US4514581A
Expired / Lapsed
US
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Solar cells having ultrathin active layers
Assignee: Massachusetts Institute of Technology
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Filing: 1982-11-08
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Granted: 1985-04-30
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Expires: 2002-11-08
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 mulitple 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
2026-11-02 19:28
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: 17
Claim 1
Independent Claim
61 words
In a solar cell having an active semiconductor layer which has 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 L m and greater than about 0.1 t.sub.α and providing said active layer with a back surface reflector.
Claim 2
Dependent Claim
61 words
In a solar cell having an active semiconductor layer which has 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 L m and greater than about 0.1 t.sub.α and providing said active layer with a back surface reflector.
Claim 3
Dependent Claim
12 words
The improvement of claim 1 wherein said active semiconductor layer comprises silicon.
Claim 4
Dependent Claim
20 words
The improvement of claim 2 wherein said silicon semiconductor layer is produced by deposition from a glow discharge in silane.
Claim 5
Dependent Claim
18 words
The improvement of claims 1, 2 or 3 wherein said back surface reflector comprises a layer of silver.
Claim 6
Dependent Claim
87 words
A solar cell comprising: a. an active layer of a semiconductor having an inherent minority carrier diffusion length, L m , which is less than its solar spectrum absorption thickness t.sub.α, said semiconductor layer having a thickness of less than L m and greater than about 0.1 t.sub.α ; b. a junction for maintaining separation of photogenerated charge carrier, 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 7
Dependent Claim
87 words
A solar cell comprising: a. an active layer of a semiconductor having an inherent minority carrier diffusion length, L m , which is less than its solar spectrum absorption thickness t.sub.α, said semiconductor layer having a thickness of less than L m and greater than about 0.1 t.sub.α ; b. a junction for maintaining separation of photogenerated charge carrier, 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 8
Dependent Claim
15 words
A solar cell of claim 5 wherein said semiconductor layer comprises a layer of silicon.
Claim 9
Dependent Claim
33 words
A solar cell of claim 6 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 10
Dependent Claim
15 words
A solar cell of claim 7 wherein said metal comprises silver, platinum, palladium or aluminum.
Claim 11
Dependent Claim
14 words
A solar cell of claim 8 additionally including an antireflection coating on said metal.
Claim 12
Dependent Claim
13 words
A solar cell of claim 6 wherein said junction comprises a p-n junction.
Claim 13
Dependent Claim
13 words
A solar cell of claim 6 wherein said junction comprises a p-i-n junction.
Claim 14
Dependent Claim
11 words
A solar cell of claim 6 wherein said substrate comprises glass.
Claim 15
Dependent Claim
13 words
A solar cell of claim 6 wherein said substrate comprises a polymeric film.
Claim 16
Dependent Claim
19 words
A solar cell of claim 4, 6, 7, 9 or 13 wherein said solar cell has a light-trapping structure.
Claim 17
Dependent Claim
13 words
A solar cell of claim 14 wherein said back surface reflector comprises silver.
References Cited (Backward Citations)
DE2715471A1
Cited
US4376228A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-04-29 | 1988-10-29 | 1989-04-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-04-29 | 1992-10-29 | 1993-04-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-04-29 | 1996-10-29 | 1997-04-30 | $7700.00 | Window Closed / Lapsed |