JP2021174884A - Perovskite type solar battery - Google Patents

Abstract

To provide a perovskite type solar battery having an excellent durability under a high-temperature, high-humidity environment.SOLUTION: A solar battery 100 is configured by laminating a base material 1, an electrode 21, a photoelectric conversion layer 22, a counter electrode 23, an encapsulation material 3, and a cover material 4 in this order. The photoelectric conversion layer 22 contains a perovskite compound represented by a general formula R-M-X3 (here, R represents an organic molecule; M represents a metal atom; and X represents a halogen atom). The encapsulation material 3 has an adhesive force equal to or more than 1 N/25 mm at 23°C, and has a water vapor permeability less than 50 g/m2/day. An end surface of the photoelectric conversion layer 22 is covered with the encapsulation material 3 with a thickness equal to or more than 3 mm.SELECTED DRAWING: Figure 1

Description

The present invention relates to a solar cell having excellent durability under high temperature and high humidity.

A solar cell containing a perovskite compound represented by the general formula R-MX ₃ (where R is an organic molecule, M is a metal atom, and X is a halogen atom), which is called a perovskite solar cell, is organic. It is known to exhibit particularly high power generation efficiency among thin-film solar cells.

Further, since the perovskite solar cell can be formed on a film by a coating process, it is possible to form a lightweight and highly flexible solar cell with relatively low material cost and processing cost. In particular, it is expected as a wearable device and a film-type solar cell that can be carried in the event of a disaster.

However, the materials that make up perovskite solar cells generally have poor durability against components contained in the outside air such as moisture and oxygen. Therefore, in order to use it for a long time, it is necessary to sufficiently seal the constituent materials so that they do not come into contact with the outside air.

For example, Patent Document 1 and Patent Document 2 show that durability is improved by applying a specific resin material and heat-curing it.

However, since the encapsulant is heat-cured after coating, the constituent materials must be resistant to the temperature applied during curing, and equipment for coating and drying is required.

Patent No. 5926466 JP-A-2018-142597

The present invention provides a perovskite solar cell structure having high moisture and heat resistance without the need for a heat curing process after application for the encapsulant.

As a result of various studies on a sealing material that can cure a solar cell containing a perovskite compound in a low temperature process, among the adhesive sheets that have adhesiveness above a certain level at room temperature, those with a water vapor barrier performance above a certain level are used. As a result, we found a configuration of a solar cell that does not require heat curing and has high moisture and heat resistance.

Regarding the adhesiveness of the sealing material, it is possible to bond the base material on which the element is formed and the cover material having barrier performance as long as the adhesive strength is slight. However, if the adhesive strength is low, there is a risk of peeling during the process after bonding or transportation, and there is a possibility that moisture or air may enter from the interface between the adhesive sheet and the element. Specifically, if the adherend (for example, the counter electrode) has an adhesive force of 1 N / 25 mm or more at 23 ° C., there is almost no risk of peeling of the sealing material in the process or transportation, and the interface of the adhesive sheet. It is possible to prevent the invasion of moisture from. The higher the adhesive strength, the lower the above risk. Therefore, it is desirable to have even higher adhesive strength, especially when the film is used repeatedly.

Regarding water vapor permeability, the encapsulant does not need as much barrier as the film base material or cover material. However, the water vapor permeability of the sealing material needs to be low to some extent in order to prevent the invasion path of water flowing through the inside of the adhesive sheet from the side surface. Specifically, if the water vapor transmittance described in JIS Z0208 (for example, the water vapor transmittance in an atmosphere of 40 ° C. and 90% relative humidity) is 50 g / m ² · day or less, it can be practically used, and if it is low, it is low. The more, the risk of deterioration due to moisture can be reduced.

Since the intrusion of water from the end face becomes more remarkable as it is closer to the end face, it is desirable to arrange the material forming the solar cell as far as possible from the end face. Specifically, if the element is arranged 3 mm or more inward from the end face, there is no practical problem.

The thickness of the adhesive sheet may be any thickness that can absorb the step of the adherend and develop a predetermined adhesive force. However, if the thickness is large, the area of the end face that serves as a path for moisture to enter increases, making it difficult to manufacture an adhesive sheet. Specifically, it is desirable that the thickness is 5 μm or more and 200 μm or less.

