JP2011213744A - Wavelength conversion member and optical electromotive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wavelength conversion member having a wide excitation emission wavelength band and excellent in durability, and to provide an optical electromotive device having high performance and excellent reliability.SOLUTION: The wavelength conversion member includes: a first wavelength conversion layer composed of a first composition containing a first wavelength conversion material with which light in ultraviolet ray and in violet ray regions are converted into light of the longer wavelength side with respect to a direction of incident light and a first binder; and a second wavelength conversion layer composed of a second composition containing a wavelength conversion material with which an infrared ray is converted into light of the shorter wavelength side and a second binder, wherein those layers are adjacent to each other and laminated in this order. In addition, an optical electromotive device has the wavelength conversion member.

Description

  The present invention relates to a wavelength conversion member and a photovoltaic device.

  Photovoltaic devices are used as solar cells that photoelectrically convert sunlight to extract electrical energy. As this type of photovoltaic device, currently, one using single crystal silicon, polycrystalline silicon, spherical silicon, amorphous silicon, CdTe, or CIGS as a photovoltaic layer for converting light into electromotive force is mainly used. Recently, organic solar cells such as dye-sensitized solar cells have been developed, and various photovoltaic layers containing organic materials have been used.

  Many of these photovoltaic devices have a spectral sensitivity limited to the substantially visible light region, and efficiently convert regions other than visible light, such as the ultraviolet region and the infrared region, into sunlight. I can't. In addition, the crystalline silicon solar cell has a problem in that the photoelectric conversion efficiency decreases as the temperature rises due to absorption of infrared light or ultraviolet light. Furthermore, in an organic solar cell using a photovoltaic layer containing an organic material, there has been a problem that the photoelectric conversion efficiency is lowered as the organic material is deteriorated by ultraviolet rays.

  As a method using the ultraviolet region, there is a method of reaching the solar cell without cutting the ultraviolet light, but the effect is small because the spectral sensitivity of the solar cell in the ultraviolet region is low (Patent Document 1).

JP 2008-235610 A JP 2008-195664 A

An object of the present invention is to provide a wavelength conversion member having a wide excitation light emission wavelength band and excellent in durability.
Another object of the present invention is to provide a photovoltaic device with high performance and excellent reliability.

Such an object is achieved by the present invention described in the following (1) to (20).
(1) A first wavelength composed of a first composition containing a first wavelength conversion substance and a first binder that converts ultraviolet light and light in the violet region into light of a longer wavelength side with respect to the direction in which light enters. A conversion layer and a second wavelength conversion layer composed of a second composition containing a second wavelength conversion substance and a second binder for converting infrared light into light having a shorter wavelength are laminated in this order adjacent to each other. A wavelength conversion member characterized by comprising:
(2) The wavelength conversion member according to (1), wherein the first wavelength conversion layer absorbs light of more than 200 nm and not more than 430 nm and emits light of more than 430 nm.
(3) The wavelength conversion according to (1) or (2), wherein the second wavelength conversion layer absorbs light having a wavelength exceeding 850 nm and not exceeding 2500 nm and emitting light exceeding 430 nm and not exceeding 850 nm. Element.
(4) The wavelength conversion member according to any one of (1) to (3), wherein the content of the first wavelength conversion substance is 10 to 70% by volume of the entire first composition.
(5) The wavelength conversion member according to any one of (1) to (4), wherein the content of the second wavelength conversion substance is 10 to 70% by volume of the entire second composition.
(6) The above-mentioned (1) to (1), wherein the first wavelength conversion substance is at least one selected from zinc oxide (ZnO), silicon (Si), gallium nitride (GaN), and indium phosphide (InP). The wavelength conversion member according to any one of 5).
(7) The wavelength conversion member according to any one of (1) to (6), wherein an average particle diameter of primary particles of the first wavelength conversion substance is 1 to 100 nm.
(8) The wavelength conversion member according to any one of (1) to (7), wherein the second wavelength conversion substance is a semiconductor particle containing a rare earth element or an alkali metal element.
(9) The rare earth element or alkali metal element contains europium (Eu), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm) and ytterbium (Yb), lithium (Li), sodium (Na) The wavelength conversion member according to (8), which is one or more elements selected from the group consisting of:
(10) The semiconductor particles of the second wavelength conversion substance are zinc oxide (ZnO), silicon (Si), gallium nitride (GaN), yttrium oxide (Y ₂ O ₃ ), yttrium vanadate (VYO ₄ ), and phosphation. The wavelength conversion member according to (8) or (9), wherein the wavelength conversion member is at least one selected from indium (InP).
(11) The wavelength conversion member according to any one of (8) to (10), wherein the content of the rare earth element in the second wavelength conversion material is 0.01 to 30% by weight of the entire second wavelength conversion material. .
(12) The wavelength according to any one of (8) to (11), wherein the content of the alkali metal element in the second wavelength conversion substance is 1 to 20% by weight of the rare earth element in the second wavelength conversion substance. Conversion member.
(13) The wavelength conversion member according to any one of (1) to (12), wherein an average particle diameter of primary particles of the second wavelength conversion substance is 1 to 100 nm.
(14) The ratio (t1 / t2) between the thickness (t1) of the first wavelength conversion layer and the thickness (t2) of the second wavelength conversion layer is 0.01 to 30 (1) Thru | or the wavelength conversion member in any one of (13).
(15) A photovoltaic device comprising the wavelength conversion member according to any one of (1) to (14).
(16) The photovoltaic device according to (15), wherein the wavelength conversion member has a concavo-convex structure in a plane thereof.
(17) The photovoltaic device according to (16), wherein the uneven structure has a height difference of 300 nm to 100 μm.
(18) The photovoltaic device according to (16) or (17), wherein the in-plane period of the concavo-convex structure is 300 nm to 50 μm.
(19) The photovoltaic device according to any one of (16) to (18), wherein the uneven structure has a fine uneven shape smaller than the uneven structure.
(20) The photovoltaic device according to any one of (16) to (19), wherein a shape of the uneven structure is different between the first wavelength conversion layer and the second wavelength conversion layer.

According to the present invention, it is possible to provide a wavelength conversion member having a wide excitation light emission wavelength band and having excellent durability.
In addition, according to the present invention, a photovoltaic device having high performance and excellent reliability can be provided.

It is sectional drawing for demonstrating the wavelength conversion member of this invention. It is sectional drawing for demonstrating the photovoltaic apparatus of this invention. It is sectional drawing and the top view which show typically other embodiment of a photovoltaic apparatus. It is sectional drawing and the top view which show typically other embodiment of a photovoltaic apparatus. It is sectional drawing and the top view which show typically other embodiment of a photovoltaic apparatus. It is sectional drawing and the top view which show typically other embodiment of a photovoltaic apparatus. It is sectional drawing and the top view which show typically other embodiment of a photovoltaic apparatus.

Hereinafter, the wavelength conversion member and photovoltaic device of the present invention will be described.
The wavelength conversion member of the present invention is composed of a first composition containing a first wavelength conversion substance and a first binder that convert ultraviolet light and violet light into longer wavelength light in the light incident direction. The first wavelength conversion layer and the second wavelength conversion layer composed of the second composition containing the wavelength conversion substance and the second binder for converting infrared light into light having a shorter wavelength side are adjacent to each other. It is characterized by being laminated in order.
Moreover, the photovoltaic apparatus of this invention has the wavelength conversion member as described above, It is characterized by the above-mentioned.

(Wavelength conversion member)
First, the wavelength conversion member will be described.
In FIG. 1, sectional drawing of suitable embodiment of the wavelength conversion member of this invention is shown.
As shown in FIG. 1, the wavelength conversion member 100 uses the incident light 10 side of light (sunlight) as the first wavelength conversion layer 1, and the first wavelength conversion layer 1 and the second wavelength conversion layer 2 are mutually connected. Adjacent layers are stacked in this order. Thereby, each layer can have a different absorption wavelength, whereby the excitation emission wavelength band can be widened.

  Here, the 1st wavelength conversion layer 1 is comprised by the 1st composition containing the 1st wavelength conversion substance and 1st binder which convert the light of an ultraviolet-ray and a purple area | region into the light of a longer wavelength side. As a result, light in the ultraviolet region and violet region (specifically, a wavelength of 430 nm or less) can be absorbed, and light having a wavelength exceeding 430 nm can be emitted. Furthermore, it can also suppress that the organic member contained in a wavelength conversion member etc. deteriorates with an ultraviolet-ray etc.

