Series solar cell and preparation method thereof

Abstract

The present invention provides a tandem type solar cell device and a method for manufacturing the same, which can ensure the stability of the electrical / mechanical connection between an upper cell and a lower cell by making full use of the excellent characteristics of a tandem type solar cell and omitting a recombination layer, and can maximize the process efficiency and economy due to omission of an intermediate layer, thereby improving the reliability of the tandem type solar cell device. And optical loss such as reflection loss or parasitic absorption caused by the recombination layer can be prevented, so that the photoelectric efficiency can be remarkably improved.

Description

Technical Field

[0001] The present invention relates to a tandem solar cell, and more particularly, to a tandem solar cell and a method for manufacturing the same, which do not require an additional layer to electrically connect an upper cell and a lower cell having different band gaps. Background Art

[0002] Multi-junction (tandem) solar cells vertically stack light absorbing layers with different band gaps, thereby effectively utilizing solar energy in a wider wavelength range to minimize thermalization losses. Specifically, in a tandem solar cell, multiple light absorbing layers with different band gaps absorb sunlight in multiple wavelength regions, thereby overcoming the efficiency limit of a single-junction solar cell by minimizing the phenomenon that the remaining energy of electron holes generated when the light absorbing layer absorbs photons with energy greater than the band gap in a single-junction solar cell is lost as heat energy. Recently, with the increasing attention paid to tandem solar cells as the most likely next-generation solar cell, a fierce global competition for the research and development of tandem solar cell technologies with various structures is being launched to seize the initiative.

[0003] However, commercialization of the tandem solar cell is limited due to the following problems.

[0004] First, generally, for tandem solar cells, due to the characteristics of heterojunction, the connection between the upper cell and the lower cell is extremely important, but as far as the currently known tandem solar cells are concerned, none of them can meet the stability and light efficiency of the electrical connection of these upper and lower cells. That is, when preparing a tandem solar cell, the lower cell should be protected from damage during the processing of the cell, and in order to achieve good light projection from the front surface cell to the rear surface cell, the upper cell and the lower cell should be able to achieve effective charge recombination and should have high transparency. However, there has been no report of a tandem solar cell that fully utilizes the excellent optical properties and meets the electrical / mechanical stability requirements compared to a single junction solar cell.

[0005] Second, in order to overcome the above problem, a study on forming a recombination layer between the upper cell and the lower cell of a tandem solar cell has been reported. However, in this case, the upper process is limited by the surface texture shape of the lower cell, and the additional layer formed in the middle causes electrical / optical losses due to reflection losses, parasitic absorption, etc. of the solar cell device, thereby causing a problem of reduced photoelectric efficiency.

[0006] Third, even if the recombination layer is developed that can improve the electrical / mechanical stability by improving the interface characteristics of the tandem solar cell, in order to form the recombination layer between the upper and lower cells as described above, expensive high-vacuum evaporation equipment such as Sputtuer and PECVD is required. The process time and process cost will increase due to the addition of a new layer that has not been available before. In addition, the economic efficiency will be greatly reduced due to the incompatibility problem with existing equipment.

[0007] Therefore, there is an urgent need to study the following tandem solar cells, which do not require additional layers for charge recombination of the upper cell and the lower cell of the tandem solar cell, thereby maximizing the process efficiency. At the same time, the stability of the electrical / mechanical connection between the upper cell and the lower cell can be guaranteed. Even if no additional layer is formed, excellent light transmission and effective charge recombination can be achieved, thereby significantly improving the efficiency of the tandem solar cell. Summary of the invention

[0008] The present invention is proposed to overcome the above-mentioned problems. The technical problem to be solved by the present invention is to provide the following tandem solar cell, which does not require additional layers such as a recombination layer for electrically connecting the upper and lower cells of the existing tandem solar cell, thereby ensuring the stability of the electrical / mechanical connection between the upper cell and the lower cell.

[0009] Furthermore, an object of the present invention is to provide a tandem solar cell that can utilize the excellent characteristics of a tandem solar cell and omit a recombination layer, thereby maximizing process efficiency and economy, and preventing optical losses such as reflection loss or parasitic absorption caused by an additional layer formed in the middle, thereby significantly improving photoelectric efficiency.

