High-stability carbon nanotube electrode for solar cell, manufacturing method therefor, and solar cell comprising same

Abstract

The present invention provides a high-stability carbon nanotube electrode for a solar cell, a manufacturing method therefor, and a solar cell comprising same. More specifically, the present application provides a high-stability carbon nanotube electrode for a solar cell, a manufacturing method therefor, and a solar cell comprising same, the high-stability carbon nanotube electrode being stably doped with a functional group so as to have improved electrical conductivity and thermal stability.

Description

Carbon nanotube electrode for high-stability solar cells, method for manufacturing the same, and solar cell including the same

[0001] The present invention relates to a carbon nanotube electrode for a high-stability solar cell, a method for manufacturing the same, and a solar cell comprising the same. More specifically, the present invention relates to a carbon nanotube electrode for a high-stability solar cell having improved electrical conductivity and thermal stability through stable doping of functional groups, a method for manufacturing the same, and a solar cell comprising the same.

[0002] Solar cells have evolved from silicon solar cells to thin films and, more recently, to perovskite solar cells for sustainable development, including reducing dependence on fossil fuels, achieving carbon neutrality, and responding to climate change.

[0003] Perovskite solar cells are attracting attention as a next-generation solar cell technology because they are thin, lightweight, and flexible, offering a wide range of applications as well as excellent photoelectric conversion efficiency. Perovskites form electrons and holes upon receiving light, but charge loss can occur due to the difference in work functions between the metal and organic / inorganic active layers depending on the composition of the solar cell. To date, perovskite solar cells have been manufactured by sequentially stacking a substrate, an electron transport layer and / or a hole transport layer, a perovskite layer, an electron transport layer and / or a hole transport layer, and a metal electrode.

[0004] Metal electrode layers are characterized by their ability to prevent corrosion caused by oxidation and their good electrical conductivity. Gold is particularly commonly used for metal electrode layers. However, metal electrodes made of metals including gold can cause degradation due to ions generated from perovskite, which can reduce long-term stability. Additionally, they are heavy and expensive, making mass production and commercialization difficult.

[0005] For this reason, carbon nanotube electrodes have recently been attracting attention. However, replacing gold electrodes with carbon nanotube electrodes has resulted in issues such as increased resistance, decreased work function, reduced reflectivity due to lower current density, and moisture penetration due to porosity.

[0006] Furthermore, conventional carbon nanotube doping has a problem of performance degradation due to the low quality of the interface between the perovskite and carbon nanotubes. In addition, conventional carbon nanotubes are highly unstable during processes such as washing and heat treatment because they introduce dopants through adsorption. As an alternative, there is a doping method that substitutes carbon with nitrogen or boron, but this can lead to defects in the carbon nanotubes, which may degrade their electrical and mechanical properties. Consequently, carbon nanotube electrodes have lower electrical conductivity and work function compared to gold electrodes, resulting in a problem of reduced solar cell efficiency.

[0007] Therefore, there is a need for technological development regarding electrodes utilizing carbon nanotubes that can minimize defects and charge loss, improve long-term stability, and enhance electrical conductivity and work function, methods for manufacturing the same, and solar cells containing the same.

[0008] As background technology of the present invention, Korean registered patent No. 2318356 describes a solid-state thin-film solar cell using a perovskite-based dye and a method for manufacturing it.

[0009] The objective of the present invention is to provide a carbon nanotube electrode for solar cells that minimizes defects and charge loss while simultaneously improving long-term stability.

[0010] Another objective of the present invention is to provide a method for manufacturing a carbon nanotube electrode for a solar cell that improves electrical conductivity and work function while minimizing defects and charge loss and simultaneously improving long-term stability.

[0011] Another objective of the present invention is to provide a solar cell utilizing carbon nanotube electrodes that improves electrical conductivity, work function, and photoelectric conversion efficiency while minimizing defects and charge loss and simultaneously enhancing long-term stability.

[0012] Other objects and advantages of the present invention will become more apparent from the following detailed description of the invention, claims, and drawings.

[0013] According to one aspect, a carbon nanotube electrode for a solar cell is provided, which improves the stability of the solar cell, comprising carbon nanotubes surface-treated with maleic anhydride.

[0014] According to one embodiment, the maleic anhydride may be surface-treated on carbon nanotubes by cycloaddition in a polar solvent.

[0015] According to one embodiment, the carbon nanotube of the carbon nanotube electrode for a solar cell of the present invention may have the following structural formula:

[0016]

[0017] Here, X may be selected from the group consisting of an amine group (-NH2), an aromatic amine group, an aliphatic amine group, a vinyl group (-CH=CH2), a thiol group (-SH), and a sulfonyl group (-SO3H).

[0018] According to one embodiment, the work function can be controlled by X.

[0019] According to one embodiment, the electrode may be an N-type electrode or a P-type electrode.

