Preparation method of laminated solar cell and laminated solar cell

Abstract

The invention provides a preparation method of a laminated solar cell and the laminated solar cell. The preparation method of the laminated solar cell comprises the following steps: respectively manufacturing a plurality of top cells and a plurality of bottom cells; electrical performance testing is carried out on the top battery and the bottom battery respectively, the electrical performance testing at least comprises short-circuit current, and the short-circuit current density of the top battery and the bottom battery is calculated according to the area of the top battery and the bottom battery; and stacking and electrically connecting the top cell and the bottom cell of which the short-circuit current density difference value is within a preset range to form the laminated solar cell. According to the preparation method of the laminated solar cell, the current density of the top cell and the current density of the bottom cell can be better matched, the comprehensive electrical performance of the laminated cell is maximized, and the photoelectric conversion efficiency of the laminated cell is greatly improved.

Description

Technical Field

[0001] This application belongs to the field of solar cell processing technology, specifically, it relates to a method for preparing a tandem solar cell and a tandem solar cell. Background Technology

[0002] With the continuous advancement of crystalline silicon solar cell technology, its photoelectric conversion efficiency has gradually approached its theoretical limit. Tandem solar cells, due to their potential to break through the efficiency bottleneck of single-junction cells, have become an important research direction in the photovoltaic industry. Currently, the mainstream tandem structure mainly adopts the connection methods of two-terminal (2T) and four-terminal (4T) to connect the bottom and top cells in series and parallel to achieve electrical integration.

[0003] In a 2T structure, the top and bottom cells are connected in series. If the currents of the top and bottom cells are not well matched, the overall output current will be limited to a small value, significantly reducing the overall photoelectric conversion efficiency of the tandem solar cell. In contrast, while a 4T structure allows for independent control of the operating states of the top and bottom cells, avoiding current matching limitations, its modules require two separate sets of electrodes. Furthermore, at the photovoltaic power plant system level, at least two combiner systems are needed to handle the power generation of the top and bottom cells, significantly increasing the wiring complexity and operation and maintenance costs of the power plant, which is not conducive to large-scale commercial applications.

[0004] Therefore, there is an urgent need to develop a method for fabricating tandem solar cells and tandem solar cells that can maintain the advantages of series-parallel compatibility of 2T structure modules, effectively alleviate the strict dependence of top and bottom cells on current matching, and fully realize the photoelectric conversion efficiency potential of tandem cells. Summary of the Invention

[0005] In view of this, this application provides a method for preparing a tandem solar cell and a tandem solar cell.

[0006] This application proposes a method for fabricating a tandem solar cell, characterized by comprising:

[0007] S100, manufacture multiple top batteries and multiple bottom batteries respectively;

[0008] S200. Perform electrical performance tests on the top battery and the bottom battery respectively. The electrical performance tests include at least the short-circuit current.

[0009] S300: Stack and electrically connect the top cell and bottom cell with short-circuit current density difference within a preset range to form multiple stacked solar cells; wherein, short-circuit current density = short-circuit current / area.

[0010] As a further example, in step S100, the bandgap width of the top battery matches the bandgap width of the bottom battery.

[0011] As a further example, the top cell is a perovskite cell, and the bottom cell is a crystalline silicon cell; step S100 includes:

[0012] The perovskite layer composition of the perovskite solar cell is adjusted to make its bandgap 1.6eV~1.9eV.

[0013] As a further example, step S200 includes:

[0014] When testing the electrical performance of the top battery, a standard solar intensity of AM1.5G solar spectrum was used; when testing the electrical performance of the bottom battery, the spectral wavelength range used was (653nm~775nm)~1200nm.

[0015] As a further example, the preset range is 0~0.1mA / cm. 2 .

[0016] As a further example, step 300 includes:

[0017] The multiple top cells and multiple bottom cells are divided into graded gradients based on their respective preset current differences. The short-circuit current is divided into several grades from high to low. Top cells and bottom cells of the same grade are stacked and electrically connected. The difference in short-circuit current density between the top cells and bottom cells in each stacked solar cell is within the preset range.

[0018] As a further example, the electrical performance test also includes photoelectric conversion efficiency; step S300 includes:

[0019] First, the multiple top batteries and multiple bottom batteries are divided into graded gradients based on their respective preset current differences. Then, based on the short-circuit current from high to low, they are divided into several grades. Top batteries and bottom batteries with the same grade are considered as a set of matching units.

[0020] Multiple top cells and multiple bottom cells within the same set of matching units are divided into graded gradients based on their respective preset efficiency differences. They are further divided into several grades according to the photoelectric conversion efficiency from high to low. Top cells and bottom cells of the same grade are stacked. The difference in short-circuit current density between the top cells and bottom cells in each stacked solar cell is within the preset range.

[0021] As a further example, between step S100 and step S200, at least one of EL detection, PL detection, and AOI detection is also included.

[0022] As a further example, the top battery includes an intermediate transition layer. When the top battery is manufactured, the intermediate transition layer is used as the bottom layer. The intermediate transition layer is a transparent insulating material and has multiple through holes. The through holes are filled with conductive material. The top battery and the bottom battery are electrically connected through the conductive material.

