Heterojunction solar cell and photon sintering method thereof
By processing conductive silver paste using photonic sintering and combining it with water vapor and hydrogen, the problems of high grid line resistance and damage to the transparent conductive film in HJT solar cells were solved, achieving high conductivity and stability of the cells and improving fill factor and conversion efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-22
- Publication Date
- 2026-04-07
AI Technical Summary
In existing technologies, HJT solar cells have high grid line resistance and the transparent conductive film is easily damaged at high temperatures, resulting in increased resistance, reduced fill factor, and decreased conversion efficiency.
The conductive silver paste was processed using a photonic sintering method, with the silver content in the conductive silver paste controlled at 8%~25%. Water vapor and hydrogen were introduced during the sintering process, and the total content of conductive materials in the conductive silver paste was limited to not less than 90%. The sintering temperature was controlled to not exceed 200℃, and a DC power supply was used for photonic sintering to ensure the bonding density between the silver powder and the TCO film layer and the stability of the transparent conductive film.
Without damaging the underlying silicon wafer and amorphous silicon layer, the gate line resistance is reduced, the fill factor and conversion efficiency are improved, the stability of the heterojunction structure is maintained, and the mechanical and electrical properties of the transparent conductive film are enhanced.
Smart Images
Figure CN121815795A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of photovoltaic technology, and more specifically, to a heterojunction solar cell and its photonic sintering method. Background Technology
[0002] Photonic sintering is a technique that uses high-intensity pulsed light to rapidly heat and sinter materials. Within an extremely short time (typically microseconds to milliseconds), the pulsed light energy is absorbed by the material, causing it to rapidly heat up to the sintering temperature and complete the sintering process.
[0003] In existing technologies, photonic sintering is commonly used in the fabrication of TOPCON cells because the surface of TOPCON cells has a layer of high-temperature resistant, non-conductive SiN. x Materials: This type of battery requires high-temperature conditions, utilizing the high temperatures generated when glass powder melts to deposit SiN on the surface. x Contact is achieved through burn-through. Therefore, during the fabrication of TOPCON cells, the silver grid lines can be pushed into the cell interior as a whole under the action of a laser in photonic sintering, achieving a good state of metallized ohmic contact, reducing resistance, and simultaneously improving the SiN surface. x The material can protect the battery cells from damage.
[0004] Based on this, some researchers have tried to use the photonic sintering method commonly used in TOPCON cells in the fabrication process of HJT products to solve the problem of high grid line resistance in HJT solar cells. However, compared with TOPCON cells, the surface of HJT products is a transparent conductive film. Under high temperature conditions, the transparent conductive film in HJT products will be severely damaged, resulting in increased resistance, reduced fill factor and conversion efficiency of the cell.
[0005] In view of this, the present invention is proposed. Summary of the Invention
[0006] The purpose of this invention is to provide a heterojunction solar cell and its photonic sintering method to solve or improve the above-mentioned technical problems, reduce the grid line resistance while reducing or improving the damage of the transparent conductive film in the HJT solar cell, and improve the fill factor and conversion efficiency of the HJT solar cell.
[0007] This invention can be implemented as follows: In a first aspect, the present invention provides a photonic sintering method for heterojunction solar cells, the method comprising: photonic sintering a conductive silver paste; wherein, by mass percentage, the silver content in the conductive silver paste is 8% to 25%, and the total content of conductive materials in the conductive silver paste is not less than 90%; and water vapor is introduced during the photonic sintering process.
[0008] In an optional embodiment, a reducing gaseous medium containing H but free of C, S and halogens is also introduced during the photonic sintering process.
[0009] In an optional implementation, water vapor and hydrogen are simultaneously introduced during the photon sintering process.
[0010] In an optional implementation, the water vapor flow rate does not exceed 100 ppm, and the hydrogen flow rate is 40 sccm to 50 sccm.
[0011] In an optional implementation, the water vapor flow rate is 20 ppm to 25 ppm.
[0012] In an optional embodiment, the silver content in the conductive silver paste is 10% to 22% by mass percentage.
