CN102176474A - N-type solar battery prepared by film masking process of one multi-purpose film and preparation method of N-type solar battery - Google Patents

Abstract

The invention relates to the field of N-type solar cells, in particular to an N-type solar cell prepared by a multi-purpose mask method and a preparation method thereof. The N-type solar cell is: with n-type Czochralski single crystal silicon as the substrate, the back of the silicon wafer is a P-type emitter junction prepared by boron diffusion covered with _SiO2 and SiNx double-layer passivation film, and the front of the silicon wafer is made of phosphorus The front surface field prepared by diffusion is covered with a passivation and anti-reflection film. The method of preparing the N-type solar cell is: using n-type Czochralski monocrystalline silicon as the substrate, firstly preparing a P-type emitter junction by boron diffusion, and then etching off the front P-type emitter junction, and the P-type emitter junction on the back of the silicon wafer. The SiO ₂ thin film is made on the junction, the SiO ₂ thin film is not only a mask for the subsequent phosphorus diffusion to prepare the front surface field, but also a passivation film for the P-type emitter junction, and finally the front surface field is prepared by phosphorus diffusion. The invention has the beneficial effects of simple process, easy control, low cost and high photoelectric conversion efficiency.

Description

N-type solar cell prepared by one-film multi-purpose mask method and preparation method thereof

technical field

The invention relates to the field of N-type solar cells, in particular to an N-type solar cell prepared by a multi-purpose mask method and a preparation method thereof.

Background technique

At present, the crystalline silicon solar cells produced by major domestic solar energy companies are all p-type silicon substrates, but due to the high resistance of n-type silicon substrates to impurities and no problem of light-induced attenuation, theoretically higher efficiency can be achieved , In fact, Germany, the United States, Japan and other developed countries attach great importance to renewable energy, especially solar energy resources, and have made great breakthroughs in the research and production of n-type solar cells. For example, the German Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE) announced that the solar cells developed by the institution based on n-type monocrystalline silicon have a conversion efficiency of 23.4%. The n-type back-contact solar cell of Sunpower Corporation of the United States has a maximum efficiency of 24.3%, and it has been mass-produced for many years. In addition, the HIT cell of Japan Sanyo Corporation has a conversion efficiency of 23%, and has been mass-produced. However, the above n The process of solar cells is complicated and the cost is high. In this situation, it is of great significance to study and produce N-type crystalline silicon solar cells suitable for mass production.

Contents of the invention

The technical problem to be solved by the present invention is to provide an N-type solar cell suitable for large-scale industrial production and a preparation method thereof.

The technical scheme adopted by the present invention to solve the technical problem is: an N-type solar cell prepared by a multi-purpose mask method, using n-type Czochralski monocrystalline silicon as the substrate, and the back side of the silicon wafer is covered with a passivation film The P-type emitter junction prepared by boron diffusion, the front surface of the silicon wafer is the front surface field prepared by phosphorus diffusion, and the front surface field is covered with a passivation and anti-reflection film.

The passivation film on the back of the silicon wafer is a double-layer passivation film of SiO2 and SiNx, and the SiNx passivation film is on the outer layer of the SiO2 film.

A method for preparing N-type solar cells with a multi-purpose mask method, using n-type Czochralski monocrystalline silicon as the substrate, firstly preparing a P-type emitter junction through boron diffusion, and then etching off the front P-type emitter junction. A SiO2 thin film is fabricated on the P-type emitter junction on the back of the silicon wafer. The SiO2 thin film is not only a mask for the subsequent phosphorus diffusion to prepare the front surface field, but also a passivation film for the P-type emitter junction. Finally, the front surface field is prepared by phosphorus diffusion. The invention has the beneficial effects of simple process, easy control, low cost and high photoelectric conversion efficiency.

Description of drawings

Below in conjunction with accompanying drawing and embodiment the present invention is further described;

Fig. 1 is a schematic view of the battery structure of the present invention;

In the figure, 1. substrate, 2. P-type emitter junction, 3. front surface field, 4. SiO2 film, 5. SiNx passivation film, 6. SiNx film.

Detailed ways

As shown in Figure 1, an N-type solar cell prepared by a multi-purpose mask method uses n-type Czochralski monocrystalline silicon as the substrate 1, and the back side of the silicon wafer is covered with a double-layer passivation film of SiO2 and SiNx The P-type emitter junction 2 prepared by boron diffusion, the SiNx passivation film 5 in the outer layer of the SiO2 film 4 in the double-layer passivation film. The front surface of the silicon wafer is a front surface field 3 prepared by phosphorus diffusion, and the front surface field 3 is covered with a passivation and anti-reflection film.

Specifically, this is achieved:

a) The surface of the n-type Czochralski monocrystalline silicon wafer forms a positive pyramid textured structure to reduce reflection;

b) P-type emitter junction 2 is prepared by a boron diffusion source, and the sheet resistance is 20-150 ohm/Sq;

c) Etching off the front P-type emitter junction with acid mixture or laser or corrosive slurry;

d) HF acid removes BSG;

e) growing the SiO2 thin film 4 by thermal oxidation method, or depositing the SiO2 thin film 4 on one side by CVD, and the thickness of the SiO2 thin film 4 is 100-400nm. When growing SiO2 thin film 4 by thermal oxidation method, it is necessary to etch the SiO2 thin film on the non-emitter surface with mixed acid etching solution or laser or corrosive slurry or plasma or other methods that can etch SiO2, and clean the etching reactant. The SiO2 film prepared by CVD single-sided deposition method does not require the step of etching the SiO2 film on the non-emitter side by mixing acid solution or laser or corrosive slurry or plasma or other methods that can etch SiO2;

f) SiO2 thin film 4 is used as the mask layer for phosphorus diffusion, the surface field 3 is prepared before the phosphorus diffusion source, and the sheet resistance is 10-150ohm/Sq;

g) Plasma etching to remove the PN junction formed at the edge of the silicon wafer;

h) HF acid cleaning to remove PSG and part of the SiO2 film 4, retaining 10-150nm SiO2 film 4 as the passivation film of the P-type emitter junction 2;

i) Deposit 10-100nm SiNx passivation film 5 between the refractive index 1.9-2.5 by PECVD method on the emitter surface;

j) Deposit 70-100nm SiNx film 6 with a refractive index of 1.9-2.5 by PECVD method for passivation and anti-reflection in the front surface field;

k) printing silver aluminum paste on the back;

l) drying;

m) Printing silver paste on the front side;

n) sintering.

