Multifunctional ultrathin layer based on free radicals, preparation method of multifunctional ultrathin layer and application of multifunctional ultrathin layer in solar cell device

Abstract

The invention discloses a multifunctional ultrathin layer based on free radicals, a preparation method of the multifunctional ultrathin layer and application of the multifunctional ultrathin layer in a solar cell device, and belongs to the technical field of solar cells. Free radical molecules used by the ultrathin layer contain a plurality of oxygen free radicals and have a strong conjugation effect and a steric hindrance effect; phosphonic acid is used as an anchoring group and is connected with a high-reaction-activity carbon site in an N-containing condensed ring through a double bond, so that conjugation is effectively prolonged, the rigidity of a long-axis plane of molecules is increased, the arrangement orderliness and density of the molecules are enhanced, and the interface charge transmission efficiency is remarkably improved. The perovskite solar cell structure prepared by the invention comprises a transparent conductive electrode layer, an ultrathin layer, a perovskite active layer, a transmission layer and a back electrode layer. According to the ultrathin layer structure provided by the invention, the device structure of the perovskite cell is simplified, the preparation process is shortened, the processing technology is optimized, the material consumption is reduced, the preparation cost is reduced, large-area device preparation is easy, and a preferable direction is provided for industrialization of the solar cell.

Description

Technical Field

[0001] The present invention belongs to the technical field of solar cells, and in particular relates to a multifunctional ultra-thin layer based on free radicals, a preparation method thereof, and an application thereof in solar cell devices. Background Art

[0002] Perovskite solar cells use perovskite materials as the active layer and are a new type of solar cell technology. Perovskites have excellent photoelectric conversion properties and can convert sunlight into electrical energy. Perovskite solar cell devices are usually composed of multiple functional layers, including a transparent conductive electrode layer, a hole transport layer, an interface modification layer, a perovskite active layer, an electron transport layer, and a back electrode. Light enters the perovskite active layer through the transparent conductive layer. After photoelectric conversion, electrons are collected and transferred to the electron transport layer and finally exported through the back electrode. Perovskite solar cells have become a research hotspot in the photovoltaic field due to their high photoelectric conversion efficiency, low cost, and solution processing. However, their commercialization process still faces key challenges such as interface defects, insufficient carrier transport efficiency, and poor long-term stability.

[0003] In the perovskite cell structure, the design of the hole transport layer and the interface modification layer is crucial to the device performance. In the traditional device structure, the hole transport layer and the interface modification layer are usually designed as independent functional layers, respectively assuming the role of charge transport and interface modification, and usually need to be prepared layer by layer. Not only is the process complicated, but it is also easy to cause charge recombination and efficiency loss due to poor interface contact or energy level mismatch. For example, poly [bis (4-phenyl) (2,4,6-trimethylphenyl) amine (PTAA), PEDOT:PSS, nickel oxide (NiO x ) can effectively extract holes, but there are problems such as energy level mismatch and insufficient passivation of interface defects; and although self-assembled monolayers (SAMs) can improve interface contact, the SAM materials of traditional alkyl chain linking groups have limited charge transport capacity due to disordered molecular arrangement and low density, making it difficult to meet the needs of efficient charge extraction and interface passivation at the same time. In addition, interface defects between the perovskite layer and the transport layer can easily lead to carrier recombination, reducing the open circuit voltage and fill factor of the battery. In the prior art, Renshuo Photonics proposed a self-assembling functionalized auxiliary molecule to improve the uniformity of SAM film formation by destroying the symmetry of the micelles, but did not solve the problem of insufficient intrinsic transport performance of the molecule; Xiannan Optoelectronics modified the interface with additives containing sulfur / phosphorus groups, which can passivate defects, but requires the introduction of an additional interface layer, which increases the complexity of the process. In addition, Southern University of Science and Technology uses conjugated linking groups to enhance the transport delocalization ability of SAM, but its function is still concentrated in a single direction of transport or passivation, making it difficult to take into account the dual needs of efficient charge extraction and interface stability. Summary of the Invention

[0004] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of this application to avoid obscuring the purpose of this section, the abstract and the title of the invention, and such simplifications or omissions should not be used to limit the scope of the present invention.

[0005] The technical problem to be solved by the present invention is that in traditional device structures, the hole transport layer and the interface modification layer are usually designed as independent functional layers, respectively assuming the functions of charge transport and interface modification. They usually need to be prepared layer by layer, which is not only complicated in process, but also prone to charge recombination and efficiency loss due to poor interface contact or energy level mismatch.

