Perovskite solar cell, preparation method thereof and photovoltaic module

Abstract

The invention discloses a perovskite solar cell and a preparation method thereof, and a photovoltaic module, the perovskite solar cell comprises a perovskite layer, the perovskite layer is doped with a fluoropyridine derivative, and fluorine ions of the fluoropyridine derivative, a perovskite layer bulk phase and Pb < 2 + > on a perovskite layer interface form a Pb-F bond. According to the invention, the ionic migration of the bulk phase of the perovskite layer can be effectively reduced, so that the defects of the perovskite layer are reduced, and the photoelectric conversion efficiency and stability of the solar cell are effectively improved.

Description

Technical Field

[0001] The present application relates to the technical field of solar cells, and in particular to a perovskite solar cell and a preparation method thereof, and a photovoltaic module. Background Art

[0002] Perovskite solar cells are photovoltaic devices that use perovskite materials as their core light-absorbing layer. These cells offer excellent potential for photoelectric conversion efficiency and a relatively simple fabrication process, demonstrating enormous commercial application prospects. However, inherent defects in the perovskite layer severely restrict further improvements in photoelectric conversion efficiency and significantly impact the long-term operational stability of the device. Summary of the Invention

[0003] In order to reduce the inherent defects of the perovskite layer and improve the photoelectric conversion efficiency of the cell, the embodiments of the present application provide a perovskite solar cell and a preparation method thereof, and a photovoltaic module.

[0004] In a first aspect, an embodiment of the present application provides a perovskite solar cell.

[0005] A perovskite solar cell comprises a perovskite layer, wherein the perovskite layer is doped with a fluoropyridine derivative, wherein the fluorine ions of the fluoropyridine derivative interact with the bulk of the perovskite layer and the Pb at the interface of the perovskite layer. 2+ Formation of Pb-F bonds.

[0006] As an optional embodiment, in the embodiment of the present application, the N atom of the pyridine group in the fluoropyridine derivative and the Pb in the perovskite layer 2+ Form a coordination bond.

[0007] As an optional embodiment, in the examples of the present application, the fluoropyridine derivative includes one or more combinations of fluoropyridinecarboxylic acid derivatives, 2-bromo-3-fluoropyridine, 5-bromo-3-fluoropyridine or 2-chloro-3-bromo-5-fluoropyridine.

[0008] As an optional embodiment, in the examples of the present application, the fluoropyridinecarboxylic acid derivatives include 4-fluoropyridine-3-carboxylic acid and / or 3-fluoropyridine-2-carboxylic acid ethyl ester;

[0009] and / or,

[0010] The carboxylic acid group of the fluoropyridinecarboxylic acid derivative is bound to the Cs + and Pb 2+ Form a coordination bond.

[0011] As an optional implementation manner, in an embodiment of the present application, the mass proportion of the fluoropyridine derivative in the perovskite layer is 0.5% to 5.5%.

[0012] As an optional implementation, in an embodiment of the present application, the thickness of the perovskite layer is 450 nm to 500 nm, and the band gap of the perovskite layer is 1.63 eV to 1.70 eV.

[0013] As an optional embodiment, in an embodiment of the present application, the perovskite solar cell further includes a bottom cell, the surface of which is sequentially stacked with a composite layer, a first transport layer, the perovskite layer, a second transport layer, a transparent conductive layer, and a first electrode, wherein one of the first transport layer and the second transport layer is a hole transport layer, and the other is an electron transport layer;

[0014] or;

[0015] The perovskite solar cell also includes a transparent conductive substrate, and a first transport layer, the perovskite layer, a second transport layer and a first electrode are sequentially arranged on the surface of the transparent conductive substrate. One of the first transport layer and the second transport layer is a hole transport layer, and the other is an electron transport layer.

[0016] In a second aspect, an embodiment of the present application provides a method for preparing a perovskite solar cell.

[0017] A method for preparing a perovskite solar cell, as described in the first aspect, comprises the following steps:

[0018] Pretreatment of the lead halide skeleton layer: providing the lead halide skeleton layer, coating the surface of the lead halide skeleton layer with a solution containing the fluoropyridine derivative, and performing a first annealing treatment;

[0019] The cationic solution is coated on the surface of the lead halide skeleton layer, and a second annealing treatment is performed to obtain the perovskite layer.

[0020] As an optional implementation manner, in an embodiment of the present application, the first annealing treatment includes annealing at 50° C. to 100° C. for 1 minute to 20 minutes, and then annealing at 100° C. to 160° C. for 10 minutes to 30 minutes;

[0021] and / or

[0022] The second annealing treatment includes annealing at 100° C. to 150° C. for 15 min to 30 min;

[0023] and / or,

[0024] In the fluoropyridine derivative solution, the concentration of the fluoropyridine derivative is 0.01 mmol / mL to 0.08 mmol / mL.

[0025] As an optional embodiment, in the examples of the present application, the solvent in the fluoropyridine derivative solution includes one or a combination of γ-valerolactone, anhydrous ethanol, dimethyl sulfoxide, N,N-dimethylformamide or isopropanol.