[0020]

[0021] According to another aspect, a method for manufacturing a carbon nanotube electrode for a solar cell is provided, comprising: 1) a step of preparing a maleic anhydride; and 2) a step of mixing the maleic anhydride with a carbon nanotube and surface treating the carbon nanotube by a cyclization addition reaction.

[0022] According to one embodiment, the method for manufacturing a carbon nanotube electrode for a solar cell according to the present invention may further include the step of adding a dopant.

[0023] According to one embodiment, in the method for manufacturing a carbon nanotube electrode for a solar cell according to the present invention, the dopant may be a material comprising a functional group selected from the group consisting of an amine group (-NH2), an aromatic amine group, an aliphatic amine group, a vinyl group (-CH=CH2), a thiol group (-SH), and a sulfonyl group (-SO3H).

[0024] According to one embodiment, step 2) can be carried out in a polar solvent at 150 to 200°C for 20 to 30 hours.

[0025] According to one embodiment, after step 2), a step of heat treatment at 300°C or higher for 1 to 5 hours may be further included.

[0026] According to one embodiment, in the method for manufacturing a carbon nanotube electrode for a solar cell according to the present invention, the carbon nanotube may have the following structural formula:

[0027]

[0028] Here, X may be selected from the group consisting of an amine group (-NH2), an aromatic amine group, an aliphatic amine group, a vinyl group (-CH=CH2), a thiol group (-SH), and a sulfonyl group (-SO3H).

[0029]

[0030] According to another aspect, a perovskite solar cell comprising a substrate, an electron transport layer, a perovskite layer, and a carbon nanotube electrode layer is provided, wherein the carbon nanotube electrode layer comprises a carbon nanotube electrode for a solar cell as described herein.

[0031] According to one embodiment, the carbon nanotube electrode layer in the solar cell of the present invention may include a hole transport layer.

[0032] According to one embodiment, in the solar cell of the present invention, the carbon nanotube electrode is reacted with an N-type dopant or a P-type dopant, and the N-type dopant is selected from dimethyl-p-phenylenediamine, ethylenediamine, p-phenylenediamine, phenylamine, methylamine, dimethylethylenediamine, 4-aminoacetanilide, and triazabicyclodecene; and the P-type dopant is selected from 4-nitroaniline and benzamidine, and an N-type carbon nanotube electrode can be formed by reaction with the N-type dopant, or a P-type carbon nanotube electrode can be formed by reaction with the P-type dopant.

[0033] According to one embodiment, the solar cell of the present invention can increase the power conversion efficiency (PCE) by more than 2%p compared to a solar cell containing undoped carbon nanotubes.

[0034] According to one embodiment, the carbon nanotube electrode for a high-stability solar cell of the present invention can minimize defects and charge loss while improving long-term stability by doping with an additional material to induce stable bonding between the carbon nanotube and the dopant.

[0035] According to one embodiment, the method for manufacturing a carbon nanotube electrode for a high-stability solar cell according to the present invention can efficiently manufacture carbon nanotubes for a solar cell that minimize defects in the carbon nanotubes to minimize charge loss and simultaneously improve long-term stability, while improving electrical conductivity and work function.

[0036] According to one embodiment, the solar cell of the present invention utilizes carbon nanotubes of the present invention that prevent degradation by ions, minimize defects and charge loss of carbon nanotubes, and simultaneously improve long-term stability, thereby improving work function, electrical conductivity, and photoelectric conversion efficiency.

[0037] FIG. 1 is a schematic diagram showing the process of attaching maleic anhydride and a dopant to the surface of a carbon nanotube according to one embodiment of the present invention.

[0038] FIG. 2 is a schematic cross-sectional view of a perovskite solar cell that does not include a hole transport layer according to one embodiment of the present invention.

[0039] FIG. 3 is a schematic cross-sectional view of a perovskite solar cell including a hole transport layer according to one embodiment of the present invention.

[0040] Figure 4 is a graph showing the results of analyzing the electrical conductivity of carbon nanotube electrodes with and without cyclization addition reaction compared to undoped PCNTs.

[0041] Figure 5 is a graph showing the results of analyzing the electrical conductivity of carbon nanotube electrodes according to heat treatment temperature and time.

[0042] Figure 6 is a graph showing the solar cell efficiency of a carbon nanotube electrode doped by a cyclization addition reaction compared to an undoped PCNT electrode.

[0043] The object, specific advantages, and novel features of the present disclosure will become more apparent from the following detailed description and embodiments in conjunction with the accompanying drawings.

[0044] Prior to this, terms and words used in this specification and claims should not be interpreted in their ordinary and dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of this disclosure, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0045] In this specification, where a component, such as a layer or part, is described as being "connected" or "combined" to another component, it may be directly "connected" or "combined" to another component, or it may have one or more other components interposed between the two components. In contrast, where a component is described as being "directly connected" or "directly combined" to another component, no other components may be interposed between the two components.

