JP2010278180A - Substrate for solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate for a solar cell for inducing optical confinement effect by a transparent composite sheet with the selective wavelength reflection rate improved therein and obtaining high conversion efficiency in the solar cell. <P>SOLUTION: The substrate for the solar cell is constituted of the transparent composite sheet containing a transparent resin and spherical nanoparticles, where the spherical nanoparticles constitute a filling array structure. It is favorable that a whole light beam transmittance is ≥80% under light irradiation and also light by structure coloring is reflected in the transparent composite sheet, and the average particle size of primary particles in the spherical nanoparticles is 15-500 nm. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a solar cell substrate using a transparent composite sheet with enhanced reflectance in a selective wavelength region.

Conventionally, in order to increase the conversion efficiency of a thin-film silicon solar cell, a concavo-convex structure called a texture is given by forming a SnO ₂ film, which is a transparent conductive film, by a CVD method. Since the light path length is increased by the uneven shape of the transparent conductive film, a light confinement effect is obtained and the conversion efficiency is increased. However, this method increased the short-circuit current density (Jsc), but it was also observed that the open circuit voltage (Voc) and fill factor (FF) decreased due to the structural defects caused by the uneven structure.

  With regard to the light confinement effect in solar cells, it has been proposed to provide a concavo-convex structure such as a moth-eye structure or a honeycomb structure with the aim of forming a smooth structure. In addition, a technique for forming irregularities by causing fine particles to be present on the substrate surface has also been proposed (see, for example, Patent Document 1). However, as a light confinement effect technique, a transparent composite sheet that exhibits a light confinement effect by increasing the reflectance of light of a specific wavelength by an array structure with high filling of spherical particles has not been obtained.

JP 2001-26085 A.

  An object of the present invention is to increase the conversion efficiency of a solar cell by inducing a light confinement effect by a transparent composite sheet having an enhanced reflectance at a selective wavelength.

The present invention is as follows.
(1) A solar cell substrate comprising a transparent composite sheet containing a transparent resin and spherical nanoparticles, wherein the spherical nanoparticles form a packed array structure.
(2) The solar cell substrate according to (1), wherein the transparent composite sheet has a total light transmittance of 80% or more under light irradiation and reflects light due to structural color development.
(3) The solar cell substrate according to (1) or (2), wherein the primary particles of the spherical nanoparticles have an average particle diameter of 15 to 500 nm.
(4) The solar cell substrate according to any one of (1) to (3), wherein the content of the spherical nanoparticles is 0.1 to 70% by volume.

  By using the transparent composite sheet according to the present invention, the conversion efficiency of the solar cell can be increased.

Data of small-angle X-ray scattering measurement of the transparent composite sheet of Example 1 (A) Total light reflectance data of the transparent composite sheet of Example 1 and (b) Total light reflectance data of the transparent composite sheet of Example 2 (horizontal axis: wavelength (nm), vertical axis: total light Reflectance (%) Data on wavelength dependence of quantum yield of photoelectric conversion element (solid line) using the transparent composite sheet of Experimental Example 2 and photoelectric conversion element (dotted line) using the transparent composite sheet of Comparative Example 1 (horizontal axis: wavelength (nm) ), Vertical axis: quantum yield)

The present invention is a substrate for a solar cell, which is a transparent composite sheet containing a transparent resin and spherical nanoparticles, and is composed of a transparent composite sheet in which spherical nanoparticles form a packed array structure.
The transparent resin used in the present invention is not particularly limited, but a resin obtained by curing and crosslinking a resin composition containing a compound having two or more functional groups with heat, light or the like is preferable. Examples of the compound having two or more functional groups include (meth) acrylates, epoxy compounds, glycidyl type epoxy resins, oxetane compounds, compounds having an oxetanyl group, vinyl ether compounds, and the like.

  Examples of glycidyl type 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 isocyanurate skeletons. Epoxy resin having a cardo skeleton, epoxy resin having a polysiloxane structure, and examples of the alicyclic epoxy resin include 3,4-epoxycyclohexylmethyl 3 ′, 4′-epoxycyclohexanecarboxylate, 2,8,9-diepoxy limonene and ε-caprolactone oligomer having 3,4-epoxycyclohexylmethanol and 3,4-epoxycyclohexanecarboxylic acid ester-bonded to both ends, Attachment biphenyl skeleton, and cycloaliphatic epoxy resins having hydrogenated bisphenol A skeleton. Etc.) are preferably used.

