Abstract:
A solar cell management system for increasing the efficiency and power output of a solar cell and methods for making and using the same. The management system provides an electric field across an individual solar cell, an array of solar cells configured as a panel, or a group of solar panels. The imposed electric field exerts a force on both the electrons and holes created by light incident on the solar cell and accelerates the electron-hole pairs towards the electrodes of the solar cell. Compared to conventional solar cells, these accelerated electron-hole pairs travel a shorter distance from creation (by incident optical radiation) and spend less time within the solar cell material, therefore the electron-hole pairs have a lower likelihood of recombining within the cells&#39; semiconductor&#39;s material. This reduction in the electron-hole recombination rate results in an overall increase in the solar cells&#39; efficiency and greater power output.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a divisional application of co-pending U.S. patent application Ser. No. 14/628,079, filed Feb. 20, 2015, which claims the benefit of U.S. Provisional Application No. 61/943,127, filed Feb. 21, 2014; U.S. Provisional Application No. 61/943,134, filed Feb. 21, 2014; U.S. Provisional Application No. 61/947,326, filed Mar. 3, 2014; and U.S. Provisional Application No. 62/022,087, filed Jul. 8, 2014, the disclosures of which are hereby incorporated by reference in their entirety and for all purposes. 
     
    
     FIELD 
       [0002]    The present disclosure relates generally to photovoltaic devices and more specifically, but not exclusively, to systems and methods for maximizing the power or energy generated and the overall efficiency of one or more solar cells, for example, by applying and adjusting an external electric field across the solar cells. 
       BACKGROUND 
       [0003]    A solar cell (also called a photovoltaic cell) is an electrical device that converts the energy of light directly into electricity by a process known as “the photovoltaic effect.” When exposed to light, the solar cell can generate and support an electric current without being attached to any external voltage source. 
         [0004]    The most common solar cell consists of a p-n junction  110  fabricated from semiconductor materials (e.g., silicon), such as in a solar cell  100  shown in  FIG. 1 . For example, the p-n junction  110  includes a thin wafer consisting of an ultra-thin layer of n-type silicon on top of a thicker layer of p-type silicon. Where these two layers are in contact, an electrical field (not shown) is created near the top surface of the solar cell  100 , and a diffusion of electrons occurs from the region of high electron concentration (the n-type side of the p-n junction  110 ) into the region of low electron concentration (the p-type side of the p-n junction  110 ). 
         [0005]    The p-n junction  110  is encapsulated between two conductive electrodes  101   a ,  101   b . The top electrode  101   a  is either transparent to incident (solar) radiation or does not entirely cover the top of the solar cell  100 . The electrodes  101   a ,  101   b  can serve as ohmic metal-semiconductor contacts that are connected to an external load  30  that is coupled in series. Although shown as resistive only, the load  30  can also include both resistive and reactive components. 
         [0006]    Typically, multiple solar cells  100  can be coupled (in series and/or parallel) together to form a solar panel  10  (shown in  FIG. 2 ). With reference to  FIG. 2 , a typical installation configuration using at least one solar panel  10  is shown. The solar panels  10  can be connected either in parallel as shown in  FIG. 2 , series, or a combination thereof, and attached to a load, such as an inverter  31 . The inverter  31  can include both resistive and reactive components. 
         [0007]    Returning to  FIG. 1 , when a photon hits the solar cell  100 , the photon either: passes straight through the solar cell material—which generally happens for lower energy photons; reflects off the surface of the solar cell; or preferably is absorbed by the solar cell material—if the photon energy is higher than the silicon band gap—generating an electron-hole pair. 
         [0008]    If the photon is absorbed, its energy is given to an electron in the solar cell material. Usually this electron is in the valence band and is tightly bound in covalent bonds between neighboring atoms, and hence unable to move far. The energy given to the electron by the photon “excites” the electron into the conduction band, where it is free to move around within the solar cell  100 . The covalent bond that the electron was previously a part of now has one fewer electron—this is known as a hole. The presence of a missing covalent bond allows the bonded electrons of neighboring atoms to move into the hole, leaving another hole behind. In this way, a hole also can move effectively through the solar cell  100 . Thus, photons absorbed in the solar cell  100  create mobile electron-hole pairs. 
         [0009]    The mobile electron-hole pair diffuses or drifts toward the electrodes  101   a ,  101   b . Typically, the electron diffuses/drifts towards the negative electrode, and the hole diffuses/drifts towards the positive electrode. Diffusion of carriers (e.g., electrons) is due to random thermal motion until the carrier is captured by electrical fields. Drifting of carriers is driven by electric fields established across an active field of the solar cell  100 . In thin film solar cells, the dominant mode of charge carrier separation is drifting, driven by the electrostatic field of the p-n junction  110  extending throughout the thickness of the thin film solar cell. However, for thicker solar cells having virtually no electric field in the active region, the dominant mode of charge carrier separation is diffusion. The diffusion length of minor carriers (i.e., the length that photo-generated carriers can travel before they recombine) must be large in thicker solar cells. 
         [0010]    Ultimately, electrons that are created on the n-type side of the p-n junction  110 , “collected” by the p-n junction  110 , and swept onto the n-type side can provide power to the external load  30  (via the electrode  101   a ) and return to the p-type side (via the electrode  101   b ) of the solar cell  100 . Once returning to the p-type side, the electron can recombine with a hole that was either created as an electron-hole pair on the p-type side or swept across the p-n junction  110  from the n-type side. 
         [0011]    As shown in  FIG. 1 , the electron-hole pair travels a circuitous route from the point the electron-hole pair is created to the point where the electron-hole pair is collected at the electrodes  101   a ,  101   b . Since the path traveled by the electron-hole pair is long, ample opportunity exists for the electron or hole to recombine with another hole or electron, which recombination results in a loss of current to any external load  30 . Stated in another way, when an electron-hole pair is created, one of the carriers may reach the p-n junction  110  (a collected carrier) and contribute to the current produced by the solar cell  100 . Alternatively, the carrier can recombine with no net contribution to cell current. Charge recombination causes a drop in quantum efficiency (i.e., the percentage of photons that are converted to electric current when the solar cell  100 ), and, therefore, the overall efficiency of the solar cell  100 . 
         [0012]    The cost of the solar cell  100  or the solar panel  10  is typically given in units of dollars per watts of peak electrical power that can be generated under normalized conditions. High-efficiency solar cells decrease the cost of solar energy. Many of the costs of a solar power system or plant are proportional to the number of solar panels required as well as the (land) area required to mount the panels. A higher efficiency solar cell will allow for a reduction in the number of solar panels required for a given energy output and the required area to deploy the system. This reduction in the number of panels and space used might reduce the total plant cost, even if the cells themselves are more costly. 
         [0013]    The ultimate goal is to make the cost of solar power generation comparable to, or less than, conventional electrical power plants that utilize natural gas, coal, and/or fuel oil to generate electricity. Unlike most conventional means of generating electric power that require large centralized power plants, solar power systems can be deployed at large centralized locations by electric utilities, on commercial buildings to help offset the cost of electric power, and even on a residence by residence basis. 
         [0014]    Recent attempts to reduce the cost and increase the efficiency of solar cells include testing various materials and different fabrication techniques used for the solar cells. Another approach attempts to enhance the depletion region formed around the p-n junction  110  for enhancing the movement of charge carriers through the solar cell  100 . For example, see U.S. Pat. No. 5,215,599, to Hingorani, et al. (“Hingorani”), filed on May 3, 1991, and U.S. Pat. No. 8,466,582, to Fornage (“Fornage”), filed on Dec. 2, 2011, claiming priority to a Dec. 3, 2010 filing date, the disclosures of which are hereby incorporated by reference in their entireties and for all purposes. 
         [0015]    However, these conventional approaches for enhancing the movement of charge carriers through the solar cell  100  require a modification of the fundamental structure of the solar cell  100 . Hingorani and Fornage, for example, disclose applying an external electric field to the solar cell using a modified solar cell structure. The application of the external electric field requires a voltage to be applied between electrodes inducing the electric field (described in further detail with reference to equation 2, below). Without modifying the fundamental structure of the solar cell  100 , applying the voltage to the existing electrodes  101   a ,  101   b  of the solar cell  100  shorts the applied voltage through the external load  30 . Stated in another way, applying voltage to the electrodes  101   a ,  101   b  of the solar  100  is ineffective for creating an external electric field and enhancing the movement of charge carriers. Accordingly, conventional approaches—such as disclosed in Hingoriani and Fornage—necessarily modify the fundamental structure of the solar cell  100 , such as by inserting an external (and electrically isolated) set of electrodes on the base of the solar cell  100 . There are several disadvantages with this approach. 
         [0016]    For example, the external electrodes must be placed on the solar cell  100  during the fabrication process—it is virtually impossible to retrofit the external electrodes to an existing solar cell or panel. This modification to the fabrication process significantly increases the cost of manufacturing and decreases the manufacturing yield. Additionally, placement of the external electrodes over the front, or incident side, of the solar cell  100  reduces the optical energy which reaches the solar cell  100 , thereby yielding a lower power output. 
         [0017]    As a further disadvantage, to yield significant improvements in power output of the solar cell  100 , sizeable voltages must be applied to the external electrodes of the solar cell  100 . For example, Fornage discloses that voltages on the order of “1,000&#39;s” of volts must be placed on the external electrodes for the applied electric field to be effective and increase the power output of the solar cell  100 . The magnitude of this voltage requires special training for servicing as well as additional high voltage equipment and wiring that does not presently exist in existing or new solar panel deployments. As an example, an insulation layer between the external electrodes and the solar cell  100  must be sufficient to withstand the high applied voltage. In the event of a failure of the insulation layer, there is a significant risk of damage to not only the solar cell  100 , but also all solar panels  10  connected in series or parallel to the failed solar cell as well as the external load  30  (or the inverter  31 ). 
         [0018]    As a further disadvantage, varying illumination conditions (e.g., due to cloud coverage of the sun and/or normal weather fluctuations) can cause instability in the power output of conventional solar cells and solar panels. For example, with reference to  FIG. 2 , the inverter  31  typically requires a static, non-varying voltage and current input. As shown in  FIG. 2 , the solar panels  10  provide the input voltage and current to the inverter  31 . However, time-varying illumination conditions can cause the output from solar panels  10  to fluctuate (e.g., on the order of seconds or less). The fluctuation of the voltage and current supplied to the inverter  31  compromises the quality of the power output by the inverter  31 , for example, in terms of frequency, voltage, and harmonic content. Conventional efforts to combat varying illumination conditions include placing batteries or capacitors at the input of the inverter  31  and, unfortunately, only minimize these variations. 
         [0019]    In view of the foregoing, a need exists for an improved solar cell system and method for increased efficiency and power output, such as with increased mobility of electron-hole pairs, in an effort to overcome the aforementioned obstacles and deficiencies of conventional solar cell systems. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  is an exemplary top-level cross-sectional diagram illustrating an embodiment of a solar cell of the prior art. 
           [0021]      FIG. 2  is an exemplary top-level block diagram illustrating one embodiment of a solar panel array of the prior art using the solar cells of  FIG. 1 . 
           [0022]      FIG. 3  is an exemplary top-level block diagram illustrating an embodiment of a solar cell management system. 
           [0023]      FIG. 4  is an exemplary block diagram illustrating an alternative embodiment of the solar cell management system of  FIG. 3 , wherein a solar panel array is coupled to a voltage source through a switch. 
           [0024]      FIGS. 5A-D  are exemplary waveforms illustrating the applied voltage as a function of time of the inputs and outputs of the switch used with the solar panel array of  FIG. 4 . 
           [0025]      FIG. 6  is an exemplary block diagram illustrating another alternative embodiment of the solar cell management system of  FIG. 3 , wherein a solar panel array is coupled to a voltage pulser circuit. 
           [0026]      FIG. 7  is an exemplary waveform illustrating the applied voltage as a function of time used with the solar panel array of  FIG. 6 . 
           [0027]      FIG. 8  is an exemplary block diagram illustrating one embodiment of the voltage pulser circuit of  FIG. 6 . 
           [0028]      FIG. 9A  is an exemplary block diagram illustrating an alternative embodiment of the solar cell management system of  FIG. 4 , wherein the solar cell management system includes a control circuit. 
           [0029]      FIG. 9B  is an exemplary flow-chart illustrating a state diagram for the control circuit shown in  FIG. 9A . 
           [0030]      FIG. 10A  is an exemplary block diagram illustrating an alternative embodiment of the solar cell management system of  FIG. 6 , wherein the solar cell management system includes a control circuit. 
           [0031]      FIG. 10B  is an exemplary flow-chart illustrating a state diagram for the control circuit shown in  FIG. 10A . 
           [0032]      FIGS. 11A-C  are exemplary waveforms illustrating an embodiment of the relationship between applied voltage, pulse frequency, and pulse width to the improved current output of the photovoltaic device of  FIG. 3 . 
       
