Crystalline silicon solar cell structure based on MXene transparent electrode

Abstract

The invention discloses a crystalline silicon solar cell structure based on an MXene transparent electrode, and belongs to the technical field of photovoltaics. The structure is based on a crystalline silicon substrate, a passivation layer, a carrier transport layer and an MXene transparent conductive layer are sequentially arranged on at least one surface of the crystalline silicon substrate, and a metal grid line electrode is prepared on the surface of the MXene layer. The structure can be adapted to various crystalline silicon cell types such as a silicon heterojunction solar cell (SHJ) and a tunneling oxide passivation contact cell (TOPCon). The MXene transparent electrode has high conductivity, an adjustable work function and high transmittance, can realize energy level matching with different battery structures and improve the charge collection function, and meanwhile, avoids damage of a traditional magnetron sputtering process to a functional layer. The MXene transparent electrode is prepared through a solution method, so that the production cost is reduced, the photoelectric conversion efficiency of the cell is effectively improved in combination with the optimized interface design, and a novel high-performance transparent electrode solution is provided for the crystalline silicon solar cell.

Description

Technical Field

[0001] This application relates to the field of crystalline silicon photovoltaic technology, specifically to a crystalline silicon solar cell structure based on MXene transparent electrodes. Background Technology

[0002] Crystalline silicon solar cells, including monocrystalline and polycrystalline silicon cells, are currently the mainstream products in the photovoltaic market, with mature technology and a market share exceeding 90%. In traditional crystalline silicon cell structures, especially high-efficiency structures such as crystalline silicon heterojunction (SHJ) cells and tunneling oxide passivated contact (TOPCon) cells, transparent conductive oxides (TCOs) such as indium tin oxide are commonly used as electrodes to achieve lateral current collection, reduce series resistance, and allow light to penetrate the silicon absorption layer to the maximum extent. However, the application of TCO materials faces some inherent technical bottlenecks and challenges: indium, the raw material, is a rare metal with limited crustal reserves, high price, and large price fluctuations, which is not conducive to the continuous reduction of photovoltaic power generation costs; its preparation requires a vacuum sputtering process, which involves high-energy particle bombardment, potentially causing plasma damage to the crystalline silicon surface, especially to the passivation layer (such as amorphous silicon passivation layer); and the low utilization rate of the target material increases manufacturing costs.

[0003] Since the discovery of MXene materials, experimental and theoretical studies have shown that these materials exhibit excellent electrical, optical, and electrochemical properties, such as extremely high metallic conductivity (above 20,000 S / cm) and excellent optical transmittance, while also possessing advantages such as solution processability, flexibility, and tunable work function. These characteristics make them ideal candidate materials to replace TCOs as novel transparent electrodes.

[0004] Currently, the application of MXene as a transparent electrode in crystalline silicon solar cells is still in the early stages of research. The core problem this invention aims to solve is how to effectively integrate it with existing, mature crystalline silicon cell structures (such as TOPCon and SHJ), address engineering issues such as interface contact, work function matching, and long-term stability, and achieve performance superior to or equivalent to that of TCO electrodes. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing TCO transparent electrodes and provide a crystalline silicon solar cell structure based on MXene transparent electrodes. This structure utilizes the high conductivity, high light transmittance, and good mechanical flexibility of MXene material to replace traditional TCO thin films, aiming to reduce process damage, decrease dependence on rare metals, lower production costs, and potentially improve the photoelectric conversion efficiency of the cell.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A crystalline silicon solar cell structure based on MXene transparent electrodes includes a crystalline silicon substrate, on at least one surface of which a passivation layer and a carrier transport layer are sequentially disposed; characterized in that it further includes an MXene transparent conductive layer disposed on the carrier transport layer; the MXene transparent conductive layer serves as the front and / or back electrode of the cell for laterally collecting and transporting carriers; the cell structure further includes metal grid electrodes disposed on the MXene transparent conductive layer.

[0008] Furthermore, the crystalline silicon substrate is an N-type or P-type single-crystal silicon wafer with a thickness of 10~500 μm;

[0009] Furthermore, the battery structure is a silicon heterojunction (SHJ) structure, a tunnel oxide passivated contact (TOPCon) structure, or a passivated emitter and back surface (PERC) structure.

[0010] Furthermore, regarding the SHJ battery structure;

[0011] The passivation layer material is any one or more of a-Si:H, a-SiOx:H, a-SiCx:H, a-SiNx:H, a-SiNxOy:H, a-SiCxOy:H, and a-SiCxNy:H, with a thickness of 1~20nm;

[0012] The carrier transport layer comprises electron and hole transport layers; wherein...

