JP2009267324A - Wavelength conversion type light trapping film solar-battery module using the film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wavelength conversion type light trapping film of a solar-battery module for enhancing optical use efficiency and improving generation efficiency by reducing a sunlight loss caused by spectrum mismatch while improving generation efficiency, and to provide a solar-battery module using this light trapping film. <P>SOLUTION: When defined as a first layer, a second layer, ..., a m-th layer from an incidence side of light in order, and then a first refractive index n<SB>1</SB>, a second refractive index n<SB>2</SB>, ..., and a m-th refractive index n<SB>m</SB>, are the refractive index of each layer, a relation of n<SB>1</SB>≤n<SB>2</SB>≤...≤n<SB>m</SB>is established in the wavelength conversion type light trapping film which is used for at least one optical transparency layer of the solar-battery module containing a plurality of optical transparency layers. One face thereof is filled all over with a plurality of minute projected or recessed polygon pyramids or cones formed without a gap, and the refractive index is 1.6-2.4, while an organic phosphor is contained. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wavelength conversion type light trapping film for solar cells and a solar cell module using the same. More specifically, incident light is efficiently introduced into a solar cell and has a wavelength region that does not contribute to power generation. The present invention relates to a solar cell module that increases power generation efficiency by converting the wavelength of light into light in a wavelength region that can contribute to power generation.

  For example, Non-Patent Document 1 below discloses a conventional silicon crystal solar cell module. A conventional solar cell module will be described with reference to the schematic diagram (cross-sectional view) of FIG. A conventional solar cell module includes a solar cell 100, a protective glass 200, a sealing material (filler) 201, a tab wire 202, and a back film 203.

  A protective glass (also referred to as a cover glass) 200 is provided on the side on which the incident light 204 is incident. As the protective glass 200, tempered glass is used in consideration of impact resistance. The protective glass 200 has an uneven shape on one side 200b by embossing in order to improve adhesion to the sealing material 201 laminated immediately below. Moreover, the uneven | corrugated shape is formed in the inner side, ie, the lower surface of the protective glass 200 in FIG. 1, and the surface 200a of a solar cell module is smooth.

  The sealing material 201 is usually a resin mainly composed of ethylene vinyl acetate copolymer, and is also referred to as a filler, and serves to seal the solar battery cell 100. The solar battery cell 100 converts incident light 204 introduced through the protective glass 200 and the sealing material 201 into electric power. For the solar cell 100, for example, a polycrystalline silicon substrate or a single crystal silicon substrate is used. A back film 203 is formed on the side opposite to the incident side of the sealing material 201.

  Non-Patent Document 2 listed below uses a insect-eye structure to allow external light from any angle including an oblique angle to be efficiently taken into a solar cell with reduced reflection loss. A battery module is disclosed. As described in Non-Patent Document 3 below, the insect-eye structure can reduce reflection loss and reduce efficiency by forming transparent objects such as fine cones, triangular pyramids, and quadrangular pyramids. It is a technology that often incorporates external light.

  On the other hand, a layer that emits light in a wavelength region that can contribute to power generation by converting the wavelength of ultraviolet or infrared light that does not contribute to power generation in a sunlight spectrum using a fluorescent material (also referred to as a light emitting material). A number of methods have been proposed for providing a solar cell on the light-receiving surface side of a solar cell (for example, see Patent Documents 1 to 13).

  However, in the methods described in Patent Documents 1 to 13 below, the light emission from the wavelength conversion (light emission) layer including the fluorescent material cannot be controlled as the light traveling direction cannot be controlled, so that the expected effect cannot be obtained. . That is, since the wavelength-converted light travels in all directions, the light emitted from one part of the layer structure is not only introduced into the solar cell, but also in the incident direction and the layer direction perpendicular to the incident direction. The light travels and cannot contribute to power generation.

  Further, in the above-described conventional solar cell module (see FIG. 5), since the refractive index difference between the solar cell 100 and the sealing material 201 is large, light reflection occurs at the interface and light (incident light 204) is efficiently used. There is a problem that it cannot be done.

  In addition, for example, in a silicon crystal solar cell, light in the ultraviolet region or infrared region is not effectively used in sunlight, and about 56% of solar energy does not contribute to photoelectric conversion due to this spectrum mismatch. There are also challenges.

Yasuhiro Sasakawa, “Solar Power Generation”-Latest Technology and System, 2000, CMC Corporation Hiroshi Toyoda; “Non-reflective periodic structure”, Optics, Vol. 32, No. 8, p. 489 (2003) N. Kamata, D .; Terunuma, R.A. Ishii, H .; Satoh, S .; Aihara, Y .; Yaoita, S .; Tonsyo, J .; Organometallic Chem. , 685, 235, 2003.

JP 2000-328053 A JP 09-230396 A JP 2003-243682 A JP 2003-218379 A JP 11-345993 A JP 2006-024716 A Japanese Patent Publication No. 08-004147 JP 2001-094128 A JP 2001-352091 A Japanese Patent Laid-Open No. 10-261811 Japanese Patent No. 2660705 JP 2006-269373 A JP 63-006881 A

  The present invention has been made in order to solve the above-mentioned problems, and by using the light conversion efficiency, the wavelength conversion type light trapping film for solar cell modules capable of improving the power generation efficiency and the same are used. An object is to provide a solar cell module.

  In addition, the present invention provides a wavelength conversion type light trapping film for a solar cell module, which can reduce solar light loss due to spectrum mismatch, increase light utilization efficiency, and improve power generation efficiency, and a solar cell module using the same. The purpose is to do.

