A stacked battery, a method of manufacturing the same, and a photovoltaic module

Abstract

This application relates to the field of photovoltaic module technology, specifically to a tandem solar cell, its fabrication method, and a photovoltaic module. The tandem solar cell includes a top cell unit, a bottom cell unit, and a composite layer located between the top and bottom cell units. Along a first direction, the composite layer has at least a first structural layer, a second structural layer, and a third structural layer stacked together. The first, second, and third structural layers have different band gaps. The technical effect of making the composite layer consist of multiple structural layers with different band gaps is that when the band gap difference between the top and bottom cell units is large, the composite layer can achieve a band gap gradient transition, optimizing carrier flow between the top and bottom cell units, thereby reducing the overall voltage loss of the tandem solar cell and improving its operating efficiency. Furthermore, by setting at least three structural layers with different band gaps in the composite layer, the band gap gradient transition effect generated by the composite layer can be further optimized.

Description

Technical Field

[0001] This application relates to the field of photovoltaic module technology, specifically to a tandem cell, its preparation method, and a photovoltaic module. Background Technology

[0002] Photovoltaic modules can convert solar energy into electrical energy, offering advantages such as being pollution-free, not geographically limited, and inexhaustible, making them a major direction for developing new energy sources. A photovoltaic module comprises multiple photovoltaic cells. Tandem cells, a type of photovoltaic cell, are generally composed of three parts stacked sequentially: a wide-bandgap top cell, a composite layer, and a narrow-bandgap bottom cell. Typically, there is a significant difference in bandgap between the top and bottom cells. Summary of the Invention

[0003] This application provides a tandem battery, its preparation method, and a photovoltaic module, which addresses the technical problem of high voltage loss in tandem batteries in the prior art.

[0004] In a first aspect, this application provides a stacked battery, which includes a top battery unit, a bottom battery unit, and a composite layer located between the top battery unit and the bottom battery unit; along a first direction, the composite layer has at least a first structural layer, a second structural layer, and a third structural layer stacked together; the first structural layer, the second structural layer, and the third structural layer have different band gaps.

[0005] In this embodiment, the technical effect of using multiple structural layers with different band gaps in the composite layer is as follows: when the band gap difference between the top and bottom battery cells is large, the composite layer can achieve a gradient transition in the band gap, optimizing carrier flow between the top and bottom battery cells, thereby reducing the overall voltage loss of the stacked battery and improving its operating efficiency. For example, when the band gap of the top battery cell is larger than that of the bottom battery cell, the band gaps of the first, second, and third structural layers in the composite layer can be decreased sequentially to adapt to the band gap variation between the top and bottom battery cells. Furthermore, by providing at least three structural layers with different band gaps in the composite layer, the band gap difference between the different structural layers can be further reduced, thereby further optimizing the band gap gradient transition effect generated by the composite layer.

[0006] In one specific embodiment, the top cell unit includes a stacked perovskite layer and an electron transport layer, and the bottom cell unit includes a stacked tunneling oxide layer and a silicon substrate; the first structural layer is in contact with the electron transport layer, and the third structural layer is in contact with the tunneling oxide layer; the band gap of the first structural layer is larger than the band gap of the second structural layer, and the band gap of the second structural layer is larger than the band gap of the third structural layer.

[0007] In one specific embodiment, the first structural layer is phosphorus-doped nanocrystalline silicon oxide, the second structural layer is boron-doped hydrogenated nanocrystalline silicon carbide, and the third structural layer is phosphorus-doped microcrystalline silicon oxide.

[0008] In one specific embodiment, the band gap of the first structural layer is 1.45eV-1.55eV, the band gap of the second structural layer is 1.35eV-1.45eV, and the band gap of the third structural layer is 1.25eV-1.35eV.

[0009] In one specific embodiment, the doping concentration of the first structural layer is 4 × 10⁻⁶. 19 cm -3 -5×10 19 cm -3 The doping concentration of the second structural layer is 6 × 10⁻⁶. 19 cm -3 -7×10 19 cm -3 The doping concentration of the third structural layer is 8 × 10⁻⁶. 19 cm -3 -9×10 19 cm -3 The thickness D1 of the first structural layer satisfies 4nm≤D1≤6nm, the thickness D2 of the second structural layer satisfies 2nm≤D2≤4nm, and the thickness D3 of the third structural layer satisfies 7nm≤D3≤9nm.

