JP7102827B2 - Solar cells and solar cell manufacturing methods - Google Patents

Description

The present invention relates to a solar cell including an active layer containing a perovskite compound.

In recent years, a solar cell using a perovskite compound has been studied from the viewpoint of improving efficiency. In a solar cell having an active layer, the organic active layer sandwiched between a pair of opposing electrodes is sealed in order to prevent the organic active layer from being exposed to outside air or moisture, and to protect the organic active layer from external impact. It is generally completely sealed with a waterproof resin (see, for example, FIG. 2 of Patent Document 1).

Regarding the sealing of the organic active layer, in the field of organic EL, the organic light emitting layer is exposed to the outside air, moisture, etc. by sealing the space formed by the substrate and the cover member from the side surface of the substrate and the cover material. (See Patent Documents 2 and 3).

Patent No. 6151378 JP-A-2017-199682 JP-A-2017-062870

Since the sealing layer is usually composed of a thermoplastic resin or a thermosetting and photocurable resin, generally, when sealing a solar cell element, after covering the solar cell element with a sealing resin, It is necessary to irradiate with heat treatment or UV. On the other hand, since the active layer containing the perovskite compound does not have high resistance to heat and UV, there is a problem that the power generation performance of the solar cell element may deteriorate due to heat or UV irradiation when forming the sealing layer. Have.

Therefore, the present inventors have provided an active layer containing a perovskite compound in the sealing technique from the side end portion of the substrate and the cover material used in the field of organic EL described in Patent Documents 2 and 3. By applying it to a solar cell element, we tried to reduce the damage caused by heat and UV to the active layer. However, in general, when manufacturing a solar cell, patterning is required after forming each layer constituting the solar cell element, but the patterning of the active layer is not sufficient, and a sealing layer is provided at the end of the substrate. It was found that if the perovskite compound remains at the position, the substrate and the sealing layer may be easily peeled off depending on the type of resin used for the sealing layer. Further, in order to solve this problem, it is conceivable to pattern the position where the sealing layer is provided at the end of the substrate so that the perovskite compound is completely removed, but the perovskite compound should be completely removed. Was difficult. An object of the present invention is to provide a highly durable solar cell that can be easily manufactured, has high adhesion between a sealing layer and a substrate.

As a result of studies by the present inventors in order to solve the above problems, by providing a sealing layer at the end of the substrate using a specific resin, even if the perovskite compound remains at the position where the sealing layer is provided. , The invention was completed by finding that it is possible to provide a solar cell having high adhesion between the sealing layer and the lower substrate and having high durability.

The gist of the present invention is as follows.
[1] A solar cell element having an active layer containing a perovskite compound sandwiched between a pair of electrodes composed of a lower electrode and an upper electrode, a sealing layer, and an upper substrate are provided on the lower substrate. The sealing layer is located at the end of the lower substrate in which the solar cell element does not exist, and the sealing resin forming the sealing layer has a solubility parameter SP value of 10 or more and the sealing layer. Is a solar cell containing a perovskite compound (excluding those in which at least one of the lower substrate and the upper substrate has a thin film layer) .
[2] A solar cell element having an active layer containing a perovskite compound sandwiched between a pair of electrodes composed of a lower electrode and an upper electrode, a sealing layer, and an upper substrate are provided on the lower substrate. death,
The sealing layer is located at the end of the lower substrate in which the solar cell element does not exist.
The perovskite compound is present on the surface of the lower substrate in contact with the sealing layer,
A solar cell in which the sealing resin forming the sealing layer has a solubility parameter SP value of 10 or more, and the sealing layer contains a perovskite compound.
[ 3 ] The solar cell according to [1] or [2] , wherein the solar cell element is such that the sealing layer is not in contact with the active layer located on the lower electrode.
[ 4 ] The solar cell according to any one of [1] to [3], wherein the sealing resin forming the sealing layer is an epoxy resin.
[ 5 ] The solar cell according to any one of [1] to [ 4 ], wherein the sealing resin forming the sealing layer is a photocurable epoxy resin.
[ 6 ] The solar cell according to any one of [1] to [ 5 ], wherein the sealing layer has a film thickness of 5 μm or more.
[7] A method for producing a solar cell, which comprises a step of forming a lower electrode, an active layer containing a perovskite compound, and an upper electrode on a lower substrate to manufacture a solar cell element, and a step of forming a sealing layer. And
In the step of forming the sealing layer, the sealing layer is formed on the surface at the end of the lower substrate where the solar cell element does not exist and the perovskite compound exists.
A method for manufacturing a solar cell, wherein the sealing resin forming the sealing layer has a solubility parameter SP value of 10 or more.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a highly durable solar cell that simplifies the manufacturing process and has less peeling of the sealing layer.

It is a schematic diagram of the solar cell element 100 which concerns on one Embodiment of this invention. It is an enlarged view of the chain line portion in FIG.

Hereinafter, the present invention will be described in detail while showing specific embodiments, but it goes without saying that the present invention is not limited to the specific embodiments exemplified. In addition, although drawings are used in the description of the invention, the drawings used are all schematically showing specific embodiments, and are partially emphasized, enlarged, reduced, or omitted in order to deepen understanding. , The scale and shape of each component may not be accurately represented.

The solar cell according to the embodiment of the present invention includes a solar cell element having an active layer containing a perovskite compound sandwiched between a pair of electrodes composed of a lower electrode and an upper electrode on a lower substrate, and a sealing layer. And has an upper substrate.