[0026] As an optional embodiment, in an embodiment of the present application, the lead halide skeleton layer includes PbI2 and CsBr;

[0027] In the fluoropyridine derivative solution, the solvent is composed of anhydrous ethanol and γ-valerolactone in a volume ratio of 3:7, or is composed of dimethyl sulfoxide and γ-valerolactone in a volume ratio of 3:7.

[0028] In a third aspect, an embodiment of the present application provides a photovoltaic module.

[0029] A photovoltaic module comprises the perovskite solar cell as described in the first aspect or the perovskite solar cell prepared by the preparation method as described in the second aspect.

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] The present invention incorporates fluoropyridine derivatives into the perovskite layer of the perovskite solar cell. The fluoropyridine derivatives can be directly incorporated into the bulk phase from the surface through the gaps in the lead halide skeleton layer during the preparation process of the perovskite layer, releasing F - And with Pb in the lead halide skeleton layer 2+ Combined to form Pb-F bond, F - Precisely occupying iodine vacancies allows for effective doping, thereby reducing the likelihood of iodine vacancies being effectively occupied by large-sized cationic groups. This can reduce non-radiative recombination and effectively improve the structural stability of the perovskite layer. - The introduction of fluorinated pyridines causes the perovskite lattice to shrink, increasing the density of the perovskite layer and inhibiting ion diffusion and phase separation. Furthermore, the fluorinated layer formed on the surface of the perovskite layer by the fluorinated pyridine derivatives blocks moisture and oxygen erosion, slowing the decomposition of the perovskite and improving its environmental tolerance. In summary, this application effectively improves the photovoltaic conversion efficiency and stability of solar cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0033] Figure 1 Schematic diagram of the structure of the perovskite solar cell disclosed in the embodiment of the present application;

[0034] Figure 2 1 is a comparison chart of the stability test results of Example 1, Example 2, Example 3 and Comparative Example 1 of the present application;

[0035] Figure 3 PL (photoluminescence) test results comparison chart of Example 1, Example 2, Example 3 and Comparative Example 1 of the present application;

[0036] Figure 4 This is a comparison chart of the XRD (X-ray diffraction) test results of Example 1, Example 2, Example 3 and Comparative Example 1 of the present application;

[0037] Figure 5 This is the XPS (X-ray photoelectron spectroscopy) test result diagram of Example 1 of the present application.

[0038] Icons: 1. Perovskite layer; 11. Passivation layer; 2. Bottom cell; 21. Second electrode; 3. Composite layer; 4. Hole transport layer; 41. Hole modification layer; 5. Electron transport layer; 51. Buffer layer; 6. Transparent conductive layer; 61. Anti-reflection layer; 7. First electrode. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0040] In this application, terms such as "upper," "lower," "left," "right," "front," "back," "top," "bottom," "inner," "outer," "center," "vertical," "horizontal," "transverse," and "longitudinal" indicate positions or locations based on the positions or locations shown in the accompanying drawings. These terms are primarily intended to better describe this application and its embodiments and are not intended to limit the devices, elements, or components indicated to having a specific orientation, or to being constructed or operated in a specific orientation.

[0041] Furthermore, some of the above terms may be used to express other meanings besides indicating a position or location. For example, the term "on" may also be used to indicate a dependency or connection in certain circumstances. Those skilled in the art will understand the specific meanings of these terms in this application based on the specific circumstances.

[0042] Furthermore, the terms "installed," "disposed," "provided with," "connected," and "connected" should be interpreted broadly. For example, they can refer to fixed connections, removable connections, or integral structures; mechanical connections or electrical connections; direct connections, indirect connections through an intermediary, or internal communication between two devices, elements, or components. Those skilled in the art will understand the specific meanings of these terms in this application based on the specific circumstances.

[0043] Furthermore, the terms "first," "second," etc., are primarily used to distinguish between different devices, elements, or components (which may or may not be of the same type and configuration), and are not intended to indicate or imply the relative importance or quantity of the devices, elements, or components indicated. Unless otherwise specified, "plurality" means two or more.

[0044] During the fabrication of perovskite solar cells, iodine vacancy defects are easily formed in the perovskite layer. These defects can trigger non-radiative recombination and reduce the stability of the cell. Fluorine doping of the perovskite layer is expected to improve the photovoltaic conversion efficiency and stability of solar cells. Fluorine doping is primarily achieved through two methods: one is cation doping, such as incorporating fluoride salts such as CsF and FAF into the perovskite precursor solution. However, fluoride ions are easily encapsulated by large cations (such as Cs+ and FA+) in the system, making it difficult for fluoride ions to effectively migrate and occupy iodine vacancies in the perovskite lattice, resulting in low doping efficiency. The other is post-treatment passivation of the perovskite layer after the reaction, such as spin-coating a KPF6 (potassium hexafluorophosphate) solution onto the perovskite layer. However, this treatment method only introduces fluoride ions to the surface region of the perovskite layer. Limited by the treatment depth, fluoride ions cannot effectively penetrate into the bulk of the perovskite layer, thus having limited effect on inhibiting ion migration within the perovskite layer and failing to fully address the bulk iodine vacancy defects and the resulting instability.

