A battery back field back electrode and a preparation method, a solar cell and a preparation method

Abstract

The application discloses an isolation material, a battery back field back pole and a preparation method, and a solar cell and a preparation method, and belongs to the technical field of crystalline silicon solar cell preparation. The back field back pole comprises a silicon back surface base, an aluminum electrode and a silver electrode. The aluminum electrode is arranged on the silicon back surface base. The silver electrode is arranged on the aluminum electrode. An isolation layer is arranged between the silver electrode and the aluminum electrode. The isolation layer is composed of the following components: glass powder, auxiliary powder, an organic carrier and an additive. The weight percentage of the glass powder is 35-80%. The weight percentage of the auxiliary powder is 0.5-25%. The weight percentage of the organic carrier and the additive is 15-45%. The application inserts an isolation layer between the silver electrode and the aluminum electrode, blocks the direct contact of the silver electrode and the aluminum electrode, effectively isolates the mutual penetration of the silver paste and the aluminum paste in the sintering process, and realizes the improvement or solution of the performance of the full-aluminum back field battery, such as the quality of the battery, the welding of a module and reliability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of crystalline silicon solar cell preparation, and more particularly to an isolation material, a cell back field back electrode and a preparation method, a solar cell and a preparation method. BACKGROUND

[0002] Currently, the electrodes of a solar cell are mainly prepared by screen printing. Figures 1-3 The back electrode is composed of an aluminum electrode main grid 12, an aluminum electrode secondary grid 13 and a silver electrode 14. The silver and aluminum electrodes partially overlap to form an overlapping area 16, thereby achieving mutual connection. The aluminum electrode mainly collects carriers on the back of the cell sheet, and then the current is led out through the silver electrode. For a single-sided cell, the aluminum electrode area adopts a full-aluminum coverage design to reduce the aluminum electrode resistance and improve the collection efficiency. For a double-sided cell, the aluminum electrode adopts a design of uniformly arranged aluminum grid lines to meet the requirements of double-sided power generation.

[0003] The preparation process of a conventional cell generally involves printing a back electrode first, and then printing an aluminum electrode. The advantages of this are as follows: ① The silver electrode is directly prepared on the substrate of the silicon sheet, and after sintering, a dense electrode structure is easily formed, which has good soldering tension when soldering the solder strip of the module. ② The thermal expansion coefficient of a semiconductor silicon crystal is 2.5x10 -6 / ℃, the thermal expansion coefficients of pure silver and pure aluminum are 19.5x10 -6 / ℃ and 23.2x10 -6 / ℃, respectively, and the difference in the thermal expansion coefficients between the silver electrode and the silicon substrate is smaller than that between the aluminum electrode and the silicon substrate, which is conducive to reducing the failure of the module during cold and hot cycle tests. ③ In the overlapping area of the silver and aluminum electrodes, a dense structure is also easily formed, thereby reducing the resistivity of the electrode area.

[0004] However, the following disadvantages also exist: ① Large contact resistance and severe recombination. Direct contact between the silver electrode and the silicon substrate causes the recombination of carriers due to the gold-semiconductor contact of silver-silicon. Even for the back passivation structure of the current PERC cell, the back silver paste also has the problem of burning through the back medium layer and contacting the silicon substrate. ② Current collection blank area: for a PERC cell, when laser grooving is performed in the silver electrode area, thermal stress is caused during soldering of the module, which leads to a high breakage rate. Therefore, the method of not performing laser grooving in the back silver electrode area and the surrounding area is often used to solve this problem, but this forms a blank area for current collection. At the same time, in order to ensure the quality of MBB soldering, a blank isolation area 15 is often set between the silver electrode and the aluminum electrode in the direction of the solder strip, which further increases the blank area for current collection.