    
    
       [0033]    It should be noted that the figures are not drawn to scale and that elements of similar structures or functions are generally represented by like reference numerals for illustrative purposes throughout the figures. It also should be noted that the figures are only intended to facilitate the description of the preferred embodiments. The figures do not illustrate every aspect of the described embodiments and do not limit the scope of the present disclosure. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0034]    Since currently-available solar cell systems fail to maximize the power output of a photovoltaic cell, a solar cell system that increases the mobility of electron-hole pairs and reduces the recombination current in a semiconductor material can prove desirable and provide a basis for a wide range of solar cell systems, such as to increase the efficiency and power output of solar cells configured as a solar panel. This result can be achieved, according to one embodiment disclosed herein, by a solar cell management system  300  as illustrated in  FIG. 3 . 
         [0035]    Turning to  FIG. 3 , the solar cell management system  300  is suitable for use with a wide range of photovoltaic devices. In one embodiment, the solar cell management system  300  can be suitable for use with the solar cell  100  shown in  FIG. 1 . For example, the solar cell  100  can represent any suitable generation of solar cells such as wafer-based cells of crystalline silicon (first generation), thin film solar cells including amorphous silicon cells (second generation), and/or third generation cells. The solar cell management system  300  advantageously can be used with any generation of solar cell  100  without structural modification—and the associated drawbacks. 
         [0036]    In another embodiment, the solar cell management system  300  can be suitable for use with multiple solar cells  100 , such as the solar panels  10  shown in  FIG. 2 . As previously discussed, multiple solar cells  100  can be coupled (in series and/or parallel) together to form a solar panel  10 . The solar panels  10  can be mounted on a supporting structure (not shown) via ground mounting, roof mounting, solar tracking systems, fixed racks, and so on and can be utilized for both terrestrial and space borne applications. Similarly, the solar cell management system  300  advantageously can be used with any generation of solar panel  10  without structural modification—and the associated drawbacks—of the solar panel  10 . 
         [0037]    As shown in  FIG. 3 , the photovoltaic device  200  cooperates with an electric field  250 . In some embodiments, the polarity of the electric field  250  can be applied in either the same direction or the reverse direction as the polarity of the electrodes  101   a ,  101   b  (shown in  FIG. 1 ) in the photovoltaic device  200 . For example, if applying the electric field  250  in the same direction as the polarity of the electrodes  101   a ,  101   b  in the photovoltaic device  200 , the electric field  250  acts on the electron-hole pairs in the photovoltaic device  200  to impose a force—e − E or h + E on the electron or hole, respectively—thereby accelerating the mobility of the electron and hole towards respective electrodes. Alternatively, if the polarity of the electric field  250  is reversed, the mobility of the electron-hole pairs in the photovoltaic device  200  decreases, thereby increasing the recombination current within the photovoltaic device  200 . Accordingly, the efficiency of the photovoltaic device  200  can be diminished as desired, such as for managing the power output of the photovoltaic device  200 . 
         [0038]    Furthermore, the electric field  250  applied to the photovoltaic device  200  can be static or time varying as desired. In the case where the electric field  250  is time varying, the electric field  250  has a time averaged magnitude that is non-zero. Stated in another way, the net force on the electrons and holes is non-zero to provide increased mobility in the electron-hole pairs of the photovoltaic device  200 . 
         [0039]    If applied to the conventional solar cell  100  of  FIG. 1 , in the absence of an external load  30  (shown in  FIG. 1 ), an external voltage can be applied across the electrodes  101   a ,  101   b  of the solar cell  100  to create the electric field  250 . In one embodiment, the electric field  250  (e.g., between the electrodes  101   a ,  101   b ) is defined by Equation 1: 
         [0000]    
       
