Efficiency improving method of TBC solar cell and TBC solar cell

Abstract

The invention discloses an efficiency improving method of a TBC solar cell and the TBC solar cell, and relates to the technical field of solar cells. According to the method for improving the efficiency of the TBC solar cell, the electrode interface passivation contact effect is improved by introducing an electrode region laser-assisted sintering process processing method, so that direct contact can be formed between an electrode and a polycrystalline silicon region, an effective electron transmission path is established, good ohmic contact is formed in a contact region, and the efficiency of the TBC solar cell is improved. The interface passivation contact effect is obviously improved, the contact resistance between metal and a semiconductor is reduced, and the photoelectric conversion efficiency of the TBC battery is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of solar cells, and in particular relates to a method for improving the efficiency of a TBC solar cell and a TBC solar cell. Background Art

[0002] As a clean energy source, solar cells are increasingly used, among which interdigitated back contact (IBC) solar cell technology is gaining more and more favor due to its high conversion efficiency.

[0003] Back-contact solar cells mainly place the p+ emitter, n+ back field region and silver grid lines on the back of the cell through the back-side patterning process. It is a change in the graphic structure of the back of the cell to place all the grid lines on the back of the cell, which can greatly improve the light absorption rate of the front of the cell. Back-contact solar cells are a cell manufacturing technology that is optimized in structure, so they can be superimposed with other cell technologies, such as: IBC technology and TOPCon (Tunnel Oxide Passivated Contact) technology superimposed to obtain TBC (TOPCon Back Contact, referring to cross-passivated back contact) solar cells.

[0004] TBC back contact cell currently refers to a cell structure that uses P-type and N-type Poly Si as the emitter and BSF (Back Surface Field) on an N-type silicon wafer substrate, and a tunnel oxide layer SiO2 is deposited between the Poly Si and the doped layer. Therefore, overall, the TBC solar cell absorbs the tunnel oxide layer passivation contact technology of the TOPCon cell and the IBC cell back preparation technology of the P and N regions arranged in a forked finger-like pattern. The TBC cell has no grid line blocking on the front of the cell, eliminating the light-shielding current loss of the metal electrode. The back uses Poly Si and the tunnel oxide layer SiO2, which greatly reduces the recombination on the back and improves the open circuit voltage. The heavily doped polysilicon also greatly reduces the contact resistance, thereby bringing gains in current and open voltage, making the TBC cell have a significant improvement in solar energy conversion efficiency.

[0005] Since the positive and negative electrodes of TBC solar cells are all on the back of the battery, the interface passivation contact effect of the electrode part on the back of the battery has a significant impact on the photoelectric conversion efficiency of the battery. For TBC solar cells, during the screen printing process of the electrode, the interface passivation contact of the screen-printed electrode area will be poor, resulting in reduced power generation efficiency and cloud phenomenon, which will seriously affect the power generation effect of the TBC solar cell. Summary of the invention

[0006] In order to solve the above problems existing in the prior art, the present invention provides a method for improving the efficiency of a TBC solar cell and a TBC solar cell. The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0007] The present invention provides a method for improving the efficiency of a TBC solar cell, comprising:

[0008] Step 1: Prepare a TBC solar cell;

[0009] Step 2: performing light injection processing on the TBC solar cell;

[0010] Step 3: Using laser-assisted wire mesh sintering technology to process the electrode of the TBC solar cell after the light injection process, so that a eutectic body of metal and silicon is formed between the electrode of the TBC solar cell and the polysilicon region.

[0011] In one embodiment of the present invention, step 1 comprises:

[0012] Step 1.1: forming a first tunneling oxide layer on a first surface of a silicon substrate;

[0013] Step 1.2: forming a p+ polysilicon region and an n+ polysilicon region alternately arranged in a straight line on the surface of the first tunneling oxide layer, wherein an isolation region exists between the p+ polysilicon region and the n+ polysilicon region;

[0014] Step 1.3: forming a suede structure on the second surface of the silicon substrate;

[0015] Step 1.4: sequentially forming a stacked passivation layer and an anti-reflection layer on the surface of the p+ polysilicon region, the n+ polysilicon region and the suede structure;

[0016] Step 1.5: Prepare electrodes on the anti-reflection layers of the p+ polycrystalline silicon region and the n+ polycrystalline silicon region by using a screen printing process to obtain a TBC solar cell.

