Photoelectric conversion element, moving body, power generation system, and power generation method

Abstract

To provide a photoelectric conversion element capable of securing a desired photoelectric conversion amount.SOLUTION: The photoelectric conversion element 10 includes a first photoelectric conversion layer 26a and a second photoelectric conversion layer 26a on the first photoelectric conversion layer 26b. The first photoelectric conversion layer 26a includes CIS-based or CZTS-based compound semiconductors. The second photoelectric conversion layer 26b includes CIS-based or CZTS-based compound semiconductors.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a photoelectric conversion element, a mobile object, a power generation system, and a power generation method. [Background technology]

[0002] For example, mobile objects that travel at high altitudes, such as in the stratosphere, face a power shortage at night. One effective solution is to supply power to the mobile object using electromagnetic waves. Patent Document 1 below discloses a system that secures power for the mobile object by irradiating a photovoltaic panel (photoelectric conversion element) mounted on the mobile object with laser light. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-157026 Summary of the Invention [Problem to be solved by the invention]

[0004] The inventors of the present application have discovered the following problem with photoelectric conversion elements. A photoelectric conversion element has a photoelectric conversion layer sandwiched between a pair of electrode layers. The content ratio of elements constituting the photoelectric conversion layer varies in the thickness direction. This can reduce the depth range of the photoelectric conversion layer capable of converting laser light into electrical energy.

[0005] Therefore, there is a demand for a photoelectric conversion element capable of ensuring a desired amount of photoelectric conversion, a mobile body and a power generation system including the photoelectric conversion element, and a power generation method using the photoelectric conversion element. [Means for solving the problem]

[0006] A photoelectric conversion element according to one embodiment includes a first photoelectric conversion layer and a second photoelectric conversion layer disposed on the first photoelectric conversion layer. The first photoelectric conversion layer includes a CIS-based or CZTS-based compound semiconductor. The second photoelectric conversion layer includes a CIS-based or CZTS-based compound semiconductor.

[0007] A moving object according to one aspect includes the above-described photoelectric conversion element.

[0008] A power generation system according to one aspect includes the photoelectric conversion element described above and a laser device that irradiates laser light toward the photoelectric conversion element.

[0009] A power generation method according to one aspect includes irradiating the photoelectric conversion element with laser light. [Effects of the Invention]

[0010] According to the above aspect, it is possible to provide a photoelectric conversion element capable of ensuring a desired amount of photoelectric conversion, a mobile body and a power generation system including the photoelectric conversion element, and a power generation method using the photoelectric conversion element. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram of a power generation system according to the first embodiment. [Figure 2] FIG. 2 is a schematic cross-sectional view of the photoelectric conversion element according to the first embodiment. [Figure 3] FIG. 3 is a diagram showing an example of the energy gap of a photoelectric conversion layer that constitutes a photoelectric conversion element. [Figure 4] FIG. 4 is a graph showing the composition ratio of Ga and In in the photoelectric conversion layer having the energy gap shown in FIG. [Figure 5] FIG. 5 is a graph showing the composition ratio of S and Se in the photoelectric conversion layer having the energy gap shown in FIG. [Figure 6] FIG. 6 is a schematic cross-sectional view of a photoelectric conversion element according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments will be described with reference to the drawings. In the following drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and the ratios of the dimensions may differ from those of the actual parts.

[0013] [First embodiment] 1 is a schematic diagram of a power generation system according to a first embodiment. The power generation system includes a laser light source 300 and a power generation device 400. The power generation device 400 may be mounted on an object 500 that is separated from the laser light source 300. The object 500 that mounts the power generation device 400 may include electronic devices (not shown) that use the power. The object 500 may be located far away from the laser light source 300.

[0014] The object 500 may be a structure, a moving object, or the like. The structure may be, for example, a building or a house. The moving object may be, for example, a car, a ship, or an aircraft. The aircraft may be, for example, a drone, an airplane, or a rocket. The aircraft may be one that moves at a high altitude, such as in the stratosphere.

[0015] The laser light source 300 may be mounted on the ground or on a structure on the ground. Alternatively, the laser light source 300 may be mounted on a moving body such as a car, a ship, or an aircraft. In this case, the moving body carrying the laser light source 300 is a moving body different from the object 500 described above.

[0016] The laser light source 300 may be configured to irradiate laser light toward the power generation device 400. The laser light source 300 may be configured to be able to adjust the direction in which the laser light is irradiated in accordance with the movement of the object 500.

