JP2011116867A - Composite particle, resin composition, wavelength converting layer, and photovoltaic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide composite particles suppressing moisture absorption and discoloring property, stabilizing characteristics, and having excellent long-term dispersibility and durability, and to provide a resin composition having the composite particles, and a wavelength converting layer and a photovoltaic device having high performance and superior reliability. <P>SOLUTION: The composite particles comprise semiconductor particles of zinc oxide and particles of an inorganic compound, wherein a lithium content is ≤3 wt.%. As the composite particles have a function of changing the wavelength of emitted light with respect to the wavelength of absorbed light, the particles can be particularly used as a wavelength converting material. The composite particles 4 shown in Fig.2 contain semiconductor particles 6 and inorganic compound particles 8, wherein as one example of the distribution state of the particles 6, 8, the semiconductor particles 6 and the inorganic compound particles 8 are aggregated (adsorbed) to one another. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to composite particles, a resin composition, a wavelength conversion layer, 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.

  In the case of these photovoltaic devices, since the spectral sensitivity is limited to the substantially visible light region, it is possible to efficiently convert regions other than visible light, such as the ultraviolet region and the infrared region, into sunlight. Can not. In addition, the crystalline silicon solar cell has a problem in that the photoelectric conversion efficiency is lowered as the temperature rises due to ultraviolet light absorption. 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.

  Here, Patent Document 1 uses a quantum dot composed of semiconductor fine particles such as CdSe, CdTe, GaN, Si, InP, and ZnO, and particles (core-shell particles) obtained by making them into a core-shell type, as a wavelength conversion substance. Proposed. By using such quantum dots, light in a wavelength region that cannot be used for photoelectric conversion is converted into light in a wavelength region that can be photoelectrically converted, and an energy conversion film that can increase the photoelectric conversion efficiency of a solar cell is obtained. .

  However, the quantum dots described in Patent Document 1 have the following problems whether they are of the core-shell type or not.

1. The quantum dots easily absorb moisture, and the quantum dots are colored with ultraviolet irradiation.
2. Long-term stability is low, and light emission characteristics change over time.
Due to such problems, it has been difficult to use as a wavelength converting substance.

JP 2006-216560 A

  An object of the present invention is to provide composite particles that can suppress hygroscopicity and colorability and stabilize properties, and have excellent dispersibility and durability over a long period of time, and a resin composition having such composite particles. .

  It is another object of the present invention to provide a wavelength conversion layer and a photovoltaic device that have high performance and excellent reliability.

Such an object is achieved by the present inventions (1) to (22) below.
(1) A composite particle comprising zinc oxide semiconductor particles and inorganic compound particles,
A composite particle, wherein a lithium content in the composite particle is 3% by weight or less.

  (2) The composite particle according to (1), wherein a lithium content in the composite particle is 0.01% by weight or more.

  (3) The above composite particles (1) or (2), wherein the weight loss between 250 and 500 ° C. when the temperature is raised from room temperature to 10 ° C./min using thermogravimetric analysis is 20% or less. ).

  (4) The composite particle according to any one of (1) to (3), wherein the content of acetic acid in the composite particle is 20% by weight or less.

  (5) The composite particles according to any one of (1) to (4), wherein the semiconductor particles contain a rare earth element.

  (6) The composite particle according to (5), wherein the rare earth element is one or more elements selected from the group consisting of europium (Eu), ytterbium (Yb), erbium (Er), and thulium (Tm).

  (7) The composite particle according to (5) or (6), wherein the content of the rare earth element is 0.01 to 20% by weight of the entire composite particle.

  (8) The composite particle according to any one of (1) to (7), wherein an average particle size of primary particles of the semiconductor particles is 1 to 10 nm.

  (9) The composite particles according to any one of (1) to (8), wherein the content of the semiconductor particles is 10 to 80% by volume of the entire composite particles.

  (10) The composite particles according to any one of (1) to (9), wherein the inorganic compound particles are oxide particles.

(11) The composite particles according to (10), wherein the oxide particles are at least one of silica (SiO ₂ ) particles and zirconia (ZrO ₂ ) particles.

  (12) The composite particle according to any one of (1) to (11), wherein the composite particle is formed by aggregation of the semiconductor particles and the inorganic compound particles.

  (13) A resin composition comprising the composite particles according to any one of (1) to (12) above and a curable resin.

  (14) The resin composition according to (13), wherein the content of the composite particles is 30 to 70% by volume of the entire resin composition.

  (15) A wavelength conversion layer obtained by curing a layer composed of the resin composition according to (13) or (14).

  (16) A photovoltaic device comprising the wavelength conversion layer according to (15).

  (17) The photovoltaic device according to (16), wherein the wavelength conversion layer has an uneven structure in a plane thereof.

  (18) The photovoltaic device according to (17), wherein the uneven structure has a height difference of 300 nm to 100 μm.

  (19) The photovoltaic device according to (17) or (18), wherein the in-plane period of the concavo-convex structure is 300 nm to 50 μm.

  (20) The photovoltaic device according to any one of (17) to (19), wherein the uneven structure has a fine uneven shape smaller than the uneven structure.

(21) It has a laminate formed by laminating two or more wavelength conversion layers,
The photovoltaic device according to any one of (17) to (20), wherein the uneven structure has a different shape between the two wavelength conversion layers.

  (22) The light according to any one of (16) to (21), wherein the wavelength conversion layer is formed by supplying the resin composition by an inkjet method and curing the supplied resin composition. Electromotive device.

  According to the present invention, composite particles having excellent dispersibility and durability over a long period of time and a resin composition having such composite particles are obtained by suppressing hygroscopicity and colorability and stabilizing properties. It is done.

  Further, according to the present invention, by using the resin composition, a wavelength conversion layer and a photovoltaic device excellent in performance and reliability can be obtained.

It is sectional drawing which shows typically 1st Embodiment of the photovoltaic apparatus of this invention provided with the wavelength conversion layer of this invention containing the composite particle of this invention. It is sectional drawing which shows typically embodiment of the wavelength conversion layer of the composite particle of this invention and this composite particle containing this composite particle. It is sectional drawing which shows typically 2nd Embodiment of the photovoltaic apparatus of this invention. It is sectional drawing which shows typically 3rd Embodiment of the photovoltaic apparatus of this invention. It is sectional drawing and the top view which show typically 4th Embodiment of the photovoltaic apparatus of this invention. It is sectional drawing and the top view which show typically 4th Embodiment of the photovoltaic apparatus of this invention. It is sectional drawing and the top view which show typically 4th Embodiment of the photovoltaic apparatus of this invention. It is sectional drawing and the top view which show typically 4th Embodiment of the photovoltaic apparatus of this invention. It is sectional drawing and the top view which show typically 4th Embodiment of the photovoltaic apparatus of this invention. It is sectional drawing and the top view which show typically 4th Embodiment of the photovoltaic apparatus of this invention.

