TW201630201A - Nano silicon boron slurry and method for preparing PERL solar battery by utilizing nano silicon boron slurry - Google Patents

Abstract

The invention discloses nano silicon boron slurry and a method for preparing a PERL solar battery by utilizing the nano silicon boron slurry and a PERL battery structure. A silk screen printing technology which is suitable for the industrialized mass production is adopted, the nano silicon boron slurry is printed on the surface of a silicon chip, and the local boron diffusion is completed by virtue of high temperature diffusion or laser doping process route. A boron tribromide gas diffusion source with high toxicity is avoided, and the corresponding complicated technological procedures such as masking, etching, washing and the like for realizing the local boron diffusion is avoided. Compared with a produced PERC battery, the upgrading of the PERC battery can be completed, and the battery efficiency can be improved by only adding a printer and a drying furnace to the production process of the PERL battery.

Description

Nano bismuth boron paste and method for preparing same for PERL solar battery

The invention belongs to the field of nano materials, and particularly relates to a nano-boron-boron slurry and a method thereof for preparing a PERL solar battery.

At present, the efficiency of ordinary P-type crystal germanium solar cells is usually less than 20%. Currently, a PERC battery with an efficiency higher than 20% is out of the laboratory.

Different from ordinary P-type batteries, the key to PERC batteries is back passivation and point contact. Typically, one or more dielectric films are deposited on the back side of the cell to passivate the back surface of the wafer. There are two main functions of the passivation film: one, the dangling bond of the helium atom on the surface of the saturated breeze; and the second, establish a surface electric field. Thereby, the surface recombination rate of minority carriers is reduced, and the photoelectric conversion efficiency is improved. The passivation film is generally an insulator. In order to export the current to the battery, the PERC battery is usually laser-blasted to form a hole having a diameter of about 40 μm, and then the aluminum paste is poured into the hole, and the aluminum paste is sintered to form an aluminum electrode and come into contact with the ruthenium. . Since the contact surface is small, it is called a point contact.

As shown in Fig. 1, 1 is a ruthenium, usually a P-type ruthenium; 2 is a first passivation film, usually Al ₂ O ₃ or SiO ₂ ; 3 is a second passivation film, usually SiNx; It is an aluminum electrode, usually sintered by aluminum paste; 5 is a contact point (ie, at the opening of the passivation film).

The preparation of the contact points 5 is generally carried out by sintering the front and back electrodes. The sintering temperature is usually as high as 830 ° C, which is much higher than the yttrium aluminum eutectic temperature of 577 ° C. When the sintering temperature rises to the eutectic eutectic, the bismuth and aluminum at the contact point 5 are eutectic, and the ruthenium overflows the passivation film along the opening and diffuses to the surrounding aluminum electrode 4. During the cooling process, when the temperature falls to the eutectic eutectic precipitation, a part of the overflowed ruthenium remains in the aluminum electrode 4, causing a void at the contact point 5. Poor aluminum contact, battery efficiency is impaired.

The object of the present invention is to provide a nano bismuth boron paste and a method thereof for preparing a PERL solar cell, which can solve the problem of poor contact often occurring in a PERC battery, improve battery efficiency, and upgrade the PERC battery to a PERL battery.

Meanwhile, the present invention discloses a structure of a PERL solar cell.

In order to achieve the above object, the present invention adopts the following technical scheme: a nano-boron-boron slurry characterized by containing 10 to 50 parts of nano-powder powder, 20 to 100 parts of solvent, and 0 to 20 parts by weight. The additive has a particle size of 10 to 200 nm; wherein the nano-powder powder contains elemental boron or a boron compound or a mixture of the two, and the composition thereof is 50-100 parts of hydrazine, 0.05-50 parts of boron, and 0. - 50 parts of a boron compound; the boron compound contains lanthanum boride or boron trioxide or a mixture of the two.

Preferably, the solvent is terpineol, or sandalwood or a mixture of the two, the mixture is 0-80 parts of terpineol and 20-100 parts of sandalwood; and the additive is ethyl cellulose.

