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Silicon-lithium-lead System, Conductive Paste and Preparation Method thereof

20220144689 · 2022-05-12

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    Abstract

    The present disclosure discloses a silicon-lithium-lead system, a conductive paste and a preparation method thereof, and belongs to the field of solar cells. A silicon-lead-lithium oxide frit includes the following composition: Si.sub.a—Pb.sub.b—Li.sub.c—(B.sub.x—Al.sub.y—Bi.sub.z)—M.sub.e—O.sub.f, where, 0<a<0.6, 0<b<0.8, 0<c<0.6, x+y+z=d, the x and the y are not zero at the same time, and the z is greater than zero. In the present disclosure, by adding B.sub.2O.sub.3 and Bi.sub.2O.sub.3, Al.sub.2O.sub.3 and Bi.sub.2O.sub.3, or B.sub.2O.sub.3, Al.sub.2O.sub.3 and Bi.sub.2O.sub.3 at the same time, the prepared frit has greater water resistance, and therefore, a solar cell prepared by using the conductive paste containing glass has good water resistance. In addition, the photoelectric conversion efficiency of the solar cell prepared by using the conductive paste prepared in the present disclosure can also be maintained, or even be slightly improved.

    Claims

    1. A silicon-lead-lithium oxide frit, comprising the following component:
    Si.sub.a—Pb.sub.b—Li.sub.c—(B.sub.x—Al.sub.y—Bi.sub.z)—M.sub.e—O.sub.f   (I) wherein, 0<a<0.6, 0<b<0.8, 0<c<0.6, x+y+z=d, at least one of x, y and z is greater than zero, 0<d<0.6, c:d=(5:95)-(95:5), M is one or a mixture of more of Na, K, Mg, Ca, Sr, Ti, Zr, V, Cr, Mo, W, Mn, Cu, Ag, Zn, Cd, Ga, TI, Ge, P and Te, and a+b+c+d+e=1.

    2. The silicon-lead-lithium oxide frit according to claim 1, wherein the x and the y are not zero at the same time, and the z is greater than zero.

    3. The silicon-lead-lithium oxide frit according to claim 1, wherein all the x, the y and the z are greater than zero.

    4. The silicon-lead-lithium oxide frit according to claim 1, wherein 0<a<0.4, 0<b<0.5, 0<c<0.4, 0<d<0.4, and c:d=(30:70)-(90:10).

    5. The silicon-lead-lithium oxide frit according to claim 1, wherein 0<a<0.3, 0<b<0.4, 0<c<0.3, 0<d<0.3, and c:d=(40:60)-(90:10).

    6. The silicon-lead-lithium oxide frit according to claim 2, comprising the following components based on oxides in mol %: 5-15% of SiO.sub.2, 19-25% of PbO, 18-25% of Li.sub.2O, 0-2% of B.sub.2O.sub.3, 0-2% of Al.sub.2O.sub.3, 4-8% of Bi.sub.2O.sub.3 and the balance of MO.sub.x, wherein contents of Bi.sub.2O.sub.3 and Al.sub.2O.sub.3 are not 0 at the same time.

    7. The silicon-lead-lithium oxide frit according to claim 6, comprising the following components based on oxides in mol %: 8%-15% of SiO.sub.2, 19%-22% of PbO, 20%-25% of Li.sub.2O, 1%-2% of B.sub.2O.sub.3, 1%-2% of Al.sub.2O.sub.3, 4%-7% of Bi.sub.2O.sub.3 and the balance of MO.sub.x.

    8. The silicon-lead-lithium oxide frit according to claim 6, comprising the following components based on oxides in mol %: 15% of SiO.sub.2, 20% of PbO, 20% of Li.sub.2O, 2% of B.sub.2O.sub.3, 2% of Al.sub.2O.sub.3, 6% of Bi.sub.2O.sub.3 and 35% of MO.sub.x.

    9. A conductive paste of a silicon-lead-lithium oxide frit, comprising, by weight percentage, 84%-94% of a conductive metal, 0.1-9% of the silicon-lead-lithium oxide frit according to claims 1 and 5%-15% of an organic vehicle.

    10. The conductive paste of a silicon-lead-lithium oxide frit according to claim 9, wherein the conductive metal is one or more of silver, gold, platinum, rhodium, copper, nickel and aluminum; and the organic vehicle comprises an organic binder, an organic solvent, a thixotropic agent and a surfactant.

    11. The conductive paste of a silicon-lead-lithium oxide frit according to claim 10, wherein the conductive metal is silver.

