# US 12,009,448 B2 · Front contact solar cell with formed electrically conducting layers on the front side and backside

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- Number: US 12,009,448 B2
- Document ID: US12009448B2
- Status: Granted
- Kind: B2
- Application number: 16/594,417
- Filed: 2019-10-07
- Published: 2020-02-13
- Granted: 2024-06-11
- Earliest claimed: 2008-07-01
- Assignees: Maxeon Solar Pte. Ltd.
- Applicants: Maxeon Solar Pte, Ltd.
- Inventors: Peter John Cousins
- Web page: https://patentgrep.com/patent/US12009448B2

## CPC

- H10F 10/146: {Back-junction photovoltaic cells, e.g. having interdigitated base-emitter regions on the back side}
- H10F 10/16: Photovoltaic cells having only PN heterojunction potential barriers
- H10F 10/165: the heterojunctions being Group IV-IV heterojunctions, e.g. Si/Ge, SiGe/Si or Si/SiC photovoltaic cells
- H10F 71/121: {The active layers comprising only Group IV materials}
- H10F 71/1221: {comprising polycrystalline silicon}
- H10F 77/1642: {including only Group IV materials}
- H10F 77/215: {Geometries of grid contacts}
- H10F 77/315: {the coatings being antireflective or having enhancing optical properties}
- H10F 77/48: Back surface reflectors [BSR]
- H10F 77/703: {of the semiconductor bodies, e.g. textured active layers}
- Y02E 10/52: PV systems with concentrators
- Y02E 10/546: Polycrystalline silicon PV cells
- Y02E 10/547: Monocrystalline silicon PV cells
- Y02P 70/50: Manufacturing or production processes characterised by the final manufactured product
- 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
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

A bipolar solar cell includes a backside junction formed by a silicon substrate and a first doped layer of a first dopant type on the backside of the solar cell. A second doped layer of a second dopant type makes an electrical connection to the substrate from the front side of the solar cell. A first metal contact of a first electrical polarity electrically connects to the first doped layer on the backside of the solar cell, and a second metal contact of a second electrical polarity electrically connects to the second doped layer on the front side of the solar cell. An external electrical circuit may be electrically connected to the first and second metal contacts to be powered by the solar cell.

## Claims

### Claim 1

A solar cell comprising:
a substrate of a first conductivity type, the substrate having a front surface that faces the sun during normal operation and a back surface that is opposite the front surface, the front surface comprising a plurality of substantially flat and planar portions, and the front surface comprising a textured portion, the textured portion directly connected to the plurality of substantially flat and planar portions, and the plurality of substantially flat and planar portions of the front surface of the substrate parallel with the back surface of the substrate;
a first dielectric layer disposed on the back surface of the substrate;
a first layer of doped polysilicon disposed on the first dielectric layer, the first dielectric layer being disposed between the first layer of doped polysilicon and the back surface of the substrate, the first layer of doped polysilicon being of a second conductivity type that is opposite to the first conductivity type;
a first metal contact that is electrically connected to the first layer of doped polysilicon;
pluralities of second metal contacts spaced apart along the substantially flat and planar portions of the substrate and electrically connected to the front surface of the substrate, each plurality of second metal contacts vertically over a corresponding one of the substantially flat and planar portions of the front surface of the substrate but not extending laterally beyond the corresponding one of the substantially flat and planar portions so as to not extend vertically over the textured portion of the front surface of the substrate;
a doped region under the textured portion of the front surface of the substrate, the doped region being of opposite conductivity type to the first layer of doped polysilicon; and
a second dielectric layer comprising contact holes disposed over the first layer of doped polysilicon, wherein the first metal contact is electrically connected to the first layer of doped polysilicon through the contact holes.

### Claim 2 (depends on 1)

The solar cell of claim 1, further comprising:
a third dielectric layer disposed on the front surface of the substrate; and
a second layer of doped polysilicon of the first conductivity type, the third dielectric layer being disposed between the second layer of doped polysilicon and the front surface of the substrate, wherein the second metal contact is disposed on and is electrically connected to the second layer of doped polysilicon.

### Claim 3 (depends on 1)

The solar cell of claim 1, further comprising an antireflective layer on the textured portion of the front surface of the substrate.

### Claim 4 (depends on 3)

The solar cell of claim 3, wherein the antireflective layer comprises silicon nitride.

### Claim 5 (depends on 1)

The solar cell of claim 1, wherein the first dielectric layer comprises silicon dioxide.

### Claim 6 (depends on 1)

The solar cell of claim 1, wherein the first dielectric layer has thickness between 10 and 50 Angstroms.

### Claim 7 (depends on 1)

The solar cell of claim 1, further comprising a third metal contact disposed over the first metal contact.