[0010] In order to solve the above problems, the present invention provides a tandem solar cell device, which includes: a silicon lower cell; a perovskite upper cell; and a multifunctional layer directly connected between the silicon lower cell and the perovskite upper cell.

[0011] Furthermore, according to one embodiment of the present invention, the present invention is characterized in that the multifunctional layer can be NiO x , WO x 、Vo x , CuO x Etc. p-type inorganic oxides.

[0012] Furthermore, the present invention is characterized in that the silicon lower cell and the perovskite upper cell may be in a series connection state.

[0013] Furthermore, the present invention is characterized in that the silicon lower cell may include a p-type silicon layer and an n-type emitter layer formed on the p-type silicon layer, and the n-type emitter layer performs charge recombination with the multifunctional layer at an upper portion of the silicon lower cell.

[0014] Furthermore, the present invention is characterized in that the thickness of the multifunctional layer can be 5 nm to 50 nm.

[0015] Furthermore, the present invention provides a method for preparing a tandem solar cell device, the method comprising: a first step of forming an emitter layer on the upper surface of a silicon lower cell including a p-type silicon layer; a second step of forming a multifunctional layer on the emitter layer formed on the upper surface of the silicon lower cell; and a third step of forming a perovskite upper cell on the upper surface of the multifunctional layer to connect the silicon lower cell and the perovskite upper cell in series.

[0016] Furthermore, according to an embodiment of the present invention, the present invention is characterized in that, in the first step, the doping concentration of the emitter used to form the emitter layer can be 10E 19 cm -3 above.

[0017] Furthermore, the present invention is characterized in that the second step may be a step of forming the multifunctional layer by electron beam evaporation or sputtering.

[0018] Furthermore, the present invention is characterized in that the third step may be a step of forming the perovskite upper cell on the multifunctional layer by one of a solution process and sputtering.

[0019] Furthermore, the present invention provides a solar cell module including the solar cell device.

[0020] In the present invention, the excellent characteristics of the tandem solar cell can be fully utilized and the recombination layer can be omitted, so the stability of the electrical / mechanical connection between the upper cell and the lower cell can be guaranteed, the process efficiency and economy can be maximized due to the omission of the intermediate layer, and optical losses such as reflection loss or parasitic absorption caused by the recombination layer can be prevented, thereby significantly improving the photoelectric efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 FIG. 1 is a schematic diagram showing a tandem solar cell device according to an embodiment of the present invention.

[0022] Figure 2 FIG. 1 is a schematic diagram showing a tandem solar cell device according to another embodiment of the present invention.

[0023] Figure 3 and Figure 4Graph showing the photoelectric efficiency of an embodiment of the present invention.

[0024] Figure 5 FIG. 1 is a scanning electron microscope (SEM) image of an embodiment of the present invention.

[0025] Figure 6 It is a graph showing the external quantum efficiency (EQE) of an example of the present invention and a comparative example. DETAILED DESCRIPTION

[0026] The embodiments of the present invention are described in detail below so that those skilled in the art can easily implement the present invention. The present invention can be embodied in many different forms and is not limited to the embodiments described herein.

[0027] As described above, the commercialization of conventional tandem solar cells is limited due to problems such as reduced photoelectric efficiency and reduced process efficiency caused by the recombination layer for electrically connecting the upper and lower cells.

[0028] Therefore, the present invention provides a tandem solar cell device and a method for preparing a tandem solar cell device to explore solutions to the problems of the existing tandem solar cells. The tandem solar cell device includes a silicon lower cell, a multifunctional layer that performs hole transport and charge recombination, and includes a perovskite upper cell that is configured so that the multifunctional layer and the silicon cell are connected. The method for preparing the tandem solar cell device includes: a first step of forming an emitter layer on the upper surface of the silicon lower cell including a p-type silicon layer; a second step of forming a multifunctional layer on the emitter layer formed on the upper surface of the silicon lower cell; and a third step of forming a perovskite upper cell on the upper surface of the multifunctional layer to connect the silicon lower cell and the perovskite upper cell in series.

