A spatial radiation-resistant silicon solar cell and a preparation method thereof

Abstract

The application discloses a space radiation-resistant silicon solar cell and a preparation method thereof. The cell comprises a Ga-doped P-type ultrathin silicon substrate, a defect trapping layer formed by lithium ion deep implantation, a hetero-PN junction comprising a gradient-doped quantum well, an anti-radiation modification layer made of W / Ce co-doped indium oxide (IWCO) and a back reflector, and a low-temperature silver paste electrode. The application shortens the minority carrier transport path through the ultrathin substrate, passivates radiation damage through the lithium-doped defect trapping layer, strengthens carrier collection through the quantum well assisted built-in electric field, and realizes high-efficiency radiation shielding and light management through the IWCO layer. The four work together to significantly improve the performance stability of the cell in a space charged particle radiation environment. The cell has an efficiency decay rate of ≤15% and a specific power of ≥200 W / kg after 1MeV electron irradiation with a fluence of 1×10 14 cm ‑2 , and the preparation process is compatible with large-scale production, and is suitable for power systems of space equipment such as low-orbit satellites and deep space probes.

Description

Technical Field

[0001] This invention relates to the field of space photovoltaic technology, specifically to a silicon solar cell and its preparation method that meet the requirements of high radiation and lightweight space environments, and is suitable for long-term energy supply for space equipment such as low-orbit satellites, deep space probes, and space computing centers. Background Technology

[0002] In the era of commercial spaceflight, space equipment such as low-Earth orbit communication satellites, deep space probes, and space computing centers have placed multiple demands on solar energy technology, including lightweight design, high efficiency, high reliability, and low cost. Silicon solar cells, with their mature manufacturing processes, low cost, and good compatibility, have become an important development direction in the field of space photovoltaics. Compared to III-V group cells such as gallium arsenide (GaAs), silicon solar cells have significant advantages in achieving large-scale production and cost control.

[0003] However, the space environment contains a large number of high-energy electrons, protons and other charged particles. Irradiation by these particles can cause severe displacement radiation damage to silicon solar cells. The interaction between incident particles and silicon atoms leads to lattice distortion and defects such as vacancies and interstitial atoms. These defects form recombination centers, which can capture effective charge carriers in the active region, resulting in a decrease in charge carrier lifetime and degradation of IV characteristics. Ultimately, this leads to a significant decrease in photoelectric conversion efficiency and seriously affects the on-orbit service life of the cells.

[0004] Existing silicon solar cells are mostly 90-150 μm thick, which is not only heavy, making it difficult to meet the lightweight requirements of space equipment, but also has poor radiation resistance and severe efficiency degradation after irradiation. Although some studies have used ultrathin silicon substrates (thickness ≤100 μm) to improve radiation resistance, most studies remain at the qualitative level, lacking a quantitative design framework, and have not addressed the problems of insufficient light absorption and low carrier transport efficiency caused by ultrathin structures. Furthermore, existing radiation resistance modification methods mostly rely solely on ion implantation or coating protection, failing to achieve a synergistic effect between structural optimization and material modification, making it difficult to simultaneously meet the requirements of radiation resistance, lightweight design, and high conversion efficiency. In addition, the protective coatings of existing space silicon solar cells mostly only have anti-reflection functions, lacking targeted radiation shielding designs, making it difficult to withstand the complex radiation environment of space.

[0005] Therefore, developing a space silicon solar cell that is lightweight, highly radiation resistant, and has high conversion efficiency, and whose fabrication process is compatible with large-scale production, has become an urgent technical problem to be solved in the field of space photovoltaic technology. Summary of the Invention

[0006] To address the technical shortcomings of existing silicon solar cells in space radiation environments, such as severe efficiency degradation, insufficient lightweight design, and difficulty in meeting multiple performance requirements, this invention provides a space-resistant radiation-tolerant silicon solar cell and its fabrication method. Through the synergistic design of multi-level structural optimization and material modification from substrate to surface, it achieves a balance between radiation resistance, lightweight design, and high conversion efficiency, meeting the energy supply needs of various space devices in the Space 2.0 era. Furthermore, the fabrication process is compatible with large-scale production and is suitable for power systems of space equipment such as low-Earth orbit satellites and deep space probes.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] The present invention provides a space radiation-resistant silicon solar cell, comprising, from bottom to top, a back reflector layer, an ultrathin silicon substrate, a defect trapping layer, a heterojunction PN junction structure, a radiation-resistant modification layer, and an electrode structure penetrating each layer;

[0009] The ultrathin silicon substrate is Ga-doped P-type single crystal silicon with a thickness of 50-80 μm and a resistivity of 1-15 Ω·cm.

