Double-sided flexible solar cell

Abstract

The utility model discloses a double-sided flexible solar cell. The solar cell sequentially comprises a flexible semitransparent photovoltaic cell, a curved surface reflector and a flexible photovoltaic cell from top to bottom, wherein the flexible semitransparent photovoltaic cell sequentially comprises a packaging layer, a second transparent electrode, an electron transport layer, a light absorption layer, a hole transport layer and a first transparent electrode from top to bottom; the curved-surface reflecting mirror comprises a curved-surface substrate, a high-reflectivity metal layer and a weather-resistant protective layer from top to bottom in sequence. The flexible photovoltaic cell is one of a perovskite solar cell, an organic solar cell, a CIGS solar cell, a dye-sensitized solar cell, a monocrystalline silicon solar cell, an amorphous silicon solar cell, a cadmium telluride thin film solar cell and a quantum dot solar cell. The double-sided flexible solar cell provided by the utility model can solve a series of problems of low solar spectrum utilization rate, insufficient collaboration of photovoltaic and photo-thermal systems, poor adaptability of complex curved surfaces and the like of the traditional flexible solar cell.

Description

Technical Field

[0001] This utility model relates to the field of flexible solar cell technology, and in particular to a bifacial flexible solar cell. Background Technology

[0002] With the continued growth of global energy demand and the accelerated pursuit of carbon neutrality, the research and application of clean energy technologies have become a global focus. Among numerous renewable energy sources, solar energy, with its abundance and environmental friendliness, has become a core area of ​​energy development. Photovoltaic power generation and solar thermal utilization, as the two main ways of utilizing solar energy, each have their own advantages and limitations in practical applications. Photovoltaic power generation directly converts sunlight into electricity, featuring high efficiency and flexible application, but its utilization range of the solar spectrum is limited, especially the energy of infrared light cannot be fully converted. In addition, traditional photovoltaic cells have low utilization efficiency for scattered light and ground-reflected light, and their performance is significantly limited in high-latitude, cloudy areas, or complex environments. Solar thermal systems are mainly used to collect infrared energy from sunlight and generate electricity or store energy through thermal energy conversion, but their system design is complex, and their ability to utilize ultraviolet and visible light is weak, resulting in insufficient overall utilization efficiency of the solar spectrum.

[0003] Traditional photovoltaic (PV) and solar thermal (CSP) systems are typically deployed independently. While they can be functionally complementary, their high land consumption, construction costs, and integration difficulties limit their economic benefits in large-scale applications. To address these issues, solar energy technology has been increasingly developing towards integration and flexibility in recent years. On one hand, by optimizing spectral selectivity techniques, different wavelengths of sunlight can be precisely separated and utilized, enabling the synergistic operation of PV and CSP. On the other hand, the development of flexible photovoltaic materials has provided new possibilities for integrated PV-CSP applications with complex curved surfaces, particularly important in scenarios such as parabolic trough and dish CSP plants that require adaptation to complex reflective surfaces.

[0004] Despite significant progress in photovoltaic and solar thermal technologies, the following issues remain regarding spectral utilization efficiency and system integration: 1. Insufficient synergy between existing photovoltaic and solar thermal systems: Currently, photovoltaic power generation and solar thermal collection systems are mostly designed independently, making it difficult to achieve comprehensive and efficient utilization of the solar spectrum, resulting in low energy utilization efficiency; 2. Low utilization rate of indirect light: Traditional photovoltaic systems mainly rely on direct sunlight for power generation, with limited utilization of scattered light, ground-reflected light, and ambient light, especially under non-ideal climatic conditions (such as cloudy environments) where efficiency decreases; 3. Limitations of the single function of solar thermal reflectors: Most existing solar thermal reflectors are only used for reflection. 4. Photovoltaic cells have poor adaptability to complex curved surface structures. The rigid structure of traditional photovoltaic cells makes it difficult to adapt to the curved shape of trough or dish reflectors, resulting in high installation complexity, incomplete coverage, and affecting system performance. 5. The heat dissipation performance of photovoltaic and solar thermal systems is insufficient. Existing photovoltaic-solar thermal hybrid systems are prone to efficiency decline or even equipment damage under high-intensity radiation due to heat accumulation. 6. The utilization efficiency of trough and dish solar thermal power plant systems is limited. In the design of traditional trough and dish solar thermal power plants, the energy utilization mode is singular, and the power generation efficiency and heat collection efficiency have not reached the optimal level.

[0005] Against this background, this utility model is proposed. Utility Model Content

[0006] The purpose of this invention is to provide a bifacial flexible solar cell that can solve a series of problems of traditional flexible solar cells, such as low solar spectrum utilization, insufficient synergy between photovoltaic and photothermal systems, and poor adaptability to complex curved surfaces.

[0007] This invention provides a bifacial flexible solar cell, comprising, from top to bottom, a flexible semi-transparent photovoltaic cell, a curved reflector, and a flexible photovoltaic cell. The flexible semi-transparent photovoltaic cell comprises, from top to bottom, an encapsulation layer, a second transparent electrode, an electron transport layer, a light absorption layer, a hole transport layer, and a first transparent electrode; wherein the positions of the electron transport layer and the hole transport layer can be interchanged.

[0008] The curved reflector comprises, from top to bottom, a curved substrate, a high-reflectivity metal layer, and a weather-resistant protective layer;

[0009] The flexible photovoltaic cell is one of the following: perovskite solar cell, organic solar cell, copper indium gallium selenide solar cell, dye-sensitized solar cell, monocrystalline silicon solar cell, amorphous silicon solar cell, cadmium telluride thin-film solar cell, and quantum dot solar cell.

