Method of manufacturing photoelectric conversion element and method of manufacturing tandem type solar cell

Abstract

To provide a method of manufacturing a photoelectric conversion element capable of improving photoelectric conversion efficiency of a photoelectric conversion layer consisting of a perovskite layer, and a method of manufacturing a tandem type solar cell.SOLUTION: Disclosed is a method of manufacturing a photoelectric conversion element in which at least a first electrode layer, a photoelectric conversion layer containing a perovskite compound represented by a general formula ABX3, a carrier transport layer and a second electrode layer are disposed in this order. The method of manufacturing the photoelectric conversion element includes a storage step. The storage step is a step of storing an intermediate product including at least a part of or all of the first electrode layer, the photoelectric conversion layer and the carrier transport layer formed on the photoelectric conversion layer in an atmospheric environment, in a light-shielded state and under a condition that an index represented by the following formula (1) ranges from 110 or more to 490 or less, the formula (1): index=water vapor content in environment (g / m3)×storage time (h).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD Embodiments of the present invention relate to a method for manufacturing a photoelectric conversion element and a method for manufacturing a tandem solar cell. [Background technology]

[0002] Recently, attention has been focused on power generation systems that effectively utilize natural energy or have low environmental impact, such as low carbon dioxide emissions. In this context, solar cells using photoelectric conversion elements have been actively researched and developed. A highly productive manufacturing method for such solar cells is desirable. To meet this need, a method for producing the photoelectric conversion layer that constitutes the solar cell by coating or printing has been proposed. Such a method may potentially enable solar cells to be manufactured at lower cost than conventional methods. However, when manufacturing a perovskite layer as a photoelectric conversion layer, it is considered necessary to control the atmosphere in order to improve the photoelectric conversion efficiency. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-82006 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-82003 Summary of the Invention [Problem to be solved by the invention]

[0004] The problem to be solved by the present invention is to provide a method for manufacturing a photoelectric conversion element and a method for manufacturing a tandem solar cell that can improve the photoelectric conversion efficiency of a photoelectric conversion layer made of a perovskite layer. [Means for solving the problem]

[0005] The method for manufacturing a photoelectric conversion element according to the embodiment is a method for manufacturing a photoelectric conversion element in which at least a first electrode layer, a photoelectric conversion layer containing a perovskite compound represented by the general formula ABX3, a carrier transport layer, and a second electrode layer are arranged in this order, and includes a storage step. The storage step is a step of storing an intermediate including the first electrode layer, the photoelectric conversion layer, and at least a part or all of the carrier transport layer formed on the photoelectric conversion layer in an air atmosphere, in a light-shielded state, under conditions where the index represented by the following formula (1) is in the range of 110 or more and 490 or less. wherein A contains one or more ions of Cs, CH4N2, CH3NH2, C2H5NH2, C3H7NH2 or C4H9NH2, B is one or two of Pb or Sn, and X is one or two or more of F, Cl, Br, I or At. Index = amount of water vapor in the atmosphere (g / m 3 )×Storage time (h) …(1) [Brief explanation of the drawings]

[0006] [Figure 1] Figure 1 is a cross-sectional schematic diagram showing the structure of a single-type solar cell. [Figure 2] FIG. 2 is a process diagram illustrating a first example of a method for manufacturing a single solar cell according to the first embodiment. [Figure 3] FIG. 3 is a process diagram illustrating a first example of a method for manufacturing a single solar cell according to the first embodiment, showing a storage step. [Figure 4] FIG. 4 is a process diagram illustrating a first example of a method for manufacturing a single solar cell according to the first embodiment, showing a process for manufacturing a transparent electrode layer. [Figure 5] Figure 5 is a cross-sectional schematic diagram showing the configuration of a tandem solar cell. [Figure 6] FIG. 6 is a process diagram illustrating an example of a method for manufacturing a tandem solar cell according to the second embodiment. [Figure 7] FIG. 7 is a process diagram illustrating an example of a method for manufacturing a tandem solar cell according to the second embodiment, showing a storage step. [Figure 8] FIG. 8 is a process diagram illustrating an example of a method for manufacturing a tandem solar cell according to the second embodiment, showing a process for manufacturing a transparent electrode layer. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, a method for manufacturing a photoelectric conversion element, a method for manufacturing a tandem solar cell, and a method for manufacturing a single solar cell according to embodiments will be described with reference to the drawings.

[0008] (First embodiment) FIG. 1 shows an example of a photoelectric conversion element manufactured by the manufacturing method of the first embodiment. The photoelectric conversion element 10 shown in FIG. 1 is also called a single-type solar cell having one photoelectric conversion layer, and has a first electrode layer 11, a first carrier transport layer 12, a photoelectric conversion layer 13, a second carrier transport layer 14, and a second electrode layer 15 stacked on a substrate 16. The first electrode layer 11 and the second electrode layer 15 function as an anode or a cathode, and electricity is extracted from them. The second electrode layer 15 includes one or both of a metal electrode layer and a transparent electrode layer. The second electrode layer is an electrode layer that is formed after the photoelectric conversion layer 13 is formed.

[0009] The photoelectric conversion layer 13 is a layer that functions as a photoelectric conversion layer of a so-called perovskite solar cell. The photoelectric conversion layer 13 is excited by light incident from the substrate 16 side through the substrate 16, the first electrode layer 11, and the first carrier transport layer 12, or by light incident from the second electrode layer 15 side through the second electrode layer 15 and the second carrier transport layer 14, generating electrons or holes in the first electrode layer 11 and the second electrode layer 15. The first carrier transport layer 12 and the second carrier transport layer 14 are layers that exist between the photoelectric conversion layer 13 and the two electrode layers 11 and 15, and have the function of transporting holes or electrons to the photoelectric conversion layer 13.

[0010] The components of the single-type solar cell, which is the photoelectric conversion element shown in FIG. 1, will be described below.

