Abstract:
A multi-junction solar module apparatus. The apparatus has a substrate member. The apparatus has a plurality of first photovoltaic devices arranged in a first spatial configuration, which is preferably disposed on a first planar region. In a specific embodiment, the plurality of first photovoltaic devices are numbered from 1 through N, where N is an integer greater than 1. Each of the plurality of first solar cells has a first bandgap characteristic. The apparatus has a plurality of second photovoltaic devices arranged in a second spatial configuration, which is preferably disposed in a second planar region. The plurality of second photovoltaic devices are numbered from 1 through M, where M is an integer greater than 1. In a preferred embodiment, N is not equal to M. Each of the second solar cells has a second band gap characteristic. In a specific embodiment, a first connector interconnects the plurality of first solar cells in a serial configuration. The first connector has a first terminal end and a second terminal end. A second connector interconnects the plurality of second solar cells in a serial configuration. The second connector has a first terminal end and a second terminal end. In a specific embodiment, a third connector connecting the second terminal end of the first connector and the first terminal end of the second connector. In a specific embodiment, a Vss node is coupled to the first terminal end of the first connector. In a specific embodiment, a Vdd node is coupled to the second terminal end of the second connector. In a preferred embodiment, N and M are selected to match a first current through the plurality of first solar cells and a second current through the plurality of second solar cells.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Patent Application No. 61/092,383, filed Aug. 27, 2008, entitled “MULTI-JUNCTION SOLAR MODULE AND METHOD FOR CURRENT MATCHING BETWEEN A PLURALITY OF FIRST PHOTOVOLTAIC DEVICES AND SECOND PHOTOVOLTAIC DEVICES” by inventors HOWARD W. H. LEE et al. This application is also related to U.S. patent application Ser. No. 11/748,444, filed May 14, 2007, U.S. patent application Ser. No. 11/804,019, filed May 15, 2007, and U.S. Provisional Patent Application No. 60/988,099, filed Nov. 14, 2007, all commonly assigned and incorporated by reference herein for all purposes. 
     
    
     STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable 
       REFERENCE TO A “SEQUENCE LISTING,” A TABLE, OR A COMPUTER PROGRAM LISTING APPENDIX SUBMITTED ON A COMPACT DISK. 
       [0003]    Not applicable 
       BACKGROUND OF THE INVENTION 
       [0004]    The present invention relates generally to photovoltaic materials. More particularly, the present invention provides a method and structure for manufacture of multi-junction solar module using a current matching structure and method for thin and thick film photovoltaic materials. Merely by way of example, the present method and structure have been implemented using a solar module having multiple thin film materials, but it would be recognized that the invention may have other configurations. 
         [0005]    From the beginning of time, human beings have been challenged to find way of harnessing energy. Energy comes in the forms such as petrochemical, hydroelectric, nuclear, wind, biomass, solar, and more primitive forms such as wood and coal. Over the past century, modern civilization has relied upon petrochemical energy as an important source. Petrochemical energy includes gas and oil. Gas includes lighter forms such as butane and propane, commonly used to heat homes and serve as fuel for cooking. Gas also includes gasoline, diesel, and jet fuel, commonly used for transportation purposes. Heavier forms of petrochemicals can also be used to heat homes in some places. Unfortunately, petrochemical energy is limited and essentially fixed based upon the amount available on the planet Earth. Additionally, as more human beings begin to drive and use petrochemicals, it is becoming a rather scarce resource, which will eventually run out over time. 
         [0006]    More recently, clean sources of energy have been desired. An example of a clean source of energy is hydroelectric power. Hydroelectric power is derived from electric generators driven by the force of water that has been held back by large dams such as the Hoover Dam in Nev. The electric power generated is used to power up a large portion of Los Angeles, Calif. Other types of clean energy include solar energy. Specific details of solar energy can be found throughout the present background and more particularly below. 
