Solar cell and method for manufacturing a solar cell

Abstract

The solar cell (1000) of the present disclosure includes a support material (2), a photoelectric conversion element (1), and a sealing material (3). The photoelectric conversion element (1) is disposed inside a sealed space sealed by the support material (2) and the sealing material (3). The photoelectric conversion element (1) includes, in order, a first electrode, a photoelectric conversion layer, and a second electrode. The oxygen concentration in the sealed space is less than 10 ppm by volume fraction, and the water vapor concentration in the sealed space is 100 ppm or more and 5000 ppm or less by volume fraction.

Description

Technical Field

[0001] This disclosure relates to solar cells and methods for manufacturing solar cells. Background Technology

[0002] In recent years, research and development have been conducted on perovskite solar cells using perovskite crystals and similar structures (hereinafter referred to as "perovskite compounds") represented by the formula ABX3 (A being a monovalent cation, B being a divalent cation, and X being a halide anion) as photoelectric conversion materials. Various studies are underway to improve the photoelectric conversion efficiency and durability of perovskite solar cells.

[0003] Non-Patent Literature 1 reports that water vapor in the atmosphere reacts with perovskite compounds, thereby forming substances such as lead iodide, methyl ammonium iodide, or hydrated compounds on the surface or grain boundaries of the perovskite compounds that do not contribute to power generation.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2017-103450

[0007] Non-patent literature

[0008] Non-patent literature 1: Q. Sun et al. 8, Advanced Energy Materials, July 2017, Vol. 7, p. 1700-977

[0009] Non-Patent Literature 2: Taka.T, Synthetic Metals, January 1993, Vol. 57, p. 5014 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] The purpose of this disclosure is to improve the durability of solar cells.

[0012] Methods for solving problems

[0013] This disclosure relates to a solar cell, which comprises:

[0014] Supporting materials

[0015] Photoelectric conversion elements, and

[0016] Sealing material,

[0017] The photoelectric conversion element is disposed inside a sealed space that is sealed by the support material and the sealing material.

[0018] The photoelectric conversion element sequentially comprises a first electrode, a photoelectric conversion layer, and a second electrode.

[0019] The oxygen concentration in the sealed space is less than 10 ppm by volume.

[0020] The water vapor concentration in the sealed space is above 100 ppm and below 5000 ppm by volume.

[0021] Invention Effects

[0022] This disclosure can improve the durability of solar cells. Attached Figure Description

[0023] Figure 1 This is a diagram illustrating a simplified configuration of the solar cell 1000 according to an embodiment of the present disclosure.

[0024] Figure 2 This is a simplified cross-sectional view showing a first configuration example of the photoelectric conversion element 1 in the solar cell 1000 according to an embodiment of the present disclosure.

[0025] Figure 3 This is a simplified cross-sectional view showing a second configuration example of the photoelectric conversion element 1 in the solar cell 1000 according to an embodiment of the present disclosure.

[0026] Figure 4 This is a simplified cross-sectional view showing a third configuration example of the photoelectric conversion element 1 in the solar cell 1000 according to an embodiment of the present disclosure.

[0027] Figure 5 This is a graph showing the dependence of the standardized photoelectric conversion efficiency of the solar cells of Examples 1, 4, 6 and Comparative Example 1 on water vapor concentration.

[0028] Figure 6 This is a graph showing the dependence of the standardized photoelectric conversion efficiency of the solar cells of Examples 1, 4, 6 and Comparative Example 1 on the amount of water vapor.

[0029] Figure 7 This is a graph showing the dependence of the standardized photoelectric conversion efficiency of the solar cells of Examples 2, 3, 5, 7 and Comparative Example 2 on water vapor concentration.

[0030] Figure 8 This is a graph showing the dependence of the standardized photoelectric conversion efficiency of the solar cells of Examples 2, 3, 5, 7 and Comparative Example 2 on the amount of water vapor. Detailed Implementation

[0031] <Insights that form the basis of this disclosure>

[0032] As reported in Non-Patent Document 1, lead-containing perovskite compounds react with water to form substances such as lead iodide, methylammonium iodide, or hydrated compounds on the surface or grain boundaries of the perovskite compound, which are not conducive to power generation. These reaction products are highly insulating materials. Therefore, if these reaction products are formed in large quantities, they hinder the movement of photogenerating charge carriers, thus reducing the performance of perovskite solar cells. Therefore, generally speaking, perovskite solar cells can be used in a nitrogen atmosphere with minimal ambient water (e.g., water vapor concentration of 0.1 ppm or less by volume fraction). Furthermore, in this specification, the water vapor concentration and oxygen concentration mentioned below refer to volume fraction concentrations.

[0033] Patent Document 1 discloses a perovskite solar cell with a sealed structure containing oxygen and moisture within the sealed space. It discloses that the heat resistance of the solar cell is improved by controlling the oxygen concentration in this space to be 5% or higher and the moisture concentration (volume fraction) to be 300 ppm or lower. However, Non-Patent Document 1 reports that, in addition to the reduced performance of the solar cell caused by the aforementioned water vapor, oxygen also affects the solar cell. Specifically, Non-Patent Document 1 discloses that the standardized photoelectric conversion efficiency of the perovskite solar cell after a light irradiation test, based on an oxygen concentration of 0% around the solar cell, decreases monotonically as the oxygen concentration increases from 1% to 20%. Thus, Non-Patent Document 1 reports a decrease in light resistance at an oxygen concentration of 5%. Therefore, it is predicted that if the oxygen concentration is above 5%, it will be difficult to balance thermal stability and light stability.

[0034] Non-Patent Document 2 discloses improving the conductivity of a hole transport material, i.e., a π-conjugated polymer, by placing water near the main chain of the polymer. However, to date, there are no reports on improving thermal and light stability through water vapor; the presence of water vapor is a major cause of reduced durability.

[0035] As mentioned above, regarding the light stability and thermal stability that are important in practical use, there are no reports that the presence of water vapor helps to improve stability.

[0036] In view of these existing technologies, the inventors, while suppressing the oxygen concentration in the sealed space to below 2 ppm, meticulously investigated the threshold value of water vapor concentration, i.e., the value of water vapor concentration that significantly affects the durability of solar cells. As a result, it was found that the durability of solar cells exists within a water vapor concentration range of 0% to 1%. Specifically, it was found that in solar cells with a sealed structure, when the water vapor concentration in the sealed space is in the range of 100 ppm to 5000 ppm, the photoelectric conversion efficiency after light irradiation and after heat resistance tests are improved. Furthermore, it was found that when the water vapor concentration in the sealed space is in the range of 100 ppm to 1000 ppm, the photoelectric conversion efficiency after light irradiation and after heat resistance tests is further improved. Therefore, when the water vapor concentration in the sealed space is in the range of 100 ppm to 5000 ppm, both the light stability and thermal stability of the solar cell can be balanced, and further, when the water vapor concentration in the sealed space is in the range of 100 ppm to 1000 ppm, the aforementioned performance is further improved.

[0037] <Implementation Methods of this Disclosure>

[0038] Embodiments of this disclosure relate to a solar cell comprising a support material, a photoelectric conversion element, and a sealing material. The photoelectric conversion element is disposed within a sealed space sealed by the support material and the sealing material. The photoelectric conversion element sequentially comprises a first electrode, a photoelectric conversion layer, and a second electrode. The oxygen concentration within the sealed space is less than 10 ppm, and the water vapor concentration within the sealed space is more than 100 ppm and less than 5000 ppm.

[0039] Based on the above structure, it is possible to suppress photodegradation and thermal degradation induced by defects in photoelectric conversion materials. Therefore, it is possible to improve the durability of solar cells.

[0040] Furthermore, for example, when the photoelectric conversion element further includes a hole transport layer, since the water vapor concentration within the sealed space is within the aforementioned range, the conductivity of the hole transport layer can be improved by suppressing the reaction between moisture and the photoelectric conversion material while distributing water within the hole transport material. This improves the conductivity of the solar cell. As a result, recombination at the interface is difficult due to the efficient extraction of holes. Therefore, for example, when the photoelectric conversion element further includes a hole transport layer, the durability of the solar cell can be further improved based on the above configuration.

