Full-perovskite laminated solar cell and preparation method thereof

Abstract

The invention provides a full-perovskite laminated solar cell and a preparation method thereof, and relates to the technical field of solar cells. The full-perovskite laminated solar cell comprises a wire, a narrow-band-gap bottom cell, a transparent insulating layer and a wide-band-gap top cell, the narrow-band-gap bottom cell, the transparent insulating layer and the wide-band-gap top cell are sequentially arranged in a laminated mode, the wide-band-gap top cell is a reverse wide-band-gap top cell or a formal wide-band-gap top cell, and the wire is connected with electrode layers with corresponding polarities in the wide-band-gap top cell and the narrow-band-gap bottom cell. The two sides of the transparent insulating layer are respectively provided with a plurality of trapezoid structures which are periodically arranged and aligned, and the protruding directions of the trapezoid structures on the two sides are the same. According to the technical scheme, the preparation sequence flexibility of the upper sub-cell and the lower sub-cell is improved, a process window is widened, the top cell and the bottom cell are electrically connected through the wires, and reflection of long-wave-band light is reduced through the trapezoidal structures; on the basis of optimizing the current matching characteristic of the full-perovskite laminated solar cell, the overall photoelectric conversion efficiency is synergistically improved.

Description

A fully perovskite tandem solar cell and its fabrication method Technical Field

[0001] This invention relates to the field of solar cell technology, and in particular to an all-perovskite tandem solar cell and its preparation method. Background Technology

[0002] Perovskite solar cells have become a star of next-generation photovoltaic technology due to their excellent photoelectric conversion efficiency, low raw material cost, and simple solution processing. To overcome the Shockley-Quisser theoretical efficiency limit of single-junction perovskite cells, all-perovskite tandem solar cells significantly improve photoelectric conversion efficiency by constructing perovskite sub-cells with different bandgapes to achieve hierarchical absorption of the solar spectrum. In the all-perovskite tandem solar cell structure, the intermediate interconnect layer is located between the top and bottom cells. It not only needs to achieve efficient electrical connection between the upper and lower sub-cells but also needs good optical transmittance and modulation capabilities to ensure that long-wavelength photons not absorbed by the top cell can be effectively transmitted to the bottom cell and reused. Therefore, the optical and electrical performance of the intermediate interconnect layer has a decisive influence on the overall performance of the tandem device.

[0003] However, existing technologies often employ transparent conductive materials to construct continuous conductive structures for the intermediate interconnect layers, enabling electrical connections between upper and lower sub-cells. However, this type of structure still has significant shortcomings in practical applications. Firstly, the transparent conductive layer, as an intermediate connecting layer, is relatively thin, requiring the bottom cell, transparent conductive layer, and top cell to be formed sequentially in a traditional order, with a stringent fabrication process window. Secondly, the interfaces of the intermediate interconnect layers are often relatively flat, easily generating strong Fresnel reflections during light propagation, preventing some incident light from effectively entering the bottom cell and reducing light utilization efficiency. Furthermore, because the intermediate interconnect layer requires synergistic optimization between optical transmittance and electrical conductivity, its structure and material design are subject to performance coupling constraints. Improving conductivity often comes at the cost of sacrificing optical transmittance, and vice versa, thus limiting the space for device performance optimization. Summary of the Invention

[0004] One objective of this invention is to provide an all-perovskite tandem solar cell to solve the technical problems in the prior art that it is difficult to ensure electrical connection between the upper and lower sub-cells while reducing the reflection of long-wavelength light by the intermediate connecting layer, and the fabrication process is also very demanding.

[0005] A further objective of this invention is to further improve the absorption of long-wavelength light.

[0006] Another object of the present invention is to provide a method for fabricating an all-perovskite tandem solar cell.

[0007] Specifically, this invention provides an all-perovskite tandem solar cell, comprising conductive wires and a narrow bandgap bottom cell, a transparent insulating layer, and a wide bandgap top cell stacked sequentially from bottom to top; the wide bandgap top cell is either an inverted wide bandgap top cell or a conventional wide bandgap top cell. The conventional wide bandgap top cell comprises a first electrode layer, a first electron transport layer, a wide bandgap perovskite absorber layer, a first hole transport layer, and a second electrode layer stacked sequentially from top to bottom. The difference between the inverted wide bandgap top cell and the conventional wide bandgap top cell is that the positions of the first electron transport layer and the first hole transport layer are interchanged in the stacking direction. The narrow bandgap bottom cell comprises a third electrode layer, a second hole transport layer, a narrow bandgap perovskite absorber layer, a second electron transport layer, and a fourth electrode layer stacked sequentially from top to bottom. Multiple periodically arranged and aligned trapezoidal structures are respectively provided on both sides of the transparent insulating layer, and the convex directions of the trapezoidal structures on both sides are the same, so that concave sections are formed on both sides of the transparent insulating layer. The trapezoidal array structure and the protrusion array structure are used, wherein the third electrode layer, the second hole transport layer, the second electrode layer, and the target transport layer are all identical in shape to the transparent insulating layer, and the target transport layer is either the first hole transport layer of the formal wide-bandgap top cell or the first electron transport layer of the inverse wide-bandgap top cell; wherein the thickness of the transparent insulating layer is any value between 100nm and 300nm, the top width of each trapezoidal structure is any value between 50nm and 100nm, the bottom width is any value between 10nm and 50nm, the height is any value between 5nm and 20nm, and the spacing between the centers of two adjacent trapezoidal structures is any value between 100nm and 2000nm; when the wide-bandgap top cell is an inverse wide-bandgap top cell, the wire is used to connect the second electrode layer and the third electrode layer; when the wide-bandgap top cell is a formal wide-bandgap top cell, the wire is used to connect the first electrode layer and the third electrode layer.

[0008] Optionally, the thickness of the wide bandgap perovskite absorber layer is any value between 400 nm and 500 nm, and the thickness of the narrow bandgap perovskite absorber layer is any value between 1200 nm and 1300 nm.

