Ceramic glass powder and solar cell metallization paste containing ceramic glass powder

Abstract

The present disclosure discloses a ceramic glass powder and a solar cell metallization paste containing the ceramic glass powder, and belongs to the technical field of solar cells. The present disclosure provides a novel formula mode of a glass powder including a crystallization nucleus component and a glass network component, that is, a formula of a ceramic glass powder that has a special crystallization behavior, a low crystallinity before sintering and a high crystallinity after the sintering, and a conductive metallization paste containing the ceramic glass powder is further obtained. The present disclosure solves the technical problem that by using metallization pastes in the prior art, a balance between corrosion of a silicon wafer and an ohmic contact is difficult to achieve. The efficiency of a solar cell is improved.

Claims

1. A ceramic glass powder, wherein the ceramic glass powder has a crystallinity of less than 5% (m/m) and comprises a crystallization nucleus forming component and a glass network component; wherein the crystallization nucleus forming component comprises 4-5 wt % of zinc oxide (ZnO), 2-3 wt % of magnesium oxide (MgO), 0-5 wt % of sodium oxide (Na.sub.2O), 0-8 wt % of zirconium oxide (ZrO.sub.2), and 0-5 wt % of copper oxide (CuO); and wherein the glass network component comprises 0.1-10 wt % of alkali metal oxide, 0.1-5 wt % of aluminum oxide (Al.sub.2O.sub.3), 10-80 wt % of tellurium oxide (TeO.sub.2), 10-80 wt % of lead oxide (PbO), 10-20 wt % of silicon oxide (SiO.sub.2), 1-20 wt % of boron oxide (B.sub.2O.sub.3), 1-30 wt % of bismuth oxide (Bi.sub.2O.sub.3), and 0-5 wt % of titanium oxide (TiO.sub.2), wherein the alkali metal oxide is selected from the group consisting of Li.sub.2O, K.sub.2O and combinations thereof; wherein all the weight percentages are based on the weight of the glass network component.

2. The ceramic glass powder according to claim 1, wherein the glass network component comprises 1 wt % of Al.sub.2O.sub.3, 30 wt % of PbO, 5 wt % of Bi.sub.2O.sub.3, 1 wt % of B.sub.2O.sub.3, 10 wt % of SiO.sub.2, 43 wt % of TeO.sub.2 and 10 wt % of Li.sub.2O; or wherein the glass network component comprises 1 wt % of Al.sub.2O.sub.3, 29 wt % of PbO, 5 wt % of Bi.sub.2O.sub.3, 1 wt % of B.sub.2O.sub.3, 10 wt % of SiO.sub.2, 43 wt % of TeO.sub.2, 10 wt % of Li.sub.2O and 1 wt % of TiO.sub.2; wherein all the weight percentages are based on the weight of the glass network component.

3. The ceramic glass powder according to claim 1, wherein the crystallization nucleus forming component comprises 0-2 wt % of Na.sub.2O, 0-1 wt % of ZrO.sub.2 and 0-1 wt % of CuO; wherein all the weight percentages are based on the weight of the glass network component.

4. The ceramic glass powder according to claim 1, wherein the weight of the crystallization nucleus forming component is 8% of the weight of the glass network component.

5. The ceramic glass powder according to claim 1, wherein the crystallization nucleus forming component comprises 4 wt % of ZnO, 3 wt % of MgO and 1 wt % of Na.sub.2O; or wherein the crystallization nucleus forming component comprises 4 wt % of ZnO, 3 wt % of MgO and 1 wt % of CuO; wherein all the weight percentages are based on the weight of the glass network component.

6. A method for preparing the ceramic glass powder of claim 1, comprising: (1) uniformly mixing and melting the oxides of the crystallization nucleus forming component to obtain a glass melt; and (2) adding the oxides of the glass network component into the glass melt obtained in step (1) for secondary melting to obtain a melt, conducting quenching on the melt to obtain a glass slag, and then conducting grinding and sieving to obtain the ceramic glass powder.

7. A solar cell metallization paste containing the ceramic glass powder according to claim 1, wherein the solar cell metallization paste comprises: (a) a conductive metal component, (b) the ceramic glass powder and (c) an organic carrier.

8. The solar cell metallization paste according to claim 7, wherein the conductive metal component comprises silver, gold, platinum, palladium, copper, nickel and a combination thereof.

9. The solar cell metallization paste according to claim 7, wherein the ceramic glass powder is 1-10% of the paste by weight percentage.

