Electron transmission structure, preparation method thereof and perovskite-crystalline silicon laminated solar cell

Abstract

The invention discloses an electron transmission structure and a preparation method thereof, and a perovskite-crystalline silicon laminated solar cell, the electron transmission structure is applied to a perovskite solar cell or a perovskite-crystalline silicon laminated solar cell, the electron transmission structure comprises a non-stoichiometric MgOx layer, and x is greater than or equal to 0.5 and less than or equal to 0.99. According to the invention, the MgOx layer (x is greater than or equal to 0.5 and less than or equal to 0.99) prepared by a thermal evaporation process or an atomic layer deposition process is adopted to completely or partially replace the existing C60 electron transport layer, and the MgOx layer has relatively wide band gap and conductivity, so that parasitic absorption and series resistance of the cell are reduced, and the conversion efficiency of the cell is improved.

Description

Technical Field

[0001] This invention belongs to the field of solar energy technology, specifically relating to an electron transport structure and its preparation method, and a perovskite-crystalline silicon tandem solar cell. Background Technology

[0002] Energy shortages and climate change are major challenges facing human society. Against this backdrop, vigorously developing clean energy technologies based on photovoltaic cells has become an international consensus. Silicon-based solar cells, with their excellent photoelectric performance and relatively low manufacturing cost, have become the mainstream product in the current commercial photovoltaic power generation field. Perovskite solar cells have advantages such as low cost, adjustable bandgap, and excellent photoelectric performance, and have enormous development potential. Multi-junction solar cells based on perovskite and silicon-based cells can further improve conversion efficiency and reduce the cost per kilowatt-hour. Among them, the two-terminal perovskite-crystalline silicon tandem solar cell is currently a research hotspot, with its efficiency already exceeding 33%.

[0003] Currently, the most commonly used perovskite-silicon tandem solar cell at both ends has an inverted top structure (i.e., a cell structure fabricated in the order of hole transport layer, perovskite light-absorbing layer, and electron transport layer). The commonly used hole transport layer material is SAM (2PACz, MeO-2PACz, etc.); the commonly used electron transport layer material is C. 60 Its function is to extract and transport electrons and block holes. C 60 With its excellent electron transport capability and minimal damage to the perovskite absorber layer caused by the thermal evaporation process, it has become the most commonly used electron transport layer material for inverted devices and perovskite-crystalline silicon tandem solar cells.

[0004] But because of C 60 The high cost, severe nonradiative recombination at the perovskite layer interface, and significant parasitic absorption limit the efficiency of tandem devices and their application in industrial production. Finding a wide-bandgap, stable electron transport layer material is crucial for improving the efficiency and stability of tandem solar cells.

[0005] Therefore, in order to address the above-mentioned technical problems, it is necessary to provide an electron transport structure and its preparation method, as well as a perovskite-crystalline silicon tandem solar cell. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide an electron transport structure and its preparation method, and a perovskite-crystalline silicon tandem solar cell.

[0007] To achieve the above objectives, an embodiment of the present invention provides the following technical solution:

[0008] An electron transport structure is used in a perovskite solar cell or a perovskite-crystalline silicon tandem solar cell, wherein the electron transport structure includes a non-stoichiometric MgOx layer, wherein 0.5 ≤ x ≤ 0.99.

[0009] In one embodiment, the electron transport structure is a single-layer MgOx layer with a thickness of 10 nm to 100 nm, wherein 0.5 ≤ x ≤ 0.83.

[0010] In one embodiment, the electron transport structure includes a first electron transport layer and a second electron transport layer stacked together;

[0011] The first electron transport layer is composed of titanium oxide, barium oxide, tin oxide, niobium oxide, tantalum oxide, PCBM, and C. 60 A combination of one or more layers;

[0012] The second electron transport layer is an MgOx layer, wherein 0.5 ≤ x ≤ 0.75.

[0013] In one embodiment, the perovskite solar cell or perovskite-crystalline silicon tandem solar cell includes a perovskite layer, with a first transport layer and a second transport layer sequentially stacked on the surface of the perovskite layer, or the second transport layer and the first transport layer sequentially stacked on the surface of the perovskite layer, wherein the thickness of the first electron transport layer is 1 nm to 50 nm, and the thickness of the second electron transport layer is 1 nm to 50 nm.

[0014] Another embodiment of the present invention provides the following technical solution:

[0015] A method for fabricating an electron transport structure, the method comprising:

[0016] The MgOx layer was prepared by thermal evaporation, with the evaporation rate controlled at 0.01 nm / s to 0.08 nm / s, so that the range of x was controlled to be 0.5 ≤ x ≤ 0.99.