Examples of the first wavelength converting substance include inorganic semiconductor particles, luminescent metal clusters, luminescent metal complexes, and luminescent organic substances. Among these, inorganic semiconductor particles are preferable. Thereby, the durability of the first wavelength conversion layer 1 and the stability of the light emission characteristics can be improved.
Examples of the inorganic semiconductor particles include zinc oxide (ZnO), silicon (Si), cadmium selenide (CdSe), cadmium telluride (CdTe), gallium nitride (GaN), and indium phosphide (InP). It is done. Among these, at least one selected from zinc oxide (ZnO), silicon (Si), gallium nitride (GaN) and indium phosphide (InP) is preferable, and zinc oxide is particularly preferable. Zinc oxide is useful from the viewpoint of production cost and ease of work for producing composite particles described later, since there is little risk of resource depletion and low toxicity.

  The average particle diameter of the first wavelength conversion substance is not particularly limited, but is preferably 1 to 10 nm, and particularly preferably 1 to 5 nm. When the average particle diameter is within the above range, the absorption and emission characteristics are improved due to the quantum size effect and the like. The said average particle diameter can be evaluated in the state of a transparent dispersion liquid, for example using a dynamic light-scattering apparatus (The Malvern company make, Zetasizer nano ZS).

The first wavelength conversion substance (particularly inorganic semiconductor particles) as described above is not particularly limited, but may contain a rare earth element (may be doped). Thereby, the excitation light emission wavelength band can be adjusted to a more preferable wavelength region.
As the rare earth element, for example, a lanthanoid element having an atomic number of 57 to 71 and 17 elements composed of scandium (Sc) and yttrium (Y) can be used alone or in combination of two or more. One or more selected from (Eu), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm) and ytterbium (Yb) are preferred. Since these rare earth elements have a particularly excellent wavelength conversion function, they are suitable as rare earth elements contained in the first wavelength conversion material (inorganic semiconductor particles).

  As described above, when the first wavelength conversion substance (inorganic semiconductor particles) includes the rare earth element, the emission characteristics such as the emission wavelength can be controlled. For example, in the case of use in a solar cell, the photoelectric conversion efficiency of the solar cell can be improved by converting ultraviolet light that is not used for photoelectric conversion of the solar cell into the wavelength of light used for photoelectric conversion of the solar cell. .

  The first wavelength conversion substance (inorganic semiconductor particles) preferably contains two or more kinds of rare earth elements. If two or more kinds of rare earth elements are contained in the first wavelength conversion material, energy is exchanged because they have excited states with different energies. As a result, the semiconductor particles can absorb a larger amount of light, and the light emission characteristics are improved.

  The first wavelength conversion substance (particularly inorganic semiconductor particles) may further contain an alkali metal element. With such a first wavelength conversion substance (inorganic semiconductor particles), the emission characteristics can be improved.

  The alkali metal element is preferably caused to act synergistically with the rare earth element, rather than acting on the first wavelength conversion substance alone. That is, when the rare earth element and the alkali metal element are added to the first wavelength conversion substance (particularly, inorganic semiconductor particles), the first wavelength conversion substance used in the present invention contains these elements alone. Compared to the above, it has both a relatively excellent wavelength conversion function and high light emission characteristics (light emission efficiency). This is because an alkali metal element has a function of neutralizing a deactivation site that inhibits light emission derived from a rare earth element. Due to this function, this type of first wavelength converting material is considered to emit light even with a smaller particle size.

  The alkali metal element is not particularly limited as long as it is an element belonging to Group 1A in the long-period element periodic table, but lithium (Li) and sodium (Na) are preferably used, and lithium is more preferably used. Since these alkali metal elements are incorporated into the first wavelength conversion material (inorganic semiconductor particles) to block the cause of the deactivation of light emission, the light emission of the first wavelength conversion material (inorganic semiconductor particles) This greatly contributes to the improvement of characteristics. Lithium is more preferably used because it has a smaller ionic radius than sodium and is more easily taken into the crystal of the first wavelength conversion substance (inorganic semiconductor particles), and thus has an effect of preventing the deactivation of light emission. Because.

  The content of the alkali metal element is not particularly limited, but is preferably about 1 to 20% by weight of the rare earth element content, and more preferably about 3 to 15% by weight. The effect mentioned above becomes more remarkable by making content of an alkali metal element into the said range. In addition, when content of an alkali metal element is less than the said lower limit, there exists a possibility that the effect which added the alkali metal element may not be acquired. On the other hand, if the content of the alkali metal element exceeds the upper limit, expression of the wavelength conversion function in the rare earth element may be hindered.

  Examples of the method for doping the first wavelength converting substance (inorganic semiconductor particles) with a rare earth element include a liquid phase method such as a sol-gel method and a solvothermal method, and a gas phase method such as a flame method and a sputtering method. It is done.

Further, when inorganic semiconductor particles are used as the first wavelength conversion substance, composite particles including the inorganic semiconductor particles and particles of an inorganic compound different from the inorganic semiconductor particles are preferable. Thereby, the durability of the first wavelength conversion layer 1 can be further improved.
Here, the composite particles, when the inorganic compound particles and the inorganic semiconductor particles are mixed, when the inorganic semiconductor particles and the inorganic compound are adhered on the surface, When inorganic semiconductor particles are contained in the inorganic compound particles, the inorganic semiconductor particles may be covered with the inorganic compound particles. Among these, the case where the circumference | surroundings of the said inorganic type semiconductor particle are coat | covered with the particle | grains of the said inorganic compound is preferable. Thereby, durability can be improved more.

Examples of the inorganic compound particles include ZnO, SiO ₂ , ZnS, GaN, CdS, GaP, CdS, ZrO ₂ , YVO ₄ , and Y ₂ O ₃ particles. Among these, at least one particle of silica (SiO ₂ ) and zirconia (ZrO ₂ ) is preferable. Thereby, the light emission characteristics such as durability and the light emission quantum yield can be improved.

  Although content of the said inorganic type semiconductor particle is not specifically limited, It is preferable that it is 10-80 volume% of the said composite particle whole, and 30-60 volume% is especially preferable. When the content is within the above range, the durability and light emission characteristics are particularly excellent.

The average particle size of the composite particles is not particularly limited, but is preferably 20 to 100 nm, and particularly preferably 45 to 55 nm. When the average particle diameter is within the above range, the dispersibility in the resin is particularly improved, the composite particles can be highly filled in the resin to improve the light emission characteristics, and a transparent resin composition in the visible light region can be obtained. it can.
The said average particle diameter can be evaluated in the state of a transparent dispersion liquid, for example using a dynamic light-scattering apparatus (The Malvern company make, Zetasizer nano ZS). When a field emission transmission electron microscope (FE-TEM, manufactured by Hitachi, Ltd., HF-2200) is used, the particle size of the composite particles can be evaluated in a powder state.

  Particularly in the case of composite particles using zinc oxide, the lithium content in the composite particles is preferably 3% by weight or less, preferably 2% by weight or less, more preferably 1% by weight or less. Aggregation of semiconductor particles in the particles can be suppressed. Although the reason for this is not clarified in detail, it is considered that lithium inhibits adsorption (aggregation) between semiconductor particles and inorganic compound particles by adsorbing moisture in the atmosphere. Lithium may be doped with zinc oxide or may be present as an impurity. Among these, it is preferable that lithium content which exists as an impurity is below the said range.

  That is, lithium is distributed in the composite fine particles and prevents smooth adsorption (aggregation) between the inorganic semiconductor particles and the inorganic compound particles, so that the composite particles are not easily spherical and have an irregular shape. It is considered to be. Furthermore, when it becomes irregularly shaped, the inorganic semiconductor particles are likely to be exposed, so that the activity of the exposed semiconductor particles cannot be controlled. As a result, it is considered that the light resistance and long-term stability of the first composition are lowered. Furthermore, the emission quantum yield can be increased.

  Examples of the method of bringing the lithium content into the above range include a method of washing the inorganic semiconductor particles or composite particles, a method of passing a dispersion of semiconductor particles through an ion exchange resin (permeable membrane), and the like. It is done.

  Moreover, even if it uses the manufacturing method (for example, zinc oxide synthesis method etc.) of the inorganic type semiconductor particle which does not use lithium in a raw material, lithium content can be made into the said range.

  Further, if the lithium content is less than or equal to the above upper limit value, the effects as described above can be obtained, but preferably 0.01% by weight or more, more preferably 0.1% by weight or more, and further preferably 0.5% by weight. A lower limit value of% or more may be set. By making lithium content more than this lower limit, said subject can be solved more reliably. Although the effect of solving the above-mentioned problem becomes conspicuous as the lithium content decreases, there is a maximum value in the magnitude of the effect, and this maximum value contains lithium from the lower limit. This is because it is located in a region having a large amount. That is, when the lithium content is less than the lower limit, the light emission characteristics may be deteriorated.

