Perovskite laminated cell

Abstract

The invention provides a perovskite laminated cell which comprises a first solar cell unit and a second solar cell unit, the first solar cell unit is used for absorbing front light, and the second solar cell unit is used for absorbing back light. The first solar cell unit and the second solar cell unit are connected through a first packaging adhesive film, and the difference between the refractive index of the first packaging adhesive film and the refractive index of the first lower electrode and the difference between the refractive index of the first packaging adhesive film and the refractive index of the second upper electrode are both larger than a first preset value. Therefore, in the application, the backlight side of the first solar cell unit is connected with the second solar cell unit through the first packaging adhesive film, and the second solar cell unit absorbs and converts the back light, so that the utilization of the back light of the perovskite laminated cell is improved; and the difference between the refractive index of the first packaging adhesive film and the refractive indexes of the two electrodes at the boundary is large, so that the secondary utilization of the reflected light is improved, and the power generation efficiency of the second solar cell unit is further improved.

Description

Technical Field

[0001] The present application relates to the field of solar cells, and in particular to a perovskite tandem cell. Background Art

[0002] Perovskite solar cells and crystalline silicon solar cells are both carriers for generating electricity using solar energy. In order to achieve higher power generation efficiency, perovskite solar cells and crystalline silicon solar cells are combined in a stacked manner to form crystalline silicon perovskite stacked cells. Currently, photovoltaic modules are generally installed in an optimal tilt angle, with one side facing the light and the other side facing away from the light. Since crystalline silicon solar cells can usually only absorb and convert the front light, the light resources on the backlight side cannot be utilized, resulting in low cell efficiency. Summary of the invention

[0003] The present application provides a perovskite tandem cell, in which a second solar cell unit is connected to the backlight side of the first solar cell unit through a first packaging film, and the backlight is absorbed and converted by the second solar cell unit, thereby improving the utilization of the backlight of the perovskite tandem cell. The refractive index of the first packaging film is set to be significantly different from the refractive index of the two electrodes at its junction, thereby improving the secondary utilization of reflected light and further improving the power generation efficiency of the second solar cell unit.

[0004] In a first aspect, the present application provides a perovskite stack cell, comprising: a first solar cell unit, comprising a first sub-cell, the first sub-cell comprising a first upper electrode, a first light absorbing layer, and a first lower electrode, the first solar cell unit being used to absorb the front light of the perovskite stack cell; a second solar cell unit, comprising a second sub-cell, the second sub-cell comprising a second upper electrode, a second light absorbing layer, and a second lower electrode, the second solar cell unit being used to absorb the back light of the perovskite stack cell; wherein the first lower electrode and the second upper electrode are connected by a first packaging film, the difference between the refractive index of the first packaging film and the refractive index of the first lower electrode, and the difference between the refractive index of the first packaging film and the refractive index of the second upper electrode are both greater than a first preset value, so that the reflectivity of part of the back light passing through the second light absorbing layer when passing through the first interface and the second interface is greater than the first preset reflectivity, so that the part of the back light is reflected back to the second light absorbing layer again; the first interface is the interface between the second upper electrode and the first packaging film, and the second interface is the interface between the first packaging film and the first lower electrode.

[0005] In some embodiments, the first sub-cell is a crystalline silicon cell; or, the first sub-cell is a thin film cell, and the first light absorption layer includes a perovskite thin film or a CIGS thin film.

[0006] In some embodiments, the second sub-cell is a thin film cell, and the second light absorbing layer includes a perovskite thin film or a CIGS thin film; the band gap width of the second sub-cell is 0.9-1.2 eV.

[0007] In some embodiments, the refractive index of the first packaging film is 1.4-1.6, and the refractive index of the first lower electrode and the second upper electrode is 1.8-2.1.

[0008] In some embodiments, the first upper electrode, the first lower electrode, and the second upper electrode are metal oxides, and the metal oxides include at least one of FTO, ITO, AZO, and ZnO; the second lower electrode is the metal oxide, and the perovskite stack cell also includes a third packaging film and a first photovoltaic substrate, and the third packaging film is connected to the second lower electrode and the first photovoltaic substrate respectively; the first photovoltaic substrate is a glass substrate or a high molecular polymer material coated with metal oxide, and the refractive index of the first photovoltaic substrate is less than or equal to 1.55; or, the second lower electrode is a second photovoltaic substrate, and the thickness of the second photovoltaic substrate is different from that of the first photovoltaic substrate.

