JP2018163939A - Solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solar cell having excellent flexibility and capable of suppressing the infiltration of moisture in the atmosphere. SOLUTION: The solar cell 1 has at least a photoelectric conversion layer 4 and an upper electrode 6 on a flexible base material 2. The photoelectric conversion layer 4 contains an organic-inorganic perovskite compound, and further comprises a photoelectric conversion layer 4. It has an outer frame 9 made of an organic insulating layer arranged on the flexible base material 2 so as to surround the side surface, and an inorganic layer 10 covering the outer frame 9 made of the organic insulating layer. [Selection diagram] Fig. 2

Description

The present invention relates to a solar cell that is excellent in flexibility and can suppress the intrusion of moisture in the atmosphere.

Conventionally, as a solar cell, a laminate in which an N-type semiconductor layer and a P-type semiconductor layer are arranged between opposing electrodes has been actively developed, and inorganic semiconductors such as silicon are mainly used as the N-type and P-type semiconductors. It is used. However, such inorganic solar cells are expensive to manufacture and difficult to increase in size, and have a problem in that the range of use is limited.
Therefore, in recent years, a perovskite solar cell using an organic / inorganic perovskite compound having a perovskite structure using lead, tin or the like as a central metal for a photoelectric conversion layer has attracted attention (for example, Patent Document 1, Non-Patent Document 1). . Perovskite solar cells can be expected to have high photoelectric conversion efficiency and can be manufactured by a printing method, so that manufacturing costs can be greatly reduced.

On the other hand, in recent years, flexible solar cells based on polyimide, polyester-based heat-resistant polymer materials or metal foils have attracted attention. The flexible solar cell has advantages such as transportation and ease of construction due to reduction in thickness and weight, resistance to impact, and the like. For example, a photoelectric conversion layer having a function of generating current when irradiated with light on a flexible substrate It is manufactured by laminating a plurality of layers such as a thin film. Furthermore, a solar cell sealing sheet is laminated | stacked and sealed on the upper and lower surfaces of a flexible solar cell as needed.
For example, Patent Document 2 describes a semiconductor device substrate including a sheet-like aluminum base material, and an organic thin film solar cell including the semiconductor device substrate.

JP 2014-72327 A JP 2013-253317 A

M.M. M.M. Lee, et al, Science, 2012, 338, 643

An object of this invention is to provide the solar cell which is excellent in flexibility and can suppress the penetration | invasion of the water | moisture content in air | atmosphere.

The present invention is a solar cell having at least a photoelectric conversion layer and an upper electrode on a flexible substrate, wherein the photoelectric conversion layer contains an organic-inorganic perovskite compound and further surrounds a side surface of the photoelectric conversion layer. A solar cell having an outer frame made of an organic insulating layer disposed on the flexible substrate and an inorganic layer covering the outer frame made of the organic insulating layer.
The present invention is described in detail below.

ADVANTAGE OF THE INVENTION According to this invention, the solar cell which is excellent in flexibility and can suppress the permeation of the water | moisture content in air | atmosphere can be provided.

It is a schematic diagram which shows an example of the crystal structure of an organic inorganic perovskite compound. It is sectional drawing which shows typically an example of the solar cell of this invention. It is sectional drawing which shows typically another example of the solar cell of this invention.

Hereinafter, the present invention will be described with reference to embodiments.

The present inventors have studied solar cells that have at least a photoelectric conversion layer and an upper electrode on a flexible substrate, and the photoelectric conversion layer contains an organic-inorganic perovskite compound. However, since the organic / inorganic perovskite compound is very sensitive to moisture, the solar cell in which the photoelectric conversion layer contains the organic / inorganic perovskite compound is more susceptible to the intrusion of moisture in the atmosphere than other solar cells (for example, CIGS solar cells). Deterioration of the photoelectric conversion layer was likely to be a problem.
In order to solve the above problem, the present inventors have provided an outer frame disposed on the flexible substrate so as to surround the side surface of the photoelectric conversion layer, thereby allowing moisture to enter from the side surface of the photoelectric conversion layer. We studied to suppress this. Among them, the present inventors include an outer frame made of an organic insulating layer disposed on a flexible substrate so as to surround a side surface of the photoelectric conversion layer, and an inorganic layer covering the outer frame made of the organic insulating layer; It has been found that the infiltration of moisture in the atmosphere can be suppressed while ensuring the flexibility of the solar cell, and the present invention has been completed.

The solar cell of the present invention has at least a photoelectric conversion layer and an upper electrode on a flexible substrate.
In the present specification, “layer” means not only a layer having a clear boundary but also a layer having a concentration gradient in which the contained elements gradually change. In addition, the elemental analysis of a layer can be performed by performing the FE-TEM / EDS ray analysis measurement of the cross section of a solar cell, and confirming the element distribution of a specific element etc., for example. In addition, in this specification, a layer means not only a flat thin film-like layer but also a layer that can form a complicated and complicated structure together with other layers.

