Lithium and Tellurium-Silicate Binary Glass-oxide-Complex System and Conductive Paste Containing Such Complex System

Abstract

The present disclosure discloses a lithium and tellurium-silicate binary glass-oxide-complex system and a conductive paste containing the complex system, and belongs to the technical field of solar cells. The present disclosure uses a “functional modularity” strategy in the formula design of a glass-oxide-complex system (GOC). Alkali metal ions with high migration and reactivity are separated from a glass body with high fluidity, thus a binary complex system is constructed, that is, a lithium-containing glass-oxide-complex (Li-GOC) with high activity and a tellurium-silica-containing glass-oxide-complex (Si—Te-GOC) with high fluidity. Through the modularized formula strategy, active ingredients can be better controlled, so as to obtain more balanced contact and open circuit voltage and improve the photoelectric conversion efficiency of a solar cell.

Claims

1. A lithium and tellurium-silicate binary glass-oxide-complex system for a solar cell conductive paste, prepared by mixing a lithium-containing glass-oxide-complex (Li-GOC) and a tellurium-silica-containing glass-oxide-complex (Si—Te-GOC); wherein, the Li-GOC is obtained by mixing and fusing Li.sub.2O, Bi.sub.2O.sub.3, PbO, and a metal oxide M1 to form a glass and oxide frit, and then performing quenching and grinding; the Si—Te-GOC is obtained by mixing and fusing SiO.sub.2, TeO.sub.2, and a metal oxide M2 to form a glass and oxide frit, and then performing quenching and grinding; and the metal oxide M1 is at least one oxide of Na, K, Mg, Ca, Sr, Ba, Zn, P, B, Ti, Sb and Ge; and the metal oxide M2 is at least one oxide of Zn, P, B, Ag, Al, Ti, W, V, Cr, Mn, Co, Ni, Cu, Nb, Ta, Th, Ge, Mo, La, Sb, Bi and Ce.

2. The lithium and tellurium-silicate binary glass-oxide-complex system for a solar cell conductive paste according to claim 1, wherein the Li-GOC and the Si—Te-GOC are at a mass ratio of 1:(1-9).

3. The lithium and tellurium-silicate binary glass-oxide-complex system for a solar cell conductive paste according to claim 1, wherein the Li-GOC has a formula as follows:
[Li.sub.2O].sub.x—[Bi.sub.2O.sub.3—PbO].sub.y-[M1].sub.z-O.sub.n, wherein x, y and z are mass fractions of the corresponding oxides in the Li-GOC; x+y+z=100%, 2%<x<50%, 5%<y<85% and 1%<z<10%; and the value of n is used to balance positive and negative charges of the entire formula.

4. The lithium and tellurium-silicate binary glass-oxide-complex system for a solar cell conductive paste according to claim 1, wherein the Si—Te-GOC contains tellurium-silica-containing glass or a crystalline oxide and has a formula as follows:
[TeO.sub.2].sub.a—[SiO.sub.2].sub.b-[M2].sub.c-O.sub.m, wherein a, b and c are mass fractions of the corresponding oxides in the Si—Te-GOC; a+b+c=100%, 10%<a<90%, 10%<b<90% and 1%<c<10%; and the value of m is used to balance positive and negative charges of the entire formula.

5. The lithium and tellurium-silicate binary glass-oxide-complex system for a solar cell conductive paste according to claim 1, wherein the Li-GOC has a formula of 15%-20% of Li.sub.2O, 25%-65% of PbO, 10%-20% of Bi.sub.2O.sub.3, 0-6% of ZnO and 0.5%-3% of B.sub.2O.sub.3 according to the mass percentage of the Li-GOC.

6. The lithium and tellurium-silicate binary glass-oxide-complex system for a solar cell conductive paste according to claim 1, wherein the Si—Te-GOC has a formula of 10%-20% of SiO.sub.2, 70%-80% of TeO.sub.2, 2%-10% of Bi.sub.2O.sub.3, 0.5%-1.0% of B.sub.2O.sub.3 and 0.5%-2% of Na.sub.2O.

