Solar cell, preparation method thereof and photovoltaic module

Abstract

The invention relates to the field of solar cells, and discloses a solar cell, a preparation method thereof and a photovoltaic module, and the preparation method comprises the following steps: manufacturing a lead halide skeleton layer on a substrate; coating the lead halide framework layer with a cation solution with an additive, and annealing to obtain a perovskite layer; wherein R1 and R5 are respectively and independently selected from-CH = CH2, R2 and R4 are respectively and independently selected from carbonyl, R3 comprises-(CF2) 2 or-(CF2) 3, and the molecular radius of the additive is that the molar concentration of the additive in the cationic solution is 1-15 mol / mL; and post-processing to obtain the solar cell. The distribution uniformity of the cation solution of the perovskite layer is high, the cation solution is fully reacted with the skeleton layer, and the prepared solar cell has high stability.

Description

TECHNICAL FIELD

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

[0002] The perovskite cell is a new type of solar cell based on perovskite material. Because the perovskite material is not sensitive to impurities, the optical band gap is adjustable, and has a high charge diffusion length and a high light absorption coefficient, etc., so that the perovskite cell has a great application prospect in the photovoltaic field.

[0003] At present, the preparation methods of the perovskite cell mainly include one-step method and two-step method. The one-step method is only suitable for small-scale scientific experiments and cannot be applied to large-scale production lines. The two-step method is more suitable for mass production lines, but there are still some problems to be overcome. The two-step method for preparing the perovskite layer has the problems of incomplete reaction of the skeleton layer with the cation solution, uneven cation composition, ion migration and enrichment in the solid perovskite layer, etc. These problems will further cause the prepared perovskite layer to have more defects, a large number of grain boundaries and lattice distortion, etc., which affect the structural stability of the perovskite layer and reduce the service life of the solar cell. SUMMARY

[0004] The embodiments of the present application disclose a solar cell, a preparation method thereof and a photovoltaic module, so as to solve the problems of uneven distribution of the cation solution in the skeleton layer and insufficient reaction, thereby reducing the defects of the perovskite layer, reducing the grain boundaries and lattice distortion, and improving the stability of the perovskite layer.

[0005] In a first aspect, the embodiments of the present application disclose a preparation method of a solar cell, which comprises the following steps:

[0006] A lead halide skeleton layer is prepared on a substrate;

[0007] A cation solution with an additive is coated on the lead halide skeleton layer, and a perovskite layer is obtained through annealing; wherein the structure of the additive is wherein R1 and R5 are each independently selected from -CH=CH2, R2 and R4 are each independently selected from a carbonyl group, R3 includes -(CF2)2 or -(CF2)3, and the molecular radius of the additive is The molar concentration of the additive in the cation solution is 1 mol / mL to 15 mol / mL;

[0008] Post-processing to obtain the solar cell.

[0009] Further, the additive comprises 2,2,3,3,4,4-hexafluoro-1,5-pentyl diacrylate or 2,2,3,3-tetrafluoro-1,4-butyl butyl diacrylate.

[0010] Further, the cationic solution comprises formamidinium iodide and formamidinium bromide, and the sum of the molar concentrations of the formamidinium iodide and the formamidinium bromide in the cationic solution is 0.6 mol / L to 0.7 mol / L.

[0011] Further, the thickness of the lead halide skeleton layer is 300 nm to 500 nm, and the thickness of the perovskite layer is 450 nm to 650 nm.

[0012] Further, in the annealing step, the annealing temperature is 150℃ to 170℃, and the annealing time is 15 min to 20 min.

[0013] In a second aspect, the embodiments of the present application disclose a solar cell prepared by the preparation method of the solar cell.

[0014] Further, in the perovskite layer, the ratio of the peak intensity of the characteristic diffraction peak of the residual lead halide to the characteristic diffraction peak of the 001 crystal plane is 0.17 to 0.25.

[0015] Further, the substrate has a pyramid texture structure, the perovskite layer is consistent with the texture structure of the substrate, the base length of the pyramid texture structure of the perovskite layer is 3 μm to 6 μm, and the height of the pyramid texture structure of the perovskite layer is 4 μm to 7 μm.

[0016] Further, the solar cell is a stacked cell, the substrate comprises a bottom cell, an electron-hole recombination layer arranged on the bottom cell, and a first transport layer, the perovskite layer is arranged on a side of the first transport layer away from the electron-hole recombination layer, the solar cell further comprises a second transport layer, a transparent conductive layer, a first electrode, and a second electrode arranged in sequence on a side of the perovskite layer away from the first transport layer, the first electrode is in ohmic contact with the transparent conductive layer, and the second electrode is in ohmic contact with the bottom cell, wherein one of the first transport layer and the second transport layer is an electron transport layer, and the other is a hole transport layer, one of the first electrode and the second electrode is a positive electrode, and the other is a negative electrode.

[0017] Alternatively, the solar cell is a single-junction cell, the substrate comprises a transparent conductive substrate and a first transport layer disposed on the transparent conductive substrate, the perovskite layer is disposed on a side of the first transport layer away from the electron-hole recombination layer, the solar cell further comprises a second transport layer disposed on a side of the perovskite layer away from the first transport layer, and a first electrode and a second electrode, the first electrode is in ohmic contact with the second transport layer, and the second electrode is in ohmic contact with the transparent conductive substrate, wherein one of the first electrode and the second electrode is a positive electrode, and the other is a negative electrode.