  Hereinafter, the composite particle, resin composition, wavelength conversion layer, and photovoltaic device of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

(Composite particles)
First, the composite particles of the present invention will be described.

  FIG. 1 is a cross-sectional view schematically showing a first embodiment of the photovoltaic device of the present invention including the wavelength conversion layer of the present invention including the composite particles of the present invention, and FIG. It is sectional drawing which shows typically embodiment of the wavelength conversion layer of this invention containing a composite particle.

  The composite particles of the present invention are particles containing zinc oxide semiconductor particles and inorganic compound particles, and have a feature that the lithium content is 3% by weight or less.

  Since such composite particles have a function of changing the emission wavelength with respect to the absorption light wavelength, they are particularly used as a wavelength conversion material. A photovoltaic device 1 (photovoltaic device of the present invention) 1 shown in FIG. 1 is applied to, for example, a solar cell, etc., and includes a photovoltaic layer 2 that generates an electromotive force with light irradiation, and a photovoltaic device. It has the wavelength conversion layer (wavelength conversion layer of the present invention) 3 provided on the light incident surface side of the layer 2 and containing the composite particles of the present invention. The wavelength conversion layer 3 can convert light (electromagnetic waves) in a wavelength region unsuitable for photoelectric conversion into light in a wavelength region capable of photoelectric conversion, and can improve the photoelectric conversion efficiency of the photovoltaic device 1.

  The wavelength conversion layer 3 shown in FIG. 2 is obtained by dispersing composite particles 4 (composite particles of the present invention) in a curable resin 5.

  The composite particles 4 shown in FIG. 2 include semiconductor particles 6 and inorganic compound particles 8, but the distribution form of these particles 6 and 8 is not particularly limited. An example of a preferable distribution form is (a) a form in which the semiconductor particles 6 are covered with inorganic compound particles 8 (see FIG. 2A). Since the semiconductor particles 6 have high activity, the durability of the curable resin 5 is reduced. However, since the inorganic compound particles 8 are disposed so as to cover the semiconductor particles 6, the activity of the semiconductor particles 6 is increased. As a result, the durability of the curable resin 5 can be further increased. As a result, the wavelength conversion layer 3 using the composite particles 4 of the present invention is highly durable.

  More specifically, this form is a form in which the semiconductor particles 6 and the inorganic compound particles 8 are aggregated (adsorbed) to each other, and are classified into several forms based on the aggregation pattern.

  As the form of the composite particles 4 classified based on the aggregation pattern of the particles 6 and 8, for example, (b-1) a form in which the semiconductor particles 6 and the inorganic compound particles 8 are randomly distributed (FIG. 2). (See (b-1)), (b-2) a form in which the semiconductor particles 6 are connected in a chain shape, and the gaps are filled with inorganic compound particles 8 (see FIG. 2 (b-2)), ( b-3) The form (refer FIG.2 (b-3)) etc. with which the particle | grains 8 of an inorganic compound are arrange | positioned so that the circumference | surroundings of the semiconductor particle 6 may be mentioned. In FIG. 2, the small circles indicate the semiconductor particles 6, and the large circles indicate the inorganic compound particles 8.

  Among these, the form of (b-2) and the form of (b-3) are preferable, and the form of (b-2) is more preferable. The composite particles 4 having these forms are connected (aggregated) with a plurality of semiconductor particles 6 so that excellent emission characteristics (especially, an excitation absorption band can be expanded). And a characteristic of shifting to the long wavelength side. And the said form is useful from a viewpoint that the said effect is acquired even if it does not increase the addition amount of the semiconductor particle 6 very much. Particularly in the case of (b-2), the semiconductor particles 6 linked in a chain form have excellent light emission characteristics equivalent to particularly large semiconductor particles with a particularly small addition amount, so that a great effect is obtained.

  In addition, in such a form, the cross section of the composite particle 4 is scanned with various electron microscopes such as a scanning electron microscope (SEM) and a transmission electron microscope (TEM, FE-TEM), an atomic force microscope (AFM), and scanning. It can be confirmed and evaluated by observing with a scanning tunneling microscope (STM), a three-dimensional atom probe device (3D-AP), an energy dispersive X-ray analyzer (EDX) or the like. Moreover, the cross section of the composite particle 4 can be produced by, for example, a focused ion beam processing observation apparatus (FIB) or the like.

  Further, when the semiconductor particles 6 are covered with the inorganic compound particles 8, it is not necessary that the semiconductor particles 6 are completely covered with the inorganic compound particles 8, and a portion that is not partially covered is provided. There may be.

  Furthermore, the inorganic compound particles 8 may be arranged so as to cover not only the single semiconductor particle 6 but also the aggregate of the plurality of semiconductor particles 6, and in this case, the inorganic compound particles 8. The number of is not particularly limited.

  As described above, since the semiconductor particles 6 and the inorganic compound particles 8 are composited, the composite particles 4 of the present invention control the activity of the semiconductor particles 6 and prevent aggregation of the semiconductor particles 6. Thus, the semiconductor particles 6 can be uniformly dispersed in the dispersion medium. For this reason, the absorption and emission characteristics are improved, and it can be used as a high-performance wavelength conversion material.

Hereinafter, semiconductor particles and inorganic compound particles will be sequentially described.
The semiconductor particles used in the present invention are composed of zinc oxide (ZnO) particles. Zinc oxide is useful from the viewpoint of production cost and ease of work for producing composite particles because it has little risk of resource depletion and low toxicity.

  As the semiconductor particles, those containing rare earth elements are preferably used. By adding a rare earth element to the semiconductor particles, the composite particles can control the absorption characteristics such as the absorption wavelength and the emission characteristics such as the emission wavelength. Thereby, for example, ultraviolet rays, infrared rays and the like that are not used for photoelectric conversion can be converted into light having a wavelength capable of photoelectric conversion, so that a wavelength conversion material capable of realizing a solar cell with higher photoelectric conversion efficiency can be obtained.

  As the rare earth elements contained in the semiconductor particles, 17 elements consisting of lanthanoid elements having atomic numbers 57 to 71 and scandium (Sc) and yttrium (Y) can be used alone or in combination of two or more. However, a combination of one or more of europium (Eu), erbium (Er), thulium (Tm) and ytterbium (Yb) is particularly preferable.

  Among these, by including europium (Eu) as a rare earth element in particular, the composite particles have a wavelength conversion function of absorbing ultraviolet light and emitting visible light.

  In particular, the composite particles include one of erbium (Er), thulium (Tm) and ytterbium (Yb) as rare earth elements, so that the composite particles absorb ultraviolet rays and emit infrared rays, or absorb infrared rays. In addition, it has a wavelength conversion function for emitting visible light.

  Note that the above-described zinc oxide can be doped with rare earth elements without using a large-scale apparatus such as a vacuum apparatus. For this reason, by using zinc oxide particles as the semiconductor particles, it is possible to uniformly and efficiently dope rare earth elements to a plurality of semiconductor particles, and as a result, obtain composite particles having excellent absorption and emission characteristics. Can do.

