Laminated solar cell and method for manufacturing laminated solar cell

Abstract

The invention provides a laminated solar cell and a preparation method of the laminated solar cell, and relates to the field of photovoltaic technology, and the laminated solar cell comprises a perovskite sub-cell; the crystalline silicon sub-cell is arranged below the perovskite sub-cell, the crystalline silicon sub-cell comprises a first doped microcrystalline silicon layer, a first intrinsic amorphous silicon layer, a silicon substrate, a second intrinsic amorphous silicon layer and a second doped silicon layer which are sequentially stacked in the direction away from the perovskite sub-cell, the atomic percent of oxygen elements in the first doped microcrystalline silicon layer is not larger than 1%, the atomic percent of oxygen elements in the second doped microcrystalline silicon layer is not larger than 1%, and the atomic percent of oxygen elements in the silicon substrate is not larger than 1%. The first doped microcrystalline silicon layer is provided with a first surface far away from the silicon substrate, the average grain size of silicon grains on the first surface is 20nm-50nm, and the doping type of the first doped microcrystalline silicon layer is opposite to that of the second doped microcrystalline silicon layer.

Description

TECHNICAL FIELD

[0001] The present application mainly relates to the field of photovoltaic technology, and particularly relates to a laminated solar cell and a preparation method of the laminated solar cell. BACKGROUND

[0002] Solar cell technology is undergoing a major transformation from traditional crystalline silicon cells to high-efficiency laminated solar cells, among which the theoretical limit efficiency of perovskite / crystalline silicon laminated solar cells is significantly higher than that of single-junction crystalline silicon cells, and is one of the current hot researches. In perovskite / crystalline silicon laminated solar cells, heterojunction cells (HJT) become the ideal choice for crystalline silicon cells in perovskite / crystalline silicon laminated solar cells due to their unique symmetrical structure and excellent surface passivation characteristics. When combining heterojunction cells with perovskite to form perovskite / crystalline silicon laminated solar cells, the traditional heterojunction cell needs to be optimized to better match the heterojunction cell. SUMMARY

[0003] The technical problem to be solved by the present application is to provide a laminated solar cell and a preparation method of the laminated solar cell, which can improve the performance of the laminated solar cell.

[0004] The present application provides a laminated solar cell, comprising: a perovskite sub-cell; a crystalline silicon sub-cell arranged below the perovskite sub-cell, the crystalline silicon sub-cell comprising a first doped microcrystalline silicon layer, a first intrinsic amorphous silicon layer, a silicon substrate, a second intrinsic amorphous silicon layer and a second doped silicon layer which are sequentially stacked in a direction away from the perovskite sub-cell, wherein the atomic percentage of oxygen in the first doped microcrystalline silicon layer is not greater than 1%, the first doped microcrystalline silicon layer has a first surface away from the silicon substrate, the average grain size of silicon grains located at the first surface is 20-50 nm, and the doping type of the first doped microcrystalline silicon layer is opposite to that of the second doped silicon layer. The present application also provides a photovoltaic module comprising the laminated solar cell as described above and / or the laminated solar cell prepared by the preparation method of the laminated solar cell as described above.

[0005] The present application also provides a preparation method of a laminated solar cell, comprising: preparing a crystalline silicon sub-cell, the crystalline silicon sub-cell comprising a first doped microcrystalline silicon layer, a first intrinsic amorphous silicon layer, a silicon substrate, a second intrinsic amorphous silicon layer and a second doped silicon layer which are sequentially stacked, wherein no oxygen is introduced during the preparation of the first doped microcrystalline silicon layer, and the doping type of the first doped microcrystalline silicon layer is opposite to that of the second doped silicon layer; and preparing a perovskite sub-cell on the crystalline silicon sub-cell.

[0006] Compared with the prior art, the present application has the following advantages:

[0007] (1) By controlling the atomic percentage of oxygen element in the first doped microcrystalline silicon layer to be not more than 1%, the silicon grain growth is promoted, the large-size grains increase the roughness of the surface of the first doped microcrystalline silicon layer, the first doped microcrystalline silicon layer with high roughness provides a good substrate for the nucleation and growth of the perovskite absorption layer, thereby facilitating the formation of a perovskite absorption layer with excellent performance, and further improving the open-circuit voltage and fill factor of the stacked solar cell; in addition, the large-size grains are also beneficial to improving the carrier mobility;

