A wide temperature window glass powder, and a preparation method and application thereof

Abstract

The present application relates to the technical field of solar cells, and particularly relates to a wide temperature window glass powder, a preparation method and application thereof, and the preparation raw materials include PbO 15-70 parts, TeO2 10-70 parts, Bi2O3 5-45 parts, ZnO 0.1-8 parts, WO3 3-30 parts, SiO2 5-20 parts, CuO 1-10 parts, and Li2O 5-25 parts in terms of weight parts. The wide temperature window glass powder prepared by the present application can balance the contact resistivity and metal composite to a large extent through experiments, and the high-tellurium low-zinc glass system is formed by taking PbO-TeO2-Bi2O3 as the main component and ZnO-WO3-SiO2-CuO-Li2O as the auxiliary component, the melting state of the glass powder is good at a wide high-temperature sintering temperature, and the system is beneficial to forming a good ohmic contact.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solar cells, in particular to a wide temperature window glass powder and a preparation method and application thereof. BACKGROUND

[0002] Energy transformation has become a consensus, and the photovoltaic track has both certainty and growth. The N-type cell technology is in fierce competition, and its mainstream trend is becoming clear. Among them, TOPCon cell technology has become one of the important directions of N-type cell technology. TOPCon cell technology was first proposed by Fraunhofer Solar Institute in Germany in 2014 as a new type of passivated contact solar cell. From the structure, TOPCon is a tunnel oxide passivated contact (1-2nm) based on the principle of selective carrier, and then a layer of doped silicon thin layer (60-100nm) is deposited, which forms a passivated contact structure together, effectively reducing surface recombination and metal contact recombination.

[0003] Compared with PERC cells, the ultra-thin silicon oxide layer uses quantum tunneling effect to complete current transmission without electrode contact with the silicon wafer, reducing the efficiency loss caused by electrode recombination, thereby giving TOPCon cells higher limit efficiency and conversion efficiency. The theoretical limit efficiency of TOPCon cells is as high as 28.7%, which is the closest to the theoretical limit efficiency (29.43%) of crystalline silicon solar cells, much higher than PERC (24.5%), and has great research and development potential. At present, the highest laboratory efficiency of TOPCon cells is 26.70%, and the highest mass production conversion efficiency is 25.62%, with sufficient efficiency improvement potential.

[0004] At present, the N-type TOPCon cell back fine grid conductive silver paste is composed of silver powder, glass powder and organic carrier. Among them, the glass powder is the key component to ensure that the silver paste can realize silver-silicon ohmic contact. During the metallization process, the corrosion of the glass powder is very important. If the SiNx layer is not etched completely, a good ohmic contact cannot be formed; if the corrosion is too much, the p-n junction will be broken down, which will ultimately affect the overall electrical performance of the cell. And this depends on the composition of the glass powder, including the element composition and the proportion of each component, to ensure that a good ohmic contact is formed while the metal recombination is well balanced. In addition, glass powder with a wide sintering temperature window can better regulate the sintering densification process of silver powder to obtain a good ohmic contact, which is also more in line with the current mainstream demand.

[0005] Chinese patent CN 115836032 A discloses a glass material and its preparation method, as well as a conductive paste and its preparation method. The glass material contains the following components by the molar percentage of oxides: 20-49% PbO, 10-30% SiO2, 15-35% B2O3, 5-15% ZnO, 0-10% first alkaline earth metal oxides, and 0.1-5% alkali metal oxides. However, its peak sintering temperature is limited to 725℃ and 740℃. Low-temperature sintering at around 700℃ cannot guarantee stability, and high-temperature sintering is not conducive to the product quality and cost control of the battery cells. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a glass powder for the fine grid silver paste on the back of an N-type TOPCon battery that has a greater balance between contact resistance and metal composite and a wide temperature window.

[0007] The first aspect of the present invention provides a wide temperature window glass powder, the raw materials for which, by weight, are: 15-70 parts PbO, 10-70 parts TeO2, 5-45 parts Bi2O3, 0.1-8 parts ZnO, 3-30 parts WO3, 5-20 parts SiO2, 1-10 parts CuO, and 5-25 parts Li2O.

