Tandem solar cell manufacturing method

Abstract

The present invention relates to a method for manufacturing a multi-junction tandem solar cell. With the manufacturing method of the present invention, a tandem solar cell with three or more layers can be realized, thereby achieving a high photoelectric efficiency close to the theoretical efficiency of the solar cell. In addition, since the range of material selections applied to each solar cell layer is expanded, a more diverse combination of materials can be made possible.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing a multi-junction tandem solar cell. According to the manufacturing method of the present invention, various combinations of materials of the light absorption layer are possible, and a tandem solar cell with three or more layers can be manufactured. Background Technology

[0002] A solar cell is a device that converts solar energy into electrical energy, operating on the principle that photons excite electrons within a semiconductor to generate current and power. Currently, single-layer silicon solar cells account for the majority of the solar cell market. While the theoretical efficiency of single-layer solar cells is around 30%, the photoelectric efficiency of actual commercially available solar cells falls short of this. Consequently, active research and development is underway on tandem solar cells, which consist of multiple stacked solar cell layers rather than a single layer, to improve the photoelectric efficiency of solar cells. As the number of solar cell layers increases, the cumulative value of the theoretical efficiency tends to increase, while the rate of increase gradually becomes more gradual. Theoretically, the efficiency of a double-junction tandem solar cell with two stacked layers is known to be approximately 45%, and the efficiency of a triple-junction tandem solar cell with three stacked layers is approximately 51%.

[0003] Meanwhile, solar cells are classified into silicon-based, organic-based, and compound-based types depending on the materials used, and tandem solar cells can be composed of combinations of these. Currently, silicon-based solar cells, which are predominantly used, have disadvantages such as high manufacturing costs due to the requirement of high-temperature processing, heavy weight, and the need for thicker dimensions to increase solar absorption. Organic solar cells allow for low-temperature processing and are lightweight and flexible, but they have relatively low photoelectric efficiency. Organic-inorganic hybrid materials such as perovskites and compound semiconductors are attracting attention due to their high photoelectric efficiency and ease of band gap tuning. Considering the characteristics of each of these materials, it is necessary for tandem solar cells to strike a balance in various aspects, including photoelectric efficiency and manufacturing costs.

[0004] Meanwhile, tandem solar cell stacking methods are broadly classified into monolithic and mechanical stacking. Monolithic stacking involves stacking multiple solar cell layers on a single substrate, whereas mechanical stacking can be described as a method of physically integrating solar cell layers stacked on separate substrates.

[0005] In particular, silicon-based or compound semiconductors have very high processing temperatures compared to organic-based or perovskite materials, so they must be formed first at the bottom when manufacturing tandem solar cells using a monolithic method. For example, forming an organic-based or perovskite layer first and then forming a compound semiconductor on top can lead to problems such as thermal damage or melting and deformation of the underlying organic or perovskite layer, making it difficult to ensure safety. Generally, solar cells manufactured using a monolithic method allow for smooth current flow and increased light efficiency, but the materials that can be used are inevitably limited by the stacking order when manufacturing tandem solar cells.

[0006] In manufacturing tandem solar cells, a mechanical stacking method is sometimes adopted to solve the aforementioned problems by manufacturing each solar cell layer on a separate substrate and stacking them. In the mechanical stacking method, each layer can be manufactured independently under optimal process conditions, which can overcome the process temperatures of different materials. However, currently, the limit for manufacturing tandem solar cells using the mechanical stacking method is two layers, and methods for manufacturing multi-junction tandem solar cells with three or more layers remain in the research stage. Therefore, if a method for manufacturing tandem solar cells with three or more layers using the mechanical stacking method is developed, it is expected that the range of material choices can be expanded regardless of the stacking order of the solar cells, and solar cells with improved photoelectric efficiency can be realized. Prior art literature

[0007] Republic of Korea Published Patent Application No. 10-2016-0105120 The problem to be solved

[0008] The present invention can provide a method for manufacturing a tandem solar cell with excellent photoelectric efficiency. With the method for manufacturing a tandem solar cell of the present invention, three or more solar cell layers can be stacked, and since each solar cell layer is stacked on a separate substrate, it is not affected by the process temperature, so various combinations of materials for the light absorption layer can be made. means of solving the problem