The above problems are solved by the present invention described below.
(1) In order from the light incident side, the first layer, the second layer,..., The m-th layer are used, and the refractive index of each layer is the first refractive index n ₁ and the second refractive index n _{2, respectively.} , when the refractive index n _m of the ... first m, as at least one layer light transmissive layer of the solar cell module including a plurality of light transmitting layer _{n 1 ≦ n 2 ≦ ··· ≦} n m holds A wavelength conversion type light trapping film used,
It is formed so that a large number of fine convex or concave polygonal pyramids or cones are spread on one surface without gaps, the refractive index is 1.6 to 2.4, and an organic fluorescent material is included. Wavelength conversion type light trapping film.

ただし、Ｔは透過率、Ｌは波長変換型ライトトラッピングフィルムの平均厚み（μｍ）である。 (2) The wavelength conversion according to (1), wherein the value of the normalized absorbance a represented by the following formula (1) is 0.1 or less when the wavelength of light incident from the light incident side is 400 to 1200 nm. Type light trapping film.

Here, T is the transmittance, and L is the average thickness (μm) of the wavelength conversion type light trapping film.

(3) The wavelength conversion type light trapping film according to (1) or (2), wherein the organic fluorescent material absorbs light having a wavelength of 400 to 550 nm and emits light having a wavelength of 550 to 1200 nm.

(4) The organic fluorescent substance has at least one of (I) coumarin or a derivative thereof, (II) rhodamine or a derivative thereof, (III) pyromethene or a derivative thereof and (IV) a dimethylaminophenyl group in the structure. The wavelength conversion type light trapping film according to any one of (1) to (3).

（ｎは１〜６の整数である。） (5) The wavelength conversion type light trapping film according to any one of (1) to (4), wherein the organic fluorescent substance is a compound having a partial structure represented by the following general formula (1).

(N is an integer of 1-6.)

(6) A solar battery module, wherein the wavelength conversion type light trapping film according to any one of (1) to (5) is provided on a light receiving surface side of a solar battery cell.

The wavelength conversion type light trapping film of the present invention includes, in order from the light incident side, first refraction in a plurality of light transmission layers that can be referred to as a first layer, a second layer,. rate _{n 1,} second refractive index _n 2, the refractive index _{n m} of the ... first m, thereby hold the relationship of _{n 1 ≦ n 2 ≦ ··· ≦} n m, further of these light-transmitting layer The at least one layer is a wavelength conversion type light trapping film in which the incident light incident side has an uneven shape, the refractive index is 1.6 to 2.4, and an organic fluorescent material is included, and the solar cell module The light utilization rate (power generation efficiency) can be improved.

Moreover, it is possible to reduce sunlight loss due to spectrum mismatch, increase light utilization efficiency, and improve power generation efficiency.
Furthermore, the wavelength conversion type light trapping film for solar cell modules of the present invention is efficient when, for example, an organic fluorescent material that absorbs light having a wavelength of 400 to 550 nm and emits light having a wavelength of 550 to 1200 nm is used. Wavelength conversion is performed and the spectral mismatch can be overcome.

  In other words, since the wavelength conversion type light wrapping film of the present invention contains an organic fluorescent material, it is possible to further enhance the effect by wavelength conversion, compared to a configuration in which the refractive index is controlled by a conventional light trapping film alone. It has become. Furthermore, the direction of light is controlled by the fine uneven shape, and both incident light and light emission are efficiently introduced into the solar battery cell.

In the wavelength conversion type light trapping film of the present invention, the light transmitting layer from the light incident side is the first layer, the second layer,..., The mth layer, and the refractive index of each layer is the first. refractive index _{n 1} of the second refractive index _n 2, and the refractive index _{n m} of the ... first m, sun including a plurality of light transmitting _{layer n 1 ≦ n 2 ≦ ··· ≦} n m holds A wavelength conversion type light trapping film formed so that a large number of fine convex or concave polygonal pyramids or cones are spread without gaps, which is used as at least one of the plurality of light transmissive layers of the battery module, The refractive index is 1.6 to 2.4, and an organic fluorescent material is included.
In particular, the wavelength conversion type light trapping film of the present invention has a fine concavo-convex shape and contains an organic fluorescent material, so that the refractive index is controlled solely by the light trapping film employed in Patent Document 1 and others. In this configuration, the effect can be further enhanced by wavelength conversion. Furthermore, the directivity of light can be controlled by the fine uneven shape, and both incident light and light emission can be efficiently introduced into the solar battery cell. That is, the wavelength conversion type light trapping film of the present invention, in short, efficiently converts the incident light into light having a wavelength that can be generated by the solar cell, and at the same time efficiently introduces the light into the solar cell. To do.

Further, the solar cell module of the present invention is characterized in that the wavelength conversion type light trapping film of the present invention is provided on the light receiving surface side of the solar cell.
Since the solar cell module of the present invention reduces sunlight loss due to spectrum mismatch and further controls the traveling direction of light, light utilization efficiency can be improved and power generation efficiency can be improved.

  Below, the wavelength conversion type light trapping film and solar cell module of this invention are demonstrated.

FIG. 1 shows a cross section of a solar cell module using solar cells made of a silicon substrate. In this solar cell module, a plurality of light transmissive layers of a protective glass 200, a sealing material 201, and a wavelength conversion type light trapping film 300 are arranged in order from the incident side of incident light 204, and transmitted through each light transmissive layer. It is a solar cell module that generates power by introducing incident light into the solar cell 100.
The light transmissive layer in this case indicates the configuration of the light transmissive member in the solar cell module and is a specific example. As another example, an antireflection film on glass can be provided before the protective glass 200 on the light incident side. However, most antireflection films on glass are not present in conventional solar cell modules, and are not essential in the present invention.