The lithium content can be measured, for example, by ion chromatography analysis. In the case of ion chromatography analysis, the above-described lithium content is measured as the lithium ion content. Here, the ion chromatographic analysis is performed by the following procedure, for example, using ion chromatography.
First, a sample to be analyzed is placed in a container and diluted with ultrapure water. Then, after sealing the container, the container is put into a thermostat, and the container is subjected to hot water treatment at, for example, 125 ° C. × 20 hours. Next, the container subjected to the hot water treatment is gradually cooled to room temperature. Then, the sample in the container is subjected to a centrifugal separation process and a filter filtration process, and the sample after each process is used as a test solution for ion chromatography analysis. Subsequently, the obtained test solution and an ion standard sample having a known concentration are introduced into ion chromatography, and the content of each ion in the test solution is quantified by a calibration curve method. As described above, the lithium content can be measured.

  Further, the content of the rare earth element described above is not particularly limited, but is preferably 0.01 to 20% by weight, particularly preferably 0.02 to 10% by weight, based on the entire composite particle. When the content is within the above range, the emission characteristics such as the emission quantum yield are particularly excellent.

  Although content in the 1st composition of the semiconductor particle in the said inorganic type is not specifically limited, 10-70 volume% with respect to the said 1st composition whole, Especially 40-60 volume% is preferable. When the content is within the above range, the moldability of the resin composition can be particularly secured, and the filling property of the inorganic semiconductor particles (composite particles) is ensured in the resin composition. The semiconductor particles (composite particles) of the system are easily arranged regularly and uniformly. As a result, when the resin composition is formed into a layer, the transparency of the layer can be improved.

The first wavelength conversion substance (composite particles) is immobilized by a first binder. For example, when the first binder is a resin described later, the resin serves as a base resin together with the function of the binder, and forms the basis of the first wavelength conversion layer 1.
Examples of the first binder include a resin, a coupling agent, the inorganic semiconductor particles, and an inorganic material different from the inorganic compound (specifically, silica, zirconia, glass, quartz, etc.). Of these, resins are preferred. Thereby, formation of the 1st wavelength conversion layer 1 can be made easy. Such a first binder is preferably transparent (no absorption with respect to ultraviolet light to infrared light). This makes it possible to easily transmit wavelengths other than the absorption wavelength of the first wavelength conversion substance.

Examples of the resin include an epoxy resin, an acrylic resin, a silicone resin, and an ethylene vinyl acetate (EVA) resin. By using these, the light transmittance of the resin composition can be further enhanced.
Among these, examples of the epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, naphthalene type epoxy resin or hydrogenated products thereof, epoxy resin having a dicyclopentadiene skeleton, Examples thereof include an epoxy resin having a glycidyl isocyanurate skeleton, an epoxy resin having a cardo skeleton, and an epoxy resin having a polysiloxane structure. When the resin composition requires heat resistance, such as directly forming a photovoltaic layer such as amorphous silicon or an antireflection film, those having an alicyclic structure are preferred. Examples of the alicyclic epoxy resin include 3,4-epoxycyclohexylmethyl 3 ′, 4′-epoxycyclohexanecarboxylate, 1,2,8,9-diepoxylimonene, and ε-caprolactone oligomer at both ends, respectively. Examples include an ester-bonded 4-epoxycyclohexylmethanol and 3,4-epoxycyclohexanecarboxylic acid, a hydrogenated biphenyl skeleton, and an alicyclic epoxy resin having a hydrogenated bisphenol A skeleton.

  The acrylic resin is not particularly limited as long as it is a (meth) acrylate having two or more functional groups, but a resin composition such as directly forming a photovoltaic layer or an antireflection film such as amorphous silicon. When a thing needs heat resistance, what has an alicyclic structure is preferable. As the (meth) acrylate having an alicyclic structure, an acrylic resin obtained by polymerizing at least one (meth) acrylate selected from the following general formula (1) and general formula (2) is particularly preferable.

More preferably, in the general formula (1), R ¹ and R ² are hydrogen, a is 1 and b is 0. In the general formula (2), X is — Perhydro-1,4; 5,8-dimethananaphthalene-2,3,7- (oxymethyl) tri having a structure in which CH ₂ OCOCH═CH ₂ , R ³ , R ⁴ are hydrogen and P is 1 An acrylate, and at least one acrylate selected from acrylates having a structure in which X, R ³ and R ⁴ are all hydrogen and P is 0 or 1, are more preferable in consideration of viscosity and the like. In this case, norbornane dimethylol diacrylate having a structure in which X, R ³ and R ⁴ are all hydrogen and P is 0 is used.

A water-dispersed acrylic resin can be used as the acrylic resin. A water-dispersed acrylic resin is an acrylic monomer, oligomer, or polymer that is dispersed in a dispersion medium containing water as the main component. In a dilute state like an aqueous dispersion, the crosslinking reaction hardly proceeds, but water is evaporated. If this is done, the crosslinking reaction will proceed and solidify at room temperature, or it will have a functional group capable of self-crosslinking, and it will be crosslinked and solidified only by heating without the use of additives such as catalysts, polymerization initiators, and reaction accelerators. Acrylic resin.
In the former type, the crosslinking reaction hardly proceeds in a dilute state such as an aqueous dispersion, and if water is evaporated and the crosslinking reaction proceeds and solidifies at room temperature, it is not particularly limited. Additives such as a polymerization initiator and a reaction accelerator may be used, or a functional group capable of self-crosslinking may be used. Further, heating for the purpose of completing the reaction is not limited. The self-crosslinkable functional group is not particularly limited. For example, carboxyl groups, epoxy groups, methylol groups, vinyl groups, primary amide groups, alkoxysilyl groups, methylol groups and alkoxymethyl groups, carbonyl groups And hydrazide group, carbodiimide group and carboxyl group. The water-dispersed acrylic resin is suitably used when the composite particles containing the wavelength conversion substance have an affinity for water.

  On the other hand, examples of the silicone-based resin include commercially available silicone resins for LEDs.

  Further, as the ethylene vinyl acetate resin having crosslinkability, those having a vinyl acetate content (VA content) of 25% by weight or more are preferably used. For example, Solar Eva (registered trademark) of Mitsui Chemicals Fabro Co., Ltd. It can be used suitably.

  Note that the curable resin as described above may be any resin that finally forms a network structure, and ionomer resins that form a network using ions as a medium can also be used.

  In addition to the curable resin and the first wavelength conversion material described above, the first resin composition using a resin includes a catalyst for promoting crosslinking, a crosslinking agent, other wavelength conversion materials, composite particles and a resin. It may contain various additives such as a compound having an alkoxy group, a coupling agent, and a surfactant for improving the affinity of the compound and improving the dispersibility of the composite particles.

  Examples of such additives include silicon alkoxide compounds such as tetraethoxysilane and tetramethoxysilane, various coupling agents containing silicon such as aminosilane, epoxysilane, and acrylic silane, and silicon other than silicon such as aluminum and titanium. Examples thereof include an alkoxy group-containing compound containing an element.

  In addition, when the first wavelength converting substance (inorganic semiconductor particles, composite particles) is dispersed in the first binder, which is a curable resin, it is preferable to use a silicon-containing silane coupling agent as a dispersing agent. As the silane coupling agent, those having nitrogen or an amino group are preferably used, and aminosilane, azasilane and the like are preferably used. When aminosilane is used, disilane having a bifunctional alkoxy group or monosilane having a monofunctional alkoxy group is preferable, and N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane and the like are preferable from the balance of cost and performance. Preferably used. When azasilane is used, cyclic azasilane or the like is preferably used, and 2,2-dimethoxy-1,6-diaza-2-silacyclooctane or N-methyl-aza-2,2,4 is used from the balance of cost and performance. -Trimethylsilacyclopentane and the like are preferably used.

  Although content of the said resin is not specifically limited, 20 to 65 volume% of the whole said 1st resin composition is preferable, and 30 to 55 volume% is especially preferable. When the content is within the above range, the light emission characteristics and durability are particularly excellent.

  The first resin composition as described above is applied by, for example, a doctor blade method, spin coating method, dipping method, table coating method, spray method, applicator method, curtain coating method, die coating method, ink jet method, dispenser method, etc. The first wavelength conversion layer 1 can be obtained by adding a curing agent as necessary) and curing the resin composition by heating or ultraviolet irradiation.

  Such a first wavelength conversion layer preferably absorbs light of more than 200 nm and not more than 430 nm and emits light of more than 430 nm. Thereby, the ultraviolet-ray which is not normally used for photoelectric conversion can be converted into the wavelength conversion light which can be photoelectrically converted, and the wavelength conversion material which can implement | achieve the solar cell with higher photoelectric conversion efficiency is obtained.

  Although the thickness of such a 1st wavelength conversion layer 1 is not specifically limited, 1-100 micrometers is preferable and 5-50 micrometers is especially preferable. When the thickness is within the above range, the light transmittance exceeding 430 nm and the conversion of light below 430 nm are particularly excellent.

