Stacked solar cell

Abstract

The present disclosure relates to the technical field of solar cells, and discloses a laminated solar cell. The laminated solar cell comprises a cell body, a first electrode, a second electrode, a third electrode and a fourth electrode; the cell body comprises a top cell and a bottom cell; the first electrode and the second electrode are arranged on the side surface of the top cell opposite to the bottom cell, and the polarities of the first electrode and the second electrode are opposite; the third electrode and the fourth electrode are arranged on the side surface of the bottom cell opposite to the top cell, and the polarities of the third electrode and the fourth electrode are opposite. The present disclosure solves the limitation of current matching conditions, and the wiring mode is more simple, thereby reducing the preparation cost.

Description

Technical Field

[0001] This disclosure relates to the field of solar cell technology, and more specifically, to a tandem solar cell. Background Technology

[0002] In the field of solar cell technology, to overcome the photoelectric conversion efficiency limit of single-junction solar cells, tandem solar cells have been designed. Tandem solar cells achieve segmented absorption and more efficient utilization of the solar spectrum by stacking sub-cells with different bandgap widths. Currently, tandem cell architectures are mainly divided into two categories: monolithic two-terminal tandem solar cells and mechanically stacked four-terminal tandem solar cells.

[0003] Monolithic tandem solar cells are fabricated by directly mounting two or more sub-cells with different bandgap onto each other, achieving monolithic integration through internal tunneling junctions or composite layers. Ultimately, power is output only through two electrodes located on the upper and lower surfaces of the monolithic tandem solar cell. The biggest advantage of this structure is its simple end-user interface, requiring no additional external circuitry. However, this simplicity comes at the cost of stringent internal matching requirements. Specifically, monolithic tandem solar cells must face the inherent current matching challenge; that is, because the sub-cells are connected in series, the output current of the entire device is strictly limited by the sub-cell with the smaller current.

[0004] Mechanically stacked four-terminal tandem solar cells are fabricated by separately preparing two independently functioning sub-cells and then physically stacking them. Each sub-cell has independent positive and negative electrodes, with a pair of positive and negative electrodes located on the top and bottom surfaces of each sub-cell, resulting in a total of four output terminals. This fundamentally eliminates the constraints of current matching. However, this architectural advantage comes at the cost of significantly higher system costs, with complex wiring and a surge in overall system expenses. Summary of the Invention

[0005] This disclosure provides a tandem solar cell to solve the problems of limited output current and complex structure of existing tandem solar cells.

[0006] This application provides a tandem solar cell, including a cell body, a first electrode, a second electrode, a third electrode, and a fourth electrode; the cell body includes a top cell and a bottom cell stacked together; the first electrode and the second electrode are disposed on the surface of the top cell opposite to the bottom cell, and the first electrode and the second electrode have opposite polarities; the third electrode and the fourth electrode are disposed on the surface of the bottom cell opposite to the top cell, and the third electrode and the fourth electrode have opposite polarities.

[0007] Beneficial effects: First, the photocurrent generated by the top and bottom cells is output through their respective output terminals, thereby structurally solving the current matching limitations of traditional monolithic two-terminal tandem solar cells and avoiding the series current limiting phenomenon where a specific solar cell limits the overall output current, thus improving output stability and long-term energy yield in actual photovoltaic power generation environments. Second, the top and bottom cells of this disclosure do not contain an intermediate composite layer, a metal intermediate electrode, or a TCO-based bonding layer, which not only simplifies the manufacturing process and reduces process costs, but also effectively suppresses the increase in contact resistance and parasitic light absorption, improving the reliability of long-term operation. Finally, the wiring method of this disclosure is simpler, reducing manufacturing costs, and this design can improve structural simplicity, electrical stability, and optical efficiency. Furthermore, this disclosure has good compatibility with existing two-terminal photovoltaic module systems.

[0008] In some optional embodiments, the top cell is configured as a perovskite cell, which includes a perovskite absorber layer, a first charge transport layer, and a second charge transport layer; the perovskite absorber layer is formed on one side surface of the bottom cell; the first charge transport layer and the second charge transport layer are alternately formed on the side surface of the perovskite absorber layer opposite to the bottom cell, the first charge transport layer is connected to the first electrode, and the second charge transport layer is connected to the second electrode. In some optional embodiments, the first charge transport layer and the second charge transport layer are spaced apart; and / or, multiple first charge transport layers and multiple second charge transport layers are provided.

[0009] Beneficial effects: Incident light is converted into charge carriers in the perovskite absorption layer. Hole carriers and electron carriers are output from the first electrode and the second electrode after passing through the first charge transport layer and the second charge transport layer, respectively, thereby converting light energy into electrical energy and improving photoelectric conversion efficiency.

[0010] In some alternative embodiments, the bottom battery is configured as a back contact battery, the back contact battery including a substrate layer, a first passivated contact structure and a second passivated contact structure; the substrate layer is formed on one side surface of the top battery; the first passivated contact structure and the second passivated contact structure are alternately formed on the side surface of the substrate layer opposite to the top battery, the first passivated contact structure is connected to the third electrode and the second passivated contact structure is connected to the fourth electrode.