Regarding the resin material that composes the adhesive sheet, it is necessary that the material that composes the solar cell does not dissolve or chemically change, but there are no particular restrictions on the main agent or curing agent.

According to the present invention, it is possible to provide a solar cell that adheres at room temperature, does not require a curing process, and has excellent durability.

FIG. 1 is a cross-sectional view showing a first configuration which is an example of the solar cell module according to the present invention. FIG. 2 shows Example 2 of the present invention. FIG. 3 compares the cell voltages of Example 1, Comparative Example 1 and Comparative Example 2 of the present invention for each elapsed time.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. The present invention is not limited to the forms described below, and includes those which are appropriately modified by those skilled in the art from the following forms to the extent obvious to those skilled in the art.

FIG. 1 is a cross-sectional view showing a first configuration which is an example of the solar cell module according to the present invention.
The solar cell module 100 is composed of a base material 1, an element portion 2, a sealing material 3, and a cover material 4. The element unit 2 is composed of an electrode 21, a photoelectric conversion layer 22, and a counter electrode 23. The element portion 2 has a size smaller than that of the base material 1 except for a part of the electrode 21 and the counter electrode 23, and has a configuration in which the periphery thereof is covered with the sealing material 3. The cover material 4 has the same size as the base material, and the element portion has a structure covered with the base material, the sealing material, and the cover material.

Since the base material 1 receives light from the surface opposite to the surface on which the electrodes are laminated, an insulating material having light transmission is used. Examples of the material include glass, acrylic, polycarbonate, polyethylene terephthalate (PET), polyethylene naphthalate (PEN) and the like. In order to enhance the water vapor barrier property, a light-transmitting moisture-proof layer such as alumina may be provided on the surface.

For the electrode layer 21, a material having conductivity and light transmission is selected. Examples include indium tin oxide (ITO), fluorine-doped tin oxide (FTO), zinc oxide (ZnO), titanium oxide (TiO ₂ ) and the like.

The photoelectric conversion layer 22 _{contains a perovskite compound represented by the general formula R-MX 3} (where R is an organic molecule, M is a metal atom, and X is a halogen atom).
The photoelectric conversion layer 22 includes an electron transport layer, a perovskite layer (light absorption layer), and a hole transport layer in this order. The perovskite solar cell may be a normal type in which an n-type semiconductor layer is provided on a transparent electrode, or an inverted type in which a p-type semiconductor layer is provided on a transparent electrode.

Electron transport layer The electron transport layer is formed to increase the active surface area of the perovskite layer (light absorption layer), improve the photoelectric conversion efficiency, and facilitate electron collection. The electron transport layer may be formed on the substrate, but is preferably formed on the (hole) blocking layer. Further, the above-mentioned (hole) blocking layer may function as an electron transporting layer, or the electron transporting layer may also serve as a (hole) blocking layer. The electron transport layer may be a flat layer using an organic semiconductor material such as a fullerene derivative. Further, the electron transport layer may be titanium oxide (TiO ₂ ) ( _{including mesoporous TiO 2} ), SnO ₂ layer, or ZnO layer. The electron transport layer preferably has a porous structure such _{as mesoporous nitro 2.} It is preferable that the porous structure has, for example, an aggregate of granular bodies, needle-like bodies, tubular bodies, columnar bodies, and the like, and has a porous property as a whole. The pore size is preferably nanoscale. Since it has a porous structure and is nanoscale, it significantly increases the active surface area of the light absorption layer, improves the solar cell characteristics (particularly photoelectric conversion efficiency), and makes it a porous electron transport layer with excellent electron collection. be able to.

The electron transport layer may be a layer made of a metal oxide such as titanium oxide or tin oxide. If the metal compound is a semiconductor, or if a semiconductor is used, the donor can be doped. As a result, the electron transport layer becomes a window layer for introducing into the perovskite layer (light absorption layer), and the electric power obtained from the perovskite layer (light absorption layer) can be taken out more efficiently.