The 2nd wavelength conversion layer 2 is comprised with the 2nd composition containing the 2nd wavelength conversion substance and 2nd binder which convert infrared rays into the light of a shorter wavelength side. Accordingly, light having a wavelength exceeding 850 nm and not more than 2500 nm can be absorbed, and light having a wavelength exceeding 430 nm and not more than 850 nm can be emitted.
Conventionally, it has been technically difficult to wavelength-convert long wavelength light such as infrared rays to the short wavelength side. On the other hand, in the present invention, it is possible to more efficiently convert infrared rays to light on the short wavelength side by using a multiphoton excitation mechanism.

  Examples of the second wavelength converting substance include inorganic semiconductor particles, luminescent organic compounds such as rhodamine and benzothiadiazole. Among these, inorganic semiconductor particles are preferable. Thereby, the efficiency which wavelength-converts the light of the long wavelength side to the short wavelength side can be improved.

Examples of the inorganic semiconductor particles include zinc oxide (ZnO), silicon (Si), cadmium selenide (CdSe), cadmium telluride (CdTe), gallium nitride (GaN), yttrium oxide (Y ₂ O ₃ ), Examples thereof include yttrium vanadate (VYO ₄ ) and indium phosphide (InP). Among these, 1 selected from zinc oxide (ZnO), silicon (Si), gallium nitride (GaN), yttrium oxide (Y ₂ O ₃ ), yttrium vanadate (VYO ₄ ), and indium phosphide (InP) More than species are preferred. These have a proven record as substances that absorb infrared rays and emit light in the visible region, and thus can improve light conversion efficiency.

  The average particle diameter of the second wavelength converting substance (particularly inorganic semiconductor particles) is not particularly limited, but is preferably 1 to 10 nm, and particularly preferably 1 to 5 nm. When the average particle diameter is within the above range, the absorption and emission characteristics are improved due to the quantum size effect and the like. The said average particle diameter can be evaluated in the state of a transparent dispersion liquid, for example using a dynamic light-scattering apparatus (The Malvern company make, Zetasizer nano ZS).

The second wavelength converting substance (particularly inorganic semiconductor particles) as described above preferably has a rare earth element (doped). Thereby, the excitation light emission wavelength band can be adjusted to a more preferable wavelength region.
As the rare earth element, for example, a lanthanoid element having an atomic number of 57 to 71 and 17 elements composed of scandium (Sc) and yttrium (Y) can be used alone or in combination of two or more. A combination of one or more of (Eu), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm) and ytterbium (Yb) is preferred. Since these rare earth elements have a particularly excellent wavelength conversion function, they are suitable as rare earth elements contained in inorganic semiconductor particles.

  As described above, when the second wavelength conversion substance (inorganic semiconductor particles) includes the rare earth element, the emission characteristics such as the emission wavelength can be controlled. For example, in the case of use in a solar cell, the photoelectric conversion efficiency of the solar cell can be improved by converting infrared light that is not used for the photoelectric conversion of the solar cell into the wavelength of light used for the photoelectric conversion of the solar cell. .

  The second wavelength converting substance (particularly inorganic semiconductor particles) preferably contains two or more rare earth elements. When two or more types of rare earth elements are contained in the semiconductor particles, energy is exchanged between them because they have excited states with different energies. As a result, the semiconductor particles can absorb a larger amount of light, and the light emission characteristics are improved.

  The second wavelength converting substance (particularly inorganic semiconductor particles) may further contain an alkali metal element. This can further improve the light emission characteristics of the second wavelength converting substance.

  The alkali metal element is preferably caused to act synergistically with the rare earth element, rather than acting on the semiconductor material alone. That is, by adding a rare earth element and an alkali metal element to the second wavelength conversion substance (inorganic semiconductor particles), a relatively superior wavelength conversion function compared to the case where these elements are contained alone. It is possible to have both high light emission characteristics (light emission efficiency). This is because an alkali metal element has a function of neutralizing a deactivation site that inhibits light emission derived from a rare earth element. Due to this function, it is considered that this type of second wavelength conversion material emits light even with a smaller particle size.

  The alkali metal element is not particularly limited as long as it is an element belonging to Group 1A in the long-period element periodic table, but lithium (Li) and sodium (Na) are preferably used, and lithium is more preferably used. Since these alkali metal elements are incorporated into the second wavelength conversion material (inorganic semiconductor particles) and block the cause of light emission deactivation, they greatly contribute to the improvement of the light emission characteristics of the second wavelength conversion material. Is. In addition, lithium is more preferably used because it has a smaller ionic radius than sodium and is more easily incorporated into the crystal of the second wavelength conversion substance (particularly, inorganic semiconductor particles), thereby further preventing the deactivation of light emission. Because there is.

  The content of the alkali metal element is not particularly limited, but is preferably about 1 to 20% by weight of the rare earth element content, and more preferably about 3 to 15% by weight. The effect mentioned above becomes more remarkable by making content of an alkali metal element into the said range. In addition, when content of an alkali metal element is less than the said lower limit, there exists a possibility that the effect which added the alkali metal element may not be acquired. On the other hand, if the content of the alkali metal element exceeds the upper limit, expression of the wavelength conversion function in the rare earth element may be hindered.

  Examples of the method of doping the second wavelength conversion substance (inorganic semiconductor particles) with a rare earth element include a liquid phase method such as a sol-gel method and a solvothermal method, and a gas phase method such as a flame method and a sputtering method. It is done.

In addition, when inorganic semiconductor particles are used as the second wavelength conversion substance, composite particles including the inorganic semiconductor particles and particles of an inorganic compound different from the inorganic semiconductor particles are preferable. Thereby, the durability of the second wavelength conversion layer 2 can be further improved.
Here, the composite particles, when the inorganic compound particles and the inorganic semiconductor particles are mixed, when the inorganic semiconductor particles and the inorganic compound are adhered on the surface, When inorganic semiconductor particles are contained in the inorganic compound particles, the inorganic semiconductor particles may be covered with the inorganic compound particles. Among these, the case where the circumference | surroundings of the said inorganic type semiconductor particle are coat | covered with the particle | grains of the said inorganic compound is preferable. Thereby, durability can be improved more.

Examples of the inorganic compound particles include ZnO, SiO ₂ , ZnS, GaN, CdS, GaP, CdS, ZrO ₂ , YVO ₄ , and Y ₂ O ₃ particles. Among these, at least one particle of silica (SiO ₂ ) and zirconia (ZrO ₂ ) is preferable. Thereby, the light emission characteristics such as durability and the light emission quantum yield can be improved.

  Although content of the said inorganic type semiconductor particle is not specifically limited, It is preferable that it is 10-80 volume% of the said composite particle whole, and 30-60 volume% is especially preferable. When the content is within the above range, the durability and light emission characteristics are particularly excellent.

The average particle size of the composite particles is not particularly limited, but is preferably 20 to 100 nm, and particularly preferably 45 to 55 nm. When the average particle diameter is within the above range, the dispersibility in the resin is particularly improved, the composite particles can be highly filled in the resin to improve the light emission characteristics, and a transparent resin composition in the visible light region can be obtained. it can.
The said average particle diameter can be evaluated in the state of a transparent dispersion liquid, for example using a dynamic light-scattering apparatus (The Malvern company make, Zetasizer nano ZS). When a field emission transmission electron microscope (FE-TEM, manufactured by Hitachi, Ltd., HF-2200) is used, the particle size of the composite particles can be evaluated in a powder state.

  The second wavelength converting substance is immobilized by a second binder. For example, when the second binder is a resin described later, the resin becomes a base resin together with the function of the binder, and forms the basis of the second wavelength conversion layer 2.

  The second binder is the same as the first binder such as an inorganic material (specifically, silica, zirconia, glass, quartz, etc.) different from the resin, the coupling agent, the semiconductor particles, and the inorganic compound. Things can be used. Among these, a resin is preferable. Thereby, formation of the 2nd wavelength conversion layer 2 can be made easy. Such a second binder is preferably transparent. Thereby, it becomes possible to easily transmit wavelengths other than the absorption wavelength of the second wavelength converting substance.

  Although content in the 2nd composition of the said 2nd wavelength conversion substance is not specifically limited, 10-70 volume% of the whole said 2nd composition is preferable, and 40-60 volume% is especially preferable. When the content is within the above range, the moldability of the resin composition can be particularly secured, and the filling property of the inorganic semiconductor particles (composite particles) is ensured in the resin composition. The semiconductor particles (composite particles) of the system are easily arranged regularly and uniformly. As a result, when the resin composition is formed into a layer, the transparency of the layer can be improved.

  The second resin composition using a resin as the second binder as described above is, for example, a doctor blade method, spin coating method, dipping method, table coating method, spray method, applicator method, curtain coating method, die coating method, ink jet method. The second wavelength conversion layer 2 can be obtained by coating by a dispenser method or the like (adding a curing agent if necessary) and curing the resin composition by heating or ultraviolet irradiation.

