A tellurium-lead-lithium oxide glass powder for BC battery N zone conductive paste and a preparation method thereof

Abstract

The present invention discloses a tellurium-lead-lithium oxide glass powder for BC cell N-region conductive paste and its preparation method, belonging to the field of photovoltaic silver paste. The glass powder adopts components with high Pb, Te, and Li: aTeO2 - bPbO - cLi2O - dBi2O3 - eWO3 - fZnO - gSiO2 - hNa2O; where a + b + c + d + e + f + g + h = 1, 0.2 < a < 0.4, 0.1 < b < 0.4, 0.1 < c < 0.25, 0 < d < 0.1, 0 < e < 0.1, 0 < f < 0.1, 0 < g < 0.1, 0 < h < 0.05, and a + b > 0.5, and the ratio of c to h is (3 - 10):1. By controlling the specific Pb, Te, and Li contents and the specific Li / Na ratio in the present invention, a strong corrosion effect on the poly layer of the cell is achieved, enabling more silver ions dissolved in the glass liquid to recrystallize on the surface of the silicon wafer, thereby achieving good ohmic contact.

Description

Technical Field

[0001] This invention belongs to the field of BC battery technology, specifically relating to a tellurium-lead-lithium oxide glass powder for N-region conductive paste in BC batteries and its preparation method. Background Technology

[0002] With the continuous growth of global demand for clean energy, the photovoltaic industry has developed rapidly. Back-contact (BC) cells, as a high-efficiency solar cell technology, have attracted widespread attention due to their high photoelectric conversion efficiency and aesthetic appeal. In the fabrication process of BC cells, photovoltaic silver paste plays a crucial role, and glass powder, as a key component of photovoltaic silver paste, directly affects the quality of the silver paste and the performance of the BC cells.

[0003] Currently, there are several issues with the glass powder used in BC solar cell photovoltaic silver paste. For example, some glass powders have high sintering temperatures, which can easily damage the silicon wafer during sintering, affecting the cell's performance and lifespan. Some glass powders have poor compatibility with silver powder, reducing the conductivity and adhesion of the silver paste, thus affecting the cell's photoelectric conversion efficiency. Furthermore, existing glass powders may exhibit uneven etching of the silicon nitride layer, leading to inconsistent contact resistance between the electrode and the silicon wafer, impacting the overall cell performance. Therefore, there is an urgent need to develop a high-performance glass powder for BC solar cell photovoltaic silver paste. Summary of the Invention

[0004] [Technical Issues]

[0005] BC (Bulk-Cooled) cell technology is a novel photovoltaic cell technology. The front surface of the cell has no grid lines to obstruct the light, maximizing the utilization of incident light, reducing optical losses, and resulting in a larger effective power generation area and a more aesthetically pleasing appearance. In BC cells, charge carriers need to be transported laterally to the back electrode, requiring extremely high uniformity of the back passivation layer. Inconsistent passivation layer thickness or doping can lead to increased local recombination and a decrease in open-circuit voltage. This necessitates good compatibility and matching between the silver paste and the passivation layer to ensure efficient charge carrier transport. Previously commercially available traditional back conductive pastes showed significantly insufficient contact capability in the N-region of BC cells.

[0006] [Technical Solution]

[0007] To solve the above-mentioned technical problems, the present invention provides a tellurium-lead-lithium oxide glass powder for conductive paste in the N region of BC battery, wherein the composition of the glass powder is: aTeO2-bPbO-cLi2O-dBi2O3-eWO3-fZnO-gSiO2-hNa2O;

[0008] Wherein, a, b, c, d, e, f, g, h respectively refer to the proportion of the molar amount of each metal oxide relative to the total molar amount of the glass powder, and a + b + c + d + e + f + g + h = 1 (I).

[0009] 0.2 < a < 0.4, 0.1 < b < 0.4, 0.1 < c < 0.25, 0 < d < 0.1, 0 < e < 0.1, 0 < f < 0.1, 0 < g < 0.1, 0 < h < 0.05, and a + b > 0.5, and the ratio of c to h is (3 - 10):1.

[0010] In an embodiment of the present invention, preferably 0.15 < c < 0.20.