[0041] In the solar cell of this embodiment, the water vapor concentration in the sealed space can be between 100 ppm and 1000 ppm.

[0042] Based on the above composition, it is more difficult to induce structural changes in the photoelectric conversion material caused by heat or light. Therefore, based on the above composition, the thermal and light stability of solar cells can be further improved.

[0043] In the solar cell of this embodiment, the water vapor concentration in the sealed space can also exceed 300 ppm.

[0044] The solar cell of this embodiment, as described above, has an oxygen concentration of less than 10 ppm within the sealed space. By maintaining a low oxygen concentration of less than 10 ppm within the sealed space, the light resistance of the solar cell is improved, thus achieving a balance between thermal stability and light stability. To further improve light resistance, the oxygen concentration within the sealed space can also be less than 2 ppm.

[0045] The concentration of water vapor in a sealed space can be determined using atmospheric pressure ionization mass spectrometry (API-TDS 600, manufactured by API Corporation of Japan). For example, using an API-TDS 600, the sample packaging (i.e., a solar cell module) is destroyed in a destruction chamber under a purified argon atmosphere. The gas composition within the packaging (i.e., the gas composition in the sealed space) is detected, and the gas composition is quantitatively determined using a separately prepared calibration curve. This allows for the determination of the gas composition within the sealed space. Furthermore, in addition to destroying the sample packaging in the destruction chamber as described above, the gas within the sealed space can also be extracted using a syringe.

[0046] The oxygen concentration within a sealed space can be determined using atmospheric pressure ionization mass spectrometry, gas chromatography, and electrochemical oxygen concentration meters. The method for recovering the gas within the sealed space is, for example, the same as the method used for determining the water vapor concentration described above.

[0047] Here, as an example, a method is described to measure the water vapor and oxygen concentrations in the gas released from the sealed space of a solar cell into a closed space such as the aforementioned destruction chamber, using an atmospheric pressure ionization mass spectrometer. For example, a solar cell module is placed in a chamber filled with an inert gas such as argon or krypton. The module is then destroyed within the chamber, allowing the gas contained within the sealed space of the solar cell to escape. Next, an atmospheric pressure ionization mass spectrometer is used to quantitatively analyze the gas within the chamber. By quantifying all the components in the gas within the chamber, the proportion of oxygen in the total volume is calculated, thereby determining the oxygen concentration. Gases other than water vapor and oxygen contained in the sealed space include inert gases such as nitrogen and rare gases, as well as carbon dioxide. Furthermore, if the sealed space contains the same type of inert gas as the inert gas used in the chamber filling the gas analysis, accurate gas analysis may be difficult. Therefore, when the types of gas contained in the sealed space are unknown, two identical solar cell modules are prepared as the inert gases filling the chamber. Different types of inert gases are used, and gas analysis is performed on both solar cell modules according to the steps described above. By comparing the two analysis results, the composition of the gas contained in the sealed space can be determined.

[0048] The partial pressure of water vapor in a sealed space can be 1×10⁻⁶. -4 above atm and 5×10 -3 Below atm, it can also be 1×10 -4 above atm and 1×10 -3 Below atm.

[0049] Based on the above structure, it is easy to suppress photodegradation and thermal degradation induced by defects in the photoelectric conversion material. Therefore, the durability of solar cells can be improved.

[0050] If the solar cell disclosed herein is fabricated under atmospheric pressure, the pressure within the sealed space is approximately one atmosphere. Under this condition, the partial pressure of water vapor within the sealed space is 1 × 10⁻⁶. -4 above atm and 1×10 -3 Below atm.

[0051] The partial pressure of water vapor within a sealed space can be determined, for example, by measuring the mass or molar concentration of the water vapor-containing gas within the sealed space using the water vapor concentration measurement method described above, and then the volume of the sealed space can be determined and calculated from the gas law. The volume of the sealed space can be estimated, for example, by injecting liquid into the sealed space. Alternatively, it can be estimated by disassembling the solar cell and measuring the shape of the space. The various measurements described above are typically performed at room temperature, but are not limited to this. That is, to account for the effects of gas adsorption and desorption within the sealed space, measurements can also be performed at a temperature assuming the actual operating environment.

[0052] Modifications to the solar cells according to the embodiments of this disclosure will be described. Repeated descriptions may be omitted as appropriate.

[0053] The solar cell disclosed herein, as described above, includes a support material, a photoelectric conversion element, and a sealing material. The photoelectric conversion element is disposed within a sealed space sealed by the support material and the sealing material. The photoelectric conversion element sequentially includes a first electrode, a photoelectric conversion layer, and a second electrode. The amount of water vapor in the sealed space can also be 2.3 × 10⁻⁶ relative to the surface area of ​​the face of each photoelectric conversion element facing the sealed space. -6 mol / m 2 Above and 1.2×10 -4 mol / m 2 In other words, the value obtained by dividing the amount of water vapor in the sealed space by the surface area of ​​the photoelectric conversion element facing the sealed space can also be 2.3 × 10⁻⁶. -6 mol / m 2 Above and 1.2×10 -4 mol / m 2 The following is an explanation. Therefore, it is possible to suppress the degradation of solar cells caused by long-term operation.

[0054] To further suppress the degradation of solar cells caused by long-term operation, the amount of water vapor in the sealed space can also be 2.3 × 10⁻⁶, relative to the surface area of ​​the face of each photoelectric conversion element facing the sealed space. -6 mol / m 2 Above and 2.3×10 -5 mol / m 2 the following.

[0055] To suppress oxygen-induced degradation, the oxygen content within the sealed space can also be 7.0 × 10⁻⁶ relative to the surface area of ​​the face of each photoelectric conversion element facing the sealed space. -5 mol / m 2 In other words, the value obtained by dividing the oxygen content in the sealed space by the surface area of ​​the face of the photoelectric conversion element facing the sealed space can also be 7.0 × 10⁻⁶.-5 mol / m 2 the following.

[0056] The main surface of the first electrode of the photoelectric conversion element can face the supporting material, and the main surface of the second electrode can also face the supporting material.

[0057] The solar cell disclosed herein can be fabricated, for example, by the following methods.

[0058] First, the photoelectric conversion element is fabricated using the method described later.

[0059] The obtained photoelectric conversion element was sealed with sealing material in a glove box with adjusted oxygen concentration.

[0060] The oxygen concentration in the glove box is less than 10 ppm by volume, and the water vapor concentration is between 100 ppm and 5000 ppm by volume. Alternatively, the amount of water vapor in the sealed space reaches 2.3 × 10⁻⁶ per square meter of surface area relative to the face of each photoelectric conversion element facing the sealed space. -6 mol / m 2 Above and 1.2×10 -4 mol / m 2 The following adjustments will be made.

[0061] As described above, solar cells with the desired oxygen and water vapor concentrations can be obtained.

[0062] As described above, a solar cell can also be fabricated by sealing a photoelectric conversion element having a first electrode, a photoelectric conversion layer, and a second electrode in sequence in an atmosphere having an oxygen concentration of less than 10 ppm by volume and a water vapor concentration of more than 100 ppm and less than 5000 ppm by volume.

[0063] Figure 1 This is a diagram illustrating a simplified configuration of the solar cell 1000 according to an embodiment of the present disclosure.

[0064] The solar cell 1000 of this embodiment includes a photoelectric conversion element 1, a support material 2, and a sealing material 3. The photoelectric conversion element 1 is disposed inside a sealed space that is sealed by the support material 2 and the sealing material 3.

[0065] The photoelectric conversion element 1 can also be in contact with the support material 2.

[0066] The support material 2 and the sealing material 3 can also be made of the same material. This material can, for example, have a gas barrier function. This material can also be glass.

[0067] Hereinafter, the photoelectric conversion element 1 will be described in more detail using the first to third configuration examples. Furthermore, the photoelectric conversion element 1 is not limited to the photoelectric conversion elements of the first to third configuration examples described below.

