JP2006066550A - Photoelectric conversion element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric conversion element which can effectively make use of light transmitted by a photoelectric conversion layer to improve conversion efficiency by a simple structure. <P>SOLUTION: An electric field formation substance 4 is arranged on another surface 13 in the widthwise direction of a photoelectric conversion layer 2. A part of a light entering the photoelectric conversion layer 2 passes through the photoelectric conversion layer 2. The electric field formation substance 4 can form an electric field in the photoelectric conversion layer 2 by being given a light with a larger wavelength band than a band gap of the photoelectric conversion layer 2 among the lights passing through the photoelectric conversion layer 2. In the photoelectric conversion layer 2 where the electric field is formed, the electric field causes excitation to generate electrons and holes. The photoelectric conversion layer 2 can produce more electric energy, and lights not contributing to the conversion to electric energy in the photoelectric conversion layer 2 are converted into electric field, thereby allowing them to contribute to the generation of electric energy in the photoelectric conversion layer 2. As a result, the conversion efficiency can be improved. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a photoelectric conversion element that improves the efficiency of photoelectric conversion in a wavelength band where the absorption coefficient of a photoelectric conversion layer is low and efficiently converts light energy into electric energy.

  A silicon crystal widely used as a photoelectric conversion material of a photoelectric conversion element has a band gap of about 1.1 eV, and the energy of this band gap is about 1100 nm when converted to the wavelength of light. Shorter wavelength light can be converted into electrical energy. Hereinafter, the crystalline silicon is referred to as crystalline silicon.

  However, since crystalline silicon is an indirect transition semiconductor, its absorption coefficient is small for light with a wavelength in the range of 800 nm to 1100 nm, and most of this wavelength band is formed by crystalline silicon without being converted into electrical energy. It passes through the photoelectric conversion layer.

  For this reason, the photoelectric conversion element formed using crystalline silicon prevents loss due to transmission of infrared light by setting the thickness of the photoelectric conversion layer to, for example, 200 μm to 300 μm. The conversion efficiency of energy into electrical energy is low. In particular, in a solar cell that generates electric energy from sunlight, the surface area of the photoelectric conversion element is large. Therefore, when the photoelectric conversion layer is formed in the thickness as described above, the weight of the solar cell increases, Problems arise such as difficulty in installation on the roof or the like, and the need for extra materials for forming the photoelectric conversion elements, resulting in increased manufacturing costs.

  In the first conventional technique, an N-type layer is formed on the light incident side of a P-type semiconductor substrate, and a microcrystal having a carrier concentration higher than that of the P-type semiconductor substrate on the side opposite to the light incident side of the P-type silicon substrate. A solar cell in which a back surface electric field layer made of silicon and a back surface electrode are stacked in this order is disclosed. An insulating film layer is provided between the back surface electric field layer and the back surface electrode. The back surface field layer has a higher concentration of carriers than the semiconductor substrate included in the photoelectric conversion layer, and minority carriers generated by the semiconductor substrate due to the action of the internal electric field of the back surface field layer are generated between the semiconductor substrate and the back surface field layer. A barrier that does not flow on the contact surface is formed, and the insulating film layer increases the amount of light reflected in the semiconductor substrate. This increases the photoelectric conversion efficiency (see, for example, Patent Document 1).

  In the second conventional technique, a photovoltaic element is provided with a layer made of a material that emits visible light upon receiving infrared light, and the solar cell is irradiated with visible light generated from the outer layer, thereby generating power generation efficiency. (For example, refer to Patent Document 2).

  In the third conventional technique, the photoelectric conversion layer is provided with a layer made of a material that emits visible light when receiving ultraviolet light and a layer made of a material that shows visible light emitted when receiving infrared light. There has been proposed a method for increasing the power generation efficiency by irradiating the photoelectric conversion layer with visible light (see, for example, Patent Document 3).

JP-A-6-310740 JP-A 63-244688 JP 2003-142716 A

  In the first conventional technique, the internal electric field layer transmits the light transmitted through the N-type layer and the P-type semiconductor substrate, reflects the transmitted light through the insulating film layer, and makes it incident on the P-type semiconductor substrate again. However, since the light reflected by the insulating film is likely to pass through the N-type and P-type semiconductor substrates again, the improvement in conversion efficiency of light energy into electrical energy in such a wavelength band is slight. Further, in the first conventional technique, it is necessary to form an insulating film layer and a back surface electric field layer, which increases the manufacturing process of the photoelectric conversion element. In addition, in order to stack these layers on a substrate, it is necessary to use a vacuum deposition apparatus in all the processes for forming each layer because of the compatibility with the adjacent layers and the electrical characteristics, etc. Therefore, there is a problem that manufacturing is not easy and manufacturing cost and tact time are increased.

  In the second and third conventional techniques, one visible light photon is extracted from a plurality of long wavelength photons, so that the conversion efficiency is low with respect to light having a wavelength of 800 to 1100 nm that can be photoelectrically converted by one photon. There is a problem.

  The objective of this invention is providing the photoelectric conversion element which can improve the conversion efficiency by using effectively the light which permeate | transmits a photoelectric converting layer with simple structure.

The present invention comprises a photoelectric conversion layer that receives light from one surface side in the thickness direction and converts light energy into electrical energy;
And an electric field forming material that forms an electric field in the photoelectric conversion layer by being given light of a predetermined wavelength band that is transmitted through the photoelectric conversion layer and has energy larger than the band gap of the photoelectric conversion layer. It is a photoelectric conversion element.

Further, in the present invention, the electric field forming substance includes fine particles that form localized surface plasmons,
The fine particles are arranged such that the minimum distance between the surface of the fine particles and the other surface in the thickness direction of the photoelectric conversion layer is equal to or smaller than the particle size of the fine particles.

Further, in the present invention, the photoelectric conversion layer is formed including a silicon crystal,
The predetermined wavelength band is in a range of 800 nm to 1100 nm.

  According to the present invention, the fine particles are made of metal, have a rod shape, are arranged in parallel in the longitudinal direction on the other surface in the thickness direction of the photoelectric conversion layer, and have an energy equal to the band gap of the photoelectric conversion layer. When the wavelength is N (nm), the dimension in the short direction of the fine particles is N / 10 nm or less, and is selected to be 10 nm or more, and the dimension in the long direction of the fine particles is one time the dimension in the short direction. And 20 times or less.

  In the present invention, the fine particles have an inner layer portion made of a dielectric and an outer layer portion made of a metal and formed outside the inner layer portion. The fine particles are formed in a substantially spherical shape and face the photoelectric conversion layer. When the wavelength of light having energy equal to the band gap of the photoelectric conversion layer is N (nm), a part of the inner layer portion is exposed from the outer layer portion, the thickness of the outer layer portion is N / 10 nm or less and 10 nm The particle size of the fine particles selected above is N nm or less and is selected to be 20 nm or more.