10. A solar cell containing the solar cell metallization paste according to claim 7 on a surface.

11. The solar cell metallization paste according to claim 7, wherein the organic carrier comprises an organic solvent and one or any combination selected from the group consisting of a binder, a surfactant and a thixotropic agent.

12. The solar cell metallization paste according to claim 11, wherein the organic solvent is one or any combination selected from the group consisting of carbitol, terpineol, hexyl carbitol, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, butyl carbitol, butyl carbitol acetate and dimethyl adipate glycol ether.

13. The solar cell metallization paste according to claim 11, wherein the binder is one or any combination selected from the group consisting of ethyl cellulose, phenolic resin, polyacrylic acid, polyvinyl butyral, polyester resin, polycarbonate, polyethylene resin, polyurethane resin and a rosin derivative.

14. The solar cell metallization paste according to claim 11, wherein the surfactant is one or any combination selected from the group consisting of polyethylene oxide, polyethylene glycol, benzotriazole, poly(ethylene glycol) acetic acid, lauric acid, oleic acid, capric acid, myristic acid, linoleic acid, stearic acid, palmitic acid, stearate and palmitate.

Description

BRIEF DESCRIPTION OF FIGURES

(1) FIG. 1 is a schematic diagram showing a temperature curve of a solar cell during rapid sintering.

(2) FIG. 2 is a schematic structural diagram of a solar cell.

DETAILED DESCRIPTION

(3) The crystallinity of a glass powder in the present disclosure is determined.

(4) The crystallinity of glass is determined by referring to two reliable determination methods (with reference to the literatures: Determination of crystallinity in crystallized glasses by X-ray diffraction. Journal of Non-Crystalline Solids. 1976, Volume 21, Issue 1, Pages 125-136; and A method to quantify crystallinity in amorphous metal alloys: A differential scanning calorimetry study. PLoS One. 2020, 22; 15(6)). One method includes determining the crystallinity of a glass powder before and after sintering by using DSC and observing changes of the crystallinity. The other method includes adding crystallized SiO.sub.2 as an internal standard in powder XRD, determining a specific crystallinity and then accurately determining the crystallinity of a glass powder before and after sintering. The crystallinities obtained by using the two determination methods are highly consistent. Therefore, in the following examples, the relatively simple and easy-to-operate method for determining the crystallinity by using the DSC is mainly used.

Example 1 Preparation of Ceramic Glass Powders

(5) Ceramic glass powders (CG1 to CG5) were prepared by using components in Table 1. A glass powder G0 without a crystallization nucleus forming component was also prepared as a control. The ceramic glass powders were prepared by mixing oxide components in weight percentage specified in Table 1 (200 g of a glass network component was prepared in batches).

(6) In the first step, a mixture of the oxides in the crystallization nucleus forming component were put in a platinum crucible with a volume of 0.5 L, and then the crucible was put in a glass melting furnace at 1,300° C. for 30 min to obtain a glass melt.

(7) In the second step, the glass network component was added into the glass melt obtained in the first step and subjected to melting at 1,000° C. for 60 min, the melt was taken out and poured into a counter-roller cooler for quenching (an ST155 counter-roller cooling pulverizer for glass, made by Fred in Changzhou, with operating conditions: rotation speed 50 rpm, and ice water for cooling) to obtain a glass slag, and the glass slag was ground by using a 1 L planetary ball mill and then sieved with a 325-mesh sieve to obtain the ceramic glass powder.

(8) TABLE-US-00001 TABLE 1 Comparisons of crystallinity results of the ceramic glass powders before and after sintering according to different formulas G0 CG1 CG2 CG3 CG4 CG5 CG6 CG7 Crystallization ZnO —  5%  4%  4%  4%  4%  3%  1% nucleus MgO —  3%  3%  2%  3%  3%  2%  3% forming Na.sub.2O —  1%  2% — —  1%  1% component CuO — — — —  1% —  1%  3% ZrO.sub.2 — — — — —  1%  1% — Glass Al.sub.2O.sub.3  1%  1%  1%  1%  1%  1%  1%  1% network PbO 30% 29% 30% 29% 30% 30% 30% 30% component Bi.sub.2O.sub.3  5%  5%  5%  5%  5%  5%  5%  5% B.sub.2O.sub.3  1%  1%  1%  1%  1%  1%  1%  1% SiO.sub.2 10% 10% 10% 10% 10% 10% 10% 10% TeO.sub.2 43% 43% 43% 43% 43% 43% 43% 43% Li.sub.2O 10% 10% 10% 10% 10% 10% 10% 10% TiO.sub.2 —  1% —  1% — — — — Crystallinity before  2%  2%  3%  4%  4%  4% 20% 20% sintering Crystallinity after  3% 60% 70% 70% 70% 70% 30% 30% sintering

(9) The “sintering” process in Table 1 indicated that the ceramic glass powder was subjected to sintering in a RTP sintering furnace at 900° C. for 30 s.

