Solar cell, preparation method thereof and photovoltaic module

Abstract

The invention provides a solar cell and a preparation method thereof, and a photovoltaic module, the solar cell comprises a substrate, and a hole transport layer, a hole modification layer and a perovskite layer which are sequentially arranged on the substrate, and the hole modification layer is located between the hole transport layer and the perovskite layer; the hole modification layer comprises a self-assembled monomolecular layer material, and the self-assembled monomolecular layer material comprises at least one of [bis (5-ethyl phosphate)-bis (imidazoline ethyl) phosphonic acid and an isomer thereof. According to the invention, the photoelectric conversion efficiency and other performances of the perovskite solar cell can be greatly improved.

Description

TECHNICAL FIELD

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

[0002] The perovskite solar cell is a device for converting solar energy into electrical energy, which has good photoelectric characteristics, and simple device structure and low manufacturing cost.

[0003] In the perovskite solar cell, the hole transport layer plays an important role in the photoelectric conversion performance of the solar cell. The hole modification layer is a thin film containing self-assembled monolayer material, which can improve the performance of the hole transport layer. How to further improve the photoelectric conversion efficiency of the perovskite solar cell by improving the hole modification layer has become a technical problem to be solved. SUMMARY

[0004] In order to solve the above technical problems, the present application discloses a solar cell, a preparation method thereof and a photovoltaic module, so as to improve the photoelectric conversion efficiency of the perovskite solar cell.

[0005] In a first aspect, the present application provides a solar cell, comprising a substrate and a hole transport layer, a hole modification layer and a perovskite layer sequentially arranged on the substrate, wherein the hole modification layer is located between the hole transport layer and the perovskite layer.

[0006] The hole modification layer comprises a self-assembled monolayer material, and the self-assembled monolayer material comprises at least one of [bis(5-ethylphosphonic acid)-bisimidazoline ethyl] phosphonic acid and its isomers.

[0007] In some embodiments of the present application, the [bis(5-ethylphosphonic acid)-bisimidazoline ethyl] phosphonic acid and its isomers comprise:

[0008]

[0009]

[0010] In some embodiments of the present application, the self-assembled monolayer material has an imidazoline group at one end away from the hole transport layer, and the nitrogen element in the imidazoline group is covalently coordinated with defects in the perovskite layer.

[0011] In some embodiments of the present application, the solar cell comprises a perovskite tandem solar cell, the substrate comprises a bottom cell and a composite layer stacked on the bottom cell, the hole transport layer, the hole modification layer and the perovskite layer are sequentially stacked on the composite layer, and the surface of one side of the composite layer facing the hole transport layer has a textured structure.

[0012] In some embodiments of the present application, an electron transport layer, a buffer layer, a first transparent electrode layer and an anti-reflection layer are further sequentially stacked on the perovskite layer.

[0013] In some embodiments of the present application, the photoelectric conversion efficiency of the solar cell is 30% to 32%.

[0014] In a second aspect, the present application provides a preparation method of the solar cell according to the first aspect, comprising the following steps:

[0015] providing a substrate, and preparing a hole transport layer on the surface of the composite layer of the substrate, wherein the hole transport layer comprises nickel oxide;

[0016] applying a first solution on the surface of the hole transport layer to form the hole modification layer, wherein the first solution comprises a self-assembled monolayer material selected from at least one of [bis(5-ethylphosphonic acid)-bisimidazoline ethyl] phosphonic acid and its isomers;

[0017] sequentially preparing other functional layers on the surface of the hole modification layer, wherein the other functional layers at least comprise a perovskite layer, an electron transport layer and a first transparent electrode layer.

[0018] In some embodiments of the present application, the concentration of the self-assembled monolayer material in the first solution is 0.5 mg / mL to 1.5 mg / mL.

[0019] In some embodiments of the present application, the preparation process of the hole modification layer is as follows:

[0020] applying the first solution on the surface of the hole transport layer by spin coating, and obtaining the hole modification layer after annealing, wherein the spin coating acceleration is 1500 rpm / s to 2500 rpm / s, the spin coating rotation speed is 3500 rpm to 4000 rpm, the spin coating time is 25 s to 35 s, the annealing temperature is 90°C to 110°C, the annealing time is 8 min to 12 min, and the annealing relative humidity is 4% to 6%.