[0010] The defect trapping layer is disposed inside the ultrathin silicon substrate and is formed by lithium-ion deep implantation and annealing activation, and is used to trap lattice defects generated by space irradiation.

[0011] The back reflector layer is a multilayer IWCO film stack.

[0012] The above technical solution is adopted:

[0013] The thickness of the ultrathin silicon substrate is controlled at 50-80 μm. This thickness design represents a significant reduction compared to traditional silicon solar cells (130-150 μm), resulting in a substantial decrease in cell weight and meeting lightweight requirements. Furthermore, experimental verification shows that ultrathin silicon substrates within this thickness range can reduce displacement damage caused by high-energy particles. The relationship between irradiation attenuation and silicon wafer thickness is shown in [reference needed]. Figure 1 As shown.

[0014] Because the ultrathin structure can shorten the carrier transport path, reduce the capture of carriers by defects, and improve radiation resistance; the back reflector structure on the back side enhances the long-wavelength light capture capability, makes up for the problem of insufficient light absorption of the ultrathin substrate, and improves the photoelectric conversion efficiency.

[0015] Inside the ultrathin silicon substrate, a defect trapping layer is formed through lithium (Li) ion deep implantation and annealing activation processes. This layer is not a physical thin film, but rather a three-dimensional doped network formed by lithium ions throughout the silicon substrate.

[0016] Furthermore, the lithium-ion implantation dose is 5 × 10⁻⁶. 14 -3×10 15cm -3 After implantation, the lithium ions are subjected to thermal diffusion treatment at 400-450℃ for 15-25 minutes to allow them to diffuse evenly throughout the entire interior of the silicon substrate, forming a stable defect trapping network.

[0017] This invention precisely controls the lithium-ion implantation dose and annealing conditions to allow lithium ions to occupy interstitial or substitutional sites in the silicon lattice. These lithium ions and the complexes they form possess unique functions: they can act as traps or getter centers, effectively capturing primary irradiation defects such as migratory vacancies and interstitial silicon atoms generated by space irradiation in the silicon substrate through Coulomb attraction or stress field effects. By fixing these harmful defects at locations far from the active region of the PN junction, they are prevented from agglomerating into more stable defect clusters with strong recombination activity, thereby curing irradiation damage and maximizing the protection of the electrical properties of the PN junction region.

[0018] In addition, the combination of lithium doping and ultrathin substrates produces a synergistic effect: the ultrathin substrates reduce the total amount of irradiation defects generated, while the lithium doping layer efficiently removes the remaining defects, and the two together ensure carrier lifetime.

[0019] The optimized Li ion doping level was determined through simulation using TCAD software, and the changes in IV characteristics were monitored using battery samples. For an 80 μm silicon wafer thickness, when the Li doping level was 1*10... 15 cm -3 At that time, the battery efficiency and radiation resistance are optimal, such as Figure 2 As shown, this further enhances the resistance to displacement radiation.

[0020] Furthermore, the back reflector layer is composed of 3-5 stacked IWCO sub-films, with a total thickness of 200-300 nm. The refractive index of adjacent sub-films differs by 0.2-0.3, and the refractive index of each sub-film decreases progressively away from the ultrathin silicon substrate. For example, the refractive indices of the film layers from top to bottom are 2.0 / 1.8 / 1.6 / 1.4. This multilayer structure has both anti-reflection and radiation protection functions. The IWCO film stack can further reduce the secondary reflection of long-wavelength light after silicon wafer thinning, improving light absorption efficiency. At the same time, it can protect the battery surface from corrosion by the high vacuum environment of space, extending the battery's on-orbit service life.

