Perovskite solar cell and method for producing same

Abstract

Provided are a perovskite solar cell capable of suppressing generation of a leakage current in a groove formed by laser scribing from a second electrode surface side and a method for manufacturing the same. The perovskite solar cell comprises a translucent first electrode (transparent conductive film layer 2), a second electrode 6 serving as a counter electrode to the first electrode, and a photoelectric conversion layer 4 positioned between the two electrodes. The photoelectric conversion layer 4 of the perovskite solar cell contains a perovskite compound and the perovskite solar cell has a groove 8 that passes through the second electrode 6 and the photoelectric conversion layer 4. When a portion of the groove 8 that passes through the photoelectric conversion layer 4 is set as a first groove portion and a portion of the groove 8 that passes through the second electrode 6 is set as a second groove portion, the second groove portion has a region with a larger groove width than the first groove portion.

Description

Perovskite solar cell and manufacturing method thereof

[0001] The present disclosure relates to perovskite solar cells and methods for making the same.

[0002] Solar cells, which convert sunlight into electricity, are becoming increasingly popular as a representative example of renewable energy utilization. Silicon-based solar cells, CIGS-based solar cells, CdTe-based solar cells, etc. are becoming increasingly popular.

[0003] Meanwhile, research is being conducted into using organic materials as photoelectric conversion materials instead of the inorganic materials typically used in solar cells, and the development of organic thin-film solar cells and dye-sensitized solar cells is also progressing. These solar cells can be manufactured using a coating process without using a vacuum process, which has the potential to significantly reduce manufacturing costs, and they are therefore expected to be next-generation solar cells. However, organic thin-film solar cells and dye-sensitized solar cells currently have insufficient photoelectric conversion efficiency and poor durability compared to solar cells using inorganic materials.

[0004] In recent years, perovskite solar cells, which use perovskite compounds as photoelectric conversion materials, have attracted attention because they have been able to achieve photoelectric conversion efficiencies comparable to those of silicon-based solar cells.

[0005] These solar cells generally have a multilayer structure including a first electrode (transparent electrode) that is light-transmitting (optically transparent), a photoelectric conversion layer, and a second electrode (counter electrode) that serves as the opposite electrode to the first electrode.

[0006] For example, Patent Document 1 discloses that in a silicon-based photoelectric conversion device, in order to increase photoelectric conversion efficiency, a first groove is provided to separate a first electrode (transparent electrode) and a photoelectric conversion layer, and a second groove is provided to separate the photoelectric conversion layer and a second electrode (counter electrode), and the gap separating the second electrodes by the second groove is larger than the gap separating the photoelectric conversion layers.

[0007] Furthermore, Patent Document 2 discloses that in a perovskite solar cell having a photoelectric conversion layer between a first electrode (transparent electrode) and a second electrode (counter electrode), the photoelectric conversion layer includes a porous semiconductor film of a metal oxide such as titanium oxide, and the surface of the metal oxide is coated with a perovskite compound, a thin layer made of a conductive material containing carbon nanotubes is provided on the photoelectric conversion layer in order to increase the fill factor and photoelectric conversion efficiency.

[0008] JP 2011-40462 A JP 2014-72327 A

[0009] When a metal with high light reflectivity is used for the second electrode, which is the counter electrode of the first electrode having light transparency, the second electrode reflects light that has not been absorbed by the photoelectric conversion layer and has passed through, and the reflected light is absorbed by the photoelectric conversion layer, thereby improving light utilization efficiency. In other words, the photoelectric conversion efficiency can be improved.

[0010] Incidentally, in the manufacturing process of solar cells, when a groove (notch) is provided in a desired layer of a multilayer structure, for example, to separate a photoelectric conversion layer into a plurality of photoelectric conversion elements, laser scribing is widely used, in which the irradiated portion is removed by irradiating it with a laser.

[0011] However, in laser scribing, in which laser light is irradiated from the surface side of the second electrode, a large power (laser output) is required to remove the second electrode due to the high optical reflectivity of the second electrode. Therefore, in the laser scribing process (see Figure 11) during the manufacture of perovskite solar cells, the photoelectric conversion layer containing the perovskite compound absorbs the laser light and explodes, causing the second electrode to be removed as collateral damage from the explosion, resulting in residues of the second electrode (see Figure 12) at the opening edges of the grooves formed by laser scribing (the second electrode remains as burrs), and there is a problem that leakage current may occur between adjacent cells and the bottom of the formed grooves.

[0012] The contents of the present disclosure were discovered in light of the above-mentioned circumstances surrounding perovskite solar cells, and the present disclosure provides a perovskite solar cell and a manufacturing method thereof that can suppress the generation of leakage current in grooves formed by laser scribing from the second electrode surface side.

[0013] In order to solve the above problems, the perovskite solar cell disclosed herein comprises a first electrode having light-transmitting properties, a second electrode that is the counter electrode of the first electrode, and a photoelectric conversion layer located between the two electrodes, wherein the photoelectric conversion layer contains a perovskite compound, and the perovskite solar cell has a groove that penetrates the second electrode and the photoelectric conversion layer, and wherein the portion of the groove that penetrates the photoelectric conversion layer is defined as a first groove portion, and the portion of the groove that penetrates the second electrode is defined as a second groove portion, and the second groove portion has a groove width that is wider than the first groove portion.

