JP4694892B2 - Concentrating solar cell module - Google Patents

Description

  The present invention relates to a technology of a concentrating solar cell module, and more specifically to a fixing and back electrode connection structure of a concentrating solar cell.

In recent years, development of clean energy has been demanded due to problems such as depletion of energy resources and global environmental problems such as increased CO ₂ in the atmosphere. In particular, solar power generation using solar cells has been developed and used as a new energy source. It has become. The solar power generation system is desired to be reduced in cost for further spread. The concentrating solar power generation system is promising as a system that reduces the amount of solar cells that are the most expensive components in the solar power generation system and reduces the cost of the entire system.

A conventional example of a concentrating solar cell module will be described with reference to the drawings. FIG. 10 is a schematic view of a conventional concentrating solar cell module. As shown in FIG. 10, the solar cell module is designed so that sunlight always enters the Fresnel lens 12 fixed to the sunlight incident side of the rectangular parallelepiped case 11. In order to design so that sunlight enters the Fresnel lens 12 perpendicularly, it is necessary to track the entire case 11 so that it always faces the sun. In general, two rotation shafts are provided between the case 11 and the system installation surface, and the sun tracking is performed by rotationally driving the two shafts by a motor or hydraulic drive. The solar azimuth and solar altitude are calculated from the theoretical formula of the solar orbit and the latitude, longitude and time of the installation location, and the sun tracking is performed by controlling the drive system.
FIG. 11 shows a concentrating solar cell module viewed from the Fresnel lens 12 side, and FIG. 12 shows a cross-sectional view taken along 2a-2b in FIG. Sunlight incident on the Fresnel lens 12 is collected by the Fresnel lens 12 and irradiated to the solar cells 23 installed on the support plate portion 11 a of the case 11 facing the Fresnel lens 12. Concentration magnification is several tens to several hundred times, and solar cells 23 are irradiated with sunlight having a large energy density, and the temperature of solar cells 23 rises.
Since the power generation efficiency of the solar battery cell 23 decreases as the temperature rises, a heat dissipation mechanism is necessary. In general, the support plate portion 11a is made of a material having a high thermal conductivity such as a metal, and the support plate portion 11a uses the support plate portion 11a to dissipate heat through the back surface of the solar battery cell 23. The structure which provided the fin for heat radiation is taken so that the surface area of the back side may become large. The solar cell has electrodes on the front surface and the back surface, and the back electrode is formed on substantially the entire back surface of the cell. The wiring taking out from the back electrode has a structure that also serves as the heat dissipation function described above.

In Patent Document 1, regarding solar cell fixing in a concentrating solar power generation system, a metal foil is soldered to the entire back electrode of the solar cell, the electrode is taken out by this metal foil, and the metal foil is thermally conductive. The structure which implement | achieves fixation of a photovoltaic cell and heat dissipation is adhere | attached by adhering to a seat plate with the thermal radiation layer which consists of an epoxy resin adhesive containing a filler. According to this structure, since a very thin metal foil is used, the generation of stress due to the difference in thermal expansion coefficient between the solar cell substrate and the metal foil when the back electrode and the metal foil are soldered can be reduced. . In addition, it is disclosed that the solar cell is sufficiently radiated through the metal foil, the heat dissipation layer and the seat plate, and can be secured with an epoxy resin so that durability and long-term reliability can be ensured. Yes. Further, there is a description that the width of the metal foil is preferably larger than the width of the solar battery cell for efficient heat dissipation.
JP 2003-174179 A

However, in fixing the solar battery cell of Patent Document 1, in order to join the metal foil to the entire cell back electrode, it is necessary to use a sufficient amount of solder and to apply a certain amount of pressure to the solar battery cell during solder joining, At that time, there is a problem that the solder protrudes from the back surface of the solar battery cell, adheres to the side surface of the solar battery cell due to surface tension, and leaks in the solar battery cell. Furthermore, when the width of the metal foil is increased for the purpose of improving heat dissipation characteristics, there is a problem that the solar battery leaks easily due to the protrusion of the solder.
The present invention has been made in view of the above points. In particular, the present invention relates to fixing solar cells in a concentrating solar cell module in which the temperature rise of the solar cells is a problem. It is an object of the present invention to provide a concentrating solar cell module that does not adhere to the side surface, does not cause solar cell leakage, and has sufficient heat dissipation characteristics of the solar cell.

