Batteries: thermoelectric and photoelectric – Photoelectric – Panel or array
Reexamination Certificate
1999-12-09
2001-07-24
Diamond, Alan (Department: 1753)
Batteries: thermoelectric and photoelectric
Photoelectric
Panel or array
C136S244000, C136S246000, C136S248000, C136S256000, C136S262000, C257S432000, C257S436000, C257S443000, C257S448000, C257S461000, C257S466000, C250S3960ML, C250S216000, C250S227110, C322S00200R, C323S906000
Reexamination Certificate
active
06265653
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an array of photovoltaic cells, and more particularly to photovoltaic arrays that are illuminated with an optical homogenized laser beam.
2. Description of Related Art
Voltage transformers have usually been employed to increase voltage output where insufficient voltage is generated in a system.
Voltage generation from photovoltaic cells can be useful for several remote sensing applications. However, a single photovoltaic cell (diode) generates an insufficient output voltage to be useful in most applications. Fabricating arrays of photovoltaic cells monolithically (on a common substrate) using mass production techniques common to the semiconductor industry is normally preferable to the manual assembly and interconnection of individual diodes. Monolithically fabricated arrays can be adversely affected by parasitic electrical currents (e.g., photo-induced photocurrents) flowing between the individual diodes through the substrate reducing the usable current and voltage produced by the array.
Attempts to fabricate multiple electrically isolated photovoltaic cells in series have met with limited success. For instance, silicon-containing cells mounted on sapphire provide outputs of about 0.7 volts/diode (or cell). A limitation in voltage scaleup and forming a compact, integrated photocell array is excessive leakage current due to the parasitic electric fields as arrays of series diodes are placed in parallel to minimize footprint. The result is a collapse of the voltage across each component of the array, thereby degrading the overall voltage generated by the photocell(s).
A need exists for a high voltage photovoltaic power-induced converter that can be tailored to meet the voltage requirements of most sensing and other applications without the use of voltage transformers.
SUMMARY OF THE INVENTION
The invention is directed to an array of photovoltaic cells connected in series, yet each cell being electrically isolated from others of the array located on a monolithic semi-insulating substrate. An interconnection scheme for the cells includes interconnected arrays of cells, interconnected substrates, and reflective coatings on the substrate between each cell. The reflective coatings include a metal reflective layer that covers an insulator material normally in contact with the semi-insulating substrate, and such coatings can serve as an interconnect for the p-n or n-p junction between cells. The array materials normally contain single crystal, direct bandgap semiconductor materials, such as Group III-V composites, e.g., GaAs.
A plurality of interconnected arrays are usually illuminated in a system of the invention that includes a source of laser energy which is transmitted via an optical fiber through an optical homogenizer to create a uniform flat top optical beam profile for illuminence upon the array of cells to produce the photoconductive or photo-induced electrical current having high voltage. Preferably the array is rectangular, and optimally square, to create a uniform potential gradient across the array.
An advantage of the invention is the elimination of photoconductive current in the semi-insulating substrate by the intercell reflective coatings including insulators, thus preventing the shunting of each array and/or the substrate, i.e, enhancing efficiency. The invention provides an essentially wireless system that feeds a relatively low voltage laser energy source through optic fiber, casts the uniform beam profile upon the photovoltaic cell array and prevents stray electrical signals prior to use of the high voltage current from the array. Useful applications of the system include locations where high voltages are provided to confined spaces such as in explosive detonation, accelerators, photo cathodes and medical appliances.
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Borden, “A Monolithic Series Connected AI.93Ga.07 As/GaAs Solar Cell Array,” Conference Record, 14th IEEE Photovoltaic Specialists Conf., pp. 554-562, San Diego, CA, Jan. 7-10, 1980.*
Patent abstract of Japan, abstract for JP 04109882, date, Apr. 10, 1992.
Hagans Karla G.
Haigh Ronald E.
Jacobson Gerard F.
Wojtczuk Steve
Diamond Alan
The Regents of the University of California
Thompson Alan H.
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