阅读说明：本技术 一种半导体掺杂组合物及其制备方法以及太阳能电池 (Semiconductor doping composition, preparation method thereof and solar cell ) 是由 徐芳荣 李平 池田武史 于 2020-05-27 设计创作，主要内容包括：本发明公开了一种半导体掺杂组合物,所述组合物含有溶剂、粘度调节剂、以及外层氧化的硼化硅微粒子。使用该半导体掺杂组合物可以实现适用激光掺杂方法得到高硼浓度的掺杂。(The invention discloses a semiconductor doping composition which contains a solvent, a viscosity regulator and outer layer oxidized silicon boride microparticles. The semiconductor doping composition can realize the doping of high boron concentration by using a laser doping method.)

1. A semiconductor doping composition, characterized by: the composition contains a solvent, a viscosity modifier, and outer layer oxidized silicon boride microparticles.

2. The semiconductor doping composition of claim 1, wherein: the viscosity regulator is organic polymer, inorganic microparticle, or mixture of the two.

3. The semiconductor doping composition of claim 2, wherein: the inorganic microparticles are silica gel microparticles with the average diameter of less than 1 micron.

4. The semiconductor doping composition of claim 1, wherein: the composition further comprises a polyborosiloxane polymerized from monomers represented by formula 1 and formula 2:

wherein R1 is alkyl or aryl with 1-8 carbon atoms; r2 is alkyl, aryl or alkoxy with 1-8 carbon atoms; r3 and R4 may be the same alkyl group or different alkyl groups; r5 is alkyl, aryl or alkoxy with 1-8 carbon atoms; r6 and R7 can be any combination of hydrogen and alkyl.

5. A method for preparing a semiconductor doping composition according to any one of claims 1 to 4, wherein: which comprises the following steps:

a. preparing the outer layer oxidized silicon boride micro-particle:

oxidizing the silicon boride micro-particles at 300-1000 ℃ for 0.2-24 hours to obtain outer-layer oxidized silicon boride micro-particles, wherein the thickness of an oxide layer oxidized on the outer layer is 5-70% of the radius of the micro-particles, and the molecular formula of the silicon boride micro-particles is SiBx, wherein x is 2, 3, 4 and 6;

b. uniformly mixing the solvent, the viscosity regulator and the outer-layer oxidized silicon boride micro-particles under stirring to prepare slurry;

c. and mixing, dispersing and filtering the slurry to obtain the semiconductor doping composition.

6. A solar cell, characterized in that it is boron-doped using the semiconductor doping composition according to any one of claims 1 to 4.

7. The solar cell of claim 6, wherein: the boron doping is carried out by means of laser.

8. The solar cell of claim 7, wherein: the laser is green laser with the wavelength of 532 nanometers.

Technical Field

The present invention relates to a semiconductor doping composition, a method of preparing the same, and a solar cell, and more particularly, to a semiconductor doping composition that can be suitably used for a solar cell by using a laser diffusion method.

Background

In the conventional production of semiconductors or solar cells, thermal diffusion is generally used for doping of boron. The thermal diffusion method has the problems of influence or damage of formed PN junction, high cost, non-uniform diffusion, pollution and the like in some selective emitter processing. For example: the back selective emitter of the p-type PERC cell is made after passivation and antireflection film formation, if thermal diffusion is adopted, the front PN junction formed by phosphorus diffusion will be damaged because the boron diffusion temperature is higher than the phosphorus diffusion temperature, and the cell performance will be affected. Therefore, there has not been a technique for mass production of a PERC back high concentration selective emitter.

Reference documents: CN201410219780.9, CN201410554156.4, CN 200910038909.5.

Disclosure of Invention

Problems to be solved by the invention

Aiming at the problems of PN junction damage, high cost, uneven diffusion, pollution and the like caused by thermal diffusion in the prior art, the invention provides a semiconductor doping composition suitable for laser diffusion. The method can realize low material usage by screen printing, and can realize local selective emitter processing by diffusing with laser at low temperature even room temperature without damaging the formed PN junction.

Means for solving the problems

In order to solve the above problems, the present invention discloses a semiconductor doping composition containing a solvent, a viscosity modifier, and fine particles of silicon boride whose outer layer is oxidized.

Because the selective emitter needs very high boron doping amount, the invention balances the aspects of realizing high boron content and cost, and can obtain doping slurry with high cost performance. In addition, in order to achieve high boron doping, metal ions which influence the performance are not introduced, so that the material selection of the invention is also considered.

Since the selective emitters are locally doped, typically less than 10% of the total area, if the total area is coated with insignificant loss, the paste viscosity needs to be adjusted so that screen printing can be achieved, thereby reducing the cost. The invention uses the viscosity regulator and has made great work in the aspect of regulating the balance of organic and inorganic components.

