A thin-film solar cell based on negative refractive index metamaterial

Abstract

The present invention is a thin-film solar cell based on a negative refractive index metamaterial. The present invention improves the absorption of infrared light and part of the visible spectrum by thin-film solar cells through a negative refractive index metamaterial with a fishnet structure, so that more light reaches the surface of the solar cell, achieving effective light capture and high solar cell efficiency; the structure is manufactured using a simple etching technology, and its fishnet structure is arranged periodically, thereby having large broadband absorption. In the system composed of the fishnet structure and the thin-film solar cell of the present invention, under the action of the fishnet structure, the bandwidth of light absorption of the thin-film solar cell becomes larger, thereby improving the efficiency of the thin-film solar cell.

Description

Technical Field

[0001] The present invention belongs to the technical field of solar cells, and in particular relates to a thin-film solar cell based on a negative refractive index metamaterial. Background Art

[0002] There are two ways to utilize solar energy: photothermal conversion and photoelectric conversion. Solar power generation is an emerging renewable energy source. As an inexhaustible, clean and environmentally friendly energy source, solar energy has achieved unprecedented development in recent years and is expected to become the dominant new energy source in the 21st century. Solar cells are devices that use the photovoltaic effect to directly convert sunlight energy into electrical energy. The mainstream on the market are crystalline silicon solar cells and thin-film solar cells, each with its own advantages and disadvantages. Crystalline silicon solar cells have mature technology and relatively high photoelectric conversion efficiency, but the material consumption and battery cost are very high; thin-film solar cells are prepared on cheap substrates, with very low material consumption and battery cost, but the photoelectric conversion efficiency needs to be improved.

[0003] Cadmium telluride (CdTe) thin film solar cells have become the most competitive battery in the field of solar photovoltaics, and the industrialized battery efficiency has reached more than 16%. However, it is still difficult for cadmium telluride (CdTe) thin film solar cells to achieve a higher conversion efficiency, which to a certain extent limits the application of cadmium telluride (CdTe) thin film solar cells. At present, improving the conversion efficiency of cadmium telluride thin film solar cells mainly involves improving the utilization rate of sunlight in the short-wave region and improving the utilization of sunlight in the near-infrared region.

[0004] Negative refractive index metamaterials (NIMs) are artificially designed materials with negative dielectric constants and negative magnetic permeability. In recent years, they have been a hot topic in the research fields of electromagnetics, optics, and materials. They show a series of special properties that do not exist in natural materials, such as perfect lenses and negative refraction effects. Negative refractive index metamaterials refract light on the same side perpendicular to the surface. When applied to solar cells, more light can be absorbed instead of being reflected by the solar cell. By designing the subwavelength structural unit and size of the metamaterial, the magnetic resonance characteristics of the metamaterial can be controlled, so that it can produce a strong local field effect under the action of an electromagnetic field within a wavelength range and absorb more light. Summary of the invention

[0005] In view of the problems in the prior art and the current research status, the present invention provides a thin-film solar cell based on a negative refractive index metamaterial.

[0006] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a thin-film solar cell based on negative refractive index metamaterial, characterized in that the whole system is divided into two parts: a thin-film solar cell and a fishing net structure; incident light from different directions reaches the light-receiving surface of the thin-film solar cell through the fishing net structure. The thin-film solar cell is a cadmium telluride thin-film solar cell, which is composed of a glass substrate, a transparent conductive oxide layer, a cadmium sulfide window layer, a light absorption layer and a metal electrode; the light absorption layer is made of cadmium telluride photovoltaic material, and the cadmium telluride photovoltaic material is coated with a carbon nanotube film on the surface of the cadmium telluride material. The fishing net structure is composed of a dielectric plate in the middle and metal plates and double connecting wires on both sides of the dielectric plate, wherein the metal plates and double connecting wires on both sides are exactly the same, and it is a mixture of a cross and a circle.

