Batteries: thermoelectric and photoelectric – Photoelectric – Panel or array
Reexamination Certificate
2001-11-21
2004-03-16
Diamond, Alan (Department: 1753)
Batteries: thermoelectric and photoelectric
Photoelectric
Panel or array
C136S261000, C136S262000, C136S264000, C136S265000, C136S260000, C136S252000, C257S431000, C257S464000, C257S461000, C438S063000, C438S094000, C438S095000, C438S093000
Reexamination Certificate
active
06706959
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photovoltaic apparatus and to a mass-producing apparatus for mass-producing spherical semiconductor particles, suitable for manufacture of photovoltaic apparatus and the like.
In the disclosure herein described, the term “pin junction” is to be construed as including a structure that n-, I- and p-type semiconductor layers are formed on an approximately spherical photoelectric conversion element so as to be arranged in this order outward from the inside of the approximately spherical photoelectric conversion element or inward from the outside.
2. Description of the Related Art
A typical related art technique provides a photovoltaic apparatus comprising a photoelectric conversion element composed of a crystal silicon semiconductor wafer. The related art photovoltaic apparatus is of cost expenditure because the step for producing a crystal is complex. Furthermore, the step for manufacturing a semiconductor wafer is not only complex because it includes cutting of a bulk single crystal, slicing, and polishing, but also the step is wasteful because crystal waste produced by the cutting, slicing, polishing etc. amounts to about 50% by volume or more of the original bulk single crystal.
Another related art technique provides a photovoltaic apparatus comprising a photoelectric conversion element composed of an amorphous silicon (abbreviated as “a-Si”) thin film, which solves the above-mentioned problems. Since a thin-film photoelectric conversion layer is formed by the plasma CVD (chemical vapor deposition) method, this related art photovoltaic apparatus has advantages that the steps which are conventionally required, such as cutting of a bulk single crystal, slicing, and polishing, are not necessary and that a deposited film can be used in its entirety as device active layers. The amorphous silicon photovoltaic apparatus, however, has a drawback that the semiconductor has a number of crystal defects (i.e., gap states) inside the semiconductor due to the amorphous structure, the amorphous silicon solar battery has a problem that the photoelectric conversion efficiency decreases due to a photo-induced deterioration phenomenon. To solve this problem, conventionally, a technique of inactivating crystal defects by applying hydrogenation treatment has been developed, whereby the manufacture of such electronic devices as an amorphous silicon solar battery has been realized.
Even such a treatment, however, cannot entirely eliminate the adverse effects of crystal defects, and for example, the amorphous silicon solar battery still has a weak point that the photoelectric conversion efficiency decreases by 15% to 25%.
A recently developed technique for suppressing the photo-induced deterioration has realized a stack-type solar battery in which a photoelectrically active i-type layer is made extremely thin and 2-junction or 3-junction solar cells are used, and has succeeded in suppressing the photo-induced deterioration to about 10%. It has become apparent that the degree of photo-induced deterioration decreases when the operation temperature of solar cells is high. Although a module technique in which solar cells are caused to operate in such a condition is now being developed, it does not satisfy all the requirements and further improvements are required.
Still another related art technique in which the above problem is eliminated is disclosed in Japanese Examined Patent Publication JP-B27-54855 (1995). According to this related art technique, a solar array is formed in the following manner. Spherical particles each having a p-type silicon sphere and an n-type silicon skin are buried in a flat sheet of aluminum foil having holes. The internal p-type silicon spheres are exposed by etching away the n-type silicon skins from the back side of the aluminum foil. The exposed-type silicon spheres are connected to another sheet of aluminum foil.
In this related art technique, to reduce the costs by decreasing the used amount of high-purity silicon, it is necessary to decrease the average thickness of the entire device by decreasing the outer diameter of the particles. To increase the conversion efficiency, it is necessary to enlarge the light-receiving surface, and to this end, it is necessary to arrange the particles closer to each other. In summary, a number of particles having a small outer diameter need to be arranged densely and connected to the sheets of aluminum foil. This makes complex the step of connecting the particles to the sheets of aluminum foil, with the result that a sufficient cost reduction is not achieved.
Such spherical semiconductor particles are required in order to manufacture a solar array such as one disclosed in JP-B2 7-54855. In such a solar array, photoelectromotive force generated by applying light to silicon spherical semiconductor particles can be obtained by electrically connecting the silicon spherical semiconductor particles to the metal foil matrix.
As disclosed in U.S. Pat. No. 5,012,619, for example, such spherical particles are manufactured in such a manner that a solid-state material is crushed into particles having irregular outer shapes, resulting particles are put in a cylinder that is provided with a lining for grinding, and a gas eddy flow is formed in the cylinder to thereby collide the particles with the lining or with each other.
This related art technique requires much time and labor to manufacture spherical semiconductor particles and hence is inferior in cost reduction aspect.
Yet another related art technique is disclosed in Japanese Unexamined Patent Publication JP-A 8-239298 (1996). In this related art technique, a thin silicon rod is manufactured in the following manner. A tip portion of a silicon rod that is vertically held is melted by high-frequency heating. After a seed silicon crystal is fusion-bonded to the molten silicon rod, the seed silicon crystal and the silicon rod are moved away from each other in the vertical direction, whereby a thin silicon rod that is less than 1 mm in thickness is obtained. According to this prior art technique, a thin silicon rod is manufactured at a rate of 5 mm/min to 10 mm/min, for example. It is desired that a large number of spherical semiconductor particles be manufactured at much higher rate.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a highly reliable, highly efficient photovoltaic apparatus that can be mass-produced easily while the used amount of semiconductor material such as high-purity silicon is decreased, that is, a highly reliable, high-efficiency photovoltaic apparatus that can be manufactured at low costs with smaller amounts of consumption of resources and energy.
Another object of the invention is to provide an apparatus capable of mass-producing spherical semiconductor particles easily by simple manipulations.
A first aspect of the invention provides a photovoltaic apparatus comprising:
(a) a plurality of photoelectric conversion elements, each being of an approximately spherical shape and including a first semiconductor layer and a second semiconductor layer which is located outside the first semiconductor layer, for generating photoelectromotive force between the first and second semiconductor layers, the second semiconductor layer having an opening through which a portion of the first semiconductor layer is exposed; and
(b) a support including a first conductor, a second conductor, and an insulator disposed between the first and second conductors for electrically insulating the first and second conductors from each other, the support having a plurality of recesses which are arranged adjacent to each other and of which inside surfaces are constituted by the first conductor or a coating formed thereon, the photoelectric conversion elements being disposed in the respective recesses so that the photoelectric conversion elements are illuminated with light reflected by part of the first conductor or coating formed thereon which constitutes the recess, the first conductor being
Hamakawa Yoshihiro
Murozono Mikio
Takakura Hideyuki
Bacon & Thomas PLLC
Clean Venture 21 Corporation
Diamond Alan
LandOfFree
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