A laminated solar cell

Abstract

The present disclosure relates to the technical field of solar cells, and discloses a laminated solar cell, which comprises a bottom cell and a top cell, the top cell comprising a perovskite absorption layer, a first carrier transport layer, a second carrier transport layer, a first carrier selection layer, a second carrier selection layer, a first electrode and a second electrode; the perovskite absorption layer is arranged on the light-receiving side surface of the bottom cell; the first carrier transport layer and the second carrier transport layer are arranged on the side surface of the perovskite absorption layer away from the bottom cell; the first carrier selection layer is arranged between the first carrier transport layer and the perovskite absorption layer, and the second carrier selection layer is arranged between the second carrier transport layer and the perovskite absorption layer; the first electrode and the second electrode are arranged on the first carrier transport layer and the second carrier transport layer, respectively, and the present disclosure improves the problems of local carrier recombination and contact-induced degradation caused by the local formation of the first electrode and the second electrode.

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 recent years, tandem solar cells have become a research hotspot in the photovoltaic field due to their potential to break through the Shockley-Quisser theoretical efficiency limit of single-junction cells. By combining perovskite top cells with wide bandgap cells with crystalline silicon bottom cells with narrow bandgap cells, spectral absorption is performed according to the bandgap difference. The perovskite top cells selectively absorb short-wavelength light, while the crystalline silicon bottom cells selectively absorb long-wavelength light, thereby achieving light absorption over a wider wavelength range.

[0003] Existing tandem solar cells mainly include two-terminal and four-terminal tandem solar cells. These two types differ in efficiency, fabrication process, and module design, among other technical characteristics and limitations. Specifically, in two-terminal tandem solar cells, the perovskite top cell and crystalline silicon bottom cell are connected in series via tunnel junctions or interconnect layers, requiring current matching and resulting in lower photoelectric conversion efficiency. In four-terminal tandem solar cells, the perovskite top cell and crystalline silicon bottom cell are mechanically stacked. While current matching is not required, the need for additional transparent electrodes / optical interfaces increases light losses due to parasitic absorption or reflection, process complexity, and manufacturing costs. Both two-terminal and four-terminal tandem solar cells suffer from excessively rapid carrier recombination and low carrier extraction efficiency at the interface, further reducing photoelectric conversion efficiency and failing to meet application requirements. Summary of the Invention

[0004] This disclosure provides a tandem solar cell to solve the problem of low carrier extraction efficiency in existing tandem solar cells.

[0005] This disclosure provides a tandem solar cell, comprising a bottom cell and a top cell stacked together. The bottom cell includes a light-receiving side and a back-lighting side opposite to each other, and the top cell is disposed on the light-receiving side of the bottom cell. The top cell includes a perovskite absorber layer, a first carrier transport layer, a second carrier transport layer, a first carrier selection layer, a second carrier selection layer, a first electrode, and a second electrode. The perovskite absorber layer is disposed on the light-receiving side surface of the bottom cell. The first carrier transport layer and the second carrier transport layer are spaced apart and disposed on the side surface of the perovskite absorber layer opposite to the bottom cell. The first carrier transport layer and the second carrier transport layer have opposite conductivity types. The first carrier selection layer and the second carrier selection layer are adapted to extract different types of carriers respectively. The first carrier selection layer is disposed between the first carrier transport layer and the perovskite absorber layer, and the second carrier selection layer is disposed between the second carrier transport layer and the perovskite absorber layer. The first electrode is disposed on the first carrier transport layer, and the second electrode is disposed on the second carrier transport layer.

[0006] Beneficial effects: This disclosure comprises a stacked solar cell consisting of a bottom cell and a top cell. A first carrier selection layer is disposed between a first carrier transport layer and a perovskite absorber layer in the top cell, and a second carrier selection layer is disposed between a second carrier transport layer and a perovskite absorber layer. The first and second carrier selection layers are adapted to enhance the extraction efficiency of one type of carrier while blocking the transport of another type of carrier, thereby improving the problems of local carrier recombination and contact-induced degradation caused by local formation of the first and second electrodes, thus improving the carrier extraction efficiency and photoelectric conversion efficiency to meet the application requirements. Based on this, a first carrier selection layer, a first carrier transport layer, and a first electrode are formed as a set of contact structures in a portion of the light-receiving side of the perovskite absorption layer. A second carrier selection layer, a second carrier transport layer, and a second electrode are formed as another set of contact structures in another portion of the light-receiving side of the perovskite absorption layer. Electron carriers and hole carriers are transported vertically on the two sets of contact structures, which can delay the lateral diffusion of carriers and the concentration of electric field, and reduce the possibility of leakage current and bypass resistance formation.

