Thin solar cell

• US 5,320,685 A
• Filed: 08/12/1992
• Issued: 06/14/1994
• Est. Priority Date: 10/04/1991
• Status: Expired due to Term

• Current Assignee: RWE Space Solar Power GmbH
• Original Assignee: Telefunken Systemtechnik AG
• Inventors: Frese, Volker, Braun, Matthias, Hilgarth, Just
• Primary Examiner(s): Weisstuch, Aaron
• Application Number:
  US07/928,323
• Time in Patent Office: 671 Days
• Field of Search: 136/244, 136/255, 136/256, 136/262, 136/259, 136/251, 437/2-5
• US Class Current: 136/259
• CPC Class Codes: B64G 1/443 Photovoltaic cell arrays
• CPC Class Codes: H01L 31/02008 for solar cells or solar cell modules
• CPC Class Codes: H01L 31/022433 Particular geometry of the grid contacts
• CPC Class Codes: H01L 31/0488 Double glass encapsulation, e.g. photovoltaic cells arranged between front and rear glass sheets
• CPC Class Codes: H01L 31/0508 the interconnection means having a particular shape
• CPC Class Codes: H01L 31/184 the active layers comprising only AIIIBV compounds, e.g. GaAs, InP
• CPC Class Codes: Y02E 10/544 Solar cells from Group III-V materials

Abstract

A method and apparatus for forming a thin solar cell having a substantially planar body comprising a first layer which includes at least one photoactive semiconductor layer. This first layer has a frontal light entrance face, a rear face, and side edge face. A second layer comprising an electrically conductive grid-shaped front contact and an anti-reflection layer is located on the frontal light entrance face. A third layer comprising a front cover glass is fastened substantially adjacent the anti-reflection layer and the front grid-shaped contact. A fourth layer, comprising an electrically conductive rear conductive contact, is located on the rear face of the first layer. Spaced apart from the first layer are two electrically interconnection pads. Each pad has a face suitable for an electrical interconnection. A first connection for electrically connecting one pad to the front grid shaped contact and a second connection for electrically connecting the other pad to the rear conductive contact are disposed on one side of the solar cell.

Claims

1. A solar cell having a substantially planar body comprising:

a first layer comprising at least one photoactive semiconductor layer having a frontal light entrance face, a rear face, and side edge faces;

a second layer comprising an electrically conductive grid-shaped front contact and an anti-reflection layer, both located on said frontal light entrance face;

a third layer comprising a front cover glass fastened substantially adjacent to said anti-reflection layer and said front contact;

a fourth layer comprising an electrically conductive rear contact located on said rear face of said first layer;

first and second electrically conductive interconnection pads each having an electrically conductive body and a connection face suitable for an electrical interconnection, said interconnection pads both being disposed on one side of the solar cell and spaced apart from said first layer;

a first connection means for electrically connecting the connection face of the first interconnection pad to said front contact;

a second connection means for electrically connecting the connection face of the second interconnection pad to said rear contact.

2. A solar cell as defined in claim 1, wherein the at least one photoactive semiconductor layer comprises gallium arsenide.

3. A solar cell as defined in claim 1, wherein said first and second interconnection pads are disposed on a side of the front cover glass facing the semiconductor layer such that the connection faces of the interconnection pads are connected to the front and rear contacts.

4. A solar cell as defined in claim 1, further comprising a dielectric intermediate layer disposed between said third and fourth layers wherein the interconnection pads are disposed in the dielectric intermediate layer and the connection faces of said interconnection pads are connected to the front and rear contacts.

5. A solar cell as defined in claim 4, wherein said dielectric intermediate layer comprises an adhesive layer.

6. A solar cell as defined in claim 4, wherein said dielectric intermediate layer comprises an anti-reflection layer.

7. A solar cell as defined in claim 1, wherein said solar cell has a photoactive surface area and said interconnection pads are disposed near an edge region of said photoactive surface area.