Embodiment 1: Select an n-type Czochralski single-crystal silicon wafer with a crystal plane (100) and a doping concentration of 6Ωcm.

1. Silicon wafers undergo conventional surface cleaning and pyramidal surface texturing;

2. Prepare P-type emitter junction 2 with BBr3 liquid boron diffusion source, the diffusion temperature is 930°C, the time is 50min, and the sheet resistance is 60ohm/Sq;

3. Use RENA's post-cleaning machine to etch off the P-type emitter junction on the back and remove the BSG at the same time;

4. Growing SiO2 film 4 by thermal oxidation method as a mask layer, the thickness is 300nm;

5. Etching the SiO2 film on the non-emitter surface with corrosive slurry;

6. The surface field 3 before the preparation of POCl3 liquid phosphorus diffusion source, the diffusion temperature is 850°C, the time is 40min, and the sheet resistance is 40ohm/Sq;

7. Plasma etching to remove the edge PN junction;

8. Remove PSG and part of the SiO2 thin film 4 with 5% HF acid for 30s, and finally the thickness of the SiO2 thin film 4 is 20nm;

9. Deposit 60nm SiNx passivation film 5 with a refractive index of 2.05 by PECVD on the back;

10. Deposit 70-100nm SiNx film 6 with a refractive index greater than 2.25 on the front side;

11. Silver and aluminum paste printed on the back;

12. Drying;

13. Printing silver paste on the front side;

14. Sintering.

The efficiency of the battery sheet produced in this step is 18.1% after testing.

Claims (8)

1. A kind of N-type solar cell prepared by the multi-purpose mask method of one film, it is characterized in that: take n-type Czochralski monocrystalline silicon as substrate (1), the back side of silicon chip is to be covered with the boron diffusion preparation of passivation film A P-type emitter junction (2), the front surface of the silicon chip is a front surface field (3) prepared by phosphorus diffusion, and the front surface field (3) is covered with a passivation and anti-reflection film. 2. the N-type solar cell prepared by a kind of multi-purpose mask method of one film according to claim 1 is characterized in that: the passivation film on the back side of the silicon wafer is SiO2 and SiNx double-layer passivation film, SiNx The passivation film (5) is on the outer layer of the SiO2 film (4). 3. A method for preparing an N-type solar cell by a multi-purpose mask method, characterized in that: taking n-type Czochralski monocrystalline silicon as a substrate (1), at first preparing a P-type emitter junction (2) by boron diffusion, Then etch away the P-type emitter junction on the front side, and make SiO2 film (4) on the P-type emitter junction (2) at the back of the silicon wafer, and this SiO2 film (4) is the surface field (3) before the subsequent phosphorus diffusion preparation. The mask is also the passivation film of the P-type emitter junction (2), and finally the front surface field (3) is prepared by phosphorus diffusion. 4. the method for preparing N-type solar cell by a kind of multi-purpose mask method of one film according to claim 3 is characterized in that: its specific steps are: a) A textured structure is formed on the surface of the n-type Czochralski monocrystalline silicon wafer to reduce reflection; b) P-type emitter junction (2) is prepared by boron diffusion, and the sheet resistance is 20-150ohm/Sq; c) Etching off the P-type emitter junction on the front side; d) borosilicate glass; e) Fabricate SiO2 film (4) on the P-type emitter junction (2) on the back of the silicon wafer. This SiO2 film (4) is the mask of the surface field before the subsequent phosphorus diffusion preparation and the passivation of the P-type emitter junction. membrane; f) Surface field (3) before phosphorus diffusion preparation, sheet resistance is 10-150ohm/Sq; g) Remove the PSG and the PN junction formed at the edge; h) making a SiNx passivation film (5) on the emitter surface, and making a SiNx film (6) with passivation and anti-reflection effects on the front surface; i) Making grid lines. 5. According to claim 4, a method for preparing N-type solar cells by using a multi-purpose mask method with one film, is characterized in that: after the boron diffusion is completed, the front side is etched with mixed acid solution or laser or corrosive slurry P-type emitter junction. 6. according to claim 4, the method for preparing N-type solar cell by a multi-purpose mask method of one film is characterized in that: SiO2 thin film (4) is grown and formed by thermal oxidation method, must use mixed acid solution or laser Or corrosive slurry or plasma etching the SiO2 thin film on the non-emitter surface, the thickness of the SiO2 thin film (4) on the emitter surface is 100-400nm. 7. according to the method for preparing N-type solar cell by a kind of multi-purpose mask method of one film according to claim 4, it is characterized in that: SiO2 film (4) is formed by CVD mode single-sided deposition, and the SiO2 film on emitter face ( 4) The thickness is 100-400nm. 8. According to claim 4, 6 or 7, a method for preparing N-type solar cells by a multi-purpose mask method with one film is characterized in that: after phosphorus diffusion, PSG needs to be removed with low-concentration HF acid, while retaining P The SiO2 film (4) on the surface of the type emitter is used as a passivation film, and the remaining SiO2 film (4) has a thickness of 10-150nm.

Images