[0006] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0007] Therefore, the purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for preparing a multifunctional ultra-thin layer based on free radicals. This method simplifies the device structure of perovskite solar cells, shortens the preparation process, optimizes the processing technology, facilitates the preparation of large-area devices, saves materials, and reduces preparation costs, providing new ideas for the industrial application of perovskite solar cells.

[0008] In order to solve the above technical problems, the present invention provides the following technical solutions, including:

[0009] The free radical molecule CPA is dissolved in an organic solvent to obtain a CPA solution with a mass concentration of 0.5 to 1.5 mg / ml; the CPA solution is directly coated on the surface of a transparent conductive electrode, and annealed and dried to obtain an ultra-thin layer;

[0010] The free radical molecule CPA is composed of an electron donor, a conjugated linking group, a phosphonic acid anchoring group and a methoxyphenyl group; and the organic solvent includes C1-C4 low-carbon alcohol.

[0011] As a preferred embodiment of the method for preparing the multifunctional ultra-thin layer based on free radicals according to the present invention, the electron donor is an electron-rich group, the conjugated connecting group is a carbon-carbon double bond conjugated structure, and the C1-C4 low-carbon alcohol includes methanol, ethanol, isopropanol, and ethyl acetate.

[0012] As a preferred embodiment of the method for preparing the multifunctional ultra-thin layer based on free radicals of the present invention, the structural formula of the free radical molecule CPA is as shown in Formula I:

[0013]

[0014] This molecule contains multiple oxygen free radicals, exhibiting strong conjugation and steric hindrance effects. Using phosphate as an anchoring group, the molecule is connected via double bonds to highly reactive carbon sites in N-containing fused rings (number of rings ≥ 3), effectively extending conjugation and increasing the planar rigidity of the molecule's long axis. Furthermore, functional groups are introduced into the short axis, resulting in a molecule with both good hole transport properties and strong interfacial passivation capabilities.

[0015] As a preferred embodiment of the method for preparing the free radical-based multifunctional ultra-thin layer of the present invention, the coating method includes slit coating, spraying, printing, blade coating, and spin coating.

[0016] As a preferred embodiment of the method for preparing the free radical-based multifunctional ultra-thin layer of the present invention, the annealing temperature is 80 to 120° C. and the annealing time is 25 to 35 minutes.

[0017] Another purpose of the present invention is to overcome the deficiencies in the prior art and provide a new type of multifunctional, dense ultra-thin layer structure based on free radical molecules. This layer structure has the dual functions of a charge transport layer and an interface modification layer. This multifunctional ultra-thin layer structure can reduce interfacial energy loss while improving carrier mobility and interface stability, thereby significantly improving the photoelectric conversion efficiency and long-term stability of perovskite cells. This layer has the following functions: 1. Transport layer function: achieving efficient hole / transport through conjugated groups and improving carrier mobility; 2. Interface modification function: passivating interface defects between perovskite and transport layer, enhancing interface bonding, and inhibiting charge recombination; inducing perovskite crystallization and improving the quality of perovskite films. This multifunctional ultra-thin layer structure can reduce interfacial energy loss while improving carrier mobility and interface stability, thereby significantly improving the photoelectric conversion efficiency and long-term stability of perovskite cells.

[0018] The third purpose of the present invention is to overcome the deficiencies in the prior art and provide an application of a multifunctional ultra-thin layer based on free radicals in large-area solar cells. The solar cells include perovskite solar cells and organic solar cells.

[0019] The fourth purpose is to simplify the device structure of perovskite solar cells, shorten the preparation process, save materials, reduce preparation costs, and facilitate large-scale preparation.

[0020] As a preferred embodiment of the large-area perovskite solar cell described in the present invention, the perovskite solar cell comprises a transparent conductive electrode layer, an ultra-thin layer, a perovskite active layer, a transport layer, and a back electrode layer; wherein the ultra-thin layer has a thickness of 0.1 to 2 nm. This method simplifies the device structure of the perovskite solar cell, shortens the preparation process, optimizes the processing technology, facilitates the preparation of large-area devices, saves materials, and reduces preparation costs, providing new ideas for the industrial application of perovskite solar cells.