  The content of the rare earth element in the entire composite particle is preferably 0.01 to 20% by weight, and more preferably 0.02 to 10% by weight. By setting the content of the rare earth element within the above range, composite particles excellent in absorption and emission characteristics such as emission quantum yield can be obtained.

  Such semiconductor particles preferably have an average primary particle diameter of 1 to 10 nm, more preferably 1 to 5 nm. By setting the average particle size within the above range, the quantum size effect appears more remarkably in the semiconductor particles, and thus the absorption / emission characteristics of the semiconductor particles are particularly improved. As a result, a wavelength conversion material capable of realizing a photovoltaic device with higher photoelectric conversion efficiency is obtained. In addition, by setting the average particle diameter within the above range, the semiconductor particles are smaller than the wavelength of visible light, so the influence of the semiconductor particles on the transmitted light is reduced, and the transparency of the semiconductor particle dispersion is improved. To do.

  The average particle size of the primary particles of the semiconductor particles is evaluated in the state of a transparent dispersion formed by dispersing the semiconductor particles in a dispersion medium using, for example, a dynamic light scattering device (Zetasizer Nano ZS manufactured by Malvern). can do.

  Further, the content of the semiconductor particles in the whole composite particle is preferably 10 to 90% by volume, more preferably 30 to 80% by volume, and further preferably 50 to 80% by volume. By setting the content of the semiconductor particles within the above range, the absorption and emission characteristics of the semiconductor particles can be enhanced, and the durability of the semiconductor particles can be enhanced.

  In addition, when content of a semiconductor particle is less than the said lower limit, there exists a possibility that the wavelength conversion function by a semiconductor particle may fall in a composite particle. On the other hand, when the content of the semiconductor particles exceeds the upper limit, the semiconductor particles and the inorganic compound particles are not uniformly dispersed, and the action of the inorganic compound particles such as controlling the activity of the semiconductor particles is reduced. Therefore, the stability and durability of the composite particles may be reduced.

  Examples of the inorganic compound particles used in the present invention include particles having a composition different from that of the semiconductor particles. Examples thereof include particles of various metals, non-metal nitrides, oxides, phosphides, sulfides, and the like. However, oxide particles are particularly preferably used. By using oxide particles as the inorganic compound particles, the chemical stability of the composite particles, particularly in the atmosphere, can be improved, and durability over a long period of time can be improved.

Here, specific examples of the inorganic compound particles include at least one selected from the group consisting of ZnO, SiO ₂ , ZnS, GaN, CdS, GaP, CdS, ZrO ₂ , YVO ₄ , and Y ₂ O ₃ . Particles are preferably used, and at least one of silica (SiO ₂ ) particles and zirconia (ZrO ₂ ) particles is more preferably used. Since these oxides are particularly excellent in chemical stability, the activity of the semiconductor particles can be controlled and the durability of the resin composition can be reliably increased. As a result, absorption / emission characteristics such as emission quantum yield in the composite particles can be enhanced.

  The average particle size of the primary particles of such inorganic compound particles is not particularly limited, but is preferably about 1.5 to 10 times the average particle size of the primary particles of the semiconductor particles, and about 2 to 8 times. More preferably. By setting the average particle size of the inorganic compound particles within the above range, the packing properties of the semiconductor particles and the inorganic compound particles are improved, so that denser composite particles can be obtained.

  By the way, the composite particles of the present invention include semiconductor particles and inorganic compound particles as described above, and are particularly characterized in that the lithium content is 3% by weight or less.

  Composite particles containing semiconductor particles and inorganic compound particles have the advantage of being superior in dispersibility and durability in dispersion media compared to semiconductor particles alone, but on the other hand, the particle shape has been unusually different from before. It has many problems that it is easy to absorb, moisture absorption, low light resistance, and low long-term stability. For this reason, these subjects have been the cause of hindering the use of composite particles.

  The present inventor has intensively studied the cause of the above problem and found that lithium contained in the composite particles is one of the causes. And when lithium content in a composite particle was made into 3 weight% or less, it discovered that said subject could be solved and came to complete this invention.

  By making the lithium content 3% by weight or less, preferably 2% by weight or less, and more preferably 1% by weight or less, the above-mentioned problem in the composite particles can be solved. 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.

  In other words, lithium is distributed in the composite fine particles and hinders smooth adsorption (aggregation) between the semiconductor particles and the inorganic compound particles, so that the composite particles are not likely to have a spherical particle shape and are likely to have an irregular shape. Furthermore, when it becomes an irregular shape, the 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 resin composition are lowered.

  On the other hand, according to the present invention, the above-described problems can be reliably solved by controlling the lithium content within the above range. Further, by setting the lithium content within the above range, the emission quantum yield can be increased.

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

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

  On the other hand, if the lithium content is less than or equal to the above upper limit, 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.

  In the present invention, the content of acetic acid in the composite particles is preferably 20% by weight or less, the content of acetic acid in the composite particles is more preferably 10% by weight or less, and 9% by weight or less. More preferably, it is most preferably 8% by weight or less. By setting the content of acetic acid within the above range, heat resistance and weather resistance are improved.

  For acetic acid, a lower limit of preferably 0.01% by weight or more, more preferably 0.1% by weight or more may be set. By setting the acetic acid content to be equal to or higher than this lower limit, the above-mentioned problems can be solved more reliably and the emission quantum yield can be increased.

  Furthermore, in the present invention, the total content of other ionic impurities in the composite particles is preferably 0.5% by weight or less, and more preferably 0.3% by weight or less. Since these ionic impurities also affect the characteristics of the composite particles, the effect of the present invention becomes more remarkable by reducing the content thereof.

As the other ionic impurities, eg, F _{^{over, Cl -, NO 2 -,}} Br -, NO 3 -, PO 4 3-, SO 4 2-, (COO) 2 2-, HCOO -, Na ⁺ , NH ₄ ⁺ , K ⁺ , Mg ²⁺ , Ca ^{2+ and the} like.

  Such contents of lithium, acetic acid, and ionic impurities can be measured by, for example, ion chromatography analysis. In the case of ion chromatography analysis, the above-described lithium content and acetic acid content are measured as lithium ion content and acetate ion content, respectively.

  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 thermostatic chamber, 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, the acetic acid content, and the content of other ionic impurities can be measured.

  The composite particles of the present invention preferably satisfy the following conditions in thermogravimetric analysis.

  For example, the composite particles are subjected to thermogravimetric analysis for measuring the weight loss (reduction rate) between 250 and 500 ° C. when the temperature is raised from room temperature at 10 ° C./min.

  In the composite particles of the present invention, the weight loss measured by thermogravimetric analysis is preferably 20% or less, and more preferably 15% or less. Such a composite particle indicates that the content of a substance to be measured for weight loss in thermogravimetric analysis, in particular, the content of organic impurities, is very small, and can solve the above problems more reliably. It becomes. In addition, the emission quantum yield is higher.

