Silicon-based thin film solar cell with surface concave texture structure

Abstract

The invention provides a silicon-based thin-film solar cell with a surface sunken texture structure. The silicon-based thin-film solar cell is characterized in that a front electrode layer 2, an amorphous silicon layer 3, a hole transport layer 4 and a back electrode layer 5 are sequentially deposited at the bottom of prepared texture structure glass 1 to form the silicon-based thin-film solar cell. According to the silicon-based thin-film solar cell, efficient reflection resistance is formed on the surface of the texture structure at the top of the silicon-based thin-film solar cell, incident sunlight 6 is scattered and then enters the cell, then the texture structure at the bottom further captures the incident light into the amorphous silicon layer 3, the absorption capacity of the cell to the incident light is enhanced, the reflectivity of a cell device is reduced, and the light emitting efficiency of the cell is improved. Light energy escape is reduced, the optical path is prolonged, and the short-circuit current and photoelectric conversion efficiency of the cell are finally improved.

Description

Technical Field

[0001] The invention relates to a silicon-based thin-film solar cell with a surface concave texture structure, belongs to the field of solar cells, and specifically relates to photovoltaic devices and micro-nano processing. Background Art

[0002] Silicon, as the main material of solar cells, has a reflectivity of 36%. The high reflectivity reduces the utilization rate of solar light by the cell. In order to improve the absorption of light by the cell, light-trapping structures came into being. Traditional technologies for preparing light-trapping structures include surface texturing technology, reactive ion etching technology, photonic crystal technology, etc. By forming nanostructures such as nanowires and nanospheres on the surface of the cell to increase the scattering of incident light, more light is coupled into the cell, thereby increasing the absorption of incident light by the solar cell. The nanostructure on the surface of the solar cell can reduce the reflection of sunlight and increase the optical path of the incident light, thereby improving the photoelectric conversion efficiency and short-circuit current density of the solar cell and other photoelectric properties.

[0003] For silicon-based thin-film cells, light trapping means allowing more incident light to enter the cell and be effectively utilized by the photoresponse layer and converted into electrons. Light trapping technology mainly works in three aspects: first, reducing surface reflection to allow more photons to enter the semiconductor photoresponse layer in the solar cell; second, increasing internal absorption, which is significant in that the photons entering the cell can be absorbed more effectively and reduce the escape of photons; third, spectrum conversion, which aims to convert photons with poor response of semiconductor materials into photons with better response, expand the absorption spectrum width, and improve the utilization of the full spectrum. Light trapping technology can not only improve the absorption rate of thin-film cells to full-spectrum photons and improve the photoelectric conversion efficiency, but also further reduce the thickness of the response layer in photovoltaic devices, providing more possibilities for cost reduction. A light-trapping structure, a method for making the same, and a thin-film solar cell using the same (Chinese Patent: 201510815200.7) disclosed by Guo Xiaowei et al. in 2016 provide a light-trapping structure with a two-dimensional right-angled quadrangular pyramid-shaped light-trapping silicon layer, a method for making the same, and a thin-film solar cell using the same to enhance the wide-spectrum absorption efficiency; a new thin-film solar cell using a double-layer metal metamaterial disclosed by Liu Junxing et al. in 2023 (Chinese Patent: 202321213444.4) uses two layers of two-dimensional nano-grating structures to form an interface contact with a semiconductor heterojunction thin film to form a light-trapping structure, reduce the transmission of the exit surface, and limit the incident light to the semiconductor heterojunction thin film to the maximum extent; a three-dimensional light-trapping electrode back-contact solar cell disclosed by Li Yuelong et al. in 2024 (Chinese Patent: 202410247198.7) designs the planar electrode of the back-contact solar cell into a three-dimensional light-trapping structure. The improved three-dimensional light-trapping electrode significantly improves the overall photoelectric conversion efficiency while avoiding light shading loss. The above-mentioned light trapping technologies have improved the conversion efficiency of solar cells, but there is still no discussion on depositing silicon-based thin-film solar cell materials on the surface of the light trapping structure in sequence so that the surface light trapping structure and the internal texture structure of the silicon-based thin-film solar cell can act simultaneously. This limits the possibility of light trapping technology to improve the conversion efficiency of silicon-based thin-film solar cells.

[0004] The present invention discloses a silicon-based thin-film solar cell with a surface concave texture structure. The invention uses textured glass as a substrate, and deposits thin-film solar cell materials on the bottom surface of the textured glass in sequence to construct a silicon-based thin-film solar cell with a surface concave texture structure. Compared with the prior art, the surface light-trapping structure can make the incident light reflect multiple times in its concave structure, and the internal texture structure will further "capture" the incident light in the active layer, increase the effective light absorption area, optimize the scattering of light, and improve the cell's ability to capture light, and increase the area of ​​the carrier transport layer, shorten the charge transfer distance, and reduce the charge recombination rate, thereby improving the overall photoelectric conversion efficiency. Summary of the invention

[0005] The object of the present invention is to provide a silicon-based thin-film solar cell with a surface concave texture structure.