[0017] The power generation device 400 generates electrical energy from the laser light emitted from the laser light source 300. The object 500 or electronic devices mounted on the object 500 may use the electrical energy generated by the power generation device 400.

[0018] The laser light emitted from the laser light source 300 is preferably highly directional. The laser light includes a wavelength band that can be converted into electrical energy by the power generation device 400. The laser light source 300 may output laser light having a wavelength in the infrared region, for example.

[0019] When the laser light emitted from the laser light source 300 travels a long distance in the atmosphere, in order to suppress attenuation of the laser light, it is preferable that the laser light has a wavelength at which the atmospheric light has a high transmittance, that is, a wavelength corresponding to the so-called "atmospheric window." From this perspective, the laser light may have a wavelength of 1070 nm±100 nm, for example.

[0020] The power generation method according to this embodiment includes irradiating the power generation device 400 with laser light, that is, laser light emitted from the laser light source 300.

[0021] The power generating device 400 may be a device that converts laser light into electrical energy. The power generating device 400 may have a module array 420. The multiple photoelectric conversion elements 10 included in the module array 420 may be arranged adjacent to one another. The multiple photoelectric conversion elements 10 may be aligned in at least one direction, preferably in a lattice pattern. In this case, the multiple photoelectric conversion elements 10 may be electrically connected to one another in series and / or parallel.

[0022] Fig. 2 is a schematic cross-sectional view of the photoelectric conversion element 10 according to the first embodiment. It should be noted that the thickness of each layer constituting the photoelectric conversion element 10 is exaggerated in Fig. 2.

[0023] The photoelectric conversion element 10 has a substrate 20. There are no particular limitations on the material that constitutes the substrate 20. The substrate 20 may be made of, for example, glass, ceramics, resin, or metal.

[0024] The photoelectric conversion element 10 has a plurality of photoelectric conversion layers 26a, 26b, and 26c. In the illustrated embodiment, the photoelectric conversion element 10 includes a first photoelectric conversion layer 26a, a second photoelectric conversion layer 26b, and a third photoelectric conversion layer 26c.

[0025] The first photoelectric conversion layer 26a is provided on the substrate 20. The second photoelectric conversion layer 26b is provided on the first photoelectric conversion layer 26a. The third photoelectric conversion layer 26c is provided on the second photoelectric conversion layer 26b.

[0026] Electrode layers 22a, 24a, 22b, 24b, 22c, and 24c are provided to sandwich the first photoelectric conversion layer 26a, the second photoelectric conversion layer 26b, and the third photoelectric conversion layer 26c, respectively. More specifically, the photoelectric conversion element 10 may have a first electrode layer 22a on the substrate 20, a second electrode layer 24a on the first photoelectric conversion layer 26a, a third electrode layer 22b on the second electrode layer 24a, a fourth electrode layer 24b on the second photoelectric conversion layer 26b, a fifth electrode layer 22c on the fourth electrode layer 24b, and a sixth electrode layer 24c on the third photoelectric conversion layer 26c.

[0027] The first photoelectric conversion layer 26a is sandwiched between the first electrode layer 22a and the second electrode layer 24a. The first electrode layer 22a corresponds to one of the positive electrode or the negative electrode, and the second electrode layer 24a corresponds to the other of the positive electrode or the negative electrode.

[0028] The second photoelectric conversion layer 26b is sandwiched between the third electrode layer 22b and the fourth electrode layer 24b. The third electrode layer 22b corresponds to one of the positive electrode or the negative electrode, and the fourth electrode layer 24b corresponds to the other of the positive electrode or the negative electrode.

[0029] The third photoelectric conversion layer 26c is sandwiched between the fifth electrode layer 22c and the sixth electrode layer 24c. The fifth electrode layer 22c corresponds to one of the positive electrode or the negative electrode, and the sixth electrode layer 24c corresponds to the other of the positive electrode or the negative electrode.

[0030] In the first embodiment, the second electrode layer 24a and the third electrode layer 22b are sandwiched between the first photoelectric conversion layer 26a and the second photoelectric conversion layer 26b. In this case, the photoelectric conversion element 10 may have an insulating layer 40a between the second electrode layer 24a and the third electrode layer 22b. The insulating layer 40a electrically insulates the second electrode layer 24a and the third electrode layer 22b from each other. This allows the second electrode layer 24a and the third electrode layer 22b to constitute electrodes having different polarities from each other. However, the second electrode layer 24a and the third electrode layer 22b may also constitute electrodes having the same polarity from each other.

