JP5517775B2 - Photoelectric conversion element - Google Patents

Description

  The present invention relates to a photoelectric conversion element that converts light energy into electrical energy by photoelectric conversion.

  In photoelectric conversion elements such as solar cells, further reduction in the thickness of the photoelectric conversion layer is desired in order to save resources and reduce costs. When the photoelectric conversion layer is simply thinned, the amount of light absorption in the photoelectric conversion layer decreases, so a technique for increasing the amount of absorption in the photoelectric conversion layer is essential.

  As such a technique, a texture structure is produced on the front surface and / or back surface of the photoelectric conversion layer, and incident light and reflected light are scattered on the front surface and back surface of the photoelectric conversion layer, respectively, so that the optical path length in the photoelectric conversion layer is increased. There are ways to increase it. In addition, a technique for processing a periodic fine structure in a photoelectric conversion element is known. In this case, the light to be transmitted through the photoelectric conversion layer is diffracted by the periodic fine pattern, and the light is confined in the photoelectric conversion layer by setting the condition that the reflected light is totally reflected in the photoelectric conversion layer. The photoelectric conversion efficiency is improved.

JP 61-288473 A JP-A-4-133360 JP 2000-294818 A Special table 2009-533875

  In a conventional structure in which a texture structure is formed on the front surface and / or back surface of a photoelectric conversion layer, the texture structure is random, so there is no regularity in light scattering, and light emitted outside the photoelectric conversion element. Is inherently difficult to reduce. Further, when a periodic fine structure is processed in the photoelectric conversion element, it is expensive to produce a periodic array, and it is difficult to reduce the cost of the photoelectric conversion element.

  This invention is made | formed in view of such a subject, The objective is to provide the technique which can raise the light absorption rate of a photoelectric conversion element and improve photoelectric conversion efficiency, suppressing manufacturing cost.

One embodiment of the present invention is a photoelectric conversion element. The photoelectric conversion element includes a photoelectric conversion layer and a plurality of metal nanoparticles provided in a two-dimensional array on the main surface side of the photoelectric conversion layer opposite to the light receiving surface, and the plurality of metal nanoparticles. The number density is in a range of 5.0 × 10 ⁸ pieces / cm ² or more and 3.0 × 10 ⁹ pieces / cm ² or less.

  According to the photoelectric conversion element of this aspect, incident light that could not be absorbed by the photoelectric conversion element is scattered and reflected by the plurality of metal nanoparticles provided on the main surface side of the photoelectric conversion element opposite to the light receiving surface. Therefore, the optical path length of the incident light in the photoelectric conversion layer is increased, and the incident light can be efficiently absorbed.

  In the photoelectric conversion element of the above aspect, the metal nanoparticles may be made of Au, Ag, Al, Cu, or an alloy of these metals. A dielectric layer having a refractive index of 1.3 or more that covers the surface of the metal nanoparticles may be further provided. A transparent thin film provided between the metal nanoparticles and the photoelectric conversion layer may be further provided. Further, the oxygen content of the transparent thin film may be 5 atm% or more.

  A combination of the above-described elements as appropriate can also be included in the scope of the invention for which patent protection is sought by this patent application.

  ADVANTAGE OF THE INVENTION According to this invention, the light absorption rate of a photoelectric conversion element can be raised and photoelectric conversion efficiency can be improved, suppressing manufacturing cost.

FIG. 1A is a schematic cross-sectional view illustrating the structure of the photoelectric conversion element according to Embodiment 1. FIG. FIG. 1B is a plan view showing the arrangement of the metal nanoparticles when the semiconductor substrate is viewed from the back side. 5 is a process cross-sectional view illustrating the method for manufacturing the photoelectric conversion element according to Embodiment 1. FIG. 6 is a schematic cross-sectional view showing a configuration of a photoelectric conversion element according to Embodiment 2. FIG. 4 is a graph showing the quantum yield of the solar cell of Example 2.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate.