Process route 1: using laser processing method

The method for preparing a PERL solar cell by using the nano-boron-boron slurry as described above comprises the following steps: 1. cleaning the flock by bracts; 2, diffusing POCl ₃ , preparing an emitter; 3. cleaning the back surface, polishing; a back deposited Al ₂ O ₃ passivation film; 5, a double-sided deposition of SiNx film, 6, a printed aluminum paste / silver paste; 7, a sintered aluminum paste / silver paste; characterized in that after the step 5, before step 6, Printing and drying the nano-boron-boron slurry on the back surface of the enamel film. When printing, the nano-boron-boron slurry is completely covered on the back surface of the enamel sheet or partially covered on the back surface of the enamel sheet. After the drying is completed, the nano-boron boron is dried. The slurry is subjected to laser treatment.

Preferably, the process parameters for laser treatment of the nano-boron boron paste are: laser wavelength is 532 nm, laser power is 10-100 w, frequency is 0.1-50 MHz, scanning speed is 1-50 m/s, spot size is 1 -200um.

Process route 2: using high temperature processing method

The method for preparing a PERL battery by using the nano-boron-boron slurry as described above comprises the following steps: 1. front side flocking of the bract sheet, back side polishing; 2, POCl ₃ diffusion, preparing an emitter; 3. cleaning the phosphorous bismuth glass 4, a back deposited Al ₂ O ₃ passivation film; 5, double-sided deposition of SiNx film; 6, laser opening through the passivation film, 7, printing aluminum paste / silver paste; 8, sintered aluminum paste / silver paste; The method is characterized in that, after the step 1 and before the step 2, the nano-boron-boron paste is printed on the back surface of the cymbal sheet, covered with a full cover on the back surface of the cymbal sheet or partially covered, and after drying, the nano-n-boron syrup is applied. High temperature treatment.

Preferably, the high temperature treated nano bismuth boron paste is carried out in an industrial tube diffusion furnace at a temperature ranging from 900 to 1050 ° C for a period of from 1 to 2 hours.

Preferably, in the above process route 1 and the process route 2, after the printing of the nano-boron-boron slurry is completed, drying in an industrial infrared drying oven, the drying temperature is 100-200 ° C, and the drying time is 1 ~5 minutes.

The PERL solar cell obtained by using the above process route 1 or process route 2 is characterized in that an Al ₂ O ₃ passivation film and a SiNx passivation film are sequentially deposited on the back surface of the ruthenium, and a metal electrode is printed on the SiNx passivation film. Slurry. The metal electrode penetrates the Al ₂ O ₃ passivation film and the SiNx passivation film by sintering. A metal electrode is brought into contact with the cymbal at the opening, the opening being filled with a nano boring slurry, and the cymbal is a P-shaped cymbal.

Preferably, the metal electrode at the opening is an aluminum electrode, and the metal electrode at the non-opening is an aluminum electrode or a silver electrode.

Preferably, the metal electrode at the opening is a silver electrode, and the metal electrode at the non-opening is an aluminum electrode.

Preferably, during the high temperature or laser treatment, the boron is diffused into the interior of the crucible, and the crucible at the opening forms a P+ region, and the boron concentration of the P+ region is equal to or greater than the P-type. The boron concentration of the bracts. The boron concentration of the P+ region is between 2*10 ²⁰ -5*10 ²¹ atm/cm ³ .

Principle description:

After the high temperature or laser treatment, the nano bismuth boron paste forms a crystal ruthenium and fills the opening of the passivation film to prevent voids from forming at the contact point of the yttrium aluminum, thereby solving the problem of poor contact often occurring in the PERC battery. On the other hand, boron diffuses into the interior of the crucible during high temperature or laser processing, and a P+ region is formed at the opening of the passivation film. Since the boron concentration in the P+ region is much higher than the boron concentration in the P-type germanium, a chemical shift is generated, forming a so-called local boron back field. The barrier established by the boron back field prevents photo-generated carriers from migrating to the opening of the passivation film and recombination is consumed. In short, the formation of boron back field directly upgrades PERC to PERL to achieve battery efficiency improvement.

