JP6991464B2 - Photoelectric conversion element and solar cell module - Google Patents

Description

The present invention relates to a photoelectric conversion element and a solar cell module.

In the photoelectric conversion element, an electron transport layer, an active layer, a hole transport layer, and the like are arranged between the pair of electrodes. The use of an organic-inorganic hybrid semiconductor material in the active layer of such a photoelectric conversion element has attracted attention for its high efficiency.

As the organic-inorganic hybrid semiconductor material of the active layer, the use of a perovskite semiconductor compound, for example, a halide-based organic-inorganic perovskite semiconductor compound has been studied. Further, although gold is used as an electrode, since gold is expensive, the use of a metal other than gold, for example, silver, is being considered in consideration of practicality.

It has been reported that halides or halogen elements of halide-based organic-inorganic perovskite semiconductor compounds, such as iodide, diffuse through the electron transport layer or the hole transport layer and reach the electrodes. When gold was used as the electrode, it did not pose a problem because it did not easily react with the diffused iodide and the like. However, when silver is used as an electrode, it may react with iodide or the like in which silver is diffused, deteriorating the electrode, and lowering the durability of the photoelectric conversion element. Further, Non-Patent Document 1 reports that ITO (indium tin oxide) is used as an electrode.

KEVIN A. Bush et al., "Thermal and Environmental Stability of Semi-Transparent Perovskite Solar Cells for Tandems Enabled by a Solution-Processed Nanoparticle Buffer Layer and Sputtered ITO Electrode", Advanced Materials, 2016, Vol. 28, p. 3937- 3943.

When the present inventors considered using a metal oxide such as ITO as an electrode to improve the durability of the photoelectric conversion element, the output characteristics (particularly, the initial output characteristics) of the photoelectric conversion element deteriorate. I found that. An object of the present invention is to improve the output characteristics and durability of a photoelectric conversion element.

According to the prior art, when one of the electrodes is configured to include a metal layer and a metal oxide layer, the electrodes react with iodide or the like to reduce the durability of the photoelectric conversion element. Contrary to the prediction, it was found that the durability of the photoelectric conversion element does not decrease. Moreover, it has also been found that the output characteristics of the photoelectric conversion element do not deteriorate even if the electrode contains a metal oxide. The present inventors have completed the present invention based on these findings.

That is, the gist of the present invention lies in the following.
[1] A photoelectric conversion element having a pair of electrodes and an active layer located between them.
The active layer has a halide-based organic-inorganic perovskite semiconductor compound.
One of the pair of electrodes has a metal layer or a metal alloy layer and a metal oxide layer.
The metal layer or the metal alloy layer is located between the active layer and the metal oxide layer .
One electrode further comprises another metal layer or metal alloy layer, wherein the metal oxide layer is located between the metal layer or the metal alloy layer and the other metal layer or the metal alloy layer . A photoelectric conversion element characterized by this.
[2] The photoelectric conversion element according to [1] , wherein one of the electrodes is a non-transparent electrode.
[3] The photoelectric conversion element according to [1] or [2] , wherein the metal layer or the metal alloy layer contains silver or copper.
[4] The photoelectric conversion element according to any one of [1] to [3] , wherein the active layer contains an iodine atom.
[5] The photoelectric conversion element according to any one of [1] to [4] , wherein the photoelectric conversion element has an electron transport layer and a hole transport layer.
[6] A solar cell module having the photoelectric conversion element according to any one of [1] to [5] .

The output characteristics and durability of the photoelectric conversion element can be improved.

It is sectional drawing which shows typically the photoelectric conversion element as one Embodiment. It is sectional drawing which shows typically the photoelectric conversion element as another embodiment. It is sectional drawing which shows typically the solar cell as one Embodiment. It is sectional drawing which shows typically the solar cell module as one Embodiment.

The photoelectric conversion element according to the present invention has a pair of electrodes and an active layer containing a halide-based organic-inorganic perovskite semiconductor compound located between the electrodes. Further, one of the pair of electrodes has a metal layer or a metal alloy layer and a metal oxide layer, and the metal layer or the metal alloy layer is located between the active layer and the metal oxide layer. There is.

By assuming that one of the electrodes has a metal layer and a metal oxide layer, the durability of the photoelectric conversion element does not decrease even if the metal contained in the metal layer reacts with iodide. It is presumed that the metal oxide layer suppresses the increase in the sheet resistance of the electrode and improves the durability. Further, even if the electrode contains a metal oxide, the output characteristics of the photoelectric conversion element are not deteriorated. This suppresses damage to the lower layers (active layer, electron transport layer, hole transport layer, etc.) that occurred in the process of forming the metal oxide layer by using the metal layer as a wall, and improves the output characteristics of the photoelectric conversion element. It is estimated to improve.

Hereinafter, embodiments of the present invention will be described in detail. The description of the constituent elements described below is an example (representative example) of the embodiment of the present invention, and the present invention is not limited to these contents as long as the gist thereof is not exceeded.

[1. Photoelectric conversion element according to one embodiment]
FIG. 1 is a cross-sectional view schematically showing an embodiment of a photoelectric conversion element according to the present invention. The photoelectric conversion element shown in FIG. 1 is a photoelectric conversion element used in a general thin-film solar cell, but the photoelectric conversion element according to the present invention is not limited to that shown in FIG. In the photoelectric conversion element 100 shown in FIG. 1, the active layer 103 is located between the pair of electrodes composed of the lower electrode 101 and the upper electrode 105. Further, in the photoelectric conversion element 100, the electron transport layer 102 may be arranged between the lower electrode 101 and the active layer 103, and the hole transport layer 104 may be arranged between the upper electrode 105 and the active layer 103. May be placed. Further, as shown in FIG. 1, the photoelectric conversion element 100 may have other layers such as a base material 106, an insulator layer, and a work function tuning layer.

