JP7623681B2 - Perovskite solar cell and its manufacturing method - Google Patents

Description

This invention relates to perovskite solar cells and their manufacturing methods.

JP 2019-55916 A describes a perovskite solar cell and its manufacturing method. A perovskite solar cell has a layered structure including a front substrate, a front electrode, a perovskite layer, a back electrode, and a back electrode. The manufacturing method is to form each layer in order. When layers are formed in order to obtain a layered structure, there are problems in that the upper layer is easily affected by the lower layer, and that the patterning and etching work of each layer is time-consuming.

JP 2019-55916 A

One of the objectives of this invention is to provide a perovskite solar cell that is easy to manufacture, and is less susceptible to the influence of layers underneath.

The above problem is basically solved by preparing two pieces of film and combining them to create a solar cell.

This invention makes it possible to provide perovskite solar cells that have not only excellent initial characteristics but also high durability.

FIG. 1 is a conceptual diagram showing the basic structure of a solar cell. FIG. 2 is a flow chart for explaining an example of a method for manufacturing a solar cell. FIG. 3 is a conceptual diagram showing the first film and the second film. FIG. 4 is a conceptual diagram showing a first film having a first connecting electrode and a second film having a second connecting electrode. FIG. 5 is a conceptual diagram showing a second film having a second connection electrode. FIG. 6 is a flow chart showing the process in which the order of forming the hole transport layer and the electron transport layer is reversed from that shown in FIG. FIG. 7 is a flow chart illustrating an example of manufacturing a solar cell using a first film having a hole transport layer and a second film having an electron transport layer and a perovskite layer. FIG. 8 is a conceptual diagram showing the first and second films obtained according to the flow chart of FIG. FIG. 9 is a conceptual diagram showing a first film and a second film each having a perovskite precursor layer. FIG. 10 is a conceptual diagram showing a first film and a second film each having a perovskite layer.

Below, the embodiments for carrying out the present invention will be explained using the drawings. The present invention is not limited to the embodiments described below, but also includes appropriate modifications of the embodiments below within the scope that would be obvious to a person skilled in the art.

Regarding solar cells The first invention relates to solar cells. Fig. 1 is a conceptual diagram showing the basic structure of a solar cell. As shown in Fig. 1, this solar cell 1 has a first flexible substrate 3, a first electrode 5, photoelectric conversion layers 7, 9, 11 having a perovskite layer, a second electrode 13, and a second flexible substrate 15, in this order. The photoelectric conversion layers 7, 9, 11 may have a hole transport layer 7, a perovskite layer 9, and an electron transport layer 11.

Flexible substrate 3, 15
As the flexible substrate 3, 15, a known substrate in an organic solar cell, an organic EL element, or the like can be appropriately used. Specific examples of the substrate include glass, ceramics, and a resin film. Specific examples of the resin film include an ionomer film, a polyethylene film, a polyethylene terephthalate film, a polyethylene naphthalate film, a polyvinyl chloride film, a polyvinylidene chloride film, a polyvinyl alcohol film, a polypropylene film, a polyester film, a polycarbonate film, a polystyrene film, a polyacrylonitrile film, an ethylene-vinyl acetate copolymer film, an ethylene-vinyl alcohol copolymer film, an ethylene-methacrylic acid copolymer film, and a nylon film, and the resin film may be formed alone or from a mixture of two or more kinds. These films may also be laminated. Substrates having at least one of a metal film, a semiconductor film, a conductive film, and an insulating film formed on a part or all of the surface of the substrate may also be used.

Examples of the metal include one or more metals selected from gallium, iron, indium, aluminum, vanadium, titanium, chromium, rhodium, nickel, cobalt, zinc, magnesium, calcium, silicon, yttrium, strontium, and barium. Examples of the constituent material of the semiconductor film include simple elements such as silicon and germanium, compounds containing elements of groups 3 to 5 and groups 13 to 15 of the periodic table, metal oxides, metal sulfides, metal selenides, metal nitrides, etc., which may be used alone or in combination of two or more kinds. Examples of the material of the conductive film include tin-doped indium oxide (ITO), fluorine-doped indium oxide (FTO), zinc oxide (ZnO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide ( _GZO ), tin oxide (SnO2), titanium oxide ( _TiO2 ), indium oxide ( _In2O3 ), and tungsten _oxide ( _WO3 ), which may be used alone or in combination of two or _more of them. Examples of the material of the insulating film include aluminum oxide ( _Al2O3 ), silicon oxide ( _SiO2 ) _, silicon nitride ( _Si3N4 ), _{and silicon oxynitride (Si4O5N3 ) .}

Examples of the shape of the substrate include plate-like such as flat plate or disc, fiber-like, rod-like, cylindrical, prismatic, tubular, spiral, spherical, and ring-like, and may also be a porous structure. Of these, plate-like substrates are preferred. Examples of the thickness of the substrate are preferably 0.1 μm to 100 mm, and more preferably 1 μm to 10 mm.

