r between the openings of the porous thin film 501 and the strength of the localized electric field at the observation point D. FIG. Indicates the relationship between the aperture diameter l of the Al porous thin film 501 and the strength of the localized electric field at the observation point D. The local electric field strength (electric field strength) in FIG. 5 is the strength of the Ez electric field that appears in the vicinity of the opening end of the Al porous thin film 501, and the observation point D of the electric field strength is the opening of the porous thin film 501. The distance is between 530 and 10 nm. The Ez electric field does not exist for plane waves.

<(1) Opening Diameter and Interval of Preferred Porous Thin Film (Lower Limit)>
From the result of FIG. 5B, a localized electric field is generated when the metal width r between the openings of the porous thin film 501 is 10 nm or more. Further, it has been found that the electric field enhancing effect is particularly strong when r is 20 nm to 500 nm.

Further, as shown in FIG. 5C, a local electric field is also generated when the opening diameter l of the porous thin film 501 is 10 nm or more, that is, the area per opening is 80 nm ² or more. In particular, the electric field enhancement effect is stronger when l is 20 nm or more and 500 nm or less, that is, when the area per opening is 300 nm ² or more and 0.2 μm ² . Even when the opening is not circular, a localized electric field is generated when the area per opening is 80 nm ² or more, and particularly when the area per opening is 300 nm ² or more and 0.2 μm ^2. I know that is stronger.

<(2) Preferred Diameter and Interval of Small Objects (Lower Limit)>
When the micro object 510 is used as the fine structure 50, the same simulation as in the case of the porous thin film 501 is performed. When the micro object 510 is a sphere, the diameter r ′ is 2 nm to 1 μm, that is, the volume is It is known that the enhanced electric field is strong when the thickness is 4 nm ³ or more and 0.52 μm ³ . In particular, the electric field enhancement effect is stronger when the average value of the diameters of the micro objects 510 is 10 nm or more and 500 nm or less, that is, when the volume is in the range of 520 nm ³ or more and 6.5 × 10 ⁻² μm ³ . In addition, even when the micro object 510 is not a sphere, if the volume is 4 nm ³ or more and 0.52 μm ³ or less, the enhanced electric field is strong, especially when the volume is in the range of 520 nm ³ or more and 6.5 × 10 ⁻² μm ^3. It is known that the electric field enhancement effect is stronger.

On the other hand, when the distance l ′ between the micro objects 510 is short and another micro object 510 exists within the spread of the localized electric field of one particle, the electric field energy moves between the micro objects 510, and energy loss occurs. May occur. For this reason, in order to effectively use the enhanced electric field for semiconductor carrier excitation, the distance l ′ between the minute bodies 510 should not be too small. The spread of the localized electric field varies depending on the size of the micro object 510. FIG. 6 is a diagram showing the radius of the micro object and the range in which the local electric field spreads for the spherical micro object. The radius of the micro object indicates a range of 1 nm to 1000 nm, which corresponds to the above-described range of 4 nm ³ or more and 0.52 μm ³ or less. When the dimension of the micro object 510 is small, the spread of the local electric field is about ½ of the dimension. Specifically, when the micro object 510 is a micro sphere having a radius of 1 nm (volume 4 nm ³ ), the spread of the localized electric field is about 1 nm (about the radius). However, if the size of the micro object 510 is large, the spread of the local electric field is not large, and if the dimension of the micro object 510 exceeds a certain value, the local electric field spreads only to about 100 nm or less. Specifically, when the radius of the micro object 510 is a sphere having a radius of 100 nm (volume 4 × 10 ⁻³ μm ³ ) or more, the local electric field is about 100 nm or less.

Similarly, in the case where the micro object 510 is not a sphere, when the volume of the micro object 510 is less than 4 × 10 ⁻³ μm ³ , the micro object is regarded as a sphere, and a length corresponding to the radius of the sphere (Equation 1 ), The local electric field has a spread, and when the volume is 4 × 10 ⁻³ μm ³ or more, the spread of the local electric field is about 100 nm or less.

Therefore, it is preferable that the interval l ′ between the minute bodies 510 is not less than the value of Formula 1 when the volume of the minute bodies is less than 4 × 10 ⁻³ μm ³ . When the volume of the micro object is 4 × 10 ⁻³ μm ³ or more, the interval l ′ between the micro objects 510 is preferably 100 nm or more.

<(3) Preferred density of fine structure (upper limit of width and interval)>
In the case where the structure of the fine structure 50 is in the above-described range, a structure having a high end density is preferable in order to increase the electric field per unit area. FIG. 7 is an overhead view of the fine structure 50 of the electric field enhancement layer 40 as viewed from the incident surface side. A preferred structure of the fine structure will be described with reference to FIG.

  Specifically, a case where the fine structure 50 is the minute object 510, the shape of the minute object 510 is spherical, and the minute object 510 is periodically arranged in the electric field enhancement layer 40 is shown. As shown in FIG. 7A, when the interval l ′ between the minute bodies 510 is a certain value L ′, the smaller the diameter r ′ of the minute bodies 510, the larger the number of the minute bodies 510 included in the unit area. The total amount at the end of the micro object 510 is also large. On the other hand, as shown in FIG. 7B, when the diameter r ′ of the micro object 510 is a certain value R ′, the total amount at the end of the micro object 510 becomes larger when the interval l ′ of the micro object 510 is smaller. .

Therefore, from the viewpoint of density, the volume of the micro object 510 is preferably 0.52 μm ³ (1 μm diameter in the case of a sphere) or less. Moreover, it is preferable that the interval l ′ between the micro objects 510 is 1 μm or less.

  Specifically, a case where the microstructure 50 is a porous thin film 501, the shape of the opening of the porous thin film 501 is circular, and the openings are periodically arranged is shown in FIG. As shown in c), when the diameter of the opening is a constant value L, the number of openings per unit area is larger when the distance between openings r is smaller, and the total amount of outer edges (ends) of the openings is larger. On the other hand, as shown in FIG. 7D, when the width of the metal portion existing between the openings is a constant value R, the smaller the diameter l of the opening, the larger the total amount of the metal end portions.

Therefore, from the viewpoint of density, it is preferable that the opening area of the porous thin film 501 is 0.8 μm ² or less (1 μm diameter in the case of a circle). Further, the opening diameter l is preferably 1 μm or less.

Therefore, from the viewpoint of electric field strength and density, a preferable structure of the fine structure 50 is in the following range. When the microstructure 50 is the porous thin film 501, particularly when the opening is circular, the diameter of the opening is 10 nm or more and 1 μm or less, and the area per opening is 80 nm ² or more and 0.8 μm ² or less. A range is desirable. In particular, it is more preferable that the diameter of the opening is 20 nm or more and 500 nm or less, that is, the area per opening is in the range of 300 nm ² or more and 0.2 μm ² or less. However, even when the shape of the opening is not circular, the area per opening is preferably in the range of 80 nm ^{2 to} 0.8 μm ^{2, and} more preferably in the range of 300 nm ^{2 to} 0.2 μm ^2. .

  The opening diameter is preferably 10 nm or more and 1 μm or less, and more preferably 20 nm or more and 500 nm or less.

Further, when the microstructure 50 is the minute body 510, particularly when the minute body 510 is spherical, it is assumed that the average value of the diameter of the minute body 510 is 2 nm or more and 1 μm or less, and the volume per one minute body 510 is Is preferably in the range of 4 nm ³ or more and 0.52 μm ³ , and the average value of the diameter of the micro object 510 is 10 nm or more and 500 nm or less, that is, the average volume per micro object 510 is 520 nm ³ or more. A range of 5 × 10 ⁻² μm ³ is more preferable.

Further, the average value of the interval between the minute bodies 510 is equal to or more than the value of Formula 1 when the volume of the minute bodies 510 is less than 4 × 10 ⁻³ μm ³ , and the volume of the minute bodies 510 is 4 × 10 ⁻³ μm ^3. In the case of the above, it is preferably 100 nm or more and 1 μm or less in any volume.

<(4) Preferred thickness of microstructure>
Since the electric field enhancement effect is caused by electron density due to the skin effect, the thickness d of the microstructure 50 needs to be about the skin thickness. The skin depth δ, that is, the penetration length of an electromagnetic wave whose amplitude is attenuated to 1 / e is expressed by Equation 2.

