A preparation method of a crystalline silicon perovskite laminated solar cell

Abstract

The application belongs to the technical field of solar cells, and provides a preparation method of a crystalline silicon perovskite laminated solar cell, which comprises the following steps: preparing a P+ emitter on a front surface of an n-type crystalline silicon substrate; sequentially preparing tunneling silicon oxide and doped polycrystalline silicon on a back surface of the silicon substrate, and then selectively doping to form a heavily doped region, i.e. a selective back surface field; after preparing a first passivation layer and a second passivation layer, preparing a first metal electrode and a second metal electrode, i.e. a crystalline silicon bottom cell; sequentially preparing a laminated electron transport layer and a perovskite absorption layer on a front surface of a transparent adhesive layer; then preparing MoO x a hole transport layer by an electrochemical method; preparing a third metal electrode and a fourth metal electrode, i.e. a perovskite top cell; and laminating the perovskite top cell on the front surface of the crystalline silicon bottom cell by using the transparent adhesive layer. The method can solve the problem of a large number of light-generated carrier recombination losses in the existing laminated solar cell, improve the carrier collection capacity of the cell, and further improve the cell efficiency.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, and in particular to a method for preparing a crystalline silicon perovskite tandem solar cell. Background Technology

[0002] Crystalline silicon solar cells have a band gap of 1.12 eV. Incident photons with energies equal to or higher than 1.12 eV can be absorbed by the silicon substrate to generate electron-hole pairs, i.e., photogenerated carriers, and excess energy is dissipated as heat. However, incident photons with energies lower than 1.12 eV cannot be absorbed by the silicon substrate, thus failing to generate photogenerated carriers, resulting in spectral energy loss; more than 50% of all energy loss is wasted in the form of spectral energy loss. To reduce spectral energy loss, an effective approach is to design multi-junction solar cells. In this way, under the condition of shared incident light, pn junctions with different band gap materials can absorb incident photons of different energies, thereby broadening the absorption range of the spectrum. This is beneficial for improving the open-circuit voltage and short-circuit current of the solar cell, and consequently, improving the cell efficiency.

[0003] Among tandem solar cells, crystalline silicon / perovskite tandem solar cells are the most representative. Perovskite materials are ideal photoelectric materials due to their high absorption coefficient, steep absorption edge, and tunable bandgap. Moreover, compared to crystalline silicon with a bandgap of 1.12 eV, perovskite materials have a bandgap that is adjustable between 1.5 and 2.3 eV, which helps reduce spectral energy loss and makes them very suitable as the top cell material in tandem solar cells. Furthermore, currently fabricated perovskite cells are less than 1 μm thick, essentially absorbing no long-wavelength photons, thus effectively achieving uniform spectral dispersion and exhibiting good light transmittance, allowing unabsorbed incident light to enter the bottom cell and be fully absorbed, further reducing spectral energy loss.

[0004] Existing methods for fabricating crystalline silicon / perovskite tandem solar cells, such as the low-cost, high-efficiency method disclosed in publication CN110767777A, involve spin-coating poly-3-hexylthiophene, small-molecule hole transport materials, or inorganic hole transport materials onto the surface of the perovskite film after the deposition of the electron transport layer and the perovskite thin film, forming a hole transport layer. While this spin-coating method is convenient, the particle size and film density of the hole transport layer are difficult to control; moreover, the production capacity of the spin-coating method is low, making large-scale simultaneous spin-coating impossible; furthermore, the spin-coating method is highly wasteful of resources, with 80% of the resources being lost during spin-coating and unusable. Another example is the crystalline silicon perovskite tandem solar cell and its fabrication method disclosed in publication CN113013277A, where the bottom cell uses a conventional tunneling oxide passivation contact structure, and the hole transport layer of the top cell is prepared using a thermal evaporation method. The drawback of this preparation method is that the thermal evaporation method requires high temperatures and vacuum levels, making it difficult to control the morphology and microstructure of the film. It is evident that the existing methods for fabricating crystalline silicon / perovskite tandem solar cells result in difficulty controlling the density, morphology, and microstructure of the hole transport layer. This leads to poor conversion efficiency and stability of the perovskite top cell and poor matching performance between the perovskite top cell and the crystalline silicon bottom cell. Consequently, there is significant recombination loss of photogenerated carriers near the metal electrodes, limiting the improvement of the cell efficiency of crystalline silicon / perovskite tandem solar cells.

