Solar cell and preparation method thereof

Abstract

The invention discloses a solar cell and a preparation method thereof, and solves the problems of poor efficiency and stability of the solar cell in the prior art. The preparation method comprises the steps that a magnetron sputtering process is adopted, a first hole transport layer is prepared on a first preset substrate by utilizing a first process parameter, and the first preset substrate comprises a light active layer; adjusting process parameters of a magnetron sputtering process; a second hole transport layer is prepared on the side, away from the first preset substrate, of the first hole transport layer through a second technological parameter, the activation degree of the second hole transport layer is higher than that of the first hole transport layer, and the compactness of the first hole transport layer is higher than that of the second hole transport layer; the second process parameter is different from the first process parameter by oxygen content and sputtering power density; and preparing an electrode layer on one side, deviating from the first preset substrate, of the second hole transport layer to obtain the solar cell.

Description

Technical Field

[0001] This application relates to the field of solar cell technology, specifically to a solar cell and its fabrication method. Background Technology

[0002] Perovskite solar cells have become a research hotspot in the field of new energy due to their advantages such as high photoelectric conversion efficiency and low manufacturing cost. However, the efficiency and stability of perovskite solar cells in related technologies need to be improved. Summary of the Invention

[0003] In view of this, the present application provides a solar cell and a method for its fabrication, which solves the problem of poor efficiency and stability of solar cells in the prior art.

[0004] The first aspect of this application provides a method for fabricating a solar cell, comprising: fabricating a first hole transport layer on a first pre-embedded substrate using a magnetron sputtering process and employing first process parameters, the first pre-embedded substrate including a photoactive layer; adjusting the process parameters of the magnetron sputtering process; fabricating a second hole transport layer on the side of the first hole transport layer opposite to the first pre-embedded substrate using second process parameters, wherein the second hole transport layer has a higher degree of activation than the first hole transport layer, and the first hole transport layer has a higher density than the second hole transport layer, wherein the difference between the second process parameters and the first process parameters lies in the oxygen content and sputtering power density; and fabricating an electrode layer on the side of the second hole transport layer opposite to the first pre-embedded substrate to obtain a solar cell.

[0005] In conjunction with the first aspect, in some possible implementations, in the magnetron sputtering process for fabricating the first hole transport layer on the first pre-embedded substrate, the spacing between the target and the first pre-embedded substrate is 6-10 cm, and the vacuum degree of the magnetron sputtering chamber is <5×10⁻⁶. -4 Pa; A mixed atmosphere of argon, argon-hydrogen, and oxygen is introduced, with a process pressure of 0.2 Pa-1 Pa, an oxygen content of 2%-8%, and a sputtering power density of 5-10 W / cm². 2 .

[0006] In conjunction with the first aspect, among some possible implementations, adjusting the process parameters of the magnetron sputtering process includes: adjusting the oxygen content from 2%-8% to 10%-18%; and / or adjusting the sputtering power density from 5-10 W / cm³. 2 Adjust to 2-5W / cm 2 .

[0007] In conjunction with the first aspect, in some possible implementations, the target material in the magnetron sputtering process is a doped target material, wherein the doped target material is based on NiO and doped with Li and Mg, with the doping mass fraction of Li being 0.5-1.2% and the doping mass fraction of Mg being 0.3-0.8%.

[0008] In conjunction with the first aspect, in some possible implementations, after the second hole transport layer is prepared on the side of the first hole transport layer away from the first pre-embedded substrate, the preparation method further includes: performing vacuum annealing on the second hole transport layer and the first hole transport layer; before preparing the first hole transport layer on the side of the first pre-embedded substrate using magnetron sputtering, the preparation method further includes: purging and cleaning the surface of the first pre-embedded substrate with nitrogen gas at a flow rate of 8-12 L / min.

[0009] In conjunction with the first aspect, in some possible implementations, the thickness of the first hole transport layer is 25-55 nm, the thickness of the second hole transport layer is 5-25 nm, and the total film thickness of the first hole transport layer and the second hole transport layer is approximately 40-80 nm.

