Photoelectric conversion element, solar cell module, paddle, and photoelectric conversion element manufacturing method

Abstract

Provided is a photoelectric conversion element having high adherence strength. A photoelectric conversion element (10) includes a chalcogen compound layer (26). The chalcogen compound layer includes a first region (R1) that contributes to photoelectric conversion, and a second region (R2) that does not contribute to photoelectric conversion. The thickness (T2) of the second region of the chalcogen compound layer is less than the thickness (T1) of the first region of the chalcogen compound layer.

Description

Photoelectric conversion element, solar cell module, paddle, and method for manufacturing photoelectric conversion element

[0001] The present invention relates to a photoelectric conversion element, a solar cell module, a paddle, and a method for manufacturing a photoelectric conversion element.

[0002] A photoelectric conversion element that converts light energy into electrical energy is known (Patent Document 1). The photoelectric conversion element described in Patent Document 1 has a so-called CIS-based or CIGS-based light absorption layer. The CIS-based or CIGS-based light absorption layer is a I-III-VI type having a chalcopyrite structure. ２ The compound semiconductor is a group compound semiconductor.

[0003] Such a CIS-based or CIGS-based light absorption layer is formed by depositing a precursor film made of group I elements (Cu, etc.) and group III elements (In, Ga, etc.), and then selenizing and / or sulfurizing the precursor film.

[0004] The precursor film expands as it reacts with selenium and / or sulfur and grows into a light-absorbing layer with a chalcopyrite structure. This volume expansion causes distortion inside the light-absorbing layer, forming gaps of 0.1 μm to several μm in size called voids within the light-absorbing layer. Patent Document 1 describes that the presence of voids within a certain range in the light-absorbing layer enables the production of a high-quality light-absorbing layer.

[0005] JP 2012-004427 A

[0006] Patent Document 1 states that it is preferable for a certain number of voids to exist in the light absorption layer in order to improve photoelectric conversion efficiency. However, the presence of voids may contribute to a decrease in the adhesion strength between the materials constituting the photoelectric conversion element. In particular, the inventors of the present application have found that, depending on the environment in which the photoelectric conversion element is used, further improvement in the adhesion strength between the materials constituting the photoelectric conversion element is desired. When the photoelectric conversion element is used in a harsh environment, such as in the atmosphere or outside the atmosphere, it is desirable for the adhesion strength between the materials constituting the photoelectric conversion element to be higher.

[0007] Therefore, a photoelectric conversion element having high adhesion strength and a method for manufacturing the same are desired.

[0008] A photoelectric conversion element according to one aspect includes a chalcogen compound layer including a first region that contributes to photoelectric conversion and a second region that does not contribute to photoelectric conversion, wherein the thickness of the second region of the chalcogen compound layer is smaller than the thickness of the first region of the chalcogen compound layer.

[0009] A method for manufacturing a photoelectric conversion element according to one aspect includes a first step of forming a precursor film across a first region that contributes to photoelectric conversion and a second region that does not contribute to photoelectric conversion, and a second step of forming a chalcogen compound layer by chalcogenizing the precursor film, wherein in the first step, the precursor film is formed so that the thickness of the precursor film in the second region is smaller than the thickness of the precursor film in the first region.

[0010] 2A is a schematic plan view of a photoelectric conversion element according to one embodiment. FIG. 2B is a schematic cross-sectional view of the photoelectric conversion element taken along line 2A-2A in FIG. 1. FIG. 3A is a schematic enlarged view of region A4 in FIG. 3. FIG. 4A is a schematic view showing the state after the precursor film shown in FIG. 4 has been chalcogenized. FIG. 5B is a schematic view showing a step in another method of manufacturing a photoelectric conversion element according to one embodiment. FIG. 6B is a schematic view showing a step subsequent to FIG. 6. FIG. 7A is a schematic plan view of a solar cell module including a photoelectric conversion element. FIG. 8A is a schematic perspective view of an artificial satellite including a solar cell module.

[0011] 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.

[0012] Fig. 1 is a schematic plan view of a photoelectric conversion element according to one embodiment, and Fig. 2 is a schematic cross-sectional view of the photoelectric conversion element taken along line 2A-2A in Fig. 1.

[0013] The photoelectric conversion element 10 according to this embodiment may be a thin-film type photoelectric conversion element, and is preferably a solar cell element that converts light energy into electrical energy.

[0014] The photoelectric conversion element 10 has a substrate 20 that serves as a base on which each film is formed. The substrate 20 may be made of, for example, glass, ceramics, resin, or metal. The substrate 20 may be a flexible substrate. The shape and dimensions of the substrate 20 are determined appropriately depending on the size of the photoelectric conversion element 10, etc.

[0015] When a metal substrate is used as the substrate 20, the substrate 20 is formed of, for example, titanium (Ti), stainless steel (SUS), copper, aluminum, or an alloy thereof. Alternatively, the substrate 20 may have a laminated structure in which a plurality of metal base materials are laminated, and for example, a stainless steel foil, a titanium foil, or a molybdenum foil may be formed on the surface of the substrate.

[0016] The photoelectric conversion element 10 may include at least a first electrode layer 22, a second electrode layer 24, and a photoelectric conversion layer 26 provided between the first electrode layer 22 and the second electrode layer 24. The photoelectric conversion layer 26 is a layer that contributes to the mutual conversion of light energy and electrical energy. In a solar cell element that converts light energy into electrical energy, the photoelectric conversion layer 26 is sometimes called a light absorption layer.

[0017] The first electrode layer 22 and the second electrode layer 24 are adjacent to the photoelectric conversion layer 26. In this specification, the term "adjacent" means not only that both layers are in direct contact with each other, but also that both layers are close to each other via another layer.

