Patent Publication Number: US-2012042944-A1

Title: Photovoltaic panel with flexible substrate and optical prism layer

Description:
RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Application Ser. No. 61/375,880, filed Aug. 23, 2010, which is herein incorporated by reference 
    
    
     BACKGROUND 
     1. Field of Invention 
     The present invention relates to a photovoltaic panel. More particularly, the present invention relates to a photovoltaic panel to be used in a portable electronic device and a home appliance. 
     2. Description of Related Art 
     A conventional photovoltaic panel is costly due to the multiple manufacturing steps and expensive material to meet harsh environmental requirement. For example, a transparent front glass is used to protect from the environment. A transparent and conductive top layer or grid is used to collect electrical currents and carry them away. Various intermediate processing steps, e.g. laser scribing and depositions to interconnect strips solar cells, annealing steps to activate or complete certain components; lamination to attach encapsulation; glass or other substrates handling, cleaning and heating, add more costs to a photovoltaic panel manufacturing. 
     However, the costly photovoltaic panel is to be used in a complete outdoor environment. For a portable electronic device and a home appliance, the above-mentioned photovoltaic panel is too expensive to be applied in an electronic device. Therefore, an efficiency-enhanced and cost-effective photovoltaic panel is required for portable devices and home appliances. 
     SUMMARY 
     It is therefore an objective of the present invention to provide an efficiency-enhanced and cost-effective photovoltaic panel. 
     In accordance with the foregoing and other objectives of the present invention, a photovoltaic panel includes a flexible substrate, an optical prism layer, and a photoelectric layer disposed between the plastic flexible substrate and the optical prism layer. The optical prism layer includes a transparent layer and a plurality of prisms attached to the transparent layer and disposed between the transparent layer and photoelectric layer. 
     According to an embodiment disclosed herein, the transparent layer includes polycarbonate or polyester. 
     According to another embodiment disclosed herein, each of the prisms includes a triangular prism. 
     According to another embodiment disclosed herein, the prism comprises a round prism tip. 
     According to another embodiment disclosed herein, the photovoltaic panel further includes a first electrically conductive layer disposed between the photoelectric layer and the optical prism layer, and a second electrically conductive layer disposed between the photoelectric layer and the flexible substrate. 
     According to another embodiment disclosed herein, the photovoltaic panel further includes two conductive ribbons attached to be respectively connected with the electrically conductive layers for outputting electrical current. 
     According to another embodiment disclosed herein, the photovoltaic panel further includes an adhesive layer disposed between the optical prism layer and the electrically conductive layer. 
     According to another embodiment disclosed herein, the adhesive layer comprises a thickness ranging from about 10 μm to about 15 μm. 
     According to another embodiment disclosed herein, each of the prisms is made from acrylic resin. 
     According to another embodiment disclosed herein, each of the prisms has an apex angle ranging from about 70 degrees to about 115 degrees. 
     According to another embodiment disclosed herein, the prisms have a prism pitch ranging from about 50 μm to about 80 μm. 
     According to another embodiment disclosed herein, each of the prisms has a prism thickness ranging from about 30 μm to about 50 μm. 
     According to another embodiment disclosed herein, the transparent layer has a thickness ranging from about 120 μm to about 150 μm. 
     According to another embodiment disclosed herein, the optical prism layer has a thickness ranging from about 150 μm to about 200 μm. 
     According to another embodiment disclosed herein, the flexible substrate includes a plastic sheet of a thickness ranging from about 0.3 mm to about 2 mm. 
     According to another embodiment disclosed herein, the flexible substrate includes a metal sheet of a thickness ranging from about 0.1 mm to about 0.6 mm. 
     According to another embodiment disclosed herein, the prism includes a sharp prism tip. 
     It is to be understood that both the foregoing general description and the following detailed description are by examples, and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings, 
         FIG. 1  illustrates a cross-sectional view of a photovoltaic panel according to one preferred embodiment of this invention; 
         FIG. 2  illustrates a cross-sectional view of a photovoltaic panel according to another preferred embodiment of this invention; 
         FIG. 3  illustrates a cross-sectional view of an optical prism layer according to another preferred embodiment of this invention; 
         FIG. 4  illustrates a perspective view of the optical prism layer in  FIG. 1 ; 
         FIG. 5  illustrates a cross-sectional view of an optical prism layer according to yet another preferred embodiment of this invention; and 
         FIG. 6  illustrates a diagram to explain how the optical prism layer enhances the incident light intensity and reduces the reflection lose. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. 
       FIG. 1  illustrates a cross-sectional view of a photovoltaic panel according to one preferred embodiment of this invention. Instead of using high-cost material to protect a photoelectric layer to meet harsh environment requirement, the photovoltaic panel  100  herein basically has its photoelectric layer  106  secured between a flexible substrate  102  and an optical prism layer  110 . The flexible substrate  102  permits the photovoltaic panel  100  to be bendable such that the photovoltaic panel  100  can be used on portable devices and home appliances. The optical prism layer  110  is to enhance the photovoltaic panel&#39;s efficiency for converting solar radiation into electricity. Besides, the photovoltaic panel  100  should at least includes an electrically conductive layer  104  and an transparent electrically conductive layer  108  for collecting electricity from the photoelectric layer  106 , which converts solar radiation into electricity. The electrically conductive layer  104  is sandwiched between the flexible substrate  102  and the photoelectric layer  106 . In this embodiment, the flexible substrate  102  is a plastic sheet of a thickness ranging from about 0.3 mm to about 2 mm. The electrically conductive layer  108  is sandwiched between the optical prism layer  110  and the photoelectric layer  106 . Two conductive ribbons  108   a  and  104   a  are attached to be respectively connected with the electrically conductive layers  104  and  108  for outputting electrical current. 