First electrode 5, second electrode 13
The electrode is a layer that supports the electron transport layer and has a function of extracting electrons from the perovskite layer (light absorbing layer). The electrode includes a first electrode 5a and a second electrode 5b formed on a substrate 3 and spaced apart from each other. Spaced apart means that they are not in physical contact with each other and that the first electrode 5a and the second electrode 5b are not short-circuited. The electrode is preferably a transparent electrode or a metal electrode.

Examples of the transparent electrode include carbon, metal, and conductive metal oxide. Examples of carbon include carbon black, carbon nanotubes, and graphene, and examples of metal include gold, silver, copper, aluminum, nickel, indium, and titanium. Examples of oxide semiconductors include a tin-doped indium oxide (ITO) film, an impurity-doped indium oxide (In ₂ O ₃ ) film, an impurity-doped zinc oxide (ZnO) film, a fluorine-doped tin dioxide (FTO) film, and a laminated film formed by laminating these. The metal electrode means an electrode containing a metal. Examples of the metal electrode are gold, silver, and copper. The metal electrode may be not only a metal, but also a tin-doped indium oxide (ITO) film, an impurity-doped indium oxide (In ₂ O ₃ ) film, an impurity-doped zinc oxide (ZnO) film, a fluorine-doped tin dioxide (FTO) film, and a laminated film formed by laminating these on the surface of the metal. These films may function as, for example, a diffusion prevention layer. The thickness of these electrodes is not particularly limited, and it is usually preferable to adjust the sheet resistance to 5 to 15 Ω/□ (per unit area). The electrodes can be obtained by a known film formation method depending on the material to be formed.

The first electrode may also be of a structure that allows light to pass through, such as a mesh or stripe. Furthermore, a metal lead wire may be used in combination with the first electrode to reduce electrical resistance. Examples of metal lead wires include aluminum, silver, gold, and titanium.

Electron transport layer 11
The electron transport layer 11 is formed to increase the active surface area of the perovskite layer (light absorbing layer), improve the photoelectric conversion efficiency, and facilitate electron collection. The electron transport layer may be a flat layer using an organic semiconductor material such as a fullerene derivative. The electron transport layer may also be a layer containing a metal oxide such as titanium oxide (TiO ₂ ) (including mesoporous TiO ₂ ), tin oxide (SnO ₂ ), or zinc oxide (ZnO). 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 absorbing layer). The electron transport layer 11 may contain an n-type metal oxide semiconductor or may be made of an n-type metal oxide semiconductor. In particular, when a solar cell is manufactured by bonding a first film and a second film as in the present invention, the electron transport layer 11 preferably contains an n-type metal oxide semiconductor.

Hole transport layer 7
The hole transport layer 7 is a layer having a function of transporting charges. The hole transport layer 7 is a layer formed on the perovskite layer 9. For example, a conductor, a semiconductor, an organic hole transport material, etc. can be used for the hole transport layer. The material can function as a hole transport material that receives holes from the perovskite layer (light absorbing layer) and transports the holes. The hole transport layer is formed on the perovskite layer (light absorbing layer). Examples of the conductor and semiconductor include compound semiconductors containing monovalent copper such as CuI, CuSCN, CuInSe ₂ , and CuS; and compounds containing metals other than copper such as GaP, NiO, CoO, FeO, Bi ₂ O ₃ , MoO ₂ , and Cr ₂ O _3. Among them, from the viewpoint of more efficiently receiving only holes and obtaining higher hole mobility, semiconductors containing monovalent copper are preferred, and CuI and CuSCN are more preferred. Examples of organic hole transport materials include polythiophene derivatives such as poly-3-hexylthiophene (P3HT) and polyethylenedioxythiophene (PEDOT); fluorene derivatives such as 2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (Spiro-OMeTAD); carbazole derivatives such as polyvinylcarbazole; triphenylamine derivatives such as poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA); diphenylamine derivatives; polysilane derivatives; polyaniline derivatives, etc. Among these, from the viewpoint of more efficiently receiving only holes and obtaining higher hole mobility, triphenylamine derivatives, fluorene derivatives, etc. are preferred, and PTAA, Spiro-OMeTAD, etc. are more preferred. However, when a solar cell is manufactured by laminating a first film and a second film as in the present invention, the hole transport layer preferably contains a polythiophene derivative.

In order to further improve the hole transport properties, the hole transport layer may contain an oxidizing agent such as lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), silver bis(trifluoromethylsulfonyl)imide, trifluoromethylsulfonyloxysilver, NOSbF ₆ , SbCl ₅ , SbF ₅ , tris(2-(1H-pyrazol-1-yl)-4-tert-butylpyridine)cobalt(III)tri[bis(trifluoromethane)sulfonimide], 4-isopropyl-4'-methyldiphenyliodonium tetrakis(pentafluorophenyl)borate, etc. In addition, the hole transport layer may contain a basic compound such as t-butylpyridine (TBP), 2-picoline, 2,6-lutidine, etc. The contents of the oxidizing agent and basic compound may be the amounts that have been conventionally used. The thickness of the hole transport layer is preferably, for example, 10 to 1000 nm, and more preferably 100 to 500 nm, from the viewpoint of more efficiently receiving only holes and obtaining higher hole mobility.