8. A solar cell as defined in claim 1, wherein said first and second electrical connection means comprise a first and a second conductive bridge contact, respectively.

9. A solar cell as defined in claim 8, further comprising an insulating layer between said first layer and said second conductive bridge contact.

10. A solar cell as defined in claim 9, wherein said insulating layer comprises one of air and an evacuated space.

11. A solar cell as defined in claim 1, wherein side edge faces of said at least one photoactive semiconductor layer are passivated by a dielectric material.

12. A solar cell as defined in claim 1, wherein said first layer comprises a sequence of photoactive semiconductor layers, and is light sensitive on said frontal light entrance face and on said rear face, said rear contact of said fourth layer comprises an electrically conductive grid-shaped contact;

said fourth layer further comprises an anti-reflection layer; and

said solar cell further comprises a fifth layer comprising a rear cover glass fastened substantially adjacent to said fourth layer.

13. A method of producing a solar cell, comprising the steps of:

(a) producing a photoactive semiconductor layer on a carrier substrate, the photoactive semiconductor layer having a front light entrance face, a rear face and an edge region, said rear face being disposed on the substrate;

(b) applying an anti-reflection layer and an electrically conductive grid-shaped front contact to the front light entrance face of the photoactive semiconductor layer;

(c) covering the anti-reflection layer and the grid-shaped contact with a front cover glass;

(d) removing at least partially the carrier substrate from the photoactive semiconductor layer;

(e) removing a portion of the edge region, a first partial region of the photoactive semiconductor layer to create a first recess which exposes a portion of the front contact used to form a first electrically conductive interconnection pad disposed on the same side of the solar cell as the front cover glass and spaced from the photoactive semiconductor layer, and a second partial region of the photoactive semiconductor to form a second recess;

(f) insulating the edge region of the photoactive semiconductor layer where the second partial region was removed to form an insulated edge region;

(g) applying a rear contact to the rear face of the photoactive semiconductor layer having the carrier substrate at least partially removed therefrom, the rear contact extending through the second recess in the photoactive semiconductor layer over the insulated edge region of the photoactive semiconductor layer to the side of the front cover glass facing the semiconductor layer to form a second electrically conductive interconnection pad disposed on the same side of the solar cell as the front cover glass and spaced from the photoactive semiconductor layer; and

(h) connecting respective solar cell electrical connectors to the electrically conductive interconnection pads.

14. A method as defined in claim 13, further comprising forming a dielectric intermediate layer disposed between the front cover glass and the photoactive semiconductor layer.

15. A method as defined in claim 13, including passivating the side end face of the photoactive semiconductor layer.

16. A method as defined in claim 13, wherein said step (d) includes removing the carrier substrate and any existing epitaxial or intermediate layers from the photoactive semiconductor layer by a CLEFT process.

17. A method as defined in claim 13, wherein said step (d) includes removing the carrier substrate and any existing epitaxial or intermediate layers from the photoactive semiconductor layer by a lift-off process employing a chemically selectively-etchable epitaxially grown intermediate layer.

18. A method as defined in claim 13, wherein said step (d) comprises etching away the carrier substrate and any existing epitaxial layers or intermediate layers to an epitaxially grown stop layer.

19. A method as defined in claim 13, wherein said step (d) includes at least partially removing the carrier substrate and any existing epitaxial layers or intermediate layers from the photoactive semiconductor layer by one of lapping, polishing, or etching.

20. A method as defined in claim 13, wherein said step (a) includes producing on the carrier an epitaxial layer sequence wherein the front and rear faces are light sensitive;

said step (g) includes applying the rear contact in the form of an electrically conductive grid-shaped contact; and

said method further includes applying an anti-reflective layer to the rear face and covering the rear face with a rear cover glass.

21. A method as defined in claim 13, wherein said step (c) includes applying the front cover glass by way of a temperature resistant cover glass adhesive.

22. A method as defined in claim 13, wherein said step (c) includes melting the front cover glass directly onto the solar cell.