Ultrathin silicon-based solar cell and preparation method thereof
By fabricating an ordered nanopore array on the surface of an ultrathin silicon-based solar cell and embedding a ZnO/Au heterojunction, combined with an Ag reflective layer, the problem of insufficient light absorption in the ultraviolet and long-wavelength regions of ultrathin silicon-based solar cells was solved, achieving enhanced full-spectrum light absorption and high power generation efficiency, making it suitable for large-scale production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-15
- Publication Date
- 2026-03-27
AI Technical Summary
Existing ultrathin silicon-based solar cells have insufficient light absorption capacity in the ultraviolet and long-wavelength regions, and the existing nanostructure processes are complex, making it difficult to achieve high-efficiency light absorption performance in large-scale production.
An ordered array of nanopores was fabricated on the surface of an ultrathin silicon substrate, and a ZnO/Au nanostructure was embedded therein to form a heterojunction. Combined with an Ag reflective layer, a nanostructure array with an embedded ZnO/Au heterojunction was constructed by AAO template-assisted plasma etching and thermal evaporation-oxidation process.
It significantly improves the light absorption capacity across the entire 0.2-1.2μm wavelength range, reduces production costs, and enhances the power generation efficiency and long-term operational stability of solar cells, making them suitable for mass production.
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Figure CN121751812A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of solar cell manufacturing technology, and in particular to an ultrathin silicon-based solar cell and its preparation method. Background Technology
[0002] Ultrathin silicon-based solar cells have become a research hotspot in the field of solar cells due to their ability to reduce silicon material usage and manufacturing costs. However, because the thickness of the light-absorbing layer is only about 2 μm, its absorption and utilization rate of sunlight is low, especially in the ultraviolet region and long-wavelength (0.85~1.2 μm) regions where there is a significant problem of insufficient absorption. In existing technologies, nanostructure arrays are often prepared on the surface or bottom of the silicon substrate to improve light absorption performance. However, the absorption enhancement effect of directly prepared silicon-based nanostructures on ultraviolet and infrared light is limited, and the process of preparing nanostructure back gratings on the bottom is complex. ZnO materials have excellent optical properties at the nanoscale. The bandgap of 3.37 eV gives it strong intrinsic absorption in the ultraviolet region, and the surface plasmon resonance effect can enhance the light coupling efficiency and enhance the absorption of light in the long-wavelength band. However, how to effectively combine ZnO nanostructures with silicon substrates, introduce Au to form heterojunctions to further optimize light absorption performance, and ensure the controllability of the process and the feasibility of large-scale production are currently urgent technical problems to be solved. Summary of the Invention
[0003] The technical problem to be solved by the present invention is to provide an ultrathin silicon-based solar cell and its preparation method that can improve the absorption capacity of sunlight in the full spectrum of 0.2-1.2μm, and improve production efficiency and reduce production costs.
[0004] The technical solution adopted by the present invention to solve its technical problem is: an ultrathin silicon-based solar cell, comprising an ultrathin silicon substrate; an ordered nanopore array is disposed on the surface of the ultrathin silicon substrate; and a ZnO / Au nanostructure is disposed within the ordered nanopore array to form a ZnO / Au nanostructure array;
[0005] The ZnO nanostructure is embedded and filled within ordered nanopores, and partially protrudes from the surface of the ultrathin silicon substrate; an Au-modified layer with a thickness of 10-50 nm is deposited at the bottom of the ZnO nanostructure; the ZnO nanostructure and the Au-modified layer form a ZnO / Au heterojunction; an Ag reflective layer with a thickness of 100 nm-1 μm is deposited on the bottom surface of the ultrathin silicon substrate.
[0006] Furthermore, the effective period of the ZnO nanostructure is 0.2-0.4 μm, the effective fill factor is 0.3-0.7, the effective depth of the ZnO / Au heterostructure embedded in the silicon substrate surface is 100-500 nm, and the effective height of the ZnO nanostructure protruding from the ultrathin silicon substrate surface is 100-400 nm.
[0007] Furthermore, the ultrathin silicon substrate is prepared by AAO template-assisted plasma etching; the AAO template is a double-through type with a thickness of 500nm-1μm.
[0008] Furthermore, the ZnO nanostructure is prepared from high-purity metallic zinc via a thermal evaporation-oxidation reaction.
[0009] This invention also provides a method for fabricating an ultrathin silicon-based solar cell, comprising the following steps:
[0010] S1. AAO template preprocessing and bonding;
[0011] The double-channel AAO template was ultrasonically cleaned in acetone solution for 15-20 minutes to remove organic residues on the surface. The double-channel AAO template was then transferred to the surface of the ultrathin silicon substrate using the water flotation method. After purging with nitrogen to remove bubbles, it was air-dried in a cool place at room temperature for 10-30 minutes to ensure that the double-channel AAO template and the ultrathin silicon substrate were tightly bonded.
