CN105023971A - Preparation method of low-surface recombination back electrode solar cell - Google Patents

Abstract

The invention discloses a method for preparing a low-surface composite back electrode solar cell, which comprises the following steps: a) sequentially performing texturing on a silicon wafer, forming a p-n junction by thermal diffusion, polishing the back of the silicon wafer, and removing phosphorus silicon glass; Perform PECVD coating on the front of the silicon wafer to form a SiNx anti-reflection film; c) print nano-silicon paste on the back of the silicon wafer to form a nano-silicon electrode; d) quickly sinter the nano-silicon electrode in a sintering furnace at 700-850 ° C Finally, P+ silicon is formed on the back side of the silicon wafer under the nano-silicon electrode. e) preparing an Ag back electrode on the nano-silicon electrode; f) preparing an Al back electric field on the back of the silicon wafer; g) preparing an Ag positive electrode on the front of the silicon wafer; h) sintering the silicon wafer at high temperature to form a solar cell. Compared with the prior art, the present invention has the advantages of reducing the resistance of the back electrode and greatly reducing the recombination rate of carriers on the back of the silicon chip, thereby improving the conversion efficiency of the battery.

Description

A kind of preparation method of low surface composite back electrode solar cell

technical field

The invention relates to the technical field of solar cells, in particular to a method for preparing a low-surface composite back electrode solar cell.

Background technique

With the depletion of fossil energy, the energy problem has gradually become a major concern of the world; coupled with the increasingly serious environmental pollution, it has prompted people to strive to develop new energy, especially renewable energy. As a green energy, solar energy is one of the most promising new energy sources. Solar cells use the photovoltaic effect to convert solar energy into electricity. Crystalline silicon solar cells account for 90% of solar cells and are currently the main solar cell products on the market. The manufacturing cost of crystalline silicon solar cells is mainly divided into two parts, one is the silicon wafer, and the other is the metal electrode, and the metal electrode is divided into a front electrode and a back electrode. The back electrode is composed of an Ag back electrode and an Al back field: the role of the Ag back electrode is to conduct electricity on the one hand, and on the other hand to facilitate the welding of components; the Al back field can not only invert the back of the silicon wafer, form a p+ layer, and reduce the The carrier recombination on the back of the battery improves the conversion efficiency and can also realize the conductive function.

Due to the poor flatness of the back of the silicon wafer, the poor contact between the back electrode and the back of the silicon wafer will reduce the conductivity of the back electrode and the inversion effect of the Al back field; in addition, the Ag back electrode cannot form a p+ layer, which is not conducive to the improvement of cell conversion efficiency. Therefore, how to develop a low-surface composite back electrode high-efficiency solar cell has become a hot spot for researchers.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for preparing a low-surface composite back electrode solar cell, which can greatly reduce the carrier recombination rate on the back of the silicon wafer under the premise of reducing the resistance of the back electrode, and reduce the conversion of the battery Efficiency improvement.

In order to solve the above-mentioned technical problems, the present invention provides a method for preparing a low-surface composite back electrode solar cell, comprising the following steps:

a) Carry out texturing, heat diffusion p-n junction, silicon wafer back polishing and dephosphorous silicon glass sequentially on the silicon wafer;

b) performing PECVD coating on the front side of the silicon wafer to form a SiNx anti-reflection film;

c) printing nano-silicon paste on the back side of the silicon wafer to form nano-silicon electrodes;

d) Rapidly sintering the nano-silicon electrode in a sintering furnace at 700-850° C. to form P+ silicon on the back of the silicon wafer under the nano-silicon electrode.

e) preparing an Ag back electrode on the nano-silicon electrode;

f) preparing an Al back electric field on the back side of the silicon wafer;

g) preparing an Ag positive electrode on the front side of the silicon wafer;

h) Sintering the silicon wafer at high temperature to form a solar cell.

Preferably, the nano-silicon electrode has a thickness of 1-5 μm and a resistivity of 0.01-0.5Ω.cm.

Preferably, the P+ silicon has a thickness of 100-500 nm and a resistivity of 0.5-1Ω.cm.

Preferably, in step a), NaOH solution with a mass concentration of 5-25% is used for polishing the backside of the silicon wafer.

Preferably, in step a), the backside of the silicon wafer is polished using HNO3/HF solution with a mass concentration of 1-10% and 0.1-6% respectively.

Preferably, in step a), the backside reflectance of the silicon wafer after the backside polishing is 30-55%.

Preferably, in step c), the nano-silicon slurry includes silicon nanoparticles and B compound.

Preferably, the particle size of the silicon nanoparticles is 1-40nm, the B compound is B2H6, and the mass content of B2H6 in the nano-silicon slurry is 0.1-5%.

Preferably, in step c), there are 3 to 6 nano-silicon electrodes, each nano-silicon electrode is arranged parallel to each other, and the nano-silicon electrodes occupy 3-11% of the area of the back surface of the silicon wafer.

Correspondingly, the present invention also provides a selectively textured crystalline silicon solar cell, which is prepared by the above preparation method.