[0007] In some alternative implementations, the first carrier selection layer and / or the second carrier selection layer are configured as one or more of a discontinuous island structure, a mesh structure, and a gradient structure.

[0008] Beneficial effects: Through the above-mentioned structural characteristics, this disclosure enables the first carrier selection layer and / or the second carrier selection layer to effectively suppress the lateral diffusion of carriers while allowing carriers to be transported in the vertical direction with the electrode contact region as the center.

[0009] In some alternative implementations, in a direction parallel to the light-receiving side surface, the thickness of the first carrier selection layer and / or the second carrier selection layer gradually increases or decreases from the first region to the second region, where the first region is the region in direct contact with the first electrode or the second electrode, and the second region is the region outside the first region.

[0010] Beneficial effects: When the thickness of the first carrier selective layer and / or the second carrier selective layer gradually increases from the first region to the second region, the fabrication difficulty of the electrodes can be reduced, which is beneficial to improving the connection stability between the first electrode and the first carrier transport layer, and / or the connection stability between the second electrode and the second carrier transport layer. When the thickness of the first carrier selective layer and / or the second carrier selective layer gradually decreases from the first region to the second region, electron carriers are concentrated in the region where the first electrode and the first carrier selective layer are in direct contact, and / or hole carriers are concentrated in the region where the second electrode and the second carrier selective layer are in direct contact, thereby improving the vertical transport efficiency of carriers.

[0011] In some alternative embodiments, in a direction parallel to the light-receiving side surface, the component content of the first carrier selective layer and / or the second carrier selective layer gradually increases or decreases from the first region to the second region, where the first region is the region in direct contact with the first electrode or the second electrode, and the second region is the region outside the first region.

[0012] Beneficial effects: Whether the component content of the first carrier selection layer and / or the second carrier selection layer gradually increases from the first region to the second region, or the component content of the first carrier selection layer and / or the second carrier selection layer gradually decreases from the first region to the second region, the purpose of improving carrier extraction efficiency can be achieved. The difference lies in the carrier flow path.

[0013] In some optional embodiments, the first carrier selection layer includes a plurality of first selection units distributed along the thickness direction, the plurality of first selection units being made of different materials and / or having a gradient variation in the composition ratio of the materials; and / or, the second carrier selection layer includes a plurality of second selection units distributed along the thickness direction, the plurality of second selection units being made of different materials and / or having a gradient variation in the composition ratio of the materials.

[0014] Beneficial effects: The first selection unit and the second selection unit of this disclosure can be made of different materials or the composition ratio of the materials can vary in a gradient, thereby forming a first carrier selection layer and / or a second carrier selection layer that varies along the thickness direction.

[0015] In some optional embodiments, one of the first carrier selection layer and the second carrier selection layer is an electron selection layer and the other is a hole selection layer; the electron selection layer includes at least one of lithium fluoride, cesium fluoride, potassium fluoride, cesium carbonate, tin oxide, zinc oxide, titanium oxide, and aluminum oxide; the hole selection layer includes at least one of molybdenum oxide, vanadium oxide, nickel oxide, and tungsten oxide.

[0016] Beneficial effects: The present disclosure provides a lower potential barrier for one type of carrier (electron or hole) and a higher potential barrier for the other type of carrier by configuring one of the first carrier selection layers and the second carrier selection layer as an electron selection layer and the other as a hole selection layer, thereby guiding selective carrier collection in the local electrode contact region and suppressing undesired recombination, improving open-circuit voltage and fill factor.

[0017] In some alternative implementations, the thickness of the first carrier selection layer and the second carrier selection layer ranges from 1 to 5 nm.

