Perovskite solar cell including interface bonding layer and method for manufacturing same

Abstract

The present invention relates to a perovskite solar cell comprising an interfacial junction layer and a method for manufacturing the same. More specifically, the invention discloses a solar cell in which a first electrode, a hole transport layer, a photoactive layer, an electron transport layer, and a second electrode are sequentially stacked, wherein the photoactive layer is formed by including a perovskite compound of the formula APbX3 or ASnX3 (wherein A is a metal cation, an organic cation, or a combination thereof, and X is selected from at least one of I, Br, and Cl), the electron transport layer is formed by including a fullerene compound, and further comprises an interfacial junction layer formed of an interfacial junction compound of the following formula 1, having a simple arene core capable of bonding with the fullerene compound and an oxygen-containing functional group terminal capable of bonding with A of the perovskite compound, between the photoactive layer and the electron transport layer. [Chemical Formula 1] TR-Ar-RT (However, in the above Chemical Formula 1, Ar is a polycyclic aromatic or heteroaromatic arene compound, R is an alkyl having 1 to 20 carbon atoms, and T is one or more selected from -OH, -C(=O), -COO, and -C(=O)CH3)

Description

Technology Field

[0001] The present invention relates to a perovskite solar cell and a method for manufacturing the same, which provides a passivation effect on the surface of the photoactive layer of the perovskite solar cell and introduces a new bonding layer to overcome the delamination phenomenon caused by weak bonding force between a perovskite layer and a fullerene, a widely used electron transport thin film material, thereby strengthening the bond and simultaneously improving the electron transport effect. Background Technology

[0003] With the recent focus on climate change, solar cells, a type of renewable energy, are garnering attention. Solar cells are devices that convert sunlight into electrical energy through the photoelectric effect; among them, perovskite solar cells are next-generation solar cells that utilize materials with a perovskite structure as the photoactive layer, allowing for lightweight and simple fabrication methods, and thus various research is continuously being conducted. These perovskite solar cells refer to solar cells that use an organic-inorganic composite as the light-absorbing material. This composite consists of organic cations containing methylammonium or formamidinium at the A cation site, lead metal ions at the B cation site, and halogen anions containing iodine, bromine, or chlorine at the X anion site, all having a three-dimensional crystal structure of ABX3. Since the announcement in 2012 of a perovskite solar cell with a photoelectric conversion efficiency of 9.7% using a solid hole transport material, active research has been conducted on these cells as they are the most promising type among third-generation solar cells. Perovskite solar cells can be classified into NIP and PIN structures depending on the direction of electron and hole movement generated within the device. In NIP-type devices, a thin film of n-type semiconductors, such as TiO2 or SnO2, is formed on a transparent electrode, followed by a perovskite photoactive layer, and then a p-type semiconductor is coated as a hole transport material. Conversely, PIN-type devices, also known as inverted structures, are formed by first creating a p-type semiconductor on a transparent electrode, followed by a perovskite photoactive layer and then an n-type semiconductor electron transport material. While NIP-type devices exhibit high photoelectric conversion efficiencies exceeding 20%, hysteresis—a phenomenon where performance varies depending on the measurement direction—is cited as a drawback. PIN-type devices have relatively lower efficiency but exhibit less hysteresis, making them advantageous for stable device operation, and they have the advantage of all manufacturing processes being carried out at low temperatures below 150 °C. Generally, electron transport materials for PIN-type devices include approximately -4.Fullerene or fullerene derivative PCBM (phenyl-C61-butyric acid methyl ester) having an energy bandgap that matches well with the LUMO (lowest unoccupied molecular orbital) level of the perovskite photoactive layer at 0 eV is used.

[0004] However, the above fullerene (C 60 The bonding strength with the perovskite thin film is weak, and fullerene materials are mainly coated on the perovskite layer by thermal evaporation, but there is a limitation in that the mechanical stability is reduced because the chemical bonding strength is weak and it peels off easily.

[0005] In addition, PCBM, a fullerene derivative, is suitable as an electron transport layer coated on a perovskite photoactive layer because it has excellent electron mobility and can be dissolved in non-polar organic solvents that do not decompose the perovskite photoactive layer. However, since PCBM is a fullerene-based derivative, its solubility is limited, and because low-viscosity solvents such as chlorobenzene are used, it is difficult to form a uniform, thick, and defect-free PCBM layer on a pinhole-free perovskite layer using the conventional spin coating process. Furthermore, since the morphology and crystallinity of the PCBM layer change over time, it is required to form the existing PCBM layer more stably and robustly. In other words, there is a need for a method to improve the power loss caused by direct contact between the perovskite photoactive layer and the metal electrode, and the low perovskite photoactive layer protection ability due to the thin PCBM layer, by forming a defect-free, thick, and uniform PCBM layer on a rough-surfaced perovskite layer without loss of the electron transfer ability of the PCBM.