[0031] Furthermore, the fourth electrode layer 24b and the fifth electrode layer 22c are sandwiched between the second photoelectric conversion layer 26b and the third photoelectric conversion layer 26c. In this case, the photoelectric conversion element 10 may have an insulating layer 40b between the fourth electrode layer 24b and the fifth electrode layer 22c. The insulating layer 40b electrically insulates the fourth electrode layer 24b and the fifth electrode layer 22c from each other. This allows the fourth electrode layer 24b and the fifth electrode layer 22c to constitute electrodes having different polarities. However, the fourth electrode layer 24b and the fifth electrode layer 22c may also constitute electrodes having the same polarity.

[0032] The insulating layers 40a and 40b may be transparent insulating layers. That is, the insulating layers 40a and 40b may be made of a light-transmitting material. Examples of such materials include glass, polycarbonate, acrylic (PMMA), fluorine-based resin, silicone rubber, polyurethane, polyester, polyimide, epoxy resin, polystyrene, polyolefin, EVA, and oxide semiconductors with high insulating properties (wide-gap oxide semiconductors). Examples of wide-gap oxide semiconductors include zinc oxide (ZnO), alumina (Al2O3), indium oxide (In2O3), and yttria (Y2O3).

[0033] If necessary, the photoelectric conversion element 10 may have a first buffer layer 27a between the first electrode layer 22a and the first photoelectric conversion layer 26a.If necessary, the photoelectric conversion element 10 may have a second buffer layer 28a between the second electrode layer 24a and the first photoelectric conversion layer 26a.

[0034] If necessary, the photoelectric conversion element 10 may have a third buffer layer 27b between the third electrode layer 22b and the second photoelectric conversion layer 26b.If necessary, the photoelectric conversion element 10 may have a fourth buffer layer 28b between the fourth electrode layer 24b and the second photoelectric conversion layer 26b.

[0035] If necessary, the photoelectric conversion element 10 may include a fifth buffer layer 27c between the fifth electrode layer 22c and the third photoelectric conversion layer 26c. If necessary, the photoelectric conversion element 10 may include a sixth buffer layer 28c between the sixth electrode layer 24c and the third photoelectric conversion layer 26c.

[0036] The first electrode layer 22a may be made of an opaque conductive material or a transparent conductive material. The first electrode layer 22a may be made of a metal such as molybdenum, titanium, or chromium. Although not particularly limited, the thickness of the first electrode layer 22a may be, for example, 50 nm to 1500 nm.

[0037] The second electrode layer 24a, the third electrode layer 22b, the fourth electrode layer 24b, the fifth electrode layer 22c, and the sixth electrode layer 24c may be transparent electrode layers. That is, the second electrode layer 24a, the third electrode layer 22b, the fourth electrode layer 24b, the fifth electrode layer 22c, and the sixth electrode layer 24c may be made of a transparent conductive material. In this specification, "transparent conductive material" refers to a conductive material that is translucent. In this specification, "translucent" refers to transmitting 10% or more of light at any wavelength between 200 nm and 2000 nm. More preferably, the second electrode layer 24a, the third electrode layer 22b, the fourth electrode layer 24b, the fifth electrode layer 22c, and the sixth electrode layer 24c have a translucency of 10% or more at the wavelength of the laser light emitted from the laser light source 300.

[0038] When the second electrode layer 24a, the third electrode layer 22b, the fourth electrode layer 24b, the fifth electrode layer 22c, and the sixth electrode layer 24c are made of a transparent conductive material, light incident on each of the photoelectric conversion layers 26a, 26b, and 26c passes through the second electrode layer 24a, the third electrode layer 22b, the fourth electrode layer 24b, the fifth electrode layer 22c, and the sixth electrode layer 24c.

[0039] The material forming the second electrode layer 24a, the third electrode layer 22b, the fourth electrode layer 24b, the fifth electrode layer 22c, and the sixth electrode layer 24c can be selected from, for example, indium tin oxide (In2O3:Sn), indium titanium oxide (In2O3:Ti), indium zinc oxide (In2O3:Zn), tin-zinc-doped indium oxide (In2O3:Sn,Zn), tungsten-doped indium oxide (In2O3:W), hydrogen-doped indium oxide (In2O3:H), indium gallium zinc oxide (InGaZnO4), zinc tin oxide (ZnO:Sn), fluorine-doped tin oxide (SnO2:F), gallium-doped zinc oxide (ZnO:Ga), boron-doped zinc oxide (ZnO:B), aluminum-doped zinc oxide (ZnO:Al), etc.

[0040] Although not particularly limited, the thickness of the second electrode layer 24a, the third electrode layer 22b, the fourth electrode layer 24b, the fifth electrode layer 22c, and the sixth electrode layer 24c may be, for example, 50 nm to 1500 nm.

