TWI536597B - A low cost, suitable for mass production of back contact with the battery production methods - Google Patents

Description

Back-contact battery production method with low cost and suitable for mass production

The invention is a method for producing a back contact battery, in particular for the production of a solar cell.

As shown in Fig. 1, the conventional conventional solar cell has 2-4 silver main gate lines as positive and negative electrodes on the front and back sides, and these main gate lines not only cause more silver paste consumption, but also block incident light. The battery efficiency has dropped. The back contact solar cell moves the silver grid line on the front side of the conventional battery to the back through a special design, which effectively reduces the power loss caused by the blockage of the silver grid line, improves the utilization of incident sunlight and the photoelectric conversion efficiency of the battery. One of the easier ways to implement a back contact battery is the so-called metal perforated winding structure, which uses a conductive material to direct the current generated by the front of the battery through the hole to the back. Typical examples are the MWT developed by the National Energy Research Center (ECN) of the Netherlands. The battery, as shown in Fig. 2, the current concentrated by the front side of the cell is led to the back through the silver paste in the hole. The process steps are as follows: laser drilling, cleaning and texturing, double-sided diffusion to prepare pn junction, dephosphorization glass, preparation of anti-reflection film, screen printing electrode, drying and sintering, laser insulation isolation perimeter and hole, and test sorting.

Compared with conventional solar cells, the above MWT batteries have increased the number of processes of laser drilling and insulation isolation, and it is necessary to change the single-sided diffusion to double-sided diffusion. This requires a doubling of the number of diffusion furnaces. These increased equipment and processes significantly increase the investment and production costs of the production line, and are not suitable for low-cost and large-scale production. This is also an important reason for the slow industrialization of the technology. .

In view of the problems of complicated process steps, high equipment investment and high production cost in the prior art, the present invention provides a method for producing a back contact battery with less equipment and simple process, and is suitable for large-scale production with low cost and large capacity.

A low-cost, large-scale mass production of back contact battery production method, using only one laser process (laser drilling), adopting conventional single-sided diffusion, adopting special anti-leakage protection measures near the hole, and other processes and conventional batteries Consistent, simple process, low equipment investment, and superior product performance and yield over existing solutions.

The specific method is as follows: (1) using a laser to open a hole in the crystal cymbal; (2) pre-cleaning and texturing the punctured cymbal to remove the damaged layer on the surface of the cymbal and the hole, reducing the photogeneration The recombination rate of the carriers, while the surface of the ruthenium is made into a suede to reduce the reflectivity; (3) depositing a doping source on the ruthenium substrate and performing diffusion to prepare a PN junction, and the cymbal is inserted in a conventional back-to-back manner Doping source diffusion in the quartz card slot of the diffusion furnace; commonly used diffusion sources include POCl3 (for P-type cymbals) and BBr3 (for N-type cymbals); (4) on the back surface of solar cells, with holes Preparing a layer of insulating protective layer at the center; (5) After cleaning, remove the unprotected back junction of the solar cell and the back side, and remove the antimony glass; (6) evaporate the anti-reflection film on the front side of the solar cell; (7) print the front side by screen printing The back electrode; (8) is dried, sintered or annealed to form a good ohmic contact.

It should be noted that in the diffusion step of step (3), the existing mature back-to-back single-side diffusion process is adopted, and in the process of single-sided diffusion, part of the diffusion source will diffuse from the hole to the back surface, and the diffusion range is With a diameter of about 10 mm, the protective mask (insulating protective layer) of step (4) can retain the hole and the peripheral portion of the PN junction to prevent leakage.

Further, the thickness of the insulating protective layer in the step (4) is 1 to 10 μm, and the material of the protective layer is an acid- or alkaline-resistant organic or inorganic material, and the preparation methods include screen printing, inkjet printing, and coating.

In addition, it should be noted in the step (4) that the recommended insulating protective material is an acid-resistant alkaline material such as paraffin wax or polyester film. This layer of insulation protection can also be placed in the step (6) coating process at the same time, because some of the conventional batteries are now also adopting the method of coating on both sides of the front and back. By adjusting the type and thickness of the coating on the reverse side of the battery, it is also possible to provide insulation near the hole. The role of protection.