[0018] Further, the hole transport layer is a nickel oxide layer; and / or,

[0019] The thickness of the hole transport layer is 20-30 nm; and / or,

[0020] The electron transport layer is a C 60 layer; and / or,

[0021] The thickness of the electron transport layer is 15-20 nm; and / or,

[0022] The transparent conductive layer is an indium zinc oxide layer; and / or,

[0023] The thickness of the transparent conductive layer is 70-140 nm; and / or,

[0024] The positive electrode and / or the negative electrode is silver, and the thickness of the positive electrode and / or the negative electrode is 300-350 nm.

[0025] Further, when the solar cell is a stacked cell, the solar cell further comprises a buried bottom modification layer disposed on the first transport layer on a side away from the electron-hole recombination layer; and / or,

[0026] The solar cell further comprises a buffer layer disposed on a surface of the second transport layer on a side away from the perovskite layer, and the thickness of the buffer layer is 20-50 nm.

[0027] In a third aspect, the embodiments of the present application disclose a photovoltaic module, comprising: the solar cell prepared by the preparation method of the solar cell according to the first aspect, or the solar cell according to the second aspect.

[0028] Compared with the prior art, the present application has the following beneficial effects:

[0029] The application provides a preparation method of a solar cell.

[0030] First, a lead halide skeleton layer is prepared on a substrate. Since the cation solution contains an additive, and the molecular radius of the additive is The molar concentration of the cation solution is 1 mol / mL to 15 mol / mL, which promotes diffusion of the cation solution into the interior of the skeleton layer, so that the cation solution is uniformly distributed in the lead halide skeleton, thereby facilitating full reaction of the cation solution and the lead halide skeleton layer. Not only is a crystal structure prepared, but also the adaptability to the substrate is high. Secondly, the functional groups in the additive include carbonyl, fluorine, and olefin. The carbonyl has high binding capacity with uncoordinated lead ions in the perovskite layer, which can effectively passivate defects in the perovskite layer and reduce non-radiative recombination. The fluorine has strong hydrophobicity, which can improve the water vapor stability of the perovskite film. The olefin groups at both ends of the molecule undergo in-situ thermal crosslinking to form a polymer during the annealing process. Due to the concentration limitation, the molecular radius of the prepared polymer is small, which is beneficial to release the residual stress of the perovskite layer and inhibit ion migration, thereby reducing the recombination of interface charges and the degradation of the perovskite layer, and improving the stability of the solar cell.

[0031] That is, the use of the above additive not only makes the cation solution uniformly distributed in the perovskite skeleton layer by taking advantage of the small molecular weight, but also the functional groups in the additive act on the perovskite layer, thereby improving the crystalline quality and stability of the perovskite layer. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings used in the embodiments will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0033] Figure 1 is a cross-sectional view of a laminated solar cell provided by the present application;

[0034] Figure 2 is a cross-sectional view of a single-junction solar cell provided by the present application;

[0035] Figure 3is a scanning electron microscope image of the perovskite layer provided by Example 1 of the present application;

[0036] Figure 4 is a scanning electron microscope image of the perovskite layer provided by Comparative Example 1 of the present application;

[0037] Figure 5 is an X-ray diffraction pattern of the perovskite layer provided by Example 1 and Comparative Example 2 of the present application;

[0038] Figure 6 is a photoluminescence test image of the perovskite layer provided by Example 1 of the present application;

[0039] Figure 7 is a photoluminescence test image of the perovskite layer provided by Comparative Example 2 of the present application.

[0040] Figure: 1, substrate; 11, bottom cell; 12, electron-hole recombination layer; 13, first transport layer; 14: transparent conductive substrate; 2, perovskite layer; 3, second transport layer; 4, transparent conductive layer; 5, first electrode; 6, second electrode; 7, buried bottom modification layer; 8, buffer layer. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0042] In the present application, the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal" and the like indicate the orientation or positional relationship shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.

[0043] In addition, in addition to indicating the orientation or positional relationship, the above-mentioned part of the terms can also be used to indicate other meanings, for example, the term "upper" can also be used to indicate a certain dependent relationship or connection relationship in some cases. Those of ordinary skill in the art can understand the specific meaning of these terms in the present application according to the specific circumstances.

[0044] In addition, the terms "first", "second", and the like are mainly used to distinguish different devices, elements or components (the specific types and configurations can be the same or different), and are not intended to indicate or imply the relative importance and quantity of the indicated devices, elements or components. Unless otherwise stated, the meaning of "a plurality" is two or more.

[0045] The technical solutions provided by the present application will be further described below in combination with embodiments and drawings.

[0046] The perovskite layer is the core of the perovskite solar cell, and the perovskite layer prepared by the two-step method first needs to deposit a lead halide skeleton layer, and then spin-coat a cation solution on the skeleton layer. Subsequently, the organic cation solution penetrates the inorganic skeleton layer and undergoes a self-assembly reaction, converting the inorganic skeleton layer framework into a perovskite phase. However, in this process, due to the dense structure of the skeleton layer and the poor diffusivity of the cation solution, the cation solution mainly concentrates in the top area of the skeleton layer and is difficult to enter the bottom of the skeleton layer, resulting in insufficient reaction of the skeleton layer with the cation solution, affecting the transport of carriers, and causing poor crystallinity of the crystals at the bottom of the perovskite layer and poor adaptability to the substrate, thereby resulting in poor texture structure of the perovskite layer, limiting the light-trapping effect of the texture structure. In addition, the perovskite layer prepared by the two-step method results in a large number of defects in the perovskite layer, a large number of grain boundaries, and lattice distortion, thereby greatly increasing non-radiative recombination, affecting the fill factor and open-circuit voltage of the solar cell, and resulting in poor stability and reduced service life of the solar cell.