[0009] A method for manufacturing a tandem solar cell according to one embodiment of the present invention may include the following steps: (S10) sequentially stacking an n-th solar cell layer and a transparent electrode on an n-th substrate; (S20) sequentially stacking a transparent electrode and an (n+1)-th solar cell layer on a (n+1)-th substrate; (S30) stacking the n-th solar cell layer and the (n+1)-th solar cell layer so that they are in contact; (S40) removing the (n+1)-th substrate; and (S50) stacking a solar cell layer on a transparent substrate, and stacking the transparent substrate such that it is positioned at the top of the substrate removed in step (S40). Additionally, steps (S20) to (S40) may be repeated 1 to 4 times.

[0010] In one embodiment, n may mean an integer from 1 to 4.

[0011] In one embodiment, the solar cell layer may each independently include one or more of a group IV element, a silicon (Si)-based material, an organic material, a perovskite material, and a compound semiconductor material.

[0012] In one embodiment, the organic material may include one or more electron donors selected from the group consisting of P3HT, PTB7, PBDB-T, PEDOT, DPP, and SubPc, and one or more electron acceptors selected from the group consisting of PCBM, ITIC, and Y6.

[0013] In one embodiment, the perovskite material comprises a compound having an ABX3 structure, wherein A comprises a cation selected from methylammonium, formamidinium, and cesium, B comprises a metal ion of divalent cation, and X may comprise a halogen ion.

[0014] In one embodiment, the compound semiconductor material may include one or more materials selected from the group consisting of Cu(In,Ga)Se2(CIGS), CuZnSnS(CZTS), CdTe, GaAs, GaInP, CuInSe2(CIS), CuZnSnSe4(CZTSe), Sb2Se3, SnS, PbS, and InP.

[0015] In one embodiment, the tandem solar cell may comprise a material in which the (n+1) solar cell layer has a higher band gap than the n solar cell layer.

[0016] In one embodiment, the transparent electrode may include one or more materials selected from the group consisting of ITO (Indium Tin Oxide), ATO (Antimony-doped Tin Oxide), IZO (Indium Zinc Oxide), AZO (Aluminum-doped Zinc Oxide), AGZO (Aluminum and Gallium co-doped Zinc Oxide), and FTO (Fluorine-doped Tin Oxide).

[0017] In one embodiment, in step (S40), the substrate may be removed by chemical mechanical planarization (CMP) or etching.

[0018] In one embodiment, in step (S20), a sacrificial layer may be formed on the substrate before stacking the transparent electrode, and in step (S40), the substrate may be removed by removing the sacrificial layer.

[0019] In one embodiment, the substrate may comprise one or more of silicon, glass, metal, ceramic, or plastic. Effects of the invention

[0020] The tandem solar cell manufacturing method provided in the present invention can realize a tandem solar cell with three or more layers, and by triple-stacking material layers having different band gaps and placing a transparent and conductive material between the layers, a high photoelectric efficiency close to the theoretical efficiency of the solar cell can be achieved. In addition, since the range of material selections applied to each solar cell layer is expanded, a more diverse combination of materials can be made possible. Brief explanation of the drawing

[0021] Figure 1 illustrates the step of stacking a lower solar cell layer on a substrate. Figure 2 illustrates the step of stacking an upper solar cell layer on a substrate. Figure 3 illustrates the upper and lower bonding and substrate removal steps. Figure 4 illustrates a method of using a transparent substrate on top of the uppermost solar cell layer without removing it. Specific details for implementing the invention

[0022] Unless otherwise defined in this specification, all technical and scientific terms have the same meaning as generally understood by those skilled in the art to which the present invention pertains. The terms used in the description herein are merely for the purpose of effectively describing specific embodiments and are not intended to limit the present invention.

[0023] The singular form used in this specification is intended to include the plural form unless specifically indicated otherwise in the context.

[0024] Throughout this specification, the terms “comprising,” “having,” “containing,” or “having” any component mean that, unless specifically stated otherwise, other components are not excluded but may be included, and do not exclude elements, materials, or processes not additionally listed.

[0025] The numerical ranges used herein include lower and upper limits and all values ​​within the range, increments logically derived from the form and width of the defined range, all of which are limited, and all possible combinations of upper and lower limits of the numerical range defined in different forms. Unless otherwise specifically defined in this specification, values ​​outside the numerical range that may occur due to experimental error or rounding are also included in the defined numerical range.