[0012] S2. Plasma etching of silicon-based surfaces to prepare nanopores;
[0013] An ultrathin silicon substrate, fitted with an AAO template, is placed in a plasma etching machine, and a vacuum is drawn until the pressure inside the chamber is ≤5×10⁻⁶. -4 Pa, etch gas is introduced; total flow rate 20~30sccm, etch source is turned on, etch for 30s~10min, and nanopores are formed on the surface of ultrathin silicon substrate that are arranged in an orderly manner with AAO template.
[0014] S3, Au-modified layer deposition;
[0015] An ultrathin silicon substrate with nanopores was placed in a metal evaporation furnace and evacuated to a vacuum level of ≤1×10⁻⁶. -4 Pa, with a thermal evaporation deposition rate of 0.05~0.1nm / s, deposits a 10nm-50nm thick Au layer to modify the bottom of the nanopore;
[0016] S4 and ZnO nanostructure growth;
[0017] An alumina crucible containing high-purity zinc metal is placed in a metal evaporation furnace, and a vacuum of 5 × 10⁻⁶ is applied. -3 ~1×10 - 2 Pa, heated to 460-480℃, oxidizing gas was introduced, the evaporation rate of zinc was controlled at 1.5~1.8 Å / s, the distance between the silicon substrate and the evaporation source was 20cm-50cm, the substrate temperature was 320~380℃, and the deposition was carried out for 5~10h, so that zinc atoms were oxidized and deposited in the nanopores and on the AAO surface of the silicon substrate to form an embedded ZnO nanostructure.
[0018] S5. Template removal and annealing;
[0019] The sample obtained in step S4 was immersed in acetone solution to remove the remaining AAO template. After being dried with nitrogen, it was placed in a high-temperature oxidation furnace and annealed at 300~500℃ in a pure oxygen atmosphere with a heating rate of 5~10℃ / min.
[0020] S6: Preparation of Ag reflective layer; A 100nm-1μm thick Ag film is deposited on the bottom surface of an ultrathin silicon substrate to obtain a solar cell.
[0021] Furthermore, in step S2, the etching gas is a mixture of SF6 and O2, wherein the volume ratio of SF6 to O2 is 5:1.
[0022] Furthermore, in step S4, the oxidizing gas is a mixture of argon and oxygen, with a volume ratio of argon to oxygen of 12:1 to 16:1; and the purity of both argon and oxygen is 99.999%.
[0023] Furthermore, in steps S1-S4, the nanopores, Au-modified layers, and ZnO nanostructures prepared on the surface of the ultrathin silicon substrate all have the same period and fill factor as the dual-channel AAO template.
[0024] The beneficial effects of this invention are as follows: The ultrathin silicon-based solar cell and its preparation method described in this invention have the following advantages:
[0025] The ultrathin silicon-based solar cell described in this application establishes a two-dimensional nanostructure array with an embedded ZnO / Au heterojunction using AAO as a template, which can greatly improve the absorption capacity of sunlight in the full spectrum of 0.2-1.2μm. Furthermore, the fabrication of an embedded ZnO / Au heterojunction nanostructure in the ultrathin silicon-based solar cell proposes a low-cost, high-efficiency application of ZnO / Au heterojunction in ultrathin solar cells that can be mass-produced.
[0026] The method for fabricating ultrathin silicon-based solar cells described in this invention employs mature technologies such as thermal evaporation-oxidation, plasma etching, and thermal oxidation annealing in its core processes, eliminating the need for complex equipment and reducing industrial production costs.
[0027] Secondly, oxidation at a low evaporation rate and in a low-oxygen environment prevents the agglomeration of oxide particles, while high-temperature annealing optimizes the crystal quality of the ZnO / Au nanostructure, preventing cracking and improving the long-term working stability of the battery.
