Solar laminated cell, preparation method thereof and photovoltaic module

Abstract

The invention provides a solar laminated cell and a preparation method thereof, and a photovoltaic module, and relates to the field of photovoltaic technology, the solar laminated cell comprises a bottom cell and a top cell which are laminated along a first direction, and a composite layer is arranged between the bottom cell and the top cell. The top cell comprises a first transmission layer, a perovskite layer, a second transmission layer, a transparent conducting layer and a first electrode which are arranged in the first direction, the surface, facing the transparent conducting layer, of the perovskite layer is provided with a first suede structure, the first suede structure comprises a plurality of protruding parts, the height of the protruding parts in the first direction is D1, and the height of the second transmission layer is D1; the thickness of the perovskite layer along the first direction is D2, D1 and D2 meet the condition that D1 / D2 is greater than or equal to 0.1 and less than or equal to 0.3, the first suede structure is arranged on the perovskite layer, so that the solar laminated cell can absorb larger incident light, meanwhile, the contact area of the perovskite layer and the second transmission layer is increased, and the short-circuit current and the filling factor of the solar laminated cell are improved.

Description

Technical Field

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

[0002] Solar tandem cells are used to convert solar energy into electrical energy. They can be composed of three parts stacked together: a top cell, a composite layer, and a bottom cell. Currently, solar tandem cells have problems with short-circuit current and fill factor, which are difficult to improve, affecting their efficiency. Summary of the Invention

[0003] In view of this, this application provides a solar tandem cell and its preparation method, as well as a photovoltaic module, to help solve the problems of short-circuit current and fill factor that are difficult to improve in the prior art.

[0004] In a first aspect, embodiments of this application provide a solar tandem battery, including a bottom battery and a top battery stacked along a first direction, with a composite layer disposed between the bottom battery and the top battery. The top battery includes a first transport layer, a perovskite layer, a second transport layer, a transparent conductive layer, and a first electrode arranged along the first direction. The surface of the perovskite layer facing the transparent conductive layer has a first textured structure, which includes a plurality of protrusions. The height of the protrusions along the first direction is D1, and the thickness of the perovskite layer along the first direction is D2. D1 and D2 satisfy: 0.1≤D1 / D2≤0.3.

[0005] In one possible implementation, the height D1 of the protrusion along the first direction satisfies: 50nm≤D1≤500nm, and / or the thickness D2 of the perovskite layer along the first direction satisfies: 500nm≤D2≤1500nm.

[0006] In one possible implementation, the width of the protrusion along the second direction gradually decreases toward the transparent conductive layer.

[0007] In one possible implementation, the protrusion includes a first bottom wall and a first side wall connected to both sides of the first bottom wall along the second direction, wherein the included angle α between the first side wall and the first bottom wall satisfies: 35°≤α≤65°.

[0008] In one possible implementation, the protrusion has a triangular cross-sectional shape along the first direction.

[0009] In one possible implementation, the protrusion further includes a first top wall, which is arranged along the first bottom wall in the first direction and connected to the first side wall. The width of the first top wall in the second direction is smaller than the width of the first bottom wall in the second direction.

[0010] In one possible implementation, the width W1 of the first top wall along the second direction satisfies: 500nm≤W1≤5μm, and the width W2 of the first bottom wall along the second direction satisfies: 500nm≤W2≤5μm.

[0011] In one possible implementation, the first velvet structure further includes recesses, which are arranged alternately with the protrusions, and the cross-sectional shape of the recesses along the first direction is triangular, trapezoidal, or arched.

[0012] In one possible implementation, one of the first transport layer and the second transport layer is an electron transport layer and the other is a hole transport layer, and the surface of the second transport layer facing the transparent conductive layer has a second textured surface structure.

[0013] In one possible implementation, the thickness D3 of the first transport layer along the first direction satisfies: 10nm≤D3≤40nm, and / or the thickness D4 of the second transport layer along the first direction satisfies: 10nm≤D4≤30nm.

[0014] In one possible implementation, the solar tandem cell further includes a protective layer located along the first direction on the side of the transparent conductive layer away from the second transport layer, and the surface of the transparent conductive layer facing the protective layer has a third textured structure.

[0015] In one possible implementation, the thickness D5 of the transparent conductive layer along the first direction satisfies: 30nm≤D5≤100nm, and / or the thickness D6 of the protective layer along the first direction satisfies: 50nm≤D6≤200nm.

[0016] In one possible implementation, a second electrode is provided on the side of the bottom battery away from the composite layer, and the thickness D7 of the composite layer along the first direction satisfies: 5nm≤D7≤30nm, and / or the thickness D8 of the substrate of the bottom battery satisfies: 100μm≤D8≤260μm.

[0017] Secondly, embodiments of this application provide a photovoltaic module, including a cover plate, an encapsulation layer, and a battery string, wherein the battery string includes a plurality of solar tandem cells as described above.

[0018] Thirdly, embodiments of this application provide a method for preparing a solar tandem cell, comprising: A substrate is prepared, the substrate comprising a bottom cell, a composite layer, and a first transport layer arranged along a first direction; A perovskite layer with a thickness of D2 is formed on the substrate, and the perovskite layer is located on the side of the first transport layer away from the composite layer; The perovskite layer is etched to form a first textured structure on the surface of the perovskite layer away from the substrate. The first textured structure includes a plurality of protrusions with a height of D1, where D1 and D2 satisfy: 0.1≤D1 / D2≤0.3. A second transport layer is formed on the first velvet structure; A transparent conductive layer is formed on the second transport layer; A first electrode is formed on the transparent conductive layer.