[0047] Based on the above problems, the embodiments of the present application provide a preparation method of a solar cell, which improves the uniformity of the distribution of the cation solution in the skeleton layer, improves the sufficiency of the reaction of the cation solution with the skeleton layer, and at the same time improves the crystallinity and stability of the perovskite layer.

[0048] In a first aspect, the embodiments of the present application provide a preparation method of a solar cell, which comprises the following steps:

[0049] A lead halide skeleton layer is made on a substrate;

[0050] A cation solution with an additive is coated on the lead halide skeleton layer, and a perovskite layer is obtained after annealing; wherein the structure of the additive is wherein R1 and R5 are each independently selected from -CH=CH2, R2 and R4 are each independently selected from a carbonyl group, R3 includes -(CF2)2 or -(CF2)3, and the molecular radius of the additive is The molar concentration of the additive in the cation solution is 1 mol / mL to 15 mol / mL;

[0051] Post-processing to obtain a solar cell.

[0052] The perovskite layer is prepared by a two-step method. In order to make the cation solution diffuse into the bottom of the framework layer and uniformly distribute on the framework layer, the molecular radius of the additive used in the application is The molecular weight of the additive is close to the atomic radius of lead, and the concentration of the additive in the cation solution is 1 mol / mL to 15 mol / mL. The additive has a small molecular weight, and the resistance to migration in the lead halide framework layer is small. The additive can fully act on the cation solution at the above concentration range, promote the diffusion of the cation solution to the bottom of the framework layer, and make it uniformly distributed on the framework layer to achieve the fullness of the reaction. In addition, due to the full reaction at the bottom of the framework layer, a perovskite layer with good compactness and high adaptability to the base structure is obtained. In addition, due to the cross-linking of the additive to form a polymer during annealing, and the polymer has a small molecular weight at the above concentration range, which is beneficial to reduce the migration rate of ions, thereby improving the reaction fullness of the framework layer and the cation solution, and preparing a perovskite layer with high crystalline quality and good uniformity of crystalline quality in each region. If the molecular radius of the additive is too large, it is difficult for the additive to enter the interior of the framework layer, and it is also difficult to promote the diffusion of the cation solution into the interior of the framework layer, so that the uniformity of the distribution of the cation solution is poor. If the molecular radius of the additive is too small, the additive enters the interior of the framework layer too easily, which promotes the diffusion of the cation solution into the bottom of the framework layer, and the uniformity of the distribution is poor. For example, the molecular radius of the additive is etc. If the molar concentration of the additive in the cation solution is too high, the molecular weight of the finally prepared polymer is large, thereby the effect of hindering ion migration is large, the distribution of the cation solution in the perovskite layer is hindered, and the uniformity of the reaction of the cation solution is affected. For example, the molar concentration of the additive is 1 mol / mL, 5 mol / mL, 10 mol / mL, 15 mol / mL, etc.

[0053] It should be noted that the molecular radius of the additive of the application can be calculated by software Chemdraw or Multiwfn. The measurement method of the molecular radius of the application is not limited herein, as long as the purpose of the application can be achieved, that is, the molecular radius is measured.

[0054] Secondly, since R2 and R4 in the additive are each independently selected from a carbonyl group, the uncoordinated Pb 2+ The defects have a low formation energy, so that the content of the defects in the perovskite layer is high. According to the Lewis acid-base theory, the uncoordinated Pb 2+ can accept an electron pair to form a Lewis acid, and the carbonyl group in the R2 group is a Lewis base, and the oxygen therein can provide a lone pair of electrons. Therefore, the carbonyl group in the R2 group reacts with the uncoordinated Pb 2+ in the perovskite layer to form a Lewis acid, thereby reducing the uncoordinated Pb 2+The content of the additive reduces the non-radiation recombination of the perovskite layer; the fluorine element has hydrophobic characteristics, so the number of fluorine elements provided is larger due to R3 including -(CF2)2- or -(CF2)3-, which improves the hydrophobicity of the perovskite layer and improves the stability against water vapor; and R1 and R5 are each independently selected from -CH=CH2, the double bond is broken during the annealing process and cross-linked at the grain boundary to form a polymer, so that the polymer can act as a barrier layer and a protective layer, as a protective layer, it can effectively regulate the nucleation and growth rate of the crystal, overcome the problem of perovskite crystal lattice strain caused by temperature change during the annealing process, improve the stability of the solar cell, and as a barrier layer, it can reduce the migration rate of the cation solution, further improve the completeness of the reaction, and make the crystalline quality of the perovskite layer more uniform.

[0055] Specifically, the additive is preferably 2,2,3,3,4,4-hexafluoro-1,5-pentyl diacrylate or 2,2,3,3-tetrafluoro-1,4-butyl butyl diacrylate. The molecular structure of 2,2,3,3,4,4-hexafluoro-1,5-pentyl diacrylate is The molecular structure of 2,2,3,3-tetrafluoro-1,4-butyl butyl diacrylate is

[0056] Further, the cation solution includes formamidinium iodide and formamidinium bromide, and the sum of the molar concentrations of formamidinium iodide and formamidinium bromide in the cation solution is 0.6 mol / L to 0.7 mol / L.