Where c is the speed of light in vacuum (3.0 × 10 ⁸ [m / s]), ω is the angular frequency of light, ε is the dielectric constant of the metal, ε ₁ is the real part of the dielectric constant, and ε ₂ is It is the imaginary part of the dielectric constant (ε = ε ₁ + iε ₂ ). However, since the dielectric constant ε depends on the metal, the skin thickness also varies depending on the type of metal. For example, if the dielectric constant of Al at the wavelength λ = 500 nm (ω = 3.8 × 10 ¹⁵ [rad / s]) is ε ₁ = −37 and ε ₂ = 9.5, the skin thickness is about 13 nm. . When the dielectric constant of Ag at the wavelength λ = 318 nm (ω = 5.9 × 10 ¹⁵ [rad / s]) is ε ₁ = 0.6 and ε ₂ = 0.9, the skin thickness is about 100 nm. In the case of d << δ, the local electric field is weak because the electron density difference is small between the irradiation side surface (upper surface) of the microstructure 50 and the opposite surface (lower surface). When d >> δ, the electric field of light cannot reach the lower surface side, and free electrons on the lower surface side do not vibrate, so the local electric field is weak. From the above, if the thickness d of the fine structure 50 is within the range of d _min = 2 nm or more and d _max = 200 nm or less, an electron density difference occurs between the irradiation side surface and the opposite surface of the fine structure 50. A strong local electric field is generated.

<(5) Preferred shape of metal microstructure>
Further, for example, when the fine structure 50 is the porous thin film 501, it is not always necessary that the openings are periodically formed, and this effect can be obtained even with pseudo-periodic openings, randomly formed openings, and the like. Therefore, the present invention does not limit the arrangement of the openings. Further, the shape of the opening is not limited to a circle. Rather, even if the opening area is the same, the opening having a shape such as a star shape (FIG. 3B) or a C shape (FIG. 3C) is more preferable than a circular shape (FIG. 3A). Since the length of the outer edge portion (end portion) becomes longer, it is advantageous from the viewpoint of the electric field enhancement effect. On the other hand, when the shape of the opening is circular, the fine structure 50 can be easily manufactured.

  For example, when the fine structure 50 is composed of a plurality of fine bodies 510, the shape of the fine body 510 is arbitrary, and as shown in FIG. 3, the microsphere 502 (FIG. 3 (d)) or the micro pillar body is used. It may be 503 (FIG. 3E) or a micro cone 504 (FIG. 3F). In addition, this effect can be obtained even if the micro-objects 510 are arranged periodically, pseudo-periodically, or randomly.

<(6) Arrangement of Preferred Fine Structure>
Although the electric field in the vicinity of the end of the fine structure 50 is enhanced by the structure of the fine structure 50 as described above, the photoelectric conversion efficiency is improved by the electric field enhancement effect reaching the photoactive layer 31. . For this reason, when the arrangement of the electric field enhancement layer 40 is an arrangement in which the photoactive layer 31 in the semiconductor layer 30 includes at least a part of the microstructure 50, the localized electric field is more effectively used for carrier generation. be able to.

<(7) Preferred metal microstructure material>
As described above, the structure of the solar cell according to the embodiment of the present invention has been described from the viewpoint of the shape, but the material constituting such a structure can be selected and used from any conventionally known materials.

  The metal forming the fine structure 50 is arbitrarily selected. Here, the metal refers to a metal element that is a single conductor, has a metallic luster, is ductile, and is solid at room temperature, and an alloy made thereof. Since the electric field enhancing effect is induced by the entry of electromagnetic waves into the fine structure 50, in one embodiment, the material forming the fine structure 50 preferably has a metallic luster. Further, it is desirable that the material forming the fine structure 50 has little light absorption in the wavelength region of light to be used.

  Specific examples of such materials include Al, Ag, Au, Pt, Ni, Co, Cr, Cu, Ti, etc. From the viewpoint described above, among these, Al, Ag, Au, Pt, Ni, Co Is preferred. In addition, an alloy having at least one selected from Al, Ag, Au, Pt, Ni, Co, Cr, Cu, and Ti can be used as the material of the microstructure 50. However, these are not limited as long as the metal has a metallic luster.

(Semiconductor materials for solar cells, junction structure)
Various materials are known for the semiconductor layer 30 constituting the solar cell, and an arbitrary material can be selected from them. For example, a single crystal, polycrystal, microcrystal, or III-V compound semiconductor such as amorphous Si or GaAs, a II-VI compound semiconductor, or a chalcopyrite compound semiconductor can be used as the material. Moreover, an organic substance can also be used as the material of the semiconductor layer, and specifically, it is composed of a p- type organic semiconductor, an n-type organic semiconductor, and a hole transport material.
Examples of p-type organic semiconductors include polythiophene and its derivatives, polypyrrole and its derivatives, pyrazoline derivatives, arylamine derivatives, stilbene derivatives, triphenyldiamine derivatives, oligothiophene and its derivatives, polyvinylcarbazole and its derivatives, polysilane and its derivatives, side Examples include polysiloxane derivatives having an aromatic amine in the chain or main chain, polyaniline and derivatives thereof, phthalocyanine derivatives, porphyrin and derivatives thereof, polyphenylene vinylene and derivatives thereof, polythienylene vinylene and derivatives thereof, and the like. Moreover, you may use said copolymer, For example, a thiophene-fluorene copolymer, a phenylene ethynylene-phenylene vinylene copolymer, etc. are mentioned.
Preferable p-type organic semiconductors are polythiophene, which is a conductive polymer having π conjugation, and derivatives thereof. Polythiophene and derivatives thereof are not particularly limited as long as they are compounds having a thiophene skeleton. Specific examples of polythiophene and derivatives thereof include polyalkylthiophenes such as poly-3-methylthiophene, poly-3-butylthiophene, poly-3-hexylthiophene, poly-3-octylthiophene, poly-3-decylthiophene, poly-3-dodecylthiophene, etc. Polyarylthiophene such as poly-3-phenylthiophene and poly-3- (p-alkylphenylthiophene); poly-3-butylisothionaphthene, poly-3-hexylisothionaphthene, poly-3-octylisothionaphthene, poly-3- And polyalkylisothionaphthene such as decylisothionaphthene; polyethylenedioxythiophene and the like. PCDTBT (poly [N-9 "-hepta-decanyl-2,7-carbazole-alt-5,5- (4 ', 7'-di-2), which is a copolymer of carbazole, benzothiadiazole and thiophene, is also used. Derivatives such as -thienyl-2 ′, 1 ′, 3′-benzothiadiazole)]) are known as compounds capable of obtaining excellent photoelectric conversion efficiency.
Examples of the n-type organic semiconductor include fullerene and derivatives thereof. The fullerene derivative is not particularly limited as long as it is a derivative having a fullerene skeleton. Specific examples include derivatives composed of C ₆₀ , C ₇₀ , C ₇₆ , C ₇₈ , C _{84 and the} like as a basic skeleton. In the fullerene derivative, carbon atoms in the fullerene skeleton may be modified with an arbitrary functional group, and these functional groups may be bonded to each other to form a ring. Fullerene derivatives also include fullerene bonded polymers. Examples of the functional group in the fullerene derivative include hydrogen atom; hydroxyl group; halogen atom such as fluorine atom and chlorine atom; alkyl group such as methyl group and ethyl group; alkenyl group such as vinyl group; cyano group; methoxy group and ethoxy group. Alkoxy groups such as phenyl groups, aromatic hydrocarbon groups such as naphthyl groups, and aromatic heterocyclic groups such as thienyl groups and pyridyl groups. Specific examples include hydrogenated fullerenes such as C ₆₀ H ₃₆ and C ₇₀ H ₃₆ , oxide fullerenes such as C ₆₀ and C ₇₀ , fullerene metal complexes, and the like. Among the above, a fullerene derivative, 60PCBM ([6,6] - phenyl _{C 61} butyric acid methyl ester), or 70PCBM - it is particularly preferred to use ([6,6] phenyl _{C 71} butyric acid methyl ester). When using the unmodified fullerene, it is preferred to use a C _70.
Examples of the material for the hole transport layer include polythiophene polymers such as PEDOT / PSS (poly (3,4-ethylenedioxythiophene) -poly (styrenesulfonate)), and organic conductive polymers such as polyaniline and polypyrrole.
As a structure for photoelectric conversion, a semiconductor layer of a pn junction type, a pin type, a tandem structure type, or the like can be used.

(Method for manufacturing solar cell)
Next, the manufacturing method of the solar cell which is one Embodiment of this invention is demonstrated.

The solar cell manufactured in the present invention includes at least a p-type semiconductor layer and an n-type semiconductor layer as the semiconductor layer 30 in the photoelectric conversion layer 60, and further includes an i-type semiconductor layer in a solar cell using amorphous Si. It is out. An electric field enhancement layer 40 made of a metal microstructure 50 is provided in the semiconductor layer 30 or at the junction between the semiconductor layers 30.