[0007] The thin-film solar cell based on negative refractive index metamaterial is characterized in that the glass substrate of the thin-film solar cell is a soda-lime glass cover layer, and the thickness of the cadmium sulfide window layer is 100-200 nm.

[0008] The thin-film solar cell based on negative refractive index metamaterial is characterized in that the metal electrode deposited on the carbon nanotube film is a gold Au electrode or a nickel electrode.

[0009] The thin-film solar cell based on negative refractive index metamaterial is characterized in that the thickness of the cadmium telluride photovoltaic material is 5 to 10 μm, and the thickness of the carbon nanotube film covering the surface of the cadmium telluride is 50 to 100 nm.

[0010] The thin-film solar cell based on negative refractive index metamaterial is characterized in that the size of the entire thin-film solar cell is (10-20)*(10-20) cm, its fishing net structure has (20-30)*(20-30) units, the thickness of the metal plates on both sides of the dielectric plate is 15-18 μm, and each fishing net unit period contains a mixture of crosses and circles, a=5-10 mm, thickness t=750-800 μm, cross line width w=1-2 mm, and circle radius R=2-3 mm.

[0011] The thin-film solar cell based on negative refractive index metamaterial is characterized in that: the fishing net structure is manufactured by etching technology, the dielectric plate material in the middle is magnesium fluoride, and the metal material on both sides of the dielectric plate is gold.

[0012] The absorption principle of the fishing net structure is: the fishing net structure unit undergoes magnetic resonance with the incident electromagnetic wave, the fishing net unit is strongly coupled with the magnetic field of the incident electromagnetic wave, and the metal substrate is coupled with the electric field of the incident electromagnetic field. The entire fishing net structure forms impedance matching with the free space, which greatly reduces the reflectivity in the band where the magnetic resonance occurs. Since the metal substrate on the back makes the transmittance also 0, according to the sum of the absorption rate, transmittance and reflectivity being 1, it can be inferred that a very high absorption rate can be achieved in the frequency band where the magnetic resonance occurs at the fishing net unit. Therefore, the thin-film solar cell of the negative refractive index metamaterial can improve the absorption of infrared and part of the visible spectrum, and achieve higher conversion efficiency than ordinary cadmium telluride thin-film solar cells.

[0013] Compared with the prior art, the present invention has the following beneficial effects.

[0014] 1. The polycrystalline semiconductor material of cadmium telluride has the advantage of high chemical stability, and compared with silicon solar cells, the deposition process required to manufacture cadmium telluride thin-film solar cells is simpler and less expensive.

[0015] 2. This specific fishing net structure on the surface of the cell can improve the absorption of infrared and part of the visible spectrum, achieving higher conversion efficiency than general cadmium telluride thin-film solar cells.

[0016] 3. Since carbon nanotubes have good thermal stability, the battery will not experience efficiency loss like copper Cu doped back electrodes, and the service life can be extended; the carbon nanotube film is prepared by spin coating, which is simple and low-cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of a solar cell of the present invention.

[0018] Figure 2 It is a schematic diagram of the overall structure of the present invention.

[0019] Figure 3 It is a schematic diagram of the fishing net structure of the present invention. DETAILED DESCRIPTION