[0006] The object of the present invention is achieved in that:

[0007] A silicon-based thin-film solar cell with a surface concave texture structure is composed of a front electrode layer 2, an amorphous silicon layer 3, a hole transport layer 4, and a back electrode layer 5 deposited in sequence on the lower surface of a prepared textured structure glass 1. When irradiated by sunlight 6, the textured structure glass 1 is a relatively high anti-reflection structure, which reduces the reflection of the incident light on the surface of the cell, allowing more sunlight to couple into the cell, thereby increasing the overall light absorption of the solar cell, thereby providing more incident photons for the active layer. The front electrode layer 2 is indium tin oxide, which serves as the front contact of the cell to collect electrons. Then, the amorphous silicon layer 3 realizes energy conversion by generating electron-hole pairs, serving as the main light absorption layer of the entire device; the hole transport layer 4 is used to prevent the passage of electrons; the back electrode layer 5 prevents the underutilized long-wavelength light from passing through the cell. In order to increase the utilization rate of sunlight, the back reflection layer reflects the overflowing light back to the amorphous silicon layer 3 to increase the absorption of the solar cell. In this process, the incident sunlight 6 is first scattered by the light trapping structure at the top, and no longer propagates in the original direction perpendicular to the plane, and the optical path is extended. Then it contacts the recessed structure front electrode layer 2, and the light is scattered again. The light energy is collected into the amorphous silicon layer through refraction, which enhances the cell's absorption of the incident light energy, thereby improving the short circuit and further improving the cell's photoelectric conversion efficiency.

[0008] The specific preparation process of the recessed structure on the upper surface of the textured structure glass is as follows: first, the experimental glass substrate is thoroughly cleaned by a standard cleaning method to remove impurities on the glass surface, ensure the high cleanliness of the glass, and put into a drying oven for standby; second, due to the poor bonding force between copper or gold and the glass substrate, a layer of chromium is first sputtered on the clean glass surface by a magnetron sputtering method, and then a layer of copper or gold is sputtered to form a composite metal seed layer structure; third, photoresist is spin-coated, and after the coating is completed, a drying treatment is performed to harden the film; fourth, the photoresist is irradiated with ultraviolet light, and then developed in a developer, the pattern on the mask is transferred to the photoresist on the substrate surface, and then baked in an oven; fifth, the seed layer is etched by an ion beam etching method, and then the sample is immersed in acetone for degumming; sixth, the glass substrate with a structured metal seed layer mask is etched by a hydrofluoric acid solution; seventh, the etched glass substrate is immersed in ammonium cerium nitrate and high chloride etching solution until the residual metal seed layer is removed, and a glass with a textured structure is obtained. The size of the texture structure glass pit array is at the micro-nano level.

[0009] The specific preparation process of the convex structure on the lower surface of the textured structure glass is as follows: using PDMS as a casting material and the above-mentioned pit array structure glass as a simulation, the "replication" of the micro-nano structure is achieved through a casting process to form a PDMS glue mold of the surface convex array, and apply it to a silicon thin-film solar cell. The specific steps are: first, prepare a clean micro-nano structure glass substrate and clean the glass substrate; second, prepare a structural glass template; third, cast PDMS glue; fourth, demold to form a PDMS glue with a structure. The size of the pit array of the textured structure glass is at the micro-nano level.

[0010] The specific steps of depositing the silicon-based thin-film solar cell on the lower surface of the textured glass are as follows: first, a front electrode layer is sputtered on the lower surface of the textured glass by a magnetron sputtering method; second, an electron transport layer is deposited on the front electrode layer of the battery by an electron beam evaporation method; third, an amorphous silicon film is deposited on the transparent electrode to form an amorphous silicon layer; fourth, a hole transport layer is deposited on the amorphous silicon layer by an electron beam evaporation method; and finally, a back electrode layer is sputtered on the hole transport layer by a magnetron sputtering method. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a three-dimensional schematic diagram of a silicon-based thin-film solar cell with a surface concave texture structure.

[0012] Figure 2 It is a cross-sectional view of a silicon-based thin-film solar cell with a pit array aspect ratio of about 0.5 and a surface concave texture structure.

[0013] Figure 3 This is a comparison diagram of the active layer absorption of a silicon-based thin-film solar cell with a surface concave texture structure and a planar silicon-based thin-film solar cell.

[0014] Figure 4 This is a reflection comparison diagram of a silicon-based thin-film solar cell with a concave texture structure on the surface and a flat silicon-based thin-film solar cell.

[0015] In the figure, 1 is textured structural glass; 2 is the front electrode layer; 3 is the amorphous silicon layer; 4 is the hole transport layer; 5 is the back electrode layer; and 6 is incident sunlight. DETAILED DESCRIPTION

[0016] The present invention will be further described below in conjunction with specific embodiments.