         [0007]    Solar energy generally converts electromagnetic radiation from our sun to other useful forms of energy. These other forms of energy include thermal energy and electrical power. For electrical power applications, solar cells are often used. Although solar energy is clean and has been successful to a point, there are still many limitations before it becomes widely used throughout the world. As an example, one type of solar cell uses crystalline materials, which form from semiconductor material ingots. These crystalline materials include photo-diode devices that convert electromagnetic radiation into electrical current. Crystalline materials are often costly and difficult to make on a wide scale. Additionally, devices made from such crystalline materials have low energy conversion efficiencies. Other types of solar cells use “thin film” technology to form a thin film of photosensitive material to be used to convert electromagnetic radiation into electrical current. Similar limitations exist with the use of thin film technology in making solar cells. That is, efficiencies are often poor. Additionally, film reliability is often poor and cannot be used for extensive periods of time in conventional environmental applications. There have been attempts to form heterojunction cells using a stacked configuration. Although somewhat successful, it is often difficult to match currents between upper and lower solar cells. These and other limitations of these conventional technologies can be found throughout the present specification and more particularly below. 
         [0008]    From the above, it is seen that improved techniques for manufacturing photovoltaic materials and resulting devices are desired. 
       BRIEF SUMMARY OF THE INVENTION 
       [0009]    According to the present invention, techniques related to photovoltaic materials are provided. More particularly, the present invention provides a method and structure for manufacture of multi-junction solar module using a current matching structure and method for thin and thick film photovoltaic materials. Merely by way of example, the present method and structure have been implemented using a solar module having multiple thin film materials, but it would be recognized that the invention may have other configurations. 
         [0010]    In a specific embodiment, the present invention provides a multi-junction solar module apparatus. The apparatus has a substrate member, e.g., glass. The apparatus has a plurality of first photovoltaic devices arranged in a first spatial configuration, which is preferably disposed on a first planar region. In a specific embodiment, the plurality of first photovoltaic devices are numbered from 1 through N, where N is an integer greater than 1. Each of the plurality of first solar cells has a first bandgap characteristic. The apparatus has a plurality of second photovoltaic devices arranged in a second spatial configuration, which is preferably disposed in a second planar region. The plurality of second photovoltaic devices are numbered from 1 through M, where M is an integer greater than 1. In a preferred embodiment, N is not equal to M. Each of the second solar cells has a second band gap characteristic. In a specific embodiment, a first connector interconnects the plurality of first solar cells in a serial configuration. The first connector has a first terminal end and a second terminal end. A second connector interconnects the plurality of second solar cells in a serial configuration. The second connector has a first terminal end and a second terminal end. In a specific embodiment, a third connector connecting the second terminal end of the first connector and the first terminal end of the second connector. In a specific embodiment, a Vss node is coupled to the first terminal end of the first connector. In a specific embodiment, a Vdd node is coupled to the second terminal end of the second connector. In a preferred embodiment, N and M are selected to match a first current through the plurality of first solar cells and a second current through the plurality of second solar cells. 
         [0011]    Depending upon the specific embodiment, one or more of these features may also be included. The present technique provides an easy to use process that relies upon conventional technology that is nanotechnology based. In some embodiments, the method may provide higher efficiencies in converting sunlight into electrical power using a multiple junction design and method. Depending upon the embodiment, the efficiency can be about 10 percent or 20 percent or greater. Additionally, the method provides a process that is compatible with conventional process technology without substantial modifications to conventional equipment and processes. In a specific embodiment, the present method and structure can also be provided using large scale manufacturing techniques, which reduce costs associated with the manufacture of the photovoltaic devices. In another specific embodiment, the present method and structure can also be provided using any combination of suitable single junction solar cell designs to form top and lower cells, although there can be more than two stacked cells depending upon the embodiment. Depending upon the embodiment, one or more of these benefits may be achieved. These and other benefits will be described in more throughout the present specification and more particularly below. 