Further, in the step (6), it is recommended to use a tantalum nitride film as the front side vapor-deposited anti-reflection film of the solar cell, which may alternatively have a large refractive index, has compatibility with ruthenium treatment, and has a good interface with ruthenium. Other materials of characteristics (such as visible light transparent dielectric materials, including but not limited to TiO2 or Al2O3, SiNxCy or SiNxOy, etc.); wherein, the xN of the SiNxCy is 0<x<1.33, and the y is 0<y<1.0, The x of the SiNxOy is 0<x<1.33, and the y is 0<y<2.0.

Compared with the prior art, the invention provides a low-cost, mass-production mass-produced back contact battery production method, which simplifies the prior art process and reduces the complicated process of double-sided diffusion and laser insulation isolation around the cell sheet and the hole. It also greatly reduces the cost of equipment investment and production, and at the same time reduces the loss of laser to the battery, suitable for large-scale production needs.

1‧‧‧ battery front main grid electrode

2‧‧‧Battery front fine grid line

3‧‧‧Battery main grid electrode on the back of the battery

4‧‧‧Aluminum back field

21‧‧‧P type 矽 substrate

22‧‧‧Laser holes

23‧‧‧Double PN junction diffusion layer

24‧‧‧Front grid electrode

25‧‧‧Aluminum back field

26‧‧‧ Back electrode

27‧‧‧Laser insulation isolation

31‧‧‧P type 矽 substrate

32‧‧‧Laser holes

33‧‧‧PN junction diffusion layer

34‧‧‧Front grid electrode

35‧‧‧Aluminum back field

36‧‧‧Back electrode

41‧‧‧ hole electrode

42‧‧‧fine grid line

43‧‧‧Back electrode

44‧‧‧Aluminum back field

Figure 1 is a plan view of the front and back sides of a conventional solar cell in the prior art.

Figure 2 is a cross-sectional view of the current back contact cell structure.

Figure 3 is a cross-sectional view showing the structure of the back contact battery of the present invention.

Fig. 4 is a plan view showing the front and back sides of the back contact battery of the present invention.

The invention is further clarified by the following examples, which are to be construed as illustrative only and not to limit the scope of the invention. Modifications are within the scope defined by the scope of the invention as claimed.

The solar cell produced by the back contact battery production method of the present invention is as shown in Fig. 3. During the implementation of the method, only one laser drilling process is used, and conventional single-sided diffusion is adopted, and special leakage protection measures are taken near the hole. Other processes are consistent with conventional batteries, the process is simple, the equipment investment is increased, and the product performance and yield are superior to the existing ones. The following two specific embodiments are described.

Example 1

The method for producing a back contact battery comprises the following specific steps: (1) using a solar grade P-type single crystal or a polycrystalline silicon wafer as a substrate; (2) according to the laser opening shown in FIG. 4, the shape of the hole is circular, and the diameter is 0.1~0.5mm; further, a hole is formed in the crystal cymbal by using a laser, and the shape of the hole may be circular, square or tapered, and the size is between 0.05 and 1 mm, and the number and distribution of the holes are not limited to the fourth figure. (3) cleaning and texturing using conventional chemical cleaning and texturing methods; (4) high-temperature back-to-back single-sided diffusion using a POCl3 diffusion source, with diffusion resistance controlled at 40~120 Ω/□; (5) A circular paraffin mask having a diameter of 2 to 8 mm is prepared on the back surface of the cymbal, and the preparation method is an inkjet printing method or a screen printing method; (6) chemical cleaning is performed using a chemical solution to remove the periphery and the back surface. a backing layer that is not protected by an organic thin layer, cleans the organic thin layer, and removes the phosphorous glass formed on the surface of the germanium substrate after diffusion; (7) vapor-deposits the SiNx antireflection film with a PECVD apparatus, and has a refractive index of between 1.9 and 2.1. Thickness is 70~90nm; (8) Printing backlight by screen printing 36, 35 and a front aluminum BSF gate line electrode 34; (9) in the chain by drying and sintering furnace. After sintering, both the front and back electrodes form a good ohmic contact.