[0011] Beneficial effects: By setting the first passivation contact structure and the second passivation contact structure on the back surface of the substrate, the light-blocking area of ​​the light-receiving surface is reduced to the greatest extent, the light-receiving area is expanded, and the effects of reducing optical loss, improving light incident efficiency and increasing the photocurrent of the bottom cell are achieved.

[0012] In some optional embodiments, the first passivation contact structure includes a first tunneling layer and a first doped polysilicon layer stacked together, the second passivation contact structure includes a second tunneling layer and a second doped polysilicon layer stacked together, the third electrode is adapted to be connected to the first doped polysilicon layer, and the fourth electrode is adapted to be connected to the second doped polysilicon layer; or, at least one of the first passivation contact structure and the second passivation contact structure includes an intrinsic amorphous silicon layer and a doped amorphous silicon layer stacked together.

[0013] Beneficial effects: This disclosure utilizes a doped polycrystalline silicon layer or a doped amorphous silicon layer to achieve carrier transport.

[0014] In some alternative embodiments, the first passivation contact structure and the second passivation contact structure are spaced apart; or, the first passivation contact structure and the second passivation contact structure are in contact with each other.

[0015] In some alternative embodiments, the tandem solar cell further includes a first dielectric layer formed on the surface of the top cell on the side opposite to the bottom cell.

[0016] Beneficial effects: The first dielectric layer can passivate, reduce reflection and light transmission, suppress recombination caused by surface defects, reduce leakage current and improve the electrical insulation characteristics between the first electrode and the second electrode.

[0017] In some alternative embodiments, the tandem solar cell further includes a second dielectric layer formed between the top cell and the bottom cell.

[0018] Beneficial effects: The second dielectric layer can passivate, reduce reflection and transmit light. It can passivate and reduce reflection on the bottom cell below, reduce surface defects, reduce light reflectivity, and thus improve the amount of incident light and photoelectric conversion efficiency.

[0019] In some alternative embodiments, the first electrode or the second electrode is configured as a semi-transparent electrode structure, wherein the semi-transparent electrode structure has a light transmittance of greater than or equal to 70% for incident light with wavelengths between 550 and 1100 nm.

[0020] Beneficial effects: Configuring the first and second electrodes as semi-transparent electrode structures can increase light transmittance, providing as much incident light as possible to the top and bottom cells, thereby improving the amount of incident light and photoelectric conversion efficiency.

[0021] In some alternative embodiments, among the first electrode, the second electrode, the third electrode, and the fourth electrode, a group of electrodes with the same polarity is configured to be connected, and another group of electrodes with the same polarity is configured to be connected; and / or, the tandem solar cell is a monolithic tandem solar cell. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the specific embodiments of this disclosure or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 This diagram illustrates the structure of a monolithic two-terminal tandem solar cell in the prior art. Figure 2 This diagram illustrates the structure of a mechanically stacked four-terminal tandem solar cell in the prior art. Figure 3 A schematic diagram of the structure of the stacked solar cell in an embodiment of this disclosure is shown; Figure 4 An equivalent circuit diagram of a tandem solar cell according to an embodiment of this disclosure is shown; Figure 5 Another structural schematic diagram of a stacked solar cell in an embodiment of this disclosure is shown.

[0024] Explanation of reference numerals in the attached figures: 1. Monolithic two-terminal tandem solar cell; 11. Perovskite solar cell; 12. Crystalline silicon solar cell; 13. Composite layer; 14. Front electrode; 15. Back electrode; 2. Mechanically stacked four-terminal tandem solar cell; 21. Perovskite solar cell; 22. Crystalline silicon solar cell; 23. First positive electrode; 24. First negative electrode; 25. Second positive electrode; 26. Second negative electrode; 3. Tandem solar cell; 31. Top cell; 310. Perovskite absorber layer; 311. First charge transport layer; 312. Second charge transport layer; 31a. First photocurrent source; 31b. First diode; 32. Bottom cell; 320. Substrate layer; 321. First passivation contact structure; 321a. First tunneling layer; 321b. First doped polycrystalline silicon layer; 322. Second passivation contact structure; 322a. Second tunneling layer; 322b. Second doped polycrystalline silicon layer; 32a. Second photocurrent source; 32b. Second diode; 33. First electrode; 34. Second electrode; 35. Third electrode; 36. Fourth electrode; 37. First dielectric layer; 38. Second dielectric layer; 39. First external terminal; 40. Second external terminal. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0026] Figure 1 A schematic diagram of a conventional single-substrate monolithic two-terminal tandem solar cell 1 is shown. The conventional monolithic two-terminal tandem solar cell 1 includes a perovskite solar cell 11 on top and a crystalline silicon solar cell 12 on the bottom. The perovskite solar cell 11 and the crystalline silicon solar cell 12 are electrically connected in series via a composite layer 13. In this structure, the front electrode 14 of the perovskite solar cell 11 and the back electrode 15 of the crystalline silicon solar cell 12 serve as external output terminals. The two front electrodes 14 act as positive electrodes, and the two back electrodes 15 act as negative electrodes, so that the entire tandem solar cell appears externally as a monolithic two-terminal tandem solar cell 1 with only two terminals.