[0011] The substrate 16 is used to support other components. It is necessary to form the first electrode layer 11 on the surface of this substrate 16. For this reason, it is preferable that the substrate 16 is one that will not be altered by the heat applied during the formation of the electrode layer or by organic solvents that it comes into contact with. Examples of materials for the substrate 16 include inorganic materials such as alkali-free glass and quartz glass, organic materials such as polyethylene, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide, polyamide, polyamideimide, liquid crystal polymers, and cycloolefin polymers, and metal materials such as stainless steel (SUS) and silicon.

[0012] The substrate 16 may be transparent or opaque, and is appropriately selected depending on the structure of the intended photoelectric conversion element. For example, a transparent substrate is used when light is incident from the surface of the substrate 16 or when transparency is required as a solar cell (for example, when installed on a window). Furthermore, when light is incident from the side opposite to the substrate 16, the second electrode layer 15 can be transparent or translucent, and the substrate 16 can be opaque.

[0013] The thickness of the substrate 16 is not particularly limited as long as it has sufficient strength to support the other components.

[0014] When the substrate 16 is disposed on the light incident surface side, an anti-reflection film with a moth-eye structure, for example, can be provided on the light incident surface. This structure allows for efficient capture of light and improves the energy conversion efficiency of the cell. The moth-eye structure has a regular array of protrusions on the surface, each of which is approximately 100 nm in size. This protrusion structure causes the refractive index to change continuously in the thickness direction. Therefore, by using an anti-reflection film as an intermediary, the surface where the refractive index changes discontinuously is eliminated, reducing light reflection and improving cell efficiency.

[0015] The first electrode layer 11 and the second electrode layer 15 can be selected from any conventionally known materials as long as they are conductive. However, the material of the electrode layer on the light incident side is preferably selected from transparent or semitransparent conductive materials. Examples of transparent or semitransparent electrode materials include transparent conductive metal oxide films and semitransparent metal thin films. The second electrode layer is formed after the photoelectric conversion layer 13 is formed.

[0016] Examples of metal oxide films include indium oxide, zinc oxide, tin oxide, and their composites, such as indium tin oxide (ITO), fluorine-doped tin oxide (FTO), indium zinc oxide (IZO), and films made from conductive glass (such as NESA). ITO, FTO, or IZO are particularly preferred as conductive oxides. Examples of metal thin films include gold, platinum, silver, and copper.

[0017] When the material of each electrode layer 11, 15 is ITO, the thickness of each electrode layer 11, 15 is preferably 30 to 300 nm. If the thickness of each electrode layer 11, 15 is thinner than 30 nm, the conductivity tends to decrease and the resistance tends to increase. High resistance may cause a decrease in photoelectric conversion efficiency. On the other hand, if the thickness of each electrode layer 11, 15 is thicker than 300 nm, the flexibility of the ITO film tends to decrease. As a result, if the film is thick, it may crack when stress is applied. It is preferable that the sheet resistance of each electrode layer 11, 15 is as low as possible, preferably 10 Ω / □ or less.

[0018] Each of the electrode layers 11 and 15 may have a single layer structure or a multi-layer structure in which layers made of materials with different work functions are stacked. In the example shown in Fig. 1, the second electrode layer 15 is composed of a transparent electrode layer 15a and a comb-shaped metal electrode layer 15b formed on the transparent electrode layer 15a. The second electrode layer 15 may also be composed of only a metal electrode layer.

[0019] When forming each electrode layer 11, 15 adjacent to the electron transport layer, it is preferable to use a material with a low work function as the electrode layer material. Examples of low work function materials include alkali metals and alkaline earth metals. Specific examples include Li, In, Al, Ca, Mg, Sm, Tb, Yb, Zr, Na, K, Rb, Cs, Ba, and alloys thereof. Furthermore, alloys of metals selected from the low work function materials and metals with relatively high work functions selected from gold, silver, platinum, copper, manganese, titanium, cobalt, nickel, tungsten, tin, and the like may be used. Examples of alloys that can be used as electrode layer materials include lithium-aluminum alloys, lithium-magnesium alloys, lithium-indium alloys, magnesium-silver alloys, calcium-indium alloys, magnesium-aluminum alloys, indium-silver alloys, and calcium-aluminum alloys. When such metal materials are used, the film thickness of the electrode layer is preferably 1 nm to 500 nm, more preferably 10 nm to 300 nm. If the film thickness is thinner than the above range, the resistance will be too high and the generated charge may not be transmitted sufficiently to the external circuit. If the film thickness is thick, it will take a long time to form the electrode layer, which will increase the material temperature and damage other materials, resulting in performance degradation. Furthermore, since a large amount of material is used, the film formation equipment will be occupied for a long time, which may lead to increased costs.

[0020] Organic materials can also be used as electrode layer materials. For example, polythiophene-based polymers such as polyethylenedioxythiophene (hereinafter sometimes referred to as PEDOT) are preferred. Such polythiophene-based polymers are commercially available, such as Clevios PH 500, Clevios PH, Clevios P ​​VP Al 4083, and Clevios HIL 1,1 (all trade names, manufactured by Starck). The work function of PEDOT is 4.4 eV, but it can be adjusted by combining it with other materials. For example, by mixing PEDOT with polystyrene sulfonate (hereinafter sometimes referred to as PSS), the work function can be adjusted to a range of 5.0 to 5.8 eV. However, in a layer formed by combining a conductive polymer compound with another material, the proportion of the conductive polymer compound is relatively reduced, which may result in a decrease in carrier transport properties. Therefore, in such cases, the thickness of the electrode layer is preferably 50 nm or less, and more preferably 15 nm or less.

[0021] The photoelectric conversion layer 13 has a perovskite structure. This perovskite structure is one type of crystalline structure, and refers to the same crystalline structure as perovskite. Typically, the perovskite structure is composed of ions A, B, and X, and may take on a perovskite structure when ion B is smaller than ion A. The chemical composition of this crystalline structure can be expressed by the following general formula (1).