[0014] In the perovskite solar cell described above, it is preferable that the second electrode comprises an inner layer and an outer layer, in that order from the photoelectric conversion layer side, and that the outer layer has a higher light absorptance at a wavelength than the light absorptance of the inner layer.

[0015] In the perovskite solar cell described above, it is preferable that the groove width of the first groove portion is 10 μm or more and less than 100 μm, and the groove width of the second groove portion is 100 μm or more and 200 μm or less.

[0016] In the perovskite solar cell, the perovskite compound preferably contains an organic group.

[0017] In the perovskite solar cell described above, it is preferable that the optical absorptance of the outer layer is higher than the optical absorptance of the inner layer at at least one wavelength of 200 nm or more and 1100 nm or less.

[0018] In the perovskite solar cell described above, the outer layer preferably has a wavelength at which the light absorptance is 20% or more.

[0019] Furthermore, in the perovskite solar cell described above, the outer layer is preferably made of at least one of nickel and titanium, and more preferably made of nickel.

[0020] In the perovskite solar cell described above, the inner layer preferably has a wavelength at which the light reflectance is 50% or more.

[0021] In the perovskite solar cell described above, the inner layer is preferably made of at least one material selected from the group consisting of gold, silver, aluminum, and platinum, and more preferably made of silver.

[0022] In order to solve the above problems, the method for manufacturing a perovskite solar cell disclosed herein includes a step of irradiating a laser beam from the surface side of the second electrode to perform laser scribing to form a groove that penetrates from the second electrode to the photoelectric conversion layer, thereby separating the photoelectric conversion layer into a plurality of photoelectric conversion elements.

[0023] The perovskite solar cell and manufacturing method thereof disclosed herein exhibit excellent effects, such as being able to suppress the occurrence of leakage current in grooves formed by laser scribing from the second electrode surface side.

[0024] 5 is a cross-sectional view schematically illustrating an embodiment of a perovskite solar cell according to the present disclosure, in which the second electrode comprises an inner layer and an outer layer. FIG. 6 is a cross-sectional view schematically illustrating an embodiment of a perovskite solar cell according to the present disclosure, in which the second electrode has a single-layer structure. FIG. 7 is a cross-sectional view schematically illustrating grooves provided in the perovskite solar cell according to the embodiment shown in FIG. 1. FIG. 8 is a cross-sectional view schematically illustrating a state after a groove having a groove width W1 has been formed by laser scribing in the manufacture of the perovskite solar cell according to the embodiment shown in FIG. 1. FIG. 9 is a cross-sectional view schematically illustrating a step of forming a groove having a groove width W1. FIG. 5 is a cross-sectional view schematically illustrating a step after the step shown in FIG. 6. FIG. 9 is a cross-sectional view schematically illustrating a state after a groove having a groove width W2 has been formed by laser scribing in the manufacture of the perovskite solar cell according to the embodiment shown in FIG. 1. 12 is a cross-sectional view schematically showing a method of forming a groove with groove width W2 in which laser scribing is performed multiple times by shifting the position of laser irradiation. FIG. 13 is a cross-sectional view schematically showing laser scribing in a perovskite solar cell having a single-layer second electrode. FIG. 14 is a cross-sectional view schematically showing a groove formed by laser scribing in FIG. 11. FIG. 15 is an optical microscope image taken from the surface side of the second electrode of a perovskite solar cell in which the second electrode is silver, showing the state of the second electrode when laser scribing is attempted at a relatively low output. FIG. 16 is an optical microscope image taken from the surface side of the second electrode of a perovskite solar cell in which the second electrode is silver, showing the state of a groove formed by laser scribing at an increased laser output.

[0025] Hereinafter, embodiments of the perovskite solar cell and the manufacturing method thereof according to the present disclosure will be described with reference to the drawings. In the following, an embodiment in which the second electrode has a structure including an inner layer and an outer layer will be described, and an embodiment in which the second electrode has a single-layer structure will be described in the "Other Embodiments" section below.

[0026] Figure 1 is a cross-sectional view schematically illustrating a perovskite solar cell according to one embodiment of the present disclosure. The perovskite solar cell C1 shown in Figure 1 comprises, on a transparent substrate 1, a transparent conductive film layer 2 as a first electrode, an electron transport layer 3, a photoelectric conversion layer 4 containing a perovskite compound, a hole transport layer 5, and a second electrode 6 serving as a counter electrode to the first electrode, in this order. The second electrode 6 is a counter electrode to the first electrode. When the perovskite solar cell C1 generates electricity, light is incident from the transparent substrate 1 side. The incident light is transmitted through the transparent substrate 1 and the transparent conductive film layer 2 and absorbed by the photoelectric conversion layer 4.

[0027] First, the characteristics of the second electrode 6 and groove 8 provided in the perovskite solar cell C1 will be described, and then the transparent substrate 1, first electrode (transparent conductive film layer 2), electron transport layer 3, photoelectric conversion layer 4, and hole transport layer 5 will be described in this order.

[0028] <Second Electrode> As shown in FIG. 1, the second electrode 6 in the perovskite solar cell C1 includes an inner layer 6A and an outer layer 6B in this order from the photoelectric conversion layer 4 side (hole transport layer 5 side).