The wavelength conversion type light trapping film 300 is a wavelength conversion type light trapping film having a concave-convex shape on one surface on the side on which incident light is incident, and has a refractive index of 1.6 to 2.4, and is organic. Contains fluorescent material and is transparent. The one surface of the wavelength conversion type light trapping film 300 is formed so as to spread a large number of fine recesses or projections without any gaps, and the shape of each of the fine recesses or projections is a substantially conical shape. Or it is a polygonal pyramid shape.
In addition, in the solar cell module, in the ultraviolet region, in consideration of the fact that light does not reach the solar cell due to absorption of the protective glass with respect to a wavelength shorter than 400 nm, the organic phosphor contained in the wavelength conversion type light trapping film However, it is preferable that the wavelength can be converted so as to absorb light having a wavelength of 400 to 550 nm and emit light having a wavelength of 550 to 1200 nm.

The solar battery cell 100 includes, for example, a p-type silicon substrate, an n-type layer, an antireflection film, a surface electrode, a back electrode, and a p ⁺ layer. The wavelength conversion type light trapping film 300 is in contact with the antireflection film of the solar battery cell 100.

  The solar battery cell 100 is a silicon crystal solar battery cell using a polycrystalline silicon substrate or a single crystal silicon substrate. For example, a p-type silicon substrate having a thickness of several hundreds μm is used. An n-type layer is uniformly formed on the surface of the p-type silicon substrate.

  The antireflection film of the solar battery cell 100 prevents unnecessary reflection of incident light efficiently collected by the wavelength conversion type light trapping film 300, and is composed of, for example, silicon Si, nitrogen N, and hydrogen H. A silicon nitride film having a refractive index in the range of 1.8 to 2.7 is used. The range of film thickness is 70-90 nm. Further, a titanium oxide film may be used as the antireflection film.

  The wavelength conversion type light trapping film 300 is formed so that a large number of fine convex or concave polygonal pyramids or cones are regularly spread on one side 300a which is the one side as described above. The polygonal pyramids have substantially the same shape. The cone has substantially the same shape.

The one side 300 a is formed on the light incident side (incident light 204 is incident), and the opposite side 300 b on the light incident side is in contact with the antireflection film of the solar battery cell 100.
Moreover, as will be described later, the opposite side 300b on the light incident side may follow the unevenness on the surface of the solar battery cell 100 without any gap.

  The wavelength conversion type light trapping film 300 has a refractive index as follows. In order to efficiently introduce external light (incident light 204) entering from all angles into the solar cell 100 with less reflection loss, the refractive index of the wavelength conversion type light trapping film 300 is higher than the refractive index of the sealing material 201, And it must be lower than the antireflection film on the solar battery cell 100, and is 1.6 to 2.4, preferably 1.6 to 2.2, and more preferably 1.6 to 2.0.

A back surface aluminum paste is formed on the back surface side opposite to the incident side (front surface side) of the p-type silicon substrate, and a back electrode is further formed thereon.
On the back side, aluminum in the aluminum paste reacts with silicon on the back side to form a p + layer, thereby forming a BSF (Back Surface Field) layer that improves power generation capability.

In the wavelength conversion type light trapping film 300, in order to efficiently introduce incident light from all angles into the solar battery cell, the fine concave or convex surface of the convex surface of the wavelength conversion type light trapping film 300 is used. A narrow apex angle is advantageous.
However, when there is a reflection loss at the interface between the wavelength conversion type light trapping film 300 and the solar battery cell 100, the reflected light leaks to the outside again if the apex angle is too narrow.

  In order to reflect the reflected light again by the wavelength conversion type light trapping film 300 (retroreflection) and return it to the solar battery cell 100, the apex angle is preferably 75 to 115 degrees, and ideally the apex angle is 90 degrees. . If the apex angle is 90 degrees, it can be said that the angle is the best in terms of performance and processing accuracy.

According to Non-Patent Document 2, the size of the base is a value obtained by dividing the shortest wavelength to be used by the refractive index of the material. For example, when the refractive index is 2.0, It is about 175 nm. In order to obtain such an ultrafine structure, the processing method is also limited.
However, the present invention does not require such an ultrafine structure as will be described later.

  FIG. 2 is a view for explaining the structure of the wavelength conversion type light trapping film 300. In the wavelength conversion type light trapping film 300 used in the present invention, as shown in FIG. 2, the wavelength conversion type light trapping film 300 is divided into a pedestal portion 300b and an uneven portion 300a.

  Since the pedestal portion 300b needs to be embedded following the uneven shape of the solar battery cell 100, the thickness must be greater than or equal to the unevenness. Usually, the surface of the solar battery cell 100 is textured, and the depth thereof is 0 to 20 μm.

  On the other hand, the height of fine concaves or convexes formed so as to be regularly spread without gaps, which is an essential part of the wavelength conversion type light trapping film 300, is 1 to 100 μm mainly due to processing requirements.

  In addition, the wavelength conversion type light trapping film having a refractive index of 1.6 to 2.4 must follow the unevenness of the solar cell as described above, and the original fine uneven shape of the wavelength conversion type light trapping film must be transferred. Therefore, it is important to obtain a semi-cured resin composition.

  The wavelength conversion type light trapping film 300 having a high refractive index and satisfying the shape transfer property is an organic-inorganic hybrid composition containing titanium tetraalkoxide, and further needs to contain an organic fluorescent material for wavelength conversion. There is.

  The wavelength-converting light trapping film 300 is a semi-cured film that is vacuum-laminated on the solar battery cell 100 or varnished with a polymer, a monomer, an initiator, a solvent, etc., applied to the cell, and solvent-dried. The At this point, the unevenness of the solar battery cell can be completely embedded.

  Further, if the wavelength conversion type light trapping film 300 is originally in the form of a film, the separator film is peeled off, and the mold film having the fine uneven shape inherent to the wavelength conversion type light trapping film is further vacuum-laminated to transfer the shape.

  Alternatively, a wavelength conversion type light trapping film with a type film that is left on the wavelength conversion type light trapping film 300 without removing the type film 301 may be used.