[0020] like Figure 2As shown, a thin-film solar cell based on a negative refractive index metamaterial is divided into two parts: a thin-film solar cell 1 and a fishing net structure 2. Incident light from different directions reaches the light-receiving surface of the thin-film solar cell 1 through the fishing net structure 2. The thin-film solar cell 1 is a cadmium telluride thin-film solar cell, in which a superstrate structure and a heterodyne junction structure are adopted; it is composed of a soda-lime glass cover layer 6 as a supporting material, a transparent conductive oxide layer 7, a cadmium sulfide window layer 8 with a thickness of 100 to 200 nm, a light absorption layer 9 and a metal electrode 11. The light absorption layer 9 is made of cadmium telluride photovoltaic material, and the cadmium telluride photovoltaic material is coated with a carbon nanotube film 10 on the surface of the cadmium telluride material. The thickness of the cadmium telluride photovoltaic material is 5 to 10 μm, and the thickness of the carbon nanotube film covering the surface of the cadmium telluride is 50 to 100 nm. The fishnet structure 2 is suitable for arbitrary linear polarization, and is composed of a dielectric plate 10 in the middle, metal plates 3, 5 on both sides of the dielectric plate, and double connecting wires, wherein the metal plates and double connecting wires on both sides are exactly the same, and it is a mixture of a cross and a circle; the dielectric plate material in the middle is magnesium fluoride, and the metal material on both sides of the dielectric plate is gold. The thickness of the metal plates 3, 5 on both sides of the dielectric plate is 15-18 μm, the fishnet structure has (20-30)*(20-30) units, and the size of the entire thin film solar cell is (10-20)*(10-20) cm.

[0021] like Figure 3 The figure shows a schematic diagram of a fishing net structure. The structure can be manufactured using etching technology; each fishing net unit period contains a mixture of crosses and circles, a (period) = 5-10 mm, thickness t = 750-800 μm, cross line width w = 1-2 mm, and circle radius R = 2-3 mm. The periodic arrangement of the fishing net structure makes the current density on the structure very high, produces high magnetic resonance, and achieves a large negative refractive index metamaterial bandwidth with a negative refractive index of about 1. This specific fishing net structure on thin-film solar cells can improve the absorption of infrared and part of the visible spectrum, helping solar cells achieve more efficient light capture and higher efficiency.

[0022] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A thin-film solar cell based on negative refractive index metamaterial, characterized in that: The entire system is divided into two parts: a thin-film solar cell (1) and a fishing net structure (2); incident light from different directions passes through the fishing net structure (2) to reach the light-receiving surface of the thin-film solar cell (1); The fishing net structure (2) is composed of a dielectric plate in the middle, metal plates on both sides of the dielectric plate, and double connecting wires, wherein the metal plates and the double connecting wires on both sides are completely the same; The fishing net structure has (20~30)*(20~30) periodically arranged fishing net units, and the fishing net units are arranged as a mixture of a cross and a circle. The thickness of the metal plate (3) (5) is 15~18μm. In each of the fishing net units, the period a=5~10mm, the thickness t=750~800μm, the cross line width w=1~2mm, and the circle radius R=2~3mm.

2. A thin-film solar cell based on negative refractive index metamaterial according to claim 1, characterized in that: The thin-film solar cell (1) is a cadmium telluride thin-film solar cell, which is composed of a glass substrate (6), a transparent conductive oxide layer (7), a cadmium sulfide window layer (8), a light absorption layer (9) and a metal electrode (11); the light absorption layer (9) is made of a cadmium telluride photovoltaic material, and the cadmium telluride photovoltaic material is coated with a carbon nanotube film (10) on the surface of the cadmium telluride material.

3. A thin-film solar cell based on negative refractive index metamaterial according to claim 1, characterized in that: The glass substrate of thin-film solar cells is a soda-lime glass cover layer, and the thickness of the cadmium sulfide window layer is 100~200nm.

4. The thin-film solar cell based on negative refractive index metamaterial according to claim 1, characterized in that: The metal electrode deposited on the carbon nanotube film is a gold Au electrode or a nickel electrode.

5. The thin-film solar cell based on negative refractive index metamaterial according to claim 2, characterized in that: The thickness of the cadmium telluride photovoltaic material is 5-10 μm, and the thickness of the carbon nanotube film covering the surface of the cadmium telluride is 50-100 nm.

6. The thin-film solar cell based on negative refractive index metamaterial according to claim 1, characterized in that: The fishing net structure is manufactured by etching technology, wherein the dielectric plate in the middle is made of magnesium fluoride, and the metal materials on both sides of the dielectric plate are gold.

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