Solar cell capable of enhancing light absorption based on nano material and preparation method of solar cell

Abstract

The invention relates to the technical field of solar cells, in particular to a solar cell capable of enhancing light absorption based on a nano material and a preparation method of the solar cell, and the solar cell comprises metal organic framework nano particles, DMF (N, N-dimethylformamide), ethanol and water. Metal organic framework nanoparticles are introduced into a texturing process of the crystalline silicon heterojunction cell to form a surface with a nanoscale porous structure, so that the light absorption capability and the surface passivation effect are enhanced.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, specifically to a solar cell based on nanomaterials to enhance light absorption and its preparation method. Background Technology

[0002] Crystalline silicon heterojunction solar cells (HJTs) are a high-efficiency solar cell technology that combines a crystalline silicon substrate with an amorphous silicon thin film. Their core structure includes an N-type monocrystalline silicon substrate, on which silicon-based thin film stacks with different properties and a transparent conductive thin film are deposited, respectively, on the front and back surfaces. Traditional texturing processes mainly employ the alkaline pyramid etching method, with the following specific steps: Silicon wafer cleaning: Removes surface contaminants and oxide layers.

[0003] Alkaline etching: Etching is performed in a KOH / IPA (isopropanol) solution at 80-85℃ for 30 minutes to form a random pyramid structure.

[0004] Surface passivation: An intrinsic hydrogenated amorphous silicon layer, typically 10-20 nm thick, is deposited on the textured surface by PECVD (plasma-enhanced chemical vapor deposition).

[0005] Doped layer deposition: A doped hydrogenated amorphous silicon layer is deposited on the intrinsic layer to form selective contacts. Transparent conductive film deposition: Typically an ITO (transparent conductive oxide) layer, such as ITO or AZO.

[0006] Electrode fabrication: Metal electrodes are formed by screen printing or physical vapor deposition.

[0007] Another texturing process is copper-catalyzed inverted pyramid texturing. This process is carried out in an acidic etching solution at 50°C, which shortens the etching time to 10 minutes and reduces the reflectivity to about 5%, which is lower than the reflectivity of traditional pyramid structures (about 10%). However, it also faces the problems of interface porosity and recombination rate.

[0008] Among the many problems, the limited light absorption efficiency is the most serious. Although the traditional pyramid structure can increase light absorption through two reflections, there is still about 10% reflection loss, especially insufficient absorption in the near-infrared band. Summary of the Invention

[0009] The purpose of this invention is to provide a solar cell based on nanomaterials to enhance light absorption and its preparation method, thereby solving the technical problem of limited light absorption efficiency in the prior art.

[0010] This invention discloses a mixed solution for texturing solar cells, which is used in the texturing process of solar cells and includes metal-organic framework nanoparticles, DMF (N,N-dimethylformamide), ethanol and water.

[0011] Furthermore, the metal-organic framework nanoparticles are MOF-199 nanoparticles.

[0012] Furthermore, the size of the metal-organic framework nanoparticles is 50-100 nm.

[0013] Furthermore, the volume ratio of DMF:ethanol:water is 1:1:1.

[0014] Furthermore, the concentration of metal-organic framework nanoparticles in the mixed solution is 0.5-2 wt%.

[0015] A method for fabricating a solar cell based on nanomaterial-enhanced light absorption includes the following steps: in a pyramid texturing process, a mixed solution of metal-organic framework nanoparticles is used, and acoustic waves are used to assemble the mixture to form a pyramid structure.

[0016] Furthermore, the texturing is carried out in an alkaline texturing solution at 80-85°C.

[0017] Furthermore, the mixed solution is continuously introduced into the alkaline texturing solution at a flow rate of 0.1-0.5 mL / min for acoustic assembly.

[0018] Furthermore, the frequency of the acoustic wave assembly is 20-50kHz.

[0019] Furthermore, after forming the pyramid structure, the silicon wafer surface is rinsed and then annealed.

[0020] Enhance the adhesion between MOF-199 nanoparticles and the silicon wafer surface.

[0021] Furthermore, the annealing is performed at 150-200°C for 30-60 minutes.

[0022] Furthermore, after texturing is completed, a passivation layer, a transparent conductive film, and an electrode are prepared sequentially.

[0023] Furthermore, the passivation layer is formed by depositing an intrinsic amorphous silicon layer with a thickness of 5-15 nm on the textured surface via PECVD, followed by depositing a doped microcrystalline silicon layer with a thickness of 15-25 nm on the intrinsic layer.

[0024] Furthermore, the transparent conductive oxide (ITO) layer has a thickness of 100-120 nm.

[0025] Furthermore, the electrode is prepared by screen printing.

[0026] A solar cell based on nanomaterials to enhance light absorption was prepared using the method described above.