In order to achieve the above object, the present invention provides a concentrating solar cell module case , a condensing lens disposed on an upper surface of the concentrating solar cell module case, and a concentrating surface that faces the condensing lens. Solar cell having electrodes on the front and back surfaces, respectively, disposed on the support plate of the optical solar cell module case, and disposed between the solar cell and the support plate, by the back electrode of the solar cell and the conductive paste A method for manufacturing a solar cell module, comprising: an electrode plate that is electrically joined; and a heat dissipation electrical insulating layer interposed between the electrode plate and the support plate, wherein the electrode plate includes a back surface of the solar cell. When the solar battery cell is joined to the electrode plate around the joint surface to be joined with the electrode, the conductive paste is placed outside the solar battery cell by applying pressure to the solar battery cell from above. A groove lower than the bonding surface is formed to guide the protruding conductive paste, and the solar battery cell is bonded to the bonding surface, and then, at least a part of the groove is coated with aluminum oxide or oxide on an epoxy resin or silicone resin. It is characterized by inserting a material having thermal conductivity and electrical insulation mixed with one or more of metal oxides containing magnesium and zinc oxide, boron nitride, aluminum nitride and glass fiber as additives .
In the present invention, the conductive paste is a paste containing a conductive material such as metal and carbon, and includes solder. In addition, the heat-dissipating electrical insulating layer is preferably as long as it has electrical insulating properties and high thermal conductivity, and an additive having high thermal conductivity is added to a resin having electrical insulating properties. Further, the support plate preferably has mechanical strength to support the electrode plate and has excellent thermal conductivity, and examples thereof include a metal plate.
According to this structure, even when the solar battery cell back electrode and the electrode plate are joined with the conductive paste, even if pressure is applied to the solar battery cell and the conductive paste protrudes outside the solar battery cell, the electrode is pulled by gravity. Since it is led to the lower part provided around the joint surface of the plate, it does not adhere to the side surface of the solar battery cell, and the solar battery cell does not leak. In addition, the concentrating solar cell module collects sunlight on the solar cell, so that the temperature of the solar cell rises, but when the electrode plate is joined to the solar cell, the solar cell is pressed from above. The solar cell and the electrode plate are tightly joined to each other, so that the heat generated in the solar cell can be diffused to the outside of the solar cell, and then from the electrode plate to the heat dissipating electrical insulating layer, the support Heat can be dissipated through the board. In this way, once the heat is diffused to the outside of the solar battery cell by the electrode plate, the cross-sectional area at the time of heat conduction is increased and the thermal resistance is increased in the heat dissipation electrical insulating layer having a smaller thermal conductivity than the electrode plate or the support plate. It can be reduced and the heat dissipation efficiency is improved. In addition, thermal conductivity in which one or more of metal oxide including aluminum oxide, magnesium oxide, zinc oxide, boron nitride, aluminum nitride, and glass fiber are mixed as an additive in a part of the groove with epoxy resin or silicone resin, Since a material having electrical insulation is inserted, the heat dissipation effect is improved.

In the present invention, the joint surface is constituted by a convex portion provided on the electrode plate.
According to this structure, even when the solar battery cell back electrode and the electrode plate are joined with the conductive paste, even if pressure is applied to the solar battery cell and the conductive paste protrudes outside the solar battery cell, the electrode is pulled by gravity. Since it is led to the lower part provided on the plate, it does not adhere to the side surface of the solar battery cell, and the solar battery cell does not leak.

In the present invention, the low part is constituted by a groove provided around the joint surface.
According to this structure, even when the solar battery cell back electrode and the electrode plate are joined with the conductive paste, even if pressure is applied to the solar battery cell and the conductive paste protrudes outside the solar battery cell, the electrode is pulled by gravity. Since it is led to the groove provided in the plate, it does not adhere to the side surface of the solar battery cell, and the solar battery cell does not leak.

Further, the present invention has a structure in which a material having good thermal conductivity is inserted into at least a part of the groove. A material having good thermal conductivity is an epoxy resin or silicone resin containing one or more of metal, metal oxide, carbon, glass fiber, boron nitride, and aluminum nitride, or solder.
According to this structure, since the thermal conductivity in the groove provided around the joint surface of the electrode plate with the solar cell back surface electrode is improved, the thermal conductivity characteristic in the planar direction of the electrode plate is improved, and the heat dissipation characteristic is further improved. improves.

Further, according to the present invention, the material having good thermal conductivity is an epoxy resin or a silicone resin in which aluminum oxide, magnesium oxide, metal oxide containing zinc oxide, boron nitride, and aluminum nitride are mixed as additives. It is desirable that the material has insulating properties.
According to this structure, the thermal conductivity in the groove provided around the joint surface of the electrode plate with the back surface electrode of the solar battery cell is improved, and since the material has electrical insulation, the material adheres to the side surface of the solar battery cell. However, no leakage of solar cells occurs.
In the present invention, the main material of the electrode plate is preferably a metal.
According to this configuration, the conductivity of the electrode plate is large and suitable as an electrode, and at the same time, the thermal conductivity is large. Therefore, the heat of the solar cell is diffused throughout the electrode plate, and the thermal resistance of the heat dissipation electrical insulating layer is reduced. Is possible.