[0068] Figure 2 This is a simplified cross-sectional view showing a first configuration example of the photoelectric conversion element 1 in the solar cell 1000 according to an embodiment of the present disclosure.

[0069] The photoelectric conversion element 100 of the first embodiment sequentially includes a substrate 4, a first electrode 5, an electron transport layer 6, a photoelectric conversion layer 7, a hole transport layer 8, and a second electrode 9. Like the photoelectric conversion element 100 of the first embodiment, the photoelectric conversion element 1 of the solar cell 1000 of this embodiment may further include an electron transport layer between the first electrode and the photoelectric conversion layer, and may further include a hole transport layer between the photoelectric conversion layer and the second electrode.

[0070] When light is irradiated onto the photoelectric conversion element 100, the photoelectric conversion layer 7 absorbs the light, generating excited electrons and holes. The excited electrons move to the first electrode 5 via the electron transport layer 6. On the other hand, the holes generated in the photoelectric conversion layer 7 move to the second electrode 9 via the hole transport layer 8. Thus, the photoelectric conversion element 100 can extract current from the first electrode 5, which serves as the negative electrode, and the second electrode 9, which serves as the positive electrode.

[0071] The photoelectric conversion element 100 may or may not have a substrate 4.

[0072] The photoelectric conversion element 100 may or may not have an electron transport layer 6. When the photoelectric conversion element 100 has an electron transport layer 6, electrons can move towards the first electrode 5 with high efficiency. As a result, the photoelectric conversion element 100 can extract current with high efficiency.

[0073] The photoelectric conversion element 100 may or may not have a hole transport layer 8. When the photoelectric conversion element 100 has a hole transport layer 8, holes can move towards the second electrode 9 with high efficiency. As a result, the photoelectric conversion element 100 can extract current with high efficiency.

[0074] The photoelectric conversion element 100 can be manufactured, for example, by the following methods.

[0075] First, a first electrode 5 is formed on the surface of substrate 4 using a chemical vapor deposition (CVD) or sputtering method. Next, an electron transport layer 6 is formed using a CVD, sputtering, or solution coating method. Then, a photoelectric conversion layer 7 is formed on the electron transport layer 6. The photoelectric conversion layer 7 can also be formed using a solution-based coating, printing, or CVD method. Alternatively, a perovskite compound can be cut to a predetermined thickness and disposed as the photoelectric conversion layer 7 on the electron transport layer 6. Next, a hole transport layer 8 is formed on the photoelectric conversion layer 7 using a CVD, sputtering, or solution coating method. Then, a second electrode 9 is formed on the hole transport layer 8 using a CVD, sputtering, or solution coating method. Through these steps, a photoelectric conversion element 100 is obtained.

[0076] Figure 3 This is a simplified cross-sectional view showing a second configuration example of the photoelectric conversion element 1 in the solar cell 1000 according to an embodiment of the present disclosure.

[0077] The photoelectric conversion element 200 of the second embodiment sequentially includes a substrate 4, a first electrode 5, an electron transport layer 6, a porous layer 10, a photoelectric conversion layer 7, a hole transport layer 8, and a second electrode 9. Like the photoelectric conversion element 200 of the second embodiment, the photoelectric conversion element 1 in the solar cell 1000 of this embodiment may further include a porous layer. The porous layer is, for example, disposed between the electron transport layer and the photoelectric conversion layer.

[0078] The porous layer 10 contains porous material. The porous material contains voids.

[0079] The photoelectric conversion element 200 may or may not have a substrate 4.

[0080] The photoelectric conversion element 200 may or may not have an electron transport layer 6. When the photoelectric conversion element 200 does not have an electron transport layer 6, the porous layer 10 is disposed between the first electrode 5 and the photoelectric conversion layer 7. When the photoelectric conversion element 200 has an electron transport layer 6, electrons can move towards the first electrode 5 efficiently. As a result, the photoelectric conversion element 200 can extract current efficiently.

[0081] The photoelectric conversion element 200 may or may not have a hole transport layer 8. When the photoelectric conversion element 200 has a hole transport layer 8, holes can move towards the second electrode 9 with high efficiency. As a result, the photoelectric conversion element 200 can extract current with high efficiency.

[0082] Figure 4 This is a simplified cross-sectional view showing a third configuration example of the photoelectric conversion element 1 in the solar cell 1000 according to an embodiment of the present disclosure.

[0083] The photoelectric conversion element 300 of the third embodiment sequentially comprises a substrate 4, a first electrode 5, an electron transport layer 6, a porous layer 10, an intermediate layer 11, a photoelectric conversion layer 7, a hole transport layer 8, and a second electrode 9. Like the photoelectric conversion element 300 of the third embodiment, the photoelectric conversion element 1 in the solar cell 1000 of this embodiment may further include an intermediate layer. The intermediate layer may, for example, be disposed between the porous layer and the photoelectric conversion layer.

[0084] The photoelectric conversion element 300 may or may not have a substrate 4.

[0085] The photoelectric conversion element 300 may or may not have an electron transport layer 6. When the photoelectric conversion element 300 has an electron transport layer 6, electrons can move towards the first electrode 5 with high efficiency. As a result, the photoelectric conversion element 300 can extract current with high efficiency.

[0086] The photoelectric conversion element 300 may or may not have a hole transport layer 8. When the photoelectric conversion element 300 has a hole transport layer 8, holes can move towards the second electrode 9 with high efficiency. As a result, the photoelectric conversion element 300 can extract current with high efficiency.

[0087] The photoelectric conversion element 300 may or may not have a porous layer 10. When the photoelectric conversion element 300 does not have a porous layer 10, the intermediate layer 11 is disposed between the electron transport layer 6 and the photoelectric conversion layer 7.

[0088] The following is a detailed explanation of each component of the photoelectric conversion element.

[0089] (Substrate 4)

[0090] Substrate 4 is an accessory component. Substrate 4 serves to hold the layers of the photoelectric conversion element. Substrate 4 can be formed of a transparent material. For example, a glass substrate or a plastic substrate can be used as substrate 4. The plastic substrate can also be, for example, a plastic film.

[0091] When the second electrode 9 is transparent, the substrate 4 can also be formed of a non-transparent material. Such materials can be metals, ceramics, or resins with low transparency.

[0092] When the first electrode 5 has sufficient strength, since each layer can be held in place by the first electrode 5, the substrate 4 may not be required.

[0093] (Electrode 1, 5)

[0094] The first electrode 5 is conductive.

[0095] The first electrode 5 is transparent. For example, it can transmit light from the visible region to the near-infrared region.

[0096] The first electrode 5 is, for example, made of a transparent and conductive material. Examples of such materials are metal oxides or metal nitrides. Examples of such materials are: (i) titanium oxide doped with at least one of lithium, magnesium, niobium and fluorine; (ii) gallium oxide doped with at least one of tin and silicon; (iii) gallium nitride doped with at least one of silicon and oxygen; (iv) tin oxide doped with at least one of antimony and fluorine; (v) zinc oxide doped with at least one of boron, aluminum, gallium and indium; (vi) indium-tin composite oxide; or (vii) composites thereof.

[0097] The first electrode 5 can also be formed by designing a light-transmitting pattern. Examples of light-transmitting patterns include linear, wavy, grid-like, or perforated metallic patterns with multiple fine through-holes arranged regularly or irregularly. If the first electrode 5 has these patterns, light can pass through the parts where there is no electrode material. Therefore, by designing a light-transmitting pattern, opaque materials can be used. Examples of opaque electrode materials include platinum, gold, silver, copper, aluminum, rhodium, indium, titanium, iron, nickel, tin, zinc, or alloys containing any of these. Conductive carbon materials can also be used as opaque electrode materials.