[0005] In view of the above shortcomings, the authorized patent CN201110208995.7 provides a kind of crystalline silicon cell back field back electrode and its printing process;The application first prints aluminum paste on the back surface of crystalline silicon wafer, dries aluminum paste at a certain temperature to form aluminum back field, and then prints back electrode paste on the surface of dried aluminum paste to form back electrode pattern. Thus, by covering the entire back surface of the silicon wafer with the aluminum back field, the area of the crystalline silicon cell aluminum back field is increased, the crystalline silicon back surface recombination is reduced, the gettering effect of the aluminum back field is increased, and the back surface passivation and carrier collection effect are improved.

[0006] Patent CN201810739434.1 also provides a kind of full aluminum back field back silver paste and its preparation method and application;The application includes the following according to weight fraction: special requirement silver powder with purity greater than 99.99% 10-80 parts, self-made lead-free main glass powder 0.5-5 parts, low melting point auxiliary glass powder 0-3 parts, special requirement low melting point metal powder 1-50 parts, organic binder 15-50 parts, organic auxiliary agent 0.01-1 parts. The application increases low melting point metal in back silver paste to block silver and aluminum, thereby solving the interpenetration problem between silver and aluminum, and increases auxiliary glass powder to adjust glass body softening temperature and thermal expansion performance, thereby improving back silver electrode density and weldability.

[0007] However, the full aluminum back field scheme of the authorized patent CN201110208995.7 has the problem of low silver electrode tension or direct inability to weld, which cannot meet the component welding requirements. The full aluminum back field scheme of patent CN201810739434.1 solves the component welding problem, but has the problem of component cold and hot cycle test failure. In addition, the current electrode preparation method of printing silver electrode first and then printing aluminum back field has problems such as current collection blank area, and the conversion efficiency of the battery sheet has room for improvement. Moreover, the current full aluminum back field scheme has deficiencies in battery quality or reliability, and needs to be further improved and optimized before it can be widely used. SUMMARY

[0008] 1. Technical problems to be solved by the invention

[0009] In order to overcome the above-mentioned deficiencies of the prior art, the present application provides a kind of isolation material, battery back field back electrode and preparation method, solar cell and preparation method;The present application inserts a layer of isolation layer between silver electrode and aluminum electrode, blocks the direct contact of silver electrode and aluminum electrode, effectively isolates the interpenetration of silver paste and aluminum paste during sintering process, and solves the welding problem of silver electrode prepared on full aluminum back field. At the same time, by selecting and optimizing the component materials in the isolation paste, the hot cycle test performance of full aluminum back field battery is effectively improved. The present application realizes the improvement or solution of battery quality, component welding and reliability performance of full aluminum back field battery, and solves the technical difficulties of mass production.

[0010] 2. Technical solution

[0011] To achieve the above-mentioned purpose, the technical solution provided by the present application is:

[0012] The isolation material of the present application is composed of the following components: glass powder, auxiliary powder, organic carrier and auxiliary agent; wherein the weight percentage of the glass powder is 35-80%, the weight percentage of the auxiliary powder is 0.5-25%, and the weight percentage of the organic carrier and auxiliary agent is 15-45%.

[0013] Further, the glass powder is prepared by dissolving several of PbO, Bi2O3, TeO2, WO3, Li2O, N2O, B2O3, Fe2O3, CaO, MgO, SiO2 and Al2O3, and the particle size of the glass powder is controlled within 0.1-10 μm, and the softening temperature is controlled between the softening temperatures of the silver paste and the aluminum paste.

[0014] Further, the auxiliary powder is composed of one or several of base metal, rare metal and ceramic powder, the base metal is preferably Cu and Sn, the rare metal is preferably Bi and Te, and the ceramic powder is preferably Al2O3, MgO and BeO.

[0015] Further, the particle size of the auxiliary powder is controlled within 0.5-10 μm, and the linear expansion coefficient is controlled within 5-25×10 -6 / ℃.