[0017] In one embodiment of the present invention, the material of the silicon substrate is n-type doped single crystal silicon.

[0018] In one embodiment of the present invention, step 1.2 comprises:

[0019] Step 1.21: depositing an intrinsic silicon layer on the surface of the first tunneling oxide layer and annealing the layer to form a first polysilicon layer;

[0020] Step 1.22: doping the first polysilicon layer with boron atoms to form a p+ polysilicon layer and forming a BSG mask layer on the p+ polysilicon layer;

[0021] Step 1.23: Using laser patterning, remove the BSG mask layer and the p+ polysilicon layer in a part of the area to form an interval p+ polysilicon area with a BSG mask layer;

[0022] Step 1.24: sequentially forming a stacked second tunneling oxide layer and a second polysilicon layer on surfaces of the first tunneling oxide layer and the BSG mask layer;

[0023] Step 1.25: doping the second polysilicon layer with phosphorus atoms to form an n+ polysilicon layer and forming a PSG mask layer on the n+ polysilicon layer;

[0024] Step 1.26: removing the PSG mask layer, the n+ polysilicon layer, the second tunneling oxide layer and the BSG mask layer on the p+ polysilicon region by laser patterning to form an n+ polysilicon region having a PSG mask layer which is arranged in a straight line alternately with the p+ polysilicon region;

[0025] Step 1.27: removing the PSG mask layer on the n+ polysilicon region and a portion of the n+ polysilicon region to form the isolation region between the n+ polysilicon region and the p+ polysilicon region.

[0026] In one embodiment of the present invention, the material of the first tunneling oxide layer and the second tunneling oxide layer is SiO2.

[0027] In one embodiment of the present invention, the material of the passivation layer is aluminum oxide, and the material of the anti-reflection layer is silicon nitride or silicon oxynitride.

[0028] In one embodiment of the present invention, in step 2, the peak temperature of light injection is 220-290° C., the light intensity is 20%-50%, and the light injection time is 20-40 s.

[0029] In one embodiment of the present invention, step 3 comprises:

[0030] Laser is irradiated on the electrode of the TBC solar cell to stimulate partial dissolution of the electrode and its contact area and to exchange particles, thereby forming a eutectic body of metal and silicon between the electrode and the polysilicon region.

[0031] In one embodiment of the present invention, the laser is a green pulse laser with a wavelength of 500-600nm, and the laser power parameter is 25-35W.

[0032] The present invention also provides a TBC solar cell obtained by using the method for improving the efficiency of a TBC solar cell described in any one of the above embodiments.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The efficiency improvement method of the TBC solar cell of the present invention improves the electrode interface passivation contact effect by introducing a process method of laser-assisted sintering of the electrode area, so that the electrode can form a direct contact with the polysilicon area, establish an effective electron transmission path, and form a good ohmic contact in the contact area, thereby significantly improving the interface passivation contact effect, reducing the contact resistance between the metal and the semiconductor, and improving the photoelectric conversion efficiency of the TBC battery.

[0035] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the following specifically cites a preferred embodiment and describes it in detail with the accompanying drawings as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a schematic diagram of a method for improving the efficiency of a TBC solar cell provided by an embodiment of the present invention;

[0037] Figure 2 is a schematic structural diagram of a TBC solar cell provided by an embodiment of the present invention;

[0038] Figure 3 It is a schematic diagram of the working principle of laser assisted sintering provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0039] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following is a detailed description of a TBC solar cell efficiency improvement method and a TBC solar cell proposed in accordance with the present invention in combination with the accompanying drawings and specific implementation methods.