7. The lithium and tellurium-silicate binary glass-oxide-complex system for a solar cell conductive paste according to claim 1, wherein a preparation process of the lithium and tellurium-silicate binary glass-oxide-complex system for a solar cell conductive paste comprises the following steps: (1) respectively preparing the Li-GOC and the Si—Te-GOC; and (2) mixing the two GOCs of the Li-GOC and the Si—Te-GOC.

8. A solar cell conductive paste containing the lithium and tellurium-silicate binary glass-oxide-complex system of claim 1, wherein the solar cell conductive paste comprises a conductive metal component, the lithium and tellurium-silicate binary glass-oxide-complex system and an organic carrier.

9. The solar cell conductive paste according to claim 8, wherein the conductive metal component comprises silver, gold, platinum, palladium, copper, nickel and a combination thereof.

10. The solar cell conductive paste according to claim 8, wherein the conductive metal component accounts for 80%-99% by weight of the entire conductive paste.

11. The solar cell conductive paste according to claim 8, wherein the lithium and tellurium-silicate binary glass-oxide-complex system accounts for 0.2%-5% by weight of the entire conductive paste.

12. The solar cell conductive paste according to claim 8, wherein the organic carrier accounts for 2%-10% by weight of the entire conductive paste.

13. The solar cell conductive paste according to claim 8, wherein the organic carrier comprises an organic solvent and one or any combination of a binder, a surfactant and a thixotropic agent.

14. The solar cell conductive paste according to claim 13, wherein the organic solvent is selected from carbitol, terpineol, hexyl carbitol, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, butyl carbitol, butyl carbitol acetate, dimethyl adipate glycol ether, and any combination thereof.

15. The solar cell conductive paste according to claim 13, wherein the binder is selected from ethyl cellulose, phenolic resin, polyacrylic acid, polyvinyl butyral, polyester resin, polycarbonate, polyethylene resin, polyurethane resin, a rosin derivative, and any combination thereof.

16. The solar cell conductive paste according to claim 13, wherein the surfactant is selected from polyoxyethylene, polyethylene glycol, benzotriazole, poly(ethylene glycol)acetic acid, lauric acid, oleic acid, capric acid, myristic acid, linoleic acid, stearic acid, palmitic acid, stearate, palmitate, and any combination thereof.

17. A solar cell containing the solar cell conductive paste of claim 8 on a surface.

18. The solar cell according to claim 17, wherein solar cell metallic silver paste and aluminum paste are respectively printed on front and back sides of a silicon wafer in a predetermined pattern by screen printing, and drying is conducted; the printed silicon wafer is placed in an environment of 400-900° C. for sintering; and after the sintering is completed, the silicon wafer is cooled to room temperature to prepare the solar cell.

Description

BRIEF DESCRIPTION OF FIGURES

[0047] The FIGURE is a schematic structural diagram of a solar cell.

DETAILED DESCRIPTION

Example 1

[0048] Preparation of Glass-Oxide-Complex System (GOC):

[0049] Different Li-GOC1 and Si—Te-GOC1 were prepared with the components described in Table 1 and a single component Mix1 without separation was also prepared as a control. Samples were prepared in 200 g batches by mixing the oxide components in the amounts specified in Table 1. An oxide mixture was loaded into a platinum crucible with a volume of 0.5 L and the crucible was placed into a glass smelting furnace at 1300° C. for 30 min to obtain a glass and oxide frit; the frit was taken out and poured into a counter-roll cooler for quenching to obtain glass slags, and after the glass slags were ground in a 1 L planetary ball mill, the ground glass slags passed through a 325-mesh sieve to obtain Li-GOC1 powder, Si—Te-GOC1 powder and Mix1 powder respectively.

