Light injection passivation method of TOPCon cell

Abstract

The invention provides a light injection passivation method of a TOPCon battery, and relates to the technical field of TOPCon battery processes. The method comprises the following steps: carrying out light injection on a metalized TOPCon battery piece under normal pressure, and heating the battery piece while carrying out light injection to finish passivation; the heating treatment process sequentially comprises a first heating section, a first heat preservation section, a first cooling section, a second heating section, a second heat preservation section and a second cooling section. According to the method, the traditional one-time temperature rise is adjusted into two-time temperature rise, the whole process time is consistent with that before improvement, the injected light intensity is consistent, the productivity is not influenced, and the repairing effect on the battery substrate can be ensured. However, the step of cooling is added between the two times of heating, so that a large amount of hydrogen on the silicon nitride layer and the aluminum oxide layer of the battery piece caused by a long-time high-temperature state can be prevented from overflowing, the situations that a passivation film layer is damaged and the passivation effect is influenced are reduced, and the photoelectric conversion effect of the improved battery is obviously improved.

Description

Technical Field

[0001] The present application relates to the technical field of TOPCon cell process, and in particular to a light injection passivation method for a TOPCon cell. Background Art

[0002] Tunnel Oxide Passivated Contact solar cell (TOPcon) is a new type of passivated contact solar cell first proposed by the Fraunhofer Institute for Solar Energy in Germany at the 28th European PVSEC Photovoltaic Conference in 2013. As a high-efficiency solar cell technology, photovoltaic TOPCon solar cells have higher conversion efficiency and lower energy costs and have received widespread attention.

[0003] The structure of a TOPcon cell usually includes a silicon wafer, the front side of which is stacked with a boron diffusion layer, a passivation layer, a front anti-reflection layer, and a front electrode, and the back side of which is stacked with a tunneling oxide layer, a (doped) polysilicon layer, a back anti-reflection layer, and a back electrode. The tunneling oxide layer and the (doped) polysilicon layer on the back side of the cell together form a passivation contact structure, providing good interface passivation for the back side of the silicon wafer. In particular, the N-type TOPCon cell has a lower boron content in phosphorus-doped N-type crystalline silicon than the P-type PERC cell (Passivated Emitter Rear Cell, passivated reflector and back cell structure), and has a better passivation effect.

[0004] The development of production technology and the promotion of large-scale production have gradually reduced the cost of TOPCon solar cells, and the future market competitive advantage is obvious. Usually, the light injection process of mass production line is a one-time heating process, which is divided into a heating stage and a heat preservation stage. However, the process is prone to unstable efficiency improvement. Summary of the invention

[0005] The purpose of the present application is to provide a light injection passivation method for TOPCon cells. The overall photon injection time of this method remains the same as before the improvement, and the injected light intensity is consistent, which can ensure the repair effect on the cell matrix; but it can avoid the damage to the passivation film layer caused by long-term high-temperature passivation in traditional processes.

[0006] In order to solve the above technical problems, the technical solution adopted in this application is:

[0007] The present application provides a light injection passivation method for a TOPCon cell, comprising the following steps:

[0008] Light is injected into the metallized TOPCon cell under normal pressure, and the cell is heated while the light is injected to complete the passivation.

[0009] The heating treatment process sequentially includes 1 stage of heating, 1 stage of heat preservation, 1 stage of cooling, 2 stages of heating, 2 stages of heat preservation and 2 stages of cooling.

[0010] Compared with the prior art, the embodiments of the present application have at least the following advantages or beneficial effects:

[0011] This application adjusts the heating treatment conditions of the light injection process, and adjusts the traditional one-time heating to two-time heating, but the entire process time is consistent with that before the improvement, the injection light intensity is consistent, the production capacity is not affected, and the repair effect on the battery matrix can be guaranteed. However, by adding a cooling step between the two heatings, this application can avoid the large amount of hydrogen overflow from the silicon nitride and aluminum oxide layers of the battery cell caused by a long-term high temperature state of more than 500°C, reduce the damage to the passivation film layer, and affect the passivation effect. Experiments have shown that the photoelectric conversion effect of the improved battery is significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0013] Figure 1 This is a schematic diagram of the temperature change in the cavity of the experimental group in the experimental example of this application;

[0014] Figure 2 This is a schematic diagram of the temperature change in the cavity of the control group in the experimental example of this application;

[0015] Figure 3 This is a microscopic picture of the damage to the passivation film layer of the battery cell after treatment in the control group of the experimental example of this application. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0017] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to specific embodiments.

