Solar Cells

Our Approach

A SUPER cell™ is an integrated circuit containing millions of nano-scale Surface Plasmon Polariton (SPP) vacuum tube resonator-diodes, called plasmonotrons. The plasmonotrons are driven into standing-wave oscillations by sunlight and have a nano-scale cathode, anode and gap. Electrons are extractable from SPPs because multiple stages of electric field enhancements, such as concentrating the sunlight using a concentrator lens, ultimately provide an electric field strength sufficient to generate efficient ballistic electron generation via SPP self-induced field-emission and via quantum tunneling between the cathode and anode on every half-cycle of SPP oscillation, when the E-field assists tunneling. This provides usable electricity.

In contrast to current semi-conductor photovoltaic cells, we create quantized SPP excitations in a metal-dielectric matrix, instead of electron-hole pairs in a semi-conductor. The SPP are hybrid quasi particles that have properties between a photon and an electron. This hybrid character provides a novel mechanism to transition from sunlight to electrons, especially when utilizing an indirect rectification technique. Moreover, the intrinsic asymmetry in the plasmonotron is due to: first, only using negatively charged electrons as electrical energy carriers; second, optics and a nano-scale plasmonotron resonator geometry that enhances the electric field strength by many orders of magnitude asymmetrically at the cathode so that a plasmonotron is capable of ripping the electrons out of an SPP excitation by quantum tunneling thus generating ballistic electrons that travel to the anode of the plasmonotron. Both the liberated electron and the extremely large electric-field doing the liberating come from the SPP when the proper nano-scale geometry is present.

The images below show the basic idea schematically. Obviously, there is a lot more to the technology than is being discussed here. There is a rich physical theory, a number of variations on the theme suggested, and a lot of nano-scale fabrication issues. This idea is currently at the initial stages of research and development at XE and we are putting the idea out into the public domain to stimulate discussion and interaction with interested high-tech industrial and academic partners in order to more quickly make progress on the technology. We are doing this because our perspective is that the world is too close to a significant energy crisis and an "all-hands-on-deck" effort is required to have solutions become available as soon as possible.

 

FIG 4.2 A Surface Plasmon Polariton (SPP) is shown schematically here as an evanescent electromagnetic wave that is tightly bound to an oscillating electron charge density wave that is propagating along the surface of the metal-dielectric interface. The metal is the blue material and the dielectric is white. The resulting system may be considered to be composed of SPP quasi-particles that exhibit both particle and wave properties and have quantized energy states. The SPP is therefore a hybrid between light and electricity and makes certain new types of solar cells possible. It should be noted that exciting the the SPP requires different conditions for different physical structures. The planar geometry above has serious restrictions on the incident photon energy, the angle of incidence, and the polarization of the exciting electromagnetic wave. These restrictions are significantly reduced in the geometry of the next figure.

 

 

FIG 4.3 SUPER CellTM Geometry. A section of a SUPER Cell™ is shown here. It comprises an array of nano-scale cavity resonator-diodes (plasmonotrons) that also incorporate field enhancing anodes and cathodes. There are many variations on the above theme. For example, the cavities could be cylindrical instead of spherical, the exact shape and position of the anode and cathode can be chosen to optimize the interaction with the cavity modes, and the materials are not limited to Homogeneous, Isotropic, and Linear (HIL) materials like silver, aluminum, or simple glasses. Additionally, the structure is chosen to actually enhance the excitation of SPPs on the cavity walls of the plasmonotrons from all angles and polarizations. It is actually more efficient to excite SPPs in this structure than in the planar structure of Fig. 4.2.

 

 

FIG 4.4 A

FIG 4.4 B

FIG 4.4 C

FIG 4.4. The Plasmonotron. Artistic interpretation of electricity generation using plasmonotron arrays. (A) highly concentrated sunlight from an optical lens systems is focused onto the SUPER cell™ (plasmonotron array) and couples into the cavities as SPP standing waves on the wall of each vacuum tube resonator-diode plamonotron. This is indicated by the high and low concentrations of electrons---red and blue respectively. The geometry on the SUPER cell™ is carefully chose to allow full absorption of sunlight over a wide range of sunlight incident angles and polarizations. (B) when the intensity of the SPP electric fields is high enough on each half oscillation of the SPP then the probability of quantum tunneling asymmetrically across the “spark” gap, from the cathode to the anode, is high. (4) The electrons are moved out of the plasmonotron and into an external circuit to do useful work. The cycle then repeats---so go to (A) etc... Only simple and relatively abundant metals and dielectrics need be used to make this device.

 

FIG 4.5 The Potential Barrier. A simple to understand model of the energy level diagram of the metal that is supporting SPP excitations is shown. The indirect rectification of light is qualitatively seen to be an oscillating potential barrier (blue) which acts as a gate for the generation of ballistic electron generation. When the gate is open then the probability of electrons passing through the barrier is maximized. The energy barrier is the gap between anode and cathode, and it changes on every half cycle of SPP excitations.