[0021] As a preferred solution of the large-area perovskite solar cell of the present invention, wherein: the transparent conductive electrode layer comprises an ITO or FTO glass substrate, and the material of the transmission layer comprises C 60 、C 70 Or one or more of PCBM, the material of the back electrode layer is one of Cu, Ag, Au, Al, Cr, Ni or Ti.

[0022] As a preferred embodiment of the method for preparing a large-area perovskite solar cell according to the present invention, the method comprises: ultrasonically cleaning transparent conductive electrodes of different sizes with alkaline solution, deionized water, acetone, and isopropyl alcohol in sequence, and finally boiling and drying with nitrogen gas;

[0023] The cleaned transparent conductive electrode is first subjected to a 30-minute UV-ozone treatment or a 2-minute plasma treatment; then an ultra-thin layer is directly prepared on the transparent conductive electrode;

[0024] Prepare a perovskite active layer by dissolving ABX3 material in an organic solvent to prepare a perovskite precursor solution, and then apply the solution to obtain a perovskite active layer;

[0025] Prepare the transport layer at 2×10 -4 Pa, C60, BCP, and LiF were vacuum-deposited on the perovskite active layer in sequence;

[0026] Prepare the back electrode at 2×10 -4 Pa, evaporate silver or copper electrodes with a thickness of 200nm.

[0027] Beneficial effects of the present invention:

[0028] (1) The present invention introduces a multifunctional ultrathin layer structure that performs both hole transport and interface modification. In perovskite solar cell devices, it can replace the hole transport layer and the interface modification layer above it, while avoiding charge recombination and efficiency loss caused by poor interface contact or energy level mismatch.

[0029] (2) The ultra-thin layer structure provided by the present invention simplifies the device structure of the perovskite battery, shortens the preparation process, optimizes the processing technology, reduces the material usage, reduces the preparation cost, facilitates the preparation of large-area devices, and provides an optimal direction for the industrialization of solar cells.

[0030] (3) The perovskite active layer is directly prepared on the surface of the multifunctional ultra-thin layer. The perovskite material at the bottom will combine with the free radicals of the molecules in the ultra-thin layer, forming a one-dimensional / two-dimensional perovskite between the perovskite layer and the ultra-thin layer, inducing the bottom crystal to form an α-phase perovskite. At the same time, it grows vertically with the α-phase perovskite as the core, thus forming a dense longitudinal perovskite film. The one-dimensional / two-dimensional perovskite acts as a bridge between the interfaces, passivating interface defects, reducing interface energy loss, and promoting efficient carrier transmission, thereby improving the photoelectric conversion efficiency and stability of the perovskite solar cell.

[0031] (4) The ultra-thin layer provided by the present invention enhances the molecular arrangement orderliness and density within the film through the structure of the conjugated group, significantly improving the charge transfer efficiency at the interface and inside. At the same time, it forms a stable bond with the metal oxide transparent electrode through the phosphonic acid group, improving the interface contact. In addition, the molecule forms a dipole on the surface of the conductive electrode, regulates the surface work function, and promotes hole extraction. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. Among them:

[0033] Figure 1 Schematic diagram of the structure of the perovskite solar cell device prepared in Example 1 of the present invention.

[0034] Figure 2 Schematic diagram of the structure of the perovskite solar cell device prepared in Comparative Example 1 of the present invention.

[0035] Figure 3 This is a graph showing the photoelectric conversion efficiency of the perovskite solar cell prepared in Example 1 of the present invention.

[0036] Figure 4 This is a graph showing the photoelectric conversion efficiency of a conventional inverted perovskite solar cell prepared in Comparative Example 1 of the present invention.

[0037] Figure 5 This is an SEM electron microscope image of the ITO / ultra-thin layer / perovskite active layer in Example 2 provided by the present invention. DETAILED DESCRIPTION

[0038] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0039] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0040] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0041] Unless otherwise specified, the raw materials used in the present invention are all commercially available.

[0042] The synthetic reaction formula of CPA is as follows:

[0043]

[0044] Synthesis of Intermediate 2: Under argon, 1 (1.4 g) was weighed into a 50 mL Schlenk flask. 20 mL of chloroform and 1.2 mL of N,N-dimethylformamide were added sequentially. The temperature was cooled to 0°C, and 1.4 mL of phosphorus oxychloride was added. The mixture was stirred for 0.5 hours, then raised to 70°C and stirred for 2 hours. The mixture was cooled to room temperature, and the pH of the reaction mixture was adjusted to 7 with aqueous sodium hydroxide. The organic phase was separated and washed three times with distilled water and then with aqueous sodium chloride, then dried over anhydrous sodium sulfate. The organic phase was concentrated and separated on a silica gel column to obtain Intermediate 2 (1.2 g, 78% yield).