  In the method for manufacturing a solar cell proposed in the present invention, the order of assembling the photoelectric conversion layer 60 is not particularly limited. Moreover, the semiconductor layer 30 can be formed using arbitrary methods according to the kind. For example, the semiconductor layer 30 can be formed by partially doping impurities on a p-type or n-type semiconductor substrate, or by laminating other semiconductor layers by vapor deposition or the like. The lamination method can be performed using known techniques such as vapor deposition, PVD, various CVD, sputtering, precipitation, spin coating, drop coating, and the like. Alternatively, the semiconductor layer 30 may be formed by stacking an electrode layer on a transparent substrate and stacking a p-type, n-type, or i-type semiconductor layer thereon.

  The solar cell according to the embodiment of the present invention is characterized in that the electric field enhancement layer 40 including the microstructure 50 is present in the semiconductor layer 30, but the p-type, n-type, or i-type semiconductor layer 30 is formed. The structure of the solar cell proposed in the present invention can be formed by forming a metal microstructure in the middle of the process.

(Doping method)
For example, by forming the fine structure 50 in the process of forming a p-type, n-type, or i-type semiconductor layer, a substrate including the fine structure 50 in the semiconductor layer 30 is manufactured, and impurities are partially added to the substrate. May be doped.

(Lamination method)
Alternatively, a process for forming the microstructure 50 may be provided in the middle of the stacking process of the p-type, n-type, or i-type semiconductor layer.

(Surface, back electrode, other high efficiency methods)
As the light irradiation surface electrode 10 and the back surface electrode 20, any material can be adopted as long as it can be in ohmic contact with the semiconductor layer 30 to be in contact. Specifically, Ag, Al, Ag / Ti, etc. are generally used. Or a transparent electrode etc. can also be used. In general, improvement of the efficiency by examining the front and back surfaces of the photoelectric conversion layer, such as providing an antireflection film on the light-irradiated surface of the semiconductor layer 30 or using texture etching or BSF, has been studied. Yes. These improvements can be combined with the solar cell according to the embodiment of the present invention as long as the effects of the present invention are not impaired.

  An example of a method for manufacturing the microstructure 50 that is a feature of the solar cell according to the embodiment of the present invention will be described below.

<Method for producing metal porous thin film>
For example, when the microstructure 50 is a porous thin film 501, an opening may be provided after forming a metal thin film on the surface of a p-type, n-type or i-type semiconductor layer, or a metal thin film having an opening in advance. May be stacked on the p-type, n-type, or i-type semiconductor layer 30.

  Also, any method can be used as a method for forming a fine opening in the metal thin film. For example, the most generally known method includes a method of etching using an electron beam exposure apparatus that can form an ultrafine structure. According to such a method, a fine opening can be easily formed.

Specifically, there are the following methods.

(A. Particle array method)
A resist is applied on the metal thin film that is the basis of the porous thin film 501 to form a resist layer, a single particle layer of fine particles is formed on the surface of the resist layer, and the dot pattern is formed using the single particle layer as an etching mask. A method of forming a fine pattern by forming a resist pattern, filling the resist pattern with an inorganic substance, forming a reverse pattern mask, and etching the metal thin film through the reverse pattern mask.

Specifically, including a step of forming a semiconductor layer, a step of forming a first semiconductor layer, a step of forming a metal thin film layer having a thickness of 2 nm to 200 nm on the first semiconductor layer, Applying a resist to at least a part of the metal thin film layer or at least a part of the semiconductor layer to form a resist coating layer; forming a fine particle single particle layer on the surface of the resist coating layer; The step of forming a resist pattern having a fine concavo-convex pattern using the single particle layer as an etching mask, and an average of one opening area in the metal thin film layer using the resist pattern or a pattern layer obtained by using the resist pattern Forming a pattern having a plurality of openings of 80 nm ² or more and 0.8 μm ² or less, and forming a second pattern on the metal thin film on which the pattern is formed Forming a semiconductor layer.

(B. Block copolymer method)
A composition containing a block copolymer is applied onto a metal thin film that is the basis of the porous thin film 501, a block copolymer film is formed, and dot-like microdomains of the block copolymer are generated. Is used to form a reverse pattern mask, and a metal thin film is etched through the reverse pattern mask to form fine openings.

Specifically, including a step of forming a semiconductor layer, a step of forming a first semiconductor layer, a step of forming a metal thin film layer having a thickness of 2 nm to 200 nm on the first semiconductor layer, A step of forming an intermediate layer on the surface of at least a part of the metal thin film layer or at least a part of the semiconductor layer; a step of generating a microdomain of a block copolymer on the surface of the intermediate layer; Forming a pattern having a plurality of openings having an average opening area of 80 nm ² or more and 0.8 μm ² or less in the metal thin film layer using the microdomain pattern; and on the metal thin film on which the pattern is formed And a step of forming a second semiconductor layer.

(C. Nanoimprint method)
A stamper having a fine concavo-convex pattern corresponding to the shape of the porous thin film 501 to be formed on the surface is prepared, and the resist pattern is transferred onto the metal thin film that is the basis of the porous thin film 501 by using the stamper. A method of forming a pattern on a metal thin film through the resist pattern.

Specifically, including a step of forming a semiconductor layer, a step of forming a first semiconductor layer, a step of forming a metal thin film layer having a thickness of 2 nm to 200 nm on the first semiconductor layer, A step of preparing a stamper having a fine concavo-convex pattern corresponding to the opening on the surface, a step of forming a resist pattern using the stamper, and an average of one opening area in the metal thin film layer using the resist pattern Forming a pattern having a plurality of openings having a thickness of 80 nm ² or more and 0.8 μm ² or less, and forming a second semiconductor layer on the metal thin film on which the pattern is formed.

(D. Lift-off method)
A method of forming a porous thin film 501 by forming a resist or inorganic material pattern directly on the semiconductor layer 30 and depositing a metal in the gap by vapor deposition or the like.

<Production method of micro object>
Further, for example, when the microstructure 50 is the minute body 510, the minute body 510 is formed by providing a discontinuous portion after forming a metal thin film layer on the surface of the p-type, n-type, or i-type semiconductor layer 30. Alternatively, the micro object 510 may be previously stacked on the p-type, n-type, or i-type semiconductor layer 30.

  In addition, an arbitrary method can be used as the method for forming the micro object 510 from the metal thin film.

Specifically, there are the following methods.

(E. Particle array method)
A resist is applied on the metal thin film that forms the micro-object 510 to form a resist layer, a fine particle single particle layer is formed on the surface of the resist layer, and a resist pattern is formed using the single particle layer as an etching mask. And forming a microscopic object 510 by etching a metal thin film through the resist pattern.

Specifically, including the step of forming the semiconductor layer, the step of forming the first semiconductor layer, the step of forming the metal thin film layer on the first semiconductor layer, and at least one of the metal thin film layers Forming a resist coating layer by applying a resist to at least part of the semiconductor layer or the semiconductor layer, forming a fine particle single particle layer on the surface of the resist coating layer, and using the single particle layer as an etching mask A step of forming a resist pattern having a fine concavo-convex pattern, and an average volume of 4 nm ^{3 to} 0.52 μm ³ from the metal thin film layer using the resist pattern or a pattern layer obtained by using the resist pattern, and Forming a plurality of microscopic bodies having an average of two adjacent intervals of 1 nm to 1 μm, and forming a second semiconductor layer on the microscopic bodies And the extent, is carried out.

(F. Block copolymer method)
A composition containing a block copolymer is applied to a metal thin film that is the basis of the minute body 510 to form a block copolymer film, and dot-like microdomains of the block copolymer are generated. Through the generated microdomain pattern, A method of forming a microscopic object 510 by etching a metal thin film.

Specifically, including the step of forming the semiconductor layer, the step of forming the first semiconductor layer, the step of forming the metal thin film layer on the first semiconductor layer, and at least one of the metal thin film layers A step of forming an intermediate layer on at least a part of the surface of the semiconductor layer, a step of generating a microdomain of a block copolymer on the surface of the intermediate layer, and a pattern of the microdomain of the block copolymer film. Forming a plurality of minute bodies having an average volume of 4 nm ³ or more and 0.52 μm ³ or less from the metal thin film layer, and an average of two adjacent intervals being 1 nm or more and 1 μm or less; Forming a second semiconductor layer.