The present invention has the following beneficial effects: polishing the back of the silicon chip, strengthening the flatness of the back of the silicon chip, can greatly improve the contact performance between the back electrode and the silicon chip, so that the contact resistance of the back electrode is reduced, and an excellent ohmic contact is formed; doping The nano-silicon electrode of the B compound forms a P++ layer. After rapid high-temperature sintering, B rapidly diffuses into the silicon wafer, and forms a B heavily doped region in the silicon wafer area under the nano-silicon electrode, forming a P+ layer; nano-silicon electrodes, B heavy Doping and P-type silicon substrates form P++/P+/P high-low junctions; the excellent flatness of the back of the silicon wafer is conducive to the formation of uniform P+/P high-low junctions on the Al back field and the back of the silicon, which can reduce the resistance of the back electrodes at the same time, It can also greatly reduce the carrier recombination rate on the back of the silicon wafer and improve the conversion efficiency of the battery.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail with examples below.

Embodiment one:

A method for preparing a low-surface composite back electrode solar cell, comprising the steps of:

a) Carry out texturing, thermal diffusion p-n junction, silicon wafer back polishing and dephosphorous silicon glass in sequence on the silicon wafer; the back polishing of the silicon wafer adopts NaOH solution with a mass concentration of 5%, or adopts HNO3/HF solution, the mass concentration of which is 1% and 0.1% respectively;

b) performing PECVD coating on the front side of the silicon wafer to form a SiNx anti-reflection film;

c) printing nano-silicon slurry on the back of the silicon chip to form a nano-silicon electrode; the nano-silicon slurry includes silicon nanoparticles and B compounds, the silicon nanoparticles particle size is 1-40nm, and the B compound is B2H6, B2H6 in the described The mass content of the nano-silicon slurry is 0.1%.

d) Rapidly sintering the nano-silicon electrode in a sintering furnace at 700° C. to form P+ silicon on the back of the silicon wafer under the nano-silicon electrode.

e) preparing an Ag back electrode on the nano-silicon electrode;

f) preparing an Al back electric field on the back side of the silicon wafer;

g) preparing an Ag positive electrode on the front side of the silicon wafer;

h) Sintering the silicon wafer at high temperature to form a solar cell.

The thickness of the nano-silicon electrode is 1-5μm, and the resistivity is 0.01-0.5Ω.cm; the thickness of P+ silicon is 100-500nm, and the resistivity is 0.5-1Ω.cm; 30-55%; there are 3 to 6 nano-silicon electrodes, each nano-silicon electrode is arranged parallel to each other, and the nano-silicon electrodes account for 3-11% of the area on the back of the silicon chip.

Embodiment two:

A method for preparing a low-surface composite back electrode solar cell, comprising the steps of:

a) Carry out texturing, thermal diffusion p-n junction, back polishing of silicon wafer and dephosphorous silicon glass to silicon wafer sequentially; the back polishing of silicon wafer adopts NaOH solution with a mass concentration of 15%, or adopts HNO3/HF solution, the mass concentration of which is 5% and 3% respectively;

b) performing PECVD coating on the front side of the silicon wafer to form a SiNx antireflection film;

c) printing nano-silicon slurry on the back of the silicon chip to form a nano-silicon electrode; the nano-silicon slurry includes silicon nanoparticles and B compounds, the silicon nanoparticles particle size is 1-40nm, and the B compound is B2H6, B2H6 in the described The mass content of the nano-silicon slurry is 2%.

d) Rapidly sintering the nano-silicon electrode in a sintering furnace at 770° C. to form P+ silicon on the back of the silicon wafer under the nano-silicon electrode.

e) preparing an Ag back electrode on the nano-silicon electrode;

f) preparing an Al back electric field on the back side of the silicon wafer;

g) preparing an Ag positive electrode on the front side of the silicon wafer;

h) Sintering the silicon wafer at high temperature to form a solar cell.

The thickness of the nano-silicon electrode is 1-5μm, and the resistivity is 0.01-0.5Ω.cm; the thickness of P+ silicon is 100-500nm, and the resistivity is 0.5-1Ω.cm; 30-55%; there are 3 to 6 nano-silicon electrodes, each nano-silicon electrode is arranged parallel to each other, and the nano-silicon electrodes account for 3-11% of the area on the back of the silicon chip.

Embodiment three:

A method for preparing a low-surface composite back electrode solar cell, comprising the steps of:

a) Carry out texturing, thermal diffusion p-n junction, back polishing of silicon wafer and dephosphorous silicon glass to the silicon wafer in sequence; NaOH solution with a mass concentration of 25% or HNO3/HF solution with a mass concentration of 25% is used for the back polishing of the silicon wafer. 10% and 6% respectively;

b) performing PECVD coating on the front side of the silicon wafer to form a SiNx anti-reflection film;

c) printing nano-silicon slurry on the back of the silicon chip to form a nano-silicon electrode; the nano-silicon slurry includes silicon nanoparticles and B compounds, the silicon nanoparticles particle size is 1-40nm, and the B compound is B2H6, B2H6 in the described The mass content of the nano-silicon slurry is 5%.

d) Rapidly sintering the nano-silicon electrode in a sintering furnace at 850° C. to form P+ silicon on the back of the silicon wafer under the nano-silicon electrode.

e) preparing an Ag back electrode on the nano-silicon electrode;

f) preparing an Al back electric field on the back side of the silicon wafer;

g) preparing an Ag positive electrode on the front side of the silicon wafer;

h) Sintering the silicon wafer at high temperature to form a solar cell.