In order to increase the content of boron in the slurry, the invention adopts high-boron-containing silicon boride micro-particle SiB_x(wherein x is 2, 3, 4, 6, preferably x is 6) to prepare fine particles of silicon boride oxidized at the outer layer, which is suitable for laser diffusion, without breaking PN junctions already formed at low temperatures, even at room temperature. In order to achieve uniformity of diffusion, fine particles of silicon boride having a particle size of 10 μm or less, preferably 1 μm or less, are used.

In order to effectively adjust the viscosity, the invention adopts inorganic particles, organic polymers or a mixture of the inorganic particles and the organic polymers. In order to further optimize the diffusivity of the slurry and reduce carbon contamination in the organic material, it is preferable to add inorganic fine particles at a high ratio or to use pure inorganic fine particles.

Specifically, the present invention includes the following aspects:

1. a semiconductor doping composition contains a solvent, a viscosity modifier, and outer layer oxidized silicon boride microparticles.

2. The semiconductor doping composition according to claim 1, wherein the viscosity modifier is an organic polymer, an inorganic fine particle, or a mixture of the two.

3. The semiconductor doping composition according to claim 2, wherein the inorganic fine particles are silica fine particles having an average diameter of 1 μm or less.

4. The semiconductor doping composition according to the foregoing 1, further comprising a polyborosiloxane polymerized from monomers represented by formula 1 and formula 2:

wherein R1 is alkyl or aryl with 1-8 carbon atoms; r2 is alkyl, aryl or alkoxy with 1-8 carbon atoms; r3 and R4 may be the same alkyl group or different alkyl groups; r5 is alkyl, aryl or alkoxy with 1-8 carbon atoms; r6 and R7 can be any combination of hydrogen and alkyl.

5. A method of preparing a semiconductor doping composition according to any of the preceding 1-4, comprising the steps of:

a. preparing the outer layer oxidized silicon boride micro-particle:

oxidizing the silicon boride micro-particles at 300-1000 ℃ for 0.2-24 hours to obtain outer-layer oxidized silicon boride micro-particles, wherein the thickness of an oxide layer oxidized on the outer layer is 5-70% of the radius of the micro-particles, and the molecular formula of the silicon boride micro-particles is SiBx, wherein x is 2, 3, 4 and 6;

b. uniformly mixing the solvent, the viscosity regulator and the outer-layer oxidized silicon boride micro-particles under stirring to prepare slurry;

c. and mixing, dispersing and filtering the slurry to obtain the semiconductor doping composition.

6. A solar cell doped with boron using the semiconductor doping composition according to any one of the above 1 to 4.

7. The solar cell according to the above 6, wherein the boron doping is performed by using a laser.

8. The solar cell according to the above 7, wherein the laser is green laser with a wavelength of 532 nm.

ADVANTAGEOUS EFFECTS OF INVENTION

By using the silk-screen printing type semiconductor doping composition suitable for laser diffusion, selective emitter processing of boron can be realized. Particularly, in the case of an existing PN junction structure, boron selective emitter processing can be realized without destroying the existing PN junction.

Drawings

FIG. 1 is a top view of a blank silicon wafer for a solar cell.

FIG. 2 is a silicon wafer having a single side coated with a semiconductor doping composition of the invention on the silicon wafer of FIG. 1.

Fig. 3 is a surface of the silicon wafer of fig. 2 after local laser doping on the side coated with the semiconductor doping composition of the invention, wherein the light-colored portions are the laser-doped surface.

Detailed Description

The invention will now be described in more detail.

The invention discloses a semiconductor doping composition which contains a solvent, a viscosity regulator and outer layer oxidized silicon boride microparticles.

Solvents

The solvent may be a single organic solvent without adding water, a mixed solvent of an organic solvent, or a mixed solvent of an organic solvent and water. In the case of a single solvent, an organic solvent having a boiling point higher than 150 ℃ is preferable, so that the solvent is prevented from volatilizing to affect the quality of the coating film. In the case of a mixed solvent, a small amount of an organic solvent having a boiling point of less than 100 ℃ may be selected, and if an organic solvent having a boiling point of less than 100 ℃ is used, it is desirable to use a mixed solvent of an organic solvent having a boiling point of more than 100 ℃ and water in an amount of 40 mass% or more based on the total mass of the solvent. In order to prevent the solvent from volatilizing too quickly in the coating process to affect the performance, a solvent having a boiling point higher than 150 ℃ is also preferable even in the mixed solvent.