[0057] When the molar concentration of the cation solution is within this range, it is beneficial to provide sufficient cation solution to react with the lead halide framework layer, and the use of formamidinium iodide and formamidinium bromide as the cation solution, due to the large molecular weight of the formamidinium group in these two substances, the uniformity of diffusion is poor, and it is usually enriched at the top of the perovskite layer. Under the action of the additive, the cation solution migrates to the bottom of the lead halide framework layer, improving the uniformity of the distribution of the cation solution in the lead halide framework layer and improving the completeness of the reaction. In addition, the use of the additive can effectively reduce the migration of the cation solution due to the cross-linking of the olefins at the ends of the additive molecules, further promoting the completeness of the reaction. If the molar concentration is too low, part of the lead halide framework layer does not participate in the reaction, thereby affecting the migration of the carriers and the photoelectric conversion efficiency of the solar cell; if the molar concentration is too high, part of the cation solution does not participate in the reaction, resulting in residual cation solution in the framework layer, affecting the performance of the solar cell. Illustratively, the molar concentration of formamidinium iodide and formamidinium bromide in the perovskite cation solution with the additive is 0.6 mol / L, 0.62 mol / L, 0.65 mol / L, 0.68 mol / L, 0.7 mol / L, etc.

[0058] In the above solar cell, the thickness of the lead halide framework layer is 300-500 nm, and the thickness of the perovskite layer is 450-650 nm. When the thickness of the lead halide framework layer is in the range, on the one hand, it is conducive to preparing a perovskite layer with good shape retention effect; on the other hand, within the thickness range, the final perovskite layer thickness can be ensured to be in the above range, which is conducive to increasing the transport distance of the carriers, reducing the recombination of the carriers in the perovskite layer, and increasing the photoelectric conversion efficiency of the solar cell.

[0059] It should be emphasized that, although the above thickness of the lead halide framework layer is conducive to reducing recombination and improving shape retention effect, it also increases the difficulty of the cation solution diffusing into the bottom of the lead halide framework layer, and by using the above additive, the cation solution is diffused to the bottom of the framework layer, and the crystallization effect and stability of the prepared perovskite layer are uniform. If the thickness of the lead halide framework layer is lower than the range, the thickness of the prepared perovskite layer is lower, the transport distance of the carriers in the perovskite layer is shorter, thereby increasing the probability of recombination of the carriers; if the thickness of the lead halide framework layer is higher than the range, the morphology control of the perovskite layer is more difficult, which affects the diffusion of the carriers and the effective extraction of the charges, leading to serious non-radiative recombination and energy loss, and due to the thicker framework layer, the cation solution is difficult to uniformly exist in the framework layer, affecting the photoelectric conversion efficiency of the solar cell. Exemplarily, the thickness of the lead halide framework layer is 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, etc.; the thickness of the perovskite layer is 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, etc.

[0060] Although the porous framework layer is constructed, the pore structure provides a channel for the cation solution to enter the inside of the framework layer, reduces the difficulty of the cation solution diffusing into the inside of the framework layer, and improves the problem of insufficient reaction, but due to the diffusion degree of the cation solution and the thickness of the framework layer, when the cation solution diffuses from the outside to the inside, the resistance becomes large, thereby it is difficult to effectively solve the uniformity problem of the reaction, and the more abundant the pore structure of the framework layer, the more sensitive it is to water vapor, light and heat, and the more likely it is to cause decomposition of the perovskite layer. By using the above additive, on the one hand, the molecular weight of the additive is small, which can promote the diffusion of the cation solution into the inside of the framework layer, and realize the fullness and uniformity of the reaction; on the other hand, the cross-linking effect of the double bond of the additive during annealing effectively inhibits the ion migration of the solid-state perovskite layer, and improves the stability. Based on this, by the action of the additive, the fullness of the reaction is realized, and the prepared perovskite layer has high crystallization quality and good stability.

[0061] In addition, in the step of annealing, the annealing temperature is 150-170°C, and the annealing time is 15-20 min.

[0062] Although at the annealing temperature and parameters, it is beneficial to remove volatile substances in the perovskite layer, accelerate the reaction of the cation solution with the lead halide framework layer, and improve the quality of the perovskite layer crystallization, but due to the difference in thermal expansion coefficient between the substrate and the perovskite layer, the perovskite layer and the substrate shrink to different degrees after annealing, the perovskite layer has residual stress, which affects the stability of the perovskite layer. In order to solve the problem of residual stress, the additive used in the present application is in-situ crosslinked with olefins, and a polymer is formed at the grain boundary, which acts as an ion barrier and a protective layer. When used as a protective layer, it can release the residual stress in the perovskite thin film during the annealing process, further improving the stability of the solar cell. When used as an ion barrier, it inhibits ion migration in the perovskite lattice. If it is lower than the time and temperature, the removal effect of volatile substances is poor, which has an adverse effect on the crystallization of the perovskite layer, and the crosslinking effect of the olefin is poor, which is difficult to release the residual stress in the perovskite thin film; if it is higher than the time and temperature, the perovskite layer has a decomposition probability, and the amount of lead halide produced is too much, which increases the recombination of carriers and affects the photoelectric conversion efficiency of the perovskite solar cell; if the temperature is too high and the time is too short, the evaporation rate of the solvent is too fast, which leads to a faster nucleation rate of the battery and smaller grain size, and the reaction rate of the cation with the lead halide framework layer is limited, so that the crystallization quality and stability of the perovskite layer are reduced. Exemplarily, the temperature of the perovskite layer annealing is 150℃, 160℃, 170℃, and the annealing time is 15min, 16min, 18min, 20min, etc.

[0063] In a second aspect, the embodiments of the present application disclose a solar cell, comprising: the solar cell prepared by the preparation method of the solar cell of the first aspect.

[0064] Further, in the perovskite layer, the ratio of the peak intensity of the characteristic diffraction peak of the residual lead halide to the characteristic diffraction peak of the 001 crystal plane of the perovskite layer is 0.17-0.25.

[0065] It can be understood that the molecular weight of a single additive does not differ much, but after annealing, the olefin molecules of the additive are crosslinked to form a polymer, and the molecular weight of the polymer differs greatly, which affects the crystallization quality of the perovskite layer finally prepared when the polymer is used as an ion migration barrier.