[0040] The above and other technical contents, features and effects of the present invention are clearly presented in the following detailed description of the specific implementation modes in conjunction with the accompanying drawings. Through the description of the specific implementation modes, the technical means and effects adopted by the present invention to achieve the predetermined purpose can be more deeply and specifically understood. However, the attached drawings are only for reference and explanation purposes and are not used to limit the technical solutions of the present invention.

[0041] In the first aspect, the present invention provides a method for improving the efficiency of a TBC solar cell. Figure 1 , Figure 1 is a schematic diagram of a method for improving the efficiency of a TBC solar cell provided by an embodiment of the present invention, such as Figure 1 As shown, the method for improving the efficiency of a TBC solar cell of this embodiment includes:

[0042] Step 1: Prepare a TBC solar cell.

[0043] In an optional embodiment, step 1 includes:

[0044] Step 1.1: Form a first tunneling oxide layer on a first surface of a silicon substrate.

[0045] Optionally, the material of the silicon substrate is n-type doped single crystal silicon.

[0046] It is understandable that before forming the first tunneling oxide layer on the first surface of the silicon substrate, the silicon substrate must first be double-sided polished. This is because the edge of the silicon wafer is damaged after cutting, the lattice structure of silicon is destroyed, and the surface is seriously recombined. Therefore, the main purpose of double-sided polishing is to remove the surface damage of the silicon substrate, increase light absorption, and improve the minority carrier lifetime.

[0047] Optionally, the material of the first tunneling oxide layer is SiO2, and the thickness is generally 0.5nm-□3nm. As an example, the thickness of the first tunneling oxide layer can be 0.5nm, 1.0nm, 1.8nm or 3nm, etc. The method for forming the first tunneling oxide layer includes but is not limited to low pressure chemical vapor deposition (LPCVD), plasma enhanced chemical vapor deposition (PECVD), physical vapor deposition (PVD), and atomic layer deposition (ALD).

[0048] Step 1.2: forming a p+ polysilicon region and an n+ polysilicon region alternately arranged in a straight line on the surface of the first tunneling oxide layer, wherein an isolation region exists between the p+ polysilicon region and the n+ polysilicon region;

[0049] In an optional embodiment, step 1.2 includes:

[0050] Step 1.21: Deposit an intrinsic silicon layer on the surface of the first tunneling oxide layer and perform annealing to form a first polysilicon layer.

[0051] Optionally, the thickness of the first polysilicon layer is 200nm-500nm. As an example, the thickness of the first polysilicon layer can be 200nm, 300nm, 400nm or 500nm, etc. The method of forming the intrinsic silicon layer includes but is not limited to LPCVD, PECVD, PVD or ALD.

[0052] Step 1.22: doping the first polysilicon layer with boron atoms to form a p+ polysilicon layer and forming a BSG mask layer on the p+ polysilicon layer.

[0053] Optionally, the first polysilicon layer may be doped with boron atoms by single-sided boron diffusion. When the first polysilicon layer is doped with boron atoms, ion implantation equipment may be used to perform boron diffusion treatment, which may achieve more uniform doping, better doping consistency, and more stable and controllable doping surface concentration and junction depth.

[0054] In this embodiment, the BSG mask layer is a borosilicate glass layer formed when the surface of the p+ polysilicon layer is oxidized in contact with air after the p+ polysilicon layer is formed.

[0055] Step 1.23: Use laser patterning to remove the BSG mask layer and the p+ polysilicon layer in a partial area to form an interval p+ polysilicon region with a BSG mask layer.

[0056] Step 1.24: A stacked second tunneling oxide layer and a second polysilicon layer are sequentially formed on the surfaces of the first tunneling oxide layer and the BSG mask layer.

[0057] Optionally, the material of the second tunneling oxide layer is SiO 2. In this embodiment, the preparation process of the second tunneling oxide layer and the second polysilicon layer is similar to that of the first tunneling oxide layer and the first polysilicon layer, which will not be described in detail.