[0029] Therefore, in the present invention, the excellent characteristics of the tandem solar cell can be fully utilized and the recombination layer can be omitted, so the stability of the electrical / mechanical connection between the upper cell and the lower cell can be guaranteed, the process efficiency and economy can be maximized due to the omission of the intermediate layer, and optical losses such as reflection loss or parasitic absorption caused by the recombination layer can be prevented, thereby significantly improving the photoelectric efficiency.

[0030] In this specification, the lower cell refers to a silicon solar cell formed at the lower portion of the tandem solar cell, and the upper cell refers to a perovskite solar cell formed at the upper portion of the tandem solar cell.

[0031] Furthermore, in this specification, the texture structure refers to a structure formed on a silicon solar cell, which means to include a structure formed by texturing widely used in silicon solar cells and a structure derived therefrom.

[0032] Furthermore, in this specification, a silicon lower cell as a light absorbing layer refers to a solar cell including silicon, and a perovskite upper cell as a light absorbing layer refers to a solar cell including a material having a perovskite structure.

[0033] Below, refer to Figures 1 to 6 , the tandem solar cell device of the present invention is specifically described.

[0034] The tandem solar cell device 100 of the present invention comprises a silicon lower cell 200, a perovskite upper cell 400, and a multifunctional layer 300 directly connected between the silicon lower cell 200 and the perovskite upper cell 400. That is, it comprises the silicon lower cell 200 formed on the upper surface of the front electrode, the multifunctional layer 300 performing hole transport and charge recombination, and the perovskite upper cell 400 arranged so that the multifunctional layer 300 is connected to the silicon lower cell 200.

[0035] like Figure 1 As shown, the silicon lower cell 200 includes a silicon layer 210 and an emitter layer 220 formed on the silicon layer 210 .

[0036] The silicon layer 210 may have one of the structures of known silicon solar cells, and is not limited to a specific structure. For example, the silicon layer 210 may include a crystalline silicon substrate (not shown), a p-type amorphous or crystalline silicon layer (not shown), an n-type amorphous or crystalline silicon layer (not shown), and an amorphous intrinsic silicon layer (not shown). Although not shown in the figure, additional layers may be included as needed. According to a more preferred embodiment, generally, compared with n-type silicon, considering the industrial advantages of p-type silicon in terms of ease of internal doping or process simplification in helping to improve battery efficiency, the silicon layer 210 may be a p-type silicon layer, and an n-type emitter layer 220 is formed on the upper part.

[0037] According to the preferred embodiment of the present invention, the structure of the silicon layer 210 can be formed on the surface of the p-type silicon through n ++ The Al-BSF (Aluminum Back Surface Field) structure formed by the emitter, the Passivated Emitter and Rear Cell (PERC), the Passivated Emitter Rear Totally Diffused (PERT), and the Passivated Emitter and Rear Locally Diffused (PERL) structures or by forming SiO x Tunnel layer / n ++The polysilicon tunnel oxide passivated contact (TOPCon) structure and the like are therefore not particularly limited.

[0038] On the other hand, at least a portion of one or the other side of the silicon layer 210 is textured to improve light efficiency. Figure 2 As shown, a concave-convex surface is formed along the direction of light incidence, and the incident light is scattered by the concave-convex surface, so as to increase the path of the light incident to the silicon layer 210 to improve light capture, thereby improving the absorption rate of sunlight.

[0039] The n-type emitter layer 220 may perform charge recombination with the multifunctional layer 300 on an upper portion of the silicon layer 210 .

[0040] In the case of existing general tandem solar cells, a silicon lower cell is physically combined with a perovskite upper cell, and a recombination layer is formed as an intermediate layer to achieve electrical connection, thereby improving the electrical / mechanical stability by improving the interface characteristics of the tandem solar cell.

