# US 8,785,236 B2 · Solar cell contact formation using laser ablation

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- Number: US 8,785,236 B2
- Document ID: US8785236B2
- Status: Granted
- Kind: B2
- Application number: 13/669,147
- Filed: 2012-11-05
- Published: 2013-03-14
- Granted: 2014-07-22
- Earliest claimed: 2009-12-01
- Assignees: SunPower Corporation
- Applicants: SunPower Corporation
- Inventors: Gabriel Harley; David D. Smith; Peter John Cousins
- Web page: https://patentgrep.com/patent/US8785236B2

## CPC

- H10F 77/935: {for photovoltaic devices or modules}
- H10F 10/146: {Back-junction photovoltaic cells, e.g. having interdigitated base-emitter regions on the back side}
- H10F 77/219: {Arrangements for electrodes of back-contact photovoltaic cells}
- Y02E 10/546: Polycrystalline silicon PV cells
- Y02E 10/547: Monocrystalline silicon PV cells
- 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

The formation of solar cell contacts using a laser is described. A method of fabricating a back-contact solar cell includes forming a poly-crystalline material layer above a single-crystalline substrate. The method also includes forming a dielectric material stack above the poly-crystalline material layer. The method also includes forming, by laser ablation, a plurality of contacts holes in the dielectric material stack, each of the contact holes exposing a portion of the poly-crystalline materiat layer; and forming conductive contacts in the plurality of contact holes.

## Claims

### Claim 1

A method of fabricating a solar cell, the method comprising:
forming a poly-crystalline material layer above a single-crystalline substrate;
forming a dielectric material above the poly-crystalline material layer;
forming, by laser ablation, a plurality of contacts holes in the dielectric material, the plurality of the contact holes exposing P-type and N-type doped regions that are formed in the poly-crystalline material layer; and
forming conductive contacts in the plurality of contact holes, a first conductive contact of the conductive contacts being formed to electrically connect to a corresponding P-type doped region in the poly-crystalline material layer and a second conductive contact of the conductive contacts being formed to electrically connect to a corresponding N-type doped region in the poly-crystalline material layer.

### Claim 2 (depends on 1)

The method of claim 1, wherein forming the poly-crystalline material layer above the single-crystalline substrate comprises forming a layer of poly-crystalline silicon above a single-crystalline silicon substrate.

### Claim 3 (depends on 1)

The method of claim 1 wherein forming the dielectric material above the poly-crystalline material layer comprises forming a stack of dielectric materials above the poly-crystalline material layer.

### Claim 4 (depends on 3)

The method of claim 3, wherein forming the stack of dielectric materials above the poly-crystalline material layer comprises forming a silicon dioxide layer on the poly-crystalline material layer, and forming a silicon nitride layer on the silicon dioxide layer.

### Claim 5 (depends on 4)

The method of claim 4, wherein the silicon dioxide layer is formed to have a thickness approximately in a range of 1-50 nanometers.

### Claim 6 (depends on 1)

The method of claim 1, wherein forming the dielectric material above the poly-crystalline material layer comprises forming only a silicon nitride layer.

### Claim 7 (depends on 1)

The method of claim 1, wherein forming the plurality of contact holes is performed without the use of a patterned mask.

### Claim 8 (depends on 1)

The method of claim 1, wherein forming the plurality of contact holes comprises ablating with a laser having a wavelength approximately at, or less than, 1064 nanometers.

### Claim 9

A method of fabricating a solar cell, the method comprising:
forming a poly-crystalline material layer above a single-crystalline substrate;
forming a dielectric material above the poly-crystalline material layer;
using a laser to form a contact hole in the dielectric material to form a recast poly signature in the poly-crystalline material layer, the contact hole exposing the recast poly signature in a doped region of the poly-crystalline material layer, the poly-crystalline material layer including P-type and N-type doped regions; and
forming a conductive contact in the contact hole, the conductive contact being coupled to the P-type doped region or the N-type doped region in the poly-crystalline material layer and in alignment with the recast poly signature.

### Claim 10 (depends on 9)

The method of claim 9, wherein forming the poly-crystalline material layer above the single-crystalline substrate comprises forming a layer of poly-crystalline silicon above a single-crystalline silicon substrate.

### Claim 11 (depends on 9)

The method of claim 9, wherein forming the dielectric material above the poly-crystalline material layer comprises forming a stack of dielectric materials above the poly-crystalline material layer.

### Claim 12 (depends on 11)

The method of claim 11, wherein forming the stack of dielectric materials above the poly-crystalline material layer comprises forming a silicon dioxide layer on the poly-crystalline material layer, and forming a silicon nitride layer on the silicon dioxide layer.

### Claim 13 (depends on 12)

The method of claim 12, wherein forming the silicon dioxide layer comprises forming the layer to have a thickness approximately in a range of 1-50 nanometers.

### Claim 14 (depends on 9)

The method of claim 9, wherein forming the dielectric material above the poly-crystalline material layer comprises forming only a silicon nitride layer.