[0017] Another embodiment of the present invention provides the following technical solution:

[0018] A method for fabricating an electron transport structure, the method comprising:

[0019] The MgOx layer was prepared using atomic layer deposition (ALD) with the substrate heating temperature controlled at 200℃~300℃ to control the range of x to be 0.5≤x≤0.99.

[0020] In one embodiment, in the atomic layer deposition process, the substrate heating temperature is 225℃~275℃, and x is in the range of 0.5≤x≤0.75.

[0021] The technical solution provided by another embodiment of the present invention is as follows:

[0022] A perovskite-crystalline silicon tandem solar cell, the tandem cell comprising a crystalline silicon cell and a perovskite solar cell stacked sequentially, the perovskite solar cell comprising a perovskite layer and an electron transport structure stacked on the perovskite layer, the electron transport structure being the aforementioned electron transport structure.

[0023] In one embodiment, the perovskite layer is one or a combination of two of the following: an AX layer and a BX2 layer, wherein A is CH3NH 3 + CH3CH2NH 3+ CH(NH2) 2+ C(NH2) 3+ Contains at least one short-chain organic cation from the elements carbon, oxygen, sulfur, nitrogen, and hydrogen, or Li + Na + K + 、Rb + Ag + Cu + Cs + At least one monovalent inorganic cation in the composition, where B is Ge 2+ Sn 2+ Pb 2+ Be 2+ Mg 2+ Ca 2+ 、Sr 2+ Ba 2+ Cu 2+ Fe 2+ Mn 2+ Zn 2+ Co 2+ Ni 2+ At least one divalent metal ion in it, where X is F - Cl - CH3COO - ,Br - I - SCN - At least one monovalent anion; and / or,

[0024] The thickness of the perovskite layer is 10 nm to 1500 nm; and / or,

[0025] The band gap of the perovskite layer is 1.60 eV to 1.75 eV.

[0026] In one embodiment, the crystalline silicon cell is a TOPCon cell or an HJT cell; and / or,

[0027] The perovskite-silicon tandem solar cell is a two-terminal perovskite-silicon tandem solar cell or a four-terminal perovskite-silicon tandem solar cell; and / or

[0028] The perovskite solar cell includes a hole transport layer, which comprises one or more of nickel oxide, cuprous oxide, cuprous iodide, cuprous sulfide, spiro-TTB, and a self-assembled layer. The material of the self-assembled layer includes 2-PACz, 4-PACz, Me-4PACz, MeO-2PACz, MeO-4PACz, and imidazole phosphate derivatives.

[0029] The present invention has the following beneficial effects:

[0030] This invention uses MgOx layers (0.5≤x≤0.99) prepared by thermal evaporation or atomic layer deposition to completely or partially replace existing C layers. 60 The electron transport layer, the MgOx layer, has a wide band gap and high conductivity, which reduces parasitic absorption and series resistance of the battery and improves the battery's conversion efficiency. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the structure of a perovskite-crystalline silicon tandem solar cell in a pair of proportions of the present invention;

[0033] Figure 2 This is a schematic diagram of the perovskite-crystalline silicon tandem solar cell in Embodiment 1 of the present invention;

[0034] Figure 3 This is a voltage-current density curve of the perovskite-crystalline silicon tandem solar cell in Example 1 of the present invention;

[0035] Figure 4a , 4b These are schematic diagrams of the perovskite-crystalline silicon tandem solar cell in Embodiment 2 of the present invention.

[0036] Figure 5 This is a voltage-current density curve of the perovskite-crystalline silicon tandem solar cell in Embodiment 2 of the present invention. Detailed Implementation

[0037] To enable those skilled in the art to better understand the technical solutions in the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are only a part rather than all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0038] In the present invention, unless otherwise clearly defined and limited, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0039] The present invention discloses an electron transport structure applied to a perovskite solar cell or a perovskite-silicon heterojunction solar cell. The electron transport structure includes a MgOx layer, where 0.5 ≤ x ≤ 0.99.

[0040] The present invention also discloses a method for preparing an electron transport structure, including:

[0041] Preparing the MgOx layer based on a thermal evaporation process, controlling the evaporation rate to be 0.01 nm / s to 0.08 nm / s to control the range of x to be 0.5 ≤ x ≤ 0.99.