  Further, according to the present invention, the fine particles are made of metal, have a ring shape, have an axis line disposed substantially perpendicularly on the other surface in the thickness direction of the photoelectric conversion layer, and have energy equal to the band gap of the photoelectric conversion layer. When the wavelength is N (nm), the thickness between the inner diameter and the outer diameter of the fine particles is N / 10 nm or less, is formed to be 10 nm or more, the outer diameter is Nnm or less, and is selected to be 20 nm or more. Features.

  According to the present invention, when light is incident on the photoelectric conversion layer from the one surface side in the thickness direction, the photoelectric conversion layer can generate electric energy by converting the energy of the incident light into electric energy.

  A part of the light incident on the photoelectric conversion layer is transmitted through the photoelectric conversion layer. The light transmitted through the photoelectric conversion layer includes light that can theoretically be converted into electric energy in the photoelectric conversion layer, in other words, light having energy larger than the band gap of the photoelectric conversion layer.

  The electric field forming substance can form an electric field in the photoelectric conversion layer by being given light having a wavelength band larger than the band gap of the photoelectric conversion layer among the light transmitted through the photoelectric conversion layer. In the photoelectric conversion layer in which the electric field is formed, excitation is generated by this electric field, and electrons and holes are generated. Accordingly, the number of electrons and holes generated by the photoelectric conversion layer can be increased, and more electric energy can be generated in the photoelectric conversion layer.

  In this way, light that has not contributed to the conversion to electric energy in the photoelectric conversion layer can be converted into an electric field and contribute to the generation of electric energy in the photoelectric conversion layer, so that light can be used effectively. Thus, the conversion efficiency for converting light energy into electrical energy can be improved.

  According to the invention, the electric field forming substance includes fine particles that form localized surface plasmons. The optical properties of microparticles with a diameter comparable to or smaller than the wavelength of light are explained by Mie's theory, which strongly absorbs or scatters light of a specific wavelength, depending on the physical properties of the material and the shape of the microparticles. It has been known. In particular, fine particles made of a material having a negative dielectric constant, such as a metal, generate an electric field called localized surface plasmon on the surface of the fine particles due to the resonance phenomenon between the light and the fine particles during the strong light absorption described above. . It is known that the electric field intensity of this localized surface plasmon is about two to three orders of magnitude greater than the electric field of incident light. Localized surface plasmons are synonymous with light-enhanced electric fields. The resonance phenomenon between such light and fine particles made of metal is called plasmon resonance. This localized surface plasmon usually exists only in the vicinity of the surface of the fine particle, and its intensity decreases rapidly as the distance from the surface increases. By arranging the fine particles so that the minimum distance between the surface of the fine particles and the other surface in the thickness direction of the photoelectric conversion layer is less than the size of the fine particles, a strong electric field due to localized plasmons is given to the photoelectric conversion layer. This can further improve the conversion efficiency. The particle size of the fine particles is a peak value of the particle size distribution of a plurality of fine particles, and the particle size of one fine particle is obtained by averaging the longitudinal direction of the fine particles and the dimensions of the short method.

  According to the invention, the photoelectric conversion layer is formed of a silicon crystal, and the electric field forming substance generates an electric field with light having a wavelength band in the range of 800 nm to 1100 nm. Silicon crystal includes single crystal silicon, polycrystalline silicon, and microcrystalline silicon. Since the crystalline body of silicon has a low absorption coefficient in the wavelength band of 800 nm to 1100 nm, light in this wavelength band is easily transmitted. By forming an electric field with light having a wavelength that easily passes through such a photoelectric conversion layer, light in this wavelength band can be effectively used to improve conversion efficiency.

  Further, according to the present invention, the efficiency of absorption by long-wavelength light, in other words, infrared fine particles, is improved by selecting and forming fine particles made of metal and having a rod shape as described above. As a result, the fine particles can form a strong electric field on the surface thereof. The rod shape includes a substantially cylindrical shape and a substantially spheroid shape.

  The plasmon resonance peak is mainly determined by the ratio between the longitudinal dimension and the lateral dimension of the fine particles having a rod shape, and the longitudinal dimension is more than 1 time and less than 20 times the lateral dimension. The effect of plasmon resonance is obtained in the range. In the case where a silicon crystal is used for the photoelectric conversion layer, it is more preferable that the longitudinal dimension of the fine particle is in the range of 3 to 5 times the lateral dimension, since the resonance peak falls within the wavelength range of 800 nm to 1100 nm. .

  Plasmon resonance occurs when the dimension in the short direction of the fine particle is 1/10 or less of the wavelength of the light. However, if it is less than 10 nm, the peak of the plasmon resonance becomes sharp, but the resonance becomes extremely weak, which is sufficient. Can not get a good effect. Therefore, when the wavelength of the light is N (N is a positive number) nm, the dimension in the short direction of the fine particles is N / 10 or less, and is selected to be 10 nm or more, and more preferably 15 nm to 30 nm.

  According to the invention, the inner layer portion made of a dielectric and the outer layer portion made of metal and formed outside the inner layer portion are formed in a substantially spherical shape, facing the photoelectric conversion layer, and the outer layer portion. By selecting and forming the fine particles from which a part of the inner layer portion is exposed to a size as described above, it is possible to improve the absorption efficiency of long-wavelength light, in other words, infrared fine particles. Can form a strong electric field on its surface.

  When the thickness of the outer layer portion is N / 10 nm, no plasmon is generated. On the other hand, if the thickness of the outer layer portion is less than 10 nm, the resonance peak becomes sharp, but the strength itself becomes very weak, so that an effect cannot be obtained. Further, as the particle size of the particles is reduced, the plasmon resonance peak shifts to a shorter wavelength, and if it is less than 20 nm, there is no effect on wavelengths of 800 to 1100 nm. In addition, when the particle diameter exceeds Nnm, which is 1 times the wavelength, plasmon is not generated. Therefore, when the wavelength of light having energy equal to the band gap of the photoelectric conversion layer is N (nm) (N is a positive number), the thickness of the outer layer portion is N / 10 nm or less, and is selected to be 10 nm or more, The particle diameter of the fine particles is Nnm or less and is selected to be 20 nm or more. The particle diameter is more preferably about 150 nm to 300 nm, which shows a resonance peak in light in the range of 800 to 1100 nm.