         
           
             
               
                 
                   E 
                   = 
                   
                     
                       ( 
                       
                         
                           V 
                           App 
                         
                         - 
                         
                           V 
                           P 
                         
                       
                       ) 
                     
                     t 
                   
                 
               
               
                 
                   ( 
                   
                     Equation 
                      
                     
                         
                     
                      
                     1 
                   
                   ) 
                 
               
             
           
         
       
     
         [0040]    In Equation 1, E represents the electric field  250 , V App  is the voltage applied externally to the photovoltaic device  200 , V P  is the voltage output of the photovoltaic device  200  (e.g., ˜30 volts), and t is the thickness of the semiconductor material in the photovoltaic device  200  from electrode  101   a  to  101   b . For example, assuming V App −V P =200 Volts (nominally) and a thickness t of about 0.02 cm, the electric field  250  is about 10K Volts/cm. It can be seen from Equation 1 that as the thickness t of the photovoltaic device  200  decreases (e.g., less than 0.01 cm), higher electric fields  250  can be generated using the same or lower voltages. 
         [0041]    As discussed above, the photovoltaic device  200  typically drives an external load, such as the load  30  of the solar cell  100 . With reference to Equation 1, if applying an external voltage V App  directly to the photovoltaic device  200  that drives the external load  30 , the external load  30  can include resistive components that draw current from the source of the applied voltage V App . Stated in another way, applying the external voltage V App  to the photovoltaic device  200  can effectively deliver power to the overall circuit represented by Equation 2: 
         [0000]    
       
         
           
             
               
                 
                   
                     Power 
                     Input 
                   
                   = 
                   
                     
                       
                         ( 
                         
                           V 
                           App 
                         
                         ) 
                       
                       2 
                     
                     
                       R 
                       L 
                     
                   
                 
               
               
                 
                   ( 
                   
                     Equation 
                      
                     
                         
                     
                      
                     2 
                   
                   ) 
                 
               
             
           
         
       
     
         [0042]    In Equation 2, R L  represents the impedance of the external load  30 . In some cases, the input power can be substantially greater than the power output of the photovoltaic device  200 . Accordingly, the solar cell management system  300  is configured to apply the electric field  250  across the photovoltaic device  200  without injecting more energy than the photovoltaic device  200  is capable of producing or more energy than would be gained by applying the electric field across the photovoltaic device  200 . 
         [0043]    The solar cell management system  300  can apply the external voltage V App  to the photovoltaic device  200  using any suitable means described herein, including using a switch  55  as shown in  FIG. 4 . Turning to  FIG. 4 , the photovoltaic device  200  can represent any number of photovoltaic devices such as the solar cell  100  and/or the solar panels  10  as illustrated. The solar panels  10  are connected to the switch  55 , such as a single pole, double throw (or three-way) switch as shown. In one embodiment, the switch  55  is also coupled to a voltage source  50  and an external load R L  (e.g., shown as the inverter  31 ). The inverter  31  can convert a DC voltage and current into an AC voltage and current, which is typically compatible in voltage and frequency with conventional AC power grids. The output frequency of the inverter  31  and the amplitude of the AC current/voltage can be based upon country, location, and local grid requirements. 
         [0044]    The voltage source  50  can include any suitable means for maintaining a constant voltage, including ideal voltage sources, controlled voltage sources, and so on. However, in some embodiments—such as the embodiment shown below with reference to  FIG. 9A —the voltage source  50  can have a variable, adjustable output (e.g., time varying voltage). A switch control (or controller)  45  is coupled to the switch  55  to control the duration of connection and/or the frequency of switching, such as between the voltage source  50  and the inverter  31  to the solar panels  10 . The switch controller  45  can be preset to operate at a fixed switching duration D and switching frequency f (shown in  FIGS. 5A-C ). The voltage applied in the first position of the switch  55  can be fixed and based on the voltage source  50 . In some embodiments, the magnitude of the voltage applied by voltage source  50 , the duration D of connection, and/or the frequency f of switching can be preset and/or vary based on load conditions. 
         [0045]    For example, the switch  55  connects the solar panels  10  with the voltage source  50  in a first position (as shown with the arrow in the switch  55  of  FIG. 4 ). When connected in the first position, the voltage source  50  applies a voltage V APP  across the electrodes  101   a ,  101   b  (shown in  FIG. 1 ) of the solar panels  10  and induces the electric field  250  (shown in  FIG. 3 ) across each solar panel  10 . Once the electric field  250  has been established across the solar panels  10 , the switch  55  switches to connect the solar panels  10  to the inverter  31  (i.e., the load R L ) in a second position. Accordingly, the voltage source  50  can provide the electric field  250  without being connected to the solar panels  10  and the inverter  31  at the same time. Therefore, with reference again to Equation 2, applying the external voltage V APP  does not allow the load R L  (e.g., the inverter  31 ) to draw current directly from the voltage source  50 . 
         [0046]    Application of the electric field  250  to the solar panels  10  can increase the current and power output of the solar panels  10  by a predetermined amount when the solar panels  10  subsequently are connected to the inverter  31  in the second position. The predetermined amount is dependent upon an intensity of light incident on the solar panels  10 , the voltage applied V APP  to the solar panels  10  by the voltage source  50 , the thickness of the solar panels  10 , the frequency f that the voltage source  50  is connected to the solar panels  10 , and the duty cycle of the switching process between the first position and the second position—with the duty cycle being defined as the amount of time that the solar panels  10  are connected to the voltage source  50  divided by 1/f the switching time (i.e., multiplied by the frequency f or divided by the total period of the signal). It should be noted that the switch duration time D, the switching frequency f, and the duty cycle are all interrelated quantities such that quantifying any two of the quantities allows for determination of the third quantity. For example, specifying the switching frequency and the duty cycle allows for determination of the switch duration time D. For example, under high intensity light conditions, the improvement in power output can be on the order of 20%; under low light conditions, 50+%. 
         [0047]    The embodiment shown in  FIG. 4  advantageously provides the electric field  250  to the photovoltaic device  200  without the need to modify the solar panels  10  and/or solar cells  100  to include additional, external electrodes. 
         [0048]    In some embodiments, an energy storage device—such as a capacitor  41 , an inductor  42 , and/or a battery  43 —can be placed before the inverter  31  to mitigate any voltage drop-out being seen by the inverter  31  while the switch  55  is in the first position. Accordingly, while the inverter  31  (i.e., load) is disconnected from the solar panels  10  when the switch  55  is in the first position and the electric field  250  is being established across the solar panels  10  (i.e., switching time D shown in  FIGS. 5A-D ), the energy storage device supplies energy to the inverter  31  to keep current flowing during this switched period. Stated in another way, the energy storage device can discharge while the solar panels  10  are disconnected from the inverter  31 . 
         [0049]    Therefore, a constant voltage from the voltage source  50 —which in turn creates the electric field  250 —need not be applied continuously to see an improvement in the power output of the solar panels  10 . For example, with duration switching times D of nominally 10-2000 ns, V App &#39;s of nominally 100-500+ Volts, and a switching frequency f of 20 μseconds, the duty cycle of nominally 0.1-10% can be used. The inductor  42 , the capacitor  41 , and/or the battery  43  are chosen to be of sufficient size to provide enough discharge while the solar panels  10  are disconnected while the electric field  250  is being placed across the solar panels  10  so as not to cause a drop out on the output of the inverter  31 . 
         [0050]    For example, the size of the capacitor  41  that is placed across the load (e.g., the inverter  31 ) is determined by the acceptable voltage droop that the inverter  31  can tolerate during the switching time D. For example, if the voltage droop during the switching time D is not to be less than 90% maximum voltage generated by the photovoltaic device  200 , the capacitor needs to be sized such according to Equation 3: 
         [0000]    
       