TABLE-US-00001 TABLE 1 Formulas of Li-GOC1, Si—Te-GOC1 and Mix1 Mix1 Li-GOC1 Si—Te-GOC1 Li-GOC Li.sub.2O  9.1%  9.1% / PbO 27.3% 27.3% / Bi.sub.2O.sub.3 /  7.3% / ZnO  2.7%  2.7% / B.sub.2O.sub.3 / 0.45% / Si—Te-GOC SiO.sub.2  9.1% /  9.1% TeO.sub.2 40.9% / 40.9% Bi.sub.2O.sub.3  9.1% /  1.8% B.sub.2O.sub.3  0.9% / 0.45% Na.sub.2O  0.9% /  0.9%

[0050] Preparation of Conductive Paste:

[0051] A list of components used in the following examples and comparative examples is as follows:

[0052] (1) conductive powder: spherical silver powder (AG-4-8, Dowa HighTech Co., Ltd.) with an average particle diameter (D50) of 2 μm;

[0053] (2) a glass-oxide-complex (GOC): Mix1 or a binary mixture of Li-GOC1 and Si—Te-GOC1;

[0054] (3) an organic carrier;

[0055] (3a) a binder: ethyl cellulose (Dow Chemical Co., Ltd., STD4);

[0056] (3b) a solvent: terpineol (Nippon Terpine Co., Ltd.); and

[0057] (3c) a thixotropic agent: DISPARLON 6500 disparlon (Kusumoto Chemicals, Ltd.).

[0058] 1 wt % of the ethyl cellulose and 1 wt % of the thixotropic agent were fully dissolved in 6 wt % of the terpineol at 50° C. and 90 wt % of the Ag powder and 2.5 wt % of the GOC were added to be mixed uniformly, and an obtained mixture passed through a three-roll mixer to be mixed and dispersed to obtain metallization silver paste P0-1 and P1-P4.

[0059] 80 mg of each metallization silver paste and 600 mg of an aluminum paste were printed on front and back sides of a silicon wafer with the square resistance of 110-150 Ohm/sq in a predetermined pattern by screen printing and dried in an infrared drying oven. The silicon wafer was rapidly sintered in a rapid sintering furnace at 900° C. for 30 min and cooled to room temperature, and thus a solar cell was prepared.

[0060] The structure of the obtained solar cell was shown in the FIGURE. The metallic silver paste was sintered to become a front electrode and the aluminum paste was sintered to form back partial contact; and the structure of the pure silicon wafer included: front SiN.sub.x-silicon wafer-Al.sub.2O.sub.3-back SiN.sub.x.

[0061] The series resistance (Rs), the open circuit voltage (Voc), the fill factor (FF) and the photoelectric conversion efficiency (Eff., %) of the solar cell were measured with a solar cell IV tester (HALM). Results were shown in Tables 2-3. It could be seen that the metallic paste with the separated GOC could significantly improve the photoelectric conversion efficiency.

TABLE-US-00002 TABLE 2 Formula of conductive paste and electrical test results of cell piece 150 Ohm/sq P0-1 P1 P2 P3 P4 Mix1 (wt %) 2.5 / / / / Li-GOC1 (wt %) / 0.3 0.6 1 1.25 Si—Te-GOC1 (wt %) / 2.2 1.9 1.5 1.25 Series resistance (Rs) 1.22 1.43 1.23 1.15 1.2 Open circuit voltage 688 689.2 689 688.9 688.5 (Voc) Fill factor (FF) 81.22 79.8 81 81.5 81.4 Photoelectric conversion efficiency 22.84 22.14 22.78 23.1 22.95 (Eff.)

TABLE-US-00003 TABLE 3 Formula of conductive paste and relative electrical test results of cell piece 150 Ohm/sq P0-1 P1 P2 P3 P4 Mix1 (wt %) 2.5 / / / / Li-GOC1 (wt %) / 0.3 0.6 1.0 1.25 Si—Te-GOC1 (wt %) / 2.2 1.9 1.5 1.25 Series resistance 100% 117% 101%  94%  98% (Rs) Open circuit 100% 100% 100% 100% 100% voltage (Voc) Fill factor (FF) 100%  98% 100% 100% 100% Photoelectric conversion 100%     96.94%     99.74%   101.14%   100.48% efficiency (Eff.)