[0018] A light injection passivation method for a TOPCon cell comprises the following steps:

[0019] Light is injected into the metallized TOPCon cell under normal pressure, and the cell is heated while the light is injected to complete the passivation.

[0020] The heating treatment process sequentially includes 1 stage of heating, 1 stage of heat preservation, 1 stage of cooling, 2 stages of heating, 2 stages of heat preservation and 2 stages of cooling.

[0021] In some embodiments of the present application, the above-mentioned heating stage 1 is specifically from 150°C to 559-570°C, and the heating rate is 145-155°C / s.

[0022] In some embodiments of the present application, the temperature of the insulation section 1 is 500-570°C, and the insulation time is 2-5s. The temperature of the insulation section 1 and the insulation section 2 of the present application must be guaranteed to be above 500°C, specifically including the process from 500°C to the highest temperature of the heating section, and also including the process of cooling from the highest temperature to 500°C in the cooling section. The total time of a single insulation section is 2-5s.

[0023] In some embodiments of the present application, the above-mentioned cooling stage 1 is specifically cooling from the temperature of the insulation stage 1 to 210-220°C, and the cooling rate is 58-62°C / s.

[0024] In some embodiments of the present application, the above-mentioned temperature rise stage 2 is specifically to increase the temperature from the temperature of the temperature drop stage 1 to 559-570°C, and the heating rate is 145-155°C / s.

[0025] In some embodiments of the present application, the temperature of the insulation stage 2 is 500-570° C., and the insulation time is 2-5 s.

[0026] In some embodiments of the present application, the above-mentioned cooling stage 2 is specifically cooling from the temperature of the insulation stage 2 to 35-40°C, and the cooling rate is 35-42°C / s.

[0027] In some embodiments of the present application, the radiation intensity of the light injection is 7 suns, and the time of the light injection is 20-28 seconds.

[0028] The features and performance of the present application are further described in detail below in conjunction with the embodiments.

[0029] Example 1

[0030] A light injection passivation method for a TOPCon cell, comprising the steps of: injecting light into a metallized TOPCon cell under normal pressure, wherein the radiation intensity of the light injection is 7 suns, the light injection time is 25 seconds, and heating the cell while injecting light to complete passivation;

[0031] The heating process of this embodiment includes heating stage 1, heat preservation stage 1, cooling stage 1, heating stage 2, heat preservation stage 2 and cooling stage 2 in sequence.

[0032] In the first heating stage, the temperature of the battery cell is rapidly increased from 150°C to 560°C at a heating rate of 148°C / second. Then, while ensuring the insulation time of the first stage (temperature above 500°C) for 3s, the battery cell enters the cooling stage 1 at a cooling rate of 60.9°C / second and cools to 216°C. Then, the battery cell enters the second heating stage. The temperature of the battery cell is rapidly increased from 216°C to 560°C at a heating rate of 149.2°C / second in the second heating stage. After ensuring the insulation time of the second stage (temperature above 500°C) for 2.8s, the battery cell enters the cooling stage 2 at a cooling rate of 38.1°C / second and cools to 37°C to complete the cooling.

[0033] Example 2

[0034] A light injection passivation method for a TOPCon cell, comprising the steps of: injecting light into a metallized TOPCon cell under normal pressure, wherein the radiation intensity of the light injection is 7 suns, the light injection time is 22 seconds, and heating the cell while injecting light to complete passivation;

[0035] The heating process of this embodiment includes heating stage 1, heat preservation stage 1, cooling stage 1, heating stage 2, heat preservation stage 2 and cooling stage 2 in sequence.

[0036] In the first heating stage, the temperature of the battery cell is rapidly increased from 150°C to 565°C at a heating rate of 150°C / second. Then, while ensuring that the insulation time of the first stage (temperature above 500°C) is 2.9s, the battery cell enters the first cooling stage at a cooling rate of 60.9°C / second and cools to 215°C. Then, the battery cell enters the second heating stage. In the second heating stage, the temperature of the battery cell is rapidly increased from 215°C to 565°C at a heating rate of 150.2°C / second. After ensuring that the insulation time of the second stage (temperature above 500°C) is 2.9s, the battery cell enters the second cooling stage at a cooling rate of 39.0°C / second and cools to 37°C to complete the cooling.