[0013] In an optional implementation, the temperature of photonic sintering does not exceed 200°C.
[0014] In an optional implementation, the photonic sintering temperature is 175°C to 185°C.
[0015] In an optional implementation, photonic sintering further includes at least one of the following features: Feature 1: The marking speed of photonic sintering is 800mm / s~1200mm / s; Feature 2: The wavelength of light in photonic sintering is 500nm~1000nm; Feature 3: The power density of photonic sintering is 750 W / cm². 2 ~850W / cm 2 .
[0016] In an optional implementation, photonic sintering uses a DC power supply.
[0017] In an optional implementation, the DC power supply has a voltage of 8V to 12V and a current of 7A to 12A.
[0018] Secondly, the present invention provides a heterojunction solar cell, wherein the preparation process of the heterojunction solar cell is carried out by photon sintering method according to any of the foregoing embodiments.
[0019] The beneficial effects of this invention include: In HJT cell fabrication, without photonic sintering, the silver content in the conductive paste needs to be increased to 28wt%~30wt% to achieve the desired effect. This invention, using photonic sintering technology, significantly reduces the silver content in the conductive paste while achieving essentially the same effect as existing technologies with a silver content of 28wt%~30wt%. Furthermore, by limiting the total content of conductive materials in the conductive silver paste to no less than 90%, the silver content in the conductive paste is significantly reduced while ensuring good conductivity of the solar cell. During the photonic sintering process, under the action of a laser, the silver powder in the paste undergoes micro-melting, increasing the bonding density between the silver powder and the TCO film layer and reducing the contact resistance between them. By introducing water vapor during the photonic sintering process, the water vapor can strip out hydrogen elements, saturating the hydrogen escaping from the TCO film surface and reducing defects and damage to the TCO film; in addition, the water vapor can also protect the passivation layer. Photonic sintering of the silver paste with the aforementioned silver content in this manner allows for the formation of a good ohmic contact between the metal electrode and the TCO layer without damaging the underlying silicon wafer and amorphous silicon layer. This reduces contact resistance and improves the fill factor and conversion efficiency of the battery. Simultaneously, the photonic sintering process suppresses the diffusion of impurities at the interface, maintaining the stability of the heterojunction structure. Attached Figure Description
[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0021] Figure 1 The SEM image of the conductive silver paste with a silver content of 10 wt% in Experiment 4 is the corresponding control group. Figure 2 The image shows the SEM image of the conductive silver paste sample group with a silver content of 10 wt% in Experimental Example 4. Figure 3 The SEM image of the conductive silver paste with a silver content of 17wt% in Experiment 4 is the corresponding control group. Figure 4 The image shows the SEM image of the conductive silver paste sample group with a silver content of 17 wt% in Experimental Example 4. Figure 5 The SEM image of the conductive silver paste with a silver content of 22 wt% in Experiment 4 is the corresponding control group. Figure 6 The image shows the SEM image of the conductive silver paste sample group with a silver content of 22 wt% in Experimental Example 4. Figure 7The SEM image of the conductive silver paste with a silver content of 30 wt% in Experiment 4 is the corresponding control group. Figure 8 The image shows the SEM image of the conductive silver paste sample group with a silver content of 30 wt% in Experimental Example 4. Detailed Implementation
[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.
[0023] The heterojunction solar cell and its photonic sintering method provided by the present invention will be described in detail below.
[0024] This invention provides a photonic sintering method for heterojunction solar cells, the method comprising: photonic sintering of conductive silver paste; wherein, by mass percentage, the silver content in the conductive silver paste is 8% to 25%, and the total content of conductive material in the conductive silver paste is not less than 90%; and water vapor is introduced during the photonic sintering process.
[0025] In some alternative implementations, the silver content in the conductive silver paste can be 8%, 10%, 12%, 15%, 18%, 20%, 22%, or 25% by mass, or other values within the range of 8% to 25%.