  Further, according to the present invention, particles made of a metal and having a substantially ring shape are arranged on the other surface in the thickness direction of the photoelectric conversion layer so that the axis of the ring is substantially vertical. This increases the surface area of the fine particles facing the photoelectric conversion layer, and concentrates the plasmon resonance effect by the fine particles on the region facing the photoelectric conversion layer, thereby increasing the region with a strong electric field formed in the photoelectric conversion layer. be able to. In addition, by selecting and forming fine particles of the size described above, the absorption efficiency of long-wavelength light, in other words, infrared fine particles can be improved, thereby forming a strong electric field on the surface of the fine particles. can do.

  If the thickness between the inner diameter and the outer shape of the fine particles is N / 10 nm, plasmons are not generated. On the other hand, when the thickness between the inner diameter and the outer shape of the fine particles is less than 10 nm, the resonance peak becomes sharp, but the strength itself becomes very weak, so the effect cannot be obtained. Further, as the particle size of the particles is reduced, the plasmon resonance peak shifts to a shorter wavelength, and if it is less than 20 nm, there is no effect on wavelengths of 800 to 1100 nm. In addition, when the outer shape of the particle exceeds Nnm, which is one time the wavelength, plasmon is not generated.

  Therefore, when the wavelength of light having energy equal to the band gap of the photoelectric conversion layer is N (N is a positive number) (nm), the thickness between the inner diameter and the outer diameter of the fine particles is N / 10 nm or less and 10 nm. The outer diameter is Nnm or less and is selected to be 20 nm or more.

  FIG. 1 is a cross-sectional view illustrating a configuration of a photoelectric conversion element 1 according to an embodiment of the present invention. In the present embodiment, the photoelectric conversion element 1 is a solar cell that receives sunlight and converts light energy into electric energy. As used herein, the term “light” includes visible light, infrared light and ultraviolet light.

  The photoelectric conversion element 1 includes a photoelectric conversion layer 2, a transparent electrode 3, an electric field forming material 4, and a back electrode 5.

  The photoelectric conversion layer 2 receives light from the thickness direction one surface 6 side, and converts light energy into electric energy. The photoelectric conversion layer 2 is formed by laminating a first conductive semiconductor layer and a second conductive semiconductor layer. The first conductive type semiconductor layer is formed of one of P and N type semiconductors, and the second conductive type semiconductor layer is formed of one of P and N type semiconductors. The first and second conductive semiconductor layers of the photoelectric conversion layer 2 are formed including silicon (Si) crystals, in other words, crystalline silicon. Crystalline silicon is realized by, for example, any of polycrystalline silicon, single crystal silicon, and microcrystalline silicon. In the present embodiment, the crystalline silicon is realized by polycrystalline silicon. The first conductivity type semiconductor layer is formed by diffusing either one of a group III or group V element in crystalline silicon, and the second conductivity type semiconductor layer is formed in the group III or V group in crystalline silicon. It is formed by diffusing any one of these elements. In the present embodiment, the first conductive semiconductor layer is plate-shaped and is formed of a P-type crystalline silicon substrate, and the second conductive semiconductor layer is one surface in the thickness direction of the P-type crystalline silicon substrate. It is formed by diffusing a group V element in the part. The thickness T1 of the photoelectric conversion layer 2 is selected to be less than 200 μm, for example, 0.1 μm to 5 μm. Moreover, the thickness direction one surface 6 and the other surface 13 of the photoelectric conversion layer 2 are formed in a substantially flat surface. In the present embodiment, the substantially plane includes a plane.

The transparent electrode 3 is formed on the one surface 6 in the thickness direction of the photoelectric conversion layer 2, that is, on the second conductivity type semiconductor layer, and is formed to a predetermined layer thickness T2. The transparent electrode 3 is transparent to light having a predetermined wavelength, specifically, ultraviolet rays, visible rays, and infrared rays. In other words, ultraviolet rays, visible rays, and infrared rays pass through the transparent electrode 3. The transparent electrode 3 has conductivity and covers the entire region of the surface 6 in the thickness direction of the photoelectric conversion layer 2. The transparent electrode 3 is made of, for example, tin oxide (SnO ₂ ) or zinc oxide (ZnO). The transparent electrode 3 is formed by, for example, chemical vapor deposition (
Chemical Vapor Deposition method: abbreviated CVD method). The predetermined layer thickness T2 is selected to be about several μm, for example.

  The electric field forming substance 4 is transmitted through the transparent electrode 3 and the photoelectric conversion layer 2, and is given an electric field in the photoelectric conversion layer 2 by being given light of a predetermined wavelength band having energy larger than the band gap of the photoelectric conversion layer 2. Form. The electric field forming material 4 includes a plurality of fine particles 11. The fine particles 11 form an electric field when given light of a predetermined wavelength band. The predetermined wavelength band ranges from 800 nm (nanometers) to 1100 nm (nanometers). A part of the light incident on the photoelectric conversion layer 2 passes through the photoelectric conversion layer 2. The light transmitted through the photoelectric conversion layer 2 includes light that can theoretically be converted into electric energy in the photoelectric conversion layer 2, in other words, light having energy larger than the band gap of the photoelectric conversion layer 2. ing. In the present embodiment, the photoelectric conversion layer 2 is formed of crystalline silicon. Since crystalline silicon has a low absorption coefficient in a wavelength band in the range of 800 nm to 1100 nm, light in this wavelength band is easily transmitted through the photoelectric conversion layer 2. The fine particles 11 can form an electric field in the photoelectric conversion layer 2 by being given light having a wavelength band larger than the band gap of the photoelectric conversion layer 2 out of the light transmitted through the photoelectric conversion layer 2. In the photoelectric conversion layer 2 in which an electric field is formed, excitation is generated by this electric field, and electrons and holes are generated. Thereby, the number of electrons and holes generated by the photoelectric conversion layer 2 can be increased, and more electric energy can be generated in the photoelectric conversion layer 2.

  Thus, the electric field forming material 4 can convert light that has not contributed to the conversion to electric energy in the photoelectric conversion layer 2 into an electric field, and can contribute to the generation of electric energy in the photoelectric conversion layer 2. Light can be used effectively, and the photoelectric conversion element 1 can improve the conversion efficiency for converting light energy into electric energy. The fine particles 11 are arranged such that the minimum distance W1 between the surface 12 of the fine particles 11 and the other surface 13 in the thickness direction of the photoelectric conversion layer 2 is equal to or smaller than the particle diameter D1 of the fine particles 11.