[0010] Furthermore, the curved substrate of the curved reflector is made of transparent flexible glass, the high reflectivity metal layer is made of silver or aluminum, and the weather-resistant protective layer is made of one of aluminum oxide, silicon dioxide, titanium dioxide, or polymer.

[0011] Furthermore, the flexible photovoltaic cell is a perovskite solar cell, comprising, from top to bottom, a first transparent electrode, a hole transport layer, a light absorption layer, an electron transport layer, a second transparent electrode, and an encapsulation layer; wherein the positions of the electron transport layer and the hole transport layer of the flexible photovoltaic cell can be interchanged; the material band gap of the light absorption layer of the flexible semi-transparent photovoltaic cell is 1.65eV-2.30eV, and the material band gap of the light absorption layer of the flexible photovoltaic cell is 1.40eV-2.30eV.

[0012] Furthermore, both the flexible semi-transparent photovoltaic cell and the flexible photovoltaic cell are provided with a flexible substrate, which is located on the side of the first transparent electrode away from the hole transport layer; the flexible substrate of the flexible semi-transparent photovoltaic cell is made of a transparent material.

[0013] Furthermore, both the upper and lower surfaces of the curved reflector are provided with adhesive layers.

[0014] Furthermore, the lower surface of the curved reflector is provided with a thin glass sheet, the thickness of which is 1mm-2cm.

[0015] Furthermore, the light-absorbing layer of the flexible photovoltaic cell has a microstructure on its surface, the flexible substrate of the flexible photovoltaic cell is made of a transparent material, a metal reflective layer is provided on the side of the flexible substrate away from the first transparent electrode, and a titanium dioxide protective layer is provided on the surface of the metal reflective layer away from the flexible substrate.

[0016] Furthermore, the upper surface of the curved reflector is provided with a spectrally selective coating, which includes an interference film and an infrared transmission film from top to bottom; the interference film includes multiple layers of high refractive index material and low refractive index material layer arranged alternately in sequence, the high refractive index material layer is made of titanium dioxide, and the low refractive index material layer is made of silicon dioxide or magnesium fluoride.

[0017] Furthermore, the thickness of the infrared transmitting film is 100-300 nm, the thickness of the interference film is 300-500 nm, the thickness of the high refractive index material layer is 30-100 nm, and the thickness of the low refractive index material layer is 50-200 nm.

[0018] Furthermore, the lower surface of the curved substrate of the curved reflector is provided with a heat-conducting channel or embedded structure, the heat-conducting channel or embedded structure is provided with a heat-conducting material, and the contact surface between the heat-conducting material and the curved substrate is provided with heat-conducting paste; the upper surface of the curved substrate is provided with a spectrally selective coating, and the upper surface of the spectrally selective coating is provided with a microstructure.

[0019] In summary, compared with the prior art, this utility model has the following advantages:

[0020] This invention integrates a flexible semi-transparent photovoltaic cell, a curved reflector, and a flexible photovoltaic cell into a single unit through a unique three-layer structure design, achieving efficient utilization of the solar spectrum across different wavelengths. The upper flexible photovoltaic cell primarily absorbs ultraviolet and visible light, while allowing infrared light to pass through to the curved reflector in the middle layer for heat collection; the lower flexible photovoltaic cell utilizes ground-reflected light and ambient scattered light to generate electricity.

[0021] The bifacial flexible solar cell provided by this invention significantly improves the synergistic efficiency of photovoltaic and solar thermal systems, increases thermal energy conversion efficiency, and significantly enhances the ability to capture indirect light, effectively making up for the shortcomings of existing photovoltaic technology in low utilization of scattered light and ground reflected light. Both the upper and lower flexible cells can adapt to the complex curved surface reflector structure of trough and dish solar thermal power plants, further enhancing the adaptability of the flexible cells. Attached Figure Description

[0022] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the structure of the double-sided flexible solar cell in Embodiment 1 of this utility model;

[0024] Figure 2 This is a cross-sectional view of the flexible semi-transparent photovoltaic cell in Embodiment 1 of this utility model;

[0025] Figure 3 This is a cross-sectional view of the flexible photovoltaic cell in Embodiment 1 of this utility model;

[0026] Figure 4 This is a cross-sectional view of the curved reflector in Embodiment 1 of this utility model;

[0027] Figure 5 This is a cross-sectional view of the bifacial flexible solar cell in Embodiment 2 of this utility model;

[0028] Figure 6 This is a cross-sectional view of the curved reflector in Embodiment 3 of this utility model;

[0029] Figure 7 This is a cross-sectional view of the flexible photovoltaic cell in Embodiment 4 of this utility model.

[0030] Figure 8 This is a cross-sectional view of the curved reflector in Embodiment 5 of this utility model;

[0031] Figure 9 This is a schematic diagram illustrating the application of the bifacial flexible solar cell in a solar thermal power plant.

[0032] Note: Among them Figure 2-8 The plan view is only intended to clearly show the positional relationship between the curved reflector, the flexible semi-transparent photovoltaic cell, or the layers of the flexible photovoltaic cell. It does not represent that the actual shape of the object is planar. The actual shape of the object is the arc shape of conventional flexible cells in this field.