  The average particle size of the composite particles of the present invention is not particularly limited, but is preferably 20 to 100 nm, more preferably 45 to 55 nm. When the average particle size is within the above range, the dispersibility in the dispersion medium is particularly improved, and the composite particles can be filled in the dispersion medium at a high density. Thereby, the light emission characteristics of the composite particle dispersion are improved, and a transparent dispersion (for example, a resin composition described later) in the visible light region is obtained.

  The average particle size of the composite particles can also be evaluated in the state of a transparent dispersion using, for example, a dynamic light scattering device (Malvern, Zetasizer Nano ZS).

  As described above, the composite particles as described above have high absorption / emission characteristics and are used as a high-performance wavelength conversion material. For this reason, it can use for optical materials with which various devices, such as EL illumination, optical communication, EL display body, LED illumination, a solar cell, bioimaging, are provided, for example. In particular, it can be used for a wavelength conversion material provided in LED lighting, solar cells and the like.

  Further, when used in the above-described applications, the emission quantum yield of the composite particles of the present invention is preferably 30% or more at the excitation wavelength in the visible light region or near ultraviolet region, and preferably 40% or more. It is more preferable that

  Next, a method for manufacturing semiconductor particles and a method for manufacturing composite particles as described above will be described.

[1] Production of Semiconductor Particles First, a method for producing semiconductor particles will be described. Examples of the method for producing semiconductor particles include various liquid phase methods such as a sol-gel method, a solvothermal method (including a hydrothermal synthesis method), and a synthesis method using zinc nitrate, a flame method, and a sputtering method. Examples include various gas phase methods.

Here, the sol-gel method will be described as an example.
First, zinc acetate or a hydrate thereof (for example, zinc acetate dihydrate) is prepared as a raw material and dissolved in a solvent. Examples of the solvent include ethanol and propanol.

  Next, an alkali metal hydroxide is added to the obtained solution, and the mixture is allowed to stand at a low temperature (eg, 10 ° C. or lower). Thereby, the dispersion liquid of a zinc oxide semiconductor particle is obtained. Examples of the alkali metal include lithium and sodium.

When producing semiconductor particles doped with rare earth elements, in addition to zinc acetate or hydrates thereof, acetates of rare earth elements or hydrates thereof (for example, erbium acetate tetrahydrate, europium acetate tetrahydrate) Etc.) may be added.
Semiconductor particles can be manufactured as described above.

  The obtained dispersion of semiconductor particles is preferably subjected to a washing treatment. As a result, various impurities such as lithium, acetic acid, ionic impurities, and organic impurities attached to the semiconductor particles can be removed.

  Examples of the cleaning treatment include a method of adding the semiconductor particle dispersion to the cleaning liquid. You may add a vibration, an ultrasonic wave, etc. to a washing | cleaning liquid as needed.

  Examples of the cleaning liquid include hexane, pentane, heptane, octane, cyclohexane, and acetone.

  Of these, hexane is particularly preferably used for the cleaning liquid. Since hexane has a relatively low polarity, the polarity of the dispersion liquid of semiconductor particles can be greatly changed. As a result, the effect of improving the separation performance between the semiconductor particles, the ionic impurities, and the organic impurities, that is, the efficiency of the cleaning process can be obtained.

  As a method for removing various impurities such as lithium, acetic acid, ionic impurities and organic impurities adhering to the semiconductor particles, in addition to the above-described cleaning treatment, (i) Examples include a method of performing the same cleaning treatment, and (ii) a method of passing a dispersion of semiconductor particles through an ion exchange resin (permeable membrane).

  Furthermore, composite particles having a low lithium content can be produced by using a method for producing semiconductor particles that does not use lithium (for example, a zinc oxide synthesis method).

Further, the addition amount of the cleaning liquid is preferably about 1 to 10 and more preferably about 2 to 5 in volume ratio, where the volume of the semiconductor particle dispersion is 1. When the addition amount of the cleaning liquid falls below the lower limit, the above-described cleaning effect is impaired. On the other hand, when the addition amount of the cleaning liquid exceeds the upper limit, no further improvement in the cleaning liquid effect can be expected.
In addition, the frequency | count of a washing process is not specifically limited, Multiple times may be sufficient.

[2] Manufacture of Composite Particles Next, a method for manufacturing composite particles will be described. The composite particles of the present invention may be produced by any method. For example, a dispersion of semiconductor particles and a dispersion of inorganic compound particles are mixed, and the mixture is finely divided by various atomization methods. A spray-drying method in which droplets are formed and dried is preferably used.

  For the various atomization methods, any method can be used as long as the mixed liquid is made into fine droplets, but an atomization method using an ultrasonic atomizer or a two-fluid nozzle is preferably used. A sonic atomizer is preferably used. The ultrasonic atomizer can produce droplets having a size of several microns without heating the mixed liquid. This makes it possible to atomize the liquid mixture without causing the semiconductor particles to deteriorate due to heat. Moreover, it is preferable that the droplets produced by various atomization methods are separated into smaller sized droplets by a classifier such as a cyclone. By using the classification device, uniform composite fine particles having a particle diameter of several tens of nanometers or less can be finally produced.

Any method may be used for drying the droplets as long as the solvent in the droplets can be dried. For example, a method of passing through a heated furnace or a method of irradiating with laser or microwave is used.
The details of the spray drying method are described in J. Appl. Phys. 89 (2001) 6431.

  When producing the composite particles, the atmosphere during the production is not particularly limited, but an inert atmosphere or a reducing atmosphere is preferable from the viewpoint of avoiding deterioration and deterioration of the composite particles.

Moreover, you may make it use the composite particle after manufacture for a grinding | pulverization process as needed. Examples of the pulverization method include a method using various pulverizers such as a ball mill and a bead mill, and various dispersers such as an ultrasonic dispersion apparatus.
Furthermore, classification processing may be performed as necessary.

(Resin composition)
The resin composition of the present invention has the composite particles of the present invention and a curable resin. Such a resin composition can easily supply (apply) the composite particles of the present invention to various devices without using an expensive vacuum apparatus or heat treatment at a high temperature by using various application methods. And can be fixed. Thereby, the wavelength conversion function mentioned above can be added with respect to various devices, and the function improvement of various devices can be aimed at.

  As the curable resin, a photocurable resin, a thermosetting resin, or the like can be used, and in particular, a resin having light permeability is preferably used. Examples of such curable resins include epoxy resins, acrylic resins, silicone resins, and ethylene vinyl acetate (EVA) resins. By using these, the light transmittance of the resin composition can be further enhanced.

  Among these, examples of the epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, naphthalene type epoxy resins or hydrogenated products thereof, epoxy resins having a dicyclopentadiene skeleton, and triglycidyl. Examples thereof include an epoxy resin having an 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 heat resistance is required, those having an alicyclic structure are 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.