[0028] Furthermore, an ordered ZnO / Au heterojunction nanostructure was constructed using an AAO template-assisted process. Combined with an Ag reflective layer, this enhanced full-spectrum light absorption improved the power generation efficiency of ultrathin silicon-based solar cells. The AAO template approach offers advantages such as low cost, precise control over the period, size, and distribution of the ZnO / Au heterojunction nanostructure, easily adjustable process parameters, and strong process controllability, making it suitable for large-scale, large-area production. Attached Figure Description
[0029] Figure 1 This is a physical image of the AAO template electron microscope in an embodiment of the present invention;
[0030] Figure 2 This is a three-dimensional model of the ultrathin silicon-based solar cell and schematic diagrams of its xz and yz cross-sectional structures in an embodiment of the present invention;
[0031] In the picture, Figure 2 (a) is a schematic diagram of a three-dimensional model of an ultrathin silicon-based solar cell; Figure 2 (b) is a schematic diagram of the xz section structure of a three-dimensional model of an ultrathin silicon-based solar cell; Figure 2 (c) is a schematic diagram of the yz section structure of a three-dimensional model of an ultrathin silicon-based solar cell;
[0032] The diagram shows: 100 - ultrathin silicon substrate, 200 - Ag reflective layer, 300 - Au modification layer, 400 - ZnO nanostructure;
[0033] Figure 3 This is a process flow diagram of growing ZnO / Au heterojunction nanostructures on an ultrathin silicon substrate in an embodiment of the present invention;
[0034] In the picture, Figure 3 (a) is a schematic diagram of the pretreated ultrathin silicon substrate. Figure 3 (b) is a schematic diagram of an AAO template applied to an ultrathin silicon substrate; Figure 3 (c) Schematic diagram of an ultrathin silicon substrate after plasma etching; Figure 3 (d) is a schematic diagram of the Au-modified layer grown on an ultrathin silicon substrate; Figure 3 (d) is a schematic diagram of the ZnO / Au heterojunction nanostructure grown on an ultrathin silicon substrate; Figure 3 (f) is a schematic diagram of the ultrathin silicon substrate after the AAO template has been removed; Figure 3 (g) is a schematic diagram of an ultrathin silicon substrate after high-temperature annealing;
[0035] Figure 4 This is a comparison chart of the light-harvesting capabilities of the ultrathin silicon-based solar cell prepared in Example 1 and the light-harvesting capabilities of a conventional planar solar cell.
[0036] Figure 5This is a comparison chart of the light-harvesting capabilities of the ultrathin silicon-based solar cell prepared in Example 2 and the light-harvesting capabilities of a traditional planar solar cell.
[0037] Figure 6 This is a comparison chart of the light-harvesting capabilities of the ultrathin silicon-based solar cell prepared in Example 3 and the light-harvesting capabilities of a traditional planar solar cell. Detailed Implementation
[0038] The present invention will be further described below with reference to the accompanying drawings and embodiments.
[0039] like Figure 2 As shown, the ultrathin silicon-based solar cell of the present invention includes an ultrathin silicon substrate 100; an ordered nanopore array is disposed on the surface of the ultrathin silicon substrate 100; and ZnO nanostructures 400 are disposed within the ordered nanopore array to form a ZnO nanostructure array. Specifically,
[0040] The ultrathin silicon substrate 100 was prepared by AAO template-assisted plasma etching; the AAO template was a double-channel type with a thickness of 500 nm-1 μm. The ZnO nanostructure 400 was prepared by thermal evaporation-oxidation reaction of high-purity metallic zinc.
[0041] The ZnO nanostructure 400 is embedded and filled within ordered nanopores, and partially protrudes from the ultrathin silicon substrate surface. An Au modification layer 300 with a thickness of 10-50 nm is deposited at the lower end of the ZnO nanostructure 400. The ZnO nanostructure 400 and the Au modification layer 300 form a ZnO / Au heterojunction. Specifically, as shown... Figure 2 As shown, the ZnO / Au heterojunction nanostructure array is embedded within nanopores and exhibits a symmetrical triangular lattice periodic distribution. The effective period of the ZnO nanostructure 400 is 0.2-0.4 μm, the effective fill factor is 0.3-0.7, the effective embedding depth of the ZnO / Au heterojunction on the silicon substrate surface is 100-500 nm, and the effective protrusion height of the ZnO nanostructure 400 from the surface of the ultrathin silicon substrate 100 is 100-400 nm. The quantum size effect of ZnO is utilized to enhance ultraviolet light absorption. An Ag reflective layer 200 with a thickness of 100 nm-1 μm is deposited on the bottom surface of the ultrathin silicon substrate 100.
[0042] The ultrathin silicon-based solar cell and its fabrication method described in this invention utilize an AAO template, which offers advantages such as low cost, precise control over the period, size, and distribution of the ZnO / Au heterojunction nanostructure, easily adjustable process parameters, and strong process controllability, making it suitable for large-scale, large-area production. The core processes employ mature technologies such as thermal evaporation-oxidation, plasma etching, and thermal oxidation annealing, eliminating the need for complex equipment and reducing industrial production costs. The designed and fabricated solar cell avoids oxide particle agglomeration through a low evaporation rate and low-oxygen oxidation environment. High-temperature annealing optimizes the crystallinity of the ZnO / Au nanostructure, preventing cracking and improving the long-term operational stability of the cell. Furthermore, the AAO template-assisted process constructs an ordered ZnO / Au heterojunction nanostructure, which, combined with an Ag reflective layer, enhances full-spectrum light absorption, thereby improving the power generation efficiency of the ultrathin silicon-based solar cell.