[0018] Beneficial effects: The first and second carrier selection layers in this disclosure are ultra-thin structures. While allowing carriers to transport along the vertical direction, this structure can alleviate lateral carrier diffusion and electric field concentration, and acts as an interface protection layer to suppress contact-induced degradation, thereby improving long-term operational stability and reliability. Furthermore, this disclosure limits the thickness of the first and second carrier selection layers to the aforementioned range. On the one hand, this avoids the inability to collect carriers due to excessive thinness; on the other hand, it avoids the failure of the tunneling mechanism due to excessive thickness.

[0019] In some optional embodiments, one of the first carrier transport layer and the second carrier transport layer is an electron transport layer and the other is a hole transport layer; the thickness of the electron transport layer ranges from 10 to 60 nm, and the thickness of the hole transport layer ranges from 10 to 100 nm.

[0020] Beneficial effects: In this disclosure, the electron transport layer and hole transport layer are locally formed at intervals and electrically connected to the corresponding first and second electrodes, respectively. That is, the electron transport layer and hole transport layer do not continuously cover the entire surface of the perovskite absorber layer, but are selectively formed only in local electrode contact areas. Furthermore, this disclosure limits the thickness of the electron transport layer and hole transport layer to the aforementioned range, which can improve the carrier transport efficiency.

[0021] In some alternative embodiments, the top cell further includes a dielectric layer formed on the surface of the perovskite absorber layer opposite to the bottom cell and located between the first carrier selection layer and the second carrier selection layer.

[0022] Beneficial effects: The dielectric layer disclosed herein helps reduce surface defects in the perovskite absorber layer and improves its chemical and electrical stability to the external environment. Furthermore, this dielectric layer can further alleviate electric field concentration in local electrode contact areas and works synergistically with the first and second carrier selection layers to enhance interface stability.

[0023] In some optional embodiments, the bottom cell is configured as a back contact cell, which includes a substrate layer, a first passivated contact structure, a second passivated contact structure, a third electrode, and a fourth electrode. The substrate layer includes a light-receiving surface and a back-lighting surface disposed opposite to each other, and the perovskite absorption layer of the top cell is directly disposed on the light-receiving surface. The first passivated contact structure and the second passivated contact structure are alternately formed on the back-lighting surface of the substrate layer, and the conductivity types of the first passivated contact structure and the second passivated contact structure are opposite. The third electrode is disposed on the first passivated contact structure, and the fourth electrode is disposed on the second passivated contact structure.

[0024] Beneficial effects: The top cell of this disclosure is a perovskite solar cell, used to absorb short-wavelength sunlight and generate a first photogenerated carrier containing electrons. The bottom cell is a back-contact cell, used to absorb long-wavelength sunlight transmitted through the perovskite solar cell and generate a second photogenerated carrier containing holes, thereby realizing a stacked operation mode based on spectral segmentation. Specifically, this disclosure utilizes a first passivated contact structure and a second passivated contact structure to achieve selective collection of the second photogenerated carriers. Attached Figure Description

[0025] 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.

[0026] Figure 1 A schematic diagram of the structure of a stacked solar cell in an embodiment of this disclosure is shown.

[0027] Explanation of reference numerals in the attached figures: 1. Top cell; 11. Perovskite absorber layer; 12. First carrier transport layer; 13. Second carrier transport layer; 14. First carrier selection layer; 15. Second carrier selection layer; 16. First electrode; 17. Second electrode; 18. Dielectric layer; 2. Base cell; 21. Substrate layer; 22. First passivation contact structure; 221. First tunneling layer; 222. P-type doped polysilicon layer; 23. Second passivation contact structure; 231. Second tunneling layer; 232. N-type doped polysilicon layer; 24. Third electrode; 25. Fourth electrode. Detailed Implementation

[0028] 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.

[0029] In related technologies, electrodes are provided on both the front and back sides of tandem solar cells. The electrodes are electrically connected to the carrier transport layer by screen printing and sintering. Due to the influence of the screen printing and sintering process, a large number of dangling bonds exist at the interface of the carrier transport layer, which causes a large number of carrier recombinations and reduces the carrier extraction efficiency.