[0041] The existing recombination layer uses a light-transmitting conductive material, for example, indium tin oxide (ITO), indium cerium oxide (ICO), indium tungsten oxide (IWO), zinc indium tin oxide (ZITO), zinc indium oxide (ZIO), zinc tin oxide (ZTO), gallium indium tin oxide (GITO), gallium indium oxide (GIO), gallium zinc oxide (GZO), aluminum doped zinc oxide (AZO), fluorine tin oxide (FTO), ZnO and other TCO materials, or uses a nc-Si:H material layer to physically connect the upper and lower batteries and achieve electrical connection.

[0042] However, in the case of a tandem solar cell having a recombination layer formed of the above-mentioned substance, the upper process is limited by the surface texturing shape of the lower cell, thereby being limited in improving the light efficiency of the upper perovskite layer. There is a problem of reducing the photoelectric efficiency due to reflection losses of the solar cell device caused by the additional layer formed in the middle and electrical / optical losses caused by parasitic absorption, etc.

[0043] Furthermore, in order to form the recombination layer between the upper and lower batteries, expensive high-vacuum evaporation equipment such as Sputtuer and PECVD is required. Since a new layer is added, the process time and process cost will increase. Not only that, the economic efficiency will be greatly reduced due to the incompatibility problem with existing equipment.

[0044] In this regard, the present invention solves the problem by allowing the n-type emitter layer 220 to perform charge recombination with the multifunctional layer 300 on the upper portion of the silicon layer 210 .

[0045] That is, in the present invention, a transparent conductive oxide (TCO) material layer or a nc-Si:H material layer is not formed between the multifunctional layer 300 and the silicon lower cell 200 or between the multifunctional layer 300 and the perovskite upper cell 400, and the silicon lower cell and the perovskite upper cell can be connected in series through the multifunctional layer 300.

[0046] More specifically, refer to Figure 1 and Figure 2 The multifunctional layer 300 of the present invention can be formed on the upper part of the n-type emitter layer 220 and the lower part of the perovskite upper cell 400, so that the silicon lower cell 200 and the perovskite upper cell 400 are physically / electrically connected and charge recombination is performed to achieve electrical series connection.

[0047] In this case, a plurality of holes formed in the perovskite upper cell 400 may move toward the n-type emitter layer 220 through the multifunctional layer 300, and, similarly, a plurality of electrons formed in the silicon layer 210 may move toward the multifunctional layer 300 through the n-type emitter layer 220 and perform recombination. In other words, the multifunctional layer 300 of the present invention may perform the role of a recombination layer that joins upper and lower cells in an existing tandem solar cell.

[0048] To this end, the doping concentration of the n-type emitter layer 220 connected to the multifunctional layer 300 can be controlled to be 10E 19 cm -3 Thus, the surface resistance of the n-type emitter layer 220 can be less than 100 ohm / sq. In this case, when the surface resistance of the n-type emitter layer 220 is greater than 100 ohm / sq, the movement of a plurality of electrons formed in the silicon lower cell to the upper part will be limited, which may cause a decrease in efficiency.

[0049] Furthermore, the thickness of the multifunctional layer 300 may be 5 nm to 50 nm, more preferably, 5 nm to 20 nm. In this case, when the thickness of the multifunctional layer 300 is less than 5 nm, uneven electron movement or ineffective recombination may be caused due to the formation of an uneven film, and when the thickness of the multifunctional layer 300 is greater than 50 nm, the efficiency may be reduced due to electrical loss caused by insulation characteristics and optical loss caused by increased parasitic absorption.

[0050] On the other hand, the multifunctional layer 300 may be made of a material selected from NiO x , WO x 、Vo x , CuO x The p-type inorganic oxide is formed of one of the group consisting of, preferably, nickel oxide (NiO x When the p-type inorganic oxide is evaporated, grains can grow in the vertical direction, so that they can have a vertical column shape. In this case, it is possible to reduce the conductivity in the horizontal direction, thereby preventing the shunting effect caused by the subsequent upper process, and it is advantageous in ensuring the reproducibility of the device and increasing the area.