[0006] Accordingly, prior patents have reported improving the performance of perovskite solar cells using fullerene and fullerene derivatives as electron transport layers, controlling the characteristics of fullerene derivatives (Korean Registered Patent 10-1717430 and Published Patent 10-2017-0047370), or forming a derivative thin film by adding a surfactant to a fullerene derivative solution (Korean Published Patent 10-2020-0022122). However, relying solely on the characteristics of the fullerene derivatives or forming a fullerene derivative thin film still does not facilitate bonding with the perovskite photoactive layer, which limits the protection of the perovskite photoactive layer and the improvement of solar cell performance.

[0008] Meanwhile, although current perovskite solar cells demonstrate high performance with an efficiency reaching 26%, commercialization is difficult due to long-term stability and environmental stability issues arising from the use of lead (Pb) materials. Therefore, technologies capable of improving the long-term and environmental stability of existing high-efficiency solar cells are required, and among these, interfacial engineering is a commonly used method to enhance long-term stability. Since perovskite solar cells consist of multiple layers and possess numerous interfaces, and solar cell degradation primarily originates at these interfaces, many researchers are attempting to resolve this through interfacial engineering.

[0009] Accordingly, the inventors confirmed that by forming a thin film capable of bonding a perovskite photoactive layer and a fullerene electron transport layer, it is possible to achieve interface treatment during the fabrication process of perovskite solar cell devices, strengthen bonding strength between thin films, and improve physical properties required for the modularization process, and thus completed the present invention. Prior art literature

[0011] Republic of Korea Registered Patent No. 10-1717430 Republic of Korea Published Patent No. 10-2017-0047370 Republic of Korea Published Patent No. 10-2020-0022122 The problem to be solved

[0012] Accordingly, the present invention has as its technical problem to provide a perovskite solar cell comprising an interface junction layer.

[0013] In addition, the present invention has another technical problem to solve by providing a method for manufacturing a perovskite solar cell including an interfacial junction layer. means of solving the problem

[0015] In order to solve the above technical problem, the present invention,

[0016] In a solar cell in which a first electrode, a hole transport layer, a photoactive layer, an electron transport layer, and a second electrode are sequentially stacked,

[0017] The above photoactive layer is formed by including a perovskite compound of the chemical formula APbX3 or ASnX3 (wherein A is a metal cation, an organic cation, or a combination thereof, and X is selected from at least one of I, Br, and Cl), and

[0018] The above electron transport layer is formed by including a fullerene compound, and

[0019] A perovskite solar cell is provided, further comprising, between the photoactive layer and the electron transport layer, an interfacial junction layer formed of an interfacial junction compound of the following chemical formula 1, having a simple arene core capable of bonding to the fullerene compound and an oxygen-containing functional group terminal capable of bonding to A of the perovskite compound:

[0020] [Chemical Formula 1]

[0021] TR-Ar-RT

[0022] (However, in the above Chemical Formula 1, Ar is a polycyclic aromatic or heteroaromatic arene compound, R is an alkyl group having 1 to 20 carbon atoms, and T is one or more functional groups selected from -OH, -C(=O), -COO, and -C(=O)CH3.)

[0023] In the present invention, the above chemical formula 1 is characterized in that Ar is a naphthalene diimide compound and T is COOCH3.

[0024] In addition, in the present invention, the interface bonding layer is characterized by having a surface roughness of up to 10 nm.

[0025] In addition, the present invention is characterized in that the interface bonding layer is formed with a thickness of 2 to 10 nm.

[0026] In addition, in the present invention, the first electrode comprises at least one selected from the group consisting of a flexible transparent electrode substrate, indium tin oxide (ITO), fluorinated tin oxide (FTO), aluminum zinc oxide (AZO), boron-doped zinc oxide (BZO), niobium titanium oxide (NTO), zinc tin oxide (ZTO), and indium zinc tin oxide (IZTO).

[0027] The second electrode is characterized by comprising at least one selected from the group consisting of silver (Ag), aluminum (Al), platinum (Pt), tungsten (W), copper (Cu), molybdenum (Mo), gold (Au), nickel (Ni), palladium (Pd), and carbon (C).