[0026] In the fabrication of HJT batteries, without photonic sintering, the silver content in the conductive paste needs to be increased to 28%–30% to achieve the desired effect. This invention, by using photonic sintering technology, can significantly reduce the silver content in the conductive paste while achieving essentially the same effect as existing technologies with a silver content of 28%–30%. However, if the silver content in the conductive paste is below 8%, the conductivity will not meet the requirements.
[0027] In some preferred embodiments, the silver content in the conductive silver paste is 10% to 22% by mass, such as 10%, 12%, 15%, 18%, 20%, or 22%. Within this preferred range, the line resistance is significantly improved after sintering compared to before sintering.
[0028] In some optional embodiments, the total content of conductive material in the conductive silver paste is not less than 90%, such as 90%, 92%, 95%, 98%, etc., or other values within the range of not less than 90%. In some more typical embodiments, the total content of conductive material in the conductive silver paste can be 92% to 95%.
[0029] This invention, by limiting the total content of conductive materials in the conductive silver paste to no less than 90%, significantly reduces the silver content in the conductive paste compared to existing technologies (to 8%~25%) while ensuring good conductivity of the solar cell. If the total content of conductive materials in the conductive silver paste is less than 90%, the silver content in the paste will decrease to 8%~25%, resulting in poor conductivity in the prepared solar cell, which is difficult to meet application requirements.
[0030] This invention employs photonic sintering, where the silver powder in the paste undergoes micro-melting under laser irradiation, increasing the bonding density between the silver powder and the TCO film and reducing their contact resistance. By introducing water vapor during photonic sintering, the presence of water vapor prevents excessive localized heat generation at the grid lines, thus avoiding over-melting of the powder. Furthermore, the water vapor during photonic sintering can strip hydrogen (H) elements, saturating the H escaping from the TCO film surface and reducing defects and damage to the TCO film. Additionally, the water vapor ionizes under high pressure, diluting some of the instantaneous high energy of the high-power laser, protecting the passivation layer and reducing blue film damage. Photonic sintering of the aforementioned silver paste using this method allows for good ohmic contact between the metal electrode and the TCO film without damaging the underlying silicon wafer and amorphous silicon layer, reducing contact resistance and improving the cell's fill factor and conversion efficiency. Simultaneously, the photonic sintering process features rapid heating and cooling, suppressing impurity diffusion at the interface and maintaining the stability of the heterojunction structure.
[0031] Furthermore, a reducing gaseous medium containing H but free of C, S, and halogens is introduced during the photonic sintering process. For example, the aforementioned gaseous medium may include hydrogen.
[0032] The aforementioned gaseous medium can carry water vapor, rapidly introducing it into the photonic sintering equipment. Furthermore, this gaseous medium has reducing properties, preventing elemental oxidation; additionally, it is free of C, S, and halogens, thus avoiding negative impacts on the battery structure.
[0033] It should be noted that the gas medium in this invention cannot be methane or inert gases, as inert gases cannot saturate the H dangling bonds on the TCO film surface. Furthermore, if methane gas containing C and H is used as the gas medium, under the action of a transient high pulse, it decomposes to provide H elements while also decomposing to release carbon elements. The generated carbon elements will damage the silicon lattice, significantly reducing the minority carrier lifetime. Moreover, HJT technology relies on an ultra-clean interface between crystalline and amorphous silicon; carbon-based impurities will form defect states at the interface, hindering effective charge separation and transport. In addition, methane will compete with silane for decomposition, leading to structural inhomogeneity in the microcrystalline silicon layer or the formation of harmful compounds such as silicon carbide, resulting in impaired electrical and optical properties.
[0034] In some typical implementations, water vapor and hydrogen are introduced simultaneously during photon sintering.
[0035] Among them, the -H generated by water vapor ionization can saturate the surface defects of TCO thin films, increase the passivation effect, and reduce the recombination of surface defects and charge carriers; hydrogen has strong reducing properties, which can increase the surface activity of transparent conductive thin films; and during photonic sintering, the -H generated by hydrogen ionization can also saturate the dangling bonds of TCO thin films, thereby improving the passivation effect.