[0029] 5 is a cross-sectional view schematically illustrating one step of laser scribing for a perovskite solar cell C1 according to an embodiment of the present disclosure. As shown in FIG. 5, a transparent conductive film layer 2, an electron transport layer 3, a photoelectric conversion layer 4, a hole transport layer 5, and a second electrode 6 are formed in this order on a transparent substrate 1, and then laser scribing is performed by irradiating a laser beam from the surface side of the second electrode 6 to remove layers up to the photoelectric conversion layer 4, thereby separating the photoelectric conversion layer 4 into a plurality of photoelectric conversion elements. Furthermore, as shown in FIG. 1, a perovskite solar cell C1 having grooves 8 can be manufactured. The structure and method of forming the grooves 8 will be described in detail below.

[0030] In the perovskite solar cell C1, the second electrode includes an inner layer 6A and an outer layer 6B, which increases light utilization efficiency during power generation while suppressing the generation of laser scribe residue on the electrode during manufacturing. Here, the mechanism by which this effect can be achieved will be explained.

[0031] Figures 11 and 12 show problems that arise in laser scribing in conventional perovskite solar cells. Specifically, Figure 11 is a cross-sectional view that schematically shows the state of laser scribing in a perovskite solar cell having a single-layer second electrode, and Figure 12 is a cross-sectional view that schematically shows a groove formed by the laser scribing in Figure 11. In the example of perovskite solar cell C' shown in Figure 12, a transparent conductive film layer 2', an electron transport layer 3', a photoelectric conversion layer 4', a hole transport layer 5', and a second electrode 6' are provided in this order on a transparent substrate 1'.

[0032] 11 and 12, by using a metal with high light reflectivity for the second electrode 6', the photoelectric conversion layer 4' can absorb sunlight reflected by the second electrode 6', thereby increasing light utilization efficiency, but a large power (laser output) is required to remove the second electrode 6' by laser scribing. Figure 13 is an optical microscope image taken from the surface side of the second electrode of a perovskite solar cell in which the second electrode has a single-layer silver structure, showing the state of the second electrode when laser scribing was attempted at a relatively low output. It can be seen that the silver second electrode was not removed, and that part of the photoelectric conversion layer behind the second electrode was altered.

[0033] Therefore, when laser scribing is performed with increased laser output to remove the second electrode 6', the photoelectric conversion layer 4' containing a perovskite compound absorbs the laser light and explodes, resulting in the removal of the second electrode 6'. As a result, as shown in FIG. 12 , residues 9' (burrs of the second electrode 6') of the second electrode 6' are generated at the opening edges of the grooves 8' formed by laser scribing, which may result in leakage between adjacent cells and the bottom of the formed grooves 8'. Furthermore, the photoelectric conversion layer 4' may absorb the laser light and explode, potentially damaging the transparent substrate 1 and the transparent conductive film layer 2'. FIG. 14 is an optical microscope image of a groove formed by laser scribing with increased laser output in a perovskite solar cell having a single-layer silver second electrode. It can be seen that a large amount of residue (burrs) of the second electrode is generated at the opening edges of the grooves.

[0034] In contrast, in the perovskite solar cell C1 according to an embodiment of the present disclosure, the second electrode 6 has a multi-layer structure including, in order from the photoelectric conversion layer 4 side, an inner layer 6A and an outer layer 6B, and the materials constituting the inner layer 6A and the outer layer 6B are selected so that the light absorptance of the outer layer 6B is higher at wavelengths than the light absorptance of the inner layer 6A.

[0035] As a result, when laser scribing is performed at a wavelength at which the optical absorptivity of the outer layer 6B is higher than that of the inner layer 6A, the energy of the laser light is absorbed by the outer layer 6B, and the outer layer 6B is removed, as well as the adjacent inner layer 6A. Therefore, even if a material with high optical reflectivity is used for the inner layer 6A, it is possible to remove the second electrode 6 (the inner layer 6A and the outer layer 6B) with a relatively small laser output.

[0036] Furthermore, it is possible to avoid irradiating the photoelectric conversion layer 4 containing a perovskite compound with high-power laser light, thereby preventing the photoelectric conversion layer 4 from absorbing the laser light and causing an explosion. As a result, the perovskite solar cell C1 according to the embodiment of the present disclosure can increase the light utilization efficiency during power generation, while suppressing the generation of residues on the electrodes due to laser scribing during manufacturing.

[0037] In the perovskite solar cell C1, it is preferable that the optical absorptance of the outer layer 6B is higher than that of the inner layer 6A at at least one wavelength of 200 nm or more and 1100 nm or less. This range is more preferably 200 nm or more and 800 nm or less, and particularly preferably 300 nm or more and 800 nm or less. When the wavelength at which the optical absorptance of the outer layer 6B is higher than that of the inner layer 6A is within the above range, laser scribing can be performed in a wavelength band that is less affected by heat, thereby further suppressing the generation of residues due to laser scribing. A laser light with a wavelength of 532 nm is suitable for use in laser scribing, as this can be easily shared with processing layers other than the second electrode.

[0038] Specifically, for example, if the optical absorptivity of the outer layer 6B at wavelengths of 355 nm and 532 nm is higher than that of the inner layer 6A, by performing laser scribing using laser light with a wavelength of 355 nm or 532 nm, the energy of the laser light will be absorbed largely by the outer layer 6B, and therefore, even if a material with high optical reflectivity is used for the inner layer 6A, the second electrode 6 can be removed with a relatively small laser output.

