Solar battery

Abstract

To provide a solar battery that has practical output and in which the yield has been improved.SOLUTION: A solar battery 200 according to the present disclosure includes a first electrode 20, a short-circuit prevention layer 80, an electron transport layer 30, a light absorbing layer 40, and a second electrode 60, and the short-circuit prevention layer 80 is disposed between the first electrode 20 and the electron transport layer 30, the band gap of the short-circuit prevention layer 80 is equal to or greater than 3.9 eV and equal to or less than 15.5 eV, and the thickness of the short-circuit prevention layer 80 is equal to or greater than 0.4 nm and less than 3.0 nm.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to solar cells. [Background technology]

[0002] In recent years, research and development of perovskite solar cells using perovskite crystals represented by the composition formula ABX3 (A is a monovalent cation, B is a divalent cation, and X is a halogen anion) and similar structures (hereinafter referred to as "perovskite compounds") as photoelectric conversion materials has been progressing. Various efforts have been made to improve the photoelectric conversion efficiency and durability of perovskite solar cells. Generally, perovskite solar cells have a light absorption layer disposed between a first electrode and a second electrode, and if the first electrode and the second electrode are short-circuited, the solar cell will not operate.

[0003] Patent Document 1 discloses a method for preventing short circuits between a first electrode (rear electrode in Patent Document 1) and a second electrode (upper electrode in Patent Document 1) caused by through holes in a light absorbing layer (undoped gallium nitride layer in Patent Document 1) between the first electrode and the second electrode, and improving the yield. In the structure disclosed in Patent Document 1, an aluminum layer is provided between the light absorbing layer and the second electrode, and the aluminum layer in the through holes is selectively oxidized by thermal annealing using lamp heating from the rear side, thereby providing insulation. It has been shown that this insulation process prevents short circuits in the through holes and improves the yield.

[0004] Patent Document 2 discloses a structure in which a first buffer layer and a second buffer layer are provided between a light absorbing layer (active layer in Patent Document 2) and a second electrode, and the second buffer layer is in contact with the first buffer layer, the light absorbing layer, and the second electrode, as a means for reducing short circuits or leaks and increasing yields while maintaining high performance of a photoelectric conversion element. As an example, a case is given in which the first buffer layer is a hole transport layer and the second buffer layer is molybdenum oxide, and it is shown that the introduction of molybdenum oxide increases the parallel resistance, which is an index of current leakage. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2010-267940 A [Patent Document 2] Patent Publication No. 2021-77788 Summary of the Invention [Problem to be solved by the invention]

[0006] The present disclosure provides a solar cell having a practical output and improved yield. [Means for solving the problem]

[0007] The solar cell of the present disclosure comprises: A first electrode, a short-circuit prevention layer, an electron transport layer, a light absorbing layer, and a second electrode are provided. the short circuit prevention layer is disposed between the first electrode and the electron transport layer; The band gap of the short circuit prevention layer is 3.9 eV or more and 15.5 eV or less, The thickness of the short circuit prevention layer is not less than 0.4 nm and less than 3.0 nm. Effect of the Invention

[0008] The present disclosure provides a solar cell having practical output and improved yield. [Brief description of the drawings]

[0009] [Figure 1A] FIG. 1A is a schematic cross-sectional view showing a first example of the structure of a conventional solar cell and a short-circuit location. [Figure 1B] FIG. 1B is a schematic cross-sectional view showing a second example of the structure of a conventional solar cell and a short-circuit location. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing a first example of a solar cell according to the present embodiment. [Diagram 3] FIG. 3 is a schematic cross-sectional view showing a second example of a solar cell according to the present embodiment. [Figure 4] FIG. 4 is a schematic cross-sectional view showing a third example of a solar cell according to the present embodiment. [Diagram 5] FIG. 5 is a schematic cross-sectional view showing a fourth example of a solar cell according to the present embodiment. [Figure 6A] FIG. 6A is a schematic cross-sectional view showing an example of an integrated structure that is a fifth example of the solar cell according to this embodiment. [Figure 6B] FIG. 6B is a schematic cross-sectional view showing another example of an integrated structure which is the fifth example of the solar cell according to this embodiment. [Figure 6C] FIG. 6C is a schematic cross-sectional view showing another example of an integrated structure which is the fifth example of the solar cell according to this embodiment. [Figure 6D] FIG. 6D is a schematic cross-sectional view showing another example of an integrated structure which is the fifth example of the solar cell according to this embodiment. [Figure 6E] FIG. 6E is a schematic cross-sectional view showing another example of an integrated structure, which is the fifth example of the solar cell according to this embodiment. [Figure 6F] FIG. 6F is a schematic cross-sectional view showing another example of an integrated structure which is the fifth example of the solar cell according to this embodiment. [Figure 7] FIG. 7 is a diagram showing the dependency of yield and output on the thickness of the short circuit prevention layer in Examples 1 to 17 and Comparative Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] <Knowledge that formed the basis of this disclosure> As the size of a perovskite solar cell increases, the number of pinholes caused by particles that may occur during the manufacturing process increases, causing a short circuit between the first electrode and the second electrode. In addition, a carrier transport layer (i.e., an electron transport layer or a hole transport layer) is disposed between the first electrode and the light absorbing layer, or between the second electrode and the light absorbing layer, in order to improve the efficiency of electron or hole extraction, and the perovskite solar cell has a structure in which these layers are stacked in order. However, if the upper layer penetrates through grain boundary defects or voids in the underlayer, or if there are uncovered or extremely thin parts due to variations in the film thickness within the surface, it is not possible to completely prevent leakage even if the generation of pinholes due to particle adhesion is suppressed as much as possible. Leakage causes a decrease in yield and power generation characteristics, and the impact is particularly noticeable when the solar cell is operated at low illuminance.

[0011] FIG. 1A is a schematic cross-sectional view showing a first example of the structure of a conventional solar cell and a short-circuited portion. FIG. 1B is a schematic cross-sectional view showing a second example of the structure of a conventional solar cell and a short-circuited portion. For example, as shown in FIG. 1A, in a solar cell 100A in which the electron transport layer 3 formed on the first electrode 2 has a porous structure, the light absorbing layer 4 formed on the electron transport layer 3 contacts the first electrode 2 through the short-circuited portion 7. Also, as shown in FIG. 1B, in a solar cell 100B in which the electron transport layer is composed of a dense layer 3a and a porous layer 3b and the dense layer 3a has a pinhole, the light absorbing layer 4 formed on the electron transport layer also contacts the first electrode 2 through the short-circuited portion 7. When the light absorbing layer 4 is made of a polycrystalline material and grain boundary defects or voids exist, the hole transport layer 5 formed on the light absorbing layer 4 penetrates into the grain boundaries or voids in the light absorbing layer 4 and reaches the first electrode 2. As a result, a leak occurs between the first electrode 2 and the hole transport layer 5. There has been a problem that the short circuit or leakage as described above reduces the yield and output of perovskite solar cells, especially when they are operated under low illumination conditions.

[0012] In Patent Document 1, the short-circuited portion is insulated by selectively oxidizing the aluminum layer through rapid thermal annealing (at a high temperature of 500°C) using lamp heating. However, such high-temperature treatment decomposes perovskite materials and other organic materials, making it difficult to apply to all solar cells, and particularly unsuitable for application to perovskite solar cells.

[0013] In Patent Document 2, leakage is reduced by disposing molybdenum oxide between the hole transport layer and the second electrode, but since the band gap of typical molybdenum oxide is narrow at 3.4 eV, it cannot be said that the material has sufficient function of preventing leakage, as shown in the comparative example described later. Also, as described above, depending on the formation method, the hole transport layer may contact the first electrode through grain boundaries or voids in the light absorption layer, so leakage cannot be completely suppressed.

[0014] Therefore, a structure that can better suppress short circuits and leakage in solar cells is needed.

[0015] <Embodiment> Solar cells according to embodiments of the present disclosure will now be described in detail, with reference to the drawings, in which five examples of solar cell structures (first to fifth examples) and methods for manufacturing the same will be described.

[0016] The solar cell according to this embodiment includes a first electrode, a short-circuit prevention layer, an electron transport layer, a light absorbing layer, and a second electrode. The short-circuit prevention layer is disposed between the first electrode and the electron transport layer. The band gap of the short-circuit prevention layer is 3.9 eV or more and 15.5 eV or less. The thickness of the short-circuit prevention layer is 0.4 nm or more and less than 3.0 nm.

[0017] Fig. 2 is a schematic cross-sectional view showing a first example of a solar cell according to the present embodiment. The solar cell 200 includes a substrate 10, a first electrode 20, a short-circuit prevention layer 80, an electron transport layer 30, a light absorbing layer 40, and a second electrode 60, in this order. As shown in Fig. 2, in the solar cell 200, the short-circuit prevention layer 80 is disposed between the first electrode 20 and the electron transport layer 30. Here, in Fig. 2, short-circuit points as shown in Figs. 1A and 1B are omitted. The solar cell 200 does not need to have a substrate 10.

[0018] When the solar cell 200 is irradiated with light, the light absorbing layer 40 absorbs the light and generates excited electrons and holes. The excited electrons pass through the electron transport layer 30 and move to the first electrode 20. Meanwhile, the holes generated in the light absorbing layer 40 move to the second electrode 60. This allows the solar cell 400 to extract a current from the first electrode 20, which serves as a negative electrode, and the second electrode 60, which serves as a positive electrode.