[0051] Furthermore, according to a preferred embodiment of the present invention, when the multifunctional layer 300 is formed of nickel oxide, the multifunctional layer 300 can function as a hole transport layer HTL. Figure 1 and Figure 2 As shown, in the case where nickel oxide is formed as the multifunctional layer 300, the multifunctional layer 300 can function as a recombination layer for bonding the silicon lower cell 200 and the perovskite upper cell 400, and can also function as a corresponding hole transport layer HTL included in the electron transport layer ETL of the perovskite upper cell 400. In this case, the nickel oxide formed in the vertical direction has excellent conductivity in the vertical direction, but low conductivity in the horizontal direction, so that the loss caused by the shunting effect of the tandem solar cell device 100 including the silicon lower cell 200 and the perovskite upper cell 400 can be minimized.

[0052] In this case, the nickel oxide (NiO) introduced as the multifunctional layer 300 x ) can be controlled in the range of 0<x<3. Considering the target work function range (4.5<WF<5.0) and the valence band maximum (VMB) range (0.3<VBM<1), it is most preferred to control it in the range of 0<x<1.

[0053] Furthermore, the thickness of the multifunctional layer may be 5 nm to 50 nm, more preferably, 5 nm to 20 nm. In this case, when the thickness of the multifunctional layer 200 is less than 5 nm, uneven electron movement or ineffective recombination may be caused due to the formation of an uneven film, and when the thickness of the multifunctional layer 200 is greater than 50 nm, the efficiency may be reduced due to electrical loss caused by insulation characteristics and optical loss caused by increased parasitic absorption.

[0054] More specifically, refer to Figure 3 In the case of a tandem solar cell based on a passivated emitter and a back cell including the tandem solar cell device 100 of the present invention, the silicon lower cell 200 and the perovskite upper cell 400 are in a series state, thereby having a Voc of about 1.6 V and exhibiting a photoelectric efficiency of more than 21%.

[0055] And, refer to Figure 4 In the case of a tandem solar cell based on tunnel oxide passivation contact including the tandem solar cell device 100 of the present invention, the silicon lower cell 200 and the perovskite upper cell 400 are in a series state, thereby having a Voc of about 1.6V and exhibiting a photoelectric efficiency of more than 20%.

[0056] Next, the perovskite upper cell 400 serves as an upper cell connected to the silicon lower cell 200 , and a perovskite absorption layer 410 , an electron transport layer 420 , and a transparent conductive oxide electrode layer 430 may be sequentially stacked on the upper portion of the multifunctional layer 300 .

[0057] As described above, according to a preferred embodiment of the present invention, when the multifunctional layer 300 functions as a hole transport layer, a tandem solar cell device can be realized in which electrons move upward and holes move downward to form energy. However, this is only an example when the multifunctional layer 300 functions as a hole transport layer. When the multifunctional layer 300 functions as an electron transport layer, the electron transport layer 420 can be a hole transport layer. The positions of the hole transport layer and the electron transport layer 420 can be changed as needed.

[0058] The perovskite absorption layer 410 may be formed so that hole-electron pairs generated by receiving light energy from the sun are separated into electrons or holes. In one embodiment, electrons formed in the perovskite absorption layer 410 may be transferred to the electron transport layer 420, and holes formed in the perovskite absorption layer 410 may be transferred to the hole transport layer.

[0059] In this case, the perovskite absorption layer 410 may include organic halide perovskites such as methylammonium iodide (MAI) and formamidinium iodide (FAI), or metal halide perovskites such as lead iodide (PbI2), bromine iodide (PbBr), and lead chloride (PbCl2). That is, the perovskite absorption layer 410 may be a multilayer structure including at least one of an organic halide perovskite or a metal halide perovskite. More specifically, the perovskite absorption layer 410 may be represented as AMX3 (wherein A is a monovalent organic ammonium cation or a metal cation; M is a divalent metal cation; and X is a halogen anion). As a non-limiting example, CH3NH3PbI3, CH3NH3PbI x Cl 3-x 、CH3NH3PbI x Br 3-x 、CH3NH3PbCl x Br 3-x 、HC(NH2)2PbI3、HC(NH2)2PbI x Cl 3-x 、HC(NH2)2PbI x Br 3-x 、HC(NH2)2PbCl x Br 3-x 、(CH3NH3)(HC(NH2)2) 1-y PbI3, (CH3NH3)(HC(NH2)2) 1-y PbI x Cl 3-x 、(CH3NH3)(HC(NH2)2) 1-y PbI x Br 3-x or (CH3NH3)(HC(NH2)2) 1-y PbCl x Br 3-x etc. (0=x, y=1).