Perovskite layer 9
The perovskite layer (light absorption layer: photoactive layer) 9 in a perovskite solar cell is a layer that performs photoelectric conversion by absorbing light and transferring excited electrons and holes.
The perovskite layer uses a compound represented by the general formula (ABX ₃ ). This compound may be a perovskite crystal or a perovskite complex.
Examples of A include monovalent cations formed from organic amino compounds such as methylamine, ethylamine, n-butylamine, di-n-butylamine, di-n-hexylamine, trimethylamine, triethylamine, methyl-n-hexylamine, methyldiethylamine, tri-n-hexylamine, tri-t-butylamine, imidazole, pyrrole, aziridine, carbazole, formamidine, guanidine, aniline, pyridine, 4-t-butylpyridine, phenethylamine, and 5-aminovaleric acid, cesium, potassium, rubidium, and the like, and A may be used alone or as a mixture of two or more kinds.
B may be a divalent cation such as lead or tin, which may be used alone or in combination, or may be mixed with a small amount of a trivalent cation such as indium or antimony.
X may be a halogen atom such as chlorine, bromine or iodine, or an anion source, and may be used alone or in combination of two or more kinds.

The perovskite layer (light absorbing layer) contains a perovskite material or a perovskite complex. The thickness of the perovskite layer (light absorbing 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 diffusion length of electrons and holes, and the absorption efficiency of light reflected by the electrode. The thickness of the perovskite layer (light absorbing layer) of the present invention may be measured by a cross-sectional scanning electron microscope (cross-sectional SEM).
Furthermore, the flatness of the perovskite layer (light absorbing layer) of the present invention is preferably such that the height difference is 50 nm or less (-25 nm to +25 nm) in a range of 500 nm x 500 nm in the horizontal direction of the surface as measured by a scanning electron microscope, and more preferably the height difference is 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 light reflected by the electrode.

The photoelectric conversion layers 7, 9, and 11 may have a hole transport layer 7, a perovskite layer 9, and an electron transport layer 11 in this order. In this case, the electron transport layer 11 or the second electrode 13 preferably contains a conductive polymer containing poly3,4-ethylenedioxythiophene:poly4-styrenesulfonate.

Alternatively, the photoelectric conversion layers 7, 9, and 11 may each include, in this order, an electron transport layer 11, a perovskite layer 9, and a hole transport layer 7. In this case, it is preferable that the electron transport layer 11 contains _SnO2 or _TiO2 .

Figure 2 is a flow chart for explaining an example of a method for manufacturing a solar cell. As shown in Figure 2, this method includes a step of preparing a first film 21 including a first flexible substrate 3 and a first electrode 5. In parallel with this, a step of preparing a second film 23 including a second electrode 13 and a second flexible substrate 15 is also included. The step of forming electrodes on a flexible substrate is known. Either or both of the first film 21 and the second film 23 may further include photoelectric conversion layers 7, 9, 11 and connection electrodes 25, 27. The method of providing these is also known. Electrodes may be formed on the flexible substrate by sputtering. Electrodes may also be formed on the flexible substrate using a conductive paste.

Connection electrodes 25, 27
The connection electrode is an electrode for achieving electrical continuity between the first electrode 5 and the second electrode 13 .

An example of the process for preparing a first film 21 including a first flexible substrate 3 and a first electrode 5 is shown in steps 201 and 202 in FIG. 2. A substrate with a rear pattern electrode is prepared (S201). The electrode may be used as a connection electrode. Next, a connection electrode is formed in contact with the rear pattern electrode (S202). The second film 21 thus obtained is as shown in FIG. 3. FIG. 3 is a conceptual diagram showing the first film and the second film. The method of forming an electrode on a flexible substrate and forming a photoelectric conversion layer on the electrode is well known.

A process of preparing a substrate with a rear pattern electrode (S201)
An electrode is formed on the substrate. The electrode may include a first electrode and a second electrode that are spaced apart. Methods for forming the electrode on the substrate are known. Examples of known methods include etching using a resist pattern and patterning using a laser.

A process of forming a connection electrode in contact with the rear pattern electrode (S202)
The connection electrodes can be formed by, for example, screen printing, or by evaporating metal using a mask.

An example of the process for preparing a second film 23 including a second electrode 13 and a second flexible substrate 15 is shown in steps 101 to 105 in FIG. 2. A substrate with a surface patterned electrode is prepared (S101). Next, an electron transport layer is formed (S102). Next, a perovskite layer is formed (S103). Next, a hole transport layer is formed (S104). After that, the photoactive layer (photoelectric conversion layer) is patterned. The second film 23 obtained in this manner is as shown in FIG. 3.

A step of preparing a substrate with a surface pattern electrode (S101)
An electrode is formed on the substrate. The electrode may include a first electrode and a second electrode that are spaced apart. Methods for forming the electrode on the substrate are known. Examples of known methods include etching using a resist pattern and patterning using a laser.

Step of forming an electron transport layer (S102)
The electron transport layer can be obtained by using a known film formation method according to the material to be formed. For example, it can be prepared by applying an aqueous dispersion of tin oxide fine particles of 3 to 15 mass % (particularly 5 to 10 mass %) onto the electrode. A known or commercially available tin oxide fine particle aqueous dispersion can be used. The preferred application method is spin coating. The application can be performed at, for example, about 15 to 30°C. After the electrode and the electron transport layer are formed on the substrate, etching with a resist pattern or patterning using a laser may be performed.