[0058] Step 1.25: Doping the second polysilicon layer with phosphorus atoms to form an n+ polysilicon layer and forming a PSG mask layer on the n+ polysilicon layer.

[0059] Optionally, the second polysilicon layer can be doped with phosphorus atoms by single-sided phosphorus diffusion. When the second polysilicon layer is doped with phosphorus atoms, ion implantation equipment can be used to perform phosphorus diffusion treatment, which can achieve more uniform doping, better doping consistency, and more stable and controllable surface concentration and junction depth of the doping.

[0060] In this embodiment, the PSG mask layer is a phosphorus silicon glass layer formed when the surface of the n+ polysilicon layer is oxidized in contact with air after the n+ polysilicon layer is formed.

[0061] Optionally, the second polysilicon layer and the second surface of the silicon substrate may be doped with phosphorus atoms by double-sided phosphorus diffusion, and an n+ polysilicon layer and a PSG mask layer may be formed on the second surface of the silicon substrate while an n+ polysilicon layer and a PSG mask layer are formed on the second polysilicon layer.

[0062] Step 1.26: Use laser patterning to remove the PSG mask layer, n+ polysilicon layer, second tunneling oxide layer and BSG mask layer on the p+ polysilicon region to form an n+ polysilicon region with a PSG mask layer that is arranged in a straight line alternately with the p+ polysilicon region.

[0063] It is understandable that when double-sided phosphorus diffusion is used for phosphorus atom doping, the PSG mask layer on the second surface of the silicon substrate needs to be removed by laser patterning.

[0064] Step 1.27: Remove the PSG mask layer on the n+ polysilicon region and a portion of the n+ polysilicon region to form an isolation region between the n+ polysilicon region and the p+ polysilicon region.

[0065] Optionally, the width of the isolation region is generally 30 μm-50 μm, and the depth is generally 2 μm-5 μm. As an example, the width of the isolation region can be 30 μm, 40 μm or 50 μm, and the depth can be 2 μm, 4 μm or 5 μm, etc.

[0066] Step 1.3: Form a textured structure on the second surface of the silicon substrate.

[0067] In this embodiment, a pyramid-structured textured surface structure can be formed on the second surface of the silicon substrate by groove texturing, and impurities after laser patterning can also be washed away.

[0068] Step 1.4: A stacked passivation layer and an anti-reflection layer are sequentially formed on the surface of the p+ polysilicon region, the n+ polysilicon region and the textured structure.

[0069] Optionally, the material of the passivation layer is aluminum oxide, and the material of the anti-reflection layer is silicon nitride or silicon oxynitride. The anti-reflection layer formed is helpful to reduce the reflectivity of the silicon substrate surface, improve the incident light utilization rate of the battery, and enhance the battery performance.

[0070] Step 1.5: Prepare electrodes on the anti-reflection layers of the p+ polycrystalline silicon region and the n+ polycrystalline silicon region using a screen printing process to obtain a TBC solar cell.

[0071] Optionally, the electrode material is silver. Specifically, a first silver electrode can be formed by printing silver paste on the anti-reflection layer of the p+ polysilicon region using a screen printing process, so that the first silver electrode passes through the passivation layer and the anti-reflection layer of the p+ polysilicon region and is electrically connected to the p+ polysilicon region; a second silver electrode is formed by printing silver paste on the n+ polysilicon region, so that the second silver electrode passes through the passivation layer and the anti-reflection layer of the n+ polysilicon region and is electrically connected to the n+ polysilicon region, thereby obtaining a TBC solar cell.

[0072] Step 2: Perform light injection treatment on the TBC solar cell.

[0073] In this embodiment, the TBC solar cell is subjected to light injection treatment, and the Fermi level change can be adjusted by temperature and light intensity, and the total amount and valence of H can be controlled to improve the passivation performance. At the same time, the light injection treatment can also remove most of the organic solvent in the silver paste, avoiding the gas bubbles generated during the subsequent laser-assisted screen sintering to affect the electrode contact quality.