  Although the thickness (t2) of such 2nd wavelength conversion layer 2 is not specifically limited, 1-100 micrometers is preferable and 5-50 micrometers is especially preferable. When the thickness is within the above range, the light transmittance after converting the wavelength and the conversion of light having a wavelength of more than 850 nm and not more than 2500 nm are excellent.

  The second wavelength conversion layer 2 preferably absorbs light having a wavelength exceeding 850 nm and not more than 2500 nm and emitting light having a wavelength exceeding 430 nm and not more than 850 nm. Thereby, it has an infrared region different from the first wavelength conversion layer 1 as an absorption wavelength band, and can broaden the excitation wavelength band.

  The ratio (t1 / t2) between the first wavelength conversion layer 1 (t1) and the thickness (t2) of the second wavelength conversion layer 2 is not particularly limited, but is preferably 0.01 to 30, particularly It is preferable that it is 0.05-10. Thereby, light of each wavelength can be converted particularly effectively.

The wavelength conversion member 100 of the present invention can be obtained by bonding the first wavelength conversion layer 1 and the second wavelength conversion layer 2 as described above.
Examples of the method of laminating include a method of sequentially forming the first wavelength conversion layer and the second wavelength conversion layer above the photovoltaic layer.
An adhesive or the like may be provided between the first wavelength conversion layer 1 and the second wavelength conversion layer 2, but in terms of light transmittance, the first wavelength conversion layer 1 and the second wavelength conversion layer. 2 are preferably arranged adjacent to each other.

In addition, although the wavelength conversion member 100 comprised by the 1st wavelength conversion layer 1 and the 2nd wavelength conversion layer 2 was demonstrated in FIG. 1, this invention is not limited to this, Furthermore, it has a 3rd wavelength conversion layer. Or may have a fourth wavelength conversion layer.
Such a third wavelength conversion layer and a fourth wavelength conversion layer may be provided between the first wavelength conversion layer 1 and the second wavelength conversion layer 2 or on the upper side of the first wavelength conversion layer 1 (see FIG. 1 may be provided, or may be provided below the second wavelength conversion layer 2 (lower side in FIG. 1).

(Photovoltaic device)
Next, the photovoltaic device of the present invention will be described.
As shown in FIG. 2, the photovoltaic device (photovoltaic device of the present invention) 5 has a photovoltaic layer 3 that generates an electromotive force with the irradiation of sunlight. From the side, the first wavelength conversion layer 1, the second wavelength conversion layer 2, and the photovoltaic layer 3 are laminated in this order. Thereby, it can have a wide excitation wavelength band with respect to sunlight.

The photovoltaic layer 3 generates electromotive force by light, and includes a semiconductor layer composed of a p-type semiconductor layer, an intrinsic semiconductor layer, and an n-type semiconductor layer, a sealing material such as an EVA resin composition, and one surface of the semiconductor layer. Or the transparent electrode layer provided in the surface of both sides is provided.
The material constituting the semiconductor layer is not particularly limited as long as it is a semiconductor material, and examples thereof include single crystal silicon, polycrystalline silicon, spherical silicon, amorphous silicon, a compound semiconductor, an organic semiconductor, and a quantum dot semiconductor.
The transparent electrode is not particularly limited, and is formed of, for example, an ITO film or a tin oxide film. The configuration of the photovoltaic device 5 is not limited to this, and can be applied to various photovoltaic devices 5. In particular, when a commercially available photovoltaic layer 3 is prepared and a wavelength conversion layer is attached thereto, it is preferable that a glass, a transparent electrode, a non-reflective layer, a protective layer, etc. are further formed on the photovoltaic layer 3. . In this case, a wavelength conversion layer may be attached on or below glass, a transparent electrode, a non-reflective layer, a protective layer, or the like.

  In the embodiment shown in FIG. 2, the first wavelength conversion layer 1 absorbs light having a wavelength in the ultraviolet to violet region (specifically, a wavelength of 430 nm or less) and converts it into light having a wavelength exceeding 430 nm. In addition, the second wavelength conversion layer 2 mainly absorbs infrared light (specifically, a wavelength of more than 850 nm and not more than 2500 nm) and converts it into light of more than 430 nm and not more than 850 nm. The converted sunlight enters the photovoltaic layer 3. Therefore, compared with the case where a wavelength conversion layer is not provided, the photoelectric conversion efficiency in the photovoltaic layer 3 is increased, and when an organic material is used for the photovoltaic layer 3, the deterioration can be suppressed. . As a result, the lifetime of the photovoltaic layer 3 such as a photoelectric conversion layer in a solar cell is improved.

  In this embodiment, each wavelength conversion layer includes semiconductor particles (inorganic semiconductor particles, organic semiconductor particles) dispersed in a binder. In particular, when the inorganic semiconductor particles are composite particles, the activity of the inorganic semiconductor particles is controlled and the inorganic semiconductor particles can be uniformly dispersed in the first binder. Therefore, in the first wavelength conversion layer 1, The composite particles are uniformly dispersed. Therefore, the first wavelength conversion layer 1 can make the wavelength-converted light uniformly incident on the entire photovoltaic layer 3. Furthermore, the first wavelength conversion layer 1 can suppress transmission of wavelengths in the ultraviolet region to the second wavelength conversion layer 2. Therefore, it can promote that the 2nd wavelength conversion layer 2 converts infrared rays into visible light more efficiently.

  The photovoltaic device 5 can be applied to various devices such as EL lighting, optical communication, EL display, LED lighting, solar cell, bioimaging, and the like.

<Other embodiments>
Next, another embodiment (second embodiment) of the photovoltaic device of the present invention will be described.
3 to 8 are a sectional view and a plan view, respectively, schematically showing another embodiment of the photovoltaic device 5 of the present invention.

Hereinafter, although the second embodiment will be described, the description will focus on the differences from the first embodiment, and the description of the same matters will be omitted. In the present embodiment, the same components as those of the first embodiment are denoted by the same reference numerals as those of the components described above, and detailed description thereof is omitted.
In the present embodiment, the photovoltaic device is the same as that in the first embodiment, except that the photovoltaic device has a regularly distributed cured product of the dot-like resin composition.

The photovoltaic device 5 shown in FIG. 3 (a) is provided above the photovoltaic layer 3 and has a plurality of cured products of the resin composition in the form of dots. The cured product of each resin composition includes a first wavelength conversion material and a first binder that convert ultraviolet light and violet light into longer wavelength light in the light incident direction. And a second wavelength conversion layer composed of a second composition containing a wavelength conversion material and a second binder for converting infrared light into light on a shorter wavelength side, are adjacent to each other. The wavelength conversion member 100 is formed by laminating in this order.
The cured products of the plurality of resin compositions are spaced apart from each other at substantially equal intervals, and are regularly arranged on the upper surface of the photovoltaic layer 3. In other words, the wavelength conversion member 100 has a concavo-convex structure formed of the cured product of the resin composition of the present invention formed on the upper surface of the photovoltaic device 5. In the case of the wavelength conversion member 100 shown in FIG. 3B, the wavelength conversion member 100 has a discontinuous structure because the cured product of the resin composition having a dot-like shape is scattered. However, even in such a structure, it is referred to as a wavelength conversion member in this specification.

  When the wavelength conversion member 100 has a concavo-convex structure, when the light incident on the cured product of one resin composition is reflected, there is a probability that the light is reflected not in the upper direction of FIG. Get higher. The light reflected in the left-right direction is incident again on the adjacent cured product and incident on the photovoltaic layer 3 with refraction. As a result, when the wavelength conversion member 100 does not have a concavo-convex structure, the light incident on the photovoltaic layer 3 is lost due to reflection, whereas the wavelength conversion member 100 shown in FIG. In this case, a part of the light that would have been lost without the uneven structure can be incident on the photovoltaic layer 3. That is, the wavelength conversion member 100 shown in FIG. 3 has an antireflection function in addition to the wavelength conversion function as described above. As a result, the photoelectric conversion efficiency in the photovoltaic device 5 can be further increased.

  The height difference of the concavo-convex structure is preferably from 300 nm to 100 μm, more preferably from 1 to 50 μm, and even more preferably from 10 to 50 μm, from the balance between the absorption of sunlight from the oblique direction and the cost. . The height difference of the concavo-convex structure can be measured using various microscopes such as an atomic force microscope, a confocal microscope, and a laser microscope.