The said flexible base material is not specifically limited, For example, the flexible base material which has a polyimide, a polyester type heat resistant polymer, and metal foil is mentioned. Especially, it is preferable to have a metal foil.
By using the metal foil, costs can be reduced as compared with the case of using a heat-resistant polymer, and high-temperature treatment can be performed. That is, even when thermal annealing (heat treatment) is performed at a temperature of 80 ° C. or higher for the purpose of imparting light resistance (resistance to photodegradation) when forming a photoelectric conversion layer containing an organic / inorganic perovskite compound, generation of distortion is minimized. And high photoelectric conversion efficiency can be obtained.

The said metal foil is not specifically limited, For example, metal foil which consists of metals, such as aluminum, titanium, copper, gold | metal | money, and alloys, such as stainless steel (SUS), is mentioned. These may be used independently and 2 or more types may be used together. Of these, aluminum foil is preferable. By using the aluminum foil, costs can be reduced as compared with the case of using other metal foils, and workability can be improved because of the flexibility.

The flexible substrate may be composed only of the metal foil. In this case, the metal foil may also serve as a lower electrode.
The flexible substrate may further have an insulating layer formed on the metal foil. In this case, it is preferable that the solar cell of the present invention further has a lower electrode formed on the insulating layer.

The insulating layer is not particularly limited, and examples thereof include an inorganic insulating layer made of aluminum oxide, silicon oxide, zinc oxide, etc., and an organic insulating layer made of epoxy resin, polyimide, or the like. Especially, when the said metal foil is an aluminum foil, it is preferable that the said insulating layer is an aluminum oxide film.
By using the aluminum oxide film as the insulating layer, it is possible to prevent moisture in the atmosphere from passing through the insulating layer and deteriorating the photoelectric conversion layer containing the organic / inorganic perovskite compound as compared to the case of the organic insulating layer. Can do. In addition, by using the aluminum oxide film as the insulating layer, it is possible to suppress the phenomenon that the photoelectric conversion layer containing the organic / inorganic perovskite compound is discolored and corroded over time due to contact with the aluminum foil. it can.
In other general solar cells, it has not been reported that the photoelectric conversion layer reacts with aluminum to cause discoloration, and the phenomenon that the above corrosion occurs is that the photoelectric conversion layer is an organic-inorganic perovskite compound. The present inventors have found as a problem peculiar to perovskite solar cells including

The thickness of the aluminum oxide film is not particularly limited, but a preferable lower limit is 0.1 μm, a preferable upper limit is 20 μm, a more preferable lower limit is 0.5 μm, and a more preferable upper limit is 10 μm. When the thickness of the aluminum oxide film is 0.5 μm or more, the aluminum oxide film can sufficiently cover the surface of the aluminum foil, and the insulation between the aluminum foil and the lower electrode is stabilized. If the thickness of the aluminum oxide film is 10 μm or less, the aluminum oxide film is hardly cracked even if the flexible base material is curved.
The thickness of the aluminum oxide film can be measured, for example, by observing a cross section of the flexible base material with an electron microscope (for example, S-4800, manufactured by HITACHI) and analyzing the contrast of the obtained photograph. it can.

The ratio of the thickness of the aluminum oxide film is not particularly limited, but a preferable lower limit with respect to 100% of the thickness of the flexible substrate is 0.1%, and a preferable upper limit is 15%. When the ratio is 0.1% or more, the hardness of the aluminum oxide film is increased, and when the lower electrode is patterned, the aluminum oxide film can be favorably patterned while suppressing the peeling of the aluminum oxide film, resulting in poor insulation. And the occurrence of poor conduction can be suppressed. When the ratio is 15% or less, the aluminum oxide film and / or the film is formed on the aluminum foil due to the difference in thermal expansion coefficient from the aluminum foil when the heat treatment is performed when forming the photoelectric conversion layer containing the organic / inorganic perovskite compound. It can suppress that a crack arises in the above-mentioned lower electrode. Thereby, it can suppress that the resistance value of a solar cell rises or the said aluminum foil exposes and corrosion occurs in the photoelectric converting layer containing an organic inorganic perovskite compound. A more preferable lower limit of the ratio is 0.5%, and a more preferable upper limit is 5%.