[0010] In one specific embodiment, along the first direction, the top battery cell includes a stacked hole transport layer, the perovskite layer, the exciton multiplication layer, and the electron transport layer; wherein the exciton multiplication layer includes a quantum dot array structure.

[0011] In one specific embodiment, the exciton multiplication layer comprises germanium-doped cesium lead bromide quantum dots for forming the quantum dot array structure.

[0012] In one specific embodiment, the germanium-doped cesium lead bromide quantum dots have a size of 3nm-5nm and a band gap of 2.8eV-3.2eV.

[0013] In one specific embodiment, the thickness D4 of the exciton multiplication layer satisfies 15nm ≤ D4 ≤ 20nm.

[0014] Secondly, embodiments of this application also provide a method for preparing a stacked battery, the method comprising:

[0015] Fabrication of bottom battery cells;

[0016] A third structural layer is sputtered to form on top of the bottom battery cell;

[0017] A second structural layer is deposited on top of the third structural layer using PECVD.

[0018] A first structural layer is deposited on top of the second structural layer using HWCVD.

[0019] A top battery cell is fabricated on top of the first structural layer;

[0020] The first structural layer, the second structural layer, and the third structural layer have different band gaps.

[0021] In this embodiment, a composite layer with three structural layers having different band gaps is prepared between the top battery cell and the bottom battery cell to achieve a band gap gradient change between the top battery cell and the bottom battery cell, optimize carrier flow between the top battery cell and the bottom battery cell, reduce voltage loss, and improve the working efficiency of the stacked battery.

[0022] In one specific embodiment, the method for fabricating the stacked battery further includes the following steps during the fabrication of the top battery cell:

[0023] An electron transport layer is fabricated on top of the first structural layer;

[0024] An exciton multiplication layer was prepared on top of the electron transport layer using a solution method.

[0025] The exciton multiplication layer includes a germanium-doped cesium lead bromide quantum dot array.

[0026] In one specific embodiment, during the process of preparing the exciton multiplication layer on top of the electron transport layer using a solution method, the fabrication method of the stacked battery specifically includes:

[0027] A precursor was prepared by mixing cesium lead bromide and germanium iodide at a predetermined molar ratio.

[0028] Germanium-doped cesium lead bromide quantum dots were prepared by adding a mixed solvent of toluene and ethyl acetate to the precursor and using an antisolvent crystallization method.

[0029] The germanium-doped cesium lead bromide quantum dots are subjected to annealing heat treatment at a temperature of 170℃-190℃ in a nitrogen atmosphere to form the germanium-doped cesium lead bromide quantum dot array.

[0030] Thirdly, embodiments of this application provide a photovoltaic module, which includes the aforementioned tandem battery.

[0031] In this embodiment, by incorporating a composite layer with a bandgap gradient in the tandem solar cell, carrier flow between the top and bottom cells is optimized, voltage loss is reduced, and the overall efficiency of the photovoltaic module is improved. Furthermore, an exciton multiplication layer with a quantum dot array structure can be incorporated into the top cell of the tandem solar cell to enhance the utilization of short-wavelength photons, thereby further improving the overall photoelectric conversion efficiency of the photovoltaic module. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of the structure of the stacked battery provided in this application in a specific embodiment.