         
           
             
               
                 
                   
                     C 
                     41 
                   
                   = 
                   
                     
                       - 
                       D 
                     
                     
                       
                         R 
                         L 
                       
                        
                       
                         ln 
                          
                         
                           ( 
                           MaxV 
                           ) 
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   
                     Equation 
                      
                     
                         
                     
                      
                     3 
                   
                   ) 
                 
               
             
           
         
       
     
         [0051]    In Equation 3, D is the duration the switch is connected to the voltage source  50  and MaxV is the percentage of the maximum voltage required (e.g., 90% in the example above). In a similar manner, the inductance and/or the battery can be calculated. 
         [0052]      FIG. 5A  illustrates control voltage as a function of time from the switch controller  45  to activate and control the switch  55  using the solar cell management system  300  of  FIG. 4 . In this example, the solar panels  10  are disconnected from the inverter  31  and connected to the voltage source  50  in the first position of the switch  55  for the duration D, which is repeated every 1/f seconds.  FIG. 5B  illustrates the voltage as a function of time from the voltage source  50  provided to the switch  55  at the first position.  FIG. 5C  illustrates the output voltage of the switch  55  from the solar panels  10  (when wired in parallel) as a function of time at the output of the switch  55  that couples to the inverter  31  in the second position. Similarly,  FIG. 5D  illustrates the voltage as a function of time at the output of the switch  55  that couples to the inverter  31  having a capacitor  41  coupled there between. 
         [0053]    The drop in voltage seen by the inverter  31  shown in  FIG. 5D  at the end of the switching duration D is designated the voltage droop discussed above. The voltage droop is dependent on the size of the capacitor  41 , the inductor  42 , and/or the battery  43 . In one example of the system  300  that does not include the capacitor  41 , the inductor  42 , or the battery  43 , the voltage applied across the input of the inverter  31  appears as the output voltage illustrated in  FIG. 5C . 
         [0054]      FIG. 6  illustrates an alternative embodiment of the solar cell management system  300  of  FIG. 3 . Turning to  FIG. 6 , the photovoltaic device  200  can represent any number of photovoltaic devices such as the solar cell  100  and/or the solar panels  10  as illustrated. As shown, the solar panels  10  are wired in parallel, but can also be wired in series and any combination thereof. 
         [0055]    A voltage pulser  60 , such as a high voltage pulse generator, can apply a time varying voltage pulse  71  (shown in  FIG. 7 ) across one or more of the solar panels  10 . In one embodiment, a duration D P  of the voltage pulse  71  can be short—nominally 10-2000 ns—and a magnitude can be high—nominally 100-500+ Volts. In the embodiment shown in  FIG. 6 , the voltages applied, the pulse width, and the pulse repetition rate are fixed at a predetermined level to provide optimum performance under selected operating conditions. For example, with reference to  FIGS. 6 and 7 , the voltage pulse  71  has the duration D P  of about 1000 ns, which voltage pulse  71  is repeated with a period of 1/f. The duration D P  of the voltage pulse  71  and the frequency f of the voltage pulse  71  are chosen such that the reactance of inductors in the voltage inverter  31  present a high impedance to the voltage pulser  60 , which high impedance allows a high voltage to be developed across the electrodes  101   a ,  101   b  (shown in  FIG. 1 ) of the solar panels  10  and not be shorted out by the inverter  31 . 
         [0056]    Additionally, series inductors (not shown) can be placed at the input of the inverter  31 , which series inductors are capable of handling the current input to the inverter  31  and act as an RF choke such that the voltage pulses  71  are not attenuated (or effectively shorted) by the resistive component of the inverter  31 . The duty cycle (time the pulse is on/time the pulse is off) can be nominally 0.1-10%. 
         [0057]    The strength of the electric field  250  imposed on the photovoltaic device  200  is a function of the construction of the photovoltaic device  200 , such as the thickness of the photovoltaic device  200 , the material and dielectric constant of the photovoltaic device  200 , the maximum breakdown voltage of the photovoltaic device  200 , and so on. 
         [0058]    For the voltage pulse  71  shown in  FIG. 7 , a Fourier analysis of this waveform results in a series of pulses with frequencies ω=nω 0  where ω 0 =2πf and the strength of the pulses is given by Equation 4: 
         [0000]    
       
         
           
             
               
                 
                   