[0019] The short-circuit prevention layer 80 has a sufficiently wide band gap and therefore has high insulating properties. In addition, the short-circuit prevention layer 80 has an appropriate thickness, so that it suppresses the occurrence of leakage and does not inhibit electron transport. In addition, by disposing the short-circuit prevention layer 80 between the first electrode 20 and the electron transport layer 30, electrons accelerated by the built-in electric field generated between the electron transport layer 30 and the light absorption layer 40 can tunnel through the short-circuit prevention layer 80. As a result, the short-circuit prevention layer 80 can suppress the occurrence of short circuits and leakage while having electron transport properties, and the solar cell has a practical output and improves the yield.

[0020] In the solar cell 200, even if the electron transport layer 30 has a porous structure or has pinholes, the short-circuit prevention layer 80 prevents the first electrode 20 from contacting the light absorbing layer 40, so that the second electrode 60 does not contact the first electrode 20 through the gaps in the light absorbing layer 40 and the electron transport layer 30. In addition, even if there is a portion where the light absorbing layer 40 does not exist due to the variation in the in-plane film thickness, or even if there is an extremely thin portion in the light absorbing layer 40, the short-circuit prevention layer 80 covering the first electrode 20 prevents the second electrode 60 from contacting the first electrode 20 through the gaps in the electron transport layer 30. Therefore, in the solar cell according to this embodiment, short circuits and leaks are reduced, so that the yield can be significantly improved while maintaining a practical output. The solar cell according to this embodiment has high output even when operated at low illuminance, and can improve the yield.

[0021] At least a part of the light absorbing layer 40 may be in contact with the short-circuit prevention layer 80. For example, when the electron transport layer 30 has a porous structure or has pinholes, the light absorbing layer 40 may be in contact with the short-circuit prevention layer 80. Even in such a case, in the solar cell according to this embodiment, the short-circuit prevention layer 80 is provided, thereby reducing short circuits and leakage, and thus the yield can be significantly improved while maintaining a practical output. Therefore, for example, a coating film produced by coating, which is generally difficult to form into a dense film, can be applied to the electron transport layer.

[0022] The solar cell according to the first embodiment may further include a hole transport layer. The hole transport layer is disposed between the light absorbing layer and the second electrode. FIG. 3 is a schematic cross-sectional view showing a second example of the solar cell according to the present embodiment. The solar cell 300 shown in FIG. 3 includes a substrate 10, a first electrode 20, a short circuit prevention layer 80, an electron transport layer 30, a light absorbing layer 40, a hole transport layer 50, and a second electrode 60 in this order. The solar cell 300 may not have a substrate 10.

[0023] When the solar cell 300 is irradiated with light, the light absorbing layer 40 absorbs the light and generates excited electrons and holes. The excited electrons move to the first electrode 20 through the electron transport layer 30. Meanwhile, the holes generated in the light absorbing layer 40 move to the second electrode 60 through the hole transport layer 50. This allows the solar cell 300 to extract current from the first electrode 20 as the negative electrode and the second electrode 60 as the positive electrode. Therefore, by further providing the hole transport layer 50 to the solar cell, carriers can be efficiently extracted to the second electrode 60, thereby further improving the output.

[0024] At least a part of the hole transport layer 50 may be in contact with the short-circuit prevention layer 80. For example, when the electron transport layer 30 has a porous structure or has a pinhole, the hole transport layer 50 may be in contact with the short-circuit prevention layer 80 through the gap in the light absorption layer 40 and the electron transport layer 30. Even in such a case, in the solar cell according to this embodiment, the short-circuit prevention layer 80 is provided, so that the first electrode 20 and the hole transport layer 50 do not come into contact with each other. Therefore, in the solar cell according to this embodiment, even when the electron transport layer 30 has a porous structure or has a pinhole, short circuits and leaks can be reduced, so that the yield can be significantly improved while maintaining a practical output. Therefore, for example, a coating film prepared by coating, which is generally difficult to form into a dense film, can be applied to the electron transport layer 30.

[0025] At least a part of the second electrode 60 may be in contact with the short-circuit prevention layer 80. For example, when the electron transport layer 30 has a porous structure or has pinholes, and when there is a portion where the light absorption layer 40 and the hole transport layer 50 are not present, or when there are extremely thin portions in the light absorption layer 40 and the hole transport layer 50, the second electrode 60 may be in contact with the short-circuit prevention layer 80. Even in such a case, in the solar cell according to this embodiment, the short-circuit prevention layer 80 is provided, so that the first electrode 20 and the second electrode 60 do not come into contact with each other. Therefore, in the solar cell according to this embodiment, even when the electron transport layer 30 has a porous structure or has pinholes, short circuits and leaks can be reduced, so that the yield can be significantly improved while maintaining a practical output. Therefore, for example, a coating film prepared by coating, which is generally difficult to form into a dense film, can be applied to the electron transport layer 30.

[0026] The solar cell 300 can be produced, for example, by the following method.

[0027] First, the first electrode 20 is formed on the surface of the substrate 10 by chemical vapor deposition, sputtering, or the like. Next, the short-circuit prevention layer 80 is formed on the first electrode 20 by chemical vapor deposition, sputtering, solution coating, chemical vapor deposition, atomic layer deposition, or the like. Next, the electron transport layer 30 is formed on the short-circuit prevention layer 80 by chemical vapor deposition, sputtering, solution coating, or the like. Next, the light absorption layer 40 is formed on the electron transport layer 30 by sputtering, solution coating, or a combination of these. For example, a perovskite compound may be cut to a predetermined thickness to form the light absorption layer 40, which is then placed on the electron transport layer 30. Next, the hole transport layer 50 is formed on the light absorption layer 40 by chemical vapor deposition, sputtering, solution coating, or the like. Next, the second electrode 60 is formed on the hole transport layer 50 by chemical vapor deposition, sputtering, or the like. In this manner, the solar cell 300 can be obtained. Moreover, the solar cell 200 can be produced by forming the second electrode 60 on the light absorbing layer 40 without forming the hole transport layer 50.

[0028] In the solar cell of the present disclosure, the electron transport layer 30 may be formed on the short circuit prevention layer 80 by a solution coating method of a nanoparticle dispersion liquid or the like. In this case, the electron transport layer 30 has a porous structure. Fig. 4 is a schematic cross-sectional view showing a third example of a solar cell according to this embodiment. In the solar cell 400 shown in Fig. 4, the electron transport layer 30 has a porous structure containing nanoparticles.

[0029] The electron transport layer 30 may be formed by stacking two or more layers. Fig. 5 is a schematic cross-sectional view showing a fourth example of a solar cell according to the present embodiment. In the solar cell 500 shown in Fig. 5, the electron transport layer 30 includes a first layer 31 and a second layer 32.

[0030] In the solar cell of the present disclosure, the first layer 31 of the electron transport layer may be formed on the short circuit prevention layer 80 by chemical vapor deposition, sputtering, solution coating, or the like, and the second layer 32 of the electron transport layer may be formed on the first layer 31 by solution coating of a nanoparticle dispersion, or the like. In this case, the second layer 32 of the electron transport layer has a porous structure.

[0031] The solar cell according to this embodiment may have a structure in which a plurality of cells are connected together, that is, the solar cell according to this embodiment may have a structure in which a plurality of cells are integrated together.

[0032] Fig. 6A is a schematic cross-sectional view showing an example of an integrated structure that is a fifth example of a solar cell according to this embodiment. Fig. 6A shows a solar cell 600A having a structure in which three cells are integrated in series as an example. In the solar cell 600A shown in Fig. 6A, the second electrode 60 and the electron transport layer 30 are in contact with each other at a connection portion 90 of the cells. In this case, the second electrode 60 and the short-circuit prevention layer 80 can be in contact with each other through a gap in the electron transport layer 30.

[0033] 6B is a schematic cross-sectional view showing another example of an integrated structure of a fifth example of a solar cell according to the present embodiment. In a solar cell 600B shown in FIG. 6B, the second electrode 60 and the short-circuit prevention layer 80 are in direct contact with each other at a connection portion 90 of the cell.

[0034] Fig. 6C is a schematic cross-sectional view showing another example of an integrated structure, which is a fifth example of a solar cell according to this embodiment. In a solar cell 600C shown in Fig. 6C, the second electrode 60 and the first electrode 20 are in contact with each other at a cell connection portion 90. In this case, the second electrode 60 can penetrate the electron transport layer 30 and the short circuit prevention layer 80 to be in contact with the first electrode 20. Here, there is no problem if the second electrode 60 and the first electrode 20 are in contact with each other at the connection portion 90 for the purpose of electrically connecting adjacent cells.

[0035] FIG. 6D is a schematic cross-sectional view showing another example of an integrated structure that is a fifth example of a solar cell according to this embodiment. In the solar cell 600D shown in FIG. 6D, a short-circuit prevention layer 80 is arranged between the first electrodes 20 of adjacent cells so as to cover the side surfaces of the first electrodes 20 and the substrate 10. According to the above configuration, the short-circuit prevention layer 80 can more reliably insulate the first electrodes 20 of adjacent cells, so that leakage can be further suppressed. The solar cell 600D is formed, for example, by partially removing the first electrodes 20, forming the short-circuit prevention layer 80 and the electron transport layer 30, and then partially removing only the electron transport layer 30, and providing the light absorption layer 40, the hole transport layer 50, and the second electrode 60.