[0019] In one possible implementation, prior to the step of forming the second transport layer on the first textured structure, the method for fabricating the solar tandem cell further includes: The first velvet structure is cleaned.

[0020] In one possible implementation, the step of cleaning the first velvet structure includes: A cleaning solution is spin-coated onto the first velvety structure. The spin-coating speed V satisfies: 4000rpm≤V≤5000rpm, and the spin-coating time t1 satisfies: 5s≤t1≤15s. The first velvet structure is subjected to annealing treatment, with the annealing temperature T satisfying: 85℃≤T≤115℃, and the annealing time t2 satisfying: 5min≤t2≤10min.

[0021] In one possible implementation, the etching process for etching the perovskite layer is plasma etching, ion beam etching, or focused ion beam etching.

[0022] In one possible implementation, the step of forming the second transport layer on the first velvet structure includes: A second transport layer with a thickness D4 is formed, satisfying: 10nm≤D4≤30nm, and the surface of the second transport layer away from the perovskite layer has a second textured structure.

[0023] In one possible implementation, the step of forming a transparent conductive layer on the second transport layer includes: A transparent conductive layer with a thickness D5 is formed, satisfying 30nm≤D5≤100nm, and the surface of the transparent conductive layer opposite to the perovskite layer has a third textured structure.

[0024] The beneficial effects of this application are as follows: setting the first textured surface structure enables the solar tandem cell to absorb more incident light, reduce optical loss, thereby increasing the short-circuit current of the solar tandem cell and improving the photoelectric conversion efficiency of the solar tandem cell. At the same time, it increases the contact area between the perovskite layer and the second transport layer, reduces recombination loss, and improves the carrier extraction efficiency, thereby improving the short-circuit current and fill factor of the solar tandem cell.

[0025] It should be understood that the above general description and the following detailed description are merely exemplary and do not limit this application. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of a solar tandem cell in one embodiment of this application; Figure 2 for Figure 1 A schematic diagram of the perovskite layer in a solar tandem cell; Figure 3 for Figure 2 Enlarged view of section I; Figure 4 This is a schematic diagram of a solar tandem cell in another embodiment of this application; Figure 5 for Figure 4 Enlarged view of Part II; Figure 6 This is a schematic diagram of a solar tandem cell in yet another embodiment of this application; Figure 7 for Figure 6 Method diagram for Part III; Figure 8 This is a flowchart of a method for preparing a solar tandem cell according to one embodiment of this application; Figure 9 This is a schematic diagram of a photovoltaic module in one embodiment of this application.

[0028] Figure label: 1000 - Photovoltaic module; 1001 - First cover plate; 1002 - First encapsulation layer; 1003 - Battery string; 1004 - Second encapsulation layer; 1005 - Second cover plate.

[0029] 100-Solar tandem cell; 10-Top cell; 11-First transport layer; 12-Perovskite layer; 121-First textured structure; 1211-Protrusion; 1211a-First end; 1211b-Second end; 1211c-First bottom wall; 1211d-First side wall; 1211e-First top wall; 1212-Recess; 122-Body part; 1221-Third end; 1222-Fourth end; 13-Second transport layer; 131-Second textured structure; 14-Transparent conductive layer; 141-Third textured structure; 15-First electrode; 16-Protective layer; 20-Bottom cell; 21-Substrate; 2-Second electrode; 30-Composite layer; D1 - Height of the protrusion along the first direction; D2 - Thickness of the perovskite layer along the first direction; W1 - Width of the first top wall along the second direction; W2 - Width of the first bottom wall along the second direction; α - Angle between the first side wall and the first bottom wall. Detailed Implementation

[0030] To better understand the technical solution of this application, the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0031] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0032] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0033] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0034] like Figure 1 As shown, this application provides a solar tandem battery 100, including a bottom battery 20 and a top battery 10 stacked along a first direction Z. A composite layer 30 is disposed between the bottom battery 20 and the top battery 10. The first direction Z can be the thickness direction of the solar tandem battery 100.

[0035] The top cell 10 can be a perovskite cell, comprising a first transport layer 11, a perovskite layer 12, a second transport layer 13, a transparent conductive layer 14, and a first electrode 15 arranged along a first direction Z. The first transport layer 11 is disposed on the composite layer 30, the perovskite layer 12 is disposed on the first transport layer 11, and the second transport layer 13 is disposed on the side of the perovskite layer 12 opposite to the first transport layer 11. One of the first transport layer 11 and the second transport layer 13 is an electron transport layer, and the other is a hole transport layer. The electron transport layer can be a metal oxide or a fullerene derivative, and the hole transport layer can be a metal oxide or a SAM (self-assembled molecular layer). The transparent conductive layer 14 is disposed on the second transport layer 13, and the first electrode 15 is disposed on the transparent conductive layer 14 and electrically connected to the transparent conductive layer 14. The conductive layer can be IZO (indium zinc oxide), which is a transparent conductive oxide with excellent light transmittance and good conductivity. The first electrode 15 can be sintered from a metal paste, which can include at least one of silver, copper, tin, gold, lead, or nickel.

[0036] The base cell 20 can be a crystalline silicon cell, such as a PERC cell (emitter and back passivation cell), a PERT cell (passivated emitter and back fully diffused cell), a TOPCon cell (tunneling oxide passivated contact cell), or an HJT cell (intrinsic thin-film heterojunction cell). The base cell 20 includes a substrate 21, which can be an N-type substrate or a P-type substrate. The N-type substrate 21 can be a silicon substrate doped with an N-type element, specifically one or a combination of pentavalent elements such as phosphorus, arsenic, or antimony. The P-type substrate 21 can be a silicon substrate doped with a P-type element, specifically one or a combination of trivalent elements such as boron, indium, or gallium.