[0010] A second aspect of this application provides a method for fabricating a solar cell, comprising: fabricating a second hole transport layer on a second pre-embedded substrate using a magnetron sputtering process and second process parameters; adjusting the process parameters of the magnetron sputtering process; fabricating a first hole transport layer on the side of the second hole transport layer away from the second pre-embedded substrate using a first process parameter, wherein the second hole transport layer has a higher degree of activation than the first hole transport layer, and the first hole transport layer has a higher density than the second hole transport layer, wherein the difference between the second process parameter and the first process parameter lies in the oxygen content and the sputtering power density; and sequentially fabricating a photoactive layer and an electrode layer on the side of the first hole transport layer away from the second pre-embedded substrate to obtain a solar cell.

[0011] In conjunction with the second aspect, in some possible implementations, before fabricating the second hole transport layer on the second pre-embedded substrate using the magnetron sputtering process and the second process parameters, the fabrication method further includes: performing an ultrasonic cleaning process to clean the second pre-embedded substrate once and then drying it; and performing a plasma cleaning process to clean the dried second pre-embedded substrate a second time.

[0012] A third aspect of this application provides a solar cell, comprising: a substrate; a photoactive layer located on one side of the substrate; and a hole transport layer located on the side of the photoactive layer close to or away from the substrate. The hole transport layer includes a first hole transport layer and a second hole transport layer stacked in a direction perpendicular to the substrate. The first hole transport layer is located between the second hole transport layer and the photoactive layer. The second hole transport layer has a higher degree of activation than the first hole transport layer, and the first hole transport layer has a higher density than the second hole transport layer.

[0013] In conjunction with the third aspect, in some possible implementations, the thickness of the first hole transport layer is greater than the thickness of the second hole transport layer; the materials of the first hole transport layer and the second hole transport layer are the same.

[0014] According to the solar cell and its fabrication method provided in the embodiments of this application, a two-layer hole transport layer with gradients in density and activation degree, namely a first hole transport layer and a second hole transport layer, is prepared sequentially by adjusting sputtering parameters in stages. This optimizes both the charge extraction interface and the charge-selective contact interface without introducing an additional interface layer, avoiding performance contradictions associated with a single process parameter. Attached Figure Description

[0015] Figure 1 This is a schematic flowchart illustrating the method for fabricating a solar cell according to the first embodiment of this application.

[0016] Figures 2a-2d To execute Figure 1 A schematic diagram of the structure of the intermediate product obtained during the preparation method shown.

[0017] Figure 3 This is a schematic flowchart illustrating the method for fabricating a solar cell according to the second embodiment of this application.

[0018] Figure 4 This is a schematic flowchart illustrating the method for fabricating a solar cell according to the third embodiment of this application.

[0019] Figure 5 This is a schematic flowchart illustrating the method for fabricating a solar cell according to the fourth embodiment of this application.

[0020] Figure 6 To execute Figure 5 A schematic diagram of the cross-sectional structure of the solar cell prepared by the method shown.

[0021] Figure 7 Execution provided for another embodiment Figure 5 A schematic diagram of the cross-sectional structure of the solar cell prepared by the method shown.

[0022] Figure label: First pre-placed substrate 10; second pre-placed substrate 20; transparent conductive substrate 1; hole transport layer 30; first hole transport layer 2; second hole transport layer 3; photoactive layer 4; electron transport layer 5; electrode layer 6; transparent electrode 7; carrier exchange layer 8; crystalline silicon bottom cell 9. Detailed Implementation

[0023] Perovskite solar cells have become a research hotspot in the new energy field due to their high photoelectric conversion efficiency and low fabrication cost. The hole transport layer, as one of the core functional layers of a perovskite solar cell, primarily functions to extract holes from the photoactive layer and transport them to the electrode layer, while simultaneously preventing electrons from migrating in the reverse direction. Therefore, the performance of the hole transport layer directly determines the photoelectric conversion efficiency and long-term stability of the cell. Nickel oxide (NiO) xDue to its suitable conduction and valence band energy levels, good optical transparency, excellent chemical stability, and low cost, it is considered an ideal material for the hole transport layer of perovskite solar cells.

[0024] Currently, the main methods for preparing nickel oxide hole transport layers include sol-gel method, pulsed laser deposition method, and magnetron sputtering method. Among them, magnetron sputtering method has advantages such as controllable deposition rate, good film uniformity, high film quality, and ease of large-scale industrial production, and is widely used in the field of thin film preparation.

