Patent Publication Number: US-2010126584-A1

Title: Solar cells and solar cell modules

Description:
This U.S non-provisional patent application claims priority to Korean Patent Application No. 10-2008-0116297, filed on Nov. 21, 2008, and all the benefits accruing therefrom under 35 U.S.C. §119, the contents of which in its is herein incorporated by reference. 
     BACKGROUND 
     1. Field 
     The disclosure relates to solar cells and solar cell modules using the same. 
     2. Description of the Related Art 
     Solar cells generally include a semiconductor in which an electron-hole pair is generated when light is incident upon the solar cell. Due to an electric field generated at a PN junction in the semiconductor, electrons migrate to an N-type semiconductor while holes migrate to a P-type semiconductor, thereby generating electrical power. Since components used in the solar cell are expensive, there is difficulty in manufacturing a large-sized solar cell. Sunlight condensing technologies have been developed to manufacture large-sized solar cells and increase their manufacturing costs and efficiency. 
     SUMMARY 
     An aspect of the present invention provides a solar cell. In one embodiment, the solar cell may include a substrate and a light-receiving body including a first semiconductor region of a first conductivity type and a second semiconductor region of a second conductivity type, which are formed on the substrate. The first semiconductor region is in contact with the second semiconductor region, and the second conductivity type is different from the first conductivity type. The first and second semiconductor regions have a PN junction surface, which is substantially perpendicular to the substrate. 
     The first semiconductor region may have a hollow column and include a first inner surface and a first outer surface; the first outer surface being opposed to the first inner surface. The second semiconductor region may include a second inner surface, which is in contact with the first outer surface. The PN junction surface may be disposed between the first outer surface and the second inner surface. 
     The solar cell may further include a first electrode, which is in contact with the first inner surface of the first semiconductor region and a second electrode, which is in contact with a second outer surface of the second semiconductor region. The second outer surface is opposed to the second inner surface of the second semiconductor region. 
     Another aspect of the present invention provides a solar cell module. In some embodiments, the solar cell module may include a support, a solar cell disposed adjacent to a center area of the support and provided to expose an edge area of the support, and an optical waveguide layer provided on the edge area of the support to concentrate and direct light to the solar cell. 
     The solar cell may have a PN junction surface, which is substantially perpendicular to the support. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, advantages and features of this disclosure will become more apparent by describing in further detail exemplary embodiment thereof with reference to the accompanying drawings, in which: 
         FIG. 1A  is an exemplary schematic plan (top view) of a solar cell according to some embodiments, and  FIG. 1B  is an exemplary cross-sectional view taken along the line I-I′ in  FIG. 1A . 
         FIG. 2  is an exemplary schematic plan (top view) of a solar cell. 
         FIGS. 3A to 7A  are exemplary schematic plans (top views) illustrating a method of manufacturing a solar cell, and  FIGS. 3B to 7B  are exemplary schematic cross-sectional views taken along the lines II-II′ in  FIGS. 3A to 7A , respectively. 
         FIG. 8  is an exemplary schematic cross-sectional view of a solar cell module. 
         FIGS. 9A and 9B  are exemplary schematic top surface views of the solar cell module shown in  FIG. 8 . 
         FIGS. 10A and 10B  illustrate examples of a first optical coupler. 
         FIG. 11  illustrates the procedure of transmitting light through an optical waveguide. 
         FIG. 12  is an exemplary schematic cross-sectional view of a solar cell module. 
         FIGS. 13 to 15  are exemplary schematic cross-sectional views of a solar cell module. 
         FIG. 16  is an exemplary schematic diagram illustrating a solar cell array using solar cells. 
         FIG. 17  illustrates an example of a photovoltaic system using solar cells. 
     
    
    
     DETAILED DESCRIPTION 
     The disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention, however, may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. 
     In the specification, the dimensions of layers and regions are exaggerated for clarity of illustration. It will also be understood that when a layer (or film) is referred to as being “on” another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may also be present. Also, though terms like a first, a second, and a third are used to describe various regions and layers in various embodiments, the regions and the layers are not limited to these terms. These terms are used to tell one region or layer from another region or layer. Therefore, a layer referred to as a first layer in one embodiment can be referred to as a second layer in another embodiment. An embodiment described and exemplified herein includes a complementary embodiment thereof. 
     It will be understood that, although the terms first, second, third etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present invention. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” or “includes” and/or “including” when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof. 
     Furthermore, relative terms, such as “lower” or “bottom” and “upper” or “top,” may be used herein to describe one element&#39;s relationship to another elements as illustrated in the Figures. It will be understood that relative terms are intended to encompass different orientations of the device in addition to the orientation depicted in the Figures. For example, if the device in one of the figures is turned over, elements described as being on the “lower” side of other elements would then be oriented on “upper” sides of the other elements. The exemplary term “lower,” can therefore, encompasses both an orientation of “lower” and “upper,” depending on the particular orientation of the figure. Similarly, if the device in one of the figures is turned over, elements described as “below” or “beneath” other elements would then be oriented “above” the other elements. The exemplary terms “below” or “beneath” can, therefore, encompass both an orientation of above and below. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     Exemplary embodiments are described herein with reference to cross section illustrations that are schematic illustrations of idealized embodiments. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments described herein should not be construed as limited to the particular shapes of regions as illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, a region illustrated or described as flat may, typically, have rough and/or nonlinear features. Moreover, sharp angles that are illustrated may be rounded. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region and are not intended to limit the scope of the present claims. 
     Referring to  FIGS. 1A to 1B , a solar cell  100  will now be described. The solar cell  100  may include a light-receiving body  110 , which may be provided on a substrate (not shown). The substrate may include a material selected from the group consisting of single-crystalline silicon, silicon on insulator (“SOI”), polysilicon, amorphous silicon, glass, ceramic such as alumina, stainless steel, polymer, metal, silicon germanium (“SiGe”), and single-crystalline germanium. 
     The light-receiving body  110  may include a first semiconductor region  112  of a first conductivity type and a second semiconductor region  115  of a second conductivity type; the second conductivity type being different from the first conductivity type. For example, the first conductivity type may P-type and the second conductivity type may be N-type. The first semiconductor region  112  and the second semiconductor region  115  may include, for example, silicon (“Si”), gallium arsenide (“GaAs”), gallium indium phosphide (“GaInP”), cadmium telluride (“CdTe”), cadmium sulfide (“CdS”) or Cu(In,Ga)(S,Se) 2  (referred sometimes to as “ClGs”). 
     The first semiconductor region  112  and the second semiconductor region  115  may be in communication with one another. As can be seen in the  FIG. 1A , the first semiconductor region  112  is disposed upon the second semiconductor region  115 . In one embodiment, a PN junction  118  may be formed by directly contacting the first and second semiconductor regions  112  and  115  with each other. The contours of the PN junction  118  may be substantially perpendicular to the substrate. That is, the solar cell  100  may have a PN junction  118  in a direction that is perpendicular to the substrate. In one embodiment, the PN junction  118  is circular in shape and has a surface that is perpendicular to a radius drawn from the central axis of the solar cell  100 . 
     With reference now to the  FIG. 1B , the first semiconductor region  112  may have a first inner surface  113  and a first outer surface  114 . The first outer surface  114  is opposed to the first inner surface  113 . The first inner surface  113  may surround a hollow column. That is, the first semiconductor region  112  may have a hollow region  111  at its central portion, and the hollow region  111  may be surrounded by the first inner surface  113 . The column may have, for example, a circular section, as shown in  FIG. 1 . However, the section of the column is not limited to the circular section and may be one of polygonal sections. Other cross-sectional geometries for the column may be square, rectangular, triangular, hexagonal, pentagonal, decagon, tetragon, or the like. The hollow column may be disposed at the center of the inner surface  113  and may be concentric with it. In one embodiment, the hollow column may be disposed within the inner surface  113 , but may not be concentric with the surface  113 . 
     The second semiconductor region  115  may have a second inner surface  116  that is in contact with the first outer surface  114  and a second outer surface  117  that is opposed to the first inner surface  116 . The PN junction  118  may be formed between the first outer surface  114  and the second inner surface  116 . 
     A first electrode  121  may be in electrical communication with the first semiconductor region  112 , for example, in electrical communication with the first inner surface  113 . In one embodiment, the first electrode  121  is disposed upon and physically contacts the first inner surface  113  of the first semiconductor region  112 . A second electrode  125  may be in electrical communication with the second semiconductor region  115 , for example, the second outer surface  117 . In one embodiment, the second electrode  125  is disposed upon and physically contacts the second outer surface  117  of the second semiconductor region  116 . 
     The second electrode  125  may be formed of a transparent electrically conductive material. The transparent electrically conductive materials can be inorganic materials, organic materials or combinations thereof. Examples of electrically conductive inorganic materials that can be used for the second electrode  125  are indium tin oxide (“ITO”), indium zinc oxide (“IZO”), zinc oxide (“ZnO”), an alloy of zinc oxide a aluminum (“ZnO:Al”), or the like, or a combination comprising at least one of the foregoing electrically conductive inorganic materials. Examples of electrically conductive organic materials that can be used for the second electrode  125  are polyaniline, polypyrrole, polythiophene, polyacetylene, or the like, or a combination comprising at least one of the foregoing electrically conductive organic materials. 
     A first lead  131  is in electrical communication with the first electrode  121  and a second lead  133  is in electrical communication with the second electrode  125 , transferring the electrical power generated by the solar cell  100  to the exterior. 
     Referring to  FIG. 2 , the first electrode  121  may include a plurality of sub-electrodes  122 ,  123 , and  124  that are isolated from each other. The second electrode  125  may also include a plurality of second sub-electrodes  126 ,  127 , and  128  that are isolated from each other. The first sub-electrodes  122 ,  123 , and  124  and the second sub-electrodes  126 ,  127 , and  128  may be set to face each other, respectively. The light-receiving body  110  may include at least one isolation recess  119  that intersects with the first inner surface  113  of the first semiconductor region  112 . A connection electrode  129  may be provided in the at least one isolation recess  119 . The connection electrode  129  may connect one of the first sub-electrodes  122 ,  123 , and  124  to one of the adjacent second sub-electrodes  126 ,  127 , and  128 , electrically connecting the first sub-electrodes  122 ,  123 , and  124  to the second sub-electrodes  126 ,  127 , and  128 . An insulating spacer (not shown) may be provided on a sidewall of the isolation recess  119  to prevent the connection electrode  129  from coming in direct contact with the light-receiving body  110 . 
     Referring to  FIGS. 3A to 7A  and  FIGS. 3B to 7B , an exemplary method of fabricating a solar cell  100  will now be described. 
     Referring to  FIGS. 3A and 3B , a molding pattern  90  is provided on a substrate  101 . The substrate  101  may include a material selected from the group consisting of single-crystalline silicon, silicon on insulator, polysilicon, amorphous silicon, glass, ceramic such as alumina, stainless steel, polymer, metal, silicon germanium, and single-crystalline germanium. The molding pattern  90  may be formed of a material having an etch selectivity with respect to a material constituting the light-receiving body  110  (not shown). The molding pattern  90  may include, for example, silicon oxide. The molding pattern  90  may have a cross-sectional area that exhibits the shape of, for example, a circle, a square, a rectangle, a triangle, or a polygon including hexagons, pentagons, decagons, tetragons, or the like. 
     Referring to  FIGS. 4A and 4B , a first semiconductor material  112  of a first conductivity type may be formed on a sidewall of the molding pattern  90 . The first conductivity type may be P-type. The first semiconductor material  112  may include, for example, GaAs, GaInP, CdTe, CdS or Cu(In,Ga)(S,Se) 2 . A second semiconductor material  115  of a second conductivity type may be formed on a sidewall of the first semiconductor material  112 . The second conductivity type is different from the first conductivity type. That is, the second conductivity type may be N-type. The second semiconductor material  115  may include, for example, Si, GaAs, GaInP, CdTe, Gds or Cu(In,Ga)(S,Se) 2 . The first and second materials  112  and  115  may be formed by, for example, a deposition process using chemical vapor deposition (“CVD”), plasma enhanced chemical vapor deposition (“PECVD”), remote plasma-enhanced chemical vapor deposition (“RPECVD”) hybrid physical-chemical vapor deposition (“HPCVD”), microwave plasma-assisted chemical vapor deposition (“MPCVD”), aerosol assisted chemical vapor deposition (“AACVD”), or the like, or a combination comprising at least one of the foregoing process. The first and second semiconductor materials  112  and  115  may further be formed by an etch-back process. 
     Referring to  FIGS. 5A and 5B , a second electrically conductive material  125  (which forms the second electrode  125 ) may be formed on a sidewall of the second semiconductor material  115 . The second electrically conductive material  125  may be a transparent conductive material. As noted above, indium tin oxide, indium zinc oxide, zinc oxide, an alloy of zinc oxide a aluminum, polyaniline, polypyrrole, polythiophene, polyacetylene, or the like, or a combination comprising at least one of the foregoing electrically conductive organic materials may be used as the transparent electrically conductive material. The second conductive material  125  may be formed by, for example, a sputtering deposition process and an etch-back process. When the transparent conductive material comprises an electrically conducting polymer, the material can be applied to the second semiconductor material  115  by coating processes such as spin coating, painting, dip coating, or the like, or a combination comprising at least one of the foregoing processes. 
     Referring to  FIGS. 6A and 6B , the molding pattern  90  may be selectively removed to expose a first inner surface  113  of the first semiconductor material  112 . The first inner surface  113  may provide a hollow column, i.e., a hole  114 . A mask pattern  330  may be provided to cover the first semiconductor material  112 , the second semiconductor material  115 , and the second conductive material  125  while exposing the hole  114 . The mask pattern  330  may be formed of, for example, silicon oxide. A first conductive material  121  may be formed on the first inner surface  113  of the first semiconductor material  112  and a sidewall of the mask pattern  33 . The first conductive material  121  may include a metal such as molybdenum, copper, iron, steel, or the like, or a combination comprising at least one of the foregoing metals. The first conductive material  121  may be formed by, for example, a sputtering deposition process and an etch-back process. 
     Referring to  FIGS. 7A and 7B , a mold layer (not shown) is formed to fill the hole  140 . The mold layer, the mask pattern  330 , the first conductive material  121 , the second semiconductor material  112 , the first semiconductor material  115 , and the second conductive material  125  may be polished by a chemical mechanical polishing (“CMP”) process. The mold layer and the mask pattern  330  may be removed. A light receiving body  110  may be formed, which includes a first semiconductor region  112  of a first conductivity type and a second semiconductor region  115  of a second conductivity type. A first electrode  121  and a second electrode  125  may be formed on an inner surface and an outer surface of the light-receiving body  110 , respectively. 
     Referring to  FIG. 8 , a solar cell module  201  will now be described. The solar cell module  201  may include the solar cell  100  described in  FIGS. 1A and 1B . The solar cell module  201  may include a support  210 , the solar cell  100  being provided on the support  210  to be disposed adjacent to a center area  211  of the support  210 , and an optical waveguide  220  provided on the support  210  to be disposed adjacent to an edge portion  213  of the support  210 . The solar cell  100  may be provided to expose the edge area  213 . The solar cell  100  may have a PN junction surface, which is substantially perpendicular to the support  210 . 
     The support  210  may be made of a material that does not absorb light within a suitable wavelength range that makes only a slight contribution to power generation in the solar cell  100  while simultaneously generating a heat. Generally, light within the infrared range of the electromagnetic spectrum makes only a slight contribution to power generation in the solar cell  100  and generate a heat to degrade the performance of the solar cell  100 . For this reason, the support  210  may be made of an infrared-transmitting material. 
     The optical waveguide  220  may concentrate and direct the incident light to the solar cell  100 . The optical waveguide  220  may be set to have a refractive index and a thickness to reduce impingement of light above a specific wavelength on the solar cell  100 . The optical waveguide  220  may include a high-k dielectric having a higher refractive index than the support  210 . The optical waveguide  220  may comprise a material selected from the group consisting of aluminum oxide, zinc oxide, silicon oxynitride or titanium oxide. 
     A first optical coupler  230  may be provided on the optical waveguide  220  within the edge area  213 . The first optical coupler  230  may be set such that light impinging from the upper portion of the support  210  travels to the solar cell  100  through the optical waveguide  220 . The first optical coupler  230  may include a material having the same or a smaller refractive index as compared with the refractive index of the optical waveguide  220 . The first optical coupler  230  may extend to surround the solar cell  100  at the edge area  213 , forming a closed curve such as circle or polygon, as shown in  FIGS. 9A and 9B  respectively. 
     As shown in  FIG. 8 , an upper surface of the first optical coupler  230  may be inclined toward the edge of the support  210 . Alternatively, as shown in  FIG. 10A , the first optical coupler  230  may include a coupling thin film  232  covering the edge area  213 . The coupling thin film  232  may have a concave portion  233  extending to surround the solar cell  100 . The bottom of the concave portion  233  may be inclined toward the edge of the support  210 . The surface of the concave portion  233  is concave with respect to the external incident light. Alternatively, as shown in  FIG. 10B , a top surface of the coupling thin film  232  may be inclined toward the edge of the support  210  and may be a convex prism. The surface of the convex portion  230  is convex with respect to the external incident light. 
     A first reflection layer  241  is disposed on an edge sidewall of the optical waveguide  220  such that light directed away from the solar cell may be reflected to travel towards the solar cell  100 . The first reflection layer  241  may be a multi-layer structure including silicon oxide and silicon nitride or a layer of metal such as silver. Light within a specific wavelength range may be effectively reflected by suitably adjusting the kind and the thickness of the multi-layer structure. 
     A procedure for propagating light impinging from the above of the support  210  to the solar cell  100  will now be described below with reference to  FIG. 11 , in which n 1 , n 2 , and n 3  represent refractive indexes of the first optical coupler  230 , the optical waveguide  220 , and the support  210 , respectively. The refractive index n 1  of the first optical waveguide  230  may be equal to or smaller than the refractive index n 2  of the optical waveguide  220 . 
     The light impinging on the first optical coupler  230  from above the support  210  may be refracted at the inclined surface of the first optical coupler  230  to travel to the optical waveguide  220 . When the reactive index n 1  of the first optical coupler  230  is different from the refractive index n 2  of the optical waveguide  220 , the light travelling to the optical waveguide  220  may be refracted again at a first boundary  221  between the first optical coupler  230  and the optical waveguide  220  to enter the optical waveguide  220 . The light of the optical waveguide  220  may be refracted or reflected at a second boundary  222  between the optical waveguide  220  and the support  210 . Since the refractive index n 2  of the optical waveguide  220  is greater than the refractive index n 3  of the support  210 , most of the light from the optical waveguide  220  may be totally reflected at the second boundary  222 . The condition of total reflection at the first and second boundaries  221  and  222  is expressed with an equation [Equation 1], in which λ represents the refractive index of light, m represents an integer (m=0, 1, 2, 3), and t represents the thickness of the optical waveguide  220 . Although  FIG. 11  shows that rays of light travelling to the first optical coupler  230  are all reflected at the first boundary  221 , they may be refracted to the first optical coupler  230  to enter the optical waveguide  220  again. Since the refractive index of the first optical coupler  230  is greater than that of air, light entering the first optical coupler  230  may travel to the optical waveguide  220 . 
     
       
         
           
             
               
                 
                   
                     
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     When the material of the support  210  is determined, light within a wavelength range that can be absorbed by the solar cell  100  is substantially and totally reflected at the second boundary  222  to be propagated within the optical waveguide  220  by adjusting the thickness and the refractive index of the optical waveguide  220  according to the equation [Equation 1]. According to the equation [Equation 1], light of a greater wavelength than the total reflection wavelength (e.g., infrared light) may be substantially transmitted to the support  210  without being totally reflected at the second boundary  222 . Thus, light of a greater wavelength than the total reflection wavelength may be lost at the optical waveguide  220  during its propagation. That is, light of a greater wavelength than the total reflection wavelength may not be substantially transmitted to the solar cell  100 . For instance, in case of a group III-V multijunction solar cell using InGaAsP or the like, light of a wavelength below 1.55 micrometers may be transmitted to the solar cell  100 . 
     Referring to  FIG. 12 , a solar cell module  202  according to other embodiments will now be described. Explanations of the same or similar elements in  FIG. 12  as those in  FIG. 8  will be omitted, but their differences will be explained in detail. The solar cell module  203  may include a second optical coupler  250  and a second reflection layer  243 , which reflects light impinging on a top surface of the second optical coupler  250  to the solar cell  100 . The second reflection layer  243  may be a multi-layer structure including silicon oxide and silicon nitride or a layer of metal such as silver. Light within a specific wavelength range may be effectively reflected by suitably adjusting the kind and thickness of the multi-layer structure. The solar cell  100  may have a PN junction surface, which is substantially parallel with the support  210 . The second optical coupler  250  may be made of the same material as the first optical coupler  230 . 
     Referring to  FIG. 13 , a solar cell module  203  will now be described. Explanations of the same or similar elements in  FIG. 13  as those in  FIG. 8  will be omitted, but their differences will be explained in detail. The solar cell module  203  may include an external reflection mirror  260  spaced apart from the optical waveguide  220  over the support  210 . The external reflection mirror  260  may cover up the support  210  and be concave toward the support  210 . Light impinging from below the support  210  may be reflected by the external reflection mirror  260  to impinge on the first optical coupler  230  and the optical waveguide  220 . As a result of this arrangement, light of a larger cross section may be concentrated and redirected to the solar cell  100 . 