[0037] The composite layer 30 can be a transparent conductive oxide, such as ITO (indium tin oxide), AZO (aluminum-doped zinc oxide), FTO (fluorine-doped tin oxide), or ATO (antimony-doped tin oxide).

[0038] Please also refer to Figure 2The surface of the perovskite layer 12 facing the transparent conductive layer 14 in the top cell 10 has a first textured structure 121. This first textured structure 121 includes multiple protrusions 1211. In other words, the surface of the perovskite layer 12 facing the transparent conductive layer 14 is a textured surface with raised areas. Compared to having a flat surface, the first textured structure 121 reduces light reflection from the incident light, thus reducing the reflectivity of the solar tandem cell 100. This allows the solar tandem cell 100 to absorb more incident light, reducing optical losses and thereby increasing the short-circuit current and photoelectric conversion efficiency of the solar tandem cell 100. Simultaneously, the multiple protrusions 1211 of the first textured structure 121 result in a larger surface area, increasing the contact area between the perovskite layer 12 and the second transport layer 13, reducing recombination losses, and improving carrier extraction efficiency. This further enhances the short-circuit current and fill factor of the solar tandem cell 100.

[0039] The perovskite layer 12 also includes a body portion 122, with a protrusion 1211 disposed on the side of the body portion 122 facing the transparent conductive layer 14, and the protrusion 1211 connected to the body portion 122. Along the first direction Z, the protrusion 1211 includes a first end 1211a facing the transparent conductive layer 14 and a second end 1211b away from the transparent conductive layer 14. The body portion 122 includes a third end 1221 facing the transparent conductive layer 14 and a fourth end 1222 away from the transparent conductive layer 14. The second end 1211b of the protrusion 1211 is connected to the third end 1221 of the transparent conductive layer 14. The height of the protrusion 1211 along the first direction Z (i.e., the height of the first textured structure 121) is D1, where D1 is the distance from the first end 1211a to the second end 1211b of the protrusion 1211 along the thickness direction of the solar tandem cell 100. The thickness of the perovskite layer 12 along the first direction Z is D2, which is the distance from the first end 1211a of the protrusion 1211 to the fourth end 1222 of the body portion 122 along the thickness direction of the solar tandem cell 100.

[0040] The height D1 of the protrusion 1211 along the first direction Z and the thickness D2 of the perovskite layer 12 along the first direction Z satisfy: 0.1≤D1 / D2≤0.3. The ratio of D1 to D2 can be 0.1, 0.12, 0.14, 0.16, 0.18, 0.2, 0.22, 0.24, 0.26, 0.28 or 0.3, or other values ​​within the above range.

[0041] If the ratio of D1 to D2 decreases, that is, if the height D1 of the protrusion 1211 is too small and the height D2 of the perovskite layer 12 is too large, the morphology of the first textured structure 121 becomes too flat, resulting in increased reflectivity of the surface of the perovskite layer 12, which increases optical loss and is not conducive to increasing the surface area of ​​the first textured structure 121, affecting the contact area between the perovskite layer 12 and the second transport layer 13. At the same time, if the overall thickness of the perovskite layer 12 is too large, it will lead to increased recombination loss and increased resistance, thereby affecting the short-circuit current and fill factor of the solar tandem cell 100.

[0042] If the ratio of D1 to D2 increases, that is, if the height D1 of the protrusion 1211 is too large and the height D2 of the perovskite layer 12 is too small, the part between adjacent protrusions 1211 in the first textured structure 121 is prone to breakage or holes, increasing recombination loss and leakage risk. At the same time, if the height of the protrusion 1211 is too large, the perovskite layer 12 is prone to stress concentration, which reduces the reliability of the perovskite layer 12 structure and causes the perovskite layer 12 to detach from other film layers, thereby causing the solar tandem cell 100 to fail to work properly.

[0043] As can be seen from the above, both excessively small height D1 of the protrusion 1211 and excessively large height D2 of the perovskite layer 12, and excessively large height D1 of the protrusion 1211 and excessively small height D2 of the perovskite layer 12, will affect the performance of the solar tandem cell 100. Therefore, this application limits the relationship between the height D1 of the protrusion 1211 and the height D2 of the perovskite layer 12, so that the thickness of the first textured structure 121 matches the thickness of the perovskite layer 12. This reduces the optical loss of the solar tandem cell 100, increases the contact area between the perovskite layer 12 and the second transmission layer 13, and improves the reliability and stability of the first textured structure 121 and the entire perovskite layer 12 structure, thereby improving the performance of the solar tandem cell 100, increasing its power, and enabling the solar tandem cell 100 to operate normally and stably.

[0044] like Figure 2 As shown, in one possible implementation, the height D1 of the protrusion 1211 along the first direction Z satisfies: 50nm≤D1≤500nm, for example 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm or 500nm, or other values ​​within the above range.

[0045] The thickness D2 of the perovskite layer 12 along the first direction Z satisfies: 500nm≤D2≤1500nm, for example, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, 850nm, 900nm, 950nm, 1000nm, 1100nm, 1200nm, 1300nm, 1400nm or 1500nm, or other values ​​within the above range.