[0011] In an embodiment of the present invention, the ratio of c to h can be specifically selected as 10:1, 9:1, 8:1, 4:1, 3.5:1. In an embodiment of the present invention, the ratio of c to h is preferably (8 - 10):1.

[0012] In an embodiment of the present invention, the composition of the glass frit is as follows: by mol%, it consists of: 30% - 40% TeO2, 20% - 30% PbO, 15% - 20% Li2O, 6% - 8% Bi2O3, 3% - 5% WO3, 3% - 5% ZnO, 4 - 10% SiO2, 2% - 4% Na2O.

[0013] In an embodiment of the present invention, the composition of the glass frit is as follows: by mol%, it consists of: 36% TeO2, 26% PbO, 16% Li2O, 6% Bi2O3, 3% WO3, 3% ZnO, 8% SiO2, 2% Na2O.

[0014] In an embodiment of the present invention, the preparation method of the tellurium - lead - lithium oxide glass powder for the BC cell N - region conductive paste includes:

[0015] 1) Convert the formula molar ratio to a mass ratio, accurately weigh, mix evenly, place in a corundum crucible, use a lifting furnace, heat with silicon molybdenum rods to 1000 - 1300 °C for 20 - 50 minutes, and cold - roll to obtain glass sheets;

[0016] 2) Place the glass sheets and 20 - mm zirconium beads in a 500 - ml nylon ball - milling jar according to a mass ratio of 1:6, use a planetary ball - mill to ball - mill at 450 r / min for 40 - 90 min, and pass through a 100 - mesh sieve to obtain glass coarse powder;

[0017] 3) Add coarse glass powder, 2mm zirconium beads, and alcohol in a mass ratio of 1:6:3 to a 500ml nylon ball mill jar. Use a planetary ball mill at 350r / min for 30-120min. During the process, use a laser particle size analyzer to test the particle size every 30min. Place the jar in a vacuum drying oven to dry for 3h. Pass the powder through a 120-mesh sieve to obtain the desired inorganic glass powder.

[0018] Preferably, the particle size distribution of the laser particle size analyzer is within the range of D50: 1.2-1.7μm, and Dmax≤8μm.

[0019] The present invention provides a conductive paste for the N-region of a BC battery, comprising, by weight fraction, 88% to 92% conductive metal, 2% to 8% tellurium-lead-lithium oxide glass powder for the above-mentioned conductive paste for the N-region of a BC battery, and 6% to 12% organic carrier.

[0020] The conductive metal is one or more of silver, gold, platinum, and aluminum, preferably silver;

[0021] The organic carrier includes organic solvents, binders, thixotropic agents, surfactants, and additives.

[0022] Organic solvents include one or more of acetone, terpineol, hexylcarbitol, butylcarbitol acetate, dimethyl adipate diol ether, and butylcarbitol.

[0023] The binder includes one or more of the following: ethyl cellulose, phenolic resin, polyvinyl butyral, polyethylene resin, polyacrylic acid, polyurethane resin, and rosin derivatives.

[0024] Thixotropic agents include one or more of castor oil derivatives, polyamides, polyamide derivatives, and fatty acid derivatives.

[0025] Surfactants include one or more of polyethylene oxide, dodecylaminopropionic acid, benzotriazole, polyethylene glycol, silicone oil, lauric acid, oleic acid, decanoic acid, myristic acid, stearate, and palmitic acid ester.

[0026] This invention provides a method for preparing a conductive paste for the N-region of a BC battery, comprising:

[0027] The organic carrier, conductive metal powder, and the above-mentioned conductive paste in the N region of the BC battery are mixed with tellurium-lead-lithium oxide glass powder and repeatedly rolled and ground by a ceramic three-roll mill until they are uniformly mixed to obtain the conductive paste.

[0028] The present invention also provides a BC battery, which is made by printing the above-mentioned conductive paste onto the N region of the BC battery using a battery cell screen printing machine, followed by sintering.

[0029] The present invention also provides the application of the tellurium-lead-lithium oxide glass powder for the N-region conductive paste of the BC cell, the above-mentioned conductive paste, or the above-mentioned BC cell in the field of photovoltaic solar energy.

