Back contact device for photovoltaic cells and method of manufacturing a back contact device

• US 20080072953A1
• Filed: 09/25/2007
• Published: 03/27/2008
• Est. Priority Date: 09/27/2006
• Status: Abandoned Application

• Current Assignee: Thinsilicon Corporation
• Original Assignee: Thinsilicon Corporation
• Inventors: Hussen, Guleid, Stephens, Jason M., Coakley, Kevin Michael
• Application Number:
  US11/903,787
• Publication Number:
  US 20080072953A1
• Time in Patent Office: Days
• US Class Current: 136/249
• CPC Class Codes: H01L 31/022441 Electrode arrangements specially adapted for back-contact solar cells
• CPC Class Codes: H01L 31/0516 specially adapted for interconnection of back-contact solar cells
• CPC Class Codes: H01L 31/0682 back-junction, i.e. rearside emitter, solar cells, e.g. interdigitated base-emitter regions back-junction cells
• CPC Class Codes: H01L 31/1804 comprising only elements of Group IV of the Periodic Table
• CPC Class Codes: Y02E 10/547 Monocrystalline silicon PV cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

One or more embodiments of the presently described invention provide a method for fabricating an all-back contact photovoltaic cell. The method includes the steps of depositing a semiconductor layer on a non-opaque substrate, increasing a level of crystallinity of the semiconductor layer by exposing it to a focused beam of energy, doping the semiconductor layer with first and second dopants on one side to create at least two doped regions, and providing electrical contacts to the doped regions by depositing a conductive layer on the semiconductor layer so that the electrical contacts are on the same side of the semiconductor layer while incident light strikes the layer from an opposing side.

Claims

1. A method for fabricating an all-back contact photovoltaic cell, said method including:

depositing a semiconductor layer on a non-opaque substrate;

increasing a level of crystallinity of said semiconductor layer by exposing said semiconductor layer to a focused beam of energy;

doping said semiconductor layer with first and second dopants on a side of said semiconductor layer to create at least two doped regions in said semiconductor layer; and

providing electrical contacts to said doped regions by depositing a conductive layer on said side of said semiconductor layer so that said electrical contacts are on said side of said semiconductor layer and incident light strikes said semiconductor layer from an opposing side.

2. The method of claim 1, wherein said depositing step includes depositing said semiconductor layer in at least one of an amorphous state and a microcrystalline state.

3. The method of claim 1, wherein said increasing step includes melting at least a portion of said semiconductor layer.

4. The method of claim 3, wherein said increasing step includes melting at least said portion of said semiconductor layer with one or more electron beams.

5. The method of claim 1, wherein said substrate includes one or more materials having a softening point below 750°

C.

6. The method of claim 1, further including depositing a barrier layer adjacent to said substrate and between said substrate and said semiconductor layer, said barrier layer impeding diffusion of one or more impurities from said substrate into said semiconductor layer during said increasing step.

7. The method of claim 1, further including depositing a passivation layer adjacent to said semiconductor layer and between said substrate and said semiconductor layer, said passivation layer electrically passivating a surface of said semiconductor layer.

8. The method of claim 1, further including:

depositing a capping layer adjacent to said side of said semiconductor layer;

etching said capping layer to expose a first set of areas of said semiconductor layer before doping said semiconductor layer with said first dopant;

etching said capping layer to expose a second set of areas of said semiconductor layer before doping said semiconductor layer with said second dopant, wherein said second set of areas include said first set of areas.

9. An all-back contact thin film photovoltaic cell including:

a non-opaque substrate;

a semiconductor layer deposited in at least one of an amorphous state and a microcrystalline state, wherein a level of crystallinity of said semiconductor layer is increased by exposing at least a portion of said semiconductor layer to one or more focused beams of energy;

a capping layer deposited adjacent to said semiconductor layer, said capping layer etched a first time to expose a first set of areas of said semiconductor layer and a second time to expose a second set of areas of said semiconductor layer, wherein said first set of areas is doped with a first type of dopant and said second set of areas is doped with a second type of dopant; and

a conductive layer deposited on a first side of said semiconductor layer opposite said substrate to provide electrical contacts with said first and second areas,

wherein incident light passes through said substrate and strikes said semiconductor layer on a second side that is opposite said first side.