The method for forming the aluminum oxide film is not particularly limited. For example, the method for anodizing the aluminum foil, the method for applying an aluminum alkoxide to the surface of the aluminum foil, and the surface of the aluminum foil by heat treatment. Examples thereof include a method of forming a natural oxide film. Especially, since the whole surface of the said aluminum foil can be oxidized uniformly, the method of anodizing to the said aluminum foil is preferable. That is, the aluminum oxide film is preferably an anodized film.
When anodizing the aluminum foil, the thickness of the aluminum oxide film can be adjusted by changing the treatment concentration, treatment temperature, current density, treatment time, etc. in the anodization. Although the said processing time is not specifically limited, From a viewpoint of the ease of preparation of the said flexible base material, a preferable minimum is 5 minutes, a preferable upper limit is 120 minutes, and a more preferable upper limit is 60 minutes.

Although the thickness of the said flexible base material is not specifically limited, A preferable minimum is 5 micrometers and a preferable upper limit is 500 micrometers. When the thickness of the flexible substrate is 5 μm or more, a solar cell having sufficient mechanical strength and excellent handleability can be obtained. When the thickness of the flexible substrate is 500 μm or less, a solar cell having excellent flexibility can be obtained. The minimum with more preferable thickness of the said flexible base material is 10 micrometers, and a more preferable upper limit is 100 micrometers.
When the flexible substrate has the metal foil and an insulating layer formed on the metal foil, the thickness of the flexible substrate includes the thickness of the entire flexible substrate including the metal foil and the insulating layer. Means.

As described above, when the flexible substrate has the metal foil and the insulating layer formed on the metal foil, the solar cell of the present invention further includes a lower electrode formed on the insulating layer. Is preferred. The lower electrode is disposed on the insulating layer side of the flexible base material.
Either the lower electrode or the upper electrode may be a cathode or an anode. Examples of the material of the lower electrode and the upper electrode include FTO (fluorine-doped tin oxide), sodium, sodium-potassium alloy, lithium, magnesium, aluminum, magnesium-silver mixture, magnesium-indium mixture, aluminum-lithium alloy, Al / Al ₂ O ₃ mixture, Al / LiF mixture, metal such as gold, CuI, ITO (indium tin oxide), SnO ₂ , AZO (aluminum zinc oxide), IZO (indium zinc oxide), GZO (gallium zinc) Conductive transparent materials such as oxides) and conductive transparent polymers. These materials may be used alone or in combination of two or more.

The photoelectric conversion layer contains an organic / inorganic perovskite compound.
By using the organic-inorganic perovskite compound for the photoelectric conversion layer, the photoelectric conversion efficiency of the solar cell can be improved. The organic inorganic perovskite compound is preferably represented by the general formula R-M-X ₃ (where R is an organic molecule, M is a metal atom, and X is a halogen atom or a chalcogen atom).

The R is an organic molecule, and is preferably represented by C ₁ N _m H _n (l, m, and n are all positive integers).
Specifically, R is, for example, methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, trimethylamine, triethylamine, tripropyl. Amine, tributylamine, tripentylamine, trihexylamine, ethylmethylamine, methylpropylamine, butylmethylamine, methylpentylamine, hexylmethylamine, ethylpropylamine, ethylbutylamine, imidazole, azole, pyrrole, aziridine, azirine, Azetidine, azeto, imidazoline, carbazole, methylcarboxyamine, ethylcarboxyamine, propylcarboxyamine, butyl Rubokishiamin, pentyl carboxyamine, hexyl carboxyamine, formamidinium, guanidine, aniline, pyridine and these ions (e.g., 3 _{NH 3)} such as methyl ammonium (CH) and the like or phenethyl ammonium and the like. Of these, methylamine, ethylamine, propylamine, propylcarboxyamine, butylcarboxyamine, pentylcarboxyamine, formamidinium, guanidine and their ions are preferred, and methylamine, ethylamine, pentylcarboxyamine, formamidinium, guanidine and These ions are more preferred. Among these, methylamine, formamidinium, and these ions are more preferable because high photoelectric conversion efficiency can be obtained.

M is a metal atom, for example, lead, tin, zinc, titanium, antimony, bismuth, nickel, iron, cobalt, silver, copper, gallium, germanium, magnesium, calcium, indium, aluminum, manganese, chromium, molybdenum, Europium etc. are mentioned. Among these, lead or tin is preferable from the viewpoint of overlapping of electron orbits. These metal atoms may be used independently and 2 or more types may be used together.

X is a halogen atom or a chalcogen atom, and examples thereof include chlorine, bromine, iodine, sulfur, and selenium. These halogen atoms or chalcogen atoms may be used alone or in combination of two or more. Among these, the halogen atom is preferable because the organic / inorganic perovskite compound becomes soluble in an organic solvent and can be applied to an inexpensive printing method by containing halogen in the structure. Furthermore, iodine is more preferable because the energy band gap of the organic-inorganic perovskite compound becomes narrow.