[0030] Compared with the prior art, the present invention has the following advantages and effects:

[0031] The glass powder of the present invention has a relatively low sintering temperature, and good sintering effect can be achieved at 750°C - 850°C, greatly reducing the risk of damage to the battery silicon wafer during the sintering process, which is beneficial to improving the performance and lifespan of the battery.

[0032] By controlling the specific contents of Pb, Te, and Li, as well as the specific Li / Na ratio, the present invention enables specific synergistic effects among various components, achieving a strong corrosive effect on the poly layer of the cell wafer, enabling more silver ions dissolved in the glass liquid to recrystallize on the surface of the silicon wafer, effectively improving the conductivity and adhesion of the silver paste, achieving good ohmic contact, and thus enhancing the photoelectric conversion efficiency of the BC cell. Description of the Drawings

[0033] Figure 1 It is the interface diagram after sintering the conductive pastes of Examples 1 - 2 and Comparative Examples 1 - 2 screen-printed on the BCN-region cell wafers. It can be clearly seen that there are many evenly arranged silver crystals at the interfaces of Examples 1 - 2, which indicates that the glass powder corrodes the N-region poly layer of the cell wafer, and the silver ions dissolved in the glass recrystallize on the surface of the silicon wafer. While there are almost no silver crystals at the interfaces shown in Comparative Examples 1 - 2, which shows that the glass has insufficient corrosion ability for the poly layer and cannot make a large number of silver ions recrystallize on the surface of the silicon wafer. Detailed Embodiments

[0034] It should be noted that the following embodiments are for explaining the present invention in detail and are not intended to limit the present invention.

[0035] The present invention will be further described below in conjunction with the embodiments.

[0036] In order to provide sufficient corrosive effect on the passivation layer of the BC cell, the inorganic glass powder of the present invention adopts components with high Pb, Te, and high Li: aTeO2 - bPbO - cLi2O - dBi2O3 - eWO3 - fZnO - gSiO2 - hNa2O; where a + b + c + d + e + f + g + h = 1, 0.2 < a < 0.4, 0.1 < b < 0.4, 0.1 < c < 0.25, 0 < d < 0.1, 0 < e < 0.1, 0 < f < 0.1, 0 < g < 0.1, 0 < h < 0.05, and a + b > 0.5, and the ratio of c to h is (3 - 10):1.

[0037] The particle size was characterized using a laser particle size analyzer, the hemispherical temperature was observed using a high-temperature microscopy (HSM), the glass transition temperature (Tg) and the crystallization initiation temperature (Tc) were characterized using differential scanning calorimetry (DSC), the slurry viscosity was analyzed using a viscometer, the slurry was screen-printed onto solar cells, and after sintering and densification, the contact resistivity (ρc) was tested using a line transport model (TLM) to characterize its corrosion resistance. The photoelectric conversion efficiency was tested using specialized BC printing equipment and an IV machine.

[0038] Example 1

[0039] Accurately weigh the glass powder according to the molar ratio of the glass powder formula in Table 1, converting it to a mass ratio. Use oxides or carbonates with an analytical purity greater than 99.9% for the raw materials. Mix them evenly using a shaker, place them in a corundum crucible, and put them in a lifting furnace. Heat to 1000℃ and hold for 30 minutes using a silicon molybdenum rod. Remove and pour into a cold rolling mill to crush into glass flakes. Place the glass flakes and 20mm zirconium beads at a mass ratio of 1:6 in a 500ml nylon ball mill jar. Use a planetary ball mill at 450r / min for 60 minutes and pass through a 100-mesh sieve to obtain coarse glass powder. Add the coarse glass powder, 2mm zirconium beads, and alcohol at a mass ratio of 1:6:3 to a 500ml nylon ball mill jar. Use a planetary ball mill at 350r / min for 75 minutes. Place in a vacuum drying oven and dry for 3 hours. Pass through a 120-mesh sieve to obtain inorganic glass powder, designated as TBL-1. The particle size was measured using a laser particle size analyzer, the characteristic temperature was measured using differential scanning calorimetry, and the hemispherical temperature was measured using HSM. The above data are shown in Table 2.