The in-plane period of the concavo-convex structure is preferably 300 nm to 50 μm. By setting the in-plane period of the concavo-convex structure within the above range, the probability that light is reflected on the surface of the concavo-convex structure can be particularly reduced, and the antireflection function of the concavo-convex structure can be particularly enhanced.
Furthermore, it is preferable that the period is substantially the same as or less than the absorption wavelength region of the wavelength conversion member 100. Thereby, when light enters the wavelength conversion member 100, Fresnel reflection is less likely to occur. Then, regardless of the shape of the concavo-convex structure, the reflection of light by the wavelength conversion member 100 decreases, and the amount of light incident on the wavelength conversion member 100 increases. As a result, the amount of light incident on the photovoltaic layer 3 also increases.

  Moreover, the uneven | corrugated period of an in-plane perpendicular direction (X direction, Y direction) may be the same, or may differ. There may also be variations in the in-plane cycle in the same direction. The in-plane period of the concavo-convex structure is obtained by Fourier transforming image information acquired using various microscopes such as an atomic force microscope, a confocal microscope, a laser microscope, and a field emission scanning electron microscope (FE-SEM). Can do.

  Examples of the shape of the concavo-convex structure include various shapes such as dots, microlenses, line and space (L & S), honeycombs, cells, square pyramids, moth eyes, and cones. From the viewpoint of cost and efficiency, the shape of a dot, microlens, L & S, cell, or quadrangular pyramid is preferable, and the shape of a dot or microlens is more preferable.

  The concavo-convex structure shown in FIGS. 3 to 5 and FIG. 7 is an example of the concavo-convex structure in the form of dots or microlenses. These concavo-convex structures have a substantially circular shape in plan view, while the vertical cross-sectional shape has a substantially semicircular shape.

  In addition to the discontinuous structure as shown in FIG. 3, the concave-convex structure provided in the wavelength conversion member 100 is a resin composition having a flat plate shape covering the upper surface of the photovoltaic layer 3 as shown in FIG. 4. It may be a structure of a laminate of the cured product and a cured product of the resin composition that is provided on the cured product and has a regularly distributed spot shape. If it is such a structure, the light which injected into area | regions other than the hardened | cured material of the resin composition which makes a dot-like form also injects into the wavelength conversion member 100, and can convert the wavelength. In other words, according to the wavelength conversion member 100 shown in FIG. 4, the wavelength conversion can also be performed for light that could not be converted by the wavelength conversion member 100 shown in FIG. 3. The ratio of light in the wavelength region that can be photoelectrically converted can be increased.

  In the uneven structure, the distribution of the cured product of the resin composition in the form of a dot may be regular or irregular. In the case of regularity, the pattern of distribution is not particularly limited.

  Further, as shown in FIG. 5A, the concavo-convex structure is convex on the side of the photovoltaic layer 3 as shown in FIG. 5B, even if the light irradiation side (upstream side) is convex. However, from the viewpoint that a large amount of light is incident on the photovoltaic layer 3, it is preferable that the photovoltaic layer 3 side is convex. In this case, the concavo-convex structure may be embedded in the photovoltaic layer 3 as shown in FIG. In this case, the in-plane period of the concavo-convex structure is preferably in the range of 300 nm to 1 μm.

  Moreover, even if the uneven | corrugated structure is comprised with the same resin composition, the adjacent unevenness | corrugation may be comprised with a different resin composition. When the light absorption wavelength range of the resin composition is relatively narrow, the power generation efficiency of the photovoltaic device 5 is set by setting different resin compositions with adjacent irregularities for the purpose of expanding the light absorption wavelength range. Can be improved easily.

  Furthermore, as shown in FIG. 5C, the concavo-convex structure may have a smaller fine concavo-convex shape at each convex portion. Thereby, the light confinement effect is generated by the fine uneven shape, and the reflection of light by the wavelength conversion member 100 can be further reduced. The height difference of the fine uneven shape is preferably 100 to 500 nm.

The concavo-convex structure is a structure in which the concavo-convex structure in FIG. 5A and the concavo-convex structure in FIG. 5B are combined, that is, both the light irradiation side and the photovoltaic layer 3 side are convex. Such a structure may be used (see FIG. 5D). In this case, it is preferable that the in-plane period of the concavo-convex structure in which the photovoltaic layer 3 side is convex is smaller than the in-plane period of the concavo-convex structure in which the light irradiation side is convex. Thereby, the light quantity which injects into the photovoltaic layer 3 can be increased.
The in-plane position of the concavo-convex structure in which the photovoltaic layer 3 side is convex and the in-plane position of the concavo-convex structure in which the side irradiated with light is convex are preferably shifted from each other. Thereby, the area of the wavelength conversion member 100 in a plan view can be secured larger, and the amount of light incident on the wavelength conversion member 100 can be increased.

The uneven structure shown in FIG. 6 is an example of an uneven structure having an L & S shape. Specifically, as shown in FIG. 6B, the concavo-convex structure shown in FIG. 6 has an elongated plan view shape extending along the Y direction, while the longitudinal sectional shape is substantially semicircular. ing.
Furthermore, the concavo-convex structure shown in FIG. 7 is also an example of the concavo-convex structure having an L & S shape, but the concavo-convex structure shown in FIG. 7 is an elongated shape extending along the Y direction as shown in FIG. 7B. A cured product of a plurality of resin compositions having a shape in plan view and provided at equal intervals, and a cured product of a plurality of resin compositions provided in an elongated plan view shape extending in the X direction at equal intervals. Are arranged so as to be orthogonal to each other. Thereby, the concavo-convex structure shown in FIG. 7 has a lattice shape in plan view.

The wavelength conversion member 100 having the concavo-convex structure as described above is formed by applying the resin composition of the present invention by various application methods as described above, and then curing the applied material. It is preferable to apply by an inkjet method. According to the inkjet method, a predetermined amount of the resin composition can be accurately applied to a desired region. For this reason, the shape of the concavo-convex structure can be accurately reproduced.
Moreover, it is preferable to perform a surface treatment on the coated surface in advance so as to control the liquid repellency of the resin composition. Thereby, the resin composition discharged by the inkjet method is naturally formed into a hemispherical shape by the surface tension. As a result, the wavelength conversion member 100 as shown in FIG. 3 can be formed more easily.

  Inkjet devices include various ejection methods such as a piezo method, an electrostatic method, and a thermal method. From the viewpoint that a relatively high viscosity resin composition can be ejected, a piezo method or an electrostatic method ink jet is available. An apparatus is preferably used.

Further, after forming the concavo-convex structure, another resin composition may be overcoated on the concavo-convex structure. Thereby, the fall of stain resistance, durability, etc. in the photovoltaic apparatus 5 can be suppressed.
In the present embodiment as described above, the same operations and effects as those in the first embodiment can be obtained.

  As mentioned above, although embodiment of the wavelength conversion member and photovoltaic device of this invention was described, this invention is not limited to this, For example, arbitrary structures are added to the photovoltaic device. May be.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example and a comparative example, this invention is not limited to this.

Example 1
1. Production of first wavelength conversion material <1> First, ethanol is added so that the concentration of zinc acetate dihydrate (Zn (CH ₃ COO) ₂ .2H ₂ O) is 0.1 M, and zinc acetate dihydrate is added. 400 ml of an ethanol solution of the product was prepared. The ethanol solution was concentrated with heating and stirring at about 80 ° C. for about 3 hours until the total amount of the solution reached 120 ml. After concentration, 120 ml of ethanol was further added and cooled to room temperature. Next, the obtained ethanol solution was added so that the concentration of lithium hydroxide monohydrate (LiOH.H ₂ O) was 0.14 M, and sonicated at a temperature of 23 ° C. or lower for 20 minutes. As a result, 400 ml of an ethanol dispersion was obtained. This ethanol dispersion emitted green light when irradiated with ultraviolet rays, and it was confirmed that ethanol contained semiconductor particles.
Then, hexane was added to 400 ml of the obtained ethanol solution, and centrifugation treatment was performed at 10,000 G for 1 minute. Hexane was added in such an amount that the volume ratio was about 3 (1200 ml) when the volume of the ethanol solution of semiconductor particles was 1. Thereafter, the supernatant was removed to obtain 4.9 g of a paste-like residue. Then, 400 ml of ethanol was added to the pasty residue and redispersed. As a result, an ethanol dispersion of the washed semiconductor particles was obtained.

<2> Next, an organosilica sol (product number: IPA-ST, average particle diameter of silica particles: about 12 nm, concentration of silica particles: 30% by weight, dispersion medium: 2-propanol) manufactured by Nissan Chemical Industries, Ltd. It was diluted about 34 times with ethanol to prepare a dispersion having a silica particle concentration of 0.15M. Next, 10 ml of this dispersion and 40 ml of the semiconductor particle ethanol dispersion prepared in the above <1> were mixed to prepare a mixed dispersion.
Next, composite particles of semiconductor particles and silica particles were obtained from the obtained mixed dispersion by a spray drying method. The furnace temperature during spray drying was 400 ° C., and nitrogen was used as the carrier gas.