[0028] In addition, to solve the aforementioned other technical problems, the present invention,

[0029] Forming a first electrode,

[0030] A step of forming a hole transport layer on the first electrode;

[0031] A step of forming a photoactive layer by coating and heat-treating a perovskite compound on the hole transport layer;

[0032] A step of forming an interface bonding layer formed of an interface bonding compound on the above photoactive layer;

[0033] A step of forming an electron transport layer by depositing a fullerene compound on the above interface bonding layer; and

[0034] The method includes the step of forming a second electrode on the electron transport layer;

[0035] A method for manufacturing a perovskite solar cell is provided, characterized by manufacturing the solar cell described above. Effects of the invention

[0037] According to the present invention, a passivation effect can be imparted to the perovskite thin film by forming an interfacial junction layer through the coating of an interfacial junction compound between the perovskite layer and the electron transport layer of a perovskite solar cell. Long-term stability of the device can also be secured through the interfacial junction compound, which possesses thermal, chemical, and physical stability. Furthermore, effective treatment of the perovskite surface interface through this interfacial junction layer can contribute to the formation of a uniform electric field. In addition, this interfacial junction compound can be fabricated using a spin coating method in a solution process, allowing for simple and low-cost deposition, and long-term stability against moisture can be improved by preventing moisture penetration through the interfacial junction layer. Brief explanation of the drawing

[0039] Figure 1 shows the structure of an NDI derivative compound as an interfacial bonding compound according to one embodiment of the present invention. Figure 2 shows the binding energy of naphthalene diimide (NDI), ethyl acetate, and NDI having an acetyl terminal according to one embodiment of the present invention. Figure 3 shows the complex formation and binding energy at the interface between the perovskite photoactive layer, the interfacial junction layer, and the fullerene electron transport layer of a perovskite solar cell. FIG. 4a shows the structural formula of an NDI derivative with different terminal functional groups used in one embodiment of the present invention, and FIG. 4b shows the AFM measurement results of a thin film coated with an NDI derivative and heat-treated on a perovskite thin film, showing the roughness and uniformity of the electric field. Figure 5 shows the process and results of a taping experiment conducted after fabricating a perovskite solar cell device with or without an interfacial junction compound coating, according to one embodiment of the present invention. FIG. 6 shows, according to one embodiment of the present invention, the case without an interfacial bonding compound and the case where NDI-C11 and NDI-C9-Ace materials are a perovskite thin film and C 60 This shows the results of a peeling experiment in which the top thin film was removed using carbon tape on a completed single device fabricated by deposition at the interface. Figure 7 shows an SEM image comparing the surface shape of a perovskite thin film surface with and without an interfacial bonding compound coating after coating a perovskite layer on a glass substrate according to one embodiment of the present invention, and Figure 8 shows Atomic Force Microscopy (AFM, left) and Electron Force Microscopy (EFM, right) data images comparing the surface shape and the charge accumulation and dissipation shapes. FIG. 9 shows Confocal Laser Scanning Microscopy (CLSM) data images of surface roughness and shape that change when fullerene is subsequently deposited depending on the presence or absence of an interfacial bonding compound coating, according to one embodiment of the present invention. FIG. 10 is a graph of UV-Vis transmittance according to the presence or absence of a perovskite-fullerene interface junction compound coating and an electron transport layer coating after coating a perovskite layer on a glass substrate according to one embodiment of the present invention. Figure 11 is an Ultraviolet Photoelectron Spectroscopy (UPS) analysis graph according to one embodiment of the present invention, with respect to the presence or absence of a perovskite-fullerene interface junction compound coating and an electron transport layer coating after coating a perovskite layer on a silicon substrate. FIG. 12 is an X-ray Photoelectron Spectroscopy (XPS) analysis graph according to one embodiment of the present invention, after coating a perovskite layer on a silicon substrate, with or without a perovskite-fullerene interface junction compound coating and with or without an electron transport layer coating. FIG. 13 is a graph of time-resolved photoluminescence analysis according to one embodiment of the present invention, after coating a perovskite layer on a glass substrate, with or without a perovskite-fullerene interface junction compound coating and with or without an electron transport layer coating. FIG. 14 is an impedance analysis graph based on the results of performing an impedance analysis after fabricating a perovskite solar cell device according to one embodiment of the present invention. Specific details for implementing the invention

[0040] The present invention will be described in detail below.

[0041] Furthermore, throughout the specification, when a part is described as "including" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0043] In one embodiment, the present invention relates to a perovskite solar cell, wherein a first electrode, a hole transport layer, a photoactive layer, an electron transport layer, and a second electrode are sequentially stacked, wherein the photoactive layer is formed by including a perovskite compound of the formula APbX3 or ASnX3 (wherein A is a metal cation, an organic cation, or a combination thereof, and X is selected from at least one of I, Br, and Cl), the electron transport layer is formed by including a fullerene compound, and further comprising, between the photoactive layer and the electron transport layer, an interfacial bonding layer formed of an interfacial bonding compound of the following formula 1, having a simple arene core capable of bonding with the fullerene compound and an oxygen-containing functional group terminal capable of bonding with A of the perovskite compound.