[0008] In some embodiments, the raw materials prepared by weight include: 20-62 parts PbO, 15-50 parts TeO2, 5-32 parts Bi2O3, 0.1-6 parts ZnO, 5-20 parts WO3, 5-15 parts SiO2, 1-5 parts CuO, and 5-16 parts Li2O.

[0009] In this invention, PbO, TeO2, and Bi2O3 are used as the main oxides of the glass system, which belongs to a high-tellurium, low-zinc glass system. The inventors discovered that in this system, a specific amount of PbO can significantly reduce the softening temperature of the glass powder and improve the wettability between the glass powder and the matrix material, thus enhancing the silver-dissolving ability; the addition of TeO2 can lower the melting point of the glass system, enhance its etching reaction with Si, and improve the reactivity of the glass powder; the addition of an appropriate amount of Bi2O3 can also significantly reduce the viscosity of the glass, thereby increasing its fluidity.

[0010] Furthermore, the inventors discovered that the addition of an appropriate amount of ZnO can lower the softening point of the glass, giving it suitable fluidity during melting and reducing its coefficient of thermal expansion; the addition of an appropriate amount of WO3 can enhance the stability of the glass structure and reduce its viscosity, resulting in better wettability with other components; SiO2, as a network forger, makes the glass network structure more stable, increasing its chemical and thermal stability, while also appropriately increasing its viscosity and surface tension; CuO can appropriately raise the softening temperature of the glass, compensating for the low viscosity of the glass powder in the high-temperature region and ensuring better sintering of the silver layer even at high temperatures; a certain amount of Li is added to this system. + It can improve the overall chemical stability of glass and accelerate the melting of glass at high temperatures, which may be due to Li. + With a small ionic radius and a high electric field strength, it has a stronger synergistic effect with other components.

[0011] In some embodiments, the glass powder has a particle size D50 of 1.0-5.0 μm.

[0012] In some embodiments, the glass powder has a particle size D50 of 1.0-3.5 μm.

[0013] In some embodiments, the glass powder has a particle size D50 of 1.3-2.6 μm.

[0014] A second aspect of the present invention provides a method for preparing a wide temperature window glass powder, comprising the following steps:

[0015] T1. Add the glass powder preparation material to the crucible and mix well;

[0016] T2. Place the crucible in a sintering furnace at a temperature of 900-1250℃ and hold for 30-60 minutes to obtain molten glass. After rapid cooling, glass slag or glass fragments are obtained.

[0017] T3. Grind or crush the glass shards or fragments to obtain the finished glass powder.

[0018] The crucible described in this invention may be selected from, but is not limited to, an alumina crucible, a quartz crucible, or a platinum crucible.

[0019] The cooling process described in this invention can be selected from, but is not limited to, water quenching in cold water or dry quenching in a stainless steel roller mill.

[0020] The ball milling or pulverizing process described in this invention can be selected from, but is not limited to, a combination of dry and wet ball milling or an air jet mill.

[0021] A third aspect of the invention provides the application of wide-temperature-window glass powder in the preparation of fine grid silver paste on the back of N-type TOPCon cells.

[0022] In some implementations, the battery printed with silver paste can be sintered through a firing temperature window of 700-780°C.

[0023] A fourth aspect of the present invention provides a conductive silver paste, the raw materials of which include glass powder.

[0024] In some embodiments, the amount of glass powder added to the conductive silver paste is 1-5 wt%.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The wide temperature window glass powder prepared by this invention has been experimentally verified to be able to balance the contact resistivity and metal composite to a large extent.

[0027] 2. A high tellurium and low zinc glass system is formed by using PbO-TeO2-Bi2O3 as the main component and ZnO-WO3-SiO2-CuO-Li2O as the auxiliary component. This system exhibits good melting state of the glass powder over a wide range of high-temperature sintering temperatures, which is conducive to forming good ohmic contacts.

[0028] 3. Extensive experiments have confirmed that silver paste containing the glass powder prepared in this invention exhibits good quality stability when sintered in a temperature range of 700-780℃. Compared with existing technologies, it has a wider temperature window and higher stability, especially when sintered at a low temperature of around 700℃.

[0029] 4. By adding specific amounts of ZnO, WO3, SiO2 and Li2O, not only can the glass softening point be reduced, but the glass viscosity can also be reduced, and the wettability between components can be enhanced.

[0030] 5. The preparation process of this invention is simple, the raw materials are readily available, the cost is low, it is suitable for industrial production, and has good application prospects. Detailed Implementation

[0031] Example

[0032] A wide temperature window glass powder, the raw materials for its preparation are shown in Table 1 by weight.

[0033] Table 1

[0034] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 PbO 29.25 20 62 28.42 35 40 TeO2 24.60 15 50 20.05 38 35 Bi2O3 17.70 5 32 20.23 22 15 ZnO 2.20 0.1 6 4.5 / 2.5 WO3 8.50 5 20 10.48 3 15 SiO2 7.95 5 15 8.52 2 8 CuO 1.25 1 5 / 1.25 / Li2O 8.55 5 16 7.8 6 1 D50 (pm) 1.85 1.65 1.78 1.80 1.75 1.60

[0035] A method for preparing a wide temperature window glass powder includes the following steps:

[0036] T1. Add the glass powder preparation material to the crucible and mix well;

[0037] T2. Place the crucible in a sintering furnace at a temperature of 1000℃ and hold for 30 minutes to obtain molten glass. After rapid cooling, glass slag is obtained.

[0038] T3. The glass slag is ball-milled to obtain the finished glass powder.

[0039] Performance testing

[0040] Preparation of fine grid silver paste on the back of N-type TOPCon cells:

[0041] The silver paste components prepared in the embodiments and comparative examples comprise, by total mass, 89% silver powder, 2.4% glass powder, 7.8% organic carrier (ethyl cellulose organic carrier, Maclean) and 0.8% solvent (silicone oil, Aladdin).

[0042] Silver paste was screen-printed onto the back of the N-type TOPCon cell, and sintered in a sintering furnace at a peak temperature of 700–780°C. The resulting cells were then subjected to current-voltage performance tests, including open-circuit voltage (Uoc), series resistance (Rs), fill factor (FF), and conversion efficiency (Eta). The contact resistivity (ρc) of the fine grid electrode on the back of the N-type TOPCon cell was also tested using a TLM device. The results are shown in Table 2.

[0043] Table 2

[0044]

[0045]

[0046]

[0047] As can be seen from the above test results, the glass powder provided by the present invention, when applied to the fine grid silver paste on the back of the N-type TOPCon battery, has a wider high-temperature sintering window that is conducive to forming good ohmic contact and can balance the contact resistance and metal composite to a large extent. It can achieve good performance stability in the temperature range of 700-780℃.

Claims

1. A wide temperature window glass powder, characterized in that, The raw materials for preparation consist of 29.25 parts PbO, 24.60 parts TeO2, 17.70 parts Bi2O3, 2.20 parts ZnO, 8.50 parts WO3, 7.95 parts SiO2, 1.25 parts CuO, and 8.55 parts Li2O by weight. The glass powder has a particle size D50 of 1.85 μm.

2. A method for preparing a wide temperature window glass powder according to claim 1, characterized in that, Includes the following steps: T1. Add the glass powder preparation material to the crucible and mix well; T2. Place the crucible in a sintering furnace at a temperature of 900-1250℃ and hold for 30-60 minutes to obtain molten glass. After rapid cooling, glass slag or glass fragments are obtained. T3. Grind or crush the glass shards or fragments to obtain the finished glass powder.

3. The application of the wide temperature window glass powder of claim 1 in the preparation of fine grid silver paste on the back side of N-type TOPCon cells.

4. The application according to claim 3, characterized in that, After being printed with silver paste, the battery can be sintered at a temperature window of 700-780℃.

5. A conductive silver paste, characterized in that, The raw materials used in the preparation include the glass powder described in claim 1.

6. The conductive silver paste according to claim 5, characterized in that, The amount of glass powder added to the conductive silver paste is 1-5 wt%.

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