[0045] Elemental analysis structure (C20 H15 NO3): theoretical value C, 75.70; H, 4.76; N, 4.41; measured value C, 75.73; H, 4.77; N, 4.42.

[0046] ESI-MS analysis: theoretical value 317.3; found value 318.3 ([M+H]+).

[0047] Synthesis of intermediate 3: Under argon atmosphere, intermediate 2 (1.7 g) and zinc chloride (0.8 g) were weighed into a 50 mL Schlenk flask, and 20 mL of 1,4-dioxane and 0.6 mL of diethyl cyanomethylphosphonate were added to the flask in sequence. The temperature was then raised to 70°C and stirred for 0.5 hour. 1.2 mL of triethylamine was then added and the stirring reaction continued for 4 hours. After cooling to room temperature, the reaction solution was extracted with ethyl acetate. The organic phase was washed three times with aqueous sodium chloride solution and then dried over anhydrous sodium sulfate. The organic phase was concentrated and separated on a silica gel column to obtain intermediate 3 (1.3 g, yield: 67%).

[0048] Elemental analysis structure (C26 H25 N2 O5 P): theoretical value C, 65.54; H, 5.29; N, 5.88; measured value C, 65.57; H, 5.30; N, 5.89.

[0049] ESI-MS analysis: theoretical value 476.4; found value 477.4 ([M+H]+).

[0050] Synthesis of CPA: Under argon atmosphere, intermediate 3 (1.0 g) was weighed into a 50 mL Schlenk flask. 20 mL of dichloromethane and 3 mL of trimethylsilyl bromide were added to the flask in sequence. The mixture was stirred at room temperature for 24 hours and then dried. 5 mL of methanol was added and the mixture was stirred at room temperature for another 8 hours. The mixture was dried and ultrasonically washed with water three times to obtain compound CPA (0.4 g, yield: 46%).

[0051] Elemental analysis structure (C 22 H 17 N2O5P): Theoretical value, 62.86; H, 4.08; N, 6.66; Measured value C, 62.89; H, 4.09; N, 6.67.

[0052] ESI-MS analysis: theoretical value 420.3; experimental value 419.3 ([MH] + ).

[0053] The perovskite solar cell structure in the specific embodiment of the present invention is an inverted perovskite solar cell structure, including a transparent conductive electrode, an ultra-thin layer, a perovskite active layer, a transport layer and a back electrode layer; the perovskite solar cell structure in the comparative example includes a transparent conductive electrode, nickel oxide, Me-4PACz, a perovskite active layer, a transport layer and a back electrode layer.

[0054] To test the battery performance, in a specific embodiment of the present invention, the forward and reverse sweep current-voltage characteristics of the perovskite solar cell are measured, and the short-circuit current (Jsc), open-circuit voltage (Voc), photoelectric conversion efficiency (Eff), and fill factor (FF) of the perovskite solar cell are recorded. The test method is as follows:

[0055] The light source was turned on and the irradiance was allowed to reach a stable value after 10 min. The volt-ampere characteristic (IV) curve of the solar cell was recorded by a Keithley 2400 digital source meter. The light source was a xenon lamp (Osram XBO 450) simulating AM 1.5 sunlight with an intensity of 1000 W / m 2 , calibrated by silicon cells, test temperature 25℃.

[0056] Example 1

[0057] This embodiment provides a method for preparing a perovskite cell with a substrate size of 3 cm × 3 cm. Figure 1 , which are transparent conductive electrode layer, ultra-thin layer, perovskite active layer, transmission layer and back electrode layer in sequence.

[0058] Specifically:

[0059] A 3cm x 3cm transparent conductive electrode (ITO glass substrate) was ultrasonically cleaned in lye, deionized water, acetone, and isopropyl alcohol, sequentially for 30 minutes in each solvent. The cleaned electrode was then boiled and dried with nitrogen. The cleaned transparent conductive electrode was then treated with UV-ozone for 30 minutes.

