CN107425085A - A kind of preparation method of the back contacts crystal silicon solar batteries of passivating back - Google Patents

Abstract

The invention discloses a method for preparing a back-contact crystalline silicon solar cell with passivation on the back. The steps include laser drilling, texturing, diffusion, etching, plating a passivation film on the back, plating a protective film on the back, and plating an anti-reflection film on the front , laser grooving, screen printing, and sintering. The front electrode of the fabricated cell is guided to the back through laser drilling to increase the effective light area on the front. The back is coated with a passivation film, and the inside of the hole and the back pass through A layer of protective film is used to protect the front electrode leading to the back and the aluminum back field on the back to reduce leakage, and this film is grooved by laser before printing, which can increase the contact between the aluminum back field and the silicon wafer substrate. At the same time, it can also play a certain role in light reflection. The method can use less equipment investment, and greatly improve the conversion efficiency of the crystalline silicon battery, and compared with the conventional perforated battery, the leakage value and leakage rate are lower, and the yield is higher.

Description

A kind of preparation method of rear contact crystalline silicon solar cell with back passivation

technical field

The invention relates to a method for manufacturing a solar cell, in particular to a method for manufacturing a back-passivated back-contact silicon solar cell.

Background technique

With the rapid development of photovoltaic solar cell technology in recent years, especially under the leadership of the national photovoltaic leader plan, the efficiency of polycrystalline silicon cells with traditional structures has reached 18.8%, and that of monocrystalline cells has reached 20.4%. What is more prominent than the conventional one is the back-contact battery with the positive and negative electrodes of the battery on the same side on the basis of the improvement of the traditional process. Compared with the traditional crystalline silicon battery, the efficiency is improved by 0.5%, but it is limited by its own Compared with the traditional battery, the electrode is only led to the back, and it itself is the same as the traditional structure of the battery, there is not much room for improvement, and due to the characteristics of its own perforated structure, the leakage is not easy to control, and in the square resistance As high as 100Ω/□ (□ is a measurement unit in the technical field) and the efficiency cannot be improved by further increasing the square resistance, how to improve the conversion efficiency, reduce the leakage ratio and improve the yield becomes difficult become more and more important.

Contents of the invention

In order to overcome the shortcomings of the above-mentioned prior art and be compatible with the traditional technology, it is possible to further improve the conversion efficiency significantly on the basis of the traditional perforated battery technology, and without making major changes to the traditional perforated battery technology, the present invention provides a compatible It is a manufacturing method with good performance and mass production at low cost. It includes in turn: laser drilling, texturing, diffusion, etching, coating the back passivation film, coating the back protective film, coating the front anti-reflection film, laser slotting, screen printing, and sintering steps. Compared with conventional perforated batteries, It only needs to combine the steps of back passivation, back protective layer plating, and laser grooving to achieve a much higher efficiency than conventional perforated cells, and there are few additional equipment. The leakage is lower and easier to control, which is suitable for the upgrade of conventional perforated battery production lines.

In order to solve the above-mentioned technical problems, a technical solution adopted in the present invention is: a method for preparing a rear contact silicon solar cell with passivation on the back, comprising the following steps:

(1) Use a laser to drill holes on the surface of the silicon wafer;

(2) Carry out texturing to the silicon chip after punching, remove surface damage layer, and prepare the textured structure that reduces front surface reflectivity;

(3) Diffusion to prepare a PN junction under high temperature conditions, and prepare a PN junction near the back of the hole;

(4) Carry out edge etching, phosphorus silicon glass removal, and acid and alkali resistant film treatment to the diffused PN junction, wherein, a layer of acid and alkali resistant protective film can also be printed before edge etching;

(5) Prepare an aluminum oxide passivation layer on the back of the battery, prepare 1-4 layers of protective film, and prepare an anti-reflection film on the front;

(6) Use a laser to carve grooves on the back protection layer away from the hole area;

(7) prepare back electrode, aluminum back electric field, front electrode by screen printing, and dry;

(8) Sintering at high temperature to form a good ohmic contact

In a preferred embodiment of the present invention, backside acid polishing or alkali polishing can also be used in step 4.

In a preferred embodiment of the present invention, the passivation layer in step 5 can also be silicon dioxide, with a thickness of 5-20nm, and the protective layer is 1-4 layers, with a thickness of 50-200nm, and its main material is pure or combined Silicon nitride, silicon dioxide, titanium dioxide, amorphous silicon and other materials that cannot be penetrated by silver paste, aluminum paste, etc., the preparation sequence of the protective film layer and the anti-reflection film layer is not in particular order.

In a preferred embodiment of the present invention, in step 6, a laser is used to perform local grooving on the area more than 2mm away from the center of the hole, which can be divided into square, circular, strip and other groove shapes.