[0036] It is important to emphasize that in this invention, hydrogen gas is not introduced alone during the photon sintering process; rather, hydrogen gas is introduced in combination with water vapor. If only hydrogen gas is introduced, the instantaneous high energy of the high-power laser during ionization under high laser pressure can easily damage the passivation layer and the blue film. However, when water vapor is present, it can dilute some of the instantaneous high energy of the high-power laser, effectively protecting the passivation layer and the blue film.
[0037] Furthermore, compared to simply introducing water vapor, the electrolysis process using only water vapor for ionization includes both direct ionization and dissociative ionization, with direct ionization producing H2O. + Ions (ground state or excited state) dissociate from H2O + Rapid dissociation, producing fragment ions such as OH- + O + H + That is, water vapor may ionize to form H2O. + OH + O + H + Of these, only H + Only then can the effect of saturating free H be achieved, and H2O + OH + O + It possesses certain oxidizing properties, which may have some impact on the blue film and the substrate. Therefore, this invention combines hydrogen and water vapor, both of which can ionize into free hydrogen, to replenish the dangling bonds left by escaping H, saturating the surface defects of the TCO film. Furthermore, after ionization, the hydrogen gas completely generates reducing hydrogen elements, effectively reducing the H2O generated by water vapor ionization. + OH + O + Potential adverse effects on the blue film and substrate.
[0038] Continuing from the above, this invention introduces water vapor and hydrogen gas simultaneously in the form of a gas passing through water. Under the action of the pulse voltage of photon sintering, the two gases decompose to release H element. At the same time, the H escapes from the surface by utilizing thermal energy, thereby achieving H saturation. This can effectively saturate the crystallinity and defect state density of the transparent conductive film. On the one hand, it can stabilize the mechanical properties of the transparent conductive film, and on the other hand, it can avoid carbonization of the surface of the transparent conductive film, thereby improving the optical and electrical properties of the conductive film.
[0039] In some optional embodiments, the water vapor introduction rate does not exceed 100 ppm, such as 100 ppm, 80 ppm, 60 ppm, 50 ppm, 30 ppm, 20 ppm, or 10 ppm, or other values within the range of greater than 0 ppm but not exceeding 100 ppm. By controlling the water vapor introduction rate within the above range, the smooth introduction of hydrogen can be ensured, thereby improving photoelectric performance, while hydrogen poisoning can be avoided.
[0040] In some preferred embodiments, the water vapor introduction rate is 20ppm to 25ppm, such as 20ppm, 21ppm, 22ppm, 23ppm, 24ppm, or 25ppm. Within this range, the open-circuit voltage and fill factor of the HJT battery are significantly improved.
[0041] In some alternative implementations, the hydrogen flow rate is controlled at 40 sccm to 50 sccm, such as 40 sccm, 45 sccm, or 50 sccm, or other values within the range of 40 sccm to 50 sccm. By controlling the hydrogen flow rate within the above range, requirements for lattice defects, optical, and electrical performance can be met.
[0042] In this invention, the temperature of photonic sintering does not exceed 200°C, such as 200°C, 190°C, 180°C, 170°C or 160°C.
[0043] If the temperature of photonic sintering is too high, on the one hand, it is easy to cause uneven thermal stress during the photonic sintering process, which will damage the TCO film and increase the probability of surface hydrogen escape. On the other hand, it is easy to cause silicon wafer warping or passivation layer failure.
[0044] In other words, by using a photonic sintering temperature not exceeding 200°C, this invention can, on the one hand, avoid damage to amorphous silicon and TCO films caused by high temperatures, reduce the escape of hydrogen from the battery surface, and improve the effective bonding between the TCO film and the grid lines; on the other hand, it can quickly melt the silver powder inside the grid lines, rapidly complete the sintering process of the silver paste, improve the density inside the grid lines, and help reduce the grid line resistance.
[0045] In some preferred embodiments, the photonic sintering temperature can be 175°C to 185°C, such as 175°C, 176°C, 177°C, 178°C, 179°C, 180°C, 181°C, 182°C, 183°C, 184°C or 185°C, or other values within the range of 175°C to 185°C.