  FIG. 1A is a schematic cross-sectional view illustrating the structure of the photoelectric conversion element according to Embodiment 1. FIG. FIG. 1B is a plan view showing the arrangement of the metal nanoparticles when the photoelectric conversion element is viewed in plan from the side opposite to the light receiving surface. FIG. 1A corresponds to a cross-sectional view taken along the line AA in FIG. As shown in FIG. 1A, the photoelectric conversion element 10 includes a photoelectric conversion layer 20, an antireflection film 32, a plurality of metal nanoparticles 36, and a dielectric layer 38. In the present embodiment, the photoelectric conversion element 10 is a solar cell.

  The photoelectric conversion layer 20 has a pn junction in which a p-type semiconductor and an n-type semiconductor are joined, and light energy from the sun is converted into electric energy by the photovoltaic effect of the pn junction. Direct current can be taken out of the photoelectric conversion element 10 by attaching electrodes (not shown) to the n-type semiconductor and the p-type semiconductor, respectively. The photoelectric conversion layer 20 is, for example, a single crystal Si substrate, and has a pn junction that is well-known as a solar cell formed of a group IV semiconductor substrate.

As shown in FIGS. 1A and 1B, the antireflection film 32 is provided on the first main surface of the photoelectric conversion layer 20 on the light receiving surface side of the photoelectric conversion element 10. The antireflection film 32 is not particularly limited in form and material as long as it has both transparency in the wavelength region of light received by the photoelectric conversion element 10 and a function of preventing reflection of light received by the photoelectric conversion element 10. but, for _example, SiO _2, SiN _x, etc. TiO 2, ITO and the like.

  The plurality of metal nanoparticles 36 are two-dimensionally arranged on the second main surface of the photoelectric conversion layer 20 on the side opposite to the light receiving surface of the photoelectric conversion element 10. In other words, the plurality of metal nanoparticles 36 are scattered in a two-dimensional array on the second main surface of the photoelectric conversion layer 20.

  The material of the metal nanoparticle 36 is not particularly limited as long as it is a metal material. A material having a wavelength close to the above wavelength is desirable, and examples thereof include Au, Ag, Al, Cu, and alloys of these metals.

A preferable range of the number density of the metal nanoparticles 36 per unit area when the photoelectric conversion layer 20 is viewed in plan is 5.0 × 10 ⁸ pieces / cm ^{2 to} 3.0 × 10 ⁹ pieces / cm ² , more preferably 7.0 × ¹⁰ 8 ~2.5 × ^{10 9} pieces / cm ^2, more preferably 1.0 × ^{10 9} ~2.0 × ¹⁰ 9 pieces / cm ^2.

  The shape of the metal nanoparticles 36 is not particularly limited, and examples thereof include a spherical shape, a hemispherical shape, a cylindrical shape, a prismatic shape, a rod shape, and a disc shape. The diameter D of the metal nanoparticles 36 in a plan view of the photoelectric conversion layer 20 is, for example, in the range of 80 to 400 nm. The height H of the metal nanoparticles 36 when the second main surface of the photoelectric conversion layer 20 is the reference plane is, for example, in the range of 5 to 500 nm.

The dielectric layer 38 is provided on the second main surface side of the photoelectric conversion layer 20 so as to cover at least the surface of the metal nanoparticles 36. The refractive index of the dielectric layer 38 is preferably 1.3 or more. Moreover, the property of the dielectric layer 38 includes transparency to light received by the photoelectric conversion element 10. That is, the band gap of the dielectric layer 38 is larger than the band gap of the photoelectric conversion layer 20. Moreover, when forming an electrode on the dielectric layer 38, it is preferable that it has electroconductivity from a viewpoint of improvement of current collection property. The material of the dielectric layer 38 includes calcium fluoride, magnesium fluoride, barium fluoride, lithium fluoride, silicon carbide, sapphire, alumina, crystal, fluororesin, SnO ₂ , FTO (fluorine-doped tin oxide), ITO, _{ZnO, SiO 2, TiO 2,} ZrO 2, Mn 3 O 4, Y 2 O 3, WO 3, Nb 2 O 5, La 2 O 3, Ga 2 O 3, Ag 2 O, CuO, a-Si: H , Μc-Si: H, SiO _x : H, SiC, SiN _x , AlO _x : H, polyethylene terephthalate, polycarbonate, polymethyl methacrylate, polyethylene, polypropylene, ethylene-vinyl acetate copolymer, polystyrene, polyimide, polyamide, Polybutylene terephthalate, polyethylene naphthalate, polysulfone, Examples include polyethersulfone, polyetheretherketone, polyvinyl alcohol, polyvinyl chloride, polyvinylidene chloride, triacetyl cellulose, polyurethane, and cycloolefin polymer. Although the thickness of the dielectric material layer 38 is not specifically limited, For example, it is 5-2000 nm.