[0046] As mentioned above, both excessively small heights (D1) of the protrusion 1211 and excessively large heights (D2) of the perovskite layer 12, and excessively large heights (D1) of the protrusion 1211 and excessively small heights (D2) of the perovskite layer 12, will affect the performance of the solar tandem cell 100. Therefore, in this embodiment, the height of the protrusion 1211 and the thickness of the perovskite layer 12 are specifically limited to improve the performance and power of the solar tandem cell 100, thereby enabling the solar tandem cell 100 to operate normally and stably.

[0047] In another possible implementation, the height D1 of the protrusion 1211 along the first direction Z satisfies: 50nm ≤ D1 ≤ 500nm, or the thickness D2 of the perovskite layer 12 along the first direction Z satisfies: 500nm ≤ D2 ≤ 1500nm. The solar tandem cell 100 in this embodiment satisfies at least one of the above conditions D1 and D2.

[0048] like Figure 1 and Figure 2 As shown, in one possible implementation, the width of the protrusion 1211 along the second direction X gradually decreases toward the transparent conductive layer 14.

[0049] The second direction X is perpendicular to the first direction Z mentioned above. The second direction X can be the length direction and / or width direction of the solar tandem cell 100. The width of the protrusion 1211 gradually decreases towards the transparent conductive layer 14 along the second direction X, making the shape of the protrusion 1211 approximately pyramidal. That is, the protrusion 1211 can reflect incident light in multiple directions, which is beneficial for the incident light to be reflected multiple times inside the perovskite layer 12, thereby improving the light absorption efficiency of the solar tandem cell 100 and improving the efficiency of the solar tandem cell 100. On the other hand, in the embodiments of this application, the first textured structure 121 with the protrusion 1211 can be prepared by processes such as dry etching, which is conducive to large-scale mass production.

[0050] like Figure 3As shown, in one possible implementation, the protrusion 1211 includes a first bottom wall 1211c and a first side wall 1211d connected to both sides of the first bottom wall 1211c along the second direction X. The included angle α between the first side wall 1211d and the first bottom wall 1211c satisfies: 35°≤α≤65°, for example 35°, 40°, 45°, 50°, 55°, 60° or 65°, or other values ​​within the above range.

[0051] Please also refer to Figure 1 and Figure 2 As mentioned above, the protrusion 1211 includes a first end 1211a facing the transparent conductive layer 14 and a second end 1211b facing away from the transparent conductive layer 14. A first bottom wall 1211c is located at the first end 1211a and is connected to the body portion 122 of the perovskite layer 12. The orientation of the first bottom wall 1211c can be parallel to the second direction X. The smaller the included angle α, the smaller the inclination of the first sidewall 1211d, in other words, the first sidewall 1211d is set more gently. If the included angle α is too small, the protrusion 1211 will appear flat overall, which will not only fail to increase the light absorption efficiency but also hinder the increase of the surface area of ​​the perovskite layer 12. This will affect the contact area between the perovskite layer 12 and the second transport layer 13, and thus affect the short-circuit current and fill factor of the solar tandem cell 100. The larger the included angle α, the greater the inclination of the first sidewall 1211d, in other words, the steeper the first sidewall 1211d is. If the included angle α is too large, the protrusion 1211 will have a tall and narrow shape, resulting in poor structural stability of the protrusion 1211 itself, making it prone to stress concentration and cracking, thus affecting the overall structural stability and reliability of the solar tandem cell 100.

[0052] Based on this, this application restricts the angle α between the first sidewall 1211d and the first bottom wall 1211c of the protrusion 1211, that is, restricts the shape of the protrusion 1211, so as to increase the absorption effect of the first textured structure 121 on sunlight while ensuring the stability of the protrusion 1211 structure, thereby reducing the optical loss of the solar tandem cell 100, and increasing the surface area of ​​the first textured structure 121, thereby increasing the contact area between the perovskite layer 12 and the second transport layer 13 and the transparent conductive layer 14, thereby improving the short-circuit current and fill factor of the solar tandem cell 100.

[0053] like Figure 2As shown, in one possible implementation, the protrusion 1211 has a triangular cross-sectional shape along the first direction Z, making the protrusion 1211 have a pyramidal structure, thereby enabling the protrusion 1211 to reflect incident light in multiple directions and improve the light absorption efficiency of the solar tandem cell 100.

[0054] like Figure 4 and Figure 5 As shown, in one possible implementation, the protrusion 1211 further includes a first top wall 1211e, which is arranged with the first bottom wall 1211c along the first direction Z, and the first top wall 1211e is connected to the first side wall 1211d. The width of the first top wall 1211e along the second direction X is smaller than the width of the first bottom wall 1211c along the second direction X.

[0055] The cross-sectional shape of the protrusion 1211 along the first direction Z can be trapezoidal, and the area of ​​the first top wall 1211e can be smaller than the area of ​​the first bottom wall 1211c, making the protrusion 1211 have a frustum-shaped structure. The first top wall 1211e of the protrusion 1211 can also reflect light, thus enabling the protrusion 1211 to reflect incident light in multiple directions, improving the light absorption efficiency of the solar tandem cell 100. The frustum-shaped protrusion 1211 structure is more stable, reducing the risk of stress concentration, and is also easier to fabricate, improving the overall stability and reliability of the solar tandem cell 100.

[0056] like Figure 5 As shown, in one possible implementation, the width W1 of the first top wall 1211e along the second direction X satisfies: 500nm ≤ W1 ≤ 5μm, for example, 500nm, 600nm, 700nm, 800nm, 900nm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm or 5μm.

[0057] The width W2 of the first bottom wall 1211c along the second direction X satisfies: 500nm ≤ W2 ≤ 5μm. For example, 500nm, 600nm, 700nm, 800nm, 900nm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, or 5μm.