Example 2 Preparation of Solar Cell Metallization Pastes

(10) A list of components used in the following examples and comparative examples was as follows:

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

(12) (2) a ceramic glass powder: GO and CG1-CG7 were separately selected; and

(13) (3) an organic carrier:

(14) (3a) a binder: ethyl cellulose (Dow Chemical Co., Ltd., STD4),

(15) (3b) a solvent: terpilenol (Nippon Terpine Co., Ltd.), and

(16) (3c) a thixotropic agent: DISPARLON 6500 (Kusumoto Chemicals, Ltd.).

(17) 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., 90 wt % of the Ag powder and 2 wt % of the crystallized glass powders were added to obtain uniformly mixed solutions, and the solutions were mixed by using a three-roller mixer and then dispersed to obtain solar cell metallization silver pastes P0-P7 respectively.

Example 3 Preparation of Solar Cells

(18) The solar cell metallization silver pastes P0-P7 obtained in Example 2 and an aluminum paste were printed on the front surfaces and back surfaces of silicon wafers in predetermined patterns by screen printing and then dried in an infrared drying oven. The printed silicon wafers were rapidly sintered in a sintering furnace at 900° C. for 30 s and then cooled to room temperature to obtain solar cells.

(19) The structure of the obtained solar cell was shown in FIG. 2. The metallization silver paste was sintered to serve as a front electrode, and the aluminum paste was sintered to form a partial back contact. The pure silicon wafer was of a front surface SiN.sub.x-silicon wafer-Al.sub.2O.sub.3-back surface SiN.sub.x structure.

(20) The series resistance (Rs), open circuit voltage (Voc), fill factor (FF) and photoelectric conversion efficiency (Eff., %) of the solar cells were determined by using a solar cell IV tester (HALM). Results were shown in Table 2 and Table 3. It could be seen that by using the metallization paste including the ceramic glass, the photoelectric conversion efficiency could be significantly improved.

(21) TABLE-US-00002 TABLE 2 Performance results of the solar cells prepared from different ceramic glass powders P0 P1 P2 P3 P4 P5 P6 P7 Series 1.05 1.02 0.96 0.98 0.95 1.03 1.2 1.25 resistance Rs (mΩ) Open circuit 690 690.5 690.6 690 691 691 690 689 voltage Voc (mV) Fill factor FF 82.32 82.44 82.57 82.3 82.6 82.3 82 82.4 (%) Photoelectric 22.98 23.1 23.17 23.07 23.14 23.09 22.6 22.4 conversion efficiency Eff. (%)

(22) TABLE-US-00003 TABLE 3 Relative performance results of the solar cells prepared from different ceramic glass powders relative to a control (with reference to P0 as a 100% control) P0 P1 P2 P3 P4 P5 P6 P7 Series 100%     97%     91%     93%     90%     98%   114%   119% resistance (Rs) Open circuit 100%    100%    100%    100%    100%    100%   100%   100% voltage (Voc) Fill factor 100%    100%    100%    100%    100%    100%   100%   100% (FF) Photoelectric 100% 100.52% 100.83% 100.39% 100.70% 100.48% 98.35% 97.48% conversion efficiency (Eff.)

(23) At present, the photoelectric conversion efficiency of the crystalline silicon solar cell PERC-SE is about 23%, which is obtained by improving the absolute efficiency by 0.1-0.2% every year for more than ten years. Therefore, it is a huge improvement that the absolute efficiency is improved by 0.1% when the metallization paste is used. Based on the photoelectric conversion efficiency of 23%, when the absolute efficiency is improved by 0.1%, the relative efficiency is improved by 0.43%.

(24) During testing of the solar cells of the present disclosure, based on the electrical performance test results (series resistance, open circuit voltage, fill factor and efficiency), statistical confidence analysis (p-value analysis) is conducted. There are significant differences (p<0.05) between the test samples and the reference sample. Therefore, differences caused by test errors are avoided.