[0098] When the photoelectric conversion element lacks the electron transport layer 6, the first electrode 5 has the property of blocking holes from the photoelectric conversion layer 7. In this case, the first electrode 5 does not make ohmic contact with the photoelectric conversion layer 7. Furthermore, the property of blocking holes from the photoelectric conversion layer 7 refers to the property of allowing only electrons generated in the photoelectric conversion layer 7 to pass through while preventing holes from passing through. Materials with this property have a Fermi level higher than the valence band top level of the photoelectric conversion layer 7. The Fermi level of materials with this property can also be higher than the Fermi level of the photoelectric conversion layer 7. Aluminum can be listed as a specific example of such a material.

[0099] When the photoelectric conversion element has an electron transport layer 6, the first electrode 5 may not have the ability to block holes from the photoelectric conversion layer 7. In this case, the first electrode 5 may be made of a material that can form an ohmic contact with the photoelectric conversion layer 7. In this case, the first electrode 5 may or may not have an ohmic contact with the photoelectric conversion layer 7.

[0100] The light transmittance of the first electrode 5 can be, for example, 50% or more, or 80% or more. The wavelength of the light that the first electrode 5 should transmit depends on the absorption wavelength of the photoelectric conversion layer 7.

[0101] The thickness of the first electrode 5 can be, for example, greater than 1 nm and less than 1000 nm.

[0102] (Electron transport layer 6)

[0103] Electron transport layer 6 contains a semiconductor. Electron transport layer 6 can also be formed of a semiconductor with a band gap of 3.0 eV or higher. This allows visible and infrared light to be transmitted to photoelectric conversion layer 7. An example of a semiconductor is an inorganic n-type semiconductor.

[0104] Examples of inorganic n-type semiconductors are metal oxides, metal nitrides, or perovskite oxides. Examples of metal oxides are oxides of Cd, Zn, In, Pb, Mo, W, Sb, Bi, Cu, Hg, Ti, Ag, Mn, Fe, V, Sn, Zr, Sr, Ga, Si, or Cr. Examples of metal oxides include TiO2 or SnO2. Examples of metal nitrides include GaN. Examples of perovskite oxides include SrTiO3 or CaTiO3.

[0105] The electron transport layer 6 may also contain a material with a band gap greater than 6.0 eV. Examples of such materials are (i) alkali metal or alkaline earth metal halides such as lithium fluoride and calcium fluoride, (ii) alkali metal oxides such as magnesium oxide, or (iii) silicon dioxide. In this case, the electron transport layer 6 may also have a thickness of less than 10 nm to ensure electron transport.

[0106] The electron transport layer 6 may also contain multiple layers made of different materials.

[0107] (Photoelectric conversion layer 7)

[0108] The photoelectric conversion layer 7 contains photoelectric conversion materials.

[0109] Photoelectric conversion materials can also be perovskite compounds, for example. That is, photoelectric conversion layer 7 can also contain perovskite compounds. Perovskite compounds have high light absorption coefficients and high carrier mobility in the wavelength region of the solar spectrum. Therefore, photoelectric conversion elements containing perovskite compounds have high photoelectric conversion efficiency.

[0110] Perovskite-type compounds can be represented by the formula ABX3, for example. A is a monovalent cation. Examples of monovalent cations are alkali metal cations or organic cations. An example of an alkali metal cation is the potassium cation (K). + ), cesium cation (Cs) + ) or rubidium cation (Rb + An example of an organic cation is the methylammonium cation (MA). + or CH3NH3 + ), formamidinium cation (FA) +or HC(NH2)2 + ), ethylammonium cation (CH3CH2NH3) + ) or guanidinium cation (CH6N3) + B is a divalent cation. An example of a divalent cation is the lead cation (Pb). 2+ ) or tin cation (Sn) 2+ X is a monovalent anion. An example of a monovalent anion is the halide anion. The sites of A, B, and X can also be occupied by multiple ions.

[0111] Photoelectric conversion materials can also be, for example, lead-containing perovskite compounds.

[0112] The thickness of the photoelectric conversion layer 7 is, for example, 50 nm or more and 10 μm or less.

[0113] The photoelectric conversion layer 7 can be formed, for example, by solution-based coating, printing, or vapor deposition. The photoelectric conversion layer 7 can also be formed by dicing a perovskite-type compound.

[0114] The photoelectric conversion layer 7 may also primarily contain a perovskite-type compound represented by the formula ABX3. Here, "the photoelectric conversion layer 7 primarily contains a perovskite-type compound represented by the formula ABX3" means that the photoelectric conversion layer 7 contains at least 90% by mass of a perovskite-type compound represented by the formula ABX3. The photoelectric conversion layer 7 may also contain at least 95% by mass of a perovskite-type compound represented by the formula ABX3. The photoelectric conversion layer 7 may also be composed entirely of a perovskite-type compound represented by the formula ABX3. The photoelectric conversion layer 7 may contain a perovskite-type compound represented by the formula ABX3, or it may contain defects or impurities.

[0115] The photoelectric conversion layer 7 may further contain other compounds that are different from the perovskite-type compounds represented by the formula ABX3. Examples of such other compounds are compounds with a Ruddlesden-Popper type layered perovskite structure.

[0116] (Hole transport layer 8)

[0117] Hole transport layer 8 contains a hole transport material. The hole transport material is a material that transports holes. The hole transport material can be, for example, an organic semiconductor or an inorganic semiconductor.

[0118] The hole transport layer 8 may also contain organic semiconductors. The organic semiconductors form a good interface with the photoelectric conversion layer 7, suppressing interface defects generated during bonding. As a result, the photoelectric conversion element can have high photoelectric conversion efficiency and durability.

[0119] Examples of organic semiconductors include triphenylamine, triallylamine, phenylbenzidine, phenylenevinylene, tetrathiofulvalene, vinylnaphthalene, vinylcarbazole, thiophene, aniline, pyrrole, carbazole, tripterene, fluorene, azulene, pyrene, pentacene, dinaphthalene, acridine, or phthalocyanine.

[0120] Representative examples of organic semiconductors used as hole transport materials include 2,2',7,7'-tetratetra[N,N-di(p-methoxyphenyl)amino]-9,9'-spirodifluorene, poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (hereinafter also referred to as "PTAA"), poly(3-hexylthiophene-2,5-diyl), poly(3,4-ethylenedioxythiophene), or copper phthalocyanine. These organic semiconductors possess excellent hole transport properties, thus improving the photoelectric conversion efficiency of photoelectric conversion elements.

[0121] Organic semiconductors may also contain at least one selected from 2,2',7,7'-tetratetra[N,N-di(p-methoxyphenyl)amino]-9,9'-spirodifluorene and poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine].

[0122] The inorganic semiconductors used as hole transport materials are p-type semiconductors. Examples of inorganic semiconductors include Cu₂O, CuGaO₂, CuSCN, CuI, and NiO. x MoO x Carbon materials such as V2O5 or graphene oxide. Here, x > 0.

[0123] The hole transport layer 8 may also comprise multiple layers formed of mutually different materials. For example, multiple layers may be stacked in such a way that the ionization potential of the hole transport layer 8 is gradually reduced relative to the ionization potential of the photoelectric conversion layer 7. This improves the hole transport characteristics.

[0124] The thickness of the hole transport layer 8 can be greater than 1 nm and less than 1000 nm, or greater than 10 nm and less than 50 nm. This allows for the expression of sufficient hole transport characteristics. Consequently, the low resistance of the solar cell can be maintained, thereby achieving high photoelectric conversion efficiency.

[0125] The hole transport layer 8 can be formed, for example, by coating, printing, or vapor deposition. This is the same as the photoelectric conversion layer 7. Examples of coating methods include blade coating, rod coating, spray coating, dip coating, or spin coating. An example of printing methods is screen printing. The hole transport layer 8 can also be fabricated by mixing multiple materials, followed by pressure application or firing, etc. When the material of the hole transport layer 8 is an organic low-molecular-weight material or an inorganic semiconductor, the hole transport layer 8 can also be fabricated by vacuum vapor deposition.

[0126] To improve conductivity, hole transport layer 8 may contain not only hole transport material but also additives. Examples of additives include supporting electrolytes, solvents, or dopants. Supporting electrolytes and solvents stabilize the holes in hole transport layer 8. Dopants increase the number of holes in hole transport layer 8.