[0033] Explanation of reference numerals in the attached figures: 1-Flexible semi-transparent photovoltaic cell; 101-Flexible substrate; 102-First transparent electrode; 103-Hole transport layer; 104-Light absorption layer; 105-Electron transport layer; 106-Second transparent electrode; 107-Encapsulation layer; 2-Curved reflector; 201-Curved substrate; 202-High reflectivity metal layer; 203-Weather-resistant protective layer; 204-Infrared transmission film; 205-Interference film; 206-Heat conduction channel; 207-Heat conduction material; 208-Spectral selective coating; 209-Thin glass sheet; 210-Adhesive layer; 3-Flexible photovoltaic cell; 301-Metal reflective layer; 302-Titanium dioxide protective layer; 4-Support; 5-Collector. Detailed Implementation

[0034] The technical solution of this utility model will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0035] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0036] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0037] Example 1

[0038] A type of bifacial flexible solar cell, such as Figure 1 As shown, from top to bottom, it includes a flexible semi-transparent photovoltaic cell 1, a curved reflector 2, and a flexible photovoltaic cell 3.

[0039] The flexible semi-transparent photovoltaic cell 1 includes, from top to bottom, an encapsulation layer 107, a second transparent electrode 106, an electron transport layer 105, a light absorption layer 104, a hole transport layer 103, and a first transparent electrode 102.

[0040] The curved reflector 2 includes, from top to bottom, a curved substrate 201, a high reflectivity metal layer 202, and a weather-resistant protective layer 203. The upper surface of the curved substrate 201 and the lower surface of the weather-resistant protective layer 203 are provided with adhesive layers 210 for bonding and fixing to the flexible semi-transparent photovoltaic cell 1 and the flexible photovoltaic cell 3.

[0041] The flexible photovoltaic cell 3 is a perovskite solar cell, which includes, from top to bottom, a first transparent electrode 102, a hole transport layer 103, a light absorption layer 104, an electron transport layer 105, a second transparent electrode 106, and an encapsulation layer 107.

[0042] In this embodiment, both the flexible semi-transparent photovoltaic cell 1 and the flexible photovoltaic cell 2 are provided with a flexible substrate 101. The positions of the electron transport layer 105 and the hole transport layer 103 of the flexible semi-transparent photovoltaic cell 1 and the flexible photovoltaic cell 3 can be interchanged.

[0043] The specific process for fabricating the aforementioned bifacial flexible solar cell is as follows:

[0044] S1. Preparation of curved surface mirror 2

[0045] The curved reflector 2 combines a high-reflectivity metal layer 202 and a weather-resistant protective layer 203 to improve the reflection of unabsorbed light. The curved substrate 201 can be made of high-transparency flexible glass with a thickness of 0.5-5 cm. The curved substrate 201 is cleaned and polished to remove oxides and impurities, ensuring coating adhesion. A thin film of silver or aluminum is uniformly deposited on the lower surface of the finely polished curved substrate 201 using vacuum evaporation or magnetron sputtering to obtain the high-reflectivity metal layer 202. Subsequently, a weather-resistant protective layer 203 (made of SiO2 or TiO2) is prepared on the lower surface of the high-reflectivity metal layer 202 using chemical vapor deposition (CVD) or spin coating to enhance its corrosion resistance and durability. The thickness of the high-reflectivity metal layer 202 can be 50-500 nm, more preferably 100-200 nm; the thickness of the weather-resistant protective layer 203 can be 30-300 nm, more preferably 80-100 nm. The structure of the prepared curved mirror is as follows: Figure 4 As shown.

[0046] S2. Assemble bifacial flexible solar cells

[0047] S21. Preparation of flexible semi-transparent photovoltaic cells 1

[0048] A. Preparation of flexible substrate 101

[0049] Flexible substrates play a crucial role in the photovoltaic field, primarily serving to support photovoltaic layers. To better fulfill their function, these substrates require excellent light transmittance and outstanding mechanical flexibility. The fabrication process employs techniques such as solution casting, hot pressing, electrospinning, and melt extrusion. Melt extrusion involves first heating one of the following materials to a molten state: polyethylene terephthalate (PET), polyimide (PI), or polyvinyl naphthalene ester (PEN). In this state, the material exhibits good fluidity, facilitating subsequent processing. Next, the molten material is extruded into a film. To further enhance the film's mechanical properties, it undergoes stretching. Stretching makes the film's molecular structure more ordered, thereby improving its strength and toughness. Subsequently, to enhance the adhesion between the film surface and subsequent coatings, the film surface is treated using plasma cleaning. Plasma cleaning removes impurities and contaminants from the film surface while activating surface molecules, increasing surface energy, and thus enhancing the bonding force with subsequent coatings.

[0050] B. Fabrication of the first transparent electrode 102

[0051] A first transparent electrode 102 is deposited on a flexible substrate 101 to collect charge carriers in the photovoltaic cell while ensuring high light transmittance. One of the following materials, indium tin oxide, aluminum zinc oxide, or fluorine-doped tin oxide, is deposited on the flexible substrate 101 using magnetron sputtering. To ensure the uniformity of the first transparent electrode 102, a multi-target spin sputtering process can be used, and finally, heat treatment is applied to enhance the conductivity and light transmittance of the thin film.

[0052] C. Preparation of hole transport layer 103

[0053] A hole transport layer 103 is deposited on the first transparent electrode 102 to effectively transport holes generated by the light absorption layer 104 and prevent electrons from being transported in reverse. The hole transport material (either poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate or poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine]) is deposited on the first transparent electrode 102 by solution spin coating, and then annealed at 80-120°C to remove the solvent and enhance the stability of the layer.

[0054] D. Preparation of light-absorbing layer 104

[0055] The light-absorbing layer 104, deposited on the hole transport layer 103, is the core component of the photovoltaic cell, responsible for converting sunlight into electron-hole pairs. The material band gap of the light-absorbing layer 104 is 1.65 eV-2.30 eV, with an optimal band gap of 1.70 eV. Perovskite and organic quantum dot precursor solutions are coated onto the hole transport layer 103 using methods such as solution spin coating and slot coating, forming a uniform perovskite thin film through wet chemical deposition. Then, annealing at 100-150℃ forms a well-crystallized perovskite light-absorbing layer 104.