[0008] (2) By controlling the average grain size of the surface of the first doped microcrystalline silicon layer to be 20-50 nm, and the average thickness of the first doped microcrystalline silicon layer to be 20-60 nm, under the synergistic effect of the increase in thickness and grain size, the short-circuit current density of the crystalline silicon sub-cell is improved, and the short-circuit current density of the stacked solar cell is further improved, thereby reducing the current mismatch risk. BRIEF DESCRIPTION OF DRAWINGS

[0009] The accompanying drawings are included to provide a further understanding of the present application, and they are collected and constitute a part of the present application, the drawings show the embodiments of the present application, and together with the present specification, they play a role in explaining the principles of the present application. In the drawings:

[0010] Figure 1 is a cross-sectional schematic view of a stacked solar cell in an embodiment of the present application;

[0011] Figure 2 is a flowchart of the preparation method of the stacked solar cell in an embodiment of the present application;

[0012] Figure 3 and Figure 4 are cross-sectional schematic views of the stacked solar cell in different steps;

[0013] Figure 5 is a microscopic image of the stacked solar cell in Comparative Example 1;

[0014] Figure 6 is a microscopic image of the stacked solar cell in Example 1.

[0015] Reference signs: perovskite sub-cell 110, first charge transport layer 114, second intrinsic amorphous silicon layer 124, second electrode 111, crystalline silicon sub-cell 120, second doped silicon layer 125, second transparent conductive layer 111a, first doped microcrystalline silicon layer 121, first electrode 126, second gate line 111b, first surface 121a, first transparent conductive layer 126a, second charge transport layer 112, first intrinsic amorphous silicon layer 122, first gate line 126b, perovskite absorption layer 113, silicon substrate 123, connecting layer 130. DETAILED DESCRIPTION

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required to be used in the embodiment description will be briefly introduced as follows. Obviously, the drawings in the following description are only some examples or embodiments of the present application, and for those skilled in the art, the present application can also be applied to other similar scenarios without creative labor on the basis of these drawings. Unless the context clearly indicates otherwise or otherwise stated, the same reference signs in the drawings represent the same structure or operation.

[0017] As shown in the present application and claims, unless the context clearly indicates otherwise or otherwise stated, the words "one", "a", "an", and / or "the" do not specifically refer to the singular, but can also include the plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of the steps and elements explicitly identified, and these steps and elements do not constitute an exclusive list, and the method or device can also include other steps or elements.

[0018] Unless otherwise specifically stated, the relative arrangement of the components and steps, numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that the sizes of the various parts shown in the drawings are not drawn in proportion to the actual proportions. The technology, methods and devices known to those skilled in the relevant art can not be discussed in detail, but in appropriate cases, the technology, methods and devices should be considered as part of the authorized specification. In all examples shown and discussed here, any specific value should be interpreted as merely exemplary, and not as a limitation. Therefore, other examples of exemplary embodiments can have different values. It should be noted that similar reference signs and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0019] In the description of the present application, it needs to be understood that the orientation words such as "front, back, up, down, left, right", "transverse, vertical, perpendicular, horizontal" and "top, bottom" and the like indicated orientation or position relationship generally based on the orientation or position relationship shown in the drawings, only for the convenience of describing the present application and simplifying the description, without making the opposite statement, these orientation words do not indicate and imply that the device or element indicated must have a particular orientation or be constructed and operated in a particular orientation, therefore, it cannot be understood as a limitation on the scope of protection of the present application; the orientation words "inner, outer" refer to the inner and outer relative to the contour of each component itself.

[0020] For the convenience of description, spatial relative terms such as "over", "above", "upper surface", "upper" and the like can be used herein to describe the spatial position relationship of one device or feature with other devices or features as shown in the drawings. It should be understood that the spatial relative terms are intended to include different orientations in use or operation in addition to the orientation of the device described in the drawings. For example, if the device in the drawing is inverted, the device described as "above" or "over" other devices or structures will be positioned "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below" orientations. The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein are interpreted accordingly.

[0021] In addition, it needs to be noted that the use of "first", "second" and the like to define parts is only for the convenience of distinguishing the corresponding parts, and the above words have no special meaning unless otherwise stated, therefore, it cannot be understood as a limitation on the scope of protection of the present application. In addition, although the terms used in the present application are selected from the commonly known and used terms, some terms mentioned in the specification of the present application may be selected by the applicant according to his or her judgment, and the detailed meaning of each term is described in the relevant part of the description. In addition, the present application is required to be understood not only by the actual terms used, but also by the meaning implied by each term.