[0009] In some embodiments, the first solar cell unit also includes a third sub-cell, and the third sub-cell includes a third upper electrode, a third light absorbing layer and a third lower electrode; the third lower electrode and the first upper electrode are connected by a second packaging film; the difference between the refractive index of the second packaging film and the refractive index of the third lower electrode, and the difference between the refractive index of the second packaging film and the refractive index of the first upper electrode are both less than a second preset value; so that the reflectivity of part of the front light passing through the third light absorbing layer is less than the second preset reflectivity when passing through the third interface and the fourth interface, the third interface is the interface between the third lower electrode and the second packaging film, and the fourth interface is the interface between the second packaging film and the first upper electrode.

[0010] In some embodiments, the third sub-cell is a thin film cell, and the third light-absorbing layer includes a perovskite thin film; the band gap width of the first sub-cell is 0.9-1.3eV, and the band gap width of the third sub-cell is 1.7-1.8eV; the third sub-cell is used to absorb short-wavelength light in the front light, and the second sub-cell is used to absorb long-wavelength light in the front light, the wavelength of the short-wavelength light is less than 720nm, and the wavelength of the long-wavelength light is greater than 720nm.

[0011] In some embodiments, the refractive index of the second packaging film is 1.6-1.9; the refractive index of the third lower electrode and the first upper electrode is 1.6-1.9.

[0012] In some embodiments, the third lower electrode is a metal oxide, and the metal oxide includes at least one of FTO, ITO, AZO, and ZnO; the third upper electrode is a third photovoltaic substrate, and the third photovoltaic substrate is a glass substrate or a high molecular polymer material coated with metal oxide; the refractive index of the second upper electrode is lower than 1.55.

[0013] In some embodiments, the reflectivity of the first interface is calculated according to the following formula: R = (n1-n2) 2 / (n1+n2) 2 ; Wherein, R is the reflectivity, n1 and n2 represent the refractive index of the second upper electrode and the refractive index of the first packaging film respectively.

[0014] It can be seen that in the embodiment of the present application, the perovskite tandem cell includes a first solar cell unit, including a first sub-cell, the first sub-cell includes a first upper electrode, a first light absorbing layer, and a first lower electrode, and the first solar cell unit is used to absorb the front light of the perovskite tandem cell; the second solar cell unit includes a second sub-cell, the second sub-cell includes a second upper electrode, a second light absorbing layer, and a second lower electrode, and the second solar cell unit is used to absorb the back light of the perovskite tandem cell; wherein the first lower electrode and the second upper electrode are connected by a first packaging film, and the difference between the refractive index of the first packaging film and the refractive index of the first lower electrode, and the difference between the refractive index of the first packaging film and the refractive index of the second upper electrode are both greater than a first preset value, so that the reflectivity of part of the back light passing through the second light absorbing layer when passing through the first interface and the second interface is greater than the first preset reflectivity, so that part of the back light is reflected back to the second light absorbing layer again; the first interface is the interface between the second upper electrode and the first packaging film, and the second interface is the interface between the first packaging film and the first lower electrode. Therefore, in the present application, the second solar cell unit is connected to the backlight side of the first solar cell unit through the first packaging film, and the back light is absorbed and converted by the second solar cell unit to improve the utilization of the back light of the perovskite stacked cell. The refractive index of the first packaging film is set to be significantly different from the refractive index of the two electrodes at its junction, thereby improving the secondary utilization of the reflected light and further improving the power generation efficiency of the second solar cell unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0016] Figure 1 A schematic diagram of the structure of a two-terminal stacked perovskite battery provided in an embodiment of the present application;

[0017] Figure 2 A schematic diagram of the structure of a four-terminal stacked perovskite battery provided in an embodiment of the present application;

[0018] Figure 3 A schematic diagram of the structure of a perovskite tandem battery provided in an embodiment of the present application;