  The fine particles 11 are made of a material having a negative dielectric constant, and are made of a metal in the present embodiment. The dielectric constant of the fine particles 11 varies depending on the material, the wavelength of light applied to the fine particles 11, and the shape of the fine particles. The fine particles 11 are provided on the other surface 13 in the thickness direction of the photoelectric conversion layer 13 and on the other surface 13 side in the thickness direction. The fine particles 11 have a particle diameter D1 that is approximately equal to or less than the wavelength of light. Such optical properties of the fine particles 11 are explained by Mie's theory, and are known to strongly absorb or scatter light of a specific wavelength depending on the physical properties and shape of the material. The fine particles 11 made of a material having a negative dielectric constant, such as a metal, generate an electric field called localized surface plasmon on the surface 12 of the fine particles 11 when the light is strongly absorbed, and the intensity of the electric field is incident light. It is known that it becomes a large value of about 2 to 3 digits with respect to the electric field. This localized surface plasmon is usually present only in the vicinity of the surface 12 of the fine particle 11, and its intensity rapidly decreases as the distance from the surface 12 increases.

  FIG. 2 is a graph showing the distance from the surface 12 of the fine particles 11 and the electric field strength. As shown in FIG. 2, the electric field formed on the surface 12 of the fine particles 11 and the vicinity thereof rapidly decreases in strength as the electric field is separated from the surface 12 of the fine particles 11. The region where a strong electric field is generated by the localized surface plasmon is in the range of the same distance as the particle diameter D1 from the particle surface. By arranging the fine particles 11 so that the minimum distance W1 between the surface 12 of the fine particles 11 and the other surface 13 in the thickness direction of the photoelectric conversion layer 2 is equal to or smaller than the particle size D1 of the fine particles 11, the localized surface plasmon A strong electric field can be applied to the photoelectric conversion layer 2, thereby further improving the conversion efficiency. The particle diameter D1 of the fine particles 11 is the peak value of the particle size distribution of the plurality of fine particles 11, and the particle diameter D1 of one fine particle 11 is the longitudinal direction of the fine particles 11. The dimension of the short method is averaged.

  3 is an enlarged plan view showing the fine particles 11, FIG. 4 is a perspective view showing the fine particles 11, and FIG. 5 is a cross-sectional view of the fine particles 11. The fine particles 11 have a rod shape, and in this embodiment, have a substantially cylindrical shape. The fine particles 11 are arranged substantially in parallel in the longitudinal direction on the other surface 13 in the thickness direction of the photoelectric conversion layer 2. In this specification, the substantially cylindrical shape includes a cylindrical shape and a shape approximated to a cylindrical shape.

Plasmon resonance in the fine particles 11 depends on the dielectric constant and shape of the particles, the dielectric constant of the material surrounding the particles, and the like. For example, in the case of a particle having a spherical shape, the resonance wavelength showing an absorption peak changes with an increase in diameter, but in this case, the effect of light scattering of the particle increases and the intensity of the resonance effect itself decreases. On the other hand, by changing the shape, not the size of the particle, and using a fine particle made of metal that has a shape other than a sphere, it exhibits a strong resonance effect against long-wavelength light, that is, infrared light. Have been reported (for example, Physical Review
Letters Vol. 88 (7), p77402-1 (2002)). Hereinafter, a particle having a spherical shape may be referred to as a spherical particle, and a particle having a cylindrical shape may be referred to as a cylindrical particle.

  FIG. 6 is a graph in which the wavelength dependence of light absorption when gold is used as the material of the fine particles is plotted for each of the spherical particles and the cylindrical particles. In FIG. 6, the horizontal axis indicates the wavelength of light, and the vertical axis indicates the absorption coefficient. Here, the ratio of the length of the columnar particles in the short side direction and the long side direction is set to 1: 4. Here, the longitudinal direction of the cylindrical particles is the axial direction of the cylinder, and the short direction is the radial direction of the cylinder. In the case of cylindrical particles, the peak of the absorption coefficient occurs in a longer wavelength than spherical particles, specifically in the wavelength band of infrared light compared to spherical particles, and shows strong absorption compared to spherical particles. I understand that. The diameter of the spherical particles is selected to be, for example, about the wavelength of light. Spherical particles that are generally used as fine particles for generating localized surface plasmons are silver and gold that exhibit strong plasmon resonance at relatively long wavelengths, but the wavelengths having the strongest plasmon resonance are about 320 nm and 530 nm, respectively. A large effect cannot be obtained for light having a wavelength of 800 to 1100 nm that is transmitted through the photoelectric conversion layer 2 of the embodiment.

  In the present embodiment, when the wavelength of light having energy equal to the band gap of the photoelectric conversion layer 2 is N (N is a positive number) (nm), the dimension D2 in the short direction of the fine particles 11 is the wavelength of the light. N / 10 nm or less which is 1/10 or less of N and 10 nm or more is selected. Further, the dimension D3 in the longitudinal direction of the fine particles 11 is selected to be more than 1 time and not more than 20 times the dimension D2 in the lateral direction. The plasmon resonance peak is mainly determined by the ratio of the longitudinal dimension D3 of the rod-shaped fine particles 11 to the lateral dimension D2, and the longitudinal dimension D3 exceeds 1 times the lateral dimension D2. In the range of 20 times or less, the effect of plasmon resonance can be obtained. When a silicon crystal is used for the photoelectric conversion layer 2, the resonance peak is in the wavelength range of 800 nm to 1100 nm when the longitudinal dimension D3 of the fine particles 11 is in the range of 3 to 5 times the lateral dimension D2. It is more preferable to enter.

  Plasmon resonance occurs when the dimension D2 in the short direction of the microparticles 11 is 1/10 or less of the wavelength of light, but when it is less than 10 nm, the peak of the plasmon resonance becomes sharp but the resonance becomes extremely weak. Therefore, a sufficient effect cannot be obtained. Therefore, the dimension D2 in the short direction is N / 10 nm or less and is selected to be 10 nm or more, and more preferably 15 nm to 30 nm.

  The dimension D2 in the short direction of the fine particles 11 having the absorption coefficient as shown in FIG. 6 needs to be sufficiently smaller than the wavelength of the light to be absorbed. It is desirable that it is 80 nm or less which is 1 time. Further, the dimension D3 in the longitudinal direction of the fine particles 11 can exhibit strong plasmon resonance in the range of 1 to 20 times the dimension D2 in the lateral direction. By providing such fine particles 11 on the surface opposite to the light incident surface of the photoelectric conversion layer 2, the light transmitted through the photoelectric conversion layer 2 is strongly absorbed by the fine particles 11 and strong on the surface 12 of the fine particles 11. An electric field is generated. By exciting the electrons in the photoelectric conversion layer 2 with this electric field, the power generation efficiency for converting the light energy in the photoelectric conversion layer 2 into electric energy can be increased.