Step of forming a perovskite layer (S103)
An example of the process for forming a perovskite layer includes a process of applying a solution containing a perovskite compound to a substrate, a process of applying a poor solvent to the substrate, and a process of annealing the substrate, in this order. In order to apply the solution containing a perovskite compound to the substrate, spin coating, dip coating, screen printing, roll coating, die coating, transfer printing, spraying, or slit coating may be used. Among these, it is preferable to apply the solution to the substrate by spin coating. Spin coating is a method in which the substrate is rotated while dropping the solution, and the solution is applied to the substrate. Alternatively, the substrate carrying the solution may be rotated, and the solution may be further applied to the substrate. The rotation speed may be a maximum speed of 1,000 to 10,000 rpm for 30 seconds to 5 minutes, 2 to 15 seconds to reach the maximum speed, and 2 to 15 seconds to stop from the maximum speed.

Next, the step of applying a poor solvent to the substrate will be described.
A poor solvent means a solvent that has the ability to dissolve a solute but does not have a high solubility in the solute. Examples of poor solvents include substituted aliphatic hydrocarbons such as dichloromethane and chloroform; aromatic hydrocarbons such as toluene and benzene; substituted aromatic hydrocarbons such as chlorobenzene, orthodichlorobenzene, and nitrobenzene; ethers such as acetic acid, diethyl ether, and tetrahydrofuran (THF); alcohols such as methanol, ethanol, isopropanol, butanol, and octanol; long-chain hydrocarbons such as hexane (especially C4-10 hydrocarbons); and acetonitrile. These poor solvents can be used alone or in combination of two or more. Among these, chlorobenzene or toluene is preferred.

Next, the process of annealing the substrate will be described. Annealing refers to a process of heating the substrate. The annealing process is preferably performed promptly after the poor solvent is dropped or after the substrate is stopped after spin coating is completed. As shown in the examples described later, the annealing process preferably includes a process of gradually heating the substrate in a closed system containing solvent vapor. In the closed system, it is preferable that the vapor of the solvent contained in the solution containing the Sn-based perovskite compound is present, and it is preferable that the solvent is at saturated vapor pressure or a partial pressure of 90% or more of the saturated vapor pressure in the closed system.

Step of forming a hole transport layer (S104)
The hole transport layer may be formed by any known method. For example, a solution containing an organic hole transport material is applied (by spin coating, inkjet, die coater, or the like) onto the perovskite layer (light absorbing layer) in a dry atmosphere, and then heated at 30 to 150° C. (particularly 50 to 100° C.) to form the hole transport layer 11. The element material 21 can be obtained by forming the hole transport layer.

Then, the first film 21 and the second film 23 are bonded together (S301). This results in the solar cell shown in FIG. 1 being obtained. The first film 21 and the second film 23 may be laminated together by overlapping them and applying pressure. Heating may be applied during this process.

The first film 21 may further include photoelectric conversion layers 7, 9, and 11. That is, the first film 25 may include the photoelectric conversion layers 7, 9, and 11 in addition to the second electrode 13 and the second flexible substrate 15.

Figure 4 is a conceptual diagram showing a first film having a first connection electrode and a second film having a second connection electrode. A solar cell is obtained by bonding the two films shown in Figure 4 together. The first electrode 5 and second electrode 13 of this solar cell are electrically connected via the first connection electrode portion 25 and the second connection electrode portion 27. In this way, the two films may each have a connection electrode.

Figure 5 is a conceptual diagram showing a second film having a second connection electrode. A solar cell is obtained by bonding the two films shown in Figure 5 together. The first electrode 5 and second electrode 13 of this solar cell are electrically connected via the second connection electrode portion 27. In this way, the second film 23 may be one in which each of the two films has a connection electrode.

Figure 6 is a flow chart showing the reverse order of creating the hole transport layer and the electron transport layer from that shown in Figure 2. In this way, the hole transport layer and the electron transport layer may be reversed from that shown in Figure 1.

In the above method, the first film 21 may have a part of the photoelectric conversion layer, and the second film 23 may have the remainder of the photoelectric conversion layer. Then, after the first film 21 and the second film 23 are bonded together, the photoelectric conversion layer is completed.

Figure 7 is a flow chart showing an example of manufacturing a solar cell using a first film having a hole transport layer and a second film having an electron transport layer and a perovskite layer. The first film and the second film obtained according to the flow chart of Figure 7 are outlined in Figure 8. Figure 8 is a conceptual diagram showing the first film and the second film obtained according to the flow chart of Figure 7. As shown in Figure 8, in this example, the first film 21 has a hole transport layer 7, and the second film 23 has an electron transport layer 11 and a perovskite layer 9. In this example, after the first film and the second film are bonded together, the photoelectric conversion layers 7, 9, and 11 are completed.

In the above method, the first film 21 may further have a first perovskite precursor layer 31, and the second film 23 may further have a second perovskite precursor layer 33. FIG. 9 is a conceptual diagram showing the first film and the second film each having a perovskite precursor layer. In this case, the first perovskite precursor layer 31 and the second perovskite precursor layer 33 form the perovskite layer 9 after the first film 21 and the second film 23 are bonded together.