[0018] The first electrode layer 22 is provided between the photoelectric conversion layer 26 and the substrate 20. The second electrode layer 24 is located on the opposite side of the photoelectric conversion layer 26 from the substrate 20. Therefore, the first electrode layer 22 is located on the opposite side of the photoelectric conversion layer 26 from the second electrode layer 24.

[0019] In the present embodiment, the second electrode layer 24 may be formed of a transparent electrode layer. When the second electrode layer 24 is formed of a transparent electrode layer, light incident on the photoelectric conversion layer 26 or emitted from the photoelectric conversion layer 26 passes through the second electrode layer 24.

[0020] When the second electrode layer 24 is a transparent electrode layer, the first electrode layer 22 may be an opaque electrode layer or a transparent electrode layer. The first electrode layer 22 may be formed of a metal such as molybdenum, titanium, or chromium. Although not particularly limited, the thickness of the first electrode layer 22 may be, for example, 50 nm to 1500 nm.

[0021] In the present embodiment, as a preferred example, the second electrode layer 24 may be formed of an n-type semiconductor, more specifically, a material having n-type conductivity and relatively low resistance. The second electrode layer 24 can function both as an n-type semiconductor and a transparent electrode layer. The second electrode layer 24 includes, for example, a metal oxide doped with a Group III element (B, Al, Ga, or In). Here, the "group" of an element in this specification is based on the short periodic table (the same applies hereinafter).

[0022] Examples of the metal oxide constituting the second electrode layer 24 include ZnO and SnO. ２ The second electrode layer 24 is made of, for example, indium tin oxide (In ２ O ３ : Sn), indium titanium oxide (In ２ O ３ :Ti), indium zinc oxide (In ２ O ３ :Zn), tin-zinc-doped indium oxide (In ２ O ３ : Sn, Zn), tungsten-doped indium oxide (In ２ O ３ :W), hydrogen-doped indium oxide (In ２ O ３ :H), indium gallium zinc oxide (InGaZnO ４ ), zinc tin oxide (ZnO:Sn), fluorine-doped tin oxide (SnO ２:F), gallium-doped zinc oxide (ZnO:Ga), boron-doped zinc oxide (ZnO:B), aluminum-doped zinc oxide (ZnO:Al), and the like can be selected.

[0023] Although not particularly limited, the thickness of the second electrode layer 24 is, for example, 0.5 μm to 2.5 μm.

[0024] The photoelectric conversion layer 26 may include, for example, a p-type semiconductor. In a specific example, the photoelectric conversion layer 26 may function as, for example, a polycrystalline or microcrystalline p-type compound semiconductor layer.

[0025] In this embodiment, the photoelectric conversion layer 26 includes a chalcogen compound layer. The chalcogen compound is a compound containing at least one chalcogen element. The chalcogen compound includes, for example, sulfide, selenide, and / or telluride. Specifically, the photoelectric conversion layer 26 includes a I-III-VI chalcogen compound having a chalcopyrite structure. ２ The photoelectric conversion layer 26 may include a group I compound semiconductor layer. Here, the group I element may be selected from copper (Cu), silver (Ag), gold (Au), etc. The group III element may be selected from indium (In), gallium (Ga), aluminum (Al), etc. Furthermore, the photoelectric conversion layer 26 may include tellurium (Te) as a group VI element in addition to selenium (Se) and sulfur (S). Furthermore, the photoelectric conversion layer 26 may include an alkali metal such as Li, Na, K, Rb, or Cs.

[0026] Instead, the photoelectric conversion layer 26 is made of I, which is a CZTS-based chalcogen compound containing Cu, Zn, Sn, S, or Se. ２ -(II-IV)-VI ４ A typical example of a CZTS-based chalcogenide semiconductor is a Cu ２ ZnSnSe ４ , Cu ２ ZnSn(S,Se) ４ and the like.

[0027] The photoelectric conversion element 10 may have a first buffer layer 27 between the photoelectric conversion layer 26 and the first electrode layer 22, as needed. In this case, the first buffer layer 27 may be made of a semiconductor material having the same conductivity type as the first electrode layer 22, or may be made of a semiconductor material having a different conductivity type. The first buffer layer 27 may be made of a material having a higher electrical resistance than the first electrode layer 22.

[0028] The first buffer layer 27 is not particularly limited, and may be, for example, a layer containing a chalcogenide compound of a transition metal element having a layered structure. Specifically, the first buffer layer 27 may be composed of a compound made of 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 27 may be, for example, M(Se,S) ２ Layer, MоSe ２ Layer or MoS ２ The first buffer layer 27 can be formed on the surface of the first electrode layer 22 when the photoelectric conversion layer 26 is formed by chalcogenizing a precursor layer used as a precursor of the photoelectric conversion layer 26.

[0029] The photoelectric conversion element 10 may have a second buffer layer 28 between the photoelectric conversion layer 26 and the second electrode layer 24, as needed. In this case, the second buffer layer 28 may be made of a semiconductor material having the same conductivity type as the second electrode layer 24, or may be made of a semiconductor material having a different conductivity type. The second buffer layer 28 may be made of a material having a higher electrical resistance than the second electrode layer 24.

[0030] The second buffer layer 28 is formed on the photoelectric conversion layer 26. Although not particularly limited, the thickness of the second buffer layer 28 may be, for example, 10 nm to 100 nm.