(G. Nanoimprint method)
A stamper having a surface with a fine concavo-convex pattern corresponding to the shape of the micro object 510 to be formed is prepared, and a resist pattern is transferred onto the metal thin film that forms the micro object 510 by using the stamper. A method of forming a pattern on a metal thin film through a resist pattern.

Specifically, including a step of forming a semiconductor, a step of forming a first semiconductor layer, a step of forming a metal thin film layer on the first semiconductor layer, and a stamper having a fine concavo-convex pattern on the surface 2, forming a resist pattern using the stamper, and using the resist pattern, the average volume of the metal thin film layer is 4 nm ³ or more and 0.52 μm ³ or less, and 2 adjacent to each other. A step of forming a microscopic body having an average of two intervals of 1 nm to 1 μm and a step of forming a second semiconductor layer on the microscopic body are performed.

(H. Lift-off method)
A method of forming an opening pattern of a resist or an inorganic substance directly on the semiconductor layer 30 and depositing a metal in the opening by vapor deposition or the like to form the micro object 510.

(I. Solid phase precipitation method)
A method of depositing a micro object 510 in a semiconductor layer 30 to be a substrate.

(J. Aperture expansion method)
A method of forming the minute body 510 by increasing the opening size so that adjacent openings have a continuous structure in the methods (A) to (D) of forming the porous thin film 501.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[Example 1]
In this example, a manufacturing method and characteristics of a single crystal Si type solar cell having an electric field enhancement layer 40 made of a minute body 510 will be described.

  First, in this embodiment, an example in which a pn junction is formed in a single crystal Si substrate by doping, and a Cu micro-particle 510 is deposited in the vicinity of the pn junction will be described with reference to FIG.

(Pn junction Si substrate)
First, a p-type Si substrate was prepared as a semiconductor substrate. Here, a p-type single crystal Si substrate 30p having a B doping of 6 × 10 ¹⁵ atoms / cm ³ and a thickness of 380 μm was prepared (FIG. 8A). An n + layer 30n was formed on one surface of the single crystal p-type Si substrate by a thermal diffusion method to form a pn junction (FIG. 8B). The conditions of the thermal diffusion method were 1100 ° C. and 15 minutes in a POCl ₃ gas atmosphere. In this embodiment, polycrystalline silicon may be used as the semiconductor substrate, or a generally known impurity other than B and P may be doped as the impurity. Further, an ion implantation method may be used as a doping method.

(Cu deposition on Si substrate)
Next, a minute body 510 was formed in the Si substrate 30 in the vicinity of the formed pn junction (FIG. 8C). The Si substrate was irradiated with a Cu ion beam having an acceleration energy of 60 keV to implant Cu ions. The range in this case is estimated to be about 50 nm. When irradiated with a dose rate of 45 μA / cm ² and an integrated dose of 3 × 10 ¹⁶ ions / cm ² , a fine particle depletion layer of about 10 nm is present directly under the surface by observation of a cross-sectional TEM, and a diameter of 10 to 15 nm is present thereunder. It was confirmed that the Cu microparticles (micro objects 510) were distributed two-dimensionally.

As a result of annealing at 800 ° C. and analysis by SIMS, the peak concentration of the impurity was about 5 × 10 ²⁰ atoms / cm ³ , and it was estimated that the depletion layer was formed around 100 nm from the surface. Further, since the particle depth distribution was widened by annealing, fine particles were dispersed in the semiconductor layer 30 within a depth of 120 nm. A portion in the semiconductor layer 30 where the fine particles 510 are dispersed corresponds to the electric field enhancement layer 40.

  However, the size of the fine particles can be controlled by the dose rate, and the depth distribution in the substrate can be controlled by the thermal annealing treatment after the ion implantation, and these can be arbitrarily selected.

(Structure of electric field enhancement layer)
Through the above-described steps, an electric field enhancement layer in which a plurality of Cu microscopic bodies are randomly arranged sandwiched between the p-layer and n-layer of single crystal Si was obtained. The average diameter per minute body was 12 nm (the average volume was 900 nm ³ ), and the average distance between the minute bodies was 10 nm.

(Production of solar cells)
In order to obtain a solar battery cell, a light irradiation surface electrode 10 was formed on the surface of the n + type Si layer 30n, and a back electrode 20 was formed on the surface of the p type Si layer 30p. The electrodes were produced by a screen printing method using an epoxy thermosetting Ag paste. As for the shape of the electrode, the back electrode 20 was formed with a thickness of about 40 μm on one side, and the light irradiation surface electrode 10 was formed with a plurality of thin wire electrodes with a thickness of about 40 μm and a width of about 200 μm at a pitch of about 2 mm (FIG. 8). (D)).

(Characteristics of solar cells)
The solar cell of Example 1 produced as described above was irradiated with artificial sunlight of AM1.5, and the photoelectric conversion efficiency at room temperature was evaluated. As a result, the photoelectric conversion efficiency was as good as 10.1%. From this, it can be said that the effect of the electric field enhancement layer 40 appears. The same investigation was performed when a metal material other than Cu was used as the material of the micro object 510. For example, 10.5% for Au and 10.6% for Ag were shown, and it was confirmed that the effects of the present invention were obtained.

[Reference Example 1]
In the same manner as in Example 1, after forming a single crystal Si pn junction, the conversion efficiency in the case of producing a solar battery cell without depositing metal fine particles (microparticles 510) was 8.9%.

[Example 2-1]
In this example, a method for manufacturing a polycrystalline Si solar cell having an electric field enhancement layer 40 made of a porous thin film 501 and its characteristics will be described. In this embodiment, an Al thin film is etched on a polycrystalline Si substrate to form an Al porous thin film 501, and further, polycrystalline Si is deposited by CVD to form a porous thin film 501 in the semiconductor layer 30. Will be described with reference to FIG.

(P-type Si substrate)
First, a p-type polycrystalline Si substrate 30p having a B doping of 10 ¹⁵ atoms / cm ³ and a thickness of 300 μm was prepared as a semiconductor substrate (FIG. 9A). In the present embodiment, a generally known impurity other than B may be doped as the impurity, or an n-type substrate may be prepared and a p-layer may be formed later.

(Al porous film on Si substrate)
Next, the fine structure 50 was formed on the Si substrate. Here, an Al porous thin film 501 was produced. First, a thin film 520 having a thickness of 30 nm was formed by depositing Al on the main surface of the Si substrate p layer 30p by vacuum deposition.

A positive thermosetting resist for i-line was spin-coated on the substrate on which the Al thin film 520 was deposited, annealed at 250 ° C. for 1 hour in a nitrogen atmosphere, and thermoset to form a resist layer 102 having a thickness of about 240 nm ( FIG. 9B).

  Next, a dispersion liquid (PL-13 (trade name), manufactured by Fuso Chemical Industry Co., Ltd.) containing silica fine particles 106s having a particle diameter of 200 nm is diluted to 5 wt% with a composition 106a containing an acrylic monomer and filtered. To remove secondary particles to obtain a silica fine particle dispersion for coating. This solution was spin-coated on the substrate on which the resist layer 102 had been formed at 2000 rpm for 60 seconds (FIG. 9C), and then annealed at 150 ° C. for 1 hour in a nitrogen atmosphere.

  Thereafter, by cooling at room temperature, an ordered single particle layer of silica fine particles 106 s was obtained on the hydrophilized resist layer 102 (FIG. 9D). Here, silica fine particles are used as the fine particles 106s. However, any inorganic or organic fine particles can be used as long as they can achieve a difference in etching speed as described later. The size of the fine particles 106 s is selected according to the target opening pitch of the porous thin film 501, but generally a size of 60 to 700 nm is selected.

Next, the silica fine particle 106s single particle film is etched by using a reactive reactive etching (RIE) apparatus (manufactured by Samco Co., Ltd.) at O ₂ : 30 sccm, 10 mTorr, and RF power of 100 W for 20 seconds. The composition 106a containing an acrylic monomer was removed (FIG. 9 (e)). Next, etching was performed for 2 minutes with CF ₄ : 30 sccm, 10 mTorr, and RF power of 100 W, and silica particles were slimmed. When observed with an electron microscope, the particle system of the silica fine particles 106s was about 120 nm, and the gap between the silica fine particles 106s was about 80 nm (FIG. 9F).

Next, using the remaining silica fine particles 106s as an etching mask, the underlying thermosetting resist was etched for 270 seconds under the conditions of O ₂ : 30 sccm, 2 mTorr, and RF power of 100 W. As a result, a columnar resist pattern having a high aspect ratio was obtained at the site where the silica fine particles 106 s were initially present (FIG. 9G).