[0036] Fig. 6E is a schematic cross-sectional view showing another example of an integrated structure that is a fifth example of a solar cell according to this embodiment. In the solar cell 600E shown in Fig. 6E, an electron transport layer 30 is arranged between the first electrodes 20 of adjacent cells so as to cover the side surfaces of the first electrodes 20 and the substrate 10. The solar cell 600E is formed, for example, by forming the first electrodes 20 and the short-circuit prevention layer 80, partially removing them, and then providing the electron transport layer 30, the light absorption layer 40, the hole transport layer 50, and the second electrode 60.

[0037] FIG. 6F is a schematic cross-sectional view showing another example of an integrated structure, which is a fifth example of a solar cell according to this embodiment. In the solar cell 600F shown in FIG. 6F, a short-circuit prevention layer 80 and an electron transport layer 30 are arranged between the first electrodes 20 of adjacent cells so as to cover the side surfaces of the first electrodes 20 and the substrate 10. With the above configuration, leakage can be further suppressed. The solar cell 600F is formed, for example, by providing the short-circuit prevention layer 80, the electron transport layer 30, the light absorption layer 40, the hole transport layer 50, and the second electrode 60 after partially removing the first electrodes 20.

[0038] The first electrode 20, the short-circuit prevention layer 80, or the electron transport layer 30 is partially removed by, for example, laser scribing using laser irradiation or mechanical scribing using a metal blade.

[0039] A solar cell having an integrated structure such as that shown in Figures 6A to 6F can obtain a high voltage while maintaining a high yield.

[0040] Each component of the solar cell according to this embodiment will now be described in detail.

[0041] (Substrate 10) The substrate 10 is an auxiliary component. The substrate 10 plays a role of holding each layer of the solar cell. The substrate 10 can be formed from a transparent material. For example, a glass substrate or a plastic substrate can be used as the substrate 10. The plastic substrate can be, for example, a plastic film. Examples of materials that can be used for such plastic films include polyimide, polyethylene terephthalate, polyethylene naphthalate, and cycloolefin polymer. When using a plastic substrate, it is preferable to form a barrier layer having a weather-resistant function. In addition, when the second electrode 60 has translucency, the material of the substrate 10 may be a material that does not have translucency. For example, the material of the substrate 10 can be metal, ceramics, or a resin material with low translucency. When the first electrode 20 has sufficient strength, the first electrode 20 can hold each layer, so the substrate 10 does not need to be provided.

[0042] (1st electrode 20) The first electrode 20 has electrical conductivity. The first electrode 20 may be made of a material that does not form an ohmic contact with the light absorbing layer 40, or may be made of a material that can form an ohmic contact with the light absorbing layer 40. The first electrode 20 may or may not have a property of blocking holes moving from the light absorbing layer 40. The blocking property against holes from the light absorbing layer 40 means a property of passing only electrons generated in the light absorbing layer 40 and not passing holes. A material having such a property is a material whose Fermi energy is higher than the energy of the top of the valence band of the light absorbing layer 40. The above material may be a material whose Fermi energy is higher than the Fermi energy of the light absorbing layer 40. A specific example of the material is aluminum.

[0043] The first electrode 20 has a translucent property. For example, it transmits light from the visible region to the near infrared region. The first electrode 20 can be formed, for example, using a transparent and conductive metal oxide and / or metal nitride. Examples of such materials include titanium oxide doped with at least one selected from the group consisting of lithium, magnesium, niobium, and fluorine, gallium oxide doped with at least one selected from the group consisting of tin and silicon, gallium nitride doped with at least one selected from the group consisting of silicon and oxygen, tin oxide doped with at least one selected from the group consisting of antimony and fluorine, zinc oxide doped with at least one selected from the group consisting of boron, aluminum, gallium, and indium, indium-tin composite oxide, and composites thereof.

[0044] The first electrode 20 can be formed by using a non-transparent material and providing a light-transmitting pattern. Examples of light-transmitting patterns include linear, wavy, lattice, and punched metal patterns in which many fine through-holes are regularly or irregularly arranged. When the first electrode 20 has these patterns, light can be transmitted through the portions where no electrode material is present. Examples of non-transparent electrode materials include platinum, gold, silver, copper, aluminum, rhodium, indium, titanium, iron, nickel, tin, zinc, or alloys containing any of these. Also, a conductive carbon material can be used.

[0045] The light transmittance of the first electrode 20 may be, for example, 50% or more, or 80% or more. The wavelength of light to be transmitted depends on the absorption wavelength of the light absorption layer 40. The thickness of the first electrode 20 is, for example, in the range of 1 nm to 1000 nm.

[0046] (Short circuit prevention layer 80) The short-circuit prevention layer 80 can be made of a wide-gap material having insulating properties. Such a material has a band gap in the range of 3.9 eV to 15.5 eV. The short-circuit prevention layer 80 may have a band gap in the range of 4.6 eV to 9.1 eV. According to the above configuration, the band gap of the short-circuit prevention layer 80 is in a more suitable range, so that the layer has higher insulating properties. This allows a sufficiently thin film thickness to be applied to cover the first electrode 20, for example. Therefore, the yield can be improved while maintaining a practical output. If the band gap of the short-circuit prevention layer 80 is less than 3.9 eV, the layer has poor insulating properties, so that even if the layer is made thick, short circuits and leaks cannot be sufficiently prevented. Also, if the band gap of the short-circuit prevention layer 80 exceeds 15.5 eV, the layer has too high insulating properties, so that the layer needs to be made extremely thin, which is not preferable since it leads to an increase in short circuits and leaks.

[0047] The bandgap of the anti-shorting layer 80 can be measured by X-ray photoelectron spectroscopy (XPS) or electron energy loss spectroscopy (EELS).

[0048] The short prevention layer 80 may include at least one selected from the group consisting of metal chalcogenides, metal pnictogenides, metal halides, and organic compounds.

[0049] For example, the short-circuit prevention layer 80 may include at least one selected from the group consisting of silicon oxynitride, silicon nitride, aluminum nitride, boron nitride, silicon oxide, aluminum oxide, zirconium oxide, gallium oxide, hafnium oxide, yttrium oxide, beryllium oxide, lanthanum oxide, magnesium oxide, scandium oxide, tantalum oxide, strontium zirconate, lithium fluoride, barium fluoride, sodium fluoride, calcium fluoride, magnesium fluoride, and parylene. Silicon oxynitride, silicon nitride, and boron nitride are included in metal pnictogenides. Silicon oxide is included in metal chalcogenides. Here, a typical band gap value of silicon nitride is 4.6 eV. A typical band gap value of aluminum nitride is 6.0 eV. A typical band gap value of boron nitride is 5.6 eV. A typical band gap value of silicon oxide is 9.1 eV. Typical band gap values ​​for aluminum oxide are 6.0 eV for the gamma phase and 8.8 eV for the alpha phase. Typical band gap values ​​for zirconium oxide are 6.0 eV. Typical band gap values ​​for gallium oxide are 4.9 eV and hafnium oxide are 6.0 eV. Typical band gap values ​​for yttrium oxide are 5.7 eV. Typical band gap values ​​for beryllium oxide are 7.8 eV. Typical band gap values ​​for lanthanum oxide are 5.8 eV. Typical band gap values ​​for magnesium oxide are 7.4 eV. Typical band gap values ​​for scandium oxide are 5.8 eV. Typical band gap values ​​for tantalum oxide are 5.8 eV. Typical band gap values ​​for strontium zirconate are 5.4 eV. Typical band gap values ​​for lithium fluoride are 11.4 eV. Typical band gap values ​​for barium fluoride are 8.9 eV. A typical bandgap value for sodium fluoride is 6.7 eV. A typical bandgap value for calcium fluoride is 11.0 eV. A typical bandgap value for magnesium fluoride is 11.5 eV. A typical bandgap value for parylene is 5.1 eV.It should be noted that the above materials do not function as the electron transport layer 30 because they have extremely poor electron transport properties.

[0050] According to the above configuration, the short-circuit prevention layer 80 contains a highly insulating material, which reduces short circuits and leaks, and therefore the yield can be further improved while still providing a practical output.

[0051] The short-circuit prevention layer 80 may consist of at least one material selected from the group consisting of the above-mentioned materials.

[0052] When the short-circuit prevention layer 80 includes an inorganic material, the inorganic material can be detected by EELS and XPS. When the short-circuit prevention layer 80 includes an organic material, the organic material can be detected by secondary ion mass spectrometry (TOF-SIMS).

[0053] The short-circuit prevention layer 80 may contain Si and N, or may contain Si, O, and N. The short-circuit prevention layer 80 has the chemical formula SiO α N β Here, α is 0.0 or more and 2.0 or less, and β is 0.1 or more and 1.7 or less. α may be 0.7 or more and 2.0 or less, and β may be 0.3 or more and 1.0 or less, or α may be 0.7 or more and 1.8 or less, and β may be 0.3 or more and 0.7 or less.

[0054] The short circuit prevention layer 80 may further contain H.