The thickness of the electron transport layer is not particularly limited, and is preferably about 10 to 300 nm, more preferably about 10 to 250 nm, from the viewpoint of being able to collect more electrons from the perovskite layer (light absorption layer). The electron transport layer can be obtained by using a known film forming method depending on the material to be molded. For example, it can be prepared by applying an alcohol solution (for example, ethanol solution) of titanium oxide paste of 5 to 50% by mass (particularly 10 to 30% by mass) on the (hole) blocking layer. As the titanium oxide paste, a known or commercially available product can be used. The coating method is preferably a spin coating method. The coating can be performed at, for example, about 15 to 30 ° C.

Perovskite layer (light absorption layer)
The perovskite layer (light absorption layer) in a perovskite type solar cell is a layer that performs photoelectric conversion by absorbing light and moving excited electrons. The perovskite layer (light absorption layer) contains a perovskite material and a perovskite complex. The perovskite layer may be produced according to the method described above. The perovskite layer preferably realizes mass production by roll-to-roll. It is preferable to apply the mixed solution on the substrate by spin coating, dip coating, screen printing method, roll coating, die coating method, transfer printing method, spray method, slit coating method, etc., preferably by spin coating.

The film thickness of the perovskite layer (light absorption layer) is preferably, for example, 50 to 1000 nm, more preferably 200 to 800 nm, from the viewpoint of the balance between the light absorption efficiency and the exciton diffusion length and the absorption efficiency of the light reflected by the transparent electrode. preferable. The film thickness of the perovskite layer (light absorption layer) is preferably in the range of 100 to 1000 nm, and more preferably in the range of 250 to 500 nm. Specifically, it is preferable that the lower limit of the film thickness of the perovskite layer (light absorption layer) is 100 nm or more (particularly 250 nm) or more, and the upper limit is 1000 nm or less (particularly 500 nm or less). The film thickness of the perovskite layer (light absorption layer) is measured by a cross-section scanning electron microscope (cross-section SEM) of a film made of a complex.

The flatness of the perovskite layer (light absorption layer) is preferably such that the height difference is 50 nm or less (-25 nm to +25 nm) in the horizontal direction of 500 nm × 500 nm of the surface measured by a scanning electron microscope. Is more preferably 40 nm or less (-20 nm to + 20 nm). This makes it easier to balance the light absorption efficiency and the exciton diffusion length, and further improves the absorption efficiency of the light reflected by the transparent electrode. The flatness of the perovskite layer (light absorption layer) is defined by using an arbitrarily determined measurement point as a reference point, the upper limit of the difference from the thickest film thickness in the measurement range, and the difference from the smallest measurement point. It is the lower limit and is measured by a cross-section scanning electron microscope (cross-section SEM) of the perovskite layer (light absorption layer).

Hole transport layer The hole transport layer is a layer that has the function of transporting electric charges. For the hole transport layer, for example, a conductor, a semiconductor, an organic hole transport material, or the like can be used. The material can function as a hole transport material that receives holes from the perovskite layer (light absorption layer) and transports holes. The hole transport layer is formed on the perovskite layer (light absorption layer). Examples of the conductor and semiconductor _{include compound semiconductors containing monovalent copper such as CuI, CuInSe 2} , and CuS; other than copper such as GaP, NiO, CoO, FeO, Bi ₂ O ₃ , MoO ₂ , and Cr ₂ O _3. Examples include compounds containing the above metals. Among them, a semiconductor containing monovalent copper is preferable, and CuI is more preferable, from the viewpoint of receiving only holes more efficiently and obtaining higher hole mobility. Examples of the organic hole transport material include polythiophene derivatives such as poly-3-hexylthiophene (P3HT) and polyethylenedioxythiophene (PEDOT); 2,2', 7,7'-tetrax- (N, N-di). Fluolene derivatives such as -p-methoxyphenylamine) -9,9'-spiro-OMeTAD; carbazole derivatives such as polyvinylcarbazole; poly [bis (4-phenyl) (2,4,6-trimethylphenyl) ) Amine] (PTAA) and other triphenylamine derivatives; diphenylamine derivatives; polysilane derivatives; polyaniline derivatives and the like. Among them, triphenylamine derivatives, fluorene derivatives and the like are preferable, and PTAA, spiro-OMeTAD and the like are more preferable, from the viewpoint of receiving only holes more efficiently and obtaining higher hole mobility.