[0005] Furthermore, in recent years, non-stoichiometric transition metal oxides have attracted considerable attention due to their excellent photoelectric properties in novel high-performance photoelectric or photocatalytic devices. Among them, non-stoichiometric molybdenum oxide (MoO2) is a prime example. x Due to its advantages of being non-toxic, having a large band gap, and possessing deep electronic states, MoO₂ (2≤x≤3) shows promise as a candidate hole transport material for use in novel perovskite solar cells. However, if the existing preparation methods described above are used to prepare MoO₂... x Hole transport layer, then MoO x Morphology, composition, and microstructure are highly susceptible to the influence of control parameters and environmental conditions, which limits their practical application in novel perovskite solar cells. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for preparing crystalline silicon perovskite tandem solar cells. This method aims to solve the problem of high recombination loss of photogenerated carriers in existing tandem solar cells, thereby improving the carrier collection capability of the metal electrodes in the obtained crystalline silicon perovskite tandem solar cells and ultimately enhancing the cell efficiency.

[0007] Based on this, the present invention discloses a method for preparing a crystalline silicon perovskite tandem solar cell, the preparation steps of which are as follows:

[0008] Step S1, Fabrication of crystalline silicon bottom solar cells:

[0009] Step S11: Prepare a P+ emitter on the front surface of an n-type crystal silicon substrate;

[0010] Step S12: After tunneling silicon oxide and doped polycrystalline silicon are sequentially prepared on the back surface of the silicon substrate, selective doping is performed on the back side of the doped polycrystalline silicon to form a heavily doped region, thus obtaining a selective back surface field.

[0011] Step S13: After preparing the first passivation layer and the second passivation layer on the back surface of the selective back surface field and the front surface of the P+ emitter, respectively, an outwardly extending first metal electrode and a second metal electrode are prepared on the heavily doped region and the P+ emitter, respectively.

[0012] Step S2, fabrication of the perovskite top solar cell:

[0013] Step S21: Sequentially prepare a stacked electron transport layer and a perovskite absorber layer on the front surface of the transparent adhesive layer;

[0014] Step S22: MoO2 is prepared on the front surface of the perovskite absorber layer using an electrochemical method. x Hole transport layer;

[0015] Step S23, on the back surface of the electron transport layer and MoO x A third metal electrode and a fourth metal electrode extending outward are respectively fabricated on the front surface of the hole transport layer;

[0016] Step S3: A transparent adhesive layer is used to stack the perovskite top cell onto the front surface of the crystalline silicon bottom cell.

[0017] Preferably, in step S12, the heavily doped region is prepared by laser doping or secondary diffusion doping.

[0018] More preferably, in step S12, the heavily doped region is prepared by laser doping.

[0019] Preferably, the doping concentration of the doped polycrystalline silicon is greater than 2 × 10⁻⁶. 19 cm -3 Junction depth less than 0.3 μm, doping concentration in heavily doped regions greater than 2 × 10⁻⁶ 20 cm -3 The junction depth is greater than 0.2 μm;

[0020] The thickness of the tunneling silicon oxide is 0.5–2 nm; the thickness of the doped polycrystalline silicon is 50–200 nm.

[0021] Preferably, in step S22, the MoO xThe hole transport layer is prepared by depositing MoO on an FTO-coated glass substrate using an electrochemical method with voltage scanning. x Hole transport layer, then MoO x The hole transport layer is placed on the front surface of the perovskite absorber layer;

[0022] The MoO x The thickness of the hole transport layer is 20–80 nm.

[0023] Preferably, in step S21, the electron transport layer is prepared by spin-coating a solution containing dissolved titanium dioxide or fullerene derivative material onto the surface of a transparent adhesive layer to solidify and form an electron transport layer.

[0024] The thickness of the electron transport layer is 20–80 nm.

[0025] Preferably, the thickness of the perovskite absorber layer is 300–600 nm.

[0026] Preferably, in step S11, the surface concentration of the P+ emitter is 1×10⁻⁶. 19 ~5×10 19 cm -3 The junction depth is 0.3–1 μm.

[0027] Preferably, in step S11, before preparing the P+ emitter, the method further includes selecting an n-type single-crystal silicon substrate, removing the damage layer and cleaning the silicon substrate, and then texturing the silicon substrate.

[0028] Preferably, the first passivation layer is silicon nitride, and the thickness of the first passivation layer is 50-150 nm;

[0029] The second passivation layer is a stacked structure of silicon oxide / silicon hydrogen nitride, wherein the thickness of silicon oxide in the second passivation layer is 1-10 nm and the thickness of silicon hydrogen nitride is 50-150 nm.