  Next, spin-on-glass (hereinafter referred to as SOG) (SOG-14000 (trade name), manufactured by Tokyo Ohka Kogyo Co., Ltd.) was spin-coated on the columnar resist pattern 102 and annealed at 250 ° C. for 1 hour in a nitrogen atmosphere. Thus, SOG was filled in the gaps between the resist patterns 102 (FIG. 9H).

Next, the SOG layer 103 formed by the above process and the finely divided silica fine particles 106 s contained in the SOG layer 103 are etched for 11 minutes under the conditions of CF ₄ : 30 sccm, 10 mTorr, and RF power of 100 W. It was. By this treatment, the SOG 103 and the silica fine particles 106 s on the columnar resist pattern 102 were removed, and a structure in which the SOG 103 was filled in the gap between the columnar resist pattern 102 was formed (FIG. 9 (i)).

Next, an SOG mask 103 (second etching mask) having a structure in which the columnar resist pattern is inverted by etching the columnar thermosetting resist 102 at O ₂ : 30 sccm, 10 mTorr, RF power 100 W for 150 seconds. Was prepared on the Al thin film 520 (FIG. 9 (j)).

Next, the Al thin film 520 was etched with an ICP-RIE apparatus (manufactured by Samco Corporation) through the SOG mask 103. The natural oxide film Al ₂ O ₃ formed on the surface is removed by sputter etching for 1 minute under the conditions of Ar: 25 sccm, 5 mTorr, ICP power 50 W, Bias power 150 W, and then Cl ₂ / Ar: _{2.5 /} 25 sccm mixed gas The Al thin film 520 was etched for 50 seconds under the conditions of 5 mTorr, ICP power 50 W, and Bias power 150 W (FIG. 9K).

Thereafter, etching was performed for 150 seconds under the conditions of CF ₄ : 30 sccm, 10 mTorr, and RF power of 100 W, and the remaining SOG mask 103 was removed.

(Structure of electric field enhancement layer)
Through the above steps, an Al porous thin film 501 having an opening having a thickness of 30 nm, an average opening area of 9.9 × 10 ³ nm ² (opening diameter of 112 nm), and an average opening ratio of 28.4% is formed on the p layer 30p. (FIG. 9 (l)).

(Polycrystalline Si regrowth on Al porous film)
A 50 nm thick n + polycrystalline Si layer 30n was formed on the produced Al porous thin film 501 by plasma CVD. The silicon thin film layer stack 30n was formed using a substrate temperature of 400 ° C. and SiH ₄ , H ₂ , and PH ₃ as source gases. At this time, the opening of the Al porous thin film 501 was filled with n + polycrystalline Si 30n (FIG. 9 (m)).

(Production of solar cells)
In order to form a solar battery cell, a light irradiation surface electrode 10 was formed on the surface of the n + type Si layer 30n, and a back electrode 20 was formed on the surface of the p type Si layer 30p by screen printing (FIG. 9 (n)). The electrode fabrication conditions and specifications were the same as in Example 1.

(Characteristics of solar cells)
The solar cell of Example 2-1 produced as described above was evaluated in the same manner as in Example 1. As a result, the photoelectric conversion efficiency was a good value of 6.5%. From this, it can be said that the effect of the electric field enhancement layer 40 appears. In this embodiment, the case where the p layer 30p is formed first is described. However, even if the microstructure 50 and then the p layer 30p are formed using the n layer 30n as a substrate, the effect of this embodiment does not change. The same examination was performed when a metal material other than Al was used as the material of the porous thin film 501. For example, the photoelectric conversion efficiencies of 6.7% for Au, 6.8% for Ag, and 6.1% for Cu were confirmed, and it was confirmed that the effect of this example was obtained. In addition, any of the above-described methods can be used for producing the porous thin film 501, and the method is not limited.

[Example 2-2]
In the present embodiment, an example in which an Au microscopic body 510 layer is formed instead of the metallic porous thin film 501 in the embodiment 2-1 will be described with reference to FIG.

(P-type Si substrate)
Similar to Example 2-1, a p-type polycrystalline Si substrate 30p was prepared as a semiconductor substrate.

(Au fine particles)
Here, the Au microparticles 510 produced by a method using phase separation of a block copolymer will be described.

  First, a 30 nm thick Au film is formed by vacuum evaporation using a transparent substrate 100 having a light-transmitting electrode 10 as a light irradiation surface electrode and p-type polycrystalline Si 30p (FIG. 10A) deposited thereon as a substrate. 520 was formed. A resist was spin-coated thereon and annealed at 250 ° C. for 1 hour to form a resist layer 102 having a thickness of about 100 nm. Further, an SOG solution was spin-coated on the resist layer 102 and annealed at 250 ° C. for 1 hour to form an SOG layer 103 having a thickness of about 30 nm. Thus, an intermediate layer made of resist and SOG was obtained.

  Next, a polymer obtained by mixing PMMA (Mw: 1500) at a weight ratio of 6: 4 with a block copolymer of polystyrene (PS) -polymethyl methacrylate (PMMA) was dissolved in propylene glycol monomethyl ether acetate (PGMEA) at 3 wt%. The solution was applied on the substrate by spin coating at 2000 rpm for 30 seconds. Thereafter, the film was pre-baked at 110 ° C. for 90 seconds to evaporate the solvent and obtain a 120 nm thick film.

  Next, annealing was performed at 210 ° C. for 4 hours in a nitrogen atmosphere, and PS and PMMA were phase-separated to form the block copolymer layer 104. The molecular weight of the block copolymer was 78000 g / mol for the PS part and 170000 g / mol for the PMMA part, and a morphology in which PS dot-like microdomains 105 with a diameter of about 50 to 90 nm were obtained in the PMMA matrix was obtained ( FIG. 10B).

Next, the block copolymer layer 104 is etched under the conditions of O ₂ : 30 sccm, 100 mTorr, and RF power 100 W so that the PMMA matrix in the block copolymer layer 104 is selectively removed, and the SOG layer 103 immediately below the PMMA domain. Was completely exposed (FIG. 10C). Next, the SOG layer 103 was etched by CF ₄ -RIE using the remaining PS105 as a mask. By this etching, the PS dot shape 105 is transferred to the SOG layer 103, and a pattern of the SOG layer 103 corresponding to the phase separation of the block copolymer is formed. Subsequently, by performing O ₂ -RIE using the pattern of the SOG layer 103 as a mask, the underlying thermosetting resist was etched, and a columnar pattern having a high aspect ratio was obtained at a position where the PS 105 was present (FIG. 10). (D)).

  The Au thin film 520 was etched by an ion beam milling apparatus using the obtained pattern as a mask. The etching conditions were Ar gas: 5 sccm, ion source output: 500 V, 40 mA, and the etching time was 45 s.

Through the above steps, an Au micro-object 510 array having a thickness of 30 nm, an average volume of the micro-elements of 5.9 × 10 ⁴ nm ³ , and an average center-to-center distance of 76 nm was obtained. The Au occupied volume in the electric field enhancement layer was 39%. Next, the mask on the Au micro-object 510 array was removed by ultrasonic cleaning (FIG. 10E).

  An n + layer 30n was formed thereon by plasma CVD as in Example 2-1 (FIG. 10 (f)). Further, an electrode was mounted in the same manner as in Example 1 to produce a solar battery cell (FIG. 10 (g)).

  The conversion efficiency of the solar cell produced as described above was evaluated in the same manner as in Example 1. As a result, the conversion efficiency was a good value of 6.4%. At the same time, the same experiment was performed when a metal material other than Au was used as the metal thin film 520. For example, the photoelectric conversion efficiencies of 6.4% for Al, 6.5% for Ag, and 6.1% for Cu were confirmed, and it was confirmed that the effect of this example was obtained.

[Reference Example 2]
A polycrystalline Si p-type substrate 30p provided with the light-irradiated surface electrode 10 was produced in the same manner as in Examples 2-1 and 2-2. Next, when the solar cell was produced by sequentially stacking the n + layer 30n and the back electrode 20 without forming the fine structure 50, the photoelectric conversion efficiency was 6.0%.

[Example 3-1]
The case where a polycrystalline p-type Si thin film is used as the Si substrate will be described with reference to FIG. The p-type Si thin film 30p to be the substrate was formed by plasma CVD using dichlorosilane, H ₂ and N ₂ on the substrate 100 having the back electrode 20 formed on the SiO ₂ surface. A polycrystalline Si thin film 30p having a film thickness of 1 μm was obtained at a substrate temperature of 400 ° C. (FIG. 11A). Next, the Al porous thin film 501 (FIG. 11 (b)) and the n + layer 30n are deposited (FIG. 11 (c)) in the same manner as in Example 2-1, and the light irradiation surface electrode 10 is mounted thereon, A battery was produced (FIG. 11 (d)). The solar cell of Example 3-1 produced as described above was evaluated in the same manner as in Example 1. As a result, the photoelectric conversion efficiency was a good value of 4.9%. At the same time, the same experiment was performed when a metal material other than Au was used as the metal thin film 520. For example, it was confirmed that the photoelectric conversion efficiency was 5.0% with Au, 5.0% with Ag, and 4.7% with Cu, and the effects of the present invention were obtained.