The thickness of the nano-silicon electrode is 1-5μm, and the resistivity is 0.01-0.5Ω.cm; the thickness of P+ silicon is 100-500nm, and the resistivity is 0.5-1Ω.cm; 30-55%; there are 3 to 6 nano-silicon electrodes, each nano-silicon electrode is arranged parallel to each other, and the nano-silicon electrodes account for 3-11% of the area on the back of the silicon chip.

Correspondingly, the present invention also provides a selectively textured crystalline silicon solar cell, which is prepared by the preparation methods of the above three embodiments.

The present invention has the following beneficial effects: polishing the back of the silicon chip, strengthening the flatness of the back of the silicon chip, can greatly improve the contact performance between the back electrode and the silicon chip, so that the contact resistance of the back electrode is reduced, and an excellent ohmic contact is formed; doping The nano-silicon electrode of the B compound forms a P++ layer. After rapid high-temperature sintering, B rapidly diffuses into the silicon wafer, and forms a B heavily doped region in the silicon wafer area under the nano-silicon electrode, forming a P+ layer; nano-silicon electrodes, B heavy Doping and P-type silicon substrates form P++/P+/P high-low junctions; the excellent flatness of the back of the silicon wafer is conducive to the formation of uniform P+/P high-low junctions on the Al back field and the back of the silicon, which can reduce the resistance of the back electrodes at the same time, It can also greatly reduce the carrier recombination rate on the back of the silicon wafer and improve the conversion efficiency of the battery.

The above description is a preferred embodiment of the present invention, it should be pointed out that for those skilled in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications are also considered Be the protection scope of the present invention.

Claims (10)

1. A preparation method for a low-surface composite back electrode solar cell, characterized in that, comprising the following steps: a) Carry out texturing, heat diffusion p-n junction, silicon wafer back polishing and dephosphorous silicon glass sequentially on the silicon wafer; b) performing PECVD coating on the front side of the silicon wafer to form a SiNx anti-reflection film; c) printing nano-silicon paste on the back side of the silicon wafer to form nano-silicon electrodes; d) Rapidly sintering the nano-silicon electrode in a sintering furnace at 700-850° C. to form P+ silicon on the back of the silicon wafer under the nano-silicon electrode. e) preparing an Ag back electrode on the nano-silicon electrode; f) preparing an Al back electric field on the back side of the silicon wafer; g) preparing an Ag positive electrode on the front side of the silicon wafer; h) Sintering the silicon wafer at high temperature to form a solar cell. 2 . The method for preparing a low-surface composite back electrode solar cell according to claim 1 , wherein the thickness of the nano-silicon electrode is 1-5 μm, and the resistivity is 0.01-0.5 Ω.cm. 3 . The method for preparing a low-surface composite back electrode solar cell according to claim 1 , wherein the thickness of the P+ silicon is 100-500 nm, and the resistivity is 0.5-1 Ω.cm. 4 . The method for preparing a low-surface composite back-electrode solar cell according to claim 1 , wherein, in step a), the backside of the silicon wafer is polished using a NaOH solution with a mass concentration of 5-25%. 5. the preparation method of a kind of low-surface composite back electrode solar cell as claimed in claim 1, is characterized in that, in step a), described silicon wafer back polishing adopts HNO3/HF solution, and its mass concentration is respectively 1 -10% and 0.1-6%. 6 . The method for preparing a low-surface composite back electrode solar cell according to claim 1 , characterized in that, in step a), the back reflectance of the silicon wafer is 30-55% after said back polishing. 7 . The method for preparing a low-surface composite back electrode solar cell according to claim 1 , wherein, in step c), the nano-silicon paste includes silicon nanoparticles and B compound. 8 . 8. the preparation method of a kind of low-surface composite back electrode solar cell as claimed in claim 7, is characterized in that, described silicon nanoparticle particle diameter is 1-40nm, and B compound is B2H6, and B2H6 is in described nano-silicon paste The mass content of the material is 0.1-5%. 9. the preparation method of a kind of low-surface composite back electrode solar cell as claimed in claim 1, is characterized in that, in step c), described nano-silicon electrode is 3 to 6, and each nano-silicon electrode is parallel to each other Arranged, the nano-silicon electrodes account for 3-11% of the area on the back of the silicon wafer. 10. A low-surface composite back electrode solar cell, characterized in that it is produced by the preparation method described in any one of claims 1-9.