         [0012]    Various additional objects, features and advantages of the present invention can be more fully appreciated with reference to the detailed description and accompanying drawings that follow. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a simplified diagram of a connection structure for a module having a multi-junction cell according to a specific embodiment of the present invention; 
           [0014]      FIG. 2  is a simplified diagram of further details of a connection structure for a module having a multi-junction cell according to a specific embodiment of the present invention; 
           [0015]      FIG. 3  is a simplified side-view diagram of a connection structure for a multi-junction cell according to a specific embodiment of the present invention; 
           [0016]      FIG. 4  is a simplified illustration of current and voltage for a module according to an embodiment of the present invention; 
           [0017]      FIG. 5  is a simplified diagram of a connection structure for a module having a multi-junction cell according to another embodiment of the present invention; 
           [0018]      FIG. 6  is a simplified diagram of a method of matching a plurality of first photovoltaic devices to a plurality of second photovoltaic devices in forming a solar module according to an embodiment of the present invention; and 
           [0019]      FIGS. 7  is a simplified diagram illustrating an example of photovoltaic device that can be arranged as first, second, third, and Nth devices according to a specific embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    According to the present invention, techniques related to photovoltaic materials are provided. More particularly, the present invention provides a method and structure for manufacture of multi-junction solar module using a current matching structure and method for thin and thick film photovoltaic materials. Merely by way of example, the present method and structure have been implemented using a solar module having multiple thin film materials, but it would be recognized that the invention may have other configurations. 
         [0021]      FIG. 1  is a simplified diagram of a connection structure for a module  100  having a multi-junction cell according to a specific embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. One of ordinary skill in the art would recognize other variations, modifications, and alternatives. As shown, photovoltaic module  100  is formed on a substrate (not shown) and includes sub-module  101  and sub-module  102 . In the embodiment shown in  FIG. 1 , sub-module  101  includes photovoltaic devices labeled as cells  111 - 118 , with each cell shown schematically as a diode. Sub-module  101  also has a first connector  103  interconnecting photovoltaic devices labeled as cells  111 - 118  in a serial configuration. The first connector has a first terminal end  104  and a second terminal end  105 . As shown in  FIG. 1 , sub-module  102  includes photovoltaic devices labeled as cells  121 - 126 , with each cell shown schematically as a diode. Sub-module  102  also has a second connector  106  interconnecting solar cells  121 - 126  in a serial configuration. The second connector has a first terminal end  107  and a second terminal end  108 . Of course, there can be other variations, modifications, and alternatives. 
         [0022]    In the specific embodiment shown in  FIG. 1 , photovoltaic module  100  has a third connector  131  connecting terminal end  105  of sub-module  102  to terminal end  107  of sub-module  102 . Module  101  also includes a first output node  133  connected to terminal end  104  of terminal end  104  and a second output node  135  connected to terminal end  108  of sub-module  102 . As shown, sub-modules  101  and  102  are serially connected in module  100 . 
         [0023]    In a specific embodiment, cells  111 - 118  in sub-module  101  are made of a semiconductor material having a first bandgap and are constructed so that each cell provides substantially the same current, designated as I 1 . As shown, cells  111 - 118  are serially connected between terminal ends  104  and  105  of sub-module  101 . A terminal voltage V 1  is provided between terminal ends  104  and  105 . The terminal voltage V 1  is substantially a sum of the voltages provided in each of cells  111 - 118 . 
         [0024]    Similarly, cells  121 - 126  in sub-module  102  are made of a second semiconductor material having a second bandgap and are constructed so that each cell provides substantially the same current, designated as I 2 . As shown, cells  121 - 126  are serially connected between terminal ends  107  and  108  of sub-module  102 . A terminal voltage V 2  is provided between terminal ends  107  and  108 . The terminal voltage V 2  is substantially a sum of the voltages provided in each of cells  121 - 126 . 
         [0025]    According to an embodiment of the invention, sub-module  101  and sub-module  102  are connected in series to form module  100 , as shown in  FIG. 1 . A first output node  133  of module  100  is coupled to the first terminal end  104  of the first connector  103 , and a second output node  135  is coupled to the second terminal end  108  of the second connector  106 . Additionally, a third connector  131  in module  100  connects the second terminal end  105  of the first connector and the first terminal end  107  of the second connector. In this embodiment, current I 1  in sub-module  101  and current I 2  in sub-module  102  are substantially matched. As a result, the current I provided by module  100  is substantially the same as I 1  and I 2 . In this configuration module  100  now provides a terminal voltage V between the output nodes  133  and  135  which is substantially a sum of V 1  and V 2 , the terminal voltages of sub-modules  101  and  102 , respectively. 