[0022] Flowcharts are used in the present application to illustrate the operations performed by the system according to the embodiments of the present application. It should be understood that the preceding or following operations are not necessarily performed in sequence. On the contrary, various steps can be processed in reverse order or simultaneously. Meanwhile, or other operations are added to these processes, or one or more steps of operation are removed from these processes.

[0023] Next, the laminated solar cell and the preparation method (hereinafter referred to as the preparation method) of the laminated solar cell of the present application are described by examples.

[0024] Reference Figure 1 The laminated solar cell includes a perovskite sub-cell 110 and a crystalline silicon sub-cell 120, and the crystalline silicon sub-cell 120 is arranged below the perovskite sub-cell 110. The laminated solar cell can effectively utilize incident light of different wavelengths by arranging the perovskite sub-cell 110 and the crystalline silicon sub-cell 120 in layers, thereby improving the overall photoelectric conversion efficiency.

[0025] In an embodiment, the perovskite sub-cell 110 includes a second electrode 111, a second charge transport layer 112, a perovskite absorption layer 113, and a first charge transport layer 114, which are sequentially stacked from top to bottom. The first charge transport layer 114 is a hole transport layer, and the second charge transport layer 112 is an electron transport layer, or the first charge transport layer 114 is an electron transport layer, and the second charge transport layer 112 is a hole transport layer. The band gap of the perovskite absorption layer 113 can be 1.68 eV. The second electrode 111 includes a second transparent conductive layer 111a and a second grid line 111b, and the second grid line 111b is arranged on the second transparent conductive layer 111a. In an embodiment, the second transparent conductive layer 111a includes a transparent conductive oxide (TCO), and the transparent conductive oxide can include one or more of indium tin oxide (ITO), aluminum-doped zinc oxide (AZO), fluorine-doped tin oxide (FTO), antimony-doped tin oxide (ATO), and indium zinc oxide (IZO). The second grid line 111b can include silver, and the second grid line 111b can be prepared using a magnetron sputtering process.

[0026] In Figure 1 , the crystalline silicon sub-cell 120 includes a first doped microcrystalline silicon layer 121, a first intrinsic amorphous silicon layer 122, a silicon substrate 123, a second intrinsic amorphous silicon layer 124, a second doped silicon layer 125, and a first electrode 126, which are sequentially stacked from top to bottom.

[0027] The first doped microcrystalline silicon layer 121 is P-type doped or N-type doped. The silicon substrate 123 is P-type doped or N-type doped, and the silicon substrate 123 can be a single crystal silicon substrate. The second doped silicon layer 125 is P-type doped or N-type doped, and the second doped silicon layer 125 can include doped amorphous silicon and / or doped microcrystalline silicon, and the doping type of the second doped silicon layer 125 is opposite to the doping type of the first doped microcrystalline silicon layer 121. In an embodiment, the first doped microcrystalline silicon layer 121 is N-type doped, the silicon substrate 123 is N-type doped, and the second doped silicon layer 125 is P-type doped.

[0028] The atomic percentage of oxygen in the first doped microcrystalline silicon layer 121 is not greater than 1%, for example, the atomic percentage is 0%, or equal to or less than 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1%. The atomic percentage of oxygen in the first doped microcrystalline silicon layer 121 can be measured by Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS). The oxygen content is the average value of the oxygen content of multiple points or multiple regions (for example, a region with a length of 472.6 nm and a width of 630 nm at 200k magnification) on the measured sample. When the Time-of-Flight Secondary Ion Mass Spectrometry method cannot detect the oxygen element in the first doped microcrystalline silicon layer 121, it is considered that the first doped microcrystalline silicon layer 121 does not contain oxygen elements.

[0029] The first doped microcrystalline silicon layer 121 has a first surface 121a away from the silicon substrate 123. The average grain size of the silicon grains on the first surface 121a is 20-50 nm, and more specifically, the average grain size is 25-50 nm, for example, the average grain size is 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm or 50 nm. The average grain size of the silicon grains is measured by using a scanning electron microscope (SEM) to obtain a microscopic image of the first surface 121a at 200k magnification, and then using the measurement function of the SEM image analysis software to measure the grain size of a plurality of silicon grains (for example, 100 randomly selected silicon grains) in the microscopic image, and then averaging the measured grain sizes to determine the average grain size.

[0030] In an embodiment, the average thickness of the first doped microcrystalline silicon layer 121 is 20-60 nm, and more specifically, the average thickness is 30-60 nm, for example, the average thickness is 20 nm, 30 nm, 40 nm, 50 nm or 60 nm. The average thickness of the doped microcrystalline silicon layer in the related art is usually 2-17 nm. The average thickness of the first doped microcrystalline silicon layer 121 is greater than that in the prior art, which can improve the lateral carrier transport capability of the first doped microcrystalline silicon layer 121.