In a preferred embodiment of the present invention, if an acid and alkali resistant protective film is printed in step 4, step 7 can directly print a conductive paste with a penetrating passivation layer for printing.

In a preferred embodiment of the present invention, if no acid and alkali resistant protective film is printed in step 4, the conductive paste that does not penetrate the passivation layer is printed in step 7.

The beneficial effects of the present invention are: the present invention provides a method for preparing a back-passivated back-contact crystalline silicon solar cell, which overcomes the deficiencies of the prior art and is compatible with the traditional process, making it further larger on the basis of the traditional perforated cell process. It is possible to greatly improve the conversion efficiency without making major changes to the traditional perforated battery process.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings that need to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative work, wherein:

Figure 1 is a cross-sectional view of a conventional back contact battery;

Fig. 2 is a structural sectional view of a back passivated back contact battery according to Example 1 of the present invention

Figure 3 is a cross-sectional view of another back-passivated back-contact cell structure according to Example 2 of the present invention

The marks of the components in the drawings are as follows: 1. The back electrode connected to the front and back, 2. The front sub-gate electrode,

3. Silicon nitride reflective layer, 4. Diffused inversion n-type silicon, 5. P-type silicon, 6. Aluminum back field, 7. Back electrode, 8 and 9 are both back passivation layers.

detailed description

The following will clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Embodiment 1 of the present invention comprises:

A method for preparing a back contact crystalline silicon solar cell with passivation on the back, comprising the following steps:

(1) Use a laser to drill holes on the surface of P-type polysilicon wafers. The diameter of the holes is 0.1-0.5mm. , equal quantity multiplication (such as 5 * 5 or 6 * 6) form to punch, also can punch with the form of unequal distance, unequal quantity multiplication (such as 5 * 6 or 6 * 8).

(2) Use a chemical mixed solution of HF+HNO3=1:4 to make texture on the perforated silicon wafer. The corrosion weight is 0.15-0.45g. At the same time, the damaged layer on the surface is removed, and the texture that reduces the reflectivity of the front surface is prepared. surface structure.

(3) Use POCl3 to diffuse at 800-840°C to prepare a PN junction, and prepare a PN junction near the center and back of the hole, with a square resistance of 40-150Ω/□. During diffusion, the PN junction can be diffused on both sides of a single chip, and also Two pieces can be put together back to back for single-sided diffusion PN junction.

(4) Cover the hole area on the back with an acid and alkali resistant film with a diameter of 1-5mm.

(5) Use chemical cleaning on the diffused PN junction to remove the edge PN junction and remove the phosphosilicate glass on the surface, and at the same time use KOH or HF alone to remove the acid and alkali resistant film during the process.

(6) Prepare a 5-20nm aluminum oxide layer on the entire back of the battery, including the holes, and finally prepare a 50-200nm thick silicon nitride protective layer on the back and inside the holes, and finally continue to deposit a layer of 60-nm thick on the front. 90nm silicon nitride.

(7) Groove the protective layer on the back surface away from the hole region by using a laser, and divide it into several square grooves with equal intervals of 10mm×10mm and a depth of 80-110nm.

(8) Screen print a layer of conductive paste with penetrating effect in and around the hole on the back and dry it, then print a layer of aluminum back electric field and dry it (excluding the hole area), and finally print the front electrode.

(9) High-temperature sintering in a sintering furnace at 200-900°C to form a good ohmic contact, and then test.

Under the conditions of AM1.5 and 25°C, the open circuit voltage Voc, short circuit current Isc, fill factor FF, conversion efficiency Eff, and reverse leakage IRev2 are measured. The comparison data are as follows:

category Voc Isc FF Eff IRev2 IRev2>1 ratio conventional plan 0.633 9.515 79.79 19.10% 0.296 0.85% this invention 0.641 9.604 79.98 19.61% 0.284 0.81%

In this embodiment, compared with the traditional polycrystalline back contact cell with a conversion efficiency of about 19.1%, its conversion efficiency can reach about 19.6%, and the conversion efficiency has increased by 0.5%. , the leakage values are not much different, and there is almost no difference in the leakage ratio.

In this embodiment, the conversion efficiency is increased by 0.5% compared with the conventional back contact cell.

Embodiment 2 of the present invention includes:

A method for preparing a back contact crystalline silicon solar cell with passivation on the back, comprising the following steps:

(1) A laser is used to drill a hole on the surface of the P-type single crystal silicon wafer, and the diameter of the hole is 0.1-0.5 mm.

(2) Texturing the perforated silicon wafer.