The back contact solar cell prepared by the polycrystalline silicon wafer used in this embodiment was tested, and the conversion efficiency of the battery was improved by 0.5%.

Example 2

The method for producing a back contact battery comprises the following specific steps: (1) using a solar-grade P-type single crystal or a polycrystalline silicon wafer as a substrate; (2) according to the laser opening shown in FIG. 4, the shape of the hole is circular, and the diameter (0.1) using conventional chemical cleaning and texturing methods for cleaning and texturing; (4) using POCl3 diffusion source for high-temperature back-to-back single-sided diffusion, diffusion resistance is controlled at 40~120Ω/□; (5) chemical cleaning after chemical cleaning, removing the peripheral and back pn junctions, removing the phosphorous glass formed on the surface of the germanium substrate after diffusion; (6) vapor-depositing the SiNx anti-reflection film on the front side of the cell sheet, the refractive index is 1.9~2.1 Between the film thickness of 70~90nm; AlOx/SiNx laminated passivation protective film is deposited on the back side of the cell sheet, AlOx thickness is 5~50nm, SiNx is 50~200nm, which is consistent with the conventional back passivation cell preparation process; (7) The front and back electrodes 43 are printed by screen printing in the same manner as the conventional back passivation battery; (8) drying and sintering are carried out in a chain furnace. After sintering, both the front and back electrodes 43 form a good ohmic contact; the back contact solar cell prepared by the polycrystalline silicon wafer used in this embodiment was tested, and the conversion efficiency of the battery was increased by 1%.

1‧‧‧P type 矽 substrate

2‧‧‧Laser holes

3‧‧‧PN junction diffusion layer

4‧‧‧Front grid electrode

5‧‧‧Aluminum back field

6‧‧‧Back electrode

Claims (5)

The invention relates to a low-cost, mass-produced method for producing a back contact battery, which comprises the steps of: (1) using a laser to open a hole in a crystal cymbal; and (2) performing the boring after the punching. Pre-cleaning and texturing, removing the damage layer on the surface of the cymbal and the hole, reducing the recombination rate of the photo-generated carriers, and forming a suede on the surface of the cymbal to reduce the reflectivity; (3) on the cymbal substrate Depositing a doping source and performing diffusion to prepare a PN junction, the ruthenium is inserted into a quartz card slot of the diffusion furnace in a back-to-back manner for doping source diffusion; commonly used diffusion sources include POCl3 and BBr3; (4) in solar cells a back surface, an insulating protective layer is prepared centering on the hole; (5) post-cleaning, removing the unprotected back junction of the solar cell and the back surface, and removing the phosphoric acid glass; (6) depositing the front side of the solar cell An anti-reflection film; (7) printing the front and back electrodes by screen printing; (8) drying, sintering or annealing to form a good ohmic contact. The method for producing a low-cost, mass-produced back contact battery according to the first aspect of the patent application, wherein the thickness of the insulating protective layer in the step (4) is 1 to 10 μm, and the material of the protective layer is resistant. Acid-alkaline organic or inorganic materials, including preparation methods such as screen printing, inkjet printing and coating. The method for producing a low-cost, mass-produced back contact battery according to the first or second aspect of the patent application, wherein the insulating protective material in the step (4) is an acid-resistant such as a paraffin wax or a polyester film. Alkaline material. The method for producing a low-cost, mass-produced back contact battery according to claim 3, wherein the insulating protective layer in the step (4) can also be placed in the coating step of the step (6). This is because some of the conventional batteries are now adopting the positive and negative coating methods. By adjusting the type and thickness of the coating on the reverse side of the battery, the insulation protection around the hole can also be achieved. The method for producing a low-cost, mass-produced back contact battery according to the first aspect of the patent application, wherein the step (6) recommends using a tantalum nitride film as the front surface evaporation antireflection film of the solar cell; Other materials having compatibility with the ruthenium treatment and having good interface properties may alternatively be used; other materials are visible light transparent dielectric materials, including TiO2 or Al2O3, SiNxCy or SiNxOy; wherein, the SiNxCy x is 0<x<1.33, y is 0<y<1.0, and x of SiNxOy is 0<x<1.33, and y is 0<y<2.0.