[0055] The short circuit prevention layer 80 has the chemical formula SiO x N y H z Here, x is 0.0 or more and 2.0 or less, y is 0.1 or more and 1.7 or less, and z is 0.0 or more and 1.6 or less.

[0056] The composition of the short prevention layer 80 can be analyzed using XPS. If XPS is not available, it can also be measured using Rutherford Backscattering Spectroscopy / Hydrogen Forward Scattering Spectroscopy (RBS / HFS). For example, the composition of Si, O, and N can be determined by XPS, and the composition of H can be measured by RBS / HFS.

[0057] Chemical formula SiO x N y H z The short-circuit prevention layer 80 containing the compound represented by the formula (I) is formed by, for example, chemical vapor deposition (CVD) or atomic layer deposition (ALD). According to the above-mentioned configuration, the short-circuit prevention layer 80 has a high coverage and is a dense film with good crystallinity, so that it is possible to further reduce short circuits and leaks and further improve the output and yield.

[0058] In the above chemical formula, x may be 0.7 or more and 2.0 or less, y may be 0.3 or more and 1.0 or less, and z may be 0.0 or more and 1.0 or less, or x may be 0.7 or more and 1.8 or less, y may be 0.3 or more and 0.7 or less, and z may be 0.0 or more and 1.0 or less.

[0059] According to the above-mentioned configuration, the short circuit prevention layer 80 contains the compound of the chemical formula SiO x N y H z Since the chemical composition of the compound represented by the formula (I) is in a more suitable range, it has higher insulating properties. This allows a sufficiently thin film thickness to be applied to cover the first electrode 20, for example. Therefore, it is possible to improve the yield while maintaining a practical output.

[0060] The thickness of the short-circuit prevention layer 80 is equal to or greater than 0.4 nm and less than 3.0 nm. The thickness of the short-circuit prevention layer 80 may be equal to or greater than 1.2 nm and less than 2.5 nm.

[0061] According to the above-mentioned configuration, the thickness of the short-circuit prevention layer 80 is in a more suitable range, so that the short-circuit prevention layer 80 has higher insulation properties and suppresses the occurrence of leakage current, while not impeding electron transport. Therefore, the yield can be improved while providing a practical output.

[0062] The thickness of the short circuit prevention layer 80 can be measured, for example, by cross-sectional TEM-EDX (transmission electron microscopy-energy dispersive X-ray spectroscopy) and SIMS.

[0063] The short-circuit prevention layer 80 can be formed by chemical vapor deposition, sputtering, or solution coating. It is preferable to form the short-circuit prevention layer 80 by a method that can obtain a dense film with high coverage and good crystallinity, such as chemical vapor deposition or atomic layer deposition.

[0064] (Electron transport layer 30) The electron transport layer 30 contains an electron transport material. The electron transport material is a material that transports electrons. The electron transport material may be a semiconductor. The electron transport layer 30 may be a semiconductor with a band gap of 3.0 eV or more and 3.8 eV or less. By forming the electron transport layer 30 with a semiconductor with a band gap of 3.0 eV or more, visible light and infrared light can be transmitted to the light absorption layer 40. An example of the semiconductor is an inorganic n-type semiconductor. Before forming the electron transport layer 30, the surface of the base may be cleaned and modified by UV ozone treatment using a low-pressure mercury lamp or the like.

[0065] As inorganic n-type semiconductors, for example, oxides of metal elements, nitrides of metal elements, and perovskite oxides can be used. More specific examples include TiO2 (rutile type 3.0 eV, anatase type 3.2 eV), SnO2 (3.6 eV), Nb2O5 (3.4 eV), GaN (3.4 eV), SrTiO3 (3.2 eV), and CaTiO3 (3.4 eV). Here, the numbers in parentheses indicate general band gap values.

[0066] At least a portion of the electron transport layer 30 may have a porous structure.

[0067] The electron transport layer 30 may include a plurality of layers made of different materials, or may include a plurality of layers having different structures. The electron transport layer 30 may include, for example, a first layer 31 and a second layer 32, and the first layer 31 and the second layer 32 may have different materials or structures. For example, by forming the electron transport layer 30 into a porous structure, or by arranging a porous structure on the light absorption layer 40 side of the electron transport layer 30, that is, by forming the second layer 32 into a porous structure, the material of the light absorption layer 40 penetrates into the voids of the porous structure, and the porous structure becomes a foothold for the light absorption layer 40. Therefore, the material of the light absorption layer 40 is unlikely to be repelled or aggregated on the surface of the electron transport layer 30 having a porous structure. Therefore, the light absorption layer 40 can be easily formed as a uniform film. This provides the effect of easily forming the light absorption layer 40. Examples of materials that form a porous structure in the electron transport layer 30 include porous bodies in which insulating or semiconductor particles are connected. For example, titanium oxide or tin oxide particles can be used as the particles of the porous body having electron transport properties. On the other hand, when aluminum oxide or silicon oxide particles are used as the particles of the porous body having poor electron transport properties, they only function as a scaffold for forming the light absorbing layer 40, and do not have the effect of the electron transport layer 30 or the short circuit prevention layer 80. The electron transport layer 30 having a porous structure is formed, for example, by coating a nanomolecular dispersion of the porous body.

[0068] The surface roughness of the electron transport layer 30 having a porous structure may have a surface roughness coefficient given by effective area / projected area of ​​10 or more, or may be 100 or more. The projected area is the area of ​​a shadow cast behind an object when the object is illuminated with light from the front. The effective area is the actual surface area of ​​the object. The effective area can be calculated from the volume determined from the projected area and thickness of the object, and the specific surface area and bulk density of the material constituting the object. The specific surface area is measured, for example, by a nitrogen adsorption method.

[0069] The voids in the electron transport layer 30 having a porous structure may be connected from one main surface to the other main surface of the electron transport layer 30. This allows the material of the light absorbing layer 40 to fill the voids in the electron transport layer 30.

[0070] The porous structure of the electron transport layer 30 is expected to cause light scattering and increase the optical path length of light passing through the light absorbing layer 40. It is predicted that the amount of electrons and holes generated in the light absorbing layer 40 will increase as the optical path length increases.

[0071] (Light absorbing layer 40) The light absorbing layer 40 includes a light absorbing material. The light absorbing layer 40 may include a perovskite compound represented by the composition formula ABX3. A is a monovalent cation. Examples of monovalent cations include monovalent cations such as alkali metal cations and organic cations. More specifically, methylammonium cation (MA + or CH3NH3 + ), formamidinium cation (FA + or HC(NH2)2 + ), ethylammonium cation (CH3CH2NH3 + ), guanidinium cation (CH6N3 + ), potassium cation (K + ), Cesium cation (Cs + ), and the rubidium cation (Rb + ) B is a divalent cation, for example, a divalent lead cation (Pb 2+ ), tin cation (Sn 2+ ) and germanium cation (Ge 2+ ) X is a monovalent anion such as a halogen anion. Each of the A, B, and X sites may be occupied by multiple types of ions.

[0072] The thickness of the light absorbing layer 40 is, for example, 50 nm or more and 10 μm or less. The light absorbing layer 40 can be formed by using a solution coating method, a printing method, a vapor deposition method, etc. The light absorbing layer 40 may be formed by cutting out a perovskite compound.

[0073] The light absorbing layer 40 may mainly contain a perovskite compound represented by the composition formula ABX3. Here, "the light absorbing layer 40 mainly contains a perovskite compound represented by the composition formula ABX3" means that the light absorbing layer 40 contains 90% by mass or more of the perovskite compound represented by the composition formula ABX3. The light absorbing layer 40 may contain 95% by mass or more of the perovskite compound represented by the composition formula ABX3. The light absorbing layer 40 may be made of a perovskite compound represented by the composition formula ABX3. The light absorbing layer 40 may contain a perovskite compound represented by the composition formula ABX3, and may contain defects or impurities.

[0074] The light absorbing layer 40 may further contain another compound different from the perovskite compound represented by the composition formula ABX3. For example, the other compound may include a compound having a Ruddlesden-Popper type layered perovskite structure.

[0075] (Hole transport layer 50) The hole transport layer 50 contains a hole transport material. A hole transport material is a material that transports holes. The hole transport material can be an organic or inorganic semiconductor. The hole transport layer 50 is composed of a hole transport material.

[0076] Representative examples of organic compounds used as hole transport materials include 2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenylamine)9,9'-spirobifluorene, poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (hereinafter sometimes abbreviated as "PTAA"), poly(3-hexylthiophene-2,5-diyl), poly(3,4-ethylenedioxythiophene), and copper phthalocyanine.

[0077] Inorganic semiconductors used as hole transport materials are p-type semiconductors. Examples of inorganic semiconductors are Cu2O, CuGaO2, CuSCN, CuI, NiO x , MoO x , V2O5, or carbon materials such as graphene oxide.

[0078] The hole transport layer 50 may include multiple layers made of different materials. For example, multiple layers are stacked so that the ionization potentials (or HOMO levels) of the hole transport layer 50 are successively shallower than the ionization potential of the light absorbing layer 40, thereby improving the hole transport properties.

[0079] The thickness of the hole transport layer 50 may be 1 nm or more and 1000 nm or less, or 10 nm or more and 50 nm or less. Within this range, sufficient hole transport properties can be exhibited and low resistance can be maintained, allowing photovoltaic power generation to be performed with high efficiency.