[0040] Glass powder TBL-1 was mixed with silver powder (D50 = 1.8), organic carrier (40 wt% dimethyl adipate glycol ether, 40 wt% butylcarbidol acetate, 15 wt% ethyl cellulose and butylcarbidol acetate mixture, 2 wt% sodium oleate, 1 wt% polyether-modified siloxane, 2 wt% hydrogenated castor oil) at a ratio of 3.5:87.5:9 and homogenized. The mixture was then milled using a three-roll mill to form a conductive paste, designated YJ-1. Its viscosity was measured using a viscometer and is shown in Table 3. The paste was printed onto the N-region of a BC cell using a cell screen printing machine. The cells were sintered in a chain furnace at a maximum temperature of 790℃. Defects in the cells were repaired using a light injection device. The contact resistivity was measured using a TLM device, and the photoelectric conversion efficiency was measured using specialized equipment. The results are shown in Table 4.

[0041] Example 2

[0042] Accurately weigh the glass powder according to the molar ratio of the glass powder formula in Table 1, converting it to a mass ratio. Use oxides or carbonates with an analytical purity greater than 99.9% for the raw materials. Mix them evenly using a shaker, place them in a corundum crucible, and put them in a lifting furnace. Heat to 1000℃ and hold for 30 minutes using a silicon molybdenum rod. Remove and pour into a cold rolling mill to crush into glass flakes. Place the glass flakes and 20mm zirconium beads at a mass ratio of 1:6 in a 500ml nylon ball mill jar. Use a planetary ball mill at 450r / min for 50 minutes and pass through a 100-mesh sieve to obtain coarse glass powder. Add the coarse glass powder, 2mm zirconium beads, and alcohol at a mass ratio of 1:6:3 to a 500ml nylon ball mill jar. Use a planetary ball mill at 350r / min for 65 minutes. Place in a vacuum drying oven and dry for 3 hours. Pass through a 120-mesh sieve to obtain inorganic glass powder, designated as TBL-2. The particle size was measured using a laser particle size analyzer, the characteristic temperature was measured using differential scanning calorimetry, and the hemispherical temperature was measured using HSM. The above data are shown in Table 2.

[0043] Glass powder TBL-2 was mixed with silver powder (D50 = 1.8), an organic carrier (40 wt% dimethyl adipate, 40 wt% butylcarbidol acetate, 15 wt% ethyl cellulose and butylcarbidol acetate mixture, 2 wt% sodium oleate, 1 wt% polyether-modified siloxane, 2% hydrogenated castor oil) in a ratio of 3:88:9, and then milled using a three-roll mill to form a conductive paste, designated YJ-2. Its viscosity was measured using a viscometer and is shown in Table 3. The paste was printed onto the N-region of a BC cell using a cell screen printing machine, and sintered in a chain furnace at a maximum temperature of 790℃. Cell defects were repaired using a light injection device, and the contact resistivity was measured using a TLM device. The photoelectric conversion efficiency was measured using specialized equipment, and the results are shown in Table 4.

[0044] Example 3

[0045] Accurately weigh the glass powder according to the molar ratio of the glass powder formula in Table 1, converting it to a mass ratio. Use oxides or carbonates with an analytical purity greater than 99.9% for the raw materials. Mix them evenly using a shaker, place them in a corundum crucible, and put them in a lifting furnace. Heat to 1050℃ using a silicon molybdenum rod and hold for 30 minutes. Remove and pour into a cold rolling mill to crush into glass flakes. Place the glass flakes and 20mm zirconium beads at a mass ratio of 1:6 in a 500ml nylon ball mill jar. Use a planetary ball mill at 450r / min for 60 minutes and pass through a 100-mesh sieve to obtain coarse glass powder. Add the coarse glass powder, 2mm zirconium beads, and alcohol at a mass ratio of 1:6:3 to a 500ml nylon ball mill jar. Use a planetary ball mill at 350r / min for 70 minutes. Place in a vacuum drying oven to dry for 3 hours and pass through a 120-mesh sieve to obtain inorganic glass powder, designated TBL-3. The particle size was measured using a laser particle size analyzer, the characteristic temperature was measured using differential scanning calorimetry, and the hemispherical temperature was measured using HSM. The above data are shown in Table 2.