  However, in terms of heat resistance and linear expansion coefficient, (meth) acrylate having an alicyclic structure and having two or more functional groups is preferable, and having two or more functional groups including an alicyclic structure ( Although it will not restrict | limit especially if it is a meth) acrylate, At least 1 or more types of (meth) acrylate selected from following Chemical formula (1) and Chemical formula (2) from the point of heat resistance or transparency is preferable.

（式（１）中、Ｒ¹及びＲ²は、互いに異なっていても良く、水素原子又はメチル
基を示す。ａは１又は２を示し、ｂは０又は１を示す。）

(In formula (1), R ¹ and R ² may be different from each other and represent a hydrogen atom or a methyl group. A represents 1 or 2, and b represents 0 or 1.)

Among the (meth) acrylates represented by the formula (1) and the formula (2), at least one acrylate selected from the formula (1) and the formula (2) is preferable from the viewpoint of reactivity and thermal stability. More preferably, dicyclopentadienyl diacrylate having a structure in which R ¹ and R ² are hydrogen, a is 1 and b is 0 in the general formula (1), and in the general formula (2), X is — _{CH 2 OCOCH = CH 2, R} 3, with R ⁴ is hydrogen, p has a structure which is 1 perhydro-1,4; 5,8-dimethanol naphthalene -2,3,7- (oxymethyl) triacrylate , X, R ³ and R ⁴ are all at least one acrylate selected from acrylates having a structure in which p is 0 or 1, and most preferably, in view of viscosity and the like, X , R ³ and R ⁴ are all hydrogen and p Is norbornane dimethylol diacrylate having a structure in which is 0. The (meth) acrylate represented by the formula (2) can be obtained by a known method disclosed in JP-A-5-70523.

  In the compound having a functional group used in the present invention, a monofunctional compound can be contained for the purpose of imparting flexibility and the like within a range that does not extremely impair the required characteristics.

  The spherical nano-particles used in the present invention are not particularly limited, and examples thereof include silicon-containing inorganic compound particles and semiconductor particles. As fine particles containing silicon, dried powdery silica fine particles and colloidal silica (silica sol) dispersed in an organic solvent can be used. From the viewpoint of dispersibility, it is preferable to use colloidal silica (silica sol) dispersed in an organic solvent.

  In the case of using colloidal silica (silica sol) dispersed in an organic solvent, it is preferable to use an organic solvent in which an organic component used in the resin composition is dissolved. For example, alcohols, ketones, esters, Examples include glycol ethers. Colloidal silica, silica sol, silica fine particles dispersed in alcoholic solvents such as methanol, ethanol, isopropyl alcohol, butyl alcohol and n-propyl alcohol, and ketone organic solvents such as methyl ethyl ketone and methyl isobutyl ketone for ease of solvent removal Is preferable, and colloidal silica dispersed in isopropyl alcohol is more preferable. In particular, when colloidal silica dispersed in isopropyl alcohol is used, it is suitable for stably producing a composite composition having a low viscosity after solvent removal compared to other solvent systems and a low viscosity.

  Colloidal silica (silica sol) and silica fine particles dispersed in these organic solvents are surface-treated with coupling agents such as silane coupling agents and titanate coupling agents as long as the required properties are not significantly impaired. In order to disperse in an organic solvent, a dispersant such as a surfactant may be used.

The semiconductor fine particle is not particularly limited as long as it has a property of emitting light having a wavelength inversely proportional to the difference between the two energy orders by absorbing energy such as light and electron beam, but contains a chalcogenide. The fine particles to be used are preferably used.
As a chalcogenide, a compound containing chalcogen (a general term for five elements of the VI group of the periodic table, oxygen (O), sulfur (S), selenium (Se), tellurium (Te), polonium (Po)) In particular, II-VI group compounds which are compounds of Group II and Group VI elements of the periodic table are preferred. More preferably, it is at least one selected from ZnS, CdS, ZnSe, CdSe, ZnTe, CdTe, and ZnO.