         [0026]    Depending on the embodiments, the present invention provides various methods for matching the currents in sub-modules  101  and  102 . In a specific embodiment, a cell in sub-module  101 , e.g. cell  111 , may have different characteristics from a cell in sub-module  102 , e.g. cell  121 . For example, cell  111  may have a different bandgap in the absorber layer from cell  121 . As another example, cell  111  may have different optical absorption properties from cell  121 . For instance, they may absorb light from different parts of the optical spectrum, or they may have different optical absorption coefficients or different carrier generation efficiencies. One or more of these parameters can be used to modify the current generated in each cell. Additionally, in a specific embodiment of the invention, the cell area is selected to provide a predetermined cell current or to match currents from two different cells. 
         [0027]    For example, if cell  111  is formed using a first material to provide a current density of i 1  per unit area and has a cell area A 1 , then the cell current for cell  111  is I 1 =A 1 *i 1 . Similarly, if cell  121  is formed using a second material to provides a current density of i 2  per unit area and has a cell area A 2 , then the cell current for cell  121  is I 2 =A 2 *i 2 . Given i 1  and i 2 , cell area A 1  for cell  111  and cell area A 2  for cell  121  can then be selected such that A 1 *i 1 =A 2 *i 2 , which will substantially match the currents, i.e. I 1 =I 2 . 
         [0028]    If the sub-modules have the same total area, then there can be different numbers of cells in each of the sub-modules. Accordingly, in a specific embodiment, the number of cells in each sub-module can be selected for current matching. For example, if sub-module  101  has N cells and sub-module  102  has M cells, where N and M are integers, then N and M are selected to match a first current through the plurality of first photovoltaic devices in sub-module  101  and a second current through the plurality of second photovoltaic devices in sub-module  102 . 
         [0029]    In a specific embodiment shown in  FIG. 1 , the areas of cells  111 - 118  and the areas of cells  121 - 126  are selected such that the currents I 1  and I 2  are matched. In this embodiment, cells in a sub-module can be optimized for performance independent of the other sub-modules. Alternatively, various other parameters can be selected for current matching purposes. For example, semiconductor materials having different bandgaps and optical absorption properties can also be used to determine the cell current. Of course, one of ordinary skill in the art would recognize many variations, modifications, and alternatives. 
         [0030]    In a specific embodiment, module  100  can be constructed to better utilize the optical spectrum of the light source. As an example, sub-module  101  is constructed to absorb the shorter wave length portion of the sunlight spectrum, and sub-module  102  is constructed to absorb the longer wavelength portion of the sunlight. In a specific example, sub-module  101  can be made from a wider bandgap material than sub-module  102 . By stacking sub-module  101  over sub-module  102 , the sun light not absorbed by sub-module  101  will be absorbed by sub-module  102 . Optionally, a third sub-module can be added to convert the sunlight in a portion of the spectrum not used by sub-module  101  and sub-module  102 . The third sub-module can be connected to sub-module  102  in a similar way as described above. 
         [0031]    In an alternative embodiment, each cell in module  100  can be a multi-junction cell. For example, each of cells  111 - 118  in sub-module  102  can include stacked multiple junctions which absorb different portions of the sunlight spectrum. The multi-junction cells can have two external terminals or three external terminals. 
         [0032]      FIG. 2  is a simplified diagram of further details of a connection structure for a module having a multi-junction cell according to a specific embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. One of ordinary skill in the art would recognize other variations, modifications, and alternatives. As shown, photovoltaic module  200  includes sub-modules  201 ,  203 , and  205 , etc. Each of the sub-modules includes multiple solar cells connected in series. For example, sub-module  201  includes multiple solar cells such as  207 . Sub-module  201  is shown schematically as device  213 , which is characterized by voltage V 1  and current I 1 . Similarly, sub-module  203  includes multiple solar cells such as  209  connected serially. Sub-module  203  is shown schematically as device  215 , which is characterized by voltage V 2  and current I 2 . Additionally, sub-module  205  includes multiple solar cells such as  211  serially connected. Sub-module  202  is shown schematically as device  217 , which is characterized by voltage V 3  and current I 3 . 
