AN IMPROVED SOLAR CELL MODULE AND METHOD FOR ITS FABRICATION
FIELD OF THE INVENTION
The present invention, in general relates to an improved solar cell module and method for its fabrication and in particular, to an improved solar cell module having an improved design of optical concentrator, whereby utilization of amount of photo-voltaic material, such as silicon based material is minimized.
BACKGROUND OF THE INVENTION
The solar cell modules known in the art, fundamentally includes a plurality of interconnected cells and optical concentrators for concentration of solar energy, on array of solar cells. However, it has been observed that such solar cell modules, consume substantial amount of photovoltaic material such as silicon based material as light absorbing material, for ensuring generation of maximum output, resulting in increase in the overall cost of production and consequently, in increase in the cost of the final product.
Over the years, attempts have been made to substantially reduce the use of photovoltaic material as light absorbing material, for the purpose of reducing the overall cost of production and consequently, the cost of the final product. US Patent 6,840,636 discloses means to capture reflected energy from adjacent surfaces and redirecting such energy towards the focal plane, adapted to selectively reflect (total internal reflection [T.I.R]) the light waves passing there through, thereby focusing and concentrating said light for the storage and usage thereof. US Patent 4,069,812 discloses a curved prismatic, Fresnel-type lens primarily used for concentrating sunlight in a solar energy collector. US Patent 4,124,017 describes an improved solar energy collector which passively

concentrates the rays of the sun.
US Patent 4,711,972 discloses a solar energy collector including a primary optical concentrator, one or more solar cells and an improved solar cell cover design. Each of the solar cells includes a flexible cell cover which significantly reduces optical losses due to grid line obscuration of active cell area and also due to reflection from the cover itself.
U.g. Pat. No. 5,255,666 discloses a solar energy concentrator, including a thin flexible Fresnel lens for focusing incident solar radiation not normal to the lens onto a target area by refraction.
U.S. Pat. No. 4,848,319 also describes solar electric conversion unit and system includes substantially increased efficiency with reduced losses and increased acceptance angles.
U.S. Pat. No. 5,339,382 discloses a prism light guide luminaire having opaque and light emitting surface portions, which together form a selected cross-sectional configuration. The opaque surface portion has a light reflecting characteristic. The light emitting suri'ace portion is prism light guide material which confines, within the luminaire, light rays which strike the material at angles falling within the material's acceptance angular range. US 5460659 discloses solar cell having a dice structure which means cubical. The discrete solar concentrating elements are mounted over respective dices. For concentration, concentrator lens are applied, which can be formed of either Fresnel or curved surface refractory lenses, on a transparent acrylic sheet.
In all of the prior art documents the solar concentrator structure has the limitation that these can not use the complete incident solar beam from all angles, thereby reducing their effectiveness. Hence, in the aforesaid prior art documents no concrete teaching exists, to substantially reduce the cost of production and consequently, the cost of the final product, by substantially reducing the use of photovoltaic material in manufacturing solar cell modules.

Accordingly, there was a long felt need to develop a solar cell module, which minimizes application of photovoltaic material such as silicon based material, as light absorbing material, whereby, the overall cost of production is reduced and consequently, the cost of the final product is also reduced. The present invention meets the aforesaid long felt need. OBJECTS OF THE INVENTION
It is a prime object of t|ie present invention, to provide a solar cell module, which ensures minimization of application of photovoltaic material such as silicon based material as light absorbing material, by providing a novel optical concentrator, for maximum concentration of solar energy incident on photovoltaic material.
It is a further object of the present invention to provide a solar cell module, which ensures reduction in overall cost of production and consequently, reduction in the cost of the final product.
It is yet another object of the present invention to provide a method for fabrication of solar cell module, which ensures minimization of application of phptovoltaic material such as silicon based material, as light absorbing material. It is yet another object of the present invention to provide a method for fabrication of solar cell module, which ensures reduction in overall cost of production and consequently, reduction in the cost of the final product. How the aforesaid objects are met and the other aspects of the invention will be clear from the following description, which is purely by way of understanding and not by way of any sort of limitation. SUMMARY OF THE INVENTION
Accordingly, the present invention provides a solar cell module including an array of plurality of interconnected solar cells, optical concentrators, operatively connected to the substrate of each solar cell, said substrate being made of photovoltaic material, wherein each optical concentrator includes a hemispherical structure for ensuring maximum concentration of solar energy incident on the substrate made of photovoltaic material, thereby enabling