[0031] By controlling the average grain size of the surface of the first doped microcrystalline silicon layer 121 to be 20-50 nm and the average thickness of the first doped microcrystalline silicon layer 121 to be 20-60 nm, the short-circuit current density (Jsc) of the crystalline silicon sub-cell 120 can be improved (in some experiments, the short-circuit current density is improved by 1.5-2.0 mA / cm2) under the synergistic effect of the increase in thickness and the increase in grain size, thereby improving the short-circuit current density of the tandem solar cell and reducing the risk of current mismatch. Although the increase in average thickness will increase the parasitic absorption of the first doped microcrystalline silicon layer 121 to long waves, the contribution of the short-circuit current density to the performance improvement of the tandem solar cell is greater than the loss caused by the parasitic absorption.

[0032] In yet another embodiment, the first doped microcrystalline silicon layer is N-type doped. To compensate for the increase in the longitudinal resistance of the first doped microcrystalline silicon layer 121 caused by the increase in the average thickness, the doping concentration of the N-type doping element in the first doped microcrystalline silicon layer 121 is increased to 1x10² 0 cm⁻³-3x10² 0 cm⁻³, for example, the doping concentration is 1x10² 0 cm⁻³, 2x10² 0 cm⁻³, or 3x10² 0 cm⁻³.

[0033] In an embodiment, the crystallization rate of the first doped microcrystalline silicon layer 121 is in the range of 50-70%, for example, the crystallization rate is in the range of 50-60% or 60-70%. The crystallization rate of the first doped microcrystalline silicon layer 121 can be measured using Raman spectroscopy. The higher the crystallization rate, the higher the conductivity of the first doped microcrystalline silicon layer 121, but the grain boundary will also increase, which will lead to an increase in recombination. The present application sets the crystallization rate of the first doped microcrystalline silicon layer 121 in the range of 50-70% to simultaneously meet the conductivity and interface passivation requirements of the first doped microcrystalline silicon layer 121, thereby obtaining an optimal solution with high conversion rate.

[0034] The first electrode 126 includes a first transparent conductive layer 126a and a first gate line 126b. In an embodiment, the first transparent conductive layer 126a includes a transparent conductive oxide, and the first gate line 126b can include silver, which can be prepared using a magnetron sputtering process.

[0035] In an embodiment, the tandem solar cell is a two-terminal tandem solar cell or a three-terminal tandem solar cell, and a connection layer 130 is arranged between the perovskite sub-cell 110 and the crystalline silicon sub-cell 120. The average thickness of the connection layer 130 can be 5-20 nm, for example, the average thickness is 5 nm, 10 nm, 15 nm, or 20 nm.

[0036] This application also proposes a method for fabricating tandem solar cells, referring to... Figure 2 The flowchart shown, and Figure 3 and Figure 4 The cross-sectional schematic diagrams of the stacked solar cells shown in different steps illustrate the fabrication method, which includes the following steps S110 and S120.

[0037] S110: Fabrication of a crystalline silicon sub-cell 120. The crystalline silicon sub-cell 120 includes a first doped microcrystalline silicon layer 121, a first intrinsic amorphous silicon layer 122, a silicon substrate 123, a second intrinsic amorphous silicon layer 124, a second doped silicon layer 125, and a first electrode 126, which are stacked sequentially. No oxygen is introduced during the fabrication of the first doped microcrystalline silicon layer 121, and the doping type of the first doped microcrystalline silicon layer 121 is opposite to the doping type of the second doped silicon layer 125.

[0038] S120: A perovskite sub-cell 110 is fabricated on top of a crystalline silicon sub-cell 120.

[0039] For details, please refer to Figure 3 A crystalline silicon sub-cell 120 is fabricated, which has a first doped microcrystalline silicon layer 121. No oxygen is introduced during the fabrication of the first doped microcrystalline silicon layer 121 to promote silicon grain growth. Larger grains improve carrier mobility and lateral carrier transport capability. Furthermore, the oxygen-free first doped microcrystalline silicon layer 121 avoids performance degradation caused by oxygen diffusion at high temperatures. The tandem solar cell of this application exhibits an efficiency degradation of less than 3% after a damp heat aging test (temperature 85°C, humidity 85%RH, duration 1000h), compared to efficiency degradation greater than 7% in related technologies. Moreover, the absence of oxygen introduction saves on the equipment required for oxygen introduction and also improves the deposition rate of the first doped microcrystalline silicon layer 121.