[0009] Optionally, the thickness of the first electron transport layer is any value between 20nm and 30nm, and its material is... , Or ZnO; the thickness of the first hole transport layer is any value between 10nm and 100nm, and its material is Spiro-OMeTAD, PTAA, or .

[0010] Optionally, the thickness of the first electrode layer is any value between 80nm and 150nm, and its material is selected from any one of ITO, IZO, FTO or AZO; the thickness of the second electrode layer is any value between 50nm and 200nm, and its material is selected from any one of ITO, IZO, FTO or AZO.

[0011] Optionally, the thickness of the second hole transport layer is any value between 10nm and 100nm, and its material is (PEDOT:PSS), PTAA, or The thickness of the third electrode layer is any value between 50nm and 200nm, and its material is selected from any one of ITO, IZO, FTO or AZO.

[0012] Optionally, the thickness of the second electron transport layer is any value between 20nm and 80nm, and its material is C60, PCBM, or The thickness of the fourth electrode layer is any value between 50nm and 200nm, and its material is selected as Au, Ag or Al.

[0013] Optionally, the transparent insulating layer is made of soda-lime glass or quartz glass.

[0014] In particular, the present invention also provides a method for fabricating the above-mentioned all-perovskite tandem solar cell, comprising the following steps: providing a transparent insulating layer to be imprinted; using thermal nanoimprinting technology to form a recessed array structure and a raised array structure on both sides of the transparent insulating layer to be imprinted, respectively, to obtain a transparent insulating layer; forming a wide bandgap top cell on the side of the transparent insulating layer where the recessed array structure is provided; forming a narrow bandgap bottom cell on the side of the transparent insulating layer where the raised array structure is provided; and connecting wires at the corresponding electrodes of the wide bandgap top cell and the narrow bandgap bottom cell.

[0015] In this invention, the transparent insulating layer possesses high light transmittance while isolating the electrical connection between the narrow bandgap bottom cell and the wide bandgap top cell in the stacking direction. Simultaneously, corresponding electrode layers in the narrow bandgap bottom cell and the wide bandgap top cell are connected by wires, forming an electrical series structure between the wide bandgap top cell and the narrow bandgap bottom cell in the external circuit. Multiple periodically arranged trapezoidal structures are provided on both sides of the transparent insulating layer to introduce multiple refractions at the interface between the transparent insulating layer and adjacent electrode layers, reducing reflection of long-wavelength light and extending the effective path of long-wavelength light in the narrow bandgap perovskite absorption layer. The trapezoidal structures on both sides of the transparent insulating layer are aligned along the stacking direction, allowing long-wavelength light to form continuous optical propagation channels at corresponding positions when passing through the transparent insulating layer, helping to reduce disordered scattering losses caused by the randomness of the trapezoidal structures. The convex directions of the trapezoidal structures on both sides of the transparent insulating layer are aligned, resulting in a synergistic geometric change at the upper and lower interfaces. This macroscopically reduces the abrupt change in interface refractive index, weakening light reflection at the interface, and microscopically enhances the transmission efficiency of long-wavelength light through dual-interface coupling. Furthermore, by synergistically optimizing the periodic and dimensional parameters of the trapezoidal structures, the characteristic size of the trapezoidal structures is made smaller than the incident light wavelength range corresponding to the visible to near-infrared bands. Combined with the periodic arrangement of multiple trapezoidal structures and the alignment of their stacking directions, the recessed and convex array structures on both sides of the transparent insulating layer exhibit an equivalent dielectric response in the interface region. Since the trapezoidal structures gradually narrow along the incident light direction, the equivalent refractive index of the trapezoidal structures changes continuously along the stacking direction, effectively reducing long-wavelength light reflection loss and improving the photoelectric conversion efficiency of the all-perovskite tandem solar cell. In addition, the transparent insulating layer can serve as a substrate and support two structural forms of wide-gap top cells, thereby increasing the flexibility of the fabrication sequence and broadening the process window. Meanwhile, the electrical isolation between the upper and lower sub-cells weakens the coupling constraints between materials and processes, allowing for more diverse material choices and thus improving the controllability of the fabrication process.

[0016] Furthermore, the third electrode layer, the second hole transport layer, the second electrode layer, and the target transport layer all have the same shape as the transparent insulating layer, together constructing a gradient transition layer with an equivalent refractive index that continuously changes along the stacking direction. By suppressing Fresnel reflection at each interface within the gradient transition layer through the gradient change of refractive index, the incident light is guided to undergo propagation path reconstruction and optical field distribution modulation in the interface region, thereby extending the effective optical path of long-wavelength light in the narrow bandgap perovskite absorption layer and further improving the absorption efficiency of long-wavelength photons.

[0017] Furthermore, compared to the vacuum deposition process required to rely on transparent conductive materials as intermediate interconnect layers, this invention achieves electrical connection between the upper and lower batteries by using a transparent insulating layer in conjunction with wires. Moreover, a transparent insulating layer with multiple trapezoidal structures on both sides can be obtained through low-cost thermal nanoimprinting technology, thereby reducing the dependence on high-cost preparation equipment and helping to reduce the overall manufacturing cost.

[0018] The above and other objects, advantages and features of the present invention will become more apparent to those skilled in the art from the following detailed description of specific embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0019] The following description will focus on specific embodiments of the invention by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar parts or components. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings: FIG1 is a schematic structural diagram of an all-perovskite tandem solar cell according to an embodiment of the invention; FIG2 is a partially enlarged view of an all-perovskite tandem solar cell at the transparent insulating layer according to an embodiment of the invention; FIG3 is a schematic structural diagram of a trapezoidal structure according to an embodiment of the invention; FIG4 is a schematic flowchart of a method for fabricating an all-perovskite tandem solar cell according to an embodiment of the invention; FIG5 is a photocurrent density diagram of an all-perovskite tandem solar cell according to Example 1; FIG6 is a photocurrent density diagram of an all-perovskite tandem solar cell according to Comparative Example 1; FIG7 is a reflectance diagram of an all-perovskite tandem solar cell according to Example 1; FIG8 is a reflectance diagram of an all-perovskite tandem solar cell according to Comparative Example 1; FIG9 is an optical field intensity distribution diagram of the narrow bandgap perovskite absorber layer in the all-perovskite tandem solar cells according to Example 1 and Comparative Example 1.