<3> 3.0 g of composite particles obtained by repeating the above operation were mixed with 100 g of ethanol, and dispersion treatment was performed using zirconia beads to obtain a transparent dispersion liquid in which the composite particles were dispersed.

2. Production of first resin composition Norbornane dimethylol diacrylate having a structure in which X, R ³ , and R ⁴ are all hydrogen and P is 0 in the general formula (2) (prototype No. TO-2111; Toagosei ( Co.) 0.30 g, N-methyl-aza-2,2,4-trimethylsilacyclopentane (manufactured by Gelest, SIM6501.4) 0.24 g, and a transparent dispersion of composite particles prepared in <3> 60 g was mixed. Thereafter, the transparent dispersion was stirred at 40 ° C. under 30 hPa for 3 hours to remove volatile components.
Then, 0.003 g of 2-hydroxy-2-methyl-1-phenyl-propan-1-one (Ciba Japan, Darocur 1173) was dissolved as a photopolymerization initiator in the transparent dispersion. This obtained the 1st resin composition.

3. Manufacture of the 1st wavelength conversion layer The 1st resin composition obtained above was apply | coated on the ETFE (tetrafluoroethylene and ethylene copolymer) film which gave the surface treatment of thickness 50 micrometers. The thickness after drying was about 20 μm. Then, the first resin composition was cured by irradiating with UV light of about 500 mJ / cm ² from both sides, and further heat-treated at about 180 ° C. for 1 hour in a vacuum oven to remove the solvent. This formed the 1st wavelength conversion layer (thickness 20 micrometers).

4). Production of Second Wavelength Conversion Substance (1) <4-1> Zinc nitrate hexahydrate (Zn (NO ₃ ) ₂ .6H ₂ O) 0.1M, Erbium nitrate hexahydrate (Er (NO ₃ ) ₃ · _6H 2 O), ytterbium nitrate hexahydrate _{(Yb (NO 3) 3 ·} 6H 2 O), was dissolved in 100ml of distilled water and lithium nitrate (LiNO _3). At this time, the addition amount of zinc ion, rare earth element ion and lithium ion is such that the molar ratio is zinc ion: erbium ion: yttrium ion: lithium ion = 97: 0.2: 1.3: 1.0. Prepared. While maintaining this temperature at 80 ° C., 3 equivalents of citric acid were added, and then neutralized with ammonium hydroxide. The solution was stirred for 2 hours to obtain a desired dispersion of semiconductor particles.

<4-2> Next, organosilica sol (product number: IPA-ST, manufactured by Nissan Chemical Industries, Ltd., average particle diameter of silica particles: about 12 nm, concentration of silica particles: 30% by weight, dispersion medium: 2-propanol ) Was diluted about 34 times with ethanol to prepare a dispersion having a silica particle concentration of 0.15M. Next, 10 ml of this dispersion and 40 ml of the semiconductor particle dispersion prepared in <4-1> were mixed to prepare a mixed dispersion.
Next, the obtained mixed dispersion was burned and dried by a flame method to synthesize target composite particles. The furnace temperature during combustion was 1100 ° C., and oxygen was used as the carrier gas.

  The composite particles 3.0g obtained by repeating the above operation were baked at 900 ° C. for 30 minutes in the atmosphere, then mixed with 100 g of ethanol, subjected to dispersion treatment using zirconia beads, and a transparent dispersion liquid in which the composite particles were dispersed. (1) was obtained.

5. Production of Second Wavelength Conversion Material (2) <5-1> 0.1 M zinc acetate dihydrate (Zn (CH ₃ COO) ₂ .2H ₂ O) and thulium acetate x hydrate (Tm (CH ₃ COO) ₃ · xH ₂ O) and ytterbium acetate x hydrate (Yb (CH ₃ COO) ₃ · xH ₂ O) were dispersed in 100 ml of ethanol. The amount of each of zinc acetate dihydrate, erbium acetate x hydrate, and ytterbium acetate x hydrate was adjusted so that the weight ratio was Zn ²⁺ : Tm ³⁺ : Yb ³ = 97: 1: 2. .
The ethanol solution was concentrated with heating and stirring at about 80 ° C. for about 3 hours until the total amount of the solution reached 120 ml. After concentration, 120 ml of ethanol was further added and cooled to room temperature. Next, the obtained ethanol solution was added so that the concentration of lithium hydroxide monohydrate (LiOH.H ₂ O) was 0.14 M, and sonicated at a temperature of 23 ° C. or lower for 20 minutes. Thus, 400 ml of an ethanol dispersion of semiconductor particles was obtained.

<5-2> Thereafter, hexane was added to 400 ml of the obtained ethanol solution, and centrifugation treatment was performed at 10,000 G for 1 minute. Hexane was added in such an amount that the volume ratio was about 3 (1200 ml) when the volume of the ethanol solution of semiconductor particles was 1. Thereafter, the supernatant was removed to obtain 4.9 g of a paste-like residue. Then, 400 ml of ethanol was added to the pasty residue and redispersed. As a result, an ethanol dispersion of the washed semiconductor particles was obtained.

<5-3> Next, an organosilica sol (product number: IPA-ST, manufactured by Nissan Chemical Industries, Ltd., average particle diameter of silica particles: about 12 nm, concentration of silica particles: 30% by weight, dispersion medium: 2-propanol ) Was diluted about 34 times with ethanol to prepare a dispersion having a silica particle concentration of 0.15M. Next, 10 ml of this dispersion and 40 ml of the semiconductor particle dispersion prepared in <5-2> were mixed to prepare a mixed dispersion.
Next, the obtained mixed dispersion was burned and dried by a flame method to synthesize target composite particles. The furnace temperature during combustion was 1100 ° C., and oxygen was used as the carrier gas.

  The composite particles 3.0g obtained by repeating the above operation were baked at 900 ° C. for 30 minutes in the atmosphere, then mixed with 100 g of ethanol, subjected to dispersion treatment using zirconia beads, and a transparent dispersion liquid in which the composite particles were dispersed. (2) was obtained.

6). Production of Second Resin Composition Norbornane dimethylol diacrylate having a structure in which X, R ³ and R ⁴ are all hydrogen and P is 0 in the general formula (2) (prototype No. TO-2111; Toagosei ( Co.) 0.30 g, N-methyl-aza-2,2,4-trimethylsilacyclopentane (manufactured by Gelest, SIM6501.4) 0.24 g, and transparent dispersion of the two types of composite particles prepared above 30 g of liquids (1) and (2) were mixed. Thereafter, the transparent dispersion was stirred at 40 ° C. under 30 hPa for 3 hours to remove volatile components.
Then, 0.003 g of 2-hydroxy-2-methyl-1-phenyl-propan-1-one (Ciba Japan, Darocur 1173) was dissolved as a photopolymerization initiator in the transparent dispersion. This obtained the 2nd resin composition.

7). Manufacture of 2nd wavelength conversion layer The 2nd resin composition obtained above was apply | coated on the 1st wavelength conversion layer obtained above. The thickness of the newly applied layer after drying was about 20 μm. Then, the second resin composition was cured by irradiating UV light of about 500 mJ / cm ² from both sides, and further heat-treated at about 180 ° C. for 1 hour under vacuum in a vacuum oven to remove the solvent. Thereby, the 2nd wavelength conversion layer (thickness 20 micrometers) was formed on the 1st wavelength conversion layer.

8). Production of Wavelength Conversion Member and Photovoltaic Device Next, a solar cell sealing material EVA (VA content 28%, cross-linked type) sheet is laid on the CIGS solar cell, and further, a second wavelength conversion layer is formed thereon. Then, the first wavelength conversion layer and the ETFE film were arranged and subjected to vacuum heat treatment to produce a photovoltaic device.

(Example 2)
The second wavelength conversion material of the second resin composition was the same as Example 1 except that only one type of the second wavelength conversion material (1) described above was used.

(Example 3)
The second wavelength conversion material was the same as that of Example 1 except that the following two types were used.
<1> Yttrium nitrate hexahydrate (Y (NO ₃ ) ₂ .6H ₂ O) 0.1M, erbium nitrate hexahydrate (Er (NO ₃ ) ₃ · 6H ₂ O), dissolved in 100 ml of distilled water I let you. At this time, the addition amount of yttrium ions and rare earth element ions was adjusted so that the molar ratio was yttrium ions: erbium ions = 98: 2. While maintaining this solution at a temperature of 80 ° C., 3 equivalents of citric acid was added, and then neutralized with ammonium hydroxide. The solution was stirred for 2 hours to obtain a desired dispersion of semiconductor particles.

