JP2011228458A - Solar cell and manufacturing method thereof, and electrode for solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solar cell that has high conversion efficiency and can be manufactured at low cost, a manufacturing method of the solar cell, and an electrode structure for a solar cell.SOLUTION: A solar cell 1 comprises an electron donor in which an electron is excited by irradiation with light and a metal layer 2 in which a localized surface plasmon electric field is generated by irradiation with light and the electronic excitation of the electron donor is facilitated. In the case where light is irradiated to the metal layer 2, a greatly strong localized surface plasmon electric field is generated and the electronic excitation of the electron donor is greatly facilitated since the metal layer 2 is formed by electrolytic plating.

Description

  The present invention relates to a solar cell, a manufacturing method thereof, and an electrode for a solar cell, and more particularly to a solar cell that promotes photoelectric conversion using a localized surface plasmon electric field, a manufacturing method thereof, and an electrode for a solar cell. .

  In recent years, the shift from energy use centering on fossil fuels, which are feared to be depleted, to the use of environmentally friendly natural energy has been promoted. In particular, solar cells have been widely developed to utilize inexhaustible and non-polluting solar energy.

Under such circumstances, various types of solar cells have been proposed so far. For example, a solar cell using an inorganic semiconductor such as silicon or a GaS compound, a solar cell using an organic semiconductor such as phthalocyanine or polyacetylene, or TiO ₂ particles carrying a dye in an electrolyte filled between both electrodes are disposed. A wet solar cell is mentioned.

  On the other hand, it is known that when light is applied to metal fine particles, electrons in the fine particles interact with light, local surface plasmon resonance occurs, and as a result, the electric field on the surface of the fine particles is remarkably enhanced. And the technique which raises the conversion efficiency of a solar cell using this localized surface plasmon resonance is proposed.

  For example, in Patent Document 1, metal nanoparticles are deposited in a thin film on a conductive substrate, and electron donating dye molecules and / or electron accepting dye molecules are formed on the surfaces of the nanoparticles via metal-sulfur bonds. A photoelectric conversion element in which is fixed is described.

  In addition, Patent Document 2 discloses a nanoparticle having a size of 0.1 to 500 nm that absorbs light through a surface plasmon or polaron mechanism between an n-doped charge transport layer and a p-doped charge transport layer. A solar cell provided with a photosensitive layer comprising nanostructures is described. Patent Document 2 also describes combining nanoparticles or nanostructures having different compositions and / or sizes from the viewpoint of light absorption in a wide wavelength range.

JP 2002-270865 A Special table 2009-533857

  As described in Patent Documents 1 and 2, the conversion efficiency of the solar cell is surely improved by utilizing localized surface plasmon resonance. In particular, as described in Patent Document 2, by combining nanoparticles or nanostructures having different compositions and / or sizes, light absorption occurs appropriately in a wide wavelength range of sunlight, and a solar cell The conversion efficiency is improved.

  However, in order to disseminate solar cells widely and generally, it is necessary to drastically improve the conversion efficiency and reduce the manufacturing cost as compared with conventional solar cells using localized surface plasmon resonance. .

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a solar cell that has high conversion efficiency and can be manufactured at low cost, a method for manufacturing the solar cell, and an electrode structure for the solar cell.

  The solar cell according to the present invention includes an electron donor in which electrons are excited by light irradiation, and a metal layer that generates a localized surface plasmon electric field by the light irradiation and promotes excitation of the electrons of the electron donor. The metal layer is formed by electrolytic plating.

As a result of intensive studies, the present inventors have found that the use of a metal layer formed by electrolytic plating significantly increases the localized surface plasmon electric field generated when light is applied to the metal layer. The existence of the irradiation light scattering effect was also confirmed.
The above-described solar cell was devised based on this finding by the present inventors, and a metal layer that promotes excitation of electrons of an electron donor by the generation of a localized surface plasmon electric field is formed by electrolytic plating. Yes. Thereby, the excitation of electrons of the electron donor is remarkably accelerated by the remarkably strong localized surface plasmon electric field, so that the conversion efficiency of the solar cell can be improved.
Moreover, in the above-mentioned solar cell, since the metal layer formed by electrolytic plating is used, mass production is easy and the manufacturing cost of a solar cell can be reduced.

  In the solar cell, the metal layer has a porous fine structure composed of an aggregate of metal particulates having protrusions, and the protrusion angle of the protrusions is 10 to 170 degrees, and the metal layer has an apparent surface area. The ratio of the effective surface area of the microstructure is preferably 10 to 1000.