[0046] The terms used herein are merely for describing specific embodiments and are not intended to limit the disclosure. The singular expression includes the plural expression unless the context clearly indicates otherwise.

[0047] In this specification, terms such as “comprising” or “having” are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should not be understood as precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0048] In this specification, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components. Furthermore, throughout the specification, "on" means located above or below the subject part, and does not necessarily mean located on the upper side with respect to the direction of gravity.

[0049] The present disclosure is capable of various modifications and may have various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present disclosure to specific embodiments, and it should be understood that it includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the present disclosure. In describing the present disclosure, if it is determined that a detailed description of related prior art may obscure the essence of the present disclosure, such detailed description is omitted.

[0050] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In describing with reference to the accompanying drawings, identical or corresponding components are given the same reference numerals, and redundant descriptions thereof will be omitted.

[0051]

[0052] Hereinafter, the structure of an embodiment of the present invention will be described in detail with reference to the attached drawings.

[0053] FIG. 1 is a schematic diagram showing the process of attaching maleic anhydride and a dopant to the surface of a carbon nanotube according to one embodiment of the present invention.

[0054] Referring to FIG. 1, a carbon nanotube electrode for a solar cell according to one aspect of the present invention improves the stability of the solar cell by including carbon nanotubes surface-treated with maleic anhydride. According to the above configuration, the occurrence of defects in the carbon nanotubes can be minimized, while doping stability can be secured through the formation of covalent anchors.

[0055] Although not limited thereto, the maleic anhydride may be surface-treated on carbon nanotubes by cycloaddition in a polar solvent.

[0056] Although not limited thereto, the polar solvent may be one or more of dimethyl sulfoxide (DMSO, (CH3)2SO), dimethylformamide (DMF, HCON(CH3)2), and tetrahydrofuran (THF, C4H8O). Although not limited thereto, when the above solvent is used, nucleophilic substitution reactions are promoted so that cyclization addition reactions can occur sufficiently.

[0057] Cyclic addition is a reaction in which two compounds with π electrons combine to form a new ring structure, which can be carried out primarily by heat and light. In the present invention, a [4+2] cyclic addition reaction can occur in which a dynophyle with low electron density and a diene with high electron density react to form a ring structure in the form of six atoms. Although not limited to this, the present invention enables the efficient synthesis of compounds by inducing a selective cyclic addition reaction, and in particular, by forming a ring of six carbon atoms, ring strain is low, and a conjugated system can facilitate stable bonding.

[0058]

[0059] Although not limited thereto, the carbon nanotubes of the carbon nanotube electrode for a solar cell of the present invention may have the following structural formula:

[0060]

[0061] Here, X can be selected from the group consisting of an amine group (-NH2), an aromatic amine group, an aliphatic amine group, a vinyl group (-CH=CH2), a thiol group (-SH), and a sulfonyl group (-SO3H), and an amine group (-NH2) may be suitable.

[0062] Although not limited to this, when the above maleic anhydride and dopant are combined, an imide group having a structure in which one nitrogen atom is bonded to two acyl groups (RC=O) is formed, thereby ensuring high thermal stability. The formed imide group may be maleimide.

[0063] Although not limited thereto, the above dopant (D in FIG. 1) may not be limited to any specific type as long as it can combine with maleic anhydride or maleimide to form a functional group containing maleimide. The above dopant may be a substance containing a functional group selected from the group consisting of an amine group (-NH2), an aromatic amine group, an aliphatic amine group, a vinyl group (-CH=CH2), a thiol group (-SH), and a sulfonyl group (-SO3H). Although not limited thereto, the above dopant may be selected from compounds such as dimethyl-p-phenylenediamine, 4-nitroaniline, ethylenediamine, p-phenylenediamine, phenylamine, benzamidine, 4-aminoacetanilide, dimethyl ethylenediamine, methylamine, triazabicyclodecene, (perfluoroalkyl)aniline, vinylaniline, 4-(trifluoromethyl)aniline, and 4-aminothiophenol.

[0064] Although not limited thereto, the above dopant may be selected from compounds of the following chemical formula.

[0065] [Chemical Formula]

[0066]

[0067]

[0068] Although not limited thereto, the carbon nanotube electrode for a solar cell according to the present invention may be able to change the electron density and control the work function by the above X. Although not limited thereto, the above X may be determined as N-type doping or P-type doping. N-type doping can increase the electron density of the carbon nanotube, thereby increasing electrical conductivity, lowering the work function, and inducing N-type characteristics. In this case, the carbon nanotube acts as an acceptor and the dopant as a donor, allowing for the manufacture of a carbon nanotube electrode for an N-type solar cell in which electrons move from the dopant to the carbon nanotube. On the other hand, P-type doping can decrease the electron density of the carbon nanotube, thereby increasing the work function. In this case, the carbon nanotube acts as a donor and the dopant as an acceptor, allowing for the manufacture of a carbon nanotube electrode for a P-type solar cell in which electrons move from the carbon nanotube to the dopant.