[0034] Figure label:

[0035] 1-Stacked battery;

[0036] 11-Top battery cell;

[0037] 111-Transparent conductive oxide layer;

[0038] 112 - Hole transport layer;

[0039] 113-Perovskite layer;

[0040] 114-exciton multiplication layer;

[0041] 115 - Electron transport layer;

[0042] 12-bottom battery cell;

[0043] 121-Tunneling oxide layer;

[0044] 122-Silicon substrate;

[0045] 123 - Passivation layer;

[0046] 13-Composite layer;

[0047] 131 - First structural layer;

[0048] 132 - Second structural layer;

[0049] 133 - Third structural layer;

[0050] 14-Electrode. Detailed Implementation

[0051] To better understand the technical solution of this application, the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0052] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0053] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0054] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0055] Photovoltaic modules convert solar energy into electrical energy, offering advantages such as being pollution-free, geographically unrestricted, and inexhaustible, making them a major direction for developing new energy sources. A photovoltaic module comprises multiple photovoltaic cells. Tandem cells, a type of photovoltaic cell, typically consist of three parts stacked sequentially: a wide-bandgap top cell, a composite layer, and a narrow-bandgap bottom cell. Due to the significant bandgap difference between the top and bottom cells, the carrier flow stability between them is poor, resulting in substantial voltage drops in tandem cells.

[0056] To solve the above technical problems, such as Figure 1 As shown, this application embodiment provides a stacked battery 1, including a top battery unit 11, a bottom battery unit 12, and a composite layer 13 located between the top battery unit 11 and the bottom battery unit 12. Along the first direction X, the composite layer 13 may have at least a first structural layer 131, a second structural layer 132, and a third structural layer 133 stacked together, wherein the first structural layer 131, the second structural layer 132, and the third structural layer 133 have different band gaps.

[0057] By employing this design approach, the composite layer 13 is composed of multiple structural layers with different band gaps. This allows for a gradual transition of the band gap when the band gap difference between the top cell 11 and the bottom cell 12 is significant. This optimizes carrier flow between the top and bottom cell cells, reducing the overall voltage drop of the stacked battery 1 and thus improving its efficiency. For example, when the band gap of the top cell cell 11 is larger than that of the bottom cell cell 12, the band gaps of the first structural layer 131, the second structural layer 132, and the third structural layer 133 in the composite layer 13 can be sequentially reduced to accommodate the band gap variation between the top and bottom cell cells 11 and 12. Furthermore, by incorporating at least three structural layers with different band gaps in the composite layer 13, the band gap difference between these layers can be further reduced, thereby further optimizing the band gap gradient transition effect produced by the composite layer 13.

[0058] In other embodiments, the structural layers in the composite layer 13 may be set to four or more layers. The present application does not limit the specific number of structural layers in the composite layer 13, and can be adapted according to the actual situation.

[0059] In this embodiment, the first direction X can be the thickness direction of the stacked battery 1.

[0060] In the above embodiments, such as Figure 1 As shown, the top cell 11 can be a perovskite cell including a stacked perovskite layer 113 and an electron transport layer 115, and the bottom cell 12 can be a topcon cell including a stacked tunneling oxide layer 121 and a silicon substrate 122. The top cell 11 (i.e., the perovskite top cell) has a bandgap of 1.6 eV, and the bottom cell 12 (i.e., the topcon bottom cell) has a bandgap of 1.12 eV. The first structural layer 131 in the composite layer 13 can abut against the electron transport layer 115, and the third structural layer 133 can abut against the tunneling oxide layer 121, meaning that the first structural layer 131, the second structural layer 132, and the third structural layer 133 in the composite layer 13 are arranged sequentially from the top cell 11 to the bottom cell 12. In this embodiment, the band gap of the structural layers in the composite layer 13 can be set as follows: the band gap of the first structural layer 131 is greater than the band gap of the second structural layer 132, and the band gap of the second structural layer 132 is greater than the band gap of the third structural layer 133.

[0061] By using this design, the band gaps of the first structural layer 131, the second structural layer 132, and the third structural layer 133 in the composite layer 13 are reduced sequentially, thereby achieving a band gap gradient transition from the top battery cell 11 to the bottom battery cell 12. This optimizes carrier flow between the top battery cell 11 and the bottom battery cell 12, reduces voltage loss, and improves the working efficiency of the stacked battery 1.

[0062] The following description uses the top cell unit 11 as a perovskite cell and the bottom cell unit 12 as a topcon cell as an example.