### Claim 8 (depends on 1)

The solar cell of claim 1, wherein the first metal contact, in conjunction with the second dielectric layer, is an infrared reflecting layer on the back surface of the substrate.

### Claim 9 (depends on 1)

The solar cell of claim 1, wherein the first layer of doped polysilicon comprises a P-type doped polysilicon and the substrate comprises an N-type silicon substrate.

### Claim 10 (depends on 1)

The solar cell of claim 1, wherein the first metal contact comprises silver.

### Claim 11

A solar cell comprising:
a first dielectric layer disposed on a back surface of an N-type silicon substrate, the back surface being opposite a front surface of the N-type silicon substrate, the front surface facing the sun during normal operation, the front surface comprising a plurality of substantially flat and planar portions, and the front surface comprising a textured portion, the textured portion directly connected to the plurality of substantially flat and planar portions, and the plurality of substantially flat and planar portions of the front surface of the N-type silicon substrate parallel with the back surface of the N-type silicon substrate;
an antireflective layer on the textured portion of the front surface of the N-type silicon substrate;
a layer of P-type doped polysilicon, the first dielectric layer being disposed between the back surface of the N-type silicon substrate and the layer of P-type doped polysilicon;
a first metal contact that is electrically connected to the layer of P-type doped polysilicon;
pluralities of second metal contacts spaced apart along the substantially flat and planar portions of the substrate and that are electrically connected to the front surface of the N-type silicon substrate, each plurality of second metal contacts vertically over a corresponding one of the substantially flat and planar portions of the front surface of the N-type silicon substrate but not extending laterally beyond the corresponding one of the substantially flat and planar portions so as to not extend vertically over the textured portion of the front surface of the N-type silicon substrate;
an N-type doped region under the textured portion of the front surface of the N-type silicon substrate; and
a second dielectric layer comprising contact holes disposed over the first layer of doped polysilicon, wherein the first metal contact is electrically connected to the layer of P-type doped polysilicon through the contact holes.

### Claim 12 (depends on 11)

The solar cell of claim 11, further comprising:
a third dielectric layer disposed on the front surface of the substrate; and
a layer of N-type doped polysilicon, the third dielectric layer being disposed between the layer of N-type doped polysilicon and the front surface of the N-type silicon substrate, wherein the second metal contact is disposed on and is electrically connected to the second layer of doped polysilicon.

### Claim 13 (depends on 11)

The solar cell of claim 11, wherein the antireflective layer comprises silicon nitride.

### Claim 14 (depends on 11)

The solar cell of claim 11, wherein the first metal contact and second metal contact comprise silver.

### Claim 15

A solar cell comprising:
a substrate of a first conductivity type, the substrate having a front surface that faces the sun during normal operation and a back surface that is opposite the front surface, the front surface comprising a plurality of substantially flat and planar portions, and the front surface comprising a textured portion, the textured portion directly connected to the plurality of substantially flat and planar portions, and the plurality of substantially flat and planar portions of the front surface of the substrate parallel with the back surface of the substrate;
a first dielectric layer disposed on the back surface of the substrate;
a first layer of doped polysilicon disposed on the first dielectric layer, the first dielectric layer being disposed between the first layer of doped polysilicon and the back surface of the substrate, the first layer of doped polysilicon being of a second conductivity type that is opposite to the first conductivity type;
a first metal contact that is electrically connected to the first layer of doped polysilicon;
pluralities of second metal contacts spaced apart along the substantially flat and planar portions of the substrate and electrically connected to the front surface of the substrate, each plurality of second metal contacts vertically over a corresponding one of the substantially flat and planar portions of the front surface of the substrate but not extending laterally beyond the corresponding one of the substantially flat and planar portions so as to not extend vertically over the textured portion of the front surface of the substrate;
a doped region under the textured portion of the front surface of the substrate, the doped region being of opposite conductivity type to the first layer of doped polysilicon;
a second dielectric layer comprising contact holes disposed over the first layer of doped polysilicon, wherein the first metal contact is electrically connected to the first layer of doped polysilicon through the contact holes; and
a first bus bar disposed on the front surface of the substrate, wherein the first metal contact is in electrical contact with, and is perpendicular to, the first bus bar.

### Claim 16 (depends on 15)

The solar cell of claim 15, further comprising a second bus bar disposed on the front surface of the substrate, wherein the second bus bar is parallel to the first bus bar.

### Claim 17 (depends on 16)

The solar cell of claim 16, wherein the first metal contact is in electrical contact with, and perpendicular to, the first bus bar and the second bus bar.

### Claim 18 (depends on 15)

The solar cell of claim 15, further comprising a third bus bar disposed on the back surface of the substrate.

### Claim 19 (depends on 18)

The solar cell of claim 18, further comprising a fourth bus bar disposed on the back surface of the substrate, wherein the fourth bus bar is parallel to the third bus bar.