[0080] The hole transport layer 50 can be formed by coating, printing, vapor deposition, or the like. This is the same as the light absorption layer 40. Examples of the coating method include doctor blade, bar coating, spray, dip coating, and spin coating. Examples of the printing method include screen printing. If necessary, the hole transport layer 50 may be prepared by mixing a plurality of materials, and then pressurized or baked. When the material of the hole transport layer 50 is an organic low molecular weight substance or an inorganic semiconductor, the hole transport layer 50 can also be prepared by vacuum vapor deposition.

[0081] The hole transport layer 50 may contain a supporting electrolyte and a solvent. The supporting electrolyte and the solvent have the effect of stabilizing holes in the hole transport layer 50.

[0082] Examples of the supporting electrolyte include ammonium salts and alkali metal salts. Examples of the ammonium salt include tetrabutylammonium perchlorate, tetraethylammonium hexafluorophosphate, imidazolium salts, and pyridinium salts. Examples of the alkali metal salt include lithium perchlorate and potassium boron tetrafluoride.

[0083] The solvent contained in the hole transport layer 50 may be one having excellent ion conductivity. Either an aqueous solvent or an organic solvent may be used. In order to further stabilize the solute, the solvent contained in the hole transport layer 50 may be an organic solvent. Specific examples include heterocyclic compound solvents such as tert-butylpyridine, pyridine, and n-methylpyrrolidone.

[0084] As the solvent, an ionic liquid may be used alone or in combination with other types of solvents. Ionic liquids are desirable because they have low volatility and high flame retardancy.

[0085] Examples of the ionic liquid include imidazolium-based ionic liquids such as 1-ethyl-3-methylimidazolium tetracyanoborate, pyridine-based ionic liquids, alicyclic amine-based ionic liquids, aliphatic amine-based ionic liquids, and azonium amine-based ionic liquids.

[0086] (2nd electrode 60) The second electrode 60 has electrical conductivity. When the solar cell does not include the hole transport layer 50, the second electrode 60 is made of a material that does not make ohmic contact with the light absorbing layer 40. Furthermore, the second electrode 60 has blocking properties against electrons from the light absorbing layer 40. Here, the blocking properties against electrons from the light absorbing layer 40 refer to a property of passing only holes generated in the light absorbing layer 40 and not passing electrons. A material having such properties is a material whose Fermi energy is lower than the energy of the conduction band bottom of the light absorbing layer 40. The above material may be a material whose Fermi energy is lower than the Fermi energy of the light absorbing layer 40. Specific examples of the material include platinum, gold, and carbon materials such as graphene.

[0087] When the solar cell includes the hole transport layer 50, the second electrode 60 does not need to have a blocking property against electrons from the light absorbing layer 40. In other words, the material of the second electrode 60 may be a material that is in ohmic contact with the light absorbing layer 40. Therefore, the second electrode 60 can be formed to have light transmitting properties.

[0088] Of the first electrode 20 and the second electrode 60, it is sufficient that the electrode on the side where light is incident has light-transmitting properties. Therefore, one of the first electrode 20 and the second electrode 60 does not have to have light-transmitting properties. In other words, one of the first electrode 20 and the second electrode 60 does not have to use a material having light-transmitting properties, and does not have to have a pattern including an opening portion that transmits light.

[0089] The solar cell of the present embodiment may be a solar cell having a configuration in which a plurality of solar cells are stacked on one another. For example, it may be a tandem solar cell in which two solar cells are stacked, or a triple solar cell in which three solar cells are stacked. The tandem solar cell and the triple solar cell may include a perovskite compound. The tandem solar cell and the triple solar cell may be a perovskite solar cell having a configuration in which a plurality of solar cells using perovskite compounds with different band gaps are stacked on one another.

[0090] (Other embodiments) (Additional Note) The above description of the embodiments discloses the following techniques.

[0091] (Technology 1) A solar cell comprising a first electrode, a short-circuit prevention layer, an electron transport layer, a light absorbing layer, and a second electrode, the short-circuit prevention layer being disposed between the first electrode and the electron transport layer, the band gap of the short-circuit prevention layer being 3.9 eV or more and 15.5 eV or less, and the thickness of the short-circuit prevention layer being 0.4 nm or more and less than 3.0 nm. This configuration provides a practical output and improves yield.

[0092] (Technology 2) The solar cell according to Technology 1, wherein the band gap is 4.6 eV or more and 9.1 eV or less. This configuration makes it possible to further improve yield while providing practical output.

[0093] (Technology 3) The solar cell according to Technology 1 or 2, wherein the short-circuit prevention layer includes at least one selected from the group consisting of metal chalcogenides, metal pnictogenides, metal halides, and organic compounds. This configuration provides a practical output and improves yield.

[0094] (Technology 4) The solar cell according to any one of techniques 1 to 3, wherein the short-circuit prevention layer includes at least one selected from the group consisting of silicon oxynitride, silicon nitride, aluminum nitride, boron nitride, silicon oxide, aluminum oxide, zirconium oxide, gallium oxide, hafnium oxide, yttrium oxide, beryllium oxide, lanthanum oxide, magnesium oxide, scandium oxide, tantalum oxide, strontium zirconate, lithium fluoride, barium fluoride, sodium fluoride, calcium fluoride, magnesium fluoride, and parylene. This configuration makes it possible to further improve yield while maintaining practical output.

[0095] (Technology 5) The short circuit prevention layer has the chemical formula SiO x N y H z The solar cell according to any one of Techniques 1 to 4, comprising a compound represented by the formula: where x is 0.0 or more and 2.0 or less, y is 0.1 or more and 1.7 or less, and z is 0.0 or more and 1.6 or less. With this configuration, the short circuit prevention layer can be produced by a method that can obtain a dense film with good crystallinity, thereby further improving the yield.

[0096] (Technology 6) The solar cell according to technique 5, wherein the x is 0.7 or more and 1.8 or less, the y is 0.3 or more and 0.7 or less, and the z is 0.0 or more and 1.0 or less. This configuration makes it possible to further improve yield while having a practical output.

[0097] (Technology 7) The solar cell according to any one of Techniques 1 to 6, wherein the thickness is 1.2 nm or more and 2.5 nm or less. This configuration allows for a higher output and a higher yield.

[0098] (Technology 8) The solar cell according to any one of Techniques 1 to 7, wherein at least a part of the electron transport layer has a porous structure. The solar cell according to Technique 8 can have a practical output and improve yield even if, for example, a coating film produced by coating, which is generally difficult to form into a dense film, is applied to the electron transport layer.

[0099] (Technology 9) The solar cell according to any one of Techniques 1 to 8, wherein at least a part of the light absorbing layer is in contact with the short-circuit prevention layer. The solar cell according to Technique 9 can improve yield while maintaining practical output even when, for example, a coating film produced by coating, which is generally difficult to form into a dense film, is applied to the electron transport layer, or when pinholes during production cannot be completely prevented.

[0100] (Technology 10) The solar cell according to any one of the first to ninth aspects of the present invention further comprises a hole transport layer, the hole transport layer being disposed between the light absorbing layer and the second electrode. This configuration can further improve the output.

[0101] (Technology 11) The solar cell according to technique 10, wherein at least a part of the hole transport layer is in contact with the short-circuit prevention layer. With this configuration, even when a coating film produced by coating, which is generally difficult to form into a dense film, is applied to the electron transport layer, or even when pinholes in each layer during production cannot be completely prevented, the solar cell can have a practical output and improve yield.

[0102] (Technology 12) The solar cell according to any one of Techniques 1 to 11, wherein at least a part of the second electrode is in contact with the short-circuit prevention layer. With this configuration, even when a coating film produced by coating, which is generally difficult to form into a dense film, is applied to the electron transport layer and the hole transport layer, or when pinholes in each layer during production cannot be completely prevented, it is possible to improve yield while maintaining practical output. EXAMPLES

[0103] Hereinafter, the present disclosure will be described in more detail with reference to examples and comparative examples.

[0104] In the examples and comparative examples, solar cells using perovskite compounds were fabricated and the initial characteristics of the solar cells were evaluated. Here, in order to evaluate the yield, a plurality of solar cells fabricated under the same conditions were prepared.

[0105] The solar cells of Examples 1 to 19 and Comparative Examples 1 to 2, and 6 to 10 had the following configurations. Substrate 10: Glass substrate (thickness: 0.7 mm) First electrode 20: Indium-tin composite oxide (thickness: 200 nm) Short circuit prevention layer 80: Silicon oxynitride (SiO x N y ), silicon nitride (SiN x ), silicon oxide (SiO x ) Electron transport layer 30: Porous tin oxide (tin oxide nanoparticles, np-SnO2) (thickness: 30 nm) Light absorbing layer 40: Layer mainly containing HC(NH2)2PbI3 (thickness: 500 nm) Hole transport layer 50: Buffer layer / layer mainly containing PTAA (thickness: 50 nm) Second electrode 60: Indium-tin composite oxide (thickness: 100 nm)

[0106] The configurations of the solar cells of Examples 20 to 22 and Comparative Examples 3 to 5 were as follows. Substrate 10: Glass substrate (thickness: 0.7 mm) First electrode 20: Indium-tin composite oxide (thickness: 200 nm) Short circuit prevention layer 80: Silicon oxynitride (SiO x N y ), bathocuproine (BCP) First layer of electron transport layer 31: tin oxide (c-SnO2) (thickness: 20 nm) Second layer 32 of the electron transport layer: Porous tin oxide (tin oxide nanoparticles, np-SnO2) (thickness: 30 nm) Light absorbing layer 40: Layer mainly containing HC(NH2)2PbI3 (thickness: 500 nm) Hole transport layer 50: Buffer layer / layer mainly containing PTAA (thickness: 50 nm) Second electrode 60: Indium-tin composite oxide (thickness: 100 nm)

[0107] <Fabrication of solar cells> Example 1 First, a substrate 10 was prepared. In this example, a glass substrate having a thickness of 0.7 mm was used as the substrate 10.