[0063] The first structural layer 131 has a bandgap of 1.45 eV-1.55 eV, the second structural layer 132 has a bandgap of 1.35 eV-1.45 eV, and the third structural layer 133 has a bandgap of 1.25 eV-1.35 eV. This design allows the composite layer 13 to have a bandgap gradient, thus enabling a smooth transition between the top cell 11 and the bottom cell 12. This optimizes carrier flow between the top and bottom cells, reducing voltage loss. Specifically: the band gap of the first structural layer 131 can be 1.45eV, 1.47eV, 1.49eV, 1.52eV, 1.55eV, etc.; the band gap of the second structural layer 132 can be 1.35eV, 1.37eV, 1.39eV, 1.42eV, 1.45eV, etc.; and the band gap of the third structural layer 133 can be 1.25eV, 1.27eV, 1.29eV, 1.32eV, 1.35eV, etc.

[0064] In addition, in other embodiments, the band gaps of the first structural layer 131, the second structural layer 132, and the third structural layer 133 can be other values. In this embodiment, the specific values ​​of the band gaps of the three structural layers are not limited, and can be adjusted adaptively according to the actual situation.

[0065] In the above embodiments, the first structural layer 131 can be phosphorus-doped nanocrystalline silicon oxide, the second structural layer 132 can be boron-doped hydrogenated nanocrystalline silicon carbide, and the third structural layer 133 can be phosphorus-doped microcrystalline silicon oxide.

[0066] Specifically, the first structural layer 131 is made of phosphorus-doped nanocrystalline silicon oxide, which allows the first structural layer 131 to have a wider band gap, thereby reducing the band gap difference between the first structural layer 131 and the perovskite top cell unit 11. Simultaneously, this enables the first structural layer 131 to have good light transmittance, and phosphorus doping also provides electron-selective channels, promoting the transport of electrons from the top cell unit 11 to the bottom cell unit 12. The nanocrystalline structure also reduces parasitic absorption, simultaneously improving the absorption effect of the top cell unit 11 for short-wavelength light and reducing the optical loss of the top cell unit 11.

[0067] The second structural layer 132 is made of boron-doped hydrogenated nanocrystalline silicon carbide, which facilitates the adjustment of the band gap of the second structural layer 132 so that its band gap is smaller than that of the first structural layer 131, thereby achieving a band gap gradient from the first structural layer 131 to the second structural layer 132. Furthermore, boron doping enables the formation of an electron-hole transport channel between the first structural layer 131 and the second structural layer 132, further optimizing carrier flow between them.

[0068] The third structural layer 133 is made of phosphorus-doped microcrystalline silicon oxide, which gives it a smaller band gap. This band gap is smaller than that of the second structural layer 132 but larger than that of the bottom cell 12, thus achieving a band gap gradient transition from the top cell 11 to the bottom cell 12. Furthermore, phosphorus doping allows for the formation of an ohmic contact with the bottom cell 12, thereby improving electron collection efficiency. Simultaneously, it also gives the third structural layer 133 good electrical conductivity, reducing series resistance.

[0069] In addition, by making the first structural layer 131 a phosphorus-doped nanocrystalline silicon oxide, the second structural layer 132 a boron-doped hydrogenated nanocrystalline silicon carbide, and the third structural layer 133 a phosphorus-doped microcrystalline silicon oxide, the composite layer 13 can form a double-sided electric field distribution with an "npn" structure, thereby reducing the surface recombination rate and further improving the photoelectric conversion efficiency of the tandem solar cell 1.

[0070] Furthermore, in other embodiments, the specific structural forms of the first structural layer 131, the second structural layer 132, and the third structural layer 133 can be adaptively adjusted according to the actual situation. The embodiments of this application do not limit the specific structural forms of the three structural layers.

[0071] In the above embodiments, the doping concentration of the first structural layer 131 can be 4 × 10⁻⁶. 19 cm -3 -5×10 19 cm -3 For example, the doping concentration of the first structural layer 131 can be 4 × 10⁻⁶. 19 cm -3 4.5×10 19 cm -3 4.8×10 19 cm -3 5×10 19 cm -3 By adjusting the doping concentration of the first structural layer 131, the band gap size of the first structural layer 131 can be adjusted to be close to that of the top cell 11, thereby reducing the band gap difference between the first structural layer 131 and the top cell 11. It can also improve the electron mobility of the first structural layer 131, enhance the electron extraction capability, and reduce the series resistance.

