A single glass powder, a front silver paste, a solar cell and a preparation method

Abstract

The present application relates to the field of glass powder materials, in particular to H01B1 / 22, more particularly, the present application relates to a single glass powder, front silver paste, solar cell and preparation method.Single glass powder, including CuO, SiO2, ZnO, PbO, MgO, MoO3, Li2O, WO3, Bi2O3, TeO2, CdO one or more kinds;The glass softening temperature of the single glass powder is 300-550 DEG C.The glass powder has low contact resistance, high fill factor, high open circuit voltage and high conversion efficiency, and the glass component particularly contains cadmium oxide, and the maximum advantage is that it has a wide sintering window and a suitable corrosion rate.

Description

Technical Field

[0001] This invention relates to the field of glass powder materials, specifically to H01B1 / 22, and more specifically, to a single glass powder, a front-side silver paste, a solar cell, and a preparation method thereof. Background Technology

[0002] Currently, PERC technology remains the "king" of solar cells. The core of a solar cell is the PN junction, and the quality of the junction plays a decisive role in the cell's photoelectric conversion efficiency. After light enters the silicon wafer surface, the light absorption coefficient of the silicon wafer decreases exponentially with the depth of penetration. Especially when the surface doping concentration is high, the surface recombination rate is high, resulting in a lower probability of collecting photogenerated carriers closer to the cell surface. In particular, holes generated by high-energy light at the surface cannot reach the potential barrier region, which greatly reduces the utilization rate of incident light.

[0003] High sheet resistance emitter junctions are one of the effective ways to achieve high-efficiency PERC solar cells. Utilizing low-concentration shallow junctions can significantly reduce the minority carrier recombination velocity on the surface of solar cells and improve the short-wavelength spectral response. However, the shallow junction diffusion process poses significant challenges to subsequent processes, especially sintering and front-side silver paste, as well as to process stability.

[0004] Shallow junction diffusion results in a PN junction depth of less than 0.3 μm, making most commercially available front-side silver pastes unsuitable for current applications. Although glass powder constitutes only 2-2.5% of the front-side silver paste, it plays a crucial role in forming ohmic contacts across the PN junction for current output. Excessive sintering temperature or time can cause the glass powder to burn through the emitter junction, leading to leakage current and a very low open-circuit voltage. Conversely, insufficient sintering temperature or time prevents the glass powder from penetrating the reflective film, hindering the formation of good ohmic contacts, resulting in large contact electrons and a low fill factor. Therefore, a wider sintering window and a suitable etching rate are the current development trends and challenges for glass powder in high-sheet-resistivity solar cell front-side silver paste. Summary of the Invention

[0005] To address some problems existing in the prior art, the first aspect of the present invention provides a single glass powder for silver paste on the front side of a solar cell, comprising one or more of CuO, SiO2, ZnO, PbO, MgO, MoO3, Li2O, WO3, Bi2O3, TeO2, and CdO; the glass softening temperature of the single glass powder is 300-550℃.

[0006] The addition of SiO2 improves the thermal stability of the single glass powder, ensuring the stability of the silver paste during sintering and guaranteeing its adhesion to the solar cell. The addition of MoO3 improves the compatibility between the glass powder and silver powder, resin, and other components, increasing the compactness between particles. The addition of Bi2O3 increases the density of the glass powder to some extent. The addition of PbO lowers the melting point of the single glass powder and improves its silver melting ability. The addition of WO3 increases the surface tension of the single glass powder. The addition of ZnO improves the density of the silver paste layer after sintering. The addition of MgO facilitates film formation of the silver paste during sintering. The addition of Li2O increases the strength of the single glass powder to some extent and also matches the coefficient of thermal expansion of the silver paste and the solar cell.

[0007] Preferably, the D50 particle size of the single glass powder is 0.1-5 μm, and the maximum particle size does not exceed 10 μm. More preferably, the D50 particle size of the single glass powder is 1.8-2.3 μm.