The organic / inorganic perovskite compound preferably has a cubic structure in which a metal atom M is disposed at the body center, an organic molecule R is disposed at each vertex, and a halogen atom or a chalcogen atom X is disposed at the face center.
FIG. 1 shows an example of a crystal structure of an organic / inorganic perovskite compound having a cubic structure in which a metal atom M is arranged at the body center, an organic molecule R is arranged at each vertex, and a halogen atom or a chalcogen atom X is arranged at the face center. It is a schematic diagram. Although details are not clear, since the orientation of the octahedron in the crystal lattice can be easily changed by having the structure described above, the mobility of electrons in the organic-inorganic perovskite compound is increased, and the photoelectric properties of the solar cell are increased. It is estimated that the conversion efficiency is improved.

The organic / inorganic perovskite compound is preferably a crystalline semiconductor. The crystalline semiconductor means a semiconductor capable of measuring the X-ray scattering intensity distribution and detecting a scattering peak.
If the organic / inorganic perovskite compound is a crystalline semiconductor, the mobility of electrons in the organic / inorganic perovskite compound is increased, and the photoelectric conversion efficiency of the solar cell is improved. In addition, if the organic / inorganic perovskite compound is a crystalline semiconductor, it is easy to suppress a decrease in photoelectric conversion efficiency (photodegradation) caused by continuing to irradiate light on a solar cell, particularly a photodegradation due to a decrease in short-circuit current. .

In addition, the degree of crystallization can be evaluated as an index of crystallization. The degree of crystallinity is determined by separating the crystalline-derived scattering peak detected by the X-ray scattering intensity distribution measurement and the halo derived from the amorphous part by fitting, obtaining the respective intensity integrals, Can be obtained by calculating the ratio.
A preferable lower limit of the crystallinity of the organic-inorganic perovskite compound is 30%. If the crystallinity is 30% or more, the mobility of electrons in the organic / inorganic perovskite compound is increased, and the photoelectric conversion efficiency of the solar cell is improved. Moreover, if the said crystallinity is 30% or more, it will become easy to suppress the photodegradation resulting from the fall (photodegradation) of photoelectric conversion efficiency by continuing irradiating a solar cell with light, especially the fall of a short circuit current. A more preferred lower limit of the crystallinity is 50%, and a more preferred lower limit is 70%.
Examples of a method for increasing the crystallinity of the organic / inorganic perovskite compound include thermal annealing (heat treatment), irradiation with intense light such as a laser, and plasma irradiation.

The crystallite diameter can also be evaluated as another crystallization index. The crystallite diameter can be calculated by the holder-Wagner method from the half-value width of the scattering peak derived from the crystalline substance detected by the X-ray scattering intensity distribution measurement.
When the crystallite diameter of the organic / inorganic perovskite compound is 5 nm or more, a decrease in photoelectric conversion efficiency (photodegradation) caused by continuing to irradiate light to the solar cell, particularly a photodegradation due to a decrease in short-circuit current is suppressed. . Further, the mobility of electrons in the organic / inorganic perovskite compound is increased, and the photoelectric conversion efficiency of the solar cell is improved. A more preferred lower limit of the crystallite diameter is 10 nm, and a more preferred lower limit is 20 nm.

The photoelectric conversion layer may further contain an organic semiconductor or an inorganic semiconductor in addition to the organic / inorganic perovskite compound as long as the effects of the present invention are not impaired.
Examples of the organic semiconductor include compounds having a thiophene skeleton such as poly (3-alkylthiophene). In addition, for example, conductive polymers having a polyparaphenylene vinylene skeleton, a polyvinyl carbazole skeleton, a polyaniline skeleton, a polyacetylene skeleton, and the like can be given. Further, for example, compounds having a porphyrin skeleton such as a phthalocyanine skeleton, a naphthalocyanine skeleton, a pentacene skeleton, or a benzoporphyrin skeleton, a spirobifluorene skeleton, etc., and carbon-containing materials such as carbon nanotubes, graphene, and fullerene that may be surface-modified Also mentioned.

Examples of the inorganic semiconductor include titanium oxide, zinc oxide, indium oxide, tin oxide, gallium oxide, tin sulfide, indium sulfide, zinc sulfide, CuSCN, Cu ₂ O, CuI, MoO ₃ , V ₂ O ₅ , WO ₃ , _{MoS 2, MoSe 2, Cu 2} S , and the like.

In the case where the photoelectric conversion layer includes the organic-inorganic perovskite compound and the organic semiconductor or the inorganic semiconductor, the photoelectric conversion layer is a laminated body in which a thin-film organic semiconductor or an inorganic semiconductor portion and a thin-film organic-inorganic perovskite compound portion are stacked. Alternatively, a composite film in which an organic semiconductor or inorganic semiconductor part and an organic / inorganic perovskite compound part are combined may be used. A laminated body is preferable in that the production method is simple, and a composite film is preferable in that the charge separation efficiency in the organic semiconductor or the inorganic semiconductor can be improved.