[0027] However, since the perovskite solar cell 11 and the crystalline silicon solar cell 12 are connected in series, both must carry the same current, inevitably resulting in a current-limited structure. Consequently, the output current of the entire tandem solar cell is limited by the smaller current generated by either the perovskite solar cell 11 or the crystalline silicon solar cell 12. Based on this structural characteristic, current matching between the perovskite solar cell 11 and the crystalline silicon solar cell 12 becomes an essential design requirement. In other words, it is necessary to precisely control the absorption spectrum, thickness, band gap, light absorption coefficient, and carrier transport characteristics of both the perovskite solar cell 11 and the crystalline silicon solar cell 12 to ensure they generate the same photocurrent.

[0028] The aforementioned current matching conditions can be achieved to some extent in laboratory environments using artificial light sources or limited spectral conditions. However, in actual solar power generation environments, the solar spectrum continuously changes with time, season, climate conditions, and installation location, making it difficult to maintain a stable current matching state between the perovskite solar cell 11 and the crystalline silicon solar cell 12 over a long period. In particular, the perovskite solar cell 11, which is sensitive to short wavelength regions, and the crystalline silicon solar cell 12, which mainly responds to long wavelength regions, exhibit significantly different current response characteristics when facing spectral changes, leading to frequent current mismatch phenomena under actual operating conditions.

[0029] Furthermore, when the thickness, absorption characteristics, or carrier transport characteristics of the perovskite solar cell 11 and the crystalline silicon solar cell 12 are artificially limited to meet current matching conditions, the perovskite solar cell 11 and the crystalline silicon solar cell 12 often fail to fully realize their optimal photoelectric conversion performance. This not only limits the overall maximum output power and energy output of the tandem solar cell, but may also lead to increased efficiency fluctuations and decreased system output stability during long-term operation.

[0030] Finally, the composite layer 13 located between the perovskite solar cell 11 and the crystalline silicon solar cell 12 directly affects the performance and reliability of the entire device due to its electrical, chemical, and structural stability. Increased resistance, interface defects, or material degradation in the composite layer 13, in a series connection structure, directly lead to a decrease in the output performance of the entire tandem solar cell. This is especially true when combined with the inherent ion migration characteristics, thermal stress, and long-term operating conditions of the perovskite solar cell 11, causing even more serious problems regarding the long-term reliability of the device.

[0031] Figure 2 This diagram illustrates a mechanically stacked four-terminal tandem solar cell 2, specifically a tandem solar cell structure consisting of an upper perovskite solar cell 21 and a lower crystalline silicon solar cell 22 physically superimposed. In this structure, the perovskite solar cell 21 and the crystalline silicon solar cell 22 are electrically separated and each has an independent set of electrodes. This structural design avoids current matching issues. For example, the perovskite solar cell 21 has a first positive electrode 23 and a first negative electrode 24, while the crystalline silicon solar cell has a second positive electrode 25 and a second negative electrode 26. A gap or insulating layer exists between the first negative electrode 24 and the second positive electrode 25. However, this mechanically stacked four-terminal tandem solar cell 2 requires separate electrodes and wiring structures for the perovskite solar cell 21 and the crystalline silicon solar cell 22, increasing the number of external output terminals, complicating the module wiring structure, and requiring additional interconnect structures and power conversion devices. This not only increases the complexity of the module manufacturing process but also leads to increased system costs and decreased reliability, while also hindering compatibility with existing crystalline silicon solar cell modules and power systems.

[0032] Therefore, in the existing technology, there is no sufficient solution that can simultaneously solve the problem. Figure 1 The inherent current matching and composite layer 13 dependence problems of monolithic two-terminal tandem solar cells 1, and Figure 2 A technical solution to the problems of increased wiring complexity and system cost caused by mechanically stacked four-terminal tandem solar cells 2.

[0033] Based on this, refer to Figure 3 and Figure 4This disclosure provides a tandem solar cell 3, which includes a cell body, a first electrode 33, a second electrode 34, a third electrode 35, and a fourth electrode 36. The cell body includes a top cell 31 and a bottom cell 32 stacked together. The first electrode 33 and the second electrode 34 are disposed on the surface of the top cell 31 opposite to the bottom cell 32, and the polarities of the first electrode 33 and the second electrode 34 are opposite. The third electrode 35 and the fourth electrode 36 are disposed on the surface of the bottom cell 32 opposite to the top cell 31, and the polarities of the third electrode 35 and the fourth electrode 36 are opposite. In some embodiments, among the first electrode 33, the second electrode 34, the third electrode 35, and the fourth electrode 36, a set of electrodes with the same polarity is configured to connect to a first external terminal 39, and another set of electrodes with the same polarity is configured to connect to a second external terminal 40. In other embodiments, the first electrode 33 and the second electrode 34 of the top cell 31 and the third electrode 35 and the fourth electrode 36 of the bottom cell 32 are independent of each other, and the current of the top cell 31 and the bottom cell 32 is output independently. In some embodiments, the tandem solar cell 3 is a monolithic tandem solar cell.