[0046] Glass powder TBL-3 was mixed with silver powder (D50 = 1.8), an organic carrier (45 wt% dimethyl adipate, 35 wt% butylcarbidol acetate, 15 wt% ethyl cellulose and butylcarbidol acetate mixture, 2 wt% sodium oleate, 1.5 wt% polyether-modified siloxane, 1.5% hydrogenated castor oil) in a ratio of 3.2:88:8.8 and homogenized. The mixture was then milled using a three-roll mill to prepare a conductive paste, designated YJ-3. Its viscosity was measured using a viscometer and is shown in Table 3. The paste was printed onto the N-region of a BC cell using a cell screen printing machine. The cells were sintered in a chain furnace at a maximum temperature of 790℃. Defects in the cells were repaired using a light injection device. The contact resistivity was measured using a TLM device, and the photoelectric conversion efficiency was measured using specialized equipment. The results are shown in Table 4.

[0047] Example 4

[0048] Referring to Example 1, glass powder TBL-1 was replaced with an equal amount of glass powder TBL-4, and other steps were the same as in Example 1 to obtain a conductive paste. Its viscosity was measured using a viscometer and is shown in Table 3. The paste was printed onto the N-region of a BC cell using a cell screen printing machine, and sintered in a chain furnace at a maximum temperature of 790°C. Cell defects were repaired using a light injection device, and its contact resistivity was measured using a TLM device. Its photoelectric conversion efficiency was measured using specialized equipment, and the test results are shown in Table 4.

[0049] Example 5

[0050] Referring to Example 1, glass powder TBL-1 was replaced with an equal amount of glass powder TBL-5, and other steps were the same as in Example 1 to obtain a conductive paste. Its viscosity was measured using a viscometer and is shown in Table 3. The paste was printed onto the N-region of a BC cell using a cell screen printing machine, and sintered in a chain furnace at a maximum temperature of 790°C. Cell defects were repaired using a light injection device, and its contact resistivity was measured using a TLM device. Its photoelectric conversion efficiency was measured using specialized equipment, and the test results are shown in Table 4.

[0051] Example 6

[0052] Referring to Example 1, glass powder TBL-1 was replaced with an equal amount of glass powder TBL-6, and other steps were the same as in Example 1 to obtain a conductive paste. Its viscosity was measured using a viscometer and is shown in Table 3. The paste was printed onto the N-region of a BC cell using a cell screen printing machine, and sintered in a chain furnace at a maximum temperature of 790°C. Cell defects were repaired using a light injection device, and its contact resistivity was measured using a TLM device. Its photoelectric conversion efficiency was measured using specialized equipment, and the test results are shown in Table 4.

[0053] Example 7

[0054] Referring to Example 1, replace the glass powder TBL-1 with an equal amount of glass powder TBL-7, and the other steps are the same as in Example 1 to obtain a conductive paste. Test its viscosity with a viscometer, and the results are shown in Table 3. Print the paste onto the N region of the BC cell through a cell screen printer, sinter it in a chain furnace with a maximum temperature of 790 °C, repair the cell defects through a light injection device, test its contact resistivity through a TLM device, and test its photoelectric conversion efficiency under a dedicated device. The test results are shown in Table 4.

[0055] Comparative Example 1

[0056] Referring to Example 1, replace the glass powder TBL-1 with an equal amount of glass powder TBL-8, and the other steps are the same as in Example 1 to obtain a conductive paste. The glass powder TBL-8 does not meet the condition of 0.1 < c < 0.25 in aTeO2 - bPbO - cLi2O - dBi2O3 - eWO3 - fZnO - gSiO2 - hNa2O. Test its performance using the same method as in Example 1.

[0057] Test its viscosity with a viscometer, and the results are shown in Table 3. Print the paste onto the N region of the BC cell through a cell screen printer, sinter it in a chain furnace with a maximum temperature of 790 °C, repair the cell defects through a light injection device, test its contact resistivity through a TLM device, and test its photoelectric conversion efficiency under a dedicated device. The test results are shown in Table 4.

[0058] Comparative Example 2

[0059] Referring to Example 1, replace the glass powder TBL-1 with an equal amount of glass powder TBL-9, and the other steps are the same as in Example 1 to obtain a conductive paste. The glass powder TBL-9 does not meet the condition of a + b > 0.5 in aTeO2 - bPbO - cLi2O - dBi2O3 - eWO3 - fZnO - gSiO2 - hNa2O. Test its performance using the same method as in Example 1.

