Batteries: thermoelectric and photoelectric – Photoelectric – Cells
Reexamination Certificate
2000-08-29
2001-12-25
Diamond, Alan (Department: 1753)
Batteries: thermoelectric and photoelectric
Photoelectric
Cells
C136S249000, C136S256000, C136S261000, C257S431000, C257S452000, C257S461000, C257S463000, C250S200000, C438S068000, C438S057000
Reexamination Certificate
active
06333457
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to silicon solar and photo cells, and more particularly the invention relates to a silicon cell with edge passivation and the method of manufacturing same.
The silicon solar cell is a well known device for use in converting radiant energy into electrical energy. See, for example, Swanson, U.S. Pat. No. 4,927,770, and Sinton, U.S. Pat. No. 5,164,019. As described in the Swanson patent, a silicon solar cell comprises a plurality of p and n conductivity type regions in a silicon body which generate voltage potential and a current when electron-hole pairs are created in a semiconductor body in response to impinging radiation, and the holes and electrons migrate to the p-doped regions and the n-doped regions, respectively. In a solar cell having interdigitated back surface contacts, the p and n regions are formed in alternating rows with a metal contact provided for contacting all doped regions in one row and with rows of like doped regions being connected in parallel.
Heretofore, small area solar cells having a surface area of less than 50 cm
2
have been batch processed in an intrinsic (including lightly doped) single crystal silicon substrate by the selective diffusion of n+ and p+ regions in one surface of the substrate. The wafer is subsequently scribed and broken or sawed into a plurality of small individual chips or cells. Because small solar cells are normally sawed from a wafer after metallization, traditional high-temperature passivation techniques such as surface doping or thermal oxide growth cannot be used for edge passivation. Further, low temperature passivating films or coatings are less effective and are extremely difficult to selectively deposit on the sawed cell edges. Recombination of photogenerated carriers at the unpassivated edge surfaces can be a major current loss mechanism for high efficiency silicon solar cells, particularly for the small area solar cells.
SUMMARY OF THE INVENTION
In accordance with the invention, a small area silicon cell is provided with efficient edge passivation to reduce recombination of photogenerated carriers. The silicon cell in accordance with the invention is readily manufactured in a batch process in which edge passivation is provided before sawing the silicon substrate and forming the individual cells.
Briefly, a silicon cell in accordance with one embodiment of the invention comprises an intrinsic (including lightly doped) monocrystalline silicon chip having two opposing major surfaces, a plurality of n+ doped regions and p+ doped regions in one major surface, and a doped (n or p-type) peripheral region around the periphery of the silicon chip and extending from one major surface to the other major surface, the peripheral region functioning as a passivation layer for repelling carriers and reducing recombination of carriers. Preferably the n-type or p-type dopants used in forming the peripheral region are phosphorous and aluminum, respectively, due to their relatively high diffusion coefficients.
In fabricating the silicon solar cell in accordance with the above embodiment of the invention, an intrinsic including lightly doped monocrystalline silicon substrate is provided, and a repeating pattern of p-doped regions and n-doped regions are formed in one major surface with the pattern defining an individual solar cell. Each solar cell is separated from adjacent solar cells by streets along which the substrate is separated after cell fabrication to provide individual cells. Prior to fabrication of the individual cells, a doped region is formed in the streets extending from one major surface to the other major surface, the dopant concentration in the doped regions being at least 10 times greater than photogenerated carrier concentration in each solar cell or 10 times the substrate doping level (whatever is larger). Preferably, dopant is diffused from both major surfaces into the silicon substrate in doping the streets. Thereafter, the substrate is sawed to form each individual silicon solar cell die.
The invention and objections and features thereof will be more readily apparent from the following detailed description and the appended claims when taken with the drawing.
REFERENCES:
patent: 4797720 (1989-01-01), Lindner et al.
patent: 4927770 (1990-05-01), Swanson
patent: 5164019 (1992-11-01), Sinton
patent: 5609694 (1997-03-01), Asai
Mulligan et al, “Development of Chip-Size Silicon Solar Cells,” Conference Record of the Twenty-Eighth IEEE Photovoltaic Specialists Conference, Sep. 15-22, 2000, pp. 158-163.*
Davis, J.R. and Rohatgi, A., “Theoretical Design Considerations for Back Surface Field Solar Cells”, Westinghouse Research and Development Center, Fourteenth IEEE Photovoltaic Specialists Conference, Jan. 1980.
Mulligan William P.
Verlinden Pierre J.
Diamond Alan
Sunpower Corporation
Townsend and Townsend / and Crew LLP
Woodward Henry K.
LandOfFree
Edge passivated silicon solar/photo cell and method of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Edge passivated silicon solar/photo cell and method of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Edge passivated silicon solar/photo cell and method of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2579181