[0072] The doping concentration of the second structural layer 132 can be 6 × 10⁻⁶. 19 cm -3 -7×10 19 cm -3 For example, the doping concentration of the second structural layer 132 can be 6 × 10⁻⁶. 19 cm -3 6.5×10 19 cm -3 6.8×10 19 cm -3 7×10 19 cm -3 By adjusting the doping concentration of the second structural layer 132, the band gap size of the second structural layer 132 can be adjusted to be smaller than that of the first structural layer 131, so as to realize the band gap gradient change between the first structural layer 131 and the second structural layer 132, and to enhance the hole selectivity of the second structural layer 132 and suppress electron reverse injection.

[0073] The doping concentration of the third structural layer 133 can be 8 × 10⁻⁶. 19 cm -3 -9×10 19 cm -3 For example, the doping concentration of the third structural layer 133 can be 8 × 10⁻⁶. 19 cm -3 8.5×10 19 cm -3 8.8×10 19 cm -3 9×10 19 cm -3 By adjusting the doping concentration of the third structural layer 133, the band gap size of the third structural layer 133 can be adjusted to be smaller than the band gap size of the second structural layer 132 and larger than the band gap size of the bottom cell 12, thereby realizing the band gap gradient change from the top cell 11 to the bottom cell 12, and balancing the conductivity and passivation effect of the third structural layer 133.

[0074] In addition, in other embodiments, the doping concentrations of the first structural layer 131, the second structural layer 132, and the third structural layer 133 may be other values. In this application embodiment, the specific values ​​of the doping concentrations of the first structural layer 131, the second structural layer 132, and the third structural layer 133 are not limited, and can be adaptively adjusted according to the actual situation.

[0075] In the above embodiments, the thickness D1 of the first structural layer 131 can satisfy 4nm≤D1≤6nm. For example, the thickness D1 of the first structural layer 131 can be 4nm, 4.5nm, 5nm, 5.5nm, 6nm, etc. While ensuring that the thickness of the first structural layer 131 can provide the necessary passivation effect, it can also avoid the light transmittance of the first structural layer 131 being affected due to the excessive thickness of the first structural layer 131, thereby increasing optical loss.

[0076] The thickness D2 of the second structural layer 132 can satisfy 2nm≤D2≤4nm. For example, the thickness D2 of the second structural layer 132 can be 2nm, 2.5nm, 3nm, 3.5nm, 4nm, etc., so that the second structural layer 132 can effectively block electron tunneling, reduce leakage current, and also avoid high parasitic absorption of the second structural layer 132 due to excessive thickness.

[0077] The thickness D3 of the third structural layer 133 can satisfy 7nm≤D3≤9nm. For example, the thickness D3 of the third structural layer 133 can be 7nm, 7.5nm, 8nm, 8.5nm, 9nm, etc., thereby ensuring the coverage effect of the third structural layer 133, avoiding local contact failure, and at the same time, reducing the series resistance of the third structural layer 133 to improve the overall working efficiency of the stacked battery 1.

[0078] In addition, in other embodiments, the thicknesses of the first structural layer 131, the second structural layer 132, and the third structural layer 133 may be other values. In this application embodiment, the specific values ​​of the thicknesses of the first structural layer 131, the second structural layer 132, and the third structural layer 133 are not limited, and can be adaptively adjusted according to the actual situation.

[0079] In the above embodiments, since the top cell unit 11 is a perovskite cell with a fixed bandgap, there is a technical problem that the utilization rate of short-wavelength light (i.e. light with wavelengths in the range of 390nm to 470nm) is low.

[0080] To solve the above technical problems, such as Figure 1 As shown, the top cell unit 11 in the stacked battery 1 provided in this application embodiment may include a hole transport layer 112, a perovskite layer 113, an exciton multiplication layer 114 and an electron transport layer 115 stacked along the first direction X, wherein the exciton multiplication layer 114 may include a quantum dot array structure.

