Photovoltaic / photo-thermal / photovoltaic top cover type laminated structure and preparation method thereof

Abstract

The invention relates to the technical field of solar energy utilization, in particular to a photovoltaic / photo-thermal / photovoltaic top cover type laminated structure and a preparation method thereof.The photovoltaic / photo-thermal / photovoltaic top cover type laminated structure comprises a rigid semitransparent photovoltaic cell, a curved-surface-shaped photo-thermal reflector and a back photovoltaic cell which are sequentially arranged from top to bottom, and the back photovoltaic cell comprises a flexible photovoltaic cell and a rigid photovoltaic cell. The system not only can effectively absorb ultraviolet light and visible light of the sun for photovoltaic power generation, but also can efficiently utilize infrared light for photo-thermal conversion through the curved-surface-shaped photo-thermal reflecting mirror, and meanwhile, the back photovoltaic cell can utilize ambient light and ground reflected light which are not absorbed by the top rigid semitransparent photovoltaic cell, so that the photovoltaic power generation efficiency is improved. And the overall energy utilization efficiency of the photo-thermal power station is further improved. Therefore, through structure innovation and performance optimization, efficient comprehensive utilization of solar energy is achieved, the system efficiency, the light absorption capacity and the service life of the battery are remarkably improved, excellent technical indexes and economic benefits are shown, and great popularization value is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of solar energy utilization, and in particular to a photovoltaic / photothermal / photovoltaic top cover type stacked structure and a preparation method thereof. Background Art

[0002] With the continuous growth of the global economy and the continuous expansion of the population, the demand for energy has shown an unprecedented growth trend. Traditional fossil energy can no longer meet the needs of sustainable development due to its limited reserves and serious impact on the environment. Therefore, the development and utilization of renewable energy has become a hot research issue worldwide. As a clean, endless and widely distributed energy source, the development and utilization of solar energy is of great significance to alleviating the energy crisis and protecting the environment.

[0003] Among solar energy utilization technologies, photovoltaic power generation and photothermal conversion are the two most common and mature technologies. Photovoltaic power generation mainly converts sunlight directly into electrical energy through photovoltaic cells, and has the advantages of high conversion efficiency and low maintenance cost; while photothermal conversion uses sunlight to generate heat energy, which is used in many fields such as heating, hot water, refrigeration and power generation, and has the characteristics of wide application range and good stability. However, a single photovoltaic or photothermal utilization method has obvious limitations in terms of comprehensive utilization rate and efficiency improvement of solar energy resources.

[0004] To overcome this limitation, the photovoltaic-photothermal synergistic system came into being. By combining photovoltaic power generation with photothermal conversion technology, this system achieves a more comprehensive and efficient use of solar energy. The photovoltaic / photothermal superposition structure is the concentrated embodiment of this innovative idea. Through clever design, it uses sunlight of different wavelengths for power generation and heat conversion respectively, thus maximizing the use of solar energy resources.

[0005] However, the realization of photovoltaic / photothermal stacking structure is not easy, and it faces many technical challenges. First of all, as the top element of the stacking structure, the semi-transparent photovoltaic cell needs to have both high spectral selectivity and photoelectric conversion efficiency, and also needs to be able to effectively transmit a certain proportion of the spectrum in order to provide the necessary infrared light for the photothermal conversion structure below. This requirement greatly increases the difficulty of the research and development of semi-transparent photovoltaic cells.

[0006] Secondly, the design of the curved photothermal reflector is also a major difficulty. It needs to achieve the best balance in terms of reflection efficiency, weather resistance and mechanical stability, and it also needs to achieve efficient coupling with the upper semi-transparent photovoltaic cells to ensure the efficiency of photothermal conversion. In addition, the design of the back photovoltaic cell is also crucial, which can further improve the photoelectric conversion efficiency of the entire system by utilizing ambient light and ground reflected light. However, the existing back photovoltaic cells still have obvious deficiencies in light capture ability and heat dissipation performance.

[0007] In summary, although the photovoltaic / photothermal hybrid structure has great potential and application prospects, the technical challenges faced in its implementation process cannot be ignored.

[0008] In view of this, the present invention is proposed. Summary of the invention

[0009] The purpose of the present invention is to provide a photovoltaic / photothermal / photovoltaic top cover type stacked structure, which realizes the efficient comprehensive utilization of solar energy and significantly improves the system efficiency, light absorption capacity and battery life.

[0010] In a first aspect, the present invention provides a photovoltaic / photothermal / photovoltaic top cover type stacked structure, comprising a rigid semi-transparent photovoltaic cell, a curved photothermal reflector and a back photovoltaic cell arranged in sequence from top to bottom, wherein the back photovoltaic cell comprises a flexible photovoltaic cell and a rigid photovoltaic cell.

[0011] As a preferred embodiment of the present technical solution, a heat conductive layer is provided on the side of the back photovoltaic cell close to the curved thermal reflector, and a light capture layer is provided on the inside of the back photovoltaic cell and / or on the outer surface away from the curved thermal reflector.

[0012] As a preferred embodiment of the present technical solution, the outer surface of the back photovoltaic cell away from the curved light-heat reflector is further provided with a low-reflection anti-reflection layer and a diffuse reflection scattering layer, wherein the low-reflection anti-reflection layer is close to the back photovoltaic cell or the light capture layer.

[0013] As a preferred embodiment of the present technical solution, the heat-conducting layer is a graphene film or an aluminum oxide nanosheet, and the heat-conducting layer is bonded to the back surface of the back photovoltaic cell via a heat-conducting adhesive.

[0014] As a preferred embodiment of the present technical solution, the light capture layer is arranged on the outer surface of the back photovoltaic cell away from the curved photothermal reflector, the light capture layer is a periodic nanocolumn, nanohole array or randomly distributed nanoparticle structure, and the material of the light capture layer is indium tin oxide or zinc oxide.

[0015] As a preferred embodiment of the present technical solution, the light capture layer is arranged on the light absorption layer of the back photovoltaic cell, and the light capture layer is a nanostructure induced by a femtosecond laser on the light absorption layer of the back photovoltaic cell.

[0016] As a preferred embodiment of the present technical solution, the light capture layer is arranged on the electron transport layer of the back photovoltaic cell, and the light capture layer is a light trapping nanostructure.

[0017] As a preferred embodiment of the present technical solution, the light capture layer is arranged between the glass in the back photovoltaic cell and the top surface packaging layer, and the light capture layer is a nano high-transmittance color film layer.

[0018] As a preferred embodiment of the present technical solution, the low-reflection anti-reflection layer is a Bragg reflector formed by alternately depositing a high-refractive index material and a low-refractive index material;

[0019] The material of the diffuse reflection and scattering layer is aluminum oxide or titanium dioxide nanoparticles.

[0020] As a preferred embodiment of the present technical solution, the back photovoltaic cell includes any one of a flexible photovoltaic cell and a rigid photovoltaic cell, wherein the flexible photovoltaic cell is tightly fitted on the curved photothermal reflector, and at least one point of the rigid photovoltaic cell is tightly fitted to the curved photothermal reflector.

