Assembly and characterization of colloid-based antireflective coatings on multicrystalline silicon solar cells

Evaporation from a moving meniscus was used for controlled convective assembly of colloidal silica nanoparticles into antireflective coatings (ARCs) onto the rough uneven surfaces of polycrystalline silicon solar cells. The nanocoatings reduced the reflectance of the solar cells by approximately 10% across the near UV to near IR spectral range, which provided a 17% increase in the output power of the devices (which translated to a 10% relative increase in the efficiency). Microstructural analysis via SEM showed that while the surface coverage was uniform over long ranges, the thickness of the particle coatings varied locally due to the rough, undulating substrate surface. The UV/vis reflectance data of the silica coated solar cells could be modelled with the Fresnel reflectance relation by assuming a distributed range of thicknesses for the coatings, in good agreement with the microstructural data. We show that particulate films deposited on rough surfaces can function as ARCs even though they do not attain 0% reflectance. These silica particle-based coatings can be further modified by attachment of monolayers of fluorosilanes, which may make them superhydrophobic and/or self-cleaning.