[0060] Test its viscosity with a viscometer, and the results are shown in Table 3. Print the paste onto the N region of the BC cell through a cell screen printer, sinter it in a chain furnace with a maximum temperature of 790 °C, repair the cell defects through a light injection device, test its contact resistivity through a TLM device, and test its photoelectric conversion efficiency under a dedicated device. The test results are shown in Table 4.

[0061] Comparative Example 3

[0062] Referring to Example 1, replace the glass powder TBL-1 with an equal amount of glass powder TBL-10, and the other steps are the same as in Example 1 to obtain a conductive paste. The glass powder TBL-10 does not meet the conditions of 0.1 < c < 0.25 and 0 < d < 0.1 in aTeO2 - bPbO - cLi2O - dBi2O3 - eWO3 - fZnO - gSiO2 - hNa2O. Test its performance using the same method as in Example 1.

[0063] Test its viscosity using a viscometer, and the results are shown in Table 3. Print the paste onto the N region of the BC cell using a cell screen printer, sinter it in a chain furnace with a maximum temperature of 790 °C, repair the cell defects using a light injection device, test its contact resistivity using a TLM device, and test its photoelectric conversion efficiency under a dedicated device. The test results are shown in Table 4.

[0064] Comparative Example 4

[0065] Referring to Example 1, replace the glass powder TBL-1 with an equal amount of glass powder TBL-11, and the other steps are the same as in Example 1 to obtain a conductive paste. The glass powder TBL-11 does not meet the conditions of 0.1 < c < 0.25 and the ratio of c to h is (3 - 10):1 in aTeO2 - bPbO - cLi2O - dBi2O3 - eWO3 - fZnO - gSiO2 - hNa2O. Test its performance using the same method as in Example 1.

[0066] Test its viscosity using a viscometer, and the results are shown in Table 3. Print the paste onto the N region of the BC cell using a cell screen printer, sinter it in a chain furnace with a maximum temperature of 790 °C, repair the cell defects using a light injection device, test its contact resistivity using a TLM device, and test its photoelectric conversion efficiency under a dedicated device. The test results are shown in Table 4.

[0067] Comparative Example 5

[0068] Referring to Example 1, replace the glass powder TBL-1 with an equal amount of glass powder TBL-12, and the other steps are the same as in Example 1 to obtain a conductive paste. The glass powder TBL-12 does not meet the condition that the ratio of c to h is (3 - 10):1 in aTeO2 - bPbO - cLi2O - dBi2O3 - eWO3 - fZnO - gSiO2 - hNa2O. Test its performance using the same method as in Example 1.

[0069] Test its viscosity using a viscometer, and the results are shown in Table 3. Print the paste onto the N region of the BC cell using a cell screen printer, sinter it in a chain furnace with a maximum temperature of 790 °C, repair the cell defects using a light injection device, test its contact resistivity using a TLM device, and test its photoelectric conversion efficiency under a dedicated device. The test results are shown in Table 4.

[0070] Table 1. Glass powder formulations for Examples 1-7 and Comparative Examples 1-5 (in mol%)

[0071] glass powder <![CDATA[TeO2]]> <![CDATA[PbO2]]> <![CDATA[Li2O]]> <![CDATA[Bi2O3]]> <![CDATA[WO3]]> ZnO <![CDATA[SiO2]]> <![CDATA[Na2O]]> Example 1 TBL-1 36 26 16 6 3 3 8 2 Example 2 TBL-2 30 24 20 6 5 5 8 2 Example 3 TBL-3 32 26 18 8 4 4 6 2 Example 4 TBL-4 32 24 16 8 5 5 8 2 Example 5 TBL-5 36 22 16 8 5 5 4 4 Example 6 TBL-6 32 26 14 6 5 5 8 4 Example 7 TBL-7 36 24 14 6 3 3 10 4 Comparative Example 1 TBL-8 32 22 8 8 10 10 6 4 Comparative Example 2 TBL-9 20 20 20 10 10 5 10 5 Comparative Example 3 TBL-10 36 26 6 16 3 3 8 2 Comparative Example 4 TBL-11 33 22 25 4 3 3 8 2 Comparative Example 5 TBL-12 36 26 12 6 3 3 8 6

[0072] Table 2. Glass powder properties of Examples 1-7 and Comparative Examples 1-5

[0073]

[0074]

[0075] As shown in Table 2, in Comparative Example 4, the excessive amount of Li and in Comparative Example 5, the excessive amount of Na both caused the temperature of the glass hemisphere to rise sharply and the fluidity to deteriorate. The actual sintering temperature of the BC battery is around 710-730°C, which makes it impossible to achieve the effect of dissolving silver, resulting in poor contact.