  According to the photoelectric conversion element 10 according to the first embodiment described above, incident light that could not be absorbed by the photoelectric conversion element 10 is a plurality of metal nano-crystals provided on the second main surface side of the photoelectric conversion element 10. Since the light is scattered and reflected by the particles 36, the optical path length of the incident light in the photoelectric conversion layer 20 is increased, and the incident light can be efficiently absorbed.

More specifically, light scattering by the single metal nanoparticle 36 has no directionality, and light that collides with the single metal nanoparticle 36 is randomly reflected. However, by controlling the particle density of the plurality of metal nanoparticles 36, the direction of reflected light from the metal nanoparticles 36 can be controlled from the interaction between the metal nanoparticles 36. In particular, by setting the particle density of the plurality of metal nanoparticles 36 to a range of 5.0 × 10 ⁸ particles / cm ^{2 to} 3.0 × 10 ⁹ particles / cm ² , scattering of reflected light from the metal nanoparticles 36 is performed. An angle becomes large and the optical path length in the photoelectric converting layer 20 can be increased. As a result, the received light is efficiently absorbed in the photoelectric conversion layer 20, and the photoelectric conversion efficiency of the photoelectric conversion element 10 can be increased.

  In the photoelectric conversion element 10 of the present embodiment, a plurality of metal nanoparticles 36 are covered with a dielectric layer 38. Thereby, since it is suppressed that the metal nanoparticle 36 is exposed to air | atmosphere or water, stability of the metal nanoparticle 36 can be improved. Moreover, in the photoelectric converting layer 20, when long wavelength side light is easy to permeate | transmit, a scattering characteristic can be improved, shifting the active wavelength of the metal nanoparticle 36 to the long wavelength side.

(Method for manufacturing photoelectric conversion element)
FIG. 2 is a process cross-sectional view illustrating the method for manufacturing the photoelectric conversion element according to Embodiment 1. A method for manufacturing the photoelectric conversion element according to Embodiment 1 will be described with reference to FIGS.

First, as shown in FIG. 2A, an antireflection film 32 having a film thickness of 50 to 200 nm is laminated on the first main surface S1 of the photoelectric conversion layer 20 to be a light receiving surface. The photoelectric conversion layer 20 includes a p-type single crystal Si substrate, and a pn junction is formed on the photoelectric conversion layer 20 in advance using a known thermal diffusion method, ion implantation method, vacuum film formation method, or the like. Yes. The method of laminating the antireflection film 32 is not particularly limited, and examples thereof include a method of forming a transparent material such as SiN _x or ITO on the photoelectric conversion layer 20 by a vacuum film formation method.

  Next, as shown in FIG. 2B, a mask 40 is formed on the second main surface S2 of the photoelectric conversion layer 20 on the side opposite to the light receiving surface. In the mask 40, a plurality of openings 42 are formed so that the metal nanoparticle formation region of the second main surface S2 of the photoelectric conversion layer 20 is exposed. For example, after anodizing the surface of the aluminum substrate, the mask 40 removes the aluminum substrate other than the anodized surface (porous alumina film), and forms a through hole in the porous alumina film using a phosphoric acid solution. Can be produced. In addition, the mask 40 can be made of a resist in which a predetermined opening is patterned. By using a resist as the mask 40, the metal nanoparticles can be regularly arranged two-dimensionally.