[0021] In a second aspect, the present invention further provides a method for preparing the above-mentioned photovoltaic / photothermal / photovoltaic top cover type stacked structure, which specifically comprises the following steps:

[0022] The rigid semi-transparent photovoltaic cell is mounted on the top of the curved photothermal reflector through a bracket, and the back photovoltaic cell is arranged under the curved photothermal reflector to obtain a photovoltaic / photothermal / photovoltaic top cover type stacked structure;

[0023] Wherein, when the back photovoltaic cell is a flexible photovoltaic cell, the back photovoltaic cell is pasted to the back side of the curved photothermal reflector;

[0024] When the back photovoltaic cell is a rigid photovoltaic cell, the back photovoltaic cell is fixed below the curved photothermal reflector by gluing, hinges or buckles, and the fixed angle and position are determined according to different lighting requirements.

[0025] The photovoltaic / photothermal / photovoltaic top cover type stacked structure of the present invention has at least the following beneficial effects:

[0026] The photovoltaic / photothermal / photovoltaic top cover type superimposed structure of the present invention effectively integrates rigid semi-transparent photovoltaic cells, curved photothermal reflectors and back photovoltaic cells, realizing efficient distribution and utilization of the solar spectrum. The system can not only effectively absorb the ultraviolet and visible light of the sun for photovoltaic power generation, but also efficiently utilize infrared light for photothermal conversion through the curved photothermal reflector. At the same time, the back photovoltaic cell can utilize the ambient light and ground reflected light that are not absorbed by the top rigid semi-transparent photovoltaic cell, further improving the overall energy utilization efficiency of the photothermal power station. In addition, the present invention also provides a heat-conducting layer on the side of the back photovoltaic cell close to the curved photothermal reflector, effectively ensuring the stability of the overall structure and the long-term efficient operation of the battery. At the same time, a light capture layer is also provided on the inner part of the back photovoltaic cell and / or the outer surface of the side away from the curved photothermal reflector, which greatly improves the light absorption capacity of the back photovoltaic cell.

[0027] Studies have shown that the photovoltaic / photothermal / photovoltaic composite structure of the present invention can achieve high performance under typical solar radiation conditions (light intensity of 1000W / m 2 , standard AM1.5 spectrum) can achieve a total energy conversion efficiency of 45%-50%, which is 10%-20% higher than the average efficiency of traditional split photovoltaic or solar thermal systems (25%-35%). Among them, the photoelectric conversion efficiency of the upper rigid semi-transparent photovoltaic cell for ultraviolet and visible light can reach 15%-20%.

[0028] In addition, the utilization rate of ambient light and ground reflected light of the back photovoltaic cells has increased by 20%-30%. Combined with the design of the nanostructured light capture layer, the light absorption capacity of the back photovoltaic cells has increased by 10%-15% compared with ordinary cells without light capture layers, and the power generation efficiency has increased by about 5%-8%. Experimental data shows that when the ambient light intensity is 200W / m 2 Under low light conditions, the additional power generation of the rear photovoltaic cells accounts for 8%-10% of the total system power generation, significantly enhancing the low-light performance of the overall system.

[0029] In terms of thermal management, after adopting the thermal conductive layer design, the operating temperature of the photovoltaic cell is reduced by 15-20°C compared with the traditional design. According to the results of the life acceleration test, the temperature reduction effectively extends the service life of the photovoltaic cell, and the fatigue life can be increased by 25%-30%. For example, when working continuously under high temperature conditions of 70°C, the efficiency of ordinary photovoltaic cells will drop by about 5% due to thermal attenuation, while the efficiency of the photovoltaic cell of the present invention will only drop by 2%.

[0030] In summary, the present invention realizes the efficient and comprehensive utilization of solar energy through structural innovation and performance optimization, and significantly improves the system efficiency, light absorption capacity and battery life, showing superior technical indicators and economic benefits, and is of great promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 It is a schematic diagram of the photovoltaic / photothermal / photovoltaic top cover type stacked structure of the present invention (the back photovoltaic cell is a flexible photovoltaic cell);

[0033] Figure 2 This is one of the schematic diagrams of the photovoltaic / photothermal / photovoltaic top cover type stacked structure of the present invention (the back photovoltaic cell is a rigid photovoltaic cell);

[0034] Figure 3 This is the second schematic diagram of the photovoltaic / photothermal / photovoltaic top cover type stacked structure of the present invention (the back photovoltaic cell is a rigid photovoltaic cell);

[0035] Figure 4 This is the third schematic diagram of the photovoltaic / photothermal / photovoltaic top cover type stacked structure of the present invention (the back photovoltaic cell is a rigid photovoltaic cell);

[0036] Figure 5 This is the fourth schematic diagram of the photovoltaic / photothermal / photovoltaic top cover type stacked structure of the present invention (the back photovoltaic cell is a rigid photovoltaic cell);

[0037] Figure 6 This is one of the structural schematic diagrams of the back photovoltaic cell of the present invention;

[0038] Figure 7 This is the second structural schematic diagram of the back photovoltaic cell of the present invention;

[0039] Figure 8 This is the third structural schematic diagram of the back photovoltaic cell of the present invention.

[0040] Reference numerals:

[0041] 1: Rigid semi-transparent photovoltaic cell; 2: Back photovoltaic cell; 3: Curved photothermal reflector; 4: Bracket; 5: Sunlight; 6: Infrared light; 7: Collector; 8: Thermal conductive layer; 9: Light capture layer; 10: Low reflection and anti-reflection layer; 11: Diffuse reflection and scattering layer; 12: Encapsulation layer; 13: Top electrode; 14: Electron transport layer; 15: Light absorption layer; 16: Bottom electrode; 17: Substrate. DETAILED DESCRIPTION

[0042] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0043] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form also includes the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this description, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0044] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] Example 1

[0046] like Figure 1-8 As shown, this embodiment provides a photovoltaic / solar thermal / photovoltaic top cover type stacked structure, including a rigid translucent photovoltaic cell 1, a curved thermal reflector 3 and a back photovoltaic cell 2 arranged in sequence from top to bottom, wherein a thermal conductive layer 8 is provided on the side of the back photovoltaic cell 2 close to the curved thermal reflector 3, and a light capture layer 9 is provided on the interior of the back photovoltaic cell 2 and / or on the outer surface of the side away from the curved thermal reflector 3.

[0047] In the photovoltaic / photothermal / photovoltaic top cover type superimposed structure of the present embodiment, the rigid semi-transparent photovoltaic cell 1 is covered on the curved photothermal reflector 3, and the back photovoltaic cell 2 is directly prepared or pasted on the curved reflector. When sunlight 5 irradiates the rigid semi-transparent photovoltaic cell 1, ultraviolet light and visible light are absorbed by the rigid semi-transparent photovoltaic cell 1, infrared light 6 is reflected by the curved photothermal reflector 3 to the collector 7 and absorbed, and the back photovoltaic cell 2 can further absorb ambient light and ground reflected light. In addition, a solar tracking axis can also be set in the photovoltaic / photothermal / photovoltaic top cover type superimposed structure of the present embodiment, and the solar tracking axis can adjust the direction of the photovoltaic cell to receive as much sunlight 5 as possible.