[0020] Reference numerals: 100-All-perovskite tandem solar cell, 1-Wire, 2-Wide bandgap top cell, 3-Transparent insulating layer, 4-Narrow bandgap bottom cell, 21-First electrode layer, 22-First electron transport layer, 23-Wide bandgap perovskite absorber layer, 24-First hole transport layer, 25-Second electrode layer, 41-Third electrode layer, 42-Second hole transport layer, 43-Narrow bandgap perovskite absorber layer, 44-Second electron transport layer, 45-Fourth electrode layer, 46-Trapezoidal structure. Detailed Implementation

[0021] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0022] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, it should be noted that, for ease of description, only the parts relevant to this application are shown in the accompanying drawings, not the entire structure. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0023] The terms “comprising” and “having”, and any variations thereof, used in this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus.

[0024] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0025] Figure 1 is a schematic structural diagram of a full perovskite tandem solar cell according to an embodiment of the present invention, and Figure 2 is a partial enlarged view of the full perovskite tandem solar cell at the transparent insulating layer according to an embodiment of the present invention.

[0026] As shown in Figures 1 and 2, the all-perovskite tandem solar cell 100 includes a conductor 1 and, from bottom to top, a narrow bandgap bottom cell 4, a transparent insulating layer 3, and a wide bandgap top cell 2, stacked sequentially. The wide bandgap top cell 2 is either an inverted wide bandgap top cell or a conventional wide bandgap top cell. The conventional wide bandgap top cell includes, from top to bottom, a first electrode layer 21, a first electron transport layer 22, a wide bandgap perovskite absorber layer 23, a first hole transport layer 24, and a second electrode layer 25, stacked sequentially. The only difference between the inverted wide bandgap top cell and the conventional wide bandgap top cell is that the positions of the first electron transport layer 22 and the first hole transport layer 24 are interchanged in the stacking direction. The narrow bandgap bottom cell 4 includes, from top to bottom, a third electrode layer 41, a second hole transport layer 42, a narrow bandgap perovskite absorber layer 43, a second electron transport layer 44, and a fourth electrode layer 45, stacked sequentially. Multiple periodically arranged and aligned trapezoidal structures 46 are provided on both sides of the transparent insulating layer 3, and the convex directions of the trapezoidal structures 46 on both sides are the same, as shown in Figure 2. The trapezoidal structures 46 on both sides convex downwards in Figure 2, so that the two sides of the transparent insulating layer 3 form a recessed array structure and a convex array structure, respectively. The third electrode layer 41, the second hole transport layer 42, the second electrode layer 25, and the target transport layer are all the same shape as the transparent insulating layer 3. The target transport layer is the first hole transport layer 24 of the formal wide-bandgap top cell or the first electron transport layer 22 of the inverse wide-bandgap top cell. The thickness of the transparent insulating layer 3 is any value between 100nm and 300nm. It should be noted that the wide-bandgap perovskite absorption layer 23 has a planar structure on the side facing the incident light, and the other side is conformally arranged with the first hole transport layer 24 of the formal wide-bandgap top cell or the first electron transport layer 22 of the inverse wide-bandgap top cell. The narrow bandgap perovskite absorption layer 43 is conformally disposed with the second hole transport layer 42 on the side facing the incident light, and the other side is a planar structure.

[0027] Figure 3 is a schematic structural diagram of a trapezoidal structure according to an embodiment of the present invention.

[0028] As shown in Figure 3, the top width W1 of each trapezoidal structure 46 is any value between 50nm and 100nm, the bottom width W2 is any value between 10nm and 50nm, the height H is any value between 5nm and 20nm, and the distance L between the centers of two adjacent trapezoidal structures 46 is any value between 100nm and 2000nm. When the wide-bandgap top cell 2 is an inverse wide-bandgap top cell, the wire 1 is used to connect the second electrode layer 25 and the third electrode layer 41. When the wide-bandgap top cell 2 is a standard wide-bandgap top cell, the wire 1 is used to connect the first electrode layer 21 and the third electrode layer 41.

[0029] In this embodiment, while the transparent insulating layer 3 has high light transmittance, it isolates the electrical connection between the narrow bandgap bottom cell 4 and the wide bandgap top cell 2 in the stacking direction. Simultaneously, the corresponding electrode layers in the narrow bandgap bottom cell 4 and the wide bandgap top cell 2 are connected by wires 1, forming an electrical series structure between the wide bandgap top cell 2 and the narrow bandgap bottom cell 4 in the external circuit. Multiple periodically arranged trapezoidal structures 46 are provided on both sides of the transparent insulating layer 3 to introduce multiple refractions at the interface between the transparent insulating layer 3 and adjacent electrode layers, reducing reflection of long-wavelength light and extending the effective path of long-wavelength light in the narrow bandgap perovskite absorption layer 43. The trapezoidal structures 46 on both sides of the transparent insulating layer 3 are aligned along the stacking direction, allowing long-wavelength light to form continuous optical propagation channels at corresponding positions when passing through the transparent insulating layer 3, which helps reduce disordered scattering losses caused by the randomness of the trapezoidal structures 46. The convex directions of the trapezoidal structures 46 on both sides of the transparent insulating layer 3 are consistent, resulting in a synergistic change in the geometric morphology of the upper and lower interfaces of the transparent insulating layer 3. This macroscopically reduces the degree of abrupt change in the interface refractive index, weakens the reflection intensity of light at the interface, and microscopically enhances the transmission efficiency of long-wavelength light through dual-interface coupling. Furthermore, through synergistic optimization of the periodic and dimensional parameters of the trapezoidal structures 46, the characteristic size of the trapezoidal structures 46 is made smaller than the incident light wavelength range corresponding to the visible to near-infrared bands. Combined with the periodic arrangement of multiple trapezoidal structures 46 and the alignment of the stacking direction, the recessed array structure and the convex array structure disposed on both sides of the transparent insulating layer 3 exhibit an equivalent dielectric response in the interface region. Since the trapezoidal structures 46 gradually narrow along the incident light direction, the equivalent refractive index of the trapezoidal structures 46 changes continuously along the stacking direction, effectively reducing the reflection loss of long-wavelength light and improving the photoelectric conversion efficiency of the all-perovskite tandem solar cell 100. Furthermore, the transparent insulating layer 3 can serve as a substrate and support two structural forms of the wide-gap top cell 2, thereby improving the flexibility of the fabrication sequence and broadening the process window. At the same time, the electrical isolation between the upper and lower sub-cells weakens the coupling constraints between materials and processes, allowing for more diverse material choices and thus improving the controllability of the fabrication process.