[0016] The back field back electrode of the solar cell of the present application comprises a silicon back surface substrate, an aluminum electrode and a silver electrode, the aluminum electrode is arranged on the silicon back surface substrate, the silver electrode is arranged on the aluminum electrode, and an isolation layer is arranged between the silver electrode and the aluminum electrode, and the isolation layer uses the isolation material.

[0017] Further, the outer dimension of the isolation layer is smaller than the dimension of the silver electrode, the silver electrode and the aluminum electrode form an overlapping area around the silver electrode, and the silver electrode and the aluminum electrode are connected through the overlapping area.

[0018] Further, the isolation layer is provided with hollow points, and the silver electrode is connected with the aluminum electrode through the hollow point area of the isolation layer.

[0019] Further, the aluminum electrode of the full-aluminum back field is arranged on the silicon back surface substrate; for the single-sided cell, the aluminum electrode of the full-aluminum back field covers the entire surface of the silicon back surface substrate; for the double-sided cell, the aluminum electrode of the full-aluminum back field covers the silicon back surface substrate in the silver electrode area.

[0020] Further, the thickness of the isolation layer is 0.5-20 μm.

[0021] The preparation method of the back field back electrode of the solar cell of the present application comprises the following steps:

[0022] (1) First, prepare an aluminum electrode in a full-aluminum back field mode on a silicon back surface substrate;

[0023] (2) After printing the aluminum electrode, prepare the isolation material on the cell sheet in each silver electrode area by screen printing or inkjet printing, and then form an isolation layer by co-sintering;

[0024] (3) Prepare a silver electrode on the isolation layer.

[0025] A solar full-aluminum back field cell according to the present application includes the solar cell back field back electrode.

[0026] A preparation method of a solar full-aluminum back field cell according to the present application includes the following steps of preparing a cell back field back electrode:

[0027] Step 1: Perform laser opening on the passivation film of the silicon back surface substrate, and perform back laser grooving in a full-through mode, then prepare an aluminum electrode in a full-aluminum back field mode, and the aluminum electrode auxiliary grid area corresponds to the laser grooving area one by one.

[0028] Step 2: After printing the aluminum electrode, prepare the isolation material on the cell sheet in each silver electrode area by screen printing or inkjet printing, and then form an isolation layer by co-sintering.

[0029] Step 3: Prepare a silver electrode on the isolation layer.

[0030] 3. Beneficial effects

[0031] Compared with the prior art, the technical scheme provided by the present application has the following remarkable effects:

[0032] (1) The solar cell back field back electrode according to the present application prepares an isolation layer between the silver electrode and the aluminum electrode. The isolation layer effectively isolates the mutual penetration of the silver paste and the aluminum paste during the sintering process, and solves the problem of welding the silver electrode prepared on the full-aluminum back field.

[0033] (2) The solar cell back field back electrode according to the present application prepares an aluminum electrode below the silver electrode, and benefits from the improvement of the sintering density and the coefficient of thermal expansion of the isolation paste on the aluminum electrode. Laser grooving of the back passivation layer in the silver electrode area will not cause stress concentration during the welding process of the module, thereby eliminating or significantly reducing the current collection blank area, greatly improving the current collection effect, and improving the conversion efficiency.

[0034] (3) A solar full-aluminum back field cell of the present application, by selecting and optimizing the component materials in the isolation paste, and after sintering, the isolation paste significantly improves the sintering density of the aluminum paste powder in the bottom aluminum electrode layer, adjusts the thermal expansion coefficient of the aluminum electrode, and alleviates the difference in thermal expansion coefficient between the silver electrode and the aluminum electrode, thereby effectively improving the thermal cycle test performance of the full-aluminum back field cell.

[0035] (4) A solar full-aluminum back field cell of the present application, the silver electrode is directly connected with the aluminum electrode through the isolation zone periphery, or is directly connected with the aluminum electrode through the hollowed-out zone set in the isolation zone, realizing the export of current.