       FIG. 2  illustrates a cross-sectional view of a photovoltaic panel according to another preferred embodiment of this invention. The difference between this embodiment and the embodiment of  FIG. 1  lies in that the flexible substrate  202  is a metal substrate. The photovoltaic panel  200  basically has its photoelectric layer  204  secured between a flexible substrate  202  and an optical prism layer  208 . The flexible substrate  202  permits the photovoltaic panel  200  to be bendable such that the photovoltaic panel  200  can be applicably used on portable devices and home appliances. The optical prism layer  208  is to enhance the photovoltaic panel&#39;s efficiency for converting solar radiation into electricity. Besides, the photovoltaic panel  200  should at least includes an transparent electrically conductive layer  206  for outputting electricity from the photoelectric layer  204 , which converts solar radiation into electricity. The electrically conductive layer  206  is sandwiched between the optical prism layer  208  and the photoelectric layer  204 . Since the flexible substrate  202  is a metal substrate, it can perform the same function, e.g. outputting electricity from the photoelectric layer  204 , as the electrically conductive layer does, an extra electrically conductive layer is not necessary. In this embodiment, the flexible substrate  102  can be a metal sheet, e.g. an aluminum sheet, of a thickness ranging from about 0.1 mm to about 0.6 mm. Two conductive ribbons  204   a  and  206   a  are attached to be respectively connected with the flexible substrate  202  and the electrically conductive layer  206  for outputting electrical current. 
       FIG. 3  illustrates a cross-sectional view of an optical prism layer according to another preferred embodiment of this invention. The optical prism layer  310  aims to collect more incident light  320  so as to enhance the photovoltaic panel&#39;s efficiency for converting solar radiation into electricity. The optical prism layer  310  basically includes a transparent layer  310   a  and a plurality of triangular prisms  310   b  attached under the transparent layer  310   a.  The triangular prisms  310   b  is able to direct the incident light  320  along the directions  325 , thereby penetrating the layers under thereof, e.g. an adhesive layer  308 , an electrically conductive layer  306  and a photoelectric layer (not illustrated in  FIG. 3 ). The adhesive layer  308  is to fasten prism tips of the triangular prisms  310   b  to the electrically conductive layer  306 . In this embodiment, the adhesive layer  308  has a thickness ranging from about 10 μm to about 15 μm. The thickness of adhesive layer  308  should be thick enough to firmly secure the triangular prisms  310   b  and be thin enough to leave air gaps  310   d  among the adhesive layer  308  and any adjacent-two triangular prisms  310   b.  If the adhesive layer  308  is not thin enough, the air gaps  310   d  may be filled with the adhesive, thereby causing the triangular prisms  310   b  to malfunction, i.e. unable to direct the incident light  320  along the directions  325  that is able to penetrate the layers under thereof. In this embodiment, each of the triangular prisms  310   b  has an apex angle θ ranging from about 70 degrees to about 115 degrees. Besides, the triangular prisms  310   b  has a prism pitch P 1  (which refers to an interval between the peaks of adjacent triangular prisms) ranging from about 50 μm to about 80 μm. 
       FIG. 4  illustrates a perspective view of the optical prism layer in  FIG. 1 . The optical prism layer  310  basically includes a transparent layer  310   a  and a plurality of triangular prisms  310   b  attached under the transparent layer  310   a.  In this embodiment, the transparent layer  310   a  can be made from but not limited to polycarbonate, polyester or a transparent material equipped with abrasive resistance and non-yellowing. Besides, the triangular prisms  310   b  can be made from but not limited to acrylic resin. The transparent layer  310   a  has a thickness Wranging from about 120 μm to about 150 μm. Each of the triangular prisms  310   b  has a prism thickness W 3  ranging from about 30 μm to about 50 μm. Thus, the optical prism layer  310  has a thickness W 2  ranging from about 150 μm to about 200 μm. 
       FIG. 5  illustrates a cross-sectional view of an optical prism layer according to yet another preferred embodiment of this invention. This embodiment is different from the embodiment illustrated in  FIG. 3  in that the triangular prisms  310   b  have a round prism tip  310   c.  The round prism tip  310   c  is more easily secured by the adhesive layer than a sharp prism tip, which is illustrated in  FIG. 3 . 
       FIG. 6  illustrates a diagram to explain how the optical prism layer enhances the incident light intensity and reduces the reflection lose. As mentioned above, the triangular prism  310   b  aims to collect more incident light so as to enhance the photovoltaic panel&#39;s efficiency for converting solar radiation into electricity. particular, the triangular prism  310   b  directs an incident light  330   a,  which is reflected by a conventional glass of a photovoltaic panel and not used by a photoelectric layer of the photovoltaic panel, along a direction  330   a ′, thereby causing the incident light to easily penetrate an under layer  340 , e.g. a photoelectric layer. Besides, the triangular prism  310   b  directs an incident light  330   b,  which is reflected by a conventional glass of a photovoltaic panel and not used by a photoelectric layer of the photovoltaic panel, along a direction  330   b ′, thereby causing the incident light to easily penetrate an under layer  340 , e.g. a photoelectric layer. Therefore, a wider range of incident light, i.e. a range between the incident lights  330   a  and  330   b,  can be collected by means of the triangular prism  310   b  to enhance the incident light intensity and reduces the reflection lose. 
     According to the above-discussed embodiments, the photovoltaic panel disclosed herein has its photoelectric layer secured between a flexible substrate and an optical prism layer. The optical prism layer collects more incident light so as to enhance the photovoltaic panel&#39;s efficiency for converting solar radiation into electricity. The flexible substrate allows the photovoltaic panel to be bendable. In sum, the photovoltaic panel can be applicably used on portable devices and home appliances. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.