[0022] ABX3…(1)

[0023] Here, A comprises one or more ions of Cs, CH4N2, CH3NH2, C2H5NH2, C3H7NH2 or C4H9NH2.

[0024] Also, B is a divalent metal ion, Pb 2+ or Sn 2+ Preferably, but not limited to, X is a halogen ion, for example, F - , Cl - , Br- , I - , and At - Selected from Cl - , Br - , I - is preferred, but is not limited to this.

[0025] The materials that make up ions A, B, and X may each be a single material or a mixture. The constituent ions do not necessarily need to match the stoichiometric ratio of ABX3 to function.

[0026] The ions A constituting the perovskite of the photoelectric conversion layer 13 preferably have an atomic weight or the sum of the atomic weights (molecular weight) of the ions constituting the ions of 45 or more. More preferably, they contain ions with a sum of atomic weights (molecular weight) of 133 or less. Because ions A satisfying these conditions have low stability alone, they may be mixed with common MA (molecular weight 32). However, mixing MA approaches the band gap of silicon, 1.1 eV, which is undesirable for a tandem ion that splits wavelengths to improve efficiency, as this reduces the overall characteristics. Furthermore, when ions A are a combination of multiple ions and include Cs, it is more preferable that the ratio of the number of Cs to the total number of ions A is 0.1 to 0.9.

[0027] This crystal structure has a unit lattice such as a cubic, tetragonal, or rectangular crystal, with A at each vertex, B at the body center, and X at each face center of the cubic crystal centered around this. In this crystal structure, an octahedron consisting of one B and six Xs contained in the unit lattice is easily distorted by interaction with A, undergoing a phase transition to a symmetrical crystal. It is presumed that this phase transition dramatically changes the physical properties of the crystal, causing electrons or holes to be released from the crystal, resulting in electricity generation.

[0028] Increasing the thickness of the photoelectric conversion layer 13 increases the amount of light absorption and the short-circuit current density (Jsc), but the carrier transport distance increases, which tends to increase loss due to deactivation. Therefore, to obtain maximum efficiency, there is an optimal thickness, and the thickness is preferably 30 nm to 1000 nm, and more preferably 60 to 600 nm.

[0029] For example, by individually adjusting the thickness of the photoelectric conversion layer 13, it is possible to adjust the photoelectric conversion element 10 according to the embodiment and other general elements so that they have the same conversion efficiency under sunlight irradiation conditions. However, due to the difference in film quality, under low illumination conditions such as 200 lux, the photoelectric conversion element 10 according to the embodiment can achieve a higher conversion efficiency than general elements.

[0030] The first carrier transport layer 12 and the second carrier transport layer 14 are sandwiched between the photoelectric conversion layer 13 and the first electrode layer 11 or the second electrode layer 15. One of these layers functions as a hole transport layer, and the other functions as an electron transport layer. The second carrier transport layer 14 may have a laminated structure of two or more layers. For example, the side in contact with the photoelectric conversion layer 13 may be a layer containing an organic semiconductor, and the side in contact with the electrode layer 15 may be a layer containing a metal oxide.

[0031] The electron transport layer has the function of efficiently transporting electrons. When the carrier transport layer functions as an electron transport layer, this layer preferably contains either a halogen compound or a metal oxide. Suitable examples of halogen compounds include LiF, LiCl, LiBr, LiI, NaF, NaCl, NaBr, NaI, KF, KCl, KBr, KI, and CsF. Of these, LiF is particularly preferred.

[0032] Suitable examples of metal oxides include titanium oxide, molybdenum oxide, vanadium oxide, zinc oxide, nickel oxide, lithium oxide, calcium oxide, cesium oxide, and aluminum oxide. Of these, titanium oxide is preferred. As titanium oxide, amorphous titanium oxide obtained by hydrolyzing titanium alkoxide using a sol-gel method is preferred.

[0033] The electron transport layer may also be made of an inorganic material such as metallic calcium.

[0034] The thickness of the electron transport layer is preferably 20 nm or less. This is because the film resistance of the electron transport layer can be reduced and the conversion efficiency can be increased. On the other hand, the thickness of the electron transport layer can be 5 nm or more. By providing an electron transport layer and ensuring a certain thickness or more, the hole blocking effect can be fully exerted, and it is possible to prevent the generated excitons from being deactivated before releasing electrons and holes. As a result, current can be extracted efficiently.

[0035] An n-type organic semiconductor can be used for the electron transport layer. The n-type organic semiconductor is preferably, but not limited to, fullerene and its derivatives. Specific examples include derivatives having a basic skeleton of C60, C70, C76, C78, ​​C84, etc. The fullerene derivative may have carbon atoms in the fullerene skeleton modified with any functional group, and these functional groups may be bonded to each other to form a ring. The fullerene derivative includes a fullerene-bonded polymer. A fullerene derivative having a functional group with high affinity for a solvent and high solubility in the solvent is preferred.

[0036] Examples of functional groups in fullerene derivatives include hydrogen atoms, hydroxyl groups, halogen atoms such as fluorine atoms and chlorine atoms, alkyl groups such as methyl groups and ethyl groups, alkenyl groups such as vinyl groups, cyano groups, alkoxy groups such as methoxy groups and ethoxy groups, aromatic hydrocarbon groups such as phenyl groups and naphthyl groups, and aromatic heterocyclic groups such as thienyl groups and pyridyl groups. Specific examples include hydrogenated fullerenes such as C60H36 and C70H36, oxide fullerenes such as C60 and C70, and fullerene metal complexes.

[0037] Among the above, it is particularly preferable to use

[60] PCBM ([6,6]-phenyl C61 butyric acid methyl ester) or

[70] PCBM ([6,6]-phenyl C71 butyric acid methyl ester) as the fullerene derivative.

