JP2014165296A - Solar cell module and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solar cell module which has a wide effective wavelength range of sunlight and is superior in conversion efficiency and a manufacturing method thereof.SOLUTION: The solar cell module includes: a photoelectric conversion element 101; an electrode 104 which is electrically connected to the photoelectric conversion element 101; a first transparent resin 102 for protecting the photoelectric conversion element 101; a back sheet 103; a protection glass 105; and a second transparent resin 106 which is in close contact with the protection glass 105. The second transparent resin 106 contains fluorescence substance and an air bubble group 107 or a transparent particle group. The volume density of the air bubble group 107 or transparent particle group increases in a continuous or stepwise manner toward the surface where the sunlight comes in.

Description

  The present invention relates to a solar cell module in which a phosphor is disposed on the front surface of a photoelectric conversion element and a method for manufacturing the same.

  Solar cells generally have low sensitivity characteristics in the short wavelength region and cannot effectively use light in the short wavelength region such as ultraviolet rays contained in sunlight. Conventionally, a phosphor that absorbs light in the short wavelength region and emits fluorescence in the long wavelength region, so-called wavelength conversion materials, is used to increase the amount of light in the long wavelength region with high sensitivity characteristics and improve the conversion efficiency of solar cells. Efforts have been made.

  For example, in Patent Document 1 and Patent Document 2, an organic phosphor is included in a transparent resin on a solar cell, and incident short-wavelength light is efficiently converted into longer-wavelength light and absorbed by the solar cell. Is disclosed.

  Patent Document 3 discloses that in a solar cell module, a rare earth phosphor is blended in an ethylene-vinyl acetate copolymer, which is a protective resin for a photoelectric conversion element, to improve efficiency.

  Although the above-described approaches are known, in the case of a phosphor material uniformly mixed on the upper surface of the photoelectric conversion element, there is a problem that the converted light does not sufficiently reach the solar cell.

  As a means for solving this problem, a method has been proposed in which the refractive index of the transparent resin layer containing the wavelength conversion material is changed stepwise (Patent Document 4). That is, as the transparent layer for dissolving the phosphor, a plurality of layers having different refractive indexes of the resin in stages in the direction from the photoelectric conversion element toward the light incident surface are provided. The composition ratio of the transparent layer is continuously changed to obtain layers having different refractive indexes.

  By adopting such a configuration, even if the fluorescence emitted from the wavelength conversion material contained in the transparent layer is emitted in the direction where there is no photoelectric conversion element, a part of the change in refractive index occurs. As a result, the direction is bent to reach the photoelectric conversion element, and the efficiency is improved accordingly.

JP 57-28149 A JP-A-57-189 WO2008 / 047427 publication JP 2011-071504 A

  However, in order to form layers having different refractive indexes stepwise or continuously described in Patent Document 4, it is necessary to adjust the composition of the phosphors of each layer, which requires many man-hours and is complicated and expensive. Met.

  An object of the present invention is to realize a simple structure for increasing the refractive index of a resin on a photoelectric conversion element continuously or stepwise from an incident surface in a thickness direction.

  In order to solve the above problems, a photoelectric conversion element, an electrode electrically connected to the photoelectric conversion element, a first transparent resin containing the photoelectric conversion element inside, and an upper surface of the first transparent resin A protective glass positioned on a light incident surface, a back sheet positioned on the lower surface of the first transparent resin, a second transparent resin formed on the protective glass and containing a phosphor, and the second transparent A solar cell module comprising a bubble group or a transparent particle group contained in a resin, wherein the volume density of the bubble group or the transparent particle group is light incident from a light exit surface in the second transparent resin. The volume density is an average volume density in a layer having a certain thickness of the second transparent resin parallel to the light incident surface or the light emitting surface. Using solar cell module .

  In the solar cell module of the present invention, a layer whose refractive index is increased stepwise or continuously in the direction from the light incident surface toward the photoelectric conversion element surface is formed. With the wavelength conversion material blended in the layer, short wavelength light with poor conversion efficiency is converted into light with high conversion efficiency and absorbed by the photoelectric conversion element. As a result, the conversion efficiency can be increased.