[0058] As mentioned above, the width of the first top wall 1211e along the second direction X is smaller than the width of the first bottom wall 1211c along the second direction X. By designing the widths of the first top wall 1211e and the second bottom wall, it is beneficial to increase the absorption effect of the perovskite layer 12 on sunlight while ensuring the structural stability of the protrusion 1211, thereby improving the stability and reliability of the solar tandem cell 100.

[0059] like Figure 6 and Figure 7 As shown, in one possible implementation, the first velvet structure 121 further includes a recess 1212, the recess 1212 and the protrusion 1211 are arranged alternately, and the cross-sectional shape of the recess 1212 along the first direction Z is triangular, trapezoidal or arched.

[0060] Along the first direction Z, the depth of the recess 1212 is the same as the height of the protrusion 1211. A second transmission layer 13 is disposed on the first textured structure 121, extending into the recess 1212 to fill it. By defining the shape of the recess 1212, the second transmission layer 13 can effectively fill it, reducing the risk of voids between the second transmission layer 13 and the perovskite layer 12 and improving the contact quality between them. Simultaneously, the recess 1212 can reflect light; defining its shape also helps improve the overall light absorption efficiency of the first textured structure 121, thereby reducing optical losses in the solar tandem cell 100.

[0061] like Figure 6 As shown, in one possible implementation, one of the first transport layer 11 and the second transport layer 13 is an electron transport layer, and the other is a hole transport layer. When the first transport layer 11 is an electron transport layer and the second transport layer 13 is a hole transport layer, the top cell 10 is a formal perovskite cell (i.e., a positive perovskite cell). The fabrication process of a formal perovskite cell is simple and its efficiency is high. When the first transport layer 11 is a hole transport layer and the second transport layer 13 is an electron transport layer, the top cell 10 is an inverted perovskite cell (i.e., an inverted perovskite cell). The fabrication process of an inverted perovskite cell is simple, its structural stability is high, and it is suitable for stacking with a crystalline silicon cell (i.e., the bottom cell 20) to form a solar tandem cell 100.

[0062] The surface of the second transport layer 13 facing the transparent conductive layer 14 has a second textured structure 131. The shape of the second textured structure 131 is the same as that of the first textured structure 121. The second textured structure 131 increases the surface area of ​​the second transport layer 13 facing the transparent conductive layer 14, thereby increasing the contact area between the second transport layer 13 and the transparent conductive layer 14. The transparent conductive layer 14 is used to collect and discharge charge carriers inside the solar tandem cell 100. The increase in the area between the transparent conductive layer 14 and the second transport layer 13 reduces the contact resistance between the transparent conductive layer 14 and the second transport layer 13, improves the charge carrier collection efficiency, and thus improves the short-circuit current and fill factor of the solar tandem cell 100, thereby improving the efficiency of the solar tandem cell 100.

[0063] In this embodiment, the perovskite layer 12 has a first textured structure 121 and the second transport layer 13 has a second textured structure 131, thereby increasing the contact area between the perovskite layer 12 and the second transport layer 13 and between the second transport layer 13 and the transparent conductive layer 14. In other words, the contact area between the perovskite layer 12 and the transparent conductive layer 14 is increased, thereby improving the short-circuit current and fill factor of the solar tandem cell 100, and thus improving the efficiency of the solar tandem cell 100.

[0064] like Figure 6 As shown, in one possible implementation, the thickness D3 of the first transmission layer 11 along the first direction Z satisfies: 10nm≤D3≤40nm, for example 10nm, 15nm, 20nm, 25nm, 30nm, 35nm or 40nm, and of course other values ​​within the above range are also possible.

[0065] The thickness D4 of the second transport layer 13 along the first direction Z satisfies: 10nm≤D4≤30nm, for example, 10nm, 15nm, 20nm, 25nm or 30nm, or other values ​​within the above range.

[0066] If the thickness of the first transport layer 11 and the second transport layer 13 is too large, it will affect the carrier transport efficiency and the stability of the film structure of the first transport layer 11 and the second transport layer 13, making them prone to cracking. If the thickness of the first transport layer 11 and the second transport layer 13 is too small, it will affect the extraction of carriers, thereby affecting the efficiency of the solar tandem cell 100, and also affecting the mechanical strength of the first transport layer 11 and the second transport layer 13, reducing the stability of their film structure. Based on this, this application designs the thickness of the first transport layer 11 and the second transport layer 13 to improve the extraction and transport efficiency of carriers while ensuring the structural stability of the first transport layer 11 and the second transport layer 13, thereby improving the efficiency of the solar tandem cell 100 and extending its service life.

[0067] In another possible implementation, the thickness D3 of the first transport layer 11 along the first direction Z satisfies: 10nm ≤ D3 ≤ 40nm, or the thickness D4 of the second transport layer 13 along the first direction Z satisfies: 10nm ≤ D4 ≤ 30nm. In this embodiment, the solar tandem cell 100 satisfies at least one of the above conditions D3 and D4.

[0068] like Figure 6As shown, in one possible implementation, the solar tandem cell 100 further includes a protective layer 16 located along a first direction Z on the side of the transparent conductive layer 14 away from the second transmission layer 13, and the surface of the transparent conductive layer 14 facing the protective layer 16 has a third textured structure 141.

[0069] The shape of the third textured structure 141 can be the same as the shape of the first textured structure 121 and the second textured structure 131 described above. The transparent conductive layer 14 has the third textured structure 141 to reduce the light reflection loss of the solar tandem cell 100 and increase the light absorption efficiency of the solar tandem cell 100.