[0008] In one embodiment, the single glass powder comprises, by weight percentage, 0-5% CuO, 0.1-20% SiO2, 0.5-18% ZnO, 10-65% PbO, 0-7% MgO, 0.5-12% MoO3, 1-20% Li2O, 0.5-20% WO3, 5-35% Bi2O3, 20-70% TeO2, and 0.5-25% CdO.

[0009] In this invention, a specific amount of PbO is added to the single glass powder, which gives the single glass powder a wider sintering window and a suitable corrosion rate.

[0010] In one embodiment, the single glass powder comprises, by weight percentage, 0.5-5% CuO, 3.5-10% SiO2, 1-7% ZnO, 10-25% PbO, 0-5% MgO, 2.5-10% MoO3, 2-10% Li2O, 3-14% WO3, 8-25.5% Bi2O3, 21-35% TeO2, and 1-10% CdO.

[0011] In a preferred embodiment, the single glass powder comprises, by weight percentage, 1% CuO, 4% SiO2, 3% ZnO, 25% PbO, 1% MgO, 5% MoO3, 5% Li2O, 4% WO3, 15% Bi2O3, 32% TeO2, and 5% CdO.

[0012] The glass powder composition of this application has a suitable melting temperature, which promotes adhesion between the glass powder and the silver powder in the silver paste, avoids the problem of partial glass powder precipitation, and results in a dense silver paste layer. This reduces electrical resistance and avoids problems such as incomplete glass powder melting, reduced adhesion, or reduced etching properties caused by unsuitable glass powder melting temperatures. Furthermore, the silver paste composed of a single glass powder in this application, after sintering, matches the coefficient of thermal expansion of the solar cell, avoiding warping issues in the resulting solar cell and improving the yield.

[0013] The second aspect of the present invention provides a method for preparing the single glass powder, comprising: mixing the components of the single glass powder, then heating and melting it at 950-1300℃ for 20-40 minutes, cooling and grinding it to obtain the powder.

[0014] In one embodiment, the method for preparing the single glass powder includes: mixing the components of the single glass powder, then heating and melting it at 950-1300℃ for 20-40 minutes to obtain a uniform and clear glass solution, then quenching it in a two-roll mill or deionized water to obtain sheet glass or glass fragments, the glass fragments need to be dried; then successively undergoing dry coarse grinding and wet fine grinding to obtain the final product.

[0015] Preferably, the heat preservation and melting temperature is 1150℃ and the melting time is 30min.

[0016] Preferably, the obtained glass solution is quenched in a twin-roll mill to obtain sheet glass.

[0017] A third aspect of the present invention provides a front-side silver paste for a wide-window, high-sheet-resistance solar cell, the raw materials for which include the single glass powder.

[0018] In one embodiment, the raw materials for preparing the front-side silver paste of the wide-window high sheet resistance solar cell, by weight percentage, include 1-3% glass powder, 86-92% silver powder, 5-10% organic carrier, and 0.5-1% organic additives.

[0019] In a preferred embodiment, the raw materials for preparing the front-side silver paste of the wide-window high sheet resistance solar cell, by weight percentage, include 2% glass powder, 90.2% silver powder, 7% organic carrier, and 0.8% organic additives.

[0020] The fourth aspect of the present invention provides a method for preparing the front-side silver paste of the wide-window high sheet resistance solar cell, comprising: mixing glass powder, silver powder, organic carrier and organic additive in a certain proportion, and grinding to obtain the paste.

[0021] The fifth aspect of the present invention provides a high sheet resistance solar cell, wherein the surface of which is printed and sintered with the front silver paste of the wide-window high sheet resistance solar cell.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] The glass powder of this invention has low contact resistance, high fill factor, high open circuit voltage and high conversion efficiency. The glass composition contains cadmium oxide in particular, and its greatest advantage is that it has a wide sintering window and a suitable corrosion rate. Detailed Implementation

[0024] The present invention will be described below through specific embodiments, but is not limited to the specific embodiments given below.

[0025] Example 1

[0026] A single glass powder for front-side silver paste in solar cells has a glass transition softening temperature of 405°C, and its composition by weight percentage is as follows:

[0027] 3% CuO, 10% SiO2, 1% ZnO, 12% PbO, 2.5% MgO, 3% MoO3, 6% Li2O, 8% WO3, 25.5% Bi2O3, 21% TeO2, and 8% CdO.

[0028] The preparation method of this single glass powder is as follows:

[0029] 1. Weigh all the above raw material components according to the proportions, pour them into a horizontal ball mill jar, and roll them to mix thoroughly and evenly to obtain a mixture;

[0030] 2. The prepared mixture is placed into a platinum crucible, and the platinum crucible is placed in a high-temperature box furnace at room temperature and heated to 1150°C for 30 minutes to obtain a uniform and clear glass melt.

[0031] 3. The molten high-temperature glass is slowly poured into a two-roll mill to obtain thin glass sheets;

[0032] 4. The obtained thin glass sheets are coarsely ground into powder using a planetary ball mill and then passed through a 100-mesh sieve.

[0033] 5. Pour the coarsely ground powder into a zirconia ball mill jar and wet grind it into glass powder with a D50 of 1.8-2.3μm. The wet ball milling medium is anhydrous ethanol. Then pour it into a stainless steel pan and dry it in an 80℃ oven. Finally, pass it through a 200-mesh sieve to obtain the final product.

[0034] A silver paste for the front side of a wide-window, high-sheet-resistance solar cell, prepared from the following raw materials by weight percentage:

[0035] Example 1: 2.0 wt% glass powder, 90.2 wt% silver powder, 7.0 wt% organic carrier, and 0.8 wt% organic additives.

[0036] The silver powder has a D50 of 1.9-2.5 μm and a specific surface area of ​​0.2-0.35 m². 2 / g, tap density is 6-6.5g / cm³ 3 The organic carrier is specifically composed of 42.5 wt% terpineol, 3.5 wt% ethyl cellulose, and 54 wt% diethylene glycol butyl ether. These three components are all supplied by Shanghai Maclean Biochemical Technology Co., Ltd., with model numbers T818820 (terpineol), E915394 (ethyl cellulose), and B802753 (diethylene glycol butyl ether). The 0.8 wt% organic auxiliary agent consists of 0.3 wt% castor oil and 0.5 wt% glyceryl monooleate.

[0037] The preparation method of the front-side silver paste for this wide-window, high-sheet-resistance solar cell is as follows:

[0038] Glass powder, silver powder, organic carrier, and organic additives are mixed in a certain proportion and then put into a planetary mixer to be stirred evenly. Then, the evenly mixed premixed slurry is ground with a three-roll mill to obtain the front silver paste of wide-window high sheet resistance solar cells.

[0039] A method for preparing a high sheet resistance solar cell involves screen printing the silver paste from the front side of a wide-window high sheet resistance solar cell onto a high sheet resistance blue film, followed by sintering to obtain the high sheet resistance solar cell.

[0040] Example 2

[0041] A single glass powder for front-side silver paste in solar cells has a glass transition softening temperature of 411°C, and its composition by weight percentage is as follows:

[0042] 3% CuO, 8% SiO2, 7% ZnO, 10% PbO, 5% MgO, 6% MoO3, 10% Li2O, 14% WO3, 10% Bi2O3, 26% TeO2, and 1% CdO.

[0043] The preparation method of this single glass powder is the same as in Example 1.

[0044] A silver paste for the front side of a wide-window, high-sheet-resistance solar cell is the same as in Example 1, except that the glass powder in Example 1 is replaced with the glass powder in Example 2.

[0045] The preparation method of the front silver paste for the wide-window high sheet resistance solar cell and the preparation method of the high sheet resistance solar cell are the same as in Example 1.

[0046] Example 3

[0047] A single glass powder for front-side silver paste in solar cells has a glass transition softening temperature of 386°C, and its composition by weight percentage is as follows:

[0048] 1% CuO, 4% SiO2, 3% ZnO, 25% PbO, 1% MgO, 5% MoO3, 5% Li2O, 4% WO3, 15% Bi2O3, 32% TeO2, and 5% CdO.

[0049] The preparation method of this single glass powder is the same as in Example 1.

[0050] The preparation method of this single glass powder is the same as in Example 1.

[0051] A silver paste for the front side of a wide-window, high-sheet-resistance solar cell is the same as in Example 1, except that the glass powder of Example 1 is replaced with the glass powder of Example 3.

[0052] The preparation method of the front silver paste for the wide-window high sheet resistance solar cell and the preparation method of the high sheet resistance solar cell are the same as in Example 1.

[0053] Example 4

[0054] A single glass powder for front-side silver paste in solar cells has a glass transition softening temperature of 398°C, and its composition by weight percentage is as follows:

[0055] 0.5% CuO, 4% SiO2, 7% ZnO, 20.5% PbO, 10% MoO3, 2% Li2O, 3% WO3, 20% Bi2O3, 30% TeO2, and 3% CdO.

[0056] The preparation method of this single glass powder is the same as in Example 1.

[0057] The preparation method of this single glass powder is the same as in Example 1.

[0058] A silver paste for the front side of a wide-window, high-sheet-resistance solar cell is the same as in Example 1, except that the glass powder in Example 1 is replaced with the glass powder in Example 4.

[0059] The preparation method of the front silver paste for the wide-window high sheet resistance solar cell and the preparation method of the high sheet resistance solar cell are the same as in Example 1.

[0060] Example 5

[0061] A single glass powder for front-side silver paste in solar cells has a glass transition softening temperature of 419°C, and its composition by weight percentage is as follows:

[0062] 5% CuO, 5% SiO2, 1.5% ZnO, 22% PbO, 2% MgO, 2.5% MoO3, 3% Li2O, 6% WO3, 8% Bi2O3, 35% TeO2, and 10% CdO.

[0063] The preparation method of this single glass powder is the same as in Example 1.

[0064] The preparation method of this single glass powder is the same as in Example 1.

[0065] A silver paste for the front side of a wide-window, high-sheet-resistance solar cell is the same as in Example 1, except that the glass powder in Example 1 is replaced with the glass powder in Example 5.

[0066] The preparation method of the front silver paste for the wide-window high sheet resistance solar cell and the preparation method of the high sheet resistance solar cell are the same as in Example 1.

[0067] Example 6

[0068] A single glass powder for front-side silver paste in solar cells has a glass transition softening temperature of 427°C, and its composition by weight percentage is as follows:

[0069] 1% CuO, 3.5% SiO2, 5% ZnO, 16% PbO, 2.5% MgO, 5.5% MoO3, 6.5% Li2O, 6% WO3, 24% Bi2O3, 25% TeO2, and 5% CdO.

[0070] The preparation method of this single glass powder is the same as in Example 1.

[0071] A silver paste for the front side of a wide-window, high-sheet-resistance solar cell is the same as in Example 1, except that the glass powder in Example 1 is replaced with the glass powder in Example 6.

[0072] The preparation method of the front silver paste for the wide-window high sheet resistance solar cell and the preparation method of the high sheet resistance solar cell are the same as in Example 1.

[0073] Comparative Example 1

[0074] Comparative Example 1 is a front-side silver paste made from imported high sheet resistance glass powder from South Korea, with the grade M161.