In this way, by using a fine-structured metal layer composed of an aggregate of metal particulates having protrusions having a protrusion angle of 10 to 170 degrees, the localized surface plasmon electric field generated upon light irradiation to the metal layer is enhanced, The conversion efficiency of the solar cell can be further improved. Note that the “projection angle” of the protrusions of the fine structure constituting the metal layer means the angle of the uneven protrusions on the surface of the metal particulate formed by electrolytic plating, and is observed from directly above. This is the angle of the angular part of the outer periphery of the particle.
Further, by setting the ratio of the effective surface area of the microstructure to the apparent surface area of the metal layer to 10 to 1000, a wide reaction field between the metal layer and the electron donor can be taken, so that the electron donation by the localized surface plasmon electric field The excitation of the body electrons can be further promoted, and the conversion efficiency of the solar cell can be further improved. Here, the “apparent surface area of the metal layer” refers to the area of the region where the metal layer is formed, and the “effective surface area of the fine structure” is a surface area considering the irregularities and pores of the fine structure, Specifically, the oxide film formed on the metal surface is measured by an electrochemical redox method.

  In the solar cell, the metal layer preferably includes at least one of gold, silver, copper, platinum, and palladium.

  In this way, the use of metals that easily cause localized surface plasmon resonance (gold, silver, copper, platinum, palladium) as the material of the metal layer further promotes the excitation of electrons in the electron donor and conversion of solar cells. Efficiency can be further improved.

  The solar cell is disposed between the first electrode carrying the metal layer, the second electrode disposed to face the first electrode, the first electrode and the second electrode, and p-type And an organic thin film layer including an organic semiconductor and an n-type organic semiconductor, and the electron donor may be the p-type organic semiconductor at a junction between the p-type organic semiconductor and the n-type organic semiconductor.

  In solar cells having an organic thin film layer (so-called organic thin film solar cells), in general, there is a problem that conversion efficiency in a long wavelength region including the near infrared region (wavelength region longer than about 550 nm) is low. As described above, the conversion efficiency in the long wavelength region including the near infrared region can be remarkably improved by using the strong localized surface plasmon electric field generated by the metal layer formed by electrolytic plating.

  In this case, the solar cell further includes a hole transport layer that is disposed between the metal layer and the first electrode and supplies holes to the first electrode, and the metal layer includes the hole transport layer. It is preferable that the organic thin film layer is in contact with the surface opposite to the contact surface.

In this way, by providing a hole transport layer that supplies holes to the first electrode between the metal layer and the first electrode, the hole transport is rate-limiting in the photoelectric conversion process of the solar cell. It is possible to prevent and improve the conversion efficiency of the solar cell.
Furthermore, since the metal layer is in contact with the organic thin film layer on the surface opposite to the contact surface with the hole transport layer, electron donation in the organic thin film layer is caused by the localized surface plasmon electric field formed by the metal layer. Electron excitation of the body (p-type organic semiconductor at the pn junction) can be more reliably promoted.

  Furthermore, in the solar cell, the organic thin film layer is preferably composed of a mixture of the p-type organic semiconductor and the n-type organic semiconductor.

  In this way, by using a solar cell having an organic thin film layer made of a mixture of a p-type organic semiconductor and an n-type organic semiconductor (so-called bulk hetero-type organic thin-film solar cell), the pn junction area increases, The distance between the metal layer and the pn junction surface is reduced. Therefore, the excitation of electrons of the electron donor (p-type organic semiconductor at the pn junction) can be further promoted by the localized surface plasmon electric field of the metal layer.

  Alternatively, the solar cell is filled between the first electrode carrying the metal layer, the second electrode arranged to face the first electrode, and the first electrode and the second electrode. An electrolyte solution, and the electron donor may be a dye fixed to the metal layer.

In a solar cell (so-called dye-sensitized solar cell) in which a metal layer having a dye fixed in an electrolyte solution filled between electrodes is generally used, a long wavelength region including the near infrared region (about 550 nm or more) Low conversion efficiency in the long wavelength region) is a problem, but as described above, by using the strong localized surface plasmon electric field generated by the metal layer formed by electrolytic plating, the near infrared region is reduced. It is possible to significantly improve the conversion efficiency in the long wavelength region including the same.
In dye-sensitized solar cells, attempts have been made to improve conversion efficiency by developing new dyes. However, according to the solar cell, conversion efficiency is improved without changing the molecular structure of the dye itself. This increases the degree of freedom in the molecular design of the dye.

  Alternatively, the solar cell includes a first electrode that carries the metal layer, a second electrode that is disposed to face the first electrode, and a p that is disposed between the metal layer and the second electrode. The electron donor may further include a p-type inorganic semiconductor and an n-type inorganic semiconductor, and the electron donor may be the p-type inorganic semiconductor at a junction between the p-type inorganic semiconductor and the n-type inorganic semiconductor.

  In a solar cell using an inorganic semiconductor, the p-type inorganic semiconductor and the n-type inorganic semiconductor generally have a low absorption coefficient. Therefore, it is necessary to increase the thickness of the semiconductor in order to obtain sufficient conversion efficiency. However, as described above, by using the strong localized surface plasmon electric field generated by the metal layer formed by electrolytic plating, sufficient conversion efficiency can be obtained even if the semiconductor is thinned, so that the solar cell is reduced in weight. At the same time, material costs can be reduced.