                     V 
                      
                     
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         [0059]    In Equation 4, n is a series of integers from −∞ to +∞. Accordingly, the 0th order pulse (i.e., n=0) has a DC component that is shorted through the resistive load R L . The first order of the voltage pulse  71  applied across the solar panels  10  is V App  (1−D P /f), where D P /f is the duty cycle of the pulse, D P  is the pulse duration, and f is the repetition rate of the pulse. Since the inductance of the inverter  31  acts as a high impedance Z to the voltage pulse  71  generated by the embodiment of  FIG. 6 , a high voltage pulse  71  is developed across each of the solar panels  10 , which, in turn, creates a high electric field  250  across the solar panels  10 . 
         [0060]    As shown in  FIG. 6 , the voltage inverter  31  represents the external load R L . However, the external load R L  can include purely resistive components such that a set of inductors can be placed in series with the load R L  to act as the RF choke so that the voltage pulse  71  (and the electric field  250 ) is applied across the solar panels  10 . 
         [0061]    Any number of circuits can be used in the voltage pulser  60  to apply the voltage pulse  71  as desired. One such exemplary circuit used in the voltage pulser  60  is shown in  FIG. 8 . As illustrated, the voltage pulser  60  includes a pulse generator  61  (not shown), a high voltage source  69  (not shown), and a switching transistor  68  for impressing the high voltage pulse  71  on the solar panels  10  (e.g., by switching the output of the high voltage source  69  to the solar panels  10 ) shown in  FIG. 6 . The voltage pulser  60  of  FIG. 8  contains a device that transfers electrical signals between two, electrically isolated, circuits using light, such as an opto-isolator  62  to isolate the pulse generator  61  from the high voltage switching transistor  68 . Advantageously, the opto-isolator  62  prevents a high voltage (e.g., from the high voltage source  69 ) from affecting the pulse signal  71 . The opto-isolator circuit  62  is illustrated with pins 1-8 and is shown as part of the input circuit to the voltage pulser  60 . 
         [0062]    A bias voltage supply  63  (not shown) provides voltage (e.g., 15 VDC) to the opto-isolator  62  to supply the required bias for the opto-isolator  62 . A capacitor  64  isolates the bias voltage supply  63 , creating an AC path for any signal from distorting the bias supply to the opto-isolator  62 . Pins 6 and 7 of the opto-isolator  62  are the switching signal output of the opto-isolator  62  used to drive the high voltage switching transistor  68 . A diode  66 —such as a Zener diode—is used to hold the switching threshold of the switching transistor  68  to above the set point of the diode  66 , eliminating any noise from inadvertently triggering the switching transistor  68 . Resistor  67  sets the bias point for the gate G and emitter E of the switching transistor  68 . When the voltage applied across pins 6 and 7 of the opto-isolator  62  exceeds the threshold set by the resistor  67 , the switching transistor  68  is turned “on” and current flows between the collector C and the emitter E of the high voltage switching transistor  68 . Accordingly, the high voltage switching transistor  68  presents an Injected High Voltage source to the solar panels  10  until the Control Pulse IN from the pulse generator  61  drops below the set threshold on the G of the high voltage switching transistor  68 , which stops the current flow across C-G shutting the switching transistor  68  “off.” 
         [0063]    As in the previous embodiments described above, application of the electric field  250  to the solar panels  10  can increase the current and power output of the solar panels  10  when subsequently connected to the inverter  31  by a predetermined amount (e.g., dependent upon the intensity of light incident on solar panels  10 , the voltage applied V APP  to the solar panels  10  by the voltage source  50 , the thickness of the solar panels  10 , the pulse width Dp, and the frequency f that the voltage pulse  71  is applied to the solar panels  10 , and so on). Similarly, under high intensity light conditions, the improvement in power output of the solar panels  10  can be on the order of 20%; and under low light conditions can be 50+%. 
         [0064]    The improvement in the performance of the photovoltaic device  200  cooperating with the electric field  250  can be measured as an increase in the short circuit current of the solar cell, I sc , as shown in Equation 5: 
         [0000]        I   sc   =I   Base [1+ c ( V (τ, f ), t ,∈)*( p   max   −p )]  (Equation 5)
 
         [0065]    where I Base  is the short circuit current when no external electric field  250  is applied and p max  is the maximum optical power whereby any additional power does not create any additional electron-hole pairs. As the improvement in the current output of the solar cell is driven by the electric field  250 , the form of c(V(τ, f),t,∈) can be described by Equation 6: 
         [0000]        c ( V (τ, f ), t ,∈)= m ( t ,∈) V   App *(1−exp)τ/τ 0 ))*exp(− f   decay   /f )  (Equation 6)
 