    12. The conductive paste of a silicon-lead-lithium oxide frit according to claim 9, wherein the preparation method of the conductive paste of a silicon-lead-lithium oxide frit comprises: weighing the conductive metal, the silicon-lead-lithium system frit and the organic vehicle according to a proportion of a formula, uniformly mixing and stirring the raw materials of the conductive paste by using a mixer, repeatedly milling the conductive paste by using a three-roll mill, and further mixing the conductive paste uniformly by using a shearing force between rollers of the three-roll mill.

    13. The conductive paste of a silicon-lead-lithium oxide frit according to claim 9, wherein the preparation method of the conductive paste of a silicon-lead-lithium oxide frit comprises: weighing the conductive metal, the silicon-lead-lithium system frit and the organic vehicle according to a proportion of a formula, uniformly mixing and stirring the raw materials of the conductive paste by using a mixer, repeatedly milling the conductive paste by using a three-roll mill, and further mixing the conductive paste uniformly by using a shearing force between rollers of the three-roll mill.

    14. The conductive paste of a silicon-lead-lithium oxide frit according to claim 9, wherein the preparation method of the conductive paste of a silicon-lead-lithium oxide frit comprises: weighing the conductive metal, the silicon-lead-lithium system frit and the organic vehicle according to a proportion of a formula, uniformly mixing and stirring the raw materials of the conductive paste by using a mixer, repeatedly milling the conductive paste by using a three-roll mill, and further mixing the conductive paste uniformly by using a shearing force between rollers of the three-roll mill.

    15. A solar cell device, wherein the solar cell device comprises the silicon-lead-lithium oxide frit according to claims 1.

    16. A solar cell device, wherein the solar cell device comprises the conductive paste of a silicon-lead-lithium oxide frit according to claim 9.

    Description

    BRIEF DESCRIPTION OF FIGURES

    [0030] FIG. 1 shows that an inorganic oxide is printed on an Al.sub.2O.sub.3 substrate and then sintered to form a smooth and uniform film. 001 refers to the Al.sub.2O.sub.3 substrate, and 002 refers to an oxide film.

    DETAILED DESCRIPTION

    [0031] The present disclosure is further described below in conjunction with examples, but embodiments of the present disclosure are not limited thereto.

    [0032] In order to reduce the corrosion of an oxide in a conductive electrode mixture by water vapor, a silicon-lead-lithium oxide of the present disclosure includes the following component:


    Si.sub.a—Pb.sub.b—Li.sub.c—(B.sub.x—Al.sub.y—Bi.sub.z)—M.sub.e—O.sub.f   (I)

    [0033] where, 0<a<0.6, 0<b<0.8, 0<c<0.6, x+y+z=d, at least one of x, y and z is greater than zero, 0<d<0.6, c:d=(5:95)-(95:5), M is one or a mixture of more of Na, K, Mg, Ca, Sr, Ti, Zr, V, Cr, Mo, W, Mn, Cu, Ag, Zn, Cd, Ga, TI, Ge, P and Te, and a+b+c+d+e=1.

    [0034] Preferably, the x and the y are not zero at the same time, and the z is greater than zero. More preferably, the x and the y are not zero at the same time, and the z is greater than zero.

    [0035] Firstly, when the radius of an alkali metal ion is increased, the bond strength of an alkali metal oxide is lowered, and the chemical stability is reduced. For the water resistance, Li.sup.+>Na.sup.+>K.sup.+. Therefore, Li is the first choice among the alkali metal elements.

    [0036] Secondly, the water corrosion resistance of the alkali metal oxide can be improved by using several trivalent oxides. When boron oxide is used, a glass has a “boron oxide anomaly” phenomenon of chemical stability. When B.sub.2O.sub.3 is added, B.sup.3+ borrows electrons from Li.sup.+, and an original [BO.sub.3] triangle is changed into a [BO.sub.4] tetrahedron, and this can reconnect broken bonds, so that a network structure is strengthened, and a water corrosion effect is significantly reduced. When Al.sub.2O.sub.3 is added into the alkali metal oxide, the chemical stability can also be greatly improved. This is because Al.sup.3+ borrows electrons from the Li.sup.+ to form a [AlO.sub.4] tetrahedron, and this achieves a supplement effect on a silicon-oxygen network. Similarly, it is found in experiments that when Bi.sub.2O.sub.3 is added, a complex network structure of [BiO.sub.6] also achieves a supplement effect on the silicon-oxygen network, and the water corrosion resistance of the alkali metal oxide is improved.

