Colloidal Dispersions of Core-Shell Nanoparticles as Precursors to Porous Thin Film Coatings in PV Applications

The use of hollow nanoparticles has recently gained considerable attention with applications in many fields ranging from drug delivery to filtration membranes¹. DSM has developed a single layer nanoporous antireflective cost-effective coating which can be deposited / processed from solution on a wide variety of substrates such as glass to by-pass the costly traditional interference-type multilayer coating currently available in the market. To obtain a one-layer coating with good antireflective properties, very low refractive index materials are necessary. The optimum refractive index n for a one-layer antireflective coating is 1.23 @ 700nm. There are, however, very few low index inorganic solid materials that display a refractive index lower than 1.37, therefore the best method to realize materials with a low n, is to reduce their packing density or increase porosity.

DSM managed to develop a coating technology based on silica / latex core-shell nanoparticle colloidal dispersion. The desired shell-density can be tuned by controlling the silica reaction conditions and self-assembly mechanisms at the latex particle / solvent interface. The resulting antireflective coating is mechanically robust, with a transmission of 98% or higher, and shows excellent outdoor durability. Added functionalities to the anti-reflective coating for PV applications will also be discussed.