[0021] In some embodiments of the present application, the preparation method further comprises:

[0022] sequentially preparing a perovskite layer, a passivation layer, an electron transport layer, a buffer layer, a first transparent electrode layer and an anti-reflection layer on the surface of the hole modification layer.

[0023] In a third aspect, the present application provides a photovoltaic module, wherein the photovoltaic module comprises the solar cell according to the first aspect, or the photovoltaic module comprises the solar cell prepared by the preparation method according to the second aspect.

[0024] Compared with the prior art, this application has at least the following beneficial effects:

[0025] This application provides a solar cell and its preparation method, as well as a photovoltaic module. The hole-modifying layer of the solar cell includes a self-assembled monolayer (SAM) material. The SAM material includes at least one of [bis(5-ethylphosphono)-bisimidazoline ethyl]phosphonic acid and its isomers. Compared to existing 2PACz-type SAM materials, the SAM material of this application has more anchoring groups in its molecular structure, which can significantly enhance the interaction with NiO in the hole transport layer. X The surface anchoring effect; and, the SAM material of this application, when separated from NiO... X One end of the material has an imidazoline group structure, in which the nitrogen element carries a lone pair of electrons, enabling covalent bonding with defects in the perovskite layer. This passivates the perovskite layer defects, thereby improving the crystallinity of the perovskite layer. Furthermore, the SAM material of this application possesses a bisymmetric structure, specifically a pair of spatially symmetrical imidazoline-polyethyl phosphate groups. This bisymmetric structure allows for dual-site bonding, simultaneously enhancing both the modification effect on the hole transport layer and the passivation effect on perovskite layer defects. In summary, the SAM material of this application simultaneously modifies the hole transport layer and passivates the perovskite layer, improving non-radiative recombination at the interface and reducing the open-circuit voltage (V0) of the device. OC This reduces losses and significantly improves the photoelectric conversion efficiency and other performance characteristics of perovskite solar cells. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the structure of a solar cell in one embodiment of this application;

[0028] Figure 2 This is a schematic diagram of the structure of a solar cell in another embodiment of this application;

[0029] Figure 3a X-ray photoelectron spectroscopy (XPS) image of 2PACz material before rinsing with ethanol solution;

[0030] Figure 3b XPS images of 2PACz material after rinsing with ethanol solution;

[0031] Figure 4aThis is an XPS image of compound (I) of this application before rinsing with ethanol solution;

[0032] Figure 4b This is an XPS image of compound (I) of this application after rinsing with ethanol solution.

[0033] Explanation of reference numerals in the attached figures: 1-substrate, 2-hole transport layer, 3-hole modification layer, 4-perovskite layer, 6-buffer layer, 7-first transparent electrode layer, 8-antireflection layer, 10-bottom cell, 11-second transparent electrode layer, 12-P-type doped crystalline silicon layer, 13-first intrinsic amorphous silicon layer, 14-N-type silicon wafer, 15-second intrinsic amorphous silicon layer, 16-N-type doped crystalline silicon layer, 17-composite layer, 21-positive electrode, 22-back electrode, 51-passivation layer, 52-electron transport layer. Detailed Implementation

[0034] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0035] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0036] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0037] Furthermore, the terms "installation," "setup," "equipped with," "connection," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0038] Furthermore, the terms "first," "second," etc., are primarily used to distinguish different devices, elements, or components (which may be the same or different in specific type and construction), and are not intended to indicate or imply the relative importance or quantity of the indicated devices, elements, or components. Unless otherwise stated, "a plurality of" means two or more.

[0039] The technical solution of this application will be further described below with reference to the embodiments and accompanying drawings.

[0040] Currently, common hole-modifying materials are mostly SAM materials, such as 2PACz, MeO-2PACz, and MeO-4PACz. The general structural formula of these SAM materials is mostly R1-N-R2-H2PO3, in which the -P-OH in the phosphate group interacts with NiO. X Hydrogen bonds form between Ni and O on the surface. Although the aforementioned SAM material can form hydrogen bonds with NiO in the hole transport layer... X The surface is anchored to the hole transport layer via hydrogen bonds. However, since each molecule of the aforementioned SAM contains only one -H2PO3 group, its anchoring effect on the hole transport layer is limited, thus limiting its modification effect on the hole transport layer. Furthermore, this type of material cannot passivate the perovskite layer, restricting further improvements in the performance of perovskite solar cells.