  In order to increase the issuance efficiency, the semiconductor fine particles are preferably formed into fine particles obtained by uniformly dispersing semiconductor ultrafine particles having a particle diameter smaller than twice the Bohr radius without aggregation in the matrix. Various inorganic substances and organic substances can be used for the matrix. Examples of inorganic substances include silicon compounds. Examples of the organic material include polyimide and a resin having an alicyclic structure from the viewpoint of heat resistance. A coupling agent containing silicon or titanium in the matrix can also be used.

  The content of the spherical nanoparticle in the transparent composite sheet is preferably 0.1 to 70 vol%, more preferably 15 to 60 vol%, more preferably 20 to 60 vol%, and most preferably 20 to 35 vol%. Within this range, since the fluidity and dispersibility of the composite composition before the production of the transparent composite sheet is good, it is easy to produce, and a sheet that exhibits structural color development while maintaining transparency is produced. Can do.

  The average particle size of the primary particles of the spherical nanoparticle is preferably 15 to 500 nm, more preferably 50 to 150 nm, and most preferably 80 to 120 nm in terms of the balance between transparency and fluidity. When the average particle size is less than the lower limit, the viscosity of the composite composition produced is extremely increased, so that the amount of silica fine particles is limited and the dispersibility deteriorates, and sufficient transparency cannot be obtained. was there. Moreover, since transparency may be remarkably deteriorated when the upper limit is exceeded, it is not preferable.

  In order not to lower the light transmittance in the visible light region having a wavelength of 400 to 800 nm, it is preferable to use fine particles in which fine particles having a primary particle size of 500 nm or more are present in a ratio of 5% or less, and the ratio is 0%. It is more preferable.

  In the transparent composite sheet in the present invention, in order to exhibit high reflectance while maintaining transparency, it is necessary that the array of fine particles in the transparent composite sheet is a packed array.

  In the transparent composite sheet in the present invention, transparency means the amount of light transmitted through the sheet, and the composite sheet having high transparency means that the amount of transmitted light is large. The transparency is determined by measuring the total light transmittance of the transparent composite sheet in a D65 standard light source, and determining that the transparency is 70% or more.

  In the transparent composite sheet of the present invention, the packed arrangement means an arrangement in which primary particles or higher order particles are regularly arranged, and means a state in which a non-uniform aggregated structure is not observed. The determination of whether or not it is a packed arrangement can be carried out quantitatively as follows. In the small-angle X-ray scattering profile obtained by the small-angle X-ray scattering measurement of the transparent composite sheet, there are at least one peak corresponding to the particle diameter, preferably up to the higher order peak, more preferably up to the 10th order peak at regular intervals. When the peak top is observed, it is determined that the primary particles of the fine particles have a packed arrangement structure. Usually, the small-angle X-ray scattering measurement used for these judgments should use high-intensity synchrotron radiation having an output of about 8 GEV as a radiation source.

  In the transparent composite sheet in the present invention, it is preferable to exhibit structural coloration reflection. Structural coloration reflection is a phenomenon in which light is reflected due to regularly arranged three-dimensional structures. The determination of whether or not reflection is present can be quantitatively performed as follows. The light transmittance in the wavelength region of the color reflected by structural color development in the light transmittance of the wavelength dispersion of the transparent composite sheet, for example, a decrease of 10% or more with respect to the highest total light transmittance in the light transmittance of 300 to 500 nm for blue When a uniform peak is observed in the same wavelength region in the total light reflectance measurement, it is determined that the reflection due to the structural color development is exhibited.

  The method for producing a transparent composite sheet of the present invention comprises curing and crosslinking a composite composition comprising a resin composition containing a compound having a functional group as a raw material of a transparent resin and spherical nano-particles by heat, light or the like. Obtained.

  The composite composition produced in the present invention may contain a polymerization inhibitor for the purpose of preventing the polymerization reaction from proceeding at the time of producing the composite composition and increasing the viscosity.

  In the composite composition, if necessary, a thermoplastic or thermosetting oligomer or polymer can be used in combination as long as the properties such as transparency, solvent resistance, and heat resistance are not impaired. If necessary, a small amount of a filler such as an antioxidant, an ultraviolet absorber, a dye, and other inorganic fillers, as long as the properties such as transparency, solvent resistance, liquid crystal resistance, and heat resistance are not impaired. Etc. may be included.