  By enhancing the electric field of the porous thin film 501, sufficient absorption of light occurred even in the thin film semiconductor, and high conversion efficiency could be obtained.

[Example 3-2]
A solar cell in which the Al porous thin film 501 in the polycrystalline Si thin film solar cell of Example 3-1 was replaced with the Au micro object 510 was produced. The Au minute body 510 was produced at the boundary between the p layer 30p and the n + layer 30n in the same manner as in Example 2-2. When the same evaluation as in Example 1 was performed, the photoelectric conversion efficiency was a favorable value of 4.9%. At the same time, the same experiment was performed when a metal material other than Au was used as the metal thin film 520. For example, the photoelectric conversion efficiencies of 4.8% for Al, 4.9% for Ag, and 4.6% for Cu were confirmed, and the effects of the present invention were confirmed.

  Due to the electric field enhancement of the fine structure 50, even a thin film semiconductor sufficiently absorbs light, and high conversion efficiency can be obtained.

[Reference Example 3]
A back electrode 20 and a polycrystalline Si p-type thin film substrate 30p were fabricated on a SiO ₂ substrate in the same manner as in Examples 3-1 and 3-2. Next, when the solar cell was produced by sequentially laminating the n + layer 30n and the light irradiation surface electrode 10 without forming the fine structure 50, the photoelectric conversion efficiency was 4.2%.

[Example 4-1]
In this embodiment, the Au porous thin film 501 is formed between the p layer 30p and the i layer 30i having an amorphous Si pin structure. Here, an example is shown in which the Au thin film on the p-type substrate 30p is etched to form the Au porous thin film 501, and the fine structure 50 is formed in the semiconductor layer by laminating the i layer 30i and the n layer 30n. Use 12 to describe.

(P-type Si substrate)
As a first step, a film containing tin oxide (SnO ₂ ) as a main component is formed on a light-transmitting glass substrate 100 at a film thickness of about 500 nm to 800 nm at a temperature of about 500 ° C. using a thermal CVD apparatus. The irradiation surface electrode 10 was formed. At this time, a texture with appropriate irregularities is formed on the surface of the light irradiation surface electrode 10. Next, a p-layer 30p was formed using a plasma CVD apparatus. The p layer 30p was formed on the light irradiation surface electrode 10 by mixing SiH ₄ gas and H ₂ gas as main materials and B ₂ H ₆ as a doping gas (FIG. 12A).
(Au porous film on p-type Si substrate)
The substrate was taken out from the vacuum chamber, and a metal thin film 520 made of Au having a thickness of 30 nm was vacuum deposited (FIG. 12B). Next, a positive thermosetting resist for i-line was spin-coated to form a resist layer 102 having a thickness of about 150 nm. A fine concavo-convex pattern corresponding to the designed opening structure was transferred to the resist layer 102 using a stamper as a mold. In this example, a stamper having a surface structure in which holes having a depth of 120 nm and a diameter of about 300 nm are arranged in a close-packed array with a period of 500 nm was prepared on quartz by electron beam lithography. In the solar cell manufacturing method, the material of the stamper and the method for creating the fine uneven structure of the stamper are not limited. For example, the stamper can be formed by a method using the fine particles described above or a method using a block copolymer. As the release treatment, the surface of the stamper was coated with a fluorine-based release agent such as perfluoropolyether, and the release energy was improved by reducing the surface energy of the stamper. The stamper is pressed onto the resist layer 102 using a heater plate press at a substrate temperature of 125 ° C. and a stamping pressure of 6.7 kN / cm ² , returned to room temperature over 1 hour, and then released vertically. A reversal pattern of the template was transferred to 102. As a result, a periodic opening resist pattern 102 having a structure in which columnar protrusions having a diameter of 320 nm are periodically arranged was created (FIG. 12C). Note that the present embodiment is not limited to thermal nanoimprinting, and the present embodiment provides even when similar patterns are formed using various imprinting techniques such as optical imprinting and soft imprinting. It does not impair the function of the solar cell.

Using this resist pattern as an etching mask, the Au thin film 520 was etched by an ion beam milling apparatus (FIG. 12D). The etching conditions were Ar gas: 5 sccm, ion source output: 500 V, 40 mA, and the etching time was 45 s. Next, the resist layer 102 on the Au thin film 520 was removed by O ₂ -RIE.

Through the above steps, an Au porous thin film 501 having an opening having a thickness of 30 nm, an average opening area of 8.0 × 10 ⁻² μm ² (opening diameter of 320 nm), and an average opening ratio of 37.1% was obtained (FIG. 12). (E)).

(I layer, n layer on Au porous film)
The substrate was again placed in the chamber, and an amorphous Si i layer 30 i and an n layer 30 n were formed on the Au porous thin film 501. Similar p layer 30p, a plasma CVD apparatus, SiH ₄ gas by i-type Si layer in which the i-layer 30i to 300 nm (FIG. 12 (f)), 30nm are sequentially deposited an n layer 30n by PH ₃ and SiH ₄ gas mixture A pin type photoelectric conversion layer 60 was formed (FIG. 12G). At this time, the opening of the Au porous thin film 501 was filled with i-type amorphous Si 30i. Next, the back electrode 20 was mounted on the surface of the n layer 30n (FIG. 12 (h)).

(Production and characteristics of solar cells)
As for the conversion efficiency of the solar cell produced as described above, the back electrode 20 was attached in the same manner as in Example 1, and the photoelectric conversion efficiency was evaluated. As a result, the conversion efficiency was a good value of 4.8%. At the same time, the same study was performed when a metal material other than Au was used as the metal thin film 520. For example, Al was 4.7%, Ag was 4.9%, and Cu was 4.7%, and it was confirmed that the effect of this embodiment can be obtained.

Further, a buffer layer may be provided between the p layer film 30p and the i layer film 30i in order to improve interface characteristics.

(Au porous film between i layer and n layer)
Further, when the Au porous thin film 501 was formed not only between the p layer and the i layer but also between the i layer and the n layer, a good value of 4.9% was shown. At the same time, the same investigation was performed when a metal material other than Au was used as the metal thin film 520. For example, Al was 4.8%, Ag was 4.9%, and Cu was 4.7%, confirming that the effects of the present invention were obtained.

[Example 4-2]
In this example, an example in which an Ag minute body is used instead of the Au porous thin film in the amorphous Si solar cell of Example 4-1, will be described with reference to FIG.

First, similarly to Example 4-1, the light irradiation electrode 10 and the p-type amorphous Si 30p were laminated on the glass substrate 100 (FIG. 13A).

Next, an Ag minute body 510 was formed on the surface of the p-type amorphous Si 30p. The manufacturing method of the micro object 510 is as follows. First, the resist thin film 102 was laminated on the p-type amorphous Si 30p by spin coating (FIG. 13B).

  A fine concavo-convex pattern corresponding to the designed fine particle structure was transferred to the resist thin film 102 using a stamper as a mold. In this example, a stamper having a surface structure in which pillars having a depth of 120 nm and a diameter of 320 nm are arranged in a close-packed arrangement with a period of 500 nm is prepared on quartz by electron beam lithography, and the same as in Example 4-1. A porous resist mask 102 was formed by this method (FIG. 13C). Next, Ag was vacuum-deposited on the porous resist mask 102 by 30 nm (FIG. 13D), and the resist was removed by ultrasonic cleaning, whereby an Ag dot pattern 510 was formed on the p-type amorphous Si 30p. (FIG. 13 (e)).

An i layer 30i (FIG. 13 (f)) and an n layer 30n (FIG. 13 (g)) were stacked by CVD using p-type amorphous Si 30p loaded with Ag fine particles 510 as a substrate. Furthermore, the back electrode 20 was mounted in the same manner as in Example 4-1, and a solar battery cell was produced (FIG. 13 (h)).

When the photoelectric conversion efficiency of the solar cell produced by the above procedure was evaluated in the same manner as in Example 1, it showed a good value of 4.7%. At the same time, the same study was performed when a metal material other than Ag was used as the metal micro-object 510. For example, Al was 4.6%, Au was 4.6%, and Cu was 4.5%, confirming that the effects of the present invention were obtained.