Sectional drawing of the 1st Embodiment of this invention (A)-(h) Sectional drawing of each process showing the manufacturing process of the 1st Embodiment of this invention. Sectional drawing of the 2nd Embodiment of this invention (A)-(f) Sectional drawing of each process showing the manufacturing process of the 2nd Embodiment of this invention. Sectional drawing of the 3rd Embodiment of this invention (A)-(m) Sectional drawing of each process showing the manufacturing process of the 3rd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a cross-sectional view showing the structure of the solar cell module according to the first embodiment of the present invention. The solar cell module of this embodiment includes at least a photoelectric conversion element 101, a first transparent resin 102 that protects the photoelectric conversion element 101, a back sheet 103, and a wiring that connects the photoelectric conversion elements 101 to each other.

  Furthermore, it is contained in the electrode 104 for taking out the electric current obtained to the outside, the protective glass 105, the second transparent resin 106 containing the phosphor, and the second transparent resin 106, and directed toward the incident direction of light. Thus, a bubble group 107 having a high volume density is provided.

  In FIG. 1, the phosphor is present in the second transparent resin 106 but is not shown. In the second transparent resin 106 containing the phosphor, the bubble group 107 has a configuration in which the volume density increases in the light incident direction. As a result, the refractive index of the second transparent resin 106 decreases as it goes to the light incident surface. As a result, most of the fluorescence emitted from the phosphor contained in the second transparent resin 106 is directed toward the photoelectric conversion element 101, so that the photoelectric conversion efficiency can be increased.

  The photoelectric conversion element 101 is not particularly limited, but may be a silicon semiconductor such as a single crystal silicon, a polycrystalline silicon, or an amorphous silicon, or a compound semiconductor such as gallium arsenide or cadmium telluride.

  The electrode 104 for electrically joining the photoelectric conversion element 101 can be a known metal material or alloy material.

  The first transparent resin 102 that includes and protects the photoelectric conversion element 101 is not particularly limited, but is an ethylene vinyl acetate copolymer, a bisphenol epoxy resin cured product, an acrylic resin, a silicone resin, a polycarbonate resin, or the like. be able to.

  The first transparent resin 102 may contain a known ultraviolet absorber that absorbs light of 350 nm or less that has low sensitivity characteristics and causes deterioration for the photoelectric conversion element 101.

  The protective glass 105 is not particularly limited, and may be a known plate-like glass having translucency and water shielding properties. The second transparent resin 106, which is disposed on the protective glass 105 and contains the phosphor and the bubble group 107 whose volume density becomes dense toward the light incident surface, is an important part of the present invention. The details will be described below.

  The second transparent resin 106 can be, but is not limited to, an ethylene vinyl acetate copolymer, a bisphenol epoxy resin cured product, an acrylic resin, a silicone resin, and a polycarbonate resin. The thickness can be 0.5 μm or more and 100 μm or less.

  If the thickness is less than 0.5 μm, the absolute amount of the phosphor contained is reduced, and a sufficient effect of converting the wavelength of light with low sensitivity characteristics into light with high sensitivity characteristics cannot be obtained. If it is thicker than 100 μm, the conversion efficiency of the photoelectric conversion element 101 is lowered due to the absorption of the resin itself.

  For example, the refractive index of the light incident surface of the second transparent resin 106 can be 1.3, and the refractive index of the surface opposite to the light incident surface can be 1.5. The change in the existence frequency of the bubble group is not limited. When the cross section perpendicular to the axis along the light incident direction or the light emitting direction is observed in the second transparent resin 106 layer, the photoelectric conversion element 101 is used. When the first cross section near the first cross section is compared with the second cross section farther from the photoelectric conversion element 101 than the first cross section and 250 nm or more away from the first cross section, it is observed in the second cross section. It is only necessary that the number of bubbles to be larger than that of the first cross section. That is, it is only necessary that the average volume of the bubbles for each layer having a thickness of 250 nm increases from the light emitting side to the incident side.

(About phosphor)
The phosphor contained in the second transparent resin 106 is not limited in both composition and system, but an inorganic compound, an organic compound, an inorganic-organic complex compound, etc. may be used alone or in combination, as appropriate. Can do. In the present invention, it absorbs light having a wavelength with low sensitivity characteristics of the solar cell, emits light with wavelength with high sensitivity characteristics as fluorescence, and absorbs ultraviolet light of 400 nm or less from the viewpoint of improving photoelectric conversion efficiency, It is preferable to emit fluorescence having a wavelength longer than 400 nm. In this example, (1,10-Phenanthroline) tris [4,4,4-trifluoro-1- (2-thienyl)-, which is an Eu (trivalent) complex, is used. 1,3-butanedionato] europium (III) is added in an amount of 0.6% by weight.