[0060] The electron transport layer 420 plays a role in separating and transporting electrons formed in the perovskite absorption layer 410, and can be formed of a known general material that meets the purpose of the present invention. As a non-limiting example, Ti oxide, Zn oxide, In oxide, Sn oxide, W oxide, Nb oxide, Mo oxide, Mg oxide, Zr oxide, Sr oxide, Yr oxide, La oxide, V oxide, Al oxide, Y oxide, Sc oxide, Sm oxide, Ga oxide, In oxide and SrTi oxide can be used.

[0061] As described above, the present invention can fully utilize the excellent characteristics of the tandem solar cell through the multifunctional layer 300 and omit the recombination layer, thereby ensuring the stability of the electrical / mechanical connection between the upper cell and the lower cell, omitting the intermediate layer to maximize the process efficiency and economy, and preventing optical losses such as reflection loss or parasitic absorption caused by the recombination layer, thereby significantly improving the photoelectric efficiency.

[0062] Thus, the present invention provides a solar cell module including a solar cell device exhibiting the above-mentioned excellent photoelectric efficiency. In this case, the solar cell module may include electrodes, a sealant, an additional stacking structure, etc. in addition to the solar cell device, but is not particularly limited thereto.

[0063] Next, a method for producing a tandem solar cell device will be described.

[0064] However, in order to avoid duplication of description, the description of the same technical concept as that of the tandem solar cell device will be omitted.

[0065] The manufacturing method of the tandem solar cell device of the present invention comprises: a first step of forming an emitter layer on the upper surface of a silicon lower cell including a p-type silicon layer; a second step of forming a multifunctional layer on the emitter layer formed on the upper surface of the silicon lower cell; and a third step of forming a perovskite upper cell on the upper surface of the multifunctional layer to connect the silicon lower cell and the perovskite upper cell in series.

[0066] The first step is a step of forming an n-type emitter layer on the upper surface of the silicon lower cell including a p-type silicon layer.

[0067] That is, the present invention can perform charge recombination with the multifunctional layer on the upper part of the silicon layer through the first step. In this case, the method for forming the n-type emitter layer can be a known general method and is not particularly limited. However, in the first step, the doping concentration of the emitter used to form the emitter layer can be 10E 19 cm -3 More preferably, it can be achieved through 10E 20 cm -3 The emitter layer is formed with a doping concentration of 10E or more. In this case, it is more advantageous in terms of efficient electron movement. However, when the doping concentration of the emitter is less than 10E 19 cm -3 When the electrons are limited in their mobility, there may be a problem of reduced recombination.

[0068] Furthermore, forming an n-type emitter on a p-type silicon layer to induce recombination of charges may be particularly advantageous due to the aforementioned industrial advantages, compared to forming a p-type emitter on an n-type silicon layer to induce recombination of charges.

[0069] On the other hand, the texture structure of the silicon lower cell can be introduced by using one of the methods of wet chemical etching, dry chemical etching, electrochemical etching, and mechanical etching, but is not limited to these. The front electrode can be formed on the lower surface of the silicon lower cell 200 by metal evaporation or metal slurry coating.

[0070] Next, the second step is a step of forming a multifunctional layer on the emitter layer formed on the upper surface of the silicon lower cell.

[0071] Generally, for a tandem solar cell device that is connected in series through a recombination layer, in order to form a recombination layer between the same upper and lower cells, expensive high vacuum evaporation equipment such as Sputtuer and PECVD is required. Due to the addition of a new layer, the process time and process cost will increase. In addition, there is a problem of incompatibility with existing equipment, which greatly reduces the economic efficiency.

[0072] Furthermore, the existing method of forming a hole transport layer by a solution process uses polymer materials such as PTAA and SAM, and the upper process is restricted by the surface texturing shape of the lower cell, which is limited in improving the light efficiency of the upper perovskite layer.