[0043] The ultrathin silicon-based solar cell of this invention uses AAO as a template to fabricate an embedded ZnO / Au heterojunction nanostructure on the surface of an ultrathin silicon substrate through plasma etching and metal evaporation-oxidation, forming an ultrathin silicon-based solar cell with an embedded ZnO / Au heterojunction nanostructure. The ultrathin silicon-based solar cell with the embedded ZnO / Au heterojunction nanostructure includes ZnO nanostructures 400 with an AAO array arrangement extending beyond the surface of an ultrathin silicon substrate 100; ZnO nanostructures 400 with an AAO array arrangement embedded inside the ultrathin silicon substrate; an Au modification layer 300 with an AAO array arrangement embedded inside the ultrathin silicon substrate 100 and located at the bottom of the ZnO nanostructure array; the gaps between the ZnO nanostructures 400 and the silicon-based material between the bottom of the Au modification layer 300 and the Ag reflective layer 200 are both absorption layers and a back electrode Ag metal layer.
[0044] Specifically, the ultrathin silicon substrate 100 has a thickness of 2 μm and serves as the core light-absorbing layer, reducing the amount of silicon material used while ensuring structural stability. The ordered nanopore array on the surface of the ultrathin silicon substrate 100 is prepared by AAO template-assisted plasma etching, with pore sizes adapted to the ZnO / Au heterojunction nanostructure to achieve an ordered arrangement. The Au-modified layer 300, with a thickness of 10-50 nm, is deposited at the bottom of the ZnO nanostructure 400. Figure 2 As shown, a ZnO / Au heterojunction is formed, enhancing optical coupling and absorption through surface plasmon resonance. The Ag reflective layer 200, with a thickness of 100 nm-1 μm, is deposited on the bottom surface of the ultrathin silicon substrate 100. Figure 2 As shown, light that penetrates the ultrathin silicon substrate 100 is reflected back to the absorption layer, achieving secondary absorption and improving light utilization.
[0045] like Figure 3As shown, the present invention also provides a method for fabricating an ultrathin silicon-based solar cell, characterized by comprising the following steps:
[0046] S1. AAO template preprocessing and bonding;
[0047] The dual-channel AAO template was ultrasonically cleaned in acetone solution for 15-20 minutes to remove organic residues on the surface. The dual-channel AAO template was transferred to the surface of the ultrathin silicon substrate 100 by water flotation. After purging with nitrogen to remove bubbles, it was air-dried in a cool place at room temperature for 10-30 minutes to ensure that the dual-channel AAO template and the ultrathin silicon substrate 100 were tightly bonded.
[0048] S2. Plasma etching of silicon-based surfaces to prepare nanopores;
[0049] The ultrathin silicon substrate 100, which is aligned with the AAO template, is placed in a plasma etching machine, and the cavity pressure is evacuated to ≤5×10⁻⁶. -4 Pa, etch gas is introduced; total flow rate 20~30 sccm, etch source is turned on, etch for 30s~10min, and nanopores are formed on the surface of ultrathin silicon substrate 100 that are arranged in an orderly manner with the AAO template; wherein, the etch gas is a mixture of SF6 and O2, wherein the volume ratio of SF6 to O2 is 5:1.
[0050] S3, Au-modified layer deposition;
[0051] An ultrathin silicon substrate 100 with nanopores was placed in a metal evaporation furnace and evacuated to a vacuum level of ≤1×10⁻⁶. -4 Pa, with a thermal evaporation deposition rate of 0.05~0.1nm / s, deposits a 10nm-50nm thick Au layer to modify the bottom of the nanopore;
[0052] S4 and ZnO nanostructure growth;
[0053] An alumina crucible containing high-purity zinc metal is placed in a metal evaporation furnace, and a vacuum of 5 × 10⁻⁶ is applied. -3 ~1×10 - 2 The solution is heated to 460-480℃, and an oxidizing gas is introduced. The evaporation rate of zinc is controlled at 1.5-1.8 Å / s. The distance between the silicon substrate and the evaporation source is 20-50 cm. The substrate temperature is 320-380℃. Deposition is carried out for 5-10 hours, which oxidizes zinc atoms and deposits them in the nanopores and on the AAO surface of the silicon substrate, forming an embedded ZnO nanostructure 400. The oxidizing gas is a mixture of argon and oxygen, with a volume ratio of argon to oxygen of 12:1-16:1. The purity of both argon and oxygen is 99.999%.
[0054] S5. Template removal and annealing;
[0055] The sample obtained in step S4 was immersed in acetone solution to remove the remaining AAO template. After being dried with nitrogen, it was placed in a high-temperature oxidation furnace and annealed at 300~500℃ in a pure oxygen atmosphere with a heating rate of 5~10℃ / min.
[0056] S6: Preparation of Ag reflective layer; A 100nm-1μm thick Ag film is deposited on the bottom surface of an ultrathin silicon substrate 100 to obtain a solar cell.