[0023] As a further example, the conductive material includes a transparent conductive oxide material or a metallic material; the transparent insulating material includes any one of glass, sapphire, transparent ceramic, PI, POE, and PET.

[0024] As a further example, the thickness of the intermediate transition layer is 10μm~500μm, and the light transmittance is >90%.

[0025] As a further example, if the top electrode of the bottom battery is a metal electrode, the orthographic projection of the through hole on the bottom battery at least partially coincides with the metal electrode region.

[0026] As a further example, if the functional layer material in the top battery that contacts the intermediate transition layer is a transparent conductive oxide and the conductive material is also a transparent conductive oxide material, the through-hole is filled at the same time as the functional layer is prepared.

[0027] According to another aspect of this application, a tandem solar cell is also proposed, which is prepared by any of the above-described methods for preparing tandem solar cells.

[0028] The method for fabricating tandem solar cells proposed in this invention involves separately fabricating the top and bottom cells, and conducting electrical performance tests on both cells before stacking them. The top and bottom cells with matching short-circuit current densities are then stacked and connected, achieving a better current match between them. This maximizes the overall electrical performance of the tandem solar cell and significantly improves its photoelectric conversion efficiency. This method solves the current mismatch problem that may exist in traditional 2T structures, combining the advantages of both traditional 2T and 4T structures while avoiding their respective drawbacks. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0030] The structures, proportions, sizes, etc., shown in the accompanying drawings are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the implementation conditions of this application. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size should still fall within the scope of the technical content disclosed in this application, provided that they do not affect the effects and purposes that this application can produce.

[0031] Figure 1 This is a schematic diagram of the structure of a stacked solar cell according to an embodiment of this application;

[0032] Figure 2 A schematic diagram of the structure of an intermediate transition layer according to an embodiment of this application;

[0033] Figure 3 A schematic diagram of the intermediate transition layer provided in another embodiment of this application.

[0034] Explanation of reference numerals in the attached figures: 100 - Top cell; 110 - Intermediate transition layer; 120 - Functional layer; 130 - Other top cell material layers; 111 - Conductive material; 200 - Bottom cell; 210 - Top electrode; 220 - Other bottom cell material layers. Detailed Implementation

[0035] The embodiments of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0036] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] As described in the background art, in existing stacked cells, it is often difficult to achieve a good current match between the top cell and the bottom cell. In the stacked structure at both ends, since the top and bottom cells are connected in series, the output current of the entire cell depends on the one with the smaller current / current density. If the two are mismatched, some photogenerated carriers will not be effectively collected, resulting in a significant reduction in the overall conversion efficiency.

[0038] This application proposes a method for fabricating a tandem solar cell, comprising:

[0039] S100, manufacture multiple top batteries and multiple bottom batteries respectively;

[0040] The top cell is preferably a perovskite cell, and the bottom cell includes any one of crystalline silicon cells, amorphous silicon cells, compound semiconductor solar cells (e.g., gallium arsenide (GaAs), indium phosphide (InP), cadmium telluride (CdTe), copper indium gallium selenide (CIGS)), perovskite cells, silicon heterojunction cells, and organic photovoltaic cells.

[0041] To maximize the overall electrical performance of tandem solar cells, the bandgap widths of the top and bottom cells must be designed collaboratively; that is, the bandgap width of the fabricated top cell must match that of the bottom cell. This bandgap matching refers to the existence of an optimal bandgap width range for the top cell for a given bottom cell type. Within this range, the solar spectrum can be efficiently segmented, and the photocurrent generated by the stacked top and bottom cells tends to be balanced, effectively reducing current mismatch losses and improving overall photoelectric conversion efficiency. Therefore, the top cell should be fabricated according to the corresponding optimal bandgap width range as much as possible. For different types of bottom cells, the optimal bandgap width range for the matching top cell (perovskite cell) differs. See the example below for specific optimal bandgap width ranges.

[0042] In this application, matching the bandgap widths of the top and bottom cells during fabrication helps improve the current matching degree between them. Specifically, during the fabrication of the top cell, its composition can be adjusted to match the bandgap width of the top cell with that of the bottom cell.

[0043] For example, when the bottom cell is a crystalline silicon cell, its band gap is ~1.12 eV, and the optimal band gap for the top perovskite cell is ~1.68 eV; when the bottom cell is a copper indium gallium selenide cell, its band gap is 1.0 eV to 1.2 eV, and the optimal band gap for the top perovskite cell is 1.7 eV to 1.8 eV; when the bottom cell is a low-bandgap perovskite cell, its band gap is 1.2 eV to 1.3 eV, and the optimal band gap for the top perovskite cell is 1.7 eV to 1.9 eV; when the bottom cell is an organic photovoltaic cell, its band gap is 1.3 eV to 1.5 eV, and the optimal band gap for the top perovskite cell is 1.8 eV to 2.0 eV.

[0044] In a preferred embodiment, the top cell is a perovskite cell and the bottom cell is a crystalline silicon cell; step S100 includes: when fabricating the top cell, adjusting the perovskite layer composition of the perovskite cell so that the bandgap of the top cell is 1.6eV~1.9eV.