[0056] E. Fabrication of electron transport layer 105

[0057] An electron transport layer 105 is deposited on the light absorption layer 104 to conduct electrons generated in the light absorption layer 104 to the electrode. [6,6]-phenyl-C is applied via solution spin coating or spray coating processes. 61 Methyl butyrate or nanocrystalline TiO2 solution is deposited on the light-absorbing layer 104 and subjected to low-temperature annealing at 70-120℃ to enhance the crystallinity and electron transport properties of the layer.

[0058] F. Fabrication of the second transparent electrode 106

[0059] A second transparent electrode 106 is deposited on the electron transport layer 105 to collect electrons and conduct current while maintaining light transmittance. One of indium tin oxide, aluminum zinc oxide, silver nanowires, or graphene is uniformly deposited on the electron transport layer 105 using magnetron sputtering or thermal evaporation. For graphene or silver nanowires, spin coating or spray coating methods are typically used, combined with a flexible substrate 101 for transfer processing.

[0060] G. Preparation of the encapsulation layer 107

[0061] The encapsulation layer 107 protects the battery from moisture and oxygen in the environment, extending its lifespan. Using a lamination process, the encapsulation material (one of ethylene-vinyl acetate, polyvinylidene fluoride, butyl rubber, or silicone) is hot-pressed in a vacuum or nitrogen atmosphere to tightly wrap the entire battery structure, preventing environmental damage and resulting in a flexible, semi-transparent photovoltaic cell 1, with the structure shown below. Figure 2 As shown.

[0062] S22. Fabrication of flexible photovoltaic cells 3

[0063] The structure of the flexible photovoltaic cell 3 is as follows Figure 3As shown, its fabrication process is the same as that of the flexible semi-transparent photovoltaic cell 1. The difference lies in the band gap of the perovskite light-absorbing layer 104. The band gap of the flexible photovoltaic cell 3 is 1.40 eV-2.30 eV, with an optimal value of 1.5 eV. Another difference is that the flexible substrate 101 of the flexible photovoltaic cell 3 can be either transparent or opaque, with no requirement for transparency.

[0064] S23. Assembly: Attach the prepared flexible semi-transparent photovoltaic cell 1 and flexible photovoltaic cell 3 to the curved mirror 2.

[0065] S231. Surface cleaning treatment: First, rinse the upper and lower surfaces of the curved mirror 2 with industrial ethanol, isopropanol and deionized water in sequence, and finally blow dry with nitrogen or bake dry.

[0066] S232. Adhesive Layer Coating: Apply adhesive (using high-performance silicone adhesive or UV-curable adhesive) evenly to the upper and lower surfaces of the curved reflector 2 to ensure the battery can be firmly adhered to the mirror surface. The adhesive coating thickness should be uniform, generally controlled between 100-200 μm, to ensure sufficient adhesion and battery flatness. After coating, wait a few minutes to allow the adhesive layer 210 to dry slightly to a semi-cured state for subsequent bonding operations.

[0067] S234. Battery Positioning: Place the prepared flexible semi-transparent photovoltaic cell 1 on the adhesive layer 210 on the upper surface (inner side of the bending direction) of the curved reflector 2, and place the flexible photovoltaic cell 3 on the adhesive layer 210 on the lower surface (outer side of the bending direction) of the curved reflector 2. Start bonding from one side and gradually adhere the cells, ensuring no air bubbles exist between the cells and the surface of the curved reflector 2. During the bonding process, rollers or other flexible tools can be used for light pressure to ensure the photovoltaic cells are tightly bonded to the curved surface and remain uniform.

[0068] S235. Compaction and Curing Treatment: The entire system is compacted using a vacuum compaction system and a roller press to maintain uniform pressure and ensure complete and firm adhesion between the battery and the curved reflector 2. The compaction time is generally 30 minutes to 1 hour to ensure full adhesion. If UV-curing adhesive is used, the battery surface can be irradiated with a UV light source to accelerate the curing of the adhesive. The final result is a double-sided flexible solar cell, the structure of which is as follows: Figure 1 As shown.

[0069] The fabrication processes of the flexible semi-transparent photovoltaic cell 1, the curved reflector 2, and the flexible photovoltaic cell 3 in this invention are all conventional techniques in the field.

[0070] Example 2

[0071] A type of bifacial flexible solar cell, such as Figure 5As shown, from top to bottom, it includes: flexible semi-transparent photovoltaic cell 1, curved reflector 2, and flexible photovoltaic cell 3.

[0072] The flexible semi-transparent photovoltaic cell 1 includes, from top to bottom, an encapsulation layer 107, a second transparent electrode 106, an electron transport layer 105, a light absorption layer 104, a hole transport layer 103, and a first transparent electrode 102.

[0073] The curved reflector 2 comprises, from top to bottom, a curved substrate 201, a high-reflectivity metal layer 202, and a weather-resistant protective layer 203. A thin glass sheet 209 with a thickness of 1 mm to 2 cm is disposed on the lower surface of the weather-resistant protective layer 203.

[0074] The flexible photovoltaic cell 3 includes, from top to bottom, a first transparent electrode 102, a hole transport layer 103, a light absorption layer 104, an electron transport layer 105, a second transparent electrode 106, and an encapsulation layer 107.