  In addition, when two types of phosphors are used, if the phosphors are selected so that the fluorescence wavelength emitted by the first phosphor and the absorption wavelength of the second phosphor overlap, fluorescence having a wider range of wavelengths can be obtained. From the viewpoint of improving photoelectric conversion efficiency.

  The concentration of the phosphor depends on the extinction coefficient at each wavelength of the phosphor and the thickness of the second transparent resin 106. For example, the absorbance at the absorption peak wavelength of each phosphor is greater than 0.1 and less than 10. Concentration can be obtained. This is because if the absorbance is less than 0.1, a sufficient amount of fluorescence cannot be obtained, and if the absorbance is greater than 10, the luminous efficiency is reduced by concentration quenching due to absorption of the phosphor itself.

  As an inorganic fluorescent substance, it does not specifically limit and a well-known thing can be used. In general, an oxide, nitride, sulfide, or the like in which a metal element is activated as a luminescent ion in a mother crystal can be used. One or more elements such as B, Gd, O, S, Al, Ga, Ba, Sr, K, V, La, Cl, P, In, Zn, Y, Ca, and Mg are used, and Zn, Ho are used as luminescent ions. , Tb, Nd, Ag, Mn, Ce, Eu, Dy, Tm and the like, and an inorganic phosphor in which one or more types are activated and used.

  In addition, when using inorganic fluorescent substance for this invention, it is desirable for the particle size to be smaller than 300 nm and larger than 30 nm. In the case of 300 nm or more, light having a wavelength with high sensitivity characteristics for the photoelectric conversion element is lost due to scattering by the particles of the inorganic phosphor. When the thickness is 30 nm or less, the influence of surface defects of the inorganic phosphor increases, and the light emission efficiency decreases.

  Although it does not specifically limit as an organic fluorescent substance, For example, a hydrocarbon type can be used. Generally, hydrocarbons are represented by CnH2n + 2-2a-2b-4c, where a, b, and c are represented by the number of rings, the number of double bonds between carbons, and the number of triple bonds between carbons, respectively. Is done. However, it is possible to use one having n larger than 5 and smaller than 40 and emitting fluorescence.

  In the case of 5 or less, few substances function as a phosphor that absorbs ultraviolet rays as hydrocarbons and emits a phosphor having a wavelength longer than 400 nm, which has a high sensitivity characteristic. This shifts and absorbs light with high sensitivity characteristics, leading to a decrease in photoelectric conversion efficiency of the photoelectric conversion element.

  In the above structural formula, the part corresponding to carbon may be appropriately replaced by an oxygen atom, a nitrogen atom or a sulfur atom, and it is not limited whether it is ionized or not. From the viewpoint of properties, for example, a fused ring compound such as anthracene, phenanthrene, pentacene, pyrene, perylene, benzpyrene, coronene, or a derivative thereof can be preferably used.

  Specific examples of other organic phosphors include rhodamines, coumarin derivatives, quinacridone derivatives, benzoxazole derivatives, arylamine derivatives, distyrylpyrazine derivatives, carbazole derivatives, silole derivatives, spiro compounds, triphenylamine derivatives, naphthalimide derivatives, Trifumanylamine derivative, pyrazoloquinoline derivative, hydrazone derivative, pyridine ring compound, fluorene derivative, benzoxazinone derivative, phenanthroline derivative, quinazolinone derivative, quinophthalone derivative, phenylene compound, perinone derivative, rubrene derivative, styryl derivative (distyrylbenzene derivative) , Distyrylarylene derivatives, stilbene derivatives), thiophene derivatives (oligothiophene derivatives), dienes (cyclopentadiene derivatives) , Tetraphenylbuta derivatives), azole derivatives (oxadiazole derivatives, oxazole derivatives, triazole derivatives, benzoazatriazole derivatives), pyrazole derivatives (pyrazoline derivatives), pyrrole derivatives (porphyrin derivatives, phthalocyanine derivatives) Etc.

  Here, the phosphor may be a complex phosphor. The complex phosphor is not particularly limited, but based on a general definition, at least one or more kinds of ligands are coordinated to at least one or more kinds of central metal atoms by coordination bonds or hydrogen bonds. I will be ranked. Furthermore, it is a molecular compound in which the central metal atom is the emission center, and it is not limited whether the central metal atom is an ion.

  Examples of the central metal atom serving as the emission center include transition metals such as Fe, Cu, Zn, Al, and Au. In particular, Gd, Yb, Y, Eu, Tb, Yb, Nd, Er, and the like belonging to the lanthanoid series. Sm, Dy, Ce, and the like are preferable because they have advantages such as a large difference between the wavelength of light to be absorbed and the wavelength of light to be emitted, a small decrease in light emission efficiency due to fluorescence reabsorption, and high quantum efficiency.

