Solar cell efficiency is set to greatly increase in the next few years thanks to newly created next-gen antireflection coatings. The new nanomaterial coatings will help to limit the amount of light that is reflected away by the surfaces of solar cells.
In the past few years, materials with a ‘tunable’ refractive index have been developed, and are showing a lot of potential for use in photovoltaics. New research led by Professor E. Fred Schubert, of Rensselaer Polytechnic Institute’s Department of Electrical, Computer, and Systems Engineering, has been exploring possible uses for this in the solar power field.
“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,” a press release on the new research notes. “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.”
Most gases, including air, possess a refractive index that is very near 1.0, but obviously their potential use in thin-film optoelectronic applications would be extremely limited. “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.”
The range between 1.0 and 1.39 had remained more or less unexplored until the recent advent of tunable-refractive-index materials.
“Optical thin-film materials with a refractive index as low as 1.05 have been demonstrated. Tunable-refractive-index materials are based on ‘nanoporous’ silicon dioxide (SiO2), indium-tin oxide (ITO), and titanium dioxide (TiO2), and we can precisely control porosity by using oblique-angle deposition — a technique in which the substrate is at non-normal angle of incidence with respect to the deposition source,” says Schubert.
The researchers used those materials to create a four-layer antireflection coating. “The fabrication process of this coating is additive and purely physical, so it’s fully compatible with current manufacturing processes of solar cells,” he notes. “Our customizable approach readily lends itself to the incorporation of antireflection coating design into solar cell device structures for application-specific requirements.”
The new coating is readily applicable, viable, and is a huge plus to the development of next-gen antireflection solar panel coating technologies.
Source: AVS: Science & Technology of Materials, Interfaces, and Processing
Image Credits: University of Houston