[0039] The outer layer 6B preferably has a wavelength at which the light absorptance is 20% or higher, and more preferably has a wavelength at which the light absorptance is 40% or higher. Even if the light absorptance is not 40% or higher but is in the range of 20% to 40%, in the grooves 8 of the perovskite solar cell C1, the groove width W2 of the second groove portion is wider than the groove width W1 of the first groove portion, as shown in FIG. 1 . This prevents laser scribing residue from reaching the bottom of the second groove portion but from reaching the inside of the first groove portion. This makes it possible to suppress leakage current in the grooves 8.

[0040] Furthermore, since the outer layer 6B has a wavelength at which the light absorption rate is 40% or more, when laser scribing is performed using laser light of that wavelength, the energy of the laser light is sufficiently absorbed by the outer layer 6B, so that the second electrode 6 can be removed with a smaller laser output, and ultimately the generation of residue due to laser scribing can be further suppressed.

[0041] The outer layer 6B is preferably made of at least one of nickel and titanium. This allows the outer layer 6B to have a high light absorption rate and to have a low resistance, thereby improving the power generation efficiency of the perovskite solar cell C1. From the viewpoints of being an inexpensive material and being easy to form a film, the outer layer 6B is more preferably made of nickel.

[0042] The thickness of the outer layer 6B is preferably 30 nm or more and 300 nm or less, and more preferably 50 nm or more and 150 nm or less. If the thickness is less than the lower limit, the resistance of the outer layer 6B may increase, which may reduce the power generation efficiency of the perovskite solar cell C1. If the thickness exceeds the upper limit, it may become difficult to remove the outer layer 6B by laser scribing.

[0043] Examples of methods for forming the outer layer 6B include known film-forming methods such as sputtering and vapor deposition.

[0044] The inner layer 6A preferably has a wavelength at which the light reflectance is 50% or higher, and more preferably has a wavelength at which the light reflectance is 60% or higher. This allows a larger amount of light that has not been absorbed by the photoelectric conversion layer 4 and has passed through to be reflected by the inner layer 6A, and the reflected light is absorbed by the photoelectric conversion layer 4, thereby improving the light utilization efficiency. In other words, the photoelectric conversion efficiency of the perovskite solar cell C1 can be improved.

[0045] The inner layer 6A preferably has an optical reflectance of 50% or more at at least one wavelength of 300 nm or more and 800 nm or less. When the wavelength at which the optical reflectance is 50% or more is within the above range, light in a wavelength band suitable for absorption by the photoelectric conversion layer 4 and power generation is reflected by the inner layer 6A, thereby increasing the photoelectric conversion efficiency of the perovskite solar cell C1.

[0046] The inner layer 6A is preferably made of at least one material selected from the group consisting of gold, silver, aluminum, and platinum. This allows the inner layer 6A to have a high light reflectance, thereby improving the light utilization efficiency during power generation. From the viewpoints of ease of material handling and film formation, the inner layer 6A is more preferably made of silver.

[0047] The thickness of the inner layer 6A is preferably 30 nm or more and 300 nm or less, and more preferably 50 nm or more and 150 nm or less. If the thickness is less than the lower limit, the resistance of the inner layer 6A may increase, which may reduce the power generation efficiency of the perovskite solar cell C1. If the thickness exceeds the upper limit, it may become difficult to remove the inner layer 6A by laser scribing.

[0048] Examples of methods for forming the inner layer 6A include known film-forming methods such as sputtering and vapor deposition.

[0049] <Grooves> As shown in Figure 1, the perovskite solar cell C1 has grooves 8 that open into the surface of the second electrode 6. The grooves 8 penetrate from the second electrode 6 to the photoelectric conversion layer 4, separating the photoelectric conversion layer 4 into a plurality of photoelectric conversion elements. Note that the "surface of the second electrode 6" referred to in this specification is the surface that forms the outside of the perovskite solar cell C1, and corresponds to the surface located at the top in Figure 1.

[0050] FIG. 3 is a cross-sectional view schematically showing grooves 8 provided in perovskite solar cell C1. As shown in FIG. 3, if the portions of grooves 8 that penetrate the photoelectric conversion layer 4 are defined as first grooves, and the portions that penetrate the second electrode 6 are defined as second grooves, the second grooves have portions where the groove width is wider than the first grooves. That is, the groove width of at least a portion of the second grooves is groove width W2 that is wider than groove width W1 of the first grooves. In particular, it is not necessary for the entire second groove to have a groove width wider than the entire first groove, and it is sufficient for the second grooves to have at least one portion where the groove width is wider than the first grooves.

[0051] Furthermore, when the groove width of the entire second groove portion is groove width W2 and the groove width of the entire first groove portion is groove width W1, the groove 8 is preferably formed such that the groove width W2 of the second groove portion is wider than the groove width W1 of the first groove portion. In other words, it is more preferable that the groove widths of all the second groove portions are wider than groove width W1.

[0052] By forming the groove 8 in this manner, even if residues of the second electrode 6 (burrs of the second electrode 6) occur at the opening edge of the groove 8 formed by laser scribing, it is possible to prevent the residues from coming into contact with adjacent cells across the groove 8 or the residues from coming into contact with the bottom of the groove 8 (first groove portion), thereby making it possible to suppress the generation of leakage current in the groove 8.