The method for producing the composite composition is not particularly limited, but an example in which silica (silica sol) is used as the spherical nanoparticle will be shown below.
(1) A method of removing an organic solvent by mixing colloidal silica (silica sol) dispersed in an organic solvent with a resin composition and other blends and, if necessary, reducing the pressure while stirring,
(2) A method in which colloidal silica (silica sol) dispersed in an organic solvent is mixed with a resin composition and other blends, and if necessary, after removing the solvent, casting and further removing the solvent,
(3) A method of mixing powdery silica fine particles with a resin composition and other blends, and then drying and dispersing using a mixing device having a high dispersion capacity,
Etc.

  Examples of the apparatus having a high dispersion ability include a film mix manufactured by Tokushu Kika Kogyo Co., Ltd. and various bead mills. When using a device with high dispersion capacity, care must be taken not to raise the temperature too much during mixing or kneading so that the reaction does not proceed rapidly.

  The temperature of the composite composition when producing the composite composition is preferably maintained at 30 to 100 ° C., more preferably 30 to 70 ° C., and most preferably 35 to 35 ° C. in balance with the solvent removal speed. 60 ° C. If the temperature is raised too much, the fluidity will be extremely lowered or gelled, making it impossible to form a sheet.

  When using colloidal silica dispersed in an organic solvent, the organic solvent may be left in the composite composition. When the organic solvent is contained, a post-treatment step such as heat treatment may be provided, and the organic solvent may be finally desorbed from the composite sheet. The content of the organic solvent in the composite composition is a composite in order to avoid problems such as foaming, waviness in the sheet, and coloring in the process of removing volatile components by a crosslinking process or heat treatment. 10% by weight or less of the body composition is preferable, more preferably 5% by weight or less, and most preferably 3% by weight or less.

The composite composition is cured and crosslinked with heat, light, etc. to obtain a transparent composite sheet.
As a method for forming a sheet, a method of casting a composite composition and drying it as necessary, a spacer so that a desired sheet thickness can be obtained between a glass plate, a plastic plate, a metal plate, etc. having surface smoothness. There is a method of sandwiching the composite composition. When the latter is used for curing with active energy rays or the like, at least one of them needs to use a transparent glass plate or plastic plate.

As a method of crosslinking the composite composition, there are a method of curing with active energy rays, a method of thermal polymerization by applying heat, and the like, and these can be used in combination. The active energy ray used is preferably ultraviolet rays. Examples of the lamp that generates ultraviolet rays include a metal halide type and a high-pressure mercury lamp.
For the purpose of completing the curing reaction and removing volatile matter, it is preferable to use a heat treatment step at a higher temperature in combination.

  When the composite composition is cured by active energy rays such as ultraviolet rays, it is preferable to contain a photopolymerization initiator that generates radicals, cations, and the like in the composite composition. As the photopolymerization initiator used in that case, for example, as a radical generator, benzophenone, benzoin methyl ether, benzoin propyl ether, diethoxyacetophenone, 1-hydroxy-cyclohexyl-phenyl ketone, 2,6-dimethylbenzoyl diphenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide is exemplified, and examples of the cation generator include aromatic sulfonium salts and aromatic iodonium salts. Two or more of these photopolymerization initiators may be used in combination.

  The content of the photopolymerization initiator in the composite composition may be an appropriate amount to be cured, and is 0.01 to 2 weights with respect to 100 parts by weight of the organic component containing the functional group in the composite composition. Part, preferably 0.02 to 1 part by weight, and most preferably 0.1 to 0.5 part by weight. When the amount of the photopolymerization initiator added is too large, the polymerization proceeds rapidly, and problems such as increased birefringence, coloring, and cracks during curing occur. On the other hand, if the amount is too small, the composition cannot be sufficiently cured, and problems such as being unable to adhere to the mold after crosslinking occur.

  In the case where heat is applied to the composite composition for thermal polymerization, a thermal polymerization initiator can be contained in the composite composition as necessary. Examples of the thermal polymerization initiator used in this case include benzoyl peroxide, diisopropyl peroxycarbonate, t-butylperoxy (2-ethylhexanoate) and the like as radical generators, and aromatic as a cation generator. Examples include sulfonium salts, aromatic iodonium salts, ammonium salts, aluminum chelates, and boron trifluoride amine complexes. The amount used is preferably 3 parts by weight or less with respect to 100 parts by weight of the organic component containing the functional group in the composite composition.