minimization of application of photovoltaic material as light absorbing material, which ensures reduction in overall cost of production and consequently, reduction in the cost of the final product.
In accordance with preferred embodiments of the solar cell module of the present invention:
-said hemispherical structure is made of a transparent material such as polycarbonate, polystyrene, acrylic or a combination of these, such that, the transparency of the material is not more than 85 % in visible spectrum region of the sun rays.
-refractive index of said material is selected, such that it is 5:1.4 and its melting point is grater than 100 degrees centrigrade.
-the photovoltaic material and each solar cell are of polygonal shape.
-in each sub module, the number of solar cells each having one photovoltaic material substrate and the number of hemispherical surfaces are same and the solar cells are placed on the center of the hemispherical surfaces.
-the interconnection of the photovoltaic strips are adapted to be done from both sides and at the end, there are two points for onward connection to another module.
-the photovoltaic material is made of semiconductor materials or alloys like Si,
Ge , Si-H , CdTe, CdS, GaAs , CIS & CIGS Solar cell ,or triple junction tandem
sofar cell, or organic material.
The present invention also provides a super module comprising a plurality of
solar cell modules as described hereinabove.
The present invention also provides a method for fabricating a solar cell module
comprising:
-interconnecting a plurality of polygonal solar cells each having a photovoltaic
substrate

-molding optical concentrating elements, each as a single unit having a hemispherical structure of suitable material,
-fixing the polygon shaped photovoltaic material on the molded optical concentrating element wherein the solar cell module is so designed such that the number of solar cells and the number of hemispheres are same in each module and each solar cell having said photovoltaic substrate, is placed on the center of each hemispherical surface, each hemisphere being kept at a closest possible distance with each other and designed to have a diameter, in accordance with the photovoltaic material dimension, thereby enabling minimization of application of photovoltaic material as light absorbing material, which ensures reduction in overall cost of production and consequently, reduction in the cost of the final product.
In accordance with a preferred embodiment of the method in accordance with the present invention:
-said hemispherical structure is made of a transparent material such as polycarbonate, polystyrene, acrylic or a combination of these, such that, the tr^ansparency of the material is not more than 85 % in visible spectrum region of the sun rays.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The nature and scope of the present invention will be better understood from the accompanying drawings, which illustrate preferred embodiments of the present invention. The drawings are meant for the purpose of illustration and understanding and not by way of any sort of limitation. In the accompanying drawings;
FIG 1 illustrates a cross sectional view of a preferred embodiment of the solar cell module , in accordance with the invention.

Fig 2: illustrates a preferred embodiment, showing a square photovoltaic material, being placed at the center of a hemi-spheric surface of the optical concentrator, in accordance with the invention.
BRIEF DESCRIPTION OF THE INVENTION
The following, includes description of some preferred embodiments of the
present invention which are purely for the sake of understanding and not by way
of any limitation.
As stated aforesaid, the present invention aims at reducing the application of photovoltaic material, such as silicon based material, as light absorbing material in'solar cell modules, with the prime objective of reducing the overall cost of production and consequently, the cost of the final product.
From the extensive research and development work which was undertaken to meet this prime objective, it was found that application of hemispherical structures as optical concentrators, gives very positive result in that perspective. Thereby, the novel optical concentrator in accordance with the present invention reduces the amount of photovoltaic material, such as silicon based material, applied to manufacture the solar cell modules. The optical elements used for this purpose have easy manufacturability and can be produced cheaply, in mass production. The manufacturing process of the optical elements can make the system economically significant and less complicated.
The technical advancement and/or economic significance, as stated aforesaid was not known or conceivable by persons skilled in the art.
To concentrate the light to fall on the photovoltaic material, optical concentrators having hemi-spherical structures are utilized. The hemispherical structures are designed to have a diameter, in accordance with the photovoltaic material dimension. The hemisphere structure is made of a transparent material, non-limiting examples of which may be polycarbonate, polystyrene, acrylic and so on.