In the present invention, the heat-dissipating electrical insulating layer is mainly composed of epoxy resin or silicone, and the additive is any one of metal, metal oxide, carbon, glass fiber, boron nitride, and aluminum nitride, or two of them. The above is added.
According to this configuration, it is possible to improve the thermal conductivity while maintaining the electrical insulation characteristics of the heat dissipation electrical insulation layer.
In the present invention, the main material of the support plate is preferably a metal.
According to this configuration, the support plate has a large thermal conductivity, and the heat conducted from the heat dissipation electrical insulating layer can be efficiently radiated from the other surface of the support plate.

  According to the structure of the present invention, when the solar cell back electrode and the electrode plate are joined with the conductive paste, even when the conductive paste protrudes outside the solar cell by applying pressure from above the solar cell. Since it is led to the lower part provided on the electrode plate by gravity, it does not adhere to the side surface of the solar battery cell, and leakage of the solar battery cell can be prevented.

Hereinafter, an embodiment according to the first aspect of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a concentrating solar cell module according to an embodiment of the present invention. One end surface of the rectangular parallelepiped case 11 is open, and the non-imaging Fresnel lens 12 is fixed to the opening. As the material of the case 11, aluminum that is lightweight and has good thermal conductivity is suitable. However, a stainless plate, a steel plate, or a steel plate plated with an alloy such as zinc, aluminum, or silicon may be used. Further, examples of the material of the Fresnel lens 12 include translucent materials such as acrylic resin, polycarbonate, UV curable resin, and glass.
In FIG. 1, a solar battery cell 23 is fixed to a support plate portion 11 a which is a surface facing the Fresnel lens 12 of the case 11, and sunlight condensed by the Fresnel lens 12 is irradiated. The concentration factor of sunlight is about 700 times at maximum. As the solar cell 23, an inorganic solar cell made of Si, GaAs, CuInGaSe, CdTe, or the like, or an organic solar cell such as a dye-sensitized solar cell is used, and the solar cell has a single structure. A junction type cell, a monolithic multi-junction type cell, a mechanical stack cell in which various solar cells having different sensitivity regions are connected, and the like are used.

FIG. 2 is an enlarged view of a portion where the solar battery cell 23 is fixed to the support plate portion 11a. A structure in which a heat-dissipating electrical insulating layer 41 made of a material having electrical insulation and high thermal conductivity is provided on the upper surface of the support plate portion 11a that fixes the solar battery cell 23, and is in contact with the lower surface of the electrode plate 42 on the upper side To do. As the material of the heat-dissipating electrical insulation layer, the main agent such as epoxy resin, silicone resin, etc., and metal such as gold, silver, copper, aluminum, magnesium, iron and stainless steel, and metal such as aluminum oxide, magnesium oxide and zinc oxide as additives A mixture of at least one of oxide, boron nitride, aluminum nitride, carbon and the like is used. The thermal conductivity of the heat radiation insulating layer can be adjusted by the material or ratio of the main agent and the additive. However, in order to have sufficient electrical insulation in this embodiment, the thermal conductivity is 10 W / m · K at the maximum. However, it is even lower when long-term weather resistance is considered.
A convex portion 42a is provided on the upper surface of the electrode plate 42 as shown in the figure. A joint surface 42 b is provided on the top of the convex portion 42 a, and the shape of the joint surface 42 b is the same as the outer periphery of the solar battery cell 23, but may be smaller than the solar battery cell 23. The cross-sectional shape of the convex part 42a should just be a shape which inclines below toward the flat surface from the outer periphery of the joint surface 42b and the joint surface 42b. The shape of the inclined portion may be a shape combining only straight lines, a shape combining only arcs, or a shape combining them. A low portion 42e is provided around the joint surface 42b and may be lower than the joint surface 42b. The electrode plate 42 is preferably made mainly of a metal or alloy having a high thermal conductivity. For example, it can be a simple metal such as gold, silver, copper, aluminum, magnesium, iron, nickel, tin, stainless steel, or an alloy thereof.

  The back electrode of the solar battery cell 23 is fixed to the joint surface 42 b of the electrode plate 42 with the conductive paste 43 so that the joint surface 42 b does not protrude outside the solar battery cell 23. Examples of the conductive paste include a material containing one or more of metals such as gold, silver, copper, aluminum, magnesium, iron, nickel, tin, and stainless steel, or an organic material, or solder. The solar battery cells are fixed by firing or brazing the conductive paste. At this time, it is desirable to hold the joining surface 42b of the electrode plate substantially horizontally.

  With the above structure, when the back electrode of the solar battery cell 23 and the joint surface 42b of the electrode plate 42 are joined by the conductive paste 43, the conductive paste 43a is applied by applying pressure to the solar battery cell 23 from above. Even if it protrudes to the outside of the solar battery cell, it is guided toward the electrode plate 42 along the side face 42c of the electrode plate protrusion by gravity, so that it does not adhere to the solar battery side face 23a, and the solar battery leaks. Can be prevented.

