JP2020126965A - Electrolyte, solar cell, solar cell module, and manufacturing method of solar cell - Google Patents

Abstract

To further enhance the durability of a solar cell including a copper complex.SOLUTION: An electrolyte is used by being interposed between a photoelectrode having a light absorbing layer and a counter electrode arranged so as to face the photoelectrode of a solar cell having the photoelectrode and the counter electrode. The electrolyte includes a copper complex having an organic ligand and copper having a plurality of valences, and includes an organic solvent having a boiling point of 200°C or higher, a relative dielectric constant εr of 30 or more and 100 or less, and a viscosity η at 25°C of 0.5 mPa s or more and 10 mPa s or less, and a solvent containing at least one of ionic liquids having a viscosity η at 25°C of 300 mPa s or less.SELECTED DRAWING: Figure 2

Description

Disclosed herein are an electrolyte, a solar cell, a solar cell module, and a method for manufacturing a solar cell.

Conventionally, as a solar cell, a dye-sensitized solar cell using a copper complex as a redox couple has been proposed (see, for example, Patent Document 1). This solar cell is said to have good photoelectric conversion characteristics without corroding the platinum counter electrode by containing the monovalent and divalent copper complexes. As a solar cell, a copper complex of copper(I) bis(2,9-dimethyl-1,10-phenanthroline) or copper(II) bis(2,9-dimethyl-1,10-phenanthroline) is used as a solid electrolyte. A dye-sensitized solar cell used as the above has been proposed (for example, see Non-Patent Document 1). It is said that this solar cell can improve power generation efficiency.

JP, 2006-302849, A

Energy Environ. Sci. , 2015, 8, 2634-2637

By the way, in a solar cell using a copper complex as a solid electrolyte, such as the above-mentioned Patent Document 1, after pouring an electrolytic solution containing a copper complex and a solvent into a porous TiO ₂ electrode adsorbing a dye, the solvent is removed. May be filled with electrolyte. However, the solar cell manufactured in this way has a problem of durability that the characteristics of the solar cell deteriorate with the passage of time. In a solar cell provided with an electrolyte containing a copper complex, it has been required to further enhance the durability of the solar cell.

The present disclosure has been made in view of such problems, and provides an electrolyte, a solar cell, a solar cell module, and a method for manufacturing a solar cell, which include a copper complex and can further enhance the durability of the solar cell. The main purpose is to do.

As a result of intensive research to achieve the above-mentioned object, the present inventors have found that when the solvent of the electrolyte is less likely to volatilize, the power density is further improved and the durability at high temperature is further improved. The inventors have found that the characteristics can be further improved, and have completed the present disclosure.

That is, the electrolyte disclosed herein is
A photoelectrode having a light absorption layer, and an electrolyte used by being interposed between the photoelectrode and the counter electrode of a solar cell having a counter electrode arranged so as to face the photoelectrode,
It contains a copper complex having an organic ligand and a plurality of valences of copper, has a boiling point of 200° C. or higher, a relative dielectric constant εr of 30 or more and 100 or less, and a viscosity η at 25° C. of 0.5 mPa. An organic solvent in the range of s or more and 10 mPa·s or less and a solvent containing at least one of the ionic liquids having a viscosity η at 25° C. of 300 mPa·s or less.

The solar cell disclosed herein is
A photoelectrode having a light absorption layer,
A counter electrode arranged to face the photoelectrode,
The above-mentioned electrolyte interposed between the photoelectrode and the counter electrode,
It is equipped with.

The solar cell module disclosed in this specification includes a plurality of solar cells described above.

The method for manufacturing a solar cell disclosed in the present specification,
A method of manufacturing a solar cell comprising a photoelectrode having a light absorbing layer, and a counter electrode arranged so as to face the photoelectrode,
It contains a copper complex having an organic ligand and a plurality of valences of copper, has a boiling point of 200° C. or higher, a relative dielectric constant εr of 30 or more and 100 or less, and a viscosity η at 25° C. of 0.5 mPa. An electrolyte containing a solvent containing at least one of an organic solvent in the range of s or more and 10 mPa·s or less and an ionic liquid having a viscosity η at 25° C. of 300 mPa·s or less is applied or discharged onto the photoelectrode. And a forming step of forming an electrolyte.

The electrolyte, the solar cell, the solar cell module, and the method for manufacturing the solar cell, which include the copper complex, can further enhance the solar cell characteristics. The reason why such an effect is obtained is presumed as follows. For example, in a solar cell using a copper complex as a solid electrolyte, as described above, the solvent may be removed after the solvent is added and the electrolyte is filled. However, in order to obtain high power generation characteristics, the copper complex is solvated. It was found from the above that it is desirable to be in a state capable of molecular movement (amorphous state). Further, although the solvent is removed at the time of filling the electrolyte, the remaining solvent shows relatively high solar cell characteristics at the initial stage, while the solvent decreases with the elapse of time, whereby the crystallization of the copper complex proceeds. It is estimated that the output will drop significantly. On the other hand, in the present disclosure, a high power density in the initial characteristics can be secured by adding an organic solvent and/or an ionic liquid having a boiling point, a relative dielectric constant, a viscosity, etc. within a predetermined range, and It is presumed that the solar cell characteristics can be further improved, for example, the durability, particularly the high temperature durability when left at a high temperature in the dark at 60° C. can be obtained.

Sectional drawing which shows an example of a schematic structure of the solar cell module 10. FIG. Sectional drawing which shows an example of a schematic structure of the solar cell 40. Measurement results of the measurement time after injection of the electrolytic solution and Jsc of the open cell. The measurement result of the electrolyte composition of the evaluation cell of Experimental example 1, 2. Solar cell characteristics of the evaluation cells of Experimental Examples 2-5 and 2-6. The measurement result of the electrolyte composition of the evaluation cell of Experimental example 2-4-2-6. The NMR measurement result of the electrolyte composition of the evaluation cell of Experimental example 2-4-2-6. The measurement result of the output density of Experimental Examples 3 and 4 when left in a high temperature dark place. The measurement result of the output retention rate (%) at the time of leaving it in the high temperature dark place of Experimental Examples 3 and 4. Initial power density of Experimental Examples 5-14. Output maintenance rate after leaving 60 degreeC dark place of Experimental Examples 5-13.

(Electrolytes)
The electrolyte of the present disclosure is used by being interposed between a photoelectrode and a counter electrode of a solar cell including a photoelectrode having a light absorption layer and a counter electrode arranged so as to face the photoelectrode. This electrolyte contains a copper complex having an organic ligand and copper having a plurality of valences, a boiling point of 200° C. or higher, a relative dielectric constant εr of 30 or more and 100 or less, and a viscosity η at 25° C. Of 0.5 mPa·s or more and 10 mPa·s or less, and a solvent containing at least one of an ionic liquid having a viscosity η at 25° C. of 300 mPa·s or less. Since the position of the valence band of the copper complex is considerably deeper than that of a conventional inorganic p-type semiconductor (for example, CuI), the conduction band lower end CBM of titanium oxide, which is the n-type semiconductor layer, and the valence end upper end VBM of the electrolyte, are formed. There is an advantage that the theoretical open circuit voltage (Voc) determined by the difference between the two becomes high. Here, the presence of the solvent reliably improves the solar cell characteristics using the copper complex.

