TOPCON battery and preparation method thereof

Abstract

The present invention provides a TOPCON cell and a method for preparing the same, relating to the field of solar cell technology. The method comprises the following steps: growing a thin silicon oxide film as a tunneling layer on a cell sheet using the LPCVD thermal oxidation method; then depositing an intrinsic layer on the tunneling layer by thermal decomposition of silane; and finally depositing amorphous silicon on the intrinsic layer by PECVD to obtain the TOPCON cell. The present invention solves the technical problem of natural oxide layer growth after the tunneling oxide layer is prepared by thermal oxidation in TOPCON cells in the prior art. This method achieves better passivation of the tunneling oxide layer and prevents the growth of a natural oxide layer.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a TOPCON cell and a preparation method thereof. Background Art

[0002] Solar cells are devices that directly convert light energy into electrical energy through the photoelectric or photochemical effects. TOPCON (Thin Oxide Passivated Contact) cells, a type of solar cell, are widely used due to their high photovoltaic conversion efficiency.

[0003] Currently, TOPCON cell membranes are primarily fabricated using two methods. The first involves using LPCVD (Low Pressure Chemical Vapor Deposition) to deposit a tunneling oxide layer and an amorphous silicon layer, followed by phosphorus diffusion to convert the amorphous silicon layer into a polycrystalline silicon layer. The second method involves using PECVD (Plasma Enhanced Chemical Vapor Deposition) to simultaneously deposit a tunneling oxide layer and an amorphous silicon layer, followed by in-situ doping to convert the amorphous silicon layer into a polycrystalline silicon layer.

[0004] The LPCVD method has high losses on quartz parts, and the tunneling oxide layer prepared by the thermal oxidation method based on the LPCVD equipment has a better passivation effect than the tunneling oxide layer prepared by the PECVD method. However, after the tunneling oxide layer is prepared by the thermal oxidation method alone, a natural oxide layer is easily grown.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of the present invention is to provide a TOPCON battery and a preparation method thereof, which can solve the technical problem of natural oxide layer growth after the tunnel oxide layer of the TOPCON battery is prepared by thermal oxidation, thereby achieving a better passivation effect of the tunnel oxide layer and avoiding the growth of the natural oxide layer.

[0007] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0008] In a first aspect, a method for preparing a TOPCON battery comprises the following steps:

[0009] The cell is made by growing a silicon oxide film as a tunneling layer through the LPCVD thermal oxidation method, then depositing an intrinsic layer on the tunneling layer through silane thermal decomposition, and then depositing amorphous silicon on the intrinsic layer through the PECVD method to obtain a TOPCON cell.

[0010] Compared with the prior art, the present invention has at least the following beneficial effects:

[0011] The preparation method of the TOPCON battery provided by the present invention grows a tunneling oxide layer by the LPCVD thermal oxidation method and then deposits the intrinsic layer. Since the interface state density is lower, the passivation effect is better. At the same time, after the tunneling oxide layer is prepared by the thermal oxidation method, because it is covered by the intrinsic layer, the influence of the production time on the natural oxide layer can be reduced, thereby avoiding the problem of the tunneling oxide layer easily growing a natural oxide layer. Subsequently, the poly layer can be in-situ doped by the PECVD method.

[0012] In addition, the preparation method of the present invention is not only simple and efficient, but also has a high success rate, and is very suitable for factory production.

[0013] In some embodiments, the preparation method further comprises the following steps:

[0014] During the deposition of amorphous silicon, a phosphorus source is used for in-situ doping.

[0015] In some embodiments, the in-situ doping further includes an annealing step.

[0016] In some embodiments, the cell comprises a pre-treated cell;

[0017] The pretreatment steps include texturing, primary boron diffusion, SE, secondary boron diffusion, BSG removal and alkali polishing and cleaning.

[0018] In some embodiments, the reaction temperature of the LPCVD thermal oxidation method for growing the silicon oxide film is 600° C. to 800° C.;

[0019] The reaction time of growing the silicon oxide film by the LPCVD thermal oxidation method is 1 hour to 2 hours.

[0020] In some embodiments, the reaction operation steps include vacuuming before the reaction, introducing O2 during the reaction, and vacuuming after the reaction.