[0040] In one embodiment, a first doped microcrystalline silicon layer 121 is deposited using plasma-enhanced chemical vapor deposition (PECVD). During the deposition of the first doped microcrystalline silicon layer 121, the volume ratio of hydrogen (H2) to silane (SiH4) is greater than 10, and the process temperature is 180°C to 220°C. In this embodiment, the volume ratio of hydrogen to silane is greater than that of related technologies, and the process temperature is lower than that of related technologies, which helps to control the crystallinity of the first doped microcrystalline silicon layer 121 within the range of 50% to 70%. In some embodiments, a very high frequency plasma-enhanced chemical vapor deposition (VHF-PECVD) process is used to deposit the first doped microcrystalline silicon layer 121 to improve the uniformity of the first doped microcrystalline silicon layer 121. The process frequency of the VHF-PECVD process is 60MHz to 100MHz.

[0041] In an embodiment, after the first doped microcrystalline silicon layer 121 is prepared, the first doped microcrystalline silicon layer 121 is subjected to a plasma annealing treatment, which can be a hydrogen plasma annealing treatment. When the hydrogen plasma annealing treatment is adopted, the power of the hydrogen plasma annealing treatment is 200 W to 500 W, and the time is 30 s to 120 s. The plasma annealing treatment can passivate dangling bonds, reduce the interface state density, and also reduce the erosion of the surface of the first doped microcrystalline silicon layer 121 by the subsequent perovskite solution.

[0042] Reference is made to Figure 4 In an embodiment, the first doped microcrystalline silicon layer 121 has a first surface 121a away from the silicon substrate 123, and the average grain size of the silicon grains on the first surface 121a is 20 nm to 50 nm, and further, the average grain size is 25 nm to 50 nm. In an embodiment, the average thickness of the first doped microcrystalline silicon layer 121 is 20 nm to 60 nm, and further, the average thickness is 30 nm to 60 nm. In an embodiment, the first doped microcrystalline silicon layer 121 is N-type doped, and the doping concentration of the N-type doping element in the first doped microcrystalline silicon layer 121 is 1 x 10² 0 cm⁻³ to 3 x 10² 0 cm⁻³. In an embodiment, the crystallization rate of the first doped microcrystalline silicon layer 121 is 50% to 70%.

[0043] For other descriptions of the crystalline silicon sub-cell 120, please refer to the foregoing, which will not be expanded here.

[0044] Reference is made to Figure 2 , Figure 3 and Figure 4 The perovskite sub-cell 110 is prepared above the first doped microcrystalline silicon layer 121.

[0045] In an embodiment, the stacked solar cell is a two-terminal stacked solar cell or a three-terminal stacked solar cell, and before the perovskite sub-cell 110 is prepared, a connecting layer 130 is prepared, and the average thickness of the connecting layer 130 is 5 nm to 20 nm.

[0046] In an embodiment, the perovskite sub-cell 110 includes a second electrode 111, a second charge transport layer 112, a perovskite absorption layer 113, and a first charge transport layer 114, which are arranged in a stack from top to bottom.

[0047] Reference is made to Figure 4As described above, compared with the prior art, the average grain size of the silicon grains on the surface of the first doped microcrystalline silicon layer 121 is larger than that in the prior art, the larger average grain size increases the roughness of the surface of the first doped microcrystalline silicon layer 121, the first doped microcrystalline silicon layer 121 with high roughness provides a good substrate for the nucleation and growth of the perovskite absorption layer, thereby facilitating the formation of a perovskite absorption layer with excellent performance (for example, facilitating the control of the thickness of the perovskite absorption layer and improving the crystallization performance of the perovskite absorption layer), and further improving the open-circuit voltage and the fill factor of the stacked solar cell.

[0048] Embodiment 1 and Comparative Example 1 are designed in the present application, which are specifically described as follows.

[0049] Embodiment 1

[0050] Step 1: cleaning and double-side texturing of a single crystal silicon substrate (resistivity of 1 Ω·cm, average thickness of 160 μm), to form a pyramid structure (height of the pyramid of 1 μm~3 μm) on both sides of the single crystal silicon substrate.

[0051] Step 2: deposition of a first intrinsic amorphous silicon layer and a second intrinsic amorphous silicon layer.

[0052] The first intrinsic amorphous silicon layer and the second intrinsic amorphous silicon layer are deposited on the opposite two sides of the single crystal silicon substrate, and the first intrinsic amorphous silicon layer and the second intrinsic amorphous silicon layer comprise hydrogenated amorphous silicon, with an average thickness of 6 nm and a deposition temperature of 180 °C.