The copper complex has, for example, an organic ligand, and copper has a valence change. Examples of the organic ligand include phenanthroline-based ligands, bipyridylalkyl-based ligands, bipyridine-based ligands, sparteine-based ligands, bisbenzimidazolylthiomethylpyridine-based ligands, and bisbenzimidazole ligands. One or more of a ruthiomethylmethylamine-based ligand, a bisbenzimidazolylylpyridine-based ligand, and a bisethylthiomethylpyridine-based ligand are preferable. The phenanthroline-based ligand includes a phenanthroline structure and its derivative. The bipyridylalkyl-based ligand has a structure in which a pyridyl group is bonded to the end of an alkyl chain, and includes a bipyridylethane structure and its derivative. The bipyridine-based ligand includes a bipyridine structure and its derivative. The sparteine-based ligand includes a sparteine structure or a derivative. The bisbenzimidazolylthiomethylpyridine-based ligand includes a benzimidazolylylthiomethylpyridine structure or a derivative thereof. The bisbenzimidazolylthiomethylmethylamine-based ligand includes a benzimidazolylthiomethylmethylamine structure and its derivative, and the bisbenzimidazolylylpyridine-based ligand includes a benzimidazolylylpyridine structure and its derivative. The bisethylthiomethylpyridine-based ligand includes an ethylthiomethylpyridine structure and its derivative.

This copper complex may have a structure of any one or more of the chemical formulas (1) to (4). The organic ligand may have, for example, a heterocyclic structure having 1 or 2 or more nitrogen atoms. Examples of the organic ligand include 2,9-dimethyl-1,10-phenanthroline (dmp, chemical formula (1)) and 1,1-bis(2-pyridyl)ethane (bpye, chemical formula (2)). , 4,4',6,6'-tetramethyl-2,2'-bipyridine (tmby, chemical formula (3)), 6,6'-dimethyl-2,2'-bipyridine (dmby, chemical formula (4)) And so on. Examples of the organic ligand include 1,10-phenanthroline (phen, chemical formula (5)), [(−)-sparteine-N,N′] (SP, chemical formula (6)), 2, 6-bis(benzimidazol-2'-ylthiomethyl)pyridine (bbtmp, chemical formula (7)), N,N-bis(benzimidazol-2'-ylthiomethyl)methylamine (bbtma, chemical formula (8)), 2,6 -Bis(benzimidazol-2'-yl)pyridine (bzmpy, chemical formula (9)), 2,6-bis(ethylthiomethyl)pyridine (betmp, chemical formula (10)) and the like can be mentioned. Further, the copper complex may have one or more other ligands, for example, monodentate ligands (monovalent anion ligands). When there are a plurality of ligands, they may be the same ligand or different ligands. Of these, it is more preferable that all of these ligands are the same. This ligand may be, for example, one or more selected from -F, -Cl, -Br, -I, -OH, -CN, -SCN, -NCS. Among these, -SCN and -NCS are preferable, and -NCS is more preferable. The copper complex may be composed of a cation having an organic ligand and containing copper, and an anion. Examples of the anion include trifluoromethylsulfonic acid (CF ₃ SO ₃ ), bis(trifluoromethylsulfonyl)imide (TFSI), bis(fluorosulfonyl)imide (FSI), and hexafluorophosphoric acid (PF ₆ ). Can be mentioned.

Specific examples of such a copper complex include, for example, copper(I) bis(2,9-dimethyl-1,10-phenanthroline)bis(trifluoromethylsulfonyl)imide (Cu(dmp) ₂ TFSI), copper( II) bis(2,9-dimethyl-1,10-phenanthroline)bis[bis(trifluoromethylsulfonyl)imide](Cu(dmp) ₂ (TFSI) ₂ ), copper(I)bis(1,10-phenanthroline) ) Bis(trifluoromethylsulfonyl)imide (Cu(phen) ₂ TFSI), copper(II) bis(1,10-phenanthroline)bis[bis(trifluoromethylsulfonyl)imide](Cu(phen) ₂ (TFSI) ₂ ), [(−)-sparteine-N,N′](maleonitriledithiolato-S,S′) copper ([Cu(SP)(mmt)]), 2,6-bis(benzimidazole-2) Examples include'-ylthiomethyl)pyridine nitrate ([Cu(bbtmp)(NO ₃ )]NO ₃ ).

The electrolyte preferably contains two or more kinds of copper complexes having different organic ligand structures. When two or more copper complexes are contained, the copper complex is less likely to crystallize and the amorphous state is easily maintained. Therefore, it is possible to further suppress deterioration of solar cell characteristics that may occur due to crystallization of the copper complex. The structure of the organic ligand may be, for example, a derivative having the same basic structure and different substituents, or different basic structures, but different basic structures are more preferable. When the basic structure is different, alignment of the copper complex, that is, crystallization is likely to be structurally hindered, which makes it easier to maintain an amorphous state, which is more preferable. For example, as an organic ligand having the same basic structure, a combination of a phenanthroline-based ligand and its derivative, a combination of a bipyridylalkyl-based ligand and its derivative, a combination of a bipyridine-based ligand and its derivative, etc. Is mentioned. Organic ligands having different basic structures include phenanthroline-based ligands and bipyridylalkyl-based ligands, phenanthroline-based ligands and bipyridine-based ligands, and bipyridylalkyl-based ligands and bipyridine-based ligands. A combination with a system ligand and the like can be mentioned. Specific examples of such an electrolyte include bis(2,9-dimethyl-1,10-phenanthroline) copper complex and bis(4,4′,6,6′-tetramethyl-2,2′-bipyridine. ) A combination of two kinds of copper complexes and the like are preferable. The compounding ratio of the copper complex is, for example, the number of moles M1 of the first copper complex and the number of moles Ma of the entire copper complex when at least a first copper complex and a second copper complex having different organic ligands are included. The ratio M1/Ma×100 (mol%) is preferably in the range of 30 mol% or more and 70 mol% or less, more preferably in the range of 33 mol% or more and 67 mol% or less, and in the range of 40 mol% or more and 60 mol% or less. It may be present. Also, the range similar to the above is preferable when only two kinds of copper complexes are contained. Further, the copper complex may have a molar ratio X(Cu ^II /(Cu ^I +Cu ^II ) of divalent copper to the entire copper (monovalent+divalent) within the range of 0≦X<0.2. The presence of the divalent copper complex in the molar ratio X is preferably smaller.

This electrolyte has an organic solvent having a boiling point of 200° C. or higher, a relative dielectric constant εr of 30 or more and 100 or less, and a viscosity η at 25° C. of 0.5 mPa·s or more and 10 mPa·s or less (hereinafter, And a solvent containing at least one of an ionic liquid). From the viewpoint of volatility, the organic solvent preferably has a higher boiling point, for example, 220° C. or higher, preferably 240° C. or higher, and more preferably 260° C. or higher. The boiling point of the organic solvent may be, for example, 400° C. or lower. This organic solvent preferably has a relative permittivity εr of 35 or more, more preferably 40 or more, and may be 50 or more. The organic solvent may have a relative permittivity εr of 90 or less, or 80 or less. The organic solvent preferably has a lower viscosity, has a viscosity at 25° C. of 8 mPa·s or less, more preferably 6 mPa·s or less, and may be 5 mPa·s or less. Further, the organic solvent may have a viscosity at 25° C. of 0.5 mPa·s or more, or 1 mPa·s or more.