Further, when the Ag minute body 510 was formed not only between the p layer and the i layer but also between the i layer and the n layer, a good value of 4.9% was shown. At the same time, the same investigation was performed when a metal material other than Au was used as the metal thin film 520. For example, Al was 4.8%, Au was 4.8%, and Cu was 4.6%, confirming that the effects of the present embodiment can be obtained.

[Reference Example 4]
Using the same method as in Examples 4-1 and 4-2, an amorphous Si solar cell not including the metal microstructure 50 was produced, and the conversion efficiency was 4.5%.

[Example 5-1]
In the present embodiment, a case where a microcrystalline Si pin structure is formed by plasma CVD and an Ag porous thin film 510 is formed between the p layer 30p and the i layer 30i will be described.

(Deposition of microcrystalline Si (p, i, n) layer)
As a first step, as in Example 4-1, a p-type microcrystalline Si layer 30p was deposited on the glass substrate 100 on which the light irradiation surface electrode 10 was formed. The microcrystalline Si layer 30p was formed at a substrate temperature of 200 ° C. or lower using plasma CVD. The preparation of the microcrystalline Si layer 30p, an SiH ₄ diluted with _{H 2} as the material gas, using _B 2 _{H 6} diluted with _{H 2} as the doping gas.

  Next, an Ag porous thin film 501 was formed on the microcrystalline Si layer 30p. The same method as in Example 4-1 was used as a method of disposing the Ag porous thin film 501.

  An i layer 30i and an n layer 30n were formed on the Ag porous thin film 520 by plasma CVD. At this time, the opening of the Ag porous thin film 501 was filled with i-type microcrystalline Si30i. Next, the back electrode 20 was mounted on the surface of the n layer 30n to produce a cell.

  The conversion efficiency of the solar cell produced as described above was evaluated in the same manner as in Example 1. As a result, the conversion efficiency was a good value of 4.8%. At the same time, the same experiment was performed when a metal material other than Ag was used as the metal thin film 520. For example, Al was 4.5%, Au was 4.6%, and Cu was 4.4%, and it was confirmed that the effect of this embodiment can be obtained.

[Example 5-2]
In this example, a microcrystalline Si pin structure was formed by plasma CVD, and an Au micro object 510 was formed between the p layer 30p and the i layer 30i.

The substrate 100, the light irradiation surface electrode 10, and the p-layer 30p of microcrystalline Si were produced in the same manner as in Example 5-1. Next, an Au minute body 510 was formed on the p layer 30p. As a manufacturing method of the Au micro object 510, the imprint method described in Example 4-1 was used. However, a stamper having a reversal pattern of the stamper used in Example 4-1 was used. As a result, a layer in which cylindrical Au micro objects 510 were arranged in a triangular lattice pattern was obtained. The micro body 510 had a height of 30 nm, an average diameter of 320 nm, an average volume of 2.4 × 10 ⁻³ μm ³ , and an average distance between the centers of two adjacent cylinders was 500 nm.

  On top of that, similarly to Example 5-1, an i layer 30i and an n layer 30n were formed by plasma CVD, and a back electrode 20 was mounted to fabricate a cell.

  The conversion efficiency of the solar cell produced as described above was evaluated in the same manner as in Example 1. As a result, the conversion efficiency was a good value of 4.5%. At the same time, the same experiment was performed when a metal material other than Al was used as the metal thin film 520. For example, Al is 4.5%, Ag is 4.5%, and Cu is 4.4%, and it was confirmed that the effect of this embodiment can be obtained.

[Reference Example 5]
A microcrystalline Si solar cell not including the fine structure 501 was produced using the same method as in Examples 5-1 and 5-2, and the conversion efficiency was 4.1%.

[Example 6-1]
In this embodiment, a method for manufacturing a compound semiconductor solar cell using GaAs having an electric field enhancement layer 40 made of a porous thin film 501 and its characteristics will be described with reference to FIG. Here, an Al porous thin film 501 was formed as the porous thin film 501.

First, an Al porous thin film 501 was formed on a p-type GaAs wafer 30p.

The production method of the porous thin film 501 is as follows. First, a resist pillar pattern 102 having a high aspect ratio was formed on a p-type GaAs substrate 30p in the same manner as in Example 2-2 (FIG. 14A). Al was vapor-deposited on the finished columnar pattern 102 to a film thickness of 30 nm (FIG. 14B). Then, after performing an ashing process using O ₂ plasma, a lift-off process of removing the columnar pattern portion 102 by immersing in water and performing ultrasonic cleaning, the porous thin film 501 having a desired opening is p-type GaAs. Obtained on the substrate 30p (FIG. 14C).

Through the above steps, Al porous having openings with a thickness of 30 nm, an average opening area of 2.0 × 10 ³ nm ² (opening diameter of 50 nm), an average distance between centers of adjacent openings of 70 nm, and an average opening ratio of 52%. A thin film 501 was obtained.

  Using the p-type GaAs 30p on which the Al porous thin film 501 was deposited as a substrate, n + type GaAs 30n was deposited by MOCVD (FIG. 14D). At this time, the opening of the Al porous thin film 501 was filled with n + type GaAs.

  As an electrode, Au / Au—Zn (3%) (light irradiation surface electrode 10) is applied to the surface of the p-type GaAs 30p that is the irradiation surface, and Au—Ge (0.5%) is applied to the surface of the n + -type GaAs 30n that is the back surface. Electrode 20) was used. The electrodes (light-irradiated surface electrode 10 and back surface electrode 20) were formed by vapor deposition so as to have the same shape as in Example 1 (FIG. 14E).

  When the photoelectric conversion efficiency of the GaAs solar cell produced by the above procedure was evaluated by the same method as in Example 1, it was a good value of 6.2%. At the same time, the same experiment was performed when a metal material other than Au was used as the metal thin film 520. For example, 6.5% for Au, 6.6% for Ag, and 6.4% for Cu, and it was confirmed that the effect of the present embodiment can be obtained.

[Example 6-2]
In this example, a method for manufacturing a compound semiconductor solar cell using GaAs having an electric field enhancement layer 40 made of a minute body 510 and its characteristics will be described with reference to FIG. Here, an Al micro body was formed as the micro body 510.

First, an Al micro body 510 was formed on the surface of a p-type GaAs wafer.

  The manufacturing method of the micro object 510 is as follows.

First, a thin film 520 having a thickness of 30 nm was formed by depositing Al on the p-type GaAs substrate 30 (FIG. 15A) by vacuum deposition (FIG. 15B). Next, a resist pillar 102 having a high aspect ratio was formed on the Al thin film 520 using silica fine particles in the same manner as in Example 2-1 (FIG. 15C). Next, the Al thin film 520 was etched by an ICP-RIE apparatus using the resist pattern 102 as a mask (FIG. 15D). Etching conditions were the same as those in Example 2-1. Next, the remaining resist mask 102 was removed by O ₂ etching using a reactive reactive etching apparatus, and an Al micro-object 510 was formed (FIG. 15E). As a result, the average diameter of the minute bodies 510 was 112 nm, and the average distance between the centers of the minute bodies was 200 nm.

  An n + type GaAs 30n was deposited by MOCVD using the p-type GaAs 30p on which the Al microparticles 510 were deposited as a substrate (FIG. 15 (f)).

  As an electrode, Au / Au—Zn (3%) (light irradiation surface electrode 10) is applied to the surface of the p-type GaAs 30p that is the irradiation surface, and Au—Ge (0.5%) is applied to the surface of the n + -type GaAs 30n that is the back surface. Electrode 20) was used. The electrode was fabricated by vapor deposition so as to have the same shape as in Example 1 (FIG. 15G).

  When the photoelectric conversion efficiency of the GaAs solar cell produced by the above procedure was evaluated in the same manner as in Example 1, it showed a good value of 6.4%. At the same time, the same experiment was performed when a metal material other than Al was used as the metal thin film 520. For example, 6.5% for Au, 6.6% for Ag, and 6.3% for Cu, confirming that the effects of the present embodiment can be obtained.

[Reference Example 6]
Using the same method as in Examples 6-1 and 6-2, a compound semiconductor type solar cell using GaAs not including the fine structure 50 was produced. The conversion efficiency was 5.5%.