  A method for manufacturing a solar cell according to the present invention is a method for manufacturing a solar cell that performs photoelectric conversion by irradiating light to an electron donor, and generates a localized surface plasmon electric field by irradiation with light, and Forming a metal layer that promotes excitation of the electrons of the donor on the first electrode by electroplating; providing the electron donor on the first electrode on which the metal layer is formed; and And a step of providing a second electrode so as to face the first electrode across a donor.

This solar cell manufacturing method is devised based on the knowledge of the present inventors that a localized surface plasmon electric field generated when light is applied to a metal layer is remarkably increased by using a metal layer formed by electrolytic plating. A metal layer that promotes excitation of electrons of the electron donor by generation of a localized surface plasmon electric field is formed by electrolytic plating. Therefore, since the excitation of electrons of the electron donor is remarkably accelerated by the extremely strong localized surface plasmon electric field, the conversion efficiency of the solar cell can be improved.
Moreover, in this solar cell manufacturing method, since the metal layer is formed by electrolytic plating, mass production is easy, and the manufacturing cost of the solar cell can be reduced.

  The electrode structure for a solar cell according to the present invention is an electrode structure used for a solar cell that performs photoelectric conversion by irradiating light to an electron donor, and has an electrode having conductivity and electrolysis on the electrode. A metal layer that is formed by plating, generates a localized surface plasmon electric field by irradiation of light, and promotes excitation of the electrons of the electron donor.

This electrode structure for solar cells is based on the knowledge of the present inventors that a localized surface plasmon electric field generated when light is applied to a metal layer is remarkably strong by using a metal layer formed by electrolytic plating. Invented, a metal layer that promotes excitation of electrons of an electron donor by generation of a localized surface plasmon electric field is formed by electrolytic plating. Therefore, since the excitation of electrons of the electron donor is remarkably accelerated by the extremely strong localized surface plasmon electric field, the conversion efficiency of the solar cell can be improved.
Moreover, in this electrode structure for solar cells, since the metal layer is formed by electrolytic plating, mass production is easy, and the manufacturing cost of the solar cells can be reduced.

In the present invention, a metal layer that promotes excitation of electrons of the electron donor by the generation of a localized surface plasmon electric field is formed by electrolytic plating. Therefore, when this metal layer is irradiated with light, the localized surface is much stronger. A plasmon electric field is generated, and the excitation of electrons in the electron donor is significantly accelerated. Therefore, the conversion efficiency of the solar cell can be improved.
Furthermore, since the metal layer is formed by electrolytic plating suitable for mass production, the manufacturing cost of the solar cell can be reduced.

It is sectional drawing which shows the structural example of the solar cell of 1st Embodiment. It is sectional drawing which shows the other structural example of the solar cell of 1st Embodiment. It is sectional drawing which shows the structural example of the solar cell of 2nd Embodiment. It is sectional drawing which shows the structural example of the solar cell of 3rd Embodiment. 2 is a SEM photograph showing the microstructure of the metal layer obtained in Example 1. 3 is a graph showing a measurement result of a photocurrent flowing in a sample of Example 1. 4 is a SEM photograph showing the microstructure of the metal layer obtained in Example 2. 6 is a graph showing a measurement result of a photocurrent flowing in a sample of Comparative Example 1.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, and are merely illustrative examples. Only.

[First Embodiment]
First, the solar cell according to the first embodiment will be described.
FIG. 1 is a cross-sectional view illustrating a configuration example of the solar cell according to the first embodiment. As shown in the figure, the solar cell 1 mainly faces a metal layer 2 that generates a localized surface plasmon electric field by light irradiation, a first electrode 4 that carries the metal layer 2, and the first electrode 4. And the organic thin film layer 8 disposed between the first electrode 4 and the second electrode 6.

  As a result of intensive studies, the present inventors have found that a metal layer 2 that generates a localized surface plasmon electric field that is much stronger than before can be formed by light irradiation by employing an electrolytic plating method.

  The solar cell 1 according to this embodiment has been devised based on this finding by the present inventors, and the metal layer 2 is formed by electrolytic plating. As a result, a metal layer 2 having a fine structure in which a strong localized surface plasmon electric field is likely to be generated, specifically, a porous fine structure composed of an aggregate of metal particulates having protrusions is obtained.

  The metal material constituting the metal layer 2 is not particularly limited as long as it generates a localized surface plasmon electric field. For example, gold, silver, copper, platinum and palladium, a mixture of these metals, and these metals An alloy containing can be used. Among these, gold and silver are metal materials that can form a strong localized surface plasmon electric field, and thus are suitable as materials for the metal layer 2.