[0075] The specific process for fabricating the aforementioned bifacial flexible solar cell is as follows:

[0076] S1. Preparation of curved surface mirror 2

[0077] The curved substrate 201 is made of high-transparency flexible glass with a thickness of 0.5-5 cm. Silver or aluminum is uniformly deposited on the finely polished curved substrate 201 using vacuum evaporation or magnetron sputtering to form a high-reflectivity metal layer 202. Subsequently, a weather-resistant protective layer 203 (made of SiO2 or TiO2) is prepared on the lower surface of the high-reflectivity metal layer 202 using chemical vapor deposition (CVD) or spin coating. The thickness of the high-reflectivity metal layer 202 can be 50-500 nm, more preferably 100-200 nm; the thickness of the weather-resistant protective layer 203 can be 30-300 nm, more preferably 80-100 nm.

[0078] S2. A first transparent electrode 102, a hole transport layer 103, a light absorption layer 104, an electron transport layer 105, a second transparent electrode 106, and an encapsulation layer 107 are sequentially fabricated on the upper surface of the curved reflector 2 to form a flexible semi-transparent photovoltaic cell 1. Simultaneously, a flexible photovoltaic cell 3 is fabricated on the lower surface of the curved reflector 2. The fabrication methods for the first transparent electrode 102, hole transport layer 103, light absorption layer 104, electron transport layer 105, second transparent electrode 106, and encapsulation layer 107 are the same as those in Example 1 and will not be repeated here. The same layer of battery material can be fabricated simultaneously on both the upper and lower surfaces of the curved reflector 2, or one side can be fabricated first and then the other.

[0079] Alternatively, flexible semi-transparent photovoltaic cells 1 or flexible photovoltaic cells 3 can be directly prepared on the upper or lower surface of the curved reflector 2, and then the prepared flexible photovoltaic cells 3 or flexible semi-transparent photovoltaic cells 1 can be pasted onto the curved reflector 2 to obtain a double-sided flexible solar cell.

[0080] It is particularly important to note that when directly fabricating the flexible photovoltaic cell 3 on the lower surface of the curved reflector 2, a thin glass sheet 209 needs to be fixed on the lower surface of the curved reflector 2. The thickness of the thin glass sheet 209 is 1mm-2cm. On the lower surface of the thin glass sheet 209, the first transparent electrode 102, hole transport layer 103, light absorption layer 104, electron transport layer 105, second transparent electrode 106, and encapsulation layer 107 are sequentially fabricated.

[0081] Example 3

[0082] A bifacial flexible solar cell, the technical solution of which is basically the same as that of Embodiment 1 or Embodiment 2, the difference being: the curved reflector 2 is improved, such as... Figure 6 As shown, the curved reflector 2 includes, from top to bottom, a spectrally selective coating, a curved substrate 201, a high-reflectivity metal layer 202, and a weather-resistant protective layer 203. The spectrally selective coating includes, from top to bottom, an interference film 205 and an infrared-transmitting film 204.

[0083] The principle of the improved technology is as follows:

[0084] By designing a spectrally selective coating on the surface of the curved reflector 2, the transmission and reflection behavior of light in different wavelength bands can be controlled: infrared light passes through the spectrally selective coating and is transmitted to the heat energy collection system for heat energy conversion; ultraviolet and visible light that is not absorbed by the upper photovoltaic cell is efficiently reflected by the coating and reused.

[0085] Materials and Coating Design

[0086] Spectro-selective coating materials use oxide or nitride materials as the base coating material, such as titanium dioxide, silicon oxide, and silicon nitride; curved substrates use metals such as silver (Ag) or aluminum (Al) to enhance reflectivity; multilayer structure coating design: based on the principle of interference films, high refractive index (such as TiO2) and low refractive index (such as SiO2) materials are alternately deposited to form a multilayer structure to optimize spectral selectivity performance.

[0087] Functional layer design

[0088] An infrared transmission functional layer, with adjusted refractive index and thickness, enables high transmittance (greater than 90%) in the infrared light band (700-2500nm). An ultraviolet and visible light reflection functional layer enhances reflection characteristics through interference, achieving high reflectivity (greater than 95%) for light in the 300-700nm wavelength range. A scattering enhancement coating introduces micro / nano structures (such as nanoparticle coatings or etched patterns) onto the curved mirror surface to enhance light scattering performance.

[0089] The specific preparation process is as follows:

[0090] S11. The curved substrate 201 is made of high-transparency flexible glass with a thickness of 0.5-5 cm. An aluminum or silver metal layer is used to enhance the reflectivity. The curved substrate 201 is cleaned and polished to remove oxides and impurities, ensuring coating adhesion. A silver or aluminum thin film is uniformly deposited on the lower surface of the finely polished curved substrate 201 using vacuum evaporation or magnetron sputtering to obtain a high-reflectivity metal layer 202. Subsequently, a weather-resistant protective layer 203 is prepared on the lower surface of the high-reflectivity metal layer 202 using chemical vapor deposition (CVD) or spin coating. The thickness of the high-reflectivity metal layer 202 can be 50-500 nm, more preferably 100-200 nm; the thickness of the weather-resistant protective layer 203 can be 30-300 nm, more preferably 80-100 nm.

[0091] S12. Preparation of spectrally selective coatings

[0092] A spectrally selective transmissive layer is prepared on the upper surface of the curved substrate 201. The spectrally selective transmissive layer includes an infrared transmissive film 204 and an interference film 205.

