Shallow-homojunction solar cells

• US 4,227,941 A
• Filed: 03/21/1979
• Issued: 10/14/1980
• Est. Priority Date: 03/21/1979
• Status: Expired due to Term

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Bozler, Carl O., Fan, John C. C., McClelland, Robert W., Chapman, Ralph L.
• Primary Examiner(s): Weisstuch, Aaron
• Application Number:
  US06/022,405
• Time in Patent Office: 573 Days
• Field of Search: 136/89 SJ, 136/89 GA, 136/89 CC, 136/89 CR, 357/30
• US Class Current: 136/255
• CPC Class Codes: H01L 31/02168 the coatings being antireflective or having enhancing optical properties for the solar cells
• CPC Class Codes: H01L 31/0693 the devices including, apart from doping material or other impurities, only AIIIBV compounds, e.g. GaAs or InP solar cells
• CPC Class Codes: Y02E 10/544 Solar cells from Group III-V materials

Abstract

Improvements in shallow-homojunction solar cells based upon a plurality of layers of a direct gap semiconductor material such as GaAs, as well as their fabrication, are disclosed. The shallow-homojunction solar cells have a n⁺ /p/p⁺ structure in which the n⁺ top layer is limited to a thickness which permits significant carrier generation to occur in a lower semiconductor layer. An anodic antireflection coating is applied over the n⁺ top layer, and a particularly preferred method for applying the antireflection coating is by anodization. These solar cells can be grown on relatively inexpensive substrates, if desired, such as silicon or germanium.

Claims

1. A shallow-homojunction photovoltaic device formed from a direct bandgap semiconductor material doped to provide an n⁺ /p/p⁺ layered structure, said n⁺ layer having a thickness below about 1500 Angstroms thereby allowing significant carrier generation to occur in the p layer upon irradiation of said device with light on the n⁺ side.

2. A shallow-homojunction photovoltaic device of claim 1 wherein said device has an antireflection coating over said n⁺ layer.

3. A shallow-homojunction photovoltaic device of claim 2 wherein said direct bandgap semiconductor material comprises GaAs.

4. A shallow-homojunction photovoltaic device of claim 3 wherein said device has a substrate formed from a different material than GaAs.

5. A shallow-homojunction photovoltaic device of claim 4 wherein said substrate is formed from silicon or germanium.

6. A shallow-homojunction photovoltaic device of claims 2, 3, 4 or 5 wherein said antireflection coating comprises an anodic coating.