The electrodeposition conditions for the metal layer 2 are not particularly limited. For example, electrolytic plating is performed using a 1 wt% HAuCl ₄ solution at a current density of 1 to 60 mA / cm ² and a treatment time of 1 to 600 seconds. Also good. Especially, the metal layer 2 which forms a remarkably strong localized surface plasmon electric field can be obtained by performing electroplating on conditions with a current density of 30 mA / cm ² and a treatment time of 15 seconds. In the metal layer 2, the absorbance in the visible region is about 2 at the maximum, and it is possible to perform spectroscopic measurement with transmitted light and has a certain degree of light transmittance.

  As described above, the metal layer 2 has a porous microstructure composed of an aggregate of metal particulates having protrusions. Here, the protrusion of the metal granular material in the fine structure of the metal layer 2 preferably has a protrusion angle of 10 to 170 degrees from the viewpoint of enhancing the localized surface plasmon electric field generated when the metal layer 2 is irradiated with light. 10 to 90 degrees is more preferable. The fine structure of the metal layer 2 is preferably such that the ratio of the effective surface area to the apparent surface area of the metal layer 2 is 10 to 1000 from the viewpoint of widening the reaction field between the metal layer 2 and the electron donor described later. More preferably, it is 30-1000. From the viewpoint of further enhancing the surface plasmon electric field, the fine structure of the metal layer 2 is preferably a structure in which metal particulates constituting the metal layer 2 are stacked in multiple layers.

  The first electrode 4 is an electrode that carries the metal layer 2, and the constituent material of the first electrode 4 takes into account the incident direction of light and whether the first electrode 4 is to be a hole extraction electrode or an electron extraction electrode. It is determined appropriately.

  For example, when light is incident from the first electrode 4 side (arrow direction indicated by hν in FIG. 1) and the first electrode 4 is a hole extraction electrode, the first electrode 4 has a relatively large work function, And it is preferable to comprise with the material which permeate | transmits at least one part of incident light. Specifically, a transparent thin film such as In—Zn—O (IZO), In—Sn—O (ITO), ZnO—Al, Zn—Sn—O is formed on a transparent substrate (glass substrate, plastic substrate, etc.). The first electrode 4 may be used, or a metal thin film such as gold, silver, cobalt, nickel, platinum, or copper may be formed on the transparent substrate to form the first electrode 4. Among them, those using a transparent thin film such as In—Zn—O (IZO), In—Sn—O (ITO), ZnO—Al, and Zn—Sn—O are used for light in the wavelength region including the visible light region. Since the transmittance is very high, it is suitable as a material for the first electrode 4 when the first electrode 4 is on the light incident side.

  The second electrode 6 is a counter electrode disposed to face the first electrode 4, and the constituent material thereof is the incident direction of light, and the second electrode 6 is desired to be either a hole extraction electrode or an electron extraction electrode. It is determined as appropriate.

  For example, when light is incident from the first electrode 4 side (in the arrow direction indicated by hν in FIG. 1) and the second electrode 6 is an electron extraction electrode, whether or not the second electrode 6 has optical transparency. However, it is preferable to use a material having a relatively small work function. Specifically, the second electrode 6 may be made of a material such as Li, In, Al, Ca, Mg, Sm, Tb, Yb, Zr, or LiF.

  The organic thin film layer 8 is provided between the first electrode 4 and the second electrode 6, and includes a p-type organic semiconductor (donor) having an electron donating property and an n-type organic semiconductor (acceptor) having an electron accepting property. Consists of including.

Examples of the p-type organic semiconductor used for the organic thin film layer 8 include polythiophene derivatives such as poly-3-hexylthiophene (P3HT), poly-2-methoxy-5- (3′7′-dimethyloctyloxy)- Visibility of polyparaphenylene vinylene derivatives such as 1,4-phenylene vinylene (MDMO-PPV) and polyfluorene derivatives such as poly (9,9-dioctylfluorenyl-2,7-diyl) (PFO) A conjugated polymer having a light absorption region in the light region can be used. On the other hand, the n-type organic semiconductor used in the organic thin film layer 8, for example, [6,6] - or fullerene derivative, such as phenyl -C ₆₁ butyl carboxylic acid methyl ester (PCBM), perylene derivatives can be cited .

  The organic thin film layer 8 may be formed by laminating a p-type organic semiconductor and an n-type organic semiconductor as separate layers, or may be formed of a mixture of a p-type organic semiconductor and an n-type organic semiconductor. In particular, the solar cell 1 in which the organic thin film layer 8 is formed of a mixture of a p-type organic semiconductor and an n-type organic semiconductor (so-called bulk hetero-type organic thin-film solar cell) has an increased pn junction area and a metal layer 2. This is preferable in that the distance between the pn junction surface and the pn junction surface is reduced, and the excitation of electrons of the electron donor (p-type organic semiconductor in the pn junction portion) by the localized surface plasmon electric field of the metal layer 2 can be further promoted.