[0025] However, the inventors discovered that existing techniques for preparing nickel oxide hole transport layers using magnetron sputtering still have many shortcomings: Firstly, traditional nickel oxide targets are mostly pure-phase nickel oxide or simple single-element doped targets. During sputtering, problems such as uneven oxidation on the target surface and excessively deep etching trenches are prone to occur, resulting in a target utilization rate of less than 60%. Furthermore, the hole mobility of the prepared thin film is usually less than 10 due to the uneven distribution of doped elements. -3 cm 2 ·V -1 ·s -1 This cannot meet the rapid transmission requirements of high-efficiency perovskite solar cells; Secondly, the use of a single, fixed sputtering process parameter, such as constant sputtering power and oxygen-argon atmosphere ratio, makes it difficult to simultaneously achieve film density and surface activity. Insufficient density can lead to poor wetting of the perovskite precursor solution, resulting in pinhole defects, while excessively low surface activity can reduce hole extraction efficiency. Third, the interfacial bonding between the thin film and the fluorine-doped tin dioxide conductive glass (FTO) substrate and the photoactive layer is weak, and there are a large number of defects such as dangling bonds at the interface, which easily lead to carrier recombination, resulting in a decrease in the open circuit voltage of the battery and insufficient long-term stability (efficiency decay of more than 20% after 1000h damp heat test).

[0026] To address at least one of the aforementioned problems, embodiments of this application provide a method for fabricating a solar cell and a solar cell. By adjusting sputtering process parameters, rationally designing the target material, and adding post-processing measures, the film-forming performance of the hole transport layer is improved, thereby enhancing the efficiency and stability of the perovskite solar cell.

[0027] 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.

[0028] In the accompanying drawings, the dimensions of layers and regions may be exaggerated for clarity. It is understood that when a structure is referred to as being "on" or "below" another structure, the structure may be directly on or below the other structure, or there may be intermediate structures. The same reference numerals always indicate the same structure. Structures referred to herein include any of the following: membrane, element, device, component, assembly.

[0029] When a structure is referred to as being “connected” to another structure, it can be directly connected to the other structure or indirectly connected to the other structure by means of one or more intermediate structures placed between them.

[0030] The first aspect of this application provides a method for fabricating a solar cell. Exemplarily, this method for fabricating a solar cell is applicable to fabricating a solar cell with an upright structure.

[0031] Figure 1 This is a schematic flowchart illustrating the method for fabricating a solar cell according to the first embodiment of this application. Figure 1 As shown, the preparation method 100 includes: Step S110: Using magnetron sputtering, a first hole transport layer is prepared on a first pre-set substrate using first process parameters. The first pre-set substrate includes a photoactive layer.

[0032] Step S120: Adjust the process parameters of the magnetron sputtering process, including at least one of sputtering power density and oxygen content.

[0033] In step S130, a second hole transport layer is prepared on the side of the first hole transport layer away from the first pre-formed substrate using second process parameters. The activation level of the second hole transport layer is higher than that of the first hole transport layer, and the density of the first hole transport layer is higher than that of the second hole transport layer. The difference between the second and first process parameters lies in the oxygen content and sputtering power density.

[0034] In step S140, an electrode layer is prepared on the side of the second hole transport layer away from the first pre-formed substrate to obtain a solar cell.

[0035] In one embodiment, the first hole transport layer and the second hole transport layer are fabricated using the same target material. That is, the first hole transport layer and the second hole transport layer are made of the same material.

[0036] Figures 2a-2d To execute Figure 1 A schematic diagram of the intermediate product obtained during the preparation method shown is presented below. Figures 2a-2d The execution process of preparation method 100 is explained.

[0037] See Figure 2aThe first pre-embedded substrate 10 is an intermediate product obtained during the fabrication of a solar cell. The first pre-embedded substrate 10 includes a photoactive layer 4, which may be, for example, a perovskite layer. The first pre-embedded substrate 10 also includes a conductive substrate 1, which may be, for example, fluorine-doped tin dioxide conductive glass (FTO).

[0038] In one embodiment, the first pre-placed substrate 10 further includes an electron transport layer 5, which is located between the conductive substrate 1 and the photoactive layer 4.

[0039] According to step S110, refer to Figure 2b The first hole transport layer 3 is prepared on the first pre-placed substrate 10 using a magnetron sputtering process and first process parameters.

[0040] In the magnetron sputtering process, the target material is a doped target material. The doped target material is based on NiO and doped with Li and Mg. The mass fraction of Li doping is 0.5-1.2%, and the mass fraction of Mg doping is 0.3-0.8%.