[0057] Furthermore, in steps S1-S4, the nanopores, Au-modified layer 300, and ZnO nanostructure 400 prepared on the surface of the ultrathin silicon substrate 100 all have the same period and fill factor as the dual-channel AAO template.
[0058] The method for fabricating ultrathin silicon-based solar cells described in this invention employs mature technologies such as thermal evaporation-oxidation, plasma etching, and thermal oxidation annealing in its core processes, eliminating the need for complex equipment and reducing industrial production costs.
[0059] Secondly, oxidation at a low evaporation rate and in a low-oxygen environment prevents the agglomeration of oxide particles, while high-temperature annealing optimizes the crystal quality of the ZnO / Au nanostructure, preventing cracking and improving the long-term working stability of the battery.
[0060] Furthermore, an ordered ZnO / Au heterojunction nanostructure was constructed using an AAO template-assisted process. Combined with an Ag reflective layer, this enhanced full-spectrum light absorption improved the power generation efficiency of ultrathin silicon-based solar cells. The AAO template approach offers advantages such as low cost, precise control over the period, size, and distribution of the ZnO / Au heterojunction nanostructure, easily adjustable process parameters, and strong process controllability, making it suitable for large-scale, large-area production.
[0061] Example 1
[0062] I. Core Parameter Settings
[0063] Au-modified layer thickness: 30nm
[0064] ZnO nanostructure 400: period 0.3 μm, fill factor 0.5, embedding depth 300 nm, protrusion height 250 nm
[0065] AAO template: dual-channel type, original thickness 580nm
[0066] Ag reflective layer thickness: 500nm
[0067] Key process parameters: Argon-oxygen volume ratio 14:1, zinc evaporation rate 1.6 Å / s, substrate temperature 350℃, distance between silicon substrate and evaporation source 30cm.
[0068] II. Detailed Operating Procedures
[0069] S1. Select a 550nm thick double-channel AAO template, immerse it in acetone solution, and ultrasonically clean it for 18 minutes to remove surface organic residues. Figure 3 As shown in (a), the template was smoothly transferred to the surface of the ultrathin silicon substrate 100 using a water flotation method. The ultrathin silicon substrate 100 is a 2μm thick single-crystal silicon substrate (1cm × 1cm in size). Bubbles were gently removed by blowing with a nitrogen gun at a flow rate of 5L / min, and the substrate was air-dried in a cool, shaded place at room temperature for 20 minutes to ensure a seamless fit between the template and the silicon substrate. Figure 3 As shown in (b).
[0070] S2. Place the ultrathin silicon substrate 100 with the template into the plasma etching machine, close the chamber, and evacuate to 4×10⁻⁶. -4 Pa. An etching gas mixture of SF6 and O2 is introduced, with a volume ratio of SF6 to O2 of 5:1. The total flow rate is adjusted to 25 sccm, the etching source is turned on, and etching is performed for 5-10 minutes to form a nanopore array with a target depth of 330 nm on the surface of the ultrathin silicon substrate 100, which is uniformly arranged with the AAO template. Figure 3 As shown in (c).
[0071] S3. Transfer the ultrathin silicon substrate 100 with nanopores into a metal evaporation furnace and evacuate it to 8×10⁻⁶. -5 At a set evaporation rate of 0.07 nm / s, a 30 nm thick Au-modified layer 300 was deposited via thermal evaporation, uniformly covering the bottom of the nanopores. Figure 3 As shown in (d).
[0072] S4. Place an alumina crucible containing 99.999% high-purity zinc metal inside the metal evaporation furnace, and fix the silicon substrate 30 cm directly above the evaporation source. Evacuate to 8 × 10⁻⁶. -3 Pa, the heating device was activated and the temperature was raised to 470℃. When a uniform metallic luster appeared on the surface of the ultrathin silicon substrate 100, a mixture of argon and oxygen gas was introduced, with both argon and oxygen having a purity ≥99.99% and a volume ratio of 14:1. The zinc evaporation rate was controlled at 1.6 Å / s, the substrate temperature at 350℃, and deposition continued for 7 hours, causing zinc atoms to oxidize and deposit within the nanopores and on the silicon substrate surface, forming an embedded ZnO / Au nanostructure, such as... Figure 3 As shown in e.
[0073] S5. Immerse the sample in acetone solution for 30 min to completely remove any remaining AAO template. Rinse three times with deionized water and then dry with nitrogen. Place the sample in a high-temperature oxidation furnace, purge with pure oxygen, control the heating rate at 7℃ / min, raise the temperature to 400℃ and anneal for 2 h. Allow to cool naturally to room temperature. Figure 3 (f) and Figure 3 As shown in (g).