(About bubbles)
From the viewpoint that the bubbles constituting the bubble group 107 do not scatter light having a wavelength longer than 400 nm, which has high sensitivity characteristics of the photoelectric conversion element 101, and do not scatter light having a wavelength longer than 300 nm absorbed by the phosphor. The diameter is preferably smaller than 300 nm.

  Furthermore, the bubble group 107 has a volume density that increases stepwise or continuously toward the light incident surface, and as a result, a refractive index gradient is provided to the second transparent resin 106 of the present invention.

  The ratio of bubbles is not limited, but in the case of acrylic resin, it is sufficient that the volume is 40 volume% in the vicinity of the light incident surface and decreases toward the surface opposite to the light incident surface, and the difference in refractive index is increased. From the viewpoint of achieving this, 0% is desirable on the surface opposite to the incident surface.

  When it is larger than 40% by volume, it causes a decrease in strength of the second transparent resin 106. When the volume is 0% by volume on the side opposite to the incident surface, the refractive index is increased, and the difference in refractive index from the incident surface is increased. Light is more likely to go to the photoelectric element.

  Here, continuously changing means that the volume density is monotonously and continuously increasing means that the volume is changing. The volume density does not decrease or become constant on the way.

  When the volume density is increased stepwise, it means that the whole volume changes monotonously and there is a certain place on the way. This is shown in the third embodiment.

  That is, the refractive index decreases stepwise or continuously toward the light incident surface. Although the amount of change in the refractive index is not limited, the amount of change in the refractive index is configured to be directed to the photoelectric element due to more change in the fluorescence emitted from the fluorescence emitted in the direction without the photoelectric conversion element 101. From the viewpoint of, the larger one is preferable.

  The gas in the bubble is not particularly limited, and is preferably a single atom such as hydrogen, nitrogen, oxygen, or a rare gas, or a monoatomic molecule, carbon dioxide, hydrocarbon gas, or the like that is not chemically active. Can be used. When a material that is not chemically active is used, a large amount of inert gas microbubbles, dissolved molecules, or dissolved atoms are present between the polymer chains of the second transparent resin.

  As a result, the amount of oxygen in the atmosphere entering the second transparent resin 106 can be suppressed, and an organic phosphor having high reactivity with oxygen, which has been inferior in long-term use reliability, is used. It is preferable from the viewpoint of being able to do so.

(Production method)
Although it does not limit as a manufacturing process of the 1st Embodiment of this invention, the construction method as demonstrated below, for example is possible. FIG. 2A to FIG. 2H are cross-sectional views of each process showing the manufacturing process of the first embodiment of the present invention. Each figure is a schematic sectional view.

  In FIG. 2 (a), a gas 109 having poor reactivity such as nitrogen gas is introduced into a liquid through a glass tube 110 into a monomer solution 108 made of a transparent resin such as acrylic, in which a phosphor is dissolved or dispersed in advance. A solution is prepared by bubbling until dissolved. In this production process, 0.6% by weight of (1,10-Phenanthroline) tris [4,4,4-trifluoro-1- (2-thienyl) -1,3-butanedionato] europium (III) is blended as a phosphor. ing.

  Next, in FIG. 2B, an appropriate amount of the monomer solution 108 is dropped on the protective glass 105 to obtain the state shown in FIG. Thereafter, a uniform film thickness as shown in FIG. 2D is obtained by a method such as spin coating or screen printing. At this stage, the monomer solution 108 is in an uncured state. Although it does not limit as a film thickness, it can be 0.5 micrometer or more and 100 micrometers or less, for example. When the thickness is less than 0.5 μm, the absolute amount of the phosphor contained is reduced, and a sufficient effect of converting the wavelength of light with low sensitivity characteristics into light with high sensitivity characteristics cannot be obtained. Absorption causes a decrease in conversion efficiency of the photoelectric conversion element 101.

  Next, in FIG. 2 (e), the protective glass 105 coated with the monomer solution 108 is left almost horizontally so that the monomer solution 108 is on the upper side, and is saturated in the previous step in the monomer solution 108. Among the gases, the bubbles dissolved as microbubbles 119 are left until they are concentrated in the opposite direction to the protective glass 105 due to buoyancy, and the state shown in FIG.