[0013] The electron transport layer is any one or more of N-type doped a-Si:H, a-SiOx:H, a-SiCx:H, a-SiNx:H, a-SiNxOy:H, a-SiCxOy:H, a-SiCxNy:H, or low work function oxides, nitrides, oxynitrides, and fluorides, with a thickness of 1~50 nm;

[0014] The hole transport layer material is any one or more of the following: P-type doped and N-type doped a-Si:H, a-SiOx:H, a-SiCx:H, a-SiNx:H, a-SiNxOy:H, a-SiCxOy:H, a-SiCxNy:H, or high work function oxides, with a thickness of 1~50 nm;

[0015] The MXene transparent conductive layer shown is disposed on the corresponding carrier transport layer;

[0016] Furthermore, regarding the TOPCon battery structure;

[0017] The passivation layer comprises any one or more of aluminum oxide (Al2O3), tunneling oxide (SiOx), and hafnium oxide (HfOx), with a thickness of 1~20 nm;

[0018] The carrier transport layer is one or more of the following doped poly-Si, poly-SiOx, poly-SiCx, poly-SiNx, poly-SiNxOy, poly-SiCxOy, and poly-SiCxNy, with a thickness of 1~50 nm;

[0019] The MXene transparent conductive layer is disposed on the carrier transport layer;

[0020] Furthermore, the general chemical formula of the MXene transparent electrode material is M n+1 X n T x Where M represents the transition metal Ti, V, Ta, V, Mo, or Nb; X represents C, N, or CN; T x The surface functional groups are represented as =O, -OH, -F; Furthermore, the MXene transparent conductive material is Ti3C2T. x Mo2CT x V2CT x Ti3N2T x Mo2NT x Mo2TiC2T x Mo2Ti2C3T x One or more of these components have a thickness of 1–500 nm, a sheet resistance of 0.1–200 Ω / Sq, and a transmittance of 70–99%.

[0021] Furthermore, the MXene transparent conductive layer is formed by solution coating, which includes, but is not limited to, spin coating, blade coating, spray coating, dip coating, or screen printing.

[0022] The beneficial effects of this invention include:

[0023] (1) Construct a synergistic system of "passivation layer-carrier transport layer-MXene transparent electrode", in which the carrier transport layer is responsible for efficient selective transport, while the MXene transparent electrode is responsible for efficient conductivity, thus realizing functional separation and performance superposition.

[0024] (2) MXene has the characteristic of adjustable work function, which can be adapted to the contact layer of different battery structures to form good ohmic contact or low barrier contact, thereby improving carrier collection efficiency.

[0025] (3) The MXene surface can be modified by different functional groups to passivate the interface defects of the carrier transport layer and reduce the carrier recombination loss at the interface.

[0026] (4) This design concept is applicable to various mainstream high-efficiency crystalline silicon cell structures such as SHJ, TOPCon, and PERC, and has strong universality.

[0027] (5) The solution method is used to avoid plasma damage, and the process is simple and low cost. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the SHJ battery structure based on the MXene transparent electrode in a specific embodiment of the present invention.

[0029] Figure 2 This is a schematic diagram of the TOPCon battery structure based on the MXene transparent electrode in a specific embodiment of the present invention. Detailed Implementation

[0030] The following detailed description, in conjunction with the accompanying drawings, illustrates specific embodiments of the SHJ battery and TOPCon battery with MXene electrodes. Obviously, the described embodiments are only a portion, not all, of the embodiments described herein. Other embodiments derived by those skilled in the art based on the embodiments of this application without inventive effort are all within the scope of protection of this application.

[0031] Example 1: Illumination Figure 1 This embodiment provides a silicon heterojunction (SHJ) solar cell based on MXene transparent electrodes.

[0032] Its preparation method includes the following steps:

[0033] a) Provide an N-type single crystal silicon wafer with a thickness of 150 μm as a substrate (1), and perform double-sided texturing and cleaning on it.

[0034] b) Using PECVD, an a-Si:H passivation layer (2, thickness ~5 nm) and a P-type a-Si:H (as hole transport layer 3b, thickness ~10 nm) are sequentially deposited on the front side of the silicon wafer; an a-Si:H passivation layer (2) and an N-type a-Si:H (as electron transport layer 3a, thickness ~10 nm) are sequentially deposited on the back side.

[0035] c) Configure Ti3C2T x MXene isopropanol dispersion (concentration 3 mg / mL). It was coated onto the P-type a-Si:H layer on the front side and the N-type a-Si:H layer on the back side of the battery using ultrasonic spraying.

[0036] d) Annealing was performed at 180°C in a nitrogen atmosphere for 15 minutes to form an MXene transparent conductive layer with a thickness of approximately 20 nm (4). The sheet resistance of this layer was approximately 45 Ω / sq, and the transmittance was 90%.

[0037] e) Finally, silver grid lines (5) are prepared on the MXene layer on the front and back sides by low-temperature silver paste screen printing technology to complete the battery fabrication with MXene transparent electrodes.

[0038] Example 2: See Figure 2 This embodiment provides a TOPCon solar cell based on MXene transparent electrodes.