[0021] This back reflector has three main functions:

[0022] (1) Light management function: By utilizing the interference effect between multilayer films and the gradient refractive index structure, the long-wavelength infrared light passing through the ultrathin silicon substrate is efficiently reflected back into the silicon wafer, increasing the optical path and significantly compensating for the defect of insufficient light absorption of the ultrathin substrate, thereby improving the short-circuit current density.

[0023] (2) Backside protection function: As a dense oxide film layer, it can effectively protect the backside of the battery from the erosion and damage of harsh environments such as space atomic oxygen and high vacuum.

[0024] (3) Stress balancing function: It forms a symmetrical oxide film structure with the IWCO layer on the front side, which helps to balance the thermal stress of the battery in the alternating hot and cold environment and improve the reliability of the structure.

[0025] Furthermore, the radiation-resistant modification layer is a W / Ce co-doped indium oxide (IWCO) film with a thickness of 100-150 nm.

[0026] Specifically, cerium is represented by Ce. 3+ and Ce 4+ The presence of mixed valence states allows the film to capture lattice defects (such as oxygen vacancies and lattice distortions) generated by high-energy particles (e.g., protons, electrons, gamma rays) in the environment, reducing the damage to the conductivity and light transmittance of IWO films. Simultaneously, cerium doping optimizes the lattice structure of ITO (indium tin oxide), reduces lattice defect density, enhances the structural integrity of the film, better resists lattice damage caused by high-energy particle bombardment, reduces resistivity spikes, and possesses a certain degree of defect healing capability, mitigating radiation-induced performance degradation. Experimental results demonstrate a significant improvement in the effective shielding capability of IWCO films against electron radiation.

[0027] Furthermore, the heterojunction structure is an amorphous silicon / crystalline silicon heterojunction architecture, including a P-type base region and an N-type emitter region. A quantum well is disposed in the P-type base region and / or the N-type emitter region to form an auxiliary built-in electric field. The direction of the auxiliary built-in electric field is configured to promote the drift of photogenerated minority carriers to the PN junction interface.

[0028] Specifically, the PN junction structure employs an amorphous silicon / crystalline silicon heterojunction (HJT) architecture. Compared to traditional diffused PN structures, this reduces the physical displacement of the active region and improves resistance to radiation decay. Furthermore, the HJT structure optimizes the PN junction state through the amorphous silicon structure, mitigating spectral response loss caused by junction radiation decay. Phosphorus-doped amorphous silicon thin-film quantum wells are fabricated at the interface between the N-type emitter region and the intrinsic amorphous silicon thin film, and gradient n-type doping is performed to create an auxiliary built-in electric field. On the other side of the battery, a boron-doped amorphous silicon thin-film quantum well is fabricated in the back-side field structure and gradient p-type doping is performed to form a back-side high-low junction, increasing the number of charge carriers.

[0029] Furthermore, the electrode structure is formed by screen printing, pre-curing and sintering of low-temperature conductive silver paste. The low-temperature conductive silver paste uses a mixture of nano-spherical and flake-shaped silver powder as the conductive phase, and the electrode structure is designed with a fishbone grid.

[0030] Specifically, the electrode structure is prepared by screen printing Ag paste. The sintered and cured electrode is porous, which can effectively release the stress during high and low temperature impact and improve the electrode contact firmness. At the same time, the electrode adopts a fishbone design, which can release the stress problem of series welding. When the electrode is interconnected with the solder ribbon by parallel gap resistance welding or tin soldering, the connection reliability is ensured, which can adapt to the complex assembly requirements of space equipment.

[0031] The present invention also provides a method for preparing the above-mentioned space radiation-resistant silicon solar cell, comprising the following steps:

[0032] S1. Substrate preparation: Ga-doped P-type single-crystal silicon wafers are provided, which are thinned to 50-80μm by silicon rod cutting and chemical etching, and then cleaned and dried for later use.

[0033] S2. Defect trapping layer formation: Lithium ions are injected into the ultrathin silicon substrate by ion implantation or thermal diffusion, and thermal diffusion treatment is performed to activate the lithium ions and allow them to diffuse and distribute into the interior of the ultrathin silicon substrate, forming a lithium-doped defect trapping network framework.

