A low-VOCs environmentally friendly PERC back silver and its preparation method

Abstract

The present invention provides a low-VOCs environmentally friendly PERC back silver, which is composed of the following components by weight: 60-70% silver powder, which is monodisperse spherical silver powder; 1-3% glass powder; 0.1-1% inorganic sintering inhibitor; 0.1-1% thermite; 28-38% organic carrier, which includes resin and solvent; 0.1-2% other additives; the preparation method is to sequentially mix, stir and disperse, three-roll grind, and sieve the obtained low-VOCs environmentally friendly PERC back silver. The present invention uses a stable oily system to reduce the emission of VOCs, and the selected resin has a suitable softening point and good solubility, while solving the problem that bubbles are easily generated in the back silver and poor sintering of aluminum paste on the back silver.

Description

Technical Field

[0001] The invention belongs to the technical field of solar cells, and in particular relates to a low-VOCs environmentally friendly PERC back silver and a preparation method thereof. Background Art

[0002] All industries need to strictly control the emission of VOCs (volatile organic compounds) during the manufacturing process. Among them, the coating, ink, and paste industries have higher VOCs emissions because they involve more organic carriers and solvents. Therefore, the solar cell industry has gradually restricted the VOCs of the paste to less than 10%, which is very challenging for the current PERC back silver paste with a high solvent content.

[0003] At present, the existing PERC back silver solvent content is more than 30%, which is far greater than the VOCs limit threshold of 10%, resulting in VOCs emissions not meeting the standard. Some improved PERC back silver uses water-based solutions to reduce VOCs emissions, but the formula system is complex and easily unstable; some PERC back silver uses an oily system, but the resin softening point is too high and the solubility with the solvent is poor; some PERC back silver is prone to bubbles during the preparation process, and the aluminum paste on the back silver is prone to poor sintering. Summary of the invention

[0004] The first object of the present invention is to provide a low-VOCs environmentally friendly PERC back silver, so as to achieve the effect that the stable oily system formula is simple and stable and reduces the emission of VOCs, the resin softening point is suitable and has good solubility, the back silver is not easy to generate bubbles, and the aluminum paste on the back silver is not easy to have poor sintering problems.

[0005] A low-VOCs environmentally friendly PERC back silver, composed of the following components in parts by weight:

[0006] Silver powder 60-70%, the silver powder is monodisperse spherical silver powder;

[0007] Glass powder 1-3%;

[0008] Inorganic sintering inhibitor 0.1-1%;

[0009] Thermite 0.1~1%;

[0010] 28-38% organic carrier, organic carrier includes resin and solvent;

[0011] Other additives 0.1~2%.

[0012] By adopting the above technical scheme, VOCs mainly include alkanes, aromatic hydrocarbons, olefins, halogenated hydrocarbons, esters, aldehydes, ketones and other organic compounds. The weight of the organic carrier in the formula of the present invention is controlled within 40%, and the weight of the solvent is controlled within 10%. The reduction of the weight of the organic compound reduces the emission of VOCs. At the same time, the present invention uses an oily system formula to prepare the back silver, because the water-based system formula is generally complex in composition, and the formula mainly includes multiple components such as water-based resin, film-forming aid, antifoaming agent, leveling agent, dispersant, rheological aid, etc. The type of polymer, the performance of the emulsion and the dispersion and other factors increase the difficulty of the ratio balance, and are more likely to cause the problem of system imbalance, so the oily system is simpler than the water-based system formula and the system is more stable.

[0013] Preferably, the silver powder has a particle size of 0.5 to 1 μm, a specific gravity of 1.0 to 2.5 m2 / g, a tap density of 3 to 5 g / ml, and a burning loss of <1%.

[0014] Preferably, the inorganic sintering inhibitor is one or more of nano-silicon oxide, nano-silicon nitride, nano-silicon carbide, nano-aluminum oxide, and nano-titanium oxide.

[0015] By adopting the above technical solution, when high-boiling-point organic matter is concentratedly decomposed in the high-temperature zone, the addition of inorganic sintering inhibitor can inhibit the sintering of silver powder and avoid the formation of bubbles on the back silver.

[0016] Preferably, the thermite is one or more of manganese dioxide, vanadium pentoxide, iron oxide and chromium oxide.

[0017] By adopting the above technical solution, when high-boiling-point organic matter is concentratedly decomposed in the high-temperature zone, the addition of thermite can promote the sintering of the aluminum paste on the back silver, avoiding the problem of poor sintering of the aluminum paste on the back silver.

[0018] Preferably, the resin accounts for 80-90% of the weight of the organic carrier, the resin includes PAMS resin and other resins, and the content of PAMS resin in the resin is not less than 70%;

[0019] Other resins are one or more of ethyl cellulose, acrylic resin, PVB resin, and CAB resin.

[0020] By adopting the above technical solution, PAMS resin has a low softening point, good solubility in solvents, and can replace solvent components, simplifying the process, reducing the weight of the solvent in the formula, and is conducive to reducing VOCs emissions.