[0019] Figure 4 One of the structural schematic diagrams of the perovskite tandem battery provided in the embodiment of the present application;

[0020] Figure 5 A schematic diagram of the back-illumination light path provided in an embodiment of the present application;

[0021] Figure 6 One of the structural schematic diagrams of the second sub-battery is provided for the embodiment of the present application;

[0022] Figure 7 The second structural schematic diagram of the second sub-battery provided in the embodiment of the present application;

[0023] Figure 8 The second structural schematic diagram of the perovskite tandem battery provided in the embodiment of the present application;

[0024] Fig. 9 A schematic diagram of the front illumination light path provided in an embodiment of the present application.

[0025] Description of reference numerals:

[0026] 1-perovskite stacked cell, 10-first solar cell unit, 20-second solar cell unit, 30-first packaging film, 40-second packaging film, 11-first sub-cell, 111-first upper electrode, 112-first light absorption layer, 113-first lower electrode, 21-second sub-cell, 211-second upper electrode, 212-second light absorption layer, 213-second lower electrode, 214-hole transport layer, 215-electron transport layer, 216-third packaging film, 217-first photovoltaic substrate, 218-second photovoltaic substrate, 31-third sub-cell, 311-third upper electrode, 312-third light absorption layer, 313-third lower electrode. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0028] The terms "first", "second", etc. in the specification and claims of this application and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices.

[0029] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0030] In the embodiments of the present application, "and / or" describes the association relationship of the associated objects, indicating that three relationships may exist. For example, A and / or B can represent the following three situations: A exists alone; A and B exist at the same time; B exists alone. Among them, A and B can be singular or plural.

[0031] In the embodiment of the present application, the symbol " / " can indicate that the objects associated with each other are in an "or" relationship. In addition, the symbol " / " can also indicate a division sign, that is, performing a division operation. For example, A / B can indicate A divided by B.

[0032] In the embodiments of the present application, "at least one item" or similar expressions refer to any combination of these items, including any combination of single items or plural items, and refer to one or more, and multiple refers to two or more. For example, at least one item of a, b, or c can represent the following seven situations: a, b, c, a and b, a and c, b and c, a, b, and c. Among them, each of a, b, and c can be an element or a set containing one or more elements.

[0033] In the embodiments of the present application, "equal to" can be used in conjunction with greater than, and is applicable to the technical solution adopted when greater than, and can also be used in conjunction with less than, and is applicable to the technical solution adopted when less than. When equal to is used in conjunction with greater than, it is not used in conjunction with less than; when equal to is used in conjunction with less than, it is not used in conjunction with greater than.

[0034] The perovskite cell stacked cell structure includes a top electrode layer, an electron transport layer, a perovskite layer, a hole transport layer, and a bottom electrode layer. After laser scribing, an independently divided sub-cell area is formed. Because the band gap of the perovskite material is adjustable, it can be superimposed with photovoltaic cell technologies of other different technical solutions to form a stacked cell. The different spectral ranges of natural light absorption by solar photovoltaic cell technology materials of different technical solutions are inconsistent, and the band gap width of the solar cell is adjusted to improve the power generation efficiency of the stacked cell. Common stacked cell technology solutions include perovskite-crystalline silicon, perovskite-organic materials, perovskite-thin film, perovskite-perovskite, etc. As a new type of solar cell technology, compared with single-junction solar cells, stacked cells can better utilize different wavelengths of the solar spectrum, solve the absorption loss and heat loss of single-junction cells, thereby improving the utilization efficiency of photons and the energy conversion efficiency of solar cells, and overcoming the theoretical efficiency limit of single-junction cells.

[0035] Perovskite / crystalline silicon two-junction tandem solar cells are generally composed of a transparent top perovskite cell and a crystalline silicon bottom cell. The two-terminal two-junction tandem cell structure is to grow a perovskite cell directly on a crystalline silicon cell. Figure 1 The two sub-cells are connected in series through a composite layer or tunnel junction in the middle. This type of cell only requires one transparent electrode, which is beneficial to reduce parasitic absorption and reduce costs. However, the two-end stacked cells face higher process difficulties in technical implementation, especially in the process of preparing perovskite films on the surface of crystalline silicon. There are problems such as current matching that need to be solved, and the preparation processes of stacked layers of different crystalline silicon routes are different.