[0048] The present invention integrates two layers of photovoltaic cells on the curved photothermal reflector 3, and the visible light is absorbed by the rigid semi-transparent photovoltaic cell 1 on the top cover and converted into electrical energy, and the infrared light 6 enters the curved photothermal reflector 3 through the rigid semi-transparent photovoltaic cell 1 on the top cover for photothermal conversion, maximizing the comprehensive utilization rate of solar energy, and the back photovoltaic cell 2 can be used to absorb unused ambient light and ground reflected light. Therefore, under the synergistic effect of the rigid semi-transparent photovoltaic cell 1, the curved photothermal reflector 3 and the back photovoltaic cell 2, the present invention can achieve the triple benefits of photovoltaic power generation and photothermal utilization, greatly improving the overall energy utilization efficiency of the curved reflector type photothermal power station, and realizing efficient utilization of the spectrum.

[0049] In this embodiment, the rigid semi-transparent photovoltaic cell 1 includes, from bottom to top, a high-transmittance glass substrate, a first transparent electrode, a first interface modification layer, a hole transport layer / electron transport layer, a second interface modification layer, a semi-transparent light absorption layer, a third interface modification layer, an electron transport layer / hole transport layer, a fourth interface modification layer, a second transparent electrode, an encapsulation layer and an anti-reflection layer, wherein one or more of the first interface modification layer, the hole transport layer / electron transport layer, the second interface modification layer, the third interface modification layer, the electron transport layer / hole transport layer, the fourth interface modification layer and the anti-reflection layer may not exist.

[0050] In this embodiment, the curved photothermal reflector 3 includes, from bottom to top, a base layer, a reflective layer (including one or more layers of metals such as silver / copper), and glass (including float glass, ultra-white glass, low-iron glass, high-strength tempered glass, etc.).

[0051] In addition, in order to further improve the light-heat reflection efficiency and structural stability of the curved light-heat reflector 3, a first reflection film layer, a heat insulation layer, a second reflection film layer, a protective layer, an anti-reflection layer and a dust-proof self-cleaning layer can also be added. At this time, the curved light-heat reflector 3 includes a base layer, a first reflection film layer, a heat insulation layer, a second reflection film layer, a protective layer, an anti-reflection layer and a dust-proof self-cleaning layer from bottom to top.

[0052] The first reflective film layer is located on the base layer and is made of a high-reflectivity metal coating (such as silver or aluminum) and is nano-processed to improve its effect of reflecting infrared light 6. The main function of this film layer is to efficiently reflect light in the infrared band of the spectrum to more efficiently concentrate heat energy into the photothermal system, thereby improving the photothermal efficiency.

[0053] The heat insulation layer is used to form a heat insulation effect between the base layer and the first reflective film layer to prevent heat caused by high temperature from being transferred to the base material. Usually, high temperature resistant and low thermal conductivity materials such as ceramic matrix composite materials or aerogels are used to effectively isolate heat and prevent heat from diffusing to the reflective base layer. This layer design helps the photothermal system to operate stably at high temperatures and prolongs the service life of the base layer of the curved photothermal reflector 3.

[0054] The second reflective film layer is adjacent to the heat insulation layer and usually adopts a multi-layer dielectric film structure to enhance its reflective performance. This layer further improves the reflectivity of visible light and infrared light 6 by multiple reflections and concentrations of light, ensuring that the light energy in the system is maximized.

[0055] The protective layer is located on the second reflective film layer and is made of an anti-oxidation and anti-corrosion material (such as silicon dioxide or silicon nitride) to protect the reflective layer from environmental influences (such as moisture, acid and alkali, temperature fluctuations, etc.).

[0056] The anti-reflection layer is used to reduce the reflection loss of light on the surface of the curved light-heat reflector 3 due to interface refraction. This layer is preferably a low refractive index material, such as magnesium fluoride or aluminum oxide nanolayer, which can improve the overall optical anti-reflection effect. This structure can also improve the incident angle range of light, so that the optical performance of the curved light-heat reflector 3 can be fully utilized under different illumination angles.

[0057] The dustproof self-cleaning layer uses super-hydrophobic or super-hydrophilic materials, and can selectively use nanostructured self-cleaning coatings to prevent the adhesion of dust, rain and pollutants, reducing the cleaning frequency and maintenance costs. This layer design is particularly suitable for outdoor dusty environments and can effectively improve the reflection effect of the curved photothermal reflector 3 under long-term outdoor exposure.

[0058] In this embodiment, the back photovoltaic cell 2 includes any one of a flexible photovoltaic cell and a rigid photovoltaic cell, wherein the flexible photovoltaic cell is closely attached to the curved photothermal reflector 3, and at least one point of the rigid photovoltaic cell is closely attached to the curved photothermal reflector 3, and is attached to the lowest point of the curved photothermal reflector 3 as much as possible to ensure the stability of the structure. Among them, the flexible photovoltaic cell includes any one of a perovskite solar cell, an organic solar cell, a copper indium gallium selenide photovoltaic cell, a flexible dye-sensitized solar cell, a flexible monocrystalline silicon solar cell, an amorphous silicon flexible cell, a flexible cadmium telluride solar cell, and a quantum dot solar cell; the rigid photovoltaic cell includes any one of a silicon solar cell, a perovskite solar cell, a cadmium telluride solar cell, a gallium arsenide solar cell, an organic solar cell, a quantum dot solar cell, and a copper indium gallium selenide solar cell. In addition, rigid photovoltaic cells can also form V-shaped structures, L-shaped structures, U-shaped structures, etc., including horizontal single back photovoltaic cells, oblique single back photovoltaic cells, oblique multiple back photovoltaic cells, horizontal oblique multiple back photovoltaic cells and other structural forms.

[0059] In addition, a heat-conducting layer 8 is provided on the side of the back photovoltaic cell 2 close to the curved light-heat reflector 3, and a light-capturing layer 9 is provided on the inside of the back photovoltaic cell 2 and / or the outer surface of the side away from the curved light-heat reflector 3. The heat-conducting layer 8 can accelerate heat dissipation through high thermal conductivity materials, reduce the operating temperature of the cell, and extend the service life; while the light-capturing layer 9 can improve the absorption efficiency of the back photovoltaic cell 2 for ambient light and ground reflected light, and optimize the path extension and scattering of light.

[0060] Specifically, the heat-conducting layer 8 can be made of graphene film or alumina nanosheet with high thermal conductivity, which can be realized by sputtering or lamination technology. The back photovoltaic cell with the heat-conducting layer 8 is further firmly attached to the curved light-heat reflector 3 by a heat-conducting adhesive (such as silver paste or silica gel), and the bonding strength is ensured by vacuum hot pressing.

[0061] The light capture layer 9 can be arranged inside the back photovoltaic cell 2 , or on the outer surface of the back photovoltaic cell 2 away from the curved photothermal reflector 3 .