[0041] In view of this, firstly, this application provides a solar cell, such as Figure 1 As shown, the solar cell includes a substrate 1 and a hole transport layer 2, a hole modification layer 3, and a perovskite layer 4 sequentially disposed on the substrate 1. The hole modification layer 3 is located between the hole transport layer 2 and the perovskite layer 4. The hole modification layer 3 includes a SAM material, which includes at least one of [bis(5-ethylphosphono)-bisimidazoline ethyl]phosphonic acid and its isomers.

[0042] The SAM material of this application, namely [bis(5-ethylphosphono)-bisimidazoline ethyl]phosphonic acid and its isomers, has more anchoring groups -H2PO3 in its molecular structure, which can significantly enhance the interaction with NiO in the hole transport layer. X The surface anchoring effect. Furthermore, the inventors unexpectedly discovered that the SAM material of this application can also passivate the perovskite layer above the hole modification layer. This may be because the SAM material of this application, when moving away from NiO... XOne end of the material has an imidazoline group, in which the nitrogen element carries a lone pair of electrons. This allows it to covalently coordinate with defects in the perovskite layer, passivating these defects and improving the crystallinity of the perovskite layer. Furthermore, the SAM material of this application possesses a bisymmetric structure, specifically a pair of spatially symmetrical imidazoline-polyethyl phosphate groups. This bisymmetric structure enables dual-site bonding, simultaneously enhancing both the modification effect on the hole transport layer and the passivation effect on perovskite layer defects. In summary, the SAM material of this application simultaneously modifies the hole transport layer and passivates the perovskite layer, reducing the device's Vt. OC This reduces losses and significantly improves the photoelectric conversion efficiency and other performance characteristics of perovskite solar cells.

[0043] In one alternative embodiment, [bis(5-ethylphosphate)-bisimidazoline ethyl]phosphonic acid and its isomers include:

[0044]

[0045] The SAM material of this application includes at least one of the compounds shown in formula (I), formula (II), and formula (III) above, and has a bisymmetric structure, which can simultaneously modify the hole transport layer and passivate the perovskite layer.

[0046] In one optional embodiment, the SAM material of this application has an imidazoline group at the end facing away from the hole transport layer, and the nitrogen element in the imidazoline group covalently coordinates with defects in the perovskite layer. During the formation of the hole modification layer, the end of the SAM material having the polyethyl phosphate structure spontaneously faces the hole transport layer, and the end having the imidazoline group spontaneously faces the perovskite layer. The lone pairs of electrons in the nitrogen element of the imidazoline group covalently coordinate with defects in the perovskite layer, thereby passivating the defects in the perovskite layer.

[0047] In one alternative implementation, refer to Figure 1 The solar cell includes a perovskite tandem solar cell. The substrate 1 includes a base cell 10 and a composite layer 17 stacked on the base cell 10. A hole transport layer 2, a hole modification layer 3, and a perovskite layer 4 are sequentially stacked on the composite layer 17, and the surface of the composite layer 17 facing the hole transport layer 2 has a textured surface. The base cell 10, from bottom to top, includes a second transparent electrode layer 11, a P-type doped crystalline silicon layer 12, a first intrinsic amorphous silicon layer 13, an N-type silicon wafer 14, a second intrinsic amorphous silicon layer 15, and an N-type doped crystalline silicon layer 16. Furthermore, a passivation layer 51, an electron transport layer 52, and a first transparent electrode layer 7 are sequentially stacked on the perovskite layer 4.

[0048] The substrate of this application can be a solar cell based on a crystalline silicon substrate, and this application is not limited thereto. To better absorb solar energy, the composite layer of this application has a textured structure on the surface facing the hole transport layer (i.e., the light incident surface). For example, this textured structure can be a pyramid-shaped textured structure. This textured structure provides a higher surface area for the solar cell while reducing light reflection and diffusion. The surface of the hole transport layer and the textured structure of the composite layer have the same shape, both being pyramid-shaped, thus achieving the shape retention requirement of the textured structure. This application does not particularly limit the preparation method of the textured structure, as long as it achieves the purpose of this application; for example, it can be prepared using existing magnetron sputtering methods.

[0049] In one alternative implementation, such as Figure 2 As shown, a passivation layer 51, an electron transport layer 52, a buffer layer 6, a first transparent electrode layer 7, and an antireflection layer 8 are sequentially stacked on the perovskite layer 4. The buffer layer 6 is located on the surface of the electron transport layer 52 opposite to the perovskite layer 4 (i.e., the light incident surface), and the antireflection layer 8 is located on the surface of the first transparent electrode layer 7 opposite to the buffer layer 6. Solar cells incorporating the aforementioned antireflection layer exhibit higher photoelectric conversion efficiency.