[0036] The four-terminal two-junction stacked cell structure is made by stacking crystalline silicon cells and perovskite cells, which can avoid the complex process stacking problem of the two-terminal stacking. Figure 2 , the perovskite cell with the highest bandgap width is on the top layer, and the crystalline silicon cell with the second highest bandgap width is set on the lower layer. When sunlight irradiates the stacked device, the wide-bandgap solar cell absorbs the short-wavelength sunlight. As for the long-wavelength sunlight, since its photon energy is lower than the bandgap width of the wide-bandgap solar cell, it cannot be absorbed by the wide-bandgap solar cell. Therefore, the long-wavelength sunlight will pass through the wide-bandgap solar cell into the narrow-bandgap solar cell and be absorbed by the narrow-bandgap solar cell. In this combined structure, each solar cell acts as a filter to cut off high-energy photons, and reasonably distributes sunlight to each solar cell.

[0037] The sub-cells of the multi-terminal stacked structure are connected by an insulating layer or even an air layer. Each sub-cell is independent of each other and is not electrically restricted by other sub-cells. Therefore, this type of stacked solar cell is also called a mechanical stacked stacked cell. In addition to not being restricted by current matching, the adjustment of a single sub-cell will not affect the performance of other sub-cells except for the optical performance. However, since the sub-cell connection part of the mechanical stacked cell is a thicker insulating layer, sunlight will produce greater optical losses in this part, and the back light of the stacked solar cell cannot be used.

[0038] In order to solve the above problems, the present application provides a perovskite tandem cell, in which a second solar cell unit is connected to the backlight side of the first solar cell unit through a first packaging film, and the back light is absorbed and converted by the second solar cell unit, thereby improving the utilization of the back light of the perovskite tandem cell. The refractive index of the first packaging film is set to be significantly different from the refractive index of the two electrodes at its junction, thereby improving the secondary utilization of the reflected light and further improving the power generation efficiency of the second solar cell unit.

[0039] The technical solution of the present application and how the technical solution of the present application solves the above-mentioned technical problems are described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0040] See also Figure 3 , Figure 3 A schematic diagram of the structure of a perovskite tandem cell provided in an embodiment of the present application, the perovskite tandem cell 1 includes a first solar cell unit 10 and a second solar cell unit 20, the first solar cell unit 10 is used to absorb the front light of the perovskite tandem cell 1, and the second solar cell unit 20 is used to absorb the back light of the perovskite tandem cell 1. The first solar cell unit 10 and the second solar cell unit 20 are stacked together through a first packaging film 30. Specifically, the first solar cell unit 10 includes a first sub-cell 11, the second solar cell unit 20 includes a second sub-cell 21, and the first sub-cell 11 and the second sub-cell 21 are connected through the first packaging film 30.

[0041] Among them, see Figure 4 The first sub-cell 11 includes a first upper electrode 111, a first light absorbing layer 112, and a first lower electrode 113. The second sub-cell 21 includes a second upper electrode 211, a second light absorbing layer 212, and a second lower electrode 213. The first lower electrode 113 and the second upper electrode 211 are connected by a first packaging film 30.

[0042] Among them, the first lower electrode 113 and the second upper electrode 211 are made of one or more metal oxides (TCO) such as FTO / ITO / AZO / ZnO, and the first lower electrode 113 and the second upper electrode 211 both have a certain refractive index, and the first packaging film 30 also has a certain refractive index.

[0043] In the process of the back light passing through the second sub-cell 21, Figure 5 , the back light E0 is reflected at the interface between the air and the second lower electrode 213 to generate reflected light E1, and the back light passing through the second lower electrode 213 enters the second light absorption layer 212, and the second light absorption layer 212 absorbs and converts part of the back light, and the remaining back light passes through the second upper electrode 211; wherein, the light is basically not reflected inside a single sub-cell because the refractive index is basically uniform. It is reflected at the interface between the second upper electrode 211 and the first packaging film 30 to generate reflected light E2. The back light passing through the first packaging film 30 is reflected again when passing through the interface between the first packaging film 30 and the first lower electrode 113, generating reflected light E3. Both reflected light E2 and reflected light E3 pass through the second light absorption layer 212 again, and are absorbed and converted again by the second light absorption layer 212, and part of the reflected light E4 passes through the second lower electrode 213 back to the air.