[0030] Based on this, refer to Figure 1 This disclosure provides a tandem solar cell, which includes a bottom cell 2 and a top cell 1 stacked together. The bottom cell 2 includes a light-receiving side and a back-lighting side opposite to each other, and the top cell 1 is disposed on the light-receiving side of the bottom cell 2. The top cell 1 includes a perovskite absorber layer 11, a first carrier transport layer 12, a second carrier transport layer 13, a first carrier selection layer 14, a second carrier selection layer 15, a first electrode 16, and a second electrode 17. The perovskite absorber layer 11 is disposed on the light-receiving surface of the bottom cell 2. The first carrier transport layer 12 and the second carrier transport layer 13 are spaced apart. The perovskite absorber layer 11 is located on the side of the bottom cell 2 facing away from the surface; the first carrier transport layer 12 and the second carrier transport layer 13 have opposite conductivity types; the first carrier selection layer 14 and the second carrier selection layer 15 are adapted to extract different types of carriers respectively; the first carrier selection layer 14 is disposed between the first carrier transport layer 12 and the perovskite absorber layer 11, and the second carrier selection layer 15 is disposed between the second carrier transport layer 13 and the perovskite absorber layer 11; the first electrode 16 is disposed on the first carrier transport layer 12, and the second electrode 17 is disposed on the second carrier transport layer 13.

[0031] This disclosure comprises a stacked solar cell consisting of a bottom cell 2 and a top cell 1. A first carrier selection layer 14 is disposed between a first carrier transport layer 12 and a perovskite absorber layer 11 in the top cell, and a second carrier selection layer 15 is disposed between a second carrier transport layer 13 and a perovskite absorber layer 11. The first carrier selection layer 14 and the second carrier selection layer 15 are adapted to enhance the extraction efficiency of a certain type of carrier while blocking the transport of another type of carrier, thereby improving the problems of local carrier recombination and contact-induced degradation caused by the local formation of the first electrode 16 and the second electrode 17, and thus improving the carrier extraction efficiency and photoelectric conversion efficiency to meet the application requirements. Based on this, the first carrier selection layer 14, the first carrier transport layer 12, and the first electrode 16 are sequentially formed as a set of contact structures in a portion of the light-receiving side of the perovskite absorption layer 11. The second carrier selection layer 15, the second carrier transport layer 13, and the second electrode 17 are sequentially formed as another set of contact structures in another portion of the light-receiving side of the perovskite absorption layer 11. Electron carriers and hole carriers respectively travel along the two sets of contact structures. Figure 1 Vertical transmission can delay the lateral diffusion of charge carriers and the concentration of electric field, reducing the possibility of leakage current and bypass resistance formation.

[0032] For example, the band gap of the perovskite absorber layer 11 is larger than the band gap of the silicon-based material of the bottom cell 2. Taking the band gap of the bottom cell 2 as 1.12 eV as an example, the perovskite absorber layer 11 can be designed to have a band gap in the range of 1.55 to 1.80 eV, and its material can be FA. 1-x MA x Pb(I 1-γ Br γ 3. FAPbI3, mixed cation / halogen perovskite with partial Cs introduction, or any combination thereof. The thickness of the perovskite absorber layer 11 ranges from 350 to 800 nm, preferably from 450 to 650 nm, to simultaneously satisfy the light absorption efficiency of the top cell 1 and the light transmittance characteristics to the bottom cell 2.

[0033] In some embodiments, the thickness of the first carrier selection layer 14 and the second carrier selection layer 15 ranges from 1 to 5 nm, and preferably, the thickness ranges from 1.5 to 3 nm.

[0034] In this disclosure, the first carrier selection layer 14 and the second carrier selection layer 15 are configured as ultrathin structures. While allowing carriers to transport vertically, this design mitigates lateral carrier diffusion and electric field concentration, and acts as an interface protection layer to suppress contact-induced degradation, thereby improving long-term operational stability and reliability. Furthermore, the first carrier selection layer 14 and the second carrier selection layer 15 can form electric dipoles at their respective interfaces to adjust the band alignment between the first carrier transport layer 12 and the perovskite absorber layer 11, and between the second carrier transport layer 13 and the perovskite absorber layer 11, thereby lowering the energy barrier for carrier extraction. Therefore, despite the ultrathin structure of the first carrier selection layer 14 and the second carrier selection layer 15, quasi-ohmic carrier collection characteristics based on a tunneling mechanism can still be provided. In summary, this disclosure limits the thickness of the first carrier selection layer 14 and the second carrier selection layer 15 to the above-mentioned range. On the one hand, it can avoid the inability to achieve carrier collection due to excessive thickness, and on the other hand, it can avoid the failure of the tunneling mechanism due to excessive thickness.