[0060] Ultrathin layers were directly prepared on transparent conductive electrodes. CPA (the structural formula of Formula I) was dissolved in ethanol and gently shaken without stirring to form a clear, transparent solution of 1 mg / ml.

[0061]

[0062] 80 μl of the solution was dropped onto a transparent conductive electrode and spin-coated at 4000 rpm for 40 seconds. After the spin coating, the film was annealed at 100°C for 30 minutes to obtain an ultra-thin layer with a thickness of about 1 nm.

[0063] The perovskite active layer is directly prepared on the ultra-thin layer through a two-step method. Specifically, after adding 80μl of perovskite precursor solution, it is first rotated at 1000rpm for 20s, then the speed is changed to 6000rpm for 30s. In the remaining 10s, 200μl of chlorobenzene is quickly dropped in the middle of the rotating substrate. After the spin coating is completed, the film is annealed at 100°C for 30min. Subsequently, when the substrate is spun at 5000rpm for 20s, 100μl of CH3NH3I (MAI) solution (10mg / ml dissolved in isopropanol) is drop-coated, and the spin coating is continued for 10s and then stopped. After the spin coating is completed, the film is annealed at 70°C for 5min. The perovskite active layer is obtained.

[0064] Prepare the transport layer at 2×10 -4Pa, 30nm of C60, 10nm of BCP, and 1nm of LiF were vacuum-deposited on the perovskite active layer in sequence.

[0065] Prepare the back electrode at 2×10 -4 Pa, evaporate silver or copper electrodes with a thickness of 200nm.

[0066] Comparative Example 1

[0067] This comparative example provides a method for preparing a conventional inverted perovskite solar cell with a substrate size of 3 cm×3 cm, referring to Figure 2 The device structure consists of a transparent conductive electrode layer, a nickel oxide hole transport layer, a Me-4PACz interface modification layer, a perovskite active layer, an electron transport layer, and a back electrode layer. The preparation method differs from that of Example 1 in that the ultra-thin layers are modified to be the nickel oxide hole transport layer and the Me-4PACz interface modification layer.

[0068] The preparation method of the nickel oxide hole transport layer is as follows:

[0069] Nickel oxide was dissolved in analytical grade H2O and sonicated for 30 minutes to prepare a 10 mg / ml nickel oxide solution. The solution was then filtered through a 45 μm aqueous filter and 80 μl of the solution was dropped onto a 3 cm × 3 cm transparent conductive electrode substrate. The spin coating speed was set at 2000 rpm for 40 seconds and the solution was annealed at 150°C for 30 minutes to a thickness of approximately 30 nm.

[0070] The preparation method of the interface modification layer Me-4PACz is as follows:

[0071] Me-4PACz was dissolved in isopropanol at a concentration of 1 mg / ml, stirred and dissolved after shaking, and filtered using a 45 μm filter head. 80 μl of the solution was dropped on the nickel oxide layer. The spin coating speed was set to 6000 rpm for 40 seconds, and the layer was annealed at 100°C for 10 minutes to a thickness of about 5 nm.

[0072] The remaining preparation processes were the same as those in Example 1 to prepare a traditional inverted perovskite solar cell.

[0073] The performance of the solar cell prepared in the comparative example was tested, and the comparison results with those in Example 1 are shown in Table 1.

[0074] Table 1

[0075]

[0076] Combined with Table 1 and Figure 3 、 Figure 4It can be seen that compared with the comparative example, after using the ultra-thin layer structure, the perovskite solar cell has significantly enhanced device performance under the premise of simplifying the device structure and reducing the manufacturing process. The fill factor and open circuit voltage of the battery in Example 1 are significantly improved. The fill factor of the device based on Me-4PACz is 84.16%, while the fill factor based on the present invention can even reach 85.70%; the open circuit voltage of the device based on the present invention can reach a maximum of 1.195V, while the open circuit voltage of the device based on Me-4PACz can only reach 1.140V; in addition, the photoelectric conversion efficiency of the device based on the present invention is 26.42%, which is also significantly higher than the 23.19% of the comparative example device. The ultra-thin layer structure prepared by the present invention has the dual functions of charge transport layer and interface modification layer: on the one hand, it realizes efficient hole / transport through conjugated groups, improves carrier mobility and realizes the transport layer function of traditional batteries; on the other hand, the ultra-thin layer passivates the interface defects between the perovskite and the transport layer, enhances the interface bonding force, and inhibits charge recombination; it induces perovskite crystallization, improves the quality of the perovskite film, and realizes the interface modification function.