         [0066]    In Equation 6, m(t, ∈) is dependent on the photovoltaic device  200 . The improvement in the short circuit current I sc  due to the electric field  250  can be linear with respect to the applied voltage V App . The improvement observed with respect to the pulse repetition rate has a characteristic decay rate of (1/f decay ) and to behave exponentially with respect to the pulse rate f. The improvement observed with respect to the pulse width τ can also behave exponentially and describe how quickly the applied voltage V App , reaches full magnitude. The improvement observed with respect to the pulse width τ is dependent upon the details of the voltage pulser  60 . The increase in the short circuit current I sc , as a function of applied voltage V App , the pulse repetition rate f, and the pulse width τ, are shown in  FIGS. 11A-C , respectively. 
         [0067]      FIG. 11A  shows the expected improvement in the short circuit current I sc , for the solar panel  10  (shown in  FIG. 2 ) as a function of the magnitude of the applied voltage pulse V APP . As shown, the pulse width and the pulse repetition rate are fixed and the magnitude of the pulse voltage is varied from 50 to 250 volts. The improvement in the short circuit current ΔI SC  increases from nominally 0.1 to 2 Amps. The change in the short circuit current ΔI SC  as a function of the applied voltage pulse V APP  is, to first order, approximately linear.  FIG. 11B  shows the change in the improvement of the short circuit current ΔI SC  as a function of the pulse repetition rate for a fixed pulse width and a fixed voltage pulse. As shown in  FIG. 11B , the improvement in the short circuit current ΔI SC  decreases from approximately 1.7 amps to about 0.45 amps as the pulse repetition rate increases from 10 to 100 in arbitrary time units. This behavior is approximately exponential.  FIG. 11C  shows the change in the improvement of the short circuit current ΔI SC  as a function of the pulse width for a fixed pulse repetition rate and a fixed voltage pulse. For this example, the improvement of the short circuit current, ΔI SC  increases from 0 to 1.2 amperes as the pulse width increases from 0 to 2000 over time. 
         [0068]    In each of the described embodiments, increasing the strength of the electric field  250  across the electrodes  101   a ,  101   b  of the solar cell  100  or solar panel  10  increases the efficiency of the solar cell  100  or panel  10 , for example, up to a maximum electric field strength of E max . Stated another way, once the strength of the electric field  250  reaches a maximum strength, the electron-hole recombination rate has been minimized. Accordingly, it can be advantageous to configure the control circuit of the photovoltaic device  200  to maximize the output current and voltage under varying operating conditions. 
         [0069]    For example, turning to  FIG. 9A , a current sensor  33  and a voltage probe  32  are shown coupled to the solar cell management system  300  of  FIG. 4 . As illustrated, the current sensor  33  is coupled in series between the solar panel  10  and the inverter  31 . The current sensor  33  can monitor the current output of the solar panel  10 . Similarly, the voltage probe  32  is connected across the solar panels  10  and the inverter  31  to monitor the output voltage of the solar panel  10 . 
         [0070]    A control circuit  35  is coupled to both of the current sensor  33  via control leads  33   a  and the voltage probe  32  via control leads  32   a . The current sensor  33  can be an inline or inductive measuring unit and measures the current output of the solar panels  10 . Similarly, the voltage sensor  32  is used to measure the voltage output of the solar panels  10 . The product of the current measured from the current sensor  33  and the voltage measured from the voltage probe  32  is the power output from the solar panels  10  to the inverter  31 . 
         [0071]    In some embodiments, the voltage probe  32  may also serve as a power source for the control circuit  35  and is active only as long as the solar panels  10  are illuminated and provide sufficient power to activate control circuit  35 . The control circuit  35  further is coupled to the switch  55  to determine switching times and frequency discussed with reference to  FIG. 4 . The duration of the switching times and the frequency can be controlled to apply the voltage V App  across the solar panels  10  such that both the current generated within the solar cell  100  and measured by the current sensor  33  and voltage probe  32  are maximized under various operating conditions, such as under differing or variable lighting conditions. 
         [0072]    In one embodiment for applying the electric field  250 , the solar panel  10  initially does not generate power, for example, during the night or heavy cloud coverage. As the solar panels  10  are illuminated (for example, during the morning), voltage and current are generated by the solar panels  10 , and the leads  32   a  begin to deliver both current and voltage to the control circuit  35 . The control circuit  35  contains a low voltage logic power supply (not shown) to drive control logic within the control circuit  35 . The control circuit  35  also includes the power source  50  for providing a high voltage power supply. The voltage source  50  has a variable output which can be adjusted by the control circuit  35  and is responsible for placing V App  on a lead  38 . The high voltage output V App  from the control circuit  35  drives the lead  38  and is connected to the switch  55 . The lead  38  is used to apply voltage V App  through the switch  55  to the solar panels  10 . In this example, the control circuit  35  is configured not to apply any voltage V App  to the solar panels  10  until enough power is generated by the solar panels  10  to activate both the low voltage logic power supply and the high voltage power supply. 
         [0073]    In an alternative embodiment, the control circuit  35  can be configured to apply the electric field  250  and maximize the power output as the illumination in the day increases and decreases. The control circuit  35  can provide the electric field  250  and stabilize the power output of the solar panels  10  according to any method described above, including process  9000  shown in  FIG. 9B . 
         [0074]    Turning to  FIG. 9B , the process  9000  includes initializing power, at step  900 . Enough power must be present from the output of the solar panels  10  to activate both the low voltage logic power supply, which operates the control logic in control circuit  35 , and the high voltage power supply necessary to place a high voltage on the lead  38  and through the switch  55 . Alternatively, the control circuit  35  can be powered from an external source (not shown)—for example, a battery, a large capacitor, an external AC power supply—which allows the low voltage logic power supply to operate and the control circuit  35  to monitor the power output of the solar panels  10  until the solar panels  10  generate enough power output to warrant applying the electric field  250  on the solar panels  10  to augment their power output. Since the control circuit  35  is starting up, all of the parameters (e.g., the applied high voltage V App , the switch duration time D, and the switching frequency f) are initialized. In one embodiment, the applied high voltage V App  is set to zero while the switching duration D and the switching frequency f are set to nominal values of D=τ 0  and f=f 0 . All of the control indices, n, i, and j are initialized to zero. 
         [0075]    The control circuit  35  then determines, at step  901 , whether the voltage as measured on the voltage probe  32  is above or below a predetermined minimum v min  and whether the current as measured on the current sensor  33  is above a predetermined minimum, i min . The combination of v min  and i min  have been chosen such that the solar panels  10  are determined to be illuminated and generating some nominal percentage, for example, 5%, of their average rated power and that there is enough power being generated to supply the power source  50  within the control circuit  35  to augment the output of the solar panels  10 . If the control circuit  35  determines that both the measured current and voltage are above the respective predetermined minimums, the control circuit  35  is now operational and process  9000  moves to step  903 ; otherwise, the process  9000  goes into a wait state, at step  902 , and returns to step  900 . 
         [0076]    In step  903 , the control circuit  35  measures the current flowing into the inverter  31  via the current sensor  33 , the voltage across the inverter  31  via the voltage sensor  32 , and calculates the power (nominally, current×voltage) flowing through the inverter  31 . A control index n is incremented to n+1. 
         [0077]    In step  904 , the control circuit  35  compares V App  with V max . V max  can be a preset value and represents the maximum voltage that can be placed on the solar panels  10  without damaging either the solar panels  10  or the inverter  31 . Depending upon the type of the solar panel  10 , V max  is typically between 600 V and 1,000 V. If V App  is less than V max , then process  9000  proceeds to step  906 ; otherwise, process  9000  waits in step  905 . 
         [0078]    In step  906 , the control circuit  35  increments the applied high voltage V App  by an amount nΔV, and activates the switch  55 . Activating the switch  55  disconnects the solar panels  10  from the inverter  31  and connects the solar panels  10  to V App  from the control circuit  35  on leads  38 . For this example, ΔV can be a fixed voltage step of 25 Volts although larger or smaller voltage steps can be used. The voltage V App  imposes the electric field  250  on the solar panels  10  such that the strength of the electric field  250  is proportional to the applied voltage V App . The duration of the connection of the solar panels  10  to V App  within the control circuit  35  is chosen to not interrupt operation of the inverter  31 . For this example, the duty cycle is chosen to be 5% (the solar panels  10  are connected 5% of the time to V App  within the control circuit  35 ) and the default duration of the switching time is chosen to be nominally 1000 ns. Alternative switching times can be used as desired. The control circuit  35  again receives the measurement of the current flowing into the inverter  31  via the current sensor  33 , receives the measurement of the voltage across the inverter  31  via the voltage sensor  32 , and recalculates the power flowing through the inverter  31 . 
         [0079]    In step  908 , the control circuit  35  compares the power output of the solar panels  10  before V App  was placed on the solar panel  10  to the most recent measurement. If the power has increased, the process  9000  returns to step  901  and is repeated. The voltage applied on the lead  38  is increased by ΔV until either the applied high voltage V App  is greater than V max  or until the increase in the applied high voltage V App  does not yield an increase in output power of the solar panels  10 . V max  is defined here as the maximum voltage that can be placed on a solar panel without causing it any damage. Depending upon the type of the solar panel  10 , V max  is typically approximately 600 to 1,000 V. In both cases, process  9000  waits in step  905 . The duration of the wait state could be from seconds to minutes. 