[0053] A method for forming groove 8 composed of a first groove portion and a second groove portion includes a method for completing groove 8 by combining laser scribing for forming groove 8A shown in Fig. 4 with laser scribing for forming groove 8B shown in Fig. 8. The order of forming groove 8A and groove 8B is not limited, and groove 8A may be formed first and then groove 8B, or groove 8B may be formed first and then groove 8A.

[0054] The groove 8A shown in Fig. 4 has a groove width W1 and penetrates from the second electrode 6 to the photoelectric conversion layer 4. In the laser scribing step for forming this groove, by appropriately adjusting the laser output, the groove 8A may be completed by a single laser processing step as shown in Fig. 5, or the groove 8A may be formed by multiple laser processing steps.

[0055] An example of a method for forming the groove 8A by multiple laser processing steps is to form a groove 8a by irradiating the laser a first time as shown in Fig. 5, removing almost only the second electrode 6, as exemplified in Fig. 6, and then perform a second laser processing step on the groove 8a as shown in Fig. 7 to complete the groove 8A shown in Fig. 5. By forming the groove 8A in this manner, the laser output can be reduced, thereby suppressing damage to other layers (layers that are not removed) caused by the laser processing.

[0056] 8 has a groove width W2 and penetrates the second electrode 6. In the laser scribing step for forming this groove, the groove 8B may be completed by a single laser processing step, or the groove 8B may be formed by multiple laser processing steps.

[0057] As a method for forming the groove 8B by one laser processing, there is a method in which the beam diameter is set to W2 by defocusing and then laser irradiation is performed, as shown in Fig. 9. As a method for forming the groove 8B by multiple laser processing, there is a method in which a groove 8b having a groove width narrower than W2 is formed by a first laser processing, and then a second laser processing is performed at a position adjacent to the groove 8b, thereby completing the groove 8B shown in Fig. 8, as shown in Fig. 10.

[0058] In the groove 8, it is preferable that the groove width W1 of the first groove portion is 10 μm or more and less than 100 μm, and the groove width W2 of the second groove portion is 100 μm or more and 200 μm or less. Furthermore, it is more preferable that the groove width W1 of the first groove portion is 30 μm or more and 70 μm or less, and it is more preferable that the groove width W2 of the second groove portion is 120 μm or more and 180 μm or less. If the groove width is less than the lower limit, there is a risk of failure in insulation between cells, resulting in a decrease in yield. If the groove width exceeds the upper limit, power generation is not performed in the grooved region (laser scribed region), and power generation efficiency may decrease.

[0059] <Transparent Substrate> The transparent substrate 1 is a substrate capable of transmitting light. It may also be a light-transmitting substrate. The substrate may be the same as or include the base or substrate. It is preferable that the substrate is non-conductive. It is also preferable that the substrate is a sheet-like member. The transparent substrate 1 is desirably made of a material that prevents deterioration inside the photoelectric conversion layer 4 due to moisture, oxygen, etc. in the air. The terms "transparent" and "light-transmitting" mean that the substrate transmits light, but do not exclude materials that reflect or absorb light even slightly. It is sufficient that the substrate is disposed on the light-receiving surface side of the solar cell (including a portion through which light can enter, as in the present disclosure) and transmits light appropriately. This can be considered synonymous with being disposed on the light-receiving surface side of the solar cell. Therefore, being disposed at least on the light-receiving surface side can be considered to have transparency or light-transmitting properties. In other words, a transparent substrate refers to a substrate disposed on the light-receiving surface side of the solar cell.

[0060] Examples of materials constituting the transparent substrate 1 include glass and resin. Examples of resins constituting the transparent substrate 1 include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), polyetherimide (PEI), polytetrafluoroethylene (PTFE), polyamideimide (PAI), polyethylene naphthalate (PEN), etc. In the perovskite solar cell C1, the second electrode includes an inner layer 6A and an outer layer 6B, thereby reducing damage to the transparent substrate 1 during laser scribing, which is particularly effective when the material constituting the transparent substrate 1 is a resin film.

[0061] <First Electrode (Transparent Conductive Film Layer)> The first electrode is a transparent conductive film layer 2 that is translucent like the transparent substrate 1 and conductive. As described above, being transparent or translucent can be defined as being transparent or translucent by being provided at least on the light-receiving surface side. That is, a transparent conductive film layer refers to a conductive film layer provided on the light-receiving surface side of a solar cell. Note that the term "film," "layer," or "film layer" does not specify thickness or width, and includes patterned or island-shaped structures and structures with portions of different thicknesses. Preferably, a film, layer, or film layer has a substantially constant thickness. Note that, unless otherwise specified, "approximately" or "approximately" means that variations within the range of manufacturing error are permitted, and preferably indicates that variations of plus or minus 15% of the numerical value are permitted. In this disclosure, unless otherwise specified, thickness, width, etc. are confirmed by cross-sectional observation, and SEM observation is performed by observing a single 400 nm wide cross-sectional SEM image, and it is sufficient to confirm the thickness, width, etc. within that range, and it is not necessary to confirm all cross sections. In other words, the term "substantially constant thickness" can be said to be approximately constant if the thickness in a single 400 nm wide cross-sectional SEM image is within a range of plus or minus 15% of the average thickness.