[0077] Example 2

[0078] The difference between this embodiment and embodiment 1 is that the concentration of the CPA solution for preparing the ultra-thin layer is adjusted to 0.5 mg / ml, and the rest of the preparation process is the same as that of embodiment 1 to prepare a perovskite battery.

[0079] Example 3

[0080] The difference between this embodiment and embodiment 1 is that the concentration of the CPA solution for preparing the ultra-thin layer is adjusted to 1.5 mg / ml, and the rest of the preparation process is the same as that of embodiment 1 to prepare a perovskite battery.

[0081] The performance of the perovskite cells prepared in Examples 2 and 3 was tested, and the comparison results with those in Example 1 are shown in Table 2.

[0082] Table 2 Effect of free radical molecule solution concentration on perovskite cell performance

[0083]

[0084] As shown in the table above, adjusting the CPA solution concentration used to prepare the ultrathin layer significantly affects the performance of the perovskite cell. This is because excessively high or low solution concentrations can affect the uniformity, coverage, and crystallization quality of the ultrathin layer. Uneven ultrathin layers can impair the nucleation and growth of the subsequent perovskite active layer. The uniformity of the perovskite active layer is crucial to the photovoltaic performance of the cell. Uneven ultrathin layers can lead to defects in the perovskite layer, such as holes or discontinuous regions, which can reduce the cell's short-circuit current density (Jsc) and fill factor (FF). High-concentration solutions can also cause crystallization defects during the spin coating process due to rapid solvent evaporation, disrupting the crystal structure of the ultrathin layer and affecting its electron transport properties. Crystallization defects can reduce the charge mobility of the ultrathin layer, increasing the resistance to charge transfer within the layer and thus reducing the overall performance of the cell. Ultrathin layers formed from low-concentration solutions may have poor crystallinity and fail to provide effective charge transfer pathways, resulting in reduced charge transfer efficiency between the ultrathin layer and the perovskite active layer. Furthermore, ultra-thin layers with poor crystallinity may not effectively block charge recombination between the electrode and the perovskite layer, further reducing battery efficiency. However, compared to the comparative examples, the battery performance is significantly improved. Based on the results in the table above, the optimal technical effect is achieved when the CPA solution concentration for preparing the ultra-thin layer in the present invention is 1 mg / ml. However, this does not rule out the possibility of achieving even better device efficiency through further experiments at concentrations near this concentration.

[0085] Example 4

[0086] This embodiment provides the application of the ultra-thin layer in a perovskite cell with a substrate size of 5cm×5cm, 10cm×10cm, 20cm×20cm, 30cm×30cm, or other larger sizes (the size can be larger and is not limited to these sizes). The device structure comprises: a transparent conductive electrode layer, an ultra-thin layer, a perovskite active layer, a transmission layer, and a back electrode layer. The perovskite cell preparation method includes the following steps:

[0087] The cleaning and pretreatment methods of the transparent conductive electrode are the same as those described in Example 1.

[0088] The preparation method of the ultra-thin layer is as follows:

[0089] CPA is dissolved in ethanol and gently shaken without stirring to form a clear, transparent solution at a concentration of 1 mg / ml. This solution is then dropped onto a pretreated transparent conductive electrode and coated using a one-step doctor blade process. A specific amount of solution (depending on substrate size) is applied, followed by doctor blade coating at a specific speed and slit width. The film is then rapidly dried with nitrogen to remove the solvent, and annealed at 100°C for 30 minutes. The resulting ultrathin film is approximately 1 nm thick.

[0090] Directly fabricate the perovskite active layer on an ultra-thin layer:

[0091] The multifunctional ultra-thin layer is applied via a one-step doctor blade coating process. A specific amount of perovskite precursor solution (depending on substrate size) is applied, followed by a doctor blade coating at a specific speed and slit width to form a film. This is followed by a rapid nitrogen blow-off to remove the solvent, followed by annealing at 100°C for 30 minutes. This results in a perovskite active layer with a thickness of approximately 500-700nm.

[0092] Prepare the transport layer at 2×10 -4 Pa, 30nm of C60, 10nm of BCP, and 1nm of LiF were vacuum-deposited on the perovskite active layer in sequence.

[0093] Prepare the back electrode at 2×10 -4 Pa, evaporate silver or copper electrodes with a thickness of 200nm.