[0021] In some embodiments, the reaction temperature of the silane thermal decomposition to deposit the intrinsic layer is 400-500°C;

[0022] The reaction time of thermal decomposition of silane to deposit the intrinsic layer is 0.5 to 1 hour.

[0023] In some embodiments, the phosphorus source comprises PH3 gas.

[0024] In some embodiments, the annealing temperature is 890° C. to 950° C., and the annealing time is 2 h to 3 h.

[0025] In a second aspect, a TOPCON battery is prepared using any of the preparation methods described above.

[0026] The TOPCON cell provided by the present invention has high photovoltaic conversion rate and good working performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 This is a flow chart for preparing the TOPCON battery provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0030] According to a first aspect of the present invention, there is provided a method for preparing a TOPCON battery, comprising the following steps:

[0031] The cell is made by growing a silicon oxide film as a tunneling layer through the LPCVD thermal oxidation method, then depositing an intrinsic layer on the tunneling layer through silane thermal decomposition, and then depositing amorphous silicon on the intrinsic layer through the PECVD method to obtain a TOPCON cell.

[0032] In the present invention, thermal oxidation (O2+N2 atmosphere) is used to prepare the tunneling oxide layer at high temperature. Since the interface state density is lower, the passivation effect is better than that of the silicon oxide film (SiO2) prepared by the plasma assisted nitrous oxide gas oxidation method (PANO). x ); and after the tunnel oxide layer is prepared by the thermal oxidation method, the coverage of the intrinsic layer reduces the influence of the preparation time on the natural oxide layer, thereby effectively avoiding the growth of the natural oxide layer after the tunnel oxide layer is prepared by the thermal oxidation method; the present invention can deposit amorphous silicon on the intrinsic layer by the PECVD method.

[0033] In a preferred embodiment, the preparation method of the present invention further comprises the following steps:

[0034] During the deposition of amorphous silicon, a phosphorus source is used for in-situ doping.

[0035] In a preferred embodiment, the in-situ doping further includes an annealing step.

[0036] In the present invention, the battery cells include but are not limited to pre-treated battery cells, and the battery cells are subjected to a pre-treatment process to obtain the pre-treated battery cells.

[0037] In a preferred embodiment, the pretreatment includes but is not limited to the process steps of texturing, primary boron diffusion, SE, secondary boron diffusion, BSG removal and alkali polishing.

[0038] In the present invention, an N-type crystalline silicon substrate can be selected as a battery cell, and the process steps of texturing, primary boron diffusion, SE, secondary boron diffusion, BSG removal and alkaline polishing cleaning can be carried out in sequence to obtain a pretreated battery cell, which is more conducive to further ensuring the effect of preparing a tunneling oxide layer at high temperature using thermal oxidation (O2+N2 atmosphere) in the subsequent process.

[0039] In a preferred embodiment, the reaction temperature for growing silicon oxide film by LPCVD thermal oxidation method can be 600℃~800℃, and its typical but non-limiting reaction temperatures are, for example, 600℃, 620℃, 640℃, 660℃, 680℃, 700℃, 720℃, 740℃, 760℃, 780℃, and 800℃. The reaction time for growing silicon oxide film by LPCVD thermal oxidation method can be 1h~2h, and its typical but non-limiting reaction time is, for example, 1h, 1.2h, 1.4h, 1.6h, 1.8h, and 2h. The above reaction temperature and time are more conducive to further improving the formation effect of tunneling oxide layer.

[0040] In the present invention, when the silicon oxide film is grown as the tunneling layer by the LPCVD thermal oxidation method, vacuum treatment is performed before the reaction, O2 is introduced during the reaction, and vacuum treatment is performed again after the reaction. This is more conducive to fully ensuring the growth effect of the tunneling layer, and then silane is introduced for thermal decomposition to deposit the intrinsic layer.