         [0080]    After the wait step  905 , process  9000  continues to step  907 . If the power, as measured through the leads  32   a  and  33   a , has not changed, the index n is decremented (n=n−1), the applied voltage V App  on the leads  38  to the solar panel(s)  10  is decreased by the amount ΔV, and the control circuit  35  activates the switch  55 . Process  9000  continues in step  909  where the power output is measured by the current sensor  33  and voltage probe  32 . If the power output shows a drop, process  9000  continues to step  910 . If the power output has increased, the process  9000  returns to step  907  and the applied voltage V App  continues to decrement until the power output of the solar panels  10  ceases to diminish. The process  9000  proceeds to step  910 . 
         [0081]    In step  910 , the control circuit  35  increases the duration that the switch  55  is connected to the solar panels  10  on the lead  38  in the first position discussed above. The amount of time that the switch  55  is connected to the voltage source  50  is increased by an amount iΔτ 0 . The switch  55  is activated and the power output of the solar panels  10  is again monitored by the current sensor  33  and the voltage probe  34 . The process  9000  proceeds to state  912  to determine whether the power output of the solar panels  10  increases. If so, process  9000  moves to step  910  and the duration that the solar panels  10  are connected to the voltage source  50  is increased again. The switching duration will increase until the output power of the solar panels  10  reaches a maximum (or until a fixed duration limit—for example, 3-5 μseconds is reached)—at which point the switch duration changes driven by the control circuit  35  stops. However, if at step  912 , the control circuit  35  determines that increasing the switch duration D causes a decrease in the power output as measured by the current sensor  33  and the voltage probe  32 , process  9000  continues to step  911  and the switch duration D is decreased by iterating between steps  911  and  913  until the power output of the solar panels  10  is maximized again. After the control circuit  35  has determined that the switching duration has been optimized for maximum output power of solar panels  10  by repeating step  910  to step  913 , process  9000  continues to step  914 . 
         [0082]    In step  914 , the control circuit  35  begins to increase the frequency of connection f at which the switch  55  is connected to the control circuit  35 . The frequency f that the switch  55  is connected to the voltage source  50  is increased by jΔf from the original switching frequency f 0  such that f=/f 0 +jΔf. In step  914 , the switch  55  is connected between the lead  38  and the solar panels  10  at a new frequency, f, and the power output of the solar panels  10  is again monitored by the current sensor  33  and the voltage probe  34 . The process  9000  continues to step  916 . If the power output of the solar panels  10  has increased, the process  9000  moves back to step  914  and the rate at which the solar panels  10  are connected to the voltage source  50  is increased again. The rate of connection will increase until the output power of the solar panels  10  reaches a maximum or until a maximum frequency f max , at which point the process  9000  moves to step  915 . In step  914 , the frequency the switch  55  connects to the high voltage  50  on the lead  38  is now decremented by an amount jΔf and the switch  55  is activated again and the power output of the solar panels  10  is again monitored by the current sensor  33  and the voltage probe  32 . At that point, the control circuit  35  decides whether the decrease in the rate of connection increases the power output of solar panels  10  in step  917 . If so, the process  9000  returns to step  915 . Alternatively, if the frequency of switching reaches some minimum frequency f min , the process  9000  moves to step  918  to wait. 
         [0083]    In step  918 , once the power output of the solar panels  10  has been maximized, the control circuit  35  goes into a wait state for a period of time. The period of wait time can be seconds or minutes. After waiting in step  918 , the process  9000  moves to step  901  where process  9000  again begins to vary the voltage, the switch connection time and the switching rate from the previous optimized values to validate the solar panels  10  are still operating at their maximum output levels. The applied voltage  50  from the control circuit  35 , the switching duration, and the switching rate are all varied over the course of operation during a day to be sure that the solar panels  10  are operating under with maximum output power under the operational conditions of that particular day. 
         [0084]    If at step  901 , the voltage as measured on voltage sensor  32  drops below the predetermined minimum v min , and the current as measured on current sensor  33  drops below a predetermined minimum i min , the control circuit  35  will remove any voltage on lines  38 , and the control circuit  35  will move to step  902  to wait before returning to step  900  (where the system will reinitialize all of the parameters and indices). Process  9000  will alternate from step  900  to  901  to  902  to  900  until both the voltage as measured on the voltage probe  32  and the current as measured on the current sensor  33  are both above v min  and i min  respectively, at which point the process  9000  will move from step  901  to step  903 . 
         [0085]    Different state machines within control circuit  35  can be implemented to yield similar results and are covered by this disclosure. However, the process  9000  described above advantageously minimizes the magnitude of the applied voltage V App  to the lowest value possible such that the product of the current measured by the current probe  33  and the voltage measured by the voltage probe  32  are maximized. The applied voltage V App  is dithered—that is changed by small amounts both up and down—over the course of operation in a day to account for changes the incident optical power, p, on the solar cell  100 , the solar panel  10 , or the plurality of solar panels  10  over the course of a day so that the maximum power output can always be maintained. 
         [0086]    Most of the steps described in process  9000  above were designed to address adiabatic changes in illumination that occur slowly over periods of multiple minutes or hours. In an alternative embodiment, if the illumination variances were to occur at a higher rate of change, the process  9000  can be adapted to minimize the high frequency variations in DC power output to the inverter by attempting to hold the DC output power from varying at too high a rate of change, hence making the quality of the inverter higher. 
         [0087]    In another example, turning to  FIG. 10A , the current sensor  33  and the voltage probe  32  are shown coupled to the solar cell management system  300  of  FIG. 6 . As illustrated, the current sensor  33  is coupled in series between the solar panel  10  and the inverter  31 . The current sensor  33  can monitor the current output of the solar panel  10 . Similarly, the voltage probe  32  is connected across the solar panels  10  and the inverter  31  to monitor the output voltage of the solar panel  10 . 
         [0088]    A control circuit  36  is coupled to both the current sensor  33  via control leads  33   a  and the voltage probe  32  via control leads  32   a . The current sensor  33  can be an inline or inductive measuring unit and measures the current output of the solar panels  10 . Similarly, the voltage sensor  32  is used to measure the voltage output of the solar panels  10 . The product of the current measured from the current sensor  33  and the voltage measured from the voltage probe  32  allow for a calculation of the power output from the solar panels  10  to the inverter  31 . 
         [0089]    In some embodiments, the voltage probe  32  may also serve as a power source for the control circuit  36  and is active only as long as the solar panels  10  are illuminated and provide sufficient power to activate control circuit  36 . The control circuit  36  further is coupled to voltage pulser  60  to control the amplitude of the voltage pulse V App , the pulse duration D P  and the pulse frequency f discussed with reference to  FIG. 6 . The pulse duration Dp, the pulse frequency f and the pulse voltage V App  applied across the solar panels  10  can be controlled and adjusted such that both the current generated within the solar panel  10  and measured by the current sensor  33  and voltage probe  32  are maximized under various operating conditions, such as under differing or variable lighting conditions. 
         [0090]    In one embodiment for applying the electric field  250 , the solar panel  10  initially does not generate power, for example, during the night or heavy cloud coverage. As the solar panels are illuminated (for example, during the morning), voltage and current are generated by the solar panels  10 , and the leads  32   a  begin to deliver both current and voltage to the control circuit  36 . The control circuit  36  contains a low voltage logic power supply (not shown) to drive control logic within the control circuit  36 . The pulser circuit  60  contains both a low voltage and high voltage power supply (not shown). The high voltage power supply in voltage pulser  60  has a variable output which can be adjusted by control circuit  36  and is responsible for placing V App  on solar panels  10 . In this example, the control circuit  36  is configured not to apply any voltage to the solar panels  10  until enough power is being generated by the solar panels  10  to activate both the low voltage logic power supply and the high voltage power supply in pulser  60 . 
         [0091]    In an alternative embodiment, the control circuit  36  is configured to control the electric field  250  and maximize the power output as the illumination in the day increases and decreases. The control circuit  36  can control the electric field  250  applied by voltage pulser  60  and stabilize the power output of the solar panels  10  according to any method described above, including process  10000  shown in  FIG. 10B . 