[0062] When the light capture layer 9 is arranged on the outer surface of the back photovoltaic cell 2 away from the curved photothermal reflector 3, the light capture layer 9 can be a periodic nanocolumn, a nanohole array or a randomly distributed nanoparticle structure to achieve wide-spectrum light absorption, and the material of the light capture layer 9 can be a transparent conductive material such as indium tin oxide or zinc oxide.

[0063] The preparation method is as follows:

[0064] A layer of polymer mask material (such as PMMA) is spin-coated on the surface of the back photovoltaic cell 2, and a nanostructure pattern is generated on the mask material using electron beam lithography or laser interference lithography technology. The pattern is transferred to the surface of the back photovoltaic cell 2 by plasma etching to form a periodic nanostructure.

[0065] In practical applications, the size of the periodic nanostructure can be optimized and designed according to the wavelength of the target spectrum. For example, the size of the periodic nanocolumns ranges from 50 to 200 nm, the spacing is 100 to 300 nm, and the height is 100 to 500 nm.

[0066] When the light capture layer 9 is arranged in the light absorption layer 15 of the back photovoltaic cell 2, a femtosecond laser is used to induce the formation of a nanostructure inside the light absorption layer 15 of the back photovoltaic cell 2. By studying the kinetic process and mechanism of femtosecond laser-induced nanostructure formation inside the silicon substrate, the shape and scale of the femtosecond laser-induced nanostructure are controlled. During the preparation process, different atmospheres, temperatures, thermal annealing and other methods can be combined to improve the carrier mobility of the nanostructured silicon material, thereby expanding the infrared absorption spectrum of the silicon material.

[0067] When the light capture layer 9 is disposed in the electron transport layer 14 of the rear photovoltaic cell 2 , the ZnO with the light trapping nanostructure is used as the electron transport layer 14 of the rear photovoltaic cell 2 .

[0068] The preparation method is as follows:

[0069] First, a suitable substrate 17 material is selected and a ZnO seed layer is deposited thereon to provide a basis for the subsequent growth of nanorods;

[0070] Next, Mg-doped ZnO nanorods are grown on the seed layer by techniques such as chemical vapor deposition (CVD), physical vapor deposition (PVD), or hydrothermal method;

[0071] Mg doping can improve the light scattering ability of ZnO in the 300-430nm band. This is because the introduction of Mg will change the energy band structure of ZnO, thereby affecting its absorption and scattering properties of light.

[0072] Before or after the growth of ZnO nanocolumns, the seed layer is annealed. The annealing temperature and time need to be precisely controlled to optimize the crystallization quality of the seed layer, improve the growth quality of ZnO nanocolumns, and regulate the wide spectrum scattering ability. Through this process, the controllability of the scattering ability of the ZnO nanocolumn film in the wide spectrum range of 300-850nm can be achieved.

[0073] On the basis of the ZnO nanorod film, a layer of Al-doped ZnO film is further deposited. Al doping can improve the conductivity of the film while maintaining its light scattering ability.

[0074] The Al-doped ZnO film is then subjected to a two-step annealing treatment. The first step of annealing is to remove residual stress and defects in the film and stabilize the film structure; the second step of annealing further improves the crystal quality and conductivity of the film. By precisely controlling the temperature and time of the two-step annealing, an Al-doped ZnO film with a conductivity of 2.76e-03s / cm and good light scattering ability can be obtained.

[0075] The ZnO nanorod film and the Al-doped ZnO film processed in the above steps are combined to form a light-trapping ZnO nanostructure light-capturing layer 9, which serves as an electron transport layer 14 and is located between the active layer and the top electrode 13 of the photovoltaic cell.

[0076] The light-trapping ZnO nanostructure light-capturing layer 9 utilizes its unique nanostructure and light-scattering properties, combined with the back-reflecting electrode of the battery, to increase the optical path of light in the active layer through light scattering and multiple reflections, thereby improving the light absorption efficiency and further enhancing the photoelectric conversion performance of the photovoltaic cell.

[0077] When the light capture layer 9 is disposed between the glass in the back photovoltaic cell 2 and the top surface encapsulation layer 12 , the nano metal oxide high-transmittance color film layer is used as the light capture layer 9 .

[0078] The preparation method is as follows:

[0079] Under nitrogen protection, a sulfur source, zinc salt, cadmium salt, noble metal nanoparticles, and a surface modifier are added into a polar organic solvent at one time, and the reaction mixture is reacted at 180-200° C. for 10-15 hours;

[0080] The surface-modified nanoparticles are precipitated by using a poor solvent, and after centrifugal separation, washing, and drying, a solid powder of the surface-modified nanoparticles is obtained;

[0081] The nanoparticle solid powder and the additive are mixed evenly in proportion, and then plasticized by a screw, extruded, flowed out from a die head, and pressed by a roller to obtain a nano metal oxide high-transmittance color film layer;

[0082] It is attached to the glass surface through a casting process, that is, the nano metal oxide high-transmittance color film layer is located between the glass and the top surface packaging layer 12, and its optical effect of strong interference with light is utilized to reduce the loss of light when it is irradiated from the top surface EVA film to the battery cell, thereby improving the power generation efficiency.

[0083] On the basis of the above technical solution, it is further preferred that the outer surface of the back photovoltaic cell 2 away from the curved light-heat reflector 3 is also provided with a low-reflection anti-reflection layer 10 and a diffuse reflection scattering layer 11, wherein the low-reflection anti-reflection layer 10 is close to the back photovoltaic cell 2 or the light capture layer 9.

[0084] When a light capture layer 9 is provided on the outer surface of the back photovoltaic cell 2 away from the curved photothermal reflector 3 , the light capture layer 9 , the low reflection and transmittance enhancement layer 10 and the diffuse reflection and scattering layer 11 are sequentially provided on the surface of the back photovoltaic cell 2 from the inside to the outside.

[0085] When the light capturing layer 9 is disposed inside the back photovoltaic cell 2 , the low reflection and anti-reflection layer 10 and the diffuse reflection and scattering layer 11 are sequentially disposed on the surface of the back photovoltaic cell 2 from the inside to the outside.

[0086] When the light capture layer 9 is disposed on both the inner and outer surfaces of the back photovoltaic cell 2 , the low reflection and anti-reflection layer 10 and the diffuse reflection and scattering layer 11 are sequentially disposed on the surface of the back photovoltaic cell 2 from the inside to the outside.

[0087] Specifically, the low-reflection anti-reflection layer 10 is a Bragg reflector formed by alternately depositing a high-refractive index material (such as titanium dioxide) and a low-refractive index material (such as silicon dioxide) to further reduce light reflection loss.

[0088] The preparation method is as follows:

[0089] Select appropriate substrate materials and clean and treat them to ensure good adhesion and uniformity of the deposited films;

[0090] Depositing a layer of high refractive index material (such as titanium dioxide) on the substrate using an appropriate deposition technique (such as electron beam evaporation, ion beam sputtering or atomic layer deposition);

[0091] Depositing a layer of low refractive index material (such as silicon dioxide) on the high refractive index material;

[0092] Repeat steps 2 and 3 as needed to form a multi-layer Bragg reflector;

[0093] The deposited Bragg reflector is subjected to necessary annealing, cleaning and testing to ensure that it has good optical performance and stability.