  Moreover, since the sunlight condensed by the Fresnel lens 12 is irradiated to the solar cells, the temperature of the solar cells rises, but the heat generated in the solar cells by the metal electrode plate having the above structure. Can be diffused in the outward direction of the solar battery cell, and thereafter, heat can be radiated from the electrode plate through the heat dissipation electrical insulating layer and the support plate. By once diffusing heat to the outside of the solar cell with the electrode plate, the heat conduction of the heat dissipation electrical insulation layer with a small thermal conductivity compared to the electrode plate or support plate can be increased and the thermal resistance can be reduced. , Heat dissipation efficiency is improved.

  The extraction of the solar cell current from the surface electrode to the outside is performed by patterning a metal foil such as gold, silver, copper, and tin on an electrical insulating layer such as acrylic, nylon, PET, polyimide provided on the upper surface of the electrode plate, The metal foil is spot welded to the solar cell surface electrode. The surface of the solar cell and the metal foil electrode are laminated with a translucent resin or the like to improve the weather resistance. Laminating materials include polyethylene resin film such as polyethylene tetrafluoroethylene, polytrifluoride ethylene, polyvinyl fluoride, ethylene vinyl acetate copolymer (EVA) resin, butyral resin, silicone resin, epoxy resin, fluorinated polyimide Transparent resins such as resin, acrylic resin, and PET can be used.

  An embodiment according to the second aspect of the present invention will be described with reference to FIG. The embodiment of the second invention has the same overall configuration as the first invention, but the shape of the electrode plate 42 is different. FIG. 3 is an enlarged cross-sectional view of a solar battery cell fixing portion. A groove 42d was provided around the joint surface of the electrode plate 42 with the solar battery cell, and the cross-sectional shape thereof was an arc shape. The cross-sectional shape of the groove 42d is not limited to the arc shape, and may be a shape combining straight lines, a shape combining arcs, or a combination of both. The groove 42d constitutes a low portion 42e. Even when the conductive paste protrudes to the outside of the solar cell by applying pressure to the solar cell from above when joining the back electrode of the solar cell and the electrode plate with the conductive paste. The solar cell is not leaked without being guided to the groove 42d by gravity and adhering to the side surface of the solar cell.

  Furthermore, in the structure, the thermal conductivity in the planar direction of the electrode plate, which has been lowered by providing the groove 42d, can be improved by inserting a material having good thermal conductivity into the groove 42d. Materials with good thermal conductivity include epoxy resin or silicone resin, metal such as gold, silver, copper, aluminum, magnesium, iron, stainless steel, metal oxide such as aluminum oxide, magnesium oxide, zinc oxide, boron nitride, A mixture of one or more of aluminum nitride, carbon, or the like, or solder can be used. More preferably, an epoxy resin or a silicone resin to which a metal oxide such as magnesium oxide or zinc oxide, a fine powder having high conductivity without conductivity such as boron nitride or aluminum nitride is added is used. By using the material which does not have electroconductivity, even when they adhere to the side surface of the solar battery cell, cell leak of the solar battery device can be prevented. The material having a good thermal conductivity has a thermal conductivity substantially equal to that of the heat dissipation insulating layer. With this structure, the heat dissipated from the back surface of the solar battery cell easily diffuses the electrode plate in the plane direction, and the heat dissipation characteristics are improved.

In the present embodiment, an example in which only one set of the light collecting means and the solar battery cell is provided in the case is shown, but a plurality of them may be provided in one case. If the case is enlarged, a larger number of solar cells can be installed.
Moreover, in the structure which provided the groove | channel around the photovoltaic cell junction part of the electrode plate, the planes of parts other than the said groove | channel do not need to be in the same plane. When the electrode plate is grooved, the planes of the portions other than the groove are in the same plane, but there is an advantage that the processing becomes easy.

Embodiment 1 of the present invention will be described below with reference to the drawings. The basic configuration is the same as in FIGS. One end face of a case 11 made of aluminum having a rectangular parallelepiped shape is opened, and a non-imaging Fresnel lens 12 made of acrylic resin is fixed to the opening by an epoxy resin adhesive. The external shape of the Fresnel lens 12 was 200 mm × 200 mm, the thickness was 2 mm, and the focal length was 200 mm. The outer shape of the case 11 was 200 mm × 200 mm × 190 mm, and the thickness was 3 mm. A solar battery cell 23 is fixed to a surface (supporting plate portion) 11 a facing the Fresnel lens 12 of the case 11, and sunlight condensed by the Fresnel lens 12 is irradiated.
With this configuration, when the collected light is set to strike the entire surface of the solar battery cell, the light collection magnification is about 300 times. As the solar cell 23, an InGaP / InGaAs / Ge three-junction compound solar cell was used. The thickness of the support plate part 11a was 3 mm. On the upper surface of the support plate portion 11a, a heat-dissipating electrical insulating layer 41 containing an epoxy resin adhesive as a main component and containing aluminum oxide as an additive was provided and adhered to the lower surface of the upper electrode plate. The heat dissipation electric insulation layer 41 had a thermal conductivity of 1.0 W / m · K and a thickness of 0.2 mm. The maximum thickness of the electrode plate 42 was 2 mm, and a convex portion 42a was provided on the upper surface of the electrode plate as shown in the figure. The level difference of the convex part 42a was 1 mm. The thickness of the electrode plate 42 may be a thickness that allows sufficient heat diffusion in the direction of the electrode plate surface. The shape of the electrode plate, the thermal conductivity, the amount of heat generated from the solar cells, the solar cell set temperature, Although it is determined in consideration of weight, in the embodiment of the present invention, it may be in the range of about 0.5 mm to 10 mm.

  FIG. 4 is a view of the electrode plate 42 as viewed from above. The outer shape of the electrode plate 42 is a square of 50 mm × 50 mm, but is not limited to this shape, and may be a polygon, a circular arc, or a combination thereof. The outer size of the electrode plate 42 is preferably as large as possible from the viewpoint of heat dissipation characteristics, but is set to several tens of mm in the embodiment of the present invention because of the weight reduction of the module. The shape of the joint surface 42b was 10 mm square, the same size as the solar cell size.

  The electrode plate 42 is preferably made of a metal having a high thermal conductivity, and copper is used in this embodiment. The shape of the joint surface 42 b at the top of the convex portion was the same as the outer periphery of the solar battery cell 23. The back electrode of the solar battery cell 23 was fixed to the joint surface 42b by soldering, and the joint surface 42b was fixed so as not to protrude from the outer periphery of the solar battery cell 23. The size of the solar cell used was 10 mm square. The shape of the solar battery cell is generally rectangular from the viewpoint of ease of processing and effective utilization of materials, but may be circular, elliptical, polygonal, or the like. Further, the size of the solar battery cell is determined from the size of the Fresnel lens and a desired condensing magnification, and may be any size.

The size and material of the support plate, the heat dissipation electric insulation layer, the electrode plate, and the solar battery cell are determined from the desired values of the incident light energy and the solar cell temperature to the solar battery cell, and the three-dimensional heat dissipation simulation software (COSMOSDesignSTAR4.0). Determined by. In this embodiment, the direct solar radiation energy received by the Fresnel lens surface is 850 W / m ^2, and the amount of energy obtained by removing the solar cell power generation energy from the amount of energy calculated from the area of the Fresnel lens is given to the solar cell surface. As a simulation. Moreover, the atmospheric temperature of the back surface of the support plate was assumed to be convection at 25 ° C., and the solar battery cell temperature was designed to be about 65 ° C.

A method for manufacturing an InGaP / InGaAs / Ge three-junction compound solar cell used in this example will be described below. FIG. 5 shows the structure of the three-junction compound solar cell used in this example. In order to fabricate the three-junction compound solar cell, a p-type Ge substrate having a diameter of about 50 mm and a thickness of 150 μm is put into a vertical MOCVD apparatus, and the layer structure is sequentially epitaxially grown.
First, the n ⁺ -type InGaAs [Si] layer was formed as a buffer layer 73 on the p-type Ge substrate upper surface doped with Ga, the n ⁺ -type InGaAs [Si] n-type by As is diffused into the Ge substrate the layer Ge A layer is formed. Through this process, the Ge bottom cell 72 is formed.

Then, an n ⁺⁺ type InGaP [Si] layer is formed as a tunnel junction layer 74 on the n ⁺ type InGaAs [Si] layer, and a p ⁺⁺ type AlGaAs [C] layer is formed on the n ⁺⁺ type InGaP [Si] layer. Then, an InGaAs middle cell 75 is formed on the p ⁺⁺ type AlGaAs [C] layer. [Si] and [C] indicate impurities for n-type or p-type doping, and will be described in the same manner.
Below, the formation process of the InGaAs middle cell 75 is demonstrated. A p ⁺ type InGaP [Zn] layer is formed on the p ⁺⁺ type AlGaAs [C] layer, a p type InGaAs [Zn] layer is formed on the p ⁺ type InGaP [Zn] layer, and the p type InGaAs An n ⁺ type InGaAs [Si] layer is formed on the [Zn] layer, and an n ⁺ type AlInP [Si] layer is formed on the n ⁺ type InGaAs [Si] layer. By this process, an InGaAs middle cell 75 is formed.

Subsequently, an n ⁺⁺ type InGaP [Si] layer is formed on the n ⁺ type AlInP [Si] layer, and a p ⁺⁺ type AlGaAs [C] layer is formed on the n ⁺⁺ type InGaP [Si] layer. As a result, the tunnel junction layer 76 is formed. An InGaP top cell 77 is formed on the p ⁺⁺ type AlGaAs [C] layer.
Below, the formation process of the InGaP top cell 77 is demonstrated. A p-type AlInP [Zn] layer is formed on the p ^++- type AlGaAs [C] layer, a p-type InGaP [Zn] layer is formed on the p-type AlInP [Zn] layer, and the p-type InGaP [Zn] is formed. ] the n ⁺ InGaP [Si] layer is formed on the layer to form an n ⁺ AlInP [Si] layer on the n ⁺ InGaP [Si] layer. By this step, the InGaP top cell 77 is formed.

Subsequently, an n ⁺ InGaAs layer is formed as a cap layer 79 on the n ⁺ AlInP [Si] layer.
In the epitaxial growth described above, the growth temperature is 700 ° C. In the InGaAs layer formation, trimethylindium (TMI), trimethylgallium (TMG) and arsine (AsH ₃ ) were used as raw materials. In the InGaP layer formation, TMI, TMG and phosphine (PH ₃ ) were used as raw materials. In forming the AlGaAs layer, trimethylaluminum (TMA), TMG, and AsH ₃ were used. Further, TMA, TMI, and PH ₃ were used in forming the AlInP layer.

In the InGaAs, InGaP and AlInP layers, monosilane (SiH ₄ ) was used as an impurity for n-type doping, and diethylzinc (DEZn) was used as an impurity for p-type doping.
Carbon tetrabromide (CBr ₄ ) was used as an impurity for p-type doping of the AlGaAs layer of the tunnel junction layer.

After the solar cell structure is formed by epitaxial growth using the MOCVD method, a resist pattern is formed on the surface electrode pattern on the surface of the solar cell by photolithography. A layer made of Au containing 12% Ge is formed on a resist-formed substrate by resistance heating vapor deposition. The thickness of the Au layer was 100 nm. Next, a Ni layer and an Au layer are formed on the Au layer with thicknesses of about 20 nm and about 5000 nm, respectively, by EB vapor deposition. Thereafter, the surface electrode 80 having a desired pattern is formed by a lift-off method.
Next, using the surface electrode 80 as a mask, the cap layer n ⁺ InGaAs layer where the mask is not formed is etched with an alkaline aqueous solution.
Subsequently, a resist having a mesa etching pattern region formed thereon is formed on the surface of the solar cell by photolithography, and the epitaxial layer in the region where the resist is not formed is etched with an alkaline aqueous solution and an acid aqueous solution to form a Ge substrate. To expose.

Next, an Ag layer is formed as a back electrode 71 with a thickness of about 1000 nm on the back surface of the solar cell by EB vapor deposition. Thereafter, a TiO ₂ film and an Al ₂ O ₃ film are formed on the surface of the solar cell as an antireflection film 78 with a thickness of about 50 nm and about 85 nm by EB vapor deposition.
Subsequently, a heat treatment is performed at 380 ° C. in a nitrogen atmosphere for both the sintering of the front electrode and the annealing of the back electrode 71 and the antireflection film 78. Thereafter, the cell is cut by dicing on the mesa etching line. In this example, the cell size was 10 mm × 10 mm.
The top cell, middle cell and bottom cell are electrically connected in series, and each absorption wavelength band is different from 300 to 600 nm, 600 to 900 nm, 900 to 1800 nm, and can absorb sunlight in a wide wavelength range, so high conversion efficiency Is obtained.

For the soldering of the solar battery cell and the electrode plate, the electrode plate was placed on a hot plate installed substantially horizontally, and the temperature was maintained at 190 ° C. Subsequently, solder was placed on the flat surface of the electrode plate and melted, and the solar cell was pressed from above with a pressure of 1 kgf / cm ² . At this time, when preform solder is used, the back surface electrode of the solar battery and the flat portion of the electrode plate can be joined over the entire surface, and the protrusion of the solder to the outside of the solar battery cell can be minimized. Thereafter, while maintaining the pressure on the solar cell, it was naturally cooled to room temperature together with the electrode plate, and the solar cell and the electrode plate were joined. FIG. 6 shows a cross-sectional view after the solar battery cell 23 is soldered to the electrode plate bonding surface 42b. By applying pressure to the solar battery cell 23, the solder protrudes to the outside of the solar battery, but since the solder falls to the electrode plate side along the convex side surface 42 c of the electrode plate 42, the solder adheres to the solar battery cell side surface 23 a. Without leaking solar cells. In particular, in order to improve cell characteristics by reducing the series resistance of solar cells, or to reduce costs by reducing the amount of substrate material, the thickness of the solar cell substrate is reduced. Is liable to cause a phenomenon that solder adheres to the side surface of the solar battery cell, and easily deteriorates cell characteristics. According to the structure of this embodiment, the solar battery cell can be soldered without causing the above-described problems.

For taking out the surface electrode of the solar cell, an electric insulating layer was provided on an electrode plate using a polyimide film having a thickness of 25 μm, a silver ribbon was placed on the electric insulating layer, and the surface electrode and the silver ribbon were joined by spot welding. Thus, after taking out an electrode, the solar cell on an electrode plate was sealed with the translucent epoxy resin. The sealing material only needs to be a translucent material. In this structure, since the heat dissipation effect from the back surface of the solar cell is large, the sealing material does not need a heat dissipation function, that is, thermal conductivity, and more transparent. There is an advantage that a resin excellent in light resistance and weather resistance can be used.
After fixing and sealing the solar battery cell on the electrode plate in the above-described process, the back surface of the electrode plate was fixed to the support plate via the heat dissipation electrical insulating layer. The heat-dissipating electrical insulating layer was obtained by adding aluminum oxide to an epoxy resin adhesive and having a thermal conductivity of 1.0 W / m · K.

With this structure, the heat generated in the solar cell part diffuses in the direction of the electrode plate surface, that is, toward the outside of the solar cell through the electrode plate soldered to the back electrode, and then to the outside air through the heat-dissipating electrical insulating layer and the support plate. It is possible to dissipate heat. By increasing the area of the electrode plate, the conduction cross-sectional area of the heat-dissipating electrical insulating layer portion having a smaller thermal conductivity than that of the electrode plate is increased, and it is possible to reduce the thermal resistance when radiating heat. Heat dissipation characteristics can be secured.
In the above structure, when sunlight of 850 W / m ² was actually condensed and applied to the solar cell, the solar cell back surface temperature could be suppressed to about 65 ° C.
In addition, when the entire surface of the solar cell back electrode is fixed to the metal plate by soldering, the cell is stressed due to the difference in thermal expansion coefficient, and there are concerns about problems such as cell cracking or deterioration of cell characteristics. The structure was subjected to a thermal cycle test from liquid nitrogen temperature (−about 195 ° C.) to 120 ° C., and as a result, problems such as cell cracking and characteristic deterioration did not occur even in 30 cycles.

  Embodiment 2 of the present invention will be described below with reference to the drawings. The basic structure is the same as in Example 1, and the shape of the electrode plate is different. FIG. 3 is an enlarged view of a portion where solar cells are fixed to the case. As shown in FIG. 3, the groove 42d was provided on the surface of the electrode plate 42 having a thickness of 2 mm so as to be positioned around the bonding surface 42b. The cross-sectional shape of the groove 42d was an arc shape having a radius of 1 mm, and the solar battery cell was structured to be joined to the electrode plate only by the joining surface 42b.

  FIG. 7 is a view of the electrode plate 42 as viewed from above. A dotted line shows the position where the outer periphery of the photovoltaic cell 23 is installed. The groove 42d was provided along the outer periphery of the solar battery cell 23 so that the end of the groove 42d hitting the inner side of the solar battery cell was 0.5 mm inside from the outer periphery of the rear surface of the solar battery cell. With this configuration, the size of the joint surface 42b of the electrode plate 42 with the solar battery cell is 1 mm smaller than the solar battery cell size, but the size of the joint surface 42b may be equal to or smaller than the solar battery cell size.

Further, the groove 42d is provided at least around the bonding surface 42b when viewed from the upper surface of the electrode plate. Grooves may be provided in other portions for ease of processing. For example, in order to provide a groove in the groove 42d shown in FIG. 7, the groove may be processed from one side of the electrode plate to the opposite side.
The back surface electrode of the solar battery cell was fixed by soldering to the joining surface 42b surrounded by the groove 42d by the same method as in Example 1.

  The structure of this example was also determined by three-dimensional heat radiation simulation software as in Example 1. In this example, the conditions such as irradiation energy were the same as those in Example 1, and the solar cell temperature was designed to be about 63 ° C.

FIG. 8 shows a cross-sectional view when the solar battery cell 23 is soldered to the electrode plate bonding surface 42b. As in the case of Example 1, when pressure is applied to the solar battery cell 23 from above, the solder protrudes to the outside of the solar battery, but the solder 43a is guided to the electrode plate side along the groove 42d of the electrode plate 42. The solder does not adhere to the solar cell side surface 23a, and the solar cell does not leak. According to the structure of the present embodiment, the solder does not adhere to the side surface of the solar battery cell as in the case of the first embodiment. Therefore, the problem of the solar battery cell leak does not occur, and the electrode plate and the solar battery are not deteriorated. Battery cells can be soldered.
The solar cell surface electrode was taken out and laminated in the same structure as in Example 1.
In the above structure, when sunlight of 850 W / m ² was actually condensed and applied to the solar cell, the solar cell back surface temperature could be suppressed to about 63 ° C.
Further, as a result of the same temperature cycle test as in Example 1, there were no problems such as cell cracking and characteristic deterioration.

  Embodiment 3 of the present invention will be described below with reference to the drawings. FIG. 9 is an enlarged view of a portion where solar cells are fixed to the electrode plate. The basic structure is the same as that of Example 2. After fixing the solar cell to the electrode plate by the method of Example 2, a material 44 with good thermal conductivity is placed in the groove 42d provided on the upper surface of the electrode plate 42. Added. As the material 44 having good thermal conductivity, a material obtained by dispersing magnesium oxide in an epoxy resin was used. The thermal conductivity in this case is 5.0 W / m · K. Other materials with good thermal conductivity include epoxy resin, silicone resin, metal oxides such as gold, silver, copper, aluminum, magnesium, iron, stainless steel, and metal oxides such as aluminum oxide, magnesium oxide, and zinc oxide. A mixture of at least one of a material, boron nitride, aluminum nitride, carbon and the like can be used. More preferably, those additives that do not have electrical conductivity are preferred. The conductive additive may cause cell leakage when adhering to the side surface of the solar battery cell, and may deteriorate the solar cell characteristics.

In the above structure, when sunlight of 850 W / m ² was actually condensed and applied to the solar cell, the solar cell back surface temperature could be suppressed to about 60 ° C.
Further, as a result of the same temperature cycle test as in Example 2, there were no problems such as cell cracking and characteristic deterioration.

It is sectional drawing of the concentrating solar cell module which concerns on embodiment of this invention. It is an expanded sectional view of the photovoltaic cell fixed part which concerns on embodiment of this invention 1st invention. It is an expanded sectional view of the photovoltaic cell fixed part which concerns on embodiment of this invention 2nd invention. It is the figure which looked at the electrode plate which concerns on Example 1 of this invention from upper direction. It is a figure which shows the structure of the compound solar cell used in the Example of this invention. 3 is an enlarged cross-sectional view of a solar cell fixing portion according to Example 1. FIG. It is the figure which looked at the electrode plate which concerns on Example 2 of this invention from upper direction. 6 is an enlarged cross-sectional view of a solar cell fixing portion according to Example 2. FIG. 6 is an enlarged cross-sectional view of a solar cell fixing portion according to Example 3. FIG. It is the schematic which shows the conventional concentrating solar cell module. A concentrating solar cell module viewed from the Fresnel lens side. It is sectional drawing cut | disconnected by 2a-2b of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Case 12 Fresnel lens 11a Support plate part 23 Solar cell 23a Solar cell side surface 41 Radiation electrical insulation layer 42 Electrode plate 42a Electrode plate convex portion 42b Electrode plate joint surface 42c Electrode plate convex side surface 42d Electrode plate Groove 42e provided in the lower portion 43 conductive paste 43a protruding conductive paste 44 material with good thermal conductivity 71 back electrode 72 bottom cell 73 buffer layer 74 tunnel junction layer 75 middle cell 76 tunnel junction layer 77 top cell 78 antireflection film 79 Cap layer 80 Surface electrode

Claims (6)

A concentrating solar cell module case;
A condensing lens disposed on the upper surface of the concentrating solar cell module case;
Solar cells having electrodes on the front and back surfaces, respectively, disposed on a support plate of a concentrating solar cell module case that is a surface facing the condensing lens,
An electrode plate disposed between the solar cell and the support plate, and electrically joined by a back surface electrode of the solar cell and a conductive paste;
A heat-dissipating electrical insulating layer interposed between the electrode plate and the support plate;
A solar cell module manufacturing method comprising:
When the solar battery cell is joined to the electrode plate around the joint surface to be joined to the back electrode of the solar battery cell, the conductive paste is applied to the electrode plate by applying pressure to the solar battery cell from above. A groove lower than the bonding surface is formed to guide the conductive paste protruding outside the solar battery cell, and the solar battery cell is bonded to the bonding surface, and then an epoxy resin or silicone is formed on at least a part of the groove. It is characterized by inserting a material having thermal conductivity and electrical insulation mixed with one or more of metal oxide including aluminum oxide, magnesium oxide, zinc oxide, boron nitride, aluminum nitride, and glass fiber as an additive. A method for manufacturing a concentrating solar cell module. The method for manufacturing a concentrating solar cell module according to claim 1, wherein the joint surface is a protrusion provided on the electrode plate. The method for manufacturing a concentrating solar cell module according to claim 1, wherein the bottom is a groove provided in the electrode plate. The method for manufacturing a concentrating solar cell module according to any one of claims 1 to 3, wherein the electrode plate is mainly made of metal. Claims wherein the heat dissipating electrical insulating layer is an epoxy resin or a silicone resin as a main material, a metal as an additive, a metal oxide, carbon, glass fibers, characterized in that the boron nitride, one or more of aluminum nitride is added Item 5. The method for producing a concentrating solar cell module according to any one of Items 1 to 4 . The method for manufacturing a concentrating solar cell module according to any one of claims 1 to 5, wherein the support plate is mainly made of metal.

Images