[0030] Compared with the prior art, the present invention has at least the following beneficial effects:

[0031] In this invention, the hole transport layer of the perovskite top solar cell is made of MoO. x Thin films were obtained, and uniform, smooth non-stoichiometric MoO₂ films were prepared using a novel and controllable electrochemical method. x Hole transport layer, MoO obtained by this electrochemical method x The stoichiometry, morphology, and microstructure of the hole transport layer can be effectively controlled using simple physical / chemical parameters to enhance the performance of this MoO2. xThe oxygen vacancy concentration, density, and crystallinity of the hole transport layer improve the conversion efficiency and stability of perovskite as a top cell. This electrochemical method also offers advantages such as low cost and ease of large-area application, facilitating mass production. Furthermore, the crystalline silicon bottom cell of this invention employs a selective back surface field structure, significantly enhancing the matching performance between the perovskite top cell and the crystalline silicon bottom cell. This effectively avoids recombination losses of photogenerated carriers near the metal electrodes, resulting in a crystalline silicon perovskite tandem solar cell with higher carrier collection efficiency, thereby effectively improving the cell efficiency of the crystalline silicon perovskite tandem solar cell. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the structure of a silicon-based perovskite tandem solar cell in Example 1.

[0033] Reference numerals: 1. First metal electrode; 2. First passivation layer; 3. Doped polycrystalline silicon; 4. Heavily doped region; 5. Tunneling silicon oxide; 6. Silicon substrate; 7. P+ emitter; 8. Second passivation layer; 9. Second metal electrode; 10. Transparent adhesive layer; 11. Third metal electrode; 12. Electron transport layer; 13. Perovskite absorber layer; 14. MoO x Hole transport layer 14, fourth metal electrode 15. Detailed Implementation

[0034] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to specific embodiments.

[0035] Example 1

[0036] This embodiment describes a method for fabricating a crystalline silicon perovskite tandem solar cell, referring to... Figure 1 The crystalline silicon perovskite tandem solar cell comprises a crystalline silicon bottom cell, a transparent adhesive layer 10, and a perovskite top cell stacked sequentially, and its fabrication method includes the following steps:

[0037] Step 1, Fabrication of crystalline silicon bottom solar cells:

[0038] Step 11, Fabrication of silicon substrate 6 and P+ emitter 7: An n-type single-crystal silicon substrate 6 is selected. After removing the damaged layer and cleaning, the silicon substrate 6 is texturized. Then, a P+ emitter 7 is fabricated on the front surface of the silicon substrate 6. One example of this embodiment is that the silicon substrate 6 after removing the damaged layer and cleaning is placed in a mixed solution of NaOH and isopropanol for texturization, wherein the concentration of the NaOH alkaline solution is 1%–3%, and the concentration of the isopropanol solution is 2%–10%. A boron source is introduced using a diffusion method to form the P+ emitter 7, wherein the surface concentration of the P+ emitter 7 is 1 × 10⁻⁶. 19 ~5×10 19 cm -3The junction depth is 0.3–1 μm.

[0039] Step 12, selective back surface field preparation: After etching the back surface of the silicon substrate 6, a layer of tunneling silicon oxide 5 is first prepared, and then a layer of doped polysilicon 3 is deposited on the back surface of the tunneling silicon oxide 5. Then, selective doping is performed locally on the back surface of the doped polysilicon 3 to form a heavily doped region 4, thus obtaining the selective back surface field.

[0040] The tunneling silicon oxide 5 is preferably prepared by LPCVD, and its thickness is 0.5–2 nm. The doped polycrystalline silicon 3 and the heavily doped region 4 are preferably phosphorus-doped, and the heavily doped region 4 is preferably prepared by laser doping or secondary diffusion doping. The thickness of the doped polycrystalline silicon 3 is 50–200 nm, and the doping concentration of the doped polycrystalline silicon 3 is greater than 2 × 10⁻⁶. 19 cm -3 The junction depth is less than 0.3 μm, and the doping concentration of heavily doped region 4 is greater than 2 × 10⁻⁶. 20 cm -3 The junction depth is greater than 0.2μm.

[0041] Step 13, preparation of passivation layer, first metal electrode 1 and second metal electrode 9: First passivation layer 2 and second passivation layer 8 are prepared on the back surface of selective back surface field and the front surface of P+ emitter 7, respectively. Then, using a metal paste that has burn-through properties to the passivation layer, the first metal electrode 1 and the second metal electrode 9 extending outward are prepared on the heavily doped region 4 and P+ emitter 7, respectively, to obtain a crystalline silicon bottom cell with selective back surface field.