[0041] According to step S120, the process parameters of the magnetron sputtering process are adjusted. In one embodiment, the process parameters include at least one of sputtering power density and oxygen content.

[0042] According to step S130, refer to Figure 2c The second hole transport layer 2 is prepared on the side of the first hole transport layer 3 away from the first pre-placed substrate 10 using the second process parameters.

[0043] According to step S140, refer to Figure 2d An electrode layer 6 is fabricated on the side of the second hole transport layer 2 opposite to the first pre-placed substrate 10 to obtain a solar cell. The electrode layer 6 can be a metal electrode.

[0044] Combining steps S110, S120, and S130, it can be seen that steps S110 and S130 both employ magnetron sputtering for film preparation. However, the process parameters differ between steps S110 and S130. Before transitioning from step S110 to step S130, step S120 is performed, which involves adjusting the process parameters. The result of this parameter adjustment is that the activation level of the second hole transport layer 2 is higher than that of the first hole transport layer 3, and the density of the first hole transport layer 3 is higher than that of the second hole transport layer 2.

[0045] Density primarily focuses on the physical microstructure of the thin film, such as the presence or absence of pinholes, pores, and grain boundary continuity, which directly affect its ability to block electrons. For example, density can be detected using elliptic polarization spectroscopy. Specifically, the refractive index of the film is obtained by measuring the change in polarization state of light passing through it. A higher refractive index indicates a denser film.

[0046] The degree of activation primarily focuses on the electrical properties of the thin film, such as carrier concentration, mobility, and conductivity, which directly determine its ability to transport holes. For example, the degree of activation can be detected using the Hall effect. Specifically, parameters such as the Hall voltage and resistance of the thin film in a magnetic field are measured, and the carrier concentration and conductivity are determined based on these parameters. Higher carrier concentration and higher conductivity indicate a higher degree of film activation.

[0047] In one embodiment, step S120 specifically involves: adjusting the oxygen content from 2%-8% to 10%-18%; and / or adjusting the sputtering power density from 5-10 W / cm². 2 Adjust to 2-5W / cm 2 Here, oxygen content refers to the volume content of oxygen, that is, the percentage of oxygen volume to the total volume of the entire gas atmosphere. For example, in a magnetron sputtering process, the entire gas atmosphere includes a mixture of argon, argon-hydrogen, and oxygen. Oxygen content refers to the percentage of oxygen volume to the sum of the volumes of argon, argon-hydrogen, and oxygen. This allows the second hole transport layer 2 to have a higher degree of activity than the first hole transport layer 3, and the first hole transport layer 3 to have higher density than the second hole transport layer 2. In other words, the first hole transport layer 3 mainly serves as a sealing and interface modification layer; the second hole transport layer 2 undertakes the main hole transport function.

[0048] For example, the execution process of steps S110-S130 includes: placing the first pre-placed substrate 10 into the magnetron sputtering chamber, setting the distance between the target and the first pre-placed substrate 10 to 6-10 cm, and setting the vacuum degree of the magnetron sputtering chamber to <5×10⁻⁶. - 4 Pa. A mixed atmosphere of argon, argon-hydrogen, and oxygen is introduced. The total gas flow rate is determined based on the volume of the magnetron sputtering chamber, resulting in a process pressure of 0.2 Pa-1 Pa, an oxygen content of 2%-8%, and a sputtering power density of 5-10 W / cm³. 2 This forms a dense bottom layer, namely the first hole transport layer 3, in contact with the photoactive layer 4. For example, the oxygen content is 4%, and the sputtering power density is 8 W / cm². 2 Keep the argon flow rate constant, adjust the oxygen content to 10%-18%, and reduce the sputtering power density to 2-5 W / cm³. 2 This forms an active surface layer, namely the second hole transport layer 2. For example, the oxygen content is 16%, and the sputtering power density is 3 W / cm². 2 .