Advantages of the invention:

The traditional PERL battery structure is completed by a boron tribromide diffusion process, and the process involves a series of mask processes, cleaning processes, high temperature processing processes, complicated processes, high production costs, and boron tribromide is a very dangerous The highly toxic chemicals limit industrial mass production. The invention adopts the simplest and suitable industrialized mass-produced screen printing technology to print the nano-boron-boron paste on the surface of the enamel sheet, and completes the boron diffusion in the P+ region by a high-temperature diffusion or laser doping process route. Nano bismuth paste is non-toxic and environmentally friendly. Screen printing technology directly prints the boron source to the desired boron diffusion region, avoiding the diffusion of gaseous source (boron tribromide). The mask and cleaning process in the process. Compared with the PERC battery, you only need to increase the printing press and drying oven to complete the PERL upgrade. The process of the invention has simple process and low cost.

1‧‧‧ Picture

2‧‧‧Al ₂ O ₃ passivation film

3‧‧‧SiNx passivation film

4‧‧‧Aluminum electrode

5‧‧‧Contact point/passivation film opening

6‧‧‧Nano-boron

7‧‧‧P+ District

1 is a schematic partial structural view of a back surface of a PERC battery; FIG. 2 is a partial structural view of a back surface of a PERL battery according to the present invention; FIG. 3 is a flow chart of a process route 1 of the present invention; and FIG. 4 is a process route of the present invention. The flow chart of the second.

The following embodiments further illustrate the technical solutions of the present invention.

Example 1: According to process route 1, as shown in Figure 3:

(1) According to the normal PERC battery preparation process, the following processes are completed: 1. Flocking and cleaning flocking; 2. POCl ₃ diffusion preparation of emitter; 3. Cleaning, backside polishing; 4. Backside deposition of Al ₂ O ₃ passivation film; , double-sided deposition of SiNx film;

(2) The nano-boron boron paste is locally printed on the passivation film after the (1) process by using a screen printing device; the composition of the nano-boron-boron slurry is: 80 parts of sandalwood and 20 parts of nano-powder powder, Nai Rice bran has an average particle size of 50 nm and a boron content of 5%. The printed pattern of the boron paste is a set of side squares which are evenly arranged parallel to the edge of the cymbal, and have a side length of 100 um and an adjacent margin of 500 um. The thickness of the boron paste is 2.5 um.

(3) The printed slab is dried in an industrial infrared drying oven at a drying temperature of 150 ° C and a drying time of 5 minutes.

(4) Laser treatment of the nano-boron-impregnated area with a nanosecond laser. The spot of the laser beam focused on the surface of the cymbal is 50 um, the wavelength is 532 nm, the power is 45 W, and the frequency is 500 kHz. The speed is 8m/s.

(5) Printing the silver paste on the front side of the aluminum paste on the back side of the slab, printing the silver paste, sintering, and completing the preparation of the PERL battery.

The partial structure of the back surface of the prepared PERL battery is as shown in Fig. 2: the crucible 1 is a P-type 156 x 156 cm, a CZ crucible, a thickness of 180 um, and a resistivity of 1.2 Ω-cm. After the laser treatment in step (4), the nano bismuth boron paste 6 is passed through a thickness of 8 nm of the Al ₂ O ₃ passivation film 2 and a thickness of 75 nm of the SiNx passivation film 3 and the ruthenium film is integrated into the nano bismuth boron paste. 6 The local average thickness is about 1 um. At the same time, the concentration of boron in the P+ region 7 formed during the laser treatment was reduced from the highest concentration of the surface 2*10 ²¹ atm/cm ³ to the substrate value of the ruthenium sheet. The P+ region 7 has a thickness of about 12 um. The corresponding laser doping square resistance is usually less than 10 Ω / _□ . Due to the nano bismuth boron paste 6 and the P+ region 7, the aluminum electrode 4 forms a good contact with the cymbal sheet 1.

Example 2: According to process route 2, as shown in Figure 4:

(1) Finishing the front side of the crepe and polishing the back surface according to the normal PERC battery preparation process;

(2) The nano-boron boring paste is locally printed on the back surface of the crepe after the process of (1) by means of a screen printing device, that is, the polished surface; the composition of the nano bismuth boron paste is: 70 parts of sandalwood, 9 parts of pine oil Alcohol, 1 part ethyl cellulose, 20 parts of nano bismuth powder, nano bismuth has an average particle diameter of 70 nm and a boron content of 8%. The printed boron paste is a set of side square patterns arranged in parallel with the edges of the cymbals, with a side length of 100 um and a margin of 500 um.