[0041] In a preferred embodiment, the reaction temperature of silane thermal decomposition deposition of the intrinsic layer can be 400°C to 500°C, and its typical but non-limiting reaction temperatures are, for example, 400°C, 420°C, 440°C, 460°C, 480°C, and 500°C. The reaction time of silane thermal decomposition deposition of the intrinsic layer can be 0.5h to 1h, and its typical but non-limiting reaction times are, for example, 0.5h, 0.6h, 0.7h, 0.8h, 0.9h, and 1h. The reaction temperature and time of silane thermal decomposition are more conducive to further improving the deposition effect of the intrinsic layer.

[0042] In a preferred embodiment, when performing in-situ doping, the phosphorus source used includes but is not limited to PH3 gas. Amorphous silicon is deposited on the intrinsic layer by PECVD, and PH3 gas is introduced at the same time to achieve in-situ doping, which is more conducive to further improving the in-situ doping effect of the poly layer.

[0043] In a preferred embodiment, the annealing temperature can be 890°C to 950°C, and typical but non-limiting temperatures include 890°C, 900°C, 910°C, 920°C, 930°C, 940°C, and 950°C. The annealing time can be 2 to 3 hours, and typical but non-limiting times include 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h, and 3h. The above annealing temperature and time can fully anneal the battery cell.

[0044] In a preferred embodiment, the annealed cell may first undergo a surface passivation treatment step and then a metallization treatment step to obtain a battery product.

[0045] According to a second aspect of the present invention, a TOPCON battery is provided, which is prepared by any of the preparation methods described above.

[0046] The TOPCON cell provided by the present invention has high photovoltaic conversion rate and good working performance.

[0047] The present invention is further described below by way of examples. Unless otherwise specified, the materials in the examples were prepared according to existing methods or directly purchased from the market.

[0048] Example 1

[0049] A method for preparing a TOPCON battery, the flow chart of which is shown in Figure 1 , including the following steps:

[0050] S1: Select an N-type crystalline silicon substrate for pretreatment, that is, perform the process steps of texturing, primary boron diffusion, SE, secondary boron diffusion, BSG removal and alkaline polishing in sequence to obtain a pretreated cell;

[0051] S2: After the pretreatment in step S1, the cell is subjected to LPCVD thermal oxidation to grow a silicon oxide film as a tunneling layer. The conditions of the thermal oxidation method are a reaction temperature of 600°C, a reaction time of 1.5 hours, vacuuming before the reaction, and introducing O2 during the reaction;

[0052] After the thermal oxidation reaction, the vacuum is evacuated, and then silane is introduced for thermal decomposition to deposit an intrinsic layer. The thermal decomposition conditions are a reaction temperature of 450°C and a reaction time of 0.8h, thereby depositing an intrinsic layer on the tunneling layer.

[0053] S3: After the intrinsic layer is deposited in step S2, amorphous silicon is deposited on the intrinsic layer of the cell by PECVD, and PH3 gas is introduced for in-situ doping;

[0054] S4: The cell after in-situ doping in step S3 is annealed at a temperature of 920° C. for 2.5 hours to obtain an annealed cell;

[0055] S5: After the annealing treatment in step S4, the cell is first surface passivated and then metallized to form a battery, that is, a TOPCON cell.

[0056] Example 2

[0057] The difference between this embodiment and embodiment 1 is that in step S2 of this embodiment, the conditions of the thermal oxidation method are a reaction temperature of 610° C. and a reaction time of 1.4 h;

[0058] The remaining steps and process parameters are the same as those in Example 1 to obtain a TOPCON battery.

[0059] Example 3

[0060] The difference between this embodiment and embodiment 1 is that in step S2 of this embodiment, the conditions of the thermal oxidation method are a reaction temperature of 620° C. and a reaction time of 1.3 h;

[0061] The remaining steps and process parameters are the same as those in Example 1 to obtain a TOPCON battery.

[0062] Example 4

[0063] The difference between this embodiment and embodiment 1 is that in step S2 of this embodiment, the conditions for thermal decomposition are reaction temperature 400° C. and reaction time 1 h;

[0064] The remaining steps and process parameters are the same as those in Example 1 to obtain a TOPCON battery.

[0065] Example 5

[0066] The difference between this embodiment and embodiment 1 is that in step S2 of this embodiment, the conditions for thermal decomposition are reaction temperature 500° C. and reaction time 0.5 h;

[0067] The remaining steps and process parameters are the same as those in Example 1 to obtain a TOPCON battery.