[0069] Although not limited thereto, the carbon nanotube electrode for solar cells of the present invention can be manufactured as an N-type or P-type carbon nanotube electrode for solar cells depending on the dopant, and thus may be used not only as an electrode but also as an electron transport layer or a hole transport layer.

[0070]

[0071] According to another aspect of the present invention, a method for manufacturing a carbon nanotube electrode for a solar cell comprises: 1) a step of preparing a maleic anhydride; and 2) a step of mixing the maleic anhydride with a carbon nanotube and surface-treating the carbon nanotube by a cyclization addition reaction.

[0072] Step 1) above is a step of preparing maleic anhydride for surface treatment of carbon nanotubes. The maleic anhydride is a substance with the chemical formula C4H2O3, which may be manufactured for use or commercially available. The structural formula of maleic anhydride is as follows.

[0073] [constitutional formula]

[0074]

[0075]

[0076] Although not limited to this, in step 2) above, the maleic anhydride is electron-deficient and the carbon nanotube has a high π-electron density, so a Diels-Alder reaction may occur in which two carbon atoms in the π-bond of the carbon nanotube and two carbon atoms in the double bond of the maleic anhydride interact to form a six-membered ring. The Diels-Alder reaction is a [4+2] cyclization reaction between an electron-rich diene and an electron-deficient dienophile, in which the carbon nanotube can act as the diene and the maleic anhydride can act as the dienophile.

[0077] That is, through the above cyclization addition reaction, maleic anhydride can form a new cyclic compound on the surface of the carbon nanotube and be chemically bonded through covalent bonding, thereby facilitating bonding with hydrophilic substances, functional groups, etc.

[0078]

[0079] Although not limited thereto, a method for manufacturing a carbon nanotube electrode may further include a step of adding a dopant. The dopant may be added in step 1) or step 2).

[0080] That is, after binding a dopant to maleic anhydride in step 1), it can be mixed with carbon nanotubes in step 2) to form an imide group through a cyclization addition reaction. Additionally, in step 2), maleic anhydride, a dopant, and carbon nanotubes can be mixed to form an imide group through a cyclization addition reaction. The imide group formed at this time can improve the thermal stability of the carbon nanotubes.

[0081] Although not limited thereto, the above dopant may refer to a substance containing a functional group that is added in small amounts to an existing substance to control the chemical, electrical, and physical properties of the substance. That is, although not limited thereto, the functional group provided by the above dopant may be selected from the group consisting of amine groups (-NH2), aromatic amine groups, aliphatic amine groups, vinyl groups (-CH=CH2), thiol groups (-SH), and sulfonyl groups (-SO3H). Although not limited thereto, the above dopant may be a compound such as dimethyl-p-phenylenediamine, 4-nitroaniline, ethylenediamine, p-phenylenediamine, phenylamine, benzamidine, 4-aminoacetanilide, dimethyl ethylenediamine, methylamine, triazabicyclodecene, (perfluoroalkyl)aniline, vinylaniline, 4-(trifluoromethyl)aniline, and 4-aminothiophenol.

[0082] Although not limited thereto, it may be suitable to use one of the compounds containing the amine group described above as the dopant. Although not limited thereto, carbon nanotubes formed with amine groups can secure high thermal stability and tensile strength.

[0083] Although not limited thereto, the above dopant may be selected from compounds of the following chemical formula.

[0084] [Chemical Formula]

[0085]

[0086] Step 2) is a step of surface treating the carbon nanotubes by mixing the maleic anhydride with the carbon nanotubes and performing a cyclization addition reaction.

[0087] Although not limited thereto, step 2) above may be suitable for promoting the cyclization addition reaction by reacting at 100 to 200°C for 20 to 30 hours in a polar solvent, and may be more suitable by reacting at 150 to 200°C for 20 to 25 hours. Although not limited thereto, if the reaction time is less than 20 hours or the reaction temperature is less than 100°C, a thermally stable cyclic compound may not be sufficiently formed, making thermodynamic stabilization difficult. Additionally, although not limited thereto, if the reaction time exceeds 30 hours or the reaction temperature exceeds 200°C, the cyclized compound may decompose thermally or revert to the original single compound.

[0088] Although not limited thereto, the polar solvent may be one or more of dimethyl sulfoxide (DMSO, (CH3)2SO), dimethylformamide (DMF, HCON(CH3)2), and tetrahydrofuran (THF, C4H8O). Although not limited thereto, when the above solvent is used, nucleophilic substitution reactions are promoted so that cycloaddition reactions can occur sufficiently.

[0089]

[0090] Although not limited thereto, after step 2) above, a step of heat treatment at 300°C or higher for 1 to 5 hours may be further included. According to the above configuration, the electrical conductivity of the carbon nanotube electrode for a solar cell may be increased. In step 2) above, when the maleic anhydride sufficiently undergoes a cyclization addition reaction with the carbon nanotube for a solar cell to form a covalent bond and form a cyclic compound, the carbon nanotube, maleic anhydride, and dopant are stably bonded, resulting in excellent bonding stability and thermal stability. Therefore, even when the doped carbon nanotube of the present invention is heat-treated at 300°C or higher for 1 to 5 hours, the electrical conductivity of the formed carbon nanotube electrode may be increased.