    [0037] In order to test the water corrosion resistance of the alkali metal oxide, a following test method is used in the present disclosure. An inorganic oxide and an organic vehicle are uniformly mixed according to a certain proportion and then prepared into an oxide paste by using a three-roll mill. Several Al.sub.2O.sub.3 substrates are taken out and weighed to obtain a tare weight W.sub.T. The oxide paste is printed on the Al.sub.2O.sub.3 substrate. Then, the substrate is heated to 600-800° C. in a high-temperature furnace. The organic vehicle is completely volatilized and burned off, and the inorganic oxide is sintered on the Al.sub.2O.sub.3 substrate to form a smooth and uniform film. The structure of the substrate is shown in FIG. 1, 001 refers to the Al.sub.2O.sub.3 substrate, and 002 refers to an oxide film. A sample is weighed to obtain an initial gross weight W.sub.0. The oxide film and the Al.sub.2O.sub.3 substrate are soaked in deionized water. A cover is used for sealing to prevent water from completely evaporating. The sample is heated to 75° C. for 24 hours. The sample is taken out, thoroughly washed with deionized water and then heated to 75° C. again for 30 minutes. After a surface of the sample is completely dry, the sample is taken out and weighed again to obtain a gross weight W.sub.1.

    [0038] An oxide corroded by the water can be calculated in weight percentage by using the following formula: ΔW %=(W.sub.1−W.sub.0)/(W.sub.0−W.sub.T)×100%, and the measurement error is ±0.05‰.

    [0039] Determination method of photoelectric conversion efficiency: The photoelectric conversion efficiency of a cell is determined by using a HALM IV tester.

    EXAMPLE 1

    [0040] Mixing was conducted according to proportions of S1-S3 in Table 1 to obtain a mixed composition. The mixed composition was melted at about 900-1,300° C. and then quenched to about 25° C. An obtained material was pulverized by using a planetary mill and then dried to obtain a uniform glass powder. The glass powder and an organic vehicle (a mixture of ethyl cellulose and butyl carbitol acetate in a mass ratio of 1:7) were uniformly mixed in a ratio of 75%:25% and then prepared into a glass paste by using a three-roller mill. Several Al.sub.2O.sub.3 substrates were taken out and weighed to obtain a tare weight W.sub.T. An oxide paste was printed on the Al.sub.2O.sub.3 substrate. Then, the substrate was heated to 800° C. in a high-temperature furnace. The organic vehicle was completely volatilized and burned, and an oxide was sintered on the Al.sub.2O.sub.3 substrate to form a smooth and uniform film. The water corrosion resistance was tested by using the method above, and results were shown in Table 1.

    [0041] 0.6% (mass percentage, the same below) of an organic binder (ethyl cellulose and polyvinyl butyral in a mass ratio of 7:3), 0.4% of a thixotropic agent (polyamide), 0.5% of a surfactant (organic silicone oil), 0.3% of a surfactant (tallow diamine dioleate), and 6.4% of an organic solvent (a mixture of butyl carbitol acetate and dimethyl adipate in a mass ratio of 5:5) were stirred under a high shear force at 50-60° C. for 1-2 hours. 2.4% of the glass powder prepared above and 89.4% of a silver powder were added into the mixture above and then stirred thoroughly to form a mixture. The paste composition was repeatedly ground by using a three-roll grinder to obtain a conductive paste. Then, the conductive paste was printed on a silicon wafer substrate by using a screen-printing technology. A cell slice was dried in an infrared drying furnace, sintered by using a belt type firing furnace at 750-850° C. and then cooled to form a cell. The photoelectric conversion efficiency of the cell was determined by using a HALM IV tester. The photoelectric conversion efficiency of the cell was shown in Table 1.

    [0042] From Table 1, it could be seen that when lithium oxide was changed into sodium oxide or potassium oxide, the weight of an oxide corroded by water in the prepared conductive paste was significantly increased, and the photoelectric conversion efficiency of the conductive paste was also significantly reduced. This was because when the radius of an alkali metal ion was increased, the bond strength was lowered, and the chemical stability was reduced. Therefore, for the water resistance, Li.sup.+>Na.sup.+>K.sup.+. Therefore, when an alkali metal oxide was selected in the present disclosure, the Li.sup.+ was preferably selected to improve the water corrosion resistance of the conductive paste.

