Photovoltaic cell efficiency may soon get a big boost, thanks to next-generation antireflection coatings crafted from nanomaterials capable of cutting down on the amount of light reflected away from a cell's surface.

Materials boasting a "tunable" refractive index have been developed within the past few years, and they show tremendous potential for photovoltaic applications. Professor E. Fred Schubert, of Rensselaer Polytechnic Institute's Department of Electrical, Computer, and Systems Engineering, is investigating ways to exploit this newly gained controllability and will present his findings at the upcoming AVS 59th International Symposium and Exhibition, held Oct. 28 - Nov. 2, in Tampa, Fla.

The refractive index is the property of a material that changes the speed of light, and is computed as the ratio of the speed of light in a vacuum to the speed of light through the material. Among the most fundamental properties of optical materials, the refractive index determines important optical characteristics such as Fresnel reflection, Bragg reflection, Snell refraction, diffraction, and the phase and group velocity of light.

Air and other gases have a refractive index very close to 1.0, but unfortunately aren't viable for thin-film optoelectronic applications. Among transparent dense materials suitable for use in thin-film optoelectronic applications, magnesium fluoride (MgF2) has the lowest refractive index (n=1.39); no dense materials with a lower refractive index are known to exist.