[0044] The intensity of the reflected light is determined by the refractive index of the material through which the light passes. The greater the refractive index, the greater the reflectivity, and the more reflected light; the smaller the refractive index, the smaller the reflectivity, and the less reflected light. On this basis, the greater the difference in the refractive index of two adjacent materials, the further the reflection is enhanced. In some implementations, the calculation formula for reflectivity is as follows:

[0045] R=(n1-n2) 2 / (n1+n2) 2 Formula (1)

[0046] Among them, R is the reflectivity, and n1 and n2 are the refractive indices of two adjacent materials.

[0047] exist Figure 5In the embodiment, since the first subcell 11 can only absorb and convert the front light, the utilization rate of the back light can only be enhanced by the second subcell 21. One solution is to increase the light absorption rate of the second light absorption layer 212. Specifically, for the back light E0, it is necessary to reduce the reflected light E1 as much as possible and increase the back light passing through the second lower electrode 213, so the second lower electrode 213 needs to be set with a smaller refractive index; for the reflected light E2 and the reflected light E3, the stronger the reflected light E2 and the reflected light E3, the more back light the second light absorption layer 212 can absorb and utilize, so the second upper electrode 211 and the first lower electrode 113 need to be set with a higher refractive index. On this basis, according to the above formula (1), the greater the difference between the refractive index of the first packaging film 30 and the refractive index of the second upper electrode 211, and the difference between the refractive index of the first packaging film 30 and the refractive index of the first lower electrode 113, the higher the reflectivity, and the stronger the reflected light E2 and the reflected light E3.

[0048] In some embodiments, the refractive indexes of the first lower electrode 113 and the second upper electrode 211 are substantially the same, the refractive indexes of the first lower electrode 113 and the second upper electrode 211 are 1.8-2.1, and the refractive index of the first packaging film 30 is 1.4-1.6.

[0049] In some embodiments, the second sub-cell 21 is a thin film cell, and the second light absorbing layer 212 includes a perovskite thin film or a CIGS thin film; the band gap width of the second sub-cell 21 is 0.9-1.2 eV. The second light absorbing layer 212 mainly absorbs scattered light of natural light, ground radiation, and secondary reflected light, etc., which can help improve the photoelectric efficiency of the entire perovskite stacked cell 1.

[0050] In some embodiments, see Figure 6 , the second lower electrode 213 is a metal oxide (TCO), including at least one of FTO, ITO, AZO, and ZnO. The perovskite stacked cell 1 also includes a third packaging film and a first photovoltaic substrate. The third packaging film is used to connect the second lower electrode 213 and the first photovoltaic substrate. The first photovoltaic substrate is a glass substrate or a polymer material coated with a metal oxide. The polymer material includes but is not limited to polycarbonate (PC) and polymethyl methacrylate (PMMA). The refractive index of the first photovoltaic substrate is less than or equal to 1.55. The structural order of the second sub-cell 21 is the second upper electrode 211, the hole transport layer 214, the second light absorption layer 212, the electron transport layer 215, the second lower electrode 213, the third packaging film 216, and the first photovoltaic substrate 217.

[0051] In some embodiments, see Figure 7, the second lower electrode 213 is directly the second photovoltaic substrate 218. The structural order of the second sub-cell 21 is the second upper electrode 211, the electron transport layer 215, the second light absorption layer 212, the hole transport layer 214, and the second photovoltaic substrate 218.