[0049] According to the solar cell fabrication method provided in this embodiment, in step S120, a relatively high power density (5-10 W / cm²) is used. 2A first hole transport layer 3 is prepared with a low oxygen content (2%-8%). High-power particle bombardment helps form a dense, defect-free, and virtually pinhole-free first hole transport layer 3 on the relatively mild surface of the photoactive layer 4. The first hole transport layer 3 provides effective encapsulation for the underlying photoactive layer 4, suppresses nonradiative recombination at the interface, and prevents the intrusion of potentially harmful substances in subsequent processes. In step S130, the power density is reduced to 2-5 W / cm². 2 Meanwhile, the oxygen content is increased to 10%-18%. Low power reduces the risk of damage to the first hole transport layer 3, and the high oxygen atmosphere promotes the full oxidation of NiO, forming a "highly active" second hole transport layer 2 with better stoichiometry, better oxygen vacancy control, and higher hole concentration. This is beneficial for the second hole transport layer 2 to efficiently extract and transport holes to the second electrode layer 6.

[0050] In one embodiment, the thickness of the first hole transport layer 3 is greater than the thickness of the second hole transport layer 2. This has the advantage of strengthening the physical barrier function of the first hole transport layer 3 and improving device stability; simultaneously, it provides a more stable and higher-quality growth surface for the second hole transport layer 2.

[0051] In one embodiment, the thickness of the first hole transport layer 3 is 35-55 nm; and / or, the thickness of the second hole transport layer 2 is 5-25 nm. The total film thickness of the first hole transport layer 3 and the second hole transport layer 2 is approximately 40-80 nm. For example, the thickness of the first hole transport layer 3 is 45 nm, and the thickness of the second hole transport layer 2 is 20 nm. The thickness ratio of the first hole transport layer 3 to the second hole transport layer 2 can be optimized.

[0052] According to the solar cell fabrication method provided in this embodiment, a staged adjustment of sputtering parameters is used to sequentially fabricate a double-layer hole transport layer with gradients in density and activation degree, namely, a first hole transport layer 3 and a second hole transport layer 2. Without introducing an additional interface layer, both the charge extraction interface and the charge-selective contact interface are optimized, avoiding performance contradictions associated with a single process parameter.

[0053] Figure 3 This is a schematic flowchart illustrating the method for fabricating a solar cell according to the second embodiment of this application. Figure 3 Preparation method 100 shown Figure 1 The difference between the preparation method 100 shown is that, in this embodiment, before step S110, the preparation method 100 further includes: Step S101: Using NiO as a substrate, doping with Li and Mg to prepare the target material required for the magnetron sputtering process, wherein the mass fraction of Li doping is 0.5-1.2% and the mass fraction of Mg doping is 0.3-0.8%. For example, the mass fraction of Li doping is 0.8% and the mass fraction of Mg doping is 0.5%.

[0054] Specifically, NiO is used as the substrate, doped with Li and Mg. The mass fraction of Li is 0.5-1.2%, and the mass fraction of Mg is 0.3-0.8%, with the sum of the mass fractions of Li and Mg being 1%-2%. Among these, Li... + Replace Ni 2+ Generates a large number of hole carriers, Mg 2+ With a stable crystal lattice structure, Li can synergistically enhance carrier transport performance. + and Mg 2+ The combined effect optimizes the electronic structure and reduces the band gap. This results in a 10-12 fold increase in conductivity when pure nickel oxide is doped with 1%-2% Li and Mg.

[0055] In one embodiment, the target material is prepared by vacuum hot pressing sintering. The sintering temperature is 1200-1400℃, the holding time is 2-5 hours, and the sintering vacuum degree is ≤5×10⁻⁵. -3 Pa yielded a cylindrical target with a density >96%.

[0056] According to the solar cell fabrication method provided in this embodiment, an innovative dual-element composite doped target is designed, overcoming the limitations of traditional single-element doped or pure-phase targets. Li and Mg are selected for composite doping; Li, as a shallow acceptor dopant, significantly increases the hole concentration, while Mg enhances the chemical stability of the thin film and inhibits excessive grain growth. Combined with a vacuum hot-pressing sintering process, doping uniformity is ensured. Using the target provided in this embodiment, the contradiction between the electrical properties and structural stability of the hole transport layer material can be fundamentally resolved, providing a superior material basis for the fabrication of high-performance, highly stable gradient hole transport layers.

[0057] Figure 4 This is a schematic flowchart illustrating the method for fabricating a solar cell according to the third embodiment of this application. Figure 4 Preparation method 100 shown Figure 1 Preparation method 100 shown Figure 3 The difference in the preparation method 100 shown is that, in this embodiment, the preparation method 100 further includes: step S102, performed before step S110, to pre-treat the first pre-placed substrate 10; and step S103, performed after step S130, to perform vacuum annealing on the second hole transport layer 2 and the first hole transport layer 3.