[0045] In order to better reduce the ion migration in the bulk phase of the perovskite layer and reduce the defects of the perovskite layer, the present application provides a perovskite solar cell and a preparation method thereof, and a photovoltaic module.

[0046] The technical solution of the present application will be further described below with reference to the embodiments and drawings.

[0047] In a first aspect, an embodiment of the present application provides a perovskite solar cell.

[0048] A perovskite solar cell, referring to Figure 1 , including a perovskite layer 1, wherein the perovskite layer 1 is doped with a fluoropyridine derivative, the fluorine ions of the fluoropyridine derivative are in the bulk phase of the perovskite layer 1, and the Pb at the interface of the perovskite layer 1 2+ Formation of Pb-F bonds.

[0049] The present invention incorporates a fluoropyridine derivative into the perovskite layer 1. The fluoropyridine derivative can be directly incorporated into the bulk phase from the surface through the gaps in the lead halide skeleton layer during the preparation process of the perovskite layer 1, releasing F - And with Pb in the lead halide skeleton layer 2+ Combined to form Pb-F bond, F - Precisely occupying iodine vacancies to achieve effective doping, effectively reducing the possibility of iodine vacancies being difficult to effectively occupy due to being wrapped by large-sized cationic groups. This can reduce non-radiative recombination and effectively improve the structural stability of the perovskite layer 1. At the same time, the above-mentioned F - The introduction of fluorinated pyridines causes the perovskite lattice to shrink, increasing the density of the perovskite layer 1 and inhibiting ion diffusion and phase separation. Furthermore, the fluorinated layer formed on the surface of the perovskite layer 1 by the fluorinated pyridine derivatives blocks moisture and oxygen corrosion, slowing the decomposition of the perovskite and improving its environmental tolerance. In summary, this application effectively improves the photovoltaic conversion efficiency and stability of solar cells.

[0050] In some embodiments, the nitrogen atom of the pyridine group in the fluoropyridine derivative is bound to the Pb 2+ Form a coordination bond.

[0051] The pyridine group has a lone pair of electrons in the nitrogen atom, which interacts with the uncoordinated Pb in the perovskite layer 1. 2+ Coordinated bonding forms a [Pb-N (Pyridine)] coordination bond, thereby further enhancing the passivation effect of the perovskite layer 1. Through this coordination effect, the Pb 2+ The possibility of migration can be reduced, the number of non-radiative recombination centers can be reduced, and the photoelectric conversion efficiency and stability of solar cells can be improved.

[0052] In some embodiments, the fluoropyridine derivative includes one or more combinations of fluoropyridinecarboxylic acid derivatives, 2-bromo-3-fluoropyridine, 5-bromo-3-fluoropyridine, or 2-chloro-3-bromo-5-fluoropyridine.

[0053] These different fluoropyridine derivatives can be incorporated into the bulk phase from the surface of the perovskite layer 1 and provide the F required for binding to the perovskite. - The present application provides a variety of selectable dopants, which can select appropriate fluoropyridine derivatives according to different process conditions and performance requirements, thereby improving the flexibility and adaptability of fluorine doping treatment and helping to achieve better solar cell performance.

[0054] In some embodiments, the fluoropyridinecarboxylic acid derivatives include 4-fluoropyridine-3-carboxylic acid and / or ethyl 3-fluoropyridine-2-carboxylate;

[0055] and / or, the carboxylic acid group of the fluoropyridinecarboxylic acid derivative is bound to the Cs + and Pb 2+Form a coordination bond.

[0056] The carboxylic acid group is reacted with Cs + and Pb 2+ It combines with bidentate coordination to form a complex, which can reduce Cs + During the preparation of the perovskite layer 1 without the addition of fluoropyridinecarboxylic acid derivatives, Cs + It is easy to escape from the lattice site, causing the lead halide skeleton layer to lose support and triggering the local collapse of the lead halide skeleton layer. Through this coordination effect, the ion migration and the collapse of the lead halide skeleton layer can be effectively inhibited, thereby improving the overall efficiency and stability of the device. Both 4-fluoropyridine-3-carboxylic acid and 3-fluoropyridine-2-carboxylic acid ethyl ester can fully utilize the activity of the carboxylic acid group to achieve Cs + Effective inhibition of diffusion.

[0057] In some embodiments, the mass percentage of the fluoropyridine derivative in the perovskite layer 1 is 0.5% to 5.5%.

[0058] By controlling the content of the fluoropyridine derivative, the perovskite layer 1 can achieve better passivation and good crystal quality, optimizing solar cell performance. When the fluoropyridine derivative content is too low, the passivation effect is poor; while an excessively high content can affect perovskite nucleation and lead to poor perovskite crystal quality. For example, the weight percentage of the fluoropyridine derivative in the perovskite layer 1 can be 0.5%, 1.5%, 2.5%, 3.5%, 4.5%, or 5.5%.

[0059] In some embodiments, the thickness of the perovskite layer 1 is 450 nm to 500 nm, and the band gap of the perovskite layer 1 is 1.63 eV to 1.70 eV.