    TABLE-US-00001 TABLE 1 Formulae of S1 to S3 (in mol %) and performance test data thereof Sample S1 S2 S3 SiO.sub.2 15% 15% 15% PbO 20% 20% 20% Li.sub.2O 20% — — Na.sub.2O — 20% — K.sub.2O — — 20% B.sub.2O.sub.3 — — — Al.sub.2O.sub.3 — — — Bi.sub.2O.sub.3 — — — MgO — — — CaO — — — ZnO — — — Cr.sub.2O.sub.3 — — — MoO.sub.3  1%  1%  1% WO.sub.3  4%  4%  4% Ag.sub.2O  2%  2%  2% TeO.sub.2 38% 38% 38% Total 100.0%   100.0%   100.0%   ΔW 1.7‰ 2.3‰ 2.6‰ Eta (%) 22.83%   21.63%   20.55%  

    EXAMPLE 2

    [0043] A glass paste and a conductive paste were separately prepared according to formulae in Table 2. Samples S4-S10 were prepared by using the same preparation method in Example 1. The water resistance and the photoelectric conversion efficiency were determined, and results were shown in Table 2.

    [0044] From Table 2, it could be seen that when B.sub.2O.sub.3, Al.sub.2O.sub.3, or Bi.sub.2O.sub.3 was added into the sample S1, compared with the sample S1, the water resistance of the samples S4-S6 was improved to a certain extent, the mass loss of the samples after water corrosion was decreased by 0.2-0.3‰, and the photoelectric conversion efficiency of the sample S4 and the sample S6 was not significantly changed in comparison with S1. However, when Al.sub.2O.sub.3 was added, the photoelectric conversion efficiency of the sample S5 was reduced to a certain extent. When MgO, CaO, ZnO, or Cr.sub.2O.sub.3 was added into the sample S1, the water resistance of the samples S7-S10 was not significantly increased, or even reduced, indicating that MgO, CaO, ZnO, or Cr.sub.2O.sub.3 had no obvious effect of improving the water resistance of the conductive paste. Therefore, in order to improve the water resistance of the conductive paste, B.sub.2O.sub.3, Al.sub.2O.sub.3, or Bi.sub.2O.sub.3 was preferably added, and Al.sub.2O.sub.3 was not added separately.

    TABLE-US-00002 TABLE 2 Formulae of S4-S10 (in mol %) and performance test data thereof Sample S1 S4 S5 S6 S7 S8 S9 S10 SiO.sub.2   15%   15%   15%   15%   15%   15%   15%   15% PbO   20%   20%   20%   20%   20%   20%   20%   20% Li.sub.2O   20%   20%   20%   20%   20%   20%   20%   20% Na.sub.2O — — — — — — — — K.sub.2O — — — — — — — — B.sub.2O.sub.3 —    2% — — — — — — Al.sub.2O.sub.3 — —    2% — — — — — Bi.sub.2O.sub.3 — — —    6% — — — — MgO — — — —    3% — — — CaO — — — — —    3% — — ZnO — — — — — —    6% — Cr.sub.2O.sub.3 — — — — — — —    2% MoO.sub.3    1%    1%    1%    1%    1%    1%    1%    1% WO.sub.3    4%    4%    4%    4%    4%    4%    4%    4% Ag.sub.2O    2%    2%    2%    2%    2%    2%    2%    2% TeO.sub.2   38%   36%   36%   32%   35%   35%   32%   36% Total 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% ΔW   1.7‰   1.5‰   1.4‰   1.5‰   1.7‰   2.0‰   1.9‰   1.6‰ Eta (%) 22.83% 22.82% 22.78% 22.84% 22.81% 22.80% 22.84% 22.83%

    EXAMPLE 3

    [0045] A glass paste and a conductive paste were separately prepared according to formulae in Table 3. Samples S11-S18 were prepared by using the same preparation method in Example 1. The water resistance and the photoelectric conversion efficiency were determined, and results were shown in Table 3.