[0058] Specifically, the pretreatment in step S102 mainly involves cleaning the first pre-placed substrate 10. In one embodiment, step S102 includes purging the first pre-placed substrate 10 with nitrogen gas. For example, the flow rate of nitrogen gas is 8-12 L / min.

[0059] Next, proceed with steps S110-S130.

[0060] After completing step S130, according to step S103, maintain a vacuum of 4 × 10⁻⁶ in the magnetron sputtering chamber. -3 Pa is heated to 200℃ at a heating rate of 6℃ / min, held at that temperature for 10-25min, and then naturally cooled to room temperature to obtain a nickel oxide hole transport layer, which includes a first hole transport layer 3 and a second hole transport layer 2.

[0061] According to the solar cell fabrication method provided in this embodiment, by combining "plasma pretreatment + vacuum annealing" for interface control, the surface of the photoactive layer 4 is significantly purified and activated without the need to introduce an additional interface modification layer. This optimizes the quality of the heterojunction between the photoactive layer 4 and the first hole transport layer 3, reduces interface defects, and strengthens the internal bonding between the first hole transport layer 3 and the second hole transport layer 2, thereby improving the efficiency and stability of the solar cell.

[0062] According to the solar cell fabrication method provided in this embodiment, the following beneficial effects can be achieved by adjusting sputtering process parameters, rationally designing the target material, and adding post-processing measures: (1) The open-circuit voltage of the solar cell is increased to 1.12V, and the efficiency is increased by 2-3 percentage points compared with the traditional solar cell; (2) The target material utilization rate is increased to more than 80%, and the hole mobility of the hole transport layer 30 reaches 5×10 -3 -1×10 -2 cm 2 ·V -1 ·s -1 (3) The density of the hole transport layer 30 is ≥98%, and the number of surface active sites is increased by more than 40%; (4) The peel strength between the film and the substrate is increased to more than 15MPa. After 1000h of damp heat test (temperature 60℃, relative humidity 60%), the battery efficiency decay rate is ≤8%, which is far better than the 20% decay rate of the traditional process; (5) The entire process does not require complex equipment modification. The magnetron sputtering and annealing processes can be carried out continuously, the production efficiency is increased by more than 30%, and the unit area film preparation cost is reduced by 20%, which meets the needs of large-scale mass production.

[0063] A second aspect of this application provides another method for fabricating a solar cell. Exemplarily, this method is applicable to fabricating solar cells with an inverted structure.

[0064] Figure 5 This is a schematic flowchart illustrating the method for fabricating a solar cell according to the fourth embodiment of this application. Figure 6 To execute Figure 5 A schematic diagram of the cross-sectional structure of the solar cell obtained by the fabrication method shown. Figure 5 The difference between the fabrication method of the solar cell shown and the fabrication method of the solar cell provided in any of the above embodiments lies only in the interchange of the fabrication order of the first hole transport layer 3 and the second hole transport layer 2. Specifically, as shown... Figure 5 As shown, the method 200 for fabricating a solar cell includes: Step S210, see Figure 6 A second hole transport layer 2 is fabricated on a second pre-foundation substrate 20 using a magnetron sputtering process and second process parameters. In one embodiment, the second pre-foundation substrate 20 includes a transparent conductive substrate 1.

[0065] Step S220, see below. Figure 6 Adjust the process parameters of the magnetron sputtering process, including at least one of sputtering power density and oxygen content.

[0066] Step S230, see below. Figure 6 A first hole transport layer 3 is fabricated on the side of the second hole transport layer 2 facing away from the second pre-placed substrate 20 using the first process parameters. The activation degree of the second hole transport layer 2 is higher than that of the first hole transport layer 3, and the density of the first hole transport layer 3 is higher than that of the second hole transport layer 2. The difference between the second and first process parameters lies in the oxygen content and sputtering power density.

[0067] Step S240, see below. Figure 6 A photoactive layer 4 and an electrode layer 6 are sequentially prepared on the side of the first hole transport layer 3 away from the second pre-placed substrate 20 to obtain a solar cell.

[0068] In one embodiment, step S240 further includes preparing an electron transport layer 5 between the photoactive layer 4 and the electrode layer 6.