  2E and 2F are enlarged views for explaining this process. The direction indicated by G in the figure is the direction of gravity. The standing time depends on the viscosity of the monomer solution 108 and is not limited. As an example, it can be 0.5 minutes or more and 24 hours or less. When the microbubbles 119 are densely packed in the opposite direction to the protective glass 105, the monomer solution 108 is cured by irradiating with ultraviolet rays to become the second transparent resin 106 in the present invention as shown in FIG.

  If the time is shorter than 0.5 minutes, the bubbles are uniformly dispersed, the volume density gradient is insufficient, and if left for more than 24 hours, the bubbles are degassed from the uncured resin. There is. In curing, ultraviolet rays are irradiated in the case of an ultraviolet curable resin, but in the case of a thermosetting resin, the resin is cured by heating. What is necessary is just to make it harden | cure by the suitable hardening method with the selected resin.

  Further, when the bubbles rise due to buoyancy, if the bubbles are left under reduced pressure, the degree of pressure reduction can be controlled. Alternatively, it is possible to control the bubble volume density gradient according to the standing time under atmospheric pressure. For example, when controlling by the decompression time, several types of decompression time are set, and the gradient of bubbles of the cured product that has been cured is observed. By setting the decompression time based on the result, it is possible to control the bubble volume density gradient.

(Bubble distribution)
From the viewpoint of the present invention that the second transparent resin 106 is provided with a refractive index gradient in the incident direction of light, there is no need for bubbles to exist immediately above the protective glass 105. It can be formed by a setting method.

  With respect to the surface direction, it is not necessary until all regions have a uniform bubble distribution throughout, but at least half of the total area needs to have the bubbles. In some cases, there may be areas where there are no bubbles. Further, it is only necessary to be on the upper surface of the conversion elements, and is not necessary between the conversion elements. As such, a distribution may be provided.

  The initial size of the bubbles can be controlled by the diameter of the pipe, the gas flow rate from the pipe, and the gas flow interval, and then can be performed at the atmospheric pressure setting in the process such as thermal curing or ultraviolet curing. For example, several types of pressure settings are set and the size of the bubbles in the cured product is observed, and what size is set at which pressure setting is evaluated in advance, and the pressure is set based on the evaluation result. By doing so, the bubble size can be controlled.

  Although there may be a distribution of the size of the bubbles, it is necessary to make it smaller than the diameter of 300 nm. Moreover, the volume density of bubbles should just be distribution as mentioned above.

  Next, in FIG. 2 (h), the protective glass 105 coated with the second transparent resin 106 containing microbubbles with a volume density gradient with the phosphor is applied to the first transparent resin 102a in the solar cell, Laminating is performed by a known method together with the two layers of the first transparent resin 102b, the photoelectric conversion element 101 and the back sheet 103 in which the electrode 104 is electrically joined. Thus, since the fluorescence emitted from the phosphor has a gradient in refractive index, a solar cell module with high power generation efficiency that reaches the photoelectric conversion element 101 more efficiently can be obtained (FIG. 1).

  In FIG. 2 (d), when the microbubbles 119 in the monomer solution 108 are left to concentrate, the rising speed of the bubbles is increased, and the bubbles are left under reduced pressure in a closed system in order to concentrate the bubbles more efficiently. You may do it. If time is required, the monomer solution 108 can be heated for the purpose of reducing the viscosity.

  When the monomer solution 108 is a thermosetting resin, it needs to be heated at a temperature lower than the reaction start temperature. In that case, the volume density gradient of the microbubbles is larger, the refractive index gradient is larger in the second transparent resin 106, and the rate of arrival of the fluorescence amount emitted from the contained phosphor to the photoelectric element becomes higher. It is preferable from the viewpoint.

  In addition, when the microbubbles 119 are left to concentrate, the bubble size in the monomer solution 108 may be increased to about 500 nm to increase the rising speed. However, when the bubble size is large, light in a wavelength range in which the sensitivity characteristic of the photoelectric conversion element is large is scattered, resulting in a decrease in efficiency. For this reason, when the bubbles are concentrated and the monomer solution 108 is cured, it is necessary to cure the bubbles while reducing the bubbles to 100 nm under a high pressure of about 125 times the atmospheric pressure.

  In general, since the volume of gas and the pressure are in an inversely proportional relationship, when the atmospheric pressure is increased by 125 times, the volume becomes 1/125. Since the volume is proportional to the cube of the size, when the volume becomes 1/125, the size (diameter) becomes the third root of 1/125, that is, 1/5.