<Upper board and lower board>
The lower substrate is a support member that constitutes a solar cell. The upper substrate is a member that seals the solar cell element together with the sealing layer described later. The material of the lower substrate and the upper substrate is preferably a flexible substrate made of a resin material having flexibility enough to be wound around a roll so that it can be applied to a roll-to-roll method, but it is transparent. It may be a glass substrate or a ceramic substrate.
When the lower substrate and / or the lower substrate is formed of a resin material, for example, polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyether sulfone, polyimide, nylon, polystyrene, polyvinyl alcohol, ethylene vinyl alcohol copolymer, and fluororesin. Film, polyvinyl chloride, polyethylene, polypropylene, cyclic polyolefin, cellulose, acetyl cellulose, polyvinylidene chloride, aramid, polyphenylene sulfide, polyurethane, polycarbonate, poly (meth) acrylic resin, phenol resin, epoxy resin, polyarylate, polynorbornene, etc. Organic materials and the like. Among these, polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyimide, and poly (meth) acrylic resin films are preferable in terms of ease of forming a flexible substrate. Further, from the viewpoint of heat resistance, polyethylene naphthalate and polyimide film are particularly preferable. As the material of the upper substrate and the lower substrate, one kind may be used, or two or more kinds may be used in any combination and ratio. Further, the upper substrate and the lower substrate may be the same type of substrate or may be different substrates.

The thickness of the upper substrate and the lower substrate is not particularly limited, but is usually 20 μm or more, preferably 50 μm or more, while usually 1000 μm or less, preferably 500 μm or less, more preferably 200 μm or less. The film thicknesses of the upper substrate and the lower substrate may be the same or different.

<Pair of electrodes>
The pair of electrodes is composed of a lower electrode and an upper electrode, and one of the pair of electrodes has a function of collecting holes generated by the active layer absorbing light (hereinafter referred to as an anode). ), And the other electrode is an electrode having a function of collecting electrons generated by the active layer absorbing light (hereinafter, referred to as a cathode). When the lower electrode is used as an anode, the upper electrode is preferably used as a cathode, and when the lower electrode is used as a cathode, the upper electrode is preferably used as an anode.

Of the pair of electrodes, at least one electrode is preferably a transparent electrode, and the other electrode does not necessarily have to be a transparent electrode. The transparent electrode usually means an electrode having a visible light transmittance of 60% or more, but in order to improve the conversion efficiency, the visible light transmittance of the transparent electrode is preferably 70% or more. The upper limit is not particularly limited, but is usually 90% or less. The visible light transmittance of the electrode can be measured by a spectrophotometer, for example, by using an ultraviolet visible near infrared spectrophotometer UV-3600 (manufactured by Shimadzu Corporation) and a film sample holder. can. As for the measurement result, the transmittance of the wavelengths from 380 nm to 780 nm is calculated according to JIS R 3106: 1998, and the transmittance of the transparent electrode can be calculated as the average of the transmittances in these wavelength regions.

When the lower electrode and / or the upper electrode is a transparent electrode, the lower electrode and / or the upper electrode is formed of a single layer of a transparent conductive layer or a metal layer as long as it has the above-mentioned visible light transmittance. It may be formed by laminating a transparent conductive layer and a metal layer. However, when the transparent electrode is formed only by the transparent conductive layer, the resistance is high and the conversion efficiency tends to be lowered because it tends not to show good conductivity. Further, when the transparent electrode is formed only by a thin metal layer, the metal layer is easily corroded and the photoelectric conversion element tends to deteriorate over time. Therefore, the electrode to be the transparent electrode is made of a transparent conductive layer and a metal layer. It is preferably formed by laminating.

The material used for the transparent conductive layer is not particularly limited, but tin-doped indium oxide (ITO), zinc-doped indium oxide (IZO), tungsten-doped indium oxide (IWO), and the like. Oxides of zinc and aluminum (AZO), indium oxide (In ₂ O ₃ ), and the like. Among these, non-tin-doped indium oxides (ITO), zinc-doped indium oxides (IZO), tungsten-doped indium oxides (IWO), zinc-tin composite oxides (ZTO), etc. It is preferable to use a crystalline oxide.

Further, the transparent conductive layer preferably has a sheet resistance of 100 Ω / □ or less, more preferably 50 Ω / □ or less, and more preferably 0.1 Ω / □ or more.

The material of the metal layer is not particularly limited, and examples thereof include metals such as gold, platinum, silver, aluminum, nickel, titanium, magnesium, calcium, barium, sodium, chromium, copper, and cobalt, or alloys thereof. Among these, the material forming the metal layer is preferably silver or an alloy of silver, which exhibits high electrical conductivity and high visible light transmittance in a thin film. As silver alloys, in order to be less susceptible to sulfide or chlorination and to improve stability as a thin film, silver-gold alloys, silver-copper alloys, silver-palladium alloys, silver-copper alloys, etc. Examples include alloys of palladium and alloys of silver and platinum.

The thickness of the metal layer is not particularly limited as long as it can maintain a visible light transmittance of 70% or more as a transparent electrode, but is preferably 1 nm or more in order to obtain good conductivity, and is preferably 5 nm or more. On the other hand, in order to prevent the light transmittance from decreasing and the amount of light incident on the active layer from decreasing, it is preferably 15 nm or less, and more preferably 10 nm or less.

As described above, as long as one electrode is a transparent electrode, the other electrode does not necessarily have to be a transparent electrode, and may be a non-transparent electrode. When a non-transparent electrode is used, there is no particular limitation, but for example, the non-transparent electrode can be formed by forming a thick metal layer as described above. When both the lower electrode and the upper electrode are transparent electrodes, it is preferable that both the lower electrode and the upper electrode have a laminated structure of a metal layer and a transparent conductive layer.

The total thickness of the lower electrode and the upper electrode is not particularly limited and may be arbitrarily selected in consideration of optical characteristics and electrical characteristics. Among them, in order to suppress the sheet resistance, the film thickness of each of the lower electrode and the upper electrode is preferably 10 nm or more, more preferably 20 nm or more, further preferably 50 nm or more, while it is more preferable. In order to maintain a high transmittance, it is preferably 10 μm or less, more preferably 1 μm or less, and further preferably 500 nm or less.

The method for forming the lower electrode and the upper electrode is not particularly limited, and the lower electrode and the upper electrode can be formed by a known method according to the material to be used. Examples of the film forming step in coating include a vacuum method such as a vapor deposition method and a sputtering method, or a wet method in which an ink containing nanoparticles or a precursor is applied. The electrical characteristics, wettability, and the like may be improved by surface-treating the lower electrode and the upper electrode.