[0060] This optimized thickness and bandgap range is well-suited for a variety of photovoltaic devices requiring specific perovskite layer 1 parameters (such as perovskite subcells in tandem cells), enhancing the compatibility and applicability of the solar cell in complex photovoltaic architectures. For example, the thickness of the perovskite layer 1 can be 450nm, 460nm, 480nm, or 500nm.

[0061] In some embodiments, the perovskite solar cell further comprises a bottom cell 2, on the surface of which a composite layer 3, a first transport layer, a perovskite layer 1, a second transport layer, a transparent conductive layer 6 and a first electrode 7 are sequentially stacked, one of the first transport layer and the second transport layer is a hole transport layer 4, and the other is an electron transport layer 5;

[0062] or;

[0063] The perovskite solar cell also includes a transparent conductive substrate, on the surface of which a first transport layer, a perovskite layer 1, a second transport layer and a first electrode 7 are sequentially arranged. One of the first transport layer and the second transport layer is a hole transport layer 4, and the other is an electron transport layer 5.

[0064] The bottom cell 2 can be a textured silicon bottom cell, such as a heterojunction bottom cell. The pyramid texture structure of the textured silicon bottom cell can effectively reduce reflection loss and enhance light absorption efficiency. Exemplarily, the pyramid texture height is 1μm to 3μm. The textured silicon bottom cell has a graphic second electrode 21 arranged corresponding to the first electrode 7. The first electrode 7 and the second electrode 21 are also used to collect photogenerated carriers to ensure that the charge can be smoothly discharged from the inside of the solar cell, thereby promoting efficient operation of the solar cell. The first electrode 7 and the second electrode 21 are both made of metal materials with good conductive properties, such as silver, copper or aluminum, with a thickness of 150nm to 300nm. The first electrode 7 and the second electrode 21 can both be made by evaporation, and the evaporation rate is

[0065] The hole transport layer 4 is required to have a high hole mobility and can be made of inorganic materials such as nickel oxide (NiO x ), or organic materials, such as Spiro-TTB. The thickness of the hole transport layer 4 is 20 nm to 30 nm.

[0066] A hole modification layer 41 is also provided on the side of the hole transport layer 4 near the perovskite layer 1. The material of hole modification layer 41 is either 2PACz or 4PACz, or a combination thereof. Hole modification layer 41 is a monolayer and is prepared by spin coating. The concentration of 2PACz or 4PACz in the spin coating solution is 0.8 mg / mL to 1 mg / mL, the spin coating speed is 3000 rpm to 5000 rpm, and the annealing temperature is 80°C to 120°C for 10 to 15 minutes.

[0067] The composite layer 3 may be made of indium tin oxide (ITO) or indium zinc oxide (IZO). The composite layer 3 has a thickness of 20 nm to 30 nm and may be formed by physical vapor deposition, vacuum deposition, or the like.

[0068] The material of the electron transport layer 5 can be C 60 , with a thickness of 15nm to 20nm. C 60 The electron transport layer 5 is prepared by evaporation method with an evaporation rate of

[0069] A passivation layer 11 is also provided on the side of the electron transport layer 5 close to the perovskite layer 1. The material of the passivation layer 11 is LiF and the thickness can be 1 nm. The LiF passivation layer 11 is made by evaporation method, and the evaporation rate can be

[0070] A buffer layer 51 is further provided on the side of the electron transport layer 5 facing away from the bottom cell 2 . The material of the buffer layer 51 is SnO 2 , and the thickness is 20 nm to 30 nm. The SnO 2 buffer layer 51 is prepared by atomic layer deposition.

[0071] The material of the transparent conductive layer 6 can be cerium indium oxide, with a thickness of 30 nm to 40 nm, and can be manufactured by reactive plasma deposition (RPD).

[0072] The transparent conductive layer 6 is further provided with an anti-reflection layer 61 on the side away from the bottom cell 2. The anti-reflection layer 61 can be made of LiF and / or MgF2 with a thickness of 100nm to 120nm. The anti-reflection layer 61 can be made by evaporation. The evaporation rate is The refractive index n value is about 1.4.

[0073] In a second aspect, an embodiment of the present application provides a method for preparing a perovskite solar cell.

[0074] A method for preparing a perovskite solar cell, as mentioned in the first aspect, comprises the following steps:

[0075] Lead halide skeleton layer pretreatment: providing a lead halide skeleton layer, coating a solution containing a fluorinated pyridine derivative on the surface of the lead halide skeleton layer, and performing a first annealing treatment;

[0076] The cationic solution is coated on the surface of the lead halide skeleton layer, and a second annealing treatment is performed to obtain the perovskite layer 1.

[0077] First, the first annealing treatment causes the CF bond to break, releasing F- and forming a Pb-FI superlattice, which enables F- to accurately occupy the iodine vacancies and achieve effective doping, thereby improving the structural stability and photoelectric performance of the perovskite layer 1. Secondly, during the cationic coating and second annealing process, the uncoordinated Pb 2+ It combines with the pyridine group in the fluoropyridine derivative to form a [Pb-(N)Pyridine] coordination bond, further enhancing the passivation effect of the perovskite layer 1. In addition, this preparation method can achieve synergistic passivation of the bulk and interface, breaking through the limitations of traditional doping methods and further improving the performance of perovskite solar cells.