[0045] Specifically, when fabricating a perovskite top solar cell, a perovskite layer (PVK layer) needs to be configured. Its composition is mainly made of organic-inorganic lead halide perovskite materials, typically with the chemical formula ABX3, where A is an organic cation (such as methylammonium or formamidinium), and B is lead ions (Pb). 2+ X represents a halide ion (such as iodine, bromine, or chlorine).

[0046] As one example, a target bandgap can be obtained by mixing three cations—formamidinium, methylammonium, and cesium—with two halide anions—iodine and bromide. More specifically, for example, Cs... X (FA （1-λ-z） MAz) 1-X Pb(I 1-λ Br λ 3. As the Br content increases, the band gap increases approximately linearly from ~1.48 eV for FAPbI3. For example, at x=0.17, FA 0.83 Cs 0.17 Pb(I 0.83 Br 0.17 3. The band gap is 1.68 eV.

[0047] Alternatively, another example could be a mixture of FAPbI3 and CsPbI3 or FAPbBr3, (FAPbI3) 1-x (CsPbBr3) x By adjusting the value of x, the band gap of pure FAPbI3 (~1.48 eV) can be increased to the target range. For example, when x=0.2, the band gap can be increased to about 1.72 eV.

[0048] S200. Perform electrical performance tests on the top and bottom batteries respectively. The electrical performance tests include at least the short-circuit current.

[0049] As one example of electrical performance testing, such as IV testing (Current-Voltage), it measures the current output of the battery at different voltages to obtain key parameters related to battery performance, such as open-circuit voltage (Voc), short-circuit current (Isc), fill factor (FF), and conversion efficiency (Eff). The electrical performance testing in this application includes at least short-circuit current. Considering the possibility that the areas of the top and bottom cells are not completely identical, short-circuit current density is used when matching the stacking of the top and bottom cells. The short-circuit current density (Jsc) of the top and bottom cells can be calculated separately based on their respective areas. It should be understood that, given the battery area, short-circuit current and short-circuit current density can be converted to each other using the formula Isc = Jsc × battery area. It should be noted that when the top and bottom batteries have almost the same area, only the short-circuit current of the top and bottom batteries can be considered. Stacking and electrically connecting the top and bottom batteries with a short-circuit current density difference within a preset range is equivalent to stacking and electrically connecting the top and bottom batteries with a short-circuit current difference (short-circuit current density difference multiplied by area) within a preset range.

[0050] Furthermore, when performing IV testing on the bottom cell, the spectral wavelength range used is (653~775nm)~1200nm. The spectrum within this wavelength range is the most realistic spectral range when the bottom cell is working, simulating the actual stacked top and bottom cells. This closely approximates the actual stacked working conditions, making the test results closer to the actual situation, thus making the test results more accurate and helping to maximize the overall electrical performance of the stacked cells.

[0051] The selection of the spectral wavelength range is based on the following: the band gap of the top cell (perovskite cell) is 1.6 eV to 1.9 eV. According to Planck's formula E = hc / λ, the corresponding wavelength range is 652.6 nm to 775 nm. In addition, the inventors found that there are fluctuations in the perovskite solution between different batches during actual testing. It is necessary to calibrate the sorting spectrum of the bottom cell according to the absorption of the spectrum of each batch of top cells. Therefore, (653~775 nm) to 1200 nm is used as the test spectral wavelength range of the bottom cell.

[0052] Specifically, the spectral wavelength range can be achieved using methods such as filters or spectral matching.

[0053] Furthermore, since the top cell is located above the stacked cells, when performing IV testing on the top cell, a standard solar intensity under the AM1.5G solar spectrum is sufficient.

[0054] S300. Stack and electrically connect the top cell and bottom cell with short-circuit current density difference within a preset range to form multiple stacked solar cells; wherein, short-circuit current density = short-circuit current / area. The short-circuit current density of the top cell and bottom cell can be calculated separately according to this formula. When the areas are the same, only the short-circuit current can be considered.

[0055] Specifically, after obtaining the short-circuit current of all the completed top and bottom cells, they can be matched and stacked according to the above requirements.

[0056] Preferably, the preset range is 0~0.1mA / cm 2 At this point, the difference in short-circuit current density between the top and bottom cells only needs to be less than 0.1 mA / cm². 2 The two can then be stacked. Within this preset range, the current mismatch of the stacked battery is small, which can maximize the overall electrical performance of the stacked battery. The preset range of this application is not limited to this.

[0057] Furthermore, as one embodiment, in order to more quickly obtain the top cell and bottom cell whose short-circuit current density difference is within a preset range among the fabricated multiple top cells and multiple bottom cells, step 300 specifically includes:

[0058] Multiple top cells and multiple bottom cells are divided into graded gradients based on their respective preset current differences. The short-circuit current is divided into several grades from high to low. Top cells and bottom cells of the same grade are stacked and electrically connected. The difference in short-circuit current density between the top cells and bottom cells in each stacked solar cell is within a preset range.

[0059] The preset current difference between the top battery and the bottom battery can be the same or different, depending on the actual situation. The goal is to expedite the current rating process and ensure the short-circuit current density difference between the top and bottom batteries remains within a preset range. Stacking and electrically connecting top and bottom batteries of the same rating means stacking the top battery with the highest short-circuit current rating with the bottom battery with the highest short-circuit current rating, stacking the top battery with the second highest short-circuit current rating with the bottom battery with the second highest short-circuit current rating, and so on, thus matching the top batteries for each rating.