FIG. 3 is a configuration diagram of a solar battery module in which a wavelength conversion type light trapping film 300 with a mold film 301 is attached on the solar battery cell 100. The wavelength conversion type light trapping film 300 side is laminated with the solar cell 100 side.
That is, one surface of the wavelength conversion type light trapping film 300 is allowed to follow the unevenness on the surface of the solar battery cell 100 without a gap and is bonded onto the solar battery cell 100. The mold film 301 used is left on the other side of the wavelength conversion type light trapping film 300 (the fine concave or convex part 300a side) without being removed. The wavelength conversion type light trapping film 300 in this state is a light trapping film with a mold film having a smooth appearance. As described above, the mold film 301 used here is bonded to the fine concave or convex side 300a of the wavelength conversion type light trapping film 300 so as to be complementary (completely meshed with no gap) to the fine concave or convex portion. In this film, a large number of fine protrusions or recesses are formed without gaps, and the refractive index is smaller than the refractive index n ₂ in the wavelength conversion type light trapping film 300.

Moreover, when using a varnish material as the wavelength conversion type light trapping film 300, after apply | coating it on a photovoltaic cell and drying a solvent, shape transfer is performed with a type | mold film. At this point, the mold film may be peeled off and cured, or may be cured while the mold film is attached.
The method for curing the resin composition may previously impart photocurability or thermosetting to the resin composition.

In the solar cell module shown in FIG. 1 using the solar cell 100, for example, the sealing material 201 is the first layer (the protective glass 200 and the sealing material 201 have substantially the same refractive index). The wavelength conversion type light trapping film 300 is the second layer, the antireflection film is the third layer, the n-type layer is the fourth layer, and the refractive index of each layer is the first refractive index. Assuming that the refractive index n ₁ , the second refractive index n ₂ , the third refractive index n ₃ , and the fourth refractive index n ₄ , n ₁ ≦ n ₂ ≦ n ₃ ≦ n ₄ is established.

  The wavelength-converting light trapping film 300 of the second layer, which is one of these light transmissive layers, has a concave-convex shape on the incident side 300a of the incident light 204 as described above. More specifically, the wavelength conversion type light trapping film 300 is formed so as to spread a large number of fine convex or concave polygonal pyramids or cones.

The wavelength conversion type light trapping film 300 has a refractive index n ₃ of 1.6 to 2.4 as described above.
Furthermore, in the wavelength conversion type light trapping film 300, the value of the normalized absorbance a represented by the following formula is preferably 0.1 or less, preferably 0.0045 or less, when the wavelength of the incident light is 400 to 1200 nm. More preferably, it is more preferably 0.001 or less. When the normalized absorbance a is 0.1 or less, the transmittance is about 80% when the thickness of the wavelength conversion type light trapping film of the present invention is 1 μm. However, when the thickness is 10 μm, the transmittance is 10%, and actual application is difficult. That is, as the normalized absorbance a is smaller, the thickness of the condensing film can be increased, and the processing accuracy of the mold film and the embedding in the cell unevenness can be afforded. The mold film unevenness has a height of 10 μm or more depending on the processing accuracy of all types, the cell unevenness has a depth of about 10 μm, the electrode has a height of about 50 μm, and the condensing film must be thick. The normalized absorbance a is preferably as small as possible, but in practice, the thickness is preferably 0.001 or less.

ただし、Ｔは透過率、Ｌは波長変換型ライトトラッピングフィルムの平均厚み（μｍ）である。

Here, T is the transmittance, and L is the average thickness (μm) of the wavelength conversion type light trapping film.

The production of the solar cell module shown in FIG. 1 will be described. As described above, the refractive index distribution of the _{layers, n 1 ≦ n 2 ≦ ···} ≦ n m as is true, that is continuous, the shallow say shallow layer (here denoted from the incident side The index of refraction gradually increases from the first, second,...

  However, the antireflection film as the third layer and the n-type layer as the fourth layer are formed in a cell process for forming the solar battery cell 100. The protective glass 200, the sealing material 201, and the wavelength conversion type light trapping film 300 (first and second layers) having a shallower layer are formed by a module process. For this reason, it has been difficult in the prior art to obtain a continuous refractive index distribution across each layer member.

  In the present invention, the refractive indexes of the antireflection film formed in the cell process and the wavelength conversion type light trapping film 300 formed in the module process are adjusted with an optimum balance.

Specifically, the refractive index n ₂ of the wavelength conversion type light trapping film 300 is set to be lower than the refractive index n _{3 of the} antireflection film. If lowering the encapsulant index of refraction n ₁ of the (first layer) 201 below the refractive index n ₂ of the wavelength conversion type light trapping film (second layer) 300 in the module step, n ₁ ≦ described above n ₂ ≦ n ₃ ≦ n ₄ can be achieved.

By the way, it was the insect-eye structure that achieves a continuous equivalent refractive index due to its physical shape.
However, as can be seen in Non-Patent Document 2, the fine weight shape required there is in the wavelength order of light to be introduced.

  On the other hand, the present invention does not require a very fine shape, and may be 10 μm or more, which allows practical die processing. This is because an optical path and multiple reflection explained by geometric optics are used rather than obtaining a continuous equivalent refractive index distribution.

  As described above, the present invention reduces the reflection loss at the optical interface on the module layer structure, which depends on the process, and the sealing material-cell interface of the prior art, and increases the amount of light introduced into the solar cell 100. That's right.

  Therefore, the most important point of the present invention is that the wavelength conversion type light trapping film 300 has a refractive index higher than that of the sealing material 201 and can realize light introduction to the pn junction of the solar battery cell 100 with the highest efficiency. It is to provide.

  More specifically, the light introduction effect of the wavelength conversion type light trapping film 300 is maximized by controlling the refractive index of the antireflection film on the wavelength conversion type light trapping film 300 and the solar battery cell 100.