[0026] Unless otherwise specifically defined in this specification, “about” may be considered to be a value within 30%, 25%, 20%, 15%, 10%, or 5% of the specified value.

[0027] The present invention will be described in detail below. However, this is merely illustrative and the present invention is not limited to the specific embodiments described illustratively.

[0028] A method for manufacturing a tandem solar cell according to one embodiment of the present invention may include the following steps: (S10) sequentially stacking an n-th solar cell layer and a transparent electrode on an n-th substrate; (S20) sequentially stacking a transparent electrode and an (n+1)-th solar cell layer on a (n+1)-th substrate; (S30) stacking the n-th solar cell layer and the (n+1)-th solar cell layer so that they are in contact; (S40) removing the (n+1)-th substrate; and (S50) stacking a solar cell layer on a transparent substrate, and stacking the transparent substrate such that it is positioned at the top of the substrate removed in step (S40). Additionally, steps (S20) to (S40) may be repeated 1 to 4 times.

[0029] In the present invention, the n-th solar cell layer is positioned closest to the surface of solar light incidence, and the first solar cell layer is positioned furthest away. That is, in the present disclosure, the lowest layer of the tandem solar cell may refer to the first solar cell layer. In the present disclosure, the direction closer to the surface of solar light incidence may be classified as the upper part, and the direction further away from the surface of solar light incidence may be classified as the lower part.

[0030] When manufacturing tandem solar cells using a conventional mechanical stacking method, the process proceeds through steps (S10) to (S30). However, this method is inevitably limited to double-junction tandem solar cells, resulting in a limit on the number of stacked tandem solar cells. Consequently, the actual improvement in efficiency compared to the theoretical efficiency of the solar cell is inevitably limited. In the manufacturing method of the present invention, a step of completely removing the substrate after stacking is completed is added, allowing for the additional stacking of solar cell layers. The initial role of the substrate is as a base substrate, which provides a flat surface to ensure uniform formation of the thin film layer and acts as a physical support to maintain the stacked layers without deformation or damage. Since the substrate is removed after the solar cell layers are stacked, any material is acceptable for the substrate. In one embodiment, the substrate may include one or more of silicon, glass, metal, ceramic, or plastic. It is preferable to use a transparent substrate for the base substrate of the uppermost solar cell layer, in which case the substrate can be used without being removed.

[0031] In one embodiment, n may represent an integer from 1 to 4. For example, when n is 1, a triple-junction tandem solar cell having 3 layers can be manufactured, and when n is 4, a tandem solar cell having 6 layers can be manufactured. Although the upper limit is not specifically restricted, as the number of layers increases, the theoretical increase in photoelectric conversion efficiency becomes gradually flatter, so the overall efficiency improvement effect may be limited. Therefore, the improvement in efficiency is not significant relative to the manufacturing cost, so economic feasibility may be lacking.

[0032] In one embodiment, the solar cell layer may each independently include one or more of a Group IV element, a silicon (Si)-based material, an organic material, a perovskite material, and a compound semiconductor material. The solar cell layer may be composed of a light absorption layer, an electron transport layer, a hole transport layer, a buffer layer, and an electrode, and the materials mentioned above may specifically be included as materials for the light absorption layer. To clearly convey the intent of the present invention, detailed descriptions of elements that are not directly modified may be omitted.

[0033] In one embodiment, the organic material is an electron donor poly(3-hexylthiophene)(P3HT), poly[{4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}](PTB7), It may include one or more substances selected from the group consisting of poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene))-alt-(5,5-(1′,3′-di-2-thienyl-5′,7′-bis(2-ethylhexyl)benzo[1′,2′-c:4′,5′-c′]dithiophene-4,8-dione))](PBDB-T), poly(3,4-ethylenedioxythiophene)(PEDOT), diketopyrrolopyrrole (DPP), and subphthalocyanine (SubPc). In addition, [6,6]-Phenyl-C₁-butyric acid methyl ester (PCBM) as an electron acceptor, 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene (ITIC) and It may include one or more substances from the group consisting of 2,2′-[[6,6,12,12-tetrakis(4-hexylphenyl)-6,12-dihydrodithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene-2,8-diyl]bis[methylidyne(3-oxo-1H-indene-2,1(3H)-diylidene)]]bispropanedinitrile(Y6).For example, the donor:acceptor combination of the above organic material may be P3HT:PCBM, PTB7:PCBM, PBDB-T:ITIC, PBDB-T:Y6, DPP:ITIC, or SubPc:PCBM, but is not limited thereto.