  Therefore, by increasing the pressure by 125 times, the volume of the bubbles becomes 1/125 and the diameter becomes 1/5. Therefore, a bubble having a size of 500 nm becomes a bubble having a size of 100 nm.

  In addition, the bubble 11 to be bubbled is an inert gas having a poor reactivity such as nitrogen or argon, so that the minute bubble of the inert gas, the dissolved molecule, or the dissolved atom is a polymer of the second transparent resin. There will be a lot between chains.

  As a result, the amount of oxygen in the atmosphere entering the second transparent resin 106 can be suppressed, and organic phosphors that have been poor in long-term use reliability can be used.

  In Embodiment 1, the refractive index was changed by controlling the bubble distribution with the second transparent resin 106. As a result, light generated in the phosphor can be guided to the photoelectric conversion element 101 with little loss, and light conversion efficiency can be improved. Since it is a bubble, control is easy.

(Embodiment 2)
FIG. 3 is a cross-sectional view showing the structure of the solar cell module according to the second embodiment of the present invention. The difference from the first embodiment of the present invention is that the second transparent resin 106 is formed on the surface of the protective glass 105 opposite to the light incident surface. Others are the same as the first embodiment of the present invention.

  In the solar cell module of this embodiment, at least the photoelectric conversion element 101, the first transparent resin 102 that protects the photoelectric conversion element 101, the back sheet 103, and the current obtained by connecting the photoelectric conversion elements to each other. An electrode 104 for taking out the light, a protective glass 105, a second transparent resin 106 containing a phosphor, and a bubble group 107 contained in the second transparent resin and having a volume density increasing toward the light incident surface. I have.

  The diameter of each bubble constituting the bubble group 107 is smaller than that which does not scatter the wavelength of light having high sensitivity characteristics of the photoelectric conversion element, and is smaller than 300 nm. In FIG. 3, the phosphor is present in the second transparent resin 106.

  As described above, the bubble group 107 in the second transparent resin 106 containing the phosphor has a structure in which the volume density increases in the light incident direction, so that the light in the second transparent resin 106 is light. The refractive index decreases toward the incident direction of the light, and the fluorescence emitted from the phosphor contained in the second transparent resin 106 is directed toward the photoelectric conversion element more than in the case where the refractive index is uniform. Efficiency can be increased. Furthermore, in this embodiment, it is preferable from the viewpoint that the long-term reliability of the wavelength conversion function is improved because the second transparent resin 106 is not in direct contact with the atmosphere.

  Although it does not limit as a manufacturing process of Embodiment 2 of this invention, the construction method as demonstrated below is possible, for example. FIG. 4A to FIG. 4F are cross-sectional views of the respective steps showing the manufacturing process of the second embodiment of the present invention. It is typical sectional drawing.

  The step of preparing a solution in which a gas, which is generally poor in reactivity, such as nitrogen gas, is bubbled into a liquid through an acrylic monomer solution 108 in which a phosphor is dissolved or dispersed in advance until it is saturated until saturated. This is common to the manufacturing process of the first embodiment of the invention.

  As shown in FIG. 4A, the monomer solution 108 is applied to the protective glass 105 by a known method such as spin coating or screen printing.

  As shown in FIG. 4 (b), the coated monomer solution 108 is left horizontally under reduced pressure so as to be downward. Among the gases saturated in the previous step in the monomer solution 108, microbubbles 119 are obtained. The remaining bubbles are left until they are concentrated in the direction of the protective glass 105 by buoyancy. It holds until it changes from FIG.4 (c) to FIG.4 (d). The monomer solution 108 is evenly adsorbed to the protective glass 105 due to the interfacial tension, and is not deformed due to gravity.

  FIGS. 4C and 4D are enlarged views of this process in the monomer solution 108, and the direction indicated by G in the figure is the direction of gravity. Although the standing time is not limited, it can be 0.5 minutes or more and 24 hours or less. When it takes time to condense bubbles, heating or the like may be performed as in the manufacturing process in the first embodiment. When the microbubbles 119 are densely packed in the opposite direction to the protective glass 105, the monomer solution 108 is cured by irradiating with ultraviolet rays to form the second transparent resin 106 in the present invention (FIG. 4E).