［一般式（１）中、Ｒ^１およびＲ^２は、互いに異なっていてもよく、水素原子またはメチル基である。また、ａは１または２であり、ｂは０または１である。］

[In General Formula (1), R ¹ and R ² may be different from each other, and are a hydrogen atom or a methyl group. Further, a is 1 or 2, and b is 0 or 1. ]

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.
In addition, 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 (trademark) manufactured by Mitsui Chemicals Fabro Co., Ltd. is suitable. Can be used.

  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.

  Although content (volume fraction) of curable resin is not specifically limited, It is preferable that it is 20-65 volume% of the whole resin composition, and it is more preferable that it is especially 30-55 volume%. When the content is within the above range, the light emission characteristics and durability are particularly excellent.

  On the other hand, the content (volume fraction) of the composite particles is not particularly limited, but is preferably 30 to 70% by volume, more preferably 40 to 60% by volume, based on the entire resin composition. When the content is within the above range, particularly the moldability of the resin composition can be ensured, and since the filling property of the composite particles in the resin composition is ensured, the composite particles are regularly and uniformly. It becomes easy to arrange. As a result, when the resin composition is molded into a layer, the transparency of the layer is increased.

  In addition to the above-described curable resin and composite particles, the resin composition of the present invention improves the affinity between the catalyst for promoting crosslinking, a crosslinking agent, other wavelength converting substances, and composite particles and the resin. In addition, various additives such as a compound having an alkoxy group for improving the dispersibility of the composite particles, a coupling agent, and a surfactant may be contained.

  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.

  Further, when the composite particles containing zinc oxide semiconductor particles are dispersed in the curable resin, it is preferable to use a silane coupling agent containing silicon as a dispersant. 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.

(Wavelength conversion layer and photovoltaic device)
The wavelength conversion layer of the present invention is formed by molding and curing the resin composition of the present invention into a predetermined shape. Such a wavelength conversion layer can make light of a specific wavelength incident on various devices by changing the emission wavelength with respect to the absorption light wavelength.

  Moreover, the photovoltaic device of the present invention has the wavelength conversion layer of the present invention. For this reason, the photovoltaic device excellent in photoelectric conversion efficiency is obtained by selecting suitably the light emission wavelength in a wavelength conversion layer according to the photoelectric conversion characteristic in a photovoltaic device.

<First Embodiment>
First, a first embodiment of the wavelength conversion layer of the present invention and the photovoltaic device of the present invention will be described.

  As described above, the photovoltaic device 1 (photovoltaic device of the present invention) 1 shown in FIG. 1 includes a photovoltaic layer 2 that generates an electromotive force in response to light irradiation, and the light of the photovoltaic layer 2. It has the wavelength conversion layer (wavelength conversion layer of this invention) 3 provided in the entrance plane side, and comprised with the hardened | cured material of the resin composition of this invention.

  The photovoltaic layer 2 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 1 is not limited to this, and can be applied to various photovoltaic devices 1. In particular, when a commercially available photovoltaic layer 2 is prepared and the wavelength conversion layer 3 is attached thereto, glass, a transparent electrode, a non-reflective layer, a protective layer, etc. are further formed on the photovoltaic layer 2. preferable. In this case, the wavelength conversion layer 3 may be attached on or below glass, a transparent electrode, a non-reflective layer, a protective layer, or the like. The wavelength conversion layer 3 converts sunlight in the ultraviolet region into a visible light region or a near infrared region. Alternatively, infrared rays in the infrared region are converted into a visible light region or a near infrared region. The converted sunlight is incident on the photovoltaic layer 2. Therefore, compared with the case where the wavelength conversion layer 3 is not provided, the photoelectric conversion efficiency in the photovoltaic layer 2 is increased, and when an organic material is used for the photovoltaic layer 2, the deterioration thereof can be suppressed. it can. As a result, the lifetime of the photovoltaic layer 2 such as a photoelectric conversion layer in a solar cell is improved.

  In this embodiment, the wavelength conversion layer 3 includes a photocurable resin 5 and composite particles 4 dispersed in the photocurable resin 5 as shown in FIG. As described above, since the composite particles 4 can control the activity of the semiconductor particles and can be uniformly dispersed in the photocurable resin 5, the composite particles 4 are photocurable in the wavelength conversion layer 3. The resin 5 is uniformly dispersed. Therefore, the wavelength conversion layer 3 can make the wavelength-converted light uniformly incident on the entire photovoltaic layer 2.

  Such a wavelength conversion layer 3 is formed by, for example, applying the above-described resin composition to the surface of the photovoltaic layer 2 and curing it. For this reason, for example, the wavelength conversion layer 3 can be formed only by apply | coating a resin composition to the commercially available photovoltaic layer 2, and making it photocure.

  Examples of the coating method include a doctor blade method, a spin coating method, a dipping method, a table coating method, a spray method, an applicator method, a curtain coating method, a die coating method, an ink jet method, and a dispenser method.

  Note that the photovoltaic device 1 can be applied to various devices such as EL illumination, optical communication, EL display, LED illumination, solar cell, bioimaging, and the like.

Second Embodiment
Next, a second embodiment of the photovoltaic device of the present invention will be described.
FIG. 3 is a cross-sectional view schematically showing a second embodiment of the photovoltaic device 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.

  The present embodiment is the same as the first embodiment except that the photovoltaic device 1 has two wavelength conversion layers 3.

  The photovoltaic device 1 shown in FIG. 3 includes, as the wavelength conversion layer 3, a first wavelength conversion layer 31 that converts sunlight in the ultraviolet region into a visible light region or a near infrared region, and visible sunlight in the infrared region. And a second wavelength conversion layer 32 that converts the light region or the near infrared region. In the second embodiment, as shown in FIG. 3, a first wavelength conversion layer 31 and a second wavelength conversion layer 32 are provided in this order above the photovoltaic layer 2 from the light incident side.

  In general, the longer the wavelength of light, the easier it is to pass through the object. Therefore, the first wavelength conversion layer 31 that converts the relatively short wavelength ultraviolet region into the visible light region is used as the incident light of the photovoltaic layer 2. The amount of light incident on the wavelength conversion layers 31 and 32 by providing the second wavelength conversion layer 32 provided on the upstream side and converting the infrared region having a relatively long wavelength into the visible light region on the downstream side of the incident light. Can be secured more. In the first wavelength conversion layer 31, ultraviolet rays of sunlight are converted into a visible light region or a near infrared region, and in the second wavelength conversion layers 32, infrared rays of sunlight are converted into a visible light region or a near infrared region. By converting into the region, the amount of visible light (or near-infrared region) incident on the photovoltaic layer 2 increases. As a result, the photoelectric conversion efficiency in the photovoltaic layer 2 can be increased.

