# US 10,373,726 B2 · Highly filled back surface field aluminum paste for point contacts in PERC cells and preparation method thereof

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- Number: US 10,373,726 B2
- Document ID: US10373726B2
- Status: Granted
- Kind: B2
- Application number: 15/571,430
- Filed: 2017-04-13
- Published: 2019-05-23
- Granted: 2019-08-06
- Earliest claimed: 2016-08-30
- Assignees: Nantong T-Sun New Energy Co., Ltd.
- Applicants: Nantong T-Sun New Energy Co., Ltd.
- Inventors: Peng Zhu
- Web page: https://patentgrep.com/patent/US10373726B2

## CPC

- H01B 1/22: the conductive material comprising metals or alloys
- H01B 13/00: Apparatus or processes specially adapted for manufacturing conductors or cables
- H10F 71/136: {Singulating, e.g. dicing}
- H10F 77/20: Electrodes
- H10F 77/211: {for photovoltaic cells}
- H10F 77/227: {for emitter wrap-through [EWT] photovoltaic cells, e.g. interdigitated emitter-base back-contacts}
- Y02E 10/50: Photovoltaic [PV] energy
- H01B: CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES (selection for magnetic properties H01F1/00; waveguides H01P {; printed circuits H05K})
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

A highly filled back surface field aluminum paste for point contacts in PERC cells and its preparation method include dissolving ethyl cellulose in organic solvent, stirring under a certain temperature to prepare a homogeneous and transparent organic carrier, adding aluminum powder, nanosized aluminum-boron-antimony alloy powder and auxiliary additive, and three-roller grinding, comprising 70-85 parts by weight of aluminum powder, 1-5 parts by weight of nanosized aluminum-boron-antimony alloy powder, 10-25 parts by weight of organic carrier, 0.1-6 parts by weight of inorganic binder and 0.01-1 part by weight of auxiliary additive.

## Claims

### Claim 1

A highly filled back surface field aluminum paste for point contacts in PERC cells, comprising: 70-85 parts by weight of aluminum powder, 1-5 parts by weight of nanosized aluminum-boron-antimony alloy powder, 10-25 parts by weight of organic carrier, 0.1-6 parts by weight of inorganic binders and 0.01-1 part by weight of auxiliary additive.

### Claim 2 (depends on 1)

An aluminum paste according to claim 1, wherein the aluminum powder is a spherical aluminum powder with an oxygen content of 0.3-0.8% and a particle size D50 of 13-17 μm.

### Claim 3 (depends on 1)

An aluminum paste according to claim 1, wherein the nanosized aluminum-boron-antimony alloy powder is prepared by a sol-gel method; Aluminum alkoxide, boron chloride and antimony acetylacetonate are used as the raw materials, the proportion of the three raw materials is equimolar for the preparation of the nanosized aluminum-boron-antimony alloy powder, and the particle size is within 20-80 nm.

### Claim 4 (depends on 1)

An aluminum paste according to claim 1, wherein the organic carrier is the mixture of ethyl cellulose and organic solvent; the organic solvent is one or two members of the group consisting of terpineol, diethylene glycol monobutyl ether, ethylene glycol monomethyl ether, butyl carbitol acetate, sorbitan monostearate and lecithin.

### Claim 5 (depends on 1)

An aluminum paste according to claim 1, wherein the inorganic binder is obtained after being ball milled, and is flaky Bi2O3—V2O5—Sb2O3—MoO3 glass powder with a particle size of 7-11 μm and an adjustable softening temperature in the range of 250-650° C.

### Claim 6 (depends on 1)

An aluminum paste according to claim 1, wherein the aluminum paste includes at least one auxiliary additive selected from the group consisting of tetrabutyl titanate and zinc methacrylate.

### Claim 7 (depends on 1)

A preparation method of the aluminum paste according to claim 1, including the following steps:
70-85 parts by weight of aluminum powder, 1-5 parts by weight of nanosized aluminum-boron-antimony alloy powder, 10-25 parts by weight of organic carrier and 0.1-6 parts by weight of inorganic binder and 0.01-1 parts by weight of auxiliary additive are weighed, mixed, dispersed with a dispersion machine at a speed of 500-2000 rpm for 1 h, grinded with a three-roller grinding machine to a fineness less than 15 μm, and viscosity of the paste is controlled within 30-50 Pa·s, which is measured with a Brookfield DV2T viscometer at 25° C.

### Claim 8 (depends on 1)

An application of the aluminum paste according to claim 1 on PERC cells: by the use of the aluminum paste, a uniform and dense back surface field layer is obtained, and the filling ratio at point contacts is 90% or more, the filling ratio at point contacts is analyzed by scanning electron microscope (SEM) and metallographic microscope, and the solar cell sample used for testing the filling ratio at point contacts is made by laser dicing and acid solution soaking.