[0034] S3. Preparation of ultrathin textured silicon substrate: The above-mentioned Li ion doped silicon wafer is textured and cleaned, and anisotropic etching with alkaline solution is used to obtain textured structure. The pyramid textured surface size is 0.5-1.5μm and the silicon wafer thickness is 50-80μm. The textured silicon wafer is then deeply cleaned again to remove surface metals and organic matter, and then passed through hydrofluoric acid solution and slowly pulled out the silicon wafer for later use.

[0035] S4. PN junction structure fabrication: An N-type emitter region and back field structure are formed using plasma-enhanced chemical vapor deposition (PECVD). Before fabricating the N-type emitter region and back field structure, a 3-5 nm thick intrinsic amorphous silicon thin film is deposited on the silicon wafer surface to obtain a good surface chemical passivation effect. Then, a phosphorus-doped amorphous silicon thin film quantum well is fabricated at the interface between the N-type emitter region and the intrinsic amorphous silicon thin film, and gradient n-type doping is performed to form an auxiliary built-in electric field. In the back field structure on the other side of the battery, a boron-doped amorphous silicon thin film quantum well is fabricated and gradient p-type doping is performed to form a high-low junction on the back side, increasing the number of charge carriers.

[0036] S5. Preparation of anti-radiation modification layer: IWCO thin films with an index thickness of 100-150 nm are prepared on the N-type emission region by strong magnetic field magnetron sputtering or reactive plasma deposition to obtain a multifunctional thin film with high conductivity and anti-radiation properties, which is used as an anti-radiation modification layer.

[0037] S6. Back reflector fabrication: Taking advantage of the adjustable refractive index of IWCO, a back reflector layer consisting of 3-5 IWCO sub-films is fabricated on the back field region of an ultrathin silicon substrate using magnetron sputtering or thermal evaporation. The total thickness of the film stack is 200-300nm, forming a double-layer protective structure.

[0038] S7. Electrode preparation: Low-temperature conductive silver paste is printed on the front and back of the battery using screen printing. After pre-curing and sintering, metal electrodes are formed, completing the overall battery preparation.

[0039] Further, in step S2, the lithium-ion implantation energy is 20-40 keV, and the implantation dose is 5 × 10⁻⁶. 14 -3×10 15 cm -3 The heat treatment temperature is 400-450℃, the heat treatment time is 15-25min, and the annealing atmosphere is high-purity argon.

[0040] Furthermore, in step S6, the refractive index of each sub-film layer of the back reflector is controlled by adjusting the oxygen-argon ratio in the magnetron sputtering process, and the oxygen-argon ratio is positively correlated with the refractive index of the corresponding sub-film layer.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] (1) This invention uses an ultrathin substrate (50-80μm thick) to reduce the total amount of irradiation defects at the source, and a lithium-doped layer to passivate residual defects in situ to prevent them from fusing into recombination active centers. The quantum well-assisted built-in electric field ensures that minority carriers can still be efficiently collected after irradiation. The IWCO layer has both physical shielding and Ce³⁺ / Ce 4 ⁺ Self-healing function for variable valence, enabling the battery to withstand 1 MeV electron irradiation flux of 1×10¹ 4 The efficiency decay rate after cm⁻² is ≤15%, and its radiation resistance is far superior to that of conventional batteries.

[0043] (2) The substrate thickness is reduced from the conventional 150μm or more to 50-80μm, and the weight is reduced by about 50%. Combined with an initial conversion efficiency of ≥20%, the power density is stably reached above 200W / kg, which fully meets the lightweight requirements of space equipment.

[0044] (3) The surface IWCO graded refractive index film stack increases the effective optical path of infrared light by 2-3 times, making up for insufficient light absorption; the quantum well gradient doping forms an auxiliary electric field to actively enhance carrier transport and compensate for electrical losses.

[0045] (4) The overall preparation process is based on existing mature photovoltaic mass production technologies such as ion implantation, PECVD, magnetron sputtering, and screen printing. The entire process is low temperature and highly compatible with HJT production lines, and has the ability to quickly industrialize. Attached Figure Description

[0046] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0047] Figure 1This graph shows the relationship between battery conversion efficiency, irradiation attenuation, and silicon wafer thickness.

[0048] Figure 2 The graph shows the irradiation effect and irradiation attenuation of an 80μm thick silicon wafer as the lithium doping concentration changes.