[0039] Its preparation method includes the following steps:

[0040] a) Provide an N-type single crystal silicon wafer with a thickness of 170 μm as a substrate (1), and perform cleaning and front-side texturing.

[0041] b) On the back of the battery, a tunneling oxide layer with a thickness of approximately 1.5 nm is grown by thermal oxidation (6), followed by deposition of phosphorus-doped poly-Si (7, thickness ~150 nm) by LPCVD, and activation and formation of TOPCon structure by high-temperature annealing. The doped poly-Si here serves as both an electron transport layer and a field passivation layer.

[0042] c) On the front side of the battery, a boron emitter is formed by diffusion, and an Al2O3 / SiNx stack is deposited as a passivation and antireflection layer.

[0043] d) On the back-side doped poly-Si(7), Ti3C2T is coated by spin coating. x The MXene aqueous dispersion was heat-treated at 200°C to form a transparent conductive layer of MXene with a thickness of about 12 nm (4).

[0044] e) A metallic aluminum electrode is formed on the MXene layer on the back side as a back field contact using screen printing technology (8).

[0045] Comparative scale and experimental results

[0046] Its structure is similar to that of Example 1, except that: an ITO thin film is prepared by magnetron sputtering as a transparent conductive layer, with a thickness of about 80 nm and a sheet resistance of about 70 Ω / sq.

[0047] Test results show that the SHJ battery of Example 1 of this invention, thanks to the non-destructive deposition of MXene and the optimized interface, has an open-circuit voltage (Voc) that is about 3-5 mV higher than that of the comparative example, with a comparable fill factor (FF), and a final conversion efficiency of 24.2%, which is better than the 12.5% ​​of the comparative example. This proves the effectiveness and superiority of the structure of this invention.

[0048] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A crystalline silicon solar cell structure based on MXene transparent electrodes, comprising a crystalline silicon substrate (1), characterized in that: A passivation layer (2 or 6), a carrier transport layer (3 or 7) and an MXene transparent conductive layer (4) are sequentially disposed on at least one surface of the crystalline silicon substrate (1), and a metal gate electrode (5) is disposed on the surface of the MXene transparent conductive layer (4).

2. The crystalline silicon solar cell structure according to claim 1, characterized in that: The crystalline silicon substrate (1) is an N-type or P-type monocrystalline silicon with a thickness of 10~500 μm.

3. The crystalline silicon solar cell structure according to claim 1, characterized in that: The battery is a silicon heterojunction (SHJ) structure, a tunnel oxide passivated contact (TOPCon) structure, or a passivated emitter and back surface (PERC) structure.

4. The crystalline silicon solar cell structure according to claim 3, characterized in that: When the battery is an SHJ structure, the passivation layer (2) is made of one or more of a-Si:H, a-SiOx:H, a-SiCx:H, a-SiNx:H, a-SiNxOy:H, a-SiCxOy:H, and a-SiCxNy:H, with a thickness of 1~20 nm; the carrier transport layer (3) includes an electron transport layer (3a) and a hole transport layer (3b), wherein the electron transport layer (3a) is made of N-type doped a-Si:H, a-SiOx:H, a-SiCx:H, a-SiNx:H, a-SiNxOy:H, a-SiCxOy:H, a-SiCxNy:H, or any one or more of low work function oxides, nitrides, oxynitrides, and fluorides, with a thickness of 1~50 nm. nm; the hole transport layer (3b) is selected from any one or more of P-type doped a-Si:H, a-SiOx:H, a-SiCx:H, a-SiNx:H, a-SiNxOy:H, a-SiCxOy:H, a-SiCxNy:H, or high work function oxides, with a thickness of 1~50 nm.

5. The crystalline silicon solar cell structure according to claim 3, characterized in that: When the battery structure is a TOPCon structure, the passivation layer (6) material is selected from any one or more of aluminum oxide (Al2O3), tunneling oxide (SiOx) or hafnium oxide (HfOx), and the thickness is 1~20 nm; the carrier transport layer (7) is one or more of poly-Si, poly-SiOx, poly-SiCx, poly-SiNx, poly-SiNxOy, poly-SiCxOy, and poly-SiCxNy, and the thickness is 1~20 nm.

6. The crystalline silicon solar cell structure according to claim 1, characterized in that: The MXene transparent conductive layer (4) is made of Ti3C2T material. x Mo2CT x V2CT x Ti3N2T x Mo2NT x Mo2TiC2T x Mo2Ti2C3T x One or more of them.

7. The crystalline silicon solar cell structure according to claim 1 or 6, characterized in that: The thickness of the MXene transparent conductive layer (4) is 1~500 nm, the sheet resistance is 0.1~200 Ω / Sq, and the transmittance in the visible light band is 70~99%.

8. The crystalline silicon solar cell structure according to claim 1, characterized in that: The MXene transparent conductive layer (4) is prepared by a solution method, which includes, but is not limited to, spin coating, blade coating, spray coating, dip coating or screen printing.

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