[0046] The above-mentioned preferred sintering temperature is compatible with the low-temperature process of HJT cells, avoiding uneven thermal stress during photonic sintering, which could lead to film damage, silicon wafer warping, or passivation layer failure. Furthermore, the above-mentioned preferred sintering temperature can quickly complete the sintering process of silver paste without damaging other layers of the cell, achieving micro-melting secondary shaping of the paste.
[0047] In some alternative implementations, the photonic sintering equipment is placed after the curing oven, that is, after the paste printing is completed, to locally correct the grid lines and improve conductivity.
[0048] In some alternative implementations, the marking speed of photonic sintering can be 800 mm / s to 1200 mm / s, such as 800 mm / s, 900 mm / s, 1000 mm / s, 1100 mm / s or 1200 mm / s, or other values within the range of 800 mm / s to 1200 mm / s.
[0049] The aforementioned "marking speed" refers to the ability to complete a marking task per unit time, usually measured by the area, length, or number of marks made per unit time. By controlling the marking speed within the aforementioned range, the contact area between powder particles can be increased and the metallization resistance reduced during the micro-melting process of the silver powder.
[0050] In some alternative implementations, the wavelength of the light wave in photonic sintering can be 500nm to 1000nm, such as 500nm, 600nm, 700nm, 800nm, 900nm or 1000nm, or other values in the range of 500nm to 1000nm.
[0051] The aforementioned long-wavelength light has a thermal effect, which can better melt silver powder and reduce metallization resistance compared to short-wavelength light. However, if the long-wavelength light is too long, it will cause local heat accumulation in the gate line, damaging the silver coating. Furthermore, if the long-wavelength light is too long, it may also have a certain penetrating effect, damaging the transparent conductive film.
[0052] In some alternative implementations, the power density of photonic sintering is 750 W / cm². 2 ~850W / cm 2 For example, 750W / cm 2 780W / cm 2 800W / cm 2820W / cm 2 Or 850W / cm 2 etc., can also be 750W / cm 2 ~850W / cm 2 Other values within the range.
[0053] The aforementioned power density range ensures effective ionization of water vapor and hydrogen into -H while avoiding damage to the TCO film and other structural layers of the HJT battery. Excessive power density can lead to breakdown, damaging the transparent conductive film; conversely, insufficient power density reduces effective contact between silver particles.
[0054] In this invention, photonic sintering uses a DC power supply. By specifically employing a DC power supply, a continuous and stable current and voltage output is provided, ensuring that the laser operates at a constant power, avoiding output instability or periodic temperature fluctuations caused by power fluctuations, and thus avoiding problems such as silver powder damage caused by AC voltage frequency switching.
[0055] In some alternative implementations, the voltage of the DC power supply can be 8V to 12V, such as 8V, 9V, 10V, 11V, or 12V, or other values within the range of 8V to 12V. The current can be 7A to 12A, such as 7A, 8A, 9A, 10A, 11A, or 12A, or other values within the range of 7A to 12A.
[0056] Under the aforementioned low-voltage and low-current conditions, the problem of excessive equipment power causing the silver shell in the silver powder to crack and making it difficult to reduce metallization contact can be avoided. In addition, under the low-voltage and low-current conditions, the bombardment of the blue film area after water vapor is introduced can also be avoided.
[0057] Building upon the above, this invention introduces water vapor into the photonic sintering equipment under the influence of hydrogen. This ensures the smooth introduction of hydrogen while preventing hydrogen poisoning, and simultaneously addresses lattice defects, optical, and electrical properties. Based on this, and considering specific wavelengths, marking speeds, and power densities, ionization is performed under a pulsed high-voltage state. The ionized hydrogen can saturate the escaping hydrogen on the surface of the transparent conductive film. Simultaneously, the water vapor ionization process consumes some energy, reducing the energy bombardment on the transparent conductive film and minimizing damage to the blue film surface. Furthermore, the high-energy pulsed state accelerates the micro-melting of the silver powder surfaces. Due to the electrical and thermal conductivity of metals, heat is rapidly transferred to the underlying layer during this micro-melting process, allowing the underlying slurry to also undergo micro-melting. This improves the metallization contact between the blue film surface and the slurry, ultimately enhancing the density of the powder layers within the grid lines. Therefore, by performing photonic sintering on HJT cells using the method provided by this invention, the contact between powders within the grid lines and the contact resistance can be improved, while also reducing lattice defects in the surface TCO film and enhancing the mechanical, optical, and electrical properties of the transparent conductive film.