The preferable lower limit of the thickness of the thin-film organic / inorganic perovskite compound site is 5 nm, and the preferable upper limit is 5000 nm. If the thickness is 5 nm or more, light can be sufficiently absorbed, and the photoelectric conversion efficiency is increased. If the said thickness is 5000 nm or less, since it can suppress that the area | region which cannot carry out charge separation generate | occur | produces, it leads to the improvement of photoelectric conversion efficiency. The more preferable lower limit of the thickness is 10 nm, the more preferable upper limit is 1000 nm, the still more preferable lower limit is 20 nm, and the still more preferable upper limit is 500 nm.

When the photoelectric conversion layer is a composite film in which an organic semiconductor or an inorganic semiconductor part and an organic / inorganic perovskite compound part are combined, a preferable lower limit of the thickness of the composite film is 30 nm, and a preferable upper limit is 3000 nm. If the thickness is 30 nm or more, light can be sufficiently absorbed, and the photoelectric conversion efficiency is increased. If the said thickness is 3000 nm or less, since it becomes easy to reach | attain an electrode, a photoelectric conversion efficiency becomes high. The more preferable lower limit of the thickness is 40 nm, the more preferable upper limit is 2000 nm, the still more preferable lower limit is 50 nm, and the still more preferable upper limit is 1000 nm.

The photoelectric conversion layer is preferably subjected to thermal annealing (heat treatment) after the photoelectric conversion layer is formed. By performing thermal annealing (heat treatment), the degree of crystallinity of the organic-inorganic perovskite compound in the photoelectric conversion layer can be sufficiently increased, and the decrease in photoelectric conversion efficiency (photodegradation) due to continued irradiation with light is further increased. Can be suppressed.
When such thermal annealing (heat treatment) is performed on a solar cell using a flexible base material made of a conventional heat-resistant polymer, distortion is caused during annealing due to the difference in thermal expansion coefficient between the flexible base material and the photoelectric conversion layer. As a result, it may be difficult to achieve high photoelectric conversion efficiency. When the metal foil is used, even if thermal annealing (heat treatment) is performed, generation of distortion can be minimized and high photoelectric conversion efficiency can be obtained.

When performing the thermal annealing (heat treatment), the temperature for heating the photoelectric conversion layer is not particularly limited, but is preferably 100 ° C. or higher and lower than 250 ° C. When the heating temperature is 100 ° C. or higher, the crystallinity of the organic / inorganic perovskite compound can be sufficiently increased. If the said heating temperature is less than 250 degreeC, it can heat-process, without thermally degrading the said organic-inorganic perovskite compound. A more preferable heating temperature is 120 ° C. or higher and 200 ° C. or lower. The heating time is not particularly limited, but is preferably 3 minutes or longer and 2 hours or shorter. When the heating time is 3 minutes or longer, the crystallinity of the organic-inorganic perovskite compound can be sufficiently increased. If the heating time is within 2 hours, the organic inorganic perovskite compound can be heat-treated without causing thermal degradation.
These heating operations are preferably performed in a vacuum or under an inert gas, and the dew point temperature is preferably 10 ° C or lower, more preferably 7.5 ° C or lower, and further preferably 5 ° C or lower.

The solar cell of this invention may have an electron carrying layer between the side used as the cathode of the said flexible base material and the said upper electrode, and the said photoelectric converting layer.
The material of the electron transport layer is not particularly limited. For example, N-type conductive polymer, N-type low molecular organic semiconductor, N-type metal oxide, N-type metal sulfide, alkali metal halide, alkali metal, surface activity Specific examples include, for example, cyano group-containing polyphenylene vinylene, boron-containing polymer, bathocuproine, bathophenanthrene, hydroxyquinolinato aluminum, oxadiazole compound, benzimidazole compound, naphthalene tetracarboxylic acid compound, perylene derivative, Examples include phosphine oxide compounds, phosphine sulfide compounds, fluoro group-containing phthalocyanines, titanium oxide, zinc oxide, indium oxide, tin oxide, gallium oxide, tin sulfide, indium sulfide, and zinc sulfide.

The electron transport layer may consist of only a thin film electron transport layer (buffer layer), but preferably includes a porous electron transport layer. In particular, when the photoelectric conversion layer is a composite film in which an organic semiconductor or an inorganic semiconductor site and an organic / inorganic perovskite compound are combined, a more complex composite film (a more complicated structure) is obtained, and the photoelectric conversion efficiency is improved. In order to increase the thickness, it is preferable that the composite film is formed on the porous electron transport layer.