[0038] Furthermore, low-molecular-weight compounds that can be formed into films by vapor deposition can be used as n-type organic semiconductors. The low-molecular-weight compounds referred to here are those in which the number-average molecular weight Mn and the mass-average molecular weight Mw are the same, with either being 10,000 or less. BCP (bathocuproine), Bphen (4,7-diphenyl-1,10-phenanthroline), TpPyPB (1,3,5-tri(p-pyrid-3-yl-phenyl)benzene), and DPPS (diphenyl bis(4-pyridin-3-yl)phenyl)silane) are more preferred.

[0039] The hole transport layer has the function of efficiently transporting holes. When the first carrier transport layer 12 or the second carrier transport layer 14 functions as a hole transport layer, this layer can contain a p-type organic semiconductor material or an n-type organic semiconductor material.

[0040] P-type organic semiconductors can be used as materials for the hole transport layer. The p-type organic semiconductor preferably includes a copolymer consisting of a donor unit and an acceptor unit. Examples of donor units include fluorene and thiophene. Examples of acceptor units include benzothiadiazole. Specifically, polythiophene and its derivatives, polypyrrole and its derivatives, pyrazoline derivatives, arylamine derivatives, stilbene derivatives, triphenyldiamine derivatives, oligothiophene and its derivatives, polyvinylcarbazole and its derivatives, polysilane and its derivatives, polysiloxane derivatives having aromatic amines in the side chain or main chain, polyaniline and its derivatives, phthalocyanine derivatives, porphyrin and its derivatives, polyphenylenevinylene and its derivatives, polythienylenevinylene and its derivatives, benzodithiophene derivatives, and thieno[3,2-b]thiophene derivatives can be used for the hole transport layer. These materials may be used in combination, or copolymers consisting of comonomers constituting these materials may be used. Among these, polythiophene and its derivatives are preferred because they have excellent stereoregularity and relatively high solubility in solvents.

[0041] In addition, as the material for the hole transport layer, a derivative such as poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (hereinafter sometimes referred to as PCDTBT), which is a copolymer containing carbazole, benzothiadiazole, and thiophene, may be used. Furthermore, a copolymer of a benzodithiophene (BDT) derivative and a thieno[3,2-b]thiophene derivative is also preferred. For example, poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]] (hereinafter sometimes referred to as PCDTBT) Other examples of suitable hole transport layers include PTB7 (sometimes referred to as PTB7 below) and PTB7-Th (sometimes referred to as PCE10 or PBDTTT-EFT), which incorporates a thienyl group with weaker electron donating properties than the alkoxy group of PTB7. Furthermore, metal oxides can also be used as the material for the hole transport layer. Suitable examples of metal oxides include titanium oxide, molybdenum oxide, vanadium oxide, zinc oxide, nickel oxide, lithium oxide, calcium oxide, cesium oxide, and aluminum oxide. These materials have the advantage of being inexpensive. Furthermore, thiocyanates such as copper thiocyanate can also be used as the material for the hole transport layer. It is more preferable that the hole transport layer have a laminated structure of zinc oxide self-assembled monolayers (SAMs).

[0042] The SAM may be used alone, and preferred examples include carbazole derivatives such as [2-(9H-carbazol-9-yl)ethyl]phosphonic acid (2PACz), [2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid (MeO-2PACz), and [4-(3,6-dimethyl-9H-carbazol-9-yl)butyl]phosphonic acid (Me-4PACz).

[0043] In addition, transport materials such as spiro-OMeTAD can be used as dopants for these semiconductor materials, including oxygen, 4-tert-butylpyridine, lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI), acetonitrile, tris[2-(1H-pyrazol-1-yl)pyridine]cobalt(III) tris(hexafluorophosphate) (commercially available under the trade name "FK102"), and tris[2-(1H-pyrazol-1-yl)pyrimidine]cobalt(III) tris[bis(trisfluoromethylsulfonyl)imide] (MY11).

[0044] Next, a method for manufacturing a single-type solar cell, which is the photoelectric conversion element shown in FIG. 1, will be described.

[0045] The method for manufacturing a single-type solar cell includes a storage step of storing an intermediate 31 including a first electrode layer 11, a first carrier transport layer 12, a photoelectric conversion layer 13, and at least a part or all of a second carrier transport layer 14 (carrier transport layer) formed on the photoelectric conversion layer 13, in an air atmosphere, in a light-shielded state, under conditions where the index represented by the following formula (1) is in the range of 110 or more and 490 or less. Index = amount of water vapor in the atmosphere (g / m 3 )×Storage time (h) …(1)

[0046] A method for manufacturing a single solar cell will be described below.

[0047] First, as shown in FIG. 2, a first electrode layer 11, a first carrier transport layer 12, a photoelectric conversion layer 13, and a second carrier transport layer 14 are formed on a substrate 16.

[0048] Specifically, the first electrode layer 11 and the first carrier transport layer 12 are formed on the substrate 16 by a film formation method such as a sputtering method, a CVD method, a vapor deposition method, or a coating method. These film formation methods may be appropriately selected depending on the materials of the first electrode layer 11 and the first carrier transport layer 12.

[0049] Next, a photoelectric conversion layer 13 made of a perovskite compound represented by the general formula ABX3 is formed on the first carrier transport layer 12. The photoelectric conversion layer 13 can be formed by any method. However, from a cost perspective, a coating method is advantageous. Therefore, the photoelectric conversion layer 13 is preferably formed by a coating method. That is, a coating liquid containing a precursor compound of a perovskite structure and an organic solvent capable of dissolving this precursor compound is applied onto the first carrier transport layer 12 to form a coating film. Note that it is preferable to perform a surface treatment in advance on the surface of the first carrier transport layer 12 so that it has high wettability with the coating liquid that forms the perovskite compound. Specific examples include UV-ozone treatment and plasma treatment.

[0050] An example of a precursor compound of the perovskite structure is a mixture of a primary ammonium halide represented by AX and a metal halide represented by BX2, where A contains one or more ions of Cs, CH4N2, CH3NH2, C2H5NH2, C3H7NH2, or C4H9NH2, B is one or two of Pb or Sn, and X is one or two or more of F, Cl, Br, I, or At.