[0075] Comparative Examples 2-4

[0076] A single glass powder for the front-side silver paste of a solar cell, the composition of which is shown in the table below by weight percentage:

[0077] raw material Comparative Example 2 Comparative Example 3 Comparative Example 4 <![CDATA[SiO2]]> 9 15 6 MgO 4 2 0.5 <![CDATA[Li2O]]> 3 0 5 PbO 22 28 18 ZnO 5 2 0 CuO 1 2.5 4 <![CDATA[WO3]]> 5.5 11 7 <![CDATA[MoO3]]> 3 2 5 <![CDATA[Bi2O3]]> 14.5 5 24.5 <![CDATA[TeO2]]> 33 27.5 22 CdO 0 5 8

[0078] The glass softening temperature of the single glass powders in Comparative Examples 2-4 was 408℃.

[0079] The electrical performance of the solar cells from Examples 1-6 and Comparative Examples 1-4 was tested, and the results are as follows:

[0080]

[0081]

[0082] The data in the table above shows that Comparative Example 2 has a lower open-circuit voltage (Voc) and a higher series resistance (Rs) in the front-side silver paste, resulting in lower efficiency. Comparative Example 3 has a much higher series resistance (Rs) in the front-side silver paste, resulting in lower efficiency. Comparative Example 4 has a much lower open-circuit voltage (Voc) in the front-side silver paste, resulting in lower efficiency. Furthermore, the efficiency of the front-side silver pastes in Examples 1-6 is higher than that of the comparative examples, with an average open-circuit voltage (Voc) about 2mV higher and an average series resistance (Rs) 0.3mΩ lower. The cadmium oxide content in the glass powder components of Examples 1-6 ranges from 1-10%, effectively controlling the high-temperature flow of the molten glass and its corrosiveness to crystalline silicon. This invention is of great help in replacing imported silver paste with wide-window domestic front-side silver paste for future high-sheet resistance solar cells.

Claims

1. A single glass powder for silver paste on the front side of a solar cell, characterized in that, The single glass powder comprises, by weight percentage, 0.5-5% CuO, 3.5-10% SiO2, 1-7% ZnO, 10-25% PbO, 0-5% MgO, 2.5-10% MoO3, 2-10% Li2O, 3-14% WO3, 8-25.5% Bi2O3, 21-35% TeO2, and 1-10% CdO; The glass softening temperature of the single glass powder is 300-550℃.

2. The single glass powder for the front-side silver paste of the solar cell according to claim 1, characterized in that, The D50 particle size of the single glass powder is 0.1-5μm, and the maximum particle size does not exceed 10μm.

3. The single glass powder for the front-side silver paste of the solar cell according to claim 2, characterized in that, The D50 particle size of the single glass powder is 1.8-2.3 μm.

4. A method for preparing a single glass powder according to any one of claims 1-3, characterized in that, It includes: The components of a single glass powder are mixed, then heated at 950-1300℃ for 20-40 minutes, cooled, and then ground to obtain the final product.

5. The method for preparing a single glass powder according to claim 4, characterized in that, The method for preparing the single glass powder includes: mixing the components of the single glass powder, then heating and melting it at 950-1300℃ for 20-40 minutes to obtain a uniform and clear glass solution, then quenching it in a two-roll mill or deionized water to obtain sheet glass or glass fragments, the glass fragments need to be dried; then successively undergoing dry coarse grinding and wet fine grinding to obtain the final product.

6. A silver paste for the front side of a wide-window, high-sheet-resistance solar cell, characterized in that, The raw materials for its preparation include the single glass powder described in any one of claims 1-3.

7. A method for preparing the front-side silver paste of a wide-window, high-sheet-resistance solar cell according to claim 6, characterized in that, The process includes the following steps: mixing glass powder, silver powder, organic carrier, and organic additives in a certain proportion, and then grinding them to obtain the final product.

8. A high sheet resistance solar cell, characterized in that, Its surface is printed with and sintered with the silver paste on the front side of the wide-window, high-sheet-resistance solar cell obtained by the preparation method described in claim 7.

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