[0062] Examples of materials that can be used to form the transparent conductive film layer 2 include conductive transparent materials such as indium tin oxide (ITO), fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide (AZO), indium zinc oxide (IZO), and gallium-doped zinc oxide (GZO). Alternatively, the transparent conductive film layer 2 may be formed by patterning thin wires of a conductive metal such as silver on an oxide.

[0063] The transparent conductive film layer 2 may have a thickness of, for example, 50 nm or more and 300 nm or less. The transparent conductive film layer 2 preferably has a sheet resistance of 10 Ω / sq or less. Furthermore, the transparent conductive film layer 2 preferably has a light transmittance of 80% or more. Examples of methods for forming the transparent conductive film layer 2 include known film formation methods such as sputtering and chemical vapor deposition (CVD).

[0064] <Electron Transport Layer> The electron transport layer 3 is a layer that has the function of transporting electrons generated in the photoelectric conversion layer 4. As long as the solar cell has a photoelectric conversion function, it naturally has this function as long as it is arranged on the electron transport side of the photoelectric conversion layer or on the electron transport side of the photoelectric conversion layer, and there is no need to confirm this function. In other words, as long as the solar cell has a photoelectric conversion function, any layer arranged on the electron transport side of the photoelectric conversion layer or on the electron transport side of the photoelectric conversion layer can be an electron transport layer. Furthermore, it is even better if it has the function of blocking holes generated in the photoelectric conversion layer 4. The electron transport layer 3 is made of a material that allows electrons generated in the photoelectric conversion layer 4 to easily move to the transparent conductive film layer 2. Examples of materials that make up the electron transport layer 3 include tin oxide, titanium oxide, and zinc oxide.

[0065] The thickness of the electron transport layer 3 can be, for example, 100 nm or more and 250 nm or less. Examples of methods for forming the electron transport layer 3 include known film formation methods such as sputtering and screen printing. The electron transport layer does not need to be provided in addition to the transparent conductive film layer and / or transparent substrate. That is, the electron transport layer can also function as the transparent conductive film layer and / or transparent substrate, and vice versa. Therefore, it is not always necessary to provide all of the electron transport layer, transparent conductive film layer, and / or transparent substrate, and the case where only one of them is provided while one of them also serves the other function is not excluded.

[0066] <Photoelectric conversion layer> The photoelectric conversion layer 4 is a layer containing a perovskite compound, which is a photoelectric conversion material, and is a layer that absorbs light incident on the perovskite solar cell C1 and generates electrons and holes. Of these, the electrons move to the electron transport layer 3, and the holes move to the hole transport layer 5. The photoelectric conversion layer 4 may be composed of a perovskite compound alone, or may contain a substance other than a perovskite compound.

[0067] A perovskite compound is composed of a compound represented by the general formula: ABX3 (1). However, although the composition ratio of each element is preferably 1:1:3, it is not necessarily 1:1:3, the content of each element may be varied as appropriate, and each constituent element does not necessarily have to be of a single type. As long as a solar cell has a photoelectric conversion function, it is believed that the perovskite compound is exhibiting this photoelectric conversion function. Therefore, it is appropriate for the perovskite compound to have the degree of freedom in its composition as described above, and it is similarly appropriate that it can be confirmed that it is a perovskite compound by the method described below.

[0068] In general formula (1), A is an organic molecule (including an organic group or an organic cation, the same applies in this disclosure) or an inorganic atom or molecule (including an inorganic group or an inorganic cation, the same applies in this disclosure) or a combination thereof, B is a metal atom or molecule (including a metal cation, the same applies in this disclosure), and X is a halogen atom or molecule or a chalcogen atom or molecule (including a halogen anion or a chalcogen anion, the same applies in this disclosure). In general formula (1), the three Xs may be the same or different from one another.

[0069] Whether a compound is a perovskite compound can be determined by knowing that it contains A, B, and X, taking into consideration whether it is capable of absorbing light and converting it into electricity when contained in the photoelectric conversion layer 4. For example, it may be determined that the compound contains organic molecules, metal atoms, and halogen atoms, or inorganic atoms, metal atoms, and halogen atoms.

[0070] Furthermore, as long as the photoelectric conversion layer has a photoelectric conversion function, the presence of a perovskite compound can be confirmed by detecting elements corresponding to A, B, and X. For example, molecules containing carbon, nitrogen, and hydrogen are suitable as organic molecules, and therefore, carbon, nitrogen, hydrogen, a metal element, and a halogen or chalcogen may be detected. Furthermore, for example, cesium or rubidium is suitable as inorganic atoms, and therefore, cesium or rubidium, a metal element, and a halogen or chalcogen may be detected.

[0071] In such solar cells, laser scribing is likely to leave residue on the second electrode, so the effect of the present disclosure of suppressing leakage current in the grooves formed by laser scribing can be further demonstrated. Furthermore, the fact that the photoelectric conversion layer is a perovskite compound does not necessarily mean that it has a crystalline structure, since it is natural that the photoelectric conversion layer must have a crystalline structure in order to have a photoelectric conversion function. This does not exclude the photoelectric conversion layer from including materials other than perovskite compounds.