  Next, as shown in FIG. 2C, a metal such as Ag, Al, Au, Cu, or an alloy containing these metals is directed toward the second main surface S <b> 2 of the photoelectric conversion layer 20 through the mask 40. Are deposited by vacuum evaporation. The metal particles pass through the opening 42 provided in the mask 40 and are selectively deposited on the second main surface S <b> 2 of the photoelectric conversion layer 20 in the opening 42. Thereby, the metal nanoparticles 36 are formed in the opening 42, and the plurality of metal nanoparticles 36 are two-dimensionally arranged on the second main surface of the photoelectric conversion layer 20. The size of the metal nanoparticles 36 when the photoelectric conversion layer 20 is viewed in plan is defined by the size of the opening 42 provided in the mask 40. When the mask 40 is formed using a porous alumina film, the size of the opening 42 is proportional to the applied voltage during aluminum anodic oxidation. For example, when 120 V is applied to an aluminum substrate with a 0.3 mol / l malonic acid electrolyte, the diameter of the opening 42 is about 150 nm and the diameter of the metal nanoparticles 36 is also about 150 nm. In addition, the height of the metal nanoparticles 36 when the second main surface of the photoelectric conversion layer 20 is the reference surface can be controlled by changing the vacuum deposition time. When the time of vacuum vapor deposition is short, the spherical surface becomes a hemisphere facing downward (in the direction away from the second main surface of the photoelectric conversion layer 20), and when the time of vacuum vapor deposition is sufficiently long, cylindrical and angular Columnar or filler shape.

  Next, as shown in FIG. 2D, after the mask 40 is removed, a dielectric layer 38 is laminated so as to cover the surface of the metal nanoparticles 36. Although the method for laminating the dielectric layer 38 is not particularly limited, for example, a method of forming a dielectric material such as ZnO by a vacuum film forming method can be cited as in the method for forming the antireflection film 32.

  Through the steps described above, the photoelectric conversion element 10 according to Embodiment 1 can be easily formed, and thus the manufacturing cost of the photoelectric conversion element 10 can be reduced.

(Embodiment 2)
FIG. 3 is a schematic cross-sectional view illustrating the configuration of the photoelectric conversion element 10 according to the second embodiment. In the photoelectric conversion element 10 of the present embodiment, the metal nanoparticles 36 are not in direct contact with the second main surface of the photoelectric conversion layer 20, and the metal nanoparticles 36 and the second main surface of the photoelectric conversion layer 20 A transparent thin film 50 is interposed therebetween. The transparent thin film 50 is transparent to the light received by the photoelectric conversion element 10. That is, the band gap of the transparent thin film 50 is larger than the band gap of the photoelectric conversion layer 20. Moreover, it is preferable that the transparent thin film 50 has electroconductivity from a viewpoint of the current collection improvement in the case of forming an electrode on the second main surface side of the photoelectric conversion layer 20. As a material of the transparent thin film 50, calcium fluoride, magnesium fluoride, barium fluoride, lithium fluoride, silicon carbide, sapphire, alumina, crystal, fluororesin, SnO ₂ , FTO (fluorine doped tin oxide), ITO, ZnO, _{SiO 2, TiO 2, ZrO 2} , Mn 3 O 4, Y 2 O 3, WO 3, Nb 2 O 5, La 2 O 3, Ga 2 O 3, Ag 2 O, CuO, a-Si: H, μc _{-Si: H, SiO x: H} , SiC, SiN x, AlO x: H, a polyethylene terephthalate, polycarbonate, polymethyl methacrylate, polyethylene, polypropylene, ethylene - vinyl acetate copolymer, polystyrene, polyimide, polyamide, polybutylene Terephthalate, polyethylene naphthalate, polysulfone, polyethylene Examples include polyethersulfone, polyetheretherketone, polyvinyl alcohol, polyvinyl chloride, polyvinylidene chloride, triacetylcellulose, polyurethane, and cycloolefin polymer. The thickness of the transparent thin film 50 is preferably in the range of 5 to 200 nm. Further, the oxygen content in the transparent thin film 50 is preferably 5 atm% or more. In addition, the refractive index n ₁ of the transparent thin film 50 is preferably in a relationship of n ₁ > 0.7n ₂ with respect to the refractive index n ₂ of the photoelectric conversion layer 20.