[0073] In this regard, in the second step of the present invention, the multifunctional layer may be formed by electron beam evaporation or sputtering, thereby solving the above problem.

[0074] That is, according to the present invention, the hole transport layer plays the role of mechanically / physically connecting the existing recombination layer of the upper and lower cells, thereby performing the multiple processes without adding the existing recombination layer, which is more advantageous in terms of process cost and speed. x When implemented, it can be formed by an electron beam evaporator, so that the process of the upper perovskite layer can be carried out without being restricted by the surface shape of the silicon lower cell, thereby improving the light efficiency of the upper perovskite layer in various forms.

[0075] In this case, the method for forming the multifunctional layer can utilize an existing general method that is consistent with the purpose of the present invention. Preferably, thermal evaporation, solution spin coating, electron beam or sputtering can be utilized. Most preferably, uniformly forming the multifunctional layer under high vacuum conditions by electron beam or sputtering method can be more advantageous in terms of reducing resistance, forming a uniform thin film and effectively moving charges in the vertical direction.

[0076] Next, the third step is a step of forming a perovskite upper cell on the upper surface of the multifunctional layer to connect the silicon lower cell and the perovskite upper cell in series.

[0077] The perovskite upper cell is an upper cell connected to the silicon lower cell. According to a known general method, a perovskite absorption layer, a charge transport layer and a transparent conductive oxide electrode layer can be sequentially stacked on the upper part of the multifunctional layer. More preferably, in the third step, forming the perovskite upper cell on the multifunctional layer by one of a solution process or sputtering is more advantageous in terms of forming a uniform thin film.

[0078] The above description is of the method for preparing the tandem solar cell device of the present invention. However, this is merely an example, and in addition to the existing layer functioning as a recombination layer, an additional layer stacking structure capable of improving the photoelectric efficiency may be included.

[0079] Hereinafter, the present invention will be described in more detail through examples. The following examples are not intended to limit the scope of the present invention but should be interpreted as helping to understand the present invention.

[0080] Example 1 - Preparation of tandem solar cell device

[0081] The lower solar cell uses a cell with a passivated emitter and a back cell structure, wherein the cell is formed by a POCl process on a silicon substrate doped with p-type impurities on which a lower passivation layer and a lower electrode made by Hanwha Qcells are formed. ++ Then, the emitter layer is deposited on n ++ An indium tin oxide (ITO) layer with a thickness of 50 nm is formed on the emitter layer as a recombination layer.

[0082] Afterwards, a 30 nm multifunctional layer was formed on the emitter layer under high vacuum conditions by electron beam evaporation. Then, CsMAFAPbI dissolved in dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) was formed by spin coating. x B 3-x solution, and formed into a thickness of 500 nm by heat treatment on a hot plate at 100° C. for minutes.

[0083] Next, as a hole transport layer, a LiF film with a thickness of less than 1 nm and a C60 film with a thickness of 20 nm were deposited by vacuum thermal evaporation, and a SnO film with a thickness of 6 nm was deposited by atomic layer deposition (ALD). x .

[0084] Next, a 100 nm thick indium-doped zinc oxide layer was formed on the hole transport layer as a transparent electrode layer by a sputtering device.

[0085] Next, under high vacuum conditions, silver (Ag) with a thickness of 200 nm was formed on the transparent electrode layer by a thermal evaporation machine to prepare a tandem solar cell device based on a passivated emitter and a back cell.

[0086] Example 2 - Preparation of tandem solar cell device

[0087] like Figure 2 As shown, the solar cell device based on tunnel oxide passivation contact of the silicon lower cell is prepared in the same manner as in Example 1. In this case, the cell with tunnel oxide passivation contact structure is a structure in which SiO is formed on the upper part of the silicon substrate doped with p-type impurities on which the lower passivation layer and the lower electrode prepared by Hanwha Qcells are formed. x As a passivation layer, doped n + polycrystalline silicon (poly-Si) layer.