[1.1 Active layer]
The active layer 103 is a layer on which photoelectric conversion is performed. When the photoelectric conversion element 100 receives light, the light is absorbed by the active layer 103 to generate carriers, and the generated carriers are taken out from the lower electrode 101 and the upper electrode 105.

In the present embodiment, the active layer 103 contains an organic-inorganic hybrid semiconductor material. The organic-inorganic hybrid semiconductor material refers to a material in which an organic component and an inorganic component are combined at the molecular level or the nano level and exhibits semiconductor characteristics.

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

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

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

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

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

The active layer 103 contains at least a halide-based organic-inorganic perovskite semiconductor compound in which X is a halide ion or a combination of a halide ion and another anion, and may contain another perovskite semiconductor compound. For example, the active layer 103 may contain a perovskite semiconductor compound in which at least one of A, B, and X is different. Further, the active layer 103 may have a laminated structure formed of a plurality of layers containing different materials or having different components.

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

The amount of the perovskite semiconductor compound contained in the active layer 103 is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more so that good semiconductor properties can be obtained. be. There is no particular upper limit. Further, the active layer 103 may contain an additive in addition to the perovskite semiconductor compound. Examples of additives include inorganic compounds, such as halides, oxides, or inorganic salts such as sulfides, sulfates, nitrates or ammonium salts, or organic compounds.

There is no particular limitation on the thickness of the active layer 103. The thickness of the active layer 103 is 10 nm or more in one embodiment, 50 nm or more in another embodiment, 100 nm or more in yet another embodiment, and 120 nm or more in yet another embodiment in that more light can be absorbed. Is. On the other hand, the thickness of the active layer 103 is 1500 nm or less in one embodiment, 1000 nm or less in another embodiment, and 600 nm or less in another embodiment in terms of lowering the series resistance or increasing the charge extraction efficiency. Is.

The method for forming the active layer 103 is not particularly limited, and any method can be used. Specific examples include a coating method and a vapor deposition method (or a co-deposited method). The coating method can be used in that the active layer 103 can be easily formed. For example, a method of forming the active layer 103 by applying a coating liquid containing a perovskite semiconductor compound or a precursor thereof and heating and drying it as necessary can be mentioned. Further, after applying such a coating solution, the perovskite semiconductor compound can be precipitated by further applying a solvent having a low solubility of the perovskite semiconductor compound.

The precursor of a perovskite semiconductor compound refers to a material that can be converted into a perovskite semiconductor compound after the coating liquid is applied. As a specific example, a perovskite semiconductor compound precursor that can be converted into a perovskite semiconductor compound by heating can be used. For example, a coating liquid can be prepared by mixing a compound represented by the general formula AX, a compound represented by the general formula MX ₂ , and a solvent, and heating and stirring the mixture. By applying this coating liquid and heat-drying it, the active layer 103 containing the perovskite semiconductor compound represented by the general formula AMX ₃ can be produced. The solvent is not particularly limited as long as it dissolves the perovskite semiconductor compound and the additive, and examples thereof include organic solvents such as N, N-dimethylformamide.

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

[1.2 Electrode]
The electrode has a function of collecting holes and electrons generated by light absorption in the active layer 103. The photoelectric conversion element 100 according to the embodiment of the present invention has a pair of electrodes, one of the pair of electrodes is referred to as an upper electrode, and the other is referred to as a lower electrode. When the photoelectric conversion element 100 has a base material or is provided on the base material, an electrode closer to the base material can be referred to as a lower electrode, and an electrode farther from the base material can be referred to as an upper electrode. Further, the transparent electrode may be referred to as a lower electrode, and the electrode having lower transparency than the lower electrode may be referred to as an upper electrode. The photoelectric conversion element 100 shown in FIG. 1 has a lower electrode 101 and an upper electrode 105.

As the pair of electrodes, an anode suitable for collecting holes and a cathode suitable for collecting electrons can be used. In this case, the photoelectric conversion element 100 may have a forward configuration in which the lower electrode 101 is the anode and the upper electrode 105 is the cathode, or the lower electrode 101 is the cathode and the upper electrode 105 is the anode. It may have a mold configuration.

One of the pair of electrodes may be translucent. Translucency means that the visible light transmittance (transmittance of light in the entire region having a wavelength of 380 to 780 nm) is 40% or more. Further, it is preferable that the visible light transmittance of the transparent electrode is 70% or more because more light passes through the transparent electrode and reaches the active layer 103. The light transmittance can be measured with a spectrophotometer (for example, U-4100 manufactured by Hitachi High-Tech).

(Upper electrode)
The upper electrode 105 has a metal layer or a metal alloy layer 105a and a metal oxide layer 105b. Further, the metal layer or the metal alloy layer 105a is located between the active layer 103 and the metal oxide layer 105b.

The halide or halogen element of the halide-based organic-inorganic perovskite semiconductor compound contained in the active layer 103, for example, iodide, may diffuse through the hole transport layer 104 and reach the upper electrode 105. Conventionally, an electrode that has reacted with iodide may accelerate the deterioration of the electrode and reduce the durability of the photoelectric conversion element, but the surface side of the metal layer or the metal alloy layer 105a opposite to the active layer 103. By providing the metal oxide layer 105b on the surface, the durability of the photoelectric conversion element does not decrease.