[0035] In some embodiments, the first carrier selection layer 14 and / or the second carrier selection layer 15 are configured as one or more of a discontinuous island structure, a mesh structure, and a gradient structure.

[0036] This disclosure, through the aforementioned structural characteristics, enables the first carrier selection layer 14 and / or the second carrier selection layer 15 to effectively suppress lateral carrier diffusion while allowing carriers to propagate vertically around the electrode contact region. The gradient structure includes at least the following different structures: In the first structure, the thickness of the first carrier selection layer 14 and / or the second carrier selection layer 15 gradually increases or decreases from the first region to the second region in a direction parallel to the light-receiving side surface. The first region is the area in direct contact with the first electrode 16 or the second electrode 17, and the second region is the area outside the first region. For example, the thickness of the first carrier selection layer 14 and / or the second carrier selection layer 15 gradually increases from the first region to the second region, that is, the first carrier selection layer 14 and / or the second carrier selection layer 15 have a shape that is low in the middle and high on the periphery. The first carrier transport layer 12 and / or the second carrier transport layer 13 also have the same shape. The electrode paste is filled and sintered in the middle recessed position. This shape can reduce the fabrication difficulty of the first electrode 16 and / or the second electrode 17, and is beneficial to improving the connection stability between the first electrode 16 and the first carrier transport layer 12, and / or the connection stability between the second electrode 17 and the second carrier transport layer 13. For example, the thickness of the first carrier selection layer 14 and / or the second carrier selection layer 15 gradually decreases from the first region to the second region, that is, the first carrier selection layer 14 and / or the second carrier selection layer 15 have a shape that is high in the middle and low on the periphery, thereby concentrating electron carriers in the region where the first electrode 16 is in direct contact with the first carrier selection layer 14, and / or concentrating hole carriers in the region where the second electrode 17 is in direct contact with the second carrier selection layer 15, so as to improve the vertical transport efficiency of carriers.

[0037] In the second structure, in a direction parallel to the light-receiving surface, the component content of the first carrier selection layer 14 and / or the second carrier selection layer 15 gradually increases or decreases from the first region to the second region. The first region is the area in direct contact with the first electrode 16 or the second electrode 17, and the second region is the area outside the first region. Whether the component content of the first carrier selection layer 14 and / or the second carrier selection layer 15 gradually increases from the first region to the second region, or gradually decreases from the first region to the second region, both can achieve the goal of improving carrier extraction efficiency. The difference lies in the carrier flow path. For example, when the component content of the first carrier selection layer 14 and / or the second carrier selection layer 15 gradually increases from the first region to the second region, the component content in the first region is lower, and the component content in the second region is higher. Carriers move from the periphery of the first region towards the first electrode 16 and / or the second electrode 17. For example, when the component content of the first carrier selection layer 14 and / or the second carrier selection layer 15 gradually decreases from the first region to the second region, the component content in the first region is higher and the component content in the second region is lower, and the carriers move from the first region to the first electrode 16 and / or the second electrode 17.

[0038] The third structure includes a first carrier selection layer 14 comprising multiple first selection units distributed along the thickness direction, wherein the materials of the multiple first selection units are different and / or the composition ratios of the materials vary gradient; and / or, a second carrier selection layer 15 comprises multiple second selection units distributed along the thickness direction, wherein the materials of the multiple second selection units are different and / or the composition ratios of the materials vary gradient. The first and second selection units of this disclosure can be made of different materials, or the composition ratios of the materials can vary gradient, thereby forming a first carrier selection layer 14 and / or a second carrier selection layer 15 varying along the thickness direction. Taking the first carrier selection layer 14 as an example, multiple materials can be selected, and the enhancement effect of different materials on carrier extraction efficiency has a gradient level. For example, the first selection unit closest to the perovskite absorption layer 11 has the lowest carrier extraction efficiency, and the subsequent first selection units arranged along the thickness direction successively enhance the carrier extraction efficiency, thereby effectively suppressing the lateral diffusion of carriers. Similarly, the enhancement effect of different composition ratios on carrier extraction efficiency has a gradient level, which will not be elaborated further here.