[0051] Examples of solvents used in the coating solution include N,N-dimethylformamide (DMF), γ-butyrolactone, and dimethyl sulfoxide (DMSO). There are no restrictions on the solvent as long as it can dissolve the materials, and a mixture of solvents may also be used. The photoelectric conversion layer 13 can be formed by coating a single coating solution in which all raw materials forming the perovskite structure are dissolved in one solution. Alternatively, multiple raw materials forming the perovskite structure may be individually dissolved in multiple solutions, each of which may be prepared as multiple coating solutions, and these may be applied sequentially. A spin coater, slit coater, bar coater, dip coater, or the like may be used for coating.

[0052] The coating liquid may further contain additives, such as 1,8-diiodooctane (DIO) and N-cyclohexyl-2-pyrrolidone (CHP).

[0053] The coating solution containing the precursor of the perovskite structure may be applied two or more times. In such a case, the photoelectric conversion layer 13 formed by the first application is likely to become a lattice-mismatched layer, so it is preferable to apply it to a relatively thin thickness. The conditions for the second and subsequent applications are preferably conditions that result in a thin film thickness, such as a relatively high rotation speed of the spin coater, a relatively narrow slit width of the slit coater or bar coater, a relatively high pull-up speed of the dip coater, and a relatively low solute concentration in the coating solution.

[0054] After the perovskite structure formation reaction is complete, annealing is preferably performed to dry the solvent. This annealing is performed to remove any remaining solvent in the photoelectric conversion layer 13, and is therefore preferably performed before forming the next layer, such as the second carrier transport layer 14, on the photoelectric conversion layer 13. The annealing temperature is 50°C or higher, more preferably 90°C or higher, with an upper limit of 200°C or lower, more preferably 150°C or lower. Care must be taken because if the annealing temperature is too low, the solvent may not be sufficiently removed, and if the annealing temperature is too high, the surface smoothness of the photoelectric conversion layer 13 may be lost.

[0055] Next, the second carrier transport layer 14 is formed on the photoelectric conversion layer 13 by a film formation method such as a sputtering method, a CVD method, a vapor deposition method, or a coating method. These film formation methods may be appropriately selected depending on the material of the second carrier transport layer 14. In this manner, an intermediate 31 including the second carrier transport layer 14 is formed.

[0056] The second carrier transport layer 14 may have a laminated structure of two layers made of different materials. In this case, the intermediate 31 may include the layer of the second carrier transport layer 14 that is in contact with the photoelectric conversion layer 13.

[0057] Next, a storage step is performed. In the storage step, as shown in FIG. 3, the intermediate 31 including the second carrier transport layer 14 is stored in a storage container H. The atmosphere in the storage container H is an air atmosphere with an adjusted water vapor content. Then, the intermediate 31 including the second carrier transport layer 14 is placed in a light-shielded state. Light-shielded refers to a state in which no ambient light or artificial light is incident. The intermediate 31 including the second carrier transport layer 14 is stored in this state. To maintain the light-shielded state, the storage container H itself may be made light-shielding, or, even if the storage container H itself does not have light-shielding properties, the light-shielding properties may be maintained by placing the storage container H in a light-shielded space.

[0058] The storage conditions are such that the index represented by the following formula (1) is in the range of 110 to 490. If the index is outside the range of 110 to 490, the photoelectric conversion characteristics of the photoelectric conversion layer 13 will deteriorate. Furthermore, if the light-shielding state is broken during storage and ambient light is incident, the photoelectric conversion characteristics of the photoelectric conversion layer 13 will also deteriorate. In formula (1), the storage time is preferably, for example, 12 to 48 hours. In this case, the amount of water vapor is 1 to 10 (g / m 3 ) is preferable. The atmospheric temperature is preferably in the range of 5 to 70° C. In the case of a single-type solar cell, it is more preferable that the index is in the range of 190 to 270, since good performance with little variation can be obtained.

[0059] Index = amount of water vapor in the atmosphere (g / m 3 )×Storage time (h) …(1)

[0060] As long as the index is within the range of formula (1), multiple combinations of water vapor amount and atmospheric temperature may be used. 3 ) does not need to be constant and may be changed during the process. For example, the water vapor content of H1 (g / m 3 ) for T1 (hr), and then the water vapor content of H2 (g / m 3 ) for T2 (hr). In this case, the index can be calculated as index = H1 x T1 + H2 x T2, and it should be in the range of 110 to 490.

[0061] Next, after the storage step is completed, the intermediate 31 is removed from the storage and carried into a film-forming device. Then, as shown in FIG. 4, a transparent electrode layer 15a is formed on the second carrier transport layer 14. The transparent electrode layer 15a is formed by a film-forming method such as a sputtering method, a CVD method, or a vapor deposition method. These film-forming methods may be selected appropriately depending on the material of the transparent electrode layer 15a.

[0062] Furthermore, by forming a metal electrode layer 15b on the transparent electrode layer 15a, a second electrode layer 15 consisting of the transparent electrode layer 15a and the metal electrode layer 15b is formed as shown in Fig. 1. In this manner, a single-type solar cell consisting of the photoelectric conversion element 10 shown in Fig. 1 is manufactured.

[0063] According to the method for manufacturing a single-type solar cell of this embodiment, the intermediate 31 including the first electrode layer 11, the first carrier transport layer 12, the photoelectric conversion layer 13, and at least a part or all of the second carrier transport layer 14 formed on the photoelectric conversion layer 13 is stored in an air atmosphere in a light-shielded state under conditions where the index represented by the following formula (1) is in the range of 110 or more and 490 or less, thereby improving the photoelectric conversion characteristics of the photoelectric conversion layer 13.

[0064] If the storage process is performed immediately after the formation of the photoelectric conversion layer 13 (perovskite layer), excessive moisture will enter the perovskite layer, so it should be performed after the formation of the second carrier transport layer 14 (e.g., a C60 layer). Even if the second carrier transport layer 14 is formed, moisture can penetrate the second carrier transport layer 14 and enter the perovskite layer, acting on the perovskite layer to improve the crystallinity of the perovskite and increase the photoelectric conversion efficiency. Furthermore, the incorporation of moisture into the second carrier transport layer 14 and the perovskite layer changes the interface state with the next process, improving carrier extraction and therefore increasing the photoelectric conversion efficiency. Furthermore, since the transparent electrode layer 15a is a material with high gas barrier properties, it is thought that if the storage step is performed with the transparent electrode layer 15a in place, moisture will be blocked by the transparent electrode layer 15a and will not act sufficiently on the perovskite layer. Therefore, by performing the storage step before laminating the transparent electrode layer, the effect of suitably improving the photoelectric conversion rate of the photoelectric conversion layer 13 can be obtained.

[0065] (Second embodiment) FIG. 5 shows an example of a photoelectric conversion element manufactured by the manufacturing method of the second embodiment. The tandem solar cell 20 comprising the photoelectric conversion element shown in FIG. 5 is also called a tandem solar cell with two photoelectric conversion layers, and is configured by stacking a first photoelectric conversion layer 26, an intermediate layer 21, a first carrier transport layer 22, a second photoelectric conversion layer 23, a second carrier transport layer 24, and a second electrode layer 25 on a first electrode layer 27. The first electrode layer 27 and the second electrode layer 25 function as an anode or cathode, and electricity is extracted from them. The second electrode layer 25 is configured from a transparent electrode layer 25a and a metal electrode layer 25b. The second electrode layer is an electrode layer that is formed after the second photoelectric conversion layer 23 is formed.

[0066] The first photoelectric conversion layer 26 is a layer that functions as a photoelectric conversion layer of a so-called silicon solar cell. The first photoelectric conversion layer 26 is excited by light incident from the second electrode layer 25 side through the transparent electrode layer 25a, the second carrier transport layer 24, the second photoelectric conversion layer 23, the first carrier transport layer 22, and the intermediate layer 21, and generates electrons or holes in the first electrode layer 27 and the second electrode layer 25. Note that functional layers having the function of transporting holes or electrons to the first photoelectric conversion layer 26 may be provided between the first photoelectric conversion layer 26 and the first electrode layer 27 and between the first photoelectric conversion layer 26 and the intermediate layer 21.

[0067] The second photoelectric conversion layer 23 is a layer that functions as a photoelectric conversion layer of a so-called perovskite solar cell. The second photoelectric conversion layer 23 is excited by light incident through the transparent electrode layer 25a and the second carrier transport layer 24, generating electrons or holes in the first electrode layer 27 and the second electrode layer 25. The first carrier transport layer 22 and the second carrier transport layer 24 are layers that exist between the second photoelectric conversion layer 23 and the two electrode layers 27 and 25, and have the function of transporting holes or electrons to the second photoelectric conversion layer 23. Prior to forming the second photoelectric conversion layer 23, an underlayer can be formed in addition to or instead of the first carrier transport layer 22.

[0068] The components of the tandem solar cell, which is the photoelectric conversion element shown in FIG. 5, will be described below.

[0069] The first electrode layer 27 may be a thin metal film made of, for example, gold, platinum, silver, copper, etc. The thickness of the first electrode layer 27 is preferably in the range of, for example, 80 nm to 3 μm.

[0070] The first photoelectric conversion layer 26 is composed of a crystalline silicon layer. The crystalline silicon constituting the first photoelectric conversion layer 26 can have a structure similar to that of silicon generally used in photovoltaic cells. Specific examples include crystalline silicon containing crystalline silicon such as single crystal silicon, polycrystalline silicon, and heterojunction silicon. The crystalline silicon layer may also be a thin film cut from a silicon wafer. The silicon wafer may be n-type silicon crystal doped with phosphorus or arsenic, or p-type silicon crystal doped with boron or gallium. Because electrons in p-type silicon crystal have a long diffusion length, p-type crystalline silicon is preferred. The thickness of the first photoelectric conversion layer 26 is preferably in the range of 80 to 500 μm, and more preferably 120 to 300 μm.

[0071] The intermediate layer 21 electrically connects the first photoelectric conversion layer 26 and the second photoelectric conversion layer 23 while isolating them from each other, and also functions to guide light not absorbed by the second photoelectric conversion layer 23 to the first photoelectric conversion layer 26. To perform this function, the intermediate layer 21 is preferably, for example, a conductive metal oxide film. More specifically, indium oxide, zinc oxide, tin oxide, or a composite thereof such as indium tin oxide (ITO) or indium zinc oxide (IZO) is used. The intermediate layer 21 made of such a metal oxide can be formed by a commonly known method. Specifically, it can be formed by sputtering. The thickness of the intermediate layer 21 is preferably, for example, in the range of 80 to 250 nm.

[0072] The first carrier transport layer 22, the second photoelectric conversion layer 23, the second carrier transport layer 24, the transparent electrode layer 25a, and the metal electrode layer 25b may have the same configurations as the first carrier transport layer 12, the photoelectric conversion layer 13, the second carrier transport layer 14, the transparent electrode layer 15a, and the metal electrode layer 15b described in the first embodiment, respectively. In other words, the second photoelectric conversion layer 23 may be any layer made of a perovskite compound represented by ABX3.

[0073] Next, a method for manufacturing a tandem solar cell, which is the photoelectric conversion element shown in FIG. 5, will be described.

[0074] 5 includes at least a storage step of storing an intermediate 41 including first electrode layer 27, first photoelectric conversion layer 26, intermediate layer 21, first carrier transport layer 22, second photoelectric conversion layer 23, and at least a part or all of second carrier transport layer 24 in an air atmosphere in a light-shielded state under conditions where the index represented by the following formula (1) is in the range of 110 to 490. In the case of a tandem solar cell, an index in the range of 170 to 270 is more preferable because good performance with little variation can be obtained.

[0075] That is, first, as shown in FIG. 6, a first electrode layer 27, a first photoelectric conversion layer 26, an intermediate layer 21, a first carrier transport layer 22, a second photoelectric conversion layer 23, and a second carrier transport layer 24 are formed.

[0076] Specifically, the first carrier transport layer 22 is formed by a film formation method such as sputtering, CVD, vapor deposition, or coating on a stack including the first electrode layer 27, the first photoelectric conversion layer 26, and the intermediate layer 21. These film formation methods may be appropriately selected depending on the material of the first carrier transport layer 22.

[0077] Next, in the same manner as in the first manufacturing example of the first embodiment, a second photoelectric conversion layer 23 made of a perovskite compound represented by the general formula ABX3 is formed on the first carrier transport layer 22 by a coating method, and then a second carrier transport layer 24 is formed on the second photoelectric conversion layer 23 by a film formation method such as a sputtering method, a CVD method, a vapor deposition method, or a coating method. These film formation methods are appropriately selected depending on the material of the second carrier transport layer 24. In this manner, an intermediate 41 including the second carrier transport layer 24 is formed.

[0078] Next, a storage step is performed. In the storage step, as shown in FIG. 7, the intermediate 41 including the second carrier transport layer 24 is stored in a storage container H. The storage container H is filled with the air atmosphere. The intermediate 41 including the second carrier transport layer 24 is placed in a light-shielded state. Light-shielded refers to a state in which no ambient light or artificial light is incident. The intermediate 41 including the second carrier transport layer 24 is stored in this state. The storage conditions are an air atmosphere, a light-shielded state, and a condition in which the index represented by the following formula (1) is in the range of 110 to 490. To maintain the light-shielded state, the storage container H itself may be made light-shielding. Alternatively, the storage container H itself may not have light-shielding properties, but the light-shielding properties may be maintained by placing the storage container H in a light-shielded space. The reasons for limiting the index and for storing in a light-shielded state are the same as those in the first embodiment.

[0079] Next, after the storage step is completed, the intermediate 41 is removed from the storage and carried into a film-forming device. Then, as shown in FIG. 8, a transparent electrode layer 25a is formed on the second carrier transport layer 24. The transparent electrode layer 25a is formed by a film-forming method such as a sputtering method, a CVD method, or a vapor deposition method. These film-forming methods may be selected appropriately depending on the material of the transparent electrode layer 25a.

[0080] Furthermore, by forming a metal electrode layer 25b on the transparent electrode layer 25a, a second electrode layer 25 consisting of the transparent electrode layer 25a and the metal electrode layer 25b is formed as shown in Fig. 5. In this manner, the tandem solar cell 20 shown in Fig. 5 is manufactured.

[0081] According to the manufacturing method of the tandem solar cell, after forming the carrier transport layer 24 on the second photoelectric conversion layer 23, the intermediate 41 including the carrier transport layer 24 is stored in an air atmosphere in a light-shielded state under conditions where the index represented by the following formula (1) is in the range of 110 or more and 490 or less, thereby improving the photoelectric conversion characteristics of the second photoelectric conversion layer 23. [Example]

[0082] (Production of intermediate 1 for single-type solar cells) As shown in Figure 2, a 100 nm thick first electrode layer made of ITO was formed on a 1.1 mm thick glass substrate 16 by sputtering, followed by a very thin first carrier transport layer made of a copolymer containing carbazole by coating, a 600 nm thick photoelectric conversion layer made of a perovskite compound represented by ABX3 by coating, and a portion of a 20 nm thick second carrier transport layer made of fullerene C60 by vacuum deposition. In the perovskite compound, A was Cs, FA, or MA, B was Pb, and X was I or Br. In this way, a single-type solar cell intermediate 1 was produced.

[0083] (Production of intermediate 2 for tandem solar cells) As shown in Figure 6, the first electrode layer was made of silver. On the top surface of a 300 μm-thick single-crystalline silicon solar cell (first photoelectric conversion layer), a 100 nm-thick intermediate layer of ITO was formed by sputtering, a first carrier transport layer made of an ultrathin carbazole-containing copolymer was formed by coating, a 600 nm-thick second photoelectric conversion layer made of a perovskite compound represented by ABX3 was formed by coating, and a 20 nm-thick second carrier transport layer made of fullerene C60 was formed by vacuum deposition. In the perovskite compound, A was Cs, FA, or MA, B was Pb, and X was I or Br. In this way, intermediate 2 of the tandem solar cell was produced.

[0084] (Production of Intermediate 3 of Single-Type Solar Cell (Comparative Example)) As a comparative example, intermediate 3 was produced in the same manner as intermediate 2, except that the storage step was not carried out.

[0085] When producing intermediates 1 to 3 and forming the perovskite compound represented by ABX3 by a coating method, DMF and DMSO were used as the solvents for the coating solution. The coating solution was a single solution containing AX and BX2. A spin coater was used as the coating method. After the perovskite structure formation reaction was completed, annealing was performed at 100°C for 10 minutes to dry the solvent.

[0086] Next, as a storage step, intermediates 1 and 2 were placed in a storage cabinet and kept in a light-shielded state. Intermediates 1 and 2 were stored in this state. The atmosphere in the storage cabinet was air with an adjusted water vapor concentration. The storage conditions were as shown in Table 1.

[0087] After the storage process was completed, a 5 nm thick BCP was formed on the fullerene C60 of intermediate 1 by vapor deposition to form a second carrier transport layer, and a 2 μm thick metal electrode layer (second electrode layer) made of silver was formed on top of that by vapor deposition to form a single-type solar cell. Furthermore, for intermediate 2, a tandem solar cell was formed by sequentially forming on the second carrier transport layer a transparent electrode layer made of tin oxide with a thickness of 20 nm by atomic layer deposition, a transparent electrode layer made of ITO with a thickness of 100 nm by sputtering, and a metal electrode layer (second electrode layer) made of silver with a thickness of 1 μm by vapor deposition.

[0088] The photoelectric conversion rate of the photoelectric conversion layer was measured for each of the obtained solar cells. To measure the photoelectric conversion rate, a probe pin was placed on the first electrode layer and the second electrode layer, and the current-voltage characteristics were measured using a solar simulator. The current-voltage characteristics were measured under two conditions: voltage sweep from the short-circuit current side and voltage sweep from the open-circuit voltage side. The solar simulator used one light source, a xenon lamp, for single solar cells, and two light sources, a xenon lamp and a halogen lamp, for tandem solar cells. The light source had a wavelength of AM1.5G, and the light intensity hitting the light-receiving surface was 1 SUN (100 W / cm). 2 ) was adjusted to be

[0089] The solar cells made of intermediates 1 and 2 that had undergone the storage step were judged to be acceptable if their photoelectric conversion efficiency was at least 1 point higher than the photoelectric conversion efficiency of the solar cell made of intermediate 3. The results are shown in the table.

[0090] In addition, since tandem solar cells have two photoelectric conversion layers, their output is greater than that of the single solar cell (a solar cell manufactured from intermediate 3) used for comparison due to the first photoelectric conversion layer made of single-crystalline silicon, and therefore it is not possible to properly compare the photoelectric conversion rates as is.

[0091] Therefore, when comparing the photoelectric conversion efficiencies, the photoelectric conversion efficiency of the perovskite layer and the photoelectric conversion efficiency of the silicon layer were separated for the tandem solar cells produced from intermediate 2. Table 1 shows the photoelectric conversion efficiency of the perovskite layer.

[0092] In the tandem solar cell, the photoelectric conversion efficiency of the perovskite layer and the photoelectric conversion efficiency of the silicon layer were separated as follows. The photoelectric conversion efficiency of the silicon layer in the tandem solar cell was calculated as follows.

[0093] Conversion efficiency of silicon layer (%) = Short circuit current density of tandem solar cell Jsc × Open circuit voltage of silicon layer in tandem solar cell Voc × Fill factor of silicon layer alone FF

[0094] The photoelectric conversion efficiency of the perovskite layer in the tandem solar cell was determined by subtracting the conversion efficiency of the silicon layer calculated by the above formula from the conversion efficiency of the tandem solar cell.

[0095] In this example, the open-circuit voltage Voc of the bottom cell (silicon layer) assumed to be applied when measuring the external quantum efficiency of the tandem solar cell was used for the calculation. The fill factor FF for the silicon layer alone was calculated on the assumption that the fill factor FF would not change even when the silicon layer was incorporated into the tandem solar cell.

[0096] [Table 1]

[0097] As shown in Table 1, Nos. 3 to 11, which met the storage conditions of this embodiment, were excellent in photoelectric conversion efficiency.

[0098] According to at least one of the embodiments described above, a storage step is included in which an intermediate comprising a first electrode layer, a photoelectric conversion layer, and at least a part or all of a carrier transport layer formed on the photoelectric conversion layer is stored in an air atmosphere in a light-shielded state under conditions in which the index represented by the following formula (1) is in the range of 110 or more and 490 or less, thereby improving the photoelectric conversion rate of the photoelectric conversion layer made of a perovskite compound.

[0099] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention described in the claims and their equivalents. [Explanation of symbols]

[0100] 10...photoelectric conversion element (single-type solar cell), 11, 27...first electrode layer, 12, 22...first carrier transport layer, 13...photoelectric conversion layer, 14, 24 second carrier transport layer, 15, 25...second electrode layer, 15a, 25a...transparent electrode layer, 15b, 25b...metal electrode layer, 16...substrate, 20...tandem solar cell, 21...intermediate layer, 23...second photoelectric conversion layer, 26...first photoelectric conversion layer, 31, 32, 41...intermediate, H...storage.

Claims

1. At least a first electrode layer and a compound of the general formula ABX ３ a carrier transport layer, and a second electrode layer, which are arranged in this order, and the photoelectric conversion layer includes a perovskite compound represented by the formula (I), a storage step of storing an intermediate comprising the first electrode layer, the photoelectric conversion layer, and at least a part or all of the carrier transport layer formed on the photoelectric conversion layer in an air atmosphere in a light-shielded state under conditions in which an index represented by the following formula (1) is in the range of 110 or more and 490 or less: However, A is Cs, CH ４ N ２ , C.H. ３ NH ２ , C ２ H ５ NH ２ , C ３ H ７ NH ２ or C ４ H ９ NH ２ wherein B is one or two of Pb or Sn, and X is one or two or more of F, Cl, Br, I, or At. Index = amount of water vapor in the atmosphere (g / m ３ )×Storage time (h)…(1)

2. At least a first electrode layer, a first photoelectric conversion layer including a silicon layer, an intermediate layer, and a compound represented by the general formula ABX ３ a carrier transport layer, and a second electrode layer, which are arranged in this order, and the second photoelectric conversion layer contains a perovskite compound represented by the formula: a storage step of storing an intermediate comprising the first electrode layer, the first photoelectric conversion layer, the intermediate layer, the second photoelectric conversion layer, and at least a part or all of the carrier transport layer formed on the second photoelectric conversion layer in an air atmosphere in a light-shielded state under conditions in which an index represented by the following formula (1) is in the range of 110 or more and 490 or less: However, A is Cs, CH ４ N ２ , C.H. ３ NH ２ , C ２ H ５ NH ２ , C ３ H ７ NH ２ or C ４ H ９ NH ２ wherein B is one or two of Pb or Sn, and X is one or two or more of F, Cl, Br, I, or At. Index = amount of water vapor in the atmosphere (g / m ３ )×Storage time (h)…(1)

3. In the storage step, the amount of water vapor in the atmosphere is 1 to 10 (g / m ３ 2. The method for producing a photoelectric conversion element according to claim 1, wherein the range of the temperature is 1000 to 2000°C.

4. In the storage step, the amount of water vapor in the atmosphere is 1 to 10 (g / m ３ 3. The method for producing a tandem solar cell according to claim 2, wherein the range of the thickness of the tandem solar cell is 100 nm.

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