[0081] With this design, an exciton multiplication layer 114 with a quantum dot array structure is set in the top cell unit 11. By adjusting the size of the quantum dots in the exciton multiplication layer 114, the band gap of the exciton multiplication layer 114 can be adjusted so that the exciton multiplication layer 114 can absorb short-wavelength photons that cannot be utilized by the perovskite layer 113. This improves the wavelength range of short-wavelength light that the top cell unit 11 can absorb and utilize, thereby improving the utilization rate of short-wavelength light by the stacked cell 1.

[0082] Meanwhile, by setting a quantum dot array structure in the exciton multiplication layer 114, multiple quantum dots in the exciton multiplication layer 114 can trigger the exciton multiplication effect after absorbing high-energy short-wavelength photons. That is, the quantum dots can convert a single high-energy photon into multiple excitons, thereby improving the utilization rate of short-wavelength light energy, reducing energy loss, and significantly improving the energy conversion efficiency of the top battery unit 11.

[0083] In the above embodiments, the exciton multiplication layer 114 may include germanium-doped cesium lead bromide quantum dots to form a quantum dot array structure.

[0084] With this design, the cesium lead bromide quantum dots set in the exciton multiplication layer 114 have a large band gap, enabling the exciton multiplication layer to absorb high-energy photons in a wavelength range that the perovskite layer 113 cannot utilize, thus filling the spectral response gap of the top cell unit 11 and improving the light absorption efficiency of the top cell unit 11.

[0085] Meanwhile, germanium doping can be added to the cesium lead bromide quantum dots, which can further widen the band gap of the quantum dots in the exciton multiplication layer 114, thereby further improving the utilization range of short-wavelength photons by the top cell unit 11.

[0086] In the above embodiments, the size of the germanium-doped cesium lead bromide quantum dots can be 3nm-5nm, for example, the size of the germanium-doped cesium lead bromide quantum dots can be 3nm, 3.5nm, 4nm, 4.5nm, 5nm, etc., so that the band gap of the germanium-doped cesium lead bromide quantum dots can be adjusted to 2.8eV-3.2eV, for example, the band gap of the germanium-doped cesium lead bromide quantum dots can be 2.8eV, 2.9eV, 3.0eV, 3.1eV, 3.2eV, etc., thereby improving the absorption range of short-wavelength light of the top cell unit 11 and reducing optical loss.

[0087] In addition, in other embodiments, the size and band gap of germanium-doped cesium lead bromide quantum dots can be other values. In this application embodiment, the specific values ​​of the two are not limited and can be adjusted adaptively according to the actual situation.

[0088] In the above embodiments, the thickness D4 of the exciton multiplication layer 114 can satisfy 15nm≤D4≤20nm. For example, D4 ​​can be 15nm, 16nm, 17nm, 18nm, 20nm, etc. This can improve the absorption effect of the exciton multiplication layer 114 on short-wavelength photons, and also avoid the increase in resistance or defect density of the exciton multiplication layer 114 due to excessive thickness, which would affect the photoelectric conversion efficiency.

[0089] In addition, in other embodiments, the thickness of the exciton multiplication layer 114 can be other values. In this application embodiment, the specific value of the thickness of the exciton multiplication layer 114 is not limited, and can be adaptively adjusted according to the actual situation.

[0090] In the above embodiments, such as Figure 1 As shown, the top battery cell 11 may also include a transparent conductive oxide layer 111 located on top of the hole transport layer 112. The transparent conductive oxide layer 111 has good light transmittance and conductivity, reduces light shading, enables it to penetrate efficiently to the perovskite layer, and can protect the perovskite layer 113.

[0091] Meanwhile, the bottom cell unit 12 may also include a passivation layer 123 located on the back side of the silicon substrate 122. The passivation layer 123 may include an aluminum oxide and silicon nitride structure, which has the functions of reducing reflection and suppressing surface recombination, so as to improve the photoelectric conversion efficiency of the bottom cell unit 12.

[0092] In addition, the stacked battery 1 may also be provided with electrodes 14.

[0093] This application also provides a method for preparing the stacked battery 1, which is used to prepare the stacked battery 1 described above.