[0052] Figure 6 and Figure 7 The difference between the two types of perovskite tandem cells 1 shown is that the thickness of the second photovoltaic substrate is different from that of the first photovoltaic substrate. Figure 7 The thickness of the photovoltaic substrate shown is generally 3mm. The strength of this type of component product is relatively weak and can only be used in centralized power stations or BIPV products in ground-floor buildings, and its application scenarios are limited. Figure 6 The perovskite stacked cell 1 structure shown encapsulates the second sub-cell 21 and the photovoltaic substrate together through a third packaging film. At this time, the first photovoltaic substrate can be selected to be 5mm, 6mm or thicker, which can greatly improve the strength of the component product, but of course also increases the cost.

[0053] In some embodiments, the first sub-cell 11 is a crystalline silicon cell; or, the first sub-cell 11 is a thin film cell, and the first light absorption layer 112 includes a perovskite thin film or a CIGS thin film.

[0054] The first sub-cell 11 may be a crystalline silicon cell technology such as HJT, Topcon, etc., or a thin film cell technology such as perovskite or CIGS, etc.

[0055] In some embodiments, the first solar cell unit 10 includes a first sub-cell 11 , and may further include other sub-cells except the first sub-cell 11 .

[0056] When the first solar cell unit 10 includes only the first sub-cell 11 , the band gap width of the first sub-cell 11 may be determined according to the required wavelength range of light to be absorbed.

[0057] When the first solar cell unit 10 includes a plurality of sub-cells, the solar spectrum is divided and two or more sub-cells are connected in series to collect light of a specific spectrum to achieve absorption and utilization of the full spectrum of solar light. The band gap widths of the plurality of sub-cells decrease in sequence, with the sub-cell with the largest band gap width being arranged on the top layer, the sub-cell with the second largest band gap width being arranged on the next layer, and so on.

[0058] In some embodiments, the first solar cell unit 10 further includes a third sub-cell 31. Figure 8 The third sub-cell 31 includes a third upper electrode 311 , a third light absorbing layer 312 and a third lower electrode 313 ; the third lower electrode 313 and the first upper electrode 111 are connected via a second packaging film 40 .

[0059] The third bottom electrode 313 is one or more metal oxides (TCO) such as FTO / ITO / AZO / ZnO, and the third bottom electrode 313 and the second packaging film 40 both have a certain refractive index.

[0060] In the process of the front light passing through the first solar cell unit 10, Fig. 9 , the front light E5 is reflected at the interface between the air and the third upper electrode 311 to generate reflected light E6. The front light passing through the third upper electrode 311 enters the third light absorption layer 312, and the third light absorption layer 312 absorbs and converts part of the front light, and the remaining front light passes through the third lower electrode 313. Reflection occurs at the interface between the third lower electrode 313 and the second packaging film 40 to generate reflected light E7. The back light passing through the second packaging film 40 is reflected again when passing through the interface between the second packaging film 40 and the first upper electrode 111, generating reflected light E8. The remaining front light E9 passes through the first upper electrode 111, enters the first light absorption layer 112, and is absorbed and converted by the first light absorption layer 112.

[0061] exist Fig. 9 In the embodiment, the third light absorbing layer 312 is used to absorb short-wavelength light in the front light, and the first light absorbing layer 112 is used to absorb long-wavelength light in the front light. The wavelength of the short-wavelength light is less than 720nm, and the wavelength of the long-wavelength light is greater than 720nm. Under this combined structure, each solar cell acts as a filter to cut off high-energy photons, reasonably distributes sunlight to each solar cell, and improves the photoelectric efficiency of the perovskite tandem cell 1.

[0062] However, in this process, reflected light such as reflected light E6, reflected light E7, and reflected light E8 are still generated. In order to further increase the photoelectric efficiency of the perovskite stacked cell 1, one solution is to reduce the generation of reflected light. Specifically: for the front light E5, it is necessary to reduce the reflected light E6 as much as possible, and the front light passing through the third upper electrode 311 becomes larger, so the third upper electrode 311 needs to be designed with a smaller refractive index; for the reflected light E7 and reflected light E8, the weaker the reflected light, the stronger the light reaching the first light absorption layer 112, and the more front light that the first light absorption layer 112 can absorb and utilize, so the third lower electrode 313 and the first upper electrode 111 need to be set with a smaller refractive index. On this basis, according to the above formula (1), the smaller the difference between the refractive index of the second packaging film 40 and the refractive index of the third lower electrode 313, and the difference between the refractive index of the second packaging film 40 and the refractive index of the first upper electrode 111, the smaller the reflectivity, and the weaker the reflected light E7 and the reflected light E8.