  In addition, the 2nd wavelength conversion layer 32 is not limited to the layer which converts the sunlight ray of an infrared region into a visible light region, Like the 1st wavelength conversion layer 31, it converts the sunlight ray of an ultraviolet region into a visible light region. It is a wavelength conversion layer, Comprising: The 1st wavelength conversion layer 31 may differ in a composition.

Further, the number of wavelength conversion layers 3 stacked is not limited to two but may be three or more.
In addition, the refractive index of the wavelength conversion layer 3 is such that the refractive index of the layer located upstream of the incident light is the smallest, and the refractive index increases as the layer closer to the photovoltaic layer 2 increases. The loss accompanying the reflection of light in can be suppressed, and the light transmittance of the wavelength conversion layer 3 can be increased. As a result, the amount of light incident on the photovoltaic layer 2 is increased, and the photovoltaic device 1 with high photoelectric conversion efficiency is obtained.

  In addition, the first wavelength conversion layer 31 and the second wavelength conversion layer 32 are formed by sequentially forming a film above the photovoltaic layer 2, but separately, the resin composition of the present invention is formed into a film. The film formed and cured may be formed by adhering to the photovoltaic layer 2 with an adhesive or the like.

  In the present embodiment as described above, the same operations and effects as those in the first embodiment can be obtained.

<Third Embodiment>
Next, a third embodiment of the photovoltaic device of the present invention will be described.
FIG. 4 is a cross-sectional view schematically showing a third embodiment of the photovoltaic device of the present invention.

  In the following, the third 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 in the first and second embodiments are denoted by the same reference numerals as those described above, and detailed description thereof is omitted.

  This embodiment is the same as the second embodiment except that the arrangement of the two wavelength conversion layers 3 is different.

  The photovoltaic device 1 shown in FIG. 4 has a first wavelength conversion layer 31 provided above the photovoltaic layer 2 and a second wavelength conversion layer 32 provided below the photovoltaic layer 2. is doing.

  As described above, the longer the wavelength of light, the easier it is to transmit light. Therefore, the infrared region having a relatively long wavelength has a transmission power enough to pass through the photovoltaic layer 2 as well. For this reason, even if the second wavelength conversion layer 32 for converting the infrared region into the visible light region is provided below the photovoltaic layer 2, the second wavelength conversion layer 32 has a sufficient amount of infrared region. Can receive sunlight.

  Further, the photovoltaic device 1 shown in FIG. 4 has a reflective layer 7 provided below the second wavelength conversion layer 32. The reflective layer 7 reflects light that has been sequentially transmitted through the first wavelength conversion layer 31, the photovoltaic layer 2, and the second wavelength conversion layer 32 upward. As a result, light that would not have contributed to photoelectric conversion without the reflective layer 7 can be incident on the photovoltaic layer 2 again. As a result, the amount of light incident on the photovoltaic layer 2 increases, and the photovoltaic device 1 with high photoelectric conversion efficiency is obtained.

  Furthermore, in this embodiment, since the second wavelength conversion layer 32 is provided below the photovoltaic layer 2 and the reflection layer 7 is further provided below the second wavelength conversion layer 32, the second wavelength conversion layer 32 is reflected by the reflection layer 7. The light before being transmitted and the light after being reflected by the reflective layer 7 are transmitted. For this reason, in this embodiment, the wavelength conversion opportunity in the 2nd wavelength conversion layer 32 becomes twice, and wavelength conversion efficiency becomes higher. From this viewpoint, the photoelectric conversion efficiency of the photovoltaic device 1 can be further improved.

  In addition, although the 1st wavelength conversion layer 31 and the 2nd wavelength conversion layer 32 are each formed by forming into a film on each surface of the photovoltaic layer 2, otherwise, the resin composition of this invention is made into a film form separately. It may also be formed by bonding a film formed and cured to the photovoltaic layer 2 with an adhesive or the like.

  Also in the present embodiment as described above, the same operations and effects as in the first embodiment can be obtained.

<Fourth embodiment>
Next, a fourth embodiment of the photovoltaic device of the present invention will be described.

  5 to 10 are a cross-sectional view and a plan view, respectively, schematically showing a fourth embodiment of the photovoltaic device of the present invention.

  In the following, the fourth 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 1 shown in FIG. 5A is provided above the photovoltaic layer 2 and has a plurality of cured products of the resin composition having a dot-like form. The cured products of the plurality of resin compositions are spaced from each other at substantially equal intervals, and are regularly arranged on the upper surface of the photovoltaic layer 2. In other words, the wavelength conversion layer 3 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 1. In the case of the wavelength conversion layer 3 shown in FIG. 5B, the wavelength conversion layer 3 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 layer in this specification.

  When the wavelength conversion layer 3 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 2 with refraction. As a result, when the wavelength conversion layer 3 does not have a concavo-convex structure, light incident on the photovoltaic layer 2 has been lost due to reflection, whereas the wavelength conversion layer 3 shown in FIG. In this case, a part of the light that should have been lost if there was no concavo-convex structure can be made incident on the photovoltaic layer 2. That is, the wavelength conversion layer 3 shown in FIG. 5 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 1 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 equal to or less than the absorption wavelength region of the wavelength conversion layer 3. Thereby, when light enters the wavelength conversion layer 3, Fresnel reflection hardly occurs. Then, regardless of the shape of the concavo-convex structure, the reflection of light by the wavelength conversion layer 3 is reduced, and the amount of light incident on the wavelength conversion layer 3 is further increased. As a result, the amount of light incident on the photovoltaic layer 2 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. 5 to 7 and FIG. 10 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. 5, the concave-convex structure provided in the wavelength conversion layer 3 is a resin composition having a flat plate shape covering the upper surface of the photovoltaic layer 2 as shown in FIG. 6. 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 layer 3, and can convert the wavelength. In other words, according to the wavelength conversion layer 3 shown in FIG. 6, the wavelength conversion can also be performed on the light that could not be converted by the wavelength conversion layer 3 shown in FIG. 5. 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. 7A, the concavo-convex structure is convex on the photovoltaic layer 2 side as shown in FIG. 7B, 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 2, it is preferable that the photovoltaic layer 2 side is convex. In this case, the concavo-convex structure may be embedded in the photovoltaic layer 2 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 1 is set by setting the adjacent uneven resin composition different for the purpose of, for example, widening the light absorption wavelength range. Can be improved easily.

  Furthermore, as shown in FIG. 7C, 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 layer 3 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 of FIG. 7A and the concavo-convex structure of FIG. 7B are combined, that is, both the light irradiation side and the photovoltaic layer 2 side are convex. Such a structure may be used (see FIG. 7D). In this case, it is preferable that the in-plane period of the concavo-convex structure in which the photovoltaic layer 2 side is convex is smaller than the in-plane period of the concavo-convex structure in which the side irradiated with light is convex. Thereby, the light quantity which injects into the photovoltaic layer 2 can be increased.