[0091] Although not limited thereto, in the method for manufacturing a carbon nanotube electrode for a solar cell according to the present invention, the carbon nanotube of the carbon nanotube electrode for a solar cell according to the present invention may have the following structural formula:

[0092]

[0093] Here, X can be selected from the group consisting of an amine group (-NH2), an aromatic amine group, an aliphatic amine group, a vinyl group (-CH=CH2), a thiol group (-SH), and a sulfonyl group (-SO3H). Although not limited thereto, the above dopant may be selected from compounds such as dimethyl-p-phenylenediamine, 4-nitroaniline, ethylenediamine, p-phenylenediamine, phenylamine, benzamidine, 4-aminoacetanilide, dimethyl ethylenediamine, methylamine, triazabicyclodecene, (perfluoroalkyl)aniline, vinylaniline, 4-(trifluoromethyl)aniline, and 4-aminothiophenol.

[0094] The carbon nanotube electrode of the above structure forms a cyclized compound through a covalent bond resulting from a cyclization addition reaction, thereby exhibiting excellent bonding stability and minimizing defects in the carbon nanotube, and allows X to be stably bonded through the formation of a covalent anchor.

[0095]

[0096] Referring to FIG. 2 and FIG. 3, a solar cell according to another aspect of the present invention comprises a substrate (100); an electrode (200); an electron transport layer (300); a perovskite layer (400); and a carbon nanotube electrode layer (500); wherein the carbon nanotube electrode layer comprises a carbon nanotube electrode (520) for a solar cell as described herein.

[0097] Although not limited thereto, the substrate (100) can be formed from various materials. For example, it may be a transparent substrate containing glass or plastic material, a metal substrate such as ceramic, stainless steel, and alumina, or a flexible substrate containing polymer, etc. The substrate is not limited in type as long as it provides mechanical and thermal stability and is transparent or translucent for light transmission.

[0098] Although not limited thereto, the electrode (200) is formed on the substrate (100) and may be transparent so that light can reach the light absorption layer in the solar cell and has high conductivity. Although not limited thereto, the electrode may include ITO, IZO, FTO, ATO, Tin Oxide, Zinc Oxide, etc. Although not limited thereto, the electrode (200) may be included in the electron transport layer (300).

[0099] Although not limited thereto, the electron transport layer (300) is formed on the substrate (100) or the perovskite layer (400) and may include TiO2, ZnO, SnO2, CeO2, ITO, IZO, FTO, ATO, Tin Oxide, Zinc Oxide, etc. Alternatively, N-type carbon nanotubes may be included. The electron transport layer (300) moves electrons generated in the perovskite layer (400) to the electrode and prevents the coupling of electrons and holes, thereby increasing the photo-conversion efficiency.

[0100] Although not limited thereto, the perovskite layer (400) is formed on an electron transport layer (300), a hole transport layer (510), or a carbon nanotube electrode layer (500) and may include Pbl2, FAl, MAPbBr3, MACl, MAPbI, CsPbI3, or CH3NH3Pbl3. The perovskite layer (400) has the advantage of being able to easily control the movement and recombination of electrons and holes, and can accumulate electrons and holes, resulting in a long lifespan and high photoelectric efficiency. In addition, compared to silicon solar cells, perovskite solar cells have the characteristics of having a low solution process and a thin thickness, which reduces limitations on application fields.

[0101] Although not limited thereto, the carbon nanotube electrode layer (500) comprises a carbon nanotube electrode for a solar cell as described herein, and includes a carbon nanotube surface-treated with maleic anhydride. Although not limited thereto, the maleic anhydride may be covalently bonded to the carbon nanotube by a cyclization addition reaction. Additionally, although not limited thereto, the maleic anhydride may further include a dopant.

[0102] Although not limited thereto, the carbon nanotube electrode of the solar cell of the present invention is formed by reacting with an N-type dopant or a P-type dopant, and the N-type dopant may be selected from dimethyl-p-phenylenediamine, ethylenediamine, p-phenylenediamine (P-phenylenediamine), phenylamine, methylamine, dimethylethylenediamine, 4-aminoacetanilide, and triazabicyclodecene, and the P-type dopant may be selected from 4-nitroaniline and benzamidine. Additionally, the carbon nanotube electrode forms an N-type carbon nanotube electrode through reaction with the N-type dopant; or a P-type carbon nanotube electrode through reaction with the P-type dopant.