[0127] Examples of supporting electrolytes are ammonium salts, alkaline earth metal salts, or transition metal salts. Examples of ammonium salts include tetrabutylammonium perchlorate, tetraethylammonium hexafluorophosphate, imidazolium salts, or pyridinium salts. Examples of alkali metal salts include lithium perchlorate or potassium tetrafluoroborate. Examples of alkaline earth metal salts include calcium(II) bis(trifluoromethanesulfonyl)imide. Examples of transition metal salts include zinc(II) bis(trifluoromethanesulfonyl)imide or tris[4-tert-butyl-2-(1H-pyrazol-1-yl)pyridine]cobalt(III)tri(trifluoromethanesulfonyl)imide.

[0128] Examples of dopants are fluorinated aromatic boron compounds. An example of a fluorinated aromatic boron compound is tris(pentafluorophenyl)borane.

[0129] The solvent contained in hole transport layer 8 can also have excellent ionic conductivity. This solvent can be either an aqueous solvent or an organic solvent. To further stabilize the solute, the solvent contained in hole transport layer 8 can also be an organic solvent. Examples of organic solvents include heterocyclic compounds such as tert-butylpyridine, pyridine, and N-methylpyrrolidone.

[0130] Ionic liquids can also be used as solvents. They can be used alone or mixed with other solvents. Ionic liquids are preferred due to their low volatility and high flame retardancy.

[0131] Examples of ionic liquids are imidazolium, pyridine, alicyclic amine, aliphatic amine, or azo amine systems, such as 1-ethyl-3-methylimidazolium tetracyanoborate.

[0132] As an additive, the hole transport layer 8 may also contain at least one selected from tert-butylpyridine, calcium (II) bis(trifluoromethanesulfonyl)imide, zinc (II) bis(trifluoromethanesulfonyl)imide, tris[4-tert-butyl-2-(1H-pyrazol-1-yl)pyridine]cobalt (III), tris(trifluoromethanesulfonyl)imide, and tris(pentafluorophenyl)borane. This improves the hole transport characteristics of the hole transport layer 8, thereby enhancing the photoelectric conversion efficiency of the photoelectric conversion element.

[0133] (Electrode 2, 9)

[0134] The second electrode 9 is conductive.

[0135] When the photoelectric conversion element lacks the hole transport layer 8, the second electrode 9 blocks electrons from the photoelectric conversion layer 7. In this case, the second electrode 9 does not make ohmic contact with the photoelectric conversion layer 7. The blocking property refers to the property of allowing only holes generated in the photoelectric conversion layer 7 to pass through while preventing electrons from passing through. Materials with this property have a Fermi level lower than the conduction band level of the photoelectric conversion layer 7. The Fermi level of materials with this property can also be lower than the Fermi level of the photoelectric conversion layer 7. Specific materials include platinum, gold, or carbon materials such as graphene.

[0136] When the photoelectric conversion element has a hole transport layer 8, the second electrode 9 may not have the property of blocking electrons from the photoelectric conversion layer 7. In this case, the second electrode 9 can be made of a material that can form an ohmic contact with the photoelectric conversion layer 7. Thus, the second electrode 9 can be formed in a light-transmitting manner.

[0137] Of the first electrode 5 and the second electrode 9, the electrode on the side through which light is incident is preferably translucent. Therefore, one of the first electrode 5 and the second electrode 9 may also be opaque. That is to say, one of the first electrode 5 and the second electrode 9 may not be made of a translucent material, and may not have a pattern that includes an opening through which light passes.

[0138] (Porous layer 10)

[0139] The porous layer 10 can be formed on the electron transport layer 6, for example, by coating. When the photoelectric conversion element does not have an electron transport layer 6, it is formed on the first electrode 5.

[0140] The porous structure introduced through the porous layer 10 serves as the substrate for forming the photoelectric conversion layer 7. The porous layer 10 does not impede the light absorption of the photoelectric conversion layer 7 or the movement of electrons from the photoelectric conversion layer 7 to the electron transport layer 6.

[0141] The porous layer 10 contains porous material.

[0142] Porous materials can be formed, for example, by a series of insulating or semiconductor particles. Examples of insulating particles are alumina particles or silicon oxide particles. Examples of semiconductor particles are inorganic semiconductor particles. Examples of inorganic semiconductors are metal oxides, perovskite oxides of metallic elements, sulfides of metallic elements, or metal chalcogenides. Examples of metal oxides are oxides of Cd, Zn, In, Pb, Mo, W, Sb, Bi, Cu, Hg, Ti, Ag, Mn, Fe, V, Sn, Zr, Sr, Ga, Si, or Cr. For example, TiO2 is a metal oxide. Examples of perovskite oxides of metallic elements are SrTiO3 or CaTiO3. Examples of sulfides of metallic elements are CdS, ZnS, In2S3, PbS, Mo2S, WS2, Sb2S3, Bi2S3, ZnCdS2, or Cu2S. Examples of metal chalcogenides are CsSe, In2Se3, WSe2, HgS, PbSe, or CdTe.

[0143] The thickness of the porous layer 10 can be greater than or equal to 0.01 μm and less than 10 μm, or greater than or equal to 0.05 μm and less than 1 μm.

[0144] Regarding the surface roughness of the porous layer 10, the surface roughness coefficient, given as effective area / projected area, can be greater than 10 or greater than 100. The projected area refers to the area of ​​the shadow cast behind the object when it is illuminated from directly in front. The effective area is the actual surface area of ​​the object. The effective area can be calculated from the volume derived from the object's projected area and thickness, and from the specific surface area and bulk density of the materials constituting the object. Specific surface area can be measured, for example, using nitrogen adsorption.

[0145] The voids in the porous layer 10 connect one main surface of the porous layer 10 to the other main surface. That is, the voids in the porous layer 10 connect the main surface of the porous layer 10 that is in contact with the photoelectric conversion layer 7 to the main surface of the porous layer 10 that is in contact with the electron transport layer 6. Therefore, the material of the photoelectric conversion layer 7 can fill the voids in the porous layer 10 and reach the electron transport layer 6. Thus, even with the porous layer 10, the photoelectric conversion layer 7 and the electron transport layer 6 can accept and transfer electrons due to direct contact.

[0146] By providing a porous layer 10, the photoelectric conversion layer 7 can be easily formed. With the porous layer 10, the material of the photoelectric conversion layer 7 penetrates into the pores of the porous layer 10, making the porous layer 10 the support for the photoelectric conversion layer 7. Therefore, the material of the photoelectric conversion layer 7 is less likely to become incompatible or aggregate on the surface of the porous layer 10. Thus, the photoelectric conversion layer 7 can be easily formed as a uniform film. The photoelectric conversion layer 7 can be formed, for example, by the coating method, printing method, or vapor deposition method described above.

[0147] Light scattering occurs through the porous layer 10, which can further increase the optical path length of light passing through the photoelectric conversion layer 7. If the optical path length increases, an increase in the amount of electrons and holes generated in the photoelectric conversion layer 7 can be predicted.

[0148] (Middle layer 11)

[0149] Intermediate layer 11 contains fullerene (C 60 C 60 Derivatives or those with C 60 A self-organized monolayer (hereinafter also referred to as "C60SAM"). Electron collection can be effectively carried out through the intermediate layer 11, thus reducing the resistance loss when transferring electrons to the electron transport layer 6.

[0150] C 60 An example of a derivative is [6,6]-phenyl-C 61 methyl butyrate or [6,6]-phenyl-C 61 -Butyl butyrate. An example of C60SAM is 4-(1′,5′-dihydro-1′-methyl-2′H-[5,6]fullerene-C 60 -IH-[1,9-C]pyrrole-2′-yl)benzoic acid, (1,2-methylenefullerene C 60 )-61-carboxylic acid or C 60 Pyrrolidine tricarboxylic acid.

[0151] The intermediate layer 11 can be formed, for example, by solution-based coating, immersion, printing or vapor deposition.

[0152] Example

[0153] The present disclosure will now be described in more detail with reference to embodiments and comparative examples.