<Buffer layer>
The solar cell element may have a buffer layer between at least one electrode of the pair of electrodes and the organically active layer. That is, an upper buffer layer may be provided between the upper electrode and the organically active layer, and / or a lower buffer layer may be provided between the lower electrode and the organically active layer.

The buffer layer is classified into an electron extraction layer or a hole extraction layer that improves electron extraction efficiency.
The material of the electron extraction layer is not particularly limited as long as it is a material capable of improving the electron extraction efficiency, and examples thereof include an inorganic compound and an organic compound.
Examples of the inorganic compound include alkali metal salts such as Li, Na, K or Cs; n-type semiconductor oxides such as titanium oxide (TiOx) and zinc oxide (ZnO). Among them, the alkali metal salt is preferably a fluoride salt such as LiF, NaF, KF or CsF, and the n-type semiconductor oxide is preferably zinc oxide (ZnO). Although the operating mechanism of such a material is unknown, it is conceivable to reduce the work function of the cathode when combined with a cathode composed of Al or the like and increase the voltage applied to the inside of the solar cell element.

Examples of organic compounds include phosphine compounds having a double bond between a phosphorus atom and a Group 16 element, such as a triarylphosphine oxide compound; substituents such as vasocuproin (BCP) or vasofenantrene (Bphenyl). A phenanthrene compound in which the 1-position and the 10-position may be replaced with a hetero atom; a boron compound such as triarylboron; an organic metal such as (8-hydroxyquinolinato) aluminum (Alq3). Oxides; compounds with one or two ring structures that may have substituents, such as oxadiazole compounds or benzoimidazole compounds; naphthalenetetracarboxylic acid anhydrides (NTCDA) or perylenetetracarboxylic acid anhydrides. Examples thereof include aromatic compounds having a condensed dicarboxylic acid structure such as dicarboxylic acid anhydride such as (PTCDA).

The material of the hole extraction layer is not particularly limited as long as it is a material capable of improving the efficiency of extraction of holes, but for example, polythiophene, polypyrrole, polyacetylene, triphenylenediamine, polyaniline and the like, and sulfonic acid. And / or a conductive polymer doped with iodine or the like; a polythiophene derivative having a sulfonyl group as a substituent, a conductive compound such as a conductive organic compound such as arylamine; copper oxide, nickel oxide, manganese oxide, molybdenum oxide, oxidation Examples thereof include metal oxide semiconductors such as vanadium and tungsten oxide; semiconductor compounds such as Nafion and p-type semiconductors described later. A conductive polymer doped with sulfonic acid is preferable, and a polythiophene derivative is doped with polystyrene sulfonic acid (3,4-ethylenedioxythiophene) poly (styrene sulfonic acid) (PEDOT: PSS). ..

The film thickness of the buffer layer is not particularly limited and can be appropriately set depending on the buffer layer material used. When a semiconductor compound is used as the buffer layer material, it is preferably 10 nm or more, more preferably 30 nm or more, and particularly preferably 50 nm or more in order to improve the electron or hole extraction efficiency. On the other hand, in order to keep the internal resistance of the solar cell element low and improve the conversion efficiency of the solar cell element, it is preferably 300 nm or less, and more preferably 200 nm or less. On the other hand, when a conductive compound is used as the buffer layer material, it is preferably 10 nm or more, more preferably 50 nm or more, and particularly preferably 100 nm or more in order to improve the electron or hole extraction efficiency. .. On the other hand, in order to keep the internal resistance of the solar cell element low and improve the conversion efficiency of the solar cell element, it is preferably 1000 nm or less, more preferably 700 nm or less, and particularly preferably 500 nm or less. The film thickness of the buffer layer can be obtained by calculating the average film thickness using spectroscopic ellipsometry.

The method for forming the electron extraction layer and the hole extraction layer is not particularly limited, and the electron extraction layer and the hole extraction layer can be formed by a known coating method according to the material to be used. For example, when a material having sublimation property is used, it can be formed by a vacuum method such as a vapor deposition method or a sputtering method. When a material soluble in a solvent is used, it can be formed by a wet method such as spin coating or inkjet. Among them, when PEDOT: PSS is used, it is preferable to form a hole extraction layer by a method of applying a dispersion liquid. Examples of the PEDOT: PSS dispersion liquid include the CLEVIOSTM series manufactured by Heraeus and the ORGACONTM series manufactured by Agfa.

<Active layer>
The active layer is a layer on which photoelectric conversion is performed. When the photoelectric conversion element receives light, the light is absorbed by the active layer to generate carriers, and the generated carriers are taken out from the lower electrode and the upper electrode.

In this embodiment, the active layer contains an organic-inorganic hybrid semiconductor material. The organic-inorganic hybrid semiconductor material refers to a material in which an organic component and an inorganic component are combined at the molecular level or the nano level, and exhibits semiconductor characteristics.

In the present embodiment, the organic-inorganic hybrid semiconductor material is a compound having a perovskite structure (hereinafter, may be referred to as a perovskite semiconductor compound). The perovskite semiconductor compound refers to a semiconductor compound having a perovskite structure. The perovskite semiconductor compound is not particularly limited, but can be selected from, for example, those listed in Galasso et al. Structure and Properties of Inorganic Solids, Chapter 7 --Perovskite type and related structures. For example, examples of the perovskite semiconductor compound include those of AMX ₃ type represented by the general formula AMX ₃ and those of A ₂ MX ₄ type represented by the general formula A ₂ MX ₄ . Here, M refers to a divalent cation, A refers to a monovalent cation, and X refers to a monovalent anion.