[0094] This embodiment provides the application of the ultra-thin layer structure in the preparation of large-area perovskite solar cells. Test results show that the efficiency of large-area cells has reached the domestic advanced level. Figure 5 Electron microscopy images show a tight bond between the ITO and perovskite layers, with the perovskite exhibiting excellent crystallinity. The cell dimensions are not limited to those mentioned in the examples; these dimensions are used to demonstrate the success of the ultra-thin layer structure in large-area cell fabrication. This ultra-thin layer structure can be applied to sizes of 60 cm x 120 cm or even larger, making it fully applicable to the industrial production of perovskite solar cells.

[0095] Table 3 Device performance of large-area perovskite cells of different sizes

[0096] Size (cm) Conversion efficiency PCE (%) Open circuit voltage Voc(V) Number of sub-batteries 5*5 23.18 5.52 5 10*10 21.04 12.06 11

[0097] The preparation examples in this embodiment are only to illustrate the excellent applicability of ultra-thin layer structures in the preparation of large-area batteries. In the preparation of perovskite solar cells, there are significant differences in the effects of spin coating and scraping coating on material utilization. Specifically: spin coating is a common method for preparing efficient devices in the laboratory, but its material utilization is extremely low, usually only about 1%. This is because most of the precursor solution is thrown off the substrate during high-speed rotation during the spin coating process, resulting in a large amount of waste. Its high waste characteristics make it difficult to apply to large-scale production. Scraping coating is a process that is more suitable for large-area preparation. Its material utilization can be greatly improved to more than 80%. When continuously coated, material utilization will be more efficient and more suitable for the industrial production of perovskite solar cells. Scraping coating is more suitable for industrial mass production because of its high material utilization and continuous coating, while spin coating is only suitable for laboratory research. Scraping coating reduces the use of organic solvents and is more in line with green manufacturing needs.

[0098] In summary, the technical problem to be solved by the present invention is that in traditional device structures, the hole transport layer and the interface modification layer are usually designed as independent functional layers, respectively assuming the functions of charge transport and interface modification, and usually need to be prepared layer by layer separately. Not only is the process complicated, but it is also easy to cause charge recombination and efficiency loss due to poor interface contact or energy level mismatch.

[0099] The present invention provides a novel, multifunctional, dense, ultrathin layer structure based on free radical molecules. This layer structure has the dual functions of a charge transport layer and an interface modification layer. This layer has the following functions: 1. Transport layer function: achieving efficient hole / carrier transport through conjugated groups, improving carrier mobility; 2. Interface modification function: passivating interface defects between the perovskite and the transport layer, enhancing interfacial bonding, and inhibiting charge recombination; inducing perovskite crystallization, and improving the quality of the perovskite film. This ultrathin layer structure, which simultaneously functions as a charge transport layer and an interface modification layer, simplifies the device structure of perovskite solar cells, shortens the preparation process, optimizes the processing technology, facilitates the preparation of large-area devices, saves materials, reduces preparation costs, and promotes the industrialization of perovskite solar cells. Furthermore, the ultrathin layer enhances the molecular arrangement order and film density through the structure of conjugated groups, significantly improving the charge transport efficiency at the interface and within the film. At the same time, the phosphonic acid groups form a stable bond with the metal oxide transparent electrode, improving interfacial contact. Furthermore, the molecules form dipoles on the surface of the conductive electrode, regulating the surface work function and promoting hole extraction.

[0100] Furthermore, a perovskite active layer is prepared on the surface of the ultrathin layer. The underlying perovskite material combines with free radical groups on the ultrathin layer surface to form a one-dimensional / two-dimensional perovskite, inducing the formation of α-phase perovskite in the bottom crystals. This α-phase perovskite simultaneously grows vertically with the core, thus forming a dense vertical perovskite film. Simultaneously, the one-dimensional / two-dimensional perovskite acts as a bridge between interfaces, passivating interface defects and promoting efficient carrier transport, thereby improving the photoelectric conversion efficiency and stability of the perovskite solar cell. A method for preparing a perovskite solar cell is also provided. This multifunctional ultrathin layer structure reduces interfacial energy loss while improving carrier mobility and interface stability, significantly enhancing the photoelectric conversion efficiency and long-term stability of the perovskite cell. It also simplifies the device structure of the perovskite solar cell, shortens the preparation process, optimizes the processing technology, facilitates large-area device preparation, saves materials, and reduces preparation costs, providing new ideas for the industrial application of perovskite solar cells.