  In the solar cell 1 having the above configuration, for example, as shown in FIG. 1, a localized surface plasmon electric field that is much stronger than before is generated in the metal layer 2 formed by electrolytic plating by light incident from the first electrode 4 side. The localized surface plasmon electric field promotes the excitation of electrons of the electron donor (p-type organic semiconductor at the pn junction) of the organic thin film layer 8. Therefore, the conversion efficiency of the solar cell 1 can be greatly improved. Moreover, in this solar cell 1, since the metal layer 2 is formed by electrolytic plating, mass production is easy and the manufacturing cost of the solar cell can be reduced.

  Moreover, in the organic thin film solar cell having the organic thin film layer 8 like the solar cell 1, generally, the conversion efficiency in a long wavelength region including the near infrared region (a wavelength region longer than about 550 nm) is low. However, as in this embodiment, by using a strong localized surface plasmon electric field generated by the metal layer 2 formed by electrolytic plating, the conversion efficiency in the long wavelength region including the near infrared region can be remarkably improved. it can.

  In addition to the metal layer 2, the first electrode 4, the second electrode 6, and the organic thin film layer 8, the solar cell 1 is provided with a hole transport layer 10 and an electron transport layer 12 shown in FIG. Alternatively, functional layers such as a protective sheet (not shown), a filler layer, a barrier layer, a protective hard coat layer, a strength support layer, an antifouling layer, a high light reflection layer, and a light containment layer may be provided.

  Here, the hole transport layer 10 is disposed on the hole extraction electrode side of the solar cell 1 and is a hole extraction layer for transporting holes from the organic thin film layer 8 side to the hole extraction electrode side. is there. For the hole transport layer 10, for example, polyethylene dioxythiophene (PEDOT), triphenyldiamine (TPD), polystyrene sulfonic acid (PSS), or the like can be used. FIG. 1 shows an example in which the first electrode 4 is a hole extraction electrode and the hole transport layer 10 is disposed on the first electrode 4 side.

  By providing the hole transport layer 10, it is possible to prevent the rate of hole transport from becoming rate-limiting in the photoelectric conversion process of the solar cell 1, and to improve the conversion efficiency of the solar cell 1. FIG. 1 shows an example in which the hole transport layer 10 is disposed between the metal layer 2 and the organic thin film layer 8, but the hole transport layer 10 is disposed between the metal layer 2 and the first electrode 4. You may arrange in.

  FIG. 2 is a cross-sectional view illustrating a configuration example of the solar cell 1 in which the hole transport layer 10 is disposed between the metal layer 2 and the first electrode 4. In the example shown in the figure, the hole transport layer 10 is disposed between the metal layer 2 and the first electrode 4, and the metal layer 2 is on the surface opposite to the contact surface with the hole transport layer 10. It is in contact with the organic thin film layer 8. Thus, by providing the hole transport layer 10 between the metal layer 2 and the first electrode 4 and disposing the metal layer 2 closer to the pn junction surface of the organic thin film layer 8, the metal layer 2 The local surface plasmon electric field to be formed can more surely promote the excitation of electrons of the electron donor (p-type organic semiconductor at the pn junction) in the organic thin film layer 8.

The electron transport layer 12 (see FIGS. 1 and 2) is an electron extraction layer that is disposed on the electron extraction electrode side of the solar cell 1 and transports electrons from the organic thin film layer 8 side to the electron extraction electrode side. Examples of the electron transport layer 12 include LiF and n-type semiconductor (TiO ₂ ).

  Then, the manufacturing method of the solar cell 1 of this embodiment is demonstrated. In order to obtain the solar cell 1 shown in FIGS. 1 and 2, first, the first electrode 4 is prepared. Next, the metal layer 2 is formed on the first electrode 4 by electrolytic plating. Here, the metal layer 2 may be formed directly on the surface of the first electrode 4 or may be formed on the first electrode 4 via the hole transport layer 10 as shown in FIG. Thereafter, the organic thin film layer 8 (i.e., p) is formed on the first electrode 4 on which the metal layer 2 is formed by an arbitrary method including a coating method such as die coating, spin coating, dip coating, roll coating, and spray coating. Type organic semiconductor and n-type organic semiconductor). Then, the second electrode 6 is formed so as to face the first electrode 4 with the organic thin film layer 8 interposed therebetween by an arbitrary method such as vacuum deposition, sputtering, or ion plating. Thereby, the solar cell 1 is obtained.

[Second Embodiment]
Next, a solar cell according to the second embodiment will be described.
FIG. 3 is a cross-sectional view illustrating a configuration example of the solar cell according to the second embodiment. The solar cell 20 according to this embodiment includes a first electrode 4 that carries the metal layer 2, a second electrode 6 that is disposed so as to face the first electrode 4, and the first electrode 4 and the second electrode 6. It has an electrolyte layer 22 provided therebetween and a dye 24 fixed to the metal layer 2. In addition, since the metal layer 2, the first electrode 4, and the second electrode 6 of the solar cell 20 are the same as those in the first embodiment described above, the description thereof is omitted here, and the electrolyte layer 22 and the dye 24 are mainly described. explain.