[0074] S6. The Ag reflective layer 200 was prepared by magnetron sputtering to deposit an Ag film on the bottom surface of an ultrathin silicon substrate 100. The sputtering power was set to 100W, the atmosphere was argon, and the deposition time was 15min. An Ag reflective layer 200 with a thickness of 500nm was prepared to obtain the target solar cell.
[0075] III. Performance Test Results
[0076] The light absorption capacity of the model prepared by the process in Example 1 was simulated using software, and its short-circuit current was 38.13 mA / cm². 2 Compared to traditional planar solar cells, this represents a 48.31% increase, as shown in Table 1. The absorption capacity curves are then analyzed. Figure 4 Observations show that within the full spectrum wavelength range of 0.2-1.2μm, the improvement is approximately 1.25 times for the short wavelength band (0.2-0.5μm) and approximately 0.33 times for the medium and long wavelength band (0.5-1.2μm).
[0077] Example 2
[0078] I. Core Parameter Settings
[0079] Au-modified layer thickness: 10nm
[0080] ZnO nanostructure 400: period 0.2 μm, fill factor 0.3, embedding depth 100 nm, protrusion height 100 nm
[0081] AAO template: dual-channel type, original thickness 300nm
[0082] Ag reflective layer thickness: 100nm
[0083] Key process parameters: argon-oxygen volume ratio 12:1, zinc evaporation rate 1.5 Å / s, substrate temperature 320℃, distance between silicon substrate and evaporation source 20cm.
[0084] II. Detailed Operating Procedures
[0085] S1. Select a 500nm thick double-channel AAO template, place it in acetone solution, and ultrasonically clean it for 15 minutes to remove surface organic residues. Figure 3 As shown in (a), the template was smoothly transferred to the surface of the ultrathin silicon substrate 100 using a water flotation method. The ultrathin silicon substrate 100 was a 2μm thick monocrystalline silicon substrate (1cm × 1cm). Bubbles were gently removed by blowing with a nitrogen gun at a flow rate of 5L / min, and the substrate was air-dried in a cool, shaded place at room temperature for 15 minutes to ensure a tight bond between the template and the silicon substrate. Figure 3 As shown in (b).
[0086] S2. Place the ultrathin silicon substrate 100 with the template into the plasma etching machine, close the chamber, and evacuate to 5×10⁻⁶. -4 Pa. An etching gas mixture of SF6 and O2 was introduced, with a volume ratio of SF6 to O2 of 5:1. The total flow rate was adjusted to 20 sccm, the etching source was turned on, and etching was performed for 30 s. This resulted in the formation of a nanopore array with a target depth of 110 nm on the surface of the ultrathin silicon substrate 100, arranged in an orderly manner consistent with the AAO template. Figure 3 As shown in (c).
[0087] S3. Transfer the ultrathin silicon substrate 100 with nanopores into a metal evaporation furnace and evacuate it to 1×10⁻⁶. -4 Pa, with an evaporation rate of 0.05 nm / s, a 10 nm thick Au-modified layer 300 was deposited via thermal evaporation, uniformly covering the bottom of the nanopores, as shown. Figure 3 As shown in (d).
[0088] S4. Place an alumina crucible containing 99.999% high-purity zinc metal inside a metal evaporation furnace, and fix the silicon substrate 20 cm directly above the evaporation source. Evacuate to 5 × 10⁻⁶. -3 Pa, the heating device was activated to raise the temperature to 460℃, and a mixture of argon and oxygen gas, both with a purity ≥99.99% and a volume ratio of 12:1, was introduced. The zinc evaporation rate was controlled at 1.5 Å / s, the substrate temperature at 320℃, and deposition continued for 5 hours, allowing zinc atoms to oxidize and deposit within the nanopores and on the silicon substrate surface, forming an embedded ZnO / Au nanostructure, such as... Figure 3 As shown in e.
[0089] S5. Immerse the sample in acetone solution for 20 min to completely remove any remaining AAO template, then dry with nitrogen. Place the sample in a high-temperature oxidation furnace, purge with pure oxygen, control the heating rate at 5℃ / min, raise the temperature to 300℃ and anneal for 2 h, then allow to cool naturally to room temperature. Figure 3 (f) and Figure 3 As shown in (g).
[0090] S6. The Ag reflective layer 200 was prepared by magnetron sputtering to deposit an Ag film on the bottom surface of an ultrathin silicon substrate 100. The sputtering power was set to 80W, the atmosphere was argon, and the deposition time was 3min. An Ag reflective layer 200 with a thickness of 100nm was prepared to obtain the target solar cell.
[0091] III. Performance Test Results
[0092] The light absorption capacity of the model prepared by the process in Example 2 was simulated using software, and its short-circuit current was 30.85 mA / cm². 2Compared to traditional planar solar cells, this represents a 19.99% increase, as shown in Table 1. The absorption capacity curves are then analyzed. Figure 5 Observations show that within the full spectrum wavelength range of 0.2-1.2μm, the improvement in short wavelength band (0.2-0.5μm) is about 1 time, while the improvement in visible light and long wavelength band (0.5-1.2μm) is insufficient.
[0093] Example 3
[0094] I. Core Parameter Settings
[0095] Au-modified layer thickness: 50nm
[0096] ZnO nanostructure 200: period 0.4 μm, fill factor 0.7, embedding depth 450 nm, protrusion height 400 nm
[0097] AAO template: double-channel type, original thickness 1μm
[0098] Ag reflective layer 200 thickness: 1μm
[0099] Key process parameters: Argon-oxygen volume ratio 16:1, zinc evaporation rate 1.8 Å / s, substrate temperature 380℃, distance between silicon substrate and evaporation source 50cm.
[0100] II. Detailed Operating Procedures
[0101] S1. Select a 1μm thick double-pass AAO template, place it in acetone solution and ultrasonically clean for 20 minutes to remove surface organic residues, such as... Figure 3 As shown in (a), the template was smoothly transferred to the surface of the ultrathin silicon substrate 100 using a water flotation method. The ultrathin silicon substrate 100 is a 2μm thick monocrystalline silicon substrate (1cm × 1cm). After nitrogen purging to remove bubbles, it was air-dried in a cool, shaded place at room temperature for 30 minutes to ensure a tight fit between the template and the silicon substrate. Figure 3 As shown in (b).
[0102] S2. Place the ultrathin silicon substrate 100 with the template into the plasma etching machine, close the chamber, and evacuate to 2×10⁻⁶. -4 Pa. An etching gas mixture of SF6 and O2 was introduced, with a volume ratio of SF6 to O2 of 5:1. The total flow rate was adjusted to 30 sccm, the etching source was turned on, and etching was performed for 10 min. This resulted in the formation of a nanopore array with a target depth of 500 nm on the surface of the ultrathin silicon substrate 100, arranged in an orderly manner consistent with the AAO template. Figure 3 As shown in (c).
[0103] S3. Transfer the ultrathin silicon substrate 100 with nanopores into a metal evaporation furnace and evacuate it to 5×10⁻⁶. -5Pa, with an evaporation rate of 0.1 nm / s, a 50 nm thick Au-modified layer 300 was deposited via thermal evaporation, uniformly covering the bottom of the nanopores, as shown. Figure 3 As shown in (d).
[0104] S4. Place an alumina crucible containing 99.999% high-purity zinc metal inside the metal evaporation furnace, and fix the silicon substrate 50 cm directly above the evaporation source. Evacuate to 1×10⁻⁶. - The heating device was activated at 2Pa to raise the temperature to 480℃. A mixture of argon and oxygen, both with a purity ≥99.99% and a volume ratio of 16:1, was introduced. The zinc evaporation rate was controlled at 1.8 Å / s, the substrate temperature at 380℃, and deposition continued for 10 hours to oxidize and deposit zinc atoms within the nanopores and on the silicon substrate surface, forming an embedded ZnO / Au nanostructure. Figure 3 As shown in e.
[0105] S5. Immerse the sample in acetone solution for 40 min to completely remove any remaining AAO template, then dry with nitrogen. Place the sample in a high-temperature oxidation furnace, purge with pure oxygen, control the heating rate at 10℃ / min, raise the temperature to 500℃ and anneal for 3 h, then allow to cool naturally to room temperature. Figure 3 (f) and Figure 3 As shown in (g).
[0106] S6. The Ag reflective layer 200 was prepared by magnetron sputtering to deposit an Ag film on the bottom surface of an ultrathin silicon substrate 100. The sputtering power was set to 120W, the atmosphere was argon, and the deposition time was 30min. An Ag reflective layer 200 with a thickness of 1μm was prepared to obtain the target solar cell.
[0107] III. Performance Test Results
[0108] The light absorption capacity of the model prepared by the process in Example 3 was simulated using software, and its short-circuit current was 40.72 mA / cm². 2 Compared to traditional planar solar cells, this represents a 58.38% increase, as shown in Table 1. The absorption capacity curves are then analyzed. Figure 6 Observations show that it has a significant improvement in absorption capability across the entire spectral wavelength range of 0.2-1.2μm, with an improvement of approximately 1.37 times in the short wavelength range (0.2-0.5μm) and approximately 0.42 times in the medium and long wavelength range (0.5-1.2μm).