[0049] Figure 3 This is a schematic diagram of the layered structure of the space radiation-resistant silicon solar cell in Example 3;

[0050] Figure 4 The graph shows the open-circuit voltage Voc of the space radiation-resistant silicon solar cells in Examples 1 and 3 as a function of temperature. Detailed Implementation

[0051] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] Example 1

[0053] A space-resistant radiation-resistant silicon solar cell includes the following structure:

[0054] Improved silicon substrate: Li-doped p-type single crystal silicon, 50 μm thick, resistivity 5 Ω·cm;

[0055] PN junction structure: The N-type emitter region and back field high-low junction structure are formed by plasma-enhanced chemical vapor deposition (PECVD).

[0056] Radiation-resistant modification layer: Both the front and back sides are IWCO thin films with a thickness of 100nm;

[0057] Electrode structure: Metal electrodes are formed by screen printing Ag paste.

[0058] Its preparation method is as follows:

[0059] Step 1: Take a P-type monocrystalline silicon wafer, remove the cut damage layer on the surface of the silicon wafer by chemical polishing, clean it with RCA, pass it through hydrofluoric acid solution, oxidize it with hot water, and then slowly pull it out for use;

[0060] Step 2: Li doping employs a composite process combining ion implantation and thermal diffusion to implant lithium ions into an ultrathin silicon substrate. The lithium ion implantation energy is 30 keV, and the implantation dose is 1 × 10¹. 5 cm⁻ 3After injection, the lithium element is subjected to thermal diffusion treatment at 450℃ for 20 minutes. During the diffusion process, high-purity argon gas (purity ≥99.999%) is used as a protective gas to ensure that the lithium element diffuses evenly into the silicon substrate and avoids excessive local concentration that could lead to lattice distortion.

[0061] Step 3: The PN junction and back field high-low junction are fabricated using a very high frequency PECVD (13.5MHz) deposition process. First, a 5nm thick intrinsic amorphous silicon film is deposited on the silicon wafer surface in two steps before the N-type emitter region and back field structure are fabricated to provide good surface chemical passivation. Then, a phosphorus-doped amorphous silicon thin film quantum well is fabricated on the intrinsic amorphous silicon film, and gradient n-type doping is performed to form an n++n+n quantum well structure with a total thickness of 10nm, forming the built-in electric field of the PN junction. Next, a boron-doped amorphous silicon film is fabricated in the back field structure on the other side of the battery, and gradient p-type doping is performed to form a back P+P++ high-low junction with a total thickness of 15nm, increasing the carrier transport capacity.

[0062] Step 4: IWCO thin film was prepared on an amorphous silicon thin film doped in the N-type emitter region by magnetron sputtering. The deposition pressure was 0.3 Pa, the power density was 3 kW / m, and the thickness was 90 nm.

[0063] Step 5: Electrodes are printed on the front and back sides using screen printing, with a fine grid width of 20 μm and a main grid width of 600 μm. The printed electrodes are pre-cured at 140℃ for 10 min. After the front and back electrodes are printed, they are sintered at 180℃ for 30 min to complete the preparation.

[0064] Example 2

[0065] A space-resistant radiation-resistant silicon solar cell has a structure that is basically the same as that of Example 1, with the main difference being:

[0066] In this embodiment, the improved silicon substrate is: Li-doped P-type single crystal silicon with a thickness of 70 μm and a resistivity of 5 Ω·cm;

[0067] The preparation method is the same as in Example 1.

[0068] Example 3

[0069] A space-resistant radiation-resistant silicon solar cell has a structure that is basically the same as that of Example 1, with the main difference being:

[0070] Improved silicon substrate: Li-doped p-type single crystal silicon, 80 μm thick, resistivity 5 Ω·cm;

[0071] The preparation method is the same as in Example 1.

[0072] Example 4

[0073] A space-resistant radiation-resistant silicon solar cell, with the following structure: Figure 1 As shown, its structure is basically the same as that of Example 2, with the main difference being:

[0074] The PN junction and the high- and low-order design have a gradient-doped quantum well structure, and the back reflection structure is designed with an ITWO reflector film stack on the back.

[0075] Among them, the PN junction structure is formed by plasma-enhanced chemical vapor deposition (PECVD) to form an N-type emitter region and a high-low back field junction structure, and the junction region is designed with a gradient-doped quantum well structure.