[0031] The second buffer layer 28 can be made of a compound selected from compounds containing zinc (Zn), cadmium (Cd), and indium (In). Examples of compounds containing zinc include ZnO, ZnS, and Zn(OH). ２, or mixed crystals thereof such as Zn(O,S) and Zn(O,S,OH), as well as ZnMgO and ZnSnO. Compounds containing cadmium include, for example, CdS, CdO, or mixed crystals thereof such as Cd(O,S) and Cd(O,S,OH). Compounds containing indium include, for example, In ２ S ３ , In ２ O ３ or a mixed crystal thereof, In ２ (O, S) ３ , In ２ (O, S, OH) ３ There is In ２ O ３ , In ２ S ３ , In(OH) ｘ The second buffer layer may have a laminated structure of these compounds.

[0032] The second buffer layer 28 has the effect of improving characteristics such as photoelectric conversion efficiency, but it can be omitted. When the second buffer layer 28 is omitted, the second electrode layer 24 is formed directly on the photoelectric conversion layer 26.

[0033] It should be noted that the stacked structure of the photoelectric conversion element 10 is not limited to the above embodiment and can take various forms. For example, the photoelectric conversion element 10 may have a configuration in which both an n-type semiconductor and a p-type semiconductor are sandwiched between a first electrode layer and a second electrode layer. In this case, the second electrode layer does not need to be composed of an n-type semiconductor. Furthermore, the photoelectric conversion element 10 is not limited to a p-n junction type structure, and may have a p-i-n junction type structure that includes an intrinsic semiconductor layer (i-type semiconductor) between an n-type semiconductor and a p-type semiconductor.

[0034] The photoelectric conversion element 10 includes a collecting electrode 30 adjacent to the second electrode layer 24. The collecting electrode 30 collects charge carriers from the second electrode layer 24 and is made of a conductive material. The collecting electrode 30 may be in direct contact with the second electrode layer 24. From the viewpoint of improving power generation efficiency, it is preferable that the area of ​​the collecting electrode 30 is as small as possible.

[0035] The collecting electrode 30 may have a plurality of substantially linear first portions 31 and second portions 32 connected to the first portions 31. The first portions 31 may also be referred to as "fingers." The second portions 32 may also be referred to as "bus bars."

[0036] The first portions 31 are arranged at intervals from one another. The plurality of linear first portions 31 are connected to the second portions 32. The first portions 31 serve to conduct electricity generated in the photoelectric conversion layer 26 to the second portions 32.

[0037] In the illustrated embodiment, the substantially linear first portion 31 extends straight in one direction (the X direction in the drawing). Alternatively, the first portion 31 may extend in a wavy or zigzag broken line. In this specification, the term "linear" is not limited to a straight line, but is defined by a concept that includes a thin, curved line such as a wavy line or a broken line.

[0038] A plurality of first portions 31 of the collecting electrode 30 may be arranged side by side in the first direction (Y direction in the figure). The plurality of linear first portions 31 may be connected to the same second portion 32.

[0039] The second portion 32 of the collecting electrode 30 may extend in a first direction (Y direction in the figure). The second portion 32 may be connected to the first portion 31 at an end of the first portion 31. In this case, the multiple first portions 31 may extend from the second portion 32 along a second direction (X direction in the figure).

[0040] The second portions 32 of the collecting electrodes 30 may extend in the first direction (the Y direction in the figure) substantially from near one end to near the other end of the photoelectric conversion element 10. The width of the second portions 32 of the collecting electrodes 30 (the width in the X direction in the figure) may be larger than the width of each of the first portions 31 (the width in the Y direction in the figure).

[0041] The collecting electrode 30 (first portion 31 and second portion 32) may be made of a material having higher conductivity than the material constituting the second electrode layer 24. The material constituting the collecting electrode 30 (first portion 31 and second portion 32) is a material that has good conductivity and can obtain high adhesion to the second electrode layer 24. For example, the material constituting the collecting electrode 30 is indium tin oxide (In ２ O ３ : Sn), indium titanium oxide (In ２ O ３ :Ti), indium zinc oxide (In ２ O ３ :Zn), tin-zinc-doped indium oxide (In ２ O ３ : Sn, Zn), tungsten-doped indium oxide (In ２ O ３ :W), hydrogen-doped indium oxide (In ２ O ３ :H), indium gallium zinc oxide (InGaZnO ４ ), zinc tin oxide (ZnO:Sn), fluorine-doped tin oxide (SnO ２ The material can be selected from at least one of aluminum-doped zinc oxide (ZnO:Al), boron-doped zinc oxide (ZnO:B), gallium-doped zinc oxide (ZnO:Ga), Ni, Ti, Cr, Mo, Al, Ag, and Cu, or a compound containing one or more of these. The current collecting electrode 30 may be formed from an alloy or a laminate formed from a combination of the above-mentioned materials.

[0042] The photoelectric conversion element 10 includes wiring 50 joined to the collecting electrode 30. The wiring 50 may be joined to the second portion 32 of the collecting electrode 30. The wiring 50 may include, for example, an interconnector 52 for electrically connecting to the outside of the photoelectric conversion element 10, and / or a connector 54 for connecting to a bypass diode that electrically bypasses a cell that cannot perform photoelectric conversion.

[0043] A plurality of interconnectors 52 may be arranged at intervals on the second portion 32 of the collecting electrode 30. The interconnectors 52 may be, for example, a ribbon wire made of a conductive metal containing Ag. Although not particularly limited, the interconnectors 52 may have a strip-like shape with a thickness of about 30 μm and a width of about 2.5 mm.

[0044] The junction between the collecting electrode 30 and the wiring 50, particularly the junction between the collecting electrode 30 and the interconnector 52, may be located at a position overlapping the photoelectric conversion layer 26 when viewed from a direction perpendicular to the interface of the photoelectric conversion layer 26 (see Figure 2).

[0045] The photoelectric conversion layer 26 including the chalcogen compound layer includes a first region R1 that contributes to photoelectric conversion and a second region R2 that does not contribute to photoelectric conversion. Specifically, the first region R1 is a region that contributes to light reception or light emission. The first region R1 may be a region that does not have an opaque layer on the surface side of the photoelectric conversion layer 26 in the thickness direction of the photoelectric conversion element 10.