[0034] In one embodiment, the perovskite material comprises a compound having an ABX3 structure, wherein A comprises a cation selected from methylammonium, formamidinium, and cesium, B comprises a metal ion of divalent cation, and X may comprise a halogen ion. For example, the perovskite material may comprise lead iodide (CH3NH3PbI3), formamidinium lead bromide (HC(NH2)2PbBr3), cesium lead chloride (CsPbCl3), or methylammonium lead iodide (MAPbI3), but is not limited thereto.

[0035] In one embodiment, the compound semiconductor material may include one or more materials selected from the group consisting of Cu(In,Ga)Se2 (CIGS), CuZnSnS (CZTS), CdTe, GaAs, GaInP, CuInSe2 (CIS), CuZnSnSe4 (CZTSe), Sb2Se3, SnS, PbS, and InP. It is known that the compound semiconductor can effectively absorb various wavelength regions of sunlight by adjusting the bandgap range from 1.0 to 1.7 eV through changes in composition. Additionally, by adjusting the bandgap through the composition of the compound semiconductor, it can be applied to the upper and lower solar cell layers, respectively.

[0036] In one embodiment, the group IV element semiconductor material may include silicon (Si) or germanium (Ge).

[0037] In one embodiment, the tandem solar cell may comprise a material in which the (n+1) solar cell layer has a higher band gap than the n solar cell layer. For example, the second solar cell layer may be arranged to have a higher band gap than the first solar cell layer, and the third solar cell layer may be arranged to have a higher band gap than the second solar cell layer. Although the combination of solar cell layers is not particularly limited, as an example, the light absorption layer of the first solar cell layer may be PbS, the second solar cell layer may be CIGS, and the third solar cell layer may be formamidinium lead bromide (HC(NH2)2PbBr3). As another example, the first solar cell layer may be composed of germanium (Ge), the second solar cell layer of CZTSe, the third solar cell layer of amorphous silicon, the fourth solar cell layer of methylammonium lead iodide bromide (MAPb(I,Br)3), and the fifth solar cell layer of PTB7:PCBM, but is not limited thereto.

[0038] In one embodiment, the transparent electrode may include one or more materials selected from the group consisting of ITO (Indium Tin Oxide), ATO (Antimony-doped Tin Oxide), IZO (Indium Zinc Oxide), AZO (Aluminum-doped Zinc Oxide), AGZO (Aluminum and Gallium co-doped Zinc Oxide), and FTO (Fluorine-doped Tin Oxide). These materials are classified as transparent conductive oxides (TCOs) and generally possess high transparency and appropriate electrical conductivity.

[0039] In one embodiment, in step (S40), the substrate may be removed by chemical mechanical planarization (CMP) or etching. The CMP method involves applying a slurry mixed with abrasive particles and chemicals to the surface of the substrate and then applying mechanical force to flatten the surface. The etching method may involve wet etching using a chemical solution or dry etching using plasma. The above method provides high surface flatness and precision without fine surface irregularities. The substrate removal method is not limited to this, and a suitable method may be used depending on the type of substrate.

[0040] In one embodiment, in step (S20), a sacrificial layer may be formed on the substrate before stacking the transparent electrode, and in step (S40), the substrate may be removed by removing the sacrificial layer. The sacrificial layer may use a material that has weak adhesion to the substrate and can be selectively removed by processes such as etching or etching, and is not particularly limited. Since the substrate separated as described above can be reused when stacking the solar cell layer, process costs can be reduced.

