Batteries: thermoelectric and photoelectric – Photoelectric – Panel or array
Patent
1996-07-24
1998-07-28
Nguyen, Nam
Batteries: thermoelectric and photoelectric
Photoelectric
Panel or array
136255, 136261, 257465, 257466, 204252, 205340, 205637, H01L 3106
Patent
active
057857687
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to photo cells and photo cell arrays, such as solar cells and photo diodes, as well as electrolytic devices having these cells and arrays as structural constituents.
Solar cells make use of the solar energy that radiates upon the Earth. Solar cells were developed because of the limits inherent in using fossil fuels as an energy source. Solar cells provide energy for calculators, wristwatches, and other common applications. One problem in employing solar cells, however, has been that solar radiation energy is available only in low energy density on the earth. To obtain the equivalent level of electric power from solar cells as can be obtained from a thermal power station would require the collection of radiation over a considerably large area.
To resolve this problem, a proposal was put forth for the use of solar cells comprising silicon semiconductors, which generate a photovoltaic power and are fabricated in spherical form, allowing the absorption of sunlight from all angles, and the use of electrolytic devices employing said solar cells (U.S. Pat. No. 4,021,323).
The method of manufacturing solar cells described in this U.S. Patent is as follows. First, molten silicon is ejected out of small nozzle into an inert gaseous atmosphere, forming a p-type or n-type silicon sphere. The surface of this silicon sphere is subjected to a gaseous diffusion process using either phosphorous (P) or boron (B) which forms a pn junction at a certain depth below the surface of the sphere. Next, the surface of the sphere is sputtered with platinum or a similar metal to create a thin, light transmissive metallic layer, on top of which a coating of insulating resin is then applied. The silicon sphere is then affixed to a temporary substrate, and a corrosion-resistant, light transmissive insulating compound, such as silicone resin, is poured around its circumference. After the insulating compound is cured, the top surface is removed, exposing the silicon sphere. A layer of aluminum or other similar metal is then ion plated onto the exposed surface of the sphere, making ohmic contact with the sphere. Finally, the temporary substrate is removed and the solar cell is completed.
With the solar cells described in the U.S. patent listed above, however, when the silicon is melted in the manufacturing process, the molten silicon does not come in contact with the seed of a single crystal, so the resultant silicon sphere does not grow as a single crystal and its energy conversion efficiency is poor. Before ion plating of the electrode made from aluminum or a similar metal, the possibility exists of large leakage current on the surface of the edge of the pn junction at the exposed silicon sphere.
The objective of the invention is to provide photo cells and photo cell arrays made from single crystal or polycrystal semiconductor material having a crystalinity close to that of single crystals and which have high photoelectric conversion efficiency, little leakage current, long life, and high reliability, as well as electrolytic devices that employ these cells and arrays.
SUMMARY OF THE INVENTION
The photo cells of this invention, in order to achieve the objectives outlined above, have base material, a light receiving section, a front surface electrode, and a back or lower surface electrode as their main components:
The base material consists of p-type (or n-type) semiconductor.
The light receiving section is an integral spherically shaped part of the base material, and protrudes outwardly from the surface of the base. On the surface of said spherical part there is attached a semiconductor layer of n-type (or p-type), that is, opposite to the base material conductivity type. Further, between the aforementioned base material and semiconductor layer there is formed a pn junction interface.
The front surface electrode is formed from conductive material that is in ohmic contact with a portion of the front surface of the aforementioned sphere.
The back or lower surface electrode is formed from
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patent: 4643817 (1987-02-01), Appleby
patent: 4722776 (1988-02-01), Murphy et al.
patent: 5081049 (1992-01-01), Green et al.
Form PCT/ISA/210 for PCT/JP95/01319.
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