  The metal used as the material of the fine particles 11 is preferably gold, silver and platinum, for example. The fine particles 11 use, for example, a photochemical method in which metal chloride is reduced and synthesized while irradiating ultraviolet light, and a seed method in which spherical particles made of metal having a diameter of several nanometers are used as a seed to react with metal chloride. Formed. Since the fine particles 11 obtained by these methods are dispersed in the solution, this solution is applied to the other surface 13 in the thickness direction of the photoelectric conversion layer 2, and the solvent is dried to remove the photoelectric conversion layer 2. The fine particles 11 can be disposed in contact with the other surface 13 in the thickness direction. As a method of applying the solution to the other surface 13 in the thickness direction of the photoelectric conversion layer 2, for example, a spin coating method, a LB method (Lagmuir Blodgett method), or the like can be used.

  Each axis L1 parallel to the longitudinal direction of the fine particles 11 is preferably oriented in a random direction as shown in FIG. 3 within a virtual surface along the other surface 13 in the thickness direction of the photoelectric conversion layer 2. By arranging the microparticles 11 in this way, the electric field formation state by the plurality of microparticles 11 does not depend on the incident angle of the light that has passed through the photoelectric conversion layer 2, so that regardless of the arrangement of the photoelectric conversion elements 1. The electric field formation state by the plurality of fine particles 11 can be made uniform, and the degree of freedom of installation of the photoelectric conversion element 1 can be improved. Further, it is desirable that all the fine particles 11 are in contact with the photoelectric conversion layer 2. Such a dispersed state is realized by adjusting the concentration of the solution and the drying method when the solution is applied. It is desirable that the adjacent fine particles 11 are not in contact with each other. In order to dispose the fine particles 11 apart from each other, for example, the concentration of the solution containing the fine particles 11 can be sufficiently reduced and applied. In addition, the surface of the fine particles 11 may be previously surrounded by a polymer layer formed of polyacryl or dodecanethiol. In this case, the fine particles 11 are separated by the thickness of the polymer layer even if the polymer layer contacts. Can be arranged.

  On the other surface 13 in the thickness direction of the photoelectric conversion layer 2, the first electrode connection region 16 formed between the fine particle arrangement region 15 and the adjacent fine particle arrangement region 15, and the fine particle arrangement region 15 and the photoelectric conversion layer 2. A second electrode connection region 18 formed between the peripheral edge 17 and the peripheral edge 17 is formed. Hereinafter, the first and second electrode connection regions 16 and 18 may be collectively referred to as an electrode connection region 19 in some cases. The fine particle arrangement region 15 has a predetermined width W2 in a predetermined first direction A1 perpendicular to the thickness direction, and the second direction of the photoelectric conversion layer 2 in the second direction A2 perpendicular to the thickness direction and the first direction A1. It extends from one side of A2 to the other. The adjacent fine particle arrangement regions 15 are arranged with a predetermined distance W3 in the first direction A1. The fine particles 11 are arranged in the fine particle arrangement region 15 as described above. Further, the fine particles 11 are not arranged in the electrode connection region 19.

  As the area of the fine particle arrangement region 15 increases, the area where the effect of the fine particles 11 can be obtained increases. On the contrary, when the area of the electrode connection region 19 decreases, the electrical resistance increases and the electrical loss increases. For this reason, the area of the fine particle arrangement region 15 and the area of the electrode connection region 19 are selected to be equal, for example. In addition, the electrical loss becomes smaller as the width W2 of the fine particle arrangement region 15 is smaller than the distance between the adjacent fine particle arrangement regions 15. The width W2 of the fine particle arrangement region 15 is selected to be about 20 μm, for example.

  The back electrode 5 is formed from the thickness direction other surface 13 side of the photoelectric conversion layer 2 to cover the electric field forming material 4 and the thickness direction other surface 13 of the exposed photoelectric conversion layer 2. The back electrode 5 is electrically connected to the photoelectric conversion layer 2. The back electrode 5 is made of a metal different from the material of the fine particles 11, for example, aluminum (Al). The back electrode 5 is formed of a material having a conductivity different from that of the fine particles 11. Thus, the fine particles 11 and the back electrode 5 are prevented from being integrated, and the shape of the fine particles 11 is maintained.

  The back electrode 5 is formed by, for example, a vacuum deposition method, and is formed by a conductive film that covers the entire region of the other surface 13 in the thickness direction of the photoelectric conversion layer 2. The other surface in the thickness direction of the conductive film forming the back electrode 5 is formed on a plane perpendicular to the thickness direction of the photoelectric conversion layer 2, and the maximum dimension T3 in the thickness direction of the back electrode 5 is selected to be 5 μm, for example.

  The back electrode 5 contacts the photoelectric conversion layer 2 in the electrode connection region 19. The back electrode 5 functions as a terminal for taking out the electric energy generated by the photoelectric conversion layer 2 to the outside, and functions as a reflector that reflects the light transmitted through the photoelectric conversion layer 2 to the photoelectric conversion layer 2 again. And have. By providing the back electrode 5, the light transmitted through the photoelectric conversion layer 2 can be reflected to the photoelectric conversion layer 2 and incident again on the photoelectric conversion layer 2, thereby improving the conversion efficiency. it can. The back electrode 5 is electrically connected to the electric field forming material 4 and can be electrically connected to the photoelectric conversion layer 2 through the fine particles 11. As described above, in the electrode connection region 19, By connecting to the conversion layer 2, it is possible to reduce the contact resistance with the photoelectric conversion layer 2 compared to connecting to the photoelectric conversion layer 2 through the fine particles 11. Thereby, the energy loss at the time of taking out the electrical energy produced | generated in the photoelectric converting layer 2 to the exterior can be reduced as much as possible.

  FIG. 7 is a flowchart showing a process for forming the photoelectric conversion element 1. The process proceeds from step S0 to step S1, the transparent electrode 3 is formed on one surface 6 in the thickness direction of the photoelectric conversion layer 2, and the process proceeds to step S2. In step S2, the fine particles 11 are arranged in the fine particle arrangement region 15 on the other surface 13 in the thickness direction of the photoelectric conversion layer 2, and the process proceeds to step S3. In order to selectively arrange the fine particles 11 only in the specific particle arrangement region 15, for example, a solution in which the fine particles 11 are dispersed is applied in a state where the region other than the fine particle arrangement region 15 on the substrate is subjected to water repellent treatment. This can be realized by arranging the fine particles 11.

  In step S3, the back electrode 5 is formed. After the fine particles 11 are placed, by forming the back electrode 5, the arranged fine particles 11 can be covered with the back electrode 5, and the fine particles 11 can be fixed on the other surface 13 in the thickness direction of the photoelectric conversion layer 2.