[0066] The characteristic peak of lead halide reflects the degree of reaction between the cation solution and the lead halide skeleton layer. The stronger the peak of lead halide, the more unreacted lead halide, which is not conducive to improving the photoelectric conversion efficiency of the solar cell. The 001 crystal plane of the perovskite layer reflects the ability of vertical transport of photo-generated carriers. When the peak strength of the two is within the range, that is, the smaller the ratio, the more complete the reaction. The larger the ratio, the more residual lead halide, and the poorer the crystalline quality of the perovskite layer. By using the above additive and annealing process, the olefins at the ends of the additive are cross-linked to form polymers. The molecular weight of the polymer molecules is small, the perovskite layer prepared has high crystallization effect, high carrier transport ability and high stability. The molecular weight of the polymer is not too large, which does not lead to too high ion inhibition effect, and the crystallinity is significantly weakened, and there is more residual lead halide in the interface, which is not conducive to improving the crystalline quality and stability of the perovskite layer.

[0067] Further, the substrate has a pyramid suede structure, the perovskite layer is consistent with the suede structure of the substrate, the base length of the pyramid suede structure of the perovskite layer is 3-6 μm, and the height of the pyramid suede structure of the perovskite layer is 4-7 μm.

[0068] When the substrate has a pyramid suede structure, the utilization rate of sunlight by the perovskite solar cell can be further improved. The suede structure has a light trapping effect, which improves the short circuit current value. When the suede structure of the perovskite layer is within the range, not only the light absorption effect is good, but also the cation solution diffuses to the bottom of the skeleton layer, so that the bottom of the perovskite layer is well adapted to the suede structure of the substrate. The suede structure of the solar cell prepared finally also has a good effect, that is, the perovskite layer prepared by the present application has a high suede shape retention effect, and also has high crystalline quality and stability. Illustratively, the base length of the suede structure of the perovskite layer is 3 μm, 4 μm, 5 μm, 6 μm, etc., and the height of the suede structure of the perovskite layer is 4 μm, 5 μm, 6 μm, 7 μm, etc.

[0069] Further, as Figure 1As shown, the solar cell is a stacked cell. The substrate 1 includes a bottom cell 11, an electron-hole recombination layer 12 disposed on the bottom cell 11, and a first transport layer 13. A perovskite layer 2 is disposed on the side of the first transport layer 13 away from the electron-hole recombination layer 12. The solar cell also includes a second transport layer 3, a transparent conductive layer 4, and a first electrode 5 and a second electrode 6, which are sequentially disposed on the side of the perovskite layer 2 away from the first transport layer 13. The first electrode 5 is in ohmic contact with the transparent conductive layer 4, and the second electrode 6 is in ohmic contact with the bottom cell 11. The first transport layer 13 and the second transport layer 3 are an electron transport layer and a hole transport layer, respectively. The first electrode 5 and the second electrode 6 are a positive electrode and a negative electrode, respectively.

[0070] Or, such as Figure 2 As shown, the solar cell is a single-junction cell. The substrate includes a transparent conductive substrate 14 and a first transport layer 13 disposed on the transparent conductive substrate 14. A perovskite layer 2 is disposed on the side of the first transport layer 13 away from the transparent conductive substrate 14. The solar cell also includes a second transport layer 3 disposed on the side of the perovskite layer 2 away from the first transport layer 13, as well as a first electrode 5 and a second electrode 6. The first electrode 5 is in ohmic contact with the second transport layer 3, and the second electrode 6 is in ohmic contact with the transparent conductive substrate 14. The first transport layer 13 and the second transport layer 3 are an electron transport layer and a hole transport layer, respectively. The first electrode 5 and the second electrode 6 are a positive electrode and a negative electrode, respectively.

[0071] The hole transport layer is made of nickel oxide; and / or, the thickness of the hole transport layer is 20 nm to 30 nm. The electron transport layer is made of C. 60 The electron transport layer has a thickness of 15 nm to 20 nm. The transparent conductive layer 4 is an indium zinc oxide layer with a thickness of 70 nm to 140 nm. The positive electrode and / or negative electrode is silver with a thickness of 300 nm to 350 nm.

[0072] By controlling the types of materials and thicknesses of the aforementioned structural layers, a high degree of compatibility between the layers can be achieved, effectively ensuring that the prepared solar cells have good photoelectric conversion efficiency.

[0073] In addition, in order to further improve the photoelectric conversion efficiency of the solar cell, when the solar cell is a stacked cell, the solar cell further comprises a buried bottom modification layer 7, which is arranged on the first transport layer 13 away from the side of the electron hole recombination 12. The presence of the buried bottom modification layer 7 can effectively improve the adaptability of the first transport layer 13 and the bottom of the perovskite layer 2, thereby facilitating the reduction of carrier recombination and improving the rate of carrier migration. In addition, the solar cell can further comprise a buffer layer 8, which is arranged on the surface of the second transport layer 3 away from the perovskite layer 2. The thickness of the buffer layer 8 is 20-50 nm. The buffer layer 8 arranged on the surface of the second transport layer 3 can avoid the adverse effects on the film layer structure of the perovskite layer 2 and the second transport layer 3 during the evaporation of the electrode or the preparation of the transparent conductive layer 4.