  In the case where the metal nanoparticles 36 are in contact with the photoelectric conversion layer 20, the carrier recombination reaction is promoted at the metal-semiconductor interface between the metal nanoparticles 36 and the photoelectric conversion layer 20. The metal atoms constituting the particles 36 may diffuse into the photoelectric conversion layer 20 and contaminate the photoelectric conversion layer 20, which may reduce the photoelectric conversion efficiency of the photoelectric conversion element 10. For this reason, like this Embodiment, when the transparent thin film 50 intervenes between the 2nd main surface of the photoelectric converting layer 20, and the metal nanoparticle 36, the metal nanoparticle 36, the photoelectric converting layer 20, and Occurrence of carrier recombination can be suppressed. Furthermore, by setting the oxygen content in the transparent thin film 50 to 5 atm% or more, it is possible to effectively suppress the diffusion of metal atoms constituting the metal nanoparticles 36 into the photoelectric conversion layer 20.

Further, since the refractive index n ₁ of the transparent thin film 50 is in the relationship of n ₁ > 0.7n ₂ with respect to the refractive index n ₂ of the photoelectric conversion layer 20, the scattering angle of the reflected light from the metal nanoparticles 36 is increased. The optical path length in the photoelectric conversion layer 20 can be further increased.

Example 1
<Preparation of photoelectric conversion layer>
On one surface of a 100 μm-thick p-type silicon wafer (resistivity 0.5-5 Ωcm), 5 nm thick a-SiO _x : H is laminated as an i layer, and 7.5 nm thick on the i layer. N-type a-Si: H was laminated to produce a photoelectric conversion layer. The refractive index of the p-type silicon wafer was measured with a spectroscopic ellipsometer and found to be 3.9 at 600 nm.

<Preparation of antireflection film>
On the n-type a-Si: H, ITO having a thickness of 75 nm was formed as an antireflection film.

<Preparation of transparent thin film layer>
On the exposed surface (back surface) of the p-type silicon wafer, 30 nm of p-type microcrystalline SiO _x : H was formed as a transparent thin film layer. As a result of evaluating the oxygen content of the p-type microcrystalline SiO _x : H film by X-ray photoelectron spectroscopy, it was 8 atm%. The refractive index at 600 nm of p-type microcrystalline SiO _x : H was measured with a spectroscopic ellipsometer and found to be 3.4.

<Production of metal nanoparticles>
After anodizing the surface of the aluminum substrate at 120 V in a 0.3 mol / L malonic acid aqueous solution, the aluminum substrate other than the oxidized surface (barrier layer) is removed, and the number of holes formed in the barrier layer is increased by 20 times. By penetrating using a diluted phosphoric acid aqueous solution, an alumina mask having an average pore diameter of 150 nm and a pore density of 1.8 × 10 ⁹ holes / cm ² was obtained. An array of metal nanoparticles having a height of 75 nm was formed by vacuum-depositing Ag on the microcrystalline SiO _x : H through this alumina mask. It was confirmed by using a scanning electron microscope (SEM) that the diameter and density of the obtained metal nanoparticles were the same as the diameter and density of the through holes formed in the alumina mask used in vacuum deposition. .

<Preparation of dielectric layer>
A ZnO film having a thickness of 200 nm was formed as a dielectric layer covering the metal nanoparticles. As a result of measuring the refractive index of ZnO with a spectroscopic ellipsometer, it was 1.9 at 600 nm.
<Production of electrode>
A thin wire electrode was formed on the ITO constituting the antireflection film using Ag. Further, a full-surface electrode was formed on the ZnO constituting the dielectric layer (on the main surface of ZnO opposite to the photoelectric conversion layer) using Ag.

  The photoelectric conversion element (solar cell) of Example 1 was produced through the above steps.

(Example 2)
The solar cell of Example 2 was produced in the same procedure as Example 1 except for the method for producing metal nanoparticles.