[0042] In one example of this embodiment, a layer of silicon nitride is deposited on the back surface of the selective back surface field as a first passivation layer 2, wherein the thickness of the first passivation layer 2 is 50-150 nm, and a silicon oxide / silicon nitride stacked structure is deposited on the front surface of the P+ emitter 7 as a second passivation layer 8, wherein the thickness of silicon oxide in the second passivation layer 8 is 1-10 nm and the thickness of silicon nitride is 50-150 nm; the first metal electrode 1 and the second metal electrode 9 are preferably prepared by screen printing.

[0043] Step 2, Fabrication of the perovskite top solar cell:

[0044] Step 21, Preparation of electron transport layer 12: Electron transport layer 12 is prepared on the front surface of transparent adhesive layer 10.

[0045] In one example of this embodiment, a solution containing titanium dioxide or fullerene derivative material is spin-coated onto the surface of the transparent adhesive layer 10 to solidify and form an electron transport layer 12; wherein the thickness of the electron transport layer 12 is 20-80 nm.

[0046] Step 22, Preparation of perovskite absorber layer 13: Prepare perovskite absorber layer 13 on the front surface of electron transport layer 12.

[0047] One example of this embodiment is that a metal halide and an organic halide are dissolved in an organic solvent and stirred to obtain a perovskite precursor solution. The perovskite precursor solution is then spin-coated onto the electron transport layer 12 and annealed to obtain a perovskite absorber layer 13. The thickness of the perovskite absorber layer 13 is 300-600 nm.

[0048] Step 23, Preparation of MoOx hole transport layer 14: MoOx hole transport layer 14 is prepared on the front surface of perovskite absorber layer 13 using an electrochemical method. Unless otherwise specified, the value of x in this MoOx hole transport layer 14 is in the range of 2 ≤ x ≤ 3.

[0049] In one example of this embodiment, a MoOx hole transport layer 14 is deposited on an FTO-coated glass substrate using an electrochemical method with voltage scanning, at voltages ranging from -1.2V to -0.8V and from -0.5V to 1.0V, and then the MoOx hole transport layer 14 is disposed on the front surface of the perovskite absorber layer 13; wherein the thickness of the MoOx hole transport layer 14 is 20 to 80 nm.

[0050] Step 24, fabrication of the third metal electrode 11 and the fourth metal electrode 15: The third metal electrode 11 and the fourth metal electrode 15 extending outward are fabricated on the back surface of the electron transport layer 12 and the front surface of the MoOx hole transport layer 14, respectively, to obtain a perovskite top cell with the MoOx hole transport layer 14.

[0051] One example of this embodiment is that the third metal electrode 11 and the fourth metal electrode 15 are prepared by screen printing, wherein the material of the third metal electrode 11 and the fourth metal electrode 15 is metal Ag.

[0052] Step 3, finally, the perovskite top cell is stacked on the front surface of the crystalline silicon bottom cell using the transparent adhesive layer 10. The perovskite top cell and the crystalline silicon bottom cell are independently connected, thus obtaining the crystalline silicon perovskite tandem solar cell of this embodiment, the structure of which is as follows. Figure 1 As shown, from bottom to top, the layers are: first metal electrode 1, first passivation layer 2, doped polycrystalline silicon 3, heavily doped region 4, tunneling silicon oxide 5, silicon substrate 6, P+ emitter 7, second passivation layer 8, second metal electrode 9, transparent adhesive layer 10, third metal electrode 11, electron transport layer 12, perovskite absorber layer 13, MoOx hole transport layer 14, and fourth metal electrode 15.

[0053] In the above-described method for fabricating a crystalline silicon perovskite tandem solar cell in this embodiment, the material, thickness, fabrication method, selective back surface field, doping concentration, and junction depth of the P+ emitter 7 of each layer are optimized to improve the matching performance between the perovskite top cell and the crystalline silicon bottom cell. This better avoids the recombination loss of photogenerated carriers near the metal electrode, and greatly improves the carrier collection efficiency and cell efficiency of the resulting crystalline silicon perovskite tandem solar cell.

[0054] In this embodiment, the crystalline silicon bottom cell of the crystalline silicon perovskite tandem solar cell is an n-type crystalline silicon TOPCon structure, and the back surface of the crystalline silicon bottom cell adopts a selective back surface field structure. Simultaneously, the front surface of the perovskite top cell is prepared with a MoOx hole transport layer 14 structure using an electrochemical method. This allows the stoichiometry, morphology, and microstructure of the MoOx hole transport layer 14 to be effectively controlled using simple physical / chemical parameters, thereby improving the oxygen vacancy concentration, compactness, and crystallinity of the MoOx hole transport layer 14, resulting in a uniform and smooth MoOx hole transport layer 14. This improves the conversion efficiency and stability of the perovskite as a top cell. Thus, the preparation method of this embodiment can significantly improve the matching performance between the perovskite top cell and the crystalline silicon bottom cell, effectively avoiding the recombination loss of photogenerated carriers near the metal electrode. This results in a crystalline silicon perovskite tandem solar cell with higher carrier collection efficiency, thereby effectively improving the cell efficiency of the crystalline silicon perovskite tandem solar cell. In addition, this electrochemical method has the advantages of being inexpensive and easy to apply over a large area, which is conducive to the large-scale production of crystalline silicon perovskite tandem solar cells.