[0070] The protective layer 16 can be magnesium fluoride, which can improve the light absorption rate of the solar tandem cell 100 and also play a protective role, reducing the possibility of foreign objects such as water vapor entering the interior of the solar tandem cell 100 and improving the stability of the transparent conductive layer 14 and other film layers. The first electrode 15 mentioned above is the top electrode of the solar tandem cell 100. At least part of the structure of the first electrode 15 extends into the protective layer 16 and is electrically connected to the transparent conductive layer 14.

[0071] like Figure 6 As shown, in one possible implementation, the thickness D5 of the transparent conductive layer 14 along the first direction Z satisfies: 30nm≤D5≤100nm, for example 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm or 100nm, or other values ​​within the above range.

[0072] If the thickness of the transparent conductive layer 14 is too large, it will affect the light transmittance of the transparent conductive layer 14, thereby affecting the light absorption rate of the solar tandem cell 100. If the thickness of the transparent conductive layer 14 is too small, it will affect the carrier collection efficiency, thereby affecting the efficiency of the solar energy. Therefore, the present application embodiment limits the thickness of the transparent conductive layer 14 in order to improve the carrier collection efficiency and improve the efficiency of the solar tandem cell 100 while ensuring the light transmittance of the transparent conductive layer 14.

[0073] The thickness D6 of the protective layer 16 along the first direction Z satisfies: 50nm ≤ D6 ≤ 200nm, such as 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 120nm, 140nm, 160nm, 180nm, or 200nm, or other values ​​within the above range. By designing the thickness of the protective layer 16, the stability of the film structure of the protective layer 16 is improved, reducing the risk of cracking, while providing reliable protection and reducing the possibility of moisture and other foreign matter intruding into the solar tandem cell 100, thereby extending the service life of the solar tandem cell 100.

[0074] In another possible implementation, the thickness D5 of the transparent conductive layer 14 along the first direction Z satisfies: 30nm≤D5≤100nm, or the thickness D6 of the protective layer 16 along the first direction Z satisfies: 50nm≤D6≤200nm. In this embodiment, the solar tandem cell 100 satisfies at least one of the above two conditions D5 and D6.

[0075] like Figure 6 As shown, in one possible implementation, a second electrode 22 is provided on the side of the bottom cell 20 away from the composite layer 30. The second electrode 22 is the bottom electrode of the solar tandem cell 100. The second electrode 22 can be sintered from a metal paste, which may include at least one of silver, copper, tin, gold, lead or nickel.

[0076] The thickness D7 of the composite layer 30 along the first direction Z satisfies: 5nm ≤ D7 ≤ 30nm, such as 5nm, 10nm, 15nm, 20nm, 25nm, or 30nm, or other values ​​within the above range. The composite layer 30 realizes the electrical connection between the top cell and the bottom cell 20. By designing the thickness of the composite layer 30, the stability and reliability of the composite layer 30 itself are ensured, guaranteeing a stable connection between the top cell 10 and the bottom cell 20.

[0077] As mentioned above, the bottom cell 20 includes a substrate 21. The thickness D8 of the substrate 21 of the bottom cell 20 satisfies: 100μm≤D8≤260μm, for example, 100μm, 120μm, 140μm, 160μm, 180μm, 200μm, 220μm, 240μm, or 260μm. Of course, it can also be other values ​​within the above range. By designing the thickness of the substrate 21 of the bottom cell 20, the bottom cell 20 can absorb the light not utilized by the top cell 10, improve the efficiency of the solar tandem cell 100, and at the same time ensure the stability and reliability of the bottom cell 20 itself.

[0078] In another possible implementation, the thickness D7 of the composite layer 30 along the first direction Z satisfies: 5nm ≤ D7 ≤ 30nm, or the thickness D8 of the substrate 21 of the bottom cell 20 satisfies: 100μm ≤ D8 ≤ 260μm. In this embodiment, the solar tandem cell 100 satisfies at least one of the above conditions D7 and D8.

[0079] The structure of the solar tandem cell has been described in detail above. The following section will introduce the preparation method of the solar tandem cell, taking the first transport layer as the hole transport layer and the second transport layer as the electron transport layer, that is, taking the top cell as an inverted perovskite cell.

[0080] like Figure 6 and Figure 8As shown in the figure, this application provides a method for preparing a solar tandem cell 100, including: S1, Prepare a substrate, the substrate including a bottom cell 20, a composite layer 30 and a first transport layer 11 arranged along the first direction Z.

[0081] The composite layer 30 can be formed on the bottom cell 20 by sputtering, and a hole transport layer (i.e., the first transport layer 11) can be formed on the composite layer 30 by vapor deposition or spin coating.

[0082] S2, a perovskite layer 12 with a thickness of D2 is formed on the substrate 21 layer, and the perovskite layer 12 is located on the side of the first transport layer 11 away from the composite layer 30.

[0083] The perovskite layer 12 can be prepared by methods such as vapor deposition, spin coating, or blade coating, and the thickness D2 of the perovskite layer 12 can meet the following requirements: 500nm≤D2≤1500nm.

[0084] S3, the perovskite layer 12 is etched to form a first textured structure 121 on the surface of the perovskite layer 12 away from the substrate 21 layer. The first textured structure 121 includes a plurality of protrusions 1211 with a height of D1, where D1 and D2 satisfy: 0.1≤D1 / D2≤0.3.

[0085] The height D1 of the protrusion 1211 can satisfy: 50nm≤D1≤500nm. The technical effects of setting the first textured structure 121 and limiting the ratio of the height D1 of the protrusion 1211 to the thickness D2 of the perovskite layer 12 have been described in detail above, and will not be repeated here.