  In the case of curing, ultraviolet rays are irradiated in the case of an ultraviolet curing resin. In the case of a thermosetting resin, it may be cured by an appropriate curing method using a selected resin such as curing by heating. Next, the first transparent resins 102 (A) and 102 (B) in the solar cell are applied to the protective glass 105 coated with the second transparent resin 106 containing microbubbles with a phosphor and a volume density gradient. Then, laminating is performed together with the photoelectric conversion element 101 and the back sheet 103 to which the electrode 104 is electrically joined (FIG. 4F).

  As a result, since the fluorescence emitted from the phosphor has a gradient in refractive index, a solar cell module with high power generation efficiency that reaches the photoelectric conversion element more efficiently can be obtained (FIG. 3).

  In this manufacturing process, when the monomer solution 108 is left horizontally so as to be downward, the surface on which the monomer solution 108 is not applied can be removed in a known manner so that the monomer solution 108 is not deformed by contact due to loading. It must be supported on the bottom of the fixed object with a double-sided adhesive tape or gel.

  In the present embodiment, the second transparent resin 106 is protected from contact with the atmosphere by the protective glass 105, can be prevented from being deteriorated by oxygen or water, and has excellent long-term reliability.

(Embodiment 3)
FIG. 5 is a cross-sectional view showing the structure of a solar cell module according to the third embodiment of the present invention. The difference from the first embodiment of the present invention is that it is layered due to the difference in volume density of the bubbles contained in the second transparent resin 106, and the volume density of the bubbles is closer to the light incident surface. The other points are the same as those in the first embodiment of the present invention.

  The ratio of bubbles in each layer is not limited, but in the case of acrylic resin, if it is 40% by volume in the vicinity of the light incident surface, and is smaller for each layer toward the surface opposite to the light incident surface, In terms of increasing the difference in refractive index, 0% is desirable on the surface opposite to the incident surface.

  In the solar cell module of this embodiment, at least the photoelectric conversion element 101, the first transparent resin 102 that protects the photoelectric conversion element, the back sheet 103, and the current obtained by connecting the photoelectric conversion elements to each other are obtained. The electrode 104, the protective glass 105, the phosphor and the bubble group 107 are layered due to the difference in volume density, and the volume density of the bubble group is gradually reduced toward the direction of incident light. A second transparent resin 106 is provided. The diameter of each bubble constituting the bubble group 107 is smaller than that which does not scatter the wavelength of light having high sensitivity characteristics of the photoelectric conversion element, and is smaller than 300 nm.

  Note that the phosphor in the second transparent resin 106 is not shown in FIG. As described above, the bubble group 107 in the second transparent resin 106 containing the phosphor has a structure in which the bubble volume density increases stepwise, so that the incident direction of light in the second transparent resin 106. As the refractive index decreases stepwise, the fluorescence emitted from the phosphor contained in the second transparent resin 106 is directed toward the photoelectric conversion element more than in the case where the refractive index is uniform. Efficiency can be increased.

  Although it does not limit as a manufacturing process of the 3rd Embodiment of this invention, the construction method as demonstrated below is possible, for example. FIG. 6A to FIG. 6M are schematic cross-sectional views of the respective steps showing the manufacturing process of the third embodiment of the present invention.

  As shown in FIGS. 6A to 6D, a transparent resin monomer solution 108 in which a phosphor is dissolved or dispersed in advance by a known method is passed through a glass tube 110 and is made generally reactive such as nitrogen gas. FIG. 6B to FIG. 6D in which the gas 109 which is considered to be poor is bubbled in the liquid, and FIG. 6A in which the gas 109 is not bubbled are prepared.

  At this time, in FIGS. 6B to 6D, the flow rate of the gas to be bubbled in stages is set from small to large. Alternatively, the bubbling time is from short to long, and the solubility of the gas in the liquid is stepwise from small to large.

  Thereafter, in the same manner as in the first embodiment of the present invention, but without setting a decompression treatment and a standing time for unevenly distributing bubbles, the step of dropping, applying, and curing the solution on the protective glass, First, the liquid shown in FIG.

  Then, FIG.6 (e)-FIG.6 (h) are performed, and FIG.6 (i)-FIG.6 (l) are then performed using the liquid of FIG.6 (b). Thereafter, FIG. 6 (m) shows that the same process can be performed using FIG. 6 (c). Similarly, the result of using the liquid of FIG. 6D is FIG. 6M. As a result, in FIG. 6 (m), the phosphor and the minute bubbles change in layers in a stepwise manner, and as a result, the second transparent resin 106 whose refractive index decreases stepwise in the light incident direction. be able to.

  In the manufacturing process of the present embodiment, since solutions containing different amounts of microbubbles are prepared in stages, decompression processing and standing time for unevenly distributing bubbles are not necessary, and productivity is improved. It is preferable from the viewpoint of.

