SOLAR CELLS CAN BE MORE EFFICIENT

Simulating more efficient solar cells

Using an exotic form of silicon could substantially improve the efficiency of solar cells.

Solar cells are based on the photoelectric effect: a photon, or particle of light, hits a silicon crystal and generates a negatively charged electron and a positively charged hole. Collecting those electron-hole pairs generates electric current.

Conventional solar cells generate one electron-hole pair per incoming photon, and have a theoretical maximum efficiency of 33 percent. One exciting new route to improved efficiency is to generate more than one electron-hole pair per photon.

This approach is capable of increasing the maximum efficiency to 42 percent, beyond any solar cell available today, which would be a pretty big deal.

There is reason to believe that if parabolic mirrors are used to focus the sunlight on such a new-paradigm solar cell, its efficiency could reach as high as 70 percent.

In particular, the probability of generating more than one electron-hole pair is much enhanced, driven by an effect called "quantum confinement.”

But with nanoparticles of conventional silicon, the paradigm works only in ultraviolet light, this new approach will become useful only when it is demonstrated to work in visible sunlight.