Perovskite precursor layer The perovskite precursor layer means a layer that becomes a perovskite layer by performing a predetermined treatment. For example, the first perovskite precursor layer 31 and the second perovskite precursor layer 33 may have a composition that contains elements that constitute a perovskite layer when the respective compositions are combined, and forms the perovskite layer 9 when the first film 21 and the second film 23 are bonded together. Perovskite precursors are known, for example, as described in JP 2019-055916 A. The perovskite precursor layer may contain a known perovskite precursor as appropriate. For example, a complex containing a compound represented by the formula (AM _n1 X _m1 ) and (1) 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)pyrimidinone (abbreviated as "DMTHP"), (2) sulfolane (tetrahydrothiophene 1,1-oxide, abbreviated as "SU"), (3) tetramethylene sulfoxide (abbreviated as "TS"), or (4) N,N-dimethylacetamide (abbreviated as "DMA") is a precursor of a perovskite.
A is a methylammonium cation (CH ₃ NH ₃ ⁺ ), a formamidinium cation (NH ₂ CHNH ₂ ⁺ ), or a cesium cation (Cs ⁺ );
M is Pb ²⁺ , Ge ²⁺ , or Sn ²⁺ ;
X is F ⁻ , Cl ⁻ , Br ⁻ , or I ⁻ ;
n1 is 0.8 to 1.2,
m1 is 2.8 to 3.2.
When the film containing the complex is heated, the molecules (L) are separated and a perovskite compound is formed. For example, the first film 21 and the second film 23 are bonded together, and then heated to obtain the perovskite layer 9.

In the above method, the first film 21 may further have a first perovskite layer 37, and the second film 23 may further have a second perovskite layer 39, and the first perovskite layer 37 and the second perovskite layer 39 may be combined to form a perovskite layer. FIG. 10 is a conceptual diagram showing a first film and a second film each having a perovskite layer. For example, a first perovskite layer is formed on the surface of the first film 21. Then, a second perovskite layer having the same composition as the first perovskite layer is formed on the surface of the second film 23. When these two films are pressed together, for example, the perovskite layers having the same composition are welded to form one perovskite layer. In this way, the two films can be easily pressed together.

In the above method, the first electrode 5 and the second electrode 13 may be connected so that electrical continuity is established via a first connection electrode portion 25 provided on the first electrode 5 in the region between the first electrode 5 and the second electrode 13 where the photoelectric conversion layers 7, 9, and 11 are not present. The first connection electrode portion 25 may have a protruding shape. If the first connection electrode portion 25 has a protruding shape, it is preferable because even if a thin layer is formed on the second electrode 13, it can penetrate the thin layer and ensure electrical continuity with the second electrode 13.

In this example, for example, a second electrode (surface electrode) 13 is provided on a second flexible substrate 15, and photoelectric conversion layers 7, 9, and 11 are provided on the surface electrode 13. However, in this example, the photoelectric conversion layers 7, 9, and 11 are not provided on the entire surface of the surface electrode 13, but there is an area on the surface of the surface electrode 13 where the photoelectric conversion layers 7, 9, and 11 are not present (this area is referred to as area A). On the other hand, a first electrode (back electrode) 5 is provided on the first flexible substrate 3. The first flexible substrate 3 and the second flexible substrate 15 have corresponding shapes and are bonded together to form a solar cell. A connection electrode portion 25 is present on the back electrode 5 in an area corresponding to area A. Then, after the first flexible substrate 3 and the second flexible substrate 15 are bonded together, the first connection electrode portion 25 comes into contact with the surface electrode 13. As a result, the first electrode 5 and the second electrode 13 are electrically connected via the first connection electrode portion 25.

The solar cell manufactured as described above has the following configuration. That is, this solar cell is composed of a first flexible substrate 3, a first electrode 5 which is a transparent electrode, photoelectric conversion layers 7, 9, 11 having a perovskite layer 9, a second electrode 13, and a second flexible substrate 15, arranged in this order. The first electrode 5 and the second electrode 13 are connected so that electrical continuity is established via a first connection electrode portion 25 provided on the first electrode 5 in the region between the first electrode 5 and the second electrode 13 where the photoelectric conversion layers 7, 9, 11 are not present.

As shown in FIG. 1, for example, this solar cell has an area between the first flexible substrate 3 and the second flexible substrate 15 where the photoelectric conversion layers 7, 9, and 11 are not present. In particular, it is preferable that this solar cell has an area between the first flexible substrate 3 and the second flexible substrate 15 where the hole transport layer 7 and the perovskite layer 9 are not present.

As shown in FIG. 1, this solar cell is preferably one in which the hole transport layer 7 covers the perovskite layer 9. The hole transport layer 7 may be wider than the perovskite layer 9. When the first film 21 and the second film are bonded together, the hole transport layer 7 becomes the adhesive surface with the first electrode. By covering the perovskite layer 9 with the hole transport layer 7 that forms the adhesive surface, the hole transport layer 7 protects the perovskite layer 9 from oxygen and moisture, improving durability.