[0021] Preferably, the solvent accounts for 10-20% of the weight of the organic carrier, and the solvent is one or more of butyl carbitol, butyl carbitol acetate, terpineol, alcohol ester dodecasol, and triethylene glycol butyl ether.

[0022] Preferably, the other additives are one or more of BYK-110, polyamide wax, and Span.

[0023] Preferably, the organic carrier is prepared by mixing, heating and stirring a resin and a solvent in sequence, with a stirring speed of 100-1000 r / min and a boiling temperature of 60-80°C.

[0024] Another object of the present invention is to provide a method for preparing the above-mentioned low-VOCs environmentally friendly PERC back silver, comprising mixing, stirring and dispersing, three-roll grinding, and sieving 60-70% by weight of silver powder, 1-3% by weight of glass powder, 0.1-1% by weight of inorganic sintering inhibitor, 0.1-1% by weight of thermite, 28-38% by weight of organic carrier, and 0.1-2% by weight of other additives in sequence to obtain low-VOCs environmentally friendly PERC back silver.

[0025] Preferably, the stirring and dispersion is performed using a stirrer at a speed of 30 to 60 r / min and a stirring time of 60 to 120 min; the three-roll grinding is performed using a three-roll grinding machine at a speed of 200 to 400 r / min; and the sieving is performed using a 300 to 500 mesh screen.

[0026] The beneficial effects of the present invention are:

[0027] First, the oil-based system formula is more stable than the water-based system formula, simpler and easier to operate, and can also achieve the purpose of reducing VOCs emissions;

[0028] Second, PAMS resin is used in large quantities. PAMS resin has a low softening point, good solubility in solvents, and can replace solvent components, simplifying the preparation process, reducing the weight of solvents, and reducing VOCs emissions;

[0029] Third, when high-boiling-point organic matter decomposes in a concentrated manner in a high-temperature zone, bubbles are easily generated on the back of the silver. Inorganic sintering inhibitors are added to inhibit the sintering of silver powder. At the same time, the aluminum paste on the back of the silver is also prone to poor sintering. Adding thermite can promote the sintering of the aluminum paste on the back of the silver. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0031] Figure 1 Schematic diagram of bubbles generated by back silver in the comparative example of the present invention;

[0032] Figure 2 It is a schematic diagram of an embodiment of the present invention in which the back silver does not generate bubbles. DETAILED DESCRIPTION

[0033] Example 1

[0034] A low VOCs environmentally friendly PERC back silver, the formula is shown in Table 1 and Table 2 below:

[0035] Table 1

[0036]

[0037] Table 2

[0038]

[0039] The organic carrier is prepared by mixing, heating and stirring the resin and the solvent in sequence, with a stirring speed of 1000 r / min and a boiling temperature of 75°C.

[0040] The method for preparing the low-VOCs environmentally friendly PERC back silver has the following specific steps:

[0041] 1) preparing silver powder, glass powder, inorganic sintering inhibitor, thermite, organic carrier and other additives according to the above formula and mixing them in sequence;

[0042] 2) After mixing, use a stirrer to disperse the mixture. The stirring speed of the stirrer is set to 30 r / min and the stirring time is 120 min.

[0043] 3) After stirring and dispersing, three-roll milling is performed, and the grinding speed of the three-roll mill is set to 200 r / min;

[0044] 4) After grinding, sieve and filter using a 500-mesh sieve.

[0045] Please refer to Figure 2 , Table 7, Table 8, the low VOCs environmentally friendly PERC back silver prepared according to the above formula and steps has normal performance in the use of PERC solar cells, and the VOCs is less than 10%.

[0046] Example 2

[0047] A low VOCs environmentally friendly PERC back silver, the formula is shown in Table 3 and Table 4 below:

[0048] Table 3

[0049]

[0050] Table 4

[0051]

[0052] The organic carrier is prepared by mixing, heating and stirring the resin and the solvent in sequence, with a stirring speed of 100 r / min and a boiling temperature of 60°C.

[0053] The method for preparing the low-VOCs environmentally friendly PERC back silver has the following specific steps:

[0054] 1) preparing silver powder, glass powder, inorganic sintering inhibitor, thermite, organic carrier and other additives according to the above formula and mixing them in sequence;

[0055] 2) After mixing, use a stirrer to disperse the mixture, the stirring speed of the stirrer is set to 60 r / min, and the stirring time is 60 min;

[0056] 3) After stirring and dispersing, three-roll milling is performed, and the grinding speed of the three-roll mill is set to 200 r / min;

[0057] 4) After grinding, sieve and filter using a 300-mesh sieve.

[0058] Please refer to Figure 2 , Table 7, Table 8, the low VOCs environmentally friendly PERC back silver prepared according to the above formula and steps has normal performance in the use of PERC solar cells, and the VOCs is less than 10%.

[0059] Example 3

[0060] A low VOCs environmentally friendly PERC back silver, the formula is shown in Table 5 and Table 6 below:

[0061] Table 5

[0062]

[0063] Table 6

[0064]

[0065] The organic carrier is prepared by mixing, heating and stirring the resin and the solvent in sequence, with a stirring speed of 500 r / min and a boiling temperature of 80°C.