[0101] The perovskite solar cell structure prepared by the present invention includes a transparent conductive electrode layer, an ultra-thin layer, a perovskite active layer, a transport layer, and a back electrode layer. The free radical molecules used in the ultra-thin layer contain multiple oxygen free radicals, which have a strong conjugation effect and a steric hindrance effect; with phosphonic acid as the anchoring group, it is connected to the highly reactive carbon site in the N-containing fused ring through a double bond, effectively extending the conjugation, increasing the rigidity of the molecular long axis plane, enhancing the orderliness and density of the molecular arrangement, and significantly improving the interface charge transfer efficiency; and introducing functional groups in the short axis to obtain a device with both good hole transport performance and strong interface passivation ability. The ultra-thin layer structure provided by the present invention simplifies the device structure of the perovskite battery, shortens the preparation process, optimizes the processing technology, reduces the material consumption, reduces the preparation cost, and is easy to prepare large-area devices, providing a preferred direction for the industrialization of solar cells.

[0102] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a multifunctional ultra-thin layer based on free radicals, characterized in that: The method comprises dissolving the free radical molecule CPA in an organic solvent to obtain a CPA solution with a mass concentration of 0.5 to 1.5 mg / ml; directly coating the CPA solution on the surface of a transparent conductive electrode, and annealing and drying to obtain an ultra-thin layer; The free radical molecule CPA is composed of an electron donor, a conjugated linking group, a phosphonic acid anchoring group and a methoxyphenyl group; and the organic solvent includes C1-C4 low-carbon alcohol.

2. The method for preparing a multifunctional ultra-thin layer based on free radicals according to claim 1, wherein: The electron donor is an electron-rich group; the conjugated connecting group is a carbon-carbon double bond conjugated structure; and the C1-C4 low-carbon alcohol includes methanol, ethanol, isopropanol, and ethyl acetate.

3. The method for preparing a multifunctional ultra-thin layer based on free radicals according to claim 1 or 2, characterized in that: The structural formula of the free radical molecule CPA is shown in Formula I:

4. The method for preparing a multifunctional ultra-thin layer based on free radicals according to claim 1, wherein: The coating methods include slit coating, spray coating, printing, blade coating, and spin coating.

5. The method for preparing a multifunctional ultra-thin layer based on free radicals according to claim 1, wherein: The annealing process has an annealing temperature of 80 to 120° C. and an annealing time of 25 to 35 minutes.

6. A multifunctional ultra-thin layer based on free radicals prepared by the preparation method according to any one of claims 1 to 2, 4 to 5.

7. A use of the free radical-based multifunctional ultra-thin layer in large-area solar cells according to claim 6, characterized in that: The solar cells include perovskite solar cells and organic solar cells.

8. A large-area perovskite solar cell, characterized in that: It comprises a transparent conductive electrode layer, the ultra-thin layer according to claim 6, a perovskite active layer, a transmission layer, and a back electrode layer; wherein the ultra-thin layer has a thickness of 0.1 to 2 nm.

9. The large-area perovskite solar cell according to claim 8, wherein: The transparent conductive electrode layer includes an ITO or FTO glass substrate, and the material of the transmission layer includes C 60 、C 70 Or one or more of PCBM, the material of the back electrode layer is one of Cu, Ag, Au, Al, Cr, Ni or Ti.

10. The method for preparing a large-area perovskite solar cell according to claim 8 or 9, characterized in that: include, Transparent conductive electrodes of different sizes were ultrasonically cleaned with alkali solution, deionized water, acetone, and isopropyl alcohol in sequence, and finally boiled and dried with nitrogen gas; The cleaned transparent conductive electrode is first subjected to a 30-minute UV-ozone treatment or a 2-minute plasma treatment; then an ultra-thin layer is directly prepared on the transparent conductive electrode; Prepare a perovskite active layer by dissolving ABX3 material in an organic solvent to prepare a perovskite precursor solution, and then apply the solution to obtain a perovskite active layer; Prepare the transport layer in 2×10 -4 Pa, C60, BCP, and LiF were vacuum-deposited on the perovskite active layer in sequence; Prepare the back electrode at 2×10 -4 Pa, evaporate silver or copper electrodes with a thickness of 200nm.

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