[0076] Radiation-resistant modification layer: The front side is an IWCO thin film with a thickness of 100 nm; the back side is an IWCO film stack with a total thickness of 300 nm.

[0077] Electrode structure: Metal electrodes are formed by screen printing Ag paste.

[0078] The preparation method is the same as in Example 1, except that the back side is an IWCO film stack formed by magnetron sputtering. The first layer of IWCO has a high oxygen / argon ratio, a coating process gas O2 / Ar ratio of 30%, a film refractive index of 2.1, and a thickness of 50 nm. The second layer of IWCO has a medium oxygen / argon ratio, a coating process gas O2 / Ar ratio of 15%, a film refractive index of 1.8, and a thickness of 80 nm. The third layer of IWCO has a low oxygen / argon ratio, a coating process gas O2 / Ar ratio of 5%, a film refractive index of 1.6, and a thickness of 100 nm. The open resistance of the thin stack is <80 ohm / sq.

[0079] Example 5

[0080] A space-resistant radiation-resistant silicon solar cell has a structure that is basically the same as that of Example 2, with the main difference being:

[0081] In Li-doped P-type single-crystal silicon, the lithium-ion implantation dose is 5 × 10⁻⁶. 14 .

[0082] Comparative Example 1

[0083] Comparative Example 1 is a comparative test example of Example 3, and its difference from Example 3 is as follows:

[0084] The comparative example uses a conventional silicon substrate: P-type single crystal silicon, 80 μm thick, resistivity 5 Ω·cm, with no lithium ion implantation to form a defect trapping layer.

[0085] The preparation method is the same as in Example 1.

[0086] Comparative Example 2

[0087] Comparative Example 2 is a comparative test example of Example 1, and its difference from Example 1 is as follows:

[0088] Improved silicon substrate: Li-doped p-type single crystal silicon, 100 μm thick, resistivity 5 Ω·cm;

[0089] The preparation method is the same as in Example 1.

[0090] Comparative Example 3

[0091] Comparative Example 3 is a comparative test example of Example 1, and its difference from Example 1 is as follows:

[0092] Improved silicon substrate: Li-doped p-type single crystal silicon, 130 μm thick, resistivity 5 Ω·cm;

[0093] The preparation method is the same as in Example 1.

[0094] Comparative Example 4

[0095] Comparative Example 4 is a comparative test example of Example 1, and its difference from Example 1 is as follows:

[0096] Improved silicon substrate: Li-doped p-type single crystal silicon, 150 μm thick, resistivity 5 Ω·cm;

[0097] The preparation method is the same as in Example 1.

[0098] Comparative Example 5

[0099] This comparative example is a comparative test case of Example 1, and its difference from Example 1 is as follows:

[0100] This comparative example is a conventional HJT solar cell, which uses a conventional silicon wafer substrate, doped with N-type monocrystalline silicon (middle ring, specification 210N half cell), with a thickness of 90μm and a resistivity of 1Ω·cm;

[0101] The preparation method is the same as in Example 1.

[0102] Comparative Example 6

[0103] This comparative example is a comparative test case of Example 2, and its difference from Example 3 is as follows:

[0104] Improved silicon substrate: Li-doped p-type single-crystal silicon with a Li doping dose of 1×10⁻⁶. 14 cm⁻ 3 Thickness 80μm, resistivity 5Ω·cm.

[0105] Comparative Example 7

[0106] This comparative example is a comparative test case of Example 3, and its difference from Example 3 is as follows:

[0107] Improved silicon substrate: Li-doped p-type single-crystal silicon with a Li doping dose of 5 × 10⁻⁶. 15 cm⁻3 Thickness 80μm, resistivity 5Ω·cm.

[0108] Comparative Example 8

[0109] This comparative example is a comparative test case of Example 3, and its difference from Example 3 is as follows:

[0110] Improved silicon substrate: Li-doped p-type single-crystal silicon with a Li doping dose of 1×10⁻⁶. 16 cm⁻ 3 Thickness 80μm, resistivity 5Ω·cm.