In the above method, the first electrode 5 and the second electrode 13 may be connected so that electrical continuity is established through the second connection electrode 27 provided on the second electrode 13 in the region (region A) between the first electrode 5 and the second electrode 13 where the photoelectric conversion layers 7, 9, and 11 are not present. In this case, the second connection electrode 27 may be provided in region A, and the second connection electrode 27 may come into contact with the first electrode (rear electrode) 5 after the first flexible substrate 3 and the second flexible substrate 15 are bonded together. On the other hand, the first connection electrode 25 may be present on the rear electrode 5 in a region corresponding to region A. In this case, the second connection electrode 27 may come into contact with the first connection electrode 25 after the first flexible substrate 3 and the second flexible substrate 15 are bonded together. In any case, in this way, the first electrode 5 and the second electrode 13 are electrically connected via the second connection electrode portion 27 (or the second connection electrode portion 27 and the first connection electrode portion 25).

The solar cell manufactured in this manner has the following configuration. This solar cell is composed of a first flexible substrate 3, a first electrode 5 which is a transparent electrode, photoelectric conversion layers 7, 9, 11 having a perovskite layer 9, a second electrode 13, and a second flexible substrate 15, arranged in this order. The first electrode 5 and the second electrode 13 are connected so that electrical continuity is established via a second connection electrode portion 27 provided on the second electrode 13 in the region between the first electrode 5 and the second electrode 13 where the photoelectric conversion layers 7, 9, 11 are not present.

The solar cell was prepared using the following equipment and tools:
PTFE filter: Agilent Technologies, 5190-5266, 0.45 μm
ITO/PEN film: Oike & Co., Itd., CX13G-125N-U0, 16 Ω/□
Laminator: Nishinbo Mechatronics Inc., PVL0202S
reagent
SnO ₂ aqueous dispersion: Alfer Acer, 044592
PEDOT:PSS dispersion: Heraeus, Clevios P VP. Al 4083.
PbI ₂ : Tokyo Chemical Industry Co., Ltd., L0279
FAI: Tokyo Chemical Industry Co., Ltd., F1263
MABr：Tokyo Chemical Industry Co., Ltd., M2589
MACl: Tokyo Chemical Industry Co., Ltd., M0138
Super dehydrated DMF: Kanto Chemical Co., Inc., 11339-85
Ultra-dehydrated DMSO: Wako Pure Chemical Industries, Ltd., 049-07213
Super dehydrated acetone: Wako Pure Chemical Industries, Ltd., 013-00356

A PEN film with ITO, which is a transparent electrode, was plasma-treated, and water-soluble _SnO2 was applied as an electron transport layer, and water-soluble PEDOT:PSS was applied as a hole transport layer. The _SnO2 layer was obtained by dropping 300 μL of a 15% _SnO2 aqueous dispersion diluted 1:1 with pure water onto the substrate, spin-coating (ramp 2 s, 3000 rpm for 20 s), and heating at 150 °C for 30 min. The PEDOT:PSS layer was also obtained by dropping 300 μL of the PEDOT:PSS dispersion onto the substrate, spin-coating (ramp 1 s, 500 rpm for 9 s, ramp 1 s, 4000 rpm for 30 s), and heating at 140 °C for 30 min. _{The SnO2} and PEDOT:PSS films were formed in air. All subsequent steps were carried out in a glove box (N ₂ gas, H ₂ O < 0.1 ppm, O ₂ < 0.1 ppm).

In a glove box, _PbI2 (1798 mg, 3.9 mmol) was dissolved in a mixture of ultra-dehydrated DMF/DMSO (2.85 mL/0.15 mL). The mixture was stirred at 70 °C for 30 min and filtered using a PTFE filter to prepare a 1.3 M _PbI2 solution. The _PbI2 solution (200 μL) was spin-coated (ramp 2 s, 1500 rpm for 30 s) on the substrate coated with _SnO2 and PEDOT:PSS, and then heated at 70 °C for 1 min to obtain a _PbI2 layer. Part of the _SnO2 layer, PEDOT:PSS layer, and _PbI2 layer were removed using an acetone:DMSO (10:1) solution, and a Cu tape was attached as an extraction electrode.

The film substrate and sealant used for fixation were larger than the substrate coated with _SnO2 and PEDOT:PSS. The sealant was placed on the film substrate and heated at 120 °C for 10 minutes, after which the substrate coated with _SnO2 and PEDOT:PSS was placed on top and fixed.

FAI (60 mg, 0.35 mmol), MABr (6.0 mg, 0.05 mmol), and MACl (6.0 mg, 0.09 mmol) were dissolved in ultra-dehydrated i-PrOH (10 mL). The mixture was stirred at 40 °C for 30 minutes and filtered using a PTFE filter to prepare an organic cation solution. 50 μL of the organic cation solution was dropped onto each substrate, and the substrates were quickly stacked. The substrates were transferred to a laminator set at 150 °C and pressed under reduced pressure for 10 minutes to form a perovskite layer. A bonded cell was fabricated using the above process. When the cross-sectional area of the obtained solar cell was measured, it was found that the PEDOT:PSS layer had a larger area than the perovskite layer. This is presumably because the soft PEDOT:PSS film spread due to the pressure applied during bonding.