The monovalent cation A is not particularly limited, but the one described in the above-mentioned Galasso's book can be used. More specific examples include cations containing Group 1 and Group 13 to Group 16 elements of the periodic table. Among these, cesium ion, rubidium ion, ammonium ion which may have a substituent or phosphonium ion which may have a substituent are preferable. Examples of ammonium ions that may have a substituent include primary ammonium ions or secondary ammonium ions. There are no particular restrictions on the substituents. Specific examples of ammonium ions that may have a substituent include alkylammonium ions or arylammonium ions. In particular, monoalkylammonium ions having a three-dimensional crystal structure are preferable in order to avoid steric hindrance, and from the viewpoint of improving stability, alkylammonium ions substituted with one or more fluorine groups are preferably used. Further, a combination of two or more kinds of cations can be used as the cation A.

Specific examples of the monovalent cation A include methylammonium ion, monofluoromethylammonium ion, difluoride methylammonium ion, trifluoride methylammonium ion, ethylammonium ion, isopropylammonium ion, n-propylammonium ion, and isobutylammonium ion. , N-butylammonium ion, t-butylammonium ion, dimethylammonium ion, diethylammonium ion, phenylammonium ion, benzylammonium ion, phenethylammonium ion, guanidium ion, formamidinium ion, acetamidinium ion or imidazolium Ions and the like can be mentioned.

The divalent cation M is also not particularly limited, but is preferably a divalent metal cation or a metalloid cation. Specific examples include cations of Group 14 elements of the periodic table, and more specific examples include lead cations (Pb ²⁺ ), tin cations (Sn ²⁺ ), and germanium cations (Ge ²⁺ ). Further, a combination of two or more kinds of cations can be used as the cation M. From the viewpoint of obtaining a stable photoelectric conversion element, it is particularly preferable to use a lead cation or two or more kinds of cations containing a lead cation.

Examples of monovalent anion X include halide ion, acetate ion, nitrate ion, sulfate ion, borate ion, acetylacetonate ion, carbonate ion, citrate ion, sulfur ion, tellurium ion, thiocyanate ion, and titanic acid. Examples thereof include an ion, a zirconate ion, a 2,4-pentandionato ion, a siliceous fluorine ion and the like. In order to adjust the bandgap, X may be one kind of anion or a combination of two or more kinds of anions. In one embodiment, X includes a halide ion, or a combination of a halide ion and another anion. Examples of the halide ion X include chloride ion, bromide ion, iodide ion and the like. It is preferable to use iodide ions from the viewpoint of not widening the band gap of the semiconductor too much.

The active layer contains at least a halide-based organic-inorganic perovskite semiconductor compound in which X is a halide ion or a combination of a halide ion and another anion, and may contain other perovskite semiconductor compounds. For example, the active layer may contain a perovskite semiconductor compound in which at least one of A, B, and X is different. Further, the active layer may have a laminated structure formed by a plurality of layers containing different materials or having different components.

Specific examples of the halide-based organic-inorganic perovskite semiconductor compound include CH ₃ NH ₃ PbI ₃ , CH ₃ NH _{3 PbBr 3} , CH ₃ NH ₃ PbCl ₃ , CH ₃ NH ₃ SnI ₃ , CH ₃ NH ₃ SnBr ₃ NH ₃ SnCl ₃ , CH ₃ NH ₃ PbI _(3-x) Cl _x , CH ₃ NH ₃ PbI _(3-x) Br _x , CH ₃ NH ₃ PbBr _(3-x) Cl _x , CH ₃ NH ₃ Pb _{( 1-y)} Sny I ₃ , CH ₃ NH ₃ Pb _(1-y) Sny Br ₃ , CH ₃ NH ₃ Pb _{(1-y) Sny Cl 3} , CH ₃ NH ₃ Pb (1- _{y )} Sn _y I _(3-x) Cl _x , CH ₃ NH ₃ Pb _(1-y) Sn _y I _(3-x) Br _x , and CH ₃ NH ₃ Pb _(1-y) Sn _y Br _(3-x) Cl _x , and those in which CFH ₂ NH ₃ , CF ₂ HNH ₃ , or CF ₃ NH ₃ is used instead of CH ₃ NH ₃ in the above compounds, and the like can be mentioned. Note that x indicates an arbitrary value of 0 or more and 3 or less, and y indicates an arbitrary value of 0 or more and 1 or less.

The amount of the perovskite semiconductor compound contained in the active layer is preferably 50% by mass or more, more preferably 70% by mass or more, and more preferably 80% by mass or more so that good semiconductor properties can be obtained. .. There is no particular upper limit. Further, the active layer may contain an additive in addition to the perovskite semiconductor compound. Examples of additives include inorganic or organic compounds such as halides, oxides, or inorganic salts such as sulfides, sulfates, nitrates or ammonium salts.

There is no particular limitation on the thickness of the active layer. The thickness of the active layer is 10 nm or more in one embodiment, 50 nm or more in another embodiment, 100 nm or more in yet another embodiment, and 120 nm or more in yet another embodiment in that more light can be absorbed. be. On the other hand, the thickness of the active layer is 1500 nm or less in one embodiment, 1000 nm or less in another embodiment, and 600 nm or less in another embodiment in terms of lowering the series resistance or increasing the charge extraction efficiency. be.

The method for forming the active layer is not particularly limited, and any method can be used. Specific examples include a coating method and a thin-film deposition method (or a co-evaporation method). The coating method can be used because the active layer can be easily formed. For example, a method of forming an active layer by applying a coating liquid containing a perovskite semiconductor compound or a precursor thereof and heating and drying it as necessary can be mentioned. Further, after applying such a coating liquid, the perovskite semiconductor compound can be precipitated by further applying a solvent having low solubility of the perovskite semiconductor compound.

The precursor of a perovskite semiconductor compound refers to a material that can be converted into a perovskite semiconductor compound after the coating liquid is applied. As a specific example, a perovskite semiconductor compound precursor that can be converted into a perovskite semiconductor compound by heating can be used. For example, a coating liquid can be prepared by mixing a compound represented by the general formula AX, a compound represented by the general formula MX ₂ , and a solvent, and heating and stirring the mixture. By applying this coating liquid and performing heat drying, an active layer containing a perovskite semiconductor compound represented by the general formula AMX ₃ can be produced. The solvent is not particularly limited as long as the perovskite semiconductor compound and the additive are dissolved, and examples thereof include organic solvents such as N, N-dimethylformamide.