         [0092]    Turning to  FIG. 10B , the process  10000  includes initializing power, at step  1000 . Enough power must be present from the output of the solar panels  10  to activate both the low voltage logic power supply, which operates the control logic in control circuit  36 , and the low and high voltage power supply in voltage pulser  60 . Alternatively, the control circuit  36  can be powered from an external source (not shown)—for example, a battery, a large capacitor, an external AC power supply—which allows the low voltage logic power supply to operate and the control circuit  36  to monitor the power output of the solar panels  10  until they have enough power output to warrant applying the electric field  250  on the solar panels  10  to augment their power output. Since the control circuit  36  is starting up, all of the parameters (e.g., applied high voltage V App , the pulse duration Dp, and the pulse repetition frequency, f) are initialized. In one embodiment, the applied high voltage V App  is set to zero while the pulse duration D P  and pulse repetition rate f are set to nominal values of D P =τ 0  and f=f 0 . All of the control indices, n, i, and j are initialized to zero. 
         [0093]    The control circuit  36  then determines in step  1001  whether the voltage as measured on the voltage probe  32  is above or below a predetermined minimum v min  and whether the current as measured on the current sensor  33  is above a predetermined minimum, i min . The combination of v min  and i min  have been chosen such that the solar panels  10  are determined to be illuminated and generating some nominal percentage, for example, 5%, of their average rated power and that there is enough power being generated to supply the high voltage power supply to augment the output of the solar panels  10 . If the control circuit  36  determines that both the measured current and voltage are above the respective predetermined minimums, then process  10000  is now operational and moves to step  1003 ; if not, process  10000  goes into a wait state  1002  and returns to step  1000 . 
         [0094]    In step  1003 , the control circuit  36  measures the current flowing into the inverter  31  via the current sensor  33 , the voltage across the inverter  31  via the voltage sensor  32 , and calculates the power flowing through the inverter  31  (nominally, I×V). A control index n is incremented to n+1. 
         [0095]    In step  1004 , process  10000  compares V App  with V max . V max  is a preset value and represents the maximum voltage that can be placed on the panels without damaging either the panels  10  or the inverter  31 . If V App  is less than V max , then process  10000  proceeds to step  1006 ; otherwise, process  10000  waits in step  1005 . 
         [0096]    In step  1006 , the control circuit  36  signals the voltage pulser  60  to increment the applied high voltage V App  by an amount nΔV, and signals the voltage pulser  60  to apply the voltage pulse to the solar panels  10 . For this example, ΔV can be a fixed voltage step of 25 Volts, although larger or smaller voltage steps can be used. The voltage V App  imposes the electric field  250  on the solar panels  10  and the strength of the electric field  250  is proportional to the applied voltage V App . For this example, the pulse width D P  is chosen to be 1000 ns and the pulse repetition rate is chosen to be 20 μseconds. Other pulse widths and pulse repetition rates could also be chosen. The control circuit  36  again receives the measurement of the current flowing into the inverter  31  via the current sensor  33 , receives the measurement of the voltage across the inverter  31  via the voltage sensor  32 , and recalculates the power flowing through the inverter  31 . 
         [0097]    In step  1008 , the control circuit  36  compares the power output of the solar panels  10  before V App  was placed on the solar panel  10  to the most recent measurement. If the power has increased, process  10000  returns to step  1001  and is repeated. The applied voltage V App  is increased by ΔV until either the applied high voltage V App  is greater than V max  or until the increase in the applied high voltage V App  does not yield an increase in output power of the solar panels  10 . Again, V max  is defined here as the maximum voltage that can be placed on a solar panel  10  without causing it any damage and depending upon solar panel type, it would typically be approximately 600 to 1,000 V. In both cases, process  10000  waits in step  1005 . The duration of the wait state could be from seconds to minutes. 
         [0098]    After the wait step  1005 , process  10000  enters step  1007 . If the power, as measured through the leads  32   a  and  33   a , has not changed, index n is decremented (n=n−1), the applied voltage pulse V App  is decreased by the amount ΔV, and the control circuit  36  activates the pulser  60 . Process  10000  continues in step  1009  where the power output as measured by the current sensor  33  and voltage probe  32 . If the power output shows a drop, process  10000  continues to step  1010 . If the power output has increased, process  10000  returns to step  1007  and the applied voltage V App  continues to decrement until the power output of the solar panels  10  ceases to diminish. The process  10000  proceeds to step  1010 . 
         [0099]    In step  1010 , the control circuit  36  begins to increase the duration D P  of the voltage pulse. The voltage pulse duration D P  is increased by an amount iΔτ 0 . The voltage pulser  60  is activated and the power output of the solar panels  10  is again monitored by the current sensor  33  and the voltage probe  34 . The process  10000  proceeds to state  1012  to determine whether the power output of the solar panels  10  increases. If so, process  10000  moves to step  1010  and the duration D P  of the voltage pulse  71  is increased again. The pulse duration D P  will increase until the output power of the solar panels  10  reaches a maximum or until a fixed duration limit—for example, a pulse duration of 5 μseconds is reached—at which point the pulse width changes driven by the control circuit  36  stops. However, if at step  1012 , it is found that the increasing the pulse width causes a decrease in the power output as measured by the current sensor  33  and the voltage probe  32 , process  10000  continues to step  1011 . The pulse width is decreased by iterating between steps  1011  and  1013  until the power output of the solar panels  10  is maximized again. After the control circuit  36  has determined that the pulse duration has been optimized for maximum output power of solar panels  10  by going through step  1010  to step  1013 , the process continues to step  1014 . 
         [0100]    In step  1014 , the control circuit  36  increases the frequency of the voltage pulses. The frequency of the voltage pulses is increased by jΔf from the original switching frequency f 0  such that f=/f 0 +jΔf. In step  1014 , voltage pulses are applied by the voltage pulser  60  to the solar panels  10  at a new frequency f, and the power output of the solar panels  10  is again monitored by the current sensor  33  and the voltage probe  34 . The process  10000  then moves to step  1016 . 
         [0101]    If the power output of the solar panels  10  has increased, the process  10000  moves back to step  1014  and the rate at which voltage pulses are applied to the solar panels  10  is increased again. The increase in the rate of voltage pulses will increase until the output power of the solar panels  10  reaches a maximum or until a maximum frequency f max , at which point the process  10000  moves to step  1015 . In step  1014 , the frequency of the voltage pulses is now decremented by an amount jΔf and the voltage pulser  60  switch is activated again and the power output of the solar panels  10  is again monitored by the current sensor  33  and the voltage probe  32 . At that point, the control circuit  36  determines whether the decrease in the rate of voltage pulses increases the power output of solar panels  10  in step  1017 . If so, the process  10000  returns to step  1015 . Alternatively, if the frequency of switching reaches some minimum frequency f min , the process  10000  moves to step  1018 , which is a wait state. 
         [0102]    In step  1018 , once the power output of the solar panels  10  has been maximized, process  10000  goes into a wait state for a period of time. The period of wait time can be seconds or minutes. After waiting in step  1018 , the process  10000  moves to step  1001  where the control circuit  36  again begins to vary the pulse voltage, the pulse duration, and the pulse repetition rate from the previous optimized values to validate the solar panels  10  are still operating at their maximum output levels. The pulse amplitude V App , the pulse duration, and the pulse repetition rate are all varied over the course of operation during a day to be sure that the solar panels  10  are operating under with maximum output power under the operational conditions of that particular day. 
         [0103]    If at step  1001 , the voltage as measured on the voltage sensor  32  drops below the predetermined minimum v min , and the current as measured on current sensor  33  drops below a predetermined minimum i min , the control circuit  36  will stop the voltage pulser  60  and the process  10000  will move to step  1002  wait state and then to step  1000  where the system will reinitialize all of the parameters and indices. The process  10000  will move from step  1000  to  1001  to  1002  to  1000  until both the voltage as measured on the voltage probe  32  and the current as measured on the current sensor  33  are both above v min  and i min  respectively, at which point process  10000  will move from step  1001  to step  1003 . 
         [0104]    Different state machines within the control circuit  36  can be implemented to yield similar results and are covered by this disclosure. However, the process  10000  described above advantageously minimizes the magnitude of the applied voltage pulse V App  to the lowest value possible such that the product of the current measured by the current probe  33  and the voltage measured by the voltage probe  32  are maximized. The applied voltage pulse V App  is dithered—that is changed by small amounts both up and down—over the course of operation in a day to account for changes the incident optical power, p, on the solar cell  100 , the solar panel  10 , or the plurality of solar panels  10  over the course of a day so that the maximum power output can always be maintained. 
         [0105]    The steps described in process  10000  can address adiabatic changes in illumination that occur slowly over periods of multiple minutes or hours. In an alternative embodiment, if the illumination variances were to occur at a higher rate of change, the process  10000  can be adapted to minimize the high frequency variations in DC power output to the inverter by attempting to hold the DC output power from varying at too high a rate of change, hence making the quality of the inverter higher. 
         [0106]    The described embodiments are susceptible to various modifications and alternative forms, and specific examples thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the described embodiments are not to be limited to the particular forms or methods disclosed, but to the contrary, the present disclosure is to cover all modifications, equivalents, and alternatives.