Examples of the organic solvent contained in the solvent include, but are not limited to: 1-methoxy-2-propanol, diacetone alcohol, 2-propanol, n-butanol, 3-methoxy-3-methylbutanol, diethylene glycol methyl ethyl ether, propylene glycol, diethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, alpha-terpineol, diethylene glycol monomethyl ether, diethylene glycol, methanol, ethanol, 1, 4-dioxane, acetone, methyl ethyl ketone, methyl lactate, ethyl lactate, xylene, dipropylene glycol dimethyl ether, diethylene glycol dimethyl ether, cyclohexanone, anisole, phenetole, isobutyl ether, ethylbenzene, or ethylbenzene.

Fine particles of silicon boride subjected to external layer oxidation

The selected outer-layer oxidized silicon boride micro-particle is prepared by oxidizing the silicon boride micro-particle for 0.2-24 hours at 300-1000 ℃, the thickness of an outer-layer oxidized oxide layer of the outer-layer oxidized silicon boride micro-particle is 5-70% of the radius of the micro-particle, the molecular formula of the silicon boride micro-particle is SiBx, wherein x is 2, 3, 4 and 6. Since the boron doping concentration of the selective emitter is relatively high, x is preferably 6. Since metal impurities such as iron and copper adversely affect the characteristics of semiconductor devices, selected SiB_xThe metal impurity levels were generally below 200 ppb.

The oxidation temperature of the fine particles of silicon boride is 300 to 1000 ℃ in order to obtain sufficiently oxidized fine particles, and the preparation temperature is preferably 300 to 500 ℃ in order to ensure the particle size and the oxidation ratio to be optimal.

In order to improve the uniformity of diffusion, the fine particles of silicon boride are selected to have an average diameter of 10 μm or less, more preferably 1 μm or less.

The degree of oxidation of the fine particles of silicon boride was measured by a scanning electron tunneling microscope (JEOL JSM-6700F Japan).

Viscosity modifier

The viscosity modifier may be a single organic polymer, inorganic fine particles, or a mixture of the two.

Examples of the organic polymer include, but are not limited to: methyl cellulose, ethyl cellulose, propyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, methyl hydroxyethyl cellulose, ethyl hydroxyethyl cellulose, methyl hydroxypropyl cellulose, cellulose acetate butyrate, polyacrylamide, polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene oxide, carbomer resin, polyacrylic acid, polyacrylate, polyurethane, or the like.

In order to improve the uniformity and the storage stability of the composition, inorganic fine particles having an average diameter of 1 μm or less, preferably 100 nm or less are selected.

Examples of the inorganic fine particles include, but are not limited to: silica gel, or talc.

Talc may be selected from, but is not limited to, the following products and properties are sufficient for the present invention: talc powder having a particle size of 1 μm (Shiraia Kasei Kabushiki Kaisha), a particle size of 2.5 μm (Shiraia Kasei Co., Ltd.) and a particle size of 4 μm (Shiraia Kasei Co., Ltd.).

The silica gel may be selected from, but is not limited to, the following products, and the properties can meet the requirements of the present invention: SO-E1(ADMATECHS Co., Ltd.), SO-E2(ADMATECHS Co., Ltd.), SO-E3(ADMATECHS Co., Ltd.), SO-E5(ADMATECHS Co., Ltd.), and #300(NIPPON AEROSIL CO., LTD).

Polyborosiloxane

The composition of the present invention further comprises a polyborosiloxane obtained by polymerizing the monomers represented by formula 1 and formula 2.

Wherein R1 is alkyl or aryl with 1-8 carbon atoms; r2 is alkyl, aryl or alkoxy with 1-8 carbon atoms; r3 and R4 may be the same alkyl group or different alkyl groups; r5 is alkyl, aryl or alkoxy with 1-8 carbon atoms; r6 and R7 can be any combination of hydrogen and alkyl.

The invention discloses a preparation method of a semiconductor doping composition, which comprises the following steps:

a. preparing the outer layer oxidized silicon boride micro-particle:

oxidizing the silicon boride micro-particles at 300-1000 ℃ for 0.2-24 hours to obtain outer-layer oxidized silicon boride micro-particles, wherein the thickness of an oxide layer oxidized on the outer layer is 5-70% of the radius of the micro-particles, and the molecular formula of the silicon boride micro-particles is SiBx, wherein x is 2, 3, 4 and 6;

b. uniformly mixing the solvent, the viscosity regulator and the outer-layer oxidized silicon boride micro-particles under stirring to prepare slurry;

c. and mixing, dispersing and filtering the slurry to obtain the semiconductor doping composition.