This is because the deterioration of the electrode due to the iodide was not due to the influence on the charge extraction, but had an influence on the increase in the sheet resistance of the upper electrode 105, and the metal layer or the metal alloy layer 105a reacted with the iodide. By laminating the metal oxide layer 105b having conductivity, which is difficult to do, the increase in the sheet resistance of the upper electrode 105 is suppressed, and the durability is improved.

Further, as will be described later, the metal oxide layer 105b is formed by a sputtering method or the like, but in this forming process, the active layer 103, the electron transport layer 102, the hole transport layer 104, and the like may be damaged. there were. However, since the photoelectric conversion element 100 of the present embodiment is provided with the metal layer or the metal alloy layer 105a on the side forming the metal oxide layer 105b, the active layer 103, the electron transport layer 102, and the hole transport layer Damage to the 104 and the like is suppressed by the metal layer or the metal alloy layer 105a forming a wall, and the output characteristics of the photoelectric conversion element are not deteriorated.

Examples of the metal of the metal layer 105a include gold, silver, copper, aluminum, calcium, titanium, cobalt, nickel, palladium and the like. Even if gold is used as the metal of the metal layer 105a, the metal layer 105a is a part of the upper electrode 105, and the amount of gold used for the upper electrode 105 as a whole is reduced, so that the cost is reduced as compared with the electrode made of gold. .. However, as the metal of the metal layer 105a, a metal other than gold may be used in consideration of practicality. In one embodiment, the metal of the metal layer 105a is silver or copper. Examples of the metal alloy of the metal alloy layer 105a include alloys containing two or more metals selected from metals such as gold, silver, copper, aluminum, calcium, titanium, cobalt, nickel, and palladium. In one embodiment, the metal alloy layer 105a is a layer of a metal alloy containing at least one of silver or copper.

As the metal oxide of the metal oxide layer 105b, one that does not easily react with a halogen element or a halide is used, and a transparent oxide containing a metal such as tin, indium, or zinc can be used. Examples of the metal oxide of the metal oxide layer 105b include indium oxide, zinc oxide, tin oxide, indium tin oxide (ITO), tin fluorinated oxide (FTO), indium zinc oxide (IZO) and the like. In one embodiment, the metal oxide layer 105b is IZO.

The lower limit of the film thickness of the upper electrode 105 is 2 nm or more in one embodiment, 10 nm or more in another embodiment, and 50 nm or more in yet another embodiment, while the upper limit is 500 nm or less in one embodiment. In one embodiment, the film thickness is 300 nm or less, and in yet another embodiment, the film thickness is 100 nm or less. Conductivity can be obtained by setting the above lower limit. In addition, cost can be reduced by setting the above upper limit.

The lower limit of the film thickness of the metal layer or the metal alloy layer 105a is 1 nm or more in one embodiment, 3 nm or more in another embodiment, and 5 nm or more in another embodiment, while the upper limit is in one embodiment. It is 200 nm or less, 100 nm or less in another embodiment, and 50 nm or less in yet another embodiment. By setting the above lower limit, damage to the lower layer caused in the formation process of the metal oxide layer 105b can be suppressed. In addition, cost can be reduced by setting the above upper limit.

The lower limit of the film thickness of the metal oxide layer 105b is 1 nm or more in one embodiment, 10 nm or more in another embodiment, and 30 nm or more in yet another embodiment, while the upper limit is 300 nm or less in one embodiment. In another embodiment, it is 200 nm or less, and in yet another embodiment, it is 100 nm or less. By setting the above lower limit, an increase in the sheet resistance of the upper electrode 105 can be suppressed. In addition, cost can be reduced by setting the above upper limit.

In one embodiment, the upper electrode 105 can be a non-transparent electrode. Non-transparent means that the visible light transmittance is less than 40%. Further, when the visible light transmittance of the upper electrode 105 is 30% or less, the upper electrode 105 blocks the light incident on the active layer 103 from the lower electrode 101 side and not absorbed by the active layer 103. At the same time, it is easy to reflect the light and return it to the active layer 103, so that the light absorption efficiency can be improved. Further, the upper electrode 105 may be non-transparent as a whole, and at least one of the metal layer or the metal alloy layer 105a and the metal oxide layer 105b may be non-transparent. For example, the metal layer or the metal alloy layer 105a can be made non-transparent, and the metal oxide layer 105b can be made transparent. The light transmittance can be measured with a spectrophotometer (for example, U-4100 manufactured by Hitachi High-Tech) as described above.

The method for forming the metal layer or the metal alloy layer 105a other than gold is not particularly limited, and any method can be used. Specific examples include a coating method, a plating method and a vacuum vapor deposition method. The method for forming the metal oxide layer 105b is not particularly limited, and any method can be used. As a specific example, it is formed by a sputtering method, an ion plating method, a vacuum vapor deposition method, a sol-gel method, a coating method, or the like.

(Lower electrode)
There are no particular restrictions on the constituent members of the lower electrode 101 and the manufacturing method thereof, and well-known techniques can be used. For example, the members described in publicly known documents such as International Publication No. 2013/171517, International Publication No. 2013/180230, and Japanese Patent Application Laid-Open No. 2012-191194, and methods for producing the same can be used.

[1.3 Electron or hole transport layer]
The electron transport layer 102 and the hole transport layer 104 are layers located between the active layer 103 and at least one of the pair of electrodes 101 and 105. The electron transport layer 102 and the hole transport layer 104 can be used, for example, to improve the carrier transfer efficiency from the active layer 103 to the lower electrode 101 or the upper electrode 105.

