A three-band spectrally selective multilayer thin film structure suitable for photovoltaic cells

Abstract

A three-band spectrally selective multilayer thin-film structure suitable for photovoltaic cells belongs to the field of photovoltaic cell thermal management and thermal radiation technology. It includes a substrate, a stack of bifunctional interference films, and an air-side emission layer, which are sequentially connected from bottom to top. Twenty-four thin films are deposited sequentially on the substrate. This structure adopts a modular design concept of "substrate-side bifunctional interference film stack" and "air-side emission layer," defining the layer closest to the air as the first layer. This constitutes a bifunctional layer that enhances the photoelectric conversion band in the 0.38-1.1 micrometer range and has high reflectivity in the near-infrared band. Then, three different dielectric thin films are sequentially deposited on top of the bifunctional layer as emission layers. The advantage is that this film system provides efficient passive cooling for photovoltaic cells under zero-energy consumption conditions, effectively improving their photoelectric conversion efficiency and operating life.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic cell thermal management and thermal radiation technology, and in particular provides a three-band spectrally selective multilayer thin film structure suitable for photovoltaic cells. The multilayer thin film structure with wide spectrum and three-band spectrally selective properties is used to passively reduce the operating temperature of photovoltaic cells and improve power generation efficiency and reliability. Background Technology

[0002] Photovoltaic cells convert unused solar energy into heat during operation, leading to increased temperature and reduced efficiency. Cell performance is extremely sensitive to temperature; for every 1°C increase in temperature, the photoelectric conversion efficiency typically decreases by 0.4-0.5%, severely impacting power generation and long-term stability. Traditional active cooling methods usually require additional energy consumption, increasing system complexity and cost. Exploring a simple and effective passive cooling method is crucial for improving the power generation efficiency and output stability of photovoltaic systems.

[0003] Passive thermal management using the principle of thermal radiation is a zero-energy solution, the core of which lies in designing surface structures with specific spectral selectivity. An ideal structure needs to possess broad-spectrum spectral selectivity, including: maintaining high transmittance in the effective photoelectric conversion band of the cell (0.38-1.1 micrometers for monocrystalline silicon cells) to maximize light energy utilization; ensuring high reflectivity in the main near-infrared thermal load band (1.1-4 micrometers) to reduce heat input at the source; and high reflectivity in the mid-infrared atmospheric window band (8-13 micrometers) to enhance radiation and achieve heat dissipation into space. Summary of the Invention

[0004] The purpose of this invention is to provide a three-band spectrally selective multilayer thin film structure suitable for photovoltaic cells, which solves the problems of traditional active cooling methods requiring additional energy consumption, increasing system complexity and cost; and achieves efficient suppression of photovoltaic cell temperature rise in a zero-energy manner.

[0005] Based on the material design principles of multilayer thin-film interference and selective emission, this invention presents a three-band spectrally selective multilayer thin-film structure for thermal management of photovoltaic cells. Through a modular stacking design of 24 thin films, this structure achieves an average transmittance exceeding 90% in the effective photoelectric conversion band of 0.38–1.1 micrometers, an average reflectance exceeding 80% in the thermal load band of 1.1–4 micrometers, and an average emissivity exceeding 0.9 in the mid-infrared band of 8–20 micrometers.

[0006] The present invention includes a substrate 1, a dual-function interference film stack 7 and an air-side emission layer 8, which are connected sequentially from bottom to top.

[0007] The air-side emission layer 8 consists of, from bottom to top, a dielectric thin film MgF2 layer 5, a dielectric flat plate SiO2 layer 4, and a dielectric thin film PDMS layer 6. The dielectric thin film MgF2 layer 5 has a thickness of 2-4 micrometers, the dielectric flat plate SiO2 layer 4 has a thickness of 3-5 micrometers, and the dielectric thin film PDMS layer 6 has a thickness of 5-8 micrometers.