[0086] S4, a second transport layer 13 is formed on the first textured structure 121. The electron transport layer (i.e., the second transport layer 13) can be prepared by methods such as vapor deposition, spin coating, or blade coating.

[0087] S5, a transparent conductive layer 14 is formed on the second transport layer 13. The transparent conductive layer 14 can be prepared by vapor deposition or sputtering.

[0088] S6, a first electrode 15 is formed on the transparent conductive layer 14. The first electrode 15 may be formed by sintering a metal paste.

[0089] In some embodiments, when preparing the hole transport layer using a spin coating process, the spin coating speed is 3000 rpm to 4000 rpm, and the spin coating time is 20 s to 35 s. After the spin coating step is completed, an annealing treatment can be performed at a temperature of 80° to 115°C for 10 min to 15 min.

[0090] In some embodiments, when preparing the perovskite layer using a spin coating process, the spin coating speed is 3000 rpm to 4000 rpm, and the spin coating time is 30 s to 45 s. After the spin coating step is completed, an annealing treatment can be performed at a temperature of 90° to 110° and an annealing time of 10 min to 15 min.

[0091] In one possible implementation, prior to the step of forming the second transport layer on the first textured structure, the method for fabricating a solar tandem cell further includes: Clean the first velvet surface structure.

[0092] By cleaning the first textured surface to remove residues from the previous etching process, a good interface is provided for the preparation of the second transport layer, thereby improving the forming quality of the second transport layer.

[0093] In one possible implementation, the step of cleaning the first velvet structure specifically includes: A cleaning solution is spin-coated onto the first velvety structure. The spin-coating speed V satisfies: 4000rpm≤V≤5000rpm, and the spin-coating time t1 satisfies: 5s≤t1≤15s.

[0094] The first velvet structure is annealed with an annealing temperature T satisfying: 85℃≤T≤115℃, and an annealing time t2 satisfying: 5min≤t2≤10min.

[0095] The cleaning solution may contain DMF, DMSO, and IPA solutions. The cleaning solution removes residues from previous etching processes and also etches the first textured structure to a depth of approximately 5 nm to 15 nm to optimize its morphology. Annealing helps repair damage caused by the etching process and improves the quality of the first textured structure.

[0096] In one possible implementation, the etching process for etching the perovskite layer is plasma etching, ion beam etching, or focused ion beam etching.

[0097] Plasma etching, ion beam etching, and focused ion beam etching are all dry etching methods. Using dry etching technology is beneficial for precise control of the morphology of the first textured surface structure, thereby improving the forming quality of the first textured surface structure.

[0098] like Figure 6 As shown, in one possible implementation, the step of forming the second transport layer 13 on the first textured structure 121 includes: A second transport layer 13 with a thickness D4 is formed, satisfying: 10nm≤D4≤30nm. The surface of the second transport layer 13 facing away from the perovskite layer 12 has a second textured structure 131.

[0099] The technical effects of the thickness design of the second transmission layer 13 and the technical effects of setting the second velvet structure 131 have been described in detail above, and will not be repeated here.

[0100] Continue as Figure 6 As shown, in one possible implementation, the step of forming a transparent conductive layer 14 on the second transport layer 13 includes: A transparent conductive layer 14 with a thickness D5 satisfying: 30nm≤D5≤100nm is formed, and the surface of the transparent conductive layer 14 facing away from the perovskite layer 12 has a third textured structure 141.

[0101] The technical effects of the transparent conductive layer 14 thickness design and the third textured structure 141 have been described in detail above and will not be repeated here.

[0102] like Figure 9 As shown in the figure, this application embodiment also provides a photovoltaic module 1000, including a cover plate, an encapsulation layer and a battery string 1003, wherein the battery string 1003 includes a plurality of the above-mentioned solar tandem cells.

[0103] The photovoltaic module 1000 has a first cover plate 1001 at the top and a second cover plate 1005 at the bottom. The encapsulation layer between the first cover plate 1001 and the battery string 1003 is a first encapsulation layer 1002, and the encapsulation layer between the second cover plate 1005 and the battery string 1003 is a second encapsulation layer 1004. The first cover plate 1001, first encapsulation layer 1002, battery string 1003, second encapsulation layer 1004, and second cover plate 1005 can be arranged along the thickness direction of the photovoltaic module 1000 and laminated together. The first cover plate 1001 can be a glass cover plate with high light transmittance. The first encapsulation layer 1002 bonds the first cover plate 1001 to the battery string 1003, thus providing encapsulation and protection for the battery string 1003. The material of the first encapsulation layer 1002 can be one or more of ethylene-vinyl acetate copolymer (EVA), polyolefin elastomer (POE), and polyvinyl butyral (PVB). The second encapsulation layer 1004 connects the battery string 1003 to the second cover plate 1005, also providing encapsulation and protection for the battery string 1003. The material of the second encapsulation layer 1004 can be one or more of EVA, POE, and PVB. The material of the second cover plate 1005 can be glass, or the second cover plate 1005 can be composed of multiple polymer film layers.

[0104] The above description is merely an optional embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A solar tandem battery, characterized in that, It includes a bottom battery and a top battery stacked along a first direction, with a composite layer disposed between the bottom battery and the top battery; The top battery includes a first transport layer, a perovskite layer, a second transport layer, a transparent conductive layer, and a first electrode arranged along the first direction; The surface of the perovskite layer facing the transparent conductive layer has a first textured structure. The first textured structure includes a plurality of protrusions. The height of the protrusions along the first direction is D1, and the thickness of the perovskite layer along the first direction is D2. D1 and D2 satisfy: 0.1≤D1 / D2≤0.