[0044] [Chemical Formula 1]

[0045] TR-Ar-RT

[0046] (However, in the above Chemical Formula 1, Ar is a polycyclic aromatic or heteroaromatic arene compound, R is an alkyl group having 1 to 20 carbon atoms, and T is one or more functional groups selected from -OH, -C(=O), -COO, and -C(=O)CH3.)

[0047] The perovskite solar cell of the present invention is characterized in that it forms an interfacial junction layer with an interfacial junction compound of Formula 1.

[0048] Figure 1 illustrates the characteristics of an interfacial bonding compound of the TR-Ar-RT structure having the above chemical formula 1. The arene compound (Ar), which is a pi-electron-deficient core, can bond with an electron-rich group and form a passivation film by imparting hydrophobicity through the alkyl group (R), and has a structure in which an oxygen-containing functional group (T) as a polar functional group at the terminal can bond with an electron-deficient group.

[0049] That is, the above interface bonding compound has a benzene ring capable of bonding with a fullerene compound, enabling pi-pi stacking interactions between the fullerene and the benzene ring, and has an oxygen-containing functional group capable of bonding with the electron-deficient cation of the perovskite compound, thereby significantly improving bonding at the interface. In addition, the hydrophobic alkyl group enables surface passivation of the perovskite thin film and provides thermal and physical stability to the solar cell device.

[0050] At this time, in the above chemical formula 1, it is preferable that Ar is a naphthalene diimide compound and T is COOCH3.

[0051]

[0052] (However, in the above formula, n is an integer from 1 to 20.)

[0053] FIG. 2 shows the binding energy of naphthalene diimide (NDI), an arene compound constituting the interfacial bonding compound of the present invention, and ethyl acetate, an oxygen-containing functional group, and an NDI derivative having an acetyl term as the interfacial bonding compound of the present invention; FIG. 3a shows the complex formation and binding energy at the interface of the perovskite photoactive layer, interfacial bonding layer, and fullerene electron transport layer of a perovskite solar cell; FIG. 3b shows the interaction between the oxygen-containing functional group term, which is an anion, and iodine (I) and lead (Pb) atoms of the perovskite thin film.

[0054] Referring to this, the interfacial bonding layer of the present invention can be formed by forming an interfacial bonding layer of a thin film through the enhancement of binding energy by the acetyl terminal, which is an oxygen-containing functional group of the interfacial bonding compound, and by interacting strongly in the horizontal direction with the iodine (I) and lead (Pb) atoms of the perovskite thin film. Furthermore, if fullerene is deposited after the interfacial bonding layer is formed, C 60 The electron-rich plane of the interface junction compound is bonded to the arene core region with high binding energy.

[0055] Therefore, preferably, the average surface roughness of the interface bonding layer may be up to 10 nm. If the average surface roughness of the interface bonding layer exceeds 10 nm, the effect of the interface bonding is reduced, and there may be a problem in that the electric field formation is not uniform.

[0056] Additionally, preferably, the interface bonding layer may be formed with a thickness of 2 to 10 nm. If the thickness of the interface bonding layer is less than 2 nm, there may be a problem with reduced coverage, and if it exceeds 10 nm, there may be a problem with reduced charge transport efficiency.

[0057] In addition, the ratio of the thickness of the interface junction layer to the total thickness of the perovskite solar cell may be 1:0.002 to 1:0.01. If the ratio of the thickness of the interface junction layer is less than the above range, there may be a problem of reduced coverage, and if it exceeds the above range, there may be a problem of reduced charge transport efficiency.

[0058] According to one embodiment, the perovskite may be an inorganic metal halide perovskite, an organic-inorganic hybrid perovskite, etc. For example, the perovskite may have a structure represented by ABX3. In some examples, in the above formula, A is an alkali metal, an organic cation (e.g., organic ammonium) and / or an inorganic cation, B is a metallic material, and X is a halogen anion, a chalcogenide anion, and SCN - It can be selected from (thiocyanate). For example, A is an alkali metal of Na, K, Rb, Cs, or Fr; (CH3NH3) n , ((C x H 2x+1 ) n NH3)2(CH3NH3) n , (RNH3)2, (C n H 2n+1 NH3)2, (CF3NH3), (CF3NH3) n, ((C x F 2x+1 ) n NH3)2(CF3NH3) n , ((C x F 2x+1 ) n NH3)2 or (C n F 2n+1 NH3)2 (n is an integer greater than or equal to 1, and x is an integer greater than or equal to 1), B is a divalent transition metal, rare earth metal, alkaline earth metal, Pb, Sn, Ge, Ga, In, Al, Sb, Bi, Po, etc., and X may be P, Cl, Br, I, etc. In some examples, the perovskite may be CH3NH3PbI3, CH3NH3PbBr3, CH3NH3PbI2Cl, CH3NH3PbI2Br, etc. In some examples, when two or more of the perovskite compounds are included, the ratio of the first perovskite compound to the second perovskite compound may be 5:5 to 9:1. In some examples, compounds represented by chemical formulas such as NaX', ZnX', KX' and CsX' (where X is selected from Cl, Br and I) may also be included, in an amount of 10% or less of the total perovskite compounds; or 5% or less.

