Nanotech provides a way to tailor the optical and electronic properties of materials through engineering their nanostructures. Nanotechnology researchers have demonstrated that quantum dots of different sizes will absorb light of different wavelengths, and that an architecture using nanotubes transports electrons better than one using nanospheres, thus making more efficient solar cells possible. In “Catching a rainbow – quantum dot nanotechnology brightens the prospects for solar energy” Michael Berger describes a recent advance:
Quantum dots have been identified as important light harvesting material for building highly efficient solar cells. Quantum dots are nanoscale semiconductor structures which, when exposed to light at certain wavelengths, can generate free electrons and create an electrical current. Quantum dot technology represents an exciting field of research in solar energy yet the actual research results to use them in solar cells are relatively limited.
By combining spectroscopic and photoelectrochemical techniques, researchers now have demonstrated size-dependent charge injection from different-sized cadmium selenide (CdSe) quantum dots into titanium dioxide nanoparticles and nanotubes, showing a way to maximize the light absorption of quantum dot-based solar cells. Termed ‘rainbow solar cells’, these next-generation solar cells consist of different size quantum dots assembled in an orderly fashion. Just as a rainbow displays multiple colors of the visible light spectrum, the ‘rainbow solar cell’ has the potential to simultaneously absorb multiple wavelengths of light and convert it to electricity in a very efficient manner.