[0093] An infrared-transmitting film 204 (material selected: silicon dioxide or silicon nitride) is deposited on the upper surface of a curved substrate 201 using methods such as sol-gel deposition, atomic layer deposition (ALD), sputtering, chemical vapor deposition, or physical vapor deposition. The infrared-transmitting film 204 exhibits good infrared light transmittance and mechanical durability, with a film thickness of 100-300 nm. To enhance ultraviolet and visible light reflection, a high-refractive-index material layer (TiO2) and a low-refractive-index material layer (SiO2 or magnesium fluoride) are sequentially deposited on the infrared-transmitting film 204 to form an interference film 205. The thickness of the high-refractive-index material layer is 30-100 nm, and the thickness of the low-refractive-index material layer is 50-200 nm. An alternating high- and low-refractive-index design forms the interference film 205, which reflects both ultraviolet and visible light. The interference film 205 has an alternating structure of 5-7 layers, with a total thickness controlled at 300-500 nm. Interference film 205 is reflective in the ultraviolet and visible light bands, with a reflectivity of over 90%.

[0094] S13. Using laser direct writing, nanoimprinting or etching techniques, a micro-nano structure array (such as conical, cylindrical or random patterned structures, structure size: micrometer or nanometer scale, optimizing scattering angle and intensity) is formed on the surface of the spectrally selective coating to finally obtain the curved reflector 2.

[0095] Example 4

[0096] A bifacial flexible solar cell is disclosed in this embodiment. The technical solution is consistent with that of Embodiment 1, 2, or 3, except that the flexible photovoltaic cell 3 has been improved in several ways to enhance its light energy capture and utilization efficiency, such as… Figure 7 As shown, the flexible photovoltaic cell 3 includes, from top to bottom, a titanium dioxide protective layer 302, a metal reflective layer 301, a flexible substrate 101, a first transparent electrode 102, a hole transport layer 103, a light absorption layer 104, an electron transport layer 105, a second transparent electrode 106, and an encapsulation layer 107. The lower surface of the light absorption layer 104 is also provided with a microstructure, and the flexible substrate 101 is made of a transparent material.

[0097] The improved technical principle is as follows:

[0098] Back-facing design: Optimizes the light absorption direction of the lower photovoltaic cells, enabling them to efficiently absorb ambient scattered light and ground reflected light.

[0099] Microstructure surface treatment: Add micro- and nanostructures to the surface of the underlying photovoltaic cells to enhance the ability to capture scattered light.

[0100] Reflective coating design: A high-reflectivity coating is added to the back of the lower battery (i.e., the upper surface of the flexible photovoltaic cell 3 near the curved reflector 2) to reflect unabsorbed light back into the battery, thereby improving the recycling rate of light.

[0101] Materials and structural design

[0102] Back-facing design: The battery material uses high-efficiency flexible perovskite photovoltaic material, which has a wide spectral response range and good light absorption capability; Transparent substrate: High light transmittance polyimide (PI) or polyethylene terephthalate (PET) is selected as the substrate material so that scattered light and reflected light can enter the lower battery.

[0103] Microstructure surface treatment: Introduce nanopillar arrays, microconical structures, or randomly distributed pit patterns; Material selection: Coat the surface with an anti-reflective coating (such as silicon dioxide SiO2) or directly etch the battery surface to enhance the light trapping effect.

[0104] Backside reflective coating: Metals such as silver or aluminum are chosen as the reflective layer, possessing high reflectivity and conductivity. A dielectric layer such as titanium dioxide or magnesium oxide is then applied over the metal reflective layer as a reflective enhancement coating to improve reflection efficiency and protect coating stability.

[0105] Specific preparation process

[0106] The fabrication of the flexible photovoltaic cell 3 in this embodiment is basically the same as that in Example 1, except that:

[0107] (1) After the light absorption layer 104 is prepared, a microstructure is fabricated on the lower surface of the light absorption layer 104. The microstructure is fabricated using one or more of the following methods:

[0108] Laser direct writing utilizes lasers to form nanopatterns on the surface of the light absorption layer 104, improving the light trapping capability;

[0109] Nanoimprinting is a method of rapidly fabricating micro and nano structures using mold imprinting, which improves the ability to capture scattered light.

[0110] Wet etching involves creating randomly distributed micropores or pits by coating a mask and using an etching solution.

[0111] (2) Deposition of back reflective coating

[0112] A metallic reflective layer 301 (Ag or Al) with a thickness of approximately 50-100 nm is deposited by magnetron sputtering. A titanium dioxide protective layer 302 is then coated onto the metallic reflective layer 301 to enhance reflectivity and extend coating life, resulting in a flexible photovoltaic cell 3.

[0113] Example 5

[0114] A bifacial flexible solar cell, the technical solution in this embodiment is basically the same as any of the technical solutions in embodiments 1-4, the difference being: the curved reflector 2 is improved, such as... Figure 8 As shown, the curved reflector 2 includes, from top to bottom: a spectrally selective coating 208, a curved substrate 201, a high reflectivity metal layer 202, and a weather-resistant protective layer 203. The lower surface of the curved substrate 201 is provided with a heat-conducting channel 206 or an embedded structure, and an introduction material 207 is provided in the heat-conducting channel 206 or the embedded structure.

[0115] The improvement principle is as follows:

[0116] By embedding thermally conductive material in the curved reflector 2, the heat transfer path is optimized and the heat collection efficiency is improved.

[0117] High-efficiency heat dissipation design: Thermally conductive materials quickly transfer heat to the heat collection system, reducing heat loss.

[0118] Photothermal synergy: While ensuring high optical reflectivity, it integrates heat dissipation and photothermal separation functions.

[0119] Materials and structural design

[0120] Thermal conductivity material selection: Copper or aluminum are used, which have high thermal conductivity (thermal conductivity coefficients of ~400W / (m·K) and ~237W / (m·K) respectively) and are easy to process into complex structures; or carbon-based materials: graphene or carbon nanotubes are used, which have ultra-high thermal conductivity (thermal conductivity coefficients of up to ~2000W / (m·K)) and are suitable for enhancing heat transfer efficiency.