[0060] It should also be noted that when classifying the top and bottom batteries according to the preset current difference, considering that all top batteries have the same area and all bottom batteries have the same area, the classification is generally based on the short-circuit current. The preset current difference is the current value. The example below takes into account the matching of top and bottom batteries with different areas and uses the short-circuit current density as the preset current difference for classification. In actual classification, either method can be used. The key is the matching of the current parameters between the top and bottom batteries during matching. The current parameter refers to the short-circuit current density (when the top and bottom batteries have the same area, the current parameter also refers to the short-circuit current).

[0061] Specifically, the preset range for the short-circuit current density difference is 0~0.1mA / cm. 2 Let's take examples to illustrate:

[0062] For example, the preset current difference between the top and bottom batteries is the same, and both are 0.1 mA / cm. 2 Examples of two of the settings: The short-circuit current density range for the first setting of the top battery is 18.4 mA / cm². 2 ~18.3mA / cm 2 The short-circuit current density range for the second tier is 18.3 mA / cm². 2 ~18.2mA / cm 2 The short-circuit current density range for the first stage of the bottom battery is 18.4 mA / cm². 2 ~18.3mA / cm 2 The short-circuit current density range for the second tier is 18.3 mA / cm². 2 ~18.2mA / cm 2 The top battery (first setting) is stacked with the bottom battery (first setting), and the top battery (second setting) is stacked with the bottom battery (second setting), with the short-circuit current density difference between the top and bottom batteries in all settings being 0~0.1mA / cm. 2 Within the range.

[0063] For example, the preset current difference between the top and bottom batteries is different; the preset current difference for the top battery is 0.1 mA / cm. 2 The preset current difference of the bottom battery is 0.08 mA / cm. 2 Example of two of the settings: The short-circuit current density range for the first setting of the top battery is 18.4 mA / cm². 2 ~18.3mA / cm 2 The short-circuit current density range for the second tier is 18.3 mA / cm². 2 ~18.2mA / cm 2 The short-circuit current density range for the first stage of the bottom battery is 18.4 mA / cm². 2 ~18.3mA / cm 2The short-circuit current density range for the second tier is 18.32 mA / cm². 2 ~18.22mA / cm 2 The top battery (first setting) is stacked with the bottom battery (first setting), and the top battery (second setting) is stacked with the bottom battery (second setting). At this point, the short-circuit current density difference between the top and bottom batteries in all settings is 0~0.1 mA / cm². 2 Within the range.

[0064] Furthermore, as another embodiment, in order to more quickly obtain top and bottom cells with short-circuit current density differences within a preset range among the fabricated multiple top and bottom cells, and to further improve adaptability and optimize the overall electrical performance of the stacked cells, the electrical performance test also includes photoelectric conversion efficiency; step S300 includes:

[0065] First, multiple top and bottom batteries are divided into gradients based on their respective preset current differences. Then, based on the short-circuit current, they are divided into several levels from high to low. Top and bottom batteries in the same level are considered as a matching unit. That is, top and bottom batteries with short-circuit current density differences within a preset range are divided into multiple matching units based on the numerical range of their short-circuit currents. The reason for multiple matching units is that, regardless of whether it's a top or bottom battery, due to the large number of batteries and their differences, the difference between the highest and lowest values ​​of the obtained short-circuit current / short-circuit current density for all batteries will be greater than the preset current difference.

[0066] Multiple top cells and multiple bottom cells in the same set of matching units are divided into graded gradients based on their respective preset efficiency differences. They are further divided into several grades according to the photoelectric conversion efficiency from high to low. Top cells and bottom cells of the same grade are stacked. The difference in short-circuit current density between the top cells and bottom cells in each stacked solar cell is within a preset range.

[0067] At this point, the process of dividing the top and bottom cells with short-circuit current density differences within a preset range into multiple matching units based on the numerical range of short-circuit current density can be considered as coarse-level division. Further classifying multiple top and bottom cells in the same matching unit based on photoelectric conversion efficiency is considered as fine-level division. Stacking top and bottom cells with the same level within the same matching unit is considered as fine-level matching.

[0068] The coarse-scale division includes: dividing multiple top batteries and multiple bottom batteries into several scales based on their respective preset current differences, and dividing them into several scales according to the short-circuit current from high to low. Top batteries and bottom batteries with the same scale are regarded as the same set of matching units, and the difference in short-circuit current density between top batteries and bottom batteries in the same set of matching units is within a preset range.

[0069] For fine-level division, the preset efficiency difference between the top battery and the bottom battery can be the same or different. Stacking top and bottom batteries of the same level means that for the same set of matching units, the top battery with the highest photoelectric conversion efficiency is stacked with the bottom battery with the highest photoelectric conversion efficiency, the top battery with the second highest photoelectric conversion efficiency is stacked with the bottom battery with the second highest photoelectric conversion efficiency, and so on, to complete the matching of top batteries with each level.

[0070] For example, the preset efficiency difference is 0.2%, that is, the photoelectric conversion efficiency is graded by a gradient of 0.2%. The preset efficiency difference in this application is not limited to this.

[0071] Specifically, when performing electrical performance tests (IV tests) on the top and bottom cells separately, not only the short-circuit current density of all top and bottom cells is measured, but also the photoelectric conversion efficiency of all top and bottom cells is measured.

[0072] Assuming the preset current difference between the top and bottom batteries is 0.1 mA / cm. 2 For example, the short-circuit current density ranges from 18.4 mA / cm². 2 ~18.3mA / cm 2 Multiple top cells, with a short-circuit current density range of 18.4 mA / cm². 2 ~18.3mA / cm 2 Multiple bottom cells form a matching unit; the short-circuit current density ranges from 18.3 mA / cm². 2 ~18.2mA / cm 2 Multiple top cells, with a short-circuit current density range of 18.3 mA / cm². 2 ~18.2mA / cm 2 The multiple bottom cells form another set of matching units.

[0073] To illustrate finer range division and matching in more detail, a further example is given for a short-circuit current density range of 18.4 mA / cm². 2 ~18.3mA / cm 2 Multiple top cells with short-circuit current densities ranging from 18.4 mA / cm² 2 ~18.3mA / cm 2The matching units under multiple bottom cells are assumed to be based on a preset efficiency difference of 0.2% for both the top and bottom cells. With finer grading, the top three gradations are 17.2%~17.4%, 17%~17.2%, and 16.8%~17%, while the bottom three gradations are 11.6%~11.8%, 11.4%~11.6%, and 11.2%~11.4%. Therefore, a top cell with a photoelectric conversion efficiency of 17.2%~17.4% is stacked with a bottom cell with a photoelectric conversion efficiency of 11.6%~11.8%; a top cell with a photoelectric conversion efficiency of 17%~17.2% is stacked with a bottom cell with a photoelectric conversion efficiency of 11.4%~11.6%; and a top cell with a photoelectric conversion efficiency of 16.8%~17% is stacked with a bottom cell with a photoelectric conversion efficiency of 11.2%~11.4%. Of course, these are just examples and not limited to them. In practice, multiple sets of matching units are divided and top and bottom cells are stacked based on actual test results. The division method is to match as many top and bottom cells as possible within the preset range of the difference in short-circuit current density between the top and bottom cells in the tandem solar cell, and further make the difference in short-circuit current density smaller.

[0074] The method for fabricating tandem solar cells proposed in this invention involves testing and sorting the top and bottom cells before stacking. Top and bottom cells with matching short-circuit current densities are then stacked and connected, achieving a better match between them. This maximizes the overall electrical performance of the tandem solar cell and significantly improves its photoelectric conversion efficiency. This method solves the current mismatch problem that may exist in traditional 2T structures, combining the advantages of both traditional 2T and 4T structures while avoiding their respective drawbacks.

[0075] Furthermore, the entire stacked battery obtained by this preparation method outputs a pair of positive and negative electrodes, which facilitates series and parallel connection design at the module end.

[0076] As another embodiment, at least one of EL detection, PL detection, and AOI detection is included between step S100 and step S200. That is, before performing the IV test in step 200, defective solar cells can be removed using these methods, thereby improving work efficiency.

[0077] Specifically, EL testing, or Electroluminescence (EL), can clearly detect problems such as microcracks, broken grids, and bright / dark areas in solar cells. PL testing, or Photoluminescence (PL), uses light to excite semiconductor materials to generate fluorescence signals, used to detect defects in solar cells (such as microcracks and impurities) and to assess process quality. AOI inspection, or Automated Optical Inspection, is a device based on optical principles to detect surface defects and sort cells by color.

[0078] EL and PL testing are used to screen for internal defects in batteries. Samples with localized blackening or darkening exceeding a certain area, or dark cracks exceeding a certain length, are typically screened. The screening target is to select samples with a uniform overall shine. AOI testing is used to select samples with consistent appearance and no visible flaws (contamination, cracks, color variations, etc.).

[0079] In another embodiment, the top cell includes an intermediate transition layer, and in step S100, the intermediate transition layer is used as the bottom layer when fabricating the top cell. Figure 1 As shown, the intermediate transition layer 110 is made of transparent insulating material and has multiple through holes. The through holes are filled with conductive material 111, and the top battery 100 and the bottom battery 200 are electrically connected through the conductive material 111.

[0080] like Figure 2 , Figure 3 The diagram shows a schematic representation of the intermediate transition layer in two different embodiments. Figure 2 The through holes are arranged in a dot matrix pattern. Figure 3 The through holes are strip-shaped, and the intermediate process layer 110 has multiple strip-shaped through holes arranged side by side.

[0081] Specifically, the transparent insulating material can be any one of glass, sapphire, transparent ceramics, polyimide film (PI), ethylene-octene copolymer (POE), or polyethylene terephthalate (PET). Glass examples include UTG glass (Ultra-Thin Glass) and quartz glass. Furthermore, the light transmittance of the intermediate transition layer 110 is >90%. Because of its excellent light transmittance, the intermediate transition layer 110 helps reduce light loss and improves the efficiency of the tandem solar cell. The thickness of the intermediate transition layer 110 is 10μm to 500μm. When the thickness of the intermediate transition layer 110 is too small, the physical support effect is poor; when the thickness of the intermediate transition layer 110 is too large, it may reduce the light transmittance.

[0082] The conductive material 111 includes a transparent conductive oxide material or a metallic material. Transparent conductive oxide materials include, for example, TCO, ITO, and FTO, while metallic materials include, for example, copper, silver, and aluminum. This conductive material 111 is conductive enough to achieve a good electrical connection between the top battery 100 and the bottom battery 200.

[0083] In addition, the top cell includes at least a top electrode, and the bottom cell includes at least a bottom electrode.

[0084] By fabricating the top cell on the intermediate transition layer and then stacking and connecting the top cell with the bottom cell, the influence of the surface morphology and roughness of the bottom cell on the electrical performance of the stacked cell can be avoided when fabricating the top cell directly on the bottom cell.

[0085] There are various ways to create through holes in the intermediate transition layer 110, such as laser modification combined with etching solution to create through holes, or physical drilling methods, such as direct laser drilling, etc. There are also many ways to fill the through holes with conductive material 110, such as screen printing, laser transfer, etc.

[0086] Furthermore, in step S100, when preparing the top cell 100, if the material of the functional layer 120 (the first layer prepared on the intermediate transition layer 110) in the top cell that contacts the intermediate transition layer 110 is a transparent conductive oxide and the conductive material 111 is also a transparent conductive oxide material, the through hole is filled at the same time as the functional layer 120 is prepared, thereby simplifying the process and saving more time.

[0087] like Figure 1 As shown, the top cell 100 also includes other top cell material layers 130. For example, the top cell 100 is a perovskite cell, and the other top cell material layers 130 include a hole transport layer, a perovskite layer, an electron transport layer, a top electrode, etc. The bottom cell 200 includes a top electrode 210 and other bottom cell material layers 220. For example, the bottom cell is an HJT cell, and the other bottom cell material layers 220 include a front transparent conductive layer, intrinsic amorphous silicon, N-type amorphous silicon or microcrystalline silicon, a silicon substrate, intrinsic amorphous silicon, P-type amorphous silicon or microcrystalline silicon, a back transparent conductive layer, and a back electrode.

[0088] As another embodiment, if the top electrode of the bottom battery 200 is a metal electrode, the orthographic projection of the through hole on the bottom battery 200 at least partially overlaps with the metal electrode area. Preferably, the pattern of the through hole is consistent with the pattern of the metal electrode. In this way, the top battery 100 is electrically connected to the top electrode of the bottom battery 200 through the conductive material 111 in the through hole, thereby enabling a better electrical connection between the top battery 100 and the bottom battery 200. For example, when the top electrode of the bottom battery 200 is a finger electrode pattern formed by metal paste (such as silver paste), the pattern of the through hole can be designed to align and match the pattern of the metal electrode. Alternatively, in addition to multiple through holes, transverse blind slots and longitudinal blind slots can be provided between the through holes. The width, depth, and arrangement of the blind slots can be adapted to the linewidth, spacing, and process tolerance of the metal electrode to ensure that the metal electrode can be effectively embedded and form a continuous conductive path with the conductive material.

[0089] According to another aspect of this application, a tandem solar cell is also proposed, which is prepared using the tandem solar cell preparation method of any of the above embodiments. This tandem solar cell features a tailored combination, with more accurate current matching between the top and bottom cells, maximizing the overall electrical performance of the tandem solar cell and significantly improving photoelectric conversion efficiency.

[0090] Example 1

[0091] 1. Fabrication of bottom-layer cells (HJT cells)

[0092] a) Silicon wafer gettering;

[0093] b) Pile making;

[0094] c) Deposit intrinsic amorphous silicon, N-type amorphous silicon, or microcrystalline silicon on the front side;

[0095] d) Deposit intrinsic amorphous silicon, P-type amorphous silicon, or microcrystalline silicon on the back side;

[0096] e) Deposit TCO (transparent conductive layer) on the front and back sides;

[0097] f) Print paste electrodes on the back side and dry them.

[0098] 2. Top cell fabrication (perovskite solar cell)

[0099] Prepare an intermediate transition layer. For example, using glass, a through hole is created on the glass using a combination of laser and etching.

[0100] a) Deposit a transparent conductive oxide material such as TCO, ITO or FTO on the upper surface of the intermediate transition layer with a thickness of 100nm~600nm, while its through holes are filled with transparent conductive oxide material;

[0101] b) Deposited hole transport layer (HTL), including NiOx, SAM layer, etc.;

[0102] c) Deposit a perovskite layer;

[0103] d) Deposition interface modification layer (including LiF, EDAI, etc.)

[0104] e) Deposit electron transport layer (ETL), including SnOx, C60, etc.;

[0105] f) Deposit a transparent conductive layer (TCO), such as ITO, IZO, IWO, or a hybrid conductive layer;

[0106] g) Surface-printed metal electrodes.

[0107] 3. IV testing and matching of test indicators

[0108] First, select all prepared top and bottom cells that are uniformly bright and free of visible defects by means of at least one of EL detection, PL detection, or AOI detection.