[0041] Each of the photoelectric conversion layers 26a, 26b, and 26c is a layer that converts light energy into electrical energy, and is sometimes called a light absorption layer.

[0042] The photoelectric conversion layers 26a, 26b, and 26c may include a CIS-based compound semiconductor. The CIS-based compound semiconductor may be a group I-III-VI2 compound semiconductor. Here, the group I element may be selected from copper (Cu), silver (Ag), gold (Au), and the like. The group III element may be selected from indium (In), gallium (Ga), aluminum (Al), and the like. The CIS-based compound semiconductor may also include tellurium (Te) as a group VI element in addition to selenium (Se) and sulfur (S). The photoelectric conversion layers 26a, 26b, and 26c may also include alkali metals such as Li, Na, K, Rb, and Cs. Herein, the term "group" of an element is based on the short periodic table (the same applies hereinafter).

[0043] Alternatively, the photoelectric conversion layers 26a, 26b, and 26c may include a I2-(II-IV)-VI4 group compound semiconductor, which is a CZTS-based compound semiconductor containing Cu, Zn, Sn, S, or Se. Typical examples of CZTS-based compound semiconductors include Cu2ZnSnSe4 and Cu2ZnSn(S,Se)4.

[0044] Each of the photoelectric conversion layers 26a, 26b, and 26c may have an energy gap smaller than the energy of light corresponding to the wavelength of the laser light emitted from the laser light source 300. When the wavelength of the laser light is 1070 nm±100 nm, the energy gap of each of the photoelectric conversion layers 26a, 26b, and 26c may be 1.28 eV or less. CIS-based compound semiconductors and CZTS-based compound semiconductors have energy gaps of this level.

[0045] CIS-based or CZTS-based compound semiconductors have high conversion efficiency for converting light with a wavelength of 1070 nm±100 nm into electrical energy. Therefore, photoelectric conversion layers 26a, 26b, and 26c including CIS-based or CZTS-based compound semiconductors can be suitably used for laser light with a wavelength of 1070 nm±100 nm.

[0046] FIG. 3 is a diagram showing an example of the energy gap of the photoelectric conversion layers 26a, 26b, and 26c that constitute the photoelectric conversion element 10. FIG. 3 shows the energy gap of one of the multiple photoelectric conversion layers 26a, 26b, and 26c. In FIG. 3, the vertical axis represents the energy gap value. In FIG. 3, the horizontal axis represents the depth of the photoelectric conversion layer (normalized position in the thickness direction). "0" on the horizontal axis represents the position of the interface on the front side of the photoelectric conversion layer. "1" on the horizontal axis represents the position of the interface on the back side of the photoelectric conversion layer.

[0047] FIG. 3 shows the energy gap of a typical CIS-based compound semiconductor. The photoelectric conversion layer showing the energy gap shown in FIG. 3 is composed of a CIS-based compound semiconductor. The compound semiconductor contains indium (In) and gallium (Ga) as group III elements and selenium (Se) and sulfur (S) as group VI elements. FIG. 4 is a graph showing the composition ratio of Ga and In in a photoelectric conversion layer having the energy gap shown in FIG. 3. FIG. 5 is a graph showing the composition ratio of S and Se in a photoelectric conversion layer having the energy gap shown in FIG. 3. The horizontal axis in FIGS. 4 and 5 indicates the depth (normalized position in the thickness direction) of the photoelectric conversion layer. "0" on the horizontal axis indicates the position of the interface on the front side of the photoelectric conversion layer. "1" on the horizontal axis indicates the position of the interface on the back side of the photoelectric conversion layer. The vertical axis in FIG. 4 indicates the ratio of the amount of Ga element to the total amount of Ga and In elements. The vertical axis in FIG. 5 indicates the ratio of the amount of S element to the total amount of S and Se elements. The composition of the photoelectric conversion layer was calculated by measuring it by GD-OES (glow discharge optical emission spectroscopy). The band gap shown in Fig. 3 was calculated based on the measured composition of the photoelectric conversion layer.

[0048] As shown in Figure 4, the composition ratio of Ga to In in the photoelectric conversion layer varies depending on the depth in the thickness direction of the photoelectric conversion layer. The ratio of the amount of Ga element to the total amount of Ga and In elements was generally in the range of 0 to 0.5. As shown in Figure 5, the composition ratio of S to Se in the photoelectric conversion layer varies depending on the depth in the thickness direction of the photoelectric conversion layer. The ratio of the amount of S element to the total amount of S and Se elements was generally in the range of 0 to 0.5.