  In the present embodiment, when more phosphors are blended in a layer far from the light incident surface, more of the fluorescence emitted by the phosphors goes to the photoelectric conversion element. It is more preferable. In order to achieve such a configuration, the phosphor concentration to be blended in the liquid may be sequentially reduced in FIGS. 6 (a) to 6 (d).

  In the first and second embodiments, the phosphor may be precipitated in the monomer solution and the concentration of the phosphor may be changed as described above. That is, the volume density of the phosphor is continuously or stepwise increased from the light incident surface toward the light exit surface in the second transparent resin. The definition of the volume density is the same as the volume density of the air bubbles. Conventionally, it has been difficult to control the phosphor concentration, but in the above method, it can be formed only by sedimentation and can be controlled.

  In addition, the transparent resin constituting each layer having different volume density of the bubble group is not necessarily the same in all layers. If the transparent resin having a smaller refractive index is closer to the light incident surface, the second resin The gradient of the refractive index in the transparent resin 106 is further increased, which is preferable.

  In addition, although the said description was carried out with the bubble, the same result is obtained even if it uses a glass filler instead of a bubble. The size needs to be a size that does not scatter visible light (<300 nm) and a refractive index lower than that of glass. Particles made of a transparent resin may be used. An effect similar to the above can be obtained by a method in which particles are unevenly distributed downward (as opposed to bubbles).

  As described above, the solar cell module of the present invention contains the phosphor in the transparent layer in which the refractive index changes stepwise due to the volume density gradient of the bubbles, and the sensitivity characteristic that is wavelength-converted by the phosphor. By guiding light having a high wavelength to the photoelectric conversion element more efficiently, the photoelectric conversion efficiency of the solar cell module can be improved, and industrial applicability is high.

101 Photoelectric conversion elements 102, 102a, 102b First transparent resin 103 Back sheet 104 Electrode 105 Protective glass 106 Second transparent resin 107 Bubble group 108 Monomer solution 109 Gas 110 Glass tube 119 Micro bubbles

Claims (12)

A photoelectric conversion element;
An electrode electrically connected to the photoelectric conversion element;
A first transparent resin containing the photoelectric conversion element therein;
Protective glass located on the light incident surface which is the upper surface of the first transparent resin;
A back sheet located on the lower surface of the first transparent resin;
A second transparent resin formed on the protective glass and containing a phosphor;
A solar cell module comprising a group of bubbles or a group of transparent particles contained in the second transparent resin,
In the second transparent resin, the volume density of the bubble group or the transparent particle group is increased from the light exit surface toward the light incident surface, and the volume density is the light incident surface or the It is an average volume density in the layer for every fixed thickness of said 2nd transparent resin parallel to a light-projection surface, The solar cell module characterized by the above-mentioned. The solar cell module according to claim 1, wherein the constant thickness is 250 nm. The solar cell module according to claim 1 or 2, wherein the second transparent resin is disposed on the light incident surface side of the upper surface of the protective glass. The solar cell module according to claim 1 or 2, wherein the second transparent resin is disposed on a lower surface of the protective glass. 5. The solar cell module according to claim 1, wherein a refractive index of the second transparent resin is lowered from a light emitting surface toward the light incident surface. The solar cell module according to claim 1, wherein the bubble group is an inert gas. 7. The solar cell module according to claim 1, wherein in the second transparent resin, a volume density of the phosphor increases from a light incident surface toward the light emitting surface. The solar cell module according to claim 1, wherein the phosphor is one of an inorganic phosphor, an organic phosphor, a complex phosphor, or a combination thereof. The organic phosphor is represented by the general formula of CnH2n + 2-2a-2b-4c, where a is the number of double bonds in the molecule, b is the number of rings in the molecule, and c is the number of triple bonds in the molecule. The solar cell module according to claim 8, wherein n is greater than 5 and less than 40 when it is a hydrocarbon. 10. The solar cell module according to claim 9, wherein, in the hydrocarbon, at least one or more carbon atoms are replaced with oxygen atoms, nitrogen atoms, phosphorus atoms, or sulfur atoms, and the number of hydrogens is changed accordingly. . The solar cell module according to claim 1, wherein the bubble group is an inert gas, and the phosphor is an organic phosphor. 12. The solar cell module according to claim 1, wherein a bubble diameter of the bubble group or a particle diameter of the transparent particle group is smaller than 300 nm.

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