JP4339238B2 - See-through photoelectric conversion device and building material using the same - Google Patents

Description

  The present invention relates to a photoelectric conversion device, and more particularly to a see-through photoelectric conversion device having functions of power generation and daylighting and a building material using the same.

  In recent years, the spread of solar power generation systems that convert solar energy into electric energy has been rapidly expanding due to increasing awareness of the environment and lowering the price of the system. The main forms of solar cell modules (photoelectric conversion devices) for photovoltaic power generation systems that are currently in widespread use are roughly divided into the following two types.

  That is, the form of a crystalline solar cell module constituted by connecting a plurality of bulk crystal solar cells, such as single crystal silicon and polycrystalline silicon, and amorphous silicon and microcrystalline silicon. It is a form of a thin film solar cell module in which a photoelectric conversion layer is formed as a thin film on a substrate. In order to increase the amount of power generation per unit area, the former crystalline solar cell module is usually modularized by arranging crystal solar cells without gaps and sealing them with glass. By arranging it, a see-through module having optical transparency can be obtained.

  As a typical structure of the latter thin film solar cell module, there are two types, a substrate type and a superstrate type. As shown in FIG. 4A, a general substrate type structure has a back electrode layer 102, a photoelectric conversion layer 103, a transparent conductive layer 104, and a grid electrode 105 on an opaque substrate 101. They are stacked in this order. In this case, the grid electrode 105 side is the light incident surface.

  On the other hand, in the super straight type structure, as shown in FIG. 4B, a transparent conductive layer 107, a photoelectric conversion layer 108, and a back electrode layer 109 are laminated in this order on a translucent substrate 106. ing. In this case, the light transmissive substrate 106 side is the light incident surface.

  In general, since the substrate of the superstrate type is a translucent substrate 106 unlike the substrate type, the translucent substrate can be obtained by increasing the light transmittance of the photoelectric conversion layer 108 and the back electrode layer 109. Part of the light incident on the thin film solar cell module from the 106 side (light incident surface side) can be transmitted through the back electrode layer 109 to the back side of the thin film solar cell module.

  In the substrate type shown in FIG. 4A, a light-transmitting substrate is used instead of the light-impermeable substrate 101, or an opening for transmitting light is formed in the light-impermeable substrate 101. As a result, a light-transmitting thin film solar cell module can be manufactured. A thin film solar cell module in which light is transmitted to the back side of the thin film solar cell module in this way is referred to as a see-through thin film solar cell module.

  As described above, as a means for increasing the light transmittance of the photoelectric conversion layer and the back electrode layer, the transparent conductive layer, the photoelectric conversion layer, and the back electrode layer are laminated in this order on the translucent substrate, and the photoelectric conversion layer There is also known a see-through thin film solar cell module in which a plurality of through holes and grooves are formed in the back electrode layer and light transmission through the through holes and grooves is utilized. Such see-through crystal solar cell modules and see-through thin film solar cell modules have both functions of power generation and daylighting.

  Further, in Patent Document 1, as shown in FIG. 5, a transparent front electrode layer 111, a photoelectric conversion unit layer 112, and a back electrode layer 113 are respectively formed on at least a part of the back surface region of the translucent substrate 110. A see-through type thin film solar cell module having an integrated solar cell structure in which a plurality of thin film solar cell unit cells are integrated is disclosed. In addition, the back surface of each thin film solar cell unit cell is sealed with a transparent film 116 via an adhesive layer 115.

  And in at least a part of the structure of the integrated solar cell module, the transparent front electrode layer 111 is exposed to constitute a light transmission window portion (see-through portion) 114, and the exposed transparent front electrode layer 111 is In the structure of the integrated see-through type thin film thin film solar cell module, the flow of electricity between the thin film solar cell unit cells is ensured. The see-through thin film solar cell module described in Patent Document 1 can be manufactured by a simple method and has an advantage that the light transmission window 114 can be formed in an arbitrary pattern.

  In the above description, the case where the see-through type thin film solar cell module (see-through type photoelectric conversion device) is viewed from the aspect of the power generation device has been described. On the other hand, the case where the see-through thin film solar cell module is viewed from the side of building materials will be described below.

  The see-through thin film solar cell module is useful in applications that require harmony with architectural design, such as windows and walls of buildings. In particular, in recent years, there has been an increase in architectural designs in which some or all of the outer walls (entire surface) are covered with glass in office buildings and the like. By using a see-through type thin-film solar cell module instead of glass as a building material in such an architectural design, the entire wall of the building can be used for power generation, and at the same time a comfortable office as an appropriate light-shielding window An environment can be created.

  In this way, when see-through type thin-film solar cell modules are viewed from the side of building materials, as with standard glass building materials, vibration-proofing, soundproofing, heat insulation, fire resistance, and ultraviolet light shielding, etc. Various functions are required.

  In addition to these various functions, a shielding property (electromagnetic wave shield) against electromagnetic waves is mentioned as a function that is newly required for building materials in recent years. In recent years, in order to cope with malfunction of OA equipment and deterioration of electromagnetic environment of communication means such as a mobile phone, the demand for electromagnetic shielding of building materials has increased.

  In particular, with the establishment of IEEE802.11b, an international standard for wireless LANs with a frequency of 2.4 GHz in 1999, the widespread use of wireless LANs, and from a different aspect such as improving communication quality and information security. The importance of electromagnetic shielding has further increased.

  Furthermore, the use location of IEEE802.11a, which is a wireless LAN standard with a frequency of 5 GHz, was limited at first. Yes. In addition, for the high frequency 19 GHz band, a domestic standard for high speed communication of 25 Mbps called RCR STD-34 has recently been formulated, while for the 60 GHz band, a domestic standard for high speed communication of 156 Mbps or higher called ARIB STD-T74 has recently been established. Has been. Therefore, it is expected that wireless communication devices using these bands will increase in the future.

  Hereinafter, the electromagnetic wave shield that has become more important with the spread of the wireless LAN will be described in more detail.

  The IEEE802.11b compliant wireless LAN and bluetooth communication (hereinafter collectively referred to as “wireless LAN”) is limited to a band of 2.4 GHz to 2.497 GHz which is called an ISM band (Industrial Scientific Medical Band). Has been. The band is a band already shared by many systems such as amateur radio, microwave oven, VICS (Vehicle Information and Communication System), and mobile satellite communication. Likely to happen.

  Therefore, for users who use a wireless LAN indoors, radio waves in the ISM band other than the wireless LAN enter the indoors from the outside in order to improve the transmission speed of wireless LAN mutual communication and the stability of the connection. It is necessary to prevent.

  In addition, with respect to high frequency bands other than the already crowded band such as the ISM band, it is considered that the problem of interference between wireless LAN communications increases with the spread of wireless LAN in the future. For example, in modern office environments, there are often situations where two or more different wireless LAN communication segments are in close proximity. The electromagnetic wave shield is useful for preventing different wireless LAN communication segments using the same frequency band from interfering with each other.

  Also, in wireless LANs, information security is unavoidably unavoidable due to external leakage of radio waves. Therefore, physically shielding radio wave leakage from indoor to outdoor in wireless LAN communication is a very useful means for improving the security of the LAN environment.

As described above, building materials having electromagnetic shielding properties can separate indoors and outdoors from the viewpoint of electromagnetic wave propagation, thus preventing leakage of unnecessary radio waves from indoors to the outdoors and intrusion of unnecessary radio waves from the outdoors to the indoors. Thus, the indoor wireless communication environment can be improved.
JP 2002-299663 A (published on October 11, 2002)

  However, the above-described conventional photoelectric conversion device has a problem that it is difficult to provide high electromagnetic shielding properties without reducing power generation efficiency.

  This problem will be described with reference to an example of a see-through thin film solar cell module shown in Patent Document 1. In general, in order to have high shielding properties, it is necessary to have high conductivity over the entire surface of the see-through thin film solar cell module. However, in the light transmission window 114 shown in FIG. 5, the conductive layer is one layer of the transparent front electrode layer 111, and the conductivity of the transparent conductive film used for the transparent front electrode layer 111 is compared with that of metal or the like. Then, since it is low, the electromagnetic wave shielding property is not high.

  Therefore, it is conceivable to improve the overall conductivity including the light transmission window 114 by increasing the film thickness of the transparent front electrode layer 111 shown in FIG. However, the increase in the film thickness increases the light absorption in the transparent front electrode layer 111, thereby reducing the amount of light reaching the photoelectric conversion unit layer 112 from the translucent substrate 110 side. Since the transmittance decreases, the power generation efficiency decreases.

  On the other hand, although it is possible to increase the film thickness of the back electrode layer 113 that is not related to the amount of light reaching the photoelectric conversion unit layer 112 and improve the conductivity of the portion other than the light transmission window 114, the light transmission window The transmission of electromagnetic waves through 114 cannot be reduced.

  The present invention has been made in view of the above problems, and an object thereof is to provide a see-through photoelectric conversion device having high electromagnetic shielding properties and a building material using the same without reducing power generation efficiency. It is in.

  In order to solve the above problems, the see-through photoelectric conversion device of the present invention has a photoelectric conversion layer sandwiched between a pair of electrode layers, and an opening through which light passes is formed in the photoelectric conversion layer. A transparent conductive layer is disposed corresponding to a position covering at least the opening.

  As described above, in order to provide a high electromagnetic wave shielding property to a see-through photoelectric conversion device having both functions of power generation and daylighting, it is necessary to have high conductivity over the entire photoelectric conversion device. It is necessary to increase the layer thickness. However, for the reasons already described, this increase in film thickness has hindered the provision of high electromagnetic shielding properties without lowering the power generation efficiency.

  On the other hand, according to the above configuration, since the transparent conductive layer is disposed at a position unrelated to light incidence on the photoelectric conversion layer, the amount of light reaching the photoelectric conversion layer does not decrease. Accordingly, the provision of such a transparent conductive layer does not cause a decrease in power generation efficiency.

  Furthermore, the transparent conductive layer is disposed corresponding to a position that covers at least the opening of the photoelectric conversion layer. Therefore, the conductivity of the portion corresponding to the opening can be improved, and transmission of electromagnetic waves through the opening can be prevented. That is, high electromagnetic shielding properties can be imparted even in the opening.

  Therefore, a see-through photoelectric conversion device having high electromagnetic shielding properties can be provided without reducing power generation efficiency.

  In the see-through photoelectric conversion device of the present invention, it is preferable that the opening is formed continuously with at least one of the pair of electrode layers. According to this configuration, the light after passing through the opening and / or the light before passing through is not blocked by the electrode layer, and can easily be formed on the back side (see the light incident side) of the see-through photoelectric conversion device. The light can be transmitted to the opposite side) and the lighting performance can be improved.

  In the see-through photoelectric conversion device of the present invention, the transparent conductive layer is preferably formed on the side opposite to the light incident side with respect to the photoelectric conversion layer. According to the said structure, even if it is a case where a transparent conductive layer is arrange | positioned with respect to not only the said opening part but the whole photoelectric conversion apparatus, it does not affect the light quantity which reaches | attains a photoelectric conversion layer. Therefore, high power generation efficiency can be maintained.

  In the photoelectric conversion device of the present invention, it is preferable that the maximum diagonal dimension of the opening is 0.6 μm or more and 0.9 mm or less. Here, the maximum diagonal dimension means, for example, a diameter when the shape of the opening is circular, a major axis when it is elliptical, and a longest diagonal dimension when it is polygonal. According to the above configuration, the shielding effect of 30 dB or more can be obtained against electromagnetic waves in a frequency band of 5 GHz or less without impairing the transmission of light having a wavelength of 1.2 μm or less in the opening.

  In the see-through photoelectric conversion device of the present invention, the sheet resistance of the transparent conductive layer is preferably 0.2Ω / □ or more and 6Ω / □ or less. According to the above configuration, a transparent conductive layer having a high light transmittance and a shielding effect of 30 dB to 60 dB can be obtained.

  In the see-through photoelectric conversion device of the present invention, a light-transmitting substrate is disposed on the side opposite to the light incident side with respect to the photoelectric conversion layer, and the transparent conductive layer is formed on the light-transmitting substrate. It is preferable that According to the above configuration, since the photoelectric conversion layer is held by the translucent substrate, the strength of the see-through photoelectric conversion device as a whole can be increased without reducing the light transmittance.

  In the see-through photoelectric conversion device of the present invention, the electrode layer between the transparent conductive layer and the photoelectric conversion layer of the pair of electrode layers is electrically insulated from the transparent conductive layer. It is preferable. According to the above configuration, since the transparent conductive layer is independent from the photoelectric conversion layer side in terms of potential, the transparent conductive layer is formed even if the photoelectric conversion layer has an integrated structure of a plurality of solar cell unit cells. Can be applied. Therefore, also in the integrated solar cell module, the electromagnetic wave shielding property can be improved without reducing the power generation efficiency.

  In the see-through photoelectric conversion device of the present invention, between the photoelectric conversion layer and an electrode layer formed on the opposite side of the pair of electrode layers from the light incident side of the photoelectric conversion layer. A further conductive layer is preferably provided. Of the pair of electrode layers, the electrode layer formed on the side opposite to the light incident side reflects light not used for photoelectric conversion in the photoelectric conversion layer in addition to the role of taking out the electrode from the photoelectric conversion layer. Thus, it returns to the photoelectric conversion layer again to increase the conversion efficiency. Therefore, if a conductive layer is provided between the electrode layer and the photoelectric conversion layer as in the above configuration, the reflectance can be further increased, and the conversion efficiency can be further increased.

  In the building material of the present invention, it is preferable to use any of the see-through photoelectric conversion devices described above. According to the above configuration, since the see-through photoelectric conversion device having high electromagnetic shielding properties is used as a building material, it is possible to realize a wireless communication environment in which unnecessary radio waves are prevented from entering and leaking.

  As described above, the see-through photoelectric conversion device of the present invention has a photoelectric conversion layer sandwiched between a pair of electrode layers, and an opening through which light passes is formed in the photoelectric conversion layer, and at least the opening A transparent conductive layer is disposed corresponding to the position covering the surface.

  Therefore, there is an effect that it is possible to provide a see-through photoelectric conversion device having high electromagnetic shielding properties without reducing power generation efficiency.

  An embodiment of the present invention will be described with reference to FIGS. 1 to 3 as follows.

  FIG. 1 is a cross-sectional view showing a see-through thin film solar cell (see-through photoelectric conversion device; hereinafter simply referred to as “photoelectric conversion device”) 1 of the present embodiment.

  As shown in the figure, the photoelectric conversion device 1 includes a front translucent substrate 2, a front transparent conductive layer (electrode layer) 3, a photoelectric conversion layer 4, a back electrode layer (electrode layer) 5, a back translucent substrate ( A transparent substrate) 6, a back surface transparent conductive layer (transparent conductive layer) 7, and an insulating layer 8. For convenience of explanation, the light incident side with respect to the photoelectric conversion layer 4 is referred to as a front surface, and the opposite side is referred to as a back surface. In addition, since the see-through type thin film solar cell is light transmissive, light can be incident from both sides. For convenience, a side with a large amount of incident light such as a side facing the sun is described as a light incident side. .

  Specifically, the photoelectric conversion device 1 includes the photoelectric conversion layer 4 and the back electrode layer 5 in this order on at least a part of the front transparent conductive layer 3 formed on one surface of the front light-transmitting substrate 2. It is formed by stacking. The photoelectric conversion device 1 generates power by sunlight (light) incident from the front translucent substrate 2 side and reaching the photoelectric conversion layer 4, while part of the sunlight is transmitted to the back side of the photoelectric conversion device 1. This is a so-called see-through photoelectric conversion device. For this reason, the photoelectric conversion device 1 is provided with the opening 9 in the photoelectric conversion layer 4 so that sunlight can be transmitted to the back surface side, and thus, the photoelectric conversion device 1 can also perform daylighting. .

  The front translucent substrate 2 and the rear translucent substrate 6 are arranged to face each other, and sandwich other members such as the photoelectric conversion layer 4 from both sides. The front translucent substrate 2 and the back translucent substrate 6 may be only one or both of them as long as one of the structural supports of the photoelectric conversion device 1 has appropriate strength. You don't have to. However, from the viewpoint of improving the weather resistance, long-term reliability, and resistance to external mechanical shock of the photoelectric conversion device 1, both the front light-transmitting substrate 2 and the back light-transmitting substrate 6 are provided. It is preferable.

  Further, the front light-transmitting substrate 2 and the back light-transmitting substrate 6 do not necessarily need to be light-transmitting substrates. Even if they are non-light-transmitting substrates, light is transmitted by a method such as forming a through hole. Any substrate having transparency can be used as the substrate of the photoelectric conversion device 1.

  In many cases, inexpensive glass is used for the front light-transmitting substrate 2 and the back light-transmitting substrate 6, but it is not limited to inexpensive glass as long as it can structurally support the entire photoelectric conversion device 1. . For example, heat resistant polymer films such as polyimide, PET (polyethylene terephthalate), PEN (polyethylene naphthalate), and PES (polyether sulfone) may be used. In addition, when the photoelectric conversion device 1 is used outdoors, it is more desirable to use tempered glass, or a laminated glass structure, a multi-layer glass structure, or the like because strength against wind pressure and falling can be secured.

  In addition, the front translucent substrate 2 and the back translucent substrate 6 are suitably about 0.1 mm to 30 mm in thickness in order to have appropriate strength and weight. Furthermore, these substrates and an insulating film, a conductive film, a buffer layer, or the like or a combination thereof may be used depending on the usage form of these substrates.

  The front transparent conductive layer 3 is formed on the surface of the front translucent substrate 2 opposite to the light incident side, and may be formed on the entire surface of the front translucent substrate 2 or partially. It may be formed. The front transparent conductive layer 3 has a role of an electrode for taking out electric power generated in the photoelectric conversion layer 4. Therefore, the front transparent conductive layer 3 is required to have high conductivity in order to reduce resistance loss, and high light transmittance is required to increase the amount of light incident on the photoelectric conversion layer 4. For this reason, tin oxide, zinc oxide, indium oxide, ITO, and the like are often used as materials that satisfy them, but these materials contain impurities such as gallium and aluminum to further improve conductivity. A thing may be used.

  The front transparent conductive layer 3 can be formed on the front translucent substrate 2 by a sputtering method, a vacuum deposition method, an EB deposition method, a CVD method, a sol-gel method, an electrodeposition method, or the like.

  From the viewpoint of conductivity, the smaller the sheet resistance of the front transparent conductive layer 3, the smaller the series resistance loss in extracting current from the photoelectric conversion layer 4 and the greater the shielding effect of the electromagnetic wave shield by the front transparent conductive layer 3. This is preferable. In general, the sheet resistance of the front transparent conductive layer 3 decreases in inverse proportion to the increase in the film thickness of the front transparent conductive layer 3. That is, it is preferable to increase the film thickness of the front transparent conductive layer 3 because the sheet resistance of the front transparent conductive layer 3 is reduced.

  However, in order to reduce the sheet resistance of the front transparent conductive layer 3, if the film thickness of the front transparent conductive layer 3 is increased without limitation, the light transmittance of the front transparent conductive layer 3 is simultaneously reduced. And when the light transmittance of the front transparent conductive layer 3 falls, as a result, the problem that the conversion efficiency of the photoelectric conversion apparatus 1 falls arises.

  Therefore, when considering not only the conductivity but also the light transmittance, that is, the conversion efficiency, the sheet resistance of the front transparent conductive layer 3 has a lower limit of 5Ω so that an appropriate light transmittance can be secured with the above-mentioned materials. / □ is often the case. The film thickness of the front transparent conductive layer 3 is not particularly limited, but is preferably about 10 nm to 2 μm from the viewpoint of conductivity and light transmittance.

  The photoelectric conversion layer 4 may be formed on at least a part of the front transparent conductive layer 3. The photoelectric conversion layer 4 is sandwiched between a pair of electrode layers (front transparent conductive layer 3 and back electrode layer 5). The photoelectric conversion layer 4 is usually formed by a pn junction having a p-type semiconductor layer and an n-type semiconductor layer, or by a pin junction having a p-type semiconductor layer, an i-type semiconductor layer, and an n-type semiconductor layer. The However, it is not limited to these, and may be formed by a Schottky junction having only one of the p-type semiconductor layer and the n-type semiconductor layer, or other known semiconductor junctions. Further, the i-type semiconductor layer may have a weak p-type or n-type conductivity type as long as the photoelectric conversion function is not impaired. Furthermore, the photoelectric conversion device 4 may be a multi-junction solar cell by stacking two or more of the semiconductor junctions in the photoelectric conversion layer 4.

  Examples of the material constituting each semiconductor layer include elemental semiconductors such as silicon, silicon alloys obtained by adding carbon, germanium, or other impurities to silicon, III-V group compound semiconductors such as gallium arsenide and indium phosphide, and tellurium. Examples include II-VI group compound semiconductors such as cadmium iodide and cadmium sulfide, multi-component compound semiconductors such as copper-indium-gallium-selenium, and porous films such as titanium oxide that are adsorbed with a dye or the like.

  Further, the p-type semiconductor layer may be one in which the semiconductor layer is doped with an impurity atom having a p conductivity type such as boron or aluminum. Further, the n-type semiconductor layer may be one in which the semiconductor layer is doped with impurity atoms having n conductivity type such as phosphorus and nitrogen. Examples of the method for producing these semiconductor layers include a CVD method, an EB vapor deposition method, a vacuum vapor deposition method, a sol-gel method, and a method in which a suspension containing the above semiconductor is applied, dried and fired. The film thickness of the photoelectric conversion layer 4 is not particularly limited, but is preferably about 0.1 μm to 100 μm from the viewpoint of reducing the manufacturing cost without impairing the conversion function.

  The back electrode layer 5 is provided on the photoelectric conversion layer 4 and is an electrode for taking out electric power generated in the photoelectric conversion layer 4, similarly to the front transparent conductive layer 3. Therefore, the same material as that of the front transparent conductive layer 3 may be used. In addition to the function as an electrode, the back electrode layer 5 reflects light that has leaked to the back side of the photoelectric conversion layer 4 without being used for photoelectric conversion out of the light incident on the photoelectric conversion layer 4. By using a material, it is more preferable because it can provide a light confinement function for returning the light to the photoelectric conversion layer 4 and increasing the conversion efficiency.

  As a material for reflecting light, metal materials such as silver, aluminum, titanium, and palladium having high visible light reflectivity and alloys thereof are used. These materials include sputtering, vacuum deposition, and electron beam. It is formed on the photoelectric conversion layer 4 by vapor deposition or the like. The film thickness of the back electrode layer 5 is not particularly limited, but is preferably about 0.1 μm to 10 μm so as to obtain an appropriate sheet resistance.

  Further, as shown in FIG. 2, for the purpose of increasing the visible light reflectance of the back electrode layer 5, it is made of the same material as that of the front transparent conductive layer 3 between the back electrode layer 5 and the photoelectric conversion layer 4. A back surface conductive layer (conductive layer) 10 may be disposed. In addition, the back surface conductive layer 10 does not necessarily need to be transparent.

  By the way, the back electrode layer 5 made of a highly conductive metal can be approximated to a perfect conductor plate, and can almost completely shield electromagnetic waves in the entire band. However, since highly conductive metals generally have high visible light reflectivity and hardly transmit light, when the back electrode layer 5 is formed of a relatively thick metal layer and is provided over the entire surface of the photoelectric conversion device 1, see-through is possible. The light transmittance, which is the original function of the type thin film solar cell, is impaired.

  Therefore, in the photoelectric conversion device 1, the photoelectric conversion layer 4 and the back electrode layer 5 are partially provided on the front light-transmitting substrate 2 in order to maintain light transmittance. That is, as shown in FIG. 1, in order to transmit a part of light (sunlight) incident from the front light transmitting substrate 2 side to the back surface side (back surface light transmitting substrate 6 side) of the photoelectric conversion device 1, An opening 9 is provided in the photoelectric conversion layer 4. Further, the opening 9 is also formed continuously in the back electrode layer 5.

  In addition, when a transparent conductive layer is used as the back electrode layer 5 or a very thin electrode layer is used so as to have light transmittance even if it is a metal, the back electrode layer 5 has an opening 9. Even in this case, the photoelectric conversion device 1 can have light transmittance. Further, the opening 9 may be continuously formed in the front transparent conductive layer 3, or the opening 9 may be continuously formed in the back electrode layer 5 and the front transparent conductive layer 3.

  For example, the opening 9 is formed by sequentially laminating the photoelectric conversion layer 4 and the back electrode layer 5 on the front transparent conductive layer 3 and then removing the photoelectric conversion layer 4 and the back electrode layer 5 by etching or laser. be able to. The opening 9 is not limited to this formation method, and the opening 9 forms a mask for covering the opening 9 on the front transparent conductive layer 3, and the photoelectric conversion layer 4 and the back electrode layer 5 are formed on the entire surface of the front transparent conductive layer 3. After sequentially laminating, it may be formed by other methods such as removing the mask.

  As the shape of the opening 9, for example, a circle, an ellipse, a polygon, and the like can be used. A circle or a rectangle is particularly preferable because it can be easily manufactured.

  As described above, since the back electrode layer 5 is similar to a conductor plate, it can shield electromagnetic waves almost completely. On the other hand, when the opening 9 is provided, the light transmittance is improved, but the shielding property of the electromagnetic wave is lowered. The reason will be described below.

  The opening 9 is considered to behave as a slot antenna for electromagnetic waves. For this reason, an electromagnetic wave having a wavelength sufficiently longer than an electromagnetic wave whose half-wavelength is the maximum diagonal dimension of the opening 9 is greatly attenuated and cannot pass through the opening 9, but the maximum diagonal dimension of the opening 9 is a half-wavelength. An electromagnetic wave and an electromagnetic wave having a shorter wavelength pass through the opening 9 with almost no attenuation. Therefore, in order to suppress a decrease in electromagnetic shielding properties due to the formation of the opening, the opening 9 of the present embodiment has the following characteristics.

  The back electrode layer 5 having the opening 9 as described above functions as a high-pass filter that attenuates as the wavelength of the incident electromagnetic wave with respect to the size of the opening 9 becomes longer. Here, the maximum diagonal dimension of the opening 9 means a diameter when the opening 9 is circular, for example, a major axis when it is elliptical, and a longest diagonal dimension when it is polygonal. Although the shape of the opening 9 is not limited to this, it is preferably a shape having high visible light permeability.

  When the maximum diagonal dimension of the opening 9 is L [m] and the wavelength of the electromagnetic wave is λ [m], the incident electric field intensity Ei [V / m] and the transmitted electric field intensity Et [V / m] is expressed as shown in the following formula (1).

When λ / 2 ≧ L Ei / Et = λ / (2L) (1)
That is, an electromagnetic wave having a maximum diagonal dimension of a half wavelength is not attenuated, but an electromagnetic wave having a longer wavelength increases in attenuation ratio Ei / Et in proportion to the wavelength λ. In general, the electromagnetic shielding effect SE of the electromagnetic shielding material is represented by a value obtained by converting the attenuation rate Ei / Et into decibels as shown in the following formula (2).

SE [dB] = 20 · log (Ei / Et) (2)
Therefore, from the above formulas (1) and (2), the shielding effect SE of the opening 9 of the back electrode layer 5 is expressed by the following formula (3).

SE [dB] = 20 · log (λ / (2L)) (3)
If the shield effect SE of the opening 9 is used, the size of the opening 9 is set to an appropriate range in the photoelectric conversion device 1 having the opening 9 in the back electrode layer 5, thereby The shield effect SE can be improved. Here, since the band used for the wireless LAN is 5.15 GHz to 5.25 GHz for IEEE802.11a and 2.4 GHz to 2.497 GHz for IEEE802.11b, the lower limit of the maximum diagonal dimension L of the opening 9 The value is good enough to obtain a high shielding effect in a band of 5.25 GHz or less.

  It is said that a DU ratio (desired wave-to-interference wave intensity ratio) of 25 dB is sufficient to ensure the wireless LAN communication environment. However, as shown in the above equation (3), the shielding effect is reduced on the high frequency side, that is, on the short wavelength side. More preferably, the shielding effect SE at 5.25 GHz which is the upper limit of the band to be shielded is ensured to 30 dB. An upper limit value of the maximum diagonal dimension L of the opening 9 may be set so as to be able to do so. If the maximum diagonal dimension L is 0.9 mm, a shield effect of 30 dB can be obtained from 5.25 GHz electromagnetic wave with a wavelength of 0.057 m from the above formula (3).

  Thus, if the maximum diagonal dimension L of the opening 9 is set to 0.9 mm or less, a shielding effect of 30 dB or more can be obtained against electromagnetic waves in a band of 5.25 GHz or less.

  On the other hand, when the maximum diagonal dimension of the opening 9 is reduced as much as possible from 0.9 mm, the upper limit of the wavelength of the electromagnetic wave that can be transmitted through the opening 9 decreases, and the sun with a wavelength of 0.3 μm to 1.2 μm. It also blocks electromagnetic waves in the region of the optical spectrum (from the ultraviolet to the visible and infrared regions), that is, light transmission. In order not to reduce the daylighting (light transmission), which is one of the important functions of the photoelectric conversion device 1, that is, to prevent the shielding effect from acting on electromagnetic waves having a wavelength of 1.2 μm or less, It is necessary to set a lower limit value of the maximum diagonal dimension L.

  If the maximum diagonal dimension L is 0.6 μm, the shielding effect against electromagnetic waves having a wavelength of 1.2 μm or less is zero from the above equation (3). Thus, if the lower limit of the maximum diagonal dimension L of the opening 9 is 0.6 μm, the light transmittance with a wavelength of 1.2 μm or less is improved, so that the photoelectric conversion device 1 with high daylighting property can be obtained. it can.

  Here, it should be particularly noted that the back surface transparent conductive layer 7 is formed on one surface of the back surface transparent substrate 6 in the photoelectric conversion device 1 as shown in FIG. As shown in FIG. 1, the back transparent conductive layer 7 may be formed on the surface on the front light transmitting substrate 2 side when viewed from the back light transmitting substrate 6, or the front surface when viewed from the back light transmitting substrate 6. Although it may be formed on the surface opposite to the translucent substrate 2, in order to prevent damage to the back surface transparent conductive layer 7 due to mechanical impact from the outside of the photoelectric conversion device 1 and improve weather resistance, It is preferable that the back transparent conductive layer 7 is formed on the surface on the front light transmitting substrate 2 side.

  Any material can be used for the back transparent conductive layer 7 as long as it has a high light transmission property, but it is preferable to use the same material as that for the front transparent conductive layer 3 described above. Moreover, even if it is a metal, it can be used as the said back surface transparent conductive layer 7 by forming very thinly so that it may have a light transmittance.

  Moreover, it is desirable that the space between the back transparent conductive layer 7 and the back electrode layer 5 and the opening 9 are sealed with an insulating layer 8 described later. The insulating layer 8 forms the front transparent conductive layer 3, the photoelectric conversion layer 4, and the back electrode layer 5 on the front transparent substrate 2, and the back transparent conductive layer 7 on the back transparent substrate 6. What is formed can be integrated. However, for example, when the integrated solar cell structure as described in Patent Document 1 is not provided, it is not always necessary to electrically insulate the back electrode layer 5 and the back transparent conductive layer 7. It is also possible to apply.

  As described above, in the conventional see-through thin film solar cell (photoelectric conversion device), it is difficult to improve the electromagnetic wave shielding property without reducing the power generation efficiency. In general, in order to improve the shielding performance of the see-through photoelectric conversion device, it is necessary to increase the conductivity over the entire module of the see-through thin film solar cell including the opening 9. Therefore, in order to reduce the propagation of electromagnetic waves through the opening 9, it is necessary to increase the film thickness of the transparent front electrode layer (front transparent conductive layer 3 in the present embodiment) in the conventional see-through photoelectric conversion device. As a result, the power generation efficiency is reduced with a decrease in the amount of incident light reaching the photoelectric conversion layer.

  However, when the back surface transparent conductive layer 7 is formed on one surface of the back surface transparent substrate 6 as in the photoelectric conversion device 1, the opening 9 has two layers of the front surface transparent conductive layer 3 and the back surface transparent conductive layer 7. Can have high conductivity. Furthermore, also about parts other than the opening part 9, high conductivity can be given to three layers, the front transparent conductive layer 3, the back electrode layer 5, and the back transparent conductive layer 7. The front transparent conductive layer 3 has a role of transmitting incident light to the photoelectric conversion layer 4, but the back transparent conductive layer 7 exists on the surface opposite to the incident light as viewed from the photoelectric conversion layer 4. The film thickness and light transmittance do not directly affect the power generation efficiency of the solar cell. Therefore, since it is possible to give high conductivity to the entire photoelectric conversion device 1 without increasing the film thickness of the front transparent conductive layer 3, electromagnetic waves are generated over the entire surface of the photoelectric conversion device 1 without causing a decrease in power generation efficiency. A high shielding effect can be obtained. Thereby, intrusion and leakage of unnecessary radio waves can be prevented, and the indoor wireless LAN communication environment can be improved.

  Further, the back transparent conductive layer 7 does not necessarily need to be provided so as to cover the entire surface of the front translucent substrate 2, and is provided corresponding to a position that covers only the opening 9 as shown in FIG. May be.

  As shown in the figure, even when the back surface transparent conductive layer 7 is provided corresponding to a position that covers only the opening 9, only the front transparent conductive layer 3 and the back surface transparent conductive layer 7 of the opening 9 are provided. The layer can be provided with high conductivity, and as a result, the photoelectric conversion device 1 as a whole including an opening that requires particularly high electromagnetic wave shielding properties can be provided with high conductivity.

  Hereinafter, the electromagnetic wave shielding effect of the back surface transparent conductive layer 7 will be described in detail. The electromagnetic wave propagating in the conductive medium has its electric field intensity exponentially attenuated with respect to the propagation distance. The distance δ at which the amplitude becomes 1 / e is called the skin depth, and is expressed by the following equation (4). Can be sought.

  Where f is the frequency [Hz] of the electromagnetic wave, μ is the magnetic permeability [H / m] of the conductive medium, and σ is the conductivity [S / m] of the conductive medium. As the magnetic permeability μ of the conductive medium, a vacuum magnetic permeability (4π × 10 −7 [H / m]) can be applied when the conductive medium is a non-magnetic material such as the above-described material.

  Therefore, the above equation (4) shows that when the electromagnetic wave enters the conductive medium from free space, the skin depth at which the electromagnetic wave can enter the conductive medium is higher as the frequency of the electromagnetic wave is higher. Also, the higher the conductivity of the conductive medium, the smaller it becomes. In other words, the conductive electromagnetic shielding material acts as a low-pass filter that attenuates a band of a predetermined frequency or higher with respect to incident electromagnetic waves. The above effect is called a skin effect, and when the thickness d of the conductive medium is smaller than the skin depth δ, the electromagnetic wave shielding effect SE by the skin effect is expressed by the following equation (5).

SE = 20 log (1 + Z0 / (2Rs)) (5)
However, Z0 is the wave impedance [Ω] of the space, and is a constant represented by the following formula (6).

  Rs is the sheet resistance [Ω / □] of the conductive medium. FIG. 3 is a graph showing the relationship of the above equation (5). In the figure, the vertical axis represents the shield effect SE [dB], and the horizontal axis represents the sheet resistance Rs [Ω / □]. According to the figure, it can be seen that the shield effect SE increases as the sheet resistance Rs of the electromagnetic shielding material decreases. Therefore, as described above, in order to secure the communication environment of the wireless LAN, it is preferable to set the sheet resistance of the conductive medium so as to obtain a 30 dB shielding effect. Therefore, according to said Formula (5), if the sheet resistance Rs of the back surface transparent conductive layer 7 shall be 6 ohms / square or less, the shield effect of 30 dB or more can be acquired.

  Furthermore, if the sheet resistance Rs of the back surface transparent conductive layer 7 is 0.2Ω / □, the shielding effect is 60 dB according to the equation (5). At this time, when combined with the shielding effect 30 dB of the back electrode layer 5 having the opening 9 described above, it has a shielding effect of 90 dB, and a shielding performance with a high anechoic chamber level can be realized. Therefore, it is desirable that the upper limit of the shielding effect is 90 dB and the sheet resistance Rs is 0.2Ω / □ as the lower limit in order to suppress the decrease in transmittance due to the increase in the thickness of the transparent conductive layer.

  Further, as shown by hatching in FIG. 1, the opening 9 is sealed between the front transparent conductive layer 3 and the back transparent conductive layer 7 with an insulating layer 8, while the opening 9 has a back surface other than the opening 9. A space between the transparent conductive layer 7 and the back electrode layer 5 is sealed with an insulating layer 8. As shown in FIG. 2, the back transparent conductive layer 7 provided so as to cover the opening 9 is sealed with the front transparent conductive layer 3 and the insulating layer 8.

  For the insulating layer 8, an ethylene-vinyl acetate copolymer (EVA resin), polyvinyl butyral, or the like is suitably used as a transparent resin having high insulation, transparency, and weather resistance. Moreover, when the back surface transparent conductive layer 7 and the back surface electrode layer 5 do not contact electrically, the layer which enclosed the air layer and the other gas in the insulating layer 8 can be used. In this case, it is possible to obtain a solar cell module with high heat insulation and sound insulation.

  Furthermore, by using a dielectric layer having an appropriate dielectric constant as the insulating layer 8, a radio wave absorption function can be provided. At that time, for example, polycarbonate having a dielectric constant of 2.7 may be used as the dielectric layer.

  When the back transparent conductive layer 7 is arranged on the opposite side of the back transparent substrate 6 from the back electrode layer 5, the back transparent conductive layer 7 and the back electrode layer 5 are insulated by the back transparent substrate 6. Therefore, the insulating layer 8 is not necessary.

  Although not shown, an opening may be provided in the front transparent conductive layer 3. Also in this case, the electromagnetic wave shielding property can be improved by increasing the film thickness of the back surface transparent conductive layer 7.

  Moreover, you may use the photoelectric conversion apparatus 1 as a building material (not shown) instead of glass, for example for the window of a building, for example.

Moreover, in the said photoelectric conversion apparatus 1, although the case of the thin film solar cell was demonstrated, it is not restricted to this, For example, the crystalline solar cell may be arranged in a suitable space | interval and sealed with glass.
〔Example〕
Specific examples of the present invention will be described below. A blue plate glass plate having a thickness of 1.8 mm was used as the front light-transmitting substrate 2, and a zinc oxide front transparent conductive layer 3 having a thickness of 800 nm was formed on the blue plate glass plate by a DC magnetron sputtering method.

  Then, when the front transparent conductive layer 3 was etched by immersing the glass plate on which the front transparent conductive layer 3 was formed in hydrochloric acid having a concentration of 0.5%, the sheet resistance of the front transparent conductive layer 3 after the etching was 16Ω / □. The average value of the film thickness was 350 nm. Moreover, the light transmittance of the front translucent substrate 2 on which the front transparent conductive layer 3 was formed was 85%.

  On the front transparent conductive layer 3 thus obtained, the photoelectric conversion layer 4 composed of a p-type silicon layer, an i-type silicon layer, and an n-type silicon layer is deposited using a high-frequency plasma CVD method. The substrate 2, the front transparent conductive layer 3, and the photoelectric conversion layer 4 were deposited so that the total film thickness was 2 μm.

  Thereafter, an opening 9 was formed by exposing the front transparent conductive layer 3 to the photoelectric conversion layer 4 by laser scribing, and then the back electrode layer 5 was deposited on the photoelectric conversion layer 4 by masking the region of the opening 9. .

  The shape of the opening 9 is a square having a diagonal dimension of 0.6 mm, and the opening 9 has an opening ratio of 30% with respect to the entire area of the blue plate glass plate (front translucent substrate 2). Formed.

  The back electrode layer 5 was formed by depositing a 50 nm thick zinc oxide layer and a 500 nm thick silver layer in this order by DC magnetron sputtering.

  As the back surface translucent substrate 6, a substrate in which a zinc oxide back surface transparent conductive layer 7 was formed on a glass plate in the same manner as the front surface translucent substrate 2 was used. The film thickness of the back transparent conductive layer 7 was 2 μm, the sheet resistance was 2.5Ω / □, and the light transmittance of the back transparent substrate 6 on which the back transparent conductive layer 7 was formed was 80%.

  The front translucent substrate 2 and the rear translucent substrate 6 on which the front transparent conductive layer 3, the photoelectric conversion layer 4, and the back electrode layer 5 are formed so that the back electrode layer 5 and the back transparent conductive layer 7 face each other. As the transparent sealing resin between the two layers, EVA resin was used.

  About the see-through type thin film solar cell produced in this way, when the shielding effect was measured according to the US military standard MIL-STD-285, the shielding effect at 2.4 GHz, 5 and 25 GHz was 65 dB and 70 dB, respectively. It showed good electromagnetic shielding performance.

  In addition, after dividing the front transparent conductive layer 3 formed on the front translucent substrate 2 into a plurality of regions by laser scribing or the like, the integrated solar cell in which the photoelectric conversion layer 4 and the back electrode layer 5 are stacked on each region. A battery structure may be used.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims. That is, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention.

  The present invention is a see-through photoelectric conversion device having a high shielding ability against GHz electromagnetic waves, and can be used particularly as a building material for building windows and skylights.

It is sectional drawing which shows the see-through type photoelectric conversion apparatus of embodiment of this invention. It is sectional drawing which shows the modification of the see-through type photoelectric conversion apparatus shown in FIG. It is a graph which shows the shielding effect of the back surface transparent conductive layer of embodiment of this invention. (A) is sectional drawing which shows schematic structure of the conventional substrate type thin film solar cell, (b) is sectional drawing which shows schematic structure of the conventional super straight type thin film solar cell. It is sectional drawing which shows schematic structure of the conventional see-through type thin film solar cell.

Explanation of symbols

1 See-through photoelectric conversion device (photoelectric conversion device)
3 Front transparent conductive layer (electrode layer)
4 Photoelectric conversion layer 5 Back electrode layer (electrode layer)
6 Back side translucent substrate (translucent substrate)
7 Back side transparent conductive layer (transparent conductive layer)
9 Opening 10 Back side conductive layer (conductive layer)

Claims (8)

It has a photoelectric conversion layer sandwiched between a pair of electrode layers, an opening through which light passes is formed in the photoelectric conversion layer, and a transparent conductive layer is disposed at least corresponding to a position covering the opening And
A further conductive layer is provided between the photoelectric conversion layer and the electrode layer formed on the side opposite to the light incident side of the photoelectric conversion layer of the pair of electrode layers ,
The see-through photoelectric conversion device, wherein a maximum diagonal dimension of the opening is 0.6 μm or more and 0.9 mm or less. The see-through photoelectric conversion device according to claim 1, wherein the transparent conductive layer has a sheet resistance of 0.2Ω / □ or more and 6Ω / □ or less. The see-through photoelectric conversion device according to claim 1, wherein the opening is formed continuously with at least one of the pair of electrode layers. The see-through photoelectric conversion device according to claim 1, wherein the transparent conductive layer is formed on a side opposite to a light incident side with respect to the photoelectric conversion layer. The said transparent conductive layer is formed in the shape where the end surface stood up with respect to the light-incidence surface and the side surface of the said photoelectric converting layer which forms the said opening part are located on the same straight line. 5. A see-through photoelectric conversion device according to 4. The translucent substrate is arranged on the opposite side to the light incident side with respect to the photoelectric conversion layer, and the transparent conductive layer is formed on the translucent substrate. The see-through photoelectric conversion device according to any one of 5. The electrode layer between the transparent conductive layer and the photoelectric conversion layer of the pair of electrode layers is electrically insulated from the transparent conductive layer. 7. The see-through photoelectric conversion device according to any one of 6 above. A building material comprising the see-through photoelectric conversion device according to any one of claims 1 to 7.

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