[0055] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present invention.

[0056] The technical solution provided by the present invention has been described in detail above. Specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for fabricating a crystalline silicon perovskite tandem solar cell, characterized in that, The preparation steps include the following: Step S1, Fabrication of crystalline silicon bottom solar cells: Step S11: A P+ emitter is fabricated on the front surface of an n-type silicon substrate; in step S11, the surface concentration of the P+ emitter is 1×10⁻⁶. 19 ~5×10 19 cm -3 The junction depth is 0.3–1 μm; Step S12: After sequentially preparing tunneling silicon oxide and doped polycrystalline silicon on the back surface of the silicon substrate, selectively doping is performed on a localized area of ​​the back surface of the doped polycrystalline silicon to form a heavily doped region, thus obtaining a selective back surface field; the doping concentration of the doped polycrystalline silicon is greater than 2 × 10⁻⁶. 19 cm -3 Junction depth less than 0.3 μm, doping concentration in heavily doped regions greater than 2 × 10⁻⁶ 20 cm -3 The junction depth is greater than 0.2 μm; Step S13: After preparing the first passivation layer and the second passivation layer on the back surface of the selective back surface field and the front surface of the P+ emitter, respectively, an outwardly extending first metal electrode and a second metal electrode are prepared on the heavily doped region and the P+ emitter, respectively. Step S2, fabrication of the perovskite top solar cell: Step S21: Sequentially prepare a stacked electron transport layer and a perovskite absorber layer on the front surface of the transparent adhesive layer; Step S22: MoO2 is prepared on the front surface of the perovskite absorber layer using an electrochemical method. x Hole transport layer; In step S22, the MoO x The hole transport layer is prepared by depositing MoO on an FTO-coated glass substrate using an electrochemical method with voltage scanning. x Hole transport layer, with voltages ranging from -1.2V to -0.8V and from -0.5V to 1.0V respectively, then MoO x The hole transport layer is placed on the front surface of the perovskite absorber layer; the MoO x The thickness of the hole transport layer is 20–80 nm, and the value of x ranges from 2 to x ≤ 3. Step S23, on the back surface of the electron transport layer and MoO x A third metal electrode and a fourth metal electrode extending outward are respectively fabricated on the front surface of the hole transport layer; Step S3: A transparent adhesive layer is used to stack the perovskite top cell onto the front surface of the crystalline silicon bottom cell.

2. The method for preparing a crystalline silicon perovskite tandem solar cell according to claim 1, characterized in that, In step S12, the heavily doped region is prepared by laser doping or secondary diffusion doping.

3. The method for preparing a crystalline silicon perovskite tandem solar cell according to claim 2, characterized in that, In step S12, the heavily doped region is prepared by laser doping.

4. A method for preparing a crystalline silicon perovskite tandem solar cell according to any one of claims 1-3, characterized in that, The thickness of the tunneling silicon oxide is 0.5–2 nm; the thickness of the doped polycrystalline silicon is 50–200 nm.

5. The method for preparing a crystalline silicon perovskite tandem solar cell according to claim 1, characterized in that, In step S21, the electron transport layer is prepared by spin-coating a solution containing dissolved titanium dioxide or fullerene derivative material onto the surface of a transparent adhesive layer to solidify and form an electron transport layer. The thickness of the electron transport layer is 20–80 nm.

6. The method for preparing a crystalline silicon perovskite tandem solar cell according to claim 1, characterized in that, The thickness of the perovskite absorber layer is 300–600 nm.

7. The method for preparing a crystalline silicon perovskite tandem solar cell according to claim 1, characterized in that, In step S11, before preparing the P+ emitter, the process further includes selecting an n-type single-crystal silicon substrate, removing the damage layer and cleaning the silicon substrate, and then texturing the silicon substrate.

8. The method for preparing a crystalline silicon perovskite tandem solar cell according to claim 1, characterized in that, The first passivation layer is silicon nitride, and the thickness of the first passivation layer is 50-150 nm; The second passivation layer is a stacked structure of silicon oxide / silicon hydrogen nitride, wherein the thickness of silicon oxide in the second passivation layer is 1-10 nm and the thickness of silicon hydrogen nitride is 50-150 nm.

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