[0046] The second region R2 is a region that does not contribute to light reception or light emission. The second region R2 may be a region having an opaque layer on the surface side of the photoelectric conversion layer 26 in the thickness direction of the photoelectric conversion element 10. The second region R2 of the photoelectric conversion layer 26 may be defined by, for example, a region that overlaps with the second portion 32 of the collecting electrode 30 in the thickness direction of the photoelectric conversion element 10.

[0047] In this embodiment, the thickness T2 of the second region R2 of the chalcogen compound layer constituting the photoelectric conversion layer 26 is smaller than the thickness T1 of the first region R1 of the chalcogen compound layer. Here, the thickness of the first region R1 of the chalcogen compound layer and the thickness of the second region R2 of the chalcogen compound layer may be calculated, for example, by averaging thicknesses measured at multiple points.

[0048] As described below, the chalcogen compound layer can be formed by chalcogenizing a precursor film. In this embodiment, the precursor film is formed so that the thickness of the precursor film in the second region R2 is smaller than the thickness of the precursor film in the first region R1. It is known that voids 60 are generated in the chalcogen compound layer during chalcogenization of the precursor film (see Patent Document 1, cited above). The thermal energy applied to the precursor film during chalcogenization is effectively applied to the second region R2, which has a relatively small thickness. Therefore, materials (elements) located in the portion of the precursor film corresponding to the second region R2 are easily diffused by the thermal energy, and the distribution of elements in the second region R2 is more easily uniformed.

[0049] Due to the uniform element distribution caused by thermal diffusion, the number of voids 60 generated in the second region R2 of the chalcogen compound layer is smaller than the number of voids 60 generated in the first region R1. Since the generation of voids 60 is suppressed in the second region R2, the adhesion strength of the chalcogen compound layer 26 is increased. This makes it possible to provide a photoelectric conversion element 10 having high adhesion strength. Furthermore, since the second region R2, in which the generation of voids 60 is suppressed, is a region that does not contribute to photoelectric conversion, the photoelectric conversion efficiency of the photoelectric conversion element 10 does not substantially decrease.

[0050] In this embodiment, the chalcogen compound layer 26 that constitutes the photoelectric conversion layer 26 has a plurality of voids 60. When the average thickness of the first region R1 of the photoelectric conversion layer 26 is "T" and the major axis of the voids 60 is "D", the voids 60 may be defined as voids that satisfy the condition "0.1T≦D≦0.7T".

[0051] The number density of the voids 60 in the second region R2 of the chalcogen compound layer constituting the photoelectric conversion layer 26 is preferably smaller than the number density of the voids 60 in the first region R1 of the chalcogen compound layer. Here, the "number density" may be defined as the number of voids 60 per unit area in a plane parallel to each layer of the photoelectric conversion element 10. This can further increase the adhesion strength of the chalcogen compound layer.

[0052] From the viewpoint of photoelectric conversion efficiency, the thickness T1 of the first region R1 of the chalcogen compound layer constituting the photoelectric conversion layer 26 is preferably in the range of 1.0 μm to 4.0 μm, for example. On the other hand, the thickness T2 of the second region R2 of the chalcogen compound layer is preferably in the range of 0.1 μm to 3.9 μm, for example, and is smaller than the thickness T1 of the first region R1. When the thickness of the chalcogen compound layer is within the above-mentioned range, for example, it is believed that the voids 60 generated in the chalcogen compound layer decrease as the thickness decreases. Therefore, from the viewpoint of increasing adhesion strength as the voids 60 decrease, the thickness T2 of the second region R2 is preferably in the above-mentioned range.

[0053] More preferably, the thickness T1 of the first region R1 of the chalcogen compound layer is 2.3 μm or more, and the thickness T2 of the second region R2 of the chalcogen compound layer is less than 2.3 μm. The adhesion of the chalcogen compound layer can change drastically at a thickness of around 2.3 μm. Therefore, by setting the thicknesses of the first region R1 and the second region R2 within the above ranges, the chalcogen compound layer can have higher adhesion in the second region R2.

[0054] Furthermore, the ratio of the thickness T2 of the second region R2 to the thickness T1 of the first region R1 of the chalcogen compound layer may be 0.9 or less. By reducing the thickness ratio in this manner, the thermal energy generated during chalcogenization can be more effectively applied to the second region R2. Therefore, the adhesion strength of the second region R2 of the chalcogen compound layer relative to the first region R1 may be more effectively improved. From this perspective, it is preferable that the ratio of the thickness T2 of the second region R2 to the thickness T1 of the first region R1 of the chalcogen compound layer is small.

[0055] [Manufacturing Method 1] Next, a manufacturing method of a photoelectric conversion element according to one embodiment will be described with reference to Figures 3 to 5. Figure 3 is a schematic diagram illustrating one step in the manufacturing method of a photoelectric conversion element according to one embodiment. Figure 4 is a schematic enlarged view of region A4 in Figure 3. Figure 5 is a schematic diagram illustrating the state after the precursor film shown in Figure 4 has been chalcogenized.

[0056] First, the first electrode layer 22, the first buffer layer 27, the photoelectric conversion layer 26, the second buffer layer 28, and the second electrode layer 24 are formed on the substrate 20. Here, the first buffer layer 27 and the second buffer layer 28 may be formed as needed.

[0057] The first electrode layer 22 is formed by depositing a film of the material constituting the first electrode layer 22 on the surface of the substrate 20 by, for example, sputtering. The material constituting the first electrode layer 22 is as described above. The sputtering method may be direct current (DC) sputtering or radio frequency (RF) sputtering. Alternatively, the first electrode layer 22 may be formed by chemical vapor deposition (CVD), atomic layer deposition (ALD), or the like instead of sputtering.