[0078] In the process of forming the solution of the fluoropyridine derivative, the fluoropyridine derivative is placed in a solvent and subjected to ultrasonic treatment to better disperse and dissolve the fluoropyridine derivative in the solvent. The ultrasonic treatment can be performed at 85° C. for 50 minutes.

[0079] In some embodiments, the first annealing treatment includes annealing at 50° C. to 100° C. for 1 minute to 20 minutes, and then annealing at 100° C. to 160° C. for 10 minutes to 30 minutes.

[0080] During the first annealing process, a low-temperature annealing at 80°C helps slowly evaporate the solvent from the fluoropyridine derivative solution, preventing the formation of holes or cracks caused by rapid drying. This promotes the uniform distribution of the fluoropyridine derivative molecules within the lead halide backbone, forming preliminary [Pb-(N)Pyridine] coordination bonds and weakening the C-F bond energy, preparing for subsequent high-temperature annealing at 135°C. The high-temperature annealing at 135°C precisely matches the C-F bond rupture threshold, ensuring the on-demand release of F- to occupy iodine vacancies, forming the Pb-FI superlattice and suppressing ion migration during perovskite crystallization at high temperatures. Compared to constant-temperature annealing, a gradient heating process reduces local fluctuations in fluorine concentration and improves doping uniformity. Illustratively, during the first annealing treatment, the prior annealing temperature may be 50°C, 60°C, 70°C, 80°C, 90°C or 100°C, etc., the prior annealing time may be 3 min, 5 min, 7 min, 11 min, 15 min or 18 min, etc., the subsequent annealing temperature may be 100°C, 110°C, 120°C, 130°C, 140°C or 150°C, etc., the subsequent annealing time may be 13 min, 16 min, 19 min, 22 min, 25 min or 28 min, etc.

[0081] In some embodiments, the second annealing treatment includes annealing at 100°C to 150°C for 15 minutes to 30 minutes. By controlling the temperature and time of the second annealing treatment, the fluoropyridine derivative can be further promoted to bind to the uncoordinated Pb 2 + combination, optimizing the performance of the perovskite layer 1. Exemplarily, the temperature of the second annealing treatment is 100° C., 110° C., 120° C., 130° C., 140° C., or 150° C., and the annealing time is 15 min, 20 min, 25 min, or 30 min.

[0082] In some embodiments, the concentration of the fluoropyridine derivative in the fluoropyridine derivative solution is 0.01 mmol / mL to 0.08 mmol / mL. This can avoid the problem of poor passivation effect caused by insufficient incorporation of fluoride ions, or the problem of excessive incorporation affecting the nucleation and crystallization quality of the perovskite, thereby ensuring that the prepared perovskite layer 1 has good performance. For example, the concentration of the fluoropyridine derivative can be 0.01 mmol / mL, 0.03 mmol / mL, 0.05 mmol / mL, 0.07 mmol / mL, or 0.08 mmol / mL, etc.

[0083] In some embodiments, the solvent in the fluoropyridine derivative solution includes one or a combination of γ-valerolactone, anhydrous ethanol, dimethyl sulfoxide, N,N-dimethylformamide, or isopropyl alcohol.

[0084] Fluoropyridine derivatives are dissolved in different solvents, and the properties of the corresponding fluoropyridine derivative solutions are different. This makes the effects of fluoropyridine derivative solutions in different solvents used for the pretreatment of lead halide skeleton layer different, which is ultimately directly reflected in the performance of perovskite solar cells. This may be because the polarity, coordination ability and volatility of the solvent determine whether the fluoropyridine derivative molecules can effectively diffuse into the gaps of the lead halide skeleton layer and smoothly release F- ions and Pb 2+ Therefore, the choice of solvent significantly affects the effective doping degree of fluoropyridine derivatives in the skeleton layer (including the depth and uniformity of bulk doping), and the device performance under different solvent systems shows certain differences.

[0085] In addition, these solvents have low or non-toxic properties, meet environmental protection requirements, reduce pollution to the environment and harm to the health of operators during the preparation process, and also provide safer and more feasible process conditions for industrial large-scale production.

[0086] In some embodiments, the lead halide skeleton layer includes PbI2 and CsBr;

[0087] In the fluoropyridine derivative solution, the solvent consists of anhydrous ethanol and γ-valerolactone in a volume ratio of 3:7, or consists of dimethyl sulfoxide and γ-valerolactone in a volume ratio of 3:7.

[0088] By optimizing the ratio of solvents, the fluoropyridine derivatives can be made to exert their passivation effect more effectively, thus affecting the performance of the final solar cell.

[0089] In a third aspect, an embodiment of the present application provides a photovoltaic module.