[0108] As the first electrode 20, a layer of indium-tin composite oxide was formed on the substrate 10 by sputtering.

[0109] Next, a silicon oxynitride layer (thickness: 0.4 nm) was formed as the short circuit prevention layer 80 by plasma CVD. In the plasma CVD, RF plasma CVD of 13.56 MHz was applied. The plasma input power density was about 50 mW / cm 2 More than 500mW / cm 2 The plasma power density was 5 mW / cm 2 More than 1000mW / cm 2 It is preferable that the hydrogen dilution ratio is set to the following value. Silane, ammonia, nitrous oxide, and hydrogen are used as the source gases, and the hydrogen dilution ratio is set to 50. Here, the hydrogen dilution ratio is calculated by silane flow rate / hydrogen flow rate×100. As the hydrogen dilution ratio and input power increase, the roughness of the silicon oxynitride film decreases, and it becomes possible to control the film thickness to 5 nm or less, but hydrogen may be mixed into the silicon oxynitride film.

[0110] A composition analysis was performed on a silicon oxynitride film (thickness: 120 nm) formed on a glass substrate under the formation conditions of the short-circuit prevention layer 80 of Example 1 by Rutherford backscattering spectrometry / hydrogen forward scattering spectrometry (RBS / HFS), and the H / Si atomic ratio was 0.90. In addition, after performing UV ozone treatment (30 min) on the film surface, a composition analysis was performed by X-ray photoelectron spectroscopy (XPS), and the O / Si atomic ratio near the film surface (region with a thickness of 5 nm or less) was 1.78, the N / Si atomic ratio was 0.37, and the band gap obtained from the energy loss spectrum was 7.9 eV. Since the thickness of the short-circuit prevention layer of Example 1 is 0.4 nm, the result of the XPS analysis can be regarded as the composition of the short-circuit prevention layer 80 of Example 1. In addition, when the film surface is subjected to UV ozone treatment, the H content is reduced. Therefore, when the short-circuit prevention layer 80 of Example 1 is subjected to UV ozone treatment, the H / Si atomic ratio is probably smaller than the above-mentioned RBS / HFS result. From the above, H can be contained in the short circuit prevention layer of the first embodiment.

[0111] After forming the short-circuit prevention layer 80 and performing UV ozone treatment (30 min), a solution in which SnO2 colloidal dispersion (15%, manufactured by Alfa Aesar) and ultrapure water (manufactured by Fujifilm Wako Pure Chemical Industries) were mixed in a volume ratio of SnO2 colloidal dispersion:ultrapure water = 2:7 was applied onto the short-circuit prevention layer 80 by spin coating. As a result, a porous tin oxide layer was formed as the electron transport layer 30.

[0112] Next, a raw material solution of a light absorbing material was applied by spin coating to form a light absorbing layer 40 containing a perovskite compound. The raw material solution of the light absorbing material was a solution containing 0.75 mol / L lead (II) iodide (Tokyo Chemical Industry Co., Ltd.), 0.45 mol / L lead (II) bromide (Tokyo Chemical Industry Co., Ltd.), 0.9 mol / L formamidinium iodide (GreatCell Solar Co., Ltd.), 0.3 mol / L methylammonium iodide (GreatCell Solar Co., Ltd.), and 0.4 mol / L methylammonium chloride (GreatCell Solar Co., Ltd.). The solvent of the raw material solution was a mixture of dimethyl sulfoxide (Acros Co., Ltd.) and N,N-dimethylformamide (Acros Co., Ltd.). The mixture ratio (DMSO:DMF) of dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF) in the raw material solution was 1:8 by volume.

[0113] Next, a hole transport layer 50 containing PTAA was formed by applying a raw material solution of a hole transport material on the light absorption layer 40 by a spin coating method. Specifically, a layer containing n-butylammonium bromide (GreatcellSolar) as a buffer was first formed, and a layer mainly containing PTAA (including 4-tert-butylpyridine (Tokyo Chemical Industry Co., Ltd.) and lithium bis(trifluoromethanesulfonyl)imide (Sigma-Aldrich Co., Ltd.) as additives) was formed thereon. The solvent of the raw material solution of the buffer layer was 2-propanol (Wako Pure Chemical Industries, Ltd.), and the solution contained 1 g / L of n-butylammonium bromide as a solute. The solvent of the raw material solution of the layer mainly containing PTAA was toluene (acros Co., Ltd.), and the solution contained 10 g / L of PTAA.

[0114] Next, an indium-tin composite oxide film was formed by sputtering on the hole transport layer 50 to form the second electrode 60. In this manner, the solar cell of Example 1 was obtained.

[0115] Example 2 In Example 2, a solar cell of Example 2 was obtained in the same manner as in Example 1, except that the thickness of the silicon oxynitride layer serving as short circuit prevention layer 80 was set to 0.7 nm.

[0116] Example 3 In Example 3, a solar cell of Example 3 was obtained in the same manner as in Example 1, except that the thickness of the silicon oxynitride layer serving as the short circuit prevention layer 80 was set to 0.9 nm.

[0117] Example 4 In Example 4, a solar cell of Example 4 was obtained in the same manner as in Example 1, except that the thickness of the silicon oxynitride layer serving as short circuit prevention layer 80 was set to 1.0 nm.

[0118] Example 5 In Example 5, a solar cell of Example 5 was obtained in the same manner as in Example 1, except that the thickness of the silicon oxynitride layer serving as short circuit prevention layer 80 was set to 1.1 nm.

[0119] Example 6 In Example 6, the solar cell of Example 6 was obtained in the same manner as Example 1, except that the thickness of the silicon oxynitride layer as the short-circuit prevention layer 80 was 1.2 nm. A composition analysis was performed by RBS / HFS on a silicon oxynitride film (thickness: 77 nm) formed on a glass substrate under the formation conditions of the short-circuit prevention layer 80 of Example 6, and the H / Si atomic ratio was 0.88. In addition, after performing UV ozone treatment (30 min) on the film surface, a composition analysis was performed by XPS, and the O / Si atomic ratio near the film surface (region with a thickness of 5 nm or less) was 1.62, the N / Si atomic ratio was 0.44, and the band gap obtained from the energy loss spectrum was 7.7 eV. Since the thickness of the short-circuit prevention layer of Example 6 is 1.2 nm, the result of the XPS analysis can be regarded as the composition of the short-circuit prevention layer 80 of Example 6. In addition, when performing UV ozone treatment on the film surface, the H content decreases. Therefore, the H / Si atomic ratio of the short circuit prevention layer 80 of Example 6 is probably smaller than the above RBS / HFS result.

[0120] Example 7 In Example 7, a solar cell of Example 7 was obtained in the same manner as in Example 1, except that the thickness of the silicon oxynitride layer serving as the short circuit prevention layer 80 was set to 1.4 nm.

[0121] Example 8 In Example 8, a solar cell of Example 8 was obtained in the same manner as in Example 1, except that the thickness of the silicon oxynitride layer serving as the short circuit prevention layer 80 was set to 1.5 nm.

[0122] Example 9 In Example 9, a solar cell of Example 9 was obtained in the same manner as in Example 1, except that the thickness of the silicon oxynitride layer serving as short circuit prevention layer 80 was set to 1.6 nm.

[0123] Example 10 In Example 10, a solar cell of Example 10 was obtained in the same manner as in Example 1, except that the thickness of the silicon oxynitride layer serving as the short circuit prevention layer 80 was set to 1.7 nm.

[0124] Example 11 In Example 11, a solar cell of Example 11 was obtained in the same manner as in Example 1, except that the thickness of the silicon oxynitride layer serving as short circuit prevention layer 80 was set to 1.8 nm.

[0125] Example 12 In Example 12, the solar cell of Example 12 was obtained in the same manner as Example 1, except that the thickness of the silicon oxynitride layer as the short circuit prevention layer 80 was 1.9 nm. When the composition analysis was performed by RBS / HFS under the formation conditions of the short circuit prevention layer 80 of Example 12, the H / Si atomic ratio was 0.67. In addition, when the composition analysis was performed by XPS after performing UV ozone treatment (30 min) on the film surface, the O / Si atomic ratio near the film surface (region with a thickness of 5 nm or less) was 1.65, the N / Si atomic ratio was 0.47, and the band gap obtained from the energy loss spectrum was 7.7 eV. Since the thickness of the short circuit prevention layer of Example 12 is 1.9 nm, the result of the XPS analysis can be regarded as the composition of the short circuit prevention layer 80 of Example 12. In addition, when the film surface is subjected to UV ozone treatment, the H content is reduced. Therefore, the H / Si atomic ratio of the short circuit prevention layer 80 of Example 12 is probably smaller than the above-mentioned RBS / HFS result. From the above, H can be contained in the short circuit prevention layer of Example 12.