In other words, a feature of the present invention is that the optimum refractive index configuration can be adjusted from both the wavelength conversion type light trapping film 300 and the antireflection film of the solar battery cell 100. For example, the refractive index of the tempered glass 200 that becomes the outermost layer (incident side), the sealing material 201 under the tempered glass, the n layer and the p layer inside the solar battery cell is difficult to change.
However, the fact that the refractive index can be adjusted by the wavelength conversion type light trapping film 300 and the antireflection film as the intermediate layer makes it easy to realize the aforementioned n ₁ ≦ n ₂ ≦ n ₃ ≦ n ₄ .

In the simplest case: Also here, since the refractive indexes of the protective glass 200 and the sealing material 201 are substantially equal, it is considered that they are optically equivalent (refractive index n ₁ ).
The refractive index n ₂ of the wavelength conversion type light trapping film _300, and the refractive index n ₄ of the refractive index n _3, n-type layer of the antireflection film, preferably expressed by the following equation.

When approximate specific numerical values are entered, n ₁ ≈1.5 and n ₄ ≈3.4 are calculated as n ₂ ≈1.97 and n ₃ ≈2.59.
In addition, the wavelength conversion type light trapping film 300 needs to further contain an organic fluorescent material for wavelength conversion. This organic fluorescent material will be described later.

  Next, an organic-inorganic hybrid material such as the semi-cured high refractive index resin composition 303 used as 300 will be described.

  In the present invention, in order to obtain a high refractive index as a wavelength conversion type light trapping film, it is preferable to use an organic-inorganic hybrid material by using a sol-gel method. The essential components in the sol-gel method are:

で表される金属アルコキシドであるが、本発明においては、このうちの次式

In the present invention, among these, the following formula:

で示されるチタニウムテトラアルコキシドを少なくとも一部として用いることが好ましい。

It is preferable to use at least part of a titanium tetraalkoxide represented by

  In the metal alkoxide represented by the above formula, n is an integer of 0 or more, m is an integer of 1 or more, and n + m is equal to the valence of M. When obtaining the organic-inorganic hybrid material by the sol-gel method, the metal alkoxide used may be one kind or plural kinds.

Complementarily, M may be a metal selected from Ge, Zn, Zr, Al, Si, Sb, Be, Cd, Cr, Sn, Cu, Ga, Mn, Fe, Mo, V, W, and Ce. Absent.
R is hydrogen or a linear or branched alkyl group having 1 to 10 carbon atoms, and a plurality of R ¹ and R ² are bonded to M, and each may be the same or different. A linear or branched alkyl group of 1 to 10 (R ² may be hydrogen).

  In order to obtain an organic-inorganic hybrid material by using the sol-gel method, a metal alkoxide, water and an acid (or alkali) catalyst are added to a resin composition made into a solution, applied to a substrate, the solvent is blown off, and heating is performed. Can be obtained.

However, depending on the reactivity of the metal alkoxide chosen, water and / or acid (or alkali) catalysts may not be required.
The heating temperature also depends on the reactivity of the metal alkoxide. A highly reactive material such as Ti requires neither water nor a catalyst, and the heating temperature may be about 100 ° C.

In the present invention, the (-MO-) three-dimensional structure is not necessarily required as long as a high refractive index can be realized. In particular, the three-dimensional structure of titanium oxide becomes a semiconductor so as to be used in a photocatalyst.
However, this structure is inconvenient in terms of photodegradation, and therefore, a technique using in combination with another metal alkoxide is effective in order to intentionally break the three-dimensional structure.

  The mold film 301 (a mold film that serves as a mold for forming the convex portion of the wavelength conversion type light trapping film) can be produced by the method described in JP-A-2002-225133. A method for producing a mold film will also be described in Examples described later.

  In the present invention, the wavelength conversion light trapping film preferably uses, as the organic fluorescent material, a material that absorbs light having a wavelength of 400 to 550 nm and emits light having a wavelength of 550 to 1200 nm, for example. As a result, the wavelength conversion type light trapping film performs wavelength conversion, guides light having a wavelength of 400 to 1200 nm to the solar cell, and photoelectrically converts the light to the solar cell. For this reason, spectrum mismatch can be overcome.

  The organic fluorescent substance according to the present invention has at least one of (I) coumarin or a derivative thereof, (II) rhodamine or a derivative thereof, (III) pyromethene or a derivative thereof and (IV) a dimethylaminophenyl group in the structure. Is preferably included.

  Moreover, it is preferable that the organic fluorescent substance according to the present invention is a compound having a partial structure represented by the following general formula (1).

（ｎは１〜６の整数である。）

(N is an integer of 1-6.)