[0074] It can be understood that the material of the buried bottom modification layer comprises at least one of (2-(9H-carbazol-9-yl)ethyl)phosphonic acid, [2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid, (4-(9H-carbazol-9-yl)ethyl)phosphonic acid, and bis(4-phenyl)-(2,4,6-trimethylphenyl)amine. The buried bottom modification layer not only optimizes the process of perovskite layer crystal nucleation and perovskite layer crystal growth, thereby making the crystal quality of the prepared perovskite layer higher, but also passivates the defects of the interface, thereby improving the fill factor and open circuit voltage of the solar cell and improving the photoelectric conversion efficiency of the solar cell.

[0075] In a third aspect, the embodiments of the present application provide a photovoltaic module, comprising: a solar cell prepared by the preparation method of the solar cell of the first aspect, or the solar cell of the second aspect.

[0076] The technical solutions of the present application will be further explained below in combination with more specific embodiments and experimental test results.

[0077] Embodiment one:

[0078] The present embodiment provides a solar cell, which is a stacked cell. The preparation method of the stacked solar cell comprises the following steps:

[0079] A substrate with a pyramid suede structure is provided: an HJT crystalline silicon bottom cell is provided, and an electron transport recombination layer is prepared by magnetron sputtering on the light-receiving surface of the bottom cell in sequence. A 20 nm thick nickel oxide hole transport layer and a buried bottom modification layer are deposited by physical vapor deposition.

[0080] A lead iodide skeleton layer with a thickness of 450 nm is made on the substrate with a pyramid suede structure.

[0081] The cation solution with the additive is coated on the lead iodide skeleton layer, and a perovskite layer is obtained through annealing; wherein the additive is 2,2,3,3-tetrafluoropropanol-1,4-butyl acrylate, the molar concentration of the additive in the cation solution with the additive is 2 mol / mL, and the sum of the molar concentrations of methylcarbamate iodide and methylcarbamate bromide in the cation solution with the additive is 0.68 mol / L; then annealing at 150℃ for 15 min to obtain the perovskite layer;

[0082] Post-processing: 15nm thick C 60 The electron transport layer; a 20nm thick buffer layer SnO2 is prepared on the electron transport layer using atomic layer deposition; a 100nm thick transparent conductive layer indium zinc oxide is prepared on the buffer layer using physical vapor deposition; a silver positive electrode is prepared on the transparent conductive layer by vacuum evaporation, and a silver negative electrode is prepared on the back of the bottom cell by vacuum evaporation.

[0083] Example two:

[0084] The difference between this embodiment and example one is that the molar concentration of the additive in this embodiment is 5 mol / mL.

[0085] Example three:

[0086] The difference between this embodiment and example one is that the molar concentration of the additive in this embodiment is 8 mol / mL.

[0087] Example four:

[0088] The difference between this embodiment and example one is that the molar concentration of the additive in this embodiment is 11 mol / mL.

[0089] Example five:

[0090] The difference between this embodiment and example one is that the additive in this embodiment is 2,2,3,3,4,4-hexafluoro-1,5-dipentyl acrylate.

[0091] Example six:

[0092] The embodiment provides a solar cell, wherein the solar cell is a single-junction cell; the structure of the solar cell comprises:

[0093] The substrate comprises a transparent conductive substrate, a first transport layer arranged on the bottom cell, and a perovskite layer arranged on the side of the first transport layer away from the transparent conductive substrate; the solar cell further comprises a second transport layer arranged on the side of the perovskite layer away from the first transport layer, a first electrode, and a second electrode; the first electrode is in ohmic contact with the second transport layer, and the second electrode is in ohmic contact with the transparent conductive substrate; wherein the first transport layer is a hole transport layer, the second transport layer is an electron transport layer, the first electrode is a positive electrode, and the second electrode is a negative electrode.

[0094] This embodiment also provides a method for fabricating this single-junction solar cell:

[0095] Provide a substrate with a textured surface: Provide a transparent conductive substrate on which a 20 nm thick nickel oxide hole transport layer is deposited using physical vapor deposition on the light-receiving surface.

[0096] A lead iodide framework layer with a thickness of 450 nm was fabricated on a substrate with a textured surface.

[0097] A cationic solution containing additives was coated onto a lead iodide framework layer, followed by annealing to obtain a perovskite layer. The additive was 2,2,3,3-tetrafluoropropanol-1,4-butyl acrylate, with a molar concentration of 2 mol / mL in the cationic solution containing additives, and the sum of the molar concentrations of formamidine iodoformin and formamidine bromoformin in the cationic solution containing additives was 0.68 mol / L. The perovskite layer was then obtained by annealing at 150 °C for 15 min.

[0098] Post-processing: A 15nm thick C layer was deposited on the perovskite layer. 60 An electron transport layer is formed; a silver positive electrode is prepared by vacuum evaporation on the electron transport layer, and a silver negative electrode is prepared by vacuum evaporation on the backlight surface of a transparent conductive substrate.

[0099] Comparative Example 1:

[0100] The only difference between this comparative example and Example 1 is that this comparative example does not contain any additives.

[0101] Comparative Example 2:

[0102] The only difference between this comparative example and Example 1 is that the additive in this comparative example is 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol diacrylate (OF-HDDA).

[0103] Comparative Example 3:

[0104] The only difference between this comparative example and Example 1 is that the molar concentration of the additive in this comparative example is 20 mol / mL.

[0105] Comparative Example 4:

[0106] The only difference between this comparative example and Example 1 is that the molar concentration of the additive in this comparative example is 0.5 mol / mL.