[0154] In the examples and comparative examples, perovskite solar cells were fabricated, and the initial characteristics, characteristics after light resistance testing, and characteristics after heat resistance testing of the solar cells were evaluated.

[0155] The configurations of the photoelectric conversion elements in the solar cells of Examples 1, 4, and 6, and Comparative Example 1, are as follows.

[0156] ●Substrate: Glass substrate (thickness: 0.7mm)

[0157] ●Electrode 1: Transparent electrode (Indium-Tin Composite Oxide Layer) (Thickness: 100nm)

[0158] ● Electron transport layer: Titanium oxide (TiO2) (thickness: 30nm)

[0159] ●Porous layer: A mixture of mesoporous titanium dioxide (TiO2) (thickness: 150 nm) and the material of the photoelectric conversion layer described below.

[0160] ● Photoelectric conversion layer: mainly containing HC(NH2)2PbI3 (thickness: 500nm)

[0161] ● Hole transport layer: A layer containing phenylethylamine iodide (manufactured by Great Cell Solar) / A layer mainly containing PTAA (with lithium bis[trifluoromethanesulfonyl]imide (manufactured by Sigma-Aldrich) and 4-tert-butylpyridine as additives) (thickness: 50 nm)

[0162] ●Second electrode: Au (thickness: 200nm)

[0163] The configurations of the photoelectric conversion elements in the solar cells of Examples 2, 3, 5 and 7 and Comparative Example 2 are as follows.

[0164] ●Substrate: Glass substrate (thickness: 0.7mm)

[0165] ●Electrode 1: Transparent electrode (Indium-Tin Composite Oxide Layer) (Thickness: 100nm)

[0166] ● Electron transport layer: Titanium oxide (TiO2) (thickness: 30nm)

[0167] ●Porous layer: Mesoporous titanium dioxide (TiO2)

[0168] ●Intermediate layer: 4-(1′,5′-dihydro-1′-methyl-2′H-[5,6]fullerene-C) 60 -IH-[1,9-C]pyrrole-2′-yl)benzoic acid (i.e., C60SAM) (manufactured by Sigma-Aldrich) (thickness: 50nm (thickness containing mesoporous titanium oxide)), and a material containing a photoelectric conversion layer in the pores.

[0169] ● Photoelectric conversion layer: mainly containing HC(NH2)2PbI3 (thickness: 500nm)

[0170] ● Hole transport layer: A layer containing n-butylammonium bromide (manufactured by Great Cell Solar) / A layer mainly containing PTAA (in which tris(pentafluorophenyl)borane (manufactured by Tokyo Chemical Industry) is contained as an additive)

[0171] ●Second electrode: Au (thickness: 200nm)

[0172] As described above, the photoelectric conversion element in the solar cells of Examples 1, 4, and 6, as well as Comparative Example 1, is... Figure 3The photoelectric conversion element shown is from the second configuration example. Furthermore, the photoelectric conversion elements in the solar cells of Examples 2, 3, 5, and 7, as well as Comparative Example 2, are... Figure 4 The photoelectric conversion element of the third configuration example shown.

[0173] <Fabrication of Photoelectric Conversion Components>

[0174] (Example 1)

[0175] First, a glass substrate with a thickness of 0.7 mm is prepared. This substrate serves as a support material in the solar cell of this disclosure.

[0176] An indium-tin composite oxide layer is formed on the substrate by sputtering. This forms the first electrode.

[0177] Next, a layer of titanium oxide is formed on the first electrode by sputtering. This forms an electron transport layer.

[0178] On the electron transport layer, 30NR-D (manufactured by Great Cell Solar) is spin-coated and then sintered at 500°C for 30 minutes, thereby forming a layer of titanium oxide with a mesoporous structure. In this way, a porous layer is formed.

[0179] Next, the substrate to which the porous layer is formed is immersed in a C60SAM solution for 30 minutes, and then removed. Here, the C60SAM solution is prepared by mixing tetrahydrofuran (manufactured by Fujifilm and Koden Chemical) and ethanol (manufactured by Fujifilm and Koden Chemical) in a 1:1 volume ratio, to achieve a concentration of 1×10⁻⁶. -5 The substrate was obtained by adding C60SAM at a concentration of mol / L. After thoroughly rinsing the substrate with an ethanol solution, it was annealed at 100°C for 30 minutes on a hot plate. After annealing, it was allowed to cool naturally to room temperature, thus obtaining a substrate modified with C60SAM. This forms the intermediate layer.

[0180] Next, a photoelectric conversion layer containing a perovskite-type compound is formed by spin-coating a raw material solution of the photoelectric conversion material. This raw material solution contains 0.92 mol / L lead(II) iodide (manufactured by Tokyo Chemical Industry), 0.17 mol / L lead(II) bromide (manufactured by Tokyo Chemical Industry), 0.83 mol / L formamidinium iodide (manufactured by Great Cell Solar), 0.17 mol / L methylammonium bromide (manufactured by Great Cell Solar), 0.05 mol / L cesium iodide (manufactured by Iwatani Corporation), and 0.05 mol / L rubidium iodide (manufactured by Iwatani Corporation). The solvent for this solution is a mixture of dimethyl sulfoxide (DMSO) (manufactured by Acros) and N,N-dimethylformamide (DMF) (manufactured by Acros). The mixing ratio (DMSO:DMF) of dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF) in this raw material solution is 1:4 by volume.

[0181] Next, a hole transport layer is formed on the photoelectric conversion layer. A 1 g / L solution of isopropanol (manufactured by Acros Organics) containing phenylethyl iodide (manufactured by Greatcell Solar) is spin-coated onto the photoelectric conversion layer. This forms a layer containing phenylethyl iodide. Then, a solution containing PTAA is spin-coated to form a layer primarily containing PTAA. The solvent for the PTAA-containing solution is toluene (manufactured by Acros). The PTAA-containing solution contains 10 g / L PTAA, lithium bis[trifluoromethanesulfonyl]imide, and 4-tert-butylpyridine.

[0182] Next, an Au film is deposited on the hole transport layer by vacuum evaporation, thereby forming the second electrode 9. As described above, a photoelectric conversion element is obtained on the supporting material, i.e., the glass substrate.

[0183] Next, the photoelectric conversion element of Example 1 was sealed in a glove box where the water vapor concentration was adjusted to 100 ppm. Here, the oxygen concentration inside the glove box was 2 ppm or less. The photoelectric conversion element of Example 1 was sealed using a UV-curable resin, a cover glass, and a glass substrate. That is, the photoelectric conversion element comprising a first electrode, an electron transport layer, a porous layer, a photoelectric conversion layer, a hole transport layer, and a second electrode was sealed using a UV-curable resin, a cover glass, and a glass substrate. As described above, the solar cell of Example 1 was obtained. In the photoelectric conversion element of Example 1, the water vapor concentration in the sealed space was 100 ppm, and the oxygen concentration was 2 ppm or less.

[0184] (Example 2)

[0185] Compared to Example 1, the solar cell was fabricated using the same method as in Example 1, except that the materials used in the formation of the intermediate layer and the fabrication of the hole transport layer were different. The formation of the intermediate layer and the materials of the hole transport layer are described below.

[0186] The intermediate layer is formed according to the following steps. The substrate to which the porous layer is formed is immersed in a C60SAM solution for 30 minutes using the same method as in Example 1, and then removed. Here, the C60SAM solution can be prepared by mixing tetrahydrofuran (manufactured by Fujifilm and Koden Chemical) and ethanol (manufactured by Fujifilm and Koden Chemical) in a 1:1 volume ratio to form a mixed solution, and then adding C60SAM to this mixed solution to achieve a concentration of 1×10⁻⁶. -5 The concentration was obtained by mol / L. After thoroughly rinsing the removed substrate with an ethanol solution, it was annealed at 100°C for 30 minutes using a hot plate. After annealing, it was allowed to cool naturally to room temperature to obtain a substrate modified with C60SAM. This forms the intermediate layer.