[0030] In this embodiment, the third electrode layer 41, the second hole transport layer 42, the second electrode layer 25, and the target transport layer all have the same shape as the transparent insulating layer 3, and together they construct a gradient transition layer with an equivalent refractive index that changes continuously along the stacking direction. By suppressing Fresnel reflection at each interface within the gradient transition layer through the gradient change of refractive index, the incident light is guided to undergo propagation path reconstruction and optical field distribution modulation in the interface region, thereby extending the effective optical path of long-wavelength light in the narrow bandgap perovskite absorption layer 43 and improving the absorption efficiency of long-wavelength photons.

[0031] In this embodiment, the top width W1 of each trapezoidal structure 46 can be, for example, 50nm, 60nm, 80nm, or 100nm, or any other value between 50nm and 100nm. Setting the top width W1 of each trapezoidal structure 46 to 50nm-100nm provides a subwavelength scale range corresponding to the wavelengths in the visible to near-infrared bands, thus providing a foundation for the trapezoidal structure 46 to exhibit equivalent medium characteristics in optical response and enhancing the coupling ability of incident light at the interface, thereby extending the effective optical path of long-wavelength light in the narrow-bandgap perovskite absorption layer 43.

[0032] In this embodiment, the bottom width W2 of each trapezoidal structure 46 can be, for example, 10nm, 20nm, 40nm, or 50nm, or any other value between 10nm and 50nm. The bottom width W2 of each trapezoidal structure 46 is set to 10nm-50nm, and the bottom width W2 is smaller than the top width W1 of the trapezoidal structure, giving the trapezoidal structure 46 a gradually narrowing geometric feature along the incident light direction. This introduces a continuous change in the filling ratio in space, resulting in a gradual distribution of the equivalent refractive index along the stacking direction. This gradual distribution effectively mitigates the abrupt change in refractive index between the transparent insulating layer 3 and the adjacent electrode layer, reduces Fresnel reflection at the interface, and provides a continuous transition propagation environment for the incident light.

[0033] In this embodiment, the height H of each trapezoidal structure 46 can be, for example, 5nm, 10nm, 15nm, or 20nm, or any value between 5nm and 20nm. Setting the height H of the trapezoidal structure 46 to 5nm-20nm limits the length of the refractive index gradient in the stacking direction, making the optical transition at the interface between the transparent insulating layer 3 and the adjacent electrode layer smooth, thereby reducing the abrupt change in refractive index at the interface and reducing reflection loss, and improving the absorption efficiency of long-wavelength photons in the narrow bandgap perovskite absorption layer 43.

[0034] In this embodiment, the spacing L between the centers of two adjacent trapezoidal structures 46 is 100nm, 500nm, 1000nm, 1500nm, or 2000nm, or any other value between 100nm and 2000nm. Setting the spacing L between the centers of two trapezoidal structures 46 to 100nm-2000nm allows multiple trapezoidal structures 46 to effectively diffract and scatter the incident light, adjusting the propagation path of long-wavelength light, extending the effective propagation distance of long-wavelength light, and thus improving the absorption and utilization efficiency of long-wavelength photons.

[0035] In this embodiment, each trapezoidal structure 46 is an isosceles trapezoid, forming a symmetrical geometric modulation morphology at the interface. This facilitates consistent refraction of incident light at both interfaces of the trapezoidal structure 46, resulting in a more uniform light field distribution in the interface region. Compared to asymmetric structures, the isosceles trapezoidal structure 46 reduces the light propagation direction shift caused by geometric asymmetry, ensuring stable light propagation in the interface region and improving the coupling consistency of incident light in the interface region of the trapezoidal structure 46. Simultaneously, the isosceles trapezoidal structure 46 helps reduce the non-uniformity of the local light field distribution and decreases the additional optical loss caused by structural irregularities, thus providing favorable conditions for extending the effective propagation path of long-wavelength light in the narrow-bandgap perovskite absorption layer 43.

[0036] In this embodiment, two adjacent trapezoidal structures 46 are continuously arranged without any other structures in between, so that a uniform optical modulation environment is formed on both sides of the transparent insulating layer 3 in the direction of incident light propagation. This allows the incident light to be continuously modulated in the interface region through refraction, reducing reflection loss and enhancing the coupling effect of light in the interface region. This is beneficial for extending the effective propagation path of long-wavelength light in the narrow bandgap perovskite absorption layer 43 and improving its absorption efficiency in the narrow bandgap perovskite absorption layer 43.

[0037] In this embodiment, the thickness of the transparent insulating layer 3 can be, for example, 100nm, 150nm, 200nm or 300nm, or any other value between 100nm and 300nm. By controlling the thickness of the transparent insulating layer 3 within the above range, the transparent insulating layer 3 has structural support properties, ensuring that a narrow bandgap bottom cell 4 or a wide bandgap top cell 2 can be formed on one side of the transparent insulating layer 3 first, thereby improving the flexibility of the cell fabrication sequence.