There are no particular restrictions on the constituent members of the electron transport layer 102 and the hole transport layer 104 and their manufacturing methods, and well-known techniques can be used. For example, the members described in publicly known documents such as International Publication No. 2013/171517, International Publication No. 2013/180230, and Japanese Patent Application Laid-Open No. 2012-191194, and methods for producing the same can be used.

[1.4 Base material]
The photoelectric conversion element 100 usually has a base material 106 as a support. However, the photoelectric conversion element according to the present invention does not have to have the base material 106. The material of the base material 106 is not particularly limited as long as the effect of the present invention is not significantly impaired. The materials described in 1 can be used.

[1.5 Other layers]
The photoelectric conversion element 100 may have other layers. For example, the photoelectric conversion element 100 has a work function tuning layer that adjusts the work function of the electrode between the lower electrode 101 and the electron transport layer 102, or between the upper electrode 105 and the hole transport layer 104. You may. Further, the photoelectric conversion element 100 has a thin insulator layer between the lower electrode 101 and the active layer 103, or between the upper electrode 105 and the active layer 103, which prevents moisture or the like from reaching the active layer 103. You may have. Further, in order to improve the durability, the photoelectric conversion element 100 may be further sealed. For example, the photoelectric conversion element 100 can be sealed by further laminating a sealing plate on the upper electrode 105 and fixing the base material 106 and the sealing plate with an adhesive.

[2. Photoelectric conversion element according to another embodiment]
FIG. 2 is a cross-sectional view schematically showing another embodiment of the photoelectric conversion element according to the present invention. The photoelectric conversion element 200 according to another embodiment shown in FIG. 2 includes a lower electrode 201, an electron transport layer 202, an active layer 203, a hole transport layer 204, and an upper electrode 205. Since the photoelectric conversion element 200 according to another embodiment is the same as the photoelectric conversion element 100 according to one embodiment shown in FIG. 1 except for the configuration of the upper electrode 205, the configuration of the photoelectric conversion element [1.1]. , And [1.3] to [1.5] will be omitted, and the configuration of the upper electrode 205 will be mainly described.

[2.1 Upper electrode]
In the photoelectric conversion element according to another embodiment, the upper electrode 205 has another metal layer or metal alloy layer 205c in addition to the metal layer or metal alloy layer 205a and the metal oxide layer 205b. Another metal layer or metal alloy layer 205c is located on the surface side of the metal oxide layer 205b opposite to the metal layer or the metal alloy layer 205a. As a result, when the metal layer or the metal alloy layer 205a is thin (when it has translucency), or when the metal oxide layer 205b is formed of a transparent metal oxide, the metal layer or the metal alloy layer 205c However, among the light incident on the active layer 203 from the lower electrode 201 side, the light that was not absorbed by the active layer 203 is blocked and reflected back to the active layer 203, so that the light absorption efficiency can be improved. can.

Further, even if the metal layer or the metal alloy layer 205a reacts with iodide or the like diffused from the active layer 103, the sheet resistance of the upper electrode 205 is provided by providing the metal oxide layer 205b and the metal layer or the metal alloy layer 205c. Is suppressed, and the durability of the photoelectric conversion element is improved. Since the metal oxide layer 205b does not easily react with iodide or the like and suppresses the diffusion of iodide or the like, even if the metal layer or the metal alloy layer 205c has a metal that easily reacts with iodide or the like, the metal The layer or the metal alloy layer 205c does not react with iodide or the like, which contributes to suppressing the increase in the sheet resistance of the upper electrode 205.

Further, since the photoelectric conversion element 200 of the present invention is provided with the metal layer or the metal alloy layer 205a on the side where the metal oxide layer 205b is formed, damage in the process of forming the metal oxide layer 205b is suppressed. The output characteristics of the photoelectric conversion element do not deteriorate.

As the metal of the metal layer 205a other than gold and the metal alloy of the metal alloy layer 205a, the same metal as the above-mentioned metal layer or the metal of the metal alloy layer 105a and the metal alloy can be used. Further, as the metal oxide of the metal oxide layer 205b, the same metal oxide as the above-mentioned metal oxide of the metal oxide layer 105b can be used.

Examples of the metal of the metal layer 205c include gold, silver, copper, aluminum, calcium, titanium, cobalt, nickel, palladium and the like. Even if gold is used as the metal of the metal layer 205c, the metal layer 205c is a part of the upper electrode 205, and the amount of gold used for the upper electrode 205 as a whole is reduced, so that the cost is reduced as compared with the electrode made of gold. .. However, as the metal of the metal layer 205c, a metal other than gold may be used in consideration of practicality. In one embodiment, it is silver or copper. Examples of the metal alloy of the metal alloy layer 205c include alloys containing two or more metals selected from metals such as gold, silver, copper, aluminum, calcium, titanium, cobalt, nickel, or palladium. In one embodiment, the metal alloy layer 205c is a layer of metal alloy containing at least one of silver or copper.

The film thickness of the upper electrode 205 and the metal layer or metal alloy layer 205a other than gold can be the same as the film thickness of the above-mentioned upper electrode 105 and the metal layer or metal alloy layer 105a.