  Moreover, it is preferable that the in-plane position of the concavo-convex structure where the photovoltaic layer 2 side is convex and the in-plane position of the concavo-convex structure where the side irradiated with light is convex are shifted from each other. Thereby, the area of the wavelength conversion layer 3 in a plan view can be secured larger, and the amount of light incident on the wavelength conversion layer 3 can be increased.

  Moreover, the concavo-convex structure shown in FIG. 8 is an example of the concavo-convex structure having an L & S shape. Specifically, as shown in FIG. 8B, the concavo-convex structure shown in FIG. 8 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. 9 is also an example of the concavo-convex structure having an L & S shape, but the concavo-convex structure shown in FIG. 9 is an elongated shape extending along the Y direction as shown in FIG. 9B. 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. 9 has a lattice shape in plan view.

  Moreover, although the uneven structure shown in FIG. 10 is comprised with the cured | curing material of the resin composition which makes the shape of a dot distributed regularly, each cured | curing material has a 2 layer structure, and is a lower layer and an upper layer. The types of the resin composition constituted by are different.

The combination of the types of resin compositions is not particularly limited. For example, the resin composition constituting the upper layer is made the same as the resin composition constituting the first wavelength conversion layer 31 in the second embodiment, and the lower layer is formed. What is necessary is just to make the resin composition to comprise the same with the resin composition which comprises the 2nd wavelength conversion layer 32 in 2nd Embodiment. That is, in the upper layer (first wavelength conversion layer 31), ultraviolet rays in the ultraviolet region are converted into the visible light region or near infrared region, and in the lower layer (second wavelength conversion layer 32), sunlight in the infrared region is visible. It is converted into the light region or near infrared region. Thereby, the light quantity of visible light (or near infrared region) which injects into the photovoltaic layer 2 increases. As a result, the photoelectric conversion efficiency in the photovoltaic layer 2 can be increased.
Note that the concavo-convex structure shown in FIG. 10 may be composed of a laminate of three or more layers.

  The wavelength conversion layer 3 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 product. 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 layer 3 as shown in FIG. 5 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 1 can be suppressed.

  In the present embodiment as described above, the same operations and effects as those in the first embodiment can be obtained.

  The embodiments of the composite particles, the resin composition, the wavelength conversion layer, and the photovoltaic device of the present invention have been described above. However, the present invention is not limited to this embodiment. The structure of may be added.

Next, specific examples of the present invention will be described.
Example 1
1. Preparation of composite particles, resin composition and wavelength conversion layer <1> First, ethanol was added so that the concentration of zinc acetate dihydrate (Zn (CH ₃ COO) ₂ .2H ₂ O) was 0.1 M, 400 ml of an ethanol solution of zinc acetate dihydrate 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 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 an ethanol dispersion of semiconductor particles prepared in <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.

<4> 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; manufactured by Toagosei Co., Ltd.) 0.30 g, N-methyl-aza-2,2,4-trimethylsilacyclopentane (manufactured by Gelest, SIM6501.4) 0.24 g, and 60 g of the composite particle transparent dispersion prepared in <3> 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. Thereby, a resin composition was obtained.

<5> The resin composition obtained above was applied onto an ETFE (tetrafluoroethylene / ethylene copolymer) film having a surface treatment of 50 μm in thickness. The thickness after drying was about 20 μm. Then, the 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. under vacuum for 1 hour in a vacuum oven to remove the solvent. Thereby, the sheet-like hardened | cured material (wavelength conversion layer) of the resin composition was formed.

<6> Next, a solar cell sealing material EVA (VA content 28%, cross-linked type) sheet is laid on the CIGS solar cell, and the wavelength conversion layer of the resin composition obtained above is further formed thereon. The formed ETFE film was disposed so that the wavelength conversion layer faced downward (EVA sheet side). This was subjected to vacuum heat treatment to produce a photovoltaic device.

2. Evaluation of Semiconductor Particles, Composite Particles, Resin Composition and Photovoltaic Device <1> Particle Size Evaluation Silica particles in organosilica sol, ethanol dispersion of the obtained semiconductor particles and composite particles were evaluated as follows. .

  1) The Z average particle diameter of the primary particles of the semiconductor particles was measured by a dynamic light scattering apparatus (Zeta Sizer Nano ZS, manufactured by Malvern).

  2) The particle diameter of the semiconductor particles was observed with a field emission transmission electron microscope (FE-TEM, manufactured by Hitachi, Ltd., HF-2200). As an observation method, an image with an appropriate magnification was taken, 30 particles included in the image were randomly selected, the particle size was measured, and the average particle size was calculated. If necessary, the fine particles were embedded in a resin and the cross section was observed.

<2> Evaluation of light emission characteristics The following light emission characteristics were evaluated for the ethanol dispersion of the obtained composite particles and the wavelength conversion layer.

  1) An approximate emission peak wavelength was observed with a fluorescence spectrophotometer (F-2500, manufactured by Hitachi, Ltd.) under irradiation with an excitation absorption wavelength of 360 nm.

  2) Using an absolute PL quantum yield measuring apparatus (C9920-02G, manufactured by Hamamatsu Photonics Co., Ltd.), the fluorescence quantum yield when irradiated with near-ultraviolet light having wavelengths of 350 nm, 360 nm, and 370 nm was measured.

<3> Evaluation of Impurities etc. About the obtained composite particles, the ion content was measured using an ion chromatograph (Nihon Dionex Co., Ltd., ICS-2000 type ion chromatograph). As a measurement sample, 0.014 g of composite particles are precisely weighed in a polycarbonate container, 15 ml of ultrapure water is added, hydrothermal treatment is performed at 125 ° C. for 20 hours, and after cooling to room temperature, the inner solution is centrifuged and filtered. Solution. This solution and ion standard solution were introduced into an ion chromatograph, and each ion was quantified by a calibration curve method.

<4> Evaluation of thermogravimetric change The following thermogravimetric change was evaluated about the obtained paste-like residue, composite particle, and wavelength conversion layer.
The weight reduction amount was measured using a differential heat / thermogravimetric simultaneous measurement device (TG / DTA6200R, manufactured by SII Nano Technology Co., Ltd.). Specifically, the temperature is increased from room temperature to a temperature of 500 ° C. at a rate of temperature increase of 10 ° C./min, and the weight decreases between 35 to 250 ° C. (a) and 250 to 500 ° C. (b) and the weight of the residue (c). % Was measured. From the results and various specific gravity data, the approximate volume ratio of the semiconductor particles and silica particles in the composite particles and the approximate volume ratio of the composite particles and resin components in the wavelength conversion layer were calculated.

<5> Evaluation of transparency The following transparency evaluation was performed about the ETFE film in which the wavelength conversion layer 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.

<6> Light Resistance Evaluation Regarding the ETFE film on which the wavelength conversion layer is formed, a black panel temperature of 63 ° C., humidity of 50% RH, and irradiance of 100 mW / cm using an iSuper UV tester (SUV-W151, manufactured by Iwasaki Electric Co., Ltd.) ² (wavelength 300-400 nm), the light resistance test was done on condition of processing time 48 hours. Before and after the light resistance test, the case where the deterioration of the transparency and the light emission characteristics was less than 10% was evaluated as “Good”, and the case where the deterioration of at least one of the transparency and the light emission characteristics was more than 10% was evaluated as “X”.