[0038] In this embodiment, the wide-gap top cell 2 can be an inverted wide-gap top cell or a conventional wide-gap top cell, and the connection position of the wire 1 can be adjusted accordingly so that the wire 1 is connected to the electrode layer of the corresponding polarity. This allows the all-perovskite tandem solar cell 100 to be applicable to different types of wide-gap top cells 2 without changing the overall configuration of the transparent insulating layer 3, thereby broadening the process window.

[0039] In a further embodiment, the thickness of the wide-bandgap perovskite absorber layer 23 is set to 400 nm-500 nm, which can reduce the recombination path of carriers within the wide-bandgap perovskite absorber layer 23. This thickness is also compatible with the optical absorption characteristics of the wide-bandgap perovskite absorber layer 23, allowing for the modulation of the propagation behavior of incident light within the wide-bandgap perovskite absorber layer 23 and improving the absorption efficiency for short-wavelength photons. The thickness of the narrow-bandgap perovskite absorber layer 43 is set to 1200 nm-1300 nm, which synergizes with the morphology of the narrow-bandgap perovskite absorber layer 43 facing the incident light, extending the effective optical path of long-wavelength photons within the narrow-bandgap perovskite absorber layer 43 and further enhancing the absorption capacity for long-wavelength photons. The thickness of the wide-bandgap perovskite absorber layer 23 can be, for example, 400 nm, 450 nm, or 500 nm, or any other value within the 400 nm-500 nm range. The thickness of the narrow bandgap perovskite absorber layer 43 can be, for example, 1200 nm, 1250 nm, or 1300 nm, or any other value between 1200 nm and 1300 nm.

[0040] In a further embodiment, the thickness of the first electron transport layer 22 is any value between 20nm and 30nm, and its material is... , Or ZnO. The thickness of the first hole transport layer 24 is any value between 10nm and 100nm, and its material is Spiro-OMeTAD, PTAA, or By optimizing the thickness and material of the first electron transport layer 22, a continuous and dense transport channel is provided while ensuring good selective transport capability of photogenerated electrons. Simultaneously, the thinner first electron transport layer 22 helps reduce series resistance and improve the extraction efficiency of photogenerated electrons. Similarly, by optimizing the thickness and material of the first hole transport layer 24, efficient selective extraction of photogenerated holes is achieved while blocking the transport of photogenerated electrons to the first hole transport layer 24, thus suppressing carrier recombination within the wide-bandgap perovskite absorber layer 23. The first electron transport layer 22 and the first hole transport layer 24 synergistically enhance the carrier separation and transport efficiency within the wide-bandgap perovskite absorber layer 23. The thickness of the first electron transport layer 22 can be, for example, 20 nm, 25 nm, or 30 nm, or any other value between 20 nm and 30 nm. The thickness of the first hole transport layer 24 can be, for example, 10 nm, 50 nm, or 100 nm, or any other value between 10 nm and 100 nm.

[0041] In a further embodiment, the thickness of the first electrode layer 21 is any value between 80 nm and 150 nm, and its material is selected from any one of ITO, IZO, FTO, or AZO. The thickness of the second electrode layer 25 is any value between 50 nm and 200 nm, and its material is selected from any one of ITO, IZO, FTO, or AZO. By optimizing the design of the thickness and material of the first electrode layer 21, the first electrode layer 21 is ensured to have high optical transmittance and excellent electrical conductivity, thereby improving the collection efficiency of photogenerated carriers transmitted to the corresponding transport layer. By optimizing the design of the thickness and material of the second electrode layer 25 and combining it with its structural morphology, the second electrode layer 25 is ensured to have high optical transmittance and excellent electrical conductivity, thereby improving the collection efficiency of photogenerated carriers transmitted to the corresponding transport layer and reducing the energy loss of incident light at the second electrode layer 25. The thickness of the first electrode layer 21 can be, for example, 80 nm, 100 nm, 120 nm, or 150 nm, or any other value between 80 nm and 150 nm. The thickness of the second electrode layer 25 can be, for example, 50 nm, 100 nm, 150 nm or 200 nm, or any other value between 50 nm and 200 nm.

[0042] In a further embodiment, the thickness of the second hole transport layer 42 is any value between 10nm and 100nm, and its material is (PEDOT:PSS), PTAA, or The thickness of the third electrode layer 41 is any value between 50nm and 200nm, and its material is selected from ITO, IZO, FTO, or AZO. The synergistic optimization of the thickness and material of the second hole transport layer 42 effectively achieves efficient extraction of photogenerated holes from the narrow bandgap perovskite absorption layer 43, and while ensuring low series resistance of the second hole transport layer 42, it utilizes its excellent energy level matching characteristics to reduce carrier recombination losses at the interface. The synergistic optimization of the thickness and material of the third electrode layer 41 ensures high transmittance of long-wavelength light while ensuring efficient collection of photogenerated holes from the narrow bandgap bottom cell 4.

[0043] The thickness of the second hole transport layer 42 can be, for example, 10 nm, 50 nm, 80 nm, or 100 nm, or any other value between 10 nm and 100 nm. The thickness of the third electrode layer 41 can be, for example, 50 nm, 100 nm, 150 nm, or 200 nm, or any other value between 50 nm and 200 nm.

[0044] In a further embodiment, the thickness of the second electron transport layer 44 is any value between 20nm and 80nm, and its material is C60, PCBM, or The thickness of the fourth electrode layer 45 is any value between 50nm and 200nm, and its material is selected as Au, Ag, or Al. The synergistic optimization of the thickness and material of the second electron transport layer 44 effectively achieves efficient extraction of photogenerated electrons in the narrow bandgap bottom cell 4, ensuring excellent film-forming properties of the second electron transport layer 44 while reducing energy loss of photogenerated electrons within it. The synergistic optimization of the thickness and material of the fourth electrode layer 45 ensures excellent ohmic contact characteristics between the fourth electrode layer 45 and the second electron transport layer 44, and utilizes the strong reflectivity of the fourth electrode layer 45 to form an effective optical back mirror, effectively reflecting long-wavelength light penetrating the narrow bandgap perovskite absorption layer 43 back into the absorption layer, thereby achieving the reabsorption and utilization of long-wavelength light and improving light energy utilization efficiency.