[0039] In some embodiments, of the first carrier selection layer 14 and the second carrier selection layer 15, one is an electron selection layer and the other is a hole selection layer; the electron selection layer includes lithium fluoride (LiF), cesium fluoride (CsF), potassium fluoride (KF), cesium carbonate (Cs2CO3), and tin oxide (SnO). x ), zinc oxide (ZnO), titanium oxide (TiO) x At least one of the following: alumina (Al2O3); the hole-selective layer includes molybdenum oxide (MoO2). x ), vanadium oxide (V2O) x Nickel oxide (NiO) x ), tungsten oxide (WO) x At least one of the following.

[0040] This disclosure utilizes a first carrier selection layer 14 and a second carrier selection layer 15, one configured as an electron selection layer and the other as a hole selection layer, to provide a lower potential barrier for one type of carrier (electrons or holes) and a higher potential barrier for the other type. This guides selective carrier collection in the local electrode contact region and suppresses unwanted recombination, thereby improving the open-circuit voltage and fill factor. For example, the first carrier selection layer 14 is an electron selection layer, which promotes electron extraction and suppresses hole transport; the second carrier selection layer 15 is a hole selection layer, which promotes hole extraction and suppresses electron transport. Electron carriers separated in the perovskite absorber layer 11 are collected in the electron selection layer, and hole carriers are collected in the hole selection layer, thereby improving carrier extraction efficiency.

[0041] In other embodiments, the electron selection layer may also be implemented as a self-assembled monolayer (SAM), an ultrathin inorganic oxide, or an ionic salt-based thin film, while the hole selection layer may include an organic molecular electric dipole layer or an interface layer based on a two-dimensional / quasi-two-dimensional perovskite.

[0042] In some embodiments, of the first carrier transport layer 12 and the second carrier transport layer 13, one is an electron transport layer and the other is a hole transport layer; the electron transport layer includes tin dioxide (SnO2), titanium dioxide (TiO2), and fullerene (C). 60 The hole transport layer comprises at least one of the following: 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene (Spiro-OMeTAD), polytriarylamine (PTAA), and nickel oxide (NiO). x At least one of the following: the electron transport layer has a thickness ranging from 10 to 60 nm, and the hole transport layer has a thickness ranging from 10 to 100 nm.

[0043] In this disclosure, the electron transport layer and hole transport layer are locally formed at intervals between each other and are electrically connected to the corresponding first electrode 16 and second electrode 17, respectively. That is, the electron transport layer and hole transport layer do not continuously cover the entire surface of the perovskite absorber layer 11, but are selectively formed only in local electrode contact areas. Exemplarily, the electron transport layer and hole transport layer can be formed by printing, deposition, or a combination thereof, and are spatially separated to avoid direct electrical connection. Furthermore, this disclosure limits the thickness of the electron transport layer and hole transport layer to the aforementioned range, which can improve carrier transport efficiency.

[0044] In summary, exemplarily, the first carrier selection layer 14 is an electron selection layer, the first carrier transport layer 12 is an electron transport layer, the first electrode 16 is a negative electrode, the second carrier selection layer 15 is a hole selection layer, the second carrier transport layer 13 is a hole transport layer, and the second electrode 17 is a positive electrode. The first electrode 16 and the second electrode 17 can be made of silver (Ag), copper (Cu), aluminum (Al), or their alloys, and their thickness ranges from 0.5 to 10 μm.

[0045] In some embodiments, the top cell 1 further includes a dielectric layer 18, which is formed on the surface of the perovskite absorber layer 11 facing away from the bottom cell 2 and is located between the first carrier selection layer 14 and the second carrier selection layer 15.