The preferable lower limit of the thickness of the electron transport layer is 1 nm, and the preferable upper limit is 2000 nm. If the thickness is 1 nm or more, holes can be sufficiently blocked. If the said thickness is 2000 nm or less, it will become difficult to become resistance at the time of electron transport, and photoelectric conversion efficiency will become high. The more preferable lower limit of the thickness of the electron transport layer is 3 nm, the more preferable upper limit is 1000 nm, the still more preferable lower limit is 5 nm, and the still more preferable upper limit is 500 nm.

The solar cell of this invention may have a hole transport layer between the said photoelectric converting layer and the side used as the anode of the said flexible base material and the said upper electrode.
The material of the hole transport layer is not particularly limited, and examples thereof include a P-type conductive polymer, a P-type low molecular organic semiconductor, a P-type metal oxide, a P-type metal sulfide, and a surfactant. Examples include compounds having a thiophene skeleton such as poly (3-alkylthiophene). In addition, for example, conductive polymers having a triphenylamine skeleton, a polyparaphenylene vinylene skeleton, a polyvinyl carbazole skeleton, a polyaniline skeleton, a polyacetylene skeleton, and the like can be given. Further, for example, compounds having a porphyrin skeleton such as phthalocyanine skeleton, naphthalocyanine skeleton, pentacene skeleton, benzoporphyrin skeleton, spirobifluorene skeleton, etc., molybdenum oxide, vanadium oxide, tungsten oxide, nickel oxide, copper oxide, tin oxide, sulfide Examples thereof include molybdenum, tungsten sulfide, copper sulfide, tin sulfide, etc., fluoro group-containing phosphonic acid, carbonyl group-containing phosphonic acid, copper compounds such as CuSCN and CuI, and carbon-containing materials such as carbon nanotubes and graphene.

A part of the hole transport layer may be immersed in the photoelectric conversion layer, or may be disposed in a thin film shape on the photoelectric conversion layer. The thickness when the hole transport layer is in the form of a thin film has a preferred lower limit of 1 nm and a preferred upper limit of 2000 nm. If the thickness is 1 nm or more, electrons can be sufficiently blocked. If the said thickness is 2000 nm or less, it will become difficult to become resistance at the time of hole transport, and a photoelectric conversion efficiency will become high. The more preferable lower limit of the thickness is 3 nm, the more preferable upper limit is 1000 nm, the still more preferable lower limit is 5 nm, and the still more preferable upper limit is 500 nm.

The solar cell of the present invention further includes an outer frame made of an organic insulating layer disposed on the flexible substrate so as to surround a side surface of the photoelectric conversion layer, and an inorganic covering the outer frame made of the organic insulating layer. And having a layer.
By providing the outer frame made of the organic insulating layer and the inorganic layer covering the outer frame made of the organic insulating layer, it is possible to suppress the intrusion of moisture in the atmosphere while ensuring the flexibility of the solar cell. .
On the other hand, when only the outer frame made of the organic insulating layer is provided without providing the inorganic layer, the water vapor barrier property of the outer frame made of the organic insulating layer is insufficient. It is difficult to sufficiently prevent moisture from entering the atmosphere. Moreover, when the outer frame which consists of an inorganic layer (inorganic insulating layer) is provided instead of the outer frame which consists of the said organic insulating layer, the flexibility of a solar cell will fall.

The material of the outer frame made of the organic insulating layer is not particularly limited, but those having sufficiently good heat resistance are preferable. Examples of such a material include thermosetting polyimide, (meth) acrylic resin, and epoxy resin.

The shape of the outer frame made of the organic insulating layer is not particularly limited as long as it is a substantially frame shape.
The cross-sectional shape of the outer frame made of the organic insulating layer is not particularly limited. For example, a square, a triangle, a trapezoid (for example, a trapezoid whose bottom is longer than the top and a trapezoid whose bottom is shorter than the top), many Examples include a shape such as a square shape, and a shape in which corner portions in these shapes are rounded. In particular, since the resistance between the electrodes can be increased, a shape in which the lower width is wider than the upper width (for example, a triangle, and a trapezoid whose lower base is longer than the upper base) is preferable.

The line width of the outer frame made of the organic insulating layer is not particularly limited, but a preferable lower limit is 5 μm and a preferable upper limit is 5000 μm. When the line width is 5 μm or more, it is easy to form an outer frame made of the organic insulating layer. If the line width is 5000 μm or less, a sufficient opening area can be secured.

The outer frame made of the organic insulating layer only needs to surround at least the side surface of the photoelectric conversion layer, but the side surface of the laminate including the electron transport layer, the photoelectric conversion layer, the hole transport layer, and the upper electrode. Surrounding is preferred. Thereby, the penetration | invasion of the water | moisture content in air | atmosphere to a solar cell can be suppressed more fully.
Further, the outer frame made of the organic insulating layer may surround side surfaces of a planarizing layer and / or a barrier layer described later.