  In the photoelectric conversion element 1 of the present embodiment, by providing the electric field forming material 4, the conversion efficiency for converting light energy into electric energy is about 2% compared to the photoelectric conversion element without the electric field forming material 4. It can be improved by ~ 5%. As a result, a solar cell with improved conversion efficiency can be obtained even if the thickness of the photoelectric conversion layer 2 is selected to be 0.1 μm to 5 μm as described above. The electric field forming substance 4 is formed by the fine particles 11, and the particle diameter D1 of the fine particles 11 is several μm as described above, and its weight is very small. Therefore, even if the electric field forming material 4 is provided in the photoelectric conversion layer 2, the increase in the weight of the photoelectric conversion element 1 by the electric field forming material 4 is minute. That is, since the conversion efficiency can be improved without increasing the weight of the photoelectric conversion element 1, the photoelectric conversion element 1 can be easily installed on the roof of a building, and the photoelectric conversion layer is formed. The number of semiconductor materials can be reduced, and more photoelectric conversion elements can be formed from a certain amount of semiconductor material, so that the manufacturing cost can be reduced.

  Moreover, in the photoelectric conversion element 1 of the present invention, the step of providing the electric field forming material 4 does not require the use of a vacuum deposition apparatus, which facilitates manufacture, thereby reducing the manufacturing cost and manufacturing time of the photoelectric conversion element. it can.

  In another embodiment of the present invention, a texture structure is formed on one surface portion in the thickness direction in contact with the transparent electrode 3 of the photoelectric conversion layer 2 of the photoelectric conversion element 1 described above, and the photoelectric conversion layer is formed from the one surface 6 side in the thickness direction. 2 may prevent reflection of light incident on 2 on the one surface 6. With this configuration, the photoelectric conversion efficiency can be further improved.

  FIG. 8 is a perspective view showing the shape of the fine particles 21 in the photoelectric conversion element of another embodiment of the present invention, and FIG. 9 is a cross-sectional view of the fine particles 21 of FIG. 8 cut along a virtual plane including the long axis. . The photoelectric conversion element of the present embodiment and the photoelectric conversion element 1 of the above-described embodiment are different only in the shape of the fine particles 11, and other portions are formed in the same manner. The fine particles 11 described above have a substantially cylindrical shape, but the fine particles 21 of the present embodiment are formed in a substantially spheroidal shape. The substantially spheroidal shape includes a spheroidal shape and a shape approximated to a spheroidal shape. The substantially spheroidal fine particles 21 are arranged so that the major axis is along the other surface 13 in the thickness direction of the photoelectric conversion layer 2. In the present embodiment, the dimension D3 in the longitudinal direction of the fine particles 11 is a major axis, and the dimension D2 in the lateral direction is a minor axis. The long diameter and short diameter dimensions D2 and D3 of the fine particles 11 are selected in the same manner as the fine particles 11 of the above-described embodiment. Thereby, like the photoelectric conversion element 1 of the above-described embodiment, conversion efficiency can be improved.

  FIG. 10 is a perspective view showing an electric field forming material 24 in a photoelectric conversion element according to still another embodiment of the present invention, and FIG. 11 is a cross-sectional view showing a process of forming the electric field forming material 24. 10 and 11, the electric field forming substance 24 arranged in the fine particle arrangement region 16 is shown in an enlarged manner. The photoelectric conversion element of the present embodiment is different from the photoelectric conversion element 1 of the above-described embodiment only in the configuration of the electric field forming material 4, specifically the shape of the fine particles 11 contained in the electric field forming material 4. These parts are similarly formed. Therefore, the same components are denoted by the same reference numerals, and the description thereof is omitted.

  In the present embodiment, the electric field forming material 24 includes fine particles 31. The fine particles 31 have an inner layer portion 32 made of a dielectric and an outer layer portion 33 made of metal and formed outside the inner layer portion 32. The fine particles 31 are formed in a substantially spherical shape, and a part of the inner layer portion 32 is exposed from the outer layer portion 32. In the present embodiment, the inner layer portion 32 is exposed at the portion facing the photoelectric conversion layer 2 from the outer layer portion 33. In the present embodiment, the substantially spherical shape includes a spherical shape and a shape approximated to a spherical shape. In other words, the outer surface 34 of the fine particle 31 has a shape having a curved surface protruding outward or a shape that can be approximated by a plurality of curved surfaces protruding outward.

  When the wavelength of light having energy equal to the band gap of the photoelectric conversion layer 2 is N (nm), the thickness T4 of the outer layer portion 33 is N / 10 or less which is 1/10 or less of the wavelength N of the light. 10 nm or more is selected. The thickness T4 of the outer layer portion 33 is the thickness of the outer layer portion 33 in the radial direction of the fine particles 31. Further, D1 of the fine particles 31 is Nnm or less, which is 1 time or less of the wavelength of the light, and is selected to be 20 nm or more. The particle size D1 of the fine particles 31 is a peak value of the particle size distribution of the plurality of fine particles 31, and the particle size D1 of one fine particle 31 averages the longitudinal direction of the fine particles 31 and the dimensions of the short method. It is a thing.

  The fine particle 31 whose thickness T4 of the outer layer portion 33 is 80 nm or less, which is 1/10 of the wavelength, and whose particle diameter D1 in which the inner layer portion 32 is filled with a dielectric is less than a predetermined wavelength, specifically 800 nm or less. In, plasmon resonance can be generated at a long wavelength, that is, an infrared wavelength band. When the thickness T4 of the outer layer portion 33 is N / 10 nm, no plasmon is generated. On the other hand, if the thickness T4 of the outer layer portion 33 is less than 10 nm, the resonance peak becomes sharp, but the strength itself becomes very weak, so that no effect is obtained. Further, the smaller the particle diameter D1 of the fine particles 31, the more the plasmon resonance peak shifts to a shorter wavelength, and if it is less than 20 nm, there is no effect on wavelengths of 800 to 1100 nm. In addition, when the particle diameter D1 of the fine particles 31 exceeds Nnm which is one time the wavelength, no plasmon is generated. Accordingly, when the wavelength of light having energy equal to the band gap of the photoelectric conversion layer 2 is N (nm), the thickness T4 of the outer layer portion 33 is selected to be N / 10 nm or less and 10 nm or more, and the fine particles 31 The particle size D1 of N is selected to be not more than Nnm and not less than 20 nm. The particle diameter D1 is more preferably about 150 nm to 300 nm showing a resonance peak in light in the range of 800 to 1100 nm.