In the hole transport layer, lithium bis (trifluoromethylsulfonyl) imide (LiTFSI), silver bis (trifluoromethylsulfonyl) imide, and trifluoromethylsulfonyloxysilver are used for the purpose of further improving the hole transport characteristics. , NOSbF ₆ , SbCl ₅ , SbF _{5 and the} like can also be included. In addition, the hole transport layer may contain basic compounds such as t-butylpyridine (TBP), 2-picoline, and 2,6-lutidine. The contents of the oxidizing agent and the basic compound can be the amounts normally used conventionally. The film thickness of the hole transport layer is preferably, for example, 30 to 200 nm, more preferably 50 to 100 nm, from the viewpoint of receiving only holes more efficiently and obtaining higher hole mobility. The method of forming the hole transport layer is preferably performed in a dry atmosphere, for example. For example, it is preferable to apply a solution containing an organic hole transport material on a perovskite layer (light absorption layer) (spin coating or the like) in a dry atmosphere and heat it at 30 to 150 ° C. (particularly 50 to 100 ° C.). ..

For the counter electrode layer 23, a material having high conductivity is selected. In addition to metal materials such as gold, silver, copper, aluminum, and nickel, metal oxides may be used as in the electrode layer 21.

An adhesive having a water vapor barrier property is used as the sealing material 3. There are no particular restrictions on the resin material, curing agent, additive, etc., and various materials such as acrylic, silicone, urethane, polyolefin, and rubber can be used. However, it is necessary to select a material that does not cause a chemical change or ion migration of the material constituting the element portion 2 with which the sealing material 3 comes into contact.

The cover material 4 may be an insulating material, and like the base material 1, an opaque film material or a plate material can be used in addition to the light transmissive material. In order to enhance the water vapor barrier property, a light-transmitting moisture-proof film such as alumina or an opaque moisture-proof film such as aluminum may be provided.

FIG. 2 is a cross-sectional view showing a second configuration which is an example of the solar cell module according to the present invention.

The solar cell module 200 is composed of a base material 1, an element portion 2, a sealing material 3, and a cover material 4. The element unit 2 is composed of an electrode layer 21, a photoelectric conversion layer 22, and a counter electrode layer 23. The base material 1 and the element portion 2 have the same size, and are surrounded by a sealing material 3. The cover material 4 has a size larger than that of the base material, and the element portion has a structure covered with the base material, the sealing material, and the cover material.

The material of each layer is basically the same as that of the configuration 1, but it is necessary to use a light-transmitting material for both the lower cover material and the sealing material in order to receive light in the photoelectric conversion layer.

In the configuration 2, it is not necessary to make the photoelectric conversion layer and the counter electrode smaller than the substrate size as in the configuration 1. Further, since the base material and the electrode are also covered with a sealing material, it is possible to prevent moisture from entering the base material, the electrode, and the interface thereof from the outside, so that higher reliability than that of the configuration 1 can be expected. ..

Example 1 has a structure having a barrier adhesive sealing material and end sealing.
That is, an electrode / photoelectric conversion layer / gold electrode is formed on a 25 mm square glass substrate, the end portion of the photoelectric conversion layer is removed so that the distance from the glass end face is 3 mm, and the surface in the range of 3 mm from the glass end portion is removed. Only the electrode layer was left in.

Next, on the formation of the gold electrode, a covering material having a layer structure of PET / aluminum foil / PET and a glass substrate were used with a polyolefin-based pressure-sensitive adhesive sheet having a ^{water vapor barrier property (water vapor transmittance: 40 g / m 2 / day).} And pasted together.

On the other hand, Comparative Example 1 had a configuration without a barrier adhesive sealing material and end sealing.
That is, an electrode / photoelectric conversion layer / gold electrode was formed on a 25 mm square glass substrate.

Next, on the formation of the gold electrode, a covering material having a layer structure of PET / aluminum foil / PET and a glass substrate were used with a polyolefin-based pressure-sensitive adhesive sheet having a ^{water vapor barrier property (water vapor transmittance: 40 g / m 2 / day).} And pasted together.