         [0033]    In a specific embodiment, sub-modules  201 ,  203 ,  205 , etc., can be configured according to the method described above in connection with  FIG. 1 . For example, sub-modules  201 ,  203 , and  205 , etc., are stacked, and each can be constructed to absorb and convert light energies from a different portion of the sunlight spectrum. In the serial combination, the currents are matched, such that I 1 =I 2 =I 3 . In a specific embodiment, the device areas are selected to match the currents. Of course, there are many variations, modifications, and alternatives. 
         [0034]      FIG. 3  is a simplified side-view diagram of a connection structure for a multi-junction module according to a specific embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. One of ordinary skill in the art would recognize other variations, modifications, and alternatives. As shown, multi-junction module  300  includes sub-modules such as  310 ,  320 , and  330 , etc. Each of the sub-modules includes a number of solar cells. For example, sub-module  310  includes cells such as  311 , sub-module  320  includes cells such as  321 , and sub-module  330  includes cells such as  331 , etc. Within each sub-module, the cells are connected serially, and the current in each cell are matched. The current for each sub-module, e.g. current I 1  for sub-module  310 , current I 2  for sub-module  320 , and current I 3  for sub-module  330 , etc, are also matched. Accordingly, I 1 =I 2 =I 3 . Let V 1 , V 2 , and V 3 , etc., represent the terminal voltage of sub-modules  310 ,  320 , and  330 , etc., respectively. Then the terminal voltage of module  300 , V TOT , is a sum of the sub-modules. In other words, V TOT =V 1 +V 2 +V 3 . 
         [0035]      FIG. 4  is a simplified illustration of current and voltage for a module according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. One of ordinary skill in the art would recognize other variations, modifications, and alternatives. As shown,  FIG. 4  includes a simplified description of current and voltage relationships between N sub-modules in a module. Let the currents for modules  1 ,  2 ,  3 , . . . , and N be I 1 , I 2 , I 3 , . . . and I N , respectively, and the corresponding voltages for modules  1 ,  2 ,  3 , . . . , and N be V 1 , V 2 , V 3 , . . . , and V N , respectively. Then all the currents are matched, and the terminal voltage of the module V TOT  is the sum of the voltages for all the sub-modules, as shown in  FIG. 4 . 
         [0036]      FIG. 5  is a simplified diagram of a connection structure for a module  500  having a multi-junction cell according to another embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. One of ordinary skill-in-the-art would recognize other variations, modifications, and alternatives. As shown, solar module  500  is formed on a substrate (not shown) and includes sub-module  510  and sub-module  520 . In the specific embodiment shown in  FIG. 5 , sub-module  510  includes N photovoltaic devices labeled as cells  511 ,  512 , . . . ,  51 N, where N is an integer. Each of the N photovoltaic devices is shown schematically as a diode. Sub-module  510  also has a first connector  531  interconnecting photovoltaic devices  511 - 51 N in a parallel configuration. The first connector  531  has a first terminal end  551  and a second terminal end  553 . As shown in  FIG. 5 , sub-module  520  includes M photovoltaic devices labeled as cells  521 - 52 M, where M is an integer. Again, each of the photovoltaic devices is shown schematically as a diode. Sub-module  520  also has a second connector  541  interconnecting solar cells  521 - 52 M in a parallel configuration. The second connector  541  has a first terminal end  555  and a second terminal end  557 . 
         [0037]    In the specific embodiment shown in  FIG. 5 , module  500  has a third connector  559  connecting terminal end  553  of sub-module  510  to terminal end  555  of sub-module  520 . Module  100  also includes a first output node  561  connected to terminal end  551  of sub-module  510  and a second output node  562  connected to terminal end  557  of sub-module  520 . As shown, sub-modules  510  and  520  are serially connected in module  500 . 
