Local heterostructure contacts

• US 20090317934A1
• Filed: 08/28/2007
• Published: 12/24/2009
• Est. Priority Date: 09/05/2006
• Status: Active Grant

• Current Assignee: CSEM Centre Suisse d'Electronique et de Microtechnique SA Recherche et Développement, Maximilian Scherff
• Original Assignee: Q-Cells Se
• Inventors: Fahrner, Wolfgang Rainer, Scherff, Maximilian
• Granted Patent: US 7,943,416 B2
• Time in Patent Office: Days
• US Class Current: 438/72
• CPC Class Codes: H01L 31/022425 for solar cells
• CPC Class Codes: H01L 31/022441 Electrode arrangements specially adapted for 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 31/0747 comprising a heterojunction of crystalline and amorphous materials, e.g. heterojunction with intrinsic thin layer
• 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
• CPC Class Codes: Y10S 977/755 Nanosheet or quantum barrier/well, i.e. layer structure having one dimension or thickness of 100 nm or less

Abstract

Disclosed is a novel method for creating local contacts in solar cells. In the method, a surface passivation that has been applied to a semiconductor substrate is locally etched away using a plasma process with the help of a thin stretched, elastic foil. If necessary, deep doping gradients are then locally created at the same points by means of a hydrogen plasma treatment with the help of thermal donors so as to increase the diffusion length of the charge carriers in the direction of the contacts. Finally, local heterostructure contacts are applied through the same mask openings. The contacts are characterized by a much lower saturation current than common diffused contacts and are therefore particularly suitable for high-performance solar cells.

Claims

1. A method and a device for producing local heterocontacts, wherein on surface-passivated semiconductor materials the surface-passivating layer of the semiconductor material, locally, is opened, by means of plasma etching, through the openings of a film that has been put in place, and the film that has been put in place subsequently serves as a mask for further deposition processes of heterocontacts, TCO or metals and/or further plasma processes.

2. The device according to claim 1, wherein instead of the film that has been put in place a mask that has been put in place is used.

3. The method according to claim 1, wherein the film or mask that has been put in place is in place as snugly as possible in order to prevent lateral etching/undercutting or deposition underneath the mask.

4. The method according to claim 1, wherein the first mask has been placed onto the surface-passivating layer, and onto said mask one or several further mask/s is/are placed or stretched, which mask/s covers/cover part of the openings of the first mask.

5. The method according to claim 1, wherein the surface-passivating layer comprises a material which in conjunction with the semiconductor substrate used comprises as low a surface recombination speed as possible.

6. The method according to claim 1, wherein the passivating layer on the solar cell front comprises a different material or a different material layer than does the back.

7. The method according to claim 1, wherein if at all possible only the surface-passivating layer is etched away, and in that location leaves no plasma residues and/or damage to the substrate material.

8. The method according to claim 1, wherein the plasma etching process is selected in such a way that plasma residues of previous deposition processes are removed as well.

9. The method according to claim 1, wherein the deposited heterostructure contacts are designed in such a way that the highest possible solar cell efficiencies are achieved.

10. The method according to claim 1, wherein the heterocontacts are prepared in such a way that they achieve good internal reflection.

11. The method according to claim 1, wherein the heterocontacts are transparent to light.

12. The method according to claim 1, wherein as the last layer/s, one or several metal layer/s is/are applied to the heterocontacts.

13. The method according to claim 1, wherein different TCO layers are applied to differently-doped heterocontacts (emitter- or base contact).

14. The method according to claim 1, wherein the cell connectors are directly bonded to the TCO with the use of electrically conductive bonding agents.

15. The method according to claim 1, wherein the bonded-on cell connectors are narrow along the heterocontacts and thus part of the TCO area is not covered and is transparent to light.

16. The method according to claim 1, wherein the cell connectors are bent in a meandering manner or are embossed in a wave shape or a waffle shape.

17. The method according to claim 1, wherein after opening the surface passivation the region which later will be the contact region is subjected to a hydrogen plasma and at the same time is heated to a temperature of between 200°

C. and 800°

C., better still of between 300°

C. and 600°

C.

18. The method according to claim 1, wherein the hydrogen plasma is applied in a first step, and annealing takes place at a subsequent point in time of processing.

19. The method according to claim 1, wherein any plasma damage to the substrate, which has been caused by the hydrogen plasma, is remedied by means of one or several plasma etching processes.