[0034] Compared to Figure 1The related technologies employ tunnel junctions or series connection of composite layers 13. This disclosure uses a tandem solar cell composed of a top cell 31 and a bottom cell 32, with the first external terminal 39 and the second external terminal 40 serving as output terminals of different polarities for the entire cell. A group of electrodes with the same polarity is connected to the same output terminal, and another group of electrodes with the same polarity is connected to a different output terminal. For example, the first electrode 33 and the third electrode 35 are a group of electrodes with the same polarity, connected to the first external terminal 39; the second electrode 34 and the fourth electrode 36 are a group of electrodes with the same polarity, connected to the second external terminal 40. Thus, the photocurrents generated by the top cell 31 and the bottom cell 32 are respectively collected and output through their corresponding output terminals. Alternatively, the currents of the top cell 31 and the bottom cell 32 can also be output independently, thus structurally solving the limitation of current matching conditions in traditional monolithic two-terminal tandem solar cells 1. Since the top cell 31 and the bottom cell 32 maintain independent photocurrent generation characteristics, even if photoelectric loss mismatch occurs between the top cell 31 and the bottom cell 32 due to changes in the solar spectrum over time, seasons, weather conditions, or installation environment, the series current limiting phenomenon of limiting the overall output current by a specific solar cell will not occur, improving the output stability and long-term energy yield in actual photovoltaic power generation environments. This disclosure connects the top cell 31 and the bottom cell 32 in parallel through a first external output terminal and a second external output terminal, allowing the top cell 31 and the bottom cell 32 to share the same external output voltage during operation. In the parallel connection structure, although the top cell 31 and the bottom cell 32 share the same output voltage, the photocurrents they generate can be different, and the currents generated by the two are superimposed at the first and second external output terminals before being output. Therefore, compared to… Figure 1 While related technologies are limited by current matching conditions, this application is not. However, to ensure the stable operation of the parallel output structure in this application, the operating voltages of the top battery 31 and the bottom battery 32 can be configured to at least partially overlap, where the operating voltage refers to the maximum power point voltage (MPP voltage). For example, the output voltage ranges of the two batteries can be made close by adjusting the bandgap, light absorption layer thickness, effective area, or series resistance of the top battery 31, and / or adjusting the structural parameters of the bottom battery 32. This disclosure achieves the parallel output structure without requiring an additional DC-DC converter for voltage conversion.

[0035] Furthermore, in the tandem solar cell disclosed herein, there is no need to set up Figure 1The intermediate layer used in the monolithic two-terminal tandem solar cell 1 is a tunnel junction or composite layer 13, so the intermediate layer formation process, high vacuum sputtering process and laser aperture process can be omitted. This not only simplifies the manufacturing process and reduces the process cost, but also effectively suppresses plasma damage, interface degradation and parasitic light absorption caused by the perovskite absorber layer 310 in the top cell 31, and improves the reliability of long-term operation.

[0036] Finally, compared to Figure 2 The mechanically stacked four-terminal tandem solar cell 2 requires multiple output terminals, complex wiring structures, and multiple maximum power point tracking (MPPT) controls. The wiring method disclosed in this invention is simpler, reducing manufacturing costs. Moreover, this design can improve structural simplicity, electrical stability, and optical efficiency. Furthermore, this invention has good compatibility with existing two-terminal photovoltaic module systems and is suitable for existing two-terminal photovoltaic modules, series and inverter systems, effectively reducing the balance of system (BOS) cost and system complexity.

[0037] like Figure 1 and Figure 3 As shown, from an electrical perspective, this disclosure structurally avoids problems such as increased contact resistance, localized short circuits, and increased series resistance due to thermal stress and long-term degradation that may occur in the composite layer 13 or the intermediate electrode. Furthermore, since the charge collection paths of the top cell 31 and the bottom cell 32 are clearly separated, unnecessary leakage current can be suppressed, thereby reducing factors that lead to a decrease in the fill factor. From an optical perspective, since this disclosure does not include a TCO-based composite layer 13 or a metal intermediate electrode with light absorption characteristics, it can minimize parasitic light absorption and reflection losses generated during the transmission of light transmitted from the top cell 31 to the bottom cell 32. This improves the light utilization efficiency of the bottom cell 32 and further enhances the overall photoelectric conversion efficiency of the tandem solar cell.

[0038] like Figure 1 , Figure 3 and Figure 4As shown, the first electrode 33 and the second electrode 34 are located on the light-receiving surface of the tandem solar cell 3, and the third electrode 35 and the fourth electrode 36 are located on the back-lighting surface of the tandem solar cell 3. This disclosure presents a tandem structure with a top cell 31 and a bottom cell 32 optically integrated on the same substrate. That is, the top cell 31 and the bottom cell 32 form a tandem structure sharing a substantially identical light propagation path, including but not limited to coaxial incident forms, optical coupling layers, light scattering layers, refractive index modulation layers, or light path deflection structures. In some embodiments, the top cell 31 and the bottom cell 32 transmit current to an external circuit in parallel through two terminals, the first external terminal 39 and the second external terminal 40, jointly forming a monolithic integrated optical tandem structure to power the external circuit. In other words, the top cell 31 and the bottom cell 32 of this disclosure form a monolithic integrated optical tandem structure at the physical level through a parallel output structure sharing the same external terminal voltage, but electrically they do not form a series connection structure based on a tunnel junction or composite layer 13. Based on this, the top cell 31 and the bottom cell 32 can be configured such that, in a parallel connection state, the voltage ranges of the top cell 31 and the bottom cell 32 at least partially overlap. Based on this, the present disclosure can adaptively adjust the band gap, the thickness of the perovskite absorption layer 310, the electrode area, the series resistance, or the light absorption characteristics of the top cell 31 and the bottom cell 32.