[0076] Table 3. Slurry viscosity of Examples 1-7 and Comparative Examples 1-5

[0077] 5R 10R 30R 50R Example 1 294 187 77 46 Example 2 271 169 69 44 Example 3 274 177 69 52 Example 4 277 171 66 55 Example 5 291 185 72 58 Example 6 268 166 78 47 Example 7 266 172 65 55 Comparative Example 1 288 185 62 50 Comparative Example 2 271 169 70 53 Comparative Example 3 254 166 81 43 Comparative Example 4 330 201 99 61 Comparative Example 5 300 195 95 59

[0078] Table 4. TLM test results of Examples 1-7 and Comparative Examples 1-5

[0079]

[0080]

[0081] As shown in Table 4, the contact resistivity ρc of Examples 1-7 remained between 0.2 and 0.6. However, the inorganic glass powder in Comparative Examples 1-3 did not meet the formulation conditions. The low Li or low Te+Pb content resulted in insufficient silver dissolution capacity of the inorganic glass powder and insufficient ability to corrode the poly layer of the silicon wafer, causing a sharp increase in ρc value and thus a decrease in efficiency. In Comparative Example 4, the excessively high Li content and the low Li / Na ratio in Comparative Example 5 caused a sharp rise in the temperature of the glass hemisphere, making it unable to flow and dissolve silver at the sintering temperature of the BC battery, resulting in a sharp increase in its ρc value and a decrease in efficiency.

[0082] Comparative Example 6

[0083] Referring to Example 1, glass powder TBL-1 was replaced with an equal amount of glass powder TBL-13, and the other steps were the same as in Example 1 to obtain a conductive paste.

[0084] The components of TBL-13 are as follows:

[0085] glass powder <![CDATA[TeO2]]> <![CDATA[PbO2]]> <![CDATA[Li2O]]> <![CDATA[Bi2O3]]> <![CDATA[WO3]]> ZnO <![CDATA[SiO2]]> <![CDATA[Na2O]]> mol% 28 22 28 4 4 3 8 3 wt% 31.3 37.2 5.8 13.2 6.2 1.5 3.5 1.3

[0086] The performance was tested using the same method as in Example 1. The paste was printed onto the N region of the BC cell using a cell screen printing machine, and sintered in a chain furnace at a maximum temperature of 790°C. Cell defects were repaired using a light injection device, and the contact resistivity was tested using a TLM device. The photoelectric conversion efficiency was tested using a dedicated device. The test results are shown in Table 5.

[0087] Table 5

[0088]

[0089] It is evident that although TBL-13 is a tellurium-lead-lithium oxide glass powder with high Te, Pb, and Li content, its excessive Li content and high Li / Na ratio result in poor overall conductive paste performance.

[0090] Comparative Example 7

[0091] Referring to Example 1, glass powder TBL-1 was replaced with an equal amount of glass powder TBL-14, and the other steps were the same as in Example 1 to obtain a conductive paste.

[0092] The components of TBL-14 are as follows:

[0093] glass powder <![CDATA[TeO2]]> <![CDATA[PbO2]]> <![CDATA[Li2O]]> <![CDATA[Bi2O3]]> <![CDATA[WO3]]> ZnO <![CDATA[SiO2]]> <![CDATA[Na2O]]> CuO AgO mol% 30.5 22.3 4.3 5.4 2.2 16.4 12.3 1.3 2 3.3 wt% 30.3 33.1 0.8 15.8 3.1 8.3 4.6 0.5 1 2.5

[0094] The performance was tested using the same method as in Example 1. The paste was printed onto the N region of the BC cell using a cell screen printing machine, and sintered in a chain furnace at a maximum temperature of 790°C. Cell defects were repaired using a light injection device, and the contact resistivity was tested using a TLM device. The photoelectric conversion efficiency was tested using a dedicated device. The test results are shown in Table 6.