         [0038]    In a specific embodiment, cells  511 - 51 N in sub-module  510  are made of a semiconductor material having a first bandgap and a first device area. Cells  511 - 51 N provide currents I 11 -I 1N , respectively. The sum of currents I 11 -I 1N  is designated as I 1 . As shown, cells  511 - 5 IN are connected in parallel between terminal ends  551  and  553  of sub-module  510 . A terminal voltage V 1  is provided between terminal ends  551  and  553 . 
         [0039]    Similarly, cells  521 - 52 M in sub-module  520  are made of a second semiconductor material having a second bandgap and a second device area. Cells  521 - 52 M provide currents I 21 -I 2M , respectively. The sum of currents I 21 -I 2M  is designated as I 2 . As shown, cells  521 - 52 M are connected in parallel between terminal ends  555  and  557  of sub-module  520 . A terminal voltage V 2  is provided between terminal ends  555  and  557 . 
         [0040]    According to an embodiment of the invention, sub-module  510  and sub-module  520  are connected in series to form module  500 , as shown in  FIG. 5 . A first output node  561  of module  100  is coupled to the first terminal end  551  of the first connector  531 , and a second output node  562  is coupled to the second terminal end  557  of the second connector  541 . Additionally, a third connector  559  in module  500  connects the second terminal end  553  of the first connector and the first terminal end  555  of the second connector. In this embodiment, the total current I 1  in sub-module  510  and the total current I 2  in sub-module  520  are substantially matched. As a result, the current provided by module  500  is substantially the same as I 1  or I 2 . In this configuration module  101  now provides a terminal voltage V 3  between the output nodes  561  and  562  which is substantially a sum of V 1  and V 2 , the terminal voltages of sub-modules  510  and  520 , respectively. 
         [0041]    Each cell in sub-modules  510  and  520  may have different characteristics which may result in different cell currents. For example, these characteristics may include energy bandgap of the absorber layer material, optical absorption properties in different portions of the optical spectrum, and carrier generation efficiencies, etc. One or more of these parameters can be used to modify the current generated in each cell. Additionally, in a specific embodiment of the invention, the cell area is selected to provide a predetermined cell current or to match currents from two different cells. 
         [0042]    According to a specific embodiment, the present invention provides a method for a parallel and serial combination of photovoltaic devices. In this embodiment, cells in a sub-module can be optimized for performance independent of the other sub-modules. As illustrated in  FIG. 5 , the current matching condition of module  500  and the terminal voltage can be expressed in the following equations. 
         [0000]        I   11   +I   12   +I   13   + . . . +I   1N   =I   21   +I   22   + . . . +I   2M    (1)
 
         [0000]        V=V   1   +V   2    (2)
 
         [0043]    As a specific example, if each of cells  511 - 51 N is formed using a first material to provide a current of i 1 , then the total cell current for sub-module  510  is I 1 =N*i 1 . Similarly, if each of cells in sub-module  520  is formed using a second material to provides a current of i 2 , then the total cell current for sub-module  520  is I 2 =M*i 2 . Sub-modules  510  and  520  can be advantageously connected in series if N and M are selected such that N*i 1 =M*i 2 , which will substantially match the currents, i.e. I 1 =I 2 . 
         [0044]    In an embodiment, sub-module  510  is constructed to absorb the shorter wave length portion of the sunlight spectrum, and sub-module  520  is constructed to absorb the longer wavelength portion of the sunlight. In a specific example, sub-module  510  can be made from a wider bandgap material than sub-module  520 . By stacking sub-module  510  over sub-module  520 , the sun light not absorbed by sub-module  510  can be absorbed and converted to electric current by sub-module  520 . Optionally, a third sub-module can be added to convert the sunlight in a portion of the spectrum not used by sub-module  510  and sub-module  520 . The third sub-module can be connected to sub-module  520  in a similar way as described above. 