[0074] Optionally, the peak temperature of light injection is 220-290° C., the light intensity is 20%-50%, and the light injection time is 20-40 s.

[0075] Step 3: Using laser-assisted wire mesh sintering technology to process the electrode of the TBC solar cell after the light injection treatment, so that a eutectic body of metal and silicon is formed between the electrode of the TBC solar cell and the polysilicon region.

[0076] In an optional embodiment, step 3 includes:

[0077] The laser is irradiated on the electrode of the TBC solar cell to stimulate partial dissolution of the electrode and its contact area and to exchange particles, forming a eutectic body of metal and silicon between the electrode and the polysilicon region.

[0078] See also Figure 3 The schematic diagram of the laser assisted sintering working principle provided by the embodiment of the present invention is shown in FIG. Figure 3 As shown, in this embodiment, laser is irradiated on the silver paste, and by precisely controlling the energy and irradiation time of the laser, the partial dissolution of the contact area between the silver paste and the polysilicon region is stimulated, so that the silver paste corrodes into the polysilicon region and performs particle exchange, thereby forming a eutectic body of silver and silicon between the silver electrode and the polysilicon region.

[0079] Optionally, the laser is a green pulse laser with a wavelength of 500-600nm, and a laser power parameter is 25-35W.

[0080] The method for improving the efficiency of a TBC solar cell in an embodiment of the present invention improves the electrode interface passivation contact effect by introducing a process method for laser-assisted sintering of the electrode region, so that the electrode can form direct contact with the polysilicon region, establish an effective electron transmission path, and form a good ohmic contact in the contact region, thereby significantly improving the interface passivation contact effect, reducing the contact resistance between the metal and the semiconductor, and improving the photoelectric conversion efficiency of the TBC cell.

[0081] In a second aspect, an embodiment of the present invention provides a method for improving the efficiency of a TBC solar cell provided in the second aspect.

[0082] See also Figure 2 , Figure 2 is a schematic diagram of the structure of a TBC solar cell provided by an embodiment of the present invention, such as Figure 2 As shown, the TBC solar cell of this embodiment includes a silicon substrate 1, a silicon oxide tunneling oxide layer 2, a p+ polysilicon region 3, an n+ polysilicon region 4, a passivation layer 5, an anti-reflection layer 6, and a silver electrode 7. The silicon oxide tunneling oxide layer 2 is deposited on the first surface of the silicon substrate 1; the p+ polysilicon region 3 and the n+ polysilicon region 4 are alternately arranged in a straight line on the surface of the silicon oxide tunneling oxide layer 2, and an isolation region 8 is provided between the p+ polysilicon region 3 and the n+ polysilicon region 4; the passivation layer 5 and the anti-reflection layer 6 are stacked in sequence on the surfaces of the p+ polysilicon region 3 and the n+ polysilicon region 4; the silver electrode 7 is provided on the surface of the anti-reflection layer 6 of the p+ polysilicon region 3 and the n+ polysilicon region 4; the second surface of the silicon substrate 1 is a velvet structure, and the passivation layer 5 and the anti-reflection layer 6 are stacked in sequence on the velvet structure. In this embodiment, the silver electrode 7 forms a eutectic body of silver and silicon through the passivation layer 5 and the anti-reflection layer 6 with the corresponding polysilicon region, and forms an ohmic contact with the polysilicon region.

[0083] For the specific contents and corresponding beneficial effects of the TBC solar cell, please refer to the relevant contents of the method for improving the efficiency of the TBC solar cell provided in the first aspect, which will not be elaborated here.

[0084] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the term "include", "comprise" or any other variant is intended to cover non-exclusive inclusion, so that the article or device including a series of elements includes not only those elements, but also other elements that are not explicitly listed. In the absence of more restrictions, the elements defined by the sentence "including one..." do not exclude the existence of other identical elements in the article or device including the elements. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The orientation or position relationship indicated by "up", "down", "left", "right", etc. is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention.