[0111] Comparative Example 9

[0112] This comparative example is a comparative test case of Example 3, and its difference from Example 3 is as follows:

[0113] Improved silicon substrate: Li-doped p-type single-crystal silicon with a Li doping dose of 5 × 10⁻⁶. 16 cm⁻ 3 Thickness 80μm, resistivity 5Ω·cm.

[0114] Comparative Example 10

[0115] This comparative example is a comparative test case of Example 3, and its difference from Example 3 is as follows:

[0116] Improved silicon substrate: Li-doped p-type single-crystal silicon with a Li doping dose of 1×10⁻⁶. 17 cm⁻ 3 Thickness 80μm, resistivity 5Ω·cm.

[0117] The electrical performance of the solar cells obtained in the above embodiments and comparative examples under AM0 and 25℃ test conditions is shown in Table 1 below.

[0118] Table 1

[0119]

[0120] 1 MeV electron irradiation was used, with an instantaneous irradiation flux of 8~9 × 10⁻⁶. 10 e / cm 2 The conversion performance degradation under different total doses is shown in Table 2 below.

[0121] Table 2

[0122]

[0123] Comparative Example 5 shows that the solar cell using an N-type silicon wafer has the highest photoelectric conversion efficiency, but the high-energy particle irradiation attenuation is the greatest. After irradiation, the device may have already inverted, resulting in almost zero electrical performance output, which cannot meet the requirements of space environment applications.

[0124] Compared to Comparative Example 5, the photoelectric conversion efficiency of the solar cell using a P-type silicon wafer decreased, but it could still maintain more than 70% of its electrical performance output after high-energy particle irradiation.

[0125] 1MeV electron irradiation dose 5×10 14 After cm⁻², the solar cell radiation efficiency of the ultrathin Li-doped silicon wafers in Examples 1, 2, and 3 decreased significantly less than that in Comparative Example 1.

[0126] The solar cells in Examples 1 and 2 were subjected to an electron injection dose of 1×10⁻⁶ at 1 MeV. 14 At cm⁻², the total irradiation dose efficiency decay is no more than 20% over 5-7 years in orbit, and the radiation resistance is significantly improved, making it suitable for power systems of space computing centers, communication satellites, etc.

[0127] Examples 2 and 5, and Comparative Examples 6-10, verified the photoelectric conversion efficiency and radiation resistance of improved P-type silicon wafers of different thicknesses under different Li doping concentrations. This indicates that the radiation resistance of the battery saturates in certain areas with increasing Li doping concentration, and the repair capability has a non-linear relationship with Li concentration (see [reference needed]). Figure 2 .

[0128] Examples 1-3 and Comparative Examples 1-4 verified the photoelectric conversion efficiency and radiation resistance of Li-doped improved P-type silicon wafers of different thicknesses. The cell efficiency initially increased and then decreased with increasing silicon wafer thickness. However, the efficiency degradation after high-energy particle irradiation increased rapidly with increasing silicon wafer thickness. Figure 3 .

[0129] In particular, compared with Example 2, Example 4 shows that the junction gradient doped quantum well design and back reflector design can effectively reduce battery irradiation decay and improve the battery photoelectric conversion efficiency. The final conversion efficiency after high-energy particle irradiation can be maintained at more than 16%, which has good space application value.

[0130] In particular, solar cells fabricated using Li-doped ultrathin p-type silicon wafers exhibit completely different open-circuit voltage (Voc) characteristics with temperature variations, such as... Figure 4 As shown, the Voc in the low-temperature region is no longer linearly related to temperature, but saturation occurs near -70℃. This can further reduce the redundancy in the battery circuit design of solar arrays used in deep space environments, providing a good foundation for low-cost design of space solar cell energy subsystems.

[0131] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A space-resistant radiation-resistant silicon solar cell, characterized in that, It includes, from bottom to top, a back reflector layer, an ultrathin silicon substrate, a defect trapping layer, a heterojunction PN junction structure, a radiation-resistant modification layer, and an electrode structure that runs through each layer; The ultrathin silicon substrate is Ga-doped P-type single crystal silicon with a thickness of 50-80 μm and a resistivity of 1-15 Ω·cm. The defect trapping layer is disposed inside the ultrathin silicon substrate and is formed by lithium-ion deep implantation and annealing activation, and is used to trap lattice defects generated by space irradiation. The back reflector layer is a multilayer IWCO film stack.