[0058] The photoelectric conversion layer 26 is formed by depositing a film on the first electrode layer 22. In a specific example, the photoelectric conversion layer 26 is formed by, for example, forming thin-film precursor films 26 a, 26 b on the first electrode layer 22 and chalcogenizing the precursor films 26 a, 26 b.

[0059] The precursor films 26 a and 26 b can be formed by, for example, physical vapor deposition (PVD), such as sputtering or evaporation. The evaporation method is a film formation method using atoms or the like that are vaporized by heating an evaporation source.

[0060] 4, the precursor films 26a, 26b are formed across a first region R1 that contributes to photoelectric conversion of the photoelectric conversion element 10 to be manufactured and a second region R2 that does not contribute to photoelectric conversion (first step). In this case, in the first step, the precursor films 26a, 26b are formed so that the thickness of the precursor films 26a, 26b in the second region R2 is smaller than the thickness of the precursor films 26a, 26b in the first region R1.

[0061] When forming a CIS-based photoelectric conversion layer 26, the precursor film may include a film 26b containing a group I element and a film 26a containing a group III element. More specifically, the precursor film may be formed as a laminate of a film 26a containing a group III element and a film 26b containing a group I element. The material constituting the film 26b containing a group I element may be selected from Ag, Cu, Au, etc. The material constituting the film 26a containing a group III element may be selected from indium, gallium, aluminum, etc. The precursor films 26a and 26b may additionally contain alkali metals such as Li, Na, K, Rb, and Cs. The precursor films 26a and 26b may additionally contain tellurium as a group VI element in addition to selenium and sulfur.

[0062] Preferably, the precursor films 26a, 26b are formed by physical vapor deposition (PVD), such as sputtering (see FIG. 3). In FIG. 3, a photoelectric conversion element (hereinafter sometimes simply referred to as "element") 10a in the process of being formed is placed on a stage 102 in a sputtering apparatus 100. A target material 200 to be deposited is placed opposite the element 10a on the stage 102. The desired precursor films 26a, 26b are formed on the element 10a by a vapor deposition method, such as sputtering.

[0063] Preferably, in the first step, the first region R1 and the second region R2 of the precursor films 26 a, 26 b are formed together by physical vapor deposition, which allows the photoelectric conversion layer 26 having multiple regions with different thicknesses to be formed simultaneously (see FIG. 4 ).

[0064] Specifically, the first step includes forming the precursor films 26a and 26b while placing a shielding plate 106 at a position away from the substrate 20 on which the precursor films 26a and 26b are to be formed and overlapping the second region R2 in a direction perpendicular to the film surface of the precursor films 26a and 26b (see FIG. 4). Because the shielding plate 106 is positioned to overlap the second region R2, the thickness of the precursor films 26a and 26b formed in the second region R2 is smaller than the thickness of the precursor films 26a and 26b formed in the first region R1 (see FIG. 5). This facilitates the formation of precursor films 26a and 26b with different thicknesses.

[0065] Next, the precursor films 26a and 26b are chalcogenized to form a chalcogen compound layer (second step). In this embodiment, the chalcogen compound layer constitutes the photoelectric conversion layer 26.

[0066] When forming the CIS-based photoelectric conversion layer 26, the precursor film including the film 26b containing a group I element and the film 26a containing a group III element is subjected to a chalcogenization treatment in an atmosphere containing a group VI element, whereby the precursor film is chalcogenized to form the photoelectric conversion layer 26.

[0067] In the chalcogenization process, for example, selenization is first performed by vapor-phase selenization. Selenization is performed by heating the precursor layer in an atmosphere of a selenium source gas (e.g., hydrogen selenide or selenium vapor) containing selenium as a Group VI element source. Although not particularly limited, selenization is preferably performed in a heating furnace at a temperature ranging from 300° C. to 600° C.

[0068] As a result, the precursor film is converted into a compound (photoelectric conversion layer 26) containing a group I element, a group III element, and selenium. Note that the compound (photoelectric conversion layer 26) containing a group I element, a group III element, and selenium may be formed by a method other than vapor-phase selenization. For example, such a compound can also be formed by solid-phase selenization, vapor deposition, ink application, electrodeposition, or the like.

[0069] Next, the photoelectric conversion layer 26 containing a group I element, a group III element, and selenium is sulfurized. The sulfurization is performed by heating the photoelectric conversion layer 26 in an atmosphere of a sulfur-containing sulfur source gas (e.g., hydrogen sulfide or sulfur vapor). As a result, the photoelectric conversion layer 26 is converted into a semiconductor compound containing a group I element, a group III element, and selenium and sulfur as group VI elements. The sulfur source gas serves to substitute sulfur for selenium in crystals composed of a group I element, a group III element, and selenium, for example, chalcopyrite crystals, on the surface portion of the photoelectric conversion layer 26.

[0070] Although not particularly limited, the sulfurization is preferably carried out in a heating furnace at a temperature in the range of 450° C. to 650° C., for example.

[0071] The selenization and sulfidation convert the precursor film into the photoelectric conversion layer 26. In addition, a first buffer layer 27 containing a compound made of a transition metal material such as M0, W, Ti, V, Cr, Nb, or Ta and a chalcogen element such as O, S, or Se is formed between the first electrode layer 22 and the photoelectric conversion layer 26.