Laser doping

The semiconductor doping composition can be used for thermal doping and laser doping of solar cells, and preferably laser doping. The light source selected for laser doping was green at 532 nm. Considering the doping productivity and the doping effect, the power of the laser light source is preferably 50-200W. The present invention is not limited to the above-described embodiments, and various design changes can be made based on the knowledge of those skilled in the art.

Examples

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Gel Permeation Chromatography (GPC)

Gel Permeation Chromatography (GPC) was used as a polymerization monitoring means, and Shimazu S3-4100 was used as a gel permeation chromatography apparatus. A chromatographic column: TSKgel SuperHM-H, size 6.0mmi.d. × 15cm, part number 0018001, microparticle size 3&5 microns. The test conditions were: mobile phase tetrahydrofuran, flow 0.2 ml/min, column temperature 40 ℃, single sample run time 30 min. The standard sample used to make the calibration curve was polystyrene.

Synthesis of Polyborosiloxane

The following silicone polysiloxane synthesis methods apply as described for polysiloxane 1, but the specific conditions (e.g., temperature, reaction time, etc.) are not limited to the following methods: a500 ml flask was charged with 1mol of siloxane monomer A1, 0.9mol of boric acid monomer B1 and 200ml of diethylene glycol methyl ethyl ether. Heating to 70-80 ℃ under nitrogen flow for 2 hours of reaction, then heating to 105-115 ℃ for 2 hours of reaction, and stopping the reaction when the measured weight average molecular weight is 2500-10000. The obtained solution is the polysiloxane, and is stored in an explosion-proof refrigerator after being cooled.

TABLE 1

Siloxane monomers:

boric acid monomer:

EXAMPLES 1-10, COMPARATIVE EXAMPLES 1-3

The preparation and evaluation of the semiconductor doping composition suitable for the present invention are described in example 1, but the specific conditions (e.g., the order of charging, the stirring temperature, the stirring time, the kneading conditions, the filtering conditions, the laser diffusion conditions, etc.) are not limited to the following methods: 50g of diethylene glycol methyl ethyl ether was added to a 250ml flask, 10g of oxidized silicon boride fine particles, 20g of propylene glycol, and 10g of talc fine particles were added while stirring. Stirring for 3 hours at the temperature of 60-80 ℃, and then naturally cooling to room temperature. Mixing with a three-roller mill (ceramic roller, roller spacing of 10 μm, rotation speed difference of 1:3:6), filtering (400 mesh filter cloth), and storing in an explosion-proof refrigerator.

And printing the obtained slurry on the surface of a silicon wafer for the solar cell, and then removing the solvent by using a thermal drying mode. Then diffusion was performed using laser condition 1, and the resulting sheet resistance was about 14 Ω/□.

The specific results are shown in Table 2.

TABLE 2

TABLE 2 continuation

Remarking: oxidation conditions 0: does not oxidize

Oxidation conditions 1: 350 deg.C, 18h, air atmosphere

Oxidation conditions 2: 600 ℃ for 4h in air atmosphere

Oxidation conditions 3: 400 ℃ for 10h in air atmosphere

Oxidation conditions 4: nitrogen-oxygen mixed atmosphere with temperature of 950 ℃, 0.5h and oxygen concentration of 15%

Oxidation conditions 5: 400 ℃ for 5h in air atmosphere

Oxidation conditions 6: nitrogen-oxygen mixed atmosphere with oxygen concentration of 30% at 500 deg.C for 5h

Oxidation conditions 7: 300 ℃ for 24h in air atmosphere

Laser condition 1: 532nm, 50um of spot side length, 150W of power and 10m/s of scanning speed

Laser condition 2: 532nm, spot side length of 50um, power of 80W and scanning speed of 5m/s

Laser condition 3: 532nm, spot diameter of 50um, power of 30W and scanning speed of 10m/s

Laser condition 4: 589nm, spot side length 50um, power 30W, scanning speed 5 m/s.

As can be seen from the comparative examples and examples, the laser diffusivity and uniformity (5-point test) of the semiconductor doping composition prepared by using the outer layer oxidized silicon boride fine particles are greatly improved compared with the composition directly using the silicon boride fine particles. The sheet resistance value obtained from diffusion can meet the requirement of solar selective emission of extremely high boron concentration doping. In addition, since thermal diffusion requires heating at 800 degrees centigrade for about 30 minutes, that is, heating at 800 degrees centigrade or more for a long time if it is to affect the PN junction that has been formed. The laser scanning is very fast and is performed at room temperature, so that the PN junction formed before the laser diffusion has no influence on the area outside the laser diffusion region. In addition, from the viewpoint of the conversion efficiency of the solar cell, the conversion efficiency of the laser diffusion using the semiconductor doping composition of the present invention is greatly improved as compared with the direct comparative example.