[0045] In a further embodiment, the transparent insulating layer 3 is made of soda-lime glass or quartz glass. Soda-lime glass or quartz glass possesses excellent optical transparency, thermal stability, and chemical stability, ensuring that the transparent insulating layer 3 has good electrical insulation properties. This achieves effective electrical isolation of adjacent electrode layers, preventing leakage or short circuits and improving the electrical stability of the all-perovskite tandem solar cell 100. Through the synergistic design of the thickness and material of the transparent insulating layer 3, the parasitic absorption of long-wavelength light by the transparent insulating layer 3 is reduced, while the absorption of long-wavelength light by the narrow bandgap perovskite absorption layer 43 is improved.

[0046] Figure 4 is a schematic flowchart of a method for fabricating an all-perovskite tandem solar cell according to an embodiment of the present invention.

[0047] In a further embodiment, as shown in FIG4, the method for fabricating an all-perovskite tandem solar cell 100 includes the following steps: Step S100, providing a transparent insulating layer to be imprinted; Step S200, using thermal nanoimprinting technology to form a recessed array structure and a raised array structure on both sides of the transparent insulating layer to be imprinted, respectively, to obtain a transparent insulating layer 3; Step S300, forming a wide bandgap top cell 2 on the side of the transparent insulating layer 3 with the recessed array structure; Step S400, forming a narrow bandgap bottom cell 4 on the side of the transparent insulating layer 3 with the raised array structure; Step S500, connecting wires 1 at the corresponding electrodes of the wide bandgap top cell 2 and the narrow bandgap bottom cell 4.

[0048] In step S200, the transparent insulating layer to be imprinted is heated to a temperature higher than its glass transition temperature or softening temperature, causing the material of the transparent insulating layer to change from a glassy state to a highly elastic state with flowability. The highly elastic transparent insulating layer is then imprinted using an imprinting template with pre-fabricated micro / nano structures to obtain a transparent insulating layer 3 with recessed array structures and raised array structures on both sides, respectively. The imprinting template has multiple preset recessed array structures and preset raised array structures on both sides corresponding to the two sides of the transparent insulating layer 3. Each preset recessed array structure and preset raised array structure has multiple preset trapezoidal structures. The depth of the preset trapezoidal structures ranges from 200nm to 500nm. The angle between the top surface and the side surface of the preset trapezoidal structure in the preset recessed array structure ranges from 50° to 70°. The distance between the centers of two preset trapezoidal structures ranges from 400nm to 800nm. The transparent insulating layer 3 after embossing is treated with oxygen plasma or ultraviolet ozone to effectively remove residual organic matter in the transparent insulating layer 3 while improving surface wettability and interfacial bonding ability.

[0049] The transparent insulating layer 3 after the above treatment is annealed at a temperature of 300℃-500℃ for a time of 10min-60min. By coordinating the annealing temperature and time, the residual stress introduced into the transparent insulating layer 3 during the imprinting process is effectively eliminated, and the structural stability and interface reliability of the transparent insulating layer 3 are improved. The annealing temperature can be, for example, 300℃, 400℃, or 500℃, or any other value within the range of 300℃-500℃; the annealing time can be, for example, 10min, 30min, 50min, or 60min, or any other value within the range of 10min-60min.

[0050] In step S300, the wide-bandgap perovskite absorber layer 23 is formed by solution method and annealing process, and the other layers in the wide-bandgap top cell 2 are prepared by thin film deposition technology, including atomic layer deposition, magnetron sputtering and chemical vapor deposition.

[0051] In step S400, the narrow bandgap perovskite absorber layer 43 is formed by solution method and annealing process, and the other layers in the narrow bandgap bottom cell 4 are prepared by thin film deposition technology, including atomic layer deposition, magnetron sputtering and chemical vapor deposition.

[0052] The execution order of steps S300 and S400 can be interchanged, and this order adjustment will not adversely affect the overall performance of the all-perovskite tandem solar cell 100, thereby improving the flexibility and adaptability of the fabrication process.

[0053] In step S500, the wire 1 connects the corresponding electrode layers of the narrow bandgap bottom cell 4 and the wide bandgap top cell 2 using a preset connection method. This preset connection method can be, for example, conductive adhesive connection, ultrasonic welding, metal pad-assisted welding, or conductive tape connection. Specifically, the conductive adhesive connection involves coating the predetermined connection area of ​​the two corresponding electrode layers with anisotropic conductive adhesive or conductive silver paste, aligning the wire 1 with the corresponding electrode layer, and then heating and pressurizing it for curing. The curing temperature range is 80℃-180℃, for example, 80℃, 150℃, or 180℃, or any value within the 80℃-180℃ range. The ultrasonic welding method uses ultrasonic welding equipment and special solder to directly weld the wire 1 to the surfaces of the two corresponding electrode layers. The metal pad-assisted welding method involves first vapor-depositing metal pads on the surfaces of the two corresponding electrode layers, and then welding the wire 1 to the metal pads. The conductive tape connection method involves attaching conductive copper foil tape to the surfaces of the two corresponding electrode layers and connecting the wire 1 to the other end of the conductive tape, thereby achieving a stable and reliable electrical connection.

[0054] The following detailed examples and comparative examples will be provided.