[0072] On the other hand, when forming a CZTS-based photoelectric conversion layer 26, the precursor layer is formed as a thin film of Cu—Zn—Sn or Cu—Zn—Sn—Se—S. In the chalcogenization treatment of the precursor layer, the precursor layer containing Cu, Zn, and Sn is sulfurized and selenized in a hydrogen sulfide atmosphere and a hydrogen selenide atmosphere at 500° C. to 650° C. As a result, Cu ２ ZnSn(S,Se) ４ Furthermore, by the sulfurization and selenization, a first buffer layer 27 is formed between the first electrode layer 22 and the photoelectric conversion layer 26.

[0073] In the above embodiment, both selenization and sulfurization are performed when converting the precursor film into the photoelectric conversion layer 26. This is not limiting, and the precursor film may be converted into the photoelectric conversion layer 26 by any chalcogenization process. Here, as described above, the thickness of the precursor film corresponding to the second region R2 is smaller than the thickness of the precursor film corresponding to the first region R1. Therefore, the thickness of the second region R2 of the photoelectric conversion layer 26 after chalcogenization is also smaller than the thickness of the first region R1 of the photoelectric conversion layer 26 after chalcogenization.

[0074] The second buffer layer 28 is formed by depositing a film on the photoelectric conversion layer 26 by a method such as CBD (chemical bath deposition), sputtering, CVD, or ALD. The material constituting the second buffer layer is as described above.

[0075] The second electrode layer 24 is formed on the second buffer layer 28 by a method such as sputtering, CVD, or ALD. Alternatively, if the second buffer layer 28 does not exist, the second electrode layer 24 is formed directly on the photoelectric conversion layer 26. The material constituting the second electrode layer 24 is as described above.

[0076] Next, the collecting electrode 30 (first portion 31 and second portion 32) is formed on the second electrode layer 24. The collecting electrode 30 can be formed by applying, for example, a sputtering method, a CVD method, an ALD method, an AD method, or a vapor deposition method, as well as a printing process such as an inkjet method or a screen printing method.

[0077] The collecting electrode 30 may include a plurality of linear first portions 31 and second portions 32 connected to the plurality of first portions 31. In this case, the collecting electrode 30 is preferably formed such that the second region R2 of the chalcogen compound layer overlaps with the second portions 32 of the collecting electrode 30 in the thickness direction of the photoelectric conversion element 10. Wiring 50 is joined to the collecting electrode 30 as necessary.

[0078] According to the above-described manufacturing method, the chalcogen compound layer is formed by chalcogenizing the precursor film. During the chalcogenization of the precursor film, voids 60 may be generated in the chalcogen compound layer due to differences in the reactivity of multiple metal elements contained in the precursor film with selenium and / or sulfur. For example, when the precursor film contains multiple elements, such as In and Ga, as Group III elements, the voids 60 may be generated due to differences in the reactivity of the multiple elements with selenium and / or sulfur.

[0079] The thermal energy applied to the precursor film is effectively applied to the second region R2, which has a relatively small thickness. Therefore, the material (element) located in the portion of the precursor film corresponding to the second region R2 is easily diffused by the thermal energy, and the distribution of the element in the second region R2 is easily made more uniform. As a result, the generation of voids 60 is suppressed in the second region R2 of the chalcogen compound layer more than in the first region R1. Because the generation of voids 60 in the second region R2 of the chalcogen compound layer is suppressed, the adhesion strength of the chalcogen compound layer is increased.

[0080] The voids 60 generated in the photoelectric conversion layer 26 may expand due to heat applied during the formation of the collecting electrode 30, particularly the second portion 32 of the collecting electrode 30, and may reduce the adhesion of the photoelectric conversion layer 26. In this embodiment, the second region R2 of the photoelectric conversion layer 26, in which the number density of voids 60 is low, is located directly below the second portion 32 of the collecting electrode 30. This reduces the risk that the adhesion of the photoelectric conversion layer 26 will be reduced due to heat applied during the formation of the second portion 32 of the collecting electrode 30.

[0081] [Manufacturing Method 2] Next, another method for manufacturing a photoelectric conversion element according to an embodiment will be described. Note that the same configurations or methods as those in the manufacturing method described above may not be described. Fig. 6 is a schematic diagram for explaining one step in another method for manufacturing a photoelectric conversion element according to an embodiment. Fig. 7 is a schematic diagram for explaining a step following Fig. 6. Note that Figs. 6 and 7 show a region corresponding to the photoelectric conversion element 10 shown in Fig. 2.

[0082] First, the first electrode layer 22, the first buffer layer 27, the photoelectric conversion layer 26, the second buffer layer 28, and the second electrode layer 24 are formed on the substrate 20. Here, the first buffer layer 27 and the second buffer layer 28 may be formed as needed. The first electrode layer 22 can be formed in the same manner as described above.

[0083] The photoelectric conversion layer 26 is formed by depositing a film on the first electrode layer 22. In a specific example, the photoelectric conversion layer 26 is formed by, for example, forming thin-film precursor films 26 a, 26 b on the first electrode layer 22 and then chalcogenizing the precursor films 26 a, 26 b. The precursor films 26 a, 26 b can be formed by, for example, physical vapor deposition (PVD).

[0084] 6, the precursor films 26a, 26b are formed across a first region R1 that contributes to photoelectric conversion of the photoelectric conversion element 10 to be manufactured and a second region R2 that does not contribute to photoelectric conversion (first step). In this case, in the first step, the precursor films 26a, 26b may be formed to have the same thickness in the first region R1 and the second region R2 (see FIG. 6).

[0085] Next, the first step includes forming precursor films 26 a, 26 b across the first region R1 and the second region R2, and then reducing the thickness of the precursor films 26 a, 26 b formed in the second region R2 (see FIG. 7 ). Specifically, the precursor films 26 a, 26 b formed in the second region R2 are preferably partially removed in the thickness direction. Thereafter, a chalcogenization process is performed, similar to the manufacturing method 1 described above.