[0041] In one embodiment, the temperature at which the solar cell layer is stacked may be from room temperature to 700°C. For example, the stacking temperature for amorphous silicon may be 150 to 300°C, and for polycrystalline silicon, it may be 500 to 700°C. For example, when an organic material is used as the light absorption layer, the stacking temperature may be from room temperature to 150°C or lower, and when a perovskite material is used, the stacking temperature may be 100 to 300°C. In addition, for compound semiconductors, a process temperature of 300 to 700°C may be required. As described above in the background art, silicon-based or compound semiconductors have a higher process temperature compared to organic-based or perovskite materials, so they must be formed first at the bottom when manufacturing a tandem solar cell in a monolithic manner. Therefore, when manufacturing a tandem solar cell in a monolithic manner, the materials that can be used are inevitably limited depending on the stacking order. On the other hand, when manufacturing a tandem solar cell using the manufacturing method of the present invention, each layer can be manufactured independently under optimal process conditions, thereby overcoming the process temperatures of different materials.

[0042] In one embodiment, the thickness of the solar cell layer (200) may be 50 nm to 5 μm. The thickness may vary depending on the material of the solar cell layer; for example, the thickness of a solar cell layer made of an organic material or a perovskite material may be 50 nm to 1 μm, and the thickness of a solar cell layer made of a compound semiconductor material may be 1 to 5 μm. Additionally, amorphous silicon may be deposited in the form of a thin film and may have a thickness of 50 nm to 3 μm. Since each material has different light absorption rates, electrical conductivity, or process conditions, the thickness range for optimal performance may be set differently.

[0043] In one embodiment, the thickness of the transparent electrode (300) may be 10 to 300 nm. For example, the thickness of the transparent electrode may be 30 to 250 nm, or 50 to 100 nm, or 100 to 200 nm, or 50 to 150 nm. When the thickness of the transparent electrode is within the above range, the desired transparency and electrical conductivity can be secured simultaneously.

[0044] FIGS. 1 to 4 are cross-sectional views schematically illustrating a method for manufacturing a tamdem solar cell according to one embodiment of the present invention.

[0045] FIG. 1 illustrates the step of stacking a lower solar cell layer on a substrate (100). A base substrate (100) is prepared, and a first solar cell layer (200) is formed on the first substrate. Subsequently, a transparent electrode (300) is formed on the upper portion of the first solar cell layer. FIG. 2 illustrates the step of stacking an upper solar cell layer on a substrate (100). A base substrate (100) is prepared, and a transparent electrode (300) is formed on the second substrate. A second solar cell layer (200) is formed on the transparent electrode. FIG. 3 illustrates the steps of upper and lower bonding and substrate removal. As shown in FIG. 3, the second solar cell layer is stacked by placing it in reverse on the upper portion of the first solar cell layer, and then the second substrate (100) is removed. The steps illustrated in FIG. 2 are additionally performed to bond the solar cell layer onto the existing stacked solar cell layer in the same manner. Figure 4 illustrates a method of using a transparent substrate on top of the uppermost solar cell layer without removing it. Since the transparent substrate transmits sunlight without loss, it can be used without separate removal.

[0046] The above-described embodiment will be explained in more detail below through examples. However, the following examples are for illustrative purposes only and do not limit the scope of the claims.

[0047] A first solar cell layer comprising a PbS (Lead sulfide) light-absorbing layer deposited by spin coating at a temperature of 150 ℃ was formed on a first substrate, and a transparent electrode was formed on the first solar cell layer. A transparent electrode was first formed on a second substrate, and a second solar cell layer comprising a CIGS light-absorbing layer vacuum-deposited at 500 ℃ was formed on the transparent electrode. The second solar cell layer was inversely positioned and bonded on the first solar cell layer.

[0048] The second substrate was removed by chemical mechanical planarization (CMP). A transparent electrode was first formed on the third substrate, and a third solar cell layer comprising a methylammonium lead iodide (MAPbI3) light-absorbing layer vacuum-deposited at 150°C was additionally formed on the transparent electrode. Subsequently, the third solar cell layer was placed in reverse and bonded to the top of the second solar cell layer, thereby manufacturing a triple-junction tandem solar cell.

[0049] The above third substrate was removed by chemical mechanical planarization (CMP). A transparent electrode was first formed on a transparent fourth substrate, and a fourth solar cell layer was formed by spin-coating PTB7:PCBM onto the transparent electrode, and the solvent was removed by heat treatment at 90°C. Subsequently, the fourth solar cell layer was placed in reverse and bonded to the top of the third solar cell layer, thereby manufacturing a quadruple-junction tandem solar cell.