[0036] (5) Through the above technical route, the performance improvement or solution of the full-aluminum back field cell to the cell quality, module welding and reliability, etc. is realized, and the technical difficulties of mass production are solved. At the same time, the PERC cell sheet photoelectric conversion efficiency is improved by more than 0.15%. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is the back electrode pattern of the prior scheme (9BB bifacial cell);

[0038] Figure 2 is a schematic diagram of the back local electrode area of the prior scheme bifacial cell;

[0039] Figure 3 is a section view of the electrode area of the prior scheme;

[0040] Figure 4 is the back electrode pattern of the present application (9BB bifacial cell),

[0041] Figure 5 is a section view of the electrode area of the present application;

[0042] Figure 6 is a laser slotting diagram of the present application;

[0043] Figure 7 is the back aluminum back field pattern of the present application;

[0044] Figure 8 is a schematic diagram of the isolation layer of the present application;

[0045] Figure 9 is the back silver electrode pattern of the present application;

[0046] Figure 10 is a section view of the cell structure of the present application.

[0047] Explanation of the reference numerals in the schematic diagram:

[0048] 11, silicon back substrate; 12, aluminum electrode main grid; 13, aluminum electrode auxiliary grid; 14, silver electrode; 15, isolation zone; 16, overlapping zone;

[0049] 21, silicon back substrate; 22, aluminum electrode; 221, aluminum electrode main grid; 222, aluminum electrode auxiliary grid; 23, passivation layer; 24, silver electrode; 25, overlapping area; 26, isolation layer; 27, laser grooving area;

[0050] 31, silicon wafer substrate; 32, front emitter; 321, shallow doped area; 322, heavily doped area; 33, front oxide layer; 34, passivation and anti-reflection layer; 35, positive electrode. DETAILED DESCRIPTION

[0051] In order to further understand the content of the present application, the present application will be described in detail in conjunction with the drawings and examples.

[0052] Example 1

[0053] In conjunction with Figures 4-9 , a solar cell back field back electrode of the present embodiment includes a silicon back substrate 21, an aluminum electrode 22, and a silver electrode 24. The aluminum electrode 22 of the full-aluminum back field is arranged on the silicon back substrate 21. For a single-sided cell, the aluminum electrode 22 of the full-aluminum back field covers the entire surface of the silicon back substrate 21. For a double-sided cell, the aluminum electrode 22 of the full-aluminum back field covers the back surface of the silicon wafer in the silver electrode area. The aluminum electrode 22 includes an aluminum electrode main grid 221 and an aluminum electrode auxiliary grid 222. The aluminum electrode auxiliary grid 222 is consistent with the design of a conventional double-sided cell. The silicon back substrate 21 is provided with a laser grooving area 27. The aluminum electrode auxiliary grid 222 area corresponds to the laser grooving area 27 one by one, realizing the contact between the aluminum electrode and the silicon back substrate 21, and realizing the collection and export of back carriers.

[0054] The silver electrode 24 is arranged on the aluminum electrode 22, and an isolation layer 26 is arranged between the silver electrode 24 and the aluminum electrode 22. Each isolation layer 26 corresponds to the silver electrode 24 one by one. The pattern of the isolation layer 26 can be consistent with the design of the silver electrode pattern. The outer dimension of the isolation layer 26 is set to be smaller than the dimension of the silver electrode 24, so that the silver electrode 24 forms an overlapping area 25 with the aluminum electrode 22 around, realizing the connection between the silver electrode 24 and the aluminum electrode 22. Or a hollow point is set in the center area of the isolation layer 26, so that the silver electrode 24 is connected with the aluminum electrode through the hollow point area in the center of the isolation layer 26.

[0055] The present embodiment prepares an isolation layer 26 between the silver electrode 24 and the aluminum electrode 22. The isolation layer 26 effectively isolates the mutual penetration of silver paste and aluminum paste in the sintering process, solving the welding problem of preparing the silver electrode 24 on the full-aluminum back field. The silver electrode 24 is directly connected with the aluminum electrode 22 through the periphery of the isolation layer 26, or is directly connected with the aluminum electrode 22 through the hollow area set in the interior of the isolation layer 26, realizing the export of current.