         [0045]    In an alternative embodiment, each cell in module  500  can be a multi-junction cell. For example, each of cells  511 - 51 N in sub-module  510  can include stacked multiple junctions which absorb different portions of the sunlight spectrum. The multi-junction cells can have two external terminals or three external terminals. 
         [0046]    In the above discussion, each photovoltaic device in  FIGS. 1 ,  2 , and  5  is shown schematically as a diode, such as devices  111  and  121  in  FIG. 1 , devices  207 ,  209 , and  211  in  FIG. 2 , and devices  511  and  521  in  FIG. 5 . Examples of photovoltaic devices can be found in U.S. patent application Ser. No. 11/748,444, filed May 14, 2007, U.S. patent application Ser. No. 11/804,019, filed May 15, 2007, and U.S. Provisional Patent Application No. 60/988,099, filed Nov. 14, 2007. All these applications are commonly assigned, and their contents are hereby incorporated by reference for all purposes. 
         [0047]    Additionally, it is also noted that each of the photovoltaic devices in embodiments of this application can be a parallel or serial combination of photovoltaic devices, or even a parallel and serial combination of photovoltaic devices. Some of these interconnect combinations are discussed throughout this application. Various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application. 
         [0048]    According to a specific embodiment of the present invention, a method for making a multi-junction solar module device can be briefly outlined below. 
         [0049]    1. Form a first sub-module, the first sub-module includes a plurality of first photovoltaic devices, each of the plurality of first photovoltaic devices being characterized by a first device area and having a first bandgap characteristic for providing a predetermined electrical current; 
         [0050]    2. Interconnect the plurality of first photovoltaic devices in a serial configuration; (This process may be integrated in the above) 
         [0051]    3. Form a second sub-module, the second sub-module includes a plurality of second photovoltaic devices, each of the plurality of second photovoltaic devices being characterized by a second device area and having a second bandgap characteristic for providing the predetermined electrical current; 
         [0052]    4. Interconnect the plurality of second photovoltaic devices in a serial configuration; (This process may be integrated in the above) 
         [0053]    5. Mount the first sub-module over the second sub-module. 
         [0054]    6. Perform other steps, as desired. 
         [0055]      FIG. 6  is a simplified diagram of a method of matching a plurality of first photovoltaic devices to a plurality of second photovoltaic devices in forming a solar module according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. One of ordinary skill in the art would recognize other variations, modifications, and alternatives. 
         [0056]      FIGS. 7 , is a simplified diagram illustrating an example of photovoltaic device that can be arranged as first, second, third, and Nth devices according to a specific embodiment of the present invention. As shown, an upper cell can be made of cadmium telluride (CdTe) material that is a crystalline compound formed from cadmium and tellurium. In a specific embodiment, the CdTe has a zinc blend (cubic) crystal structure. As an example, the CdTe crystalline form a direct bandgap semiconductor. Depending upon the embodiment, the CdTe can be sandwiched with cadmium sulfide to form a pn junction photovoltaic solar cell. Additionally, the lower cell can be made of an alternative material that receives any traversing energy through the upper cell. As an example, the lower cell can be made of a suitable material such as silicon, polysilicon, CIGS, and other materials. Of course, there can be other variations, modifications, and alternatives. Of course, there can be other variations, alternatives, and modifications. 
         [0057]    In a preferred embodiment, the upper cell can be made according to High Efficiency Photovoltaic Cell and Manufacturing Method listed under U.S. Ser. No. 61/059,253 (Attorney Docket No. 026335-002500US), commonly assigned, and hereby incorporated for all purposes. In one or more embodiments, the top cell comprises an absorber layer selected from CuInS 2 , SnS, Cu(In 2 Al)S 2 , Cu(In 1-x ), Al x )S 2 , Cu(In, Ga)S 2 , or Cu(In 1-x , Ga)S 2  or other suitable materials. In other specific embodiments, the bottom cell may comprise an absorber layer selected from CIGS, Cu 2 SnS 3 , FeS 2 , or Ge or others. 
         [0058]    It is also understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims.