Abstract:
Disclosed herein are a photovoltaic panel and a method of manufacturing the same. The panel includes a front substrate, a photovoltaic cell on the front substrate, a moisture absorbing layer covering the cell to protect the cell from moisture intrusion, a back substrate on the moisture absorbing layer, and a sealant between the substrates. The method includes the steps of forming the photovoltaic cell on the front substrate, applying the moisture absorbing layer covering the cell, applying the sealant at or near the edges of the front substrate, and securing the back substrate to the front substrate.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Application Ser. No. 61/366,162, filed Jul. 21, 2010, which is herein incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    1. Technical Field The present disclosure relates to an energy conversion device. More particularly, the present disclosure relates to a photovoltaic panel and a method of manufacturing the photovoltaic panel. 
         [0003]    2. Description of Related Art 
         [0004]    Photovoltaic (PV) devices convert light energy, particularly sunlight, into electrical energy, without producing any greenhouse gases during the conversion process, therefore may realize a green energy environment. The electrical energy generated by the photovoltaic devices can be used for all kinds of applications as those achieved by batteries or existing power generators. Recently, along with the progresses and developments of photovoltaic technology, the cost of the PV devices takes a significant price drop thereby rendering PV devices more affordable and more popular in the consumer market. For example, the PV devices can now be found on the residence rooftops and the external walls of buildings, as well as in varies electronic products such as mobile phones, personal digital assistants, digital watches, and laptops. 
         [0005]    Generally, a PV device includes a PV cell of semiconductor materials disposed on a front substrate of the device. In order to protect the PV cell, a polymer layer, such as a layer of ethyl vinyl acetate (EVA), is placed on the PV cell. However, while the. PV device is used in an outdoor environment, to maximize its exposure to the sunlight, the moisture from the environment in the form of rain, fog, or even snow becomes a major stimulant that causes EVA delamination, metal oxidation, corrosion and other quality problems. The moisture intrudes into the PV cell through the lateral sides and the back substrate of the PV device, especially when the back substrate is in the form of a polymer back sheet. The moisture gradually penetrates through the EVA and/or the back sheet for a certain time period and eventually gets to contact with the PV cell, which ultimately leads to serious power degradation of the PV is device. 
         [0006]    It is therefore an important issue for the manufacturers to improve the resistance of the PV device against moisture. 
       SUMMARY 
       [0007]    A photovoltaic panel and a method of manufacturing the photovoltaic panel are provided in the disclosure to solve the problems caused by the moisture intrusion to the photovoltaic cell. 
         [0008]    According to one aspect of the disclosure, a photovoltaic panel is provided. The photovoltaic panel includes a front substrate, a photovoltaic cell, a moisture absorbing layer, a back substrate, and a sealant. The photovoltaic cell is disposed on the front substrate. The moisture absorbing layer covers the photovoltaic cell. The back substrate is disposed on the moisture absorbing layer. The sealant is disposed between the front substrate and the back substrate and is positioned at or near the edges of the front substrate and the back substrate. The sealant substantially seals the photovoltaic cell and the moisture absorbing layer therein. 
         [0009]    In one embodiment of the disclosure, the photovoltaic panel optionally includes an encapsulant disposed between the cell and the moisture absorbing layer to encapsulate the cell. 
         [0010]    In another embodiment of the disclosure, the photovoltaic panel optionally includes an encapsulant disposed between the moisture absorbing layer and the back substrate to encapsulate the cell. 
         [0011]    In a further embodiment of the disclosure, the moisture absorbing layer optionally includes a micro-porous desiccant structured as a molecular sieve. The pore size of the micro-porous desiccant ranges from about 0.3 nm to about 1 nm, and the micro-porous desiccant includes zeolite. 
         [0012]    In yet another embodiment of the disclosure, the moisture absorbing layer optionally includes an encapsulant and a micro-porous desiccant blended in the encapsulant. The micro-porous desiccant includes zeolite, and the encapsulant includes ethyl vinyl acetate. 
         [0013]    According to another aspect of the disclosure, a method of manufacturing a photovoltaic panel is provided. The method includes the following steps: forming a photovoltaic cell on a front substrate; applying a moisture absorbing layer covering the photovoltaic cell; applying a sealant at or near the edges of the front substrate; and securing a back substrate to the front substrate such that the photovoltaic cell and the moisture absorbing layer are situated within an enclosed space formed by the front substrate, the back substrate and the sealant. 
         [0014]    In one embodiment of the disclosure, the step of applying the moisture absorbing layer optionally includes a step of laminating a film of a micro-porous desiccant onto the cell. The micro-porous desiccant includes a getter composite film containing zeolite nanoparticles. 
         [0015]    In another embodiment of the disclosure, the step of applying the moisture absorbing layer optionally includes a step of laminating a film of an encapsulant and a micro-porous desiccant blended in the encapsulant onto the cell. The encapsulant includes ethyl vinyl acetate, and the micro-porous desiccant includes zeolite. 
         [0016]    In the foregoing, the photovoltaic cell in the photovoltaic panel is protected not only by the sealant but also by the moisture absorbing layer. By trapping the water molecules of the moisture in the moisture absorbing layer, the moisture intrusion into the photovoltaic cell is prevented, and the power degradation of the photovoltaic cell is avoided. 
         [0017]    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 disclosure as claimed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The disclosure can be more fully understood by reading the following detailed description of the embodiments, with reference made to the accompanying drawings as follows: 
           [0019]      FIG. 1  is a cross-sectional view of a photovoltaic panel according to one embodiment of the disclosure; 
           [0020]      FIG. 2  is a cross-sectional view of a photovoltaic panel according to another embodiment of the disclosure; 
           [0021]      FIG. 3  is a cross-sectional view of a photovoltaic panel according to a further embodiment of the disclosure; and 
           [0022]      FIG. 4  is a flow chart of a method of manufacturing a photovoltaic panel according to one embodiment of the disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    The photovoltaic panel and the method of manufacturing the photovoltaic panel utilize a moisture absorbing layer to trap moisture and pollutant gases. The problems of material delamination, erosion, and power degradation of the is panel can therefore be prevented. Thus the life span of the panel is extended. 
         [0024]      FIG. 1  is a cross-sectional view of a photovoltaic panel according to one embodiment of the disclosure. The photovoltaic panel  100  includes a front . substrate  110 , a photovoltaic cell  120 , a moisture absorbing layer  140  and a back substrate  160 . The photovoltaic cell  120  is disposed on the front substrate  110 , and the moisture absorbing layer  140  covers the photovoltaic cell  120 . The back substrate  160  is parallel to the front substrate  110 , and the photovoltaic cell  120  and the moisture absorbing layer  140  are situated between the front substrate  110  and the back substrate  160 . 
         [0025]    In one embodiment, the material of the front substrate  110  is exemplified by a transparent conductive oxide (TCO) glass. However, the front substrate  110  is not limited to the TCO glass. Alternatively, the front substrate  110  can also be made of appropriate polymer films, such as DuPont™ Teflon® films, DuPont™ Teonex® polyethylene naphthalate (PEN) films and DuPont™ Melinex® ST polyester films. Practically, any other appropriate materials that are of high transmittance, light weighted, flexible, good UV resistance, and/or sufficient mechanical strength can be used in manufacturing the photovoltaic panel  100  of the present disclosure. 
         [0026]    On the other hand, the photovoltaic cell  120  is exemplified by a thin film photovoltaic cell having multiple metal layers deposited on the front substrate  110 . Exemplary materials of the metal layers include, but are not limited to, amorphous silicon, cadmium diselenide (CdS), cadmium telluride (Cd/Te), copper indium diselenide (CIS), and/or copper indium gallium diselenide (CIGS). The photovoltaic cell  120  may be deposited by known depositing methods, such as chemical vapor deposition (CVD), physical vapor deposition (PVD), sputtering, or any other methods known to a person skilled in the art. 
         [0027]    In the present embodiment, the moisture absorbing layer  140  includes a micro-porous desiccant structured as a molecular sieve. The micro-porous desiccant includes zeolite that is a crystalline aluminosilicate material serving as the molecular sieve to trap moisture and even pollutant gases like nitride compounds. The pore size of the micro-porous desiccant ranges from about 0.3 nm to about 1 nm, so as to trap water molecules and other molecules harmful to the photovoltaic cell  120 . Practically, the pore size of the micro-porous desiccant can be 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1.0 nm. 
         [0028]    Although the moisture absorbing layer  140  is exemplified by including zeolite in the present embodiment, it is not limited thereto. Other crystalline materials having uniform molecular-scale pores to form a molecular sieve and to separate molecules based on sizes, shapes and polarities, may be used in the photovoltaic panel  100  of the present embodiment. 
         [0029]    As shown in  FIG. 1 , the moisture absorbing layer  140  covers the photovoltaic cell  120 . More specifically, the moisture absorbing layer  140  overlays a top surface  121  of the photovoltaic cell  120 , such that the moisture penetrating through the back substrate  160  can be trapped by the moisture absorbing layer  140 . In this manner, the photovoltaic cell  120  is protected from the moisture intrusion. The problems of moisture penetrating through the back substrate  160  can be prevented, therefore would increase the life span of the photovoltaic panel  100 . 
         [0030]    In addition to the above described front substrate  110 , photovoltaic cell  120 , moisture absorbing layer  140  and back substrate  160 , the photovoltaic panel  100  of the present embodiment further includes an encapsulant  130  and a sealant  150 . In one embodiment, the encapsulant  130  is disposed between the photovoltaic cell  120  and the moisture absorbing layer  140  to encapsulate the photovoltaic cell  120 . The sealant  150  is disposed between the front substrate  110  and the back substrate  160 , and is positioned at or near the edges of the front substrate  110  and the back substrate  160  so as to seal the photovoltaic cell  120  and the moisture absorbing layer  140  therein. More specifically, the sealant  150  is exemplified by disposing in a margin area of the front substrate  110  outside the photovoltaic cell  120 , the encapsulant  130  and the moisture absorbing layer  140 . In this manner, the sealant  150  completely seals the photovoltaic panel  100  and forms an enclosed space  100   a  with the front substrate  110  and the back substrate  160 . The photovoltaic cell  120  and the moisture absorbing layer  140  are situated in the enclosed space  100   a  to be protected from moisture and/or pollutant intrusion. 
         [0031]    In the photovoltaic panel  100  as shown in  FIG. 1 , the materials of the encapsulant  130  and the sealant  150  can be selected in accordance with the practical production needs. The exemplary materials for the encapsulant  130  includes, for example, commercially obtainable DuPont™ Elvax® ethyl vinyl acetate (EVA) resins, commercially obtainable DuPont™ PV5200 series encapsulant sheets, and commercially obtainable DuPont™ PV5300 series encapsulant sheets. The exemplary materials for the sealant  150  includes, for example, polyisobutylene (PIB), butyl rubber, VAMAC™, ethylene acrylic elastomers, Hypalon™, and chlorosulfonated polyethylene. The above mentioned materials are for exemplifications only, and are not intended to limit the scope of the disclosure. 
         [0032]    In the present embodiment of  FIG. 1 , the encapsulant  130  is exemplified is by disposing between the photovoltaic cell  120  and the moisture absorbing layer  140 , yet the disposition of the encapsulant  130  it is not limited thereto.  FIG. 2  is a cross-sectional view of a photovoltaic panel according to another embodiment of the disclosure. The photovoltaic panel  200 , including the front substrate  210 , the photovoltaic cell  220 , the encapsulant  230 , the moisture absorbing layer  240 , the sealant  250 , and the back substrate  260 , differs from the photovoltaic panel  100  of  FIG. 1  in that the encapsulant  230  is disposed between the moisture absorbing layer  240  and the back substrate  260  to encapsulate the photovoltaic cell  220 . Any other appropriate dispositions of the encapsulant to fully cover the photovoltaic cell can be used in the photovoltaic panel. 
         [0033]    As shown in  FIG. 1 , the encapsulant  130  and the moisture absorbing layer  140  are illustrated as two different layers, so are the encapsulant  230  and the moisture absorbing layer  240  depicted in  FIG. 2 . However, in another embodiment, the two separate layers can be combined into one layer. 
         [0034]      FIG. 3  is a cross-sectional view of a photovoltaic panel according to a further embodiment of the disclosure. The photovoltaic panel  300  includes a front substrate  310 , a photovoltaic cell  320 , a moisture absorbing layer  340 , a sealant  350  and a back substrate  360 . The photovoltaic cell  320  is disposed on the front substrate  310 , and the moisture absorbing layer  340  covers the photovoltaic cell  320 . The back substrate  360  is parallel to the front substrate  310 , and the photovoltaic cell  320  and the moisture absorbing layer  340  are situated between the front substrate  310  and the back substrate  360 . The moisture absorbing layer  340  covers the photovoltaic cell  320 , more specifically, fully overlays a top surface  321  of the photovoltaic cell  320 . 
         [0035]    The moisture absorbing layer  340  of the present embodiment includes an encapsulant and a micro-porous desiccant blended in the encapsulant. The micro-porous desiccant is structured as a molecular sieve and includes zeolite, which is similar to that included in the moisture absorbing layer  140  of the previously described photovoltaic panel  100  (as depicted in  FIG. 1 ). The micro-porous desiccant is blended in the encapsulant by mixing a predetermined proportion of zeolite nanoparticles into the encapsulant raw material, e.g. EVA resin, during the formation of the EVA film. The micro-porous desiccant serves as a molecular sieve to trap moisture and pollutant gases. The pore size of the micro-porous desiccant ranges from about 0.3 nm to about 1 nm. On the other hand, the exemplary materials for the encapsulant includes, for example, commercially obtainable DuPont™ Elvax® ethyl vinyl acetate (EVA) resins, commercially obtainable DuPont™ PV5200 series encapsulant sheets, and commercially obtainable DuPont™ PV5300 series encapsulant sheets. 
         [0036]    The photovoltaic panel  300  uses one layer of encapsulant with micro-porous desiccant blended therein, to encapsulate the photovoltaic cell  320  and to trap moisture at the same time, thus the structure of the photovoltaic panel  300  is further simplified and the cost is reduced accordingly. 
         [0037]    The detailed description now directs to a method of manufacturing a photovoltaic panel. In order to clearly show the characteristics of the disclosure, the above mentioned photovoltaic panel  100  is taken as an example here with reference to  FIG. 1  and  FIG. 4 .  FIG. 4  is a flow chart of a method of manufacturing a photovoltaic panel according to one embodiment of the disclosure. 
         [0038]    Of the method of manufacturing the photovoltaic panel  100 , the photovoltaic cell  120  is formed on the front substrate  110  as shown in step S 1 . The photovoltaic cell  120  may be deposited by chemical vapor deposition (CVD), physical vapor deposition (PVD), sputtering, or any other methods known to a person who is skilled in the art. 
         [0039]    In step S 2 , the moisture absorbing layer  140  is applied to cover the photovoltaic cell  120 . Exemplarily, the step S 2  is performed by laminating a film of the micro-porous desiccant, zeolite for example, onto the photovoltaic cell  120 . For example, a getter composite film containing zeolite nanoparticles can be laminated onto the photovoltaic cell  120 . 
         [0040]    Optionally, a step of encapsulating the photovoltaic cell  120  by the encapsulant  130  can be performed prior to laminating the film. Alternatively, the step of encapsulating the photovoltaic cell  120  is performed after step S 2  in another embodiment. The sequence of the two steps is not limited here in the disclosure, as long as the photovoltaic cell  120  can be encapsulated by the encapsulant  130  and covered by the moisture absorbing layer  140 . 
         [0041]    In another embodiment, the step S 2  and the step of encapsulating the photovoltaic cell  120  can be combined into one step by laminating a film of the encapsulant with the micro-porous desiccant blended therein. The photovoltaic cell  120  is therefore protected from the intrusion of moisture and pollutants by the laminated film. The micro-porous desiccant can be exemplified by zeolite, and the encapsulant can be exemplified by EVA. The micro-porous desiccant is formed by mixing a predetermined proportion of zeolite nanoparticles into the encapsulant raw material, e.g. EVA resin, during the formation of the EVA film. Then, the encapsulant is laminated over the photovoltaic cell  120 . 
         [0042]    Then, the method moves on to step S 3 , in which the sealant  150  is applied at or near the edges of the front substrate  110 . In one embodiment, the sealant  150  is applied to a marginal area of the front substrate  110  outside the photovoltaic cell  120 , the encapsulant  130  and the moisture absorbing layer  140 . More specifically, the sealant  150  is disposed completely surrounding the photovoltaic cell  120 , the encapsulant  130  and the moisture absorbing layer  140 . 
         [0043]    Finally, in step S 4 , the back substrate  160  is secured onto the front substrate  110 . As a result, the photovoltaic cell  120 , the moisture absorbing layer  140  and the sealant  150  are situated within a space formed by the front substrate  110 , the back substrate  160  and the sealant  150 . Specifically, the sealant  150 , the front substrate  110  and the back substrate  160  form an enclosed space  100   a , and the photovoltaic cell  120  and the moisture absorbing layer  140  are enclosed therein or are situated in the enclosed space  100   a.    
         [0044]    After completion of step S 4 , the photovoltaic panel  100  is thereby completed. By the protection of the sealant  150  and the moisture absorbing layer  140 , the moisture intrusion to the photovoltaic cell  120  is prevented, as well as the delamination and corrosion of materials in the photovoltaic panel  100 . 
         [0045]    In the above-described photovoltaic panel and method of manufacturing the same, the moisture intrusion from the back substrate of the panel can be blocked by the moisture absorbing layer, so as to prevent the delaminations and corrosions of materials and to prolong the life span of the photovoltaic panel accordingly. Furthermore, the power degradation of the photovoltaic cell is prevented, increasing the reliability and the performance of the photovoltaic panel. Moreover, the moisture absorbing layer includes zeolite or encapsulant with zeolite blended therein, making the moisture absorbing layer cheap and easy to obtain. 
         [0046]    It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present disclosure without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the present disclosure cover modifications and variations of this disclosure provided they fall within the scope of the following claims.