# US 4,398,056 A · Solar cell with reflecting grating substrate

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- Number: US 4,398,056 A
- Document ID: US4398056A
- Status: Granted
- Kind: A
- Application number: 06/285,953
- Filed: 1981-07-23
- Granted: 1983-08-09
- Earliest claimed: 1981-07-23
- Assignees: Exxon Research & Engineering Co.
- Inventors: Ping Sheng
- Web page: https://patentgrep.com/patent/US4398056A

## CPC

- H10F 77/315: {the coatings being antireflective or having enhancing optical properties}
- H10F 77/48: Back surface reflectors [BSR]
- Y02E 10/52: PV systems with concentrators
- 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 solar cell which includes a thin layer of active material bounded on the side toward the incident light with an antireflection coating and bounded on the other side by a reflecting diffraction grating to internally reflect the incident light back into the active material.

## Claims

### Claim 1

A solar cell comprising:
(a) a rectangular diffraction grating coated with a layer of reflecting material on its grating surface; and
(b) an active layer of semiconductor material formed on said layer of reflecting material; wherein said diffraction grating has a groove periodicity and depth such that enhancement of absorption of incident light within a desired wavelength range is optimized with respect to the index of refraction and the thickness of the active material and dielectric constant of said reflecting material.

### Claim 2 (depends on 1)

The solar cell of claim 1, wherein said layer of active material is silicon.

### Claim 3 (depends on 2)

The solar cell of claim 2 wherein said reflecting material is silver.

### Claim 4 (depends on 2)

The solar cell of claim 2 wherein said desired wavelength range is 0.55 .mu.m and 1.1 .mu.m.

### Claim 5 (depends on 1)

The solar cell of claim 1 wherein said reflecting material is silver or aluminum.

### Claim 6 (depends on 1)

The solar cell of claim 1 wherein said active layer is polycrystalline silicon, said reflecting material is silver, the thickness of said active layer is about 1 .mu.m, said period of said grating has a value between 0.35 .mu.m and 0.45 .mu.m, and said depth has a value between 0.065 .mu.m and 0.085 .mu.m.

### Claim 7 (depends on 1)

The solar cell of claim 1 wherein said diffraction grating is a two-dimensional rectangular array.

### Claim 8 (depends on 7)

The solar cell of claim 7 wherein said active layer is amorphous silicon of thickness about 0.5 .mu.m, said reflecting layer is silver, said period of said grating has a value between 0.25 .mu.m and 0.35 .mu.m and said depth of said grating has a value between 0.07 .mu.m and 0.09 .mu.m.

### Claim 9 (depends on 1)

The solar cell of claim 1 wherein said diffraction grating is a square-wave diffraction grating.