<Production of metal nanoparticles>
After anodizing the surface of the aluminum substrate at 160V in a mixed aqueous solution of 0.2 mol / L malonic acid and 0.2 mol / L tartaric acid, the aluminum substrate other than the oxidized surface (barrier layer) is removed to form a barrier layer. The formed many holes were penetrated using a phosphoric acid aqueous solution diluted 20 times to obtain an alumina mask having an average pore diameter of 200 nm and a pore density of 1.0 × 10 ⁹ holes / cm ² . An array of metal nanoparticles having a height of 100 nm was formed by vacuum-depositing Ag on the microcrystalline SiO _x : H through the alumina mask.

(Example 3)
The solar cell of Example 3 was produced in the same procedure as in Example 1 except for the method for producing metal nanoparticles.

<Production of metal nanoparticles>
After anodizing the surface of the aluminum substrate at 200 V in a 0.2 mol / L tartaric acid aqueous solution, the aluminum substrate other than the oxidized surface (barrier layer) is removed, and the numerous holes formed in the barrier layer are diluted 20 times. By making the phosphoric acid aqueous solution penetrate, an alumina mask having an average pore diameter of 250 nm and a pore density of 7.0 × 10 ⁸ pieces / cm ² was obtained. An array of metal nanoparticles having a height of 125 nm was formed by vacuum-depositing Ag on the microcrystalline SiO _x : H through the alumina mask.

Example 4
The solar cell of Example 4 was produced in the same procedure as Example 1 except for the method for producing metal nanoparticles.

<Production of metal nanoparticles>
After anodizing the surface of the aluminum substrate at 120 V in a 0.3 mol / L malonic acid aqueous solution, the aluminum substrate other than the oxidized surface (barrier layer) is removed, and the number of holes formed in the barrier layer is increased by 20 times. By penetrating using a diluted phosphoric acid aqueous solution, an alumina mask having an average pore diameter of 150 nm and a pore density of 1.8 × 10 ⁹ holes / cm ² was obtained. Ag was vacuum-deposited on this alumina mask by 90 nm to obtain an average pore diameter of 100 nm and a pore density of 1.8 × 10 ⁹ holes / cm ² . An array of metal nanoparticles having a height of 50 nm was formed by vacuum-depositing Ag on the microcrystalline SiO _x : H through this alumina mask.

(Example 5)
The solar cell of Example 5 was produced in the same procedure as in Example 1 except for the method for producing metal nanoparticles.

<Production of metal nanoparticles>
After anodizing the surface of the aluminum substrate at 160V in a mixed aqueous solution of 0.2 mol / L malonic acid and 0.2 mol / L tartaric acid, the aluminum substrate other than the oxidized surface (barrier layer) is removed to form a barrier layer. The formed many holes were penetrated using a phosphoric acid aqueous solution diluted 20 times to obtain an alumina mask having an average pore diameter of 200 nm and a pore density of 1.8 × 10 ⁹ holes / cm ² . Ag was vacuum-deposited on the alumina mask by 300 nm to obtain an average pore diameter of 100 nm and a pore density of 1.0 × 10 ⁹ holes / cm ² . An array of metal nanoparticles having a height of 50 nm was formed by vacuum-depositing Ag on the microcrystalline SiO _x : H through this alumina mask.

(Example 6)
The solar cell of Example 6 was produced in the same procedure as in Example 1 except for the method for producing metal nanoparticles.

<Production of metal nanoparticles>
After anodizing the surface of the aluminum substrate at 120 V in a 0.3 mol / L malonic acid aqueous solution, the aluminum substrate other than the oxidized surface (barrier layer) is removed, and the number of holes formed in the barrier layer is increased by 20 times. By penetrating with a diluted phosphoric acid aqueous solution and further enlarging the pore diameter, an alumina mask having an average pore diameter of 200 nm and a pore density of 1.8 × 10 ⁹ holes / cm ² was obtained. An array of metal nanoparticles having a height of 100 nm was formed by vacuum-depositing Ag on the microcrystalline SiO _x : H through the alumina mask.

(Comparative Example 1)
The solar cell of Comparative Example 1 was produced in the same procedure as Example 1 except for the method for producing metal nanoparticles.