[0049] 4 and 5, the composition of the elements constituting the photoelectric conversion layer was measured by GD-OES. Alternatively, the composition of the elements constituting the photoelectric conversion layer may be measured by SIMS (Secondary Ion Mass Spectrometry).

[0050] As shown in Figure 3, the energy gap of the photoelectric conversion layer varies depending on the position in the thickness direction. Therefore, the wavelength of light that can be absorbed by the photoelectric conversion layers 26a, 26b, and 26c may vary depending on the region in the thickness direction. Here, laser light is light that includes a very narrow range of wavelengths. Therefore, the depth range of the photoelectric conversion layers 26a, 26b, and 26c that can convert laser light into electrical energy may be narrow.

[0051] For example, light with a wavelength of 1070 nm±100 nm has energy in the range of approximately 1.06 eV to 1.28 eV. Therefore, in the case of the photoelectric conversion layer shown in Fig. 3, the laser light cannot be absorbed in all regions in the thickness direction of the photoelectric conversion layer. Therefore, part of the laser light is absorbed in the third photoelectric conversion layer 26c close to the incident side, but another part of the laser light may transmit through the third photoelectric conversion layer 26c.

[0052] In this embodiment, the light transmitted through the third photoelectric conversion layer 26c near the laser light incident side reaches the second photoelectric conversion layer 26b. Therefore, a portion of the laser light not absorbed by the third photoelectric conversion layer 26c can be absorbed by the second photoelectric conversion layer 26b. Similarly, a portion of the laser light not absorbed by the second photoelectric conversion layer 26b can be absorbed by the first photoelectric conversion layer 26a. In this way, the multiple photoelectric conversion layers 26a, 26b, and 26c stacked one on top of the other absorb most of the laser light and convert it into electrical energy. This makes it possible to ensure the photoelectric conversion capacity of the photoelectric conversion element 10.

[0053] Furthermore, the first photoelectric conversion layer 26a includes a CIS-based or CZTS-based compound semiconductor, and the second photoelectric conversion layer 26b includes a CIS-based or CZTS-based compound semiconductor. Similarly, it is preferable that the third photoelectric conversion layer 26c also includes a CIS-based or CZTS-based compound semiconductor. As a result, each of the photoelectric conversion layers 26a, 26b, and 26c has approximately the same energy gap, allowing the photoelectric conversion element 10 to effectively absorb light in a narrow wavelength range, such as laser light, and convert it into electrical energy.

[0054] The energy gap range of the second photoelectric conversion layer 26b preferably at least partially overlaps with the energy gap range of the first photoelectric conversion layer 26a. The first photoelectric conversion layer 26a and the second photoelectric conversion layer 26b can absorb light of the same wavelength, such as laser light, and convert it into electrical energy within the overlapping energy gap ranges.

[0055] More preferably, both the first photoelectric conversion layer 26a and the second photoelectric conversion layer 26b have an energy gap of 1.28 eV or less, which enables the first photoelectric conversion layer 26a and the second photoelectric conversion layer 26b to absorb laser light with a wavelength of 1070 nm±100 nm and convert it into electrical energy.

[0056] The energy gap range of the third photoelectric conversion layer 26c preferably at least partially overlaps with the energy gap range of the first photoelectric conversion layer 26a. The first photoelectric conversion layer 26a and the third photoelectric conversion layer 26c can absorb light of the same wavelength, such as laser light, and convert it into electrical energy within the overlapping energy gap ranges.

[0057] More preferably, both the first photoelectric conversion layer 26a and the third photoelectric conversion layer 26c have an energy gap of 1.28 eV or less, which enables the first photoelectric conversion layer 26a and the third photoelectric conversion layer 26c to absorb laser light with a wavelength of 1070 nm±100 nm and convert it into electrical energy.

[0058] The thickness of the second photoelectric conversion layer 26b is preferably 0.9 to 1.1 times the thickness of the first photoelectric conversion layer 26a, and more preferably is substantially equal to the thickness of the first photoelectric conversion layer 26a.

[0059] Similarly, the thickness of the third photoelectric conversion layer 26c is preferably 0.9 to 1.1 times the thickness of the first photoelectric conversion layer 26a. More preferably, the thickness of the third photoelectric conversion layer 26c is substantially equal to the thickness of the first photoelectric conversion layer 26a. When the thicknesses of the photoelectric conversion layers 26a, 26b are substantially equal, the photoelectric conversion layers 26a, 26b can be manufactured under the same conditions, facilitating the manufacture of the photoelectric conversion element.