such that, the transparency of the material is not more than 85 % in visible spectrum region of the sun rays. The refractive index of this material is selected, such that it is s 1.4. The concentration achieved by this optical element is around n^.
The solar cell module in accordance with the invention comprises a plurality of interconnected solar cells of polygonal shape. In other words, such solar cells may be hexagonal, rectangular, and square triangular or it may be circular or elliptical. The present invention includes a compact concentrating element design, in which hemispheres are kept at a closest possible distance with each other and the whole concentrating element is moldable as a single unit. The polygon shaped photovoltaic material, is fixed on the molded optical concentrating element. So, there is no need of heat sink structure in the present invention, because for concentration of solar energy, application of simple optics of hemisphere design is adopted.
The light falling on the hemisphere gets diverted towards its center. The solar cell, placed around the center of the hemisphere, may be having different shapes as explained above. Diverted light falls on the solar cells. The diameter of the hemispheric surface is deciphered, according to the sides or dimension of the cell.
The hemisphere surface is made applying molding or extrusion process. The total solar panel is divided into different sub modules. Each sub module consists of n x n number of say for example, rectangular cells and the same number of hemisphere surfaces. The hemisphere surfaces are molded on the surface using molding process. Then, the rectangular solar cells are placed on the center of each n X n hemispheres.
The interconnection of the rectangular strips have to be done from both sides and at the end there are two points for onward connection to next super module.
The material used for manufacturing the hemisphere is a transparent material

having melting point greater then 100 deg C. It could be Acrylic, Polycarbonate, HPPS, Polystyrene or it may be the combination of the different materials. Photovoltaic materials would be a semiconductor material for ex Si, Si-H , Ge , GaAs , Tandem solar cell etc.
As shown In Fig 1, which is a cross sectional view of the solar cell module, in accordance with a preferred embodiment, of the present invention, As can be seen, the sun ray falling on the hemisphere surface is refracted towards the center of the hemisphere, where the photovoltaic material is placed. Fig 2 shows a preferred embodiment of the present invention, where a small square photovoltaic material, is placed at the center of a hemi-spherical surface. It has been observed that on implementing this invention, use of photovoltaic material in manufacturing of solar cell module Is reduced by more than 2 times. The novel optical concentrators, having the hemispherical structures in accordance with the present invention, are easily moldable, due to which it can be applied to mass production.
The present invention reduces the panel cost and the resultant panel has very high acceptance angle i.e. it can capture and concentrate the light falling on its surface at any angle, refracts it towards the photovoltaic material. The design leads to different packaging method and design.
The present invention has been described with reference to some drawings and preferred embodiments, purely for the sake of understanding and not by way of any limitation and the present invention includes all legitimate developments within the scope of what has been described herein before and what has been claimed hereinafter.

WE CLAIM
1. A solar cell module including an array of plurality of interconnected solar
cells, optical concentrators, operatively connected to the substrate of each solar cell module, said substrate being made of photovoltaic material, wherein each optical concentrator includes a hemispherical structure for ensuring maximum concentration of solar energy incident on the substrate made of photovoltaic material, thereby enabling minimization of application of photovoltaic material as light absorbing material, which ensures reduction in overall cost of production and consequently, reduction in the cost of the final product.
2. The solar ceil module as claimed in claim 1 wherein said hemispherical
structure is made of a transparent material such as polycarbonate, polystyrene, acrylic or a combination of these such that, the transparency of the material is not more than 85 % In visible spectrum region of the sun rays.
3. The solar cell module as claimed in claim 2 wherein refractive index
of said material is selected, such that it is s 1.4 and its melting point is grater than 100 degrees centigrade.
4. The solar cell module as claimed in any preceding claim wherein the
photovoltaic material and each solar cell are of polygonal shape.
5.The solar cell module as claimed in any preceding claim wherein in each sub module, the number of solar cells, each having one photovoltaic material substrate, and the number of hemispherical surfaces are same and the solar cells are placed on the center of the hemispherical surfaces
e.The solar cell module as claimed in claim 5 wherein the interconnection of the photovoltaic strips are adapted to be done from both sides and at the end, there are two points for onward connection to another module.