[0072] The perovskite compound contained in the perovskite solar cell C1 may be replaced with an organic-inorganic hybrid compound. In such solar cells, laser scribing tends to leave residue on the second electrode, further enhancing the effect of the present disclosure of suppressing leakage current in the grooves formed by laser scribing. An organic-inorganic hybrid compound refers to a compound containing both inorganic and organic components. Solar cells using a perovskite compound, which is one type of organic-inorganic hybrid compound, are also called organic-inorganic hybrid solar cells. "Organic" typically refers to a material composed of multiple carbon elements. Carbon materials such as graphite, graphene, carbon nanowires, carbon nanofibers, carbon nanotubes, carbon that functions as an electrode, and carbon black are not considered to be organic materials. In other words, organic refers to a material composed of multiple carbon elements, excluding the above-mentioned carbon materials such as graphite. "Inorganic" refers to a material that is not organic.

[0073] In general formula (1), examples of the organic molecule represented by A include alkylamine, alkylammonium, and nitrogen-containing heterocyclic compounds. In the perovskite compound (1), the organic molecule represented by A may be only one type of organic molecule, or may be two or more types of organic molecules.

[0074] Examples of alkylamines include methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, trimethylamine, triethylamine, tripropylamine, tributylamine, tripentylamine, trihexylamine, ethylmethylamine, methylpropylamine, butylmethylamine, methylpentylamine, hexylmethylamine, ethylpropylamine, and ethylbutylamine.

[0075] The alkylammonium is an ionized product of the alkylamine. Examples of the alkylammonium include methylammonium, ethylammonium, propylammonium, butylammonium, pentylammonium, hexylammonium, dimethylammonium, diethylammonium, dipropylammonium, dibutylammonium, dipentylammonium, dihexylammonium, trimethylammonium, triethylammonium, tripropylammonium, tributylammonium, tripentylammonium, trihexylammonium, ethylmethylammonium, methylpropylammonium, butylmethylammonium, methylpentylammonium, hexylmethylammonium, ethylpropylammonium, and ethylbutylammonium.

[0076] Examples of the nitrogen-containing heterocyclic compound include imidazole, azole, pyrrole, aziridine, azirine, azetidine, azeto, azole, imidazoline, and carbazole. The nitrogen-containing heterocyclic compound may be an ionized compound. As the ionized nitrogen-containing heterocyclic compound, phenethylammonium is preferred.

[0077] In general formula (1), the organic molecule represented by A is preferably methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, methylammonium, ethylammonium, propylammonium, butylammonium, pentylammonium, hexylammonium, or phenethylammonium, more preferably methylamine, ethylamine, propylamine, methylammonium, ethylammonium, or propylammonium, and even more preferably methylammonium.

[0078] In general formula (1), examples of the metal atom represented by B include lead, tin, zinc, titanium, antimony, bismuth, nickel, iron, cobalt, silver, copper, gallium, germanium, magnesium, calcium, indium, aluminum, manganese, chromium, molybdenum, and europium. In the perovskite compound, the metal atom represented by B may be only one type of metal atom, or may be two or more types of metal atoms. From the viewpoint of improving the light absorption properties and charge generation properties of the perovskite compound, the metal atom represented by B is preferably a lead atom or a tin atom. From the viewpoint of reducing lead, a tin atom is preferred.

[0079] In general formula (1), examples of halogen atoms represented by X include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms, and examples of chalcogen atoms include oxygen atoms, sulfur atoms, selenium atoms, and tellurium atoms. In the perovskite compound, the halogen atoms or chalcogen atoms represented by X may be one type or two or more types. As the halogen atom represented by X, an iodine atom is preferred from the viewpoint of enabling the perovskite compound to utilize light in a wide wavelength range. Specifically, of the three Xs, it is preferred that at least one X represents an iodine atom, and it is more preferred that all three Xs represent iodine atoms.

[0080] The perovskite compound may be a compound represented by the general formula "CH ３ NH ３ PbX ３ (wherein X represents a halogen atom)" is preferred, and ３ NH ３ PbI ３ As the perovskite compound, the general formula "CH ３ NH ３ PbX ３ " (particularly, compounds represented by CH ３ NH ３ PbI ３ By using the above-mentioned compound, electrons and holes can be generated more efficiently in the perovskite compound, and as a result, the photoelectric conversion efficiency of the solar cell can be further improved.

[0081] An example of a method for forming the photoelectric conversion layer 4 made of a perovskite compound is to apply a precursor solution prepared by dissolving a precursor compound of the perovskite compound in an organic solvent using a known method such as spin coating or bar coating. The thickness of the photoelectric conversion layer 4 is preferably 500 nm or more and 2 μm or less, and more preferably 700 nm or more and 800 nm or less.

[0082] <Hole Transport Layer> The hole transport layer 5 is a layer that transports holes generated in the photoelectric conversion layer 4. As long as the solar cell has a photoelectric conversion function, it naturally has this function as long as it is disposed on the hole transport side of the photoelectric conversion layer or on the hole transport side of the photoelectric conversion layer, and there is no need to confirm this function. In other words, as long as the solar cell has a photoelectric conversion function, any layer disposed on the hole transport side of the photoelectric conversion layer or on the hole transport side of the photoelectric conversion layer can be a hole transport layer. Furthermore, it is preferable that it has a function of blocking electrons generated in the photoelectric conversion layer 4. The hole transport layer 5 is composed primarily of a hole transport material. Specifically, the hole transport layer 5 preferably contains 70% by mass or more, and more preferably 85% to 100% by mass, of the hole transport material. The hole transport layer 5 may be composed solely of the hole transport material without containing an organic binder resin, a plasticizer, or the like.