[0086] The precursor films 26 a and 26 b are made of the same materials as those used in the manufacturing method described above. Furthermore, the second buffer layer 28, the second electrode layer 24, the current collecting electrode 30, and the wiring 50 may be formed by the same method as in the manufacturing method 1 described above.

[0087] [Experimental Example 1] Next, an experimental example of a photoelectric conversion element will be described. In the photoelectric conversion element according to Experimental Example 1, a first electrode layer, a first buffer layer, a photoelectric conversion layer, and a second electrode layer are stacked in this order on a titanium substrate. The first electrode layer is made of molybdenum. The first buffer layer is made of Mo(Se,S). ２ The photoelectric conversion layer is a CIS-type layer containing a chalcogen semiconductor containing a chalcogen element. Specifically, the photoelectric conversion layer is formed by selenizing and sulfurizing a metal precursor film containing Cu, In, and Ga by the selenization method described above. The second electrode layer is a transparent conductive film. Furthermore, the photoelectric conversion element according to Experimental Example 1 has a collecting electrode and wiring. The wiring (silver foil) was bonded to the collecting electrode by fusion bonding. In Experimental Example 1, the photoelectric conversion layer was formed with a uniform thickness across the first region R1 and the second region R2. In Experimental Example 1, the thickness of the photoelectric conversion layer was approximately 2.5 μm.

[0088] [Experimental Example 2] In Experimental Example 2, the thickness of the photoelectric conversion layer was different from that of the photoelectric conversion element in Experimental Example 1. In Experimental Example 2, the thickness of the photoelectric conversion layer was approximately 2.2 μm.

[0089] For the photoelectric conversion elements in Experimental Examples 1 and 2, an experiment was conducted to examine the relationship between the thickness of the wiring 50 and the tensile strength. Specifically, the adhesion strength of the layers constituting the photoelectric conversion element was evaluated by the following method. First, the tip of the interconnector after welding of the wiring was clamped with a jig, and the tip of the interconnector was pulled upward at a 45-degree angle at a rate of 5 mm / min using an autograph device. Then, the tensile strength (maximum strength) was measured at the time when the interconnector was detached from the joint between the wiring and the second electrode layer.

[0090] The measured tensile strengths are shown in Table 1 below. Table 1 shows the ratio of tensile strengths, which is expressed by normalizing the test result (tensile strength) in Experimental Example 1 to "1".

[0091] [Table 1]

[0092] The above tensile strength test shows that the adhesion strength of the photoelectric conversion layer increases as the thickness of the photoelectric conversion layer decreases. The adhesion strength increases as the thickness of the photoelectric conversion layer decreases, at least within the range of, for example, 0.1 μm to 4.0 μm. Comparing Experimental Example 1 and Experimental Example 2, it is clear that the thickness of the chalcogen compound layer can change rapidly, particularly at a thickness of about 2.3 μm. Therefore, when the thickness T1 of the first region R1 of the chalcogen compound layer is 2.3 μm or more and the thickness of the second region R2 of the chalcogen compound layer is less than 2.3 μm, it is believed that the second region of the photoelectric conversion layer 26 significantly contributes to adhesion.

[0093] In the above table, the film thickness ratio of the photoelectric conversion layer is approximately 0.88. Meanwhile, the tensile strength ratio (adhesion strength ratio) is 2.1. Thus, if the film thickness ratio of the photoelectric conversion layer is approximately 0.9 or less, the tensile strength ratio (adhesion strength ratio) is approximately two times or more. Therefore, it can be seen that it is more preferable that the ratio of the thickness T2 of the second region R2 to the thickness T1 of the first region R1 of the chalcogen compound layer is 0.9 or less.

[0094] Next, a solar cell module including a photoelectric conversion element will be described. Fig. 8 is a schematic plan view of a solar cell module including a photoelectric conversion element. A solar cell module 300 may include one or more photoelectric conversion elements 10. Fig. 8 shows a photoelectric conversion module 300 including a plurality of photoelectric conversion elements 10. The one or more photoelectric conversion elements 10 may be sealed with, for example, a sealing material.

[0095] When the photoelectric conversion module 300 includes a plurality of photoelectric conversion elements 10, the plurality of photoelectric conversion elements 10 may be arranged in at least one direction, preferably in a lattice pattern. In this case, the plurality of photoelectric conversion elements 10 may be electrically connected to each other in series and / or parallel.

[0096] In the example shown in Fig. 8, the photoelectric conversion elements 10 are arranged so as to partially overlap each other. Among the photoelectric conversion elements 10 arranged in one direction, adjacent photoelectric conversion elements 10 partially overlap each other. Specifically, as shown in Fig. 8, a certain photoelectric conversion element 10 may be arranged so as to cover the second portion 32 of the collecting electrode 30 of the photoelectric conversion element 10 adjacent thereto. Instead of the embodiment shown in Fig. 8, adjacent photoelectric conversion elements 10 may be arranged with a gap between them. The above-mentioned interconnector 52 electrically connects adjacent photoelectric conversion elements 10 to each other.

[0097] Next, a satellite equipped with a solar cell module and a paddle for the satellite will be described. Fig. 9 is a schematic perspective view of a satellite equipped with a solar cell module. The satellite 900 may have a base 910 and a paddle 920. The base 910 may include equipment (not shown) necessary for controlling the satellite 900. An antenna 940 may be attached to the base 910.

[0098] The paddle 920 may include the solar cell module 300 described above. The paddle 920 including the solar cell module 300 can be used as a power source for operating various devices provided on the base 910. In this way, the solar cell module 300 can be applied to a paddle for a satellite. In particular, since the paddle 920 for a satellite is exposed to a high temperature environment and an environment with drastic temperature changes during launch and operation of the satellite, it is desirable to use the solar cell module 300 including the photoelectric conversion element 10 having high heat resistance described above.