[0094] Specifically, the diffuse reflection and scattering layer 11 is made of aluminum oxide or titanium dioxide nanoparticles, and is mainly coated on the back shell of the back photovoltaic cell 2 to improve the re-scattering efficiency of the ground reflected light.

[0095] Example 2

[0096] This embodiment provides a method for preparing a photovoltaic / photothermal / photovoltaic top cover type stacked structure, wherein the method for preparing a rigid semi-transparent photovoltaic cell 1 top cover structure is as follows:

[0097] S1. Selection of high-transmittance glass substrate

[0098] Choose low-iron glass or ultra-white glass with high transmittance, preferably glass coated with indium tin oxide (ITO) or calcium fluoride, to increase the transmittance of ultraviolet and visible light. The thickness of the high-transmittance glass substrate is 1-2mm, which is selected according to the mechanical strength requirements. Choose a polished glass substrate, which can be used directly as a substrate after cleaning and drying. You can also form an anti-reflection coating on the glass surface through vacuum coating as needed to enhance weather resistance and optical performance.

[0099] S2. Preparation of the first transparent electrode layer

[0100] Indium tin oxide (ITO) or aluminum zinc oxide (AZO) is used as the first transparent electrode layer, and ITO is preferred to ensure conductivity and light transmittance. The thickness of the first transparent electrode layer is 80-100nm. It can be deposited on a high-transmittance glass substrate by magnetron sputtering deposition or electron beam evaporation process. After deposition, heat treatment is performed at 200-300°C to improve the conductivity and transparency of the electrode.

[0101] S3. Preparation of hole transport layer

[0102] The hole transport layer can be made of PEDOT:PSS or PTAA (polytriphenylamine) with a thickness of 20-40 nm and can be prepared by spin coating or evaporation and curing at low temperature.

[0103] S4. Preparation of light absorbing layer

[0104] A wide bandgap perovskite compound with a bandgap range of 1.62eV-2.5eV and a thickness of 300-700nm is selected. Specifically, the solution spin coating method can be used to mix the perovskite precursor solution evenly and then apply it to the interface modification layer using a slit coating method, and then perform a heat treatment at 100-150°C to crystallize the film to form a uniform and dense perovskite light-absorbing layer.

[0105] S5. Preparation of electron transport layer

[0106] The electron transport layer can be made of fullerene C 60 Or PCBM, with a thickness of 20-40nm, can be prepared by spin coating or evaporation and heat treatment at 80-100℃.

[0107] S6, second transparent electrode layer

[0108] Indium tin oxide (ITO) or aluminum zinc oxide (AZO) is used as the second transparent electrode layer, and its thickness is 80-100nm. The transparent electrode layer can be deposited on the electron transport layer by using magnetron sputtering or electron beam evaporation to form a complete electrode structure.

[0109] S7, encapsulation layer and anti-reflection layer

[0110] The encapsulation layer uses epoxy resin or polyvinylidene fluoride (PVDF), etc., and the anti-reflection layer is magnesium fluoride (MgF2) or a multi-layer nano-anti-reflection coating, wherein the thickness of the encapsulation layer is 0.5-1mm, and the thickness of the anti-reflection layer is 50-100nm. The outermost layer is coated with a layer of nanomaterial or low refractive index material with high anti-reflection performance, such as magnesium fluoride or nanostructured aluminum oxide, to reduce light reflection and improve the utilization efficiency of incident light. Specifically, the encapsulation layer can be formed into a uniform protective film by drop coating or spin coating, and the sealing performance can be ensured after curing; the anti-reflection layer can be prepared by vacuum coating or thermal evaporation to control the light transmittance.

[0111] The materials and preparation methods of the first interface modification layer, the second interface modification layer, the third interface modification layer and the fourth interface modification layer can refer to the prior art and will not be described in detail here.

[0112] The preparation method of the curved light-heat reflector 3 is as follows:

[0113] T1, selection of basal layer

[0114] The base layer can be made of lightweight and high-strength aluminum alloy (such as 6061 or 7075 aluminum alloy), composite materials (such as carbon fiber composite materials) or high-temperature resistant plastics (such as polyimide), etc. It can be formed by stamping or hot pressing to ensure the uniformity and strength of the material. Its thickness is 3-10mm, depending on the structural requirements of the design;

[0115] The base layer can provide structural support for the photothermal reflector, ensuring its stability in high temperatures and severe weather.

[0116] T2. Preparation of the first reflective film layer

[0117] Use high reflectivity metal (such as silver or aluminum), usually nano-scale metal film, to enhance the reflection of infrared light 6, with a thickness of 50-150nm. It can be prepared by vacuum evaporation or magnetron sputtering, and nano-processed to improve the reflection efficiency;

[0118] The first reflective film layer mainly improves the efficiency of the photothermal system by reflecting light in the infrared band.

[0119] T3. Preparation of thermal insulation layer

[0120] Select high temperature resistant materials with low thermal conductivity, such as ceramic matrix composites (alumina-based ceramics) or aerogels, with a thickness of 1-5 mm, wherein aerogels are sprayed or thermally sprayed, and ceramic matrix composites are sintered;

[0121] The thermal insulation layer is mainly used to prevent the heat at high temperature from being transferred to the base layer, and to insulate to extend the life of the base layer.

[0122] T4. Preparation of the second reflective film layer

[0123] A multi-layer dielectric film structure is used, usually a combination of materials such as SiO2 and TiO2, to adjust the reflection and transmission spectral characteristics. The thickness of each layer is about 50-200nm, and the total thickness of the multi-layer film can reach 500-1000nm. Specifically, the physical vapor deposition (PVD) or chemical vapor deposition (CVD) method can be used to deposit the multi-layer film structure on the thermal insulation layer;

[0124] The second reflective film layer is mainly used to enhance the reflectivity of visible light and infrared light 6 and maximize the utilization of light energy.

[0125] T5. Preparation of anti-reflection layer

[0126] A low refractive index material, such as a nanolayer of magnesium fluoride (MgF2) or aluminum oxide (Al2O3), is used, with a thickness of 100-150 nm, which is usually evenly coated on the protective layer by sputtering or evaporation;

[0127] The anti-reflection layer mainly improves the transmittance and enhances the overall optical performance by reducing the reflection loss of light caused by interface refraction.

[0128] The curved photothermal reflector 3 of the present invention integrates the functions of various layers, effectively improves the reflection efficiency and durability of the photothermal reflector, and meets the requirements of the photovoltaic / photothermal top cover coupling structure.