Any method can be used as the coating method, and for example, a spin coating method, an inkjet method, a doctor blade method, a drop casting method, a reverse roll coating method, a gravure coating method, a kiss coating method, a roll brushing method, etc. Examples thereof include a spray coating method, an air knife coating method, a wire barber coating method, a pipe doctor method, an impregnation / coating method, and a curtain coating method.

<Encapsulation layer>
In the present embodiment, the sealing layer is located at the end of the lower substrate in which the solar cell element does not exist, and the lower substrate and the upper substrate are bonded by the sealing layer. Further, the solubility parameter SP value of the resin composition for forming the sealing layer is 10 or more, and the sealing layer contains a perovskite compound. With this configuration, as will be described below, the adhesion between the lower substrate and the sealing layer is improved, and a highly durable solar cell can be provided.

Generally, when a solar cell element is formed on a lower substrate, it is necessary to form a film on each layer constituting the solar cell element and to perform patterning in order to obtain a desired pattern. However, when the active layer containing the perovskite compound is patterned by an etching method, a laser scribe method, or the like, a perovskite compound that does not function as an active layer may remain at the end of the lower substrate. In this case, for example, if a resin having a solubility parameter of less than 10 is used to seal the region where the perovskite compound remains, the compatibility between the resin and the perovskite compound is poor, and the resin and the perovskite compound do not mix. It is difficult to provide a highly durable solar cell because the adhesion between the sealing layer formed by using the resin and the perovskite compound remaining at the end of the lower substrate is weak and the sealing layer is easily peeled off. Is. However, as described above, when the sealing layer is formed using a resin having a solubility parameter of 10 or more, the perovskite compound and the resin are well mixed because the compatibility between the perovskite compound and the resin is good. As a result, it becomes a sealing layer containing a perovskite compound, and it is possible to provide a highly durable solar cell in which the sealing layer is hard to peel off.

It is preferable that the sealing layer does not come into contact with the active layer containing the perovskite compound constituting the solar cell element. As described above, when the solubility parameter of the resin contained in the resin forming the sealing layer is 10 or more, the active layer is sealed when the active layer of the solar cell element and the sealing layer come into contact with each other in order to dissolve the perovskite compound. It is preferable that the sealing layer and the active layer constituting the solar cell element are not in contact with each other because the sealing layer may be immersed in the resin forming the layer and the conversion efficiency may be lowered as a result. Further, in the case of a solar cell in which the sealing layer does not come into contact with the active layer on the lower electrode and is located only at the end of the substrate where the solar cell element does not exist, it becomes possible to partially irradiate heat or ultraviolet rays. Therefore, it becomes easy to prevent the deterioration of the solar cell element. In particular, when the resin forming the sealing layer is a photocurable resin, the sealing layer can be formed without irradiating the solar cell element with ultraviolet rays by using a mask or the like. Sometimes, it is possible to prevent the conversion efficiency from being lowered.

In the present invention, the active layer means an active layer existing on the lower electrode constituting the solar cell element. For example, a perovskite compound layer not located on the lower electrode is not an active layer. Further, the lower electrode means an electrode electrically connected to a wiring for extracting electricity to the outside such as a collecting electric wire when functioning as a solar cell.

This configuration will be described with reference to the drawings. FIG. 1 is a schematic view of a solar cell element 100 according to an embodiment of the present invention. An enlarged view of the chain line portion of FIG. 1 is shown in FIG.
In the solar cell element 100, the lower electrode 12, the active layer 14, and the upper electrode 13 are laminated in this order on the lower substrate 10. In the present embodiment, a solar cell element having an active layer 14 containing a perovskite compound sandwiched between a pair of electrodes composed of a lower electrode 12 and an upper electrode 13 on a lower substrate 10, a sealing layer 15 and the like. The sealing layer is located at the end of the lower substrate where the solar cell element does not exist, and is not in contact with the active layer located on the lower electrode.

In the present embodiment, as described above, the sealing resin forming the sealing layer has a solubility parameter (SP value) of 10 or more, so that the sealing layer can be formed with the perovskite compound existing at the edge of the substrate. Since the compatibility with the resin composition is good, the adhesion between the sealing layer and the lower substrate is good, and a highly durable solar cell can be provided. Among them, the SP value is preferably 10.5 or more, and the upper limit is not particularly limited. The SP value (δi) of the resin material forming the sealing layer in the present specification can be calculated from the following formula (1) proposed by Fedors. Δei represents the evaporation energy of the atom or atomic group of the i component, and Δvi represents the evaporation molar volume of the atom or atomic group of the i component, and the values described in "Polymer Handbook, Fourth Edition" and volume 2 can be used. can.
δi = [Δei / Δvi] ^ (1/2) (1)

The resin of the resin composition forming the sealing layer is not particularly limited as long as the SP value is 10 or more, and examples thereof include epoxy resins, vinyl resins (polyvinyl chloride, polyvinylidene chloride, etc.), polyacrylonitrile, and the like. can give. The sealing layer may be formed of one kind of resin composition or two or more kinds of resin compositions. Among them, an epoxy resin is preferable, and as described above, a photocurable epoxy resin is more preferable and an ultraviolet curable type is used in order to prevent a decrease in conversion efficiency of the solar cell immediately after the formation of the sealing layer. Epoxy resin is particularly preferable.

Further, in order to impart gas barrier properties of water and oxygen to the sealing layer, additives such as an inorganic filler, water and an oxygen getter material may be contained, and in order to prevent oxidation of the sealing layer. May contain an antioxidant.

The inorganic filler is not particularly limited, but for example, silica, mica, talc, clay, bentonite, montmorillonite, kaolinite, wallastonite, calcium carbonate, titanium oxide, alumina, barium sulfate, potassium titanate, and glass fiber. And so on. Among these, silica, clay, and talc are preferable from the viewpoint of imparting gas barrier properties of water and oxygen. The inorganic filler mixed in the resin composition may be one kind or two or more kinds. When it is desired to impart barrier properties while maintaining adhesion, the proportion of the inorganic filler in the resin composition is preferably 5% by mass or less, and more preferably 1% by mass or less.