2. The space radiation-resistant silicon solar cell according to claim 1, characterized in that, The back reflector layer is composed of 3-5 IWCO sub-films stacked together, with a total thickness of 200-300 nm. The refractive index of adjacent sub-films differs by 0.2-0.3, and the refractive index of each sub-film decreases layer by layer away from the ultrathin silicon substrate.

3. The space radiation-resistant silicon solar cell according to claim 1, characterized in that, The radiation-resistant modification layer is a W / Ce co-doped indium oxide thin film with a thickness of 100-150 nm.

4. The space radiation-resistant silicon solar cell according to claim 3, characterized in that, in, Cerium element Ce 3+ and Ce 4+ Mixed valence states exist.

5. The space radiation-resistant silicon solar cell according to claim 1, characterized in that, The lithium-ion implantation dose is 5 × 10⁻⁶. 14 -3×10 15 cm -3 After implantation, the lithium ions are subjected to thermal diffusion treatment at 400-450℃ for 15-25 minutes to allow them to diffuse evenly throughout the entire interior of the silicon substrate, forming a stable defect trapping network.

6. The space radiation-resistant silicon solar cell according to claim 1, characterized in that, The heterojunction structure is an amorphous silicon / crystalline silicon heterojunction architecture, including a P-type base region and an N-type emitter region. A quantum well is disposed in the P-type base region and / or the N-type emitter region to form an auxiliary built-in electric field. The direction of the auxiliary built-in electric field is configured to promote the drift of photogenerated minority carriers to the PN junction interface.

7. The space radiation-resistant silicon solar cell according to claim 1, characterized in that, The electrode structure is formed by screen printing, pre-curing and sintering of low-temperature conductive silver paste. The low-temperature conductive silver paste uses a mixture of nano-spherical and flake-shaped silver powder as the conductive phase, and the electrode structure is designed with a fishbone grid.

8. A method for preparing a space radiation-resistant silicon solar cell as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Substrate preparation: Ga-doped P-type single-crystal silicon wafers are provided, which are cut and chemically etched to be thinned to 50-80μm, and then cleaned and dried. S2. Defect trapping layer formation: Lithium ions are injected into the ultrathin silicon substrate by ion implantation or thermal diffusion, and thermal diffusion treatment is performed to activate the lithium ions and make them diffuse and distribute into the interior of the ultrathin silicon substrate, forming a lithium-doped defect trapping network framework. S3. Texturing: The silicon wafer obtained in step S2 is subjected to alkaline anisotropic etching to form a textured surface structure. S4. PN junction fabrication: Plasma-enhanced chemical vapor deposition is used to sequentially deposit an intrinsic amorphous silicon passivation layer and a gradient-doped phosphorus-doped amorphous silicon N-type emitter region on the front side of the silicon wafer to form a heterojunction containing a quantum well structure; an intrinsic amorphous silicon passivation layer and a gradient-doped boron-doped amorphous silicon back-side field region are sequentially deposited on the back side of the silicon wafer. S5. Preparation of anti-radiation modification layer: IWCO thin film is prepared on the N-type emitter region by strong magnetic field magnetron sputtering or reactive plasma deposition as anti-radiation modification layer; S6. Back reflector fabrication: A back reflector layer consisting of 3-5 IWCO sub-films is fabricated on the back field region of an ultrathin silicon substrate using magnetron sputtering or thermal evaporation. S7. Electrode preparation: Low-temperature conductive silver paste is printed on the front and back of the battery using screen printing. After pre-curing and sintering, the electrode structure is formed.

9. The preparation method according to claim 8, characterized in that, In step S2, the lithium-ion implantation energy is 20-40 keV, and the implantation dose is 5 × 10⁻⁶. 14 -3×10 15 cm -3 The heat treatment temperature is 400-450℃, the heat treatment time is 15-25min, and the annealing atmosphere is high-purity argon.

10. The preparation method according to claim 8, characterized in that, In step S6, the refractive index of each sub-film layer of the back reflector is controlled by adjusting the oxygen-argon ratio in the magnetron sputtering process. The oxygen-argon ratio is positively correlated with the refractive index of the corresponding sub-film layer.

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