Laser patterning multi-layer frequency conversion method for XBC battery

Abstract

The invention relates to the technical field of solar cell manufacturing, and particularly discloses an XBC cell laser patterning multi-layer frequency conversion method. Aiming at the problems of edge residue and middle thermal damage caused by fixed laser parameters of a single pattern layer due to 4-10nm thickness difference of doped film layers (BSG / PSG layers) in different regions after diffusion doping of a battery piece in an existing XBC battery laser patterning process, the method comprises the following steps of: splitting a single whole pattern layer subjected to laser patterning into a plurality of independent pattern layers on the basis of the thickness difference; under the condition that the power of a laser device is constant, the laser frequency is set for each independent pattern layer in a differentiated mode, the laser spot energy of the corresponding area is adjusted and optimized through the laser frequency, matched removal of doped film layers with different thicknesses is achieved, and accurate isolation of an N / P area is achieved. According to the method, doped film layer residues and silicon wafer thermal damage are effectively reduced, the conversion efficiency gain of the XBC battery is larger than or equal to 0.02%, the low-efficiency C1 proportion is reduced by larger than or equal to 0.03%, the efficiency and yield of a finished battery product are remarkably improved, and practicability is high.

Description

Technical Field

[0001] This invention relates to the field of solar cell manufacturing technology, specifically to a multi-layer frequency conversion method for XBC cells using laser patterning. Background Technology

[0002] XBC (cross-back contact) cells are an important type of high-efficiency solar cells, and laser patterning is one of the key steps in their production to achieve optimal cell performance. The core function of this process is to precisely remove the doped layers (mainly BSG and PSG layers) formed after boron and phosphorus doping of the silicon wafer through laser grooving and positioning. This achieves effective isolation between the N / P regions of the cell, ensuring precise interconnection of the back electrodes and preventing short-circuit failures caused by residual doped layers, which directly impacts the final cell efficiency and yield.

[0003] However, due to limitations in existing boron and phosphorus doping processes and equipment, the thickness of the BSG / PSG layer formed on the surface of silicon wafers after doping exhibits significant regional variations. Specifically, the BSG / PSG layer is thinner in the central region and thicker at the edges, with a thickness difference of 4-10 nm (assuming the thickness in the central region is n, the thickness in the edge region is 5-10 nm greater than that in the central region).

[0004] Currently, the laser patterning process commonly used in the industry is a single-layer design, meaning that only one set of fixed laser parameters (including laser frequency H0 and engraving speed S0) is used during the laser engraving process of the entire solar cell. Because the laser power is constant, the laser spot energy is fixedly correlated with the laser frequency and engraving speed. This fixed parameter setting cannot adapt to the thickness differences of the doped film layers in different areas: for thicker edge areas, the fixed parameters provide insufficient laser energy, resulting in incomplete removal of the BSG / PSG layer and localized residues; for thinner central areas, the fixed parameters provide excessive laser energy, causing thermal damage to the silicon wafer, resulting in burnt-out spots and blackening. These problems directly limit the conversion efficiency of XBC cells, increase the rate of inefficient defects, and severely impact the product's market competitiveness.

[0005] Therefore, there is an urgent need for a laser patterning method that can adapt to the thickness differences in the doped film region, solve the technical pain points of residue and thermal damage in the existing process, and further improve the performance indicators of XBC cells. Summary of the Invention

[0006] The purpose of this invention is to provide a multi-layer frequency conversion method for XBC battery laser patterning, in order to solve the problem that existing single-layer fixed laser parameters cannot adapt to the thickness differences of doped film regions, resulting in edge residue.

[0007] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: A multi-layer frequency conversion method for XBC battery laser patterning includes the following steps: Thickness distribution acquisition: Obtain the thickness distribution of the doped film after diffusion doping of XBC solar cells, and determine the thickness difference of the doped film in different regions; Layer splitting: Based on the thickness difference, the single overall layer of laser graphics is split into multiple independent layers, each independent layer corresponding to a specific area of ​​the battery cell; Parameter settings: Under the condition of constant laser power, the laser frequency is set differently for each independent layer so that the laser frequency is adapted to the doped film thickness of the corresponding region, so as to optimize the laser spot energy of the region. Laser engraving: Using multiple independent layers with pre-set laser frequencies, the solar cell is laser engraved to selectively remove doped film layers in different areas, thereby achieving N / P region isolation of the solar cell.