[0109] Then, IV tests were performed on the selected top and bottom cells, with test parameters including photoelectric conversion efficiency and short-circuit current. The short-circuit current density of the top and bottom cells was calculated based on their areas. Specifically, the spectral wavelength range used for the top cell was 300nm~1200nm. The spectral wavelength range used for the bottom cell IV test was (653nm~775nm)~1200nm, obtaining the photoelectric conversion efficiency and short-circuit current for each top and bottom cell. When performing IV tests on the top cell, the conductive material in the intermediate transition layer served as the bottom electrode, and the metal electrode printed on the surface of the top cell served as the top electrode. The test probes were then placed in contact with the top and bottom electrodes to perform the IV test.

[0110] Next, based on the short-circuit current density results, the difference in short-circuit current density between the top and bottom cells was obtained, ranging from 0 to 0.1 mA / cm². 2 After multiple sets of matching units within the range, multiple top cells and multiple bottom cells within the same set of matching units are divided into several grades based on a preset efficiency difference of 0.2% and the photoelectric conversion efficiency is divided from high to low. Top cells and bottom cells of the same grade are then stacked.

[0111] Specifically, the multiple sets of matching units are:

[0112] The short-circuit current density ranges from 18.5 mA / cm². 2 ~18.4mA / cm 2 Multiple top cells, with a short-circuit current density range of 18.5 mA / cm². 2 ~18.4mA / cm 2Multiple bottom batteries form the first set of matching units;

[0113] The short-circuit current density ranges from 18.4 mA / cm². 2 ~18.3mA / cm 2 Multiple top cells, with a short-circuit current density range of 18.4 mA / cm². 2 ~18.3mA / cm 2 Multiple bottom batteries form the second set of matching units;

[0114] The short-circuit current density ranges from 18.3 mA / cm². 2 ~18.2mA / cm 2 Multiple top cells, with a short-circuit current density range of 18.3 mA / cm². 2 ~18.2mA / cm 2 Multiple bottom batteries form the third matching unit;

[0115] And so on.

[0116] For the first set of matching units, the multiple top cells are divided into levels of 17.2%~17.4%, 17%~17.2%, 16.8%~17%..., and the multiple bottom cells are divided into levels of 11.6%~11.8%, 11.4%~11.6%, 11.2%~11.4%..., respectively.

[0117] A top cell with a photoelectric conversion efficiency of 17.2%~17.4% is stacked with a bottom cell with a photoelectric conversion efficiency of 11.6%~11.8%; a top cell with a photoelectric conversion efficiency of 17%~17.2% is stacked with a bottom cell with a photoelectric conversion efficiency of 11.4%~11.6%; a top cell with a photoelectric conversion efficiency of 16.8%~17% is stacked with a bottom cell with a photoelectric conversion efficiency of 11.2%~11.4%, and so on.

[0118] The matching and stacking of the top and bottom cells in the next set of matching units can be done in the same way.

[0119] 4. Stack the matched top and bottom batteries.

[0120] For each set of compatible batteries, a conductive adhesive material, such as solder paste or conductive glue, is applied to the lower surface of the intermediate transition layer of the top battery to bond the top battery and the bottom battery together. The adhesive material can be applied by printing, spraying, dispensing, or other methods. Then, the top battery and the bottom battery are subjected to low-temperature assisted external pressure to further ensure the reliability of the bonding.

[0121] Example 2

[0122] 1) Fabrication of bottom-layer cells (TOPCon cells)

[0123] a) Texturing silicon wafers;

[0124] b) Polishing the back side;

[0125] c) The back side consists of a tunneling oxide layer and an LP intrinsic amorphous silicon layer, in sequence.

[0126] d) Backside boron diffusion to form boron-doped polysilicon with BSG on the surface;

[0127] e) Remove the surface oxide layer on the front side, form a tunneling oxide layer and LP intrinsic amorphous silicon on the front surface, perform phosphorus diffusion to form phosphorus-doped poly silicon, and surface PSG;

[0128] f) Remove PSG and BSG from the front, back, and edges;

[0129] g) Alumina / SiNx stacked passivation film is deposited on the back side, and a transparent conductive film (TCO) or alumina / SiNx stacked passivation film is deposited on the front side;

[0130] h) The blue film is annealed;

[0131] i) Both the front and back sides are AlOx / SiNx stacked passivation films. The front side is laser-etched, and its pattern corresponds to the distribution of through holes on the intermediate transition layer. The back side is laser-etched, and the etched pattern corresponds to the back electrode pattern.

[0132] j) Low-temperature paste is printed on the front and back sides in the laser-opened area and cured to obtain the front electrode and the back electrode.

[0133] 2. Top cell fabrication (perovskite solar cell)

[0134] Same as in Example 1; the difference is that the position distribution of the through holes opened on the intermediate transition layer corresponds to the front electrode of the bottom battery.

[0135] 3. IV testing and matching of test indicators

[0136] Same as Example 1.

[0137] 4. Stack the matched top and bottom batteries.

[0138] Same as Example 1.