[0069] In one embodiment, before step S210, a pretreatment step for the second pre-substrate 20 is included. Since the surface films of the second pre-substrate 20 and the first pre-substrate 20 are different, the pretreatment processes are also different. In this embodiment, the pretreatment process for the second pre-substrate 20 includes: performing an ultrasonic cleaning process on the first pre-substrate 10 and drying it; and performing a plasma cleaning process on the dried first pre-substrate 10. For example, the first pre-substrate 10 is ultrasonically cleaned sequentially in acetone, ethanol, and deionized water for 5-20 minutes each, and then dried. Then, the first pre-substrate 10 is placed in a plasma cleaner, using argon gas as the plasma source, with a power of 50-100W, and a treatment time of 3-8 minutes, to remove residual organic matter and hydroxyl groups from the surface.

[0070] The solar cell fabrication method provided in this embodiment and the solar cell fabrication method provided in any embodiment of the first aspect belong to the same inventive concept. The difference lies in the adaptive adjustment made to the fabrication order of the first hole transport layer 3 and the second hole transport layer 2 for different film layer stacking orders of inverted, upright, and multilayer solar cells, so that the first hole transport layer 3 is always located between the second hole transport layer 2 and the photoactive layer 4. Technical details not described in this embodiment can be found in any embodiment provided in the first aspect.

[0071] Figure 7 Execution provided for another embodiment Figure 5 A schematic diagram of the cross-sectional structure of the solar cell obtained by the fabrication method shown. Figure 7 The solar cells shown are Figure 6 The difference in the solar cells shown is that, in this embodiment, the second pre-placed substrate 20 has a different configuration.

[0072] Specifically, in this embodiment, the second pre-placed substrate 20 includes a stacked crystalline silicon bottom cell 9 and a carrier exchange layer 8. The second hole transport layer 2 is formed on the side of the carrier exchange layer 8 away from the crystalline silicon bottom cell 9.

[0073] In this case, step S240 further includes the step of preparing a transparent electrode 7 between the electron transport layer 5 and the metal electrode 6.

[0074] In this embodiment, the pretreatment process for the second pre-placed substrate 20 includes purging and cleaning the first pre-placed substrate 10 with nitrogen gas. For example, the nitrogen flow rate is 8-12 L / min.

[0075] It should be noted that in the perovskite / crystalline silicon tandem solar cell structure provided in this embodiment, the perovskite solar cell adopts an inverted structure. Compared with the upright structure, the advantages are that the parasitic absorption of the perovskite solar cell is low, the compatibility with the crystalline silicon bottom cell 9 is good, and the interface energy level matching is better.

[0076] A third aspect of this application provides a solar cell. Combined with... Figure 2d , Figure 6 and Figure 7 As shown, the solar cell includes: a substrate; a photoactive layer 4 located on one side of the substrate; and a hole transport layer 30. The hole transport layer 30 is located on the side of the photoactive layer 4 near or away from the substrate. The hole transport layer 30 includes a first hole transport layer 3 and a second hole transport layer 2 stacked in a direction perpendicular to the substrate. The first hole transport layer 3 is located between the second hole transport layer 2 and the photoactive layer 4. The second hole transport layer 2 has a higher degree of activation than the first hole transport layer 3, and the first hole transport layer 3 has a higher density than the second hole transport layer 2. The substrate can be either a first pre-formed substrate 10 or a second pre-formed substrate 20.

[0077] In one embodiment, the thickness of the first hole transport layer 3 is greater than the thickness of the second hole transport layer 2. This has the advantage of strengthening the physical barrier function of the first hole transport layer 3 and improving device stability; simultaneously, it provides a more stable and higher-quality growth surface for the second hole transport layer 2.

[0078] In one embodiment, the materials of the first hole transport layer 3 and the second hole transport layer 2 are the same. For example, both the first hole transport layer 3 and the second hole transport layer 2 are Li- and Mg-doped NiO. This ensures the continuity of the energy bands of the hole transport layer 30 and avoids potential barriers caused by heterojunctions.

[0079] The basic principles of this application have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this application are merely examples and not limitations, and should not be considered as essential features of each embodiment of this application. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the application to the necessity of employing the aforementioned specific details for implementation.