The water and oxygen getter material is arbitrary as long as it can absorb water and / or oxygen. To give an example of the material, alkali metal, alkaline earth metal or alkali earth metal oxide; alkali metal or alkaline earth metal hydroxide; silica gel, zeolite compound, magnesium sulfate as substances that absorb water. , Sulfates such as sodium sulfate or nickel sulfate; organic metal compounds such as aluminum metal complexes or aluminum oxide octylates. Specifically, examples of the alkaline earth metal include Ca, Sr, Ba and the like. Examples of the oxide of the alkaline earth metal include CaO, SrO and BaO. In addition, Zr-Al-BaO, an aluminum metal complex, and the like can also be mentioned. Specific product names include, for example, OlDry (manufactured by Futaba Corporation). The inorganic filler mixed in the resin composition may be one kind or two or more kinds.

As the antioxidant, various commercially available products can be applied, and various types such as monophenol type, bisphenol type, phenol type such as polymer type phenol type, and phosphite type can be mentioned. The antioxidant may be used alone or in combination of two or more. In the present invention, phenol-based and phosphite-based antioxidants are preferably used from the viewpoint of the effect, thermal stability, economy and the like of the antioxidant, and it is more preferable to use both in combination. The amount of the antioxidant added is usually about 0.1 to 1% by mass, preferably 0.2 to 0.5% by mass, in the resin composition.

The film thickness of the sealing layer is not particularly limited, but from the viewpoint of reducing water vapor and oxygen permeability, it is usually 100 nm or more, preferably 500 nm or more, more preferably 1 μm or more, and particularly preferably 5 μm or more. On the other hand, from the viewpoint of improving the adhesion and reducing the unsealed portion, it is usually 100 μm or less, preferably 50 μm or less, and more preferably 20 μm or less.

The content of the perovskite compound in the sealing layer 15 is not particularly limited, but in order to prevent peeling between the sealing layer and the lower substrate, it is preferably 1% by mass or more, and more preferably 3% by mass or more. It is preferably 5% by mass or more, and on the other hand, in order to prevent deterioration of the function of the sealing layer itself, it is preferably 50% by mass or less, further preferably 30% by mass or less, and 10% by mass. It is particularly preferable that it is% or less.

It is preferable that the void 16 exists between the active layer 14 and the sealing layer 15. When the active layer 14 and the sealing layer 15 come into contact with each other, the active layer may deteriorate at a high temperature.

<Other layers>
The solar cell of the present embodiment may have other layers as appropriate as long as it does not impair the effects of the present invention. Examples of other layers include a current collector, an upper surface protective layer, a back surface protective layer, a barrier layer, an ultraviolet shielding layer, a moisture getter layer, an oxygen getter layer, a wavelength conversion layer, an antireflection layer and the like. These members are appropriately provided depending on the application environment of the solar cell and the like.

The solar cell according to the present invention can be used for any purpose. Examples thereof include solar cells for building materials, solar cells for automobiles, solar cells for spacecraft, solar cells for home appliances, solar cells for mobile phones, solar cells for toys, and the like. In particular, the solar cell element of the present invention is suitable for energy harvesting because it can generate electricity by utilizing indoor lighting or scattered light of sunlight in the room.

<Solar cell manufacturing method>
The method for manufacturing a solar cell is not particularly limited as long as the solar cell according to the present invention can be manufactured. As an example, a solar cell can be manufactured by a step of manufacturing a solar cell element and a sealing step.

The method for manufacturing the solar cell element is not particularly limited, and each layer constituting the above-mentioned solar cell element may be formed by forming a film on the lower substrate. Further, in order to obtain a desired pattern of the solar cell element, each layer may be appropriately patterned and formed. In particular, when the sealing layer is provided at the end of the substrate where the active layer does not exist as in the present invention, it is preferable to pattern each layer formed at the end of the substrate, but the perovskite compound formed for the active layer It is preferable that a part of the layer is not completely patterned and remains appropriately. The patterning method of each layer may be performed by a known method, and preferred examples thereof include an etching method, a laser scribe method, a mechanical scribe method, a photo etching method, and a lift-off method.

The solvent used in the etching method is not particularly limited, but for example, aliphatic hydrocarbons such as hexane, heptane, octane, isooctane, nonane, tetraline or decane; toluene, xylene, mesitylene, cyclohexylbenzene, chlorobenzene or ortho. Aromatic hydrocarbons such as dichlorobenzene; alicyclic hydrocarbons such as cyclopentane, cyclohexane, methylcyclohexane, cycloheptane, cyclooctane, tetraline or decalin; lower alcohols such as methanol, ethanol or propanol; acetone, methyl ethyl ketone , Cyclopentanone or cyclohexanone and other aliphatic ketones; acetophenone or propiophenone and other aromatic ketones; ethyl acetate, butyl acetate or methyl lactate and other esters; chloroform, methylene chloride, dichloroethane, trichloroethane or trichloroethylene and the like. Halogen hydrocarbons; ethers such as ethyl ether, tetrahydrofuran or dioxane; or amides such as N, N-dimethylformamide, dimethylformamide or dimethylacetamide can be mentioned. As the solvent, one kind of solvent may be used alone, or any two or more kinds of solvents may be used in combination at an arbitrary ratio.

The sealing step is not particularly limited as long as the solar cell according to the present invention can be manufactured, but the resin composition forming the sealing layer is applied to the end of the substrate where the solar cell element does not exist, or the like. After arranging and then stacking the upper substrates, it is preferable to cure the resin composition by heat treatment or ultraviolet irradiation. At this time, as described above, if the perovskite compound is present at the edge of the substrate, the resin composition is mixed with the perovskite compound and then cured to form a sealing layer containing the perovskite compound. It is possible to improve the adhesion between the sealing layer and the lower substrate.