The solar cell characteristics were evaluated at 1 sun under atmospheric conditions. When light was incident from _{the SnO2} layer side, the open circuit voltage was 0.70 V, the short circuit current density was 17.8 mA/ ^cm2 , the form factor was 0.64, and the conversion efficiency was 8.0%. When light was incident from the PEDOT:PSS layer side, the open circuit voltage was 0.58 V, the short circuit current density was 15.4 mA/ ^cm2 , the form factor was 0.61, and the conversion efficiency was 5.45%.

Furthermore, the solar cell characteristics were evaluated after 100 hours of continuous irradiation at 1 Sun as the light durability. The results showed that the characteristics when light was incident from the _SnO2 layer side were an open circuit voltage of 0.67 V, a short circuit current density of 16.1 mA/cm2, a fill factor of 0.63, and a conversion efficiency of 6.8%, which was 85% of the characteristics before the durability test.

[Comparative Example 1]
The device was fabricated using the same process as in Example 1 up to the formation of the perovskite layer, and a PEDOT:PSS layer was formed on top of it. The electrode thus obtained and the ITO/PEN film were attached in the same manner as in Example 1 to fabricate a cell.
The solar cell characteristics of this cell were measured under atmospheric conditions at 1 sun. When light was incident from _{the SnO2} layer side, the characteristics were an open circuit voltage of 0.41 V, a short circuit current density of 10.3 mA/ ^cm2 , a form factor of 0.33, and a conversion efficiency of 1.4%. When light was incident from the PEDOT:PSS layer side, the characteristics were an open circuit voltage of 0.33 V, a short circuit current density of 7.6 mA/ ^cm2 , a form factor of 0.33, and a conversion efficiency of 0.8%. Compared to Example 1, it is clear that the solar cell performance is inferior.

Furthermore, the solar cell characteristics after 100 hours of continuous irradiation were evaluated as the light durability at 1 Sun. The results showed that the characteristics when light was incident from the _SnO2 layer side were an open circuit voltage of 0.16 V, a short circuit current density of 6.8 mA/ ^cm2 , a fill factor of 0.31, and a conversion efficiency of 0.3%, and the retention rate compared to the characteristics before the durability test was 37.5%. It is clear that the retention rate is lower than that of Example 1.

As is clear from the above, it is clear that the solar cell of the present invention not only exhibits high initial characteristics but also has high light durability.

A 50μm thick PET film is used for the first and second flexible substrates, and an ITO film of about 150nm is formed on the electrodes on the film in advance to form a pattern. In order to make it easier to carry out subsequent processes, the flexible substrate may be attached to a glass substrate.
First, a water-soluble _SnO2 solution is applied by spin coating onto the first flexible substrate, and then dried by heating at about 150°C. On top of that, a perovskite solution is spin coated, dried, and then a hole layer is spin coated and dried. For the hole layer, a solution of Spiro-MeOTAD and LiTFSi dissolved in chlorobenzene is used. Part of the hole layer and perovskite layer are removed as necessary. The removal method was laser processing, but another method is reactive ion etching (RIE) using a metal mask.

On the other hand, silver paste was printed by screen printing in the desired locations on the second flexible substrate for electrical connection between the first and second substrates. The concentration and thickness was adjusted so that the finished thickness would be about 5 to 20 μm. To bond the films together, align both films and apply pressure with a roller. The amount of pressure applied depends on the size of the roller, but we applied a pressure of about 0.1 kg/cm. When bonding the films together, spraying chlorobenzene onto the second flexible substrate before bonding in order to soften the surface of the hole layer slightly allowed for effective bonding. Furthermore, bonding was more effective if the roller was heated to a constant temperature of about 70°C.

The film is not limited to PET, but can be any flexible film. In order to prevent moisture permeation, it is preferable to use a flexible film with a barrier layer formed in advance. In addition to silver paste, other connection materials include carbon paste, copper paste, nickel paste, and carbon nanotubes.

A 50 μm thick PET film is used for the first and second flexible substrates, and an ITO film of about 150 nm is formed on the electrodes on the film in advance to form a pattern (similar to Example 2). In order to make it easier to carry out subsequent processes, the flexible substrate may be attached to a glass substrate.
First, a water-soluble _SnO2 solution is applied by spin coating onto the first flexible substrate, and then dried by heating at about 150°C. A perovskite solution is then spin coated on top of that, and dried. If necessary, parts of the hole layer and perovskite layer are removed. Methods for removal include laser processing and reactive ion etching (RIE) using a metal mask.

On the other hand, silver paste is printed in the desired locations on the second flexible substrate using screen printing or similar methods to electrically connect the first and second substrates. The finished thickness is adjusted to be around 5 to 20 μm. After that, the hole layer is applied in the desired pattern shape using the inkjet method. Because of the unevenness caused by the material used for electrical connection, application using the spin coat method is not necessarily suitable.

When laminating, it is advisable to align the positions of both films in advance and apply pressure with a roller. The pressure applied will depend on the roller size, but we applied a pressure of about 0.1 kg/cm. When laminating, spraying chlorobenzene onto the first flexible substrate before laminating in order to soften the surface of the hole layer allows for effective lamination. Also, heating the roller to a constant temperature of about 70°C allows for more effective lamination. (The materials are the same as in Example 2.)