[0039] In some embodiments, such as Figure 3 As shown, the top cell 31 is configured as a perovskite cell, which includes a perovskite absorber layer 310, a first charge transport layer 311, and a second charge transport layer 312. The perovskite absorber layer 310 is formed on one side surface of the bottom cell 32. The first charge transport layer 311 and the second charge transport layer 312 are alternately formed on the side surface of the perovskite absorber layer 310 opposite to the bottom cell 32. The first charge transport layer 311 is connected to the first electrode 33, and the second charge transport layer 312 is connected to the second electrode 34. Hole carriers and electron carriers are output from the first electrode 33 and the second electrode 34 after passing through the first charge transport layer 311 and the second charge transport layer 312, respectively, thereby converting light energy into electrical energy and improving the photoelectric conversion efficiency.

[0040] This disclosure comprises a perovskite absorber layer 310, a first charge transport layer 311, and a second charge transport layer 312, forming a perovskite solar cell. One of the first charge transport layer 311 and the second charge transport layer 312 is an electron transport layer, and the other is a hole transport layer. The hole transport layer and the electron transport layer are alternately formed on the same side surface of the perovskite absorber layer 310. Therefore, an upper hole collecting electrode is formed on one side of the hole transport layer, and an upper electron collecting electrode is formed on the other side of the electron transport layer. One of the first electrode 33 and the second electrode 34 is a positive electrode, and the other is a negative electrode. For example, when the first charge transport layer 311 is a hole transport layer and the second charge transport layer 312 is an electron transport layer, the first electrode 33 is the positive electrode, and the second electrode 34 is the negative electrode. Incident light is converted into charge carriers in the perovskite absorber layer 310. Hole carriers are output from the positive electrode via the hole transport layer, and electron carriers are output from the negative electrode via the electron transport layer.

[0041] In some embodiments, such as Figure 3 As shown, the bottom cell 32 is configured as a back contact cell, which includes a substrate layer 320, a first passivated contact structure 321, and a second passivated contact structure 322. The substrate layer 320 is formed on one side surface of the top cell 31. The first passivated contact structure 321 and the second passivated contact structure 322 are alternately formed on the side surface of the substrate layer 320 opposite to the top cell 31. The first passivated contact structure 321 is connected to the third electrode 35, and the second passivated contact structure 322 is connected to the fourth electrode 36. In some embodiments, the substrate layer 320 is monocrystalline silicon or polycrystalline silicon.

[0042] It is understandable that the first passivated contact structure 321 and the second passivated contact structure 322 have opposite conductivity types, and one of the third electrode 35 and the fourth electrode 36 is a positive electrode, while the other is a negative electrode. This disclosure uses a back-contact battery as the bottom battery 32. Carrier transport is achieved through the first passivated contact structure 321 and the second passivated contact structure 322. Incident light is converted into carriers in the substrate layer 320, achieving photoelectric conversion. The use of a back-contact battery means that the first passivated contact structure 321 and the second passivated contact structure 322 are disposed on the back surface of the substrate layer 320, thereby minimizing the light-blocking area of ​​the light-receiving surface, expanding the light-receiving area, and achieving the effects of reducing optical loss, improving light incident efficiency, and increasing the photocurrent of the bottom battery 32. In summary, all electrodes in the top battery 31 and the bottom battery 32 are disposed on the outside of the battery, greatly reducing the wiring difficulty at both ends.

[0043] Specifically, the bottom cell 32 can be configured as an interdigitated back contact cell (IBC cell), a heterojunction back contact cell (HBC cell), a tunnel oxide passivated back contact cell (TBC cell), and a hybrid passivated back contact cell (HTBC cell), etc. Taking a TBC cell as an example, the first passivation contact structure 321 includes a first tunneling layer 321a and a first doped polysilicon layer 321b stacked together, and the second passivation contact structure 322 includes a second tunneling layer 322a and a second doped polysilicon layer 322b stacked together. The third electrode 35 is adapted to be connected to the first doped polysilicon layer 321b, and the fourth electrode 36 is adapted to be connected to the second doped polysilicon layer 322b. One of the first doped polysilicon layer 321b and the second doped polysilicon layer 322b is a P-type doped polysilicon layer, and the other is an N-type doped polysilicon layer. This disclosure utilizes the first doped polysilicon layer 321b and the second doped polysilicon layer 322b to realize carrier transport. As mentioned above, an isolation zone is formed between the first tunneling layer 321a and the second tunneling layer 322a. The function of the isolation zone is to prevent leakage current.

[0044] In some embodiments, multiple first charge transport layers 311 and second charge transport layers 312 are alternately arranged, and correspondingly, multiple first electrodes 33 and second electrodes 34 are also alternately arranged. In some embodiments, multiple first passivation contact structures 321 and second passivation contact structures 322 are alternately arranged, and correspondingly, multiple third electrodes 35 and fourth electrodes 36 are also alternately arranged. In some embodiments, the first charge transport layers 311 and second charge transport layers 312 are spaced apart. In some embodiments, the first passivation contact structures 321 and second passivation contact structures 322 are spaced apart; or the first passivation contact structures 321 and second passivation contact structures 322 are in contact with each other.