[0050] This application does not impose any particular restrictions on the electrodes of the solar cell, as long as they achieve the purpose of this application. For example, see reference... Figure 1 and Figure 2 A positive electrode 21 can be set on the light-receiving surface of the solar cell, and a back electrode 22 can be set on the back surface of the solar cell.

[0051] The hole modification layer, hole transport layer, perovskite layer, and electron transport layer of this application can also be applied to single-junction perovskite solar cells. This application does not impose any particular restrictions on the structure of single-junction perovskite solar cells; any existing single-junction perovskite solar cell structure can be used.

[0052] In one optional embodiment, the photoelectric conversion efficiency of the solar cell of this application is 30% to 32%. Compared with existing perovskite solar cells based on SAM materials, the photoelectric conversion efficiency of the solar cell of this application is significantly improved.

[0053] Secondly, this application provides a method for fabricating a solar cell as described in the first aspect, comprising the following steps:

[0054] Step A: Provide a substrate and prepare a hole transport layer on the surface of the composite layer of the substrate, the hole transport layer including nickel oxide;

[0055] Step B: The first solution is coated on the surface of the hole transport layer to form a hole modification layer. The first solution contains a self-assembled monolayer material selected from at least one of [di(5-ethylphosphono)-bisimidazolinoethyl]phosphonic acid and its isomers.

[0056] Step C: Sequentially prepare other functional layers on the surface of the hole-modified layer. The other functional layers include at least a perovskite layer, an electron transport layer, and a first transparent electrode layer.

[0057] In step A, the hole transport layer material can be deposited on the surface of the composite layer of the substrate using magnetron sputtering. Specifically, the process can involve using NiO with a content of 99.99%. x A rotating target is used, with a process pressure of 0.50 Pa to 0.52 Pa and a process atmosphere of Ar:O2 = 700:0 to 700:5 (gas flow rate in sccm). The carrier plate reciprocates 2 to 4 times to obtain NiO with a thickness of 20 nm to 25 nm. x The membrane layer serves as a hole transport layer.

[0058] In step B, the solvent for the first solution can be isopropanol or ethanol. To ensure more complete dissolution of the SAM material, the first solution can also be ultrasonically dispersed at 55℃~65℃ for 1h~2h. Furthermore, this application can employ spin coating, blade coating, spraying, slot coating, etc., to prepare the cavity modification layer; there are no particular limitations.

[0059] In step C, other functional layers may also include passivation layers, buffer layers, and antireflection layers.

[0060] In one optional embodiment, the concentration of the self-assembled monolayer material in the first solution is 0.5 mg / mL to 1.5 mg / mL, preferably 0.8 mg / mL to 1.2 mg / mL. The first solution of this application contains SAM material within the above concentration range, resulting in a hole-modified layer with better modification effect on the hole transport layer and passivation effect on the perovskite layer.

[0061] In one optional embodiment, the preparation process of the hole-modified layer includes:

[0062] The first solution was spin-coated onto the surface of the hole transport layer, and after annealing, a hole-modified layer was obtained. The spin-coating acceleration was 1500 rpm / s to 2500 rpm / s, the spin-coating speed was 3500 rpm to 4000 rpm, the spin-coating time was 25 s to 35 s, the annealing temperature was 90℃ to 110℃, the annealing time was 8 min to 12 min, and the relative humidity during annealing was 4% to 6%. By adjusting the spin-coating acceleration, spin-coating speed, spin-coating time, annealing temperature, and annealing time within the above ranges, the hole-modified layer exhibited better modification effects on the hole transport layer and passivation effects on the perovskite layer.

[0063] In one optional embodiment, the preparation method further includes:

[0064] A perovskite layer, a passivation layer, an electron transport layer, a buffer layer, a first transparent electrode layer, and an antireflection layer are then prepared on the surface of the hole-modified layer.