[0027] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention introduces MOF-199 nanoparticles into the texturing process of crystalline silicon heterojunction solar cells to form a surface with a nanoscale porous structure. The porous nanoscale MOF-199 grows on the textured pyramid surface, and the closely packed MOF-199 particles form a porous shell, which helps light to be reflected and refracted multiple times inside the material, extending the optical path; and reducing surface reflection, increasing light absorption rate, thereby enhancing light absorption capacity and surface passivation effect. 2. The synergistic passivation of MOF-199 and amorphous silicon passivation layer in this invention utilizes the high surface area of ​​MOF-199 to adsorb surface defects, while providing a uniform film-forming substrate for the amorphous silicon layer, thereby improving the passivation effect. 3. This invention significantly improves light absorption efficiency: the porous structure of MOF-199 (pore size 1-2 nm, specific surface area 1448-1876 m²) 2 / g) can effectively scatter incident light and extend the optical path, especially in the near-infrared band (800-1100nm) where absorption is significantly enhanced; 4. This invention reduces interfacial recombination rate: MOF-199 nanoparticles fill the bottom of the textured channel, reducing interfacial pores, lowering carrier recombination rate, and improving the open-circuit voltage (Voc) and fill factor (FF) of the battery. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the felt pyramid of the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0031] Example 1 This embodiment discloses a solar cell based on nanomaterial-enhanced light absorption and its fabrication method, including the following steps: 1. Silicon wafer pretreatment: N-type monocrystalline silicon wafers (thickness 110±10μm, resistivity 1-3Ω·cm) are selected. Surface impurities are removed using the RCA standard cleaning process, and surface contaminants are further removed by wet ozone (O3) cleaning for 15 minutes.

[0032] 2. MOF-199 nanosolution: MOF-199 nanoparticles were synthesized at room temperature (25℃) using a reaction-diffusion method. The mixture was prepared by adding 0.5wt% (0.3g) MOF-199 to the DMF:ethanol:water ratio of 20 mL:20 mL:20 mL and sonicating for 30 min to obtain the MOF-199 nanosolution.

[0033] 3. Texturing Process: Texturing solution formulation: 1wt% NaOH, 1wt% texturing additive, 500 mL deionized water. MOF-199 solution is continuously introduced into the texturing solution at a controlled flow rate (3 mL / min). Using acoustic assembly technology (frequency 30 kHz), MOF-199 nanoparticles are guided to oriented and align on the silicon wafer surface. The texturing time is controlled at 30 minutes, forming a pyramid structure and embedding MOF-199 nanoparticles, as shown in the diagram. Figure 1 As shown. After texturing, the silicon wafer surface is rinsed with deionized water to remove residual etching solution. It is then subjected to a low-temperature annealing treatment at 150°C for 30 minutes. 3. Amorphous Silicon Thin Film Deposition: Radio frequency plasma-enhanced chemical vapor deposition (RF-PECVD) system was used. Intrinsic layer (ia-Si:H) deposition: 8 nm thickness, 200 °C, 0.5 Pa pressure, 10% silane concentration. Doped layer (na-Si:H) deposition: 10 nm thickness, 200 °C, 0.5 Pa pressure, 10% silane concentration, phosphine (PH3) dopant. Doped layer (pa-Si:H) deposition: 15 nm thickness, 200 °C, 0.5 Pa pressure, 10% silane concentration, diborane (B2H6) dopant.

[0034] 4. Deposition of Transparent Conductive Oxide (TCO) Layer: ITO layer was deposited using magnetron sputtering. Deposition conditions: temperature 220℃, power 300W, working pressure 2Pa, Ar atmosphere. Film thickness control: 100nm each for the front and back sides.

[0035] 5. Electrode preparation: Top electrode: Silver paste (low temperature silver paste) is screen-printed on the front TCO layer with a line width of 30μm and a spacing of 150μm. Back electrode: Silver paste is screen-printed on the back TCO layer to form the main grid and fine grid structure. Sintering treatment: Sintering at 230℃ for 30 minutes to ensure good contact between the electrode and the TCO layer.

[0036] Example 2 Unlike Example 1, 1 wt% MOF-199 was added.

[0037] Example 3 Unlike Example 1, 2 wt% MOF-199 was added.

[0038] Example 4 Unlike Example 1, the annealing temperature after texturing was adjusted to 200°C.

[0039] Example 5 Unlike Example 1, the frequency of the acoustic assembly technique was adjusted to 50kHz.

[0040] Comparative Example 1 Unlike Example 1, MOF-199 is not used.

[0041] Comparative Example 2 Unlike Example 1, the frequency of the acoustic assembly technique was adjusted to 60kHz.

[0042] Comparative Example 3 Unlike Example 1, the annealing temperature after texturing was adjusted to 250°C.

[0043] The reflectance test results of the above embodiments and comparative examples are shown in Table 1.

[0044] Table 1

[0045] Experimental data shows that the reflectivity significantly decreased after using MOF-199. Adding 2wt% MOF-199 reduced reflectivity by 2.32% compared to Comparative Example 1, effectively enhancing light absorption. In Example 5, adjusting the acoustic assembly technology frequency to 50kHz slightly increased reflectivity by 0.05%. In Comparative Example 2, adjusting the acoustic assembly technology frequency to 60kHz increased reflectivity to 9.78%, indicating that excessively high frequencies are detrimental to light absorption and utilization. In Example 4, adjusting the annealing temperature after texturing to 200℃ did not significantly change reflectivity, but increasing it to 250℃ increased reflectivity, indicating that excessively high annealing temperatures reduce the gain effect of MOF-199.