[0045] In some embodiments, such as Figure 3 As shown, the tandem solar cell 3 also includes a first dielectric layer 37, which is formed on the surface of the top cell 31 opposite to the bottom cell 32. The first dielectric layer 37 can passivate, reduce reflection, and increase light transmission. Specifically, the first dielectric layer 37 is formed on the surface of the perovskite absorber layer 310 opposite to the substrate layer 320, and is located between the first charge transport layer 311 and the second charge transport layer 312. The first dielectric layer 37 suppresses recombination caused by surface defects, reduces leakage current, and improves the electrical insulation characteristics between the first electrode 33 and the second electrode 34.

[0046] In some embodiments, the tandem solar cell 3 further includes a second dielectric layer 38, which provides passivation, anti-reflection, and light transmission effects. Preferably, the second dielectric layer 38 is formed over its entire surface between the top cell 31 and the bottom cell 32. The second dielectric layer 38 provides passivation and anti-reflection effects to the bottom cell 32, reducing surface defects and light reflectivity, thereby improving the amount of incident light and photoelectric conversion efficiency. In other embodiments, the top cell 31 and the bottom cell 32 are in direct contact, i.e., the perovskite absorber layer 310 is directly formed on the substrate layer 320.

[0047] In some embodiments, the first dielectric layer 37 and the second dielectric layer 38 described above may be a silicon nitride layer and / or an aluminum oxide layer.

[0048] In some embodiments, the first electrode 33 and the second electrode 34 are configured as a semi-transparent electrode structure, wherein the light transmittance of the semi-transparent electrode structure for incident light with wavelengths between 550 and 1100 nm is greater than or equal to 70% in the wavelength region of 550 to 1100 nm. The first electrode 33 and the second electrode 34 are located on the light-receiving surface of the tandem solar cell 3. Therefore, configuring the first electrode 33 and the second electrode 34 as a semi-transparent electrode structure can increase the light transmittance and provide as much incident light as possible to the top cell 31 and the bottom cell 32, thereby improving the amount of incident light and the photoelectric conversion efficiency.

[0049] For example, the semi-transparent electrode structure can be made of indium tin oxide (ITO), indium zinc oxide (IZO), aluminum-doped zinc oxide (AZO), fluorine-doped tin oxide (FTO), ultrathin silver (Ag), silver nanowires (Ag nanowire), graphene, metal mesh, conductive polymer, or a composite structure thereof, with an electrode thickness ranging from 5 to 300 nm and a sheet resistance ranging from 3 to 200 Ω / sq.

[0050] In some embodiments, the third electrode 35 and the fourth electrode 36 may be composed of Ag, Cu, Al, Ni, Cr, Ti, Mo, etc.

[0051] In some embodiments, the tandem solar cell 3 further includes an encapsulation layer (not shown in the figures), which is disposed at least on one side surface of the cell body. For example, the encapsulation layer is disposed on the side surface of the top cell 31 opposite to the bottom cell 32, thereby sealing and protecting the tandem solar cell 3 on the light-receiving side. This disclosure improves the sealing and stability of the tandem solar cell 3 by providing an encapsulation layer, avoiding the negative impacts of the external environment and extending its service life. Specifically, the encapsulation layer can be formed of glass, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), parylene, epoxy barrier, alumina (Al2O3), silicon nitride (SiNx), a multilayer organic / inorganic barrier, or a composite structure thereof. The thickness of the encapsulation layer ranges from 100 nm to 1 mm, and the water vapor transmission rate is less than 10%. -2 g / m 2 ·day.

[0052] refer to Figure 3 and Figure 4 This disclosure also provides a method for preparing a tandem solar cell 3, which specifically includes the following steps: S100 provides a battery body, which includes a top battery 31 and a bottom battery 32 stacked together.

[0053] For example, taking the top cell 31 as a perovskite cell and the bottom cell 32 as a TBC cell, the fabrication of the cell body includes the following steps: S110, a substrate layer 320 is provided, and a plurality of alternating first passivation contact structures 321 and second passivation contact structures 322 are formed on one side surface of the substrate layer 320. The first passivation contact structure 321 includes a first tunneling layer 321a and a first doped polysilicon layer 321b, and the second passivation contact structure 322 includes a second tunneling layer 322a and a second doped polysilicon layer 322b.

[0054] For example, the substrate layer 320 can be configured as an N-type monocrystalline silicon wafer. Before forming the first passivation contact structure 321 and the second passivation contact structure 322, the N-type monocrystalline silicon wafer can be pre-processed by texturing, for example, by using wet etching or plasma etching processes to form a textured structure on the surface of the N-type monocrystalline silicon wafer that reduces light reflection. The first tunneling layer 321a and the second tunneling layer 322a can be formed by thermal oxidation, chemical oxidation, or plasma oxidation processes. The first doped polycrystalline silicon layer 321b and the second doped polycrystalline silicon layer 322b can be formed by LPCVD, PECVD, sputtering, or post-deposition thermal treatment crystallization processes. For example, the first doped polycrystalline silicon layer 321b can be configured as a P-type doped polycrystalline silicon layer formed by boron doping, and the second doped polycrystalline silicon layer 322b can be configured as an N-type doped polycrystalline silicon layer formed by phosphorus doping or arsenic doping. The P-type doped polysilicon layer and the corresponding first tunneling layer 321a form a first passivation contact structure 321, and the N-type doped polysilicon layer and the corresponding second tunneling layer 322a form a second passivation contact structure 322. The isolation region between the first passivation contact structure 321 and the second passivation contact structure 322 can be prepared by laser grooving and alkaline cleaning.