[Example 7-1]
In this example, a method for manufacturing a chalcopyrite (CIGS) compound semiconductor solar cell having an electric field enhancement layer 40 made of a porous thin film 501 will be described with reference to FIGS. In this example, first, a Mo electrode 20 serving as a lower electrode was formed on a substrate 100 made of soda lime glass by vacuum deposition. For the lower electrode 20, Ti, W or the like may be used in addition to Mo. Next, Cu, In, and Ga are deposited by sputtering to form a layer called a precursor. This precursor was put into a furnace and annealed at a temperature of about 500 ° C. in an atmosphere of H ₂ Se gas, whereby the precursor became the CIGS layer 30 (FIG. 16A).

  In the process of forming the photoelectric conversion layer 60, several techniques have been developed, such as a method of performing annealing after vapor-depositing Cu, In, Ga, and Se to form a film. Is not limited to the above method, and the photoelectric conversion layer 60 can be formed by any method.

  Next, an Au porous thin film 501 was formed on the CIGS layer 30. The Au porous thin film 501 was produced by depositing the Au thin film 520 by 30 nm on the CIGS layer 30 to form the periodic opening resist pattern 102 as in Example 4-1 (left side of FIG. 16B). The right side of FIG. 16B is an overhead view of the left side of FIG. 16B viewed from the resist pattern 102 side. Similarly to Example 4-1, Au was etched using the resist pattern 102 as a mask to form an Au porous thin film 501 (left side of FIG. 16C). The right side of FIG. 16C is an overhead view of the left side of FIG. 16C viewed from the Au porous thin film 501 side.

  The Au porous thin film 501 produced by the above steps had an average opening diameter of 320 nm and an opening ratio of 37.0%.

  A CdS layer 30 was formed on the produced Au porous thin film 501 (FIG. 16D). As the CdS layer 30, a layer having a thickness of 70 nm was formed by a solution growth method. At this time, the Al opening was filled with CdS30. On the CdS layer 30, ZnO was formed by MOCVD as the transparent conductive film 10 to produce a solar battery cell (FIG. 16 (e)).

  The photoelectric conversion efficiency of the chalcopyrite compound semiconductor solar cell produced by the above procedure was evaluated in the same manner as in Example 1. As a result, the conversion efficiency was a good value of 7.1%. At the same time, the same experiment was performed when a metal material other than Au was used as the metal thin film 520. For example, Al was 7.0%, Ag was 7.3%, and Cu was 7.1%, and it was confirmed that the effect of this embodiment can be obtained.

[Example 7-2]
In this example, a method for manufacturing a chalcopyrite compound semiconductor solar cell having an electric field enhancement layer 40 made of a minute body 510 will be described with reference to FIGS. Here, the Au minute body 510 is formed as the minute body 510.

First, as in Example 7-1, a substrate 100 made of soda lime glass, an Mo electrode 20, and a CIGS layer 30 were prepared (FIG. 17A). An Au thin film 520 was deposited on the CIGS layer 30 to a thickness of 30 nm, and a periodic opening resist pattern was formed by the same method as in Example 4-1 (left side of FIG. 17B). The right side of FIG. 17B is an overhead view of the left side of FIG. 17B viewed from the resist pattern 102 side. Next, by performing RIE for 30 s under the conditions of O ₂ : 5 sccm, Ar: 50 sccm, 0.7 Pa, 100 mTorr, and RF power 100 W, the opening shape was expanded and a triangular pyramidal resist pattern was formed (FIG. 17 (c) left side). The right side of FIG. 17C is an overhead view of the left side of FIG. 17C viewed from the resist pattern 102 side. By etching Au using the obtained resist pattern 102 as a mask, a triangular pyramid-shaped Au micro object 510 was formed (FIG. 17D). The right side of FIG. 17D is an overhead view of the left side of FIG.

The Au microparticles 510 produced by the above process had an average volume of 6.2 × 10 ³ nm ³ and an average center distance of 102 nm.

  The CdS layer 30 was formed on the CIGS 30 on which the produced Au micro object 510 was deposited (FIG. 17E). As the CdS layer 30, a layer having a thickness of 70 nm was formed by a solution growth method. On the CdS layer 30, ZnO was formed by MOCVD as the transparent conductive film 10 to produce a solar battery cell (FIG. 17 (f)).

  The photoelectric conversion efficiency of the chalcopyrite compound semiconductor solar cell produced by the above procedure was evaluated in the same manner as in Example 1. As a result, the conversion efficiency was a good value of 7.0%. At the same time, the same experiment was performed when a metal material other than Au was used as the metal thin film 520. For example, Al was 6.9%, Ag was 7.1%, and Cu was 6.8%, confirming that the effects of the present embodiment can be obtained.

[Reference Example 7]
Using the same method as in Examples 7-1 and 7-2, chalcopyrite compound semiconductor solar cells not including the fine structure 50 were produced. The conversion efficiency was 6.4%.

  Needless to say, the present invention is not limited to the above-described embodiments and can be implemented with various modifications.

  That is, the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various forms can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, some components may be omitted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

DESCRIPTION OF SYMBOLS 10 ... Light irradiation surface electrode, 20 ... Back electrode, 30 ... Semiconductor layer, 31 ... Photoactive layer, 32 ... Bulk semiconductor layer, 40 ... Electric field enhancement layer, 50 ... Fine structure, 60 ... photoelectric conversion layer, 70 ... electrons, 71 ... holes, 72 ... electron flow, _Vbi ... built-in electric field, 100 ... substrate, 102 ..Resist layer, 103 ... SOG layer, 104 ... Block copolymer layer, 105 ... Micro domain, 106a ... Composition containing acrylic monomer, 106s ... Silica fine particles, 501 ... Porous Thin film, 502 ... microsphere, 503 ... micropillar, 504 ... micropyramid, 510 ... microbody, 520 ... metal thin film, 530 ... square, p ... Semiconductor p layer, i... Semiconductor i layer, n... Semiconductor n layer, 701. ..Electrons that vibrate by light, 702... Electrons that do not vibrate, 703... Electron dense part, 704... Electron sparse part, 705, 706. Side, L ... light, T ... skin thickness, E ... local electric field, D ... observation point of electric field intensity

Claims (7)

A photoelectric conversion layer formed by two electrode layers and two semiconductor layers stacked between the two electrode layers;
A layer having a plurality of metallic microscopic bodies sandwiched between two adjacent semiconductor layers,
The average volume of each micro object is in a range of 520 nm ³ or more and 6.5 × 10 ⁻² μm ³ or less, and the average distance between two adjacent micro objects is 100 nm or more and 1 μm or less. A photoelectric conversion element.   The photoelectric conversion element according to claim 1, wherein at least one of the semiconductor layers contains an organic substance.   The organic substance is polythiophene and derivatives thereof, polypyrrole and derivatives thereof, pyrazoline derivatives, arylamine derivatives, stilbene derivatives, triphenyldiamine derivatives, oligothiophene and derivatives thereof, polyvinylcarbazole and derivatives thereof, polysilane and derivatives thereof, side chain or main chain. Polysiloxane derivatives having an aromatic amine in the chain, polyaniline and derivatives thereof, phthalocyanine derivatives, porphyrin and derivatives thereof, polyphenylene vinylene and derivatives thereof, polythienylene vinylene and derivatives thereof, fullerene and derivatives thereof, poly (3,4-ethylene The photoelectric conversion element according to claim 1, which is selected from the group consisting of dioxythiophene) -poly (styrene sulfonate). Forming a first semiconductor layer;
Forming a metal thin film layer on the first semiconductor layer;
Forming a mask having an uneven pattern on the metal thin film layer;
Using the mask, a minute body having an average volume of 520 nm ³ or more and 6.5 × 10 ⁻² μm ³ or less and an average of two adjacent intervals of 100 nm or more and 1 μm or less is formed from the metal thin film layer. Process,
Forming a second semiconductor layer on the micro body;
A process for producing a photoelectric conversion element, comprising:   5. The method of manufacturing a photoelectric conversion element according to claim 4, wherein the step of forming a mask according to claim 4 includes a step of forming a resist pattern on the metal thin film layer using a stamper. The step of forming the mask according to claim 4 comprises the steps of:
Applying a resist on at least a part of the metal thin film layer or at least a part of the semiconductor layer to form a resist coating layer;
Forming a single particle layer of fine particles on the surface of the resist coating layer;
Forming a resist pattern having a fine concavo-convex pattern using the single particle layer as an etching mask;
The method for producing a photoelectric conversion element according to claim 4, wherein: The step of forming the mask according to the claim item 4,
Forming an intermediate layer on at least a part of the metal thin film layer or at least a part of the semiconductor layer;
Generating a micro-domain of a block copolymer on the surface of the intermediate layer;
The method for producing a photoelectric conversion element according to claim 4, wherein: