JP4233260B2 - Photovoltaic power generation sheet, solar power generation unit and power generation apparatus using the same - Google Patents

Description

なお、表中のシステムの向きの状態は次の意味をもつ。
状態１：光源に対して植木鉢を図２のような向きに置いた場合。
状態２：図２の向きから植木鉢を時計回りに９０°回転させた場合。
状態３：図２の向きから植木鉢を時計回りに１８０°回転させた場合。
【００６０】
表１の結果から、本装置は水を発電に必要な循環型資源として用いて、天然の色素を用いて、太陽光を自然界の光合成のエネルギー効率（＜１％）と同等以上の効率で電気エネルギーに変換することができることが分る。また、光の照射角度すなわち輻射強度によって出力が変化する性質を使い、本装置を使って太陽光の輻射強度に対応した各種の駆動装置（屋内の喚起ファンなど）の運転の環境制御が可能である。
【００６１】
実施例２
増感色素として、クロロフィルに代えてエオシンＹ、ならびにハイビスカスの花から抽出される赤色色素をそれぞれ用いて、実施例１と同様な方法で実験を行った。クロロフィル誘導体よりは光電流密度と光エネルギー変換効率が低いが表１の結果とほぼ同様の開放起電力が得られた。
【００６２】
実施例３
太陽光発電用ユニットに形成された光発電体シートの２個について、それぞれ末端をカッターで切断し、シートの内部の電解液を外気に露出させた。補充用の水の供給を絶って、鉢内の保水材料が乾燥した状態では、切断部分には空気が入り込んで、シート内の電解液は減量し、最終的になくなってしまい、光発電の機能が停止した。しかし、鉢内に補充用の水を満たして毛管による水の供給を開始すると、ユニット内に電解液が戻り、ユニットの発電機能が復帰した。次に、シートの切断面に、水分子のみを透過する逆浸透膜用の樹脂製透過膜を貼り付けて、エポキシ接着剤で固定し、電解質の漏洩のないようにシールした。この状態で補給用の水を満たして毛管による水の供給を続け、１日間放置した結果、シートの電解液は気泡の混入や液の減少が認められず、光発電も継続的に行われた。この方法では、ユニットから浸透膜を通過する微量の水の蒸発（葉からの蒸散作用に類似）が常時起こりうるが、蒸発した水は毛管作用によって供給される補給水によって連続的に補充されると考えられる。
【００６３】
実施例４
太陽光発電用ユニットに形成した光発電体シートを紫外線を含む高照度光（１００００ｌｕｘ）の連続照射のもとに３０日間暴露した結果、シート内の増感色素（クロロフィル）の一部が分解し、脱色したことが認められた。これによりシートの光発電機能は１／３に低下した。そこで、シートを太陽光発電用ユニットから外して、内部の電解液を除去したのち、再びユニットにセットし、シートに設けたリーク栓（電解液を外気とリークさせるために設けた小孔に取り付けた栓）を外し、色素を約０．１ｍＭの濃度で溶解した純水を補給水の代わりに用いて鉢に注水し、ユニット全体に１晩循環させた。この操作によって、シート内に色素溶液が充満し、同時に色素によって半導体多孔質層が再び染まったことが認められた。次に、色素溶液の供給を止め、シートを乾燥させた後に、色素溶液に代えて電解質を含む補給水を供給した結果、ユニット内に電解質水溶液が進入し、最終的にシートは電解液で満たされた。この操作によって光発電機能はほぼ正常に復帰した。
【００６４】
【発明の効果】
本発明によれば、太陽光エネルギー変換の効率に優れ、低コストでかつ環境循環性に優れ、環境負荷の低い色素増感半導体型のたわみ性光発電体シートが提供され、これを利用することにより、光合成によるエネルギー変換を人工の植物模倣システムによって駆動させ、環境センシングやグリーンケミストリーに基づく環境循環システムの教育に活用することのできるロボットの提供が可能になる。
【図面の簡単な説明】
【図１】 本発明たわみ性光発電体シートの構造の１例を示す断面図。
【図２】 観葉植物様の太陽光発電用ユニットとした例を示す斜視図。
【図３】 図２の葉状シートの細部を示す平面図。
【符号の説明】
１，１´ たわみ性透明支持体シート
２，２´ 透明導電性層
３ 多孔質半導体層
４ 電解質水溶液
５，５´リード線
６ 下塗り層
７ 微粒子材料
８ 植木鉢
９ 保水材料
１０ 水補給用兼集電用茎部
１１ 葉柄部
１２ たわみ性光発電体シート
１３ 主葉脈
１４ 末端葉脈[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sheet-like flexible (mechanically flexible) photovoltaic sheet suitable for processing into ornamental plants and outdoor ornaments, a unit for photovoltaic power generation and a power generation apparatus with a low environmental load using the sheet. It is about.
[0002]
[Prior art]
In photoelectric conversion means widely used in the technical fields for energy conversion and optical sensing, solid-state devices using silicon pn junction semiconductors or compound semiconductors are the mainstream from the viewpoint of durability and efficiency. In solar cells aiming at high energy conversion efficiency, many photovoltaic cells using solid junctions such as single crystal silicon, polycrystalline silicon, amorphous silicon, cadmium telluride and indium copper selenide have been proposed so far. Yes.
[0003]
However, photovoltaic cells that use these solid junctions generally require high temperatures when manufacturing their elements, and require film formation and lamination using vacuum technology, so that a great deal of energy must be consumed. , The amount of carbon dioxide emission is large, and there is a big risk in terms of environmental load. In addition, amorphous silicon solar cells that are promising in terms of cost in order to spread as consumer products can use visible light up to 800 nm with respect to sunlight and can provide energy conversion efficiency close to 10%. However, the risk similar to the above cannot be avoided in that the vacuum deposition technique is indispensable for the production.
[0004]
On the other hand, photosynthesis by natural biomass is a complete environmental circulation type energy conversion system, and it is known to convert sunlight with an efficiency of up to about 1%. This system has the advantage that the energy conversion efficiency is lower than that of the amorphous silicon solar cell, but it does not pose a risk of environmental burden. However, since this system depends on the biological cycle, it has a drawback that it cannot supply a stable output over a long period of time unlike an amorphous silicon solar cell.
[0005]
Recently, a photoelectric conversion element using dye-sensitized semiconductor fine particles has been proposed ["Nature", Vol. 353, pp. 737-740 (1991), U.S. Pat. No. 4,927,721] It has been attracting attention as a wet solar cell modeled on photosynthesis. In this photoelectric conversion element, for example, a titanium dioxide porous thin film sensitized with a dye such as ruthenium complex having excellent light resistance is used as a light absorber, and there is an advantage of low cost. Since the redox electrolyte solution is used, there is a drawback in that the sustainability is unavoidable due to a decrease in the stability of the redox agent or an external leak of the electrolyte solution. In addition, since this light absorber is carried on a hard transparent substrate such as a glass plate, it cannot be used as a material that can be freely bent, and the application is naturally limited. For these reasons, wet solar cells have not yet reached the stage of practical use, despite their great feasibility in terms of environmental load suppression and environmental circulation.
[0006]
[Problems to be solved by the invention]
Under such circumstances, the present invention overcomes the shortcomings of wet solar cells using dye-sensitized porous semiconductors and provides stable output over a long period of time while maintaining the characteristics of low environmental impact. It was made for the purpose of providing a new photovoltaic power generation sheet having a physical property that can be maintained and sufficiently responding to the demand for flexibility, and a new photovoltaic power generation unit or power generation device using the physical property. It is.
[0007]
[Means for Solving the Problems]
The present inventor conducted intensive research on the practical application of wet solar cells that are superior in terms of environmental load suppression and environmental circulation in light of the evaluation of green chemistry. As a result, the present inventors were sensitized with dyes, particularly organic dyes. The flexible substrate that supports the porous semiconductor thin film is made of a flexible material, water is used as the electrolyte solvent, and the aqueous electrolyte solution is continuously replenished using the capillary action. The present inventors have found that a wet solar cell having a low environmental load can be obtained, and the present invention has been made based on this finding.
[0008]
That is, the present invention comprises an electrode A obtained by laminating a porous semiconductor layer dye-sensitized via a transparent conductive layer on a transparent support sheet, and a transparent conductive layer laminated on the transparent support sheet. In a photovoltaic sheet having a structure in which an electrode B is formed, and a porous semiconductor layer and a transparent conductive layer between the electrode B and the aqueous electrolyte solution layer C are interposed therebetween, the transparent support for the electrodes A and B is a flexible material. In addition, a lead wire for collecting generated power is disposed on at least one transparent conductive layer, and the aqueous electrolyte solution or water is continuously applied to the aqueous electrolyte solution layer C by utilizing capillary action. A flexible photovoltaic sheet provided with a replenishing mechanism, a photovoltaic power generation unit using the flexible photovoltaic sheet, and a photovoltaic power generation apparatus in which a plurality of these units are connected in series or in parallel The It is intended to provide.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Next, the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view showing an example of the structure of a flexible photovoltaic sheet of the present invention, which is a porous material dye-sensitized via a transparent conductive layer 2 on a flexible transparent support sheet 1. The semiconductor layer 3 is laminated | stacked and the electrode A is formed.
On the other hand, an electrode B which is a counter electrode of the electrode A is composed of a flexible transparent support sheet 1 ′ and a transparent conductive layer 2 ′ laminated thereon, and an electrolyte aqueous solution 4 is interposed between the electrodes A and B. An electrolyte layer C is inserted. 5 and 5 ′ are lead wires for collecting generated electric power provided in the upper and lower transparent conductive layers 2 and 2 ′, and 6 is a transparent conductive layer 2 carrying the porous semiconductor layer 3 as a counter electrode. A subbing layer provided to prevent electrical short-circuiting, 7,..., A fine particle material serving as a spacer for preventing electrode A and electrode B from making electrical contact It is.
[0010]
The flexible photovoltaic sheet of the present invention having such a structure is a kind of photoelectrochemical cell, that is, an electrochemical photovoltaic cell, and serves as a charge transport layer between two electrodes, that is, electrode A and electrode B. An ion conductive electrolyte aqueous solution layer C that achieves the above is disposed. As the semiconductor layer of the electrode A, an n-type semiconductor is usually used, and the sensitizing dye on the semiconductor gives electrons to the semiconductor under photoexcitation and generates a sensitized photocurrent whose direction is controlled in the anode direction. The excited electrons introduced into the conduction band of the n-type semiconductor move from the surface of the semiconductor to the bulk and reach the electrode A on which the semiconductor is supported.
[0011]
On the other hand, the dye molecule after giving electrons to the semiconductor becomes an oxidant radical deficient in electrons, but is electronically reduced and regenerated by the ionic reducing agent in the aqueous electrolyte solution in contact with the dye. Further, the electrons that have reached the electrode A move to the counter electrode B through the external circuit, and at this time, a current generated under light excitation is observed as a photoanode current in the external circuit.
On the other hand, when the dye is adsorbed on the p-type semiconductor and sensitizes it, the direction of the sensitized current flows is reversed, so that the generation of the photocathode current is predicted.
[0012]
In the present invention, a transparent support sheet having flexibility is used as the supports 1 and 1 '. Examples of such transparent support sheets include polyolefins such as polyethylene, polypropylene, and polybutylene, tetraacetyl cellulose (TAC), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and syndiotactic polystyrene (SPS). And a sheet made of a transparent synthetic resin such as polyphenylene sulfide (PPS), polycarbonate (PC), polyarylate (PAr), polysulfone (PSF), polyester sulfone (PES), polyetherimide (PEI), and cyclic polyolefin. Preferably, but preferably from polyolefin, polyvinyl chloride, polystyrene, polyamide, polyethylene terephthalate, polycarbonate or polyurethane or derivatives thereof. A Bareru polymers, those colorless and transparent is particularly preferred among polyimide or a derivative thereof in terms of excellent heat resistance. These polymers may be used alone or in combination of two or more.
[0013]
In addition, as the transparent conductive layers 2 and 2 ′ laminated on the supports 1 and 1 ′, conductive metal oxides (fluorine-doped tin oxide, indium-tin composite oxide (ITO), metal A thin film (for example, platinum, gold, silver, copper, aluminum), a carbon material, or the like is used, and a metal oxide layer having a high transmittance represented by tin oxide or ITO is preferable. Covering amount is 1m of flexible transparent support ² The range is 0.01 to 100 g per unit, and the thickness is preferably about 0.02 to 10 μm. Two or more kinds of the conductive layers may be laminated or combined.
The conductive support formed by integrating the resin support and the transparent conductive layer is optically transparent and flexible, and its surface resistance is preferably as low as possible. The range of the surface resistance is 100Ω / □ or less, preferably 40Ω / □ or less.
[0014]
Next, the lead wires 5,... And 5 ',... Disposed on the transparent conductive layers 2 and 2' serve to lower the surface resistance of the conductive support and collect the generated electric power. Suitable materials include metals such as copper, silver, gold, platinum, titanium, aluminum, and nickel having high electrical conductivity, and carbon materials such as graphite, graphite, glassy carbon, carbon black, carbon nanotube, and fullerene. . In the case of a metal lead wire, it is preferable to dispose on a transparent resin substrate by vapor deposition, sputtering, etc., and provide a transparent conductive layer made of tin oxide or ITO film thereon.
[0015]
In the flexible photovoltaic sheet of the present invention, the semiconductor material constituting the dye-sensitized porous semiconductor layer 3 that plays the most important role is not only a single semiconductor such as silicon and germanium, but also a metal So-called compound semiconductors represented by oxides and metal chalcogenides (for example, sulfides, selenides, etc.) or compounds having a perovskite structure can be used. Examples of these oxides and chalcogenide metals include titanium, tin, zinc, iron, tungsten, zirconium, hafnium, strontium, indium, cerium, yttrium, lanthanum, vanadium, niobium or tantalum oxide, cadmium, zinc, lead, Silver, antimony or bismuth sulfide, cadmium or lead selenide, cadmium telluride and the like. Examples of the compound semiconductor include phosphides such as zinc, gallium, indium, and cadmium, gallium arsenide, copper-indium selenide, copper-indium-sulfide, and the like.
In semiconductors, there are an n-type in which carriers involved in conduction are electrons and a p-type in which carriers are holes. In the present invention, n-type is preferable in terms of conversion efficiency.
[0016]
The n-type inorganic semiconductor preferably used in the present invention is TiO. ₂ TiSrO _Three , ZnO, Nb ₂ O _Three , SnO ₂ , WO _Three , Si, CdS, CdSe, V ₂ O _Five , ZnS, ZnSe, SnSe, KTaO _Three , FeS ₂ , PbS, InP, GaAs, CuInS ₂ , CuInSe ₂ and so on. Of these, the most preferred n-type semiconductor is titanium oxide (TiO 2). ₂ ), Zinc oxide (ZnO), tin oxide (SnO) ₂ A semiconductor material obtained by combining a plurality of these semiconductors can also be used.
[0017]
The porous semiconductor layer has a structure in which ultrafine particles of semiconductor are sintered or fused, and the average particle size of primary particles is 5 to 100 nm, particularly 5 to 50 nm. Two or more kinds of fine particles having different particle size distributions may be mixed, and semiconductor particles having a large particle size, for example, about 300 nm may be mixed for the purpose of scattering incident light and improving the light capture rate.
[0018]
For the purpose of preventing the electrically conductive support made of resin carrying the porous semiconductor from being electrically short-circuited with the counter electrode, an undercoat layer 6 provided in advance between the electrically conductive support and the porous semiconductor layer. As TiO ₂ , SnO ₂ , ZnO, Nb ₂ O _Five , Especially TiO ₂ Is preferred. This undercoat layer is, for example, Electrochim, Acta
40, 643 to 652 (1995), in addition to the spray pyrolysis method, a sputtering method can be used. The preferred thickness of the undercoat layer is 5 to 1000 nm or less, particularly 10 to 500 nm.
[0019]
The ultrafine particles constituting the porous semiconductor layer 3 are, for example, known sol-gel methods and vapor phase pyrolysis methods (published by Technical Education Publishing Co., 2001, supervised by Shozo Yanagida, “Basics and Applications of Dye-Sensitized Solar Cells”). Or “1995 Thin Film Coating Technology by Sol-Gel Method” published by the Technical Information Association).
[0020]
Next, examples of the dye that is adsorbed on the porous semiconductor layer and used to sensitize the semiconductor include organometallic complex dyes, porphyrin dyes, phthalocyanine dyes, and methine dyes. In the case of photoelectric conversion, that is, photovoltaic power generation, the dye is used for the purpose of expanding the wavelength range, controlling to a specific wavelength range, and the like. These dyes may be used alone or in combination of two or more as required.
[0021]
The dye preferably has an appropriate bonding group that is adsorbable to the surface of the semiconductor fine particles. Examples of such a linking group include a COOH group, an OH group, and SO. _Three H group, -P (O) (OH) ₂ Group or -OP (OH) ₂ An acidic group such as a group, or a chelating group having π conductivity such as oxime, dioxime, hydroxyquinoline, salicylate or α-ketoenolate.
[0022]
When the dye is a metal complex dye, a metal phthalocyanine dye, a metal porphyrin dye, or a ruthenium complex dye is preferable. Such ruthenium complex dyes include, for example, U.S. Pat. Nos. 4,927,721, 5,525,440, JP-A-7-249790, JP-A-10-504512, European Patent No. 98/50393, It is described in Japanese Patent Application Laid-Open No. 2000-26487.
[0023]
Dyes that are particularly suitable for use in the present invention are naturally occurring dyes and synthetic chemical derivatives thereof, which are used for the purpose of producing devices with a low environmental load. These naturally occurring pigments include pigments involved in plant photosynthesis, such as chlorophyll a, chlorophyll b, pheophytins, bacteriochlorophylls, and many other flowers and vegetables such as red pigments extracted from flowers such as hibiscus. Can be mentioned.
[0024]
The content of the dye in the porous semiconductor layer is 1 m per unit area of the porous semiconductor layer. ² 0.01 to 100 mmol per unit is preferable. The amount of the dye adsorbed on the semiconductor fine particles is preferably in the range of 0.01 to 1 mmol per 1 g of the semiconductor fine particles. In this adsorption, a colorless compound can be added to the dye and co-adsorbed for the purpose of reducing the interaction such as aggregation between the dyes. Compounds effective for this purpose are compounds exhibiting surface activity, and examples thereof include sulfosuccinic acid type surfactants known under trade names such as steroid compounds having a carboxyl group, alkyl sulfonates, and aerosols (AEROSOL). .
[0025]
In the flexible photovoltaic sheet of the present invention, the electrode A is formed by laminating the porous semiconductor layer 3 dye-sensitized via the transparent conductive layer 2 on the flexible transparent support sheet 1 described above. As a counter electrode, an electrode B composed of a laminate of a flexible transparent support sheet 1 ′ and a transparent conductive layer 2 ′ is used. The material of the flexible transparent support sheet 1 ′ and the transparent conductive layer 2 ′ is used. Can be appropriately selected from the same materials as those used in the transparent support sheet 1 and the transparent conductive layer 2 carrying the dye-sensitized porous semiconductor layer 3 in the electrode A. A lead wire can be arranged on the surface of the electrode B as desired.
[0026]
Next, the electrolyte aqueous solution layer C inserted between the electrode A and the electrode B is composed of a water-soluble electrolyte, water for dissolving it, and a redox agent. This water is a preferred medium in that it can be replenished as part of the environmental circulation system. In addition, the water-soluble electrolyte can be arbitrarily selected from electrochemical support salts conventionally used as charge transport layers.
[0027]
For example, KCl, NaCl, LiCl, K ₂ SO _Four , Na ₂ SO _Four There are alkali metal halides and sulfates. On the other hand, examples of the redox agent include organic compounds such as quinone-hydroquinone mixture and ascorbic acid, and S / S. ^2- , I ₂ / I ^- Inorganic materials such as LiI, NaI, KI, CsI, CaI ₂ And iodine compounds such as quaternary ammonium compounds such as tetraalkylammonium iodide, pyridinium iodide, and imidazoline iodide are also preferably used.
[0028]
In addition, metal complexes such as ferrocyanate-ferricyanate and ferrocene-ferricinium ions, sulfur compounds such as sodium polysulfide and alkylthiol-alkyldisulfides, and viologen dyes can be used. Among these I ₂ An electrolyte that combines an iodine salt of a quaternary ammonium compound such as LiI, pyridinium iodide, and imidazoline iodide is preferable. The preferable addition concentration of iodine when adding iodine is 0.01M or more and 0.5M or less. The concentration of the supporting salt is 0.1M or more and 5M or less, preferably 0.2M or more and 1M or less.
[0029]
The electrolyte aqueous solution layer C includes a water-soluble polymer [polyethylene oxide (PEO), polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), etc.], a gel thereof, or a natural polymer material (agar, gelatin, carboxy Natural derivatives such as methyl chitin) can be added as necessary to increase the viscosity of the liquid in the layer.
[0030]
The electrolyte aqueous solution layer C can also be used by gelling (solidifying) the electrolyte aqueous solution by using polymer addition, oil gelling agent addition, polymerization including polyfunctional monomers, polymer cross-linking reaction, and the like. . The method of gelation by adding a polymer is known [ELSEVIER Applied Science (ELSEVIER).
Published by APPLIED SCIENCE, co-edited by JR MacCallum and CA Vincent, “Polymer Electrolite Review (Polymer)
Electrolyte Review) 1 and 2 ”, JP-A-11-185863].
[0031]
In addition, when the electrolyte is gelled by a crosslinking reaction, examples of the crosslinkable reactive group of the polymer include an amino group and a nitrogen-containing heterocyclic ring, and a preferable crosslinking agent is capable of electrophilic reaction with a nitrogen atom. Bifunctional or higher functional compounds such as alkyl halides, halogenated aralkyls, sulfonic acid esters, acid anhydrides, acid chlorides, isocyanates, α, β-unsaturated sulfonyl groups, α, β-unsaturated carbonyl groups, α, β -Unsaturated nitrile groups and the like.
[0032]
In this electrolyte aqueous solution layer C, it becomes a spacer for the purpose of preventing an electrical short circuit between the photosensitive electrode (electrode made of a resin-made conductive support and a dye-sensitized semiconductor layer) and the counter electrode. Materials can be mixed in and intervened. These spacers may be either inorganic materials or organic materials, but are preferably spherical and uniform-sized particles, and are preferably soft materials that do not physically damage the electrodes. Examples of such a material include water-resistant polymers such as nylon beads, silicon rubber beads, and polymer latex beads.
[0033]
In the flexible photovoltaic sheet of this invention, it is necessary to provide the mechanism by which the electrolyte aqueous solution layer C which comprises it is continuously supplied from the exterior by capillary action. By utilizing the capillary action in this manner, it is possible to continuously replenish the electrolyte aqueous solution or its component water without applying an artificial or mechanical force from the outside and without requiring a special drive device. it can.
[0034]
If this mechanism is used, the sensitizing dye used in the porous semiconductor layer can be replenished from the outside as required. In other words, when the flexible photovoltaic sheet of the present invention is operated for a long period of time, the dye carried on the porous semiconductor layer is deteriorated by environmental factors such as light and heat, or is decomposed and reduced in weight. Although the required amount may be lacking, the dye reduced in such a case can be replenished by feeding it into the flexible photovoltaic sheet as a dye solution in the same manner as the replenishment of the aqueous electrolyte solution. The dye solution at this time may be an aqueous solution or a solution dissolved in a mixed solution of a water-miscible organic solvent and water. Further, the dye solution may be mixed with the electrolyte aqueous solution and replenished at the same time.
[0035]
In the present invention, the electrolyte aqueous solution or water that is a component thereof is “continuously supplied” means that the electrolyte aqueous solution or water does not have an operation for interrupting the supply, or the shortage of them or one of them. This means that it is constantly supplied or ready for supply. In other words, the electrolyte aqueous solution or water storage tank that is the supply source and the electrolyte aqueous solution of the photovoltaic sheet take a structure that is physically connected as a fluid, and the fluid in the storage layer can flow into the photovoltaic sheet. it can.
[0036]
In addition, the supply using the capillary action means that the capillary phenomenon is the power of supplying the aqueous electrolyte solution or its component water. This capillary phenomenon means a phenomenon in which the electrolyte aqueous solution or water enters a capillary or sheet-like narrow gap and rises against atmospheric pressure.
[0037]
In the flexible photovoltaic sheet of the present invention, when the fluid to be replenished using the capillary action is water, the osmotic membrane can be used together to enhance the supply power using the force of the osmotic pressure. it can. This permeable membrane is preferably provided at an inlet for supplying water to the photovoltaic sheet or at a place where water is supplied as a whole.
As the osmotic membrane, a semi-permeable membrane that permeates water molecules but does not permeate salt ions, for example, a polyamide resin or a composite thereof, or a cellulose resin is used. Can be obtained as a commercial product.
[0038]
At this time, if desired, various organic or inorganic materials having a water retention effect can be used in combination with the osmosis membrane to promote the water penetration effect. A water-absorbing polymer is suitable as the organic material having a water retention effect. Examples of the water-absorbing polymer include starch-polyacrylonitrile hydrolyzate, starch-polyacrylate cross-linked product, carboxylmethylcellulose-based, vinyl acetate-methyl acrylate saponified product, and polyacrylic acid soda cross-linked product. In addition to these, there are various synthetic polymers used for commercially available disposable diapers. These water retaining materials may contain various antiseptic inorganic or organic compounds in solid or liquid form for the purpose of preventing the propagation of bacteria in water and the decay of water, as desired.
[0039]
FIG. 2 is a perspective view showing an example of a foliage plant-like unit for photovoltaic power generation by designing and processing a flexible photovoltaic sheet having the above configuration into a leaf shape. In this figure, a flower pot 8 made of a water-resistant material contains a water retention material 9, and a water replenishment / current collection stem 10 is erected on the water retention material 9. A flexible photovoltaic sheet (hereinafter referred to as a leaf sheet) 12,... Formed in a leaf shape is held.
[0040]
FIG. 3 is a plan view showing details of the leaf-like sheet 12, and the lead wire 5 introduced into the leaf portion as an extension of the petiole portion 11 is further divided into a main vein 13 and a terminal vein 14 branched from the main vein. Is forming. The stem portion 10 and the petiole portion 11 are formed of the same material as the lead wire, and the electrolyte aqueous solution or water absorbed in the water retention material 9 together with the current collecting lead wire is the electrolyte aqueous solution layer of each leaf-like flexible photovoltaic sheet. A capillary focusing body for feeding into the container is accommodated.
In this manner, the lead wire 5 is electrically connected from the terminal vein 14 through the main vein 13 to the current collecting lead wire of the stem portion, and is taken out as an output from a proper portion of the stem portion. On the other hand, the electrolyte aqueous solution or water ascends the stem 10 from the water retention material 9 by capillary action or osmotic pressure, and reaches the electrolyte aqueous solution layer 4 of the photovoltaic sheet through the petiole 11.
[0041]
In the unit for photovoltaic power generation that mimics the shape of the above-mentioned houseplant, it is preferable that the water injection portion for replenishing the electrolyte aqueous solution using capillary force is provided in a flower pot for fixing the unit. In this case, water that is a component of the aqueous electrolyte solution is supplied by pouring water into the flower pot. In this case, for the purpose of water retention, the above-mentioned material having a water retention effect (for example, a water-absorbing polymer) can be disposed to improve the efficiency of storing water for supply.
The structure of the capillary, the osmotic membrane, and the water-absorbing material having a water retention effect may be changed in any way without departing from the object of the present invention.
[0042]
When a photovoltaic power generation unit having such a structure is used, the light receiving area is 1 cm under sunlight irradiation. ² A maximum output of 20 mA and a voltage of 0.4 to 0.8 V can be obtained.
In addition, it is known that when a thin groove is provided at a period of 0.4 μm or less in the dye-sensitized porous semiconductor layer 3, photoelectric conversion efficiency can be remarkably increased (Japanese Patent Laid-Open No. 7-176773). Gazette), and by providing fine streak imitating fine veins on each leaf piece, the photoelectric conversion efficiency can be further increased.
[0043]
Further, when a plurality of photovoltaic power generation units having such a structure are combined with each other and electrically connected in series or in parallel, a considerably high output photovoltaic power generation apparatus can be configured. In this case, it is preferable that the electrolyte aqueous solution supplied by capillary action or the piping for supplying water of the component is also connected to each other. If it does in this way, supply to each unit can be collectively performed in one supply position provided in the system.
[0044]
Next, the method for producing the flexible photovoltaic sheet of the present invention is not particularly limited. For example, a coating method, that is, a dispersion containing a porous semiconductor is applied onto the support and heated and dried. It is advantageous to immobilize the porous layer on a support. At this time, in order to prepare a dispersion of semiconductor fine particles, in addition to the sol-gel method described above, a method of precipitating fine particles as a coprecipitation product of a chemical reaction in a solvent, ultrasonic irradiation or mechanical grinding is used. A method of pulverizing and dispersing into fine particles can be used.
[0045]
As a dispersion medium, water or various organic solvents are used. When dispersing, for example, a polymer such as polyethylene glycol, hydroxyethyl cellulose, carboxymethyl cellulose, a surfactant, an acid or a chelating agent is used as a dispersion aid. Add a small amount, apply onto a support, and form a film. This coating should be performed using any method conventionally used for coating processing, such as the roller method, dipping method, air knife method, blade method, wire bar method, slide hopper method, extrusion method, and curtain method. Can do. Further, a spin method or a spray method using a general-purpose machine can also be used. Application may be made using wet printing such as intaglio, rubber plate, screen printing, as well as the three major printing methods of letterpress, offset and gravure. From these, a preferred film forming method is selected according to the liquid viscosity and the wet thickness.
[0046]
It is preferable to heat-treat the coated layer of semiconductor fine particles in order to enhance the electronic contact between the semiconductor fine particles and improve the adhesion to the support. The temperature range for the heat treatment is 100 ° C. or more and 250 ° C. or less, but for the purpose of reducing the deformation due to heating of the resin support and the resistance increase of the conductive layer, the preferred temperature range is 100 ° C. or more and 150 ° C. or less. is there. In addition, the semiconductor fine particles can be irradiated with ultraviolet light that is strongly absorbed by the fine particles, or the fine particle layer can be heated by irradiating the microwaves to enhance the physical bonding between the fine particles. .
[0047]
In addition, a method of supporting a thin film of particles by electrodeposition can be used. That is, the semiconductor fine particles are added to an appropriate low-conductivity solvent such as pure water, polar organic solvents such as alcohol, acetonitrile and THF, nonpolar organic solvents such as hexane and chloroform, or a mixed solvent thereof, so that there is no aggregation. The conductive resin sheet electrode to be electrodeposited and the counter electrode are made to face each other in parallel at a constant interval, the dispersion liquid is injected into the gap, and a DC voltage is applied between the electrodes. In this way, by selecting the concentration of the dispersion and the electrode interval, an electrodeposition film having a constant and uniform thickness is formed on the substrate electrode.
[0048]
In this case, the thickness of the entire semiconductor fine particles is selected in the range of 1 to 30 μm, preferably 2 to 10 μm. For the purpose of increasing transparency, 2 to 6 μm is preferable. The coating amount is 1 m of a semiconductor fine particle support. ² Per 0.5-5-20g / m ² , Especially 5-10g / m ² Is preferred.
[0049]
The flexible photovoltaic sheet of the present invention is irradiated with light on either or both sides of the dye-sensitized porous semiconductor electrode and counter electrode. Moreover, the light which irradiated one photovoltaic sheet can permeate | transmit this sheet | seat, and it can also utilize in the form which further irradiates another photovoltaic sheet. The direction of the surface of each photovoltaic sheet relative to the direction of incidence of light may be aligned or random, but the light receiving surface of each sheet is alternately arranged in a direction that improves the light collection rate. It is preferable.
[0050]
Sensing elements necessary for environmental monitoring, such as measurement of light radiation conditions and temperature measurement, can be attached to the photovoltaic sheet of the present invention. For example, a sensor that measures the amount of ultraviolet radiation in sunlight, a sensor that measures dust or gas in the atmosphere, and a sensor that detects humidity are attached, and this sheet is applied as an environmental measurement robot. be able to.
[0051]
The electric power output by the photovoltaic sheet of the present invention can be used for the purpose of driving various outdoor and indoor devices. For example, rotation of circulating ventilation fan, input of signal to dimming device and driving of device, driving of IT related device, management of crime prevention device, driving, driving of audio device, and power supply to local community Can be used as
[0052]
【Example】
Next, the present invention will be described in more detail with reference to examples.
[0053]
Example 1
(1) Production of transparent resin conductive support
Transparent polyimide (manufactured by IST Co., Ltd.) is stretched into a film with a thickness of 0.5 mm, and fluorine-doped tin dioxide is uniformly coated on the entire surface by a CVD method. The thickness is 500 nm, and the surface resistance is about 18Ω / cm ² A flexible transparent conductive support made of plastic, in which a conductive tin dioxide film having a light transmittance (500 nm) of 85% was coated on one side, was formed. On the tin oxide conductive layer, platinum was deposited as an auxiliary lead wire to a thickness of about 200 nm by vacuum sputtering so as to form a leaf vein pattern, and carbon was further deposited on top of the leaf vein pattern to a thickness of about 100 nm. .
[0054]
(2) Coating of a thin porous semiconductor layer on a conductive support
Titanium dioxide ultrafine particles having an average primary particle size of 20 nm and an anatase content of 70% were prepared by a vapor phase thermal hydrolysis method using a vapor of a titanium chloride solution as a raw material. The obtained particles were dispersed in a mixed solvent of water and ethyl alcohol (volume ratio 9: 1) at a concentration of 15% by mass, and 3% by mass of polyethylene glycol (PEG) having a molecular weight of 200,000 was added to obtain a highly viscous emulsion. Prepared. The emulsion was applied on the transparent resin conductive support with a uniform thickness, dried, and then heat-treated at 350 ° C. for 50 minutes in the air. Furthermore, the treatment was performed at 200 ° C. for 20 minutes while irradiating the coated surface of the support with ultraviolet light from a 100 W high-pressure mercury lamp. In this way, a uniform thin film of titanium oxide having a thickness of 5 μm was formed on the support.
[0055]
(3) Preparation of dye-sensitized porous semiconductor thin layer
As a sensitizing dye having absorption up to 670 nm on the long wavelength side, a mixture of water-soluble chlorophyll a derivative and chlorophyll b derivative (molar ratio 1: 1) ^-Four Dissolved in mol / liter. In this dye solution, a sulfosuccinic surfactant was dissolved as an additive to a concentration of 0.01 mol / liter to prepare a dye adsorption solution. The transparent conductive resin support carrying the titanium oxide thin film was immersed in the adsorption dye solution and allowed to stand at 40 ° C. for 3 hours with stirring. After the dye was adsorbed on the porous semiconductor layer in this way, the electrode was washed with water to produce a dye-sensitized porous semiconductor electrode.
[0056]
(4) Fabrication of flexible photovoltaic sheet
A dye-sensitized porous semiconductor electrode including a resin support is processed by cutting into a green leaf shape, and the semiconductor layer at the peripheral edge is scraped off to obtain a light receiving area of 25.0 cm. ² The light receiving layer was formed. For this electrode, the polyimide transparent conductive support (supporting the platinum / carbon auxiliary lead pattern) prepared in (1) above as a counter electrode was used as a frame spacer made of a thermocompression-bonding polyethylene film. (Thickness 20 μm) was inserted and overlapped, the spacer part was heated to 120 ° C., and both substrates were pressure bonded. Furthermore, the edge part of the cell was sealed with an epoxy resin adhesive. Thus, the outer structure of the sheet was produced. Next, 3% by mass of lithium iodide and iodine (molar ratio 3: 2) as an electrolyte and 3% by mass of nylon beads having an average particle diameter of 20 μm as a spacer through a small hole for electrolyte injection provided in advance in the corner of the sheet. An aqueous electrolyte solution was prepared, and the capillarity was applied from the small holes so that it was infiltrated into the space between the electrodes. After injecting the electrolytic solution, the sheet was sucked for several hours under reduced pressure, the inside of the sheet including the porous electrode and the electrolytic solution was deaerated, and finally the small holes were sealed with an epoxy resin adhesive.
[0057]
(5) Manufacture of photovoltaic power generation unit
The two electrode output terminals of the photovoltaic sheet produced as described above were connected to two positive and negative current collector plates of a current collector tube in the form of a stem of a foliage tree. This stem structure consists of a hollow tube, and on the wall of the tube, two types of metal electrodes, a positive electrode and a negative electrode for current collection, are printed in a strip shape. A positive electrode and a negative electrode of each sheet (artificial leaf) are connected to the strip-shaped metal electrode. The hollow portion of the tube is filled with a water-retaining resin material, and the resin material is impregnated with water, that is, water for replenishing the electrolyte without causing a gap due to bubbles or the like. When the photovoltaic sheet is physically and mechanically coupled to the stem structure and electrically connected, the aqueous electrolyte solution of the unit is connected to the water filling the inside of the stem. An osmotic membrane film (ion exchange resin film) for ensuring osmotic pressure is inserted into the water connecting portion that fills the unit and the stem. The output of the photovoltaic sheet is input to the current collector of the stem, and then is subjected to current and voltage enhancement by a parallel or series circuit provided inside the stem. In the system of the present embodiment, four units are connected in series on the equivalent circuit, and a set of four series units are connected in parallel to collect power. The total number of units (leaves) used in this experiment is 16, and four series circuits composed of four units are connected in parallel. In this way, the electric power from the plurality of photovoltaic sheets is combined into one DC electric power on the photovoltaic device, and is output outside the system as shown in FIG.
[0058]
(5) Measurement of photovoltaic power generation performance of photovoltaic device
A 500 W xenon lamp (made by USHIO ELECTRIC CO., LTD.) Is equipped with a correction filter for sunlight simulation (AM 1.5 Global made by Oriel), and the incident light intensity is 100 mW / cm with respect to the above photovoltaic generator. ² Were irradiated with various incident angles with respect to the horizontal plane. The system was left indoors at a temperature of 18 ° C. and a humidity of 50%.
Using a current-voltage measuring device (Keutley source measure unit 238 type), the DC voltage applied to the system is scanned at a constant speed of 10 mV / second, and the photocurrent output from the device is measured, so that photocurrent-voltage Characteristics were measured.
In this measurement, the performance obtained by changing the incident angle, that is, the average photocurrent density (Jsc), the open circuit electromotive force (Voc), and the light energy conversion efficiency (η) are shown in Table 1. Here, the average photocurrent density (Jsc) is a value obtained by dividing the photocurrent output by the entire system by the sum of the projected light receiving areas of all the units constituting the system.
[0059]
[Table 1]

The system orientation in the table has the following meaning.
State 1: When a flower pot is placed in the direction shown in FIG. 2 with respect to the light source.
State 2: When the flower pot is rotated 90 ° clockwise from the direction of FIG.
State 3: When the flower pot is rotated 180 ° clockwise from the direction of FIG.
[0060]
From the results in Table 1, this device uses water as a recyclable resource necessary for power generation, uses natural pigments, and produces sunlight with an efficiency equal to or greater than the energy efficiency of natural photosynthesis (<1%). It turns out that it can be converted into energy. In addition, by using the property that the output changes depending on the light irradiation angle, that is, the radiation intensity, it is possible to control the operating environment of various driving devices (such as indoor arousing fans) corresponding to the radiation intensity of sunlight using this device. is there.
[0061]
Example 2
Experiments were conducted in the same manner as in Example 1 using eosin Y instead of chlorophyll and red pigment extracted from hibiscus flowers as sensitizing dyes. Although the photocurrent density and the light energy conversion efficiency were lower than that of the chlorophyll derivative, an open electromotive force almost the same as the result in Table 1 was obtained.
[0062]
Example 3
About the two photovoltaic power generation sheet | seats formed in the unit for photovoltaic power generation, the terminal was cut | disconnected with the cutter, respectively, and the electrolyte solution inside the sheet | seat was exposed to the open air. When the water supply for replenishment is cut off and the water-retaining material in the pot is dry, air enters the cut portion, the electrolyte in the sheet is reduced, and eventually disappears. Stopped. However, when the pot was filled with replenishing water and the supply of water through the capillaries was started, the electrolyte returned to the unit and the power generation function of the unit was restored. Next, a resin permeable membrane for a reverse osmosis membrane that allows only water molecules to pass through was attached to the cut surface of the sheet, fixed with an epoxy adhesive, and sealed to prevent leakage of the electrolyte. In this state, the water for replenishment was filled and the water supply by the capillary was continued, and as a result of being left for one day, the electrolytic solution of the sheet was not observed to contain bubbles or decrease in the liquid, and the photovoltaic power generation was continuously performed. . In this method, a small amount of water evaporating from the unit through the osmosis membrane (similar to the transpiration from the leaves) can always occur, but the evaporated water is continuously replenished by make-up water supplied by capillary action. it is conceivable that.
[0063]
Example 4
As a result of exposing the photovoltaic sheet formed on the unit for photovoltaic power generation for 30 days under continuous irradiation of high-intensity light (10000 lux) containing ultraviolet rays, part of the sensitizing dye (chlorophyll) in the sheet decomposes. It was observed that the color was decolored. This reduced the photovoltaic power generation function of the sheet to 1/3. Therefore, after removing the sheet from the unit for photovoltaic power generation and removing the internal electrolyte, set the sheet in the unit again, and install it in the leak plug provided on the sheet (to attach the electrolyte to the outside air to leak) The water was poured into the pot using pure water in which the pigment was dissolved at a concentration of about 0.1 mM instead of make-up water, and was circulated throughout the unit overnight. By this operation, it was recognized that the dye solution was filled in the sheet, and at the same time, the semiconductor porous layer was dyed again by the dye. Next, after the supply of the dye solution was stopped and the sheet was dried, supply water containing electrolyte instead of the dye solution was supplied. As a result, the aqueous electrolyte solution entered the unit, and finally the sheet was filled with the electrolyte solution. It was done. By this operation, the photovoltaic power generation function returned to normal.
[0064]
【The invention's effect】
According to the present invention, there is provided a dye-sensitized semiconductor-type flexible photovoltaic sheet having excellent solar energy conversion efficiency, low cost, excellent environmental circulation, and low environmental load, and utilizing this Thus, it is possible to provide a robot that can drive energy conversion by photosynthesis by an artificial plant imitation system and can be used for education of environmental circulation systems based on environmental sensing and green chemistry.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of the structure of a flexible photovoltaic sheet of the present invention.
FIG. 2 is a perspective view showing an example of a foliage plant-like unit for photovoltaic power generation.
FIG. 3 is a plan view showing details of the leaf-like sheet in FIG. 2;
[Explanation of symbols]
1,1 'flexible transparent support sheet
2,2 'transparent conductive layer
3 Porous semiconductor layer
4 Electrolyte aqueous solution
5,5 'lead wire
6 Undercoat layer
7 Fine particle material
8 Flowerpot
9 Water retention materials
10 Stem for collecting water and collecting electricity
11 Petiole part
12 Flexible photovoltaic sheet
13 Main veins
14 Terminal vein

Claims (9)

An electrode A formed by laminating a porous semiconductor layer dye-sensitized via a transparent conductive layer on a transparent support sheet, an electrode B formed by laminating a transparent conductive layer on a transparent support sheet, In the photovoltaic sheet having a structure in which the porous aqueous solution layer C is interposed between the porous semiconductor layer and the transparent conductive layer therebetween, the transparent support of the electrodes A and B is formed of a flexible material, A lead wire for collecting generated electric power is disposed on at least one transparent conductive layer, and a mechanism for continuously supplying an aqueous electrolyte solution or water to the electrolytic aqueous solution layer C by using a capillary action is provided. A flexible photovoltaic sheet characterized by that. The flexible photovoltaic sheet according to claim 1, wherein the electrolyte aqueous solution or water is replenished through a capillary by osmotic pressure from a water retaining material provided outside. The flexible photovoltaic sheet according to claim 1 or 2, wherein the transparent support sheet is a transparent synthetic resin sheet. The flexible photovoltaic sheet according to claim 3, wherein the transparent synthetic resin sheet is a sheet of polyolefin, polyvinyl chloride, polystyrene, polyamide, polyethylene terephthalate, polycarbonate, polyurethane, or polyimide. The flexible photovoltaic sheet according to any one of claims 1 to 4, wherein the dye-sensitized porous semiconductor layer contains at least one selected from titanium oxide, zinc oxide, and tin oxide. The flexible photovoltaic sheet according to any one of claims 1 to 5, wherein the flexible photovoltaic sheet is formed in a leaf shape of a plant and the lead wires are arranged in a vein shape. The flexible photovoltaic sheet according to any one of claims 1 to 6, wherein the lead wire is composed of at least one selected from a carbon material and a metal material. A unit for photovoltaic power generation using the flexible photovoltaic sheet according to any one of claims 1 to 7. A photovoltaic power generation apparatus in which a plurality of photovoltaic power generation units according to claim 8 are connected in series or in parallel.

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