[0060] Alternatively, the thickness of the first photoelectric conversion layer 26a may be greater than the thickness of the second photoelectric conversion layer 26b. The amount of light incident on the first photoelectric conversion layer 26a is smaller than the amount of light incident on the second photoelectric conversion layer 26b. Therefore, when the thickness of the first photoelectric conversion layer 26a is greater than the thickness of the second photoelectric conversion layer 26b, the magnitude of the electrical energy generated by the first photoelectric conversion layer 26a and the second photoelectric conversion layer 26b is uniform. Similarly, the thickness of the second photoelectric conversion layer 26b may be greater than the thickness of the third photoelectric conversion layer 26c.

[0061] The type of main component element contained in the second photoelectric conversion layer 26b is preferably the same as the type of main component element contained in the first photoelectric conversion layer 26a. Here, the main component element may be an element that accounts for 10% or more of the elements constituting the photoelectric conversion layer. This is considered to make the energy bands of the first photoelectric conversion layer 26a and the second photoelectric conversion layer 26b similar. Therefore, the first photoelectric conversion layer 26a and the second photoelectric conversion layer 26b can have approximately the same energy gap.

[0062] More preferably, the chemical composition of the second photoelectric conversion layer 26b is substantially the same as the chemical composition of the first photoelectric conversion layer 26a.

[0063] The type of main component element contained in the third photoelectric conversion layer 26c is preferably the same as the type of main component element contained in the first photoelectric conversion layer 26a. This is thought to make the energy bands of the first photoelectric conversion layer 26a and the third photoelectric conversion layer 26c similar. Therefore, the first photoelectric conversion layer 26a and the third photoelectric conversion layer 26c can have approximately the same energy gap.

[0064] More preferably, the chemical composition of the third photoelectric conversion layer 26c is substantially the same as the chemical composition of the first photoelectric conversion layer 26a.

[0065] The materials constituting the first buffer layer 27a, the third buffer layer 27b, and the fifth buffer layer 27c are not particularly limited. The first buffer layer 27a, the third buffer layer 27b, and the fifth buffer layer 27c may be, for example, layers containing a chalcogenide compound of a transition metal element having a layered structure. Specifically, the first buffer layer 27a, the third buffer layer 27b, and the fifth buffer layer 27c may be composed of a compound containing a transition metal material such as M, W, Ti, V, Cr, Nb, or Ta and a chalcogen element such as O, S, or Se. The first buffer layer 27a, the third buffer layer 27b, and the fifth buffer layer 27c may be, for example, a M(Se,S)2 layer, a Mose2 layer, or a M0S2 layer.

[0066] The materials constituting the second buffer layer 28a, the fourth buffer layer 28b, and the sixth buffer layer 28c are not particularly limited. The second buffer layer 28a, the fourth buffer layer 28b, and the sixth buffer layer 28c can be selected from compounds containing zinc (Zn), cadmium (Cd), and indium (In), for example. Examples of compounds containing zinc include ZnO, ZnS, Zn(OH)2, or mixed crystals thereof, such as Zn(O,S) and Zn(O,S,OH), as well as ZnMgO and ZnSnO. Examples of compounds containing cadmium include CdS, CdO, or mixed crystals thereof, such as Cd(O,S) and Cd(O,S,OH). Examples of compounds containing indium include In2S3, In2O3, or mixed crystals thereof, such as In2(O,S)3 and In2(O,S,OH)3, as well as In2O3, In2S3, and In(OH). x The second buffer layer 28a, the fourth buffer layer 28b, and the sixth buffer layer 28c may have a stacked structure of these compounds.

[0067] The photoelectric conversion element 10 may have a sealing layer 30 on the third electrode layer 24c. In Fig. 2, the sealing layer 30 is provided only on the third electrode layer 24c. Alternatively, the sealing layer 30 may be formed so as to cover the top of the third electrode layer 24c and the side surfaces of each layer constituting the photoelectric conversion element 10.

[0068] The photoelectric conversion element 10 can be suitably used as a photoelectric conversion element for generating electricity using laser light, for example, laser light having a wavelength of 1070 nm±100 nm. However, it should be noted that the photoelectric conversion element 10 can also be used for other purposes.

[0069] 2, the photoelectric conversion element 10 includes three photoelectric conversion layers 26a, 26b, and 26c. Alternatively, the photoelectric conversion element 10 may include only two photoelectric conversion layers 26a and 26b. Alternatively, the photoelectric conversion element 10 may include four or more photoelectric conversion layers. Even in this case, the material, film thickness, and chemical composition constituting each photoelectric conversion layer may be as described above.