[0121] Filler material: High thermal conductivity ceramic (one of boron nitride, aluminum nitride or silicon carbide) is used, which is suitable as a filler reinforcement layer for metal and carbon-based materials, and has both thermal conductivity and high temperature resistance.

[0122] Multifunctional reflector structure design

[0123] Heat conduction channels: channels with high thermal conductivity are designed on the back of the curved mirror (the lower surface of the curved mirror) to improve heat dissipation efficiency by optimizing the geometry (such as honeycomb or striped distribution).

[0124] Channel arrangement: spaced out, covering the high-heat area of ​​the reflector to evenly transfer heat.

[0125] A thermal coupling interface is created by adding an interfacial thermally conductive material (such as thermal paste or thermal adhesive film) between the thermally conductive material and the curved substrate to reduce thermal resistance and improve heat transfer efficiency.

[0126] The photothermal separation structure is designed with a layered structure. The upper layer is a spectrally selective coating for light separation, and the lower layer is an embedded thermally conductive layer for heat dissipation and heat transfer.

[0127] Specific preparation process

[0128] S11. Substrate Processing

[0129] The curved substrate 201 is made of high-transparency flexible glass with a thickness of 0.5-5cm. The curved substrate 201 is cleaned and polished to ensure its surface optical performance. A heat conduction channel 206 or an embedded structure is prefabricated on the lower surface of the curved substrate 201 by laser cutting or CNC machining. The heat conduction material 207 is embedded in the prefabricated channel 206 or the embedded structure. A strong connection is ensured by welding or hot pressing. For interface treatment, thermal paste is applied to the contact surface between the curved substrate 201 and the heat conduction material 207 to reduce the interface thermal resistance. Vacuum pressing technology is used to ensure good adhesion between the embedded material and the substrate.

[0130] S12. A silver or aluminum thin film is uniformly deposited on the surface of the thermally conductive material 207 and the lower surface of the curved substrate 201 using vacuum evaporation or magnetron sputtering to obtain a high-reflectivity metal layer 202. Subsequently, a weather-resistant protective layer 203 is prepared on the lower surface of the high-reflectivity metal layer 202 using chemical vapor deposition (CVD) or spin coating to enhance its corrosion resistance and durability. The thickness of the high-reflectivity metal layer 202 can be 50-500 nm, more preferably 100-200 nm; the thickness of the weather-resistant protective layer 203 can be 30-300 nm, more preferably 80-100 nm.

[0131] S13. Prepare a spectrally selective coating 208 (such as the spectrally selective coating in Example 3 or multiple alternating layers of silicon dioxide and titanium dioxide) on the upper surface of the curved substrate 201 to obtain the curved reflector 2.

[0132] Embodiments 3-5 provided by this utility model are all improvements based on Embodiments 1 and 2, and the technical solutions in each embodiment can be combined with each other.

[0133] The working principle of the double-sided flexible solar cell provided by this utility model is as follows: Figure 9 As shown, when sunlight shines on the flexible semi-transparent photovoltaic cell 1, ultraviolet and visible light are absorbed by the flexible semi-transparent photovoltaic cell 1, while infrared light is reflected by the curved reflector 2 and absorbed at the collector 5. The flexible photovoltaic cell 3 on the back can further absorb ambient light and ground-reflected light. In addition, the solar tracking axis can adjust the orientation of the photovoltaic cell to receive as much sunlight as possible. By integrating two layers of photovoltaic cells on the curved reflector 2, the triple benefits of photovoltaic power generation and solar thermal utilization are achieved, significantly improving the overall energy utilization efficiency of the curved reflector-type solar thermal power plant.

[0134] The bifacial flexible solar cells prepared by the above method can be applied to trough solar thermal power generation systems and dish solar thermal power generation systems, which helps to improve the utilization rate of the solar spectrum and significantly improve the synergistic utilization efficiency of photovoltaic power generation and solar thermal utilization, and has broad application prospects.

[0135] This invention significantly improves solar energy utilization efficiency through a unique three-layer structure design, selective spectral utilization, and deep coupling of photovoltaic and photothermal systems, offering clear advantages over existing technologies. The innovative three-layer structure integrates a flexible semi-transparent photovoltaic cell, a curved reflector, and a lower flexible photovoltaic cell, achieving efficient utilization of the solar spectrum across different wavelengths. The upper flexible semi-transparent photovoltaic cell primarily absorbs ultraviolet and visible light, while allowing infrared light to pass through to the curved reflector in the middle layer for heat collection; the lower flexible photovoltaic cell utilizes ground-reflected light and ambient scattered light to generate electricity. Experiments show that this design increases the synergistic efficiency of the photovoltaic and photothermal systems by 15%–20%, increases power generation per unit area by 18% compared to traditional systems, increases thermal conversion efficiency by approximately 12%, significantly reduces the waste of solar energy resources, and achieves a photoelectric conversion efficiency of over 50%.

[0136] Through spectrally selective coating technology, the intermediate curved reflector not only has high transmittance for infrared light but also reflects unabsorbed ultraviolet and visible light, maximizing spectral distribution efficiency. Furthermore, adding a metal reflective layer and introducing microstructure surface treatment technology to the back of the lower flexible photovoltaic cell significantly enhances the ability to capture indirect light, increasing the power generation efficiency of the lower flexible photovoltaic cell by 8%, effectively compensating for the shortcomings of existing photovoltaic technologies in the low utilization of scattered and ground-reflected light.