[0107] Test data 1:

[0108] like Figure 3 , Figure 4As shown in the figure, Figure 3 The scanning electron microscope image provided by Example 1 of the present application, Figure 4 The scanning electron microscope image provided by Comparative Example 1 of the present application, after Example 1 and Comparative Example 1 were placed in an external environment with an ambient temperature of 25°C and a relative humidity of 30% to 40% for 72 hours, Figure 3 The perovskite layer in Example 1 has a complete structure and does not decompose, and the perovskite layer has no pores and obvious defects, while Figure 4 The perovskite layer in Comparative Example 1 decomposes obviously at the interface and generates a large number of pores, further accelerating the degradation of the perovskite, thereby causing a large decrease in the efficiency of the stacked device; this is because the perovskite layer preparation process in Example contains an additive, the introduction of which improves the structural stability of the perovskite film, and thus the perovskite layer in the entire solar cell does not significantly attenuate.

[0109] Test Data 2:

[0110] Table 1 X-ray spectrum data of the perovskite layer

[0111] Experimental conditions Peak (PbI2) Peak (001) Peak intensity ratio Example 1 549 2695 0.20 Comparative Example 2 531 2381 0.22

[0112] As shown in the figure, Figure 5 , Figure 5 The X-ray diffraction pattern of the perovskite layer of Example 1 and Comparative Example 2 provided by the present application, the characteristic diffraction peak at a position of 12.6° in the figure is a characteristic peak of unreacted lead iodide, and the characteristic diffraction peak at a position of 14° is a perovskite layer with a crystal face orientation of (001); the intensity of the characteristic diffraction peak at this position in Example 1 is lower than that in Comparative Example 2, because the molecular weight of the additive used in Example 1 is less than that in Comparative Example 1, thereby facilitating the diffusion of the cation solution to the bottom of the perovskite layer, achieving the sufficiency and uniformity of the reaction of the skeleton layer with the cation solution, and thus the crystallization effect of the perovskite layer with a crystal face orientation of (001) is better, which is more conducive to the vertical transport of photo-generated carriers, has a stronger ability to transport carriers, and thus improves the crystallinity of the perovskite layer.

[0113] Test Data 3:

[0114] Test method: the laser light source of the photoluminescence instrument was injected into the solar cells containing the perovskite layer and not subjected to the post-processing step of Example 1 and Comparative Example 2, respectively, and the photoluminescence test data was measured.

[0115] Table 2 Photoluminescence test data of the perovskite layer

[0116]

[0117] As shown in the figure, Figure 6 , Figure 7 , Figure 6The photoluminescence test diagram of the perovskite layer provided by Example One of the present application; Figure 7 The photoluminescence test diagram of the perovskite layer provided by Comparative Example Two of the present application, which is tested in the lower right, middle and upper left regions of the perovskite layer, respectively, wherein the peak height of the three regions of Example One is close and the peak position is 748 nm, 747 nm and 747 nm, the peak height of the three regions of Comparative Example Two is quite different and the peak position is 756 nm, 752 nm and 749 nm, and the ratio of the peak intensity of any two peaks of the three peaks of the upper left, middle and lower right is higher than that of Example One, which indicates that the composition uniformity of the perovskite layer of Example One is higher and the film quality is better, because the additive of the present application effectively promotes the diffusion of the cation solution to the bottom of the lead iodide framework layer, ensures the uniformity of the distribution of the cation solution, and because the polymer formed by the crosslinking of the olefin in the additive during the annealing process, the polymer acts as a barrier layer for ion migration, reduces the migration rate of the cation solution, and is conducive to improving the sufficiency of the reaction of the cation solution with the framework layer, thereby improving the crystalline quality of the perovskite layer and realizing the uniformity of the crystalline quality of each region of the perovskite layer.

[0118] Test data four:

[0119] The solar cells prepared in Examples One to Six and Comparative Examples One to Four were subjected to the following relevant tests:

[0120] The solar cell provided by the present application was subjected to performance tests such as open-circuit voltage, short-circuit current and fill factor using a halm test sorting device, which is a device for simulating sunlight, and is equipped with electronic load, data acquisition and calculation devices, etc., for testing the electrical performance of photovoltaic devices (including solar cells, such as Eta, Voc, Jsc, FF, etc., which are used to reflect the performance of solar cells. The silicon wafer of the solar cell controlled for testing is 1.07 cm 2 , the calibrated light intensity is 1000±50 W / m 2 , and the experimental test results are as follows, wherein Voc represents open-circuit voltage, Jsc represents short-circuit current density, FF represents fill factor, and Eta represents photoelectric conversion efficiency. The experimental test results are shown in Table 3.

[0121] Table 3 Performance test results of solar cells

[0122]

[0123]

[0124] From the data of Example 1 to Example 5 and Comparative Example 1, it can be seen that the photoelectric conversion efficiency of the examples is better than that of Comparative Example 1, because the additive is added in the preparation process of the examples, the functional groups of the additive can passivate the defects of the perovskite layer, and can also promote the diffusion of the cations into the interior of the framework layer, so that the cation solution and the lead iodide framework layer can fully react, thereby improving the crystallization quality and stability of the perovskite layer, and improving the photoelectric conversion efficiency of the solar cell.

[0125] From the data of Example 1, Example 5 and Comparative Example 2, it can be seen that the photoelectric conversion efficiency of the examples is better than that of Comparative Example 2, because the molecular weight of the additive of Example 1 and Example 5 is small, so the additive can promote the reaction of the cation solution and the framework layer, and the radius of gyration of the polymer formed after crosslinking of the additive is small, which is helpful for releasing residual stress and inhibiting ion migration, thereby improving the photoelectric conversion efficiency of the solar cell.