[0066] The method for preparing the low-VOCs environmentally friendly PERC back silver has the following specific steps:

[0067] 1) preparing silver powder, glass powder, inorganic sintering inhibitor, thermite, organic carrier and other additives according to the above formula and mixing them in sequence;

[0068] 2) After mixing, use a stirrer to disperse the mixture, the stirring speed of the stirrer is set to 50 r / min, and the stirring time is 80 min;

[0069] 3) After stirring and dispersing, three-roll milling is performed, and the grinding speed of the three-roll mill is set to 300 r / min;

[0070] 4) After grinding, sieve and filter using a 400-mesh sieve.

[0071] Please refer to Figure 2 , Table 7, Table 8, the low VOCs environmentally friendly PERC back silver prepared according to the above formula and steps has normal performance in the use of solar cells, and VOCs is less than 10%.

[0072] Please refer to Figure 1 and Figure 2 The back silver of the above-mentioned embodiments 1-3 and the PERC back silver of the comparative example 1 on the existing market were respectively used in solar cells, and the conversion efficiency (EFF), open circuit voltage (Voc), short circuit current (Isc), fill factor (FF), series resistance (Rs), parallel resistance (Rsh), welding tension and VOCs emission content of the manufactured cells were analyzed. The results are shown in the following Tables 7 and 8:

[0073] Table 7

[0074] serial number EFF(%) Voc(V) Isc(A) FF(%) Example 1 22.83 0.6953 13.744 80.45 Example 2 22.84 0.6951 13.751 80.44 Example 3 22.84 0.6955 13.749 80.41 Comparative Example 1 22.83 0.6952 13.748 80.43

[0075] Table 8

[0076] serial number Rs(Ω) Rsh(Ω) Welding tension (N) VOCs content (%) Example 1 0.0017 413 5.1 6-8％ Example 2 0.0017 348 4.9 6-8％ Example 3 0.0017 321 5.3 6-8％ Comparative Example 1 0.0017 319 5.2 30-35％

[0077] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A low VOCs environmentally friendly PERC back silver, characterized in that: It is composed of the following ingredients in parts by weight: Silver powder 60~70%, silver powder is monodisperse spherical silver powder; Glass powder 1~3%; Inorganic sintering inhibitor 0.1~1%; Thermite 0.1~1%; Organic carrier 28~38%, organic carrier includes resin and solvent; Other additives 0.1~2%; The resin accounts for 80-90% of the weight of the organic carrier, and the resin includes PAMS resin and other resins, and the content of PAMS resin in the resin is not less than 70%; Other resins are one or more of ethyl cellulose, acrylic resin, PVB resin and CAB resin.

2. The low VOCs environmentally friendly PERC back silver according to claim 1, characterized in that: The silver powder has a particle size of 0.5-1 μm, a specific gravity of 1.0-2.5 m2 / g, a tap density of 3-5 g / ml, and a burning loss of <1%.

3. The low VOCs environmentally friendly PERC back silver according to claim 1, characterized in that: The inorganic sintering inhibitor is one or more of nano silicon oxide, nano silicon nitride, nano silicon carbide, nano aluminum oxide, and nano titanium oxide.

4. The low VOCs environmentally friendly PERC back silver according to claim 1, characterized in that: The thermite is one or more of manganese dioxide, vanadium pentoxide, iron oxide and chromium oxide.

5. The low VOCs environmentally friendly PERC back silver according to claim 1, characterized in that: The solvent accounts for 10-20% of the weight of the organic carrier, and the solvent is one or more of butyl carbitol, butyl carbitol acetate, pineol, alcohol ester dodeca and triethylene glycol butyl ether.

6. The low VOCs environmentally friendly PERC back silver according to claim 1, characterized in that: Other additives include one or more of BYK-110, polyamide wax, and Span.

7. The low VOCs environmentally friendly PERC back silver according to claim 1, characterized in that: The organic carrier is prepared by mixing, heating and stirring the resin and the solvent in sequence, with a stirring speed of 100-1000r / min and a boiling temperature of 60-80°C.

8. A method for preparing low VOCs environmentally friendly PERC back silver according to claim 1, characterized in that: 60-70% by weight of silver powder, 1-3% by weight of glass powder, 0.1-1% by weight of inorganic sintering inhibitor, 0.1-1% by weight of thermite, 28-38% by weight of organic carrier, and 0.1-2% by weight of other additives are sequentially mixed, stirred and dispersed, three-roll ground, and sieved to obtain low-VOCs environmentally friendly PERC back silver.

9. The method for preparing low VOCs environmentally friendly PERC back silver according to claim 8, characterized in that: A mixer is used for stirring and dispersing at a speed of 30-60 r / min and a stirring time of 60-120 min. A three-roll grinder is used for three-roll grinding at a speed of 200-400 r / min. A 300-500 mesh sieve is used for sieving.

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