[0046] The performance test results of the above embodiments and comparative examples are shown in Table 2.

[0047] Table 2

[0048] Experimental data shows that the use of MOF-199 significantly improves battery efficiency. Adding 1 wt% MOF-199 increases efficiency by 0.73% compared to Comparative Example 1, representing the optimal concentration. Adding an excess of 2 wt% MOF-199 increases the short-circuit current, but decreases the open-circuit voltage and flyback factor (FF). This may be because the excess MOF prevents thorough cleaning of the cell surface after texturing, leading to increased non-radiative recombination and thus reduced efficiency.

[0049] In Example 5, adjusting the frequency of the acoustic wave assembly technology to 50kHz resulted in a 0.08% decrease in battery efficiency. In Comparative Example 2, adjusting the frequency of the acoustic wave assembly technology to 60kHz resulted in a 0.92% decrease in battery efficiency, indicating that excessively high frequencies can actually reduce battery efficiency. In Example 4, adjusting the annealing temperature after texturing to 200℃ resulted in only a 0.04% decrease in efficiency; however, when the annealing temperature was increased to 250℃, the battery efficiency decreased significantly by 0.3%, indicating that excessively high annealing temperatures reduce the gain effect of MOF-199 and also affect carrier transport efficiency.

[0050] As can be seen from Tables 1 and 2, the photoelectric conversion efficiency is improved by enhancing light absorption and reducing recombination rate through MOF-199 nanoparticles, resulting in an overall improvement of 0.27%-0.73% in battery efficiency.

[0051] Reduced reflectivity: The synergistic effect of the MOF-199 porous structure and inverted pyramid structure reduces reflectivity from 10% in traditional processes to 7.8%, significantly improving battery efficiency.

[0052] Increased open-circuit voltage and short-circuit current: Reduced interfacial porosity and lower recombination rate result in an increase of 3-10mV in open-circuit voltage and 28mA / cm in short-circuit current. 2 .

[0053] Fill factor optimization: Enhanced surface passivation improves carrier collection efficiency and increases fill factor (FF) by 0.1-0.7%.

[0054] The above are the embodiments listed in this example. However, this example is not limited to the optional embodiments described above. Those skilled in the art can arbitrarily combine the above methods to obtain other various embodiments. Anyone can derive other various forms of embodiments based on the inspiration of this example. The above specific embodiments should not be construed as limiting the scope of protection of this example. The scope of protection of this example should be determined by the claims, and the specification can be used to interpret the claims.

Claims

1. A mixed solution for texturing solar cells, used in the texturing process of solar cells, characterized in that: It includes metal-organic framework nanoparticles, N,N-dimethylformamide, ethanol, and water.

2. The mixed solution for texturing solar cells according to claim 1, characterized in that: The metal-organic framework nanoparticles are MOF-199 nanoparticles.

3. The mixed solution for texturing solar cells according to claim 1, characterized in that: The metal-organic framework nanoparticles have a size of 50-100 nm.

4. The mixed solution for texturing solar cells according to claim 1, characterized in that: The volume ratio of N,N-dimethylformamide:ethanol:water is 1:1:

1.

5. The mixed solution for texturing solar cells according to claim 1, characterized in that: The concentration of metal-organic framework nanoparticles in the mixed solution is 0.5-2 wt%.

6. A method for fabricating a solar cell based on nanomaterial-enhanced light absorption, characterized in that: The process includes the following steps: in the pyramid texturing process, a mixed solution of metal-organic framework nanoparticles is used, and acoustic waves are used to assemble the mixture to form a pyramid structure.

7. The method for preparing a solar cell based on nanomaterial-enhanced light absorption according to claim 6, characterized in that: The texturing process is carried out in an alkaline texturing solution at 80-85℃; And / or after forming the pyramid structure, rinse the silicon wafer surface and then anneal; After texturing is completed, a passivation layer, a transparent conductive film, and an electrode are prepared sequentially. And / or the frequency of the acoustic wave assembly is 20-50kHz.

8. The method for preparing a solar cell based on nanomaterial-enhanced light absorption according to claim 7, characterized in that: The mixed solution is continuously introduced into the alkaline texturing solution at a flow rate of 0.1-0.5 mL / min before acoustic assembly; And / or the annealing is performed at 150-200°C for 30-60 minutes.

9. The method for preparing a solar cell based on nanomaterial-enhanced light absorption according to claim 7, characterized in that: The passivation layer is formed by depositing an intrinsic amorphous silicon layer with a thickness of 5-15 nm on the textured surface by PECVD, and then depositing a doped microcrystalline silicon layer with a thickness of 15-25 nm on the intrinsic layer. And / or the transparent conductive film, with a thickness of 100-120 nm; And / or the electrodes are prepared by screen printing.

10. A solar cell based on nanomaterial-enhanced light absorption, characterized in that: The solar cell was prepared using any one of the methods for preparing a nanomaterial-based light-absorbing solar cell according to claims 6-9.

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