  The organic fluorescent substance according to the present invention includes 2,3,6,7-tetrahydro-11-oxo-1H, 5H, 11H- [1] benzopyrano [6,7,8-ij] quinolidine-10-carvone. Acid ethyl ethyl ester, 2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-11-oxo-1H, 5H, 11H- [1] benzopyrano [6,7,8-ij] quinolidine -10-carboxylic acid ethyl ethyl ester, 2,3,6,7-tetrahydro-10- (3-pyridinyl) -1H, 5H, 11H- [1] benzopyrano [6,7,8-ij] quinolidine-11 ON, 7- (diethylamino) -3- (1-methyl-1H-benzimidazol-2-yl) -2H-1-benzopyran-2-one, 2,3,6,7-tetrahydro-11-oxy -1H, 5H, 11H- [1] benzopyrano [6,7,8-ij] quinolidine-10-carboxylic acid, 10-acetyl-2,3,6,7-tetrahydro-1H, 5H, 11H- [1] Benzopyrano [6,7,8-ij] quinolidin-11-one, 10-acetyl-2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H, 5H, 11H- [1] Benzopyrano [6,7,8-ij] quinolizin-11-one, 2,3,6,7-tetrahydro-11-oxo-1H, 5H, 11H- [1] benzopyrano [6,7,8-ij] quinolidine -10-carbonitrile, 10- (2-benzoxazolyl) -2,3,6,7-tetrahydro-1H, 5H, 11H- [1] benzopyrano [6,7,8-ij] quinolidine-11 ON, 3- ( H-benzimidazol-2-yl) -7- (diethylamino) -2H-benzopyran-2-one, 3- (2-benzothiazolyl) -7- (diethylamino) -2H-1-benzopyran-2-one, 2, 3,6,7-tetrahydro-9- (trifluoromethyl) -1H, 5H, 11H- [1] benzopyrano [6,7,8-ij] quinolizin-11-one, 10- (2-benzothiazolyl) -2 , 3,6,7-tetrahydro-1H, 5H, 11H- [1] benzopyrano [6,7,8-ij] quinolizin-11-one, 2 ′, 7′-dichloro-3 ′, 6′-dihydroxy- Spiro [isobenzofuran-1 (3H), 9 '-[9H] xanthen] -3-one, 3', 6'-dihydroxy-spiro [isobenzofuran-1 (3H), 9 '-[9H] Santen] -3-one, disodium salt, 2-butyl-6- (butylamino) -1H-benzo [de] isoquinoline-1,3 (2H) -dione, 9- (2-carboxyphenyl) -3, 6-bis (diethylamino) xanthylium chloride, N- [6- (diethylamino) -9- [2- (ethoxycarbonyl) phenyl] -3H-xanthen-3-ylidene] -N-ethyl-ethanaminium, peroxy Chlorate, 2- (6-amino-3-imino-3H-xanthen-9-yl) -benzoic acid, monohydrochloride, 2- [6- (ethylamino) -3- (ethylimino) -2,7 -Dimethyl-3H-xanthen-9-yl] -benzoic acid, 2- [6- (ethylamino) -3- (ethylimino) -2,7-dimethyl-3H-xanthen-9-yl] -benzoic acid, peroxy Borate, 2- [6- (ethylamino) -3- (ethylimino) -2,7-dimethyl-3H-xanthen-9-yl] -benzoic acid ethyl ester chloride, 2- [6- (ethylamino) ) -3- (Ethylimino) -2,7-dimethyl-3H-xanthen-9-yl] -benzoic acid ethyl ester, tetrafluoroborate, 2- [6- (ethylamino) -3- (ethylimino)- 2,7-Dimethyl-3H-xanthen-9-yl] -benzoic acid ethyl ester, perchlorate, N- [9- (2-carboxyphenyl) -6- (diethylamino) -3H-xanthen-3-ylidene ] -N-ethyl-ethanaminium chloride, N- [9- (2-carboxyphenyl) -6- (diethylamino) -3H-xanthen-3-ylidene] -N-ethyl-ethan Ni, perchlorate, N- [6- (diethylamino) -9- (2,4-disulfophenyl) -3H-xanthen-3-ylidene] -N-ethyl-ethanaminium hydroxide, inner salt , Sodium salt, 9- (2-carboxyphenyl) -2,3,6,7,12,13,16,17-octahydro-1H, 5H, 11H, 15H-xantheno [2,3,4-ij: 5 , 6,7-i′j ′]-diquinolidine-4-ium, perchlorate, 2 ′, 3 ′, 6 ′, 7 ′, 12 ′, 13 ′, 16 ′, 17′-octahydro-spiro [ 3H-2,1-benzooxathiol-3,9 ′-[1H, 5H, 9H, 11H, 15H] xantheno [2,3,4-ij: 5,6,7-i′j ′] diquinolidine] − 6-sulfonic acid, 1,1-dioxide, sodium salt, 1,3 5,7,8-pentamethylpyromethene-difluoroboric acid complex, disodium-1,3,5,7,8-pentamethylpyromethene-2,6-disulfonic acid-difluoroboric acid complex, 1,3 , 5,7,8-pentamethyl-2,6-diethylpyromethene-difluoroboric acid complex, 1,3,5,7,8-pentamethyl-2,6-di-n-butylpyromethene-difluoroboric acid complex, , 3,5,7,8-pentamethyl-2,6-di-t-butylpyromethene-difluoroborate complex, 2,6-di-t-butyl-8-nonyl-1,3,5,7-tetramethyl Pyromethene-difluoroboric acid complex, 8-acetoxymethyl-2,6-diethyl-1,3,5,7-tetramethylpyromethene-difluoroboric acid complex, 1,2,3,5,6,7-hexamethyl -8- Anopyromethene-difluoroborate complex, 3-ethyl-2- [5- (3-ethyl-2 (3H) -benzoxazolylidene) -1,3-pentadienyl] -benzoxazolium iodide, [2- [ 2- [4- (Dimethylamino) phenyl] ethenyl] -6-methyl-4H-pyran-4-ylidene] -propanedinitrile, [2-methyl-6- [2- (2,3,6,7- Tetrahydro-1H, 5H-benzo [ij] quinolizin-9-yl) ethenyl] -4H-pyran-4-ylidene] propanedinitrile, 2- [4- [4- (dimethylamino) phenyl] -1,3- Butadienyl] -1-ethylpyridinium, monoperchlorate, benzoxazolium, 2-[[2- [2- [4- (dimethylamino) phenyl] ethenyl] -6-methyl-4H- Lan-4-ylidene] methyl] -3-ethyl iodide, 4- [4- [4- (dimethylamino) phenyl] -1,3-butadienyl] -1-ethylpyridinium, perchlorate, 2- [4 -[4- (dimethylamino) phenyl] -1,3-butadienyl] -1,3,3-trimethyl-3H-indolium, perchlorate, 2- [4- [4- (dimethylamino) phenyl] -1,3-butadienyl] -3-ethyl-naphtho [2,1-d] thiazolium, perchlorate, 4- [4- [4- (dimethylamino) phenyl] -1,3-butadienyl] -1 -Ethylquinolinium, perchlorate, 2- [6- [4- (dimethylamino) phenyl] -1,3,5-hexatrienyl] -3-ethyl-benzothiazolium, perchlorate 2- (6- (p-dimethylamino) Nophenyl) -2,4-neopentylene-1,3,5-hexatrienyl) -3-ethylbenzothiazolium, perchlorate, 5-imino-5H-benzo [a] phenoxazine-9-amine, Monoperchlorate, 3-ethyl-2- [7- (3-ethyl-2 (3H) -benzoxazolylidene) -1,3,5-heptatrienyl] -benzoxazolium iodide, 2- [ 7- (1,3-dihydro-1,3,3-trimethyl-2H-indole-2-ylidene) -1,3,5-heptatrienyl] -1,3,3-trimethyl-3H-indolium iodide, 5-chloro-2- [2- [3-[(5-chloro-3-ethyl-2 (3H) -benzothiazolylidene) ethylidene] -2- (diphenylamino) -1-cyclopentan-1-yl ] Ethenyl] -3 Ethyl benzothiazolium include perchlorate, etc., but not intended to limit thereto.