     Referring to  FIG. 14 , a solar cell module  204  according to other embodiments will now be described. Explanations of the same or similar elements in  FIG. 14  as those in  FIG. 8  will be omitted, but their differences will be explained in detail. The solar cell module  204  may include a light-transmitting panel  270  covering the optical waveguide  220  and having a larger area than the support  210 . The solar cell module  204  includes a reflection structure  280  provided on a top surface of the light-transmitting panel  270  to reflect light to the light waveguide  220 . 
     The light-transmitting panel  270  may be made of a light-transmitting material such as, for example, glass. The reflection structure  280  may be a light-reflecting layer, which, may for example be a multi-layer structure including silicon oxide and silicon nitride or a layer of metal such as silver. Light within a specific wavelength range may be effectively reflected by suitably adjusting the kind and thickness of the multi-layer structure. As illustrated in  FIG. 15 , the reflection structure  280  may include a prism  281  protruding to the light-transmitting panel  270 . The prism  281  may have a greater refractive index than the light-transmitting panel  270 . A bottom surface of the prism  281  may have a surface inclined toward the center of the light-transmitting panel  270 . Light reflected by the inclined surface may impinge on the first optical coupler  230 . 
     According to the above-described embodiments, impingement of light within the wavelength range effective to make a small contribution to power generation on a solar cell may be reduced as much as possible. This is done to prevent efficiency degradation, which occurs when long-wavelength light such as ultraviolet light makes a contribution that increases the inner temperature of the solar cell. It is also desirable to assemble the light condensing unit (i.e., the reflection layer and a reflection structure) with the solar cell in such a manner so that misalignment may not occur thereby preventing any degradation in efficiency of the solar cell. 
     In the aforementioned embodiments, it is set forth that one solar cell is provided at the center area of the support to form the solar cell module. However, a plurality of solar cells may also be provided on a single support. 
     Referring to  FIG. 16 , a solar cell array  300  using a solar cell module will now be described. The solar cell array  300  may include at least one solar cell module  200  mounted at a main frame (not shown). The solar cell module  200  may include those solar cell modules previously described in  FIGS. 8 to 15 . The solar cell array  300  may be mounted so as to be fully exposed to the sun at all times. In one embodiment, the solar cell array  300  may be mounted at a regular angle toward the south to be fully exposed to the sun. 
     The above-described solar cell module or solar cell array may be mounted on automobiles, houses, buildings, ships, lighthouses, traffic signal systems, portable electronic devices, and various structures. Referring to  FIG. 17 , an example of a photovoltaic power generation system employing solar cells according to embodiments will now be described. The photovoltaic power generation system may include a solar cell array  300  and a power control system  400  transmitting power provided from the solar cell array  300  to the exterior. The power control system  400  may include an output unit  410 , an electric condenser system  420 , a charge/discharge controller  430 , and a system controller  440 . The output unit  410  may include a power conditioning system (“PCS”)  412 . 
     The PCS  412  may be an inverter for converting direct current from the solar cell array  300  to alternating current. Since sunlight does not exist at night is significantly reduced on cloudy days, power generation may be reduced too. The electric condenser system  420  may store electricity to prevent power generation from changing with the weather. The charge/discharge controller  430  may store power provided from the solar cell array  300  in the electric condenser system  420  or output to the electricity stored in the electric condenser system  420  to the output unit  410 . The system controller  440  may control the output unit  410 , the electric condenser system  420 , and the charge/discharge controller  430 . 
     As mentioned above, converted alternating current may be supplied to various AC loads  500  such as home and automobiles. The output unit  410  may further include a grid connect system  414 , which may provide connections to another power system  600  to transmit power to the exterior. 
     According to the embodiments, the manufacturing cost of solar cells can be reduced and efficiency of the solar cells can be improved. Moreover, disadvantages resulting from optical misalignment can be addressed. 
     Although the present invention has been described in connection with the embodiments illustrated in the accompanying drawings, it is not limited thereto. It will be apparent to those skilled in the art that various substitutions, modifications and changes may be made without departing from the scope and spirit of the invention.