JP2012204598A - Solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solar cell which can minimize decrease in transmittance of sunlight.SOLUTION: The see-through type solar cell transmitting at least a part of sunlight includes a photoelectric conversion layer which converts at least a part of sunlight into electricity, a front surface protective material provided on the sunlight incident side of the photoelectric conversion layer, a back surface protective material provided on the reverse side of the sunlight incident side of the photoelectric conversion layer, a first transparent conductive film layer provided between the photoelectric conversion layer and the front surface protective material, and a second transparent conductive film layer provided between the photoelectric conversion layer and the back surface protective material. An air catalyst layer which reacts on at least one of oxygen or moisture to decompose an organic matter is formed on the side of the back surface protective material opposite from the sunlight incident side.

Description

  The present invention relates to a solar cell, and more particularly, to a see-through solar cell that transmits at least part of sunlight.

  In recent years, solar cells have been widely used, and solar cells have been used in various places. For example, a solar cell that transmits sunlight of a wavelength necessary for plant growth is placed on the ceiling surface of a greenhouse that grows plants such as vegetables and fruits, and electricity generated by the solar cell is used as a power source for the greenhouse. It has been proposed (see Patent Document 1).

  Further, since the surface of the solar cell is exposed to the outside air, dust adheres and the surface becomes dirty. When the surface of the solar cell becomes dirty, the amount of power generation decreases because sunlight is blocked. In order to prevent this, it has been proposed to improve the antifouling property of the solar cell surface by applying an air catalyst (eg, titania phosphate) excellent in transparency to the surface of the solar cell (see Patent Document 2). .

JP 2010-213684 A JP 2008-205080 A

In the proposal of Patent Document 1, light necessary for plant growth is introduced into a greenhouse through a solar cell. However, in Patent Document 1, the back surface of the solar cell is in contact with the atmosphere in the greenhouse, and the ultraviolet light having a bactericidal action is the transparent electrode layer of the solar cell, the photoelectric conversion layer, and a cover glass for protecting them. It is absorbed by the back of the solar cell and does not reach the back side of the solar cell, fungi such as molds propagate on the back side of the solar cell, the back side is soiled, and the plant growth is inhibited by blocking the light necessary for plant growth. There is a risk.
In the proposal of Patent Document 2, the dirt on the back surface of the solar cell is not taken into consideration, and the air catalyst is applied to the surface of the solar cell, so that propagation of mold or the like on the back surface of the solar cell cannot be suppressed.
When a chlorinated chemical such as a disinfectant is used to remove dirt caused by the mold, the chemical may adversely affect the plant. In addition, silver (Ag) may be applied to the back surface as an antibacterial agent. However, since sunlight transmitted through the solar cell is reflected or absorbed by the silver, light necessary for growing plants in the greenhouse is blocked. And the growth of the plant will be hindered.
This invention is made | formed in response to said situation, and it aims at providing the solar cell which can suppress the fall of the transmittance | permeability of sunlight.

  The solar cell of the present invention is a see-through solar cell that transmits at least a part of sunlight, and includes a photoelectric conversion layer that converts at least a part of sunlight into electricity, and a sunlight incident side of the photoelectric conversion layer. The provided surface protective material, the back surface protective material provided on the side opposite to the sunlight incident side of the photoelectric conversion layer, and the first transparent conductive film layer provided between the photoelectric conversion layer and the surface protective material And a second transparent conductive film layer provided between the photoelectric conversion layer and the back surface protective material, and reacts with at least one of oxygen or moisture on the side opposite to the sunlight incident side of the back surface protective material. An air catalyst layer for decomposing organic substances is formed.

  ADVANTAGE OF THE INVENTION According to this invention, the solar cell which can suppress the fall of the transmittance | permeability of sunlight can be provided.

It is an external view of the greenhouse which concerns on embodiment. It is sectional drawing of the greenhouse which concerns on embodiment. It is sectional drawing of the solar cell module which concerns on embodiment. It is sectional drawing (other examples) of the solar cell module which concerns on embodiment.

