Of the many ways to improve the efficiency of solar power, increasing the amount of light that hits the photoelectric material is likely the most obvious, but is not the easiest to achieve. This is in part because the refractive index of the coating on top of the panel affects how much light is reflected away, and that is limited by Nature. However researchers at Rensselaer Polytechnic Institute are working to change that, as reported by the American Institute of Physics.
The lowest naturally occurring refractive index for a solid is 1.39, and nothing between that and 1, the refractive index of air and other gases, has been discovered. However, materials with tunable refractive indexes have been developed recently, and the researchers are investigating how those may work as an antireflective coating for solar panels. These materials are actually thin-films with special structures that enable them to reach as low as 1.05 for their refractive index. With such a low value it will be possible to minimize multiple kinds of optical phenomena including Fresnel reflection, Bragg reflection, diffraction and more.
Perhaps most importantly though, the addition of an anti-reflective coating, like what the researchers are investigating, is not going to disrupt the regular production of solar cells. A purely additive process is used which deposits the material onto the panel, and can be done without affecting the cell itself.