[0062] The photoelectric conversion efficiency of the current crystalline silicon solar cell PERC-SE is about 23%. This is achieved after more than ten years of an absolute efficiency increase of 0.1-0.2% per year. Therefore, increase of the absolute efficiency of the metallic paste by 0.1% is a huge improvement. Based on the photoelectric conversion efficiency of 23%, an increase of 0.1% of the absolute efficiency is an increase of the relative efficiency of 0.43%.

[0063] In the solar cell test process, a statistical confidence analysis (p-value analysis) for the electrical test results (the series resistance, the open circuit voltage, the fill factor and the efficiency) was conducted. The obtained test samples and the reference sample had significant differences (p<0.05), thus the differences caused by test errors were excluded.

Example 2

[0064] Preparation of Glass-Oxide-Complex System (GOC):

[0065] Different Li-GOC2 and Si—Te-GOC2 were prepared with the components described in Table 4 and a single component Mix2 without separation was also prepared as a control. Samples were prepared in 200 g batches by mixing the oxide components in the mass fraction specified in Table 4. An oxide mixture was loaded into a platinum crucible with a volume of 0.5 L and the crucible was placed into a glass smelting furnace at 1300° C. for 30 min to obtain a glass and oxide frit; the frit was taken out and poured into a counter-roll cooler for quenching to obtain glass slags, and after the glass slags were ground in a 1 L planetary ball mill, the ground glass slags passed through a 325-mesh sieve to obtain GOC powder and Mix2 powder respectively.

TABLE-US-00004 TABLE 4 Formulas of Li-GOC2, Si—Te-GOC2 and Mix2 Mix2 Li-GOC2 Si—Te-GOC2 Li-GOC Li.sub.2O  8.6% 8.6% / PbO 26.9% 26.9%  / Bi.sub.2O.sub.3 / 5.4% / ZnO / / / B.sub.2O.sub.3 / 1.1% / Si—Te-GOC SiO.sub.2  8.6% 8.6% TeO.sub.2 43.0% 43.0%  Bi.sub.2O.sub.3 10.8% 5.4% B.sub.2O.sub.3  1.6% 0.5% Na.sub.2O  0.5% 0.5%

[0066] Preparation of Conductive Paste:

[0067] A list of components used in the following examples and comparative examples is as follows:

[0068] (1) conductive powder: spherical silver powder (AG-4-8, Dowa HighTech Co., Ltd.) with an average particle diameter (D50) of 2 μm;

[0069] (2) a glass-oxide-complex (GOC): Mix1, Mix2, LiGOC1, LiGOC2, SiTeGOC1 and SiTeGOC2;

[0070] (3) an organic carrier;

[0071] (3a) a binder: ethyl cellulose (Dow Chemical Co., Ltd., STD4);

[0072] (3b) a solvent: terpineol (Nippon Terpine Co., Ltd.); and

[0073] (3c) a thixotropic agent: DISPARLON 6500 disparlon (Kusumoto Chemicals, Ltd.).

[0074] 1 wt % of the ethyl cellulose and 1 wt % of the thixotropic agent were fully dissolved in 6 wt % of the terpineol at 50° C. and 90 wt % of the Ag powder and 3.0 wt % of the GOC were added to be mixed uniformly, and an obtained mixture passed through a three-roll mixer to be mixed and dispersed to obtain metallic silver paste P0-2 and P4-P5.

[0075] 80 mg of each metallic silver paste and 600 mg of an aluminum paste were printed on front and back sides of a silicon wafer with the square resistance of 110 Ohm/sq in a predetermined pattern by screen printing and dried in an infrared drying oven. The silicon wafer was rapidly sintered in a rapid sintering furnace at 900° C. for 30 min and cooled to room temperature, and thus a solar cell was prepared. The series resistance (Rs), the open circuit voltage (Voc), the fill factor (FF) and the photoelectric conversion efficiency (Eff., %) of the solar cell were measured with a solar cell IV tester (HALM). Results were shown in Tables 5-6. It could be seen that the metallic paste with the separated GOC could significantly improve the photoelectric conversion efficiency.