In the above embodiment, spin coating was mainly used for application, but each layer may be formed by the inkjet method. In that case, the connection electrodes are also formed in advance on the first flexible substrate, so that the resistance of the connection electrodes can be easily and stably reduced. The connection electrodes formed on the first flexible substrate may be formed by depositing a thin metal film of a single metal such as Pt, Au, Cu, Ag, Ni, Ti, etc., or an alloy of these metals on ITO by vapor deposition, or by using a paste of these metals.

For example, a 50 μm PET film is used for the first and second flexible substrates, and an ITO film of about 150 nm is formed on the electrodes on the substrate in advance to form a pattern. In order to make it easier to carry out subsequent processes, the flexible substrate may be attached to a glass substrate.
After _SnO2 was applied by spin coating on the ITO on the first flexible substrate, a metal mask was set and a film was formed by sputtering to attach Cu/Pt for connection to a part of it. A perovskite layer and a hole layer were applied on top of it in sequence as in Example 2. When a connection electrode is formed with a thin film, the spin coating method does not cause significant unevenness in the coating thickness, but when it is formed by screen printing, the unevenness in the film thickness becomes large due to the large step. In that case, the occurrence of unevenness in the film thickness can be suppressed by applying it by the inkjet method. On the other hand, the process of the second flexible substrate and the bonding can be the same as in Example 2.

This invention can be used in fields such as solar cells.

REFERENCE SIGNS LIST 1 Solar cell 3 First flexible substrate 5 First electrode 7 Electron transport layer 9 Perovskite layer 11 Hole transport layer 13 Second electrode 15 Second flexible substrate 21 First film 23 Second film 31 First perovskite precursor layer 33 Second perovskite precursor layer 37 First perovskite layer 39 Second perovskite layer

Claims (6)

A method for manufacturing a solar cell having, in this order, a first flexible substrate (3), a first electrode (5), a photoelectric conversion layer (7, 9, 11) having a perovskite layer, a second electrode (13), and a second flexible substrate (15), comprising:
A first film (21) including a first flexible substrate (3) and a first electrode (5);
Providing a second film (23) including a second electrode (13) and a second flexible substrate (15);
A method for manufacturing a solar cell , comprising a step of bonding a first film (21) and a second film (23),
The first film (21) has a first connection electrode portion (25) having a protruding shape provided on the first electrode (5),
The first electrode (5) and the second electrode (13) are
In a region between the first electrode (5) and the second electrode (13) where the photoelectric conversion layer (7, 9, 11) is not present,
It is connected so as to be electrically conductive via the first connection electrode portion (25),
The second electrode (13) has a first portion and a second portion adjacent to each other across a region where the photoelectric conversion layer (7, 9, 11) is not present on the surface of the second film (23), and the surface of the first portion of the second electrode (13) facing the second portion of the second electrode (13) is covered with the perovskite layer (9).
How solar cells are manufactured . The method for manufacturing a solar cell according to claim 1, wherein the first film (21) further comprises a first perovskite precursor layer (31) and the second film (23) further comprises a second perovskite precursor layer (33). The method for manufacturing a solar cell according to claim 1, wherein the first film (21) further comprises a first perovskite layer (37), the second film (23) further comprises a second perovskite layer (39), and the first perovskite layer (37) and the second perovskite layer (39) constitute the perovskite layer. The method for manufacturing a solar cell according to claim 1, further comprising the step of forming a second electrode (13) on a second flexible substrate (15) by sputtering or the step of forming a second electrode (13) on a second flexible substrate (15) using a conductive paste to obtain a second film (23). A method for producing a solar cell according to claim 1, comprising the steps of:
In the step of bonding the first film (21) and the second film (23),
A method for manufacturing a solar cell, in which a first connection electrode portion (25) penetrates a thin layer formed on a second electrode (13), thereby ensuring electrical continuity between a first electrode (5) and a second electrode (13). A method for manufacturing a solar cell having, in this order, a first flexible substrate (3), a first electrode (5), a photoelectric conversion layer (7, 9, 11) having a perovskite layer (9), a second electrode (13), and a second flexible substrate (15), comprising:
A first film (21) including a first flexible substrate (3) and a first electrode (5);
Providing a second film (23) including a second electrode (13) and a second flexible substrate (15);
A method for manufacturing a solar cell, comprising a step of bonding a first film (21) and a second film (23),
The second film (23) has a second connection electrode portion (27) having a protruding shape provided on the second electrode (13),
The first electrode (5) and the second electrode (13) are
In a region between the first electrode (5) and the second electrode (13) where the photoelectric conversion layer (7, 9, 11) is not present,
It is connected so as to be electrically conductive via the second connection electrode portion (27),
The second electrode (13) has a first portion and a second portion adjacent to each other on the surface of the second film (23) with a region in which the photoelectric conversion layer (7, 9, 11) is not present therebetween, and the surface of the first portion facing the second portion of the second electrode (13) is covered with the perovskite layer (9).
How solar cells are manufactured.

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