[0042] The present invention also discloses a method for preparing an electron transport structure, including:

[0043] Preparing the MgOx layer based on an atomic layer deposition process, controlling the substrate heating temperature to be 200°C to 300°C to control the range of x to be 0.5 ≤ x ≤ 0.99.

[0044] The present invention also discloses a perovskite-silicon heterojunction solar cell, including a silicon solar cell and a perovskite solar cell stacked in sequence. The perovskite solar cell includes a perovskite layer and an electron transport structure stacked on the perovskite layer.

[0045] The following further illustrates the present invention with specific embodiments.

[0046] Comparative example:

[0047] Refer Figure 1The diagram shows a schematic representation of a perovskite-crystalline silicon tandem solar cell in a comparative example of the present invention. It is a two-terminal perovskite-crystalline silicon tandem solar cell, comprising a crystalline silicon cell (bottom cell) and a perovskite solar cell (top cell) stacked sequentially. The crystalline silicon cell can be a tunneling silicon oxide passivated contact (TOPCon) cell or a heterojunction (HJT) cell, etc. This comparative example uses an HJT cell as an example. In other embodiments, the perovskite-crystalline silicon tandem solar cell can also be a four-terminal perovskite-crystalline silicon tandem solar cell, and the crystalline silicon cell can also be other types of cells.

[0048] Specifically, the crystalline silicon cell in this comparative example includes a silicon substrate 10, a first intrinsic layer 11, an N-type doped layer 12 and a first transparent conductive layer 13 sequentially stacked on the front side of the silicon substrate, and a second intrinsic layer 14, a P-type doped layer 15, a second transparent conductive layer 16 and a back electrode 17 sequentially stacked on the back side of the silicon substrate.

[0049] Preferably, in this embodiment, the silicon substrate 10 is an N-type silicon substrate, the first intrinsic layer 11 and the second intrinsic layer 14 are both intrinsic hydrogenated amorphous silicon layers, the P-type doped layer 14 is a P-type doped hydrogenated nano-silicon oxide layer, the N-type doped layer 12 is an N-type doped hydrogenated nano-silicon oxide layer, the first transparent conductive layer 13 is an ITO transparent conductive layer, the second transparent conductive layer 16 is an IMO transparent conductive layer, and the back electrode is an Ag electrode.

[0050] In other embodiments, the crystalline silicon cell may use other types of cells, or there may be no crystalline silicon cell, but only a perovskite solar cell, which will not be described in detail here.

[0051] The perovskite solar cell in this comparative example includes, sequentially stacked on top of a crystalline silicon cell, a hole transport layer 21, a perovskite layer 22, a passivation layer 23, an electron transport layer 24, a barrier layer 25, a third transparent conductive layer 26, a positive electrode 27, and an antireflection layer 28. Wherein:

[0052] The hole transport layer 21 comprises one or more of nickel oxide, cuprous oxide, cuprous iodide, cuprous sulfide, spiro-TTB, and a self-assembled layer, with a thickness of 1 nm to 100 nm. The self-assembled layer material includes 2-PACz, 4-PACz, Me-4PACz, MeO-2PACz, MeO-4PACz, and imidazole phosphate derivatives.

[0053] Perovskite layer 22 is one or a combination of two of the following: AX layer and BX2 layer, wherein AX is CH3NH. 3+ CH3CH2NH 3+ CH(NH2) 2+ C(NH2) 3+ Contains at least one short-chain organic cation from the elements carbon, oxygen, sulfur, nitrogen, and hydrogen, or Li+ , Na + , K + , Rb + , Ag + , Cu + , Cs + At least one monovalent inorganic cation selected from the group consisting of, B is Ge 2+ , Sn 2+ , Pb 2+ , Be 2+ , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2 + , Cu 2+ , Fe 2+ , Mn 2+ , Zn 2+ , Co 2+ , Ni 2+ At least one divalent metal ion selected from the group consisting of, X is F - , Cl - , CH3COO - , Br - , I - , SCN - At least one monovalent anion selected from the group consisting of; the thickness of the perovskite layer is 10 nm to 1500 nm; the band gap of the perovskite layer is 1.60 eV to 1.75 eV.

[0054] The electron transport layer 24 includes one or more of titanium oxide, barium oxide, tin oxide, niobium oxide, tantalum oxide, PCBM, and C 60 Among them, exemplarily, in this comparative example, C 60 The electron transport layer is taken as an example for illustration.

[0055] The blocking layer 25 includes, but is not limited to, one or more of tin oxide, tin oxide, titanium oxide, and aluminum oxide, and the thickness is 1 nm to 100 nm.