[0080] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this application to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. A method for preparing a solar cell, characterized in that, include: A first hole transport layer is prepared on a first pre-embedded substrate using a magnetron sputtering process and first process parameters. The first pre-embedded substrate includes a photoactive layer. Adjust the process parameters of the magnetron sputtering process; A second hole transport layer is prepared on the side of the first hole transport layer away from the first pre-formed substrate using second process parameters. The activation degree of the second hole transport layer is higher than that of the first hole transport layer, and the density of the first hole transport layer is higher than that of the second hole transport layer. The difference between the second process parameters and the first process parameters lies in the oxygen content and sputtering power density. An electrode layer is fabricated on the side of the second hole transport layer opposite to the first pre-formed substrate to obtain the solar cell.

2. The method for preparing a solar cell according to claim 1, characterized in that, In the magnetron sputtering process for fabricating the first hole transport layer on the first pre-embedded substrate, the distance between the target and the first pre-embedded substrate is 6-10 cm, and the vacuum degree of the magnetron sputtering chamber is <5×10⁻⁶. -4 Pa; A mixed atmosphere of argon, argon-hydrogen, and oxygen is introduced, with a process pressure of 0.2 Pa to 1 Pa, an oxygen content of 2% to 8%, and a sputtering power density of 5 to 10 W / cm³. 2 .

3. The method for preparing a solar cell according to claim 2, characterized in that, The adjustment of the process parameters of the magnetron sputtering process includes: Adjust the oxygen content from 2%-8% to 10%-18%; and / or The sputtering power density is reduced from 5-10 W / cm² 2 Adjust to 2-5W / cm 2 .

4. The method for preparing a solar cell according to claim 1, characterized in that, In the magnetron sputtering process, the target material is a doped target material, wherein the doped target material is based on NiO and doped with Li and Mg, wherein the mass fraction of Li is 0.5-1.2% and the mass fraction of Mg is 0.3-0.8%.

5. The method for preparing a solar cell according to claim 1, characterized in that, After fabricating a second hole transport layer on the side of the first hole transport layer away from the first pre-formed substrate, the fabrication method further includes: Vacuum annealing is performed on the second hole transport layer and the first hole transport layer; Before fabricating the first hole transport layer on one side of the first pre-formed substrate using magnetron sputtering, the fabrication method further includes: The surface of the first pre-placed substrate was purged and cleaned using nitrogen gas at a flow rate of 8-12 L / min.

6. The method for preparing a solar cell according to claim 1, characterized in that, The thickness of the first hole transport layer is 35-55 nm, and the thickness of the second hole transport layer is 5-25 nm. The total thickness of the first hole transport layer and the second hole transport layer is approximately 40-80 nm.

7. A method for preparing a solar cell, characterized in that, include: A second hole transport layer is prepared on a second pre-set substrate using a magnetron sputtering process and second process parameters. Adjust the process parameters of the magnetron sputtering process; The first hole transport layer is prepared on the side of the second hole transport layer away from the second pre-set substrate using the first process parameters. The activation degree of the second hole transport layer is higher than that of the first hole transport layer, and the density of the first hole transport layer is higher than that of the second hole transport layer. The difference between the second process parameters and the first process parameters lies in the oxygen content and sputtering power density. A photoactive layer and an electrode layer are sequentially fabricated on the side of the first hole transport layer away from the second pre-fabricated substrate to obtain the solar cell.

8. The method for preparing a solar cell according to claim 7, characterized in that, Before fabricating the second hole transport layer on the second pre-formed substrate using the magnetron sputtering process and the second process parameters, the fabrication method further includes: The second pre-placed substrate is cleaned once using an ultrasonic cleaning process and then dried. The second pre-placed substrate after drying is cleaned a second time using a plasma cleaning process.

9. A solar cell, characterized in that, include: substrate; A photoactive layer is located on one side of the substrate; as well as A hole transport layer is located on the side of the photoactive layer that is close to or far from the substrate. The hole transport layer includes a first hole transport layer and a second hole transport layer stacked in a direction perpendicular to the substrate. The first hole transport layer is located between the second hole transport layer and the photoactive layer. The activation degree of the second hole transport layer is higher than that of the first hole transport layer, and the density of the first hole transport layer is higher than that of the second hole transport layer.

10. The solar cell according to claim 9, characterized in that, The thickness of the first hole transport layer is greater than the thickness of the second hole transport layer; The material of the first hole transport layer is the same as the material of the second hole transport layer.

Images