[0126] Example 13 In Example 13, a solar cell of Example 13 was obtained in the same manner as in Example 1, except that the thickness of the silicon oxynitride layer serving as short circuit prevention layer 80 was set to 2.1 nm.

[0127] Example 14 In Example 14, a solar cell of Example 14 was obtained in the same manner as in Example 1, except that the thickness of the silicon oxynitride layer serving as short circuit prevention layer 80 was set to 2.3 nm.

[0128] Example 15 In Example 15, a solar cell of Example 15 was obtained in the same manner as in Example 1, except that the thickness of the silicon oxynitride layer serving as short circuit prevention layer 80 was set to 2.4 nm.

[0129] (Example 16) In Example 16, the solar cell of Example 16 was obtained in the same manner as in Example 1, except that the thickness of the silicon oxynitride layer as the short-circuit prevention layer 80 was 2.5 nm. A composition analysis was performed by RBS / HFS on a silicon oxynitride film (thickness: 70 nm) formed on a glass substrate under the formation conditions of the short-circuit prevention layer 80 of Example 16, and the H / Si atomic ratio was 0.60. In addition, a composition analysis was performed by XPS after performing UV ozone treatment (30 min) on the film surface, and the O / Si atomic ratio near the film surface (region with a thickness of 5 nm or less) was 1.66, the N / Si atomic ratio was 0.44, and the band gap obtained from the energy loss spectrum was 7.7 eV. Since the thickness of the short-circuit prevention layer of Example 16 is 2.5 nm, the result of the XPS analysis can be regarded as the composition of the short-circuit prevention layer 80 of Example 16. In addition, when performing UV ozone treatment on the film surface, the H content decreases. Therefore, the H / Si atomic ratio of the short circuit prevention layer 80 of Example 16 is probably smaller than the above RBS / HFS result.

[0130] (Example 17) In Example 17, a solar cell of Example 17 was obtained in the same manner as in Example 1, except that the thickness of the silicon oxynitride layer serving as short circuit prevention layer 80 was set to 2.7 nm.

[0131] (Example 18) In Example 18, a silicon nitride layer (thickness: 1.7 nm) was formed by plasma CVD as the short circuit prevention layer 80. Here, silane, ammonia, and hydrogen were used as the raw material gas, and the hydrogen dilution ratio was 50. Otherwise, the solar cell of Example 18 was obtained in the same manner as in Example 1.

[0132] (Example 19) In Example 19, a silicon oxide layer (thickness: 2.3 nm) was formed by plasma CVD as the short circuit prevention layer 80. Here, silane and ammonia were used as raw material gases. Otherwise, the solar cell of Example 19 was obtained in the same manner as in Example 1.

[0133] (Example 20) First, a substrate 10 was prepared. As the substrate 10, a glass substrate having a thickness of 0.7 mm was used.

[0134] As the first electrode 20, a layer of indium-tin composite oxide was formed on the substrate 10 by sputtering.

[0135] Next, a silicon oxynitride layer (thickness: 1.5 nm) was formed as the short circuit prevention layer 80 by plasma CVD.

[0136] After forming the short-circuit prevention layer 80 and performing UV ozone treatment (30 min), a solution of stannic chloride pentahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) dissolved in ethanol (manufactured by Wako Pure Chemical Industries, Ltd.) was applied by spin coating onto the short-circuit prevention layer 80, thereby forming a tin oxide layer as the first layer 31 of the electron transport layer. Next, a solution of SnO2 colloidal dispersion (15%, manufactured by Alfa Aesar Co., Ltd.) and ultrapure water (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) mixed at a volume ratio of SnO2 colloidal dispersion:ultrapure water=2:7 was applied by spin coating onto the first layer 31, thereby forming a porous tin oxide layer as the second layer 32 of the electron transport layer.

[0137] The light absorbing layer 40, the hole transport layer 50, and the second electrode 60 were formed in the same manner as in Example 1. In this manner, the solar cell of Example 20 was obtained.

[0138] Example 21 In Example 21, a solar cell of Example 21 was obtained in the same manner as in Example 20, except that the thickness of the silicon oxynitride layer serving as short circuit prevention layer 80 was set to 2.0 nm.

[0139] Example 22 In Example 22, a solar cell of Example 22 was obtained in the same manner as in Example 20, except that the thickness of the silicon oxynitride layer serving as short circuit prevention layer 80 was set to 2.5 nm.

[0140] Comparative Example 1 In Comparative Example 1, no short circuit prevention layer 80 was formed. Except for that, the solar cell of Comparative Example 1 was obtained in the same manner as in Example 1.

[0141] Comparative Example 2 In Comparative Example 2, a solar cell of Comparative Example 2 was obtained in the same manner as in Example 1, except that the thickness of the silicon oxynitride layer serving as short circuit prevention layer 80 was set to 3.0 nm.

[0142] Comparative Example 3 In Comparative Example 3, a silicon oxynitride layer (thickness: 3.0 nm) was used as the short circuit prevention layer 80. Except for that, the solar cell of Comparative Example 3 was obtained in the same manner as in Example 20.

[0143] Comparative Example 4 In Comparative Example 4, a silicon oxynitride layer (thickness: 4.6 nm) was used as the short circuit prevention layer 80. Except for that, the solar cell of Comparative Example 4 was obtained in the same manner as in Example 20.

[0144] Comparative Example 5 In Comparative Example 5, a layer of bathocuproine (thickness: 5.0 nm) was used as the short-circuit prevention layer 80. Except for that, the solar cell of Comparative Example 5 was obtained in the same manner as in Example 20.

[0145] Comparative Example 6 In Comparative Example 6, a tin oxide layer was formed on the first electrode 20 as the electron transport layer 30 by first applying a solution of stannic chloride pentahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) dissolved in ethanol (manufactured by Wako Pure Chemical Industries, Ltd.) by spin coating, and then a silicon oxynitride layer (thickness: 0.5 nm) was formed on the electron transport layer 30 by using a plasma CVD method as the short circuit prevention layer 80, and then a raw material solution of the light absorbing material was applied by spin coating. Otherwise, the solar cell of Comparative Example 6 was obtained in the same manner as in Example 1.

[0146] Comparative Example 7 In Comparative Example 7, the short-circuit prevention layer 80 and the electron transport layer 30 were not formed. Except for this, the solar cell of Comparative Example 7 was obtained in the same manner as in Example 1.

[0147] Comparative Example 8 In Comparative Example 8, the electron transport layer 30 was not formed, and a silicon oxynitride layer (thickness: 0.5 nm) was used as the short circuit prevention layer 80. Except for that, the solar cell of Comparative Example 8 was obtained in the same manner as in Example 1.

[0148] Comparative Example 9 In Comparative Example 9, a silicon oxynitride layer (thickness: 1.0 nm) was used as the short circuit prevention layer 80. Other than that, the solar cell of Comparative Example 9 was obtained in the same manner as in Comparative Example 8.

[0149] Comparative Example 10 In Comparative Example 10, a silicon oxynitride layer (thickness: 1.5 nm) was used as the short circuit prevention layer 80. Other than that, the solar cell of Comparative Example 10 was obtained in the same manner as in Comparative Example 8.

[0150] The solar cells of Examples 1 to 19 and Comparative Example 2 had the same structure as the solar cell 400 shown in FIG. 4. The solar cell of Comparative Example 1 had a structure in which the solar cell 400 did not include the short-circuit prevention layer 80. The solar cells of Examples 20 to 22 and Comparative Examples 3 to 5 had the same structure as the solar cell 500 shown in FIG. 5. The solar cell of Comparative Example 6 had a structure in which the short-circuit prevention layer was disposed between the electron transport layer and the light absorption layer. The solar cell of Comparative Example 7 had a structure in which the solar cell 400 did not include the short-circuit prevention layer 80 and the electron transport layer 30. The solar cells of Comparative Examples 8 to 10 had a structure in which the solar cell 400 did not include the electron transport layer 30.

[0151] <Measurement of solar cell characteristics> The characteristics of the obtained solar cells of Examples 1 to 22 and Comparative Examples 1 to 10 were measured.

[0152] The current-voltage characteristics of the solar cell under light irradiation were measured using an electrochemical analyzer (ALS440B, BAS) and a fluorescent lamp. Before the measurement, the light intensity was calibrated to 200 lux using a silicon photodiode. The voltage sweep rate was 100 mV / s. No preconditioning such as light irradiation or long-term forward bias application was performed before the start of the measurement. The aperture was set to 1.0 cm to fix the effective area and reduce the effect of scattered light. 2 The solar cell was masked with a black mask and irradiated with light from the mask / substrate side. The output was measured at room temperature in dry air (<2% RH).