  Hereinafter, details of the present invention will be described with reference to the drawings.

(Embodiment)
FIG. 1 is an external view of a greenhouse 1 according to the embodiment. FIG. 2 is a cross-sectional view of the greenhouse 1 according to the embodiment. The greenhouse 1 includes a frame 10, a base 11 that supports the frame 10, a transparent panel 12 that forms a wall surface of the greenhouse 1, a plurality of solar cell modules 13 that are disposed on the roof of the greenhouse 1 and generate power using sunlight L 1, A storage / discharge device 14 that stores electricity generated by the solar cell module 13, converts it to a desired voltage as necessary, and discharges it; and an air conditioner 15 such as a fan or an air conditioner that controls the temperature inside the greenhouse 1; And a lighting device 16 for controlling the growth and flowering cycle of plants in the greenhouse 1 and providing nighttime lighting.

  The transparent panel 12 is made of a transparent material (for example, glass or plastic) that transmits sunlight L1.

  Since the solar cell module 13 needs to introduce the light L2 necessary for plants to carry out photosynthesis into the greenhouse 1, it is preferable that the solar cell module 13 transmits a part of the sunlight L1. The installation direction of the solar cell module 13 is preferably set to the south in consideration of sunlight. The installation angle of the solar cell module 13 is preferably about 20 ° to 35 ° in Japan. The configuration of the solar cell module 13 will be described later with reference to FIG.

  The storage / discharge device 14 is a storage battery (for example, a lead storage battery, a lithium ion battery, etc.) capable of storing and discharging electricity generated by the solar cell module 13, and boosts or steps down the electricity discharged from the storage battery to a desired voltage. And a conversion circuit including a DC-DC converter that converts the direct current into an alternating current, and the like. The electricity stored in the storage battery of the storage / discharge device 14 is supplied to the air conditioning equipment 15 and the lighting device 16 as necessary.

  The illumination device 16 includes a fluorescent lamp or a light emitting diode (LED). Note that it is preferable to use a light emitting diode with high light emission efficiency from the viewpoint of suppressing power consumption.

Although not shown in FIGS. 1 and 2, a plurality of ventilation holes or ventilation windows may be provided on the wall or roof of the greenhouse 1, or an automatic watering system may be provided in the greenhouse 1. .
Moreover, as a cultivation method of a plant, it is possible to grow on the ground or a multi-layer cultivation shelf, and also in this case, a soil cultivation method, an air cultivation method, a hydroponics method, or the like can be selected.

(Solar cell module 13)
As described above, in this embodiment, it is preferable to use, as the solar cell module 13, a solar cell that transmits part of sunlight, particularly light in a wavelength band necessary for plant growth. Chlorophyll a for photosynthesis has sharp absorption bands at 430 nm (B band) and 622 nm (Q band) derived from tetrapyrrole. Accordingly, those that transmit a wavelength around 430 nm or 622 nm are preferable. As such a solar cell, a see-through solar cell in which the photoelectric conversion layer of the solar cell module 13 is very thin to about 150 nm to 600 nm is known.

  FIG. 3 is an example of a cross-sectional view of the solar cell module 13 according to the present embodiment. In FIG. 3, sectional drawing of the solar cell module 13 in the see-through type solar cell using an amorphous silicon thin film as a photoelectric converting layer was shown. Hereinafter, the configuration of the solar cell module 13 in the see-through solar cell using an amorphous silicon thin film as the photoelectric conversion layer will be described with reference to FIG.

As shown in FIG. 3, the solar cell module 13 includes a surface glass substrate 101 (surface protective material), ITO (indium oxide doped with tin) and SnO ₂ (tin oxide (II)) arranged on the sunlight incident side. ), A transparent surface electrode (transparent conductive film) 102 (first transparent conductive film layer) made of ZnO (zinc oxide) or the like, and an amorphous silicon layer 103 (photoelectric conversion layer) that converts at least part of sunlight into electricity. A transparent back electrode (transparent conductive film) 104 (second transparent conductive film layer) made of ITO, SnO ₂ , ZnO or the like disposed on the back side opposite to the sunlight incident side, and EVA (ethylene vinyl acetate) And a back surface glass substrate 106 (back surface protection material) disposed on the back surface opposite to the sunlight incident side, and a back surface protection material comprising a sealing material 105 made of a resin film such as PVB (polyvinyl butyral) That opposite to the rear surface side and the solar incident side of the back glass substrate 106 has a structure in which an air catalyst layer 107 for decomposing an organic material by at least one reaction of oxygen or moisture is formed. 3 shows an example in which the sealing agent 105 is provided between the transparent back electrode 104 and the back glass substrate 106, the sealing material 105 is not provided between the transparent back electrode 104 and the back glass substrate 106. The surface glass substrate 101 and the transparent surface electrode 102 may be provided.

(Amorphous silicon layer 103)
The amorphous silicon layer 103 is a photoelectric conversion layer having a thickness of about 150 to 600 nm. Light incident on the solar cell module 13 is converted into electricity in the amorphous silicon layer 103. The amorphous silicon layer 103 has a pin structure in which an amorphous silicon p-type layer 103a, an amorphous silicon i-type layer 103b, and an amorphous silicon n-type layer 103c are stacked.

  Note that when a microcrystalline silicon thin film solar cell is used as the photoelectric conversion layer, the amorphous silicon layer 103 illustrated in FIG. 3 is replaced with a microcrystalline silicon layer. Also in this case, the microcrystalline silicon layer has a pin structure in which a p-type layer of microcrystalline silicon, an i-type layer of microcrystalline silicon, and an n-type layer of microcrystalline silicon are stacked.

  In the see-through solar cell, since the photoelectric conversion layer is very thin, part of the incident sunlight passes through the solar cell module 13. That is, part of the sunlight is used for power generation, and the remainder passes through the solar cell module 13 and enters the greenhouse 1, so that light necessary for growth can be supplied to the plants in the greenhouse 1. it can.

  When the amount of transmitted sunlight is small, as shown in FIG. 4, a plurality of holes or slits (grooves) 103d penetrating the amorphous silicon layer 103 are provided by a laser or the like to improve the transmittance of sunlight. Also good.

  Further, the front glass substrate 101 and the back glass substrate 106 shown in FIG. 3 may be replaced with a polyimide film. By replacing the front glass substrate 101 and the back glass substrate 106 with a polyimide film, a flexible solar cell module 13 having flexibility can be obtained, and the solar cell module 13 is also disposed on a curved surface or rounded portion of the greenhouse 1. It becomes possible. Furthermore, since the solar cell module 13 is reduced in weight, the frame 10 and the base 11 that support the solar cell module 13 can be simplified, and the production cost of the greenhouse 1 can be suppressed.

(Transparent back electrode 104)
The see-through solar cell transmits sunlight that has passed through the photoelectric conversion layer to the back surface side of the solar cell module. Therefore, the back surface electrode provided on the photoelectric conversion layer lower surface, it is necessary to use an ITO or a transparent electrode material of SnO 2, _ZnO and the like. However, these transparent electrode materials transmit light in the visible light region but absorb light in the ultraviolet light region. For this reason, light in the ultraviolet region does not reach the back side of the solar cell module 13.

(Air catalyst layer 107)
The air catalyst layer 107 is formed so that fungi such as mold do not propagate on the back surface of the solar cell module 13 disposed on the roof of the greenhouse 1. As such an air catalyst, it is preferable to use titania phosphate (TiXPO ₄ ). Titania phosphate reacts with oxygen and moisture contained in the air to produce OH (hydroxide radical) and O- (superoxide anion) called active oxygen, and it is an organic matter of fungi and fungi Disassemble itself.

  As described above, since the solar cell module 13 does not transmit ultraviolet light having a bactericidal action due to the transparent electrode material, fungi such as molds propagate on the back surface of the solar cell module 13 and grow not only ultraviolet light but also plants. The necessary light will be blocked. Therefore, in the solar cell module 13 according to this embodiment, a phosphate titania layer that decomposes organic substances is formed on the back surface as the air catalyst layer 107 to suppress the growth of fungi such as mold.

In general, titania (TiO ₂ ), which is a photocatalyst, is often used as a catalyst for decomposing organic substances. However, in this embodiment, ultraviolet light is used for decomposition of organic substances because it is used on the back side where ultraviolet light does not reach. Titania that requires light cannot be used.

  In addition, titania phosphate, which is an air catalyst, does not require an organic binder (binder), and can be easily formed on the work surface (back surface of the solar cell module) by spraying or impregnation, and does not require curing. Cost can be suppressed. Further, it has advantages such as excellent washing resistance and scratch resistance, and little change in color and catalyst function over time.

  As described above, the solar cell module 13 of the greenhouse 1 according to this embodiment has a configuration in which a phosphoric titania layer that is an air catalyst is formed on the back surface, so that even on the back surface of the solar cell module 13 where ultraviolet light does not reach. The organic matter can be decomposed to suppress the growth of fungi such as mold. For this reason, it is possible to prevent fungi such as molds from propagating on the back surface of the solar cell module 13 to block the light necessary for plant growth and to reduce the transmittance of sunlight, which may hinder plant growth. Can be reduced. Moreover, there is no possibility of adversely affecting plants because it is not necessary to use a chlorinated chemical such as a disinfectant.

  DESCRIPTION OF SYMBOLS 1 ... Greenhouse, 10 ... Frame, 11 ... Base, 12 ... Transparent panel, 13 ... Solar cell module, 14 ... Storage / discharge device, 15 ... Air-conditioning equipment, 16 ... Illumination device, 101 ... Surface glass substrate (surface protection material), DESCRIPTION OF SYMBOLS 102 ... Transparent surface electrode (1st transparent conductive film layer), 103 ... Amorphous silicon layer (photoelectric conversion layer), 104 ... Transparent back surface electrode (2nd transparent conductive film layer), 105 ... Sealing material, 106 ... Back surface Glass substrate (back surface protective material), 107 ... air catalyst layer.

Claims (8)

A see-through solar cell that transmits at least part of sunlight,
A photoelectric conversion layer for converting at least part of the sunlight into electricity;
A surface protective material provided on the sunlight incident side of the photoelectric conversion layer;
A back surface protective material provided on the side opposite to the sunlight incident side of the photoelectric conversion layer;
A first transparent conductive film layer provided between the photoelectric conversion layer and the surface protective material;
A second transparent conductive film layer provided between the photoelectric conversion layer and the back surface protective material,
A solar cell, wherein an air catalyst layer that reacts with at least one of oxygen and moisture to decompose an organic substance is formed on a side opposite to the sunlight incident side of the back surface protective material.   The solar cell according to claim 1, wherein the solar cell is disposed on a roof of a greenhouse.   The solar cell according to claim 1, wherein the surface protective material and the back surface protective material are made of polyimide.   The solar cell according to claim 1, wherein the surface protective material and the back surface protective material are made of a glass substrate.   The solar cell according to any one of claims 1 to 4, wherein the photoelectric conversion layer is made of a thin film amorphous silicon having a thickness of 150 to 600 nm. The solar cell according to claim 5, wherein the second transparent conductive film layer is made of any one of ITO, SnO ₂ and ZnO.   The solar cell according to any one of claims 1 to 6, wherein a through hole or a slit that transmits at least part of the sunlight is formed in the photoelectric conversion layer.   It further includes a sealing material provided between the surface protective material and the first transparent conductive film layer or between the back surface protective material and the second transparent conductive film layer. The solar cell according to any one of claims 1 to 7.

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