  When heat treatment is performed at a high temperature after curing by active energy rays and / or crosslinking by thermal polymerization, 200 ° C. to 300 ° C. in a nitrogen atmosphere or in a vacuum state for the purpose of reducing the linear expansion coefficient during the heat treatment step. It is preferable to include a heat treatment step at 1 ° C. for 1 to 24 hours.

  This invention is a solar cell substrate comprised from the said transparent composite sheet, It is preferable that the thickness of a transparent composite sheet is 4-2000 micrometers, More preferably, it is 5-400 micrometers. You may use the transparent composite sheet which consists of another structural requirement as a core layer, and the transparent composite sheet of this invention as a coating layer.

Hereinafter, the contents of the present invention will be described in detail by way of examples. However, the present invention is not limited to the following examples unless it exceeds the gist.

Example 1
(1) Composite composition Norbornane dimethylol diacrylate (TO-2111; manufactured by Toagosei Co., Ltd.) 5 having a structure in which X, R ³ and R ⁴ are all hydrogen and p is 0 in chemical formula (2). Part by weight, 1 part by weight of γ-acryloxypropylmethyldimethoxysilane, 20 parts by weight of isopropyl alcohol-dispersed colloidal silica (silica content 30% by weight, average particle size 100 nm, manufactured by Nissan Chemical Co., Ltd.) Volatiles were removed under reduced pressure. Then, 0.03 parts by weight of 1-hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184 manufactured by Ciba Specialty Chemicals) as a photopolymerization initiator was added and dissolved, and then the volatile components were removed under reduced pressure to obtain a composite. A composition was obtained. The solvent content in the composite composition was less than 10%.
The silica volume fraction was 33 vol% from the weight residue after heating at 400 ° C. for 1 hour after curing annealing of the composite composition.

(2) Sheeting The composite composition obtained in (1) is heated in an oven at a predetermined temperature (60 to 80 ° C.), poured into a 0.4 mm thick frame formed on a glass plate, and the upper part A glass plate was placed thereon and the composite composition was filled into the frame.
(3) Crosslinking The composite composition obtained in (2) sandwiched between glass plates was cured by irradiation with UV light of about 500 mJ / cm ² from both sides, and the sheet was peeled from the glass.
(4) Heat treatment The sheet obtained in (3) was heated at about 100 ° C. for 3 hours in a vacuum oven, and further heated at about 275 ° C. for 3 hours to obtain a transparent composite sheet having a thickness of 232 μm.

Example 2
T glass cloth (thickness 100 μm, refractive index 1.523, manufactured by Nittobo), hydrogenated biphenyl type alicyclic epoxy resin (Cel8000 manufactured by Daicel Chemical Industries), 100 parts by weight of aromatic sulfonium-based thermal cation catalyst (three SI-100L (manufactured by Shin Chemical Co., Ltd.) was impregnated with a resin composition (refractive index after curing of 1.520) in which 1 part by weight was melt-mixed and defoamed. This glass cloth was sandwiched between release-molded glass plates, heated in an oven at 80 ° C. for 2 hours, and further heated at 200 ° C. for 2 hours to obtain a transparent plastic sheet having a thickness of 0.1 mm. Next, the composite composition used in Example 1 is uniformly applied to one side of a transparent plastic sheet (core layer) using a coater, and is irradiated with an active energy ray of 500 mJ / cm ² and then heat-treated at a higher temperature. As a result, a transparent composite sheet composed of a core layer (thickness 100 μm) / coat layer (thickness 5 μm) was obtained.