[0090] A photovoltaic module comprises the perovskite solar cell as mentioned in the first aspect or the perovskite solar cell prepared by the preparation method as mentioned in the second aspect.

[0091] The technical solution of the present application will be further described below in conjunction with more specific embodiments.

[0092] Example 1

[0093] The present invention provides a method for preparing a perovskite solar cell, comprising the following steps:

[0094] Provide heterojunction bottom cells;

[0095] A composite layer was prepared on the surface of the heterojunction bottom cell using physical vapor deposition. The composite layer was made of indium tin oxide and had a thickness of 25 nm.

[0096] NiO is deposited by physical vapor deposition on the side of the composite layer away from the heterojunction bottom cell. xlayer, NiO x layer, thickness of 25 nm;

[0097] A 2PACz layer was prepared by solution method on the side of the hole transport layer away from the heterojunction bottom cell. The 2PACz layer was a monolayer.

[0098] On the side of the 2PACz layer facing away from the heterojunction bottom cell, a perovskite layer is prepared by evaporating a lead iodide skeleton layer combined with a cationic solution spin coating process:

[0099] The lead iodide skeleton layer has a thickness of 380nm. The lead iodide skeleton layer is prepared by co-evaporating PbI2 and CsBr raw materials at an evaporation rate of 8:1 through dual-source co-evaporation. The evaporation rate error during the evaporation process is less than 5%, and the film thickness uniformity is less than 5%.

[0100] Lead iodide skeleton layer pretreatment:

[0101] 0.06 mmol of 4-fluoropyridine-3-carboxylic acid was dissolved in 1 mL of a mixed solvent of dimethyl sulfoxide and γ-valerolactone (volume ratio 3:7), and the mixture was treated with ultrasound at 85°C for 50 min until the 4-fluoropyridine-3-carboxylic acid was completely dissolved, obtaining a solution containing 4-fluoropyridine-3-carboxylic acid with a concentration of 0.06 mmol / mL;

[0102] Spin coat the 4-fluoropyridine-3-carboxylic acid solution at 100 μL / slice at 4000 rpm for 30 seconds. The spin coating environment should be kept at a humidity of less than 10% RH and a temperature of 25°C.

[0103] The first annealing was performed at a humidity of 5% RH to 40% RH, first at 80°C for 5 minutes and then at 135°C for 15 minutes;

[0104] Spin coating cationic solution: the cationic material is a mixed solution of iodoformamidine, bromomethylamine and chloromethylamine, the solvent is anhydrous ethanol, wherein the concentration of iodoformamidine is 0.5M, the concentration of bromomethylamine is 0.15M, and the concentration of chloromethylamine is 0.1M. The spin coating speed is 5000 rpm and the spin coating time is 30 seconds. The spin coating environment requires a humidity of less than 10% RH and a temperature of 25°C. After the spin coating is completed, a second annealing is performed under the condition of a humidity of 5% RH to 40% RH. The second annealing temperature is 120°C and the annealing time is 20 minutes to form a perovskite layer with a thickness of 480 nm.

[0105] A passivation layer is prepared on the side of the perovskite layer facing away from the heterojunction bottom cell. The passivation layer is made of LiF and has a thickness of 1 nm.

[0106] The electron transport layer is prepared on the side of the passivation layer away from the heterojunction bottom battery. The material of the electron transport layer is C 60 , thickness is 18nm,

[0107] A buffer layer is prepared on the side of the electron transport layer away from the heterojunction bottom cell. The buffer layer is made of SnO2 and has a thickness of 25nm.

[0108] A transparent conductive layer is prepared on the side of the buffer layer away from the heterojunction bottom cell. The material of the transparent conductive layer is indium cerium oxide with a thickness of 35nm.

[0109] A first electrode is prepared on the transparent conductive layer, wherein the first electrode is a silver electrode with a thickness of 200 nm;

[0110] A second electrode is prepared on the heterojunction bottom cell. The second electrode is a silver electrode with a thickness of 200 nm.

[0111] An anti-reflection layer is deposited on the non-metallized area on the transparent conductive layer by an evaporation method. The material of the anti-reflection layer is MgF2 and the thickness is 110 nm.

[0112] Example 2

[0113] This embodiment of the present application provides a method for preparing a perovskite solar cell, which differs from Example 1 in that the concentration of 4-fluoropyridine-3-carboxylic acid in the solution containing 4-fluoropyridine-3-carboxylic acid used for pretreatment of the lead iodide skeleton layer is 0.01 mmol / mL, and the rest is consistent with Example 1.

[0114] Example 3

[0115] This embodiment of the present application provides a method for preparing a perovskite solar cell, which differs from Example 1 in that the solvent in the solution containing 4-fluoropyridine-3-carboxylic acid used for pretreatment of the lead iodide skeleton layer is ethanol, and the concentration of 4-fluoropyridine-3-carboxylic acid is 0.04 mmol / mL. The rest is consistent with Example 1.

[0116] Example 4

[0117] The embodiment of the present application provides a method for preparing a perovskite solar cell, which differs from the first embodiment in that the solution used for pretreatment of the lead iodide skeleton layer is a solution of ethyl 3-fluoropyridine-2-carboxylate, the concentration of ethyl 3-fluoropyridine-2-carboxylate is 0.06 mmol / mL, and the rest is consistent with the first embodiment.