[0053] Step 3: deposition of an N-type first doped microcrystalline silicon layer.

[0054] An N-type first doped microcrystalline silicon layer is deposited on the first intrinsic amorphous silicon layer by VHF-PECVD (frequency of 80 MHz) process, with a doping element of phosphorus (P) and no oxygen gas in the deposition process. The first doped microcrystalline silicon layer has an average thickness of 30 nm, a phosphorus doping concentration of 2×10² 0 cm⁻³, and a crystallization rate of 60%. In the operation of the stacked solar cell, the first doped microcrystalline silicon layer faces the sun.

[0055] Step 4: deposition of a P-type second doped silicon layer.

[0056] A P-type second doped silicon layer is deposited on the second intrinsic amorphous silicon layer, the second doped silicon layer comprises microcrystalline silicon, with a doping element of boron (B) and hydrogenation treatment of the second doped silicon layer. The second doped silicon layer has an average thickness of 10 nm and a boron doping concentration of 5×10¹ 9 cm⁻³. In the operation of the stacked solar cell, the second doped silicon layer faces away from the sun.

[0057] Step 5: hydrogen plasma treatment.

[0058] The first doped microcrystalline silicon layer is subjected to hydrogen plasma treatment, the power of the hydrogen plasma treatment is 400 W, the treatment time is 60 s, and the hydrogen flow rate is 1000 sccm.

[0059] Step 6: Preparation of the connecting layer and the first transparent conductive layer.

[0060] ITO is sputtered on the first doped microcrystalline silicon layer and the second doped silicon layer, the ITO on the first doped microcrystalline silicon layer is the connecting layer, and the ITO on the second doped silicon layer is the first transparent conductive layer. The average thickness of the ITO is 80 nm, and the square resistance is 40 Ω / sq.

[0061] Step 7: Preparation of the perovskite sub-cell.

[0062] A hole transport layer (the hole transport layer includes NiOx, and the average thickness is 30 nm) is spin-coated on the connecting layer; a perovskite absorber layer (the perovskite absorber layer includes FA0.8Cs0.2PbI2.8Br0.2, the band gap is 1.68 eV, and the average thickness is 400 nm) is deposited on the hole transport layer; and an electron transport layer (the electron transport layer includes C60, and the average thickness is 20 nm) is evaporated on the perovskite absorber layer.

[0063] Step 8: Preparation of the electrode.

[0064] IZO with an average thickness of 120 nm is sputtered on the first charge transport layer as the second transparent conductive layer, and a silver grid line is sputtered on the second transparent conductive layer as the second grid line. A silver grid line is sputtered on the first transparent conductive layer as the first grid line.

[0065] Comparative Example 1

[0066] Comparative Example 1 and Example 1 are different in that oxygen is introduced during the deposition of the N-type first doped microcrystalline silicon layer. The atomic percentage of oxygen in the deposited first doped microcrystalline silicon layer is 1.5%, the average thickness of the first doped microcrystalline silicon layer is 17 nm, and the phosphorus doping concentration is 1×10² 0 cm⁻³.

[0067] A scanning electron microscope is used to take microscopic images of the first doped microcrystalline silicon layer in Comparative Example 1 and Example 1, as shown in Figure 5 and Figure 6 The average grain size of the silicon grains is calculated according to the microscopic images. The short-circuit current density (Jsc), open-circuit voltage (Voc), fill factor (FF), photoelectric conversion efficiency (PCE) of the stacked solar cell in Comparative Example 1 and Example 1, and the oxygen content (atomic percentage), average thickness, carrier mobility, refractive index, and resistance of the first doped microcrystalline silicon layer are measured. The measurement results are shown in Table 1.

[0068] Referring to Table 1, the oxygen content of the first doped microcrystalline silicon layer in Example 1 is less than that of Comparative Example 1, which makes the average grain size of the first doped microcrystalline silicon layer in Example 1 significantly larger than that of Comparative Example 1. In addition, the thickness of the first doped microcrystalline silicon layer in Example 1 is greater than that of Comparative Example 1, which can effectively improve the carrier mobility of the first doped microcrystalline silicon layer in Example 1.

[0069] The short-circuit current density of the stacked solar cell in Example 1 is greater than that of Comparative Example 1, which is mainly due to the increase in the grain size and thickness of the first doped microcrystalline silicon layer.

