Solar cell

• US 4,540,843 A
• Filed: 02/29/1984
• Issued: 09/10/1985
• Est. Priority Date: 03/09/1983
• Status: Expired due to Fees

• Current Assignee: Licentia Patent-Verwaltungs-GmbH, Telefunken Systemtechnik GmbH
• Original Assignee: Licentia Patent-Verwaltungs-GmbH, Telefunken Electronic GmbH
• Inventors: Schmidt, Wilfried, Gochermann, Hans, Tentscher, Karl-Heinz, Rasch, Klaus-Dieter
• Primary Examiner(s): Weisstuch, Aaron
• Application Number:
  US06/585,221
• Time in Patent Office: 559 Days
• Field of Search: 136/255, 136/256, 136/244, 136/251, 136/258 PC, 357/30
• US Class Current: 136/251
• CPC Class Codes: H01L 31/02168 the coatings being antireflective or having enhancing optical properties for the solar cells
• CPC Class Codes: H01L 31/022425 for solar cells
• CPC Class Codes: H01L 31/048 Encapsulation of modules
• CPC Class Codes: H01L 31/0508 the interconnection means having a particular shape
• CPC Class Codes: H01L 31/0684 double emitter cells, e.g. bifacial solar cells
• CPC Class Codes: Y02E 10/547 Monocrystalline silicon PV cells

Abstract

The invention relates to a solar cell for exposure to light rays on both sides. The solar cell contains only one pn junction on one surface side of the semiconductor body. The base of the solar cell is uniformly and less strongly doped than the thin surface zone of the conduction type opposite to that of the semiconductor base. Both zones of the solar cell are in contact with a structured conduction path system on opposite surface sides.

Claims

1. A solar cell comprising:

a plate-shaped semiconductor body, containing a pn-junction (4) and having front and rear opposite surface sides (15,

     16) and a base zone (2) of a first conduction type disposed on one surface side, for exposure to rays on both sides, wherein the semiconductor base zone (2) of the first conduction type is uniformly doped;

a thin zone (3) of a second conduction type with a higher doping than the base zone disposed on the other surface side of the semiconductor body;

front and rear structured conduction path systems (5,

     6) each including a contact having spaced apart adjacent structures, wherein said zones (2,

     3) of the solar cell are each in contact with a respective one of said structured conduction path systems so as to leave substantial areas of the semiconductor surface uncovered, wherein the doping of the semiconductor base zone (2) of the first conduction type is relatively high and the spacing between the adjacent structures (11) of the rear side conduction path system (6) is relatively small whereby the resulting fraction of the series resistance of the cell is small compared to the total series resistance, and wherein the distances between the structures (7) of the conduction path system (5) in the case of the front side contact are larger than those in the case of the rear side contact (6).

2. A solar cell according to claim 1, wherein the zone of the second conduction type is disposed on the front surface side and is more sensitive to incident light than said base zone which is disposed on the rear surface side, and wherein the front surface side (15) of the semiconductor body is provided for the incident light from the main direction of incidence (9) of higher intensity, while the less sensitive, opposite rear surface side (16) of the semiconductor body (1) is provided for the incident light from the direction of incidence (10) of less intensity.

3. A solar cell according to claim 1, wherein the solar cell consists of single or polycrystalline silicon, said polycrystalline material being subjected to a passivation process to increase the effective diffusion length of the minority carriers and, consequently, increase the light sensitivity.

4. A solar cell according to claim 3, wherein hydrogen is used for the passivation.

5. A solar cell according to claim 1, wherein the semiconductor body (1) of the solar cell is thin enough for a substantial fraction of the minority carriers produced on the rear side by incident light to reach the pn-junction (4).

6. A solar cell according to claim 5, wherein the semiconductor body (1) is thinner than 0.3 mm and wherein the surface zone (3) of the second conduction type has a layer thickness of less than 0.5 μ

m.

7. A solar cell according to claim 1, wherein the semiconductor base zone has a specific resistance of approximately 0.1-1 Ohm cm, and the surface zone of the second conduction type has a sheet resistance of approximately 30-200 Ohms/square.

8. A solar cell according to claim 1, wherein the conduction path systems each consist of finger structures (7, 11), with the structures on the cell front side extending parallel or perpendicularly to those on the rear side.

9. A solar cell according to claim 1, wherein the conduction path system on the cell front side consists of a finger structure and on the cell rear side of a grid mesh structure.

10. A solar cell according to claim 1, wherein at least portions of the rear side (16) of the semiconductor body (1) are covered with a transparent, good conducting layer (14).

11. A solar cell according to claim 10, wherein the transparent, good conducting layer (14) covers the rear side surface (16) of the semiconductor body and wherein the conduction path system (6) of the rear side contact is arranged on this layer.

12. A solar cell according to claim 10, wherein the exposed areas of the rear side surface (16) between the structures (11) of the conduction path system disposed directly on the semiconductor surface (16) are covered with the conductive, transparent layer (14).

13. A solar cell according to claim 10, wherein the rear side surface of the solar cell provided with the structured conduction path system is totally covered with the conductive, transparent layer (14).

14. A solar cell according to claim 10 wherein the transparent, conductive layer (14) is of a thickness selected so as to reduce the series resistance of the solar cell and simultaneously act as an antireflection layer.

15. A solar cell according to claim 14, wherein the front side (15) of the solar cell is also provided with an antireflection layer (13), and wherein both antireflection layers (13, 14) on the front and rear sides of the solar cell are adapted with respect to the spectral distribution to the incident light conditions to which these surfaces are subjected.

16. A solar cell according to claim 1, wherein the structured conduction path system on the rear side surface of the solar cell is adapted to the conduction path system on the front side in a manner such that said cell is connectable with another cell of the same type to form a solar generator.

17. A solar generator comprising a plurality of adjacent solar cells each according to claim 16 and a plurality of connector members (24) which connect adjacent solar cells and, wherein the conduction path systems on the front and rear sides of each solar cell are so constructed that the connector members (24) which connect adjacent solar cells (20-23) in the generator are as short as possible.

18. A solar generator according to claim 17, wherein the connection points (8, 12) for the connector members (24) to the conduction path systems (5, 6) on the front and rear sides (15, 16) of each solar cell (1) are arranged on opposite or adjacent sides of the solar cell.

19. An orbital or terrestrial solar generator comprising a plurality of solar cells according to claim 1.

20. A solar generator comprising a plurality of solar cells each according to claim 1, in which the cells are transparently encapsulated or covered on both sides.

21. A terrestrial laminated glass solar generator comprising a plurality of solar cells each according to claim 1, wherein the cells (1) are arranged in a symmetrical bond between two glass panes (30), with the bond between the glass panes (30) and the cells (1) being effected by transparent, elastic materials (31).

22. A terrestrial solar generator comprising a plurality of solar cells each according to claim 1, wherein the cells (1) are embedded in transparent, glass fiber reinforced resin (32).

23. An orbital solar generator comprising a plurality of solar cells each according to claim 1, wherein the cells (1) are attached on their rear side to a transparent carrier member (33), comprised of a foil, a glass fiber reinforced foil, or a material with a honeycomb structure, by means of a light-permeable adhesive (34), while the front sides of the cells each comprise a cover glass (36) attached by a transparent adhesive (35).