[0118] Example 5

[0119] The embodiment of the present application provides a method for preparing a perovskite solar cell, which differs from the first embodiment in that the solution used for pretreatment of the lead iodide skeleton layer is a solution of 2-bromo-3-fluoropyridine, the concentration of 2-bromo-3-fluoropyridine is 0.06 mmol / mL, and the rest is consistent with the first embodiment.

[0120] Comparative Example 1

[0121] The comparative example of the present application provides a method for preparing a perovskite solar cell, which differs from Example 1 in that 4-fluoropyridine-3-carboxylic acid is not doped into the perovskite layer, that is, the lead iodide skeleton layer is not pretreated, and the cationic solution is directly coated on the surface of the lead iodide skeleton layer for annealing treatment. The rest is consistent with Example 1.

[0122] Comparative Example 2

[0123] The comparative example of the present application provides a method for preparing a perovskite solar cell, which differs from Example 1 in that an ethanol solution of CsF is used in the pretreatment of the lead iodide skeleton layer instead of a solution containing 4-fluoropyridine-3-carboxylic acid, and the rest is consistent with Example 1.

[0124] Comparative Example 3

[0125] The comparative example of the present application provides a method for preparing a perovskite solar cell, which differs from Example 1 in that an ethanol solution of KPF6 is used for pretreatment of the lead iodide skeleton layer instead of a solution containing 4-fluoropyridine-3-carboxylic acid, and the rest is consistent with Example 1.

[0126] Experiment 1

[0127] The performance of perovskite solar cells was tested using a Wavelabs solar simulator under the following conditions: AM1.5, 1000W / m 2 The test environment temperature was 25°C. Before testing, the simulated sunlight intensity of the light source was calibrated using a standard silicon cell. The corresponding perovskite solar cell open-circuit voltage (Voc), short-circuit current (Jsc), fill factor (FF), and photoelectric conversion efficiency (PCE) test values ​​were recorded.

[0128] The test results of the above embodiments and comparative examples are shown in Table 1.

[0129] Table 1

[0130]

[0131]

[0132] According to the data comparison between Example 1 and Comparative Example 1 in Table 1, it can be seen that the open circuit voltage and fill factor of Example 1 are significantly improved, and ultimately the photoelectric conversion efficiency is improved. This proves that the incorporation of 4-fluoropyridine-3-carboxylic acid into the perovskite layer can significantly reduce non-radiative recombination, improve carrier transport, and ultimately improve the electrical performance of the solar cell.

[0133] From the comparison of the data of Example 1 and Comparative Example 2, it can be seen that whether the lead iodide skeleton layer is pretreated with an ethanol solution of CsF (Comparative Example 2) or the lead iodide skeleton layer is pretreated with an ethanol solution of KPF6 (Comparative Example 3), the effect of fluorine incorporation into the lead iodide skeleton layer is not good, resulting in a significant decrease in the open circuit voltage and short circuit current of the solar cells of Comparative Example 2 and Comparative Example 3 compared to that of Example 1, and ultimately a decrease in the photoelectric conversion efficiency of Comparative Example 2 and Comparative Example 3.

[0134] Experiment 2

[0135] Under nitrogen atmosphere and temperature of 25°C, the stability test of the perovskite solar cells of Example 1, Example 2, Example 3 and Comparative Example 1 was carried out. Figure 2 .

[0136] from Figure 2 It can be seen that compared with Comparative Example 1, the decrease in photoelectric conversion efficiency of the solar cells in Example 1, Example 2 and Example 3 with the extension of the test time is significantly slowed down, which proves that the passivation performance of the perovskite layer in Example 1, Example 2 and Example 3 is improved, which promotes the improvement of the stability of the solar cells.

[0137] Experiment 3

[0138] The PL test was performed on the perovskite layer of the perovskite solar cells of Example 1, Example 2, Example 3 and Comparative Example 1. The test results are shown in FIG. Figure 3 .

[0139] from Figure 3 It can be seen that the PL absorption peak intensities of Example 1, Example 2 and Example 3 are significantly higher than those of Comparative Example 1, indicating that the pyridine group containing the lone pair electrons of the N atom in 4-fluoropyridine-3-carboxylic acid binds to the uncoordinated Pb in the perovskite lattice. 2+ Form a stable [Pb-N(Pyridine)] coordination bond, effectively passivating Pb 2+ Dangling bonds reduce non-radiative recombination centers.

[0140] Experiment 4

[0141] The perovskite layers of the perovskite solar cells of Example 1, Example 2, Example 3 and Comparative Example 1 were subjected to XRD (X-ray diffraction) tests, and the test results are shown in FIG. Figure 4 .