(3) The printed enamel film is dried in an industrial infrared drying oven at a drying temperature of 170 ° C and a drying time of 4 minutes.

(4) The step (3) ruthenium was subjected to high-temperature diffusion under an atmosphere of 20% oxygen and 80% nitrogen using an industrial tube type diffusion furnace at a temperature rising rate of 1 ° C / min, and a diffusion temperature and time of 960 ° C and 1.5 hours, respectively.

(5) Complete the following processes according to the normal process: 1. Prepare the emitter by POCl ₃ diffusion; 2. Clean the phosphorous glass; 3. Deposit the Al ₂ O ₃ passivation film on the back side; 4. Deposit the SiNx film on both sides; 5. In the boron paste The coverage area is subjected to laser opening through the passivation film, 6. printing aluminum paste/silver paste; 7. sintering aluminum paste/silver paste; completing cell sheet production.

(6) The partial structure of the back surface of the PERL battery after the fabrication was completed was basically the same as that of the first embodiment. The main difference is that boron in the P+ region 7 has a lower surface concentration and a thinner thickness on the ruthenium sheet. The difference is reflected in the corresponding square resistance value of 35Ω / _□ , which is higher than the square resistance of the laser processing.

Example 3: According to process route 1, as shown in Figure 3:

(1) According to the normal PERC battery preparation process, the following processes are completed: 1. Flocking and cleaning flocking; 2. POCl ₃ diffusion preparation of emitter; 3. Cleaning, backside polishing; 4. Backside deposition of Al ₂ O ₃ passivation film; , double-sided deposition of SiNx film;

(2) The nano-boron boron paste is locally printed on the passivation film after the (1) process by using a screen printing device; the composition of the nano-boron-boron slurry is: 60 parts of sandalwood, 19 parts of terpineol, and 1 part. Ethyl fiber And 20 parts of nano-powder powder, the average particle size of nano-nose is 70 nm, and the boron content is 3%. The printed pattern of the boron paste is a set of side squares which are evenly arranged parallel to the edge of the cymbal, and have a side length of 100 um and a margin of 500 um. The boron paste printing thickness is 3.5 um.

(3) The printed slab is dried in an industrial infrared drying oven at a drying temperature of 200 ° C and a drying time of 3 minutes.

(4) Laser treatment of the nano-boron-impregnated area with a nanosecond laser, the spot of the laser beam focused on the surface of the cymbal is 50um, the wavelength is 532nm, the power is 15w, the frequency is 1000KH, scanning The speed is 8m/s.

(5) Printing silver paste on the front side of the aluminum paste on the back side of the conventional process, sintering, and completing the preparation of the PERL battery.

The partial structure of the back surface of the PERL battery after the production was completed was substantially the same as that of the first embodiment. The difference is that the local average thickness of nano-boron boron paste 6 is about 1.3 um; the highest concentration of boron in P+ region 7 is 5*10 ²⁰ atm/cm ³ , the thickness of P+ region 7 is about 10 um, and the square resistance value is about 15 Ω/□. .

Performance Testing:

The electrical performance tests of the above three embodiments and conventional PERC batteries are as follows:

The PERL cell of the example utilizes local boron doping with nano-boron boring to form a P+ layer at the opening of the passivation film as compared to a conventional PERC cell structure. The formation of the P+ layer effectively repairs the damage caused by the opening of the passivation film, enhances the passivation effect, and improves the open circuit voltage of the battery. At the same time, the P+ layer significantly improves the metal electrode contact and improves the fill factor and current of the battery. Improve battery conversion efficiency. In addition, the process route 1 has a substantially uniform effect compared to the process route 2, confirming the superiority of the nano bismuth boron paste and PERL battery structure disclosed in the present invention.

It should be noted that the above description is only for the purpose of explaining the preferred embodiments of the present invention, and is not intended to limit the invention in any way, so that the invention is made in the spirit of the same invention. Any modifications or alterations are still intended to be included in the scope of the invention.

