US4376228A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Solar cells having ultrathin active layers
Assignee: Massachusetts Institute of Technology
•
Filing: 1979-07-16
•
Granted: 1983-03-08
•
Expires: 1999-07-16
Abstract
Abstract Improvements in solar cells based upon low cost semiconductors, such as amorphous silicon, are disclosed. The improved solar cells of this invention have ultrathin active semiconductor layers having a thickness between 0.1 t.sub.α and L m wherein t.sub.α is the solar spectrum absorption length and L m is the diffusion length for photogenerated minority charge carriers in the active layer. The back surface reflector has a solar spectrum reflectivity of 70% or greater, so that incident energy not absorbed in a direct pass through the active layer is reflected for another pass. The most preferred embodiment of the cells described herein are shaped to have a light-trapping structure so that light makes multiple passes through the thin semiconductor layers.
Inventors
- 👤 John C. C. Fan
- 👤 Carl O. Bozler
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 19:53
CPC Classifications
H; H10; H10F; H10F10/00; H10F10/10; H10F10/17; H10F77/00; H10F77/10; H10F77/14; H10F77/147; H10F77/40; H10F77/42; H10F77/48; H10F77/488; Y; Y02; Y02E; Y02E10/00; Y02E10/50; Y02E10/52; Y02E10/548
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
85 words
In a solar cell having an active semiconductor layer consisting essentially of silicon produced from an alloy of amorphous silicon and hydrogen in a glow discharge in silane, said layer having a minority carrier diffusion length, L m , which is less than the solar spectrum absorption thickness t.sub.α ; the improvement of limiting said active layer to a thickness of less than 0.25 μm and providing said active layer with a back surface reflector having a solar spectrum reflectivity of at least about 70%.
Claim 2
Dependent Claim
85 words
In a solar cell having an active semiconductor layer consisting essentially of silicon produced from an alloy of amorphous silicon and hydrogen in a glow discharge in silane, said layer having a minority carrier diffusion length, L m , which is less than the solar spectrum absorption thickness t.sub.α ; the improvement of limiting said active layer to a thickness of less than 0.25 μm and providing said active layer with a back surface reflector having a solar spectrum reflectivity of at least about 70%.
Claim 3
Dependent Claim
15 words
The improvement of claim 1, wherein said back surface reflector comprises a layer of silver.
Claim 4
Dependent Claim
78 words
A solar cell comprising: a. an active layer of a semiconductor consisting essentially of silicon produced from an alloy of amorphous silicon and hydrogen in a glow discharge in silane, said layer having a thickness of less than 0.25 μm; b. a junction for maintaining separation of photogenerated charge carriers; c. a back surface reflector for said active semiconductor layer, said back surface reflector having a solar spectrum reflectivity of at least about 70%; and, d. a substrate.
Claim 5
Dependent Claim
78 words
A solar cell comprising: a. an active layer of a semiconductor consisting essentially of silicon produced from an alloy of amorphous silicon and hydrogen in a glow discharge in silane, said layer having a thickness of less than 0.25 μm; b. a junction for maintaining separation of photogenerated charge carriers; c. a back surface reflector for said active semiconductor layer, said back surface reflector having a solar spectrum reflectivity of at least about 70%; and, d. a substrate.
Claim 6
Dependent Claim
33 words
A solar cell of claim 3 wherein said junction comprises a Schottky barrier formed between said semiconductor layer and a metal having a thickness at which said metal is transparent to solar radiation.
Claim 7
Dependent Claim
15 words
A solar cell of claim 4 wherein said metal comprises silver, platinum, palladium or aluminum.
Claim 8
Dependent Claim
14 words
A solar cell of claim 5 additionally including an antireflection coating on said metal.
Claim 9
Dependent Claim
13 words
A solar cell of claim 4 wherein said junction comprises a p-n junction.
Claim 10
Dependent Claim
13 words
A solar cell of claim 4 wherein said junction comprises a p-i-n junction.
Claim 11
Dependent Claim
11 words
A solar cell of claim 4 wherein said substrate comprises glass.
Claim 12
Dependent Claim
13 words
A solar cell of claim 4 wherein said substrate comprises a polymeric film.
Claim 13
Dependent Claim
18 words
A solar cell of claim 2, 4, 6 or 10 wherein said solar cell has a light-trapping structure.
Claim 14
Dependent Claim
13 words
A solar cell of claim 11 wherein said back surface reflector comprises silver.
Claim 15
Dependent Claim
42 words
A solar cell comprising an active layer of silicon having a thickness of from about 0.1 μm to about 0.25 μm, a back surface reflector for said layer of silicon, a junction for maintaining separation of photogenerated charge carriers, and a substrate.
Claim 16
Dependent Claim
42 words
A solar cell comprising an active layer of silicon having a thickness of from about 0.1 μm to about 0.25 μm, a back surface reflector for said layer of silicon, a junction for maintaining separation of photogenerated charge carriers, and a substrate.
Claim 17
Dependent Claim
16 words
A solar cell of claim 13 wherein said silicon was deposited by glow discharge in silane.
Claim 18
Dependent Claim
21 words
A solar cell of claim 14 wherein said back surface reflector has a solar spectrum reflectivity of at least about 70%.
Claim 19
Dependent Claim
13 words
A solar cell of claim 15 wherein said substrate comprises a polymeric film.
References Cited (Backward Citations)
DE2715471A1
Cited
US4166919A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1986-03-07 | 1986-09-06 | 1987-03-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-03-07 | 1990-09-06 | 1991-03-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-03-07 | 1994-09-06 | 1995-03-08 | $7700.00 | Window Closed / Lapsed |