[0065] In preparing the perovskite layer, a framework layer can be prepared first, and then an organic salt solution can be spin-coated onto the surface of the framework layer. After thermal annealing, the perovskite layer is obtained. The framework layer can be obtained by vapor deposition of PbI2 and CsX (where X represents a halogen element). This application does not particularly limit the type of organic salt. For example, at least two of formamidine hydroiodide (FAI), formamidine hydrobromide (FABr), formamidine hydrochloride (FACl), methylamine iodide (MAI), methylamine bromide (MABr), and methylamine chloride (MACl) can be dissolved in a solvent to obtain an organic salt solution. This application does not particularly limit the coating method. For example, spin coating, spray coating, slot coating, and blade coating can be used. The thickness of the perovskite layer is 400 nm to 500 nm.

[0066] This application does not impose any particular limitations on the fabrication methods of the electron transport layer, buffer layer, first transparent electrode layer, antireflection layer, and electrodes. For example, the electron transport layer material C can be used. 60 An electron transport layer with a thickness of 10 nm to 20 nm can be obtained by thermal evaporation deposition using a metal evaporation device; a buffer layer with a thickness of 10 nm to 17 nm can be prepared using an atomic layer deposition (ALD) device using SnO2 as the buffer layer material; a first transparent electrode layer with a thickness of 70 nm to 110 nm can be prepared using indium gallium zinc oxide (IZO) as the transparent electrode layer material using a magnetron sputtering (PVD) device; an antireflection layer with a thickness of 80 nm to 130 nm can be obtained by thermal evaporation deposition using LiF or MgF2 as the antireflection layer material using a metal evaporation device; and positive and back electrodes with an electrode thickness of 300 nm to 500 nm can be obtained by thermal evaporation deposition using Ag as the electrode material using a metal evaporation device.

[0067] The solar cell fabrication method provided in this application incorporates the SAM material of this application into the hole modification layer, which can simultaneously modify the hole transport layer and passivate the perovskite layer, thereby significantly improving the photoelectric conversion efficiency and other performance characteristics of the perovskite solar cell. Furthermore, the fabrication method of this application has the advantages of simple fabrication process and convenient operation, which is conducive to industrial production and suitable for large-scale manufacturing of perovskite-silicon tandem solar cells.

[0068] Thirdly, this application provides a photovoltaic module, which includes a solar cell as described in the first aspect, or the photovoltaic module includes a solar cell prepared by the preparation method described in the second aspect.

[0069] This application also provides a photovoltaic module for converting received light energy into electrical energy and transmitting it to an external load. The photovoltaic module includes: at least one cell string, which is composed of multiple solar cells connected together; an encapsulating film for covering the surface of the cell string; and a cover plate for covering the surface of the encapsulating film facing away from the cell string.

[0070] The solar cells, their fabrication methods, and photovoltaic modules of this application will be further described below with reference to more specific embodiments.

[0071] Synthesis example 1

[0072] A method for preparing a compound of formula (Ⅰ-1), the reaction formula of which is as follows:

[0073]

[0074]

[0075] The reaction specifically includes the following steps:

[0076] S1. Weigh out 2 mmol (0.818 g) of di(bromoethane) symmetrical bisimidazoline, i.e., compound a, and dissolve it in 10 mL of dibromoethane, 0.5 mmol (0.16 g) of tetrabutylammonium bromide, and 20 mmol (1.1 mL) of 50% KOH aqueous solution to obtain a mixture. Then heat the mixture to 70 °C and stir for 12 h to carry out the reaction. After the reaction is completed, extract the reaction product with dichloromethane (DCM), dry the organic layer on anhydrous Na2SO4, and remove the solvent under reduced pressure to obtain the crude product. The crude product is purified by column chromatography (PE:DCM = 1:1 v / v) to obtain white crystalline compound b.

[0077] S2. Compound b (1.5 mmol, 0.894 g) was dissolved in triethyl phosphite (10 mL, 52.49 mmol), heated overnight at 140 °C, and then the solvent was removed under reduced pressure to obtain the crude product. The crude product was purified by column chromatography (DCM:EtOAc = 1:2 v / v) to obtain a pale yellow resin. The pale yellow resin was dissolved in anhydrous 1,4-dioxane (15 mL), and bromotrimethylsilane (11 mmol, 1.5 mL) was added dropwise under an argon atmosphere. The reaction was stirred at 25 °C under argon atmosphere for 22 h, and methanol (2 mL) was added. The stirring was continued for 3 h. Finally, distilled water (15 mL) was added dropwise until the solution became opaque. The mixture was stirred for 2 hours, filtered, washed with pure water, and recrystallized in a mixture of tetrahydrofuran (THF) and DCM (THF to DCM volume ratio 2:1) to obtain 0.40 g (57.7%) of white powder, which is product c: [bis(5-ethylphosphono)-bisimidazoline ethyl]phosphonic acid.