<7> Evaluation of power generation efficiency The short-circuit current density Jsc (mA / cm ² ) and photoelectric conversion efficiency measurement 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.
The above evaluation results are shown in Table 1.

(Example 2)
1. Preparation of composite particles, resin composition and wavelength conversion layer In the preparation of semiconductor particles, ethanol was added so that the concentration of zinc acetate dihydrate (Zn (CH ₃ COO) ₂ · 2H ₂ O) was 0.1M. The composite particles were the same as in Example 1 except that 1600 ml of an ethanol solution of zinc acetate dihydrate was prepared, 4800 ml of hexane was added, and 17.6 g of a paste-like residue was obtained. A resin composition and a wavelength conversion layer were prepared.

2. Evaluation of Semiconductor Particles, Composite Particles, Resin Composition, and Photovoltaic Device Various evaluations were performed in the same manner as in Example 1.
The above evaluation results are shown in Table 1.

(Example 3)
1. Preparation of Composite Particle, Resin Composition and Wavelength Conversion Layer In the preparation of semiconductor particles, an ethanol solution of zinc acetate dihydrate thus prepared was further added to erbium acetate x hydrate (Er (CH ₃ COO) ₃ · xH ₂ Composite particles, a resin composition, and a wavelength conversion layer were prepared in the same manner as in Example 1 except that O) was added and the concentration of erbium acetate x hydrate was adjusted to 0.002M. At this time, the addition amount of zinc acetate dihydrate and the rare earth element compound was adjusted so that the weight ratio was zinc ion: erbium ion = 95: 5.

2. Evaluation of Semiconductor Particles, Composite Particles, Resin Composition, and Photovoltaic Device Various evaluations were performed in the same manner as in Example 1.
The above evaluation results are shown in Table 1.

Example 4
1. Preparation of composite particles, resin composition and wavelength conversion layer In the preparation of semiconductor particles, the same procedure as in Example 1 was conducted except that an ethanol solution was prepared so that the concentration of lithium hydroxide monohydrate was 0.28M. Thus, composite particles, a resin composition, and a wavelength conversion layer were produced.

2. Evaluation of Semiconductor Particles, Composite Particles, Resin Composition, and Photovoltaic Device Various evaluations were performed in the same manner as in Example 1.
The above evaluation results are shown in Table 1.

(Comparative Example 1)
1. Preparation of Composite Particle, Resin Composition, and Wavelength Conversion Layer Composite particles, a resin composition, and a wavelength conversion layer were obtained in the same manner as in Example 1 except that cleaning with hexane was omitted in the preparation of semiconductor particles.

2. Evaluation of Semiconductor Particles, Composite Particles, Resin Composition, and Photovoltaic Device Various evaluations were performed in the same manner as in Example 1.
The above evaluation results are shown in Table 1.

(Comparative Example 2)
1. Preparation of Composite Particle, Resin Composition and Wavelength Conversion Layer In the same manner as in Example 1 except that washing with hexane was omitted in the preparation of semiconductor particles and addition of organosilica sol was omitted in the preparation of composite particles. Particles, a resin composition, and a wavelength conversion layer were obtained.

2. Evaluation of Semiconductor Particles, Composite Particles, Resin Composition, and Photovoltaic Device Various evaluations were performed in the same manner as in Example 1.
The above evaluation results are shown in Table 1.

  As is clear from Table 1, it was recognized that the photoelectric conversion layers obtained in the respective examples were superior in light resistance and weather resistance as compared with the comparative examples.

DESCRIPTION OF SYMBOLS 1 Photovoltaic apparatus 2 Photovoltaic layer 3 Wavelength conversion layer 31 1st wavelength conversion layer 32 2nd wavelength conversion layer 4 Composite particle 5 Photocurable resin 6 Semiconductor particle 7 Reflective layer 8 Inorganic compound particle

Claims (22)

A composite particle comprising zinc oxide semiconductor particles and inorganic compound particles,
A composite particle, wherein a lithium content in the composite particle is 3% by weight or less.   The composite particle according to claim 1, wherein a lithium content in the composite particle is 0.01% by weight or more.   3. The composite particle according to claim 1, wherein the composite particle has a weight loss of 20% or less between 250 and 500 ° C. when the temperature is increased from room temperature to 10 ° C./min using thermogravimetric analysis. .   The composite particle according to any one of claims 1 to 3, wherein the content of acetic acid in the composite particle is 20% by weight or less.   The composite particle according to claim 1, wherein the semiconductor particles contain a rare earth element.   The composite particle according to claim 5, wherein the rare earth element is one or more elements selected from the group consisting of europium (Eu), ytterbium (Yb), erbium (Er), and thulium (Tm).   The composite particle according to claim 5 or 6, wherein a content of the rare earth element is 0.01 to 20% by weight of the entire composite particle.   The composite particle according to any one of claims 1 to 7, wherein an average particle diameter of primary particles of the semiconductor particles is 1 to 10 nm.   The composite particles according to any one of claims 1 to 8, wherein the content of the semiconductor particles is 10 to 80% by volume of the whole composite particles.   10. The composite particle according to claim 1, wherein the inorganic compound particle is an oxide particle. The composite particle according to claim 10, wherein the oxide particles are at least one of silica (SiO ₂ ) particles and zirconia (ZrO ₂ ) particles.   The composite particle according to any one of claims 1 to 11, wherein the composite particle is formed by aggregation of the semiconductor particles and the particles of the inorganic compound.   A resin composition comprising the composite particles according to claim 1 and a curable resin.   The resin composition according to claim 13, wherein the content of the composite particles is 30 to 70% by volume of the entire resin composition.   A wavelength conversion layer obtained by curing a layer composed of the resin composition according to claim 13 or 14.   A photovoltaic device comprising the wavelength conversion layer according to claim 15.   The photovoltaic device according to claim 16, wherein the wavelength conversion layer has a concavo-convex structure in a plane thereof.   The photovoltaic device according to claim 17, wherein the height difference of the concavo-convex structure is 300 nm to 100 μm.   The photovoltaic device according to claim 17 or 18, wherein an in-plane period of the concavo-convex structure is 300 nm to 50 µm.   The photovoltaic device according to claim 17, wherein the uneven structure has a fine uneven shape smaller than the uneven structure. It has a laminate formed by laminating two or more wavelength conversion layers,
21. The photovoltaic device according to any one of claims 17 to 20, wherein a shape of the concavo-convex structure is different between the two wavelength conversion layers.   The photovoltaic device according to any one of claims 16 to 21, wherein the wavelength conversion layer is formed by supplying the resin composition by an ink jet method and curing the supplied resin composition.

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