[0056] Example 2

[0057] The back field and back electrode structure of the solar cell of the present embodiment is as in Embodiment 1, and the preparation process of the back field and back electrode is as follows:

[0058] (1) An aluminum electrode 22 in the full-aluminum back field mode is first prepared on the silicon back substrate 21. For a single-sided cell, the aluminum electrode 22 in the full-aluminum back field covers the entire back surface of the silicon wafer. For a double-sided cell, the aluminum electrode 22 in the full-aluminum back field covers the back surface of the silicon wafer with an aluminum electrode in the silver electrode area. The aluminum electrode sub-grid 222 is consistent with the design of a conventional double-sided cell, and the area corresponds to the laser grooving area 27 one-to-one, realizing the contact between the aluminum electrode 22 and the silicon back substrate 21 and the collection and export of the back surface carriers.

[0059] (2) After the printing of the aluminum electrode 22, an isolation layer 26 is provided in each silver electrode area, i.e., a barrier paste containing a barrier material component is prepared on the cell by screen printing (preferably), inkjet printing, and the like, and then the isolation layer 26 is formed by co-sintering. The thickness of the isolation layer 26 is preferably 0.5-20 μm, and in the present embodiment, the thickness of the isolation layer 26 is 0.5 μm. Each isolation layer 26 corresponds to a silver electrode 24. The pattern of the isolation layer 26 can be consistent with the pattern design of the silver electrode 24.

[0060] (3) The silver electrode 24 is prepared on the isolation layer 26. By setting the outer dimension of the isolation layer 26 to be smaller than the dimension of the silver electrode 24, an overlapping area 25 is formed between the silver electrode 24 and the aluminum electrode 22, realizing the connection between the silver electrode 24 and the aluminum electrode. Or a hollow point is set in the center area of the isolation area, so that the silver electrode 24 is connected to the aluminum electrode 22 through the hollow point area in the center of the isolation area.

[0061] In the present embodiment, the aluminum electrode 22 is prepared below the silver electrode 24, and thanks to the improvement of the sintering density and the coefficient of thermal expansion of the isolation paste for the aluminum electrode 22, the laser grooving of the back passivation layer in the silver electrode area will not cause stress concentration during the soldering process of the assembly, thereby eliminating or significantly reducing the current collection blank area, greatly improving the current collection effect, and improving the conversion efficiency. An isolation layer is prepared between the silver electrode and the aluminum electrode. The isolation layer effectively isolates the mutual penetration of the silver paste and the aluminum paste during the sintering process, solving the soldering problem of the preparation of the silver electrode on the full-aluminum back field.

[0062] Embodiment 3

[0063] The back field and back electrode structure and the preparation process of the solar cell of the present embodiment are basically the same as those of Embodiments 1 and 2, and the features of the isolation layer 26 inserted between the silver electrode 24 and the aluminum electrode 22 to isolate the direct contact between the silver electrode and the aluminum electrode are as follows:

[0064] The isolation layer 26 is composed of the following ingredients by weight percentage: glass powder 35-80%; organic carrier and auxiliary agent: 15-45%; auxiliary powder 0.5-25%.

[0065] It is worth mentioning that the present application solves the reliability problem of the full aluminum back field route by the barrier material. The barrier material is mainly composed of glass powder. On the one hand, the glass powder physically isolates the silver paste and the aluminum paste, avoiding mutual penetration during co-sintering to cause welding problems. In addition, by adjusting the composition of the glass powder, the softening temperature is adjusted between the softening temperatures of the glass powder in the silver paste and the aluminum paste, so as to eliminate or improve the mutual influence between the glass powders in the silver paste and the aluminum paste during the co-sintering process, thereby stabilizing the sintering density and the tinning performance of the silver paste, and improving the weldability and welding tension of the silver electrode prepared on the aluminum paste. At the same time, the introduction of sufficient glass body provides adjustment for the sintering performance of the lower aluminum back field, and improves or adjusts the sintering density, adhesion and linear expansion coefficient thereof.