[0046] The dielectric layer 18 disclosed herein helps reduce surface defects in the perovskite absorber layer 11 and improves its chemical and electrical stability to the external environment. Furthermore, the dielectric layer 18 can further alleviate electric field concentration in local electrode contact areas and works synergistically with the first carrier selection layer 14 and the second carrier selection layer 15 to enhance interface stability.

[0047] Specifically, the dielectric layer 18 is made of at least one material selected from organic polymers and inorganic oxides, and / or the thickness of the dielectric layer 18 ranges from 5 to 30 nm. The thickness of the dielectric layer 18 is less than or equal to the sum of the thicknesses of the first electrode 16, the first carrier transport layer 12, and the first carrier selection layer 14, or the thickness of the dielectric layer 18 is less than or equal to the sum of the thicknesses of the second electrode 17, the second carrier transport layer 13, and the second carrier selection layer 15. This disclosure uses the dielectric layer 18 to reduce surface defects in the perovskite absorber layer 11 and alleviate electric field concentration in local electrode contact areas.

[0048] In some embodiments, the bottom battery 2 can be configured as a back contact battery, which includes a substrate layer 21, a first passivation contact structure 22, a second passivation contact structure 23, a third electrode 24, and a fourth electrode 25. The substrate layer 21 includes a light-receiving surface and a back-lighting surface disposed opposite to each other, and the perovskite absorption layer 11 of the top battery 1 is directly disposed on the light-receiving surface. The first passivation contact structure 22 and the second passivation contact structure 23 are alternately formed on the back-lighting surface of the substrate layer 21, and the conductivity types of the first passivation contact structure 22 and the second passivation contact structure 23 are opposite. The third electrode 24 is disposed on the first passivation contact structure 22, and the fourth electrode 25 is disposed on the second passivation contact structure 23.

[0049] The top cell 1 of this disclosure is a perovskite solar cell, used to absorb short-wavelength sunlight and generate a first photogenerated carrier containing electrons. The bottom cell 2 is a back-contact cell, used to absorb long-wavelength sunlight transmitted through the perovskite solar cell and generate a second photogenerated carrier containing holes, thereby realizing a stacked operation mode based on spectral segmentation. Specifically, this disclosure utilizes a first passivated contact structure 22 and a second passivated contact structure 23 to achieve selective collection of the second photogenerated carriers.

[0050] The aforementioned back contact battery can be an interdigitated back contact battery (IBC battery), a heterojunction back contact battery (HBC battery), a tunneling oxide passivated back contact battery (TBC battery), or a hybrid passivated back contact battery (HTBC battery), etc. Taking a TBC battery as an example, the substrate layer 21 is an N-type monocrystalline silicon wafer, the first passivation contact structure 22 consists of a first tunneling layer 221 and a P-type doped polycrystalline silicon layer 222, the second passivation contact structure 23 consists of a second tunneling layer 231 and an N-type doped polycrystalline silicon layer 232, the third electrode 24 is the positive electrode, and the fourth electrode 25 is the negative electrode. Specifically, the resistivity of the N-type monocrystalline silicon wafer ranges from 0.5 to 2.5 Ω·cm, and the thickness ranges from 120 to 180 μm, preferably from 140 to 165 μm. The thickness of the first tunneling layer 221 and the second tunneling layer 231 ranges from 0.8 to 2.0 nm to suppress surface recombination and improve selective carrier transport characteristics. The doping concentration of the P-type doped polysilicon layer 222 and the N-type doped polysilicon layer 232 is 1×10⁻⁶. 19 ~5×10 20 cm -3 The thickness ranges from 80 to 250 nm.

[0051] In the first electrode 16, the second electrode 17, the third electrode 24, and the fourth electrode 25, 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.

[0052] This disclosure uses one connected set of electrodes as one terminal and another connected set of electrodes as another terminal to form a two-terminal structure. Therefore, the structure of this disclosure is simple, suitable for large-area manufacturing processes, and ensures the output stability of the tandem solar cell. Specifically, the photogenerated carriers generated in the top cell 1 and the bottom cell 2 are transported to the two-terminal structure through spatially separated carrier collection paths, so that the tandem solar cell still operates externally as a monolithic tandem solar cell with only two terminals. Taking the first electrode 16 and the fourth electrode 25 as having the same polarity, and the second electrode 17 and the third electrode 24 as having the same polarity as an example, the first electrode 16 and the fourth electrode 25 are connected to form one terminal, and the second electrode 17 and the third electrode 24 are connected to form another terminal.

