CN103594534B - Aluminum emitter stage back junction back contact crystalline silicon solar cell and manufacture method thereof - Google Patents

Abstract

The invention discloses an aluminum emitter back-junction back-contact crystalline silicon solar cell and a manufacturing method thereof. The passivation layer is covered outside the N-type doped layer on the back surface, and P-type doped layers are embedded at intervals on the N-type silicon substrate on the back surface. Embedded with the negative terminal of the battery. The manufacturing method includes the steps of texturing, doping layer making, opening, etching, cleaning, depositing, sintering and the like. The invention has the advantages of low cost and mass production.

Description

Aluminum emitter back junction back contact crystalline silicon solar cell and manufacturing method thereof

technical field

The invention relates to a structure and a manufacturing method of a solar cell, in particular to an aluminum emitter back-junction back-contact crystalline silicon solar cell and a manufacturing method thereof.

Background technique

Solar cells can directly convert solar energy into electrical energy, which is an effective way to utilize solar energy resources. Since no harmful substances are produced during use, solar cells have been favored in solving energy and environmental problems in recent years. market expectation. Solar energy is also known as the most ideal energy source and an important resource for the survival and development of human society.

The current mainstream solar cell material uses a P-type silicon substrate to form a pn junction through high-temperature phosphorus diffusion. However, there is a phenomenon of light-induced attenuation due to the influence of boron-oxygen pairs in the P-type crystalline silicon cell, and the N-type silicon material is relatively insensitive to metal impurities and many non-metal defects due to its insensitivity to metal impurities and many non-metal defects. There are fewer boron-oxygen pairs, so the stability of performance is higher than that of P-type crystalline silicon cells; at the same time, due to the higher minority carrier lifetime of N-type cells, this lays the foundation for the preparation of more efficient solar cells.

Back-junction and back-contact solar cells began to come into people's sight as early as 1977, and it is still a research hotspot in the solar cell industry until now. Compared with conventional silicon cells, the advantages of back-junction and back-contact solar cells are obvious, mainly in the following aspects: (1) Back-junction and back-contact solar cells use N-type crystalline silicon as the substrate, which has a high minority carrier life and is suitable for It is suitable for the preparation of high-efficiency cells, especially suitable for back-junction and back-contact solar cells, which have a pn junction on the back surface of the cell structure, because the photo-generated carriers generated on the front surface must migrate to the pn junction on the back surface of the cell to be utilized. A higher minority carrier lifetime is the guarantee to reduce the recombination of photogenerated carriers on the surface and in the body of the solar cell; (2) The boron content of the N-type substrate is extremely low, so the light-induced attenuation caused by the boron-oxygen pair is not as obvious as that of the P-type substrate material, The improvement of the efficiency of the packaged components is more obvious; (3) There is no electrode on the front of the back junction solar cell, which reduces the shading area and increases the photo-generated current. The positive and negative electrodes of the cell are distributed on the back of the cell in a finger shape ; (4) Back-junction and back-contact solar cells are easy to package. Compared with conventional batteries, there is no need to cross the negative electrode of the previous sheet to the positive electrode of the latter sheet, which is easy to operate.

Contents of the invention

Purpose of the invention: In order to overcome the deficiencies in the prior art, the present invention provides an aluminum emitter back-junction back-contact crystalline silicon solar cell and its manufacturing method, which is safe, reliable and compatible with traditional solar cell production lines, and is suitable for current solar Battery production line upgrade.

Technical solution: In order to solve the above-mentioned technical problems, the aluminum emitter back-junction back-contact crystalline silicon solar cell provided by the present invention includes a plate-shaped N-type silicon substrate covered on the front surface and the back surface of the N-type silicon substrate. There is an N-type doped layer, the N-type doped layer is covered with a passivation layer, the N-type silicon substrate on the back surface is embedded with P-type doped layers at intervals, above the P-type doped layer The positive pole of the battery is connected, and the negative pole of the battery is embedded in the N-type doped layer on the back surface.

Preferably, the square resistance of the N-type doped layer is 30-120 ohm/sq.

Preferably, the passivation layer on the front surface of the N-type silicon substrate is a SiNx passivation layer, and the passivation layer on the back surface is a SiO ₂ , SiOx/SiNx, Al ₂ O ₃ /SiNx or SiCx passivation layer.

The present invention simultaneously proposes a method for manufacturing the above-mentioned aluminum emitter back-junction back-contact crystalline silicon solar cell, comprising the following steps:

(1) Double-sided texturing of N-type silicon wafers with alkaline solution;

(2) N-type doped layers are made on both sides of N-type silicon wafers, and the square resistance of the doped layers is 30-120ohm/sq;

(3) Partially open the p ⁺ patterned area on the back of the N-type silicon wafer to remove the PSG in this area;

(4) Polishing and etching the patterned p ⁺ region of the N-type silicon wafer to remove the n-type doped layer on the p ⁺ patterned region;

(5) Remove PSG from other areas and perform wet cleaning;

(6) Deposit a passivation layer on the front and back surfaces of the silicon wafer;

(7) Dielectric film openings in the p+ patterned area on the back;

(8) Screen printing back electrode, sintering.