[0008] Furthermore, the doped film is one or both of BSG and PSG layers, and is the main film to be removed formed in the XBC battery doping process.

[0009] Furthermore, the thickness of the doped film in different regions of the solar cell varies from 4 to 10 nm, and the thickness of the doped film in the edge region of the solar cell is greater than that in the middle region. This difference is the core basis for the layer splitting and parameter differentiation settings of the present invention.

[0010] Furthermore, the number of the multiple independent layers is at least three, corresponding to the middle area, edge area and transition area between the middle area and edge area of ​​the battery cell, respectively. By setting the transition area, the laser energy is smoothly transitioned, and the performance abrupt change at the boundary of the area is avoided.

[0011] Furthermore, the laser spot energy is inversely proportional to the laser frequency. This correlation is the theoretical basis for parameter setting: when the doped film layer is thick, a lower laser frequency is configured to increase the laser spot energy and ensure complete removal of the film layer; when the doped film layer is thin, a higher laser frequency is configured to reduce the laser spot energy and avoid thermal damage to the silicon wafer.

[0012] Furthermore, in order to optimize the energy adjustment accuracy, the engraving speed can be set differently for each independent layer in step (3). The laser spot energy is inversely proportional to the engraving speed. By coordinating the adjustment of laser frequency and engraving speed, the laser spot energy can be accurately matched, thereby further improving the engraving effect.

[0013] The present invention has the following beneficial effects: This invention solves the technical problems of edge residue and central thermal damage in existing processes by splitting a single overall layer into multiple independent layers and setting laser frequencies (with optional coordinated adjustment of engraving speed) for different regions of the layer. After adopting this method, the conversion efficiency gain of XBC batteries is ≥0.02%, with a maximum of 0.06%, and the proportion of inefficient C1 decreases by ≥0.03%, with a maximum of 0.05%, resulting in a significant improvement in battery product efficiency and yield. This method only optimizes the laser layer division and parameter settings, while keeping other process conditions such as laser power unchanged. It can be directly adapted to existing XBC battery production equipment without large-scale production line modifications, thus reducing the cost of technology implementation. Attached Figure Description

[0014] Figure 1 This is a diagram showing localized thermal damage in the middle of the battery cell of the present invention; Figure 2 This is a diagram showing the cutting of a half-cell battery. Figure 3 The diagram illustrates the specific steps of the method of the present invention. Detailed Implementation

[0015] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0016] I. Experimental Preparation Experimental subjects: Several whole XBC solar cells and half XBC solar cells were selected. After boron diffusion and phosphorus diffusion doping treatment, the thickness distribution of their surface BSG / PSG layer was as follows: the thickness of the middle region was n, the thickness of the edge region was 5-10 nm greater than that of the middle region, and the thickness of the transition region was between that of the middle region and the edge region. Figure 1 Due to the difference in BSG / PSG thickness between the edges and the center after diffusion, the laser frequency engraving speed of the entire single-layer battery cell remains unchanged. Residue will appear at the corners of the battery cell, and local thermal damage and blackening of focal points will occur in the center, affecting the efficiency of the battery cell. Figure 2 Based on the characteristics of thickness differences in different regions of BSG / PSG after diffusion of whole / half solar cells, the single layer of laser-graphicated material will be divided into multiple layers. Different laser engraving parameters (frequency / speed) will be matched to different regions of the layer, such as laser frequencies H1, H2, H3; engraving speeds S1, S2, S3; other parameters will remain unchanged, and the values ​​of H1, H2, H3, S1, S2, S3 will be set according to the effect of BSG / PSG removal. Experimental equipment: Existing laser patterning equipment was used, and the laser power was kept constant; Group settings: Control group (BSL): Using existing single-layer process, laser frequency H0=700, engraving speed S0=70000; Experimental group: Using the multi-layer frequency conversion method of this invention, the laser layer is split into 3 independent layers, corresponding to the middle area, transition area and edge area respectively. 3 experimental schemes (SY1, SY2, SY3) are set up, and the specific parameters are shown in the table below; ; II. Experimental Procedure Laser patterning was performed on the control group and the experimental group of battery cells respectively. The only difference in the processing was the division of the laser layer and the parameter settings. Other process conditions (such as laser power, engraving path, etc.) remained the same. After laser engraving is completed, observe the cleaning effect of each group of solar cells and test the performance indicators such as conversion efficiency (ETA), open circuit voltage (Uoc), short circuit current (Isc), fill factor (FF), series resistance (RS), and proportion of inefficient C1.