[0129] The following is a method for preparing the back photovoltaic cell 2:

[0130] (1) When a flexible perovskite photovoltaic cell is selected as the back photovoltaic cell 2, the preparation method thereof is as follows:

[0131] a. Selection of Flexible Substrate 17

[0132] Polyimide (PI) or polyethylene terephthalate (PET) is used as the flexible substrate 17. The substrate 17 needs to be cleaned (ultrasonic water washing, acetone and isopropyl alcohol cleaning) and plasma treated to improve surface adhesion;

[0133] b. Preparation of bottom electrode 16

[0134] Depositing a layer of transparent conductive oxide (such as ITO or FTO) on the flexible substrate 17 by magnetron sputtering, and controlling the deposition thickness to be 100-200 nm to ensure conductivity and light transmittance;

[0135] c. Preparation of perovskite layer

[0136] A perovskite precursor solution is prepared, and the precursor solution is coated on the bottom electrode 16 using a slit coating process, and annealed by gradient heating (such as 70° C., 100° C., and 150° C.) to form a dense perovskite film layer;

[0137] d. Preparation of electron transport layer 14 (ETL)

[0138] PCBM, SnO2 or TiO2 were selected as electron transport materials and deposited by solution method (spin coating) or vacuum evaporation;

[0139] e. Preparation of top electrode 13

[0140] A layer of metal (such as Ag or Au) is evaporated, or Ag nanowires are deposited by magnetron sputtering as the top electrode 13 .

[0141] f. Packaging

[0142] Use UV-curable resin or flexible film for encapsulation to protect the battery from water and oxygen corrosion.

[0143] (2) When a flexible organic photovoltaic cell (OPV) is selected as the back photovoltaic cell 2, its preparation method is as follows:

[0144] a. Selection of Flexible Substrate 17

[0145] Using PET or polybutylene terephthalate (PBT) as substrate 17, the surface treatment method is the same as that of flexible perovskite photovoltaic cells;

[0146] b. Preparation of bottom electrode 16

[0147] Using ITO or graphene or flexible metal mesh (such as Ag NWs) as the bottom electrode 16;

[0148] c. Preparation of active layer

[0149] Prepare a P3HT:PCBM mixed solution (or other high-efficiency donor / acceptor material system) and apply it on the bottom electrode 16 by blade coating, spray coating or spin coating;

[0150] d. Preparation of electron / hole transport layer (ETL / HTL)

[0151] The electron transport layer 14 is selected from ZnO or TiO2, and the hole transport layer is selected from PEDOT:PSS, and both can be prepared by spraying or spin coating;

[0152] e. Preparation of top electrode 13

[0153] A thin layer of metal (such as Al or Ag) is used as the top electrode 13, with a thickness of 50-100 nm to ensure flexibility;

[0154] f. Packaging

[0155] Use flexible transparent film for packaging to avoid mechanical damage and environmental corrosion.

[0156] (3) When a flexible heterojunction silicon photovoltaic cell is selected as the back photovoltaic cell 2, the preparation method thereof is as follows:

[0157] a. Preparation of silicon wafer

[0158] Select thin crystalline silicon (thickness 50 μm) and prepare flexible silicon wafers by cutting or chemical etching. Flexible amorphous silicon can also be prepared by thermal decomposition.

[0159] b. Preparation of heterostructures

[0160] A thin film (such as silicon nitride or silicon oxide) is deposited on the surface of the silicon wafer using a chemical vapor deposition (CVD) method as a passivation layer, and then an electron or hole transport material (such as PEDOT:PSS or TiO2) is prepared by solution coating;

[0161] c. Preparation of electrodes

[0162] Use Ag or Cu thin films as electrodes, deposited by spraying or magnetron sputtering, and divided into cell areas by laser patterning to improve efficiency;

[0163] d. Packaging

[0164] Encapsulated using high temperature resistant and flexible polymer film.

[0165] (4) When a flexible quantum dot photovoltaic cell is selected as the back photovoltaic cell 2, its preparation method is as follows:

[0166] a. Preparation of ZnO nanosheet arrays grown on titanium mesh

[0167] Clean the titanium mesh: Place the cut titanium mesh in a beaker filled with concentrated hydrochloric acid, ultrasonically clean it for 10 minutes, then clean it twice with deionized water and alcohol, and finally dry it in nitrogen at room temperature;

[0168] Preparation and application of seed solution: 0.02M zinc acetate and 0.02M lithium hydroxide were mixed and stirred to dissolve to obtain ZnO seed solution; the cleaned titanium mesh was gently immersed in the seed solution with tweezers, and after swinging for about 1 minute, it was taken out, the surface liquid was shaken off, and the remaining water was blown off in nitrogen, and then annealed in a sintering furnace at 350°C for 15 minutes;

[0169] Growth of ZnO nanosheet array structure: 0.2M zinc nitrate and 1M urea were dissolved in deionized water to obtain ZnO growth solution. The titanium mesh with the seed layer was placed in a reaction kettle at an angle, and the growth solution was poured in to completely immerse the titanium mesh. The titanium mesh was heated at 90°C in a drying oven for 12 hours, and then rinsed with deionized water, dried at room temperature, and annealed at 450°C for 1 hour.

[0170] b. Preparation of ZnO / ZnSe / CdSe Electrode

[0171] Preparation of ZnO / ZnSe electrodes: The titanium mesh with ZnO nanosheets was immersed in a Se solution containing 12 mM selenium powder and 24 mM sodium borohydride. 2- Ionic aqueous solution, kept at 55°C for 30 min;

[0172] Preparation of ZnO / ZnSe / CdSe electrodes: The ZnO / ZnSe electrodes were placed in a solution containing 80 mM cadmium nitrate and kept at 55°C for 15 min to 4 h to obtain CdSe nanolayers of different thicknesses, and then washed with deionized water and dried in air at 60°C.

[0173] Preparation of polysulfide solid electrolyte: Dissolve 1M sodium sulfide, 1M sulfur and 0.1M sodium hydroxide in deionized water and stir at 80°C for 2h to obtain a transparent orange-red liquid, which is the electrolyte;

[0174] c. Preparation of Cu2S counter electrode

[0175] A 0.5 mm thick copper sheet was cut into small pieces, polished on sandpaper to remove the surface oxide layer, and then placed in a concentrated hydrochloric acid solution at 70°C for 10 minutes. After being taken out, the hydrochloric acid was rinsed with deionized water, and then the polysulfide solid electrolyte was evenly dropped onto the surface of the cleaned copper sheet with a dropper until the surface of the copper sheet turned uniformly black.

[0176] d. Battery packaging

[0177] Use a puncher to make a hole with a size of 0.25 cm on the 60 μm thick packaging film. 2 The photoanode is made of a small hole, and it is glued to both sides of the photoanode and dried. A flexible light-transmitting film and a Cu2S counter electrode are placed on the upper and lower sides of the photoanode respectively, and finally a polysulfide solid electrolyte is dripped into the gap between the two electrodes.

[0178] (5) When a monocrystalline silicon cell (rigid) is selected as the back photovoltaic cell 2, a high-efficiency monocrystalline silicon photovoltaic cell can be prepared by using high-purity silicon ingots through slicing, surface treatment, doping and other steps. The preparation method is as follows:

[0179] a. Silicon wafer cutting

[0180] Cut silicon wafers with a thickness of about 150-200μm from high-purity single crystal silicon ingots. Diamond wire cutting can be used to ensure slicing accuracy and surface flatness.