[0103] N-type dopants can induce N-type characteristics by increasing the electron density of carbon nanotubes, and maleic anhydride acts as an acceptor while the dopant acts as a donor, allowing electrons to move from the dopant to the carbon nanotube, thereby enabling the fabrication of carbon nanotube electrodes for N-type solar cells. On the other hand, P-type dopants decrease the electron density of carbon nanotubes, and maleic anhydride acts as a donor while the dopant acts as an acceptor, allowing electrons to move from the carbon nanotube to the dopant, thereby enabling the fabrication of carbon nanotube electrodes for P-type solar cells.

[0104] Although not limited thereto, the carbon nanotube electrode layer (500) may further include a hole transport layer (510). Although not limited thereto, a carbon nanotube electrode (520) containing a carbon nanotube that has reacted with the P-type dopant may serve as the hole transport layer (510).

[0105] Although not limited thereto, the carbon nanotube electrode can be used as an electron transport layer (300). A carbon nanotube electrode containing a carbon nanotube that has reacted with the N-type dopant can serve as an electron transport layer (300).

[0106]

[0107] Although not limited thereto, according to one embodiment of the present invention, the solar cell of the present invention can provide a solar cell in which the power conversion efficiency (PCE) increases by 2%p or more compared to a control group that does not apply the doping method of the present invention.

[0108] Although not limited thereto, strong covalent bonds are formed by the cycloaddition reaction of carbon nanotubes, maleic anhydride, and dopants of the present invention, thereby minimizing defects in the solar cell, ensuring high thermal stability, facilitating work function control, increasing electrical conductivity, and increasing the efficiency of the solar cell.

[0109]

[0110] Examples

[0111] Example 1. Preparation of carbon nanotubes

[0112] Dimethyl Sulfoxide (DMSO) solvent, carbon nanotubes, maleic anhydride, and a selected dopant were each mixed in a beaker or container at a concentration of 25 mM. The mixed solution was heated to 180°C and reacted for 24 hours. After the reaction was complete, the carbon nanotube electrode was removed, washed three times each with acetone and water, and dried.

[0113] At this time, the dopant used was dimethyl-p-phenylenediamine, 4-nitroaniline, ethylenediamine, p-phenylenediamine, or phenylamine, as shown in Table 1.

[0114]

[0115] Example 2. Preparation of a perovskite solar cell

[0116] 1. Substrate manufacturing stage

[0117] FTO glass was prepared as a transparent substrate.

[0118] 2. Electrode (cathode) manufacturing step

[0119] Titanium diisopropoxide bis(acetylacetonate) was dissolved in ethanol at a concentration of 7.5 wt%, sprayed onto FTO glass, and then heat-treated at 450°C to prepare a TiO2(c-TiO2) layer.

[0120] 3. Electron transport layer manufacturing stage

[0121] A solvent was prepared by mixing terpineol and 2-Me at a ratio of 1:3.5 wt%, and TiO2 paste was dissolved in the prepared solvent at a ratio of 1:5 wt%. The prepared meso-TiO2 solution was filtered through a 0.45 μm PVDF filter, and then spin coating was performed at 2500 rpm for 50 seconds after loading 85 μm. After evaporating the solvent at 150°C, heat treatment was performed at 500°C for 1 hour.

[0122] 4. Perovskite layer manufacturing step

[0123] A perovskite precursor solution was prepared by dissolving PbI2 1.60M, FAI 1.47M, MAPbBr3 0.07M, and MACI 0.53M in a solution of DMF and DMSO (8:1 v / v). Subsequently, the perovskite precursor solution was spin-coated onto a TiO2 (c-TiO2) layer at 500 rpm for 5 seconds, and heat-treated at 150°C for 10 minutes to form a perovskite layer.

[0124] The manufactured perovskite film was washed with IPA while rotating at 5000 rpm.

[0125] 5. Hole transport layer manufacturing stage

[0126] 100 mg of spiro-OMeTAD, 23 μL of Li-TFSI (540 mg / mL acetonitrile), 39 μL of tBP, and 10 μL of Co(III) salt solution (376 mg / mL acetonitrile) were dissolved in 1.1 mL of chlorobenzene to prepare a hole transport layer (HTL). The prepared solution was spin-coated at 2000 rpm for 3 seconds to prepare a hole transport layer (HTL).

[0127] 6. Carbon nanotube electrode manufacturing step

[0128] A carbon nanotube electrode was prepared by placing a free-standing carbon nanotube prepared according to Example 1 on a hole transport layer and pressing it. At this time, as a comparative example, a gold electrode was deposited on the hole transport layer using a thermal evaporator.

[0129]

[0130] Experimental Example

[0131] Experimental Example 1. Analysis of Electrical Conductivity of Carbon Nanotubes According to Maleimide and Dopant

[0132] The change in electrical conductivity of carbon nanotubes prepared by the method of Example 1 was investigated and analyzed compared to carbon nanotubes (hereinafter CNT) not surface-treated with maleimide (Comparative Example), and the results are shown in Table 1. Referring to Table 1, it was confirmed that the electrical conductivity of the carbon nanotubes prepared by the method of Example 1 increased compared to the CNT not surface-treated with maleimide (Comparative Example). In addition, since there was a change in electrical conductivity depending on the dopant bonded to the maleimide, it was confirmed that either a P-type or N-type dopant could be used depending on the selection of the dopant. In other words, it was confirmed that the electrical conductivity is improved due to the maleimide doping of carbon nanotubes, and that the change in electrical conductivity due to the dopant and the resulting increase in the usability of the carbon nanotubes can be achieved.