[0059] The above photoactive layer can perform the role of separating electrons and holes into two electrodes and separating electrons and holes into an electron transport layer and a hole transport layer, respectively.

[0060] The size of the perovskite crystal grains in the above photoactive layer may be 1 nm to 900 nm; 1 nm to 800 nm; 5 nm to 600 nm; 5 nm to 300 nm; 10 nm to 300 nm; 10 nm to 100 nm; or 10 nm to 50 nm.

[0061] The thickness of the above photoactive layer is 500 nm to 800 nm; 550 nm to 700 nm; preferably, to improve the performance of the photoactive layer, it may be 550 nm to 650 nm.

[0062] Also preferably, the first electrode comprises at least one selected from the group consisting of a flexible transparent electrode substrate, indium tin oxide (ITO), fluorinated tin oxide (FTO), aluminum zinc oxide (AZO), boron-doped zinc oxide (BZO), niobium titanium oxide (NTO), zinc tin oxide (ZTO), and indium zinc tin oxide (IZTO).

[0063] The second electrode may comprise at least one selected from the group consisting of silver (Ag), aluminum (Al), platinum (Pt), tungsten (W), copper (Cu), molybdenum (Mo), gold (Au), nickel (Ni), palladium (Pd), and carbon (C).

[0064] As such, the perovskite solar cell of the present invention forms an interfacial junction layer to facilitate the bonding of the perovskite photoactive layer and the fullerene compound electron transport layer, thereby protecting the perovskite photoactive layer and improving solar cell performance. Specifically, by including oxygen-containing functional groups at the ends of the interfacial junction compound to attract electrons, charge transfer is enhanced upon bonding with the perovskite structure. Furthermore, by controlling the growth and morphology of the perovskite crystals and regulating interfacial characteristics such as the movement of electrons and holes while forming the interfacial junction layer, cell performance can be improved. In addition, the stability of the perovskite solar cell device structure can be enhanced, thereby extending the lifespan of the device.

[0066] In another aspect, the present invention relates to a method for manufacturing a perovskite solar cell as described above, comprising the steps of: forming a first electrode and forming a hole transport layer on the first electrode; forming a photoactive layer by coating and heat-treating a perovskite compound on the hole transport layer; forming an interface junction layer formed of an interface junction compound on the photoactive layer; forming an electron transport layer by depositing a fullerene compound on the interface junction layer; and forming a second electrode on the electron transport layer.

[0067] According to one embodiment, when forming the first electrode, the first electrode mentioned in the present invention may be prepared, and, for example, a conductive material layer may be formed on a substrate coated with a conductive material layer on a substrate or by using sputtering, CVD, deposition, solution process, coating, printing, etc. on a substrate.

[0068] In addition, when forming the hole transport layer, the hole transport layer can be formed using sputtering, CVD, deposition, solution process coating, printing, etc., but is not limited thereto.

[0069] In addition, when forming the above photoactive layer, a coating or deposition process may be used, and for example, a perovskite layer may be formed by at least one method among spin coating, spray coating, slot die coating, blade coating, and deposition. For example, deposition may use at least one of chemical vapor deposition (CVD), atomic layer deposition (ALD), plasma-enhanced atomic layer deposition (PEALD), molecular beam epitaxy deposition, and physical vapor deposition, but is not limited thereto.

[0070] In addition, when forming the electron transport layer, a coating process may be used, and the coating process may use at least one method among spin coating, spray coating, slot die coating, and blade coating, but is not limited thereto.

[0071] In addition, when forming the above interface bonding layer, a hole transport layer can be formed using sputtering, CVD, deposition, solution process coating, printing, etc., but is not limited thereto.

[0072] In addition, when forming the second electrode, the electrode can be formed by a high-temperature process, for example, by a sputtering process under at least one process condition among 10 W to 200 W, a temperature of 25 ℃ to 100 ℃, and an oxygen flow rate of 0 sccm to 100 sccm.