Organic solvents include carbonates containing ethylene carbonate, propylene carbonate and butylene carbonate, cyclic esters containing γ-butyl lactone and γ-valerolactone, nitriles containing adiponitrile, pyrrolidones containing N-methylpyrrolidone, 3-methyl. One or more of oxazolidones including 2-oxazolidone and dinitriles including glutaronitrile may be used. Among these, oxazolidones and dinitriles are more preferable, and 3-methyl-2-oxazolidone and glutaronitrile are more preferable from the viewpoint of boiling point, viscosity, relative dielectric constant and the like.

The solvent may include an ionic liquid having a viscosity η at 25° C. of 300 mPa·s or less (hereinafter, simply referred to as an ionic liquid). The viscosity of this ionic liquid is preferably lower, and the viscosity at 25° C. is preferably 250 mPa·s or less, more preferably 160 mPa·s or less, and further preferably 100 mPa·s or less. Further, the ionic liquid may have a viscosity at 25° C. of 10 mPa·s or more, or 20 mPa·s or more. The ionic liquid preferably has a relative permittivity εr of 5 or more and 30 or less, and may be 8 or more and 20 or less. The ionic liquid preferably has a lower melting point, more preferably 20° C. or lower, more preferably 15° C. or lower, still more preferably 10° C. or lower.

This ionic liquid may contain one or more cations such as imidazolium cations, pyridinium cations, alicyclic amine cations and aliphatic amine cations, sulfonium ions and phosphonium ions. The imidazolium cation includes an imidazolium structure and its derivative. The pyridinium cation includes a pyridinium structure and its derivative. The alicyclic amine-based cation includes an alicyclic amine structure and its derivative. The aliphatic amine cation includes an aliphatic amine structure and its derivative. This ionic liquid preferably contains one or more cations of chemical formulas (11) to (17). However, in the chemical formula, R and R ^{1 to} R ⁴ may be the same group or different groups, and are either a chain hydrocarbon group having 1 to 6 carbon atoms or H. The chain hydrocarbon group may have an ether bond or may have one or more substituents. The substituent may include, for example, an alkyl group having 3 or less carbon atoms, halogen, or the like. Examples of the imidazolium cation include the cation represented by the chemical formula (11). Examples of the pyridinium cation include cations represented by the chemical formula (12). Examples of the alicyclic amine cation include cations represented by chemical formulas (13) and (14). Examples of the aliphatic amine cation include cations represented by the chemical formula (15). Examples of the sulfonium ion include the cation represented by the chemical formula (16). Examples of the phosphonium ion include the cation represented by the chemical formula (17). Further, this ionic liquid contains Br ⁻ , Cl ⁻ , SCN ⁻ , HSO ₄ ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , CF ₃ SO ₃ ⁻ , CF ₃ CO ₂ ⁻ , (C ₂ F ₅ ) ₃ PF ₃ ^−. , (CF ₃ SO ₂ ) ₂ N ⁻ and (FSO ₂ ) ₂ N ⁻ may contain one or more anions. Specific examples of such an ionic liquid include one or more of the ionic liquids represented by the chemical formulas (18) to (38). Of these, 1-ethyl-3-methylimidazolium tetracyanoborate (EMITCB) and the like are preferable.

By including an organic solvent and/or an ionic liquid, this electrolyte can further suppress the crystallization of the copper complex. More preferably, this solvent contains a high boiling point organic solvent and an ionic liquid. When these two types are included, the volatility (boiling point), the viscosity, the relative dielectric constant, and the like can be set in more preferable ranges. This solvent preferably has a ratio Mi/Ms×100 (mol %) of the number of moles Mi of the ionic liquid to the number of moles Ms of the organic solvent in the range of 10 mol% to 50 mol %. Within this range, the volatility, viscosity, relative dielectric constant, etc. can be made more suitable. This mol ratio is preferably 15 mol% or more, more preferably 20 mol% or more, and may be 30 mol% or more. Further, this molar ratio is preferably 45 mol% or less, more preferably 40 mol% or less, and may be 35 mol% or less.

Further, this electrolyte preferably further contains an additive. Examples of the additive include a heterocyclic compound having one or more nitrogen atoms and two or more rings, and one or more cyclic compounds among monocyclic heterocyclic compounds having two or more nitrogen atoms. The cyclic compound may have one or more of an imidazole structure, a pyridine structure, a pyrimidine structure, an oxazole structure and a thiazole structure. This cyclic compound preferably has basicity, and preferably has an imidazole structure. In addition, the cyclic compound may have a substituent, a hetero atom, a hydrogen group, an alkyl group substituted with a hydrogen group, or the like in its structure. The alkyl group preferably has 1 to 6 carbon atoms. Specifically, the cyclic compound may be any one of the chemical formulas (39) to (46). In this formula, R may be hydrogen (H) and an alkyl group having 1 to 6 carbon atoms. The alkyl group may be linear or may have a branched chain. Chemical formulas (39) to (43) are heterocyclic compounds containing one or more nitrogens and two or more rings. The chemical formula (39) is benzimidazole and its derivatives, and examples thereof include N-methylbenzimidazole and N-butylbenzimidazole. The chemical formula (40) is a pyrimidine base, for example, 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine or 1,3,4,6,7, 8-hexahydro-1-methyl-2H-pyrimido[1,2a]pyrimidine and the like can be mentioned. The chemical formula (41) is quinoline, and may be a derivative thereof. The chemical formula (42) is benzoxazole and may be a derivative thereof. The chemical formula (43) is benzothiazole and may be a derivative thereof. Chemical formulas (44) to (46) are monocyclic heterocyclic compounds having two or more nitrogen atoms. Formula (44) is imidazole and its derivatives. Chemical formula (45) is pyrazole and its derivatives. Formula (46) is imidazoline and its derivatives. This cyclic compound is preferably contained in the electrolytic solution in a molar ratio X, which is the ratio of the number of moles of the cyclic compound to the number of moles of the copper complex, in the range of 0.4≦X≦4. Within this range, the effect of adding the cyclic compound can be sufficiently exhibited, which is preferable. The molar ratio X may be 0.8 or more, or 1.0 or more. Alternatively, the molar ratio Y may be 3.0 or less, or 2.0 or less. As the additive, for example, as to increase the electron injection efficiency to improve the short-circuit current density Jsc of lowering the conduction band of the photoelectrode material (CBM) from the dye to the TiO _2, such as TiO _2, LiTFSI, LiI etc. are mentioned. These may be used alone or in combination of two or more.