[0139] Example 3

[0140] 1) Fabrication of bottom-layer cells (perovskite cells)

[0141] a) FTO glass is cut to a size similar to that of the top battery;

[0142] b) Deposition of hole transport layer on the upper surface (SAM, NiOx, etc.);

[0143] c) Redeposit the perovskite layer;

[0144] d) Subsequent functional layer deposition (including interface modification layers such as LiF and EDAI);

[0145] e) Electron transport layer deposition (C60, SnOx, etc.)

[0146] f) Deposition of a surface TCO conductive layer;

[0147] Alternatively, P1, P2, P3, and P4 laser scribing lines can be imported into it as needed;

[0148] 2. Top cell fabrication (perovskite solar cell)

[0149] Same as in Example 1;

[0150] 3. IV testing and matching of test indicators

[0151] Same as Example 1.

[0152] 4. Stack the matched top and bottom batteries.

[0153] Same as Example 1.

[0154] It should be noted that the method for fabricating the tandem solar cell protected in this application does not limit the order in which the top cell and bottom cell are fabricated; the above embodiments are merely examples.

[0155] The various embodiments in this specification are described in a progressive, parallel, or combined manner. Each embodiment focuses on its differences from other embodiments, and similar or identical parts between embodiments can be referred to interchangeably. For the apparatuses disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple, and relevant parts can be referred to the method section.

[0156] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for fabricating a tandem solar cell, characterized in that, include: S100, manufacture multiple top batteries and multiple bottom batteries respectively; S200. Perform electrical performance tests on the top battery and the bottom battery respectively. The electrical performance tests include at least the short-circuit current. S300: Stack and electrically connect the top cell and bottom cell with short-circuit current density difference within a preset range to form multiple stacked solar cells; wherein, short-circuit current density = short-circuit current / area.

2. The method for preparing a tandem solar cell according to claim 1, characterized in that, In step S100, the bandgap width of the top battery matches the bandgap width of the bottom battery.

3. The method for preparing a tandem solar cell according to claim 2, characterized in that, The top cell is a perovskite cell, and the bottom cell is a crystalline silicon cell; step S100 includes: The perovskite layer composition of the perovskite solar cell is adjusted to make its bandgap 1.6eV~1.9eV.

4. The method for preparing a tandem solar cell according to claim 1, characterized in that, Step S200 includes: When testing the electrical performance of the top battery, a standard solar intensity of AM1.5G solar spectrum was used; when testing the electrical performance of the bottom battery, the spectral wavelength range used was (653nm~775nm)~1200nm.

5. The method for preparing a tandem solar cell according to claim 1, characterized in that, The preset range is 0~0.1mA / cm 2 .

6. The method for preparing a tandem solar cell according to claim 1, characterized in that, Step 300 includes: The multiple top cells and multiple bottom cells are divided into graded gradients based on their respective preset current differences. The short-circuit current is divided into several grades from high to low. Top cells and bottom cells of the same grade are stacked and electrically connected. The difference in short-circuit current density between the top cells and bottom cells in each stacked solar cell is within the preset range.

7. The method for preparing a tandem solar cell according to claim 1, characterized in that, The electrical performance test also includes photoelectric conversion efficiency; step S300 includes: First, the multiple top batteries and multiple bottom batteries are divided into graded gradients based on their respective preset current differences. Then, based on the short-circuit current from high to low, they are divided into several grades. Top batteries and bottom batteries with the same grade are considered as a set of matching units. Multiple top cells and multiple bottom cells within the same set of matching units are divided into graded gradients based on their respective preset efficiency differences. They are further divided into several grades according to the photoelectric conversion efficiency from high to low. Top cells and bottom cells of the same grade are stacked. The difference in short-circuit current density between the top cells and bottom cells in each stacked solar cell is within the preset range.

8. The method for preparing a tandem solar cell according to claim 1, characterized in that, Between step S100 and step S200, at least one of EL detection, PL detection, and AOI detection is also included.

9. The method for preparing a tandem solar cell according to claim 1, characterized in that, The top battery includes an intermediate transition layer. When the top battery is manufactured, the intermediate transition layer is used as the bottom layer. The intermediate transition layer is a transparent insulating material and has multiple through holes. The through holes are filled with conductive material. The top battery and the bottom battery are electrically connected through the conductive material.

10. The method for preparing a tandem solar cell according to claim 9, characterized in that, The conductive material includes transparent conductive oxide materials or metallic materials; the transparent insulating material includes any one of glass, sapphire, transparent ceramics, PI, POE, and PET.

11. The method for preparing a tandem solar cell according to claim 9, characterized in that, The thickness of the intermediate transition layer is 10μm~500μm, and the light transmittance is >90%.

12. The method for preparing a tandem solar cell according to claim 9, characterized in that, If the top electrode of the bottom battery is a metal electrode, the orthographic projection of the through hole on the bottom battery at least partially coincides with the metal electrode region.

13. The method for preparing a tandem solar cell according to claim 9, characterized in that, If the functional layer material in the top battery that contacts the intermediate transition layer is a transparent conductive oxide and the conductive material is also a transparent conductive oxide material, the through-hole is filled at the same time as the functional layer is prepared.

14. A tandem solar cell, characterized in that, The tandem solar cell was prepared using the method described in any one of claims 1 to 13.

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