[0099] The paddle 920 may have a connecting portion 922 and a hinge portion 924. The connecting portion 922 corresponds to the portion that connects the paddle 920 to the base portion 910.

[0100] The hinge portion 924 extends in one direction, allowing the paddle 920 to be folded around the hinge portion 924 as a rotation axis. Each paddle 920 may have at least one, and preferably a plurality of, hinge portions 924. This allows the paddle 920 equipped with the solar cell module 300 to be configured to be foldable into a small size. When the satellite 900 is launched, the paddle 920 may be in a folded state. The paddle 920 may be deployed when receiving sunlight to generate power.

[0101] Instead of the structure shown in FIG. 9 , the paddle 920 may have a cylindrical shape formed by being wound. This allows the paddle 920 to assume a generally flat, deployed state by rotating the wound portion. When the satellite 900 is launched, the paddle 920 may maintain a generally cylindrical shape. The paddle 920 may be deployed to a generally flat state when receiving sunlight and generating power.

[0102] 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.

[0103] For example, in the photoelectric conversion element 10 according to the above embodiment, the photoelectric conversion layer (light absorption layer) 26 includes a chalcogen compound layer. Alternatively, the chalcogen compound layer may constitute another layer among the layers constituting the photoelectric conversion element 10. Even in this case, the adhesion strength of the layers constituting the photoelectric conversion element 10 can be increased by adjusting the thickness of the chalcogen compound layer.

[0104] This application claims priority to Japanese Patent Application No. 2021-210926, filed on December 24, 2021, the entire contents of which are incorporated herein by reference.

Claims

1. An optoelectronic conversion element comprising at least a first electrode layer, a second electrode layer, and a photoelectric conversion layer provided between the first electrode layer and the second electrode layer, wherein the photoelectric conversion layer has a chalcogen compound layer, the chalcogen compound layer includes a first region contributing to photoelectric conversion and a second region not contributing to photoelectric conversion, the thickness of the second region of the chalcogen compound layer is smaller than the thickness of the first region of the chalcogen compound layer, and the types and stacking order of the layers located between the first electrode layer and the second electrode layer are the same in the region corresponding to the first region and the region corresponding to the second region.

2. An optoelectronic conversion element according to claim 1, having a current collecting electrode including a plurality of linear first portions and a second portion connected to the plurality of first portions, wherein the second region of the chalcogen compound layer is defined by a region overlapping the second portion of the current collecting electrode in the thickness direction of the optoelectronic conversion element.

3. The chalcogen compound layer has a plurality of voids, and the number density of the voids in the second region of the chalcogen compound layer is smaller than the number density of the voids in the first region of the chalcogen compound layer.

4. The chalcogen compound layer is I-III-VI ２ group compound semiconductor, and / or I ２ -(II-IV)-VI ４ group compound semiconductor, and the photoelectric conversion element according to claim 1.

5. The second electrode layer is located on the side where light incident on or exiting from the photoelectric conversion layer passes through, and the surface of the chalcogen compound layer in the second region facing the second electrode layer is located closer to the first electrode layer side than the position of the surface of the chalcogen compound layer in the first region facing the second electrode layer.

6. There is a first buffer layer between the first electrode layer and the photoelectric conversion layer, and the first buffer layer is in contact with both the first electrode layer and the photoelectric conversion layer in the region corresponding to the second region.

7. An optoelectronic conversion element according to claim 1, wherein an insulating layer is not included between the chalcogen compound layer and the first electrode layer in the region corresponding to the second region.

8. A first step of forming a precursor film over a first region contributing to photoelectric conversion and a second region not contributing to photoelectric conversion, and a second step of forming a chalcogen compound layer by chalcogenating the precursor film. In the first step, the precursor film is formed such that the thickness of the precursor film in the second region is smaller than the thickness of the precursor film in the first region. A method for manufacturing a photoelectric conversion element.

9. In the first step, the first region and the second region of the precursor film are formed together by physical vapor deposition. The method for manufacturing a photoelectric conversion element according to claim 8.

10. The first step includes forming the precursor film in a state where a shielding plate is disposed at a position away from the substrate on which the precursor film is to be formed and overlapping the second region in a direction orthogonal to the film surface of the precursor film. The method for manufacturing a photoelectric conversion element according to claim 8.

11. The first step includes reducing the thickness of the precursor film formed in the second region after forming the precursor film over the first region and the second region. The method for manufacturing a photoelectric conversion element according to claim 8.

12. In the first step, the surface of the precursor film in the second region facing the second electrode layer is positioned closer to the first electrode layer than the position of the surface of the precursor film in the first region facing the second electrode layer. The precursor film is formed as such. The method for manufacturing a photoelectric conversion element according to claim 8.

13. In the first step, the precursor film is formed directly on the first electrode layer over the first region and the second region. The method for manufacturing a photoelectric conversion element according to claim 8.

14. In the first step, the precursor film is formed on the first electrode layer over the first region and the second region without an intervening insulating layer. The method for manufacturing a photoelectric conversion element according to claim 8.

15. In the first step, the precursor film is formed over the first region and the second region on the first electrode layer. The method for manufacturing a photoelectric conversion element includes, after the second step, a step of forming a second electrode layer on the chalcogen compound layer. The photoelectric conversion element is formed such that the types and stacking orders of the layers located between the first electrode layer and the second electrode layer are the same in the region corresponding to the first region and the region corresponding to the second region. The method for manufacturing a photoelectric conversion element according to claim 8.

16. A solar cell module comprising the photoelectric conversion element according to any one of claims 1 to 7.

17. A paddle comprising the solar cell module according to claim 16.