[0050] Thus, the tandem solar cell of the present invention has transparent and conductive layers between the solar cell layers, allowing sunlight to be transmitted to the lower layer and improving photoelectric efficiency. In addition, the light absorption layer of the first solar cell layer is deposited at a process of 150°C, and the second solar cell layer is deposited at a higher process of 500°C, and since the process temperature does not affect the light absorption layer, various combinations of materials are possible.

[0051] As described above, the present invention has been explained by specific details and limited embodiments; however, this is provided merely to aid in a more comprehensive understanding of the invention, and the invention is not limited to the above embodiments. Those skilled in the art can make various modifications and variations from this description.

[0052] Accordingly, the present invention is not limited to the embodiments described above, and all things equivalent to or having equivalent variations to the claims set forth below, as well as the claims set forth below, shall be considered to be within the scope of the present invention. Explanation of the symbols

[0053] 100: Substrate (not limited to specific materials) 101: Transparent substrate 200: Solar cell layer 300: Transparent electrode

Claims

Claim 1 (S10) A step of sequentially stacking an n-th solar cell layer and an n-th transparent electrode on an n-th substrate; (S20) A step of sequentially stacking a (n+1)-th transparent electrode and a (n+1)-th solar cell layer on an (n+1)-th substrate; (S30) A step of stacking the n-th transparent electrode and the (n+1)-th solar cell layer so that they come into contact with each other; (S40) A step of removing the (n+1)-th substrate to expose the (n+1)-th transparent electrode upward; and (S50) A step of sequentially stacking an uppermost transparent electrode and an uppermost solar cell layer on a transparent substrate, and stacking the (n+1)-th transparent electrode exposed in step (S40) and the uppermost solar cell layer so that they come into contact with each other; A method for manufacturing a tandem solar cell, comprising: a step (S10) in which n is an integer from 1 to 4, wherein n is 1, and steps (S20) to (S40) are performed 1 to 4 times, and if performed 2 or more times, n is increased by 1. Claim 2 delete Claim 3 A method for manufacturing a tandem solar cell according to claim 1, wherein each of the solar cell layers independently comprises one or more of a group IV element, an organic material, a perovskite material, and a compound semiconductor material. Claim 4 A method for manufacturing a tandem solar cell according to claim 3, wherein the organic material comprises one or more electron donors selected from the group consisting of P3HT, PTB7, PBDB-T, PEDOT, DPP, and SubPc, and one or more electron acceptors selected from the group consisting of PCBM, ITIC, and Y6. Claim 5 A method for manufacturing a tandem solar cell according to claim 3, wherein the perovskite material comprises a compound having an ABX3 structure, wherein A comprises a cation selected from methylammonium, formamidinium, and cesium, B comprises a metal ion of divalent cation, and X comprises a halogen ion. Claim 6 A method for manufacturing a tandem solar cell according to claim 3, wherein the compound semiconductor material comprises one or more materials selected from the group consisting of Cu(In,Ga)Se2(CIGS), CuZnSnS(CZTS), CdTe, GaAs, GaInP, CuInSe2(CIS), CuZnSnSe4(CZTSe), Sb2Se3, SnS, PbS, and InP. Claim 7 A method for manufacturing a tandem solar cell according to claim 1, wherein the tandem solar cell comprises a material in which the (n+1) solar cell layer has a higher band gap than the n solar cell layer. Claim 8 A method for manufacturing a tandem solar cell according to claim 1, wherein the transparent electrode comprises one or more materials selected from the group consisting of ITO (Indium Tin Oxide), ATO (Antimony-doped Tin Oxide), IZO (Indium Zinc Oxide), AZO (Aluminum-doped Zinc Oxide), AGZO (Aluminum and Gallium co-doped Zinc Oxide), and FTO (Fluorine-doped Tin Oxide). Claim 9 A method for manufacturing a tandem solar cell according to claim 1, wherein in step (S40), the substrate is removed by chemical mechanical planarization (CMP) or etching. Claim 10 A method for manufacturing a tandem solar cell according to claim 1, wherein in step (S20), a sacrificial layer is first formed on the substrate before stacking the transparent electrode, and in step (S40), the substrate is removed by removing the sacrificial layer. Claim 11 A method for manufacturing a tandem solar cell according to claim 1, wherein the substrate comprises one or more of silicon, glass, metal, ceramic, or plastic.

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