[0058] Furthermore, the specific structure of the HJT battery in this invention, as well as other preparation processes and conditions besides photon sintering, can be found in the relevant prior art, and will not be elaborated upon here. Accordingly, the present invention also provides a heterojunction solar cell, which is prepared by sintering using the above-mentioned photon sintering method.
[0059] Through the aforementioned photonic sintering, the silver paste sintering process can be rapidly completed without damaging the underlying silicon wafer and amorphous silicon layer. This achieves micro-melting and secondary shaping of the paste, enabling the metal electrode to form a good ohmic contact with the TCO layer, reducing contact resistance, and improving the fill factor and conversion efficiency of the battery. Simultaneously, the rapid heating and cooling during photonic sintering can suppress the diffusion of impurities at the interface, maintaining the stability of the heterojunction structure.
[0060] The features and performance of the present invention will be further described in detail below with reference to embodiments.
[0061] Example 1 This embodiment provides an HJT battery, which includes a silicon substrate. The front side of the silicon substrate is provided with a first intrinsic silicon layer with a thickness of 6nm, a first doped silicon layer with a thickness of 25nm, a first TCO film layer with a thickness of 100nm, and a first metal electrode in sequence from the inside to the outside. The back side of the silicon substrate is provided with a second intrinsic silicon layer with a thickness of 6nm, a second doped silicon layer with a thickness of 30nm, a second TCO film layer with a thickness of 85nm, and a second metal electrode in sequence from the inside to the outside.
[0062] Both the first and second metal electrodes were prepared using a photonic sintering method: printing was performed using a silver-copper paste with a silver content of 10 wt%, followed by photonic sintering at 180°C under conditions of simultaneous introduction of water vapor and hydrogen. The silver-copper paste, by mass percentage, consisted of: 10% nano-silver powder, 80% silver-coated copper powder, 5% resin, 3% organic solvent, with the balance being additives composed of antioxidants, dispersants, and coupling agents. Water vapor was introduced via hydrogen as a medium, with a water vapor flow rate of 20 ppm and a hydrogen flow rate of 45 sccm. Photonic sintering used a DC power supply with a voltage of 10V, a current of 10A, a light wavelength of 800nm, a marking speed of 1000mm / s, and a power density of 850W / cm². 2 .
[0063] Example 2 The difference between this embodiment and Embodiment 1 lies in the photonic sintering conditions, specifically as follows: A silver-copper paste with a silver content of 15wt% is used, and photonic sintering is performed at 175°C under conditions of simultaneous introduction of water vapor and hydrogen. The water vapor is introduced via hydrogen as a medium, with a water vapor introduction rate of 22 ppm and a hydrogen flow rate of 40 sccm. Photonic sintering uses a DC power supply with a voltage of 8V, a current of 7A, a light wavelength of 500nm, a marking speed of 800mm / s, and a power density of 750W / cm². 2 .
[0064] Example 3 The difference between this embodiment and Embodiment 1 lies in the photonic sintering conditions, specifically as follows: A silver-copper paste with a silver content of 22 wt% is used, and photonic sintering is performed at 185°C under conditions of simultaneous introduction of water vapor and hydrogen. The water vapor is introduced via hydrogen as a medium, with a water vapor introduction rate of 25 ppm and a hydrogen flow rate of 50 sccm. Photonic sintering uses a DC power supply with a voltage of 12V, a current of 12A, a light wavelength of 1000nm, a marking speed of 1200mm / s, and a power density of 850W / cm². 2 .