<< Comparative Example 1 >>
T glass cloth (thickness 100 μm, refractive index 1.523, manufactured by Nittobo), hydrogenated biphenyl type alicyclic epoxy resin (Cel8000 manufactured by Daicel Chemical Industries), 100 parts by weight of aromatic sulfonium-based thermal cation catalyst (three SI-100L (manufactured by Shin Chemical Co., Ltd.) was impregnated with a resin composition (refractive index after curing of 1.520) in which 1 part by weight was melt-mixed and defoamed. This glass cloth was sandwiched between release-molded glass plates, heated in an oven at 80 ° C. for 2 hours, and further heated at 200 ° C. for 2 hours to obtain a transparent plastic sheet having a thickness of 0.1 mm. Next, 80 parts by weight of hydrogenated biphenyl type alicyclic epoxy, 17 parts by weight of silsesquioxane having an oxetanyl group, and 3 parts by weight of a photocationic initiator (SP-170 manufactured by Adeka) are mixed uniformly to be transparent. After coating with a wire bar on one side of the plastic sheet, irradiate 1100 mJ / cm ² of ultraviolet light with a high-pressure mercury lamp, apply the resin layer on the other side in the same way, and then heat at 250 ° C. for 2 hours. A cured resin layer (coat layer) having a thickness of 5 μm was laminated on both sides of the transparent plastic sheet (core layer). The obtained transparent composite sheet was composed of a coat layer (thickness 5 μm) / core layer (thickness 100 μm) / coat layer (thickness 5 μm), and the roughness of the sheet surface was 1.2 nm as measured by Rms.

《Experimental example》
First, a GZO film having a thickness of 500 nm was formed as a transparent conductive film on the surface of the transparent composite sheet obtained in Examples 1 and 2 and Comparative Example 1 by sputtering at a temperature of 300 ° C., a surface temperature of about 200 ° C. Next, an amorphous silicon film (photoelectric conversion layer) having a total thickness of 300 nm with a PIN junction of P = about 20 nm, I = about 250 nm, and N = about 30 nm was formed on the conductive film by plasma CVD. Thereafter, a GZO film having a thickness of 45 nm was formed at room temperature, and finally, an Ag electrode was formed by a sputtering method with a thickness of 200 nm to produce a photoelectric conversion element for a thin film solar cell. In the conversion efficiency of this photoelectric conversion element, Example 1 showed a value 10 to 30% higher than that of the photoelectric conversion element using Comparative Example 1. Moreover, the production yield of the photoelectric conversion element using the base material of Example 1 was about 20% higher than the production yield of the photoelectric conversion element using the base material according to Comparative Example 1.

  About the transparent composite sheet produced as mentioned above and the photoelectric conversion element shown in the experimental example, various characteristics were measured by the evaluation methods shown below.

(A) Haze and total light transmittance Measured using NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd.
(B) Wavelength-dependent total light transmittance and total light reflectance Measured with a spectrophotometer US3200 (manufactured by Hitachi, Ltd.).
(C) Thickness of the substrate The film center (retardation measurement point) was measured with a micrometer.
(D) Small angle X-ray scattering measurement
Measurements were made with a small-angle scatterometer equipped with an imaging plate detector adjusted to a wavelength of 1.5 mm and a camera length of 6 m using the SPring8 BL08B2 line.

(E) The photoelectric conversion element was irradiated with 100 mW / cm ² of AM1.5 standard simulated sunlight by a solar simulator. Then, short circuit current density Jsc, open circuit voltage Voc, fill factor FF, and conversion efficiency η were measured. The wavelength dependence of the quantum yield was also measured.

  Table 1 shows the evaluation results of the transparent composite sheets of Examples and Comparative Examples.

The data of the total light reflectance of the transparent composite sheet of Example 1 and Example 2 is shown in FIG. In the sheet of Example 1, the transmittance in the wavelength region of 250 to 400 nm is decreased, and the reflectance is increased in the same region.

Table 2 shows the evaluation results of the photoelectric conversion element of the experimental example.

FIG. 3 shows data on the wavelength dependence of the quantum yield of the photoelectric conversion element using the transparent composite sheet of Example 2 and the photoelectric conversion element using the transparent composite sheet of Comparative Example 1. The peak of 620 to 660 nm seen in the former shows the light confinement effect.

Claims (4)

A solar cell substrate comprising a transparent composite sheet comprising a transparent resin and spherical nanoparticles, wherein the spherical nanoparticles form a filled array structure. The solar cell substrate according to claim 1, wherein the transparent composite sheet has a total light transmittance of 80% or more under light irradiation and reflects light generated by structural coloring. The solar cell substrate according to claim 1 or 2, wherein the primary particles of the spherical nanoparticles have an average particle diameter of 15 to 500 nm. Content of the said spherical nanoparticle is 0.1-70 volume%, The board | substrate for solar cells as described in any one of Claims 1-3.

Images