[0137] The two layers of flexible photovoltaic cells provided by this invention can adapt to the complex curved surface reflector structures of both trough and dish-type solar thermal power plants. The three-layer design of the trough reflector optimizes the synergistic power generation mode of photovoltaics and solar thermal, significantly improving the overall light energy utilization efficiency when applied in high-radiation areas. The application of the dish reflector further expands the potential for comprehensive utilization of direct and diffused light, making it suitable for deployment in complex terrain or high-scattered light environments. Data shows that the total light energy utilization efficiency of this invention is approximately 20% higher than that of conventional systems in actual tests.

[0138] Furthermore, this invention optimizes the heat transfer path by embedding thermally conductive materials in the curved reflector, effectively solving the efficiency loss problem caused by heat retention in traditional solar thermal systems. Experiments showed that the surface temperature of the curved reflector prepared in Example 5 was reduced by 10-15°C, and the heat transfer efficiency was improved by over 20%, significantly enhancing the overall performance of the heat harvesting system. This design balances high efficiency and high adaptability, making it particularly suitable for large-scale deployment in areas with high radiation and extreme temperature differences. Compared to existing technologies, this invention not only optimizes the synergistic utilization mode of photovoltaics and solar thermal energy but also significantly improves energy conversion efficiency and system operational stability, providing an innovative solution for the development of photovoltaic-thermal coupling systems.

[0139] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model.

Claims

1. A bifacial flexible solar cell, characterized in that, From top to bottom, the structure includes a flexible semi-transparent photovoltaic cell (1), a curved reflector (2), and a flexible photovoltaic cell (3). The flexible semi-transparent photovoltaic cell (1) includes, from top to bottom, an encapsulation layer (107), a second transparent electrode (106), an electron transport layer (105), a light absorption layer (104), a hole transport layer (103), and a first transparent electrode (102). The positions of the electron transport layer (105) and the hole transport layer (103) can be interchanged. The curved reflector (2) comprises, from top to bottom, a curved substrate (201), a high reflectivity metal layer (202), and a weather-resistant protective layer (203); The flexible photovoltaic cell (3) is one of the following: perovskite solar cell, organic solar cell, copper indium gallium selenide solar cell, dye-sensitized solar cell, monocrystalline silicon solar cell, amorphous silicon solar cell, cadmium telluride thin film solar cell, and quantum dot solar cell.

2. The bifacial flexible solar cell according to claim 1, characterized in that, The curved substrate (201) of the curved reflector (2) is made of transparent flexible glass, the high reflectivity metal layer (202) is made of silver or aluminum, and the weather-resistant protective layer (203) is made of one of aluminum oxide, silicon dioxide, titanium dioxide, or polymer.

3. The bifacial flexible solar cell according to claim 1, characterized in that, The flexible photovoltaic cell (3) is a perovskite solar cell, which includes, from top to bottom, a first transparent electrode (102), a hole transport layer (103), a light absorption layer (104), an electron transport layer (105), a second transparent electrode (106), and an encapsulation layer (107); wherein the positions of the electron transport layer (105) and the hole transport layer (103) of the flexible photovoltaic cell (3) can be interchanged; the material band gap of the light absorption layer (104) of the flexible semi-transparent photovoltaic cell (1) is 1.65eV-2.30eV, and the material band gap of the light absorption layer (104) of the flexible photovoltaic cell (3) is 1.40eV-2.30eV.

4. The bifacial flexible solar cell according to claim 3, characterized in that, Both the flexible semi-transparent photovoltaic cell (1) and the flexible photovoltaic cell (3) are provided with a flexible substrate (101), and the flexible substrate (101) is located on the side of the first transparent electrode (102) away from the hole transport layer (103); the flexible substrate (101) of the flexible semi-transparent photovoltaic cell (1) is made of transparent material.

5. The bifacial flexible solar cell according to claim 4, characterized in that, The upper and lower surfaces of the curved reflector (2) are provided with adhesive layers (210).

6. The bifacial flexible solar cell according to claim 3, characterized in that, The lower surface of the curved reflector (2) is provided with a thin glass sheet (209), the thickness of which is 1mm-2cm.

7. The bifacial flexible solar cell according to claim 4, characterized in that, The light absorption layer (104) of the flexible photovoltaic cell (3) has a microstructure on its surface. The flexible substrate (101) of the flexible photovoltaic cell (3) is made of transparent material. A metal reflective layer (301) is provided on the side of the flexible substrate (101) away from the first transparent electrode (102). A titanium dioxide protective layer (302) is provided on the surface of the metal reflective layer (301) away from the flexible substrate (101).

8. The bifacial flexible solar cell according to claim 1, characterized in that, The upper surface of the curved mirror (2) is provided with a spectrally selective coating, which includes an interference film (205) and an infrared transmitting film (204) from top to bottom. The interference film (205) includes multiple layers of high refractive index material and low refractive index material layer arranged alternately in sequence. The high refractive index material layer is made of titanium dioxide, and the low refractive index material layer is made of silicon dioxide or magnesium fluoride.

9. The bifacial flexible solar cell according to claim 8, characterized in that, The thickness of the infrared transmitting film (204) is 100-300 nm, the thickness of the interference film (205) is 300-500 nm, the thickness of the high refractive index material layer is 30-100 nm, and the thickness of the low refractive index material layer is 50-200 nm.

10. The bifacial flexible solar cell according to claim 1, characterized in that, The curved substrate (201) of the curved mirror (2) has a heat-conducting channel (206) or an embedded structure on its lower surface. The heat-conducting channel (206) or embedded structure has a heat-conducting material (207) in it. The contact surface between the heat-conducting material (207) and the curved substrate (201) has a heat-conducting paste. The upper surface of the curved substrate (201) has a spectrally selective coating (208). The upper surface of the spectrally selective coating (208) has a microstructure.

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