[0070] [Second embodiment] A power generating device according to the second embodiment will be described. In the power generating device according to the second embodiment, the laser light source 300 and the module array 420 are the same as those in the first embodiment. In the second embodiment, the configuration (layer structure) of each photoelectric conversion element 10 is different from that in the first embodiment.

[0071] FIG. 6 is a schematic cross-sectional view of a photoelectric conversion element according to a second embodiment. It should be noted that the thickness of each layer constituting the photoelectric conversion element 10 is exaggerated in FIG. 6. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals. It should be noted that the description of the same components as those in the first embodiment may be omitted.

[0072] The photoelectric conversion element 10 according to the second embodiment has a plurality of photoelectric conversion layers 26a, 26b, and 26c. In the illustrated embodiment, the photoelectric conversion element 10 includes a first photoelectric conversion layer 26a, a second photoelectric conversion layer 26b, and a third photoelectric conversion layer 26c.

[0073] The first photoelectric conversion layer 26a is provided on the substrate 20. The second photoelectric conversion layer 26b is provided on the first photoelectric conversion layer 26a. The third photoelectric conversion layer 26c is provided on the second photoelectric conversion layer 26b.

[0074] The photoelectric conversion element 10 may have a first electrode layer 22a on the substrate 20, a second electrode layer 24a on the first photoelectric conversion layer 26a, a fifth electrode layer 22c on the second photoelectric conversion layer 26b, and a sixth electrode layer 24c on the third photoelectric conversion layer 26c.

[0075] The first photoelectric conversion layer 26a is sandwiched between the first electrode layer 22a and the second electrode layer 24a. The first electrode layer 22a corresponds to one of the positive electrode or the negative electrode, and the second electrode layer 24a corresponds to the other of the positive electrode or the negative electrode.

[0076] The second photoelectric conversion layer 26b is sandwiched between the second electrode layer 24a and the fifth electrode layer 22c. The third photoelectric conversion layer 26c is sandwiched between the fifth electrode layer 22c and the sixth electrode layer 24c. The fifth electrode layer 22c corresponds to one of the positive electrode or the negative electrode, and the sixth electrode layer 24c corresponds to the other of the positive electrode or the negative electrode.

[0077] In the first embodiment, the second electrode layer 24a is sandwiched between the first photoelectric conversion layer 26a and the second photoelectric conversion layer 26b. However, an insulating layer 40a is not provided between the first photoelectric conversion layer 26a and the second photoelectric conversion layer 26b. Furthermore, the fifth electrode layer 22c is sandwiched between the second photoelectric conversion layer 26b and the third photoelectric conversion layer 26c. However, an insulating layer 40b is not provided between the second photoelectric conversion layer 26b and the third photoelectric conversion layer 26c.

[0078] In the second embodiment, the second electrode layer 24a functions as an electrode for both the first photoelectric conversion layer 26a and the second photoelectric conversion layer 26b. Therefore, the second electrode layer 24a functions as both the second electrode layer 24a and the third electrode layer 22b in the first embodiment. Similarly, the fifth electrode layer 22c functions as an electrode for both the second photoelectric conversion layer 26b and the third photoelectric conversion layer 26c. Therefore, the fifth electrode layer 22c functions as both the fourth electrode layer 24b and the fifth electrode layer 22c in the first embodiment.

[0079] If necessary, the photoelectric conversion element 10 may have a first buffer layer 27a between the first electrode layer 22a and the first photoelectric conversion layer 26a.If necessary, the photoelectric conversion element 10 may have a second buffer layer 28a between the second electrode layer 24a and the first photoelectric conversion layer 26a.

[0080] If necessary, the photoelectric conversion element 10 may have a fourth buffer layer 28b between the second electrode layer 24a and the second photoelectric conversion layer 26b. If necessary, the photoelectric conversion element 10 may have a third buffer layer 27b between the fifth electrode layer 22c and the second photoelectric conversion layer 26b.

[0081] If necessary, the photoelectric conversion element 10 may include a fifth buffer layer 27c between the fifth electrode layer 22c and the third photoelectric conversion layer 26c. If necessary, the photoelectric conversion element 10 may include a sixth buffer layer 28c between the sixth electrode layer 24c and the third photoelectric conversion layer 26c.

[0082] The materials and film thicknesses of the electrode layers 22a, 24a, 22c, and 24c and the buffer layers 27a, 27b, 27c, 28a, 28b, and 28c may be the same as those in the first embodiment.