The amount of the perovskite compound present at the contact interface between the sealing layer 15 and the lower substrate 10 is not particularly limited, and as shown in FIG. 2, it may be present in the form of the remaining etching, but it is abbreviated as the active layer 14. Perovskite compounds having a similar film thickness may be present. In this case, the encapsulating resin is formed as it is without etching to prepare the end region of the lower substrate. Even in such a case, the compatibility between the perovskite compound and the encapsulating resin is formed. Therefore, the adhesion between the sealing layer and the lower substrate does not matter.

Further, the resin is preferably a thermosetting resin or a photocurable resin, but since the perovskite compound tends to be sensitive to heat, the resin that can be partially irradiated with light is a photocurable resin. Is preferable.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to the description of the following Examples as long as the gist of the present invention is not exceeded. First, the measurement / evaluation test performed in this example will be described. The SP value of the resin forming the sealing layer was calculated based on the above formula (1). The SP value of each resin is as shown in Table 1.

<Example 1>
The solar cell shown in the schematic cross-sectional view of FIG. 1 was manufactured by the following procedure.
First, lead (II) iodide (1014 mg) and methylammonium iodide (CH ₃ NH ₃ I, 350 mg) were weighed into vials so that the molar ratio was 1: 1 and N, N-dimethylformamide (2 mL) was used. Was added. Next, the obtained mixture was heated and stirred at 70 ° C. for 1 hour. Then, the obtained solution was filtered through a polytetrafluoroethylene (PTFE) filter (pore size 0.2 μm) to prepare an active layer coating liquid.
Cleaning agent (Yokohama Yushi Kogyo Co., Ltd., cleaning agent for precision glass substrate, Semi-clean M) for glass substrate (made by Geomatec, thickness 0.7 mm, 40 mm square) provided with indium tin oxide (ITO) transparent conductive film as the lower electrode The lower substrate was prepared by performing ultrasonic cleaning using -LO), ultrasonic cleaning using ultrapure water, drying by nitrogen blow, and UV-ozone treatment.

Poly (3,4-ethylenedioxythiophene) poly (styrene sulfonic acid) dispersion (PEDOT: PSS, Heleus AI4083) is dissolved in 2 mL of a mixed solvent of acetone: water = 1: 1 (weight ratio), and the motorcycle is used. A coating liquid for a hole extraction layer was prepared by filtering with Al (pore size 0.45 μm). The hole extraction layer coating liquid was spin-coated on the entire surface of the glass substrate at room temperature at a speed of 3000 rpm to form a hole extraction layer having a thickness of about 30 nm. The obtained substrate was heated at 120 ° C. for 30 minutes.

The substrate on which the hole extraction layer was formed was introduced into a glove box and heat-treated at 100 ° C. for 10 minutes in a nitrogen atmosphere. After cooling, the active layer coating solution (160 μL) prepared as described above is spin-coated on the entire surface of the substrate at a speed of 4000 rpm, and after about 8 seconds, chlorobenzene (320 μL) is further spin-coated into the coating solution film. The solvent composition of the above was changed to precipitate crystals having a perovskite composition. Further, by heating on a hot plate at 100 ° C. for 10 minutes to grow crystals, an active layer having a thickness of about 350 nm was formed.

The peripheral edges of the four sides of the lower substrate, specifically, about 5 mm from the edge of the substrate, were wiped with N, N-dimethylformamide soaked in a cotton swab so that the active layer remained.

Fullerene C ₆₀ (manufactured by Frontier Carbon) was formed on the active layer excluding the wiping portion at 30 nm, followed by bathocuproine (BCP) (manufactured by Sigma-Aldrich) at 15 nm, respectively, by a resistance heating type vacuum deposition method. Then, an electron extraction layer was formed.

A silver film having a thickness of about 100 nm was deposited on the electron extraction layer by a resistance heating type vacuum vapor deposition method using a patterning mask to form an upper electrode.

Next, an ultraviolet curable epoxy resin (TB3124) manufactured by ThreeBond Co., Ltd. was prepared as a sealing resin. Under a light source from which ultraviolet rays are cut, the above-mentioned sealing resin is applied to the peripheral edges of the four sides of the lower substrate, specifically, about 3 mm from the edge of the substrate, and the sealing glass (manufactured by Technoprint Co., Ltd., thickness) is applied. 0.7 mm, 40 mm square) were overlapped as an upper substrate. Subsequently, the active layer portion was masked, and the entire surface of the substrate was irradiated with xenon light for about 2 minutes using a spot light source (LIGHTNINGCURE LC8 manufactured by Hamamatsu Photonics Co., Ltd.). Then, a sufficiently photocured sealing layer having a thickness of 5 μm and a solar cell were obtained.

<Example 2>
The sealing resin is a thermosetting epoxy resin (TB1651D) manufactured by ThreeBond Co., Ltd. instead of the UV curable epoxy resin (TB3124) manufactured by ThreeBond Co., Ltd. A solar cell was obtained by the same method as in Example 1 except that it was changed to. The vacuum laminate is made by stacking the sealing resin and the upper substrate on the lower substrate, then putting them in a vacuum laminator (NPC, NLM-270 x 400), holding the inside of the laminator under reduced pressure for 15 minutes, and then crimping at atmospheric pressure. It was kept in a state at 120 ° C. for 10 minutes, and then cooled to room temperature. The thickness of the obtained sealing resin was 20 μm.

<Comparative example 1>
A solar cell was obtained in the same manner as in Example 2 except that the sealing resin was an olefin resin (Cranbetter), which is a polyethylene-based copolymer manufactured by Kurabou Co., Ltd., instead of the thermosetting epoxy resin (TB1651D) manufactured by ThreeBond Co., Ltd. rice field. The thickness of the obtained sealing resin was 20 μm.