  The electrolyte layer 22 contains a charge transport material that delivers electrons to the dye 24 in the oxidized state and is oxidized, and receives and reduces electrons flowing from the second electrode 6 side. For example, an electrolyte layer containing an electrolyte solution in which a redox counter ion is dissolved in a solvent, a room temperature molten salt containing the redox counter ion, a gel electrolyte in which a solution of the redox counter ion is impregnated in a low molecular gelling agent, or the like 22 can be used.

  The dye 24 has a role as an electron donor in which electrons are excited by light irradiation, and exchanges electrons with the first electrode 4 and the electrolyte layer 22. As the dye 24, for example, a ruthenium metal complex dye such as a tris (2,2′-bipyridine) ruthenium (II) complex, or an organic dye such as a porphyrin dye, a phthalocyanine dye, a cyanine dye, or a merocyanine dye is used. Can do.

  Here, as described in the first embodiment, the metal layer 2 to which the dye 24 is fixed is formed by electrolytic plating, and has a fine structure in which a strong localized surface plasmon electric field is likely to be generated. Has a porous microstructure composed of an aggregate of metal particulates having protrusions. Therefore, when irradiated with light, a strong localized surface plasmon electric field is generated in the metal layer 2, and excitation of electrons of the dye 24 (electron donor) is promoted by the localized surface plasmon electric field. Therefore, the conversion efficiency of the solar cell 20 can be greatly improved. Moreover, in this solar cell 20, since the metal layer 2 is formed by electroplating, mass production is easy and the manufacturing cost of the solar cell can be reduced.

Further, in the dye-sensitized solar cell having the electrolyte layer 22 like the solar cell 20, generally, the conversion efficiency in the long wavelength region including the near infrared region (wavelength region longer than about 550 nm) is low. However, the conversion efficiency in the long wavelength region including the near infrared region is remarkably improved by using the strong localized surface plasmon electric field generated by the metal layer 2 formed by electrolytic plating as in this embodiment. Can do.
In addition, in the dye-sensitized solar cell, attempts have been made to improve the conversion efficiency by the new development of the dye 24. However, as in this embodiment, a strong station where the metal layer 2 formed by electrolytic plating is generated. By using the surface plasmon electric field, the conversion efficiency can be improved without changing the molecular structure of the dye 24 itself.

  Then, the manufacturing method of the solar cell 20 of this embodiment is demonstrated. In order to obtain the solar cell 20 shown in FIG. 3, first, the first electrode 4 is prepared. Next, the metal layer 2 is formed on the first electrode 4 by electrolytic plating. Thereafter, the dye 24 is immobilized on the metal layer 2 by covalent bonding or electrostatic interaction. Then, the second electrode 6 is provided so as to face the first electrode 4 on which the metal layer 2 carrying the pigment 24 is formed. Finally, the solar cell 20 is obtained by filling the electrolyte layer 22 between the first electrode 4 and the second electrode 6 and sealing with an adhesive or the like.

[Third Embodiment]
Next, a solar cell according to the third embodiment will be described.
FIG. 4 is a cross-sectional view illustrating a configuration example of the solar cell according to the present embodiment. The solar cell 30 according to this embodiment includes a first electrode 4 that carries the metal layer 2, a second electrode 6 that is disposed so as to face the first electrode 4, and the first electrode 4 and the second electrode 6. A p-type inorganic semiconductor 32 and an n-type inorganic semiconductor 34 are provided therebetween. In addition, since the metal layer 2, the first electrode 4, and the second electrode 6 of the solar cell 30 are the same as those in the first embodiment, the description thereof will be omitted here, and the p-type inorganic semiconductor 32 and the n-type inorganic will be omitted. The semiconductor 34 will be mainly described.

The p-type inorganic semiconductor 32 and the n-type inorganic semiconductor 34 are made of a crystalline semiconductor material such as single crystal silicon, single crystal germanium, and polycrystalline silicon, an amorphous semiconductor material such as amorphous silicon, GaAs, InP, AlGaAs, CdS, A compound semiconductor material such as CdTe, Cu ₂ S, CuInSe ₂ , or CuInS ₂ doped with an impurity such as boron, aluminum, phosphorus, or arsenic can be used.

  The p-type inorganic semiconductor 32 is in contact with the n-type inorganic semiconductor 34 at the pn junction surface, and an internal electric field from the n-type inorganic semiconductor 34 toward the p-type inorganic semiconductor 32 is formed in the depletion layer including the pn junction surface. Yes. When the electrons of the p-type inorganic semiconductor 32 are excited by light irradiation, they move to the n-type inorganic semiconductor 34 by the internal electric field formed in the depletion layer and are taken out from the second electrode 6. On the other hand, vacancies (holes) generated by light irradiation move to the p-type inorganic semiconductor 32 by an internal electric field formed in the depletion layer and are taken out from the first electrode 4. That is, the p-type inorganic semiconductor 32 at the pn junction serves as an “electron donor”.

