Dye-sensitized solar cells are more flexible, easier to manufacture, and cheaper than existing solar technologies. Current lab prototypes are about half as efficient as the silicon-based cells used in rooftop panels and calculators. By using a popcorn-ball design - tiny kernels clumped into much larger porous spheres - researchers at the University of Washington are able to manipulate light and more than double the
efficiency of converting solar energy to electricity.
One quandary in making an efficient solar cell is the size of the grains. Smaller grains have bigger surface area per volume, and thus absorb more rays. But bigger clumps - closer to the wavelength of visible light - cause light to ricochet within the thin light-absorbing surface, so it has a higher chance of being absorbed. The UW group made tiny grains about 15 nanometers across, and then clumped these into larger masses about 300 nanometers across.
The overall efficiency using only small particles was 2.4 percent, but with the popcorn-ball design, results show an efficiency of 6.2 percent. The experiments were performed using zinc oxide, and the researchers are working on transferring this concept to titanium oxide. Titanium oxide based dye-sensitized solar cells are now at 11 percent maximum efficiency. The UW researchers hope their popcorn-ball strategy could push dye-sensitized solar cells' efficiency significantly over that threshold.