[0056] The third transparent conductive layer 26 is IZO, ITO, IZrO, etc., and preferably IZO.

[0057] The positive electrode 27 is a patterned electrode, and preferably an Ag electrode.

[0058] The antireflection layer 28 is one or more of magnesium fluoride, magnesium fluoride, sodium fluoride, and silicon oxide, and the thickness is 1 nm to 200 nm.

[0059] Example 1:

[0060] Refer Figure 2As shown, the perovskite-crystalline silicon tandem solar cell in this embodiment has a structure that is roughly the same as the perovskite-crystalline silicon tandem solar cell in the comparative example, with the only difference being the structure of the electron transport layer.

[0061] Specifically, the electron transport layer in the comparative example is C. 60 In this embodiment, the electron transport layer is a non-stoichiometric MgOx layer, wherein 0.5 ≤ x ≤ 0.99.

[0062] The MgOx layer in this embodiment can be prepared by thermal evaporation or atomic layer deposition. This embodiment will use thermal evaporation as an example for detailed explanation.

[0063] The MgOx layer was prepared by thermal evaporation, with the evaporation power controlled at 55W to 60W and the evaporation rate controlled at 0.01nm / s to 0.08nm / s, so that the range of x was controlled to be 0.5≤x≤0.99.

[0064] The thermal evaporation process is as follows:

[0065] First, by using both mechanical and molecular pumps, the pressure in the thermal evaporation chamber was reduced to below 5E-4 Pa, and an electric current was applied to begin evaporating the pre-placed magnesium oxide powder. Starting from zero, the evaporation power was gradually increased to 55W–60W. By adjusting the evaporation power, the evaporation rate of magnesium oxide was adjusted to reach 0.01 nm / s–0.08 nm / s. Once the evaporation rate stabilized, the thermal evaporation process was complete. Finally, the resulting MgOx layer was tested to obtain the final value of x.

[0066] In this embodiment, the value of x is controlled by the evaporation rate in the process of preparing the MgOx layer by thermal evaporation. The minimum evaporation rate is 0.01 nm / s, at which point the maximum value of x is 0.99. As the evaporation rate gradually increases, the value of x gradually decreases, reaching a minimum of 0.5 at an evaporation rate of 0.08 nm / s. It can be seen that the value of x is negatively correlated with the evaporation rate in the thermal evaporation process.

[0067] The relationship between different evaporation rates and x values ​​is shown in the table below:

[0068] Evaporation rate (nm / s) x value in MgOx 0.01 x＝0.99 0.03 x＝0.83 0.04 x＝0.75 0.07 x＝0.60 0.08 x＝0.50

[0069] The steps for preparing pure magnesium oxide (MgO, i.e., x=1) using the solution method in the existing technology are as follows:

[0070] After preparing a magnesium acetate tetrahydrate solution, the substrate was placed in a spin coater. A certain amount of solution was dropped onto the substrate using a pipette. The spin coater program was then turned on, and the substrate was spin-coated at a rotation speed of 1000 rpm to 6000 rpm and annealed at 100℃ to 250℃ to prepare a pure magnesium oxide film. The film thickness decreased as the rotation speed increased.

[0071] For the perovskite-silicon tandem solar cell in this embodiment, different x values in MgOx will affect the electrical performance of the cell, as shown in the following table:

[0072] x value in MgOx <![CDATA[V OC (V)]]> <![CDATA[Jsc(mA / cm 2 )]]> Fill Factor Efficiency (%) x＝0.99 1.50 6.01 17.00 1.54 x＝0.83 1.61 17.81 63.11 18.10 x＝0.75 1.85 18.99 75.87 26.68 x＝0.60 1.80 17.33 67.74 21.13 x＝0.50 1.77 15.29 71.36 19.31 x＝1 1.36 1.49 9.33 0.19

[0073] Combined with Figure 3 As shown, when the value of x is within the range of 0.5 to 0.83, the electrical performance of the tandem cell is better and the photoelectric conversion efficiency is higher. The corresponding evaporation rate in the thermal evaporation process is 0.03 nm / s to 0.08 nm / s.

[0074] Example 2:

[0075] Refer to Figure 4a and 4b As shown, the perovskite-silicon tandem solar cell in this embodiment has a substantially same structure as that in the comparative example, and the difference lies only in the structure of the electron transport layer.

