# US 8,772,894 B2 · Trench process and structure for backside contact solar cells with polysilicon doped regions

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- Number: US 8,772,894 B2
- Document ID: US8772894B2
- Status: Granted
- Kind: B2
- Application number: 13/893,005
- Filed: 2013-05-13
- Published: 2013-09-19
- Granted: 2014-07-08
- Earliest claimed: 2008-06-12
- Assignees: SunPower Corporation
- Applicants: David D. Smith
- Inventors: David D. Smith
- Web page: https://patentgrep.com/patent/US8772894B2

## CPC

- H10F 10/146: {Back-junction photovoltaic cells, e.g. having interdigitated base-emitter regions on the back side}
- H10F 10/14: Photovoltaic cells having only PN homojunction potential barriers
- H10F 10/165: the heterojunctions being Group IV-IV heterojunctions, e.g. Si/Ge, SiGe/Si or Si/SiC photovoltaic cells
- H10F 10/166: the Group IV-IV heterojunctions being heterojunctions of crystalline and amorphous materials, e.g. silicon heterojunction [SHJ] photovoltaic cells
- H10F 71/121: {The active layers comprising only Group IV materials}
- H10F 71/1221: {comprising polycrystalline silicon}
- H10F 71/129: {Passivating}
- H10F 77/122: comprising only Group IV materials
- H10F 77/14: Shape of semiconductor bodies; Shapes, relative sizes or dispositions of semiconductor regions within semiconductor bodies
- H10F 77/147: {Shapes of bodies}
- H10F 77/1642: {including only Group IV materials}
- H10F 77/211: {for photovoltaic cells}
- H10F 77/219: {Arrangements for electrodes of back-contact photovoltaic cells}
- H10F 77/227: {for emitter wrap-through [EWT] photovoltaic cells, e.g. interdigitated emitter-base back-contacts}
- H10F 77/311: {for photovoltaic cells}
- H10F 77/703: {of the semiconductor bodies, e.g. textured active layers}
- H10F 77/707: {of the substrates or of layers on substrates, e.g. textured ITO layer on a glass substrate}
- H10F 77/935: {for photovoltaic devices or modules}
- 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 solar cell includes polysilicon P-type and N-type doped regions on a backside of a substrate, such as a silicon wafer. A trench structure separates the P-type doped region from the N-type doped region. Each of the P-type and N-type doped regions may be formed over a thin dielectric layer. The trench structure may include a textured surface for increased solar radiation collection. Among other advantages, the resulting structure increases efficiency by providing isolation between adjacent P-type and N-type doped regions, thereby preventing recombination in a space charge region where the doped regions would have touched.

## Claims

### Claim 1

A solar cell comprising:
a solar cell substrate having a front side configured to face the sun during normal operation and a backside opposite the front side;
a P-type doped region and an N-type doped region of the solar cell over the backside of the solar cell substrate;
a first dielectric layer between the solar cell substrate and the P-type and N-type doped regions; and
a trench structure separating the P-type doped region and the N-type doped region, and dividing the first dielectric layer.

### Claim 2 (depends on 1)

The solar cell of claim 1 wherein the P-type and N-type doped regions comprise polysilicon.

### Claim 3 (depends on 1)

The solar cell of claim 1 wherein the solar cell substrate comprises an N-type doped silicon substrate.

### Claim 4 (depends on 1)

The solar cell of claim 1 wherein the first dielectric layer comprises silicon dioxide formed to a thickness between 5 to 40 Angstroms on a backside surface of the solar cell substrate.

### Claim 5 (depends on 1)

The solar cell of claim 1 wherein the trench has a textured surface that absorbs solar radiation incident on the backside of the solar cell substrate.

### Claim 6 (depends on 1)

The solar cell of claim 1 further comprising a second dielectric layer in the trench.

### Claim 7 (depends on 6)

The solar cell of claim 6 further comprising:
a passivation layer between the second dielectric layer and the solar cell substrate.

### Claim 8 (depends on 1)

The solar cell of claim 1 further comprising a diffused passivation region in the solar cell substrate under the trench, wherein the diffused passivation region is doped with an N-type dopant.

### Claim 9 (depends on 1)

The solar cell of claim 1 further comprising interdigitated metal contact fingers electrically coupled to the P-type and N-type doped regions.

### Claim 10

A solar cell comprising:
a P-type doped region and an N-type doped region formed on a backside of a solar cell substrate, each of the P-type and N-type doped regions being formed over a first dielectric layer; and
a trench structure separating the P-type doped region and the N-type doped region, and dividing the first dielectric layer.

### Claim 11 (depends on 10)

The solar cell of claim 10 further comprising:
a second dielectric layer formed in the trench structure.

### Claim 12 (depends on 11)

The solar cell of claim 11 further comprising metal contacts electrically coupled to the P-type and N-type doped regions through the second dielectric layer.

### Claim 13 (depends on 10)

The solar cell of claim 10 wherein the solar cell substrate comprises an N-type silicon substrate.

### Claim 14 (depends on 10)

The solar cell of claim 10 wherein the P-type doped region and the N-type doped region comprise polysilicon.

### Claim 15 (depends on 10)

The solar cell of claim 10 wherein a surface of the trench structure is randomly textured.