[0008] This invention relates to a 24-layer thin film deposited sequentially on a substrate 1. The structure employs a modular design concept of a "substrate-side bifunctional interference film stack" and an "air-side emission layer," defining the layer closest to the air as the first layer. This constitutes a bifunctional layer that enhances transmission in the photoelectric conversion band (0.38-1.1 micrometers) and exhibits high reflectivity in the near-infrared band. Then, three different dielectric thin films are sequentially deposited on top of the bifunctional layer as emission layers, thereby designing a multilayer thin film structure that achieves synergistic spectral modulation across three bands: high transmission in the photoelectric conversion band, high reflectivity in the near-infrared band, and high emission in the mid-infrared band.

[0009] The materials and functions of the 24 thin films in this invention, from substrate 1 to the air side, are as follows: ①A bifunctional interference film stack is defined with the air side as the first layer and layers 24 to 4 as the substrate side. It is composed of three dielectric materials, SiO2, MgF2 and TiO2, stacked alternately at predetermined thicknesses, with a metallic Ag layer embedded in the 12th layer. The function of the bifunctional interference film stack is to achieve high transmittance in the 0.38-1.1 micrometer photoelectric conversion band and high reflectance in the near-infrared band.

[0010] ②The layer from the 3rd layer to the 1st layer is the air-side emission layer. From the inside out, there is a layer of MgF2, SiO2 and PDMS. Its function is to achieve high emission in the mid-infrared atmospheric window band.

[0011] The substrate 1 material is SiO2.

[0012] The first to third layers are air-side emission layers, consisting of a dielectric thin film PDMS layer 6, a dielectric flat plate SiO2 layer 4, and a dielectric thin film MgF2 layer 5, respectively. The dielectric thin film PDMS layer 6 has a thickness of 5-8 micrometers, the dielectric flat plate SiO2 layer 4 has a thickness of 3-5 micrometers, and the dielectric thin film MgF2 layer 5 has a thickness of 2-4 micrometers.

[0013] The bifunctional interference film stack 7 on the substrate 1 side consists of layers 4 to 24, for a total of 21 layers. It uses three dielectric materials, namely, a dielectric flat SiO2 layer 4, a dielectric thin film MgF2 layer 5, and a dielectric thin film PDMS layer 62, which are stacked alternately at a set thickness. A metal Ag layer with a thickness of 5~5 nanometers is provided in the 12th layer.

[0014] The beneficial effects of the above-described technical solution of the present invention are as follows: In the above scheme, the structure has an average transmittance of over 90% in the 0.38-1.1 micrometer band, an average reflectance of over 80% in the 1.1-4 micrometer band, and an average emissivity of over 0.9 in the 8-20 micrometer band, and has application prospects in fields such as photovoltaic cell thermal management. Attached Figure Description

[0015] Figure 1 This is a perspective view of the structure of the present invention.

[0016] Figure 2 This is a cross-sectional view of the structure of the present invention.

[0017] Figure 3 This is a graph showing the transmittance and reflectance of the three-band multilayer thin-film cooler of the present invention within the wavelength range of 0.38-4 micrometers.

[0018] Figure 4 This is an emissivity curve of the three-band multilayer thin-film cooler of the present invention within the wavelength range of 8-20 micrometers.

[0019] The structure consists of: substrate 1, dielectric thin film TiO2 layer 2, metal thin film Ag layer 3, dielectric flat plate SiO2 layer 4, dielectric thin film MgF2 layer 5, dielectric thin film PDMS layer 6, bifunctional interference film stack 7, and air-side emission layer 8. Detailed Implementation

[0020] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0021] like Figure 1 , Figure 2 As shown, the structure includes a substrate 1, a stack of bifunctional interference films 7, and an air-side emission layer 8, which are connected sequentially from bottom to top. The air-side emission layer 8 consists of a dielectric thin film MgF2 layer 5, a dielectric flat plate SiO2 layer 4, and a dielectric thin film PDMS layer 6, from bottom to top. The MgF2 layer 5 has a thickness of 2-3 micrometers, the SiO2 layer 4 has a thickness of 3-5 micrometers, and the PDMS layer 6 has a thickness of 5-8 micrometers.

[0022] The substrate 1 material is SiO2.