Preferably, the doped layer in step 2) can be fabricated by POCl3 diffusion, ion implantation or solid state source diffusion.

Preferably, the method of opening holes in the step 3) is opening holes with corrosive slurry or laser opening.

Preferably, the method for polishing the patterned P+ region in step 4) is to use an alkaline solution that can selectively etch silicon and PSG.

Preferably, in step 7), the method of opening the dielectric film on the back side is to print corrosive paste or use laser to open the film; if aluminum paste that can burn through the dielectric film is used, this step is skipped.

Beneficial effects: the invention adopts N-type crystalline silicon chip as the base material, which has high minority carrier life and small light-induced attenuation, which has advantages for the preparation of batteries and packaging components; the use of passivation film passivation on the front and rear surfaces of the battery can effectively reduce the surface minority The recombination rate of carriers improves the lifetime of minority carriers on the surface, and the purpose of preparing anti-reflection coatings on both sides is to reduce the reflection of photons, increase the absorption of photons, increase the photogenerated current and increase the final conversion efficiency of the battery. Both the positive and negative electrodes of the battery are made on the back of the battery, which reduces the shading area, increases the photo-generated current, and can better collect the current generated by the silicon wafer, while forming a good ohmic contact between the metal and the silicon wafer; using silk screen The method of printing Al paste or sputtering aluminum to form the emitter on the back can reduce the process steps, reduce cost and time; all process steps are completed under the existing process conditions, and high-efficiency back-junction back-contact solar cells.

Description of drawings

Fig. 1 is a schematic structural diagram of Embodiment 1 of the present invention;

Fig. 2 is a process diagram of Embodiment 1 of the present invention;

Each label in the figure: N-type silicon substrate 1 , silicon nitride film 2 , N-type doped layer 3 , P-type doped layer 4 , battery positive electrode 5 , and battery negative electrode 6 .

detailed description

Embodiment one

The structure of the aluminum emitter back-junction and back-contact crystalline silicon solar cell of this embodiment is shown in Figure 1, including an N-type silicon substrate 1, a silicon nitride film 2, an N-type doped layer 3, and a P-type doped layer 4 , the positive pole 5 of the battery, and the negative pole 6 of the battery. Wherein the N-type silicon substrate 1 is plate-shaped, and the front surface and the back surface of the N-type silicon substrate 1 are covered with an N-type doped layer 3, and the N-type doped layer is covered with a passivation layer, and the passivation layer is Silicon nitride film 2, P-type doped layers 4 are embedded at intervals on the N-type silicon substrate 1 on the back surface, and the positive electrode 5 of the battery is connected above the P-type doped layer, and the N-type doped layer 3 on the back surface The negative electrode 6 of the battery is embedded.

The procedure of the preparation method of the above-mentioned novel back-junction and back-contact structure N-type silicon solar cell is as follows:

(1) Choose an N-type silicon substrate, and the resistivity of the N-type silicon substrate is 3-5ohm.cm, and the minority carrier lifetime is greater than 300us;

(2) Use sodium hydroxide solution to prepare a pyramid-shaped light-trapping structure on the surface of the N-type single crystal silicon substrate, and then perform chemical cleaning with a mixed solution of hydrochloric acid and hydrofluoric acid; the concentration range of the sodium hydroxide solution is 0.5% ; In hydrochloric acid and hydrofluoric acid mixed solution, hydrochloric acid: hydrofluoric acid ratio is 1:2.5; The concentration of hydrochloric acid and hydrofluoric acid mixed solution is 1.1%;

(3) Diffusion furnace tubes are used for double-sided phosphorus diffusion. The phosphorus source is POCl ₃ , the temperature is 840°C, and the square resistance requirement is 70ohm/sq;

(4) Use the method of printing Merck paste to remove the PSG in the p ⁺ patterned area on the back;

(5) Polishing the p ⁺ patterned area with an organic alkali solution, and removing PSG after polishing;

(6) A 75nm thick silicon nitride film is prepared on the diffusion surface by plasma chemical vapor deposition, and a 130nm thick silicon nitride oxide film is prepared on the back;

(7) Prepare the electrode area:

a) Grooving: The emitter area is regrooved by the Merck hole opening method to remove the silicon oxynitride layer. The groove width is 200 μm. After completion, chemical cleaning and drying are carried out;

b) Align by screen printing and print silver paste fine grids in the unopened areas;

c) Align by screen printing and print a fine grid of aluminum paste in the opening area;

d) printing the main grid by screen printing;

e) Sintering.