[0053] 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: A bottom battery and a top battery are stacked, the bottom battery including a light-receiving side and a backlight side, and the top battery disposed on the light-receiving side of the bottom battery; the top battery includes: A perovskite absorption layer is disposed on the light-receiving surface of the bottom cell; A first carrier transport layer and a second carrier transport layer are disposed at intervals on the surface of the perovskite absorber layer opposite to the bottom cell; the first carrier transport layer and the second carrier transport layer have opposite conductivity types. The first carrier selection layer and the second carrier selection layer are adapted to extract different types of carriers respectively; the first carrier selection layer is disposed between the first carrier transport layer and the perovskite absorber layer, and the second carrier selection layer is disposed between the second carrier transport layer and the perovskite absorber layer. A first electrode and a second electrode, wherein the first electrode is disposed on the first carrier transport layer and the second electrode is disposed on the second carrier transport layer.

2. The tandem solar cell according to claim 1, characterized in that, The first carrier selection layer and / or the second carrier selection layer are configured as one or more of the following: discontinuous island structure, mesh structure, and gradient structure.

3. The tandem solar cell according to claim 2, characterized in that, In a direction parallel to the light-receiving side surface, the thickness of the first carrier selection layer and / or the second carrier selection layer gradually increases or decreases from the first region to the second region. The first region is the region in direct contact with the first electrode or the second electrode, and the second region is the region outside the first region.

4. The tandem solar cell according to claim 2, characterized in that, In a direction parallel to the light-receiving side surface, the component content of the first carrier selection layer and / or the second carrier selection layer gradually increases or decreases from the first region to the second region. The first region is the region in direct contact with the first electrode or the second electrode, and the second region is the region outside the first region.

5. The tandem solar cell according to claim 2, characterized in that, The first carrier selection layer includes a plurality of first selection units distributed along the thickness direction, wherein the plurality of first selection units are made of different materials and / or the composition ratio of the materials varies. And / or, the second carrier selection layer includes a plurality of second selection units distributed along the thickness direction, wherein the plurality of second selection units are made of different materials and / or the composition ratio of the materials varies.

6. The tandem solar cell according to any one of claims 1 to 5, characterized in that, In the first carrier selection layer and the second carrier selection layer, one of them is an electron selection layer and the other is a hole selection layer; The electron selective layer includes at least one of lithium fluoride, cesium fluoride, potassium fluoride, cesium carbonate, tin oxide, zinc oxide, titanium oxide, and aluminum oxide; the hole selective layer includes at least one of molybdenum oxide, vanadium oxide, nickel oxide, and tungsten oxide.

7. The tandem solar cell according to any one of claims 1 to 5, characterized in that, The thickness of the first carrier selection layer and the second carrier selection layer ranges from 1 to 5 nm.

8. The tandem solar cell according to any one of claims 1 to 5, characterized in that, In the first carrier transport layer and the second carrier transport layer, one of them is an electron transport layer and the other is a hole transport layer; The thickness of the electron transport layer ranges from 10 to 60 nm, and the thickness of the hole transport layer ranges from 10 to 100 nm.

9. The tandem solar cell according to any one of claims 1 to 5, characterized in that, The top battery also includes: A dielectric layer is formed on the surface of the perovskite absorber layer opposite to the bottom cell and is located between the first carrier selection layer and the second carrier selection layer.

10. The tandem solar cell according to any one of claims 1 to 5, characterized in that, The bottom battery is configured as a back contact battery, and the back contact battery includes: The substrate includes a light-receiving surface and a backlight surface arranged opposite to each other, and the perovskite absorption layer of the top battery is directly disposed on the light-receiving surface; A first passivation contact structure and a second passivation contact structure are alternately formed on the backlight surface of the substrate layer, and the first passivation contact structure and the second passivation contact structure have opposite conductivity types. A third electrode and a fourth electrode, wherein the third electrode is disposed on the first passivation contact structure and the fourth electrode is disposed on the second passivation contact structure.

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