[0055] Example 1: This Example 1 provides an all-perovskite tandem solar cell 100, including the following steps: Step S111, providing a transparent insulating layer to be imprinted; Step S121, using thermal nanoimprinting technology, forming multiple periodically arranged and aligned trapezoidal structures 46 on both sides of the transparent insulating layer to be imprinted, with the convex directions of the trapezoidal structures 46 on both sides being the same, to obtain a transparent insulating layer 3 with a recessed array structure and a convex array structure on both sides respectively; subjecting the imprinted transparent insulating layer 3 to oxygen plasma treatment with a treatment power of 100W for 3 minutes, followed by annealing at 400℃ for 30 minutes; wherein, the material of the middle insulating layer is glass with a thickness of 140nm, each The trapezoidal structure 46 has a top width W1 of 100 nm, a bottom width W2 of 50 nm, a height H of 20 nm, and a center spacing L of 1 μm between two adjacent trapezoidal structures 46. In step S131, a second electrode layer 25 and a first electron transport layer 22 are sequentially deposited on the side of the transparent insulating layer 3 with the recessed array structure by magnetron sputtering. Then, a wide-bandgap perovskite absorption layer 23 is formed on the surface of the first electron transport layer 22 by solution method and annealing process. Afterward, a first hole transport layer 24 and a first electrode layer 21 are sequentially deposited on the surface of the wide-bandgap perovskite absorption layer 23 by chemical vapor deposition, thereby forming an inverse wide-bandgap perovskite on the side of the transparent insulating layer 3 with the recessed array structure. Top-mounted battery; wherein, the first electrode layer 21 is made of ITO with a thickness of 150 nm, the first hole transport layer 24 is made of PTAA with a thickness of 20 nm, the wide bandgap perovskite absorber layer 23 has a thickness of 470 nm, the first electron transport layer 22 is made of C60 with a thickness of 30 nm, and the second electrode layer 25 is made of ITO with a thickness of 50 nm; in step S141, the third electrode layer 41 and the second hole transport layer 42 are sequentially deposited on the side of the transparent insulating layer 3 with the protrusion array structure by magnetron sputtering, and then a narrow bandgap perovskite absorber layer 43 is formed on the surface of the second hole transport layer 42 by solution method and annealing process, and then a narrow bandgap perovskite absorber layer 43 is formed on the surface of the narrow bandgap perovskite absorber layer 42 by chemical vapor deposition technology. A second electron transport layer 44 and a fourth electrode layer 45 are sequentially deposited on the surface of the bandgap perovskite absorber layer 43, thereby forming a narrow bandgap bottom cell 4 on the side of the transparent insulating layer 3 with a protrusion array structure; wherein, the material of the third electrode layer 41 is ITO and the thickness is 50nm, the material of the second hole transport layer 42 is (PEDOT:PSS) and the thickness is 80nm, the thickness of the narrow bandgap perovskite absorber layer 43 is 1250nm, the material of the second electron transport layer 44 is C60 and the thickness is 30nm, and the material of the fourth electrode layer 45 is Au and the thickness is 100nm; in step S151, the first electrode layer 21 and the third electrode layer 41 are connected by a wire 1 using ultrasonic welding.

[0056] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that the transparent insulating layer 3 does not have a trapezoidal structure 46 on both sides.

[0057] Figure 5 is a photocurrent density diagram of the all-perovskite tandem solar cell according to Example 1, and Figure 6 is a photocurrent density diagram of the all-perovskite tandem solar cell according to Comparative Example 1.

[0058] As shown in Figures 5 and 6, although the current density of Example 1 is [missing information] for an inverted wide-gap top cell, [missing information] The current density of Comparative Example 1 is The current density decreased by 0.868% compared to the previous example. This is because the wide-bandgap perovskite absorber layer 23 has the same structure as the multiple trapezoidal structures 46 on the side near the narrow-bandgap bottom cell 4. Due to the small size of the trapezoidal structures 46, the characteristic size of the wide-bandgap perovskite absorber layer 23 near the narrow-bandgap bottom cell 4 is smaller than the wavelength of the short-wavelength incident light. This changes the refractive index at the interface between the wide-bandgap perovskite absorber layer 23 and the first hole transport layer, resulting in a small amount of short-wavelength light experiencing reflection loss or a change in propagation path at this interface. Consequently, the current density of the inverted wide-bandgap top cell in Example 1 decreased slightly. However, the current density of the narrow-bandgap bottom cell 4 in Example 1 increased by 5.078% compared to the narrow-bandgap bottom cell 4 in Comparative Example 1. Furthermore, for the all-perovskite tandem solar cell 100, the current density increased from that of Comparative Example 1. Upgraded to Example 1 This demonstrates that the trapezoidal structure 46 can effectively extend the effective path of long-wavelength light in the narrow bandgap perovskite absorption layer 43, thereby improving the absorption efficiency of long-wavelength photons by the narrow bandgap bottom cell 4 and thus enhancing the overall electrical output of the all-perovskite tandem solar cell 100.

[0059] Figure 7 is a reflectance diagram of the all-perovskite tandem solar cell according to Example 1, and Figure 8 is a reflectance diagram of the all-perovskite tandem solar cell according to Comparative Example 1.

[0060] As shown in Figures 7 and 8, in the visible light band of 700nm-1000nm, Example 1 exhibits superior reflection suppression compared to Comparative Example 1. Specifically, in the wavelength range of 700nm-800nm, the reflectivity of Example 1 is reduced by an average of 5%-7.24% compared to Comparative Example 1, with the maximum reflectivity reduction of 7.24% reaching 790nm. In the wavelength range of 800nm-900nm, the reflectivity reduction of Example 1 compared to Comparative Example 1 is 1.46%-5.19%, with a reduction of 5.19% at 810nm and a reduction of 3.2%-4.2% in the 830nm-860nm band. Furthermore, even at a visible light wavelength of 900nm, a reflectivity reduction of 1.46% is maintained, with gains of 1.60% and 3.44% at 950nm and 1000nm, respectively. The above data shows that the trapezoidal structure 46 used in this application can achieve stable and continuous light-trapping gain and reflection suppression in a wide spectral range of 700nm-1000nm. Furthermore, calculations show that the 5%-7% reduction in reflectivity in Example 1 compared to Comparative Example 1 directly translates to a 4%-7% increase in the effective incident photon flux in the narrow bandgap bottom cell 4, indicating that the narrow bandgap bottom cell 4 of Example 1 improves the absorption of long-wavelength photons.