Various semi-finished states of the battery in this embodiment are arranged according to the process sequence as shown in FIG. 2 .

Embodiment two

The structure of the aluminum emitter back-junction back-contact crystalline silicon solar cell of this embodiment is the same as that of Embodiment 1, but the manufacturing method adopted is different:

(1) Choose an N-type silicon substrate, and the resistivity of the N-type silicon substrate is 3-5ohm.cm, and the minority carrier lifetime is greater than 300us;

(2) Use sodium hydroxide solution to prepare a pyramid-shaped light-trapping structure on the surface of the N-type single crystal silicon substrate, and then perform chemical cleaning with a mixed solution of hydrochloric acid and hydrofluoric acid; the concentration range of the sodium hydroxide solution is 0.5% ; In hydrochloric acid and hydrofluoric acid mixed solution, hydrochloric acid: hydrofluoric acid ratio is 1:2.5; The concentration of hydrochloric acid and hydrofluoric acid mixed solution is 1.1%;

(3) Diffusion furnace tubes are used for double-sided phosphorus diffusion. The phosphorus source is POCl ₃ with a temperature of 840°C and a square resistance requirement of 50ohm/sq;

(4) Using the laser method to remove the PSG in the p ⁺ region on the back;

(5) Chemically polish the p ⁺ region on the back, and remove PSG after polishing;

(6) Prepare a silicon nitride film with a thickness of 80nm on the diffusion surface by plasma chemical vapor deposition, and a silicon nitride oxide film with a thickness of 130nm on the back;

(7) Prepare the electrode area:

a) Grooving: The emitter area is regrooved by laser drilling method to remove the silicon oxynitride layer. The groove width is 200 μm. After completion, chemical cleaning and drying are carried out;

b) Align by screen printing and print a silver paste fine grid in the unopened area;

c) Align by screen printing and print a burn-through aluminum paste fine grid in the opening area;

d) printing the main grid by screen printing;

e) Sintering.

The invention provides a new production mode concept for mass production of high-efficiency crystalline silicon solar cells, has strong applicability and operability, and implies huge use value.

Inspired by the above-mentioned ideal embodiment according to the present invention, through the above-mentioned description content, relevant workers can make various changes and modifications within the scope of not departing from the technical idea of the present invention. The technical scope of the present invention is not limited to the content in the specification, but must be determined according to the scope of the claims.

Claims (1)

1. An aluminum emitter back-junction back-contact crystalline silicon solar cell is characterized in that: it comprises a plate-shaped N-type silicon substrate, and the front surface and the back surface of the N-type silicon substrate are covered with n-type doping layer, the n-type doped layer is covered with a passivation layer, the n-type silicon substrate on the back surface is embedded with p-type doped layers at intervals, and the positive electrode of the battery is connected above the p-type doped layer, The negative electrode of the battery is embedded in the n-type doped layer on the back surface; the passivation layer on the front surface of the N-type silicon substrate is a SiNx passivation layer, and the steps of its preparation method are as follows: 1) Select an N-type silicon substrate, and the resistivity of the N-type silicon substrate is 3-5Ω.cm, and the minority carrier lifetime is greater than 300μs; 2) Using sodium hydroxide solution to prepare a pyramid-shaped light-trapping structure on the surface of the N-type single crystal silicon substrate, and then chemically cleaning with a mixed solution of hydrochloric acid and hydrofluoric acid; the concentration range of the sodium hydroxide solution is 0.5%; In the mixed solution of hydrochloric acid and hydrofluoric acid, the ratio of hydrochloric acid to hydrofluoric acid is 1:2.5; the concentration of the mixed solution of hydrochloric acid and hydrofluoric acid is 1.1%; 3) Use a diffusion furnace tube for double-sided phosphorus diffusion. The phosphorus source is POCl3, the temperature is 840°C, and the square resistance requirement is 70Ω/□; 4) Remove the PSG in the p ⁺ patterned area on the back by printing corrosive paste; 5) Polishing the p ⁺ patterned area with an organic alkali solution, and removing PSG after polishing; 6) Prepare a 75nm thick silicon nitride film on the diffusion surface by plasma chemical vapor deposition, and prepare a 130nm thick silicon nitride oxide film on the back; 7) Prepare the electrode area: a) Grooving: re-grooving the emitter area by using the corrosive slurry drilling method to remove the silicon oxynitride layer. The width of the groove is 200 μm. After completion, chemical cleaning and drying are carried out; b) Align by screen printing and print silver paste fine grids in the unopened areas; c) Align by screen printing and print a fine grid of aluminum paste in the opening area; d) printing the main grid by screen printing; e) Sintering.