[0065] Example 4 The difference between this embodiment and Embodiment 1 lies in the photonic sintering conditions, specifically as follows: A silver-copper paste with a silver content of 8wt% is used, and photonic sintering is performed at 200°C under conditions of simultaneous introduction of water vapor and hydrogen. The water vapor is introduced via hydrogen as a medium, with a water vapor introduction rate of 100 ppm and a hydrogen flow rate of 45 sccm. Photonic sintering utilizes a DC power supply with a voltage of 10V, a current of 10A, a light wavelength of 800nm, a marking speed of 1000mm / s, and a power density of 850W / cm². 2 .
[0066] Example 5 The difference between this embodiment and Embodiment 1 lies in the photonic sintering conditions, specifically as follows: A silver-copper paste with a silver content of 25 wt% is used, and photonic sintering is performed at 160°C under conditions of simultaneous introduction of water vapor and hydrogen. The water vapor is introduced via hydrogen as a medium, with a water vapor introduction rate of 10 ppm and a hydrogen flow rate of 45 sccm. The photonic sintering uses a DC power supply with a voltage of 10V, a current of 10A, a light wavelength of 800nm, a marking speed of 1000mm / s, and a power density of 850W / cm². 2 .
[0067] Example 6 The difference between this embodiment and Embodiment 1 is that hydrogen gas was not introduced during the photon sintering process; only water vapor was introduced.
[0068] Comparative Example 1 The difference between this comparative example and Example 1 is that photonic sintering was not performed, and the metal electrode was prepared using conventional methods: silver-copper paste was screen printed, then dried at 180°C for 5 min to dry the organic matter, and then sintered at 180°C for 30 min to solidify and form metallization.
[0069] Comparative Example 2 The difference between this comparative example and Example 1 is that no water vapor was introduced during the photon sintering process; only hydrogen gas was introduced.
[0070] Comparative Example 3 The difference between this comparative example and Example 1 is that water vapor is replaced with nitrogen gas during the photonic sintering process.
[0071] Comparative Example 4 The difference between this comparative example and Example 1 is that hydrogen is replaced with nitrogen during the photonic sintering process.
[0072] Comparative Example 5 The difference between this comparative example and Example 1 is that hydrogen is replaced with methane during the photonic sintering process.
[0073] Experimental Example 1 The performance of HJT batteries prepared in Examples 1-6 and Comparative Examples 1-5 was compared, and the results are shown in Tables 1 and 2. Line resistance was measured using a TLM analyzer, and other electrical performance tests were performed using an IV analyzer.
[0074] Table 1 Performance Data
[0075] Table 2 Performance Data
[0076] As can be seen from Tables 1 and 2, the method provided by the embodiments of the present invention can enable HJT batteries to have higher photoelectric conversion efficiency and better electrical parameter results.
[0077] Experimental Example 2 Taking Example 1 as an example, the effect of different photon sintering temperatures on the performance of solar cells was studied. At the same time, a control group without photon sintering was set up (using the solidification sintering in Comparative Example 1). The results are shown in Table 3.
[0078] Table 3 Performance Data
[0079] As can be seen from Table 3, the line resistance gradually decreases with the increase of photonic sintering temperature; however, when the photonic sintering temperature exceeds 185℃, the overall electrical parameter effect is significantly reduced.
[0080] Experimental Example 3 Taking Example 1 as an example, the effect of different power densities on the performance of solar cells was studied. At the same time, a control group without photonic sintering was set up (using the solidification sintering in Comparative Example 1). The results are shown in Table 4.
[0081] Table 4 Performance Data
[0082] As shown in Table 4, the line resistance first decreases and then increases with increasing optical power density. Considering the overall electrical parameters, the optimal power density is 750 W / cm². 2 ~850W / cm 2 The effect is even better.
[0083] Test Example 4 Taking Example 1 as an example, the effect of different silver content pastes on the resistance of solar cells was studied. The remaining photonic sintering conditions were the same as in Example 1, serving as the sample group. A control group (using the curing sintering method in Comparative Example 1) was also set up, without photonic sintering. The results are as follows: Figures 1 to 8 And as shown in Table 5.