  In the present embodiment, the fine particles 31 are connected to each other near the other surface 13 in the thickness direction of the photoelectric conversion layer 2. The connecting portion 35 where the fine particles 31 are connected to each other is in close contact with the photoelectric conversion layer 2 and has a predetermined thickness T4. By providing the connecting portion 35 of the fine particles, the fine particles 31 can be prevented from falling off the photoelectric conversion layer 2. By forming the outer layer portion 33, the above-described embodiment and effects can be obtained. In other embodiments of the present invention, the same effect can be obtained even if the inner layer portion 32 and the connecting portion 35 are removed. Obtainable.

  The fine particles 31 described above can be formed by the following process. First, the inner layer portion 32 is disposed on the other surface 13 in the thickness direction of the photoelectric conversion layer 2.

  FIG. 11 (1) is a cross-sectional view showing the inner layer portion 32 arranged on the other surface 13 in the thickness direction of the photoelectric conversion layer 2. The inner layer portion 32 has a substantially spherical shape. In this specification, the substantially spherical shape includes a spherical shape and a shape approximated to a spherical shape. Inner layer portion 32 is formed of a dielectric material that is transparent to light. For example, polystyrene is selected as the dielectric material. The inner layer portions 32 are arranged at a predetermined interval W5. The predetermined interval W5 is selected to be approximately equal to the particle size of the inner layer portion 32.

  FIG. 11 (2) is a cross-sectional view showing the fine particles 31 arranged on the other surface 13 in the thickness direction of the photoelectric conversion layer 2. After the inner layer portion 32 is disposed, a coating film 36 made of metal is formed so as to cover the inner layer portion 32 and the other surface 13 in the thickness direction of the photoelectric conversion layer 32. The coating film 36 is formed, for example, by chemically modifying the inner layer portion 32 or by vacuum deposition. The peritoneum 36 is preferably formed of any one of gold, silver and platinum, for example. The peritoneum 36 becomes the outer layer portion 33 of the fine particles 31.

  Since the inner layer portion 32 of the fine particles 31 is optically transparent, plasmons are generated not only on the outer surface of the fine particles 31 but also on the inner surface, that is, the surface of the outer layer portion 33 on the inner layer portion 32 side, and strengthen each other. Therefore, high-order mode plasmons corresponding to long-wavelength light can be efficiently generated.

  Since such a fine particle 31 has a symmetrical structure, it has no polarization dependency. The symmetrical structure is a structure that is parallel to the thickness direction of the photoelectric conversion layer 2 and is rotationally symmetric with respect to an axis that passes through the center of the fine particles 31. Due to the absence of polarization dependency, the electric field formed around the fine particles 31 is hardly affected by the direction of light incident through the photoelectric conversion layer 2. Therefore, when the photoelectric conversion element 1 is arranged, the photoelectric conversion element 1 can be arranged without worrying about the direction of the photoelectric conversion element 1, so that the degree of freedom of installation can be improved.

  Further, when the electric field forming substance is formed by the fine particles 31, the fine particles 31 are arranged at a higher density on the other surface 13 in the thickness direction of the photoelectric conversion layer 2 as compared with the columnar fine particles 11 of the above-described embodiment. Can do. The inner layer portion 32, which is a spherical particle made of polystyrene having a diameter of about several hundreds of nanometers, is easier to control the size than particles made of metal and cylindrical particles. Since it can be formed easily, the characteristics of plasmon resonance can be easily controlled. That is, the wavelength band in which the fine particles 31 should form an electric field by plasmon resonance can be easily selected simply by polarizing the diameter of the inner layer portion 32. As a result, the degree of freedom in design can be improved.

  In still another embodiment of the present invention, the inner layer portion 32 of the fine particles 31 may be formed of air. Such a shape can be realized by forming the outer layer portion 33 hollow. The inner layer portion 32 of the fine particles 31, in other words, the particles serving as the nucleus of the fine particles 31 may be any material as long as the material transmits light such as a dielectric.

  FIG. 12 is a perspective view showing the configuration of the fine particles 51 contained in the electric field forming substance 44 in the photoelectric conversion element of still another embodiment of the present invention, and FIG. 13 is a cross section taken along the section line XIII-XIII in FIG. FIG. The photoelectric conversion element of the present embodiment and the photoelectric conversion element 1 of the embodiment shown in FIG. 1 described above are different only in the shape of the fine particles 11, and the other parts are formed in the same manner. The fine particles 51 in the present embodiment are made of metal and have a ring shape. Specifically, the fine particles 51 have an annular shape. Hereinafter, the fine particles 51 of the present embodiment may be referred to as annular fine particles 51. In the present embodiment, the ring shape includes a substantially ring shape and a shape that can approximate the ring shape.

  The annular fine particles 51 are arranged on the other surface 13 in the thickness direction of the photoelectric conversion layer 2 so that the axis L2 is substantially vertical. Assuming that the wavelength of light having energy equal to the band gap of the photoelectric conversion layer 2 is N (nm), the thickness T6 between the inner diameter D4 and the outer diameter D5 of the annular fine particle 51 is 1/10 or less of the wavelength N of the light. It is not more than a certain N / 10 nm and 10 nm or more, and the outer diameter D5 is not more than 1 nm of the wavelength N of light and not more than Nnm, and is selected to be 20 nm or more. The inner diameter D4 of the annular fine particle 51 is an average of the maximum inner diameter and the minimum inner diameter, and the outer diameter D5 is an average of the maximum outer diameter and the minimum inner diameter.

  By making the fine particles 51 substantially annular as in the present embodiment, the area where one circular fine particle 31 is in contact with the photoelectric conversion layer 2 can be made larger than the fine particles formed in a spherical shape. it can. Since the electric field enhanced by the resonance of the fine particles 51 exists only in the vicinity of the surface 52 of the fine particles 51, the larger the area where the surface 52 of one fine particle 51 is in contact with the photoelectric conversion layer 2, the larger the electric field on the surface 52 of the fine particles 51. The generated light-enhanced electric field can contribute to photoelectric conversion in the photoelectric conversion layer 2. Thereby, the conversion efficiency in the photoelectric conversion layer 2 can be improved.

  FIG. 14 is a cross-sectional view showing a process for forming the annular fine particles 51. FIG. 14 (1) is a cross-sectional view showing the annular forming auxiliary particles 53 arranged on the other surface 13 in the thickness direction of the photoelectric conversion layer 2. First, the annular forming auxiliary particles 53 are arranged in the fine particle arrangement region 15 on the other surface 13 in the thickness direction of the photoelectric conversion layer 2. The annular forming auxiliary particles 53 are made of, for example, polystyrene. The adjacent annular forming auxiliary particles 53 are provided with a predetermined interval W6 therebetween. The predetermined interval W6 is selected to be approximately equal to the particle size of the annular forming auxiliary particles 53.