[0063] In some embodiments, the refractive indexes of the third lower electrode 313, the second packaging film 40, and the first upper electrode 111 are substantially the same, and the second preset threshold is a value close to 0, which is determined according to the level that can be achieved by actual technology. The second preset reflectivity is a value close to 0.

[0064] In some embodiments, the refractive index of the second packaging film 40 is 1.6-1.9; the refractive index of the third lower electrode 313 and the first upper electrode 111 is 1.6-1.9.

[0065] In some embodiments, the third sub-cell 31 is a thin film cell, and the third light absorbing layer 312 includes a perovskite thin film; the band gap width of the first sub-cell 11 is 0.9-1.3 eV, and the band gap width of the third sub-cell 31 is 1.7-1.8 eV.

[0066] In some embodiments, the third lower electrode 313 is a metal oxide, and the metal oxide includes at least one of FTO, ITO, AZO, and ZnO; the third upper electrode 311 is a second photovoltaic substrate, and the second photovoltaic substrate is a glass substrate or a polymer material coated with a metal oxide; the refractive index of the second upper electrode 211 is lower than 1.55. The polymer material includes but is not limited to polycarbonate (PC) and polymethyl methacrylate (PMMA).

[0067] It can be seen that in the embodiment of the present application, the perovskite tandem cell includes a first solar cell unit, including a first sub-cell, the first sub-cell includes a first upper electrode, a first light absorbing layer, and a first lower electrode, and the first solar cell unit is used to absorb the front light of the perovskite tandem cell; the second solar cell unit includes a second sub-cell, the second sub-cell includes a second upper electrode, a second light absorbing layer, and a second lower electrode, and the second solar cell unit is used to absorb the back light of the perovskite tandem cell; wherein the first lower electrode and the second upper electrode are connected by a first packaging film, and the difference between the refractive index of the first packaging film and the refractive index of the first lower electrode, and the difference between the refractive index of the first packaging film and the refractive index of the second upper electrode are both greater than a first preset value, so that the reflectivity of part of the back light passing through the second light absorbing layer when passing through the first interface and the second interface is greater than the first preset reflectivity, so that part of the back light is reflected back to the second light absorbing layer again; the first interface is the interface between the second upper electrode and the first packaging film, and the second interface is the interface between the first packaging film and the first lower electrode. Therefore, in the present application, the second solar cell unit is connected to the backlight side of the first solar cell unit through the first packaging film, and the back light is absorbed and converted by the second solar cell unit to improve the utilization of the back light of the perovskite stacked cell. The refractive index of the first packaging film is set to be significantly different from the refractive index of the two electrodes at its junction, thereby improving the secondary utilization of the reflected light and further improving the power generation efficiency of the second solar cell unit.

[0068] Mentioning "embodiment" and "implementation method" in this application means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present application. The appearance of the phrases in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in this application can be combined with other embodiments. In addition, it should also be understood that the features, structures or characteristics described in the various embodiments of the present application can be arbitrarily combined to form another embodiment that does not deviate from the spirit and scope of the technical solution of the present application, provided that there is no contradiction between them.

[0069] Finally, it should be noted that the above implementation modes are only used to illustrate the technical solution of the present application and are not intended to limit it. Although the present application has been described in detail with reference to the above preferred implementation modes, a person of ordinary skill in the art should understand that the technical solution of the present application may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present application.