[0070] The photoelectric conversion efficiency of the stacked solar cell in Example 1 is greater than that of Comparative Example 1, which is mainly because: on the one hand, the increase in the grain size and thickness of the first doped microcrystalline silicon layer improves the short-circuit current density of the stacked solar cell; on the other hand, the first doped microcrystalline silicon layer with a large grain size is conducive to the formation of a perovskite absorption layer with excellent performance, thereby improving the open-circuit voltage and fill factor of the stacked solar cell.

[0071] Table 1. Various parameters of the stacked solar cells in Comparative Example 1 and Example 1 Comparative Example 1 Example 1 Oxygen content (atomic %) 1.5% 0.8% Average thickness 17 nm 30 nm Average grain size 15 nm 25 nm Carrier mobility 7 cm2 / V-s 20 cm2 / V-s Refractive index 2.7 3.6 Resistance 200 Ω / sq 90 Ω / sq Short-circuit current density 20.51 mA / cm 2 ]]> 20.60 mA / cm 2 ]]> Open-circuit voltage 1.983 V 1.990V Fill factor 82.50% 82.74% Photoelectric conversion efficiency 33.55% 33.92%

[0072] The foregoing merely illustrates the principles of the application. Furthermore, those skilled in the art will readily recognize that various modifications, changes, and substitutions can be undertaken to the present application without materially departing from the spirit and scope of the application. It is intended that all such modifications, changes, and substitutions be included within the spirit and scope of the present application.

[0073] In addition, the use of the terms "one embodiment", "an embodiment”, “some embodiments”, “one alternative”, “some alternatives” or “one alternative embodiment” throughout this description does not necessarily refer to the same embodiment or alternative. Furthermore, the use of the terms “one embodiment”, “an embodiment”, “some embodiments”, “one alternative”, “some alternatives” or “one alternative embodiment” in different places throughout this description does not necessarily refer to the same embodiment or alternative. In addition, certain features, structures, or characteristics of an embodiment or alternative can be combined with features, structures, or characteristics of another embodiment or alternative.

[0074] In addition, the use of the terms “one embodiment”, “an embodiment”, “some embodiments”, “one alternative”, “some alternatives” or “one alternative embodiment” throughout this description does not necessarily refer to the same embodiment or alternative. Furthermore, the use of the terms “one embodiment”, “an embodiment”, “some embodiments”, “one alternative”, “some alternatives” or “one alternative embodiment” in different places throughout this description does not necessarily refer to the same embodiment or alternative. In addition, certain features, structures, or characteristics of an embodiment or alternative can be combined with features, structures, or characteristics of another embodiment or alternative.

[0075] Some embodiments use numerical descriptors of ingredients, amounts of ingredients, and properties. It should be understood that such numerical descriptors used in the description of embodiments are, in some examples, modified by the terms "about," "approximately," or "generally." Unless otherwise stated, "about," "approximately," or "generally" indicates that a deviation of ±20% is allowed on the stated number. Accordingly, numerical parameters in the specification and claims are approximations, and should be considered in the context of the overall description of the embodiments. In some embodiments, numerical parameters are approximations and should be considered in the context of the overall description of the embodiments. In some embodiments, numerical parameters should be considered in the context of the specification and the claims, and are approximations that vary from the numerical parameters in some examples. Although the numerical ranges and parameters setting forth the broadest scope of the embodiments herein are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values set forth in the specific examples are provided to be as precise as reasonably possible. However, some variations may occur depending on the implementation desired.

[0076] Although the present application has been described with reference to the current embodiments, persons having ordinary skill in the art will recognize that changes may be made in form and detail without departing from the spirit and the scope of the application. Therefore, the disclosed embodiments should be considered in a descriptive sense only and not for purposes of limiting the applicability of the application, as broadly construed.

Claims

1. A tandem solar cell, characterized in that, include: Perovskite sub-cells; A crystalline silicon sub-cell is disposed below the perovskite sub-cell. The crystalline silicon sub-cell includes a first doped microcrystalline silicon layer, a first intrinsic amorphous silicon layer, a silicon substrate, a second intrinsic amorphous silicon layer, and a second doped silicon layer, which are sequentially stacked in a direction away from the perovskite sub-cell. The atomic percentage of oxygen in the first doped microcrystalline silicon layer is not greater than 1%. The first doped microcrystalline silicon layer has a first surface away from the silicon substrate. The average grain size of the silicon grains on the first surface is 20 nm to 50 nm. The doping type of the first doped microcrystalline silicon layer is opposite to that of the second doped silicon layer.

2. The tandem solar cell as described in claim 1, characterized in that, The average grain size of the silicon grains located on the first surface is 25nm~50nm.