(Solar cell)
The solar cell of the present disclosure includes a photoelectrode having a light absorption layer, a counter electrode arranged to face the photoelectrode, and any one of the above-mentioned electrolytes interposed between the photoelectrode and the counter electrode. Is. The photoelectrode may include an n-type semiconductor layer (electron transport layer) covered with a light absorption layer on a light transmissive conductive substrate. FIG. 1 is a cross-sectional view showing an example of a schematic configuration of the solar cell module 10. As shown in FIG. 1, the solar cell module 10 has a configuration in which a plurality of solar cells 40 (hereinafter also referred to as cells) are sequentially arranged on a light-transmissive conductive substrate 14. These cells are connected in series. In this solar cell module 10, the sealing material 32 is formed so as to fill the spaces between the cells, and the flat protective member 34 is formed on the surface of the sealing material 32 on the side opposite to the light transmissive conductive substrate 14. Has been done. The solar cell 40 includes a photoelectrode 20 provided with an electron transport layer 24 including a light absorption layer and an n-type semiconductor layer on the light transmissive conductive substrate 14 via the underlayer 22, and is arranged so as to face the photoelectrode 20. The counter electrode 30, the electrolyte layer 26 interposed between the photoelectrode 20 and the counter electrode 30, and the separator 29 are provided. The photoelectrode 20 includes a light-transmitting conductive substrate 14 in which a light-transmitting conductive film 12 through which light is transmitted is formed on the surface of a light-transmitting substrate 11 through which light is transmitted, and an electron transport layer formed on the light-transmitting conductive film 12. 24 is provided. The electron transport layer 24 is a layer that is disposed on the light-transmitting conductive film 12 that is separately formed on the surface of the light-transmitting substrate 11 opposite to the light-receiving surface 13, and emits electrons as light is received. In the solar cell 40, the electron transport layer 24 is provided with a light absorbing material that absorbs light.

The light-transmissive conductive substrate 14 is composed of the light-transmissive substrate 11 and the light-transmissive conductive film 12, and is light-transmissive and conductive. Specific examples thereof include fluorine-doped SnO ₂ coated glass, ITO coated glass, ZnO:Al coated glass, antimony-doped tin oxide (SnO ₂ —Sb) coated glass, and the like. Further, a light-transmitting electrode in which tin oxide or indium oxide is doped with cations or anions having different valences, or a metal electrode having a structure capable of transmitting light such as a mesh shape or a stripe shape is provided on a substrate such as a glass substrate. Can also be used. Current collecting electrodes 16 and 17 are provided at both ends of the light transmitting conductive substrate 14 on the light transmitting conductive film 12 side, and the electric power generated by the solar cell 40 is used via the current collecting electrodes 16 and 17. can do.

Examples of the light transmitting substrate 11 include transparent glass, transparent plastic plates, transparent plastic films, and inorganic transparent crystal bodies, and among these, transparent glass is preferable. The light transmitting substrate 11 may be a transparent glass substrate, a substrate on which the surface of the glass substrate is appropriately roughened to prevent light reflection, or a frosted glass-like semitransparent glass substrate which transmits light. The light-transmitting conductive film 12 can be formed, for example, by depositing tin oxide on the light-transmitting substrate 11. In particular, if a metal oxide such as tin oxide (FTO) doped with fluorine is used, the suitable light-transmitting conductive film 12 can be formed. Grooves 18 are formed in the light-transmissive conductive film 12 at predetermined intervals, and a plurality of regions of the light-transmissive conductive film 12 are separately formed at intervals corresponding to the width of the groove 18.

The underlayer 22 is a layer that suppresses or prevents a leak current (reverse electron transfer) from the light-transmissive conductive substrate 14 to the electrolyte layer 26. For example, a material having a light-transmitting property and a conductivity is preferable, and for example, an oxide is used. Examples thereof include n-type semiconductors such as titanium, zinc oxide, and tin oxide, of which titanium oxide is more preferable. This is because titanium oxide suppresses/prevents leakage current and makes it easy for electrons to flow from the electron transport layer 24 to the light transmissive conductive substrate 14. The base layer 22 is preferably made of a denser material than the electron transport layer 24. Even if the underlying layer 22 is not formed, the underlying layer 22 may be omitted because the solar cell 40 sufficiently functions.

The electron transport layer 24 is formed of a light absorbing material and a porous n-type semiconductor layer containing the light absorbing material. Suitable n-type semiconductors are metal oxide semiconductors and metal sulfide semiconductors, such as titanium oxide (TiO ₂ ), tin oxide (SnO ₂ ), zinc oxide (ZnO), cadmium sulfide (CdS), and sulfide. At least one of zinc (ZnS) is preferable, and porous titanium oxide is more preferable. An excellent porous n-type semiconductor layer can be formed by thinning these semiconductor materials into a microcrystalline or polycrystalline state to form a thin film. In particular, the porous titanium oxide layer is suitable as the n-type semiconductor layer of the photoelectrode 20. As titanium oxide, anatase-type TiO ₂ is preferable to rutile-type TiO ₂ because it has a higher energy level at the lower end of the conduction band and a higher open-circuit voltage.

The light absorbing layer may include one or more light absorbing materials selected from organic dyes, metal complexes, and organic metal halide compounds. The light absorbing material may be an organic dye. Examples of organic dyes include BODIPY dyes (BODIPY-FL, etc.), indoline dyes (D131, D149, D205, D358, etc.), carbazole dyes (MK2, etc.), coumarin dyes (C343, NKX-2587, NKX-). 2677 and the like) and squarylium dyes (SQ2 and the like) and the like. The organic dye may have an aromatic amine as a donor and a cyanocarboxylic acid anchor group through a π-conjugated molecule. Examples of such a dye include, for example, 3-[6-[4-[bis(2',4'-dibutyloxybiphenyl-4yl)amino-]phenyl]-4,4-dihexyl-cyclopenta-[2,1 Examples include -b;3,4-b']dithiophene-2-yl]-2-cyanoacylic acid dye (chemical formula (A)), and it is preferable to use this dye. Further, the light absorbing material may be a metal complex. Examples of the metal contained in the metal complex include Zn, Cu, Fe, Pd, Pt, Ni, Co and Ru. Among these, Ru complexes (Ruthenizer470 (Ru470), N719, Z907, etc.), metalloporphyrin dyes (PtTPTBP, PdTPTBP, DTBC, etc.), metal phthalocyanine dyes (CuPc, ZnPc, etc.) and metal naphthalocyanine dyes (CuNc, ZnNc). Etc.) and the like. These light absorbing materials may be used alone or in combination. Among these, Ru complex compounds (Z907, N719), Zn porphyrin compounds (DTBC), carbazole dyes (MK2), and indoline double rhodanin compounds (D149 and D358) are preferable as the dyes. Examples of the organic metal halide compound used as the light absorbing material include perovskite crystals such as CH ₃ NH ₃ PbI ₃ . The structural formulas of the exemplified compounds are shown in the following chemical formulas. Although not shown in the following chemical formula, PdTPTBP is Pt of PtTPTBP changed to Pd, ZnPc is Cu of CuPc changed to Zn, and ZnNc is changed of Cu of CuNc to Zn.

The electrolyte layer 26 is formed adjacent to the photoelectrode 20. This electrolyte layer 26 contains any of the above-mentioned electrolytes. The structure of the solar cell module 10 can be adopted when the electrolyte layer 26 contains a solid.

