Get three services for $100/moA new record in solar cells
The University of Delaware has inched up the record for solar cell efficiency with a new device that can convert 42.8 percent of the light that strikes it into electricity.
That beats the old record of 40.7 percent hit in December. The Defense Advanced Research Projects Agency, or DARPA, has been funding research to get efficiency up to 50 percent.
The cell, created by Christina Honsberg and Allan Barnett of UD, splits incoming light into three buckets: high energy, low energy, and medium energy light. The light is then directed to different materials, which then extract electrons out of the photons that make up sunlight.
The device also has an optical concentrator, sort of like a lens that directs more sunlight to the solar cell than would occur naturally and thereby increasing efficiency.
Various materials (silicon, germanium, etc.) react differently to different parts of the solar spectrum. Crystalline solar cells, for instance, can currently convert 22 percent of light into electricity (without concentrators). The theoretical maximum is 29 percent sans concentration. Combining different materials into multi-junction cells or adding concentrators helps get around the limitations of the materials.
Multi-junction solar cells and concentrators, however, are expensive. The initial customers for devices like this will be the military. Possible applications include portable charging packs for soldiers.
Concentrators can often add girth to solar cells, but the UD device is a little less than a centimeter thick.
Unfortunately the key thing is not so much in reaching this new, higher level of efficiency, but rather taking the knowledge learned from such a design and applying it in a useful and economical package for widespread production. Right now the very best (and most expensive) solar cells are only about 22% efficient, and most are more like 15-18%. Given that the amount of solar energy hitting a given chunk of the earth is fixed, the only way to increase the energy out of the system is to up the efficiency.
It's all about the money...
You don't extract the electrons out of the photons, it's impossible to do so. Photons are elementary particles just like electrons, but have zero mass. You use the energy of the photons to extract electrons out of the semiconductors they use. By bombarding the material with photons, you increase the energy level of the electrons and thus make them break out of their bond with the atom.