10. The photovoltaic cell of claim 9, wherein said semiconductor layer is melted when exposed to said focused beams of energy.

11. The photovoltaic cell of claim 9, wherein said focused beams of energy include one or more electron beams.

12. The photovoltaic cell of claim 9, wherein said substrate includes one or more materials having a softening point below 750°

C.

13. The photovoltaic cell of claim 9, further including a barrier layer deposited adjacent to said substrate and between said substrate and said semiconductor layer,

wherein said barrier layer impedes diffusion of one or more impurities from said substrate into said semiconductor layer.

14. The photovoltaic cell of claim 9, further including a passivation layer deposited adjacent to said semiconductor layer and between said substrate and said semiconductor layer, said passivation layer electrically passivating said second side of said semiconductor layer.

15. The photovoltaic cell of claim 9, wherein said second set of areas includes said first set of areas.

16. A method for fabricating an all-back contact photovoltaic module, said method including:

providing a semiconductor layer and a non-opaque substrate on a first side of said module;

increasing a level of crystallinity of said semiconductor layer by exposing said semiconductor layer to one or more focused beams of energy;

doping said semiconductor layer in each of a plurality of adjacent photovoltaic cells of said photovoltaic module with a first dopant in a first set of volumes in each of said photovoltaic cells;

doping said semiconductor layer with a second dopant in a second set of volumes in each of said photovoltaic cells;

removing a portion of said semiconductor layer to define a gap between said photovoltaic cells;

depositing an insulating material in said gap;

depositing a conductive material on said semiconductor layer at each of said first and second sets of volumes of each of said photovoltaic cells and on said insulating material; and

etching said conductive material to create electrical contacts (a) to said first set of volumes for each of said photovoltaic cells, (b) to said second set of volumes for each of said photovoltaic cells and (c) between said first set of volumes in one of said photovoltaic cells and said second set of volumes in another one of said photovoltaic cells,

wherein said electrical contacts are on a second side of said module that is opposite said first side and incident light passes through said substrate on said first side of said module and strikes said semiconductor layer.

17. The method of claim 16, wherein said providing step includes providing said semiconductor layer in at least one of an amorphous state and a microcrystalline state.

18. The method of claim 16, wherein said second set of volumes includes said first set of volumes in each of said photovoltaic cells.

19. The method of claim 18, wherein an amount of said second dopant that is deposited in said second set of volumes is less than an amount of said first dopant that is deposited at said first set of volumes for each of said photovoltaic cells.

20. The method of claim 16, wherein said substrate includes one or more materials having a softening point below 750°

C.

21. An all-back contact photovoltaic module including:

a plurality of photovoltaic cells each including a semiconductor layer and a non-opaque substrate on a first side of said module, each of said semiconductor layers including a first set of volumes doped with a first dopant and a second set of volumes doped with a second dopant,

wherein a level of crystallinity of each of said semiconductor layers is increased by exposing said layers to one or more focused beams of energy;

an insulating material located in one or more gaps between adjacent ones of said photovoltaic cells, said gaps created by removing one or more portions of said semiconductor material in said module; and

a conductive material deposited adjacent to said first set of volumes and said second set of volumes for each of said cells and adjacent to said insulating material, said conductive material then etched to create electrical contacts (a) to said first set of volumes for each of said photovoltaic cells, (b) to said second set of volumes for each of said photovoltaic cells and (c) between said first set of volumes in one of said photovoltaic cells and said second set of volumes in another one of said photovoltaic cells;

wherein said electrical contacts are on a second side of said module that is opposite said first side and incident light passes through said substrate on said first side of said module and strikes said semiconductor layer.

22. The photovoltaic module of claim 21, wherein said semiconductor layer is initially deposited in at least one of an amorphous state and a microcrystalline state.

23. The photovoltaic module of claim 21, wherein said second set of volumes includes said first set of volumes in each of said photovoltaic modules.

24. The photovoltaic module of claim 23, wherein an amount of said second dopant that is deposited in said second set of volumes is less than an amount of said first dopant that is deposited in said first set of volumes for each of said photovoltaic cells.

25. The photovoltaic module of claim 23, wherein said substrate includes one or more materials having a softening point below 750°

C.