<2> yttrium nitrate hexahydrate _{(Y (NO 3) 2 ·} 6H 2 O) 0.1M, holmium nitrate hexahydrate _{(Ho (NO 3) 3 ·} 6H 2 O), ytterbium nitrate hexahydrate _{(Yb (NO 3) 3 ·} 6H 2 O), was dissolved in 100ml of distilled water and lithium nitrate (LiNO _3). At this time, the addition amount of yttrium ion, rare earth element ion and lithium ion is such that the molar ratio is yttrium ion: holmium ion: yttrium ion: lithium ion = 97: 0.2: 1.3: 1.0. Prepared. While maintaining this solution at a temperature of 80 ° C., 3 equivalents of citric acid was added, and then neutralized with ammonium hydroxide. The solution was stirred for 2 hours to obtain a desired dispersion of semiconductor particles.

Example 4
The same procedure as in Example 1 was performed except that the thickness of the first wavelength conversion layer was 1 μm and the thickness of the second wavelength conversion layer was 50 μm.

(Example 5)
Example 1 was repeated except that the thickness of the first wavelength conversion layer was 50 μm and the thickness of the second wavelength conversion layer was 2.5 μm.

(Example 6)
The same operation as in Example 1 was performed except that the following materials were used as the first wavelength conversion substance.
Disperse 0.1M zinc acetate dihydrate (Zn (CH ₃ COO) ₂ · 2H ₂ O) and erbium acetate x hydrate (Er (CH ₃ COO) ₃ · xH ₂ O) in 100 ml of ethanol. It was. The amount of zinc acetate dihydrate and erbium acetate x hydrate was adjusted so that the weight ratio was Zn ²⁺ : Er ³⁺ = 98: 2. The ethanol solution was concentrated with heating and stirring at about 80 ° C. for about 3 hours until the total amount of the solution reached 120 ml. After concentration, 120 ml of ethanol was further added and cooled to room temperature. Next, the obtained ethanol solution was added so that the concentration of lithium hydroxide monohydrate (LiOH.H ₂ O) was 0.14 M, and sonicated at a temperature of 23 ° C. or lower for 20 minutes. Thus, 400 ml of an ethanol dispersion of semiconductor particles was obtained.

(Comparative Example 1)
Example 1 was performed except that the second wavelength conversion layer was not provided.

(Comparative Example 2)
Example 1 was performed except that the first wavelength conversion layer was not provided.

(Comparative Example 3)
The same procedure as in Example 1 was performed except that the order of lamination of the first wavelength conversion layer and the second wavelength conversion layer was reversed.

  The following evaluation was performed about the electromotive force apparatus obtained by each Example and the comparative example. The evaluation items are shown together with the contents. The obtained results are shown in Table 1.

1) Particle size evaluation About the obtained composite particle, the particle size of the composite particle was observed with the field emission type transmission electron microscope (FE-TEM, the Hitachi make, HF-2200). As the observation method, 100 images observed at an appropriate magnification of about 1 million times were observed, and the average particle size of the particles in the image was calculated.

2) Evaluation of luminous characteristics The following wavelength characteristics were evaluated for the obtained wavelength conversion member.
-An approximate excitation peak wavelength was observed under irradiation with excitation absorption wavelengths of 500 nm and 550 nm with a fluorescence spectrophotometer (F-2500, manufactured by Hitachi, Ltd.).
-An approximate emission peak wavelength was observed under irradiation with excitation absorption wavelengths of 370 nm and 980 nm using a fluorescence spectrophotometer (F-2500, manufactured by Hitachi, Ltd.).

3) Evaluation of transparency The following transparency was evaluated about the ETFE film in which the wavelength conversion member was formed.
Total light transmittance and haze were measured using a haze meter (Nippon Denshoku Industries Co., Ltd., NDH2000). The total light transmittance of the ETFE film alone was 94.2%, and the haze was 2.4.

4) Evaluation of power generation efficiency and weather resistance The measurement of the short-circuit current density Jsc (mA / cm ² ) and photoelectric conversion efficiency of the photovoltaic device will be described. Irradiation of 1 kW / m ² of light using a simulated solar irradiation device (manufactured by Spectrometer Co., Ltd., OTENTO-SUNV type solar simulator), and the current and voltage generated at that time are measured by an IV tester (Keutley Instruments Co., Ltd.). ), 2400 type source meter), and measured according to JIS C 8913.
Separately, a photovoltaic device produced in the same manner as described above was prepared as a comparative photovoltaic device, except that the wavelength conversion layer was not formed. The value obtained by subtracting the short-circuit current density Jsc measured for the comparative photovoltaic device from the short-circuit current density Jsc measured for the photovoltaic device obtained in Example 1 was defined as the short-circuit current density difference ΔJsc. .
In addition, after installing the obtained photovoltaic device outdoors for one month, the same evaluation as described above was performed, and when Jsc and photoelectric conversion efficiency were hardly decreased, the weather resistance was ○, and a remarkable decrease was observed. When it was seen, the weather resistance was set to x.

As is clear from Table 1, Examples 1 to 6 have excitation peaks in both the wavelength regions of 370 nm and 980 nm, and from this, the excitation light emission wavelength band extends not only in the ultraviolet region but also in the infrared region. It was suggested that
Examples 1 and 6 were also excellent in power generation efficiency.

DESCRIPTION OF SYMBOLS 1 1st wavelength conversion layer 2 2nd wavelength conversion layer 3 Photovoltaic layer 5 Photovoltaic device 10 Incident light of sunlight 100 Wavelength conversion member

Claims (20)

  A first wavelength conversion layer composed of a first composition containing a first wavelength conversion material and a first binder that converts ultraviolet light and violet light into longer-wavelength light with respect to the direction in which the light is incident; And a second wavelength conversion layer composed of a second wavelength conversion material that converts infrared light into light having a shorter wavelength and a second composition containing a second binder, and laminated in this order adjacent to each other. A wavelength conversion member characterized by the above.   2. The wavelength conversion member according to claim 1, wherein the first wavelength conversion layer absorbs light of more than 200 nm and not more than 430 nm and emits light of more than 430 nm.   3. The wavelength conversion member according to claim 1, wherein the second wavelength conversion layer absorbs light having a wavelength exceeding 850 nm and not more than 2500 nm and emitting light having a wavelength exceeding 430 nm and not more than 850 nm.   The wavelength conversion member according to any one of claims 1 to 3, wherein the content of the first wavelength conversion substance is 10 to 70% by volume of the entire first composition.   The wavelength conversion member according to any one of claims 1 to 4, wherein the content of the second wavelength conversion substance is 10 to 70% by volume of the entire second composition.   The first wavelength conversion material is at least one selected from zinc oxide (ZnO), silicon (Si), gallium nitride (GaN), and indium phosphide (InP). The wavelength conversion member as described.   The wavelength conversion member according to any one of claims 1 to 6, wherein an average particle diameter of primary particles of the first wavelength conversion substance is 1 to 100 nm.   The wavelength conversion member according to any one of claims 1 to 7, wherein the second wavelength conversion substance is a semiconductor particle containing a rare earth element or an alkali metal element.   The rare earth element or alkali metal element is composed of europium (Eu), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm) and ytterbium (Yb), lithium (Li), and sodium (Na). The wavelength conversion member according to claim 8, wherein the wavelength conversion member is one or more elements selected from the group. The semiconductor particles of the second wavelength conversion material include zinc oxide (ZnO), silicon (Si), gallium nitride (GaN), yttrium oxide (Y ₂ O ₃ ), yttrium vanadate (VYO ₄ ), and indium phosphide (InP). The wavelength conversion member according to claim 8 or 9, wherein the wavelength conversion member is one or more selected from the group consisting of   11. The wavelength conversion member according to claim 8, wherein a content of the rare earth element in the second wavelength conversion material is 0.01 to 30 wt% of the entire second wavelength conversion material.   The wavelength conversion member according to any one of claims 8 to 11, wherein the content of the alkali metal element in the second wavelength conversion material is 1 to 20% by weight of the rare earth element of the second wavelength conversion material.   The wavelength conversion member according to any one of claims 1 to 12, wherein an average particle diameter of primary particles of the second wavelength conversion substance is 1 to 100 nm.   14. The ratio (t 1 / t 2) between the thickness (t 1) of the first wavelength conversion layer and the thickness (t 2) of the second wavelength conversion layer is 0.01 to 30 14. The wavelength conversion member according to any one of the above.   A photovoltaic device comprising the wavelength conversion member according to claim 1.   The photovoltaic device according to claim 15, wherein the wavelength conversion member has a concavo-convex structure in a plane thereof.   The photovoltaic device according to claim 16, wherein the uneven structure has a height difference of 300 nm to 100 μm.   The photovoltaic device according to claim 16 or 17, wherein an in-plane period of the concavo-convex structure is 300 nm to 50 µm.   The photovoltaic device according to claim 16, wherein the uneven structure has a fine uneven shape smaller than the uneven structure.   The photovoltaic device according to any one of claims 16 to 19, wherein a shape of the uneven structure is different between the first wavelength conversion layer and the second wavelength conversion layer.