[0187] The solution used to form the hole transport layer containing n-butylammonium bromide was the same as that used in Example 1, but n-butylammonium bromide (manufactured by Great Cell Solar) was used instead of phenylethyl iodide. Furthermore, the solution used to form the layer mainly containing PTAA was a solution of tris(pentafluorophenyl)borane used instead of lithium bis[trifluoromethanesulfonyl]imide and 4-tert-butylpyridine in the PTAA-containing solution used in Example 1. Otherwise, the hole transport layer was formed in the same manner as in Example 1.

[0188] As described above, the solar cell of Example 2 was obtained.

[0189] (Example 3)

[0190] In Example 3, the photoelectric conversion element was sealed inside a glove box where the water vapor concentration was adjusted to 500 ppm. Otherwise, the solar cell of Example 3 was obtained in the same manner as in Example 2.

[0191] (Example 4)

[0192] In Example 4, the photoelectric conversion element was sealed inside a glove box where the water vapor concentration was adjusted to 1000 ppm. Otherwise, the solar cell of Example 4 was obtained in the same manner as in Example 1.

[0193] (Example 5)

[0194] In Example 5, the photoelectric conversion element was sealed inside a glove box where the water vapor concentration was adjusted to 1000 ppm. Otherwise, the solar cell of Example 5 was obtained in the same manner as in Example 2.

[0195] (Example 6)

[0196] In Example 6, the photoelectric conversion element was sealed inside a glove box where the water vapor concentration was adjusted to 5000 ppm. Otherwise, the solar cell of Example 6 was obtained in the same manner as in Example 1.

[0197] (Example 7)

[0198] In Example 7, the photoelectric conversion element was sealed inside a glove box where the water vapor concentration was adjusted to 5000 ppm. Otherwise, the solar cell of Example 7 was obtained in the same manner as in Example 2.

[0199] (Comparative Example 1)

[0200] In Comparative Example 1, the photoelectric conversion element was sealed inside a glove box where the water vapor concentration was adjusted to 10 ppm. Otherwise, the solar cell of Comparative Example 1 was obtained in the same manner as in Example 1.

[0201] (Comparative Example 2)

[0202] In Comparative Example 2, the photoelectric conversion element was sealed inside a glove box where the water vapor concentration was adjusted to 10 ppm. Otherwise, the solar cell of Comparative Example 2 was obtained in the same manner as in Example 2.

[0203] <Determination of photoelectric conversion efficiency>

[0204] The photoelectric conversion efficiency of the solar cells of Examples 1-7 and Comparative Examples 1-2 was measured.

[0205] The photoelectric conversion efficiency of solar cells was measured using an electrochemical analyzer (ALS440B, BAS manufacturer) and a xenon light source (BPS X300BA, spectrometer manufacturer) for initial conditions, after light resistance testing, and after heat resistance testing. Before measurement, the light intensity was calibrated to 1 Sun (100 mW / cm²) using a silicon photodiode. 2 The voltage scan rate was set to 100 mV / s, and the current-voltage characteristics were measured. No prior adjustments were made before the measurement, such as light irradiation or prolonged application of a positive bias voltage. To fix the effective area and reduce the influence of scattered light, an opening of 0.1 cm was used. 2 The state of the solar cell was concealed by a black mask, and light was irradiated from the mask / substrate side. The power output under the condition of maximum current and voltage was taken as the photoelectric conversion efficiency. The photoelectric conversion efficiency was measured at room temperature and in dry air (<2% RH).

[0206] <Lightfastness test>

[0207] Light-resistance tests were conducted on the solar cells of Examples 1-7 and Comparative Examples 1-2. During the light-resistance tests, the voltage and current of the solar cells were maintained near their operating point where the power reached its maximum, and the power values ​​were measured. The substrate temperature was maintained at 50°C, and light equivalent to 1 Sun was irradiated from the substrate side for 90 hours. After the light-resistance tests, the photoelectric conversion efficiency of the solar cells was determined using the methods described above.

[0208] <Heat Resistance Test>

[0209] Heat resistance tests were conducted on the solar cells of Examples 1-7 and Comparative Examples 1-2. The solar cells were maintained at 85°C for 190 hours in a constant temperature bath. After the heat resistance test, the photoelectric conversion efficiency of the solar cells was measured using the method described above.

[0210] Table 1 shows the experimental results above, namely the measurement results of the photoelectric conversion efficiency of the solar cells in the initial state, after the light resistance test, and after the heat resistance test. In the table, regarding the additives contained in the raw material solution of the hole transport layer, lithium bis[trifluoromethanesulfonyl]imide is recorded as "LiTFSI", and tris(pentafluorophenyl)borane is recorded as "TPFPB". In addition, in order to evaluate the efficiency difference caused by water vapor concentration for each additive, Table 1 shows the efficiency degradation rate of each additive based on the maximum efficiency. The efficiency degradation rate of each additive based on the maximum efficiency is recorded in the table as "conversion efficiency degradation rate".

[0211] Table 1

[0212]

[0213] Regarding the efficiency of each additive after lightfastness and heatfastness tests, in order to compare the effect of water vapor concentration on durability, the standardized photoelectric conversion efficiency was determined based on the photoelectric conversion efficiency at the water vapor concentration showing the maximum efficiency after the test.

[0214] Figure 5 This is a graph showing the dependence of the normalized photoelectric conversion efficiency of the solar cells of Examples 1, 4, 6, and Comparative Example 1 on water vapor concentration. In other words, Figure 5 This is a graph showing the dependence of the normalized photoelectric conversion efficiency on water vapor concentration when the additive in the hole transport layer is LiTFSI.

[0215] Figure 6 This is a graph showing the dependence of the normalized photoelectric conversion efficiency of the solar cells of Examples 1, 4, 6, and Comparative Example 1 on the amount of water vapor. In other words, Figure 6 This is a graph showing the dependence of the normalized photoelectric conversion efficiency on the amount of water vapor when the additive in the hole transport layer is LiTFSI. Figure 6Will Figure 5 The horizontal axis is converted from the water vapor concentration in the sealed space to the value obtained by dividing the amount of water vapor by the surface area of ​​the sealed space facing the photoelectric conversion element.

[0216] Figure 7 This is a graph showing the dependence of the normalized photoelectric conversion efficiency of the solar cells of Examples 2, 3, 5, 7, and Comparative Example 2 on water vapor concentration. In other words, Figure 7 This is a graph showing the dependence of the normalized photoelectric conversion efficiency on water vapor concentration when the additive in the hole transport layer is TFPB.

[0217] Figure 8 This is a graph showing the dependence of the normalized photoelectric conversion efficiency of the solar cells of Examples 2, 3, 5, 7, and Comparative Example 2 on the amount of water vapor. In other words, Figure 8 The dependence of the normalized photoelectric conversion efficiency on the amount of water vapor is shown when the additive in the hole transport layer is LiTFSI. Figure 8 Will Figure 7 The horizontal axis is converted from the water vapor concentration in the sealed space to the value obtained by dividing the amount of water vapor by the surface area of ​​the face of the photoelectric conversion element facing the sealed space.

[0218] The sealed space volume of the solar cells in the embodiments and comparative examples is approximately 1.4 × 10⁻⁶. -7 m 3 The surface area of ​​the photoelectric conversion element facing the sealed space is 2.6 × 10⁻⁶. -4 m 2 .

[0219] <The effect of water vapor concentration on the initial characteristics of solar cells>

[0220] As shown in Table 1, the initial photoelectric conversion efficiency showed no significant difference when the water vapor concentration in the sealed space was below 5000 ppm, and remained stable without light irradiation or heating.