[0142] from Figure 4 It can be seen that the absorption peaks at about 14.06° in Examples 1, 2, and 3 are red-shifted compared to that in Comparative Example 1, proving that fluoride ions are incorporated into the perovskite lattice. Since fluoride ions have a smaller ionic radius than iodide ions, they react with Pb after incorporation. 2+The formation of strong Pb-F bonds causes the perovskite lattice to shrink, so after the incorporation of fluorine ions, the absorption peak of the perovskite layer is red-shifted.

[0143] Experiment 5

[0144] The perovskite layer of the perovskite solar cell of Example 1 was subjected to XPS (X-ray photoelectron spectroscopy) testing, and the test results are shown in Figure 5 .

[0145] F(1s) is a characteristic peak at the core energy level of the fluorine (F) element and is a key signal for identifying whether a sample contains fluorine (typically peaking between 686 and 689 eV). The perovskite of Example 1 of the present application exhibits a distinct peak at a binding energy of 686.3 eV, demonstrating the introduction of fluorine. Comparative Example 1, however, exhibits no peak between 686 and 689 eV, indicating the absence of fluorine.

[0146] The above is a detailed introduction to the technical solutions disclosed in the embodiments of the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the technical solutions and core invention points of the embodiments of the present application. At the same time, for those skilled in the art, based on the ideas of the present application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A perovskite solar cell, characterized in that: The perovskite layer comprises a fluoropyridine derivative doped therein, wherein the fluorine ions of the fluoropyridine derivative are in contact with the bulk of the perovskite layer and the Pb 2+ Formation of Pb-F bonds.

2. The perovskite solar cell according to claim 1, characterized in that The nitrogen atom of the pyridine group in the fluoropyridine derivative and the Pb in the perovskite layer 2+ Form a coordination bond.

3. The perovskite solar cell according to claim 1, characterized in that The fluoropyridine derivatives include one or more combinations of fluoropyridinecarboxylic acid derivatives, 2-bromo-3-fluoropyridine, 5-bromo-3-fluoropyridine or 2-chloro-3-bromo-5-fluoropyridine.

4. The perovskite solar cell according to claim 3, characterized in that The fluoropyridinecarboxylic acid derivatives include 4-fluoropyridine-3-carboxylic acid and / or 3-fluoropyridine-2-carboxylic acid ethyl ester; and / or, The carboxylic acid group of the fluoropyridinecarboxylic acid derivative is bound to the Cs + and Pb 2+ Form a coordination bond.

5. The perovskite solar cell according to claim 1, characterized in that The mass proportion of the fluoropyridine derivative in the perovskite layer is 0.5% to 5.5%.

6. The perovskite solar cell according to any one of claims 1 to 5, characterized in that The thickness of the perovskite layer is 450 nm to 500 nm, and the band gap of the perovskite layer is 1.63 eV to 1.70 eV.

7. The perovskite solar cell according to any one of claims 1 to 5, characterized in that The perovskite solar cell further comprises a bottom cell, on the surface of which a composite layer, a first transport layer, the perovskite layer, a second transport layer, a transparent conductive layer and a first electrode are sequentially stacked, wherein one of the first transport layer and the second transport layer is a hole transport layer, and the other is an electron transport layer; or; The perovskite solar cell also includes a transparent conductive substrate, and a first transport layer, the perovskite layer, a second transport layer and a first electrode are sequentially arranged on the surface of the transparent conductive substrate. One of the first transport layer and the second transport layer is a hole transport layer, and the other is an electron transport layer.

8. A method for preparing a perovskite solar cell, characterized in that: The method for preparing a perovskite solar cell according to any one of claims 1 to 7 comprises the following steps: Pretreatment of the lead halide skeleton layer: providing the lead halide skeleton layer, coating the surface of the lead halide skeleton layer with a solution containing the fluoropyridine derivative, and performing a first annealing treatment; The cationic solution is coated on the surface of the lead halide skeleton layer, and a second annealing treatment is performed to obtain the perovskite layer.

9. The method for preparing a perovskite solar cell according to claim 8, wherein: The first annealing treatment includes annealing at 50°C to 100°C for 1 minute to 20 minutes, and then annealing at 100°C to 160°C for 10 minutes to 30 minutes; and / or, The second annealing treatment includes annealing at 100° C. to 150° C. for 15 min to 30 min; and / or, In the fluoropyridine derivative solution, the concentration of the fluoropyridine derivative is 0.01 mmol / mL to 0.08 mmol / mL.

10. The method for preparing a perovskite solar cell according to claim 8, wherein: The solvent in the fluoropyridine derivative solution includes one or a combination of gamma-valerolactone, anhydrous ethanol, dimethyl sulfoxide, N,N-dimethylformamide or isopropyl alcohol.

11. The method for preparing a perovskite solar cell according to claim 10, wherein: The lead halide skeleton layer includes PbI2 and CsBr; In the fluoropyridine derivative solution, the solvent is composed of anhydrous ethanol and γ-valerolactone in a volume ratio of 3:7, or is composed of dimethyl sulfoxide and γ-valerolactone in a volume ratio of 3:

7.

12. A photovoltaic module, characterized in that: The invention comprises the perovskite solar cell according to any one of claims 1 to 7 or the perovskite solar cell prepared by the preparation method according to any one of claims 8 to 11.

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