[0023] The bifunctional interference film stack consists of 21 layers, which are composed of SiO2, MgF2 and TiO2 dielectric layers stacked alternately at specific thicknesses, and an extremely thin Ag metal layer is embedded in the 12th layer.

[0024] In the actual design, SiO2 is selected as the substrate material. The bifunctional interference film stack (layers 4-24) constructs the desired optical interference effect through the alternating stacking of SiO2, MgF2, and TiO2 at the 20-nanometer level. Among them, the 12th layer is an Ag layer with a thickness of approximately 5-15 nanometers, used to selectively enhance reflection in specific wavelength bands. In the air-side emission layer, the outermost PDMS layer has a thickness of approximately 5-8 micrometers, ensuring strong mid-infrared thermal radiation capability.

[0025] Figure 3 The figure shows the transmittance and reflectance curves of the three-band multilayer thin film structure of the present invention in the wavelength range of 0.38-4 micrometers. As shown in the figure, the structure has high transmittance in the 0.38-1.1 micrometer band, with an average transmittance of over 90%; and in the 1.1-4 micrometer band, its average reflectance is over 80%. Figure 4 The emissivity curves of the structure of this invention in the wavelength range of 8-20 micrometers are presented. The curves in the figure show that the average emissivity of this structure is higher than 0.90 in the mid-infrared broadband band of 8-20 micrometers. As can be seen from the figure, the three-band multilayer thin film structure designed in this invention has significant spectral selectivity.

[0026] This invention relates to a multilayer thin film structure with three-band spectral selectivity over a wide frequency range. Through a specific combination of materials such as SiO2, MgF2, TiO2, Ag, and PDMS, and the optimized design of a 24-layer film system, a multilayer thin film structure exhibiting high transmittance in the 0.38-1.1 micrometer band, high reflectivity in the 1.1-4 micrometer band, and high emissivity in the 8-20 micrometer band was obtained. This provides a foundation for the design and application of wide-spectrum spectrally selective surface structures for photovoltaic cell thermal management.

[0027] This invention is applicable to fields such as photovoltaic cell thermal management.

[0028] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A three-band spectrally selective multilayer thin film structure suitable for photovoltaic cells, characterized in that: It includes a substrate (1), a bifunctional interferometric film stack (7), and an air-side emission layer (8); the substrate (1), the bifunctional interferometric film stack (7), and the air-side emission layer (8) are connected sequentially from bottom to top; The air-side emission layer (8) consists of a dielectric thin film MgF2 layer (5), a dielectric flat plate SiO2 layer (4), and a dielectric thin film PDMS layer (6) from bottom to top. 24 thin films were sequentially deposited on the substrate (1), from the substrate (1) to the air side. The materials and functions of the 24 thin films are as follows: The air side is defined as the first layer, and the 24th to 4th layers are the substrate side of the bifunctional interference film stack (7), which is composed of three dielectric materials, SiO2, MgF2 and TiO2, stacked alternately with a set thickness, and a metal Ag layer is embedded in the 12th layer; the function of the bifunctional interference film stack (7) is to achieve high transmittance in the 0.38-1.1 micrometer photoelectric conversion band and high reflectance in the near-infrared band; The layer from the 3rd layer to the 1st layer is the air-side emission layer, and the layer from the inside to the outside consists of MgF2, SiO2 and PDMS, which are used to achieve high emission in the mid-infrared atmospheric window band.

2. The three-band spectrally selective multilayer thin film structure suitable for photovoltaic cells according to claim 1, characterized in that: The substrate (1) material is SiO2.

3. The three-band spectrally selective multilayer thin film structure suitable for photovoltaic cells according to claim 1, characterized in that: The thickness of the embedded Ag layer is 5-15 nanometers.

4. A three-band spectrally selective multilayer thin film structure suitable for photovoltaic cells according to claim 1, characterized in that: The thickness of the dielectric thin film PDMS layer (6) in the air-side emission layer is 5~8 micrometers, the thickness of the dielectric flat SiO2 layer (4) in the air-side emission layer is 3~5 micrometers, and the thickness of the dielectric thin film MgF2 layer (5) in the air-side emission layer is 2~4 micrometers.

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