  Here, as described in the first embodiment, the metal layer 2 is formed by electrolytic plating, and has a fine structure in which a strong localized surface plasmon electric field is likely to be generated, specifically, a metal having protrusions. It has a porous microstructure consisting of aggregates of granular materials. Therefore, when irradiated with light, a strong localized surface plasmon electric field is generated in the metal layer 2, and the electron excitation of the electron donor (p-type inorganic semiconductor 32 at the pn junction) is excited by this localized surface plasmon electric field. Promoted. Therefore, the conversion efficiency of the solar cell 30 can be greatly improved. Moreover, in this solar cell 30, since the metal layer 2 is formed by electrolytic plating, mass production is easy and the manufacturing cost of the solar cell can be reduced.

  In a solar cell using an inorganic semiconductor, the p-type inorganic semiconductor and the n-type inorganic semiconductor generally have a low absorption coefficient. Therefore, it is necessary to increase the thickness of the semiconductor in order to obtain sufficient conversion efficiency. However, as in this embodiment, by using a strong localized surface plasmon electric field generated by the metal layer 2 formed by electrolytic plating, sufficient conversion efficiency can be obtained even if the semiconductor is thinned. Can be reduced in weight and the material cost can be reduced.

  In order to evaluate the conversion efficiency of the solar cell according to the present invention, the following samples were prepared and experiments for measuring photocurrent were performed.

[Example 1]
A metal layer 2 made of gold was formed by electrolytic plating on a glass substrate (corresponding to the first electrode 4) having an ITO thin film deposited on the surface, using galvanostat (manufactured by Fuso Seisakusho, HECS 315B). Electrolytic plating was performed using an aqueous solution in which 1 wt% of HAuCl ₄ was dissolved as a plating bath, using an ITO thin film as an anode and a platinum electrode as a cathode, with a current density of 30 mA / cm ² and a plating time of 15 seconds.

FIG. 5 is an SEM photograph showing the fine structure of the metal layer 2 obtained in Example 1. As can be seen from FIG. 5, the metal layer 2 obtained by electrolytic plating has a porous microstructure composed of an aggregate of metal particulates having protrusions. In the SEM photograph of this fine structure, the projection angle of the projections of the metal granular material is mostly 90 degrees or less, and the ratio of the effective surface area to the apparent surface area of the metal layer 2 is about 50. It was found that the structure was a multilayered structure.
The film thickness of the metal layer 2 was about 420 nm as calculated from the plating conditions in consideration of the film density (≈30%) of the metal layer 2.

On the other hand, a porphyrin derivative ([Po] ₂ ) is synthesized as an electron donor, and the first electrode 4 having the metal layer 2 formed thereon is impregnated for 5 days in a CH ₂ Cl ₂ solution containing the porphyrin derivative. Porphyrin was immobilized on the surface of layer 2. The coverage of porphyrin at this time was evaluated by measuring the oxidation wave of the Po part in a CH ₂ Cl ₂ solution containing 0.5 mol / dm ₃ of n-Bu ₄ NClO ₄ using cyclic voltammetry. However, it was 9.8 × 10 ⁻¹¹ mol / cm ² .

The photocurrent flowing through the sample thus obtained was subjected to potentiostat (manufactured by Fuso Mfg. Co., Ltd., HECS) in the presence of methyl viologen (5 mM) as a sacrificial electron acceptor in a 0.1 M NaClO ₄ aqueous solution. 318).

FIG. 6 is a graph showing the measurement result of the photocurrent flowing through the sample. In addition, in FIG. 6, the photoelectric current at the time of replacing the smooth metal layer formed by vacuum-depositing gold | metal | money with the metal layer 2 was also shown as a comparison.
As can be seen from FIG. 6, compared to the case where the metal layer has a smooth structure formed by vacuum deposition (graph indicated by □ in the figure), the metal layer is formed by electrolytic plating as in this example. In the case of a structure (a graph indicated by ● in the figure), a remarkably large photocurrent was obtained (in particular, a photocurrent nearly 50 to 300 times larger was obtained in a long wavelength region exceeding 550 nm).

[Example 2]
A sample was produced under the same conditions as in Example 1 except that the plating time was 1 second.
FIG. 7 is an SEM photograph showing the fine structure of the metal layer 2 obtained in Example 2. As can be seen from FIG. 5, the metal layer 2 obtained by electrolytic plating has a porous microstructure composed of an aggregate of metal particulates having protrusions. In the SEM photograph of this fine structure, the projection angle of the projection of the metal granular material was 90 degrees or less as in the first embodiment, but the angular shape portion was significantly fewer than in the first embodiment. It was found that the rounded surface-shaped portion was remarkably wide, and the ratio of the effective surface area to the apparent surface area of the metal layer 2 was about 5.
Using this sample, the photocurrent was measured in the same manner as in Example 1. As a result, a much larger photocurrent was obtained as compared with the case where the metal layer had a smooth structure formed by vacuum deposition.