[0133]

[0134]

[0135] Experimental Example 2. Analysis of Change in Work Function of Carbon Nanotubes According to Heating Time

[0136] The change in work function according to heating time of carbon nanotubes prepared by the method of Example 1 was investigated and analyzed, and the results are shown in Table 2.

[0137] Referring to Table 2, the change in the work function of carbon nanotubes according to heat treatment can be observed. After treatment with an excitation source of He, 21.22 eV, CNT-N (CNT + maleic anhydride + 4-nitroaniline) doped by the method of Example 1 was compared with PCNT, an undoped sample. It was confirmed that CNT-N maintained a higher work function value compared to PCNT when heat-treated at room temperature, at 300°C for 1 hour, and at 300°C for 5 hours, indicating excellent thermal stability and doping stability.

[0138]

[0139]

[0140] Experimental Example 3. Analysis of Electrical Conductivity of Carbon Nanotubes with and Without Cyclic Addition Reaction

[0141] The electrical conductivity of carbon nanotubes by cyclization addition reaction was analyzed and is shown in Figure 4.

[0142] Figure 4 is a graph showing the analysis of electrical conductivity and thermal stability when comparing electrical conductivity after heat treatment in an air atmosphere at 300°C for 6 hours and 12 hours.

[0143] Electrical conductivity was determined by applying an external voltage to observe the current flow and using the measured current, the area, and the thickness of the sample. The formula is as follows.

[0144]

[0145] S·cm 2 / g: Electrical conductivity per unit of mass

[0146] σ: Electrical conductivity

[0147] m: Mass of the sample

[0148] Referring to Figure 4, it was confirmed that the electrical conductivity of the example of the present invention (CNT-N, CNT + Maleic anhydride + 4-Nitroaniline cycloaddition) doped through a cycloaddition reaction increased. On the other hand, SA-CNT (Sulfuric acid dipping), NA-CNT (Nitric acid dipping), Fe-CNT (Iron(III) chloride dipping), PEI-CNT (polyethylenimine dipping), and TETA-CNT (triethylenetetramine dipping) doped by dipping CNTs in a solvent and then washing them showed improved electrical conductivity compared to untreated PCNT after doping, but it was confirmed that the electrical conductivity decreased sharply after heat treatment in an air atmosphere at 300°C for 6 hours and 12 hours. In the case of general adsorption doping, electrical conductivity decreases because the dopant evaporates after heat treatment, but when doped by the method described in the embodiments of the present invention, high electrical conductivity is maintained due to excellent doping stability.

[0149] That is, it can be confirmed that the embodiments of the present invention, doped with maleic anhydride and 4-nitroaniline through a cyclization addition reaction, have excellent electrical conductivity and thermal stability.

[0150]

[0151] Experimental Example 4. Analysis of Work Function of Carbon Nanotubes According to Dopant

[0152] The work function of carbon nanotubes according to the dopant was analyzed and is shown in Table 3.

[0153] Referring to Table 3, the change in the work function of carbon nanotubes according to doping can be observed. After treatment with an excitation source of He, 21.22 eV, it was confirmed that the work functions of CNT-D (CNT + maleic anhydride + dimethyl-p-phenylenediamine) and CNT-N (CNT + maleic anhydride + 4-nitroaniline) doped by the method of Example 1 were all different compared to the undoped sample, PCNT (Comparative Example). In the case of CNT-D, it was confirmed that the work function decreased due to the binding of the N-type dopant, while in the case of CNT-N, the work function increased due to the binding with the P-type dopant. In other words, it was confirmed that not only is it possible to control the work function by changing the type of dopant, but it is also possible to manufacture N-type CNTs and P-type CNTs.

[0154]

[0155]

[0156] Experimental Example 5. Analysis of Electrical Conductivity of Carbon Nanotubes According to Heat Treatment Temperature and Time

[0157] The electrical conductivity of carbon nanotubes according to heat treatment temperature and time was analyzed and is shown in Figure 5.

[0158] Figure 5 shows the results of obtaining electrical conductivity by heating PCNT (Comparative Example), which is an undoped sample, and CNT-D (CNT + maleic anhydride + dimethyl-p-phenylenediamine) and CNT-N (CNT + maleic anhydride + 4-nitroaniline) doped by the method of Example 1 at 100 to 300°C under conditions of Air, 10°C / min.