[0055] In some embodiments, the first tunneling layer 321a and the second tunneling layer 322a may be formed of SiOx, SiOyNz or a composite structure thereof, and their thickness may be from about 0.5 nm to 3 nm, preferably from 0.8 nm to 2 nm. The thickness of the first doped polysilicon layer 321b and the second doped polysilicon layer 322b may be from about 20 nm to 300 nm, preferably from 40 nm to 180 nm. S120, a perovskite absorber layer 310 is formed on the surface of the substrate 320 opposite to the tunneling layer, and then a first charge transport layer 311 and a second charge transport layer 312 are alternately formed on the surface of the perovskite absorber layer 310 opposite to the substrate 320.

[0056] For example, the perovskite absorber layer 310, the first charge transport layer 311, and the second charge transport layer 312 can be formed using processes such as spin coating, blade coating, slot coating, inkjet printing, evaporation deposition, or hybrid deposition. After the perovskite absorber layer 310 is formed, the first charge transport layer 311 and the second charge transport layer 312 are formed. For example, the first charge transport layer 311 is configured as a hole transport layer, and the second charge transport layer 312 is configured as an electron transport layer.

[0057] In some embodiments, the perovskite absorber layer 310 employs a composition having a band gap in the range of about 1.50 eV to 1.90 eV, preferably a composition with a band gap in the range of about 1.60 eV to 1.78 eV. For example, the perovskite absorber layer 310 may employ FA. 1- x MAx Pb(I 1- Br 3. Components include formamidinium-cesium dication perovskite, cesium-formamidinium-methylammonium trication perovskite, rubidium-cesium co-doped perovskite, and bromine-rich wide-bandgap perovskite. The thickness of the perovskite absorber layer 310 can be approximately 200 nm to 1500 nm, preferably 400 nm to 900 nm. The electron transport layer can be made of SnO2, TiO2, ZnO, C... 60 PCBM, ICBA, or their composite structures. For example, SnO2 monolayer, SnO2 / C... 60 Layered structures, TiO2 / SnO2 composite structures, etc. The electron transport layer thickness can be approximately 5 nm to 100 nm, preferably 10 nm to 40 nm. The hole transport layer can be PTAA, Poly-TPD, Spiro-OMeTAD, NiOx, CuSCN, CuI, MeO-2PACz, 2PACz, or composite structures thereof. The hole transport layer thickness can be approximately 3 nm to 100 nm, preferably 10 nm to 50 nm.

[0058] In some optional embodiments, before the perovskite absorber layer 310 is formed, a second dielectric layer 38 is formed on the surface of the substrate layer 320 opposite to the first tunneling layer 321a and the second tunneling layer 322a. The second dielectric layer 38 may be composed of AlxOy, SiOx, SiNx, etc. The thickness of the second dielectric layer 38 may be from about 1 nm to 100 nm.

[0059] In some optional embodiments, after the first charge transport layer 311 and the second charge transport layer 312 are formed, a first dielectric layer 37 is formed between the first charge transport layer 311 and the second charge transport layer 312. The first dielectric layer 37 may be composed of AlxOy, SiOx, SiNx, MgF2, LiF, etc. The thickness of the first dielectric layer 37 may be from about 1 nm to 100 nm, preferably in the range of 5 nm to 30 nm.

[0060] In summary, a stacked solar cell 3 is formed by stacking a top cell 31 and a bottom cell 32.

[0061] S200, a first electrode 33 and a second electrode 34 are formed on the surface of the top battery 31 that is opposite to the bottom battery 32, and the first electrode 33 and the second electrode 34 have opposite polarities.

[0062] Specifically, the first electrode 33 and the second electrode 34 can be formed after the formation of the first charge transport layer 311 and the second charge transport layer 312.

[0063] S300, a third electrode 35 and a fourth electrode 36 are formed on the surface of the bottom cell 32 on the side opposite to the top cell 31, and the polarities of the third electrode 35 and the fourth electrode 36 are opposite.

[0064] Specifically, the formation of the third electrode 35 and the fourth electrode 36 can also occur after the formation of the first passivation contact structure 321 and the second passivation contact structure 322, but before the formation of the perovskite absorber layer 310.

[0065] like Figure 3 As shown, in some optional embodiments, the first electrode 33 and the third electrode 35 are a pair of electrodes with the same polarity, and the second electrode 34 and the fourth electrode 36 are a pair of electrodes with the same polarity. Figure 3 From the top view, the first electrode 33 and the third electrode 35 are both located on the left side, and the second electrode 34 and the fourth electrode 36 are both located on the right side. At this time, the first charge transport layer 311 is configured as a hole transport layer, the second charge transport layer 312 is configured as an electron transport layer, the first doped polysilicon layer 321b is configured as a P-type doped polysilicon layer, and the second doped polysilicon layer 322b is configured as an N-type doped polysilicon layer.