TABLE-US-00005 TABLE 5 Formula of conductive paste and electrical test results of cell piece 110 Ohm/sq P0-2 P5 P6 P7 P8 Mix2 (wt %) 3.0 / / / / Li-GOC2 (wt %) / 0.3 0.6 1.0 1.5 Si-Te-GOC2 (wt %) / 2.7 2.4 2.0 1.5 Series resistance (Rs) 1.09 1.3 1.12 1.11 1.09 Open circuit voltage (Voc) 683 684 686.2 686 685 Fill factor (FF) 82.11 80.04 81.9 82.4 82.32 Photoelectric conversion 22.75 22.07 22.5 22.94 22.85 efficiency (Eff.)

TABLE-US-00006 TABLE 6 Formula of conductive paste and relative electrical test results of cell piece 110 Ohm/sq P0-2 P5 P6 P7 P8 Mix2 (wt %) 3.0 / / / / Li-GOC2 (wt %) / 0.3 0.6 1.0 1.5 Si—Te-GOC2 / 2.7 2.4 2.0 1.5 (wt %) Series resistance 100% 119% 103% 102% 100% (Rs) Open circuit 100% 100% 100% 100% 100% voltage (Voc) Fill factor (FF) 100%  97% 100% 100% 100% Photoelectric conversion 100%     97.01%    98.90%   100.84%   100.44% efficiency (Eff.)

Comparative Example 1

[0076] Preparation of Glass-Oxide-Complex System (GOC):

[0077] Different Na-GOC and Si—Te-GOC1 were prepared with the components described in Table 7 and a single component Mix3 without separation was also prepared as a control. Samples were prepared in 200 g batches by mixing the oxide components in the amounts specified in Table 7. An oxide mixture was loaded into a platinum crucible with a volume of 0.5 L and the crucible was placed into a glass smelting furnace at 1300° C. for 30 min to obtain a glass and oxide frit; the frit was taken out and poured into a counter-roll cooler for quenching to obtain glass slags, and after the glass slags were ground in a 1 L planetary ball mill, the ground glass slags passed through a 325-mesh sieve to obtain GOC powder and Mix3 powder.

[0078] Preparation of conductive paste and cell piece: formulas and manufacture of pastes P0-3 and P9-P12 were implemented according to the process in Example 1.

TABLE-US-00007 TABLE 7 Formulas of Na-GOC, Si—Te-GOC1 and Mix3 Mix3 Na-GOC Si—Te-GOC1 Na-GOC Li.sub.2O  9.1%  9.1% / PbO 27.3% 27.3% / Bi.sub.2O.sub.3  0.0%  7.3% / ZnO  2.7%  2.7% / B.sub.2O.sub.3 /  0.45% / Si—Te-GOC SiO.sub.2  9.1% /  9.1% TeO.sub.2 40.9% / 40.9% Bi.sub.2O.sub.3  9.1% /  1.8% B.sub.2O.sub.3  0.9% /  0.45% Na.sub.2O  0.9% /  0.9%

TABLE-US-00008 TABLE 8 Formula of conductive paste and electrical test results of cell piece 110 Ohm/sq P0-3 P9 P10 P11 P12 Mix3 (wt %) 3.0 / / / / Na-GOC (wt %) / 0.3 0.6 1.0 1.5 Si-Te-GOC1 (wt %) / 2.7 2.4 2.0 1.5 Series resistance (Rs) 1.85 3 2.9 2.5 2.2 Open circuit voltage 674 654 660 655 658 (Voc) Fill factor (FF) 78.3 76.2 77.2 77 77.2 Photoelectric 21.2 19.8 20.3 20.2 20.5 conversion efficiency (Eff.)