[0078] Synthesis example 2

[0079] The difference from Synthesis Example 1 is that compound a is replaced with di(bromoethane) symmetrical bis(3-imidazoline), i.e., compound a', and the resulting compound c is the compound shown in formula (II).

[0080] The structural formula of compound a' is as follows:

[0081]

[0082] Synthesis example 3

[0083] The difference from Synthesis Example 1 is that compound a is replaced with di(bromoethane) symmetrical bis(4-imidazoline), i.e., compound a”, and the resulting compound c is the compound shown in formula (Ⅲ).

[0084] The structural formula of compound a” is as follows:

[0085]

[0086] Example 1

[0087] <Substrate Preparation>

[0088] A textured base cell is provided, and a 20 nm thick indium tin oxide (ITO) film is prepared on the light-receiving surface of the base cell as a composite layer to obtain the substrate. The base cell, from bottom to top, comprises a second transparent electrode layer with a thickness of 100 nm, a P-type doped crystalline silicon layer with a thickness of 10 nm, a first intrinsic amorphous silicon layer with a thickness of 7 nm, an N-type silicon wafer with a thickness of 120 μm, a second intrinsic amorphous silicon layer with a thickness of 7 nm, and an N-type doped crystalline silicon layer with a thickness of 6 nm.

[0089] <Preparation of Hole Transport Layer>

[0090] The substrate was heated at 150°C for 15 minutes on a heating stage to activate it. Then, the substrate was placed on a carrier plate of a magnetron sputtering apparatus, and a 20 nm thick NiO layer was deposited on the surface of the ITO composite layer. X Hole transport layer.

[0091] <Preparation of Hole-Modified Layer>

[0092] The compound of formula (I) obtained in Synthesis Example 1 was dissolved in ethanol and ultrasonically dispersed at 60°C for 2 h to obtain a first solution with a SAM material concentration of 0.5 mg / mL. Then, 100 μL of the first solution was pipetted onto the surface of the hole transport layer. The spin coating acceleration was 2000 rpm / s, the spin coating speed was 4000 rpm, and the spin coating time was 30 s. The solution was then annealed at 100°C for 10 min at a relative humidity of 5% to obtain the hole-modified layer. Since the hole-modified layer is a monolayer, its thickness was not measured.

[0093] <Preparation of Perovskite Layer>

[0094] A semi-finished solar cell with a hole-modified layer was placed in an organic-inorganic multi-source evaporation equipment. PbI2 and CsBr were co-evaporated at a rate of 10:1, and the resulting substrate layer was obtained after thermal evaporation. 300 mg of organic salt FAI, 70 mg of MABr, and 40 mg of MACl were dissolved in 5 mL of ethanol to obtain a cationic solution. 100 μL of the cationic solution was then spin-coated onto the surface of the substrate layer using a pipette. The spin-coating process parameters were as follows: spin-coating atmosphere of 5% RH (air humidity), spin-coating speed of 4000 rpm, acceleration of 4000 rpm / s, spin-coating time of 30 s, followed by annealing at 135 °C for 30 min. After the organic salt cationic solution reacted fully with the substrate layer, a perovskite layer with a thickness of 450 nm was obtained.

[0095] <Preparation of other functional layers>

[0096] The semi-finished solar cell with a perovskite layer was placed in a metal evaporation device, and 200 mg of LiF and 200 mg of C were weighed out respectively. 60 Inside the first metal evaporation boat and the second metal evaporation boat, respectively, with The LiF film with a thickness of 1 nm and a C film with a thickness of 25 nm were obtained by sequential evaporation deposition. 60 The LiF film serves as a passivation layer, and C... 60The film layer serves as an electron transport layer. Then, the semi-finished solar cell is placed in an ALD device for chemical deposition of SnO2 at a process temperature of 80℃ for 40 minutes, resulting in a SnO2 film layer with a thickness of 17nm, which serves as a buffer layer. The semi-finished solar cell is then placed in a PVD device for magnetron sputtering, resulting in an IZO film layer with a thickness of 100nm, which serves as the first transparent electrode layer.