[Comparative Example 1]
In a state where a liquid-liquid interface between a colloidal solution containing gold particles having an average particle diameter of 14 nm and hexane is formed, methanol is poured to form a gold particle film on the liquid-liquid interface, and this gold particle film is scooped on the ITO thin film. I took it. Thereafter, porphyrin was immobilized on the surface of the gold particle film in the same manner as in Example 1.

  The photocurrent flowing through the sample thus obtained was subjected to potentiostat (manufactured by Fuso Seisakusho, HECS 318) in the presence of oxygen as a sacrificial electron acceptor in 0.1 M NaClO 4 aqueous solution. It was measured.

FIG. 8 is a graph showing the measurement result of the photocurrent flowing through the sample. FIG. 8 also shows the photocurrent when the metal layer has a smooth structure formed by vacuum deposition as a comparative control.
As can be seen from FIG. 8, when the metal layer is a gold particle film as in this comparative example, compared to the case where the metal layer has a smooth structure formed by vacuum deposition (graph indicated by □ in the figure). A large current was obtained to some extent (graph indicated by ● in the figure).

  However, as can be seen by comparing FIG. 6 and FIG. 8, the photocurrent in Example 1 was significantly greater than that in Comparative Example 1. This tendency was particularly remarkable in a long wavelength region exceeding 550 nm. This is considered to be because the localized plasmon electric field generated when the metal layer 2 is irradiated with light is remarkably stronger than that of Comparative Example 1 by using the metal layer 2 formed by electrolytic plating as in Example 1. It is done.

  As described above, by using the metal layer 2 formed by electrolytic plating, the local plasmon electric field generated when the metal layer 2 is irradiated with light is remarkably strengthened, and drastic improvement in the conversion efficiency of the solar cell can be expected. Was confirmed.

DESCRIPTION OF SYMBOLS 1 Solar cell 2 Metal layer 4 1st electrode 6 2nd electrode 8 Organic thin film layer 10 Hole transport layer 12 Electron transport layer 20 Solar cell 22 Electrolyte layer 24 Dye 30 Solar cell 32 p-type inorganic semiconductor 34 n-type inorganic semiconductor

Claims (10)

An electron donor in which electrons are excited by light irradiation;
A local surface plasmon electric field is generated by irradiation with the light, and a metal layer that promotes excitation of the electrons of the electron donor, and
The solar cell, wherein the metal layer is formed by electrolytic plating.   The metal layer has a porous fine structure composed of an aggregate of metal particulates having protrusions, and the protrusion angle of the protrusions is 10 to 170 degrees, and the effective structure of the microstructure with respect to the apparent surface area of the metal layer is The solar cell according to claim 1, wherein the surface area ratio is 10 to 1000.   The solar cell according to claim 1, wherein the metal layer contains at least one of gold, silver, copper, platinum, and palladium. A first electrode carrying the metal layer;
A second electrode disposed to face the first electrode;
An organic thin film layer disposed between the first electrode and the second electrode and including a p-type organic semiconductor and an n-type organic semiconductor;
The solar cell according to any one of claims 1 to 3, wherein the electron donor is the p-type organic semiconductor at a junction between the p-type organic semiconductor and the n-type organic semiconductor. A hole transport layer disposed between the metal layer and the first electrode and supplying holes to the first electrode;
The solar cell according to claim 4, wherein the metal layer is in contact with the organic thin film layer on a surface opposite to a contact surface with the hole transport layer.   The solar cell according to claim 4, wherein the organic thin film layer is made of a mixture of the p-type organic semiconductor and the n-type organic semiconductor. A first electrode carrying the metal layer;
A second electrode disposed to face the first electrode;
An electrolyte solution filled between the first electrode and the second electrode,
The solar cell according to any one of claims 1 to 3, wherein the electron donor is a dye fixed to the metal layer. A first electrode carrying the metal layer;
A second electrode disposed to face the first electrode;
A p-type inorganic semiconductor and an n-type inorganic semiconductor disposed between the metal layer and the second electrode;
4. The solar cell according to claim 1, wherein the electron donor is the p-type inorganic semiconductor at a junction between the p-type inorganic semiconductor and the n-type inorganic semiconductor. 5. A method for producing a solar cell that performs photoelectric conversion by irradiating light to an electron donor,
Forming a localized surface plasmon electric field by light irradiation and forming a metal layer on the first electrode by electrolytic plating to promote excitation of the electrons of the electron donor;
Providing the electron donor on the first electrode on which the metal layer is formed;
And a step of providing a second electrode so as to face the first electrode with the electron donor in between. An electrode structure used in a solar cell that performs photoelectric conversion by irradiating light to an electron donor,
An electrode having conductivity;
An electrode for a solar cell, comprising: a metal layer formed by electrolytic plating on the electrode, generating a localized surface plasmon electric field by light irradiation, and promoting excitation of the electrons of the electron donor. Construction.