[0017] Figure 2An embodiment of a silicon-based thin-film solar cell with a surface concave texture structure and a pit array aspect ratio of about 0.5 is given. The specific implementation steps are as follows: first, prepare double-sided textured structural glass. First, thoroughly clean and dry the glass substrate for standby use. Then, sputter a 50nm chromium metal layer on the upper surface of the glass, and then sputter a 150nm copper metal layer. Spin-coat a 3-5μm photoresist, a positive photoresist. Use 415nm ultraviolet light to photolithography for 60s in double-sided alignment contact lithography, then develop for 60s, and finally bake in an oven at 70-90 degrees for about 10 minutes. Use a combination of ion beam and hydrofluoric acid to etch the seed layer in sequence, with the etching time being 10 minutes respectively, and finally remove the seed layer. The convex structure on the lower surface of the glass uses PDMS as a casting material, and the above-mentioned pit array structure glass is used as a template. Through a casting process, the "replication" of the micro-nano structure is achieved. Finally, a double-sided textured light-trapping structure glass with a radius of about 0.2μm and a pit aspect ratio of about 0.5 is obtained.

[0017] Then, the silicon-based thin-film solar cell materials are deposited on the textured glass in sequence. Using the magnetron sputtering method, a 70nm thick ITO layer is sputtered on the bottom of the textured structure glass 1 as the front electrode layer 2 of the battery; on the transparent electrode, a 235nm amorphous silicon film is deposited to form an amorphous silicon layer 3, and silane gas (SiH4) is passed into the deposition chamber. Under the action of the radio frequency electromagnetic field, the amorphous silicon is decomposed by glow discharge silane and deposited on the transparent electrode. In order for the amorphous silicon film to have a photovoltaic effect, a pin layer structure must be formed. That is, when P-type amorphous silicon is doped, diborane (B2H6) or a mixed gas of methane (CH4) and diborane is added to the silane gas to form B2H6. + When doping N-type amorphous silicon, a mixed gas of phosphine (PH3) and silane (SiH4) is added to the silane gas to form a P layer. + Doping is performed to obtain an n-layer. The middle interlayer is the i-layer, i.e., the intrinsic absorption layer; a back electrode is sputtered on the amorphous silicon film using a metal organic compound chemical vapor deposition method, a combination of zinc oxide and metallic silver, with a zinc oxide thickness of 40nm forming a hole transport layer 4, and a metallic silver thickness of 100nm forming a back electrode layer 5.

[0018] Figure 3 The absorption comparison of the active layer of silicon-based thin-film solar cells with surface concave texture structures and the corresponding planar silicon-based thin-film solar cells is given. In the wavelength range of 300-900nm, the absorption of silicon-based thin-film solar cells with surface concave texture structures is higher than that of planar structure cells. According to calculations, the average absorption is increased by 26.52%, which is mainly due to the excellent anti-reflection and light trapping properties of the double-sided texture light trapping structure, which realizes multiple absorption of light.

[0019] Figure 4The reflection comparison diagram of silicon-based thin-film solar cells with concave surface texture and corresponding planar silicon-based thin-film solar cells is given. In the wavelength range of 300-900nm, the absorption of silicon-based thin-film solar cells with concave surface texture is lower than that of planar structure cells, and the average reflectivity decreases by 25.40%.

[0020] The above is a detailed description of the specific implementation of the present invention, but it must be reiterated that the core content of the present invention is to use textured glass as a substrate, and sequentially deposit silicon-based thin-film solar cell materials on the bottom surface of the textured glass to construct a silicon-based thin-film solar cell with a surface concave texture structure. This surface concave texture structure can also be applied to silicon-based or other solar cells. The present invention is not limited to the above specific implementation, and technicians in this field can make various deformations and improvements within the scope of the rights, which does not affect the essential content of the design of the present invention.

Claims

1. A silicon-based thin-film solar cell with a surface concave texture structure, characterized in that: The textured glass 1 comprises a light trapping structure on the upper and lower surfaces of the textured glass 1. The parameters of the upper and lower structures are the same. The front electrode layer 2, the amorphous silicon layer 3, the hole transport layer 4 and the back electrode layer 5 are sequentially deposited on the lower surface of the light trapping structure.

2. The silicon-based thin-film solar cell with a surface concave texture structure according to claim 1, characterized in that: The textured structure glass 1 is prepared by using a fused quartz glass substrate, and the light trapping structure is a periodically arranged hemispherical pit array.

3. The silicon-based thin-film solar cell with a surface concave texture structure according to claim 1, characterized in that: The material of the front electrode layer 2 is indium tin oxide (ITO), which is a transparent conductive glass with good conductivity and transparency, and a thickness of 50-150nm; the material of the amorphous silicon layer 3 is a-Si, and the thickness is 200-500nm; the material of the hole transport layer 4 is zinc oxide (ZnO), and the thickness is 50-100nm; the material of the back electrode layer 5 can be one of gold, silver, and aluminum, and the thickness is 100-300nm.

4. The hemispherical dimple array according to claim 2, wherein: The radius is 0.2μm-0.4μm, and the ratio of its depth to diameter is 0.5.

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