[0037] Example 3

[0038] A light injection passivation method for a TOPCon cell, comprising the steps of: injecting light into a metallized TOPCon cell under normal pressure, wherein the radiation intensity of the light injection is 7 suns, the light injection time is 26 seconds, and the cell is heated while the light injection is being performed to complete the passivation;

[0039] The heating process of this embodiment includes heating stage 1, heat preservation stage 1, cooling stage 1, heating stage 2, heat preservation stage 2 and cooling stage 2 in sequence.

[0040] In the first heating stage, the temperature of the battery cell is rapidly increased from 150°C to 570°C at a heating rate of 151.2°C / second. Then, while ensuring the insulation time of the first stage (temperature above 500°C) for 3.5s, the battery cell enters the cooling stage 1 at a cooling rate of 58.9°C / second and cools to 212°C. Then, the battery cell enters the second heating stage. The temperature of the battery cell is rapidly increased from 212°C to 565°C at a heating rate of 153.0°C / second in the second heating stage. After ensuring the insulation time of the second stage (temperature above 500°C) for 2.7s, the battery cell enters the cooling stage 2 at a cooling rate of 37.5°C / second and cools to 36°C to complete the cooling.

[0041] Example 4

[0042] A light injection passivation method for a TOPCon cell, comprising the steps of: injecting light into a metallized TOPCon cell under normal pressure, wherein the radiation intensity of the light injection is 7 suns, the light injection time is 28 seconds, and heating the cell while injecting light to complete passivation;

[0043] The heating process of this embodiment includes heating stage 1, heat preservation stage 1, cooling stage 1, heating stage 2, heat preservation stage 2 and cooling stage 2 in sequence.

[0044] In the first heating stage, the temperature of the battery cell is rapidly increased from 150°C to 562°C at a heating rate of 148.8°C / second. Then, while ensuring that the first insulation stage (temperature above 500°C) lasts for 3.7s, the battery cell enters the first cooling stage at a cooling rate of 60.5°C / second and cools to 216°C. Then, the battery cell enters the second heating stage. In the second heating stage, the temperature of the battery cell is rapidly increased from 216°C to 562°C at a heating rate of 152.5°C / second. After ensuring that the second insulation stage (temperature above 500°C) lasts for 2.5s, the battery cell enters the second cooling stage at a cooling rate of 37.3°C / second and cools to 36°C to complete cooling.

[0045] Example 5

[0046] A light injection passivation method for a TOPCon cell, comprising the steps of: injecting light into a metallized TOPCon cell under normal pressure, wherein the radiation intensity of the light injection is 7 suns, the light injection time is 25 seconds, and heating the cell while injecting light to complete passivation;

[0047] The heating process of this embodiment includes heating stage 1, heat preservation stage 1, cooling stage 1, heating stage 2, heat preservation stage 2 and cooling stage 2 in sequence.

[0048] In the first heating stage, the temperature of the battery cell is rapidly increased from 150°C to 570°C at a heating rate of 149.2°C / second. Then, while ensuring the insulation time of the first stage (temperature above 500°C) for 2.5s, the battery cell enters the cooling stage 1 at a cooling rate of 61.1°C / second and cools to 212°C. Then, the battery cell enters the second heating stage. The temperature of the battery cell is rapidly increased from 212°C to 570°C at a heating rate of 151.6°C / second in the second heating stage. After ensuring the insulation time of the second stage (temperature above 500°C) for 3.2s, the battery cell enters the cooling stage 2 at a cooling rate of 35.3°C / second and cools to 36°C to complete the cooling.

[0049] Experimental example

[0050] Experimental group: In this experimental group, light was injected into the metallized TOPCon cell under normal pressure. The radiation intensity of the light injection was 7 suns, the light injection time was 25 seconds, and the cell was heated during the light injection to complete the passivation. The heating process of this embodiment sequentially included 1 stage of heating, 1 stage of heat preservation, 1 stage of cooling, 2 stages of heating, 2 stages of heat preservation and 2 stages of cooling.