[0181] b. Surface cleaning and texturing

[0182] Use chemical solutions (such as KOH or HF) to remove the oxide layer and impurities on the surface of the silicon wafer, and use alkaline or acidic solutions to form pyramid-shaped microstructures to reduce reflectivity;

[0183] c. Diffusion doping

[0184] Diffusion of phosphorus or boron in a high-temperature furnace to form a pn junction and control the diffusion depth and concentration to optimize battery performance;

[0185] d. Surface passivation

[0186] By depositing silicon nitride (SiN x :H) or aluminum oxide (Al2O3) film for passivation to reduce surface recombination loss;

[0187] e. Electrode printing and sintering

[0188] Silver paste (positive electrode) and aluminum paste (back electrode) are printed using screen printing technology and sintered at a high temperature of 800-900°C to form an ohmic contact.

[0189] (6) When a polycrystalline silicon cell (rigid) is selected as the back photovoltaic cell 2, a polycrystalline silicon ingot is prepared by an ingot casting method, and a polycrystalline silicon photovoltaic cell is prepared by a process similar to that of single crystal silicon.

[0190] (7) When a perovskite photovoltaic cell (rigid) is selected as the back photovoltaic cell 2, it can be prepared by a solution treatment process based on an organic-inorganic hybrid perovskite material (such as MAPbI3 or CsPbBr3), and the preparation method thereof is as follows:

[0191] a. Cleaning of substrate 17

[0192] Depositing a conductive layer (such as ITO) on a glass or rigid substrate 17;

[0193] b. Preparation of perovskite layer

[0194] Depositing a perovskite precursor solution with a band gap range of 1.1 eV-2.3 eV by spin coating or spraying the solution, and promoting perovskite crystal growth by thermal annealing;

[0195] c. Interface layer deposition

[0196] Sequentially deposit an electron transport layer 14 (such as TiO2 or SnO2) and a hole transport layer (such as Spiro-OMeTAD or PEDOT:PSS);

[0197] d. Metal electrode coating

[0198] Depositing metal electrodes (such as Au or Ag) using vacuum evaporation or sputtering;

[0199] e. Packaging

[0200] Encapsulate with transparent epoxy resin or glass cover to improve stability.

[0201] (8) When a copper indium gallium selenide (CIGS) cell (rigid) is selected as the back photovoltaic cell 2, the preparation method thereof is as follows:

[0202] a. Base 17 selection

[0203] Depositing a Mo back electrode on a rigid substrate 17 (such as glass or metal sheet);

[0204] b. CIGS thin film deposition

[0205] Deposition of Cu, In, Ga, and Se elements by co-evaporation or sputtering techniques;

[0206] c. Buffer layer deposition

[0207] Depositing a CdS buffer layer by a chemical bath method;

[0208] d. Transparent conductive layer coating

[0209] Depositing ZnO or ITO as a transparent conductive layer;

[0210] e. Electrode preparation and packaging

[0211] The battery area is depicted and electrodes are added for packaging and protection. The packaging method is similar to the previous one.

[0212] The preparation methods of different types of rigid photovoltaic cells vary depending on material properties and application requirements. The specific selection needs to take into account efficiency, cost, process complexity and application scenarios.

[0213] As for the improvements to the back photovoltaic cell 2 of the present invention (the introduction of the thermal conductive layer 8, the light capture layer 9, the low reflection and transmittance enhancement layer 10 and the diffuse reflection and scattering layer 11), the corresponding improved layers are prepared on the surface or in the middle layer after the above-mentioned basic components are prepared. The specific preparation method can refer to the above content.

[0214] The preparation method of the photovoltaic / photothermal / photovoltaic top cover type stacked structure in this embodiment is as follows:

[0215] The rigid semi-transparent photovoltaic cell 1 is mounted above the curved photothermal reflector 3 through a bracket 4. The bracket 4 is made of UV-resistant metal or high-strength polymer material and is fixed on the frame of the curved photothermal reflector 3 to ensure stability.

[0216] When the back photovoltaic cell 2 is a flexible photovoltaic cell, the specific method of attaching the back photovoltaic cell 2 to the back of the curved photothermal reflector 3 is as follows:

[0217] a. Pretreatment of the back side of the curved photothermal reflector 3

[0218] Ensure that the back side of the curved photothermal reflector 3 is clean, flat and has good adhesion performance;

[0219] Surface cleaning: Use a dust-free cloth dipped in anhydrous ethanol or isopropyl alcohol to clean the back of the curved light-heat reflector 3 to remove dust, oil and other impurities. If there is an oxide layer or uneven area on the surface, use fine sandpaper (such as P1000) to gently polish it.

[0220] Surface activation: A plasma processor or UV-Ozone equipment can be used to activate the back surface of the back photovoltaic cell 2 to improve its adhesion. If there is no equipment, a primer containing an activator can be used to paint the back surface of the back photovoltaic cell 2.

[0221] Surface drying: Allow the treated surface to dry naturally at room temperature, or use hot air to dry (temperature not exceeding 80°C).

[0222] b. Preparation of back photovoltaic cell 2

[0223] Ensure that the back photovoltaic cell 2 is in close contact with the back of the curved photothermal reflector 3 .

[0224] Size cutting: The shape of the flexible photovoltaic cell is designed according to the size and curvature of the curved photothermal reflector 3, and is cut precisely.

[0225] Check the back electrode: Make sure that the back electrode of the back photovoltaic cell 2 is flat and has no scratches or peeling.

[0226] Clean the surface of the photovoltaic cell 2 on the back: Use a soft, dust-free cloth to clean the adhesive surface of the cell, making sure there is no dust or oil.

[0227] c. Adhesive selection and application

[0228] A suitable adhesive is used to ensure long-term adhesion between the rear photovoltaic cell 2 and the curved photothermal reflector 3 while meeting the requirements of thermal conductivity, anti-aging and flexibility.

[0229] Adhesive selection: Use organic silicone with high thermal conductivity (such as Dow Corning 3145) or epoxy resin adhesive (such as 3M 2216).

[0230] Uniform glue coating: Apply a thin and uniform layer of adhesive (thickness of 0.1-0.3 mm) on the back of the curved light-heat reflector 3, and use a scraper or automatic glue coating equipment to ensure that the thickness of the glue layer is uniform.

[0231] Eliminate bubbles: After coating, use vacuum degassing equipment or a scraper to gently remove bubbles.

[0232] d. Pasting of the back photovoltaic cell 2

[0233] Alignment and positioning: Align the back photovoltaic cell 2 with the position marked on the back of the curved photothermal reflector 3, ensure that the edges are aligned, and slowly fit from one side to the other to avoid bubbles.

[0234] Pressurized bonding: Use a rubber roller or a flat tool to apply gentle pressure to ensure that the back photovoltaic cell 2 and the surface of the curved photothermal reflector 3 are completely in contact with each other. For large-area bonding, negative pressure adsorption equipment can be used for pressure application.

[0235] e. Curing process

[0236] The curing process allows the adhesive to reach its maximum adhesion strength.

[0237] Room temperature curing: For low temperature adhesives, place the pasted components at room temperature for 24-48 hours.

[0238] Heat curing: If using epoxy resin or high temperature curing silicone, the component can be placed in a 60-80℃ oven for 2-4 hours.

[0239] Cooling and inspection: After curing, the components are cooled naturally to room temperature and the adhesion is checked to ensure there is no warping, bubbles or peeling.