Moreover, the outer frame which consists of several said organic insulating layers from which a magnitude | size differs may be arrange | positioned so that it may become a double, a triple, etc., for example. Thereby, the penetration | invasion of the water | moisture content in air | atmosphere to a solar cell can be suppressed more fully.

The material of the said inorganic layer is not specifically limited, For example, the material similar to the material of the said electron carrying layer or the said hole transport layer is mentioned. Among them, N-type metal oxides such as titanium oxide, zinc oxide, indium oxide, tin oxide, and gallium oxide, N-type metal sulfides such as tin sulfide, indium sulfide, and zinc sulfide, alkali metal halides, oxidation nickel, tin _{oxide, CuAlO 2, CuGaO 2, SrCuO} 2, ZnO-Rh 2 O P -type metal oxide such as ₃ are preferred.
In particular, by selecting the same material as the material for the electron transport layer or the hole transport layer as the material for the inorganic layer, the inorganic layer and the electron transport layer or the hole transport layer are combined into one by, for example, sputtering. They can be formed simultaneously in the process, and the production efficiency of the solar cell is improved.

The preferable lower limit of the thickness of the inorganic layer is 5 nm, and the preferable upper limit is 5000 nm. If the said thickness is 5 nm or more, the penetration | invasion of the water | moisture content in the air | atmosphere to a solar cell can be suppressed more fully. If the said thickness is 5000 nm or less, it can be set as the solar cell excellent in flexibility. The minimum with more preferable thickness of the said inorganic layer is 10 nm, and a more preferable upper limit is 500 nm.

Examples of the method for forming the inorganic layer include a sputtering method, an ion plating method, a vapor deposition method, a CVD method, and an ALD method.

The solar cell of the present invention preferably further has a barrier layer that covers the upper electrode. Thereby, the penetration | invasion of the water | moisture content in air | atmosphere to a solar cell can be suppressed more fully.
The material of the barrier layer is not particularly limited as long as it has a water vapor barrier property, but an inorganic material is preferable. Examples of the inorganic material include Si, Al, Zn, Sn, In, Ti, Mg, Zr, Ni, Ta, W, Cu, or an oxide, nitride, or oxynitride of an alloy containing two or more of these. . Among these, in order to impart water vapor barrier properties and flexibility to the barrier layer, oxides, nitrides, or oxynitrides of metal elements including both metal elements of Zn and Sn are preferable.

When the material of the barrier layer is an inorganic material, the barrier layer (inorganic layer) has a preferable lower limit of 30 nm and a preferable upper limit of 3000 nm. When the thickness is 30 nm or more, the inorganic layer can have a sufficient water vapor barrier property, and the durability of the solar cell is improved. If the thickness is 3000 nm or less, even if the thickness of the inorganic layer is increased, the generated stress is small, and therefore, the peeling between the inorganic layer and other layers can be suppressed. The more preferable lower limit of the thickness is 50 nm, the more preferable upper limit is 1000 nm, the still more preferable lower limit is 100 nm, and the still more preferable upper limit is 500 nm.
The thickness of the inorganic layer can be measured using an optical interference film thickness measuring device (for example, FE-3000 manufactured by Otsuka Electronics Co., Ltd.).

Among the barrier layer materials, vacuum deposition, sputtering, gas phase reaction (CVD), and ion plating are preferred as methods for coating the upper electrode with the inorganic material. Of these, the sputtering method is preferable for forming a dense layer, and the DC magnetron sputtering method is more preferable among the sputtering methods.
In the sputtering method, an inorganic layer made of an inorganic material can be formed by using a metal target and oxygen gas or nitrogen gas as raw materials and depositing the raw material on the upper electrode to form a film.

The solar cell of the present invention may further include a planarization layer disposed between the upper electrode and the barrier layer as necessary.
The material of the flattening layer is not particularly limited as long as it has a water vapor barrier property, and examples thereof include a thermosetting resin or a thermoplastic resin. Examples of the thermosetting resin or thermoplastic resin include epoxy resin, acrylic resin, silicone resin, phenol resin, melamine resin, urea resin, butyl rubber, polyester, polyurethane, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyvinyl alcohol, poly Examples include vinyl acetate, ABS resin, polybutadiene, polyamide, polycarbonate, polyimide, polyisobutylene and the like.

When the material of the flattening layer is a thermosetting resin or a thermoplastic resin, the thickness of the flattening layer (resin layer) has a preferable lower limit of 100 nm and a preferable upper limit of 100,000 nm. A more preferable lower limit of the thickness is 500 nm, a more preferable upper limit is 50000 nm, a still more preferable lower limit is 1000 nm, and a still more preferable upper limit is 20000 nm.