[0095] Table 6

[0096]

[0097] It can be seen that although TBL-14 controls an appropriate Li / Na ratio, the main component of its glass powder is tellurium-lead-zinc oxide glass powder with Te, Pb and Zn content, and more oxide components, such as copper oxide and silver oxide, are added. The overall performance of the conductive paste after the combination of these components is significantly worse than that of Example 1 of the present invention.

[0098] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A tellurium-lead-lithium oxide glass powder for the N-region conductive paste of a BC cell, the composition of the glass powder being: aTeO2 - bPbO - cLi2O - dBi2O3 - eWO3 - fZnO - gSiO2 - hNa2O; in, a, b, c, d, e, f, g, h respectively refer to the proportion of the molar amount of each metal oxide relative to the molar amount of the total glass powder, a + b + c + d + e + f + g + h = 1, 0.2 < a < 0.4, 0.1 < b < 0.4, 0.1 < c < 0.25, 0 < d < 0.1, 0 < e < 0.1, 0 < f < 0.1, 0 < g < 0.1, 0 < h < 0.05, and a + b > 0.5, the ratio of c to h is (3 - 10):

1.

2. The tellurium-lead-lithium oxide glass powder for the N-region conductive paste of the BC battery according to claim 1, characterized in that, 0.15<c<0.20。 3. The tellurium-lead-lithium oxide glass powder for the N-region conductive paste of the BC battery according to claim 1, characterized in that, The ratio of c to h is (8 - 10):

1.

4. The tellurium-lead-lithium oxide glass powder for the N-region conductive paste of the BC battery according to claim 1, characterized in that, The composition of the glass powder is as follows in mol%: 30% - 40% TeO2, 20% - 30% PbO, 15% - 20% Li2O, 6% - 8% Bi2O3, 3% - 5% WO3, 3% - 5% ZnO, 4 - 10% SiO2, 2% - 4% Na2O.

5. The tellurium-lead-lithium oxide glass powder for the N-region conductive paste of the BC battery according to claim 1, characterized in that, The composition of the glass powder is as follows in mol%: 36% TeO2, 26% PbO, 16% Li2O, 6% Bi2O3, 3% WO3, 3% ZnO, 8% SiO2, 2% Na2O.

6. A conductive paste for the N-region of a BC battery, characterized in that, By weight fraction, it includes 88% - 92% of conductive metal, 2 - 8% of the tellurium-lead-lithium oxide glass powder for the N-region conductive paste of a BC cell according to any one of claims 1 - 5, and 6% - 12% of organic carrier, and the sum of the amounts of the above three components is 100%.

7. The BC battery N-region conductive paste according to claim 6, characterized in that, The conductive metal is one or more of silver, gold, platinum, and aluminum; the organic carrier includes organic solvents, binders, thixotropic agents, surfactants, and additives; the organic solvents include one or more of acetone, terpineol, hexyl carbitol, butyl carbitol acetate, dimethyl adipate diol ether, and butyl carbitol.

8. The BC battery N-region conductive paste according to claim 7, characterized in that, The binders include one or more of ethyl cellulose, phenolic resin, polyvinyl butyral, polyethylene resin, polyacrylic acid, polyurethane resin, and rosin derivatives; the thixotropic agents include one or more of castor oil derivatives, polyamides, polyamide derivatives, and fatty acid derivatives; the surfactants include one or more of polyethylene oxide, dodecyl aminopropionic acid, benzotriazole, polyethylene glycol, silicone oil, lauric acid, oleic acid, capric acid, myristic acid, stearate, and palmitate.

9. A BC battery, characterized in that, It is to print the conductive paste according to any one of claims 6 - 8 onto the N-region of the BC cell through a cell screen printer, and then sinter.

10. The application of the tellurium-lead-lithium oxide glass powder for the N-region conductive paste of a BC cell according to any one of claims 1 - 5, the conductive paste according to any one of claims 6 - 8, or the BC cell according to claim 9 in the field of photovoltaic solar energy.

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