[0066] The glass powder can be prepared by dissolving several of PbO, Bi2O3, TeO2, WO3, Li2O, N2O, B2O3, Fe2O3, CaO, MgO, SiO2, Al2O3, the particle size of the glass powder is controlled within 0.1-10 μm, and the softening temperature is controlled within 300-600 ℃, between the softening temperatures of the glass powder in the silver paste and the aluminum paste.

[0067] The components of PbO, Bi2O3, N2O, B2O3 in the glass powder mainly reduce the melting point of the glass body and adjust the softening temperature of the glass powder; the weight percentage is 30-60%.

[0068] The components of Li2O, Fe2O3 in the glass powder mainly adjust the expansion coefficient of the glass body, and can further adjust the sintering density of the aluminum back field of the bottom layer of the isolation layer; the weight percentage is 5-20%.

[0069] The component of TeO2 in the glass powder mainly adjusts the aluminum dissolving performance of the glass body, increases the sintering density of the bottom aluminum back field, and at the same time reduces the corrosion degree of the glass body to the surface of the silicon substrate; the weight percentage is 5-15%.

[0070] The component of WO3 in the glass powder mainly adjusts the surface tension of the glass body, improves the wetting ability, and increases the sintering density and adhesion of the bottom aluminum back field; the weight percentage is 3-10%.

[0071] The components of CaO, MgO in the glass powder mainly adjust the high-temperature viscosity performance of the glass body, and improve the sintering characteristics of the glass body; the weight percentage is 5-10%.

[0072] The components of SiO2, Al2O3 in the glass powder mainly enhance the network structure strength of the glass body itself; the weight percentage is 10-25%.

[0073] The auxiliary powder is composed of one or more of base metals such as Cu, Sn; rare metals such as Bi, Te; and ceramic powder such as Al2O3, MgO, BeO, with the particle size controlled at 0.5-10 μm and the linear expansion coefficient controlled at 5-25×10 -6 / ℃. The introduction of the auxiliary powder mainly helps to physically isolate the silver paste and the aluminum paste, and the base metal also helps to supplement the conductivity of the silver electrode, and the rare metal also helps to reduce the sintering temperature of the silver electrode.

[0074] The organic carrier is composed of one or more of terpineol, butyl carbitol, butyl carbitol acetate, alcohol ester twelve, DBE, ethyl cellulose, resin, etc. The auxiliary agent is composed of one or more of stearic acid, sorbitol stearate, lecithin, oleic acid, lauric acid.

[0075] By selecting and optimizing the materials in the isolation paste, the isolation paste can significantly improve the sintering density of the aluminum paste powder in the bottom aluminum electrode layer after sintering, adjust the thermal expansion coefficient of the aluminum electrode, and relieve the difference in thermal expansion between the silver electrode and the aluminum electrode, thereby effectively improving the thermal cycle test performance of the full-aluminum back field battery. Due to the limited space, only one preferred ratio is given in this embodiment, which is as follows:

[0076] Glass powder: 60%; organic carrier and auxiliary agent: 30%; auxiliary powder: 10%.

[0077] The glass powder is prepared by dissolving 25% PbO, 15% Bi2O3, 8% TeO2, 10% WO3, 7% Li2O, 10% CaO, and 25% SiO2 by weight percentage, with the particle size controlled at 0.5-8 μm and the softening temperature controlled at 450℃.

[0078] The auxiliary powder is composed of base metal Cu, rare metal Bi, and ceramic powder Al2O3, with the particle size controlled at 1.5-10 μm and the linear expansion coefficient controlled at 20×10 -6 / ℃.

[0079] The organic carrier and auxiliary agent are composed of one or more of terpineol, butyl carbitol, ethyl cellulose, stearic acid, sorbitol stearate, and lecithin.