1‧‧‧ Picture

2‧‧‧Al ₂ O ₃ passivation film

3‧‧‧SiNx passivation film

4‧‧‧Aluminum electrode

5‧‧‧Contact point/passivation film opening

6‧‧‧Nano-boron

7‧‧‧P+ District

Claims (11)

The invention relates to a nano bismuth boron syrup, which comprises 10 to 50 parts of nano bismuth powder, 20 to 100 parts of solvent and 0 to 20 parts of additives according to a weight ratio, and the nano bismuth has a particle diameter of 10 to 200 nm. Wherein the nano-powder powder contains elemental boron or a boron compound, or a mixture of elemental boron and a boron compound, and has a composition of 50-100 parts of hydrazine, 0.05-50 parts of boron, and 0-50 parts of a boron compound; The compound contains lanthanum boride or boron trioxide or a mixture of the two. The nano-boron-boron slurry according to claim 1, wherein the solvent is terpineol or sandalwood or a mixture of the two, and the mixture is 0-80 parts of terpineol and 20-100. Sandalwood; the additive is ethyl cellulose. A method for preparing a PERL solar cell, which comprises applying the nano-boron-boron slurry according to the first or second aspect of the patent application, the method comprising the steps of: 1. cleaning the flocking of the breeze; 2, diffusing the POCl ₃ , Preparing an emitter; 3. Cleaning the back surface, polishing; 4. Depositing an Al ₂ O ₃ passivation film on the back surface; 5. Depositing a SiNx film on both sides; 6. Printing an aluminum paste/silver paste; 7. Sintering aluminum paste/silver paste; After the step 5 and before the step 6, the nano-boron-boron paste is printed and dried on the back surface of the enamel sheet, and the nano-boron-boron slurry is completely covered on the back surface of the enamel sheet or partially covered in the printing. The back surface of the slab is subjected to laser treatment after the drying is completed. The method for preparing a PERL solar cell according to the third aspect of the invention, wherein the process parameters for performing laser treatment on the nano-boron-boron slurry are: a laser wavelength of 532 nm, a laser power of 10-100 w, and a frequency. 0.1-50MHz, scanning speed 1-50m / s, spot size 1-200um. A method for preparing a PERL solar cell, which comprises applying the nano-boron-boron slurry according to claim 1 or 2, the method comprising the steps of: 1. front flocking of the bracts, back polishing; 2, POCl ₃ diffusion, preparation of emitter; 3, cleaning of phosphorous glass; 4, deposition of Al ₂ O ₃ passivation film on the back; 5, double-sided deposition of SiNx film; 6, laser opening through the passivation film; 7, printing aluminum paste / a silver paste; 8. a sintered aluminum paste/silver paste; wherein, after the step 1 and before the step 2, the nano-boron-boron paste is printed on the back side of the bract, with full coverage on the back of the bract or After partial coverage, after drying, the nano-boron boron paste is subjected to high temperature treatment. The method for preparing a PERL solar cell according to claim 5, wherein the high-temperature treatment nano-boron-boron is carried out in an industrial tube diffusion furnace at a temperature ranging from 900 to 1050 ° C for a period of 1-2 hours. . The method for preparing a PERL solar cell according to the third or fifth aspect of the invention, wherein after the printing of the nano-boron-boron slurry, drying in an industrial infrared drying oven, the drying temperature is 100. ~200 ° C, drying time is 1 to 5 minutes. A PERL solar cell prepared by the method according to any one of claims 3 to 7, wherein the PERL solar cell is sequentially deposited with an Al ₂ O ₃ passivation film and SiNx passivation on the back side of the ruthenium sheet. Membrane printing and sintering a metal electrode on the SiNx passivation film, the metal electrode forming a point contact with the cymbal through an opening through the Al ₂ O ₃ passivation film and the SiNx passivation film, The opening is filled with nano-boron boring, and the cymbal is a P-shaped cymbal. The PERL solar cell of claim 8, wherein the metal electrode at the opening is an aluminum electrode, and the metal electrode at the non-opening is an aluminum electrode or a silver electrode. The PERL solar cell of claim 8, wherein the metal electrode at the opening is a silver electrode, and the metal electrode at the non-opening is an aluminum electrode. The PERL solar cell of claim 8, wherein the boron nitride slurry is diffused into the interior of the crucible during the high temperature or laser treatment, and the opening is The bracts form a P+ zone having a boron concentration greater than or equal to the boron concentration of the P-type bracts.