[0109] The performance test results for the three embodiments are as follows:
[0110] Table 1, Performance Test Results
[0111]
Claims
1. An ultrathin silicon-based solar cell, characterized in that: It includes an ultrathin silicon substrate (100); the surface of the ultrathin silicon substrate (100) is provided with an ordered nanopore array; a ZnO nanostructure (400) is provided in the ordered nanopore array to form a ZnO nanostructure array; The ZnO nanostructure (400) is embedded and filled in ordered nanopores, and partially protrudes from the ultrathin silicon substrate surface; an Au modification layer (300) with a thickness of 10-50 nm is provided at the lower end of the ZnO nanostructure (400); The ZnO nanostructure (400) is deposited at the bottom of the ZnO nanostructure (400); the ZnO nanostructure (400) and the Au-modified layer (300) form a ZnO / Au heterojunction; an Ag reflective layer (200) with a thickness of 100 nm-1 μm is deposited on the bottom surface of the ultrathin silicon substrate (100).
2. The ultrathin silicon-based solar cell as described in claim 1, characterized in that: The effective period of the ZnO nanostructure (400) is 0.2-0.4 μm, the effective fill factor is 0.3-0.7, the effective depth of the ZnO / Au heterojunction embedded in the silicon substrate surface is 100-500 nm, and the effective height of the ZnO nanostructure (400) protruding from the surface of the ultrathin silicon substrate (100) is 100-400 nm.
3. The ultrathin silicon-based solar cell as described in claim 1, characterized in that: The ultrathin silicon substrate (100) is prepared by AAO template-assisted plasma etching; the AAO template is a double-pass type with a thickness of 500nm-1μm.
4. The ultrathin silicon-based solar cell as described in claim 1, characterized in that: The ZnO nanostructure (400) is prepared by thermal evaporation-oxidation reaction of high-purity metallic zinc.
5. A method for fabricating an ultrathin silicon-based solar cell, characterized in that, Includes the following steps: S1. AAO template preprocessing and bonding; The double-pass AAO template was ultrasonically cleaned in acetone solution for 15-20 minutes to remove organic residues on the surface. The double-pass AAO template was transferred to the surface of the ultrathin silicon substrate (100) by water flotation. After purging with nitrogen to remove bubbles, it was air-dried in a cool place at room temperature for 10-30 minutes to ensure that the double-pass AAO template and the ultrathin silicon substrate (100) are tightly bonded. S2. Plasma etching of silicon-based surfaces to prepare nanopores; The ultrathin silicon substrate (100) that conforms to the AAO template is placed in a plasma etching machine, and a vacuum is drawn until the pressure inside the chamber is ≤5×10. -4 Pa, etch gas is introduced; total flow rate 20~30 sccm, etch source is turned on, etch for 30s~10min, and nanopores are formed on the surface of ultrathin silicon substrate (100) that are arranged in an orderly manner with the AAO template. S3, Au-modified layer deposition; An ultrathin silicon substrate (100) with nanopores was placed in a metal evaporation furnace and evacuated to a vacuum level of ≤1×10⁻⁶. -4 Pa, with a thermal evaporation deposition rate of 0.05~0.1nm / s, deposits a 10nm-50nm thick Au layer to modify the bottom of the nanopore; S4 and ZnO nanostructure growth; An alumina crucible containing high-purity zinc metal is placed in a metal evaporation furnace, and a vacuum of 5 × 10⁻⁶ is applied. -3 ~1×10 -2 Pa, heated to 460-480℃, oxidizing gas was introduced, the evaporation rate of zinc was controlled at 1.5~1.8 Å / s, the distance between the silicon substrate and the evaporation source was 20cm-50cm, the substrate temperature was 320~380℃, and deposition was carried out for 5~10h, so that zinc atoms were oxidized and deposited in the nanopores and on the AAO surface of the silicon substrate to form an embedded ZnO nanostructure (400). S5. Template removal and annealing; The sample obtained in step S4 was immersed in acetone solution to remove the remaining AAO template. After being dried with nitrogen, it was placed in a high-temperature oxidation furnace and annealed at 300~500℃ in a pure oxygen atmosphere with a heating rate of 5~10℃ / min. S6: Preparation of Ag reflective layer; A 100nm-1μm thick Ag film is deposited on the bottom surface of an ultrathin silicon substrate (100) to obtain a solar cell.
6. The method for preparing an ultrathin silicon-based solar cell as described in claim 5, characterized in that: In step S2, the etching gas is a mixture of SF6 and O2, wherein the volume ratio of SF6 to O2 is 5:
1.
7. The method for preparing an ultrathin silicon-based solar cell as described in claim 6, characterized in that: In step S4, the oxidizing gas is a mixture of argon and oxygen, with a volume ratio of argon to oxygen of 12:1 to 16:1; and the purity of both argon and oxygen is 99.999%.
8. The method for fabricating an ultrathin silicon-based solar cell as described in claim 7, characterized in that: In steps S1-S4, the nanopores, Au-modified layer (300), and ZnO nanostructure (400) prepared on the surface of the ultrathin silicon substrate (100) all have the same period and fill factor as the double-pass AAO template.