  The present invention does not limit these organic fluorescent materials, and is selected according to the purpose. For example, in the silicon crystal solar cell, light in the ultraviolet region or infrared region of sunlight is not effectively used, and the solar cell module absorbs the protective glass for wavelengths shorter than 400 nm in the ultraviolet region. Therefore, since light does not reach the solar battery cell, it is advantageous to absorb light having a short wavelength of 400 nm to 550 nm and emit light having a wavelength of 550 to 1200 nm. An example of such an organic fluorescent material is LDS698 (2- [4- [4- (dimethylamino) phenyl] -1,3-butadienyl] -1-ethylpyridinium, monoperchlorate). .

  Even when the present invention is applied to, for example, an amorphous silicon solar cell, a GaAs solar cell, a CIS solar cell, a PbS photoelectric conversion device, a CdS photoelectric conversion device or the like, if an organic fluorescent material is selected according to the sensitivity spectrum thereof, Good.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the following examples.

[Example 1]
In the production of the solar cell module of the present invention, the wavelength conversion type light trapping film is pasted on the solar cell by the method described so far. As the form after the pasting, the form shown in FIG. 1 and FIG. There is a form shown in the following. That is, the form shown in FIG. 1 is a form in which the wavelength conversion type light trapping film 300 is attached to the solar battery cell, that is, the form film 301 is not left in the solar battery module. A form is a form which leaves the type | mold film 301 in a solar cell module as it is, the solar cell module which affixed the wavelength conversion type light trapping film 300 with the type | mold film 301 on the solar cell 100. FIG. However, in FIG. 1 and FIG. 3, the connecting tab line is omitted. The Example shown below is a form which leaves a type | mold film in a solar cell module shown in FIG.

<Production of mold film>
First, a method for producing the mold film 301 will be described in detail. A UV curable resin was applied on a PET film (A4300, manufactured by Toyobo Co., Ltd.) having a thickness of 50 μm as a substrate with a die coater. A roll mold having an apex angle of 90 degrees, a pitch of 20 μm, and a height of 10 μm and innumerable four-sided pyramids pressed against each other was pressed, irradiated with ultraviolet rays, and the UV curable resin was cured to obtain a mold film.

<Formation of highly refractive layer>
Next, a specific example of a method for forming a highly refractive layer that can be used as the wavelength conversion type light trapping film 300 will be described. A specific example of this forming method includes a step of preparing a high refractive resin solution and a step of forming a high refractive resin layer.
In particular, in this method, in the step of forming a high refractive resin layer, a high refractive resin solution mixed with an organic fluorescent material is applied to a light receiving surface of a polycrystalline silicon solar cell and dried to form a high refractive resin layer. ing.

-Preparation of highly refractive resin solution-
The preparation process of the highly refractive resin solution will be described. In advance, a connecting tube and a Liebig condenser were connected to one of the four-necked separable flasks so that the stirring blades, nitrogen supply to one, and volatile components could be distilled off to one.

  Diethanolamine (11.04 g), water (1.08 g) and n-methylpyrrolidone (13.46 g) were placed in a 100 ml separable flask and stirred under a stream of nitrogen. After a few minutes, it was confirmed that the stirring was sufficiently performed, and 21.32 g of titanium tetraisopropoxide was added while being careful not to touch the air as much as possible.

  When titanium tetraisopropoxide was added, the temperature of the flask increased, but after cooling to about room temperature (25 ° C.), the volatile components were distilled off using an 80 ° C. oil bath. The distillate at this time is isopropyl alcohol, which is a by-product of the hydrolysis reaction of titanium tetraisopropoxide.

  Thereafter, 3.78 g of water and 3.15 g of diethanolamine were mixed well using another sample tube, and after the above distillation was performed for 6 hours, the flask was cooled to room temperature and the mixture was added. This liquid is used as a metal-containing highly refractive intermediate. A solution obtained by mixing 5 parts by weight of SR-16HL (1,6-hexanediol diglycidyl ether, manufactured by Sakamoto Pharmaceutical Co., Ltd.) with respect to 95 parts by weight of the metal-containing highly refractive intermediate is defined as a highly refractive resin solution.

  0.05 part by weight of LDS698 (manufactured by Exciton) as an organic fluorescent substance was added to 100 parts by weight of the high refractive resin solution synthesized by the above procedure, and the mixture was sufficiently stirred. This liquid is an organic fluorescent substance mixed high refractive sap.

~ High refractive resin layer formation process ~
A process for forming the high refractive resin layer will be described. This is a step of forming a high refractive resin layer on the light receiving surface of the polycrystalline silicon solar battery cell. In this step, the organic fluorescent substance mixed high refractive sap was applied to the light-receiving surface of the polycrystalline silicon solar cell with an applicator, and the solvent was dried at 100 ° C. for 20 minutes using an explosion-proof oven.