Claims

1. A perovskite tandem battery, characterized in that: include: A first solar cell unit, comprising a first sub-cell, wherein the first sub-cell comprises a first upper electrode, a first light absorbing layer, and a first lower electrode, and the first solar cell unit is used to absorb the front light of the perovskite tandem cell; A second solar cell unit, comprising a second sub-cell, wherein the second sub-cell comprises a second upper electrode, a second light absorbing layer, and a second lower electrode, and the second solar cell unit is used to absorb the back light of the perovskite stacked cell; The first lower electrode and the second upper electrode are connected by a first packaging film, and the difference between the refractive index of the first packaging film and the refractive index of the first lower electrode, and the difference between the refractive index of the first packaging film and the refractive index of the second upper electrode are both greater than a first preset value, so that the reflectivity of part of the back light passing through the second light absorbing layer when passing through the first interface and the second interface is greater than the first preset reflectivity, so that the part of the back light is reflected back to the second light absorbing layer again; The first interface is an interface between the second upper electrode and the first packaging film, and the second interface is an interface between the first packaging film and the first lower electrode.

2. The perovskite tandem cell according to claim 1, characterized in that: The first subcell is a crystalline silicon cell; or, The first sub-cell is a thin film cell, and the first light absorption layer includes a perovskite thin film or a CIGS thin film.

3. The perovskite tandem battery according to claim 1, characterized in that: The second sub-cell is a thin film cell, and the second light absorbing layer includes a perovskite thin film or a CIGS thin film; The band gap width of the second sub-cell is 0.9-1.2 eV.

4. The perovskite tandem cell according to claim 1, characterized in that: The refractive index of the first packaging film is 1.4-1.6, and the refractive index of the first lower electrode and the second upper electrode is 1.8-2.

1.

5. The perovskite tandem cell according to claim 1, characterized in that: The first upper electrode, the first lower electrode, and the second upper electrode are metal oxides, and the metal oxides include at least one of FTO, ITO, AZO, and ZnO; The second lower electrode is the metal oxide, the perovskite stacked cell further comprises a third encapsulation film and a first photovoltaic substrate, the third encapsulation film is connected to the second lower electrode and the first photovoltaic substrate respectively; the first photovoltaic substrate is a glass substrate or a high molecular polymer material coated with a metal oxide, and the refractive index of the first photovoltaic substrate is less than or equal to 1.55; or, The second lower electrode is a second photovoltaic substrate, and the thickness of the second photovoltaic substrate is different from that of the first photovoltaic substrate.

6. The perovskite tandem cell according to claim 1, characterized in that: The first solar cell unit further includes a third subcell, the third subcell including a third upper electrode, a third light absorbing layer and a third lower electrode; The third lower electrode and the first upper electrode are connected via a second packaging film; The difference between the refractive index of the second packaging film and the refractive index of the third lower electrode, and the difference between the refractive index of the second packaging film and the refractive index of the first upper electrode are both smaller than a second preset value; The reflectivity of part of the front light passing through the third light absorbing layer is less than the second preset reflectivity when passing through the third interface and the fourth interface. The third interface is the interface between the third lower electrode and the second packaging film, and the fourth interface is the interface between the second packaging film and the first upper electrode.

7. The perovskite tandem cell according to claim 6, characterized in that: The third sub-cell is a thin film cell, and the third light absorption layer includes a perovskite thin film; The band gap width of the first sub-cell is 0.9-1.3 eV, and the band gap width of the third sub-cell is 1.7-1.8 eV; The third subcell is used to absorb short-wavelength light in the front light, and the second subcell is used to absorb long-wavelength light in the front light. The wavelength of the short-wavelength light is less than 720nm, and the wavelength of the long-wavelength light is greater than 720nm.

8. The perovskite tandem cell according to claim 6, characterized in that: The refractive index of the second packaging film is 1.6-1.9; The refractive index of the third lower electrode and the first upper electrode is 1.6-1.

9.

9. The perovskite tandem cell according to claim 6, characterized in that: The third lower electrode is a metal oxide, and the metal oxide includes at least one of FTO, ITO, AZO, and ZnO; The third upper electrode is a third photovoltaic substrate, and the third photovoltaic substrate is a glass substrate or a high molecular polymer material coated with metal oxide; the refractive index of the second upper electrode is lower than 1.

55.

10. The perovskite tandem cell according to claim 1 or 6, characterized in that: The reflectivity of the first interface is calculated according to the following formula: R=(n1-n2) 2 / (n1+n2) 2 Wherein, R is the reflectivity, n1 and n2 represent the refractive index of the second upper electrode and the refractive index of the first packaging film, respectively.

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