[0094] The method for preparing the tandem solar cell 1 includes, but is not limited to, the following steps:

[0095] S11: Fabrication of bottom battery cell 12;

[0096] S12: Sputtering a third structural layer 133 on top of the bottom cell unit 12;

[0097] S13: A second structural layer 132 is deposited on top of the third structural layer 133 using PECVD;

[0098] S14: Deposit the first structural layer 131 on top of the second structural layer 132 using HWCVD;

[0099] S15: Prepare a top cell unit 11 on top of the first structural layer 131.

[0100] The first structural layer 131, the second structural layer 132, and the third structural layer 133 have different band gaps.

[0101] In this embodiment, a composite layer 13 with three layers having different band gaps is prepared between the top battery cell 11 and the bottom battery cell 12 to achieve a band gap gradient change between the top battery cell 11 and the bottom battery cell 12, optimize the carrier flow between the top battery cell 11 and the bottom battery cell 12, reduce voltage loss, and improve the working efficiency of the stacked battery 1.

[0102] In the above embodiments, during the fabrication of the top battery cell 11, step S15 may further include, but is not limited to, the following steps:

[0103] S151: An electron transport layer 115 is prepared on top of the first structural layer 131;

[0104] S152: An exciton multiplication layer 114 is prepared on top of the electron transport layer 115 using a solution method;

[0105] The exciton multiplication layer 114 includes a germanium-doped cesium lead bromide quantum dot array.

[0106] In this embodiment, the exciton multiplication layer 114 is prepared by solution method, which has the advantages of low cost, simple process and large-area preparation, so as to simplify the preparation process of exciton multiplication layer 114 and improve the preparation quality of exciton multiplication layer 114.

[0107] In the above embodiments, during the preparation of the exciton multiplication layer 114, step S152 may further include, but is not limited to, the following steps:

[0108] S152a: A precursor is prepared by mixing cesium lead bromide and germanium iodide at a predetermined molar ratio;

[0109] Cesium lead bromide and germanium iodide can be mixed in a molar ratio of 100:1 to prepare a precursor for subsequent reactions.

[0110] S152b: Germanium-doped cesium lead bromide quantum dots were prepared by adding a mixed solvent of toluene and ethyl acetate to the precursor and using an antisolvent crystallization method.

[0111] Among them, germanium-doped cesium lead bromide quantum dots are prepared by anti-solvent crystallization, and the size of the generated germanium-doped cesium lead bromide quantum dots can be adjusted by controlling the reaction time.

[0112] S152c: Annealing heat treatment of germanium-doped cesium lead bromide quantum dots at a temperature of 170℃-190℃ in a nitrogen atmosphere to form a germanium-doped cesium lead bromide quantum dot array.

[0113] Annealing heat treatment can improve the crystallinity of germanium-doped cesium lead bromide quantum dots.

[0114] In this embodiment, by setting an exciton multiplication layer 114 including germanium-doped cesium lead bromide quantum dots, the exciton multiplication layer 114 has a large band gap, which improves the absorption effect of the exciton multiplication layer 114 on short-wavelength photons and can also trigger the exciton multiplication effect, reducing energy loss.

[0115] This application also provides a photovoltaic module, including the tandem cell 1 described in the above embodiments. By setting a composite layer 13 with a bandgap gradient in the tandem cell 1, the carrier flow between the top cell unit 11 and the bottom cell unit 12 is optimized, voltage loss is reduced, and the overall operating efficiency of the photovoltaic module is improved. Furthermore, the top cell unit 11 of the tandem cell 1 can also be provided with an exciton multiplication layer 114 with a quantum dot array structure to improve the utilization rate of short-wavelength photons by the tandem cell 1, thereby further improving the overall photoelectric conversion efficiency of the photovoltaic module.

[0116] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A stacked battery, characterized in that, The stacked battery includes a top battery unit, a bottom battery unit, and a composite layer located between the top battery unit and the bottom battery unit; Along a first direction, the composite layer has at least a first structural layer, a second structural layer, and a third structural layer stacked together; the first structural layer, the second structural layer, and the third structural layer have different band gaps; The band gap of the first structural layer is larger than the band gap of the second structural layer, and the band gap of the second structural layer is larger than the band gap of the third structural layer; The first structural layer is phosphorus-doped nanocrystalline silicon oxide, the second structural layer is boron-doped hydrogenated nanocrystalline silicon carbide, and the third structural layer is phosphorus-doped microcrystalline silicon oxide.