[0088] Comparative Example 1 - Preparation of a tandem solar cell device

[0089] As shown in the prior art, a general tandem solar cell device is prepared in which an ITO thin film is deposited on a reconstituted layer by sputtering.

[0090] Experimental Example 1-Photoelectric Efficiency Evaluation

[0091] For the tandem solar cell devices of Examples 1 and 2, the photoelectric efficiency under AM1.5G illumination conditions was measured using a solar simulator and presented in Figure 3 and Figure 4 middle.

[0092] Reference Figure 3 In the case of Example 1, it can have a Voc of about 1.6 V and exhibit a photoelectric efficiency of more than 21%.

[0093] And, refer to Figure 4 In the case of Example 2, it can have a Voc of about 1.6 V and exhibit a photoelectric efficiency of more than 20%.

[0094] Experimental Example 2 - Scanning Electron Microscope Image

[0095] Figure 5 A scanning electron microscope image of the tandem solar cell device of Example 1 is shown.

[0096] Reference Figure 5, for direct formation of NiO on silicon lower cells by electron beam (E-beam) x In Example 1, the upper perovskite layer is formed to form a perovskite layer. It can be seen that the upper perovskite layer is stably formed on the NiO x on the film.

[0097] Experimental Example 3-External Quantum Efficiency Measurement

[0098] The external quantum efficiency of the tandem solar cell devices of Example 1 and Comparative Example 1 is calculated and graphed by optical simulation and presented in Figure 6 middle.

[0099] Reference Figure 6 As shown in the prior art, in the case of Comparative Example 1 including the existing recombination layer, as shown by the dashed line icon, the external quantum efficiency is low, so the sum of the upper / lower currents is calculated to be 37.93 mA / cm 2 On the contrary, in the case of Example 1 of the present invention, as shown in the dotted line graph, the external quantum efficiency is higher, so the sum of the upper and lower currents is calculated to be 38.38 mA / cm higher than before. 2 .

[0100] In summary, in the present invention, the excellent characteristics of the tandem solar cell can be fully utilized and the recombination layer can be omitted, so the stability of the electrical / mechanical connection between the upper cell and the lower cell can be guaranteed, the process efficiency and economy can be maximized due to the omission of the intermediate layer, and the optical loss such as reflection loss or parasitic absorption caused by the recombination layer can be prevented, thereby significantly improving the photoelectric efficiency.

Claims

1. A tandem solar cell device, characterized in that: include: Silicon lower cell; Perovskite top cell; as well as A multifunctional layer is directly connected between the silicon lower cell and the perovskite upper cell.

2. The tandem solar cell device according to claim 1, characterized in that: The multifunctional layer is NiO x , WO x 、Vo x , CuO x And other p-type inorganic oxides.

3. The tandem solar cell device according to claim 1, characterized in that: The silicon lower cell and the perovskite upper cell are in a series connection state.

4. The tandem solar cell device according to claim 1, characterized in that: The silicon lower cell includes a p-type silicon layer and an n-type emitter layer formed on the p-type silicon layer, and the n-type emitter layer performs charge recombination with the multifunctional layer at an upper portion of the silicon lower cell.

5. The tandem solar cell device according to claim 1, characterized in that: The thickness of the multifunctional layer is 5 nm to 50 nm.

6. A method for preparing a tandem solar cell device, characterized in that: include: In a first step, an emitter layer is formed on the upper surface of the silicon lower cell including the p-type silicon layer; The second step is to form a multifunctional layer on the emitter layer formed on the upper surface of the silicon lower cell; as well as The third step is to form a perovskite upper cell on the upper surface of the multifunctional layer to connect the silicon lower cell and the perovskite upper cell in series.

7. The method for preparing a tandem solar cell device according to claim 6, characterized in that: In the first step, the doping concentration of the emitter used to form the emitter layer is 10E 19 cm -3 above.

8. The method for preparing a tandem solar cell device according to claim 6, characterized in that: The second step is a step of forming a multifunctional layer by one of electron beam evaporation or sputtering.

9. The method for preparing a tandem solar cell device according to claim 6, characterized in that: The third step is a step of forming the perovskite upper cell on the multifunctional layer through one of a solution process or sputtering.

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