    [0046] According to the samples S11-S14 in Table 3, it could be seen that although the water resistance of the conductive paste could be effectively improved by separately adding B.sub.2O.sub.3, Al.sub.2O.sub.3, or Bi.sub.2O.sub.3, when B.sub.2O.sub.3 and Al.sub.2O.sub.3 were added at the same time, the loss of an oxide corroded by water could be significantly decreased, the water resistance was improved, and the conversion efficiency of the obtained conductive paste was significantly reduced. However, when B.sub.2O.sub.3 and Bi.sub.2O.sub.3, Al.sub.2O.sub.3 and Bi.sub.2O.sub.3, or B.sub.2O.sub.3, Al.sub.2O.sub.3 and Bi.sub.2O.sub.3 were added at the same time, the loss of an oxide corroded by water was not greater than 1.2%0, and the photoelectric conversion efficiency could also be improved to a certain extent. Therefore, conductive pastes obtained by adding B.sub.2O.sub.3 and Bi.sub.2O.sub.3, Al.sub.2O.sub.3 and Bi.sub.2O.sub.3, or B.sub.2O.sub.3, Al.sub.2O.sub.3 and Bi.sub.2O.sub.3 at the same time were preferably selected.

    TABLE-US-00003 TABLE 3 Formulae of S11 to S18 (in mol %) and performance test data thereof Sample S1 S11 S12 S13 S14 S15 S16 S17 S18 SiO.sub.2   15%   15%   15%   15%   15%    5%   11%    8%   17% PbO   20%   20%   20%   20%   20%   25%   19%   22%   14% Li.sub.2O   20%   20%   20%   20%   20%   18%   21%   25%   12% Na.sub.2O — — — — — — — — — K.sub.2O — — — — — — — — — B.sub.2O.sub.3 —    2%    2% —    2%    1%    2%    1% — Al.sub.2O.sub.3 —    2% —    2%    2% — —    1%    1% Bi.sub.2O.sub.3 — —    6%    6%    6%    8%    4%    7%    8% MgO — — — — — — — — — CaO — — — — — — — — — ZnO — — — — — — — — — Cr.sub.2O.sub.3 — — — — — — — — — MoO.sub.3    1%    1%    1%    1%    1%    1%    1%    1%    1% WO.sub.3    4%    4%    4%    4%    4%    4%    4%    4%    4% Ag.sub.2O    2%    2%    2%    2%    2%    1%    1%    1%    1% TeO.sub.2   38%   34%   30%   30%   28%   36%   35%   28%   41% CaO    1%    2% MgO    2%    1% Total 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% ΔW   1.7‰   1.0‰   1.1‰   0.9‰   0.8‰   1.2‰   1.0‰   1.1‰   0.9‰ Eta (%) 22.83% 22.73% 22.87% 22.84% 22.86% 22.85% 22.87% 22.86% 22.79%

    [0047] When the sample S18 included a too high content of SiO.sub.2, a too low content of PbO and a too low content of Li.sub.2O, although the water corrosion resistance of the conductive paste could be effectively improved, the photoelectric conversion efficiency was significantly reduced. Therefore, the contents of the three substances needed to be controlled to achieve the effects that the water corrosion resistance was improved, and the photoelectric conversion efficiency was not reduced.

    [0048] According to a large number of experiments, it is shown that the conductive paste of the present disclosure includes, in mol %, 5-15% of SiO.sub.2, 19-25% of PbO, 18-25% of Li.sub.2O, 0-2% of B.sub.2O.sub.3, 0-2% of Al.sub.2O.sub.3, 4-8% of Bi.sub.2O.sub.3 and the balance of MO.sub.x, contents of Bi.sub.2O.sub.3 and Al.sub.2O.sub.3 are not 0 at the same time, and M is one or a mixture of more of Na, K, Mg, Ca, Sr, Ti, Zr, V, Cr, Mo, W, Mn, Cu, Ag, Zn, Cd, Ga, TI, Ge, P and Te. The conductive paste can achieve the effects that the mass loss of a sample after water corrosion is not greater than 1.2‰, and the photoelectric conversion efficiency is not reduced. Preferably, the conductive paste includes 8%-15% of SiO.sub.2, 19%-22% of PbO, 20%-25% of Li.sub.2O, 1%-2% of B.sub.2O.sub.3, 1-2% of Al.sub.2O.sub.3, 4%-7% of Bi.sub.2O.sub.3 and the balance of MO.sub.x. The conductive paste of the present disclosure optimally includes 15% of SiO.sub.2, 20% of PbO, 20% of Li.sub.2O, 2% of B.sub.2O.sub.3, 2% of Al.sub.2O.sub.3, 6% of Bi.sub.2O.sub.3 and 35% of MO.sub.x.

    [0049] Although preferred examples of the present disclosure are disclosed above, the present disclosure is not limited thereto. Various changes and modifications can be made by anyone familiar with this technology without departing from the spirit and scope of the present disclosure. Therefore, the protection scope of the present disclosure should be defined by the claims.