[0153] Table 1 shows the solar cell characteristics and yields of Examples 1 to 17 and Comparative Examples 1 to 2. The yields shown in Table 1 are the percentage of solar cells that were judged to be usable and not defective among the 20 solar cells produced for each Example, when 20 solar cells were produced. Here, cells with an open-circuit voltage of 70% or less were judged to be defective, compared to the average open-circuit voltage of the top 5 solar cells in descending order of open-circuit voltage among the 20 solar cells produced for each Example. However, all solar cells with an open-circuit voltage value of 550 mV or less were judged to be defective, regardless of the average open-circuit voltage value. The characteristics shown in Table 1 are the average values ​​of the measurement results of solar cells that were judged to be usable and not defective among the solar cells produced for each Example. Figure 7 is a diagram showing the dependence of the yield and output on the thickness of the short-circuit prevention layer for Examples 1 to 17 and Comparative Examples 1 to 2. In Figure 7, circles indicate yields, and triangles indicate output.

[0154] [Table 1]

[0155] As shown in Table 1 and FIG. 7, in Comparative Example 1 without the short-circuit prevention layer 80, all the solar cells produced did not operate as solar cells under low illuminance of 200 lux, and the yield was 0%. This is believed to be due to the occurrence of a short circuit between the first electrode 20 and the second electrode 60, or the occurrence of a leak between the first electrode 20 and the hole transport layer. In contrast to Comparative Example 1, Examples 1 to 17 in which the short-circuit prevention layer 80 (thickness: 0.4 nm or more and less than 3.0 nm) made of silicon oxynitride was disposed between the first electrode 20 and the electron transport layer 30 exhibited practical solar cell characteristics and improved yields. In particular, Examples 6 to 16 in which the thickness of the short-circuit prevention layer 80 was 1.2 nm or more and 2.5 nm or less had high solar cell characteristics and a yield of 100%. This is believed to be due to the thickness of the short-circuit prevention layer being within a range in which short circuits and leaks can be prevented while the electron transport properties are particularly excellent. Therefore, by setting the thickness of the short circuit prevention layer 80 within the range of 1.2 nm to 2.5 nm, both higher output and higher yield can be achieved.

[0156] The solar cell characteristics and yields of Examples 18 and 19 are shown in Table 2.

[0157] [Table 2]

[0158] As shown in Table 2, Example 18 in which the short-circuit prevention layer 80 is a silicon nitride layer and Example 19 in which the short-circuit prevention layer 80 is a silicon oxide layer can achieve both high output and high yield, similar to Examples 1 to 17 in which the short-circuit prevention layer 80 is a silicon oxynitride layer. Here, the band gap of silicon nitride is 4.6 eV, and the band gap of silicon oxide is 9.1 eV. Therefore, it can be seen that the short-circuit prevention layer 80 may have a band gap of 4.6 eV or more and 9.1 eV or less.

[0159] The solar cell characteristics and yields of Examples 20 to 22 and Comparative Examples 3 to 5 are shown in Table 3.

[0160] [Table 3]

[0161] As shown in Table 3, Examples 20 to 22, in which a short-circuit prevention layer 80 (thickness: 1.5 nm or more and 2.5 nm or less) made of silicon oxynitride was disposed between the first electrode 20 and the first layer 31 of the electron transport layer, operated as a solar cell and exhibited sufficient solar cell characteristics and high yields. On the other hand, Comparative Examples 3 and 4, in which the short-circuit prevention layer 80 had a thickness of 3.0 nm or more, had a 100% yield but a significant decrease in solar cell characteristics. This is thought to be because the short-circuit prevention layer 80 was too thick, and thus, although it was able to prevent the occurrence of short circuits and leaks, it had poor electron transport properties.

[0162] Comparative Example 5, in which a 5.0 nm-thick layer of bathocuproine was used as the short-circuit prevention layer 80, showed a significant decrease in solar cell characteristics and yield compared to Examples 20 to 22. This indicates that because typical bathocuproine has a narrow band gap of 3.5 eV, even if the layer was as thick as 5.0 nm, it was unable to suppress the occurrence of short circuits and leakage, and therefore did not function as a short-circuit prevention layer 80.

[0163] The solar cell characteristics and yield of Comparative Example 6 are shown in Table 4. [Table 4]

[0164] As shown in Table 4, when the short-circuit prevention layer 80 was disposed between the electron transport layer 30 and the light absorption layer 40, the yield was 100%, but the output was extremely low. This indicates that even if the short-circuit prevention layer 80 was as thin as 0.5 nm, the short-circuit prevention layer 80 prevented the generation of a built-in electric field between the electron transport layer 30 and the light absorption layer 40, making it difficult for electrons to tunnel through the short-circuit prevention layer 80, and as a result, electrons generated in the light absorption layer 40 could not be extracted to the electron transport layer 30.

[0165] Table 5 shows the solar cell characteristics and yields of Comparative Examples 7 to 10. [Table 5]

[0166] As shown in Table 5, since Comparative Example 7 does not have the short-circuit prevention layer 80, all the solar cells produced do not operate as solar cells under low illuminance of 200 lux, and the yield was 0%. Comparative Examples 8 to 10 do not have the electron transport layer 30, and the short-circuit prevention layer 80 is disposed between the first electrode 20 and the light absorption layer 40. Therefore, the built-in electric field generated between the first electrode 20 and the light absorption layer 40 is weak, and it becomes difficult for electrons to pass through the short-circuit prevention layer 80, resulting in a decrease in output. From the results of Comparative Examples 8 to 10, it can be seen that the short-circuit prevention layer 80 does not function as the electron transport layer 30. The results of Tables 4 and 5 show that the short-circuit prevention layer 80 needs to be disposed between the first electrode 20 and the electron transport layer 30. Since the built-in electric field generated between the electron transport layer 30 and the light absorption layer 40 accelerates electrons, the electrons can tunnel through the short-circuit prevention layer 80 disposed between the first electrode 20 and the electron transport layer 30, and a current can be taken out.

[0167] From the above results, it has been confirmed that a solar cell can be obtained that has a first electrode, a short-circuit prevention layer, an electron transport layer, a light absorption layer, and a second electrode, where the short-circuit prevention layer is disposed between the first electrode and the electron transport layer, has a band gap of 3.9 eV or more and 15.5 eV or less, and has a thickness of 0.4 nm or more and less than 3.0 nm, and has high output even at a low illuminance of 200 lux while improving yield. [Industrial Applicability]

[0168] INDUSTRIAL APPLICABILITY The solar cell of the present disclosure has a practical output while improving yield, and has extremely high industrial applicability. [Explanation of symbols]

[0169] 1,10 Board 2,20 1st electrode 3,30 Electron transport layer 31 First electron transport layer 32 Electron transport layer 2nd layer 4,40 Light absorbing layer 5,50 Hole transport layer 6,60 2nd electrode 7. Short circuit location 80 Short circuit prevention layer 90 Connection 100A,100B,200,300,400,500,600A,600B,600C,600D,600E,600F Solar cell

Claims

1. A semiconductor device comprising a first electrode, a short-circuit prevention layer, a light absorbing layer, and a second electrode in this order; the short-circuit prevention layer is a layer that prevents a short circuit between the first electrode and the light absorbing layer; Solar cell.

2. A semiconductor device comprising a first electrode, a short-circuit prevention layer, a light absorption layer, and a second electrode in this order; the short-circuit prevention layer is a layer that prevents a short circuit between the first electrode and the second electrode; Solar cell.

3. The thickness of the short circuit prevention layer is 0.4 nm or more and less than 3.0 nm. The solar cell according to claim 1 or 2.

4. The band gap of the short circuit prevention layer is 3.9 eV or more and 15.5 eV or less. The solar cell according to claim 3 .

5. The band gap is 4.6 eV or more and 9.1 eV or less. The solar cell according to claim 4 .

6. the short circuit prevention layer includes at least one selected from the group consisting of a metal chalcogenide, a metal pnictogenide, a metal halide, and an organic compound; The solar cell according to claim 1 or 2.

7. the short-circuit prevention layer includes at least one selected from the group consisting of silicon oxynitride, silicon nitride, aluminum nitride, boron nitride, silicon oxide, aluminum oxide, zirconium oxide, gallium oxide, hafnium oxide, yttrium oxide, beryllium oxide, lanthanum oxide, magnesium oxide, scandium oxide, tantalum oxide, strontium zirconate, lithium fluoride, barium fluoride, sodium fluoride, calcium fluoride, magnesium fluoride, and parylene; The solar cell according to claim 1 or 2.

8. The short circuit prevention layer has the chemical formula SiO x N y H z wherein x is 0.0 or more and 2.0 or less, y is 0.1 or more and 1.7 or less, and z is 0.0 or more and 1.6 or less. The solar cell according to claim 1 or 2.

9. The solar cell according to claim 8 , wherein the x is 0.7 or more and 1.8 or less, the y is 0.3 or more and 0.7 or less, and the z is 0.0 or more and 1.0 or less.

10. The solar cell according to claim 3 , wherein the thickness is 1.2 nm or more and 2.5 nm or less.

11. The light-emitting device further comprises an electron transport layer, the electron transport layer being disposed between the light absorption layer and the short-circuit prevention layer; At least a portion of the electron transport layer has a porous structure. The solar cell according to claim 1 or 2.

12. At least a portion of the light absorbing layer is in contact with the short circuit prevention layer. The solar cell according to claim 1 or 2.

13. a hole transport layer disposed between the light absorbing layer and the second electrode; The solar cell according to claim 1 or 2.

14. At least a portion of the hole transport layer is in contact with the short-circuit prevention layer. The solar cell according to claim 13.

15. At least a portion of the second electrode is in contact with the short-circuit prevention layer. The solar cell according to claim 1 or 2.

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