[0066] like Figure 5 As shown, in some alternative embodiments, the first electrode 33 and the fourth electrode 36 are a pair of electrodes with the same polarity, and the second electrode 34 and the third electrode 35 are a pair of electrodes with the same polarity. Figure 5 From the top view, the first electrode 33 and the fourth electrode 36 are located on different sides, and the second electrode 34 and the third electrode 35 are located on different sides, that is, they are arranged in an interleaved manner. At this time, the first charge transport layer 311 is configured as a hole transport layer, the second charge transport layer 312 is configured as an electron transport layer, the first doped polysilicon layer 321b is configured as an N-type doped polysilicon layer, and the second doped polysilicon layer 322b is configured as a P-type doped polysilicon layer.

[0067] The circuit principle of the parallel output structure in the tandem solar cell 3 is explained below. For example... Figure 4 As shown, the top battery 31 includes an equivalent circuit of a first photocurrent source 31a and a first diode 31b, and the bottom battery 32 includes an equivalent circuit of a second photocurrent source 32a and a second diode 32b. The top battery 31 and the bottom battery 32 are connected in parallel to the first external terminal 39 and the second external terminal 40. Therefore, the top battery 31 and the bottom battery 32 can operate under the same external voltage. Figure 3As shown, when sunlight is incident, photogenerated carriers are generated in the perovskite absorber layer 310 of the top cell 31. The generated holes can move to the first electrode 33 through the first charge transport layer 311, while electrons can move to the second electrode 34 through the second charge transport layer 312. Simultaneously, light passing through the top cell 31 can reach the substrate layer 320 of the bottom cell 32, where photogenerated carriers are generated. The generated holes can be collected to the third electrode 35 through the first doped polysilicon layer 321b, while electrons can be collected to the fourth electrode 36 through the second doped polysilicon layer 322b.

[0068] Since the top battery 31 and bottom battery 32 of this disclosure are not through Figure 1 The composite layers 13 are connected in series, thus the current matching conditions required in traditional monolithic two-terminal tandem solar cells 1 are no longer structurally necessary. That is, the top cell 31 and the bottom cell 32 can each generate independent photocurrents, and the generated currents can be superimposed and output in parallel at the first external terminal 39 and the second external terminal 40. This disclosure structurally alleviates... Figure 1 Problems that may occur in traditional series-connected monolithic two-terminal tandem solar cells include current mismatch, recombination loss, current-limited operation, degradation of the composite layer 13, and current edge effect.

[0069] Although embodiments of the present disclosure have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present disclosure, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A tandem solar cell, characterized in that, include: The battery body includes a top battery and a bottom battery stacked together. The first electrode and the second electrode are disposed on the surface of the top battery that is opposite to the bottom battery, and the polarities of the first electrode and the second electrode are opposite. The third and fourth electrodes are disposed on the surface of the bottom cell that is opposite to the top cell, and the polarities of the third and fourth electrodes are opposite.

2. The tandem solar cell according to claim 1, characterized in that, The top cell is configured as a perovskite cell, the perovskite cell comprising: A perovskite absorber layer is formed on one side surface of the bottom cell; A first charge transport layer and a second charge transport layer are alternately formed on the surface of the perovskite absorber layer that is opposite to the bottom cell. The first charge transport layer is connected to the first electrode, and the second charge transport layer is connected to the second electrode.

3. The tandem solar cell according to claim 1, characterized in that, The bottom battery is configured as a back contact battery, the back contact battery comprising: A substrate layer is formed on one side surface of the top battery; A first passivated contact structure and a second passivated contact structure are alternately formed on the surface of the substrate layer that is opposite to the top cell. The first passivated contact structure is connected to the third electrode, and the second passivated contact structure is connected to the fourth electrode.

4. The tandem solar cell according to claim 3, characterized in that, The first passivation contact structure includes a first tunneling layer and a first doped polysilicon layer stacked together; the second passivation contact structure includes a second tunneling layer and a second doped polysilicon layer stacked together; the third electrode is adapted to be connected to the first doped polysilicon layer; and the fourth electrode is adapted to be connected to the second doped polysilicon layer. Alternatively, at least one of the first passivation contact structure and the second passivation contact structure includes an intrinsic amorphous silicon layer and a doped amorphous silicon layer stacked together.

5. The tandem solar cell according to claim 3, characterized in that, The first passivated contact structure and the second passivated contact structure are spaced apart; or, the first passivated contact structure and the second passivated contact structure are in contact with each other.

6. The tandem solar cell according to any one of claims 1 to 5, characterized in that, Also includes: A first dielectric layer is formed on the surface of the top cell on the side opposite to the bottom cell.

7. The tandem solar cell according to any one of claims 1 to 5, characterized in that, Also includes: A second dielectric layer is formed between the top battery and the bottom battery.

8. The tandem solar cell according to claim 1, characterized in that, The first electrode or the second electrode is configured as a semi-transparent electrode structure, wherein the semi-transparent electrode structure has a light transmittance of greater than or equal to 70% for incident light with a wavelength between 550 and 1100 nm.

9. The tandem solar cell according to claim 2, characterized in that, The first charge transport layer and the second charge transport layer are spaced apart; And / or, the first charge transport layer and the second charge transport layer are provided with multiple layers.

10. The tandem solar cell according to claim 1, characterized in that, In the first electrode, the second electrode, the third electrode, and the fourth electrode, a group of electrodes with the same polarity are configured to be connected, and another group of electrodes with the same polarity are configured to be connected. And / or, the tandem solar cell is a monolithic tandem solar cell.

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