[0073] At this time, the sputtering mentioned above may utilize ion-beam sputtering, reactive sputtering, ion-assisted deposition, HiTUS (High-target-utilization sputtering), HiPIMS (High-power impulse magnetron sputtering), gas-flow sputtering, plasma sputtering, etc., and the deposition may utilize CVD, thermal evaporation, plasma sputtering, electron beam evaporation, atomic layer deposition (ALD), etc. The coating may utilize a solution process and may refer to a process of forming a film using a liquid solvent, such as spin coating, spray coating, dip coating, inkjet printing, roll-to-roll printing, screen printing, etc.

[0075] The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto.

[0077] <Example 1> Characteristics of the interfacial bonding layer

[0078] As interfacial bonding compounds, NDI-C9-Ace and NDI-C11 were prepared and dissolved in chlorobenzene at a concentration of 0.9 mg / ml, and then stirred at room temperature for about 1 hour to sufficiently dissolve the NDI-C9-Ace and NDI-C11 substances.

[0079] Subsequently, each material was applied to the top of the perovskite thin film using a solution process and waited for 10 seconds to improve wettability, then spin-coated at 2000 RPM for 20 seconds, and annealed at 100°C for 5 minutes. Afterward, the surface and electric field uniformity of the thin film samples prepared in this way were checked using an AFM instrument.

[0080] In addition, when NDI derivative materials are absent and when NDI-C11 and NDI-C9-Ace materials are present in the perovskite thin film and C, respectively 60 A peeling test was conducted on a completed single device fabricated by deposition at the interface, in which the top thin film was removed using carbon tape.

[0081] The above results are shown in Figures 4 to 8.

[0082] First, Figure 4a shows the structural formula of an NDI derivative with different terminal functional groups used as an interfacial bonding compound, and Figure 4b shows the AFM measurement results of a thin film coated with an NDI derivative and heat-treated on a perovskite thin film, showing the roughness and electric field uniformity.

[0083] Based on this, it was confirmed that when an interfacial bonding layer was formed with NDI-C9-Ace having an acetyl group terminal, which is an oxygen-containing functional group, a roughness of 10 nm or less was formed, resulting in a uniform bonding surface and a uniform electric field. On the other hand, when an interfacial bonding layer was formed with an NDI-C11 derivative that does not contain an acetyl group at the terminal, although it was better than when no interfacial bonding layer was formed, the surface roughness was rougher compared to the NDI-C9-Ace interfacial bonding layer, and consequently, a uniform electric field could not be formed.

[0084] In other words, the presence of an acetyl group at the terminal effectively interacts with lead ions, which are electron-deficient cations of the perovskite, allowing the interfacial bonding compound to be deposited more effectively on the perovskite thin film. This results in a more uniform surface roughness and, consequently, the formation of a uniform electric field.

[0085] Also, Figures 5 and 6 show the NDI-C9-Ace interfacial bonding compound with a perovskite thin film and C when there is no interfacial bonding compound. 60 This shows the taping peel test process and results for a finished single device made by deposition on the interface.

[0086] Fig. 5a shows a single device completed without an interfacial junction compound (left) and the NDI-C9-Ace interfacial junction compound with a perovskite thin film and C 60 This is a single device (right) completed by deposition at the interface. Fig. 5b shows the results immediately after a peeling test was performed to remove the top thin film using carbon tape for each device. Fig. 5c is an enlarged view of the results after removing the top thin film using carbon tape for each device, and it can be observed that the peeling of the electrode and the bottom thin film occurred more strongly in the region where the electrode was located, resulting in surface characteristics different from the surrounding region. In other words, this means that the NDI-C9-Ace interfacial bonding compound has a benzene ring capable of bonding with the fullerene compound, enabling pi-pi stacking interactions between the fullerene and the benzene ring, and also significantly improved bonding at the fullerene interface through the acetyl group, an oxygen-containing functional group capable of bonding with the electron-deficient cation of the perovskite compound.

[0087] Referring to Figure 6, when comparing the Normal area, where no exfoliation test was performed, with the Delaminated area, where an exfoliation test was performed, it can be observed that the change in carbon (C) atoms is significant. In other words, since the decrease in carbon atoms is large when the NDI derivative is absent as an interfacial bonding material, but small when it is present, it can be confirmed that the NDI derivative, as an interfacial bonding material, strongly interacts with materials containing a large amount of carbon atoms. Additionally, since the overall ratio of Pb (B cation) and I, Br (X anion) is maintained at approximately 1:3, it can be inferred that the perovskite thin film was not significantly damaged. That is, the fact that a decrease in carbon atoms occurred without significantly damaging the perovskite thin film suggests that the carbon atoms decreased in the fullerene thin film formed on top of the perovskite thin film, and it can be inferred that NDI acts as an effective interfacial bonding compound between the perovskite thin film and the fullerene thin film.