<Measurement method and evaluation method of adhesion of sealing layer>
The adhesion when the perovskite compound was present between the lower substrate and the sealing layer was measured and evaluated as follows.
An active layer was formed on the entire surface of the glass substrate by the same method as in Example 1. Next, a polyethylene terephthalate (PET) film having a thickness of 50 μm, which is one size larger than the glass substrate, was prepared. Subsequently, the glass substrate and the polyethylene terephthalate film were bonded together by the sealing resin used in Example 1, Example 2, and Comparative Example 1 and the sealing method. The thickness of each of the formed sealing layers was the same as in Example 1, Example 2, and Comparative Example 1. Next, cuts were made from the polyethylene terephthalate side at intervals of 10 mm to obtain a strip-shaped test sample in which the polyethylene terephthalate and the sealing layer were divided into 10 mm widths. Further, as an evaluation sample containing no perovskite compound for comparison, a sealing layer was formed on a glass substrate by the same method as described above using the sealing resins used in Example 1, Example 2, and Comparative Example 1. rice field.

A spring scale was attached to one end of the strip-shaped test sample on the unsealed side, while the glass substrate was sufficiently fixed to the laboratory table. After that, a 180-degree peeling test was performed, and the value of the spring scale when the glass substrate and the sealing layer were peeled off or when the polyethylene terephthalate was broken was read, and the adhesion was evaluated as follows. The results obtained are shown in Table 1.
◯: Polyethylene terephthalate film is broken (10 kgf / 10 mm or more)
X: Peeling between the glass substrate and the sealing layer (less than 5 kgf / 10 mm)
Further, when the same adhesion evaluation as described above was performed on the evaluation samples in which the sealing layer was formed using the resins used in Example 1, Example 2, and Comparative Example 1 prepared for comparison, all of them were polyethylene terephthalate films. Was the result of breaking the material.

<Measurement method and evaluation method of photoelectric conversion efficiency of solar cells>
A solar simulator (manufactured by Spectrometer Co., Ltd.) was used to irradiate light under the condition of AM1.5G with an irradiation intensity of 1000 W / cm ² from the lower substrate side of the solar cell, and the obtained current-voltage curve was measured. A source meter (2400 type manufactured by Keithley) was used for the measurement, and the photoelectric conversion efficiency (PCE) was calculated from the measurement results.
Further, the photoelectric conversion efficiency before and after the sealing layer curing treatment step such as photocuring, thermosetting, and heat treatment for forming the sealing layer, which will be described later, is measured, and the sealing layer curing treatment step is based on the following formula. The efficiency maintenance rate before and after was calculated and evaluated. The results obtained are shown in Table 1.
Efficiency maintenance rate before and after the sealing layer curing process = (PCE immediately after the curing process) / (PCE immediately before the curing process)
◯: Efficiency maintenance rate is 0.98 or more Δ: Efficiency maintenance rate is 0.95 or less

In the solar cell sealing configurations of Examples 1 and 2, the adhesion between the lower substrate and the sealing layer was very high, whereas in the solar cell sealing configuration of Comparative Example 1, the adhesion was poor. It was found to be sufficient and easy to peel off. From this result, it is possible to sufficiently seal the solar cell element even if the perovskite compound remains at the place where the sealing layer is arranged by using the sealing layer made of a resin having an SP value of a specific value or more. I understand. The reason for this is that the resin forming the sealing layer and the perovskite compound have good compatibility, and the area of contact between the resin of the sealing layer and the interface of the lower substrate in the sealing layer increases due to mixing in the sealing step. Therefore, it is considered that the adhesion is not impaired. On the other hand, since the resin of the sealing layer having the SP value as used in the comparative example does not have good compatibility with the organic component of the perovskite compound, it peels off at the interface between the sealing resin and the active layer containing the perovskite compound. It is considered that the adhesion becomes easier and the adhesion becomes lower. Further, comparing Example 1 and Example 2, in the solar cell according to Example 2, the conversion efficiency was lowered due to the influence of the solar cell element due to the thermal curing of the sealing layer. In the solar cell according to the first embodiment, the sealing layer can be cured without irradiating the solar cell element with ultraviolet rays, so that the solar cell can be manufactured without deteriorating the solar cell element. It seems to be.

100 Solar cell 10 Lower substrate 11 Upper substrate 12 Lower electrode 13 Upper electrode 14 Active layer 14'Etching remaining of perovskite compound 15 Sealing layer 16 Void

Claims (7)

A solar cell element having an active layer containing a perovskite compound sandwiched between a pair of electrodes composed of a lower electrode and an upper electrode, a sealing layer, and an upper substrate are provided on the lower substrate.
The sealing layer is located at the end of the lower substrate in which the solar cell element does not exist.
The sealing resin forming the sealing layer has a solubility parameter SP value of 10 or more, and the sealing layer contains a perovskite compound at the contact interface with the lower substrate (however, the lower substrate and the said Except for those having a thin film layer at least one of the upper substrates). A solar cell element having an active layer containing a perovskite compound sandwiched between a pair of electrodes composed of a lower electrode and an upper electrode, a sealing layer, and an upper substrate are provided on the lower substrate.
The sealing layer is located at the end of the lower substrate in which the solar cell element does not exist.
The perovskite compound is present on the surface of the lower substrate in contact with the sealing layer,
A solar cell in which the sealing resin forming the sealing layer has a solubility parameter SP value of 10 or more, and the sealing layer contains a perovskite compound. The solar cell according to claim 1 or 2, wherein the sealing layer is not in contact with the active layer located on the lower electrode. The solar cell according to any one of claims 1 to 3, wherein the sealing resin forming the sealing layer is an epoxy resin. The solar cell according to any one of claims 1 to 4, wherein the sealing resin forming the sealing layer is a photocurable epoxy resin. The solar cell according to any one of claims 1 to 5, wherein the sealing layer has a film thickness of 5 μm or more. A method for manufacturing a solar cell, which comprises a step of forming a lower electrode, an active layer containing a perovskite compound, and an upper electrode on a lower substrate to manufacture a solar cell element, and a step of forming a sealing layer. ,
In the step of forming the sealing layer, the sealing layer is formed on the surface at the end of the lower substrate where the solar cell element does not exist and the perovskite compound exists.
A method for manufacturing a solar cell, wherein the sealing resin forming the sealing layer has a solubility parameter SP value of 10 or more.

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