[0084] Table 5 Performance Data
[0085] Depend on Figures 1 to 8 It can be seen that, regardless of whether the conductive silver paste has a silver content of 10wt%, 17wt%, 22wt%, or 30wt%, the silver powder achieves micro-melting secondary plasticity after photonic sintering. Compared with the non-photonic sintering, this increases the contact area between powder particles and helps to reduce line resistance.
[0086] Furthermore, as can be seen from Table 5, when the silver content in the conductive silver paste is 10wt%~25wt%, the photonic sintering scheme provided by this invention can significantly reduce the line resistance compared to not performing photonic sintering; considering the conversion effect, the effect is better when the silver content in the conductive silver paste is 10wt%~22wt%.
[0087] Experimental Example 5 Taking Example 1 as an example, the effect of different hydrogen flow rates on the resistance of solar cells was studied. At the same time, a control group without photon sintering was set up (using the solidification sintering in Comparative Example 1). The results are shown in Table 6.
[0088] Table 6 Performance Data
[0089] As can be seen from Table 6, considering the overall electrical parameters, a hydrogen flow rate of 40 sccm to 50 sccm is more effective than a flow rate lower than 40 sccm or higher than 50 sccm.
[0090] Experimental Example 6 Taking Example 1 as an example, the effect of different water vapor flow rates on the resistance of solar cells was studied. At the same time, a control group without photonic sintering was set up (using the solidification sintering in Comparative Example 1). The results are shown in Table 7.
[0091] Table 7 Performance Data
[0092] As can be seen from Table 7, considering the overall electrical parameters, the electrical performance is better when the water vapor inlet is within the range of 100 ppm, specifically between 20 ppm and 25 ppm, compared to less than 20 ppm and greater than 25 ppm.
[0093] In summary, the method provided by this invention can reduce or improve the damage to the transparent conductive film in HJT solar cells while reducing grid line resistance, thereby improving the fill factor and conversion efficiency of HJT solar cells.
[0094] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. 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 photonic sintering method for heterojunction solar cells, characterized in that, include: The conductive silver paste is photonically sintered, wherein the silver content in the conductive silver paste is 8% to 25% by mass percentage, and the total content of conductive substances in the conductive silver paste is not less than 90%; water vapor is introduced during the photonic sintering process.
2. The photonic sintering method according to claim 1, characterized in that, During the photonic sintering process, a reducing gaseous medium containing H but free of C, S and halogens is also introduced.
3. The photonic sintering method according to claim 2, characterized in that, Water vapor and hydrogen are introduced simultaneously during the photonic sintering process.
4. The photonic sintering method according to claim 3, characterized in that, The water vapor flow rate is no more than 100 ppm, and the hydrogen flow rate is 40 sccm to 50 sccm.
5. The photonic sintering method according to claim 4, characterized in that, The amount of water vapor introduced is 20ppm to 25ppm.
6. The photonic sintering method according to claim 1, characterized in that, The conductive silver paste contains 10% to 22% silver by mass percentage.
7. The photonic sintering method according to claim 1, characterized in that, The temperature of the photonic sintering does not exceed 200°C; Preferably, the photonic sintering temperature is 175℃~185℃.
8. The photonic sintering method according to any one of claims 1 to 7, characterized in that, The photonic sintering also includes at least one of the following features: Feature 1: The marking speed of the photonic sintering is 800mm / s~1200mm / s; Feature 2: The wavelength of the light wave in the photonic sintering is 500nm~1000nm; Feature 3: The power density of the photonic sintering is 750 W / cm². 2 ~850W / cm 2 .
9. The photonic sintering method according to claim 1, characterized in that, The photonic sintering uses a DC power supply; Preferably, the voltage of the DC power supply is 8V~12V and the current is 7A~12A.
10. A heterojunction solar cell, characterized in that, The heterojunction solar cell is fabricated using the photonic sintering method described in any one of claims 1 to 9.