3.

2. The solar tandem battery according to claim 1, characterized in that, The height D1 of the protrusion along the first direction satisfies: 50nm≤D1≤500nm, and / or; The thickness D2 of the perovskite layer along the first direction satisfies: 500nm ≤ D2 ≤ 1500nm.

3. The solar tandem battery according to claim 1, characterized in that, The width of the protrusion along the second direction gradually decreases toward the transparent conductive layer.

4. The solar tandem battery according to claim 3, characterized in that, The protrusion includes a first bottom wall and a first side wall connected to both sides of the first bottom wall along the second direction; The included angle α between the first sidewall and the first bottom wall satisfies: 35°≤α≤65°.

5. The solar tandem battery according to claim 4, characterized in that, The cross-sectional shape of the protrusion along the first direction is triangular.

6. The solar tandem battery according to claim 4, characterized in that, The protrusion further includes a first top wall, which is arranged along the first bottom wall in the first direction, and the first top wall is connected to the first side wall; The width of the first top wall along the second direction is smaller than the width of the first bottom wall along the second direction.

7. The solar tandem cell according to claim 6, characterized in that, The width W1 of the first top wall along the second direction satisfies: 500nm≤W1≤5μm; The width W2 of the first bottom wall along the second direction satisfies: 500nm≤W2≤5μm.

8. The solar tandem cell according to any one of claims 1 to 7, characterized in that, The first velvet structure also includes recessed portions, which are alternately arranged with the raised portions; The cross-sectional shape of the recessed portion along the first direction is triangular, trapezoidal, or arched.

9. The solar tandem cell according to any one of claims 1 to 7, characterized in that, One of the first transport layer and the second transport layer is an electron transport layer, and the other is a hole transport layer; The surface of the second transport layer facing the transparent conductive layer has a second textured surface.

10. The solar tandem battery according to claim 9, characterized in that, The thickness D3 of the first transport layer along the first direction satisfies: 10nm≤D3≤40nm, and / or; The thickness D4 of the second transport layer along the first direction satisfies: 10nm≤D4≤30nm.

11. The solar tandem cell according to claim 9, characterized in that, The solar tandem battery also includes a protective layer; The protective layer is located along the first direction on the side of the transparent conductive layer away from the second transmission layer; the surface of the transparent conductive layer facing the protective layer has a third textured surface structure.

12. The solar tandem cell according to claim 11, characterized in that, The thickness D5 of the transparent conductive layer along the first direction satisfies: 30nm≤D5≤100nm, and / or; The thickness D6 of the protective layer along the first direction satisfies: 50nm ≤ D6 ≤ 200nm.

13. The solar tandem cell according to any one of claims 1 to 7, characterized in that, A second electrode is provided on the side of the bottom battery opposite to the composite layer; The thickness D7 of the composite layer along the first direction satisfies: 5nm≤D7≤30nm, and / or; The thickness D8 of the substrate of the bottom battery satisfies: 100μm≤D8≤260μm.

14. A photovoltaic module, characterized in that, This includes the cover plate, encapsulation layer, and battery string; The battery string includes a plurality of solar tandem cells as described in any one of claims 1 to 13.

15. A method for preparing a solar tandem cell, characterized in that, include: A substrate is prepared, the substrate comprising a bottom cell, a composite layer, and a first transport layer arranged along a first direction; A perovskite layer with a thickness of D2 is formed on the substrate, and the perovskite layer is located on the side of the first transport layer away from the composite layer; The perovskite layer is etched to form a first textured structure on the surface of the perovskite layer away from the substrate. The first textured structure includes a plurality of protrusions with a height of D1, where D1 and D2 satisfy: 0.1≤D1 / D2≤0.

3. A second transport layer is formed on the first velvet structure; A transparent conductive layer is formed on the second transport layer; A first electrode is formed on the transparent conductive layer.

16. The method for preparing a solar tandem cell according to claim 15, characterized in that, Before the step of forming the second transport layer on the first textured structure, the method for fabricating the solar tandem cell further includes: The first velvet structure is cleaned.

17. The method for preparing a solar tandem cell according to claim 16, characterized in that, The step of cleaning the first velvet structure includes: A cleaning solution is spin-coated onto the first velvety structure. The spin-coating speed V satisfies: 4000rpm≤V≤5000rpm, and the spin-coating time t1 satisfies: 5s≤t1≤15s. The first velvet structure is subjected to annealing treatment, with the annealing temperature T satisfying: 85℃≤T≤115℃, and the annealing time t2 satisfying: 5min≤t2≤10min.

18. The method for preparing a solar tandem cell according to any one of claims 15 to 17, characterized in that, The etching process for etching the perovskite layer is plasma etching, ion beam etching, or focused ion beam etching.

19. The method for preparing a solar tandem cell according to any one of claims 15 to 17, characterized in that, The step of forming the second transport layer on the first velvet structure includes: A second transport layer with a thickness D4 is formed, satisfying: 10nm≤D4≤30nm, and the surface of the second transport layer away from the perovskite layer has a second textured structure.

20. The method for preparing a solar tandem cell according to claim 19, characterized in that, The step of forming a transparent conductive layer on the second transport layer includes: A transparent conductive layer with a thickness D5 is formed, satisfying 30nm≤D5≤100nm, and the surface of the transparent conductive layer opposite to the perovskite layer has a third textured structure.

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