[0083] Furthermore, the materials, film thicknesses, chemical compositions, etc. that constitute each of the photoelectric conversion layers 26a, 26b, and 26c may be designed in the same manner as in the first embodiment.

[0084] Even in this case, similar to the first embodiment, the photoelectric conversion element 10 can effectively absorb light in a narrow wavelength range, such as laser light, and convert it into electrical energy by using the multiple photoelectric conversion layers 26a, 26b, and 26c.

[0085] 6, the photoelectric conversion element 10 includes three photoelectric conversion layers 26a, 26b, and 26c. Alternatively, the photoelectric conversion element 10 may include only two photoelectric conversion layers 26a and 26b. Alternatively, the photoelectric conversion element 10 may include four or more photoelectric conversion layers. Even in this case, the material, film thickness, and chemical composition constituting each photoelectric conversion layer may be as described above.

[0086] As described above, the contents of the present invention have been disclosed through the embodiments, but the descriptions and drawings that form part of this disclosure should not be understood to limit the present invention. Various alternative embodiments, examples, and operating techniques will become apparent to those skilled in the art from this disclosure. Therefore, the technical scope of the present invention is defined only by the inventive features of the claims that can be reasonably understood from the above description. [Explanation of symbols]

[0087] 10 Photoelectric conversion element 22a 1st electrode layer 24a 2nd electrode layer 22b Third electrode layer 24b 4th electrode layer 22c 5th electrode layer 24c 6th electrode layer 26a First photoelectric conversion layer 26b Second photoelectric conversion layer 26c Third photoelectric conversion layer

Claims

1. a first photoelectric conversion layer; a second photoelectric conversion layer on the first photoelectric conversion layer, the first photoelectric conversion layer contains a CIS-based or CZTS-based compound semiconductor, The photoelectric conversion element, wherein the second photoelectric conversion layer contains a CIS-based or CZTS-based compound semiconductor.

2. The photoelectric conversion element according to claim 1 , wherein the thickness of the second photoelectric conversion layer is 0.9 to 1.1 times the thickness of the first photoelectric conversion layer.

3. The photoelectric conversion element according to claim 1 , wherein the first photoelectric conversion layer has a thickness greater than a thickness of the second photoelectric conversion layer.

4. The photoelectric conversion element according to claim 1 , wherein a type of main component element contained in the second photoelectric conversion layer is the same as a type of main component element contained in the first photoelectric conversion layer.

5. The photoelectric conversion element according to claim 1 , wherein the second photoelectric conversion layer has a chemical composition substantially identical to that of the first photoelectric conversion layer.

6. The photoelectric conversion element according to claim 1 , wherein an energy gap range of the second photoelectric conversion layer at least partially overlaps with an energy gap range of the first photoelectric conversion layer.

7. The photoelectric conversion element according to claim 6 , wherein both the first photoelectric conversion layer and the second photoelectric conversion layer have an energy gap of 1.28 eV or less.

8. The photoelectric conversion element according to claim 1 , which is a photoelectric conversion element for generating electricity using laser light.

9. The photoelectric conversion element according to claim 1 , further comprising a second electrode layer between the first photoelectric conversion layer and the second photoelectric conversion layer.

10. The photoelectric conversion element according to claim 9 , wherein the second electrode layer functions as an electrode for both the first photoelectric conversion layer and the second photoelectric conversion layer.

11. The photoelectric conversion element is a second electrode layer between the first photoelectric conversion layer and the second photoelectric conversion layer; a third electrode layer between the first photoelectric conversion layer and the second photoelectric conversion layer; an insulating layer between the second electrode layer and the third electrode layer; The photoelectric conversion element according to claim 1 , wherein

12. The photoelectric conversion element according to claim 11 , wherein the third electrode layer is a transparent electrode layer.

13. The photoelectric conversion element according to claim 11 or 12, wherein the insulating layer is a transparent insulating layer.

14. The photoelectric conversion element according to claim 9 , wherein the second electrode layer is a transparent electrode layer.

15. a third photoelectric conversion layer on the second photoelectric conversion layer; The photoelectric conversion element according to claim 1 , wherein the third photoelectric conversion layer contains a CIS-based or CZTS-based compound semiconductor.

16. A moving object comprising the photoelectric conversion element according to any one of claims 1 to 15.

17. The photoelectric conversion element according to any one of claims 1 to 15, a laser device that irradiates the photoelectric conversion element with laser light.

18. A power generation method comprising irradiating a photoelectric conversion element according to claim 1 with laser light.

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