[0076] Specifically, the electron transport structure in the comparative example is C 60 , while the electron transport layer in this embodiment is a combination of MgOx layer 241 and C 60 layer 242. In Figure 4a , the MgOx layer 241 is located above the C 60 layer 242 (i.e., the MgOx layer is located in the outer layer), and in Figure 4b , the MgOx layer 241 is located below the C 60 layer 242 (i.e., the MgOx layer is located in the inner layer), where 0.5 ≤ x ≤ 0.99.

[0077] The MgOx layer in this embodiment can be prepared by thermal evaporation process or atomic layer deposition process. In this embodiment, the atomic layer deposition process is taken as an example for detailed description.

[0078] Based on the atomic layer deposition process for preparing the MgOx layer, the substrate heating temperature is controlled at 200 °C to 300 °C to control the range of x as 0.5 ≤ x ≤ 0.99.

[0079] The process of preparing the MgOx layer by atomic layer deposition controls the change of x value by controlling the substrate heating temperature, chamber pressure, source bottle heating temperature, etc. The reaction formula is

[0080] 2Mg(CpEt)2 + 2H2O → 2MgO + 4HCpEt.

[0081] The specific steps are as follows:

[0082] 1) Precursor Mg(CpEt)2 pulse adsorption reaction;

[0083] 2) N2 is used to purge excess reactants and byproducts;

[0084] 3) Pulse adsorption reaction of precursor H2O;

[0085] 4) N2 is used to purge excess reactants and byproducts, and then the process is repeated to achieve layer-by-layer growth of the thin film on the substrate surface.

[0086] The x-value is controlled by the substrate heating temperature, which varies between 200℃ and 300℃. As the temperature increases, the deposition rate first increases and then decreases, that is, the x-value first decreases and then increases. This is because the growth is limited when the temperature exceeds the saturation temperature.

[0087] The specific process is as follows: First, the sample is placed in the atomic layer deposition equipment and the vacuum is evacuated to below 0.5 Pa. Then, the deposition process is started. The temperature of the preset chamber bottom, middle and top and each pipeline is set from low to high. The dwell time and duration of each cycle are set. The deposition process is started after the temperature rise is completed.

[0088] The relationship between different substrate heating temperatures and x values ​​is shown in the table below:

[0089] Substrate heating temperature (°C) x value in MgOx 200 x＝0.99 225 x＝0.75 240 x＝0.5 275 x＝0.75

[0090] When the substrate heating temperature is 200℃, the deposition rate is 0.1nm / cycle, and x takes the maximum value of 0.99. When the substrate heating temperature is 240℃, the deposition rate is 0.025nm / cycle, and x takes the minimum value of 0.5. When the substrate heating temperature is 225℃ and 275℃, x takes the intermediate value of 0.75.

[0091] It can be seen that the value of x first decreases and then increases as the substrate heating temperature changes from 200 to 300℃.

[0092] For the perovskite-crystalline silicon tandem solar cell in this embodiment, different x values ​​in MgOx affect the electrical performance of the cell, as detailed in the table below:

[0093] x value in MgOx <![CDATA[V OC (V)]]> <![CDATA[Jsc(mA / cm 2 )]]> Fill Factor Efficiency (%) Internal-MgOx x=0.99 1.44 5.80 17.91 1.50 Internal-MgOx x=0.75 1.93 19.74 77.30 29.42 Internal-MgOx x=0.50 1.77 17.75 62.15 19.53 External-MgOx x=0.99 1.58 2.64 11.23 0.47 External-MgOx x=0.75 1.83 17.68 61.84 19.96 External-MgOx x=0.50 1.42 16.24 52.88 12.19

[0094] Combination Figure 5 As shown, when the value of x is in the range of 0.5 to 0.75, the tandem solar cell exhibits good electrical performance and high photoelectric conversion efficiency. This corresponds to a substrate heating temperature of 225℃ to 275℃ in the atomic layer deposition process.

[0095] It should be understood that the electron transport structure in this embodiment includes an MgOx layer, which replaces all or part of the C. 60In other embodiments, the MgOx layer can be used to completely or partially replace the electron transport layers such as titanium oxide, barium oxide, tin oxide, niobium oxide, tantalum oxide, and PCBM, which can also improve the electrical performance of perovskite solar cells or crystalline silicon-perovskite tandem cells.

[0096] As can be seen from the above technical solutions, the present invention has the following beneficial effects:

[0097] This invention uses MgOx layers (0.5≤x≤0.99) prepared by thermal evaporation or atomic layer deposition to completely or partially replace existing C layers. 60 The electron transport layer, the MgOx layer, has a wide band gap and high conductivity, which reduces parasitic absorption and series resistance of the battery and improves the battery's conversion efficiency.

[0098] Non-stoichiometric MgOx layers exhibit good thermal and long-term stability, thereby improving battery stability;

[0099] The presence of metallic magnesium in the thermal evaporation process can suppress the migration of halide ions from inside the perovskite towards the electrode, further improving the long-term stability of the battery.

[0100] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0101] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. An electron transport structure, applied to perovskite solar cells or perovskite-crystalline silicon tandem solar cells, characterized in that, The electron transport structure includes a non-stoichiometric MgOx layer, wherein 0.5 ≤ x ≤ 0.

99.

2. The electron transport layer according to claim 1, characterized in that, The electron transport structure is a single-layer MgOx layer with a thickness of 10nm to 100nm, wherein 0.5≤x≤0.

83.

3. The electron transport layer according to claim 1, characterized in that, The electron transport structure includes a first electron transport layer and a second electron transport layer stacked together; The first electron transport layer is composed of titanium oxide, barium oxide, tin oxide, niobium oxide, tantalum oxide, PCBM, and C. 60 A combination of one or more layers; The second electron transport layer is an MgOx layer, wherein 0.5 ≤ x ≤ 0.

75.

4. The electron transport layer according to claim 3, characterized in that, The perovskite solar cell or perovskite-crystalline silicon tandem solar cell includes a perovskite layer, with the first transport layer and the second transport layer sequentially stacked on the surface of the perovskite layer, or the second transport layer and the first transport layer sequentially stacked on the surface of the perovskite layer, wherein the thickness of the first electron transport layer is 1 nm to 50 nm, and the thickness of the second electron transport layer is 1 nm to 50 nm.

5. A method for preparing an electron transport structure, characterized in that, The preparation method includes: The MgOx layer was prepared by thermal evaporation, with the evaporation rate controlled at 0.01 nm / s to 0.08 nm / s, so that the range of x was controlled to be 0.5 ≤ x ≤ 0.

99.

6. A method for preparing an electron transport structure, characterized in that, The preparation method includes: The MgOx layer was prepared using atomic layer deposition (ALD) with the substrate heating temperature controlled at 200℃~300℃ to control the range of x to be 0.5≤x≤0.

99.

7. The preparation method according to claim 6, characterized in that, In the atomic layer deposition process, the substrate heating temperature is 225℃~275℃, and the range of x is 0.5≤x≤0.

75.

8. A perovskite-crystalline silicon tandem solar cell, characterized in that, The stacked solar cell includes a crystalline silicon solar cell and a perovskite solar cell stacked sequentially. The perovskite solar cell includes a perovskite layer and an electron transport structure stacked on the perovskite layer. The electron transport structure is the electron transport structure according to any one of claims 1 to 4.

9. The perovskite-crystalline silicon tandem solar cell according to claim 8, characterized in that, The perovskite layer is one or a combination of two of the following: an AX layer and a BX2 layer, wherein A is CH3NH 3+ CH3CH2NH 3+ CH(NH2) 2+ C(NH2) 3+ Contains at least one short-chain organic cation from the elements carbon, oxygen, sulfur, nitrogen, and hydrogen, or Li + Na + K + 、Rb + Ag + Cu + Cs + At least one monovalent inorganic cation in the composition, where B is Ge 2+ Sn 2+ Pb 2+ Be 2+ Mg 2+ Ca 2+ 、Sr 2+ Ba 2+ Cu 2+ Fe 2+ Mn 2+ Zn 2+ Co 2 + Ni 2+ At least one divalent metal ion in it, where X is F - Cl-, CH3COO - ,Br - I - SCN - At least one monovalent anion; and / or, The thickness of the perovskite layer is 10 nm to 1500 nm; and / or, The band gap of the perovskite layer is 1.60 eV to 1.75 eV.

10. The perovskite-crystalline silicon tandem solar cell according to claim 8, characterized in that, The crystalline silicon cell is a TOPCon cell or an HJT cell; and / or The perovskite-silicon tandem solar cell is a two-terminal perovskite-silicon tandem solar cell or a four-terminal perovskite-silicon tandem solar cell; and / or The perovskite solar cell includes a hole transport layer, which comprises one or more of nickel oxide, cuprous oxide, cuprous iodide, cuprous sulfide, spiro-TTB, and a self-assembled layer. The material of the self-assembled layer includes 2-PACz, 4-PACz, Me-4PACz, MeO-2PACz, MeO-4PACz, and imidazole phosphate derivatives.

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