[0068] Example 6

[0069] The difference between this embodiment and embodiment 1 is that in step S4 of this embodiment, the annealing treatment conditions are a temperature of 890° C. and a time of 3 h;

[0070] The remaining steps and process parameters are the same as those in Example 1 to obtain a TOPCON battery.

[0071] Example 7

[0072] The difference between this embodiment and embodiment 1 is that in step S4 of this embodiment, the annealing treatment conditions are a temperature of 930° C. and a time of 2.4 h;

[0073] The remaining steps and process parameters are the same as those in Example 1 to obtain a TOPCON battery.

[0074] Comparative Example 1

[0075] The difference between this comparative example and Example 1 is that in step S2, no silane is introduced for thermal decomposition, that is, no intrinsic layer is deposited on the tunneling layer;

[0076] The remaining steps and process parameters are the same as those in Example 1 to obtain a TOPCON battery.

[0077] Compared with Example 1, the defect of this comparative example is that after the tunneling oxide layer is prepared, a natural oxide layer is easily grown.

[0078] Comparative Example 2

[0079] The difference between this comparative example and Example 1 is that in step S2, this comparative example adopts PANO (plasma assisted nitrous oxide gas oxidation) plasma assisted laughing gas oxidation method to prepare the silicon oxide film as the tunneling layer;

[0080] The remaining steps and process parameters are the same as those in Example 1 to obtain a TOPCON battery.

[0081] Compared with Example 1, the defect of this comparative example is that the passivation effect of the tunneling layer is poor.

[0082] Comparative Example 3

[0083] The difference between this comparative example and Example 1 is that in step S3, PH3 gas is not introduced for in-situ doping.

[0084] The remaining steps and process parameters are the same as those in Example 1 to obtain a TOPCON battery.

[0085] Compared with Example 1, the defect of this comparative example is that the subsequent annealing process cannot activate P, and the metal-semiconductor contact resistance cannot be reduced when poly contacts the metal electrode, and the carrier flow is blocked.

[0086] Test example

[0087] The batteries prepared in Examples 1-7 and Comparative Examples 1-3 were subjected to performance tests, and the results are shown in Table 1.

[0088] Performance testing method: Make finished battery cells and test the electrical performance using Halm.

[0089] Table 1

[0090]

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a TOPCon battery, characterized in that: The following steps are involved: The cell uses the LPCVD thermal oxidation method to grow a silicon oxide film as a tunneling layer. After the thermal oxidation reaction, the cell is vacuumed and then silane is introduced to deposit an intrinsic layer on the tunneling layer by thermal decomposition of silane. Then, amorphous silicon is in-situ doped and deposited on the intrinsic layer using a phosphorus source through the PECVD method to obtain a TOPCon cell.

2. The preparation method according to claim 1, characterized in that The in-situ doping further includes an annealing step.

3. The preparation method according to claim 1, characterized in that The battery cell includes a pre-processed battery cell; The pretreatment includes texturing, primary boron diffusion, SE, secondary boron diffusion, BSG removal and alkali polishing and cleaning.

4. The preparation method according to any one of claims 1 to 3, characterized in that The reaction temperature of the LPCVD thermal oxidation method for growing silicon oxide thin films is 600°C to 800°C; The reaction time of growing the silicon oxide film by the LPCVD thermal oxidation method is 1 h to 2 h.

5. The preparation method according to claim 4, characterized in that The reaction operation steps include vacuuming before the reaction, introducing O2 during the reaction, and vacuuming after the reaction.

6. The preparation method according to any one of claims 1 to 3, characterized in that The reaction temperature of the silane thermal decomposition deposition intrinsic layer is 400° C. to 500° C.; The reaction time of thermal decomposition of silane to deposit the intrinsic layer is 0.5h~1h.

7. The preparation method according to claim 1, characterized in that The phosphorus source includes PH3 gas.

8. The preparation method according to claim 2, characterized in that The annealing temperature is 890° C. to 950° C., and the annealing time is 2 h to 3 h.

9. A TOPCon battery prepared by the preparation method according to any one of claims 1 to 8.

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