Of the materials for the flattening layer, the method for covering the upper electrode with the thermosetting resin or thermoplastic resin is not particularly limited. For example, the upper electrode is formed using the material for the sheet-like flattening layer. A method of sealing, a method of applying a solution in which the material of the flattening layer is dissolved in an organic solvent, and applying a liquid monomer to be the flattening layer on the upper electrode, and then liquidating with heat or UV Examples thereof include a method of crosslinking or polymerizing the monomer, a method of cooling the material of the planarizing layer by applying heat to the material, and the like.

In the solar cell of the present invention, the barrier layer may be covered with another material such as a resin film or a resin film coated with an inorganic material. Thereby, even if there is a pinhole in the barrier layer, water vapor can be sufficiently blocked, and the durability of the solar cell can be further improved.

FIG. 2 is a cross-sectional view schematically showing an example of the solar cell of the present invention.
A solar cell 1 shown in FIG. 2 includes a photoelectric conversion layer 4 including an electron transport layer 3 (a thin-film electron transport layer 31 and a porous electron transport layer 32) and an organic / inorganic perovskite compound on a flexible substrate 2. A hole transport layer 5, an upper electrode 6, a planarization layer 7, and a barrier layer 8 are provided in this order.
The solar cell 1 shown in FIG. 2 further includes an organic insulating layer disposed on the flexible substrate 2 so as to surround the side surface of the laminate including the thin film electron transport layer 31 to the barrier layer 8. It has the frame 9 and the inorganic layer 10 which coat | covers the outer frame 9 which consists of an organic insulating layer. By having the outer frame 9 and the inorganic layer 10 made of such an organic insulating layer, the solar cell 1 is excellent in flexibility and can suppress the intrusion of moisture in the atmosphere. In the solar cell 1 shown in FIG. 2, since the material of the inorganic layer 10 and the material of the thin film electron transport layer 31 are the same, the inorganic layer 10 and the thin film electron transport layer 31 are formed by sputtering, for example. Can be formed simultaneously in one step.

FIG. 3 is a cross-sectional view schematically showing another example of the solar cell of the present invention.
The solar cell 1 shown in FIG. 3 has each layer on the flexible base material 2, and further covers an outer frame 9 made of a plurality of organic insulating layers having different sizes and an outer frame 9 made of an organic insulating layer. The layers 10 are arranged so as to be double. Thus, the solar cell 1 is in the atmosphere by being arranged so that the outer frame 9 made of an organic insulating layer and the inorganic layer 10 covering the outer frame 9 made of an organic insulating layer are doubled. It is possible to more sufficiently suppress the intrusion of moisture. As shown in FIG. 3, the barrier layer 8 may be formed so as to cover not only the upper electrode 6 but also the inorganic layer 10.

The method for producing the solar cell of the present invention is not particularly limited. For example, the step of disposing the outer frame made of the organic insulating layer on the flexible substrate, and the inorganic layer on the outer frame made of the organic insulating layer. A step of simultaneously forming the thin film electron transport layer on the flexible substrate in one step, a step of forming the porous electron transport layer on the thin film electron transport layer, Forming the photoelectric conversion layer on the porous electron transport layer, forming the hole transport layer on the photoelectric conversion layer, and forming the upper electrode on the hole transport layer; And a production method including a step of forming the planarization layer on the upper electrode and a step of forming a barrier layer on the planarization layer.

ADVANTAGE OF THE INVENTION According to this invention, the solar cell which is excellent in flexibility and can suppress the permeation of the water | moisture content in air | atmosphere can be provided.

DESCRIPTION OF SYMBOLS 1 Solar cell 2 Flexible base material 3 Electron transport layer 31 Thin film-shaped electron transport layer 32 Porous electron transport layer 4 Photoelectric conversion layer 5 Hole transport layer 6 Upper electrode 7 Flattening layer 8 Barrier layer 9 It consists of an organic insulating layer Outer frame 10 Inorganic layer

Claims (4)

A solar cell having at least a photoelectric conversion layer and an upper electrode on a flexible substrate,
The photoelectric conversion layer includes an organic inorganic perovskite compound,
And an outer frame made of an organic insulating layer disposed on the flexible substrate so as to surround a side surface of the photoelectric conversion layer, and an inorganic layer covering the outer frame made of the organic insulating layer. A solar cell. The solar cell according to claim 1, further comprising a barrier layer covering the upper electrode. The solar cell according to claim 2, further comprising a planarization layer disposed between the upper electrode and the barrier layer. The organic-inorganic perovskite compound is represented by a general formula R-M-X ₃ (where R is an organic molecule, M is a metal atom, and X is a halogen atom or a chalcogen atom). 2. The solar cell according to 2 or 3.

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