  FIG. 14 (2) is a cross-sectional view showing the annular formation auxiliary particles 35 and the other surface 13 in the thickness direction of the photoelectric conversion layer 2 covered with a conductive film 54. After the annular formation auxiliary particles 53 are arranged, a conductive film 54 is formed so as to cover the annular formation auxiliary particles 53 and the other surface 13 in the thickness direction of the photoelectric conversion layer 2. The conductive film 54 is made of a metal such as gold, silver and platinum. The conductive film 54 is formed by, for example, a vapor deposition method.

  FIG. 14 (3) is a cross-sectional view showing a state where a part of the conductive film 54 is removed and the annular formation auxiliary particles 53 are exposed. Part of the conductive film 54 shown in FIG. 14B is removed by etching with the ion beam 55. The ion beam is irradiated from the side opposite to the annular formation auxiliary particles 53 and the photoelectric conversion element 2 of the conductive film 54. Thereby, in the conductive film 54, the portion covering the surface of each annular formation auxiliary particle 53 on the side opposite to the photoelectric conversion layer 2, specifically, in the thickness direction of the photoelectric conversion layer 2, The portion 56 covering the portion opposite to the photoelectric conversion layer 2 is removed from the central portion of the annular formation auxiliary particle 53. Further, a portion 57 formed along the other surface 13 in the thickness direction of the photoelectric conversion layer 2 between the annular formation auxiliary particles 53 in the conductive film 54 is removed.

  FIG. 14 (4) is a cross-sectional view showing a state where the annular fine particles 51 are formed on the other surface 13 in the thickness direction of the photoelectric conversion layer 2. When the above-described steps are finished, the annular formation auxiliary particles 53 are removed. Thereby, annular fine particles 51 are formed on the other surface 13 in the thickness direction of the photoelectric conversion layer 2. The diameter D5 of the annular fine particle 53 is determined by the diameter of the annular formation auxiliary particle 53 and the thickness of the conductive film 54. The dimension H1 of the annular fine particle 51 in the direction of the axis L2 is selected to be approximately equal to the radius of the annular formation auxiliary particle 53.

  In the annular fine particle 51, a strong electric field generated on the surface 52 is generated along the ring. However, the annular fine particle 51 directly formed on the surface of the photoelectric conversion layer as described above has a ring surface, that is, a surface perpendicular to the axis L2. However, since it is in contact with the other surface 13 in the thickness direction of the photoelectric conversion layer 2, more strong electric fields can be generated in the photoelectric conversion layer 2.

  In each embodiment of the present invention, the photoelectric conversion element is shown applied to a solar cell, but the photoelectric conversion element may be applied to another photoelectric conversion element such as a photodiode, for example. Even in this case, the same effect can be obtained.

It is sectional drawing which shows the structure of the photoelectric conversion element 1 of one Embodiment of this invention. 3 is a graph showing the distance from the surface 12 of the fine particles 11 and the electric field strength. It is a top view which expands and shows fine particle 11. 1 is a perspective view showing fine particles 11. FIG. 2 is a cross-sectional view of fine particles 11. FIG. It is the graph which plotted the wavelength dependence of the light absorption at the time of using gold | metal | money as a material of microparticles | fine-particles about each of a spherical particle and a cylindrical particle. 3 is a flowchart showing a formation process of the photoelectric conversion element 1. It is a perspective view which shows the shape of the microparticles | fine-particles 21 in the photoelectric conversion element of the other form of this Embodiment. It is sectional drawing which cut | disconnected the microparticles | fine-particles 21 of FIG. 8 by the virtual one plane containing a long axis. It is a perspective view which shows the electric field formation substance 24 in the photoelectric conversion element in further another form of this Embodiment. 5 is a cross-sectional view illustrating a process of forming an electric field forming substance 24. It is a perspective view which shows the structure of the fine particle 51 contained in the electric field formation substance 44 in the photoelectric conversion element of the further another form of this Embodiment. It is sectional drawing seen from the cut surface line XIII-XIII of FIG. 5 is a cross-sectional view showing a process for forming annular fine particles 51. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoelectric conversion element 2 Photoelectric conversion layer 4, 24, 44 Electric field formation substance 11, 21, 31, 51 Fine particle 32 Inner layer part 33 Outer layer part

Claims (6)

A photoelectric conversion layer that receives light from one surface side in the thickness direction and converts light energy into electrical energy;
And an electric field forming material that forms an electric field in the photoelectric conversion layer by being given light of a predetermined wavelength band that is transmitted through the photoelectric conversion layer and has energy larger than the band gap of the photoelectric conversion layer. A photoelectric conversion element. The electric field forming substance includes fine particles that form localized surface plasmons,
2. The photoelectric device according to claim 1, wherein the fine particles are arranged such that a minimum distance between a surface of the fine particles and another surface in the thickness direction of the photoelectric conversion layer is equal to or smaller than a particle size of the fine particles. Conversion element. The photoelectric conversion layer is formed including a silicon crystal,
The photoelectric conversion element according to claim 1, wherein the predetermined wavelength band is in a range of 800 nm to 1100 nm.   The fine particles are made of metal, have a rod shape, are arranged in parallel in the longitudinal direction on the other surface in the thickness direction of the photoelectric conversion layer, and the wavelength of light having energy equal to the band gap of the photoelectric conversion layer is N (nm). ), The dimension in the short direction of the fine particles is N / 10 nm or less, and is selected to be 10 nm or more, and the dimension in the longitudinal direction of the fine particles is more than 1 time and 20 times the dimension in the short direction. The photoelectric conversion element according to claim 3, wherein the photoelectric conversion element is selected as follows.   The fine particles have an inner layer portion made of a dielectric and an outer layer portion made of metal and formed outside the inner layer portion. The fine particles are formed in a substantially spherical shape and face the photoelectric conversion layer from the outer layer portion to the inner layer portion. Is exposed, and the wavelength of light having energy equal to the band gap of the photoelectric conversion layer is N (nm), the thickness of the outer layer portion is N / 10 nm or less, and is selected to be 10 nm or more, 4. The photoelectric conversion element according to claim 3, wherein the particle diameter of the fine particles is N nm or less and 20 nm or more.   The fine particles are made of metal, have a ring shape, and the axis of light is arranged on the other surface in the thickness direction of the photoelectric conversion layer substantially perpendicularly, and the wavelength of light having energy equal to the band gap of the photoelectric conversion layer is N (nm). ), The thickness between the inner diameter and the outer diameter of the fine particles is N / 10 nm or less, is formed to be 10 nm or more, the outer diameter is N nm or less, and is selected to be 20 nm or more. 3. The photoelectric conversion element according to 3.

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