[0085] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A method for improving the efficiency of a TBC solar cell, characterized in that: include: Step 1: Prepare a TBC solar cell; Step 2: performing light injection processing on the TBC solar cell; Step 3: Using laser-assisted wire mesh sintering technology to process the electrode of the TBC solar cell after the light injection process, so that a eutectic body of metal and silicon is formed between the electrode of the TBC solar cell and the polysilicon region.

2. The method for improving the efficiency of a TBC solar cell according to claim 1, characterized in that: The step 1 comprises: Step 1.1: forming a first tunneling oxide layer on a first surface of a silicon substrate; Step 1.2: forming a p+ polysilicon region and an n+ polysilicon region alternately arranged in a straight line on the surface of the first tunneling oxide layer, wherein an isolation region exists between the p+ polysilicon region and the n+ polysilicon region; Step 1.3: forming a suede structure on the second surface of the silicon substrate; Step 1.4: sequentially forming a stacked passivation layer and an anti-reflection layer on the surface of the p+ polysilicon region, the n+ polysilicon region and the suede structure; Step 1.5: Prepare electrodes on the anti-reflection layers of the p+ polycrystalline silicon region and the n+ polycrystalline silicon region by using a screen printing process to obtain a TBC solar cell.

3. The method for improving the efficiency of a TBC solar cell according to claim 2, characterized in that: The material of the silicon substrate is n-type doped single crystal silicon.

4. The method for improving the efficiency of a TBC solar cell according to claim 2, characterized in that: The step 1.2 comprises: Step 1.21: depositing an intrinsic silicon layer on the surface of the first tunneling oxide layer and annealing the layer to form a first polysilicon layer; Step 1.22: doping the first polysilicon layer with boron atoms to form a p+ polysilicon layer and forming a BSG mask layer on the p+ polysilicon layer; Step 1.23: Using laser patterning, remove the BSG mask layer and the p+ polysilicon layer in a part of the area to form an interval p+ polysilicon area with a BSG mask layer; Step 1.24: sequentially forming a stacked second tunneling oxide layer and a second polysilicon layer on surfaces of the first tunneling oxide layer and the BSG mask layer; Step 1.25: doping the second polysilicon layer with phosphorus atoms to form an n+ polysilicon layer and forming a PSG mask layer on the n+ polysilicon layer; Step 1.26: removing the PSG mask layer, the n+ polysilicon layer, the second tunneling oxide layer and the BSG mask layer on the p+ polysilicon region by laser patterning to form an n+ polysilicon region having a PSG mask layer which is arranged in a straight line alternately with the p+ polysilicon region; Step 1.27: removing the PSG mask layer on the n+ polysilicon region and a portion of the n+ polysilicon region to form the isolation region between the n+ polysilicon region and the p+ polysilicon region.

5. The method for improving the efficiency of a TBC solar cell according to claim 4, characterized in that: The material of the first tunneling oxide layer and the second tunneling oxide layer is SiO2.

6. The method for improving the efficiency of a TBC solar cell according to claim 2, characterized in that: The material of the passivation layer is aluminum oxide, and the material of the anti-reflection layer is silicon nitride or silicon oxynitride.

7. The method for improving the efficiency of a TBC solar cell according to claim 1, characterized in that: In step 2, the peak temperature of light injection is 220-290° C., the light intensity is 20%-50%, and the light injection time is 20-40 seconds.

8. The method for improving the efficiency of a TBC solar cell according to claim 1, characterized in that: The step 3 comprises: Laser is irradiated on the electrode of the TBC solar cell to stimulate partial dissolution of the electrode and its contact area and to exchange particles, thereby forming a eutectic body of metal and silicon between the electrode and the polysilicon region.

9. The method for improving the efficiency of a TBC solar cell according to claim 8, characterized in that: The laser is a green pulse laser with a wavelength of 500-600nm and a laser power parameter of 25-35W.

10. A TBC solar cell, characterized in that: The method for improving the efficiency of a TBC solar cell according to any one of claims 1 to 9 is used.

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