Further, in Comparative Example 2, a non-barrier adhesive sealing material having no barrier property against moisture was used for sealing.
That is, an electrode / photoelectric conversion layer / gold electrode was formed on a 25 mm square glass substrate.

Next, on the gold electrode formation, a cover material having a layer structure of PET / aluminum foil / PET and a glass substrate are covered with a non-water vapor barrier (water vapor transmittance: 500 g / m ² / day) acrylic pressure-sensitive adhesive sheet. It was used for bonding.

The reliability of the perovskite solar cell according to the present invention in Example 1 was evaluated by comparison with Comparative Examples 1 and 2.
The samples of Example 1 and Comparative Examples 1 and 2 were placed in a constant temperature and humidity chamber, and left under the conditions of temperature 85 ° C. and humidity 85% RH, which are generally used for evaluating the reliability of solar cells.

The voltage at the time of light irradiation was measured before the sample was charged and after a predetermined time had passed after the sample was charged.

The results are shown in Table 1 and FIG.

Comparative Example 2 showed a remarkable tendency of voltage decrease as compared with Example 1. This is because the water vapor barrier property of the encapsulant is low, so it is considered that moisture invades from the end face of the encapsulant and the characteristics of the solar cell are lost.

Although the constituent materials are the same in Example 1 and Comparative Example 1, a large difference was observed in the voltage drop after 150 hours. This is because, in the case of Example 1, since the end face of the photoelectric conversion layer is covered with a sealing material, it is considered that moisture intrusion from the photoelectric conversion layer and its interface is suppressed.

In the second embodiment, the laminated base material, the electrode, the photoelectric conversion layer, and the counter electrode are covered with a barrier adhesive sealing material.
That is, an electrode / photoelectric conversion layer / gold electrode is formed on an 80 mm square PET substrate to form an element portion on the substrate, and then both sides of the substrate are 100 mm square light-transmitting and water vapor barrier aluminum vapor deposition. The PET cover material was bonded using a polyolefin-based pressure-sensitive adhesive sheet having a water vapor barrier property (water vapor transmittance: 40 g / m ^{2 / day).}

In Example 2, since the laminated base material, the electrode, the photoelectric conversion layer, and the counter electrode, which are all the members constituting the photoelectric conversion layer, are covered with the water vapor barrier base material and the sealing material. Reliability equal to or higher than that of Example 1 can be expected.

The present invention provides a novel perovskite solar cell, which can be used as a power source in a wearable device or as a portable film solar cell in the event of a disaster.

1 ... Base material 2 ... Element part 21 ... Electrode 22 ... Photoelectric conversion layer 23 ... Counter electrode 3 ... Encapsulant 4 ... Cover material 41 ... Upper cover material 42 ... Lower cover material 100 ... Solar cell module 200 ... Solar cell module

Claims (3)

A solar cell in which a base material, an electrode, a photoelectric conversion layer, a counter electrode, a sealing material, and a cover material are laminated in this order, and the photoelectric conversion layer is a general formula RMX ₃ (where R is an organic molecule). , M is a metal atom, X is a halogen atom), and the encapsulant has an adhesive force of 1 N / 25 mm or more at 23 ° C. and a water vapor permeability of 50 g / m ² /. A solar cell having less than a day and having an end face of a photoelectric conversion layer covered with a sealing material by 3 mm or more. A solar cell in which a lower cover material, a sealing material, a base material, an electrode, a photoelectric conversion layer, a counter electrode, a sealing material, and an upper cover material are laminated in this order, and the photoelectric conversion layer is a general formula RM-. It _{contains a perovskite compound represented by X 3} (where R is an organic molecule, M is a metal atom, and X is a halogen atom), and the encapsulant has an adhesive force of 1 N / 25 mm or more at 23 ° C. A solar cell having a water vapor transmission rate of ^{less than 50 g / m 2} / day and having an end face of a photoelectric conversion layer covered with a sealing material of 3 mm or more. The solar cell according to claim 1 or 2, wherein the thickness of the sealing material is 5 μm or more and 500 μm or less.

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