[0240] f. Packaging and protection

[0241] Improve the durability and environmental adaptability of photovoltaic modules.

[0242] Edge sealing: Apply waterproof sealant (such as silicone sealant) to the joint between the back photovoltaic cell 2 and the curved photothermal reflector 3 to prevent water vapor from penetrating.

[0243] Surface coating protective layer: If enhanced weather resistance is required, a transparent protective film (such as ETFE) can be added to the outer layer of the flexible photovoltaic cell.

[0244] When the back photovoltaic cell 2 is a rigid photovoltaic cell, the back photovoltaic cell 2 can be fixed below the curved photothermal reflector 3 by gluing, hinges, snaps, etc., including a single back photovoltaic cell in a horizontal direction, a single back photovoltaic cell in an oblique direction, multiple back photovoltaic cells in an oblique direction, multiple back photovoltaic cells in a horizontal and oblique direction, etc. The selection and the parameters such as the angle of the installation components can be determined according to the light intensity and light angle in different regions.

[0245] The present invention further verifies the performance advantages of the above-mentioned most preferred photovoltaic / photothermal / photovoltaic stacked structure through experimental tests and simulation calculations. Studies have shown that the photovoltaic / photothermal / photovoltaic stacked structure of the present invention has good performance under typical solar radiation conditions (light intensity of 1000W / m 2, standard AM1.5 spectrum) can achieve a total energy conversion efficiency of 45%-50%, which is 10%-20% higher than the average efficiency of traditional split photovoltaic or solar thermal systems (25%-35%). Among them, the photoelectric conversion efficiency of the upper rigid semi-transparent photovoltaic cell 1 for ultraviolet light and visible light can reach 15%-20%.

[0246] In addition, the utilization rate of ambient light and ground reflected light of the back photovoltaic cell 2 is increased by 20%-30%. Combined with the design of the nanostructure light capture layer 9, the light absorption capacity of the back photovoltaic cell 2 is increased by 10%-15% compared with ordinary cells without light capture layer 9, and the power generation efficiency is increased by about 5%-8%. Experimental data show that when the ambient light intensity is 200W / m 2 Under low light conditions, the additional power generation of the back photovoltaic cell 2 accounts for 8%-10% of the total power generation of the system, significantly enhancing the low light performance of the overall system.

[0247] In terms of thermal management, after adopting the design of thermal conductive layer 8, the operating temperature of photovoltaic cells is reduced by 15-20°C compared with the traditional design. According to the results of accelerated life test, the temperature reduction effectively extends the service life of photovoltaic cells, and the fatigue life can be increased by 25%-30%. For example, when working continuously under high temperature conditions of 70°C, the efficiency of ordinary photovoltaic cells will decrease by about 5% due to thermal attenuation, while the efficiency of the photovoltaic cells of the present invention will only decrease by 2%.

[0248] In summary, the present invention realizes the efficient and comprehensive utilization of solar energy through structural innovation and performance optimization, and significantly improves the system efficiency, light absorption capacity and battery life, showing superior technical indicators and economic benefits, and is of great promotion value.

[0249] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A photovoltaic / solar thermal / photovoltaic top cover type stacked structure, characterized in that: It comprises a rigid semi-transparent photovoltaic cell (1), a curved photothermal reflector (3) and a back photovoltaic cell (2) which are arranged in sequence from top to bottom, wherein the back photovoltaic cell (2) comprises a flexible photovoltaic cell and a rigid photovoltaic cell.

2. The photovoltaic / solar thermal / photovoltaic top cover type stacked structure according to claim 1, characterized in that: A heat-conducting layer (8) is provided on the side of the back photovoltaic cell (2) close to the curved light-heat reflector (3), and a light-capturing layer (9) is provided on the inside of the back photovoltaic cell (2) and / or on the outer surface of the side away from the curved light-heat reflector (3).

3. The photovoltaic / solar thermal / photovoltaic top cover type stacked structure according to claim 2, characterized in that: The outer surface of the back photovoltaic cell (2) on the side away from the curved light-heat reflector (3) is also provided with a low-reflection anti-reflection layer (10) and a diffuse reflection scattering layer (11), wherein the low-reflection anti-reflection layer (10) is close to the back photovoltaic cell (2) or the light capture layer (9).

4. The photovoltaic / solar thermal / photovoltaic top cover type stacked structure according to claim 2, characterized in that: The heat-conducting layer (8) is a graphene film or an aluminum oxide nanosheet, and the heat-conducting layer (8) is bonded to the back surface of the back photovoltaic cell (2) via a heat-conducting adhesive.

5. The photovoltaic / solar thermal / photovoltaic top cover type stacked structure according to claim 2, characterized in that: The light capture layer (9) is arranged on the outer surface of the back photovoltaic cell (2) on a side away from the curved photothermal reflector (3); the light capture layer (9) is a periodic nanocolumn, a nanohole array or a randomly distributed nanoparticle structure; and the material of the light capture layer (9) is indium tin oxide or zinc oxide.

6. The photovoltaic / solar thermal / photovoltaic top cover type stacked structure according to claim 2, characterized in that: The light capture layer (9) is arranged on the light absorption layer (15) of the back photovoltaic cell (2), and the light capture layer (9) is a nanostructure induced by femtosecond laser in the light absorption layer (15) of the back photovoltaic cell (2).

7. The photovoltaic / solar thermal / photovoltaic top cover type stacked structure according to claim 2, characterized in that: The light capture layer (9) is arranged on the electron transport layer (14) of the back photovoltaic cell (2), and the light capture layer (9) is a light trapping nanostructure.

8. The photovoltaic / solar thermal / photovoltaic top cover type stacked structure according to claim 2, characterized in that: The light capture layer (9) is arranged between the glass in the back photovoltaic cell (2) and the top surface packaging layer (12), and the light capture layer (9) is a nanometer high-transmittance color film layer.

9. The photovoltaic / solar thermal / photovoltaic top cover type stacked structure according to claim 3, characterized in that: The low-reflection and anti-reflection layer (10) is a Bragg reflector formed by alternately depositing a high-refractive index material and a low-refractive index material; The material of the diffuse reflection and scattering layer (11) is aluminum oxide or titanium dioxide nanoparticles.

10. The method for preparing the photovoltaic / photothermal / photovoltaic top cover type stacked structure according to any one of claims 1 to 9, characterized in that: The following steps are involved: The rigid semi-transparent photovoltaic cell (1) is mounted above the curved photothermal reflector (3) via a bracket (4), and the back photovoltaic cell (2) is arranged below the curved photothermal reflector (3) to obtain a photovoltaic / photothermal / photovoltaic top cover type stacked structure; Wherein, when the back photovoltaic cell (2) is a flexible photovoltaic cell, the back photovoltaic cell (2) is adhered to the back side of the curved photothermal reflector (3); When the back photovoltaic cell (2) is a rigid photovoltaic cell, the back photovoltaic cell (2) is fixed below the curved photothermal reflector (3) by gluing, hinges or buckles, and the fixed angle and position are determined according to different lighting requirements.

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