[0017] III. Experimental Results and Analysis Cleaning effect: Control group (BSL): Obvious BSG / PSG layer residue was found at the corners of the cells, and there were sporadic black edges in the middle area, which was caused by thermal damage; Experimental group SY1: Only slight residue was found at the edges and corners of the battery cells, with no obvious thermal damage; Experimental groups SY2 and SY3: No residue or thermal damage was found in any area of ​​the battery cells, and the cleaning effect was normal.

[0018] Performance metrics (small-scale experiment): ; Performance metrics (batch experiments, SY2 scheme selected): ; Results analysis: In terms of cleaning effect, the multi-layer frequency conversion method of the present invention effectively solves the problems of residue and thermal damage by setting differentiated frequencies (and engraving speeds), among which the SY2 and SY3 schemes have the best effect; In terms of performance indicators, the conversion efficiency of each scheme in the experimental group was higher than that of the control group, with an increase of 0.02%-0.06% and a decrease of 0.03%-0.05% in the proportion of inefficient C1. Among them, the SY2 scheme had the best overall performance, with a conversion efficiency gain of 0.06% and a decrease of 0.05% in the proportion of inefficient C1 in the batch experiment, showing a significant improvement effect. Experimental results verified the effectiveness and practicality of the technical solution of the present invention. By splitting multiple layers and setting differentiated parameters, the precise removal of doped film layers in different regions was achieved, which significantly improved the performance of XBC cells.

[0019] IV. Key Points of Implementation The number of layers can be flexibly adjusted according to the size of the battery cell and the distribution of differences in the thickness of the doped film, and is not limited to 3, as long as the thickness of the corresponding area of ​​each layer is uniform; The specific values ​​of laser frequency (and engraving speed) need to be adapted and adjusted according to factors such as the thickness of the doped film and the laser model in actual production. The core principle is "low frequency (low speed) for thick film and high frequency (high speed) for thin film". The setting of a transition zone can avoid performance fluctuations at the boundary of the region caused by sudden changes in laser energy, and ensure the overall uniformity of the cell performance.

[0020] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. For those skilled in the art, the present invention can be modified and varied in many ways. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A multi-layered laser patterning frequency conversion method for XBC batteries, characterized in that, Includes the following steps: Step 1: Obtain the thickness distribution of the doped film after diffusion doping of the XBC solar cell, and determine the difference in the thickness of the doped film in different regions; Step 2: Based on the thickness difference, the single overall layer of laser patterning is split into multiple independent layers, each independent layer corresponding to a specific area of ​​the battery cell; Step 3: Under the condition of constant laser power, the laser frequency is set differently for each independent layer so that the laser frequency is adapted to the doped film thickness of the corresponding region, so as to optimize the laser spot energy in that region. Step 4: Using multiple independent layers with pre-set laser frequencies, laser engraving is performed on the solar cell to selectively remove doped film layers in different areas, thereby achieving N / P region isolation of the solar cell.

2. The XBC battery laser patterning multi-layer frequency conversion method according to claim 1, characterized in that, The doped film layer is one or both of BSG and PSG layers.

3. The XBC battery laser patterning multi-layer frequency conversion method according to claim 1, characterized in that, The thickness of the doped film in different regions of the solar cell varies from 4 to 10 nm, and the thickness of the doped film in the edge region of the solar cell is greater than that in the middle region.

4. The XBC battery laser patterning multi-layer frequency conversion method according to claim 1, characterized in that, There are at least three independent layers, corresponding to the middle area, edge area, and transition area between the middle and edge areas of the battery cell, respectively.

5. The XBC battery laser patterning multi-layer frequency conversion method according to claim 1, characterized in that, In step three, the engraving speed is also set differently for each independent layer. The laser spot energy is inversely proportional to the engraving speed. The laser spot energy is optimized by coordinating the adjustment of laser frequency and engraving speed.

6. The XBC battery laser patterning multi-layer frequency conversion method according to claim 1, characterized in that, The battery cell is either a full XBC battery cell or a half XBC battery cell.

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