[0088] In addition, compared to the case where an interfacial bonding layer was formed using NDI-C11, an NDI derivative having alkyl terminals, when an interfacial bonding layer was formed using NDI-C9-Ace, which has acetyl terminals as oxygen-containing functional groups, the reduction in carbon atoms decreased by more than 25% from 1.28 to 0.93, and the reduction in Pb (B cation), I, and Br (X anion) also decreased by more than 20%. In other words, it was confirmed that having acetyl groups, which are oxygen-containing functional groups, at the terminals allows the interfacial bonding compound to effectively interact with lead ions, which are electron-deficient cations of the perovskite, thereby enabling the interfacial bonding compound to be deposited more effectively on the perovskite thin film and to bond effectively with the fullerene thin film. This means that by having oxygen-containing functional group terminals on the arene core, the interfacial bonding compound has a structure capable of bonding with electron-deficient groups, thereby improving the interfacial bonding efficiency by at least 20%.

[0089] In addition, Figure 7 shows SEM images comparing the surface morphology of a perovskite thin film surface with and without the coating of an NDI-C9-Ace interfacial bonding compound after coating a perovskite layer on a glass substrate, and Figure 8 shows Atomic Force Microscopy (AFM, left) and Electron Force Microscopy (EFM, right) data images comparing the surface morphology and charge accumulation and dissipation morphology. Based on this, it can be confirmed that the crystal growth and morphology of the perovskite are controlled by the coating of the interfacial bonding compound, thereby controlling the perovskite photoactive layer into uniform and small crystals, and that the interfacial bonding layer formed by the NDI-C9-Ace interfacial bonding compound is uniformly formed, resulting in a smooth surface with reduced surface roughness.

[0090] In addition, Figure 9 shows Confocal Laser Scanning Microscopy (CLSM) data images of the surface roughness and morphology that change when fullerene is subsequently deposited depending on the presence or absence of interfacial bonding. Based on this, it can be confirmed that when an interfacial bonding compound is present, the naphthalene rings within the interfacial bonding compound and the benzene rings of the fullerene interact with each other through van der Waals interactions and pi-pi overlap, thereby forming a more uniform fullerene thin film.

[0092] <Example 2> Fabrication and Characterization of Perovskite Solar Cell Devices

[0093] The ITO substrate was cleaned using an ultrasonic cleaner with a glass cleaning solution (Hellmanex III), distilled water, and an isopropanol solution. Subsequently, a MeO-2PACz solution, used as a hole transport layer, was spin-coated onto the cleaned ITO substrate and heat-treated at 100°C for 10 minutes. After that, Cs used as a photoactive layer 0.05 FA 0.85 MA 0.10 Pb(I 0.9 Br 0.1A photoactive layer was formed by spin-coating the )3 solution and heat-treating at 100°C for 30 minutes. An interfacial bonding compound solution was spin-coated onto the heat-treated perovskite film and annealed at 100°C for 10 minutes. To deposit an electron transport layer on the interfacially treated film, the substrate was placed in a vacuum chamber and subjected to a high vacuum (10 -6 Fullerene (C) under Torr 60 ) 15nm and BCP (Bathocuproine) 5nm were thermally evaporated in sequence. To deposit the upper electrode layer, the substrate was placed in a vacuum chamber and subjected to a high vacuum (10 -6 Silver was thermally evaporated under Torr to form an upper electrode layer with a thickness of 100 nm.

[0094] The results of the characteristic evaluation of the manufactured solar cells are shown in Figures 10 to 14.

[0095] First, Figure 10 shows a graph of UV-Vis transmittance analysis according to the presence or absence of an interfacial bonding compound coating and an electron transport layer coating after coating a perovskite layer on a glass substrate. When an NDI derivative interfacial bonding compound is applied to a perovskite thin film, it can be observed that the absorbance increases in the near-ultraviolet region.

[0096] Figure 11 shows Ultraviolet Photoelectron Spectroscopy (UPS) analysis graphs depending on the presence or absence of an interfacial junction compound coating and an electron transport layer coating after coating a perovskite layer on a silicon substrate. Based on this, it can be seen that when the NDI-C9-Ace interfacial junction compound is coated between the perovskite layer and the fullerene layer, it helps to form a semiconductor thin film with a stronger N-type orientation.

[0097] Figure 12 is an X-ray Photoelectron Spectroscopy (XPS) analysis graph showing the presence or absence of an interfacial junction compound coating and an electron transport layer coating after coating a perovskite layer on a silicon substrate. It can be seen that when an NDI material is coated between the perovskite layer and the fullerene layer, the bonding between Pb 4f and I 3d becomes stronger and relatively more stable.