The separator 29 is formed in an I-shaped cross section so as to be adjacent to one side surface of the photoelectrode 20 and the electrolyte layer 26 on which the underlayer 22, the electron transport layer 24 are laminated. One end of the separator 29 is in contact with the groove 18 on the light transmissive conductive substrate 14. As a result, direct contact between the photoelectrode 20 and the counter electrode 30 is avoided. The separator 29 is made of an insulating material and may be made of, for example, glass beads, silicon dioxide (silica), rutile type titanium oxide, or the like. The separator 29 is preferably an insulator obtained by sintering silica particles. Silica particles are preferable for the separator because they have a low refractive index, a small light scattering, and good transparency. From the viewpoint of ensuring good transparency, the separator 29 preferably has an average particle size of 5 to 200 nm. Further, the separator may be air or an air layer.

The counter electrode 30 is formed in an L-shaped cross section so as to contact the outer surface of the separator 29 and the back surface 27 of the electrolyte layer 26. The counter electrode 30 has one end connected to the back surface 27 of the electrolyte layer 26 and the other end connected to the adjacent light-transmissive conductive film 12 via the connection portion 21. The surface of the counter electrode 30 in contact with the back surface 27 faces the photoelectrode 20 with a predetermined space. The counter electrode 30 is not particularly limited as long as it has conductivity and a bondability with the electrolyte layer 26, and examples thereof include Pt, Au, and carbon, and among these, carbon is preferable.

The sealing material 32 can be used without particular limitation as long as it is an insulating member. As the sealing material 32, for example, a thermoplastic resin film such as polyethylene or an epoxy adhesive can be used.

The protection member 34 is a member for protecting the solar cell 40, and may be, for example, a moisture-proof film or protective glass.

When the solar cell 40 is irradiated with light from the light-receiving surface 13 side of the light-transmitting substrate 11, the light is transmitted to the electron-transporting layer 24 via the light-receiving surface 15 of the light-transmitting conductive film 12 and the light-receiving surface 23 of the underlayer 22. After reaching, the light absorbing material absorbs light and electrons are generated. The generated electrons move from the photoelectrode 20 to the adjacent counter electrode 30 via the light transmissive conductive film 12 and the connection portion 21. In the solar cell 40, electromotive force is generated by the movement of the electrons, and the power generation action of the cell is obtained. In this solar cell module 10, the electrolyte layer 26 contains a copper complex having an organic ligand and a plurality of valences of copper, and has a boiling point of 200° C. or higher and a relative dielectric constant εr of 30 or more and 100 or less. A solvent containing at least one of an organic solvent having a viscosity η at 25° C. of 0.5 mPa·s or more and 10 mPa·s or less and an ionic liquid having a viscosity η at 25° C. of 300 mPa·s or less. Including.

The solar cell module 10 can be manufactured through a substrate manufacturing step, an electron transport layer forming step, an electrolyte layer forming step, a separator forming step, a counter electrode forming step, and a protective member forming step as a manufacturing method. In the substrate manufacturing process, the light transmitting conductive film 12 is formed on the light transmitting substrate 11 while forming the groove 18 between the plurality of light transmitting conductive films 12. In the electron transport layer forming step, an n-type semiconductor layer is formed on the light transmissive conductive film 12 with the underlayer 22 interposed therebetween, a light absorber is formed on the n-type semiconductor layer, and the electron transport layer 24 is formed. Porous titanium oxide may be used as the n-type semiconductor layer.

Next, in the electrolyte layer forming step, the electrolyte described above is supplied to the back surface 25 of the electron transport layer 24 to form the electrolyte layer 26. In this step, a copper complex containing an organic ligand and having a plurality of valences is contained, the boiling point is 200° C. or higher, the relative dielectric constant εr is in the range of 30 to 100, and the viscosity η at 25° C. Is applied in the range of 0.5 mPa·s or more and 10 mPa·s or less and an electrolyte containing a solvent containing at least one of an ionic liquid having a viscosity η at 25° C. of 300 mPa·s or less, An electrolyte is formed on the photoelectrode. As the copper complex, the organic solvent having a high boiling point, the type of the ionic liquid, the content thereof, and the compounding ratio, any of those described in the above electrolyte can be appropriately used. In this electrolyte layer forming step, an electrolyte containing a solvent containing an organic solvent excluding carbonates including ethylene carbonate, propylene carbonate and butylene carbonate may be formed on the photoelectrode in the atmosphere. When this organic solvent is used, for example, alteration due to water present in the atmosphere can be suppressed, and an electrolyte layer can be produced in the atmosphere. On the other hand, in this electrolyte layer forming step, an electrolyte containing a solvent containing an organic solvent such as a carbonate may be formed on the photoelectrode in an inert atmosphere. Even when a carbonate is used, it may be produced in an inert atmosphere so as not to be affected by water. Further, in this step, in addition to the above organic solvent and ionic liquid, a low boiling organic solvent having a boiling point of less than 200° C. may be included, and the low boiling organic solvent may be dried and removed. With this, the viscosity of the electrolyte solution can be easily adjusted, and the electrolyte layer can be easily formed on the photoelectrode. Examples of the low boiling point organic solvent include acetonitrile, acetone, and alcohol.

Subsequently, in the separator forming step, the separator 29 is formed on the side surface of the photoelectrode 20 so as to be aligned with the groove 18. In the counter electrode forming step, the counter electrode 30 is formed so as to be in contact with the separator 29 and the electrolyte layer 26. The counter electrode 30 may be carbon, for example. In the protective member forming step, the sealing material 32 is formed so as to cover each cell, and the protective member 34 is formed on the sealing material 32. In this way, the solar cell 40 and the solar cell module 10 having improved power generation characteristics can be manufactured.

The solar cell of the present disclosure described above includes a copper complex having an organic ligand and a plurality of valences of copper, having a boiling point of 200° C. or higher and a relative dielectric constant εr of 30 or more and 100 or less. An electrolyte containing an organic solvent having a viscosity η at 25° C. of 0.5 mPa·s or more and 10 mPa·s or less and a solvent containing at least one of an ionic liquid having a viscosity η at 25° C. of 300 mPa·s or less Equipped with. Therefore, in the present disclosure, the characteristics of the solar cell including the copper complex can be further improved. The reason why such an effect is obtained is presumed as follows. For example, in a solar cell using a copper complex as a solid electrolyte, the solvent may be removed and the electrolyte may be filled. However, in order to obtain high power generation characteristics, the copper complex is allowed to undergo molecular motion by solvation (amorphous). It was found that it is desirable to be in the (state). Further, although the solvent is removed at the time of filling the electrolyte, the remaining solvent shows relatively high solar cell characteristics at the initial stage, while the solvent decreases with the elapse of time, whereby the crystallization of the copper complex proceeds. It is estimated that the output will drop significantly. On the other hand, in the present disclosure, by adding an organic solvent having a characteristic such as a boiling point of 200° C. or higher and/or adding an ionic liquid that is hard to volatilize, a high power density in the initial characteristic can be secured, and the dark It is presumed that the solar cell characteristics can be further improved by, for example, further improving the high temperature durability when left at a high temperature of 60° C.

It is needless to say that the present disclosure is not limited to the above-described embodiments, and can be implemented in various modes as long as they are within the technical scope of the present disclosure.