2. The stacked battery according to claim 1, characterized in that, The top cell unit includes a stacked perovskite layer and an electron transport layer, and the bottom cell unit includes a stacked tunneling oxide layer and a silicon substrate. The first structural layer is in contact with the electron transport layer, and the third structural layer is in contact with the tunneling oxide layer; the band gap of the first structural layer is larger than the band gap of the second structural layer, and the band gap of the second structural layer is larger than the band gap of the third structural layer.

3. The stacked battery according to claim 2, characterized in that, The band gap of the first structural layer is 1.45eV-1.55eV, the band gap of the second structural layer is 1.35eV-1.45eV, and the band gap of the third structural layer is 1.25eV-1.35eV.

4. The stacked battery according to claim 3, characterized in that, The doping concentration of the first structural layer is 4×10 19 cm -3 -5×10 19 cm -3 The doping concentration of the second structural layer is 6 × 10⁻⁶. 19 cm -3 -7×10 19 cm -3 The doping concentration of the third structural layer is 8 × 10⁻⁶. 19 cm -3 -9×10 19 cm -3 ; The thickness D1 of the first structural layer satisfies 4nm≤D1≤6nm, the thickness D2 of the second structural layer satisfies 2nm≤D2≤4nm, and the thickness D3 of the third structural layer satisfies 7nm≤D3≤9nm.

5. The stacked battery according to claim 2, characterized in that, Along the first direction, the top cell unit includes a hole transport layer, the perovskite layer, the exciton multiplication layer and the electron transport layer stacked together; The exciton multiplication layer includes a quantum dot array structure.

6. The stacked battery according to claim 5, characterized in that, The exciton multiplication layer comprises germanium-doped cesium lead bromide quantum dots, used to form the quantum dot array structure.

7. The stacked battery according to claim 6, characterized in that, The germanium-doped cesium lead bromide quantum dots have a size of 3nm-5nm and a band gap of 2.8eV-3.2eV.

8. The stacked battery according to claim 7, characterized in that, The thickness D4 of the exciton multiplication layer satisfies 15nm≤D4≤20nm.

9. A method for preparing a tandem battery, used to prepare the tandem battery according to any one of claims 1-8, characterized in that, The method for preparing the stacked battery includes: Fabrication of bottom battery cells; A third structural layer is sputtered to form on top of the bottom battery cell; A second structural layer is deposited on top of the third structural layer using PECVD. A first structural layer is deposited on top of the second structural layer using HWCVD. A top battery cell is fabricated on top of the first structural layer; The first structural layer, the second structural layer, and the third structural layer have different band gaps.

10. The method for preparing a stacked battery according to claim 9, characterized in that, In the process of preparing the top cell, the method for preparing the stacked battery further includes: An electron transport layer is fabricated on top of the first structural layer; An exciton multiplication layer was prepared on top of the electron transport layer using a solution method. The exciton multiplication layer includes a germanium-doped cesium lead bromide quantum dot array.

11. The method for preparing a stacked battery according to claim 10, characterized in that, The preparation method of the tandem solar cell specifically includes the following steps during the process of preparing the exciton multiplication layer on top of the electron transport layer using a solution method: A precursor was prepared by mixing cesium lead bromide and germanium iodide at a predetermined molar ratio. Germanium-doped cesium lead bromide quantum dots were prepared by adding a mixed solvent of toluene and ethyl acetate to the precursor and using an antisolvent crystallization method. The germanium-doped cesium lead bromide quantum dots are subjected to annealing heat treatment at a temperature of 170℃-190℃ in a nitrogen atmosphere to form the germanium-doped cesium lead bromide quantum dot array.

12. A photovoltaic module, characterized in that, The photovoltaic module includes the tandem cell as described in any one of claims 1-8.

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