[0098] Figure 13 is a graph of time-resolved photoluminescence analysis according to the presence or absence of a perovskite-fullerene interface junction compound coating and an electron transport layer coating after coating a perovskite layer on a glass substrate. It can be inferred that when an NDI-C9-Ace interface junction compound is coated between the perovskite layer and the fullerene layer, the lifetime of photoelectrons is extended, allowing them to be effectively transferred to the next semiconductor thin film and external circuit.

[0099] Figure 14 is an impedance analysis graph based on the results of an impedance analysis performed after fabricating a perovskite solar cell device. When an AC voltage was applied at the operating voltage, the pattern of electron recombination with ions (or holes) was analyzed based on the mutual motion of ions and electrons. It was confirmed that when an NDI-C9-Ace interfacial junction compound was coated between the perovskite layer and the fullerene layer, the pattern of photoelectron recombination due to this interaction was relatively suppressed.

[0101] From the above results, it can be confirmed that the perovskite solar cell of the present invention can improve the protection of the perovskite photoactive layer and solar cell performance by forming an interfacial junction layer to facilitate the bonding of the perovskite photoactive layer and the fullerene compound electron transport layer. As such, according to the present invention, charge transfer is enhanced when bonded with the perovskite structure by including oxygen-containing functional groups at the ends of the interfacial junction compound to attract electrons. Furthermore, by controlling the growth and morphology of the perovskite crystals and regulating interfacial characteristics such as the movement of electrons and holes while forming the interfacial junction layer, cell performance can be improved. In addition, the stability of the perovskite solar cell device structure can be enhanced, thereby extending the lifespan of the device.

[0103] The foregoing description has broadly detailed the features and technical advantages of the present invention to better facilitate a better understanding of the claims of the invention to be described below. Those skilled in the art will understand that the present invention may be implemented in other specific forms without altering its technical concept or essential features. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims set forth below rather than by the detailed description above, and all modifications or variations derived from the claims and their equivalents should be interpreted as being included within the scope of the present invention.

Claims

Claim 1 A solar cell wherein a first electrode, a hole transport layer, a photoactive layer, an electron transport layer, and a second electrode are sequentially stacked, wherein the photoactive layer is formed by including a perovskite compound of the formula APbX3 or ASnX3 (wherein A is a metal cation, an organic cation, or a combination thereof, and X is selected from at least one of I, Br, and Cl), the electron transport layer is formed by including a fullerene compound, and further comprising, between the photoactive layer and the electron transport layer, an interfacial bonding layer formed of an interfacial bonding compound of the following formula 1, having a simple arene core capable of bonding with the fullerene compound and an oxygen-containing functional group terminal capable of bonding with A of the perovskite compound: [Formula 1] TR-Ar-RT (wherein in Formula 1, Ar is a polycyclic aromatic or heteroaromatic arene compound, R is an alkyl having 1 to 20 carbon atoms, and T is -OH, It is one or more selected from -C(=O), -COO, and -C(=O)CH3) Claim 2 A perovskite solar cell according to claim 1, characterized in that the chemical formula 1 is Ar a naphthalene diimide compound and T is COOCH3. Claim 3 A perovskite solar cell according to claim 1, wherein the interface junction layer has a surface roughness of up to 10 nm. Claim 4 A perovskite solar cell according to claim 1, characterized in that the interface junction layer is formed with a thickness of 2 to 10 nm. Claim 5 A perovskite solar cell according to claim 1, wherein the first electrode comprises at least one selected from the group consisting of a flexible transparent electrode substrate, indium tin oxide (ITO), fluorinated tin oxide (FTO), aluminum zinc oxide (AZO), boron-doped zinc oxide (BZO), niobium titanium oxide (NTO), zinc tin oxide (ZTO), and indium zinc tin oxide (IZTO), and the second electrode comprises at least one selected from the group consisting of silver (Ag), aluminum (Al), platinum (Pt), tungsten (W), copper (Cu), molybdenum (Mo), gold (Au), nickel (Ni), palladium (Pd), and carbon (C). Claim 6 A method for manufacturing a perovskite solar cell, comprising: a step of forming a first electrode and forming a hole transport layer on the first electrode; a step of forming a photoactive layer by coating and heat-treating a perovskite compound on the hole transport layer; a step of forming an interface junction layer formed of an interface junction compound on the photoactive layer; a step of forming an electron transport layer by depositing a fullerene compound on the interface junction layer; and a step of forming a second electrode on the electron transport layer; and a step of manufacturing a solar cell according to any one of claims 1 to 5.

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