[0097] <Preparation of Electrodes and Antireflective Layers>

[0098] A 350 nm thick silver layer was prepared on the first transparent electrode layer by thermal evaporation as the positive electrode, and a 300 nm thick silver layer was prepared on the second transparent electrode layer of the bottom cell by thermal evaporation as the back electrode. Then, LiF was thermally evaporated and deposited through a metal evaporation device to obtain an anti-reflection layer with a thickness of 100 nm.

[0099] Examples 2 to 5

[0100] Except for adjusting the concentration of compound (SAM material) of formula (Ⅰ) in the first solution according to Table 1 in the <Preparation of Hole Modification Layer>, the rest is the same as in Example 1.

[0101] Examples 6 to 15

[0102] Except for adjusting the type of SAM material and the concentration of SAM material in the first solution according to Table 1 in the <Preparation of Hole Modification Layer>, the rest is the same as in Example 1.

[0103] Examples 16-17

[0104] Except for adjusting the relevant preparation parameters according to Table 2 in the <Preparation of Hole Modification Layer>, the rest is the same as in Example 1.

[0105] Comparative Example 1

[0106] Except for adjusting the type of SAM material according to Table 1 in the <Preparation of Hole Modification Layer>, the rest is the same as in Example 1.

[0107] Table 1. Preparation parameters of Examples 1-15 and Comparative Example 1

[0108]

[0109]

[0110] Table 2. Relevant preparation parameters for Examples 1, 16, and 17

[0111]

[0112] Performance testing:

[0113] Open-circuit voltage, short-circuit current, and fill factor tests:

[0114] The current (I)-voltage (V) of the solar cells in each embodiment and comparative example were measured using an IV tester (model: MX-MPVC-A20, manufacturer: Suzhou Maiwei Technology Co., Ltd.) to obtain the open-circuit voltage, short-circuit current and fill factor of the solar cells.

[0115] Photoelectric conversion efficiency test:

[0116] The current (I)-voltage (V) of the solar cells in each embodiment and comparative example were measured using an IV tester (model: MX-MPVC-A20, manufacturer: Suzhou Maiwei Technology Co., Ltd.) to obtain the photoelectric conversion efficiency (PCE) of the solar cells.

[0117] SAM material anchoring effect test:

[0118] A 20nm thick NiO layer was magnetron sputtered onto the surface of a transparent electronic-grade glass slide. X Thin films were then spin-coated onto NiO using the same process, with different SAM materials being applied. X A hole-modified layer with the corresponding SAM material is formed on the surface of the thin film. After annealing, each glass slide with the hole-modified layer is spin-coated with 100 μL of ethanol solution (99.99% by volume) at 4000 rpm. X-ray photoelectron spectroscopy (XPS) is used to test the glass slides before and after rinsing. By analyzing the change in the intensity of phosphorus before and after rinsing, the strength of the SAM material anchoring effect can be determined.

[0119] Table 3 Performance data of Examples 1 to 17 and Comparative Example 1

[0120]

[0121] Combining Tables 1 and 3, it can be seen from Examples 1, 6, and 10 and Comparative Example 1 that, compared with the solar cell made of 2PACz material in Comparative Example 1, the open-circuit voltage of the solar cell of this application is significantly improved, thereby increasing the photoelectric conversion efficiency by 0.83 percentage points.

[0122] Combining Tables 1 and 3, it can be seen from Examples 2 to 5, Examples 7 to 9, and Examples 11 to 15 that, based on the use of the SAM material of this application, by adjusting the concentration of the SAM material in the first solution within the range of this application, it is beneficial to obtain a solar cell with excellent photoelectric conversion efficiency.

[0123] The relevant process parameters in the preparation of the hole modification layer also usually affect the performance of the solar cell. As can be seen from Examples 1, 16 and 17, based on Tables 2 and 3, by adjusting the above preparation parameters within the range of this application, it is beneficial to obtain a solar cell with excellent photoelectric conversion efficiency.

[0124] Figure 3a XPS images of the existing 2PACz material before rinsing with ethanol solution; Figure 3b XPS images of existing 2PACz material after rinsing with ethanol solution; Figure 4a This is an XPS image of compound (I) of this application before rinsing with ethanol solution; Figure 4b This is an XPS image of compound (I) of this application after rinsing with ethanol solution.