TABLE-US-00009 TABLE 9 Formula of conductive paste and relative electrical test results of cell piece 110 Ohm/sq P0-3 P9 P10 P11 P12 Mix3 (wt %) 3.0 / / / / Na-GOC / 0.3 0.6 1.0 1.5 (wt %) Si—Te-GOC1 / 2.7 2.4 2.0 1.5 (wt %) Series 100% 162%  157%  135%  119%  resistance (Rs) Open circuit 100% 97% 98% 97% 98% voltage (Voc) Fill factor (FF) 100% 97% 99% 98% 99% Photoelectric conversion 100%   93.40%   95.75%   95.28%   96.70% efficiency (Eff.)

[0079] It could be seen from the results of Comparative example 1 that the photoelectric conversion efficiency of the pastes manufactured from separated Na-GOC and Si—Te-GOC was not improved.

Comparative Example 2

[0080] Preparation of Glass-Oxide-Complex System (GOC):

[0081] Different Li-GOC2 and Bi—Te-GOC were prepared with the components described in Table 10 and a single component Mix4 without separation was also prepared as a control. Samples were prepared in 200 g batches by mixing the oxide components in the amounts specified in Table 10. An oxide mixture was loaded into a platinum crucible with a volume of 0.5 L and the crucible was placed into a glass smelting furnace at 1300° C. for 30 min to obtain a glass and oxide frit; the frit was taken out and poured into a counter-roll cooler for quenching to obtain glass slags, and after the glass slags were ground in a 1 L planetary ball mill, the ground glass slags passed through a 325-mesh sieve to obtain GOC powder and Mix4 powder.

[0082] Preparation of conductive paste and cell piece: formulas and manufacture of pastes P0-4 and P13-P16 were implemented according to the process in Example 2.

TABLE-US-00010 TABLE 10 Formulas of Li-GOC2, Bi—Te-GOC2 and Mix4 Mix4 Li-GOC2 Bi—Te-GOC Li-GOC Li.sub.2O  8.6% 8.6% / PbO 26.9% 26.9%  / Bi.sub.2O.sub.3 5.4% / ZnO / B.sub.2O.sub.3 1.1% / Bi—Te-GOC SiO.sub.2  1.1% / 1.1% TeO.sub.2 43.0% / 43.0%  Bi.sub.2O.sub.3 18.3% / 12.9%  B.sub.2O.sub.3  1.6% / 0.5% Na.sub.2O  0.5% / 0.5%

TABLE-US-00011 TABLE 11 Formula of conductive paste and electrical test results of cell piece 110 Ohm/sq P0-4 P13 P14 P15 P16 Mix4 (wt %) 3.0 / / / / Li-GOC2 (wt %) / 0.3 0.6 1.0 1.5 Bi—Te-GOC (wt %) / 2.7 2.4 2.0 1.5 Series resistance (Rs) 1.54 3 2.7 2.1 1.85 Open circuit voltage 650 654 652 648 652 (Voc) Fill factor (FF) 77.8 74.1 76.5 77.2 77.8 Photoelectric conversion 21.4 18.3 19.2 19.7 20.4 efficiency (Eff.)

TABLE-US-00012 TABLE 12 Formula of conductive paste and relative electrical test results of cell piece 110 Ohm/sq P0-4 P13 P14 P15 P16 Mix4 (wt %) 3.0 / / / / Li-GOC2 (wt %) / 0.3 0.6 1.0 1.5 Bi-Te-GOC (wt %) / 2.7 2.4 2.0 1.5 Series resistance 100% 195% 175% 136% 120% (Rs) Open circuit 100% 101% 100% 100% 100% voltage (Voc) Fill factor (FF) 100%  95%  98%  99% 100% Photoelectric 100% 85.51%   89.72%   92.06%   95.33%   conversion efficiency (Eff.)

[0083] It could be seen from the results of Comparative example 2 that the photoelectric conversion efficiency of the pastes manufactured from separated Li-GOC and Bi—Te-GOC was not improved.

[0084] Although the present disclosure has been disclosed with preferred examples, these examples shall not be construed as limiting the present disclosure. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present disclosure. The protection scope of the present disclosure shall be defined by the following claims.