<Production of solar cell module>
Next, a method for producing a solar cell module with a light trapping film having a polycrystalline silicon solar cell having a high refractive resin layer formed on a light receiving surface according to a specific example of the method for forming the high refractive resin layer will be described. FIG. 4 is an exploded view of a solar cell module with a light trapping film.

The smooth surface 200a of the crystalline silicon solar cell cover glass (tempered glass) 200 is faced down, and a solar cell module filler EVA (ethylene vinyl acetate copolymer) sheet 201 is laid thereon to produce the mold film. The light-receiving surface 303a of the solar cell polycrystalline cell 100 (including the high refractive resin layer 303), which is laid with the concavo-convex shape facing upward and the PET base material 302 facing downward and tab-lined, is formed. It was placed face down, and the filler EVA sheet 201 and the PET film 203 were further laid and laminated using a vacuum laminate. The conditions at this time were a hot plate temperature of 150 ° C., a vacuum time of 15 minutes, a pressurization time of 30 seconds, and a pressurization holding time of 10 minutes.
The average thickness L of the produced wavelength conversion type light trapping film was 20 μm.

In the produced solar cell module, the refractive index n ₁ of the protective glass (first layer) is 1.5, and the refractive index n ₂ of the filler EVA sheet (second layer) is 1.5. The refractive index n ₃ of the PET base material (third layer) is 1.5, and the refractive index n ₄ of the mold film (fourth layer) is 1.5. “Wavelength-converting light trapping film” upcoming refractive index _{n 5} of the high refractive resin layer (fifth layer) is 1.6 to 2.4, which satisfies the _{n 1 ≦ n 2 ≦ n 3} ≦ n 4 ≦ n 5.

A method for measuring the short-circuit current density difference ΔJsc for the solar cell module produced by the method for producing the solar cell module with a light trapping film described above will be described. Using the simulated solar irradiation device (WXS-155S-10, manufactured by WAKOM), the solar cell module produced above was irradiated with light of 100 mW / cm ² , and the current and voltage generated at that time were expressed as IV. It measured with the curve tracer (MP-160, EKO company make).

A value obtained by subtracting Jsc of the solar battery cell under the same measurement conditions from the short-circuit current density Jsc (mA / cm ² ) calculated by the IV curve tracer was defined as ΔJsc. The results are shown in Table 1 below together with the comparative example.

[Comparative Example 1]
Wavelength conversion was performed in the same manner as in Example 1 using 5 parts by weight of Eu (TTA) 3Phen as a fluorescent substance and 100 parts by weight of the highly refractive resin solution synthesized by the above-described method, and using a sufficiently stirred solution. A mold light trapping film was prepared.

  A solar cell module obtained by stacking tempered glass, EVA resin, wavelength conversion type light trapping film, solar cell (light receiving surface facing down), EVA resin, back film and laminating using a vacuum laminator It was set as Comparative Example 1. The results are shown in Table 1 below.

[Comparative Example 2]
A solar cell module obtained by laminating tempered glass, EVA resin, solar cells (light-receiving surface facing down), EVA resin, and back film and using a vacuum laminator was used as Comparative Example 2. The results are shown in Table 1 below.

From Table 1, numerical values ΔJsc in Example 1 is larger than Comparative Examples 1 and 2, the solar cell module of Example 1, the current density Jsc each ^{0.32mA / cm 2, 0.52mA / cm} 2 increased I understand that.

It is sectional drawing of the solar cell module which becomes an Example of this invention. FIG. 4 is a schematic diagram for explaining the structure of a wavelength conversion type light trapping film 300. It is sectional drawing which shows the structure of the solar cell module which affixed the light trapping film with a type | mold film on the photovoltaic cell. It is an exploded view of a solar cell module with a light trapping film. It is sectional drawing of the conventional solar cell module.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Solar cell 200 Protective glass 201 Sealing material 202 Tab line 203 Back film 204 Incident light 300 Wavelength conversion type light trapping film 301 Type film 302 PET film 303 High refractive index resin composition containing organic fluorescent substance in semi-cured state Layer

Claims (6)

In order from the light incident side, the first layer, the second layer,..., The m-th layer are used, and the refractive indexes of the respective layers are the first refractive index n ₁ , the second refractive index n ₂ ,. when - and the refractive index n _m of the m, a wavelength to be used as at least one layer light transmissive layer of the solar cell module including a plurality of light transmitting layer _{n 1 ≦ n 2 ≦ ··· ≦} n m holds A conversion type light trapping film,
It is formed so that a large number of fine convex or concave polygonal pyramids or cones are spread on one surface without gaps, the refractive index is 1.6 to 2.4, and an organic fluorescent material is included. Wavelength conversion type light trapping film. The wavelength conversion type light trapping film according to claim 1, wherein the value of the normalized absorbance a represented by the following formula (1) is 0.1 or less when the wavelength of light incident from the light incident side is 400 to 1200 nm. .

Here, T is the transmittance, and L is the average thickness (μm) of the wavelength conversion type light trapping film.   The wavelength conversion type light trapping film according to claim 1, wherein the organic fluorescent material absorbs light having a wavelength of 400 to 550 nm and emits light having a wavelength of 550 to 1200 nm.   The organic fluorescent substance includes at least one of (I) coumarin or a derivative thereof, (II) rhodamine or a derivative thereof, (III) pyromethene or a derivative thereof and (IV) a dimethylaminophenyl group in the structure. Item 4. The wavelength conversion type light trapping film according to any one of Items 1 to 3. The wavelength conversion type light trapping film according to claim 1, wherein the organic fluorescent material is a compound having a partial structure represented by the following general formula (1).

(N is an integer of 1-6.)   A solar cell module, wherein the wavelength conversion type light trapping film according to claim 1 is provided on a light receiving surface side of a solar cell.

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