(3) Use POCl3 to diffuse at 800-840°C to prepare a PN junction. A PN junction is also prepared near the center and back of the hole, with a square resistance of 40-150Ω/□. Two pieces are placed back to back to form a single-sided diffusion PN junction.

(4) Use chemical cleaning on the diffused PN junction to remove the edge PN junction and remove the phosphosilicate glass on the surface.

(5) Prepare an 8nm aluminum oxide layer on the entire back of the battery, including the holes, and then continue to deposit a layer of silicon nitride with a thickness of 75nm on the front, and finally prepare a silicon nitride protective layer with a thickness of 130nm on the back and the holes.

(6) Use a laser to scribing other areas 2 mm away from the hole area.

(7) Screen print a layer of conductive paste without penetrating effect in and around the hole on the back and dry it, then print a layer of aluminum back electric field and dry it, excluding the hole area, and finally print the front electrode.

(8) High-temperature sintering in a sintering furnace at 200-900°C to form a good ohmic contact, and then test.

Under the conditions of AM1.5 and 25°C, the open circuit voltage Voc, short circuit current Isc, fill factor FF, conversion efficiency Eff, and reverse leakage IRev2 are measured. The comparison data are as follows:

category Voc Isc FF Eff IRev2 IRev2>1 ratio conventional plan 0.638 9.682 79.71 20.33% 0.197 0.8% this invention 0.653 9.917 79.92 21.37% 0.101 0.3%

In this embodiment, compared with the traditional single crystal back contact cell with a conversion efficiency of 20.3% and a leakage ratio of about 0.8%, the conversion efficiency can reach 21.37%, the leakage rate is 0.3%, and the conversion efficiency is increased by about 1%, and The leakage ratio has been reduced by 0.5%.

The above-mentioned embodiments are only to illustrate the technical features and ideas of the present invention. The main purpose of the present invention is to allow those who understand this technology to understand the content of the invention and implement it according to the above embodiments, and are not intended to limit the protection scope of the present invention. Any equivalent change or modification made according to the spirit of the present invention belongs to the protection scope of the present invention.

Claims (6)

1. the preparation method of the back contacts crystal silicon solar batteries of a kind of passivating back, it is characterised in that comprise the following steps：

（1）Punched using laser in silicon chip surface；

（2）Making herbs into wool is carried out to the silicon chip after punching, removes surface damage layer, and prepares the matte knot for reducing front-side reflectivity Structure；

（3）The hole back side is nearby also prepared upper PN junction by diffusion for the PN junction that one layer of sheet resistance is 40-150 under the high temperature conditions；

（4）Etching edge is carried out to the PN junction after diffusion, goes phosphorosilicate glass to handle, wherein, can also first it be printed before PN junction is removed Brush one layer of acid and alkali-resistance mask；

（5）Cell backside prepare 5-20nm alumina passivation layer, the protection film layer for preparing 1-4 layer total thicknesses 50-200nm again, Front prepares 60-90nm silicon nitride antireflection layer；

（6）Cutting is carried out to protection film layer using laser；

（7）Silk-screen printing prepares back electrode, aluminum back electric field, front electrode, and dries；

（8）Sintered under high temperature, form good Ohmic contact.

2. the preparation method of the back contacts crystal silicon solar batteries of passivating back according to claim 1, its principal character It is：The hole that some diameters are less than 2mm is distributed with positive and negative electrode in the same face, silicon chip, and positive conductive electrode is in Between hole extend through the back side.

3. the preparation method of the back contacts crystal silicon solar batteries of passivating back according to claim 1, its principal character It is：Back side acid polishing or alkali polishing can be also used during the step 4 of the claim 1.

4. the preparation method of the back contacts crystal silicon solar batteries of passivating back according to claim 1, its principal character It is：Passivation layer in the step 5 of the claim 1 can also be silica, thickness 5-20nm, the back-protective film layer For 1-4 layers, gross thickness 50-200nm, its main material is simple or combination silicon nitride, silica, titanium dioxide, The material that non-crystalline silicon etc. can not be penetrated by conductive silver slurry and aluminum conductive electric slurry, the preparation order of protection film layer and antireflection layer is not Successively.

5. the preparation method of the back contacts crystal silicon solar batteries of passivating back according to claim 1, its principal character It is：Or afterwards can be using laser etc. to the area away from more than hole center 2mm during the step 5 of the claim 1 Domain carries out differential trench open processing, can be divided into 1-20mm square, diameter 1-20mm circle, 0.1 ~ 10mm of width bar line etc. Shape.

6. the preparation method of the back contacts crystal silicon solar batteries of passivating back according to claim 1, its principal character It is：In the case of not having any acid and alkali-resistance film protection in the step 4 of the claim 1, printing in step 7 does not have and worn The electrocondution slurry of saturating protective layer.