In the photoelectric conversion element of another embodiment, the metal oxide layer 205b has the main function of suppressing the diffusion of iodide and the like, so that the film thickness of the metal oxide layer 105b in the photoelectric conversion element of one embodiment is the same. The lower limit is 1 nm or more in one embodiment, 3 nm or more in another embodiment, and 10 nm or more in yet another embodiment, while the upper limit is 50 nm or less in one embodiment. 30 nm or less in one embodiment, and 20 nm or less in yet another embodiment. By setting the above lower limit, an increase in the sheet resistance of the upper electrode 105 can be suppressed. In addition, cost can be reduced by setting the above upper limit.

The lower limit of the film thickness of the metal layer or the metal alloy layer 205c is 1 nm or more in one embodiment, 10 nm or more in another embodiment, and 50 nm or more in another embodiment, while the upper limit is in one embodiment. It is 300 nm or less, 200 nm or less in another embodiment, and 100 nm or less in yet another embodiment. By setting the above lower limit, it is possible to suppress an increase in the sheet resistance of the upper electrode 105 and to shield or reflect light. In addition, cost can be reduced by setting the above upper limit.

In one embodiment, the upper electrode 205 can be a non-transparent electrode. As described above, non-transparent means that the visible light transmittance is less than 40%. Further, when the visible light transmittance of the upper electrode 205 is 30% or less, the upper electrode 205 blocks the light incident on the active layer 203 from the lower electrode 201 side but not absorbed by the active layer 203. At the same time, it is easy to reflect the light and return it to the active layer 203, so that the light absorption efficiency can be improved. Further, the upper electrode 205 may be non-transparent as a whole, and at least one of the metal layer or the metal alloy layer 205a, the metal oxide layer 205b, and the metal layer or the metal alloy layer 205c is non-transparent. Can be. As one embodiment, the metal layer or the metal alloy layer 205a and the metal layer or the metal alloy layer 205c can be made non-transparent, and the metal oxide layer 205b can be made transparent. Further, as another embodiment, the metal layer or the metal alloy layer 205c can be made non-transparent, and the metal layer or the metal alloy layer 205a and the metal oxide layer 205b can be made transparent. The light transmittance can be measured with a spectrophotometer (for example, U-4100 manufactured by Hitachi High-Tech) as described above.

The method for forming the metal layer or the metal alloy layer 205a and another metal layer or the metal alloy layer 205c is not particularly limited, and any method can be used. Specific examples include a coating method, a plating method and a vacuum vapor deposition method. The method for forming the metal oxide layer 205b is not particularly limited, and any method can be used. As a specific example, it is formed by a sputtering method, an ion plating method, a vacuum vapor deposition method, a sol-gel method, a coating method, or the like.

[3. Manufacturing method of photoelectric conversion element]
By forming each layer constituting the photoelectric conversion elements 100 and 200 according to the above method, the photoelectric conversion elements 100 and 200 can be manufactured. There are no particular restrictions on the method of forming each layer constituting the photoelectric conversion elements 100 and 200, and the layers can be formed by a sheet-to-sheet (manyo) method or a roll-to-roll method.

The roll-to-roll method is a method in which a flexible base material wound in a roll shape is unwound and processed intermittently or continuously while being wound by a take-up roll. be. According to the roll-to-roll method, it is possible to collectively process long substrates on the order of km, so that the roll-to-roll method is more suitable for mass production than the sheet-to-sheet method. On the other hand, when an attempt is made to form a film on each layer by the roll-to-roll method, the film may be scratched or partially peeled off due to contact between the film-forming surface and the roll due to its structure.

The size of the roll that can be used in the roll-to-roll method is not particularly limited as long as it can be handled by the roll-to-roll method manufacturing apparatus, but the upper limit of the outer diameter is preferably 5 m or less, more preferably 3 m or less, and more preferably. It is 1 m or less. On the other hand, the lower limit is preferably 10 cm or more, more preferably 20 cm or more, and more preferably 30 cm or more. The upper limit of the outer diameter of the roll core is preferably 4 m or less, more preferably 3 m or less, and more preferably 0.5 m or less. On the other hand, the lower limit is preferably 1 cm or more, more preferably 3 cm or more, more preferably 5 cm or more, still more preferably 10 cm or more, and particularly preferably 20 cm or more. It is preferable that these diameters are not less than the above upper limit in terms of high roll handleability, and it is preferable that these diameters are not more than the lower limit in that the layer formed in each step is less likely to be broken by bending stress. .. The lower limit of the width of the roll is preferably 5 cm or more, more preferably 10 cm or more, and more preferably 20 cm or more. On the other hand, the upper limit is preferably 5 m or less, more preferably 3 m or less, and more preferably 2 m or less. It is preferable that the width is not more than the upper limit in terms of easy roll handling, and it is preferable that the width is not more than the lower limit because the degree of freedom in the size of the photoelectric conversion element 100 is high.

Further, after stacking the upper electrodes 105 and 205, the photoelectric conversion elements 100 and 200 are 50 ° C. or higher in one embodiment and 80 ° C. or higher in another embodiment, while 300 ° C. or lower in one embodiment and another embodiment. In the temperature range of 280 ° C. or lower, and in still another embodiment, 250 ° C. or lower, heating can be performed (this step may be referred to as an annealing treatment step). Performing the annealing treatment step at a temperature of 50 ° C. or higher means that the adhesion between the layers of the photoelectric conversion elements 100 and 200, for example, the electron transport layers 102 and 202 and the lower electrodes 101 and 201, and the electron transport layers 102 and 202 and the active layer. The effect of improving the adhesion between layers such as 103 and 203 can be obtained. By improving the adhesion between the layers, the thermal stability and durability of the photoelectric conversion element can be improved. When the temperature of the annealing treatment step is set to 300 ° C. or lower, the possibility that the organic compounds contained in the photoelectric conversion elements 100 and 200 are thermally decomposed is reduced. In the annealing treatment step, stepwise heating using different temperatures within the above temperature range may be performed.

The heating time is 1 minute or more in one embodiment and 3 minutes or more in another embodiment, while 180 minutes or less in one embodiment, in order to improve adhesion while suppressing thermal decomposition. It is less than 60 minutes. The annealing process can be terminated when the open circuit voltage, short circuit current and fill factor, which are the parameters of the solar cell performance, reach constant values. Further, the annealing treatment step can be carried out under normal pressure and in an atmosphere of an inert gas in order to prevent thermal oxidation of the constituent materials. As a heating method, a photoelectric conversion element may be placed on a heat source such as a hot plate, or the photoelectric conversion element may be placed in a heating atmosphere such as an oven. Further, the heating may be performed by a batch method or a continuous method.

[4. Photoelectric conversion characteristics]
The photoelectric conversion characteristics of the photoelectric conversion elements 100 and 200 can be obtained as follows. The photoelectric conversion elements 100 and 200 are irradiated with light under AM 1.5G conditions with a solar simulator at an irradiation intensity of 100 mW / cm ² , and the current-voltage characteristics are measured. From the obtained current-voltage curve, photoelectric conversion characteristics such as photoelectric conversion efficiency (PCE), short circuit current density (Jsc), open circuit voltage (Voc), fill factor (FF), series resistance, and shunt resistance can be obtained.

The photoelectric conversion efficiency of the photoelectric conversion elements 100 and 200 is not particularly limited, but is 1% or more in one embodiment, 1.5% or more in another embodiment, and 2% or more in another embodiment. On the other hand, there is no particular upper limit, and the higher the limit, the better. The fill factor of the photoelectric conversion element 100 is not particularly limited, but is 0.6 or more in one embodiment, 0.7 or more in another embodiment, and 0.9 or more in another embodiment. On the other hand, there is no particular upper limit, and the higher the limit, the better.

The photoelectric conversion element according to this embodiment has a feature of high durability. In one embodiment, the maintenance rate of photoelectric conversion efficiency after being left in a test environment at a temperature of 85 ° C. for one day is 60% or more, 80% or more in one embodiment, and 90% in another embodiment. That is, and in still another embodiment, it is 95% or more. For example, the maintenance rate can be obtained based on the initial photoelectric conversion efficiency immediately after the photoelectric conversion element is manufactured and the photoelectric conversion efficiency after the photoelectric conversion element is placed in the test environment. Further, the retention rate can be measured after sealing the photoelectric conversion element as described above. Here, the maintenance rate can be calculated as follows based on the photoelectric conversion efficiency before and after the test environment.
Maintenance rate (%) = ((photoelectric conversion efficiency after being placed in the test environment) / (photoelectric conversion efficiency before being placed in the test environment)) x 100

Further, the maintenance rate of the photoelectric conversion efficiency after being left in a test environment at a temperature of 85 ° C. for a long time (for example, 60 hours or more) is 40% or more, 60% or more in one embodiment, and another implementation. 80% or more in one embodiment, 90% or more in yet another embodiment, and 95% or more in yet another embodiment.

[5. Solar cell]
In one embodiment, the photoelectric conversion elements 100 and 200 according to the present invention are used as a solar cell element of a solar cell, particularly a thin film solar cell. FIG. 3 is a cross-sectional view schematically showing the configuration of a solar cell according to an embodiment of the present invention, and FIG. 3 shows a thin-film solar cell which is a solar cell according to an embodiment of the present invention. As shown in FIG. 3, the thin-film solar cell 14 according to the present embodiment includes a weather-resistant protective film 1, an ultraviolet cut film 2, a gas barrier film 3, a getter film 4, a sealing material 5, and a solar cell. The element 6, the sealing material 7, the getter material film 8, the gas barrier film 9, and the back sheet 10 are provided in this order. The thin-film solar cell 14 according to the present embodiment has a photoelectric conversion element according to the present invention as the solar cell element 6. Then, light is irradiated from the side where the weather resistant protective film 1 is formed (lower part in FIG. 3), and the solar cell element 6 generates electricity. The thin-film solar cell 14 does not have to have all of these constituent members, and the necessary constituent members can be arbitrarily selected.

There are no particular restrictions on these constituent members constituting the thin-film solar cell and the manufacturing method thereof, and well-known techniques can be used. For example, the techniques described in known documents such as International Publication No. 2013/171517, International Publication No. 2013/180230 or JP-A-2012-191194 can be used.

The use of the solar cell according to the present invention, particularly the above-mentioned thin-film solar cell 14, is not limited and can be used for any purpose. For example, the solar cell according to the embodiment includes a solar cell for building materials, a solar cell for automobiles, a solar cell for interiors, a solar cell for railways, a solar cell for ships, a solar cell for airplanes, a solar cell for spacecraft, and a solar cell for home appliances. It can be used as a battery, a solar cell for a mobile phone, or a solar cell for a toy.

The solar cell according to the present invention, particularly the thin-film solar cell 14 described above, may be used as it is, or may be used as a component of the solar cell module. For example, as shown in FIG. 4, a solar cell module 13 having the solar cell according to the present invention, particularly the above-mentioned thin-film solar cell 14 mounted on a base material 12, is manufactured, and the solar cell module 13 is installed at a place of use. Can be used. A well-known technique can be used as the base material 12, and for example, as the material of the base material 12, the materials described in International Publication No. 2013/171517, International Publication No. 2013/180230, JP-A-2012-191194, etc. Can be used. For example, when a plate material for building materials is used as the base material 12, by providing a thin-film solar cell 14 on the surface of the plate material, a solar cell panel for the outer wall of a building can be manufactured as a solar cell module 13.

Hereinafter, embodiments of the present invention will be described with reference to examples. However, the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded.

[Preparation of coating liquid]
(Preparation of coating liquid for electron transport layer)
A 7.5% tin oxide aqueous dispersion was prepared by adding ultrapure water to a tin (IV) oxide 15% aqueous dispersion (manufactured by Alfa Aesar).

(Preparation of coating liquid for active layer)
Lead iodide (II) was weighed into a vial and introduced into the glove box. N, N-dimethylformamide was added as a solvent so that the concentration of lead (II) iodide was 1.3 mol / L, and then heated and stirred at 100 ° C. for 1 hour to prepare a coating liquid 1 for an active layer. ..

Next, in another vial, formamamidin hydrobromide (FAI), methylamine hydrobromide (MABr), and methylamine hydrobromide (MACl) in a mass ratio of 10: 1: 1. Weighed so that it became, and introduced it into the glove box. By adding isopropyl alcohol as a solvent there, a coating liquid 2 for an active layer having a total concentration of FAI, MAbr, and MACl of 0.49 mol / L was prepared.

(Preparation of coating liquid for hole transport layer)
64 mg of poly [bis (4-phenyl) (2,4,6-trimethylphenyl) amine] (PTAA, manufactured by Sigma-Aldrich) and 7.2 mg of 4-isopropyl-4'-methyldiphenyliodonium tetrakis (pentafluoro). Phenyl) borate (TPFB, manufactured by TCI) was weighed into a vial and introduced into a glove box. 1.6 mL of ortodichlorobenzene was added thereto as a solvent. Next, the obtained mixed liquid was heated and stirred at 150 ° C. for 1 hour to prepare a coating liquid for a hole transport layer.

[Example 1]
A glass substrate (manufactured by Geomatec Co., Ltd.) provided with a patterned indium tin oxide (ITO) transparent conductive film was subjected to ultrasonic cleaning using ultrapure water, drying by nitrogen blowing, and UV-ozone treatment.

Next, the coating liquid for the electron transport layer prepared as described above was spin-coated on the substrate at room temperature at a speed of 2000 rpm to form an electron transport layer having a thickness of about 35 nm. Then, the substrate was heated on a hot plate at 150 ° C. for 10 minutes.

Next, the substrate was introduced into the glove box, 150 μL of the coating liquid 1 for the active layer heated to 100 ° C. was dropped onto the electron transport layer, and spin coating was performed at a speed of 2000 rpm. Next, the lead iodide layer was formed by heating and annealing the substrate on a hot plate at 100 ° C. for 10 minutes. Next, after the substrate has returned to room temperature, the active layer coating liquid 2 (120 μL) is spin-coated on the lead iodide layer at a speed of 2000 rpm and heated at 150 ° C. for 20 minutes to obtain an active layer of organic-inorganic perovskite. (Thickness 650 nm) was formed.

Next, after the substrate has returned to room temperature, the hole transport layer coating solution (200 μL) is spin-coated on the active layer at a speed of 1500 rpm, and further heated on a hot plate at 90 ° C. for 5 minutes to obtain holes. A transport layer (170 nm) was formed.

Next, silver having a thickness of about 100 nm was deposited on the hole transport layer by a resistance heating type vacuum vapor deposition method to form a metal layer. An IZO having a thickness of about 30 nm was formed on the metal layer by a sputtering method to form a metal oxide layer. Further, silver having a thickness of about 100 nm was deposited on the metal oxide layer by a resistance heating type vacuum vapor deposition method to form a metal layer, which was used as an upper electrode. As described above, the photoelectric conversion element was manufactured. An electrode having the same configuration as the upper electrode is formed on a glass substrate (corning 1737) having a thickness of 0.7 mm, and the visible light transmittance of the electrode is measured by a spectrophotometer (U-4100 manufactured by Hitachi High-Tech). As a result, the visible light transmittance of the electrode was 1% or less.

[Example 2]
A photoelectric conversion element was produced in the same manner as in Example 1 except that the upper electrode was a silver metal layer of about 3 nm, an IZO metal oxide layer of about 30 nm, and a silver metal layer of about 100 nm. An electrode having the same configuration as the upper electrode is formed on a glass substrate (corning 1737) having a thickness of 0.7 mm, and the visible light transmittance of the electrode is measured by a spectrophotometer (U-4100 manufactured by Hitachi High-Tech). As a result, the visible light transmittance of the electrode was 1% or less.
[Comparative Example 1]
A photoelectric conversion element was produced in the same manner as in Example 1 except that the upper electrode was a single layer of a silver metal layer having a diameter of about 100 nm. An electrode having the same configuration as the upper electrode is formed on a glass substrate (corning 1737) having a thickness of 0.7 mm, and the visible light transmittance of the electrode is measured by a spectrophotometer (U-4100 manufactured by Hitachi High-Tech). As a result, the visible light transmittance of the electrode was 1% or less.
[Comparative Example 2]
A photoelectric conversion element was produced in the same manner as in Example 1 except that the upper electrode was a single layer of a copper metal layer having a diameter of about 100 nm. As a result of measuring the visible light transmittance of the upper electrode with a spectrophotometer (U-4100 manufactured by Hitachi High-Tech), the visible light transmittance of the upper electrode was 0%.
[Comparative Example 3]
A photoelectric conversion element was produced in the same manner as in Example 1 except that the upper electrode was a single layer of a metal oxide layer of IZO having a diameter of about 30 nm. An electrode having the same configuration as the upper electrode is formed on a glass substrate (corning 1737) having a thickness of 0.7 mm, and the visible light transmittance of the electrode is measured by a spectrophotometer (U-4100 manufactured by Hitachi High-Tech). As a result, the visible light transmittance of the electrode was 80% or more.

[Evaluation of photoelectric conversion element]
A 1 mm square metal mask was attached to the photoelectric conversion elements obtained in Example 1, Example 2, and Comparative Examples 1 to 3, and the current-voltage characteristics between the ITO electrode and the upper electrode were measured. A source meter (2400 type manufactured by Keithley Co., Ltd.) was used for the measurement, and a solar simulator with an air mass (AM) of 1.5 G and an irradiance of 100 mW / cm ² was used as the irradiation light source. From this measurement result, the open circuit voltage Voc (V), the short circuit current density Jsc (mA / cm ² ), the shape factor FF, and the photoelectric conversion efficiency PCE (%) were calculated. Table 1 shows these values calculated based on the measurement results immediately after the photoelectric conversion element was manufactured.

Here, the open circuit voltage Voc is the voltage value when the current value = 0 (mA / cm ² ), and the short circuit current density Jsc is the current density when the voltage value = 0 (V). The scherrer FF is a factor representing the internal resistance, and is expressed by the following equation when the maximum output is Pmax.
FF = Pmax / (Voc × Jsc)
Further, the photoelectric conversion efficiency PCE is given by the following equation, where the incident energy is Pin.
PCE = (Pmax / Pin) x 100
= (Voc x Jsc x FF / Pin) x 100

Further, the obtained photoelectric conversion element is sealed by bonding the glass whose central portion is dug down and the glass substrate of the photoelectric conversion element with a sealing material (photocurable resin), and the temperature is 85 ° C. under sunlight. After a day (24 hours) and a long time (50 hours or more), the current-voltage characteristics are measured by the same method to calculate the photoelectric conversion efficiency PCE, and the photoelectric conversion efficiency before and after the test is used. The maintenance rate of the photoelectric conversion efficiency was calculated. Table 2 shows the maintenance rate of photoelectric conversion efficiency.

As shown in Table 1, the initial conversion efficiency did not show a large difference between Example 1, Example 2, Comparative Example 1 and Comparative Example 2. However, the initial photoelectric conversion efficiency PCE of Example 1 and Example 2 was higher than that of Comparative Example 3. The reason for this is that in the upper electrodes of Examples 1 and 2, the IZO layer was formed after the silver layer was formed on the active layer side, so that the lower layer (active layer, which was sputtered during the formation of the IZO layer). It is considered that the damage of the hole transport layer) is suppressed by the silver layer, and the initial photoelectric conversion efficiency PCE (output characteristic) of the photoelectric conversion element is improved.

Further, as shown in Table 2, the maintenance rates of the photoelectric conversion efficiencies of Examples 1 and 2 after 1 day and after a long time were higher than those of Comparative Example 1 and Comparative Example 2. The reason for this is that in the upper electrodes of Examples 1 and 2, since the IZO layer and the silver layer were laminated on the silver layer, the electrode sheet resistance due to the reaction between the iodide diffused from the active layer and the silver layer. It is considered that the increase in the above amount was suppressed by at least one of the IZO layer and the silver layer, and the maintenance rate (durability) of the photoelectric conversion efficiency was improved.

From the above results, by configuring the upper electrode so that the metal layer or the metal alloy layer is located between the active layer and the metal oxide layer, the photoelectric conversion element has an initial high photoelectric conversion efficiency (output characteristic). And it can be seen that it has a high maintenance rate (durability) of photoelectric conversion efficiency.

1 Weather-resistant protective film 2 Ultraviolet cut film 3, 9 Gas barrier film 4, 8 Getter film 5, 7 Encapsulant 6 Solar cell element 10 Back sheet 12 Base material 13 Solar cell module 14 Thin-film solar cell 100, 200 Photoelectric conversion element 101,201 Lower electrode 102,202 Electron transport layer 103,203 Active layer 104,204 Hole transport layer 105,205 Upper electrode 105a, 205a Metal layer other than gold or metal alloy layer 105b, 205b Metal oxide layer 205c Metal layer Or metal alloy layer 106, 206 base material

Claims (6)

A photoelectric conversion element having a pair of electrodes and an active layer located between them.
The active layer has a halide-based organic-inorganic perovskite semiconductor compound.
One of the pair of electrodes has a metal layer or a metal alloy layer and a metal oxide layer.
The metal layer or the metal alloy layer is located between the active layer and the metal oxide layer .
One electrode further comprises another metal layer or metal alloy layer, wherein the metal oxide layer is located between the metal layer or the metal alloy layer and the other metal layer or the metal alloy layer . A photoelectric conversion element characterized by this. The photoelectric conversion element according to claim 1 , wherein one of the electrodes is a non-transparent electrode. The photoelectric conversion element according to claim 1 or 2 , wherein the metal layer or the metal alloy layer contains silver or copper. The photoelectric conversion element according to any one of claims 1 to 3 , wherein the active layer contains an iodine atom. The photoelectric conversion element according to any one of claims 1 to 4 , wherein the photoelectric conversion element has an electron transport layer and a hole transport layer. A solar cell module having the photoelectric conversion element according to any one of claims 1 to 5 .

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