[0051] In the first heating stage, the heating rate is 148℃ / s, so that the battery cell is quickly heated from 150℃ to 560℃. After the insulation time of the first stage (temperature above 500℃) is 3s, the cooling rate is 60.9℃ / s, and the temperature is cooled to 216℃. Then, the heating stage 2 is entered. The heating rate of the second heating stage is 149.2℃ / s, so that the battery cell is quickly heated from 216℃ to 560℃. After the insulation time of the second stage (temperature above 500℃) is 2.8s, the cooling rate is 38.1℃ / s, and the temperature is cooled to 37℃. The cooling is completed. The whole process takes 25s. The temperature change diagram of the whole process cavity is as follows: Figure 1 shown.

[0052] Control group: This control group adopts the traditional one-time heating process, which is divided into a heating stage and a heat preservation stage. In the heating stage, the temperature of the battery cell is quickly raised from 150°C to 560°C at a heating rate of 81.4°C / s. After the temperature is kept above 500°C for 5.8s, it enters the cooling zone below 500°C at a cooling rate of 28.9°C / s, and finally cools to 37°C to complete the process steps. The entire process takes 25s. The schematic diagram of the temperature change in the cavity during the entire process is shown in the figure below. Figure 2 shown.

[0053] The overall photon injection time of the experimental group and the control group was consistent, both 25 seconds, and the injected light intensity was consistent, both 7 suns. The data of the products of the experimental group and the control group are shown in Table 1.

[0054] Table 1

[0055]

[0056] From the experimental results in Table 1, we can see that compared with the control group, the important parameters conversion efficiency and fill factor of the improved experimental group are significantly improved, indicating that the photovoltaic conversion effect of the battery in the improved experimental group is significantly improved, with obvious progress. In addition, Figure 3 This is a microscopic image of the passivation film damage of the cell after light injection treatment in the control group. Figure 3 It can be seen that due to the long-term high-temperature passivation at 500°C, the passivation film layer was damaged due to hydrogen overflow from the silicon nitride and aluminum oxide layers; this did not happen to the battery cells after the experimental group's process treatment.

[0057] In summary, the light injection passivation method of a TOPCon battery in the embodiment of the present application has the following advantages: the present application adjusts the heating treatment conditions of the light injection process, and adjusts the traditional one-time heating to two-time heating, but the entire process time is consistent with that before the improvement, the injection light intensity is consistent, the production capacity is not affected, and the repair effect on the battery matrix can be guaranteed. However, by adding a cooling step between the two heatings, the present application can avoid the large amount of hydrogen overflow from the silicon nitride and aluminum oxide layers of the battery cell caused by a long-term high temperature state of more than 500°C, reduce the damage to the passivation film layer, and affect the passivation effect. Experiments have shown that the photoelectric conversion effect of the improved battery is significantly improved.

[0058] The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents the selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present application.

Claims

1. A light injection passivation method for TOPCon cells, characterized in that: The following steps are involved: Light is injected into the metallized TOPCon cell under normal pressure, and the cell is heated while the light is injected to complete the passivation. The heating treatment process sequentially includes 1 stage of heating, 1 stage of heat preservation, 1 stage of cooling, 2 stages of heating, 2 stages of heat preservation and 2 stages of cooling.

2. A method for light injection passivation of a TOPCon cell according to claim 1, characterized in that: The first heating stage is specifically from 150°C to 559-570°C, and the heating rate is 145-155°C / s.

3. A method for light injection passivation of a TOPCon cell according to claim 2, characterized in that: The temperature of the insulation stage 1 is 500-570° C., and the insulation time is 2-5 seconds.

4. The light injection passivation method of a TOPCon cell according to claim 3, characterized in that: The first cooling stage is specifically cooling from the temperature of the first insulation stage to 210-220° C., with a cooling rate of 58-62° C. / s.

5. The light injection passivation method of a TOPCon cell according to claim 4, characterized in that: The second heating stage is specifically heating from the temperature of the first cooling stage to 559-570°C, with a heating rate of 145-155°C / s.

6. A method for light injection passivation of a TOPCon cell according to claim 5, characterized in that: The temperature of the second insulation stage is 500-570° C., and the insulation time is 2-5 seconds.

7. A method for light injection passivation of a TOPCon cell according to claim 6, characterized in that: The second cooling stage is specifically cooling from the temperature of the second insulation stage to 35-40°C, and the cooling rate is 35-42°C / s.

8. The light injection passivation method of a TOPCon cell according to claim 1, characterized in that: The radiation intensity of the light injection is 7 suns, and the light injection time is 20-28 seconds.

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