[0159] It was confirmed that both CNT-D and CNT-N doped by the method described in the embodiments of the present invention maintain high electrical conductivity even after heat treatment. In other words, it is confirmed that the method described in the embodiments of the present invention maintains high electrical conductivity due to excellent doping stability.

[0160]

[0161] Experimental Example 6. Analysis of Solar Cell Efficiency

[0162] The efficiency of the solar cell according to the present invention was analyzed and is shown in Figure 6 and Table 4.

[0163] Referring to Figure 6 and Table 4, the solar cell efficiency of the example (CNT-N) was 19.39%, and the solar cell efficiency of the comparative example (CNT) was 17.39%, confirming that the solar cell efficiency was improved by 2%p. This confirms that the electrode doping method of the present invention is also effective in improving the efficiency of solar cells.

[0164]

[0165]

[0166] Although the present disclosure has been described in detail through specific embodiments, this is for the purpose of specifically explaining the present disclosure and is not limited thereto. It is evident that modifications or improvements can be made by those skilled in the art within the technical scope of the present disclosure. All simple modifications or alterations of the present disclosure fall within the scope of the present disclosure, and the specific scope of protection of the present disclosure will be clarified by the appended claims.

[0167]

[0168] [Explanation of the symbol]

[0169] 100: Substrate

[0170] 200: Electrode

[0171] 300: Electron transport layer

[0172] 400: Perovskite layer

[0173] 500: Carbon nanotube electrode layer

[0174] 510: Precision Transport Layer

[0175] 520: Carbon nanotube electrode

Claims

1. A carbon nanotube electrode for a solar cell that improves the stability of the solar cell, comprising carbon nanotubes surface-treated with maleic anhydride.

2. In Paragraph 1, The above maleic anhydride is a carbon nanotube electrode for a solar cell, the carbon nanotube being surface-treated by cycloaddition in a polar solvent.

3. In Paragraph 1, The above carbon nanotube is a carbon nanotube electrode for a solar cell having the following structural formula: Here, X is selected from the group consisting of an amine group (-NH2), an aromatic amine group, an aliphatic amine group, a vinyl group (-CH=CH2), a thiol group (-SH), and a sulfonyl group (-SO3H).

4. In Paragraph 3, A carbon nanotube electrode for a solar cell, capable of controlling the work function by the above X.

5. In Paragraph 1, The above electrode is a carbon nanotube electrode for a solar cell, which is an N-type electrode or a P-type electrode. 6.1) Step of preparing maleic anhydride; and 2) a step of mixing the maleic anhydride with carbon nanotubes and surface-treating the carbon nanotubes through a cyclization addition reaction; comprising a method for manufacturing a carbon nanotube electrode for a solar cell.

7. In Paragraph 6, A method for manufacturing a carbon nanotube electrode, further comprising the step of adding a dopant.

8. In Paragraph 7, A method for manufacturing a carbon nanotube electrode, wherein the above-mentioned dopant is a material comprising one selected from the group consisting of an amine group (-NH2), an aromatic amine group, an aliphatic amine group, a vinyl group (-CH=CH2), a thiol group (-SH), and a sulfonyl group (-SO3H).

9. In Paragraph 6, Step 2) above is a method for manufacturing a carbon nanotube electrode for a solar cell, wherein the reaction is carried out in a polar solvent at 150 to 200°C for 20 to 30 hours.

10. In Paragraph 6, A method for manufacturing a carbon nanotube electrode for a solar cell, further comprising, after step 2) above, a step of heat treating at 300°C or higher for 1 to 5 hours.

11. In Paragraph 6, A method for manufacturing a carbon nanotube electrode for a solar cell, wherein the carbon nanotubes have the following structural formula: Here, X is selected from the group consisting of an amine group (-NH2), an aromatic amine group, an aliphatic amine group, a vinyl group (-CH=CH2), a thiol group (-SH), and a sulfonyl group (-SO3H).

12. A perovskite solar cell comprising a substrate; an electron transport layer; a perovskite layer; and a carbon nanotube electrode layer, wherein The above carbon nanotube electrode layer comprises a carbon nanotube electrode for a solar cell as described in claim 1, a solar cell.

13. In Paragraph 12, A solar cell in which the carbon nanotube electrode layer comprises a hole transport layer.

14. In Paragraph 12, The above carbon nanotube electrode is one that has reacted with an N-type dopant or a P-type dopant, and The N-type dopant is selected from dimethyl-p-phenylenediamine, ethylenediamine, p-phenylenediamine, phenylamine, methylamine, dimethylethylenediamine, 4-aminoacetanilide, and triazabicyclodecene; and the P-type dopant is selected from 4-nitroaniline and benzamidine, A solar cell forming an N-type carbon nanotube electrode through reaction with the above N-type dopant; or a P-type carbon nanotube electrode through reaction with the above P-type dopant.

15. In Paragraph 12, The above solar cell is a solar cell having a power conversion efficiency (PCE) that increases by 2%p or more compared to a solar cell containing undoped carbon nanotubes.

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