Back wall solar cell

• US 4,131,486 A
• Filed: 04/24/1978
• Issued: 12/26/1978
• Est. Priority Date: 01/19/1977
• Status: Expired due to Term

• Current Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Original Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: Brandhorst, Henry W. Jr.
• Primary Examiner(s): Mack, John H.
• Assistant Examiner(s): Weisstuch, Aaron
• Application Number:
  US05/899,123
• Time in Patent Office: 246 Days
• Field of Search: 136/89 SJ, 136/89 SG, 136/89 CD, 357/30
• US Class Current: 136/255
• CPC Class Codes: H01L 31/068 the potential barriers being only of the PN homojunction type, e.g. bulk silicon PN homojunction solar cells or thin film polycrystalline silicon PN homojunction solar cells
• CPC Class Codes: Y02E 10/547 Monocrystalline silicon PV cells

Abstract

The application discloses a back-well cell, for example, a solar cell which comprises a first semiconductor material of one conductivity type with one face having the same conductivity type but more heavily doped to form a field region arranged to receive the radiant energy to be converted to electrical energy, and a layer of a second semiconductor material, preferably highly doped, of opposite conductivity type on the first semiconductor material adjacent the first semiconductor material at an interface remote from the heavily doped field region. Instead of the opposite conductivity layer, one may employ a metallic layer to form a Schottky diode. If the metallic Schottky diode layer is used, no additional back contact is needed. A contact such as a gridded contact, pervious to the radiant energy may be applied to the heavily doped field region of the more heavily doped, same conductivity material for its contact.

Claims

1. An energy converter for the conversion of radiant energy to electrical energy comprising

a first semiconductor material of one conductivity type having a face for receiving said radiant energy and an oppositely disposed back face, said first semiconductor material having a thickness between about 5 μ

M and about 500 μ

M,

a region of a semiconductor material of said one conductivity type along said energy receiving face and forming a first interface with said first semiconductor material, said region having a greater surplus of majority carriers and therefore being of greater conductivity than said first semiconductor material, said region having a thickness of between about 0.1 μ

M and about 10.0 μ

M and

a layer of second material on said back face of said first semiconductor material and forming a second interface remote from said region and selected from a metallic material and a semiconductor material of opposite conductivity type, whereby a rectifying junction is formed between said first and second materials at said second interface at said back face, said layer having a thickness of between about 0.1 μ

M and about 10.0 μ

M.

2. An energy converter as claimed in claim 1, there being on said region metallic areas pervious to said radiant energy.

3. An energy converter as claimed in claim 2, said first semiconductor material being of p-type and said region material being of p⁺ type.

4. An energy converter as claimed in claim 3, said layer material being of n-type.

5. An energy converter as claimed in claim 4, said first semiconductor material being silicon doped to a level of about 1.3 ×

10¹⁵ boron atoms/cc, and said region being doped to a maximum concentration of about 2 ×

10²⁰ boron atoms/cc. said layer being doped with phosphorus to a maximum concentration of about 2 ×

10²⁰ atoms/cc.

6. An energy converter as claimed in claim 3, said first material being of silicon, said p⁺ region being of silicon doped with an element selected from group IIIA of the periodic table.

7. An energy converter as claimed in claim 6, said element being selected from boron and aluminum.

8. An energy converter as claimed in claim 3, said first material being of silicon, said layer being of silicon doped with an element selected from group VA of the periodic table.

9. An energy converter as claimed in claim 8, said element being selected from phosphorus and arsenic.

10. An energy converter as claimed in claim 1, said first semiconductor material being of n-type, said region material being of n⁺ type.

11. An energy converter as claimed in claim 10, said second material being metallic whereby said rectifying junction is a Schottky diode.

12. An energy converter as claimed in claim 11, said second material being selected from gold, platinum, chromium, and aluminum.

13. An energy converter as claimed in claim 12, said first semiconductor material being silicon.

14. An energy converter as claimed in claim 10, said second material being of p-type.

15. An energy converter as claimed in claim 10, said second material being of p⁺ type.

16. An energy converter as claimed in claim 15, said first semiconductor material being 10 ohm-cm. silicon doped to a level of about 5 ×

10¹⁴ phosphorus atoms/cc, said region being doped with phosphorus to a maximum surface concentration of about 2 ×

10²⁰ atoms/cc, and said layer being doped with boron to a maximum surface concentration of about 2 ×

10²⁰ atoms/cc.

17. An energy converter as claimed in claim 1, further comprising a back contact applied to said layer.