[0061] Figure 9 is a light field intensity distribution diagram of the narrow bandgap perovskite absorber layer in the all-perovskite tandem solar cells according to Example 1 and Comparative Example 1.

[0062] The electric field intensity distribution of the all-perovskite tandem solar cells 100 in Example 1 and Comparative Example 1 was tested using simulation technology. The test results are shown in Figure 9. At an incident wavelength of 790 nm, a red high electric field intensity distribution region appears on the top of the narrow bandgap perovskite absorber layer 43 in Example 1, while no obvious red high electric field intensity distribution region appears in the narrow bandgap perovskite absorber layer 43 in Comparative Example 1. This indicates that when the two sides of the transparent insulating layer 3 are planar structures, the reflection of long-wavelength light is increased. When multiple trapezoidal structures 46 are provided on both sides of the transparent insulating layer 3, the reflection of long-wavelength light can be reduced, thereby improving the absorption efficiency of long-wavelength photons by the narrow bandgap perovskite absorber layer 43.

[0063] In summary, this application reduces the reflection loss of long-wavelength photons by forming multiple trapezoidal structures 46 on both sides of the transparent insulating layer, induces light field distribution modulation to extend the effective optical path of long-wavelength light in the narrow bandgap perovskite absorption layer 43, and realizes the electrical connection between the wide bandgap top cell 2 and the narrow bandgap bottom cell 4 through the wire 1. Based on optimizing the current matching characteristics of the all-perovskite tandem solar cell 100, the overall photoelectric conversion efficiency is synergistically improved.

[0064] Therefore, those skilled in the art should recognize that although numerous exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications conforming to the principles of the present invention can be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Thus, the scope of the present invention should be understood and construed as covering all such other variations or modifications.

Claims

1. A fully perovskite tandem solar cell, characterized in that, The device includes conductive wires and a narrow bandgap bottom cell, a transparent insulating layer, and a wide bandgap top cell stacked sequentially from bottom to top. The wide bandgap top cell can be either an inverted wide bandgap top cell or a standard wide bandgap top cell. The standard wide bandgap top cell includes a first electrode layer, a first electron transport layer, a wide bandgap perovskite absorber layer, a first hole transport layer, and a second electrode layer stacked sequentially from top to bottom. The difference between the inverted wide bandgap top cell and the standard wide bandgap top cell is that the positions of the first electron transport layer and the first hole transport layer are interchanged in the stacking direction. The narrow bandgap bottom cell includes a third electrode layer, a second hole transport layer, a narrow bandgap perovskite absorber layer, a second electron transport layer, and a fourth electrode layer stacked sequentially from top to bottom. Multiple periodically arranged and aligned trapezoidal structures are provided on both sides of the transparent insulating layer, with the protrusions of the trapezoidal structures on both sides having the same direction, so that the two sides of the transparent insulating layer respectively form a recessed array structure and a protrusion array structure. The third electrode layer, the second hole transport layer, the second electrode layer, and the target transport layer all have the same shape as the transparent insulating layer. The target transport layer is either the first hole transport layer of the formal wide-bandgap top cell or the first electron transport layer of the inverted wide-bandgap top cell. The thickness of the transparent insulating layer is any value between 100nm and 300nm. The top width of each trapezoidal structure is any value between 50nm and 100nm, the bottom width is any value between 10nm and 50nm, the height is any value between 5nm and 20nm, and the distance between the centers of two adjacent trapezoidal structures is any value between 100nm and 2000nm. When the wide-bandgap top cell is an inverted wide-bandgap top cell, the wire is used to connect the second electrode layer and the third electrode layer. When the wide-bandgap top cell is a formal wide-bandgap top cell, the wire is used to connect the first electrode layer and the third electrode layer.

2. The all-perovskite tandem solar cell according to claim 1, characterized in that, The thickness of the wide bandgap perovskite absorber layer is any value between 400nm and 500nm, and the thickness of the narrow bandgap perovskite absorber layer is any value between 1200nm and 1300nm.

3. The all-perovskite tandem solar cell according to claim 2, characterized in that, The thickness of the first electron transport layer is any value between 20nm and 30nm, and its material is... 、 Or ZnO; the thickness of the first hole transport layer is any value between 10nm and 100nm, and its material is Spiro-OMeTAD, PTAA, or 。 4. The all-perovskite tandem solar cell according to claim 3, characterized in that, The thickness of the first electrode layer is any value between 80nm and 150nm, and its material is selected from any one of ITO, IZO, FTO or AZO; the thickness of the second electrode layer is any value between 50nm and 200nm, and its material is selected from any one of ITO, IZO, FTO or AZO.

5. The all-perovskite tandem solar cell according to claim 4, characterized in that, The thickness of the second hole transport layer is any value between 10nm and 100nm, and its material is (PEDOT:PSS), PTAA, or The thickness of the third electrode layer is any value between 50nm and 200nm, and its material is selected from any one of ITO, IZO, FTO or AZO.

6. The all-perovskite tandem solar cell according to claim 5, characterized in that, The thickness of the second electron transport layer is any value between 20nm and 80nm, and its material is C60, PCBM, or The thickness of the fourth electrode layer is any value between 50nm and 200nm, and its material is selected as Au, Ag or Al.

7. The all-perovskite tandem solar cell according to claim 6, characterized in that, The transparent insulating layer is made of soda-lime glass or quartz glass.

8. The method for preparing an all-perovskite tandem solar cell according to any one of claims 1-7, characterized in that, The process includes the following steps: providing a transparent insulating layer to be imprinted; using thermal nanoimprinting technology to form a recessed array structure and a raised array structure on both sides of the transparent insulating layer to be imprinted, respectively, to obtain a transparent insulating layer; forming a wide bandgap top cell on the side of the transparent insulating layer with the recessed array structure; forming a narrow bandgap bottom cell on the side of the transparent insulating layer with the raised array structure; and connecting wires at the corresponding electrodes of the wide bandgap top cell and the narrow bandgap bottom cell.

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