3. The tandem solar cell as described in claim 1 or 2, characterized in that, The average thickness of the first doped microcrystalline silicon layer is 20 nm to 60 nm.

4. The tandem solar cell as described in claim 1 or 2, characterized in that, The average thickness of the first doped microcrystalline silicon layer is 30 nm to 60 nm.

5. The tandem solar cell as described in claim 1, characterized in that, The first doped microcrystalline silicon layer is N-type doped, and the doping concentration of the N-type dopant element in the first doped microcrystalline silicon layer is 1×10². 0 cm⁻³~3×10² 0 cm⁻³.

6. The tandem solar cell as described in claim 1, characterized in that, The crystallinity of the first doped microcrystalline silicon layer is 50%~70%.

7. The tandem solar cell as described in claim 1, characterized in that, It also includes a connecting layer located between the perovskite sub-cell and the crystalline silicon sub-cell.

8. The tandem solar cell as described in claim 7, characterized in that, The average thickness of the connecting layer is 5nm~20nm.

9. The tandem solar cell as described in claim 1, characterized in that, The perovskite sub-cell includes a first charge transport layer, a perovskite layer, and a second charge transport layer stacked sequentially along a direction away from the crystalline silicon sub-cell.

10. The tandem solar cell as described in claim 9, characterized in that, The first charge transport layer is a hole transport layer.

11. A method for fabricating a tandem solar cell, characterized in that, include A crystalline silicon sub-cell is fabricated, comprising a first doped microcrystalline silicon layer, a first intrinsic amorphous silicon layer, a silicon substrate, a second intrinsic amorphous silicon layer, and a second doped silicon layer, sequentially stacked. Oxygen is not introduced during the fabrication of the first doped microcrystalline silicon layer, and the doping type of the first doped microcrystalline silicon layer is opposite to that of the second doped silicon layer. A perovskite sub-cell is fabricated above the crystalline silicon sub-cell.

12. The method for preparing a tandem solar cell as described in claim 11, characterized in that, The first doped microcrystalline silicon layer is prepared using plasma-enhanced chemical vapor deposition (PECVD), wherein during the preparation of the first doped microcrystalline silicon layer, the volume ratio of hydrogen to silane introduced into the chamber is greater than 10, and the process temperature is 180℃~220℃.

13. The method for preparing a tandem solar cell as described in claim 12, characterized in that, The first doped microcrystalline silicon layer was prepared using a very high frequency plasma-enhanced chemical vapor deposition process with a process frequency of 60MHz to 100MHz.

14. The method for preparing a tandem solar cell as described in claim 11, characterized in that, After the first doped microcrystalline silicon layer is prepared, the first doped microcrystalline silicon layer is subjected to plasma annealing treatment.

15. The method for preparing a tandem solar cell as described in claim 11, characterized in that, The first doped microcrystalline silicon layer has a first surface away from the silicon substrate, and the average grain size of the silicon grains located on the first surface is 20 nm to 50 nm.

16. The method for preparing a tandem solar cell as described in claim 11, characterized in that, The first doped microcrystalline silicon layer has a first surface away from the silicon substrate, and the average grain size of the silicon grains located on the first surface is 25 nm to 50 nm.

17. The method for preparing a tandem solar cell as described in claim 15 or 16, characterized in that, The average thickness of the first doped microcrystalline silicon layer is 20 nm to 60 nm.

18. The method for preparing a tandem solar cell as described in claim 15 or 16, characterized in that, The average thickness of the first doped microcrystalline silicon layer is 30 nm to 60 nm.

19. The method for preparing a tandem solar cell as described in claim 12, characterized in that, The first doped microcrystalline silicon layer is N-type doped, and the doping concentration of the N-type dopant element in the first doped microcrystalline silicon layer is 1×10². 0 cm⁻³~3×10² 0 cm⁻³.

20. The method for preparing a tandem solar cell as described in claim 12, characterized in that, The crystallinity of the first doped microcrystalline silicon layer is 50%~70%.

21. The method for preparing a tandem solar cell as described in claim 12, characterized in that, Before fabricating the perovskite sub-cell on top of the crystalline silicon sub-cell, a connecting layer is also fabricated on the crystalline silicon sub-cell.

22. The method for preparing a tandem solar cell as described in claim 21, characterized in that, The average thickness of the connecting layer is 5nm~20nm.

23. A photovoltaic module, characterized in that, This includes tandem solar cells as described in any one of claims 1 to 10, and / or tandem solar cells prepared by the method described in any one of claims 11 to 22.

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