[0080] Example 4

[0081] In combination Figure 10 , the preparation method of a solar full-aluminum back field battery of this embodiment is as follows:

[0082] 1. Texturing: Single crystal P-type silicon wafer is used as the silicon wafer substrate 31, and alkali is used to texturize the front and back surfaces to form a textured structure.

[0083] 2. Diffusion: after the texturing of the silicon wafer, phosphorus pentachloride and the silicon wafer are reacted at high temperature to diffuse the front surface and form a PN emission junction (i.e., the front emitter 32).

[0084] 3. Laser SE: using the phosphorus-silicon glass after diffusion as a phosphorus source, the front surface of the silicon wafer and the metalized area corresponding to the positive electrode 35 grid line are laser doped to form a heavily doped region 322, and correspondingly, the other part is a shallowly doped region 321.

[0085] 4. Thermal oxidation: the silicon wafer after laser SE is subjected to oxygen oxidation to form a front surface oxide layer 33.

[0086] 5. PSG removal: the silicon wafer after thermal oxidation is subjected to HF to remove the back surface and the peripheral PSG.

[0087] 6. Alkali polishing: the silicon wafer after PSG removal is subjected to back surface and edge polishing, and the front surface is removed of PSG.

[0088] 7. Oxidation annealing: the silicon wafer after alkali polishing is subjected to oxidation and annealing treatment.

[0089] 8. Back surface deposition of passivation film: a passivation layer 23 is prepared on the back surface of the annealed silicon wafer.

[0090] 9. Front surface deposition of anti-reflective film: a passivation and anti-reflective layer 34 is prepared on the front surface of the silicon wafer.

[0091] 10. Back surface laser: laser drilling is performed on the passivation film on the back surface of the silicon wafer using the pattern of the present embodiment, and the back surface laser slotting region 27 is in a full-through mode.

[0092] 11. Aluminum electrode preparation: the aluminum electrode 22 of the back surface full-aluminum back surface is prepared by screen printing of aluminum paste, the aluminum electrode auxiliary grid 222 corresponds to the laser slotting region 27 one by one to realize the export of the back surface carriers, and then 250°C drying.

[0093] 12. Isolation region preparation: a 10 μm thick isolation layer 26 is prepared above the aluminum electrode and at the position of the silver electrode region by screen printing. The isolation layer 26 is prepared by printing of a slurry of 70% glass powder; organic carrier and auxiliary agent: 25%; auxiliary powder 5%. The glass powder is dissolved by PbO, Bi2O3, TeO2, WO3, Li2O, N2O, B2O3, Fe2O3, CaO, MgO, SiO2, Al2O3, the particle size is controlled at 0.75-0.95 μm, and the softening temperature is controlled at 420°C. The auxiliary powder is composed of Sn, Te and Al2O3, MgO, the particle size is controlled at 0.5-5.80 μm, and the linear expansion coefficient is controlled at 10×10 -6 / ℃, then 250℃ drying. The organic carrier and adjuvant is composed of butyl carbitol acetate, alcohol ester twelve, DBE, lecithin, oleic acid, lauric acid.

[0094] 13. Back silver electrode preparation: screen printing silver electrode 24 on the isolation layer.

[0095] 14. Sintering: sintering the printed front electrode silicon wafer, sintering peak temperature 780℃.

[0096] 15. Electro-injection: electro-injection treatment of the sintered battery piece.

[0097] 16. Finished product: product battery piece testing, sorting, packaging into warehouse.

[0098] Through the above technical route, the improvement or solution of the performance of the full aluminum back field battery on the battery quality, module welding and reliability is realized, and the technical difficulties of mass production are broken through. At the same time, the PERC battery piece photoelectric conversion efficiency is improved by more than 0.15%.