[0221] <The effect of water vapor concentration on the properties of solar cells after lightfastness testing>

[0222] As shown in Table 1, Figure 5 and Figure 7 As shown, the photoelectric conversion efficiency after the lightfastness test is considered good when the water vapor concentration in the sealed space is between 100 ppm and 5000 ppm. On the other hand, the decrease in photoelectric conversion efficiency is greater in the low water vapor concentration range of 10 ppm and when the additive is lithium bis[trifluoromethanesulfonyl]imide (LiTFSI). Figure 5The curves suggest that in the water vapor concentration range exceeding 5000 ppm, the photoelectric conversion efficiency further decreases from that at 5000 ppm. This can be attributed to the fact that when the water vapor concentration exceeds 5000 ppm, decomposition products (e.g., metal iodides) of the perovskite compound are generated in large quantities on the surface and / or grain boundaries due to deterioration induced by excess moisture, hindering carrier movement. Conversely, when the water vapor concentration is below 5000 ppm, the aforementioned decomposition products contribute to the sealing of defects within the perovskite compound, thus suppressing the photodeterioration induced by defects in the photoelectric conversion material and thereby inhibiting the decrease in photoelectric conversion efficiency. However, when the water vapor concentration is below 10 ppm, defects under light irradiation cannot be sufficiently sealed, resulting in decreased conductivity of the PTAA and reduced hole transport efficiency. This, in turn, leads to carrier recombination based on defect energy levels, degrading the characteristics of the solar cell. Furthermore, the efficiency degradation rate increases when lithium bis[trifluoromethanesulfonyl]imide (LiTFSI) is used as the additive for PTAA. This can be attributed to the fact that, compared to the use of the stronger acceptor molecule TFPB as an additive, the lower doping concentration of LiTFSI leads to a significant increase in the resistivity of PTAA due to the low water vapor concentration, thus amplifying the impact of increased recombination caused by the degradation of perovskite compounds.

[0223] <The effect of water vapor concentration on the characteristics of solar cells after heat resistance testing>

[0224] As shown in Table 1, Figure 5 and Figure 7As shown, the photoelectric conversion efficiency after the heat resistance test is optimal when the water vapor concentration in the sealed space is between 100 ppm and 5000 ppm. On the other hand, the photoelectric conversion efficiency decreases significantly in the low water vapor concentration range of 10 ppm. The rationale for the existence of the optimal water vapor concentration range is the same in both the light resistance and heat resistance tests. However, unlike the light resistance test, the photoelectric conversion efficiency decreases significantly in the heat resistance test when tris(pentafluorophenyl)borane is used as the additive. This can be attributed to the reduced doping ability of tris(pentafluorophenyl)borane under heating, which makes the difference in the high conductivity effect of moisture on PTAA more pronounced. Therefore, by increasing the energy of the light irradiated in the light resistance test and the heating temperature in the heat resistance test, new defects can be generated based on the activation energy of various defects. Furthermore, at low water vapor concentrations, the decreased conductivity of PTAA reduces hole extraction efficiency, thereby increasing the probability of defect recombination and decreasing the photoelectric conversion efficiency. However, since the conditions for the light resistance test and heat resistance test in this embodiment are set based on the assumption of actual outdoor operation, the optimal water vapor concentration range found through the embodiment remains unchanged in order to improve the durability of the solar cell.

[0225] The above results confirm that when the water vapor concentration in the sealed space is between 100 ppm and 5000 ppm, the light stability and thermal stability of the solar cell disclosed herein can be balanced.

[0226] Industrial availability

[0227] This disclosure can significantly improve the durability of solar cells, and its industrial applicability is very high.

[0228] Symbol explanation:

[0229] 1 Photoelectric conversion element

[0230] 2 Supporting materials

[0231] 3. Sealing materials

[0232] 4 substrates

[0233] 5. Electrode 1

[0234] 6 Electron transport layer

[0235] 7 Photoelectric conversion layer

[0236] 8 Hole transport layer

[0237] 9. Second electrode

[0238] 10 porous layers

[0239] 11 intermediate layers

[0240] 100, 200, 300 photoelectric conversion elements

[0241] 1000 solar cells

Claims

1. A solar cell, comprising: Supporting materials Photoelectric conversion elements, and Sealing material; The photoelectric conversion element is disposed inside a sealed space that is sealed by the support material and the sealing material. The photoelectric conversion element sequentially comprises a first electrode, a photoelectric conversion layer, and a second electrode. The photoelectric conversion layer contains a perovskite-type compound. The oxygen concentration in the sealed space is less than 10 ppm by volume. The water vapor concentration in the sealed space is above 100 ppm and below 5000 ppm by volume fraction.

2. The solar cell according to claim 1, wherein, The water vapor concentration in the sealed space is above 100 ppm and below 1000 ppm by volume.

3. The solar cell according to claim 1 or 2, wherein, The partial pressure of water vapor in the sealed space is 1×10⁻⁶. -4 above atm and 5×10 -3 Below atm.

4. The solar cell according to claim 1 or 2, wherein, The perovskite-type compound contains lead.

5. The solar cell according to claim 1 or 2, wherein, The photoelectric conversion element further includes a hole transport layer disposed between the photoelectric conversion layer and the second electrode. The hole transport layer contains organic semiconductors.

6. The solar cell according to claim 5, wherein, The organic semiconductor contains at least one selected from 2,2',7,7'-tetratetra[N,N-di(p-methoxyphenyl)amino]-9,9'-spirodifluorene and poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine].

7. The solar cell according to claim 5, wherein, The hole transport layer further contains additives.

8. The solar cell according to claim 7, wherein, The additive contains at least one selected from tert-butylpyridine, calcium (II) bis(trifluoromethanesulfonyl)imide, zinc (II) bis(trifluoromethanesulfonyl)imide, tri[4-tert-butyl-2-(1H-pyrazol-1-yl)pyridine]cobalt (III), tri(trifluoromethanesulfonyl)imide, and tri(pentafluorophenyl)borane.

9. A solar cell comprising: Supporting materials Photoelectric conversion elements, and Sealing material; The photoelectric conversion element is disposed inside a sealed space that is sealed by the support material and the sealing material. The photoelectric conversion element sequentially comprises a first electrode, a photoelectric conversion layer, and a second electrode. The photoelectric conversion layer contains a perovskite-type compound. The oxygen concentration in the sealed space is less than 10 ppm by volume. The value obtained by dividing the amount of water vapor in the sealed space by the surface area of ​​the face of the photoelectric conversion element facing the sealed space is 2.3 × 10⁻⁶. -6 mol / m 2 Above and 1.2×10 -4 mol / m 2 the following.

10. The solar cell according to claim 9, wherein, The value obtained by dividing the amount of water vapor in the sealed space by the surface area of ​​the face of the photoelectric conversion element facing the sealed space is 2.3 × 10⁻⁶. -6 mol / m 2 Above and 2.3×10 -5 mol / m 2 the following.

11. The solar cell according to claim 9 or 10, wherein, The partial pressure of water vapor in the sealed space is 1×10⁻⁶. -4 above atm and 5×10 -3 Below atm.

12. The solar cell according to claim 9 or 10, wherein, The perovskite-type compound contains lead.

13. The solar cell according to claim 9 or 10, wherein, The photoelectric conversion element further includes a hole transport layer disposed between the photoelectric conversion layer and the second electrode. The hole transport layer contains organic semiconductors.

14. The solar cell according to claim 13, wherein, The organic semiconductor contains at least one selected from 2,2',7,7'-tetratetra[N,N-di(p-methoxyphenyl)amino]-9,9'-spirodifluorene and poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine].

15. The solar cell according to claim 13, wherein, The hole transport layer further contains additives.

16. The solar cell according to claim 15, wherein, The additive contains at least one selected from tert-butylpyridine, calcium (II) bis(trifluoromethanesulfonyl)imide, zinc (II) bis(trifluoromethanesulfonyl)imide, tri[4-tert-butyl-2-(1H-pyrazol-1-yl)pyridine]cobalt (III), tri(trifluoromethanesulfonyl)imide, and tri(pentafluorophenyl)borane.

17. A method for manufacturing a solar cell, comprising the following steps: A photoelectric conversion element comprising a first electrode, a photoelectric conversion layer containing a perovskite-type compound, and a second electrode is sealed in an atmosphere having an oxygen concentration of less than 10 ppm by volume and a water vapor concentration of more than 100 ppm and less than 5000 ppm by volume.

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