[0125] from Figure 3a It can be seen that before rinsing, the maximum strength of the 2PACz material is approximately 1300, and the minimum is approximately 900, with a strength difference of about 400. Figure 3b It can be seen that after rinsing, the maximum strength of the 2PACz material is approximately 1300, and the minimum is approximately 1100, with a strength difference of about 200. The decrease in phosphorus strength compared to before rinsing is significant, indicating that the 2PACz material is more easily rinsed away and has a relatively weak anchoring effect. Figure 4a It can be seen that, before rinsing, the maximum strength of phosphorus in compound (I) of this application is approximately 1000, and the minimum strength is approximately 600, with a strength difference of approximately 400; from Figure 4b It can be seen that after rinsing, the maximum strength of phosphorus in compound (I) of this application is about 1000, the minimum strength is about 650, and the strength difference is about 250. The strength of phosphorus is not much reduced compared with that before rinsing, indicating that compound (I) is not easily washed away and has a stronger anchoring effect. Therefore, it has a better modification effect on the hole transport layer and is conducive to a significant improvement in the photoelectric conversion efficiency of solar cells.

[0126] The above provides a detailed description of a solar cell and its preparation method, as well as a photovoltaic module disclosed in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the technical solutions and core inventive points of the embodiments of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A solar cell, characterized in that, The invention includes a substrate and a hole transport layer, a hole modification layer, and a perovskite layer sequentially disposed on the substrate, wherein the hole modification layer is located between the hole transport layer and the perovskite layer. The hole-modified layer comprises a self-assembled monolayer material, which includes at least one of [bis(5-ethylphosphate)-bisimidazolinylethyl]phosphonic acid and its isomers.

2. The solar cell according to claim 1, characterized in that, The [bis(5-ethylphosphono)-bisimidazoline ethyl]phosphonic acid and its isomers include:

3. The solar cell according to claim 1, characterized in that, The self-assembled monolayer material has an imidazoline group at one end away from the hole transport layer, and the nitrogen element in the imidazoline group is covalently coordinated with the defects in the perovskite layer.

4. The solar cell according to any one of claims 1 to 3, characterized in that, The solar cell includes a perovskite tandem solar cell, and the substrate includes a base cell and a composite layer stacked on the base cell. The hole transport layer, the hole modification layer and the perovskite layer are stacked sequentially on the composite layer, and the surface of the composite layer facing the hole transport layer has a textured surface.

5. The solar cell according to claim 4, characterized in that, An electron transport layer, a buffer layer, a first transparent electrode layer, and an antireflection layer are also stacked sequentially on the perovskite layer.

6. The solar cell according to claim 1, characterized in that, The photoelectric conversion efficiency of the solar cell is 30% to 32%.

7. A method for preparing a solar cell according to any one of claims 1 to 6, characterized in that, Includes the following steps: A substrate is provided, and a hole transport layer is prepared on the surface of a composite layer of the substrate, the hole transport layer comprising nickel oxide; The first solution is coated on the surface of the hole transport layer to form the hole modification layer. The first solution contains a self-assembled monolayer material selected from at least one of [bis(5-ethylphosphono)-bisimidazoline ethyl]phosphonic acid and its isomers. Other functional layers are sequentially prepared on the surface of the hole-modified layer, and the other functional layers include at least a perovskite layer, an electron transport layer, and a first transparent electrode layer.

8. The preparation method according to claim 7, characterized in that, In the first solution, the concentration of the self-assembled monolayer material is 0.5 mg / mL to 1.5 mg / mL.

9. The preparation method according to claim 7, characterized in that, The preparation process of the hole-modified layer is as follows: The first solution was spin-coated onto the surface of the hole transport layer, and the hole-modified layer was obtained after annealing. The spin-coating acceleration was 1500 rpm / s to 2500 rpm / s, the spin-coating speed was 3500 rpm to 4000 rpm, the spin-coating time was 25 s to 35 s, the annealing temperature was 90 ℃ to 110 ℃, the annealing time was 8 min to 12 min, and the annealing relative humidity was 4% to 6%.

10. The preparation method according to any one of claims 7 to 9, characterized in that, The preparation method further includes: A perovskite layer, a passivation layer, an electron transport layer, a buffer layer, a first transparent electrode layer, and an antireflection layer are then prepared on the surface of the hole-modified layer.

11. A photovoltaic module, characterized in that, The photovoltaic module comprises the solar cell according to any one of claims 1 to 6, or the photovoltaic module comprises the solar cell prepared by the preparation method according to any one of claims 7 to 10.

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