[0126] From the data of Example 1 to Example 4 and Comparative Example 3, Comparative Example 4, it can be seen that the data of the examples is better than that of Comparative Example 3, because the content of the additive of the examples is low, and the molecular weight of the polymer obtained after crosslinking is small, so it is helpful to release residual stress and inhibit ion migration, thereby improving the crystallization quality and stability of the perovskite layer; the data of the examples is better than that of Comparative Example 4, because the concentration of the additive of the examples is high, so the additive can fully participate in the crystallization growth process of the perovskite layer, can effectively passivate defects and improve the completeness of the reaction, thereby improving the photoelectric conversion efficiency of the solar cell.

[0127] The above has introduced in detail a solar cell and a preparation method thereof and a photovoltaic module disclosed in the embodiments of the present application, and the principles and implementation manners of the present application have been described by applying specific examples. The above description of the embodiments is only for helping to understand the technical solutions of the present application and the core ideas thereof. Meanwhile, for those skilled in the art, according to the ideas of the present application, the specific implementation manners and application ranges can be changed, and the above description of the present application should not be understood as limiting the present application.

Claims

1. A method for producing a solar cell, characterized by, The preparation method of the solar cell comprises the following steps: a lead halide skeleton layer is prepared on a substrate; A cation solution with an additive is coated on the lead halide skeleton layer, and a perovskite layer is obtained by annealing; wherein the structure of the additive is wherein R1and R5are each independently selected from -CH=CH2, R2and R4are each independently selected from a carbonyl group, R3comprises -(CF2)2or -(CF2)3, and the molecular radius of the additive is The molar concentration of the additive in the cation solution is 1 mol / mL to 15 mol / mL. post-treatment is performed to obtain the solar cell.

2. The method for producing a solar cell according to claim 1, wherein The additive comprises 2,2,3,3,4,4-hexafluoro-1,5-dipentyl acrylate or 2,2,3,3-tetrafluoro-1,4-butyl butyl acrylate.

3. The method of claim 1, wherein the step of forming the first and second electrodes is performed by a method selected from the group consisting of sputtering, vacuum deposition, and plating. The cationic solution comprises methylformamidinium iodide and methylformamidinium bromide, and the sum of the molar concentrations of the methylformamidinium iodide and the methylformamidinium bromide in the cationic solution is 0.6 mol / L to 0.7 mol / L.

4. The method for manufacturing a solar cell according to claim 1, wherein The thickness of the lead halide skeleton layer is 300 nm to 500 nm, and the thickness of the perovskite layer is 450 nm to 650 nm.

5. The method of producing a solar cell according to any one of claims 1 to 4, characterized in that, In the annealing step, the annealing temperature is 150 DEG C to 170 DEG C, and the annealing time is 15 min to 20 min.

6. A solar cell, characterized in that, The preparation method of the solar cell according to any one of claims 1 to 5. In the perovskite layer, the ratio of the peak intensity of the characteristic diffraction peak of the residual lead halide to the characteristic diffraction peak of the 001 crystal face is 0.17 to 0.

25.

7. The solar cell according to claim 6, characterized in that The substrate has a pyramid texture structure, the perovskite layer is consistent with the texture structure of the substrate, the base side length of the pyramid texture structure of the perovskite layer is 3 μm to 6 μm, and the height of the pyramid texture structure of the perovskite layer is 4 μm to 7 μm.

8. The solar cell according to claim 6, characterized in that, The solar cell is a stacked cell, the substrate comprises a bottom cell, an electron-hole recombination layer arranged on the bottom cell, and a first transport layer, the perovskite layer is arranged on a side of the first transport layer away from the electron-hole recombination layer, the solar cell further comprises a second transport layer arranged on a side of the perovskite layer away from the first transport layer, a transparent conductive layer, a first electrode and a second electrode, the first electrode is in ohmic contact with the transparent conductive layer, and the second electrode is in ohmic contact with the bottom cell, wherein one of the first transport layer and the second transport layer is an electron transport layer, and the other is a hole transport layer, one of the first electrode and the second electrode is a positive electrode, and the other is a negative electrode.

9. The solar cell according to claim 6, characterized in that, Alternatively, the solar cell is a single-junction cell, the substrate comprises a transparent conductive substrate and a first transport layer arranged on the transparent conductive substrate, the perovskite layer is arranged on a side of the first transport layer away from the electron-hole recombination layer, and the solar cell further comprises a second transport layer arranged on a side of the perovskite layer away from the first transport layer, a first electrode and a second electrode, the first electrode is in ohmic contact with the second transport layer, and the second electrode is in ohmic contact with the transparent conductive substrate, wherein one of the first transport layer and the second transport layer is an electron transport layer, and the other is a hole transport layer, one of the first electrode and the second electrode is a positive electrode, and the other is a negative electrode. The hole transport layer is a nickel oxide layer; and / or 10. The solar cell according to claim 9, characterized in that, The thickness of the hole transport layer is 20 nm to 30 nm; and / or The thickness of the electron transport layer is 15 nm to 20 nm; and / or The electron transport layer is C 60 layer; and / or, The transparent conductive layer is an indium zinc oxide layer; and / or The transparent conductive layer is an indium zinc oxide layer; and / or, The thickness of the transparent conductive layer is 70-140 nm; and / or, The positive electrode and / or the negative electrode is silver, and the thickness of the positive electrode and / or the negative electrode is 300-350 nm.

11. The solar cell according to claim 9, characterized in that, When the solar cell is a laminated cell, the solar cell further comprises a buried bottom modification layer, which is arranged on the first transport layer and away from the side of the electron-hole recombination; and / or, The solar cell further comprises a buffer layer, which is arranged on the surface of the second transport layer and away from the side of the perovskite layer, and the thickness of the buffer layer is 20-50 nm.

12. A photovoltaic module, characterized by, The solar cell prepared by the preparation method of the solar cell according to any one of claims 1-5, or the solar cell according to any one of claims 6-11.

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