[0083] Examples of hole transport materials include P-type organic semiconductors, conductive polymers, metal oxides, and metal sulfides (e.g., Cu ２ Examples of suitable materials include oxides such as ZnO, NiO, and ZnS, and specifically, spiro-OMeTAD is preferred. Examples of methods for forming the hole transport layer 5 include known methods for coating and forming a film, such as spin coating and bar coating. The thickness of the hole transport layer 5 is preferably 20 nm or more and 500 nm or less, and more preferably 50 nm or more and 150 nm or less. The hole transport layer does not necessarily need to be provided in addition to the second electrode. In other words, the hole transport layer can also function as the second electrode, and vice versa. Therefore, it is not always necessary to provide both the hole transport layer and the second electrode, and it is not excluded that only one of them can be provided, provided that one of them also serves another function.

[0084] <Other Embodiments> The embodiments disclosed herein are illustrative in all respects and are not intended to be limiting. Therefore, the technical scope of the present disclosure should not be interpreted solely by the above-described embodiments, but should be defined based on the claims. Furthermore, all modifications within the scope and meaning equivalent to the claims are included.

[0085] For example, the perovskite solar cell C1 shown in FIG. 1 has a structure known as a planar type, but the present invention is not limited to the planar type and is applicable to any solar cell having a first electrode, a second electrode, and a photoelectric conversion layer located between the two electrodes, and the photoelectric conversion layer containing a perovskite compound.

[0086] To give a specific example, as disclosed in Patent Document 2, the present disclosure can also be applied to a perovskite solar cell that has a photoelectric conversion layer between a first electrode (transparent electrode) and a second electrode (counter electrode), the photoelectric conversion layer including a porous semiconductor film of a metal oxide such as titanium oxide, and the surface of the metal oxide coated with a perovskite compound.

[0087] Recently, solar cells have been proposed that use carbon as the material for the second electrode (counter electrode). Examples of the second electrode made of carbon include a mesoporous conductive film made of graphite or carbon black. Patent Document 2 also discloses that a solid substrate made of a carbon material can be used as the second electrode.

[0088] When the second electrode contains carbon, the light absorption rate of the second electrode increases, making it possible to perform laser scribing at a relatively low output even if the second electrode has a single-layer structure. Therefore, the present invention is also applicable to solar cells with a single-layer second electrode, such as the perovskite solar cell C2 shown in Figure 2.

[0089] DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Transparent conductive film layer (first electrode) 3 Electron transport layer 4 Photoelectric conversion layer 5 Hole transport layer 6 Second electrode (multi-layer structure) 6A Inner layer 6B Outer layer 7 Second electrode (single layer structure) 8 Groove C1 Perovskite solar cell C2 Perovskite solar cell L Laser light Ld Defocused laser light W1 Groove width of first groove portion W2 Groove width of second groove portion

Claims

1. A perovskite solar cell comprising a first electrode having translucency, a second electrode that is the counter electrode of the first electrode, and a photoelectric conversion layer located between the two electrodes, the photoelectric conversion layer containing a perovskite compound, the perovskite solar cell having a groove penetrating the second electrode and the photoelectric conversion layer, the portion of the groove that penetrates the photoelectric conversion layer being a first groove portion, and the portion of the groove that penetrates the second electrode being a second groove portion, the second groove portion having a portion where the groove width is wider than the first groove portion.

2. A perovskite solar cell as claimed in claim 1, characterized in that the groove width of the first groove portion is 10 μm or more and less than 100 μm, and the groove width of the second groove portion is 100 μm or more and 200 μm or less.

3. A perovskite solar cell according to claim 1 or 2, characterized in that the perovskite compound contains an organic group.

4. A perovskite solar cell as described in any one of claims 1 to 3, wherein the second electrode comprises an inner layer and an outer layer, in that order from the photoelectric conversion layer side, and the outer layer has a wavelength at which the light absorptance is higher than the light absorptance of the inner layer.

5. A perovskite solar cell according to claim 4, characterized in that the optical absorptance of the outer layer is higher than the optical absorptance of the inner layer at at least one wavelength between 200 nm and 1100 nm.

6. A perovskite solar cell according to claim 4 or 5, characterized in that the outer layer has a wavelength at which the light absorption rate is 20% or more.

7. A perovskite solar cell according to any one of claims 4 to 6, characterized in that the outer layer is made of at least one of nickel and titanium.

8. A perovskite solar cell according to any one of claims 4 to 6, characterized in that the outer layer is made of nickel.

9. A perovskite solar cell according to any one of claims 4 to 8, wherein the inner layer has a wavelength at which the light reflectance is 50% or more.

10. A perovskite solar cell according to any one of claims 4 to 9, characterized in that the inner layer is composed of at least one material selected from the group consisting of gold, silver, aluminum and silver-platinum.

11. A perovskite solar cell according to any one of claims 4 to 9, characterized in that the inner layer is made of silver.

12. A method for manufacturing a perovskite solar cell as described in any one of claims 1 to 11, comprising a step of irradiating a laser beam from the front surface side of the second electrode to perform laser scribing to form a groove that penetrates from the second electrode to the photoelectric conversion layer, thereby isolating the photoelectric conversion layer into a plurality of photoelectric conversion elements.

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