[0099] The above describes the present application and its embodiments in a schematic way, which is not limited, and the drawings shown are only one of the embodiments of the present application, and the actual structure is not limited thereto. Therefore, if the ordinary skilled in the art is inspired thereby, without departing from the purpose of the present application, similar structure and embodiments are not designed creatively, which shall belong to the protection scope of the present application.

Claims

1. A solar cell back field back electrode comprising a silicon back substrate (21), an aluminum electrode (22) and a silver electrode (24), the aluminum electrode (22) being provided on the silicon back substrate (21), characterized in that: The silver electrode (24) is arranged on the aluminum electrode (22), and an isolation layer (26) is arranged between the silver electrode (24) and the aluminum electrode (22), wherein the isolation layer (26) is made of an isolation material; the isolation material is composed of glass powder, auxiliary powder, organic carrier and auxiliary agent; wherein the weight percentage of the glass powder is 35-80%, the weight percentage of the auxiliary powder is 0.5-25%, and the weight percentage of the organic carrier and the auxiliary agent is 15-45%; The glass powder is made of several of PbO, Bi2O3, TeO2, WO3, Li2O, N2O, B2O3, Fe2O3, CaO, MgO, SiO2 and Al2O3, the particle size of the glass powder is controlled to be 0.1-10 μm, and the softening temperature is controlled to be between the softening temperatures of the silver paste and the aluminum paste; The auxiliary powder is composed of one or more of base metals, rare metals and ceramic powder, the base metal is selected from Cu and Sn, the rare metal is selected from Bi and Te, and the ceramic powder is selected from Al2O3, MgO and BeO; The particle size of the auxiliary powder is controlled to be 0.5-10 μm, and the linear expansion coefficient is controlled to be 5-25 x 10 -6 / °C. / °C. The outer dimension of the isolation layer (26) is smaller than the dimension of the silver electrode (24), the silver electrode (24) is surrounded by the aluminum electrode (22) to form an overlapping area (25), and the silver electrode (24) is connected to the aluminum electrode (22) through the overlapping area (25); The isolation layer (26) is provided with hollow points, and the silver electrode (24) is connected to the aluminum electrode (22) through the hollow point area of the isolation layer (26).

2. A back field back electrode for a solar cell according to claim 1, wherein: The silicon back substrate (21) is provided with the aluminum electrode (22) of the full-aluminum back field; for a single-sided cell, the aluminum electrode (22) of the full-aluminum back field covers the entire surface of the silicon back substrate (21); for a double-sided cell, the aluminum electrode (22) of the full-aluminum back field covers the silicon back substrate (21) in the silver electrode area.

3. A back field back electrode for a solar cell as claimed in claim 2, wherein: The thickness of the isolation layer (26) is 0.5-20 μm.

4. A method of producing a back field back electrode for a solar cell as claimed in any one of claims 1 to 3, characterized in that, The steps are as follows: (1) The aluminum electrode (22) of the full-aluminum back field is prepared on the silicon back substrate (21) first; (2) After the printing of the aluminum electrode (22) is completed, the isolation material is prepared on the cell sheet through screen printing or inkjet printing in each silver electrode (24) area, and then the isolation layer (26) is formed through co-sintering; (3) The silver electrode (24) is prepared on the isolation layer (26).

5. A solar all-aluminum back surface field cell characterized by: The battery comprises the solar cell back field back electrode according to any one of claims 1-3.

6. A method of fabricating a solar all-aluminum back surface field cell, characterized by, The preparation steps of the battery back field back electrode are as follows: Step one, laser drilling is performed on the passivation film of the silicon back substrate, the back laser slotting is in a full-penetration mode, and then the aluminum electrode of the full-aluminum back field is prepared, and the aluminum electrode auxiliary grid area corresponds to the laser slotting area one by one; Step two, after the printing of the aluminum electrode is completed, the isolation material in claim 1 is prepared on the cell sheet through screen printing or inkjet printing in each silver electrode area, and then the isolation layer is formed through co-sintering; Step three, the silver electrode is prepared on the isolation layer.

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