<Production of metal nanoparticles>
After anodizing the surface of the aluminum substrate at 80 V in a mixed aqueous solution of 0.1 mol / L oxalic acid and 0.1 mol / L malonic acid, the aluminum substrate other than the oxidized surface (barrier layer) is removed, and the barrier layer A large number of holes formed in 1 were penetrated using a phosphoric acid aqueous solution diluted 20 times to obtain an alumina mask having an average pore diameter of 100 nm and a pore density of 3.3 × 10 ⁹ holes / cm ² . An array of metal nanoparticles having a height of 50 nm was formed by vacuum-depositing Ag on the microcrystalline SiO _x : H through this alumina mask.

(Comparative Example 2)
The solar cell of Comparative Example 2 was produced in the same procedure as in Example 1 except for the method for producing metal nanoparticles.

<Production of metal nanoparticles>
After anodizing the surface of the aluminum substrate in an aqueous 0.15 mol / L citric acid solution at 240 V, the aluminum substrate other than the oxidized surface (barrier layer) is removed, and the number of holes formed in the barrier layer is increased by 20 times. By penetrating using a diluted phosphoric acid aqueous solution, an alumina mask having an average pore diameter of 300 nm and a pore density of 4.0 × 10 ⁸ holes / cm ² was obtained. An array of metal nanoparticles having a height of 150 nm was formed by vacuum-depositing Ag on the microcrystalline SiO _x : H through this alumina mask.

<Measurement of quantum efficiency>
Spectral sensitivity measurement was performed on the solar cells of Examples 1 to 6 and Comparative Examples 1 and 2. The spectral sensitivity measuring device is a two-lamp type of xenon lamp and halogen lamp, and irradiates a monochromatic light of 300 to 1200 nm with a monochromator to a solar cell in an AC mode. From the number of photons and the photocurrent value of each wavelength. The quantum yield was calculated. As a reference sample, a solar cell was prepared in the same procedure as in Example 1 except that metal nanoparticles were not formed, and spectral sensitivity was measured. Based on this result, the relative quantum yields of the solar cells of Examples 1 to 6 and Comparative Examples 1 and 2 with respect to the reference sample were calculated. FIG. 4 is a graph showing the quantum yield of the solar cell of Example 2. Table 1 shows the quantum yields of the solar cells of Examples 1 to 6 and Comparative Examples 1 and 2 at a wavelength of 1100 nm. As shown in Table 1, in the solar cells of Examples 1 to 6, the quantum yield is remarkably increased as compared to the solar cells of Comparative Examples 1 and 2, and in the solar cells of Examples 1 to 6, The effect of increasing absorption was confirmed.

  The present invention is not limited to the above-described embodiments, and various modifications such as design changes can be added based on the knowledge of those skilled in the art. The form can also be included in the scope of the present invention.

  For example, in the above-described embodiment, a pn junction is formed in the photoelectric conversion layer 20. However, the photoelectric conversion layer 20 may have a structure capable of performing photoelectric conversion. -N junction may be formed.

DESCRIPTION OF SYMBOLS 10 Photoelectric conversion element, 20 Photoelectric conversion layer, 32 Antireflection film, 36 Metal nanoparticle, 38 Dielectric layer, 40 Mask, 50 Transparent thin film

Claims (5)

A photoelectric conversion layer;
A plurality of metal nanoparticles provided in a two-dimensional array on the main surface side of the photoelectric conversion layer opposite to the light receiving surface;
With
The photoelectric conversion element which is a range number density 5.0 × 10 ⁸ / cm ² or more 3.0 × 10 ⁹ / cm ² or less of the plurality of metallic nanoparticles.   The photoelectric conversion element according to claim 1, wherein the metal nanoparticles are made of Au, Ag, Al, Cu, or an alloy of these metals.   The photoelectric conversion element according to claim 1, further comprising a dielectric layer having a refractive index of 1.3 or more that covers a surface of the metal nanoparticles.   The photoelectric conversion element of any one of Claims 1 thru | or 3 further provided with the transparent thin film provided between the said metal nanoparticle and the said photoelectric converting layer.   The photoelectric conversion element according to claim 4, wherein the transparent thin film has an oxygen content of 5 atm% or more.

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