Caltech creates solar cells using silicon wires

February 19, 2010

Caltech creates solar cells using silicon wires Flexible solar cells are not new but Caltech has a new method that results in high efficiency, high quality solar arrays.  The key feature of these solar cells are silicon wires that are encased in a thin transparent polymer that will make mass manufacturing these solar arrays inexpensive.

Harry Atwater, Howard Hughes Professor, professor of applied physics and materials science, and director of Caltech‘s Resnick Institute, Nathan Lewis, the George L. Argyros Professor and professor of chemistry at Caltech, and graduate student Michael Kelzenberg (creator of the above illustration), are responsible for creating these solar cells.

Each individual silicon wire within these solar arrays is actually a solar cell that absorbs light extremely well.  By combining the silicon wires into an array, it increases the amount of light that each wire absorbs.  Atwater puts it this way:

Light comes into each wire, and a portion is absorbed and another portion scatters. The collective scattering interactions between the wires make the array very absorbing

This doesn’t mean that the wires are crammed into the arrays.  In fact, the arrays only have between two to ten percent of the surface that are silicon wires. 

By developing light-trapping techniques for relatively sparse wire arrays, not only did we achieve suitable absorption, we also demonstrated effective optical concentration—an exciting prospect for further enhancing the efficiency of silicon-wire-array solar cells.

CalTech solar array - Michael Kelzenberg

Another necessary aspect of efficient solar arrays is the ability to convert the sunlight absorbed into electricity.  These solar arrays are able to convert 90 to 100 percent of the absorbed light into electricity.  Other solar cells have efficiencies between 12 and 42 percent.

The wires are between 30 and 100 microns in length and one micron in diameter.  The length of the wires determines the thickness of the solar array.  The volume of the array is composed of two percent silicon and ninety-eight percent polymer.

Being able to limit the amount of silicon to only two percent of the solar array greatly cuts down on the cost.   Along with a lower cost the solar arrays are very flexible because of the polymer used which means that the solar arrays can be manufactured in rolls, which is a much less costly manufacturing system. Further research will be conducted “to increase the operating voltage and the overall size of the solar cell”. 

Although this solar cell technology is not ready for production at this point, this is the type of technology that could make solar energy affordable and accessible to everyone.

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