For example, although the solar cell module 10 is used in the above-described embodiment, the solar cell module 10 is not particularly limited to this, and the solar cell 40 shown in FIG. 2 may be used. FIG. 2 is a cross-sectional view showing an example of a schematic configuration of the solar cell 40. In FIG. 2, the same components as those described with reference to FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. As shown in FIG. 2, when the solar cell 40 is a single unit, the cross section of the counter electrode 30 may be formed in a flat plate shape instead of the L shape. Further, the separator 29 may be omitted. The counter electrode 30 may be, for example, one having the same configuration as the light transmissive conductive substrate 14, or one having platinum attached to the light transmissive conductive film 12 or a metal thin film of platinum or the like. ..

Below, the example which produced the electrolyte of this indication and the solar cell concretely is demonstrated as an experiment example. In the following Examples, Experimental Examples 1 and 2 correspond to Reference Examples, Experimental Examples 3 to 13 correspond to Examples, and Experimental Example 14 corresponds to a Comparative Example.

[Study of electrolyte]
An evaluation cell was manufactured by a conventional manufacturing method. After forming dense TiO ₂ (10 nm) on the transparent conductive film (SnO ₂ ) electrode by the atomic layer deposition method, titanium oxide particles (particle diameter: several 10 nm to 400 nm) are printed and then sintered at 500° C., A TiO ₂ photoelectrode was prepared by immersion in a titanium compound and heating at 500°C. A rutile type TiO ₂ layer separator was printed on the photoelectrode, and then a carbon electrode was laminated thereon to prepare a three-layer structure electrode. After adsorbing the red organic dye, filling the above-mentioned electrolyte and removing the solvent, a dye-sensitized solar cell having a three-layer structure was produced. Here, a photoelectrode/transparent conductive film (FTO) glass and a counter electrode/glass substrate were sandwiched by a sealant, and an electrolyte solution was introduced under reduced pressure from a small hole for electrolyte injection provided on the glass substrate. Then, reduced pressure drying was performed to remove the solvent to form an electrolyte layer on the photoelectrode (filling method). The material used was a compound of the chemical formula (A) as the dye. Cu(dmp) ₂ TFSI (monovalent: chemical formula (1)) and Cu(dmp) ₂ TFSI ₂ (divalent) were used as the copper complex. This was used as Experimental Example 1 as a closed cell. Regarding the component ratio of the copper complexes having different valences, the divalent concentration was 0.05M, and the total concentration of monovalent and divalent was 0.25M. In addition, Cu(tmby) ₂ TFSI (chemical formula (3)) was similarly used as the copper complex. In addition, 0.1 M LiTFSI as an additive and 0.5 M N-butylbenzimidazole (NBBI) were added to acetonitrile (ACN) as a solvent. The above copper complex was added thereto to form an electrolyte solution, which was formed on the photoelectrode.

Here, the electrolyte was examined using an open cell that was not hermetically sealed. The open cell is an evaluation cell which is manufactured by a dropping method described later and is opened without using a sealing material. This open cell was produced using the raw materials (dye, additive, etc.) having the same composition as in Experimental Example 1 which is a closed cell. One using Cu(dmp) ₂ TFSI as a copper complex was referred to as an open cell reference example 1, and one using Cu(tmby) ₂ TFSI as a copper complex was referred to as an open cell reference example 2. FIG. 3 shows the measurement results of Jsc (mA/m ² ) with respect to the measurement time (S) after the injection of the electrolytic solution of the open cells of Reference Examples 1 and ² . As shown in FIG. 3, in the open cell, high Jsc was initially shown, but decreased with the passage of time. This is probably because the solvent remained in the electrolyte layer in the initial stage, but the solvent volatilized with the passage of time and disappeared from the open cell, and the copper complex was crystallized with the passage of time and the Jsc decreased. It was From this result, it was inferred that the presence of a solvent was desirable in the electrolyte.

Next, the composition of the electrolyte of the evaluation cell of Experimental Example 1 which was the above-described closed cell was evaluated. Table 1 summarizes the results of analysis of the composition (prepared composition) when the evaluation cell was prepared as Experimental Example 1-1, and the components inside the cell after the test as Experimental Example 1-2. Further, FIG. 4A shows the compositions of Experimental Examples 1-1 and 1-2. In Table 1 and FIG. 4A, the molar ratios of the other components are shown, where the molar ratio of the monovalent copper complex was normalized to 0.25. Moreover, the molar ratio of Experimental Example 1-2 was determined from the NMR measurement value. As shown in Table 1 and FIG. 4A, acetonitrile as a solvent had a molar ratio of 19 in the charged composition, but the molar ratio decreased to 3.4 after power generation.

Next, the method for producing the evaluation cell and the solvent were changed and examined. Here, instead of the above-described filling method, a dropping method of dropping a small amount of an electrolyte solution onto the photoelectrode in the atmosphere was performed to form the electrolyte on the photoelectrode. The photoelectrode had a size of 1 cm×0.75 cm, and 3 μL of the electrolyte solution was dropped. After that, a counter electrode was superposed with a frame seal of Himilan, and then an evaluation cell was produced by a method of sealing the outer periphery of the cell with an epoxy curing resin. In the evaluation cell manufactured by this dropping method, when the electrolyte solution of Experimental Example 1 was used, almost no power was generated. It was speculated that this is because the amount of the solvent in the charged composition was small and the solvent volatilized quickly during the production, and the solvent did not exist during power generation. Therefore, the solvent was a mixed solvent in which propylene carbonate (PC), valeronitrile (VALN), and acetonitrile (ACN) were mixed at a volume ratio of 32:14:54. Then, an electrolyte solution was prepared by adding 0.5 M Cu(dmp) ₂ TFSI, 1 M NBBI, and 0.4 M LiTFSI to the solvent. In Table 2, the composition (preparation composition) at the time of preparation of the evaluation cell prepared by the dropping method is defined as Experimental Example 2-1, and the results of analyzing the components inside the evaluation cell after preparation are Experimental Examples 2-1 and 2-2. Summarized as. Experimental Example 2-1 is an evaluation cell prepared by dropping with an electrolyte solution micropipette, and Experimental Example 2-2 is an evaluation cell prepared by applying an electrolyte solution in a mist form. Table 2 shows the molar ratios of the other components in which the molar ratio of the monovalent copper complex was standardized to 0.50. The molar ratio of Experimental Example 2 was determined from the NMR measurement value. FIG. 4 shows the measurement results of the electrolyte composition of the evaluation cells of Experimental Examples 1 and 2, FIG. 4A being the composition of Experimental Examples 1-1 and 1-2, and FIG. 4B being Experimental Examples 2-1-2-2. -3 composition. As shown in FIG. 4 and Table 2, assuming that the concentration in Experimental Example 2 is about ½ including the volume of the electrolyte, the number of moles of the Cu complex in Experimental Example 1 is about 6 in Experimental Example 2. It is estimated to be about 16 times that of Experimental Example 2. That is, it was estimated that the experimental example 2 produced by the dropping method had a considerably smaller amount of electrolyte and solvent than the experimental example 1.

Next, an electrolyte in which valeronitrile of Experimental Example 2-1 was changed to dimethylformamide (DMF) was examined. An evaluation cell using an electrolyte prepared in the same manner as in Experimental Example 2-1 was used as Experimental Example 2-4, except that the solvent was a mixture of PC, DMF, and ACN. Further, Experimental Example 2-5 was prepared by leaving Experimental Example 2-4 in a dark place at room temperature for 3 weeks. Further, Experimental Example 2-6 was obtained by leaving Experimental Example 2-4 in a dark place at 60° C. for 300 hours. The solar cell characteristics when the evaluation cells of Experimental Examples 2-5 and 2-6 were irradiated with 1000 (lux) of the LED light source were measured. Further, the compositions of the electrolytes of Experimental Examples 2-4 to 2-6 were measured. FIG. 5 shows the solar cell characteristics of the evaluation cells of Experimental Examples 2-5 and 2-6. FIG. 6 shows the measurement results of the electrolyte composition of the evaluation cells of Experimental Examples 2-4 to 2-6. In FIG. 6, the molar ratios of the other components are shown, where the molar ratio of the monovalent copper complex was standardized to 0.50. As shown in FIGS. 6 and 7, the evaluation cell of Experimental Example 2-6 left at 60° C. has lower solar cell characteristics and a larger amount of PC-altered substance than those of Experimental Example 2-5 left at room temperature. I found out that FIG. 7 shows the NMR measurement results of the electrolyte composition of the evaluation cells of Experimental Examples 2-4 to 2-6. As shown in FIG. 7, in Experimental Examples 2-5 and 2-6, new generation peaks were observed, which were presumed to be propylene glycol, which is a hydrolyzate of PC. In Experimental Example 2, since the electrolyte solution was prepared by dropping in the atmosphere, it was speculated that water was mixed in the solvent and the hydrolysis of PC was promoted especially at high temperature.

Next, an evaluation cell was prepared by the dropping method using the following electrolytes, and the time course of the output density and the output retention rate was examined. As a copper complex, Cu(dmp) ₂ TFSI (monovalent) was 0.2M, Cu(tmby) ₂ TFSI (monovalent) was 0.1M, LiTFSI was 0.24M, and N-butylbenzimidazole (NBBI) was 0.2. The solvent was mixed with the following solvent so as to be 6M. The solvent used was a mixture of ACN, PC, and an ionic liquid in a volume ratio of 70:20:10. Using this electrolyte solution, the dropping method was performed in a glove box in a nitrogen atmosphere to form an electrolyte layer on the photoelectrode. The evaluation cell obtained through these steps was used as Experimental Example 3. Further, as a copper complex, Cu(dmp) ₂ TFSI (monovalent) was mixed with 0.3 M, LiTFSI was 0.24 M, and NBBI was mixed with the following solvent so as to be 0.6 M. The solvent used was a mixture of ACN and PC at a volume ratio of 70:30. An evaluation cell obtained through the same steps as in Experimental Example 3 above using this electrolyte solution was referred to as Experimental Example 4. The evaluation cells of Experimental Examples 3 and 4 were irradiated with 1000 (lux) from the LED light source at predetermined time intervals, and the solar cell characteristics were measured. FIG. 8 shows the measurement results of the output density of Experimental Examples 3 and 4 when left in a high temperature dark place. FIG. 9 shows the results of measuring the output retention rate (%) of Experimental Examples 3 and 4 when left in a high temperature dark place. Further, in Table 3, the initial output density (mW / m ²⁾ Experimental Examples 3 and 4, the output density after standing 60 ° C. dark (mW / m ^2), the output retention rate after standing 60 ° C. dark (% ) And are collectively shown. Although not shown in the figure, in the evaluation cell prepared by the dropping method using the electrolyte of Experimental Example 1, the initial power generation amount could not be obtained. On the other hand, as shown in FIGS. 8 and 9, it was found that Experimental Examples 3 and 4 produced by the dropping method exhibited a high initial power density. Further, by producing the cell in nitrogen, the hydrolysis of PC in the organic solvent due to the mixing of water was suppressed, but in Experimental Example 4, a decrease in output was observed with the passage of time in the high temperature durability test. It is speculated that this is because the PC gradually volatilizes from the pores of the titanium oxide by heating and the crystallization of the copper complex progresses, thereby deteriorating the power generation characteristics. On the other hand, in Experimental Example 3 in which the refractory ionic liquid was further added, the high temperature durability was significantly improved without deteriorating the initial power generation characteristics due to the volatilization suppressing effect of PC which is the organic solvent due to the increase in the molar boiling point. I found that it could be improved.

[Study of Electrolytes of Experimental Examples 5 to 14]
The evaluation cells manufactured through the same steps as in Experimental Example 2 were used as Experimental Examples 5 to 14 using the electrolytes having the composition ratios described in Table 4. As the ionic liquid contained in the solvent, 1-ethyl-3-methylimidazolium-tetracyanoboron (EMI-TCB, chemical formula (18)) was used. Further, 3-methyl-2-oxazoline (NMO) and PC were appropriately used as the high boiling point organic solvent. Using this evaluation cell, the initial power generation characteristics and the solar cell characteristics after endurance after being left in the dark at 60° C. for 1000 hours were measured. Here, the solar cell characteristics when irradiated with 1000 lux by the LED light source were measured. The measurement results are summarized in Table 5. FIG. 10 is the initial power density of Experimental Examples 5-14. FIG. 11 shows the output retention rate of Experimental Examples 5 to 13 after being left in the dark at 60° C. As shown in Table 5 and FIGS. 10 and 11, in Experimental Example 14 prepared by a dropping method using an organic solvent having a low boiling point, the initial power density was extremely low, and power generation could not be performed immediately, so that durability evaluation could not be performed. On the other hand, an organic solvent having a boiling point of 200° C. or higher, a relative dielectric constant εr of 30 or more and 100 or less, and a viscosity η at 25° C. of 0.5 mPa·s or more and 10 mPa·s or less (NMO), A very high initial power density was obtained in the evaluation cells of Experimental Examples 5 to 13 using the organic solvent containing PC and the Experimental Examples 5 to 9 evaluation cell prepared by the dropping method using the electrolytic solution containing the ionic liquid. It was In addition, since Experimental Examples 10 to 12 obtained higher output density and output retention rate than Experimental Example 13, it was found that NMO having higher chemical stability than PC was more preferable. Further, since Experimental Examples 10 to 12 obtained higher power densities and output retention rates than Experimental Example 9, it was found that NMO alone is more preferable than the ionic liquid having high viscosity. Further, since the output maintenance ratios of Experimental Examples 5 to 7 were higher than those of Experimental Examples 9 to 12, it is more preferable to include both of them in comparison with only the high boiling organic solvent or the ionic liquid. I understood it. Furthermore, in Experimental Examples 5 to 12, it was inferred that the crystallization of the copper complex could be further suppressed by including a plurality of kinds of copper complexes, and this also contributed to the improvement of the solar cell characteristics. Further, in Experimental Examples 5 to 12, it was found that even if a solar cell was produced in the atmosphere by a simple method such as a dropping method, high solar cell characteristics could be obtained, and the manufacturing method could be simplified. ..

Next, a solvent with low volatility and viscosity and high relative dielectric constant was investigated. Table 6 shows the relative permittivity of typical organic solvents, the viscosity (mPa·s) at 25° C., the melting point mp (° C.), and the boiling point bp (° C.). Table 7 shows the viscosities (mPa·s) of typical ionic liquids at 25°C and the melting points mp (°C). Among organic solvents, those having a boiling point of 200° C. or higher, a relative permittivity εr of 30 or more and 100 or less, and a viscosity η at 25° C. of 0.5 mPa·s or more and 10 mPa·s or less are promising. It was speculated that there is. In addition, it is assumed that the ionic liquid having a viscosity η at 25° C. of 300 mPa·s or less is promising. Since the ionic liquid tends to have a relatively high viscosity and melting point, it is presumed that it is more effective to use the ionic liquid in a mixture with an organic solvent.

From the above results, it was found that the copper complex and the electrolyte containing the above-described high-boiling organic solvent or ionic liquid exhibit higher power density and can further enhance the durability of the solar cell. .. Further, it was found that the solvent of the electrolyte more preferably contains an organic solvent having a high boiling point and an ionic liquid. Further, it was found that it is preferable to use two or more kinds of copper complexes having different basic structures of organic ligands. Furthermore, it is assumed that the solvent is more preferably oxazolidones containing 3-methyl-2-oxazolidone and dinitriles containing glutaronitrile, which have higher boiling points. It was also found that 1-ethyl-3-methylimidazolium (EMI) can be used as the ionic liquid.

The present disclosure can be suitably used for solar cells and solar cell modules.

10 solar cell module, 11 light transmissive substrate, 12 light transmissive conductive film, 13 light receiving surface, 14 light transmissive conductive substrate, 15 light receiving surface, 16, 17 current collecting electrode, 18 groove, 20 photoelectrode, 21 connection part, 22 Underlayer, 23 light receiving surface, 24 electron transport layer, 25 back surface, 26 electrolyte layer, 27 back surface, 29 separator, 30 counter electrode, 32 sealing material, 34 protective member, 40 solar cell.

Claims (19)

A photoelectrode having a light absorption layer, and an electrolyte used by being interposed between the photoelectrode and the counter electrode of a solar cell having a counter electrode arranged so as to face the photoelectrode,
It contains a copper complex having an organic ligand and a plurality of valences of copper, has a boiling point of 200° C. or higher, a relative dielectric constant εr of 30 or more and 100 or less, and a viscosity η at 25° C. of 0.5 mPa. An electrolyte containing an organic solvent in the range of s or more and 10 mPa·s or less and a solvent containing at least one or more of an ionic liquid having a viscosity η at 25° C. of 300 mPa·s or less. The electrolyte according to claim 1, wherein the solvent includes the organic solvent and the ionic liquid. The electrolyte according to claim 2, wherein the ratio Mi/Ms×100 (mol %) of the number Mi of moles of the ionic liquid to the number Ms of moles of the organic solvent is in the range of 10 mol% or more and 50 mol% or less. The organic solvent includes carbonates containing ethylene carbonate, propylene carbonate and butylene carbonate, cyclic esters containing γ-butyl lactone and γ-valerolactone, nitriles containing adiponitrile, pyrrolidones containing N-methylpyrrolidone, 3- The electrolyte according to any one of claims 1 to 3, which is one or more of oxazolidones containing methyl-2-oxazolidone and dinitriles containing glutaronitrile. The electrolyte according to any one of claims 1 to 4, wherein the ionic liquid contains one or more cations of chemical formulas (1) to (7).
The ionic liquid is Br ⁻ , Cl ⁻ , SCN ⁻ , HSO ₄ ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , CF ₃ SO ₃ ⁻ , CF ₃ CO ₂ ⁻ , (C ₂ F ₅ ) ₃ PF ₃ ⁻ , ( CF ₃ SO _{2) 2} N ^- and (FSO _{2) 2} N ^- comprises one or more anions of electrolyte according to any one of claims 1 to 5. The electrolyte according to any one of claims 1 to 6, which contains two or more kinds of the copper complexes having different structures of the organic ligand. The organic ligand is a phenanthroline-based ligand, a pyridylethane-based ligand, a bipyridine-based ligand, a sparteine-based ligand, a bisbenzimidazolylthiomethylpyridine-based ligand, a bisbenzimidazolylthio. 8. The copper complex which is one or more of a methylmethylamine-based ligand, a bisbenzimidazolylylpyridine-based ligand, and a bisethylthiomethylpyridine-based ligand, is contained. The electrolyte according to. The copper complex includes any two or more of the chemical formulas (8) to (17),
The electrolyte according to any one of claims 1 to 8.
A bis(2,9-dimethyl-1,10-phenanthroline) copper complex and a bis(4,4',6,6'-tetramethyl-2,2'-bipyridine) copper complex are contained at least two kinds. The electrolyte according to any one of 1 to 9. A ratio M1/Ma×100 (mol%) of the number of moles M1 of the first copper complex and the number of moles Ma of the entire copper complex, which contains at least a first copper complex and a second copper complex having different organic ligands. Is 30 mol% or more and 70 mol% or less, The electrolyte according to any one of claims 1 to 10. 11. The heterocyclic compound having one or more nitrogens and having two or more rings, and one or more cyclic compounds among the monocyclic heterocyclic compounds having two or more nitrogens, further comprising any one of claims 1 to 10. The electrolyte according to. A photoelectrode having a light absorption layer,
A counter electrode arranged to face the photoelectrode,
The electrolyte according to any one of claims 1 to 12, which is interposed between the photoelectrode and the counter electrode,
Solar cell with. The solar cell according to claim 13, wherein the photoelectrode has the light absorption layer containing one or more of an organic dye, a metal complex, and an organic metal halide compound. The solar cell according to claim 13 or 14, wherein the photoelectrode comprises an n-type semiconductor layer covered with the light absorption layer on a light transmissive conductive substrate. A solar cell module comprising a plurality of the solar cells according to claim 13. A method of manufacturing a solar cell comprising a photoelectrode having a light absorbing layer, and a counter electrode arranged so as to face the photoelectrode,
It contains a copper complex having an organic ligand and a plurality of valences of copper, has a boiling point of 200° C. or higher, a relative dielectric constant εr of 30 or more and 100 or less, and a viscosity η at 25° C. of 0.5 mPa. An electrolyte containing a solvent containing at least one of an organic solvent in the range of s or more and 10 mPa·s or less and an ionic liquid having a viscosity η at 25° C. of 300 mPa·s or less is applied or discharged onto the photoelectrode. A forming step of forming an electrolyte,
Method for manufacturing solar cell. The solar cell according to claim 17, wherein in the forming step, an electrolyte containing the solvent containing the organic solvent excluding carbonates including ethylene carbonate, propylene carbonate and butylene carbonate is formed on the photoelectrode in the atmosphere. Manufacturing method. The solar cell according to claim 17, wherein in the forming step, an electrolyte containing the solvent containing the organic solvent of carbonates including ethylene carbonate, propylene carbonate and butylene carbonate is formed on the photoelectrode in an inert atmosphere. Manufacturing method.